Positive synchromesh gears

Claim 1

In a speed change gear having a driving member, a driven member, a free member freely rotatably mounted on the driven member, and transmission means coupling the free member to the driving member, a positive synchromesh gear device of the free ring type comprising: i. respective members having frusto-conical coupling surfaces and having means drivingly connecting said members to the driving member and the free member respectively; ii. first and second synchronizing rings mounted on the frustoconical coupling surfaces of said respective members; iii. a coupling member mounted on the driven member and coupled to the latter for rotation therewith, said coupling member being slidable axially on the driven member, and having a plurality of through bores; iv. a plurality of pins extending axially from each respective ring towards the other ring, said pins passing through respective said bore in the coupling member; v. selector means for moving the coupling member axially to connect the driven member selectively to the driving member for direct drive therefrom and to the free member for drive through said transmission means; vi. inner and outer cylindrical coaxial portions on each respective pin, and a respective frusto-conical surface portion, tapering towards the free end of the pin, interconnecting said cylindrical portions, each said bore being generally cylindrical with a diameter substantially equal to that of the inner cylindrical portion of the respective pin, and each bore having, on that side which faces the inner portion of the respective pin, a frusto-conical counter-sunk surface, said pins being normally disposed in a rest position with their outer cylindrical portions within the respective bores, wherein the improvement consists in that: vii. said outer cylindrical portion of each pin is provided with a coaxial cylindrical cavity, said cavity being open at the free end of the respective pin, and housing resiliently biased friction means urged into frictional contact with the ring other than that to which said pin is attached, urging said two rings constantly into contact with said respective frustoconical coupling surfaces, and causing said first ring to tend to draw said second ring into rotation, keeping the outer cylindrical portion of each said pin laterally in contact with part of the cylindrical surface of the respective bore in said coupling member.