Abstract:
A device for absorbing shocks, in particular for two-wheeled vehicles, having
       at least a chamber filled with a fluid medium;   at least a piston means ( 20 ) movable in the longitudinal direction of the chamber which divides the chamber at least into a first subchamber ( 21 ) and at least a second subchamber ( 22 );   at least a valve positioned between the first subchamber ( 21 ) and the second subchamber ( 22 ) which can be brought into at least two different positions, wherein at least in a, first valve position with the piston means applying a force relative to the chamber substantially no medium flow occurs at least in a first direction from the second subchamber ( 22 ) into the first subchamber ( 21 );   wherein at least in a second position of the valve ( 28 ), with the piston, means applying a force relative to the chamber, medium flow occurs at least in the first direction from the second subchamber ( 22 ) into the first subchamber ( 21 ).

Description:
BACKGROUND 
   The present invention relates to a device for absorbing shocks. Although the invention is described with reference to bicycles, it should be noted that it can as well be used with other two-wheeled vehicles such as motorbikes, mopeds, motor scooters and the like. 
   Such absorber devices for bicycles are known from the prior art. Such devices allow to buffer or damp the front wheel or the rear wheel relative to the frame in the case of impacts acting on the wheels such as they occur in rides across bumpy terrain or over the curb. 
   Such absorber devices use a chamber filled with a liquid medium within which a piston moves such that the medium passes through. For this purpose the piston may be provided with apertures. The cross-sectional area of said apertures allows to regulate the quantity of the medium passing through the piston and thus the absorbing factor. 
   However, not every riding situation calls for an absorber response. For example during pedaling the load on the bicycle rear construction varies. In these cases, an absorber response damping the rear construction relative to the frame is not always desired to the same degree. On the other hand, when the bicycle rides across rough terrain such as over rocks and the like or over curbs, the absorber should be full in action. 
   SUMMARY 
   It is therefore the object of the present shock absorber to provide an absorber means with different absorbing reactions to impacts of different strength on the bicycle. 
   It is a further object to provide an absorber device having reduced weight compared to the prior art. 
   A device for absorbing shocks for two-wheeled vehicles comprises at least a chamber filled with a fluid medium and at least a piston means movable in the longitudinal direction of the chamber and dividing the chamber at least into a first subchamber and at least a second subchamber. In addition there is preferably provided between the two subchambers a valve adapted to take at least two different positions wherein at least in a first valve position, when the piston means applies a force relative to the chamber at least in a first direction, there is substantially no medium flow from the second subchamber into the first subchamber wherein the first subchamber preferably is on the actuating shaft side. Moreover, at least in a second valve position, when the piston means moves in a first direction relative to the chamber, medium flow occurs from the second subchamber into the first subchamber, and when the piston means moves in a second direction of movement relative to the chamber, there is medium flow from the first subchamber into the second subchamber. 
   This means that the valve has at least an open position and a closed position. In the open position the fluid medium can pass through the valve and thus between the two subchambers from one subchamber into the other subchamber. In this case the piston means is capable of moving relative to the chamber. The chamber is preferably the interior of a substantially cylindrical body. Said second valve position, presently the open position, thus allows the piston means to move relative to the chamber in both directions. Contrary to this, in the closed position, i.e. the first valve position, no medium can flow at least in a first direction and thus there is substantially no movement relative to the chamber. It is preferred though that some absorbing capacity is maintained in the gas cushion behind the floating piston. Preferably the first direction is the direction of compression, i.e. the direction in which the absorber is compressed. The second direction is preferably the direction of expansion, i.e. an expansion of the absorber occurs. 
   The piston means is substantially guided such within the chamber that at least in one direction of movement the fluid medium can pass only through the valve between the two subchambers such that when the valve is closed movement is substantially prohibited. 
   Another preferred embodiment provides in the first valve position, when the piston means moves in the second direction relative to the chamber, that medium can flow from the first subchamber into the second subchamber. This means that even when the valve is closed, movement is possible in the second direction. This means that the absorber can expand even when the valve is closed. The advantage is that even when the valve is closed, the absorber can be transferred into a completely: expanded state and thus the entire piston travel can be used for absorbing when bumps occur. 
   In another preferred embodiment, a specified pressure in the liquid medium can be used to shift the valve from the first position into the second position. This means that below a specified pressure, the valve remains in the closed position and in said closed position the absorber can only be compressed to a very slight extent. As soon as the pressure applied to the valve or the piston means exceeds said specified value, the valve opens, allowing the piston means to move in the direction of compression, and the absorber can operate in the direction of compression stage. 
   Pressures below said specified pressure occur for instance by simple pedaling such that in this case the absorber only allows said very slight movement in the direction of compression. 
   It is preferred that as soon as the pressure applied to the valve reaches a specified threshold level, the valve shifts from the first position to the second position. The specified threshold level is for example reached or exceeded in rides across rough terrain, over rocks and the like. The first valve position is understood to be the closed position and the second valve position, the open position. 
   Said specified threshold level is preferably adjustable by means of a regulating means coupled to the valve. For this purpose the actuating shaft comprises a hollow space extending axially which functionally connects the master and slave components of the valve means. 
   The hollow space contains a fluid medium which acts preferably on the valve. There is furthermore provided a master piston, preferably in the end region of the actuating shaft opposite the valve. Due to the position of said master piston, more precisely through spring forces acting on the master piston, the pressure applied to the valve and thus the specified threshold level for shifting the valve from the first position to the second position, can be varied. 
   For this purpose the regulating means preferably comprises biasing means for biasing the master piston. Said biasing means may for example be springs which bias the master piston such that a specified pressure of the medium is applied to the valve. As soon as the valve closing force effected by the spring force is overcome by the pressure occurring in the second subchamber, the valve opens, allowing a distinct spring deflection. 
   Thus a hydraulically operated regulating mechanism is proposed for regulating the threshold pressure level at which the valve shifts from the first position to the second position. Said hydraulically operated regulating means is reduced in weight compared to mechanically operated devices since force is not transferred for example by means of metal elements but by means of a fluid medium. 
   It is also preferred to vary the position of the master piston relative to the device and thus also the pressure acting on the valve, by means of an adjusting mechanism. This configuration is advantageous insofar as the rider can readily adjust the specified pressure of the medium for shifting the valve from the first position to the second position without needing accessories such as tire pumps and the like. Adjustment is done via the control equipment which serves for example to vary the force which the biasing means applies to the master piston or else the position of the master piston. 
   Another advantage of the preferred embodiment is that the master component can be freely positioned which, unlike mechanical actuation, does not require axially operating an actuating shaft. 
   An additional advantage of the preferred embodiment is the freedom obtained in designing and shaping the end cover region of the actuating shaft at the end away from the piston which allows a larger volume of the pneumatic spring while maintaining the construction length. 
   In another preferred embodiment the path on which the fluid medium passes from the first subchamber through the piston means into the second subchamber is at least in portions different from the path on which the fluid medium passes from the second subchamber through the piston means in the first subchamber. The advantage of said configuration is that independent of open or closed valve positions the piston can expand at all times even though to a limited, adjustable, extent. 
   It is also conceivable that the medium, as it passes from one subchamber for example from the first subchamber into the second subchamber, can travel on one path only whereas as it passes from the second subchamber into the first subchamber it can additionally travel on other pathways. The individual paths may also be selected reversely, meaning that as the medium passes from the second subchamber into the first subchamber, two pathways may be provided whereas as it passes from the first subchamber into the second subchamber only one of the two pathways is available. 
   In another preferred embodiment a substantially annular sealing element is attached to the valve. This may for example be a disk-shaped element having a center aperture that covers flow-through means in the region of the valve under specified conditions. 
   In another preferred embodiment the medium is at least in portions guided on a rotationally symmetric path as it flows from the second subchamber into the first subchamber. This means that the aperture in the piston means through which the medium is allowed to pass, extends substantially around the entire circumference of the valve means wherein substantially is understood to mean that connecting links and the like may be provided. 
   In another preferred embodiment a second chamber filled with a second medium is positioned substantially rotationally symmetrical in the first chamber. This means that preferably the outer wall of the first chamber at least in part doubles as the inner wall of the second chamber. It is particularly preferred to vary the pressure of the second medium within the second chamber. The second chamber serves for example to guarantee the springing properties of the absorber device. The second medium is preferably a gaseous medium and particularly preferred it is air. The air is fed into a second chamber at a specified pressure wherein pushing the entire absorber means together causes the air to be compressed so as to achieve pneumatic springing. 
   Instead of air or pneumatic springing other absorbing or springing mechanisms such as coil springs or the like can be used. The absorber device preferably comprises a valve through which the second chamber can be filled with air. 
   The first medium is preferably oil or the like, particularly preferred it is a medium with a higher viscosity than water. 
   In another preferred embodiment the actuating shaft comprises an outer shaft element and an inner shaft element wherein the inner shaft element can rotate relative to the outer shaft element. It is preferred that rotating the inner shaft element relative to the outer shaft element also causes the inner shaft element to shift in longitudinal direction relative to the outer shaft element. For this purpose a thread is provided between the two shaft elements such that rotation results in axial displacement of the inner shaft element relative to the outer shaft element. 
   Said displacement serves to regulate the quantity of fluid medium, i.e. preferably of oil that is allowed to pass the piston means as the piston means moves preferably in the direction of expansion. 
   For this purpose a control means is provided at the end of the shaft element opposite the piston means so as to enable the user to control or regulate the quantity of the oil passing through the piston means by displacing the shaft elements relative to one another. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and embodiments of the present shock absorber can be taken from the accompanying drawings. 
       FIG. 1   a  is a schematic representation illustrating the present shock absorber; 
       FIG. 1   b  is another schematic representation illustrating the present shock absorber; 
       FIG. 2   a  is a detailed representation illustrating the present shock absorber; 
       FIG. 2   b  is another detailed representation illustrating the present shock absorber; 
       FIG. 2   c  is another detailed representation illustrating the present shock absorber; 
       FIG. 3  is a cross-sectional view of a portion of the absorber according to the present shock absorber; 
       FIG. 4  is a cross-sectional view of the entire absorber according to the present shock absorber; 
       FIG. 5   a  is a cross-sectional view of the piston means when the valve is closed; 
       FIG. 5   b  is a cross-sectional view of the piston means when the valve is open; 
       FIG. 6  is a complete illustration of the absorber device according to the present shock absorber; 
       FIG. 7  is a sectional detailed view of the absorber device according to the present shock absorber in  FIG. 4 ; 
       FIG. 8  is a control means for the absorber device of the present shock absorber; 
       FIG. 9  is an illustration of an actuating shaft for the absorber device of the present shock absorber; 
       FIG. 10  is another illustration of the actuating shaft and the valve for the absorber device of the present shock absorber; 
       FIG. 11   a  is an illustration of the function of the valve provided with two stepped front faces; 
       FIG. 11   b  is an illustration of the function of the valve provided with two stepped front faces; 
       FIG. 11   c  is an illustration of the function of the valve provided with two stepped front faces; 
       FIG. 12  is another complete illustration of the present shock absorber with the housing of the actuating shaft cut away; and 
       FIG. 13  is another embodiment of the shock absorber according to the present shock absorber; 
   

   DETAILED DESCRIPTION 
     FIG. 1   a  is a schematic representation of an absorber device. Reference numeral  26  indicates an oil chamber in the interior of which a piston means  20  can in principle move in the direction of the double arrow “P”. A piston means  20  serves to divide the chamber formed in the oil chamber  26  into a subchamber  21  on the right and a subchamber  22  on the left. 
   The devices known from the prior art provide that as the piston means  20  moves to the left relative to the oil chamber  26 , a fluid medium provided both in the subchamber  21  and subchamber  22  passes through the piston means  20  from the subchamber  22  into the subchamber  21 . In the reverse direction, as the piston moves to the right in the direction of the arrow, the fluid medium passes from a subchamber  21  into a subchamber  22 . 
   Reference numeral  28  indicates a valve which can be positioned at least in an open position shown in  FIG. 1   a  and a closed position shown in  FIG. 1   b . When the valve  28  is in the open position shown in  FIG. 1   a , the medium can pass in the direction of the arrow “P 1 ” both from the subchamber  22  on the left into the subchamber  21  on the right and reversely from the subchamber  21  on the right into the subchamber  22  on the left. 
   When the valve  28  is in the closed position shown in  1   b , a passage of the fluid medium from the second subchamber  22  into the first subchamber  21  through the piston means  20  is substantially prohibited. In this case movement of the piston means  20  relative to the oil chamber  26  is substantially prohibited. 
   A regulating means  41  serves to adjust the position of the valve  28 . For this purpose a fluid medium is provided in the hollow space  45  of the actuating shaft  43 . A movement of the master piston  41  for example to the left causes the position of the valve  28  to shift towards closed. Reversely, a movement of the master piston  41  to the right causes the position of the valve  28  to shift towards open. 
   A movement of the piston means  20  to the left causes the medium provided in the subchamber  22  to apply a specified force to the valve  28 . If that force exceeds the force applied through the medium in the chamber  45 , which is adjustable through the master piston  41 , the valve  28  opens, allowing medium to flow through in the direction of the arrow “P 1 ”. 
   While the valve  28  is in the left position shown in  FIG. 1   b , no medium flows from the subchamber  22  on the left into the subchamber  21  on the right. 
     FIGS. 2   a  through  2   c  show a more detailed illustration of the present shock absorber.  FIG. 2   a  illustrates a situation where when the valve  28  is closed, the absorber device expands, i.e. the piston means  20  moves to the right relative to the oil chamber  26 .  FIG. 2   b  illustrates a situation where the valve  28  is open and the absorber device is compressed. 
     FIG. 2   c  illustrates the idle position of the absorber or the situation where the pressure rise in the chamber on the compression side is still too low for opening the valve. 
   Above the piston means a first sealing means  30  is provided which is an annular element covering the end in the right of the passage  24  of the piston means. 
   Reference numeral  32  indicates a substantially disk-shaped sealing means on the left which, depending on the direction of movement of the piston means  20  relative to the oil chamber  26  either contacts the piston means  20  or is spaced from it. 
   The arrow “P 1 ” indicates the direction of flow of the medium from the subchamber  21  on the right into the subchamber  22  on the left during expansion of the absorber device. Accordingly the medium flows along a channel  35 , then into the connecting channel  24  and finally past the sealing means  32  on the left into the subchamber  22  on the left. 
   It can be seen that although the valve  28  is closed in  FIG. 2   a , in the case of the absorber device expanding, i.e. the piston means  20  moving to the right, medium flow from the subchamber  21  into the subchamber  22  is still possible, meaning that it does not depend on the open or closed position of the valve  28 . 
     FIG. 2   c  in contrast illustrates the situation where when the valve  28  is closed, compression of the absorber device occurs. In this case the sealing means  32  on the left prohibits a medium flow from the second subchamber  22  into the first subchamber  21 . In this way, movement in the direction of compression is substantially prohibited. 
     FIG. 2   b  illustrates a situation when the valve is open. In this case the fluid medium can pass through the open center of the sealing means  30  via the channel  24  from the second subchamber  22  into the first subchamber  21 . It should be noted that the medium substantially flows through the channel  24  on the illustrated path P 2 . However, small quantities can also flow through the channel  35  of the piston means from the subchamber  22  on the left into the subchamber  21  on the right. 
   Preferably the flow cross-section in a portion of the channel  35  is smaller than in channel  24  since it is particularly preferred to obtain a compression stage resistance significantly reduced relative to the rebound stage when the valve is open. The pressure to the rear of the valve  28  can be varied through the master piston  41 . 
   Preferably a biasing means (not shown) is provided which according to  FIGS. 2   a  through  2   c  applies a specified upward force to the master piston  41 . In this way a specified pressure is applied to the piston valve  28 . Not before the pressure preset by said biasing means such as a spring is overcome can the valve  28  shift from the closed position to the open position. Said pressure can further be adjusted through the pressure applied to said master piston  41  and thus can the pressure required for shifting the valve  28  from the closed position into the open position. 
   The biasing means further causes the valve to return from the open position into the closed position when the pressure in the chamber  22  falls below the specified threshold pressure level. 
   Moreover, the relation of the piston cover surface Al of the master piston  41  to the valve cover surface A 2  serves to achieve a gear ratio step-up or reduction between displacement of the master piston  41  and the resulting changed pressure acting on the valve  28 . If for example a small surface Al and a comparatively large surface A 2  is selected, the master piston  41  requires a comparatively small biasing force to effect a change of the specified pressure threshold at the valve  28 . Or reversely, if a large surface Al of the master piston is selected, then a low biasing force acting on the master piston  41  relative to the actuating shaft  43  causes considerable change in the pressures acting on the valve  28 . 
     FIG. 3  is a detailed cross-sectional illustration of the present shock absorber. Reference numeral  61  indicates an end surface cover of the absorber device. In a preferred embodiment said cover is at least in portions formed as a sleeve which receives the regulating elements of the absorber device. 
   Reference numeral  63  refers to a guide ring for a pivot head and reference numeral  64  to a bearing ball in the pivot head. The guide ring and the bearing ball serve to join the absorber device to frame components or other bicycle components. The guide ring  63  and the bearing balls  64  and  164  further ensure that the absorber device is supported to be rotatable about all of its axes relative to the frame component that it is attached to. The guide ring  63  is preferably a component made of reinforced material. 
   Reference numeral  72  illustrates an inner, extended actuating shaft for regulation. At its upper end region it comprises preferably a polygon end portion that engages with a corresponding aperture in an adjusting knob  76 . Turning the adjusting knob  76  rotates the inner actuating shaft  43 , displacing it in longitudinal direction. This is the preferred way for regulating the flow cross-section of the pathway where the medium flows from the first subchamber  21  into the second subchamber  22 . In this way the rebound damping or the rebound damping factor of the absorber device can be adjusted. 
   The reference numerals  79 ,  81 ,  82  refer to sealing means for preventing fluid medium, i.e. oil, to leak from the device. O-rings are preferably used. Reference numeral  74  refers to a grooved ring positioned opposite the support component  73  for sealing the rotatable inner actuating shaft  43 . Reference numeral  78  illustrates a radial shaft seal ring, preferably a lip seal with garter spring, positioned between the control knob and the support component  73 . 
   Reference numeral  75  indicates an end portion of a closing means that serves to feed oil into the regulating means. Said closing means can open and close by means of an adjustment means  84  and it is sealed by means of another sealing ring which is preferably an O-ring so as to prevent oil leaks from the closed circuit in the closed state. 
   The mode of operation of the regulating means of the valve  28  will now be described. 
   Reference numeral  41  indicates the master piston which is biased to the right in the Figure, i.e. in the direction of the actuating shaft  43 , by means of biasing means  58  which in the present embodiment is a spring. The adjustment chamber  86  positioned to the right of the master piston  41  contains oil to which more or less pressure can be applied through biasing the spring  58  correspondingly. 
   The regulating force is adjusted in the present embodiment by axially displacing the end portion  56 . In the present embodiment, said end portion  56  is a tappet. Reference numeral  53  indicates a sealing means and reference numeral  54  a retaining ring around the tappet. 
   The adjustment chamber  86  is in fluid connection with the vertical hollow space  89  in the lower portion of the actuating shaft  43 , through the horizontal passage  87  and the vertical passage  88  which is preferably positioned rotationally symmetrically around the actuating shaft  43 . In this way the oil can pass into the second adjustment chamber  90  above the valve  28 . 
   By laterally displacing the biasing means  58  relative to the master piston  41  the pressure on the oil can be increased or reduced so as to directly affect the pressure within the adjustment chamber  90 . In this way the user can preset the specified pressure at which the valve is to shift from the closed position to the open position. 
     FIG. 4  is another cross-sectional view of the present shock absorber. Reference numeral  145  refers to a piston means positioned in the second subchamber  22 . Reference numeral  146  indicates a sealing means for prohibiting a medium flow past the side of the piston means  145 . 
   Reference numeral  143  indicates a receiving means for another valve through which the chamber between the piston  145  and a lower cover means  161  can be filled with compressed gas. The valve is closed by a valve lid  140  and a sealing means prevents leaks of compressed gas from the closed valve. 
     FIGS. 5   a  and  5   b  are detailed views of the piston means to illustrate the flow path of the fluid in a compressed ( FIG. 5   b ) and an extended ( FIG. 5 ) absorber device. 
   When the absorber device is compressed while the valve  28  is in the open position, the oil flows on the path indicated at arrow Pf 2 . The oil first enters the region beneath the valve in the piston means  20 . From there it is diverted to the side or in radial direction past the valve  28 , leaves the piston means at the open sealing means  30  and enters into the subchamber  21 . 
   An expansion of the piston device results in the situation shown in  FIG. 5   a . In the portion  35  the oil flows substantially parallel to the longitudinal direction of the actuating shaft and it is ultimately led out of the piston means, also past the side of the valve  28 . 
   Both pathways Pf 1  and Pf 2  are rotationally symmetrical with respect to the actuation means. Generally speaking, the path shown at Pf 1  can also be used when the valve  28  is open while the absorber device is being compressed. However, said path has a smaller flow cross-section relative path Pf  2  such that when the valve is open, most of the oil passes along the path Pf  2 . 
   The path Pf  2  is preferably not available while the absorber device is expanding since this is prevented by the sealing means  30 . 
   The dashed line in  FIG. 5   b  indicates the region where the regulating fluid, i.e. the fluid medium is located which hydraulically operates the valve  28 . 
     FIG. 6  is a total illustration of the present shock absorber Herein there is provided, adjacent to the upper cover means  61  that comprises a guide ring  63  and a bearing ball, also the lower cover means  161  that also comprises a guide ring  163  and a bearing ball  164 . The reference numeral  204  refers to a control wire which may for example run to an adjust means attached to the handlebar. By means of said control wire the user can turn an adjustment knob  202  and thus preset the specified pressure at which the valve  28  shifts from the closed position to the open position. 
   Reference numeral  205  indicates an outer absorber element which in the present embodiment is configured substantially cylindrically and arranged rotationally symmetrically around the oil chamber  26 . Compressed gas is fed through a valve (not shown) into the hollow space generated between the oil chamber  26  and the outer absorber element  205 . Movement of the oil chamber  26  in one or the other direction relative to the outer absorber element compresses or expands said pneumatic spring resulting in the effect of an air spring. 
     FIG. 7  is a sectional detailed view of the present shock absorber. Reference numeral  210  indicates the third chamber or pneumatic spring, respectively. Said chamber is compressed as the absorber means is compressed such as to achieve a springing effect. 
     FIG. 8  shows an adjust means that attaches for example to the handlebar or other frame elements. 
   Reference numeral  111  indicates a control knob having a plurality of apertures  114 . Said apertures serve as snap-in apertures for engagement with a correspondingly configured pin (not shown) of the shifting means  112 . Turning the shifting means relative to the adjust knob operates a control wire (not shown) and thus the adjust means  202  shown in  FIG. 4 . 
     FIG. 9  is a detailed view of the actuating shaft with the piston means  20  positioned at the lower end. Displacing the master piston  41  in the direction of double arrow P will, as described above, expand or reduce the adjustment chamber  86 . In this way the piston means  20  can be shifted from the open to the closed position. As can be taken from the Figure, the adjustment chamber  86  is in fluid connection with the valve  28  through a horizontal connection  87 , the vertical connection  88  and the second vertical connection  89 . The oil flows in the intermediate region  94  from the vertical connection  88  into the vertical connection  89 . 
   Reference numeral  105  indicates a thread which causes the actuating shaft  43  to be displaced lengthwise as it is rotated. Reference numeral  95  indicates the cover portion of the piston means  20 . It comprises a plurality of apertures  130  positioned around a center opening  132 . 
   The piston means  20  further comprises a wall section  114  extending substantially annularly inwardly which extends annularly around the valve  28  in  FIG. 10 . Reference numeral  91  refers to a sealing means to prohibit oil flow in exchange between control fluid and absorber fluid. Preferably the means is a quadring. 
   The actuating shaft  43  has a larger diameter region  119  and a smaller diameter region  113  along its longitudinal direction. The smaller diameter region  113  preferably serves as an oil flow path as the absorber device expands. 
     FIG. 10  is another detailed illustration of the valve  28  of the present shock absorber. It comprises a lower sealing element  125  comprising a central projection  123 . Said projection extends into the center opening  132  in the closed position, preferably without closing it. The basic valve shape is substantially cylindrical, i.e. the valve diameter is constant around its longitudinal axis, interrupted only by the sealing ring recess. 
   The shape of the projection  123  preferably serves to optimize control of the flow direction of the medium. The projection is preferably not intended to have a sealing function. 
     FIG. 11   a  shows the valve cross-section of the particularly preferred embodiment in a first, closed position. 
   Herein the first end face  140  contacts the inside  141  of an upper closing means of the valve chamber which may for example comprise the piston means  20 . 
   Thus the cross-section acting on the valve which the oil in the second subchamber applies pressure to, substantially corresponds to the cross-section of the flow passage  142  in the upper closing means of the valve chamber. 
     FIG. 11   b  shows the situation as the force generated by the oil pressure in the first subchamber in conjunction with the cross-section mentioned above, exceeds the counterforce which is substantially generated by the oil pressure in the control circuit  143  in conjunction with the effective valve cross-section. 
   As soon as the first end face  140  lifts off the inside  141  of the closing means, the oil from the first subchamber can also apply pressure to the second end face  144  which allows the valve to open particularly fast. 
     FIG. 11   c  illustrates the fully open valve. 
     FIG. 12  illustrates the absorber with optional remote control, with the shaft housing cut away. 
   The cam joined to the shaft actuates the tappet  56  which loads the spring  58  through axial displacement. 
   In a preferred embodiment the shaft and the cam contour are configured integrally. 
   In another preferred embodiment the fluid connection  86 ,  87 ,  88 ,  89  between master piston  41  and valve  28  comprises a control device (not shown) which has different passage resistances in the two directions of movement. 
   As a result of this the valve shifts to the closed position at a lower speed than that with which the force of the spring  58  acts on the master piston  41 . 
     FIG. 13  is a schematic illustration of another embodiment of the present shock absorber. In the present preferred embodiment the absorber system shown in  FIG. 3  is modified in respect of the connection between the master piston  41  and the valve  28 . The embodiment shown in  FIG. 3  comprises a direct oil connection between the master piston  41  and the valve  28 .  FIG. 13  shows as an alternative, a biasing means  328  which is positioned directly at the valve  28 . Between the biasing means  328  contacting the valve and the oil head or the chamber  45  there is also positioned an additional piston means  327  inside the hollow space  45  or the hollow space  89  shown in  FIG. 3 . By means of applying force to the master piston  41  the spring is biased via the oil head in chamber  45  and said additional piston means  327 , wherein the spring in turn defines the counterforce of the oil required inside the chamber  22  to open the valve. Herein the oil provided in the chamber where the biasing means  328  is positioned, is not in fluid connection with oil in the chambers  21 ,  22 ,  24  (i.e. with oil at any point of the path P 2 ).