Hydraulic accumulator

Abstract

The invention relates to a hydraulic accumulator comprising an accumulator housing (18) and a separating element (10) which is arranged therein in a longitudinally movable manner and which separates two media chambers (12, 14) within the accumulator housing (18), in particular a chamber with a working gas, such as nitrogen gas, from another chamber with a liquid, such as hydraulic oil, and a bursting device (66) for reducing an inadmissibly high pressure in the accumulator housing (18), wherein the bursting device (66) is arranged in the separating element (10), and when the bursting device bursts, a media-conducting connection (84) between the two media chambers (12, 14) is released via the separating element (10).

Description

[0001] The invention relates to a hydraulic accumulator with the features in the preamble of claim 1.

[0002] To ensure the safety of the operation of equipment with pressurized gas containers, such as hydraulic accumulators, it is necessary to consider all hazards that may arise at the installation site of such equipment, with particular importance being possible hazardous external influences, especially the temperature increases that occur in the immediate vicinity of such gas-pressurized containers during a fire, which can lead to container failure.

[0003] To meet these requirements, DE 10 2010 011 879 A1 proposes a safety device for containers pressurized by gas, in particular for safeguarding the working space gas side of hydropneumatic devices, such as hydraulic accumulators, with a relief device for reducing increased gas pressure in the respective container caused by heat exposure, wherein the relief device is a component subjected to buckling or bulging under the influence of a shear or pressure force, the change in shape of which, when exposed to heat, takes place in an externally closed space in such a way that a gas-carrying connection from the gas side of the container to the outside in the direction of the environment is enabled.

[0004] DE 10 2015 014 797 A1 discloses a safety device with a connection point for a pressure or hydraulic accumulator, which is connected via this connection point on the gas side to a bursting device that can be triggered by means of a controllable force element, which, in the triggered state, allows gas-side discharge of the pressure accumulator. In particular, in this known solution, the bursting device has a bursting disc that triggers when a maximum gas-side pressure is exceeded, especially by actuating a force element, which may be of a pyrotechnic nature, so that, upon ignition of a propellant charge, a wall section of a housing is deformed or destroyed in such a way that the bursting device contained therein is triggered or that the bursting disc is destroyed by means of an actuating pin.The well-known solution is particularly suitable for applications in mobile systems where hydraulic accumulators are present, such as in vehicles that are equipped with an energy recovery system in conjunction with a hydrostatic drive.

[0005] DE 31 39 600 A1 describes a hydraulic accumulator with the features in the preamble of claim 1, comprising an accumulator housing and a separating element arranged longitudinally therein, which separates two media spaces from each other within the accumulator housing, in particular a space with a working gas, such as nitrogen gas, from another space with a liquid, such as hydraulic oil, and with a bursting device for reducing an impermissibly high pressure in the accumulator housing, wherein the bursting device is arranged in the separating element, upon bursting of which a media-carrying connection between the two media spaces is released via the separating element.

[0006] Further hydraulic accumulators are shown in DE 10 2013 204 220 A1, DE 10 2016 009 776 A1, DE 10 2008 061 559 A1 and DE 41 41 929 A1.

[0007] Based on this prior art, the invention aims to improve upon known solutions in the prior art. A hydraulic accumulator with the features of claim 1 as a whole solves this problem.

[0008] According to the characterizing feature of claim 1, the bursting device formed from a bursting plug has an engagement part which is inserted into a through-opening in the separating element and which is an integral part of the bursting device with a contact part, that the outer diameter of the contact part is larger than the outer diameter of the engagement part, that the contact part is in planar contact with the separating element, and that a longitudinal channel runs in the engagement part, which opens at one end into the second media chamber containing the liquid and at the other end into the contact part in such a way that a type of membrane is formed on the head side of the contact part which borders the first media chamber containing the working gas.

[0009] By arranging the bursting device within the separating element, and by releasing a media-carrying connection between the two media chambers via the separating element upon its bursting, this design, unlike known solutions, prevents parts of the bursting device from unintentionally escaping into the environment in the event of failure. This ensures that persons or machine parts located near the failing hydraulic accumulator are never endangered. Furthermore, the working gas on the gas side of the hydraulic accumulator is typically under a very high pre-charge pressure, meaning that any release of this pressure into the environment could also pose safety risks. This is avoided by the solution according to the invention.

[0010] Because the bursting device is located within the separating element inside the hydraulic accumulator, no parts of the bursting device escape into the environment in the event of a failure. Instead, they remain within the accumulator housing, which is typically designed and safety-certified as a high-pressure component. Consequently, in the event of a failure, the working or pressurized gas is released onto the liquid side of the accumulator, and due to the strong damping effect of the liquid, the pressure on the accumulator housing is largely relieved.It is also possible to integrate such hydraulic accumulators with the bursting device according to the invention into the separating element between the two media chambers of the hydraulic accumulator, within the operation of complete hydraulic systems, into a defined, permissible failure zone, so that in the event of failure the associated hydraulic circuit and connected hydraulic devices need not be adversely affected. In this way, the reduction of an impermissible pressure increase can be shifted to less critical areas in predefined sections of the hydraulic network via appropriate safety devices.Even if the hydraulic accumulator according to the invention is subjected to a high number of load cycles with corresponding pressure fluctuations and extremely high gas temperatures, which can also occur during the dynamic operation of the hydraulic accumulator, it is designed as a closed system even in the event of failure, so that a safety hazard to the environment is excluded.

[0011] According to the invention, the bursting device is formed from a bursting plug which is inserted into a through-opening in the separating element. In this way, the bursting device can be implemented at a central location in the separating element in a particularly cost-effective manner.

[0012] Preferably, the engagement part is screwed into the separating element via a threaded section along the through-opening. This ensures a secure, releasable attachment of the rupture device to the separating element. This is further enhanced by the fact that the rupture device has a contact element whose outer diameter is larger than the outer diameter of the engagement part. This contact element rests in a supportive, planar position against the separating element, resulting in a planar force transmission into the separating element. From a manufacturing perspective, it is also advantageous that the engagement and contact elements are integral components of the rupture device.

[0013] The intervention section contains at least one longitudinal channel, which opens at one end into the second media chamber containing the liquid and at the other end into the system component in such a way that a type of membrane is formed on the head side of the system component, bordering the first media chamber containing the working gas. Thanks to this membrane, whose thickness can be predefined, a kind of predetermined breaking point is formed, in the event of its failure, a defined discharge of the working gas under high pressure is enabled via the longitudinal channel in the intervention section towards the liquid chamber of the hydraulic accumulator.

[0014] To prevent the media contained in the media spaces, especially working gas and liquid, from coming into unwanted exchange with each other during normal operation, a sealing device is arranged between the bursting device and the separating element.

[0015] The hydraulic accumulator can preferably be designed as a bellows accumulator, but also as a piston accumulator, in which case the separating element is formed from a bellows or from a separating piston.

[0016] In any case, it is ensured that in the event of failure of the bursting device, all fragments remain sealed inside the storage housing and that any resulting, impermissibly high gas pressure is released onto the liquid side of the storage unit, thus preventing the working gas from unintentionally escaping into the environment. This has no equivalent in the prior art.

[0017] The hydraulic accumulator according to the invention will now be explained in more detail with reference to exemplary embodiments shown in the drawing. The drawings are presented in a general and not to-scale representation. Fig. 1 shows a bellows storage unit as a whole in the form of a longitudinal section; Fig. 2 shows an enlarged view of the bottom area of ​​the bellows storage unit after the Fig. 1 ; Fig. 3, in the form of a longitudinal section, shows a piston accumulator as a further embodiment; and Fig. 4, in an enlarged view, shows the separating element in the form of a separating piston, as in Fig. 3 depicted.

[0018] The in Fig. 1 The bellows accumulator shown is a special type of hydraulic accumulator in which a bellows 16, serving as a movable separating element 10 between a first media chamber 12, in the form of a gas side, and a second media chamber 14, in the form of a liquid side, has at its axially movable end 20 within a storage housing 18 a sealing element 24 that seals the interior 22 of the bellows 16 in a media-tight manner and is guided longitudinally within the storage housing 18. At its other end 26, the bellows 16 is fixed immovably within the storage housing 18. This is achieved by a locking ring 28, which is welded to the end of the bellows 16 and to the inner surface 30 of the storage housing 18 in the usual manner.The storage housing 18 consists of three separate housing parts connected or welded together, wherein the upper housing part 32 and the lower housing part 34 are dome-shaped and an intermediate cylindrical housing part 36 can be provided with a fiber winding 38 on its outer circumference in the usual manner for pressure stabilization.

[0019] A compressible medium, for example a working gas such as nitrogen gas, is introduced into the first media chamber 12, which is under a predetermined pre-charge or pre-fill pressure. A metal part 40 with a glass insert, similar to a sight glass, allows inspection of the internal components of the hydraulic accumulator from the outside. The hydraulic accumulator can be filled with working gas, such as nitrogen gas, via a closure part (not shown) in the upper housing part 32. Furthermore, the bellows 16 is located in the Fig. 1 The bellows 16 is shown in its possible, fully extended position, and its associated movement is limited by the individual folds of the bellows 16 when they contract, coming into contact with each other, i.e., colliding. Preferably, the bellows 16 is made of a stainless steel material that is resistant to various media and pressure-stable, and ensures that the working gas introduced into the media chamber 12 under pre-charge pressure cannot pass into the second media chamber 14 containing the fluid, such as hydraulic oil, during normal operation. These bellows accumulators are typically connected on their fluid side to hydraulic supply circuits (not shown).

[0020] As can be further seen from the Fig. 1 and 2The closure body 24 is designed in the form of a hemispherical shell, which, in the possible fully extended state of the bellows 16, defines a small chamber volume 52 for receiving fluid on the fluid side 46 of the hydraulic accumulator. The fluid side 46 has a hollow cylindrical connection part 54, which is preferably provided with an external thread and serves in the usual manner to secure the hydraulic accumulator to a third component, such as a storage block (not shown). The connection part 54 encompasses a cylindrical fluid guide, the diameter of which decreases conically towards the spherical closure body 24 by means of a step 56 that tapers towards the closure body 24, forming a connection point 58. The connection point 58 is encompassed by a planar annular surface 60, which, according to the illustration in the Fig. 2 in a horizontal plane, viewed perpendicular to the longitudinal axis of the hydraulic accumulator. Adjoining this, the further inner circumferential side 61 of the lower housing part 34 extends along a convex curve, viewed from the inside of the hydraulic accumulator, to a wall section 63 as a transition point, which is cylindrical and coaxial to the longitudinal axis of the hydraulic accumulator. The curvature in this section is less pronounced than the corresponding convex curvature on the outer surface 65 of the closure body 24. In cross-section, this creates a free chamber volume 52, which tapers to a point at its free ends in a shell-like structure and extends approximately in the lower third in the direction of the Fig. 2 seen, it has the largest free cross-section. Overall, this creates a curved lens shape for the chamber volume 52, which is filled with liquid during operation of the storage unit.

[0021] Viewed concentrically to the longitudinal axis of the storage housing 18, the locking body 24 is located towards the first media chamber 12, in the direction of the Figuren 1 and 2 Viewed from above, the upper section is provided with a hollow cylindrical shoulder 62, which has an internal thread 64. A bursting device, designated as a whole by 66, is inserted into the recess formed by the shoulder 62. This device serves to relieve an impermissibly high pressure in the storage housing 18 on its gas side. The bursting device 66, designed in the manner of a burst plug, is arranged in a through-opening 68 in the separating element 10, which is formed from the sealing body 24 of the bellows 16.

[0022] The plug-like bursting device 66 has a cylindrical engagement part 72 which is inserted into the through-opening 68 and, in particular, is screwed into the separating element 10 via a threaded section along the through-opening 68. For this purpose, the engagement part 72 has an external thread 74 on its outer circumference that fits precisely with the internal thread 64 of the shoulder 62.

[0023] Furthermore, the bursting device 66 has a contact part 76 whose diameter is larger than the diameter of the engagement part 72. The contact part 76 is in planar contact with the separating element 10 with its underside, and is supported on the upper side of the connecting part in the form of the cylindrical shoulder 62. The contact part 76 can be provided with contact surfaces on its outer circumference to allow, for example, the engagement of an actuating tool such as a wrench (not shown) in order to insert or screw the bursting device 66 as a whole into the shoulder 62.

[0024] The corresponding screw connection is detachable, so that in the event of failure of the bursting device 66, it can be replaced with a new element. As can further be seen from the Fig. 1 and 2The engagement part 72 and the attachment part 76 each form an integral component of the bursting device 66 as a whole. In this case, the lower end of the engagement part 72 projects slightly beyond the underside of the closure body 24, which acts as the separating element 10, with a small projection 77 corresponding to the threaded runout of the external thread 74. The engagement part 72 contains a longitudinal channel 78 that runs concentrically to the longitudinal axis of the hydraulic accumulator. One free end of the channel opens into the second media chamber 14 containing the fluid, while the other, opposite end opens into the block-like attachment part 76. This creates a thin-walled membrane 80 on the head side of the attachment part 76, which borders the first media chamber 12 containing the working gas.Furthermore, a sealing device 82, not shown in detail, is arranged at the transition point between the plant part 76 and the cylindrical shoulder 62, which ensures media separation between the two media spaces 12, 14 with their respective fluid contents during normal operation of the hydraulic accumulator.

[0025] If an unintended increase in the pre-charge pressure occurs on the gas side of the accumulator, for example due to thermal heating, such as that which regularly occurs during a fire, the increased pressure of the working gas causes the diaphragm 80 of the bursting device 66 to rupture. This opens a media- or fluid-carrying connection between the two media chambers 12, 14 via the separating element 10 through the longitudinal channel 78 thus created. The gas then expands onto the depressurized liquid side of the accumulator, and any fragments of the diaphragm 80 remain on the gas and / or liquid side of the accumulator housing 18. In this way, the surrounding area is protected from the escape of working gas and / or parts of the bursting device 66 in the event of failure.

[0026] The outer diameter of the engagement part 72 with its external thread 74 is slightly smaller than the inner diameter of the connection point 58 in the lower housing part 34. Thus, the projection of the engagement part 72 in the extended state of the bellows 16 forms an annular throttling point 81, which is part of a gap 83 extending from the throttling point 81 to the chamber volume 52, which widens from the gap 83. The gap 83 can have individual gap channels that radiate outwards from the fictitious center of the flat closure body 24 in this area, until the plane extends into the curved area of ​​the closure body 24. The gap 83 can also be implemented differently, for example, by using spacers between the adjacent flat surfaces of the closure body 24 and the inner surface 61 of the lower housing part 34.The throttling point 81 and / or the aforementioned gap guide 83 enables low-pressure-loss and low-turbulence inflow and outflow of the fluid from the hydraulic accumulator, so that material-damaging cavitations cannot occur.

[0027] Fig. 3 Figure 1 now shows a modified embodiment of the solution according to the invention in the form of a piston accumulator, wherein the separating element 10 is formed from a separating piston 86. The present embodiment will only be explained insofar as it differs substantially from the preceding embodiment, whereby the same components are accordingly provided with the same reference numerals and the explanations given for the preceding embodiment also apply to the further embodiment designed as a piston accumulator. In a known design, the hydraulic accumulator according to the Fig. 3 The accumulator has a hollow cylindrical housing 18, which is closed by a bottom cover 88 and a top cover 90. The separating piston 86 is, in the usual way, a pot piston axially displaceable within the accumulator housing 18, which in turn separates a first media chamber 12 containing the working gas from the second media chamber 14 containing the hydraulic fluid. Thus, the separating piston 86 separates an oil side from a gas side of the accumulator. The second media chamber 14 can be connected to the hydraulic system (not shown) via an oil connection 92 coaxial with the longitudinal axis of the accumulator. A gas filling connection 94, also coaxial with the longitudinal axis, is located in the top cover 90, through which the first media chamber 12 containing the working gas, such as nitrogen, can be pressurized to a predetermined pressure.A gas filling connection 94 can be closed in the usual manner by means of a closing device (not shown in detail). The through-opening 68 is provided in the base of the separating piston 86, which, when viewed from the outside, is oriented as follows: Fig. 3 seen with its upper free end opening into the first media room 12 with the working gas.

[0028] The bursting device 66 according to the illustration according to the Fig. 3 and 4 is like the bursting device 66 already described Fig. 1 and 2 constructed, i.e., it has an engagement part 72 screwed into the through-opening 68 of the separating element 10, which is provided with a central longitudinal channel 78 that opens downwards into the second media chamber 14 and is bounded upwards by the membrane 80 of the system part 76. This differs from the solution according to the Figuren 1 and 2The feature is that a ring-shaped central recess 96 is provided in the shallow base of the pot, along which the system component 76 is supported by an overlapping contact with the separating piston 86. In this respect as well, in the event of failure, the working gas would expand towards the liquid side after being released through the damaged membrane 80.

[0029] The hydraulic accumulator solution according to the invention has been explained in more detail with reference to the construction of a bellows and a piston accumulator; however, it is also possible to introduce the bursting device 66 into the wall part of the elastomer membrane (not shown) in a membrane or bladder accumulator in order to achieve burst protection in this type of hydraulic accumulator as well.

Claims

1. Hydraulic accumulator having an accumulator housing (18) and a separating element (10) which is arranged therein in a longitudinally displaceable manner and which separates two media chambers (12, 14) within the accumulator housing (18) from one another, one chamber with a working gas, such as nitrogen gas, from another chamber with a liquid, such as hydraulic oil, and having a bursting device (66) for reducing an inadmissibly high pressure in the accumulator housing (18), wherein the bursting device (66) is arranged in the separating element (10), and when the bursting device bursts, a media-conducting connection (84) between the two media chambers (12, 14) is released via the separating element (10), characterised in that the bursting device (66) formed by a bursting plug has an engagement part (72) that is inserted in a through opening (68) in the separating element and which, with an abutting part (76), is an integral part of the bursting device (66), the outer diameter of the abutting part (76) is larger than the outer diameter of the engagement part (72), the abutting part (76) is in surface contact with the separating element (10), and a longitudinal channel (78) runs in the engagement part (72), one end of said channel emerging into the second media chamber (14) with the liquid and its other end emerging into the abutting part (76), such that a kind of membrane (80) arises on the top side of the abutting part (76), said membrane abutting the first media chamber (12) with the working gas.

2. Hydraulic accumulator according to claim 1, characterised in that the engagement part (72) is screwed into the separating element (10) via a threaded section (64, 74) along the through opening (68).

3. Hydraulic accumulator according to any of the preceding claims, characterised in that a sealing device (82) is arranged between the bursting device (66) and the separating element (10).

4. Hydraulic accumulator according to any of the preceding claims, characterised in that the separating element (10) is formed by the sealing body (24) of a bellows (16) of a bellows accumulator, the inside (30) of which at least partially forms the first media chamber (12) with the working gas.

5. Hydraulic accumulator according to any of claims 1 to 3, characterised in that the separating element (10) is formed by a separating piston (86) of a piston accumulator.

6. Hydraulic accumulator according to any of the preceding claims, characterised in that, in the event of the bursting device (66) failing, all fragments of the bursting device (66) remain sealed from the outside in the accumulator housing (18) and in that an associated inadmissibly high gas pressure is relieved onto the liquid side (46) of the accumulator.

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