ZA201003538B

ZA201003538B - Penetration resistant material

Info

Publication number: ZA201003538B
Application number: ZA2010/03538A
Authority: ZA
Inventors: Stephen Mark Forber
Original assignee: Knitwire Trading (Pty) Ltd
Priority date: 2010-05-19
Filing date: 2010-05-19
Publication date: 2011-03-30

Description

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FIELD OF THE INVENTION . : This invention relates to a penetration resistant material . :

BACKGROUND TO THE INVENTION

Internationally crime statistics are rising, and the need for self protection has become a priority for most private citizens, police officials, private security guards and bodyguards.

Security guards and police officers are often placed in situations where they are atrisk of a knife or gun attacks, and protection from gunshot wounds, cuts and punctures are needed.

A conventional approach for providing increased protection against gunshot wounds is 15 . the wearing of a ballistic vest, bulletproof vest or bullet-resistant vest to assist in absorbing the impact from firearm-fired projectiles and shrapnel from explosions. These vests are worn on the torso, and the vests are made from many layers of woven or laminated fibres. These vests basically work on the principle that a bullet is captured by means of several layers of fabric, and the vests assist greatly in protecting the wearer from injuries caused by small calibre handgun and shotgun projectiles, and small fragments from explosives such as hand grenades. These vests can however be penetrated by sharp objects such as knife blades. ~ One method of protection against cuts by sharp objects is the wearing of hard-plate reinforced vests, which are mainly worn by combat soldiers, police tactical units and hostage rescue teams. These vests are resistant to penetration by a sharp object, but - are uncomfortable due to their weight, and the inflexibility of the material.

Some knife resistant garments rely on metal plates that are positioned to overlap one another. These type of garments are however heavy and cumbersome to wear.

Other protective garments comprise separate welded rings joined together to make a sheet of chain mail. Even though chain mail is effective in resisting cutting from blades, it is extremely heavy and expensive to manufacture. oo

Accordingly, there is a need for a garment that -is flexible, provides freedom of movement, has ventilation, and that protects a person against an attack with a blade : and other sharp pointed instruments.

The present invention seeks to provide a penetration resistant material that is flexible, cost effective and protects against injuries from blades and other sharp pointed instruments.

SUMMARY OF THE INVENTION

~ According to a first aspect of the invention, there is provided a knitted sheet material that is resistant to penetration by a sharp object, said sheet material being knitted from yarn comprising a metal wire and a strand of synthetic fiber. ~ Said wire and said strand of synthetic fiber may be continuous and intertwined.

The material may be textured.

The synthetic fiber may be fibrous, textured or a monofilament of plastic.

Co The synthetic fiber may be para-aramid synthetic fiber. © The wire may be stainless steel or galvanised steel.

The synthetic fiber may be Kevlar.

Astrand of fire retardant material or insulation material may be knitted withthe wire and : the synthetic fiber.

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The sheet may be flexible. -

The sheet may be used to manufacture a protective garment or a furniture cover.

The sheet may be anti-ballistic and may be resistance to heat, fire or abrasive wear.

According to a second aspect of the invention there is provided a method for manufacturing a sheet material that is resistant to penetration by a sharp object, said a method comprising knitting a sheet material with interlocking loops of yarn comprising a : 10 metal wire and a strand of synthetic fiber.

Said method may include intertwining said continuous wire and said continuous strand - of synthetic fiber. Co

Said method may include texturing said material.

Said method may include knitting a strand of fire retardant material or insulation material with the wire and the synthetic fiber.

Said method may include manufacturing a protective garment or a furniture-cover. :

DETAILED DESCRIPTION OF THE INVENTION :

The invention will now be described by way of non limiting examples.

According to the invention there is provided a knitted sheet material that is resistant to penetration by a sharp object, such as a knife. The material can be used for manufacturing a garment that will protect the wearer from possible injury caused by an electrical or manual cutting tool or blade. The material is knitted from yarn comprising a metal wire and a strand of synthetic fiber.

The:wire and the synthetic fiber strand are continuous, and intertwined with one another, both having different tensile strengths, elasticity, elongation and yield. -

The material can be knitted in such a manner that it appears textured. The appearance .of the material can also be changed by combing the fibers. 9

Ina preferred embodiment of the invention, the strand of synthetic fiber used is Kevlar (a registered Trademark of DuPont). Kevlar is a light, strong para-aramid synthetic fiber that although very light has a very high tensile strength-to-weight ratio. The Kevlar also : assist in making the sheet material more flexible. The synthetic fiber can also be fibrous, textured or a monofilament of plastic. Suitable synthetic fibers can be selected : from a wide range of natural and synthetic yarns. Preferably a non-abrasive material oo should be used to reduce the abrasiveness of the sheet material, thereby making it more comfortable when in contact with the skin or clothing fabrics. :

The wire can be stainless steel or galvanised steel. The wire should preferably have a a

Vickers hardness of at least 450 Hv 0.2, and should not be thicker than about 0.5mm.

A strand of fire retardant material or insulation material can also be knitted with the wire or ‘and the synthetic fiber to form a sheet material that can provide insulation and that is fire retardant.

Garments and furniture covers manufactured from the material as hereinbefore described are anti-ballistic and resistant to heat, fire and abrasive wear.

The knitted sheet material can also be used to make covers for seating on public ) transport to minimize the damage caused by vandals who tear apart vulnerable parts of seating on public transport. : - The number of layers of knitted sheet material may be altered to obtain varying degrees ofresistance to attack. Providing multiple layers will however decrease the flexibility of : ‘the garment, while simultaneously increasing the weight and the cost.

The knitted sheet material has an area density of approximately 0.4 to 1.9 kg/m 2

Because stainless steel and galvanized steel are naturally rigid materials, the steel is oo drawn into a thin fine wire before knitted, thereby providing flexibility to the material to. make it easier to manipulate the material to be able to use it for making a garment or a furniture cover. : ~

A thicker wire with a higher tensile strength may be used to strengthen the sheet material, but this usually results in reduced flexibility of the material, and will not always be desirable. Furthermore, the thicker wire will result in the material being heavier and more difficult to handle. Another disadvantage of using a thicker wire is that the wire will be difficult to straighten after it has been wound into a reel or a spool

When a sharp object is pushed into a sheet material comprising only knitted wire, the i 15 individual loops of the material give little resistance to sideways movement and the . loops of the knitted material forming the stitches are pushed sideways to open. When sufficient force is put behind the sharp object, the stitch being deformed by the sharp object tends to pull wire from neighboring stitches allowing the stitch to deform larger thereby allowing the object to penetrate the material without cutting or breaking any of the strands of wire. However, the strand of synthetic fiber knitted with the wire prevents the sideways movement of the individual loops of the material, thereby resisting the penetration of the sharp object, with the wire providing protection against cutting.

Furthermore, when a sharp object is used to attempt to cut the sheet material, the interlocking loops of the material resists cutting ’ ~~ The strand of synthetic fiber frictionally secures the stitches of the knitted material to one another, thereby preventing sideways movement of the individual loops of the : stitches and penetration by a sharp object. The strand of synthetic fiber does nothave to be cut resistant, but must be inherently resilient to prevent the sideways movement of the stitches. However, by using Kevlar the resistance to cuts will be improved, as Kevlar oe also has an inherent resistance to penetration.

& : oo The synthetic material thus protects the sheet material from deformation, and the wires prevent the cutting of the material. oo The sheet material can be laminated or coated with a plastics material to fill the spaces between the individual stitches. This could improve the handling of the material for certain applications. h The knitted sheet material is a self supporting sheet, and has the ability to distribute : stresses over a large area.

In order. to provide increased cut-resistance without significantly increasing the difficulties of knitting, said cut-resistant structure may be formed by two or more lengths : of wire, which are co-knitted. Co-knitting involves knitting more two strands of material’ simultaneously, in that both strands of material are fed into the knitting machine simultaneously, and pass side by side through the knitted sheet. The feed can be from separate bobbins in a parallel feed. The knitting machine may be a circular knitting machine producing a tube, which can be slit and opened out to provide a single layer or, alternatively, the tube may be flattened to provide a double layer of material. A knitting machine can also be adjusted to knit a preferred shape such as a garment.

The invention will now be illustrated with reference to the following example:

Example: :

Sheet material was knitted with two lengths of wire, and a strand of 1640 denier Kevlar.

The wire was 0.7% stainless steel 304, that was 0.32mm in diameter, hard drawn and with strength of 139-142 tons per sq in (45-46 MN/m?) tensile.

The sheet material was formed by co-knitting on a circular knitting machine. The machine was fed simultaneously with two continuous wires and one continuous strand of Kevlar. The machine was set to produce knitting with loops spaced by approximately : 4 to 6 mm. A tube was produced, with each length of wire having a length of Kevlar

FON running along with it. Specifically, each loop of the knitted tube had three approximately parallel components two of wire and one of Kevlar.

The knitted tube was flattened. Each side of the tube had an area density of 1.772kg/m>. The tube was then cut into the shape of a vest, and all visible wires were covered with material. The vest also comprised facing layers of fabric and a conventional ballistic pack consisting of 21 layers of woven para-aramid fibre.

The complete vest was subjected to a standard stabbing test in which a standard knife was dropped onto the vest from 1.5 meter with a loading of 3kg. The knife penetrated the vest by less than 5mm, which is within acceptable prescribed limits. :

For comparison purposes, a vest similar to the illustrative example was prepared with only the two wires. Each layer of the component had an area density of 1.433kg/m?.

The standard stabbing test was repeated, and the knife penetrated the vest with11 mm.

The recommended limit for a safety vest is 5 mm.

Claims

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1. A knitted sheet material that is resistant to penetration by a sharp object, said sheet material being knitted from yarn comprising a metal wire and a strand of synthetic fiber.

2. A sheet material as claimed in claim 1, wherein said wire and said strand of : synthetic fiber are continuous. :

3. A sheet material as claimed in claim 1 or claim 2, wherein said wire and said strand of synthetic fiber are intertwined.

4. A sheet material as claimed in any one of claims 1 to 3, wherein said material is textured.

5. A sheet material as claimed in any one of the previous claims, wherein said - synthetic fiber is fibrous.

6. A sheet material as claimed in any one of claims 1 to 5, wherein said synthetic : 20 fiber is textured. :

7. A sheet material as claimed in any one of claims 1 to 6, wherein said synthetic fiber is a monofilament of plastic.

8. A sheet material as claimed in any one of claims 1 to 6, wherein the synthetic : fiber is a para-aramid synthetic fiber.

9. A sheet material as claimed in claim 8, wherein the synthetic fiber is Kevlar.

10. A sheet material as claimed in any one of the previous claims, wherein the wire is stainless steel.

11. A sheet material as claimed in any one of the previous claims, wherein the wire is galvanised steel. Co

12. A sheet material as claimed in any one of the previous claims, which includes a

A Ly ‘ : strand of fire retardant material knitted with the wire and the synthetic fiber.

13. A sheet material as claimed in any one of the previous claims, which includes a strand of insulation material knitted with the wire and the synthetic fiber. ; :

14. A sheet material as claimed in claims 12 and 13, wherein the sheet material is resistant to heat and fire. :

15. Asheet material as claimed in any one of the previous claims, wherein the sheet 10 material is resistant to abrasive wear.

16. Asheet material as claimed in any one of the previous claims, wherein the sheet material is flexible.

17. Asheet material as claimed in any one of the previous claims, wherein the sheet material is anti-ballistic. . 18. A method for manufacturing a sheet material that is resistant to penetration by a sharp object, said method comprising knitting a sheet material with interlocking loops of yarn comprising a metal wire and a strand of synthetic fiber. .

18. A method as claimed in claim 18, which includes intertwining said wire and said strand of synthetic fiber. :

20. A method as claimed in claim 18 and claim 19, which includes texturing said ; material.

21. A method as claimed in any one of claims 18 to 20, which includes knitting a strand of fire retardant material with the wire and the synthetic fiber.

22. A method as claimed in any one of claims 18 to 21, which includes knitting a strand of insulation material with the wire and the synthetic fiber. :

23. A method as claimed in any one of claims 18 to 22, which includes manufacturing a protective garment from the sheet material.