Abstract:
A suspension system for an amphibious vehicle is able to be locked in either a lowered or in a retracted position according to whether the vehicle is on land or in water, respectively. The suspension system includes a main suspension arm pivoted to a vehicle hull at one end thereof and has a rotably mounted road wheel thereon at an opposite end thereof. A moving mechanism operably attached to the pivoted main suspension arm enables the arm and the road wheel to be retracted relative to the hull. An upper suspension link is operably and pivotally connected to the road wheel end of said main suspension arm and has a pivoted joint intermediate its ends. The upper suspension link is operably engagable with a suspension position locking mechanism in both the lowered and retracted positions.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a retractable suspension system for an amphibious vehicle, the suspension system being able to be raised when the vehicle is floating in water and lowered again prior to the vehicle being beached. 
     2. Related Art 
     Amphibious vehicles having retractable suspension systems are known, for example, from WO93/15923. In prior art suspension systems the suspension is held in the lowered or retracted positions by means of either a hydraulic ram, for example, or by utilisation of the weight of the suspension system itself. However, hydraulic cylinders can fail and using the weight of the suspension system itself can be problematic especially when the vehicle is in the water and being subjected to rough weather pounding. 
     Thus it is an object of the present invention to provide a suspension system which may be locked in the lowered or retracted positions without having to rely upon hydraulic cylinders or inertia forces due to the suspension mass. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a suspension system for an amphibious vehicle, the suspension system being able to be locked in either a lowered or in a retracted position according to whether the vehicle is on land or in water, respectively, the suspension system comprising: a main suspension arm pivoted to a vehicle hull at one end thereof, the arm having a rotatably mounted road wheel thereon at an opposite end thereof. A moving mechanism is operably attached to the pivoted main suspension arm to enable the arm and the road wheel to be retracted relative to said hull. An upper suspension link is operably and pivotably connected to the road wheel end of the main suspension arm and has a pivoted joint intermediate its ends. The upper suspension link is pivoted on the hull at an axis remote from the pivoted joint. The upper suspension link is operably engagable with a suspension position locking mechanism in both the lowered and retracted positions. 
     In this specification the term “hull” is used to denote any part of the body of the vehicle on which the suspension system according to the present invention is mounted or interacts with. The suspension arms and links may not be directly pivotally mounted onto the hull but may be mounted on sub-frame or bracket means, for example, which sub-frame means are mounted on the hull. In this way whole suspension units may be attached to a hull rather than in piecemeal fashion. The term “hull” thus includes suspension units or components fixed either directly to the vehicle hull or indirectly to the vehicle hull by sub-frames, brackets and the like. 
     The term “suspension system” as used herein in its broadest sense denotes the running gear which is retractable and lowerable and on which the vehicle rests and travels when on land. Thus, in its broadest sense the term “suspension system” need not include suspension springs and shock absorbing means. 
     In a preferred embodiment of the present invention, the suspension system according to the present invention further includes spring and shock absorbing devices. 
     The spring device may be any suitable device such as coil springs and/or torsion bars for example. The shock absorbing device may also be any type suitable for the application such as telescopic dampers or lever arm shock absorbers or any known system which is suitable, for example. 
     The moving mechanism may be selected from any that is suitable for the application such as hydraulic or pneumatic cylinders, ball-screw type actuators, chain or belt drives, for example. 
     The suspension raising and lowering mechanism may alternatively be in the form of a torsion bar rotating about the axis where the main suspension arm, or the axis where any other suspension arm, is pivoted to the hull. In such cases, the torsion bar may also act as the road-going suspension spring. 
     The suspension system according to the present invention is suitable for a rear, non-steering suspension or, with the addition of a swivel hub at the road wheel to main suspension arm junction, a steerable suspension system may be provided. 
     A drive mechanism may also be provided to the road wheel by any suitable means such as by articulated drive shaft to the road wheel or by belt or chain drive means to the road wheel. 
     The suspension position locking mechanism may comprise mechanical means which operably engage with the upper suspension link to prevent further movement of this component when in either of two extreme positions resulting from the suspension system being lowered or retracted. 
     When being lowered or raised, the wheel of the suspension system generally moves in the plane of the wheel, i.e. normal to the axis of rotation thereof. 
    
    
     THE DRAWINGS 
     In order that the present invention may be more fully understood, examples will now be described by way of illustration only with reference to the accompanying drawings, of which: 
     FIG. 1 shows a schematic side view of part of a mechanism in a suspension system according to the present invention for raising and lowering a road wheel; 
     FIG. 2 shows part of the mechanism of FIG. 1 connected to the remaining suspension components and a locking mechanism according to a first embodiment according to the present invention; 
     FIG. 3 shows the locking mechanism of FIG. 2 in greater detail; 
     FIG. 4 shows a perspective schematic view of a second embodiment of a suspension system according to the present invention in lowered and locked position; and 
     FIG. 5 which shows a side view of the suspension system of FIG. 4 in alternative retracted, intermediate and lowered positions. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIGS. 1 to  3  and where the same features are denoted by common reference numerals. 
     FIG. 1 shows a road wheel  12  raising and lowering mechanism which is depicted generally at  10 . The raising and lowering mechanism comprises a main suspension arm  14  having the wheel  12  mounted thereon via a hub  16  which locates the wheel and incorporates bearings (not shown) and a drive chain or shaft (both not shown) to deliver driving power to the wheel  12 . The suspension arm  14  is pivotally mounted to the vehicle hull at a strong point  18  such as a bracket or sub-frame as shown in FIG. 1, the pivot  20  being marked with reference to its axis. Drive may be provided to the wheel  12  via a chain (not shown) within the suspension arm  14  which is in the form of a hollow casing which may be filled with lubricant, the drive being provided via a shaft (not shown) rotating about the axis  20 . At the hub  16  end of the suspension arm  14  is a mounting  22  for a suspension coil spring and concentric shock absorber (not shown) unit  24  as is known to those people skilled in the suspension art. The other end of the coil spring shock absorber unit  24  is fixed to one end  25  of a second suspension arm  26  which is also pivoted about the axis  20  and mounted on the hull strong point  18 . Thus, the arms  14  and  26  may rotate relative to each other about the axis or pivot point  20  depending on the degree of compression or extension of the coil spring  24  and damper unit. The arms  14  and  26 , and coil spring damper unit  24  may be considered to be a suspension unit and may be raised or lowered as a unit by means of a cylinder and piston unit  30  which is fixed to the vehicle hull at one end via a pivot  32  and at the other end to the second suspension arm  26  via a bracket  34  and pivot  36 . The suspension unit and wheel  12  depicted at  10  is shown in two positions in FIG. 1, a first lowered position, indicated generally by the arrow “I” and, in a second, raised position, indicated generally by an arrow “II”. As will be appreciated, the suspension unit  10  is lowered and retracted by pivoting around the axis  20  on the hull  18 . In the raised position II, the wheel is retracted into a wheel/suspension receiving well  40  in the vehicle hull and the wheel  12  and suspension unit  10  are thus raised out of the water when the vehicle is afloat. 
     The lowered position I corresponds to a road going position and the retracted position II corresponds to a water-borne situation of the vehicle. Clearly, when the vehicle is about to leave the water and be driven onto land, the suspension system will be lowered whilst the vehicle is still afloat. 
     FIGS. 2 and 3 illustrate the load bearing or suspension position locking mechanism which ensures that the suspension unit  10  of FIG. 1 does not rely solely upon the cylinder and ram  30  to support the weight of the vehicle when in road use nor the weight of the retracted suspension when the vehicle is water borne. The suspension position locking mechanism comprises a strong fixed pivot bracket  50  fixed to the vehicle hull, the pivot bracket  50  having a stub shaft  52  on which is pivotally mounted an upper suspension locking link  54  which comprises a first generally U-shaped bracket member  56  and a pair of extension arms  58  which are pivoted at  60  to the open ends of the U-shaped bracket  56  at one end and pivoted at  64  to the outer swinging end  25  of the second suspension arm  26  at a bracket  65  which also receives the top end of the spring damper unit  24 . The suspension unit  10  is locked in the lowered or retracted positions by a rod  70  which is attached to the open end of the U-shaped bracket  56  by means of a yoke  68  (not shown in FIG. 2 for the sake of clarity) which is also pivoted at the pivot  60  and connected at the middle to one end of the rod  70  (see FIG. 3) at a pivot  71 . The rod  70  comprises a rigid strut member  72  having a roller  74  at its upper extremity and which bears upon a locking device  80  which will be described in greater detail with reference to FIG.  3 . The strut  72  is constrained to slide in a trunnion member  76  which is itself pivotally mounted at  77  and held in a bracket  78 . In the absence of the locking device  80 , the wheel may be lowered or retracted as desired. 
     FIG. 2 shows the suspension link  54  of the suspension unit  10  in three positions. Position I shows the link  54  when the wheel is in the fully lowered position; position II shows the suspension link  54  when the wheel is in the fully retracted position; and, position III shows suspension link  54  when the wheel is in an intermediate position between positions I and II either being raised or lowered. In the fully lowered position (I) the U-shaped upper suspension link member  56  and the extension arms  58  are linearly disposed with respect to each other. In position II the link  54  and extension arms are folded back on each other such that the faces  82 ,  84  meet. Position III shows the link member  56  and arms  58  in a mid-position between the extremes of positions I and II. 
     In order to lock the suspension in position I in the road-going position, the locking device  80  which is in the form of a tapered wedge  100 , which is moveable on rollers  102  in a strong rectangular section tube  104  fixed to the hull, is moved to a position where the roller  74  bears upon the underside of the wedge member  100 . Thus, the roller  74  on the strut  72  bears against the wedge member  100  preventing the suspension from collapsing. It should be remembered that the piston cylinder unit  30  is also present as a secondary locking facility. When the suspension is to be raised, the wedge member  100  is withdrawn by means of a second hydraulic cylinder (not shown) or other comparable means connected to the eye  106  allowing the suspension unit  10  to be raised into position II. When this happens the strut  72  passes initially through the aperture  110  in an upper face of the tube  104  whilst the link  54  and arms  58  are folding together. In the latter half of the suspension retraction cycle the strut  72  begins to be retracted until eventually at the end of the folding and retraction cycle it is again in the same position as when the suspension is in the fully lowered position and the wedge member  100  may be repositioned to close the aperture  110  and lock the strut  72  in position with the suspension in position II. In FIG. 2 the strut  72  is shown passing through the wedge  100  when in position II, however, the wedge  100  is not present during the raising or lowering cycles and is only inserted into its locking position when the suspension unit  10  is either fully retracted or fully lowered. It should be understood that the suspension system is both raised and lowered whilst the vehicle is afloat thus, only the weight of the suspension system, not that of the whole vehicle, is initially borne by the ram and cylinder  30 . 
     An advantage of the first embodiment of the suspension system according to the present invention is that it cannot jam in either the locked up or locked down positions. The locking member  100  moves on rollers  102  and the suspension strut  72  has a roller at the locking end thereof thus, the locking mechanism of the suspension system according to the present invention does not rely on pins and the like fitting into tight holes which a liable to jamming. Furthermore, the loads imposed on the individual components of the suspension system are relatively low which provides for reliable operation and relatively light weight. 
     A second locking mechanism according to the present invention is shown schematically in FIGS. 4 and 5. The main suspension unit is analogous to unit  10  shown in FIGS. 1 to  3  and is essentially the same in that it possesses the same basic elements of main suspension arm  14 , second suspension arm  26 , spring damper unit  24 , actuating piston and cylinder unit  30  and upper suspension link member and extension arms  58 . However, in this second embodiment, the upper U-shaped link member is denoted by numeral  120  in this case and has an elongated finger  122  having a roller  124  pivotally mounted thereto at the outer end thereof. The link  120  is still pivotally mounted on a stub shaft  52  fixed to hull strong point  50  (the U-shaped nature of the link  56  may be more easily appreciated from FIG.  4  and is essentially similar in the first embodiment described with reference to FIGS. 1 to  3  except that the first embodiment does not possess the extension finger  122 ). 
     When the suspension is in the lowered, road going configuration at position I, the arms  58  and upper link  120  are generally linearly disposed relative to each other. At this point the extended finger  122  and roller  124  engage with the jaw  130  of a swinging claw member  132  which is pivoted at  126  on a bracket  128  fixed ultimately to the hull  18 . The claw  132  is biased towards the finger  122  by a spring  136  acting between the hull and the claw  132 . The claw is also connected to a second hydraulic cylinder (not shown) or other actuating means by a rod  138  so as to enable the claw to be retracted away from the finger  122  and roller  124 . When the suspension is to be retracted into the wheel well  40  in the hull from the lowered position I, the claw is withdrawn from the roller  124  by the rod  138  allowing the piston cylinder unit  30  to retract and begin to raise the suspension unit  10 . As the link  120  and arms  58  begin to fold about the pivot axis  60  (shown in position III in FIG.  5 ), the finger descends to a lowest position (about commensurate with that shown in FIG. 5 when in position III) after which, in the second half of the raising cycle the finger and roller begin to rise again. Eventually the roller  124  engages the curved face  140  of the claw  132  and pushes the claw to the right as seen in FIG. 5 whereupon the roller eventually reaches the jaw  130  into which it snaps by virtue of the biasing of the claw to the left by the spring  136 . 
     Thus, the suspension unit may be locked in either the retracted or lowered positions by mechanisms which are independent of the piston cylinder unit  30  thus ensuring the safe operation and dependability of the suspension system in both the road-going and water-borne modes. 
     The two embodiments shown with reference to FIGS. 1 to  5  are non-steering, driven wheel suspension systems. However, by the introduction of a suitable swivel hub at  16 , a steering system may be introduced. When the wheels are steered they may not need to be driven and comments relating to drive means may be disregarded in this case. Furthermore, even when the wheels  12  are not steering road wheels, they may not be driven and may be passive. 
     Although actuating means utilising hydraulic cylinders have been described any suitable means such as pneumatic cylinders, electric motors and the like may be employed. 
     Although suspension arms  14  and  26  are shown as having a common pivot axis this need not necessarily be the case. The pivot axis of the inner end of the upper link  26  may be raised above that of arm  14  and the pivot axes, arms  14  and  26  and the spring unit  24  may, for example, form a parallelogram action such that the spring unit  24  is raised and lowered in a generally vertical direction. In this case suspension raising and lowering mechanism may alternatively be by, for example, a torsion bar rotating about the axis of the second suspension arm  26 , irrespective of whether the road wheel  12  is driven or passive. Such a torsion bar may also provide, when locked in the down position, the road-going spring suspension mechanism.