GB2343227A

GB2343227A - Composite gearbox fork with reinforcing piece in crosshead

Info

Publication number: GB2343227A
Application number: GB9925200A
Authority: GB
Inventors: Dominique Benoit
Original assignee: MGI Coutier SA
Current assignee: Akwel SA
Priority date: 1998-10-27
Filing date: 1999-10-25
Publication date: 2000-05-03
Anticipated expiration: 2019-10-25
Also published as: GB9925200D0; ITMI992231A0; GB2343227B; FR2785030B1; IT1313903B1; DE19951783A1; FR2785030A1; ITMI992231A1

Abstract

A composite gearbox fork comprises a crosshead 1 which is fitted with a reinforcing piece 2 having a U-shaped cross-section that accepts two arms 11, 12 of the crosshead 1. After assembly with the crosshead 1 two deformations 24 (25, fig 2) are produced in side walls 23,24 of the piece 2. These deformations 24, (25), because of the relative low hardness of the crosshead 1 material, hook into the fork thereby connecting the piece 2 to the crosshead 1. In another embodiment tabs (34, fig 3) are furnished on the piece 2 which cooperate with cavities (44) in the crosshead 1 so as to provide a connection. The fork may be made of plastics material or a light alloy material.

Description

COMPOSITE GEARBOX FORK The present invention relates to a gearbox fork including a guide shaft and a crosshead to actuate the control arm of a gearbox.

There are numerous embodiments of gearbox forks. These forks have the common disadvantage of being relatively complex in shape and production. Moreover, these forks are generally relatively substantial in nature and thus heavy.

The invention has the object of overcoming these disadvantages and proposes production of a gearbox fork which is simple to produce, is light and resistant to wear.

To this end the invention relates to a fork of the type defined above, characterised in that; -the fork is formed from a body of a material with a low level of hardness (shaft and crosshead), -the surface of the crosshead in contact with the arm is fitted with a reinforcing piece of folded or stamped plate.

In a particularly advantageous manner, the crosshead comprises two branches and a transverse part and the folded or buckled plate part is of a general U shape with turned-back portions forming a U-shaped cross-section which is open towards the outside to cover the two branches and the transverse part of the crosshead.

This folded or buckled plate part, which is of a double U shape, on the one hand the overall shape and, on the other hand, the shape of its cross-section which is open towards the outside, can thus fit easily over the three sides of the branches and of the transverse part of the crosshead to enclose the crosshead which is of low-hardness material and protect it against wear caused by contact with the arm.

This reinforcing piece is advantageously fixedly attached to the branches and to the transverse part of the crosshead by a mechanical connection. This mechanical connection can be produced by deformation of the wall of the reinforcing piece which becomes embedded into the body of the crosshead.

This deformation can be achieved by one or more tabs provided at different places on the reinforcing piece, in particular, on the parts covering the branches and/or the transverse part of the crosshead, i. e. surfaces of the reinforcing piece which will not come into contact with the arm.

In a particularly advantageous manner, the deformation is provided by an elastic tab stamped into the wall of the reinforcing piece, the free end of this tab pointing in the direction opposite to that in which the reinforcing piece is fitted onto the crosshead, and the branch or branches of the crosshead include, at the location which corresponds to that of the tab, a cavity forming an abutment to receive the tab when the reinforcing piece is in the fitted position.

Thus a snap fit effect is achieved which firmly holds the reinforcing piece without necessitating any particular connection operation.

It is also possible to provide a part which is stamped, for example with a punch, once the reinforcing piece is engaged on the crosshead.

According to the invention the low-hardness material forming the body of the crosshead is a plastics material or a light alloy. Thus a gearbox fork is obtained which is light and perfectly resistant to wear caused by movement.

Embodiments of the present invention will be described in more detail herein under with the aid of the attached drawings in which: -Figure 1 is an exploded perspective view of a first embodiment of the invention showing the crosshead of a gearbox fork and a reinforcing piece intended to cover the fork, -Figure 2 is a cross-sectional view on the line II II of Figure 1 in the assembled state, -Figure 3 is an exploded view similar to that of Figure 1 of another embodiment of the invention, -Figure 4 is a cross-sectional view on the line IV IV of Figure 3, the parts being assembled, and -Figure 5 is a cross-sectional view on the line V-V of Figure 3, the parts also being assembled.

Figure 1 shows a gearbox fork embodying the invention.

Only the crosshead comprising two arms 11,12 and a transverse connecting part 13 is shown schematically in Figure 1. Above this part and in position for mounting (arrows F) is a reinforcing piece 2. This reinforcing piece 2 of stamped plate is of a general U shape with an inner wall 21 and two side walls 22,23. The cross-section of the inside wall and of the two side walls is a U which is open towards the outside. The inner cross-section of the piece corresponds to the cross-section of the arms 11,12 and of the connecting part 13.

This reinforcing piece 2 is intended to cover the two arms 11,12 and the transverse connecting part 13 of the crosshead 1 in order to cover the surfaces likely to come into contact with the arm D which is shown schematically by a circle. The piece 2 is positioned as indicated by the arrows F in Figure 1.

Once positioning is completed deformations 24,25 are created in the two side walls 22,23 of the reinforcing piece 2 so that these deformations hook into the material of the transverse connecting part 13 of the body of the fork to attach together the reinforcing piece 2 and the body 1 of the fork (locations 14,15) (Figure 2).

Figure 3 shows another embodiment. In this variation all the parts have the same reference numbers as in Figures 1 and 2, supplemented by the suffix A. The view is also similar to that of Figure 1.

The difference in this embodiment resides in the means for attaching the reinforcing piece 2A to the body of the crosshead. These means are formed by tabs 34 stamped into the outer walls 22A, 23A of the reinforcing piece 2A. These tabs 34 are elastic pieces joined to the main part of the reinforcing piece 2A along one side 341. The free ends 342 of the tabs 34 are directed towards the rear in the direction (F) in which this reinforcing piece 2A is positioned on the crosshead 1A.

Although the tabs 34 alone can ensure that they are held on the crosshead 1A of the fork (arms 11A, 12A and transverse piece 13A), it is preferable to produce in the arms 11A, 12Aat the corresponding position of the tabs 34 of the reinforcing piece 2A-cavities 44 in which the tabs 34 of the reinforcing piece 2A make a snap fit so that the reinforcing piece is then captively held.

Figure 4 is a cross-sectional view which shows the positioning of the lower part of the reinforcing piece 2A on the transverse connecting part 13A of the crosshead 1A.

Figure 5 is a cross-sectional view through the arms 11A, 12A showing how the tabs 34 hook into the cavities 44 forming abutment surfaces in the direction opposite to the positioning direction (arrow F).

It should be noted that the piece described above can be formed by the shaft, the fork and the crosshead; the latter can be in any position with respect to the fork. The piecf can also be limited merely to the shaft and the crosshead, the fork being attached or duplicate moulded.

In accordance with the present invention the body of the fork including, in particular, the two arms and the transverse part and the shaft, which is not shown, is preferably producec from a low-hardness material such as a plastics material ox light alloy.

Claims

CLAIMS:

1. A gearbox fork comprising a guide shaft and a crosshead to receive the control arm of the gear box, the fork being formed from a body of a material with a low level of hardness, and the surface of the crosshead in contact with the arm being fitted with a reinforcing piece, wherein the crosshead comprises two branches and a transverse part and the reinforcing piece is formed from folded or stamped plate and is generally of a U shape and has turned-back portions forming a U-shaped cross-section which is open towards the outside to cover the two branches and the transverse part of the crosshead, the reinforcing piece being fitted over the crosshead to which it is fixedly attached by at least one deformed portion of the wall of the reinforcing piece and which becomes embedded in the body of the crosshead.

2. A fork according to claim 1, wherein the or each deformed portion is formed by an elastic tab stamped into the wall of the reinforcing piece, the free end of the tab being directed in the direction opposite to that in which the reinforcing piece is fitted over the crosshead and the branch or branches of the crosshead include, at a location which corresponds to that of the tab, a cavity forming an abutment to receive the tab when the reinforcing piece is in its fitted position.

3. A fork according to claim 1, the body of which is made from a plastics material or from a light alloy.

4. A gearbox fork substantially as hereinbefore described with reference to the drawings.