GB2333127A - Molecular drag compressors having finned rotor construction - Google Patents

Abstract

A molecular drag vacuum pumping stage includes a rotor disk 100 coupled to a drive shaft for rotation about an axis 110, a stator 102 disposed around the rotor disk 100, and a baffle 140-146. The stator 102 defines a channel having an inlet and an outlet, and the rotor disk 100 includes two or more spaced-apart, circumferentially invariant fins 120-126 disposed in the channel. The fins 120-126 define one or more tangential flow subchannels, each connected to the inlet and the outlet. The baffles 140-146 and the fins 120-126 have complementary geometries, such that the baffle 140-146 substantially blocks the tangential flow subchannels. Gas is pumped through the tangential flow subchannels from the inlet to the outlet as the disk 100 rotates relative to the stator 102. The fins 120-126 provide increased exhaust pressure for a given configuration of the molecular drag vacuum pumping stage. The stator may have spaced-apart fins and the rotor may have a baffle (figs 10-14). The fins may extend axially (figs 8 and 9).

Description

2333127 1 MOLECULAR DRAG COMPRESSORS HAVING FINNED ROTOR CONSTRUCTION This

invention relates to molecular drag compressors used for evacuating an enclosed chamber and, more particularly, to molecular drag compressors having a finned rotor or finned stator construction for improved performance.

Conventional turbomolecular pumps include a housing having an inlet port, an interior chamber containing a plurality of axial pumping stages and an exhaust port. Each axial pumping stage includes a stator having inclined blades and a rotor having inclined blades. The rotor blades are rotated at high speed to provide pumping of gases between inlet port and the exhaust port.

Vacuum pumping systems which utilize axial pumping stages in combination with other types of pumping stages are known in the prior art. In one prior art configuration, one or more of the axial pumping stages are replaced with disks which rotate at high speed and function as molecular drag stages. This configuration is disclosed in U.S. Patent No. 5,23 8,3 62 issued August 24, 1993 to Casaro et al and assigned to the assignee of the present invention. A vacuum pump including an axial turbomolecular compressor and a molecular drag compressor in a common housing is sold by Varian Associates, Inc. under Model No. 969-9007. Vacuum pumps utili i g molecular drag disks and regenerative impellers are disclosed in German 2 Patent No. 3,919,529 published January 18, 1990.

Molecular drag compressors include a rotating disk and a stator. The stator defines a tangential flow channel and an inlet and an outlet for the tangential flow channel. A stationary baffle, often called a stripper, disposed in the tangential flow channel separates the inlet and the outlet. As known in the art, the momentum of the rotating disk is transferred to gas molecules within the tangential flow channel, thereby directing the molecules toward the outlet. The rotating disk and the stator of the molecular drag compressor are separated by a small gap, typically on the order of about 0.005 inch, selected to permit unrestricted rotation of the disk, while minimizing leakage through the gap.

A version of the molecular drag pump designed by W. Gaede is referenced in Vacuum Science and Technology, Pioneers of the 20th Century pp. 47-48, P.A. Redhead Editor, ALP Press, 1994. The pump included several stages arranged in series. The rotor appears to be finned.

Prior art vacuum pumps which include an axial turbomolecular compressor and a molecular drag compressor provide generally satisfactory performance under a variety of conditions. However, one drawback of such pumps is the tradeoff between pumping speed, which is the volume of gas pumped per unit time, and exhaust pressure. When the pump design is optimized for high pumping speed, the attainable exhaust pressure is decreased, and vice versa. With reference to the molecular drag stage, the pumping speed may be increased by increasing the cross-sectional area of the tangential flow channel. However, this results in increased backflow through the tangential flow channel, thereby reducing the attainable exhaust pressure. It is desirable to be able to exhaust to atmospheric pressure, thereby avoiding the need for a roughing pump.

Accordingly, it is desirable to provide a molecular drag compressor construction which simultaneously achieves high exhaust pressure and high 3 pumping speed.

According to a first aspect of the invention, a molecular drag vacuum pumping stage is provided. The molecular drag vacuum pumping stage comprises fixed and rotating elements disposed in cooperative relationship to pen-nit rotation of the rotating element relative to the fixed element. The fixed and rotating elements define a channel having an inlet and an outlet. One of the fixed and rotating elements includes spaced-apart, circumferentially invariant fins disposed in the channel. The fins define one or more tangential flow subchannels, each connected to the inlet and the outlet. The other of the fixed and rotating elements includes a baffle disposed in the channel. The baffle and the fins have complementary geometries such that the baffle substantially blocks the tangential flow subchannels. Gas is pumped through the tangential flow subchannels from the inlet to the outlet as the rotating element rotates relative to the fixed element.

In a first configuration, the fins are attached to the rotating element and the baffle is attached to the fixed element In a second configuration, fins are attached to the fixed element and the baffle is attached to the rotating element. In each case, rotation of the rotating element produces movement of the fins relative to the baffle.

According to another aspect of the invention, a molecular drag vacuum pumping stage is provided. The molecular drag vacuum pumping stage comprises a rotor disk coupled to a drive shaft for rotation about an axis, a stator disposed around the rotor disk, and a baffle. The stator defines a channel having an inlet and an outlet, and the rotor disk includes two or more spaced-apart, circumferentially invariant fins disposed in the channel. The fins define one or more tangential flow subchannels, each connected to the inlet and the outlet. Ilie baffle and the fins have complementary geometries, such that the baffle substantially blocks the tangential flow subchannels. Gas is 4 pumped through the tangential flow subchannels from the inlet to the outlet as the disk rotates relative to the stator.

In a first embodiment, the fins extend radially into the cavity. In a second embodiment, the fins extend axially into the cavity. The one or more tangential flow subchannels have total a cross-sectional area that defines the pumping speed of the molecular drag compressor.

According to a ftirther aspect of the invention, an integral high vacuum pump is provided. The vacuum pump comprises an outer pump housing having an axis, an axial turbomolecular compressor disposed in the housing and a molecular drag compressor disposed in the housing. The turbomolecular compressor and the molecular drag compressor each have a rotating portion coupled to a single motor drive shaft aligned along the axis. The molecular drag compressor includes at least one molecular drag stage having a finned rotor or finned stator construction as described above.

For a better understanding of the present invention, embodiments will now be described by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is a cross-sectional elevation view of a high vacuum pump which includes an axial turbomolecular compressor and a molecular drag compressor; FIGURE 2 is a cross-sectional schematic plan view of a first embodiment of a molecular drag vacuum pumping stage in accordance with the invention; FIGURE 3 is a partial cross-sectional schematic elevation view of the molecular drag stage of FIGURE 2, showing tangential flow subchannels defined by rotor fins; FIGURE 4 is a partial cross-sectional schematic elevation view of the molecular drag stage of FIGURE 2, showing a stationary baffle between the inlet and the outlet; FIGURE 5 is a partial cross-sectional schematic elevation view of the molecular drag stage of FIGURE 2, showing a first example of an inlet 5 configuration; FIGURE 6 is a partial cross-sectional schematic elevation view of the molecular drag stage of FIGURE 2, showing a second example of an inlet configuration; FIGURE 7 is a graph of compression as a function of pressure, illustrating the performance of a molecular drag stage of the embodiments of the present invention and the performance of a prior art molecular drag stage;

FIGURE 7A is a partial cross-section schematic elevation view of the tested molecular drag stage, which performance is shown with comparison to the conventional molecular drag stage performance in FIGURE 7.

FIGURE 8 is partial cross-sectional schematic elevation view of a second embodiment of a molecular drag stage in accordance with the invention, showing tangential flow subchannels defined by rotor fins; FIGURE 9 is a partial cross-sectional schematic elevation view of the molecular drag stage of FIGURE 8, showing a stationary baffle; FIGURE 10 is a partial cross-sectional schematic view of a third embodiment of a molecular drag stage in accordance with the invention, showing tangential flow subchannels defined by stator fins; FIGURE 11 is a partial cross-sectional schematic elevation view of the molecular drag stage of FIGURE 10, showing a baffle defined by the rotor; FIGURE 12 is a cross-sectional schematic view of the rotor shown in FIGURES 10 and 11; and FIGURE 13 is a top view of the rotor shown in FIGURES 10 and 11; FIGURE 14 is a bottom view of the rotor shown in FIGURES 10 and 6 11.

An integral high vacuum pump suitable for incorporation of the present invention is shown in FIGURE 1. A housing 10 defines an interior chamber 12 having an inlet port 14 and an exhaust port 16. The housing 10 includes a vacuum flange 18 for sealing the inlet port 14 to a vacuum chamber (not shown) to be evacuated. The exhaust port 16 is typically connected to a roughing vacuum pump (not shown). In cases where the vacuum pump is capable of exhausting to atmospheric pressure, the roughing pump is not required. Located within housing 10 is an axial turbomolecular compressor 20, which typically includes several axial turbomolecular stages, and a molecular drag compressor 22, which typically includes several molecular drag stages. Each stage of the axial turbomolecular compressor 20 includes a rotor 24 and a stator 26. Each rotor and stator has inclined blades as is known in the art. Each stage of the molecular drag compressor 22 includes a rotor disk 30 and a stator 32. The molecular drag compressor 22 is described in detail below. The rotor 24 of each turbomolecular stage and the rotor 30 of each molecular drag stage are attached to a drive shaft 34. The drive shaft is rotated at high speed by a motor located in a motor housing 38.

A first embodiment of a molecular drag stage suitable for use in the molecular drag compressor 22 is shown in FIGURES 2-4. The molecular drag stage includes a rotor disk 100 and a stator 102, which may be mounted within a housing as shown in FIGURE I and described above. The stator defines a channel 104 in which the rotor disk 100 rotates. As known in the art, the stator 102 may be fabricated in sections. For example, an upper stator section may be located in proximity to an upper surface of rotor disk 100, and a lower stator section may be located in proximity to a lower surface of rotor disk 100.

The stator sections are secured together to form a unitary stator. The disk 100 is attached to a shaft 108 for rotation about an axis 110.

7 The rotor disk 100 may be provided with two or more spacedapart, circumferential IY invariant fins 120, 122, 124 and 126. In the embodiment of FIGS. 2-4, fins 120, 122, 124 and 126 extend radially with respect to axis 110 into channel 104. The fins define one or more tangential flow subchannels. In the embodiment of FIGURES 2-4, fins 120 and 122 define a tangential flow subchannel 130; fins 122 and 124 define a tangential flow subchannel 132; and fins 124 and 126 define a tangential flow subchannel 134. The fins 120, 122, 124 and 126, in the embodiment of FIGURES 2-4, extend around the circumference of rotor disk 100 and are circumferentially invariant. Thus,'fins 120, 122, 124 and 126 have annular shapes. In a cylindrical coordinate system defined by axis 110, fins 120, 122, 124 and 126 lie in r - 0 planes.

Except in tangential flow subchannels 130, 132 and 134, a small spacing is provided between rotor disk 100 and stator 102. In particular, a small clearance spacing is provided between an upper surface 120a, of fin 120 and stator 102, and a small clearance spacing is provided between a lower surface 126a of fin 126 and stator 102. Similarly, a small clearance spacing is provided between the outer peripherie s of fins 120, 122, 124 and 126 and an inside wall 102a of stator 102. The clearance spacing is typically a few thousandths of an inch and is selected to limit gas leakage between the rotor disk 100 and the stator 102, while permitting unrestricted rotation of rotor disk 100.

The dimensions of fins 120, 122, 124 and 126 and the spacing between fins are selected based on the desired performance of the molecular drag stage.

Typically, fins 120, 122, 124 and 126 may have radial dimensions on the order of one to three centimeters and thicknesses on the order of 0.5 to 1.0 millimeters (mm). The separation between fins may be on the order of I to 2 mm. The dimensions of the fins are selected to provide structural rigidity during high speed rotation. 'Me dimensions of the tangential flow subchannels 8 130, 132 and 134 are selected to provide a desired pumping speed, as described below. The rotor disk 100 typically has a diameter on the order of 10 to 20 centimeters. It will be understood that the above dimensions are given by way of example only and are not limitin, is to the scope of the present invention.

The stator 102 includes a baffle 140 which blocks each tangential flow subchannel at a circumferential location. The fins 120, 122, 124 and 126, and the baffle 140 have complementary geometries, so that the baffle substantially blocks each of the tangential flow subchannels. In particular, the baffle 140 includes a finger 142 that extends into tangential flow subchannel 130, a finger 144 that extends into tangential flow subchannel 132 and a finger 146 that extends into tangential flow subchannel 134. The fingers 142, 144 and 146 are dimensioned with respect to fins 120, 122, 124 and 126 to provide a small clearance spacing between rotor disk 100 and baffle 140. As shown in FIGURE 2, stator 102 defines an inlet 150 to each of the tangential flow subchannels and an outlet 152 from each of the tangential flow subchannels.

Typically, inlet 150 and outlet 152 are located on opposite sides of baffle 140.

Tile molecular drag stage of the present inventio may have different inlet and outlet configurations. Examples of axial and radial inlet configurations are shown in FIGURES 5 and 6, respectively. Like elements in FIGURES 2-6 have the same reference numerals. An axial inlet 150a is shown in FIGURE 5. The inlet is typically located at one circumferential location of the molecular drag stage. The inlet 150a receives gas axially with respect to axis 110 near the periphery of rotor 100. Inlet 150a includes a passage 160 for distributing the gas to tangential flow subchannels 130, 132 and 134. A radial inlet 150b is illustrated in FIG. 6. Inlet 150b receives gas radially with respect to axis I 10. The gas is distributed through a passage 162 to tangential flow subchannels 130, 132 and 134. The outlet of the molecular drag stage may utilize similar configurations. For example, the molecular drag 9 stage may have an axial inlet on one side and an axial outlet on the other side. This configuration is particularly useful in vacuum pumps having more than one stage. It will be understood that a variety of different inlet and outlet configurations may be utilized within the scope of the invention. However, it is important to allow the maximum gas conductance from the previous stage to all of the fins to avoid any decrease of the pumping speed. If the axial gas inlet is in the middle of the fin 120, the speed of the stage will be reduced dramatically. Furthermore, the molecular drag stage may have more than one inlet and more than one outlet, as illustrated in FIGURES 12-14 and described below.

In operation, gas is received from a previous stage or other source of gas through inlet 150. The previous stage can be a molecular drag stage, an axial turbornolecular stage or any other suitable vacuum pumping stage. The gas enters tangential flow subchannels 130, 132 and 134 is pumped around the circumference of the tangential flow subchannels by molecular drag produced by rotation of disk 100. The gas then passes through outlet 152 to the next stage or to the exhaust port of the pump.

It may be observed that the molecular drag stage shown in FIGURES 2-4 and described above differs from prior art molecular drag pumps in an important respect As best shown in FIGURE 3, each of the tangential flow subchannels 130, 132 and 134 is bounded on three sides by rotor disk 100. For example, tangential flow subchannel 130 is bounded on its upper and lower surfaces by fins 120 and 122, respectively, and on its inside edge 130a by rotor disk 100. By contrast, the tangential flow channels in prior art molecular drag stages are typically bounded on only one side by a rotating surface. Thus, gas molecules in the tangential flow subchannels impact three moving surfaces of the rotor disk in the molecular drag stage of FIGURES 2-4, as compared with one moving surface in prior art molecular drag stages. Since the molecular drag stage operates by transferring the momentum of the rotating disk to gas molecules, gas pumping efficiency is increased in the molecular drag stage of the present invention, where the moving surface area is large in comparison with the fixed surface area. In addition, the exhaust pressure is substantially increased in comparison with prior art molecular drag pumps. The exhaust pressure of molecular drag pumps in accordance with the embodiment is increased by a factor of about two in comparison with prior art molecular drag pumps.

The tangential flow subchannels 130, 132 and 134 each have an inlet and an outlet and operate in parallel. The fins 120, 122, 124 and 126 may be considered to subdivide channel 104 into subchannels 130, 132 and 134, which are connected in parallel between the inlet and outlet of the molecular drag stage. The total pumping speed of the molecular drag stage is proportional to the total cross-sectional areas of tangential flow channels 130, 132 and 134. By increasing the number of tangential flow channels and/or their cross-sectional areas, the pumping speed may be increased.

A test was made to compare the performance of the finned rotor structure of the embodiment with a structure of molecular drag stages of prior artA rotor disk including three fins, having radial depths of 19.5 mm, thicknesses of 1.6 mm, and spacings between fins of 2.0 mm, was tested in a molecular drag stage. This molecular drag compressor has been studied in particularly as an additional stage on the rotor of the large size pump where it is necessary to maintain both high pumping speed and compression ratio in viscous flow. The tested finned rotor structure is shown in FIG. 7A. A similar disk without fins was tested in a molecular drag stage. The results are shown in FIG. 7, where compression is plotted as a function of foreline pressure in millibars. Curve 170 represents the performance of the molecular drag stage having a finned rotor, and curve 172 represents the performance of the molecular drag stage having a conventional non-finned rotor. The compression of the finned rotor stage, represented by curve 170, is clearly 11 extended to a higher pressure, from 2 millibar to 10 millibar. The higher maximum compression ratio of the prior art stage was due to a larger transverse separation between the rotor and the channel wall. A second embodiment of a molecular drag stage in accordance with the invention is shown schematically in FIGURES 8 and 9. The molecular drag stage includes a rotor disk 200 and a stator 202, which may be mounted within a housing as shown in FIGURE I and described above. The stator 202 defines a channel 204 in which the rotor disk 200 rotates. The rotor disk 200 is attached to a shaft (not shown) for rotation about a central axis 210. 10 The rotor disk 200 is provided with two or more spaced-apart, circumferentially invariant fins 220, 222, 224 and 226. In the embodiment of FIGURES 8 and 9, fins 220, 222, 224 and 226 extend axially into channel 204 with respect to axis 210. The fins define a plurality of tangential flow subchannels. In the embodiment of FIGURES 8 and 9, fins 220 and 222 15 define a tangential flow subchannel 230; fins 222 and 224 define a tangential flow subchannel 232; and fins 224 and 226 define a tangential flow subchannel 234. T"he fins 220, 222, 224 and 226 extend around the circumference of rotor disk 200 and are circumferentially invariant. Thus, fins 220, 222, 224 and 226 are cylindrical and concentric. As in the embodiment 20 of FIGURES 2-4, the dimensions of fins 220, 222, 224 and 226 and the spacing between fins are selected based on the desired performance of the molecular drag stage. The dimensions of the tangential flow subchannels 230, 232 and 234 are selected to provide a desired pumping speed. The stator 202 includes a baffle 240 which blocks each tangential flow subchannel at a circumferential location. T'he fins, and the baffle have complementary geometries, so that the baffle substantially blocks each of the tangential flow subchannels. In particular, the baffle 240 includes a finger 242 that extends into tangential flow subchannel 230, a finger 244 that extends into tangential flow subchannel 232 and a finger 246 that extends into tangential

12 flow subchannel 234. The fingers 242, 244 and 246 are dimensioned with respect to fins 220, 222, 224 and 226 to provide a small clearance spacing between rotor disk and baffle 240. The stator 202 ftirther defines and inlet and an outlet to each of the tangential flow subchannels 230, 232 and 234 as described above in connection with FIGURES 2, 5 and 6.

It will be understood that numerous variations of the molecular drag stages are included within the scope of the present invention. The molecular drag stage may have any practical number of fins, with fin dimensions and fin spacing selected for a particular application. The rotor disk 100 in the example of FIGURES 2-4 has a larger axial dimension in the region of fins 120, 122, 124 and 126 than in its central region. In general, the rotor disk may have a uniform or non-uniform axial dimension, with the stator having a complementary geometry. It may be convenient to utiliZe a rotor disk having a uniform axial thickness in a multiple stage vacuum pump. A rotor disk having increased axial thickness near its outer periphery provides the opportunity for additional fins. The dimensions of the fins and the spacings between fins are selected for a particular application. A vacuum pump may include one or more molecular drag stages in accordance with the invention.

The molecular drag stage of the present invention has been described above as having circumferentially invariant fins attached to a rotor disk and a baffle attached to the stator. However, the fins may be attached to either the rotor or the stator. In configurations where the fins extend from the stator into the cavity in which the rotor disk rotates, the baffle may be attached to the rotor.

A molecular drag stage having an inverted finned geometry wherein the stator is provided with fins, is described with reference to FIGURES 1014. Like elements in FIGURES 10-14 have the same reference numerals. A stator 300 has a generally cylindrical inside wall 302 with a central axis 320. Annular fins 310, 312 and 314 extend inwardly from cylindrical wall 302.

13 The fins 310, 312 and 314 are circumferentially invariant and lie in r - 0 planes with respect to axis 320. A rotor disk 324, positioned for rotation about axis 3 20, includes a flange 3 26 in closely-spaced relationship to fin 3 10 and a flange 328 in closely-spaced relationship to fin 314. The flanges 326 and 328 define a channel between them. The fins 310 and 312 androtor disk 324 define a tangential flow subchannel 330; and fins 312 and 314 and rotor disk 324 define a tangential flow subchannel 332.

As best shown in FIGURES 11 and 12, rotor disk 324 includes baffles 340 and 342. The baffles 340 and 342 are preferably spaced apart by 180E with respect to axis 320 to ensure that the rotor disk 324 is balanced during rotation. As shown in FIGURE 11, baffle 340 includes a finger 344 that extends into subchannel 330 and a finger 346 that extends into subchannel 332. The fingers 344 and 346 are dimensioned with respect to fins 310, 312 and 3 14 to provide a small clearance spacing between baffle 340 and fins 3 10, 312 and 314. The fins and the baffle have complementary geometries, so that the baffle substantially blocks each of the tangential flow subchannels. Baffle 342 has a similar structure.

As shown in FIGURES 12 and 13, rotor disk 324 is provided with inlets 3 50 and 3 52 that extend downwardly from an upper surface 3 54 of rotor disk 324 to provide access to tangential flow subchannels 330 and 332 adjacent to each baffle. As shown in FIGURES 12 and 14, rotor disk 324 is provided with outlets 360 and 362 which extend upwardly from a lower surface 364 of rotor disk 324 to provide access to tangential flow subchannels 330 and 332 adjacent to each baffle. The molecular drag stage of FIGURES 10-14 includes an inlet and an outlet for each baffle. Inlet 350 and outlet 362 are located on opposite sides of baffle 342; and inlet 352 and outlet 360 are located on opposite sides of baffle 340. The structure thus operates as two pumping stages in parallel, with each pumping stage constituting one-half of the circumference of the rotor disk. In operation, gas is received through inlets 14 350 and 352 and enters the tangential flow subchannels 330 and 332. The gas is pumped around the circumference of the tangential flow subchannels by molecular drag that results from rotation of rotor disk 324. The gas then passes through outlets 360 and 362 to the next stage or to 'he exhaust port of the pump.

In general, the molecular drag stage of the present invention may include fixed and rotating elements having a cooperative relationship to permit rotation of the rotating element relative to the fixed element. The fixed and rotating elements define a channel having an inlet and an outlet. One of the fixed and rotating elements includes spaced apart, circurnferentially invariant fins disposed in the channel. The fins define one or more tangential flow subchannels. Each of the subchannels is connected to the inlet and the outlet. The other of the fixed and rotating elements includes a baffle disposed in the channel. The baffle and the fins have complementary geometries, such that the baffle substantially blocks the tangential flow subchannels. Thus, the fins may rotate (as in the embodiments of FIGURES 2-6, 8 and 9) or may be fixed (as in the embodiments of FIGURES 10-14). When the fins are fixed, the baffle rotates relative to the fins.

While there have been shown and described what are at present considered the preferred embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims (26)

1. A molecular drag vacuum pumping stage comprising:

   fixed and rotating elements disposed in cooperative relationship to permit rotation of said rotating element relative to said fixed element, said fixed and rotating elements defining a channel having an inlet. and an outlet, one of said fixed and rotating elements having spaced apart, circumferentially invariant fins disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outlet; and the other of said fixed and rotating elements having a baffle disposed in said channel, said baffle and said fins having complementary geometries such that said baffle substantially blocks said tangential flow subchannels, wherein gas is pumped through said tangential flow subchannels from said inlet to said outlet as said rotating element rotates relative to said fixed element.
2. 2. The molecular dm vacuum pumping stage as defined in claim 1, wherein said fins are attached to said rotating element and said baffle is attached to said fixed element.
3. 3. The molecular drag vacuum pumping stage as defined in claim 1, wherein said fins are attached to said fixed element and said baffle is attached to said rotating element.
4. 4. The molecular drag vacuum pumping stage as defined in claim 1, wherein said tangential flow subchannels have a total cross-sectional area that defines a pumping speed of said molecular drag vacuum pumping stage.
5. 5. lle molecular drag vacuum pumping stage as defined in claim 1, 16 wherein said fins extend radially with respect to an axis of rotation of said rotating element.
6. 6. The molecular drag vacuum pumping stage as defined in claim 1, wherein said fins extend axially with respect to an axis of rotation of said rotating element.
7. 7. The molecular drag vacuum pumping stage as defined in claim 1, wherein said fins define a plurality of tangential flow subchannels.
8. 8. A molecular drag vacuum pumping stage comprising: a rotor disk coupled to a drive shaft for rotation about an axis; a stator disposed around said rotor disk, said stator defining a channel having and inlet and an outlet, said rotor disk including two or more spaced- apart, circurnferentially invariant fins disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outlet; and a baffle disposed in said channel, said baffle and said fins having complementary geometries such that said baffle substantially blocks said one or more tangential flow subchannels, wherein gas is pumped through said one or more tangential flow subchannels from said inlet to said outlet as said disk rotates relative to said stator.
9. 9. The molecular drag vacuum pumping stage as defined in claim 8, wherein said fins extend radially into said channel.
10. 10. The molecular drag vacuum pumping stage as defined in claim 8, wherein said fins extend axially into said channel.
11. 17 The molecular drag vacuum pumping stage as defined in claim 8, wherein said fins define a plurality of tangential flow subchannels.
12. 12. The molecular drag vacuum pumping stage as defined in claim 8, wherein said baffle comprises fingers that extend into each of said one or more tangential flow subchannels.
13. 13.

    An integral high vacuum pump comprising: a pump housing having an axis; an axial turbomolecular compressor disposed in said housing; and a molecular drag compressor disposed in said housing, said turbomolecular compressor and said molecular drag compressor each having a rotating portion coupled to a single motor drive shaft aligned along said axis, said molecular drag compressor including at least one molecular drag stage comprising:

    a rotor disk coupled to said drive shaft for a rotation about said axis; a stator disposed around said rotor disk, said stator defining a channel having an inlet and an outlet, said rotor disk including two or more spaced-apart, circurnferentially invariant fins disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outlet; and a baffle disposed in said channel, said baffle and said fins having complementary geometries such that said baffle substantially blocks said one or more tangential flow subchannels, wherein gas is pumped through said one or more tangential flow subchannels from said inlet to said outlet as said disk rotates relative to said stator.
14. 14. Ilic integral high vacuum pump as defined in claim 13, wherein said 18 fins extend radially into said channel.
15. 15. The integral high vacuum pump as defined in claim 13, wherein said fins extend axially into said channel.
16. 16. The integral high vacuum pump as defined in claim 13, wherein said fins define a plurality of tangential flow subchannels having a total crosssectional area that defines a pumping speed of said molecular drag vacuum pumping stage.
17. 17. The integral high vacuum pump as defined in claim 13, wherein said baffle comprises fingers that extend into each of said one or more tangential flow subchannels.
18. 18. An integral high vacuum pump comprising: a pump housing having an axis; an axial turbomo16cular compressor disposed in said housing; and; a molecular drag compressor disposed in said housing, said turbomolecular compressor and said molecular drag compressor each having a rotating portion coupled to a single motor drive shaft aligned along said axis, said molecular drag compressor including at least one molecular drag stage comprising fixed and rotating elements disposed in cooperative relationship to permit rotation of said rotating element relative to said fixed element, said fixed and rotating elements defining a channel having an inlet and an outlet, one of said fixed and rotating elements having spaced-apart, circumferentially invariant fins disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outle and the other of said fixed and rotating elements having a baffle disposed in said channel, said baffle and said fins having complementary geometries such that 19 said baffle substantially blocks said tangential flow subchannels, wherein gas is pumped through said tangential flow subchannels from said inlet to said outlet as said rotating element rotates relative to said fixed element.
19. 19. The integral high. vacuum pump as defined in claim 18, wherein said fins are attached to said rotating element and said baffle is attached to said fixed element.
20. 20. The integral high vacuum pump as defined in claim 18, wherein said fins are attached to said fixed element and said baffle is attached to said rotating element.
21. 21. A molecular drag vacuum pumping stage comprising: fixed and rotating elements disposed in cooperative relationship to permit rotation of said rotating element relative to said fixed element, said fixed and rotating elements defining a channel having an inlet and an outlet, said rotating element having spaced-apart, circumferentially invariant fins disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outlet said inlet being disposed at circumferential location of said fins; and said fixed element having a baffle disposed in said channel, said baffle and said fins having complementary geometries such that said baffle substantially blocks said tangential flow subchannels, wherein gas is pumped through said tangential flow subchannels from said inlet to said outlet as said rotating element rotates relative to said fixed element.
22. The molecular drag vacuum pump stage as defined in claim 21, wherein said inlet has an axial configuration.
23. 23. The molecular drag vacuum pump stage as defined in claim 21, wherein said inlet has a radial configuration.
24. 24. A molecular drag vacuum pumping stage substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of FIGS. 2 to 14 of the accompanying drawings.
25. 25. An integral high vacuum pump substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of FIGS. 2 to 14 of the accompanying drawings.
26. 26. A molecular drag vacuum pump substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of FIGS. 2 to 14 of the accompanying drawings.

    26. A molecular drag vacuum pump substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of FIGS. 2 to 14 of the accompanying drawings.

    J1 Amendments to the claims have been filed as follows 1. A molecular drag vacuum pumping stage comprising:

    fixed and rotating elements disposed in cooperative relationship to permit rotation of said rotating element relative to said fixed element, said fixed and rotating elements defining a channel having an inlet and an outlet, one of said fixed and rotating elements having spaced apart, circumferentially invariant flu disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outlet; and the other of said fixed and rotating elements having a baffle disposed in said channel, said baffle and said fins having complementary geometries such that said baffle substantially blocks said one or more tangential flow subchannels, wherein gas is pumped through said one or more tangential flow subchannels from said inlet to said outlet as said rotating element rotates relative to said fixed element.

    2. The molecular drag vacuum pumping stage as defined in claim 1, wherein said fins are attached to said rotating element and said baffle is attached to said fixed element- 3. The molecular drag vacuum pumping stage as defined in claim 1, wherein said fins are attached to said fixed element and said baffle is attached to said rotating element.

    4. The molecular drag vacuum pumping stage as defined in claim 1, 2 or 3), wherein id one or more tangential flow subchannels have a total cross-sectional area that defines sai p a pumping speed of said molecular drag vacuum pumping stage.

    0 The molecular drag vacuum pumping stage as defined in claim 1, 2, 3 or 4, wherein said fins extend radially with respect to an axis of rotation of said rotating element.

    6. The molecular drag vacuum pumping stage as defined in claim 1, 2, 3 or 4, wherein said fins extend axially with respect to an axis of rotation of said rotating element.

    7. The molecular dra., vacuum pumping stage as defined in any one of the preceding claims, wherein said fins define a plurality of tangential flow subchannels.

    8. A molecular drag vacuum pumping stage comprising: a rotor disk coupled to a drive shaft for rotation about an axis; a stator disposed around said rotor disk, said stator defining a channel having an inlet and an outlet, said rotor disk including two or more spaced- apart, circurnferentially invariant fins disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outlet; and a baffle disposed in said channel, said baffle and said fins having complementary geometries such that said baffle substantially blocks said one or more tangential flow subchannels, wherein gas is pumped through said one or more tangential flow subchannels from said inlet to said outlet as said disk rotates relative to said stator.

    9. The molecular drag vacuum pumping stage as defined in claim 8, 0 wherein said fins extend radially into said'channel.

    10. The molecular drag vacuum pumping stage as defined in claim 8, wherein said fins extend axially into said channel.

    said baffle substantially blocks said one or more tangential flow subchannels, wherein gas is pumped through said one or more tangential flow subchannels from said inlet to said outlet as said rotating element rotates relative to said fixed element.

    19. The integral high vacuum pump as defined in claim 18, wherein said fins are attached to said rotating element and said baffle is attached to said fixed element.

    20. The integral high vacuum pump as defined in claim 18, wherein said fins; are attached to said fixed element and said baffle is attached to said rotating element.

    1 21. A molecular drag vacuum pumping stage comprising: fixed and rotating elements disposed in cooperative relationship to permit rotation of said rotating element relative to said fixed element, said fixed and rotating elements defining a channel having an inlet and an outlet, said rotating element having spaced-apart, circumferentially invariant fins disposed in said channel, said fins defining one or more tangential flow subchannels, each connected to said inlet and said outlet, said inlet being disposed at a circumferential location of said fins; and said fixed element having a baffle disposed in said channel, said baffle and said fins having complementary geometries such that said baffle substantially blocks said one or more tangential flow subchannels, wherein gas is pumped through said one or more tangential flow subchannels from said inlet to said outlet as said rotating element rotates relative to said fixed element.

    22. The molecular drag vacuum pump stage as defined in claim 21, ilt wherein said inlet has an axial configuration.

    23. The molecular drag vacuum pump stage as defined in claim 21, wherein said inlet has a radial configuration.

    24. A molecular drag vacuum pumping stage substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of FIGS. 2 to 14 of the accompanying drawings.

    25. An integral high vacuum pump substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of FIGS. 2 to 14 of the accompanying drawings.