Reversible anti-backlash power transmission

A method for removing all the free-play between meshing gear teeth of the gears in a gear train of a selectively reversible power transmission including a first gear box for transmitting power in one direction comprising a first drive shaft, first gear means associated with the first drive shaft for rotation therewith, a first driven shaft, second gear means associated with the first driven shaft for rotation therewith in meshing engagement with the first gear means of the first drive shaft, first driven gear means associated with the first driven shaft for rotation therewith, a second gear box for transmitting power in the opposite direction comprising a second drive shaft, third gear means associated with the second drive shaft for rotation therewith, a second driven shaft, fourth gear means associated with the second driven shaft for rotation therewith in meshing engagement with the third gear means of the second drive shaft, second driven gear means associated with the second driven shaft for rotation therewith, final drive gear means in meshing engagement with the first driven gear means of the first gear box to be moved in a first direction thereby and in meshing engagement with the second driven gear means of the second gear box to be moved in a second direction opposite to the first direction thereby, and electro-magnetic friction coupler means for selectively coupling and uncoupling the first drive shaft of the first gear box and the second drive shaft of the second gear box, the method comprising the steps of:

• de-energizing the electro-magnetic coupler thereby uncoupling the first drive shaft of the first gear box from the second drve shaft of the second gear box;
• turning the first drive shaft of the first gear box in the rotational direction moving the final drive means in the first direction until the meshing teeth of the first gear means of the first drive shaft of the first gear box and the teeth of the second gear means of the first driven shaft of the first gear box are in positive mutual contact, until the meshing teeth of the first driven gear means of the first drive shaft of the first gear box and the teeth of the final drive gear means are in positive mutual contact, until the meshing teeth of the final drive gear means and the teeth of the foruth driven gear means of the second driven shaft of the second gear box are in positive mutual contact, until the meshing teeth of the fourth gear means of the second driven shaft of the second gear box and the teeth of the third gear means of the second drive shaft of the second gear box are in positive mutual contact;
• re-energizing the electro-magnetic coupler thereby coupling the first drive shaft of the first gear box to the second drive shaft of the second gear box while continuing to turn the first drive shaft of the first gear box in the same rotational direction to maintain the meshing teeth of all of the gears of the gear train of the transmission in positive mutual contact;
• and,
• ceasing the turning of the first driven shaft of the first gear box.