| 摘要 |
Within a piston cylinder of a pneumatic engine, the system includes a piston proportioned for complemental travel within a piston cylinder, the piston having a radial compression surface and elements for effecting the axial reciprocation of the piston within the piston housing. The system further includes a piston seal including an element for securement to the compression surface of the piston and an integrally dependent resilient annular skirt normally biased inwardly toward a longitudinal system axis, the skirt, in combination with the securement elements, defining a radius of less than that from the system axis to interior walls of the cylinder during low pressure (return stroke) phases of a work cycle of the pneumatic engine and, during high pressure/compression stroke phases, defining a radius greater than that from the system axis to the inner wall of the cylinder. The inward bias of the skirt is overcome causing axial and radial lifting of the skirt against inner walls of the cylinder to effect a piston seal of a high integrity during high pressure phases of the engine work cycle. No seal exists during low pressure phases, since the skirt is not yet expanded.
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