| 摘要 |
A sequence of pneumatic cylinders arranged in tandem relation upon a common stationary shaft and coupled for movement in concert. The cylinders comprise cylinder portions in the form of shell-shaped-housings with closed opposite ends containing central openings through which the shaft passes, and annular piston heads slidably arranged upon the shaft within the housings and having tubular piston stems that slide upon the shaft and project from one of the end walls of the housings. Each housing, but the first in the sequence of cylinders, is firmly mounted upon the projecting end portion of the tubular piston stem of the directly preceeding cylinder in juxtaposition with the housing of said preceeding cylinder. Means are provided to positively and yet adjustably limit the extent to which the piston stem of each cylinder may penetrate its housing which in turn limits positively the maximum contraction of which the cylinder is capable; these means have the form of an externally threaded bushing that is slidably mounted upon the tubular piston stem and threadably engages the cylinder housing along the opening of the end wall through which the piston stem protrudes. By adjusting the position of the bushing within said end wall relative to the cylinder housing, and by providing an abutment at the outer end of the piston stem, the extent to which the stem may penetrate the housing and hence the minimum axial length to which the cylinder can be contracted, may be predetermined very precisely.
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