Electric motor control system

Claim 2

A control system for energizing two electric motors from an electrical power source comprising: a pulse modulation switching means for producing a power pulse output at a selected level; a means for energizing either one or both of the motors from the power output; means operable when only one motor is energized and maximum power operation is selected for connecting the energized motor directly to the power source; means operable automatically when both motors are energized and maximum power operation is selected for connecting one motor directly to the power source and the other motor to receive the pulse output; and means operable automatically when both motors are energized and maximum power operation is selected for controlling the switching means to produce a selected limited power level output.

Claim 3

A control system according to claim 1 wherein said one motor is a pump motor and the other motor is a traction motor in an industrial truck and said limited power level output is selected to produce an inching speed for the traction motor.

Claim 4

A control system according to claim 2 wherein said switching means is controlled by a movable speed control device having a maximum power operation position that effects connection of the operating motor directly to the power source.

Claim 5

A control system according to claim 2 also comprising means for braking the industrial truck and means responsive to the means for braking for controlling the switching means to reduce the power output level to zero.

Claim 6

A control system according to claim 2 wherein said speed control device is a potentiometer having a tap connected as an input to the switching means and said maximum power operation position activates a switch that effects connection of the operating motor directly to the power source.

Claim 7

A control system according to claim 5 wherein a resistance is connected in series with the potentiometer to decrease the output level at the tap to produce the inching speed for the traction motor.

Claim 8

A control system according to claim 6 wherein said power source is a battery.

Claim 9

An industrial truck power control system comprising: a battery; a traction motor adapted to drive the truck; a pump motor adapted to provide hydraulic pressure for operation of the hydraulic system of the truck; a pulse modulation power switching unit connectable to the battery and adapted to produce a power pulse output variable from a zero level to a maximum level; a speed control device adapted to control the power switching unit output level in response to selective positioning of said control device; first means for connecting the traction motor to receive the power output; second means for connecting the pump motor to receive the power output; third means for connecting the traction motor directly to the battery to thereby bypass the power switching unit; fourth means for connecting the pump motor directly to the battery to thereby bypass the power switching unit; fifth means responsive to a selected position of the speed control device for limiting the power switching means to produce a power output level selecTed to move the industrial truck at inching speed; sixth means for automatically actuating one or both of the first means and the second means; seventh means for automatically actuating the third means in response both to actuation of the first means only by the sixth means and to the selected position of the speed control device; eighth means for automatically actuating the fourth means in response both to actuation of the second means only by the sixth means and to the selected position of the speed control device; and ninth means for simultaneously actuating the fourth means and the fifth means in response both to actuation of both the first means and the second means by the sixth means and to the selected position of the speed control device.

Claim 10

An industrial truck power control system comprising: a battery; a traction motor adapted to drive the truck; a pump motor adapted to provide hydraulic pressure for operation of the hydraulic system of the truck; a pulse modulation power switching unit connectable to the battery and adapted to produce a power pulse output variable from a zero level to a maximum level; a speed control device adapted to control the power switching unit output level in response to selective positioning of said control device; first means for connecting the traction motor to receive the power output; second means for connecting the pump motor to receive the power output; third means for connecting the traction motor directly to the battery to thereby bypass the power switching unit; fourth means for connecting the pump motor directly to the battery to thereby bypass the power switching unit; fifth means responsive to a selected position of the speed control device for limiting the power switching means to produce a power output level selecTed to move the industrial truck at inching speed; sixth means for automatically actuating one or both of the first means and the second means; seventh means for automatically actuating the third means in response both to actuation of the first means only by the sixth means and to the selected position of the speed control device; eighth means for automatically actuating the fourth means in response both to actuation of the second means only by the sixth means and to the selected position of the speed control device; and ninth means for simultaneously actuating the fourth means and the fifth means in response both to actuation of both the first means and the second means by the sixth means and to the selected position of the speed control device.

Claim 11

A power control system according to claim 8 also comprising means for making the third means inoperative upon deenergization of the pump motor following actuation of the ninth means.

Claim 12

A power control system according to claim 8 also comprising means for braking the vehicle, and means for controlling the power switching means to reduce the pulse output to the zero level in response to actuation of the means for braking.

Claim 13

A control system for energizing two electric motors from a common DC power source comprising: a pulse modulation power switching means capable of producing a power pulse output at selected levels; a movable controller; means on initial moving of said controller to increase the selected level of the power pulse output to energize both of said motors in parallel; means on further movement of said controller to energize one of said motors directly from said power source and the other of said motors from said pulse modulation switching means.

Claim 14

A control system for energizing two electric motors from a common DC power source comprising: a pulse modulation power switching means capable of producing a power pulse output at selected levels; a movable controller; means on initial moving of said controller to increase the selected level of the power pulse output to energize both of said motors in parallel; means on further movement of said controller to energize one of said motors directly from said power source and the other of said motors from said pulse modulation switching means.

Claim 15

A control system for electric motors as claimed in claim 11 also comprising: means for braking the vehicle, and means for controlling the power switching means to reduce the pulse output to the zero level in response to actuation of said means for braking.