Mold level control system

Claim 1

In a continuous casting machine of the type having a mold, and hydraulic drive motors for withdrawing a cast metal strand from said mold; a mold level control system comprising: a. a variable displacement pump for supplying power fluid to said drive motors to operate said motors, said Pump having a stem projecting therefrom to control the displacement of said pump and hence the power level of said power fluid, b. a double-acting piston and cylinder, c. a yoke connected to said double-acting piston and to said stem, and means pivoting said yoke, so that movement of said double-acting piston in one direction moves said stem to increase the power level of said power fluid, and movement of said double-acting piston in the other direction moves said stem in a direction to decrease the power level of said power fluid, d. a source of control fluid, and a four-way directional valve connecting said source to said double-acting piston and cylinder, said valve including a valve member having a first position in which said control fluid is disconnected from said cylinder, so that said piston and stem remain stationary, a second position in which said control fluid is connected to said cylinder in a direction to move said piston at a predetermined rate in said one direction, and a third position in said control fluid is connected to said cylinder in a direction to move said piston at a predetermined rate in said other direction, e. said valve further including first and second solenoids selectively actuable to move said valve member to said second or third positions respectively, and spring means biasing said valve member to said first position in the absence of actuation of said solenoids so that the power level of said fluid remains constant in the absence of actuation of said solenoids, and f. control means for said valve, said control means including a joystick, means mounting said joystick in an orientation with its its axis substantially horizontal, for up and down movement of said joystick from a neutral horizontal position to a raised position or to a lowered position, a first switch mounted for actuation by said joystick when said joystick is in its lowered position and being off when said joystick is in a position other than its lowered position, a second switch mounted for actuation when said joystick is in its raised position and being off when said joystick is in a position other than its raised position, and means connecting said switches with said solenoids so that when said first switch is actuated, said first solenoid is actuated and when said second switch is actuated, said second solenoid is actuated, whereby movement of said joystick to its lowered position increases the speed of said drive motors to increase the rate of strand withdrawal from said mold, and movement of said joystick to its raised position decreases the speed of said drive motors to decrease the rate of strand withdrawal from said mold, and when said joystick is in its neutral position, said double-acting piston remains stationary and the power level of power fluid supplied to said drive motors remains fixed.