Abstract:
Bump stop for an amphibious vehicle suspension having a member selectively movable between an operating position, and an inoperative position. This allows the suspension to retract road wheels along locus for conversion to marine mode. Bump stop free end may be moved by filling cavities with pressurized fluid. Alternatively, the entire bump stop may be rotated on a pivot by a hydraulic cylinder, an electric solenoid, manually or by any other mechanical means. Alternatively, the movable member may be a position in a cylinder, withdrawn against a return spring by hydraulic pressure, and may act against resilient snubber on the vehicle suspension. Bump pad has a curved undersurface, allowing the bump stop to be bent out of the way when the suspension is lowered.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a bump stop and more particularly to a bump stop for the suspension of an amphibious vehicle. 
     An amphibious vehicle with a wheel retraction system requires a suspension bump stop in order to prevent excessive upward wheel travel movement when the vehicle is in land travel mode. However, when the wheels of the vehicle retract for marine mode, the bump stop should not interfere with the upward movement of the suspension. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided, a bump stop for an amphibious vehicle, the bump stop comprising a member having a stop portion for engagement with part of a vehicle suspension to limit travel of the suspension system relative to the vehicle body, in which the member is selectively movable between an operative position, in which the stop portion is deployed for engagement with the part of the vehicle suspension system, and an inoperative position, in which the stop portion is not deployed for engagement with the part of the vehicle suspension system, the bump stop further comprising means for moving the stop portion between the operative and inoperative positions. 
     In a first preferred arrangement the member is resilient and is provided with at least one internal cavity connected to a fluid supply line. Preferably the stop portion moving means is provided by pressurised fluid supplied to the internal cavity, which pressurised fluid expands the cavity of the resilient member causing the resilient member to distort. 
     In a second preferable arrangement, the member is resilient and is adapted to be pivotally mounted to a fixed part of the vehicle. In this arrangement, the stop portion moving means may be provided by a fluid operated cylinder, a piston of which is connected to the resilient member. Movement of the piston causes the resilient member to rotate about the pivotal mounting. Alternatively, the resilient member may be moved by an electrically operated solenoid or manually, or by any other appropriate mechanical or electrical means. 
     In a third preferable arrangement, the member is slidably mounted in a cylinder. One end of the member may be formed as a piston which is biased by a spring to move the stop portion of the member to the operative position. Preferably pressurised fluid causes the piston and member to retract into the cylinder, against the bias of the spring, to the inoperative position. 
     In accordance with a second aspect of the invention, there is provided an amphibious vehicle having a bump stop in accordance with the first aspect of the invention. In a preferred embodiment, the part of the vehicle suspension system which engages the member is resilient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Several embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is a sectional view through a first embodiment of a bump stop for an amphibious vehicle in accordance with the invention, showing the bump stop in an operative position; 
         FIG. 2  is a view similar to that of  FIG. 1  but showing the bump stop in an inoperative position; 
         FIG. 3  is sectional view through a second embodiment of a bump stop for an amphibious vehicle in accordance with the invention, showing the bump stop in the operative position; 
         FIG. 4  is a view similar to that of  FIG. 3  but showing the bump stop in an inoperative position; 
         FIG. 5  is a view similar to that of  FIG. 3  but showing an modification to the second embodiment in which the stop portion is moved by an electric solenoid; 
         FIG. 6  is a view similar to that of  FIG. 5  but showing the bump stop in an inoperative position; 
         FIG. 7  is a side view partly in section, a suspension system of an amphibious vehicle including a bump stop of the type shown in  FIGS. 1 &amp; 2 ; 
         FIG. 8  is an enlarged sectional view of part of the suspension system of  FIG. 7  showing the bump stop in the operative position; 
         FIG. 9  is a view similar to that of  FIG. 8  showing the bump stop in the operative position, with the bump stop limiting upward movement of the suspension system; 
         FIG. 10  is a view similar to that of  FIG. 8  but showing the bump stop in the inoperative position, and the movement of part of the suspension system towards a retracted position for marine use; 
         FIG. 11  is a view similar to that of  FIG. 10  showing movement of part of the suspension system from the retracted position towards an extended position for road mode use; and 
         FIG. 12  is a sectional view through a third embodiment of a bump stop in accordance with the invention, showing the bump stop in the operative position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring firstly to  FIG. 1 , a first embodiment of a bump stop is indicated generally at  10 . The bump stop  10  comprises a resilient member  12  which is attached at one end  13  to a rigid base  14 , and has a free end  16  which forms a stop portion for contact with part of a vehicle suspension. The resilient member  12  is shaped substantially as a truncated cone or pyramid and is made of rubber, but may be made of any suitable resilient material. The base  14  is mounted to the structure  24  of a vehicle, see  FIG. 7 . 
     A series of elongate internal cavities  18  are provided to one side of the resilient member  12  and are connected by a connecting cavity  20 . A fluid supply line  22  in the base  14  connects with the connecting cavity  20  for supplying pressurised fluid to the internal cavities  18 . As can be seen from  FIG. 2 , when the internal cavities  18  are expanded by the force of pressurised fluid, the resilient member  12  distorts to one side, (to the right hand side as viewed). 
     Referring now to  FIG. 7 , a bump pad  26  is integrally formed with, or attached to a wheel support upright  27  of a suspension system of an amphibious vehicle. The resilient member  12  and rigid base  14  are mounted on the structure  24  of the vehicle in alignment with the bump pad  26 . The wheel support upright  27  is mounted between lower and upper control arms  28 , 30  which are pivotally mounted to the structure  24  of the vehicle in conventional manner. The wheel support upright  27  mounts a wheel  29 , also in conventional manner. The upper surface  19  of the bump pad  26  is cup shaped for receiving the end  16  of the bump stop  10 . Furthermore, the lower surface  25  of the bump pad  26  is formed as a smooth curve, the purpose of which will be described below. The wheel  29  is shown in the lowered position for use of the vehicle in a road mode and a retracted position in which the wheel is raised for use of the vehicle on water in a marine mode. 
     The operation of the bump stop  10  will now be described with reference to  FIGS. 7 to 11 . In  FIGS. 7 &amp; 8 , the bump stop  10  is shown in an operative position, in which the resilient member  12  assumes its rest shape. The bump pad  26  is positioned below the end  16  of the resilient member  12 , and moves with the wheel support upright  27  relative to the vehicle body as the vehicle travels over land in road mode, as indicated by arrow A. The tip  21  of the bump pad  26  moves in an arc, as indicated by the dotted line  23 . 
     As can be seen from  FIG. 9 , when the suspension system moves upwards relative to the vehicle in the direction indicated by arrow B, the cup shaped upper surface  19  of bump pad  26  contacts the end or stop portion  16  of the resilient member  12 . The resilient member  12  is compressed until the resilient member  12  prevents the pad  26 , and hence the wheel support upright  27 , wheel  29  and control arms  28 , 30 , from further relative upward movement. 
     The bump stop  10  can be selectively moved between the operative position and the inoperative positions by pumping pressurised fluid, for example hydraulic oil, water or air into or out from the fluid supply line  22 . As described with reference to  FIG. 2 , the pressurised fluid flows into the connecting cavity  20  and into the internal cavities  18 , which causes the cavities  18  to expand. The expansion of the cavities  18  forces the resilient member  12  to distort, and the end  16  of the resilient member  12  moves out of axial alignment with the base  14  in a direction away from the side of the internal cavities  18 . 
     Referring now to  FIG. 10 , when the amphibious vehicle has entered water and it is necessary to retract the suspension system, pressurised fluid is pumped into the cavities  18 , and the resilient member distorts as described above into the inoperative position. The end  16  of the resilient member  12  is now positioned away from the bump pad  26 , allowing the tip  21  of the bump pad to move past the resilient member  12 , as indicated by arrow C, so that the wheel can be moved to the retracted position. When the bump pad  26  has moved past the bump stop  10  to the retracted position, release of the pressurised fluid allows the resilient member  12  to assume its rest or operative shape. 
     When it is required to deploy or lower the suspension system for land travel mode from the retracted position, the wheel support upright  27  moves downwards as indicated by arrow D in  FIG. 11 . As the tip  21  of the bump pad  26  follows the arc  23 , shown in dotted outline, the underside  25  of the bump pad  26  contacts the resilient member  12  and forces the resilient member to distort towards the inoperative position. Consequently, the bump pad  26  is able to move past the bump stop  10  in the downward direction without need for supplying pressurised fluid to the cavities  18 . The fluid control circuit (not shown) is therefore simpler than the circuit would be if the pressurised fluid had to be supplied for movement of the bump stop  10  during wheel deployment. 
     A second embodiment of a bump stop in accordance with the invention will now be described with reference to  FIGS. 3 and 4 . The bump stop is indicated generally at  40 , and comprises a resilient member  42  which is attached at one end  43  to a support member  44 , and has a free end  46  which forms a stop portion. The resilient member  42  is shaped substantially as a truncated cone or pyramid and is made of rubber, but may be made of any suitable resilient material. The support member  44  is pivotally mounted  48  to a rigid base  50 , which is mounted to the structure  24  of a vehicle, see  FIG. 7 , as in the previous embodiment described. 
     A fluid operated cylinder  52  is mounted to one side of the base  50 , and comprises a single port  53 , a piston  54 , a piston rod  56  and a spring  58 . An end  60  of the piston rod  56  is pivotally mounted  62  to the support member  44 . The spring  58  is positioned between a back wall  64  of the cylinder  52  and the piston  54 , and biases the piston  54  and piston rod  56  to an extended position. Pressurised fluid supplied to the cylinder  52  through the port  53  acts against the piston  54  and the bias of the spring  58  to retract the piston rod  56  into the cylinder  52 . 
     In operation, when no pressurised fluid is supplied to the cylinder  52 , the piston rod  56  is extended, and the resilient member  42  is in the operative position, shown in  FIG. 3 . When it is desired to retract the suspension system of the vehicle, pressurised fluid is supplied to the cylinder  52  and the piston rod retracts as described. This causes the support member  44  to rotate about the pivotal mounting  48  and moves the end  46  of the resilient member  42  out of the path of the bump pad  26 , to the position shown in  FIG. 4 . As in the previous embodiment described, when the suspension system is deployed to road mode from the retracted position in marine mode, the underside  25  of the bump pad  26  forces the resilient member  12  to one side. 
       FIGS. 5 &amp; 6  show a modification to the second embodiment in which the fluid operated cylinder  52  is replaced by a double acting electric solenoid  152 . Parts in common with those shown in  FIGS. 3 &amp; 4  are given the same reference numerals. 
     The solenoid  152  has coils  153  and  155 , a yoke  154 , rod  156 , and electrical connections  157 . The yoke  154  is connected to the support member  44  by the rod  156 . Preferably, the solenoid is a latching solenoid. Depending on the electrical signals fed to the coils, the bump stop can be moved between the operative position shown in  FIG. 5  and the inoperative position shown in  FIG. 6 . 
     Rather than a double acting solenoid, a single acting solenoid could be used, rendered reversible by changing the polarity. 
     A third embodiment of a bump stop in accordance with the invention will now be described with reference to  FIG. 12 . The bump stop, indicated generally at  70 , comprises a member  72  slidably mounted in a cylinder  74 . A piston  76  is formed at one end of the member  72  and is located in a piston chamber  77  within the cylinder  74 . A spring  78 , which locates in an internal recess  79  of the member  72  and engages an end cap  80  of the cylinder  74 , biases the member  72  out of the cylinder to the operative position. The other end of the member  72  extends out of the cylinder  74  in the operative position and is formed as a latch  82 , having a flat lower surface  84  which forms a stop portion, and a curved upper surface  86 . 
     A pressure fitting  88  is provided in the cylinder  74 , in communication with a port  90 , which opens into the piston chamber  77 . Pressurised fluid supplied to the fitting  88  enters the chamber  77  and causes the piston  76  and consequently the member  72  to move to the right, as viewed, against the action of the spring  78 . Seals  92  seal between the piston  76  and the internal wall of the cylinder  74 , and seals  94  seal between the member  72  and the internal wall of the cylinder  74 . The member  72  including the latch  82  can therefore be drawn into the cylinder  74 , which is the inoperative position. When the pressure of the fluid is relieved, the bias of the spring extends the member  72  to the operative position. The cylinder  74  is mounted to the vehicle body. 
     In this arrangement, the member  72  is not resilient, and therefore a resilient snubber  93  is attached to the cup shaped upper surface  19  of the bump pad  26 . 
     In operation, the member  72  is biased out of the cylinder  74  by the spring  78  in operational mode, and the latch  82  is positioned in the path of the bump pad  26 . As in the previous arrangements, the bump pad  26  moves in an arc, and the path of the tip  21  is indicated by the dotted line  23 . The wheel support upright  27  and the bump pad  26  are prevented from moving upwards past the latch  82  of the member  72 , because the bump pad  26  and snubber  93  engage the flat surface  84  of the latch  82 , and limit the upward movement. 
     When it is desired to retract the wheels for marine mode, pressurised fluid is supplied through the port  90 , which causes the piston  76  and the member  72  to retract by sliding into the cylinder  74 , against the bias of the spring  78 , to the inoperative position. The latch  82  is contained in the cylinder  74  and allows the bump pad  26  with snubber  93  to pass to the retracted position. Relief of the fluid pressure allows the bias of the spring  78  to push the member  72  and latch  82  from the inoperative position to the operative position. 
     When the suspension moves back towards the road mode position from the retracted marine mode position, the smooth curved underside  25  of the bump pad  26  frictionally engages the upper curved surface  86  of the latch  82 , and pushes the latch  82  and member  72  into the cylinder against the bias of the spring  78 . 
     In all of the embodiments it should be noted that if the pressurised fluid supply to the bump stop  10 ,  40 ,  70  fails, then the bump stop is always resiliently deployed to the operative position. Furthermore, the suspension system can always be deployed to road mode because in the movement of the bump pad from the retracted to the deployed position, the member is moved to one side by frictional engagement. 
     In other arrangements (not shown), the member may be moved manually, or by any other appropriate mechanical or electrical means.