Patents Assigned to SRE Controls, Inc.
  • Patent number: 6226582
    Abstract: A control system for an electric lift truck that controls a traction motor and a hydraulic pump motor is disclosed. The speed of rotation of both motors is controlled by a pulse width modulated current supplied from a battery source by the controller in direct response to a demand communicated to the controller through an interface manipulated by an operator. A pump driven by the pump motor supplies pressurized hydraulic fluid to a lift mechanism and a power assisted steering unit. A joystick with function switches mounted thereto is provided so that the operator steers with one hand while controlling truck propulsion and all functions of the lift mechanism with the other hand. The direct control of the pump motor speed enables a fully proportional control of the hydraulic system. The control system is a compact structure that requires minimal cabling and ensures that the hydraulic system operates with energy efficiency and minimal wear.
    Type: Grant
    Filed: July 21, 1998
    Date of Patent: May 1, 2001
    Assignee: SRE Controls, Inc.
    Inventors: Robert T. Adsett, Pierre C. Gadbois