Automatic mechanical variable ratio transmission

A variable ratio transmission system for use with a controllable source of rotational power for powering a variable load, comprising:

• (a) a selector shaft having a selector gear axially movable thereon, the selector gear having an axial selector face width;
• (b) a selector actuator for driving the selector gear along the selector shaft in response to an external signal, the actuator comprising a fork dolly supported for movement parallel to the selector shaft, a lead screw rotatably mounted in parallel relation to the selector shaft and threadingly coupled thereto, and a control motor coupled for rotating the lead-screw shaft;
• (c) a cluster shaft having a plurality N of spur gears rotatably supported thereon, the cluster shaft being inclined relative to the selector shaft, the spur gears each having a cluster face width and being sized and spaced along the cluster shaft for being selectively meshed with the selector gear, at least N-1 of the spur gears being variably coupled to the cluster shaft by a one-way clutch for rotation therewith, the selector shaft and the cluster shaft being series-coupleable between the source of rotational power and a load for driving the load through the selector gear and one of the spur gears;
• and
• (d) a controller for activating the control motor of the selector actuator while preventing substantial torque-loading of any of the spur gears unless that spur gear is axially in mesh with the selector gear at least approximately 25% of the lesser of the selector face width and the cluster face width of that spur gear, the controller including means for comparing a set of operating conditions of the power source with a predetermined operating envelope, and means for activating the actuator for bringing the set of operating conditions within the operating envelope, the operating conditions including an input operating speed and a set point variable, the set point variable including a member of the group consisting of throttle position, torque, power, applied voltage, applied current, modulation duty cycle, and acceleration, the controller being operative for interrupting power from the source for an interval t, the interval t being less than approximately 0.2 second.