Patent Publication Number: US-6988514-B2

Title: Hydroaccumulator, in a particular a bladder accumulator

Description:
FIELD OF THE INVENTION 
   The present invention relates to a hydroaccumulator, in particular a bladder accumulator, with a pressure tank and a separating element located in and separating a gas space from a fluid space in the pressure tank. The gas space borders a gas-side access. The fluid space borders a fluid-side access having a fluid connecting sleeve and a valve arrangement located in the connecting sleeve. The valve includes a valve body having at least one transverse hole and is normally pretensioned into its open position to clear the fluid passage, and can be moved into its closed position by the displacement of the separating element. The inside surface of the connecting sleeve for the valve body directly adjoining the valve body forms the guide for its displacement between the open position and the closed position. 
   BACKGROUND OF THE INVENTION 
   Hydraulic accumulators with valves operated by the separating element are commercially available. In the technical reference published by Mannesmann Rexroth GmbH “Hydraulic Guide Volume 1”, on page 165, a bladder accumulator of this type is depicted and described. In the known bladder accumulator, the valve arrangement comprises a seat valve. A conical surface is formed on the end edge of a connecting sleeve facing the fluid space to provide a stationary valve seat. The conical surface interacts with a corresponding conical surface on the valve plate of the movable valve body. The valve is made similarly to the control valves conventionally used in valve-controlled internal combustion engines, i.e., the valve plate is located on a shaft guided in a valve guide for the valve lifting motion between the open position and closed position. The valve guide is installed in the connecting sleeve. 
   The disadvantage is the resulting high production costs due to the required cost for producing and machining of a host of individual parts as a result of this known valve design. To ensure proper operation of the valve arrangement, the valve guide installed in the connecting sleeve must be made carefully with respect to production tolerances for both alignment and fit. Moreover the corresponding machining of the conical surfaces which form the valve seat is necessary. 
   PCT/WO 00/31420 discloses a generic hydraulic accumulator with a separating element formed from metal bellows. Within the bellows is a compression spring which keeps the separating element in the pretensioned state. On its bottom, the bellows is provided with an end plate which interacts with a valve body accommodated in the fluid connecting sleeve of the housing of the known hydraulic accumulator and held under spring pretension. The valve body is made as a valve lifter and is larger in dimensions in its lengthwise alignment than in the transverse direction. Thus, the known valve body occupies considerable space in its direction of displacement in the connecting sleeve. The end of the valve body interacting with the end plate is made dome-like. In conjunction with the different diameters, grooves and recesses, beveled surfaces and the transverse hole on the other end of the valve body, a resulting complex geometry requires a complex and costly machining process in production. The complex geometrical structure of the closing body continues in the area of the fluid guide. As a result of the repeated deflection of the fluid flow, especially in the area of the incident flow of the medium into the fluid space, unfavorable flow behavior is implemented so that the known approach to hydraulic accumulators with sensitive membrane bladders is not suitable. U.S. Pat. No. 4,068,684 discloses a generic hydraulic accumulator. In the known approach, the spring-loaded valve body is a sleeve-shaped plug neck with a height measured in the direction of displacement of the valve body. The height is several times larger than its diameter. The valve body is formed on its side facing the separating element as a plate. The plate is flat. Its sleeve-like outside jacket has transverse holes diametrically opposite one another and connected to the fluid side of the hydraulic accumulator in the open position of the valve to carry fluid. The known valve body approach accordingly has a very large structure in the axial direction of the hydraulic accumulator. Due to the fluid-carrying transverse holes, the flow behavior cannot be choked and is consequently unfavorable in the area of inflow of the medium into the fluid space. 
   SUMMARY OF THE INVENTION 
   Objects of the present invention are to provide a hydraulic accumulator where the valve body occupies little space, is geometrically simple in structure, can be economically implemented, and allows optimized flow behavior in the area of the flow into the fluid space. 
   By virtue of the diameter of the valve body being larger than its height measured in the direction of displacement of the valve and because the respective transverse hole in the valve piston is made as a fluid channel, the valve arrangement is made in the manner of a plate valve occupying little space and can be economically implemented. The respective fluid channel is integrated into the interior of the valve body allowing controlled triggering of the fluid flow. The fluid channels can be chosen in terms of their number and cross-sectional size. As fluid passes, the desired choking takes place, with the possibility of stipulating the damping conditions which are optimum when the hydraulic accumulator is in operation, depending on the intended application. 
   By integrating the fluid channels into the interior of the valve body, complex machining for differentiated shaping of the outside surface of the valve body, as in the known approaches, is unnecessary. Moreover, by means of the respective fluid channels, a homogeneous outflow behavior of the fluid into the fluid space is ensured. Especially when a bladder accumulator is implemented, flow then takes place carefully around the separating membrane which is sensitive to pressure peaks and which ordinarily is formed of a rubber-elastic material. This arrangement leads to an increased service life for the hydraulic accumulator of the present invention. 
   Production is especially simple if the valve arrangement is a sliding valve, with the connecting sleeve being used as the valve housing and with its circular cylindrical inside surface defining the piston bore for the valve body which is made as a sliding piston. 
   In these embodiments, the end edge of the piston bore of the connecting sleeve, which edge borders the fluid space, forms the control edge for clearing and closing one or more fluid channels of the sliding piston. 
   The piston bore which guides the sliding piston can preferably have, on its end area adjacent to the fluid space, a tapered hole section. An annular shoulder surface is then formed, which in interaction with an opposing shoulder surface which projects radially on the sliding piston, forms a stop against which the sliding piston rests in the open position of the valve. 
   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 which form a part of this disclosure: 
       FIG. 1  is a partial, side elevational view in section of a bladder accumulator according to a first embodiment of the present invention, with only the part of the accumulator adjacent to the fluid-side connecting sleeve being illustrated and with the valve arrangement illustrated in the open position; 
       FIG. 2  is a side elevational view in section of only the fluid connecting sleeve of a bladder accumulator according to a second embodiment of the present invention, on a much larger scale compared to  FIG. 1 , with the valve arrangement illustrated in the closed position; and 
       FIG. 3  is a partial, side elevational view in section of a bladder accumulator according to a third embodiment of the present invention on the left side and according to a fourth embodiment of the present invention on the right side, with the valve arrangement being shown in the open position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , only the section of the pressure tank adjacent to the fluid-side access  3  is shown. The opposite end area (not shown) of the pressure tank  1  has a conventionally configured gas-side access to the interior space of a storage bladder  5  (only schematically illustrated in FIG.  3 ). Storage bladder  5  forms the movable separating element separating the gas space  7  from the fluid space  9  in the interior of the pressure tank. 
   In the embodiment shown in  FIG. 1 , the fluid-side access  3  comprises a fluid connecting sleeve  11  welded onto the end wall of the pressure tank  1  adjacent to the fluid space  9 . The connecting sleeve  11  is a circularly cylindrical sleeve and has an inside thread  13  on its outer free end for the connection of a fluid line (not shown). In the end area adjacent to the fluid space  9 , the connecting sleeve  11  forms a piston bore  15  in which a sliding piston  17  is movably guided. The connecting sleeve  11  thus forms the valve housing for a sliding valve with the sliding piston  17  used as the movable valve body and guided on the inside surface of the piston bore  15  of the connecting sleeve  11  directly for its displacement along the lengthwise axis  19  of the piston bore  15 . Sliding piston  17  can be moved between the open position shown in  FIGS. 1 and 3 , and the closed position shown in FIG.  2 . 
   The sliding piston  17  is pretensioned by a helical compression spring  21  into the open position shown in  FIGS. 1 and 3 . From this position, the sliding piston can be moved with the corresponding expansion of the storage bladder  5  against the force of the compression spring  21  into the closed position shown in  FIG. 2  when the storage bladder presses against the top  23  of the accumulator sliding piston  17 . 
   The compression spring  21  is supported with its end facing away from the sliding piston  17  on a support plate  25 . The support plate adjoins a shoulder located on the adjacent end of the piston bore  15  in the connecting sleeve  11 . In the embodiment of  FIG. 1 , support plate  25  is held by a retaining ring  27 . In the second embodiment of  FIG. 2 , the support plate  25  is secured by a flat snap ring  29 . Aside from this difference, the embodiment of  FIG. 2  corresponds to that of FIG.  1 . 
   The compression spring  21  is tensioned between the support plate  25  and the sliding piston  17 , and extends into an axial hole  31  in the sliding piston  17  from its end facing away from the fluid space  9 . Axial hole  31  is concentric to the lengthwise axis  19 , and discharges into transverse holes  33  in the sliding piston  17 . These transverse holes extend radially in the vicinity of the top  23  of the sliding piston  17 , and at a right angle to one another so that they intersect on the lengthwise axis  19 . These transverse holes  33  in the sliding piston  17  form fluid channels which interact with the valve control edge and which form the fluid access to the fluid space  9 , by way of the axial hole  31  of the sliding piston  17  and the through holes  35  in the support plate  25  when the sliding piston is in the open position shown in  FIGS. 1 and 3 . 
   In the position of the sliding piston  17  shown in  FIG. 2 , the orifices of the transverse hole  33  are closed by the control edge of the connecting sleeve  11  used as the valve housing. The control edge is formed on the sleeve upper end edge  37 , see FIG.  2 . As shown in  FIG. 2 , the piston bore  15  in its end section forms a tapered bore section with an annular shoulder surface  39 . Shoulder surface  39  interacts with an opposing shoulder surface  41  on the sliding piston  17  (see  FIG. 2 ) forming a stop limiting the displacement of the sliding piston  17  in the direction to the fluid space  9 .  FIG. 1  shows the corresponding position of the sliding piston  17  fixed by this stop. 
   In the two embodiments shown in  FIG. 3 , the support plate  25 , formed as an abutment for the compression spring  21 , is provided with an outside thread and is screwed into an inside thread  13  formed in the connecting sleeve  11 . 
   In the embodiment shown on the left side in  FIG. 3 , the connecting sleeve  11  in the section adjacent to the end edge  37  has an outside thread  43  which is screwed to the corresponding inside thread of the wall of the pressure tank  1 . The wall thickness of the pressure tank  1  is made greater in the threaded area for this purpose. 
   The embodiment shown on the right side in  FIG. 3  has a connecting sleeve  11  which is molded on the pressure tank  1  in one piece by hot or cold forming. Otherwise, the right side embodiment does not differ from the embodiment shown on the left side in the same figure. 
   The invention is described above using embodiments in the form of bladder accumulators. The invention can be equally used advantageously in hydraulic accumulators of a different design, for example in membrane accumulators or piston accumulators. 
   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 appended claims.