GB1604115A

GB1604115A - Derailleur assembly for a cycle

Info

Publication number: GB1604115A
Application number: GB86181A
Authority: GB
Original assignee: Shimano Industrial Co Ltd
Current assignee: Shimano Inc
Priority date: 1977-05-20
Filing date: 1978-05-18
Publication date: 1981-12-02

Description

(54) A DERAILLEUR ASSEMBLY FOR A CYCLE (71) We, SHIMANO INDUSTRIAL COMPANY LIMITED, a Corporation organized and existing under the laws of Japan, of 77, 3-cho, Oimatsu-cho, Sakai-shi, Osaka, Japan do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a derailleur for a cycle.

The derailleur of the invention is intended for use with a multi-sprocket assembly on the rear hub of a cycle so that a drive chain may be shifted to any selected one of the sprockets.

A conventional derailleur for this purpose comprises a base member fixed to the cycle, a movable member movable with respect to the base number axially of the rear hub of the cycle and a chain-shift member pivotally mounted upon the movable member. A tension sprocket and a guide sprocket are rotatably mounted on the chain-shifting member and meshed with the drive chain of the cycle. Normally, the sprockets of the multi-sprocket assembly are arranged in decreasing order of dlameter (increasing order of gear ratio) outwardly along the hub and the derailleur is disposed axially outwardly of the smallest sprocket. A control cable attached to the derailleur controls the derailleur to shift the chain axially inwardly against the bias of a return spring, shifting of the chain in the opposed direction being effected by the action of the return spring.

A typical prior art chain-shift member for a derailleur is shown in Figure 5 of the accompanying drawings and comprises two parallel plates al and a2 between which are sandwiched the tension and guide sprockets pZ and P2 respectively. The plate a1 lies axially outwardly of the tension and guide sprockets and serves to guide the chain.

However, because the spacing between the plates a1 and a2 is much larger than the width of the chain, when the chain-shift member is moving the chain between the various sprockets of the multi-sprocket assembly on the rear hub, the chain tends to be deflected from its proper course over the tension and guide sprockets and to contact one of the plates a, and a2. This tends to make gear-changing very noisy and may lead to difficulties in effecting proper gear changes. If attempts are made to reduce these difficulties by decreasing the spacing between the plates al and a2, the chain tends to contact one or other of the plates even when gear-changing is not being effected, thereby hindering smooth and quiet running of the chain.

The present invention seeks to provide a derailleur which reduces or eliminates one or more of the aforementioned problems and renders gear changing quieter and smoother.

Accordingly the invention provides a derailleur for shifting a drive chain to any one of a plurality of sprockets of a multi-speed sprocket assembly, said derailleur comprising: a base member; a movable member movable relative to said base member; a chain-shift member pivotally connected to said movable member, said chain member comprising a single plate and carrying a tension sprocket and a guide sprocket mounted so as to be rotatable independently of each other, said tension and guide sprockets having teeth for meshing with said dnve chain in use of the derailleur; a guide member formed integrally with the chainshift member and having an engagement portion disposed radially outwardly of the guide sprocket teeth in proximity thereto for retaining the chain, in use of the derailleur, in engagement with the guide sprocket teeth against radial disengagement therefrom.

When the axis of rotation of the tension sprocket lies substantially perpendicular to the plate of the chain-shift member, the preferred form of guide member comprises a first portion extending substantially parallel to said plate and a second portion connected at one end thereof to the first portion and extending substantially perpendicular to said plate, the opposed end of the second portion being connected to the engement portion of the guide member, whlcn engagement portion extends radially inwardly towards the axis of the guide sprocket.

With such a guide member, the part of the engagement portion thereof nearest the guide sprocket may either lie adjacent the tips of the teeth on that sprocket so as to pass between the link plates of a drive chain engaged with said teeth, or be disposed on the opposed side of the guide sprocket from the chain-shifting member so as to abut or lie adjacent the outer surfaces of the link plates on one side of a drive chain engaged with the teeth on the guide sprocket.

The invention also extends to a cycle incorporating a derailleur of the inventlon.

Preferred embodiments of the invention will now be described in more detail, though by way of illustration only, with reference to the accompanying drawmgs, in which like reference numbers indicate like parts and in which: Figure 1 is a side elevation of part of a first derailleur of the invention; Figure 2 is a view of the part of the derailleur shown in Figure f from the opposed side thereof; Figure 3 is a top plan view of the part of the derailleur shown in Figures 1 and 2; Figure 4 is a rear elevation of the derailleur shown in Figures 1 to 3, mounted upon the rear hub of a cycle; and Figure 5 is as already mentioned a rear elevation of part of a prior art derailleur.

Figures 1 to 4 show a derailleur of the invention which comprises a base member 2, on which is pivotally mounted a bracket 1 by means of which the base member 2 can be secured to the rear hub H (Figure 4) of a cycle, a pair of link members 3 (only one of which is shown in Figures 1 to 3 and a movable member 4. Each of the link members 3 is pivotally mounted at its one end upon the base member 2 and at its opposed end on the movable member 4 so that the base member, the two link members and the movable member together form a parallel gram linkage. When the bracket 1 is mounted upon the rear hub H1 the pivoting of the link members 3 renders the movable member 4 movable relative to the base member 2.

A chain-shift or shift member 7 is mounted upon the movable member 4 by means of a pivot 10. The shift member 7 is formed of a single flat plate and carries a tension sprocket 5 and a guide sprocket 6, these two sprockets being mounted on the shift member 7 by means of sprocket shafts 51 and 61 respectively which pass through bores in the shift member 7 so as to be rotatable independently of one another about axes perpendicular to the plane of the shift member 7 and each of the sprockets 5 and 6 bearing teeth capable of meshing with the drive chain of a cycle.

The derailleur includes a guide member (generally designated 8) which is formed integrally with the shift member 7. The guide member 8 comprises a first portion 81 extending in the plane of the shift member 7, a second portion 82 connected at its one end to the first portion 81 and extending perpendicular to said plane, and an engagement portion 83 which is connected to the opposed end of the second section 82 and which extends radially inwardly towards the axis of the guide sprocket 6, so that the part of the engagement portion 83 nearest the guide sprocket 6 lies adjacent the tips of the teeth on that sprocket so as to pass between the link plates C, and C2 (see Figure 3) of a drive chain C engaged with said teeth, the engagement portion 83 of course having a thickness smaller than the spacing between the link plates on opposed sides of the chain C. The engagement portion 83 of the guide member 8 thus lies radially outwardly of the teeth on the guide sprocket 6 and is capable of retaining the drive chain C engaged with the teeth on the guide sprocket 6 once the drive chain has been engaged with said teeth.

Finally, the derailleur shown includes a chain guide plate 30 (best seen in Figure 3) disposed axially of the tension sprocket 5 on the opposed side thereof from the shift member 7.

In use, as shown in Figure 4, the derailleur of the invention may be mounted on a bicycle, the bracket 1 being secured by means of a nut to the rear hub H of the bicycle axially outwardly of a set of sprockets of a multi-sprocket assembly S thereon.

The sprocket assembly S is arranged so that the smallest sprocket S, lies adjacent the derailleur whilst the largest sprocket S2 is closest to flange A which is one of a pair of flanges A and B carried on the hub H. A control wire (not shown), forming part of a control cable, may be pulled to move the movable member 4 axially inwardly of the hub H so that the shift member 7 is shifted from the position shown in full lines in Figure 4, in which position the chain (not shown) of the bicycle, which is engaged with the guide and tension sprockets 5 and 6, is also engaged with the smallest sprocket Si, to that shown in broken lines in Figure 4 (in which position the chain is engaged with the largest sprocket S2), against the bias of a return spring (not shown). When the control wire is moved in the opposed direction, the return spring moves the movable and shift members axially outwardly of the hub H.

Thus, by use of the derailleur the chain may be engaged with any desired one of the sprockets of the sprocket assembly S. During such shifting of the chain, the engagement portion 83 of the uide member 8 prevents the chain being ( deflected from its proper course; if the chain C should tend to move axially outwardly from the guide sprocket 6, the engagement portion 83 will abut the rollers C3 of the chain C, thereby keeping the chain engaged with the guide pulley 6. The tension sprocket 5 also tends to resist disengagement of the drive chain by radially outward movement of the chain from the tension and guide sprockets, by means of the force exerted by a chain tensioning spring 90 wound around the shift member mounting pivot 10 as shown in Figure 4. In this way the resistance to chain shifting is reduced and contact of the chain with the inward face of the shift member 7, which is responsible for the noises generated during gear shifting by prior art derailleurs is substantially prevented.

Furthermore, the provision of the guide member 8 in the derailleur eliminates the need for the second, axially-inward plate a2 of the prior art derailleur assembly shown in Figure 5, since the guide member 8 prevents the chain from striking the spokes D in Figure 23. The elimination of the plate a2 renders it possible to mount the derailleur assembly of the invention and the sprockets S closer to the flange A by a distance equal to the thickness of the plate a2. The presence of the chain guide plate 30 does not interfere with the axially-inward mounting of the assembly since the plate 30 is well spaced from the axis of the hub H. This reduction in the axial spacing between the sprockets S and the rim R reduces the torque about an axis perpendicular to the plane of Figure 4 passing through the centre of the hub H exerted by the chain tension on the hub H and spokes D thereby increasing the working life of the spokes and the stability of the bicycle's rear wheel.

WHAT WE CLAIM IS: 1. A derailleur for shifting a drive chain to any one of a plurality of sprockets of a multi-speed sprocket assembly, said derailleur comprising: a base member; a movable member movable relative to said base member; a chain-shift member pivotally connected to said movable member, said chainshift member comprising a single plate and carrying a tension sprocket and a guide sprocket mounted so as to be rotatable independently of each other, said tension and guide sprockets having teeth for meshing with said drive chain in use of the derailleur; a guide member formed integrally with the chain-shift member and having an engagement portion disposed radially outwardly of the guide sprocket teeth in proximity thereto for retaining the chain, in use of the derailleur, in engagement with the guide sprocket teeth.

2. A derailleur as claimed in Claim 1, in which the axis of rotation of the tension sprocket lies substantially perpendicular to the plane of the plate, and in which the guide member comprises a first portion extending substantially parallel to said plane and a second portion connected at one end thereof to the first portion and extending substantially perpendicular to said plane, the opposed end of the second portion being connected to the engagement portion of the guide member, which engagement portion extends radially inwardly towards the axis of the guide sprocket.

3. A derailleur as claimed in Claim 2, in which the part of the engagement portion nearest the guide sprocket lies adjacent the tips of the teeth on that sprocket so as to pass between the link plates of a drive chain engaged with said teeth.

4. A derailleur as claimed in an one of the preceding claims, which derailleur includes a chain guide plate disposed axially of the tension sprocket on the opposed side thereon from the chain-shift member.

5. A derailleur as claimed in any one of the preceding claims, in which the chainshift member is provided with a chain guide portion disposed radially outwardly of the tension sprocket.

6. A derailleur as claimed in any one of the preceding claims, mounted upon a cycle, the drive chain of the cycle being engaged with the teeth on the guide and tension sprocket of the derailleur.

7. A derailleur substantially as herein described, with reference to and as illustrated in any of Figures 1 to 4 of the accompanying drawings.

8. A cycle incorporating a derailleur as claimed in any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. return spring (not shown). When the control wire is moved in the opposed direction, the return spring moves the movable and shift members axially outwardly of the hub H. Thus, by use of the derailleur the chain may be engaged with any desired one of the sprockets of the sprocket assembly S. During such shifting of the chain, the engagement portion 83 of the uide member 8 prevents the chain being ( deflected from its proper course; if the chain C should tend to move axially outwardly from the guide sprocket 6, the engagement portion 83 will abut the rollers C3 of the chain C, thereby keeping the chain engaged with the guide pulley 6. The tension sprocket 5 also tends to resist disengagement of the drive chain by radially outward movement of the chain from the tension and guide sprockets, by means of the force exerted by a chain tensioning spring 90 wound around the shift member mounting pivot 10 as shown in Figure 4. In this way the resistance to chain shifting is reduced and contact of the chain with the inward face of the shift member 7, which is responsible for the noises generated during gear shifting by prior art derailleurs is substantially prevented. Furthermore, the provision of the guide member 8 in the derailleur eliminates the need for the second, axially-inward plate a2 of the prior art derailleur assembly shown in Figure 5, since the guide member 8 prevents the chain from striking the spokes D in Figure 23. The elimination of the plate a2 renders it possible to mount the derailleur assembly of the invention and the sprockets S closer to the flange A by a distance equal to the thickness of the plate a2. The presence of the chain guide plate 30 does not interfere with the axially-inward mounting of the assembly since the plate 30 is well spaced from the axis of the hub H. This reduction in the axial spacing between the sprockets S and the rim R reduces the torque about an axis perpendicular to the plane of Figure 4 passing through the centre of the hub H exerted by the chain tension on the hub H and spokes D thereby increasing the working life of the spokes and the stability of the bicycle's rear wheel. WHAT WE CLAIM IS:

1. A derailleur for shifting a drive chain to any one of a plurality of sprockets of a multi-speed sprocket assembly, said derailleur comprising: a base member; a movable member movable relative to said base member; a chain-shift member pivotally connected to said movable member, said chainshift member comprising a single plate and carrying a tension sprocket and a guide sprocket mounted so as to be rotatable independently of each other, said tension and guide sprockets having teeth for meshing with said drive chain in use of the derailleur; a guide member formed integrally with the chain-shift member and having an engagement portion disposed radially outwardly of the guide sprocket teeth in proximity thereto for retaining the chain, in use of the derailleur, in engagement with the guide sprocket teeth.