Patent GB-768495-A (GB)
Title: Improvements in and relating to exhausting and sealing equipment for glass envelopes
IPC: H01J9/385
Filed: 1955-04-06
Abstract: 768,495. Sealing glass envelopes of electronic tubes. GENERAL ELECTRIC CO. April 6, 1955 [April 6, 1954], No. 10119/55. Class 39(2) In apparatus for the evacuation and sealing of the glass envelopes of electronic tubes provided with an exhausting or tipping-off tube which is positioned within a releasable head adapted to be operated to grip the exhausting tube to hold it in sealed communication with an exhausting chamber, the exhausting tube being sealed or tipped-off very close to the glass envelope after evacuation of the latter, the exhaust head provided with releasable means, for gripping an exhausting tube comprises a chamber which is subject to the accumulation of fragments of exhausting tube and is therefore provided with means for admitting compressed air thereinto in order to eject the portion of tube from the holding means and the fragments from the chamber. The exhaust head 1 is mounted on one end of an arm 2 the other end of which is pivoted at 3 on an indexing turret which is moved through a plurality of operating stations, the tubulation ejecting station being shown. An exhausting chamber 4, Fig. 2, within the head is closable by a pinch-off valve 5 of rubber of similar material fitted on its open lower end and connected by a tube 6 to a vacuum pump, closure of the valve being effected by a clamping-lever 7 pivoted within the head at a point 8 and engageable with a roller 11 mounted on the end of a lever 9 pivoted within the head at 10. When the roller 11 is disengaged from the lever 7 a vacuum can be drawn on the chamber 4 through the line 6 and open valve 5. The exhaust head 1 also comprises a compression head 12 for providing a sealed connection between the exhausting tube 13 and chamber 4, and including a port member 14 of rubber or similar resilient material seated on a shoulder 16 and provided with an axial bore 15 to receive the exhausting tube 13, the outer periphery of the boss being screw-threaded to receive an internally threaded cap 18. The top of the cap is apertured to permit the extension therethrough of the frusto-conical upper portion of the port member 14, so that rotation of the cap in one direction screws it down upon the boss and compresses the port member 14 to seal it about the exhausting tube 13 within the head. After evacuation of the envelope the exhausting tube is sealed off, leaving the tubulation 13 in the compression head 12 as shown in the drawing. Ejection of the tubulation or length of glass tube 13 from the compression head is effected by admitting a blast of compressed air after releasing the grip of the rubber port member 14 upon the tubulation. This release may be effected automatically during the indexing of the head 1 to the tubulation ejecting station when a cam 20 secured to a collar 21 fastened to the cap 18 comes into contact with an air-operated piston 20a on an adjacent fixed support, the collar 21 being thereby rotated to unscrew the cap 18. Alternatively the release may be effected manually. Compressed air is admitted into the exhaust chamber 4 through a port 22, Fig. 2, formed in the head 1 and connected to an air supply line 23, a solenoid valve 24 being mounted on the arm 2 to control the flow of air through the port 22..The solenoid valve 24 is opened automatically when the working head is indexed into the tubulation ejecting position and a pair of contacts 28 mounted on the head are contacted by resilient fingers 31 carried by a fixed support and connected to supply leads 32, 34. At this station also a vertically movable air-coupling-member 26 biased by a spring 26a to an upper position is arranged to be moved downwardly by a cam 42a depressing an arm 42 supporting the member 26 at one end, thereby bringing the latter member into coupling engagement with a nipple 25 connected to the solenoid valve 24, and thus connecting the valve to a line 27 which receives compressed air from a supply pipe 38 under the control of a solenoid valve 37. The actuating solenoid of valve 37 is connected to leads 36, 39, of which the former is connected to a switch 35 arranged to be closed by a movable contact member 40 mounted below .a roller on an arm 41 extending downwardly from the arm 42. When the head 1 is indexed to the tubulation ejection position the lever 9 is actuated by means, such as an air-operated piston 9a, mounted on the machine frame, and is rotated to operate the valve clamp 7 to close the valve 5 to prevent contamination of the vacuum system when compressed air is admitted into the chamber 4 and the compression head passage 15 is opened by ejection of the tubulation. Concurrently with the actuation of lever 9 the air piston 20a is operative to engage the cam 20 to rotate the cap 18 and relieve the pressure of the resilient member 14 on the tubulation located in the passage 15, the cam 42a operates to bring the coupling 26 into coupling engagement with the nipple 25 to complete the air circuit therethrough, the downward movement of the members 42 and 41 produces closure of switch 35. The completed electrical circuit operates solenoid valve 24 to complete the air circuit between the lines 23 and 27, and also energizes the solenoid valve 37 to admit compressed air into the line 27. A blast of compressed air is thus admitted into the exhaust chamber 4 to eject the tubulation 13 and blow any fragmentary glass out through the port 15. The blast continues until the came 42a permits the member 42 to rise.