Piston Accumulator

Abstract

A piston accumulator having an accumulator housing 4 and a separating piston 10 guided therein so as to be displaceable in the longitudinal direction, which separating piston separates two medium chambers 12, 14 from one another and has a double sealing system 16, of which one sealing system 18 is directed towards one medium chamber 12 and the other sealing system 20 is directed towards the other medium chamber 14, and at a point 58 between the two sealing systems 18, 20 a compensating device is at least partly accommodated in the separating piston 10, which compensating device allows hydrostatic pressure compensation between the two sealing systems 18, 20 to avoid undesired pressure build-up during operation.

Description

[Technical field]

[0001] The invention relates to a piston accumulator having an accumulator housing and a separating piston guided longitudinally displaceably therein, which separates two medium spaces from one another and has a double sealing system, of which one sealing system is directed towards one medium space and the other sealing system is directed towards the other medium space. [Background technology]

[0002] DE 102 48 823 A1 discloses a hydroaccumulator in the form of a piston accumulator having a piston which is axially movable in an accumulator housing and separates the gas side of the accumulator housing from the liquid side, the circumferential part of which is provided with a guide member and a number of sealing members arranged to cooperate with the wall of the accumulator housing, a pressure compensation passage which is displaced axially relative to the guide members and is arranged in a circumferential section of the piston located between them, the pressure compensation passage forming a liquid path between the liquid side and the space in the piston circumferential section, the liquid path being located between the guide member closest to the liquid side and the sealing member following it in the axial direction, and a device in the form of a blind or nozzle which reduces the passage cross section is provided in the pressure compensation passage.

[0003] The idea behind this known solution is that dirt particles that may be contained in the hydro-oil on the liquid side negatively affect the long-term behavior of the hydro-accumulator as well as the operating behavior of the sealing and guiding system between the piston circumference and the inner wall of the accumulator housing. The pressure compensation passage in the separate piston addresses the above-mentioned problem, since when a piston movement occurs during operation, no pressure difference occurs in the guide element anymore, and therefore no volume flow, possibly including dirt particles. Since the passage cross section of the pressure compensation passage is reduced via a blind or a nozzle, it is further ensured that only a small liquid volume is involved in such a pressure compensation process.

[0004] In practice, it has become evident that in the hydroneumatic piston accumulators mentioned here with a double seal system for the separated piston, a pressure build-up occurs between the two seals or seal systems during operation, which can reach the maximum drive pressure of the accumulator or in particular exceed it due to the so-called pump effect. This can result in various effects such as drive noise and an expansion of the seal system up to pinching of the piston. The problems thus arising cannot be addressed by the differently functioning pressure compensation passages described in DE 102 48 823 A1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 10248823 A1 Summary of the Invention [Problem to be solved by the invention]

[0006] Starting from this prior art, the object of the present invention is to further improve the known piston accumulator solution in such a way that the above-mentioned pressure build-up and its undesirable effects do not occur. [Means for solving the problem]

[0007] This problem is solved by a piston accumulator which has in its entirety the features of patent claim 1.

[0008] According to the characterizing part of claim 1, a compensating device is at least partially accommodated in a separating piston between the two seal systems of the double seal system, which allows hydrostatic pressure compensation between the two seal systems in order to avoid undesirable pressure build-up during actuation, so that no undesirable pressure build-up with the above-mentioned negative effects occurs.

[0009] Rather, the compensating device according to the invention between the two sealing systems allows a zone of pressure build-up between one sealing system and the compensating device, directed towards the medium chamber with the working gas, to be pressure compensated in the direction of a zone of pressure release between this pressure compensating device and the other pressure system, directed towards the other medium chamber with the liquid, usually in the form of hydraulic oil. In contrast to the known solution described in DE 102 48 823 A1, the pressure difference in the guide element on the liquid side is not eliminated in order to avoid the ingress of dirt particles, but rather a true hydrostatic pressure compensation is provided between the two sealing systems of the double seal system, which are located between the two guide systems of the separating piston towards the two end regions of the separating piston. Hydrostatic pressure compensation therefore no longer results in an impermissibly high pressure build-up during operation, so that noise formation is avoided as well as the extrusion of the seals and / or the clamping of the separating piston in the accumulator housing.

[0010] The liquid in the pressure build-up zone also provides improved liquid lubrication for the sealing system facing the side of the separating piston having the working gas, which is particularly useful when a water-based liquid, such as an HFC (hydrofluorocarbon), having significantly reduced lubricating properties is used instead of a good lubricating liquid such as hydraulic oil.

[0011] In a preferred embodiment, the compensator is accommodated in an annular groove of the separating piston and is formed by a surrounding sealing ring which is press-fitted along the inside of the accumulator housing by means of two protruding ring segments which define between them a ring chamber which is connected to the inside of the sealing ring via at least one compensation passage in a medium-guiding manner and which emerges from the sealing ring. Preferably, the method of operation of the compensator is comparable to that of a check valve with a throttling action, which opens from its closed position in the direction of the other medium chamber with the liquid. In this way, a liquid-side seal is obtained which has a pressure relief function and a surprisingly improved lubrication for the gas-side seal against the accumulator housing.

[0012] In another preferred embodiment, the passages of each of the sealing rings leave the ring chamber and are inclined by an imaginary inclination angle of about 30° to 50°, preferably 40°, onto the support ring and towards the inside of the piston, towards the side defining the other medium chamber, thereby facilitating the inflow of liquid into the passages, which facilitates the desired compensation of the pressure between the three sealing rings of the different sealing systems. This seal design allows a minimum of liquid overflow into the gaps between the seals, but ensures a reliable breakdown of the pressure built up between these seals. In so far as the piston accumulator according to the invention also allows the separation piston to be displaced at a higher speed.

[0013] Further preferred embodiments are the subject of the other dependent claims.

[0014] The piston accumulator according to the invention will now be described in more detail with the aid of the drawings, which are diagrammatic and not to scale representations. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic, simplified longitudinal section through a piston accumulator according to the invention, which for simplicity shows the separate piston without guide, sealing and compensation devices. [Diagram 2] FIG. 2 shows an enlarged partial section compared to FIG. 1 of a separate piston guided in a piston accumulator, which for simplicity is shown without a compensation device, which would otherwise be accommodated as a kind of blank in the illustrated space holder. [Diagram 3] FIG. 3 shows an enlarged partial section compared to FIG. 2 with a compensation device accommodated in the separating piston at the location of the spacer shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] FIG. 1 shows a piston accumulator according to the invention with an accumulator housing 4 and a separating piston 10 guided therein in a longitudinally displaceable manner, the separating piston 10 having a cylindrical internal space 8 extending along its longitudinal axis 6. The separating piston 10 separates a medium chamber 12 from another medium chamber 14 in the accumulator housing 4 and has a double seal system 16 (FIG. 2). A seal system 18 of the double seal system 16 is located near the medium chamber 12 and another seal system 20 of the double seal system 16 is located near the other medium chamber 14. Between the two seal systems, a compensating device 22 (FIG. 3) is at least partially accommodated in the separating piston 10. The compensating device 22 allows hydrostatic pressure compensation between the two seal systems 18, 20 to avoid undesired pressure build-up during drive.

[0017] The cylindrical accumulator housing 4 is closed at one end 21 by a terminal insert 26 fixed by means of a flange 24, which has a concentrically arranged gas-filling connection 28, via which the chamber 12 defined by the insert 26 can be filled with working gas 30 under full-fill pressure. The accumulator housing 4 is closed at the opposite end 31 by another terminal insert 32, which is also fixed by a flange 24 and has a central opening 34 for the fluid guide of the hydraulic circuit, not shown in the figures. Each terminal insert 26, 32 has an annular groove 36 on its outer periphery in which a sealing ring 38 is provided, which seals the respective terminal insert 26, 32 against the accumulator housing 4. One chamber 12 contains nitrogen as working gas 30, the other chamber 14 contains a liquid 40 in the form of hydraulic oil 32.

[0018] The separation piston 10 is essentially guided in the accumulator housing 4 in its two free end regions by surrounding guide bands 44, 52 (FIG. 2), which are respectively accommodated in surrounding annular grooves 46 in the outer periphery 48 of the separation piston 10, with the double seal system 16 arranged between them: one seal system 18 is accommodated in an annular groove 50 in the outer periphery 48 of the separation piston, axially displaced relative to the guide band 44 in the direction of the liquid chamber 14, and the other seal system 20 is accommodated in an annular groove 50 in the outer periphery 48 of the separation piston, axially displaced relative to the other guide band 52 in the direction of the gas chamber 12, with the one seal system 18 and the other seal system 20 being further axially spaced apart from each other. The compensator 22, which can be considered as a kind of encircling seal ring 56 and is arranged between the two seal systems 18, 20, is also housed in an annular groove 58 provided in the outer periphery 48 of the piston accumulator.

[0019] The annular groove 58 for receiving the compensation device 22, which is formed on the outer periphery 48 of the separation piston 10, is located in a central region 60 thereof with respect to the axial length of the separation piston 10 and is preferably located in the middle of two opposing free front sides 62, 64 of the separation piston 10. The annular grooves 46, 50, 58 for the compensation device 22, the respective sealing systems 18, 20 and the respective guide bands 44, 52, which are formed on the outer periphery 48 of the separation piston, are formed as polygons with walls 66, 68 which are perpendicular to one another in cross section. The annular grooves 46, 50 for the guide bands 44, 52 and the sealing system 18 located near the gas chamber 12 have a groove bottom 66 which is wider in the axial direction than the radial height of their annular side walls 68. In contrast, the annular grooves 50, 58 for the seal system 20 located near the compensation device 22 and the liquid chamber 14 have an annular side wall 68 that is higher in the radial direction than the axial width of the groove bottom 66.

[0020] The sealing ring 56 of the compensator 22 has two protruding ring segments 70, 72 which press against an inner wall 74 of the accumulator housing 4 in order to seal the gas chamber 12 against the liquid chamber 14. The ring segments 70, 72 define between them a ring chamber 76 which is in medium-conducting connection with the inside 80 of the sealing ring 56 via at least one compensation passage 78 and which emerges from the sealing ring 56 into an annular groove 58 for accommodating the compensator 22.

[0021] A zone 82 of pressure build-up is between the sealing system 18, which is located near the gas chamber 12, and the compensator 22. A zone 84 of possible pressure release is between the compensator 22 and the other sealing system 20, which is located near the liquid chamber 14. The way in which the compensator 22 works is roughly comparable to a check valve with a throttling action, which opens from a closed position in the direction of the liquid chamber 14.

[0022] The sealing ring 56 of the compensator 22, which surrounds the separating piston 10, is supported on its inner side 80 by a surrounding support ring 86, which are both accommodated in the annular groove 58 for the compensator 22. The support ring 86 is formed as an elastomeric O-ring and serves as a biasing member for the sealing ring 5 of the compensator 22. The sealing ring 56 of the compensator 22, which grips the O-ring, is preferably formed from a PTFE (polytetrafluoroethylene) material, but can alternatively be formed from a thermoplastic or PU (polyurethane) material. The sealing rings 18, 20 of the double seal system 16 are likewise formed from one of these materials.

[0023] The seal between the two medium chambers 12, 14 across the separating piston 10 and the accumulator housing 4, formed by the sealing ring 56 of the compensator 22 in combination with the support ring 86, is characterized by a high sealing action, low friction without stick-slip, minimal breakaway forces and high friction and temperature resistance.

[0024] The angle between the radially extending side wall 68 of the annular groove 58 for the compensator 22 and the passages 78 formed in the sealing ring 56, respectively, is approximately 40°, the passages 78 extending obliquely relative to the radial direction starting from the ring chamber 76 towards the piston interior and thus towards the support ring 86, inclining towards the side 64 of the piston 10 which together define the liquid chamber 14. Instead of the only passage 78 shown in FIG. 3, a number of passages or also other interruptions, such as perforations, can also be formed in the sealing ring 56 of the compensator 22. Preferably, the passages are arranged diametrically opposite one another with respect to the longitudinal axis 6 of the accumulator.

[0025] The contact surface of the ring segment 70 of the sealing ring 56 of the compensator 22, which is formed in the shape of a sealing lip and is adjacent to the chamber 12 containing the working gas 30, with the inner wall 74 of the accumulator housing 4 is smaller than the contact surface of the subsequent ring segment 72, which is formed in a spherical shape and is adjacent to the liquid chamber 14. The cross section of the ring chamber 76, which is jointly defined by the one ring segment 70 and the other ring segment 72, is formed in the shape of a trapezoid.

[0026] The separating piston 10 with three sealing systems 16, 22 with sealing rings 18, 20, 56 operating independently of one another in the sense of the solution according to the invention allows different fillings of the medium chambers 12, 14 in the accumulator housing 4, separated from one another by the separating piston 10, and thus besides gas / liquid also liquid / liquid, gas / gas or liquid / gas fillings. By simply reversing the direction of the pressure-conducting passage 78, the pressure compensation function is reversed, as described above. The present disclosure also includes the following inventions. The first aspect is A piston accumulator having an accumulator housing (4) and a separating piston (10) guided longitudinally displaceably therein, said separating piston separating two medium chambers (12, 14) from one another and having a double seal system (16), one seal system (18) of which is directed towards one of the medium chambers (12) and the other seal system (20) of which is directed towards the other of the medium chambers (14), The piston accumulator is characterized in that a compensating device (22) is at least partially accommodated in the separating piston (10) between the two sealing systems (18, 20), the compensating device enabling hydrostatic pressure compensation between the two sealing systems (18, 20) to avoid undesired pressure build-up during actuation. The second aspect is one chamber (12) contains a working gas (30), such as nitrogen, and the other chamber (14) contains a liquid (40), such as a hydraulic medium; and Preferably, in the piston accumulator of the first aspect, the sealing system (20) associated with the other medium chamber (14) having a liquid (40) is lubricated by this liquid (40). The third aspect is A piston accumulator according to the first or second aspect, characterized in that in the accumulator housing (4), the separated pistons (10) are guided together towards their free end regions by guide bands (44, 52), the guide bands accommodating the double seal system (16) between themselves. The fourth aspect is The piston accumulator according to any one of the first to third aspects, characterized in that the compensation device (22) is accommodated in an annular groove (58) of the separation piston (10) and is formed by a surrounding seal ring (56), the seal ring being press-fitted against an inner side (74) of the accumulator housing (4) by means of two protruding ring segments (70, 72), the ring segments defining a ring chamber (76) therebetween, the ring chamber being connected to an inner side (80) of the seal ring (56) in a medium-guiding manner via at least one compensation passage (78) and emerging from the seal ring (56). The fifth aspect is A piston accumulator according to any one of the first to fourth aspects, characterized in that a pressure build-up zone (82) is located between the sealing system (18) facing the one medium chamber (12) and the compensation device (22), and a possible pressure release zone (84) is located between this compensation device (22) and the other sealing system (20) facing the other medium chamber (14). The sixth aspect is The piston accumulator according to any one of the first to fifth aspects, characterized in that the method of operation of the compensation device (22) is comparable to that of a check valve having a throttling action, and the check valve opens from its closed position in the direction of the other medium chamber having liquid (40). The seventh aspect is The piston accumulator according to any one of the first to sixth aspects, characterized in that a seal ring (56) that encircles the separation piston (10) is supported on its inside by a support ring (86) that also encircles the separation piston (10), and the support ring is housed together with the seal ring in annular groove (58) of the separation piston (10). The eighth aspect is A piston accumulator according to any one of the first to seventh aspects, characterized in that each passage (78) of the sealing ring (56) starts from the ring chamber (76) and inclines by an imaginary inclination angle of 30° to 50°, preferably 40°, onto the support ring (86) and in the direction toward the inside of the separation piston (10), toward the side defining the other medium chamber (14). The ninth aspect is The piston accumulator according to any one of the first to eighth aspects, characterized in that a contact surface formed by the ring segment (70) of the seal ring (56) adjacent to the one of the medium chambers (12) with the inner wall (74) of the accumulator housing (4) is smaller than a subsequent contact surface of the other ring segment (72), which is preferably formed spherically. A tenth aspect is The piston accumulator according to any one of the first to ninth aspects, wherein the ring chamber (76) of the circumferential seal ring (56) is trapezoidal in cross section.

Claims

1. A piston accumulator having an accumulator housing (4) and a separating piston (10) guided longitudinally displaceably therein, said separating piston separating two medium chambers (12, 14) from one another and having a double seal system (16), one seal system (18) of which is directed towards one of said medium chambers (12) and the other seal system (20) of which is directed towards the other of said medium chambers (14), a compensating device (22) is at least partially accommodated in the separating piston (10) between the two sealing systems (18, 20), said compensating device enabling hydrostatic pressure compensation between the two sealing systems (18, 20) to avoid undesired pressure build-up during actuation, 1. A piston accumulator, comprising: a compensating device (22) housed in an annular groove (58) of the separating piston (10) and formed by a surrounding sealing ring (56), said sealing ring being press-fitted against an inner side (74) of the accumulator housing (4) by means of two projecting ring segments (70, 72) which define between them a ring chamber (76), said ring chamber being connected via at least one compensation passage (78) in a liquid or gaseous medium conducting manner with an inner side (80) of the sealing ring (56), said ring chamber emerging from said sealing ring (56).

2. one chamber (12) contains a working gas (30), such as nitrogen, and the other chamber (14) contains a liquid (40), such as a hydraulic medium; and 2. The piston accumulator according to claim 1, characterized in that the sealing system (20) associated with the other medium chamber (14) having a liquid (40) is lubricated by this liquid (40).

3. 3. A piston accumulator according to claim 1 or 2, characterized in that in the accumulator housing (4), the separate pistons (10) are guided together towards their free end regions by guide bands (44, 52) which accommodate the double seal system (16) between themselves.

4. 4. The piston accumulator according to claim 1, characterized in that a zone (82) of pressure build-up is located between the sealing system (18) facing the one medium chamber (12) and the compensation device (22) and a zone (84) of possible pressure release is located between this compensation device (22) and the other sealing system (20) facing the other medium chamber (14).

5. 5. The piston accumulator according to claim 1, wherein the compensation device (22) has a throttling action, the non-return valve opening from its closed position in the direction of the other medium chamber containing liquid (40).

6. 6. A piston accumulator according to claim 1, characterized in that a sealing ring (56) surrounding the separated piston (10) is supported on its inside by a surrounding support ring (86), the support rings being housed together in an annular groove (58) of the separated piston (10).

7. 7. The piston accumulator according to claim 1, wherein the passages (78) of the sealing rings (56) start from the ring chamber (76) and incline by an imaginary inclination angle of between 30° and 50° onto the support ring (86) and in the direction of the inside of the separating piston (10), towards the side defining the other medium chamber (14).

8. A piston accumulator as described in any one of claims 1 to 7, characterized in that the sealing ring is composed of the two protruding ring segments (70, 72), and the contact surface formed by the ring segment (70) of the two protruding ring segments (70, 72) of the sealing ring (56) adjacent to one of the medium chambers (12) with the inner wall (74) of the accumulator housing (4) is smaller than the subsequent contact surface formed by the other ring segment (72) of the two protruding ring segments (70, 72) with the inner wall (74) of the accumulator housing (4), which is spherically formed.

9. 9. A piston accumulator according to any one of the preceding claims, characterized in that the ring chamber (76) of the encircling sealing ring (56) is trapezoidal in cross section.

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