Hydraulic Accumulator

Abstract

The hydraulic accumulator comprises an accumulator housing (18), a separation element (10) arranged longitudinally movably therein for separating two medium chambers (12, 14) within the accumulator housing (18), in particular a chamber containing a working gas, such as nitrogen gas, from another chamber containing a liquid, such as hydraulic oil, and a rupture device (66) for reducing an unacceptably high pressure within the accumulator housing (18), the rupture device (66) being arranged within the separation element (10) and, upon rupture, opening a medium communicating connection (84) between the two medium chambers (12, 14) via the separation element (10).

Description

[Technical field]

[0001] The present invention relates to a hydraulic accumulator comprising an accumulator housing, a separating element arranged longitudinally movably therein and separating two medium chambers within the accumulator housing, in particular a chamber containing a working gas, such as nitrogen gas, from a chamber containing a liquid, such as hydraulic oil, and a bursting device for relieving unacceptably high pressures within the accumulator housing. [Background technology]

[0002] To ensure the safety of the operation of equipment with containers containing compressed gas, such as hydraulic accumulators, all possible hazards must also be taken into account, particularly at the installation site of such equipment, where potentially dangerous external influences are important, in particular the temperature rises that occur in the event of a fire in the immediate vicinity of such a container filled with compressed gas, which could lead to the failure of the container.

[0003] In order to meet these requirements, patent document 1 proposes a safety device for gas-pressurized containers, in particular for protecting the gas side of the working chamber of hydro-pneumatic equipment, such as hydraulic accumulators, with a relief device for reducing the gas pressure caused by thermal effects in the respective container, where the relief device is a component that is subject to kinking or buckling under the action of shear or compressive forces, and when heat is applied to the safety device, it changes shape in such a way that a gas-communicating connection with the outside is possible from the gas side of the container towards the periphery.

[0004] From DE 10 200 03 13 599 A1 a safety device is known which has a connection point for connecting a pressure or hydraulic accumulator. The accumulator is connected via this connection point on the gas side with a rupture device which can be triggered by an actuable force element, and in the triggered state the rupture device can empty the pressure accumulator on the gas side. In particular in this known solution the rupture device has a rupture disk which is activated by operating a force element which can in particular have a pyrotechnic nature when the maximum pressure on the gas side is exceeded, and when the propellant is ignited a wall part of the housing is deformed or destroyed, which activates the rupture device contained therein or the rupture disk is destroyed by an actuating pin. This known solution is particularly suitable for application in mobile systems in which hydraulic accumulators are present, for example vehicles with energy recovery in combination with hydrostatic running gear. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102010011879(A1) [Patent Document 2] DE 102015014797(A1) Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to proceed from this prior art and to improve the known solutions in the prior art. The above object is achieved by a hydraulic accumulator having the overall features of claim 1. [Means for solving the problem]

[0007] According to the characterizing part of claim 1, due to the fact that the rupture device is arranged in the separating element and that in the event of rupture the medium-communicating connection between the two medium chambers is released via the separating element, in comparison with known solutions, an unintentional release of parts of the rupture device to the surroundings in the event of a fault is avoided in any case, so that persons or machine parts in the vicinity of such a faulty hydraulic accumulator are not exposed to any danger in any case. As the working gas on the gas side of the hydraulic accumulator is also usually under a very high filling pressure, a pressure release to the surroundings could likewise entail a safety risk, which is avoided in the solution according to the invention.

[0008] Due to the location of the bursting device in the solution according to the invention in a separating element inside the hydraulic accumulator, in the event of a fault, parts of the bursting device never reach the outside world, but rather remain in the accumulator housing of the hydraulic accumulator, which is normally designed as a high-pressure component and safety-tested. In the event of a fault, the working or compressed gas also escapes to the liquid side of the accumulator, but the accumulator housing is significantly depressurized due to the strong damping effect of the liquid. Within the scope of the operation of the entire hydraulic system, it is also possible to install such a hydraulic accumulator with a bursting device according to the invention in a defined position in the permitted fault zone, in the separating element between the three medium chambers of the hydraulic accumulator. In this way, the associated hydraulic circuit together with the connected hydraulic device is not adversely affected in the event of a fault. In this way, the relief of the impermissible pressure increase can be transferred to a less dangerous area via the corresponding safety device in a defined area of ​​the hydraulic circuit. Even if the hydraulic accumulator according to the invention is subjected to a large number of load changes with corresponding pressure fluctuations and very high gas temperatures, which may also occur during dynamic operation of the hydraulic accumulator, no safety hazard to the surroundings is present, since the hydraulic accumulator according to the invention is designed as a closed system even in the event of a fault.

[0009] In a preferred embodiment of the hydraulic accumulator according to the invention, the bursting device is formed from a burst plug which is inserted into a through opening in the separation element, in this way the bursting device can be realized centrally in the separation element in a particularly cost-effective manner.

[0010] Preferably, the plug-like rupture device has an engagement part which is inserted into the through-opening and is screwed into the separation element via a thread, in particular along the through-opening, in such a way that a secure, removable attachment of the rupture device to the separation element is achieved, in part because the rupture device has an abutment part, the diameter of which is preferably larger than the diameter of the engagement part, which abuts in a surface-like manner against the separation element in a supporting manner, so that a force is introduced surface-wise into the separation element via the abutment part.

[0011] Furthermore, it is advantageous from the point of view of manufacturing technology if the engagement part and the abutment part are each integral components of the rupture device.

[0012] In a particularly preferred embodiment of the hydraulic accumulator according to the invention, at least one longitudinal channel extends in the engagement part, opening at one end into the second medium chamber containing the liquid and at the other end into said abutment part, so that a kind of diaphragm adjoins the first medium chamber containing the working gas at the head side of the abutment part, the diaphragm having an appropriately adjustable thickness forming a kind of predetermined breaking point, the rupture of which allows the working gas under high pressure to be discharged through the longitudinal channel in the engagement part towards the liquid chamber of the hydraulic accumulator.

[0013] In order to prevent the media contained in the medium chamber, in particular the working gas and the liquid, from exchanging with each other in an undesirable manner during normal operation, a sealing device is arranged between the rupture device and the separation element.

[0014] The hydraulic accumulator can particularly preferably be designed as a bellows-type accumulator, but can also be designed as a piston-type accumulator, in which case the separating element is formed either from a bellows or from a separating piston.

[0015] In any case, it is ensured that in the event of failure of the rupture device, all fragments of the rupture device remain sealed against the outside inside the accumulator housing and that the associated unacceptably high gas pressure is vented to the liquid side of the accumulator, thus preventing the working gas from likewise unintentionally escaping to the surroundings. Nothing comparable exists in the prior art.

[0016] In the following, the hydraulic accumulator according to the invention will be explained in more detail with reference to an embodiment according to the drawings, which are principle diagrams and are not drawn to scale. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a vertical cross-sectional view of the entire bellows-type accumulator. [Diagram 2] FIG. 2 is an enlarged view of the bottom region of the bellows-type accumulator shown in FIG. [Diagram 3] FIG. 3 is a vertical cross-sectional view of another embodiment of a piston-type accumulator. [Figure 4] FIG. 4 shows an enlarged view of a separation element in the form of a separation piston as shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The bellows-type accumulator shown in Fig. 1 is a concrete representative of a hydraulic accumulator, in which a bellows 16, which serves as a movable separating element 10 between a first medium chamber 12, in particular in the form of a gas side, and a second medium chamber 14, in particular in the form of a liquid side, has, at one bellows end 20, which is axially movable when expanding and contracting in an accumulator housing 18, a closing body 24 which closes the interior 22 of the bellows 16 in a medium-tight manner and which is guided so as to be movable longitudinally in the accumulator housing 18. At the other bellows end 26, the bellows 16 is fixed in the accumulator housing 18 so as to be immovable relative to it. For this purpose, a fixing ring 28 is used which is welded in the usual way to the end of the bellows 16 and to the inside 30 of the accumulator housing 18. The accumulator housing 18 therefore consists of three individual housing parts connected or welded together, the upper housing part 32 and the lower housing part 34 being formed hemispherically and the cylindrical housing part 36 located between them may be provided with a textile coil 38 on its outer periphery in the usual way for pressure stabilization.

[0019] In the first chamber 12, a compressible medium is introduced under a settable pre-pressure or filling pressure, for example in the form of a working gas, such as nitrogen gas. A metal part 40 with a glass insert in the form of a sight glass allows the interior of the hydraulic accumulator to be inspected from the outside. The hydraulic accumulator can be filled with a working gas, such as nitrogen gas, through a closure in the upper housing part 32, not shown in detail. Furthermore, in FIG. 1, the bellows 16 is shown in the most extended position possible, the associated movement during contraction of the bellows 16 being limited by the individual pleats of the bellows 16, which abut against each other and, so to speak, form a block. The bellows 16 is preferably made of a medium-resistant and pressure-stable stainless steel material, which ensures that the working gas introduced under pre-pressure in the chamber 12 cannot get into the second chamber 14 together with a liquid, such as hydraulic oil, during normal operation. Such a bellows-type accumulator is usually connected on its liquid side to a hydraulic supply circuit (not shown).

[0020] As can be further seen from Figures 1 and 2, the closure body 24 is formed in the form of a hemispherical shell and defines a small defined chamber volume 52 for receiving liquid on the liquid side 46 of the hydraulic accumulator when the bellows 16 is as fully extended as possible. The liquid side 46 has a hollow cylindrical connection part 54, which is preferably provided with an external thread and which is used in the usual way to fasten the hydraulic accumulator to a third component, such as an accumulator block (not shown). The connection part 54 embraces and grips a cylindrical fluid guide which, as seen in the direction of the dome-shaped closure body 24, is reduced in diameter by a step 56 which tapers conically towards the closure body 24 to form a connection part 58. The connection part 58 is surrounded by a flat torus surface 60 which, as shown in Figure 2, extends in a horizontal plane when seen transversely to the longitudinal axis of the hydraulic accumulator. This is followed by a further convex curved surface of the inner side 61 of the lower housing part 34, seen from the inside of the hydraulic accumulator, up to a transition wall element 63, which is cylindrically formed and runs coaxially with the longitudinal axis of the hydraulic accumulator. The curvature of this curved surface is not as strong as the corresponding convex curved surface of the outer side 65 of the closure body 24. In this way, a free chamber volume 52 is formed in cross section. This chamber volume 52 is formed in the shape of a shell, tapering towards its free end and having a maximum free cross section approximately in the lower third in the direction of FIG. 2. Overall, a curved lens shape is thus formed for the chamber volume 52, which is filled with liquid during operation of the accumulator.

[0021] Viewed concentrically with the longitudinal axis of the accumulator housing 18, the closure body 24 has, towards the first medium chamber 12, i.e. upwards as viewed in the direction of observation of Figures 1 and 2, a hollow cylindrical shoulder 62 with an internal thread 64. Into the receptacle of the shoulder 62 thus formed, a bursting device, generally designated 66, is inserted and serves to reduce an unacceptably high pressure in the accumulator housing 18 on its gas side. The bursting device 66, formed in the form of a bursting plug, is arranged in a through opening 68 in the separation element 10 formed from the closure body 24 of the bellows 16.

[0022] The plug-like rupture device 66 has a cylindrical engagement part 72 which is inserted into the through-opening and is screwed into the separation element, in particular via a thread along the through-opening. For this purpose, the engagement part 72 has an external thread 74 on its outer periphery which precisely fits into the internal thread 64 of the shoulder 62.

[0023] Furthermore, the rupturing device 66 has an abutment part 76, the diameter of which is greater than the diameter of the engagement part 72, which abuts with its underside in a surface manner against the separating element 10. The abutment part 76 then bears against the upper side of a connection in the form of a cylindrical shoulder 62. The abutment part 76 has an abutment surface on its outer periphery, which can be grasped with an operating tool, for example a wrench (not shown), so that the entire rupturing device 66 can be inserted or screwed into the shoulder 62.

[0024] Such a screw connection is removable and can be replaced by a new element in the event of a breakdown of the rupture device 66. As can be seen further from FIGS. 1 and 2, the engagement part 72 and the abutment part 76 are each integral components of the rupture device 66 as a whole. In this example, the lower end of the engagement part 72 projects above the lower surface of the closure body 24 as the separating element 10 with a slight projection 77 corresponding to the incomplete thread of the male thread 74. In the engagement part 72, there is a longitudinal flow passage 78 extending concentrically with the longitudinal axis of the hydraulic accumulator, which opens at one free end into the second medium chamber 14 containing the liquid and at the other opposite end into the block-shaped abutment part 76, on the head side of which a thin-walled diaphragm 80 is formed adjacent to the first medium chamber 12 containing the working gas. Furthermore, at the transition between the abutment portion 76 and the cylindrical shoulder portion 62, a sealing device 82, not shown in detail, is arranged, which ensures media separation between the two media chambers 12, 14 containing their respective fluid contents during normal operation of the hydraulic accumulator.

[0025] If the pre-pressure on the gas side of the bellows-type accumulator increases unintentionally, for example due to heating, which usually occurs in the event of a fire, the working gas bursts the diaphragm 80 of the rupture device 66 due to the increased pressure. Via the longitudinal flow passage 78 thus opened, the medium- or fluid-communicating connection between the two medium chambers 12, 14 through the separation element 10 is opened. The gas then escapes to the depressurized liquid side of the hydraulic accumulator, while any resulting fragments of the diaphragm 80 remain on the gas side and / or liquid side of the accumulator housing 18. In this way, the surroundings are in any case protected from leakage of the working gas and / or parts of the rupture device 66 in the event of a fault.

[0026] The outer diameter of the engagement part 72 with the external thread 74 is slightly smaller than the inner diameter of the connection part 58 in the lower housing part 34. In this way, the projection of the engagement part 72 in the expanded state of the bellows 16 results in an annular throttle 81, which is part of the air gap 83. The air gap 83 extends from the throttle 81 to the chamber volume 52, which expands from the air gap 83. In this case, the air gap 83 can have individual air gap channels which extend radially outwards from the imaginary centre of the closure body 24, which is formed flat in this region, until the plane passes into the curved region of the closure body 24. This air gap 83 can also be realised in another way, for example by inserting spacers between the adjacent facing flat faces of the closure body 24 and the inside 61 of the lower housing part 34. The throttle 81 and / or the above-mentioned air gap passages 83 allow the liquid to flow in and out of the hydraulic accumulator with low pressure losses and little turbulence, without the occurrence of material-damaging cavitation.

[0027] FIG. 3 now shows a modified embodiment of the solution according to the invention in the form of a piston-type accumulator, in which the separating element 10 is formed from a separating piston 86. This embodiment is described only insofar as it differs substantially from the preceding embodiment, the same components are given the same reference numbers, and the description given for the preceding embodiment also applies to the further embodiment designed as a piston-type accumulator. In a known construction, a hydraulic accumulator in the form of a piston-type accumulator according to FIG. 3 has a hollow cylindrical accumulator housing 18 closed by a bottom cover 88 and a top cover 90. The separating piston 86 is usually a cup piston axially movable in the accumulator housing 18, which also separates the first medium chamber 12 containing the working gas from the second medium chamber 14 containing the working fluid. The separating piston 86 thus separates the oil side of the piston-type accumulator from the gas side. The second chamber 14 can be connected to a hydraulic system (not shown) via an oil connection 92 coaxial with the longitudinal axis of the hydraulic accumulator, and in the head cover 90, likewise coaxial with the longitudinal axis, there is a gas-filling connection 94, by means of which a working gas, such as nitrogen, can be supplied to the first chamber 12 at a predefined filling pressure. Such a gas-filling connection 94 can be closed in the usual way via a closing device (not shown in detail). The separating piston 86 is provided in its cup bottom with a through-opening 68, which opens at its upper free end, as viewed in the manner of observing FIG. 3, into the first chamber 12 containing the working gas.

[0028] The rupture device 66 shown in Figures 3 and 4 is constructed similarly to the rupture device 66 already described with reference to Figures 1 and 2 and has an engagement part 72 which is screwed into the through opening 68 of the separation element 10. This engagement part 72 has a central longitudinal flow passage 78 which opens downwards into the second medium chamber 14 and is defined upwards by the diaphragm 80 of the abutment part 76. It differs from the solution according to Figures 1 and 2 in that the cup bottom is provided with a shallow annular central recess 96 along which the abutment part 76 is supported so as to overlap the separation piston 86. Here too, the working gas will escape towards the liquid side after being released by the ruptured diaphragm 80 in the event of a fault.

[0029] Although the hydraulic accumulator solution of the present invention has been described in detail with reference to bellows and piston type accumulator designs, it is possible for diaphragm or bladder type accumulators to incorporate the burst device 66 into the wall of an elastomeric diaphragm (not shown) to provide burst protection for these types of hydraulic accumulators as well.

Claims

1. 1. A hydraulic accumulator comprising: an accumulator housing (18); a separation element (10) arranged longitudinally movably within the accumulator housing (18) and separating two medium chambers (12, 14) from each other within the accumulator housing (18), in particular separating a chamber containing a working gas such as nitrogen gas from another chamber containing a liquid such as hydraulic oil; a bursting device (66) for reducing unacceptably high pressure within the accumulator housing (18), The hydraulic accumulator is characterized in that the rupture device (66) is arranged in the separation element (10), and when the rupture device (66) ruptures, the medium-communicating connection (84) between the two medium chambers (12, 14) is released via the separation element (10).

2. 2. A hydraulic accumulator according to claim 1, characterized in that the rupture device (66) is formed by a burst plug inserted in a through opening (68) in the separation element (10).

3. 3. A hydraulic accumulator according to claim 2, characterized in that the rupture device (66) has an engagement part (72) inserted into the through opening (68), in particular screwed into the separation element (10) via a threaded part (64, 74) along the through opening (68).

4. 4. The hydraulic accumulator according to claim 3, wherein the rupture device (66) has an abutment portion (76) whose diameter is larger than the diameter of the engagement portion (72), and the abutment portion (76) abuts the separation element (10) in a surface-like manner.

5. 5. A hydraulic accumulator according to claim 4, characterized in that the engagement portion (72) and the abutment portion (76) are each integral components of said bursting device (66).

6. 6. A hydraulic accumulator according to claim 5, characterized in that at least one longitudinal flow passage (78) extends in the engagement portion (72), opening at one end into the second medium chamber (14) containing the liquid and at the other end into the abutment portion (76), so that a kind of diaphragm (80) adjacent to the first medium chamber (12) containing the working gas is formed on the head side of the abutment portion (76).

7. Hydraulic accumulator according to any one of claims 1 to 6, characterized in that a sealing device (82) is arranged between the rupture device (66) and the separation element (10).

8. 7. The hydraulic accumulator according to claim 1, wherein the separating element (10) is formed from a closure body (24) of a bellows (16) of a bellows-type accumulator, the inside (30) of the closure body (24) at least partially defining a first medium chamber (12) containing a working gas.

9. Hydraulic accumulator according to any one of claims 1 to 6, characterized in that the separating element (10) is formed from a separating piston (86) of a piston-type accumulator.

10. 7. A hydraulic accumulator according to any one of claims 1 to 6, characterized in that in the event of failure of the rupture device (66), all fragments of the rupture device (66) remain sealed against the outside within the accumulator housing (18) and any associated unacceptably high gas pressures are released to the liquid side (46) of the hydraulic accumulator.

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