Abstract:
A pressure accumulator has at least one accumulator housing ( 403 ) with at least one connection ( 411 ) for a pressure medium ( 421 ), especially in the form of a fluid that can be accumulated in the accumulator housing ( 403 ). The filling material ( 419 ) has hollow chambers or forms at least one hollow chamber for accommodating at least part of pressure medium ( 421 ) and/or at least one further pressure medium ( 449 ) introduced into at least sections of the accumulator housing ( 403 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to a pressure accumulator having at least one accumulator housing with at least one connection for a pressure medium, in particular in the form of a fluid, which can be stored in the accumulator housing. A filling material is introduced at least partially into the accumulator housing. This material has cavities or forms at least one cavity for at least partial accommodation of this pressure medium and/or at least one additional pressure medium. 
     BACKGROUND OF THE INVENTION 
     Pressure accumulators are known in various embodiments in the prior art. For example, DE 20 2007 008 175 U1 discloses a hydropneumatic pressure accumulator or hydraulic accumulator having a movable separation element disposed in an accumulator housing. The separation element separates a first working space, preferably a gas space, from a fluid space, as the second working space, and is formed by a diaphragm of a flexible material, in particular an elastomer. At least one housing opening, forming an access to the housing, is provided on the accumulator housing for accommodating and dispensing fluid, in particular in the form of hydraulic fluid. 
     Pressure accumulators of this type, in particular hydraulic accumulators, are subjected to high demands during operation in hydraulic systems because frequent and intense movements of the elastomeric separation element occur in predefinable operating cycles due to the fluid flowing into and out of the accumulator. This operation causes loading and relaxation separately by the separation element with respect to the gas supply in the accumulator. Overloading and local wrinkling of the material may then occur due to shearing stresses on the separation element and may result in tearing. Tearing would fundamentally make the accumulator useless and would require the hydraulic system to be shut down, at least partially, for replacement purposes. The known pressure accumulators and hydraulic accumulators can be used regularly only as an individual solution for a restricted range of applications in hydraulic systems because of their accumulator capacity and/or their damping characteristics. This restriction leads to a corresponding increase in costs at both the manufacturing end and the consumer end. 
     DE 197 43 007 A1 describes an accumulator of the pressure accumulator type, having a housing with a connection for a pressure medium in the manner of a hydraulic medium that can be stored in the housing. The housing contains a filling agent in the form of one or more hollow bodies filled with a pressure medium that can be compressed when a higher pressure prevails outside of the filling agent. 
     DE 695 15 899 T2 relates to an energy accumulator, among other things, formed from a rigid outer casing of two parts clamping a separation diaphragm. A heterogeneous structure for accumulation or dissipation of energy, having a capillary porous solid matrix surrounded by a lyophobic liquid, is provided in a compartment of the energy accumulator bordered by the separation diaphragm. The compartment is isolated from any contact with another hydraulic fluid. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide improved pressure accumulators, in particular in the form of hydraulic accumulators, while retaining the prior art advantages, namely to ensure a high accumulator capacity, to have a longer lifetime and to be adapted well to given application fields, based on their damping characteristics and/or accumulator capacity, accordingly, so that various applications are possible with only a few accumulator concepts to reduce costs. 
     According to the invention, this object is basically achieved by a pressure accumulator having at least one elastomeric separation element, preferably in the form of a separation diaphragm or a separation bladder, subdividing the accumulator housing into at least two working spaces. One working space accommodates the one pressure medium in the form of a liquid. The other working space accommodates the other pressure medium in the form of a working gas, such as nitrogen gas. The filling material is bordered or enclosed at least partially by the separation element. 
     A filling material having cavities and/or forming at least one cavity for at least partial accommodation of this pressure medium and/or at least one additional pressure medium is thus introduced at least partially into the accumulator housing. 
     The particular advantage of the pressure accumulator according to the invention is that, on flowing into the accumulator housing through the assignable housing opening, the pressure medium, that is to be controlled by the accumulator and that is usually in the form of hydraulic fluid or a working gas in a pneumatic application, encounters the filling material that has been introduced into the accumulator housing. Meanwhile, the accumulator housing is filled at least partially with the filling material, so the accumulator capacity of the accumulator for the respective application case can be adjusted in the case of a hydraulic or pneumatic system. Depending on the degree of filling with the filling material, one and the same accumulator, depending on its fundamental accumulator design, can be adapted for a variety of application cases in the aforementioned technical systems. Standardized accumulators can thus be mass produced and filled with different amounts of filling material. This ability leads to low manufacturing costs because of the benefits of mass production. For the first time, a delivered accumulator can be replaced with another accumulator filled to a different extent with filling material, so that the accumulator can be adapted to modified specifications of the system even on site, i.e. at the user&#39;s end, permitting cost reductions for the user&#39;s end to this extent. 
     To be able to adjust the accumulator capacity in the accumulator housing accordingly, the filling material may be introduced as a solid block into the accumulator with a predefinable volume, in particular introducing it by molding or injection molding. The filling material then leaves free a cavity, at least within the accumulator housing, which cavity defines the accumulator capacity of the accumulator and can be filled with the respective working medium (fluid and/or gas). Especially preferably, that filling material can be provided in the form of a cellular structure introduced into the respective accumulator housing of the pressure accumulator or hydraulic accumulator, wherein the filling material is designed to have cavities, possibly with closed pores, but preferably with open pores in its interior. The individual cavities then communicate primarily with one another through permeable fluid channels accordingly. The more the cavities are then integrated into the filling material and are formed by the filling material itself, the greater the increase in accumulator capacity of the accumulator modified in this way. 
     The two types of cavity design described above can also be combined with one another. 
     The cavity volume or hollow compartment volume, which is adjustable and introduced into the accumulator through the filling material, is also suitable for damping the respective medium penetrating accordingly. The damping characteristic of the accumulator can then be adjusted to this extent. In particular, the stiffness of the damping can be influenced in this way. A further adaptation to predefinable damping characteristics can be achieved if the filling material is designed to be at least partially flexible. A type of spring constant can then be stipulated as a damping constant at the manufacturing end for the respective pressure accumulator in a manner comparable to that with a compression spring. 
     In a particularly preferred embodiment, if the approach using the filling material according to the invention is used not only for conventional pressure accumulators in the form of gas bottles or other fluid storage bottles for conventional pressure accumulators, but instead is also used for hydraulic accumulators having a movable separation element arrangement, preferably formed from an elastomeric separation material, then the filling material or filling agent introduced into the pressure accumulator may serve to support the separation element, usually in the form of a separation bladder or in the form of a separation diaphragm in its movement. Because of the aforementioned, preferably elastic support by the filling material, overstressing in the separation element material is prevented, as are the negative effects of wrinkling, leading to designs with separation elements having a long service life, which in turn help to significantly increase the useful life or lifetime of the accumulator. Due to the delayed or limited admission of the pressure medium into the respective pressure accumulator, a homogeneous temperature profile can be developed inside the accumulator, which in turn protects the working medium, usually in the form of a hydraulic fluid or a pneumatic medium. 
     The filling material, with its cavities, is preferably formed from a sintered material and/or a cellular material such as foam, a gel or a woven or nonwoven textile or a comparable textile material. If the filling material inside the pressure accumulator does not need to be elastically flexible, for example, in the implementation of the pressure accumulator as a simple gas or other fluid storage bottle, the filling material may also be made of a sintered ceramic or metallic material or a gelatinous substance, which in a special embodiment can also allow input of the medium to be introduced into the accumulator in the form of a bubble feed. The cavities are created with the bubble feed. The gel more or less only on the introduction of medium into the accumulator. With a corresponding reduction in the working pressure on the input side of the accumulator, the bubble feed is then released again within the gelatinous substance, and the medium that is introduced can be returned to the hydraulic or pneumatic working cycle. 
     However, with the pronounced elastic characteristic of the filling material, advantageously the filling material is formed from an open-pore foam, preferably a polyurethane foam. If a textile material is used as the filling material, the textile material, in the form of a supporting structure or a supporting fabric, may serve as a backing for foam components, such as the aforementioned polyurethane foam, for example. On the whole, the filling agent or filling material can basically be used for such structures or substrates that have a high accumulator capacity accordingly, preferably having a sufficient elastic flexibility, and can be introduced well into the internal structure of the accumulator in a permanent and thermally stable form. 
     In a preferred embodiment of the approach using the pressure accumulator according to the invention, the density of the filling material inside the pressure accumulator can be varied, in particular having a cluster or sandwich-type structure. The respective change in density can preferably be provided in at least one direction of orientation, for example, in the direction of the longitudinal axis of the pressure accumulator. If the filling material is in the form of a foam, then the differences in density can be created by repeated injection or foaming. For example, a gradient-type design of the foam material would then be possible, such that a very dense material is used on the input end of the accumulator. Then, with open pores or with a lower density, the density changes rapidly in the direction of the opposite end of the accumulator housing. Instead of the pressure medium entering into the accumulator housing body, an increased resistance can then be built up in that the barrier property of the foam or some other filling material is increased accordingly. To ensure different densities and cavity structures, different filling materials can be used in some sections in the sense outlined above. 
     Advantageously, in particular, when the one working space can contain the pressure medium in the form of a fluid together with the filling material. Much higher pressure energies can be stored in the pressure accumulator with this configuration, if necessary. 
     More preferably, the separation element has the filling material on one of its two sides, preferably on the side adjacent to a pressure medium, preferably in the form of a liquid. The filling material is then at least partially in direct contact with the side of the separation element in that regard. Such contact provides a favorable influence on the deformation of the separation element, so that the deformation can be shifted into those regions, resulting in a longer lifetime of the separation element. Another possibility is using a corresponding filling material on both sides of the respective separation element, so that the accumulator values and the damping values on the gas side of the accumulator can be influenced. Depending on the design of the accumulator, however, other media can also be separated from one another by the respective separation element, for example, separating gas from gas or liquid from liquid. Furthermore, pasty or gelatinous media can also be stored there, depending on the accumulator capacity, and then retrieved from the accumulator cyclically. 
     The accumulator housing may be in multiple parts, in particular two parts. The accumulator housing parts that are joined together may secure the separation element in the accumulator housing. One accumulator housing part preferably has at least one connection for the one pressure medium, preferably in the form of a liquid. This arrangement has proven to be especially advantageous to manufacture. The accumulator housing parts may be manufactured as cast parts or as laminates. The separation element may then be disposed between the accumulator housing parts and secured there especially advantageously in welding the accumulator housing parts. By an additional connection in the accumulator housing, preferably disposed on the side opposite the first connection, the additional pressure element, preferably in the form of a working gas, may be checked, refilled and placed as needed. 
     In a further embodiment, the accumulator housing parts can be connected to one another by way of a threaded connection, preferably using a union nut. Meanwhile, the accumulator housing may be opened for inspection and repair purposes. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings that form a part of this disclosure and that are schematic and not to scale: 
         FIG. 1  is a side view in section of a diaphragm accumulator according to a first exemplary embodiment of the invention; 
         FIG. 2  is a side view in section of a diaphragm accumulator according to a second exemplary embodiment of the invention; and 
         FIG. 3  is a side view in section of a bladder accumulator according to a third exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a diaphragm accumulator  201 . The diaphragm accumulator  201  has an accumulator housing  203  having two rotationally symmetrical accumulator housing parts  205 ,  207  made of a metallic material. Openings  208 ,  209 , to which connections  211 ,  213  are welded, are provided in the accumulator housing parts  205 ,  207 . The connection  213 , at the top in the plane of the figure, is closed during operation by a removable stopper (not shown) or a screw. A dividing element  215  in the form of a dividing diaphragm made of an elastomer is disposed in the accumulator  203 . The separation diaphragm  215  has a peripheral edge bead  217  on its one end. The edge bead  217  of the separation diaphragm  215  is held in a form-fitting manner by a retaining ring  223  and a peripheral groove  225  in the lower accumulator housing part  205 . The retaining ring  223  is surrounded by a metal ring  227 . At the upper end of the retaining ring  223 , a beveled face  229  is formed. Furthermore, the metal ring  227  is inserted into a peripheral groove  231  having recessed outlets  233  at the edge. The metal ring  227  is disposed in the region  235  of the neighboring contact faces  237  of the accumulator housing parts  205 ,  207  and protects the sensitive dividing diaphragm  215  and the retaining ring  223  from thermal damage and/or welding splashes when welding the accumulator housing parts  205 ,  207  to one another. A piston-shaped valve body  239  having a central recess  241  on the bottom side  243  is provided in the separation diaphragm  215 . In the unloaded state of the diaphragm accumulator  201  illustrated, this valve body comes to rest against the fluid-side opening  208  of the lower accumulator housing part  205  to form a seal. 
     A lower first working space  245 , at the bottom in the plane of the figure, for a first pressure medium  221 , in particular a fluid such as a hydraulic fluid, is formed by the separation element  215 . Above that, a second working space  247  is provided and is filled with another pressure medium  249 , in particular a gas such as nitrogen (N 2 ), for example. In addition, an elastically compressible filling material  219 , in particular an open-pore polyurethane film, is in the second working space  249 . The filling material  219  supports the separation diaphragm  215  in its movement over the full surface, thereby preventing overloading or wrinkling of the separation diaphragm  215 , which overloading or wrinkling could otherwise shorten the lifetime of the separation diaphragm  215 . 
     The cavities and the foam filling material  219  are essentially interconnected, so that the additional pressure medium  249  can diffuse into the filling material  219 . The density of the filling material  219  determines how much of the additional pressure medium  249  can be accommodated in the second working space  247 . The damping characteristic of the diaphragm accumulator  201  is also partially determined by the compression characteristics of the filling material  219 . The damping becomes greater as the rigidity of the filling material  219  is greater. 
     The varying density profile of the filling material  219  is suggested by the different dashes in some sections. In the lower region  251 , the density is higher accordingly to additionally support the separation diaphragm  215 . 
     In a preferred embodiment of the hydraulic diaphragm accumulator (not shown here), the foam-type filling material may also be filled into individual sandwich-type layers. The density profile, and thus the damping properties, of the foam can be adjusted accurately in this way, in particular in the longitudinal direction LR of the accumulator. Furthermore, a homogeneous temperature profile is also achieved within the accumulator during operation, which profile protects the media introduced into the accumulator. 
       FIG. 2  shows another diaphragm accumulator  301 . This diaphragm accumulator  301  has an accumulator housing  303  with two accumulator housing parts  305 ,  307  made of the metallic materials that are generally used for this purpose. However, one or both of the accumulator housing parts  305 ,  307  can be manufactured from a plastic laminate. The accumulator housing parts  305 ,  307  can be joined by a threaded connection  309 . To do so, a shoulder  317  is provided on the upper accumulator housing part  307  with a type of clamp ring  323  serving as a union nut being placed on this shoulder. Between a peripheral edge bead  325  of a separation element  315 , a separation diaphragm, made of an elastomer here, is held in a form-fitting manner between the accumulator housing parts  305 ,  307 . A valve plate  339  is provided on the separation diaphragm  315 . In the unactuated state of the diaphragm accumulator  301  shown here, this valve plate covers an opening  327  in the accumulator housing part  305  at the bottom of the plane of the figure. 
     A first working space  345  for a first pressure medium  321  in the form of a fluid is formed by the separation diaphragm  315  in the lower accumulator housing part  305 . On the opposite side of the separation diaphragm  315 , a second working space  347  is filled with a second pressure medium  349  in the form of nitrogen and a filling material  319 . The filling material  319  fills the second working space uniformly in the drawing. The filling material  319  in the present case has two elastically compressible foam parts  329 ,  331  designed in the form of blocks. The lower foam part  329  has a higher density and thus has a greater damping effect. Due to the fact that the lower foam part  329  is in contact with the separation diaphragm  315 , the separation diaphragm  315  is supported in movement and the overstressing or wrinkling that shortens the lifetime is again prevented. The filling material  319  helps to ensure a more homogeneous temperature profile in the diaphragm accumulator  301  during operation. The first pressure medium  321  flowing into the first working space  347  is also protected in this way. An opening  333  in the upper accumulator housing part  307  is provided with an internal thread  335 , into which a replacement screw  337  is screwed. This thread and screw form a connection  313  covered on the outside by a screwed-on cap  341 . 
       FIG. 3  shows a bladder accumulator  401  as an additional approach to a hydraulic accumulator with a separation element. A separation element  415  in the form of an elastomeric separation bladder is disposed in a one-piece bottle-shaped accumulator housing  403 , which housing may also be made of a plastic laminate. The separation bladder  415  in the unactuated state is in the form of a rotational body having a uniform shape. The separation bladder  415  has a reinforcement  407  on one end  405  with a connection  413  incorporated into it and protruding out of the accumulator housing  403 , where it is sealed with respect to the outside by a closing stopper  408 . A cap  409  is placed on or screwed onto the connection  413 . The connection  413  is secured accordingly with a nut  417  on the outside  423  of the accumulator housing  403 . In addition, a plate  425  is secured with the nut  417  on the accumulator, which plate may have an inscription identifying the accumulator and/or manufacturer&#39;s information, for example. 
     A connection  411  with a valve  429  is provided at the other end  427  of the accumulator housing  403 . In addition, an accommodating part  433  is disposed on the inside  431  of the accumulator housing  403 , centering the part of the connection  411  that protrudes into the accumulator housing  403  and securing it accordingly. The outside wall  435  of the connection  411  is sealed by an O-ring gasket  437  with respect to the accumulator housing  403 . The connection  411  is secured on the outside  423  of the accumulator housing  403  by a centering ring  439  and a nut  441 . Supports  451  extending transversely are arranged in diametric opposition to one another, relative to the longitudinal axis of the accumulator in the interior  443  of the connection  411 , permanently limiting the fluid passage within the connection  411  and accommodating a bushing  453 . A rod-type valve body  459 , acted upon by a spring  457 , is guided through this bushing  453 . A valve disk  461  of the valve body  459  protrudes into the interior  463  of the accumulator housing  403 , so that the separation bladder  415  acts on the valve disk  461 . At maximum extension of bladder  415 , valve disk  461  comes into sealing contact with a valve seat  465  of the connection  411  against the action of the compression spring or return spring  457 . Furthermore, a screw  467  is provided in the outside wall  435  of the connection  411 , such that when the screw is removed, a corresponding fluid sensor (not shown) can be screwed into that connection  411 . 
     The accumulator housing  405  is again divided by the separation bladder  415  into a first working space  445  for a first pressure medium  421 , in particular a fluid, and a second working space  447  situated in the separation bladder  415  for a second pressure medium  449  in the form of nitrogen. The separation bladder  415  is filled by a filling material  419 . The filling material  419  is a thermally stable, elastically compressible low-density foam. A plurality of cavities with open pores is provided in the filling material  419 . The filling material  419  is in full surface contact with separation bladder  415 . The separation bladder  415  is supported in its movement in this way. Overloading of sections of the separation bladder  415  is prevented, along with wrinkling and its negative effects. In addition, the first working space  445  may be formed with an additional filling material, preferably in the form of a fluid-resistant foam, so that the diaphragm  415  can be supported in its movement in two opposite directions of movement during operation of the accumulator. 
     Meanwhile, the separation bladder  415  has a much longer lifetime than conventional approaches. On the whole, the bladder accumulator  401  according to the invention is therefore characterized by a longer lifetime, a greater accumulator capacity for compression energy and a better damping characteristic. 
     While various embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the claims.