WO1993000252A1

WO1993000252A1 - Bicycle rear wheel suspension

Info

Publication number: WO1993000252A1
Application number: PCT/GB1992/001176
Authority: WO
Inventors: Ben Collins
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-28
Filing date: 1992-06-29
Publication date: 1993-01-07
Anticipated expiration: 1993-12-28
Also published as: WO1993000251A1; GB9214020D0; GB9214025D0; GB9214026D0; WO1993000249A1

Abstract

A bicycle rear wheel suspension which pivots a rear frame (10) behind the bottom bracket shell (5). The overall pivot width is greater than that of the bottom bracket shell (5), this ensures high torsional control and simplifies manufacture. At the junction of the seat stays (9) there projects a suspension housing (16) which sleeves axially or near axially over the stay runner (17). Both the suspension housing (16) and stay runner (17) feature flat sides to which bearing surfaces (19) are affixed. Between the bearing surfaces (19) there are needle roller bearing groups (20). One or both of the bearing surfaces (19) have deformable backs (21). The stepload slot (32) exerts a stepload force on the stepload pin (23) and the suspension such that only a bump loading force above that threshold stepload force would produce suspension movement. A hollow shock absorber (26) surrounds both the suspension housing (16) and stay runner (17). When a shock loading is received at the rear wheel (11), the rear frame (10) is moved arcuately about its pivot (12) with the suspension housing and mounting boss (27) acting to deform the shock absorber (26) and sleeving the stay runner (17).

Description

BICYCLE REAR WHEEL SUSPENSION

This invention relates to suspension systems for use on bicycles, motor cycles and other modes of transport utilising wheels or ski's.

Suspension on a bicycle would provide many benefits to the performance of a bicycle (too numerous to discuss), however such systems currently available are either over simple as to be ineffective in some aspects of performance or too complicated such to increase the bicycle weight and cost.

There are four principle objectives of this invention.

The first is to provide a lightweight and simple rear wheel suspension system, achieved by using a single pivot axis, this will be referred to as a "unipivot".

The second is to incorporate a stepload system in order to prevent articulation upon component pedalling loads.

The third is to ensure the arcuate movement is free to move in only two planes, this will be referred to as being "torsion locked".

The fourth is to achieve these requirements in a compact package in a manner that is compatible with most bicycle frames.

The fifth is to offer an option of frame size reduction for transport, making use of the pivot which forms part of the suspension.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:-

Figure 1 is a side elevation of a bicycle frame including the rear suspension components.

Figure 2 is a perspective view of the suspension unit (not including pivot) and frame surrounding elements.

Figure 3 is a side elevation of the suspended bearing arrangement.

Figure 4 is a front elevation of a linear roller bearing.

Figure 5 is a perspective view of the shock absorber and clamp.

Figure 6 is a centre-sectioned side elevation of the shock absorbing system and surrounding frame components.

Figure 7 is a perspective view of a complete frame and utilising the removable stay clamp.

Figure 8 is a side elevation of an alternative shock absorber position.

Figure 9 is centre sectioned elevation of the pivot system.

Figure 10 is a side elevation of the bottom bracket shell with pivot system attached.

In figure 1 there is illustrated a bicycle mainframe 1 which includes a toptube 2, down tube 3, seat tube

4, bottom bracket shell 5 and according to the present invention a suspension unit 7.

Also illustrated is a bicycle rear frame 10 comprising a pair of seat stays 9 and chain stays 8 respectively and a rear wheel 11.

Also illustrated are other well known bicycle components such as handlebars 6 and a head tube 24.

Said rear frame 10 is pivotally attached directly behind said bottom bracket shell 5.

In figure 9 there is a pivot system comprising rear frame axle 13 and mainframe axle 14. Both these axles have inner bearing surfaces 15 which mate to a pivot pin 12. The overall pivot width is greater than that of the bottom bracket shell 5 but not too great as to interfere with the pedalling action 33 of the bicycle when ridden.

In figure 6 at the junction of the seat stays 9 there projects a suspension housing 16 which sleeves axially or near axially over the stay runner 17.

Both the suspension housing 16 and stay runner 17 feature flat sides 18 to which bearing surfaces 19 are affixed.

Between the bearing surfaces 19 there are needle roller bearing groups 20 as shown in figure 3.

The bearing surfaces may feature deformable backing 21 as shown in figure 3. This allows the bearing surface 19 to provide a controlled level of movement, this facilitates manufacture and tolerancing and guarantees proper torsional control.

The suspension housing 16 is holed on both sides 22, one hole being threaded, this permits entry within the housing of a stepload bolt 23. The stay runner 17 has a vertical, axial stepload slot 32 running part of its length.

Also a stepload adjustment bolt 25 is located in the open end of the stay runner 17, threading axially through a tapped hole until reaching the stepload slot 32.

A hollow shock absorber 26 surrounds both the suspension housing 16 and stay runner 17, its top end mates against the seat tube 4 and its lower end mates against the seat stays 9 or part way down the suspension housing 16 to a mounting boss 27 as shown. This mounting boss 27 can be moved up or down the suspension housing 16 to increase or decrease respectively the preload of the shock absorber

26. This preload level will determine the spring rate of the arrangement.

When a shock loading is received at the rear wheel 11 , the rear frame 10 is moved arcuately about its pivot 12 with the suspension housing 16 acting to deform the shock absorber 26 and sleeving the stay runner 17. The shock absorber 26 attempts to retrieve the stay runner 7 from within the suspension housing 16 but is prevented from doing so by the stepload bolt 23 which is trapped within the stepload slot 32 of the stay runner 17.

The stepload bolt 23, attached to the suspension housing 16 is in place through the stepload slot 32, a stepload adjustment bolt 25 can be used to decrease the length of the stepload slot and thus increase the level of stepload on the suspension system.

A further refinement of the design can be seen in figure 7 where at the end of each seat stay 9 there are components to create a rear frame removal clamp 33 which permits attachment and detachment of the top of the seat stays 9 to/from the suspension housing 16/stay runner 17(depending on their configuration). On detachment, components of seat stay removal clamp 33 may remain attached to the top of each seat stay 9. The rear frame 10 then moves arcuately about its pivot 1 and manoeuvres the top of the seat stays 9 to mate to a junction 34 on the down tube 3, where it can be affixed, thus producing a reduction in frame size when required.

The said pivot pin 12 about which the rear frame moves arcuately is located above or adjacent to the bottom bracket shell 5. The pivot is of a special type described thus:

A removable pivot pin 12 which passes through the left side of a pivot eye bush 28, then through a pivot axle bush 29 and then through the right side of the pivot eye bush 30. The pair of pivot eyes (28 and 30) and pivot axle 29 are attached either; to the rear frame axle 13 and above or near the bottom bracket shell 5 respectively, or attached above or near the bottom bracket shell 5 and to the rear frame axle 13 respectively.

The rear frame axle 13 is attached to the rear frame 10 in such a way as to achieve maximum width of the pivot components. The rear frame axle 13 extends beyond the normal width of the bottom bracket shell 5 but is modified to just avoid contact with transmission components 33. This provides better tyre 35 to rear frame 10 clearance and permits the use of shorter chain stays 8, but most importantly achieves greater torsional control of the suspension system.

Shown if Figure 7 is a dirt cover 31 which is made from a deformable and curable material. This allows the frame builder to create a dirt cover 31 to exactly fit and protect the pivot system, whatever the exact frame construction configuration.

Claims

1 A rear wheel suspension system for a bicycle, said bicycle including a seat tube a bottom bracket shell, rear frame pivot, outer member, inner member, pairs of seat and chain stays.

The bicycle having a rear frame (seat and chain stays, outer member) which is pivotally attached on, near or above the bottom bracket shell.

The rear frame moves arcuately about said rear frame pivot and the outer member sleeves axially or near axially the inner member which is attached to the mainframe. When a shock loading is received on the rear frame, a shock absorber mounting boss, attached to the outer member acts to compress a hollow shock absorber which is trapped between the said shock absorber seat and the seat tube.

The inner member has two bearing surfaces on it's external left and right sides respectively.

The outer member has two bearing surfaces on it's internal left and right sides respectively.

These bearing surfaces allow axial or near axial sleeving of the inner member by the outer member but do not permit twisting, thereby providing a torsion lock on the inner and outer members and therefore a torsion lock on the suspension system.

2 A rear suspension described in claim 1 except where the locations of the inner and outer members are reversed, ie the inner member is attached to the rear frame and the outer member is attached to the mainframe.

3 A rear suspension as claims 1 or 2 except the shock absorber is not located on the outside of the outer member but within it.

4 A rear suspension system described in claims 1 , 2 or 3 which also incorporates a stepload system wherein a stepload pin is located and fixed through the outer member, passing through a slot in the inner member. This pin moves arcuately together with the rear frame. The inner member's slot prevents the stepload pin and subsequently the rear frame to which it is affixed from fully returning to a position where the shock absorber is unloaded. This steploads the shock absorber and suspension system, such that only a shock loading on the rear frame greaterthan the steploading permits suspension articulation. 5 A rear suspension system described in claims 1 -4 where the inner member incorporates an axial screw adjustment of the length of the stepload slot, such that by decreasing the length of the slot the stepload on the shock absorber is increased.

6 A rear suspension system described in claims 1-5 except where on unorthodox frames, the location of the inner member, outer member is in the region where the seat tube and top tube junction would be on a conventional diamond frame.

7 A bicycle rear wheel suspension system incorporating a pivot system which is located above or adjacent to the bottom bracket, whereby the pivot system is of a special type described thus: a removable pivot pin which passes through one side of a pivot eye, then through a pivot axle and then through the other side of the pivot eye. The pair of pivot eyes and pivot axle are attached either; to the rear frame axle and above or near the bottom bracket respectively, or attached above or near the bottom bracket and to the rear frame axle respectively.

The pair of pivot eyes is attached to the frame in such a way in which to achieve maximum width of the pivot components, i.e. the rear frame axle extends beyond the normal width of the bottom bracket but avoids contact with the transmission components.

8 A bicycle rear wheel suspension as described in claims 1 -7 which also incorporates a rear frame removal clamp which permits attachment and detachment of the top of the seat stays to the suspension housing/stay runner (depending on configuration). On detachment components of seat stay removal clamp remain attached to/from the top of each seat stay. The rear frame assembly then moves arcuately about its pivot and manoeuvres the top of the stays to mate to a junction on the down tube, where it can be affixed, thus producing a reduction in frame size when required.

9 A bicycle rear suspension system incorporating a pivot system dirt cover which is made from a deformable and curable material. This protects the pivot system, whatever the exact frame construction configuration. 10 A rear suspension system which utilises a pivot which is attached to the bottom bracket shell by means of a spacer which has a profile with two adjacent concave faces, one of which mate to the bottom bracket shell and the other to the mainframe pivot axle.

11 A bicycle rear suspension system as claims 1 -10 which has a bearing arrangement between the outer member and inner member utilising needle roller or ball bearings running on flat surfaces.

12 A bicycle rear suspension system as claims 1-11 which has a bearing arrangement between the outer member and inner member utilising needle roller or ball bearings running on flat surfaces which a backed by a deformable layer. This deformable layer being formed so that its top surface mates to a flat sided surface and its lower surface mates to a curved surface. This deformable layer may also have enlarged edges which are used to retain either bearings balls or bearing rollers.

13 A rear suspension system which incorporates a stepload system as described in claims 4-12 which has the shock absorber located at the pivot system, adjacent to the seat tube and bottom bracket shell.

7