VEHICLE WITH RETRACTABLE WHEEL
Field of Invention
This invention relates to vehicles with retractable wheels, especially, but not exclusively, suitable for use in amphibious craft. In particular, the invention concerns the supporting of the wheel position while the wheel is in use.
Background to the Invention
In most known amphibious craft or vehicles the wheels are movable between a lower position in which they engage the ground and via which the vehicle is driven on land, and a raised position in which they are stored while they are not in use. It is necessary to support the wheels in at least the lower position. The wheels may be held in the lower position by the retraction mechanism which raises and lowers the wheels by, for instance, a hydraulic ram. Such an arrangement does not provide adequate safety and it does not cater for ram failure.
WO 93/15923A discloses a vehicle having a wheel retraction mechanism in which a support element is connected to the wheel via a coupling on the element. Means are provided for moving the support element in a path encompassing a highest position of the coupling, a lowest position of the coupling, and an upward return beyond the lowest position. The means for moving the element comprises a rotary member and the mechanism includes an abutment disposed in the path of the element to limit the upward return of the element. In a preferred arrangement, and as illustrated in the
drawings, the wheel is also stopped in the raised position by an abutment disposed in the path of the support limit to limit the down return of the element past the highest position of the coupling.
It is stated that, by overcentering the support element at upper and lower positions, the wheel is held in position by the prevailing forces on the support element, thus removing the necessity for other locking mechanisms.
Although this arrangement works well in normal conditions, there is a danger that the support element can lift away from the abutment when the vehicle is in rough seas. Furthermore, there is also a problem in that the suspension can develop rattles when the vehicle is in use on a bumpy road.
In addition there is a need for a safety mechanism preventing the support element being moved to the point where it is no longer over centre and the weight of the vehicle is then taken by the retraction mechanism instead of directly by the chassis/hull of the vehicle. This could result in the accidental retraction of the wheel and the suspension.
Statements of Invention
According to a first aspect of the present invention there is provided a wheel retraction mechanism for a vehicle having a wheel which is movable between a lower position and a raised position by a wheel retraction mechanism, the wheel retraction mechanism comprising a support element connected to the wheel via a coupling on the element means for moving the element in a path
encompassing a highest position of the coupling, a lowest position of the coupling, and an upward return beyond the said lowest position, the means for moving the element comprising a rotary member and the mechanism including an abutment disposed in the path of the element to limit the upward return of the element, the support element being further connected to means urging it into engagement with the abutment .
Preferably the mechanism includes a further abutment disposed in the path of the support element to limit the down return of the element past the highest position of the coupling, and the urging means also acts to urge the support member into engagement with said further abutment.
Preferably the urging means includes a flexible elongate element attached to the support element and being spring urged into engagement with the abutment and the further abutment .
Preferably the flexible elongate element extends from the support element to a spring arrangement along a path of travel which passes between said abutment and said further abutment. More preferably the path of travel passes substantially midway between said abutment and said further abutment.
According to a second aspect of the present invention, there is provided a vehicle having the suspension raising and lowering mechanism of the first aspect.
Brief Description of the Drawings
Figure 1 shows a perspective view of a front suspension wheel supporting system on which the safety mechanism of the present invention may be employed; and
Figure 2 which shows a front elevation of a safety mechanism according to the present invention and which may be used in conjunction with a suspension system of the type shown in Figure 1.
Detailed Description of the Invention
The invention will now be further described, by way of example only, with reference to the accompanying drawings which show a chain lifting mechanism for a front suspension of an amphibious vehicle described below with reference to Figure 1.
A typical front suspension on which the safety mechanism of the present invention may be used includes a pillar which comprises a lower section C mounted for sliding movement over an upper section B. The upper section B of the pillar is pivotally anchored at its upper end at A and steering arm S is linked to the steering mechanism and a driver' s steering wheel (both not shown) . Lower section C of the pillar moves up and down the upper section B as a result of road movement. Furthermore, lower section C is designed to slide partially or fully up to the top of upper section B when the wheel and suspension are fully retracted.
A spring Q extends within the hollow pillar sections B and C from top pivot A to a lower pivot T associated with
bottom suspension arm F (referred to below) . Spring Q provides sufficient force to counter-balance the weight of suspension wishbone arm F and pillar C which is pivotally connected at T and maintaining contact with the carriage frame R (referred to below) as it rises and falls with suspension movement when the retraction mechanism is operated.
A collar E is fitted on lower section C of the pillar to be slidable up and down and rotatable with the pillar. In this case the section of the pillar and that of the collar are both square. However, the shape is not important so long as the sections co-operate to prevent relative rotation between the pillar and the collar.
The road wheel (not shown) is fitted on the wheel hub D which is mounted directly onto the collar E.
A collar carrier or carriage frame R transfers the load from the road wheel and the collar E via the suspension unit H and onto the chassis or body (not shown) . The carriage frame R also allows movement of the collar E up and down section C of the pillar. Carriage frame R is connected to the lower end of a spring and damper arrangement H, this arrangement H being located on the opposite side of pillar section C to the road wheel hub D.
The spring and damper arrangement H provides a suspension device or shock absorber with a compression spring fitted around a piston and damper in the usual way. The upper end of the arrangement is hinged to a support arrangement comprising a rod M mounted on and fixed to travel with a double chain K (one chain only being shown in the
drawing) . The double chain K is a strong continuous chain mounted about three pairs of rotary members in the form of sprockets. The sprockets forming each of the sprocket pairs are locked together on respective common shafts to maintain parallel motion of the chains and thereby prevent tilting of the rod to which the mechanism H is attached. The shafts are supported for rotation on a frame or chain carrier N which is bolted to the chassis/hull 100 of the vehicle by bolts P. Chain carrier N includes opposed side walls which are connected together by means of a rear wall through which bolts P extend. Shaft J is a drive shaft which extends outwardly from one of the side walls of chain carrier N and is driven either clockwise or anti-clockwise by a rotary motor such as an electric motor (not shown) causing the rod M, to which arrangement H is attached, to move up or down in a path determined by the movement of the chains K and the sprockets. This in turn lifts or lowers the suspension device H. The cross-bar M is supported on upper rests L (and corresponding lower rests) .
Lower section C of the pillar is pivotally mounted to the chassis/hull via a bottom wishbone-shaped suspension arm F which is hinged to the chassis/hull at G. Suspension arm F moves up and down with the road wheel along with the lower pillar member C.
As illustrated in Fig. 1, the wheel (not shown) is in its lowered position for road use. To retract the wheel when the vehicle is on water, the operator causes the motor to turn the drive shaft J and move the sprockets and chains in a clockwise direction. The cross-bar M is thereby carried from the position shown in Fig. 1 initially downwardly and then upwardly along the length of the
chain carrier N. There is then a further downward movement until cross-bar M engages in inset rests L.
During this movement the suspension arrangement H causes the carriage frame R to rise to its maximum height carrying with it the collar E, wheel hub D and the road wheel (not shown) . At the same time the spring Q maintains an upward force on the wishbone arm F and pillar member C on the carriage frame R and when the pillar C reaches its upper limit, the carriage frame arm R continues to lift by sliding up lower pillar section C, thereby carrying collar E, wheel hub D and the road wheel (not shown) to a position just below steering arm S at the top of the telescoped pillar sections B and C. The wishbone arm F having reached the limit of its arc of movement may not necessarily be able to follow the carriage frame R to the extremity of its upper movement.
Figure 2 shows an illustration of a spring loaded safety mechanism as an additional feature over Fig. 1 and which safety mechanism is the particular subject of the present invention. The overall wheel retraction mechanism is as described with reference to Fig. 1.
As shown in Fig. 2 the safety mechanism of the present invention includes a stainless steel wire strop X secured at one end to the suspension cross bar M. From cross bar M, strop X extends along a path which passes between two pulleys U and V. Pulley U is a freely rotating pulley which is mounted on a spindle extending between the sprockets of a driven double sprocket W. Pulley V is mounted on a bracket below driven double sprocket W. The path of travel of strop X then passes over a further pulley Y which in this example is located internally on
the wheel arch section of the hull where it can be more easily seen. Strop X then passes through a strong compression spring Z which is retained in a cylinder. At its end remote from cross bar M, strop X is attached to a toggle T which sits in a socket which in turn compresses spring Z when tension is applied to the strop X. Tension is indeed applied to the strop X when the cross bar M is at the upper and lower abutments L and also throughout the movement of cross bar M around the top and bottom sprockets.
When the cross bar M is carried by the chains K from the top to the bottom rests L, the bar traverses along the path of the chains. Between the top and bottom sprockets there can be considerable slack in the strop X and, in some cases, the sprockets are wide apart. This slack is taken up by a long tension spring Zz which is attached at one end to toggle T and the other end to an anchoring point secured to the hull. When there is slack, the toggle T comes out of its socket and the strop runs through the compression spring Z until all the slack is taken up. The two pulleys ϋ and V are located substantially midway between the upper and lower abutments L so that the strop is guided thereby onto the single pulley Y, whether the cross bar M is in its lower position or its upper position.
Generally speaking, the two pulleys U and V are located above the centre line of the chain carrier M in order to create more tension in the strop when the cross bar M is in its lower position, as illustrated in the drawing. In this way the cross bar M is clamped more firmly into its rests during road use of the vehicle.
The above described mechanism prevents the cross bar M, which carries the suspension H dropping away from the lower rests L or lifting away from the upper rests L. The cross bar M transfers the load of the vehicle directly to the chassis/hull at the position of the lower rests L when the vehicle is on land. Furthermore, the cross bar M supports at the upper rest L the weight of the suspension, hub and wheel when retracted when the vehicle is in water. It could otherwise lift away from rests L when in rough seas, for example. Furthermore the cross bar M is held firmly into its lower rest sockets, thereby preventing rattles in the suspension when in use on a bumpy road, for example.
In addition, the above described mechanism acts as a safety mechanism preventing the chains moving and the sprockets rotating to the point where the cross bar M is no longer over-centred and the weight of the vehicle is then taken by the chain instead of directly by the chassis/hull. Without the safety mechanism, the wheel and suspension could be accidentally retracted.