Reverse drive control device for vehicle gearbox

Claim 1

In a vehicle gearbox having: (a) sliding rings movable axially for engaging forward ratios, (b) an idler gear movable axially for engaging a reverse drive, (c) forward selector shafts, each associated with one of said sliding rings and axially shiftable for moving said ring between an intermediate neutral position and end engagement positions, (d) a reverse drive selector shaft axially shiftable for moving said idler gear between a rest position not in engagement and an active position in meshing engagement with first and second reverse gears, (e) forward notched yokes, each fixed to one of said forward selector shafts for operating said shafts, (f) a reverse drive notched yoke fixed to said reverse drive selector shaft, (g) a gear ratio selector and engagement control element having a forward peg with a first end head engageable selectively in notches of said forward notched yokes, and a reverse drive peg with a second end head engageable selectively in a notch of said reverse drive notched yoke, said element being movable in rotation around an axis by a determined angular stroke from a neutral position for operating axially the selected notched yoke, the improvement wherein: (h) said idler gear is rotatably mounted directly on said reverse drive selector shaft to be axially carried thereby, (i) one of said first and second reverse gears is fixed to one of said sliding rings and is axially movable therewith, and (j) said second end head of said reverse drive peg is substantially twice as distant from said axis of said control element as said first end head of said forward peg, whereby said determined angular stroke causes an axial stroke of said reverse drive selector shaft, when selected, greater than the axial strokes of said forward selector shafts, when selected, to such an extent that said idler gear in said rest position cannot engage said one reverse gear fixed to said sliding ring when shifted in its engagement positions toward said rest position.