Output split type hydrostatic transmission

A steplessly adjustable hydrostatic-mechanical compound transmission, comprising:

• an input drive shaft;
• a four-shaft drive system disposed upon the output side of said transmission, one of said four shafts being the output drive shaft, and the other three of said four shafts being mechanically and hydrostatically driven by means of said input drive shaft and mechanically connected to said output drive shaft for driving the same;
• a hydrostatic speed differential drive means including a first, non-adjustable positive displacement pump-motor, and a second positive displacement pump-motor driven by means of said input shaft and adjustable in both directions of pumping and which is disposed, along with said first pump-motor, in a closed hydraulic circuit serving as hydraulic communication means between said two pump-motors;
• a drive power train selector means including a two-speed reversing drive means, having two operative mode positions and a neutral position, interposed between and connecting said input drive shaft with one of said three shafts, said first displacement pump-motor being connected, through means of a hydraulic coupling drive, with the other two of said three shafts;
• and
• operating means disposed within said selector means and operatively connected with an adjustment means of said second adjustable pump-motor for facilitating synchronization of the movement of said reversing drive means between said two operative mode positions.