GB1308135A - Gauges - Google Patents

Abstract

1308135 Wall thickness gauge ASSOCIATED ENG Ltd 11 June 1970 [17 June 1969, 22 Aug 1969] 30692/69 and 42110/69 Heading G1A A gauge measuring the wall thickness of a hollow body 1 such as a turbine blade comprises (see Fig. 2 for basic arrangement) a source of radio-activity 3 opposite a detector 6 and 7 and arranged so that the source 3 can enter into a bore 2 in said body and means for effecting relative movement between said body on the one hand and said source and detector on the other hand and means for maintaining the source central of the bore, whereby the source can effectively travel along the bore. The detector can consist of a scintillation crystal 6 on which is directly mounted a photo-multiplier tube 7. The output of the photo-multiplier tube 7 is connected to a ratemeter (8), Fig. 1 (not shown), whose output in turn drives the pen of a chart recorder (9). The relative movement can consist of rotating the blade whilst the source is moved along the bore, the movement being continuous or in steps. In a practical embodiment, Fig. 3, the gauging apparatus has a turret 50 having a number of blade handling stations, for blades 51 having eight bores each. The blade 51 in Fig.3 is held by fixture 52 so that the source 54 and detector 55 can be moved by means of slide 56 mounted on pillar 57 along the axis 53 of a bore in the blade. The slide 56 may be activated electrically by motor 59, clutch 60, with a pinion (61), Fig. 4 (not shown), and a rack (62), or it may be activated manually by handwheel (63) engaging pinion (61). The source is mounted at the end of a flexible rod 64, Fig. 10, including a plurality of spring steel wires 81 connected to a fixed collar 79 and a movable collar 80 thereby ensuring that the source is maintained concentric within the bore. The description discloses safety arrangements to prevent the source being effective when the blades are not aligned or correctly positioned or when the source meets an obstruction within the blade.