This invention relates to a spring mattress, or a \ spring upholstery pad of the type used to form a seating pad, back rest or other sprung pad of the type used in the assembly of chairs, settees and beds.

The invention has been developed primarily with a view- to provide improved manufacture and design of a spring mattress, though it should be understood that the invention is also applicable to "divan units" and to spring unholstery pads of the type referred to above, and therefore, for convenience, a spring mattress, a divan unit and a spring upholstery pad of the type just mentioned, will be referred to hereinafter as "a covered spring unit of the type specified".

In the manufacture of spring mattresses, it has been conventional practice for many years to form a spring assembly which is composed of upper and lower rectangular wire frames, and an arrangement of coil springs which are connected to each other, and also to the upper and lower frames, so as to form a unitary spring assembly. The coil springs are usually interconnected at their upper and lower ends by connecting wires or "pigtail" linkages, which are anchored at their ends to the upper or lower rectangular wire frames.

Semi-automatic (and also automatic) spring making machines are used which "wire up" an assembly of coil springs so as to form the unitary assembly, and to enable the machines to perform efficiently and without undue complications, it is essential that the coil springs should be of uniform size and/or uniform distribution throughout the assembly.

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However, it is a fact that certain areas of a mattress are normally subjected to a greater load than others, and over a period of time the springs supporting these areas

over a period of time the springs supporting these areas tend to become deformed with resultant formation of permanent depressions in the surface of the mattress. While it might be desirable to seek to anticipate such additional loading in certain areas of a mattress (in order to increase the service life of the mattress), by using stronger springs, or a more dense array of springs to support these areas, this cannot presently be achieved with existing machines. Thus, the use of stronger (larger) springs, or a variable density of springs, cannot be accepted by existing machines which require a uniform size, and distribution of the springs in order to carry out semi¬ automatic assembly of the springs.

The invention therefore seeks, in one aspect, (to which application the invention is not restricted) to permit coil springs to be assembled in a mattress without the necessity for the springs to be mechanically interconnected by wire or other mechanical linkages to the usual upper and lower rectangular supporting frames.

It is already known from GB 1,433,686 to bond mattress coil springs at their upper and lower ends to pre-formed plastics foam slabs, but there still remains the necessity for the upper and lower ends of the springs to be fastened together by pigtail linkages which are interconnected to usual rectangular arrangements of framing rods. However, the invention uses a bonding technique in order to secure the springs in position, and without the necessity for any mechanical linkages to be provided, and also without the necessity for plastics foam slabs to be used.

The use of plastics foam slabs is becoming unnacceptable, from a fire hazard point of view, in view of the lethal toxic fumes which are generated during a fire. This is particularly the case for unholstered pads used in aircraft, or other environments where the prevention of fire hazards is paramount.

According to the invention there is provided a covered spring assembly comprising a number of laterally spaced compression springs extending between upper and lower layers of flexible textile material, in which at least some of the spring ends are adhesively secured to at least one of the layers of textile material.

The adhesive securement of the ends of the springs to the layers of textile material can provide a durable unitary assembly. Further, it is preferred that usual metal rods or wires are arranged to form upper and lower frames in which the spring assembly is mounted, without the necessity for the provision of the usual pigtail or other mechanical linkages to interconnect the ends of the springs to the upper and lower frames. The textile layers themselves maintain the springs in the required position in the assembly, and, by suitable attachment to the upper and lower frames, complete the assembly of the spring unit.

The coil springs used in the spring unit may be of uniform size and type, and also uniform density of distribution, though it should be understood that different types and/or arrangements of springs can readily be achieved without any significant adverse effect on the production of the unit.

The invention is particularly, though not exclusively, concerned with the formation of a covered spring unit in the form of a spring mattress.

Any suitable adhesive may be used in order to achieve a necessary substantially permanent bond between the end of each spring and the fabric piece, and it has been found that "hot melt" adhesives are particularly suitable. The layers of textile material may be made of any suitable fabric material, whether woven or non-woven, and in any suitable synthetic, natural or a combination of synthetic and natural textile fibre materials.

The coil springs used in the spring unit may be of

convention helical type used in mattresses, namely a formation having enlarged circular ends, which are interconnected by an integral and narrower diameter spiral. However, other arrangements of coil spring may be used if required.

The ends of the coil springs may be secured adhesively to fabric covering pieces of the unit on an automatic, or semi-automatic production run using suitably designed machines. When it is desired to vary the size, type and/or distribution of the springs, this can be achieved readily by suitable adjustment, without any serious interference with the production operation.

A single piece of fabric may be applied so as to cover the opening of each frame, and preferably separate side pieces of fabric are attached to the frames so as to cover the sides of the unit. The securement of the fabric covering pieces to the frames may be achieved in any convenient manner e.g. by stitching' thereto, though other means may be adopted, such as the use of adhesives. Also, if desired, a single piece of fabric may be used which forms the entire covering layer for the spring unit.

One embodiment of covered spring unit according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawing, in which:

Figure 1 is a side view of a typical spring which may be incorporated in a covered spring pad unit according to the invention;

Figure 2 is a plan view of the spring shown in Figure 1;

Figure 3 is a schematic side view of the assembly of the spring unit from a plurality of the springs shown in Figures 1 and 2 _?

Figure 4 is a schematic plan view of the assembly shown in Figure 3; and,

Figure 5 is a detail view of the adhesive securement of a spring end to a flexible piece of textile material.

Referring now to the drawings, a covered spring unit according to the invention is designated generally by reference 10 and takes the form, in the illustrated embodiment, of a mattress unit. The unit 10 has usual upper and lower rigid wire or rod frames 11 and 12 which are rectangular, and each of which defines a respective opening which requires covering. A respective piece of fabric covering 13 and 14 covers the openings in the rectangular frames 11 and 12 respectively. In Figure 3, the fabric pieces 13 and 14 are shown above and below the general planes of the frames 11 and 12 respectively, but this is for illustration purposes only, and the fabric pieces may be arranged generally within the planes of the frames. The pieces 13 and 14 can be secured to the individual frame elements on the frames 11 and 12 by any suitable means, such as stitching.. However, other means, such as the use of adhesive may be used.

The compression springs which are used in the unit are shown in Figures 1 and 2, which comprise conventional helical "bed" springs 15 having larger diameter circular ends 16 which are interconnected by an integral formation of a smaller diameter helical or spiral winding 17. The shape of the circular ends 16 are maintained in known manner by the provisions of knots 18.

In order to complete the assembly of a desired arrangement of the coil springs 15 in the mattress unit 10, the springs 15 are arranged so as to extend between the fabric pieces 13 and 14, with each spring being adhesively secured at each end 16 to a respective adjacent portion of the covering fabric piece. By this means, the springs 15 are securely held in a desired assembly with the upper and lower frames 11 and 12.

As shown schematically in Figure 4, the springs 15 can

be attached to the fabric pieces by blobs of a suitable adhesive. It has been found in tests that a "hot melt" adhesive is particularly suitable, which can be readily applied by automatic or semi-automatic dispensing machines, and which has the necessary properties of providing a substantially permanent and durable fastening of the springs in position in the mattress, via the securement to the fabric pieces.

In Figures 3 and 4, the springs 15 are of uniform size and distribution. However, if desired, the sizes and/or types, and/or also the distribution may be varied to suit any desired distribution of resilient properties throughout the surface of the spring unit. While there has been described and illustrated a spring mattress, it will be appreciated that the features of the invention may readily be applied in the provision of spring upholstery pads of the type suitable for use as seat pads, backrests, or other spring pads'of the type used in chairs, settees or 'beds. Given that the use of plastics foam material is falling out of favour, in view of the serious fire hazard risks caused by emission of toxic f mes, it is believed that the present invention will have substantial utility, in providing covered spring units which do not require the use of plastics foam materials, and which provide a unit assembly of springs which can be manufactured simply and which can be altered to provide different resilient properties without undue complication in the operation of automatic or semi-automatic machines developed to make the units.

Standard bedding type springs may be used in the making of the unit, and of the type used in the bedding and upholstery trades. The springs produced on a "Spuhl" wire coiler or similar, would be suitable for use in the unit. Typically, the springs may have an end coil diameter of 80 to 85mm, tapering to 45 to 50mm in the centre with three convolutions.

Concerning the fabric material used in the covering of the unit, any suitable woven or non-woven fabric (e.g. a needled mat of non-woven fibres) may be used, and in any suitable synthetic, natural or combination of synthetic and τ natural textile materials.

The springs could be purchased separately, or manufactured on a machine for feeding into a magazine or similar. A purpose built machine, capable of holding and feeding, a top and bottom roll of the fabric covering could be- attached to a "spring feeder", which would pass the springs: through an applicator of the adhesive (adhesive hot metl) and position the springs at regular intervals and in rows between the top and bottom sheets of material. The machine would then index the material forward at a predetermined rate, and further springs introduced via the feeder unit to the space now created.

Various sizes of spring unit could be supplied, depending upon market requirements.

Conveniently, the fabric covering material may be suitable for use, simultaneously, as a mattress or upholstery "insulator", with the springs sandwiched between and attached at regular intervals thereto by hot melt adhesive or the like.

As mentioned above, the spring unit disclosed herein has the advantage of being more readily varied in its formation than existing spring units, because of the method of linking these springs together with fabric material, preferably an insulator pad, instead of wire linkages. Furthermore, because of the insulating properties which may be provided in the cover material, no further insulator is required, whereas it is essential to provide a separate insulator in existing units.

In addition, it will be possible to vary the quantity and configuration of the springs provided in any particular unit, which is not possible with current machining for

making spring units, because of the complex operating steps in making "wired-up" spring units with existing sophisticated machines.

The advantages listed above should speed up production, and particularly by eliminating the need for a separate insulator pad. Furthermore, the mode of assembly of the springs in the unit lends itself to automated production, with further savings in productivity.

Furthermore, it is envisaged that the spring unit may also have application within the car and aircraft industry, where currently plastics foam is used which is causing serious concern because of the emission of toxic fumes under fire conditions.

Although the illustrated embodiment of the invention provides upper and lower wire or rod frames (11 and 12) which define the overall shape of the spring unit, the invention also includes the formation of a spring unit composed only of the fabric covering- (which forms an enclosure), and the springs bonded at each end to respective upper and lower fabric surfaces of the unit and enclosed within the covering.

The flexible textile material to which the spring ends are directly secured by adhesive may be, as indicated above, an insulator pad composed of a non-woven needled felt. A typical form of insulator pad to which the springs may be secured comprises a needled and bonded synthetic fibre at 2oz per square foot, and preferably having a scrim of e.g. polypropylene bonded within it. One suitable insulator pad comprises that available in the United Kingdom from Rawsons under the Trade Name SPRING LOCK.

Concerning the adhesive securement of the spring ends, in fact it is not essential that the spring ends should remain permanently bonded to the adhesive material, but that the blobs or drops of adhesive should become moulded into a shape in which the spring ends are restrained

This can be seen from the schematic illustration of Figure 5, which shows a drop of adhesive 19 which is partly embedded into a non-woven insulator pad 20 having an internal reinforcing scrim 21. The adhesive is moulded into a shape which defines a trough 22 into which the wire 23 (forming the spring end 16) is received.

The spring end 16 is prevented from moving laterally by the side walls of the trough 22, but is maintained pressed towards the base of the trough by spring compression, in that the springs are held captive against axial expansion by the covering layers 13 and 14. These layers are either secured to the outer framework (11, 12), or in the absence of this f amework the layers are held together by textile pieces bridging the gap between the layers 13, 14 e.g. as shown by dotted outline 24 in Figure 3.