GB1188457A - Web Guide Apparatus - Google Patents

Abstract

1,188,457. Feeding webs. ROCKFORD SERVO CORP. 15 Oct., 1968 [25 March, 1968], No. 48906/68. Heading B8R. Apparatus for guiding a longitudinally travelling web W of varying width so that the centre line of the web follows a preselected path A comprises: two pneumatic edge detectors 10, 11 mounted at equal distances on opposite sides of the path A, detector 10 producing a signal which uniformly decreases or increases in magnitude as the associated web edge Wa moves respectively outwardly or inwardly relative to the path A, and detector 11 producing a similar signal decreasing or increasing in magnitude as the web edge Wb moves respectively inwardly or outwardly relative to the path A; a control device (Fig. 3, not shown) having means for averaging the signals from the two detectors, this average signal remaining constant whilst the centre line of the web is following the path A, whereas it increases or decreases from the constant value when the centre line deviates to one side or other of the path A; and a centering device M which is operated by the control device to change the course of the web so that the centre line of the web is returned to the path A. The centering device M may be of the type described in Specification 1,220,379, may shift the web unwind roll to laterally position the web, or may shift a device D, which performs an operation on the web, to cause the device to follow the lateral movements of the web. The control device may be of the type described in Specification 1,155,798. Each web detector includes a sensing orifice and a transmitting orifice, and detector 11 has a second transmitting orifice so arranged that the signal from detector 11 is inverted with respect to the signal from detector 10, as is required (Figs. 4 to 11, not shown). The detectors 10, 11 are mounted on a guide bar 112 for movement to accommodate webs of widely different widths. This movement may be effected manually but, as shown, a motor 118 is automatically controlled to move the detectors as necessary, the control circuit 16 for the motor being responsive to a further edge detector 122, 121 associated with the detector 10. A suitable relay arrangement for the circuit 16 is described with reference to Fig. 2 (not shown).