WO2003000049A1

WO2003000049A1 - An improved horseshoe

Info

Publication number: WO2003000049A1
Application number: PCT/AU2002/000814
Authority: WO
Inventors: Brent James Cran; Alan Charles Tait; Gary Robin Tait; Thomas Harry Hill
Original assignee: Brent James Cran; Alan Charles Tait; Gary Robin Tait; Thomas Harry Hill
Priority date: 2001-06-21
Filing date: 2002-06-21
Publication date: 2003-01-03

Abstract

A plastic horseshoe is formed with a metal insert embedded in the plastic, the insert having a toe clip. The horseshoe can be made from polyurethane.

Description

AN IMPROVED HORSESHOE

FIELD OF THE INVENTION This invention relates to an improved horseshoe. In particular, the invention is directed to a horseshoe can be formed principally of a plastic material (for instance polyurethane), and which can be formed with a small metal insert to improve the characteristics and properties of the horseshoe.

BACKGROUND ART Conventional horseshoes are normally made of metal. Traditionally, horseshoes were made of cast iron, but in recent times, lighter alloys have been used, particularly for racing horseshoes.

However, metal horseshoes have several inherent disadvantages. For example, if a shoe (sometimes called a "plate") is thrown by a horse during a race, it can cause serious personal injury to a following jockey or to another horse. A thrown shoe can also cause serious injury to another limb of the same horse, and even if the metal shoe remains attached to the hoof, it can cause injury to another limb of the horse if that hoof strikes the limb, e.g. if the horse stumbles or falls.

Often, the shoe is bent when it is thrown and therefore has an upstanding portion when it rests on the ground. Other horses may puncture the frog of a hoof on the exposed upstanding end of a thrown shoe.

The weight of a metal shoe is also a significant disadvantage, particularly when racing.

Metal plates also do not permit flexing or spreading of the hoof.

In order to overcome such problems of metal shoes, plastic horseshoes have been suggested. For example, U.S. patents 3,469,631 and 3,490,536 describe horseshoes made from polyurethane. However, most polyurethane compounds are not considered to be entirely suitable for horseshoes. Although horseshoes of conventional polyurethane compounds permit spreading of the hoof on impact, the flexible polyurethane does not limit the spreading action, thereby leading to cracking or splitting of the hoof.

To overcome this problem, it has been suggested to construct horseshoes from a combination of polyurethane and metal components. For example, U.S. patent 3,519,079 describes a plastic horseshoe having a pre-stressed transverse tension bar to resist overspreading of the hoof. U.S. patent 3,907,036 describes a racing horseshoe comprising a plastic sole plate within which is embedded an aluminium horseshoe. U.S. patent 4,580,637 describes a multi-component horseshoe having segments formed from plastics material injection moulded onto steel inserts. U.S. patent 4,972,909 describes a moulded plastic horseshoe having a core segment of fibreglass reinforced polyurethane encapsulated in clear polyurethane. However, these particular composite horseshoes can be relatively difficult to construct, and are expensive.

Some plastic horseshoes have been specially shaped (e.g. slipper-shaped) in an effort to compensate for the otherwise unsatisfactory stiffening properties of pure polyurethane horseshoes, and examples can be found in U.S. patents 4,503,914, 4,189,004, 4,513,824, 4,237,981 , and 4,892,150. Such shaped slipper or sock type shoes give rise to other disadvantages however, such as increased weight and cost, and difficulty in shoeing.

U.S. patent 3,921 ,721 describes a method of attaching plastic horseshoes using thermosetting adhesive, but such method requires too specialised equipment to be universally applicable, and is too time consuming to be acceptable.

Finally, U.S. patent 4,957,168 describes plastic horseshoes made of polyphenylene sulfide resin which possesses the unique property of rendering a metallic sound. Although such shoes are much lighter than conventional metal shoes, they are considered to be mainly novelty items and not designed for horseracing.

Patent JP 269515 A (Nitta KK) makes use of paraphenylene diisocyanate as the isocyanate component of the polyurethanes used to make rollers with a frictional surface. The specification also makes use of 1 ,6-hexane polycarbonate polyol as part of the prepolymer mix, whose polarity contributes to the frictional properties of the roller. The resultant polymer contains a structural unit which is linear (carbamate side chains are 180° relative to each other) and planar. Hence the repeating units are more closely packed together and can form a fairly dense resin composite.

The structure of this polyurethane results in a product of exceptional hardness (Shore D value = 94). Since polycarbonates are thermoplastics characterised by their toughness, the hardness of this product described in patent JP 269515 A is also due in part to the inclusion of a polycarbonate polyol in the prepolymer mix. However, the hardness value is too excessive to be used as a horseshoe.

Patents JP 285508 (Toyoda Gosei KK) and JP 285509 (Toyoda Gosei KK) make use of 4,4'-diphenyl methane diisocyanate as the isocyanate component in producing the foaming composition for a polyurethane steering wheel. The paint composition which is also described in the patent uses aliphatic polyisocyanates as the isocyanate component. The isocyanate derived sub-unit comprises two aromatic rings joined by a methylene bridge. Although the structural unit is non-linear, there is a much greater degree of flexibility and free rotation about the methylene bridge which could explain the suitability of this compound for use as a foam, and furthermore, its unsuitability for use as a horseshoe.

Patent DE 007141 (Bottcher F GmbH) describes high temperature resistant rollers with a coating made from poly-2-oxazolidinone, isocyanurates and other additives. The patent abstract describes how the poly-2-oxazolidinone is prepared by the reaction of diepoxides with diisocyanates in the presence of a catalyst. Use of a diisocyanate to form a polymer is the only common factor with the other patent specifications. The type of diisocyanates and diepoxides used to form the poly-2-oxazolidinones are not specified, nor are the isocyanurates which are subsequently mixed in (along with other additives), so a general structure of the type of polymer patent DE 007141 describes cannot be given. However, the type of structure which results from such a sequence of chemical reactions is clearly very different to those structures described above. It is assumed that the rollers made from such a product are of comparable hardness to the rollers described in patent JP 269515 A (Nitta KK), thus also making it unsuitable for use as a horseshoe. The high temperature resistance properties are noteworthy, but would only be relevant in an industrial capacity. The frictional heat generated at the shoe by a 450kg horse repeatedly striking the ground is worth considering when designing a horseshoe, but it is unlikely that high enough temperatures would be reached to cause significant problems and render 'high temperature resistance' a necessary property of the polymer.

A horseshoe which is formed only of plastics material may have some disadvantages, particularly a possible lack of rigidity and strength to the front portion of the horseshoe. OBJECT OF THE INVENTION

The present invention is directed to an improved horseshoe . In particular, it is found that an improved horseshoe can be manufactured from a particular type of plastic, and suitably from a particular type of polyurethane. The present invention is also directed to a horseshoe which may be formed principally of plastic, but which is provided with a metal insert to provide improvements to the horseshoe.

In one form, the invention resides in a horseshoe which is at least partially formed of plastic material and which contains an insert which is at least partially in the plastic material, the insert being curved and being formed with at least one opening through which a nail can pass, the insert being positioned in the horseshoe such that the at least one opening is aligned with the at least one opening in the horseshoe through which a nail passes to nail the horseshoe to the hoof of a horse.

In another form, the invention resides a horseshoe which is at least partially formed of plastic material and which contains an insert which is at least partially in the plastic material, the insert containing a toe clip After much research and experimentation, we have discovered that particular types of polyurethanes provide advantages in the manufacture of horseshoes. It is an object of the present invention to provide an improved lightweight plastics horseshoe which overcomes or ameliorates the disadvantages of known horseshoes, or which at least provides the consumer with a useful choice.

In one broad form, the invention provides an improved horseshoe comprised substantially of a hot castable polyurethane. The polyurethane can be formed from the reaction of an aromatic diisocyanate with an aromatic diisocyanate reactive polyether.

Polyurethanes are condensation polymers formed from the reaction of polyhydroxylated compounds (or 'polyols') with polyisocyanates. The structural unit of polyurethanes can be described with the general formula.

Figure 1 where R is derived from the polyol component and X is derived from the isocyanate component, and can be aromatic or aliphatic in nature. The partial double bond character and polarity of the two carbamate functional groups which are present give a certain amount of rigidity to the structural unit, which is enhanced or reduced depending on the types of isocyanates (X) and polyols (R) used. After curing of the resin composite, this rigidity and polarity would be translated into the polymers physical properties i.e. hardness, shock absorbency, frictional character, etc.

The pre-polymers may contain toluene 2,4-diisocyanate (an aromatic diisocyanate), hence the structural unit of the horseshoe resin composite can be generally represented as in Figure 2. The polyol component R is a polyether polyol also present in the prepolymer mixtures. Polyurethanes prepared from toluene 2,4-diisocyanate have a non-linear, or 'bent' structural unit i.e. the carbamate side groups are at 120° relative to each other. The methyl group (CH3) on the aromatic ring sterically crowds the carbonyl oxygen of the adjacent carbamate side chain, hence the structural unit is also non-planar, or 'twisted'.

Figure 2

The non-linear and non-planar character of this structural unit (Figure 2), combined with the polarity of the polyether polyol R group, gives the resultant polyurethane a unique, stable structure which has physical 5 properties suitable for use as a horseshoe e.g. adequate hardness with good abrasive resistance. The polyurethanes made from toluene 2,4-diisocyanate have a significantly different structural unit arrangement from those polymers described in patents JP 269515 A, DE 007141 , JP 285508 and JP 285509, which use different isocyanates to give polymers of significantly different 0 physical properties and consequently would not be suitable for use as a horseshoe.

Suitably, the aromatic diisocyanate is toluene diisocyanate and a particularly preferred polyurethane is ADIPRENE* (* - registered trade mark of Uniroyal, Inc.) and the term ADIPRENE as used in this specification refers 5 to the family of urethane rubbers and resins sold under the ADIPRENE L, M and LW trade names.

Preferably, the horseshoe is constructed of ADIPRENE L-213 (or its Australian equivalent L-213A). It has been found that the selection of this particular urethane results in a horseshoe having exceptional strength, o wear resistance and lightweight properties.

Alternatively, the horseshoe can be made of VIBRATHANE**, ROYALCAST** 2505 (** trade marks of Uniroyal, Inc.), CONATHANE*** RN 1526 or DPRN 12098 (*** trade mark of Conap, Inc.), ETX 65D or ETX 80D (trade mark of ERA Polymers Pty. Ltd.), or ERAPOL ET-75D (trade mark of 5 ERA Polymers Pty. Ltd.). The horseshoes are suitably manufactured by hot cast moulding for which the above urethanes have been specially selected.

The invention is also directed to an insert which can be cast or moulded into a plastic horseshoe. The insert may comprise a metal insert. The metal insert may be substantially planar. The metal insert may comprise a forward toe clip, and an arcuate strap like portion which may extend from each side of the toe clip and in the horseshoe. This portion may be formed with a plurality of openings. The openings may align with nail holes in the formed horseshoe. BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings, in which

Figure 1. Illustrates a plan view of a plastic horseshoe fitted with a metal insert according to an embodiment of the invention.

Figure 2. Illustrates a plan view of a horseshoe this time better illustrating the metal insert.

Figure 3. Illustrates the metal insert.

Figure 4. Illustrates a side view of a horse hoof fitted with a horseshoe according to an embodiment of the invention .

BEST MODE As shown in the drawings, the horseshoe of the preferred embodiment of this invention is of conventional horseshoe shape. However, the horseshoe is of novel construction. In the embodiment, the horseshoe is formed of a polyurethane. Examples are as follows: EXAMPLE 1

A horseshoe is constructed from ADIPRENE™, a class of urethane compounds containing polyether toluene diisocyanate. Preferably, ADIPRENE L-213 (or its Australian-made equivalent L-213A) is used. Horseshoes constructed from ADIPRENE L-213 have several advantages over conventional metal horseshoes and other polyurethane horseshoes, including high load bearing capacity, hardness and abrasion resistance, high impact resistance, and oil, chemical, ozone and radiation resistance. Moreover, the mechanical properties of horseshoes constructed from ADIPRENE L-213 are much superior to those of conventional elastomers. By way of example, some of the principal properties of horseshoes constructed of cured ADIPRENE L-213 material (after vulcanization with MBCA curative) are as follows:

Durometer Shore "D" Hardness 73 (can range between 65-75)

Tear Strength (ASTM D-470) [KN/M] 25.4 Resilience Rebound 50%

Heat Distortion Temperature 85°C

Brittleness Temperature -65°C

NBS Abrasion - Index % of STD 500

Impact Resistance (notched Izod) [J/m] 800 Flexural Modules (ASTM D-790) [MPa] 800

Specific Gravity 1.19

ADIPRENE prepolymer is mixed with MBCA (4,4'-methylene- bis-(2-chloroani!ine)) curative in the ratio of approximately 100:26.6 by weight at a mix temperature of about 66°C . Moulds are preheated to approximately 100°C, and the heated liquid ADIPRENE polymer mixture is poured into the moulds. After pouring, the moulds and castings remain in an oven at approximately 100°C for a minimum cure time of typically six hours.

After curing, the cast horseshoes are removed from the moulds, and allowed to cool. Typically, the shoes are trimmed (if required), and inspected prior to packaging.

Horseshoes constructed substantially of ADIPRENE L-213 compound are stronger and more durable than conventional polymers and do not require added reinforcing. In addition, horseshoes constructed substantially of ADIPRENE L-213 resin possess all the safety features of polymer horseshoes over conventional metal shoes. If an ADIPRENE horseshoe is thrown, it is less likely to cause injury if it strikes another limb of the horse, or a following jockey. The flexibility of the ADIPRENE horseshoe ensures that if another horse steps on a thrown shoe, the shoe will not puncture the frog of the horse's hoof.

The ADIPRENE horseshoes also have practical benefits in use. For example, the weight of an ADIPRENE horseshoe is approximately 32 grams as compared to 86 grams for a known metal racing shoe. The weight saving is a considerable advantage in horseracing. The resilient nature of the ADIPRENE material also results in a springing effect in the shoe, and tests have demonstrated that it reduces shin soreness. Example 2 ERAPOL* ET-75D is mixed with CONAP CONATHANE** RN-

1526 in the ratio of 3:1 by weight.

* - (a Trade Mark of Era Polymers Pty. Ltd. of 26 Byrnes Street, Botany, New South Wales, Australia)

** - (a trade mark of Conap Inc. of 1405 Buffalo Street, Olean, New York, U.S.A.).

ERAPOL ET-75D is a liquid isocyanate terminated prepolymer based on PTMEG polyether polyol. CONATHANE RN-1526 is also a liquid isocyanate terminated prepolymer which produces a semi-rigid urethane with the elasticity of rubber. However, a combination of the two prepolymers is used to obtain the desired hardness in the end product.

A suitable polymer filler may also be added to the prepolymer mixture for strength.

The prepolymer mixture is heated to approximately 80°C and then mixed with a suitable curing agent. The curing agent may be MBCOA (4,4'-MethyIene-bis-(2-chloroaniline), a commonly available liquid curing agent, heated to about 120°C.

MBOCA has been listed in some countries as a suspected carcinogen. As an alternative curing agent, CONACURE** AH-40 may be used. CONACURE AH-40 is a liquid curing agent for isocyanate-containing polymers. It is a low viscosity liquid at room temperature, and eliminates the need for melting and processing at high elevated temperatures. If CONACURE AH-40 is used as the mixing agent, a mixing temperature of about 70°C is suitable.

The mixture of prepolymers, curing agent and filler is then poured into a mould pre-heated to approximately 100°C. After approximately 15 minutes demoulding time, the poured castings are cured for approximately 16 hours at about 100°C. Further Examples

CONATHANE** RN-1515, RN-1513, RN-1525, RN-1527, ETX 65D or ETX 80D may be substituted for CONATHANE RN-1526 in the above example. The use of these alternative prepolymers enables further variation in flexibility and hardness of the horseshoes to be obtained. In this manner, the horseshoes can be made to exhibit desired properties. For example, the elasticity of the horseshoes may be increased to cushion the ground impact of the hoof, or the abrasion resistance may be increased to prolong the life of the shoe. In particular, the hardness of the horseshoe can be varied to suit particular uses and applications.

Preferably, the horseshoes of this invention are manufactured by hot cast moulding, rather than conventional injection moulding techniques. Hot cast moulding has several advantages over convention injection moulding. For example, hot cast moulding does not require the base material to be broken down with additives to permit pumping through the injection machine, and thereby results in a finished product of higher quality and superior physical properties.

Another advantage of the horseshoe of this invention is that it can be nailed to the horse's hoof in a convention manner, and does not require the glues and thermostatting adhesives used with other polymer plates.

In the embodiment, horseshoe 10 is formed with a insert. The insert 11 is best illustrated in figure 2 and figure 3. Insert 11 can be formed from any suitable metal including mild steel, stainless steel, or other metals. It is also envisaged that the metal insert may be formed from materials which are not pure metals but may comprise metal composites or other materials which have the strength of metal. Insert 11 is substantially planar, and in the embodiment is formed from stainless steel. The thickness of the insert can vary, but in the embodiment, the insert has a thickness of approximately 1.6 mm. Insert 11 has two main parts, which comprises a rear arcuate strap portion 12, and a 5 forward flat toe clip 13. Strap portion 12 extends from each side of toe clip 13, and each side portion is formed with a pair of spaced apart holes 14. These holes align with the nail holes which are normally formed in horseshoe 10. Thus, when the horseshoe is nailed to the horse's hoof, the nails will pass through holes 14. This feature provides a form of bracing between the 0 nails, thereby forcing the nails to share pressure equally rather than independently.

Insert 11 as illustrated in the drawings passes along the forward part of the horseshoe, up to the second nail hole. Of course, the insert can be longer or shorter. 5 The insert 11 is cast into the polyurethane or plastic horseshoe, and therefore forms part of the formed horseshoe. The casting process is such that the toe clip 13 projects in front of the horseshoe. This is best illustrated in figure 4. Figure 4 shows horseshoe 10 attached to a horse's hoof 15, and shows toe clip 13 initially projecting horizontally in front of the 0 horseshoe. Toe clip 13 can then be hammered up to overlie the forward part of horse 15, this position being illustrated in phantom and by reference numeral 16. As toe clip 13 is formed with the remainder of the insert 11 , it allows for an easier production process with a plastic horseshoe as it is not necessary to cast a separate toe clip by itself. By having toe clip 13 formed of 5 metal, it can be hammered up or shaped in the manner illustrated in figure 4, which could not be possible if clip 13 was formed of plastic material which may have a plastic memory.

Conventional aluminium horseshoes have toe clips made from aluminium and approximately 2.5 mm thick. The toe clip is hammered up to o overlie the front of the horses of, and the horse is filed away to form a recess to accommodate the toe clip such that the toe clip remains substantially flush with the hoof. As the toe clip is approximately 2.5 mm thick it is necessary to file this depth of material off the hoof. In the embodiment, the toe clip is formed of steel having a much reduced thickness of 1.6 mm, requiring less filing to make the clip flush with the horse's hoof.

Insert 11 can be punched out using a specially designed

5 punched die. However, other way use of forming insert 11 can also be used.

The foregoing describes only one embodiment of the invention, and modifications which are obvious to those skilled in the art may be made thereto without departing from the scope of the invention. For example, the horseshoe can be constructed of other ADIPRENE compounds, l o VIBRATHANE, ROYALCAST 2505 or CONATHANE compounds.

Claims

CLAIMS:

I . A horseshoe which is at least partially formed of plastic material and which contains an insert which is at least partially in the plastic material, the insert containing a toe clip. 2. The horseshoe of claim 1 , wherein the plastic material comprises polyurethane.

3. The horseshoe of claim 1 , or claim 2, wherein the polyurethane is formed from the reaction of an aromatic diisocyanate with an aromatic diisocyanate reactive polyether. 4. The horseshoe of claim 3, wherein the aromatic diisocyanate is a toluene 2,4-diisocyanate.

5. The horseshoe as claimed in any one of the preceding claims, wherein the horseshoe is substantially entirely formed of the plastic material.

6. The horseshoe as claimed in any one of the preceding claims, wherein the horseshoe is formed by hot cast moulding.

7. The horseshoe as claimed in claim 6, wherein a ADIPRENE™ prepolymer is mixed with MBCA curative in a ratio of about 100:26.6 by weight at a mix temperature of about 66°C, and the mix is poured into a heated mould, the mould is kept at about 100°C until cured. 8. The horseshoe as claimed in any one of the preceding claims, wherein the metal insert is substantially planar.

9. The horseshoe as claimed in any one of the preceding claims, wherein the metal insert comprises a forward toe clip, and a strap portion extending from each side of the toe clip. 10. The horseshoe as claimed in claim 9, wherein the strap portion is provided with at least one opening adapted to accommodate a nail.

I I . The horseshoe as claimed in claim 10, wherein the at least one opening is aligned with an opening in the horseshoe through which a nail passes to nail the horseshoe to the hoof of a horse. 12. A horseshoe which is at least partially formed of plastic material and which contains an insert which is at least partially in the plastic material, the insert being curved and being formed with at least one opening through which a nail can pass, the insert being positioned in the horseshoe such that the at least one opening is aligned with the at least one opening in the horseshoe through which a nail passes to nail the horseshoe to the hoof of a horse. 13. The horseshoe of claim 12, wherein the plastic material comprises polyurethane.

14. The horseshoe of claim 12 or claim 13, wherein the polyurethane is formed from the reaction of an aromatic diisocyanate with an aromatic diisocyanate reactive polyether. 15. The horseshoe of claim 14, wherein the aromatic diisocyanate is a toluene 2,4-diisocyanate.

16. The horseshoe as claimed in any one of claims 12-15, wherein the horseshoe is substantially entirely formed of the plastic material.

17. The horseshoe as claimed in any one of claims 12-16, wherein the horseshoe is formed by hot cast moulding.

18. The horseshoe as claimed in claim 17, wherein a ADIPRENE™ prepolymer is mixed with MBCA curative in a ratio of about 100:26.6 by weight at a mix temperature of about 66°C, and the mix is poured into a heated mould, the mould is kept at about 100°C until cured. 19. The horseshoe as claimed in any one of claims 12-18, wherein the metal insert is substantially planar.

20. The horseshoe as claimed in any one of claims 12-19, wherein the metal insert comprises a forward toe clip, and a strap portion extending from each side of the toe clip. 21. A horseshoe substantially as hereinbefore described with reference to the accompanying drawings.