EP3257391A1 - Non-metallic protective tip - Google Patents

Abstract

The invention relates to a tip (10) for non-metallic protection for a safety shoe of the type comprising an inner plate (2), an outer plate (1) separated from one another by partitions (3) forming cells empty (4). An elastomer or a thermoplastic material (13) is injected into the cells (4) and in that the plates (1, 2) and partitions (3) are made of a polymeric material or a resin.

Description

The technical sector of the present invention is that of safety shoe tips.

The safety shoe tips meet precise standards and must withstand the fall of a mass of 20 kg mass over a height of 1 m. These tips must not undergo any degradation, crack or even a break.

There are two groups of safety tips on the market namely metal tips and tips in organic materials such as injected thermoplastics and compressed or laminated thermosetting materials.

We are looking more and more to replace the metal tips by non-metallic tips for their advantages of weight, chemical resistance, electrical and magnetic, etc ....

However, the nonmetallic tips have disadvantages because of their poor mechanical properties for injected tips and the high cost for laminated or composite thermoset tips.

It was proposed in the document WO2014007818 a solution for mechanically reinforcing the walls of a mouthpiece by ribbing. This mechanical improvement makes it possible to gain weight but does not solve the energy absorption of the impact. On the other hand, the complexity of making the molds makes the industrial application expensive.

The Japanese document is also known 3177478 describing a tip consisting of two plates between which a damping element is disposed. Note that this tip is disposed against the vertical front portion of the shoe.

The patent is also known US 6428865 which describes a shock absorbing material applicable in various places of a knee shell, racquet handle, a shoe or a cap. No example of use of the intended material is given for a shoe tip. In addition, the proposed material is designed to absorb shocks by simple deformation and not to withstand without destruction shocks.

The document is still known US 2011/185602 which describes a shoe tip consisting of a plate shaped at the end of the shoe comprising a number of perforations. There is neither an outer plate nor an inner plate and a fortiori a rubber material in the perforations.

No organic material mouthpiece is available on the market and no thermoplastic shoe tip currently meets the ISO 20344-2004 standard.

The object of the present invention is to provide a tip of organic material for safety shoes offering both a mass reduction and good impact resistance.

The subject of the invention is therefore a non-metallic protective boot for a safety shoe of the type comprising an inner plate, an outer plate separated from one another by partitions forming empty cells, characterized in that an elastomer or a thermoplastic material is injected into the cells and in that the plates are made of a polymeric material or a resin.

According to one characteristic of the invention, the injection of elastomer or thermoplastic material is carried out by adding molten material.

Advantageously, the injection of elastomer or thermoplastic material is carried out in the form of a 3D printing.

According to another characteristic of the invention, the polymer material or the resin of the plates has a modulus of elasticity of between 5 and 20 GPa, and a tensile strength of between 80 and 200 MPa.

Advantageously, the polymer material or the resin of the plates has a modulus of elasticity of 15 GPa, and a tensile strength of 150 MPa.

According to yet another characteristic of the invention, the cells are of hexagonal shape.

According to yet another characteristic of the invention, the elastomer or the thermoplastic material has an elongation of between 200 and 1000%, and a Shore hardness of between 30 and 100 Sh.

Advantageously, the elastomer or the thermoplastic material has an elongation of 500%, and a Shore hardness of 75 Sh.

The invention also relates to a method for manufacturing a non-metallic protective tip, characterized in that the elastomer or the thermoplastic material is vulcanized or heat-cured, the injection temperature being between 120 and 140 ° C, and the vulcanization or crosslinking temperature being between 110 and 200 ° C, preferably 160 ° C.

A first advantage of the invention lies in the increased resistance against impact of the tip.

Another advantage of the invention lies in the important mechanical properties of the nozzle, such as rigidity and impact resistance.

Another advantage of the present invention lies in the fact that the tip meets the criteria of ISO 20344-2004 shoe mounted.

• la figure 1 est une coupe de l'embout selon l'invention,
• la figure 2 est une coupe AA selon la figure 1,
• la figure 3 est une vue en coupe d'un autre mode de réalisation de l'embout,
• la figure 4 représente la vue de dessus d'un embout de protection de la chaussure de sécurité,
• la figure 5 représente la vue en coupe BB de la figure 4, et
• la figure 6 représente la vue en coupe CC de la figure 5.

Other features, details and advantages of the invention will be better understood on reading the additional description which will follow of embodiments given by way of example in relation to drawings in which:

• the figure 1 is a section of the tip according to the invention,
• the figure 2 is a AA cut according to the figure 1 ,
• the figure 3 is a sectional view of another embodiment of the mouthpiece,
• the figure 4 represents the top view of a protective toe of the safety shoe,
• the figure 5 represents the sectional view BB of the figure 4 , and
• the figure 6 represents the sectional view CC of the figure 5 .

The figure 1 illustrates the principle of making a tip 10 according to the invention for a safety shoe. This tip 10 consists of two plates 1 and 2 between which partitions 3 delimit cells 4. These cells 4 are of any shape and in this figure we see that these cells are hexagonal shape.

The plates 1 and 2 and the partitions 3 are constituted by a polymer or a resin having a high modulus of elasticity. Thus, these materials have for example a modulus of elasticity of between 5 and 20 GPa, preferably 15 GPa and a tensile strength of between 80 and 200 MPa, preferably 150 MPa. This combination makes it possible to manufacture tips endowed with the mechanical properties equivalent to those of metal end pieces.

The cells 4 may advantageously be made using a computer program controlling a 3D printer. Thus, the material supply can be achieved with multiple injection heads.

According to an advantageous embodiment of the invention, the cells 4 are filled with an elastomeric material, a thermoplastic polymer, a thermoplastic elastomer (TPE) or polyvinyl butyral (PVB) 13. For reasons of convenience, has shown in the drawing a single cell 4 filled with elastomer or thermoplastic material 13. This elastomer rubber or silicone is injected into the empty cells 4. Preferably, this elastomer or the thermoplastic material 13 is subjected to vulcanization or crosslinking to hot. The thermoplastic elastomers may be of the silicone mono or bi-component type, TPE, PVB, mon or bi-component PU.

Thus, the injection temperature of the elastomer 13 can be between 120 and 140 ° C, followed by a vulcanization or crosslinking temperature of between 110 and 200 ° C, preferably 160 ° C.

The amount of heat required for this reaction will be borrowed from the partitions 3 delimiting the cells 4 and the plates 1 and 2 thus contributing to the cooling of the entire structure.

The mechanical properties of the vulcanizate introduced into the cells 4 are characterized by an elongation of between 200 and 1000%, preferably 500%, and a Shore hardness of between 30 and 100 Sh, preferably 75 Sh.

Advantageously, the manufacturing technology by adding molten material still called 3D printing, allows the injection of elastomers in the cells 4 of any shape preferably hexagonal.

The tip 10 thus obtained provides excellent mechanical properties, such as stiffness and impact resistance.

It is however possible to fill the cells 4 with a cold elastomer.

On the figure 2 , the AA section of the figure 1 and we find the plates 1 and 2 between which the partitions 3 are interposed.

On the figure 3 another embodiment of the tip 10 according to the invention is shown. The tip module of the figure 1 here is completed by a second module consisting of a set of partitions 6 delimiting the cells 7. The partitions 6 are applied to the plate 2 and then covered with the plate 5.

This embodiment makes it possible to meet all the requirements of the users in terms of security.

It goes without saying that the production of the plates and partitions is adapted according to the desired mechanical requirements. For this purpose, the thickness and volume parameters of the cells 4 and 7, the partitions 3 or 6 and the plate 5 will be varied.

On the figure 4 a top view of the end piece 10 is shown. For example, the plate 1 which forms the outer envelope of the nozzle 10 and the plate 2 or 5 dotted delimiting the inner envelope.

On the figure 5 there is shown a longitudinal section of the tip 10 shown on the figure 1 . The plates 1 and 2, the partitions 3 and the cells 4 are found. It can be seen that the end piece 10 has, at the front, a thick portion 11 at the endpiece itself and a substantially horizontal tapered rear portion 12.

On the figure 6 , it is seen that in the front portion 11 there are two rows of cells 4 while at the rear portion 12 there is provided a single row of cells. This figure shows two cells 4 filled with elastomer or thermoplastic material 13 for the sake of clarity.

• essai de choc à 200 Joules soit la chute d'une masse de 20 kg d'une hauteur de 1 mètre,
• essai de compression sous 20 000 N avec une vitesse de 5 mm par minute.

The following examples are given as an indication to illustrate the composition of the tip. The two conformance tests are conducted as follows:

• impact test at 200 Joules is the fall of a mass of 20 kg from a height of 1 meter,
• compression test under 20,000 N with a speed of 5 mm per minute.

Example 1

The plates 1 and 2 and the partitions 3 of the tip 10 are made of polylactil acid (PLA).

The free height is 23 mm (distance between the tip and the foot of the user).

After the tests no break was observed.

Example 2

The plates 1 and 2 and the partitions 3 of the tip 10 are made of polylactil acid (PLA).

The free height is 25 mm (distance between the tip and the foot of the user).

After the tests, only the top plate is damaged.

Example 3

The plates 1 and 2 and the partitions 3 of the tip 10 consist of a mixed composition polymer of polylactil acid (PLA) and an ethylpropylenedimeric polymer (EPDM) in a proportion 80/20. EPDM polymer is a rubber.

The free height is 25 mm (distance between the tip and the foot of the user).

After the tests, no break was observed.

Example 4

The plates 1 and 2 and the partitions 3 of the tip 10 consist of a mixed composition polymer of polycaprolactone (PCL) and polyvinylbutyral (PVB) in a proportion 80/20. The free height is 38 mm (distance between the tip and the foot of the user).

After the tests, no break was observed.

Claims (9)

Non-metallic protective boot end piece (10) of the type comprising an inner plate (2), an outer plate (1) separated from one another by partitions (3) forming empty cells (4), characterized in that an elastomer or a thermoplastic material (13) is injected into the cavities (4) and in that the plates (1, 2) and partitions (3) are formed using a polymeric material or of a resin. Non-metallic protection tip (10) according to claim 1, characterized in that the injection of elastomer or thermoplastic material (13) is carried out by adding molten material. Non-metallic protection tip (10) according to claim 3, characterized in that the injection of elastomer or thermoplastic material (13) is performed in the form of 3D printing. Non-metallic protection tip (10) according to one of the preceding claims, characterized in that the polymer material or resin of the plates (1, 2) and partitions (3) has a modulus of elasticity of between 5 and 20 GPa, and a tensile strength of between 80 and 200 MPa. Non-metallic protection tip (10) according to Claim 4, characterized in that the polymer material or the resin of the plates (1, 2) and partitions (3) has a modulus of elasticity of 15 GPa, and a resistance to 150 MPa traction. Non-metallic protection tip (10) according to any one of the preceding claims, characterized in that the cells (4) are of hexagonal shape. A non-metallic protection tip (10) according to claim 2, characterized in that the elastomer or thermoplastic material has an elongation of between 200 and 1000%, and a Shore hardness of between 30 and 100 Sh. A non-metallic tip (10) according to claim 2, characterized in that the elastomer or thermoplastic material has an elongation of 500%, and a Shore hardness of 75 Sh. A method of manufacturing a non-metallic protective tip (10) according to any one of the preceding claims, characterized in that the elastomer or thermoplastic material is vulcanized or heat-crosslinked, the injection temperature being between 120.degree. and 140 ° C, and the vulcanization or crosslinking temperature being between 110 and 200 ° C, preferably 160 ° C.

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