US2652188A

US2652188A - Automatic tank pump down

Info

Publication number: US2652188A
Application number: US37681A
Authority: US
Inventors: Cyr Rob Roy
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-07-08
Filing date: 1948-07-08
Publication date: 1953-09-15
Anticipated expiration: 1970-09-15

Description

Sept. 15, 1, 53 R CYR 2,652,188 AUTOMATIC TANK PUMP DOWN Filed July 8, 1948 4 Sheets-Sheet 1 INVENTOR. Eob RoyC'yr 1 :15.4.

Sept. 15, 1953 V R. R. CYR 2,652,188

AUTOMATIC TANK PUMP DOWN Filed July 8, 194a 4 SheetSSheet 2 INVENTORQ Aob Pay cfyr' v Sept. 15, 1953 R. R. CYR

AUTOMATIC TANK PUMP DOWN 4 Sheets-Shet 5 Filed July 8, 1948 P/ran/ P0 wer Okra/Z k L 0&2 P6: We: Oez

T0 lnckout Relay fi i 56 uence C/fcu/z awe/mm Rob Fay C30 Sept. 15, 1953 R. R. CYR 2,652,188

AUTOMATIC TANK PUMP DOWN Filed July 8, 1948 4 Sheets-Sheet 4 'Pob Roy Cyr Q EL 3 Til jg.

Patented Sept. 15, 1953 AUTOMATIC TANK PUMP DOWN Rob Roy Cyr, Berkeley, Calif., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application July 8, 1948, Serial No. 37,681

8 Claims.

My invention relates to vacuum systems, and more particularly to a system for automatically controlling the sequence of operations of a series of pumps for creating a vacuum.

The procedure involved in pumping down a tank or vacuum system in the past has been a manually controlled rather than an automatic procedure. In view of the low pressures required for certain processes, a mechanical pump is not suitable for that function. On the other hand, dlifusion pumps capable of exhausting to low pressures will not operate against air pressure. Accordingly, it has been necessary to provide a vacuum system wherein both mechanical and diffusion pumps are arranged to work together. In this arrangement one or more diffusion pumps is connected to the tank or chamber to be exhausted, through gate valves. The outputs of the diffusion pumps are preferably tied together and fed through a finishing valve to the input of amechanical pump so that the diffusion pumps may work into a pressure lower than atmospheric pressure. Either an additional mechanical pump may be provided for partially evacuating or making the initial evacuation of the tank or chamber, or a by-pass line may be provided so that by the use of a roughing valve, a single mechanical pump may be employed for roughing down purposes and for cooperation with the diffusion pumps in exhausting the tank or vacuum system to a low vacuum.

The actuation of these valves has been accomplish-ed manually or through manual control. Under usual operating conditions the equipment in question is large and bulky. Pumps, tanks, and valves are ordinarily separated by considerable distances and may be located in different rooms or even different floors of a building. Intercommunication systems and several operators may be required to manually operate the controls in. their proper sequence. When meters are at some distance from the valves, and a single operator is employed to take care of the manual controls, it requires a great deal of moving about from place to place where the different controls and meters are located. Further, manual controls are slower, and require continual watchin of the gauges, and mistakes are quite often made in the manipulation of the valves or in the operation of the system. These mistakes are in some instances quite costly, causing damage not only to process materials but to the pumping fluids.

Applicant with a knowledge of all of these defects in and objections to the prior art has for an object of his invention the provision of a system for automatically pumping down a tank or reservoir to high vacuum by a sequence of operations.

Applicant has as another object of his invention the provision of an electrical control circuit for controlling the operation of a series of pumps in the proper sequence to pump down a tank or reservoir to high vacuum, or to evacuate a chamber.

Applicant has as a further object of his invention the provision of an electrical control circuit for automatically controlling the pumping down of a tank or reservoir to a high vacuum so that upon closing the circuit, the finishing valve, the roughing valve, and the main gate valves, which regulate the operation of a series of pumps, are made to open and close in a predetermined sequence.

Applicant has as a further object of his invention the provision of an electric circuit control for automatically associating mechanical and diffusion pumps in a certain predetermined sequence to pump a tank, reservoir, or chamber to high vacuum.

Other objects and advantages of my invention will appear from the following specification and agcompanying drawings, and the novel features thereof will be particularly pointed out in the annexed claims.

In the drawings, Fig. l is a fragmental detail of a torque limiting switch, used on the valve operator in my improved system. Fig. 2 is a schematic of the pumping arrangement employed in connection with my improved system. Fig. 3 is a perspective of a gear limiting switch. used on valves in my improved vacuum system. Fig. 4 is a diagram indicating the sequence of operation of the various valves and pumps shown in Fig. 2. Fig. 5 is a schematic of the hot wire gauge used in my improvedsystem. Fig. 6 is a detail showing the relation of the segments used in the hot wire gauge. Fig. '7 is a schematic of the circuits known as the Pirani power supply circuit or Pirani power circuit and the Pirani signal circuit. Fig. 8 is a schematic of the sequence circuit. Fig. 9 is a schematic of the control circuit. Fig. 10 is aschematic of the valve power circuit.

The procedure involved in pumping down a tank in the past has been a manual rather than an automatic procedure, the sequence involved being that as shown in the flow diagram of Fig. 4 of the drawings. Briefly the automatic sequence is as follows: A manual push button is pressed which causes the finishing valve to close, the finishing valve being in open position when the tank is down to air; next the roughing valve opens, and when it opens the pressure at the Pirani gauge will be at or will rise to a value above 100 microns; when it falls to a value below 100 microns the roughing valve closes and then the finishing valve opens; when the finishing valve opens, the air from within the diffusion pumps will again cause the pressure at the Pirani gauge to rise above 100 microns; when the pressure again falls below 100 microns, the mechan cal pump being in operation, of course, the mam gate valve will open, as indicated by the chart of Fig. 4.

The arrangement of the pumps and valves and their connections are as shown in the drawings, each element being identified by legend. It will be noted from Fig. 2 that the roughing valve 23 is in a by-pass line extending around the

main gate valves

24, 25, the diffusion pumps I9, 20 and the finishing valve 28.

In this system it is contemplated that the roughing, finishing and gate valves will be electrically actuated. The valve operators used in connection with this system are preferably of the motor driven type such as those manufactured by the Philadelphia Gear Works of Philadelphia, Pennsylvania and sold under the name of- Limitorque. While the particular structure of these operators constitutes no part of applicants invention, one form thereof is disclosed in Fig. l in orderto give a better understanding of the system as a whole. In that figure a motor I, coupled to an appropriate power source, is directly connected through its shaft 2 by a flanged coupling to a splined shaft 3 carrying a worm 4 which floats thereon and is free to move longitudinally thereof. The shaft 3 is rotatably mounted in bearings 5, 6 and the coiled torque springs I, 8 are interposed between the ends of worm 4 and the bearings 5, 6 and are disposed about shaft 3 in order to limit axial movement of worm 4. The worm 4 drives a worm gear Wheel 9 mounted directly on stem or shaft III which by rotation opens and closes the valve (not shown). Formed in worm 4 adjacent one end thereof is a circumferential groove II which is adapted to seat in an appropriate slot in pivoted arm I2 and is interlockingly engaged therewith. Arm I2 is pivotally mounted at its lower end on bracket I3, and its upper end which is angularly bent is recess seated in shaft I4, slidably mounted in standards I5, I5. Engaged at opposite ends of shaft I4 are limiting switches such as A and E, and interposed between the limiting switches and their corresponding standards I5, I are compression springs l1, l7. Operation of motor I rotates shaft 2 and in turn shaft 3, carrying worm 4. The rotation of shaft 3, depending upon the direction of the rotation of motor I, rotates worm gear 4 in a clockwise or counterclockwise direction, turning gear wheel 9 and shaft III, to open or close the valve, as the case may be. When the valve stem has reached the limit of its travel, either in the closed or open position, worm gear wheel 9 stops rotating, and as motor I continues its rotation, worm 4 is forced to move longitudinally along shaft 3 compressing spring 1 or spring 8 depending upon the direction of rotation of motor I. Worm 4 carries pivoted arm I2 with the sliding shaft I4 in standards I5, I5 until the shaft actuates one or other of the limiting switches A or E opening the motor circuit and stopping the motor either directly or through appropriate control circuits.

It may be pointed out that the main gate valves referred to hereinafter employ both torque and gear limiting switches. The gear limiting switch is preferably of the type manufactured by the Philadelphia Gear Works. A suitable type is shown in Fig. 3 of the drawings wherein a motor operated gear 32 actuates a train of

gears

33, 34, 35, 36, 31, 38, and 39 connected after the fashion of speedometer gearing, to rotate member 40 carrying transversely extending contact 43 which bridges spring contacts M, 42 suspended from terminals mounted on the frame, when in closed position. In this way many revolutions of gear 32 are required to rotate the insulated member 40 a single revolution. No detailed description of these elements and their operation is given, however, since they constitute no part of this invention but are well known in the prior art.

In one preferred form of the system, the main gate valves may be large 20 inch valves, and operators may be of the type described above. The finishing and roughing valves may be of the 6 inch type and may be operated by what are known as Pee Wee operators. These operators are of the same general type as those described above. The valves are preferably of the double seating type, i. e. the valve seats in both directions of movement of the stem. The operators for the small valves have torque limit switches operable on movement of the valve stems in both directions. The motors driving these valves are preferably of the three phase type and may be reversed to open and close them by reversing two of the three power leads as will appear from the connections of the two sets of switch contacts employed to operate the motors for these valves.

Referring to Fig. 2 ShOWiIlga layout of the tank, pumps, and valves, IB designates a tank or reservoir to be evacuated. Difiusion pumps I9, 25 are connected in series with mechanical pump 2i. The mechanical pump 2| is directly connected to the tank I8 through a by-pass line 22 having a roughing valve 23 therein.

Gate valves

24, 25 are interposed in

lines

26, 21 between diffusion pumps I9, 20 and reservoir tank I8, and a finishing valve 28 is interposed in line 29. be-

tween the diffusion pumps and mechanical pump.

A Pirani gauge 30 is connected into the system through line 3 I.

In operation, the finishing valve 28 and

gate valves

24, 25 are closed and the roughing valve 23 is open. This permits the mechanical pump 2| to exhaust the tank I8 through the by-pass line 22 until the Pirani gauge 30 indicates a pressure of less than microns, approximately the lowest value which can be obtained by the mechanical pump. At this point the roughing valve 23 closes and the finishing valve 28 opens thereby causing the pressure of the Pirani gauge 30 to rise, temporarily, due to gas or air in the diffusion pumps and/or leaks in the system. Thereafter, the pressure of the Pirani gauge 30 again drops to a value below 100 microns at which point the

gate valves

24, 25 open and the diffusion pumps I9, 20 and mechanical pump 2| function in series to evacuate the tank to a very low pressure.

For convenience in following the sequence of operation of the various circuits and the relays in Figs. 7-10, inclusive, letters have usually been employed for the main elements. Capital letters have generally been employed to designate re-- lays. Where these capital letters also have been followed by a small letter, the legend refers to a sub-element, such as a particular armature of a relay, since relays may have a number of armatures. In order to aid, in locating a particular element or it su -element, the circui disclosed a be n vided i to live cate o i n mely, the Pirani power circuit, the Pirani signal circuit the Sequence circuit, the Control circuit, and the Vol o Po er ci u t I th se figu the r fere e t s of ea h lement, where such desi n tion used, will be Iollowed with a sufiix numo al of 1, i 3 4, or respe t v ind catin in the order enumerated above the circuit in which the el ents is ocate The Pirani power supply circuit, used to control various operations and their sequences, will first be considered and it will be noted that this circult is conventional in the art, However, it will e r e e to br efly i rder to i a clear nderstanding of the relation it bears to the various other circuits described in detail hereinafter. T e p s espo ive elements 61. 58 of the sual Pirani gauge are exposed to pressure in the system and comprise a part of the gauge 30,. To gether with resistance elements 69, '10 they form the four legs of a Wheatstone bridge. Power is supplied from a power source 18 through a power transformer H and conventional rectifier arrangement 12. The rectifier feeds into one set f opposite c rne s o the h a t ne bridge While the oth r set il pposite r ers a e c nnected tothe indicator or meter 80.

Th nbalance of t e br ge result f m a cha ce n resis an

o resistors

61,68 esp s to a chang i p e sur in t sy t m. i refle t d y t e mete 8 whose arm 5 in Fi s. 5 and 6-, mov s. a r ss sector 81 t n ns to han ing re sure cond t ns.

in the meter of the Pirani system the arm 57, which swings about a pivot 58, carries a contact 9 whi h pa ses ad cent t secto til ii and between them and a third sector 52 which is fixedly m unted and ubst nti lly coextensive with hem The s ctors 60 and E a e preferably arri d y an rm hr ugh a ake ite or other ulatins strip to insulat t m fr m each ther and ar pivo a ly mount dat 53 t u t m- An extension 64 carried by the lower end of the arm and ppropr atel supp rt d nga i h a rotating cam 55, preferably driven at a uniform rate. As cam 85 rotates, sector Gil or 51 is brought into engagement with contact 59 and presses it ainst. sector 62 comp ting the circu t indicated hereinaftor. Whether it, is sector 60 or 5| depends pon the pos t ono the need e or a m 1 with respect to those sectors. However, no claim is made to any invention in the construction of the meter. It may be the usual Allis-Chalmers Hot wire gauge which has been slightly modified by re-arranging the sectors as indicated above. The general mode of operation or" that conven tional gauge has not been changed, and the expianation herein is merely for the purpose of difiGlQSiIig its function in this system.

The Pirani ge meter fin is norm lly in the position between 0 and 100 microns, thus the contact 59 of the meter makes periodic engage,- ment With sector 62 as the moving sector til acts upon it.

When contact 59 bridges sectors GI and 62, relay L2 is energized through normally closed contacts R3112 loadin to A. C. power source 18, and seals itself in through contacts Lag. The energizing or relay Lz closes contactLbz and complates the circuit. through relay Q2 referred to he oineiten Th s closes contact bz which o mpletes the circuit through the lock out relay in the hig ltage cubi le (not shown) which furnishes power tothe equipment to be used in connection with the evacuated tank or chamber when it has been prepared. Contacts Obi, when closed, allow the high voltage cubicle control circuits to be energized. Naturally it is not do! sirable for these contacts to be closed when the tank is being rougheddown. However, the prime purpose of this feature is to de-energize the high voltage cubicle if and when a failure inthe vac. uum system causes the pressure in the system to rise above microns as pressures of this'magnitude will allow discharges in the tank which may damage equipment in the tank as well as equip-. ment in the high \voltage cubicle. Normally closed contacts 082 are opened extinguishing the red light BI and de-energizing relay SS2. When SS2 is deeenergized, contacts SSa'zreturn to closed position completing the circuit through winding of relay EH2 to sector of the meter.

This feature is peculiar to this particularapplication and might not be necessary in other processes.

When the pressure rises above 100 microns, such as by the opening of the roughing valve, contact 59 moves opposite sector 60, and it period ically completes contact between that sector and sector 62 energizing the winding of relay BB2. Contacts RRaz are opened deeenergizing the winding of relay L2 and the relay in the high voltage cubicle, due to the opening of contacts Lbz and the de-energizing of relay 02 which. opens contacts 052. Contacts RRbz close completing the circuit through QQz and through push button contacts .66. Relay QQz then seals itself in through contacts QQaz. It also closes QQbzrinm ing the bell 82 if the contacts Ggz are closed. Since the winding G4 is in the circuit controlled by main gate valve contacts MMhl, the normally closed contacts Ggz are closed only when the

main gate valves

24, 25 are open. Since winding 02 is die-energized, contacts 062 are closed which coma pletes the circuit to and lights the red light at through the power transformer, and also ener-l gizes relay winding SS2. When winding SS2 is 5 energized, normally closed contacts SSaa are opened breaking the circuit through the winding of relay RRz. This is done to prevent

segments

60 and 62 and finger 59 from periodically making andbreaking the circuit to coil RR: which will result in damage to the contact surfaces from arcing. If it is desired to silence the bell 82, push button 66 may be depressed de-energizingrelay QQz and opening the contacts QQbz which complete the power circuit to bell 82.

Preliminary steps In the sequence of operations detailed herein-f HHb5, and HHca in the power circuit of the driving motor 4 2 for gate valve 24 as well as closing contacts HHdd to provide a locking in circuit. Relay II4 closes the power circuit to the driving motor 45 for valve 25 by closing contacts Has,

11b5, H05 and completes a holding circuit. by closing contacts IId/l. When the valves are closed, the contacts MMcl, Mar, respectively, of torque limit switches thereon open breaking the circuits through windin s of relays EH4 and IIarespectively, and opening contacts HHa5, HHbs, HI-Ics} and Has, 11b5, 1105, respectively, in the power circuits to the driving motors 44, 45 for

gate valves

24 and 25. Contacts HHd4 and IId4 also open breaking the locking in circuits for the windings of relays HHi, I14. In addition the action of the torque limit switches permits contacts M174 and MMZM to close completing a circuit through the winding of relay G4 energizing it and changing the positions of many contacts to be referred to hereinafter.

To start the roughing down sequence, the push button 13 in the sequence circuit is depressed closing its contacts. This energizes the coil of relay J3 which closes contacts 11414 in the control circuit to control the closing of the finishing valve 28, in Fig. 2, and contacts Jbs in the sequence circuit. Closing of contacts Jos completes the circuit energizing coil of relay K3 through push button 56 and contacts Gbs, which are maintained in closed position by winding of relay G4 which is normally energized through contacts Mb4 and MMbi, since the latter contacts are closed when the

main gate valves

24, 25 are in closed position. These contacts are a part of the switches controlled by the

main gate valves

24, 25 and open and close with them. When the coil of relay K3 is energized, it seals itself in through the closing of armature contacts K113 and also closes contacts K173 which energizes the sequence circuit.

Normally closed contacts K04 in the control circuit are opened de-energizing coil of relay N4. This opens contacts Nai, Nba, N04, NCZ4, N64, and Nfi. It will be noted that these contacts are in the various control circuits for

motors

44, 45, 46 and 41 which open and

close gate valves

24, 25, finishing valve 28, and roughing valve 23, respectively, except in the closing circuits for the motors 44, 45 of

gate valves

24 and 25. The action of these relays is to prevent operation of the valves by the accidental closing of their control circuits with the manually operated

push buttons

48, 50, 52, 53, 54, and 55. As indicated, the circuits of switches 49, 5| are not broken at this point, since the circuits control the closing of

main gate valves

24, 25 by motors 44, 45. As these valves are already closed, no false operation can be initiated through push buttons 49, 51, and a protective relay for each of those circuits would not be necessary.

The energizing of the sequence circuit energizes the winding of timing relay 2%, sequence starting pilot light 83, and buzzer transformer 81 to provide energy for the buzzer alarm 84 when breakdown or other trouble develops in the system. Timing relay X3 is set to close contacts Xas at the end of a predetermined time, such as 20 minutes, in order to give the system an opportunity to complete its cycle in the normal course of events and to alter the condition of the relay circuit prior to the time of lighting the lamp or giving an alarm. Closing of contacts Xaa energizes relay Z3 and trouble light 85 through contacts G03 and step down transformer 86 to indicate that the

main gate valves

24, 25 are closed. It will be remembered that winding G4 is energized through a circuit including contacts Mb. and MMb4 which are closed when

main gate valves

24, 25 are closed. The energizing of relay Z3 closes contacts Z113 operating buzzer 84 from the transformer 81, indicating that the cycle of operations has not been completed within the requisite time, i. e. that the main gate valves have not opened, that trouble of some kind exists within the system, and that proper vacuum level has not been reached.

8 Closing finishing valve The first step in the evacuating operations is the closing of the finishing valve 28. As previously indicated, the closing of switch 13 in the sequence circuit energizes relay coil J3 which in turn closes contacts Jim in the control circuit and starts the closing of the finishing valve. This is accomplished by completing a circuit which energizes relay F4 through contacts Gfr, which are normally closed when

gate valves

24, 25 are closed since relay G4 is energized through closed contacts M124 and MMbl, and through the normally closed contacts Aar. The energizing of relay F4 closes contacts F115, F175, F05 completing the three phase power circuit to the motor 46 for operating it to close the finishing valve 28. It also completes a locking in circuit by the closing of contacts F114. When the finishing valve 28' has closed, torque limit switch contacts Aa4 open breaking the circuit through relay F4 and permitting contacts F115, F195, F04 to open stopping the motor 46. This action also closes normally open contacts Abs of the torque limit switch in the sequence circuit.

Open roughing valve.

The next step is to open the roughing valve 23. Since the roughing valve is closed, limit switch contacts Bba are open, and relay R3 is de energized. Contacts Rag are normally closed when relay winding R: is de-energized. As contacts Abs have been closed as previously indicated, a circuit through closed contacts Bus and the coil of relay Y3 is completed and the winding of that relay is energized so that contacts Ya. in the opening control circuit of the roughing valve 28 are closed. When the pressure in the header is below microns at the start of the sequence operation, relay C3, controlled by the Pirani pressure gauge in a manner heretofore described, remains de-energi'zed by the action of relay 0-.1 in opening the contacts 0]3, permitting contacts Cd; in the opening control circuit of roughing valve to remain closed. Since contacts Gar are closed by energizing relay G4 in response to the closing of the

main gate valves

24, 25 and through relay contacts M114 and MMb4 as heretofore described, a circuit is completed through coil of relay VV4 locking itself in by closing contacts VVd4 and closing contacts VVas,

V'Vbs, VVc5 for connecting the motor 41 of roughing valve 23 to the power supply for driving the roughing valve to open position. When roughing valve 23 opens, normally closed torque limit switch contacts B114 are driven to open position breaking the circuit through winding of relay VV4 and permitting contacts Was, VVb5 and VVc5 as well as'holding contacts VVd4 to open removing the power from the motor and. opening air to enter the vacuum pump, the Pirani sys-- tem acts in a manner hereinbefore described, to de-energize relay O2, permitting contacts 0]: to close energizing relay C3 which seals in through contacts Ca; and opens contacts Cd; in the opening control circuit for the roughing valve, thus preventing subsequent opening of the roughing valve 23 by motor 41 during the sequence when pressure may reach a level below 100 microns. By the same operation, contacts CD3 and C04 are closed.

Closing roughing valve The next step in the sequence is the closing of the roughing valve 23, after the mechanical pump has completed the roughing operation.

With the contacts Rb-i closed as previously described, the pressure having reached a point below 100 microns, the Pirani control system operates as hereinbefore described to energize relay 02, open contacts Oh and close contacts 003 to complete the circuit to relay winding Q3 energizing it and closing contacts Qas in the closing control circuit for the roughing valve. This completes the circuit through relay winding V4. When winding V4 is energized, contacts V115, Vb5, Vcs are closed completing the power circuit to the driving motor 41 for the roughing valve 23, causing it to drive the valve to closed position. This same action closes contacts V034 creating a holding circuit for the relay Winding V4. When roughing valve 23 has closed, torque limit switch opens contacts Sal breaking the circuit through the relay winding V4 and opening contacts Va5, Vbs, V05 removing the power from the motor 41. The torque, limit switch also closes contacts $193 in the sequence circuit, completing the circuit through normally closed contacts U03, and energizing relay winding W3 which closes contacts The next, step is the opening of the finishing valve 28. When the pressure rose and relay 02 was de-energized as heretofore described in connection with the Pirani control circuits, relay Cs was energized. This took place when the roughing valve 23 was opened and the pressure rose, so that contacts C6; in the opening control circuit for the motor 46 of the finishing valve. 28 are closed, and the closing of locking in contacts Caz keep relay C3 energized while relay O2 is still energized; Likewise, the energizing of relay W3 through action of the torque limiting switch upon the closing of roughing valve 23 and closing of the contacts W614 in the opening control circuit for finishing valve 28 as described above completes the circuit through coil of relay FFi.

This closes a locking-in circuit through contacts FFd4, and also closes contacts FFas. FFb5, FFCs completing the power circuit to the motor 46 for opening finishing valve 28. When finishing valve 28 has opened, torque limiting switch opens contacts E614 and breaks the circuit through relay FE; de-energizing that relay and permitting contacts FFCts, FFbs, FFCs to open, breaking the power circuit to the motor 46 driving finishing valve 28. The opening of the finishing valve acts to close contacts. Eba of the torque limiting switch, energizing relay U3. It may also permit the pressure in the vacuum chamber to rise above 100 microns when communication is established with vacuum pumps [9, 20.

Opening main gate valves The last step in the sequence is the opening of the main gate valves. The energizing of relay U3 described above closes contacts Uas and U64 in the opening control circuits for the main gate Valves. When the pressure drops below microns, or if it has remained below that level, relay O2 is energized as describedhereinbefore in connection with the Pirani system. Contacts 003 are closed and relay Q3 is energized. Contacts Qbi and Q04 are closed, and since contacts Mb4 and MMbi are also closed when

gate valves

24, 25 are closed, relay G4 is energized and contacts Gds and Gel are closed completing circuits through the opening control circuit for the main gate valves 2 25 to energize coils H4, I4. They close contacts Has, Hbs. H05 and Ice and lbs and I05 to operate the driving motors 44, 45 for the

main gate valves

24, 25 to the power supply moving the main gate valves to open position, in addition they close locking in contacts Hdi and Ids, respcctively. When

main gate valves

24, 25 start to open. limit switches Mbi and MMb4 are opened (lo-energizing relay G4. This opens contacts Gbs which de-energizes relay K3 and opens contacts Kba which in turn opens the sequence circuit and permits contacts Kfs to close which lights sequence completed lamp 88 through transformer 89. It also opens contacts Gal in the opening control circuit for the motor 4'! of roughing valve 23. preventing accidental operation thereof. When main gate valves 24. 25 have opened gear limit switches Pan and Tai open de-energizing relays H4 and I4, respectively, re-opening the power circuits to the operating motors 44, 45 for

valves

24, 25 and stopping them. This completes the sequence.

When contacts IVHM and MMb open at the finish of the sequence, relay G4 is de-energized closing contacts Gcz which were open during the sequence operation. Since during the operation of the sequence the pressure rose above 100 microps. coil. BB2 was at one time energized closing contacts RRb2. This action energized QQZ which sealed itself in through QQaz and closed contacts QQZJZ. Thus when contacts Gog close as described above. energy is supplied to the bell which rings signalling the end of the sequence operations. The hell, can be silenced as indicated hereinbefore.

If at any time it is desirable to stop the seouence circuit, it can be done by merely depressing button 55 (sequence stop) located in the sequence circuit. which de-energizes relay K3 and opens contacts K173 and K514. This disables the sequence circuit. de-energizes relay N and returns all of the valve operation circuits to manual operation through manual switches is to 55, inclusive, by the closing of contacts No.4, Nbi, N04, Ndl, N84, Nfi.

If desired. pilot lights Bil, BI, 82, 93, 94, 95. 96, and 9! may be connected to the various opening and closing control circuits of the

valves

24, 25, 25' and 23 through a propriate coupling transformers 98. 99. Hill. IM. H32, H33, H94 and its to indicate the operation of these various circuits.

It will also be understood that line [08 of the power circuit is connected to and feeds line H11, and that lines H39 and I H! are connected together. Rwitches l i l l [2 serve to complete the circuit to the main power line H3 which furnishes power at conventional voltages and frequency.

Having thus described my invention, I claim:

1. A system for evacuating a chamber comprising a mechanical pump and plurality of diffusion pumps, valve means connecting each of said p ps to the chamber and to each other, means responsive to pressures above a predetermined value for operating said valve means to connect the mechanical pump with the chamber to partially evacuate it, and means responsive to pressures below the predetermined Value for operating the valve means to connect the mechanical pump in series with the difiusion pumps to receive their outputs and evacuate the chamber to a high vacu- 2. A control system of the character described comprising a chamber, a low vacuum mechanical pump, high vacuum diffusion pumps, valves for connecting the diffusion pumps to the chamber, a finishing valve for connecting the mechanical pump to the diffusion pumps, a by-pass line for connecting said mechanical pump to said chamber for roughing down purposes, a roughing valve in said by-pass line, means responsive to a predetermined pressure in the system for controlling the opening of the roughing valve to connect said mechanical pump with the chamber and partially evacuate it, and means responsive to a predetermined lower pressure for closing the roughing valve and opening the other valves to place the mechanical pump in series with the diffusion pumps and evacuate the chamber to a low pressure.

3. A vacuum system of the character described comprising a chamber, mechanical and diffusion pumps for evacuating the chamber, valves for connecting the diffusion pumps to the chamber,

a finishing valve and a roughing valve for connecting the mechanical pump to the diffusion pump and to the chamber through a common inlet, a circuit for selectively actuating said first named valves, said finishing valve, and said roughing valve, and pressure responsive means in communication with said common inlet, said pressure means being responsive to predetermined changes in pressure for controlling the operation of said circuit to open and close the roughing valve in time relation to the opening of the other valves to connect the mechanical pump, and then the diffusion and mechanical pumps in series to said chamber and eifect partial and substantially complete evacuation of the chamber.

4. A control system of the character described comprising a chamber to be evacuated, a high vacuum and a low vacuum pump, valve means for connecting said high vacuum pump and said low vacuum pump to the chamber in a predetermined sequence for evacuating the chamber, said means including a circuit responsive to pressure conditions in said chamber, a sequence circuit coupled to and responsive to the action of the circuit for determining the sequence of coupling of the high vacuum pump and the low vacuum pump to said chamber, and a power control circuit coupled to and responsive to said sequence circuit for carrying out the coupling sequence of the low vacuum pump and the high vacuum pump to said chamber in a predetermined manner.

5. A control system of the character described comprising a chamber, a high vacuum pump and a low vacuum'pump, valve means for coupling said high vacuum pump to said chamber and said low' vacuum pump to said chamber and said high vacuum pump, a pressure device responsive to pressure conditions in the system, a signal circuit coupled to and controlled by said pressure device, a sequence circuit coupled to and controlled by the signal circuit for determining the order of o eration of the low vacuum pump and the high vacuum pumps in the system, and a power control circuit responsive to the action of the sequence circuit for altering the coupling of the high vacuum pump and low vacuum pump in the system.

6. A control system of the character described comprising a chamber, a high vacuum pump and a low vacuum pump, valve means for coupling the low vacuum pump to the chamber and to the output of the high vacuum pump, valve means for coupling the high vacuum pump to said chamber, means for controlling the action of said first and said second coupling means including a pressure controlled circuit responsiveto pressure conditions in the system, a sequence circuit coupled to and activated by the pressure controlled circuit for determining the order of coupling of the low vacuum pump and the high vacuum pump to the chamber and to each other, and a power circuit coupled to and energized in response to the action of the sequence circuit to actuate the coupling means for the low vacuum pump in a predetermined manner and the high vacuum pump.

7. A control system of the character described comprising a chamber to be evacuated, a low vacuum pump and a high vacuum pump, means for controlling the order of coupling of the low vacuum pump and the high vacuum pump to the chamber and to each other, said means including a pressure responsive circuit responsive to predetermined pressure conditions within the system, a signal circuit mechanically coupled to said pressure responsive circuit and energized in response thereto, a sequence circuit coupled to and electrically controlled by the signal circuit for determining the coupling arrangement of the said low vacuum pump and the high vacuum pump at predetermined pressures, and a power control circuit activated by said sequence circuit to bring the low vacuum pump and the high vacuum pump into coupling relation in a predetermined manner. 1

8. A vacuum control system of the character described comprising a chamber, a low vacuum pump and a high vacuum pump, means for bringing the low vacuum pump and the high vacuum pump into communication with said chamber, a signal circuit, pressure responsive means coupled to the signal circuit for controlling its operation, a sequence circuit coupled to and operated by signals from said signal circuit, power control circuits connected to and responsive to the operation of said sequence circuit to actuate said communicating means and connect the low vacuum pump and high vacuum pump to said chamber in a predetermined sequence to exhaust said chamber to a high vacuum.

ROB ROY CYR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,716,160 Zworykin et a1 June 4, 1929 2,063,665 Edwards Dec. 8, 1936 FOREIGN PATENTS Number Country Date 203,702 Great Britain Jan. 10, 1924