| 摘要 |
A hydraulic brake system for the hoist drum of a lifting crane to achieve good control over loads being held or lowered by the load line wrapped on the hoist drum comprises a brake band for exerting a braking force on the hoist drum. The system further comprises a brake cylinder for operating the brake band; a brake valve for controlling the supply of fluid from a fluid source to the brake cylinder; a brake pedal for operating the brake valve and movable between a brake release position and a brake applied position; a valve toggle linkage connected between the foot pedal and the brake valve piston to cause the brake valve to supply fluid to the brake cylinder at a predetermined pressure when the pedal is depressed to a first brake applied position and for applying fluid at a greater pressure when said pedal is moved to a second brake applied position which offers a mechanical advantage; and a hydraulic simulator for adjusting the position to which the foot pedal can be depressed. The hydraulic simulator includes a cylinder, a piston, a biasing spring for biasing the piston to a position wherein all fluid is expelled from the cylinder, and an adjustable stop screw for limiting piston travel, the stop screw being adjustable to control the amount of fluid that can be supplied from the brake valve to the hydraulic simulator when the pedal is depressed to thereby control the extent to which said pedal can be depressed.
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