Piston Accumulator

Abstract

The invention relates to a piston accumulator having an accumulator housing 10 and a separating piston 12 arranged so as to be longitudinally movable, which separates two medium chambers 14, 16 from each other in the accumulator housing 10, in which the accumulator housing 10 is elastically constructed in a sandwich structure from individual, partially distinct layers 18, 20, 22, 24, so as to be capable of bending as a whole under the action of at least one external force starting from an initial state and to return to the initial state when the respective force is removed.

Description

[Technical field]

[0001] The present invention relates to a piston accumulator having an accumulator housing and a separating piston arranged in the accumulator housing so as to be longitudinally movable and separating two medium chambers from each other. [Background technology]

[0002] Piston accumulators of this type are commercially available. They are widely used in hydraulic systems, for example for energy storage, for emergency operation to damp mechanical or pressure shocks, for vehicle suspensions, etc.

[0003] Patent Document 1 (German Patent No. 10161797) describes In a piston accumulator, the piston accumulator comprises: An accumulator housing; a piston separating the gas side medium chamber from the fluid side medium chamber within the accumulator housing and being axially movable; a housing cover that closes the fluid-side medium chamber and has a fluid passage opening; and a stop device for limiting the path of the piston, the stop device having several contact surfaces formed on the piston and the housing cover and surrounding a fluid passage opening, which contact surfaces abut each other when the piston is in an end position approaching the housing cover, the contact surfaces of the stop device being provided as several sealing surfaces, at least one of the sealing surfaces having a convexly curved contour for continuous line contact with the other contact surface, the piston and the housing cover respectively being made of a steel material having a ductility selected in each case to obtain an optimal sealing effect at their contact lines. Due to this design of the contact surface, the stop device limiting the movement of the piston forms a double-function metal seal, sealing the piston against the fluid passage opening of the fluid side chamber when the piston is in its end position, and the line contact caused by at least one curved configuration of the contact surface results in a reliable seal due to the high surface pressure of the metal seal configuration, so that perfect tightness is guaranteed over a very wide temperature range, which may include the lowest values ​​of -40°C. This feature of permanent plastic deformation before possible failure allows such piston accumulators to be used even in harsh outdoor applications under extreme environmental conditions. For example, Patent Document 2 (German Patent No. 102016003345) states: a rotor blade having two piston accumulators extending along its longitudinal direction, the separate pistons being preloaded via a compressible medium and connected to each other in a medium-conveying manner via a fluid line using a non-compressible medium; a control valve for establishing a medium connection between or isolating two piston accumulators of a pair when the control valve is connected to a respective fluid line; An acceleration sensor; A rotor position sensor; The present invention shows an application relating to a balancing device for compensating for imbalance of a rotor of a wind turbine, comprising at least one of: a control system that evaluates sensor data and operates at least one pair of piston accumulators by controlling a control valve. This balancing device makes it possible to balance each rotor of the wind turbine during operation, which is usually necessary since imbalances can occur especially during operation, e.g. due to the accumulation of dirt on the rotor blades or when turbulence occurs, e.g. during wind power operation.

[0004] The rotor blades are also usually subjected to deformations during the operation of the wind turbine. To account for these deformations, kinematic models are used that are able to account for the deformations of the rotor blades, for example based on the Euler-Bernoulli beam assumption. The theoretically determinable deformations on each rotor blade correspond to the acquisition of practical measurements, which are preferably based on a combination of photogrammetry and laser scanner measurements. In any case, in practice, the deformations of the rotor blades usually occur in the form of reversible deflections along the rotor's longitudinal axis, and according to the teaching of the document WO 2006 / 023366, the piston accumulators hinged to the rotor blades must be able to follow these deformations resulting from the changing bending curves caused by the changing wind currents and turbulences during operation. Despite the ductility of the above-mentioned subcomponents, the piston accumulators, which are usually made of solid steel material, change over time and can no longer follow the changing bending curves of the rotor blades, which often leads to failure of the connection points between the piston accumulators and the rotor blades and thus to the unusability of the balancing device as a whole.

[0005] Notwithstanding the initial conditions described above for wind turbines, piston accumulators may also be subjected to other changing and alternating bending forces, for example when the piston accumulators are subjected to strong vibrations during operation of the hydraulic system, such as when used in aircraft, rockets, military vehicles, agricultural machinery, etc. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent No. 10161797 [Patent Document 2] German Patent No. 102016003345 Summary of the Invention [Problem to be solved by the invention]

[0007] Based on this state of the art, the present invention is therefore based on the object of further improving a piston accumulator of the above-mentioned type in such a way that safe operation is guaranteed even in the event of strong bending stresses, even in conjunction with third-party components. [Means for solving the problem]

[0008] A piston accumulator having the features of claim 1 solves this problem in its entirety.

[0009] According to the characterizing part of claim 1, the sandwich-constructed piston accumulator is elastically constructed from individual layers different from each other so that starting from an initial state, it allows bending as a whole under the action of at least one external force and returns to its initial state when the respective force is removed, so that even in the case of large deflections of the accumulator housing under load, it returns to its initial state without deformation when the load is removed and remains functional even in the case of deflections. The above-mentioned sandwich structure, which can realize a linear elastic behavior (Hooke's law) for the accumulator housing, contributes greatly to this. In addition, the sandwich structure using multi-layer technology allows a very lightweight construction, which, together with third-party components such as the rotor blades of a wind turbine, leads to extremely favorable operating behavior since only a small mass has to be moved.

[0010] In a particularly preferred embodiment of the piston accumulator according to the invention, it is provided that the innermost layer of the accumulator housing, as part of a sandwich structure, consists of a first layer that is impermeable to gases, and each subsequent outer layer is formed from a fiber winding. Preferably, in terms of wall thickness, the first layer is a thin steel tube, which is preferably manufactured by flow forming and forms on its inner circumference a running surface for the separating piston. The steel tube forms a steel liner and, even in the deformed state, forms a smooth running surface at the outer circumference of the separating piston with its guide and sealing system. Furthermore, if it is intended to replace the inner steel liner with a plastic liner as part of an improved lightweight construction, it is guaranteed in any case that the steel liner is gas impermeable and there is no risk of the working gas permeating the plastic or of leakage as a result of resin failure, so-called inter-fiber breaks in the laminate.

[0011] Each fiber winding for the accumulator housing, following the steel liner, has in each case a different winding direction than the fiber winding preceding it in the winding sequence. The fibers to be wound are in each case preferably aligned according to the load path occurring, so that, for example, a radial winding of less than 90° around the tubular steel liner can be followed by another fiber winding, the respective fiber alignment of which is 0°-45°, after which another winding can be preferably performed exclusively radially, i.e. in the direction of a load path of less than 90°, perpendicular to the axial direction of the tubular steel liner. For example, less than 90° means a winding direction of 87° or 88°. Depending on the strength requirements, further fiber windings with the same or different orientation can be applied. To affect the strength in different directions, a fabric or scrim can be used instead of the individual fibers, which must be manufactured before contacting with the matrix. In any case, this must be produced using the individual fibers to be wound as a multiphase or mixed material, generally consisting of at least two main components: the reinforcing fibers to be wound and a regularly formed base matrix of suitable fillers and adhesives between the fibers. In order to obtain a high strength fiber composite, it is preferable to use carbon materials in this piston accumulator. However, other chemical fibers can also be used, in particular those made of glass, aramid and high strength polyesters. Overall, a kind of CFRP tube is formed, which has a thin steel liner inside, with all the individual fiber layers forming together with the steel liner an inherently pressure-resistant elastic liner composite.

[0012] In a further preferred embodiment of the piston accumulator according to the invention, at least one free end face of the accumulator housing, the connection part is partially surrounded by at least a part of the fiber winding. More preferably, the connection part is at least partially pierced by the innermost layer on its cylindrical inner periphery side and has an annular receiving groove on the outer periphery side for receiving the fiber layer of the individual winding. It is particularly preferred that the receiving groove is at least partially defined by an inclined part against which at least one inner fiber winding is arranged and which is further overlapped by at least one subsequent fiber winding facing outward. In this way, the respective fiber winding at the free end of the accumulator housing can be connected with high strength to the connection part, which at this point forms a receiving flange for mounting a cover part closing the accumulator housing at each end. The corresponding cover part can be joined to the free front face of the connection part such that the interior of the accumulator housing is sealed against the environment. Furthermore, a high-strength connection can be formed if the respective cover part is firmly screwed to the connection part. If the cover part is joined to the connection, it can preferably be provided that the liner winding is at least partially guided over the cover part in order to create a high-strength connection between the accumulator housing and the cover part. However, if necessary, the cover part needs a connection point, preferably in the center and regularly in the form of a connection hole, to connect the interior of the accumulator housing to the fluid circuit or to ensure the filling of one of the two medium chambers with working gas. Instead of the above-mentioned cover part, depending on the configuration of the accumulator housing, one end of the tube can be configured at least as a hemisphere or with a type of dished bottom. If possible, the corresponding end side should also be provided with a fiber winding in order to make the interior of the accumulator housing sufficiently pressure-resistant.In any case, the above liner configuration ensures that, within normal limits, the accumulator housing is able to absorb bending forces in such a way that an associated curvature is created that allows the accumulator housing to return to its initial state after the bending forces are removed without permanent deformation due to the elasticity of the liner composite.

[0013] In order to achieve a rigid connection of each fiber winding with the associated connection, it is further provided that several retaining pins penetrate the liner composite with several fiber windings, which have a constant radial distance from each other and connect the fiber windings to the connection in a predefined manner, despite this connection the flexibility of the accumulator housing is not affected.

[0014] In a particularly preferred embodiment of the solution according to the invention, the use of a piston accumulator of the above mentioned lightweight construction is provided in a wind turbine as part of a balancing device for compensating for the imbalance of rotors of the above mentioned system, at least one of these rotors being rigidly connected to the accumulator housing of the piston accumulator at a number of separate fixing points, in such a way that when the rotor is bent, the accumulator housing can follow this bending path without impairing its function, which is not comparable to the prior art.

[0015] In the following, the piston accumulator according to the invention is explained in more detail using an embodiment according to the drawings.

[0016] The drawings are shown in principle and are not to scale. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 shows, in longitudinal section, the edge end region of an accumulator housing constructed in a sandwich construction as a liner composite. [Diagram 2] FIG. 2 shows a front view of the housing cover for the accumulator housing according to FIG. [Diagram 3] FIG. 3 shows an enlarged detail of the end section of the accumulator housing indicated by arrow X in FIG. [Figure 4] FIG. 4 shows a schematic diagram of a possible curvature of the accumulator housing according to FIG. 1 when a bending force is applied in the direction of the arrow. [Diagram 5] FIG. 5 shows a side view of a separation piston for the accumulator housing according to FIG. [Figure 6] FIG. 6 shows a front view of a separation piston for the accumulator housing according to FIG. [Figure 7] FIG. 7 shows the separation piston shown in FIG. 5, inserted into the accumulator housing according to FIG. [Figure 8] FIG. 8 illustrates the use of a piston accumulator according to the embodiment of FIG. 7 in a wind turbine having three rotating rotor blades. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] FIG. 1 shows a longitudinal section through an accumulator housing 10 of a piston accumulator, and FIG. 7 shows the accumulator housing 10 with a separating piston 12 arranged so as to be longitudinally movable, which separates two chambers 14, 16 from one another in the accumulator housing 10 and is shown in more detail in FIGS. 5 and 6. The chamber 14 can be used to contain a working gas in the form of nitrogen gas, for example, and the further chamber 16 is used to contain a working fluid, for example hydraulic oil. The accumulator housing 10 can have a correspondingly large overall length, for example of the order of 2 meters, so that, although the accumulator housing 10 is shown only in its end regions in FIGS. 1 and 7, in the central region the accumulator housing 10 also corresponds to an edge end region design as far as the liner structure of the accumulator housing 10 is concerned. Thus, the accumulator housing 10 is elastically constructed in a sandwich design from individual layers 18, 20, 22 and 24, some of which differ from one another, such that starting from an initial state as shown in Figures 1 and 7, it is capable of bending as a whole under the action of at least one external force F, and that, once the respective force F is removed, the accumulator housing 10 elastically returns to its initial state, according to the simplified representation according to Figure 4. In this respect, the sandwich structure allows for a linear elastic behavior for the accumulator housing 10.

[0019] With respect to the sandwich structure described above, the innermost layer 18 of the housing 10 is gas-impermeable and each of the subsequent outer layers 20, 22 and 24 is formed from a textile winding. The layer composite in question is shown in particular in FIG. 3, which is an enlarged copy of the detail marked with reference X in FIG. 1. The innermost layer 18 is designed as a thin steel tube with respect to wall thickness, which is preferably manufactured in one piece by flow-forming, as shown in FIG. 7, and forms on its inner circumference a smooth running surface 26 for the separating piston 12. The steel liner 18 extends over the entire length of the accumulator housing 10 up to its free front end. Each textile winding for the accumulator housing 10 has in each case a winding direction different from the textile winding preceding it in the winding sequence. Each fibre winding is preferably made of carbon fibre material, the fibre windings of the layer 20 being wound circumferentially on the steel layer 18 and therefore having a winding direction of less than 90° relative to the longitudinal direction 28 of the accumulator housing 10. On the other hand, the subsequent layers 22 may deviate from the abovementioned 90° winding direction by 0° to 45°, but it is also possible to apply the relevant layer 22 to the winding 20 substantially parallel to the longitudinal direction 28 of the accumulator housing 10. Here, other winding directions are also possible, as well as the application of additional layers, depending on the respective application and the required stiffness of the accumulator housing 10 as a whole. The outermost layer 24 then consists of fibre windings having a radial winding direction of 90° in the same direction as the wound layer 20, i.e. for example 87° or 88° relative to the longitudinal direction 28.

[0020] As further shown in particular in FIG. 3, each end of the accumulator housing 10 is provided with an annular connecting part 30, which is in each case constructed as an identical part. The annular or tubular connecting part 30 is pierced at its inner circumference by the steel liner 18 and opens at the front side at the free end of the connecting part 30. Each connecting part 30 has at its outer circumference an annular receiving groove 32 for receiving the fiber layers of the two outermost windings 22 and 24. The receiving groove 32 is bounded on one side by a connecting flange 34 and on the inside by a fixed ramp 36. Both the connecting flange 34 and the fixed ramp 36 have contact surfaces 38, 40 extending obliquely on their adjacent sides, which form a cone with each other in an imaginary extension in the direction of the groove base 42. In this case, the fixed ramp 36 is overlapped by the third layer 22, which at this point is in direct contact with the groove base 42 of the receiving groove 32. The third layer 22 tapers to a point at its free front end and ends at the base of the obliquely extending contact surface 38. The leading end of the third layer 22 defines an obliquely extending wall 44 of this third layer 22, which together with the obliquely extending contact surface 38 of the connection part 30 forms a further V-shaped engagement groove 46, which is also designed as an annular groove, used to engage with the free end of the outer layer 24. In contrast, the second layer 20 following the steel layer 18 in the winding sequence nests against the inclined part 48 of the fixed inclined part 36, which in this area adjoins the innermost layer 18 at its foot end with a slight inclination angle. In this way, a solid layer or liner composite of the individual layers 18, 20, 22 and 24 is achieved as part of a sandwich structure in their free end face area via the connection flange 34 and the respective connection part 30 with the fixed inclined part 36.

[0021] At the transition point between the steeply extending contact surface 40 and the uniformly rising surface with the ramp 48, the fixed ramp 36 has a substantially horizontally extending circumferential or engagement surface 50, as shown in FIG. 3, through which serve for the passage of individual, preferably metallic, retaining pins 52, evenly distributed radially at discrete distances from one another around the accumulator housing 10, rigidly connecting the layer composite of the individual layers 18, 20, 22 and 24 to the connection 30 and thus ensuring a robust layer composite.

[0022] The free end face of each connection flange 34 of the connection part 30 has pin recesses 54 evenly distributed around the circumference of the connection flange 34. Each cover part 56 can be pinned to the associated connection part 30 via the corresponding pin recesses 54, the cover part 56 being present at each free end of the accumulator housing 10. The associated pin, not shown in detail in this respect, should be attached to the cover part 56 along an annular surface 58 provided for this purpose, the imaginary inner curve of which is shown by a dashed and dotted line 60. In addition, the annular surface 58 is used, on its inside facing the accumulator housing 10, to apply adhesive in order to create a media-tight connection between the two media chambers 14, 16 and the environment. Furthermore, within the scope of the embodiments not shown in detail, it is possible to connect the respective cover part 56 to the accumulator housing 10 in a media-tight and pressure-tight manner via a textile winding. In the central area of ​​each cover part 56 there is a connection opening 62 which can be closed tightly with the medium chamber 14 on the gas side of the accumulator housing 10 and which remains open on the liquid side to connect the further medium chamber 16 to a conventional hydraulic circuit (not shown). In order to separate the two medium chambers 14, 16, i.e. the gas side from the liquid side in a medium-tight manner, a separation piston 12 is inserted into the accumulator housing 10 as shown in more detail in figures 5 and 6 and as shown in figure 7, figure 6 showing a front view from the right side of the separation piston 12 according to figure 5. The separation piston 12 thus has two piston parts 13, 15 which are designed as disks with the same outer diameter and are held firmly at a distance from each other via an elastically flexible piston rod 17 which allows bending as a whole under the action of at least one external force F starting from an initial state and returning to the initial state when the respective force F is removed. In this way, the double disc piston configuration of the separation piston 12 is adapted to follow the curvature of the accumulator housing 10, as shown by way of example in FIG.Like the two piston parts 13, 15, the piston rod 17 is made of a suitable metallic material, the piston rod 17 being preferably configured to be more flexible in bending than the disks 13, 15. In particular, the piston rod 17 prevents the relatively thin disks for the two piston parts 13, 15 from tilting into the guide along the running surface 26 of the accumulator housing 10 and thus blocking the movement sequence of the separation piston 12.

[0023] One piston part 13 facing one medium chamber 14 has a guide band 19 on its outer circumference, while the other piston part 15 facing the further medium chamber 16 has a further guide band 21 and a ring seal 23 made of a conventional elastomeric material. The two annular guide bands 19, 21 are designed as one and the same part and consist of a material with good sliding properties, such as a PTFE material, which is preferably correspondingly heat-resistant. Both the guide bands 19, 21 and the ring seal 23 are inserted into an annular receiving groove of the corresponding piston part 13, 15 and slide along the inner circumferential side of the accumulator housing 10 in the form of a running surface 26. In this regard, according to the illustration of FIG. 5, the ring seal 23 is arranged between the two guide bands 19, 21 on the other piston part 15. Due to the disk-like arrangement of the two piston parts 13, 15, an annular space 25 is formed between them, which contains the medium of one medium chamber 14, in particular in the form of a working gas. In order to avoid the above-mentioned tilting of the disk-shaped piston parts 13, 15 and nevertheless ensure that the separated piston 12 as a whole is able to follow the curved course of the accumulator housing 10 subjected to bending forces, the distance between the two disk-shaped piston parts 13, 15 is greater than 1 / 3 of the diameter of the respective piston parts 13, 15. Furthermore, in order to ensure a reliable displacement course, the disk thickness of the piston part 13 with the guide band 19 is selected to be smaller than the disk thickness of the other piston part 15 with the further guide band 21 and the sealing ring 23. For unhindered operation, it is further provided that the piston rod 17 with two opposing shoulders 27 merges flatly into the mutually facing free end faces 29, 31 of each of the two piston parts 13 and 15. The piston rod 17 thus engages the respective piston portion 13, 15 with its opposite end region and is secured along this end region to the associated piston portion 13, 15 via threads 33 by a conventional lock nut 35 which is only shown in FIG. 6.

[0024] As can be further seen from figures 5, 6 and 7, the disks of the two piston parts 13, 15 are provided with annular recesses 37, which serve on the one hand to save weight and also to increase the elasticity of the disks 13, 15. The recesses 37 are configured essentially identically on the opposite end faces of the two piston parts 13, 15 and are arranged concentrically with a central recess 39 which receives the associated threads 33 of the piston rod 17 and the locknut 35, respectively. Furthermore, on the inner end wall of the piston part 15, in a concentric arrangement with these recesses 37, there is an annular recess 37 which extends both on the outer periphery and on the inner periphery. The separated piston 12 designed in such an elastic manner can also be used in a "normal" accumulator housing 10, and the accumulator housing 10 of the presented type can also be used in a "conventional" separated piston.

[0025] Figure 4 now shows the accumulator housing 10 supported on two bearing blocks 64, with a compressive force F applied from above at a central entry point 66, such that the accumulator housing 10 bends as shown in Figure 4. The accumulator housing 10 is shown in Figure 4 in an idealized form, specifically without the two end cover parts 56. When the force F is removed, the accumulator or accumulator housing 10 returns to its original position, as shown in Figures 1 and 7. It will be appreciated that if the accumulator housing 10 is held at the entry point 66 and a force is applied from below through the bearing blocks 64, a deflection equivalent to that shown in Figure 4 will result.

[0026] If the piston accumulator is mounted as part of a balancing device for compensating rotor imbalances of a wind turbine, as shown by way of example in FIG. 8, the piston accumulator is fixed to one of the two blade sides of each rotor blade 68 along the two bearing blocks 64. In FIG. 8, a partially illustrated tower of a wind turbine is indicated with the reference number 70. As in a wind turbine, a machine house 72, also called a "nacelle", is arranged at the top end of the tower 70 and is rotatable around the vertical axis of the tower, so that it can rotate back and forth by two to three revolutions. The rotor hub for the three rotor blades 68 of the three-bladed rotor rotatably mounted in the nacelle 72 is not visible in the simplified representation according to FIG. 8. Within each rotor blade 68 there is a pair of piston accumulators, comprising an inner piston accumulator 74 and an outer piston accumulator 76. Each piston accumulator 74, 76 is essentially constructed as shown in FIG. 7 with corresponding end parts, such as the respective cover parts 56, at the ends. Each piston accumulator 74 , 76 is mounted to an associated rotor blade 68 via an associated bearing block 64 .

[0027] The inner piston accumulators 74 are in each case disposed in the region of the blade root adjacent the rotor hub, while the outer piston accumulators 76 are offset toward the respective blade tips by a distance extending along the longitudinal orientation of the respective rotor blade 68. Preferably, the outer piston accumulators 76 are dimensioned narrower than their counterpart inner piston accumulators 74 in response to the smaller installation space available within the respective rotor blade 68 near the blade tips.

[0028] In the inner piston accumulator 74, a medium or working chamber 14 carrying a compressible pressure medium, such as a working gas, preferably in the form of nitrogen gas, faces the blade root, and in the outer piston accumulator 76, a working chamber 14 carrying a compressible medium faces the blade tip. If necessary, the medium chamber 14 of the inner piston accumulator 74 can also carry ambient air and be kept decompressed. In the other medium chamber 16 of each of the piston accumulators 74 and 76, which are opposite each other in the rotor blade 68, an incompressible medium, such as a hydraulic fluid, is arranged as a mass that can be displaced in the respective rotor blade 68 for imbalance compensation. These fluid-carrying medium chambers 16 facing each other are connected to each other via fluid lines 78, for example in the form of pipes or hoses. A control valve 80, for example in the form of an electromagnetically operated switching valve that can be centrally controlled by a control system 82, is arranged in each fluid line 78 adjacent to each inner piston accumulator 74. In order to transmit values ​​of lateral accelerations acting on the support structure of the wind turbine transversely to the rotor shaft to the control system 82, an acceleration sensor 84 is arranged in the tower head or nacelle 72 and is connected to the control system 82 via corresponding measurement signal lines. Furthermore, a rotor position sensor 86 in the form of a rotor speed sensor or rotor rotational position sensor on the rotor shaft is provided, which determines the position of the rotor blades 68 and transmits it to the control system 82 via further measurement signal lines.

[0029] To perform the imbalance compensation process using the balancing device, the wind turbine is initialized by increasing the rotor speed by the motor to a speed at which the working fluid located in the fluid carrying medium chambers 16 of the piston accumulators 74, 76 and in the fluid lines 78 between them is displaced outward toward the blade tips under the action of centrifugal force when the control valve 80 is open, thereby compressing the working gas in the respective medium chambers 14 of the outer piston accumulators 76 so that the outer piston accumulators 76 are in a filled state. To detect the presence of an imbalance, the wind turbine must be operated at critical speeds, and if an imbalance exists, operation at these speeds will result in the generation of lateral tower vibrations and thus an acceleration signal from the acceleration sensor 84. The determination of which of the multiple rotor blades 68 have different mass moments of inertia is performed using a rotor rotational position sensor on the rotor shaft, which determines the exact position of the rotor blades 68 at any time. From the instantaneous value of the rotor position lateral acceleration, control system 82 determines which rotor blades 68 have different mass moments of inertia and provides control signals to control valves 80 to partially discharge the corresponding filled piston accumulators 76 to shift the mass of incompressible hydraulic fluid such that lateral acceleration is no longer measured. The rotor is then collectively balanced.

[0030] It will be appreciated that during operation of the rotor blades 68, deformations due to bending forces occur as a result of wind influences, leading to bending, especially in the longitudinal direction, of the respective rotor blade 68 during the occurrence of turbulence. Thanks to the above-mentioned piston accumulator solution with the accumulator housing 10 and / or the flexible separating piston 12, which are flexible against bending, the bending deformations of the respective rotor blades 68 can be absorbed in all directions, so that the piston accumulator pair 74, 76 can ensure the functional performance of mass balancing to compensate for the imbalance of the rotor blades 68 even in the event of the above-mentioned deflections.

Claims

1. A piston accumulator comprising an accumulator housing (10) and a separating piston (12) arranged longitudinally movably within said accumulator housing (10) and separating two medium chambers (14, 16) from each other within said accumulator housing (10), 1. A piston accumulator, characterized in that the accumulator housing (10) is elastically constructed in a sandwich structure from individual layers (18, 20, 22, 24) that are distinct from one another, so as to be capable of bending as a whole under the action of at least one external force (F) starting from an initial state and to return to said initial state when the respective force (F) is removed.

2. 2. A piston accumulator according to claim 1, characterized in that the sandwich structure provides a linear elastic behavior to the accumulator housing (10).

3. 3. A piston accumulator according to claim 1 or 2, characterized in that the innermost layer (18) of the accumulator housing (10), as part of the sandwich structure, is gas impermeable and each succeeding outer layer (20, 22, 24) is formed from textile windings.

4. 4. A piston accumulator according to claim 1, characterized in that the first innermost layer (18) is a steel tube having a thin wall thickness, said steel tube being preferably manufactured by flow forming and forming on its inner circumference a running surface (26) for the separating piston (12).

5. 5. A piston accumulator according to claim 1, characterized in that each of the fibre windings for the accumulator housing (10) has in each case a winding direction different from the respective preceding fibre winding in the winding sequence.

6. 6. The piston accumulator according to claim 1, characterized in that at at least one free end face of the accumulator housing (10), a connection portion (30) is partially surrounded by at least a part of the textile winding.

7. 7. A piston accumulator according to claim 1, characterized in that the connecting part (30) is at least partially penetrated by the innermost layer (18) on its cylindrical inner periphery and has annular receiving grooves (32) on its outer periphery for receiving the fibre layers (20, 22, 24) of the individual windings.

8. 8. A piston accumulator according to claim 1, characterized in that the receiving groove (32) is at least partially defined by a fixed inclined portion (36) in which at least one inner textile winding (20) is arranged in contact and which is overlapped by at least one subsequent textile winding (22, 24) facing further outwardly.

9. 9. A piston accumulator according to any one of claims 1 to 8, characterized in that at least one outer textile winding (22, 24) is penetrated by a plurality of retaining pins (52), preferably at a distance from one another and penetrating the connecting portion (30) in a radial direction.

10. Use of a piston accumulator according to any one of claims 1 to 9 for a wind turbine as part of a balancing device for compensating for imbalance of a plurality of rotor blades (68) of the wind turbine, Use of a piston accumulator, wherein at least one rotor blade (68) of the plurality of rotor blades (68) is rigidly connected to an accumulator housing (10) of the piston accumulator (74, 76) at a plurality of separate fastening points (64).

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