Hydraulic accumulator

Abstract

The invention relates to a hydraulic accumulator, in particular in the form of a piston-type accumulator, having a separating element (10) which is arranged in an accumulator housing (14) and separates two fluid chambers (16, 18) from one another in a fluid-tight manner, in particular a closed accumulator chamber (20) comprising a working gas from a liquid chamber (22) comprising an operating liquid such as hydraulic oil, wherein a fluid connector (24) is fluidically connected to one of the fluid chambers (18), characterised in that outside the accumulator housing (14) and fixed thereto there is an attachment part (26) with a magnetic field generating device (44) which acts on a fluid connection (46) between the fluid connector (24) of the accumulator housing (14) and a fluid connector (25) of the attachment part (26) in such a way that magnetisable particles can be separated in a cleaning manner from the fluid passing through the fluid connection (46).

Description

[0001] HYDAC TECHNOLOGY GMBH

[0002] Industriestraße, 66280 Sulzbach / Saar, Germany

[0003] hydraulic accumulator

[0004] The invention relates to a hydraulic accumulator, in particular in the form of a piston accumulator, with a separating element which, arranged in an accumulator housing, separates two fluid spaces, in particular a closed storage space with a working gas from a liquid space with an operating fluid, such as hydraulic oil, in a fluid-tight manner, wherein a fluid connection is connected to one of the fluid spaces in a fluid-conducting manner.

[0005] Hydraulic accumulators, such as (hydropneumatic) piston accumulators, are used in hydraulic systems to hold specific volumes of pressurized fluid, such as hydraulic oil, and return it to the system when needed. In the commonly used hydropneumatic piston accumulators, in which the piston separates the oil-side fluid chamber from the storage chamber enclosed in the accumulator housing, which holds a working gas, such as nitrogen gas, the position of the piston changes during operation of the hydraulic accumulator so that when the pressure rises, the hydraulic accumulator holds hydraulic oil, while at the same time the working gas in the other fluid or storage chamber is compressed. When the pressure drops, the compressed gas expands again, displacing stored hydraulic oil back into the hydraulic working circuit.The resulting changes in the volumes of the working chambers during operation result in a corresponding axial movement of the piston within the accumulator housing.

[0006] In this respect, such hydraulic accumulators are connected to the hydraulic working circuit within the scope of hydraulic equipment, such as working cylinders. This hydraulic circuit generally has filter devices with filter elements for removing particulate contamination from a working fluid, such as hydraulic oil. These filter elements can be replaced with new elements if necessary. Despite these filter devices, it cannot be ruled out that contamination particles may reach the clean side of the fluid and, once in the hydraulic accumulator, cause damage to the accumulator and its components. Filter elements are also limited in their flow capacity, so they cannot always be used with very high volume flows and the associated high fluid pressures.Particularly when using piston accumulators, particle contamination can inadvertently enter the sealing system of the separating piston, which can lead to the failure of the accumulator and associated hydraulic devices. Since the resulting particle contamination is often caused by abrasion on the hydraulic devices, these are usually metallic in nature. Particularly in the event of mechanical failure, such particles can be large enough to cause the sealing devices on the separating piston and their elastomer material to leak or even be destroyed.

[0007] DE 10 2016 007 798 A1 discloses a hydropneumatic piston accumulator comprising an accumulator housing having a cylinder tube defining a longitudinal axis, which is hermetically sealed at both ends by a housing cover, and in which a piston is guided longitudinally as a separating element, which separates a fluid chamber for a compressible fluid, such as a working gas, from another fluid chamber for an incompressible fluid, such as hydraulic oil, and comprising a displacement measuring device which non-contactably determines the position of the piston in the housing, which has a non-magnetic measuring tube which extends through a passage formed in the piston along the longitudinal axis from one housing cover to the other housing cover and is sealed from the interior of the housing. A position sensor is movably guided in the tube itself, which follows the piston movements by means of a magnetic force acting between the position sensor and the piston in the measuring tube.To generate the magnetic force that forces the position sensor to move in the measuring tube, a permanent magnet is provided on the piston. This permanent magnet, which continuously moves along with the separating piston during accumulator operation, is housed in the fluid chamber containing the compressible working gas.

[0008] DE 41 16 482 A1 discloses a method and device for measuring the pressure of a working gas in a gas pressure accumulator that can be connected to a hydraulic working circuit and in which the working gas is separated from the operating or working fluid by a separating element in the form of an elastomeric accumulator bladder. When the accumulator bladder is in a predeterminable position, the gas pressure attributable to it in this position is measured by a pressure transducer arranged on the fluid side, for which purpose the position of a poppet valve of the accumulator is monitored by a monitoring device.For this purpose, the poppet valve in a fluid connection of the accumulator has a switching element with a permanent magnet. The associated sensor consists of a switch that can be actuated by the magnet or utilizes the so-called Hall effect as soon as the switching element passes the corresponding sensor depending on the actuating position of the poppet valve and triggers it. The cube-shaped magnet, which constantly moves back and forth during operation of the accumulator, is just as unsuitable as the ring magnet on the gas side of the accumulator housing for effectively counteracting particle contamination occurring on the liquid side of the accumulator.

[0009] Based on this state of the art, the object of the invention is to further improve the known hydraulic accumulator solutions in such a way that failure can be excluded even in the event of metallic particle contamination.

[0010] A hydraulic accumulator having the features of patent claim 1 in its entirety solves this problem.

[0011] Due to the fact that, according to the characterizing part of patent claim 1, an attachment part with a magnetic field generating device is provided outside the storage housing and fixed to the latter, which device acts on a fluid connection between the fluid connection of the storage housing and a fluid connection of the attachment part in such a way that magnetizable particles can be separated in a cleaning manner from the fluid passing through the fluid connection, a possibility is created to create such a strong, stationary magnetic field in the fluid connection area of ​​the storage housing that magnetizable, in particular metallic, particles cannot reach the liquid side of the storage device in the first place and therefore do not cause any damage, in particular not damage to the separating element, such as a separating piston.In particular, the magnetizable particles are reliably trapped outside the accumulator housing, preventing them from inadvertently reaching the fluid side of the accumulator. This ensures that particle contamination cannot reach the sealing side of the separating piston with its sealing rings and guide bands of a hydropneumatic piston accumulator. This could otherwise lead not only to sealing problems but also to the separating piston "eating" the interior of the accumulator housing due to friction, with the result that the separating piston can no longer move, rendering the hydraulic accumulator unusable. Particularly when managing fluid flows, where filter systems reach their limits, reliable removal of metallic, magnetizable particles from the fluid flow is achieved by means of the magnetic separation system installed upstream of the hydraulic accumulator.

[0012] In a preferred embodiment of the hydraulic accumulator according to the invention, the attachment is cube- or cuboid-shaped and is provided with an engagement part, screwed into the accumulator housing, or connected flush with the accumulator housing via a plate-shaped flange connection. In this way, the attachment can be mounted in a space-saving manner on the underside of the hydraulic accumulator in its vertical operating position and is thus part of an associated piping system by means of which the piston accumulator can be connected to a conventional hydraulic circuit with associated pressure supply devices, such as hydraulic pumps, and hydraulic consumers, such as working cylinders.

[0013] In this respect, it is preferably provided that the storage housing has a cylindrical housing wall which is closed at least at one end with a housing cover which has the attachment part on its outer side or underside facing away from the separating piston.

[0014] In a further preferred embodiment of the hydraulic accumulator according to the invention, the fluid connection within the attachment part runs in a straight line coaxial with the fluid connection or at right angles thereto, and the magnetic field-generating device is arranged transversely to at least parts of the fluid guide and engaging therein in the attachment part. The transverse extension of the magnetic field-generating device to the fluid flow moving within the fluid connection ensures that fluid is guided past the device over a relatively long distance, thus achieving a particularly efficient "fishing out" of the particle contamination in question before the fluid enters the accumulator housing.

[0015] In a particularly preferred embodiment of the hydraulic accumulator according to the invention, the magnetic field-generating device is formed from a permanent magnet, allowing the removal of magnetizable particles from the fluid flow without the introduction of external energy. In special cases, however, it would also be conceivable to use an energizable magnet instead of the permanent magnet to increase efficiency. However, this would then require a corresponding energy supply to the accumulator housing of the hydraulic accumulator and / or its attachments.

[0016] Preferably, the permanent magnet comprises a magnetic rod which is inserted into the fluid connection by means of a fixing screw at an axial and radial distance from the housing parts of the attachment. Since the use of filter elements in the hydraulic working circuit means that magnetizable particle contamination is unlikely to occur in this respect, manual cleaning of the magnetic field generating device is not absolutely necessary due to the large amount of dirt that may be expected. However, it is always possible to remove the magnetic field generating device from the fluid connection via the fixing screw for cleaning and / or replacement purposes and, after cleaning or after carrying out the maintenance work, to reinsert it into the fluid guide in the attachment for renewed operation.In order to remove the permanent magnet for inspection purposes, it is then not necessary to disconnect the hydraulic accumulator from the rest of the hydraulic circuit. In a further advantageous embodiment, the locking screw can be designed as a so-called magnetic screw, thus forming part of the effective permanent magnet. Furthermore, the attachment is preferably made of a non-magnetizable material, such as stainless steel, to prevent metallic particles from becoming trapped in the locking opening in the attachment when unscrewing the locking screw as part of the permanent magnet or the magnetic screw. This also makes it easier to completely remove the particles from the magnetic field-generating device.

[0017] To prevent any leaks and possible corners, a seal is provided at the connection point between the attachment and the storage housing, usually in the form of at least one O-ring. However, such a seal can also be omitted if the attachment is an integral part of the corresponding housing cover of the storage housing.

[0018] For energy-efficient use at full working capacity, it is preferably provided that the hydraulic accumulator is designed such that the separating element is formed from a separating piston that can be moved longitudinally within the accumulator housing. In one of its possible stop positions, the piston is flush with the housing cover with the fluid connection and covers the latter without a step when the fluid chamber is completely emptied. During operation of the separating piston, high fluid flow velocities occur, particularly when the hydraulic fluid is returned from the fluid chamber towards the hydraulic working circuit. This may allow the magnetic field generating device to be cleaned by this fluid flow. The particulate contamination that is captured and released from the fluid flow can then be cleaned by a filter element as part of the usual filtration operation.In this way, when fluid is fed into the accumulator, the contamination can be cleaned off by the magnetic field-generating device, and in countercurrent or during discharge operation of the hydraulic accumulator, the device can be cleaned of the aforementioned particle contamination in the return flow, i.e. during accumulator discharge. The separating piston can form a hollow piston to increase the volume of the gas chamber towards the gas side; however, such a hollow piston design is also possible additionally or alternatively in a reverse arrangement on the fluid side, so that at high pressure conditions the piston does not impact the housing cover on the liquid side with its entire surface. Furthermore, it is also possible to design the separating piston as a solid, cylindrical plate, to ensure that at high working pressures the separating piston cannot strike the housing cover on the gas side.

[0019] In the following, the hydraulic accumulator according to the invention is explained in more detail using four exemplary embodiments. The following are schematic and not to scale illustrations of the

[0020] Figure 1 in the form of a longitudinal section, the essential

[0021] Construction of a hydraulic accumulator as a whole;

[0022] Figure 2 is an enlarged view of a section marked X in Figure 1;

[0023] Figure 3 a bottom view of the hydraulic accumulator after

[0024] Figure 1 ;

[0025] Figures 4 and 5 show a representation of a second embodiment corresponding to Figures 1 and 2;

[0026] Figures 6 to 8 show a representation of a third embodiment corresponding to Figures 1 to 3; and Figures 9 to 11 show a representation of a fourth embodiment corresponding to Figures 1 to 3.

[0027] The hydraulic accumulator according to the invention, shown in Figure 1 in the form of a so-called piston accumulator, has a separating piston 12 as the separating element 10, which is arranged in an accumulator housing 14 and separates two fluid chambers 16, 18 from one another. The upper fluid chamber 16, as viewed in the direction of Figure 1, forms a closed storage chamber 20 for receiving a working gas, such as nitrogen gas. The lower fluid chamber 18, in contrast, forms a liquid chamber 22 for receiving an operating fluid, such as hydraulic oil. The respective fluid chamber 18, or liquid chamber 22, is provided with a channel-like fluid connection 24, via which the accumulator can be connected to an attachment part 26. The respective attachment part 26, and thus also the hydraulic accumulator, can in turn be connected to a conventional hydraulic working circuit, for example via piping (not shown in detail).

[0028] The accumulator housing 14 is designed in the manner of a round hollow cylinder or cylindrical tube, which is tightly closed at each of its two free ends by a screwed-in housing cover 28, 30, between which the separating piston 12 is freely movable along the housing's longitudinal axis 32. The upper housing cover 28 has a continuous fluid channel 34, which, as shown in Figure 1, is closed by a screw plug 36. Via the corresponding connecting arrangement 34, 36, the accumulator can be emptied of working gas in space 16 if necessary, for example, for maintenance purposes; but the corresponding space 16 can also be filled if there is no working gas. The separating piston 12 itself is designed as a so-called hollow piston for the purpose of increasing the effective gas volume on the side of the fluid chamber 16. However, the separating piston 12 can also have a hollow space on the liquid side of the accumulator or be designed as a solid cylindrical body.On the outer circumference, the separating piston 12 is guided by at least one sealing ring 38 and at least one guide band 40 along the inside of the cylindrical storage housing 14. In a practical implementation, several such sealing rings and guide bands, also in combination with one another, can be attached to the outer circumference of the separating piston 12.

[0029] As can further be seen from the illustration in Figure 3, a handling aid 42 can be arranged on the outside of the respective housing cover 28, 30, here in the form of four blind holes arranged diametrically opposite the longitudinal axis 32, which allow the engagement of a corresponding operating tool for the purpose of easier screwing in and unscrewing of the respective housing cover 28, 30 into the associated threaded section on the inner circumferential side of the storage housing 14.

[0030] The previous design of such a hydraulic accumulator, here in the form of a piston accumulator, is common and will therefore no longer be described in detail and only to the extent that it is necessary for understanding the invention.

[0031] As can be seen in particular from the enlarged view in Figure 2, a magnetic field generating device 44 is incorporated into the attachment part 26, which acts on a tubular or channel-shaped fluid connection 46 in the attachment part 26, which runs between the fluid connection 24 of the accumulator housing 14 and an associated fluid connection 48 of the attachment part 26. Via this fluid connection 46, fluid originating from the hydraulic supply circuit flows into the fluid chamber 18; during an accumulator charging and accumulator discharging process of the hydraulic accumulator, this fluid is displaced from the second fluid chamber 18 back into the hydraulic working circuit under the preload pressure of the working gas in the first fluid chamber 16.In particular, the fluid flowing into the reservoir can be provided with a magnetizable, in particular metallic, particle contamination and, via the magnetic field generating device 44 within the fluid connection 46 of the attachment part 26, the particle contamination in question is prevented from entering the reservoir on its liquid side, formed by the second fluid chamber 18.

[0032] The attachment part 26 is formed from a cuboid-shaped solid block part with an engagement part 48 arranged on a free end face, which engagement part 48 can be screwed into the lower housing cover 30 to form a threaded section 50 for the purpose of establishing a fluid guide to the fluid connection 46 in the attachment part 26. Between the attachment part 26 arranged on the bottom side and the adjacent opposite housing wall of the lower housing cover 30 there is a seal 52, for example in the form of an O-ring, which engages around the pin-like engagement part 48, through which the fluid connection 46 passes centrally.

[0033] Arranged coaxially with the housing's longitudinal axis 32, the fluid connection 46 opens into the atmosphere at its lower end via a section 54, which, provided with an internal thread on the inner circumference, allows the screwing in of conventional piping leading to a hydraulic supply circuit (not shown). In this way, the hydraulic accumulator, with its accumulator housing 14 and the attachment part 26, can be connected to other hydraulic components in a fluid-conducting manner.

[0034] The magnetic field generating device 44 is introduced into the fluid connection 46 in the attachment part 26 from the outside, as viewed from the right in Figures 1 to 3. For this purpose, the fluid connection is designed in the manner of a T-connector, forming a centrally arranged fluid chamber 56 in the manner of a blind hole with the largest free channel cross-section of the entire fluid connection 46, which extends with its longitudinal orientation transversely to the longitudinal axis 32 of the housing and thus transversely to the other connecting parts of the fluid connection 46. The free diameter in section 54 is selected to be larger than the inner diameter area of ​​the hollow cylindrical engagement part 48. The magnetic field generating device 44 is formed from a permanent magnet with a magnetic rod 58, which is screwed into the fluid chamber 56 transversely to the other fluid connection 46 by means of a fixing screw 60 at an axial and radial distance from the housing parts of the attachment part 26.To increase the magnetic force, the locking screw 60 can also be made of a magnetic material. However, the housing parts of the attachment 26 themselves are preferably made of non-magnetizable material, for example stainless steel. If magnetizable particles collect on the rod 58 and / or the screw 60, the magnetic rod 58 can be removed from the attachment 26 and cleaned via the locking screw 60 as part of normal maintenance work, without having to dismantle the accumulator itself. After screwing in the magnetic field-generating device 44 in the form of the permanent magnet presented here, the particle collection function is then available again during operation of the hydraulic accumulator. If the change in the magnetic field lines is taken into account in the design, the attachment 26 could also be made of magnetizable material.

[0035] As can be further seen from Figures 1 and 2, the attachment part 26 can also be retrofitted to previously delivered hydraulic accumulators as a so-called retrofit kit. It is also possible, in principle, to form the attachment part 26 as a single piece with the housing cover 30, so that the threaded section 50 and the engaging part 48 can be omitted, as can the seal 52 in the area of ​​the attachment part 26 and the lower end wall or outer wall of the housing cover 30.

[0036] The exemplary embodiments presented below will only be explained insofar as they differ significantly from the preceding exemplary embodiment. The same components are provided with the same reference numerals, and the statements made so far also apply to the modified exemplary embodiments.

[0037] In the solution according to Figures 4 and 5, the magnetic field generating device is incorporated in the T-shaped fluid connection area on the underside of the attachment part 26 as viewed in the direction of the figures, so that the free fluid flow is guided to the right over the attachment part 26. The piping of a hydraulic working circuit (not shown) can in turn be connected to the corresponding inlet and / or outlet point 62. The fluid chamber 56 with the magnetic field generating device 44 is now accommodated coaxially to the longitudinal housing axis 32 of the piston accumulator in the block-shaped attachment part 26. To this extent, the magnetic rod 58 or a magnetic screw 60 is inserted, in particular screwed, into the attachment part 26 from below, coaxially to the longitudinal housing axis 32, with a corresponding axial and radial distance from the fluid chamber 56.In this embodiment, the free end of the magnetic rod 58 opens into the associated fluid connection 46 below the engagement part 48.

[0038] Because the fixing screw 60 with the magnetic rod 58 is screwed into the attachment part 26 from below, a type of fluid barrier is created which promotes the right-angled deflection of the fluid flow during the discharge process of the accumulator in the direction of the inlet and / or outlet point 62.

[0039] In the embodiment according to Figures 6 to 8, the cuboid-shaped attachment 26 is detachably connected to the underside of the lower housing cover 30 via a flat flange plate 64, which is only schematically shown in Figure 8, and via four fastening screws 66. Similar to the embodiment according to Figures 4 and 5, the magnetic field generating device 44 is also introduced into the attachment 26 from below, with a right-angled connection point 62. Here, the free end of the magnetic rod 58 just reaches into the inlet opening of the channel-like fluid connection 24 in the lower housing cover 30. An O-ring seal again serves to seal 52 between the attachment 26 and the lower housing cover 30.As a direct comparison of the embodiments according to Figures 1 to 5 with the embodiment according to Figures 6 to 8 shows, the flange plate fastening for the attachment part 26 on the storage housing 14 can lead to a small attachment depth, which saves space.

[0040] Compared to the previously described embodiment, according to the design shown in Figures 9 to 12, as viewed in the direction of Figures 9 and 10, the magnetic field generating device 44 is arranged on the left side of the attachment part 26. In this respect, too, the attachment part 26 is fastened to the storage housing base in the manner of a flange plate using individual screws 66 and is thus firmly connected to the lower housing cover 30. In a particularly pressure-resistant design, the base of the attachment part 26 is closed, with the fluid connection 46 again being designed as a T-piece.

[0041] The above embodiments make it clear that, in the manner of a modular system, the attachment part 26 can be designed more or less identically. By appropriately selecting the fluid connection 46 and the selected installation space for the magnetic field generating device 44 in the attachment part 26, the magnetic field generating device 44 can always be detachably attached to the storage housing 14 at easily accessible locations. This has no equivalent in the prior art.

Claims

Patent claims for a hydraulic accumulator, in particular in the form of a piston accumulator, with a separating element (10) arranged in an accumulator housing (14) that separates two fluid chambers (16, 18), in particular a closed accumulator chamber (20) with a working gas from a liquid chamber (22) with an operating fluid, such as hydraulic oil, in a fluid-tight manner, wherein a fluid connection (24) is fluid-carrying to one of the fluid chambers (18), characterized in that an attachment part (26) with a magnetic field-generating device (44) is provided outside the accumulator housing (14) and fixed to it, which acts on a fluid connection (46) between the fluid connection (24) of the accumulator housing (14) and a fluid connection (25) of the attachment part (26) in such a way that magnetizable particles can be separated from the fluid passing through the fluid connection (46) in a cleaning manner.Hydraulic accumulator according to claim 1, characterized in that the attachment part (26) is cube- or cuboid-shaped and provided with an engagement part (48) and is screwed into the accumulator housing (14) or is connected to the accumulator housing (14) in a plane via a flange plate (64). Hydraulic accumulator according to claim 1 or 2, characterized in that the accumulator housing (14) has a cylindrical housing wall which is closed at at least one end with a housing cover (30) which has the attachment part (26) on its outer surface facing away from the separating piston (12). A hydraulic accumulator according to one of the preceding claims, characterized in that the fluid connection (46) within the attachment part (26) runs in a straight line coaxially to the fluid connection (24) in the accumulator housing (14) or perpendicular to it, and that the magnetic field-generating device (42) is arranged transversely to at least parts of the fluid connection (46) and engaging in it within the attachment part (26). A hydraulic accumulator according to one of the preceding claims, characterized in that the magnetic field-generating device (44) is formed from a permanent magnet. A hydraulic accumulator according to one of the preceding claims, characterized in that the permanent magnet has a magnetic rod (58) which is inserted into the fluid connection (46) by means of a fixing screw (60) at an axial and radial distance to housing parts of the attachment part (26).Hydraulic accumulator according to one of the preceding claims, characterized in that the locking screw (60) is designed as a magnetic screw and is part of the permanent magnet. Hydraulic accumulator according to one of the preceding claims, characterized in that the attachment part (26) is made of a non-magnetizable material, such as stainless steel. Hydraulic accumulator according to one of the preceding claims, characterized in that a seal (52) is provided at a connection point between the attachment part (26) and the accumulator housing (14). Attachment part, in particular provided as a retrofit kit for a piston accumulator according to the preamble of claim 1, in that. characterized in that a magnetic field generating device (44) is inserted into a fluid connection (46) within a receiving block which has two outwardly leading fluid connection points (24, 25).

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