RATHGE ROBERT D
| US3189264A | 1965-06-15 | |||
| DE2757599A1 | 1979-06-28 | |||
| GB2114663A | 1983-08-24 | |||
| US4535457A | 1985-08-13 | |||
| US3623826A | 1971-11-30 | |||
| FR2305617A1 | 1976-10-22 |
| 1. | A turbomolecular blower for increasing the flow velocity of gases, for increasing the compression ratio therethrough up to 107, for providing noncontaminated, high purity gas for use in a laser system or other system requiring gas flow, said turbomolecular blower comprising: a blower assembly, said blower assembly further including: a housing; a stator, said stator mounted within said housing; and a rotor, said rotor mounted within said housing and operably connected to the stator; said rotor mounted within said housing by seal means to prevent the contamination of the gases flowing through said turbomolecular blower; and a motor assembly, said motor assembly powering said blower assembly. |
| 2. | A turbomolecular blower as defined in claim 1 further including means for cooling placed about said housing. |
| 3. | A turbomolecular blower as defined in claim 1 further including means for gearing between said motor assembly and said blower assembly. |
| 4. | A turbomolecular blower as defined in claim 1 wherein said rotor and said stator have turbinelike blades for increased aerodynamic efficiency. |
| 5. | A turbomolecular blower as defined in claim 1 wherein said motor assembly has an electric motor therein having an output shaft that is connected to said rotor by means of a flexible coupler. |
| 6. | A turbomolecular blower as defined in claim 1 wherein said rotor has a rotor shaft and said rotor shaft is held within said housing by means of a shaft alignment bearing to allow adjustment between said rotor and said stator. |
| 7. | A turbomolecular blower as defined in claim 1 wherein said motor assembly has a motor therein of at least one horsepower. |
| 8. | A turbomolecular blower as defined in claim 1 further including means to prevent any particles from entering the rotor/stator creating catastrophic damage. |
| 9. | A turbomolecular blower as defined in claim 1 wherein said seal means provides a noncontaminating environment. |
| 10. | A turbomolecular blower as defined in claim 9 wherein said means to prevent is a chemically resistant, rotating oilfree, ferrofluidic seal. |
| 11. | A turbomolecular blower as defined in claim 1 wherein said turbomolecular blower operates at a pressure from about 0.1 to about 100 torr. |
| 12. | A turbomolecular blower defined in claim 1 wherein an output of said turbomolecular blower is a gas flow having a velocity from about 1 meter per second to about several hundred meters per second. |
| 13. | A turbomolecular blower as defined in claim 1 wherein the molecular weight of the gas ranges from about 2 to about 1000 amuls. |
| 14. | A turbomolecular blower as defined in claim 13 wherein the molecular weight is preferably from about 250 to about 1000 amuls. |
| 15. | A turbomolecular blower as defined in claim 14 wherein the gas is an alkyliodide. |
| 16. | A turbomolecular blower as defined in claim 15 wherein the gas in C.FI. |
| 17. | A turbomolecular blower as defined in claim 1 wherein a motor in said motor assembly operates either at a fixed or variable speed, said speed being up to at least 20,000 rpm. |
| 18. | A turbomolecular blower as defined in claim 1 further including heating and/or cooling means before or after said blower to condition said gas. AMENDED CLAIMS [received by the International Bureau on 24 January 1994 (24.01.94) original claims 118 replaced by amended claims 113 (4 pages)] 1 A laser system, said laser system having a high molecular weight gas as a laser fuel, said laser system requiring a high velocity flow of said laser fuel, said laser system having a closed cycle fuel system and requiring said laser fuel to be of very high purity, said laser system comprising: a means for lasing, said means for lasing having a laser gain cell for receiving said laser fuel, said laser gain cell requiring said laser fuel to be flowing at a high velocity and at a selected low pressure, said lasing means causing said laser fuel to lase, said lasing means outputting said laser fuel with byproducts therein; a means for circulating said laser fuel at said high velocity flow, at said selected low pressure through said means for lasing, said means for circulating providing said high flow velocity in a range of about 1 m/s to 100 m/s, said means for circulating increasing a compression ratio therethrough up to about 107:1, said laser fuel being output from said means for circulating having said selected pressure in a range of about 0.1 to 100 torr, said means for circulating not contaminating said laser fuel of said closed cycle fuel system; and a means for generating said laser fuel in a gaseous form and for removing lasing byproducts from an output of said lasing means, said means for generating condensing said gaseous laser fuel to a liquid fuel and gasifying said liquid fuel, said means for generating inputting said laser fuel into said means for circulating. |
| 19. | A laser system as defined in claim 1 wherein said means for circulating said laser fuel at said high velocity flow, said high velocity flow, at said selected low pressure, is a turbomolecular blower, said turbomolecular blower comprising: a blower assembly, said blower assembly providing a continuous, high velocity and pressurized gas flow, said high velocity flow being in the range from 1 m/s to 100 m/s and said laser fuel having a pressure in the range of about 0.1 to 100 torr, said blower assembly further comprising: a housing, said housing having at least one inlet and at least one outlet for said laser fuel, said housing having cooling means thereabout to reduce heating caused by said high molecular weight gas flowing therethrough; a stator, said stator mounted within said housing; a rotor, said rotor mounted within said housing and operably connected to said stator, said rotor and said stator operably connected to produce a compression ratio of about 107:1; a means for rotatably mounting said rotor in said housing and for preventing contamination of said laser fuel being of very high purity flowing through said blower and into said means for lasing; and a motor assembly, said motor assembly mounted externally to said housing and thereon for powering said rotor of said blower assembly, said motor assembly having a motor of at least one horsepower. |
| 20. | A laser system as defined in claim 1 wherein said high velocity flow ranges from about 10 m/s to about 100 m/s. |
| 21. | A laser system as defined in claim 1 wherein selected low pressure ranges from about 5 to 60 torr. |
| 22. | A laser system as defined in claim 1 being of high power laser output. |
| 23. | A laser system as defined in claim 1 wherein said high molecular weight gas has a molecular weight in the range from about 2 to 1000 amu's. |
| 24. | A laser system as defined in claim 6 wherein said gas is an alkyliodide. |
| 25. | A laser system as defined in claim 7 wherein said alkyliodide is C3F7I. |
| 26. | A laser system as defined in claim 2 wherein said rotor and stator produce a compression ratio in the range of about 10:1 to 1000:1. |
| 27. | A laser system as defined in claim 2 further including means for changing the speed of said rotor, said means for changing the speed being located between said motor assembly and said blower assembly. |
| 28. | A laser system as defined in claim 2 wherein said rotor and said stator have turbinelike blades for increased aerodynamic efficiency, said blades being curved to create more forward gas motion for increasing the compression ratio. |
| 29. | A laser system as defined in claim 2 further including means to prevent any particles from entering the rotor/stator area to prevent damage thereto. |
| 30. | A laser system as defined in claim 2 further including heating and/or cooling means before or after said blower to condition said gas. |
Turbo-Molecular Blower
Statement of Government Interest
The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.
Background of the Invention
The present invention relates to a gas blower, and in particular, to a gas blower used in lasers- Typical gas lasers such as CO , CO, HF/DF and photolytic iodine lasers require a flow of the gas medium in order to remove gas heating or discharge/photolytic by-products. For open cycle lasers where the gas is not recirculated, there exists many types of blowers and pumps exhibiting good pumping capacity for pressures greater than a few tenths of torr as illustrated in Figure 2. These blowers, Figures 2A and 2B, for example, are not suitable in closed cycle gas handling systems requiring minimal contamination because the rotating seals and bearings are oil lubricated. For high pressures (> 100 torr) , closed cycle laser systems, a van-axial fan blower using ferrofluidic seals have been used with some success. Unfortunately, at pressures below 100 torr, no blowers exist having any reasonable pumping capacity to produce high flow velocities without creating gas contamination. A C ,
pulsed photolytic atomic iodine laser at 1.315 microns uses a very heavy molecule C_F_I as the starting gaseous species for promoting lasing. Previously, only passive C F_I flow systems have been used providing flow velocities of only 1-2 m/sec. For higher power cw and higher repetition rate pulsed photolytic iodine lasers, much higher flow velocities are required. To overcome this limitation, an internal blower capable of flow velocities greater than 10 m/s for C F_I while operating at relatively low pressures of 20-60 torr is required. Previous pumps operating at very fast rpms (- 20,000) had rotors interleaved between stators which provided excellent pumping capacity for pressures of 10 -9 to approximately 10 -3 torr. Figure 5 shows typical pumping curves for such turbo-molecular pumps. The loss of pumping capacity for pressures greater than a millitorr occurs because the torque power provided by the internal motor of conventional pumps is insufficient to pump the higher gas densities experienced as the pressure increases. Another deficiency of existing turbo-molecular pumps is the oil-lubricated bearings and elastomer or 0-ring rotating seal. Many of these pumps overcome oil contamination problems by exhausting gas to the external environment through the rotating seal. Two conventional non-contaminating blowers being the piston drive and centrifugal could not simultaneously produce the flow velocity and sustained operation with this heavy molecule. These problems prevented their use as an internal, closed cycle blower of gases at pressures in the 0.1 to 100 torr range while still providing contamination-free gas.
Summary of the Invention
The present invention is a turbo-molecular blower for use in a closed cycle laser system using high molecular weight gases.
The turbo-molecular pump of the present invention comprises, basically, a series of axial, rotating high-speed rotor disks being interleaved with stationary stator blades. The rotor shaft is mounted in the blower housing by means of a ferrofluidic rotating seal which prevents oil contamination and provides vacuum integrity. Because of the high molecular weight gases and the velocities needed of such, an external multi-horsepower motor drives the blower. External cooling is further provided to reduce heat generated by the blower. Due to the high torque available, pressures from 0.1 to 100 torr are possible with high density gases and high flow velocities.
Therefore, one object of the present invention is to provide a turbo-molecular blower providing high velocity gas flow of low and high molecular weight gas
I vapors at low ( < 0.1 torr ) to intermediate pressure ( < 100 torr ) .
Another object of the present invention is to provide a turbo-molecular blower capable of large compressions of circulated molecular gases.
Another object of the present invention is to provide a turbo-molecular blower that provides impurity/contaminant free flow and a flow of atomic/molecular gases over large pressure ranges (0.1 to 100 torr) .
Another object of the present invention is to provide a turbo-molecular blower that provides uniformly constant gas flow of atomic/molecular gases necessary to create non-perturbative gas flow in
pulsed/cw high power/energy photolytic atomic iodine laser at 1.315 microns.
Another object of the present invention is to provide a turbo-molecular blower that creates continuous and reliable gas flow of alkyl iodides in pulsed and cw iodine laser in the presence of high electromagnetic field intensities (emi) .
Another object of the present invention is to provide a turbo-molecular blower that operates in conjunction with condensative/evaporative iodine (I-) removal system for the alkyl iodide laser "fuel"
C 3 F 7 I.
Another object of the present invention is to provide a turbo-molecular blower that provides operation of a laser system such that a variable velocity is selectable via changing the rotational speed of the rotors by employing variable speed a.c. or d.c. motors.
Another object of the present invention is to provide a turbo-molecular blower employing rotor and stator blades being aerodynamically shaped for higher efficiencies.
Another object of the present invention is to provide a turbo-molecular blower that provides an internal blower with an easily exchangeable external motor.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the pertinent art from the following detailed description of preferred embodiments of the invention and the related drawings.
Brief Description of the Drawings
Figure 1 illustrates by schematic the turbo-molecular blower of the present invention.
Figures 2A and 2B illustrate two prior types of pumps.
Figure 3 is a side view cross section of the turbo-molecular blower of the present invention. Figure 4 illustrates an application whereby the turbo-molecular blower of this invention is coupled with a I laser (fuel) C_F I supply, condenser and evaporator sections, and an I_ removal system.
Figure 5 illustrates by graph pumping speed in relation to pressure created.
Figures 6 illustrates by graph a pumping speed curve for conventional turbo-molecular pumps.
Detailed Description of the Preferred Embodiment
Referring to Figure 4, a partial laser system 10 is shown. A laser cavity 12 is connected to a turbo-molecular blower 14 that receives a heavy molecular weight gas such as C F_I from a fuel/byproduct removal section 16. The fuel with by-products therein leaving laser cavity 12 are input into the fuel/byproduct removal section 16 for appropriate treatment therein. Fuel is output therefrom and is circulated back to the laser cavity 12, i.e., thus a closed cycle system. Although the turbo-molecular blower 14 was specifically made with the above system in mind, it can be used with other systems.
The following patents are incorporated by reference U.S. Patent 4,535,457; U.S. Patent 5,055,741; and U.S. Patent 5,008,593. Further, any published article before the filing date by either inventor is incorporated by reference..
Referring to Figure 1, the turbo-molecular blower 14 is shown schematically. Therein, an axial rotor 18 having a set of rotor blades 20 are interleaved with a
set of stator blades 24 of stator 22. The rotor blades 20 are attached to a rotor shaft 26. The inside of the turbo-molecular blower 14 is vacuum isolated from the external environment by means of a ferrofluidic rotating vacuum seal 28 about the shaft 26. The rotor shaft 26 is secured in axial alignment by means of an external shaft alignment bearing 30 which is essential for high rpm operation. The rotor shaft 26 is further connected by a flexible coupling 32 to a multi-horsepower motor 34, for example, 2 h.p. a.c, to transfer torque and minimize any vibration on the rotor shaft 26. At the gas inlet 36, a fine screen 38 is placed to prevent any particles from impinging on the rotor blades 20 or the stator blades 24. Due to the higher gas densities at typically 2000-3400 rmp rotor shaft rotations present in this blower 14, external water cooling coils 40 on the blower housing 42 is required. Such wall heating occurs due to the increased kinetic energy of the gases being transported. At the bottom of the blower 14, many different output ports 44 are available, if needed.
Referring to Figure 3, a detailed cross section of the turbo-molecular blower 14 is shown. Similar items as seen in Figure 1 are identified therein. The turbo-molecular blower 14 has a low pressure section 46 and a high pressure section 48. The pressure change from the low to the high pressure section would be gradual. The additional details as seen in Figure 3 provide means for holding the elements noted in Figure 1.
As seen in Figure 3, a blower assembly 50 is connected to a motor assembly 52. The blower assembly 50 comprises a blower inlet flange 54 connected to an inlet flange 56. This is connected to a blower
housing 58 having connected at the base thereof a baseplate 60 and the outlet ports 44. A rotor 18 is attached in a rotor support 62.
The motor assembly 52 comprises the electric motor 34 attached to a motor flange 66. This is connected to the baseplate 60. The electric motor 34 has its output shaft 68 connected to a flexible coupler 32. The rotor shaft 26 is also connected to the flexible coupler 32 as explained above. The rotor shaft 26 is centered by means of the shaft alignment bearing 30 and farther attached therein is the ferrofluidic rotating seal 28 which vacuum protects the interior of the blower assembly 50 from contamination. A seal cap 64 retains the seal 28 within the rotor support 62. The rotor 18 comprises the rotor shaft 26 connected to a rotor body 72 with the rotor blades 20 connected thereon. A rotor cap 74 and a cover plate 76 are placed on top of the rotor body 72. The stator 22 comprises a spacer ring 70 which has the stator blades 24 attached thereon.
The gas of concern enters through the inlet 36 and flows into the low pressure section 46, high pressure sections 48, and out the outlet ports 44.
The manner of connecting/attaching or otherwise securing the above items in considered conventional. The turbo-molecular blower 14 used a casing from an Airco-Corp turbo-molecular pump 1514. The Airco-Corp turbo-molecular pump Model 1514 was modified by removing the internally mounted low torque, high rpm frequency controlled motor and installing the rotor support 62 to hold the vacuum and pressure seal. This rotor support 62 contained the non-oil contaminating, vacuum or pressure Ferrofluidic (MIN sc-1000-C) rotating seal 28 and the external alignment bearing 30 which is mounted around the rotor
shaft 26 to assure concentric rotor 18 rotation protecting both the stators and the ferrofluidic seal. A flexible coupling 32 was employed to connect the rotor shaft 26 to the motor 34. The motor 34 was attached to the blower housing via 10 motor support rods. Although the motor is mounted externally in the present application, an internal motor is possible but this is complicated by motor heating and the space available in the housing. Greater flexibility is achieved when the motor is mounted external to the blower housing. Finally, the rotor shaft 26 was driven by either an a.c. motor, for example, 2 h.p., rotating at, for example, 3400 rpm or a variable d.c. motor. The diameter of the rotors and stators were 16". This size was required because of an existing housing but, clearly, any size may be appropriate depending on the driven gas and other requirements. The turbo-molecular blower 14 is capable of operating up to about 20,000 rpm. Because of the heat generated when driving high amu molecules, the cooling coils 40, Figure 1, were placed about the blower housing 58. At the bottom compression side of the blower 14, Figure 1 shows two exit ports which provide C_F--I at flow velocities greater than 10 m/s to the iodine gain cells. The flow velocities were initially measured using a 1 inch Vortex flow meter, M/N YF102.
Figure 4 depicts the integration of this turbo-molecular blower 14 into a C F_I laser "fuel"/iodine (I ) removal system 10 employed in both cw and pulsed photolytically excited atomic iodine lasers. C 3 F 7 I molecule has a mass of 293 amu. At the left side of the turbo-molecular blower 14 is the condenser 80/evaporator 82 sections which provide "clean" C F7I absent of any of the excited iodine quencher I , The condenser section 80 liquifies the
gas from the laser gain cell 12 whereas the evaportor section 82 causes the desired gas to evaporate from the liquid state and enter the turbo-molecular blower 14. The C F I gas output from this system is connected to the input of the turbo-molecular blower 14 where its gas pressure is increased generating a fast flow velocity through the iodine gain cells. Using this system, flow velocities greater than 10 m/s for 5 - 60 torr C F_I pressures occurred when the motor rotated at 3400 rmp were generated. Water cooling was required on the outside of this turbo-molecular blower 14 due to gas heating of the wall generated due to the higher C-F..I flow velocities. The flow velocity was uniform and satisfied both cw and pulsed modes of laser operation. Use of this turbo-molecular blower for other gases at pressures anywhere from 0.1 to 100 torr is very practical.
The above turbo-molecular blower 14 can further be improved by aerodynamic assistance using gas turbine blade configurations having curved rotors/stators with increasing radii along the direction of flow and by using a gear box to increase the rotor speed. With the above turbo-molecular blower 14, the turbo-molecular blower 14 provides for the establishment of fast gas flow of high molecular weight alkyl iodide gaseous vapors at low (< 0.1 torr) to intermediate pressure (< 100 torr ) ; creates large compressions of circulated molecular gases; provides impurity/contaminant free flow of alkyl iodides over large temperatures and pressure range; provides uniformly constant gas flow in pulsed/cw high power/energy photolytic atomic iodine laser at 1.315 microns; creates continuous and reliable gas flow of
alkyl iodides in pulsed and cw iodine laser in the presence of high electromagnetic field intensities (emi) ; operates in conjunction with condensative/evaporative chemical iodine removal system for the alkyl iodide laser "fuel" C F I; incorporates either a pulsed or cw photolytic iodine laser utilizing longitudinal or transverse flow or any gas flow system as a series component; operates at low pressure while still producing large pumping speeds. Clearly, many modifications and variations of the present invention are possible in light of the above teachings and it is therefore understood, that within the inventive scope of the inventive concept, the invention may be practiced otherwise than specifically claimed.
What is claimed is: