Transmission for power take-off

摘要

A PTO transmission includes a split power transmission unit having an output member connected to a PTO shaft, a first input connected to an engine output shaft and a second input connected the output of a variable speed drive unit. A control unit controls the speed of the variable speed drive unit as a function of sensed engine speed and maintains the PTO shaft at a constant speed. The split power transmission is preferably a planetary gear unit. The variable speed drive unit preferably includes a variable displacement hydrostatic pump driving a fixed displacement hydrostatic motor which drives a sun gear of the planetary gear unit. This system transmits power to the PTO shaft from both the engine and from the variable speed drive unit. The control unit may also control the variable speed drive unit so that the speed of the PTO shaft is maintained at a desired ratio with respect to the ground speed, or so that the speed of the PTO shaft is maintained at a speed set by an operator.