Transmission for tractors

Abstract

A speed change mechanism for a transmission comprises a main shaft provided with a plurality of power transmitting gears, and a propelling speed change gear system and a power takeoff speed change gear system supported on the opposite sides of the main shaft in parallel thereto. Each of the propelling and power takeoff speed change systems includes a speed change shaft freely rotatably carrying a suitable number of speed change gears meshing with the power transmitting gears on the main shaft at all times. The speed change shaft accommodates an axially slidable speed change rod which, when moved, forces pins outward or inward radially of the shaft to couple the speed change shaft to the corresponding speed change gear or disconnect the shaft from the gear. The freely rotatable speed change gears are held against axial movement, while axially slidable engaging members which are otherwise provided between the adjacent speed change gears are eliminated. The transmission therefore has a shortened axial length and does not require a clutch which must be usually provided between the engine and the main shaft. The propelling speed change system further incorporates a creeping assembly of the planetary roller type for super-speed reduction and is provided with a secondary speed change assembly. The transmission also includes a power takeoff assembly for driving the front wheels of the tractor utilizing the secondary speed change assembly.