US2805689A - Gas charging apparatus - Google Patents

Description

Sept. 10, 1957 Filed March 51 1955 c. T. DE GROAT 2,805,689

GAS CHARGING APPARATUS 2 Sheets-Sheet l 4 INVENTOR: Ix CHARLES T. DEGROAT,

Sept. 10, 1957 c. T. DE GROAT 2,805,689

GAS CHARGING APPARATUS Filed March 31, 1955 2 Sheets-Sheet 2 I'NV'ENTORI CHARLES T. DEGROAT,

HISA ORNE United States Pate GAS CHARGING APPARATUS Charles Thomas De Great, Ballston Lake, N. Y., assigner to General Electric Company, a corporation of New York Application March 31, W55, Serial No. 49%,209

1'7 Claims. (Cl. 141-66) My invention relates to improved evacuating and gas charging apparatus of a type which is particularly adapted for the manufacture of small volume evacuated devices, such as vacuum tubes, transistors, and the like.

In making gas filled devices or in gas charging or loading devices for treating internal atmospheres, elements or surfaces thereof, considerable difliculty has been generally encountered in providing apparatus for eflectively introducing the gas into the devices following evacuation thereof without wasting a volume of gas substantially larger than that actually used. When the gas to be loaded is xenon or some other expensive gas, waste of this kind can prove extremely costly. Additionally, difiiculty has been experienced as a result of contamination of the gas in the charging system due to defective or leaking tubes or an unloaded or open tube port on the equipment.

In my United States Patent No. 2,542,636 issued February 20, 1951, and assigned to the same assignee as my present invention, I have disclosed an improved automatic evacuating and gas charging apparatus which has proved completely effective in overcoming both of the abovementioned difi'iculties when the devices charged or loaded with gas volumes in the order of ten cc. and larger and the loading or charging is to pressures of 200 microns and higher. Many evacuated devices currently being produced, however, such as those referred to in the art as sub-miniature electronic tubes, transistors, etc. have volumes less than cc. and as little as 1 cc. and are required to be gas filled or charged to pressures as low as approximately 25 to 200 microns. Additionally, these devices are generally produced on high speed equipment such as that known in the industry as the Sealex machine. On such equipment each device dwells in an operating station for only a very short period. This necessitates the provision of equipment or apparatus which will not only gas charge a device quickly but will also purge the system of contamination substantially immediately upon detection of a leak to the atmosphere and will recover substantially immediately thereafter in order to stand ready to gas charge a succeeding device at the desired pressure and thereby avoid spoilage of other devices due to contamination of the system caused by a leak.

Accordingly, the primary object of my invention is to provide a new and improved gas charging system.

Another object of my invention is to provide a new and improved evacuating and gas charging apparatus.

Another object of my invention is to provide a new and improved gas charging apparatus adapted for effectively gas charging devices of volumes down to approximately 1 cc. and at pressures as low as 25 microns.

Another object of my invention is to provide new and improved gas charging apparatus including a charging system adapted for being purged of contamination substantially immediately upon detection of a leak and further adapted for recovering substantially immediately following purging.

Still another object of my invention is to provide gas charging apparatus which is suitable for use in any type ice 2 of processing equipment but has all the attributes necessary for use with high speed equipment.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a controlled gas supply system adapted for having devices to be charged connected in sealed communication therewith. Adjustable control means is provided for replenishing the controlled gas supply from a reservoir upon reduction of the pressure therein below the minimum pressure of a predetermined preset range and until the maximum pressure of the predetermined preset range is attained. Other control means are provided and are effective for substantially immediately closing the controlled gas supply system to the reservoir and evacuating the controlled gas supply system substantially immediately upon a pressure increase above the maximum pressure of the present range and subsequently substantially immediately restoring the controlled gas supply to the predetermined pressure range. A gas pressure gauge including a pressure chamber substantially equal in volume to one of the devices to be charged is adapted for being connected to the controlled gas supply while the adjustable control means is adjusted and until the gauge reads a pressure corresponding to that desired to be obtained in devices to be charged. Additionally, means is provided for purging the controlled supply system and the reservoir.

For a better understanding of my invention reference may be had to the accompanying drawing in which:

Fig. 1 is a schematic illustration of my invention; and

'Fig. 2 is an enlarged sectional view of the adjustable control valve in my system.

Referring now to Fig. 1 of the drawing, I have shown my invention embodied in an automatic exhaust and gas charging machine of the type generally known in the industry as a Sealex machine and adapted for producing electric discharge devices. The machine includes a plurality of identical exhaust heads generally designated 1 and supported on a moveable support or turret 2 which is rotatably mounted on a stationary support or machine frame 3. In a practical machine embodying my invention, sixteen exhaust heads 1 are provided at equally spaced points around the turret 2. Only two of the heads are shown in the drawingto simplify the illustration and description.

It will be appreciated that the moveable turret is moved intermittently by a suitable indexing system (not shown), thereby to position the exhaust heads successively at a plurality of operation stations located spacedly about the machine. It will be further appreciated that in very high speed equipment the turret may move continuously instead of indexed. Each of the heads 1 includes an exhaust chamber 4. The bottom side of the chamber 4 is adapted for being closed by a valve 5. The valve 5 may be any suitable valve such as a pinch-off valve formed of rubber or any similar material. The valve 5 is connected to one end of an exhaust line 6 and is adapted for being operated rubber valve for thereby closing the chamber 4 to the line 6. In another rotative position of the cam 7 the natural resilience of the valve 5 prevents the clamp 10 from clos- Patented Sept. 10, 1957.

ing the valve and thus communication is afforded between the chamber 4 and the line 6.

The heads 1 each further include a compression head generally designated 13 and adapted for being operated to grip and maintain or hold the exhaust tubulation 14 of an electronic tube or device 15 to be exhausted and gas charged in sealed communication with the chamber 4. It will be seen that while I have shown an electronic tube 15 held in the exhaust headv any device to be eX-.,

hausted and gas charged and provided with a suitable tubulation may be held in place in communication with the exhaust chamber by the compression head 13. It will be seen further that my invention is not limited to the processing of tabulated devices. For example, it may be used in the processing of evacuated devices in bell-jet arrangements. Additionally,,each of the heads 1 includes a gas charging port to which is suitably connected a line 21 which extends toward the center of the machine. This arrangement and the purpose thereof will be brought out in detail hereinafter.

From the heads 1 the lines 6 extend toward the center of the machine and are each connected to one of a plurality of inlet ports 22 (only one of which is shown) formed in suitably spaced relation in a rotatable portion 23 of a rotary valve generally designated 24. The rotatable portion 23 is mounted about and suitably secured to a central hub 25 formed on the turret 3 and rotatably mounted on a central vertical pivot post of the frame 3. A stationaryportion 26 of the valve 24is suitably secured to the stationary frame 3. Additionally, the stationary portion 26 of the valve is formed to include a plurality of outlet ports 27 (only one of which is shown) corresponding in number and spacing to the inlet ports 22 in the rotatable portion of the valve. The rotary valve is further constructed to include a pluralityof suitable oil glands 30 on both the inner and outer sides of the ports 22 and 27, thereby to render the valve vacuum-tight.

The operation of the just-described rotary valve is such that in each of the indexed positions of the turret 2, one

of the inlet ports 22 in the rotary portion 23 of the valve is in communication with one of the outlet ports 27 in the stationary portion 260i? the valve for permitting fluid passage therethrough. Between indexed positions, the p0rts22 and 27 are all out of alignment or register. and communication and fluid passage across the valve is prevented.

At several of the operating stations at which the heads are indexed the devices 15 are adapted for being exhausted.

or evacuated. To accomplish this and in advance of the exhaust stations stationary camming means (not shown) on the machine frame 3 is effective for engaging and actuating the cam 7 of each head 1 as it moves therepast, thereby to open the valve 5 in the head. Additionally, at these stations the corresponding outlet ports 27 of the rotary valve 24 are suitably connected, as by an arrange ment of a manifold and line generally designated 31, t0 vacuum pumping means such as that generally designated 32 and suitably mounted'on the stationary frame 3 of the machine. Thus, the devices 15 carried in the heads 1 are adapted for being exhausted at one or more of the various indexing or operating stations of the machine.

After being positioned at the various operating stations whereat exhaustion occurs each head lmoves to a tip-off station (not shown), whereat the tubulation 14 of the tube or device 15 held in the head is suitably sealed off. By means not shown and in advance ofthe tip-0E station, the cam 7 is rotated or actuated for closing the head valve 5. r My invention, as applied to the machine illustrated and above-described is adapted for gasfilling or charging each tube or device 15 just before tip-off and after the valve 5 is closed, and preferably on-the-fiy between the station immediately preceding the tip-off station and the tip-off station. I find it preferable to charge the tube on-the-fly before tip-off inasmuch as thisallows the gas greater time tion 23 of the rotary valve 24 and disposed radially inwardly of the corresponding exhaust inlet ports 22.. Provided for cooperating with the ports 35 is a single port 36 formed in the stationary portion 26 of the rotary valve between the two outlet ports 27 corresponding to the tip-otf station and the station immediately preceding the tip-off station. Thus, just before each head 1 moves into the tip-off station and after the pinch-off valve 5 is closed communication is provided to the exhaust chamber 4 of the head through the line 21 and across the valve arrangement comprising the corresponding port 35 in the rotatable portion of the rotary valve and the single port 36 in the stationary portion of the valve.

Port 36 is connected to a controlled gas supply system generally designated 40 and comprising a line 41 connected to a terminal block 42, a line 43 connected to a pressure sensitive device or control 44, a pressure chamt her 45 in the device 44, a line 46 connected to 8. normally closed solenoid controlled vacuum valve 47, and a line 48 connected to the outlet side of an adjustable control valve generally designated 50. i

As perhaps better seen in Fig. 2, the adjustable control valve 50 comprises a housing 51 suitably mounted on the frame 3 and formed to include an upstanding or raised valve seat 52. The valve seat 52 includes a substantially frusto-conical internal surface 53;and provided for cooperating with the surface 53 is a frusto-conical portion 54 of a valve pin or needle 55. The surfaces 53 and 54 are lapped and in the closed position of the needle the upper end thereof is as perfectly even with the upper.

edge of the valve seat 52 as possible. Formed on the pin 55 is an enlarged portion 56 further formed to provide a suitable sealing surface for cooperating with an O-ring seal 57 for avoiding leakage across the valve pin. The lower end of the valve pin 55 is fixedly secured in the center of a worm wheel 58 suitably rotatably mounted in the lower side of the housing 50. Meshing with the worm wheel 58 is a worm 59. Fitted in oneend of the worm and extending through the housing wall is a stem carrying a knurled knob 59a. With this, arrangement very fine .adjustments may be madeto the position. of the valve pin in the valve. seat. thereby to control with a high degree of accuracy any gas. supplied through the valve 50 and into the controlled gas supply system 40.

Also included in. the valve 50 is an on o arrangement including a coil 60, a magnetic plunger 61 and a coil spring 61a normally biasingthe plunger 61 toward the valve seat 52. The lower, end of the plunger. 61 is fitted with a resilient cap 62 adapted for moving into and out of engagement with the valve seat 52 for closing the valve under theiniluence ofthe spring 61a when the coil is deenergized and for. being raised from the valve seat and opening the valve when the coil is energized.

Connected to the inlet side of the valve 50 by means of a line 63 is a gas reservoir 64 adapted for being supplied with a suitablegassuch as xenon from a tank thereof 65. The gas is supplied from the tank to the reservoir through a pressure regulator 66 and a solenoid controlled valve 67 which is mounted on the frame 3 and controlled by a bellowoperated switch 68. The switch 68 is usually set at approximately 1200 millimeters or just slightly above atmospheric pressure as indicated on a dial, type pressure gauge 69 connected to a reservoir 64.

The pressure of the gas admitted into the system 40 through the valve SOIdetermines the operation ofv the above-mentioned pressure sensitive control 44; The control 44 may be of any suitable type, for. detectingpressure changes and providing suitable. proportional electrical signals. For example, when xenon or other heavy gases are used an ionization type gauge such as an Alphatron Vacuum Gauge of the type designated 510 and manufactured by the National Research Company of Boston, Massachusetts, may be used. If lighter gases, such as hydrogen or helium are used, the device or control 44 may comprise a thermo-cond-uctivity gauge of the thermocouple or Pirani types and which are well-known in the art. Additionally, the control 44 is adapted for operating in unison with a pressure recorder or recording controller generally designated 70 and which may be of the type designated Type 153 Electronik Recorder manufactured by the Brown Instruments Division of the Minneapolis- Honeywell Regulator Company of Philadelphia, Pennsyl- Vania.

The recorder or recording controller 70 is adapted for receiving electric signals of varying magnitudes from the pressure control 44. In the controller 70 these signals operate an electromotive device 71 which actuates a marker 72 adapted for cooperating with a scroll 73 arranged to move in coordination with the operation of the machine. Also included in the controller 70 is a shaft 74 carrying a plurality of control disks 75 and adapted for rotating and counter-rotating in accordance with the movement of the marker 72. In a manner which will be described in detail hereinafter, the pressure in the system 40 is normally caused to fluctuate between the high and low values of a predetermined preset pressure range. This causes the marker 72 to scribe a substantially symmetrical mark designated A on the scroll and the shaft 74 and the plurality of control disks 75 to assume positions substantially the same as those shown in Fig. 1. When the pressure in the system exceeds the upper value of the preset range, the marker moves to the right of A and the shaft and disks are caused to rotate clockwise from the positions of Fig. 1. When the pressure falls below the lower level of the predetermined range the marker 72 moves to the left of A and the shaft and disks are causedv to rotate counterclockwise from the positions of Fig. l.

The disks 75 comprise three independent controlling disks. The first disk designated 80 operates a mercury switch 81 and is positioned on the shaft 74 for opening the mercury switch when the pressure in the system 40 stands above the lower level of the predetermined range. When the pressure in the system 40 falls below the lower level of the predetermined pressure range the control 44 varies the magnitude of the signal of the recorder 70 which causes the shaft'74 to rotate counterclockwise and r the disk 80 thereon to actuate and close the mercury switch 81. This results in completion of a circuit through a normally closed pair of contacts 82 in a relay 83. This circuit when completed energizes the coil 60 in the control valve 50 for raising the plunger 61 against the bias of the spring 61a and thereby admitting gas into the system 40 from the reservoir 64.

When the system 40 attains the upper level of the predetermined pressure range, the control 44 again varies the signal to the recorder 70 which counter rotates the shaft 75 causing the disk 80 to open the mercury switch 81 and thereby deenergize the coil 60 for enabling the spring 61a to move the plunger 61 toward the valve seat 52 and close the valve 50. This is the operation of the system under normal operating conditions. That is, as the gas port of the rotary valve associated with each exhaust head 1 flies or moves past the stationary port 36 a quantity of the gas in the controlled supply system is admitted through the corresponding line 21 and exhaust chamber 4 into the device 15 held in the head. In accordance with the volume of the devices being charged the pressure in the system40 is reduced by substantially equal increments. Ultimately, this pressure is reduced to the pressure where-the disk 80 is again effective for closing the mercury switch 81 and thereby opening the valve for admitting more gas from the reservoir into the system 40 for again raising or restoring the controlled pressure to the upper level of the predetermined range.

It will be seen that through adjustments to the valve 50 I am able to determine with extreme accuracy the amount of gas admissible into the system 40 when the valve 50 is opened. Additionally, by presetting the pressure control 44 and presetting the position of the disk on the shaft 74 I am able normally to maintain the pressure in the system 40 within a preset predetermined pressure range. For example, when it is desired to charge devices of a volume of approximately 1 cc. to a pressure of approximately 25 microns the valve 50 may be adjusted and the control 44 and the disk 80 may be preset for closing the valve 50 when the pressure in the system 40 stands at approximately 500 microns, which would represent the upper level of the normal range, and opening the valve 50 when the pressure stands at the lower level of the range which may be 5% below the upper level. The pres sure in the system 40 will drop to the lower level of the predetermined range after a predetermined plurality of the devices 15 have been moved into and out of communication with the system and thereby charged with gas to the prescribed pressure.

Now in the event of a leak into the system 40 from the atmosphere, as might be effected by a leaking device 15 in" one of the heads 1, it is desirable to detect such a leak, close the valve 50 to avoid waste of gas, purge the controlled gas supply system 40 and restore the pressure in the controlled gas supply system 40 to the preset pressure range all before the port 35 corresponding to the next succeeding head moves into register with the stationary port 36, thereby to avoid spoilage of the device of the next succeeding head. To accomplish this I have provided a second control disk 85 on the recorder shaft 75. The disk 85 is adapted for closing 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, as would be effected by a leak or open head. The switch 86 when closed energizes the coil 87 of the relay 83 whereby the normally closed contacts 82 are opened for deenergizing the coil 60 in the event the latter is energized and assuring that the plunger 61 is in its lower position for closing the valve 50.

Additionally, energization of the coil 87 results in the closing of a pair of normally open contacts 88 which is effective for energizing the above-mentioned normally closed vacuum control solenoid valve 47 for thereby opening the valve 47. The outlet side of the valve 47 is connected by a suitable line 90 to a constantly operating vacuum pump generally designated 91 and suitably mounted on a portion of the machine frame 3. The pump 91 is of such capacity as to evacuate and thereby purge the system 40 of contamination completely substantially immediately or well within the time required for movement of an exhaust head 1 from one operating position to the immediately next succeeding positions This evacuation of the system 40 results in a corresponding movement of the shaft 75 in the controller 70. Provided on the shaft 75 to take advantage of this movement is a third controlling disk 95. The disk 95 operates a mercury switch 96 which is normally closed above a preset minimum pressure below the predetermined range and corresponding to a satisfactorily low purging pressure.

The circuit completed by the switch 96 maintains the coil 87 energized and thus maintains the vacuum valve 47 open after the pressure in the system is reduced to the point where the switch 86 is normally opened and until the pressure is reduced by the pump 91 to the preset minimum value at which the switch 96 will open. Opening of the switch 96 deenergizes the coil 87 whereby the contacts 88 are opened and the contacts 82 are closed. At

this "stage of the operation, inasmuch as the pressure in the system 40 will be below the predetermined preset pressure range, the disk 80 .will be .eltective for closing the switch81 and thereby resulting in a circuit being.

completed through the normally closed contacts 82 and the coil60 in the control 50 thereby to open the valve 50 and permit the: pressure in the system 40 to return to the normal preset maximum pressure. Thus, my system is adapted for avoiding contamination of the next succeeding device 15 moved into communication with the system 40 following a leaking device or open head.

When devices of predetermined volume are to be processed by the. machine and gas charged, I set up the machine byinserting a tube 97 in one of the heads 1 instead of the tubulation of a device to be charged. The tube 97 is connected to a pressure gauge generally designated 98 and suitably secured to the turret 2. By means of a pair of brushes 99 resiliently contacting a pair of commutator rings 100 mounted on the rotatable hub 25 of the turret and connected to a suitable power source, the gauge 98 is provided with required power for operation. The gauge 98 may be of any suitable type. For example, when xenon or other heavy gases are used the gauge may be of this ionization type similar tothat manufactured by the National Research Company of Boston and designated ACXB-l Alphatron-Miniature cylinder. If lighter gases, such as helium or hydrogen,

pressure at which it is desired that the devices 15 be gascharged at the particular operating speed of the machine. With this accomplished the control gas supply system 40 will stand at the maximum pressure ofthe desired or preset normal pressure range. While it is possible to set up the machine in this manner and then remove the tube 97 from the exhaust head in order that this head may be used for processing a device 15, it is often found desirable to leave the tube 97 in the head and thereby have a con stant check on the pressure to which the devices are be ing charged; Additionally, gauges of different chamber volumescorresponding to the volumes of different sized devices to be charged may. be provided. Thus, in accordance with the volume of the devices to be processed on the machine the proper gauge arrangement may be used in setting up the machine.

Aftera shut-down of the machine of any length of time, the system including the reservoir 64 is likely to be contaminated. Thus, in initially setting up the ma- "chine for operation an operator will open the power line to the switch .68 for deenergizing and thereby closing the reservoir control valve 67 to avoid waste of gas and then turn the knob 59a to move the needle in the valve 50-to its lowest position and close a key type switch 101. With the. switch 101 closed a lamp 102 will light indicating that purging is taking place and the relay coil 87 will be energized for closing a pair of contacts 103 and the contacts 88 and opening the contacts 82. This will cause energization of both the control valve 50 and the vacuum valve 47 for opening the system 40 and the reservoir 64 to the constantly operating vacuum pump 91 whereby the system 40 and the reservoir 64 are purged. Then the operator will open the switch 101,

and then energize and thereby oven the valve 67. This will enable the valve 47" to close and the vacuum pressure control 44 to sense a pressure lower than the minimum predetermined pressure below the preset pressure range.

Infturn, this will allow the system to recover and bev sup plied with. gas up to the predetermined range in the abovedescribed manner. Thereafter, the knob 59a may be turned to obtain a fine adjustment of the gas admitted through the valve 50 when it is energized and opened and the system will stand ready to charge the first device moved into communication with the system to the desired pressure.

It will be seen that while I have disclosed myinvention as applied to fully automatic tube processing equipment,

my invention is equally adaptable to bench systems or the like wherein my invention may be operated manually or semi-automatically.

Additionally, while I have shown and described a specific embodiment of my invention, I do not desire my invention to be limited to the particular form shown and described and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In gas charging apparatus, a gas supply system adapted for being connected to a device, thereby to charge said device, means normally maintaining the gas pressure in said system within a predetermined range, and pressure-controlled means operative for evacuating said system in response to any abnormalincrease in pressure above said predetermined range.

2. In gas charging apparatus, a gas supply system adapted for being connected to a device, thereby to charge said device, means normally maintaining the gas pressure insaid system within a predetermined range, pressurecontrolled meansoperative for evacuating said system in response to any abnormal increase in pressure above said predetermined range, and means restoring said pressure in said system to said predetermined range upon evacuation of said system to a predetermined pressure below said range.

3. In ga's charging apparatus, a gas supply system, means admitting gassto said system until the pressure therein attains the upper level of a predetermined range in which a device connected to said system is chargeable only to a predetermined desired final pressure, means for successively connecting devices to said system, thereby to charge said devices, and means effective when pressure in said system stands at the lower level of said predetermined range for restoring said: pressure to said upper level.

4.'In. gas charging apparatus, a gas supply system, means admitting. gas to said system until the pressure therein attains the upper level of a predetermined range, means for successively connecting devices to said system, thereby to charge said devices, pressure-response means efiective when pressure in said systemstands at the lower level of said predetermined range for restoring said pressure to said upper level, and means forevacuating said system in response to an increase in pressure above said upper level of said range.

5. In gas charging apparatus, a gas supply system, means admitting gas to said system until the pressure therein attains the upper level of a predetermined range, means for successively connecting devices to said system thereby to charge said devices, and means effective when pressure in said system stands at the lower level of said predetermined range for restoring said pressure to said upper level, means for evacuating said system in response to an increase in pressure above said upper level of said range, and means for terminating. said,evacuation and restoring said pressure in said systemto said upper level of said range when said pressure in said system stands at a predetermined minimumpressure below said range.

6. In evacuating and gas charging apparatus, a gas supply system, .means for successively exhausting a device and connecting said device to said supply. system, thereby to charge said device, pressure-responsive means normally operative for maintaining the gas pressure in said system at a predetermined range, and pressure-controlled means '9 for evacuating said system in response to any abnormal increase in pressure above said predetermined range.

7. In evacuating and gas charging apparatus, a gas supply system, means for successively exhausting a device and connecting said device to said gas supply system, thereby to charge said device, means for maintaining the gas pressure in said system within a predetermined range, means for evacuating said system in response to any increase in pressure above said predetermined range, and means restoring said pressure in said system to said pre: determined range upon evacuation of said system to a predetermined level below said range.

8. In gas charging apparatus, a gas supply system adapted for having devices to be charged connected thereinto, a gas reservoir, a control valve responsive to pressure conditions in said system for admitting gas into said system from said reservoir, means normally operating said control valve for maintaining the pressure in said gas supply system within a predetermined operating range, vacuum pumping means, and means closing said control valve and connecting said system and vacuum pumping means in response to any abnormal increase in pressure in said system above said operating range.

9. In gas charging apparatus, a gas supply system adapted for having devices to be charged connected thereinto, a gas reservoir, a control valve for admitting gas into said system from said reservoir, means automatically operating said control valve for maintaining the pressure in said system within a predetermined operating range, vacuum pumping means, means automatically closing said control valve and connecting said system and vacuum pumping means in response to any increase in pressure in said system above said operating range, and means automatically disconnecting said system and pumping means and opening said control valve for restoring said pressure to said predetermined operating range upon a decrease in pressure in said system to a predetermined pressure below said operating range.

10. In gas charging apparatus, a gas supply system adapted for having devices to be charged connected thereinto, a gas pressure gauge including a pressure chamber having a fixed volume substantially the same as the volume of one of said devices to be connected into said system, a gas reservoir, a control valve for admitting gas into said system from said reservoir, means automatically operating said control valve for maintaining the pressure in said system within a predetermined operating range, and adjusting means for varying said operating range in accordance with the pressure desired to be obtained in said devices and as indicated by said pressure gauge.

11. In gas charging apparatus, a gas supply system adapted for being connected to an evacuated device thereby to charge said device, pressure-responsive means operative for normally maintaining the gas pressure in said system within a predetermined operating range, and evacuating means of substantially greater capacity than said system effective in response to any increase in pressure above said predetermined operating range for substantially immediately evacuating said system.

12. In gas charging apparatus, a gas supply system adapted for being connected to an evacuated device thereby to charge said device, means for normally maintaining the gas pressure in said system within a predeter mined operating range in which a device connected to said system is initially chargeable only to a desired final pressure, and a constantly operating vacuum pump of substantially greater capacity than said system effective in response to any increase in pressure above said predetermined pressure for substantially immediately evacuating said system.

13. In gas charging apparatus, a gas supply system adapted for having devices to be charged connected thereinto, a gas reservoir, a control valve for admitting gas into said system from said reservoir, pressure-responsive means normally operating said control valve for maintaining the pressure in said system within a predetermined operating pressure range, a constantly operating vacuum pump of substantially greater capacity than said system. a normally closed vacuum valve controlling a connection between said pump and system, and pressure-responsive means closing said control valve and opening said vacuum valve in response to any abnormal increase in pressure in said system above said operating range whereby said vacuum pump is efiective for substantially immediately evacuating said system.

14. In gas charging apparatus, a gas supply system adapted for having devices to be charged connected thereinto, a gas reservoir, a control valve for admitting gas into said system, means automatically operating said control valve for normally maintaining the pressure in said system within a predetermined operating range, a constantly operating vacuum pump of substantially greater capacity than said system, a normally closed vacuum valve controlling a connection between said pump and system, means automatically ciosing said control valve and opening said vacuum valve in response to any increase in pressure on said system above said operating range whereby said vacuum pump is efieictive for substantially immediately evacuating said system, and means automatically closing said vacuum valve and opening said control valve for restoring said pressure to said predetermined operating range upon a decerase in pressure in said system to a predetermined pressure below said operating range.

15. In gas charging apparatus, a gas supply system, for having devices to be charged connected therein, a gas reservoir, means for supplying gas to said reservoir, 'a control valve for admitting gas .into said system from said reservoir, means automatically operating said control valve for normally maintaining the pressure in said system within a predetermined operating range, a constantly operating vacuum pump of substantially greater capacity than said system, a normally closed vacuum valve controlling a connection between said pump and system, means automatically closing said control valve and opening said vacuum valve in response to any increase in pressure on said system above said operating range whereby said vacuum pump is efiective for substantially immediately evacuating said system, and manually operable means for disconnecting said reservoir and said means for supplying gas thereto and for opening both said vacuum and control valves, thereby to purge said system and reservoir.

16. In evacuating and gas charging apparatus, an exhaust system, a gas supply system, means for successively connecting devices into said exhaust and gas supply systems for evacuating and gas charging said devices, a gas reservoir, a control valve for admitting gas into said gas supply system from said reservoir, pressure-responsive means normally operating said control valve for maintaining the pressure in said gas supply system within a predetermined operating range, a constantly operating vacuum pump of substantially greater capacity than said gas supply system, a normally closed vacuum valve con trolling a single connection between said pump and said gas supply system, and means for .closing said control valve and opening said vacuum valve in response to any abnormal increase in pressure in said gas supply system above said operating range, whereby said vacuum pump is efiective for substantially immediately evacuating said gas supply system.

17. In evacuating and gas charging apparatus, an exhaust system, a gas supply system, means for successively connecting devices into said exhaust and gas supply systems for evacuating and gas-(charging said devices, a gas reservoir, a control valve for admitting gas into said gas supply system from said reservoir, means automatically operating said control valve for normally maintain ing the pressure within said gas supply system within a predetermined operating range, a constantly operating vacuum pump of substantially greater capacity than. said gas supply system, a normally closed vacuum valve controlling a connection between said pump andgas supply system, and means automatically closing said control valve and opening said vacuum valve in response to any increase in pressure in said gas supply system above said operating range, whereby said vacuum pump is effective for substantially immediately evacuating said gas supply system, and means automatically closing said vacuum valve and opening said control valve for restoring said pressure in said gas supply system to said predetermined 1,763,107 Spencer June 10, 1930 2,025,579 Donovan et al Dec. 24, 1935 2,145,830 Espersen -s Jan. 31, 1939 2,267,274 Gardner Dec. 23, 1941 2,369,563

Gustin et al Feb. 13, 1945

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