Track-laying device

In combination, a transmission and direction control means suitable for use with a vehicle having laterally spaced drive elements and adapted to transmit drive from a drive motor of the vehicle to the drive elements of the vehicle, comprising:

• a transmission differential gear substantially on a longitudinal vertical line of the vehicle, and having an input which is drivingly connectable to the drive motor, and a pair of half shafts which are respectively drivingly connectable to the drive elements;
• a control differential gear for effecting stable steering and resisting self steering and transferring power from one track to the other track, said control differential gear being substantially on said longitudinal vertical plane and compressing
• a cage,
• an input spur gear wheel fast with the cage,
• a pair of co-axial, outwardly extending, half shafts providing control half shafts,
• a pair of half shaft spur gear wheels respectively fast with said control half shafts at their inner ends, and
• at least a first pair of spur pinions mounted for rotation on the cage at circumferentially spaced positions on a pitch circle about the axis of the half shaft spur gear wheels, the pitch circle diameter corresponding to the sum of the effective diameters of the half shaft spur gear wheels and the spur pinions, the circumferential spacing corresponding to the sum of the effective radii of the spur pinions, the arrangement being such that the spur pinions mesh respectively with the half shaft spur gears, and with each other;
• first connecting means interconnecting of the half shafts of each of the differential gear and the control differential gear for rotation in opposite directions and at a predetermined ratio of speed of the half shaft of the control differential gear to speed of the half shaft of the transmission differential fear larger than 1:1;
• second connecting means connecting the other of the half shafts of each of the transmission differential gear and the control differential gear for rotation in the same direction and at a speed ratio similar to said predetermined speed ratio;
• a control input drivingly connected to the input spur gear wheel;
• and
• control drive means adapted selectively to hold the control input stationary and to drive the control input in a desired direction and a desired speed.