Foam layer and foam strip for forming a foam spring and a method for manufacturing a foam spring

[0001] The present invention relates to an improved foam spring and foam layer and a foam belt for their formation, and in particular to an improved foam spring with a cylindrical elastic body made of foam with holes extending from the outside inwards, which can be used in the core of pillows, mattresses, furniture padding for armchairs and the like.

[0002] The invention also relates to a method for producing such an improved foam spring.

2. Discussion of the Related Art [0003] Foam springs are known, for example, from document EP 0 001 469 describing a resilient spring element and method of its production, characterized in that it consists mainly of a cylindrical body made of synthetic foam material or the like, wherein the body wall has many empty spaces of alternating symmetry, the cross-sectional area of ​​which changes practically from zero at the inside wall of the body, to the maximum value at the outer wall without applying a load.

[0004] In order to provide the desired spring elasticity, it is recommended to fit at least one core of elastic material into the above-mentioned cylindrical body, so that its diameter mainly corresponds to the inner diameter of the cylindrical body.

[0005] From document EP 0624332 a spring element is also known which comprises a foam cylindrical body which is provided with openings extending from the outside inwards, characterized in that it comprises a wire spring which is surrounded by the body.

[0006] A foam spring is also known from document WO2005 / 20761.

[0007] In contrast to the elastic material consisting only of foam, it is found that there is no loss of hardness in the fatigue test using normal and thus cheaper foams for making the cylindrical body.

[0008] The state of the art is also known from document US 2005/0172468 a method for producing a resilient cylindrical body for pillows, mattresses and the like, the method comprising providing cuts in the foam layer, cutting a strip from this foam layer; bending two opposite ends of the strip towards each other, and attaching both these distal ends to form a resilient cylindrical body, the foam layer being formed by so-called viscoelastic foam and wherein at least some of the cells present in the foam are open.

[0009] The cylindrical body formed in this way acquires a two-conical or almost two-conical outer shape.

[0010] It is found that, unlike the typically supplied elastic foam bodies made of low specific gravity foam, such an elastic cylindrical body does not lose its elasticity in a short time of its actual use, as a result of which it is able to retain its functionality for a longer period time when used in pillows or the like.

[0011] Foam springs disclosed in document EP 0872 198 are also known in the art, which comprise a cylindrical foam body which is provided with cavities in its walls, which cavities are directed from the outside inwards, characterized by that the body expands / narrows from one extreme to the other, thereby giving the spring an external barrel form, i.e. in the case where the initial body configuration is circular.

[0012] It is stated that the main advantage of these springs is that, unlike common embodiments, they are less prone to fatigue and do not lose their initial height and shape after a short useful life.

[0013] From document WO 2009/036524, foam springs for use in pillows, mattresses or the like are also known, having a resilient cylindrical body made of foam, with holes extending inwardly, from the outer surface to the inner surface, the cylindrical body comprising at least one cylindrical foam layer and at least one reinforcing layer applied to said foam layer over at least part of the axial length of the spring.

[0014] It is found that the elastic characteristics of such a spring can be easily adjusted by using a reinforcing layer with different tensile resistance.

[0015] These foam springs are generally made, as for example explained in document EP0001469, by providing cuts in the foam layer, which foam layer is then bent and attached to itself to form a cylindrical body that can act as a spring or be lived as a spring.

[0016] Of course, the cut pattern provided in the foam layer will be reflected in the hole pattern of the cylindrical body.

[0017] Various foam layers are known for the production of foam springs with different cut patterns, such as for example known from said document EP0001469 or WO2009 / 023940.

[0018] Although such known foam springs made of such known foam layers are very much appreciated by users of pillows, mattresses or the like, they have the disadvantage that either the spring must be given a specific external shape, thus making dense packing difficult side-by-side springs, or that additional components must be provided, such as wire springs or reinforcing cores or special underlays or reinforcing layers, which makes the manufacture of such springs more complex, more expensive, more energy-intensive and more polluting the environment.

[0019] They also have the disadvantage that they are easily damaged, for example during production, packaging, storage, transport, installation or the like, or during assembly of pillows, mattresses etc. due to the high tensile forces applied to the springs .

[0020] Hence, the handling of these springs must be carried out with some care, which requires special attention, as a result often slowing down the production process and increasing production costs.

[0021] Another disadvantage of known springs is that when compressed in the axial direction, they tend to bulge in the lateral direction, thereby affecting the behavior of adjacent springs.

[0022] Hence, the elastic characteristics of individual springs in a pillow, mattress or the like is sometimes difficult to predict and to try to match the pillow, mattress or the like to the needs of the user or to the body shape of the user are not an easy task.

SUMMARY OF THE INVENTION [0023] The object of the present invention is to provide a foam spring with improved properties for use in cushions, furniture lining, mattresses or the like which does not have any of the above-mentioned disadvantages.

[0024] To this end, the invention relates to a foam layer as defined in claim 1 for forming a foam spring as defined in claim 10.

[0025] Areas without cuts thus form reinforcing areas, compared to areas with cuts, reinforcing the entire foam spring, which makes it no longer necessary or necessary to incorporate a metal spring or additional reinforcements, or to use foam layers of different densities or similar solutions as described in the prior art.

[0026] A preferred embodiment is the foam as defined in claim 12.

[0027] Its main advantage is that the reinforcing ribs allow significantly improved distribution of compressive forces when the spring is loaded.

[0028] In addition, the reinforcing ribs formed in accordance with the invention more prevent the foam from bulging sideways when compressed under load, even when lower density foam is used.

[0029] The use of lower density foam without losing the main static and dynamic properties of the spring not only reduces the costs of raw materials and energy consumption, but also provides important gains during production, as well as provides greater comfort of touch and the possibility of adapting the foam to the shape of the body, when used in a mattress, cushion, furniture lining or the like, which is highly appreciated by the end user.

[0030] Comparable or even better static, dynamic and durability properties of the spring can thus be achieved in a much simpler and less costly way than with prior art springs.

[0031] The main advantage is that the reinforcing ribs form an integral part of the cylindrical body and are manufactured in one production step without creating any problems of adhesion, delamination, assembly, storage and delivery of individual components.

[0032] Another advantage is that, as a result, the springs are less susceptible to damage due to brutal treatment during the manufacture and assembly of a pillow, mattress or the like.

[0033] Due to this, less attention needs to be paid to avoid damaging the springs during production, assembly, handling, storage, installation and the like, which naturally leads to higher production speeds and a reduction in the overall proportion of deficiencies.

[0034] The longitudinal reinforcement ribs formed according to the invention in turn will protect the elastic properties of the springs against the influence of adjacent compressed springs, making the elastic characteristics of each individual spring more predictable when used in a cushion, mattress and the like.

[0035] Thanks to the more predictable behavior of the springs, it is easier to adjust the pillow, mattress and the like to the user's specific preferences or to his shape and body weight, providing the user with a great sense of comfort.

[0036] Another advantage of the springs according to the invention is that due to the formation of reinforcing ribs and the absence of other structural elements, such as e.g. metal wire springs in a cylindrical wall, the springs are more resistant to damage due to brutal treatment during manufacture and assembly. pillows, mattresses and the like, and their weight and complexity are significantly reduced.

[0037] Another advantage is that the elastic properties of the spring according to the invention can be matched not only by careful selection of raw materials and foam made therefrom, but also by the relative ratio of the parts equipped with and without holes, by their geometric arrangement and relative arrangement along the spring body.

[0038] These foam springs according to the invention can of course be combined with other types of springs to create different comfort zones with different softnesses in the cushion, mattress and the like.

[0039] According to a preferred example of the invention, the part of the body that is not provided with holes and thereby forms a plurality of reinforcing ribs extends from below to the top of the cylindrical body.

[0040] According to another preferred embodiment, the unstretched foam width of the portion provided with holes is substantially equal to the width of the portion not provided with holes.

[0041] According to a further preferred embodiment, the openings are not only arranged alternately with respect to each other, but also with respect to openings formed by any adjacent part that is separated from these parts by a part which is not provided with said openings.

[0042] According to another preferred embodiment, the outer surface of the part that is not provided with the holes has a sinusoidal shape over part or all of the length of the axial spring.

[0043] According to another preferred embodiment, the unperforated parts form a plurality of reinforcing ribs, equally spaced apart along the circumference of the cylindrical body and along its longitudinal axis.

[0044] According to another preferred embodiment, the number of parts that are not provided with holes and thereby form reinforcing ribs is from 4 to 12, preferably from 6 to 10, and even more preferably is 8.

[0045] According to another preferred embodiment, the spring comprises a belt with at least one foam layer and a series of cuts extending in one direction and surrounded by respective areas that do not contain any cuts and two opposite ends extending in the direction of the cuts, wherein the opposite ends of the belt are bent by bringing them together and are glued together to form said hollow cylindrical body and to form said diamond-shaped holes by stretching the cuts in the transverse direction due to the bending of the belt and the change of uncut areas into reinforcing ribs, regularly disposed along the circumference of the cylindrical body and positioned along its longitudinal axis.

[0046] According to another preferred embodiment, the intersections in the strip extend along a plurality of broken parallel lines.

[0047] According to another preferred embodiment, the intersections are arranged in an alternating pattern in which the intersections along adjacent lines are shifted in their longitudinal direction.

[0048] According to a further preferred embodiment, the intersections in the strip between two adjacent areas, which are separated by an uncut region, are arranged in an alternating pattern in which intersections along adjacent lines are displaced in their longitudinal direction.

[0049] The invention also relates to a foam layer as defined in claim 1 and a foam strip as defined in claim 7 which have the advantage of being particularly suitable for the manufacture of the springs mentioned above.

[0050] The invention also relates to the method of claim 14, for producing a foam spring with a resilient cylindrical body for use in pillows, mattresses and the like.

In a preferred embodiment, the method comprises providing intermittent cuts along lines extending in the longitudinal direction of at least one part of the foam layer and an alternate arrangement of these cuts in a regular pattern, the adjacent foam layer not having said cuts, a cut of a transverse belt from this foam, bending the two opposite ends of the belt towards each other and attaching the two opposite ends in a cylindrical shape to form a resilient cylindrical body in which, outside and along the longitudinal axis of the cylindrical body, parts with intersections and adjacent parts without intersections are arranged alternately in a regular way and in which the latter form strong, longitudinal reinforcing ribs in the cylindrical body.

[0052] Alternative aspects of the invention are described in the following paragraphs:

1.- A foam spring for use in pillows, mattresses and the like, wherein the foam spring comprises a resilient cylindrical body made of foam and forming an outer wall, with holes extending inwardly from the outer surface to the inner surface, the holes being arranged according to alternating symmetry and mainly have the shape of a diamond, characterized by that the cylindrical body has these holes only on a limited part of its surface and that this limited part is regularly arranged alternately with a limited part of the surface which is not equipped with said holes and which form longitudinal reinforcing ribs in the wall of the cylindrical spring body.

2. - A foam spring according to item 1, wherein both the limited part which is not equipped with said holes and the limited part containing these holes extend in the longitudinal direction from the top to the bottom of the cylindrical body, i.e. along the entire length of the spring.

3. - A foam spring according to item 1 or 2, wherein the width of the part provided with such openings is substantially equal to the width of the part not provided with said openings, defined on the unstretched foam belt.

4. - A foam spring according to any of the previous points, wherein the holes are not only arranged alternately with respect to each other, but also with respect to the holes formed in any adjacent part which is separated from these parts by a part which is not equipped with said holes.

5. - A foam spring according to any of the previous points, wherein the outer surface of the part, which is not provided with holes, is sinusoidal in shape over the part or along the entire axial length of the spring.

6. - A foam spring according to any of the previous points, wherein the number of parts that are not equipped with holes is from 4 to 12, preferably from 6 to 10, even more preferably equal to 8.

7. Foam spring according to any of the previous points, wherein the unperforated parts form a plurality of reinforcing ribs spaced at equal intervals along the circumference of the cylindrical body and along its longitudinal axis.

8. - A foam spring according to any of the previous points, wherein the spring comprises a belt with at least one foam layer and a series of cuts extending in one direction and surrounded by respective areas that do not contain any cuts and two opposite ends extending in the direction of the cuts, wherein the opposite ends of the belt are bent by bringing them together and are glued together to form said hollow cylindrical body and to shape said holes in diamonds by stretching the cuts in the transverse direction as a result of bending the belt and to convert the uncut areas into reinforcing ribs, regularly arranged along the circumference of the cylindrical body and positioned along its longitudinal axis.

9. - A foam spring according to any of the previous points, wherein the intersections in the waist extend along a plurality of dashed parallel lines.

10. A foam spring according to any of the previous points, wherein the intersections in the belt are arranged in an alternating pattern in which the intersections along adjacent lines are displaced in their longitudinal direction.

11. A foam spring according to any of the previous points, wherein said intersections in areas between two adjacent areas that are separated by uncut areas are arranged in an alternating pattern in which the intersections along adjacent lines are shifted in their longitudinal direction.

12. A method for producing a foam spring with a resilient cylindrical body for use in pillows, mattresses and the like, the method comprising providing intermittent cuts along parallel lines extending in the longitudinal direction of at least a portion of the foam layer and alternating arrangement of these cuts in a regular pattern with an adjacent portion of the layer foam, not equipped with the above-mentioned cuts, cut-out of the transverse belt from this foam, bending the two opposite ends of the belt towards each other and attaching the two opposite ends into a cylindrical shape to form a resilient cylindrical body in which, outside and along the longitudinal axis of the cylindrical body, parts with intersections and adjacent parts without intersections are arranged alternately in a regular manner and in which parts without cuts form reinforcing ribs in the cylindrical body of the spring.

BRIEF DESCRIPTION OF THE DRAWINGS [0053] To provide a better explanation of the features of the invention, by way of example only, the following preferred embodiment of a foam spring and method of the invention for producing such a foam spring is described, without limiting in any way, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic perspective view of a foam spring according to the invention;

Fig. 2 shows the foam layer with equally spaced areas containing cuts, alternating with the areas without cuts, used to produce the foam spring according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT [0054] The spring shown in Fig. 1 is a foam spring 1 for use in cushions, furniture lining, mattresses and the like, and includes a cylindrical resilient body 2 with holes 3 extending inwardly from the outer surface 4 to the inner surface 5 springs 1.

[0055] The cylindrical body 2 further comprises a foam layer 6.

[0056] The holes 3 are here preferably arranged relative to each other in a regular and alternating pattern.

[0057] This ensures that any deformation of the spring 1 under pressure along the direction represented by the arrow P is evenly distributed throughout the entire body of the spring 1, thus limiting any radial bulging of the spring 1 and preventing the concentration of compressive forces in only one part of the spring 1 instead of their even distribution throughout the body 2 of the spring 1.

[0058] The areas 16 (represented in Fig. 2) containing these holes 3 are staggered with the areas 18 (represented in Fig. 2) not including any holes 3, the latter forming reinforcing ribs 7 which are evenly distributed along the perimeter of the body cylindrical 2.

[0059] In a preferred embodiment, the shape of the reinforcing ribs 7 is a sine wave or runs along a continuous line Z or S in the longitudinal direction X-X 'as indicated by dotted line 14.

[0060] The advantage of the foam spring 1 shown in Fig. 1 is that when the spring is compressed in the axial direction X-X ', represented by the arrow P, the foam spring 1 does not tend to bulge in the radial or transverse direction and thus the diameter of the cylindrical spring is substantially preserved.

[0061] Another advantage of this preferred embodiment is that the elasticity, compressive strength and useful life of the spring 1 according to the invention are significantly increased, even when lower density foam was used to make it.

[0062] Fig. 2 shows the foam layer 6 from which, according to the invention, the foam spring 1 is made.

[0063] The method of forming the foam spring 1 is relatively simple and includes the following steps:

[0064] In the first stage, the rectangular strip 8 is cut from the corresponding foam layer 6 with the XX 'symmetry axis and with two pairs of parallel side walls 9-10 and 11-12, respectively.

[0065] In belt 8, areas 16 with intersections 17 are provided, in a direction which is parallel to the aforementioned symmetry axis X-X ', which are arranged alternately with areas 18 without intersections in a regular pattern.

[0066] The cuts 17 in the strip 8 are made along a plurality of intermittent parallel lines 13 at equal intervals from each other.

[0067] The intersections 17 are preferably arranged in an alternating pattern, whereby the intersections 17 along adjacent lines 13 are shifted in their longitudinal direction X-X ', for example by a length equal to half the longitudinal length of the intersections 17.

In order to form the cylindrical body 2 of the foam spring 1, the belt 8 is bent schematically represented by dotted lines 15.

[0069] In this way, the side walls 11 and 12 are close together and in the next step are permanently attached to each other, for example by means of gluing, thus forming the cylindrical body 2 of the foam spring 1.

[0070] As a result of the above-mentioned bending, the strip 8 is stretched and the cuts 17 are opened to form the aforesaid holes 3, which extend radially in the body 2, alternating with the reinforcing ribs 7 formed by surrounding areas 18, not containing cuts, and therefore not forming holes 3 when the cylindrical body 2 is formed at a later stage.

[0071] In the case where several rows 13 of intersections 17 are arranged in an alternating configuration not only with respect to each other but also with respect to intersections 17 in the next area 16, separated by the area 18 without intersections 17, thus formed in the next step and the reinforcement ribs 7 shown in Fig. 1 acquire a sine wave shape represented by dotted line 14 in Fig. 1.

[0072] This wave shape or sine wave of the reinforcement ribs 7 according to the invention is particularly suitable for converting any deflection of the spring 1 under pressure in the direction of the arrow represented by P into a tangential deformation of the sinusoid reinforcing ribs 7, thereby preventing radial bulging of the spring 1, with all the associated negative consequences explained above.

[0073] Although, according to a preferred embodiment of the invention, the reinforcing ribs 7 extend over the entire axial length L of the spring 1, it is not excluded that the reinforcing ribs 7 extend only over a part of said axial length L. [0074] The invention is not necessarily limited to cylindrical springs 1, but can also be used for other spring shapes.

[0075] The present invention is by no means limited to the above-described embodiments and methods of embodiment given as examples and represented in the accompanying drawings, on the contrary, such a foam spring and the method of producing such a spring may change while still remaining within the scope of the invention according to the appended claims.

IMHOLD, naamloze vennootschap, Belgium

Proxy:

EP 2 554 077 B1

Z-11574