Variable ratio transmission systems

A variable ratio transmission system for coupling a drive shaft of a prime mover to a load, including

• a clutch;
• an epicyclic gear train having first and second input elements and an output element, said first input element being coupled to said drive shaft via said clutch;
• a stepped-ratio gear box having an input shaft coupled to said output element of the epicyclic gear train, and an output shaft coupled to said load;
• a smoothly adjustable-ratio hydrostatic transmission subsystem having a ratio range substantially equal to the greatest ratio step of said gear box and comprising
• a variable capacity pump mechanically coupled with said drive shaft, and
• a fixed capacity motor hydraulically coupled with said pump and mechanically coupled to said second input element of the epicyclic gear train;
• and
• an electrical control system including:
• an operator-controlled load demand means,
• a plurality of actuators for varying each of the following variable parameters of said transmission system:
• the speed of said drive shaft, the engaged/disengaged condition of said clutch, the ratio of said gear box, and the ratio of said hydrostatic sub-system,
• a plurality of sensing means operative to produce signals representative of each of the said variable parameters, and
• logic means responsive to input signals received from said sensing means and from said load demand means, and generating actuator command signals in an actuator drive circuit respective to each of said actuators.