WO2004047575A1

WO2004047575A1 - Protection means

Info

Publication number: WO2004047575A1
Application number: PCT/GB2003/004788
Authority: WO
Inventors: Jane Davison; Samuel Lewin Evans
Original assignee: The Ascent Group Limited,
Priority date: 2002-11-27
Filing date: 2003-11-06
Publication date: 2004-06-10
Also published as: AU2003276471A1; GB0227639D0

Abstract

A joint protection device comprising a helix (20) of plastics material having a length greater than its width and which is resiliently compressible when a force is applied to it in a direction normal to its length, the helix (20) being composed of a strip of plastics material of uniform cross section and having uniform diameter coils disposed at an angle to the length of the helix (20), the strip of plastics material having a first surface (12) disposed as an outer surface of the helix (20) and having two edges, a second surface (16') extending from one edge of the first surface and a third surface (18') extending from the other edge of the first surface, the second and third surfaces (16', 18') being inclined towards each other and the construction and arrangement being such that when a force is applied to the first surface (12') of a coil of the helix (20) at one side of the helix (20), the second and third surfaces (16', 18') of that coil of the helix (20) may be urged in a direction to enter between the inclined surfaces of two adjacent coils of the helix (20) disposed at the opposite side of the helix (20) to the point of application of the force.

Description

Protection Means

This invention relates to protection means suitable for use on the human or animal body and is particularly concerned with impact protection devices to be worn adjacent a body joint, for example a hip joint.

It is well known to provide padding or resilient protectors for protection of various body parts against injury due to impact of those body parts during sporting activities. Such protection may be used, for example by participants in the various versions of football and hockey and a variety of constructions and designs has been proposed. Such protection aids tend to be bulky and uncomfortable to wear for long periods of time.

Fracture of bones, especially fractures at or in the joint, for example the hip joint of frail or elderly people, is a major public health issue. It has been estimated that 1.7 million hip fractures occurred world wide in 1990 and it is predicted that more than 6 million per annum will occur by the year 2050. Hip fracture is most common in women in their 80' s and is commonly associated with osteoporosis, which is a condition in which the bones become weak and porous, leaving the sufferer at increased risk of a broken hip from a relatively minor fall. Hip fracture is a significant cause of mortality, with many older people dying within six months of suffering a fracture. The costs to the National Health Service in UK for treating such patients is about £12,000 per fracture.

It is known that one may alleviate the problems of hip fracture by preventing falls, treating bone fragility and / or by wearing a hip protector to absorb and dissipate the energy of impact. The use of hip protectors is known to reduce hip fractures by as much as 70% amongst those of the population that use them. However, there is a general disinclination to wear the hip protectors which are currently available. Hip protectors currently available are protective devices which fit around the end of the thighbone to absorb the energy of a fall. They typically comprise foam pads with or without a stiff or rigid support and these are typically held in place by a stretchy undergarment.

The design of hip protectors that can reduce the forces applied to the hip in a fall without being excessively bulky has proved difficult. We believe that if one attempts to use a stiff shell to divert the impact force through soft tissues around the hip, it is necessary to provide for the shell to stick out some way from the hip to accommodate travel of the shell into the soft tissues on impact. As a result, this type of protector tends to be bulky and may be uncomfortable in wear. Further, we believe that if one attempts to employ some kind of padding over the hip itself, the selection of padding material is very important. If the padding is too hard and stiff it will provide little protection and if too soft it will collapse quickly without cushioning the impact sufficiently. The aim of the padding is to slow down the moving body over a short distance as the padding collapses and to do this most effectively a constant force should be maintained as the padding collapses. Most materials require a small force to initially deform them, increasing as they are compressed further, and this militates against optimum protection because there is relatively little resistance to impact at the beginning and excessively large impact force at the end.

Not only is it important to provide a hip protector capable of satisfactory technical performance, it is also important to provide a design which is sufficiently attractive to induce a high level of compliance i.e. routine, regular wearing of the device by those most likely to suffer broken hips. It is desirable that the protector be sufficiently comfortable that patients do not object to wearing it during the night, because it is at this time that many elderly patients are most at risk of falling.

Reluctance to wear protection devices available to those most likely to suffer broken hips can be ascribed to one or more of various factors. For example, garments using them can be difficult to put on or remove by the elderly or frail, they may fit tightly enough around the waist to induce urge incontinence or generally be incompatible with continence aids or supports. They may also be too hot or otherwise uncomfortable to wear and be perceived as bulky and restrictive of movement as well as giving rise to unflattering shaping of outer clothing.

It is one of the various objects of the present invention to provide improved protection means acceptable for prolonged wear for protection of frail persons against impact fractures resulting from the wearer falling to ground.

We have now found that protection means may be provided which is capable of improving the prospects of a wearer surviving a fall without bone fracture of the protected body part and which exhibits improved comfort and aesthetic qualities for the wearer.

The present invention provides in one of its aspects protection means comprising a helix of plastics material having a length greater than its width and which is resiliently compressible when a force is applied to it in a direction normal to its length, the helix being composed of a strip of the plastics material of uniform cross section and having uniform diameter coils disposed at an angle to the length of the helix, the strip of plastics material having a first surface disposed as an outer surface of the helix and having two edges, a second surface extending from one edge of the first surface and a third surface extending from the other edge of the first surface, the second and third surfaces being inclined towards each other and the construction and arrangement being such that when a force is applied to the first surface of a coil of the helix at one side of the helix, the second and third surfaces of that coil of the helix may be urged in a direction to enter between the inclined surfaces of two adjacent coils of the helix disposed at the opposite side of the helix to the point of application of the force.

The word "comprising" where used herein is intended to encompass the notion of "including" and the notion of "consisting essentially of.

A helix for protection means according to the invention is preferably made by first extruding the plastics material in the form of a strip and then shaping the strip on a mandrel with appropriate heating and cooling of the material. Desired lengths of the helix may then be cut from the extrudate.

In protection means according to the invention, the cross section of the strip of plastics material is such that its second and third surfaces are inclined towards each other. Although any appropriate geometrical arrangement may be employed we prefer that the angle at which the second and third surfaces extend from the first surface is from 20° to 60°, preferably 40° to 50°. In the simplest form of strip, the second and third surfaces may meet together, but strips intended for processing by shaping on a mandrel preferably have a fourth surface, preferably generally parallel to the first surface, joining the second and third surfaces which is intended for contacting the mandrel and ultimately provides the inside surface of the helix. In this preferred configuration, the strip may be given its uniform cross section by extruding the plastics material through a die having a cross section of a regular trapezium of which the longer parallel side defines the first surface, the shorter parallel side defines the shape of the fourth surface and the sloping sides of the trapezium define the second and third surfaces of the strip. Preferably the first surface of the strip is from 2 to 10 mm long, more preferably from 3 to 7 mm, most preferably about 5.0 mm. Preferably the maximum distance between the first surface and the fourth surface or the joining of the second and third surfaces is in the range from 1.3 mm to 3.0 mm, more preferably from 2 mm to 2.5 mm most preferably about 2.2 mm. As a result of characteristics of the extrusion process and materials employed, the surfaces may blend one into the next to provide rounded.

In the helix of a protection means according to the invention the coils are of uniform diameter and disposed at an angle to the length of the helix, the coils being spaced apart by a distance which is preferably in the range 0 mm to 6 mm, more preferably 0 mm to 4 mm and most preferably about 1.0 mm; the diameter of the coils is preferably such that the diameter of the outside of the helix is from 10 to 20 mm, more preferably from 10 to 15 mm, most preferably about 12.5 mm.

In protection means according to the invention, the plastics material is selected for its mechanical properties and its contribution to impact resistance of the helix. The desired mechanical properties depend to some extent at least upon the dimensions of the strip and the configuration of the helix. Suitable plastics materials include thermoplastic elastomers. One preferred plastics material is a thermoplastic polyester elastomer supplied under the trade name Hytrel 7246 by El Du Pont De Nemours which is said to have a hardness of 72 Shore D (ASTM D 2240), an ultimate tensile strength of 45.8 MPa (ASTM D 638) and a flexural modulus of 570 MPa at 40°C (ISO 178). It has an elongation at break of 360 % (ASTM D368). This material is understood to have crystalline hard segments of terephthalate and amorphous glycol soft segments. It has thermoplastic properties and offers ease of processing to form the strip and helix using commercially available extrusion or injection moulding equipment. It is understood to be a butylene / poly(alkylene ether) phthalate copolyester. Other grades of Hytrel offer combinations of hardness, tensile strength, flexibility, resilience resistance to flex cracking and may be suitable alternatives in appropriate circumstances. We believe that among these plastics materials, suitable materials include those having a hardness of from 50 to 80 Shore D, a tensile strength of 40 to 55 MPa and / or a flexural modulus of 300 to 350. The materials may have melting points in the range 150°C to 225°C, and a specific gravity in the range 1.07 to 1.28. Other materials which have a good blend of such properties may be found to be suitable for example, acetal polymers. Among other thermoplastics suitable for extrusion and having a blend of properties including good impact resistance, high fatigue resistance to constant flexing of the helix during wear, flexural modulus at 25°C, toughness at 20°C and resistance to immersion in hot water as used in a washing operation, one may also mention acrylonitrile-butadiene- styrene copolymers, olefinic based thermoplastic elastomers and elastomer modified propylene polymers and co-polymers. Olefinic based thermoplastic elastomers tend to exhibit elastomeric performance of vulcanised rubber and can be processed as thermoplastics; these materials are available in various grades and may have, for example, specific gravities of about 1.84 or about 1.88 and exhibit tensile strength of about 5, 9 or 12 MPa, elongation at break of about 250%>, 700%> or about 800% and a flexural modulus of 0.005, 0.03 or 0.16 Gpa. Polypropylenes tend to be semi-crystalline, low density materials of high fatigue resistance which are easily melt-extruded to provide products of light weight; elastomer modified polypropylenes having for example, about 10 to 15% elastomer, have enhanced low temperature impact resistance as compared with polypropylene. Suitable elastomer modified polypropylenes include those having a specific gravity of about 0.9, a tensile strength of about 23 MPa, elongation at break of about 300 % to about 350% and a flexural modulus of about 0.75GPa. Acetal materials, as well as these elastomer modified polypropylenes when containing finely divided filler, tend to be a little stiffer and also have higher temperature resistance.

Protection means according to the invention may comprise one or more lengths of the helix containing from about 10 to 20 coils per length. We have found that using such lengths of the preferred helix, a single layer of them spaced closely together is sufficient to provide adequate protection for the hip in many fall situations. We prefer to arrange the lengths of helix in side by side relationship for example as a series of parallel pieces of the helix although other configurations using one or more lengths of helix are envisaged. Preferably the lengths of helix are held spaced from each other as closely as possible and no further apart than the inner diameter of the helix. Using the preferred helix, we prefer to secure the lengths a distance of from 0 mm to 5 mm, more preferably 0 mm to 3 mm most preferably about 1 mm apart. Conveniently the lengths of helix may be secured to or in a fabric support, being of woven, non-woven or knitted material, for example by stitching, welding or adhesive. The fabric selected is preferably permeable to air and moisture and not unduly affected by laundering. One preferred fabric is a woven material formed in its manufacture to include closely spaced integral compartments into which the lengths of helix may be inserted and so secured in the fabric. By such techniques one may provide protection means according to the invention in the form of a protector of sufficient size to cover the body part which is to be protected, for example about 100mm by about 200mm for a hip joint. Such a protector may be secured to the body in any convenient way as by straps or a suitable garment. In one aspect, the protector may take the form of an article of a size commensurate with the body part to be protected and constructed so as to be inserted in a pocket of a garment or between garments in which it is held against the body. Alternatively, the protector may be constructed within a garment during its manufacture.

The helix employed in protection means according to the invention absorbs and dissipates energy of impact such as occurs in a fall. Whilst not wishing to be bound by any particular theory, we believe that when protection means according to the invention is impacted in a falling situation, the force applied widthwise of each length of the helix is taken by the first surface of one or more of its coils which in turn is induced to move across the width of the helix. The second and third surfaces of this or these coils are thus urged through and across the helix towards corresponding surfaces of coils at the opposite side of the helix. This activity dissipates some of the energy of the fall. In the case of a severe impact, we believe the energy is further dissipated or absorbed by frictional contact between the engaging inclined (second and or third) surfaces of the strip and potentially, consequent wedging apart of the coils. We believe the helix also may become significantly curved along its length during such impact, which also serves to dissipate energy. Some of the impact is transferred to adjacent lengths of the helix which serve to support the impacted coils of helix receiving the initial impact.

If desired, protection means according to the invention may comprise a layer of material to enhance the protection characteristics, for example a layer of fabric having impact resistance properties, which may be attached for example by sewing. Also, one may provide a filler element within the helix which serves to enhance the impact resistance. The filler element may be provided, for example, by one or more rods or tubes of resilient material, for example of plastics rubber or foamed material.

We understand that the force required to break the femur has been determined to be about 4100N in elderly osteoporotic subjects. By appropriate selection of the configuration and dimensions of the helix and of the plastics material, one may provide protection means offering suitable protection against such a force.

The invention provides in another of its aspects Protection means for a joint of the human body, for example a hip joint, which is flexible, permeable to air and moisture and capable of dissipating forces of impact arising from the wearer falling at least to the extent of avoiding bone fracture at that joint due to the fall, the protection means comprising a protector of sufficient size to cover the joint which comprises a single layer of one or more lengths of helix of plastics which helix is resiliently compressible when a force is applied to it in a direction normal to its length, the length or lengths of helix being held on or in a fabric support and arranged so that portions of helix are closely spaced together to form a layer sufficient to extend over the body surface at the joint to be protected, the helix being composed of uniform diameter coils of a strip of the plastics material of uniform cross section having a thickness of 1.3 to 3.0 mm, a width of 3 to 7 mm provided by a first surface disposed at an outer surface of the helix and the strip having surfaces extending at an acute angle from the first surface.

Protection means according to the invention may be used to protect a joint, in particular a hip joint. It is envisaged that the protection means may be used for protection of other parts of the human or animal body for example elbow, knee, ankle, wrist or shoulder joints or head leg or arms. Protection means according to the invention may be provided which is not only efficient in protecting body parts on impact, but also light in weight, flexible and permeable to air and liquids and sufficiently thin to enable unobtrusive, comfortable use under outer clothing, thereby offering better user compliance than heretofore. Protection means according to the invention has various other advantages, for example it may be laundered using conventional domestic washing machines and detergents.

In order that the invention may become more clear there now follows a description to be read with the accompanying drawings of two preferred protection means according to the invention selected for description to illustrate the invention by way of example. In the drawings,

Figure 1 is a sectional view of a die employed to produce strip material for use in the invention,

Figure 2 is a diagrammatic end view of a helix of plastics material for use in the invention,

Figure 3 is a diagrammatic view in section substantially along the axis of the helix of Figure 2,

Figure 4 is a view of a portion of the first illustrative protection means showing several pieces of helix located in a fabric,

Figure 5 is a schematic plan view of the first illustrative protection means, Figure 6 is a front view of a second illustrative protection means in the form of an undergarment, and

Figure 7 is a rear view of the second illustrative protection means.

Each of the first and second illustrative protection means comprises several portions of a helix (20) of plastics material having a length greater than its width. The helix (20) was made by extruding a thermoplastic polyester elastomer supplied under the trade name Hytrel 7246 by El Du Pont De Nemours through a die (10) as shown in Figure 1 and then winding the strip so formed on a mandrel using conventional techniques for moulding and forming thermoplastics. The aperture of the die (10) has a cross section of a regular trapezium having a longer parallel side (12), a shorter parallel side (14) these being joined by two sloping sides (16, 18) each disposed at an angle of about 43° to the longer parallel side (12). Although not so shown, the corners between the surfaces 12 and 16 and 12 and 18 are somewhat rounded so that the extrusion has "smooth comers". The extruded strip made by extrusion of the plastics material through the die, is of uniform cross section and has a first surface (12') and has two edges, a second surface (16') extending from one edge of the first surface and a third surface (18') extending from the other edge of the first surface (the second and third surfaces being inclined towards each other and forming an acute angle with the first surface) and a fourth surface (14') parallel to the first surface, corresponding to the cross section of the die (10). The first surface (12') of the strip is about 5.0 mm long, the fourth surface (14') of the strip is about 2.0 mm long and they are spaced apart by about 2.2mm.

The helix (20) is formed by winding the plastics strip on a cylindrical mandrel with the fourth surface (14') contacting the mandrel surface. The strip is wound uniformly, with adjacent coils spaced apart by about 1.0mm and thus at an angle of about 20° to the axis of the mandrel. The diameter of the mandrel is such that the helix has a uniform cross section having an overall diameter of about 12.5 mm and an internal diameter of about 8.1 mm.

Thus the helix (20) (Figures 2 and 3) is composed of a strip of the plastics material of uniform cross section and having uniform diameter coils disposed at an angle to the length of the helix. The first surface (12') of the strip is disposed as an outer surface of the helix and the second (16') and third (18') surfaces being inclined towards each other and joined to the fourth surface (14') which is disposed at the inner surface of the helix. The helix (20) may flex along its length and is resiliently compressible across its width. When a force is applied to it in a direction normal to its length, the force is applied to the first surface (12') of a coil of the helix at one side of the helix, that coil may be induced to move across the width of the helix and its second (16') and third (18') surfaces urged in a direction across the helix to enter between the inclined surfaces of two adjacent coils of the helix disposed at the opposite side of the helix to the point of application of the force. In the case of a severe impact, we believe the second and third surfaces may engage in the manner of a wedge.

The first illustrative protection means (Figures 4 and 5) is a protector (30) of a size (approximately 100 mm by 200 mm) suitable for application to a hip. It comprises a single layer of eleven pieces of the helix (20). They are spaced closely together in side by side, parallel relationship. They are secured in position in a woven fabric (32). The fabric (32) is woven to include closely spaced integral compartments joined at (34) (Figure 4) into which the lengths of helix (20) are inserted and so secured in the fabric. Such a protector may be secured to the body in any convenient way as by straps or in a pocket in a suitable garment. A layer of padding material (36) is secured on one outer surface of the fabric.

The second illustrative protection means (40) (Figures 6 and 7) is a garment suitable for wearing as an undergarment. It comprises a front panel (42) and a rear panel (44) each formed of knitted fabric and two side panels (46 and 48). The side panels are substantially mirror images of each other and are formed of the same woven fabric as used for the first illustrative protection means. Each contains twelve pieces of the helix (20) disposed as a single layer and spaced closely together in side by side, parallel relationship as in the first illustrative protection means. The front panel is of relatively loosely woven fabric so as to reduce pressure exerted on the stomach of the wearer. In use, the garment is worn in a similar manner to standard underwear but with the side panels being disposed to protect the hips.

Claims

CLAIMS:

1. Protection means comprising a helix of plastics material having a length greater than its width and which is resiliently compressible when a force is applied to it in a direction normal to its length, the helix being composed of a strip of the plastics material of uniform cross section and having uniform diameter coils disposed at an angle to the length of the helix, the strip of plastics material having a first surface disposed as an outer surface of the helix and having two edges, a second surface extending from one edge of the first surface and a third surface extending from the other edge of the first surface, the second and third surfaces being inclined towards each other and the construction and arrangement being such that when a force is applied to the first surface of a coil of the helix at one side of the helix, the second and third surfaces of that coil of the helix may be urged in a direction to enter between the inclined surfaces of two adjacent coils of the helix disposed at the opposite side of the helix to the point of application of the force.

2. Protection means according to Claim 1 wherein the plastics material is a thermoplastic elastomer.

3. Protection means according to Claim 1 wherein the plastics material is a butylene / poly(alkylene ether) phthalate copolyester.

4. Protection means according to Claim 1 wherein the angle at which the second and third surfaces extend from the first surface is from 20° to 60°, preferably from 40° to 50°.

5. Protection means according to Claim 1 wherein the strip has a fourth surface, generally parallel to the first surface, joining the second and third surfaces, which provides the inside surface of the helix.

6. Protection means according to Claim 1 wherein the strip has been formed by extruding the plastics material through a die having a cross section of a a triangle or regular trapezium of which the longer parallel side defines the first surface and the sloping sides of the trapezium define the second and third surfaces of the strip.

7. Protection means according to Claim 1 wherein the first surface of the strip is from 2 to 10 mm long, more preferably from 3 to 7 mm, most preferably about 5.0 mm.

8. Protection means according to Claim 5 wherein the maximum distance between the first surface and the fourth surface or the joining of the second and third surfaces is in the range from 1.3 mm to 3.0 mm, more preferably from 2 mm to 2.5 mm most preferably about 2.2 mm.

9. Protection means according to Claim 1 wherein the coils are spaced apart by a distance in the range 0 mm to 6 mm, more preferably 0 mm to 4 mm and most preferably about 1.0 mm.

10. Protection means according to Claim 1 wherein the overall diameter of the helix is from 10 to 20 mm, more preferably from 10 to 15 mm, most preferably about 12.5 mm.

11. Protection means according to Claim 1 comprising a single layer of lengths of the helix spaced closely together in side by side parallel relationship.

12. Protection means according to Claim 11 wherein the lengths are secured a distance apart of from 0 mm to 5 mm, more preferably 0 mm to 3 mm most preferably about 1 mm.

13. Protection means according to Claim 11 wherein the lengths of helix are secured to or in a fabric support, being of woven, non-woven or knitted material, for example by stitching, welding or adhesive.

14. Protection means according to Claim 13 wherein the fabric is permeable to air and moisture and not unduly affected by laundering and is a woven material formed to include closely spaced integral compartments in which the lengths of helix are held.

15. Protection means according to Claim 11 comprising a layer of material to enhance the protection characteristics and / or an adhesive coating to secure it to the body or a body garment.

16. Protection means according to Claim 11 in the form of a protector of sufficient size to cover the body part which is to be protected, for example about 100mm by about 200mm for a hip joint.

17. Protection means according to Claim 11 incorporated in a garment to overly a joint of a wearer of the garment.

18. Protection means for a joint of the human body, for example a hip joint, which is light in weight, flexible, permeable to air and moisture and capable of dissipating forces of impact arising from the wearer falling at least to the extent of avoiding bone fracture at that joint due to the fall, the protection means comprising a protector of sufficient size to cover the joint which comprises a single layer of one or more lengths of helix of plastics which helix is resiliently compressible when a force is applied to it in a direction normal to its length, the length or lengths of helix being held on or in a fabric support and arranged so that portions of helix are closely spaced together to form a layer sufficient to extend over the body surface at the joint to be protected, the helix being composed of uniform diameter coils of a strip of the plastics material of uniform cross section having a thickness of 1.3 to 3.0 mm, a width of 3 to 7 mm provided by a first surface disposed at an outer surface of the helix and the strip having surfaces extending at an acute angle from the first surface.

19. In a fabric garment having protection means for protecting a joint of the human body in the event of a fall, for example a hip joint, the use as the protection means of a layer of closely spaced portions of helix of plastics material as specified in Claim 1.