US2335224A - Coating apparatus - Google Patents

Description

Nov. 30, 1943. z. J. ATLEE COATING APPARATUS Original Filed July 13, 1939 ZELE/ela Zf 33e@ Jade@ Patented Nov. 30, 1.943 i UNVITED STATES PATENT OFFICE aasazzi COATING Zed J. Atlee, Elmhurst, Ill., assignor to General Electric X-Ray Corporation,` Chicago, lll., a corporation oi' New York `Original application July 13, 1939, Serial No. l#$84,273. Divided and this application May 25,

1940, semi No. 337,116 i claim. (ci. s1-1z.z)

` The present application is a division of my copending application. Serial No. 284,273, led July 13, 1939, said application being directed more specifically toward an X-ray generator.

' An important object of the invention is to provide means for processing a bearing in order to lubricate the same without using a lubricant having a vapor pressure such as to cause evaporation of the lubricating medium and migration thereof from the bearing under the temperature conditions to which the bearing is subjected when in operation.

destroy the vacuum condition; a further object being to utilize, as a. lubricating medium, a material ,such as barium, strontium, and magnesium, metals having a. vapor pressure of the order of 10-9 at atmospheric pressure and not to exceed i0-,6 at high temperatures of the order of 200 centigrade, whereby the lubricating medium may 'not migrate from a treated bearing operating under low pressure and high temperature conditions. -Another important object resides in providing apparatus for processing a bearing particularly for use in X-ray generators to support a rotating v element of the generator for operation within a i sealed evacuated enclosure in which the operating temperature at the processed bearingimay reach the order of,200 centigrade and up.

Another important object resides in the provision of means for applying the lubricating medium to the bearing after the same has been sealed within the evacuated enclosure.

Another important object resides in providing Ameans for applying a lubricating medium of the character mentioned by flashing the same as a vapor upon the bearing surfaces to be treated, and causing the vapor to condense upon said surfaces to form a film of relatively soft material having lubricating qualities but which will not' migrate from the treated surfaces even under conditions oi' high temperature and low pressure i through the mechanical cohesion .of the filmed material and its low vapor pressure.

Another important object resides in providing means for applying the material as a film on the surfaces to be treated by providing a supply of said material in position adjacent such surfaces,

then evaporating or flashing the material, by heating the same, to produce vapor, and directing the vapor toward and upon the surfaces to be treated; a further object being to arrange the supply of material in a capsule or casing, preferably in the form of a hollow lamentary wire having a. weakened wall portion through which the vaporized material may be expelled,the casing or capsule being mounted with its weakened wall facing towards the surfaces to be treated; a further object being to utilize an electrical current owing in said iilamentary wire capsule for thepurpose of vaporizing the material.

Another important object is to provide means for delivering electrical current for ashing the material to a supply of the material sealed within an evacuated chamber.

A further object isk to provide an X-ray generator including a bearing enclosed in the sealedevacuated envelope of the generator, and in utilizing the stem on which the bearing is mounted as a circuit forming part for the delivery of current to a supply of vaporizable material within the envelope.

'I'hese and numerous other important objects, advantages, and inherent functions of theinvention will become apparent as the same is more fully understood from the following de' scription, which, taken in connection with the accompanying drawing, discloses a. preferredembodiment of the invention.

Referring to the drawing,

Figure l is a sectional view taken through an .X-ray generator provided with a rotating anode supported by a bearing structure of a type adapted for treatment in accordance withmy present invention; Y 4

Figure 2 is an enlarged sectional view taken substantially along the line 2-2 in Figure 1, il-

lustrating vone mode of applying my present invention;

Figure 3is a sectional view taken substantially along the line 3-3 in Figure 2; and

Figure 4 is an enlarged sectional view taken substantially along the line 4-4 in .Figure 3.

To illustrate my invention I have shown on the drawing an X-ray generator Il comprising a rotating anode I3 supported within a sealed envelope Il on bearings I5, although it will be apparent, as the description proceeds. that my invention is not necessarily limited to X-ray generators or even necessarily to bearings for operation under conditions of high temperature and low pressure. Nevertheless, my invention has great value in providing improved bearing means having unusually flne operating characteristics at high temperature and low pressure, and so `I have chosen to demonstrate my invention as applied ,in X-ray generators, in the operation of which such excessive conditions of high heat and low pressure are encountered.

The generator shown, of course, includes a cathode C of any usual or preferred character,

and the anode is supported by the bearing I5 on a spindle I9, which is shown mounted on and supported by the envelopell at one end thereof. As shown, the envelope has an extension 2 I -Within which the anode I3 is snugly disposed for rotation, the envelope havingfa reentrant sleevelike portion 23 forming an annular space 25 between the envelope extension 2| and the reentrant portion 23.

The spindle I9 has an outwardly extending portion which is provided with means 29 forming an annular shoulder carrying an annular flanged member 3| sealed thereon. The'member 3| has a peripheral edge forming a glass-to-metal seal 33 with the inner end of the reentrant envelope portion 23. This seal, through the member 3|, supports the spindle on the envelope with a spindle portion 35 extending within the envelope, the anode bearings I5 being mounted on said inwardly extending spindle portion 35.

It should be understood that X-ray generators function to produce X-rays in response to the activation of the anode by'electronic action estab- "lished by the operation of the cathode C. This tion, the envelope IT is treated to remove-all gaseous and other impurities, the same being accomplished by evacuating the envelope as by means of a molecular exhaust pump while heating the elements of the generator to a high temonly robbing the bearings of lubricant but also destroying the vacuum in the tube and rendering the same inoperative. Consequently, it has not heretofore been considered feasible to lubricate bearings under conditions necessarily maintained in X-ray generators. Excessive bearing `wear results, particularly at the high temperatures encountered in the generator, with the resultant development of anode vibration, which rapidly renders the device unusable. Excessive bearing wear also results in the production of minute wear products, which also impair the perature in order to drive out gases occluded in I the envelope and all of the elements contained therein. 'I'he envelope nally is sealed after' all impurities have thus been eliminated.

During the operation of the X-ray generator as such, the anode I3 is desirably rotated at high speed, in order to minimize the danger of overheating and burning the target itself, as a result of electron impact. Considerable'diiliculty has been encountered in providing means for supporting the anode for rotation during the life of the generator, under the excessively high temperature conditions and the low pressure necessarily maintained within the envelope I1, since it is not feasible to apply usual bearing lubrication because lubricants of the character heretofore known will not remain in the bearings under the low pressure condition necessarily maintained in the envelope, but Will instantly evaporate and become dissipated within the envelope, thus not operation of the generator as the same become dissipated from the bearings within the envelope. My present invention relates to a method of lubricating bearings in a manner avoiding the aforesaid difficulties, particularly encountered in X-ray generators having rotating anodes; but the invention is by no means limited to such particular apparatus and, in fact, may be applied to advantage in any bearing structure.

In practicing my invention, I select a suitable material adapted to be applied as a vapor and to condense and form a lm upon the bearing surfaces to be treated, the selected material desirably having several qualities, including not only softness and flowability, 'with low internal coelcient of friction when in film-like form, but

also sufficient mechanical cohesion to cause the filmed material to be retained upon the treated bearing surfaces, the property of wetting the bearing surfaces to be treated, low vapor pres-- sure to prevent evaporation at the pressures and temperatures to which the treated bearing is to be exposed, and, unless the bearing is to be in operation in an oxygen-free atmosphere, the lubricating material should not normally oxidize. Where the bearing is applied in an evacuated X-ray generator, the problem of oxidation of the filmed lubricating medium will not, of course, be encountered. However, if the treated bearing is for use in the ordinary atmosphere, or elsewhere exposed to oxidation, the lubricating medium should be of a character normally resisting oxidation.

I have found that barium, strontium, andA magnesium, are metals adapted for use as lubricating media, in accordance with the teachings of my present invention; that combinations of these materials may be used; and, in fact, in treating bearings for use in X-ray generators, I prefer to employ barium as a lubricating film applied upon the bearing surfaces. The foregoing materials have vapor pressures of the order of 1I)-6 at temperatures of the order of 200 centigrade and are therefore well adapted for use as lubricants in bearings operating under low pressure conditions. Where operating pressuresare relatively higher, other metals such as caesium and potassium are available in addition to those specified for excessively low pressure service.

The selected material is applied upon the bearing surfaces, in accordance with my present invention, by vaporizing the same and directing a stream of the vaporized material upon the bearing surfaces to be treated whereby thus to condense the vapor and form a thin film of the material upon the surfaces to be treated. Vaporization and delivery of the material upon the surfacesI may be accomplished in any suitable or preferred manner. A supply of the material, for example, may be positioned in a capsule or container having an opening facing the surfaces to be treated, and the material then heated in the capsule in any convenient manner, as by the passage of an atadas-1 through the wire in order to expel the lubricating medium as a vapor upon the surfaces to be treated. Such wires as thoriated tungsten and alloys of silver and zinc Vmaybe utilized in this manner. Heating coils of tungsten wire in pocket shape,

with a small quantity of the lubricating medium enclosed in the pocket, may similarly be used. Aswthe tungsten wire is heated to the melting point of the metal so enclosed, an alloy of the lubricating medium with the-tungsten wire may be formed on the surfaces of the wire, and this alloy in turn may then be re-evaporated in order to produce a nlm of the lubricating medium' upon the surfaces to be treated.

I prefer, however, in treating bearings for use in X-ray generators, to employ a hollow lamentary wire W, preferably of iron or nickel, containing within the wire a quantity ofthe lubricating material L, such as pure barium, the hollow wire being weakened by reducing its wall thickness along one side of the wire, as indicated at S. By passing an electrical current through the wire W, the material L may be vaporized therein, the vapor products being blown out through the weakened wall section S, and of course by supporting the wire with the surface S facing toward the bearing surfaces to be treated, the vaporized medium may be directed directly upon such bearing surfaces.

As shown in the drawing, the anode I3 comprises a cylindrical body having an open endv extending in the annular envelope space 25 in position to encircle the seal 33 at the inner end of the reentrant envelope portion 23. The anode thus forms a shield for protecting the seal 33 from deterioration through impingement of stray electrons thereon. The opposite end of the anode body is enclosed, as at 39, and affords a mounting for the target 31. Externally the cylindrical walls of the anode form a seat on which is secured the rotor 4I of an electric motor, the stator 43 of which encircles theenvelope extension 2| in cooperative relationship with the rotor 4I whereby to drive the anode vWithin the envelope when the stator 43 is excited from any. suitable source of electrical power externally of the envelope.

The spindle 35 extends within the cylindrical anodeand carries the bearing means I5, said bearing means comprising in the illustrated embodiment a pair of roller bearings 44 and 46, in

spaced-apart position on the spindle portion 35.4

Each bearing comprises an outer race secured on the anode, and an innerl race secured on the spindle portion 35, roller members of any suitable or convenient form, and illustrated as balls, being conventionally retained between the inner and outer race portions.

The anode I3 may, of course, be mounted on bearing 44, the bearing being clamped in said seat and held in position on the stem preferably by means of a nut 5| threaded on the stem. The stem 35 is also threaded' to receive clamping nuts 53 and 55 between which is clampingly'secured on the stem the inner race of the bearing 46, and a heat shield 51 may be provided for the bearing 46 and supported on the clamping nut 5 5 in position extending between the targetcarrying end of the anode, in which maximum heat is encountered during the operation of the device. 'Ihis shield serves to protect the bearing from heat radiated from said target-carrying portions of the anode, and tends to equalize the temperature under which the bearings 44 and 46 function.

The spindle I9 is provided with a longitudinally extending duct 59 extending from the outwardly exposed end of the spindle to a point in the spindle portion 35 intermediate the bearings 44 and 46, said duct 59 opening laterally on the portion.

35 within the bore or channel 81 of the anode support element 85. The outer end of the duct 51 is enlarged, and has sealed therein a sleeve 6I, preferably comprising forty-two percent nickel steel, a material adapted to seal readily with glass.

A lead conductor 63 is arranged in the duct 59 l y with one end of said conductor extending outthe bearing elements in any suitable or preferred fashion, althoughV Ihave shown the same in the drawing clampingly secured on a cylindrical der 41 providing a seat for the inner race of the wardly of the sleeve 6I, and the other end projecting through the end of the duct which opens on the spindle portion 35. Suitable insulating means 65, such as a sleeve of magnesium silicate, or ,a plurality of glass beads embracing the conductor within the duct 59is provided for insulating the conductor electrically from the stem I9 in which it is arranged, the outer 'end of the ,duct being sealed preferably by means of a glass globule 61 applied within the sleeve 6I around the conductor 63.

Within the space 81 I mount suitable support means for a supply of the lubricating material L, and utilize the conductor 63 and the spindle I9 as circuit forming means for electrically energizing the material L to vaporize the same within the channel 81, in order to process the bear.- ings l5. In the illustrated embodiment this is accomplished by arranging a length of the lamentary tubular wire W on the stem portion 35, said wire being arranged to form loops 69 in position opposite the bearings I5, with the weakened surfaces ofthe wire portions forming said loops 69 facing toward the bearings. The loops.

sulating means for supporting the wire W rigidly in position, although ordinarily additional support is not required since the wire itself has sufficient rigidity to maintain itself in assembled position, at least until after the material L has been ashed in processing the bearing.

It will be seen from the foregoing that by connecting a suitable source of electrical potential between the outwardly exposed end of the conductor 63 and the spindle I9, an electrical heating current maybe caused to flow through the wire W in order to raise the temperature of the wire to a point at which the material L vaporizes, in order thus, as heretofore described, to cause the expulsion of vapor through the weakened wall S at the loops 69 and thence upon'thevu bearings.

The bearings preferably are thus processed for the application of a lm of the lubricating medium L thereon, after assembly in the envelope I1 and after the envelope has been evacuated, as heretofore described, so that flashing of the material L is accomplished substantially in vacuo and after the envelope I7 has been completely sealed. The ash products, however, will not escape to any detectable extent from the hollow anode. The vaporized products, however, impinging upon the facing surfaces of the bearings, which preferably are rotated during the flashing of the material L, immediately condense upon the surfaces to form a lm thereon, the inner face of the lm wetting the surface material of the bearing and forming an alloy therewith which holds the film in place. The rotation of the bearings causes substantially all of the surfaces thereof required to be treated to receive the coated film of the lubricating material; and since the flash products are confined substantially within the chamber 81, no migration of such products outwardly of the bearings and the hollow anode is detectable, and the vacuum condition within the envelope is not in any way impaired as a result of the iiashing operation. l

In order to seal and protect the exposed end of the conductor 63, the outer 'end of the stem I9 may be threaded, as shown at 1I, to receive a cover cap 13, the outer end of which may be )threaded as shown, or otherwise finished as desired, said cap being preferably threaded for the reception of heat dissipating means thereon by means of which heat developed at the anode may, in part, be dissipated from the generator by conduction through the anode support sleeve 85, the bearings I5, and the spindle outwardly of the envelope I1.

I have found that bearings treated in accordancewith the teachings of my present invention are able to operate substantially without wear and Without conventional lubrication throughout extended service periods, under excessive low pressure and high heat conditions. When used in X-ray generators, bearings processed in accordance with my present invention have an eX- tended service life, usually outlasting the normal life of the generator itself.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made' in the form, construction, and arrangement of the several parts without departing from the spirit and scope of the invention, nor sacrificing its attendant advantages, the forms herein disclosed being merely for the purpose of demonstrating the invention.

The invention is hereby claimed as follows:

Apparatus for processing a bearing device comprising a mounting for supporting the device in position to be processed, holder means on said mounting for supporting a supply of metallic vaporizing material, and means electrically connected with said holder and said mounting and operable to heat said material to vaporize the same, said holder means comprising a; hollow, fllamentary electrical conductor having a Wall portion of reduced thickness rupturable upon predetermined expansion of the material therein whereby, when the material is vaporized within said conductor, the resulting vapors may be projected therefrom through said wall portion of reduced thickness, said conductor being arranged in a plurality of loops around the mounting and being disposed with said wall portion facing the

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