| 摘要 |
A pressing roller is used in a sheet-advancing arrangement to press the advancing sheet material against a driven roller to control the friction between the driven roller and the sheet material and thereby reduce, if not entirely eliminate, any slippage between the driven roller and the sheet material. Two levers pivotally mount the pressing roller on a housing which, in turn, is detachably mounted on a support, the housing being extremely flat and bounding a chamber which has an open end. A diaphragm deflectably spans and sealingly closes the open end of the chamber and urges the pressing roller and thus the sheet material against the driven roller with a force proportionate to the pressure prevailing in the chamber of the housing. Each of two springs is connected to one of the levers and to the housing and moves the pressing roller away from the driven roller when the pressure in the chamber drops below a predetermined value.
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