GEAR SHIFT FORK FOR A GEARBOX WITH DISCRETE GEAR RATIOS

Abstract

The gear fork comprises a support portion arranged to be guided along a stationary rod of the gearbox, a pair of prongs which extend from the support portion and form at their distal ends respective finger-like portions adapted to act on a sliding coupling sleeve of the gearbox, and an actuating nose by means of which a sliding movement along the stationary rod for the engagement of the desired gear can be imparted to the fork. The support portion and the prongs can be integrally formed by a single sheet metal body obtained by blanking and bending or formed as two separate sheet metal pieces, each obtained by blanking and bending. The support portion is shaped and arranged with respect to the prongs so as to allow two forks having identical bodies to be mounted on the same stationary rod so as to at least partially overlap in the sliding direction along the rod.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and the advantages of the invention will become apparent from the following detailed description, given purely by way of non-limiting example with reference to the appended drawings, in which:

FIG. 1 is a perspective view which shows a shift fork according to a first preferred embodiment of the invention;

FIG. 2 is a view similar to the one of FIG. 1, in which the fork is shown without actuating nose;

FIG. 3 is a perspective view which shows an example of arrangement of four shift forks of the type shown in FIG. 1, suitable for both a hand-operated gearbox and a robotized gearbox derived therefrom;

FIG. 4 is a perspective view which shows an example of arrangement of four shift forks of the type shown in FIG. 1, suitable for both a double-clutch gearbox and a robotized gearbox derived therefrom;

FIG. 5 is a perspective view which shows a shift fork according to a further preferred embodiment of the invention; and

FIG. 6 is a view similar to the one of FIG. 5, in which the fork is shown without actuating nose.

Claims

1. A gear shift fork for a gearbox with discrete gear ratios, comprising a body including a support portion arranged to be guided along a stationary rod of the gearbox and a pair of prongs which extend on opposite sides of the support portion and form at their distal ends respective finger-like portions adapted to act on a sliding coupling sleeve of the gearbox, andan actuating nose fixed to the body, by means of which a sliding movement along the stationary rod for the engagement of the desired gear can be imparted to the fork;characterized in that the support portion is shaped and arranged with respect to the prongs so as to allow two forks having identical bodies to be mounted on the same stationary rod so as to at least partially overlap in the sliding direction along said rod.

2. Gear fork according to claim 1, wherein the two prongs have a plane of symmetry perpendicular to the stationary rod and the support portion is non-symmetrically arranged relative to said plane of symmetry.

3. Gear fork according to claim 1, wherein the prongs are formed as plate-like elongated elements, which extend in length perpendicular to the sliding direction of the fork along the stationary rod and in width parallel to said sliding direction.

4. Gear fork according to claim 1, wherein the support portion includes a central plate portion extending in the sliding direction of the fork along the stationary rod and a pair of ears arranged at a right angle to the central plate portion on the opposite sides thereof, the ears having respective coaxial guide holes adapted to guide the sliding movement of the fork along the stationary rod.

5. Gear fork according to claim 4, wherein one of the ears is arranged farther from the prongs than the other ear.

6. Gear fork according to claim 1, wherein the body has a pair of slots for the mounting of the actuating nose, arranged symmetrically relative to the finger-like ends of the prongs.

7. Gear fork according to claim 6, wherein the slots are formed in the prongs.

8. Gear fork according to claim 4, further comprising a pair of plastics bushes, each fitted in a respective guide hole.

9. Gear fork according to claim 1, wherein the finger-like ends of the prongs are provided with an antifriction plastics coating.

10. Gear fork according to claim 8, wherein the bushes and/or the antifriction coatings of the finger-like ends of the prongs are obtained by plastics overmoulding.

11. Gear fork according to claim 1, wherein the actuating nose has a recess for engaging a control member and is provided with an antifriction plastics coating around said recess.

12. Gear fork according to claim 11, wherein the antifriction plastics coating around the recess of the actuating nose is obtained by overmoulding.

13. Gear fork according to claim 1, wherein the support portion and the prongs are integrally formed by a single sheet metal body obtained by blanking and bending.

14. Gear fork according to claim 13, wherein the support portion includes a central plate portion extending in the sliding direction of the fork along the stationary rod and a pair of ears arranged at a right angle to the central plate portion on the opposite sides thereof, the ears having respective coaxial guide holes adapted to guide the sliding movement of the fork along the stationary rod, and an appendage extending from the central plate portion in the sliding direction of the fork, and wherein one of the ears is formed at an end of said appendage.

15. Gear fork according to claim 13, wherein the support portion further includes a bridge-like portion interposed between the central plate portion and one of the prongs.

16. Gear fork according to claim 15, wherein the bridge-like portion is welded to a tab extending laterally from one of the two ears, so as to stiffen the support portion.

17. Gear fork according to claim 14, wherein the support portion further includes a bridge-like portion interposed between the central plate portion and one of the prongs and wherein the appendage and the bridge-like portion of the support portion are shaped so as to allow two forks having an identical body to be mounted on the same stationary rod with the appendage of one of them being arranged under or over the bridge-like portion of the other.

18. Gear fork according to claim 14, wherein the bridge-like portion is welded to a tab extending laterally from one of the two ears, so as to stiffen the support portion, and wherein the appendage and the bridge-like portion of the support portion are shaped so as to allow two forks having an identical body to be mounted on the same stationary rod with the appendage of one of them being arranged under or over the bridge-like portion of the other.

19. Gear fork according to claim 1, wherein the support portion is formed by a first sheet metal piece obtained by blanking and bending and the prongs are formed by a second sheet metal piece obtained by blanking and bending, the two sheet metal pieces being firmly secured to each other.

20. Gear fork according to claim 19, wherein said second piece includes a bridge-like portion interposed between the two prongs and wherein the support portion is shaped so as to allow two forks having an identical body to be mounted on the same stationary rod with a length of the central plate portion of a fork passing under or over the bridge-like portion of the other fork.

21. Gear fork according to claim 19, wherein the bridge-like portion is welded to a tab extending laterally from on of the two ears, so as to stiffen the support portion.