Field shunting control for a DC series motor

DETAILED DESCRIPTION I claim: 1.
In a vehicle powered by a battery and driven by a series DC electric motor having an armature with a series connected field winding and a circuit connected in parallel with the series field winding for shunting a portion of the armature current around the field winding to increase the maximum motor speed, said circuit having a switch therein, an improved speed control including: means responsive directly to the speed of said motor, closing said switch to complete the field shunt circuit above a selected motor speed.
2.
The speed control of claim 1 wherein said speed responsive means closes said switch at a speed greater than a first selected speed and opens said switch at a speed less than a second selected speed which is less than said first selected speed.
3.
The speed control of claim 1 wherein said vehicle has an operator actuated accelerator, means responsive to a first range of actuation of the accelerator for interrupting the circuit from the battery to the motor to control vehicle speed and means responsive to further actuation of the accelerator for bypassing said circuit interrupter means, the motor speed responsive means being disabled during speed control by said interrupter circuit and said bypass means including means for enabling said motor speed responsive means.
4.
The speed control of claim 1 including a field shunt relay for actuating the normally open switch in the field shunt circuit and a circuit connecting the field shunt relay with said battery including a centrifugal switch responsive to the speed of said motor.
5.
The speed control of claim 4 wherein said vehicle has an operator actuated accelerator, means responsive to a first range of actuation of the accelerator for interrupting the circuit from the battery to the motor to control vehicle speed and a bypass relay responsive to a further actuation of the accelerator for closing a contact to bypass said circuit interrupter means, the field shunt relay circuit including a contact of said bypass relay open to disable the field shunt during speed control by said interrupter circuit and closed to enable said field shunt upon said further actuation of the accelerator