Patent ID: 6675576
Filing Date: 2004-01-13
Classification: B60T,F16H

Abstract:
A hydraulic circuit for the hydrostatic transmission of a vehicle, said hydraulic circuit comprising at least one hydraulic motor, two main ducts, serving respectively as feed and as discharge main ducts for the motor, a parking brake comprising brake means suitable for being urged by return means into a braking position in which said brake means brake the motor, and for being urged into an inactive position by feeding fluid to a brake release chamber via a brake release duct, the circuit further comprising brake release control means suitable for connecting said brake release duct to a first brake release fluid source, means for connecting the brake release chamber to an unpressurized reservoir, short-circuit valve means suitable for isolating said feed and discharge main ducts from each other or for interconnecting them, selection valve means suitable for connecting the brake release duct to the brake release chamber or for isolating said duct from said chamber, and auxiliary brake release means suitable for connecting the brake release chamber to a second brake release fluid source when said chamber is isolated from the brake release duct; said short circuit valve means and said selection valve means being comprised in a single short-circuit and selection valve having two main ports connected to respective ones of the two main ducts, and two selection ports connected respectively to the brake release chamber and to the brake release duct, the hydraulic circuit having control means for controlling said valve, which control means are suitable for causing the valve to take up a first configuration in which the main ports are mutually isolated while the selection ports are interconnected, and for causing the valve to take up a second configuration in which the main ports are interconnected while the selection ports are mutually isolated.