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Publication numberUS3720568 A
Publication typeGrant
Publication dateMar 13, 1973
Filing dateMar 22, 1971
Priority dateMar 22, 1971
Also published asCA960380A1, DE2213492A1, DE2213492B2, DE2264521A1, DE2264521B2, DE2264521C3, DE2264795A1, DE2264795B2, DE2264796A1, DE2264796B2, US3774967
Publication numberUS 3720568 A, US 3720568A, US-A-3720568, US3720568 A, US3720568A
InventorsD Rowland
Original AssigneeD Rowland
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Seating and sub-assembly for seats and backs
US 3720568 A
Abstract
Seats and backs for chairs and other seating units are made as a sub-assembly of sinuous spring wires. For example, a rim, typically having straight ends joined by usually parallel sides shaped as circular arcs, encloses, and its straight ends are attached to, the opposite ends of each of a series of the sinuous spring wires, which extend between them in a circular arc paralleling those of the rim sides. Each of the two extreme spring wires is preferably tangent at each cycle to one of those sides, and each wire touches its adjacent wire at least once per cycle. A thin sleevelike plastic coating surrounds the wires and follows their sinuous shape. It also surrounds the rim and links the wires and the rim together and links the wires themselves together wherever they touch, into a unitary assembly shaped as a cylindrical arc and intended to be flattened somewhat when installed on a chair frame, to place the springs in tension along a flatter cylindrical arc. The ends serve to mount the assembly on the frame, and the parallel sides enclose the springs and minimize their catching on clothing, while the tension provides one of the main forces retaining the assembly in place. In preferred forms of the invention the plastic coating has an A-scale Shore durometer between 45 and 90, so that the assembly is held together by the plastic coating without substantially restraining the flexing of the spring wires, while the coating also provides a spring action itself between the adjacent wires, by stretching and contracting, giving a two-way stretch.
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nited States Patent [191 Rowland 51March 13, 1973 SEATING AND SUB-ASSEMBLY FOR SEATS AND BACKS David L. Rowland, 49 West 55th Street, New York, N.Y. 10019 [22] Filed: March 22, 1971 [21] Appl. No.: 126,808

[76] Inventor:

[52] US. Cl. ..16l/48, 161/57, 161/112, 161/140, 267/111, 297/452 [51] Int. Cl. ..A47c 7/02, F16f 3/02 [58] Field of Search .267/110, 1ll;297/452; 161/48, 161/57, 55,125,109,112,l40

[56] References Cited UNITED STATES PATENTS Rowland ..267/ll1 Primary ExaminerWilliam A. Powell Attorney0wen, Wickersham 8:. Erickson [57] ABSTRACT Seats and backs for chairs and other seating units are made as a sub-assembly of sinuous spring wires. For

example, a rim, typically having straight ends joined by usually parallel sides shaped as circular arcs, encloses, and its straight ends are attached to, the opposite ends of each of a series of the sinuous spring wires, which extend between them in a circular arc paralleling those of the rim sides. Each of the two extreme spring wires is preferably tangent at each cycle to one of those sides, and each wire touches its adjacent wire at least once per cycle. A thin sleevelike plastic coating surrounds the wires and follows their sinuous shape. It also surrounds the rim and links the wires and the rim together and links the wires themselves together wherever they touch, into a unitary assembly shaped as a cylindrical arc and intended to be flattened somewhat when installed on a chair frame, to place the springs in tension along a flatter cylindrical arc. The ends serve to mount the assembly on the frame, and the parallel sides enclose the springs and minimize their catching on clothing, while the tension provides one of the main forces retaining the assembly in place. In preferred forms of the invention the plastic coating has an A-scale Shore durometer between 45 and 90, so that the assembly is held together by the plastic coating without substantially restraining the flexing of the spring wires, while the coating also provides a spring action itself between the adjacent wires, by stretching and contracting, giving a two-way stretch.

47 Claims, 53 Drawing Figures PATENTEUHARI 31975 SHEET 10F 7 FIG I 'T-T 1 HT 1 FIG; 5 Q1 INVENTOR.

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DAVID L. ROWLAND SEATING AND SUB-ASSEMBLY FOR SEATS AND BACKS BACKGROUND OF THE INVENTION This invention relates to an assembly for seats and backs, usable in chairs, sofas, stools, benches, automobile and other transportation seating, and the like. The seat and back units are sub-assemblies applicable to any of various types of frames to provide seating assem- 1 individual, this would be costly and would require carrying seats to wherever they would be used. A seat which automatically tends to shape itself to each users posterior is a better solution to the problem. A seat with proper resilience in the right places is thus an object of this invention.

The seated human body rests mainly on the ischial tuberosities, the two lower points of the pelvis. Additionally it rests on the meaty and fatty flesh in a 1 inch to 2 inch radius therefrom. The reason why a flat, hard surface becomes uncomfortable quickly is that the load is concentrated on the small area of the ischial tuberosities, and the flesh immediately covering them is compressed with great force. Spreading this load over a larger area makes a more comfortable condition as the unit area compressive force is substantially reduced. Automatically shaping the seat surface to generally conform to the sitter helps to accomplish this. On the other hand, spreading this area over too wide a surface, such as is the case when a seat is too soft, results in engulfing the sitter too deeply and also often results in a.

lack of security, which comes from feeling insufficiently supported. One often sees automobiles in which the owner has gone to the trouble of installing wooden slat accessory pads to make the seat firmer.

Dr. Bengt Akerblom, eminent Swedish authority on human posture, says in his book Standing And Sitting Posture, published by A. B. Nordiska Bokhandeln, 1948,

Naturally a rather soft seat would distribute the pressure over the tuberosities better than a hollowed rigid one. They are, however, so small that there would be very little sense in having a'very soft and resilient seat. On the contrary, such a seat might be expected to transfer a not inconsiderable proportion of the weight on to tissues which are not adapted for bearing it. The best consistency for the seat would therefore be such that although it gave under pressure, it only gave slightly."

Proper resilience alone is not enough, either. Independent freedom of movement of such as that found in a two-way stretchable material more appropriately conforms to the human posterior shape, which itself has compound curvature.

While certain spring and padding combinations can afford proper yieldability and firmness, practically all padding materials have the fault of being good heat insulators. In a cold room, this might be acceptable temporarily, but people usually wear clothes appropriate for temperature conditions anyway, and to sit for any length of time on a heat-insulative material becomes uncomfortable because of inhibition of dispersion of body heat in the human posterior area. To get to a cooler spot, the person squirms. Also, anyone who, while wearing a swim suit, has tried to sit down on the seat of a convertible car that has been out in the hot sun, knows that such heat conditions of the seat can be unbearable.

Some prior art seats have been made of spaced-apart wires, but in them the spacing hasbeen such that too much load has been concentrated on too few wires, and

0 this textural discomfort has made the use of upholstery pads requisite for such seats.

An ideal seat therefore has: 1. Proper shape (including proper compound curvature).

2. Proper resilience and firmness (resilience provides shape adaptability to each sitter).

3. Proper heat dispersion.

4. Proper surface contact area.

An object of this invention is to provide a seat more nearly approaching the ideal than has been achieved in the past.

Each unit or sub-assembly of this invention comprises a series of sinuous spring wires, partially held together by a thin sleevelike plastic coating around each of the wires, bridging the wires where they touch. In addition, however, each unit or sub-assembly of this invention is secured together at or near the ends of the spring wires, either by a rim or by welding them to each other or to another member.

The invention may be considered as an improvement over my earlier U. S. Pat. No. 2,803,293. In that patent each of the sinuous springs had a hook on each end which partially encircled a rigid frame member. This hooking did not positively prevent movement of the wires relative to the frame, nor did it hold them in proper position relative to each other prior to their being coated with plastic. Partly because there was only line contact at best between the wire and the frame (and unless the chair frame size was exactly matched with the size of the hook, there would be contact at only two points), the hook tended to rotate when subjected to force, as when someone sat on the chair. Even after the chair had been coated with plastic, this insta bility was such that when the chair was being sat upon, the wire hooks tended to walk along the chair frame as the sitter shifted his position, thereby distorting the seat area, with the result of making the seat uncomfortable. The chair of that patent was expensive to manufacture because the springs had to be put on individually, carefully positioned, and then either the entire chair had to be dipped, or at least the upper portion of the chair, from the seat up, had to be dipped. Such dipping meant that all parts of the chair that were dipped would be coated with plastic unless something could be put on some parts of the chair to repel the plastic. Either alternative added substantially to the cost. Also, the coating dulled the appearance of chrome metal furniture, and wood furniture was given a rather unpleasing appearance. Each chair had to be made individually, and the springs themselves had to be put on to a full chair frame individually, so that easy handling required by mass production was not possible. Also, great care had to be taken that the springs themselves were not distorted by the spring manufacturer during his manufacture; otherwise, the springs could not be properly bridged across by the plastic.

These difficulties are overcome in the present invention, which makes mass production quite feasible. Only the seat unit or back unit is dipped, and assembly is relatively inexpensive, and its manufacture is capable of automation and other mechanical aids. A very important feature is the provision of a sub-assembly capable of use on a wide variety of frames for different kinds and designs of seating units. The same sub-assembly may be sold to various manufacturers for incorporation into any of a wide variety of frames.

Another disadvantage of my prior chair was that the chair seat and back were substantially planar, and, even if they did have a slight bowing, they were installed in a generally flat at-rest shape of the spring, so that there was little spring tension or cushioning action. In the present invention, it becomes possible to obtain much more tension, cushioning, and resilient support from the springs by virtue of making the unit as a cylindrical segment that is somewhat flattened when it is put on a chair frame, rather than making chairs from a series of substantially flat springs. The tension of the wires pulling inwardly is one of the main forces retaining the assembly in place.

Another important feature of the invention is the provision of a two-way stretch, which is obtained by using plastic coatings lying within a prescribed range of Shore durometers. The springs can continue their flexing in the usual manner without being overly limited by the coating, and also the spring assembly can flex and stretch the plastic when it bridges the wires. In the prior patent, it was possible to use a wide variety of materials, including hard plastics such as nylon, which would certainly hold the wires together but would not itself stretch, so that all the stretch had to be accomplished by the wires when such a material was used. This would give the seat some yieldability, but usually in a cylindrical surface, rather than in the compound curve which results in a seat that has two-way stretch. Nor was this two-way stretch recognized or found in this type of chair until a desired range of durometers was discovered in the present invention and used in proper relationship to suitable gauges of wires and so enabled achievement of this goal.

Even two-way stretchability and proper wire gauge alone have been found to be insufficient. Resistance to bounciness is an important property when considering the resilience necessary for a comfortable seat and is especially necessary in transportation seating, where up-and-down motion tends to result in harmonic vibration, for harmonic vibrations subject the sitter to vertical oscillations for some time after a bump has been traversed. Bounce dampening is thus requisite, and is partly accomplished in the present invention by proper choice of durometer of the plastic coating. If the durometer is too low a value, the springs are too free and are too ready to bounce. If the durometer is too high, the seat is too stiff and lacks the proper two-way stretch quality desired. Proper choice of durometer according to the principles of this invention, enables the plastic to serve as a shock absorber and provides a snubbing action against bounce.

Additionally bounce-dampening can be achieved in this invention by employing in the assembly some wires that differ from the other wires in gauge, shape, or spring tension or temper, so that their harmonic vibration periods are different.

The amount of the seating area occupied by the metal thickness, and the thickness of the plastic coating are also important features to be considered, and little, if any, thought on these features is evident from the prior art. For example, in the drawings for U. S. Pat. No. 2,803,293, it can be shown that the metal occupies only about 14 percent of the silhouette of the area, whereas I have now found that for proper results the spring steel should occupy a minimum of 17 percent of the silhouette of the area and, preferably, but less important, a maximum of about percent, with the range of about 17 percent to about 25 percent generally preferable. The coating should generally be about one-half as thick as the wire, in order to give bridging, proper heat insulation, and proper stretchability, but a range from about one-fifth of the wire thickness to about equal to the wire thickness can be used. Also, the size of the void areas between the coated wires should be no greater than about 75 percent of the seat area used to accommodate one adult sitter and should not be less than about 2 percent, with about 60 to 75 percent being preferable.

SUMMARY OF THE INVENTION The present invention comprises a seat or back subassembly which can be secured to various frames in various manners. Basically, the sub-assembly is a cylindrical segment, later flattened somewhat upon installation, placing the springs in tension. Usually, but not always, it has a rim, which usually has straight ends, typically parallel, joined by parallel sides which are made as circular arcs. These frames enclose a series of sinuous spring wires, each of which is attached at its opposite ends to the rim, preferably the end members. The wires extend between the rim ends in a circular are that is parallel to the circular arc of the parallel sides of the rim. In most seats and backs each of the two extreme spring wires is tangent at each cycle to one of the rim sides, and each wire touches or closely approaches its adjacent sinuous spring wires at least once per cycle.

A thin sleevelike plastic coating surrounds both the rim wires and the sinuous spring wires, following the sinuous shape of the spring wires and bridging between and joining them at points where they are tangent to each other or touch each other, and also joining and bridging between the rim and some positions of the wires. This thin plastic coating, while leaving most of the area of the seat open in between the wires, does link the wires and the rim together into a unitary'assembly, shaped as a cylindrical are. When the unitary assembly is installed on a frame as either a seat or a back, it is flattened out somewhat but not fully. When used as a seat, the rise between one end and the other after flattening is between a quarter of an inch and an inch, preferably. For the back, the curvature may be somewhat greater, preferably a radius of 7 to l 1 inches. The plastic preferably is in the range of Shore A durometers between 45 and 90, and seems to be best at about 75, so that the two-way stretch action previously referred to is attained.

in some forms of the invention other shapes of rims are used, and in still other forms, no rim as such is necessary, being replaced by a special welded sub-assembly.

Note that in this invention the wires cannot go straight across. They must undulate in order to be stretchable. Moreover, they must be connected to each other by stretchable means. This contrasts with my earlier patent which may allow flexible joints but does not require stretchable joints. A ISO-pound person sitting normally on a chair of the present invention will depress it by at least 1 inch (or at least one-eighteenth part of seat height) and, at most by about 3 inches (about one-sixth part of seat height). As stated, the junctures are stretchable and flexible, but they are also so tough that they cannot be pulled apart under usual human sitting conditions. Putty and kneaded erasers have a rubbery quality, but not the elasticity, stretchability, flexibility or resilience requisite. To get the best results in this invention, the area of the silhouette of the wires prior to coating should be at least 17 percent of the seat area, especially of a typical area. For sufficient bridging, heat insulation, and surface cushioning, the coating should be at least 20 percent of the wire diameter. If the seat were made from springs alone, the comfort would be insufficient, particularly when used in moving vehicles. It would be too bouncy. Proper durometer and proper thickness of the coating relative to the wire thickness help to prevent this bounciness. The reason is similar to the reason why a car is not comfortable with metal springs alone; it also needs the rubber, air, and hydraulic fluid in the combination of rubber-pneumatic tires and hydraulic shock absorbers, before it can be comfortable.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a view in perspective of a chair embodying the principles of the invention.

FIG. 2 is a view in perspective on an enlarged scale of a seat or back unit or sub-assembly embodying the principles of the invention, shown before being installed on the chair frame of FIG. 1.

FIG. 3 is a view in section taken along the line 3-3 in FIG. 1.

FIG. 4 is a view in perspective of the fastener used in FIGS. 1 and 3 to secure the sub-assembly of FIG. 2 to the chair frame in FIG. 1.

FIG. 5 is a diagrammatic view in end elevation showing the difference in radii of the cylindrical assembly of FIG. 2 and the installed seat of FIG. 1, which has been somewhat flattened out, thereby placing the spring wires under tension.

FIG. 6 is a fragmentary enlarged view in perspective of a corner portion of the assembly of FIG. 2, somewhat flattened out. Some portions are broken away to show other portions that would otherwise be obscured.

FIG. 7 is a further enlarged view in section taken along the line 7-7 in FIG. 6.

FIG. 8 is a view in section taken along the line 8-8 in FIGS. 6 and 7.

FIG. 9 is a view in section taken along the line 9-9 in FIG. 7.

FIG. 10 is a view like FIG. 7 showing how the springs may be installed from the opposite direction in he same rim unit.

FIG. 11 is a fragmentary bottom plan view of a portion of a modified assembly of the general type of FIG. 2, with some portions broken away.

FIG. 12 is a view in section taken along the line 12- 12 in FIG. 11.

FIG. 13 is a view in section taken along the line 13- 13 in FIG. 11.

FIG. 14 is a fragmentary bottom plan view in section similar to FIG. 11 ofa modified form of rim member.

FIG. 15 is a view in section taken along the line 15- 15 in FIG. 14.

FIG. 16 is a fragmentary view in perspective of a chair frame.

FIG. 17 is a further enlarged view in section taken along the line l7-l7 in FIG. 16, omitting the chair frame.

FIG. 18 is a further enlarged view in section taken along the line 18-.-18 in FIG. 16.

FIG. 19 is a view similar to FIG. 18 showing installation of the same unit assembly on a modified form of chair frame.

FIG. 20 is another view similar to F IG.18 showing installation of the same unit assembly on another modified form of chair frame.

FIG. 21 is a fragmentary view in perspective and partly in section of another modified form of unit assembly.

FIG. 22 is a view in section taken along the line 22- 22 in FIG. 21.

FIG. 23 is a view in section similar to FIG. 22 showing the same parts at an early stage of assembly.

FIG. 24 is another similar view showing a stage of assembly intermediate between FIGS. 22 and 23.

FIG. 25 is a fragmentary view in perspective of another form of unit assembly. v

FIG. 26 is a view in section taken along the line 26- 26 in FIG. 25.

FIG. 27 is a similar view in section of the unit of FIG. 25 fastened to a chair frame.

FIG. 28 is a view in perspective of a modified form of unit assembly having a round rim and shown flattened to the position it assumes when fastened to a chair frame.

FIG. 29 is a view in perspective of yet another modified form of unit assembly, wherein the rim is eliminated and the springs secured together by a series of welds, the parts being flattened to the are they assume when secured to a chair frame.

FIG. 30 is a fragmentary view in perspective of a portion of a further modified form of unit assembly.

FIG. 31 is a view like FIG. 30 of an additional modified form of unitassembly.

FIG. 32 is a view in perspective of a modified from of chair embodying the principles of the invention.

FIG. 33 is an end view of the unit assembly for the seat of a chair like that of FIG. 32.

FIG. 34 is a view in side elevation of another modified form of chair embodying the principles of the invention.

FIG. 35 is an end view of the unit assembly for the seat of a chair like that of FIG. 34.

FIG. 36 is a fragmentary view in section showing how the seat assembly and back assembly are both fastened to a single frame member in the chairs of FIGS. 32 and 34.

FIG. 37 is a view in perspective of a modified form of chair embodying the principles of the invention, wherein the seat and back assembly are so mounted to a frame as to provide compound curved surfaces.

FIG. 38 is a view in side elevation of the chair of FIG. 37.

FIG. 39 is an enlarged top plan diagrammatic view in two halves illustrating the two-way stretch effect of the wires and plastic assembly.

FIG. 40 is a view in side elevation of an opened folding chair embodying the principles of the invention.

FIG. 41 is a view in side elevation of the folding chair of FIG. 40 in folded position.

FIG. 42 is a diagrammatic view of the relative arcs and radii of back and seat for the chair of FIG. 40.

FIGS. 43 to 51 are all top plan fragmentary views of various patterns of the arcuate sinuous members, in each instance with portions of the wire shown uncovered and with plastic linking the spring members together. Various patterns are shown as illustrative of the many, many more that are possible in this invention.

FIG. 52 is a view in front elevation of the lower portion of a modified form of chair embodying the principles of the invention.

FIG. 53 is a view in side elevation of a stool embodying the principles of the invention in another modified form.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS An Example of a Chair Embodying the Invention (FIG.

Many, many types of seating units may embody the principles of this invention, including chairs, sofas, davenports, benches, stools, automobile seats, bus seats, camp chairs, and so on.

A chair 60 is shown in FIG. 1 for the purpose of giving one example of a type of seating unit that can embody the principles of the invention. This example is not to be construed as representing all types of seating units or even all types of the chairs, which can vary greatly in frame structure, appearance, and so on. The basic part of this invention is concerned with the seating and back unit more than with the framework of the chair itself.

The chair 60 has front legs 61, 62 and rear legs 63 and 64 which continue up, preferably at an angle, to form back frame portions or members 65 and 66. The number of pieces used in making the chair frame is immaterial to this invention, and whether the frame is continuous or pieces are welded or otherwise secured together does not matter, so far as the present invention is concerned. Horizontal side frame portions or members 67 and 68 join the front legs 61 and 62 to the rear legs 63, 64 where they meet the back frame members 65 and 66. The use of bracing and top members is not significant in the present invention, though some such members are shown in the drawing, and there must be some rigid means for holding the frame members 67 and 68 apart and for holding the frame members 65 and 66 apart. In this particular form of the invention the back frame members 65 and 66 are rigidly held parallel to each other and the side frame members 67 and 68 are rigidly held parallel to each other. This parallelism need not always be present, but it is preferred.

A seat unit 70 is supported by the side frame members 67 and 68 and a back unit 70A is supported by the frame members 65 and 66. The seat unit 70 and the back unit 70A are very similar to each other; they may in some instances be identical, but usually the back unit A is somewhat smaller than the seat unit 70 and is usually made from a smaller gauge of wire.

The structure of the units 70 and 70A is highly important in this invention. So is the attachment of the units 70 and 70A to a chair frame.

The Seat Unit 70 (FIG. 2)

FIG. 2 shows the seat unit 70 before it is incorporated into the chair; the view also represents basically what the unit 70A looks like, although the unit 70A may be different in size or even in structure or appearance, where desired.

In this example the unit 70 comprises a rim 71 having spaced-apart straight ends 72 and 73 joined by parallel side members 74 and 75,which are shaped as circular arcs. Lest there be some confusion in the mind of the reader, it is pointed out that the straight end members 72 and 73 are secured to the side frame members 67 and 68 of the chair, and thus extend from front to rear at each side of the chair 60, while the side members 74 and 75 become the front and back edges of the seat in the assembled chair 60. However, so far as the seat unit 70 itself is concerned, the members 72 and 73 are the ends and the side members 74 and 75 are arcuate or circular sides.

Extending from end to end across the two end members 72 and 73 is a plurality of sinuous spring wires 76, 76a, 76b 76n, which are naturally arched into a circular arc of the same size and shape as that of the side members 74 and 75. These springs 76, 76a, etc., may have many shapes, some of which are shown in FIGS. 43 to 51. They may be of the type often called nonsagging springs and sometimes sold under the trademark NoSag. Typical wires 76, etc., of this type are of spring steel, having 0.60 to 0.75 percent carbon and 0.90 to 1.20 percent manganese. Tensile strength typically runs about 215,000 to 265,000 p.s.i., and their Rockwell hardness is about 39-41 RC range. The diameter of the wires 76, etc., preferably lies in the range of 0.05 to 0.15 inch. Too thick a wire tends to concentrate the stiffness too much and the seat is too firm, while too thin a wire makes the seat too soft.

Each end 77, 78 of each spring 76 (see FIGS. 6-15) is firmly anchored to and secured to one of the end members 72, 73 of the rim 71. Various means are employed to achieve this firm anchorage, and some of these are described below in following sections. They include friction grips and welding, among the many types of mechanical connections.

The spring members 76, 76a, 76b, 76n are placed tangent to each other, each of the two extreme spring wires 76 and 76n being substantially tangent at each cycle to one of the side members 74 and 75. Each wire 76 touches its adjacent wires at least once per cycle. The touching may be actual contact or it may be approximate touching or close approach, because, as will be seen, the assembly 70 is held together in a way that does not require actual physical contact of the metal at each tangent point, but it is always a very close relationship if not an actual touching.

A thin sleevelike plastic coating 79 surrounds the spring wires 76, follows their sinuous shape, and bridges the wires 76, 76a, etc., where they substantially touch each other. Preferably, the plastic coating 79 is about one-half of the wire thickness, or in the range of about one-fifth of the wire thickness to about equal to the wire thickness. At the junctures, the thickness may be mostly greater, though the wires themselves may touch each other. This plastic coating 79 also surrounds the rim 71 and links the wires 76 and the end and side members of the rim '71 together into the unitary assembly 70. The plastic coating 79 holds the wires 76 to each other as they span between the rim ends 72 and 73, and it holds the side wires 74 and 75 to the extreme springs 76 and 7611 at each point of tangency. The result is the arcuate or cylindrical arc shape, typically like that shown in FIG. 2, although the arc may be somewhat flatter or somewhat rounder.

Thus, the complete assembly 70 is a unit which can be sold or shipped as a unit and can be assembled to the chair 60 of FIG. I or to many other kinds of chairs, so

Various securing means are discussed in this specification, some of them being shown for example in FIGS. 16 through 20, and in FIGS. 26 and 27, among others. Basically, the securing means may be an integral part of the unit 70, or may be an integral part of the chair frame or other frame to which the unit 70 is to be secured, or it may be an independent member not an integral part of either of these. An example of the lastmentioned type is the securing member 80 shown in FIGS. 3 and 4. This may be a suitable metal or plastic member having a generally tubular rim-receiving portion 81, with an opening 82 therethrough that fits snugly around a rim member 72 or 73. The member 80 has a pair of flanges 83, 84 having an opening 85 through them. As shown in FIG. 3, the chair frame member 67 may have a series of openings 86 adapted to receive the two wings 83 and 84, after the member 80 has been fastened around the rim member 72 or 73. Then a suitable screw 87 may be inserted through a suitable opening 88 of the frame member 67 and secured by means of the openings 85 to the wings 83 and 84. As shown in FIG. 1, there may be several of these units 80 to secure the seat unit 70 and the back unit 70A to the chair 60.

From this it will be apparent that the assembly 70 and the assembly 70A may be made as units by one manufacturer and sold to another manufacturer who makes the chair frames. So long as the dimensioning is correct, the two manufacturers need not know precisely what each other is doing, for the unit 70, if made in the correct dimensions, can be secured to a variety of different types of chair frames, or to other frames of seating members, for that matter, including benches,

. automobile frames, and so on. The unit 70 enables the chair manufacturer to secure the seat or back in place in the most attractive and pleasing and most practical way.

As will be seen from later portions of the specification, there are many, many ways in which the fastening ill of the member to the chair 60 can be done, and this is just one example.

The Significance of Flattening the Cylindrical Arc (FIG. 5)

FIG. 5 shows diagrammatically what happens when the unit 70 of FIG. 2 is put into the chair 60 of FIG. 1. The round cylindrical arc of FIG. 2 with radius R1 is flattened from the shape shown at the bottom of FIG. 5 to the shape shown at the top of FIG. 5, where it has a larger radius R2. The unit 70 then has a broader span and its arc is somewhat flattened, so that it can be used as a seat. It has a crown height h, shown on the drawing, and it is still a cylindrical are, though much flatter.

This flattening of a round assembly is an important feature of the invention. By forming the unit 70 initially as a cylindrical arc, which is quite round and fairly well closed, and then flattening it considerably, a large amount of desirable tension is placed into the completed unit 70, so that the seat has a springy feel to it, acting substantially as though there was a large cushion instead of simply an assembly of thin springs. The exact amount of crown height h or of curvature depends, of course, somewhat on taste, but generally there will be about a maximum of one inch crown height h in a sixteen-inch wide seating unit 70, and the proportion is usually best considered as being a crown height h of one-sixty-fourth to one-sixteenth of the span.

The amount of force required to flatten a seat of typi cal dining chair size is important as well. For purposes of the present invention it has been found that a collection of springs in an assembly 70, requiring a force of between 340 pounds and 680 pounds to flatten it gives a seat of proper tension, (preferably around 500 pounds). This is the force exerted in pulling the two ends 72, 73 apart to be of an appropriate distance to fit onto the chair frame members 67, 68.

For the chair back, somewhat different rules apply and it will be noticed that in the chair of FIG. 1, as in most such chairs, the arc of the back extends rearwardly and is not something that the sitter tends to flatten; rather, he tends to increase the arc curvature, reducing its radius.

In both the seat and the back, the tension of the wires pulling inwardly, which results from flattening, is also one of the main forces retaining the wires in place. Significance of the Plastic Coating 79 (FIG. 39)

The plastic coating 79 may be chosen from various types of plastic, such as polyvinyl chloride, polyvinyl acetate, mixtures thereof, other vinyl compounds, polyethylene, butadiene, acrylic elastomers, and so on. The material may be transparent, where that is desired, or may be opaque and impart its own color to the unit. It may contain dye or pigment which imparts a desired color, completely preventing view of the wires 76 themselves and giving the appearance of constituting the actual seating material. The plastic coating 79 may be semi-transparent and may give shade or tone to the overall color.

It will be noticed that in this invention the plastic is confined to the unit 70 or 70A and is not applied at all to the chair frame, so that the chair frame may have any surface or treatment that is desired without interference from the nature of the plastic coating.

The sinuous wires 76 are preferably not welded to each other at their points of tangency but are held together only by the plastic coating 79, with the wires 76 either touching each other or even slightly apart but closely approaching each other. The same is true of the connection between the wires 76 and the arcuate side members 74 and 75 of the rim 71.

An important feature of the plastic coating 79 is that by choosing the proper range of durometer, a two-way stretch effect can be obtained, as illustrated in FIG. 39. The springs 76 not only stretch in the well known manner of non-sagging springs, but also the plastic coating 79 between the adjacent springs 76 may be stretched, and this two-way stretch effect gives a wide range of resilience to the seat. If the plastic 79 is too hard, there can be substantially no such stretch, and if the plastic 79 is too soft, there will be too much stretch, the springs 76 themselves are not properly availed of, and the unit 70 might even be torn apart after short use. By holding the Shore durometer of the plastic coating within critical values, the effect is right, with sufficient rigidity so that the springs 76 are taken advantage of and so that they are held apart with sufficient resilience so that the whole is not simply encased in a rigid covering. I have found that the durometer range necessary to achieve this critical action is from about 45 to about 90 Shore A-scale durometer, with a preferable value of about 75.

In FIG. 39 there are two portions. The left portion illustrates part of a seat 70 before it is sat upon, with the springs 76 therefore in their normal configuration. A typical area 280 is shown outlined, this area comprising one complete cycle of wires 76, so that it is representative of the total area of the seat 70 so far as the percentage of metal silhouette per total area is concerned. This area can therefore be used for determining accurately the silhouette of the wire and its average occupation of the seat area. Taking the gauge or wire diameter as G, the length of the wire can be determined in terms of G by measuring the length of the center lines of all the wires 76 in the area 280 in terms of G, and the value is found to be 34G. The area 280 itself measures 14.66 by [0.76, which is 156.22G. The silhouette area of the wire in the area 280 is 34G, which is 21.76 percent of the area 280. This value lies within the required range of 17 to about 75 percent of the seat area, mentioned earlier, and also within the range of the preferred range of 17 to about 25 percent.

Also, the empty spaces between the coated wires should be no greater than about 75 percent and no less than about 2% of the area of the seat surface, and the range of about 60 to about 75 percent is preferred. The minimum of about 2 percent barely provides sufficient air ventilation.

The wires 76 in the seat 70 lie closely adjacent each other and nearly touch at points of near-tangency, where the distance D1 between them, as shown in FIG. 39, may be as low as zero, and where the overall distance from the outside to the outside is T1. The plastic coating 79 forms a bridge fastening thewires 76 together at 281 and has a thickness t.

The right portion of FIG. 39 illustrates what happens when the seat 70 is stretched, as when it is sat upon. The length L1 in the left portion extends to the longer length L2 in the right portion. The width W1 in the left portion extends also to become the width W2 in the right portion. The distance D1 in the left portion has stretch to become the distance D2 in the right portion, and the distance T1 has stretched to become the distance T2. Thus is seen the importance of the bridge or juncture 281 and of the stretchability of the plastic 79 at this bridge or juncture 281. This, of course, is related also to the thickness tof the plastic coating 79.

A glance at the seat might lead one to conclude that the surface configuration would be texturally uncomfortable. However, this conclusion would be mistaken, for the seat 70 acts differently than one might at first conclude, for the following reasons:

1. The average occupation by the wire of the typical area (i.e., 17 to percent) is so great that the human posterior is supported without concentrating the load too much. In contrast, if the wire occupies less than about 17 percent of the area (e.g., the 14.4 percent occupation of the FIG. 2 area in U. S. Pat. No. 2,803,293), the seat would be texturally uncomfortable.

2. The empty spaces constitute at least 2 percent of the seat area, in order to give sufficient air ventilation, and preferably occupy much more of the seat area, up to about 75percent.

3. The wire 76 is not exposed bare metal, which would be highly heat conductive and therefore unpleasant and uncomfortable. The wire 76 is adequately coated with plastic 79 which is low in heat conductivity; so it is pleasant and comfortable to sit upon.

4. The coating 79 lies within the range of Shore A durometers (45-90) where it is neither too hard nor too soft; in fact it tends in itself to provide some cushioning effect, and its action at the bridges 281 adds to the comfort. Without this, the seat 70 could be too hard or too soft.

5. The two-way stretch discussed above provides automatic contouring, offering minimal resistance to the human posterior. Without this two-way stretch, the seat 70 might become increasingly uncomfortable.

Friction Fastening of the Wires to the Rim (FIGS. 6-10) While many means of fastening the spring 76 to the rim 71 may be employed, some are naturally preferred above others. The preference depends on many factors, such as manufacturers capabilities and preferments, specifications given by customers, and various features of cost and capital equipment required.

One desirable type of fastening employs a friction lock principle, shown in FIGS. 6 to 10. In this form, the rim 71 has end members 72 and 73 that are generally tubular; they may be made as a solid tube, but, preferably, as shown in the drawings, each member 72 or 73 is an open tube that may be made by curling a narrow strip of metal in a generally circular shape. As shown, the member 72 or 73 has a flat bottom portion which is punched through at intervals to provide openings 91 and wings 92 and 93, extending at an angle such as about 30. Machines for making these on either a batch basis or on a substantially continuous basis are readily device, so that the members 72 and 73 may be made as long strips cut into desired lengths.

As will be seen by comparing FIGS. 7 and 10, the member 73 may be considered as being the same as the member 72, so that they are reversible; in other words,

the same piece may be used in either direction and at either end of the rim. Of course, bending in one direction in reversal is a possibility, but no such reversal or sense of direction is required when the wings 92 and 93 are made as shown.

A series of side openings or slots 94 provide an entryway for the wire end 77 or 78. The wire end 77 or 78 is inserted in the opening 94 and then moved lengthwise of the member 72 or 73 until it is stopped by engaging one of the wings 92 or 93. When inserted, the wire 76 depresses the wing 92 (or 93) under pressure, but when it engages the end of the far wing 93 (or 92), it can progress no further. Thus, accurate positioning is assured, and this can be made to provide automatically the desired tangencies of the wires 76 with each other and with the side members 74 and 75 of the rim 71. Once inserted, the wire end 77 or 78 cannot be retracted, because on retraction, the depressed wing 92 (or 93) digs into the wire 76 and prevents outward movement. The intention is to prevent any relative movement between the wire end 77 or 78 and the member 72 or 73 after assembly. The wire 76 can move across a depressed wing 92 in the direction toward a stop wing 93 but cannot move back against the wing 92, once it has been moved in. As shown in FIGS. 7 and 10, the movement can be in either direction with the same effect exactly; it may be, of course, in opposite directions at opposite ends of the rim 71. Thus, the

wires 76 are locked into the complete assembly by friction in this form of the invention. The plastic coating 79 is applied after this assembly is completed.

Resistance Weld Securement of the Rim and Spring Wires (FIGS. 11 to 13) FIGS. 11 through 13 show the use of a rim end member 95 with an inverted channel or U shape and having resistance weld protrusions 96 against which the wire ends 77 or 78 are moved. An entrance opening 97 for the wire 76 is provided. Various stop means may be employed, or the stop may simply be provided by the machine which inserts the spring wire 76 through the I opening 97 into the inverted channel member 95. In any event, the spring wire end 77, once inserted, is held in position temporarily while the resistance weld is made, so that the protrusion 96 in effect becomes part of the spring wire 76 and the spring wire 76 part of the channel 95, holding the rim and wire together as a single piece. The resistance welds may be made one at a time or may be made for a whole end member at once, or for both ends at once. In this form of the invention, then, the assembly 70 is held together, not only by the plastic coating 79, but also by being welded at its ends. The plastic coating 79 is, of course, applied after the welding.

A Snap Fastening (FIGS. 14 and 15) In the structure shown in FIGS. 14 and 15, a snap-in type of friction holding is employed. In this instance a rim member 100 has a spring-like structure, being shaped as a channel with springy lips 101 and 102 that lie closer together than the thickness of the wires 76. While typically metal, the member 100 may be made from plastic. The lips 101 and 102 are spread apart when the spring wire 76 is inserted from the lower end, with the aid of a side slot 103. Once inserted, the wire end 77 is snapped into place and cannot be retracted, but is held by the rim lips 101 and 102. Stops may be provided by slight punchings or dimples that limit the course of the wire end 77, or this may be completely unnecessary due to the use of holes or openings 103 which prevent more than limited movement of the wire 76, being just large enough to allow insertion of the spring wire end 77 into the rim 100. The assembly is again dippedin plastic 79 after this.

Another Friction Lock and Securement of the Unit to Chair Frame (FIGS. 16-20) FIG. 16 shows how a tubular rim end member 105 of metal or plastic is formed to provide a series of holes 106 to receive the ends 77 or 78 of each spring wire 7 6. Approximately opposite and longitudinally apart from the holes 106 the tube 105 is formed to provide wings 107 while providing stops 108, limiting movement of the spring wire ends 77 within the tubular member 105. The tube interior 109 may fit snugly around the wire end 77, and there may be no other friction retention means other than this. FIG. 17 shows that the tube 105 makes a smooth friction fit with a wire end 77 so that the wire end 77 is held by friction against going back and forth and engages the end 108 of the succeeding wing 107 to prevent further movement and to act as a stop. The plastic coating 79 helps to prevent relative movement between the tube 105 and wire 76. There may be some additional means, such as welding if desired.

The tubular end member 105 of FIG. 16 is also shown as having depending ears 110 with an opening 111 through which suitable screws 112 or bolts or rivets may pass to secure the unit 70 to the chair frame member 65, 66, 67, or 68. For example, as shown in: FIGS. 16 and 18, a screw 112 may simply pass through the ear 110 into an opening 113 in a tubular metal frame member 67.

FIG. 19 shows another way in which the same rim member 105 can be used. In this case, a tubular metal chair frame member 114 has been provided with top openings 115 to receive the complete ear 110, and a screw 112 is put infrom the side of that member 114, passingthrough an opening 116 and the opening 11 1 in the wing 110 and holding it there.

A similar way is shown in FIG. 20 of employing the same rim member 105 with a wooden chair frame member 117 with the screw 112 passing through the wood into the opening 111. Various other means of Securement may, of course, be used.

A Flattened Type of Rim With a Friction Lock (FIGS. 21-24) Another way of securing the spring wires 76 to the rim 72 is shown in FIGS. 21 through 24. Here is shown a flattened channel rim end member 120 of metal or plastic, with an upper flat portion 121 and a lower flat portion 122. The wire end 78 is held in position by friction by a wing 123 partly punched out and bent up from the lower portion 122. The wire end 78 is also held against a stop 124 in the rim end member 120. Thus, the friction holding wing 123 and the stop 124 are both provided by a series of partly punched bent-out members having the stop portion 124 of greater depth than member 123 during the passage over it, leading to the locking action of FIG. 22.

FIG. 21 also shows a modified form of rim side member 125. The rim member 125 is not straight like the side members 74 and 75, but is itself an arcuate sinuous member. In this instance, it has a different form from that of the wires 76 and is substantially a sine curve which fills in a major portion of the recess in the wire 76 that otherwise would exist unfilled; therefore, although sinuous in form, the rim member 125 does not leave the large projections exposed which would be exposed if the member 125 were not there. Instead, the projections exposed are relatively short and do not tend to catch on clothing. The whole is again coated with the plastic 79.

FIG. 21 also shows a sinuous wire 126 that is different in length and shape from the other wires 76. The function of the wire 126 is to introduces a member with vibration characteristics different from those of the wires 76, 76a etc. The effect of this introduction is to provide bounce dampening, a feature usually found necessary in transportation seating. The wires 76, 76a, etc., characteristically having one vibration frequency are attached in the assembly to the wire 126 which has a different vibration frequency, and thereby the assembly 70 has its bounce characteristics strongly modified, if not totally eliminated.

Another Form of Rim and of Attachment to the Spring Members (FIGS. 25-27) The forms which the rims may take are practically infinite. FIG. 25 shows a corner portion of a rim 130 in which one side member 131 is continuous with a portion 132 of the end member, which may define the complete rim end member. Another member of the same metallic wire type is shown at 133 parallel to and spaced from the member 132, along each side member 131. The two are held together by resistance-welding each of them at 139 to a third rim end portion 134. The rim end portion 134 has two flat portions 135 and 136 which abut the members 132 and 133, and between these it has an open-end tubular portion 137 to receive the wire end 78 through a series of openings 138. The members 78 are slipped through the openings 138 and into the interior of the portion 137 and are pushed to the stop 139. Then the composite, held together by the springiness of the members, is dipped in the elastomer 79. After dipping, the assembly may be slid into a hollow frame member 140 which may be an integral part of the chair or seat frame and which has a continuous slot 141 through which the wires 76 extend. Note that the wires 760, etc., are larger than the wires 76a and 76b. This enables the use of heavier wires where the main seating pressure is and lighter wires at the forward edge where too stiff wires can cause discomfort. It also provides bounce dampening by putting wires of different vibration frequency adjacent to each other in the assembly.

A Sub-Assembly of This Assembly Having a Round Frame (FIG. 28)

While the rectangular type of rim, like the rim 71, is usually the most desirable, that is not always the case. It may be made in a trapezoidal shape or in other shapes. As an example of what can be done, an assembly 143 is shown in FIG. 28. The assembly 143 has a round, that is, generally circular rim 144, which is continuous and which is secured, as by welding, to a series of spring members 76, etc. After the securement, the assembly is dipped in elastomer or plastic to form the completed assembly 143. The plastic 79 again joins the wire spring members 76 together and again helps to enforce their attachment to the rim 144 and to surround it, although the attachment is adequate without that. The positive securing together is by direct welding, in this instance, of any suitable type, whether of spot welding, projection welding, or whatever. Although the rim 144 is circular, it should not be thought of as being a flat circle. It is again made in the same general cylindrical shape as that in which the unit is shown in FIG. 2, but the assembly 143 has been spread out and somewhat flat tened, but not completely, in FIG. 28 to show how it looks when mounted on a chair frame, but from this it should be gathered and should be remembered that the entire assembly is again a cylindrical segment of which the ends may almost meet until they are flattened.

A Rimless Assembly of the Invention (FIG. 29)

FIG. 29 shows an assembly 145 of the invention in which there is no rim member whatever. The wire members 76, 76a, 76b, 76n are also secured together close to their ends, but in this instance, not at them, by a series of resistance welded joints 146, 146a, 16411. This securing is only at one place along each end. This provision of a metal weld joining together the wires, in this instance in two places, one near each end but somewhat spaced from it, is again a firm attachment. Since all the members 76, 760, etc., have the same arcuate curve, they are easily kept as a unit in the general form as shown in FIG. 2, the illustration in FIG. 29 showing the assembly 145 flattened out as it would be in an installed seat.

In this instance, the wires 76, 76a, 76b, 76n have free ends 77 and 78, which may be installed in attachment members provided in the chair frame itself, or there may be members that will clamp these to the chair frame, or other attachments may be used. The assembly as a whole, after welding, is dipped in the plastic to provide the coating 79 of the wires 76 and to provide the links between the various wires.

It will be seen that, in this instance, the series of welds 146, 146a 1462: plus the wires 76, 76a. 76n in effect provides what is substantially a rim, but it is a peculiar rim, in that it is really made up of a series of segments of the wires 76, 76a, etc., which are in line with each other and with the weld joints 146. But, the unit 145 is an assembly before it is installed on the chair frame. It can be shipped as an assembly and it is held together by a very strong metal means, as well as by the plastic 79.

An Assembly Welded to a Straight-Wire Rim (FIG. 30)

A portion of an assembly 150 is shown in FIG. 30 in which the wires 76, 76a, 76b, etc., are welded to a straight end portion 151 of a rim 152 having side portions 153. The welds are at the locations 154, 154a, 154b, The wire ends 78 are shown here lying outside the rim member 151, and they may be used for fastening or they may be cut off, if that is desired, and the fastening then be by the rim portion 151. The same cylindrical shape of the unit 150 is intended to be implied as in the previous drawings, for the assembly 150 is again substantially a cylindrical segment which must be flattened out when it is installed on a chair frame.

The entire assembly 150 is coated with plastic 79 after the welding has been completed.

Another Form of Assembly with the Springs Welded to the Rim (FIG. 31)

An assembly 155 shown in FIG. 31, has a rim 156 with an end portion 157 and side portion 158 shown. The rim 156 may be continuous. The portion 157 is provided with a series of projecting portions 158 to which wire ends 78 are welded at junctures 159 by any suitable welding means. The rim 151 comprises a welded structure, and after welding the whole is again coated with the plastic 79.

A Modified Form of Chair (FIGS. 32 and 33) FIG. 32 shows a chair 160 incorporating a seat assembly 161 and a back assembly 162. The back assembly 162 is substantially like the assembly 70A, with two exceptions. In the first place, the frame members 163 and 164 to which it is secured, extend horizontally rather than being vertical, the second exception is that the assembly 162 has end rim members 165 and 166, and these, of course, extend horizontally so that they can be secured to the frame members 163 and 164, but, in this particular instance, by way of example, there are no side rim members corresponding to the members 74 and 75 of the assembly 70 in FIG. 2. Instead, the wires 76 are free at each side. Since they are at the sides of the chair, they are less likely to catch on clothing, and they may be left in their natural state. Also, the intention here is to cover them with fabric 167, so that they are not truly exposed and do not present even that apparent hazard.

The seat member 161 is basically like the member 162 for the back, but has an important difference. The similarities are that the wires are free at each side, that the seat is covered with fabric, and that it has end members 170 and 171 which are secured to chair frame members 168 and 164. The difference is that a bend 172 is provided, which is a sharp bend spaced from but relatively near the rim member 171. This bend 172 functions l to give the chair in its fore-and-aft seating pattern, which obviously differs from the side-to-side pattern of the chair shown in FIG. 1, a resiliency at the front which is extremely desirable, and (2) also an accentuated curve at the front end which makes the chair more comfortable than it would be if this were absent. Another Fore-and-Aft Chair Seat Arrangement (FIGS. 34-36) A chair 175 is shown in FIG. 34 having a seat assembly 176 and a back assembly 162, like that of the chair 160. The difference between the seat assembly 176 and the seat assembly 161 is that the seat unit 176 has what is sometimes called a fishmouth" construction with two bends 177 and 178 adjacent a forward edge 179. The rear end rim member 170 is the same as in the chair 160. The fishmouth structure gives additional springiness and comfort and is considered desirable by some manufacturers.

FIG. 36 shows how the rim members 170 and 166 can be secured to the single horizontal frame member 164, with the aid of a clip 180 which receives both of these members and has a pair of ears 181 and 182 that are secured to the frame member 164 by a screw 183 extending through an opening 184 in the frame member 164 and through an opening 185 in the ears 181 and 182, approximately at right angles to the screw 183. The attachment is similar to that already shown in a previous drawing, except that here both the seat 176 and the back 162 are simultaneously attached. It will be noted also that in this instance, the back member 162 is arched forwardly rather than rearwardly, this being because of the use of the two parallel suspensions, both being horizontal instead of vertical.

A Chair With A Compound Curve (FIGS. 37 and 38) A chair is shown in FIGS. 37 and 38. This chair makes use of the same assemblies 70 and 70A already discussed for the seat and the back. The difference in this chair is that the frame is so constructed that a compound curve is formed in the back and in the seat. Thus, the front legs 191 and 192 merge into side frame members 193 and 194 by relatively wide radius curve portions 195 and 196, and the rear frame members 197 and 198 also have upper portions 199 and 1990 that are curved. The result is, that when the seat assembly 70 is installed, it has a front portion which is curved in the direction of the chair frame, while at the same time it'is arched across between the frame members 193 and 194, and the same is true of the back member. These compound curves give added comfort through more appropriate contouring. Straight portions at the front edge of a chair are likely to cut into the legs and to be uncomfortable, and a curved portion eases that part and eliminates the sharp cutoff, insofar as the sitter is concerned.

A Folding Chair Embodying the Principles of the Invention (FIGS. 40-42) A folding chair 200 is shown in FIGS. 40 and 41, having a seat 201 and a back 202, which may be made from units 70 and 70A embodying the principles of the invention. The folding chair 200 has a pair of side frame members 203 that support the seat 201, a pair of 'rear leg members 204 extending to the front of the chair 200, and a pair of front leg and back frame members 205 that support the back 202.

FIGS. 40 to 42 show a significant feature of the invention. The seat 201 is crowned upwardly and the back 202 is crowned rearwardly, so that when the chair 200 is folded, the seat 201 can nest within the back 202 as shown in FIG. 41. This enables very compact folding of the chair 200, so that the thickness of the chair 200 in a stack of such folding chairs need be no greater than the frame thickness.

This feature of compact stackability is also applicable in a non-folding but compactly stackable chair (Cf. U.S. Pat. No. Re. 26,071) wherein seats nest compactly over seats, and backs nest compactly into backs.

Some of the features of the folding chair part are illustrated also in the diagrammatic view of FIG. 42. This shows that the seat 201 may be curved less than the back 202, and in most examples this provides a more comfortable chair 200 than if they were curved only to fit each other. The back concavity should be equal to or greater than that of the seat; in other words the radius of curvature of the seat 201 is greater than the radius of curvature of the back 202. The back 202 may vary from having a radius identical to that of the seat 201, to a radius no less than half of the radius of the seat 201, in order to secure both comfort and adequate folding. of course when the curvatures are different, the stacking may be somewhat less compact, but this is a disadvantage to be weighed against the other disadvantage of having the seat and back be uncomfortable when sat upon. In FIG. 42 is illustrated another unique feature of the invention. The seat member 201 has a crown height of between one-fourth inch and 1 inch. When the seat 201 is folded intothe back 202, its under side 206 as well as its upper surface 207 fits within the chord 208 of the back 202. Preferably, the back 202 should have a radius of curvature R3 less than the radius of curvature R4 of the seat crown 201. The preferred radius R3 is between 11 and 15 inches, and preferred R4 is 33 to 88 inches for a l7-inch span. Some of the Many Patterns of Wire Possible in This Invention (FIGS. 43 to 51) A substantially infinite number of wire patterns is possible under this invention. The one shown heretofore with the wire 76 is a very good pattern but it is not the only good one that can be used. Patterns can be used for their structural features, because of manufacturing convenience, or because of design features. Some of these features will appear from the selected forms shown, and in all of them it will be seen that the wires, whether in parallel pattern or alternate patterns, touch each other at least once per cycle; the touching may be flush to each other in the same plane, or may be by an overlap of planes with the unit still having substantially the same plane.

FIG. 43 shows a wire 211 with vinyl covering 212 and an adjacent wire 213 with vinyl covering 212 also on it. The wires 211 and 213 are bent in the same pattern but are set to alternate, so that one is rotated 180 relative to the other; instead of each wire 211 being strictly parallel to its adjacent wire 213, their sinuosities are reversed, and the alternating effect is obtained. Alternation can give some interesting designs, such as the one shown here. The length of the one cycle has been marked on the drawing, and it will be seen that the cycle is rather long, partly due to the alternation and partly due to the wire pattern itself. Thus, the wire 211, starting from the left-hand end, has a long vertical portion 214, then a horizontal portion 215 succeeded by a short vertical portion 216, then a horizontal portion 217 preferably the same length as the portion 215. The portion 217 is followed by a portion 218 identical in length to the portion 216 and then leading to another portion 219 which is parallel to and in line with the portion 215 and is again of the same length. The portion 219 is followed by a portion 220 that is longer than the portions 216 and 218 and equal in length to the portion 214, therefore raising the wire 211 up to a new level. This is succeeded by a horizontal portion 221 of the same length as the portion 215 and parallel to it but displaced from it. This in turn is succeeded by a short portion 222 the same length as the portion 218 but starting from a different place, so that the succeeding portion 223 is not in line with the portions 215 and 219. Another portion 224 equal in length to the portion 222 is followed by a portion 225 in line with and equal in length to the portion 221, and this is followed in turn by a portion 214a identical to the portion 214 and beginning a new cycle.

The wire 213 adjacent to the wire 211 has the same pattern but is reversed, so that the wires 211 and 213 touch at the portions 215 and 219. The wires 211 and 213 touch the other wires to which they are adjacent at the portions 221 and 225. These touching portions in this instance extend for the whole width, and the plastic coating 212 covers these portions as well as the individual wires.

FIG. 44 shows a wire 230 having a sinuous shape and an adjacent identical wire 231 both of them being covered by a plastic 232. The length of one cycle is in this instance much shorter. The wire 230 has a flaring portion that describes what are nearly two circles 233 and 234, with the radii displaced, and these near-circles 233 and 234 are joined by a smooth connecting curve 235. Again the pattern is interesting, and the structural effects substantially the same as what have already been described.

FIG. 45 shows a wire 240 which is made in a sinuous pattern not unlike the wire 76. The adjacent wires are overlapped so that the wire 240 lies over a wire 241 and beneath a wire 242, and the plastic covering 243 joins all the wires. This pattern provides a small opening 244 through the overlaps and a large opening 245. This makes an interesting pattern, is another way of forming the assembly, and shows that the wires do not have to actually abut or lie in the identical plane.

FIG. 46 shows a wire 250 with an adjacent wire 251 and with a plastic covering 252. Another type of square-wave pattern is shown giving a different pattern, and again the length of the cycle is shown.

FIG. 47 shows another form of pattern. In this case, a wire 255 actually overlaps itself with a succession of circles, so that no one wire actually lies in a single plane, but there is, of course, substantially a planar configuration. The successive wires abut each other.

FIG. 48 shows another square wave configuration with steps down and up, with wires 260, 261, etc., and plastic coating 262.

FIGS. 49 and 50 show an angular configuration and two different uses of the same wire 265 and coating 266. In FIG. 49 the adjacent wires are reversed to make big spaces in between, while in FIG. 50 the successive wires are parallel, to make trapezoids that are (in each row) alternately inverted. The effects are different but use the same wires. Note also that in FIG. 50 an additional wire 267 is used; this wire 267 is of different length and shape and therefore of different vibration frequency from the wires 265 and so provides a snubbing action against bounce.

FIG. 51 shows overlapped wires 270, 271 covered by a coating 272 which fastens the wires 270 and 271 together, with one wire 270 going under its adjacent wire 271, which in turn goes under its adjacent wire 273, and so on.

These are only examples of what can be done. Countless other patterns are possible.

Some Other Embodiments FIG. 52 shows the lower portion of a chair 280 having an assembly serving as a seat but inverted with respect to FIG. 1. While generally not preferable, this structure is quite usable. Here there is a simple trough shape; i.e., the seat 70 is concave instead of convex.

FIG. 53 shows a stool 285, with legs broken off, having a spring seat made by an assembly 70 installed to provide double curvature, a concave are bent into an upper or convex are as seen from the side. This seat 70 was installed on the frame of the stool 285 in a manner similar to that illustrated in FIG. 37.

The thinness of the seats and backs of this invention are especially important. Thus, the thickness of the coated wire which is the seat or back thickness should be between 1/200 and H50 of the cylindrical arc length of the assembly 70, i.e., of what is to be the span of the seat or back.

To those skilled in the art to which this invention re lates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

I claim:

1. An assembly useful as a seating member or back member when installed on a frame, comprising:

a series of arcuate, continuous, sinuous spring metal wires, each having two ends, each said wire closely approaching each of is immediately adjacent said wires at frequency intervals,

rigid fastening means for firmly securing said' wires adjacent their ends and for positively preventing relative movement of the wires to said fastening means, and

a thin sleeve plastic coating surrounding said wires and said fastening means, following the sinuosity of said wires and joining said wires together where they closely approach each other, said approaches being close enough for effective bridging between them by said coating,

whereby said wires, fastening means, and plastic coating comprise a unitary assembly defining a cylindrical arc which will be flattened somewhat when said assembly is installed on said frame, thereby placing the springs in tension along a flatter cylindrical are.

2. The assembly of claim 1 wherein said fastening means comprises a pair of parallel straight rim end members and means for securing them to the ends of said wires.

3. The assembly of claim 2 wherein said means for securing comprises friction lock means fastening each wire at each end to a said rim end member and preventing withdrawal.

4. The assembly of claim 2 wherein said means for securing comprises a series of welds, each welding a said wire closely adjacent its end to a said rim end member of metal.

5. The assembly of claim 2 wherein said means for securing comprises a close fitting tubular member as said rim end member and spring means for snapping a wire end thereinto.

6. The assembly of claim 2 having arcuate rim side members joining said rim end members together and describing an are identical to those of said wires and secured at intervals to the extreme wires.

7. The assembly of claim 1 wherein said metallic fastening means comprises a series of weldments securing successive said wires to each other adjacent each end of each said wire.

8. The assembly of claim 1 wherein said metallic fastening means comprises a continuous rim member secured to said wires adjacent each end of each said wire.

9. The assembly of claim 8 wherein said rim member is welded to each said wire adjacent each said wire.

10. The assembly of claim 1 wherein said plastic coating has a Shore A durometer in the range of 45 to 90.

11. The assembly of claim 10 wherein said coating has a Shore A durometer of about 75.

12. The assembly of claim 1 wherein said spring metal wires have a silhouette area of between 17 and percent of the area of said assembly.

13. The assembly of claim 1 wherein some of said wires are of different vibration frequency than others.

14. The assembly of claim 13 wherein some wires are of different thickness from others.

15. The assembly of claim 13 wherein some wires are of different arc-cycle length from others.

16. The assembly of claim 13 wherein some wires are of different spring tension from others.

17. The assembly of claim 1 wherein the thickness of said coating is from about one-fifth of the wire thickness to about equal to the wire thickness.

18. The assembly of claim 1 wherein the empty space between the coated wires occupies from about 2 to about 75 percent of the area of the assembly.

19. The assembly of claim 1 wherein the wire diameter is in the range of 0.05 to 0.15 inch.

20. The assembly of claim 1 wherein the force required to pull apart said ends for installation upon a chair frame is between 340 and 680 pounds.

21. A seat assembly for installation upon a chair frame, comprising a series of sinuous spring wires set beside each other and approaching each other very closely and surrounded by and bridged by a thin coating of plastic, said assembly being a cylindrical segment that is flattened to a larger radius segment when installed and requiring between 340 and 680 pounds to so flatten it, thereby placing the springs in tension so that they provide resilient support to the center along relatively flat cylindrical arc.

22. An assembly useful as a seating member or back member when installed on a frame, comprising:

a series of arcuate, continuous, sinuous wires, each having two ends, each said wire closely approaching each of its immediately adjacent said wires at frequent intervals, at least some of said wires being springs,

rigid fastening means for firmly securing said wire adjacent their ends and for positively preventing relative movement of the wires to said fastening means, and

a thin sleeve plastic coating surrounding said wires and said fastening means, following the sinuosity of said wires and joining said-wires together where they closely approach each other, said approaches being close enough for effective bridging between them by said coating,

whereby said wires, fastening means, and plastic coating comprise a unitary assembly defining a cylindrical are which will to be flattened somewhat when said assembly is installed on said frame, thereby placing the springs in tension along a flatter cylindrical are.

23. The assembly of claim 22 wherein said fastening means comprises a pair of parallel straight rim end members and means for securing them to the ends of said wires.

24. The assembly of claim 22 wherein said fastening means comprises a series of weldments securing successive said wires to each other adjacent each end of each said wire.

25. The assembly of claim 22 wherein said fastening means comprises a continuous rim member secured to said wires adjacent each end of each said wire.

26. An assembly useful as a seating or back member when installed on a frame, comprising a rim defining a closed area of a cylindrical surface, arched in one direction and straight in another direction normal to said arched direction, and having springy flexing action along said arched direction,

series of sinuous spring wires each positively anchored at opposite ends to said rim and extending across said rim in a generally circular arc parallel to the arching of said rim, the longitudinal axes of said wires being parallel to each other, each said wire very closely approaching its adjacent said wires at least once each cycle,

a thin sleeve plastic coating surrounding each said wire and following its sinuous shape and bridging two wires wherever they closely approach each other and also surrounding said rim, linking said wires together and to said rim in a unitary assembly shaped as a cylindrical are having a radius of curvature less than that desired in a seat or back and will be flattened somewhat when said rim is secured to a said frame, to place the spring wires in tension along a flatter cylindrical arc,

said rim serving to mount said assembly on a said frame and to enclose the sinuous springs.

27. The assembly of claim 26 wherein said rim has portions with tubular receptacles and openings through which said wires extend into said tubular receptacles, where they are positively anchored.

28. The assembly of claim 27 wherein the positive anchoring comprises friction locking means forming part of said rim engaging said wires.

29. The assembly of claim 27 wherein the positive anchoring comprises welds securing said wires to said rim.

30. Theassembly of claim 26 wherein said rim comprises wire members welded to said wires.

31. An assembly useful as a seating member or back member, for installation upon a frame, comprising a rim having spaced-apart straight ends joined by parallel sides shaped as circular arcs,

a series of sinuous spring wires each attached at their opposite ends to said rim ends and each extending between them in a circular arc parallel to those of said rim sides, each of the two extreme spring wires being substantially tangent at each cycle to one of said sides, each wire substantially touching its adjacent wires at least once per cycle, and

a thin sleeve plastic coating surrounding said wires and following their sinuous shape and bridging the wires where they substantially touch and also surrounding said rim and linking said wires and said rim together into a unitary assembly, shaped as a substantially cylindrical are which will be flattened somewhat when installed on a chair frame at each of said ends to place the springs in tension along a flatter cylindrical are,

said ends serving to mount said assembly on said frame.

32. The assembly of claim 31 wherein the wires adjacent one side of said assembly are of lighter gauge than the remaining wires, to give less stiffness at the front portion of a seat.

33. The assembly of claim 31 wherein the force required to pull apart said assembly to fit it to a chair frame as a seating member lies between 340 and 680 pounds.

34. The assembly of claim 31 wherein said rim ends have a series of friction lock means each secured to a said wire adjacent the end thereof.

35. The assembly of claim 34 having a series of spaced stop means each abutted by the end of a said wire and serving to obtain the correct spacing of said wires.

36. The assembly of claim 31 wherein said rim ends are welded to each of said wires adjacent the ends of said wires.

37. The assembly of claim 31 wherein said plastic coating has a Shore A durometer of 45 to 90 enabling a two-way stretch action.

38. The assembly of claim 37 wherein said plastic coating has a Shore A durometer of about 75.

39. The assembly of claim 31 wherein said spring wires have a silhouette area of between 17 and percent of the area of said assembly.

40. An assembly useful as a seating member or back member when installed on a frame, comprising a rim having parallel ends joined by parallel sides, said ends being straight line segments, said sides being springy flexible generally circular arcs,

a series of sinuous spring wires each attached at their opposite ends to said parallel ends of said rim and extending between them in a generally circular are parallel to those of said rim sides, each of the two extreme spring wires being tangent at each cycle to one of said sides, each wire touching its adjacent wires at least once per cycle, and

a thin sleeve plastic coating surrounding said wires and following their sinuous shape and bridging two wires wherever two wires touch and also surrounding said rim and linking said wires and said rim together into a unitary assembly, shaped as a cylindrical are which will be flattened somewhat when installed on a said frame at each of said parallel ends to place the spring wires in tension along a flatter cylindrical are,

said parallel ends serving to mount said assembly on said frame and said parallel sides enclosing said springs and minimizing their catching on clothing.

41. The assembly of claim 40 wherein said rim ends have a series of friction lock means each secured to a said wire adjacent the end thereof.

42. The assembly of claim 41 having a series of spaced stop means each abutted by the end of a said wire and serving to obtain the correct spacing of said wires.

43. The assembly of claim 40 wherein said rim ends are welded to each of said wires adjacent the ends of said wires.

44. The assembly of claim 40 wherein said plastic coating has a Shore A durometer of 45 to enabling a two-way stretch action.

45. The assembly of claim 40 wherein said spring wires have a silhouette area of between 17 and 75 percent of the area of said assembly.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2244469 *Dec 19, 1938Jun 3, 1941Murray CorpSpring construction
US2538855 *Nov 9, 1946Jan 23, 1951Lt a t f s pa t fn t
US2803293 *Oct 12, 1953Aug 20, 1957Rowland David LSpring assembly
US3386725 *Apr 3, 1967Jun 4, 1968Koichi FujikawaSeat frame member
US3628780 *Jul 17, 1969Dec 21, 1971Saito NobuyoshiSeat frame structure
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3981537 *May 21, 1975Sep 21, 1976Champion International CorporationPerson's body weight support in furniture assembly
US4304436 *Jun 8, 1979Dec 8, 1981Rowland David LStackable chair
US4415147 *Oct 9, 1981Nov 15, 1983Simmons Universal CorporationSeating spring assembly and method
US5934758 *Apr 30, 1997Aug 10, 1999Haworth, Inc.Membrane chair
US6726285Jun 29, 2001Apr 27, 2004Herman Miller, Inc.Cellular chair construction
US6869142Sep 12, 2002Mar 22, 2005Steelcase Development CorporationSeating unit having motion control
US6880886Jun 5, 2003Apr 19, 2005Steelcase Development CorporationCombined tension and back stop function for seating unit
US6957863Sep 13, 2004Oct 25, 2005Steelcase Development CorporationSeating unit having motion control
US7059682Apr 7, 2004Jun 13, 2006Herman Miller, Inc.Seating structure having flexible seating surface
US7165811Jun 5, 2003Jan 23, 2007Steelcase Development CorporationControl mechanism for seating unit
US7226130Jun 5, 2003Jun 5, 2007Steelcase Development CorporationSeating with comfort surface
US7234774Sep 23, 2005Jun 26, 2007Steelcase Development CorporationSeating unit with novel flexible supports
US7249802Feb 12, 2003Jul 31, 2007Herman Miller, Inc.Back support structure
US7334845May 14, 2004Feb 26, 2008Steelcase Development CorporationComfort surface for seating
US7360835Jun 4, 2007Apr 22, 2008Steelcase Inc.Seating with comfort surface
US7398567 *Mar 25, 2004Jul 15, 2008Luhao LengSteelwire-hook mode web sheet
US7419222Dec 7, 2005Sep 2, 2008Herman Miller, Inc.Support member for a seating structure
US7455365Mar 25, 2004Nov 25, 2008Herman Miller, Inc.Seating structure having flexible support surface
US7472962Apr 11, 2005Jan 6, 2009Herman Miller Inc.Seating structure having flexible support surface
US7794022Dec 5, 2008Sep 14, 2010Herman Miller, Inc.Body support structure having a molded elastomeric member
US7841666Sep 16, 2008Nov 30, 2010Herman Miller, Inc.Back support structure
US8449037Apr 11, 2011May 28, 2013Herman Miller, Inc.Seating structure with a contoured flexible backrest
WO1980002790A1 *Jun 4, 1980Dec 24, 1980D RowlandStackable chair
WO1998048671A1Apr 29, 1998Nov 5, 1998Haworth IncMembrane chair
WO2004107920A1 *Jun 4, 2004Dec 16, 2004Steelcase Dev CorpComfort surface for seating
Classifications
U.S. Classification267/111, 428/99, 297/452.64, 428/592
International ClassificationA47C7/16, A47C7/28, D01H7/02, A47C23/26, D01H7/04, A47C7/02, A47C23/00, A47C5/06, A47C5/00
Cooperative ClassificationA47C5/06, A47C7/30, A47C7/16, A47C7/285, D01H7/048, A47C7/282
European ClassificationA47C7/28B, A47C7/30, A47C7/28A, A47C5/06, A47C7/16, D01H7/04D4