US1716160A

US1716160A - Pumping system for metal-tank rectifiers

Info

Publication number: US1716160A
Application number: US210275A
Authority: US
Inventors: Vladimir K Zworykin; Errol B Shand
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1927-08-03
Filing date: 1927-08-03
Publication date: 1929-06-04
Anticipated expiration: 1946-06-04

Description

\LK. ZWORYKIN ET AL PUMPING SYSTEM FOR METAL TANK RECTIFIERS Filed Aug. 3, 1927 17 J6 /2 i; Q E 11:35 IE 1 14 Z5 5 rz m INVENTORS Vla az'mz'r/f Zworykin and Errol B, 5/2 and ATTORNEY I nism 8 comprises a cam segment 9 bearing Patented June 4, 1929.

UNITED STATES VLADIMIR K. ZWORYKIN,

PENNSYLVANIA, ASSIGNORS, TO

ATE-N T oFF1cE.

CORPORATION, A CORPORATION OF PENNSYLVANIA.

PUMPING SYSTEM FOR METAL-TANK RECTIFIERS.

Application filed August 3, 1927. Serial No. 210,275.

Our invention relates to vacuum pumping systems, and it has particular relation to such systems utilizing two pumps in series, with an interstage reservoir in between, into which the high-vacuum pump exhausts, with automatic means for starting and stopping the fore-vacuum pump in response to the degree of vacuum in the interstage reservoir.

The object of our invention is to provide an improved mechanism and system for carrying into effect the object just stated.

Our invention will best be understood by reference to the accompanying drawing, the single figure of which is a diagrammatic view of circuits and apparatus embodying our invention, in a preferred'form, some of the parts being shown in" section, others in elevation and still others by means of diagrammatic representation.

Our invention is particularly adapted for evacuating, or maintaining a high degree of evacuation in, a metal-tank rectifier, which is indicated on the drawing at 1, the rectifier being shown, however, ona somewhat reduced scale, in proportion to the other apparatus, for convenience in illustration. Connected to the rectifier tankis a highvacuum pump 2, which may be a mercuryvapor pump of well-known design, connected to the tank through the intermediation of a vacuum'valve 3 which may be automatically controlled by any suitable mechanism 4, such as that which is shown and described in the application of E. B. Shand,

' Ser. No. 210,289, filed Aug. 3, 1927.

T he high-vacuumpump 2 discharges into an interstage reservoir 5 which is, in turn, exhausted by means of a fore-vacuum pump 6, illustrated as being of the rotary type, driven by an electric motor 6. In the connections between the interstage reservoir and the fore-vacuum pump, is provided another.vacuum valve 7 to be operated by a motor mechanism 8 which may be as that already referred to.

In particular, the valve-operating mechathe sameon the top of the valve stem 10 and biased toward a valve-closing position by means of a spring 11. The cam segment 9 is moved to its valve-opening position by means of an electric motor 12 which is geared to a worm shaft 13 carrying a worm 14 which meshes with a worm gear segment 15 mounted on the same shaft as the cam segment 9. The worm shaft 13 is movable to a position in which the worm is either in or out of engagement with the worm-gearsegment 15 by means of a solenoid 16. Any suitable stopping mechanism, such as that indicated at 17 may be utilized to stop the motor 12 when the-valve has reached its full-open position.

The operation of the valve-operating .mechanism just mentioned, as well as the starting and stopping of the pump motor- 6 may be controlled by means of a manometer 20 which is connected to the interstage reservoir 5' and is thus responsive to the fore-vacuum existing therein. The manometer may conveniently comprise a glass vessel 21 having a U-shaped tube 22, connected to its bottom portion and terminating in an arm 23 extending upwardly alongside the vessel 21. In the upwardly-extending arm 23, we provide at least one, and preferably two,

contact wires

24 and 25, and a lower portion of the U-tube is provided with an I additional contact member 26. The manometer is partially filled with mercury 27.

In operation, the mercury-vapor pump is capable of pumping from a vacuum of the order of about a micron of mercury, more or less, to a fore-vacuum which may vary in pressure up to about 5 or 10 millimeters of mercury, the figures just stated being given for illustrative purposes only. The rotary pump 6 is capable of pumping from a pressure of a small fraction of a millimeter of mercury, exhausting against atmospheric pressure.

The accurate measurement of the extremely high vacua utilized in the rectifier tank 1 or, in general, in the vessel to be exhausted, is extremely difiieult, particularly when an attempt is made to utilize automatic apparatus. On the other hand, the measurement of pressures of the order of millimctcrs may be very accurately and simply accomplished by means of a manometer, such as that which is hereinabove described, and such apparatus readily lends itself to embodiment in automatic equipment.

In operation, the manometer makes a contact between the upper electrode 24: and the mercury colunm, when .a predetermlned maximum fore-vacuum pressure of 5 or 6 millimeters is present. The contact of the mercury with the upper contact electrode 24 is utilized to energize the solenoid 28 of a relay 29 for closinga switch 30 which starts the pump motor 6 from an auxiliary source of supply, such as the transformer 31. At the same time, the closing of the switch 30 energizes the valve-opening motor 12 and the valve-gear magnet 16 for bringing the gears into mesh for the purpose of starting to open the vacuum valve 7 between the interstage reservoir 5 and the rotary pump 6.

The pump 6 almost immediately attains full speed and very quickly exhausts the air from the short length of pipe intervening between it and the valve 7, but it takes the valve about eight seconds to fully open and about four seconds before it is even partially open.

We have found that there is sufficient time lag in the operation of the valve to enable the rotary pump to be in effective operation before the opening of the valve. lVe have shown, however, by way of illustration, a

dash-pot 32 associated with the gear-meshing'magnet 16 for delaying the meshing of the worm 14 with the gear segment 15 after the energization of the gear-shift magnet 16.

Any suitable mechanism may be utilized for stopping the action of the rotating pump, either after a predetermined interval, or in response to a predetermined degree of evacuation in the interstage reservoir. We have illustrated a combination of both methods of controlling the stopping of the pump.

The operation in response to the predetermined degree of evacuation in the interstage reservoir is' secured by means of the lower contact wire 25, of the manometer, which is connected to the relay magnet 28 through auxiliary switch contacts 34, which are closed when the relay is closed. Thus, after the relay has been moved to closed position by contact of the mercury with the upper electrode 24, the lower electrode 25 maintams the energization of the relay until the mercury breaks contact with said lower electrode. The lower electrode may be placed as close to the mercury level in the larger container 21 as mechanical considerations Wlll permit. In ractical operation, the lower contact may e caused to shut off the rotary pump when a vacuum of 1 millimeter,

or even one-half of a millimeter, of mercury is reached in the interstage reservoir.

After the switch magnet 28 has been deenergizedby the opening of the lower contact member 25 of the manometer, the opening of the relay may be still further delayed by means of a dash-pot 36 connected thereto in such manner as to cause the rotary pump to continue to operate for any predetermined length of time after the deenergization of the relay 29.

operative position, so that it drops downout of engagement with the worm-gear segment 15, thereby permitting the valve-closing spring 11 to snap the "alve instantaneously to its closed position. It will be understood that the dash-pot 32, if used at all. 'will be arranged to permit a substantially unopposed downward movement of the worm shaft 13, but to oppose the upward movement thereof, as indicated in the drawing.

By utilizing an interstage reservoir of sufficient capacity to enable the mercury pump to discharge into it for a considerable length of time without having the forevacuum pressure therein rise to a pressure against which the mercury pump cannot operate, and by providing a vacuum-responsive device, such as the manometer 20, which responds to mercury columns which are not microscopic in their dimensions, as in the case of the mercury columns correspondingto the vacuum in the rectifier tank 1, we have been able to provide an extremely simple and reliable automatic pumping system, as above described.

. We find it highly desirable to operate the mercury pump continuously, in order to preserve as high vacuum as possible in the rectifier tank 1, and also in order to be instantly available, in case of sudden gassing or evolution of gases or sudden. loads on the rectifier. Heretofore, in devices utilizing an automatic response to the vacuum conditions in the rectifier to start both of the pumps, there has been a time delay of the order of three-quarters of an hour before the mercury pump could be heated to an operative temperature, during which time it has been necessary to keep the valve 3, for example, closed. p

We have found that mercury pumps, as

with the automatic pressure-responsive device thereon, makes such intermittent operation of the rotary pump feasible.

While we have described our invention in a preferred embodiment and explained its advantages and operation with respect .to such preferred embodiment, we wish it to be distinctly understood that our description and explanation are largely illustrative, and that changes in degree and in the exact design or arrangement of the parts may be resorted to by those skilled in the art without sacrificing theessential principles of our invention. We desire, therefore, that the appended claims shall be given the broadest interpretation consistent with their wording and the prior art. I

We claim as our invention:

v1. In a vacuum pumping system, the combination with a vessel to be maintained at a high degree of evacuation, of a high vacuum pump, a fore-vacuum pump, an interstage reservoir therebetween, a mechanically actuated valve between said interstage reservoir and said fore-vacuum pump, and. means responsive to the fore-vacuum in said interstage reservoir for intermittently starting and stopping said forevacuum pump and opening and closing said valve, whereby the pressure in said interstage reservoir is maintained within predetermined limits.

2. In a vacuum pumping system, the combination with a vessel to be maintained at a high degree of evacuation, of a high-vacuum pump, a fore-vacuum pump, an interstage reservoir therebetween, a valve between said interstage reservoir and said fore-vacuum pump, substantially instantaneously operating closing means for said valve, relatively, slowly operating opening means therefor, means responsive to a predetermined maximum pressure in said interstage reservoir for starting said fore-vacuum pump and energizing said valve-opening means, and means for simultaneously deenergizing said fore-vacuum pump and rendering said instantaneous valve-closing means effective.

3. In a vacuum pumping system, the combination with 'a vessel adapted to be main tained at a high degree of evacuation, of a J said pump and high-vacuum ump adapted to operate continuously, a ore-vacuum pump adapted to operate intermittently, an interstage reser-. voir therebetween, a mechanically actuated valve between said interstage reservoir and said fore-vacuumpump, and automatic control means for said valve and for said'intermittently operated pump, including means responsive to a predetermined maximum pressure in said interstage reservoir for starting said pump and subsequently effecti'ng the opening of said valve, and means operativev at the termination of the desired intermittent operation of said pump to close the valve and subsequently discontinue the effective operation of the pump.

4. In a vacuum pumping system, the combination with a vessel adapted to be maintained at a high degree of evacuation, of a high-vacuum pump adapted tooperate continuously, a fore-vacuum pump adapted to operate intermittently, an interstage reservoir therebetween, a mechanically actuated valve between said interstage reservoir and said fore-vacuum pump, and automatic control means for said valve and for said intermittently operated pump, including a relay adapted, upon actuation to its closed position, to energize mechanism for starting I said pump and subsequently effecting the opening of said valve, ther adapted, upon moving to its open position, to cause the closing of the valve and the subsequent discontinuance of the effective operation of the pump, means responsive to a predetermined maximum pressure in said interstage reservoir for effecting the closing of said relay, operative after the closure of the relay and until the pressure in the interstage reservoir falls to a predetermined minimum pressure, for holding the relay closed.

5. In a vacuum pumping system, the combination with a vessel adapted to be main tained at a high degree of evacuation of the order of microns of mercury, of a highvacuum pump adapted to operate continuously and operative against a fore-vacuum of the order of millimetersof mercury, an interstage reservoir into which said highvacuum pump discharges, an intermittently operating fore-vacuum pump for maintaining the necessary stage reservoir, a mechanically actuated valve between said interstage reservoir and said fore-vacuum pump, and automatic control means for said valve and for said intermittently operated pump, including a relay adapted, upon actuation to its closed position, to energize mechanism for starting subsequently effecting the opening of said valve, said relay ther adapted, upon moving to its open position, to cause the closing of the valve and said relay being furand further means,-

being fur-" fore-vacuum in said inter- I 1 closed until after the mercury level falls below said lower contact. 10

In testimony whereof, we have hereunto subscribed our names this 26th day of July, 1927.

VLADIMIR K. ZVVORYKIN'. ERROL B. SHAND. I