Abstract:
A retractable suspension for an amphibious vehicle, the configuration of which allows the size of an opening in the hull necessary for accommodating the protraction of each wheel to be kept to a minimum. The suspension is configured such that the only component that comes to extend beyond the hull upon protraction is a generally tube shaped lower link that is pivotally attached to the hull at it is inboard end, that pivotally supports a hub carrier at its outboard end and that may simultaneously accommodate a drive shaft therein. The weight of the vehicle is supported by a spring arrangement bearing on the inboard end of the lower link.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   This application claims priority from Great Britain Application Serial No. 0423463.9, filed Oct. 22, 2004. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to vehicle suspension for driven axles of amphibious vehicles. 
   In an amphibious vehicle, it is desirable to reduce drag when in marine mode, particularly drag caused by disconformities in those parts of the vehicle in contact with the water. Some such vehicles have retracting wheels with recesses above the water-line for the wheels to retract into. In the case of a planing amphibious vehicle, the hull recesses are generally above the water-line when the vehicle is on the plane; or in the case of our co-pending application no. WO 04/103743A1, plates are fitted to the vehicle&#39;s bottom to cover as much as possible of the recesses for the rear driven wheels. Such plates are fixed after assembly of the vehicle suspension during manufacture. Nevertheless, tramping caused by hitting waves or wakes; or alternatively cornering; can cause the wheel recesses to catch the water, which may in turn slow or slew the vehicle. To minimize such effects, it is essential to minimize the length of such recesses in the longitudinal direction of the vehicle. 
   The use of upper and lower wishbone suspension has the advantage of bracing the suspension against torque input and vibration. It is also convenient to locate spring and damper units within the wheel retraction recesses; but as can be seen from WO 04/103743A1, both of these measures lead to large recesses in the vehicle hull. 
   Where an amphibious vehicle is based on passenger car conventions of vehicle packaging, seating across the vehicle will be provided, and wheel arches will be blended into the vehicle bodywork. However, if alternative packaging concepts from lighter and more compact vehicles are considered, different opportunities and challenges arise. Where seating is arranged longitudinally along the vehicle, it can be made narrower than a passenger car. Particularly where the power train is also aligned along the vehicle, a greater hull vee angle can be considered than for a passenger car type body with transverse seating and engine. The large vee angle offers agile marine handling, but requires the use of large diameter road wheels to give adequate ground clearance; which would suggest large wheel arches and bulky suspension. 
   Should these large wheel arches be integrated into the vehicle body styling, they would tend to negate the compactness and light weight of a narrow amphibious vehicle. This is emphasised with a large hull vee angle, as the wheels must be retracted through large angles to stay above the water-line when the vehicle is canted on water. However, if the wheel arches are allowed to protrude beyond the contours of the rest of the vehicle bodywork, the main structure of the vehicle can still be narrow and light in weight. Hence, a new incentive is found to provide a compact yet sturdy amphibious vehicle retractable suspension which requires minimal hull recesses. Similarly, if seating is provided substantially above the vehicle power train, rather than in front of the power train or behind it, the hull will be relatively short; so it becomes critically important to minimize interruptions to the planing surface. 
   SUMMARY OF THE INVENTION 
   One object of the present invention is therefore to provide a retractable suspension for an amphibious vehicle, in which each hull recess, at least for the lower support member of the suspension, is significantly shorter in the longitudinal direction of the vehicle than each hull recess in known retractable suspension vehicles. It is particularly suitable for use with driven wheels. 
   According to the present invention, there is provided an amphibious vehicle having a prime mover, seating arrangements, at least two road wheels and a hull, wherein two road wheels are each arranged to be driven from the prime mover at least by means of a primary shaft and an intermediate shaft between each wheel and each primary shaft, each intermediate shaft having an articulatable torque transmitting joint at each end so as to enable each driven wheel to be moved upwards from a lowered, ground engaging position to a raised position above the vehicle&#39;s water-line, wherein each said driven wheel is mounted rotatably to an intermediate suspension member, the intermediate suspension member being mounted to and between an upper suspension member and a lower suspension member, the lower suspension member being accommodated within a narrow recess or slot in the hull of the vehicle when its driven wheel is in the raised position, and wherein the intermediate shaft is encaged by a cage means mounted between the intermediate suspension member and the hull of the vehicle so as to resist torsional forces on the intermediate suspension member when the wheels are rotating or being braked. 
   For the avoidance of doubt, an articulatable torque transmitting joint in a shaft comprises an output member and an input member which may pivot relative to each other, not necessarily in the direction of rotation of the shaft, but along the axis of the shaft; and which joint is capable of transmitting torque when said members are angled relative to each other; and includes universal joints. 
   Preferably, the cage means is a tube surrounding at least mainly the intermediate shaft. The cage means may comprise the lower suspension member. The width of the recess in the hull may be less in the longitudinal direction of the vehicle than the radius of the driven wheel. The hull may be configured for planing; while the upper suspension member is preferably a wishbone mounted pivotably to the body of the vehicle. Although a wishbone conventionally comprises two converging arms, the arms may be substantially parallel to each other. Alternatively, the upper suspension member may comprise a McPherson strut. 
   The torque transmitting joints may be universal couplings; which may in turn comprise constant velocity (CV) joints. Such CV joints may be arranged with a fixed inner joint and a plunging outer joint, as described in our co-pending patent application WO 04/039614A1, the contents of which are incorporated herein by means of reference. Where a large hull vee angle is used, it may be necessary to rotate the road wheels as they are retracted, as shown in the figures, to ensure that the wheels remain clear of water when cornering. For example, an axis of rotation of a retractable road wheel which is substantially horizontal when the wheels are protracted and resting on level ground may be rotated at least thirty degrees from the horizontal when the wheels are retracted; preferably forty degrees. 
   To reduce the bulk of the suspension recesses in the hull, the spring and damper units for each road wheel may be mounted remotely from the upper and lower suspension members; preferably within a watertight interior compartment of the vehicle. The road wheel suspension retraction and protraction means may similarly be mounted remotely from the wheel suspension. Clearly both spring and damper units and retraction and protraction means must be mechanically linked to the upper and lower suspension members. The retraction and protraction means may be linked to a pivotal arm, to either end of which are mounted springs and dampers. The cage means may be sealed against ingress of water. 
   The passenger seating may be arranged along, or parallel to, the longitudinal axis of the vehicle. The prime mover may also be arranged along, or parallel to, the longitudinal axis of the vehicle. 
   These and other features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments which, taken in conjunction with the accompanying drawings, illustrate by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view of an amphibious vehicle according to the invention; 
       FIG. 2  is a partial transverse cross section through plane II—II of  FIG. 1  with the wheels up and retracted; 
       FIG. 3  is a further transverse cross section through plane II—II of  FIG. 1  with the wheels down and protracted; 
       FIG. 4  is a transverse elevation of the suspension for the rear wheels of the vehicle of  FIG. 1  with the wheels removed; 
       FIG. 5  is a side elevation of the parts of the suspension shown in  FIG. 4 , with the wheels retracted; 
       FIG. 6  is a plan view of the suspension for the rear wheels of the vehicle of  FIG. 1  with the wheels retracted; and 
       FIG. 7  is a plan view of the suspension for the rear wheels of the vehicle of  FIG. 1  with the wheels down and protracted. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Amphibious vehicle  2  comprises prime mover  4  driving marine drive means  6  through a marine transmission (not shown). Drive means  6  may be a jet. Locomotion on road is provided by wheels  8  and tyres  10 , which are driven through a road transmission (not shown). The wheels and tyres are shielded by wheel arches  12 . Body  14  and hull  16  may be formed separately and joined at split line  18 . The hull may have a planing surface  20 . At least a driver&#39;s seat  22  is provided; one or more passenger seats  24  may be provided astern of the driver&#39;s seat. The seating axis may be on the longitudinal axis of the vehicle, or parallel thereto. The axis of the prime mover may also be along, or parallel to, the longitudinal axis of the vehicle. Driver controls are provided, such as handlebars  26 . A windscreen  28  may be provided for weather and spray protection. Spray management features (not shown) may also be built into the hull, along with a keel and strake(s). 
   An advantage of a split hull/body construction as shown in  FIG. 2  and in other figures is that the mechanical components can be built up on the hull, forming a chassis or platform; then the upper body is joined to the platform to produce a complete vehicle. In  FIGS. 2 and 3 , which only show the lower part of the vehicle, the platform is designated  30 . At each side of the vehicle is a slot  32  extending upwards from planing hull surface  20 . When the wheels  8  are retracted as shown in  FIG. 2 , each slot  32  is covered at the bottom by a cover  34 , which is held in a closed position by brackets  36  and  38  extending downwardly from a suspension tube  40 . Tube  40  is pivotally mounted inboard by means of bearings; one of which is shown as a circle  42  in  FIG. 2 ; and which can be seen as  44  and  46  on  FIG. 5 . Seals (not shown) are appended to these bearings to keep the vehicle interior watertight. The vehicle interior may be divided into compartments (not shown). 
   At the outer end of each tube  40  are brackets  50  ( FIG. 4 ), which are pivotally connected to the lower end of an intermediate suspension member  52 ; which carries a bearing hub  54  to which wheel  8  is bolted. The axes about which the inboard end of tube  40  pivots and about which bracket  50  pivots are substantially parallel relative to one another. The intermediate suspension member  52  and bearing hub  54  together form a wheel hub assembly. Intermediate suspension member  52  at its upper end is attached pivotally to an upper suspension member or link  56 , which is in turn pivotally mounted at  58  to platform  30 . An outer or distal end of the tube  40  is pivotally connected to the wheel hub assembly, the tube forming a lower suspension member. The inner end of each tube  40  is fixed to a proximal end of a longitudinal shaft  64  ( FIG. 5 ). The distal end of shaft  64  is fixed to a rotating arm  66 , which is in turn fixed to a suspension unit  68  comprising a coil spring and a co-axial telescopic damper. Unit  68  is in turn fixed to a suspension retraction rocker arm  70  ( FIGS. 6 and 7 ). Arm  70  is pivotally mounted to the vehicle platform at  72 . Suspension retraction ram  74  is mounted to platform  30  at pivot  76 , and is lengthened or shortened by pneumatic or hydraulic pressure to retract or protract the wheels, as can be seen from  FIGS. 6  (retracted) and  7  (protracted). Vehicle  2  has a prime mover  4  driving road and marine transmissions. The power train includes primary shafts  60  which each drive an intermediate shaft  62 , which connects to and drives hub  54 . The intermediate shaft  62  extends within the tube  40  substantially co-axially with the tube  40 . 
   The tube  40  will absorb loading on the wheel  8  which would otherwise have to be absorbed by the intermediate shaft  62 . The tube  40  provides a lower suspension arm for the suspension. By arranging the shaft  62  in the tube  40  there needs to be only one aperture though the hull to accommodate both, which aperture can then be sealed by plate  34 . The suspension will thus comprise the upper suspension arm  56 , which is forked (see  FIG. 7 ) at its inboard end so that it can resist fore and aft loads on the wheel  8 ; and a lower suspension arm in the form of the tube  40 . As can be seen in  FIG. 3 , the centre line of the wheel  8  will be displaced vertically by some distance from the point of connection of the inboard end of the tube  40  to the shaft  64 , thus lateral forces on the wheel  8  will develop a significant moment about the inboard end of the tube  40 . This makes it very important for the tube  40  to resist loads, rather than the shaft  62 ; and in particular, rather than the articulating joints coupling the shaft  62  to the wheel  8  and to the primary shaft  60 . 
   As may be seen particularly from  FIGS. 2 and 3 , the substantially horizontal alignment of spring and damper units  68  allows the retractable suspension to be neatly packaged below split line  18  ( FIG. 1 ). This allows a low centre of gravity and metacentric height for good handling on both land and water. The springs and dampers are also packaged within the watertight interior of the vehicle, avoiding potential problems with corrosion and seizure of joints. 
   It will be appreciated that further modifications to the vehicle layout and systems may also be made as required without departing from the scope of the invention. In particular, it may be found convenient to use a lead screw driven by an electric motor to retract and protract the wheels. Suspension units  68  may be mounted vertically, or at an angle between vertical and horizontal, if this is found convenient for packaging purposes. Air spring suspension may be used; or hydraulic spring and damper units. The latter may be combined with suspension retraction means, as described in our co-pending patent application published as WO 01/74612. 
   The transmission of power from the prime mover to the wheels may comprise electric or hydraulic drive. Although the prime mover of the claims may be an internal combustion engine, it could be any other suitable driving means, for example an electric motor driven by electricity from a fuel cell. The vehicle structure may comprise an open frame, a monocoque, or any other enclosure. 
   Whilst above the member  40  is described as a closed tube, it could equally well be formed as a cage around the shaft  40  or as an arm or a plurality of arms which extend(s) substantially alongside the shaft (parallel to or substantially parallel to) the shaft  40 , in close proximity thereto. 
   While a particular form of the present invention has been illustrated and described, it will also be apparent to those skilled in the art that various modifications can be made without departing from the spirit and the scope of the present invention. Accordingly, it is not intended that the invention be limited except by the appended claims.