| 摘要 |
PURPOSE: A hydraulic boost cylinder is provided to obtain a desired output by being promptly operated in a low-load state and being automatically changed to a high pressure stroke in a high-load state. CONSTITUTION: A check valve(6) selectively supplying pneumatic pressure to a pneumatic portion(A) of the front end of a first cylinder hole(11) is installed in a hydraulic boost cylinder. In a low-load state, pneumatic pressure is supplied to another pneumatic portion(C) to move a second piston(3) toward a bore(13). A third piston(5) moves to outwardly stretch a piston rod(5a). Thus, a low pressure stroke is performed. In a high-load state, the air of the pneumatic portion(C) is exhausted by the operation of the check valve depending on the movement of a slide piston(8). Pneumatic pressure is supplied to the pneumatic portion(A), and a first piston(2) moves toward the bore. A trunk piston(2a) moves to the third piston through the bore in an airtight state. Thus, a high pressure stroke is performed. Therefore, the hydraulic boost cylinder promptly operates a low pressure stroke in a low-load state while automatically changing to a high pressure stroke in a high-load state.
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