Gear shift mechanism for automotive multi-speed transmission

A gear shift mechanism for an automotive multispeed transmission comprising:

• a manually operable gear shift lever,
• a pivotally movable selector rod linked with the gear shift lever and having an end piece, said end piece having a predetermined length in the direction of pivotal movement of the selector rod,
• at least two axially movable parallel fork shafts including a first shaft movable in one direction for selecting one forward speed and a second shaft movable in the opposite direction for selecting one reverse speed, said fork shafts having respectively generally U-shaped recesses aligned in the direction of pivotal movement of the selector rod, the end piece of the selector rod being selectively engageable in one of the recesses in accordance with shifting operation of the gear shift lever for axial movement of the corresponding fork shaft,
• each said recesses being defined by two side walls and one base wall,
• a first side wall of each said recesses on the leading side in the direction of axial movement of the corresponding fork shaft having a predetermined length generally equal to the length of the end piece and a second side wall of each said recesses on the trailing side in the direction of axial movement of the corresponding fork shaft having a length smaller than said predetermined length of the first side wall,
• the end piece of the selector rod having first and second pivot positions where it is engaged in the recesses of the first and second fork shafts, respectively and is movable together with the first or second fork shaft into a position effecting said forward or reverse speed, said end piece in said first or second pivot position being adapted to simultaneously engage the second side wall of the first or second fork shaft and the first side wall of the second or first fork shaft when erroneously moved in the opposite direction to the position effecting said forward or reverse speed, and
• means for preventing simultaneous axial movement of said first and second fork shafts or for preventing axial movement of the first and second fork shafts from their neutral positions in the opposite directions to those for selecting said forward and reverse speeds, respectively.