GB2214843A

GB2214843A - Process for making the outer ring body of a freewheel device for bicycles

Info

Publication number: GB2214843A
Application number: GB8808225A
Authority: GB
Inventors: Alfred Heinrich Thun
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-02-09
Filing date: 1988-04-08
Publication date: 1989-09-13
Also published as: CN1034884A; DE3803889A1; GB8808225D0

Description

1 2214843 PROCESS FOR MAKING THE OUTER RING BODY OF A FREEWHEEL DEVICE FOR

BICYCLES The invention concerns a process for making the outer ring body of a freewheel device for bicycles, the outer ring body having teeth directed radially outwards with which the driving chain of the bicycle engages, ratchet teeth directed radially inwards which cooperate with the ratchet pawl of the freewheel device, and circular rims projecting sideways formed on the outer ring body which have bearing races on the sides adjacent the ratchet teeth, for the balls of a ball bearing.

With the state of the art such outer ring bodies are still produced in such a way that first a disc-shaped body is forged out of solid material, from which the middle part is then punched out in order to obtain a ring body. The forged piece must then be further worked upon, especially with turning tools, in order to obtain the appropriate surface formations in the desired places.

This method of working is very time consuming and is associated with relatively high losses of material.

Starting from this state of the art, the object of the invention is to provide a process of the generic type by which much more economical production is possible and with considerable savings in material.

i 2 - 1 To provide the solution a broad aspect of the invention proposes that:

J a) a ring is bent from steel rod and the abutting ends are welded together; and b) the ring is preshaped cold and pressed flat so that a ring body with a substantially cross-shaped cross-section is formed.

An embodiment of the invention proposes that:

a) a ring is bent from steel rod and the abutting ends are welded together; b) the ring is preshaped cold and pressed flat so that a ring body with a substantially cross-shaped cross-section is formed; c) the outer edge of the ring body is adjusted to an appropriate size for the size of the corresponding chain; d) the outer set of teeth and the inner set of teeth are formed by pressing out parts of the inner edge and the outer edge; e) the edges of the teeth of the outer set of teeth and the inner set of teeth are chamfered and the teeth of the inner set of teeth are adjusted to size; and, f) the bearing races for the balls are adjusted to size.

-3 It is thought to be preferable that the process stages b) t f) should be performed in a machine press working in 5 stages.

1 Usually 5-stage machines are used, and so it is desirable to set up the production process in five operating stages.

The division of the individual production sequence into the five stages is basically optional, however the above described division is preferred. If required it can also be advantageous if stage e) and stage f) are combined into a single operation.

It is also considered to be preferable if in a continuation of stage a) the diameter and the cross-section of the ring are adjusted to size. These procedures and also stage a) are performed outside the machine press.

Moreover it is considered to be preferable if the starting material forming the ring in stage a) is bent with a material thickness of about 10 mm. to a diameter of about 55 to 60 mm.

An embodiment of the invention is described in more detail in the following, with reference to the drawings.

FIGURES 1 to 5 show the various production stages; FIGURE 6 shows a complete freewheel device in front view; and FIGURE 7 shows the same turned through 90 0, partially sectioned.

The starting point for production of an outer ring body 1 of a freewheel device 2 for a bicycle is a length of circular rod formed into a ring as shown in Figure 1. From this length of circular rod an outer ring body should be produced which has teeth 3 directed radially outwards, with which the driving chain of the bicycle should engage. In addition the outer ring body 1 has ratchet teeth 4 directed radially inwards, which cooperate with the corresponding ratchet of the freewheel device 2. Furthermore, the outer ring body 1 has circular rims 5 projedting sideways which form bearing races on their sides adjacent the ratchet teeth 4, for the balls 6 of the ball bearing of the freewheel device. The course of production is the following:

From the length of circular rod a ring is first bent as in Figure 1, which should have a diameter D of about 55 to 60 mm. The thickness d of the material of the ring should thereby be about 10 mm. The abutting ends of the bent rod are butt-welded and any resulting burrs are removed. The ring, as shown in Figure 2, produced in this way is cold shaped in stages, first into a shape as shown in Figure 3, whereby - in a shaping and pressing process the ring shape of Figure 2 is shaped and flat pressed in such a way that a substantially cross-shaped cross- section results, as is shown in Figure 3. After this first preceding shaping process it can be arranged that the diameter and cross-section of the ring body as in Figure 2 can be adjusted to size. The starting material for the ring is relatively soft steel, for example grade C 10, usually with a carbon content of less than 0.1%.

In a next process stage the outer edge of the ring body as in Figure 3 is adjusted fo r the size Of the corresponding chain as can be seen from Figure 4.

In a next process stage the outer set of teeth and the inner set of teeth are formed by pressing out parts of the inner edge and the outer edge, as can be seen from Figure 5.

In a next process stage the edges of the teeth of the outer set of teeth and the inner set of teeth are machined to provide a chamfered profile as shown in Figure 7.

In addition, preferably simultaneously or in a connected process stage, the teeth of the inner set of teeth are adjusted in size. This process stage can also be combined with a process stage in which the bearing races for the 6 - balls 6 are adjusted to size. The production is preferably, with regard to the cold shaping and size adjustment, divided 1 into a 5 stage process, since the customary machine presses work in 5 stages.

Through the process according to the invention only very little material is discarded, so that overall a material-saving method of production is obtained. Furthermore, production is possible with only cold shaping, which results in corresponding energy savings.

Moreover, the method of production is very economical to perform, so that the production costs can also be kept low.

The invention is not limited to this example of an embodiment, but can be altered in many ways within the scope of the disclosure.

All new individual features or combinations of features published in the description and/or drawing are considered to be essential parts of the invention.

7 4 111

Claims

1. A process for making the outer ring body of a freewheel device" for bicycles, the outer ring body having teeth directed radially outwards with which the driving chain of the bicycle engages, ratchet teeth directed radially inwards-which cooperate with the ratchet pawl of the freewheel device, and circular rims projecting sideways formed on the outer ring body which have bearing races on their sides adjacent the ratchet teeth, for the balls of a ball bearing; the process including the following stages: a) a ring is bent from steel rod and the abutting ends are welded together; b) the ring is preshaped cold and pressed flat so that a ring body with a substantially cross-shaped cross-section is formed; C) the outer edge of the ring body is adjusted to an appropriate size for the size of the corresponding chain; d) the outer set of teeth and the inner set of teeth are formed by pressing out parts of the inner edge and the edge; e) the edges of the teeth of the outer set of teeth and the inner set of teeth are chamfered and the teeth of the inner set of teeth are adjusted to size; and, f) the bearing races for the balls are adjusted to size.

2. A process according to claim 1, characterized in that the proce ss stages b) to f) are performed in a machine press working in 5 stages.

3) A process according to claim 1 or 2, characterized in that stage e) and stage f) are combined into a single process stage.

4. A process for making the outer ring body of a freewheel device for bicycles which includes the following stages: a) bending a ring from steel rod and welding the abutting ends together; and b) cold shaping and flat pressing the ring so that a ring body with a substantially cross- shaped cross-section is formed.

5. A process according to any one of claims 1 to 4, characterized in that in a continuation of stage a) the diameter and the cross-section of the ring are adjusted to size.

6. A process according to any one of claims 1 to 5, characterized in that the ring made in stage a) which forms the starting material has a material thickness of about 10 mm and a diameter of about 55 to 60 mm.

1 1

7. A process for making the outer ring body of a freewheel device for bicycles substantially as described herein with j reference to the accompanying drawings.

Published 1989 atThe Patent Office, State House, 66171 High Holbora, London W01R 4TP. Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Coll. 1/87