Non-hermetic vacuum pump with supersonic rotatable vaneless gas impingement surface

Abstract

To provide a non-sealed vacuum pump with a supersonically rotatable bladeless gas impingement surface.SOLUTION: A vacuum pump 10 generally comprises low-pressure and high-pressure portions separated by a gas impermeable partition. Gas molecules exit the low-pressure portion through an opening in the partition and passively impinge on a featureless rotatable surface 15 in the high-pressure portion. A driver 16 rotates the rotatable surface with tangential velocity in the supersonic range at multiple times the most probable velocity of the impinging gas molecules. The impinging gas molecules are ejected outwardly from the periphery of the rotatable surface generating a substantial net outward flow of gas and reducing the pressure in the low-pressure portion.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 16 / 849,467, filed April 15, 2020. [Background technology]

[0002] background 1. Field of the invention The present invention relates generally to the field of pumps, and more particularly to a mechanical vacuum pump for pumping various gases to lower pressures. More particularly, the present invention relates to a mechanical vacuum pump having a gas impingement surface rotatable at supersonic tangential velocities to pump impinging gas molecules without the use of seals or protruding or angled blades or vanes.

[0003] 2. Description of Related Technology Any discussion of related art throughout this specification is not intended, and should in no way be considered, as an admission that such related art is in fact prior art or is widely known or forms any part of the common general knowledge in the art.

[0004] There are several different types of mechanical pumps adapted to pump a variety of gases and gas mixtures, including gases such as water vapor, nitrogen, hydrogen, oxygen, chlorine, carbon dioxide, methane, and gas mixtures such as air, hydride gases, halogen gases, oil, water, oxidizer gases, or perfluorocarbon gases mixed with inert gases. Such pumps are used for a variety of purposes, including, among others, transferring gases from one space or location to another, and evacuating gases from a space to reduce pressure within the space. Such pumps are used in a variety of applications, including domestic vacuum cleaners, oil and gas production, distribution, and storage, low pressure drying applications, semiconductor manufacturing, coating applications, chemical manufacturing processes, and scientific research where low pressure is required.

[0005] Pumps used to evacuate gas molecules from a space to reduce the pressure in the space are sometimes called vacuum pumps because the pumps can create a partial vacuum by operating to reduce the pressure in the space relative to the surrounding environment. The highest level of vacuum, i.e., minimum pressure, that these types of pumps can create typically depends on their specific design and operation. Various applications require different values ​​and ranges of reduced pressure. For example, some applications can operate at pressures in the range of about 20-50% of atmospheric pressure (atm), i.e., down to about 0.5 atm. Other applications, including many semiconductor manufacturing applications, require pressures within the medium to high vacuum range, e.g., 10 -4 ~10 -6 Atm pressures much lower than this may be required. In some applications, even lower pressures may be required, falling into the ultra-high vacuum range, such as for particle accelerators and surface physics research. To generate such levels of low pressure, various types of vacuum pumps are used. Such pumps include positive displacement pumps such as rotary vane pumps, piston pumps, diaphragm pumps, screw pumps, dry pumps, and roots blowers, as well as momentum transfer pumps including turbomolecular pumps and molecular drag pumps. All of the above pumps are mechanical pumps, in contrast to the exemplary embodiment described in this application.

[0006] Positive displacement vacuum pumps are generally designed and operated to move a constant displacement of gas during each pumping cycle at a substantially constant volume compared to typical momentum transfer pumps. Thus, once the pressure of the pumped gas falls substantially below atmospheric pressure, such pumps generally become less and less efficient at pumping additional gas molecules, and eventually become unable to reduce the pressure further. Positive displacement vacuum pumps generally require a minimum of about 1 atm to 10 atm without the use of additional pumps or pumping stages in combination. -4 It can only reduce pressure to the atm range. A pumping stage refers to a unit set of pumping components that has a gas flow path leading to other vacuum components or similar unit sets of pumping components.

[0007] In contrast, turbomolecular and molecular drag pumps typically utilize blade structures that protrude or are angled upwards and / or downwards relative to the plane of rotation. This increases the intercepting cross-sectional area and surface area in contact with the molecules, actively intercepting and increasing the number of molecules that impinge upon them, transferring the rotational momentum of the blades to them. These types of pumps also operate at much higher rotational speeds than typical positive displacement pumps, and therefore can achieve speeds of up to about 10 -4 They can pump gases more efficiently at lower pressures than typical positive displacement pumps, including pressures below atm. However, turbomolecular and molecular drag pumps are not as effective or efficient at pumping gases at relatively high pressures approaching ambient atmospheric pressure, at least in part due to the substantial effects of drag from the transfer of momentum and kinetic energy loads of impinging gas molecules on fast rotating blades and other rotating components. In practical use, turbomolecular and molecular drag pumps are used when the gas being pumped is already at about 10 -3 ~10 -4 Atm., the turbomolecular pump is not practically effective until it is in the reduced pressure range of less than 1 atm. Moreover, such pumps are sensitive to even very small back pressure gradients, which can cause them to stall when attempting to pump gas into an exhaust space having a higher pressure. Thus, such pumps are not effective or efficient by themselves for pumping gas from higher pressures closer to atmospheric pressure, or for pumping gas directly into the ambient atmosphere. Thus, turbomolecular pumps and molecular drag pumps are typically utilized in combination with one or more foreline pumps that first reduce the pressure of the exhaust space to a relatively low pressure at which the turbomolecular pump or molecular drag pump can effectively pump gas without stalling.

[0008] Thus, one drawback of conventional mechanical vacuum pumps is that a single conventional pump generally has a vacuum pressure of about 1 atm to about 10 -4 ATM, 10 -6The problem is that the inability to effectively and efficiently pump pressures over a relatively wide range of 100 atm or lower requires multiple pumps and pumping stages, which entails significant additional cost, increased maintenance, increased use of valuable space, and increased risk of component failure and failure.

[0009] Another drawback is that many conventional mechanical vacuum pumps utilize some form of interconnected or intermeshed rotors and stators of various shapes, such as rotors with blades, vanes, pitch, gears, pawls, impellers, or similar protruding surfaces, to actively physically contact and push the molecules of the gas being pumped towards another pumping stage or outlet. Furthermore, such pumps generally require various seals, sealants, lubricants, and the like. The use of such structures to actively physically contact and push the gas molecules creates substantial drag forces that, along with the heavy mass of the rotating parts, result in mechanical friction and wear, as well as physical and chemical degradation of the seals, sealants, and lubricants. This limits the range of rotational speeds of the rotating components and therefore the range of pressures at which such pumps can effectively and efficiently operate. Furthermore, to the extent that the gas or gas mixture being pumped is caustic, corrosive, or contains abrasive particles or powders, repeated active high-speed collisions with such chemical and abrasive particles can accelerate and increase wear and damage to the moving and non-moving components of the pump. Still further, rapidly repeated high velocity collisions with gas molecules and other particles can generate significant amounts of adiabatic compression heat, which can cause further wear and damage to pump components. This can further exacerbate the problem and adversely affect the efficiency and effective pressure range of the pump.

[0010] Yet other problems and drawbacks of conventional mechanical vacuum pumps are that they generally have complex designs with numerous interconnected or interlocking moving and non-moving components, require long and very fine dimensional tolerances between such moving and non-moving components to reduce the conductance of the gas flow path and increase the gas leakage backflow resistance, and typically require the use of one or more stages and seals between the high and low pressure sides and / or between pumping stages to prevent gas leakage backflow and loss of pumping efficiency. Even in certain vacuum pumps where the low pressure side or inlet is not sealed from the high pressure side or outlet, seals are still typically required either between the low pressure sides of subsequent pumping stages in the same pump housing or between successive pumps to prevent gas from eventually leaking back.

[0011] Nearly a century ago, Tesla and Gaede experimented with vacuum pump designs using vaneless disks or cylinders. However, in the Tesla pump, the rotating surface of the disk or cylinder is designed to rotate only at relatively low subsonic velocities. The Tesla experiments were not particularly successful, and no one has been able to produce a vacuum in the medium to high vacuum range, e.g., about 10 atm, without the use of additional pumps or multiple pumping stages. -6The Tesla experiments did not produce a vacuum pump capable of effectively and efficiently pumping gas from the low pressure side of the pump over a wide range of pressures at or below atm. Furthermore, the Tesla experiments did not result in a pump capable of pumping gas over such a wide range of pressures without the need to use one or more seals to prevent gas back-leakage into the low pressure side of the pump or between pumping stages. Furthermore, the Tesla pump design did not address how to maintain pump efficiency with a drop pressure over a wide range of pressures, and as a result, the pump design was effectively only capable of efficient operation over a fairly limited and relatively high pressure range. Thus, while the Tesla pump has not been widely adopted for practical use over the last century, it remains of great technological interest. In contrast, the Gade pump has evolved into today's turbomolecular and molecular drag pumps, which have protruding, angled blades and all of the limitations of such pumps as discussed above. Summary of the Invention [Problem to be solved by the invention]

[0012] There remains a need for a vacuum pump that addresses the various deficiencies, problems, and shortcomings of the conventional mechanical vacuum pumps and others discussed above. Several exemplary embodiments of the non-hermetic vacuum pump having a supersonic rotatable vaneless gas impingement surface, as shown and described in detail herein, provide such a pump. [Means for solving the problem]

[0013] A brief summary of the invention A non-hermetic vacuum pump having a supersonic rotatable vaneless gas impingement surface includes a low pressure section and a high pressure section separated by a stationary, substantially gas impermeable partition. A gas passage for gas flow from the low pressure section to the high pressure section penetrates the partition. There are no seals or differential pumping stages to prevent gas from back leaking from the high pressure section to the low pressure section through the gas passage. A rotatable surface, which may be substantially planar, tapered, or otherwise shaped, without blades, vanes, impellers, or other substantial protrusions, is positioned within a volume in the high pressure section. The rotatable surface is featureless to minimize drag from collisions with gas molecules as it rotates. The rotatable surface is adapted to be passively impinged by molecules of gas entering the space. A drive is coupled to the rotatable surface and adapted to rotationally drive the rotatable surface such that at least a portion of the rotatable surface rotates at a tangential velocity within a supersonic range of about 1 to 6 times the most likely velocity of molecules of gas impinging on the rotatable surface. In that tangential velocity range, the random velocity is increased by about 100%. Before the slow gas molecules moving into the suction tube can leak back from the high pressure section to the low pressure section at a velocity and volume that limits further reduction in the pressure of the gas in the low pressure section, the outgoing rotatable surface redirects and ejects the impinging gas molecules substantially directly outward from its periphery at high velocity and at a rate and volume that reduces the pressure of the gas in the low pressure section to a selected target minimum pressure. One target minimum pressure may be about 0.5 atm. Another target minimum pressure may be about 10 -6 It may also be an ATM.

[0014] According to one embodiment, the partition has a stationary surface exposed to the high pressure section and the rotatable surface has a rotatable surface opposing the stationary surface of the partition, the opposing surfaces being separated by a gap, space, or distance having a dimension between about 0.5 mm and about 100 mm, which may be, and preferably is, continuous around substantially the entire peripheral edge of the rotatable surface.

[0015] According to another aspect, the rotatable surface may comprise a thin planar or tapered disk, and according to another aspect, the rotatable surface may comprise a thin planar or tapered ring with an open interior portion. The rotatable surface may also comprise another shape, such as a conical or crowned disk or ring, but regardless of the shape selected, the rotatable surface preferably does not include features that protrude outwardly from the surface. The rotatable surface has a periphery, the periphery having a peripheral surface portion extending around the periphery, an axis of rotation, and a first width dimension between the axis of rotation and the periphery. The peripheral surface portion preferably has a second width dimension that is about 0.05 to 0.5 times the first width dimension according to one aspect of the invention, and up to 1 times the first width dimension according to another aspect of the invention.

[0016] According to another aspect, a plurality of substantially parallel rotatable surfaces are arranged in a stacked configuration and can rotate together as a unitary structure or separately and independently of one another.

[0017] According to yet another aspect, the rotatable surface is disposed within an interior space defined by an open outer housing, chamber, or enclosure having a stationary, substantially gas impermeable wall. The rotatable surface is positioned within the interior space to divide the interior space into a low pressure section and a high pressure section. The low pressure section and the high pressure section are in gas communication, and no seals are present to prevent leakage of gas from the high pressure section to the low pressure section. The rotatable surface is adapted to be impinged by gas molecules in both the low pressure section and the high pressure section. The drive is adapted to rotationally drive the rotatable surface such that at least a portion of the rotatable surface rotates at a tangential velocity within a supersonic range of about 1 to 6 times the most likely velocity of the gas molecules impinging on the rotatable surface. In that tangential velocity range, the outgoing rotatable surface redirects and expels the impinging gas molecules outward from its periphery at high speeds and at a rate and volume that reduces the pressure of the gas in the low pressure section to a selected target minimum pressure before the randomly moving slow gas molecules can leak back from the high pressure section to the low pressure section at a velocity and volume that limits further reduction in the pressure of the gas in the low pressure section. One target minimum pressure may be about 0.5 atm. Another target minimum pressure may be about 10 -6It may also be an ATM.

[0018] According to another aspect, the wall of the housing, chamber, or enclosure has an inner surface that extends around the rotatable surface and defines a low pressure area with the rotatable surface. The inner surface is angled outwardly near a peripheral edge of the rotatable surface to direct gas molecules emitted outwardly from the rotatable surface away from the peripheral surface. The peripheral edge of the rotatable surface is separated from the inner surface by a gap, space, or distance having a dimension between about 0.5 mm and about 100 mm, which may be, and preferably is, continuous around substantially the entire peripheral edge of the rotatable surface.

[0019] According to yet another aspect, the rotatable surface has a first rotatable surface exposed to the low pressure section and a second rotatable surface exposed to the low pressure section. A substantially gas impermeable enclosure within the high pressure section is adjacent to and separated from the second surface by a small gap to seal a region of space around the rotatable surfaces and create a region of low pressure adjacent the second rotatable surface. It has a recessed opening. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a partial cross-sectional and partially see-through top perspective view of a non-hermetic single-stage vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds in accordance with an illustrative embodiment; [Diagram 2] FIG. 2 is a cross-sectional view of the non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds of FIG. [Diagram 3] FIG. 2 is a partial cross-sectional and partially see-through top perspective view of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds, according to another illustrative embodiment; [Figure 4] FIG. 4 is a cross-sectional view of the non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds of FIG. [Diagram 5] FIG. 13 is a partial cross-sectional and partially see-through top perspective view of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds, according to yet another illustrative embodiment; [Figure 6] FIG. 6 is a cross-sectional view of the non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds of FIG. 5, with optional components in the low pressure section of the pump. [Figure 7] FIG. 6 is a partially cutaway and partially see-through top perspective view of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds according to a variation of the exemplary embodiment of FIG. [Figure 8] FIG. 8 is a cross-sectional view of the non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds of FIG. [Figure 9] FIG. 2 is a partial cross-sectional and partially see-through top perspective view of a non-hermetic vacuum pump having a vaneless gas impingement surface and an open frame rotatable at supersonic speeds, according to yet another illustrative embodiment; [Figure 10] FIG. 10 is a cross-sectional view of the non-hermetic vacuum pump having a vaneless gas impingement surface and an open frame rotatable at supersonic speeds of FIG. [Figure 11] FIG. 10 is a partially transparent top view of the non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds of FIG. 9, omitting the open frame. [Figure 12A] FIG. 2 is a top view of one variation of a rotatable disk of a non-hermetic single-stage vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds according to an exemplary embodiment. [Figure 12B] FIG. 12B is a top perspective view of the rotatable disk of FIG. 12A. [Figure 12C] FIG. 13 is a side view of another variation of a rotatable disk of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds in accordance with an illustrative embodiment; [Figure 12D] FIG. 2 is a top view of one variation of a rotatable ring of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds according to an illustrative embodiment. [Figure 12E] FIG. 13 is a top perspective view of another variation of a rotatable ring of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds in accordance with an illustrative embodiment; [Figure 12F]FIG. 12F is a side view of the rotatable ring of FIG. 12E. [Figure 12G] FIG. 13 is a top view of yet another variation of a rotatable disk of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds in accordance with an illustrative embodiment; [Figure 12H] FIG. 12C is a top perspective view of the rotatable disk of FIG. 12G. [Figure 12I] FIG. 13 is a top view of yet another variation of a rotatable disk of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds in accordance with an illustrative embodiment; [Figure 12J] FIG. 12I is a top perspective view of the rotatable disk of FIG. 12I. [Figure 12K] FIG. 1 is a top perspective view of one variation of multiple rotatable rings of a non-hermetic vacuum pump having vaneless gas impingement surfaces rotatable at supersonic speeds in a stacked configuration according to an illustrative embodiment. [Figure 12L] FIG. 12K is a cross-sectional side view of multiple rotatable rings in a stacked configuration of FIG. [Figure 12M] FIG. 13 is a top perspective view of another variation of multiple rotatable rings of a non-hermetic vacuum pump having vaneless gas impingement surfaces rotatable at supersonic speeds in a stacked configuration in accordance with an illustrative embodiment; [Figure 12N] FIG. 12C is a cross-sectional side view of multiple rotatable rings in a stacked configuration of FIG. 12M. [Figure 12O] FIG. 13 is a top perspective view of yet another variation of a rotatable ring of a non-hermetic vacuum pump having a vaneless gas impingement surface rotatable at supersonic speeds in accordance with an illustrative embodiment; [Figure 12P] FIG. 12B is a cross-sectional side view of the rotatable ring of FIG. 12O. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description of exemplary embodiments is provided below with reference to Figures 1-12 of the accompanying drawings, in which like reference numerals refer to like parts throughout the various figures unless otherwise specified. The detailed description is provided by way of example only and is not intended to limit the scope of the invention as defined by the appended claims. Moreover, the detailed description is not intended to be limiting or exhaustive with respect to exemplary embodiments that may be possible in accordance with the present invention. Rather, various modifications to the described exemplary embodiments are believed to be understood by those skilled in the art in accordance with the present invention. It is also contemplated that those skilled in the art will understand that various features and elements of the described exemplary embodiments may be combined with various features and elements of other exemplary embodiments, thus resulting in additional exemplary embodiments also in accordance with the present invention.

[0022] Certain definitions and conventions have been adopted and are used in connection with the detailed description herein. Unless otherwise specified, the term "vacuum" as used herein to refer to exemplary embodiments of a "vacuum" pump does not necessarily imply that the pump is intended to be used or must be capable of pumping to a complete vacuum. Rather, "vacuum" is intended to be used to reduce the gas pressure in the low pressure section of the pump to a pressure sufficiently lower than the starting pressure or ambient pressure to create a partial vacuum, and is merely used as shorthand for a pump having such a capability. For example, the starting pressure or ambient pressure may be, but need not be, atmospheric pressure (atm), and the pump may be capable of pumping to less than atm, e.g., 0.5 atm, 10 atm, or 20 atm. -4 ATM, 10 -6It may be possible to pump to pressures of up to atm or less. It is to be understood that the minimum pressure values ​​for which a "vacuum" pump is intended and capable of generating will depend on the details of the construction and operation of the particular pump according to the detailed description herein. Unless otherwise specified, all references herein to pressure, temperature, and other physical parameters, such as most probable velocity, mean free path, collision velocity, etc., relate to and / or refer to a temperature of 20° C. and a pressure of 1 atm (760 Torr, 101,325 Pa, 1013.25 mbar), where the gas is air. Also, the following description uses air as the gas to be pumped as an example. However, it will be understood that the exemplary embodiment of the vacuum pump 10 is intended and suitable for use not only with air, but also with other gases and mixtures of gases, including, by way of example and not limitation, water vapor, nitrogen, hydrogen, oxygen, chlorine, carbon dioxide, methane, etc., as well as various gas mixtures such as air, hydride gases, halogen gases, oil, water, oxidizer gases, or perfluorocarbon gases mixed with inert gases. The present invention is used in a variety of applications including domestic vacuum cleaners, oil and gas production, distribution and storage, low pressure drying applications, semiconductor manufacturing, coating applications, chemical manufacturing processes and scientific research where low pressure is required.

[0023] One exemplary embodiment of a vacuum pump 10 according to the present invention is shown in Figures 1-2. In general, the vacuum pump 10 comprises a low pressure section 11, a high pressure section 12, a partition 13 separating the low pressure section 11 from the high pressure section 12, a gas flow path 14 through the partition 13, a substantially planar rotatable surface 15, and a drive 16 adapted to rotate at least a portion of the rotatable surface 15 at a very high tangential velocity, as described in more detail below. The vacuum pump 10 may be portable or may be mounted in a permanent or semi-permanent location, for example to a stationary fixed base or surface of a structure 17.

[0024] As shown in dashed outline in Figures 1-2, low pressure section 11 can include a sealed, partially sealed / partially open or open area or space 18. Low pressure section 11 can have any desired geometric shape. For example, low pressure section 11 and area or space 18 can be partially or completely dome-shaped, cylindrical, rectangular, conical, frusto-conical, or any other suitable geometric shape.

[0025] The low pressure section 11 may include a sealed interior space 18 of a closed housing, chamber, or other enclosure. As mentioned above, the housing or chamber and interior space may have any desired geometric shape and configuration. The low pressure section 11 may also include a partially sealed / partially open space 18 of any desired geometric shape, or even an open area or space. In the case of a partially sealed / partially open space 18, the low pressure section 11 may include a sealed portion of the partially sealed / partially open space 18 and an area or space 19 that is outside the sealed space 18 and in close proximity to one or more openings 20. For example, the low pressure section 11 may include an interior space 18 sealed within a housing or chamber having one or more openings 20, and a relatively narrow portion or area of ​​the space 19 that is outside and in close proximity to the openings 20. The one or more openings 20 may include a gas inlet 21 that is in gas communication with the low pressure section 11 and may be coupled or in gas communication with another housing or chamber, a gas conduit, or even the external ambient environment.

[0026] In the case of the open space 18, the low pressure section 11 may include a relatively narrow portion or region of the open space 18 in close proximity to the outside of the opening 22 of the gas flow passage 14 via the bulkhead 13 that separates the low pressure section 11 and the high pressure section 12. As a result, as will become apparent from the description herein, the low pressure region exerts a tensile force on the rotatable surface 15. Accordingly, the rotatable surface 15, central opening 24, drive shaft 25, coupler 40, drive motor 37, and base 17 are preferably designed and constructed to be structurally resistant to tensile forces and to maintain a substantially fixed and constant position of the rotatable surface 15 relative to the bulkhead 13 during operation of the vacuum pump 10.

[0027] The partition 13 is substantially gas impermeable and stationary relative to the rotatable surface 15. The partition has a surface 13a exposed on one side to the high pressure portion 12 and a surface 13b exposed on the other side to the low pressure portion 11. The partition 13 may comprise a substantially planar structure as shown in Figures 1-2, or may be curved or formed into other geometric shapes. The partition 13 functions to effectively separate the low pressure portion 11 and the high pressure portion 12, at least in the vicinity of the rotatable surface 15. The partition 13 may be, but need not be, incorporated as part of a housing, chamber, or other enclosure that seals the low pressure portion 11, the high pressure portion 12, or both. In some embodiments, either or both of the low pressure portion 11 and the high pressure portion 12 can be partially or completely open to the outside environment, except for the partition 13 between them. The bulkhead 13 should extend adjacent the preferably substantially planar rotatable surface 15 between the low pressure section 11 and the high pressure section 12 a sufficient distance relative to the circumferential dimension of the rotatable surface 15 to effectively separate the high pressure section 12 from the low pressure section 11 at least near the rotatable surface 15. For illustrative purposes, Figures 1 and 2 show the bulkhead 13 extending well beyond the periphery 15a of the rotatable surface 26, but in most practical applications the bulkhead 13 will preferably have a dimension that is approximately the same as or slightly greater than the diameter dimension of the rotatable surface 15 such that the bulkhead 13 extends to or slightly beyond the peripheral edge 26a of the rotatable surface 15. Furthermore, near the gas flow path 14 through the bulkhead 13, the rotatable surface 15 preferably has sufficient structural rigidity and integrity to effectively separate the high pressure section 12 from the low pressure section 11 without substantial deformation or damage.

[0028] The gas flow passage 14 extends through the partition wall 13 and allows gas to flow between the low pressure section 11 and the high pressure section 12. The gas flow passage 14 provides a path through which gas can flow. The gas flow passage 14 may include one or more openings 22 in the bulkhead 13, one or more tubes or conduits, and / or any other structure or combination that allows gas to flow in a confined path from one point to another, or any combination thereof. The gas flow passage 14 is preferably arranged and configured such that gas molecules flow from the low pressure section 11 through the gas flow passage 14 to the high pressure section 12 and impinge on the rotatable surface 15. The gas flow passage 14 may include an opening 22 to the high pressure section 12 adjacent a central portion 23 of the rotatable surface 15, as in the exemplary embodiment shown in Figures 1-2. The central portion 23 includes a central opening 24 that defines an axis of rotation of the rotatable surface 15 together with a drive shaft 25 of the drive 16, which will be described in more detail below. The opening 22 in the bulkhead 13 may, but need not, have a center point or axis that is coaxial with the axis of rotation of the rotatable surface 15. The openings 22 in the partition 13 may also be positioned offset a selected radial distance from the central opening 24, the central portion 23, and / or the axis of rotation of the rotatable surface 15 toward the outer periphery 26 of the rotatable surface 15. The gas flow passage 14 may also include a plurality of spaced apart openings 22 interspersed or distributed within the partition 13. The plurality of openings 22 may include openings positioned adjacent the central portion 23, the central opening 24, and / or the axis of rotation of the rotatable surface 15, and / or one or more openings positioned the same radial distance or a plurality of different radial distances from the axis of rotation of the rotatable surface 15 toward the outer periphery 26 of the rotatable surface 15.

[0029] The gas flow passage 14 and / or one or more openings 22 entering the high pressure section 12 through the bulkhead 13 may, but need not, have an axis that is substantially perpendicular to the plane of rotation of the rotatable surface 15, which is described further below. The gas flow passage 14 and / or one or more openings 22 may also have the same or different axes at one or more angles relative to the plane of rotation of the rotatable surface 15. The one or more angles may be one or more acute angles relative to the plane of rotation of the rotatable surface 15, and may be angled or extend outwardly toward the outer periphery 26 of the rotatable surface 15.

[0030] From the above, it will be appreciated that gas passages 14 and openings 22 can be positioned relative to the plane of rotation of rotatable surface 15 to impart at least some directional bias to at least some portion of the gas molecules entering high pressure section 12, such that they are at least somewhat more likely to impinge on rotatable surface 15 at one or more selected locations between the axis of rotation and periphery 26, such as locations rotating at a higher tangential velocity, and at least somewhat more likely to impinge on rotatable surface 15 at an angle relative to the rotatable surface that is inclined toward periphery 26 of rotatable surface 15. Such a configuration can thus contribute positively to the efficiency of vacuum pump 10.

[0031] Like the low pressure section 11, the high pressure section 12 can include a partially sealed / partially open or open area or space 27. The high pressure section 12 can have any desired geometric shape. For example, the high pressure section 12 can be cylindrical, cubic, rectangular, conical, frusto-conical, or any other desired geometric shape.

[0032] Also, for example, the high pressure section 12 may include a sealed interior space 27 of a housing, chamber, or other enclosure having one or more openings 28. As mentioned above, the housing or chamber and interior space 27 may have any desired geometric shape and configuration. One or more of the openings 28 may include a gas outlet in gaseous communication with the high pressure section 12. The gas outlet may also be coupled to or in gaseous communication with another chamber, a gas conduit, or the external ambient environment. The high pressure section 12 may also include an open area or space 27 that is not bounded by a housing, chamber, or other structure, except for the above-mentioned partition 13 that separates the high pressure section 12 from the low pressure section 11. The open area or space 27 may be the external ambient environment. In that case, the tangential outward flow of gas molecules impinging from the outer periphery 26 of the rotatable surface 15, as shown by the arrow in FIG. 2, may be considered to include the gas outlet.

[0033] A unique feature of the exemplary embodiments described herein is that one or more seals are not required to prevent gas molecules from back-leaking through gas flow passage 14 from high pressure section 12 to low pressure section 11, and preferably no seals are used for that purpose. The reasons for this will become apparent from the additional description below. Because no back-leak prevention seals are utilized, the exemplary embodiments of vacuum pump 10 described herein can be constructed with fewer moving parts, fewer parts requiring inspection, maintenance, repair or replacement, and fewer required tolerances. Thus, the exemplary embodiments of vacuum pump 10 are less expensive to build, assemble, and operate than conventional vacuum pumps, and are more reliable.

[0034] The rotatable surface 15 has a first side having a rotatable first surface 15a, a second side having a rotatable second surface 15b opposite the first surface 15a, and a peripheral edge 26a extending between the first surface 15a and the second surface 15b around a periphery 26 of the rotatable surface 15. The rotatable surface 15 is preferably positioned within a region or space 27 of the high pressure section 12 adjacent and in relatively close proximity to the bulkhead 13 and the gas flow passage 14 and one or more openings 22 through the bulkhead 13. More specifically, the rotatable surface 15 is preferably positioned with the first surface 15a facing, adjacent and in relatively close proximity to the surface 13a of the bulkhead 13 exposed to the high pressure section 12 and the gas flow passage 14 and the openings 22 in the bulkhead 13. Preferably, but not necessarily in all embodiments, the rotatable surface 15 is positioned such that the first surface 15a is substantially parallel to the surface 13a of the partition 13 exposed to the high pressure section 12 and is substantially perpendicular or at a selected angle to the axis of the gas flow passage 14 and / or opening 22 in the partition 13. The first surface 15a of the rotatable surface 15 and the surface 13a of the partition 13 exposed to the high pressure section 12 are separated by a small space or gap 29, such that a very large portion of the gas molecules entering the high pressure section 12 through the opening 22 are likely to impinge on the first surface 15a. For reasons that will become apparent from the further description below, the space or gap 29 is preferably in the range of about 0.5 mm to about 100 mm to facilitate operation of the vacuum pump 10 with a wide variety of gases and minimum target pressure values.

[0035] In some exemplary embodiments, such as those shown in Figures 1-8, the rotatable surface 15 is substantially planar, the first surface 15a is substantially planar, and the second surface 15b is substantially planar, with the first surface 15a and the second surface 15b being substantially parallel and coextensive and terminating in a peripheral edge 26a that extends around the periphery 26 of the rotatable surface 15. The peripheral edge 26a may be, but need not be, substantially perpendicular to the first substantially planar surface 15a and the second substantially planar surface 15b. The first surface 15a and the second surface 15b are preferably relatively smooth, at least to the eye and the touch, although not necessarily at a microscopic level. The smoothness of the first surface 15a and the second surface 15b helps to limit drag forces against the rotatable surface 15 as it rotates, and thus contributes positively to the efficient operation of the vacuum pump.

[0036] A central opening 24 of rotatable surface 15 extends through between first substantially planar surface 15a and second substantially planar surface 15b. Central opening 24 is adapted to receive a drive shaft 25 of drive device 16 to rotatably couple rotatable surface 15 to drive device 16, as described further below. Central opening 24, together with drive shaft 25, defines an axis of rotation for rotatable surface 15.

[0037] In one exemplary embodiment of a substantially planar rotatable surface 15, the rotatable surface 15 comprises a substantially circular disk 15, best shown in Figures 1-8, 12A-12C, and 12G-12J. The disk 15 may be solid, partially solid / partially hollow, or hollow. In this exemplary embodiment, the first substantially planar surface 15a and the second substantially planar surface 15b each extend from a central opening 24 to a peripheral edge 26a of the disk 15. The disk 15 may extend substantially continuously from the first substantially planar surface 15a to the second substantially planar surface 15b. The disk 15 is preferably as thin as possible without compromising its structural integrity during operation, in order to minimize its weight. For the same reasons, various slots 30 or other openings may extend through the body of the disk 15 between the first substantially planar surface 15a and the second substantially planar surface 15b, as best seen in Figures 12G-12J. The substantially circular disk embodiment of the rotatable surface 15 having a substantially continuous surface is particularly suitable for use in the exemplary embodiment of the vacuum pump 10 shown in Figures 1-4 and similar embodiments in which the structure of the rotatable surface 15 provides, in whole or in part, separation between the high pressure section 12 and the low pressure section 11 of the vacuum pump 10.

[0038] In another exemplary embodiment of the substantially planar rotatable surface 15 described above, the rotatable surface 15 comprises a substantially circular, planar ring best shown in Figures 12D-12F and 12K-12N. The ring may be solid, partially solid / partially hollow, or hollow, and is preferably as thin as possible without compromising its structural integrity during operation, in order to minimize its weight.

[0039] In this exemplary embodiment, the outer periphery 26 of the ring is substantially circular. The first substantially planar surface 15a comprises a first substantially planar circumferential portion 31, and the second substantially planar surface 15b comprises a second substantially planar circumferential portion 32. The first circumferential portion 31 and the second circumferential portion 32 are substantially parallel and coextensive. The first circumferential portion 31 and the second circumferential portion 32 each extend substantially continuously around the outer periphery 26 of the ring and terminate at an outer circumferential edge 26a of the ring. The outer circumferential edge 26a may, but need not, be substantially perpendicular to the first circumferential portion 31 and the second circumferential portion 32. The first circumferential portion 31 and the second circumferential portion 32 each extend radially inward from the outer circumferential edge 26a a selected distance and terminate at an inner circumferential edge 33.

[0040] The ring has a central hub portion 34 that accommodates the central opening 24. The central opening 24 extends through the central hub portion 34 and is adapted to receive the drive shaft 25 of the drive device 16 as previously described. The central opening 24, together with the drive shaft 25, defines an axis of rotation of the ring. A plurality of radially spaced spokes 35 extend radially outward between the central hub portion 34 and inner peripheral edge ends 33 of the first and second peripheral surface portions 31, 32 and rigidly connect the first and second peripheral surface portions 31, 32 to the central hub portion 34. Although the spokes 35 are shown as extending linearly and having square edges, one skilled in the art will appreciate that the spokes 35 can have a variety of shapes, including curved, angled, serpentine, and other shapes consistent with providing a rigid connection, and can have a variety of edge shapes, such as rounded or beveled shapes, for aerodynamic streamlining.

[0041] The distance between the outer peripheral edge 26a and the inner peripheral edge 33 comprises the width of the first peripheral surface portion 31 and the second peripheral surface portion 32. The distance between the central opening 24 and the outer peripheral edge 26a comprises the width (radius) of the ring. Those skilled in the art will appreciate that the selection of the ring width represents a trade-off. A smaller ring width has less drag at higher pressure values. However, a larger ring width provides a larger surface area for the collision of molecules with relatively long mean free paths at lower pressure values. Similar considerations apply to the dimensions of the gap 29 between the rotatable surface 15 and the partition wall 13 in terms of mean free path and pressure, i.e., a larger gap may be suitable for use in a relatively high pressure regime, while in a lower pressure regime a relatively small gap may be required to limit back leakage of gas molecules with relatively high values ​​of mean free path and high velocities. For reasons related to the surface area available for collision with gas molecules, which will become more apparent from the additional description below, the width of the first peripheral portion 31 and the second peripheral portion 32 is preferably about 0.05 to 0.5 times the width of the radius of the ring 15. This range accommodates use of a vacuum pump 10 with a wide variety of different gases and minimum target pressure values. For a target minimum pressure of about 0.5 atm, the width can be from about 0.05 to about 0.2 times the radial width. -4 For a target minimum pressure of 10 atm, the width may be about 0.1 to about 0.3 times the width of the radius. -6 For a targeted minimum pressure of atm, the width may be greater than about 0.3 times the radial width.

[0042] Similar to the exemplary disk embodiment of the rotatable surface 15, the elements of the exemplary ring embodiment of the rotatable surface 15 of Figures 12D-12F are preferably as thin as possible without compromising the structural integrity of the ring 15 during operation in order to minimize weight. In addition, the ring comprises a central hub portion 34, inner peripheral edges 33 of the first and second circumferential surface portions 31, 32, and an interior portion 36 sealed or bounded by adjacent spokes 35. The interior portion 36 is free of material and comprises open space, further reducing the weight of the ring 15. Because of the open space, the ring embodiment of the rotatable surface 15 is particularly suitable for use in the exemplary embodiment of the vacuum pump 10 shown in Figures 5-10 and similar embodiments in which pressures on opposing first and second circumferential surface portions 31, 32 (corresponding to first and second surfaces 15a, 15b of the rotatable surface 15) may be approximately equal. In other words, the ring embodiment is best suited for use in embodiments where a ring-based structure is not used or required to provide separation between the high pressure section 12 and the low pressure section 11 of the vacuum pump 10.

[0043] Regardless of the form of the rotatable surface 15, it is preferable to minimize its weight whenever possible to improve the operating efficiency of the vacuum pump 10. It will be appreciated from the following discussion that the amount of surface area of ​​the rotatable surface 15 against which gas molecules can impinge, in combination with the tangential velocity of that surface area relative to the most likely velocity of the impinging gas molecules, substantially determines the speed and efficiency with which the vacuum pump 10 can reduce the gas pressure in the low pressure section 11 from a starting or ambient value to a target minimum pressure value. By minimizing the weight of the rotatable surface 15 without substantially reducing the surface area available for impingement, the drive 16 can more easily and efficiently rotate the rotatable surface 15, particularly at higher gas pressures, and can rotate the rotatable surface 15 at a greater tangential velocity, both of which enable the vacuum pump 10 to achieve the target minimum pressure value more efficiently and quickly.

[0044] In yet another exemplary embodiment of the rotatable surface 15, best seen in Figures 9-10, the rotatable surface 15 can have a non-uniform thickness gradient between the central opening 24 and the outer periphery edge 26a. The thickness gradient may vary continuously or discretely. In one variation, the thickness gradient may vary substantially continuously such that the first surface 15a, the first circumferential surface portion 31, the second surface 15b, the second circumferential surface portion 32, or any combination thereof, tapers as they extend from the central portion 23, the central opening 24, and / or the central hub portion 34 outward toward the outer periphery 26. The taper is preferably, but need not necessarily be, substantially continuous and linear. The non-uniform thickness gradient can help maintain strength and stiffness of the rotatable surface 15 at and near its axis of rotation while reducing weight and potential drag near the outer periphery 26, where the rotatable surface is intended to rotate at very high tangential velocities in the supersonic range.

[0045] The rotatable surface 15 can have a maximum thickness dimension at or near the central opening 24, which decreases to a minimum thickness dimension at or near the peripheral edge 26a. In this configuration, the first surface 15a and the second surface 15b remain approximately parallel to one another, but are not quite parallel, as they slope outward at an angle from the central opening 24 to the peripheral edge 26a. Still in this configuration, as described above, when the rotatable surface 15 is positioned within the high pressure section 12 relative to the bulkhead 13, the gas flow passages 14, and the openings 22, the first surface 15a extends approximately parallel to the surface 13a of the bulkhead 13 that is exposed to the high pressure section 12, but is not quite parallel.

[0046] Additional weight can be removed by configuring the rotatable surface 15 to be hollow or partially hollow. Any embodiment of the rotatable surface 15, e.g., circular disk and ring, may be configured in this manner. The material used to construct the rotatable surface 15 may be selected to maintain the structural integrity, strength, and rigidity of the rotatable surface 15. Additional measures may be taken to ensure structural integrity, strength, and rigidity. Internal supports may be provided in the hollow space between the first surface 15a and the second surface 15b and / or between the first circumferential surface portion 31 and the second circumferential surface portion 32, and may extend internally between the first surface 15a and the second surface 15b and / or between the first circumferential surface portion 31 and the second circumferential surface portion 32 to provide support and help maintain the rigidity of the rotatable surface 15. Internal supports may also be provided within the spokes 35 if they are also hollow or partially hollow. The internal supports may include, for example, one or more discrete structures, such as pillars or posts, and / or one or more continuous structures, such as short circumferentially extending cylinders, or short radially extending fins or walls. If the thickness dimension of hollow or partially hollow rotatable surface 15 is substantially uniform, such as when rotatable surface 15 is substantially planar as described above, the internal supports may also have substantially uniform dimensions. If the thickness dimension of rotatable surface 15 varies, the internal supports will have correspondingly varying or tapered dimensions, as when rotatable surface 15 is tapered, as described above.

[0047] It should be noted that although the several exemplary embodiments of rotatable surface 15 described above all have a substantially circular perimeter 26, other perimeter shapes may be used as desired.

[0048] The rotatable surface 15 may be constructed as a single monolithic structure or as a composite or assembly of components. The rotatable surface 15 may be constructed using suitable machining, molding, solid printing, or other techniques. The rotatable surface 15 is preferably constructed from a material that is lightweight, rigid, has relatively high tensile and rupture strength, and has high thermal stress resistance. These properties are preferred for the rotatable surface 15 to withstand the substantial forces and heat that may be generated when the rotatable surface 15 rotates at the very high rotational and tangential speeds described herein without being damaged. Various materials and structures already used in very high speed rotary machinery are suitable. For example, various materials currently used in certain existing vacuum pumps such as turbines and turbomolecular pumps at very high rotational speeds are suitable. Suitable materials include, but are not limited to, various titanium alloys, magnesium alloys, aluminum alloys, carbon fiber and carbon fiber composites, fiberglass and fiberglass composites, carbon graphite, Kevlar®, and various composites and combinations of the foregoing.

[0049] In addition, it is preferred that rotatable surfaces 15 (and any other components of vacuum pump 10) that may cause or be subject to vibrations are precisely balanced and appropriately damped to minimize vibrations that may occur when the rotatable surfaces rotate at the very high rotational speeds described herein and the effects of such vibrations. Precision balancing and vibration damping elements and techniques already used in connection with existing very high rotational speed machines, such as high rotational speed turbines, hard disks, computer numerically controlled (CNC) cutting machines, and certain existing vacuum pumps, such as turbomolecular pumps, are suitable for this purpose.

[0050] The rotatable surface 15 is adapted to be rotatable in a rotation plane about the axis of rotation. Thus, the first surface 15a and the second surface 15b of the rotatable surface 15 are adapted to be rotatable in a rotation plane about the axis of rotation. Preferably, but not necessarily, the rotation plane is substantially perpendicular to the axis of rotation. In the exemplary embodiment shown in Figures 1-2 and described above, the rotatable surface 15, more specifically the first surface 15a of the rotatable surface 15, is preferably aligned with the surface 13a of the partition exposed to the high pressure section 12 and the opening of the partition 13. 22 within high pressure section 12. In this position, the plane of rotation of rotatable surface 15, and more specifically first surface 15a, is substantially parallel to surface 13a of bulkhead 13 and substantially perpendicular (or at one or more selected angles) to the axis of gas flow passage 14 and / or opening 22.

[0051] Generally speaking, as the first surface 15a of the rotatable surface 15 rotates in a plane of rotation, each point or location on the first surface 15a has a tangential velocity and an associated centrifugal force associated with it. As gas molecules entering the high pressure section 12 through the openings 22 in the bulkhead 13 impact the first surface 15a at various points or locations, the tangential velocities and centrifugal forces associated with those points or locations are transferred to the impinging gas molecules. If the tangential velocities and centrifugal forces are large enough, they can overcome the directional force of the impinging molecules and redirect the impinging molecules towards the periphery 26 of the first surface 15a, ultimately ejecting the impinging molecules from the periphery 26 outwardly into the high pressure section 12 with a vector combination of the reflected incoming velocity and the tangential velocity of the direction and velocity of the rotatable surface 15, where they may ultimately be directed towards the gas outlet. When a sufficient number of impinging molecules are ejected outward from periphery 26 with sufficient velocity, a net outward flow of gas molecules from low pressure section 11 to high pressure section 12 is created, as shown by the arrows in Figures 2, 4-8, etc. The outward flow of gas molecules is guided, at least in part, by surface 13a of bulkhead 13 adjacent first surface 15a of rotatable surface 15.

[0052] In order to redirect a sufficient volume of impinging molecules at a sufficient velocity to generate a substantial net outflow of gas over a wide range of pressure conditions, the inventors have discovered that rotating the rotatable surface 15, more specifically the first surface 15a, at very high rotational and tangential velocities not previously envisioned by those skilled in the art. More specifically, the inventors have discovered that rotating the rotatable surface 15, more specifically the first surface 15a, at a rotational velocity sufficient to impart to at least a portion of the rotatable surface 15, more specifically the first surface 15a, an associated tangential velocity that is a multiple of the most likely velocity of a gas molecule impinging on the rotatable surface 15, more specifically the first surface 15a. Even more specifically, the inventors have discovered that rotating the rotatable surface 15, more specifically the first surface 15a, at a rotational velocity such that at least a portion of the rotatable surface 15, more specifically the first surface 15a, rotates at a tangential velocity that is preferably within about 1 to 6 times the most likely velocity of a gas molecule impinging on the rotatable surface 15, more specifically the first surface 15a, according to the Maxwell-Boltzmann velocity distribution of the impinging gas molecule. Using air molecules at 1 atmosphere and 20° C. as an example of a representative gas with which vacuum pump 10 is intended to be used, the most probable velocity is approximately 410 m / sec, with the speed of sound in dry air at 1 atm and 20° C. being approximately 343 m / sec. This is generally supersonic and equates to a range of tangential velocities within the range of approximately 1.2 to 7.2 times the speed of sound (approximately Mach 1.2 to Mach 7.2). When operated with at least a portion of rotatable surface 15 rotating within the preferred range of tangential velocities, exemplary embodiments of vacuum pump 10 can provide excellent pumping results with a wide range of different gases and over a wide range of pressures and temperatures without the need to utilize multiple pumps or pumping stages.

[0053] The inventors have further discovered that when rotated at a rotational speed sufficient to produce tangential velocity values ​​within the described preferred ranges, the rotatable surface 15, more specifically the first surface 15a, imparts sufficient outward tangential momentum to a sufficient number of impinging gas molecules at a sufficient velocity to establish a net outward flow of gas from the periphery 26 of the rotatable surface 15, more specifically the first surface 15a, from the low pressure section 11 to the high pressure section 12 at a substantial velocity and volume, and does so without the need to use seals to prevent back leakage of gas into the low pressure section 11. Furthermore, the impinging gas molecules exiting the low pressure section 11 into the high pressure section 12 and impinging on the first surface 15a are expelled outwardly from the first surface 15a at a velocity and volume that substantially exceeds the velocity at which the gas molecules in the low pressure section 11 can be replenished by returning molecules of slower velocity. Thus, when constructed and operated as described, the exemplary embodiment of the vacuum pump 10 provides a net outward flow of gas from the low pressure section 11 to the high pressure section 12 at a substantial velocity and volume. The pressure can be reduced or decreased quickly and efficiently from a starting or ambient pressure to a target minimum pressure value.

[0054] The inventors have also discovered that, when constructed and operated as described, the exemplary embodiment of vacuum pump 10 can rapidly and efficiently reduce the pressure in low pressure section 11 over a wide range from a starting or ambient pressure to a target minimum pressure in a single pumping stage using a single pump, without the need to use multiple different pumps and / or multiple pumping stages as is typically required with conventional vacuum pumps. For example, the inventors have discovered that the exemplary embodiment of vacuum pump 10 constructed and operated as described can reduce the pressure in low pressure section 11 from a starting or ambient pressure of about 1 atm to a target minimum pressure of 0.5 atm for typical roughing vacuum applications, and even to a medium to high vacuum range, e.g., 10 atm, in a single stage using the same pump. -4 ~10 -6Atm. Additionally, as discussed above, the inventors have discovered that the exemplary embodiment of vacuum pump 10, when constructed and operated as described, can reduce the pressure in low pressure section 11 to the indicated target minimum pressure ranges without the need to use seals to prevent gas from leaking back through gas flow passage 14 from high pressure section 12 to low pressure section 11.

[0055] As will be appreciated, it is an inherent feature of the exemplary embodiments described herein that the rotatable surface 15, and more specifically the first surface 15a and the second surface 15b of the rotatable surface, are substantially smooth and preferably planar surfaces without outwardly extending blades, vanes, impellers, or other protrusions or features. Furthermore, the rotatable surface 15 is not itself arranged or configured as a blade or impeller, such as the angled or curved blade sets found in conventional turbomolecular pumps and other conventional vacuum pumps. Such blades and / or vanes are a major source of drag, especially at higher gas pressures, and multiple pump stages using different types of pumps generally require a high pressure to operate from ambient or starting pressures of about atmospheric pressure to high to medium vacuum ranges, i.e., 10 -4 ~10 -6 This is the practical reason why it is necessary to pump down to a target minimum pressure value below atm.

[0056] The fundamental difference between the exemplary embodiment of the vacuum pump 10 described herein and a conventional turbomolecular pump is that the latter set of blades or vanes are intentionally rotated through the gas to actively contact the gas molecules and physically push them in front of the blades or vanes, and are actually positioned at an angle that increases the contact cross-sectional area to actively impinge on more molecules. The gas molecules are successively pushed from one set of blades or vanes on one level / storey to another set of blades or vanes on another level / storey, with each successive set of blades or vanes rotating faster and positioned at a different angle to further compress the gas to higher pressures at multiple levels / storeys. The action of the angled blades pushing the molecules in one direction also creates a reaction force in the opposite direction, which exerts a load against the rotation of the blades or vanes, especially at higher pressure operation. Such a configuration also suffers from substantial drag effects, especially at higher starting pressures or ambient pressures. Thus, such pumps can be used to move from relatively high pressures, such as atmospheric pressure, to near vacuum pressure levels, e.g., 10 -4 ~10 -6 atm alone and without the use of multiple pump stages, e.g., a foreline pump and a backing pump. In contrast, the rotatable surface 15 of the exemplary embodiment is not angled or otherwise configured to actively contact gas molecules as it rotates. Rather, the rotatable surface 15 of the exemplary embodiment operates in a passive sense, where gas molecules impinge upon it. It does not generate the action and reaction forces or loads on rotation that angled blades generate. Furthermore, whether or not gas molecules impinge upon the rotatable surface 15 depends on the natural (random) orientation of the gas molecule velocity distribution, not on the direction or angle of rotation of the rotatable surface 15 relative to the gas molecules. Still further, the rotatable surface 15 of the exemplary embodiment is arranged and configured to minimize drag, rather than maximize drag. do.

[0057] In contrast to conventional mechanical pump designs such as molecular drag pumps, turbomolecular pumps, vane pumps, dry pumps, screw pumps, roots blowers, piston and diaphragm pumps, which are all designed with components that actively push and pull molecules, the present invention does the opposite by trying to construct all rotating components, e.g., rotatable surface 15 (rotatable disk or spoked ring), with an aerodynamically streamlined profile and to minimize drag. The fundamental difference of the present invention is that the moving surface, e.g., rotatable surface 15, passively waits for collisions by randomly freely moving molecules and releases them upon collision. With each impact, the molecules collide with a small number of closely spaced surface-bound solid atoms of surface 15a or 15b of rotatable surface 15 and undergo recoil reactions at the atomic monolayer level. The surface atoms transfer their rotational velocity to the outgoing molecule upon collision. At a given pressure, the total number of molecules colliding with rotatable surface 15 is a multiple of the surface collision rate with the projected surface area of ​​physical surface 15a, 15b, and does not depend on whether the surface is moving or stationary. Another embodiment is, for example, that even at atmospheric pressure (atm), the mean free path of air molecules is 6.58 × 10 -6cm, which is two orders of magnitude larger than the solid lattice spacing between atoms on surfaces 15a, 15b of rotatable surface 15, which is about 0.2 nm. Thus, regardless of whether the topology of surfaces 15a, 15b is macroscopically rough or microscopically smooth, the projected surface area that an impinging molecule essentially "sees" is the same. Each impinging molecule undergoes a tangential movement velocity (from the point of impact with surface 15a or 15b) that is 1-6 times the molecule's most likely velocity, which is added or subtracted from the original velocity, changing the direction of the impinging molecule. The resulting exit angle of the impinging molecule is substantially a grazing angle relative to the plane of rotation of rotatable surface 15, and the direction of the impinging molecule is tangential to the rotational velocity of the surface. Thus, when a substantially planar surface without protrusions or other outwardly extending features, such as surfaces 15a, 15b of rotatable surface 15, rotates in a plane of rotation substantially perpendicular to the axis of rotation, the impinging molecule will only impinge on the projected physical area of ​​the surface, depending on the random orientation of the molecule itself. However, if the rotating surface has an angle that is not perpendicular to the plane of rotation and the axis of rotation, or has protrusions or other features that extend outward from the plane of rotation, such as the angled blades of a turbine, some molecules will naturally impinge on the projected physical surface area of ​​the blades based on the random direction of motion of the molecules, but in addition, many molecules that are not moving in a direction that would naturally impinge on the projected area will also be actively impacted by the swept angled blades as they rotate and block the motion path of otherwise non-impinging molecules. Thus, more molecules are impacted by the angled turbine blades compared to the same total physical area of ​​the non-angled substantially planar physical surface area of ​​surfaces 15a, 15b of rotating surface 15. As a result, any rotating protrusion or angled surface, blade, impeller, and vane will experience more impacts, more momentum transfer to the molecules, and therefore more drag and more power consumption, compared to a substantially planar, non-angled, featureless surface that rotates in a plane substantially perpendicular to the axis of rotation. Thus, a substantially planar, featureless rotating surface, such as surfaces 15a, 15b of rotatable surface 15, will inherently experience less drag.Thus, the present invention is characterized in part by optimizing the number of molecules ejected outward from impinging on a rotating surface area while minimizing the drag experienced by the surface area present for impingement at a desired pumping rate within the power and torque that the drive can provide.

[0058] The drive arrangement 16 may include a drive motor 37 and a drive shaft 25. The drive motor 37 operates to rotatably drive the drive shaft 25. The drive motor 37 and the drive shaft 25 may be arranged such that the drive motor 37 directly or indirectly rotatably drives the drive shaft 25. The drive motor 37 may be located within a region or space 27 of the high pressure section 12 of the vacuum pump 10 or external to the high pressure section 12. The drive motor 37 may be removably or permanently attached to a component of the vacuum pump 10, such as the base 17, or a surface or structure separate from or external to the vacuum pump 10, using appropriate mounts and connectors. Suitable electrical wiring, cooling supply and return lines and conduits, etc. 38 may be connected, directly or indirectly, to the drive 16. Where the drive 16 is partially or completely enclosed within an area or space 27 of the high pressure section 11 by an inner enclosure 51, described below, electrical or other supply lines 38 may be fed through one or more walls 52 of the inner enclosure 51 via one or more suitably vacuum sealed feedthroughs or passages. Similarly, where the drive is located outside the high pressure section 12, but the drive shaft 25 extends into an inner enclosure 51 within the high pressure section 12, the drive shaft 25 may pass through a wall 52 of the inner enclosure 51 via a suitably sealed bearing or the like.

[0059] In an arrangement in which the drive motor 37 directly drives the drive shaft 25, the drive shaft 25 may include or be directly coupled to the rotor of the drive motor 37. In this arrangement, the drive shaft 25 extends outwardly from the drive motor 37 and is rotatable relative to the drive motor 37. In an arrangement in which the drive motor 37 indirectly drives the drive shaft 25, a set or series of gears, belts, pulleys or other devices may be used between the drive motor 37 and the drive shaft 25 to transfer the rotational motion of the rotor of the drive motor 37 to the drive shaft 25. The drive shaft 25 may be coupled to the vacuum pump 10 and rotatably supported relative to the vacuum pump 10 by suitable bearings or the like.

[0060] The drive 16, more specifically the drive motor 37, is rotatably coupled to the rotatable surface 15 via a rotatable drive shaft 25 and a coupler 40. The drive shaft 25 is received in a central opening 24 of the rotatable surface 15. As mentioned above, the central opening 24, together with the drive shaft 25, defines an axis of rotation for the rotatable surface 15. Also as mentioned above, the drive shaft 25 is preferably, but not necessarily, coupled to the rotatable surface 15 such that the plane of rotation of the rotatable surface 15 is substantially perpendicular to the axis of rotation. The drive shaft 25 is preferably removably but fixedly coupled to the rotatable surface 15 at the central opening 24 by a coupler 40 such that rotation of the drive shaft 25 is transmitted to the rotatable surface 15, which rotates with the drive shaft 25. The coupler 40 may be any suitable high rotational speed coupler. The coupler 40 may include a flexible or rigid coupler and may include vibration damping elements. The coupler 40 may be a separate component or may be part of the rotatable surface 15 or part of the drive shaft 25. Preferably, the coupler 40 is strong enough to withstand torque values ​​that may occur when the drive shaft 25 imparts rotational motion to the rotatable surface 15 without slippage or damage, at least over the range of rotational speed values ​​and pressure values ​​described herein. In an exemplary embodiment, the coupler 40 may include one or more threaded nuts, and the drive shaft 25 may be threaded such that the coupler and drive shaft may threadably engage. The coupler 40 also preferably functions as a substantially gas impermeable barrier to prevent gas from passing or leaking back from the high pressure section 12 to the low pressure section 11.

[0061] Drive motor 37 may be any type of drive motor capable of rotating rotatable surface 15 over a range of rotational speeds sufficient to rotate at least a portion of rotatable surface 15 at a tangential velocity within a range of about 1 to 6 times the most likely velocity of gas molecules impinging on rotatable surface 15. As briefly described above and more fully below, depending on the gas being pumped, this generally equates to a tangential velocity in the supersonic range of about 1.2 to about 7.2 times the speed of sound (about Mach 1.2 to Mach 7.2). Drive motor 37 may include a suitable electric motor drive, such as an AC, DC, or induction motor, or a suitable magnetic drive. For example, drive motor 37 may suitably comprise the same type of drive motor as the high rotational speed and high torque motors used as spindle motors in computer numerically controlled (CNC) machines, or the same type of drive motors used in connection with conventional high rotational speed turbomolecular vacuum pumps. Various CNC spindle drive motors are available in a variety of sizes, including 2.2 kW, 3.5 kW, 4.5 kW, 5.5 kW, 6.5 kW, 7.5 kW, 8.5 kW, 9.5 kW, 10 ... They are commercially available in a variety of ratings, including 24,000 rpm; 9.5 kW, 24,000 rpm; 13.5 kW, 18,000 rpm; 20 kW, 24,000 rpm; and 37 kW, 20,000 rpm, and are suitable for driving rotatable disks of aluminum, carbon fiber, and other materials having diameters of 12, 24, 36, 47 inches and even larger within the range of rotational and tangential speeds described herein.

[0062] As mentioned above, the drive motor 37 may, but need not, be capable of directly driving the drive shaft 25 at a rotational speed sufficient to generate tangential velocities within the preferred ranges described. Conventional gears, pulleys, and the like may be used between the drive motor 37 and the drive shaft 25 to increase the rotational speed of the drive shaft 25 as necessary to achieve tangential velocities within the preferred ranges. It is also contemplated that the drive motor 37 may be off-axis and may drive the rotatable surface 15, rather than by the central drive shaft 25, by drive members near, adjacent, or within the inner periphery 26a or outer periphery 33, or on or under the first and second surfaces 15a and 15b or the first and second circumferential portions 31 and 32 of the rotatable surface 15, via suitable rotational transmission coupling. It is also contemplated that the rotatable surface 15 may be constructed as part of the magnetic levitation ring and drive motor 37 components.

[0063] Before proceeding further, it is noted and understood that exemplary embodiments of vacuum pump 10 can be constructed, installed, and operated essentially regardless of orientation, and this applies to all exemplary embodiments described herein. Thus, for example, the embodiment shown in Figures 1-10 is shown in an "upright" or "vertical" orientation, with low pressure section 11 vertically above high pressure section 12, and with bulkhead 13 and rotatable surface 15 extending laterally below low pressure section 11. However, vacuum pump 10 may be oriented in a "side" or "sideways" orientation, with low pressure section 11 and high pressure section 12 side-by-side with bulkhead 13 and rotatable surface 15 extending vertically adjacent low pressure section 11, or in an "inverted vertical" orientation, with high pressure section 12 vertically above low pressure section 11, and with bulkhead 13 and rotatable surface 15 extending laterally below high pressure section 12, or any other orientation in between. It will further be appreciated that if gas inlets and gas outlets are included, they may be positioned in various locations and in various orientations.

[0064] As mentioned above, rotatable surface 15 is adapted to be rotatable about an axis of rotation within a plane of rotation, and at least a portion of rotatable surface 15 is rotatable at a very high tangential velocity, preferably within the range of about 1 to 6 times the most likely velocity of gas molecules impinging on rotatable surface 15. The rationale for this will be explained in more detail below.

[0065] The most probable velocity of a gas molecule can be derived from the Maxwell-Boltzmann distribution function, which can be expressed as:

[0066]

number

[0067] where m is the molecular weight and m = M / N AV and N AV is Avogadro's number, M is the molar mass of molecules per mole, k is the Boltzmann constant, and T is the temperature.

[0068] The most probable velocity represents the peak of the Maxwell-Boltzmann distribution curve, the velocity at which the largest number of molecules of a gas move at a velocity v out of the total number of molecules in a given volume. m For example, at 1 atm and 20°C, vm in dry air is 410 m / sec. , v in nitrogen (N2) m is 417 m / sec. On the other hand, the speed of sound in dry air at 1 atm and 20°C is about 343 m / sec. Therefore, v in dry air at 1 atm and 20°C is m is approximately 1.2 times the speed of sound or Mach 1.2. In other words, the most probable velocity v in dry air or nitrogen under these conditions is m is supersonic.

[0069] Most likely velocity v m Note that depends only on T / m. Thus, mixtures of different gas molecules or molecules of different masses m will have different most probable velocities v at the same temperature. mAlso, if there are statistically enough molecules present, the velocity is independent of the number of molecules N, the volume size V, and the molecular volume density n, n=N / V.

[0070] Gas molecules in a given volume of space at a given pressure (P) also exhibit a mean free path (λ) or average distance between collisions. Pressure P and mean free path λ are inversely proportional, Pλ=C*, where C* is a gas molecular characteristic parameter that characterizes the molecular cross section and mass, and is temperature dependent. Values ​​of C* for a variety of different gases can be obtained from a variety of sources, including "The Fundamentals of Vacuum Technology" (published by Leybold Vacuum). Values ​​of C* at 20° C. reported in Table III of the aforementioned publication for various gases with which exemplary embodiments of the vacuum pump 10 may be used are as follows:

[0071] [Table 1]

[0072] The well-known ideal gas equation is:

[0073]

number

[0074] where n is the particle density of the total number of molecules N in the volume V. For a surface within a volume, the gas molecules also move per unit area (cm) of the surface per second. 2 The surface collision rate (Z A ) Collision rate Z A is also given by the previous reference in Eq.

[0075]

number

[0076] Similarly, unit volume per second (cm3 The volume collision rate (Z V ) is the pressure P 2 and varies according to the following relationship:

[0077]

number

[0078] The above solution of Equation 3 and Equation 4, i.e. Z A =2.85×10 20 P and Z V =8.6×10 22 P 2 Note that is specific to air molecules at 20°C, P is measured in mbar, other gas molecules and other conditions will produce different solutions.

[0079] From the above, as the number of gas molecules, e.g., air molecules, in a given volume of space decreases and the pressure P decreases accordingly, the mean free path λ of the remaining air molecules increases, and the surface collision rate Z A and volume collision rate Z V It is clear that both the mean free path λ and the surface collision rate Z A , and the volume collision rate Z V The value of λ differs from that of air and may be larger or smaller at the same pressure value, but the same relationship applies to other gas molecules as well. As shown in Table 1, in general, larger gas molecules, such as chlorine (Cl2), will exhibit proportionally lower values ​​of mean free path λ at the same temperature over the same range of pressure values, e.g., 10 -3 For 6.67 cm of air at 10 mbar -3 At 100 mbar Cl, the distance is about 3.05 cm, whereas smaller gas molecules, such as helium (He), are 10 -3 This represents a proportionally higher value of the mean free path, for example about 18 cm at mbar.

[0080] Gas molecules in a given volume of space under given conditions of temperature and pressure move randomly in all directions with different velocities (v). The Maxwell-Boltzmann distribution function can be used to determine the distribution of velocities (v) of gas molecules under such conditions. One way in which the Maxwell-Boltzmann distribution function can be expressed can be found in the college textbook "Statistical Thermodynamics" (author: John F Lee; Francis Weston Sears: Donald L Turcotte, Addison-Wesley, 1963) and is as follows:

[0081]

number

[0082] where x=v / v m is the speed ratio, and v m is the most probable velocity, N is the total number of molecules in a given volume, and N 0→x is the number of molecules with velocities between 0 and v. erf(x) is the error function of x. The complementary equation of equation (5) is as follows:

[0083]

number

[0084] Here, N x→∞ is the number of molecules with velocity v~∞. From the above, it is clear that if molecules in a given volume are being continuously released from the volume with a velocity (v), only the molecules outside the volume with velocity v→∞ have a chance to return into the volume. Therefore, the number of molecules that can ultimately remain in the volume is the number of returning molecules with velocity v→∞ as stated by equation (6).

[0085] In a given volume, the portion of pressure due to a given number of molecules N that is less than the total number of molecules in the volume is directly proportional to the fraction that the given number of molecules N represents to the total number of molecules. Thus, the pressure for a number of molecules N in a given volume is directly proportional to the fraction of the given number of molecules to the total number of molecules in the volume. For example, assuming there are N molecules in a given volume at 1 atm, the pressure due to all the molecules in the volume is represented by the fraction N / N=1, therefore, the fraction of pressure exerted by all the molecules is 1, i.e., the initial pressure of 1 atm. Similarly, the pressure due to the fraction of molecules having velocity 0 → v is:

[0086]

number

[0087] The pressure due to the rate of molecules having velocity v →∞ is:

[0088]

number

[0089] Since the pressure in a given volume due to a number of molecules, N, is directly proportional to the ratio that number of molecules represents to the total number of molecules in the volume, Equations 7 and 8 also represent the partial pressures in a given volume due to molecules with velocities 0 → v and v → ∞, respectively. The case v=0, and therefore x=0, accounts for all molecules with all velocities in the volume. In this particular case, the ratio of molecules to all molecules is 1, and the pressure in the volume is an initial pressure of 1 atm. Similarly, Equations 5-8 can be written as x=v / v m represents a number that depends only on the ratio of m represents the most probable speed. Furthermore, the ratio x is v mdepends only on the gas molecular weight involved in the ratio x and the temperature through. For any gas, in any normal temperature range, and with the same velocity ratio x, the results of Eqs. 5-8 are universal within the assumptions of an ideal gas and the Maxwell-Boltzmann distribution function. Based on Eqs. 5-8, Table 2 shows the relationship between x and molecular velocity v=xv m 4 shows the minimum residual pressure that can be theoretically achieved in a given volume for various ratios of

[0090] [Table 2]

[0091] Equations 1-8 are derived from the Maxwell-Boltzmann distribution model, which is a statistical model that relies on a large number of sampled molecules, and are therefore valid for a very wide range of molecules and pressures, including the full practical range of molecules and pressures with which exemplary embodiments of vacuum pump 10 are intended to be used.

[0092] With particular reference to the rotatable surface 15 of the exemplary embodiment of the vacuum pump 10, assuming that the peripheral shape of the rotatable surface 15 is circular, the tangential velocity v of each point or area on the first surface 15a of the rotatable surface 15 is t is expressed by the following formula:

[0093]

number

[0094] where r is the distance of the rotatable surface from the axis of rotation and ω is the rotational speed of the rotatable surface about the axis of rotation. Relatedly, at each point, the tangential or centrifugal force (F) is given by:

[0095]

number

[0096] where m is the mass at the point, r and v t is as stated above. From the above, at the periphery 26 of the first surface 15a, the distance r is equal to the radius of the circle, and the tangential velocity v t is at its maximum value for a given rotational speed ω. Conversely, at the axis of rotation, the tangential velocity v t is at its minimum. Between these two extremes, the first surface 15a The tangential velocity v of each point on t increases linearly with incremental changes in distance r.

[0097] It is also apparent that for a given rotational speed ω, each point on first surface 15a has a tangential velocity vt and a centrifugal force F associated with the distance r from the axis of rotation. Like the tangential velocity vt, the centrifugal force F also increases with the distance r from the axis of rotation, being at a maximum value at periphery 26 and at a minimum value at the axis of rotation. It is further apparent that the range and maximum values ​​of the tangential velocity vt and the centrifugal force F that can be achieved by rotatable surface 15 can be adjusted by adjusting the value of the distance r from the axis of rotation, i.e., the radius of rotatable surface 15, or the rotational speed ω at which rotatable surface 15 rotates, or a combination of both.

[0098] Continuing using air as an example for illustrative purposes, and moving now to the operation of an exemplary embodiment of vacuum pump 10, at a starting pressure of approximately 1 atm or ambient pressure, air molecules exiting low pressure section 11 through gas passage 14 and opening 22 collide with first surface 15a of rotatable surface 15 at random angles and with a distribution of velocities. The most likely speed of the colliding air molecules is approximately Mach 1.2, or 1.2 times the speed of sound.

[0099] The rotatable surface 15 of the exemplary embodiment has a radius r and preferably rotates at a rotational speed ω such that at least a portion of the first surface 15a of the rotatable surface 15 moves with a tangential velocity v that is within a range of about 1 to 6 times the most likely velocity of an impinging air molecule. t In this example, this has a v of about Mach 1.2 to Mach 7.2, or about 1.2 to 7.2 times the speed of sound (about 412 to 2,470 m / s). t Corresponds to the range.

[0100] However, the rotatable surface 15 has a tangential velocity v over a preferred range of approximately 1 to 6 times the most probable velocity for any single gas pumped using the exemplary embodiment of the vacuum pump 10. t It should be understood that the pump need not rotate at, or even be capable of rotating at, any of the speeds described above. Rather, the preferred range of 1 to 6 times the most likely speed allows the exemplary embodiment of the vacuum pump 10 to operate at a pressure from about 0.5 atm up to a medium to high vacuum range, e.g., 10 -4 ~10 -6 Target minimum pressure values ​​ranging from 1000 to 10000 atm or even lower can be achieved for a wide variety of gases having a wide range of molecular masses and most likely velocities with tangential velocities v t Represents the range.

[0101] For example, in the specific case of air, given a starting or ambient pressure of about 1 atm, and a target minimum pressure of about 0.5 atm to be reached, a low v of about 1.1 times the most likely velocity, or about 451 m / sec, is obtained. t It can provide excellent pumping performance in the medium to high vacuum range, e.g. 10 -4 ~10 -6 The lower target minimum pressure in atm is similarly in the range of about 3.3 to 4 times the most likely velocity, i.e., about 1,353 to 1,640 m / sec v t Of course, the higher the v t is preferred to compensate for the lower tangential velocity of the inner portion of rotatable surface 15, inboard of peripheral edge 26 and closer to the axis of rotation, especially at lower pressures where the mean free path of the molecules is greater and not many molecules may impinge on peripheral edge 26 of rotatable surface 15.

[0102] As mentioned above, the tangential velocity v within the preferred range t can be achieved by various combinations of radius r (or diameter d) and rotational speed ω of the rotatable surface 15. In general, rotatable surfaces 15 having smaller values ​​of diameter d tend to have a preferred range of tangential speeds v tTo achieve this, the rotatable surface 15 having a larger diameter d can rotate at a higher value of rotational speed ω, and the rotatable surface 15 having a larger diameter d can rotate at a preferred range of tangential speeds v t A rotatable surface 15 having a larger diameter d can rotate at a lower rotational speed ω to achieve a tangential speed v t It is contemplated that it would be less demanding on the drive 16 to generate higher values ​​of rotational speed ω to achieve the preferred range of ω. Thus, the exemplary embodiment of the vacuum pump 10 may be scaled up using a larger diameter rotatable surface 15 to achieve the same results as a conventional vacuum pump. Table 3 below shows preferred ranges of tangential velocities v for various gases including air, nitrogen, chlorine, and helium at a temperature of 20° C. t 10 shows some of the many possible combinations of diameter d and rotational speed ω of rotatable surface 15 that can generate

[0103] [Table 3]

[0104] From the last column of Table 3 and Table 1, it will be clear that light molecules such as the inert gases helium and neon molecules and molecules of hydrogen have mean free paths λ that are 2 to 3 times longer than nitrogen. In addition, the most probable velocities v of neon and hydrogen are m is the v of nitrogen m are 1.2 and 3.7 times higher than the most probable velocities of other heavier gases, v m is even larger. For longer λ and higher v m Both of these reduce the effectiveness of the pumping speed and ultimate pressure that can be achieved by conventional mechanical pumps. This is because conventional mechanical pumps rely on restricting the back leakage path to maintain the pressure differential in their pump-down mechanism. They suffer from a long mean free path λ and a high v mDue to the high velocity of the light gas molecules, they are inherently more likely to back leak and cause a loss of vacuum. Traditionally, light mass molecules have been pumped using cryopumps and reactive sputter pumps, otherwise the vacuum system must deal with the consequences of oil vapor contamination if oil-sealed pumps are used. Even scaled-up versions of traditional mechanical pumps cannot overcome the inherent nature of the properties of light mass gases. In contrast, scaled-up versions of the current exemplary embodiment can be used to mechanically pump down gases with molecules having long mean free paths and high velocities. The exemplary embodiment can be scaled up by a combination of a larger diameter d, a higher rotational speed ω, and / or a wider width of the radius of the ring / disk of the rotatable surface 15 described below, and / or a smaller gap 29, to achieve the most likely velocity v m This satisfies the requirement of a preferred range of 1 to 6 times, thus increasing the number of multiple collisions and discriminating the possibility of molecules leaking back through the gap.

[0105] Depending on the particular needs of a particular application of the exemplary embodiment of the vacuum pump 10, the diameter of the rotatable surface 15 may be non-uniformly sized as compared to the diameter of a set of rotating blades or vanes of a conventional vacuum pump. It is contemplated that the pumping stage 10 may always be greater than the pumping stage 12. However, it will be appreciated that due to the unique arrangement of the rotatable surface 15 described herein compared to conventional vacuum pumps, the exemplary embodiments of the vacuum pump 10 may be constructed with a significantly lower profile than conventional vacuum pumps. Furthermore, the exemplary embodiments of the vacuum pump 10 described herein may operate over a much wider range of pressures than conventional vacuum pumps, and thus a single vacuum pump 10 including a single pumping stage described herein may be used in place of multiple conventional vacuum pumps and pumping stages to achieve equivalent or better pumping results.

[0106] It will be further appreciated that the rotatable surface 15 need not rotate at the same rotational speed ω over the entire pressure range from the starting or ambient pressure to the target minimum pressure. For example, the rotatable surface 15 may rotate at a tangential speed v of at least a portion of the first surface 15a within the preferred ranges described herein. t The rotatable surface 15 can rotate at one rotational speed ω when the pressure is at the starting pressure or ambient pressure, and at another, higher rotational speed Δω as the pressure drops toward the target minimum pressure, so long as the rotatable surface maintains a rotational speed ω sufficient to have a desired v t The first tangential velocity v is closer to the lower end of the range. t and a second tangential velocity v closer to the upper end of the preferred range when the pressure is relatively low and the remaining gas molecules exert less drag on the rotatable surface 15. t Such operation may be more efficient than continuously rotating the rotatable surface 15 at a single rotational speed value. The rotatable surface 15 may also be rotated at multiple different rotational speeds v over a range of pressure values ​​as the gas is pumped out. t and the rotational speed can be varied in discrete steps, or even continuously, as desired.

[0107] Also, the entire surface area of ​​the first surface 15a of the rotatable surface 15 is rotated at a tangential velocity v of 1 to 6 times the most probable velocity range. t It should also be appreciated that the surface need not rotate at a preferred tangential velocity v tBy rotating within the range, superior pumping performance can be achieved. For example, for the exemplary disk embodiment of the rotatable surface 15, the portion may include only the outer periphery 26, or the outer periphery 26 and all or a portion of the surface area of ​​the first circumferential portion 31 of the first surface 15a extending inwardly from the outer periphery edge 26a, or any portion of the surface area of ​​the first surface 15a extending inwardly from the outer periphery edge 26a to and including the entire surface area of ​​the first surface 15a. For the exemplary ring embodiment of the rotatable surface 15, the portion may include only the outer periphery 26, or the outer periphery 26 and the portion of the surface area of ​​the first circumferential portion 31 of the first surface 15a extending inwardly from the outer periphery edge 26a to and including the entire surface area of ​​the first circumferential portion 31. Tangential velocities v within the preferred range t It will be appreciated that the greater the surface area rotating at the axial center, the greater the number and volume of colliding gas molecules that can be pumped per unit time, and thus the exemplary embodiment of the vacuum pump 10 can more quickly and efficiently reduce the pressure in the low pressure section 11 from the starting or ambient pressure to a selected target minimum pressure.

[0108] Specifically, for the exemplary ring embodiment of the rotatable surface 15, the preferred range of widths of the first circumferential surface portion 31 can be expressed in terms of the width of the rotatable surface 15, where the width of the rotatable surface 15 corresponds to the distance from the axis of rotation to the outer peripheral edge 26a, and the width of the first circumferential surface portion 31 corresponds to the distance between the outer peripheral edge 26a and the inner peripheral edge 33, as best seen in Figures 11 and 12D. If the rotatable surface 15 is substantially circular, the width of the rotatable surface 15 corresponds to its radius r. The width of the first circumferential surface portion 31 is preferably within a range of about 0.05 to 0.5 times the radius of the rotatable surface 15, but may extend across the entire radius. Stated another way, the width of the first circumferential surface portion 31 is preferably within a range of between about 5-50% to about 100% of the width of the radius of the rotatable surface 15.

[0109] The first surface 15a has a tangential velocity v tBy rotating within the described preferred range of , a molecule striking the first surface 15a at some incidence angle and velocity v will initially receive the same forward-directed specular reflection angle change component as the incidence angle, e.g., a clockwise incidence angle of 307=270+37 degrees relative to the normal will itself have a reflection angle of 53=90-37 degrees. The velocity vector v reverses its directional angle upon total specular reflection, here designated as the velocity vector v'. The velocity vector v' is then transformed into a tangential velocity v using a vector addition triangle combination of (vt+v'). t is added vectorially to the v of the rotatable surface 15. m greater than v t In the case where v is the velocity of the impinging molecule, regardless of the initial magnitude and direction of v, all impinging molecules with any incident velocity v will eventually be redirected and will have a velocity of v after one or more collisions of these molecules with the rotatable surface 15. t The molecules that remain in the low pressure section 11 and are not pumped out are pumped outward from the outer periphery 26 of the rotatable surface 15 to the high pressure section 12 at a velocity greater than the magnitude of v t molecules with a velocity v greater than 12, which leak back from the high pressure section 12 back to the low pressure section 11. Table 1 shows, for example, m The fraction of such fast molecules with v four times higher than -7 1, which corresponds to the theoretical minimum pressure that can be achieved in the low pressure section 11.

[0110] Therefore, the rotatable surface 15 is rotated at a tangential velocity v within the preferred range described. t When rotating at tangential velocity v, gas molecules exiting low pressure section 11 and impacting first surface 15a of rotatable surface 15 are expelled outward from periphery 26 of rotatable surface 15 with a velocity and volume substantially greater than high velocity gas molecules and can leak back to fill the resulting void in low pressure section 11. This quickly and efficiently reduces the pressure within low pressure section 11. t is the most probable velocity of the colliding molecule, v m The larger the multiple of v, the greater the tangential velocity v tThe greater the surface area of ​​the first surface 15a of the rotatable surface 15 that rotates at the same speed, the greater the number and volume of impinging molecules that are redirected outward, and the more quickly the pressure in the low pressure section 11 drops to a target minimum.

[0111] The outward momentum imparted by first surface 15a of rotatable surface 15 to the impinging molecules is so great that the net velocity of the outward flow of the impinging gas molecules substantially exceeds the velocity at which the gas molecules can leak back through gas passage 14 and re-enter low pressure section 11 to fill the resulting void, and therefore no seal is necessary to prevent gas molecules from back leaking through gas passage 14 from high pressure section 12 to low pressure section 11. Even if some gas molecules may back leak, the percentage is so small compared to the number and volume of gas molecules flowing outward that a target minimum pressure, e.g., 10 -6 The number of molecules in the low pressure section 11 is gradually decreased until the pressure reaches 100 atm.

[0112] As the pressure in the low pressure section 11 continues to decrease, the mean free path of the air molecules continues to increase and the collision velocity of the air molecules with the first surface 15a of the rotatable surface 15 continues to decrease. As described above, the mean free path of the air molecules at 20° C. is approximately 6.58×10 -6 cm to approximately 13.2 × 10 at 0.5 atm -6 cm, 10 -4 Approximately 6.58 x 10 atm -2 cm, and 10 -6 atm to about 6.58 cm. The mean free path of the molecules of other gases similarly increases with decreasing pressure, some larger than air and some smaller.

[0113] A gap or space 29 between the first surface 15a of the rotatable surface 15 and the surface 13a of the partition 13 exposed to the high pressure section 12 acts as a type of conduit for the flow of gas molecules outward from the periphery 26 of the rotatable surface 15. It is preferable that the dimensions of the gap 29 be small to physically minimize and discriminate against high velocity molecules that may flow back through and near the gap 29 from the high pressure section 12 into the low pressure region 11. At the same time, making the dimensions of the gap 29 too small tends to impede the net outward flow of gas molecules, thus reducing pumping efficiency.

[0114] Additionally, the dimensions of the gap 29 affect the lowest target minimum pressure that an exemplary embodiment of the vacuum pump 10 can actually achieve. As the pressure of the gas in the low pressure section 11 decreases, the mean free path λ of the gas molecules increases, decreasing the collision rate of the molecules with the first surface 15a of the rotatable surface 15 and decreasing the pumping efficiency. However, any slower velocity molecules with shorter mean free paths that back leak from the high pressure section 12 near the peripheral edge 26a are likely to be re-ejected by multiple collisions with the first surface 15a before they can penetrate deeper into the low pressure section 11. The re-ejection of the slower returning molecules maintains / protects the low pressure section at a low pressure. If the drive 16 has the ability to further increase the rotational speed of the rotatable surface 15 as the pressure decreases, some pumping efficiency can be maintained as the pressure continues to decrease. However, at some point, the maximum rotational speed that the drive 16 can generate is reached and the pressure drops to a point where, due to a combination of the long mean free path of the gas molecules on the first surface 15a and the low collision velocity, the rotatable surface 15 can no longer eject the impinging gas molecules outward at a sufficient velocity and volume to substantially overcome back leakage of the gas molecules through the gap 29 and the gas passage 14 from the high pressure section 12 to the low pressure section 11. In other words, the vacuum pump 10 can no longer generate a sufficient pressure differential between the high pressure section 12 and the low pressure section 11 to substantially prevent back leakage of gas. This point corresponds to the lowest target minimum pressure value that the vacuum pump 10 can practically achieve. In consideration of the above tradeoffs and as indicated above, the space or gap 29 preferably has a dimension within the range of about 0.5 mm to about 100 mm, such that the exemplary embodiment of the vacuum pump 10 can be operated with a variety of gases and can be configured to operate at a variety of pressures, e.g., 100 to 200 rpm, depending on the particular configuration, dimensions, and operating parameters used. -4 ~10 -6 It becomes possible to achieve minimum target pressure values ​​up to the medium to high vacuum range, such as atm, and even lower pressures in the high vacuum to ultra-high vacuum range.

[0115] Another consideration is that at the small dimensions contemplated for the gap 29, the viscosity of the gas molecules along the surface 13a of the partition 13 may generate a drag force against the rotation of the rotatable surface 15. This is due to the fact that the surface 13a of the partition 13 is stationary. As a result, the gas molecules adjacent to the stationary surface 13a encounter a flow resistance, i.e., viscosity. The resulting drag force is proportional to the velocity gradient and is greatest at the smallest distance between the first surface 15a of the rotatable surface 15 and the surface 13a of the partition 13. This resistance is transferred to the rotatable surface 15 via the gas molecules between the stationary surface 15a and the rotating first surface 13a, and appears as a drag force against the rotation of the rotatable surface 15. To counter this effect, the rotatable surface 15 can optionally be provided with a thin cylinder 41 extending around the peripheral edge 26a, as shown in Figures 12O-12P.

[0116] The cylinder 41 includes a cylinder wall 42 having a cylinder rim 43. The cylinder wall 42 extends outwardly from the rotatable surface 15 in a direction substantially perpendicular to the first surface 15a and the second surface 15b around the peripheral edge 26a of the rotatable surface 15. The cylinder wall 42 can extend outwardly from either or both of the first surface 15a and the opposing second surface 15b that are in close proximity to a stationary surface and subject to viscosity-induced drag, whether the stationary surface includes the bulkhead 13, the interior surface of a housing, chamber, or other enclosure, or both. When the rotatable surface 15 is positioned adjacent and in close proximity to the bulkhead 13 as described above, the cylinder rim 43 is in closer proximity to the stationary surface 13a of the bulkhead 13 than to the rotatable first surface 15a. The surface area of ​​the cylinder rim 43 facing and in close proximity to the stationary surface 13a is a small fraction of the surface area of ​​the first surface 15a and therefore experiences a small fraction of the drag force from gas molecules adjacent the stationary surface 13a compared to the first surface 15a. The same is true when the rotatable surface 15 is positioned such that the first surface 15a and / or the second surface 15b are in close proximity to a stationary inner surface of a housing, chamber, or other enclosure 45 such as the exemplary embodiment shown in Figures 3-10 described below.

[0117] To prevent the outward emission of gas molecules from the periphery 26 of the rotatable surface 15 from being blocked by the cylinder wall 42, a slope, bevel, or inclined portion 44 may be provided and may extend inwardly from the cylinder wall 42 toward the axis of rotation of the rotatable surface 15. The slope, bevel, or inclined portion 44 may extend inwardly from the cylinder rim 43, but this is not required. Additionally, the slope, bevel, or inclined portion 44 may extend from the cylinder wall 42 to either or both of the first surface 15a and the second surface 15b of the rotatable surface 15, depending on the orientation and positioning of the rotatable surface 15 relative to the internal stationary surfaces of the vacuum pump 10. As the impinging gas molecules are redirected outwardly toward the periphery 26 by the rotatable surface 15, they collide with the inclined portion 44 and are deflected outwardly from the periphery 26, away from the first surface 15a and / or the second surface 15b, and beyond the cylinder rim 43 at an angle that generally corresponds to the angle of the slope, incline or inclined portion 44.

[0118] Alternative exemplary embodiments and some variations of the vacuum pump 10 are shown in Figures 3-10. Except as otherwise described and illustrated below, the alternative embodiments include substantially the same rotatable surface 15 and drive 16 as the exemplary embodiment of Figures 1-2. The alternative exemplary embodiments of the vacuum pump 10 include an outer housing, chamber, or other enclosure 45 ("outer enclosure") that is substantially gas impermeable and has a wall 46 that defines an interior space 47. The interior space 47 may be partially sealed by the outer enclosure 45. In some configurations, the wall 46 of the outer enclosure 45 may be truncated and terminate at or slightly past the peripheral edge 26a of the rotatable surface 15a such that the interior space 47 contains only the low pressure 11 portion. In other configurations, the wall 46 may extend beyond the peripheral edge 26a for some distance, and the interior space 47 may contain at least a portion of the high pressure portion 12. In that case, the interior space 47 may be partially open to the surrounding environment and partially sealed by the outer enclosure 45. The outer enclosure 45 and the wall 46 may be constructed of a suitably strong material, such as a metal or carbon composite. In an alternative embodiment, there is no partition 13 in the interior space 47, as in the exemplary embodiment of Figures 1-2. Instead, the rotatable surface 15 is disposed and positioned within the interior space 47 to divide the interior space 47 into a low pressure section 11 and a high pressure section 12. The wall 46 has an inner surface 46a and extends around the periphery 26 of the rotatable surface 15, with at least a portion of the inner surface 46a being adjacent and in close proximity to the peripheral edge 26a of the rotatable surface 15. The peripheral edge 26a and the inner surface 46a are separated by a small gap or space 29.

[0119] The portion of interior space 47 bounded by wall 46 and first surface 15a of rotatable surface 15 (excluding small gap or space 29) comprises low pressure portion 11. The portion of interior space 47 opposite rotatable surface 15 comprises high pressure portion 12. This results in first surface 15a of rotatable surface 15 being exposed facing low pressure portion 11 and second surface 15b of rotatable surface 15 being exposed facing high pressure portion 12.

[0120] High pressure section 12 can be open or partially open to the surrounding environment in the same manner as described above with respect to the exemplary embodiment of Figures 1-2. High pressure section 12 may also be at least partially sealed within an interior space 47 defined by an outer enclosure 45 and / or may be substantially closed to the surrounding environment except for one or more gas outlets in gaseous communication with high pressure section 12.

[0121] The small gap or space 29 between the peripheral edge 26a of the rotatable surface 15 and the inner surface 46a of the wall 46 comprises a kind of conduit for the outward flow of gas molecules from the low pressure section 11 to the high pressure section 12 in the same manner as described above with respect to the exemplary embodiment of Figures 1-2. Thus, the outward flow of gas molecules from the peripheral edge 26 of the rotatable surface 15 is at least partially directed by the stationary inner surface 46a of the wall 46. The low pressure section 11 and the high pressure section 12 are in direct gas communication via the gap or space 29. However, with respect to the exemplary embodiment of Figures 1-2, For the same reasons discussed above, no seal is required between the low pressure section 11 and the high pressure section 12 to prevent gas from leaking back from the high pressure section 12 to the low pressure section 11, and it is preferred that no such seal is used for that purpose.

[0122] The outer enclosure 45 can have any desired geometric shape, including a conical shape as shown in Figures 3-10. Examples include a dome shape, a cylindrical shape, a rectangular or square shape, or any other suitable shape. Regardless of the internal or external shape of the outer enclosure 45 and the interior space 47, it is preferred that at least a portion of the inner surface 46a of the wall 46 adjacent the peripheral edge 26a of the rotatable surface 15 extends at an angle outwardly away from the peripheral edge 26 and the rotatable surface 15 in order to deflect and guide gas molecules that are released outwardly from the peripheral edge 26 and away from the rotatable surface 15 into the high pressure section 12 in the direction of the arrows shown in Figures 4-8, etc. For this purpose, it is preferred that the portion of the inner surface 46a adjacent the peripheral edge 26a of the rotatable surface 15 has an angle within the range of about 10 to 80 degrees relative to the first surface 15a and the second surface 15b of the rotatable surface 15. The angular relationship between the stationary inner surface 46a of the wall 46 and the first and second surfaces 15a, 15a of the rotatable surface 15 also serves to reduce velocity gradients, even at atmospheric pressure, by directing impinging gas molecules expelled outward from the periphery 26 of the rotatable surface 15, away from the small gap or space 29 between the rotating peripheral edge 26a of the rotatable surface 15 and the stationary inner surface 46a of the wall 46, thereby reducing drag on the rotatable surface 15 due to the viscosity of the gas molecules adjacent to the stationary inner surface 46a.

[0123] In one variation shown in Fig. 6, various items 48 can be positioned in the low pressure section 11 of the interior space 47. Items 48 can include, but are not limited to, instruments, gauges, reactors or other vacuum components, and items to be depressurized. Such items 48 can be permanently or temporarily located within the low pressure section 11, and can be, for example, mounted, fixed, or attached to the inner surface 46a of the wall 46. To the extent that electrical wires 49 and the like are required for the items 48, they can pass through the wall 46 via appropriately sealed feedthroughs or passageways.

[0124] 7-10, the outer enclosure 45 can have one or more gas inlets 21 and openings 20 in gas communication with the low pressure section 11. One or more of the gas inlets 21 can have a connector such as a flange 49 for coupling with a gas line or conduit 50 to place the low pressure section 11 in gas communication with another housing or chamber or even the external ambient environment.

[0125] The alternative embodiments shown in Figures 3-10 operate in essentially the same manner and achieve substantially the same results as described above with respect to the exemplary embodiment of Figures 1-2. Moreover, all of the characteristics of the various elements common between the exemplary embodiments are the same, including all of the preferred ranges of dimensional and operating values ​​described above.

[0126] Due to the configuration of the described alternative exemplary embodiment, first surface 15a of rotatable surface 15 is bombarded by molecules of gas in low pressure section 11, which are projected outwardly from outer periphery 26 of rotatable surface 15 and directed toward high pressure section 12 in the same manner as previously described with respect to the exemplary embodiment shown in Figures 1-2, and second surface 15b of rotatable surface 15 is bombarded by molecules of gas in high pressure section 12.

[0127] As the pressure in low pressure section 11 decreases, the pressure differential between the second side and surface 15b of rotatable surface 15 exposed to high pressure section 12 and the first side and surface 15a of rotatable surface 15 exposed to low pressure section 11 increases because rotatable surface 15, rather than a fixed partition or other structure, divides or separates low pressure section 11 and high pressure section 12 (except for a small gap 29 shown in Figures 3-4). Alternative exemplary embodiments of vacuum pump 10 are illustrated in, for example, 10. -4 ~10 -6 When used to achieve a target minimum pressure in the medium to high vacuum range of atm, the first and second sides The maximum pressure difference between them can reach many orders of magnitude.

[0128] Such a large pressure differential can potentially result in temporary or permanent deformation, such as warping or bending, or even permanent damage or destruction of rotatable surface 15, especially if rotatable surface 15 is preferably constructed to be very thin and lightweight. In addition, as rotatable surface 15 rotates, second surface 15b exposed to high pressure section 12 is subjected to collisions with gas molecules within high pressure section 12. The result of this collision is an undesirable source of extra drag against the rotation of rotatable surface 15, which can reduce pumping efficiency.

[0129] To mitigate these effects, according to another variant, an additional enclosure 51 can be provided within the high pressure section 12 around the second surface 15b of the rotatable surface 15, as shown in Figures 5 to 10. The additional enclosure 51 includes a wall 52 having an inner surface 52a and an outer surface 52b. The wall 52 is constructed from a gas impermeable material and is shaped to define an interior space 53 having an opening 54. The additional enclosure 51 has an edge 55 that extends around the opening 54 between the inner surface 52a and the outer surface 52b. The additional enclosure 51 is positioned within the high pressure section 12 such that the interior space 53 of the additional enclosure 51 is adjacent to the second surface 15b of the rotatable surface 15 and seals the space or area within the high pressure section 12 where the second surface 15b is exposed. The additional enclosure 51 is also positioned such that the opening 54 is disposed adjacent the second surface 15b and an edge 55 around the opening 54 is separated from the second surface 15b by a small gap or space 56. The gap or space 56 preferably has a dimension slightly smaller than the gap 29 between the peripheral edge 26a of the rotatable surface 15 and the inner surface 46a of the wall 46 of the outer enclosure 45. The opening 54 preferably has substantially the same peripheral shape as the second surface 15b, e.g., circular, and a peripheral dimension, e.g., diameter, that is only slightly smaller than the peripheral dimension of the second surface 15b, such that the peripheral edge 26a of the rotatable surface 15 and a small portion of the second surface 15b immediately inward from the periphery 26a remain exposed to the high pressure section 12 outside the additional enclosure 51.

[0130] With the additional enclosure 51 disposed against the second surface 15b of the rotatable surface 15 as described above, the interior space 53 of the inner enclosure 51 defines a low pressure space or region adjacent the second surface 15b. This is because the rotatable surface 15 is rotated such that the tangential velocity v t 5-10 , gas molecules that collide with the second surface 15b are rapidly expelled outward from the periphery 26 of the second surface 15b in the direction of the arrows shown in Figs. 5-10 through a small gap 56 between the second surface 15b and the edge 55 of the additional enclosure 51. The molecules are expelled outward at a rate and volume substantially greater than the rate and volume that can be replaced by molecules leaking back through the gap 56, and thus the pressure in the interior space 53 of the inner enclosure 51 drops, as does the pressure in the low pressure section 11. The reduction in pressure in the space or region adjacent to and to which the second surface 15b is exposed substantially reduces the pressure difference between the first side and surface 15a and the second side and surface 15b of the rotatable surface 15 over substantially the entire pressure range from the starting pressure or ambient pressure to the intended target minimum pressure. The reduction in pressure in the space or region adjacent to second surface 15b also substantially reduces the resistance to the rotation of rotatable surface 15 from gas molecules impinging on second surface 15b.

[0131] As discussed above with respect to the outer enclosure 45, the additional enclosure 51 may also be constructed in a variety of shapes. In a preferred embodiment, the outer enclosure is configured in a conical shape and the additional enclosure 51 is configured as an inverted cone, as shown in Figures 6-10. With this configuration, the inner surface 46a of the wall 46 of the outer enclosure 45 extends outwardly from a central or truncated apex 57 on a slope around and past the peripheral edge 46a of the rotatable surface 15, and the wall 52 of the additional enclosure 51 extends outwardly from a central or truncated apex 58 on a slope towards the sloping inner surface 46a of the outer enclosure 45. 3 and 4. The additional enclosure 51 extends from the outer enclosure 45 and terminates at an edge 55 of the opening 54 of the additional enclosure 51 adjacent the second surface 15b of the rotatable surface 15. In a preferred arrangement, the angle or slope of the inner surface 46a of the outer enclosure 45 and the wall 52 of the additional enclosure 51 are not symmetrical with respect to the first surface 15a and the second surface 15b of the rotatable surface 15. In a preferred arrangement, the gap 56 between the edge 55 of the additional enclosure 51 and the second surface 15b of the rotatable surface 15 is slightly smaller than the gap 29 between the peripheral edge 26a of the first surface 15a of the rotatable surface 15 and the inner surface 46a of the wall 46 of the outer enclosure 45.

[0132] In a preferred configuration, the outward flow of gas molecules from the first surface 15a and the second surface 15b of the rotatable surface 15 is facilitated by at least some separation of the flows so that they do not interfere, which could cause congestion in the net outward flow of gas and reduce pumping efficiency. As a result of the difference in gap dimensions, a small pressure difference may remain between the first side and surface 15a and the second side and surface 15b of the rotatable surface 15 as the pressure decreases toward the intended target minimum pressure. However, the difference is small enough that there is no risk of deformation of the rotatable surface 15.

[0133] In another variation shown in Figures 9-10, the additional enclosure 51 and the outer enclosure 45 can be connected together in a frame 59. The frame 59 can be open or partially open to the surrounding environment. The frame 59 can include a single continuous perimeter member 60 or multiple discrete spaced apart perimeter members 60 and multiple cross members 61. The perimeter members 60 and cross members 61 can be arranged to form a frame 59 having a perimeter footprint that is substantially circular, square, rectangular, polygonal, irregular geometric shape, or any other shape desired. The perimeter members 60 and cross members 61 can be constructed from a rigid material such as metal and can be interconnected to form a substantially rigid frame 59. The cross members 61 can be arranged to interconnect the outer enclosure 45 and inner enclosure 51, including the drive 16 and rotatable surface 15, with the perimeter members 60 at multiple locations to produce a single unit. The single unit may be portable or may be permanently or temporarily fixed in place to a mounting base 17 or to a surface of a larger structure such as a floor or wall of a facility.

[0134] If the drive motor 37 is enclosed within the inner enclosure 51, the electrical wiring and cooling supply and return 38 may be fed to the drive motor 37 through a wall 52 of the inner enclosure 51 via a suitably sealed vacuum feedthrough or passageway. If the drive motor 37 is located outside the inner enclosure 51, the drive shaft 25 may pass through the wall 52 of the inner enclosure 51 through a suitably sealed bearing or the like.

[0135] Another variation is shown in Figures 12K-12N. In this variation, multiple rotatable surfaces 15 are arranged substantially parallel and spaced apart in a substantially stacked configuration. Arranging multiple rotatable surfaces 15 in a stack is one approach to provide additional surface area for collisions by molecules of the gas being pumped.

[0136] The multiple rotatable surfaces 15 may be interconnected to form a single integral structure as shown in Figures 12K-12N, or may be separate structures. When configured as an integral structure, the multiple rotatable surfaces 15 may be interconnected by one or more interconnecting bridges 62. The one or more interconnecting bridges 62 may extend between and interconnect adjacent surfaces of the rotatable surfaces 15 in the stack. The adjacent surfaces may include first surfaces 15a and second surfaces 15b of adjacent rotatable surfaces 15 in the stack with which gas molecules are intended to collide, and adjacent first surfaces 15a and 15b of adjacent rotatable surfaces 15 may be interconnected by one or more interconnecting bridges 62. The adjacent surfaces may include a central hub portion 34 and a first circumferential surface portion 31 and a second circumferential surface portion 32. The adjacent surfaces may also include adjacent surfaces of spokes 35 that, in the exemplary ring embodiment of rotatable surface 15, extend between a central hub portion 34 and the first circumferential surface portion 31 and the second circumferential surface portion 32. The one or more interconnecting bridges 62 may, but need not, extend between the adjacent surfaces substantially perpendicular to the plane of the adjacent surfaces.

[0137] 12K-12L, a plurality of separate, discrete interconnecting bridges 62 in the form of a plurality of columns or pillars may extend between adjacent surfaces of the stacked rotatable surfaces 15. The interconnecting bridges 62 may be spaced about the central opening 24 of the stacked rotatable surfaces 15 at a plurality of locations, including between adjacent surfaces of the spokes 35 in the case of the exemplary ring embodiment of the rotatable surfaces 15, and at various distances radially outward between the central opening 24 and the peripheral edge 26a of the stacked rotatable surfaces 15.

[0138] In another variation shown in Figures 12M-12N, the interconnecting bridges 62 can include a monolithic structure such as a cylinder having walls extending between adjacent surfaces of the stacked rotatable surfaces 15. The cylinder walls can extend circumferentially around the central portion 23 and / or central hub portion 34 and can be located at a position spaced radially outward from the central opening 24 of the rotatable surfaces 15 between the central opening 24 and the outer peripheral edge 26a of the rotatable surfaces 15. Additional cylinders can also be utilized, including located at or near the outer peripheral edge 26a of adjacent rotatable surfaces 15, if required or desired for support. The cylinders can be, but need not be, concentric or the same size as each other and / or the stacked rotatable surfaces 15. The monolithic form of the interconnecting bridges 62 need not be in the shape of a cylinder and can have other geometric shapes. For both discrete and monolithic forms of interconnected bridges 62, preferably the interconnected bridges 62 are numbered and positioned to maintain balance of the integral structure of the stacked rotatable surface 15 as the integral structure rotates at rotational and tangential velocities within the preferred supersonic ranges described herein.

[0139] Each rotatable surface 15 in a stack can have the same configuration, or can have different configurations. For example, one rotatable surface 15 in a stack can be configured according to the exemplary disk embodiment described above, and another rotatable surface 15 in a stack can be configured according to the exemplary ring embodiment described above. Different configurations of rotatable surfaces 15 can be mixed in a stack in any desired configuration and order. In one exemplary configuration, rotatable surfaces 15 configured as rings alternate with rotatable surfaces 15 configured as disks. Additionally, each rotatable surface 15 in a stack can have the same shape and dimensions, or the various rotatable surfaces 15 can have different shapes and / or dimensions.

[0140] Each rotatable surface 15 in the stack is connected to a drive shaft 25 of a drive device 16 by a coupler 40 as described above. Multiple rotatable surfaces 15 in a stack can be connected to the drive shaft 25 together with one or more common couplers 40, as shown in Figures 12K-12N. Alternatively, one or more rotatable surfaces 15 in a stack can be individually connected to the drive shaft 25 via one or more separate individual couplers 40.

[0141] Further, all of the multiple rotatable surfaces 15 in the stack can rotate with the drive shaft 25, and one or more individual rotatable surfaces 15 in the stack can be individually selectively rotated as desired. For example, one or more rotatable surfaces 15 can each be individually connected to the drive shaft by a coupler 40 adapted to be remotely controlled. For example, the coupler 40 can include a clutch adapted to be remotely controlled by a linkage or other mechanism to selectively and individually connect each rotatable surface 15 to the drive shaft 25. With this configuration, one or more of the rotatable surfaces 15 in the stack can be selectively rotated at various times to achieve desired pumping characteristics, e.g., to increase efficiency or to increase flow rate and volume. As another example, an exemplary embodiment of the vacuum pump 10 may be configured to rotate when the pressure in the low pressure section 11 is at and near the start or ambient pressure, and to rotate at the same or different tangential velocities v within a preferred range to modify the pumping characteristics. t When the pressure is reduced to select one or more additional or different rotatable surfaces 15 for rotation at a tangential velocity v within the preferred ranges described herein, t For example, when pressure is reduced, additional or different rotatable surfaces 15 can be selectively rotated to increase the surface area for collisions of gas molecules in an effort to maintain a substantially uniform flow rate and volume.

[0142] In one embodiment, a vacuum pump for pumping a gas comprises an outer enclosure that is gas impermeable or substantially gas impermeable, the outer enclosure defining an interior space having an inner surface, and a rotatable surface within the interior space, the rotatable surface having a first surface, a second surface opposite the first surface, and a peripheral edge between the first and second surfaces, the first and second surfaces being substantially planar, the rotatable surface configured to separate the interior space into a low pressure section and a high pressure section, the first surface facing the low pressure section and the second surface facing the high pressure section, the inner surface sloping outwardly around the peripheral edge of the rotatable surface within the low pressure section of the interior space, the peripheral edge of the rotatable surface and the inner surface of the outer enclosure defining a first gap, and while the vacuum pump is pumping the gas, gas can flow from the low pressure section to the high pressure section through the first gap and from the high pressure section to the low pressure section through the first gap. a drive connected or coupled to the rotatable surface, the drive being operable to rotate the rotatable surface with at least a portion of the rotatable surface having a tangential velocity within a range of about 1 to 6 times a most likely velocity of the gas molecules over a pressure range in the low pressure section from a starting pressure of about 1 atm to the target minimum pressure, to cause the gas molecules to flow outwardly from a peripheral edge of the rotatable surface through the gap to reduce the pressure in the low pressure section to the predetermined target minimum pressure in a single pumping stage, the target minimum pressure being at least about 10 -4atm and a second enclosure within the high pressure section, the second enclosure being substantially gas impermeable and defining a second interior space having an opening adjacent a second surface of the rotatable surface and having a surface that slopes outwardly toward a peripheral edge of the rotatable surface within the high pressure section, wherein the peripheral edge of the rotatable surface and the surface of the second enclosure define a second gap having a second dimension such that the second interior space and the high pressure section are in gas communication through the second gap, and the second dimension of the second gap is selected to be smaller than the first dimension of the first gap to reduce a pressure differential between the first surface of the rotatable surface and the second surface of the rotatable surface while the pump is pumping gas.

[0143] In various embodiments, for the vacuum pump, the target minimum pressure is about 10 -4 ~10 -6 atm. The outer enclosure includes an inlet in gaseous communication with the low pressure section and an outlet in gaseous communication with the high pressure section. A first dimension of the first gap is in the range of about 0.5 mm to about 100 mm. The rotatable surface includes a circular or substantially circular ring having a central opening, a radial dimension between the central opening and a peripheral edge, an interior open portion and a peripheral portion having a dimension in the range of about 0.05 to less than 0.5 times the radial dimension. A plurality of substantially parallel planar rotatable surfaces are arranged in a stacked configuration. The drive device drives at least a portion of the rotatable surfaces to have a tangential velocity having a first velocity value when the pressure in the low pressure section is about a start pressure, and a tangential velocity value when the pressure in the low pressure section is about a start pressure. The rotatable surface is operable to rotate with one or more second velocity values ​​that are progressively greater than the first velocity values ​​as pressure within the section decreases toward the target minimum pressure.

[0144] In one embodiment, a vacuum pump for pumping a gas includes an outer enclosure that is substantially gas impermeable, the outer enclosure defining an interior space having an inner surface, and a rotatable surface within the interior space, the rotatable surface having a first surface, a second surface opposite the first surface, and a peripheral edge between the first and second surfaces, the first and second surfaces being substantially planar, wherein the rotatable surface is configured to separate the interior space into a low pressure portion and a high pressure portion, the first surface facing the low pressure portion and the second surface facing the high pressure portion, the inner surface being sloped outwardly about the peripheral edge of the rotatable surface within the low pressure portion of the interior space, the peripheral edge of the rotatable surface and the inner surface of the outer enclosure defining a first gap, and while the vacuum pump is pumping the gas, the gas can flow from the low pressure portion to the high pressure portion through the first gap, a drive connected to the rotatable surface, the drive being operable to rotate the rotatable surface with at least a portion of the rotatable surface having a tangential velocity within a range of about 1 to 6 times a most likely velocity of the gas molecules over a pressure range in the low pressure section from a starting pressure of about 1 atm to the target minimum pressure, to cause the gas molecules to flow outwardly from a peripheral edge of the rotatable surface through the gap to reduce the pressure in the low pressure section to the predetermined target minimum pressure, the target minimum pressure being at least about 10 -4 and a drive mechanism, which is as low as 1 atm.

[0145] In various embodiments, for the vacuum pump, the target minimum pressure is about 10 -4 ~10 -6atm. The first dimension of the first gap is in the range of about 0.5 mm to about 100 mm. The rotatable surface includes a circular ring having a central opening, a radial dimension between the central opening and a peripheral edge, an interior open portion and a peripheral portion having a dimension in the range of about 0.05 to less than 0.5 times the radial dimension. The vacuum pump can include a plurality of substantially parallel planar rotatable surfaces arranged in a stacked configuration. The drive is operable to rotate the rotatable surfaces with at least a portion of the rotatable surfaces having a tangential velocity having a first velocity value when the pressure in the low pressure section is about a start pressure, and one or more second velocity values ​​that are progressively greater than the first velocity value as the pressure in the low pressure section decreases toward a target minimum pressure.

[0146] In one embodiment, a vacuum pump for pumping a gas includes a substantially gas impermeable outer enclosure defining an interior space having an inner surface, and a plurality of rotatable rings arranged in a stack within the interior space, the stack having a top ring and a bottom ring, each ring of the plurality of rings being substantially circular and having an interior open portion, an axis of rotation, a peripheral edge, a first circumferential surface about the peripheral edge, and a second circumferential surface about the peripheral edge opposite the first circumferential surface, the first circumferential surface and the second circumferential surface being substantially planar. and a rotatable ring, where the stack of rotatable rings separates the interior space into a low pressure section and a high pressure section, a first peripheral surface of the top ring faces the low pressure section and a second peripheral surface of the bottom ring faces the high pressure section, the inner surfaces are inclined outwardly about a peripheral edge of the rotatable surfaces within the low pressure section of the interior space, the peripheral edge of the rotatable surfaces and the inner surface of the outer enclosure define a first gap, where gas can flow from the low pressure section to the high pressure section through the first gap while the vacuum pump is pumping the gas, where there is no seal to prevent gas from leaking back from the high pressure section through the first gap, and the first gap has a first dimension. the first dimension being determined by the length of the mean free path of the gas at a predetermined target minimum pressure in the low pressure section so as to prevent gas leaking back from the high pressure section to the low pressure section from restricting the net outflow of gas from the low pressure section to the high pressure section while the vacuum pump is pumping the gas until the pressure in the low pressure section reaches the target minimum pressure; and a drive connected to the stack of rotatable rings, the drive being operable when the vacuum pump is pumping the gas to rotate the stack of rotatable rings, the first circumferential surface and the second circumferential surface of each ring having a tangential velocity within a range of about 1 to 6 times the most likely velocity of the gas molecules in the low pressure section to cause the gas molecules in the low pressure section to flow outward through the gap to reduce the pressure in the low pressure section.

[0147] In various embodiments, for the vacuum pump, the target minimum pressure is at least about 10 -4 The drive is operable as the vacuum pump pumps gas to rotate the stack of rotatable rings, the first and second circumferential surfaces of each ring having a tangential velocity within a range of about 1 to 6 times the most probable velocity of the molecules of the gas over a pressure range of the low pressure section from a starting pressure of about 1 atm to a target minimum pressure. The target minimum pressure is about 10 -4 ~10 -6 Within the ATM range.

[0148] The drive is operable when the vacuum pump is pumping gas to rotate the stack of rotatable rings, the first and second circumferential surfaces of each ring having a tangential velocity in a range of about 1 to 6 times the most likely velocity of a molecule of the gas over a pressure range of the low pressure section from a starting pressure of about 1 atm to a target minimum pressure. The drive is operable when the vacuum pump is pumping gas to rotate the stack of rotatable rings, the first and second circumferential surfaces of each ring having a tangential velocity having a first velocity value when the pressure in the low pressure section has a predetermined starting value and one or more second velocity values ​​that are progressively greater than the first velocity value as the pressure in the low pressure section decreases toward the target minimum pressure.

[0149] The foregoing description of some specific exemplary embodiments of a non-hermetic vacuum pump having a supersonic rotatable vaneless gas impingement surface and its various components and elements is given for illustrative purposes only and is not intended and should not be construed as limiting or excluding other possible embodiments. Those skilled in the art will appreciate that a wide variety of modifications and changes can be made to and / or substituted for the specific exemplary embodiments, components, and elements shown and described herein, and that various aspects of the specific exemplary embodiments shown and described can be combined in various ways to achieve yet further embodiments, without departing from the spirit or scope of the disclosure or the invention. Thus, it is intended that the scope of the invention that is the subject of this application, including any adaptations or modifications of the embodiments, whether or not specifically described herein, be defined by the appended claims.

Claims

1. a housing having an internal space, the internal space having a low pressure portion and a high pressure portion; a partition separating the low pressure section from the high pressure section, the partition being gas impermeable and stationary, the partition having a first surface facing the high pressure section and a second surface opposite the first surface facing the low pressure section; a gas flow path for gas to flow from the low pressure section to the high pressure section, no seal is provided to prevent the gas from leaking back from the high pressure section to the low pressure section via the gas flow path; a rotatable surface of the high pressure section, the rotatable surface having a planar, featureless first surface adjacent and facing the first surface of the bulkhead, the first surface adapted to be passively impacted by molecules of the gas entering the high pressure section via the gas flow passage; 1. A vacuum pump comprising: a drive coupled to the rotatable surface, the drive operable to rotate the rotatable surface having at least a portion of the rotatable surface having a tangential velocity within a range of 1 to 6 times the most likely velocity of the molecules of the gas impinging on the rotatable surface over a range of pressures in the low pressure section from a starting pressure to a target minimum pressure, the vacuum pump reducing pressure from the starting pressure to the target minimum pressure in a single pumping stage before the molecules of the gas leaking back from the high pressure section to the low pressure section limit further reduction in pressure in the low pressure section.

2. The starting pressure is 1 atm and the target minimum pressure is at least 10 -４ From 10 -６ 2. The vacuum pump of claim 1, wherein the pressure is in the range of atm.

3. 2. The vacuum pump of claim 1, wherein the starting pressure is 1 atm and the target minimum pressure is at least as low as 0.5 atm.

4. 2. The vacuum pump of claim 1, wherein the housing includes an inlet in gaseous communication with a space outside the housing and with the low pressure section, and an outlet in gaseous communication with the high pressure section.

5. 5. The vacuum pump of claim 4, wherein the space outside the housing is an ambient environment.

6. 5. The vacuum pump of claim 4, wherein the low pressure portion extends at least partially through the inlet to the space outside the housing.

7. 5. The vacuum pump of claim 4, wherein said inlet comprises a plurality of spaced first openings in said housing.

8. A vacuum pump as described in claim 1, wherein the first surface of the partition and the first surface of the rotatable surface are separated by a first gap, the first gap having a first dimension selected relative to the length of the mean free path of the gas at the target minimum pressure, such that the first gap is capable of providing a net outflow of the gas from the low pressure section to the high pressure section while the vacuum pump is pumping the gas until the pressure in the low pressure section reaches the target minimum pressure.

9. 9. The vacuum pump of claim 8, wherein the second surface is planar.

10. 9. The vacuum pump of claim 8, wherein the first dimension is in the range of 0.5 mm to 100 mm.

11. 2. The vacuum pump of claim 1, wherein the partition has a second surface, the second surface exposed to the high pressure section, the rotatable surface comprises a periphery having a peripheral edge, the peripheral edge comprising a cylinder having a cylinder wall extending outwardly relative to the first surface, the cylinder wall and the second surface of the partition being separated by a first gap.

12. 12. The vacuum pump of claim 11, wherein the first gap has a first dimension selected relative to a length of a mean free path of the gas at the target minimum pressure such that the first gap allows a net outflow of the gas from the low pressure section to the high pressure section while the vacuum pump is pumping the gas until the pressure in the low pressure section reaches the target minimum pressure.

13. the rotatable surface having a central portion, an axis of rotation within the central portion, and a periphery spaced from the axis of rotation; a distance between the axis of rotation and the periphery having a first width; the first surface of the rotatable surface has a peripheral portion extending around the peripheral edge between the axis of rotation and the peripheral edge; 2. The vacuum pump of claim 1, wherein said peripheral portion has a second width in the range of 0.05 to 1.0 times said first width.

14. 14. The vacuum pump of claim 13, wherein the gas flow passage includes a second opening in the partition, the second opening being located adjacent a central portion of the rotatable surface.

15. 14. The vacuum pump of claim 13, wherein the gas flow passage comprises a plurality of second openings in the partition, the plurality of second openings being interspersed between the axis of rotation and the periphery of the rotatable surface at one or more radial distances from the axis of rotation.

16. 10. The vacuum pump of claim 1 comprising a plurality of parallel rotatable surfaces constructed and arranged in a stacked configuration.

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