GB2171474A

GB2171474A - Anti-derailing plate for a bicycle freewheel chain

Info

Publication number: GB2171474A
Application number: GB08603857A
Authority: GB
Inventors: Edouard Monka
Original assignee: MAILLARD MAURICE ETS; MAURICE MAILLARD ETS
Current assignee: MAILLARD MAURICE ETS; MAURICE MAILLARD ETS
Priority date: 1985-02-15
Filing date: 1986-02-17
Publication date: 1986-08-28
Also published as: DE3604876A1; GB8603857D0; FR2577507A1

Abstract

A bicycle freewheel comprising a plurality of gearwheels of different diameters disposed on a freewheel hub in which a larger diameter gearwheel is secured to or integral with a circular part 7, the outside diameter of which is larger than the diameter of the largest gearwheel 6 of the freewheel and which is situated parallel to said largest gearwheel on the outside of the freewheel. <IMAGE>

Description

SPECIFICATION Anti-derailing plate for a bicycle freewheel chain This invention relates to a bicycle freewheel.

Many bicycles provided with rear wheel derailleur gears have a disc or spoke protector situated against the spokes of the bicycle rear wheel on the freewheel side in order to prevent the chain from jamming between the freewheel and the spokes of the wheel in the event of its coming off the largest gearwheel.

To be completely effective, the distance between the disc and the largest gearwheel of the freewheel should be exact and constant irrespective of the size of this large gearwheel.

In practice, however, this is impossible to achieve, firstly because the disc is not rigid enough to ensure this distance and, secondly, the distance between the disc and the largest gearwheel varies with the diameter of the largest gearwheel because of the conical arrangement of the spokes of the rear wheel.

The object of this invention is more particularly to obviate these disadvantages, and to this end the invention relates to a bicycle freewheel comprising a plurality of gearwheels of different diameter disposed on a freewheel hub, said freewheel being characterised in that the larger-diameter gearwheel is secured to a circular part whose outside diameter is larger than the diameter of the largest gearwheel of the freewheel and which is situated parallel to said largest gearwheel on the outside of the freewheel.

According to another feature of the invention, the circular part is formed integrally with the larger-diameter gearwheel and is formed by the periphery of a metal disc cut out to form the larger-diameter gearwheel.

According to another feature of the invention, the circular part and the larger-diameter gearwheel cut out from the same metal disc are connected by lugs resulting from the cutting-out operation and leading into troughs separating consecutive teeth of the gearwheel.

The invention is illustrated by way of example without limiting force in the accompanying drawings wherein: Figure 1 is an axial section of a freewheel according to the invention.

Figure 2 is a partial elevation of the largest gearwheel of the freewheel shown in Fig. 1.

Figures 3 and 4 are diagrammatic sections of two other embodiments of the freewheel.

The object of this invention is to provide a freewheel provided with a device which effectively prevents any jamming of the chain between the freewheel and the spokes of the bicycle wheel, such device also providing improved accuracy and speed of transfer of the chain from a smaller-diameter gearwheel to the larger-diameter gearwheel of the freewheel.

Referring to Fig. 1, a freewheel 1 has a hub 2 bearing a number of graduated diameter gearwheels 3, the freewheel 1 being secured to a rear bicycle wheel, the hub 4 of which is provided with spokes 5.

According to the invention, the larger-diameter gearwheel 6 of this freewheel is secured to a flat disc 7, the outside diameter of which is larger than the diameter of the gearwheel 6 and which is situated parallel to the gearwheel 6, being offset towards the exterior of the freewheel, i.e. towards the spokes 5 of the back wheel, by an amount which at maximum is slightly less than the width of the chain used. It will therefore be seen that this disc, which is of very rigid construction, prevents the chain from escaping from the largerdiameter gearwheel 6 towards the spokes 5 of the wheel.

Another advantage of this construction according to the invention is that it provides adjustment of the clearance of the derailleur mechanism of the back wheel (not shown) with a longer travel towards the back wheel, so that the chain can more readily climb on to the larger-diameter gear-wheel 6 without this longer travel involving the risk of bringing the chain between the spokes 5 and the gearwheel 6, where it would jam, this effect being obtained by means of the protective disc 7.

In the exemplified embodiment shown in Figs. 1 and 2, the disc 7 is formed integrally with the larger-diameter gearwheel 6 and is formed by the periphery of a rigid metal disc cut out to form this larger-diameter gearwheel.

In the example illustrated, the disc 7 is therefore defined internally by projections 7 which form the complement of the troughs of the teeth 61 of the gearwheel 6. In this arrangement, however, uniformly distributed lugs 8 are half cut out and suitably inclined to form joints between the gearwheel 6 and the disc 7. These lugs 8 are of a width corresponding to the spacing between two consecutive teeth of the gearwheel 6 and lead into teeth troughs 6 so as not to affect the spacing of the gearwheel teeth.

In the example illustrated, the disc 7 provided with its projections 7 forms the complement of the periphery of the gearwheel 6.

However, any other arrangement may be provided, more particularly in order to reduce weight, and in that case the teeth 7 may be dispensed with and the width of the disc 7 can be so determined as to be just enough to prevent jamming of the chain while having a rigidity compatible with its purpose.

In the exmplified embodiment shown in Fig.

3, the disc 8 providing the spoke protection is in the form of a part made independently of the larger-diameter gearwheel 6 and to that end disc 8 has a flat periphery, whose outside diameter is larger than the diameter of the gearwheel 6 and whose inside diameter is substantially level with the teeth troughs of said gearwheel 6. Inside this flat circular part 8t there is provided a conical part 82 which defines the offset of the flat circular part 8, from the gearwheel 6. This conical part 82 continues in the form of a flat circular part 83 formed with an orifice to enable it to be fitted on the hub 2 of the freewheel against the larger-diameter gearwheel 6.

In this construction, therefore, the disc 8 is mounted and fixed on the freewheel hub 2 during assembly and fixing of the gearwheel assembly on the freewheel.

In the example described and illustrated in Fig. 3, the disc 8 is a solid disc, apart from its central orifice for fitting on the hub 2.

However, the disc may be perforated in order to reduce its weight.

In the exemplified embodiment shown in Fig. 4, the disc 9 also forms a part which is made independently of the larger-diameter gearwheel 6. In this case the disc 9 has a flat and circular peripheral part 91 continuing internally as a conical part 92 formed with a flat edge 93. This edge is secured to the largerdiameter gearwheel 6 of the freewheel by any means, and more particularly riveting.

Claims

1. A bicycle freewheel comprising a plurality of gearwheels of different diameter disposed on a freewheel hub, said freewheel having a larger diameter gearwheel secured to a circular part whose outside diameter is larger than the diameter of the largest gearwheel of the freewheel and which is situated parallel to said largest gearwheel on the outside of the freewheel in order to be located between said largest diameter gearwheel and the wheel spokes.

2. A freewheel according to claim 1, in which the circular part is formed integrally with the larger diameter gearwheel and is formed by the periphery of a metal disc cut out to form the larger diameter gearwheel.

3. A freewheel according to claim 2, in which the circular part and the larger diameter gearwheel cut out from the same metal disc are connected by lugs resulting from the cutting-out operation and leading into troughs separating consecutive teeth of the gearwheel.

4. A freewheel according to claim 1, in which the circular part is made independently of the larger diameter gearwheel and is clamped on the freewheel hub against the larger diameter gearwheel.

5. A freewheel according to claim 1, in which the circular part is made independently of the larger diameter gearwheel and is secured by riveting or the like against the larger diameter gearwheel surface extending towards the outside of the freewheel.

6. A bicycle freewheel substantially as herein described with reference to, and as illustrated in the accompanying drawings.