TECHNICAL FIELD OF THE INVENTION
This invention relates generally to footwear sole or insole insert for the footwear which provide protection against penetration of sharp objects and make it puncture proof under typical conditions such as those requiring protection of all types of spikes hole traps.
BACKGROUND AND THE PRIOR ART
Many industrial and defense related activities often present the danger of sharp object penetration through the soles of footwear worn by workers as well as the soldiers. A most common example is the presence of nails around construction sites. Another, perhaps more important situation is when the soldiers have to tread long distances in deep forests and rocky mountains infested with stones with sharp pointed edges. In combat areas and in guerrilla warfare, Naxalites and army of the enemy is known to be spreading spikes and nails as well as spike hole traps on known passages to check the advance of soldiers. Such eventualities can result in large numberof injuries to workers and soldiers with resultant defeat in the war besides lost man-hours,human suffering and mounting medical costs for treatment.
Development of protective footwear has therefore attracted the attention of many inventors prior to this which would lessen the danger of injury due to puncturing the sole of footwear in the above referred situations. Many different approaches have been tried in the past to enhance the degree of protection in the footwear for such use without compromising the comfort and wearability but a perfect solution has thus far been elusive.
Many standards have also been laid in different countries for variety of safety features to be followed in footwear for specialized use such as i) slip resistant, ii) toe protection iii) electric shock-proof, iv) water-proof v) mid-sole penetration resistant. The safety shoes that meet the

required specification the latest ASTM standard F2413-18 are allowed to mark a symbol of 'PR' for 'Puncture Resistant' along with above standard number.
The Indian standard IS 15298:2011 (equivalent to ISO 20344 : 2004)also provides test procedure and performance limits for such soles on a test equipment having a pressure plate for holding the sample sole in which a test nail with a truncated sharp end drives through with a comprehensive force up to at least 2000N.
Most of the attempts to create protective footwear have resulted in the creation of footwear which is puncture resistant rather than puncture proof—the typical devicesfailing to prevent puncture by sharp objects at high impact energy.
In most of the prior art patents we found that 'puncture resistance' was achieved where a 230 pound individual jumping from a height of tenfeet generates approximately 60 foot pounds (81.3 joules) onthe ball of the foot and approximately 80 foot pounds (108.5joules) on the heel of the foot. Exceeding this limit has been the goal of a puncture proofsole or insert in this invention.
Many prior art patent devices of this nature were observed such as the following:
US4271607 teaches incorporating a single metal plate of 0.02 inches thickness in the sole and yet it was not puncture proof.US4888888 describes a sole with a multiple small plates, some of which joined with hinges to provide flexibility and comfort for the user.US5003709 teaches the use ofmultiple thin foils of amorphous metal to enhance the penetration preventionwithout sacrificing flexibility. However, this does not provide puncture proof sole. Further, US5285583 provides a protective insoleincorporating a plastic layer in and a fabric layer inside the sole.
US5546680 discloses a rubber boot with a protective plate embedded in the sole to prevent penetration of a sharp object into the wearer's foot. However, this product is not quite suitable for the purpose this invention was made.

US6151803 describes a curved insole made of polymer fiber to increase its flexibility. The insole is stated to be capable of withstanding penetration of nails and other foreign objects.US6167639 uses puncture resistant fabric Kevlar in its inner and outer sole.US6178664 uses a multiple layers of stainless steel sheets with greater number in the heel region of the sole to achieve prevention of puncturing due to sharp objects. None of these patents serve the purpose for which this invention was made.
US2005138847 uses a puncture-resistant layer of steel with a cushion layer of polyurethane above it in a special design. US2008184601 teaches the use of carbon fiber composite material mixed with a thermosetting epoxy to provide reinforced strength. The overall weight is light though, the overall cost of the product is high. WO2020089553 uses a multi-layer of metals in its shoe sole design to achieve prevention of puncturing due to sharp objects. CN110916286 describes a multi-functional protective shoe with anti-skid and anti-puncture properties using Kevlar materials only keeping the user comfort in mind.
WO 00/41583 of El. Du Pont De Nemours & Co. describes a puncture resistant footwear sole composite with a plurality of layers of woven aramid yarn fabric combined with a matrix resin that is capable of resisting a force greater than 1100N.
It was observed that puncture resistant fabric, Kevlar or an equivalent fabric along with steel plates have widely been used in different configurations as insole or embedded into the sole. In our experimental designs, we observed that unless the thickness of steel plates is appreciably increased, the 'puncture-proof quality of the sole is not achieved and even so, the user comfort is severely compromised. Therefore, a need was felt to invent a light weight puncture proof sole for shoes that can be safely used in combat areas by the soldiers.
OBJECT OF INVENTION
It is an object of this invention to provide a shoe sole that is puncture-proof and can easily be integrated with all shoe sizes used by soldiers in combat operations.

It is yet another object that this invention can suitably be customized to produce puncture-proof insole (insert) to be used with normal shoes of the soldiers.
It is yet another object of this invention that the puncture-proof sole or insole is such which is relatively lightweight and the user remains comfortable even after its prolonged use.
SUMMARY OF THE INVENTION
The present invention comprises a puncture-poof sole or insole for a shoe including multiple layers of a tightly woven fabric formed from high tensile strength synthetic or polymeric fibers. Preferred fibers include polyaramid fibers, such as Kevlar® along with titanium sheet. In the preferred embodiment, the layers of this puncture resistant material along with titanium sheet are secured between an inner and outer layer of the sole of the shoe. The layers of puncture resistant fabric and titanium sheet may be secured together within a covering material of PU resin or other types of flexible sole making material like rubber or a combination of synthetic rubberor dual density sole in combination for stuck on or injected sole making process.
STATEMENT OF INVENTION
This invention provides a puncture-proof sole or insole for the footwear used by industrial workers in demanding situations and by the soldiers in combat operation in deep forests against spike hole traps
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING(S)
Figure 1 shows the arrangement of sheets embedded in PU sole or other types of flexible sole making material like rubber and combination of rubber or synthetic rubber in single or double density sole for stuck on or injected sole making processs, of this invention

Figure 2 shows the arrangement of sole making of left and right shoe by placing desired number of. Sheets of Kevlar and titanium in appropriate grooves and then embedding in a typical PU sole or rubber or synthetic rubber or combination of dual density soles of this invention
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the present invention will now be described with reference to the drawing and various components used in making of the sole or insole of this invention. Based on background research and upon review of approaches adopted by previous inventors, it was identified that we may use poly-urethane sole or other flexible sole material like rubber and dual density sole suitably embedding other reinforcing materials like multiple layers of Kevlar® fabric and a metal sheet that can resist a puncture of spike.
Kevlar®, a polymeric fabric produced and sold by E.I, DuPont de Nemours, Inc. (later merged with Dow Chemicals), is widely used in many safety shoes for its excellent tensile strength-to-weight ratio. It is also widely used in body armour and so-called 'stab-proof clothing today. This was an essential component in our materials of choice. It is commercially produced from the monomers 1,4-phenylene-diamine (para-phenylenediamine) and terephthaloyl chloride in a condensation reaction yielding hydrochloric acid as a byproduct. The result has liquid-crystalline behavior, and mechanical drawing orients the polymer chains in the fiber's direction.
Kevlar® is known to resist very high impact, close to bullets due to its molecular structure adopting a shape of a long twisting coil.
Comparing various metal candidates, we compared titanium and steel for use as a layer in the sole. Given its strength, titanium is remarkably light. When compared to steel in a strength-to-weight ratio, titanium is far superior, as it is as strong as steel but 45% lighter. In fact, titanium has the highest strength-to-weight ratio of all known metals. Among the various grades of titanium available, we picked up the grade 5, even though the grade 2 is most commonly used commercially. The grade 5 titanium is not pure titanium, but is an alloy, that does make it

harder than pure titanium and it served our purpose admirably. In our test results, we found 0.5 to 0.6 mm titanium sheet of grade 5 gave the optimum results.
The use of poly-urethane in shoe soles is commercially well established. PU is now a new industry standard for shoe soles gaining more popularity over leather, rubber, EVA or PVC soles. It has lower density than other soles along with a soft texture and high elasticity. This makes it perfect for foot comfort. It not only provides great wear and tear resistance but also has good bending resistance and high hardness along with great shock absorption. Given these qualities and desirable properties along with its affordability, it is one of the preferred materials for our sole making although other flexible sole making material like rubber and synthetic rubber combination and double density sole is also used as a base material depending on specific application.
The polyurethane is produced by the reaction of an isocyanate prepolymer, such as methylene diphenyl isocyanate, and a polyol component in the presence of heat and an organometallic catalyst. It is common practice to prepare PU soles by pouring of these liquids (mixture poly isocyanate and polyol) into readymade hot mould by nozzles fitted into the tubes carrying PU liquids.
The moulds are generally heated in steam at a temperature of 180°C for about 10 - 20 minutes before pouring the PU liquids and retained in hydraulic steam machine for another 10 minutes till the polymer sets in. Before pouring the liquid, moulds are cleaned and coated with a multi-component liquid and then mould-realizing agent is applied inside the mould. This process makes PU duly laminated with expendable poly styrene (EPS).
In commercial operations of shoe making with PU soles, anupper (prepared separately) is lasted on the last of the mould for PU casting. And the last with the upper is placed on to the mould into which the PU liquids are poured. The computer of the machine controls the volume of PU liquid, pouring time, time period and the mould temperature. What comes out is a complete shoe with a PU sole along with an upper fixed on to it.

In another embodiment of this invention, a direct injection process is used where the sole with a combination of Kevlar® and titanium sheets is moulded directly onto the lasted upper. Here a soling material is liquid by heating or chemical reaction and is injected into a shoe mould, from which it is ejected once it has set to the shape of the mould. In this process, besides PU used for making single or double density soles as described above, combinations of i) rubber and PU for single or double density sole ii) rubber and phylon for single or dual density soles and iii) rubber and thermoplastic rubber (TPR) or any other polymer based soles can be used.
In yet another embodiment, all the above material combination for sole making along with combination of Kevlar® and titanium sheets, can also be used in stuck-on mode besides pouring and injection moulding processes as described above.
The Best Mode of Perfomance of this Invention:
To perform this invenion in the best mode, several experimental soles with different combination of sheets as described above were created and standard penetration tests were carried out with the aim of creating a sole that can withstand the penetration force within the range of 1000 to 2500N.
To achieve the desired performance limits, we used the same commercial system of shoe making with PU soles along with Kevlar® and titanium sheets. Appropriate sheets of Kevlar® and titanium are cut into the sizes and shape of desired shoes. During our trials, we found that different combinations of the layers of Kevlar® above and below the titanium resulted in different composition of the soles and their inherent strength to withhold the penetrating nail.
A set of titanium sheet (1) having 0 to 10 layers of Kevlar® sheets (2) above it and 0 - 10 layers below as shown in Figure 1 were placed into the mould (3/3a) of the shoe sole as in Figure 2 before pouring the PU liquids into the mould (4 /4a). . Some of these iterations of varying kevlar® sheets above and below a titanium sheet of 0.6 mm are tabulated below:

s.
No. No. of Kevlar® sheets used above the titanium sheet No. of Kevlar® sheets used below the titanium sheet Penetration test results -force tolerated in Newton
1 7 3 1691-2195N
2 3 7 846-201 ON
3 - 10 2240-2490N
4 10 - 2676-2862N
5 10 - 2130-3160N
Thus, we prepared the desired shoes of various sizes with experimental soles of this invention and tested for their performance. The shoes prepared with the above soles of this invention were tested as per the standard test procedure of ISO: 20344:2011 (the latest ISO standard) to its equivalent Indian standard which gave us the desired results:

CLAIMS

We claim

1. A spike proof footwear sole component comprising a plurality of layers of a polymeric fabric below and above a metallic sheet held adjacent to each other and embedded in a polymeric matrix resin.
2. A spike proof footwear sole component of Claim 1 wherein the polymeric fabric may preferably be a Kevlar® sheet used in 0 to 20 numbers.
3. A spike proof footwear sole component of Claim 1 wherein the metallic sheet is preferably made up of pure titanium or any of the titanium alloy and more preferably titanium grade 5 with the thickness between 0.3 to 0.9 mm used in 1 to 4 numbers
4. A spike proof footwear sole component of Claim 1 wherein the polymeric matrix resin is polyurethane prepared onsite by pouring the PU liquids (mixture of poly isocyanate and polyol) into readymade hot mould by nozzles fitted into the tubes carrying PU liquids.
5. A spike proof footwear sole component of Claim 1 wherein the polymeric matrix resin is flexible sole material of rubber.
6. A spike proof footwear sole component of Claim 1 wherein the polymeric matrix resin is flexible sole material made up of a combination of rubber and PU in single or double density.
7. A spike proof footwear sole component of Claim 1 wherein the polymeric matrix resin is a combination of rubber and phylon in single or double density.
8. A spike proof footwear sole component of Claim 1 wherein the polymeric matrix resin is a combination of rubber and thermoplastic rubber (TPR).

9. A spike proof footwear sole component of Claim 1 wherein the polymeric matrix resin is a combination of natural and synthetic rubber.
10. A spike proof footwear sole component of Claim 1 wherein the polymeric matrix resin is made with injection moulded single or dual density material.
11. A spike proof footwear sole component of Claim 1 which when tested for its penetration test as per ISO or BSI standards can withstand a penetrating force between 1000 to 3000N