GB2303342A - Adjustable cycle suspension using rubber rings as springs - Google Patents

Description

"Improvements relating to Suspension Systems" This invention relates to suspension systems, and it is particularly concerned with one for mountain bikes. Instead of a completely rigid frame and rigid front forks, these incorporate means giving the bike a certain resilience.

Although it is primarily intended for bicycles, it is conceivable that the invention could also be applied to tricycles, or even monocycles.

The spring most generally used at present between the main frame and the rear wheel fork is a large coil spring.

It looks crude and its rate cannot be altered. It is the aim of this invention to provide a smoother and more compact device which can be adjusted.

According to the present invention there is provided a spring suspension device for a bicycle comprising cooperating mutually captive members for attachment to relatively movable parts of a bicycle frame, the members having mating conical surfaces with elastomeric rings trapped between them.

Thus, axial movement of the members to bring the cones closer together rolls and squeezes the rings. But as the members move apart again, the rings roll back to resume their original shape and position.

The attachment of the members to the frame will usually be pivotal.

In one embodiment, there may be a single pair of mating coned surfaces with rubber rings of different sizes interposed between them, according to their positions axially of the cones.

Alternatively, there may be a plurality of mating coned surfaces, not necessarily with the same cone angle, axially aligned and with one ring interposed between the coned surfaces of each pair. The rings can then be of the same size.

The device may be made readily dismantleable, so that the spring characteristics can quickly and easily be altered by changing the elastomeric rings.

The spring device may further be adapted to provide air damping.

In one preferred embodiment, a piston formed by or fitted to one member providing one of the coned surfaces may move axially within a cylinder provided by the member providing the other coned surface. Generally, the members will be made captive to one another by a co-axial bolt, and the head of this bolt may form the piston. An air bleed passage may lead from the cylinder, and there can be means for adjusting its outlet, and thereby altering the degree of air damping.

Provision can also be made for altering the length of the spring, without necessarily altering its characteristics.

For a better understanding of the invention, some embodiments will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is an axial section of a spring device for a bicycle suspension system, Figure 2 is an axial section of another such spring, and Figure 3 is an axial section of a third such spring.

Equivalent parts in the various figures are similarly referenced.

In Figure 1, a resilient suspension device has an upper member 1 and a lower member 2 which are designed to be pivotally attached to parts (not shown) of a bicycle frame.

The member 1 is extended by a frusto-conical hood secured to its lower end and terminating in an out-turned lip 4. The upper end of the member 2 has a conical surface 5 with the same cone angle as the hood 3, and it penetrates partially into that hood and is co-axial with it. Engaged between the surface 5 of the interior of the hood 3 there are rubber rings 6 and 7. The ingress of dirt is prevented by an annular boot 8 which fits over the rim 4 at its upper end and engages in a groove 9 at its lower end.

The members 1 and 2 are coupled by a bolt 10 which screws into the lower end of the member 1 and whose head 11 is within a co-axial passage 12 of the member 2. This steps in near its upper end at a shoulder 13, and a washer 14 is interposed between the bolt head and that shoulder.

It will be appreciated that, in the condition shown, the members 1 and 2 cannot separate any further, being held mutually captive by the bolt 10. But if the forces on the bicycle frame are such as to urge the members 1 and 2 together, the rings 6 and 7 roll and deform as the cone surface 5 penetrates further into the hood 3.

Referring to Figure 2, the hood 3 is integral with the member 1, but now it has two similar internal coned surfaces 15 and 16 in tandem. Likewise, the member 2 has its upper end shaped with two coned surfaces 17 and 18, also in tandem. There is a curved shoulder 19 between the surfaces 15 and 16, and a curved shoulder 20 between the surfaces 17 and 18, and in the relaxed state of the device, as shown, rings 21 seat on them. These rings are identical in size and shape. As mentioned above, although here the cone angles are shown to be the same, they could differ.

Thus, for a slightly more complex construction, there is the advantage of not having differently sized rings.

Referring to Figure 3, this is similar to Figure 1, but it additionally has air damping. The member 2 is now made in several parts which can be fitted together, and what was the passage 12 open at the bottom now becomes a closed cylinder 22. The head 11 of the bolt 10 serves as a piston which, as the members 1 and 2 are closed together, compresses the air in the cylinder 22. A bleed passage (not shown) can lead from the cylinder to the exterior, and be fitted with a screw, or other device, that can adjust the air flow, and thus the degree of damping generated by the piston and cylinder.

Between the member 1 and the hood 3 there is a spacer 23, and the member 2 is constructed of several elements, namely a main body 24 and a cone 25 with a spacer 26 between them, surrounding a spigot of the body 24 which screws into the cone 25. It will be appreciated that either or both of these spacers 23 and 26 can be changed for ones of different thickness, thereby to alter the overall length of the device without changing the spring characteristics. This facility can be used to vary the relative positions of the wheels of the bicycle.

All these devices can readily be dismantled to change the rubber rings. This enables the supension characteristics to be altered to suit the user.

Claims (4)

Claims

1. A suspension system to be incorporated into the chassis ofpowered or non-powered (selfpropelled) lightweight vehicles, primarily cycles. To be used at the front of the vehicle, adjustable to accommodate different rider weight/loads.

2. A suspension system as claimed in 1. but incorporated into the rear of the frame/chassis of the vehicle.

3. A suspension system as claimed in 1. & 2. but incorporated into the front rear frame chassis.

4. A suspension system as claimed in 1, 2 & 3 but additionally incorporating hydraulic or air damping.