GB1377876A - Apparatus for maintaining a predetermined relative position of a moving web of material and an element - Google Patents

Abstract

1377876 Transverse web registering KELVA AB 11 April 1972 [14 April 1971] 16572/72 Heading B8R A device for maintaining a predetermined relative position of a moving web 10 and an element comprises a fluid flow web edge sensor 11 fixed relative to the element, and an air pressure servomotor 12 for adjusting said relative positions, the sensor being connected to a source 18 of pressurized air via a control valve 16 which includes two diaphragms 30, 40 controlling air flow to the servomotor in dependence upon changes of air pressure supplied to a chamber 58 between the diaphragms via the sensor the changes being due to deviation from said predetermined position. In the predetermined position, the air flow from sensor orifice 25 directed past the web edge and through conduit 28 to the chamber 58 is sufficient to hold a seal 42, connected to diaphragm 40, down against valve seat 43 and insufficient to raise diaphragm 30 to open valve 33. If the web edge projects too far into the sensor, the air flow is restricted, allowing diaphragm 40 to be raised by a spring 54 thereby opening the valve seat 43 and connecting the servomotor 12 to atmosphere via passages 57, 49, 52. This allows a servomotor spring 12<SP>11</SP> to effect a relative movement between the web 10 and element, e.g. via guide rollers engaging the web or by movement of the element mounted on a carriage. Should the web edge project not far enough into the sensor, air flow is increased raising diaphragm 30 and opening valve 33 via pin 32 thereby connecting the servomotor to the pressurized air inlet 18 via passages 21, 37, 38. This pressure actuates the servomotor to effect relative movement in the opposite sense. The bias of spring 54 is adjustable.