METHOD FOR MANUFACTURING A TOOL CONTAINING AN ELASTOMER COMPONENT AND PRODUCT ACCORDING TO THE METHOD

Description

Technical field

[0001] The present invention relates to a device comprising an elastomer part. It also relates to an associated manufacturing method.

[0002] The field of the invention is more particularly that of devices comprising an elastomer part whose aging is to be studied or monitored. State of the prior art

[0003] Document US 2012 / 0 255 999 describes a golf ball comprising an RFID circuit enabling this golf ball to be identified among other golf balls. Document US 2007 / 0 141 760 describes a method of manufacturing an RFID device. Document DE 44 35 802 describes a method of manufacturing a single or multi-layer card carrying information.

[0004] EP 2 223 814 describes a method of manufacturing a tire, incorporating an RFID sensor.

[0005] Various devices are known comprising an elastomer part such as a piston comprising a metal shaft at the end of which is arranged a rubber head arranged to move by back and forth movements inside a cylinder.

[0006] One of the issues concerning the use of such a piston is the study or monitoring of the aging of the rubber making up the head of this piston.

[0007] For example, it may be important to study this aging to understand the reasons for unusual wear or to determine inappropriate usage conditions to correct.

[0008] We know of different study or monitoring techniques for this: Visual techniques, by which the condition of rubber is visually analyzed (on a microscopic or macroscopic scale). Typically, cracks or other signs of aging are visually examined. Stress techniques, by which the rubber is subjected to stresses in order to measure a parameter representative of the structural condition of the rubber, such as its elasticity.

[0009] The aim of the present invention is to improve these techniques for studying or monitoring aging, by proposing a new device comprising an elastomer part, and an associated manufacturing method. Statement of the invention

[0010] This objective is achieved with a manufacturing method according to claim 1.

[0011] Said measuring system comprises a sensor arranged to measure at least one physical parameter to which the elastomer part is subjected.

[0012] The measuring system further includes: a memory arranged to store data of the at least one physical parameter measured by the sensor, and / or means of transmission (preferably wireless) of this data outside the elastomer part (this data being for example stored remotely after transmission in particular if the measurement system does not include means for storing this data).

[0013] This allows you to create a history of this data.

[0014] The measuring system preferably further comprises a power supply source for the sensor and / or the memory and / or the transmission means.

[0015] The elastomer is preferably a natural rubber or a synthetic rubber or a silicone type elastomer.

[0016] In a first variant, the elastomer part is preferably compression molded.

[0017] The elastomer part is preferably compression molded according to the following steps: the elastomer provided with a cavity is introduced into a hollow of the mold, the measuring system is introduced into the cavity of the elastomer, while the elastomer and the measuring system are contained in the hollow of the mold, pressure is exerted on the elastomer with a pressure element.

[0018] The pressure exerted by the pressure element on the elastomer is preferably exerted such that a portion of the pressure element initially closes the cavity with the measuring system enclosed within the cavity.

[0019] The mold may further comprise a cover which closes the mold cavity during solidification of the elastomer. When introducing the elastomer into the mold cavity, the mold cavity is preferably not yet closed by its cover.

[0020] The pressure element may include: the cover directly exerting pressure on the elastomer part, or an insert, the pressure being exerted on the elastomer by the insert so that at least a part of the insert is inserted into the elastomer, and during vulcanization or crosslinking the elastomer solidifies around the part of the insert inserted into the elastomer while coating the measuring system, then the device comprising the insert, the elastomer solidified around the part of the insert and the measuring system coated in the elastomer is demolded.

[0021] In the latter case (with insert): in the presence of a cover, when exerting pressure, the insert may comprise a portion which is not inserted into the elastomer but which is inserted into the cover so as to maintain a position of the insert, and / or the insert may have a rod shape extending along a direction of elongation and comprising a first end intended to be inserted into the elastomer and a second end intended not to be inserted into the elastomer. The pressure is preferably exerted along the direction of elongation of the rod. After solidification, the measuring system is preferably located in the elastomer in the extension of the rod along the direction of elongation, and on the side of the first end.

[0022] In a second variant, the elastomer part is molded by injection or transfer of material inside the mold.

[0023] Generally speaking, the device thus manufactured is typically either a piston or a seal.

[0024] Generally, the transmission means include an RFID marker.

[0025] Generally, the at least one physical parameter may include: a temperature of the elastomer part, and / or a force or pressure exerted on the elastomer part, and / or an electrical impedance of the elastomer part.

[0026] The method according to the invention preferably comprises, before and / or during the solidification of the elastomer, heating the elastomer, preferably to a vulcanization or crosslinking temperature of the elastomer, typically at least 100°C, preferably at least 150°C.

[0027] According to yet another aspect of the invention, there is provided a device according to claim 20. This device according to the invention may be a piston according to claim 21. Description of figures and embodiments

[0028] Other advantages and particularities of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the following appended drawings: THE figures 1 to 4 illustrate different steps of a first embodiment of the method according to the invention covered by claim 1, and the elements of which have a symmetry of revolution around the arrow 11, the Figure 5 illustrates a device according to the invention obtained by the first embodiment of the method according to the invention, the figure 6 illustrates a variant of the first embodiment of the method according to the invention, the figure 7illustrates a second embodiment of the method according to the invention covered by claim 1, and the elements of which have a symmetry of revolution around the arrow 11, and the figure 8 illustrates a device according to the invention obtained by the second embodiment of the method according to the invention.

[0029] These embodiments being in no way limiting, it will be possible in particular to consider variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described (even if this selection is isolated within a sentence comprising these other characteristics), if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one preferably functional characteristic without structural details, and / or with only a part of the structural details if this part only is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0030] We will first describe, with reference to the figures 1 to 5, a first embodiment of a method according to the invention for manufacturing a device 1 comprising an elastomer part 12. The elastomer part 12 comprises an elastomer associated or not with other ingredients (for example coloring and / or other). The elastomer part 12 comprises by weight at least 50% elastomer, preferably at least 70%, in the present case at least 90%, ideally 100% elastomer. In the case where the elastomer part 12 comprises an elastomer associated with other ingredients, it is a mixture.

[0031] Device 1 is a piston.

[0032] According to this first embodiment of the method according to the invention, the elastomer part 12 is molded in a mold 3, and solidifies by vulcanization inside the mold 3.

[0033] Mold 3 is made of steel.

[0034] Elastomer 4 is a rubber.

[0035] In the first embodiment described here, the elastomer is a synthetic rubber, for example a Viton rubber with a hardness of 70 shore A (for example reference 1710 / ND2 from SAFIC ALCAN).

[0036] This elastomer part 12 may include various additives, for example a colorant, etc.

[0037] The process includes, before and during solidification of the elastomer, heating the elastomer to 180°C.

[0038] Elastomer part 12 is compression molded. Specifically, elastomer part 12 is compression molded in the following steps: in any order: the elastomer 4 provided with a cavity 5 is introduced into a hollow 2 of the mold 3, (preferably first) a measuring system 6 is introduced into the cavity 5 of the elastomer 4, (preferably second) while the elastomer 4 and the measuring system 6 are contained in the hollow 2 of the mold 3, pressure is exerted on the elastomer 4 with a pressure element.

[0039] The measuring system 6 includes: a sensor arranged to measure at least one physical parameter (for example a temperature) to which the elastomer part is subjected, a memory arranged to store data of the at least one physical parameter measured by the sensor (this data typically comprising values ​​of the at least one physical parameter preferably as a function of time), it is possible for example to use a memory integrated into the sensor (typically of memory size 64 to 128 kbits) or a flash memory type memory (of larger memory size). means of transmission (preferably wireless) of this data outside the elastomer part, the transmission means typically comprising an RFID marker (from the English "Radio Frequency Identification" or "Identification par radiofréquence" in French).a microprocessor or an electronic unit, arranged to control the sensor, the memory and the transmission means, for example reference ID CPR30-USB, and an electrical power source (typically a Lithium battery, for example reference CR2032, arranged to electrically power the sensor, the memory, the transmission means and the microprocessor or the electronic unit, for a typical autonomy of 6 months to 2 years or more.

[0040] The RFID marker is UHF technology (Ultra High Frequency, i.e. operating at a frequency above 860 MHz, preferably between 860 MHz and 960 MHz).

[0041] The RFID marker includes an outer casing made of, for example, ceramic or nylon.

[0042] The RFID marker used is for example the reference tag RFID UHF XERAFY nano in.

[0043] This embodiment by compression is clearly preferred compared to injection molding, because it avoids a displacement of the measuring system 6 during an injection of elastomer 4 which would create a flow and a displacement of material. Thus, this first embodiment has the advantage of conferring great control over the positioning of the measuring means 6.

[0044] The at least one physical parameter includes: a temperature of the elastomer part; for this, the sensor of at least one parameter comprises a temperature sensor, for example of reference CAPT'N PIC from PICDI; and / or a force or pressure exerted on the elastomer part; for this, the sensor of at least one parameter comprises a force or pressure sensor; and / or an electrical impedance of the elastomer part; for this, the sensor of at least one parameter comprises an impedance sensor;

[0045] In the preferred variant where the data of the at least one physical parameter comprises a temperature as a function of time, the invention makes it possible to better study the aging of the device 1 and to better understand the thermal stresses undergone by the device over time.

[0046] The regularity and temperatures of cleaning cycles of device 1 can be studied.

[0047] Generally speaking, in the preferred case where the data of the at least one physical parameter comprises a physical parameter (temperature, force, pressure, electrical impedance, etc.) as a function of time, the invention makes it possible to better study the aging of the device 1 and to better understand the constraints undergone by the device over time.

[0048] Furthermore, it is noted that the invention makes it possible to study the aging of the device 1 without necessarily needing to dismantle the device outside its conditions of use (factory or other) thanks to the means of transmitting data outside the elastomer part 12.

[0049] The power source is preferably encapsulated in a thermal insulator, preferably in RTV silicone (for "Room Temperature Vulcanizing silicone"), for example reference "Rhodorsil RTV2 PartA+PartB".

[0050] Mold 3: comprises a portion forming the hollow 2, and further comprises a cover 9 arranged to close the hollow.

[0051] The heating of the elastomer (to 180°C) is done while the pressure is being exerted: before solidification ( figure 2 ) during solidification ( figure 3 ).

[0052] Heating is carried out by means of two heating plates 13, 14 which compress towards each other: the part of the mold 3 forming the hollow 2, and the cover 9 of the mold so as to exert pressure on the elastomer 4 contained in the hollow 2 blocked by the cover 9.

[0053] Platens 13 and 14 are press heating plates, typically heated to 180°C.

[0054] One of the plates 14 is in contact with the part of the mold 3 forming the hollow 2.

[0055] The other plate 13 is in contact with the cover 9, which itself is in contact with an insert 7 arranged to be in contact with the elastomer 4 in the hollow 2. The pressure element comprises this insert 7.

[0056] Insert 7 is made of stainless steel.

[0057] THE figures 1 to 5 illustrate different successive steps of a first embodiment of the method according to the invention.

[0058] In reference to the figure 1, we started: by introducing, into the hollow 2 of the mold 3, the solid elastomer 4, pre-cut according to the shape to be molded (for example in the form of several washers or pieces 25 to 28), this elastomer 4 being provided with a preferentially fixed reception zone which is not very subject to transfer (a cavity 5), this elastomer 4 being introduced in an unvulcanized or raw form, called preformed blank or raw material, the mold 3 being preheated to the vulcanization temperature (typically 180°C) and by introducing, into the cavity 5 of the elastomer 4, the measuring system 6.

[0059] We notice on the figure 1 that, when the elastomer 4 is introduced into the hollow 2 of the mold 3, the hollow 2 of the mold 3 is not yet closed by its cover 9.

[0060] Then, with reference to the figure 1that, while the elastomer 4 and the measuring system 6 are contained in the hollow 2 of the mold 3, pressure is started on the elastomer 4 with the pressure element (with a pressure typically of 15 to 20 MPa) and the elastomer 4 is heated (to 180°C).

[0061] The pressure exerted by the pressure element (and therefore the insert 7) on the elastomer 4 is exerted so that a part 8 of the pressure element initially (i.e. at the start of the pressure being exerted) closes the cavity 5 with the measuring system 6 enclosed inside the cavity 5.

[0062] In reference to the figure 2 , the mold 3 is then closed with its cover 9 while continuing to exert pressure on the elastomer 4 with the pressure element and heating the elastomer 4 to the vulcanization temperature.

[0063] In reference to the figure 2, the pressure element comprises (and even consists of) the insert 7, the pressure being exerted on the elastomer by the insert 7 so that at least the part 8 of the insert 7 is inserted into the elastomer 4, so that after solidification (vulcanization or crosslinking) of the elastomer 4 the part 8 of the insert 7 cannot be removed from the part 12 of elastomer 4 without destroying or damaging the part 12 of elastomer.

[0064] When exerting pressure, the insert 7 comprises a part 10 which is not intended to be inserted into the elastomer 4 (neither bonded nor in contact with the elastomer 4) but which is inserted into the cover 9 and fits intimately with the cover 9 so as to firmly hold (i.e. with a minimum clearance of type H7 / g6 when the materials of the insert 7 and the cover 9 are of the same nature) the insert 7.

[0065] The insert 7 has a rod shape extending along the elongation direction 11 and comprising a first end 80 (where the part 8 is located) intended to be inserted into the elastomer 4 and a second end 100 (where the part 10 is located) intended not to be inserted into the elastomer 4.

[0066] The pressure is exerted along the direction of elongation 11 of the rod.

[0067] In reference to the figure 2 , we notice that heating and exerting pressure fluidify the elastomer so that cavity 5 disappears.

[0068] We also note, always with reference to the figure 2, that before exerting pressure, the elastomer is placed in the hollow 2 slightly overweight (approximately 10%) compared to the maximum capacity of the hollow 2 closed by the cover 9. Rapid back and forth movements or oscillations of the cover 9 along the direction 11 make it possible to expel any air bubbles 23 and the excess 24 of elastomer 4.

[0069] There figure 3 illustrates the next step of solidification of the elastomer 4 by vulcanization which lasts approximately 30 minutes for a part 12 of elastomer 4 having a volume of 180cm 3< .

[0070] During solidification (vulcanization), pressure is continued to be exerted on the elastomer 4 with the pressure element and the elastomer 4 is heated to vulcanization temperature.

[0071] In reference to the figure 3 , the cover 9 closes the hollow 2 of the mold 3 during the solidification (vulcanization) of the elastomer 4.

[0072] During vulcanization, the elastomer 4 solidifies around the part 8 of the insert inserted into the elastomer 4 while coating the measuring system 6.

[0073] The measurement system 6 is: either, in the preferred variant (which avoids measurement disturbances, for example due to the temperature of the insert 7 which may be different from the temperature of the elastomer 4) fully coated in the elastomer 4, i.e. the elastomer 4 is in contact with the entire periphery or the outer surface of the system 6; or partially coated in the elastomer 4, so that the entire periphery or the outer surface of the system 6 is in contact partly with the elastomer 4 and partly with the insert 7 (i.e. for a zero distance 15).

[0074] In the preferred variant illustrated, it is noted that during the vulcanization of the elastomer part 12, the measuring system 6 is already inserted into the core of the elastomer part 12, so that after vulcanization the measuring system 6 is completely coated inside the elastomer part 12 4.

[0075] In reference to the figure 4 , the cover 9 is removed and the pressure on the elastomer 4 with the pressure element and the heating of the elastomer 4 is stopped.

[0076] In reference to the Figure 5 , the device 1 is then demolded, comprising the insert 7, the elastomer 4 solidified around the part 8 of the insert and the measuring system 6 coated in the elastomer 4.

[0077] The device 1 is allowed to finish cooling to room temperature, typically 25°C.

[0078] The position of the measuring system 6 after solidification (vulcanization) of the elastomer 4 depends directly on the initial position of the cavity 5 at the beginning of the process. It is noted that after solidification v, the measuring system 6 is located (according to the initial position of the cavity 5): either (position 16 illustrated in the figures) in the elastomer 4 in the extension of the rod along the direction of elongation 11, and on the side of the first end 80; this “median” position is optimal for measuring the average stresses (possibly zero) undergone by the elastomer; or (alternative position 17 illustrated in the Figure 5) outside the extension of the rod along the direction of elongation 11, preferably at a distance 18 less than 5 millimeters from the outside of the part 12 made of elastomer 4; this position is optimal for measuring the maximum stresses undergone by the elastomer (higher temperatures, higher friction forces, higher pressures, etc.)

[0079] Device 1 thus obtained and illustrated on the Figure 5 therefore includes: the part 12 made of solidified elastomer 4, the measuring system 6 fully coated inside the part 12 made of elastomer 6, said measuring system comprising the sensor arranged to measure the at least one physical parameter to which the part 12 made of elastomer is subjected, the memory arranged to store data of the at least one physical parameter measured by the sensor, the means for transmitting this data to the outside of the part made of elastomer, and the electrical power source.

[0080] More precisely, in the example previously illustrated, the device 1 is a piston 101 comprising: a solidified elastomer piston head 12 4 (The head of a piston is the part arranged to, when the piston is in use, be in contact with a fluid (typically milk in a dosing machine for the manufacture of dairy products such as yogurts or other) to be compressed or expanded), a piston pin comprising the insert 7 of which at least one part 8 is inserted into the elastomer 4 (The piston pin is a mechanical part which, when the piston is in use, connects the piston head 12 to motorization means to allow the movement of the piston head in a cylinder of complementary shape), the measuring system 6 fully coated inside the elastomer head, said measuring system comprising the sensor arranged to measure the at least one physical parameter to which the elastomer part is subjected, the memory arranged to store data of the at least one physical parameter measured by the sensor,the means of transmitting this data outside the elastomer part, and the electrical power source.

[0081] In variants with reference to the Figures 4 and 5 , we notice that the hollow 2 of the mold 3 can have various shapes. For example, instead of a right angle in the bottom of the mold, the bottom of the mold can have a beveled angle (along the dotted lines 19 of the figure 4 ), so that the elastomer part 12 will also have a beveled shape (along the dotted lines 20 of the Figure 5 ).

[0082] In variants with reference to the figure 6 , we note that the part of the mold 3 forming the hollow 2 can comprise a removable part 21 (for example using screws 22) in particular when the hollow 2 of the mold is arranged to give the part 12 a shape which cannot be demolded through the opening blocked by the cover 9, even after removal of the cover.

[0083] It should be noted that in other variants, it is also possible to use a synthetic elastomer (synthetic rubber) and / or a silicone elastomer, for example a silicone with a hardness of 60 Shore A (for example reference 766R100 from JEM) vulcanized with peroxides, vulcanized at 110°C (instead of 180°C), with a vulcanization time of 10 minutes for a volume of part 12 of 180 cm 3< .

[0084] We will now describe, with reference to the figures 7 and 8 , a second embodiment of the method according to the invention and a device according to the invention obtained by the second embodiment of the method according to the invention solely for their differences compared to the embodiments and variants described with reference to figures 1 to 6 .

[0085] It is noted that this second embodiment of the method according to the invention does not include an insert 7.

[0086] In reference to the figure 7, the pressure element comprises the cover 9 which is in contact with the elastomer 4 when exerting pressure so as to directly exert pressure on the elastomer part.

[0087] Device 1 thus obtained and illustrated on the figure 8 therefore includes: the part 12 made of solidified elastomer 4, the measuring system 6 fully coated inside the part 12 made of elastomer 6, said measuring system comprising the sensor arranged to measure the at least one physical parameter to which the part 12 made of elastomer is subjected, the memory arranged to store data of the at least one physical parameter measured by the sensor, the means for transmitting this data to the outside of the part made of elastomer, and the electrical power source.

[0088] More precisely, the device 1 is a cylindrical seal 102 pierced in its center.

[0089] According to the two embodiments described, the elastomer part 12 forms a seal for a piston 101 or a single seal 102.

[0090] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

[0091] For example, the elastomer part 12 can be molded by injection or transfer of material inside the mold 3.

[0092] Of course, the various features, forms, variants and embodiments of the invention can be combined with each other. In particular, all the variants and embodiments described above can be combined with each other.

Claims

1. A method of manufacturing a device (1) comprising a part (12) made from elastomer (4), wherein the elastomer part is molded in a mold (3) by compression and / or injection and / or material transfer inside the mold (3), and solidifies by vulcanization or cross-linking inside the mold, characterized in that, during the solidification by vulcanization or cross-linking of the elastomer part, a measuring system (6) is located in the elastomer part, so that after the solidification by vulcanization or cross-linking, the measuring system (6) is embedded inside the elastomer part (12), said measuring system comprising a sensor arranged to measure at least one physical parameter to which the elastomer part is subjected, a memory arranged to store data of the at least one physical parameter measured by the sensor, means for transmitting these data outside the elastomer part, and a power source.

2. The method according to claim 1, characterized in that the elastomer part is compression-molded.

3. The manufacturing method according to claim 2, characterized in that the elastomer part is compression-molded according to the following steps: - the elastomer (4) with a cavity (5) is introduced into a recess (2) in the mold (3), - the measuring system (6) is introduced into the cavity (5) of the elastomer (4), - while the elastomer (4) and the measuring system (6) are contained in the recess (2) of the mold (3), pressure is exerted on the elastomer (4) with a pressure element.

4. The method according to claim 3, characterized in that the pressure exerted by the pressure element on the elastomer (4) is exerted so that a portion (8) of the pressure element initially closes the cavity (5) with the measuring system (6) enclosed within the cavity (5).

5. The method according to claim 3 or 4, characterized in that the mold (3) further comprises a cover (9) which closes the recess (2) of the mold (3) during solidification of the elastomer (4).

6. The method according to claim 5, characterized in that when the elastomer (4) is introduced into the recess (2) of the mold (3), the recess (2) of the mold (3) is not yet closed by its cover (9).

7. The method according to claim 5 or 6, characterized in that the pressure element comprises the cover (9) exerting pressure directly on the elastomer part.

8. The method according to any one of claims 3 to 6, characterized in that the pressure element comprises an insert (7), pressure being exerted on the elastomer by the insert (7) so that at least a portion (8) of the insert (7) is inserted into the elastomer (4), and during vulcanization or cross-linking the elastomer (4) solidifies around the portion (8) of the insert inserted into the elastomer (4) while embedding the measuring system (6), then the device (1) comprising the insert (7), the elastomer (4) solidified around the portion (8) of the insert and the measuring system (6) embedded in the elastomer (4) is demolded.

9. The method according to claim 8 considered as dependent on any one of claims 5 to 6, characterized in that upon exertion of pressure, the insert (7) comprises a portion (10) which is inserted into the cover (9) so as to maintain a position of the insert (7).

10. The method according to claim 8 or 9, characterized in that the insert has the shape of a rod extending along a direction of elongation (11) and comprising a first end (80) intended to be inserted into the elastomer (4) and a second end (100) intended not to be inserted into the elastomer (4).

11. The method according to claim 10, characterized in that the pressure is exerted along the direction of elongation (11) of the rod.

12. The method according to claim 10 or 11, characterized in that after solidification, the measuring system (6) is located in the elastomer (4) in the extension of the rod along the direction of elongation (11), and on the side of the first end (80).

13. The method according to claim 1, characterized in that the elastomer part is molded by injection or transfer of material inside the mold.

14. The method according to any one of the preceding claims, characterized in that the device (1) is a piston (101) or a seal (102).

15. The method according to any one of the preceding claims, characterized in that the transmission means comprise an RFID marker.

16. The method according to any one of the preceding claims, characterized in that the at least one physical parameter comprises a temperature of the elastomer part.

17. The method according to any one of the preceding claims, characterized in that the at least one physical parameter comprises a force or pressure exerted on the elastomer part.

18. The method according to any one of the preceding claims, characterized in that the at least one physical parameter comprises an electrical impedance of the elastomer part.

19. The method according to any one of the preceding claims, characterized in that it comprises, before and / or during solidification of the elastomer, heating of the elastomer.

20. A device comprising: - a part (12) made from solidified elastomer (4), - a measuring system (6) embedded, according to a method according to any one of the preceding claims, inside the elastomer part, said measuring system comprising a sensor arranged to measure at least one physical parameter to which the elastomer part is subjected, a memory arranged to store data of the at least one physical parameter measured by the sensor, means for transmitting these data outside the elastomer part, and a power source.

21. The device according to claim 20, characterized in that the device is a piston (1), and in that: - the part (12) made from solidified elastomer (4) is a piston head (12) made from solidified elastomer (4), - the measuring system (6) is embedded inside the elastomer head, the device further comprising: - a piston pin comprising an insert (7), at least a portion (8) of which is inserted into the elastomer (4).