GB1348440A - Method of mounting a mask in a cathode-ray tube using retractable spacing units - Google Patents

Abstract

1348440 Colour television tubes RCA CORP 21 Oct 1971 [24 Dec 1970] 48932/71 Heading G1M [Also in Division H1] A method for mounting a mask to a crt (e.g. colour TV) faceplate panel 12, comprising positioning of the mask by retractable spacing units placed between the mask and panel at selected points, each unit being extendible to predetermine the separation distance and being extended to this distance prior to attachment of the mask to the panel, the spacing units being retracted after attachment of the mask to the panel and measuring the spacing between the mask and panel at points adjacent to each unit without removing same. Measurement may additionally be before or during attachment or may be continuous. This method reduces measurement errors resulting from stresses while the mask is in contact with the spacing units. Apparatus 10 also Fig. 1 (not shown) includes a thin rectangular curved sheet support 25 (e.g. #" fibreglass or plastic), whose surface conforms to the faceplate, guide members 26a through d for orientating and centering during assembly, nine distance measuring gauges 27g (a...), mounted in openings 48 in sheet 25, each gauge connected by flexible tubes (28a...i) to a source of air under pressure (not shown) and fluid e.g. water manometers such as (29a). In the gauges, body 50 is pivoted at 51 to sheet 25 and resting on arcuate button 53 at the other end. In operation, air escaping through an orifice leaf 55 being biased upwardly with button 56 against the mask. Downward movement of leaf 55 controls air escape and is monitored on gauges (29). Each spacing unit includes base (32), retainer (33) plunger assembly (34) mounted for limited movement in the retainer, flexible diaphragm (35), sealed chamber (36), connecting tube (37a) to a central air supply through a common air valve (not shown), plunger assembly (34) including contact tip element (39) threaded in plunger (38), and locking set screw (40). During assembly, a weight conforming to the inner concave surface of the mask may be positioned thereon to hold the mask in continuous contact with sheet 25. The air pressure in chamber (36) fully extends the plungers after initial assembly. Four leaf springs (23) are placed over studs (16) and welded to the mask frame, the spacer apparatus then separates from mask 17 by exhausting chambers (36), and distances measured by gauges 27.