Patent GB-753185-A (GB)
Title: Improvements relating to leak detecting apparatus for use with exhausting machinery
IPC: H01J9/385
Filed: 1954-08-20
Abstract: 753,185. Making electric lamps and discharge devices. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 20, 1954 [Aug. 26, 1953], No. 24310/54. Class 39(2). Automatic apparatus for exhausting the bulbs or envelopes of electric lamps, discharge devices and other electrical devices within a sealed envelope &c., is provided with a leak detecting device comprising pressure responsive means which operates to isolate a leaking bulb or envelope inserted into the exhausting apparatus. The lamp bulb, which is inserted through a gas-tight socket into a port 3 on the exhausting machine, is connected through a valve-controlled pipe-line 8 to the pressure responsive device consisting of two chambers 24, 25 which, together with the bulb-receiving port, can be connected momentarily by control valves to an exhausting pump, a second valve control being provided for sealing one chamber from the other and from the port, there being means for operating the two control valve systems in succession, first to cause the pressure within the two chambers to be equalized to the pressure within the bulb, and next to cause any difference in the pressure between the sealed off chamber and the chamber still connected with the bulb to effect operation of the pressurerespohsive means. The exhausting machine may be of the rotary turret type described in Specification 536,755 with a series of ports 3 around the rim of the turret 4, each port being connected by the pipeline 8 to a passage 14 in the central portion 9 of a ring-shaped rotary valve 11 with a stationary upper portion 10 provided with a passage 15. The lamp is sealed to the body 5 of the port 3 by the pressure of a cap 12 against a rubber gasket 13 and is connected to the pipeline 8 through the rubber tube 6 of a pinch clamp 7, which is normally open. During the indexing movement of the turret 4 the passage 14 associated with each bulb-carrying head is aligned with the passage 15 and connected to a vacuum plant by way of a T-connection 17, and pipes 18, 20, 21, and 16, the solenoid-operated valves 19 and 22 controlled by cam actuated switches 35, 31 being open at this stage ; at the same time the bellows 24, 25 are also connected to the vacuum plant through the T-connection 17 and pipe 23 respectively. The cams 29, 28 controlling the solenoid switches of valves 19, 22 are mounted on the main cam shaft 30 of the exhaust machine and close the circuit only long enough to bring the lamp 1 and both bellows 24 and 25 to the same pressure, with the result that a connection block 26 located between the bellows on studs 27 is maintained at a mean or neutral position. Further rotation of the cams 28 and 29 causes the vacuum plant to be sealed off by closing the valve 22, and seals off the bellows 25 from the bellows 24 and lamp bulb 1 by closing the valve 19. Bellows 25 thus hold the original exhaust pressure, whereas bellows 24 and the connected exhaust lines to the bulb 1 are subject to variation by any air leakage into the bulb. If there is no leakage the bulb is indexed to the next station in the normal manner. However, a leakage and consequent response by the bellows 24 produces upward displacement of the block 26 so that a pin 53 extending laterally therefrom bears upwardly against the offset lower end of a vertical rod 48 extending downwardly from a bar 49 mounted on a pivot 50, thereby pressing an adjustable screw 51 against the lower end of a pin 52 controlling a switch 45 ; this operates a warning light 46 and also energises a solenoid 57 which is linked to a bell-crank 58, causing a roller 60 on the latter to engage the cam 61 of the pinch clamp 7 and rotate it in a direction to squeeze the tube 6. The pinch clamp maintains this closed position throughout the subsequent steps in the exhaust cycle. Over-expansion, which causes injury to the bellows 24, 25, is prevented by stationary collars 63 on the post 43 of the bellows support.