CA1213381A - Body from resilient foam material, such as a buffer, a seat cushion or mattrass from foam rubber or synthetic foam material - Google Patents

Abstract

ABSTRACT
The invention relates to a body of resilient foam material, such as a buffer, a seat cushion or a mattress of foam rubber or synthetic foam material, which body has been provided with a plurality of slits within which tight fitting spring elements are enclosed, which in loaded condition are in contact with the two walls of the slit and cannot shift with respect to the slit walls.
The spring elements in unloaded condition are substantially free of tension and have a spring characteristic equal to or hardly differ-ent from the characteristic of the foam material. The normal decrease in rigidity of resilient foam bodies is thus completely obviated so that cheaper foam materials can be used, in particular those which also have a greater softness.

Description

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The invention relates to a body of resilient foam material, such as a buffer, a seat cushion or mattress of foam rubber or synthetic foam material, which body at a plurality spaced apart locations has been provided with compressible spring elements in incisions of the foam body.
A body of this kind in the form of a mattress is known from published German specification 2,324,101. In this known mattress which has been divided into blocks by longitudinally and transversely extending incisions, each block has been provided with a cylindrical slit within which a conical helical spring has been placed which has been compressed to one half of its length and accordingly is pretensioned and which compresses the core in radial direction. This spring is not in contact with the outer wall of the cylindrical slit.
With that known mattress one aims, when use is made-of foam material of small density or specific mass, to give the mattress additional rigidity by means of the pretensioned springs which are placed in the slits to enable the mattress to support a body and to make sure that after compression of parts of the mattress recovery of the shape can take place quickly when the load is removed. Pretensioned springs of this kind in a foam body of small specific mass and accordingly great softness are felt as hard cores, which in particular is undesirable in the application as a mattress. The same of course holds true for seat cushions whereas with the application in buffers or for packaging the springs also form hard places. A pretensioned spring only becomes compressible and accordingly only operates as a spring when the load becomes ~. ~,. .

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equal to the pretensioning force.
It is a known fact, that the rigidity of a mattress cushion, seat or the like, of Eoam rubber or synthetic foam falls off after some time of use. This has as a consequence that, as a rule, one cannot make use of a foam material which is relatively soft and accordingly not of foam material which delivers a soft mattress or cushion with high comfortability because after some time they become too soft and offer too little support due to the decrease in the rigidity. This of course holds true as well for buffers because after some time their ability to take up blows decreases so much that they become unfit for use. If one makes use of the above known pretensioned conical helical springs said springs certainly give some compensation for the reduction of the rigidity but in certain applications, such as seat cushions and mattresses, the springs then are locations which are inconveniently perceptible and accordingly useless.
In the past many proposals already have been made to place helical springs and the like in a mattress. Thus from the published Netherlands patent application 7808781 a mattress is known in which a plurality of cylindrical holes are made in the main body of foam material which holes extend transversely through the main body and within which helical springs are placed. Said helical springs are enclosed in the h~'es by attaching, e.g. by glueing, plates of foam material against the underside and upon the upper side of the main body. Comparable proposals are found as well in Swiss patent specification 452824, Australian patent specification 450041 and United States patent specification

2,540,441.

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From French patent specification 1,110,462 a mattress is known as well comprising two layers of foam material having recesses in each layer which only form part of the thickness of the layer and which are in line with each other when the layers are placed upon each other, helical springs being enclosed within said recesses. According to the proposals no slits are made in the foam body, but chambers. These chambers form large hollow spaces within which, apart from the helical spring, as a rule also air is present.
The homogeneous character of the isolating properties is disturbed therewith because each hollow space with the spring placed in it forms a cold bridge. Moreover the hollow spaces disturb the entire spring characteristic of the foam body which then in a positive sense is influenced by the helical springs placed in the chambers.
Another objection of helical springs placed in hollow chambers is that they can tilt, which means take up a position in which they partly extend transversely or curved inside the hollow space and then they no longer can operate properly.
With modern mattress support structures having a head portion and a foot portion respectively which can swing upwardly the foam mattress must be flexible. A normally interconnected mattress with inner springs cannot do this. The spring frame with interconnected springs will kink upon bending at each location where the springs are interconnected. The mattresses according to the above-mentioned known proposals with helical springs placed in hollow spaces as a rule can be bent, but the risk is increased that the spring inside the hollow space will take up an incorrect posi-tion.

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The manufacturing of hollow spaces can take place by punching them as through holes out of the massive material. How-ever, it then is not easy to obtain a pure cylindrical opening. If discontinuous recesses are used then the manufacturing is compli-cated because the recesses have to be made by means of cores to be placed in the mould in which foaming takes place at the locations where the recesses are to be made.
Each hollow space obtained by cutting away material means loss of material.
From French patent specification 1,552,214, in particular Figure 2, it is known to surround the helical spring elements com-pletely by the foam material. To this end, however, it is necessary to place the spring elements in a mould within which the foaming takes place and this makes manufacturing complicated and expensive.
Manufacturing a slit, as is known does not lead to any loss of material, and can be done in a relatively simple way by means of a cutting device making a cut without removing material.
The purpose of the invention is to provide a body of resilient foam material which is suitable for many purposes, can be manufactured in a simple way, maintains its rigidity without the spring elements used for that purpose becoming perceptible.
The invention provides in a support device including a body formed from a flexible resilient material and having a plur-ality of spaced apart chambers formed therein, said body provided with compressible spring elements within said chambers, the improvement comprising said flexible resilient material and said spring elements having substantially the same spring rates and said .3~L

spring elements being in an unstressed state when said structure is in an unloaded state.
Each spring element over its entire length is in contact in a non-shiftable manner with the one and/or the other wall of the slit defining the chamber. In the loaded condition the spring element over the entire length is in contact with the two walls of the slit and between the spring element containing slits the foam body is unin-terrupted.
Accordingly the spring elements are not pretensioned and immediately come into operation as soon as a load occurs.
Due to the fact that the spring elements are enclosed over the entire length such that they always are in contact with one wall of the slit and upon being loaded always with both walls of the slit, no shifting whatsoever of parts of the spring elements with respect to the walls of the slit takes place. The spring elements are not perceptible but ensure maintenance of the rigidity.
With the measure according to the invention in a simple way it has been achieved that the resilient foam body always maintains its properties. The foam body with the exception of the slits within which the spring elements are present is not interrupted by other incisions, slots or the like between the spring elements. In other words large portions of the foam body each comprising a plurality of spring elements can be considered as one block or plate.
The spring elements enclosed in this way cannot tilt or bend if loaded at only one side.
Preferably cylindrical slits are used within which a cylindrical helical spring is placed. The spring elements can be ~;~1 33~3~

formed by a wire the thickness of which is larger than the width of the slit. The spring elements are then enclosed completely invisibly and from the very beginning, even in unloaded condition, are completely enclosed. It is also possible, however, to give the slits a width which is larger than the thickness of the wire of the spring element, so that this spring element in unloaded con-dition is spaced from one of the walls of the slit. In loaded con-dition the foam material is displaced and immediately encloses the spring element completely.
Instead of cylindrical slits rectilinear slits can be made in the form of parallel rows with or without staggered relationship and extending transversely and/or longitudinally of the body.
Such rectilinear slits have the advantage that the spring elements can easily be placed because one only needs to place the body on a curved surface to be able to insert the spring elements in the then opened slits. It is conceivable as well to apply zig-zag shaped slits having a separate spring element in each part of the zig-zag or interconnected spring elements extending over the entire length of the zig-zag line.
Instead of spring elements made from spring steel sprin~
elements of another resilient material such as synthetic material, foam material, rubber and the like could be used.
With mattresses one preferably makes the slits in planes extending perpendicular to the main plane of the mattress because the mattress is loaded in a direction perpendicular to that plane.
With cushions such as cushions which rest against a curved back or 1213~8~L

supporting plate, it can be useful for the axis or planes of the slits in the direction of compressibility of the spring elements to extend at different angles with respect to each other. The slits can also extend perpendicular to two or more planes of the body.
Accordingly one can manufacture blocks which can take up loads in different directions. Thus with a cup-shaped chair e.g. a bucket seat of a vehicle, the supporting function, apart from by the shape of the cup also can be defined by the direction within which the spring elements are directed so that at the edges of the cup forces in transverse direction can be taken up as well.
It is observed that from published Netherlands patent application 7007648 a resilient covering system is known suitable for use in beds, seat cushions, back supports and like objects comprising a foam material which surrounds a plurality of adjacent helical springs in the form of interconnected bags which specifica-tion also states that the resilient foam material can be a resilient urethane foam having a low specific weight because the foam material need not add anything to the function of the spring.
Here, however, one has to deal with a resilient support of a con-struction such that the helical springs have to be placed first inthe mould in which the foam material that has to surround the springs is foamed. This is a very complicated expensive manner of manufacturing which does not allow foam layers to be cut from a large prefabricated block. It is observed further that from British patent specification 493,356 buffers are known having spring elements which are prepared with a vulcanizable material and are placed in a mould within which the rubber is fed. In this way a ~1331~

complete enclosure of the spring elements is obtained. This manner of manufacturing is complicated and expensive as well.
The principle underlying the invention, i.e. the complete enclosure of spring elements which in unloaded condition are free of tension and which have a spring characteristic comparable with that of the foam material, can be applied in many ways. Thus it can in principle be applied with each type of cushion such as loose cushions for furniture but also for fixed coverings of furniture, vehicle seats, in particular bucket seats, air plane seats and the like. Application is conceivable with bump free safety layers such as e.g. the dash board and the roof coverings of vehicles. Indus-trial applications are possible such as packaging materials, e.g.
with the inner coating of a box or case and with supporting cushions for vibration-free support of machines or apparatuses. Conceivable as well is an application in children's playgrounds, such as in the form of play blocks and bump free coatings of floor or wall.
The principle according to the invention in particular is suitable for the application on mattresses.
With all applications of foam materials according to the known proposals, to obtain the required rigidity and the required capacity to absorb shocks and loads respectively, one had to make use of foam materials having a relatively high specific mass and this entails a cost factor which is prohibitive for many applica-tions. This is the reason that in the older proposals some, such as the earlier mentioned German specification 2,324,101 use a foam material of low specific mass which are given a spring character-istic by enclosing spring elements therein. One, however did not 3~l understand that by placing and enclosing the correct spring elements according to the proposal of the present invention, even with bodies of resilient synthetic material having a low specific mass the decrease in rigidity can be obviated.
The invention now will be further elucidated, by way of example only, with reference to the drawings, wherein:-Figure 1 shows in cross section a first embodiment of a part of a mattress according to the invention;
Figure 2 in the same way shows a cross section through another embodiment;
Figure 3 shows a third embodiment in cross section;
Figure 4 shows a fourth embodiment in cross section;
Figure 5 shows a fifth embodiment in cross section;
Figure 6 shows a sixth embodiment in cross section;
Figure 7 shows a seventh embodiment in cross section;
Figures 8 and 9 show in top view schematically the locations where the slits can be made;
Figures 10, 11 and 12 show different possibilities of forms of slit for receiving a spring element;
Figure 13 in side view shows a spring element which can be used with the possibilities shown in Figures 10 to 12 inclusive;
Figure 14 shows still another embodiment;
Figure 15 is a perspective view of a block of foam mater-ial having spring elements in two perpendicular directions;
Figure 16 shows a cross section through a back support;
and Figure 17 shows an application in the form of a support _g_ 33~

cushion e.g. for the vibration-free mounting of some apparatus.
The mattress shown in Figure 1 comprises a main body 1 having a cylindrical incision 2 which extends through a part of the thickness of the main body 1. A helical spring 3 has been placed in the incision. The helical springs are retained within their slits covering layer 4. In the embodiment of Figure 2 the incision 5 has the same depth as in Figure 1. The helical spring 3 in unloaded condition engages the core 6 of the material of the mattress 1, which core has been left in place in the same way as with the embodiment of Figure 1.
The incision 5 has a width such that in unloaded condition the spring is not in contact with the outer wall 7 of the incision.
In loaded condition this outer wall, however, will move inwardly and engage the helical spring.
With the embodiment of Figure 3 the incision 8 is made with the same small width as in Figure 1, however, the incision 8 now extends through the entire thickness of the mattress body 1.
The core 9 thus separated, however, is placed together with the helical spring 3 in the opening obtained. Enclosure again takes place by means of the top covering layer 4 and an additional bottom covering layer 10.
With the embodiment of Figure 4, the mattress comprises two layers 11 and 12. Incisions 13 and 14 respectively are made in the two layers with a depth which is less than the thickness of the corresponding layer 11, 12 so that the cores 15 and 16 remain.
One single helical spring 3 is placed in the two incisions 13 and 14.

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The embodiment of Figure 5 is similar to Figure 4 with the difference, that the incision 17 is made with a larger width comparable to the width shown in E'igure 2.
In the embodiment of Figure 6 the mattress comprises a thick layer 18 and a thinner layer 19. Helical springs may be placed in the thick layer as shown at 20 and e.g. by means of an incision of the type shown in Figures 1, 3 and 4. Furthermore the two layers 18 and 19 can have incisions 21 and 22 respectively of a larger width comparable to the embodiment shown in Figure 5, the helical spring 23 surrounding both cores 24 and 25.
Figure 7 shows a mattress having an incision 26 in the main body 1, the incision 26 having a width of the type shown in Figures 2 and 5. The difference with the other embodiments, how-ever, is that the helical spring does not engage the core but engages the outer wall of the incision 26.
In Figures 8 and 9 top views are shown of mattresses and each circle shown represents an incision in which a helical spring is placed.
Instead of cylindrical metal helical springs, it is con-ceivable to use another circumferential shape. Instead of metal spring elements it is possible to use spring elements of other material such as synthetic material or rubber.
Figure 10 shows in top view a mattress 30 having longitu-dinally extending parallel rows of incisions 31 which do not extend through the entire thickness. In the transverse direction incisions 32 are provided.
Figure 11 shows a mattress 33 also provided with rows of ~ ;~133~31 incisions 34 extending parallel to the longitudinal direction, which incisions, however, are staggered from row to row whereas in Figure 10 the incisions of adjacent rows are aligned in the trans-verse direction.
The incisions 35 shown in Figure 11 and extending in transverse direction lie between the incisions 34.
Figure 12 shows two possibilities of zig~zag shaped incisions namely a zig-zag of rectangular angles as shown at 36 and a V-shaped zig-zag as shown at 37.

Spring elements as shown in principle in Figure 13 can be placed in the rectilinear incisions of all embodiments shown in Figures 10 to 12 inclusive, such spring elements comprising a wire or strip of spring steel 38 bent in a zig-zag and lying in a flat plane, the lower leg 39 of the spring being shorter than the upper leg 40 to facilitate insertion.
Such a spring can be manufactured in unrestricted lengths as indicated by the interrupted lines 41 and in this way one can manufacture a strip of spring elements which by bending can be adapted to the zig-zag shaped path of the incision made.

Figure 14 shows a mattress 1 of the type shown in Figure 1 but upside-down and without a covering layer 4.
The mattress shown in Figure 14 comprises exclusively a layer 1 of foam material having incisions 2 into which springs 3 are placed. The incisions are made in the bottom surface which lies upon a perforated plate 43 which is supported by lath 44 of a frame. Any other forrn of underbed is possible as well.
Figure 15 in a perspective view shows a block 47 in which a plurality of spaced parallel cylindrically shaped incisions 48 ;33~

are made, in such incisions helical springs 49 being placed.
Between the incisions 48 and in a direction perpendicular thereto there are incisions 50 having helical springs 51. This block 47 accordingly can take up loads in two perpendicular directions. The incisions 48 need not, as shown, extend through the entire thick-ness of the material.
Figure 16 shows a curved plate 52 which may be the back of a chair and on this plate is attached a foam layer 53 into which a plurality of incisions are made e.g. of the same type as shown in the preceding figures and within which are helical springs 54. In the central area of the foam layer 53 the axis of the helical springs are in principle perpendicular to the plate 52. The more outwardly located helical springs 55, 56 extend at an angle to the perpendicular and due to this also give support in the transverse direction.
Figure 17 shows a supporting surface 57 having a recess 58 into which a block 59 of foam material is placed, having spring elements comparable to the embodiment of Figure 14, namely springs 60, compressible in the vertical direction and springs 61 which are compressible in the horizontal direction. This is of importance for a block 59 the width of which is larger than the width of the recess 58 so that the foam material can be under pretension in the recess. Such a support can be useful for the vibration free mount-ing of measuring devices, laboratory apparatus, and also of machines.
Many other applications are possible on a large or small scale. Small scale is any relatively thin coating layer suitable for taking up bumps. Large scale is a cushion having a thickness 338~

of at least one meter, e.g. for sports such as high jumping or for safety purposes.

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a support device including a body formed from a flexible resilient material and having a plurality of spaced apart chambers formed therein, said body provided with compressible spring elements within said chambers, the improvement comprising said flexible resilient material and said spring elements having substantially the same spring rates and said spring elements being in an unstressed state when said structure is in an unloaded state.

2. The support structure according to claim 1 wherein the spring elements are formed from a wire, the width of which exceeds the width of said chamber.

3. A support device according to claim 1 wherein said chamber has at least one side wall and said spring element is spaced from a portion of said at least one side wall when said support device is in an unloaded condition.

4. A support device according to claim 1 wherein said chambers comprise slits.

5. A support device according to claim 4 wherein said body is rectangular in shape, having a longitudinal axis, and said slits are rectilinear and extend transverse to said longitudinal axis of said body.

6. A support device according to claim 4 wherein said body is rectangular in shape, having a longitudinal axis, and said slits comprise rectilinear slits arranged parallel to said axis.

7. A support device according to claim 4 wherein said body has a rectangular shape, having a longitudinal axis, and said slits comprise rectilinear slits arranged transverse and parallel to said longitudinal axis.

8. A support device according to claim 4 wherein said body has a rectangular shape and said slits comprise rectilinear slits arranged in parallel rows.

9. A support device according to claim 8 wherein said slits of one of said parallel rows are staggered with respect to the slits of an adjacent row.

10. A support device according to claim 4 wherein said slits comprise a plurality of zig-zag slits.

11. A support device according to claim 1 wherein said support device comprises a mattress and each of said chambers has an elongated shape with a longitudinal axis, said longitudinal axes of said chambers arranged perpendicular to the plane of a body contacting surface of said mattress.

12. A support device according to claim 1 wherein each of said chambers has a longitudinal axis arranged perpendicular to the direction of compressibility of said spring element and the axes of some chambers are arranged at varying angles with respect to the axes of other chambers.

13. A support device according to claim 1 wherein each of said chambers has a longitudinal axis arranged parallel to the direction of compression of the spring element located within that chamber and the axes of said chambers are arranged perpendicular to two or more faces of said body.