| 摘要 |
Triple action piercing structure comprising an outer cylinder, an inner cylinder, a shaft and radially extending piston means operable between the inner and outer cylinders for providing a plurality of separate pressure chambers between the inner and outer cylinders, specific, simple and efficient passage means for passing a pressure medium into and exhausting the pressure medium from the pressure chambers to produce relative axial movement between the inner and outer cylinders at a particularly high pressure for cylinders of predetermined diameter to facilitate piercing of large diameter openings in thick hard workpieces.
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