System
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- HYDAC TECH GMBH
- Filing Date
- 2024-08-21
- Publication Date
- 2026-07-08
Smart Images
Figure EP2024073426_06032025_PF_FP_ABST
Abstract
Description
[0001] System
[0002] The invention relates to a system comprising at least two separating devices, one of which comprises a bellows with individual bellows folds that separates two media spaces from each other, and the other separating device forms a compensator that is in fluid communication with one of the two media spaces of the bellows and separates a third media space, wherein a displacement volume corresponding to the volume that the bellows displaces during a movement between its predeterminable minimum and maximum bellows length can be compensated by means of the compensator. 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 individually connected bellows folds, such as a corrugated or convoluted 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 potential application area is expanded by their extremely high tightness for media, including gases. This means that they are absolutely tight in conjunction with liquids and technically gas-tight. This latter advantage makes the metal bellows accumulator unique from all other accumulator designs and is particularly important when gas loss from a hydraulic accumulator must be virtually eliminated and / or when its operating media must not be contaminated with even the smallest amounts of nitrogen gas.The best possible media tightness for liquids and gases means that metal bellows accumulators are also ideally suited for use as media separators.
[0003] When using corrugated and diaphragm bellows made of metal or plastic, referred to as bellows for short, each with a separating element made of bellows folds between the gas and liquid sides, for example in hydropneumatic accumulators, special consideration must be given to their extended 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 permissible differential pressures are exceeded, failure of the bellows wall, for example due to a crack, can lead to the loss of the bellows function, including a hydraulic supply circuit to which such bellows are regularly connected. In the case of an accumulator 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, the media to be separated would mix unintentionally in the event of failure. Even if a bellows 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 of the utmost priority to ensure that inadmissible bellows lengths and differential pressures across the bellows structure cannot occur under any of the possible operating conditions (pressure and temperature). When it is stated below that there are no differential pressures across the bellows, this does not include those differential pressures which are caused by the spring properties of the bellows structure in conjunction with compression or stretching.Stretching of the bellows folds. These bellows-specific differential pressures are usually so small that the bellows can easily tolerate 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 such 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 predeterminable minimum and maximum bellows lengths are 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] Furthermore, DE 10 2016 008 882 A1 discloses a clamping cylinder device, comprising a housing and a piston-rod unit arranged therein so as to be at least partially longitudinally movable as a further separating device and comprising a compensating element in the form of a bellows body having bellows folds as the one separating device, which is variable in length and is in media-conducting connection with a compressible working gas accommodated in one of the media spaces in the housing.In this way, the bellows separates two media spaces (gas / liquid) from each other, and the other separating device in the form of the piston-rod unit forms a type of compensator for the bellows movement, which is in fluid communication with the liquid space of the bellows and separates a third media space containing a control fluid for driving the piston-rod unit. The compensator can compensate for a displacement volume that corresponds to the volume that the bellows displaces between its predetermined minimum and maximum bellows length. Since the bellows separates a gas side from a liquid side, and the gas side is subject to pressure fluctuations in terms of its volume, as the amount of gas enclosed in the device housing during the extension and contraction of the bellows folds, this ultimately leads to the bellows also being subject to differential pressures during operation that can lead to the loss of bellows function, at least in the long term.The amount of gas trapped on the gas side of the bellows is also subject to temperature fluctuations, which can also lead to inadmissibly high differential pressures for the bellows.
[0006] Based on this prior art, the invention is based on the object of improving the known systems in such a way that inadmissibly high compression and tensile stresses as well as pressure differences relating to the bellows as the one separating device are avoided during operation.
[0007] A system having the features of patent claim 1 in its entirety solves this problem. Because, according to the characterizing part of patent claim 1, one of the two separating devices is pressurized from its connection side up to a predeterminable nominal pressure (also known in technical terms as the design pressure), while the other separating device is simultaneously depressurized on its connection side, the system comprising the two separating devices, in the special embodiment as a bellows and piston accumulator, can be pressurized from each side up to the nominal or design pressure, while simultaneously depressurizing the opposite side, so that the bellows does not experience any relevant differential pressure. The application of the nominal pressure and the establishment of the depressurized state take place alternately if necessary.Under all other operating conditions, in which the piston of the piston accumulator is located between the opposing, possible stop positions in the associated accumulator housing, the same pressure prevails in all three media spaces or chambers of the overall system and consequently there is no significant pressure difference at the bellows.
[0008] The maximum possible differential pressure across the bellows can be approximately 1 bar, which corresponds roughly to ambient pressure, and is generated by a vacuum on the connection side of the bellows accumulator when the piston of the piston accumulator reaches one of its stop positions adjacent to the bellows due to an operating pressure greater than the vacuum. In this respect, the system is used as a media separator. Alternatively, the compensator can be exposed to the pressure of an energy storage device enclosed in the third media chamber, such as a working gas or at least a compression spring, thus realizing a hydropneumatic storage application while simultaneously relieving the bellows.
[0009] In this respect, it is preferably provided that one separating device is designed as a bellows accumulator and the other separating device has a storage device as a compensator, preferably in the form of a piston accumulator. Other storage devices can also be used as a compensator if they enable their separating element to withstand an overpressure up to the nominal or design pressure of the storage system on both sides, provided that the other side is simultaneously kept depressurized. If this is not the case, as is usually the case with diaphragm and bladder accumulators, the storage system can only be subjected to maximum load on one side depending on their installation direction and can only be used to a limited extent for working pressures on the opposite side. With regard to the number of bellows and piston accumulators in the storage system, variants are also conceivable in which more than one bellows and one piston accumulator are coupled to one another for media exchange.
[0010] In a further preferred embodiment of the system according to the invention, the piston accumulator is connected to one media chamber of the bellows accumulator via a connecting line, which carries a coupling medium that can be absorbed by one of the two piston chambers of the piston accumulator that is adjacent to the bellows accumulator. By using the liquid coupling medium, which completely fills one side of the bellows accumulator and one side of the downstream piston accumulator as the compensator, it is possible to limit the maximum and minimum bellows length when the bellows is stretched and compressed and at the same time reliably prevent an inadmissible pressure difference. On the other side of the accumulator piston there is a working gas, preferably nitrogen gas, or a mechanical spring as an energy store for when the system is used as a hydropneumatic accumulator or hydraulic accumulator.If it functions as a media separator, however, the medium that is to be separated from the medium on the connection side of the bellows accumulator would be located there.
[0011] Alternatively, it can be provided that the coupling medium is accommodated in a common storage housing and delimited by the outer side of the bellows and an adjacent piston wall of the storage piston, so that a bellows-piston storage system is produced without any further connecting line, wherein the bellows and the piston are located in a common storage casing. In a further preferred embodiment of the system according to the invention, it is provided that when a connecting line is used between the two separating devices, at least one additional hydraulic system component is connected into this. For example, the system components can be part of a hydraulic block into which, for example, filling and test blocks, valves, sensors (pressure, temperature, etc.) can be integrated.
[0012] Preferably, the connecting line is selected to be long enough to allow different system states to occur in the two separating devices, particularly in the form of different temperatures. In this way, the two storage or separating devices could also be actively heated or cooled to different temperatures, or only the connection between the storage devices could be heated or cooled or temperature-controlled. In such an application, for example, by maintaining a constant temperature on the gas side of the piston accumulator, it is possible to keep its dimensions as small as possible, since the required gas volume of a storage device generally increases with the increasing operating temperature range.
[0013] In a further preferred embodiment of the system according to the invention, the bellows accumulator, with its other media chamber, can be connected to a pressure source, as can the other piston chamber, which is arranged separately from the accumulator piston on the side of the other separating device facing away from the bellows. In this way, in addition to its function as a media separator, the system can also be used to compensate for differential pressures that may arise during operation and exist on the opposite connection sides of the two separating devices.
[0014] In a further preferred embodiment of the system according to the invention, the respective separating device is accommodated in the common accumulator housing, and a stop is provided in the accumulator housing in the direction of the bellows accumulator, which limits the movement of the accumulator piston toward the bellows. In this way, the movement of the accumulator piston toward the bellows is limited, thus avoiding unacceptably high differential pressures.
[0015] Preferably, the piston accumulator is further provided with a piston position indicator for the accumulator piston. This allows any possible position of the piston during system operation to be detected and displayed. This ensures system monitoring, and any potential sources of error can be detected immediately.
[0016] The system according to the invention is explained in more detail below using an embodiment shown in the drawing. The single figure shows, in a highly simplified and not to scale representation, the basic structure of the system, consisting of two separate separating devices.
[0017] The schematic diagram in Figure 1 shows, in a highly simplified manner, the system as a whole, consisting of two separating devices 10, 12, one of which has a bellows 14 with individual, only stylized bellows folds 16, which separates two media spaces 18, 20 with variable volumes from one another, of which the media space 20 is shown with its volume at virtually zero. The other separating device 12 is designed as a compensator 21, which is in fluid communication with the media space 18 of the bellows and thereby separates a third media space 22, which, as shown in the figure, occupies its maximum possible volume. By means of the compensator 21, a displacement volume VS can be compensated for, which corresponds to the volume V that the bellows 14 displaces during a movement between its predeterminable minimum and maximum bellows length, wherein the displacement volume VS assumes its smallest value as shown.In the figure, the bellows 14 is shown in its retracted or retracted position and accordingly assumes its minimum bellows length. The bellows folds 16 are closed from their inner side towards the first media chamber 18 by a plate-shaped end body 24, which, in the maximum extension position of the bellows 14, abuts with its free end face against a flat end wall 26 on the inside of an associated bellows storage housing 28. The housing 28, as shown, can also be constructed in several parts and consists in particular of a main part 30 and a base part 32, which are preferably firmly connected to one another, in particular firmly screwed, along a threaded section 34. During operation of the separating device 10, however, the bellows 14 does not necessarily have to strike an end stop such as the end wall 26 during its maximum possible extension and retraction movement, but can rather assume a middle travel position depending on the design.While one separating device 10 is designed as a bellows accumulator 36, the other separating device 12 is constructed as a hydraulic piston and / or accumulator device in the manner of a piston accumulator 38. Piston accumulators 38 or working cylinders of this type are common, so they will not be discussed in detail here. In the following, the cylinder arrangement according to the figure will be further considered and described in more detail as a piston accumulator. The piston accumulator 38 has a cylinder tube as the accumulator housing 40, which is closed at its free ends by screwed-in cylinder covers 42, 44. The cylinder cover 42, which faces the bellows accumulator 36, is provided with a fluid passage 46 arranged on the edge. Furthermore, the other cylinder cover 44 likewise has a channel-like fluid passage 48 arranged on the edge, which, if necessary, can also be closed off in a gas-tight manner by a screw plug or a plug.
[0018] The piston accumulator 38 has an accumulator piston 50, which is guided for movement along the inner wall of the accumulator housing 40. The accumulator piston 50, in turn, has a piston rod 52, which is arranged concentrically to the longitudinal axis 54 of the separating device 12 and is guided in the cylinder cover 44 at the piston end facing the third media chamber 22. In the position shown, the piston rod 52 passes through the media chamber 22. Furthermore, the piston rod 52 is guided at its other free end in a hollow cylindrical receptacle 56 in the accumulator piston 50. In particular, the piston rod 52 is screwed to the receptacle 56 of the accumulator piston 50 at its relevant free end region along a further threaded section 58.If, as viewed in the direction of the figure, the accumulator piston 50 with its articulated piston rod 52 moves to the right and the bellows 14 is extended upwards, the volume V in the bellows accumulator 36 decreases, as does the volume of the third media chamber 22, and the displacement volume VS, which is set to almost zero according to the illustration, increases up to a maximum preset volume. The same applies in the reverse case: When the volume V and the volume in chamber 22 increase, the displacement volume VS between the accumulator piston 50 and the adjacent end or cylinder cover 42 in the accumulator housing 40 decreases.
[0019] Furthermore, concentrically to the longitudinal axis 54, the cylinder cover 42 is penetrated by parts of a piston position indicator 57, which is received with its measuring rod part 59, which is arranged stationary on the cylinder cover 42, in a hollow cylindrical central recess 61 in the piston rod 52. As the piston-rod unit 50, 52 moves, a magnet or sensor unit 63, which is inserted from a free end into the base of the accumulator piston 50, moves simultaneously, specifically along the stationary measuring rod part 59. In this way, a position indication for the piston-rod unit 50, 52 in the accumulator housing 40 is made possible via a measured value evaluation device (not shown but conventional in this field), which in turn provides a measurable conclusion about the two opposite accumulator volumes, which are separated from each other by the piston-rod unit 50, 52.Such sensor devices for indicating the position of components are also abbreviated as LVDT in technical terms.
[0020] Furthermore, the bellows accumulator 36 has two opposing proximity switches 65 of conventional design, which monitor the position of the plate-shaped end body 24 and the extension situation of the bellows 14, respectively, and in turn forward the sensor data to a suitable measured value evaluation device (not shown). This also allows the size of the individual volumes, which are separated from one another by the bellows 14, to be monitored. Due to this sensor monitoring, reliable operation of the entire system is ensured. Furthermore, the accumulator piston 50 has individual sealing and guide elements 60 on its outer circumference in the usual way. This cylinder or accumulator design is also conventional, so it will not be discussed in more detail here.
[0021] When the bellows 14 of the bellows accumulator 36 assumes its fully extended, upper position, the volume V in the first media chamber 18 is released to a fluid side 66 of the piston accumulator 38 via an accumulator housing opening 62 in this area and a connecting line 64 of a predeterminable length and the lateral fluid connection 46 in the cylinder cover 42. The accumulator piston 50 assumes a displacement position within the accumulator housing 40 such that the displacement volume VS on the fluid side 66 essentially corresponds to the displaced volume V of the bellows accumulator 36 during its extension movement. In particular, the connecting line 64 can have a very long line length. The connecting line 64 is sealed on its opposite sides and, for example, is screwed into the accumulator housing opening 62 and into the fluid connection 46 in the cover part 42.
[0022] When the bellows 14 assumes its fully retracted position shown, the accumulator piston 50 preferably moves, as viewed in the direction of Figure 1, into its far left stop position, in which the free end face of the accumulator piston 50 comes into contact with the adjacent end wall of the cylinder cover 42. Likewise, it can preferably be provided that when the volume V is completely displaced from the bellows accumulator 36 into the piston accumulator 38, the associated accumulator piston 50 assumes its far right stop position and in doing so comes into contact with the adjacent end wall of the second cylinder cover 44. However, intermediate positions are easily possible if required.
[0023] The cylindrical bellows 14 can be supported in its illustrated lower stop position on a preferably elastically flexible, annular buffer device. Furthermore, the bellows 14, with its bellows folds 16, is firmly connected to the base part 32 at its end via a metallic receiving ring 70, as well as to an edge region of the plate- or disc-shaped end body 24, which, to support the bellows 14, is movable along its outer circumference by means of an annular guide device 72 on the inside of the bellows storage housing 28. This guide device 72 (not shown in detail) has interruptions to enable fluid exchange between the first media chamber 18 and a fluid chamber 73 delimited by the outer circumference of the bellows 14 and the inner circumference of the bellows storage housing 28.In the position shown, the bellows 14 is shown in the fully retracted position, in which the bellows folds 16 are in "block" with one another under adjacent contact; however, it is preferably provided that, to relieve the load on the bellows, a small extension length of the bellows 14 is taken up by the bellows, in which an enlarged second media space 20 is created and in which the bellows folds 16 are not in direct contact with one another. A functional block (not shown) can additionally be inserted into the connecting line 64, which can accommodate one or more system components in a media-carrying manner, which will be explained in more detail below.
[0024] Furthermore, the bellows accumulator housing 28 has two inlet or outlet channels 76 for fluid located off-center in the base part 32, which open into the second media chamber 20. Both the respective channel 76 of the bellows accumulator 36 and the channel-like fluid passage 48 of the piston accumulator 38 each form the so-called connection sides of the bellows accumulator 36 and the piston accumulator 38. Thus, one channel 76 can only serve to supply fluid into the second media chamber 20 of the bellows accumulator 36, and the other fluid channel 76 can serve to discharge fluid from the second media chamber 20. A predeterminable fluid flow direction in the supply lines can be maintained via corresponding, preferably spring-loaded, check valves (not shown).
[0025] The function of an overload-proof bellows accumulator 36 will now be explained in more detail using the exemplary embodiment shown in the figure. With the system solution shown in the figure, it is possible to limit the maximum and minimum bellows length during expansion and compression of the bellows 14 and at the same time reliably prevent an inadmissible pressure difference. This is achieved by using a liquid coupling medium, such as hydraulic fluid, which completely fills the first media chamber 18 of the bellows accumulator 36 and the fluid side 66 of the downstream piston accumulator 38, for which purpose the described connection via the connecting line 64 between the two separating devices 10, 12 in the form of the accumulators is fully established. On the other side of the accumulator piston 50, a working gas, preferably in the form of nitrogen gas, should be located in the third media chamber 22.For this purpose, the channel-like fluid passage 48 in the cylinder cover part 44 is closed by means of a plug or a screw plug (neither shown). In this respect, the piston accumulator 38 functions as a hydraulic accumulator. If it were to function as a media separator, however, the (liquid) medium that is to be separated from the further (liquid) medium on the connection side 76 of the bellows accumulator 36, which is connected to a fluid supply (not shown), would be located in the third media chamber 22. In this respect, the channel-like fluid passage 48 would be open and connected, for example, to a further fluid supply (not shown) that is different from the one fluid supply.
[0026] In order to limit the movement of the bellows 14 to a predeterminable minimum compressed and maximum extended bellows length, the piston accumulator 38 has a maximum displacement volume VS between its opposite piston stop positions, which corresponds to the volume V that the bellows 14 displaces between its minimum and maximum permissible length. If the system shown in the figure, consisting of the bellows 36 and the piston accumulator 38, is loaded up to the maximum design pressure on the connection side 48 of the piston accumulator 38, but is held pressureless on the connection side 76 of the bellows accumulator 36, the bellows 14 is held in one of its permissible extreme positions, namely in its minimum retracted position, by the coupling medium enclosed in the connecting line 64. If the coupling medium in the form of coupling fluid is arranged on the outside of the bellows 14, depending on the installation position of the bellows 14, the bellows 14 is in its minimum compressed length.If, however, in a construction the coupling medium is arranged on the inside of the bellows 14, then the bellows is in its maximum stretched length (not shown).
[0027] Regardless of the installation position of the bellows 14, the coupling medium is depressurized if the connection side 76 of the bellows accumulator 36 is depressurized. Accordingly, there is then no differential pressure between the inside and outside of the bellows 14. However, if the system consisting of the bellows 36 and the piston accumulator 38 is loaded to the maximum nominal or design pressure on the connection side 76 of the bellows accumulator 36 and the piston accumulator 38 is depressurized on the connection side 48 of the piston accumulator 38, the accumulator piston 50 is pressed into its right-hand stop position by the enclosed coupling medium via the connecting line 64, as viewed in the direction of the figure. Depending on the installation position of the bellows 14, it is in its minimally compressed or maximally extended length. The pressure in the coupling medium corresponds to the pressure on the connection side 76 of the bellows accumulator 36, and there is no differential pressure between the inside and outside of the bellows 14.The greatest possible differential pressure at the bellows, which therefore acts inside and outside the bellows, can be approximately 1 bar and is generated by a "vacuum" on the connection side 76 of the bellows accumulator 36 when the accumulator piston 50 of the piston accumulator 38 is pressed into its left stop position in the accumulator housing 40 by a pressure greater than the "vacuum" as viewed in the direction of the figure.
[0028] The special feature of this system is that the combination of bellows 36 and piston accumulator 38 can be loaded from either side 22, 48 or 20, 76 up to the nominal or design pressure, while simultaneously depressurizing the opposite side 20, 76 or 22, 48, without the bellows 14 experiencing a pressure differential between the inside and outside. Under all other operating conditions, in which the accumulator piston 50 of the piston accumulator 38 is located between the opposite stop positions in the accumulator housing 40, the same pressure prevails in all three media chambers 18, 20, 22 of the accumulator system, and consequently, there is no pressure difference at the bellows 14 between its inside and outside.
[0029] A hydraulic function block (not shown) inserted between the bellows accumulator 36 and the piston accumulator 38 can have additional hydraulic system components, such as filling and test blocks, valves, sensors, etc. Furthermore, in this variant according to the figure, it is possible to spatially separate the two accumulators 36, 38 from one another by a sufficiently long connection in the form of the connecting line 64 such that different temperatures can be established in the two accumulators 36, 38. In particular, the two accumulators 36, 38 could be actively tempered to different levels, in particular by heating or cooling the liquid coupling medium. In such an application, it is, for example,By maintaining a constant temperature on the gas side in the form of the third media chamber 22 of the piston accumulator 38, it is possible to keep its dimensions as small as possible, since the required gas volume of an accumulator generally increases with increasing operating temperature range. One possible application of the system shown in the figure could be to deliver any desired fluid on the media side 20 of the accumulator housing 36 under increased pressure via the respective fluid channel to a consumer (not shown) by means of piston movements in the accumulator housing 40. One channel 76 can serve for the largely pressure-free fluid supply to the bellows 14, and the adjacent channel 76 for the fluid delivery under increased pressure.
[0030] It should also be noted that, depending on the operating condition and the friction pairing between the annular sealing and guiding elements 60 and the inner accumulator wall of the accumulator housing 40, a certain differential pressure can occur between the coupling medium and the connection side 22, 48 of the piston accumulator 38. A conventional accumulator piston 50 can easily withstand this pressure difference. However, there is no pressure difference between the inside and outside of the bellows 14, since the pressures inside the bellows and outside the bellows 14 can always equalize via an axial movement of the bellows 14. By mounting conventional piston position indicators, one 57 of which has already been partially explained for the figure in the form of a measuring rod arrangement 59, and which are arranged on the piston accumulator 38, it is possible to reliably detect and display the position of the accumulator piston 50.In addition to the mentioned rod sensor arrangement (LVDT), electrical limit switches, piston position switches, magnetic flap indicators (DE 103 10 427 AI), cable travel measuring systems, laser measuring systems and others (not shown) can also be used in the usual way.
Claims
P a t e n t a n s p r ü c h e 1. System comprising at least two separating devices (10, 12), of which one separating device (10) has a bellows (14) with individual bellows folds (16) that separates two media spaces (18, 20) from each other, and the other separating device (12) forms a compensator (21) that is in fluid communication with one of the two media spaces (18, 20) of the bellows (14) and separates a third media space (22), wherein by means of the compensator (21) a displacement volume (VS) can be compensated that corresponds to the volume (V) that the bellows (14) displaces in a movement between its predeterminable minimum and maximum bellows length, characterized in that in each case one of the two separating devices (10, 12) is loaded from its connection side (76) only up to a predeterminable nominal pressure, whereas the respective other separating device on its connection side (48) simultaneously is kept pressureless,or that the compensator (21) is exposed to a pressure of an energy storage medium, such as a working gas, accommodated in the third media space (22).
2. System according to claim 1, characterized in that one separating device (10) is a bellows accumulator (36) and the other separating device (12) has a storage device, such as a piston accumulator (38), as a compensator (21).
3. System according to claim 1 or 2, characterized in that the piston accumulator (38) is connected to the one media chamber (18) of the bellows accumulator (36) via a connecting line (64) which carries a coupling medium which can be received by one of the two piston chambers (66) of the piston accumulator (38), or that the coupling medium is received in a common accumulator housing (40), and is delimited by the outer side of the bellows (14) and an adjacent piston wall of the accumulator piston (50).
4. System according to one of the preceding claims, characterized in that at least one additional hydraulic system component is connected into the connecting line (64) between the two separating devices (10, 12).
5. System according to one of the preceding claims, characterized in that the connecting line (64) is selected to be so long that different system states, in particular in the form of different temperatures, occur in the two separating devices (10, 12).
6. System according to one of the preceding claims, characterized in that the bellows accumulator (36) with its other media chamber (20) can be connected to a pressure source, as can the other piston chamber (22), which is arranged separated from the accumulator piston (50) on the side of the other separating device (12) facing away from the bellows (14).
7. System according to one of the preceding claims, characterized in that the respective separating device (10, 12) is accommodated in the common accumulator housing (40) and that a stop is provided in the accumulator housing (40) in the direction of the bellows accumulator (36), which stop limits the movement of the accumulator piston (50) in the direction of the bellows (14).
8. System according to one of the preceding claims, characterized in that the respective separating device (10, 12) functions as a hydropneumatic accumulator and / or as a media separator.
9. System according to one of the preceding claims, characterized in that for a function as a reservoir, the piston reservoir (38) has an energy reservoir, such as a compressed working gas, in its other piston chamber (22), or for a function as a media separator is provided with a fluid connection (48) which preferably carries a different medium than the fluid connection (76) which leads to the inside of the bellows (14) of the bellows reservoir (36).
10. System according to one of the preceding claims, characterized in that the piston accumulator (38) has a piston position indicator (57) for the accumulator piston (50).