Abstract:
A suspension arrangement for a wheeled conveyance, the suspension arrangement including a mounting member, at least two pairs of wheels and a biasing structure, the mounting member supporting thereon in an operable manner the pairs of wheels, the biasing structure acting between the mounting member and a remote point so as to cause the mounting member to pivot about a pivot point provided thereon and through which the mounting member is joined to the remainder of the conveyance.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a suspension arrangement for a wheeled or self-laying tracked conveyance. More particularly, the suspension arrangement of the present invention is intended for use in providing substantially smooth transition over uneven terrain for the conveyance on which it is provided. The suspension arrangement of the present invention is further intended most particularly for use on bicycles and motorcycles but is not to be limited thereto. 
     DISCUSSION OF THE PRIOR ART 
     A number of attempts have been made previously to provide a gliding or skating sensation when utilising a bicycle or similar conveyance. In this regard reference may be made to U.S. Pat. No. 4,863,182, Australian Patent Application 32359/89 and British Patent Application 2 122 557. Each of these documents discloses a bicycle like conveyance on which the front wheel, forks and handle bars have been replaced by a single pair of small wheels, for example skateboard wheels, mounted transversely on a single axle. This arrangement requires the rider to steer entirely by shifting their body weight which in turn acts on a truck supporting the axle of the pair of wheels. Many riders find this an arrangement that is difficult to operate and may be dangerous as a result. 
     Another factor contributing to the dangerous nature of the prior art is the inability of the pair of small wheels to ride over even small obstacles. As such, a rider encountering an obstacle at speed may be thrown forward dangerously. 
     Wheelchairs and other mobile chassis suffer from similar problems in that whilst such can travel well over smooth surfaces there can be problems of instability when transversing even small obstacles, particularly if castor-type wheels are utilised. The suspension systems for such vehicles are often particularly complicated and consequently expensive. 
     The suspension arrangement of the present invention has as one object thereof to overcome substantially the above problems associated with the prior art. 
     Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with the present invention there is provided a suspension arrangement for a wheeled or self-laying tracked conveyance, the suspension arrangement characterised by a mounting member, at least two pairs of wheels and a biasing means, the mounting member supporting thereon in an operable manner the pairs of wheels, the biasing means acting between the mounting member and a remote point so as to cause the mounting member to pivot about a pivot point provided thereon and through which the mounting member is joined to the remainder of the conveyance, wherein the pairs of wheels are preferably spaced apart longitudinally along the mounting member whereby action of the biasing means acts to lift a forwardmost portion of the mounting member and in turn the wheel pair provided thereon. 
     Preferably, the pairs of wheels are mounted on axles extending transversely with respect to the mounting member. 
     The pivot point of the mounting member is preferably provided directly or indirectly with respect to a pair of forks or a single piston. The forks or piston are in turn connected to a steering means, for example a pair of handle bars, whereby in normal use the weight of a rider acting downwardly through the conveyance, handle bars and front forks or piston causes extension of the biasing means and results in both wheel pairs on the mounting member contacting a supporting surface. Upon the rider releasing the downward pressure on the mounting member the biasing means acts to lift the forwardmost portion of the mounting member and in turn the forwardmost wheel pair provided thereon. In this manner the rider effectively controls the operation of the suspension arrangement in mounting obstacles. A rider may determine that an obstacle is approaching, pull up on the handle bars and thereby allow operation of the suspension arrangement. 
     It is to be understood that the suspension arrangement of the present invention may be utilised as at least the forward wheels on a variety of conveyances including bicycles, tricycles, motorcycles, wheelchairs, trolleys, go-carts, prams. scooters and land sail-boards. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The suspension arrangement of the present invention will now be described, by way of example only, with reference to one embodiment thereof and the accompanying drawings, in which: 
     FIG. 1 is a side elevational view of a bicycle to whose front forks the suspension arrangement of the present invention is fitted; 
     FIG. 2 is an upper perspective view of the suspension arrangement of FIG. 1 showing the mounting member and biasing means thereof; 
     FIG. 3 is a side elevational view of the mounting member of FIG. 2 with the weight of the bicycle bearing thereon and showing the biasing means in an extended state: 
     FIG. 4 is a side elevational view of the mounting member of FIG. 2 with the weight relieved therefrom and allowing pivoting of the suspension arrangement; 
     FIG. 5 is a side elevational view of the mounting member of FIG. 2 with the weight relieved therefrom and showing the biasing means contracted to raise the forwardmost wheel pair; and 
     FIG. 6 is a side elevational view of the mounting member of FIG. 2 showing the first fork members having moved with respect to the second fork members to absorb the shock of mounting an obstacle. 
    
    
     DESCRIPTION 
     In FIG. 1 there is shown a bicycle  10  having a frame  12 , a rear wheel  14 , a drive means  16  and a seat  18 . The bicycle  10  is further provided with handle bars  20  and front forks  22 . The handle bars  20  and front forks  22  are rotatably located through a hollow neck  24  of the frame  12 . The front forks  22  have provided at a lower end thereof a pivotally located mounting member  26  supporting thereon two wheel pairs  28 , the mounting member  26  and wheel pairs  28  in part comprising a suspension arrangement  30 . 
     In FIGS. 2 to  4  there is shown the suspension arrangement  30  comprising the mounting member  26  and wheel pairs  28 . The wheel pairs  28  are provided in the form of skateboard wheels  32  mounted on a transverse axle  34 . The axles  34  having a flexibly resilient mounting to a base member  36  of the mounting member  26  to allow the wheels  32  to remain in contact with a surface  38  over which they are travelling even when the mounting member  26  is not positioned perpendicularly with respect thereto, in a similar manner to that of a skateboard. 
     The mounting member  26  further comprises a pair of flanges  40  extending upwardly from the base member  36  in a substantially opposed and parallel manner. The flanges  40  are provided in a substantially triangular form, being broadest at their base  42  at which they are attached/formed integrally with the base member  36 . Adjacent an apex  44  of each flange  40  there is provided a pivotal mounting to the forks  22  comprising a hollow tube  46  extending between the apex  44  of the flanges  40  and through which is received a bolt  48 . The bolt  48  further locates about the pivotal mounting a first pair of fork members  50 . 
     Each fork member  50  has fixedly attached thereto an intermediate member  52  connecting in turn to a secondary mounting member such as a fork member  54  of a second pair of fork members. The fork members  54  extend upwardly and converge to form a neck portion (not shown) that is received rotatably through the neck  24  of the frame  12  in known manner. 
     The fork members  50  have extending therebetween a first fixing point  56  for a biasing means, for example a spring  58 . The fixing point  56  comprising a pair of members  60  mounted to the members  50  and defining a pair of matching apertures through which a hook  62  of the spring is received. The spring  58  is located at its other end about a lug  64  projecting between the flanges  40 . The lug  64  is spaced forwardly with respect to the tube  46  such that contraction of the spring  58  will cause the mounting member  26  to pivot about the pivot point described by the tube  46  and bolt  48 . It is to be understood that the lug  64  may be similarly provided as a forwardly projecting lug from the tube  46  and achieve the same function. 
     The flanges  40  each have a stop member  66  provided thereon and located forwardly of the first fork members  50 . Upon pivotal movement of the mounting member  26  induced by the spring  58  the stop members  66  engage the first fork members  50  to limit that pivotal movement. 
     In FIGS. 4 to  6  there is shown a step  68  in the surface  38 . In FIG. 4 an upward force  69  exerted by the rider (not shown) allows the mounting member  26  to pivot upwardly as shown by arrow  71 . The spring  58  is seen in a contracted state drawing the forwardmost wheel pair  28  upwardly and in position to best move over the step  68 . The stop members  66  are notably in engagement with the first fork members  50  thereby limiting the pivotal movement of the mounting member  26  about the tube  46  and bolt  48 . 
     The second fork members  54  are movable with respect to the first fork members  50  through the use of the intermediate members  52 , as can be seen in FIG.  6 . Heavy upward or downward pressures can be absorbed by the first fork members  50  moving upwardly with respect to the second fork members  54 . A further biasing means  72 , shown in FIG. 1, is provided in the connection between the first and second fork members  50  and  54  to either bias the first fork members  50  downwardly or the second fork members  54  and the remainder of the bicycle  10  in an upward direction. A lower stop member  70  is provided on each flange  40  rearwardly of the bolt  48  to limit downward movement of the intermediate members  52  and thereby limit downward travel of the second fork members  54  with respect to the first fork members  50 . 
     In use, a rider (not shown) may mount the bicycle  10  in known manner and may operate the drive means  16  of the bicycle  10  also in known manner. With the weight of the bicycle  10  and also the weight of a rider being transferred downwardly through the front forks  22  the suspension arrangement  30  is positioned such that each wheel pair  28  is in contact with the surface  38  over which the bicycle  10  is being ridden, as is shown in FIGS. 1 and 3. 
     In the position of the suspension arrangement  30  shown in FIGS. 1 and 3 the spring  58  is stretched between the lugs  64  and fixing point  56  under the weight of the bicycle  10  and the rider. Any upwardly or downwardly directed sudden shocks may be absorbed by the biasing means (not shown) utilised in the connection between the first and second fork members  50  and  54  whereby the second fork members  54  move downwardly with respect to the first fork members  50  such that the intermediate member  52  moves towards the stop members  70  of the flanges  40 . This biasing means is arranged such that at rest the second fork members  54  are moved or biased upwardly with respect to the first fork members  50 . 
     Upon a rider of the bicycle  10  identifying a step  68  in the surface  38  over which the bicycle  10  is travelling he may exert a brief upward pull on the handle bars  20  which relieves downward pressure through the forks  22  such that the mounting member  26  is caused to pivot about the bolt  48  thereby “kicking up” the forwardmost wheel pair  28  to mount the step  68  in a smooth manner. The spring  58  acting through the lug  64  causes the rotation in the mounting member  26  as noted hereinabove. 
     As the rearmost wheel pair  28  subsequently mounts the step  68  this shock may be absorbed in the previously described manner through the biasing means (not shown) provided between the first fork members  50  and the second fork members  54 . These features contribute to a comparatively smooth ride over fluctuations in terrain for the rider of the bicycle  10 . Such is the case also if the rider does not identify the step  68  prior to the bicycle  10  travelling thereover as the bias in the mounting member  28  induced by the spring  58  is such that upon encountering a step  68  of this nature the suspension arrangement  38  will travel smoothly thereover rather than simply abutting against the step  68  and causing either a very rough ride or actually causing the rider to be thrown from the bicycle  10  as has been the case with many prior art arrangements. 
     It is envisaged that the particular form of the mounting member  26  may be varied in that the materials from which the member is constructed may be altered without departing from the scope of the present invention. Further, the exact nature of the wheel pairs  28  may similarly be altered without effecting the scope of the present invention and it is envisaged that even a self-laying tracked arrangement may be utilised. Still further, a single piston may replace the pair of fork members  54  to function as a secondary mounting member, the intermediate members  52  attaching thereto in the same manner. 
     It is further envisaged that forms of suspension other than the standard skateboard truck may be utilised with the present invention. For example, a form of independent suspension for each wheel provided on the mounting member  26  may be utilised, such as a cantilever arrangement. 
     It is still further envisaged that the suspension arrangement of the present invention may be applied in a similar manner to other conveyances including motor cycles, wheelchairs, trolleys, go-carts, land sail-boards, prams and scooters. It is to be appreciated that this list is not exhaustive. 
     Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.