US 3096086 A
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Description (OCR text may contain errors)
July 2, 1963 E. e. KRAKAUER 3,096,086
SINUOUS WIRE SPRING Filed May 18, 1961 ,/0 Fig.1
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Edwin G-A mkauer 3,096,086 SINUQUS WIRE PRING Edwin G. Krakauer, Roslyn Heights, N.Y., assignor to Kay Manufacturing Corp, Brooklyn, N.Y., a corporation of New York Filed May 18, 1961, Ser. No. 117,255 4 Claims. (Cl. 267-103) This invention relates to furniture springs and particularly to the springs used for the seats and backs of upholstered furniture.
Springs are employed in the hope of attaining maximum comfort, meaning restful relaxation without undue pressure on those areas of the back and seat of the body which differ considerably in their sensitivity to such pressure. In other Words, furniture and bedding have long been sought which have relatively hard areas needed for resistance to weight concentration thereby to supply adequate support, and which have at the same time relatively soft areas and depth of yield where needed to distribute and thereby to reduce concentration of pressure at those parts of the body which are unduly sensitive to such pressure.
In view of large variations in the size and weight of individuals, it has not been commercially practical to construct spring arrangements which attain the optimum in efficiency, but which are in the range of cost allowable for commercial acceptance. Those spring constructions which approximate the desired results have been relatively complex, costly and only partially effective.
The present invention therefore contemplates the provision at low cost of a simple sinuous wire spring in which angles of various acuteness or obtuseness are so located between the ends of a one piece continuous spring as to result in hard and soft areas at those places in the length of the spring best adapted for the comfort of the average user.
The invention further contemplates the provision of a spring supported in the usual manner at its ends, but pre-stressed and provided with abrupt sharp angle bends on at least one end thereof to provide a short relatively stiff leg which is designed to be pivoted to the frame and to swing about its pivoted end bar when loaded, without significant change in the angle which the leg makes with the main span of the spring, thereby to cause the adjacent part of the spring to buckle deeply.
The invention further contemplates the provision of a sinuous wire spring in which the normal profile is altered by means of an interior bend adjacent the rear end thereof, the depth of yield increased and a relatively soft area provided adjacent said bend, while the profile may be optionally lowered adjacent the front end of the spring and there stiffened by means of an exterior bend.
The invention further contemplates the rovision of an inexpensive sinuous spring structure wherein the rear end portion of the spring is softened by means of an interior bend located at the next to the last cross bar of the spring to form a short end leg having its end cross bar pivoted to a frame, thereby to stiffen the leg against buckling While permitting the leg to swing, the front end of the spring being bent to form a short leg of any one of a number of selected shapes either pivotally or rigidly secured to a frame and designed to stiffen that end to a greater or lesser extent as desired.
The invention further contemplates the provision of a spring structure wherein the softest area is arranged about two thirds of the distance rearwardly from the front end and the relatively hard front area may be retained or further stiffened if desired by a short leg of the desired shape suitably bent from the front end part of the spring, or the front area may be softened by an auxiliary spring without change in the front leg.
3,95,685 Patented July 2, 1963 The various objects of the invention will be clear from the description which follows and from the drawings, in which FIG. 1 is a fragmentary top plan view of a typical seat frame showing how one form of the invention is applied to a spring structure.
FIG. 2 is a vertical sectional View of FIG. 1 showing the abruptly angled interior and exterior bends and short legs at the extreme end portions of the spring of FIG. 1.
FIG. 3 is a similar View of a modified form of the invention in which the front leg bent from the end portion of the spring provides an integral rigid fastening means entering the frame and stiffening the front end of the spring.
MG. 4 is a similar view of another form of the invention in which a V-shaped stiffening leg is located at the front end of the spring and the end bar of the leg abuts and is pressed tightly against the frame to hold thereto by friction.
FIG. 5 is an elevational or edge view of the spring of FlGS. 1 and 2 in the initial unstressed state thereof showing the bends and end legs thereon.
FIG. 6 is a similar view of the spring of FIG. 3 showing the front fastening leg.
:FIG. 7 is a similar fragmentary View of the spring of =FiG. 4 showing the V-shaped front leg.
FIG. 8 is a fragmentary sectional view similar to FIG. 2 showing the attached auxiliary edge spring for softening the front edge of the seat.
The usual seat frame 1% as shown, is bridged by a series of substantially parallel springs 11 in the usual manner. Only one such spring of the sinuous type is shown, such springs having straight cross bars as 12 spaced longitudinally apart and joined by loops 13 alternating at opposite edges of the spring. In the form shown in FIGS. 1 and 2, the end cross bars 14 and 15 are supported for pivotal movement relatively to the frame rails 17 and 18 as by means of clips as 16. The springs are of the type having a permanent set on an arc of relatively small radius as shown in FIG. 5, and is extended by separating the ends when the spring is mounted on the frame and the are thereby changed into one of relatively large radius. Normally, as heretofore commonly used, the profile of the spring when mounted, is smoothly convex upwardly and free of abrupt changes in direction, whereby the spring deflects most at its middle under ordinary load and little or not at all near its ends, to form a profile having a double reverse curve which is convex upwardly at the end areas and concave upwardly only at and near the load. As best seen in FiGS. 2 to 4 hereof, an abrupt change in the direction of the spring curvature at the rear end is utilized herein to attain softness, to raise the profile and to increase the depth of yield near the rear part of the spring where the greater part of the load is applied, and to attain more hardness, to lower the profile and to have less yield and more resistance, rigidity or stiffness near the front end where lesser load is applied.
It has been found that a short length of sinuous wire does not flex or bend materially under normal stresses, but instead tends to act as a rigid lever in transmitting load. When one end bar of such short length is pivotally mounted, the lever swings about such end bar, which being restrained or partially restrained, acts akin to a fulcrum. On the other hand, relatively long lengths of sinuous springs are not rigid enough to act as levers when loaded. Neither do they lengthen or shorten to any significant extent under load, nor do the loops thereof open or close significantly as has been heretofore though by many to be the case. Instead, it has been found that if the spring or that part thereof under load, is long enough to yield, it will buckle or bend in a manner akin to the action of a strip spring of the same profile. It has also been found that in a continuous length of sinuous wire, a short sharp bend forming a leg of two cross bars and s'ubtending an angle of less than 180, which will be termed an interior bend, tends to soften the spring adjacent such end because the permissible angular leverlike rotation of the resulting leg about its pivoted end bar is substantially increased over the rotation possible with a corresponding unbent end of a similar spring.
i These characteristics of sinuous springs have been utilized in the present invention. As shown in FIG. 2, the spring 11 has been extended from its initial set shape and unstressed form shown in FIG. to separate the ends thereof enough to bridge the space between rails 17 and 18. The angle at the abrupt interior bend at the cross bar 20, which is the bar next to the rear end cross bar 15, is an interior angle of about 100 and should always be less than 180 to be effective. The cross bar 20 and the loop 21 connecting the bars 15 and 20 constitute the rear leg which is sufliciently short to pivot about the bar 15 as a fulcrum when the spring is loaded, and is suificiently stiff to act as a lever capable only of rotation without any buckling tendency.
' Similarly, the abrupt bend at the front end of the spring has a short stiff leg beginning at the end bar 14 and ending at the next to the end bar 23, the bars 14 and 23 being connected by the loop 24. The end bar 14 is pivotally mounted in the frame clip 16. As shown in FIG. 5, the angle subtended by the front bent leg and the normally shaped unstretched body 26 of the spring is an exterior angle of about 125 and is formed by an interior angle which is never less than and preferably materially greater than 180". These angles do not change to any significant extent when the spring is mounted in place and prestresse'd or even when the spring is under normal load. At the rear, it will be noted that the bar 20 is raised by the rear bent leg to a point which is higher than that which would normally be assumed by said bar if the interior bend were absent. This raises the profile of the spring at said bar, giving a rather flattened profile to that part to the left of the interior bend. The rear rail 18 may obviously be lowered if a raised rear edge is not desired.
At the other end however, the front bent leg lowers the bar 23 and may lower it even below the upper edge of the rail 14, to lower the profile immediately adjacent the bend. Such profile ascends relatively rapidly from the bar 23 toward the middle. The net result is a spring seat normally with a substantial convexity at the front, fiattening out toward the rear to a lesser convexity, as distinguished from a spring without end bends which has substantially equal convexity upwardly at the front and rear. Such profile is well adapted for so-called thin seats whether used with a cushion or merely with padding. Under normal load, applied mainly to the rear of the seat middle, a substantial concavity occurs at the rear of the spring as shown by the dash-dot line 27 of FIG. 2. In such springs as heretofore used without the rear bend, no such concavity occurs at the rear, but only between the ends at the point where the load is principally concentrated, while the rear part of 'the spring remains bard and unyielding and convex upwardly.
- The increased resistance to downward deflection of the spring at the front exterior bend shapes the seat to conform to the body with increased supporting comfort over springs without the exterior bend. At the same time, the rear end of the spring yields readily to the pressure of the main weight of the occupant and thereby provides adequate support without excessive pressure or resulting discomfort. Such depth of yield at the rear is attained by the angular rotation of the rear end leg about the end bar 15 in the direction of the arrowof FIG. 2 to line 27. Since the angle between the leg and the adjacent 4 part of the main span or body 26 of the spring does not change materially, said adjacent span part is forced down-' wardly substantially into the concave shape shown, to an extent dependent on the amount and position of the load. At the front end, the bar 23 is urged toward the rear end of the spring not only because of the pre-stressing of the spring, but also by reason of the buckling ofthe spring under load into a reverse curve by the inward movement of the bar with the consequent necessity of the main span of the spring to contract into the shortened space between the bars and 23. While the bar 23 is thereby urged inwardly, it may not move in that direction, but instead is prevented from rotating clockwise in the direction of the left hand arrow of FIG. 2 to any material extent with resulting stiffening of the front end of the spring.
In that form of the invention shown in FIG. 3, the rear bend is retained, but a stiffer front end is provided. The bent leg 28 (FIGS. 3 and 6) at said end constitutes a rigid fastening means whereby the front end of the spring is fixed rigidly to the rail 17 by the entrance of the leg 28 into the rail, and said end does not pivot. In such case, the initial convexity of the spring at the extreme front end is reduced from that shown in FIG. 2 and changes little under load, though the remainder of the spring defleets substantially as shown 'by the dash-dot line 29. The resulting reverse curve is similar to but not identical with that of FIG. 2, the softness at the rear being retained and the hardness at the front increased.
' As shown in FIG. 4, the front bend may take another shape, here shown as a V-shaped extension 30 of two short legs having an end bar 31 pressed against the inner face of the rail 17. Such extension pre-stresses the Spning and may even cause the end bar 31 to embed itself into a wooden rail. It prevents any movement of the extension relatively to the rail. When the second bar 32 from the end bar 31 is pivoted in the clip 16 as shown, the front end of the main span 26 yields very little, almost as little as though the bar 31 were rigidly fixed to the rail instead of being pivoted. In other words, the angular relation of the loops constituting the V-bend remains substantially constant so that the elasticity of the extension is retained and danger of a permanent set, of crystallization and of damage or breakage is avoided. Since the front spring end, while pivotally mounted at the third bar 32, acts similarly to a fixed end while pre-stressing the spring, the shape assumed by the spring when loaded is a reverse curve 333 much like the curve 29 of FIG. -3. In other words, the front end is stiffened, while the rear end is softened.
The dash-dot lines 27, 29 and 33 indicate the general positions assumed by the respective springs of FIGS. 2, 3 and 4 under average load exerted thereon by a person sitting comfortably, the line tilting downwardly from the rear to an upwardly concave part extending forwardly toward the middle of the spring and thereby forming a reverse curve instead of the upwardly convex double reverse curve depressed only at the middle, assumed by springs without the bent ends.
Should .a soft front edge be required, no change need be made over the front exterior bends above described, but the front is softened by an auxiliary spring added to the sinuous spring. As illustrated in FIG. 8, the auxiliary edge spring 35 of the type shown in Patent No. 2,851,087 is hooked on to the proper cross bars of the main span 26. Said spring softens the front edge portion of the seat structure forwardly of the cross bars 36 and 37 about which the S-shaped part 38 of the auxiliary spring is booked.
In all cases, the spring is pre-stressed and the end cross bars thereof .tend to close together to the position of FIGS. 5-7 if permitted to do so. The rear end bar pivots in the clips when loaded and unloaded. Various angles may be used for the bends and the length of the short legs varied to some extent so long as they remain relatively stiff and do not buckle. It will be seen that a given spring can be made stiif or soft without material changes other than bends, and that by the use of substantially standard sinuous springs, substantial economies in such springs and spring structures with a wide range of flexibility have adequately been attained.
While certain specific forms of the invention have herein been shown and described, various obvious changes may be made therein without departing from the spirit of the invention defined by the appended claims.
1. A spring structure comprising a frame having a pair of spaced apart rails, a pre-stressed sinuous wire spring having cross bars connected by loops and having a main portion initially set on an arc of relatively small uniform radius and extended into an arc of greater radius, said spring bridging the space between rails, profile-raising and spring-softening means adjacent the rear end of the spring to compel said end to swing readily inwardly when loaded and thereby to change the profile of said end from convex upwardly to concave upwardly when the spring is loaded, While maintaining substantially constant the angle between the leg and the adjacent part of the main portion, said means comprising a relatively short stiff leg at said end arranged at an interior angle of less than 180 to the adjacent part of the main portion, there being a common cross bar at one end of the leg and the main portion, and a second cross bar at the other end of the leg constituting a fulcrum about which the remainder of the leg and the adjacent part of the main portion are swingable as a unit, means pivotally securing the second cross bar of the leg to one rail, the spring having a relatively short stifiening bend adjacent the front end thereof, and means securing the front end of the spring to the other rail.
2. The spring structure of claim 1, the rear leg consisting of said common cross bar, the second pivoted cross 'bar and a loop connecting said cross bars, the leg thereby being short enough to resist buckling under normal loads.
3. The spring structure of claim 2, the front bend comprising a leg making an interior angle greater than to the main portion and having a first cross bar common thereto and to the main portion, and an end cross bar at the end of the spring joined by a loop to said first common cross bar, and the last mentioned means pivoting the front end bar of the spring to the rail.
4. The spring structure of claim 1, said other rail having a substantially upright inner face, the front bend constituting a V-shaped end portion on the front of the spring having the end =bar thereof in pressed frictional contact with the upright inner face of said other rail, the apex of the V-shaped portion being in inward spaced relation to said rail, said portion having a cross bar common thereto and to the main spring portion, the last mentioned means pivotally securing said last mentioned cross bar to the upper face of said other rail.
References Qited in the file of this patent UNITED STATES PATENTS 507,027 Morgan Oct. 17, 1893 2,392,254 Mayer Jan. 1, 1946 2,629,431 Flint Feb. 24, 1953 2,646,108 Norman July 21, 1953 2,696,871 Handren Dec. 14, 1954