| 摘要 |
A braking system is provided for a construction machine, including a ground engaging drive apparatus. The construction machine includes a hydraulic drive system, including a hydraulic motor connected to the ground engaging drive apparatus and a first hydraulic pump for supplying fluid under pressure to the motor, the pump and motor being connected so that a braking force may be applied to the drive apparatus by varying the discharge volume of the first pump. A first valve is connected between an inlet and an outlet of the first pump for shunting the pump. An emergency brake is connected to the ground engaging drive apparatus, and is mechanically biased in a brake applying direction. A second hydraulic pump supplies fluid to a hydraulic actuator for releasing the emergency brake. A second valve is located between the second pump and the hydraulic actuating means. A common actuator is connected to the first and second valves and is variable between a first position wherein the first valve is closed and the second valve is open, and a second position wherein the first valve is open and the second valve is closed. A sensor detects movement of the common actuating actuator between the first and second positions, and causes fluid pressure to be relieved from the hydraulic actuator so that the emergency brake is applied before the second valve is closed. Downstream of the second valve is an auxiliary pump for supplying pressure to release the emergency brake when the common actuating handle is in its second position.
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