The present invention relates to a pocketed spring unit and to a method and an apparatus for forming the same, and is concerned particularly with a pocketed spring unit that has reduced adhesive as compared with previously considered units, or is substantially free from adhesive, and to a method for forming such a unit.

Pocketed springs, otherwise known as encased springs, are used in upholstered articles such as mattresses. An example is shown schematically in FIG. 1. A resilient pocketed spring unit 100 comprises coil springs 110 encased individually in pockets 120 of fabric material formed by folding over a sheet of fabric to form two leaves that envelope the springs, and then attaching the leaves together between the springs so as to form a string of individual springs in pockets. The strings are then joined to form an array of springs as a pocketed spring unit.

The joining of the strings together to form an array is usually achieved either by gluing the strings together along the cylindrical surfaces of the pocketed springs, one string to the next, and so on until the unit is formed, or else by arranging the strings beside each other in an array, and then gluing a sheet of fabric to the cylindrical ends of the pocketed springs, above and/or below, so as to form the unit.

A problem with either method is the extensive use of glue to hold together the strings, to form the unit. For one thing the adhesive forms a significant element of the cost of manufacturing a pocketed spring unit, and for another the presence of the adhesive in the product makes it difficult to recycle the unit at the end of its useful life.

One alternative structure is described in our United Kingdom patent application no. 1702159.3. As illustrated schematically in FIG. 2, a resilient unit 200, such as for a mattress, comprises a folded pad containing rows of resilient elements 210, which in this example 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 fan-folded to form the resilient unit. The unit requires less glue to hold it together than the above example, due to the structural role of the gusset.

Embodiments of the present invention aim to provide a pocketed spring unit, and a method for manufacturing the same, in which the shortcomings of the prior art are addressed.

The present invention is defined in the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto.

According to one aspect of the present invention, there is provided a resilient unit, comprising a plurality of pocketed resilient elements arranged in an array, wherein at least some of the pocketed resilient elements are joined to a common cover sheet of elastic material.

The pocketed resilient elements may comprise resilient articles, such as springs, inside pockets formed of pocket material.

The pocket material may be substantially inelastic and/or it may have a degree of elasticity that is less than that of the cover sheet, more preferably substantially less.

Preferably the cover sheet is joined directly to the pocket material.

Preferably the pocketed resilient elements are joined to the common sheet by welds. Alternatively, or in addition, the pocketed resilient elements may be joined to the cover sheet by adhesive.

At least some of the resilient elements are arranged in use to be compressible along a compression axis. At least some of the resilient elements are arranged in use so that their compression axes are aligned and are preferably substantially parallel. In a preferred arrangement the cover sheet is arranged to extend in a direction substantially transverse to the compression axes of the resilient elements.

In a preferred arrangement the cover sheet is joined to the pocketed resilient elements at an upper side of the resilient unit in use. Alternatively the cover sheet is joined at a lower side of the resilient unit in use.

The resilient unit may comprise a cover sheet joined at each of the upper and lower sides.

In a preferred arrangement the, or each, cover sheet is joined to the pocket material of one or more of the pockets, more preferably to one or more folds in the pocket material.

Where the resilient units have one or more gussets or hinges between them, the or each cover sheet may be joined to one or more of the gussets.

In a preferred arrangement the or each cover sheet is attached to the pocketed resilient elements around at least a peripheral portion of the resilient unit.

The resilient unit may have a substantially planar upper and/or lower surface. The or each cover sheet may be joined at the planar surface.

According to another aspect of the present invention, there is provided a method of manufacturing a resilient unit, the unit comprising a plurality of pocketed resilient elements arranged in an array, wherein the method comprises joining at least some of the pocketed resilient elements to a cover sheet of elastic material.

The pocketed resilient elements may comprise resilient articles, such as springs, inside pockets formed of pocket material.

Preferably the method comprises joining at least some of the pocketed resilient elements to the cover sheet by welding, which may be by ultrasonic welding or thermal welding, for example. Alternatively, or in addition, the method may comprise joining at least some of the pocketed resilient elements to the cover sheet using adhesive.

In a preferred arrangement the cover sheet is arranged to extend in a direction substantially transverse to the compression axes of the resilient elements.

In a preferred arrangement the method comprises joining the cover sheet at an upper side of the resilient unit.

Alternatively, the method may comprise joining the cover sheet at a lower side of the resilient unit.

The method may comprise joining a cover sheet to each of the upper and lower sides.

In a preferred arrangement method comprises joining the, or each, cover sheet to one or more of the pockets, more preferably to one or more folds in the pocket material.

Where the resilient units have one or more gussets or hinges between them, method may include joining the or each cover sheet to one or more of the gussets.

In a preferred arrangement the method may include joining the or each cover sheet to the resilient unit around at least a peripheral portion thereof.

The resilient unit may have a substantially planar upper and/or lower surface. The method may comprise joining the or each cover sheet to the planar surface.

The invention also includes a resilient unit according to any statement herein or formed in accordance with a method according to any statement herein.

The invention also includes an upholstered article comprising a resilient unit in accordance with any statement herein.

The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive, or mutually inconsistent.

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:

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

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

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

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

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

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.