BRAKE CONTROLLER FOR LOWERING HOISTED LOAD AT CONSTANT SPEED

摘要

PURPOSE:To provide a brake controller which can retain the feeding speed of a main cable for hoisting a load to be regulated at braking force in a crane employing a negative type brake unit. CONSTITUTION:A tachometer generator 21 for detecting the rotating speed Vw of a crane main cable motor at cable feeding time is connected to the motor for hoisting up or down the cable for lifting a load to produce its output signal through an F-V converter 22 to first and second comparators 23, 24. The comparator 23 compares the actual motor speed Vw with constant voltage VT+K to produce its output when VwVT+K, and the comparator 24 similarly produces its output when VwVT. These outputs are applied to first and second AND gates 25, 26, respectively. This controller detects the excessive or insufficient brake force when the brake is engaged, and has a structure for producing a brake release signal from the AND gate 26 (S2) and high or low torque brake signal from the AND gate 30 (S1) or 31 (S3).