The present invention relates to compression apparatus and a compression method, and is particularly concerned with apparatus and a method for compressing resilient units for storage and/or transportation.

Resilient units such as for example pocketed spring units, for use in upholstered items such as mattresses, or in resilient pads or panels, typically comprise a plurality of springs which are encapsulated in pockets formed between layers of material. International patent application No. WO 2007/031774 describes an example of such a pocketed spring unit and a method of manufacturing the same.

Previously, such spring units have been stored and/or transported in the form of sheets which are stacked and sometimes folded. One problem with this arises from the fact that, though relatively light in weight, the spring units are bulky, and so occupy a relatively large volume. This is inefficient for storage and costly for transportation .

Embodiments of the present invention aim to address the above-mentioned problem.

The present invention is defined in the attached independent claims to which reference should now be made. Preferred features can be found in the sub-claims appended thereto. According to the present invention there is provided compression apparatus arranged to compress a resilient unit comprising a plurality of resilient elements located within one or more pockets formed between layers of material, the apparatus comprising tensioning means arranged to apply tension to the material, and winding means arranged to wind the material into a roll, wherein the application of tension to the material causes the resilient elements to become compressed prior to winding into the roll, thereby causing the resilient unit to take up less volume.

The winding means may comprise a winding roller.

Preferably the apparatus is arranged to place the resilient unit in tension by pulling the material between the winding roller and the tensioning means.

Preferably the tensioning means comprises one or more tensioning rollers, through or against which the resilient unit is arranged to pass.

Preferably the winding roller and at least one tensioning roller are allowed or caused to rotate at different speeds to apply tension to the resilient unit.

Preferably the application of tension to the material in a longitudinal direction of the resilient unit is arranged to cause the material to compress the resilient elements between the layers of material.

The resilient elements may comprise springs, which may be compression springs. The resilient unit may comprise a pocketed spring unit.

The invention also includes a method of compressing a resilient unit comprising a plurality of resilient elements located within one or more pockets formed between layers of material, the method comprising applying tension to the material so as to cause the resilient elements to become compressed and winding the material under tension into a roll .

Preferably the method comprises winding the material using a winding roller.

The method preferably comprises applying tension to the resilient unit by pulling the resilient unit between the winding roller and tensioning means, which may comprise one or more tensioning rollers.

In a preferred arrangement the method comprises allowing or causing rollers to rotate at different speeds to cause the tension to be applied to the material of the unit between the winding roller and the or each tensioning roller.

In a preferred arrangement, the application of tension to the material in a longitudinal direction of the resilient unit is arranged to bring about an extension of said unit in said longitudinal direction that is substantially proportional to a reduction in a thickness of the resilient unit . The invention may comprise any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive. A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figures la and lb are schematic views of a portion of resilient unit suitable for use with apparatus or a method according to the present invention;

Figure 2 is schematic side view of the compression apparatus according to an embodiment of the present invention; and

Figures 3a and 3b are schematic views respectively of a portion of resilient material before compression and after compression .

Turning to Figures la and lb, these show, generally at 10, a portion of a resilient unit in the form of a pocketed spring unit. The resilient unit comprises a number of springs 12 arranged in an array, each spring being encased within its own pocket formed between superposed layers 14 of material. The layers are spaced apart with the springs in between and are welded at selected positions 16 between adjacent springs, to form a grid-like pattern. International patent application No. WO 2007/031774 describes in detail one method of manufacturing such a pocketed spring unit in which the springs are compressed and then pushed between layers of material which are welded at spaced locations between the springs to form discrete pockets for the springs.

It has been found that, because of the surplus of material around the spring, the position of the welds and also the ready compressibility of the springs, that the pocketed spring unit can be made thinner, i.e. the springs can be compressed, by pulling the layers of material in a direction transverse to the axes of the springs.

If the springs are, for example, conically coiled wire springs, they may be compressed to a great extent, wherein they have a depth of the- order of the thickness of one coil - i.e. the thickness of the wire itself.

Figure 2 shows schematically apparatus for compressing the resilient unit. The resilient unit is fed as a continuous web 18 through first and second tensioning rollers 20, 22 to a winding roller 24. The winding roller is driven at a first speed, and one or both of the tensioning rollers is also driven, but at a second speed which is less than the first speed - i.e. slower than that of the winding roller.

The difference is speeds causes tension to be applied to the material of the resilient unit which stretches the resilient unit and in turn compresses the resilient elements in their pockets . The result is that the resilient unit becomes compressed in its through thickness direction - the axial direction of the springs - before it is wound into the winding roller. The resilient unit extends in length in a longitudinal direction in which tension is applied. The extension in length is substantially proportional to a reduction in a thickness of the resilient unit.

Servo-control (not shown) can be applied to one or more of the driven rollers to ensure that their relative speed, and hence the tension in the material, is maintained at a substantially constant level.

It is not necessary to drive both of the tensioning rollers 20 and 22.

When under tension the resilient unit substantially flattens, the extent depending upon the degree of tension applied, within working limits. The pockets become substantially flat and return to a shape that they had initially held during manufacture, dependent upon the pattern of the welding or gluing of the layers from which they are formed. When the desired quantity of resilient unit web has been wound on to the roller the roll of web is taped or wrapped to prevent unravelling.

Figures 3a and 3b show, respectively a portion of resilient unit before and after compression in the apparatus of Figure 2.

A benefit of compressing the resilient elements in this way is that the length of resilient unit that can be wound on to a roll 24 of a given diameter is much greater than would be the case with an uncompressed resilient unit. Therefore, the quantity of resilient unit will take up less space, perhaps anything up to 90% less space, and so is more efficiently stored and/or more cheaply transported. Once the resilient unit is needed it can be unwound from the roll, allowing it to return to an uncompressed state, and then cut to length as required for e.g. a mattress, a seat base or other pad or panel.

The example described above uses coil springs as the resilient elements. However, other resilient elements could be used, such as other types of spring, provided that the layers if material lie spaced apart in the direction of compression of the resilient element.

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.