A piston intended for use in fluid machinery, equipped with a system for pressing a seal, and a fluid machine comprising such a piston.
By integrating a cavity-based pressing system within gasket seals to maintain contact with grooves, the piston addresses sealing inefficiencies and leakage, enhancing the performance of fluid machines at low temperatures.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2026-04-09
AI Technical Summary
Existing pistons in fluid machines face issues with fluid leakage and inefficient sealing, particularly at extremely low temperatures, leading to losses in sealing integrity and machine performance due to axial gaps between gasket seals and grooves.
Incorporation of a system within the gasket seals that includes cavities to house a pressing mechanism, using either a fluid mass or solid inserts, to ensure the seals are pressed against the grooves, preventing axial gaps and ensuring fluid flow only through designated orifices.
This solution enhances sealing integrity, reduces leakage, and maintains optimal machine performance by ensuring fluid flow through designated paths, thereby improving the efficiency and reliability of fluid machines operating at low temperatures.
Smart Images
Figure 2026062514000001_ABST
Abstract
Description
Technical Field
[0001] [1] The present invention relates to a piston provided with a system for pressing a seal, intended for a fluid machine. The seal is a non-sealing seal having at least one orifice for a fluid flow.
[0002] [2] Further, the present invention relates to a fluid machine provided with such a piston. The fluid machine can be a pump or a compressor. The fluid can be in an extremely low temperature state.
Background Art
[0003] [3] A piston for a fluid machine is intended to be at least partially attached inside a liner with a relative back-and-forth movement with respect to the liner of the machine.
[0004] [4] The piston includes a head extending in a main direction and having a first end of the piston, and a shaft having a second end of the piston. The first end and the second end of the piston are defined along the main direction.
[0005] [5] The first end of the piston is intended to form a fluid expansion and / or compression chamber together with the liner of the machine.
[0006] [6] The shaft includes a side wall provided with at least one annular groove bounded between a first crenelation and a second crenelation.
[0007] [7] In particular, the annular groove is equipped with at least one gasket seal intended to cooperate with the side wall of the liner of the machine. The at least one gasket seal is provided with a through-orifice intended to allow a fluid flow to flow from the expansion and / or compression chamber towards the second end of the piston.
[0008] [8] One or more gasket seals primarily ensure that the compression chamber is sealed without hindering the relative movement of the piston relative to the liner. In other words, one or more gasket seals allow the piston to move relative to the liner with little to no friction.
[0009] [9] Furthermore, one or more gasket seals ensure the proper operation of the fluid machine and greatly contribute to meeting the specifications of the fluid machine, in particular the flow rate being pumped.
[0010]
[10] Finally, one or more seals can reduce leakage and BOG (boil-off gas).
[0011]
[11] BOG is an irreversibly evaporated fluid that cannot be reliquefied without external cold exchange or extraction of work. BOG may be caused by the generation of entropy due to heat input to the expansion chamber (imperfect adiabatic quality), or by Joule-Thomson isoenthalpy expansion and / or friction resulting from leakage.
[0012]
[12] A sufficient number of gasket seals are required to perform the various functions described above, depending on the performance of each seal, the required pressure, and other factors such as the fluid itself. Furthermore, the gasket seals must have good mechanical integrity for the optimal operation of the fluid machine at high pressure and extremely low temperatures.
[0013]
[13] In most cases, each groove is provided with a pair of gasket seals, namely a first gasket seal in contact with a first narrow section of the groove and a second gasket seal in contact with a second narrow section of the groove. Starting from the piston head, the first gasket seal is positioned in front of the second gasket seal.
[0014]
[14] The first gasket seal is equipped with a first through orifice. The second gasket seal is equipped with a second through orifice. Furthermore, the first and second gasket seals are positioned in the grooves such that their respective through orifices are angularly offset from each other with respect to the main shaft of the piston.
[0015]
[15] Thus, the fluid flow originating from the compression chamber follows a leakage path through the first orifice of the first gasket seal, then along the interface between the two gasket seals, and then through the second orifice of the second gasket seal.
[0016]
[16] When an axial clearance (i.e., a clearance in the main direction of the piston) is formed between the first gasket seal and the first gap, the fluid flow from the compression chamber does not necessarily pass through the first orifice of the first gasket seal. A portion of the flow bypasses the first and second through orifices and flows into the gap between the seal and the side wall of the piston, and / or the gap between the seal and the side wall of the liner.
[0017]
[17] Changes in the leakage path represent loss of sealing and deterioration of machine performance.
[0018]
[18] Therefore, it has become necessary to develop a new piston in which the flow generated from the compression chamber passes, in principle, only through the through orifice provided for that purpose, without bypassing the gasket seal. [Overview of the project]
[0019]
[19] For this purpose, a first aspect of the present invention relates to a piston, otherwise defined in the comprehensive definition given in the above preface.
[0020]
[20] According to this first aspect of the present invention, at least one seal comprises at least one cavity separate from the through orifice, the cavity being configured to house a system for pressing the gasket seal against a first and a second gap in the main direction of the piston.
[0021]
[21] Thus, the present invention opens up the possibility of introducing a system within the gasket seal for pressing the gasket seal in the main direction of the piston. This pressing eliminates the risk of axial gaps appearing, on the one hand between the gasket seal and the first gap, and on the other hand between the gasket seal and the second gap.
[0022]
[22] Other embodiments of the piston are, - At least one gasket seal comprises, within a single component, two lateral lips, namely, a first lip positioned facing a first gap and a second lip positioned facing a second gap. - The lips define the boundaries of the cavities between them, which are intended to house the pressing system. - Two separate gasket seals are arranged in at least one groove, facing each other, i.e., the first seal facing the first gap and the second seal facing the second gap. - The two seals have opposing surfaces, each with a notch. - Each notch in the seal is positioned to form a cavity intended to house the pressing system. - The pressing system is mechanical and / or fluid type, - The pressing system takes the form of an insert permanently placed in the cavity. - The compression system consists of a mass of fluid generated from the compression chamber and stored in the cavity. - The fluid mass is configured to press the first lip against the first gap and the second lip against the second gap in the main direction of the piston. - The insert is configured to press the first lip against the first gap and the second lip against the second gap in the main direction of the piston. - A mass of fluid is configured to press the first seal against the first gap and the second seal against the second gap in the main direction of the piston. - The insert is configured to press the first seal against the first gap and the second seal against the second gap in the main direction of the piston. - The insert and at least one seal are each made of a material having a different coefficient of thermal expansion, and the coefficient of thermal expansion of the insert is greater than that of the seal.
[0023]
[23] According to a second aspect, the present invention relates to a fluid machine, particularly a cryogenic fluid machine, such as a pump for cryogenic fluids such as hydrogen. The fluid machine includes a liner and a piston according to any one of the previous embodiments. The piston is at least partially inserted inside the liner so as to form a fluid expansion and / or compression chamber together with the liner. The piston and the liner are configured to move relative to each other so that one can move relative to the other.
[0024]
[24] Other specific features and advantages will become apparent upon reading the following description provided with reference to the following figures.
Brief Description of the Drawings
[0025] [Figure 1]
[25] It is a cross-sectional view illustrating a first embodiment of a fluid machine according to the present invention. The machine includes a liner, a piston, a set of gasket seals (plural possible), and a removable system for gaps (plural possible) along the piston. Each of the gasket seals is provided with a cavity and a pressing system. The piston includes a single gasket seal between two gaps. [Figure 2]
[26] A partial cross-sectional view illustrating another example of the machine according to the first embodiment, in which the system of the narrow section(s) is fixed to the piston. [Figure 3]
[27] A partial cross-sectional view illustrating another example of a fluid machine according to the first embodiment, wherein the seal has a C-shape defining a cavity containing a pressing system, the cavity facing the liner. [Figure 4]
[28] A partial cross-sectional view illustrating another example of a fluid machine according to the first embodiment, wherein the seal has a C-shaped configuration defining an illustrated cavity without a pressing system, the cavity facing the liner. [Figure 5]
[29] A partial cross-sectional view illustrating another example of a fluid machine according to the first embodiment, wherein the seal has a C-shape, and the seal and pressing system face the piston. [Figure 6]
[30] A partial cross-sectional view illustrating another example of a fluid machine according to the first embodiment, the seal having a Z-shaped contour that forms two cavities configured to receive a pressing system. [Figure 7]
[31] A partial cross-sectional view illustrating an example of a fluid machine according to a second embodiment, the piston comprising two separate seals between two consecutive narrow sections, each having a recess, the recess of each seal forming a cavity intended to receive a pressing system, the cavity facing a liner. [Figure 8]
[32] A partial cross-sectional view illustrating another example of the machine according to the second embodiment, with the cavity facing the piston. [Figure 9]
[33] A partial cross-sectional view illustrating another example of the machine according to the second embodiment, in which the cavity is closed and located at an intermediate position between the liner and the piston. [Figure 10]
[34] A partial cross-sectional view illustrating a third embodiment of the machine according to the present invention, the piston comprising two separate seals separated by a gap configured to receive a C-shaped pressing system between two consecutive narrow sections. [Figure 11]
[35] A partial cross-sectional view illustrating another example of the machine according to the third embodiment, the pressing system comprising a series of V-shaped inserts. [Modes for carrying out the invention]
[0026]
[36] As illustrated in Figures 1 to 11, the present invention relates to a fluid machine 1, and more particularly to a cryogenic fluid machine. The fluid machine 1 may be a pump or compressor for transferring a fluid, which may be cryogenic at a temperature below 150°C. It may be hydrogen.
[0027]
[37] Referring to [Figure 1], the fluid machine 1 extends along the principal axis Y, also called the “longitudinal axis” or “major direction” or “principal direction”.
[0028]
[38] Fluid machine 1 also has a transverse axis X perpendicular to the principal axis Y. The transverse axis X is also hereafter referred to as the “radial axis” or “radial direction”.
[0029]
[39] The fluid machine 1 comprises a liner 2 and a piston 3 at least partially located inside the liner 2. In particular, the piston 3 and the liner 2 are mounted such that one can move forward and backward relative to the other in the principal direction Y.
[0030]
[40] The piston 3 and the liner 2 form a compression and / or expansion chamber 4, which is intended to receive and deliver fluid for expansion and / or compression in a cycle comprising a stage for drawing in fluid and a stage for delivering fluid into the compression and / or expansion chamber 4.
[0031]
[41] In other words, the volume of the compression and / or expansion chamber 4 varies depending on the relative position of the piston 3 with respect to the liner 2 and on the stage (intake or discharge) of the fluid intake and discharge cycle within the chamber 4.
[0032]
[42] To move one relative to the other, the piston 3 or liner 2 may be connected to a drive member (not shown).
[0033]
[43] More specifically, the piston 3 comprises a head 31 inserted inside the liner 2 and a shaft 32 connected to the head 31. Together with the shaft 32, the head 31 forms a shoulder. The shaft 32 is connected to a rod (not shown) intended to be located outside the liner 2 and can be actuated by a drive member.
[0034]
[44] In particular, the head 31 of the piston 3 has a first end 31a. The shaft 32 of the piston 3 has a second end 32a opposite to the first end 31a.
[0035]
[45] The liner 2 has side walls 21 and a bottom 22 that form a recess into which the head 31 of the piston 3 is inserted. Thus the bottom 22 and side walls 21 of the liner 2 and the first end 31a of the piston 3 define the expansion and / or compression chamber 4.
[0036]
[46] Furthermore, the side walls 21 and / or bottom 22 of the liner 2 are provided with at least one inlet orifice and at least one outlet orifice. These orifices communicate with the compression and / or expansion chamber 4.
[0037]
[47] Referring again to [Figure 1], the machine 1 comprises a system of gaps 5 arranged on the side wall 34 of the piston 3 along the main direction Y. In particular, the system of gaps 5 is arranged on a portion of the side wall 34 located in the region of the piston 3 facing the shaft 32.
[0038]
[48] Advantageously, the system of the gap(s) 5 extends in an O-shape around the side wall 34 of the piston 3, that is, the system of the gap(s) 5 closes around the side wall 34 of the head 31 of the piston 3 in a plane perpendicular to the principal direction Y.
[0039]
[49] Advantageously, as illustrated in [Figure 1], the system of the gap(s) 5 can be manufactured separately from the piston 3. In the alternative configuration illustrated in [Figure 2], the system of the gap(s) 5 can form a single unit with the piston 3.
[0040]
[50] When manufactured separately from the piston 3, the system of the gap(s) 5 can be reversibly assembled to the piston. For example, the system of the gap(s) 5 can be removably passed through the piston 3, more specifically along the side wall 34 of the shaft 32.
[0041]
[51] In a configuration that is removable from the piston, the system of the gap(s) 5 is intended to cooperate with the side wall 34 of the piston 3 in an interference fit and sealed manner. Such interference fit is achieved by the difference in thermal contraction of the system of the gap(s) 5 relative to the piston 3.
[0042]
[52] Note that the interference fit and / or sealing between the system of the gap(s) and the piston 3 can be achieved solely by the difference in thermal expansion and contraction of the system of the gap(s) relative to the piston 3.
[0043]
[53] The system of the gap(s) 5 protrudes radially from the side wall 34 of the piston 3. Thus, the system of the gap(s) 5 defines a set of grooves(s), i.e., a set of recesses(s) or hollows(s), intended to receive a set of gasket seals(s) 6.
[0044]
[54] A set of gasket seals 6 is intended to work with the liner 2 to restrict fluid flow outside the expansion and / or compression chamber 4.
[0045]
[55] The expression “system of gaps 5” (and / or set of grooves, or set of gasket seals 6) refers to a system comprising one or more gaps 5 (or each set comprising one or more grooves, or one or more gasket seals 6).
[0046]
[56] In the examples illustrated in [Figure 1] and [Figure 2], the shoulder formed between the head 31 and the shaft 32 of the piston 3 cooperates with the first of the set of gaps 5 to form the first of the set of grooves.
[0047]
[57] Figures 1 and 2 each illustrate a machine having a plurality of gaps, grooves and gasket seals, and each has an enlarged view of a groove defined by a first gap 5a and a second gap 5b.
[0048]
[58] In the first embodiment illustrated in Figures 1 to 6, each groove defined by the first narrow section 5a and the second narrow section 5b is provided with a single gasket seal 6. In particular, Figures 1 and 2 show grooves having a single gasket seal 6.
[0049]
[59] The gasket seal 6 has an outer surface intended to cooperate with the side wall 21 of the liner 2 in an interference fit. The gasket seal 6 also has an inner surface intended to face the side wall 34 of the piston 3. Finally, the gasket seal 6 has a first cross section and a second cross section extending between the outer surface and the inner surface.
[0050]
[60] In the illustrated example, the first cross section of the seal 6 is positioned facing the first gap 5a. The second cross section of the seal 6 is positioned facing the second gap 5b.
[0051]
[61] Furthermore, the gasket seal 6 has a through orifice that allows fluid to flow from the expansion and / or compression chamber 4 toward the second end 32a of the piston 3. The through orifice extends between the first and second cross sections of the gasket seal 6.
[0052]
[62] Conveniently, the machine includes at least one expander 7 positioned between the gasket seal 6 and the shaft 32 of the piston 3. The at least one expander 7 is intended to press the gasket seal 6 radially (i.e., in direction X) against the side wall 21 of the liner 2.
[0053]
[63] According to the present invention, as illustrated in [Figures 3] to [Figure 6], the gasket seal 6 comprises at least one cavity 8 separate from the through orifice. The cavity 8 is configured to house a system 9 for pressing the gasket seal 6 in the main direction Y of the piston 3.
[0054]
[64] More specifically, the pressing system is intended to press the seal 6 against the first gap 5a and the second gap 5b in the direction Y of the piston 3.
[0055]
[65] In the examples illustrated in [Figure 3], [Figure 4], and [Figure 5], the gasket seal 6 has a C-shaped contour in the longitudinal cross-section.
[0056]
[66] In this cross section, the gasket seal 6 comprises two lateral lips, namely a first lip 61 positioned facing the first narrow section 5a and a second lip 62 positioned facing the second narrow section 5b. The lips 61, 62 define the boundary of a cavity 8 intended to house the pressing system 9 between them.
[0057]
[67] Conveniently, the cavity 8 intended to house the pressing system has an annular shape.
[0058]
[68] Referring to [Figure 3] and [Figure 4], the cavity 8 and the pressing system 9 face the liner 2. In [Figure 4], the gasket seal 6 is illustrated without the pressing system 9.
[0059]
[69] Referring to [Figure 5], the cavity 8 and the pressing system 9 are in contact with the expander 7 and face the piston 3.
[0060]
[70] In the example illustrated in [Figure 6], the gasket seal 6 has a Z-shaped contour in the longitudinal section. In this case, the gasket seal 6 comprises two horizontal branches 6a, 6b connected by an oblique branch 6c. The branches 6a, 6b, 6c define two cavities 8a, 8b, each intended to receive the pressing system.
[0061]
[71] In the second embodiment illustrated in Figures 7 to 11, each groove houses two separate gasket seals 6a and 6b facing each other, namely, a first seal 6a facing the first gap 5a and a second seal 6b facing the second gap 5b.
[0062]
[72] More specifically, the first seal 6a has a first cross section facing the first gap 5a. The second seal 6b has a second cross section facing the second gap 5b.
[0063]
[73] Furthermore, the first seal 6a is provided with a first through orifice. The second seal is provided with a second through orifice. The two through orifices are angularly offset from each other with respect to the principal direction Y of the machine 1. This angular offset between the through orifices creates a leakage path to the interface between the two seals 6a and 6b.
[0064]
[74] Referring to [Figures 7], [8], and [9], the first seal 6a and the second seal 6b, which are located in a common groove, are provided with at least one first notch 8a and at least one second notch 8b, respectively. The notches 8a and 8b are particularly visible in [Figure 9].
[0065]
[75] In particular, the notches 8a and 8b are formed in the opposing cross-sections of the seals 6a and 6b, respectively. Thus the notches 8a and 8b face each other and form a cavity 8 intended to house the pressing system 9.
[0066]
[76] Note that in the example illustrated in [Figure 9], the first seal 6a and / or the second seal 6b may also be provided with at least one further notch formed on the side of the seals 6a, 6b. Each of the further notches on the seals 6a, 6b is intended to accommodate a system for pressing the seals 6a, 6b in the radial direction X.
[0067]
[77] In this second embodiment, the cavity 8 (and consequently the pressing system 9) may occupy a position close to the side wall 21 of the liner 2 (see Figure 7), or a position close to the side wall 34 of the piston 3 (see Figure 8), or a substantially equidistant intermediate position between the side wall 21 of the liner 2 and the side wall 34 of the piston 3 (see Figure 9).
[0068]
[78] Referring to [Figure 10] and [Figure 11], the first seal 6a and the second seal 6b are positioned at a certain distance from each other. The first seal 6a and the second seal 6b form a gap between them, which constitutes a cavity 8 intended to house the pressing system 9.
[0069]
[79] In particular, in the example illustrated in [Figure 11], the first seal 6a has a first planar cross-section facing the first narrow section 5a and a second convex cross-section. The second convex surface has a V-shaped contour in the longitudinal section of the machine 1.
[0070]
[80] The second seal 6b has a first planar cross-section and a second concave cross-section, which are positioned facing the second narrow section 5b. The concave second surface has a V-shaped contour in the longitudinal section of the machine 1.
[0071]
[81] Thus, the convex cross-section of the first seal 6a and the concave cross-section of the second seal 6b are arranged facing each other and have complementary geometric shapes.
[0072]
[82] The pressing system 9 may consist of a mass of fluid generated from the compression chamber 4 and stored in the cavity 8.
[0073]
[83] In this case, the cavity 8 is in fluid communication with the through-orifice of the seal 6 (or, in the second embodiment, the multiple through-orifices of the multiple seals). This applies to the machines illustrated in [Figure 6] and [Figure 9].
[0074]
[84] In the example illustrated in [Figure 9], the mass of fluid accumulated in the cavity 8 presses the first seal 6a against the first gap 5a and the second seal 6b against the second gap 5b. This pressing occurs in the main direction Y of the piston 3.
[0075]
[85] In alternative configurations, the pressing system 9 may include a solid insert, as is the case with the machines illustrated in Figures 3 to 5, 7, 8, 10, and 11.
[0076]
[86] In the example illustrated in [Figures 3] to [Figure 5], the insert 9 presses the first lip 61 of the seal 6 against the first gap 5a and the second lip 62 of the seal 6 against the second gap 5b. This pressing is performed in the main direction Y of the piston 3.
[0077]
[87] In the examples illustrated in [Figure 7], [Figure 8], [Figure 10], and [Figure 11], the insert 9 presses the first seal 6a against the first gap 5a and the second seal 6b against the second gap 5b. This pressing is performed in the main direction Y of the piston 3.
[0078]
[88] The inserts forming the pressing system are advantageously made from a different material than the seals 6a and 6b. The thermal expansion coefficient of the inserts is greater than that of the seals 6a and 6b.
[0079]
[89] Note that the inserts may extend along the cavity 8 and have different contours in the longitudinal section of the machine 1.
[0080]
[90] In particular, referring to [Figures 3], [4], and [5], the insert 9 may have a rectangular contour complementary to the rectangular contour of the cavity 8. In this case, the insert 9 is completely positioned within the cavity 8.
[0081]
[91] Referring to [Figure 8], the insert 9 may have an inverted T-shaped contour in the longitudinal section of the machine 1. Thus, in this longitudinal section, the insert 9 comprises two branches, namely a first branch located within the cavity 8 and a second branch located in contact with the expander 7.
[0082]
[92] Referring to [Figure 10], in a longitudinal section of the machine 1, the insert 9 may have a C-shaped contour complementary to the contour of the cavity 8 formed between the first seal 6a and the second seal 6b.
[0083]
[93] Referring to [Figure 11], the insert 9 may have a V-shaped contour in the longitudinal section of the machine 1. This contour has a shape complementary to the contours of the first seal 6a and the second seal 6b.
[0084]
[94] Advantageously, a system of gaps 5 forms a first group of elements in which all gaps 5 are preferably substantially identical (in particular with respect to their physicochemical properties). Similarly, a set of gasket seals 6 forms a second group of elements in which all seals 6 are preferably substantially identical (in particular with respect to their physicochemical properties).
[0085]
[95] Advantageously, in its removable configuration, the system of the gap(s) 5 is manufactured from a different material than that of the piston 3.
[0086]
[96] Advantageously, the system of gaps 5 and / or the set of seals 6 may be made from polymers (based on PTFE, PEEK, PAEK, PA, PAI, PI, PPS, PPA). The pistons 3 and / or liners 2 may be made from metals (e.g., steel, copper alloys, aluminum alloys, etc.).
[0087]
[97] Such material selection makes it possible to limit the risk of overheating, on the one hand, between the system of gaps 5 and the piston 3, and on the other hand, between the set of seals 6 and the liner 2.
[0088]
[98] Advantageously, the piston 3 and liner 2 are made of metal, 5.10 -6 m / (mK) ~ 30.10 -6 It may have a thermal expansion coefficient of m / (mK). The system of gaps 5 and the set of seals 6 may be made of polymer. The material of the system of gaps 5 and / or the material of the set of seals 6 may have a thermal expansion coefficient greater than that of the material selected for the piston 3 and liner 2.
[0089]
[99] Regardless of the material selected for the piston 3, and regardless of the material selected for the system of the cavities 5, a sufficient difference between the respective coefficients of thermal expansion of these materials is necessary to ensure the difference in contraction of the system of cavities relative to the piston 3. Favorably, this difference is at least 2.10 -6 The value is m / (mK), preferably 2.10. -6 ~3.10 -6 It is m / (mK).
Claims
1. A piston (3) for a fluid machine (1), the piston (3) is intended to be at least partially mounted inside the liner (2) with relative forward and backward movement relative to the liner (2) of the fluid machine (1), the piston (3) comprises a head (31) having a first end (31a) of the piston (3) and a shaft (32) having a second end (32a) of the piston (3), the first end (31a) of the piston (3) being intended to define a fluid expansion and / or compression chamber (4) together with the liner (2) of the fluid machine (1), the The piston (3) has a side wall (34) having at least one annular groove with a boundary defined between a first narrow section (5a) and a second narrow section (5b), and the at least one annular groove is fitted with at least one gasket seal (6) intended to cooperate in a sealed manner with the side wall (21) of the liner (2) of the fluid machine (1), and the at least one gasket seal (6) is provided with a through orifice intended to allow the fluid flow from the fluid expansion and / or compression chamber (4) toward the second end (32a) of the piston (3), The piston (3) is characterized in that the at least one gasket seal (6) comprises at least one cavity (8) separate from the through orifice, the cavity (8) comprises a pressing system (9) for pressing the gasket seal (6) against the first narrow portion (5a) and the second narrow portion (5b) in the main direction (Y) of the piston (3), and the pressing system (9) is mechanical and / or fluid.
2. The piston (3) according to claim 1, wherein the at least one gasket seal (6) comprises, within a single component, two lateral lips, namely, a first lip (61) positioned facing the first gap (5a) and a second lip (62) positioned facing the second gap (5b), and the first and second lips (61, 62) of the seal (6) define the boundary of the cavity (8) intended to house the pressing system (9) between the first and second lips.
3. The piston (3) according to claim 1, wherein two separate gasket seals (6a, 6b) are arranged in the at least one annular groove facing each other, i.e., the first seal (6a) facing the first narrow portion (5a) and the second seal (6b) facing the second narrow portion (5b).
4. The piston (3) according to claim 3, wherein the two separate gasket seals each have opposing surfaces with notches (8a, 8b), and the notches (8a, 8b) of the first and second seals (6a, 6b) are aligned to form the cavity (8) intended to house the pressing system (9).
5. The piston (3) according to any one of claims 1 to 4, wherein the pressing system (9) is in the form of an insert permanently placed in the cavity (8) and / or consists of a mass of fluid generated from the compression chamber and accumulated in the cavity (8).
6. The piston (3) according to claim 5, dependent on claim 2, wherein the fluid mass or insert is configured to press the first lip (61) of the seal (6) against the first gap (5a) and the second lip (62) of the seal (6) against the second gap (5b) in the main direction (Y) of the piston (3).
7. The piston (3) according to claim 5, dependent on claim 3, wherein the fluid mass or insert is configured to press the first seal (6a) against the first gap (5a) and the second seal (6b) against the second gap (5b) in the main direction (Y) of the piston (3).
8. The piston (3) according to any one of claims 5 to 7, wherein the insert and the at least one gasket seal (6) are each made of materials having different coefficients of thermal expansion, and the coefficient of thermal expansion of the insert is greater than the coefficient of thermal expansion of the seal (6).
9. For example, a fluid machine (1), more particularly a cryogenic fluid machine, such as a pump for a cryogenic fluid such as hydrogen, comprising a liner (2) and a piston (3) according to any one of claims 1 to 8, wherein the piston (3) is at least partially inserted inside the liner (2) so as to form a fluid expansion and / or compression chamber (4) together with the liner (2), and the piston (3) and the liner (2) are configured to move back and forth relative to each other, with one being movable relative to the other.