| 摘要 |
PURPOSE:To provide an optimum brake force in accordance with a movable load, by providing a shut-off valve in a passage communicating between pressure variation chambers in the rear of power pistons, and as well by carrying out the open and close control of this shut-off valve in accordance with the movable load. CONSTITUTION:Pressure variation chambers 6, 10 in the rear of front and rear power pistons 4, 8 are communicated together through a communication passage 37 in which a three-way selector valve 38 is disposed. This three-way valve 38 is controlled, manually or electrically, to communicate the communication passage 37 or to shut-off the communication passage 37 while it communicates the front pressure variation chamber 6 with the atmosphere, simultaneously. Further, this three-way valve 38 is selectively controlled in accordance with the movable load condition by manually or in association with an output signal from a load detector, etc.
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