US3829244A - Automatic sequencing high vacuum mechanical valve system and apparatus - Google Patents

Abstract

A mechanical roughing vacuum pump and a high vacuum pump of the diffusion or similar type are interconnected to a high vacuum chamber and an intermediate isolation chamber. Valves are located within the chambers and are coupled with novel mechanical interlocks which provide for automatic operation of the valves by the pressure differential in the chambers and produce proper sequencing of the pumps to effect a high vacuum.

Description

U Unite States Patent 1191 1111 3,829,244 Miller Au 13 1974 [5 AUTQMATM SEQUENCING HIGH 856,828 9/1957 Great Britain 417/152 VACUUM MECHANICAL VALVE SYSTEM AND APPARATUS Primary ExaminerWilliam L. Freeh Assistant Examiner-Arnold Ward [76] Inventor' $2 2 gi 22 2 8 arbara Attorney, Agent, or Firm-Alfons Puishes [22] Filed: May 10, 1973 [57] ABSTRAQT [21] Appl' N05 359,207 A mechanical roughing vacuum pump and a high vacuum pump of the diffusion or similar type are inter- 52 us. or. 417/53, 417/152 connected to a high vacuum chamber and an interme- [51] I t, Cl, F044 19/24, F04f 9/00 diate isolation chamber. Valves are located within the [58] Field at Search ..417/152 154, Chambers and are Coupled with novel mechanical n- 417 49 53 54 9 5 427; 55 20 339 terlocks which provide for automatic operation of the valves by the pressure differential in the chambers and 5 References Cited produce proper sequencing of the pumps to effect a FOREIGN PATENTS OR APPLICATIONS high vacuum.

904,684 3/1942 Germany 417/152 10 CIaims,7Drawing Figures W m r3 1Q 44 54 m 4/ 1 I 45 4 504" g T 58 54 I ,!wm-r & "1- $\\:f\\5il\\\\v r ail /I s 1 s PATENIED w 1 W @9344 SHEU 1 [IF 2 PATENIED mm 1 31974 sum 2 0F 2 AUTOMATIC SEQUENCING HIGH VACUUM MEQHANICAL VALVE SYSTEM AND APPARATUS BACKGROUND OF THE INVENTION In the production of vacuum conditions wherein the pressures achieved are Torr or lower, a combination of two or more pumps is required. The relations of these pumps to each other and the evacuated space during start-up, operation and shut-down need to be controlled either manually or automatically in order to protect the pumps and the evacuated system against undesirable effects caused by misoperation. Usually, when, the vacuum system operates for long periods of time without shut-down, automatic start-up and shutdown controls are not justifiable and perhaps only an alarm signal is included for power failure indication. In vacuum systems that must be brought back to atmospheric pressure several times a day, automatic sequencing controls that sense the pressures, amplify the minute electrical currents of these sensors and finally operate valves and perhaps other devices are employed. In addition, automatic controls are sometimes a desirable trade-off against training of personnel in high vacuum technique.

Frequently the much higher cost of the automatic sequencing controls over the manual type can be offset by labor savings; but a much wider number of cases could justify the automatic feature if its cost were to be cut severely. Such reduction in cost I claim as one of the main features of my automatic sequencing mechanical valve system.

The particular combination of pumps mentioned above, namely a mechanical pump and a diffusion pump is commonly used because the diffusion pump can produce pressures of 10 Torr and lower but cannot discharge directly to the atmosphere. The mechanical pump of the common eccentric rotor type is not very effective at pressures below the 10 to 10" Torr range but can exhaust against atmospheric pressure. A simple series arrangement will function all right once the vacuum chamber is down to a pressure of about 10* Torr. However, initial evacuation from atmospheric pressure and the return from high vacuum to atmospheric pressures are facilitated by the addition of some valves and pumping lines as will be described later.

The diffusion pump should be isolated from the rest of the system by suitable valving arrangements. This will prevent overheating of the diffusion pumping fluid usually brought about by subjecting it to a pressure higher than about 1 Torr. Also with proper valving the diffusing pumping fluid is prevented from backstreaming, an action that would result in fouling of the vacuum chamber. With the diffusion pump thus isolated the vacuum chamber can be pumped down from atmospheric pressure to a pressure of 10 to 10 Torr. At this pressure the diffusion pump can be engaged by proper valve operation. Now the mechanical pump becomes a backing or fore pump to thediffusion pump.

Present practice employed to prevent misoperation uses pressure sensors and power driven valves. Such systems, however, have several drawbacks:

1. They are complex and costly in that the pressure sensors are electronic in nature with thermocouple or similar hot-filament gauges having low-level electrical output signal which must be amplified to control electric motors or pneumatic or hydraulic valves which, in turn, are arranged to operate the vacuum valves by means of screws, linkages or pistons. 2. They are ordinarily bulky and heavy because of the many discrete components used in the system. 3. They are inherently unreliable in that auxiliary power sources are required for the control functions which sources are in themselves subject to failure. Thus additional devices of a safety nature are necessary which will shut down the system or otherwise compensate for any of the various possible failures.

SUMMARY OF THE INVENTION.

My invention described below eliminates the disadvantages of contemporary vacuum pumping systems in that the vacuum valves are self-operating in a sequential manner using the differential pressures across each valve poppet. A single mechanical rod or shaft, hereinafter known as the operating shaft, is used to initiate the desired operating sequence or to return the system to atmospheric pressure when desired.

My invention, described more fully below in relation to the prior art consists of three valves which are functionally identical to the prior art valves, but physically arranged so that a roughing valve and a high vacuum valve are mounted in the high vacuum chamber, and an isolation valve is mounted in a separate, sealed chamber designated as the isolation valve chamber. An operating shaft connects between the isolation valve chamber and the vacuum chamber and carries the appropriate linkages by which all three valves are controlled.

Vacuum connections to the isolation valve chamber are so arranged that the outlet from the roughing valve and the inlet to the mechanical pump are both connected to the space surrounding the isolation valve, while the outlet from the diffusion pump is connected to the space below the isolation valve poppet. The isolation valve may consist of a relatively large area poppet suspended by a pivoted arm arrangement having an integral counterweight which is adjusted so that the valve is biased by the counterweight to the open position, also as described more fully below.

I have discovered that when utilizing the novel construction of my apparatus and the construction and location of my valves I am able to effect a completely automatic sequencing of the valves to operate a high vacuum system. I am further able to accomplish this without the use of complex electrical circuitry or controls. The latter feature eliminates the hazards attendant upon complete power failure.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a basic vacuum pump combination in its simplest form.

FIG. 2 is a schematic diagram illustrating a vacuum pump combination illustrating the use of an isolation valve.

FIG. 3 is a schematic diagram illustrating the combination of my invention.

FIG. 4 is a longitudinal section through the isolation chamber of my invention showing the isolation valve and related mechanism and connections.

FIG. 5 is a longitudinal section through the isolation chamber and high vacuum chamber showing the operating valves and mechanism at the starting stage of evacuation.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the figures and first to FIG. I there is shown diagrammatically conventional connections for producing a high vacuum. These comprise the vacuum chamber 1 with a vacuum breaker valve 2 used in all the systems but shown only in this FIG. The diffusion pump 3 connects to the vacuum chamber and thence to pipeline 4 to the inlet to a mechanical vacuum pump or what is known in the art as a roughing pump which exhausts to the atmosphere at 6. Such a connection presents all the problems and hazardous disadvantages enumerated under the background of the invention described above.

Referring now to FIG. 2 there is seen the vacuum chamber 21, a high vacuum valve 22 connecting to the diffusion pump 23. Twenty-four, 24a, and 24b represent lines leading from the discharge of the diffusion pump 23 and from the vacuum chamber 21 to the mechanical pump 25, having itsexhaust at 26. A pressure sensor 27 is employed to operate roughing valve 28 and isolation valve 29 whereby through suitable electrical or electronic means the roughing pump 25 is first connected to vacuum chamber 21 until the vacuum reaches a predetermined point, whereupon valve 28 is closed and valve 29 opens, or is opened, thereby producing the connections shown in FIG. 1. Such a system overcomes many of the objections as described above but necessitates the use of highly sensitive sensing equipment represented at 27 with their attendant controls and consequently results in a highly expensive, complicated and troublesome arrangement.

Referring now to FIGS. 3 and 4 there is seen first in FIG. 3 a schematic diagram of the connections forming the basis of my invention and in FIG. 4 the mechanical components comprising and located in the isolation valve chamber which forms'an important part of my invention.

Inside vacuum chamber 31 is located high vacuum valve 32 which connects to diffusion pump 33 and thence through pipeline 34 to isolation chamber 40 through isolation valve 39 which is located inside the chamber as explained more fully below. Roughing valve 38 is located inside high vacuum chamber 31, and connects to isolation chamber 40. Operating shaft 41 with its handle 42 passes through seals 43 in isolation valve chamber 40 and serves for positioning of the valves as described more fully below.

Operating shaft 41 and seals 43 located in isolation valve chamber 40 are better seen on FIG. 4. This is seen connected through linkage 44 and push rod and roller 45 to the mechanism of isolation valve 50. A lever comprising a pivot 47 and counterweight 48 is shown bearing upon the top of the poppet 50a of isolation valve 50. This combination permits biasing the valve to an open position when no pressure differential exists across the poppet 50a. The outlet from the roughing valve is shown at 51, the outlet from the diffusion pump at 52, and the inlet to the mechanical pump at 53, all communicating to the interior of isolation valve chamber 40 as shown.

On FIG. is seen isolation valve chamber 40 shown in juxtaposition with high vacuum chamber 54. Inside the latter is shown roughing valve 55 havings its valve seat 55a and its flexible tube 55b leading to the isolation chamber 40 at 51. High vacuum valve 56 with its poppet 56a is seen located inside high vacuum chamber 54. A lever mechanism comprising a pivot 57 and adiO justable counterweight 58 is shown bearing on the upper side of poppet 56a in a manner similar to that described above for the isolation valve. The inlet to the diffusion pump is seen at 59.

Operating shaft 41 described above is seen passing through high vacuum chamber 54 and having positioned upon it spring 60, collars 61 and linkage 62. Also operating shaft 41 extends (not shown) to a vacuum breaker valve (not shown) to open and close it as described more fully below. The operating shaft is equivalent to a start and stop button. It is manually controlled. In the position shown in FIG. 5 the vacuum chamber 54 is at atmospheric pressure, the vacuum breaker valve is open and the mechanical pump is pumping on the outlet of the diffusion pump through isolation valve 50. To initiate evacuation of the vacuum chamber, operating shaft 41 is moved to the left resulting in the position shown in FIG. 6. This closes isolation valve 50, opens roughing valve 55 and closes vacuum breaker valve (not shown). Now conditions have been established to permit automatic sequence operation of isolation valve 50 and high vacuum valve 56. As the pressure in isolation chamber 40 is reduced by action of the mechanical pump, isolation valve 50 opens. Similarly, and in sequence, as the pressure in the vacuum chamber 54 decreases, high vacuum valve 56 opens. In so doing it back seats against and, consequently, closes the roughing valve so that the pumping flow is as shown in FIG. 7.

OPERATION The operating shaft is operated so that the isolation valve 50 is forced closed for a portion of the travel of the operating shaft and linkage. Thus, as the operating shaft 41 moves, the isolation valve 50 is forced to its closed position, and then released at the other extreme position of the operating shaft as best seen on FIG. 6.

While I have shown a sliding shaft, I may use also a rotating shaft with appropriate connecting linkages as is well known to those skilled in the art.

As shown also on FIG. 6, the high vacuum valve is mounted in the vacuum chamber and is similar in construction and operation to the isolation valve ad described above, with the space under the high vacuum valve connected to the inlet of the diffusion pump. The separate roughing valve 55 is mounted from the same pivot shaft so that it seals against the upper surface of the high vacuum poppet 56a, but does not interfere with the action of the high vacuum valve 56 counterweight when the roughing valve is in the open position.

ber. The spring-loaded linkage 62 connecting the operating shaft to the roughing valve maintains the roughing valve sealed against the high vacuum valve during the condition when the vacuum chamber is at atmospheric pressure. To initiate operation the operating shaft is manually pulled to the left which engages the linkage to the roughing valve 55 and lifts the roughing valve off the surface of the high vacuum valve, commencing evacuation (or roughing) of the vacuum chamber 54. At the same time the operating shaft closes the isolation valve 50 and also closes the vacuum breaker valve. At the initial opening of the roughing valve, the pressure in the isolation valve chamber increases momentarily as air flows in from the vacuum chamber which was at atmospheric pressure. This maintains the isolation valve sealed closed while the air is being evacuated from the vacuum chamber as shown in FIG. 6. It should be noted that the isolation valve chamber is now connected to the vacuum chamber through flexible tube 55b and roughing valve 55. Therefore as roughing continues the pressure in the two chambers will become essentially equal, except for the slight differential due to the air flow.

When the pressure in both chambers declines to a predetermined value as determined by the setting of the isolation valve counterbalance weight 48, the pressure differential across the isolation valve poppet will no longer be sufficient to hold the isolation valve closed against the counterbalance force, thus the isolation valve will open. In practice, the isolation valve counterweight is adjusted so that the valve opens at a pressure of approximately 0.5 Torr.

With the isolation valve opened, the diffusion pump outlet is again connected to the roughing pump. As the pressure continues to decline to a second predetermined point in the vacuum chamber, the high vacuum valve is caused to open by its counterweight as shown in FIG. 7. This second pressure is characteristically set at 0.1 Torr. The physical arrangement of the roughing valve and the high vacuum valve is such that in its open position, the high vacuum valve rests against and seals the inlet of the roughing valve; thus with the high vacuum valve opened, the vacuum chamber is connected to the inlet of the diffusion pump and effectively sealed from the roughing pump by the high vacuum valve poppet. In this condition then, it can be seen that the vacuum chamber is connected through the diffusion pump to the mechanical pump in the desired configuration shown diagrammatically in FIG. 1.

When it is desired to vent the vacuum chamber to atmosphere, the operating shaft is once again caused to move to the condition shown in FIG. 5 and the vacuum chamber is vented to atmosphere by means of a vacuum breaker valve, (not shown).

It must be recognized that the particular mechanical arrangement of valves and operating linkages described above is only one of the many possible configurations of this invention, any of which may embody its unique characteristics, namely, the combination of two or more valves, some of which are directly mechanically operated and others counterbalanced by springs or weights, so arranged that actuation of the mechanically operated valves will establish the required mechanical conditions so that the counterbalanced valves will operate in some desired sequence, depending only upon the pressure differentials across the counterbalanced valves and the pressures in the chambers.

The novel construction of my apparatus and the location of the valves makes possible: their sequential operation by extremely small pressure differentials which exist in vacuum operations.

While I have disclosed a combination of a mechanical pump and a diffusion pump for use in connection with my invention, it will be evident to those skilled in the art that other suitable types of conventional and high vacuum pumps may be used in combination to effeet the novel results attained by my invention.

I claim:

1. An apparatus for effecting the evacuation of a chamber to a high vacuum by use of a mechanical pump together with a diffusion pump comprising the combination of:

an intermediate vacuum chamber communicating between said high vacuum chamber and the inlet to said mechanical pump;

a first valve positioned inside said intermediate chamber and communicating between the outlet from said diffusion pump and said intermediate chamber; said first valve being disposed to open and close automatically when the pressure differential across said valve reaches predetermined values;

a second valve positioned inside said high vacuum chamber and communicating between the inlet to said diffusion pump and said high vacuum chamber; I said second valve being disposed to open and close automatically when the pressure differential across said valve reaches predetermined values;

a third valve positioned inside said high vacuum chamber communicating between said high vacuum chamber and said intermediate chamber; said third valve being disposed to close automati cally when said second valve opens; independent means for simultaneously closing said first valve and opening said third valve.

2. The apparatus of claim 1 including means for applying a variable mechanical force to one side of said first valve and said second valve whereby said pressure differential required to open and close said valve may be varied.

3. The apparatus of claim 1 in which said independent means comprises:

a shaft mounted axially through said intermediate chamber and said high vacuum chamber;

a first linkage mechanism engaging said shaft within said intermediate chamber; said first mechanism being operably engaged with said first valve;

a second linkage mechanism engaging said shaft within said high vacuum chamber; said second mechanism being operably engaged with said third valve;

whereby movement of said shaft closes said first valve and opens said third valve simultaneously.

4. The apparatus of claim 1 including a first pivoted lever and a second pivoted lever;

one end of said first lever being disposed for contact with said first valve and one end of said second lever being disposed for contact with said second valve;

counterweights positioned on the opposite ends of each of said levers;

means for varying the position of said counterweights on said levers; whereby said pressure differential required to open and close said valves may be varied.

5. In an apparatus for effecting the evacuation of a chamber to a high vacuum by use of a mechanical pump together with a diffusion pump the combination of:

a first valve communicating between said high vacuum chamber and the inlet to said diffusion pump;

a second valve communicating between said high vacuum chamber and the inlet to said mechanical P p said first valve being disposed to open and close automatically when the pressure differential across said valve reaches predetermined values;

said second valve being positioned in cooperative relation to said first valve whereby said second valve is opened automatically when said first valve closes and is closed automatically when said first valve opens. I

6. The apparatus of claim in which said second valve is positioned adjacent to said first valve;

said valves being disposed for axial movement with relation to each other;

a seating surface positioned on a face of said second valve;

a seating surface positioned on a face of said first valve;

said surfaces being disposed for engagement with each other;

whereby opening and closing of said second valve may be effected by said relative movement of said valves.

7. In an apparatus for effecting the evacuation of a chamber to a high vacuum by use of a mechanical pump together with a diffusion pump the improved combination comprising:

a separate isolation valve chamber connecting to said high vacuum chamber and communicating with the outlet from said diffusion pump and the inlet to said mechanical pump;

a balanced isolation valve positioned within said chamber and communicating with said outlet of 8 said diffusion pump;

adjustable balancing means positioned upon one side of said valve within said chamber;

said balancing means being disposed to cause said valve to open and close at relatively low pressure differentials across said valve while said chamber is under a vacuum;

whereby sequential operation of said pumps on said high vacuum chamber may be effected.

8. A method of operating an automatic high vacuum mechanical valve system utilizing interconnected mechanical and diffusion pumps communicating with interconnected vacuum chambers and comprising balanced valves positioned within said chambers comprising the steps:

manually closing a first of said balanced valves positioned in a first of said vacuum chambers and communicating with the outlet of a diffusion pump and;

simultaneously closing a second of said balanced valves positioned in a second vacuum chamber and communicating with the inlet of said diffusion pump and;

simultaneously opening a third valve positioned in the interconnection between said first chamber and said second chamber and communicating with the inlet of a mechanical pump; operating said mechanical pump thereby reducing the pressures in said chambers and producing pressure differentials across said balanced valves;

continuing said operating until said pressure differentials and the pressures in said'chambers reach predetermined values thereby causing said balanced valves to open sequentially;

simultaneously closing said third valve as said second valve opens.

9. The method of claim 8 in which said first valve is caused to open when the pressure in said first chamber reaches approximately 0.5 Torr.

10. The method of claim 9 in which said second valve is caused to open when the pressure in said second chamber reaches approximately 0.1 Torr.

Claims (10)

1. An apparatus for effecting the evacuation of a chamber to a high vacuum by use of a mechanical pump together with a diffusion pump comprising the combination of: an intermediate vacuum chamber communicating between said high vacuum chamber and the inlet to said mechanical pump; a first valve positioned inside said intermediate chamber and communicating between the outlet from said diffusion pump and said intermediate chamber; said first valve being disposed to open and close automatically when the pressure differential across said valve reaches predetermined values; a second valve positioned inside said high vacuum chamber and communicating between the inlet to said diffusion pump and said high vacuum chamber; said second valve being disposed to open and close automatically when the pressure differential across said valve reaches predetermined values; a third valve positioned inside said high vacuum chamber communicating between said high vacuum chamber and said intermediate chamber; said third valve being disposed to close automatically when said second valve opens; independent means for simultaneously closing said first valve and opening said third valve.

2. The apparatus of claim 1 including means for applying a variable mechanical force to one side of said first valve and said second valve whereby said pressure differential required to open and close said valve may be varied.

3. The apparatus of claim 1 in which said independent means comprises: a shaft mounted axially through said intermediate chamber and said high vacuum chamber; a first linkage mechanism engaging said shaft within said intermediate chamber; said first mechanism being operably engaged with said first valve; a second linkage mechanism engaging said shaft within said high vacuum chamber; said second mechanism being operably engaged with said third valve; whereby movement of said shaft closes said first valve and opens said third valve simultaneously.

4. The appaRatus of claim 1 including a first pivoted lever and a second pivoted lever; one end of said first lever being disposed for contact with said first valve and one end of said second lever being disposed for contact with said second valve; counterweights positioned on the opposite ends of each of said levers; means for varying the position of said counterweights on said levers; whereby said pressure differential required to open and close said valves may be varied.

5. In an apparatus for effecting the evacuation of a chamber to a high vacuum by use of a mechanical pump together with a diffusion pump the combination of: a first valve communicating between said high vacuum chamber and the inlet to said diffusion pump; a second valve communicating between said high vacuum chamber and the inlet to said mechanical pump; said first valve being disposed to open and close automatically when the pressure differential across said valve reaches predetermined values; said second valve being positioned in cooperative relation to said first valve whereby said second valve is opened automatically when said first valve closes and is closed automatically when said first valve opens.

6. The apparatus of claim 5 in which said second valve is positioned adjacent to said first valve; said valves being disposed for axial movement with relation to each other; a seating surface positioned on a face of said second valve; a seating surface positioned on a face of said first valve; said surfaces being disposed for engagement with each other; whereby opening and closing of said second valve may be effected by said relative movement of said valves.

7. In an apparatus for effecting the evacuation of a chamber to a high vacuum by use of a mechanical pump together with a diffusion pump the improved combination comprising: a separate isolation valve chamber connecting to said high vacuum chamber and communicating with the outlet from said diffusion pump and the inlet to said mechanical pump; a balanced isolation valve positioned within said chamber and communicating with said outlet of said diffusion pump; adjustable balancing means positioned upon one side of said valve within said chamber; said balancing means being disposed to cause said valve to open and close at relatively low pressure differentials across said valve while said chamber is under a vacuum; whereby sequential operation of said pumps on said high vacuum chamber may be effected.

8. A method of operating an automatic high vacuum mechanical valve system utilizing interconnected mechanical and diffusion pumps communicating with interconnected vacuum chambers and comprising balanced valves positioned within said chambers comprising the steps: manually closing a first of said balanced valves positioned in a first of said vacuum chambers and communicating with the outlet of a diffusion pump and; simultaneously closing a second of said balanced valves positioned in a second vacuum chamber and communicating with the inlet of said diffusion pump and; simultaneously opening a third valve positioned in the interconnection between said first chamber and said second chamber and communicating with the inlet of a mechanical pump; operating said mechanical pump thereby reducing the pressures in said chambers and producing pressure differentials across said balanced valves; continuing said operating until said pressure differentials and the pressures in said chambers reach predetermined values thereby causing said balanced valves to open sequentially; simultaneously closing said third valve as said second valve opens.

9. The method of claim 8 in which said first valve is caused to open when the pressure in said first chamber reaches approximately 0.5 Torr.

10. The method of claim 9 in which said second valve is caused to open when the pressure in said second chamber reaches approximately 0.1 Torr.

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