Suspension Mechanism

This invention relates to a suspension mechanism which is particularly suitable in suspensions for vehicles.

In this specification extensive reference will be made to bicycles in both the disclosure of the invention and the description of the preferred embodiment. This should not be construed as limiting the nature or application of the invention.

According to the invention a suspension mechanism comprises a pair of arms extending oppositely and generally collinearly from pivot positions having parallel axes, each arm being pivotable with respect to a centrally located load bearing member fixed relative to the pivot positions, and biasing means extending between each support arm and the load bearing member to bias the support arms to support the load bearing member under load in use.

Further according to the invention the biasing means extending between the load bearing member and the support arms are independently operable.

Still further according to the invention the axes of the pivot positions of the support arms are co-axial.

The biasing means may comprise, for example, one or more elastomeric members, fluid filled compression members, coil springs or leaf springs.

Each biasing means may be fixed with respect to the load bearing member and floating with respect to the support arm, acting on a suitable bearing formation of the support arm.

The biasing means may be in the form of a single leaf spring set including at least one leaf spring, centrally fixed with respect to the load bearing member and extending between the two support arms.

Still further according to the invention the load bearing member and the two support arms may be independently mounted to co-axial cylindrical members which are rotatable with respect to each other.

More particularly, the load bearing member may be mounted to an outer cylindrical member with the support arms being mounted to middle and inner cylindrical members.

To this end, the invention provides an arrangement in which the support arm mounted to the inner cylindrical member projects through suitable apertures in the middle and outer cylindrical members, and the support arm mounted to the middle cylindrical member projects through a suitable aperture in the outer cylindrical member.

Preferably according to the invention, the apertures in the middle and outer cylindrical members act as stops to limit pivotal movement of the support arms, and the aperture in each of the middle and outer cylindrical members are open to one side of the members to allow for axial movement of the cylindrical members and separation thereof.

Still further according to the invention the inner cylindrical member may be hollow to accomodate an axle of a pedal mechanism of a bicycle.

The invention also provides a vehicle frame including a suspension mechanism of the type described.

According to this aspect of the invention, the vehicle frame may be a bicycle frame or motorcycle frame.

In such a frame, the load bearing member may provide a seat support member, one support arm includes a rear wheel support fork and the other support arm is adapted to mount a steering mechanism and front wheel support fork.

The invention also provides a bicycle or motorcycle incorporating a suspension mechanism of the type described.

The invention also provides a hub comprising outer, middle and inner cylindrical members as described herein.

An embodiment of the invention, will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a side elevation of a bicycle including a suspension mechanism according to the invention;

FIG. 2 is a more detailed side elevation of the suspension mechanism; and

FIGS. 3 to 7 are various views of the components of the hub of the suspension mechanism.

In the illustrative embodiment of the invention a bicycle 1 comprises a central suspension mechanism 2 having a front support arm 3 and an oppositely directed rear support arm 4. The support arms are generally collinear.

The front support member 3 terminates in a steering mechanism 5 including handlebars 6 a front wheel support fork 7 and a front wheel 8.

The rear support arm 4 is in the form of a rear wheel support fork which supports a rear wheel 9.

The bicycle also includes the normal pedal mechanism comprising a pair of pedals 10 on pedal arms 11 which drive a front sprocket 12. The front sprocket 12 drives a rear sprocket 13 by means of a suitable drive chain 14 which is tensioned by a tensioning device 15.

The suspension mechanism 2 includes a load besring member in the form of a seat stalk 16 to which a seat 17 for the bicycle is mounted.

From FIG. 2 of the drawing, which shows the suspension mechanism 2 in greater detail, it can be seen that the front and rear support arms 3 and 4 are pivotally mounted with the axes of their pivot positions co-axial and fixed with respect to the load bearing member 16. Thus each of the support arms 3 and 4 can move in directions towards and away from the load bearing member 16. Arms 3 and 4 are normally generally collinear and are biased against moving towards the member 16 by a leaf spring set 17 which comprises a pair of leaf spring 18 firmly clamped by a clamping mechanism 19 on the load bearing member 16. The leaf spring set includes an aperture (not shown) therethrough through which the load bearing member 16 passes before terminating in the pivotal hub 20 supporting the front and rear support arms 2 and 3.

The two ends 21 of the lower spring 18 of the leaf spring set 17 are not fixed to the front and rear support arms 3 and 4. Rather, they are floating and bear against bearing formations in the form of small roller mountings 22 fixed to the two arms. In this way this leaf spring set exerts a biasing force away from the load bearing member 16 and so provides a comfortable suspension for the bicycle which may also be used in trick riding.

The pivotal hub 20 is depicted in greater detail in FIGS. 3 to 7 of the drawings.

FIGS. 3 and 4 show that the pivotal hub 20 comprises 3 co-axial hollow cylindrical members 23, 24 and 25 having suitable bearing surfaces therebetween so as to allow them to freely rotate relative to each other. The bearing surfaces may be lubricated using suitable lubricants or made from self-lubricating material.

Mounted to the inner cylindrical member 25 is a short socket member 26 which is located in an aperture in the cylindrical wall of the cylindrical member 25 and which is welded in postion. The socket member 26 is provided for mounting of the front support arm 3 which may be inserted therein and welded in position.

The socket member 26 projects through an aperture 27 in the cylindrical wall of the middle cylindrical member 24. This aperture 27 is centrally located along the width of the cylindrical wall but is open to one side 28 of the cylindrical member 24 by way of a slot 29 (FIG. 5). It will be appreciated that this is essential to enable the inner cylindrical member 25 to be inserted into the middle cylindrical member 24 and hence the socket member 26 into the slot 27. The slot 27 is rounded at each end to accomodate the socket member 26 and the length of the slot 27 is predetermined to allow for a desired pivotal movement of the inner cylindrical member with respect to the middle cylindrical member 24.

On the opposite side of the middle cylindrical member 24 from slot 27 there is a second socket member 30 which is substantially the same as the first socket member 26 and which is welded to the middle cylindrical member in a similar manner. The rear support arm 4 of the suspension mechanism, which as stated above is in the form of a rear wheel fork, is inserted into the socket of the socket member 30 and welded in position. The outer cylindrical member 23 is provided with two diametrically opposed slots 31 and 32 (FIGS. 6 and 7) for accommodating the front and rear socket members 26 and 30 respectively. Slots 31 and 32 are open to one side 33 of the cylindrical member 23 to facilitate insertion of the middle and inner members 24 and 25 into the outer member 23 and hence the socket members 26 and 30 into the slots 31 and 32.

The lengths of the slots 31 and 32 are such as to limit the degree of travel of the socket members 26 and 30 with respect to the outer cylindrical member 23.

A third socket 34 is welded to the outer cylindrical member 23 and serves as a mounting for the load bearing member (shaft) 16 received therein and welded in position.

To prevent axial movement of the three cylindrical members 23, 24 and 25, an annular cap 35 is threaded onto the outer cylindrical member 23 at side 33. This cap effectively closes all of the openings to the slots 27, 31 and 32.

Within the inner cylindrical member 25 are located suitable bearings (not shown) for supporting an axle for the pedal mechanism described above.

As previously mentioned, when the bicycle is unloaded (that is riderless), the support arms will be substantially collinear. When a rider is mounted on the bicycle, the support arms deviate slightly from their collinear positions and the leaf spring set takes up the load, biasing the support arms and hence the wheels away from the load bearing member carrying the saddle. The suspension mechanism is now operative and will adsorb additional loads such as are occasioned by bumps and the like. Furthermore, the suspension mechanism may be utilized for doing tricks and the like. By exerting a sudden downward force, the bicycle may be "jumped" for example.

In these actions the support arms are moved further from their collinear positions and the chain tensioner 15 maintains chain tension as the sprockets move closer together. This movement of the arms is shown in broken lines in FIG. 3.

From what has been described it is clear that the invention provides a novel suspension mechanism having unique characteristics and a relatively simple construction.

It will also be appreciated that because of the nature of the pivotal hub 20, the bicycle may easily be separated into basic component parts by removal of the retaining member 35 and separation of the cylindrical members of the hub.

Other embodiments are envisaged within the scope of the invention including other forms of biasing means such as elastomeric members, springs of plastics materials, coil springs in various configurations and fluid filled compression members. Furthermore, the suspension device may be used in a wide variety of vehicles, particularly wheeled vehicles such as motor bikes.