Pocketed spring unit and method of manufacture

Abstract

A resilient unit has strings of individual coil springs (not shown) inside pockets 120 are arranged in an array. The strings together form a spring unit and are each secured to a common cover sheet S, which comprises a non-woven elastic fabric. It is welded ultrasonically or thermally whilst under tension in one or both of its major dimensions—i.e. in-plane—to the pockets 120, the material of which is substantially inelastic and non-woven. In this example the welds, labelled W, are located substantially centrally with respect to the generally circular end surfaces of the pockets.

Claims

1. A resilient unit, comprising a plurality of resilient elements within pockets of substantially inelastic and non-woven material, arranged in an array, wherein at least two of the pocketed resilient elements are joined to a common cover sheet of non-woven elastic material, and wherein the cover sheet has two major dimensions and is under tension in one or both of said major dimensions and is joined to the pockets by welds or adhesive.

2. The resilient unit according to claim 1, wherein the pocketed resilient elements comprise springs inside pockets.

3. The resilient unit according to claim 1, wherein at least two of the resilient elements are arranged in use to be compressible along a compression axis.

4. The resilient unit according to claim 1 wherein at least two of the resilient elements are arranged in use so that compression axes of at least two resilient elements are aligned.

5. The resilient unit according to claim 4, wherein the cover sheet is arranged to extend in a direction substantially transverse to the compression axes of the at least two resilient elements.

6. The resilient unit according to claim 1, wherein the cover sheet is joined to the pocketed resilient elements at an upper side of the resilient unit in use.

7. The resilient unit according to claim 1, wherein the cover sheet is joined at a lower side of the resilient unit in use.

8. The resilient unit according to claim 1, wherein the resilient unit has upper and lower sides and comprises a cover sheet joined at each of the upper and lower sides.

9. The resilient unit according to claim 1, wherein the cover sheet is joined to one or more folds in the substantially inelastic and non-woven material of one or more of the pockets.

10. The resilient unit according to claim 1, wherein the pocketed resilient elements have one or more gussets between them, and wherein the cover sheet is joined to the one or more gussets.

11. The resilient unit according to claim 1, wherein the cover sheet is attached to the pocketed resilient elements around at least a peripheral portion of the resilient unit.

12. The resilient unit according to claim 1, wherein the resilient unit has at least one of a substantially planar upper surface and a substantially planar lower surface.

13. The resilient unit according to claim 12, wherein the cover sheet is joined at at least one of the upper planar surface and the lower planar surface.

14. An upholstered article comprising the resilient unit in accordance with claim 1.

15. The resilient unit according to claim 1, wherein the cover sheet has two major dimensions and is under tension in both dimensions.

16. The resilient unit according to claim 1, wherein the cover sheet comprises an elastomeric polymer combined with a non-elastic fibre.

17. A method of manufacturing a resilient unit, the unit comprising a plurality of resilient elements within pockets arranged in an array, the material of the pockets being substantially inelastic and non-woven, wherein the method comprises joining at least two of the pocketed resilient elements to a cover sheet of non-woven elastic material, and wherein the cover sheet has two major dimensions and is joined to the pockets by welding or by adhesive while the cover sheet is under tension in one or both of said major dimensions.

18. The method according to claim 17, wherein the pocketed resilient elements comprise springs inside the pockets.

19. The method according to claim 17, wherein the method comprises joining the cover sheet at an upper side of the resilient unit.

20. The method according to claim 17, wherein the method comprises joining the cover sheet at a lower side of the resilient unit.

21. The method according to claim 17, wherein the resilient unit has upper and lower sides, and the method comprises joining a cover sheet to each of the upper and lower sides.

22. The method according to claim 17, wherein the method comprises joining the cover sheet to one or more folds in the substantially inelastic and non-woven material of one or more of the pockets.

23. The method according to claim 17, wherein the resilient units have one or more gussets or hinges between them, and the method includes joining the cover sheet to one or more of the gussets.

24. An upholstered article formed in accordance with the method according to claim 17.

25. A method according to claim 17, wherein the cover sheet has two major dimensions, and the method comprises joining the cover sheet to the pocketed resilient elements while the cover sheet is under tension in both major dimensions.

Description

(1) A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

(2) FIG. 1 shows schematically a first type of previously considered resilient unit;

(3) FIG. 2 shows schematically a second type of previously considered resilient unit;

(4) FIG. 3 shows schematically a portion of a resilient unit of a first type, modified in accordance with an embodiment of the present invention;

(5) FIG. 4 shows schematically a portion of a resilient unit that is a variant of the embodiment of FIG. 3;

(6) FIG. 5 shows schematically a portion of a resilient unit of a second type, modified in accordance with an embodiment of the present invention;

(7) FIG. 6 shows schematically a portion of a resilient unit of a third type, modified in accordance with an embodiment of the present invention; and

(8) FIG. 7 shows schematically a portion of a resilient unit of a fourth type, modified in accordance with an embodiment of the present invention.

(9) Embodiments of resilient unit described below have a cover sheet that is elastic and pocket material that is substantially inelastic, or has a degree of elasticity that is less than that of the cover sheet, more preferably substantially less than that of the cover sheet.

(10) Turning to FIG. 1, this shows the first type of resilient unit, in the form of a pocketed spring unit as described briefly above. FIG. 2 shows a second type of resilient unit as described above.

(11) FIG. 3 shows schematically a part of a resilient unit according to an embodiment of the present invention. The resilient unit in this example is of the type described in relation to FIG. 1, in which strings of individual coil springs (not shown) inside pockets 120 are arranged in an array.

(12) The strings together form a spring unit and are each secured to a common cover sheet S, which comprises a non-woven elastic fabric. It is welded ultrasonically or thermally whilst under tension in one or both of its major dimensions—i.e. in-plane—to the pockets 120, the material of which is substantially inelastic and non-woven. In this example the welds, labelled W, are located substantially centrally with respect to the generally circular end surfaces of the pockets.

(13) The cover sheet S holds the strings of springs together, so that they do not need to be glued to each other, which saves cost.

(14) FIG. 4 shows a variant of the resilient unit of FIG. 1. The cylindrical coil springs are again encased in individual pockets 120. However, in this embodiment surplus material comprising the pockets is formed into flaps or ears 130 at the axial ends of the pockets. It is to these flaps 130 that the cover sheet S is welded at points W.

(15) FIG. 4 shows the second type of resilient unit, as described above in relation to FIG. 2, with the modification that a cover sheet S has been welded thereto. As described above, the unit comprises a folded pad containing rows of resilient elements 210, in this example they are coil springs, in discrete pockets 220 formed between superposed sheets of material joined at locations between adjacent resilient elements. Between at least some adjacent resilient elements the sheets form a gusset 230 which acts as a hinge when the pad is folded to form the resilient unit.

(16) Cover sheets S are welded to the gussets on both upper and lower surfaces of the pad. Again, the sheets are of an elastic material and are held under tension prior to welding. When welding is completed and the tension is released, the cover sheets S hold the pocketed springs securely in the folded configuration shown.

(17) FIG. 6 shows schematically a portion of another type of pocketed spring unit 300. This example is of a kind made in accordance with the method described in our European patent number EP 1 993 947 B in which rows of springs 310 are encapsulated in pockets 320 formed between sheets of material that are welded together at locations L between the springs. The cover sheet S is welded to the upper sheet of pocket material.

(18) FIG. 7 shows schematically another type of pocketed spring unit 400. This example is of a unit such as is described in our European patent number EP 2 637 527 B in which a continuous coil spring 410 is encased in a continuous pocket 420, before the spring and pocket are deformed together simultaneously, by fan-folding. A plurality of encased springs, lying beside one another in an array, can be fan folded together to form the unit shown. The elastic cover sheet S is then welded under tension to the pocketing material. In FIG. 7 part of the cover sheet S and part of the pocketing have been removed to expose the structure beneath.

(19) In the examples above, the elasticated cover sheet S holds the pocketed springs together, keeping the shape of the unit. The sheet may be made from an elastomeric polymer, combined with a non-elastic fibre, such as polypropylene.

(20) The elasticity of the cover sheet adds to the resilient characteristic of the pocketed spring unit as a whole, and for example when used as an upholstered article, such as a mattress, it provides a luxurious feel. In addition, because the sheet S contributes to the resilience, the mass of spring wire may be reduced, for example by using wire of a thinner gauge.

(21) Unlike previously considered cover sheets, which do not have elasticity, the elastic sheet S allows for the deformation of smaller clusters of pocketed springs—in some cases individual pocketed springs may be deformed—without communicating, or distributing, the compressive load widely, for example to surrounding springs/clusters. This can make for a responsive characteristic and can improve the feeling of comfort to the user.

(22) The cover sheet S may be applied to an intended upper surface of the spring unit in use, or to an intended lower surface, or sheets can be applied to each of the upper and lower surfaces. A common sheet can be applied to both surfaces—eg by extending around a side of the unit. As an alternative, the or each sheet can form part of a bag or case that can extend around and substantially form the outer surface of the unit, substantially enclosing all of the pocket resilient elements.

(23) Whereas the examples above show a cover sheet S that is welded ultrasonically or thermally to the pocketing material of the unit, the sheet could also be glued to the pocketing material. In this example, while the cost of the glue would not be eliminated completely, the quantity of glue would be reduced, particularly when compared with previous examples, in which each string of springs must be glued to its neighbours in order to maintain the strength and structural integrity of the finished unit.

(24) Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.