FR3028587A1 - SEGMENT PRE-TORSION SYSTEM FOR PISTON SEALING DEVICE - Google Patents

Abstract

The segment pre-torsion system (21) for a piston sealing device (1) provided for a piston (2) comprises a male pre-torsion cone (22) arranged in the extension of a fixed skirt (5). ) and an outer circular pretorsion edge (23) arranged at the axial periphery of a sliding skirt (6), a sliding skirt spring (16) tending to bring said skirts (5, 6) closer to one another. so as to compress axially and tightly an extensible continuous segment (9) which takes, by deformation resulting from its simultaneous contact with said cone (22) and said ridge (23), a conical shape.

Description

The present invention relates to a segment pre-torsion system for a piston sealing device, said system being an improvement made to the piston sealing device, particularly with respect to the piston sealing device. intended for pistons operating under high pressure and whose French patent application No. 1357275 of July 23, 2013 belongs to the applicant. The segment pre-torsion system according to the present invention increases the efficiency of the piston sealing device, simplifies the industrial realization, reduces the cost of manufacture, and increases the robustness and service life. The pre-torsion system according to the present invention makes it possible, by means of the torsion of the extensible continuous segment and no longer by its machining, an off-center contact line on its external cylindrical face, which can therefore no longer be provided with of a simple convex centered on the axial thickness of said segment As a consequence of this axisymmetric configuration, in addition to the simpler embodiment and the lower cost price of said segment, it is no longer possible to make any mistake in the assembly of the latter on the piston sealing device; - to reduce the stress applied to the material of the continuous segment extensible during the swelling of the latter under the effect of pressure through a compression prestress deduced from the tensile stress to which said segment is subjected when It is important to avoid that minor defects in the flatness and / or perpendicularity of the extensible continuous segment and / or the fixed skirt and / or the slippery skirt compromise the seal formed between them. components. In addition, the segment pre-torsion system according to the invention does not involve any complex production method or expensive material. Said system inherits naturally and without any restriction from all the fields of application provided for the piston sealing device which it improves and perfects. The other features of the present invention have been described in the description and in the dependent claims directly or indirectly dependent on the main claim. The segment pre-twist system for a piston sealing device according to the present invention is provided for a piston operating in a cylinder with which it defines a fluid chamber, said piston comprising a piston head which has a fixed skirt connected by an inter-skid mechanical connection to a sliding skirt housed with low clearance in the cylinder and traversed axially by a pressure transmission channel while a sliding skirt spring tends to bring said skirts, one of the another so as to compress axially an extensible continuous segment sealingly interposed between said skirts, said segment having an inner cylindrical segment face subjected - via the pressure transmission channel - to the pressure of a fluid contained in the chamber to fluid, said segment also comprising an axial face segment of the fixed skirt side and an axial face of segment slippery skirt side and having a Cylindrical external cylindrical face which can come into contact with the cylinder, and comprises at least one male pre-torsion cone arranged in the axial extension of the fixed skirt, and held directly or indirectly in sealing contact with the axial face of the segment. fixed skirt side by slippery skirt spring; At least one outer circular pre-torsion edge arranged in projecting axial periphery of the sliding skirt and held directly or indirectly in leaktight contact with the axial face of the segment on the sliding skirt by the sliding skirt spring, the force produced by the latter conjugates with the male pre-torsion cone twisting the extensible continuous segment so that the latter takes - by deformation - a conical shape. The segment pre-torsion system according to the present invention comprises an axial face of a segment with a fixed skirt and an axial face of a segment with a sliding skirt which are flat and parallel.

The segment pre-torsion system according to the present invention comprises an axial face of a segment with a fixed skirt and / or an axial face of a segment on a sliding skirt which has a concave or convex curved profile centered or not on the radial thickness of the continuous segment. extensible.

The segment pre-torsion system according to the present invention comprises an outer cylindrical segment face which has a convex convex profile whose culminating point is centered on the axial thickness of the extensible continuous segment.

The segment pre-torsion system according to the present invention comprises a contact line found between the extensible continuous segment and the male pre-torsion cone when these two parts are simply brought into contact with each other without additional effort. which forms a circle of smaller diameter than that of the outer circular pre-torsion edge.

The segment pre-torsion system according to the present invention comprises a male pre-torsion cone which has a convex or concave convex radial profile.

The segment pre-torsion system according to the present invention comprises an outer circular pre-torsion edge which is constituted by the outer edge of a female pre-torsion cone axially arranged in the sliding skirt. The segment pre-torsion system according to the present invention comprises a fixed skirt which has on its outer cylindrical surface at least one decompression groove arranged near the male pre-torsion cone. The segment pre-torsion system according to the present invention comprises a decompression groove which is axially separated from the male pre-torsion cone by a segment axial bearing flange.

The segment pre-torsion system according to the present invention comprises a decompression groove which is connected to the end of the fixed skirt situated opposite the male pre-torsion cone by at least one decompression groove.

The following description with reference to the accompanying drawings and given by way of non-limiting example will better understand the invention, the features it has, and the benefits it is likely to provide.

Figure 1 is a schematic longitudinal sectional view of a piston equipped with a piston sealing device to which is applied the segment pre-torsion system according to the invention. 2 is a three-dimensional view of the segment pre-torsion system according to the invention integrated in a piston housed in a cylinder which is shown in three-dimensional view in cutaway the pison being extended by means of transmission consisting of a strut . Figure 3 is a three-dimensional cut-away view of a piston equipped with a piston sealing device to which the segment pre-torsion system according to the invention is applied. FIG. 4 is an exploded three-dimensional view of a piston equipped with a piston sealing device to which the segment pre-twist system 25 according to the invention is applied, the piston bearing face of the cooperating fixed skirt; with a leg of strength. Figure 5 is a schematic partial sectional view of the segment pre-torsion system according to the invention before the piston is assembled and the slidable skirt spring 30 axially compresses the continuous segment extensible between the slidable skirt and the skirt fixed. Figures 6 to 10 are partial diagrammatic sectional views of the segment pre-twist system according to the invention which show - the piston being assembled - the operation of said system at different pressure levels prevailing in the fluid chamber.

SUMMARY OF THE INVENTION: FIGS. 1-10 show the segment pre-twist system 21 for the piston seal 1 as well as various details of the constituent components thereof. Segment twist 21 for piston sealing device 1 is provided for a piston 2 operating in a cylinder 8 with which it defines a fluid chamber 27, said piston 2 comprising a piston head 3 which has a fixed skirt 5 connected by an inter-skid mechanical connection 7 to a sliding skirt 15 6 housed with a small clearance in the cylinder 8 and traversed axially by a pressure transmission channel 10 while a sliding skirt spring 16 tends to bring said skirts 5, 6 one of the other so as to axially compress an extensible continuous segment 9 interposed sealingly between said skirts 5, 6, said segment 9 having a segment internal cylindrical face 12 subjected - 20 via the channel pressure transmission device 10 - at the pressure of a fluid 36 contained in the fluid chamber 27. said segment 9 also comprising an axial face segment of the fixed skirt side 14 and an axial face segment of the sliding skirt side 15 and having a face outer cylindrical segment 13 which can come into contact with the cylinder 8.

It will be seen, particularly in FIGS. 1 and 3 and in FIGS. 5 to 10, that the segment pre-torsion system 21 comprises at least one male pre-torsion cone 22 arranged in the axial extension of the fixed skirt 5. and maintained directly or indirectly in sealing contact with the axial face of the segment 30 on the fixed skirt side 14 by the sliding skirt spring 16, the said male pre-torsion cone 22 also being able - according to a variant embodiment - to be arranged on the axial face fixed skirt 14 side skirt, the two variants can coexist. FIG. 1 and FIGS. 3 to 10 clearly show that the pre-torsion system 35 of segment 21 according to the invention comprises at least one outer circular pre-torsion ridge 23 projecting at the axial periphery of the sliding skirt 6 and maintained directly or indirectly in sealing contact with the axial face of the slip-skirt side segment 15 by the sliding skirt spring 16, the force produced by the sliding skirt spring 16 conjugated with the male pre-torsion cone 22 twisting the extensible continuous segment 9 of so that the latter takes - by deformation - a conical shape while the external circular pre-torsion edge 23 can also - according to 5 an alternative embodiment - be arranged on the axial face of the segment side slippery skirt 15, the two variants can coexist. In FIGS. 1 to 4, it will be noted that the fixed skirt 5 necessarily has a piston bearing face 4 capable of exerting a force on any mechanical, hydraulic or pneumatic transmission means 33, said skirt 5 also having a face of compression 11 provided to receive the pressure of the fluid 36 prevailing in the fluid chamber 27. Note that according to a particular embodiment, the transmission means 33 may consist of a strut 34 as shown in Figures 2 and 4.

As is clearly shown in FIGS. 5 to 10, the axial face of the segment on the fixed skirt side 14 and the axial side face segment of the sliding skirt 15 may be flat and parallel.

As an alternative embodiment of the segment pre-torsion system 21, the axial face of the segment on the fixed skirt side 14 and / or the axial face of the segment on the sliding skirt portion 15 may have a concave or convex curved profile, centered or not on the radial thickness of the continuous expandable segment 9.

FIGS. 5 to 10 further show that the external cylindrical segment face 13 may advantageously have a convex convex profile whose culminating point is centered on the axial thickness of the extensible continuous segment 9. As another variant, the culminating point of said bulge may also be provided off-center on the axial thickness of the extensible continuous segment 9.

From FIGS. 5 to 10, it is readily apparent that the line of contact between the expandable continuous segment 9 and the male pre-twist cone 22 when these two pieces 9, 22 are simply brought into contact with each other without contact with each other. Additional force may advantageously form a circle of smaller diameter than that of the outer circular pre-twist edge 23.

As a variant, the male pre-torsion cone 22 may have a convex or concave convex radial profile. FIG. 1 and FIGS. 3 to 10 show that according to the segment pre-torsion system 21 according to the invention, the outer circular pre-torsion edge 23 may consist of the outer edge of a pre-torsion cone; female torsion 24 axially arranged in the sliding skirt 6 said edge being able to be softened so as to be non-alive and to have a radius sufficient for the pressure of the contact made between the axial face of segment on the sliding skirt 15 and the sliding skirt 6 10 does not exceed a value acceptable by the constituent material of the continuous expandable segment 9, said radius furthermore making it possible to reduce substantially the diameter of the circle of said contact and to prevent creep of the material constituting the sliding skirt 6, said creep may result from an "edge effect" well known to those skilled in the art.

As illustrated in FIGS. 1 to 10, the fixed skirt 5 may comprise on its outer cylindrical surface at least one decompression groove 25 arranged near the male pre-torsion cone 22. According to this particular configuration, said groove 25 in particular to reduce the pressure drop that produces the fixed skirt 5 at its outer cylindrical surface and therefore reduce the pressure that the fluid 36 exerts on the outer cylindrical surface of segment 13 so as to facilitate the operation of the continuous segment extendable 9. Figures 1 to 10 also show that the decompression groove 25 may be axially separated from the male pre-torsion cone 22 by an axial bearing flange of segment 26 which gives the base of said cone 22 a large diameter so that said cone 22 provides the extensible continuous segment 9 a large axial bearing surface.

It will be noted in FIGS. 1 to 4 that the decompression groove 25 can be connected to the end of the fixed skirt 5 located opposite the male pre-torsion cone 22 by at least one decompression groove 28, last allowing the fluid 36 collected by the decompression groove 25 to escape at said end.

Said groove 28 may in particular be straight and as short as possible, or as shown in FIGS. 1 to 4 - helically preferably over at least 360 ° so as to promote the distribution of the fluid 36 over the entire external surface of the fixed skirt 5 to guarantee the skirt 5 the best possible lubrication.

It will be noted that, by way of a variant, the decompression groove 28 may be replaced by a decompression duct arranged no longer on the surface of the fixed skirt 5, but inside [the latter.

OPERATION OF THE INVENTION: The operation of the segment pre-torsion system 21 is understood from the view of FIGS. 1 to 10. These figures represent a non-limiting variant embodiment of said system 21 according to which said system 21 is equipped with a male pre-torsion cone 22 which cooperates with an outer circular pre-torsion edge 23 constituted by the outer edge of a female pi-torsion cone 24 formed in the sliding skirt 6. The variant chosen to illustrate the Operation of the invention also provides for an expandable continuous segment 9 whose axial face of the fixed skirt side segment 14 and the axial face of the sliding skirt side segment 15 are flat and parallel, this conferring on the realization of said segment 9 a great simplicity. In addition, the variant presented in FIGS. 1 to 10 provides for the outer cylindrical segment face 13 to have a convex convex profile whose peak is centered on the axial thickness of the extensible continuous segment 9, which avoids any error in mounting said segment 9 in the piston 2, simplifies the manufacture, reduces the cost of manufacturing. It is noted that the slope of the male and female cones 22, 24 and the height of the convex crown 30 arranged on the outer cylindrical segment face 13 have been deliberately exaggerated in the figures to be visible. In practice, the slope of the male pre-torsion cone 22 will not exceed a few microns per millimeter, while that of the female pre-twist cone 24 should be of the order of a few tenths of a millimeter per millimeter. With regard to the convex bulge 35 arranged on the outer cylindrical surface of segment 13, its highest point will culminate in practice at an altitude of between one micron and a few microns.

3028587 It is explained in the French patent application No. 1357275 of 23 July 2013 belonging to the applicant that for the pressure of the fluid 36 which is applied via the pressure transmission channel 10 to the inner cylindrical face of segment 12 makes it grow the diameter of the outer cylindrical segment face 13 to the point that it touches the cylinder 8 and achieves the desired sealing, said outer cylindrical face 13 must have a long slope of low inclination which descends towards the fixed skirt 5, while a steep slope of steep slope descends towards the slippery skirt 6.

This arrangement makes it difficult to manufacture the continuous expandable segment 9 because it is no longer axisymmetric in its length. In addition, said arrangement presents a risk because if the continuous expandable segment 9 is not mounted in the right direction on the piston, it can not work. Finally, to make a long slope sufficiently inclined means to increase at the bottom of said slope the clearance between the outer cylindrical segment face 13 and the cylinder 8. This increased clearance increases the local mechanical stress to which the continuous expandable segment 9 is subjected. when the internal cylindrical segment face 12 is subjected to a high pressure of the fluid 36, the bottom of the long slope of small inclination is forced to come into contact with the cylinder 8. It is understood in the vieves figures 1 to 10 that the Segment pre-torsion system 21 according to the invention solves these various problems.

FIGS. 1 and 3 and FIGS. 5 to 10 clearly show the extensible continuous segment 9, the male pre-twist cone 22 and the female pre-twist cone 24, the outer edge of which forms the outer circular edge of pre-torsion. FIG. 5 illustrates the state of these components 9, 22, 24 and 23 before the piston 2 is assembled and therefore, before the sliding skirt spring 16 tends to bring the sliding skirt 6 of the fixed skirt 5 which has the effect of compressing axially the extensible continuous segment 9 interposed sealingly between said skirts 5, 6. Figure 6 shows the segment pre-torsion system 21 once the sliding skirt spring 16 set place and the extensible continuous segment 9 compressed axially between the sliding skirt 6 and the fixed skirt 5.

It will be understood that the circular edge of the extensible continuous segment 9 which connects the internal cylindrical segment face 12 to the axial face segment of the fixed skirt side 14 has first been pressed against the male pre-twist cone 22 by the force exerted on the axial face of the segment on the slidable skirt 15 by the outer circular pre-twist edge 23, and then that said increasing force, the continuous expandable segment 9 has been subjected to torsion until the quasi the entire surface of the axial face of the segment on the fixed skirt side 14 comes into contact with the male pre-twist cone 22.

It can be seen in FIG. 6 that the torsion of the extensible continuous segment 9 has formed a long slope of slight inclination on the outer cylindrical segment face 13. As disclosed in the French patent application No. 1357275 of July 23, 2013 belonging to the applicant, said slope is necessary for the proper functioning of said segment 9. This slope has not been achieved by machining but by torsion of the extensible continuous segment 9, the diameter of said segment 9 at the bottom of said slope has been reduced by compression of the constituent material of said segment 9 while the diameter of the extensible continuous segment 9 at the top of said slope has been increased by extension of said material.

FIG. 7 illustrates what happens when the pressure of the fluid 36 contained in the fluid chamber 27 is non-zero, but still insufficient for the outer cylindrical segment face 13 to come into contact with the cylinder 8. The fluid pressure 36 a has begun to exert a force on the section S1 exposed to it by the internal cylindrical segment face 12 so that the diameter of the extensible continuous segment 9 has begun to increase, thereby bringing the outer cylindrical segment surface 13 of the cylinder closer together. 7 shows that the compressive stress c of the material constituting the extensible continuous segment 9 induced by the twisting of said segment 9 at the bottom of the long slope of small inclination is canceled, while increasing the tensile stress experienced by said material at the top of said slope. FIG. 8 shows the configuration of the segment pre-torsion system 21 according to the invention when the pressure in the fluid chamber 27 is sufficient for the outer cylindrical segment face 13 to come into contact with the cylinder 8. From FIG. at this point, the sealing previously provided by the sliding skirt 6 is now performed by the continuous segment extensible 9.

At this stage, only a tensile stress c is applied to the constituent material of said segment 9, said stress being higher at the top of the long slope of low inclination than at the bottom of said slope. The pressure of the fluid 36 exerts more effort on the section 52, reduced compared to that shown in Figure 7 Sl.

FIG. 9 illustrates the situation provided by the segment pre-torsion system 21 according to the particular embodiment chosen here to illustrate its operation when the pressure of the fluid 36 to be sealed becomes significant.

As seen in FIG. 9, the diameter of the cylinder 8 has increased significantly under the effect of the pressure of the fluid 36 while the continuous expandable segment 9 is increasingly deformed by radial inclination by said pressure. Said segment 9 is deformed and because of the curved profile of the outer cylindrical segment face 13, the latter only exhibits a section S3, lower than that S2 shown in FIG. 8. It results from S3 a lower solicitation in traction of the axial portion of the continuous expandable segment 9 located on the side of the sliding skirt 6. It also results from S3 a lower force applied by the fluid pressure 36 on the internal cylindrical segment face 12. The constriction force that In contrast to the continuous elastic segment 9, the outer cylindrical segment face 13 exerts on the cylinder 8 a lower contact force with respect to the pressure in the fluid chamber 27. This tends to reduce the relative energetic loss of friction of the piston sealing device 1.

Figure f0 shows the same situation as before, but with a pressure in the still higher fluid chamber 27 which has further reduced the section S3, the latter becoming 54. Note on the latter figure the tensile stress c applied to the extensible continuous segment 9. Said stress remains moderate in the axial part of said segment 9 situated on the side of the sliding skirt 6 because the pressure of the fluid 36 no longer produces any force, said part being situated outside of S4. It is also observed in this same figure that the stress c remains acceptable with respect to the fatigue limit Lf in the axial part of the extensible continuous segment 9 located on the side of the fixed skirt 5 because on the one hand, the initial stress of compression in this area has naturally been deduced from the tensile stress and secondly, because the long slope of small inclination on the outer cylindrical segment face 13 has been made by torsion of the continuous segment extensible 9 which has preserved in said segment 9 a greater rest diameter at the bottom of said slope than if said slope had been made by machining.

The possibilities of the segment pre-torsion system 21 according to the invention are not limited to the application which has just been described and it must moreover be understood that the above description has not been given. that by way of example and that it does not limit the field of said invention of which one would not go out by replacing the details of execution described by any other equivalent.

Claims (3)

REVENDICATIONS1. Segment pre-torsion system (21) for a piston sealing device (1) for a piston (2) operating in a cylinder (8) with which it defines a fluid chamber (27), said piston (2) comprising a piston head (3) which has a fixed skirt (5) connected by an inter-skirt mechanical connection (7) to a sliding skirt (6) housed with a small clearance in the cylinder (8) and traversed axially by a channel a sliding skirt spring (16) tends to bring said skirts (5, 6) closer to each other so as to axially compress an elastically continuous segment (9) interposed seal between said skirts (5, 6), said segment (9) having a segment internal cylindrical face (12) subjected - via the pressure transmission channel (10) - to the pressure of a fluid (36) contained therein the fluid chamber (27), said segment (9) also comprising an axial face of a segment on the fixed skirt side (14) and an ax face characterized in that it comprises at least one male pre-twist cone (22) and has a cylindrical outer segment face (13) engageable with the cylinder (8). arranged in the axial extension of the fixed skirt (5), and kept directly or indirectly in sealing contact with the axial face of the fixed skirt side segment (14) by the sliding skirt spring (16); - At least one outer circular pre-torsion edge (23) arranged projecting at the axial periphery of the sliding skirt (6) and maintained directly or indirectly in sealing contact with the axial face of the segment side sliding skirt (15) by the spring sliding skirt (16), the force produced by the latter conjugate with the male pre-torsion cone (22) twisting the extensible continuous segment (9) so that it takes - by deformation - a conical shape. 10 4. 15 5. 20 6. 25 30 8. 35 3028587 14 2. Segment pre-torsion system according to claim 1, characterized in that the axial face of the segment on the fixed skirt side (14) and the axial face of the segment on the sliding skirt side (15) are flat and parallel. 3. Segment pre-torsion system according to claim 1, characterized in that the axial face of the segment on the fixed skirt side (14) and / or the axial face of the segment on the sloping skirt (15) has a concave curved profile or convex centered or not on the radial thickness of the continuous expandable segment (9). Segment pre-torsion system according to claim 1, characterized in that the outer cylindrical segment face (13) has a convex convex profile whose culminating point is centered on the axial thickness of the continuous expandable segment (9). Segment pre-torsion system according to Claim 1, characterized in that the line of contact between the extensible continuous segment (9) and the male pre-torsion cone (22) when these two parts (9, 22) are simply brought into contact with each other without additional effort forms a circle of smaller diameter than that of the outer circular pre-torsion edge (23). Segment pre-torsion system according to Claim 1, characterized in that the male pre-torsion cone (22) has a convex or concave convex radial profile. Segment pre-torsion system according to Claim 1, characterized in that the outer circular pre-torsion edge (23) consists of the outer edge of a female pre-torsion cone (24) axially arranged in the skirt. slippery (6). Segment pre-torsion system according to Claim 1, characterized in that the fixed skirt (5) has on its outer cylindrical surface at least one decompression groove (25) arranged near the male pre-torsion cone (22). . 9. Pre-torsion segment system according to claim 8, characterized in that the decompression groove (25) is axially separated from the male pre-torsion cone (22) by a segment axial bearing flange (22). 26). Segment pre-torsion system according to Claim 8, characterized in that the decompression groove (25) is connected to the end of the fixed skirt (5) situated opposite the pre-torsion cone. male (22) by at least one decompression groove (28). 0