US 2675566 A
Description (OCR text may contain errors)
April 20, 1954 H. L. LIEBERMAN BEDSPRING CONSTRUCTION 4 Sheets-Sheet 1 Filed March 5. 1950 17017:? llz'eervza n N 39-- Mud M April 20, 1954 H. L. LIEBERMAN 4 Sheets-Sheet 2 Filed March 5, 1950 V VIII/ll April 20, 1954 H. L. LIEBERMAN BEDSPRING CONSTRUCTION 4 Sheets-Sheet 5 Filed March 5, 1950 April 20, 1954 H. L. LIEBERMAN BEDSPRING CONSTRUCTION 4 Sheets-Sheet 4 Filed March 5, 1950 #0773 Alz'eZer/zwz 5 y 9% MM Patented Apr. 20, 1954 UNITED STATES OFFICE BED SPBING CONSTRUCTION Harry L. Lieberman, Chicago, Ill, assignor to Leonard-Chicago Corp, Chicago, Ill., a corporation oflllinois Application March 3, 1950, Serial No. 147,496
.made to afiordfirm support in beds, all of which have had several inherent disadvantages, such as, for example, being complicated in construction and operation; being expensive to manufacture; being inefficient and difficult to adjust; not giving the proper support; "or being uncomfortable. It is 'a'primary object of my invention to enable a bed to be constructed in a novel and expeditious manner-"which overcomes these disadvantages.
One of the methods commonly resorted to heretofore to attempt to afford proper support in 'beds has'been to place a board-between the mattress "and the supporting springs. in :beds having the common stuffed mattress this results in a sleeping surface which is practically unyielding and, although definitely firm, is relatively uncomfortable and still does not give proper local support. In beds having the socalled inner-spring mattresses, the placing of the board between the. mattress and the bed springs merely reduces the yield or give of the entire unit "by substantially eliminating the effectiveness of the bed spring. 'With this latter type of unit the undesirable yielding features of the mattress, itself, remain unchanged, the over-all give of the complete unit merely havin been reduced to substantially the give of the mattress-itself, so that the portions of the anatomy which should be firmly supported still sink into the mattress and are yieldably supported by springs having the same resistance as tensioned.
A further object of my invention is to enable the local firmness -of a bed spring to be quickly and easily adjusted selectively.
Yet another object is to enable novel bed springs of either the open type or box spring type, and embodying the aforementioned features and advantages to be constructed.
A further object is to afford a novel bed spring of the aforementioned type which is efficient in construction and operation and may be economically manufactured commercially.
Other and further objects of the present invention will be apparent from the following description and claims and are illustrated the accompanying drawings which, byway of illustration, show preferred embodiments of the present invention and the principles thereof and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention-and the purview of the appended claims.
In the drawings:
Fig. 1 is a top plan view of a :bed spring embodying the principles of =my invention;
Fig. 2 is a sectional view taken substantially on the line 2--'2 in Fig. 1;
Fig. 3 is a sectional view taken substantially on the line 33 in Fig. 1;
Fig. 4 is a sectional view substantially the same as Fig. 3 but showing the parts therein in different adjusted position;
Fig. 5 is an-enlargeddetail sectional View taken substantially on the line5-5 in Fig. 3';
Fig. 6 is a detail sectional view taken substantially on the line 6-45 in-Fig. 5;
Fig. 7 is an enlarged detail sectional view of a portion of the bed spring shown in Fig. 2;
Fig.3 is an enlarged detail sectional view taken substantially on the line 8-8 in Fig. 5;
Fig. 9 shows a handle used in the "operation of the bed spring shown in Fig. 1';
Fig. 10 is a perspective view of modified'form of my invention; and
Fig. 11 is a side elevational view of the device shown in Fig. 10.
For the purpose of illustrating my invention, a bed spring 20 is shown in the drawings embodying the principles of my invention and comprising, in general, a supporting frame 22, aplurality of coil springs 24 and an adjusting unit Z'G, the adjusting unit being eliective to adjust the tension or compression of certain of the coil springs 24 from the bottom as will be discussed in greater detail hereinafter.
The supporting frame 22 comprises upper and lower frame members 28 and 29, respectively, Figs. 1, 3 and 5, which, in the assembled bed spring 20, are disposed in substantially parallel, vertically spaced alignment with each other, Figs. 1 and 3. The upper frame member 29 preferably comprises a modified rectangular shaped ring made of any suitable material, such as, steel, the rectangular shape thereof being modified to the extent that the four corners are somewhat rounded as best seen in Fig. 1. The lower frame member 29 comprises a rectangular shaped ring embodying side walls 3| and 32, Fig. 4, and end walls 34 and 35, Fig. 2, the side walls El and 32 and the end walls 34 and 35 being constructed of any suitable material, such as, for example, channel irons, and being welded together at their ends to afford the rectangular shaped frame member 29.
The coil springs 24 mounted between the frame members 28 and 29 comprise three groups, one group of springs 24p being disposed in a rectangular shaped row around the peripheral edge portion of the frame members 28 and 29; an-
other group of springs 240 being disposed, in a substantially rectangular shaped pattern comprising four laterally spaced parallel rows and eight longitudinally spaced parallel rows, centrally of the springs 241), with the respective longitudinally and laterally spaced rows of the cussed presently; and the third group of coil springs 242' comprising two parallel rows of springs, Figs. 1 and 2, disposed at opposite ends of the group of springs 240, each row of springs 24i being disposed in spaced parallel relation to a respective end row in the group of springs 24c between that end row and the adjacent springs 242 The springs 24p and 240 are disposed in substantially upright position between the frame members 28 and 29 in parallel spaced relation to each other, and the upper end of each coil spring 24p and 240. is connected to the corresponding upper end of each immediately adjacent spring 24p and 240 by suitable helical springs or keeper springs 31, Figs. 1 and 3. Each of the outer springs 24p is connected to the upper frame member 28 by suitable means, such as, a respective keeper ring 39, Figs. 3 and 4. Thus, it will be seen that, the top of each of the springs 24c and 2% is yieldingly connected through the other springs 24c and 2511, the springs 2410, the keeper springs 31, and the keeper rings 39 to the upper frame member 28; and the tops of the outer springs 2417 are unyieldingly connected to the upper frame member 28 by the keeper rings 39.
A retaining web 4| which comprises a plurality of intermeshed bands 42 of suitable material, such as, for example, spring steel, connected together by suitable means, such as, rivets 43, Figs. 1 and 3, is disposed over the central springs 24c and the intermediate springs 241', and is yieldably held in such position by tension coil springs '45 connected to the bands 42 and the adjacent outer springs 24p, each band 42 being preferably disposed over a respective one of the aforementioned rows of springs 22c and 241' in vertical alignment therewith.
The lower end portion of each of the outer coil springs 2410 is mounted on a suitable respective angle bracket 41, Figs. 3 and 5, attached to, and
projecting inwardly from the portion of the inner face of one of the walls 3|, 32, 34 or 35 of the lower frame member 29, disposed adjacent to the respective coil springs 24p. The lower end portion of each of the springs 25p is retained on the respective bracket 41 by a suitable cross bar 49 connected to the springs 24pand extending under the bracket ill, Figs. 3 and 5. The cross bar 49, as shown in the drawings, comprises the free end of the lower end portion of the springs 24p. However, it will be appreciated by those skilled in the art that the cross bar 49 may if desired, comprise an individual piece attached to the springs 24p and disposed under the bracket 41.
Two track members 5| and 52 extend in substantially parallel spaced relation to each other transversely across the frame 22 between the side walls 3| and 32 of the' lower frame member 29, substantially centrally of the group of coil springs 24c. The track members 5| and 52 preferably comprise angle irons which may be welded to the side members 3| and 32 in inwardly and upwardly opening position.
A slide unit or carriage 55, Figs. 2, 3 and 5, is mounted on the track members 5| and 52 for movement longitudinally thereof for a purpose which will be discussed in greater detail hereinafter. The carriage 54 comprises two elongated angle iron bars or runners 56 and 51, Figs. 2 and 3, slidably mounted on the lower webs of tracks 5| and 52, respectively, for movement longitudinally thereof. Each of the runners 56 and 51 carries two inclined planes or cam members 59 and 9B and 6| and 62, respectively, Figs. 3 and 5. The cam members 59 and 60 comprise substantially L-shaped members made of suitable material such as, for example, angle iron members having vertically disposed legs 59a and I 59a, respectively, and angularly disposed legs 5% and 60b extending downwardly from the upper end portion of the vertical legs 59a and 59a at an acute angle thereto. The cam members 59 and 65 are secured to the bar 55 by suitable means, such as, welding and are disposed in such position thereon that the angular legs 59b and 5% project upwardly from the bar 56 at an acute angle in a direction from the side rail 3| toward the side rail 32. The cam members 5| and 52, Fig. 5, are similar in construction to the cam members 59 and -60, and are similarly mounted on the bar 51 of the slide unit 54 in such position that the angular legs Slb and 62b thereof are disposed in parallel relation to the angular legs 5% and 50b, respectively, Fig. 5. Cross members 54 and 65, formed of suitable material, such as, for example, angle iron, extend between the runners 56 and 51 in parallel spaced relation to each other, Fig. 5, and are connected to cam members 59 and 6|, and 59 and 52, respectively, by suitable means, such as, welding. Thus, it will be seen that the carriage 54 comprises a frame consisting of the runners 56 and 51 slidably mounted on the tracks 5| and 52, the cross bars 52 and 55, and cam members 59B2 projecting upwardly from the side bars 55 and 51.
A bracket member 61, Figs. 5 and 6, having a suitable tapped opening 68 therein, is mounted on the cross bar 62 of the carriage 54 substantially centrally of the ends thereof, and projects upwardly therefrom. A screw 19, journaled in an opening 12 on a bracket member 14 mounted on and projecting upwardly from the central portion of the side rail 3| of the lower frame member 29, is threadedly engaged with the bracket 15 6 in the tapped opening 68 and affords means whereby the carriage 54 may be reciprocated on the tracks 51 and 52 by turning the screw 19 in the proper direction. Suitable retaining means, such as, blocks 16 and H are mounted on the screw it and secured thereto by pins 19 and 80 in position toengage opposite sides of the bracket member 14 to thereby hold the screw I'll against longitudinal movement relative to the frame 22. outwardly of the block 16, a pin -82 extends through the screw H1 and affords laterally projecting connecting members or care which are engageable by suitable means for turning the screw 10, such as, for example, the "handle or crank 84, Fig. 9, having slots 85'disposed in an end 85 thereof, the end 86 being adapted to *be *removably positioned on the end of thescrew with the pins 82 disposed in the slots 85.
An adjusting frame 8'1, Figs. 1, 3 and 5, including parallel side walls 89 and 99 and end walls 91 and 92, Fig. 5, is disposed directly below the group of coil springs 24c and is mounted on the carriage 5% for vertical adjustment thereby as will be discussed in greater detail presently. The Walls til-92 of the adjusting frame 8'! preferably comprise angle irons welded together at their ends and having upwardly projecting webs 89a, 90a, Sic, and 92a, and inwardly projecting webs 39b, 90b, 9!!) and 92?), respectively. Cross bars 94, :95, 96 and 91, extend transversely across the adjusting frame 8-! in substantially parallel,
equally spaced relation, Figs. 3 and 5, and preferably comprise metal tubular members having flattened ends Mm-QM, respectively, connected to the inwardly projecting webs 89b and 90b of the side rails 39 and 90 of the adjusting frame 91 by suitable means, such as, rivets 98.
The bottoms'of the springs in the two rows of springs 2M, disposed between the central group of springs 24c and the outer group of springs 24p are mounted on cross bars 99 and H30, Figs. 1, 2 and "7, which are similar to the cross bars 9491 but extend between and are welded to the side walls 3! and '32 of the lower frame member 29 beneath respective ones of the two'rows of springs 2%. The bottoms of the springs 242 are secured in position on the bars '99 and Hill by retaining wires I03 having one end secured to the adjacent wall 3|, 32, 34 or 35 of the lower frame member 29 and having the other end thereof bent under the bar 99 or 109 and clampingly engaged with the lower spiral of an individual one of the springs 242,Figs. 2 and 7.
As is best seen in Fig. 1 thegroup of centrally disposed coil springs 2-40 is substantially rectangular in shape and is substantially complementary in size and shape to that of the adjusting frame 81. As previously mentionedthe adjusting frame 8! is disposed below the group of centrally disposed springs 240. It will be noted that this frame is disposed in alignment with this group of springs in a manner whereby the side walls 8992 of the adjusting frame 9'! are disposed substantially directly below and in alignment with the outer ones of the centrally disposed coil Springs 240 which define the peripheral edge of the group of springs 24c. The lowermost coil of each of these latter coil springs Me, which are disposed in alignment with the side walls 89-92 of the frame 87, extend through the upwardly projecting webs 89a-92a, respectively, to thereby connect the lower end portion of these coil springs to the frame 81. The other coil springs 24c of this centrally disposed group, and which other springs are disposed inwardly of the springs attached directly to the side walls 189- 92 are mounted on corresponding ones of the cross bars 94-91 of the adjusting frame 81., and retaining wires l0! and I62, Figs. 3 and 5, extend, in parallel spaced relation to each other transversely across the cross bars 94-91, below the latter, and are threaded through the lower coils :of thesprings .z lcmounted on the cross bars 94- 3'1 tothere'by :hold'these latter springs .24cin engagement with the respective cross .bars 94-9.'l. Thussit will be seen that, in the bed spring '20 shown in Fig. 1, the springs 24 are disposed between the frame members 28 and 29, in six 1ongitudinally extending parallel rows and ten transversely extending parallel rows, and comprise three groups of springs, namely, an outer .group of springs Zip, a central group of springs 24c, and an intermediate group of springs 242'.
"Two substantially inverted U-shaped guide members 194 and W5 are connected to the outer faces of the tracks 5i and 52, respectively, Figs. 3 and 8, and are disposed over the side wall .189 in enclosing relation thereto to thereby afford guidewa-ys for the adjustin frame 87 which is 'eftecti ve to guide the adjusting frame upwardly and downwardly in a substantially straight-line vertical direction. The side rails 39 and 9 0 of "the adjusting frame 81, and the cams 59-452 of the carriage 54, are so positioned on the frame :22 that the side rails 89 and 99 may rest on the tracks :51 and 52 when the carriage 54 is positioned at its most inwardly disposed position, and upon movement ofthe carriage 54 outwardly, or to the left as viewed iin'Figs. 3 and 4, the side rails wan-(19B of the adjusting frame 8'? are engaged by, and ride upwardly onto the angular legs trib -B21201? the cams 582 and, thereby, are forced or cammed upwardly in the guide member 104 to thereby raise the lower end portion of the springs 240. Such movement, it will be seen of the adjusting frame 8?, tends to move the central springs 2'40 upwardly relative to the outer springs 24p and the intermediate springs 2M. However, it will be seen that the central springs 24c are yieldably connected to the outer springs 24p and the intermediate springs 241' by keeper springs '3! and in addition, are overlaid by the web M which is also yield-ably attached to the outer springs 24p by springs 45. Thus, it will'be seen that although the centrally disposed springs 2 10 are bodily moved upwardly somewhat, relative to the outer springs 24p and the intermediate springs 2 12', the yielding re- :sista-nce afiorded to the top portion of the central springs 240 by the keeper springs 37, the overlying web 4! and the springs Q5 are effective -torestrain this upward bodily movement of the springs 240 so that the bottom portion of the springs 240 is pressed upwardly to a greater extent by the adjusting frame 87 than is the top portion thereof, with the result that the coil springs 240 are compressed by the upward movement of the adjusting frame 8?. This, it will be seen, tends to pro-tension, or pre-compress, the centrally disposed springs 24c and afford a firmer central portion of the bed spring 20. As a rewith will be seen that when a person lies prone upon the bed spring 20, the central portion of the spring, which is the portion that supports the portion of the anatomy which normally should be given relatively firm local support, is already pie-compressed so that firm support is afforded before the prone body even initially compresses the springs. This, it will be'seen, is considerably diiferent from the effect accomplished by placing a board beneath the springs, because in this latter case, the anatomy of the person lying on the bed must first sink into the springs before firm support is afforded for any portion of the body, the effect of the board beneath the springs merely being to substantially eliminate the yielding effect of any underlying springs and shorten the distance that the body must sink into the springs. In my device, it will be seen the critically, centrally disposed springs, are already pre-tensioned, or pre-compressed, so that -a firm supporting surface is afforded when the body first is disposed on the springs and, therefore, a novel firm support is afforded.
When it is desired to relieve the tension on the springs 240, it will be seen that the carriage 54 may be moved away from the position shown in Fig. 4 to the right, or in other words toward the side wall 32 and toward the initial position shown in Fig. 3. When the carriage is moved in this manner, it will be seen that the adjusting frame 3'! is permitted to move downwardly on the angular legs 59a52a of the cams 59E2 toward the lowermost position wherein the bottom of the springs 240 are supported by the frame 87 at substantially the same height as the bottom portions of the springs Z lp so that the springs 24p and 240. are each of substantially the same strength.
It will be appreciated, of course, that between this lowermost position and the uppermost position shown in Fig. 4, the adjusting frame 81 may be stopped in any intermediate position such as, for example, the position shown in Fig. 3 wherein the springs 240 are partially compressed, this adjustment being readily accomplished by suitable adjustment of the screw 10. Therefore, it will be seen that with a bed spring constructed in accordance with the principles of my invention, the spring may be adjusted from the bottom to afford equal yielding support throughout the length and breadth thereof, or to afford various degrees of resilient but firm local support.
Also, it will be seen that the correction of the intermediate springs 242' between the springs 24p and the springs 240 is such that when the springs 24c are in adjusted compressed position, the tops of the springs 241' are pulled upwardly somewhat to afford a smooth rounded contour on the bed spring 29 and afford support which, in firmness, is between the outer springs 24p and the central springs 260.
In the modified form of my invention shown in Figs. and 11 a bed spring having the same construction as that shown in Figs. 1 to 9, inclusive, is embodied in an outer covering ZOI to thereby afford what is commonly referred to as box spring 266. The box spring 200 shown in Figs. 10 and 11 comprises a bed spring which is identical to the bed spring 20 shown in Figs. 1 to 8 the only difference between the spring shown in Figs. 1 to 8 and that shown in Figs. 10 and 11 being that padding P has been disposed on the top surface and the bottom surface of the spring 22 and a covering C has been disposed thereover. The padding P may be of any suitable material such as, for example, an inner layer of sisal fibers and an outer layer of felt, hair, floss, cotton or the like, and the covering C is preferably formed of a suitable fabric, such as, for example, the usual ticking fabric or the like.
An opening 283 is afforded in one side wall of the cover C of the box spring 200 to afford access to the screw 70 whereby, a handle such as the handle 84 shown in Fig. 9, may be inserted through the opening 203 into engagement with the end portion of the screw 70 to thereby adjust the central springs of the bed spring 20 as previously discussed with respect to Figs. 1 to 8, inclusive. Suitable means, such as, a zipperf 285 may be afforded on the cover C to control the opening and closing of the opening 203.
In practice, the cover C is made sufficiently loose that when the screw Til is turned to raise the adjusting frame of the box spring 20!] and thereby compress the central coil springs thereof, the upper wall of the cover 0 will give sufficiently to permit the coil springs to rise slightly above the outer coil springs as was previously discussed with respect to the spring shown in Figs. 1 to 9, whereby upon raising of the central coil spring, the outer cover C is disposed in substantially the same shape and conformation as that illustrated in Fig. 4, as is best shown in Fig. 11. This, it will be seen, is effective to bow the mattress M, normally overlying the spring 208, upwardly in the same manner, Fig. 11. However, it will be appreciated, that upon a person lying upon the mattress M the mattress will be pressed down into relatively fiat position, the effect of the prebowing of the mattress M merely being to pretension the central springs and thereby afford a firm local supporting surface thereon.
From the foregoing, it will be seen that I have afforded a novel spring unit which is especially well adapted for use in beds and the like, whereby the tension of the springs in the unit may be selectively adjusted in a novel and expeditious manner to afford firm local support for portions of the anatomy of a person using the spring unit.
Also, it will be seen that I have afforded. a novel, readily adjustable spring unit which may be readily and economically manufactured commercially either as an open spring or as a box spring.
In addition, it will be seen that I have afforded. a novel bed spring wherein the initial strength of the springs thereof may be adjusted from the bottom in a novel and expeditious manner to afford an initial differential in the strength of the springs in the various portions of the bed spring and thereby afford firm but comfortable local support for portions of the anatomy of a person lying on a bed incorporating the spring.
Thus, while I have illustrated and described the preferred embodiments of my invention, it is to be understood that these are capable of variation and modification, and I therefore do not .wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.
1. A spring unit for beds and the like comprising a supporting frame, a plurality of coil springs having a top and a bottom mounted on said frame, an adjusting frame mounted between predetermined ones of said coil springs and a portion of said supporting frame and connected to the bottom portions of said predetermined ones of said springs, said tops of said predetermined ones of said springs being connected to said supporting frame, and cam means slidably mounted on said supporting frame between said adjusting frame and said portion of said supporting frame, said cam means being operatively engaged with said adjusting frame in such position as to be operable upon sliding movement in one direction on said supporting frame to move said adjusting frame toward said predetermined ones of said coil springs to thereby move said bottom portions of said predetermined ones of said springs toward said top portions thereof and thereby compress said predetermined ones of said springs.
2. A spring unit for beds and the like comprising elongated supporting means having a substantially rectangular shaped bottom frame portion and a substantially rectangular shaped upper border portion disposed in substantially parallel relation to each other, a plurality of coil springs mounted in said supporting means and each having a top and a bottom portion, said coil springs being disposed in spaced parallel relation to each other, means connecting said top portions of said springs together and to said border portion, the bottom portion of the other of said springs being connected to said frame portion cross beams mounted on said bottom frame portion, and means for adjusting the compression of predetermined ones of said springs, said means for adjusting comprising an adjusting frame connected to said bottom portion of predetermined ones of said springs, and a carriage mounted on said cross beams and movable therealong below said adjusting frame, said carriage having upwardly projecting inclined members engaged with said adjusting frame and operable to effect movement of said adjusting frame upon reciprocation of said carriage along said beams.
3. A spring unit for beds and the like comprising supporting means having an elongated upper border member and an elongated lower frame member, said upper and lower members being substantially the same size and shape and being disposed in substantially parallel spaced relation to each other, compression coil springs mounted in said supporting means between said upper and lower members, said coil springs having top portions and bottom portions, the top portions of predetermined ones of said compression coil springs being connected to said upper member, a web of interconnected bands of flexible material overlying the top portions of other of said compression coil springs, tension coil springs connecting said Web to said predetermined ones of said compression coil springs, and means for moving said other compression coil springs outwardly away from said predetermined ones of said compression coil springs, said last named means comprising an adjusting member operatively connected to said bottom portions of said other compression coil springs, and a carriage reciprocably mounted on said lower member between said lower member and said adjusting member, said carriage having cam means projecting toward said other coil springs and slidingly engaged with said adjusting member for moving said adjusting member toward said other coil springs upon movement of said carriage in one direction on said supporting means.
4. A spring unit for beds and the like comprising supporting means having a substantially rectangular shaped upper border member and substantially rectangular shaped lower frame member disposed in spaced parallel relation to each other, a plurality of compression coil springs mounted between said members at the peripheral edge portions thereof and connecting said peripheral edge portions of said two members together, a plurality of other compression coil springs mounted between said members inwardly of said first mentioned springs in substantially parallel spaced relation to each other and said first mentioned springs, a web of interconnected bands of flexible metal overlying the tops of said other coil springs, tension coil springs con necting said first mentioned compression coil springs to said web, and means for moving said other compression coil springs upwardly relative to said first mentioned coil springs to thereby project said other coil springs outwardly from said first mentioned coil springs and to compress said other coil springs, said means comprising a pair of parallel tracks mounted on said lower frame member and extending transversely thereacross in substantially parallel relation to each other, a carriage mounted on said tracks for movement longitudinally thereof, said carriage having cams mounted thereon, a screw journaled in said lower frame member and operatively engaged with said carriage for moving said carriage longitudinally of said tracks, and an adjusting frame connected to the bottom of said other compression coil springs and operatively engaged with said cams on said carriage for movement toward and away from said other compression coil springs upon reciprocation of said carriage along said tracks.
5. A spring unit of the type defined in claim 4 and which includes a casing of fabric material enclosing said supporting means and having a relatively small opening in one side thereof in alignment with said screw.
6. A spring unit for beds and the like and comprising elongated supporting means having a substantially rectangular shaped bottom frame portion and a substantially rectangular shaped upper border portion disposed in substantially parallel relation to each other, two groups of coil springs mounted in said supporting means, said coil springs being disposed in spaced relation to each other and each having a top and a bottom portion, means connecting the top portions of said springs together and to said border portion, and means for moving said coil springs in one of said groups upwardly relative to said coil springs in the other of said groups to thereby project said coil springs in said one group outwardly from said coil springs in said other group and to compress said coil springs in said one group, said bottom portion of said springs in said other group being connected to said frame portion, said last named means comprising a carriage slidably mounted on said frame portion of said supporting means below said coil springs in said one group for reciprocation below said coil springs in said one group and transversely thereto, an adjusting frame connected to the bottom portion of said coil springs in said one group and operatively engaged with said carriage for movement by the latter toward and away from said coil springs in said one group upon said reciprocation of said carriage, and means mounted on said supporting means and operatively connected to said carriage for so reciprocating said carriage.
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