GB2150431A

GB2150431A - Cushioning articles

Info

Publication number: GB2150431A
Application number: GB08429384A
Authority: GB
Inventors: Janet Parker
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-11-28
Filing date: 1984-11-21
Publication date: 1985-07-03
Also published as: GB8429384D0; EP0200822A1; GB2150431B; EP0200822B1

Description

1

SPECIFICATION

Cushioning articles GB 2 150 431 A 1 This invention relates to cushioning articles.

Uniti now, cushioning has been made of springs, foam rubbers, polyurethane foam, rubber straps, horsehair, artificial fibres, wadding, felt, air inflated bags, silicone fluid/rubber filled bags etc. or combinations of these. There are also waterbeds. Cushions are available, made from plastics containers filled with a high viscosity liquid/gel, which may contain mineral cenospheres, or foamed polystyrene beads, but these cushions are heavy, not always low in flammability, and relatively expensive.

According to the present invention, light-weight cushioning can be made from gas-filled plastics or mineral enclosures, or mixtures of both, dispersed in a lubricant so that movement of gas-filled enclosures within the lubricant is possible. This dispersion of gas-filled enclosures is contained within a covering which is impermeable to the lubricant, and which in turn may be covered by conventional upholstery materials.

Thus, the present invention provides a cushioning article comprising a closed flexible envelope containing (a) a plurality of discrete, relatively movable gas-filled enclosures bounded by respective permanent flexible wal Is; and (b) a lubricantto facilitate the relative movement of the gas-filled enclosures within the envelope.

The cushioning so produced will followthe body contours of a user, thus distributing pressure evenly and providing greater comfort. The possibility of the development of ischaemia (local deficiency of blood supply 20 due to spasm or obstruction of an artery), and decubitus ulcers (pressure sores or ulcers relating from pressure on parts of the body in persons confined to bed for a long time, or needing to sit, for example in wheelchairs, for long periods), is reduced.

The gas-filled enclosures (which may, for example, consist essentially of discrete undivided bubbles or discrete spheres of a cellular material) may contain a non-flammable gas such as nitrogen, carbon dioxide or 25 helium. Alternatively, they may contain air.

The gas-filled enclosures may be made of any one or more of the folowing films, foils or coatings:polyethylene, polypropylene, polyurethane, polyvinylidene chloride, plasticised polyvinyl chloride, butyle rubber, polyester, polyamide, aluminium, chlorinated rubber orfluorinated polymers.

It is preferred that it should be rubber-like/flexible. The gas-filled enclosures may consistwholly of any one 30 of the aforementioned materials. Alternatively, the gas-filled enclosures may comprise a laminate of two or more of the materials or a coating of one on another.

The diameter of the gas-filied enclosures is preferably between 5 microns and 50 mm. The enclosures may be spherical, but can be other shapes, e.g. ellipsoidal. It has been found that a mixture of various sizes of gas-filled enclosures will minimise the mass of lubricant needed, and save weight in the cushion. For example, if spherical enclosures of 30 mm diameter are used, they will only occupy about 50% of the total envelope volume, and proportions of smaller-diameter spherical enclosures can be incorporated in the spaces, thus reducing the volume of lubricant needed (see Furnas, Ind. Eng. Chem. 1931,23(9), 10528).

The lubricant in which the gas-filled enclosures are dispersed must have a low coefficient of friction and must flow. The lubricant may be a liquid, e.g. water, aqueous salt solution, polyhydric alcohols, natural or 40 synthetic mineral or silicone oils or greases, the liquid optionally being thickened to give a pseudoplastic gel.

Alternatively, the lubricant can be a finely-divided solid, (e.g. natural silicates of plate-like structure such as talc), graphite, molybdenum disulphide or derivatives of long-chain organic materials having a plate-like structure (e.g. stearic acid and calcium stearate), soft waxes, fluorinated polymers (e.g. polytetraf luoroethylene) or mixtures of these materials. Regard should be had to the fact that some of the abovementioned lubricants are less desirable than others because of inherent flammability and/or the possibility of the evolution of toxic gases when burning.

The rheology of the liquid lubricant may be altered by using thickeners or thixotropic agents known to those skilled in the art, e.g. clays., gaseous-produced silicas, cellulose ethers, alkali-soluble acrylics, gelatine, alginates, polyacrylamide, finely divided 'fillers', glass cenospheres or mineral cenospheres.

A preferred lubricant for use in this invention is a 20% by weight aqueous sodium chloride solution, thickened by means of clays, gaseous-produced silicas or cellulose ethers. At -20'C a 25% by weight saline solution is still fluid, but a 20% by weight saline solution forms a slush at this temperature. Any lower proportion of salt in the solution produces a solid at this temperature. We have found that this lubricant gives good low-temperature properties, low flammability, low order of toxicity and low cost.

The impermeable covering constituting the envelope may be made of any one or more of the materials mentioned hereinbefore. It is preferred that the envelope should be rubber-like/flexible, without being so brittle as to be noisy in use.

The envelope may be sealed by means of radiofrequency, heat-sealing or thermoforming in the configuration most suitable for the intended use of the cushioning article and/orto reduce volume and 60 weight. Alternatively, the envelope can, in appropriate cases, be formed by rotational casting or blow-moulding.

2 GB 2 150 431A 2 The impermeable covering may be reinforced e.g. by woven or non-woven fabrics of artificial, or natural materials, or of glass. Suitable laminates/coatings for the envelope include the following:

polypropylene to polyester to polypropylene 5 polyethylene to polyester to polyethylene polypropylene to aluminium to polypropylene polyethylene to aluminium to polyethylene polyurethane to aluminium to polyurethane polyester to aluminium to polyester 10 polyurethane to polyvinylidene chloride to polyurethane polyester to polyvinylidene chloride to polyethylene The outermost covering of the envelope may be of any standard upholstery fabric or sheepskin, or leather or leathercloth and maybe wholly or partly lined with materials such as polyester wadding or polyurethane 15 foam. The outermost covering maybe made to conform to the appropriate British Standard for flammability.

Amongst the applications for cushioning articles according to the present invention are:- wheelchair cushions, orthopaedic seating,invalid car seats, pressure support products such as rings, heel and elbow pads, hospital mattresses, aircraft seats, helicopter seats, seats for buses, cars, fork-lift trucks, 20 lorries and vans, for agricultural vehicles and heavy plant, in domestic and office furniture, kneeling pads, and in shock absorbing pads for equipment.

Preferred embodiments of the present invention will be illustrated by way of the following Examples:

Example 1

Air-filled enclosures of 30 mm diameter were dispersed in a gel made to the following formulation:- 20% by mass aqueous salt solution 30 Hydrated magnesium silicate (i) Fumed silica (ii) A suitable bactericide/fungicide was incorporated.

MAvailable under the Registered Trade mark PANGEL S.

(ii) Available under the Registered Trade Mark CAB-O-SIL M-5.

The viscosity of the gel, determined on a Brookfield viscometer model R V F spindle 7 at 2WC. was:920 poise at speed 10 360 poise at speed 20 136 poise at speed 50 114 poise at speed 100

This gel is strongly pseudoplastic.

The air-filled enclosures and gel were contained in a cover fabricated from a polyurethanelpolyvinylidene chloridelpolyurethane laminate. The whole was encased in an outer cover comprising polyester wadding 45 and a flame-retardant fabric.

Example 2

Air-filled enclosures of 25 mm diameter were dispersed in a gel made to the following formation:- Glycerol B. P.

Hydrated magnesium silicate (i) Fumed silica (ii) A suitable bactericidelfungicide was incorporated. 55 (i) and (ii): See Example 1.

The viscosity of the gel, determined on a Brookfield viscometer model R V F spindle 7 at 201C. was:1560 poise at speed 10 960 poise at speed 20 528 poise at speed 50 360 poise at speed 100

This gel is also strongly pseudoplastic. The air-filled enclosures and gel were contained in a cover fabricated from polyvinylidene chloride/ polyester/polyethylene laminate. The whole was encased in an outer cover comprising polyester wadding 65 and a flame- retardant fabric.

p. b^ 12 p.b.w. 30 5 p. b^ p. b.w 50 5.25 p.b.w. 3.75 p.b.w.

3 GB 2 150 431 A 3 Example 3

Air-filled plastics enclosures of 30 mm diameter were dispersed in powdered graphite, and contained in a cover fabricated from a polyurethane film. The whole was encased in an outer cover comprising polyester wadding and a flame retardant fabric.

Claims

1. A cushioning article comprising a closed flexible envelope containing:

(a) a plurality of discrete, relatively movable gas-filled enclosures bounded by respective permanent flexible walls; and (b) a lubricant to facilitate the relative movement of the gas-filled enclosures (a) within the envelope.

2. An article according to Claim 1, in which the lubricant (b) is a liquid.

3. An article according to Claim 1 or 2, in which the lubricant (b) is a liquid including one or more thickeners.

4. An article according to Claim 1, 2 or 3, in which the lubricant (b) is water containing one or more 15 thickeners and sodium chloride.

5. An article according to Claim 1, 2 or3, in which the lubricant (b) is a gel.

6. An article according to Claim 1, in which the lubricant (b) is a powdered solid material.

7. An article according to anyone of the preceding claims, in which the gas-filled enclosures (a) consist essentially of discrete undivided bubbles.

8. An article according to anyone of Claims 1 to 6, in which the gas-f if led enclosures (a) consist essentially of discrete spheres of a cellular material.

9. A cushioning article, substantially as hereinbefore described with reference to anyone of the Examples.

Printed in the UK for HMSO, D8818935, 5185, 7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.