US3104802A

US3104802A - Unified system vacuum pump

Info

Publication number: US3104802A
Authority: US
Publication date: 1963-09-24
Anticipated expiration: 1980-09-24

Description

Sept. 24, 1963 E. E. ECKBERG UNIFIED SYSTEM VACUUM PUMP 7 Sheets-Sheet Filed Jan. 22, 1962 T i I 27 ZZMNVENTOR.

BY c/F Sept. 24, 1963 E. E. ECKBERG UNIFIED SYSTEM VACUUM PUMP 7 Sheets-Sheet 2 Filed Jan. 22, 1962 5% {M7 INVENTOR.

Sept. 24, 1963 E. E. ECKBERG 3,104,802

UNIFIED SYSTEM VACUUM PUMP Filed Jan. 22, 1962 '7 Sheets-Sheet 3 g 6U INVENTOR. Q BY S /F Sept. 24, 1963 E. E. ECKBERG 3,104,802

UNIFIED SYSTEM VACUUM PUMP Filed Jan. 22, 1962 7 Sheets-Sheet 4 40; 41-9 INVENTOR.

P 4, 1963 E. E. ECKBERG 3,104,802.

UNIFIED SYSTEM VACUUM PUMP Filed Jan. 22, 1962 7 Sheets-Sheet 5 w INVENTOR.

E. E. ECKBERG UNIFIED SYSTEM VACUUM PUMP Sept. 24, 1963 7 Sheets-Sheet 6 Filed Jan. 22, 1962 M ULTIPI! E 5555 E5 Z T Z: i: Z: 2 A

.. 6 M KLAi I ENTOR.

BY X:

Sept. 24, 1963 E. E. ECKBERG 3,104,802

UNIFIED SYSTEM YVACUUM PUMP' Filed Jan. 22, 1962 '7 Sheets-Sheet 7 PHYSICAL STATISTICS LISTING 01 APPLICABLE CONDUCTANCE DATA FOR THE UNIFIED SYSTEM VACUUM PUMP AS RATED AT A CAPACITY AT THE INLET OF 2,000 LITERS PER SECOND :Fzg- 7.

(Ref. line 1-1 FIG.1-A) S35E21??? mm: LOCATION KEY REF.

OF COMPONENT IN u.s.v.PuMP SYMBOL FIG.1-A nmzusxon counuc'rmca MAIN INLET 1n M.V.P.STAGE 1: 5o 16 cm (1) 2250 L/S onrncns 1n M.V.P.STAGE d b9 10 cm (6) 3750 LIS 00mm 151: M.V.P.STAGE o 53 6 cm (1) 325 L/S ION SPACE-axial Ionic v.9.snc1: L 66 12.7 cm) )(1) 5ooo L/S ION SPACE-radial Ionic V.P.STAGE a 66 60 cm news:

1. OPERATING PRESSURE AT ONE MICRON OF MERCURY OR BELOW 1 X 10 1mm). 2. CONDUCTANCE FACTOR I 11.3 L/S per square centimeter. (DRY AIR) 3. SCALE of SKETCH: 1/10 FULL SIZB,APPROXIMATE.

wn'mass 'ro smm'ruam f INVENTOR.

' Ed 1 E. E kb 09 MM); o E i w n c erg J. Mary Eckberg BY 5 B L F United States Patent ice 3,194,802. lJNiFED SYSTEM VACUUM PUMP Edwin E. Eekherg, llerwalk, Conn. (R0. Box 331, 29 Bonair Ave, Bedford, Mass.) Filed Jan. 22, 1962, Ser. No. 167,680 1 Claim. (Cl. 230-45) My invention relates directly to improvement in the unification and systematic consolidation of the molecular type of vacuum pumping device, the gaseous ionic bombarding type of vacuum pumping device, and the positive displacement type of vacuum pumping device, into one integrated or unified system vacuum pump. My novelty includes advanced and modern design of a mechanism which is capable of the production of lower pressures than have heretofore been used or encountered.

The objects of my invention are to produce a complete and an effective unified system vacuum pump which will embody all of the practical, useful, and proven principles of each type of individual vacuum pumping device that is considered, by the art, as being best suited for its function in that particular gas pressure range to be imposed thereto at its respective location in my unified system vacuum pump; and, to produce a unified system vacuum pump of a predictable and specific capacity, performancewise but such that all loss as due to the resistance to gas flow, as encountered in all prior similarly connected vacuum system arrangements, is to be considered as eliminate These and other objects will be presented and become apparent from my specification and the appended drawings in which FIG. l-A is a vertical section view of the unified system vacuum pump from the location of the inlet port of the pump and on through the pump to a location as indicated by the reference line 11;

FIG. l-B is a vertical section view of the unified system vacuum pump from the location as indicated by the reference line 11 and through to the outlet exhaust port location. The drawing of the positive displacement vacuum pumping stage, as a part of this figure, however, being shown in an outline form only;

FIG. 2 is an outline assembly drawing of the invention of the unified system vacuum pump. One form of stand for the assembly is indicated below the outline views, as suggested by the use of broken lines;

FIG. 3 is a schematic drawing of the complete unified system vacuum pump and illustrates the required utility connections and their respective controls for the full and useful operation of the pump. Also shown in this figure is the probable path which the gaseous molecules, and ions, take in their progress through the pump. The probable path being indicated with the use of small arrows;

FIG. 4 is a three-view drawing of the ionic discharge device, the electrode, of the unified system vacuum pump. One view includes a vertical section; the other two views are the top view, and the bottom view;

FIG. 5 is a section view of one particular form of a gasket groove and gasket material as is used in the assembly of the unified system vacuum pump, the one View at A illustrates the seal components as prior to their final assembled and compressed condition. The 'other view at B illustrates the same seal as under the conditions of its final assembly and compression;

FIG. 6 is a reference drawing. It is purported to be a semigraphic drawing of the unified system vacuum pump, as positioned graphically, and as compared to other existing forms of vacuum pump design in the mechanical category. The position has a direct reference, in each instance, to the production of vapor-free lulu-4,80 2 Patented Sept. 24, 1963 vacua for each type of vacuum pumping unit as presented and positioned in this drawing. Pressure values attainable with each type of vacuum pumping unit, respectively, are indicated in terms 'of the absolute pressure, or in millimeters of mercury pressure, and,

FIG. 7 is a drawing of certain essential data related to the discussion, ofi'ered below in the specification, of conductance observations for the unified system vacuum pump. The discussion is a part of this specification. It appears in columns 91l. T his drawing presents certain physical statistics listing and is schematically illustrated; including a table with footnotes.

The unified system vacuum pump comprises a grouping and an adjoining of several shell type and plate type casing members that may be castings modified by suitable machining: or, case member 8 is a hollow shell type cylindrically shaped casting, one end of which is open and flanged, the other end being of a dome shape and provided with webs as supporting members for the hub 9 as part of the casting, as provided. The hub 9 is bored open to form and provide the bearing boss 10. The outer lateral face of the hub is fiat and it is drilled and tapped to provide blind tapped holes, 12. A gasket groove 13 is also formed in this lateral face of the hub '9. A gasket material O-ring 14;- is inserted into the gasket groove 1-3. A cylindrical end-cap v15, which is slightly dished at its central portion, provides the closure member as applied over the'open bore of the hub 9, thus insuring a seal at that location. Holes 16 are drilled through the flat rim edge of the end-cap 15. These holes, 16, match the pattern of the tapped holes 12 in the hub. Cap screws 17 are provided and fasten the endcap 15 to the hub 9; the screws being firmly screwed into r the tapped holes, 12, as first however, passing through the holes 16 of the end-cap and then into the tapped holes 12. The flange 11 of case member 8 is positioned concentrically, and abuts, to the first member of an aggregate of cylindrical stator plates, 18, 19, 20; and 2.1. These plates form the stator group for the hard vacuum molecular pumping stage of the unified system vacuum pump. The mechanical bonding of the case member 8 to the first stator plate 18, is effected by the use of cap screws 22. Through holes 23 are drilled through the flanged edging of case member 8. Also, blind tapped holes, 24, are drilled and tapped into the stator plate 18. Cap screws 22, are screwed into place in the blind tapped holes 24 and hold the casing, 8, in place. Provided also on the fiat face of the flange ll of case member 8, as abuts stator plate 18, is gasket groove 25, and gasket material O-ring 26, which oifer a vacuum tight seal at this location. The two cylindrical stator plates is and 21, respectively, are to be observed as the outer stator member plates of the plate aggregate-or, 18 through 21, inclusively. These two stator plates are extended radially but of a somewhat thinner wall structure as extended. These radially extending walls of the two

cylindrical stator plates

18 and 21,-extend outwardly to skirt 27. Skirting member 27 is a casting and it has provided thereto as a part of its original cast a tubular inlet port member 28. This inlet port tube is provided, in turn, with a flange 29' with through holes 3%, and gasket groove 31. The latter gasket groove is formed in the upper face of the flange 2 9, or the top surface. It will be used to receive a suitable gasket material O-ring insert when the completed pump is to be connected to a work piece, as attached thereto, for certain vacuum development or production process. No specific work piece or process is illustrated. The obvious use, and the multi-purpose adaptation of the unified system vacuum pump obviates such illustration. The two inner peripheral edges of the radially extended stator plates,

3 18 and 21 respectively, are joined to the outer flat and brim-like surface of the skirt 27. Cap screws 3d pass through holes 33 drilled through the two edges of the

plates

18 and 21, they are then firmly fastened into the tapped holes 34 that are of a similar pattern to holes 33, and thus hold skirting member 27 securely to the two stator plates as extended. At this adjoinment location a vacuum tight seal is required. It is provided between

plates

18 and 21, and the skirt member 217, by the gasket groove 35, machined in the lateral flat surface of the extended stator plate 13 and 21, the gasket material O-ring 36, inserted into the groove. The unique form of gasket groove as adopted for the seal method in the present case, or throughout the entire sealing locations of the unified system vacuum pump, has proven superior to former conventional gasket groove design. The present method eliminates entrapped air bubbles, a problem with the single seal installation. The hard vacuum molecular pumping stage of the unified system vacuum pump also includes the hollowed and perforated shaft section 37, which is drilled to provide the perforations 38, and these holes, as drilled, and as provided, are of a greater mean diameter than the actual wall thickness of the shaft at their respective and several locations through the shaft 37. Likewise, the corners of these perforations are well munded to present a relatively smooth orifice in each instance. Shaft section 37 is driven by the electric motor 39, a squirrel-cage type of motor. This motor is enclosed en vacua in its casing member 8. Two main ball bearings 44) are provided and are contained in their respective bearing bosses, 41, supporting shaft section 37 in a freely rotable manner. The bearing bosses are located concentrically upon the outer lateral faces of the two stator plates, 18 and 211, respectively. The perforations 38 are located at points along the hollow shaft section 37 that closely correspond to the several termini of the conventional type of molecular pumping grooves 44, cut into the recesses 45 of the four

cylindrical stator plates

18, 19, 20, and 21; these several molecular pumping grooves being of spiral pattern in form. Rotors 46 are provided, as rotatably mounted on shaft section 37, and secured thereto by the keys 47, provided and inserted into their respective key-ways, 48, that are milled into the shaft at the required locations. Secondary inlet ports 49 are formed and are located as provided at the termination of each set, or each pair, of spiral grooves, at their outer termini. The inlet orifices extend radially from the paired molecular pumping grooves. These secondary inlet ports, 49, provide a free and an unobstructed communication, or passageway, from pair of spiralled grooves out to and with the receiver space, 50, which surrounds the hard vacuum molecular pumping stage, or group; specifically,

that space 56 as is bounded and formed by the circumferential edges of the

plates

19 and 20; the extended Walls of the two radially extending plates 18 and 2.1; and the inner surface of the skirting member 27 with its main inlet port tube, 28, respectively. This particular space 5% is designated as the hard vacuum inlet receiver, or chamber, of the unified system vacuum pump. Shaft section 37 extends through and beyond both of its supporting ball bearings, 40. The portion of the shaft section 37 which extends toward the electric motor side of the pump is solid in form, and of somewhat smaller diameter; it provides the shafting requirement for the rotor component, 39-A, of the electric motor 39. This solid portion of the shaft section 37 also extends through the rotor component 39-A and beyond, terminating within the limits of the bearing boss .10, as provided within the hub 9. Ball bearing 51 is a self-aligning type of bearing, and is provided in the boss 10 supporting the end of the solid portion of the shaft section 37. The

other end of the shaft section 37, or that end which protrudes through and beyond stator plate 21, retains its hollow form; and at its open end, 53, a flexible coupling 52, is provided and firmly fastened to shaft section 37. This open end 53 is designated as the outlet port of the hard vacuum molecular pumping stage of the unifled system vacuum pump. A shell type casing member 54, of cylindrical shape, is abutted concentrically to and adjoining with stator plate 21, at the outer lateral face of the latter plate. One end of case 54 is of a dome shape; the other end being open and provided with a flanged edge, 55. This abutment is secured by the use of substantial cap screws 56-, provided and inserted through the holes 57 that are drilled through the flange 55. The cap screws 56 are then firmly screwed into the blind tapped holes 58 that are provided in the stator plate 21. A vacuum tight seal provision is required and is accomplished at this location, or at the contacting surfaces of the flange 55 and the outer lateral face of the stator plate 2.1, by gasket groove 59 machined into stator plate 21, and gasket material O-ring 60 which is provided and inserted into the gasket groove. The cylindrical casing member 54 extends axially. At its dome shaped end casing member 54 is provided with two tubalar extension arms, these being formed as part of the original casting of this member. The two extension arms are: extension arm 61,. centrally located or coconcentric with the principal axis of the pump shafting;

and extension arm 62, located parallel and above exten-v sion arm 61. The latter, extension arm 61, is termed the central extension arm for reference purpose. Both

extension arms

61 and 62 are provided with flange members 63, and these flanges are drilled to provide bolt holes 64, and. machined to provide gasket groove 65 on their outer lateral faces, respectively, of each flange. Later, upon final assembly of the unified system vacuum pump, the gasket material O-ring 105 isprovided and inserted into these two gasket grooves, or gasket groovesv 65 of flanges 63. Within the casing member 54, at its end nearer to the hard vacuum molecular pumping stage,

a space, 66, is allotted to contain a certain arrangement of ionic vacuum pumping paraphernalia. This space, 66, is designated as the ionic vacuum pumping stage, or gaseous discharge vacuum pumping stage, of the unified system vacuum pump. The following components are provided for this ionic gaseous pumping stage: two cathode elements, or, cold cathode 67 and auxiliary bombarding cathode 68; the two being spaced apart axially with a respect to their common supporting lead wire 69. The two

cathode elements

67 and 68, are mounted upon and centered by the supporting lead wire 69, and this lead wire is provided with a glass-to-metal seal 70, formed.

about it; the lead wire being also provided with glass beading 71, which is formed from the g'lass-to-rnetal seal 70 and down to the vertex of the hollow type of cold cathode 67. A dielectric sleeve 72 is slipped over the glass beading 71 and imparts a thermal, a mechanical, and an electrical protection to the glass beading. Two additional lead wires, 73, are similarly provided. Lead wires 73 will support the heater coil, 74, as provided and welded to the lower ends of the two lead wires 73. This heater coil, 74, is considered as the ion source for the ionic gaseous discharge vacuum pumping stage, when the latter stage is in operation. The form of the outer edge of the glass-to-metal seal 70 is tubular. Metal tube, or sleeve, 75 is joined with the tubular shaped glass end of the glass-to-metal seal 70. The metal sleeve, 75, has threads provided about its lower end, 76', and these are received into the threads of the tapped portion of threaded bushing 78. A sealant material is applied to the tapped threads 77, of threaded bushing 78. Casing.

member 54 is drilled and tapped to provide the tapped hole 79, which receives the threaded end 76, of.metal sleeve 75. Permanent magnet 80 is a modified horse- 7 shoe, or U-shaped magnet, as provided. The magnetic element 80 is welded onto supportrod 81, which is provided with threads, 82, at its other end. The rod 81 is screwed into tapped hole 83, which is drilled and blind tapped into stator plate 21 of the plate aggregate. Magnet fill, for the greater part, surrounds the electrode or cathode components; it is especially positioned thereabout so as to furnish a maximum of magnetic field as applied to the auxiiiary bombarding cathode, 68. (Note: The paraphernalia, as has been described, immediately above, comprising the assembly of one bombarding electrode, and magnet with support rod, must necessarily be provided in pairs. A minimum of one pair, or two sets, is the required number of these assemblies necessary to provide for one single and complete discharge circuit of an ionic discharge, en vacua. Additional paired assemblies may, optionally, be used and provided. They are to be considered as reserve units, however.) The remaining space of the interior of the shell type casing 54, is closely occupied by a second and a smaller molecular vacuum pumping stage. This molecular vacuum pumping stage is provided in a similar form as to the hard vacuum molecular pumping stage as outlined and described in the foregoing. This second stage differs slightly from the first stage, as described, in that its inlets, 85, enter into the lateral face and extend into and through all plates but one, of the aggregate of stator plates, 86, as are provided for this secondary and intermediate molecular vacuum pumping stage of the unified system vacuum pump. Stator plates 85 are paired and are similar; their diameter being limited so that they closely slide into the confines of the casing 54, and fully occupy the spacing of the case at this locationin the radial sense. The arrangement of this secondary molecular vacuum pumping stage is designated as the intermediate molecular vacuum pumping stage of the unified system vacuum pump: the stator plates 86 are provided, having molecular pumping grooves 87, of spiral pattern, and of conventional type. These grooves 87 are formed in the recesses 83 of the paired stator plates 86. Rotors 39 are provided and used, being rotatably mounted upon and fastened to shaft section 90 provided as hollowed and as perforated. Key 91 is inserted into its key-way 92, milled in the shaft section 90'; the key 9'1 provides the bonding of the rotors 89 to the shaft section. This shaft section, 90, is supported on two ball bearings Q3.

Shaft section 99 is closed, or sealed olf, at its end which is directed toward the hard vacuum molecular pumping stage; the sealed end of the shaft section 90 being received and fastened into the flexible coupling 52. The flexible coup-ling, 52, is of an open or skeleton design of structure. it provides a reliable mechanical junction and eifects the union as required between the two shaft sections 37 and 9%), respectively. The both shaft sections are thusly held in a relatively true alignment, one with the other. The flexible coupling 52 also transmits the power and the motion of the driven shaft section 37 to the other shaft section 90'. The open and skeleton design of its structure presents but negligible resistance to the gaseous molecules as issue from and pass through the outlet 53 of the hard vacuum molecular pumping stage. The other end of the shaft section 9i? extends on through ball bearings 93, and the end of the shaft at that location remains tubular of form as provided by the hollowed and perforated character of this shaft section. A pinion member 94 is press fitted over the open end of the shaft section 90, and the slots 95 are cut through matching portions of the shaft section beneath the hub of the pinion unit, and through matching portions of the shaft section beneath the pinions hob. These slots 95, mated, provide outlets for the intermediate molecular vacuum pumping stage of the unified system vacuum pump; and they are so designated. Pinion 94, as provided is the sun gear and central drive component of a well balanced planetary set of gearing. This planetary set of gearing, as provided, comprises: pinion 94; idler gears 96; and, ring gear 97. The latter, or ring gear 97, has teeth internal to its brim; the teeth extending radially (inward) from the brim engaging with idler 5 gears 96, as provided and assembled. The idler gears 96 also engage with the pinion '94. 'In the case at hand, this set of planetary gearing serves a dual purpose. In addition to its function as a mechanical power coupling, it also functions as a speed reduction mechanism. The gear ratio of the planetary set of gearing presents an arnangement that imparts a reduced rate of rotation as from the one shaft section 99, to a solid shaft section 98, provided as extending axially from the ring gear component of the planetary set of gearing. The solid shaft section 98 is the drive shaft member of the conventional rotary sliding-vane vacuum pumping stage, 99; this rotary sliding-vane vacuum stage being a completely sealed and encased standard unit of available equipment. It is to be procured from several manufacturers. Its mechanism is submerged and sealed in oil which has a relatively low vapor pressure characteristic, usually. The unit operates at relatively low rotational speeds. Nominally this is approximately between about 32 0 r.p.m. to a maximum of 600 r.p.m. The stage is provided with both inlet and outlet ports. The former is usually a tap on the top of the casing, and the latter, or exhaust port, is a poppet-type escape valve port that is located so as to have the escaping gas below the mean oil level surrounding the mechanism. Casing 109 is provided, a casting, to enclose the entire mechanism of the rotary slidingvane vacuum pumping stage, or unit 9'9. This casing member 101 is provided with two tubular extension arms, 101 and 102, respectively. Each extension arm at its open end is flanged with flange members 110%; the two flanges being drilled to provide the bolt holes 64-A. Extension arm 101 is located over the shafting position, concentrically, and it meets in a true alignment with the extension arm 61, similarly positioned, on and from casing 54. Therefore, flanges 1013 will both meet and mate with flanges: 63, respectively. The assembly of these paired flanges with respect to their vacuum-tight adjoinment requires the use of the aforementioned, and provided, gasket material O-ring 105 as inserted into the gasket groove 65 of flanges 63. These paired and abutted flanges, so provided, are fastened together by means of machine bolts 106, and machine nuts 107, respectively. The machine screws 106 pass through bolt holes 64-A, in flange members 103'. Machine nuts 7 are screwed onto the machine screws thus bonding the paired flanges. Base plate 108' is provided, and casing 100* is lowered onto it and fastened with seal provisions. Gasket material packing, 1-10, is used, as provided, and fills the channel or gasket groove 109 that is milled in the base plate 108. This will provide the required vacuum tight sealing at this location. Cap screws 11.1 are used; the cap screws pass down through holes 112 drilled through the lip or flanged base edge of case 100, and this flanged base edge, 113, a part of the original casting of the casing member 100'. The cap screws 1-11 are firmly screwed and fastened into the tapped holes 1114 that are drilled and tapped into the base plate 108. The base plate 168 is also provided with mounting through holes, 115, drilled through the base plate and located apart and out from the lipped flanged edge of the base of case 100. The exhaust port 104, of the rotary sliding-vane stage 99 requires a free vent to the atmosphere. This vent, and the seal for it as it passes upward through the casing member 101], must be completely sealed from that region that represents a real difierentiati'on of gas pressure within casing 100 during operation; or, from the exhaust outlet port of the rotary sliding-vane stage 99', there can be absolutely no communication to that region of spacing which surrounds the rotary sliding-vane stage, sealed and contained within casing 109. The former, the exhaust port of the rotary sliding-vane stage may well be at or above atmospheric pressure, during operation whereas the latter, or that space surrounding the rotary sliding-vane vacuum pumping stage and within the confines of the casing 100, may be at a pressure in the order 7 of but a few microns of mercury, absolute pressure, during operation. This is a moderately good vacuum condition for that particular location in the unified system vacuum pump (e.g. the forepressure to the secondary molecular vacuum pumping stage), and it is certain that any in-leakage at this point could cause failure or proper operation of the pump. Hence, to effect this sealed condition, yet to provide for the free exhaust for the rotary sliding-vane stage to the atmosphere, as required, a use is made of the tapping at the exhaust port, 104, of the rotary sliding-vane vacuum pumping stage. This tapped port is standard to type of stage, and is usually provided by the manufacturer in the design of such vacuum stage equipment. A nipple, 117, is provided and it is screwed into the tapped exhaust port 164. Above the exhaust port 10 in the casing member 109, a hole of relatively large diameter is drilled and tapped, and this hole tapping, 118, is used to receive threaded bushing 119, which is provided with gland characteristics such that the packing sleeve 121, provided and inserted into the bushing 119, will seal the nipple and the bushing members from inleakage of atmospheric gas. Threaded bushing 119, has a flanged top. This flanged top of the packing bushing 119, may be used to hold a vent dust-cap, 120; or, alternately by either choice or safety policy, the exhaust may be provided by standard plumbing from nipple 117, as continued from the unified system vacuum pumps location, out to the free atmosphereexterior to the laboratory or shop. A formed packing washer, 122, is provided and placed over the shaft section 98, inside of extension arm 10 1 of casing 10%; this formed packing material 122, as provided, hermetically seals off the local regions, or that of the shaft packing location of the rotary sliding-vane vacuum pumping stage, and the planetary set of gearing. The pressure at both sides of this packing 122 is equal during operation of the pump. However, packing member 122 is indicated as being advisable in view of some slight, yet possible seepage of oil as might possibly issue from the shaft seal of the rotary slidingvane vacuum pumping stage. Electrical feed-through terminals are required for power electrical line feed through causing 8 to electric motor 39. These feedthrough terminals, 123, are provided in a manner that is quite similar to the technique used in the glass-to-metal seal 70 as previously described for the ionic electrode lead wire, 69, of the ion gaseous discharge electrode. The feed-through terminals 123 consist of: Lead wire 125, and metal sleeve 124, which are sealed to glass to form feed-through terminal 123, also through hole 126, in case 8, receives the metal tube or sleeve 124. Through hole 126 may optionally be a tapped hole, in which case sleeve 124 would necessarily be threaded'but to minimize proper sealing and fastening of the sleeve 124 to the casing 8, the indicated method used is welding the sleeve 124 to the case. The through hole 126 is drilled at locations that are close to the field winding terminals of the motor, at 3-9-B, and the juncture of the lead wire 125, to the motor field winding, is made and soldered and insulated with electricians tape. The finall assembling and adjustment of the components of the unified system vacuum pump is completely as proper torque is applied to each of the several through bolts 127; these of self sealing simpledesign. Through bolts 127 are provided to bond together all the

aggregate stator plates

18, 19, 20, and 21, which have holes, 128, drilled for the bolts. Nuts 129 are provided and tightened over both ends of the through bolts 127, securing all cylindrical stator plates. The self-sealing cap nuts 130, each having a packing groove 13 1, and packing material washer 132 as parts of their respective assembly, as procured, effect a vacuum tight seal over each respective bolt end with its nuts; thus, both ends of the through bolts 127 are secured and sealed, respectively. Similarly, through bolts 133 are provided and are used to bond all stator plates 36 of the intermediate molecular vacuum pumping stage.

. 8 Through holes, 134, are drilled through all the stator plates 86, and the bolts 134 pass through these holes as provided. Nuts 135 are used at both ends of bolts 134;

these several nuts being fastened and tightened over. respective ends of the provided through bolts 134. Nuts 10'? are screwed and tightened upon machine bolt or machine screw 106; with O-ring material gasket 105 inserted into its gasket groove 65, of flanges 63. Likewise, all cap screws are tightened: cap screws 56 of the casing group; cap screws 17 at the end-cap of the motor case 8;

cap screws 32 of the skirting components, and; cap screws 111 of casing 109. Also, cap screws 22 of the motor case flange. The completed and assembled unified sys'- tem vacuum pump is positioned and level. Optionally, it may be lowered and positioned into a cradle-type of stand and secured therein, using through holes 115 in the base plate 108 for this purpose. Electric power supply connections may now be provided as shown, schematically, in the drawing of FIGURES. Three phase power is supplied to the motor terminals 123; a cutout being provided with thermal overload protection, The latter is the motor switch, as illustrated in the'drawing of FIGURE '3. Single phase electric current is to be provided for the ionic bombarding electrodes (one pair, or two) of the ionic vacuum pumping stage contained in space 66. The power is connected to terminals 69; but

is fed from a secondary winding of a single phase stepup transformer. The primary winding of the transformer, in turn, is connected to the line with a cut-out provided with thermal overload protection. The latter, in effect, is a control switch. A current control, or choke, is in series with the primary of the transformer and permits variable current to be passed, with full control, to the primary of the transformer. The selection of the materials used for the construction of my novelty, the unified system vacuum pump, were governed in general by consideration given to such factors as: structural and mechanical characteristics; thermal conductivity and thermal expansion characteristics; electrical conductivity and dielectric property; resistance to abrasion, and, low or negligible oxidation inclination. Also; the minimum of occlusion of atmospheric gases, and with the property of being readily de-gassed of occluded gas under vacuum condition. As some examples of the materials which I have selected the following is cited: the shaft sections are of high carbon, or stainless steel; the rotors are of magnesium-aluminum alloy; the grooved stator plates are all of aluminum cast material, with a high degree of purity as is attained with an injection process of cast work; the skirting member with its port tube extending therefrom is also an aluminum casting, with some moderate bronze component; the several flange members are of high carbon or stainless steel, and, all components in the region of the ionic discharge vacuum pumping stage are essentially non-magnetic, withthe exception of the few items, as follows. The mag not itself is of course a permanent magnet. The cathode or electrode elements .are nickel and slightly magnetic. The heater coil at the mouth of the auxiliary cathode, used in bombarding, is tungsten with special emissive coating applied thereupon. The latter coating is chosen for its composition of several of the alkaliearth materials such as barium, strontium, and calcium;

Usually prepared in the carbonate form in a binder solution or mixture; this material will reduce to its several oxides when heated in vacuo. These oxides are profuse in the liberation of electrons under the conditions of.

operation in the pump. A heavy applied coating of this same material is especially applied in the hollow cathode; this to be considered a gas clean-up agent under the conditions of operation. The gasket material O-rings are synthetic rubber; it retains its desired properties at elevated temperatures and has a minimum of vaporpressure under such conditions. The cradle-type stand, if this type is used, is an aluminum casting. The machine 9. is to be grounded. I have provided mine with a grounding lead, to earth, as a part of the electrical installation. Nominal operating speeds for the unified system vacuum pump are approximated at 10,000 r.p.m. and 475 r.p.m., respectively; the former speed as applicable to the two molecular vacuum pumping stages, as coupled together, and the latter speed as applicable to the average for the rotary sliding-vane vacuum pumping stage which is driven by the ring-gear component of the planetary set of gearing as described above. Slower rotational speeds have been found to be effective for vacuum work, but since the capacity of the molecular stages is directly in the order of the peripheral velocity of the rotors, the above level of speed appears most satisfactory from all practical viewpoints. The use of velocities higher, although successful mechanically, have not given evidence of merit since the conductance problem, say at 20,000 r.p.m., appear to be less feasible than the simple enlargement of and the modification of the basic design as specified; or, as an alternate method, use of two identical unified system vacuum pumps in tandem or parallel arrangement.

(It becomes quite essential at this point that I present certain remarks that have the most important effect upon the success of the unified system vacuum pump, and relative to these matters the following is presented as a dissertation.

Conductance of a gas through a pipe, tube, or orifice is stated as being gas flow rate. The conductance is equal to the reciprocal of the resistance to gas flow which the conductor offers to the flow rate of the gas. This resistance obviously is a matter of geometry of the conductor itself; whether it be a tubular member, or only a hole or an orifice. The operating pressure level, or the range of pressure levels, and the relationship which exists between these and the geometry of the conductor, are of vital importance, and they are to be considered as having a valid application to the design of any efiicient vacuum system and any unit vacuum pump. In the following we will enlarge upon the salient principles involved, and their respective influence as governed the original design of the development of the unified system vacuum pump.

Pertinent to the full rated capacity or pumping-speed of a vacuum unit or stage, it is present and standard practice to provide an inlet port thereto having a mean internal diameter such that the cross-sectional area at that port, considered as an orifice or throat, results in a calculated gas flow-rate, or a mean conductance, equal to or approximating the full rated capacity of the vacuum pump unit or stage itself. In actual practice, however, when this physical condition is carefully evaluated for the actual fiow-rateand, obviously, a deduction made for a similar calculated conductance for the connecting tube which must run from the unit to the work piece being evacuated; the effective pumping speed at the work piece location is observed as being but a fraction of the given rated speed of the vacuum unit at its inlet port. Indeed, this situation is well known to exist, as also is the method of some improvement to partially oif-set the loss. Larger and short connecting tubes are indicated and recommended.

When two or more stages of vacuum pumping equipment are to be connected together, and one or several auxiliary items added to form the completed system (e.g. tubes, vessels, valves, and trap devices), the principles of conductance apply. And, when these components are finally connected and operative, the resistance to gas flow of each separate component is additive to the total resistance of all the other components as added. Therefore, in most cases, only a small percentage of the rated speed or capacity of the vacuum pump is made available out at the work piece location.

For these reasons, therefore, larger and faster unit vacuum pumps having increased inlet ports and connecting-control members. diametrically, have been stressed in recent years. Especially so in the case of the dynamic vacuum system in which a certain gas evolution,even a definite in-leakage-must be encountered. This, in general vacuum system design, is pre-determined and provisions are made for the throughput of gas. Also, it is general practice to make a so-called system allowance safety factor modification which in the majority of cases amounts to a system several times larger than the specific flow-rate might appear to require.

Thus far I have presented remarks that bear on the matter of flow-rate as through orifices, tubes, and general vacuum system components generally. Now, however, I wish to add to that with several similar remarks generally related to the range, or ranges, of gas pressures as are encountered as the absolute operating pressures in actual production work both in the laboratory and industry. The topic is essentially related to the foregoing, and its use and its application to the new design of the present novelty, the unified system vacuum pump, makes the presentation of this subject a useful one.

The actual operating range or ranges of the gas pressures in the vacuum system has its direct influence upon the conductance considerations given to the vacuum system components; each taken as a separate conductor, respectively. In all vacuum production, the gas molecules to be handled, and which will actually be pumped, are

considered generally as being in one of two distinct classifications or groups. The first group is the so-called viscous state of the gas molecules; and the second group or classification is the molecular state of the gas molecules. The accepted transition level as between the two states, pressurewise, is said to take its place at or near the one micron of mercury pressure level, absolute. Therefore, at pressures above this level the molecules behave in a viscous manner in which collision is statistically frequent, as between molecules themselves; and the mean-free-path is relatively small of magnitude. Below the transition level as the gas enters that state termed the molecular state collisions between gas molecules becomes far less frequent than impingement of the molecules upon and with the conductor or vessel. The mean-free-path has vastly increased, and chances of collision between molecules is far less likely than impingement with the interior walls of the gas conductor or vacuum vessel.

Modern vacuum technique for the greater part involve working with gas pressures well below the transitional level. Indeed it is now common practice to encounter pressures which approximate less than one-billionth of the earths atmosphere. (Note: This is rather less than 0.000001 millimeter of mercury pressure, absolute.)

One definition of the mean-free-path of a gas is accepted as being equal to the average distance which will be traversed by the molecule under the conditions of its measured and known pressure before the molecule will collide with another molecule.

From the remarks and the observations in the foregoing it is indicated that the condition of a gas in the molecular state will require large conductance provision to all ports, tubes, and components of control. And, as the pressurelevel may be lowered, in operation, the required conductance limits are increased. The key, of course, is the mean-free-path. As one example of this: the mean-free-path of dry nitrogen at the transitional level of one micron of mercury pressure, is. approximately 6.5 centimeters, or, 2.33 inches. However, at a pressure level but one decade lower, or rat one-tenth micron of mercury pressure, the mean-free-path increases to 65.0 centimeters, or, approx. 24.0 inches. To cite the two conductor diameters for the two conditions as stated, respectively, will better serve to illustrate this point; the first conductor of ideal inside diameter to satisfy the conditions of one micron of mercury pressure would be approximately three inches (7.6 centimeters); the other conductor having the ideal diameter to satisfy the conditions of a pressure one decade below the first, o-r one-tenth of one micron of 1 l mercury, would approximate thirty inches 'for its inside diameter (76.0 centimeters), respectively.

The task of presenting ideal conductance conditions under the conditions of the pressure cited in the foregoing would appear quite impossible; it is admittedly an insuperable problem. And, too, it is admitted that presentday paraphernalia for the production of hard vacuum is a creditable advancement it is this Workers opinion that a full and realistic recognition of the conductance problem has not been fully extended in prior art. His attempt to so meet the conductance problem from his practical experience, and his theory of design, has contributed for the greater part to the successful and practical reduction to practice of his novel unified system vacuum pump.

In summary, therefore, the salient points as have been covered in the above relating to conductance matters and certain pressure ranges; and their respective relationship to one another; especially with a regard to the method of juxtapositioning of the stages of his pump in order to minimize gas flow resistance; these have governed his design. Or, conversely, he has kept an extreme high conductance in mind at all times; specifically providing in his device at all regions and at all stages wherein pressure below one micron of mercury is encountered during operation of the pump, conductances from one point to another that exceed the flow rate of the gas under that condition of pressure. The juxtapositioned stages, and compartments as from the outlet of the one to the inlet of the other, respectively, have conductance values exceeding the conductance values of either the inlet port orifice or the outlet port orifice leading into and from that stage or compartment, respectively. In this manner the conductance of the entire unified system vacuum pump is at a maximum.

Having thus described my invention, that which I wish to secure by Letters Patent is covered in the following claim:

A unified system vacuum pump comprising a plunality of vacuum pumping stages in series and arranged in a juxtaposed manner; said plurality of vacuum pumping stages being, specifically, a primary hard vacuum rotary molecular pumping stage, a secondary hard vacuum ionic gas discharge pumping stage, a tertiary high vacuum rotary molecular pumping stage, and a quartan forevacuum rotary sliding-vane pumping stage; radially extending side-walls on the aforesaid primary hard vacuum rotary molecular pumping stage; flanged peripheral edges on the aforesaid radially extending sidewalls; gasket grooves formed in the flat lateral inner faces of the aforesaid flanged peripheral edges, said gasket grooves being of a circular pattern; a skirt member casting with a tubular and flanged inlet port as part of said casting, said inlet port being the main inlet to the aforesaid unified system vacuum pump; flanged and laterally flat outer faces on the peripheral edges of the aforesaid skirt member casting, said flat outer faces meeting with, and abutting, the aforesaid fiat lateral inner faces of the aforesaid flanged and gasket grooved peripheral edges of the aforesaid radially-extending side-Walls; an annulus hard vacuum compartment surrounding the aforesaid primary hard vacuum rotary molecular pumping stage, said annulus hard vacuum compartment as being bounded, respectively, by the inner surfaces of the aforesaid radially extending side-Walls, by the inner surface of the aforesaid skirt member casting, and by the peripheral surface of the main body of the aforesaid primary hard vacuum rotary molecular pumping stage, respectively; inlet orifices for the aforesaid primary hard vacuum rotary molecular pumping stage, said inlet orifices positioned radially about the main body periphery of the aforesaid primary hard vacuum rotary molecular pumping stage, and said inlet orifices leading from the aforesaid annulus hard vacuum compartment inwardly to and through the aforesaid primary hard vacuum rotary molecular pumping stage; a common axis concentric to axially through and extending from both sides of the aforesaid tertiary high'vacuum rotary molecular. pumping stage, and a third shaft section located axially and extending from but one side of the aforesaid quartan forevacuum rotary sliding-vane pumping stage; a flexible coupling joining the aforesaid first and second shaft sections of the aforesaid common shafting system, said flexible coupling being located centrally within the aforesaid secondary hard vacuum ionic gas discharge pumping stage; a planetary set of gearing joining the aforesaid second and third shaft sections of the aforesaid common shutting system, said planetary set of gearing having a pinion mounted on the end of theafioresaid second shaft section, the said planetary set of gearing having a plurality porting the aforesaid second shaft section of the aforesaidcommon shafting system; two small sized ball bearings rotatably mounted and supporting the aforesaid third shafit section of the aforesaid common shafting system; the aforesaid large sized, medium sized, and small sized ball bearings, respectively, being co-axi'allly located; an electric motor of squirrel-cage type having a rotor and a stator, said rotor mounted directly upon the extended portions of the aforesaid first shaft section of the afore: said common shafting system extending from the outer side-Wall of the aforesaid primary hard vacuum rotary,

molecular pumping stage, said motor being concentric to and, engaging said shaft section, said motor being capable of mechanical speed variables as the resultant of certain pro-determined and pre-imposed electrical frequency input variables; a vacuum tight motor casing, said casing closed at its outer end, said casing open land flanged at its opposite inner end, said flange 'being flat laterally; a gasket groove formed in the aforesaid fiat lateral flange of the aforesaid electric motor vacuum tight casing; an encasement of the aforesaid electric motor being thereby effected by the aforesaid vacuum tight motor casing, said casing being concentrically positioned and abutting the outer side-Wall of the aforesaid primary hard vacuum rotary molecular pumping stage, sealed thereto mechani cally and hermetically; a cylindrical vacuum tight casing surrounding and accommodating the aforesaid hard vacuum ionic gas discharge pumping stage, said cylindrical vacuum tight casing as surrounding and accom-,

modating the aforesaid tertiary high vacuum rotary molecular pumping stage, and said cylindrical vacuum tight casing also surrounding and accommodating the aforesaid planetary set of gearing, said cylindrical vacuum tight casing being a casting; two tubular and flanged sidearms extending axially from one end of the aforesaid cylindrical vacuum tight casing, one of said side a-rrns being axially and centrally located as extended, the other said side-arm being parallel to and located above the first said side-arm; gasket grooves formed in the outer lateral faces of the aforesaid flanges of the aforesaid two tubular and flanged side-arms; an open and flanged end to the aforesaid cylindrical vacuum tight casing, said open and 13 flanged end being opposite to the aforesaid side-arm tubulated end, said open and flanged end of the aforesaid cylindrical vacuum tight casing abutting the aforesaid side-Wall of the aforesaid primary hard vacuum rotary molecular pumping stage, sealed thereto mechanically and hermetically; a box shaped vacuum tight casing with an open bottom; a flat bottom flanged edge to the aforesaid box shaped vacuum tight casing; a gasket groove formed in the aforesaid flat bottom flanged edge of the aforesaid box shaped vacuum tight casing; two tubular and flanged side-arms leading from the aforesaid box shaped vacuum tight casing, one of said side-arms being located axially, as extended, from one side of the aforesaid box shaped vacuum tight casing, the other said sidearm being located, as extended, from the top of the said box shaped vacuum tight casing, said side-arms positioned and meeting with the two aforesaid side-arms extending from the aforesaid cylindrical vacuum tight casing; a base plate closure member as covering and sealing the aforesaid open bottom of the aforesaid box shaped vacuum tight casing; inlets and outlets, respectively, to the aforesaid plurality of vacuum pumping stages, each of said inlets, respectively, of each successive said vacuum pumping stage having a free gas flow access with the outlet respectively, of the next preceding said vacuum pumping stage, respectively; a minimum of one pair of bombarding electrodes, said electrodes contained the secondary hard vacuum ionic gas discharge pumping stage, being positioned radially therein; permanent magnet elements surrounding each of the aforesaid bombarding electrodes; support rods holding the aforesaid permanent magnet elements in position; gasket material Oring members provided in all gasket grooves, namely, in the aforesaid gasket groove formed in the lateral flat peripheral edges of the aforesaid radially extending sidewalls, in the aforesaid groove as formed in the aforesaid lateral flat surface of the flanged and aforesaid open end of the aforesaid cylindrical vacuum tight motor casing, in the aforesaid gasket groove as formed in the fiat lateral face of the flange 0f the aforesaid cylindrical vacuum tight casing, in the aforesaid gasket grooves formed in the aforesaid flange members of the aforesaid tubular and flanged side-arms extending from the aforesaid one end of the aforesaid cylindrical vacuum tight casing, in the aforesaid gasket groove as formed in the flat bottom edge of the aforesaid box shaped vacuum tight casing; vacuum tight electrical feed-through terminals leading to the aforesaid electric motor; vacuum tight electrical feedthrough terminals leading to the aforesaid bombarding electrodes; the connection and arrangement of the aforesaid plurality of vacuum pumping stages in the aforesaid juxtaposed manner being such that, in operation, the aforesaid unified system vacuum pump Will inherently possess a specific conductance ratio of a value equal to, or greater, than unity (1.0), said conductance being accepted as the reciprocal of the resistance to the flow of a gas in its molecular state, through any given conductor, and said conductance ratio being, actually, the ratio of the optimum rate of gas flow through the inlet of any one of the aforesaid plurality of vacuum pumping stages, to the optimum rate of gas flow from and through the outlet of the aforesaid preceding vacuum pumping stage, With the distance from said inlet to said outlet, under the specified conditions of the aforesaid juxapositioning of the aforesaid plurality of vacuum pumping stages, said distance be used as the parameter.

References Cited in the file of this patent UNITED STATES PATENTS 1,810,083 Norinder June 16, 1931 2,730,297 Van Dorsten et al Ian. 10, 1956 2,918,208 Becker Dec. 22 1959 2,954,157 Eckberg Sept. 27, 1960 3,007,311 Arnero Nov. 7, 1961 FOREIGN PATENTS 332,879 Great Britain July 31, 1930