GB2284185A

GB2284185A - Bicycle rear suspension

Info

Publication number: GB2284185A
Application number: GB9324527A
Authority: GB
Inventors: Bruce Cameron Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-11-30
Filing date: 1993-11-30
Publication date: 1995-05-31
Also published as: GB9324527D0

Abstract

The suspension comprises two main components, a housing member, A, mounted to the lower part of the frame, and a rear swinging arm, B, pivotally mounted thereto. The rear tube of housing A contains a piston and connecting rod and two springs which provide spring suspension and damping. The front tube of housing A may have, at its lower leading edge, a bush to which arm B is pivoted. Arm B has a mounting for a wheel, a crank housing and bushes which attach with, for example, a through pin or bolt, to the aforementioned bush of housing A. Arm B also has mountings to connect to the crankshaft suspension. Provision is also made for a pedal assembly. <IMAGE>

Description

BICYCLE REAR SUSPENSION SYSTEM This invention relates to a rear wheel suspension system for a bicycle.

Bicycles are a well known form of transportation which generally comprise a rigid frame with a steerable front wheel and a chain driven back wheel. The rider provides the power for propulsion by straddling the bicycle and turning pedals, set at the base of the frame1 with his or her feet. The pedals are connected via cogs and chain to the rear wheel.

Historically, suspension on a bicycle has generally been provided by the pneumatic tyre and sprung saddle. Rowever, with the advent of recreational bicycles designed for use in rougher terrain, there is a need for some form of simple suspension system, without external springs, that can be incorporated during manufacture or added to existing bicycles.

According to the present invention there is provided a rear suspension assembley for a bicycle comprising a unit of welded or cast construction, fitted to the lower rear end and the lower front end of the mainframe of the bicycle, the rear part thereof containing a piston, connecting rod and springs, the front part thereof incorporating a yoke or other form of hingeing to a rear swinging arm frame, of welded or cast construction, which supports the rear wheel and has provision for a pedal assembley and adjacent mounting for the connecting rod of the afformentioned piston.

specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows in side view, the suspension system and its relationship to a standard dimension bicycle frame.

Figure 2 shows in side view, the suspension system comprising unit A and unit B.

Figure 3 shows in plan view, the suspension system comprising unit A and unit B.

Figure 4 shows side and front view of unit A of the suspension system.

Figure 5 shows side and front view of unit B of the suspension system.

The suspension system can be fitted to existing bicycle frames or can be incorporated at manufacture, it does away with the necessity for supporting framework from the top rear of the mainframe to the rear wheel hub carrier as shown in Fig 1. The suspension system is in two parts, unit A which is attached to the frame of the bicycle by welding, brazing or some other method and unit B which is fitted to unit A as shown in Figs 2 and 3.

With reference to Fig 4. Unit A can be of cast or welded construction, it comprises a rear tube 1 connected to a front tube 2 by a reinforcing web 3 so as to create an angle between the two tubes similar to the lower frame angle of the type of bicycle frame to which it is to be fitted. In this example the internal diameter of the rear tube 1 and the front tube 2 is 2.8 cm. which is similar to the external diameter of some bicycle frames.

The rear tube 1 is threaded for 3cm. at its bottom end which allows a threaded spring cup retainer 5 to be screwed in to retain the springs 6 and to provide for spring tension adjustment. The spring retainer 5 has an oval hole through it to allow free movement of the connecting rod 4.

The spring retainer 5 can be safeguarded against loosening by use of a lock ring or similar component (not shown) after fitting. The piston 9 is located between the upper and lower springs 6 and is connected by a moveable joint, for example a gudgeon pin, to a connecting rod 4 which in this example is of a length to give a distance of 10cm. from the top of the piston 9 to the centre of the lower swivel joint, for example a gudgeon pin, of the connecting rod 4. A thin layer of shock absorbing material 7 is placed internally at the top of the rear tube 1.

Upper and lower springs 6 can be of the same or dissimilar ratings. For this example uncompressed length is 7.5cm. fully compressed length is 2cm. and spring diameter is 2.5cm.

The front tube 2 has a deeper socket, in this example 4cm., for fitting to a bicycle frame due to more stress at this site during use. At its lower front extremity, supported by a web in this example, is a bush 8 to which unit B is attached by a nut and bolt or some other means. This bush 8 needs to be strong enough to take twisting forces as it is the main linkage of the bicycle frame to the rear wheel.

With referance to Fig 5. Unit B can be of cast or welded construction and comprises a frame to hold the rear wheel (also illustrated in Fig 3) connected to or part of the crank housing 15 which is of standard size.

On the crank housing 15 are two supports 12 set, in this example, 140 from the rear frame horizontal to their centrelines and have between them an horizontal reinforcing member 14. The supports end in a bush II which connect by means of a pin or bolt (not shown ) to the bush 8 of unit A (Fig 4. ) This in effect is the axis of the rear suspension movement. In this example there is a distance of 8cm. from the centre of crank 15 to the centre of bush 11. The other feature of unit B are the mounting brackets 13 on the crank housing 15 to take a pin or bolt to hold the lower end of the connecting rod 4 in unit A (see Fig 4. ) Properly constructed, with the suspension unloaded, the centreline of the rear mainframe should pass through the centre of the piston 9, the centre of connecting rod 4, centre of mounting bracket13 and centre of the crank housing 15. The maximum piston travel from rest, in this example, is 2.5cm. up or down.

Claims

1. A rear suspension assembly for a bicycle comprising a unit of welded or cast construction fitted to the lower rear end and the lower front end of the mainframe of the bicycle, the rear part thereof containing a piston, connecting rod and springs, the front part thereof incorporating a yoke or other form of hinging to a rear swinging arm frame of welded or cast construction which supports the rear wheel of the bicycle and has provision for a pedal assembly and adjacent yoke or hinge to the connecting rod of the aforementioned piston.

2. A rear suspension assembly for a bicycle as claimed in Claim 1. wherinr adjustment for spring tension is provided for by means of the threaded spring retainer at the base of the part of the unit containing the piston, connecting rod and springs.

3. A rear suspension assembly for 'a bicycle as claimed in Claim 1. or Claim 2. wherein provision is made to fit the unit to existing bicycles.