Rotary hydraulic machine with piston

Abstract

The invention relates to a hydraulic machine comprising:-a cylinder having cavities, and-pistons (16) housed in the respective cavities, each piston comprising a top (26) and a base (28), the base (28) having a maximum dimension (Dp) in a direction perpendicular to the axis (P-P) of the piston, the base has a maximum dimension (Dt) of the apex, which is smaller than a maximum dimension (Dt) of the apex in a direction perpendicular to the axis, and the base has a recess (32) which opens on two opposite sides of the base at two respective ends of the recess opposite each other along a main axis (C-C) of the recess.

Description

Technical Field

[0001] The present invention relates to a hydraulic press, in particular to a piston of a hydraulic press. Background Art

[0002] A rotary hydraulic machine typically comprises a cylinder with a housing in which pistons are received. These pistons either move a fluid or are moved by the fluid, depending on whether the machine operates as a pump or a motor.

[0003] It is an object of the present invention to improve the operation of a rotary hydraulic machine. Summary of the Invention

[0004] To this end, according to the present invention, there is provided a hydraulic press comprising:

[0005] a cylinder having a housing and a duct for supplying fluid to the respective housing, and

[0006] - a piston, which is accommodated in a corresponding housing,

[0007] Each piston consists of a head and a foot.

[0008] The foot has a larger dimension along a direction perpendicular to the axis of the piston that is smaller than a larger dimension of the head along the direction perpendicular to the axis.

[0009] The foot has a cavity communicating with a conduit for supplying the housing of the piston,

[0010] The cavity opens to two opposite sides of the foot at two respective ends of the cavity that are opposite to each other along the main axis of the cavity.

[0011] Depending on the embodiment chosen, the cavity can serve several purposes. As will be seen, the cavity can thus have the function of facilitating fluid flow, softening the piston, or both.

[0012] Thus, the cavity may be arranged to allow fluid to pass through the piston foot via the piston foot.

[0013] This reduces interruptions in the fluid flow supplying the housing as it exits the supply duct. This reduces pressure losses. Reducing pressure losses therefore reduces the temperature of the fluid (for the same force and at the same speed). This temperature reduction reduces the need for limiting the rotational speed of the machine. It also reduces shearing of the fluid, preventing premature aging. Thus, the cavity facilitates filling the housing with fluid from the supply duct without compromising the compactness of the assembly.

[0014] The cavity may be arranged to extend at the free end of the foot.

[0015] The cavity may then be provided to allow the piston foot to deform more easily.

[0016] Furthermore, the cavity may also be provided to increase the passage cross section between the piston foot and the lower bore of the cylinder.

[0017] On the contrary, the cavity may be arranged to extend completely at a distance from the free end of the foot.

[0018] The cavity may be arranged to open in a direction opposite to the head.

[0019] The cavity may be arranged to be closed in a direction opposite to the head.

[0020] The cavity may be arranged to be bounded by at least one face oriented in a direction opposite to the head.

[0021] The cavity may be arranged to be delimited by at least one cylindrical surface having a generatrix perpendicular to the axis of the piston.

[0022] It is recalled that the cross section of the cavity can be circular, but can also be rectangular, triangular, etc.

[0023] Conversely, the face may be configured to be non-cylindrical, for example by having an elliptical or rectangular longitudinal cross-section.

[0024] The cavity may be configured to have a circular cross-section.

[0025] The main axis of the cavity may be arranged parallel to the axis of rotation of the machine.

[0026] At least one of the following features may be provided:

[0027] - each housing forms a pressure chamber configured to withstand the pressure of the hydraulic fluid;

[0028] -The foot extends completely into the pressure chamber;

[0029] - the piston, in particular the piston head, carries a sealing member in contact with the housing; and

[0030] - A sealing member extends at one end of the head adjacent to the foot.

[0031] When the machine is operated as a motor, the pressure chamber is in particular a drive chamber. In pump mode, the pressure chamber is a pressure chamber that generates a fluid circulation.

[0032] The foot may be provided with a circular lateral surface cut into by two auxiliary surfaces situated on either side of the axis of the piston.

[0033] These faces facilitate filling the housing with fluid in the direction of the piston axis, which is radial with respect to the axis of rotation of the machine.

[0034] The auxiliary surface may be arranged to form a cavity.

[0035] This makes fluid filling even easier.

[0036] One free end of the foot may be configured to have a planar surface perpendicular to the piston axis.

[0037] The machine may be arranged so that, at a position where the piston is closest to the bottom of the housing, the cavity extends opposite the supply conduit.

[0038] This applies regardless of the axial or radial orientation of the supply conduit. Thus, the term "relatively" may mean "facing" and / or "above." Thus, when the piston is in the lowered position, flow entering the housing through the supply conduit emerges toward the cavity.

[0039] The machine may be arranged so that, in the position where the piston is closest to the bottom of the housing, the piston extends closer to the bottom than to the mouth of the supply conduit to the housing.

[0040] Thus, in the absence of the cavity, the foot would extend opposite the entire mouth of the supply duct, or even completely block it. The cavity thus allows having a long foot extending very low downwards to better slidably guide the piston while maintaining good fluid flow at the outlet of the supply duct.

[0041] The machine may be arranged so that, in the position of the piston closest to the bottom of the housing, the piston leaves at least 50% of the cross-section of the mouth of the supply conduit leading to the housing.

[0042] "Leaving out" means that the projection of the piston on a plane orthogonal to the axis of rotation of the machine does not overlap with the projection of the mouth of the supply duct on this same plane.

[0043] The machine may be arranged to be configured so that in its most bottom-most position the piston clears 100% of the supply conduit cross-section.

[0044] Therefore, the piston foot does not form any obstacle to the entry of fluid into the housing.

[0045] The machine may be arranged so that, at the position where the piston is nearest the bottom of the housing, the foot leaves a passage through the foot having a cross-section which is greater than or equal to 50% of the cross-section of the mouth of the supply conduit leading to the housing over the entire length of the passage.

[0046] The machine may be arranged so that, at the position where the piston is closest to the bottom, the cross section of the passage is greater than or equal to the cross section of the mouth throughout the length of the passage.

[0047] The machine may be arranged so that, at the position where the piston is closest to the bottom of the housing, the fluid does not experience a reduction in passage cross-section when passing through the foot.

[0048] The cylinder may be arranged with a supply conduit extending in a direction parallel to the axis of rotation of the machine.

[0049] This orientation allows for compactness of the cylinder compared to a radial orientation of the duct.

[0050] The cylinder may be arranged with the supply conduit extending in a radial direction relative to the axis of rotation of the machine.

[0051] The direction may be arranged coaxially with the housing.

[0052] The machine may be arranged to include, for each piston, means for preventing rotation of the piston relative to the housing.

[0053] The preventing member may be configured to include a guide pin or a clip.

[0054] The preventing member may be arranged to extend at the piston foot on a side of the piston opposite to the supply conduit.

[0055] Each shell may be configured to include a head region and a foot region, the foot region being bounded by a main face and having a shell cavity, the shell cavity:

[0056] - cut into the main surface,

[0057] - extends in a direction from the base of the housing to the head region, and

[0058] -Does not prevent the piston from rotating.

[0059] The housing cavity thus allows for an enlarged fluid passage cross-section in areas where it would otherwise have a significantly reduced passage cross-section. This reduces fluid flow interruptions. The housing cavity thus facilitates both filling and emptying the housing with fluid. The fluid reaches the housing without prior compression, allowing the upward movement of the piston to be initiated. This arrangement reduces pressure losses and fluid temperature without reducing the limiting rotational speed and reducing fluid shear.

[0060] It may be provided that:

[0061] - the housing cavity extends on the same side of the piston as the supply duct;

[0062] - the housing cavity is of insufficient size to accommodate the pin;

[0063] - the housing has no plane of symmetry; and / or

[0064] The housing cavity opens into the head region.

[0065] The housing cavity may be arranged to extend fully at a distance from the axial direction of the housing that is less than a greater distance separating the head region and the axis.

[0066] The housing cavity does not necessarily extend over the extent of the surface of the head region of the housing.

[0067] The housing cavity may be arranged to extend completely at a distance from a mid-plane of the housing perpendicular to the axis of rotation of the machine.

[0068] The housing cavity thus extends beyond the functional region, which comprises the region of the piston and the region of the housing, which regions support one another in the circumferential direction relative to the axis of rotation. The position of the housing cavity thus remains within this region.

[0069] The housing cavity may be configured to be cylindrical.

[0070] The housing cavity may be arranged to have an axis parallel to the axis of the housing.

[0071] The housing cavity may be arranged to have an axis perpendicular to the axis of the housing.

[0072] The housing cavity may be arranged to have an axis that is inclined relative to an axis of the housing.

[0073] A supply conduit may be provided opening into the housing cavity.

[0074] This arrangement further facilitates easier entry and exit of the fluid into and out of the housing. Furthermore, this arrangement reduces the length of the supply conduit. Consequently, if necessary, the machining time for the supply conduit is also shortened to compensate for the additional time required to machine the housing cavity.

[0075] A duct for supplying the housing can be arranged to extend at the level of the foot region relative to the axis of the housing.

[0076] This is therefore an arrangement in which the duct does not open into a volume situated below the foot region, but is situated directly at the level of the foot region.

[0077] The piston can be configured to include a foot having a main surface and an auxiliary surface, the auxiliary surface cutting into the main surface of the piston foot, the housing cavity having a dimension along a direction perpendicular to the axis of the housing that is smaller than the dimension of the auxiliary surface along the direction perpendicular to the axis.

[0078] According to the present invention, a piston for a hydraulic press can also be provided.

[0079] The piston includes a head and a foot, and has a groove for receiving a sealing member,

[0080] The foot has a larger dimension along a direction perpendicular to the axis of the piston that is smaller than a larger dimension of the head along the direction perpendicular to the axis.

[0081] The foot has a cavity which opens to two opposite sides of the foot at two respective ends of the cavity which are opposite to each other along the main axis of the cavity.

[0082] The cavity extends on the same side of the groove for receiving the sealing member as the free end of the foot.

[0083] The cavity thus opens into a region of the piston which is arranged to be subjected to the pressure of the hydraulic fluid. This pressure is in particular the driving pressure when the machine is operated as a motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Embodiments and variants of the invention will now be presented by way of non-limiting examples with the support of the accompanying drawings, in which:

[0085] - Figure 1 is an axial cross-sectional view of a machine according to a first embodiment of the present invention;

[0086] - Figures 2 to 5 yes Figure 1 A view of one of the pistons of the machine;

[0087] - Figure 6 and Figure 7 is a cross-sectional and axial view of the piston in its housing in its cylinder;

[0088] - Figure 8 is a view similar to the previous one but schematically showing the channel cross-section and fluid flow in four parallel planes A, B, C and D;

[0089] - Figure 9 and Figure 10 is a partial cross-sectional view of the cylinder block of the machine, and Figure 11 It is a perspective view of the cylinder;

[0090] - Figure 12 and Figure 13 It is a schematic diagram of the functional areas of the cylinder and the piston;

[0091] - Figure 14 is a diagram showing stress in the piston foot;

[0092] - Figures 15 to 20 is a view showing a modification of the embodiment;

[0093] - Figure 21 and Figure 22 is a view of another variant showing two positions of the piston in its housing;

[0094] - Figure 23 is a cross-sectional view of the piston and housing,

[0095] - Figure 24 shows the passage of fluid in the housing, and

[0096] - Figure 25 It is a partial cross-sectional view of the piston and cylinder in the second embodiment, showing the stress of the cylinder on the piston. DETAILED DESCRIPTION

[0097] Introduction to the First Embodiment

[0098] Figures 1 to 14 A rotary hydraulic machine 2 according to one embodiment of the present invention is shown.

[0099] Machine 2 comprises a fixed part and a rotating part, the latter being movably mounted for rotation relative to the fixed part about an axis of rotation XX. The machine thus comprises a housing 4 and a central shaft 6, which is movably mounted for rotation relative to the housing by means of bearings 8. A cam 10 is rigidly fixed to the housing. A cylinder 12 is rotatably connected to shaft 6. The cylinder has a housing 14 that receives a respective piston 16, which is movably mounted for sliding movement within the housing, each piston sliding in a direction radial to axis XX. Each piston carries a roller 18 capable of rolling on a track of cam 10, which for this purpose has a lobe, known per se and not shown.

[0100] The machine comprises a distributor 20 connected to a high-pressure fluid circuit and a low-pressure fluid circuit. For each housing 14, the cylinder 12 comprises a fluid supply and discharge conduit 22 leading to the housing. The machine is arranged so that the distributor 20 connects the supply conduit 22 sometimes to the high-pressure circuit and sometimes to the low-pressure circuit, depending on the angular position of the shaft 6 (and therefore the cylinder) relative to the housing 4.

[0101] When housing 14 is supplied with high-pressure fluid, the pressure is communicated to the associated piston 16, which slides in its housing and, through the rolling of roller 18 against cam 10, causes the rotating part to rotate. The machine then operates as a motor, rotating the load. Conversely, when shaft 6 rotates relative to housing 4, the shape of cam 10 causes piston 16 to slide, which causes fluid to be discharged from each housing 14 into the high-pressure circuit. The machine then operates as a pump.

[0102] The present invention is applicable to machines having configurations other than this configuration.

[0103] As in Figures 2 to 5 As shown in FIG, each piston 16 comprises a head 26 and a foot or tail 28. The piston has a main axis PP, which extends from the head to the foot and is oriented here in a radial direction relative to the axis XX. The piston 16 in this case has a general shape that is rotationally symmetrical about this axis, but this is not mandatory.

[0104] In this example, the foot 28 and the head 26 each have a substantially cylindrical shape, with a circular section in a plane perpendicular to the axis PP.

[0105] If especially in Figure 4 As shown in FIG, the foot 28 has a larger dimension D along a direction perpendicular to the axis PP. p Similarly, the head 26 has a larger dimension D in a direction perpendicular to the axis PP. t In this case, these larger dimensions are diameters. The maximum diameter D of the foot 28 is p than the maximum diameter D of the head 26 t Smaller.

[0106] Thus, this is a stepped piston 16 which itself is housed in a complementary shaped stepped housing 14, as in Figure 6 and Figure 7 As shown in Figure 9 and Figure 10 As shown in , such a shape offers advantages in terms of compactness compared to a piston having a substantially cylindrical shape. In fact, thanks to the stepped piston, it is possible to have the same effective displacement while bringing the axes PP of the pistons closer together, as in Figure 9 . Thus, the angle α in this figure is reduced compared to the angle obtained with a non-stepped piston (i.e., in which the piston has the diameter of the head 26 over its entire length). This shape also brings the housing 14 closer to the axis of rotation XX of the cylinder 12: Figure 10 The distance d between the bottom 48 of each housing 14 and the inner face 29 of the cylinder block 12 is reduced.

[0107] The head 26 carries the roller 18 that comes into contact with the cam 10. For this purpose, it has, for example, a bracket 30 for receiving the roller 18. The bracket 30 has a cylindrical shape with an axis BB parallel to the axis of rotation XX of the machine and a circular cross-section in a plane perpendicular to the axis BB. The bracket is open in the direction opposite to the foot.

[0108] The foot 28 has a cavity 32 with a main axis CC. This cavity opens onto two opposite sides of the foot at two respective ends 34 of the cavity, which lie opposite each other along the main axis CC. In this case, the main axis CC of the cavity 32 is parallel to the axis of rotation XX of the machine. In this case, the cavity opens in the direction opposite to the head 26. It extends to the free end of the foot 28, opposite the head and bounded by a cylindrical surface 36 oriented in the direction opposite to the head 26. Surface 36 has a generatrix parallel to the axis CC and perpendicular to the axis PP of the piston 16. In this case, surface 36 has a circular cross-section.

[0109] The piston 16 has an annular groove 35 for receiving a sealing member 37 (such as a seal, particularly in Figure 4 14 and intended to come into contact with the housing 14) to ensure a seal between the piston and the housing. In this case, a groove 35 extends into the head 26 of the piston, adjacent to the foot 28 at one end of the head. The cavity 32 extends on the same side of the groove 35 as the free end of the foot opposite the head.

[0110] Due to the sealing member 37, each housing 14 forms a pressure chamber 41 which receives the foot 28 and is configured to withstand the pressure of the hydraulic fluid. The foot 28 extends completely into the pressure chamber. When the machine is operated as a motor, the pressure chamber 41 is in particular a drive chamber.

[0111] In this case, the foot 28 has a lateral surface 40 that is divided along axis PP into two cylindrical portions of different diameters, due to the reduced diameter of the portion of the foot closest to the head. This surface 40 is intersected by two auxiliary surfaces 42 located on either side of axis PP. In this example, the auxiliary surfaces 42 form cavities. Each of these cavities has a cylindrical shape with a generatrix parallel to axis PP. Each of these cavities extends from the free end of the foot 28 to the head 26.

[0112] In this case, the free end of the foot 28 has a planar face 44 perpendicular to the axis PP and divided into two parts on either side of the cavity 32 .

[0113] The piston 16 here has two planes of symmetry passing through its axis PP and being perpendicular to one another.

[0114] refer to Figure 6 and Figure 7 In the cylinder 12, the supply ducts 22 have an end 46 forming the mouth opening into the corresponding housing 14. In this case, each duct 22 has a rectilinear cylindrical shape and extends in a direction parallel to the axis of rotation XX.

[0115] The cavity 32 is in communication with the supply conduit 22. The machine is configured so that, at the position where the piston 16 is closest to the bottom 48 of the housing, the cavity 32 extends opposite the supply conduit 22. Figure 6 This was observed in Figure 15 、 Figure 16 and Figure 21 The following variations were observed in Figure 6 As shown in FIG. 4 , the piston extends with its free end closer to the bottom 48 than to the mouth 46 of the supply duct 22 leading to the housing.

[0116] The machine 2 is configured so that at the position where the piston 16 is closest to the bottom 48 of the housing 14, the piston leaves at least 50% of the cross-section of the outlet 46. Figure 8 As can be seen in FIG, in this position of the piston 16, the foot 28 provides a passage through the foot having, over the entire length of the passage, a section greater than or equal to 50% of the section of the supply duct 22 leading to the housing 14. In this case, this section of the passage is greater than or equal to the section of the duct 22. Due to the cylindrical shape of the cavity 32, the fluid does not experience a reduction in the section of the passage when passing through the foot 28 in this position of the piston 16. In particular, Figure 8 It is a schematic diagram of the present invention (with Figure 7 ), this figure allows to illustrate the fact that if one considers the cross-section of the fluid passage of the piston 16 in its lowest position in the cylinder, in particular in the lower part (that is to say below a plane P orthogonal to the axis of the piston passing through the centre of the supply duct), it can be observed that, thanks to the invention, the cross-section of the fluid passage passing through the different planes B, C or D can be no smaller than the cross-section of the fluid passage passing through plane A. Consequently, the cross-section through which the fluid portion intended to fill the lower part of the housing passes does not see, during its stroke, a reduction in cross-section that could lead to a loss of pressure. On the contrary, for each cutting plane, the corresponding channel cross-section is never smaller than the corresponding channel cross-section of the duct 22. The flow is thus improved and it is easier to flow along an axis parallel to the axis of rotation XX. The cavity 32 is arranged so as not to affect the functional surface of the piston foot 28. It is in fact known that, due to the rolling of the roller 18 on the cam 10, the piston 16 is subjected to a circumferential force 50 relative to the axis of rotation XX during its stroke in the housing, as shown in Figure 11 On the other hand, the piston is not subject to axial forces 52 along the axis XX. Therefore, the housing-piston assembly has a functional area 54 which is subject to significant forces and for which the amount of contact surface and contact material between the cylinder 12 and the piston 16 must be maintained. The functional area is the area extending in the circumferential direction on the housing and on the piston, as shown in FIG. Figure 12 and Figure 13. The functional area 54 indicated for the housing top also applies to the piston foot 28. For this reason, the area of ​​the foot 28 oriented in the circumferential direction of the cylinder allows for longer guidance of the piston along the axis PP to counteract circumferential forces. On the other hand, other areas of the foot 28 oriented in the axial direction XX and subject to lesser forces can accommodate the release of material. The main cavity 32 and the lateral cavity formed by the auxiliary surface 42 are located outside this functional area 54 and therefore do not compromise performance in this regard.

[0117] The cavity 32 also allows the piston foot 28 to deform more easily. In fact, in addition to the pressure loss, the release of material in the non-functional area of ​​the piston foot gives the material flexibility. This reduces the stress concentration on the lower part of the foot 28, as in Figure 14 , which illustrates the level of stress concentration in the foot 28 during operation. Thus, a favorable deformation zone 56 situated in the middle portion of the face 36 closest to the piston head 26 and stress concentration zones 58 situated at the ends of this face can be distinguished.

[0118] Cavity 32 is formed, for example, by milling. If necessary, a centering point (not shown) can be provided to allow machining of the piston. This point has the form of a blind cavity, extending from face 36 along piston axis PP into the foot. It provides a clamping portion for receiving the end, for securing the piston between this end and another clamping portion (e.g., another end received in the bracket or on head 26 before the bracket is manufactured).

[0119] Variations of the embodiment

[0120] Modifications of the embodiment will be described below. Features common to the embodiment described above will not be described again.

[0121] exist Figure 15 and Figure 16 In a variant of the embodiment, in the cylinder 12, the duct 22 for supplying each housing 14 extends in a radial direction relative to the axis of rotation XX. The duct extends in the direction of the axis PP of the piston. This direction is coaxial with the housing. The duct leads to the center of the cavity 32. In fact, although the invention is particularly interesting when the fluid suction / discharge occurs via a lateral duct, the invention is also interesting when the supply occurs from below along a radial axis. As can be seen in the figure, in the case of supply from below the piston foot, if the recess is made by sweeping a cross-section of a specific shape along an axis parallel to the axis of rotation of the motor (the recess does not cut into the functional area of ​​the piston, in particular the functional area of ​​the piston foot), the fluid supplying the housing is not obstructed in its path to fill the housing. It can also be provided here that the cross-section of the recess is such that it allows the fluid to enter the chamber without having to undergo a reduction in the channel cross-section.

[0122] exist Figure 17 In a variant of the embodiment of the present invention, the cylinder of the face 36 defining the cavity 32 has a V-shaped open cross section, giving the cavity a V-shaped or triangular outline shape.

[0123] exist Figure 18 In a variation of the embodiment, the column has a rectangular open cross-section.

[0124] exist Figure 19 In a variant of embodiment, the cavity 32 is closed in the direction opposite the head 26 and extends completely at a distance from the free end of the foot 28. The cavity is in this case cylindrical with a circular cross section.

[0125] exist Figure 20 In a variant of the embodiment of the present invention, the machine comprises, for each piston 16, a member for preventing the piston from rotating relative to the housing 14. This member comprises here a guide pin. Figure 3 The pin (shown in FIG) extends on the side of the piston opposite the supply conduit 22. The pin is partially mounted in a blind conduit arranged in one of the auxiliary faces 42. The conduit has an elongated shape, for example, radially relative to the piston axis PP. The pin protrudes from this face and from the envelope surface of the foot. The pin is received in an auxiliary housing 62 of the housing, which is elongated parallel to the axis PP.

[0126] exist Figures 21 to 24 In a variation of Figures 2 to 4 The pistons of the 16 are identical. This variant differs in the housing 14 of the piston.

[0127] Each housing 14 comprises a head region 66 and a foot region 68, which respectively house the head 26 and foot 28 of the piston, having a shape complementary to these parts of the piston. Thus, the foot region has a diameter, in a direction perpendicular to the axis PP of the housing, which is smaller than the diameter of the head region 66 in the same direction.

[0128] The foot region 68 is delimited by a main face 70 which, in this case, is cylindrical with a circular cross section in a plane perpendicular to the axis PP.

[0129] The foot area has an auxiliary cavity 72 which:

[0130] - cutting into the main surface 70,

[0131] - extends in a direction from the bottom 48 of the housing to the head region 66, and

[0132] - The piston 16 is not prevented from rotating.

[0133] The auxiliary cavity 72 is cylindrical in this case, having an axis parallel to the axis PP of the housing and, in this example, a circular cross section in a plane perpendicular to this axis. However, the cross section may be rectangular, triangular or of other shapes.

[0134] In this case, the auxiliary cavity 72 opens into the head region 66 via one of its axial ends.

[0135] The auxiliary cavity extends completely at a distance from the housing axis PP that is smaller than the greater distance separating the head region 66 from the axis PP. Consequently, the auxiliary cavity does not extend within the surface of the head region. Cavity 72 extends completely at a distance from the housing's midplane, which is perpendicular to the axis of rotation XX. Here, the cavity is interrupted by a plane radial to this axis. Consequently, auxiliary cavity 72 is arranged so as not to interfere with the functional surface of the foot region 68.

[0136] refer to Figure 21 and Figure 22 In the cylinder 12, the supply ducts 22 have an end 46 forming the mouth of the corresponding housing 14. In this case, each duct 22 has a rectilinear shape and extends in a direction parallel to the axis of rotation XX. The supply ducts 22 open into the auxiliary cavity 72 and extend at the level of the foot region relative to the axis PP of the housing.

[0137] Figure 21 and Figure 22 The piston 16 is shown in the lower position and the upper position in the housing 14, respectively. Figure 21 As can be seen in FIG, in the low position (which is the position where the piston is closest to the bottom 48 of the housing), the foot 28 of the piston extends at a distance from the mouth 46 of the supply duct 22, leaving a gap, in particular due to the presence of the auxiliary cavity 72. The auxiliary cavity allows the fluid that reaches the foot area 68 in motor mode to fill the housing and reach the head 26 of the piston with reduced interruptions and therefore reduced pressure losses, as in Figure 24 As shown in FIG. , the cross-section of the fluid passage near the supply conduit 22 is therefore larger. This also reduces pressure losses during discharge. In fact, the same advantages exist in pump mode, when the piston pushes the fluid out of the housing into the conduit 22 and then this fluid is used for discharge.

[0138] As in Figure 23 As shown in FIG, each lateral cavity formed by the lateral face 42 of the piston has a dimension l along a direction perpendicular to the axis PP of the housing. c , which is larger than the dimension l of the auxiliary cavity 72 of the housing arranged oppositely in the same direction. pSmaller. This arrangement allows to avoid the generation of burrs in the functional area of ​​the piston foot 28 where it slips during machining of the auxiliary cavity 72. This also allows simpler milling if necessary.

[0139] As in Figure 20 In this variant, the piston includes a pin 60 received in a slot 62 in the housing to prevent rotation of the piston within the housing. Unlike slot 62, auxiliary cavity 72 is not sufficiently large to accommodate pin 60, particularly in depth in a plane perpendicular to axis PP. This provides a secure self-locking mechanism when the piston is received in its housing. In fact, an operator cannot place the piston in its housing by attempting to insert the pin into the auxiliary cavity. Slot 62 and cavity 72 are located on either side of the midplane of cylinder 12, but not diametrically opposite each other on either side of axis PP. Consequently, foot region 68 does not have a plane of symmetry. Their positions around the axis here form an angle of approximately 150°.

[0140] The cylinder 12 can be manufactured by using conventional methods, in particular by machining and / or casting, given its overall shape. In this case, the auxiliary cavity 72 and the slot 62 are made in the foot region by removing material using the same tool (e.g., the same milling cutter).

[0141] Second embodiment

[0142] Another embodiment of the machine is Figure 25 . Only the features of the machine that differ from those of the first embodiment will be presented. The main difference is that the cavity 32 opens into two opposite sides of the foot 28 in the form of a slot. Consequently, the dimensions of the cavity in a plane perpendicular to its axis CC are reduced compared to the first embodiment, while the length along this axis remains unchanged. The cavity has, for example, a parallelepiped shape, with a cross-section in a plane perpendicular to the axis CC that is very thin in a direction perpendicular to the axis XX of the machine. The cavity extends from the free end of the piston foot. It is bounded by two planar surfaces that are parallel to each other and parallel to a direction radial to the axis XX. The cavity is similar to the cavity that would be obtained by sawing a cut in the piston from the piston foot. It can be achieved by this or other means.

[0143] During operation of the hydraulic press (during relative rotation of cylinder block 12 and cam 10), piston 16 is subjected to a tilting force F relative to its translational axis PP. This tilting force F is applied in a plane perpendicular to the axis XX of relative rotation between the cylinder block and cam. Bracket-shaped recesses 30 located at the top of the piston are oriented parallel to this axis to allow rollers 18 contained within these recesses to roll against the cam. Cavity 32 formed in piston foot 28 is also parallel to the axis XX of relative rotation between the cylinder block and cam. Due to the presence of this additional cavity in the piston foot, the portions of the guide surface adjacent to this cavity in the piston foot exhibit a slight flexibility, allowing them to deform in a plane perpendicular to the cavity axis (CC). Therefore, precisely in the plane where the tilting force F is significant, these portions of the guide surface can deform slightly and increase the contact surface. This allows the negative effects of the tilting force to be limited by increasing the contact surface, thereby reducing contact pressure and avoiding excessive local friction. This reduces wear on the piston and cylinder block in the hydraulic press. This flexibility can be achieved by providing the cavity with alternative shapes.

[0144] Many modifications may be made to the present invention without departing from its scope.

Claims

1. A hydraulic press (2), comprising: a cylinder (12) having a housing (14) and a duct (22) for supplying fluid to the respective housing, and - pistons (16) housed in said respective housings, each piston comprising a head (26) and a foot (28), The foot (28) has a larger dimension (D) along a direction perpendicular to the axis (PP) of the piston. p ), the larger size (D p ) is greater than the larger dimension (D) of the head in a direction perpendicular to the axis t ) is smaller, The foot has a cavity (32) communicating with a conduit (22) for supplying the housing of the piston, The cavity opens to two opposite sides of the foot at two respective ends (46) of the cavity that are opposite to each other along the main axis (CC) of the cavity.

2. Machine according to the preceding claim, wherein The cavity (32) extends at the free end of the foot (28).

3. The machine according to claim 1, wherein: The cavity (32) extends completely at a distance from the free end of the foot (28).

4. Machine according to at least one of the preceding claims, wherein The cavity (32) is bounded by at least one face (36) oriented in a direction opposite to the head (26).

5. Machine according to at least one of the preceding claims, wherein The cavity (32) is delimited by at least one cylindrical surface (36) having a generatrix perpendicular to the axis (PP) of the piston.

6. Machine according to at least one of the preceding claims, wherein The cavity (32) has a circular cross-section.

7. Machine according to at least one of the preceding claims, wherein The main axis (CC) of the cavity (32) is parallel to the axis of rotation (XX) of the machine.

8. Machine according to at least one of the preceding claims, wherein The foot (28) has a circular lateral surface (40) cut into by two auxiliary surfaces (42) situated on either side of the axis (PP) of the piston.

9. Machine according to the preceding claim, wherein: The auxiliary surface (42) forms a cavity.

10. Machine according to at least one of the preceding claims, configured such that, in the position where the piston (16) is closest to the bottom (48) of the housing, the cavity (32) extends opposite the supply duct (22).

11. Machine according to at least one of the preceding claims, configured so that, in the position of the piston (16) closest to the bottom (48) of the housing, the piston leaves at least 50% of the cross-section of the mouth (46) of the supply duct leading to the housing.

12. Machine according to the preceding claim, configured so that, in the position of the piston (16) closest to the bottom, the piston leaves 100% of the cross-section.

13. A machine according to at least one of the preceding claims, configured so that, at the position where the piston (16) is closest to the bottom (48) of the housing, the foot (28) leaves a passage through the foot, the passage having a cross-section that is greater than or equal to 50% of the cross-section of the mouth (46) of the supply duct leading to the housing over the entire length of the passage.

14. Machine according to at least one of the preceding claims, configured so that, in the position where the piston (16) is closest to the bottom (48) of the housing, the fluid does not experience a reduction in the passage section when passing through the foot (28).

15. Machine according to at least one of the preceding claims, wherein The supply duct (22) extends in a direction parallel to the axis of rotation (XX) of the machine.

16. Machine according to at least one of claims 1 to 14, wherein The supply duct (22) extends in a radial direction relative to the axis of rotation (XX) of the machine.

17. Machine according to at least one of the preceding claims, comprising, for each piston (16), means (60) for preventing the piston (16) from rotating relative to the housing (14).

18. Machine according to the preceding claim, wherein The preventing member extends at the piston foot on a side of the piston (16) opposite the supply conduit (22).

19. Machine according to the preceding claim, wherein The preventing member (60) includes a guide pin.

20. Machine according to at least one of the preceding claims, wherein Each housing includes a head region (66) and a foot region (68), The foot region is delimited by a main surface (70) and has a housing cavity (72) which: - cutting into said main face (70), - extends in a direction from the bottom (48) of the housing to the head region, and - The piston is not prevented from rotating.

21. Machine according to the preceding claim, wherein The housing cavity (72) extends on the same side of the piston as the supply conduit (22).

22. The machine according to claim 19 and any one of claims 20 and 21, wherein The housing cavity (72) is of insufficient size to accommodate the pin.

23. Machine according to at least one of the preceding claims, wherein The housing (14) has no plane of symmetry.

24. A piston (16) for a hydraulic press, The piston comprises a head (26) and a foot (28), and has a groove (35) for receiving a sealing member (37), The foot has a larger dimension (D) along a direction perpendicular to the axis (PP) of the piston. p ), the larger size (D p ) is greater than the larger dimension (D) of the head in a direction perpendicular to the axis t ) is smaller, The foot has a cavity (32) opening to two opposite sides of the foot at two respective ends (46) of the cavity opposite to each other along the main axis (CC) of the cavity, The cavity (32) extends on the same side of the groove (35) as the free end of the foot.

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