Patent ID: 8373375

Claim:
In an electro-mechanical drive system that includes a movable power output component and further includes a plurality of electric drive motors, apparatus comprising: a first transfer mechanism that is connectable to and disconnectable from each of said motors, for transferring power from each connected motor to cause said output component to move at a first speed relative to the motor speed, comprising a first speed ratio, and to deliver power at a specified constant level when moving at said first speed ratio; a second transfer mechanism that is connectable to and disconnectable from each of said motors, for transferring power from each connected motor to cause said output component to move at a second speed relative to the motor speed, comprising a second speed ratio, and to deliver power at said specified constant level when moving at said second speed ratio; shift means for selectively connecting each motor to, and disconnecting each motor from, the first and second transfer mechanisms, respectively; a source for selectively supplying electric current to each of said motors; and a control device connected to perform a set of tasks when each of said motors are simultaneously connected to the first transfer mechanism, said set of tasks comprising: (a) disconnecting a selected one of said motors from the first transfer mechanism, while at the same time supplying increased electric current to each remaining motor, in order to maintain movement of said output component at said first speed, and delivery of power thereby at said specified constant level; (b) bringing the speed of said selected motor to a synchronized speed associated with said second speed; and (c) responsive to said selected motor reaching said synchronized speed, connecting said selected motor to the second transfer mechanism.