Apparatus with bellows body and monitoring device

Abstract

The invention relates to an apparatus, consisting of at least one separation device (12) received in an apparatus housing (10) having a bellows body (14) with individual bellows folds (16), which separates two media chambers (18, 20) from one another within the device housing (10) in a fluid-tight manner, characterized in that that a monitoring device (22) is provided for determining the respective position of the bellows body (14) in the device housing (10), having a displacement transducer (24) which is based on the physical principle of magnetostriction.

Description

[0001] DEVICE WITH BELLOWS BODY AND MONITORING DEVICE

[0002] The invention relates to a device comprising at least one separating device accommodated in a device housing, which has a bellows body with individual bellows folds, which separates two media spaces from each other in a fluid-tight manner within the device housing. In addition to air chambers, weight and spring accumulators, as well as diaphragm, bladder or piston accumulators, there are designs in which a bellows with individual connected bellows folds, such as a corrugated or folded bellows made of metal or plastic, is used as the separating element of a separating device. The advantage of bellows made of special plastics, such as PTFE, lies in their better media and temperature resistance compared to conventional elastomer materials. The advantage of metal bellows generally includes special media and temperature resistance, and the possible area of ​​application is expanded by their extremely high tightness for media, including gases, i.e.Absolute tightness in contact with liquids and technical gas tightness are achieved. This latter advantage makes the metal bellows accumulator unique compared to all other accumulator designs and is particularly important when gas loss from a hydraulic accumulator must be virtually eliminated and / or its operating media must not be contaminated by even the smallest amounts of the accumulator's working gas. The best possible media tightness for liquids and gases makes metal bellows accumulators ideal for use as media separators.

[0003] When using corrugated and diaphragm bellows made of metal or plastic, hereinafter referred to as bellows bodies or bellows, each with a separating element consisting of individual connected bellows folds between two media sides, particularly between a gas and a liquid side, for example in hydropneumatic accumulators, special consideration must be given to their stretched and compressed catches in conjunction with the prevailing operating pressures and temperatures. In addition, depending on their design, bellows can only withstand very specific differential pressures between the inside and outside of the bellows. If the respective permissible differential pressures are exceeded, failure of the bellows wall, for example due to a crack, can lead to the loss of bellows function, including a hydraulic supply circuit to which such bellows bodies are regularly connected.In the case of a storage tank filled with nitrogen gas, a bellows rupture would result in the loss of the gas pre-fill pressure and thus the storage function. If the system were to function as a media separator or as a conveying device for media, the media to be separated would unintentionally mix with each other in the event of failure. Even if a bellows body is not immediately destroyed by an inadmissibly high differential pressure, but is merely pre-damaged, i.e. the separating function is initially retained, the bellows wall will still fail sooner or later depending on the operating mode. Therefore, when designing bellows accumulators as one of the possible separating devices, it is a top priority to ensure that none of the possible operating conditions (pressure and temperature) can lead to inadmissible bellows lengths and differential pressures on the bellows structure.When it is stated that differential pressures are preferably absent at the bellows, this excludes those differential pressures caused by the spring properties of the bellows structure in conjunction with compression or expansion of the bellows folds. These bellows-specific differential pressures are generally so small that the bellows can easily withstand them.

[0004] In view of the above problem, according to the teaching of DE 100 09 865 B4, it has already been proposed for a hydropneumatic pressure accumulator, particularly in the form of a pulsation damper, to provide an accumulator housing containing a gas chamber for receiving a gas filling generating a preload pressure, as well as an oil chamber. A bellows or metal bellows is provided separating the gas chamber and the oil chamber, which is closed at one end by an end plate and connected at its other end to the accumulator housing in such a way that its interior forms the oil chamber. Furthermore, an oil channel formed in the wall of the accumulator housing is incorporated as a connection side and opens into the oil chamber.By means of a stop device which limits the movement of the end plate of the bellows and which has a first stop which is formed by a tubular body extending inside the metal bellows along its inside from the mouth of the oil channel to the vicinity of the inside of the end plate, and a second stop which is formed by a second tubular body extending concentrically to the tubular body and extending from the wall of the storage housing in the gas space to the vicinity of the outside of the end plate of the metal bellows, a mechanical stroke limitation for the bellows is created on both sides, so that the predeterminable minimum or maximum bellows length is not exceeded for both the contraction and extension of the bellows.Since the free travel is limited in this way when the bellows is stretched and compressed, excessive pressure differences cannot occur, thus protecting the bellows from failure as outlined above. However, the separating device, designed as a bellows, is subjected to additional mechanical stress due to mechanical impact on the respective travel limit, which can reduce the service life of the bellows.

[0005] Given these uncertainties in the operation of the bellows, it is advisable to monitor it more closely. For example, EP 3 475 584 B1 already discloses the method for determining the respective piston position assumed by a hydropneumatic piston accumulator at a given fluid pressure in the oil-side working chamber. This method allows for the determination of the filling pressure of the working gas in the associated working chamber and thus for monitoring the piston accumulator for proper functioning.

[0006] For this purpose, a hydropneumatic piston accumulator is provided, with an accumulator housing defining a longitudinal axis of the housing, in which a piston is longitudinally movable between two opposite housing covers, which separates a media chamber for a compressible medium, such as a working gas, from another media chamber for an incompressible medium, such as hydraulic oil, and has at least part of a magnetostrictive measuring system of a displacement measuring device that continuously determines the respective position of the piston in the housing, wherein a rod-like guide is stationary in the accumulator housing, which completely penetrates the piston in each of its travel positions in the accumulator housing and along which the piston is guided so as to be movable until it reaches the respective stop on one of the two housing covers, wherein the piston, which has a permanent magnet as part of the measuring system, is sealed off from this guide by means of a sealing device,which separates the two media spaces from each other in a sealing manner, wherein a hollow rod forming the guide has a preferably pressure-resistant, circular cladding tube, wherein the guide of the piston has a waveguide of the magnetostrictive measuring system, wherein the storage housing has a cylindrical tube which is closed at both ends by the housing covers, wherein the cladding tube is fixed with an open end to one of the housing covers, and wherein the pulse converter connected to the waveguide of the magnetostrictive measuring system and having a pulse transmitter / receiver is arranged on the latter.

[0007] Magnetostrictive displacement sensors used for this purpose are generally used to measure the distance between two points. The sensor used here has a fixed base, a waveguide, a movable permanent magnet, and a transducer that converts a mechanical vibration into an electrical signal. The measurement result of the displacement sensor is a position, which is determined using magnetostriction. Examples of such magnetostrictive sensor systems are described in EP 2 556 344 B1 and EP 2 549 242 B1.

[0008] Based on this prior art, the invention is based on the object of improving the known solutions in such a way that inadmissibly high compression and tensile stresses for the bellows body as the separating device can be avoided during operation of a device.

[0009] A device having the features of patent claim 1 in its entirety achieves this object. Due to the fact that, according to the characterizing part of patent claim 1, a monitoring device for determining the respective position of the bellows body is provided in the device housing, which monitoring device comprises a displacement sensor based on the physical principle of magnetostriction. This allows the retraction and extension movements of the bellows body within the device housing occurring during operation of the device to be monitored without delay, so that undesirable overstretching and compression of the associated bellows folds in the direction of their respective maximum deflection during extension or retraction of the bellows body are reliably avoided.

[0010] Since the bellows body with its individual bellows folds is exposed to different fluid pressures on both sides of the media chambers in the device housing during operation, the sensor data from the magnetostrictive displacement sensor can be used, for example, using media conveying devices such as feed pumps, to control the respective fluid pressure in the assigned media chamber in such a way that the excessive stresses on the bellows body described above do not even occur. This prevents unwanted pressure differences on the bellows body, which could have a damaging effect on it.

[0011] In implementing the device according to the invention, it has proven particularly advantageous that the magnetostrictive displacement sensor can be integrated into the device housing in such a way that no additional sealing device is required between the relatively movable components of the displacement sensor system, thus preventing failure and the resulting leaks. This has no equivalent in the prior art.

[0012] Should, contrary to expectations, the device fail and thus cause the entire hydraulic system to which such devices are connected to fail, the monitoring device can detect such a fault in a timely manner to prevent consequential damage. In a preferred embodiment of the device according to the invention, the magnetostrictive displacement sensor has a waveguide in the form of a tube closed at the bottom, in which a conductor is accommodated and which extends with its other free end from a fixed base and surrounded by a housing part in the direction of the bellows body. This creates a slim monitoring device that can be connected to the device with the separating device in a space-saving manner.

[0013] In a further preferred embodiment of the device according to the invention, the magnetostrictive displacement sensor further comprises a permanent magnet, which, by means of a rod body that engages the bellows body, preferably being rigidly connected to it, engages the housing part of the waveguide in every retracted or extended position of the bellows body. This enables continuous measurement value acquisition over the entire predeterminable range of motion of the bellows body with its individual bellows folds.

[0014] In a particularly preferred embodiment of the device according to the invention, the rod body is hollow and carries the permanent magnet at its free end, which surrounds the waveguide tube in a ring shape. Due to the hollow design of the rod body, only minimal masses need to be moved during the movement of the bellows body, which helps improve the quality of the measurement results.

[0015] In another particularly preferred embodiment of the device according to the invention, the hollow rod body, free of seals, is guided back and forth along the tube in its longitudinal direction. Accordingly, no seals are necessary for the operation of the monitoring device, which could otherwise wear out and, especially if they are made of an elastomer material, could lead to obstructions in the measurement data acquisition.

[0016] In a further preferred embodiment of the device according to the invention, the interior of the hollow rod body and the interior of the housing part for the waveguide are permanently fluidically connected to one of the media chambers, which is separated from the other media chamber in the device housing by the bellows body. Due to this fluid-conducting connection, pressure-balanced, unobstructed operation of the device with the monitoring device is possible, thus preventing any falsification of the measurement results.

[0017] In another particularly preferred embodiment of the device according to the invention, the housing part of the waveguide is rigidly connected to the device housing, preferably via a screw-in section, as a hollow cylindrical connecting body, and the free length of the housing part is selected to be greater than the free travel path of the bellows body between a maximum retracted or extended position in the device housing. In this way, the monitoring device can be easily separated from the device housing and reattached, thus providing a simple replacement option, for example, if the monitoring device and / or the device with the separating device fail and these components need to be replaced with new ones.The selected lengths also ensure that the bellows body's movement or position is recorded in every position it assumes within the device housing. In a further preferred embodiment of the device according to the invention, the waveguide extends out of the housing part at the free end of the tube, preferably for the purpose of electrically connecting a transducer of the magnetostrictive displacement sensor. In this way, the transducer, which converts a mechanical vibration into an electrical signal, can be arranged outside the device, which can benefit the quality of the measured value acquisition.

[0018] In another particularly preferred embodiment of the device according to the invention, the bellows folds of the bellows body, when fully retracted, are accommodated in an annular space extending between a closure member of the device housing and its cylindrical inner wall. Thus, the bellows body, with its bellows folds, is supported in the fully retracted state against unwanted buckling when the folds are placed on top of one another in both directions, both outward and inward. This also creates a receiving space into which the bellows folds can be stacked or folded in a space-saving manner.

[0019] In a further preferred embodiment of the device according to the invention, it is provided that a further closure body is provided, and that the two closure bodies of the hollow-cylindrical device housing close it off to the outside, and that individual channels, in particular for fluid guidance, are incorporated into the closure parts, which open into one of the associated media spaces. In this way, a solid device housing can be formed that can withstand even high fluid pressure forces.

[0020] Furthermore, the invention relates to the use of a magnetostrictive displacement sensor in a device, as presented above, for monitoring a bellows body having individual bellows folds, in order to prevent material-damaging overstretching or compression of the bellows folds during their expansion toward a maximum extension position or during their contraction toward a maximum retraction position. The bellows body with its bellows folds can be designed such that a maximum extension position is reached when the bellows body ends with its wall components at an opposite stop within the device housing or comes to a stop in a maximum retraction position, in which the individual bellows folds are in contact with one another, lying one above the other.However, in order to avoid such material-stressing stop positions, the bellows body can be "moved" by means of the monitoring device in such a way that such stop positions are not assumed during operation.

[0021] The device according to the invention is explained in more detail below using an exemplary embodiment. The following are schematic and not to scale illustrations of the

[0022] Figure 1 shows a longitudinal section through the device as a whole;

[0023] Figures 2 and 3 each show a front view of the base and head-end connection area of ​​the device according to Figure 1, respectively.

[0024] According to the illustration in Figure 1, the device has a device housing 10 with a separating device 12 accommodated therein. The separating device 12 has a bellows body 14 with individual bellows folds 16. In Figure 1, the bellows body 16 is shown in its fully retracted position, in which the bellows folds 16 are in block form, i.e., they lie one above the other. When the bellows body 14 or bellows is extended, the folds 16 are pulled apart and form a zigzag-shaped bellows (not shown). This design is conventional and will therefore not be discussed further here. The bellows body 14 separates two media spaces 18, 20 from one another within the device housing 10 in a fluid-tight manner, wherein in the bellows position according to Figure 1, the media space 18 assumes its maximum position and the media space 20, in contrast, assumes its smallest volume.

[0025] The device has a monitoring device 22 for determining the respective position of the bellows body 14 in the device housing 10. The monitoring device 22 has a displacement sensor 24 based on the physical principle of magnetostriction. Thus, the magnetostrictive displacement sensor 24 has a waveguide 26 in the form of a tube 28 closed at the bottom, in which a conductor (not shown) is accommodated. As viewed in the direction of Figure 1, the tube 28 extends from its upper free end from a fixed base 32 and is enclosed by a jacket-shaped housing part 34 in the direction of the bellows body 14. The tube 28, which is closed at the bottom and open at the top, can be made of a nickel-iron alloy, for example, and a copper conductor (not shown) is threaded through this tube 28. A nickel wire could also be used instead of a copper conductor.A suitable magnetostrictive displacement sensor 24 is offered by the patent holder as a linear displacement transducer under the designation HLT 2100-R1.

[0026] The magnetostrictive displacement sensor 24 further comprises an annular permanent magnet 36, which, by means of a rod body 38 that engages the bellows body 14 and is preferably firmly connected thereto, engages the hollow cylindrical housing part 34 of the waveguide 26 in every retracted or extended position of the bellows body 14. The hollow rod body 38 carries the annular permanent magnet 36 on its free end 40 on the inside, which encloses the rod-shaped waveguide 26 in every travel position of the bellows body 14. As can be further seen from Figure 1, the hollow rod body 38 is held free of any seals along the tube 28 and is guided back and forth in its longitudinal direction.The interior space 42 of the hollow rod body 38 and the interior space 44 of the housing part 34 for the waveguide 26 are permanently fluid-connected in a pressure-balanced manner to one 18 of the media chambers 18, 20, which is separated from the other media chamber 20 in the device housing 10 by the bellows body 14. For this media connection, the hollow rod body 38 has at least one fluid passage 46 on the base side and adjacent to the bellows body 14, for example in the form of a bore that penetrates the wall of the hollow rod body 38.

[0027] The housing part 34 of the waveguide 26 is firmly connected to the device housing 10 as a hollow cylindrical connecting body along a screw-in section 48. The free length of the housing part 34, in a coaxial arrangement with the longitudinal axis 50 of the device, is greater as a whole than the free travel of the bellows body 14 between a maximum retracted and extended position in the device housing 10; likewise in a coaxial arrangement with the longitudinal axis 50. The wire-shaped conductor of the waveguide 26 is led out of the housing part 34 at the upper free end 30 of the tube 28, thus creating a connection point 52 for connecting a transducer (not shown) of the magnetostrictive displacement sensor 24.

[0028] For the purpose of guiding conductor components, the upper end of the jacket-shaped housing part 34 is hermetically sealed by a hexagon screw 54, which also forms the fixed point or base 32 for the tube 28. For a hermetic seal, an annular seal 56 can be provided at the free upper end of the housing part 34. In the fully retracted state, the bellows folds 16 of the bellows body 14 are accommodated in an annular space 58, as shown in Figure 1, which extends between a closure body 60 of the device housing 10 and its cylindrical inner wall 62. An end plate 64 of the bellows body 14, which extends transversely to the longitudinal axis 50 of the device as a whole, has a guide strip 66 on the circumference, which, as shown in Figure 1, is provided with fluid-conducting interruptions and otherwise rests against the inner wall 62 of the device housing 10 for guiding the bellows body 14.On the opposite side, the bellows body 14 is secured at the base to a receiving ring 68, in particular, it is firmly welded thereto and thus secured within the device housing 10. The annular space 58 is connected to the first media space 18 on the outside in a media-conducting manner, and to this extent, the annular space 58 is arranged adjacent to and opposite the outside of the bellows folds 16. The inside of the bellows folds 16 is, in turn, connected to the second media space 20 on the inside in a media-conducting manner.

[0029] The end plate 64 of the bellows body 14 carries a receiving sleeve 70 concentric with the longitudinal axis 50, into which the lower end of the rod body 38 engages. In particular, the lower rod end of the rod body 38 can be screwed into a thread on the inner circumferential side of the receiving sleeve 70. The receiving sleeve 70 is an integral component of the cylindrical end plate 64, and when the rod body 38 is fully inserted into the receiving sleeve 70, the bottom end of the rod body 38 sits on the top side of the end plate 64. The lower end body 60 is a solid screw-in body screwed flush into the otherwise cylindrical device housing 10, and a circumferential ring seal 74 is inserted between the corresponding screw-in section 72 and the stationary receiving ring 68 for the bellows body 14, which seals the second media chamber 20 from the environment.At the upper free end of the cylindrical device housing 10, a further closure part 76, comparable to the first closure body 60, is screwed in along a screw-in section 72' and sealed accordingly by means of an associated ring seal 78, which now seals the interior of the first media chamber 18 from the environment. As shown in Figure 1, the housing part 34 sits flush with the top side of the further closure body 76 via a shoulder 80. Furthermore, a sealing ring 82 is inserted below the screw-in section 48 along the inner circumference of the further closure part 76, which seals between the further closure part 76 and the housing part 34 in this connection area.

[0030] The housing part 34 tapers in steps towards the bellows body 14 in the area of ​​engagement with the further closing body 76; however, in the direction of the underside of the further closing body 76, it leaves free a receptacle 84 with an enlarged diameter, the geometry of which is determined such that the outer circumference of the receiving sleeve 70 can engage in the enlarged receptacle 84 in such a way that in any case the upper side of the closing plate 64 comes into contact with a circumferential stop surface 84 on the underside of the further closing part 76. A correspondingly annular further stop surface 86 is also present on the upper side of the closing body 60, which forms a stop insofar as the closing plate 64 assumes its lowest position as shown in Figure 1.Between the respective annular stop surfaces 84, 86, a front-side fluid recess 88 is introduced in the respectively assignable closing body 60, 76, which serves for improved filling of the respective media space 18, 20, provided that the closing plate 64 in its fully extended or fully retracted position assumes a stop position on the respective closing body 60, 76.

[0031] As Figure 2 shows, the lower closure body 60 has four fluid channels 90 diametrically opposed to the longitudinal axis 50, which serve to supply and discharge a medium into and out of the second media chamber 20. These channels 90 are introduced as continuous branch channels into the closure body 60 parallel to the longitudinal axis 50 of the overall device. While some of the channels 90 serve only to supply fluid and the other part to discharge, it may be sufficient to provide only a single channel 90 for the supply and discharge of fluid. Otherwise, left free fluid channels 90 can also serve to introduce a sensor system (not shown) in order to carry out temperature and / or pressure measurements.Furthermore, the lid-like closing body 60 has on its underside two handles 92 which are diametrically opposite one another with respect to the longitudinal axis 50 and which serve to engage a tool (not shown in detail) with which the closing body 60 can be screwed in and out of the cylindrical device housing 10 via its screw-in section 72.

[0032] The additional closure body 76 shown in Figure 3, which is also screwed flush into the cylindrical device housing 10, has, in addition to the monitoring device 22, a central fluid channel 94 which serves to supply and discharge a further fluid into the first media chamber 18 and which extends completely through the additional closure body 76 parallel to the longitudinal axis 50. In front of and behind the monitoring device 22, additional channels 96 can be introduced into the closure body 76, preferably again for securing sensors (not shown in detail). In this respect, too, the additional closure body 76 has handles 92 diametrically opposite one another to the longitudinal axis 50, for example in the form of engagement bores which serve to secure an actuating tool (not shown).

[0033] The device shown in Figure 1 can, for example, be operated as part of a conveying or compressor device. If fluid is intermittently fed into and discharged from the media chamber 18 via the additional fluid channel 94 by a pumping or conveying device (not shown in detail), the fluid located in the second media chamber 20, for example in the form of a gas such as hydrogen gas, is compressed by the end plate 64 in the second media chamber 20, for which purpose the bellows body 14 is displaced from an extended position (not shown) into its lower stop position according to Figure 1. Medium previously located in the second media chamber 20, such as hydrogen gas, is then expelled from the device via the respective media-carrying fluid channel 90, optionally in compressed form.Subsequently, a new cycle begins in which the first media chamber 18 is kept depressurized or subjected to negative pressure, so that, if necessary, under an existing media pressure in the lower fluid channels 90, the end plate 64 again moves upwards in the direction of view in Figure 1, and in the process, the bellows body 14 with its bellows folds 16 is extended. The first media chamber 18 then shrinks again, and the second media chamber 20 expands, namely to the extent that fluid is to be accommodated in the second media chamber 20. A new cycle then begins, and the fluid is expelled from the second media chamber 20 out of the device.

[0034] The resulting bellows movements are continuously monitored by the monitoring device 22, and corresponding position messages as well as messages regarding the functionality of the device are forwarded to an evaluation electronics unit (not shown), which includes the transducer of the magnetostrictive displacement sensor 24. However, the described monitoring device 22 can also be used if the device according to Figure 1 is to be operated as a conventional bellows accumulator in an overall hydraulic system.

Claims

Patent claims 1. Device comprising at least one separating device (12) accommodated in a device housing (10), which has a bellows body (14) with individual bellows folds (16) which separates two media spaces (18, 20) from one another in a fluid-tight manner within the device housing (10), characterized in that a monitoring device (22) for determining the respective position of the bellows body (14) is present in the device housing (10), which monitoring device has a displacement sensor (24) based on the physical principle of magnetostriction.

2. Device according to claim 1, characterized in that the magnetostrictive displacement sensor (24) has a waveguide (26) in the form of a tube (28) closed at the bottom, in which a conductor is accommodated and which extends with its other free end (30) from a fixed base (32) and from a housing part (34) in the direction of the bellows body (14).

3. Device according to claim 1 or 2, characterized in that the magnetostrictive displacement sensor (24) further comprises a permanent magnet (36) which, by means of a rod body (38) which engages the bellows body (14), preferably being firmly connected thereto, engages in the housing part (34) of the waveguide (26) in each retracted or extended position of the bellows body (14).

4. Device according to one of the preceding claims, characterized in that the rod body (38) is hollow and carries at its free end (40) the permanent magnet (36) which surrounds the tube (28) of the waveguide (26) in an annular manner.

5. Device according to one of the preceding claims, characterized in that the hollow rod body (38), held free of seals, is guided along the tube (28) so as to be movable back and forth in its longitudinal direction.

6. Device according to one of the preceding claims, characterized in that the interior (42) of the hollow rod body (38) and the interior (44) of the housing part (34) for the waveguide (26) are permanently fluid-conductingly connected to one (18) of the media spaces (18, 20), which is separated from the other media space (20) in the device housing (10) by means of the bellows body (14).

7. Device according to one of the preceding claims, characterized in that the housing part (34) of the waveguide (26) is designed as a hollow cylindrical connecting body with the device housing (10), preferably via a screw-in section (48), and that the free length of the housing part (34) is selected to be greater than the free travel path of the bellows body (14) between a maximum retracted or extended position in the device housing (10).

8. Device according to one of the preceding claims, characterized in that the waveguide (26) is led out of the housing part (34) at the free end (30) of the tube (28), preferably for the purpose of electrically connecting a transducer of the magnetostrictive displacement sensor (24).

9. Device according to one of the preceding claims, characterized in that the bellows folds (16) of the bellows body (14) are accommodated in the fully retracted state in an annular space (58) which extends between a closing body (60) of the device housing (10) and its cylindrical inner wall (62).

10. Device according to one of the preceding claims, characterized in that a further closing body (76) is provided and that the two closing bodies (60, 76) of the hollow cylindrical device housing (10) close this off to the outside and individual channels (90, 94), in particular for the fluid guide, are introduced into the closing parts (60, 76) and open into one of the assignable media spaces (18, 20). 1 1 .Use of a magnetostrictive displacement sensor (24) in a device, in particular according to one of claims 1 to 10, for Monitoring a bellows body (14) having individual bellows folds (16) for the purpose of preventing material-damaging overstretching or compression of the bellows folds (16) when they expand towards a maximum extension position or when they contract towards a maximum retraction position.

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