Patent GB-826965-A (GB)
Title: Improved apparatus for filling devices, such as electronic tubes with a predetermined quantity of gas
IPC: H01J9/395
Filed: 1956-03-29
Abstract: 826,965. Turret machines. GENERAL ELECTRIC CO. March 29, 1956 [March 31, 1955], No. 9967/56. Class 39(2) [Also in Groups XXIX and XXXV] In apparatus for introducing a quantity of gas into a container, such as an envelope of an electronic tube or transistor comprising a turret 2 provided with a number of exhaust and filling heads 1 each adapted to carry a device 15 that is to be exhausted and charged with gas, each head being connected in turn to a gas supply source through a gas charging port and a pressure controlled gas supply system 40 the pressure of which is maintained within a predetermined range, means are provided for performing a purging operation in which the system is exhausted while closed by a valve when the pressure increases due to leakage from the surrounding atmosphere and then a quantity of the pure filling gas at a pressure within the range is automatically supplied to the system. The turret may be moved intermittently step-by-step, or may move continuously. In the example a turret 2 mounted rotatably on a stationary frame 3 has sixteen exhaust heads 1 mounted upon its periphery, each head including an exhaust chamber 4 with a bottom opening that can be closed by a rubber or like tubular pinch-off valve 5 connected to an exhaust line 6 and closed automatically by .a pivoted clamping member 10 actuated by a cam lever 7 carrying a roller 12. The cams 7 are engaged by stationary cams arranged adjacent to their path of travel with the turret, so that in one position they effect the closing of the valve 5 and in another the resilience of the valve prevents its closure by the clamp 10. Each head 1 also includes a compression device 13 for gripping and holding an exhausting tube 14 of an electronic tube 15, and a gas charging port 20 connected to a line 21 extending towards the centre of the machine. Alternatively the heads may be adapted for devices not provided with exhausting tubes, e.g. in bell-jar arrangements. Each exhausting line 6 extends radially inwards to one of a series of sixteen inlet ports 22 spaced around in a rotatable valve portion 23 secured to a vertical hub 25. A stationary lower portion 26 of the valve has outlet ports 27 corresponding in number and spacing with the ports 22. At one or more operating stations the cam levers 7 of the respective heads 1 are operated to open their pinchoff valve 5 and the envelopes or devices mounted in those heads are exhausted by connecting their associated outlet port 27 of the rotary valve to an exhausting- pump 32, e.g. by a manifold 31. After exhaustion of the device 15 its pinch-off valve 5 is closed and a gas charge is supplied to it subsequently through its associated line 21. The gas-supply lines 21 of the heads are connected to ports 35 formed in the rotary valve portion 23 at positions radially inward of the exhaust ports 22, and the stationary valve,portion 26 is provided with a single inlet-port 36, at the station preceding the "tipping-off" or sealing station, which connects an envelope or device 15 to a gas supply on its arrival at that station. Port 36 is connected to the controlled gas supply system 40 which comprises a line 41 connected to a block 42 from which extends a line 43 to a pressure-sensitive control means 44, a line 46 connected to a normally closed solenoidcontrolled vacuum valve 47, and a line 48 connected to the outlet side of an adjustable control valve 50. The control valve 50 (see Group XXIX) comprises a stop valve having a valve plunger 61 operated by a solenoid 60, and a metering valve having a tapered valve 55 adjusted through screw and worm gearing 58 by an operating knob 59a. Filling gas, e.g. xenon is supplied from a gas reservoir 64, through a line 63 and the valve 50 to the lines 48 and 41 leading to the gas inlet port 36 of the stationary portion of the rotary valve. Regulation of the flow of gas is effected by vertical movement of the valve pin 55. The gas reservoir 64 is supplied from a tank 65 through a solenoid valve 67 controlled by a bellowsoperated switch 68 which can be set to operate when a pressure slightly above atmospheric is indicated on a gauge 69. The pressure of the gas admitted into the system 40 through the valve 50 determines the operation of a pressure-sensitive control means 44 of any suitable type which provides electrical signals in correspondence with changes in gas pressure, and which in the case of heavy gases may be a gauge of the ionization type,. and in the case of light gases may be a thermoconductivity gauge of the thermocouple or Pirani type. Electrical signals from the pressure control 44 are fed to a recording controller 70 and operate an electromotive device 71 which actuates a marker 72 associated with a recording strip 73 and also drives the shaft 74 of a control mechanism 75. The shaft 74 rotates clockwise or anticlockwise in accordance with movements of the marker 72 relative to the recording strip, the pressure in the system 40 being normally caused to fluctuate between the high and low values of a predetermined preset pressure range. The control mechanism 75 comprises three actuating controlling members such as discs 80, 85, 95 on the shaft 74. Disc 80 operates to open a mercury switch 81 when the pressure in the system 40 stands above the lower level of the predetermined range. When the pressure in the system falls below the said lower level, the shaft 74 operates to close the switch 81. This completes a circuit through a pair of normally closed contacts 82 of a relay 83 and energizes the coil 60 of control valve 50 to admit gas into the system 40 from the reservoir 64. The valve 50 is again closed when the system 40 attains the upper level of the predetermined pressure range. These operations take place under normal operating conditions and each time a gas port 35 moves past the stationary port 36, a quantity gas is fed through the line 21 to the device 15 held in the head. Leakage into the system 40 from the surrounding atmosphere, e.g. due to a leaking device 15 causes the valve 50 to be closed, the controlled gas supply system to be purged and the pressure therein to be restored to the preset range before the port 35 associated with the next succeeding head moves into register with the stationary port 36. The controlling means for these operations comprises a control disc 85 on the shaft 74, which acts to close a normally open mercury switch 86 when the pressure control 44 senses a pressure increase in the system above the upper level of the normal or predetermined preset pressure range. Coil 87 of the relay 83 is energized by closing switch 86, thereby opening contacts 82 to ensure that coil 60 of valve 50 is de-energized and the valve is closed. Normally open contacts 88 of the relay 83 are also closed and effect opening of the normally closed vacuum control solenoid valve 47 which is connected through line 90 to a constantly operating vacuum pump 91 which has a capacity sufficient to evacuate and purge the system while an exhaust head 1 is moving from one operating position to the next. This evacuation results in corresponding movement of the shaft 74 of the controller 75 whereby a third disc 95 on the shaft operates a mercury switch 96 which maintains the relay coil 87 energized and thus maintains vacuum valve 47 open until the pressure in the system is reduced by the pump 91 to the preset minimum value at which switch 96 will open. Opening of switch 96 de-energizes coil 87, so that contacts 88 open and contacts 82 close. Further, since the pressure in the system is now well below. the predetermined preset pressure range, the disc'80 acts to close the switch 81, thereby closing the circuit through the closed contacts 82 and energizing coil 60 to open valve 50 and permit the return to normal pressure in the system. Contamination of the next succeeding device connected to the system is thus avoided. The machine is set up by inserting in one of the heads 1 a tube 97 connected to a pressure gauge 98 secured to the turret, the volume of tube 97 plus the pressure chamber of the gauge having a volume substantially equal to that of the device to be gas charged. The control valve 50 is adjusted by turning knob 59a until the gauge 98 reads the pressure desired for the gas filling in the devices 15. The tube 97 and gauge may be retained in position during operation of the machine to provide a constant check on pressure; and gauges of different chamber volumes may be employed for different sized devices to be processed in the machine. As shown, a pair of brushes 99 connected to the gauge 98 bear upon slip rings 100 which provide operating current for the gauge. After a shut-down of the machine the possibility of contamination is removed by purging the gas system by the operator interrupting the power supply to the switch 68 to close the reservoir control valve 67, turning the knob 59a to close the valve 50, and closing a switch 101 to energize the relay coil 87. Closure of switch 101 lights a pilot lamp 102 which indicates that purging is taking place, and also closes contacts 103 and 88 and opens contacts 82. Control valve 50 and vacuum valve 47 are thus energized, the latter opening the system 40 and reservoir 64 to the constantly operating vacuum pump 91, which purges the system. The operator next opens switch 101 and also switches on the circuit of valve 67, thereby opening the latter and also allowing the vacuum pressure control 44 to sense a pressure lower than the minimum predetermined pressure below the preset range. The pressure system thereupon operates to recover pressure.