Piston provided with adjustable slots for sealing joints, fluid machine comprising such a piston, and method of manufacturing such a piston or such a machine.

Abstract

Piston (3) for a fluid machine (1), the piston (3) being intended to be mounted at least partly inside a sleeve (2) of the machine (1) according to a relative back-and-forth movement between the piston (3) and the sleeve (2), the piston (3) comprising a head (31) defined around a main direction (Y) of the piston (3) and intended to form with the sleeve (2) of the fluid machine (1) a chamber (4) for expansion and / or compression of the fluid, the piston (2) also comprising a system of notches (5) removably threaded along the head (31) and arranged to project radially relative to the head (31), the system of notches (5) being configured to delimit a set of grooves provided to receive a set of sealing gaskets (6) intended to cooperate in a sealed manner with a side wall (21) of the sleeve (2) of the fluid machine (1),characterized in that the system of crenellations (5) - extends in an O-shape around a side wall (34) of the head (31), i.e. has a closed section around the side wall (34) of the head (31) in a plane perpendicular to the main direction (Y), - is composed of a material having a coefficient of thermal expansion different from the coefficient of thermal expansion of a material of the head (31), - is configured to, in the operating configuration, cooperate with the side wall (34) of the head (31) in a tight and sealed manner, thanks to a differential thermal contraction of the system of crenellations (5) relative to the head (31). Abstract figure: Figure 1,

Description

Title of the invention: Piston provided with adjustable slots for sealing joints, fluid machine comprising such a piston, and method of manufacturing such a piston or such a machine.

[0001] The invention relates to a piston provided with adjustable notches for receiving sealing joints.

[0002] The invention also relates to a fluid machine comprising such a piston. The fluid machine may be a pump or a compressor. The fluid in question may be in a cryogenic state. It may in particular be hydrogen.

[0003] The invention finally relates to a method of manufacturing such a piston or such a fluid machine.

[0004] In a known manner, a fluid machine comprises a jacket and a piston arranged inside the jacket. The piston and the jacket are configured to be movable relative to each other in a reciprocating motion. The fluid machine also comprises an expansion and / or compression chamber formed between a bottom of the jacket and a bottom of the piston. Finally, the machine comprises a system of notches arranged around the piston in a main direction of the machine.

[0005] In particular, the system of notches forms a set of grooves provided to receive a set of sealing gaskets intended to cooperate with the jacket.

[0006] According to the prior art, in a machine such as described above, the piston and the system of notches(s) constitute a single part obtained for example by machining the piston from a raw part, or by additive manufacturing from a digital model.

[0007] In the case of manufacturing by machining the subassembly formed by the piston and the system of notches(s), the procedure is generally by removing material from the raw part in order to define machined surfaces which correspond respectively to a contour of the piston and to a contour of the system of notches(s). The areas of material removal carried out on the raw part constitute the set of groove(s).

[0008] As in any machining operation with material removal, the waste (the quantity of material removed) may be more or less significant and their treatment may prove to be more or less complicated.

[0009] In order to overcome this drawback, one solution consists of forming the system of notches(s) from elements which are obtained separately from the piston and which are configured to be reversibly assembled to the piston. The piston and / or the system of notches(s) then have a structure specifically adapted for their mechanical coupling. Such a structure can be relatively complex and of a cost of fa- relatively high construction.

[0010] Furthermore, in a fluid machine as described above, each seal extends in the shape of a C and has two ends forming an opening. Furthermore, each seal is deformable thanks to a structure comprising an external polymer strip, intended to be in contact with an internal wall of the jacket, and an internal metal strip, intended to be opposite a wall of the piston. The internal strip consists of a spring blade.

[0011] If the joints described above can be easily mounted and dismounted in the system of slot(s) by separating their respective ends, this advantage is counterbalanced by several disadvantages.

[0012] First of all, when they are mounted in the system of slot(s), and during operation of the fluid machine, the seals described above are the site of local heating due to metal / metal friction between the respective spring blades of these seals and the side wall of the piston. In addition, the sealing between the respective external bands of these seals and the side wall of the liner is far from satisfactory. Finally, premature wear of the seals is observed after only a few disassembly / assembly operations.

[0013] To overcome the insufficient sealing observed on the seals described above, one solution consists of multiplying their number, and therefore providing a system of relatively large slot(s) in order to form an equally large number of grooves. This solution leads to an increase in the manufacturing cost of the fluid machine.

[0014] In the case where the fluid machine is intended to treat a fluid such as liquid hydrogen, the risk of leakage in the event of a seal failure is particularly increased due to the properties of hydrogen. The same applies to the risk of heating at the interfaces between the spring blades of the seals and the piston, and the risk of premature wear of the seals. Furthermore, the maintenance operations (disassembly and assembly of the seals) of the fluid machine are made complex due to the properties of hydrogen.

[0015] Indeed, hydrogen has a relatively low density and characteristic size which promote leaks on a fluid machine. In addition, hydrogen has a relatively low enthalpy of vaporization which makes it more sensitive to heating. Finally, the flammable nature of hydrogen and its low temperature in the liquid state require, before any disassembly / assembly operation, several preliminary steps such as reheating, inerting with helium, etc.

[0016] These preliminary steps carried out upstream of a disassembly / assembly operation can considerably extend the period of unavailability of the fluid machine. When it is installed in a filling station (which is generally expected greater availability), prolonged shutdown of the fluid machine for maintenance reasons is highly detrimental.

[0017] Thus, it is necessary to redesign the structure of the piston and / or the seals of a fluid machine, so as to improve the sealing thereof, reduce friction and / or heating between the seals and the piston, and reduce or eliminate premature wear of the seals.

[0018] To this end, according to a first aspect, the invention relates to a piston for a fluid machine.

[0019] In particular, the piston is intended to be mounted at least partly inside a jacket of the machine according to a relative back-and-forth movement between the piston and the jacket. Furthermore, the piston is intended to form with the jacket of the fluid machine a chamber for expansion and / or compression of the fluid.

[0020] The piston comprises a head defined around a main direction of the piston and intended to form with the sleeve of the fluid machine a chamber for expansion and / or compression of the fluid. The piston also comprises a system of notches removably threaded along the head and arranged in radial projection relative to the head.

[0021] In particular, the system of notches is configured to delimit a set of grooves intended to receive a set of sealing joints intended to cooperate in a sealed manner with a side wall of the jacket of the fluid machine.

[0022] According to this first aspect of the invention, the system of crenellations extends in an O-shape around a side wall of the head, i.e. has a closed section around the side wall of the head, in a plane perpendicular to the main direction (Y). Furthermore, the system of crenellations is composed of a material having a coefficient of thermal expansion different from the coefficient of thermal expansion of a material of the head. Finally, the system of crenellations is configured to, in the operating configuration, cooperate with the side wall of the head in a tight and sealed manner, thanks to a differential thermal contraction of the system of crenellations relative to the head.

[0023] Differential thermal contraction of the castellation system(s) relative to the head may be the only means of maintaining a tight fit and seal between the castellation system(s) and the sidewall of the head.

[0024] Thus, by providing a tight fit between the system of notches(s) and the piston head, obtained by means of a differential contraction of the system of notches(s) relative to the piston head, the invention makes it possible to envisage the piston head with a simple geometry, without grooves or notches. Similarly, the invention makes it possible to envisage the system of notches(s) and / or the set of seal(s) in a geometry and / or structure that is simpler to implement.

[0025] Therefore, the invention opens up the possibility of reducing the manufacturing cost of the fluid machine, and / or of modifying as desired the position, number and height of the grooves intended to receive the seals. In other words, the invention introduces a system of modular slot(s).

[0026] Other embodiments of the piston include the following features: - the system of slot(s) and the assembly of seal(s) are respectively made of materials having different coefficients of thermal expansion; - the coefficient of thermal expansion of the slot system(s) is greater than the coefficient of thermal expansion of the joint assembly(s); - the coefficient of thermal expansion of the seal assembly(s) (6) is greater than the coefficient of thermal expansion of the head; - the system of notches(s) comprises a plurality of rings arranged in series along the side wall of the head; - each of the rings has an inner lateral face intended to cooperate with the lateral wall of the head, an outer lateral face intended to be positioned opposite the lateral wall of the sleeve, and two opposite transverse faces extending between the inner lateral face and the outer lateral face; - the set of groove(s) is delimited by the side wall of the head and the consecutive rings; - the slot system(s) comprises a sleeve intended to be threaded onto the side wall of the head; - the sleeve comprises at least one collar and at least one of the grooves of the groove assembly(s); - all or part of the grooves formed by the sleeves have an L-shaped or C-shaped profile, the profile being defined by considering a straight section of the machine along a cutting plane parallel to the main Y direction; - the head is configured to allow free sliding of the system of notches(s) without deformation of said system, from one end of the head intended to be positioned far from the compression and / or expansion chamber to a bottom of the head intended to delimit the compression and / or expansion chamber; - the head is configured to allow free sliding of the seal system(s) without deformation of said system, from one end of the head intended to be positioned far from the compression and / or expansion chamber to a bottom of the head intended to delimit the compression and / or expansion chamber; - the bottom of the head forms a first radial stop; - the piston comprises a rod configured to be reversibly fixed to the end of the head and to form with the head a second radial stop; - the system of slot(s) and the set of joint(s) are intended to be arranged between the first radial stop and the second radial stop; - an elastic return member is arranged between the system of notches and at least one of the first radial stops and the second radial stops.

[0027] According to a second aspect, the invention relates to a fluid machine and in particular a cryogenic fluid machine, comprising a piston according to any one of the embodiments defined above and a sleeve. The piston is inserted at least partly inside the sleeve so that the piston forms with the sleeve a chamber for expansion and / or compression of the fluid. The piston and the sleeve are configured to be movable relative to each other according to a relative back-and-forth movement.

[0028] Other embodiments of the fluid machine include the following features: - the expansion and / or compression chamber is delimited by the side wall of the liner, a bottom of the liner and a bottom of the piston head; - the slot system(s) has a nominal inside diameter greater than or equal to the nominal diameter of the side wall of the piston head, and a nominal outside diameter less than or equal to the nominal inside diameter of the side wall of the liner; - the slot system(s) is configured to pass from a nominal state associated with a first temperature, in which said system forms internal lateral clearances with the side wall of the piston head, and external lateral clearances with the side wall of the liner, to a first contracted state associated with a second temperature lower than the first temperature, in which said system cooperates with the side wall of the piston head according to a tight fit, and in which the external lateral clearances are widened compared to the nominal state to form external fluid leakage paths; - the seal assembly(s) is configured to transition from a nominal state associated with a first temperature, in which the seal assembly(s) has a nominal outside diameter greater than the nominal inside diameter of the sidewall of the liner, and in which the seal assembly(s) forms with the groove assembly(s) internal side clearances, to a contracted state associated with a second temperature lower than the first temperature, in which the seal assembly(s) continues to cooperate with the sidewall of the liner in a tight fit, and in which the internal side clearances are reduced compared to the nominal state to form internal fluid leakage paths; - rings alternate with gaskets along the piston head; - each ring forms a transverse leak path with an adjacent seal; - the collars alternate with the seals along the piston head; - each collar forms a transverse leak path with an adjacent joint; - the outer leak paths, the inner leak paths and the transverse leak paths define a wavy or crenellated path for a flow of the fluid, said path extending along the piston head; - the set of seal(s) comprises open C-shaped seals held pressed against the side wall of the jacket by means of a set of expander(s); - the expander assembly(s) is positioned between the side wall of the piston head and the seal assembly(s).

[0029] According to a third aspect, the invention relates to a method for manufacturing a piston or a fluid machine as described above. The method comprises a step of inserting the piston inside the sleeve and a step of arranging along the piston, in an alternating manner, rings forming the system of notches and seals forming the assembly of seals.

[0030] Other features and advantages will appear on reading the description below, given with reference to the following figures in which:

[0031] [Fig. 1] is a sectional view illustrating a first embodiment of the fluid machine according to the invention, the machine comprising a liner, a piston, a system of notches formed by a plurality of rings, a set of grooves, a set of seals, and a set of expanders, the machine being in a fully assembled configuration.

[0032] [Fig.2] is a partial sectional view illustrating another example of the fluid machine according to the first embodiment, the machine being in a partially assembled configuration and comprising a second type of seal assembly(s), the seal assembly(s) and the slot system(s) being in a nominal state.

[0033] [Fig.3] is a view of the machine of [Fig.2] illustrated in a fully assembled configuration.

[0034] [Fig.4] is a view of the machine of [Fig.2] illustrating the slot system(s) and the joint assembly(s) in a contracted state.

[0035] [Fig.5] is a sectional view partially illustrating a second embodiment of the fluid machine according to the invention, the system of notches being formed by a plurality of sleeves each comprising a collar and a groove.

[0036] [Fig.6] is a sectional view partially illustrating a third embodiment of the fluid machine according to the invention, the system of notches being formed by a plurality of sleeves each comprising two collars delimiting a groove.

[0037] [Fig.7] is a sectional view illustrating a fourth embodiment of the fluid machine according to the invention, the system of notches being formed by a single sleeve provided with a plurality of collars and a plurality of grooves.

[0038] In the following description, the term “nominal” refers to an uncontracted state or undeformed elements of the fluid machine 1.

[0039] As illustrated in [Fig.l] to [Fig.7], the invention relates to a fluid machine 1, and in particular a cryogenic fluid machine. The fluid machine 1 may be a pump or a compressor. The fluid in question may be hydrogen. The pump or compressor may thus be of the cryogenic type for transferring a fluid having a temperature below 150°C.

[0040] The fluid machine 1 extends along a main axis Y which is also referred to hereinafter as “longitudinal axis” or “longitudinal direction” or “main direction”. The fluid machine 1 also has a transverse axis X perpendicular to the main axis Y. The transverse axis X is also referred to hereinafter as “radial axis” or “radial direction”.

[0041] The fluid machine 1 comprises a jacket 2 and a piston 3 arranged at least partly inside the jacket 2. In particular, the piston 3 and the jacket 2 are configured to be mounted so as to be movable relative to each other in a relative back-and-forth movement along the main direction Y. To do this, one of the piston 3 or the jacket 2 can be connected to a motor member (not shown).

[0042] Furthermore, the machine 1 comprises a chamber 4 formed between the sleeve 2 and the piston 3. The chamber 4 is intended to receive the fluid for expansion and / or compression of this fluid according to a cycle comprising an admission phase and a discharge phase of the fluid into the chamber 4. The chamber 4 is called the expansion and / or compression chamber.

[0043] Finally, the machine 1 comprises a system of notches 5 arranged around the piston 3 in the main direction Y. The system of notches 5 delimits transversely (in the direction X) a set of grooves (i.e. a set of housings) or hollows intended to receive a set of sealing gaskets 6. The set of sealing gaskets is intended to cooperate with the sleeve 2.

[0044] The expression “system of notches 5” (respectively set of groove(s) or set of seal(s) 6” designates an assembly comprising one or more notches 5 (respectively one or more grooves, or one or more seals 6).

[0045] In more detail, the piston 3 comprises a head 31 which engages inside the sleeve 2, as well as a rod 32 which is connected to the head 31 and intended to be arranged outside the sleeve 2. In particular, the rod 32 can be actuated by the driving member.

[0046] The jacket 2 comprises a side wall 21 and a bottom 22 forming a housing in which the head 31 of the piston 3 engages to form the compression and / or expansion chamber 4.

[0047] Thus, the compression and / or expansion chamber 4 is delimited by the bottom 22 and the side wall 21 of the sleeve 2, as well as by a bottom 33 of the head 31 of the piston 3.

[0048] It should be noted that the compression and / or expansion chamber 4 communicates with at least one fluid intake orifice and at least one fluid discharge orifice. These orifices may be provided at the level of the side wall 21 of the jacket 2 or at the level of the bottom 22 of the jacket 2. Furthermore, the compression and / or expansion chamber 4 has a volume which varies as a function of the relative position of the head 31 of the piston 3 with respect to the jacket 2, and as a function of the phase (intake or discharge) of the cycle of intake and discharge of the fluid in the chamber 4.

[0049] The system of notches 5 is produced separately from the piston 3 and configured to be assembled to the head 31 of the piston 3 in a reversible manner. In particular, the system of notches 5 is removably threaded along the head 31 of the piston 3, and more specifically along a side wall 34 of the head 31 of the piston 3.

[0050] Furthermore, the system of notches 5 is arranged to project radially relative to the head 31 of the piston 3, thus delimiting the set of grooves provided to receive the set of sealing joints (6).

[0051] The set of sealing seal(s) 6 is formed by one or more seals 6 each having an outer lateral face intended to cooperate with the lateral wall 21 of the liner 2 according to a tight fit, an inner lateral face intended to be opposite the lateral wall 34 of the head 31 of the piston 3, and two opposite transverse faces which extend between the outer lateral face and the inner lateral face.

[0052] The system of notches 5 forms a first group of elements in which all the notches are preferably substantially identical (in particular from the point of view of their physicochemical properties). Similarly, the set of sealing seal(s) 6 forms a second group in which all the seals 6 are preferably substantially identical (in particular from the point of view of their physicochemical properties).

[0053] According to the invention, the system of notches 5 extends in an O-shape around the side wall 34 of the head 31 of the piston 3, that is to say, the system of notches 5 is closed around the side wall 34 of the head 31 of the piston 3, in a plane perpendicular to the main direction Y. Furthermore, the system of notches 5 is made of a material different from the material of the head 31 of the piston 3. Finally, the system of notches 5 is configured to cooperate with the side wall 34 of the head 31 of the piston 3 in a tight and sealed manner. Such a tight fit is obtained by means of a differential thermal contraction of the system of notches (5) relative to the head 31 of the piston 3.

[0054] The tight fit and / or sealing between the system of crenellations and the head 31 of the piston 3 can be obtained exclusively by the differential thermal contraction of the system of crenellations relative to the head 31 of the piston.

[0055] Thus, by providing a tight fit and / or sealing between the system of notch(s) 5 and the head 31 of the piston 3, thanks to a differential contraction of the system of notches 5 relative to the head 31 of the piston 3, the invention makes it possible to envisage the head 31 of the piston 3 with a simple geometry, without grooves or notches.

[0056] According to the invention, each of the sleeve 2, the piston 3, the system of notches 5 and the assembly of seals 6 is made of a material having a different coefficient of thermal expansion (or coefficient of thermal expansion and / or retraction).

[0057] In particular, the coefficient of thermal expansion of the material of the system of slot(s) 5 is greater than the coefficient of thermal expansion of the material of the assembly of seal(s) 6. The coefficient of thermal expansion of the material of the assembly of seal(s) 6 is itself greater than the coefficient of thermal expansion of the material of the piston 3.

[0058] It should be noted that the piston 3 can be made of a material which has a coefficient of thermal expansion close to that of the material of the liner 2.

[0059] The fact of providing for each element of the machine 1 (namely the sleeve 2, the piston 3, the system of notches 5 and the assembly of seal(s)) a material having a different coefficient of thermal expansion has the consequence that these elements do not contract in the same proportions when the machine 1 is subjected to the same cryogenic temperature (cryogenic use) from a nominal state (at ambient temperature).

[0060] Advantageously, the system of notches 5 and / or the set of seal(s) (6) can be made of polymer (based on PTFE, PEEK, PAEK, PA, PAI, PI, PPS, PPA). The piston 3 and / or the sleeve 2 can be made of metal (for example steel, copper alloy, aluminum alloy, etc.). Such a choice of materials makes it possible to limit the risk of heating, on the one hand, between the system of notches 5 and the piston 3; and on the other hand, between the set of seal(s) 6 and the sleeve 2.

[0061] Advantageously, the piston 3 and the liner 2 are metals, and may have a coefficient of thermal expansion of between 5.106 m / (mK) and 30.106 m / (mK). The system of slots 5 and the assembly of seals 6 may be made of polymer. The material of the system of slots 5 and / or the material of the assembly of seals 6 may have a coefficient of thermal expansion greater than that of the material selected for the piston 3 and the liner 2.

[0062] Whatever the material chosen for the piston 3, and whatever the material chosen for the system of crenellations 5, a sufficient difference between the respective coefficients of thermal expansion of these materials is necessary to guarantee a differential contraction of the system of crenellations relative to the piston 3. Advantageously, this difference is at least 2.106 m / (mK), and preferably between 2.106 and 3.106 m / (mK).

[0063] The following description presents different embodiments of the invention which are distinguished from each other by the structure of the system of slot(s) 5.

[0064] In a first embodiment illustrated in [Fig.l] to [Fig.4], the system of notches 5 comprises a plurality of rings 51 each having an inner lateral face intended to be positioned opposite the lateral wall 34 of the head 3 of the piston 3, an outer lateral face intended to be positioned opposite the lateral wall 21 of the sleeve 2, and two opposite transverse faces which extend between the inner lateral face and the outer lateral face.

[0065] In particular, for each ring 51, the inner lateral face is intended to cooperate with the lateral wall 34 of the head 31 of the piston 3 according to a tight fit, thus forming a sealed barrier along this lateral wall 34.

[0066] In this first embodiment, the set of groove(s) is delimited along the main Y direction by the side wall 34 of the head 31 of the piston 3 and by the rings 51. More specifically, the set of groove(s) is delimited along the main Y direction by the side wall 34 of the head 31 of the piston 3 and by the transverse faces opposite the consecutive rings 51. Such grooves are called inter-ring grooves.

[0067] The slot system 1 according to the first embodiment is said to be of type 1.

[0068] In a second embodiment illustrated in [Fig. 5], the system of notches 5 comprises a plurality of sleeves 52 intended to cooperate with the side wall 34 of the head 31 of the piston 3 according to a tight fit. In particular, the sleeves 52 each comprise a collar 53 which extends in radial projection in the direction X, and a groove which has an L-shaped (or inverted L-shaped) profile. This profile is defined by considering a section plane parallel to the main direction Y.

[0069] In the example illustrated in [Fig.5], the sleeves 52 forming the system of notches 5 have the same height along the main direction Y. As a variant, these sleeves 52 may have different heights leading to grooves of different heights.

[0070] The slot system(s) according to the second embodiment is said to be of type 2.

[0071] According to the first two embodiments described above, the number and the di The dimensions of the grooves intended to receive the seals 6 can be modified as desired along the head 31 of the piston 3 insofar as the system of notches 5 (i.e. the rings 51 or the sleeves 53) is removable along the head 31 of the piston 3, and can have different geometries. In other words, according to these first two embodiments, the grooves for receiving the seals 6 are modular in number and / or in geometry.

[0072] It should be noted that thanks to the grooves made modular (due to the removable notch(s) system, i.e. due to the removable rings 51 or sleeves 52), the invention according to the first two embodiments described above allows to envisage new geometries and / or new structures of sealing joints 6.

[0073] Thus, for example, the joints 6 according to the first two embodiments described above can each be made from a single layer of material, for example polymer, without the presence of a metal spring blade.

[0074] Furthermore, the seals 6 according to these first two embodiments can extend in the shape of an O around an axis of revolution (which merges with the main Y axis of the machine 1), that is to say the seals 6 according to these first two embodiments can each have a closed section around the side wall 34 of the head 31, in a plane perpendicular to the main Y direction.

[0075] Advantageously, the seals 6 according to these first two embodiments can each be formed from an axisymmetric body with respect to the main Y axis. The O-shaped seals 6 can thus have a shape similar to that of the rings 51 or the sleeves 52 forming the system of notches 5.

[0076] Alternatively, the seals 6 may extend in a C-shape around the main Y axis of the machine 1. In other words, the seals 6 may be formed from an open body which does not describe a complete revolution around the main Y axis of the machine 1. Such seals 6 may be pressed against the side wall 21 of the jacket 2 by means of a set of expander(s) 8 illustrated in [Fig.l] and [Fig.5]

[0077] The set of expander(s) 8 is intended to be positioned between the set of seal(s) 6 and the head 31 of the piston 3. In particular, the set of expander(s) 8 comprises one or more blades 81 which extend in a C-shape (i.e. in the shape of an arc of a circle) in a plane perpendicular to the main Y direction of the machine 1.

[0078] Each blade 81 is advantageously made of a metallic material. In addition, each blade 81 has two opposite ends which define a lateral opening in the shape of an arc of a circle. These openings can be reversibly moved apart or brought closer to each other so as to modify the arc length of the lateral opening of the blade.

[0079] Thanks to the removable nature of the system of notches 5, the seals 6 (O-shaped or C-shaped) of the machine 1 according to any one of the first two embodiments of the invention can be threaded around the side wall 34 of the head 31 of the piston 3 without needing to be deformed beforehand.

[0080] According to a third embodiment illustrated in [Fig.6], the system of notches 5 comprises a plurality of sleeves 52 intended to cooperate with the side wall 34 of the head 31 of the piston 3 according to a tight fit. Each of the sleeves 52 comprises two collars 53 which delimit a groove having a C-shaped profile. This profile is defined by considering a cross section of the machine 1 along a cutting plane parallel to the main Y direction.

[0081] The slot system(s) 5 according to this third embodiment is said to be of type 3.

[0082] According to a fourth embodiment illustrated in [Fig.7], the system of notches 5 comprises a single sleeve 52 comprising a plurality of collars 53 and a plurality of grooves each having a C-shaped profile. This profile is defined by considering a cross section of the machine 1 along a cutting plane parallel to the main Y direction. The single sleeve 52 according to the fourth embodiment has a length greater than the respective lengths of the sleeves 52 of the third embodiment.

[0083] The slot system 5 according to the fourth embodiment is said to be of type 4.

[0084] It should be noted that a machine 1 according to the invention may comprise a com combination of different slot systems 5. The machine 1 illustrated in [Fig.5] comprises a type 3 slot system and a type 2 slot system.

[0085] In the embodiments illustrated in [Fig.6] and [Fig.7], the collars 53 associated with the same sleeve 52 (respectively with the single sleeve 52) are fixed (not removable) relative to each other.). Consequently, the height of the grooves between two consecutive collars 53 is also fixed (not adaptable as previously). However, each sleeve 52 (respectively the single sleeve 52) of the system of notches 5 can be removed from the head 31 of the piston 3.

[0086] To allow their insertion into the set of groove(s) delimited by the fixed collars 53, the seals 6 of the machine 1 according to the last two embodiments extend in a C shape. These C-shaped seals 6 can be associated with a set of expander(s) 8 described above.

[0087] In order to facilitate the assembly and disassembly of the system of slot(s) 5 and the assembly of seal(s) 6 relative to the piston 3, the head 31 and the rod 32 of the piston 3 are designed as two separate parts which are configured to be assembled reversibly (see [Fig.2]).

[0088] In particular, the head 31 of the piston 3 comprises at its bottom 33 a radial projection 35 (or shoulder) against which the system of notches 5 and the assembly of seals 6 bear in the main direction Y. Furthermore, the head 31 of the piston 3 has an end 36 which is opposite the bottom 33 and from which the system of notches and the assembly of seals are threaded along the head 31 of the piston 3. The end 36 is provided with a first coupling member 37 allowing the rod 32 to be fixed to the head 31.

[0089] The rod 32 of the piston 3 comprises a second coupling member 38 which is intended to cooperate with the first coupling member 37 provided at the head 31. Furthermore, the rod 32 of the piston 3 has a diameter greater than the diameter of the head 31 of the piston 3. In this way, when it is fixed to the head 31, the rod 32 of the piston 3 forms a radial projection 39 relative to the head 31.

[0090] Thus, the system of notches 5 and the set of seals 6 bear against this radial projection 39 in the main direction Y.

[0091] Ultimately, the piston 3 may comprise two radial projections which form stops between which the system of notches 5 and the assembly of seal(s) 6 extend: a first stop 35 formed by the head 31, and a second stop 39 formed at a junction between the head 31 and the rod (32). The radial stops 35, 39 make it possible to keep the system of notches 5 and the assembly of seal(s) 6 integral with the piston 3 in the main direction Y.

[0092] In the example illustrated in [Fig.2], one between the first coupling member 37 and the second coupling member 38 is a threaded bore. The other between the first coupling member 37 and the second coupling member 38 is a threaded end piece. Thus, the first coupling member 37 and the second coupling member 38 can cooperate for example by screwing.

[0093] Alternatively, the coupling members 37, 38 may take any other form known to those skilled in the art.

[0094] According to the invention, the side wall 34 of the head 31 of the piston 3 is designed to allow free sliding of the system of notches 5 and / or the assembly of seal(s) 6 along the head 31, from the end 36 to the bottom 33 of the head 31. In other words, the side wall 34 of the head 31 of the piston 3 is smooth, without grooves or notches over the entire portion intended to receive the system of notches 5 or the assembly of seal(s) 6.

[0095] By free sliding of the system of notches 5 and / or of the assembly of seals 6, is meant a translation of said systems along the head 31 without the need to deform said systems.

[0096] Advantageously, in the nominal state, the system of notches 5 may have a nominal internal diameter greater than a nominal external diameter of the piston 3 (and more specifically than a nominal diameter of the side wall 34 of the head 31 of the piston 3), and a nominal external diameter less than a nominal internal diameter of the liner 2 (and more specifically than a nominal diameter of the side wall 21 of the liner 2). The diameters are measured along the X direction.

[0097] Thus, as better illustrated in [Fig.2] and [Fig.3], in the nominal state, the system of notches 5 forms with the side wall 34 of the head 31 of the piston 3 internal lateral clearances. The system of notches 5 forms with the side wall 21 of the sleeve 2 external lateral clearances.

[0098] When the machine 1 is subjected to a cryogenic temperature, the system of notches 5 contracts radially in a greater proportion than the contraction observed on the head 31 of the piston 3 or on the side wall 21 of the liner 2. Consequently, the system of notches 5 cooperates with the side wall 34 of the head 31 of the piston 3 according to a tight fit, thus promoting a seal at the interfaces between the system of notches 5 and this side wall 34. Furthermore, the external lateral clearances between the system of notches 5 and the side wall 21 of the jacket 2 increase to give rise to external leakage paths 7a of the fluid. These external leakage paths 7a are intended to allow flow and / or storage of the fluid.

[0099] Advantageously, in the nominal state, the system of notches 5 may have a nominal internal diameter equal to the diameter of the side wall 34 of the head 31 of the piston 3, and a nominal external diameter equal to the internal diameter of the side wall 21 of the liner 2. In other words, in the nominal state, the system of notches 5 and the side wall 21 of the liner 2 may cooperate according to a tight fit, that is to say without any external radial play. Similarly, the system of notches 5 and the side wall 34 of the head 31 of the piston 3 may cooperate according to a tight fit, without any internal radial play.

[0100] At a relatively colder temperature, the elements of the machine 1 contract. Following a contraction of the system of notches 5 greater than a contraction observed on the liner 2 and on the head 31 of the piston 3, the system of notches 5 continues to cooperate with the side wall 34 of the head 31 of the piston 3 according to a tight fit (tighter than in the nominal state). Furthermore, external leakage paths 7a of the fluid are formed between the system of notches 5 and the side wall 21 of the liner 2. These external leakage paths 7a are intended to allow a flow / storage of the fluid from the compression and / or expansion chamber 4.

[0101] Advantageously, in the nominal state (before assembly of the machine 1), the set of seal(s) 6 may have a nominal outside diameter greater than the nominal inside diameter of the side wall 21 of the liner 2, and a nominal inside diameter greater than the nominal outside diameter of the side wall 34 of the head 31 of the piston 3. After their positioning between the side wall 34 of the head 31 of the piston 3 and the side wall 21 of the liner 2, the set of seal(s) 6 forms with the side wall 34 of the head 31 of the piston 3 internal lateral clearances, and cooperates with the side wall 21 of the liner 2 according to a tight fit. For the purposes of this tight fit, a radial deformation of the seals 6 may be necessary.

[0102] When the machine 1 is subjected to a cryogenic temperature in operation, due to its relatively high expansion coefficient, the seal assembly 6 contracts radially to a greater extent than the liner 2 and the piston 3. Thus, the seal assembly 6 continues to cooperate with the side wall 21 of the liner 2 according to a tight fit. On the other hand, the internal lateral clearances between the seal assembly 6 and the side wall 34 of the head 31 of the piston 3 are maintained, but reduced to internal leakage paths 7b of the fluid. These leakage paths in interiors 7b are intended to allow flow and / or storage of the fluid from the compression and / or expansion chamber 4.

[0103] It should be noted that the tight fit between the set of seal(s) 6 and the side wall 21 of the jacket 2 promotes sealing at the interfaces between this set of seal(s) 6 and the side wall 21 of the jacket 2.

[0104] In the case of a machine 1 comprising a set of C-shaped seal(s) 6 and a set of expander(s) 8, the latter contributes to maintaining a tight fit of the former against the side wall 21 of the liner 2. The internal leakage paths 7b are then defined between the set of expander(s) and the side wall 34 of the head 31 of the piston 3 (see [Fig.5] to [Fig.7].

[0105] As illustrated in [Fig.l] to [Fig.7], the rings 51 (respectively the collars 53) alternate with the seals 6 along the side wall 34 of the head 31 of the piston 3. The rings 51 (respectively the collars 53) and the seals 6 form a longitudinal series of elements in which the transverse contact between each ring 51 (respectively each collar 53) and the adjacent seal 6 is not tight. In other words, there is between each ring 51 (respectively each collar 53) and the adjacent seal 6 a certain clearance which forms a transverse leakage path 7c of the fluid.

[0106] According to the invention, the outer leakage paths 7a, the inner leakage paths 7b and the transverse leakage paths 7c form a crenellated trajectory or a wavy trajectory or a zigzag trajectory.

[0107] In the illustrated embodiments, the trajectory is in the form of a notch. This shape is determined by the rectilinear profile of the respective faces of the rings 51 (or collars 53) and the seals 6. The rectilinear profile is defined by considering a sectional view of the machine 1 along a plane parallel to the main Y axis.

[0108] Advantageously, as illustrated in [Fig.l], [Fig.5] to [Fig.7], two or more seals 6 can be inserted in the same groove delimited by the side wall 34 of the head 31 of the piston and two consecutive rings 51 ([Fig.l]), or in a groove delimited by a sleeve 52 comprising at least one collar 53 ([Fig.5] to [Fig.7])•

[0109] For the machine 1 according to the first and second embodiments (see [Fig.l] and [Fig.5]), the seals 6 inserted in the same groove can be C-shaped and / or O-shaped. For the machine 1 according to the third and fourth embodiments (see ([Fig.6]] and [Fig.7]), the seals 6 inserted in the same groove are C-shaped.

[0110] When two or more seals 6 inserted in the same groove are C-shaped (leaking seals), these seals 6 can be positioned relative to each other in this groove in such a way that their respective lateral openings are angularly offset, such an offset complicates the trajectory formed by the paths of leak and thus improves the sealing of the fluid machine 1.

[0111] The elements of the fluid machine 1 according to the invention may be subject to longitudinal contraction when they are subjected to a cryogenic temperature. In particular, the rings 51 (respectively the collars 53) and the seals 6 may contract longitudinally, modifying the clearances between these rings 51 (respectively the collars 53) and these seals 6.

[0112] In order to compensate for the longitudinal contraction of the rings 51 (respectively the collars 53) and the seals 6, and to limit the increase in clearances between these rings 51 (respectively the collars 53) and these seals 6, with reference to [Fig.2] to [Fig.4], the fluid machine 1 advantageously comprises an elastic return member 9. Such a member is advantageously positioned at one end of the series formed by the rings 51 (respectively the collars 53) and the seals 6.

[0113] In the example illustrated in [Fig.2] to [Fig.4], the elastic return member 9 is positioned at one of the radial stops 35, 39 of the piston 3, here on the first stop 35.

[0114] To assemble the fluid machine 1 described in relation to the first embodiment, a first step consists of inserting the head 31 of the piston 3 inside the sleeve 2. This step thus makes it possible to form between the head 31 of the piston 3 and the sleeve 2 an annular space intended to receive the system of notches 5 and the set of seals 6.

[0115] A second step of the assembly method consists of alternately threading the rings 51 and the seals 6 (whether they are closed O-shaped seals or open C-shaped seals) into the annular space thus formed. A seal 6 can be threaded along the head 31 of the piston 3 against a ring 51 already mounted on the head 31 of the piston 3, and before fixing the next ring 51 which will enclose it.

[0116] Finally, a third step consists of fixing the head 31 to the rod 32. This step makes it possible to maintain the system of notches 5 and the assembly of seals 6 integral with the head 31 of the piston 3.

[0117] For the assembly of the machine 1 according to the second embodiment, a seal 6 (closed in the shape of an O or an open seal in the shape of a C) can be threaded around a sleeve 52 (in the groove formed by this sleeve 52), then the subassembly thus formed can then be threaded around the head 31 of the piston 3. The machine 1 can thus be assembled by successively threading along the head 31 of the piston 3 sleeve / seal subassemblies.

[0118] Alternatively, a seal 6 can be threaded around a sleeve 52 (i.e. in the groove formed by this sleeve 52) which is already mounted around the head 31 of the piston 3. Such an operation can be repeated for all the other seals 6 and all the other sleeves 52.

[0119] For the assembly of the machine 1 according to the third embodiment, a seal 6 (open in the shape of a C) is inserted into a groove defined by a sleeve 52 by deformation of this seal 6. The sleeve 52 may or may not be previously threaded onto the side wall 34 of the head 31 of the piston 3. The operation is repeated as many times as necessary for the rest of the seals 6 and the rest of the sleeves 52.

[0120] The assembly of the machine 1 according to the fourth embodiment is carried out according to a method similar to that of the machine according to the third embodiment except that a single sleeve is threaded around the side wall 34 of the head 31 of the piston 3.

[0121] In the embodiments illustrated in [Fig.l] to [Fig.7], the piston 3 is movable while the liner 2 is fixed. The system of notches 5 and the assembly of seal(s) 6 are integral with the head 31 of the piston 3 during operation of the machine 1 (i.e. the system of notches 5 and the assembly of seal(s) 6 follow the movement of the head 31 of the piston 3). In a variant not illustrated, the liner 2 may be movable and the piston 3 fixed. According to this variant, the system of notches 5 and the assembly of seal(s) 6 may be integral with the liner 3 during operation of the machine 1.

Claims

Claims

1. Piston (3) for a fluid machine (1), the piston (3) being intended to be mounted at least partly inside a sleeve (2) of the machine (1) according to a relative back-and-forth movement between the piston (3) and the sleeve (2), the piston (3) comprising a head (31) defined around a main direction (Y) of the piston (3) and intended to form with the sleeve (2) of the fluid machine (1) a chamber (4) for expansion and / or compression of the fluid, the piston (2) also comprising a system of notches (5) removably threaded along the head (31) and arranged in radial projection relative to the head (31), the system of notches (5) being configured to delimit a set of groove(s) provided to receive a set of sealing gasket(s) (6) intended to cooperate in a sealed manner with a side wall (21) of the sleeve (2) of the fluid machine (1),characterized in that the system of crenellations (5): - extends at 0 around a side wall (34) of the head (31), i.e. has a closed section around the side wall (34) of the head (31) in a plane perpendicular to the main direction (Y), - is composed of a material having a coefficient of thermal expansion different from the coefficient of thermal expansion of a material of the head (31), - is configured to, in the operating configuration, cooperate with the side wall (34) of the head (31) in a tight and sealed manner, thanks to a differential thermal contraction of the system of crenellations (5) relative to the head (31).,

2. Piston (3) according to the preceding claim, characterized in that the system of notches (5) and the assembly of seals (6) are respectively made of materials having different coefficients of thermal expansion, the coefficient of thermal expansion of the system of notches (5) being greater than the coefficient of thermal expansion of the assembly of seals (6), the coefficient of thermal expansion of the assembly of seals (6) being greater than the coefficient of thermal expansion of the head (31).

3. Piston (3) according to any one of claims 1 or 2, characterized in that the system of notches (5) comprises a plurality of rings (51) arranged in series along the side wall (34) of the head (31), each of the rings (51) having an inner side face intended to cooperate with the side wall (34) of the head (31), an outer side face intended to be positioned opposite the side wall (21) of the sleeve (2), and two opposite transverse faces extending between the inner side face and the outer side face, the set of groove(s) being delimited by the side wall (34) of the head (31) and consecutive rings (51).

4. Piston (3) according to any one of claims 1 or 2, characterized in that the system of notches (5) comprises a sleeve (52) intended to be slipped onto the side wall (34) of the head (31), the sleeve (52) comprising at least one collar (52a) and at least one of the grooves of the set of grooves.

5. Piston (3) according to the preceding claim, characterized in that all or part of the grooves formed by the sleeves (52) have an L-shaped or C-shaped profile, the profile being defined by considering a cross section of the machine (1) along a cutting plane parallel to the main Y direction.

6. Piston (3) according to any one of the preceding claims, characterized in that the head (31) is configured to allow free sliding of the system of notches (5) without deformation of said system, respectively of the assembly (6) of seal(s) without deformation of said assembly, from an end (36) of the head (31) intended to be positioned far from the compression and / or expansion chamber (4) to a bottom (33) of the head (31) intended to delimit the compression and / or expansion chamber (4).

7. Piston (3) according to the preceding claim, characterized in that the bottom (33) of the head (31) forms a first radial stop (35), the piston (3) comprising a rod (32) configured to be reversibly fixed to the end (36) of the head (31) and to form with the head (31) a second radial stop (39), the system of notches (5) and the set of seals (6) being intended to be arranged between the first radial stop (35) and the second radial stop (39).

8. Piston (3) according to the preceding claim, characterized in that an elastic return member (9) is arranged between the system of notches (5) and at least one between the first radial stop (35) and the second radial stop (39).

9. Machine (1) for fluid, and in particular for cryogenic fluid, comprising a jacket (2) and a piston (3) according to any one of the preceding claims, the piston (3) being inserted at least partly into the interior of the jacket (2) so as to form with the jacket (2) a chamber (4) for expansion and / or compression of the fluid, the piston (3) and the jacket (2) being configured to be movable relative to each other according to a relative back-and-forth movement.

10. Machine (1) according to the preceding claim, characterized in that the expansion and / or compression chamber (4) is delimited by the side wall (21) of the jacket (2), a bottom (22) of the jacket (2) and a bottom (33) of the head (31) of the piston (3).

11. Machine (1) according to any one of claims 9 or 10, characterized in that the system of notches (5) has a nominal internal diameter greater than or equal to the nominal diameter of the side wall (34) of the head (31) of the piston (3), and a nominal external diameter less than or equal to the nominal internal diameter of the side wall (21) of the sleeve (2).

12. Machine (1) according to the preceding claim, characterized in that the system of notches (5) is configured to pass from a nominal state associated with a first temperature, in which said system forms internal lateral clearances with the side wall (34) of the head (31) of the piston (3), and external lateral clearances with the side wall (21) of the liner (2), to a first contracted state associated with a second temperature lower than the first temperature, in which said system cooperates with the side wall (34) of the head (31) of the piston (3) according to a tight fit, and in which the external lateral clearances are widened compared to the nominal state to form external fluid leakage paths (7 a).

13. Machine (1) according to any one of claims 9 to 12, characterized in that the seal assembly (6) is configured to pass from a nominal state associated with a first temperature, in which the seal assembly (6) has a nominal outside diameter greater than the nominal inside diameter of the side wall (21) of the liner (2), and in which the seal assembly (6) forms with the groove assembly (s) internal lateral clearances, to a contracted state associated with a second temperature lower than the first temperature, in which the seal assembly (6) continues to cooperate with the side wall (21) of the liner (2) according to a tight fit, and in which the internal lateral clearances are reduced compared to the nominal state to form internal fluid leakage paths (7b).

14. Machine (1) according to any one of claims 9 to 13 taken in their connection with claim 3 or claim 4, characterized in that the rings (51), respectively the collars (53), alternate with the seals (6) along the head (31) of the piston (3), each ring (51), respectively each collar (53), forming with an adjacent seal (6) a transverse leak path (7c).

15. Machine (1) according to claims 12 to 14 taken in combination, characterized in that the outer leakage paths (7a), the inner leakage paths (7b) and the transverse leakage paths (7b) define a wavy or crenellated path for a flow of the fluid, said path extending along the head (31) of the piston (3).

16. Machine (1) according to any one of claims 9 to 15, characterized in that the set of seal(s) (6) comprises seals (6) open in the shape of a C and held pressed against the side wall (21) of the sleeve (2) by means of a set of expander(s) (8), the set of expander(s) being positioned between the side wall (34) of the head (31) of the piston (3) and the set of seal(s) (8).

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