US3125283A

US3125283A - Vacuum pump

Info

Publication number: US3125283A
Authority: US
Priority date: 1960-03-24
Publication date: 1964-03-17
Anticipated expiration: 1981-03-17
Also published as: DE1194093B; GB951465A

Description

March 1964 R. ZAPHIROPOULOS ETAL 3,125,283

VACUUM PUMP Filed March 24, 1960 2 Sheets-Sheet 1 INVENTORJ' Renn Zaphiropoulos 23 24 I William A. Lloy fforney March 17, 964 R. ZAPHIROPOULOS ETAL 3,125,283

VACUUM PUMP Filed March 24, 1960 2 Sheets-Sheet 2 Ram Zaphiropoulos William A. Lloyd 57 LJ/M 1 Attorney INVENTORY United States Patent O 3,125,283 VACUUM PUMP Renn Zapliiropoulos, Los Altos, and William A. Lloyd, Sunnyvale, Calif., assignors to Varian Associates, Palo Alto, Calif., a corporation of California Filed Mar. 24, 1960, Ser. No. 17,346 17 Claims. (Cl. 230-69) The present invention relates in general to getter ion vacuum pump apparatus and more specifically, to a novel getter ion vacuum pump configuration in which the pumping speed has been greatly enhanced and facilitates the use of more than one pump operated in series. In addition, the exhaust tubulation is located at the center of the pump to accommodate permanent magnets around the pump. Such high speed vacuum pumps are extremely useful for providing uncontaminated high vacuum as re quired in many devices such as, for example, vacuum tubes, linear accelerators, electron microscopes, ammonia masers and the like.

The present invention provides a getter ion vacuum pump containing an enlarged central exhaust tubulation having a plurality of cellular anode members extending radially outwardly therefrom. The novel shape of the anode members greatly facilitates the utilization of the permanent magnets around the pump.

In the present novel getter ion vacuum pump, a still higher pumping speed may be obtained by means of the novel construction of the pump so that several pumps can be operated in series thus greatly reducing the cost of maintaining expensive high capacity pumps.

The principal object of the present invention is to provide a novel improved high speed, high vacuum, getter ion pump which is useful in providing uncontaminated high vacuums as required in vacuum tubes, linear ac- ;terators, electron microscopes, ammonia masers and the One feature of the present invention is the provision of a novel pump construction having the cathode and anode elements extending radially outward of the central exhaust tubulation whereby permanent magnets may be positioned around the pump thus greatly increasing the pumping capacity of the pump.

Another feature of the present invention is the provision of a novel construction of the pump cathode and anode elements, exhaust tubulation and permanent magnets to facilitate the utilization of several pumps in series whereby still higher pumping speeds and capacity can be obtained.

Still another feature of the present invention is the provision of a novel pump construction having the anode and cathode elements extending outwardly from the cen- =tral exhaust tubulation whereby the impedance that the pump itself presents to the flow of gases therein is greatly reduced.

7 Another feature of the present invention is the provision of a novel pump construction which may be attached directly to the system in which a high vacuum is required.

Other and further features of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein,

FIG. 1 is a partially cutaway plan view showing the novel vacuum pump of the present invention,

FIG. 2 is a cross-sectional view of the structure of FIG. 1 taken along line 2'-2 in the direction of the arrows,

FIG. 3 is a partial cross-sectional view of the structure of the present invention showing several pumps connected in series with the magnets not shown,

FIG. 4 is a perspective view of another embodiment of the present invention,

FIG. 5 is another embodiment of the present invention showing several pumps connected together in series, and

FIG. 6 is a cross-sectional view of FIG. 4 taken at line 66.

Referring now to the drawings of FIGS. 1 and 2, there is shown one embodiment of the novel getter ion vacuum pump apparatus of the present invention. More specifically, a circular shallow cup-shaped envelope 1 having an outwardly flanged rim 2 is provided with a centrally apertured top plate or wall member 3, fixed to the flanged rim 2 of the envelope by, for example, heliarc welding. Envelope 1 and top plate 3 are made, for example, of /s inch stainless steel.

A cylindrical adaptor tubing 3' as of, for example, stainless steel is carried from the apertured top plate 3 and communicates with a central chamber 2' within the circular envelope 1 by way of the circular opening in top plate 3. An annular flange 6 as of, for example, stainless steel is suitably grooved and carried from the end of the adaptor tubing 3 in a vacuum tight manner as by, for example, heliarc welding. An exhaust tubulation 4 has affixed thereto a suitably grooved flange 5 for mating in an air tight manner with the flange 6, the exhaust tubulation being adapted for communication with structures desired to be evacuated by this pump.

Flanges

5 and 6 are pulled together via a plurality of bolts 4 and serve to compress therebetween a suitable gasket 7 as of, for example, copper sheet, thereby forming a vacuum tight seal.

Two cathode plates 8 as of, for example, inch reactive material as of, for example, titanium or zirconium are held against the bottom of envelope 1 and the top plate 3 by means of ceramic insulators 11 which will be more fully described in another part of the specification. Other suitable reactive materials are molybdenum, tungsten, tantalum, magnesium, calcium, strontium, niobium, iron, chromium, nickel, barium, thorium, plus other transition elements of the fourth, fifth, and sixth groups of the periodic table, including rare earths. It is noted that the cathode plate 8 affixed to top plate 3 is centrally apertured to permit communication between central chamber 2 and cylindrical tubing 3'.

Positioned between cathode plates 8 are rectangular cellular anodes 9 formed, for example, of titanium sheet metal strips spot welded together, the circular inner strip serving to form chamber 2. The cellular anodes 9 are carried within envelope 1 in the overall form of an annular shaped honeycomb composed of rectangular cellular anodes 9. These cellular anodes may be individual cell units which may be removed or replaced as the need may arise. The plurality of ceramic insulator assemblies 11 which extend transversely of the cathode plates 8 also fixedly hold the anode 9 at the proper spacing with respect to the cathode plates 8 and are designed to withstand high voltage applied between anode 9 and cathode 8.

These insulator assemblies 11 include an elongated centrally bored dielectric insulator body 12, as of, for example, alumina ceramic, provided with two cup-shaped insulator shield members 13 disposed coaxially of and spaced apart from the sides of the insulator body 12 and extending down over the ends of the insulator body. The insulator shields 13 are preferably made of the same material as the cathode plates 8 to prevent flaking of condensed sputtered cathode material thereon. A connecting rod 14 extends through central bores in the insulator body 12 and insulator shields 13 and thence through suitable openings provided in the cathode plates 8 for receiving, on the ends thereof, suitable retaining rings 15 which serve to fixedly hold together the entire anode cathode sub-assembly. The cellular anode assembly 9 is connected to the insulator bodies 12 by centrally apertured anode headers 16 fixedly secured to the cellular.

anode assembly and cooperating with retaining rings 17 carried from the insulator bodies 12 and capturing the anode headers therebetween.

This insulator assembly is more fully described and claimed in co-pending application, Serial No. 1,377 of William A. Lloyd et al., entitled Glow Discharge Apparatus, now US. Patent No. 3,056,902.

A high voltage insulator 19 extends from cylindrical adaptor tubing 6 and serves to insulate a high voltage lead .18 from the otherwise grounded pump envelope 1. A metal strap. 21 as of, for example, copper is clamped to the conductor 18 by means of clamp 22 and is secured to the anode. frame 9 by a screw or any other desired means.

In use, a high positive potential as of, for example, 3,000 volts is applied to the anode assembly, by way of lead 18, with respect to the cathode plates 8 and initiate a glow discharge therebetween.

-A magnetic field of LOGO-1,800 gauss is applied perpendicular to the cathode plates 8 by a plurality of permanent magnets 25 as of, for example, nickel aluminum steel. Communicating with the permanent magnets 25 are pole pieces 26 as of, for example, iron. The permanent magnets 25 and pole pieces 26 are securely fastened to envelope 1 by brackets 23 fixedly secured to envelope 1 as by, for example, welding. Bolts 24 pass through the brackets 23 and pole pieces 26 and holes in permanent magnets 25 and are anchored therein.

It is noted that pole pieces 26 may be arranged in any desired configuration as, for example, an equal number of pole pieces and permanent magnets 25 as seen in FIG. 1. Another arrangement is the use of two semi-circular pole pieces 26' fitted together around adaptor tubing 3', the advantages in this arrangementbeing that there are no gaps in the magnetic field thus allowing better efficiency. Still other arrangements of pole pieces will become apparent in the description of FIGS. 4 and 5.

In operation the sputter ion vacuum pump apparatus is evacuated to a pressure of approximately 10* millimeters of mercury by, for example, a mechanical pump, not shown. A positive potential as of, for example, 3,000 volts is applied to the cellular anodes 9 with respect to the cathode plates 8. A magnetic field is supplied by the individual permanent magnets of between 1,000 and 1,800 gau-ss. The magnetic field is directed perpendicularly to the cathode plates 8 and a glow discharge is initiated in the space between the cellular anodes 9 and the cathode plates 8.

In the glow discharge, positive ions are created which bombard the negative cathode plates 8 thereby atomizing portions of the reactive plates 8. The atomized reactive material sputters from the plates 8 and the largest percentage thereof is collected on the large area of the cellular anodes 9. Molecules in the gaseous state coming in contact with the freshly deposited reactive cathode material are entrapped thereon and eilectively removed from the gaseous state thereby evacuating the envelope 1 and other chambers communicating therewith through the exhaust tubulation 3'.

The inert gases such as argon are pumped by first burying the argon ions in the cathode plates 8 and then depositing sputtered reactive material from the cathode plates 8 (TI) :over the region where the argon ions are buried thereby permanently trappingthe buried argon.

The view in FIG. 3 is like the view depicted in FIG. 2 of a pump structure with the following changes. The bottom of envelope 1 and bottom plate of cathode 8 are centrally apertured like the top plate 3 and top cathode plate 8, and another cylindrical adaptor tube 27 is carried from the aperture in the bottomof envelope 1. An annular flange is carried from the end of cylindrical adaptor 27 for communication with the top flange of another vacuum pump 35. The magnets, which are not shown, may be held on the envelopes by securing the pole pieces together in any suitable manner. In this manner,

several pumps may be operated in series thus greatly increasing the pumping speed and capacity.

Another embodiment of the present invention is shown in FIGS. 4 and 6. A rectangular pan-shaped envelope 41 having an outwardly flanged rim is provided with a centrally apertured top plate 43 fixed to the flanged rim of envelope 41 by, for example, heliarc welding. A cylindrical adaptor tubing 44 is carried from apertured top plate 43 and communicates with rectangular hollow central chamber 42 within the envelope 41. Envelope 41, top plate 43, and adaptor tubing 44 of the present embodiment are constructed of the same material as their counterparts in FIGS. 1-3.

Flange 49 is aifixed to adaptor tubing 44 and serves the same purpose as the flange 6 in FIGS. 1-3.

Two rectangular cathode plates '48 are provided and are held in position by support rods 40.

Positioned between cathode plates 48 are rectangular anode cells 48 carried in envelope 41, the anode assembly having an 0ver-all rectangular form. The anodes are substantially identical with the anodes 9 of FIGS. 1-3 with the exception of the over-all rectangular form and are supported between cathode plates 48 by high voltage terminals 47.

High voltage is provided to the anodes of the present embodiment by high voltage -leads 47, insulated from otherwise grounded envelope 41 by high voltage insulators 4-6 and positioned in apertures located in the sides of rectangular envelope 4 1.

A magnetic field is applied by a plurality of permanent magnets 45 and pole pieces 45 secured to the envelope 41 by any desired means. It is noted that many desired forms of magnet may be utilized in the present invention, as, for example, cylindrical ferrites 56 positioned between successive pumps as in FIG. 5. The ferrites 56 communicate with pole piece 55 which is rectangular in shape having a central aperture fitting over top and bottom plates of envelope 411.

One advantage in the present embodiment is that by inserting the high voltage lead through an aperture in the rectangular envelope 4 1,. the length of adaptor tubing 44 is shortened by a length equal to the diameter of the high voltage insulator thereby reducing the size of the pumping apparatus. This reduction in size is realized especially when several pumps are stacked together and pumping in series.

-It is noted that various shapesv and designs may be utilized in the internal structure of the vacuum pump. For example, the anodespositioned between the cathode plates may be a series of parallel plates having a large central opening defining the hollow central chamber and a plurality of small apertures, being so aligned, as to form a plurality of defined columns in the series of parallel anode plates. Still further shapes and designs for the anode and cathode members are set forth in co-pending application, Serial No. 673,816, filed July 24, 1957, by Lewis D. Hall et al., now US. Patent No. 2,993,638. The 7' main feature of the present invention is the pie-shaped pump having a large central chamber with. a radially extending chamber containing the anode and cathode members and having the magnetic field parallel to the longitudinal axis of the central chamber and transverse to the radially extending chamber. This general form of pump has. been commonly called a pizza pie pump or, in the case of stacked pumps operating in series, stacked pizza pie pumps.

Since many changes could be made in the above constnuction and many aparently widely diiferent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be. interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A getter ion vacuum pump apparatus including an envelope containing a central hollow chamber, a radially extending chamber surrounding said central hollow chamber and communicating therewith, said envelope having a centrally apertured wall member, a cylindrical exhaust tubulation having an aperture therein, said cylindrical exhaust tubulation carried by said wall member and communicating with said hollow chamber through the aperture in said wall member, a high voltage insulator positioned in the aperture of said cylindrical exhaust tubula tion, a high voltage lead insulated by said insulator, anode member and cathode members disposed in said radially extending chamber with means connecting said high voltage lead to said anode member, said cathode members including a pair of spaced apart cathode members and said anode member disposed between said pair of cathode members, means to fixedly connect said anode member to said cathode members to assure proper spacing therefrom, said anode member and cathode members adapted, when energized by said high voltage lead, to produce a glow discharge therebetween for pumping gaseous matter within said envelope, permanent magnets disposed around said radially extended chamber for providing a magnetic field within said radially extending chamber to enhance the pumping speed of the pump, said cylindrical exhaust tubulation being coupled to an annular flange for communicating with the structure it is desired to evacuate.

2. The apparatus according to claim 1 wherein said magnetic field is directed substantially at right angles to the plane of the cathode members thereby further enhancing the glow discharge.

3. The apparatus according to claim 1 wherein said anode member consists of a plurality of cellular anodes connected together and alfixed to the cathode members, each cellular anode with its pair of cathode members acting together as a pumping canister, said pumping canisters disposed with the plane of said cathode members extend ing outwardly from the central hollow chamber and communicating therewith to readily permit gas access thereto from said hollow chamber.

4. The apparatus according to claim 1 wherein said radially extending chamber is transverse to an axis of said exhaust tubulation and central hollow chamber and said magnetic field is transverse to said radially extending chamber and parallel to said axis.

5, A getter ion vacuum pump apparatus including an envelope containing a central hollow chamber communicating with the structure it is desired to evacuate, an outwardly extending chamber having a pair of mutually opposed spaced apart wall portions circumferentially directed with respect to the longitudinal axis of said central hollow chamber and an end wall connecting the outer ends of said spaced apart wall portions and coaxial with respect to i said central hollow chamber and communicating therewith, an anode member and cathode members disposed within said outwardly extending chamber, said anode {member and cathode members adapted when energized to produce a glow discharge therebetween for pumping gaseous matter within said envelope, means for producing and directing a magnetic field transversely of said outwardly extending chamber for enhancing the glow discharge and said central hollow chamber further communicating with the central hollow chamber of another pump of a like kind wherein the pumps may operate in series thereby enhancing the pumping process.

6. The apparatus according to claim 5 wherein said means for producing and directing a magnetic field includes permanent magnets disposed around said outwardly extending chamber for providing a magnetic field within said outwardly extending chamber to enhance the pumping speed of the pump.

7. The apparatus according to claim 5 wherein said envelope has centrally apertured top and bottom plates, cylindrical exhaust tubulations carried by said plates communicating with said hollow central chamber, said cylindrical exhaust tubulations being coupled to annular flanges for communicating with similar pumps in a stacked manner, said pumps operating in series on the structure it is desired to evacuate thereby greatly enhancing the pumping operation.

8. The apparatus according to claim 5 wherein said cylindrical exhaust tubulation carried from the centrally apertured top plate of the envelope is apertured, a high voltage insulator positioned within said aperture, a high voltage lead connected through said insulator, and means connecting said high voltage lead to said anode member and providing high voltage thereto.

9. A getter ion vacuum pump apparatus including an envelope containing a central hollow chamber, said envelope having centrally apertured top and bottom plates, an apertured cylindrical exhaust tubulation communicating with said central hollow chamber, a high voltage insulator positioned within the aperture in said cylindrical exhaust tubulation serving to insulate a high voltage lead, a radially extending chamber within said envelope surrounding said hollow central chamber, and communicating therewith, an anode member and a pair of spaced apart cathode members disposed within said radially extending chamber, means connecting said high voltage lead to said anode member, said anode member disposed between said pair of cathode members and means fixedly connecting said anode member to said cathode members to assure proper spacing therefrom, said anode member and cathode members adapted when energized by said high voltage lead to produce a glow discharge therebetween for pumping gaseous matter within said envelope, means including permanent magnets disposed around said radially extending chamber providing a magnetic field within said radially extending chamber to enhance the pumping speed of the pump and said cylindrical exhaust tubulation being coupled to annular flanges communicating with similar pumps in a stacked manner, said pumps operating in series on the structure it is desired to evacuate thereby greatly speeding the pumping operation.

lO. The apparatus according to claim 9 wherein said magnetic field is directed substantially at right angles to the plane of the cathode members thereby further enhancing the glow discharge.

11. The apparatus according to claim 9 wherein said anode member consists of a plurality of cellular anodes connected together and affixed to the cathode member, each cellular anode with its pair of cathode members acting together as a pumping canister, said pumping canister disposed with the plane of said cathode members extending outwardly from the central hollow chamber and communicating therewith to readily permit gas access thereto from said hollow chamber.

12. The apparatus according to claim 9 wherein said radially extending chamber is transverse to an axis of said exhaust tubulation and central hollow chamber and said magnetic field is transverse to said radially extending chamber and parallel to said axis.

13. A series of stacked getter ion vacuum pump apparatus including a rectangular envelope containing a central hollow chamber, said envelope having centrally apertured top and bottom plates, cylindrical exhaust tubulations communicating with said central hollow chamber, said exhaust tubulations adapted to be coupled to exhaust tubulations of other vacuum pumps and to the structure it is desired to evacuate, an outwardly extending chamber surrounding said hollow central chamber and communieating therewith, said outwardly extending chamber being transverse to an axis of said cylindrical exhaust tubulation and central hollow chamber, an anode member and cathode members disposed in said radially extending chamber and adapted when energized to produce a glow discharge therebetween for pumping gaseous matter within said envelope, permanent magnets disposed around said outwardly extending chamber for producing and directing a 7 magnetic field transversely of said outwardly extending chamber and parallel said axis for enhancing the glow discharge.

14. The apparatus according to claim 13 wherein said rectangular envelope is apertured on one side, said ape1' ture containing a high voltage insulator positioned within said aperture, a high voltage lead connected through said insulator, and means connecting said high voltage lead to said anode member and providing a high voltage thereto.

15. A getter ion pump apparatus including an envelope containing a central hollow chamber communicating with the structure it is desired to evacuate, an outwardly extending chamber having a pair of mutually opposed, spaced apart wall portions, said outwardly extending chamber encircling the central hollow chamber, an end wall connecting the outer ends of said spaced apart wall portions and coaxial with respect to the central hollow chamber communicating therewith, anode and cathode members disposed Within said outwardly extending chamber, said anode and cathode members adapted when energized to produce a glow discharge therebetween for pumping gaseous matter within said envelope, and means for producing and directing a magnetic field transversely of said outwardly extending chamber for enhancing the glow discharge.

16. A getter ion pump apparatus including an envelope containing a central hollow chamber communicating with the structure it is desired to evacuate, an outwardly extending chamber having a pair of mutually opposed spaced apart circular wall portions, an end wall connecting the outer ends of said spaced apart circular wall portions, said outwardly extending chamber communicating with said central hollow chamber, anode and cathode members disposed within said outwardly extending chamber, said anode and cathode members adapted when energized to produce a glow discharge therebetween for pumping gaseous matter within said envelope, and. means for producing and directing a magnetic field transversely of said outwardly extending chamber for enhancing the glow discharge.

17. The apparatus according to claim 15 further including exhaust tubulation having an aperture therein, a high voltage insulator positioned within said aperture, a high voltage lead connected through said insulator, and means connecting said high voltage lead to the said anode member and providing a high voltage thereto.

References Cited in the file of this patent UNITED STATES PATENTS 2,197,079 Penning Apr. 16, 1940 2,796,555 Connor June 18, 1957 2,983,433 Lloyd et al. May 9, 1961

Claims

1. A GETTER ION VACUUM PUMP APPARATUS INCLUDING AN ENVELOPE CONTAINING A CENTRAL HOLLOW CHAMBER, A RADIALLY EXTENDING CHAMBER SURROUNDING SAID CENTRAL HOLLOW CHAMBER AND COMMUNICATING THEREWITH, SAID ENVELOPE HAVING A CENTRALLY APERTURED WALL MEMBER, A CYLINDRICAL EXHAUST TUBULATION HAVING AN APERTURE THEREIN, SAID CYLINDRICAL EXHAUST TUBULATION CARRIED BY SAID WALL MEMBER AND COMMUNICATING WITH SAID HOLLOW CHAMBER THROUGH THE APERTURE IN SAID WALL MEMBER, A HIGH VOLTAGE INSULATOR POSITIONED IN THE APERTURE OF SAID CYLINDRICAL EXHAUST TUBULATION, A HIGH VOLTAGE LEAD INSULATED BY SAID INSULATOR, ANODE MEMBER AND CATHODE MEMBERS DISPOSED IN SAID RADIALLY EXTENDING CHAMBER WITH MEANS CONNECTING SAID HIGH VOLTAGE LEAD TO SAID ANODE MEMBER, SAID CATHODE MEMBERS INCLUDING A PAIR OF SPACED APART CATHODE MEMBERS AND SAID ANODE MEMBER DISPOSED BETWEEN SAID PAIR OF CATHODE MEMBERS, MEANS TO FIXEDLY CONNECT SAID ANODE MEMBER TO SAID CATHODE MEMBERS TO ASSURE PROPER SPACING THEREFROM, SAID ANODE MEMBER AND CATHODE MEMBERS ADAPTED, WHEN ENERGIZED BY SAID HIGH VOLTAGE LEAD, TO PRODUCE A GLOW DISCHARGE THEREBETWEEN FOR PUMPING GASEOUS MATTER