Patent Publication Number: US-6669180-B2

Title: Gas-hydraulic shock absorber assembly

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a gas-hydraulic shock absorber assembly, particularly for push and/or pull devices of rail vehicles. It comprises a sleeve member, a ram member movable relative to the sleeve member, a gas chamber located in the sleeve member or in the ram member and adapted to be pressurized by means of a gaseous medium, and an oil chamber located in the ram member or in the sleeve member and containing a hydraulic medium. 
     Gas-hydraulic shock absorber assemblies to be used in push devices or pull devices of rail vehicles are well known in the prior art, for instance in the form of so-called bumpers. However, a shock absorber assembly designed according to the invention can also be used for example in couplings of rail vehicles, particularly couplings adapted to interconnect a plurality of rail vehicles. 
     In known gas-hydraulic shock absorber assemblies having no physical separation means to separate the gaseous and fluid media, the fundamental danger is present that gaseous medium collects in the fluid chamber after a certain period of use; of course, this is highly undesirable because it can impair the proper function of the shock absorber assembly, even lead to malfunction thereof. For example, too much gaseous medium in the fluid chamber can lead to an undefined or insufficient resilient behavior e.g. of a rail vehicle bumper. Particularly, if such a bumper is hit very hard, there is a high danger that gaseous medium enters the fluid chamber. 
     OBJECTS OF THE INVENTION 
     Thus, it is an object of the invention to provide a gas-hydraulic shock absorber assembly of the kind mentioned herein before which bleeds itself during its operation by automatically recycle any gaseous medium that may have collected in the fluid chamber to the gas chamber. 
     SUMMARY OF THE INVENTION 
     In order to meet this and other objects, the present invention provides a gas-hydraulic shock absorber assembly, particularly for push and/or pull devices of rail vehicles. It comprises a sleeve member, a ram member movable relative to the sleeve member, a gas chamber located in the sleeve member or in the ram member and adapted to be pressurized by means of a gaseous medium, and an oil chamber located in the ram member or in the sleeve member and containing a hydraulic medium. 
     Further, the shock absorber assembly comprises a gas-hydraulic control assembly arranged between the gas chamber and the oil chamber, and a bleeding assembly, incorporating a transfer channel opening into an upper portion of the oil chamber and providing a communication between the oil chamber and the gas chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, an embodiment of the shock absorber assembly according to the invention will be further described, with reference to the accompanying drawings, in which: 
     FIG. 1 shows a longitudinal sectional view of the gas-hydraulic shock absorber assembly in the form of a bumper; and 
     FIG. 2 shows a perspective view of a bleeding assembly. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     The general design of an assembly according to the invention will now be further explained with the help of FIG. 1, showing a longitudinal sectional view of a gas-hydraulic shock absorber assembly in the form of a bumper incorporating a bleeding assembly designed in accordance with the invention. It is to be noted that the bumper is shown in FIG. 1 in its released state, i.e. no load force acting on it. 
     The bumper comprises a bumper sleeve  1  to be connected to a rail vehicle (not shown), as well as a bumper ram member  2  including an outer ram member tube  4 , an inner plunger tube  5  and a bumper head member  3 . Both the ram member tube  4  and the plunger tube  5  are operationally connected to the bumper head member  3 . The end of the plunger tube  5  facing the rail vehicle is provided with a flange member  6 . The interior of the plunger tube  5  constitutes a gas chamber  8  adapted to contain a gaseous medium pressurized to 5-20 bar as well as a portion of a hydraulic medium. 
     In the interior of the bumper sleeve  1 , an oil chamber  9  is constituted. In the released state of the bumper, as shown in FIG. 1, the gas chamber  8  is partially filled with a hydraulic medium, while the oil chamber  9  is entirely filled with the hydraulic medium. The flange member  6  constitutes, together with a valve assembly  13 , a gas-hydraulic control device  12 , controlling the flow rate of the hydraulic medium from the oil chamber  9  into the gas chamber  8  in relation to the load force applied to the bumper head  3  during the compression of the bumper. 
     The valve body member  13   a  of the valve assembly  13  is biased in the direction towards the oil chamber  9 , due to the overpressure present in the gas chamber  8 . The flange  6  comprises an annular projection  17  located at its right side, i.e. facing the oil chamber  9 . This annular projection  17  operates, together with channels, recesses, bores, valves and a transfer channel  21 , as a bleeding assembly  7 . The transfer channel  21 , located outside the oil chamber  9  in the wall of the bumper sleeve  1 , is provided at both of its ends with a bore  22 ,  23  radially opening into the oil chamber  9 . One of the bores, i.e. the bore  22 , radially opens into the upper portion of the oil chamber  9  at the side thereof facing the control device  12 , while the other bore  23  radially opens into the upper portion of the oil chamber  9  at the side thereof remote from the control device  12 . The assembly being in its rest or released position, as shown in FIG. 1, the transfer channel  21  is connected to the control device  12  at its side facing the control device  12  via a bleeding channel  16 . Thus, it is ensured that any gas that may have collected in the rear upper portion of the oil chamber  9  can escape from the rear upper portion of the oil chamber  9  through the transfer channel  21  upon subjecting the bumper to a load. The design and the operation of the of the bleeding assembly  7  will be further explained herein below. 
     The flange  6  is provided with a central recess, located adjacent to the valve assembly  13 , to form a chamber  15 . From this chamber  15 , a bleeding channel  16  runs radially inclined upwards to the left side of the annular projection  17 , where it opens into the oil chamber  9 . Between the annular projection  17  of the flange  6  and the wall  10  of the oil chamber  9 , there is an annular gap  18 . Upon subjecting the bumper to a load force, thereby causing the bumper head  3  and its associated elements to move to the right, as seen in FIG. 1, oil and, if appropriate, gas that may have collected in the upper portion of the oil chamber  9  flow through the annular gap  18  to the left side of the annular projection  17 . Therefrom, it can flow via the bleeding channel  16  into the chamber  15  and via the valve body member  13   a , being released under the influence of the now existing overpressure, into the gas chamber  8 . As already mentioned, the upper portion of the oil chamber  9 , remote from the control device  12 , communicates via the transfer channel  21  and the bleeding channel  16  with the control device  12 , with the result that any gas collected in the rear portion of the oil chamber  9  can flow via the rear radial bore  23  into the real transfer channel  21  and, therefrom, via the front radial bore  22  into the bleeding channel  16 . Finally, the gas can flow from the bleeding channel  16  through the open valve assembly back into the gas chamber  8 . As the bumper ram member  2  is further moved to the right, one end of the transfer channel  21  is closed because the inner plunger tube  5  is moved into a position in front of the front radial bore  22  of the transfer channel  21 . 
     A further channel  20 , directly connecting the oil chamber  9  to the chamber  15 , is only partially shown in FIG.  1 . In the interior of this channel  20 , a valve flap  19  is provided which closes the channel  20  once the bumper is in its rest position. In all, four of such channels  20  are provided, each having an associated valve flap  19 ; further explanation referring thereto will be given herein after with regard to FIG.  2 . 
     In FIG. 2, the bleeding assembly  7  is shown in a perspective view. Clearly visible in FIG. 2 are the four channels  20   a ,  20   b ,  20   c  and  20   d , provided in the flange member  6 , and incorporating each a V-shaped valve flap  19   a ,  19   b ,  19   c  and  19   d . Each of these valve flaps  19   a ,  19   b ,  19   c  and  19   d  comprises two legs, whereby in the following reference is made, for simplicity&#39;s sake, only to the legs  24 ,  25  of the valve flap  19   a . The two legs  24 ,  25  of the valve flaps  19   a-d  resiliently rest against the walls of the channels  20   a - 20   d , if the bumper is in its rest position, as shown in FIGS. 1 and 2. Thereby, each of the valve flaps  19   a - 19   d  seal the associated channel  20   a - 20   d . Under the influence of the overpressure generated in the oil chamber  9 , caused by a quick compression of the bumper and urging the bumper ram member  2  to move to the right, the two legs  24 ,  25  are resiliently bent towards each other, with the result that a passage is created in the associated channel  20  through which the oil repressed from the oil chamber  9  can flow into the central chamber  15 . 
     The bleeding channel  16 , running essentially radially through the flange member  6 , is also shown in FIG.  2 . The inner diameter of the oil chamber  9  decreases towards the right side, i.e. towards the vehicle, with the result that the annular gap  18  between the annular projection  17  and the wall of the oil chamber  9  gradually decreases when the bumper ram member  2  is moved to the right side. 
     The operation of the bleeding assembly may be explained as follows: 
     Upon subjecting the bumper to a load, the outer ram member tube  4  as well as the inner plunger tube  5  and the flange  6  is moved to the right, as seen in FIG.  1 . Thereby, oil and, if appropriate, gas that may have collected in the upper portion of the oil chamber  9  flow from the oil chamber  9  through the annular gap  18  to the left side of the annular projection  17  of the flange member  6 . Due to the overpressure existing in the oil chamber  9 , the gas is repressed into the chamber  15  via the bleeding channel  16  opening into the upper portion of the oil chamber  9 ; therefrom, it flows through the valve assembly  13  into the gas chamber  8 . Since the four channels  20   a ,  20   b ,  20   c  and  20   d  provided in the flange member  6  are closed each by one of the valve flaps  19   a ,  19   b ,  19   c  and  19   d , respectively, when the bumper is in its rest position, a ram pressure is generated upon moving the bumper ram member  2  and the plunger tube  5  including the flange member  6  to the right; the result is that the gas to be repressed from the oil chamber  9  compellingly escapes through the bleeding channel  16 , even if the movement to the right of the above mentioned elements is slow. 
     Due to the difference of the specific gravity of gas and oil and due to the fact that high acceleration values occur if the bumper is hit by another rail vehicle, the gas is collected in the upper rear portion of the oil chamber  9  upon a hit. The quick movement of the bumper ram member  2  to the right also causes a high pressure differential between oil chamber  9  and the left side of the annular projection  17 . This pressure differential initiates a current flowing in the transfer channel  21  which displaces the gas from the rear portion of the oil chamber  9 , remote from the flange  6 , into the gas chamber  8  within a very short period of time. 
     During high moving speeds of the bumper ram member  2 , a correspondingly high overpressure is generated in the oil chamber  9 . That high overpressure causes the two legs  24 ,  25  of the valve flaps  19   a - 19   d  to resiliently bend towards each other, with the result that the oil can pass the valve flaps  19   a - 19   d  and flow through the channels  20   a - 20   d  without substantial drag. Thus, upon a high moving speed of the bumper ram member  2 , the oil can flow from the oil chamber  9  to the chamber  15  through all channels  16 ,  20   a ,  20   b ,  20   c  and  20   d . However, upon a low moving speed of the bumper ram member  2 , the gas collected in the oil chamber  9  compellingly flows through the bleeding channel  16  into the chamber  15 . 
     The bleeding assembly  7  according to the present invention is of simple design and can be manufactured at low costs. The V-shaped valve flaps  19   a ,  19   b ,  19   c  and  19   d  show the advantage that they incur only a very low drag to the oil flowing through the channels  20  upon high moving speeds of the bumper ram member  2 .