Abstract:
A device for increasing shock absorption by hydraulic means in the terminal section ( 19  &amp;  27 ) of hydraulic shock absorbers with a shock-absorption piston ( 3 ) that divides the shock absorber into two compartments. The width of a channel that conveys hydraulic fluid through the piston is reduced by partly blocking the access of fluid thereto. The access comprises several individual accesses that do not mutually communicate. To ensure precise and constant increased shock absorption in the vicinity of the buffers, one or more individual accesses are completely blocked.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a device for increasing shock absorption by hydraulic means in the terminal section of hydraulic shock absorbers. Devices of this genus are called decompression-stroke buffers and compression-stroke buffers. 
     Decompression-and-compression stroke buffers are employed to prevent the dynamics piston in a hydraulic shock absorber from traveling all the way to the end of its stroke unbraked, It has been demonstrated practical to provide such devices with hydraulic means. The entrance that the fluid enters the piston through at the end of its stroke is accordingly partly blocked by flat or pot-shaped caps. Since these structures are mounted on springs, the shock absorption at the end of the stroke will be increased. 
     Hydraulic decompression-and-compression stroke buffers are known from the German reference Reimpeil &amp; Stoll, Fahrwerktechnik: Stoβ- und Schwingungsdämpfer, pages 188 to 188. They have a drawback. The evident fluid-intake surfaces, bores in the event, are partly blocked, leaving crescent-shaped open cross-sections. Tolerance, displacement, and other factors make it impossible to ensure that these cross-sections will remain precise. This particular shape makes the volume of incoming fluid and hence the level of shock absorption in the vicinity of the decompression-and-compression stroke buffer highly unstable. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is accordingly to ensure precise and constant supplementary shock absorption in the vicinity of the hydraulic buffers. 
     The advantage of the present invention is that the precise and constant shock absorption can be reliably attained with simple components. 
     One particular advantage of the present invention over the prior art is that the different resilient washers or stacks thereof allow the characteristic at the exit from the decompression-and-compression stroke shock absorption intake piston to be adjusted to attain maximal or minimal absorption forces, ascending gradients, and start-up behavior as necessary, generating reproducible absorption forces while the vehicle is in operation, leading in turn to calculable performance, and contributing to safe driving. 
    
    
     One embodiment of the present invention will now be specified with reference to the accompanying drawing, wherein 
     FIG. 1 illustrates a hydraulic decompression-stroke buffer out of operation, 
     FIG. 2 a hydraulic decompression-stroke buffer in operation, 
     FIG. 3 a hydraulic compression-stroke buffer out of operation, 
     FIG. 4 a hydraulic compression-stroke buffer in operation, 
     FIG. 5 a hydraulic decompression-and-compression stroke buffer out-of operation, 
     FIG. 6 a hydraulic decompression-and-compression stroke buffer with the decompression-stroke buffer in operation, 
     FIG. 7 a hydraulic decompression-and-compression stroke buffer with the compression-stroke buffer in operation, 
     FIG. 8 the decompression-stroke buffer illustrated in FIG. 1 operating soft, and 
     FIG. 9 the decompression-stroke buffer illustrated in FIG. 3 operating soft. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hydraulic shock absorbers, especially those employed in motor vehicles, include a cylinder  1 , a shock-absorption piston  3 , and at least one dynamics piston  4 . Pistons  3  and  4  are mounted on the leading end of a piston rod  2  that travels back and forth inside cylinder  1 . The cylinder is completely occupied by shock-absorption fluid and divided by the pistons into two compartments  5  and  6 . The device also includes resilient washers . 7  and  8  or stacks thereof that act as valves, resilient washer or stack  7  when dynamics piston  4  travels in one direction and resilient washer or stack  8  when it travels in the other direction and accordingly generate the desired shock-absorption forces by alternately blocking the exits of individual non-connected sections of fluid-conveying channels  9  and  10  that extend through dynamics piston  4 . Channels  9  and  10  are conventionally equal in number, shape, and diameter. They differ in the present case in that they slope at a different angle to the longitudinal axis of piston rod  2 . This feature allows resilient washers  7  and  8  to block only the, inner, exits of channels  9  and  10 , while leaving the, outer, entrances open. Dynamics pistons of other designs, and other types of valve, finger-shaped for example, can alternatively be employed. 
     FIGS. 1 and 2 illustrate a hydraulic decompression-stroke buffer. Mounted on the end of piston rod  2  next to dynamics piston  4  is a fluid-intake piston  11  of the identical design. The exits of the fluid-conveying channels or flow surfaces  12  and  13  are blocked by resilient washers  14  and  15 . The resilient washer  14  in fluid-intake  11  that faces away from dynamics piston  4 , however, is provided with ports  16 . A compression spring  17  at the emerging end of the piston rod rests against cylinder  1  at the outer end of the piston rod  1 . Mounted on the other end is a cover with a cover plate or a cap  18 . 
     FIG. 1 represents piston rod  2  and shock-absorption piston  3  in their dynamics state, the shock absorber in normal operation. FIG. 1 illustrates the situation with the hydraulic fluid flowing in the decompression direction with piston rod  2  leaving cylinder  1 . The pressure in upper compartment  5  is higher than the pressure in lower compartment  6 , forcing fluid out of the upper and into the lower compartment. Since the upper resilient washer  14  in fluid-intake piston  11  is provided with the aforesaid ports  16 , the fluid can reach unimpeded the entrances into dynamics piston  4  through the fluid-conveying channel  12  in fluid-intake piston  11  until shock-absorption piston  3  arrives in the terminal section  19  of the device occupied by compression spring  17 , The dynamic shock absorption in the decompression direction is controlled by the structure of the resilient washer  8  on dynamics piston  4 . 
     Once shock-absorption piston  3  has arrived in the section  19  reserved for the hydraulic decompression-stroke buffer as represented in FIG. 2 with fluid-intake piston  11  resting against cap  18  over compression spring  17 , the intake opening in the fluid-conveying channel  12  in fluid-intake piston  11  will be blocked as cap  18  closes the ports  16  through resilient washer  14 . The fluid will accordingly flow through the fluid-conveying channel  13  that extends in from the outside through fluid-intake piston  11  and is blocked by resilient washer  15 . The fluid will then flow into the intake opening into the fluid-conveying channel  9  in dynamics piston  4  through intermediate space  20 . Since resilient washers  15  and  8  generate impedance, the hydraulic shock absorption in terminal section  19  will be facilitated along with the operation of the decompression-stroke buffer. 
     FIGS. 3 and 4 illustrate a hydraulic compression-stroke buffer in accordance with the present invention. It features an intake piston  21  with differing fluid-conveying channels  22  and  23  accommodated below a dynamics piston  4  near the end of the piston rod. Fluid-conveying channels  22  and  23  are blocked inside by resilient washers  24  and  25 . The resilient washer  25  near the end of the piston rod in this embodiment is provided with ports  26 . A terminal section  27 , intended in the present event for hydraulic compression-stroke buffer, is occupied by a compression spring  28  that rests against the wall of cylinder  1  at the end facing away from it. At the opposite end of the compression:spring is a pot-shaped cap  29  with a depression  30  for accommodating a nut  31  that secures shock-absorption piston  3  to piston rod  2 . 
     With the shock absorber in normal operation, as represented in FIG. 3 for instance with piston rod  2  entering cylinder  1 , the pressure in lower compartment  6  will increase to a level above that of the pressure in upper compartment  5 . The difference will force fluid out of compartment  6  and into compartment  6  through dynamics piston  4 . The ports through resilient washer  25  will allow the fluid to flow through the fluid-conveying channels  22  in intake piston  21  unimpeded and subsequently through the fluid-conveying channel  10 , only weakly blocked by resilient washer  7 , in dynamics piston  4 . Once shock-absorption piston  3  has arrived in compression-end terminal section  27  with cap  29  resting against the inner intake openings in intake piston  21  as illustrated in FIG. 4, fluid-conveying channel will be blocked. The fluid must now flow through fluid-conveying channel  23 , which is weakly blocked by resilient washer  24 . The fluid will now flow by way of intermediate space  32  to the intake opening, weakly blocked by resilient washer  7 , in the fluid-conveying channel  10  in dynamics piston  4 . The total impedance exerted by resilient washers  7  and  4  will generate the desired increased hydraulic shock absorption on the part of the compression-stroke buffer. 
     FIGS. 5 through 7 illustrate a hydraulic shock absorber with a hydraulic compression-stroke buffer and a hydraulic decompression-stroke buffer. The decompression piston end shock-absorption piston  3  in this embodiment is constituted by a dynamics piston  4  that is positioned at the middle of the device with one fluid-intake piston  11  at one end and another intake piston  21  at the other. This embodiment has two terminal sections. Terminal section  19  is occupied by a compression spring  17  with a flat cap  18 , and terminal section  27  by a compression spring  28  with a pot-shaped cap  29 . 
     With the shock absorber in normal operation, piston rod  2  and hence shock-absorption piston  3  traveling in and out as illustrated in FIG. 5, the fluid can flow unimpeded through fluid-conveying channels  12  by way of fluid-intake piston  11  and through fluid-conveying channels  22  by way of intake piston  21  because ports  16  and  28  are not blocked by resilient washers  14  and  26 . Only the resilient washers  7  and  8  now control the level of shock absorption established by shock-absorption piston  3  as it travels in and out. 
     As shock-absorption piston  3  enters the terminal section  19  associated with hydraulic decompression-stroke buffer as illustrate in FIG. 6, the intake openings into the fluid-conveying channels  12  in fluid-intake piston  11  will be blocked as heretofore specified with reference to FIG.  2 . The fluid will then flow subject to a more powerful impedance through the fluid-conveying channel  13 , blocked by the resilient washer  15 , in fluid-intake piston  11 . Since, as will be evident from FIG. 6, the ports  26  through resilient washer  25  allow free flow through fluid-conveying channels  22 , the fluid leaving dynamics piston  4 , its flow attenuated by resilient washer  8 , can now flow unimpeded through intake piston  21 . 
     Once shock-absorption piston  3  has entered its associated terminal section  27 , the operation of the hydraulic compression-stroke buffer illustrated in FIG. 7 is similar to that of the hydraulic compression-stroke buffer illustrated in FIG.  4 . Since the intake openings into the fluid-conveying channels  22  in intake piston  21  are now blocked, the fluid will overcome the impedance exerted by resilient washer  24  and flow through fluid-conveying channels  23 . Once the fluid has been distributed in intermediate space  32 , it will overcome the impedance exerted by resilient washer  7  and flow through dynamics piston  4  and subsequently, without encountering any particular impedance, through fluid-intake piston  11 . 
     FIG. 8 is similar to FIG. 1, This embodiment features between flat cap  18  and fluid-intake piston  11  an axially compressible spring  33  that can as illustrated be an undulating spring. Once shock-absorption piston  3  has entered the terminal section  19  associated with hydraulic decompression as illustrated in FIGS. 2 and 9, the cap  18  at the bottom of compression spring  17  will come to rest against spring  33 , leaving a gap  34  between the cap and the washer  14  resting against fluid-intake piston  11  that can throttle the flow of fluid out of upper compartment  5  and into fluid-conveying channel  12 . 
     The more powerfully shock-absorption piston  3  is forced against compression spring  17 , the more powerful will be the pressure exerted on cap  18  and hence on spring  33  by compression spring  17 . Gap  34  will accordingly decrease continuously and finally disappear once compression spring  17  has entered the blocking state. The decrease in gap  34  as a function of the compression of compression spring  17  depends on the design of the spring and on that of spring  33 . The gap can accordingly alternatively disappear before compression spring  17  has been compressed into its blocking state. 
     Individual accesses  11   d  can be located in at least two mutually separate annular zones  11   a ,  11   b , one inside the other. The zones can be separated by a ring-shaped region  11   c  with smooth edges  11   e.    
     List of Parts 
       1 . cylinder 
       2 . piston rod 
       3 . shock-absorption piston 
       4 . dynamics piston 
       5 . upper compartment 
       6 . lower compartment 
       7 . resilient washer 
       8 . resilient washer 
       9 . fluid-conveying channel 
       10 . fluid-conveying channel 
       11 . fluid-intake piston 
       12 . fluid-conveying channel 
       13 . fluid-conveying channel 
       14 . resilient washer 
       15 . resilient washer 
       16 . port 
       17 . compression spring 
       18 . flat cap 
       19 . terminal section 
       20 . intermediate space 
       21 . intake piston 
       22 . fluid-conveying channel 
       23 . fluid-conveying channel 
       24 . resilient washer 
       25 . resilient washer 
       26 . port 
       27 . terminal section 
       28 . compression spring 
       29 . pot-shaped cap 
       30 . depression 
       31 . nut 
       32 . intermediate space 
       33 . spring 
       34 . gap