Piston accumulator

Abstract

The invention relates to a piston accumulator comprising an accumulator housing (10) and a separator piston (12) which is longitudinally moveably arranged therein and separates two media chambers (14, 16) from one another within the accumulator housing (10), wherein the accumulator housing (10) is elastically formed in a sandwich-type structure from individual, partially differing layers (18, 20, 22, 24) in such a way that, with the influence of at least one external force, it allows for a curvature as a whole, starting from a starting state, and it returns to the starting state with the removal of the respective force.

Description

[0001] HYDAC TECHNOLOGY GMBH

[0002] Industriestraße, 66280 Sulzbach / Saar, Germany

[0003] Piston accumulator

[0004] The invention relates to a piston accumulator with an accumulator housing and a separating piston arranged therein so as to be longitudinally movable, which separates two media spaces from each other within the accumulator housing.

[0005] Piston accumulators of this type are commercially available. They are widely used in hydraulic systems, for example, for energy storage, emergency actuation, damping mechanical shocks or pressure surges, for vehicle suspension, and so on.

[0006] DE 101 61 797 C1 discloses a piston accumulator comprising an accumulator housing, a piston which separates a gas-side media chamber from a fluid-side media chamber and is movable in the axial direction, a housing cover which closes off the fluid-side media chamber and has a fluid passage opening, and a stop device which limits the travel of the piston and which has contact surfaces formed on the piston and on the housing cover, which surround the fluid passage opening and which abut one another when the piston is in the end position approaching the housing cover, wherein the contact surfaces of the stop device are provided as sealing surfaces, at least one of which has a convexly curved contour for uninterrupted line contact with the other contact surface, wherein the piston and the housing cover are manufactured from steel materials, each with a ductility selected with a view to an optimal sealing effect at their contact line.Due to this design of the contact surfaces, the stop device that limits the piston travel has a dual function: a metallic seal that seals the piston against the fluid passage opening of the fluid-side chamber when the piston is in its end position. The line contact caused by the curved design of at least one of the contact surfaces leads to a secure closure due to the high surface pressure of the metallic sealing arrangement, so that complete gas tightness is guaranteed over very wide temperature ranges, which can include lows of -40°C.

[0007] Due to this feature of permanently plastically deforming before a possible fracture, such piston accumulators can also be used in harsh outdoor applications under extreme environmental conditions. For example, DE 10 2016 003 345 B4 shows an application in this context within a balancing device for compensating the imbalance of wind turbine rotors, consisting of at least one

[0008] Rotor blade with two piston accumulators extending along its longitudinal direction, the separating pistons of which are each subject to a preload via a compressible medium and which are connected to each other via a fluid line via an incompressible medium,

[0009] A control valve, which, when connected to the respective fluid line, establishes the media connection between the two piston accumulators of a pair or separates them from each other, an acceleration sensor, a rotor position sensor, and a control system for evaluating the sensor data and actuating at least one piston accumulator pair by controlling the control valve. This balancing device makes it possible to balance the respective rotor of a wind turbine during operation. This is regularly necessary, as imbalances can develop, particularly during operation, for example due to dirt deposits on the rotor blades or due to uneven wind flow, for example due to turbulence during wind turbine operation.

[0010] The rotor blades are also regularly subject to deformations during operation of the wind turbine. Kinematic models are used to describe these deformations. These models are capable of describing the deformations of a rotor blade, for example, based on the assumptions of an Euler-Bernoulli bending beam. The theoretically deformations on the respective rotor blade correspond to practical measured values, which are preferably based on a combination of photogrammetric and laser scanner measurements. In any case, in practice, rotor blade deformations regularly occur in the form of reversible deflections along the rotor's longitudinal axis, and the piston accumulators hinged to the rotor blades according to the teaching of DE 10 2016 003 345 B4 must be able to follow these deformations, which result from a changing bending pattern caused by the changing wind flow and the turbulence that occurs during operation.The piston accumulators, which are usually constructed from solid steel materials, are then unable to follow the temporally changing bending curve of the rotor blade despite the mentioned ductility of subcomponents, which often leads to a failure of the connection point between the piston accumulator and the rotor blade and thus to the unusability of the unbalance compensation device as a whole.

[0011] Regardless of the initial situation described above,

[0012] However, in wind turbines, piston accumulators can also be exposed to other changing alternating bending stresses, for example when the piston accumulator is exposed to strong vibrations during the operation of a hydraulic system, such as when used in aircraft, rockets, military vehicles, agricultural machinery, etc.

[0013] Based on this prior art, the invention is therefore based on the object of further improving a piston accumulator of the type mentioned in such a way that safe operation is guaranteed even in the event of strong bending stresses, even in conjunction with third-party components.

[0014] A piston accumulator having the features of patent claim 1 in its entirety solves this problem.

[0015] Because, according to the characterizing part of patent claim 1, the accumulator housing is constructed in a sandwich design from individual, partially different layers, so elastic that it allows a curvature as a whole from an initial state under the influence of at least one external force and returns to the initial state when the respective force is removed, a piston accumulator is created that, even in the event of significant deflection of the accumulator housing under load, returns to its initial state without deformation when the load is removed, and remains functional even in the event of deflection. The aforementioned sandwich design contributes significantly to this, enabling linear-elastic behavior (Hooke's law) for the accumulator housing.Furthermore, the sandwich structure using multi-layer technology enables extremely lightweight construction, which, in conjunction with third-party components such as the rotor blades of a wind turbine, leads to extremely advantageous operating behavior, since only small masses have to be moved. In a particularly preferred embodiment of the piston accumulator according to the invention, the innermost layer of the accumulator housing in the sandwich structure consists of a first layer that is impermeable to gas, and the subsequent layer towards the outside is formed from a fiber winding. The first layer is preferably a steel tube with a thin wall thickness, which is preferably produced by flow forming and which forms the running surface for the separating piston on the inner circumference.The steel tube thus forms a steel liner and, even in its deformed state, provides a smooth running surface for the outer circumference of the separating piston with its guide and sealing systems. Furthermore, the steel liner is guaranteed to be gas-tight, eliminating the risk of the working gas permeating the plastic or leaks due to resin fractures, so-called interfiber fractures in the laminate, if the inner steel liner is replaced with a plastic liner as part of an improved lightweight design.

[0016] Each fiber winding for the storage housing, which follows the steel liner, has a different winding direction than the preceding fiber winding in the winding sequence. The fibers to be wound are preferably aligned according to the load paths occurring, so that, for example, a winding in a radial direction of less than 90° around the cylindrical steel liner can be followed by another fiber winding, the respective fiber orientation of which, in contrast, is between 0° and 45°. Subsequently, another winding can preferably take place in an exclusively radial direction, i.e., in the direction of a load path of less than 90°, which is perpendicular to the axial orientation of the tubular steel liner. Less than 90° means, for example, winding directions of 87° or 88°. Depending on the strength requirements, additional fiber windings with the same or a modified orientation can be applied.To influence the strength in various directions, woven or non-woven fabrics can be used instead of individual fibers, which must be produced before contact with the matrix. In any case, even using the individual fibers to be wound, a fiber composite material is to be produced. As a multiphase or mixed material, this composite generally consists of at least two main components: the reinforcing fibers to be wound and a bedding matrix, usually formed from a suitable filler and adhesive between the fibers. To achieve a high-strength fiber composite, carbon materials are preferably used for this piston accumulator. However, other chemical fibers can also be used, particularly those made of glass, aramids, high-strength polyester, etc.Overall, a type of CFRP tube is formed, which has the thin steel liner inside and, together with the steel liner, the individual fiber layers form a pressure-resistant, highly elastic liner composite.

[0017] In a further preferred embodiment of the piston accumulator according to the invention, it is provided that a connecting part is partially enclosed by at least some of the fiber windings on at least one free end face of the accumulator housing. It is preferably further provided that the connecting part is at least partially penetrated by the innermost layer on its cylindrical inner circumference and has an annular receiving groove on the outer circumference for receiving fiber layers of the individual windings. It is particularly preferably provided that the receiving groove is at least partially delimited by a ramp, against which at least one inner fiber winding is applied and which is overlapped by at least one subsequent, further outer fiber winding.In this way, the respective fiber winding at the free end of the storage housing can be connected with high strength to the connecting part, which in this respect forms a receiving flange for the attachment of a cover part that closes off the storage housing at each end. This cover part can be glued to the free end face of the connecting part, so that the interior of the storage housing is correspondingly sealed from the environment. Furthermore, a high-strength connection can be created provided the respective cover part is firmly screwed to the connecting part. If the cover part is glued to the connecting part, it can preferably be provided that the liner winding is guided at least partially over the cover part in order to thus create a high-strength connection between the storage housing and the cover part.However, if necessary, the cover part requires a connection point, preferably in the center, usually in the form of a connection hole, to connect the interior of the storage housing to a fluid circuit or to ensure the filling of one of the two media chambers with the working gas. Instead of the cover part mentioned above, depending on the design of the storage housing, at least one end of the tube can be designed as a hemisphere or using a type of dished end. If possible, the corresponding end face should also be provided with a fiber winding to ensure the interior of the storage housing is sufficiently pressure-resistant.In any case, the liner design ensures that, within the usual framework, the storage housing can absorb a bending force such that a relevant curvature is created which, once the bending force is removed, allows the storage housing to return to its original state due to the elasticity of the liner composite without any permanent deformation occurring.

[0018] To ensure a secure connection between the respective fiber winding and the associated connector, several retaining pins are provided that penetrate the liner assembly with the fiber windings. These pins maintain a constant radial distance from each other, thus firmly connecting the fiber winding to the connector. Despite this connection, the flexibility of the storage housing is not compromised.

[0019] In a particularly preferred embodiment of the inventive solution, a piston accumulator, as described above in a lightweight design, is used for a wind turbine as part of a balancing device for compensating the imbalance of rotors of such a turbine. At least one rotor of the rotor is firmly connected to the accumulator housing of the piston accumulator at discrete fixing points, in such a way that if the rotor bends, the accumulator housing can follow this bending path without being impaired in its function. This has no equivalent in the prior art.

[0020] In the following, the piston accumulator according to the invention is explained in more detail using an embodiment according to the drawing.

[0021] The diagrams are shown in principle and not to scale.

[0022] Figure 1 in the form of a longitudinal section, the edge end areas of the storage housing constructed in sandwich construction as a liner composite;

[0023] Figure 2 shows the front view of a housing cover for the storage housing according to Figure 1;

[0024] Figure 3 shows an enlarged section of the end section of the storage housing designated by X in Figure 1;

[0025] Figure 4 shows a schematic representation of the possible curvature of the storage housing according to Figure 1 when a bending force is applied in the direction of the arrow; Figures 5 and 6 show a side view and a front view of a separating piston for the storage housing according to Figure 1;

[0026] Figure 7 shows the separating piston shown in Figure 5, inserted into a storage housing according to Figure 1; and

[0027] Figure 8 shows the use of a piston accumulator according to a

[0028] Design according to Figure 7 for a wind turbine with three rotating rotor blades.

[0029] Figure 1 shows a longitudinal section through an accumulator housing 10 of a piston accumulator, and Figure 7 shows the accumulator housing 10 with a longitudinally movable separating piston 12 arranged therein, which separates two media chambers 14, 16 from one another within the accumulator housing 10 and is shown in more detail in Figures 5 and 6. The media chamber 14 can serve to hold a working gas, such as nitrogen gas, and the further media chamber 16 serves to hold an operating fluid, such as hydraulic oil. Since the accumulator housing 10 can have a correspondingly large overall length, for example on the order of 2 meters, the accumulator housing 10 is only shown in the region of its end areas in Figures 1 and 7; in the central area, however, the accumulator housing 10 also corresponds to the edge-side end area design as far as the liner structure of the accumulator housing 10 is concerned.Accordingly, the storage housing 10 is constructed in a sandwich design from individual, partially different layers 18, 20, 22, and 24 in such an elastic manner that, under the action of at least one external force F, starting from an initial state as indicated in Figures 1 and 7, it permits curvature as a whole, according to the simplified representation in Figure 4. When the respective force F is removed, the storage housing 10 elastically returns to its initial state. In this respect, the sandwich design permits linear-elastic behavior for the storage housing 10. Within the framework of the aforementioned sandwich design, the innermost layer 18 of the housing 10 is gas-impermeable, and the respective outwardly following layers 20, 22, and 24 are formed from a fiber winding. The corresponding layer composite is evident in particular from Figure 3, which shows an enlarged representation of the section designated X in Figure 1.The innermost layer 18 is designed as a thin steel tube in terms of wall thickness, which is preferably produced from a single piece by flow forming and which, on the inner circumference, forms the smooth running surface 26 for the separating piston 12, as shown in Figure 7. The steel liner 18 extends over the entire length of the storage housing 10 up to the free front end thereof. The respective fiber winding for the storage housing 10 has a different winding direction than the fiber winding preceding it in the winding sequence. The respective fiber winding is preferably made of carbon fiber material, and the fiber winding of layer 20 is wound in the circumferential direction onto the steel layer 18, thus having a winding direction of less than 90° to the longitudinal direction 28 of the storage housing 10.The subsequent layer 22, in contrast, can deviate by 0° to 45° from the aforementioned smaller 90° winding direction; however, it is also possible to apply the corresponding layer 22 to the winding 20 largely parallel to the longitudinal direction 28 of the storage housing 10. Other winding directions are possible here, as is the application of additional layers depending on the respective application and the required rigidity for the overall storage housing 10. The outermost layer 24, in turn, consists of a fiber winding in the same direction as the wound layer 20, i.e., with a radial winding direction of less than 90° to the longitudinal direction 28, for example, 87° or 88°.

[0030] As Figure 3 further shows in particular, an annular connecting part 30 is provided at each end of the storage housing 10, which are designed as identical parts. The annular or cylindrical connecting part 30 is penetrated by the steel liner 18 on its inner circumference and opens out at the free end of the connecting part 30. On the outer circumference, each connecting part 30 has an annular receiving groove 32 for receiving fiber layers of the two outermost windings 22 and 24. The receiving groove 32 is delimited on one side by a connecting flange 34 and on its inner side by a fixing ramp 36. Both the connecting flange 34 and the fixing ramp 36 have obliquely extending contact surfaces 38, 40 on their adjacent sides, which together form a cone in a fictitious extension towards a groove base 42.The fixing ramp 36 is thereby overlapped by the third layer 22, which in this way comes into 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 inclined contact surface 38. The tapered end of the third layer 22 delimits a diagonal wall section 44 of this third layer 22, which, together with the inclined contact surface 38 of the connecting part 30, forms a further V-shaped engagement groove 46, which, likewise designed as an annular groove, serves for the engagement of the free end of the outer layer 24. The second layer 20, which follows the steel layer 18 in the winding assembly, nestles against a ramp section 48 of the fixing ramp 36, which in this area borders the innermost layer 18 at the base with a slight angle of inclination.In this way, within the framework of the sandwich construction, a secure layer or liner bond of the individual layers 18, 20, 22 and 24 is achieved in their free front area via the respective connecting part 30 with connecting flange 34 and fixing ramp 36.

[0031] At the point of transition between the steeply running contact surface 40 and the flatly running ramp rise surface in contrast, including the ramp part 48, the fixing ramp 36 has, as shown in Figure 3, a substantially horizontally running circumferential or engagement surface 50, which serves for the penetration of individual, preferably metallic, retaining pins 52, which are evenly distributed in the radial direction at discrete distances from one another around the storage housing 10 and firmly connect the layer composite of the individual layers 18, 20, 22 and 24 to the connecting part 30 and thus ensure a secure layer composite.

[0032] On the free end faces of the respective connecting flange 34 of the connecting part 30 there are pin recesses 54, which are evenly distributed around the outer circumference of the connecting flange 34. The respective cover part 56 can be pinned to the associated connecting part 30 via the corresponding pin recesses 54, with such a cover part 56 being present at each free end of the storage housing 10. The corresponding pins, not shown in detail, are to be attached to the cover part 56 along an annular surface 58 provided for this purpose, the fictitious inner course of which is represented by a dash-dotted line 60. In addition, the corresponding annular surface 58 serves to apply an adhesive to its inner side facing the storage housing 10 in order to create a media-tight connection between the two media chambers 14, 16 and the environment.Lerner has the option, within the scope of an embodiment not shown in detail, of connecting the respective cover part 56 to the storage housing 10 in a media-tight and pressure-tight manner via a spring coil. In the central region of each cover part 56 there is a connection opening 62 which can be tightly closed with the media chamber 14 on the gas side of the storage housing 10 and remains open on the liquid side in order to connect the further media chamber 16 to a conventional hydraulic circuit (not shown). In order to separate the two media chambers 14, 16, i.e. a gas side from a liquid side, in a media-tight manner, a separating piston 12 is inserted into the storage housing 10 in a longitudinally movable manner as shown in Figure 7. This separating piston is shown in more detail in Figures 5 and 6, with Figure 6 showing a front view from the right of the separating piston 12 according to Figure 5.Accordingly, the separating piston 12 has two piston parts 13, 15, which are designed as disks with the same outer diameter and which are firmly connected to one another via an elastically flexible piston rod 17, held at a distance from one another. The piston rod 17, under the action of at least one external force F, allows a curvature as a whole from an initial state and returns to the initial state when the respective force F is removed. In this way, the double-disk piston arrangement of the separating piston 12 is suitable for following a curvature of the accumulator housing 10, as shown by way of example in Figure 4. Like the two piston parts 13, 15, the piston rod 17 is made of a suitable metal material, with the piston rod 17 preferably being designed to be more flexurally elastic than the disks 13, 15.In particular, the piston rod 17 prevents the relatively thin discs for the two piston parts 13, 15 from tilting along the running surface 26 in the accumulator housing 10 as part of the guide and thus inhibiting the movement of the separating piston 12.

[0033] One piston part 13, which faces one media chamber 14, has a guide band 19 on its outer circumference, and the other piston part 15, which faces the further media chamber 16, has a further guide band 21 and an annular seal 23 made of a conventional elastomer material. The two annular guide bands 19, 21 are designed as identical parts and consist of a material with good sliding properties, which is preferably correspondingly temperature-resistant, such as PTFE material. Both the guide bands 19, 21 and the annular seal 23 are inserted into annular receiving grooves in the associated piston parts 13, 15 and slide along the inner circumference of the storage housing 10 in the form of the running surface 26. In this respect, according to the illustration in Figure 5, the annular seal 23 is arranged between the two guide bands 19, 21 on the other piston part 15.Due to the disc-shaped arrangement of the two piston parts 13, 15, an annular space 25 is formed between them, which contains the medium of one media chamber 14, in particular in the form of the working gas. In order to avoid the aforementioned tilting of the disc-shaped piston parts 13, 15 and yet ensure that the separating piston 12 as a whole can follow the curved course of a storage housing 10 subject to bending stress, the distance between the two disc-shaped piston parts 13, 15 is less than 1 / 3 of the diameter of the respective piston part 13, 15. Furthermore, to ensure reliable displacement, the disc thickness of the piston part 13 with the guide band 19 is selected to be smaller than the disc thickness of the other piston part 15 with the further guide band 21 and the sealing ring 23.For unobstructed operation, it is further provided that the piston rod 17, with its two opposing shoulders 27, merges flush into the mutually facing free end faces 29, 31 of the two piston parts 13 and 15, respectively. Accordingly, the piston rod 17 extends through the respective piston part 13, 15 with its opposite end regions, and the piston rod 17 is secured to the associated piston part 13, 15 along this end region via a threaded section 33 by means of a conventional lock nut 35, only shown in the illustration according to Figure 6.

[0034] As can be further seen from Figures 5, 6, and 7, the discs of the two piston parts 13, 15 are provided with annular recesses 37, which serve to save weight and also increase the elasticity of the discs 13, 15. The recesses 37 are essentially identical on the opposite end faces of the two piston parts 13, 15 and are arranged concentrically to a central recess 39, which accommodates the respective associated threaded portion 33 of the piston rod 17 and the lock nut 35. Furthermore, an annular recess 37, widened on both the outer and inner circumferences, is provided on the inner end wall of the piston part 15, concentrically arranged to these recesses 37. The separating piston 12 designed to be elastic in this way can also be used for "normal" storage housings 10; Likewise, storage housings 10 of the type presented can be used with "conventional" separating pistons.

[0035] Figure 4 now shows the elevated storage housing 10 on two bearing blocks 64 and a compressive force F is applied from above at an inlet point 66 in the center such that the storage housing 10 deflects as shown in Figure 4. The storage housing 10 is shown in Figure 4 in idealized form, in particular without the two end cover parts 56. If the force F is removed, the accumulator or the storage housing 10 returns to its original position as shown in Figures 1 and 7. It is understood that if the storage housing 10 is held at the inlet point 66 and the force is applied from below via the bearing blocks 64, a deflection comparable to that shown in Figure 4 occurs.

[0036] If the piston accumulator is installed as part of a balancing device for compensating the imbalance of wind turbine rotors, as shown by way of example in Figure 8, it is secured along the two bearing blocks 64 on one of the two blade sides of the respective rotor blade 68. In Figure 8, the partially illustrated tower of a wind turbine is designated 70. As is usual for wind turbines, a nacelle 72, also known in technical terms as a "gondola," is arranged at the upper end of the tower 70, which can be rotated forwards and backwards by two to three revolutions. A rotor hub for three rotor blades 68 of a three-blade rotor, rotatably mounted on the nacelle 72, is not visible in the simplified illustration in Figure 8. Within each rotor blade 68 is a pair of piston accumulators, comprising an inner piston accumulator 74 and an outer piston accumulator 76.The respective piston accumulator 74, 76 is basically constructed as shown in Figure 7 with corresponding end-side closure parts, such as the respective cover part 56. The respective piston accumulator 74, 76 is attached to the associated rotor blade 68 via the associated bearing blocks 64.

[0037] The respective inner piston accumulator 74 is arranged in the area of ​​the blade root adjacent to the rotor hub, and the outer piston accumulator 76, in contrast, is offset toward the respective blade tip by a distance that extends along the longitudinal alignment of the respective rotor blade 68. Preferably, the outer piston accumulator 76 is dimensioned more slenderly than the inner piston accumulator 74 of the pair, corresponding to the smaller installation space available within the respective rotor blade 68 near the blade tip.

[0038] In the inner piston accumulators 74, the media or working chamber 14, which carries the compressible pressure medium such as the working gas, preferably in the form of nitrogen gas, faces the blade root, whereas in the outer piston accumulators 76, the working chamber 14, which carries the compressible medium, faces the blade tips. If necessary, the media chamber 14 of the inner piston accumulator 74 can also carry ambient air and be kept depressurized. In the other media chambers 16 of the piston accumulators 74 and 76, which face each other within the rotor blade 68, the incompressible medium, such as hydraulic fluid, is located as a mass that can be displaced within a respective rotor blade 68 to compensate for imbalance. These mutually facing fluid-carrying media chambers 16 are connected to one another via a fluid line 78, for example in the form of a pipe or hoses.In the respective fluid line 78, adjacent to the respective inner piston accumulator 74, a control valve 80 is arranged, for example in the form of an electromagnetically actuated switching valve, which can be centrally controlled by a control system 82. In order to transmit the values ​​of the transverse 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 the nacelle 72 and is connected to the control system 82 via corresponding measuring signal lines. Furthermore, a rotor position sensor 86 is provided, which, in the form of a rotor speed sensor or a rotor rotation position sensor on the rotor shaft, determines the position of the rotor blades 68 and transmits this data to the control system 82 via another measuring signal line.

[0039] To perform an imbalance compensation process using the balancing device, the wind turbine is brought to an initial state by increasing the rotor speed to a speed at which the hydraulic fluid located in the fluid-carrying media chambers 16 of the piston accumulators 74, 76 and in the fluid line 78 between them is displaced outward toward the blade tips under the influence of centrifugal force when the control valves 80 are open, thereby compressing the working gas in the respective media chamber 14 of the outer piston accumulators 76, so that they are in a charged state. To detect the presence of an imbalance, the wind turbine must be operated at a critical speed. If an imbalance is present, operation at these speeds leads to transverse tower vibrations and thus to the occurrence of acceleration signals from the acceleration sensor 84.The determination of which of the rotor blades 68 has a different mass moment of inertia is carried out using the rotor rotation position sensor on the rotor shaft, which determines the precise position of the rotor blades 68 at any given time. From the instantaneous value of the lateral acceleration of the rotor position, the control system 82 determines which rotor blade 68 has the different mass moment of inertia and provides a control signal to the control valves 80, which partially discharge the relevant charged piston accumulators 76 to shift the mass of the incompressible hydraulic fluid such that no more lateral acceleration is measured. The rotor is then completely balanced.

[0040] It is understood that during operation of the rotor blades 68, the influence of wind force, including in the context of turbulence, leads to deformations due to bending forces, in particular to bending of the respective rotor blade 68 in its longitudinal orientation. Thanks to the piston accumulator solution described above, using a flexurally elastic accumulator housing 10 and / or a flexurally elastic separating piston 12, the respective bending deformations of the rotor blade 68 can be absorbed in all directions, whereby the piston accumulator pairs 74, 76 can reliably perform mass balancing to compensate for the imbalance of the rotor blades 68, even in the case of the described deflection.

Claims

Patent claims for a piston accumulator with an accumulator housing (10) and a separating piston (12) arranged longitudinally therein, which separates two media chambers (14, 16) from each other within the accumulator housing (10), characterized in that the accumulator housing (10) is constructed in a sandwich design from individual, partially different layers (18, 20, 22, 24) in such an elastic manner that, under the influence of at least one external force (F), it allows curvature as a whole from an initial state and returns to the initial state when the respective force (F) is removed. Piston accumulator according to claim 1, characterized in that the sandwich design results in linear-elastic behavior for the accumulator housing (10).Piston accumulator according to claim 1 or 2, characterized in that, within the sandwich structure, the innermost layer (18) of the accumulator housing (10) is gas-tight and that the subsequent outermost layers (20, 22, 24) are formed from a fiber winding. Piston accumulator according to any one of the preceding claims, characterized in that the first innermost layer (18) is a thin-walled steel tube, preferably produced by flow forming, which forms the running surface (26) for the separating piston (12) on its inner circumference.

5. Piston accumulator according to one of the preceding claims, characterized in that the respective fiber winding for the accumulator housing (10) has a different winding direction than the preceding fiber winding in the winding sequence.

6. Piston accumulator according to one of the preceding claims, characterized in that on at least one free end face of the accumulator housing (10) a connection part (30) is partially encompassed by at least a part of the fiber windings.

7. Piston accumulator according to one of the preceding claims, characterized in that the connecting part (30) is at least partially penetrated on its cylindrical inner circumferential side by the innermost layer (18) and has an annular receiving groove (32) on the outer circumferential side for receiving fiber layers (20, 22, 24) of the individual windings.

8. Piston accumulator according to one of the preceding claims, characterized in that the receiving groove (32) is at least partially limited by a fixing ramp (36) to which at least one inner fiber winding (20) is applied and which is overlapped by at least one subsequent, further outer fiber winding (22, 24).

9. Piston accumulator according to one of the preceding claims, characterized in that at least one outer fiber winding (22, 24) is penetrated by several retaining pins (52) which preferably have a constant distance from each other and which penetrate the connecting part (30) in a radial direction. Use of a piston accumulator according to one of the preceding claims for a wind turbine as part of a balancing device for compensating the imbalance of rotor blades (68) of such a turbine, at least one of which rotor blades (68) is rigidly connected to the accumulator housing (10) of the piston accumulator (74, 76) at discrete fixing points (64).

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