Air pressure operated proximity sensor and counting apparatus incorporating same.

摘要

The disclosure relates to an air pressure sensor for use particularly in a batched counting apparatus for counting sheets or signatures in a "shingled" stream and comprising an air passage (21) terminating in a probe (17) having an orifice (19) to ride over the surface of the "shingled" stream of sheets. The jet (26, 27) delivers air from a supply line into the passage and branch passage (28) located adjacent the jet contains a floating element (31) which moves up and down the passage in accordance with static air pressure in the passage. The element is arranged to make or break a beam in a photo-electric cell arrangement (12) to operate a counting device. As the probe rides from one sheet or signature to the next, the air pressure in the passage (21) drops and the result in the fall in pressure in the branch passage causes the element (31) to fall thereby triggering the photo-electric cell to operate the counting device. The sensor is extremely sensitive, responding when passing from sheet to sheet of very thin paper and it is capable of operating at high speed.