Bellows Type Accumulator

Abstract

A bellows-type accumulator, in which a bellows 16 serving as a movable separating element 10 between a first medium side 12, in particular the gas side, and a second medium side 14, in particular the liquid side, has at its bellows end 20 movable axially in an accumulator housing 18 a closure body 24 closing the interior 22 of the bellows 16 in a medium-tight manner when it is extended or retracted, and a valve device 44 fixedly held at its other bellows end 26 relative to the accumulator housing 18 and reaching a closed position when the pressure on the liquid side 46 decreases, preventing further liquid from flowing out of the accumulator housing 18, is characterized in that the closing process of the valve device 44 is controlled by at least one energy storage means 48 arranged between the valve device 44 and the closure body 24 of the bellows 16, so that at any time a settable amount of liquid remains in the accumulator housing 18 supporting the bellows 16 in the extended position.

Description

[Technical field]

[0001] It concerns a bellows-type accumulator, in which a bellows acting as a movable separating element between a first medium side, in particular the gas side, and a second medium side, in particular the liquid side, has at its bellows end, which is axially movable in the accumulator housing when it expands or contracts, a closing body which closes the interior of the bellows in a medium-tight manner, and at its other bellows end, a valve device which is immovably fixed relative to the accumulator housing and which reaches a closed position when the pressure on the liquid side decreases, preventing further liquid from leaving the accumulator housing, the valve device being movable to the closed position also in the event of an increase in the filling pressure due to the ambient temperature. [Background technology]

[0002] From EP 2 519 748 A1 a hydraulic accumulator is known which is designed as a bellows type accumulator, namely: the bellows, which acts as a movable separating element between the gas side and the fluid side, has at its end, which is axially movable in the accumulator housing when expanding and contracting, a closing body which closes the interior of the bellows in a medium-tight manner, and is fixedly supported at its other end in relation to the accumulator housing, the sealing arrangement sealing the interior of the bellows at the end of the bellows which is immobile with respect to the accumulator housing has, in addition to a first functional area which exerts a sealing effect, a second functional area in the form of a projection which projects into the interior of the bellows and which forms a flexible buffer for the abutment of a closure body of the bellows in its fully contracted state, - the bellows is a metal bellows with a metal closure welded to the end of the bellows, the projection projecting into the bellows has at least one bulge projecting axially toward the movable bellows end as a flexible buffer for the abutment of the closure body; the stationary bellows end is secured to a retaining ring fixed to the housing by a fluid-tight welded connection, the inner ring opening of the retaining ring being adjacent to the interior of the bellows forming the fluid side; the sealing arrangement forms a seal in its first functional area between the inner ring opening of the retaining ring and the accumulator housing.

[0003] In this bellows-type accumulator, the liquid connection for connecting the accumulator to a part of the hydraulic supply circuit in the accumulator housing is formed by a connection hole passing through the connecting piece of the accumulator housing, which is directly controlled by the closure of the bellows, which opens or closes said connection hole. Such a solution of a metal bellows-type accumulator is suitable for use when the pressure difference across the bellows is small, at a few MPa. In contrast, a large pressure difference leads to a significant reduction in the dynamic service life up to the complete failure of the bellows. For this reason, bellows-type accumulators cannot be operated with high pre-pressure or filling pressures on the gas side.

[0004] In order to address these problems, Patent Document 2 (DE 10116995 A1) proposes the following hydraulic device: - hydraulic energy storage means arranged in a hydraulic housing, the hydraulic energy storage means having a movable element designed as a movable end of a bellows in a hydraulic chamber; an inductive displacement sensor connected to means for transmitting the movement of the movable element to the inductive displacement sensor; a control unit for receiving a signal from the inductive displacement sensor, - at least one solenoid valve is provided, -The inductive displacement sensor and the solenoid valve are directly mounted in the control unit. -To attach the inductive displacement sensor to the control unit, the same type of mechanical connection and electrical interface as the solenoid valve is used.

[0005] In another configuration of this known hydraulic device in the form of a bellows-type accumulator (FIG. 3), when the bellows is in a strongly expanded or stretched state, the closing body of the bellows, which acts as a cover, is brought into contact with the bottom wall of the liquid or hydraulic chamber in the accumulator housing via the support, and a spring-loaded bottom valve arranged there as a valve device is then closed, preventing further outflow of hydraulic oil from said hydraulic chamber via a liquid opening at the connection of the bottom valve and the accumulator housing. In this way, the hydraulic chamber is prevented from being completely emptied. This known bellows-type accumulator has its own inlet for hydraulic oil into the accumulator housing, which is spatially separated from the corresponding outlet by a valve device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent Application Publication No. 2519748 [Patent Document 2] DE 10116995 A1 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is based on this prior art and is to provide a solution for a bellows-type accumulator which is improved compared to the prior art. [Means for solving the problem]

[0008] The above problem is solved by a bellows-type accumulator having in its entirety the features of claim 1.

[0009] According to the characterizing part of claim 1, the closing process of the valve device is controlled by at least one energy storage means arranged between the valve device and the closing body of the bellows in such a way that a settable amount of liquid remains in the accumulator housing at all times, supporting the bellows in its extended position, so that the bellows can be operated with a high charging pressure on its first medium side or gas side, because the bellows can be supported at all times on the liquid side of the accumulator housing, even when the valve device is completely closed. In this way, even large pressure differences during operation of the bellows-type accumulator can be reliably controlled by the bellows. This means that a long service life is guaranteed even in dynamic operation, and failure of the bellows, for example due to rupture of the bellows pleats, is avoided. When the valve device is opened, no permanent pressure transmission occurs, since the valve body is essentially open.

[0010] The bellows-type accumulator according to the invention requires only a single passage opening on the liquid side of the accumulator housing, into which a valve device is inserted to control both the inflow and outflow of the (working) liquid. In this case, the energy storage means, essentially in the form of a compression spring, introduced according to the invention between this valve device and the closure of the bellows makes it possible, within the framework of increasingly dynamic damping, in particular by throttling the flow of medium or liquid by means of the valve device, to support the bellows permanently on the liquid side during its extension movement, with a supporting effect that increases as the valve device closes, until the accumulator housing is completely empty except for a settable residual amount of supporting fluid. In this way, even when the valve device is closed, a residual amount of liquid remains enclosed in the accumulator housing, so that the bellows can be supported on its inside under the action of the filling gas pressure.

[0011] In the opposite case, i.e. when the valve device is opened and a fluid connection with the hydraulic circuit connected on the liquid supply side of the accumulator is established until a fully open pass-through position is reached, a force is gently introduced into the bellows by controlling the valve device to open.

[0012] In a preferred embodiment of the bellows-type accumulator according to the invention, the valve device has a poppet valve, the valve body of which is held in an open position, allowing the passage of liquid, against the action of a further energy storage means and which, when actuated, reaches a closed position, blocking the liquid. When the valve body is pressurized on both sides with liquid at a settable pressure, the surface of the valve body acts against the pressure of the liquid remaining in the accumulator (corresponding to the filling pressure on the gas side) and against the spring force of the end part of the metal bellows. No significant pressure transmission therefore results. Since the plate-like end part of the metal bellows does not rest directly on the valve body, no pressure transmission takes place between the valve body and the different faces of the end plate. The associated further energy storage means is also preferably formed by a compression spring. Thus, from a theoretical point of view, a kind of two-mass impact vibration system is formed by two individual masses in the form of a bellows and a poppet valve. Both masses are supported at their opposite ends by energy storage means or springs, which can accelerate or damp the movement of the masses. In this case, the spring is formed above all by the preload of the gas side of the bellows, which is supported by the fluid. The valve disc is supported on the opposite side by another energy storage means in the form of another compression spring which acts at one end on the underside of the valve disc of the poppet valve and at the other end is received stationarily in a portion of the accumulator housing.

[0013] When liquid flows under pressure from the hydraulic circuit to the liquid side of the accumulator housing, the poppet valve opens more and more and is assisted in the opening movement by the second compression spring as the valve spring. The opening process of this valve device is damped by the pre-pressure of the working gas acting on the inside of the bellows and by the energy storage means or the first compression spring between the lower surface of the bellows and the upper surface of the poppet valve.

[0014] In the opposite case, i.e. when the pressure in the hydraulic circuit drops and the liquid flows out of the accumulator housing, the closing process of the poppet valve is assisted by the internal pressure of the bellows and the first compression spring. In this case, the closing process is damped by the spring action of the first compression spring between the valve device and the bellows and the second compression spring of the poppet valve, and in the fully closed position of the valve device, a residual amount of fluid remains between the outside of the bellows and the inside of the accumulator housing as supporting fluid to support the bellows. In all operating conditions, all the individual pleats of the bellows are surrounded by liquid and are therefore supported equally on all sides. The bellows can be operated with a high degree of stability and can withstand significantly higher pressures that dynamically occur on both the gas and liquid sides. Furthermore, due to the spring-damping properties of the two-mass impact vibration system, it is also possible to operate the bellows-type accumulator in a very wide temperature range, for example from -55 ° C to more than 100 ° C, with only the zigzag spring taking care of the temperature compensation.

[0015] It is advantageous, particularly in a space-saving manner, if the valve device has a common connection for the supply and discharge of liquid, which connection is at least partially penetrated by the valve device, in order to help avoid flow losses due to, for example, the occurrence of turbulence.

[0016] In another particularly preferred embodiment of the bellows-type accumulator according to the invention, the first energy storage means and the second energy storage means are each formed by a compression spring, the spring stiffness of which is greater than the spring stiffness of the second compression spring, so that the spring stiffness present on the liquid side of the accumulator housing between the bellows and the valve device is greater than the spring stiffness of the compression spring on the poppet valve side, leading to an improved spring damping characteristic of the entire two-mass-spring system.

[0017] More preferably, in the operating position of the accumulator, one compression spring is arranged on the closing body of the bellows and the other compression spring is part of the valve device.Furthermore, in this operating position, it is advantageous that, at least in the closed position of the poppet valve, one compression spring is supported at its one end above the poppet valve and at its other end below the closing body of the bellows, and the other compression spring is supported at its one end below the valve body and at its other end in a receiver for guiding the valve stem of the poppet valve.

[0018] In a particularly preferred embodiment of the bellows-type accumulator according to the invention, the valve element in the closed position abuts against a sealing device, in particular in the form of an annular soft seal, which is accommodated in a connection of the accumulator housing containing the valve device. In this way, it is ensured that, on the basis of the sealing device, when the bellows is extended to the maximum possible extension position, a residual amount of liquid remains on the liquid side of the accumulator housing, providing a sealing system which also allows the bellows to be supported for a longer period of time, without having to worry about the support fluid reaching the liquid side of the connected hydraulic circuit through a poppet valve which, in some cases, does not close completely tightly due to leakage. In particular, by using a soft seal, for example made of EPDM material, the residual amount of fluid is reliably contained even in the event of strong temperature changes occurring during operation of the bellows-type accumulator with the valve device closed.

[0019] In another preferred embodiment of the bellows-type accumulator according to the invention, the closure body is formed in the form of a hemispherical shell which defines a defined chamber volume for receiving liquid when the bellows is in the most fully extended state possible. The hemispherical shell can also be replaced by a parabolic shell, the design of each shell resulting in the formation of a counter-fluid force between the bellows to which the closure body belongs and the inner wall of the accumulator housing formed in the corresponding shell shape, in the region of connection with the valve device, which is evenly distributed around the circumference of the closure body and thus exerts an increasing support force on the bellows together with the associated closure body due to the displaced liquid. The support force can also be constant, especially at low pressures, which has no equivalent in the prior art.

[0020] In another preferred embodiment of the bellows-type accumulator according to the invention, the lower bellows end is guided in the accumulator housing by an annular guide body, which is provided with fluid passages for establishing a permanent fluid communication between the chamber volume in the region of the valve device and another chamber volume substantially defined by the inside of the accumulator housing and the outside of the bellows pleats of the bellows, via which the respective fluid volumes are evenly distributed between the respective chamber volumes and thus the bellows is evenly supported over the entire installation space in the accumulator housing.

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bellows-type accumulator according to the present invention will be described in detail below with reference to the drawings. The drawings are principle views and are not drawn to scale. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is an overall vertical cross-sectional view of a 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 plan view of an annular guide for guiding a bellows within an associated accumulator housing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The bellows-type accumulator shown in FIG. 1 is a special representative of hydraulic accumulators, in which a bellows 16, which serves as a movable separating element 10 between a first medium side 12, in particular the gas side, and a second medium side 14, in particular the liquid side, has at its bellows end 20, which is axially movable in an accumulator housing 18 when it expands or contracts, a closing body 24 which closes the interior 22 of the bellows 16 in a medium-tight manner. At its other bellows end 26, the bellows 16 is immovably fixed to the accumulator housing 18. 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. In this respect, the accumulator housing 18 consists of three individual housing parts which are joined or welded to one another, the upper housing part 32 and the lower housing part 34 being formed in a hemispherical shape, and the cylindrical housing part 36 arranged between them can be provided with a textile coil 38 on its outer periphery in the usual way for pressure stabilization.

[0024] The first medium side 12 is filled with a compressible medium in the form of a working gas, for example nitrogen gas, and is under a settable pre-pressure or filling pressure, which can be significantly higher compared to conventional bellows-type accumulator solutions of the prior art. A metal part 40 with a glass insert in the form of a sight glass opens if the internal pressure becomes too high. The accumulator can be filled with a working gas, such as nitrogen gas, through a closure 42 in the upper housing part 32. Furthermore, the bellows 16 is shown in FIG. 1 in the most extended position possible, the movement of the bellows 16 accompanying its contraction being limited by the abutment of the individual pleats of the bellows 16 against each other. The bellows 16 is preferably made of a stainless steel material, which is medium-resistant and pressure-stable, such that the working gas introduced under pre-pressure into the medium side 12 cannot penetrate into the second medium side 14, which is filled with liquid. Such a bellows-type accumulator is in principle connected on its liquid side to a hydraulic supply circuit (not shown), in which the hydraulic liquid from such supply circuit is in principle present as fluid.

[0025] Furthermore, the bellows-type accumulator has a valve device, generally designated 44, as shown in detail in FIG. 2. When the pressure on the liquid side 46 of the bellows-type accumulator decreases, the valve device 44 reaches the closed position shown in FIG. 2, thus preventing further liquid from flowing out of the accumulator housing 18. Such a closing action is facilitated by at least one energy storage means 48 arranged between the valve device 14 and the closing body 24 of the bellows 16. The energy storage means 48 controls the closing process of the valve device 14 in such a way that at any given time a settable amount of liquid still remains in the accumulator housing 18 on the second medium side 12. Such amount of liquid supports the bellows 16 with its individual pleats in the extended position shown in FIG. 1. The energy storage means 48 can be formed, for example, from a conventional compression spring 50 in the form of a disc spring or a stacked disc spring.

[0026] As shown in particular in FIG. 2, the valve device 44 comprises a disc valve 52 whose valve element 54 is held or biased towards an open position which allows liquid to pass against the action of a further energy storage means 56, essentially in the form of a compression coil spring 58, and which, when actuated accordingly, reaches a closed position which blocks liquid, as shown in FIG. 2.

[0027] The valve device 44 has a common connection 60 for the liquid supply and the liquid discharge, which opens at one end as a through opening on the second medium side 14 and at its opposite end is connected to a hydraulic circuit, not shown in detail. Instead of the hydraulic circuit described above, the bellows-type accumulator can also be connected to other hydraulic components, such as hydraulic working cylinders, which must be supplied with pressurized fluid for their proper functioning.

[0028] The spring stiffness of the compression spring 50 is selected in any case to be greater than the spring stiffness of the valve spring 58. As can be further seen from FIG. 2, one compression spring 50 is arranged in the closing body 24 of the bellows 16, while the other compression spring 58 is part of the valve device 44. To accommodate the compression spring 50, the hemispherical closing body 24 is provided on the outside with a cylindrical recess 64 concentric with the longitudinal axis 62 of the bellows-type accumulator. The compression spring 50 is therefore supported at one upper free end in the recess 64 and at the other lower free end on the upper side of the valve body 54. In contrast, the second compression spring 58 is supported at one upper free end on the lower side of the valve body 54 and at the other lower free end on a receptacle 66 for the longitudinal guiding of the valve stem 68 of the poppet valve 52. For this purpose, the fluid connection 60 is solidly formed on the wall side and is provided with a number of longitudinal holes 70 (4-8 in total). Apart from these holes 70, there is a central guide 72, through which the valve stem 68 passes, concentrically with the longitudinal axis 62 of the accumulator. Furthermore, the valve stem 68 has a stop limit 74 in the usual way on its underside and, in the uppermost position of the valve body 54, comes to rest against the lower edge limit of the central guide 72, which is the valve receptacle 66. The second compression spring 58 is therefore supported with its upper free end below the valve body 54 and with its opposite lower end against the receptacle 66 or against a stepped projection of the central guide 72.

[0029] In the closed position of the poppet valve 52 shown in Fig. 2, the valve body 54 bears with its underside against a sealing device 78 via a centrally located, outwardly projecting, annular sealing projection 76 in the form of a sealing bead. The sealing device 78 is made, in particular, of an annular soft seal (EPDM) and is accommodated in a connecting body 80 of the accumulator housing 18. The connecting body 80 contains the valve device 44 and defines the fluid connection 60 outwardly. In this respect, the connecting body 80 is an integral component of the lower housing part 34.

[0030] 1 and 2, the closure body 24 is formed in the form of a hemispherical shell and limits a defined chamber volume 82 for accommodating a fluid with the bellows 16 extended as fully as possible. To this end, as shown in particular in FIG. 2, the inner circumferential surface of the lower housing part 34 is formed following the hemispherical shape of the closure body 24, so that in the closed position of the illustrated valve device 44, the wall spacing between the closure body 24 and the lower housing part 34 is constant as long as they are adjacent and facing each other as shown. When the bellows 16 is lifted upwards in the direction of looking at FIGS. 1 and 2, the valve device 44 opens and the corresponding chamber volume 82 increases under the effect of the pressure of the fluid flowing from the fluid connection 60 into the second medium side 14 of the accumulator housing 18. The bellows-type accumulator further has an annular guide body 84, which is omitted in FIG. 2 for the sake of simplicity and is shown in a plan view in FIG. 3. 1 and 2, in the operating position of the bellows-type accumulator, the lower bellows end 20 is guided in the accumulator housing 18 by this annular guide body 84, which has individual segment-like recesses 86 separated from each other at equal radial intervals by radial projections 88, so that the outer peripheral surfaces 90 of the projections 88, which project outwardly in equal proportions, form guide surfaces for abutting against the inside 30 of the accumulator housing 18. The segment-like recesses 86 in turn enable fluid communication between the above-mentioned first chamber volume 82 and a separate second chamber volume 92 above the guide body 84. In this way, the support fluid can be exchanged in a bidirectional pressure-communicative manner between the chamber volumes 82 and 92 via the recesses 86, so that the individual pleats of the bellows 16 are surrounded by the support fluid in any operating state.

[0031] The closing body 24 is formed in a hemispherical shape, so that inside it there is also a storage space for the working gas, in which respect the operating capacity of the bellows-type accumulator is improved by the increased base capacity. The guide body 84 also prevents unintended buckling along the pleats of the bellows 16. All in all, an accumulator solution is provided which allows a fault-free operation with high filling pressures on the gas side and high overall operating pressures, because the bellows 16 can be fully supported along its outer circumference on the liquid side even when the valve device 44 is closed. This also applies when the accumulator liquid is almost empty and only a residual amount of fluid remains between the outside of the bellows 16 and the inner circumference of the accumulator housing 18 with the valve device 44 closed, as described above. This has no equivalent in the prior art.

Claims

1. The bellows-type accumulator comprises a bellows (16) acting as a movable separating element (10) between a first medium side (12), in particular a gas side, and a second medium side (14), in particular a liquid side, the bellows (16) having, at one end (20) of the bellows (16) axially movable within an accumulator housing (18) during expansion and contraction thereof, a closing body (24) closing the interior (22) of the bellows (16) in a medium-tight manner, the other end (26) of the bellows (16) being fixedly held relative to the accumulator housing (18) and reaching a closed position when the pressure on the liquid side (46) decreases. A bellows-type accumulator comprising a valve device (44) for preventing further liquid outflow from the accumulator housing (18), characterized in that the closing process of the valve device (44) is controlled by at least one energy storage means (48) arranged between the valve device (44) and the closing body (24) of the bellows (16) in such a way that a settable amount of liquid remains in the accumulator housing (18) at all times, supporting the bellows (16) in its extended position.

2. 2. The bellows-type accumulator according to claim 1, wherein the valve device (44) comprises a poppet valve (52) whose valve element (54) is held in an open position to allow liquid to pass against the action of another energy storage means (56) and reaches a closed position to block liquid when actuated.

3. 2. The bellows-type accumulator according to claim 1, characterized in that the valve device (44) has a common connection (60) for liquid supply and liquid discharge, the connection (60) being at least partially penetrated by the valve device (44).

4. 3. The bellows-type accumulator according to claim 2, wherein the one energy storage means (48) and the other energy storage means (56) are each formed from one compression spring (50, 58), and the spring stiffness of the one compression spring (50) is greater than the spring stiffness of the other compression spring (58).

5. 5. A bellows-type accumulator according to claim 4, characterized in that one compression spring (50) is arranged in the closure body (24) of the bellows (16) and the other compression spring (58) is part of the valve device (44).

6. 5. The bellows-type accumulator according to claim 4, wherein, in an operating position, the one compression spring (50) is supported at one end above the poppet valve (52) and at the other end below the closing body (24) of the bellows (16), and the other compression spring (58) is supported at one end below the valve body (54) and at the other end in a receiving portion (66) for guiding a valve stem (68) of the poppet valve (52).

7. 3. A bellows-type accumulator according to claim 2, characterized in that in the closed position, the valve body (54) abuts against a sealing device (78), in particular in the form of an annular soft seal, housed in a connecting body (80) of the accumulator housing (18) containing the valve device (44).

8. 2. A bellows-type accumulator according to claim 1, characterized in that the closure (24) is formed in the form of a hemispherical shell defining a defined chamber volume (82) for receiving liquid when the bellows (16) is fully extended.

9. 9. The bellows-type accumulator according to claim 1, wherein the bellows end (20) is guided in the accumulator housing (18) by an annular guide body (84) provided with a fluid passage (86) for establishing permanent fluid communication between a chamber volume (82) in the region of the valve device (44) and another chamber volume (92) substantially defined by the inside (30) of the accumulator housing (18) and the outside of the bellows pleats of the bellows (16).

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