Abstract:
A hydraulic accumulator includes an accumulator housing ( 1 ), in which a bellows ( 21 ) having a selectable number of pleats ( 23 ) forms a mobile separation element between the gas side ( 25 ) and the fluid side ( 13 ). A distancing device ( 33 ) is arranged inside the accumulator housing ( 1 ), and is fluidically connected to the inside of the bellows ( 21 ) or abuts the bellows ( 21 ), forming an additional medium chamber.

Description:
FIELD OF THE INVENTION 
     The invention relates to a hydraulic accumulator in the form of a bellows accumulator, having an accumulator housing with a bellows inside the housing. The bellows, has a preselectable number of pleats, and forms a movable separation element between the gas side and the fluid side inside the housing. 
     BACKGROUND OF THE INVENTION 
     Hydraulic accumulators having bellows serving as a movable separation element are known and are used in various technical fields, for example, in hydraulic brake systems for motor vehicles and in a wide variety of industrial hydraulic systems. For example, DE 10 2008 061 221 A1 discloses a bellows accumulator, in which a metal bellows is provided as the movable separation element between the gas side and the fluid side. 
     Bellows accumulators are characterized by many advantageous properties. For example, relatively great changes in volume of the media spaces in the accumulator housing can be implemented by expanding and contracting the bellows. Metal bellows provided as the movable separation element are also relatively robust with respect to alternating loads, such as those that may occur during operation, in particular in use as a pulsating damper. They also have good sealing properties without any diffusion losses. However, these properties must be balanced against the fact that metal bellows, which may be considered for use in hydraulic accumulators, are relatively expensive components, so that manufacturing the bellows accumulators is relatively cost intensive. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved bellows accumulator that can be manufactured inexpensively and economically. 
     According to the invention, this object is basically achieved by a bellows accumulator having a spacer device disposed inside the accumulator housing and in fluid connection with the interior of the bellows. The spacer device forms an additional media space or is adjacent to the bellows. A desired total volume of the working spaces in the accumulator housing can be implemented through pleated bellows having smaller dimensions and a smaller number of pleats. By the spacer device in addition to the volume of the working space forming the interior of the bellows in its working movements or lifting movements and depending on the geometry and the number of the bellows behaviors, this structure yields a significant reduction in manufacturing costs. Another advantage is that, due to the different choice of the size of the additional volume made available by the spacer device, different total volumes can be implemented with bellows of the same number of pleats. Due to the possibility of using similar bellows for hydraulic accumulators of different specifications, this structure opens the possibility of a further cost reduction due to the use of bellows, which bellows conform to a standard size and can thus be manufactured economically and inexpensively in larger numbers. 
     In advantageous exemplary embodiments, the spacer device is in the form of a pot mounted with a fluid-tight connection, with its opening on an open end of the bellows. A suitably selected depth of the pot can easily provide the desired additional volume in this way. 
     The arrangement may advantageously be made so that the pot is held immovably axially in the accumulator housing and forms the attachment point for the immovable end of the bellows at its opening. 
     Alternatively, however, the pot may be disposed as a movable element on the movable end of the bellows. Its immovable end may be secured on the accumulator housing in this case. 
     In both cases, the interior of the bellows may be assigned to the gas side in a particularly advantageous manner. The volume of the additional media space formed by the pot, together with the interior of the bellows, then forms the volume of the gas side. A large volume of working gas, accordingly, is available for operation of the hydraulic accumulator. 
     In preferred exemplary embodiments, with the pot disposed so that it is axially immovable, its bottom is at one end of the accumulator housing and has a gas filling connection for a working gas. 
     In exemplary embodiments, in which the pot is connected to the movable end of the bellows, the immovable end of the bellows may be secured on a housing part situated at one end of the accumulator housing, where a gas filling connection for working gas is provided. 
     In advantageous exemplary embodiments, a housing end part may be provided on the end of the accumulator housing opposite the end having the gas filling connection. This housing end part then delimits the fluid side, which fluid side is on the outside of the bellows and has a fluid connection. 
     The housing end part may especially advantageously form a stop limiting the movements of the bellows to a stroke corresponding to a predefined maximum volume comprised of the volume of the interior of the bellows and the additional volume of the pot. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the drawings, discloses preferred embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings that form a part of this disclosure: 
         FIG. 1  is a side view, partially in section, of a hydraulic accumulator according to a first exemplary embodiment of the invention; 
         FIG. 2  is a side view, partially in section, of a hydraulic accumulator according to a second exemplary embodiment of the invention; 
         FIG. 3  is a side view, partially in section, of a hydraulic accumulator according to a third exemplary embodiment of the invention; and 
         FIG. 4  is a side view, partially in section, of a hydraulic accumulator according to a fourth exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The exemplary embodiments illustrated in  FIGS. 1 and 2  have an accumulator housing  1  that has a cylindrical interior and is closed on the end  3  (at the top of the drawing), except for a central opening  5 . At the lower end  7 , the accumulator housing  1  is closed by a housing end part  9  that has a centrally positioned fluid connection  11  leading to the fluid side or chamber  13  in the interior. The end part  9  is secured by a snap ring  15  and is sealed with respect to the accumulator housing  1  by a sealing element  17 . The housing end part  9  is in the form of a flat plate with an elastomeric ring element  19  disposed in an annular groove in the plane facing the interior. The ring element  19  protrudes slightly above the plane of the end part  9 . 
     In the interior of the accumulator housing  1 , a metal bellows  21  having a predefined number of bellows pleats  23 , only some of which are labeled in the figures, forms the separation element between the fluid side  13  and a gas side or chamber  25 . The bellows  21  is open at the end  27  at the top in the drawing and is closed at its other lower end  29 , such that in the exemplary embodiment in  FIG. 1 , an end part  31  is in the form of a thin plate connected to the last bellows pleat  23  on the movable end  29  of the bellows  21 . In the exemplary embodiment of  FIG. 1 , the bellows  21  is connected at its other open end  27  to a spacer device, which is in the form of a pot  33  secured in the accumulator housing  1  so that it is immovable axially. The pot  33  is connected to the last pleat  23  of the bellows  21  at the edge  35  of its opening, so that the interior of the pot  33  is in fluid connection with the interior of the bellows  21 , and thus, forms an extra volume in addition to the volume of the bellows  21 . At the same time, the opening edge  35  of the pot  33  forms the locking point for the immovable end  27  of the bellows  21 . The pot  33 , which is sealed by a sealing element  37  on the outside with respect to the accumulator housing  1 , has a gas filling connection  39  on the bottom or base  43  of the pot, which connection is accessible through the opening  5  in the accumulator housing  1 . In the operating state illustrated in  FIG. 1 , in which a prestressing pressure prevails on the gas side  25 , and thus, inside the pot  33  and in the interior of the bellows  21 , and the fluid side  13  is pressureless, the housing end part  9  forms a stop to limit the stroke for the end part  31  on the movable end  29  of the bellows  21 . The ring element  19  on the end part  9  then forms a flexible contact point. 
     The example of  FIG. 2  differs from the prior art inasmuch as the immovable open end  27 , which is at the top in the figure, is no longer connected to the spacer device. Instead, open end  27  is secured on a housing part  41  situated at the upper end  3  of the accumulator housing  1 . As the pot  33  of the first exemplary embodiment housing part  41  is sealed by a sealing element  37 . In a manner similar to that with the pot  33  of the first exemplary embodiment, a gas filling connection  39  is accessible through the opening  5  and is situated in the housing part  41  in its central part. Unlike the example from  FIG. 1 , a pot  33  serving as the spacer device is not mounted on the immovable end  27 , but is on the movable end  29  of the bellows. The pot  33 , as a component that is movable with the bellows  21 , is designed with thin walls and comes to rest against the flexible ring element  19  of the housing end part  9  with the pot bottom  43  at the maximum stroke of the bellows  21  to limit the stroke. 
     The exemplary embodiment of  FIG. 3  differs from the example of  FIG. 1  only inasmuch as the accumulator housing  1  is in the form of a tube, which is continuous on the inside from the lower end  7  to the upper end  3 . In the first exemplary embodiment of  FIG. 1 , the pot  33  forming the additional volume of the bellows  21  is supported on the closed upper end  3  of the accumulator housing  1 . In the example of  FIG. 3 , the pot  33  is secured by a snap ring  61  on the upper open tube end  3  of the accumulator housing  1 . 
     The example of  FIG. 4  corresponds to the exemplary embodiment of  FIG. 2 , except for the fact that the accumulator housing  1  is again designed as a tubular body. Accordingly, the housing part  41 , which is connected to the immovable end  27 , is secured axially on the open tube end  3  of the accumulator housing  1  by a snap ring  61 . 
     Manufacturing the accumulator housing  1  from a tube body permits a particularly simple, economical and inexpensive production of the bellows accumulator. 
     Hydraulic accumulators of various specifications according to the invention can be designed with bellows  21  having the same number of bellows pleats  23 , by preselecting a minimum volume through the choice of the depth of the respective pot  33 . This volume then corresponds essentially to the volume of the pot  33  with the bellows  21  compressed. On the other hand, the maximum volume of the other media space, which is on the outside of the compressed bellows  21 , is predetermined through the choice of the axial length of the accumulator housing  1 . 
     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.