US2983832A - Fluid supported rotor - Google Patents

Description

Patented May 9, 1961 FLUID SUPPoRTED RoToR Elmer Fred Macks, Vermilion, Ohio, assigner, by direct and mesne assignments, to Air-Glide, Inc., Cleveland, Ohio, a corporation Filed Jan. 28, 1958, Ser. No. 714,454

23 Claims. (Cl. S10-90) This invention relates to dynamoelectric devices and more particularly to a dynamoelectric device having relatively rotatable rotor and stator elements in which the rotor is totally supported on a film of fluid when the device is in operation,

This application is a continuation in part of United States patent application Number 558,676 tiled January 12, 1956, by Elmer Fred Macks under the title of Fluid Supported Rotor, which application has been abandoned in favor of this application. This application is also a continuation in part of United States patent application Number 643,666 filed March 4, 1957, by Elmer Fred Macks under the title of Air Supported Rotor, now United States Patent No. 2,889,474, issued June 2, 1959. Additional patent applications which present related, but independent, inventions are Serial Number 577,828 filed April 12, 1956, under the title of Dynamoelectric Device With Fluid Supported Rotor, now United States Patent No. 2,937,295 issued May 17, 1960, Serial Number 578,536, led April 16, 1956, under the title of Fluid Dynamic Device, now United States Patent No. 2,916,642 issued December 8, 1959, Serial Number 580,- 133 led April 23, 1956, under the title of Fluid Supported Rotor and United States application Number 700,651 filed December 4, 1957, under the title of Dynarnoelectric Device, now United States Patent No. 2,928,960 issued March l5, 1960.

This invention is directed to dynamoelectric devices wherein the rotor is totally supported radially on a lm of fluid, which film is preferably an air lm generated upon relative rotation of the rotor and stator. The uid in such iilm is supplied by fluid which is ambient to the dynamoelectric device.

It has been discovered that if a smooth cylindrically contoured surface is provided in a stator, and a complemental smooth cylindrically contoured surface is provided on a rotor, the rotor may be supported in the stator for free, substantially frictionless rotation even with air ambient to the motor as the lubricant. This is achieved by providing a precision running t between the cylindrically contoured surfaces. As the elements are relatively rotated, a load carrying fluid film is produced between the elements and the rotor is totally supported radially on such fluid lm in spaced relationship with the stator.

Rotors and armatures are ordinarily provided with shafts or slides to guide their motion during rotation or translation. Dynamoelectric machines which are required .to operate for long periods present a bearing problem since continuous lubrication is required to prevent structural failure. The cost of producing a machine is materially aifected by the bearing since close tolerances must be met in producing the bearing mounts in proper align,

ment. Also, bearing material-lubricant combinations of adequate quality for long continuous use are necessarily expensive.

Accordingly, one of the principal objects of this invention is to provide a new and novel dynamoelectric device of simple and inexpensive construction and a device which, at the same time, has a long life and an increased eliiciency.

Another object of the invention is to provide a novel and improved dynamoelectric machine which has a single film of ambient fluid developed in a fluid lm producing region located between complemental surfaces on the rotor and stator, and developed upon relative rotation of the rotor and stator.

Another object of the invention is to provide a novel and improved dynamoelectric machine in which the rotating member is totally supported radially on a ilm of gas, supplied by the gas ambient to the machine, to permit the rotor to rotate about its center of mass as opposed to its geometric axis.

Still another object of the invention is to provide a machine in which the outer surface of the rotor and the inner surface of the stator form a hydrodynamic lm therebetween of the fluid ambient to the machine.

A further object of this invention is to provide a machine in which the outer surface of the rotor and the inner surface of the stator form a gas load carrying film or pneumodynamic lm therebetween of the fluid ambient to the machine.

An additional object of this invention is to provide a machine in which a gas lm of the gas ambient to the machine is formed between the outer surface of the rotor and the inner surface of a non-magnetic sleeve.

A still further object of the invention is to provide a machine in which an inner surface on the rotatable element confronts an outer surface on the stationary element with the geometric tolerance and surface iinishes being such that a pneumodynamic load carrying lm of the ambient gas such as air is formed between the surfaces, and the rotating element is supported out of contact with the stationary element during relative rotation.

Yet another object of the invention is to provide a dynamoelectric machine in which the rotor is totally supported on a film of air supplied by the ambient atmosphere to provide a small, light, quiet machine at low production costs.

Still another object of the invention is to provide a novel and improved machine made in accordance with the foregoing in which the rotor is totally supported radially on a film of ambient air to provide an efcient maintenance free machine which is eiciently operable in a wide range of temperature conditions and with a very wide speed range.

A further object of the invention is to provide an odorless dynamoelectric machine which has a high eiiiciency, an extremely long life and an ambient air supported rotor which will coast for long periods of time and operate even though only very crudely balanced as compared with prior known constructions.

These listed objects will outline the invention, but other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a sectional view of a dynamoelectric device in which a load carrying fluid dynamic lrn is developed to hold the rotor and stator elements in spaced relationship;

Figure 2 is a sectional View of a dynamoelectric device similar to the device of Figure l wherein a sleeve is carried by one of the relatively rotating elements;

Figure 3 is a sectional view of an electric motor for vertical operation;

Figure 4 is a sectional view of the device of Figure V3 as seen from the plane indicated by the line 4 4 of Figure 3; and,

Figures 5 through 10 are sectional views of dynamo- Y'disposed in any other direction.

electric machines each disclosing an alternate construction embodying the principles of this invention.

Referring to the drawing and to Figure l in particular, the dynamoelectric device disclosed may be either a motor or a generator in which a rotor 10 is an armature. The rotor Iy has a shaft 12 fixed to it as its geometric center. A stator 14, including the usual pole pieces, at least partially, surrounds the rotor 10. The stator 14 is provided with a set of windings 16 which produce'the magnetic effects in the pole pieces of the stator.

The absence of conventional bearings requires that the rotor and stator 14, as an assembly, function as vthe bearing elements. It is also considered desirable to use the ambient fluid in which the motor operates as the lubricant. In most instances air is available, but any liquid or gas can be used. The use of air as a lubricant is preferred both because of its availability and because of its superior operating characteristics in many applications. The use of air is accomplished by developing a pneumodynamic load carrying lilm of air between the relatively rotating parts. The load carrying iilm has pressure characteristics which are suicient to support the load.

The film is produced when the geometric tolerance and surface conditions are held within certain limitations which will subsequently be described in more detail. These conditions, as applied to the embodiments included herein, affect in particular the surface finish, clearance, taper and out-of-round. These conditions also vary with the operating conditions such as speed and temperature and with the viscosity of the iluid which is being used as the lubricant. A surface Vfinish is required to be in the order of 16 microinch R.M.S. or smoother with a liquid as the ambient fluid. The taper which is allowable between the surfaces with a liquid as the ambient uid is limited to the order of 0.0003 inch per inch of length. In the fluid film region designated by the letter R in Figure l, the radial clearance between the `confronting surfaces when they are concentric is limited to a ratio having a range within the limits of 0.000050 to 0.003 inch per inch of diameter. For convenience, reference is made to rotor surface diameter in the claims. However, because of the high ratio between the diameter and the clearance, either surface may be used as a reference.

The clearance ratio generally increases with both an increase in the viscosity of the ambient uid and with a decrease in diameter. With air or gas as the lubricant the preferred radial clearance is between 0.000050 to 0.0005 inch per inch of diameter, this clearance ratio generally increasing with a decrease in diameter. The clearance varies widely depending on operating variables such as the speed of rotation. For satisfactory over-all performance with air or gas as the lubricant the out-ofround tolerance of the confronting surfaces is held within approximately 0.0001 Vinch per inch of diameter and total taper is held within one-quarter the radial clearance.

A dynamoelectric machine constructed with the previ- Vously outlined characteristics operates with the rotor out of contact with the stator. Air or other gases, as well as fluids, will maintain the device operative indefinitely since there is no contact between the relatively rotating surfaces. The shaft 12 functions to transmit torque from the motor. The Vrotor is positioned axially by the magnetic eld or by an external device connected to the motor drive shaft 12. The rotor is totally supported on the load-carrying hydrodynamic film of fluid generated in the region ,R when there is relative rotation between the rotor 10 and the stator 14. This total support is radially speaking, and it is present whether the rotation is about a horizontal axis as shown, or about an axis The influence of the magnetic eld of the stator is relied upon to hold the rotor in position axiallyspeaking when the motor is in operation in a generally horizontal position. Therefore, the rotor is held totally supported by the film of uid. Thrust means may be provided for devices wherein the axis of rotation approaches a vertical and to limit axis shifting of the rotor when the eld is inactivated. The thrust means will subsequently be described in more detail. The performance of dynamoelectric machines made in accordance with this invention is outstanding. in the case of fractional horsepower induction motors, for example, it has been found that an eliiciency increase of 25 percent may be achieved. All noise, other than transformer noise, is completely eliminated, since there is no contact of the moving parts in any direction even with ambient air as the only lubricant.

With air or gas as lubricant another outstanding advantage of the invention is believed to reside in the unitary bearing concept. In all cases a single load-carrying film offers several unexpected and highly desirable results.

In the case of alternating current dynamoelectric machines, a phenomenon has been discovered which materially enhances the operation of these machines and therefore serves to contribute to the outstanding results achieved. Since the rotor is free to shift in any direction against the pressure of the load-carrying fluid film `and against the resistence of the magnetic field, the rotor in an alternating current device tends to reciprocate up and down in a very minute fashion at twice line frequency. VThis reciprocation against the load-carrying film has the effect of increasing the pressure of the lm and therefore increasing the load-carrying capacity of the film. The single fluid film associated with the unitary bearing conceptV enhances the inherent ability of an alternating current dynamoelectric device to more fully utilize the squeeze-film increase in load-carrying capacity.

Also the construction of these dynamoelectric machines with a single load-carrying gas film is such that in many instances the rotor is permitted to rotate about its own center of mass rather than its geometric center. Thus, vibration is reduced substantially and in many cases balancing of the rotating assembly may be eliminated.

Fulther, bearing stability is inherently enhanced by operation within an alternating current magnetic iield. Normally, at high speeds and high clearance ratios bearing whirl Vdevelops in pneumodynamic film devices causing vibration which ultimately leads to failure. The squeeze-film action of the alternating current device greatly extends the operating speed and clearance ratio range of unitary pneumodynamic support in dynamoelectric equipment. This increase in the ratio range also contributes to the decrease in the need for balancing discussed above.

A further contribution of the unitary pneumody-namic supported construction is the elimination of many alignment problems while inherently maintaining the air gap with a high degree of concentricity.

In Figure 2 a dynamoelectric machine is disclosed in which a sleeve 18 is carried in the stator I4. This sleeve is formed from a nonmagnetic material such as bronze or a plastic material such as a cast epoxy. The sleeve also allows formation of a continuous surface throughout the circumference of the bore. However, lthe sleeve 1S need not be continuous around the circumference, but may extend only partially around Vthe circumference, for example, the lower half.

The motor of Figure 3 is adapted for operation with the rotor 10 in a position with the axis of rotation vertical. The Weight of the rotor t0 is supported axially as well as radially. An end plate 20 is mounted on the end of the stator 14, the surface of the plate confronting the surface on the end of the rotor iti to form fa hydro'dynamic iilm therebetween which operates as a thrust bearing.

The end of the rotor 10 is modified asillustrated in Figure 4 to obtain the load supporting film. Either Ythe rotor end or the thrust plate may be modied as indicated be low while the mating surface is iiat and smooth. The surfaces 24 are below the plane of the segments 22 and rims 23 a distance of 0.000020 to 0.002 as required by the unit load to be supported, the ambient fluid, and the speed of rotation. The recesses 24 do not extend to the outer or inner peripheries thereby reducing end leakage by means of rims 23 from the hydrodynamic (film and increasing the load capacity. The number of pairs of recesses 24 and segments 22 may vary from 3 to 36 depending upon the operating conditions. The recesses forming the surfaces 24 may be obtained by etching, stamping, plating or other manufacturing methods for removing, adding or indenting thin sections of material. As an example of operative dimensions with air as a lubricant, assuming the radius of the bore 26 to be 0.2 inch, radius of inner rim 27 to be 0.3 inch, radius 28 to be 2.8 inches, and radius 29 to be 3.0 inches, the recess depth would be 0.0001 inch for a rotational speed of 1,725 revolutions per minute and a load of 4 pounds to be supported.

In Figure 5 the machine is positioned similar to the machine of Figure 3, however, a ball-type thrust bearing 30 is provided at the lower end of the rotor 10 for engaging an end of a housing 32, therefore, supporting the rotor in the vertical position. A seal 34 is disposed between the housing 32 and the shaft 12 in order to prevent the ingress of dirt which would be detrimental to fthe operation of the motor if the contamination were to enter the space between the rotor and the stator 14. Y The dynamoelectric machine of Figure 6 includes the ball-type thrust bearing 30 for positioning the rotor in one direction and a :flange portion 20 on the housing 32. The flange portion 20 has an inner surface which co- .operates with the end surface of the rotor 10 to produce a hydrodynamic load supporting film as required to 'absorb the end thrust of the rotor. The end of the rotor is modified as indicated in Figure 4. Here again the modifications of Figure 4 may be applied to the iiange lwhile Ithe rotor end is kept smooth.

In the construction shown in Figure 7, the rotor 10 includes a bore 36 concentric to the axis of rotation of the shaft 12. The cylindrical inner surface of the bore 36 having the finish characteristics and precision previously described for the critical surfaces. The stator 14 has a stud 38 rotatably aflixed thereto. The stud 38 has an outer surface concentric to the axis of rota- 'tion of the shaft 12 confronting the inner surfaces of fthe rotor 10. The cylindrical outer surface of the stud 38 is formed with the precision previously described for the critical surfaces. Upon rotation of the rotor 10 'the lubricating lm of the ambient uid is produced in the clearance between the rotor bore 36 and .the stud 38. 'i The dynamoelectric device of Figure 8 is similar to the machine of Figure 7 with the exception that thrust absorbing and sealing elements are provided. The ball- `thrust bearing 30 engages `the stator housing 32 when rthevrotor 10 moves in one direction and the end of the :rotor 10 opposite to the bearing 30 and surrounding the bore 36 being configured as shown in Figure 4 produces a hydrodynamic film of fluid between the rotor 110 and the stator 14. A seal 34 prevents the entrance of dirt into the assembly.

In Figure 9 the machine construction differs from that inFigure 8 in that the bore 36 opens away from the shaft 12 and the ball-thrust bearing 30 is disposed be- -tween the inner end of the bore and the end of the stud 38. Axial movement of the rotor 10 is prevented in `the opposite direction by a hydrodynamic film produced between the end of the rotor 10 which is modified in vthe'form shown in Figure 4 and the inwardly extending flange 20 on the stator 14. Here again, the modified lhydrodynamic surface may be on the stationary, rather ,than on the rotating, member.

A"I n Figure `10, the mechanism of Figure 9 is adapted 6 for operation with the axis of rotation vertical and with a hydrodynamic thrust bearing. The end of the stud 38 within the bore 36 is configured as shown in Figure 4 and produces a hydrodynamic film of fluid between the rotor 10 and the stud 38 to support the rotor 10 out of contact with the stud 38 during operation.

When the rotation of the rotor has ceased, the rotor 10 cornes to rest against the stator and slight rubbing contact occurs during the starting and stopping phases of the operation. To facilitate the starting of the motor and to reduce the possibility of damage to the surfaces between which the hydrodynamic film is produced, a solid lubricant such as moylbdenum disulfide is bonded to the surfaces where rubbing may occur, the solid lubricant being in the form of a very thin film. Other solid lubricants may be employed. However, the properties of molybdenum disulde are well known in that the coeiicient of friction is very low as compared to other dry substances.

In the operation of the dynamoelectric devices disclosed herein no lubricant of ordinary type is used. This is especiallyl true of the air lubricated devices. The surface is clean and dry at all times and the bonded solid lubricant, if any, functions only during the starting and stopping of the device. The air film produced by the movement of the rotor has the necessary pressure characteristics to support the rotor without benefit of contact between the parts or with any lubricant other than air. Present accelerated tests indicate that a small integral motor and blower made in accordance with the teachings of this disclosure will remain operable after the equivalent of over 75 years of operation even though starting and stopping 20 times per day. This is true even though no dry lubricant has been applied to the surfaces of test motors to facilitate starting and stopping. It thus appears that for practical purposes a motor made in accordance with the teaching of this invention even though the motor operates continuously will last indefinitely with the only limitation being the life of the insulation of the windings.

As an example of the high efficiency of this motor, coasting tests have been conducted to determine how long a motor rotor will continue to rotate after the power has been shut off. In commercially available motors the period of time for the best motor is 5 seconds with most motors coasting from 2 to 4 seconds. Test motors made in accordance with the teaching of this invention coast for from to 120 seconds or more even though rotor inertia is less than with the commercially available motors. In these tests shaded-two-pole motors of 117 volt, 60 cycle, 10 watt input were compared.

As a specific example of a dynamoelectric machine made in accordance with this invention, the first model was constructed from a 4 pole, 115 volt, 60 cycle, 1550 r.p.m., induction motor. The motor was modified by rmoving the end brackets, bearings and shaft. The rotor outside diameter was lapped round, and without taper within 0.0001 inch. The diameter of the rotor was approximately 1.6600 inches. The effective rotor length was approximately l and 5A; inches and the rotor weight was approximately 1.1 pounds. The stator was bored to 1.7500 inches and a bronze sleeve, 1.7502 inches in outside diameter, was pressed in. The bore of this bronze sleeve was then honed to 1.6605 inches in diameter. 'I'he hole was round and without taper within plus or minus 0.0001 inch. The total diametral clearance when cold was 0.0005 inch.

The motor ran with the rotor entirely supported by a pneumodynamic film of ambient air generated between the rotor and the stator sleeve surfaces. No lubrication other than ambient air was provided. This motor corresponded to the device disclosed in Figure 2.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only byway of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to Without departing from the Aspirit and the scope of the invention as hereinafter claimed.

I claim:

l. A dynamoelectric device having rotor and stator elements relatively rotatable about a horizontal axis, each of said elements having a smooth cylindrically contoured surface, said surfaces being complemental substantially coaxial, and radially spaced at least 0.000050 inch, said rotor element being totally supported radially by a dynamic lm of ambient uid produced between said surfaces when the device is in operation.

2. A ydynamoelectric device having rotor and stator elements relatively rotatable about a horizontal axis, each of said elements having a smooth cylindrically contoured surface, said surfaces being complemental substantially coaxial, and radially spaced at least 0.000050 inch, said rotor element being totally supported radially by ya fluid dynamic film of ambient gas produced between said surfaces when the device is in operation, and a thrust bearing carried by one of the elements, the thrust bearing being interactable with the other of the elements to limit relative axial'displacement of the elements.

3. A dynamoelectric device having rotor and stator elements relatively rotatable about a horizontal axis, each of said elements having a smooth cylindrically contoured surface, said surfaces being complemental substantially coaxial, and radially spaced at least 0.000050 inch, said rotor element being totally supported radially by a iiuid dynamic film of ambient gas produced between said surfaces when the device is in operation, and a uid dynamic thrust bearing and a ball type thrust bearing carried by the elements, said uid dynamic thrust bearing being disposed at one end of said rotor, said ball type thrust bearing being disposed at the other end of said rotor, said thrust bearings limiting relative axial displacement of the elements.

4. A dynamoelectric device comprising, a stator ele ment including means to induce a magnetic field, the sta-tor having a bore formed therein, the stator having a smooth cylindrically contoured surface defining the bore, and -an armature carried in the bore and having a smooth cylindrically contoured outer surface, said surfaces being substantially coaxial and being closely spaced and complementa] to define a load carrying gas film producing region therebetween, said rotor being totally supported radially on a load carrying film of gas in said region when the device is in operation, said gas film being developed by the coaction of the surfaces when the armature rotates, the gas for said filmbeing supplied by the atmosphere ambient to the device, and said gas film being disposed at least in part within said magnetic field.

'5. A dynamoelectric device comprising, a stator element including means Vto induce a magnetic field, the stator having a bore formed therein, the stator having a smooth cylindrically contoured surface defining the bore, an armature carried in the bore and having a smooth cylindrically contoured outer surface, said surfaces be; ing substantially coaxial and being closely spaced and complemental to define a load carrying gas film producing region therebetween, each of saidV surfaces having a taper not in excess of 0.0001 inch per inch of surface length and per inch of diameter and not in excess .of one-quarter of the radial clearance between said surfaces, said surfaces each having a nish of atleast 8 microinch KMS., saidV armature being totally supported radially on a load carrying filmof Ygas in said region when the device is in operation,ysaid gas film being developed lby the coactionV of the surfaces when the armature rotates, .the gas for said film being supplied by the atmosphere ambient to the device, and said gas filmbeing disposed at least in part within said magnetic field.`

. '6. A dynamoelectric device comprising, a stator velement including means to induce a magnetic field, the stator having a bore formed therein, the stator having a smooth cylindrically contoured surface dening the bore, va rotor carried `in the bore and having a smooth cylindrically contoured outer surface, said surfaces being substantially coaxial and being closely spaced and complemental to define a load carrying fluid film producing region therebetween, said fluid film region having Yan average radial dimension of from 0.000050 to 0.003 inch per inch of rotor surface diameter, said fluid film being disposed at least in part within said magnetic field, and said rotor being totally supported radially by a film of ambient fiuid developed in said region when the rotor rotates.

7. A dynamoelectric device comprising a rotor elev ment, a stator element, the elements having smooth complemental coaxial surfaces defining a gap therebetween, and a magnetic field inducing member carried by one of the elements, the other of the elements being an armature element, said elements being relatively rotatable about a horizontal axis, said gap being disposed at least in part within the induced magnetic field and being a load carrying fluid dynamic film producing region when the device is in operation, and said rotor being totally supported radially on a film of ambient uid in said region when the device is in operation.

8. A dynamoelectric machine comprising, first and secondrelements telescoped together and relatively ro tatable about a horizontal axis, the rst element including a magnetic field producing means and the second element being an armature at least partially extending into the field, the outermost of said elements having a bore formed therein, the outermost element having a surface defining said bore, the innermost element being disposed in part within said bore, the innermost element having an outer surface concentric with the outermost element surface, and a nonmagnetic sleeve member carried by one `of the elements and having inner and outer surfaces, one of the sleeve member surfaces being in fixed abutment withthe surface of said one element, Vthe other sleeve surface and the surface of said elements being complemental cylin- -drically contoured, smooth, surfaces defining a uid dynamic hn producing region therebetween, said elements being held in radially spaced relationship when the device is in operation solely by the film of fluid generated in said region, the fluid in said region being supplied .by the fluid ambient tothe machine.

9. A dynamoelectric machine comprising, first and second relatively rotatable elements, the first element having first and second ends and a bore extending longitudinally from the first end toward the second end, said first element having a projection extending axially into said bore, the projection having a smooth, cylindrically contoured outer surface, the second element having a smooth, cylindrically Vcontoured surface defining the peripheralV limits of an internal bore, said second ,element 'being disposed atleast in part within said first element bore and telescoped over said projection, `said surfaces being complemental and defining a fluid dynamic film producing region therebetween, one of said elements being totally supported vby a dynamic lm of uid generated in said region when the device is in operation, the uid in said region being supplied by the fluid ambient to the machine, and magnetic Vfield providing means forming part of the machine andVV causing relative rotation of theV 11. The device of -claim 9` wherein the `magnetic field provided bysch means is an alternating current field, where1n the elements pulsate relatively and transversely of the axis of rotation under the influence of the alternating current field thereby increasing the pressure in said film, and wherein the uid is a gas.

12. A dynamoelectric machine comprising, a rotor element and a stator element, one of said elements including alternating current means to produce an alternating magnetic field, the other of said elements being an armature element coactable with the magnetic field to produce relative rotation of the elements when the magnetic field is excited, said rotor and stator being relatively rotatable about a horizontal axis, said rotor and stator each having a cylindrically contoured surface coaxial with said axis of rotation, said surfaces defining a gas film producing region therebetween, said rotor being totally supported radially on a load carrying gas film developed in said region when the device is in operation, and said region being of sufficient dimension to permit the rotor to pulsate transversely to the axis of rotation under the influence of the alternating magnetic field and thereby increase the pressure of said film.

13. The dynamoelectric device of claim S having a thrust bearing between the rotor and the stator for limiting axial displacement of the rotor in one direction.

14. The dynamoelectric device of claim 13 wherein the thrust bearing comprises a hydrodynamic bearing.

15. The dynamoelectric device of claim 13 wherein the thrust bearing comprises a ball rotatably carried by the rotor and engaging the stator at a point substantially on the axis of rotation.

16. A dynamoelectric device comprising a rotor and a stator element relatively rotatable about a horizontal axis, one of said elements including means to induce a magnetic field, the stator having a bore therein and a projection having a cylindrically contoured outer surface disposed in the bore, the rotor having an axial bore formed therein, the rotor being disposed in the stator bore with the cylindrical projection extending into the rotor bore, the rotor having an inner surface defining said bore, the surfaces being complemental and closely spaced to define a fluid dynamic film producing region therebetween the rotor surface diameter being from 0.000050 to 0.003 inch per inch of diameter greater than the projection diameter, and the rotor being totally supported radially by a film of ambient fiuid generated in said region when the elements are relatively rotated.

17. A dynamoelectric device having rotor and stator elements relatively rotatable about a horizontal axis, each of said elements having a smooth cylindrically contoured surface, said surfaces being complemental and substantially coaxial, said surfaces being radially spaced from 0.00005 to 0.0005 inch per inch of rotor diameter, said rotor element being totally supported radially by a pneumodynamic film of ambient air produced between said surfaces when the device is in operation.

18. A dynamoelectric device having rotor and stator elements relatively rotatable about a horizontal axis, each of said elements having a smooth cylindrically contoured surface, said surfaces being complemental and substantially coaxial, said surfaces being radially spaced from 0.000050 to 0.0005 inch per inch of diameter, said rotor element being totally supported radially by a pneumodynamic film of ambient air produced between said surfaces when the device is in operation, and a thrust bearing carried by one of the elements, the thrust bearing being interactable with the other of the elements to limit relative axial displacement of the elements, said thrust bearing being a pneumodynamic bearing.

l19. A dynamoelectric device comprising a stator element including means to induce a magnetic field, the stator having a bore formed therein, the stator having a smooth cylindrically contoured surface defining the bore, an armature carried in the bore and having a smooth cylindrically contoured outer surface, said surfaces being substantially-coaxial and being closely spaced and com- `plemental to define a load carrying gas hn producing region therebetween, said region having a radial dimension of from 0.000050 to 0.0005 inch per inch of rotor surface diameter, each of said surfaces having a taper not in excess of 0.0001 inch per inch of surface length and per inch of diameter and not in excess of one-quarter of the radial dimension of said region, said rotor being totally supported radially on a load carrying film of gas in said region when the device is in operation, said gas film being developed by the coaction of the surfaces when the armature rotates, the gas for said film being supplied by the atmosphere ambient to the device, and said gas film being disposed at least in part within said magnetic field.

20. A dynamoelectric device comprising a stator element including means to induce a magnetic field, the stator having a bore formed therein, the stator having a smooth cylindrically contoured surface defining the bore, and a rotor carried in the bore and having a smooth cylindrically contoured outer surface, each of said surfaces having a finish at least as smooth as 8 microinch R.M.S., said surfaces being substantially coaxial and being closely spaced and complemental to define a load carrying gas -film producing region therebetween, said gas film region having an average radial dimension of from 0.000050 to 0.0005 inch per inch of surface diameter, each of said surfaces having a taper not in excess of 0.0001 inch per inch of surface length and per inch of diameter and not in exces of one-quarter of the radial dimension of said region, said rotor being totally supported radially on a load carrying film of gas in said region when the device is in operation, said gas film being developed by the coaction of the surfaces when the rotor rotates, the gas for said fihn being supplied by the ambient atmosphere, and said gas film being disposed at least in part within said magnetic field.

2l. A dynamoelectric device comprising a stator having a bore therein, a rotor rotatable in said bore, a nonmagnetic sleeve lining said bore and on a horizontal axis and having a smooth inner surface, the outer surface of said rotor and the inner surface of said sleeve being uniformly spaced from 0.000050 to 0.0005 inch per inch of rotor surface diameter, said rotor being totally supported radially on a film of air generated in said sleeve when the device is in operation, the air in said region being supplied by the atmosphere ambient to said dynamoelectric device.

22. A dynamoelectric device comprising a rotor and a stator element relatively rotatable about a horizontal axis, one of said elements including means to induce a magnetic field, the stator having a bore therein and a projection having a cylindrically contoured outer surface disposed in the bore, the rotor having an axial bore formed therein, the rotor being disposed in the stator bore with the cylindrical projection extending into the rotor bore, the rotor having an inner surface defining said rotor bore, the surfaces being complemental and closely spaced to define a pneumodynamic film producing region therebetween the rotor surface diameter being from 0.000050 to 0.0005 inch per inch of diameter greater than the projection diameter, and the rotor being totally supported radially by a film of ambient air generated in said region when the elements are relatively rotated.

23. A dynamoelectric machine comprising a rotor element and a stator element, one of said elements including alternating current means to produce an alternating magnetic field, the other of said elements being an armature element coactable with the magnetic field to produce relative rotation of the elements when the magnetic field is excited, said rotor and stator being relatively rotatable about a horizontal axis, said rotor and stator each having a cylindrically contoured surface coaxial with said axis of rotation, said surfaces defining a pneumodynarnic film producing region therebetween, said region having a radial References Cited in the file of this .patent UNITED STATES PATENTS Southgate "6-..-, Dec; 22 19,114

Gailloud -Y. .V. Y.- Oct. 16, 1,956

FOREIGN PAIENTS Sweden Sept. 12, 1950 Great Britain 1 May 17, 1938

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