| 摘要 |
To place a driven shaft in accurate angular alignment with respect to a continuously rotating driving shaft or, selectively, with respect to a fixed reference, the fixed reference is formed as a housing, the driving shaft has a disk with a cam track attached thereto, and the housing likewise has a disk with a cam track. The driven shaft has an engagement pin connected thereto, axially slidable and engageable, respectively, with the cam tracks of the driving shaft, or of the housing,. The cam tracks are arranged to carry along and gradually accelerate the pin coupled to the driven shaft until the pin locks at a predetermined position in the cam track to define the relative angular position of driving shaft and driven shaft; upon different axial movement, the engagement pin is permitted to slide out of engagement with the cam track disk coupled to the driving shaft and engage a similar, and stationary cam track on the housing, again formed with a stop or rest position which again determines the angular relationship of the driven shaft with respect to the housing, and hence with respect to the reference. Axial sliding movement of the engagement pin is controlled by pneumatic pressure acting on spring-loaded pistons. The clutch is particularly useful in connection with printing machinery, especially rotary screen printing machinery, to provide for accurate alignment of intermittently operating printing stencil cylinders with respect to the instantaneous angular position of the machine drive shaft. |
