| 摘要 |
<p>The mechanism lifts off and extracts individual sheets from a stack, having a lifting device with suction cups moving down onto the topmost sheet and up again. Its drive is controlled by the vacuum in the supply piping, which is in turn dependent on the presence or absence of a sheet at the cups. Operation of the lifting device drive (24) is controlled by a pneumatic switch or valve (29), actuated by pressure alteration in the suction piping (34). The drive can be an electrically-controlled crank mechanism, with a pneumatially-operated control switch. The crank can perform a single revolution at the time, lifting the cup off the stack and returning it. The rise in pressure in the pipe when a sheet is pulled off the cups actuates the switch.</p> |
