US2786954A - Electron tube - Google Patents

Description

March 26, 1957 z. J. ATLEE ELECTRON TUBE Filed June 25, 1953 ATTORNEY United States Patent ELECTRON TUBE Zed J. Atlee, Chicago, IlL, assignor to Dunlee Corporatron, Chicago, Ill., a corporation of Illinois Application June 25, 1953, Serial No. 363387 15' Claims. (Cl. 313-60) The present invention relates to electron tubes, and more particularly to X-ray tubes or generators of the rotatmg anode type.

l't is a principal object of the present invention to provide a supporting structure for a rotating anode that permits of easy assembly and disassembly when desired, yet one that will not come apart during the operation of the X-ray tube. Rotating anode structures provided heretofore have generally utilized screws or rivets to secure the various parts thereof together. Riveting has a disadvantage in that the parts cannot be disassembled readily for salvage or readjustment if that appears to be necessary, and the use of screws has proved to be undesirable because they frequently tend to loosen during operation of the tube. Furthermore, the bearing arrangements provided heretofore are relativly complex, embodying numerous parts.

it is a further object of the invention, therefore, to provide a relatively simple bearing arrangement for rotatably supporting a rotary anode within an X-ray tube.

Another object is to provide an anode supporting arrangement wherein the bearing assemblies are insulated from the heat generated in the anode.

Still another object of the invention'is to provide a rotary anode structure facilitating manufacture of rotary anode type X-ray tubes at relatively low cost.

Other objects and advantages of'the invention will become more apparent hereinafter.

In accordance with the illustrated embodiment of the invention, an anode is supported for rotation within the envelope of an X-ray tube on a cup-shaped rotor member mounted in coaxial relation about a spindle member extending into the envelope. The rotor member is supported on the spindle by a pair of longitudinally spaced- .apart bearing assemblies that are retained in position by a unique arrangement of a biasing spring and snap rings that fit cooperatively into grooves formed in the peripheral surfaces of the rotor member and spindle. The snap rings positively hold the various parts in their proper position during operation of the tube, yet permit'quick' and easy assembly of the tube and disassembly thereof if that is required.

For a more complete understanding and description of the invention, reference is made to the accompanying drawing wherein:

Fig. l is a longitudinal section of a portion of a tube embodying the present invention; and

Fig. 2 is a sectional view of the tube taken substantially along line 2-2 of Fig. l.

The embodiment of the invention illustrated in the drawing comprises an X-ray tube orgenerator including an envelope l0 and an anode target member 12 mounted upon a cup-shaped rotor 14 supported in a manner hereinafter to be described upon a spindle 15 which extends into the envelope through one end thereof. The spindle 15 is supported on a metal collar 13" secured to a reentrant portion 19 of the envelope through a conventional glass-to-metal seal.

A more complete understanding of the structure of the invention can probably best be obtained by describing the step-by-step assembly of the-tube.- lh assembling the 2,786,954 Patented Mar. 26, 1957 tube, the spindle 15 is brazed or soldered to one end of the collar 18 which fits cooperatively about an annular shoulder formed in a circular flange 20 provided on the spindle, the collar being sealed at its opposite end to' a short tube of glass which eventually is sealed to the outer portion of the envelope 10 to' form the reentrant portion 19 thereof. This assembly is placed upon a workbench with the spindie 15 standing on its shank end 22 which will extend outwardly of the envelope 10. Next, placed over the spindle 15 is a large snap ring 24 shown in plan in Fig. 2 and having a normal inner diameter less than the diameter of the flange 2t) upon whiclr'the snap ring will rest at this point of the assembly.

A tubular bearing supporting element or sleeve 28, adapted to be supported in coaxial relationship with thespindle 15, and certainother elements are next prepared for assembly on the spindle. The sleeve 28is formed of a nonmagnetic steel and preferably of a steel of relatively poor heat conductivity. The outer surface of the sleeve 28' is formed with a pair of circumferentially extending projections or ribs 29, 30, one adjacent each of itsopposite ends and of substantially equal diameter, for a purpose to'be explained. The uppermost rib 29; as the sleeve is shown, is spaced a slight distance from the upper end of the sleeve 28, and the portion 31'of the sleeve project ing' upwardly from the rib 29 is of reduced thickness to define a further rib, all for reasons explained hereinafter, The inner surface of the sleeve 28 is substantially smooth and continuous throughout except for the provision of a peripheral groove therein adjacent the lower end thereof, as it is shown assembled on the spindle 15, inwhich groove is placed a snap ring 33, A cone or slope-type outer bearing race 32 is then inserted into the opposite end of the sleeve 28 and moved into engagement with the snap ring 33, the outer bearing race 32 comprising a portion of a bearing assembly to be hereinafter described. With the snap ring 33 and race 32in position, the sleeve 28 is placed about the spindle 15 and a suitable number of ball bearings 34 are dropped into the space between the bearing race 32and the spindle 15. A" cone or slope-type inner bearing race 36 having an aperture adapted to receive slidably the spindle 15 is then mounted on the spindle in cooperative relation with the outer bearing race 32 mentionedabove. As may be seen from Fig. 1, the outer bearing race 32 is provided with a slanting bearing surface, slightly concave and facing upwardly, and theinner bearing race 36 is formed with a slanting bearing'face that faces downwardly whereby the balls 34 are engaged therebetween. The inner bearing race 36' is adapted to be held in operative position on the spindle 15' by a snap ring 33, which snap ring is placed on the spindle after the inner bearing race 36 is assembled thereon and fits cooperatively within a groove formedin the surface of the spindle 15, as shown in Fig. 1. When the snap ring 38 is in place, a coil spring 4-0 which bears against the snap ring is dropped over the spindle 15.

Another bearing assembly comprising a slope-type outer bearing race 42, a slope-type inner bearing race 46 and'a" plurality of ball bearings 44therebctween is then assembledon a suitable horizontal surface with the outer bearing race 42 restingon said surface with its slanted bearing surface facing upwardly and with the slanted bearing surface of the inner bearing race 46"facing downwardly. The spindle 15" and'the items previously assembled thereon are then inverted and the end of the spindle inserted into the aperture of the inner bearing race 46 while the sleeve 28 is placed about the outer b'earingrace 42 which is adapted to be received slidably therewithin. The complete assembly is thereafter invertedand returned to the original position on the bench with-the spindle resting on its shank end 22, whereupon the sleeve 28 will drop upon the snap: ring-24 which has previously been placed upon the flange 20 as mentioned above. It should be noted that the uncompressed length of the spring 40 is such that in thi'scondition of the assembly and with the spring 46 uncompressed only the lowermost portion of the bearing race 42, as it isshown in Fig. 1, is received within the sleeve 28.

The sleeve 28 provides a support element for the rotor 14 which comprises a tubular element 48 formed of a highly magnetic material about which is secured a blackened copper sleeve 49. The element 48 is responsive to the rotating magnetic field produced by a stator (not shown) mounted externally of the envelope to drive the anode assembly. The copper sleeve 49 abuts against an outwardly projecting shoulder 51 formed on the outer surface of the tubular element 48, the abutting end of the sleeve being recessed to provide a groove within which a strip of solder 47 may be placed and which may be melted when the tube has been completely assembled and exhausted so as to flow between the element 48 and sleeve 49 and solder them together. Such a procedure is akin to that described in my copending application, Serial No. 282,435, filed April 15, 1952, now Patent No. 2,751,514, for securing a hood member to an X-ray tube anode. Preferably the copper sleeve 49 is shrinkfitted upon the element 48 to assure a tight fit therebetween.

The upper end of the rotor as it is shown is closed and comprises an annular ring 52 of steel or other suitable material soldered or brazed to the tubular element 48. As indicated in the drawings, the sleeve 28 and outer bearing race 42 abut against the ring 52 in the assembled tube, the ring serving as a means to position the bearing race 42 as will presently appear. The ring 52 is recessed adjacent its aperture however, to provide an air gap 54 between the ring and a substantial portion of the race 42. Secured within the aperture of the ring 52 by brazing or the like is one end of a stem 53 which may be formed of molybdenum and which extends coaxially of the element 48. The opposite end of the stem 53 is adapted to support the anode target member 12. The stem 53 is preferably of as small a diameter as possible consistent with the need for adequate strength to rigidly support the target member 12.

The lower end of the tubular element 48 is flared outwardly as indicated at 55 for a purpose to be described, and the inner surface thereof is provided with a peripheral groove 57 positioned from the end ring 52 by a distance substantially equal to the length of the bearing sup porting sleeve 28 and adapted to receive the large snap ring 24, as will also be explained.

In assembling the tube, the rotor 14 is positioned in coaxial alignment over the assembly on the spindle previously completed, and with the open end thereof down, and lowered about the sleeve 28, the ribs 29, 36} of which are slidably received in a snug fit against the inner surface of the tubular element 48, the main portion of the sleeve being spaced from the element 48 by an air gap 59.

As the rotor 14 is lowered, the flared end 55 of the tubular element 48 will encompass the snap ring 24, which is of an uncompressed diameter greater than the normal inner diameter of the element 48 but less than the greatest diameter of the flared end portion 55, to cause the ring 24 to compress as the rotor body is lowered relative thereto. Also, as the rotor is moved downwardly, the end ring 52 of the rotor contacts the outer bearing race 42 before the rotor has been lowered sulficiently far to place the snap ring 24 in alignment with the groove 57 in which it is received whereby further downward movement of the rotor causes the spring 40 to be compressed.

The rotor is lowered, however, against the compression of the spring 40 until the end ring 52 engages the upper end of the sleeve 28 and the groove 57 in the tubular element 48 is positioned opposite the snap ring 24 which will then expand into the groove, releasably locking the sleeve 28 in position between the lock ring 24- and the rotor end ring 52. The downward pressure on the rotor may then be released, whereupon the spring 40 will expand until the various elements of the tube are positioned as shown in Fig. 1. It will be observed that the rotor 14, the sleeve 28, and the spindle 15 are thus secured against substantial relative axial movement by the bias of the spring 40 and the reaction of the various elements of the tube which prevent elongation of the spring to its natural length. Moreover, inasmuch as the spring as is under compression, any wear upon the ball bearings 34, 44, or the corresponding races, will be taken up by a lengthening of the spring.

Obviously, it would be ditficult, if not impossible, once the rotor is mounted, to manipulate a tool between the tubular element 45 and the spindle flange 20 to engage the opposite ends of the snap ring 24 to retract the same from the groove in which it is received for dismantling the rotor from the spindle member. In accordance with the present invention, a plurality of threaded openings 56 are provided through the copper sleeve 49 and the tubular element 48 about the snap ring groove, as shown most clearly in Fig. 2, which openings are adapted to receive screws which may be screwed inwardly of the rotor to compress the snap ring 24 to a smaller diameter than the inner diameter of the tubular element 48, whereupon the rotor may be moved upwardly relative to the spindle 15, as the tube is shown in the drawing, to effect disassembly of the various parts. It is preferred that the screws be omitted from a tube as assembled inasmuch as they would serve no useful purpose in an operating tube and can be installed when a tube is to be disassembled.

After the rotor is mounted on the spindle 15, the portion of the envelope 10 surrounding the rotor assembly may be secured to the reentrant portion 19, after which the anode target member 12 may be secured upon the stem 53 by a nut 57, and the tube assembly completed in a conventional manner.

During operation of the generator, the anode target member 12 is heated to a relatively high temperature because of the electron bombardment thereon. Some of the heat generated in the target member 12 is radiated through the envelope walls; the major portion, however, being conducted to the tubular rotor element 48 and copper sleeve 49 through the stem 53 and ring 52. As mentioned previously, the stem 53 is preferably of as small diameter as possible consistent with strength requirements so that the amount of heat conducted through the stem will be minimized. The blackened copper sleeve 49 is for the purpose of providing a radiating surface to dissipate the heat conducted thereto.

The preferred construction of the bearing supporting sleeve 28 and end ring 52 mentioned above is for the purpose of minimizing heat transfer to the bearing assemblies since excessive heating thereof is detrimental to the lubricating medium upon the bearings. While some heat will be transferred to the outer bearing race 42 through the portion thereof contacting the ring 52, the provision of the separating air gap 54 will minimize the amount of heat transferred. Also, in the case of the sleeve 28, since only the narrow ribs 29, 30 and the riblike end portion 31 are in direct contact with the rotor 14, the amount of heat conducted to the sleeve will be relatively small. As a consequence, the bearing assemblies are substantially insulated from the hot rotor.

In connection with the lubrication of the bearing assemblies, it may be noted that while any suitable lubricant may be supplied, a convenient method of forming a lubri' eating coating, and which method is adapted to be exercised in connection with the present invention is described in my prior United States Patent No. 2,754,168, issued July 10, 1956. In accordance with that method a small quantity of a silicone grease having mixed therewith a finely divided high vacuum lubricant medium, such as,

for example, gold, lead, silver, indium, molybdenum sulfide, or boron nitride, is placed upon each of the ball bearings 34, 44 as they are assembled in their races. After the tube is completely assembled and evacuated, the anode assembly is driven at slow speed, whereupon the lubricant will be distributed over the bearing surfaces in a thin, smooth coating.

Having illustrated and described a preferred embodiment of the invention, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the appended claims.

1. In a rotary anode X-ray tube, a rotor element, and support means therefor comprising a concentric support element, one of said elements extending within the other and in slidable engagement with the wall of the other of said elements, abutment means on one of said elements cooperatively engaging the other element to secure the same against relative movement in one direction, and a snap ring operatively arranged between said elements and engaging the opposite end of said other element for securing said elements against movement in the opposite direction.

2. I11 a rotor assembly for an X-ray generator, a rotor supporting spindle, a rotor including a tubular side wall portion mounted coaxially of said spindle, a bearing assembly mounted between said spindle and rotor side wall portion including a sleeve slidably received in engagement with said wall portion, and means to removably secure said rotor to said sleeve including abutment means on said rotor engaging one end of said sleeve and a snap ring fitting within a groove in said side wall portion and engaging the opposite end of said sleeve.

'3. In a rotor assembly for an X-ray generator, the combination comprising a cup-shaped rotor having a tubular side wall portion closed at one end, and a tubular bearing supporting sleeve mounted Within said side Wall portion in coaxial relation therewith, with one end of said sleeve abutting said closed end, and means for releasably secur ing said sleeve within said side wall portion comprising a snap ring abutting against the end of said sleeve facing the open end of said side wall portion and fitting within a cooperative groove formed in the inner surface of said side wall portion.

4. In a rotor assembly for an X-ray generator, the combination comprising a cup-shaped rotor body having a tubular side wall and a closed end, and a tubular sleeve element mounted within said rotor body in coaxial relation therewith, with one end of said sleeve element abutting said closed end, and means for releasably securing said sleeve element within said rotor body comprising a snap ring abutting against the end of said sleeve element facing the open end of said rotor body and fitting within a cooperative groove formed in the inner surface of said side wall, said rotor body having a plurality of openings therethrough spaced radially about said rotor body and extending outwardly of the bottom of said groove and adapted to receive means therethrough for forcing said snap ring out of said groove.

5. In a rotor assembly for an X-ray generator, the combination comprising a tubular rotor having a closed end, and a tubular bearing supporting element mounted within said rotor in coaxial relation therewith, with one end of said bearing supporting element abutting said closed end, said bearing supporting element having a narrow, outwardly extending projection adjacent each of its opposite ends, said projections having a diameter substantially equal to the inner diameter of said rotor whereby the major portion of said bearing supporting element is spaced from said rotor to reduce the heat transfer therebetween, and means for releasably securing said bearing supporting element-within said rotor comprising a snap ring abutting against the end of said bearing supporting element facing the open end of said rotor and fitting within a cooperative groove formed in the inner surface of said sidewall. a

6. In an X-ray generator, a rotating electrode mounting comprising a spindle, a sleeve mounted coaxially of said spindle, a pair of bearing assemblies each comprising an inner and an outer slope-typeraceand a plurality of ball bearings therebetween, said inner races being mounted on said spindle in longitudinally spaced relation, the inner race adjacent the free end of the spindle being mounted for movement axially thereof, means on said spindle to retain the other of said inner races at a predetermined distance from said spindle end, said outer races being mounted within said sleeve on the opposite sides of said inner races, means for restraining said outer races in predetermined spaced relation, and means on said spindle including a resilient element for urging the inner race adjacent said spindle end towards said end.

7. in an X-ray generator, a rotating electrode mounting comprising a spindle, a tubular member disposed annularly of said spindle, and a 'pair of bearing assemblies for supporting said member on said spindle each including a slope-type inner race and a cooperating slope-type outer race and a plurality of ball bearings therebetween, said inner races being mounted on said spindle in longitudinally spaced relation, said outer races being mounted within said tubular member and spaced relatively outwardly of said inner races, means on said spindle comprising a resilient element for urging said inner races relatively axially apart, and means operatively arranged with said outer races for retaining them in relatively spaced relation, said last-mentioned means including a snap ring engaged within a cooperative groove in the inner periphery of said member and engaged in cooperative relationship with one of said outer races.

In an X-ray tube including an envelope and having a rotating anode, a support arrangement for said anode comprising a spindle extending into said envelope and a rotor including a substantially tubular portion mounted coaxially of said spindle .and disposed annularly thereof, and a pair of bearing assemblies disposed between said rotor and said spindle comprising a pair of outer bearing races mounted in relatively fixed, longitudinally spaced relation within said tubular portion, each of said outer bearing races having a slanted bearing surface facing the other outer bearing race, and a pair of inner bearing races mounted on said spindle one opposite each of said outer races, a snap ring mounted on said spindle and engaging in a cooperative groove in the surface thereof to preventmovement of the inner bearing race spaced innermost from the end of the spindle within said envelope towards said end, spring means operatively connected to the other of said inner races to bias the same towardssaid spindle end, each of said inner races having a slanting bearing surface substantially parallel to the face of the opposed outer bearing race, and a plurality of ball bearings disposed between the inner and outer race of each of said bearing assemblies.

9. In an X-ray tube, a rotating electrode mounting comprising a spindle, a cup-shaped rotor mounted coaxially of said spindle, and a bearing supporting sleeve mounted within said rotor and abutting the closed end thereof, means releasably holding said sleeve against said closed end, and a pair of bearing assemblies for supporting said rotor for rotation about said spindle, said bearing assemblies comprising a pair of outer bearing races mounted in longitudinally spaced relation within said sleeve, one abutting the closed end of said rotor, a snap ring engaged in an annular recess in said sleeve for retaining the other of said outer races against movement toward the opposite end of said sleeve, each of said outer bearing races having a slanted bearing surface facing the other outer bearing race, and a pair of slope-type inner bearing races mounted on said spindle one adjacent each of said outer races in cooperative relation therewith, a snap ring mounted on said spindle and engaging in a cooperative groove in the surface thereof to prevent movement of the inner bearing race spaced most remotely from the free avs'egeee end of said spindle end, spring means operatively connected to the other of said inner races to bias the same towards said spindle end, and a plurality of ball bearings disposed between the inner and outer race of each of said bearing assemblies.

10. In an electron tube including a rotatable electrode, a -mounting arrangement for said electrode comprising a pair of coaxial, relatively rotatable members one extending within the other and a pair of bearing assemblies for supporting said members relative to one another, each of said assemblies comprising an inner and an outer bearing race, said inner races being mounted on the inner of said members, one of said inner races being relatively fixed and the other mounted for movement axially of said inner member, each of said inner races having a slanting bearing surface facing away from the other of said inner races, said outer races being mounted on the outer of said members, one relatively opposite each of said inner races and having a slanted bearing surface extending substantially parallel to the bearing surface of the corresponding inner race, ball bearings disposed between each of said inner and outer races, means on said outer member for restraining said outer races in relatively fixed position, and spring means on said inner member for urging said inner races relatively apart.

, 11. A rotary anode X-ray tube comprising an anode supporting spindle, a circular flange on said spindle spaced from the distal end thereof, a bearing sleeve surrounding said spindle and having a portion extending beyond said distal end, bearing means supporting said sleeve on said spindle including a resilient element, said bearing means being arranged to prevent movement of said sleeve axially of said spindle in the direction of said distal end beyond an operating position as a limit but permitting movement thereof toward said flange against the bias of said resilient element, a cup-shaped rotor mounted on said sleeve coaxially thereof, said sleeve extending portion engaging the closed end of said-rotor, and a snap ring engaging the end of said sleeve adjacent said flange and cooperatively engaging in a groove in the inner wall of said rotor to secure said sleeve and rotor from relative axial movement, said snap ring having a normal inner diameter less than the diameter of said flange whereby during assembly of said tube said flange will retain said ring in position as said rotor is telescoped over said sleeve and the sleeve and rotor moved axially of said spindle towards said flange to engage said ring in said groove, said resilient element causing said sleeve and the mounted rotor to return to said operating position.

12. In an electron tube having a rotatable member, a cylindrical hollow housing having a closed end, a tubular bearing mounting sleeve of lesser length than said housing for mounting coaxially within said housing with one end in abutting relation to said closed end, a spindle extending coaxially into the opposite end of said sleeve, means mounting said spindle in said sleeve for rotation of said sleeve about the axis of the spindle, a snap ring for securing said sleeve within said housing, said ring being adapted to engage said opposite end of said sleeve, said housing having a groove in the wall thereof for receiving said ring when said sleeve abuts said housing end, the inner wall of said housing adjacent the open end thereof being tapered tov provide a flaring mount, said ring having a normal diameter less than that of said mouth but greater than the inner diameter of said housing whereby said ring may be encompassed by said mount and the ring compressed as said ring moves relatively axially into said housing, and means on said spindle for securing said ring against relative movement away from the free end of the spindle whereby said housing may be mounted upon and secured to said sleeve by telescoping the same together, said last mentioned means serving to hold the ring whereby the housing may be moved thereover to compress the ring and bring said groove into alignment with'the compressed ring whereupon the ring may snap into the groove' tolock the housing to the sleeve.

13. An electron tube having an evacuated envelopeand a rotatable electrode in saidenvelope, a mounting for said electrode comprising a spindle extending inwardly of said envelope, bearing means for supporting said electrode on said spindle including an inner ball bearing race on said spindle having a bearing surface inclined relative to the axis of the spindle and facing away from the free end of said spindle, a snap ring fixed in a groove in said spindle and operatively engaging said inner race to secure the same against movement toward said free end, an electrode rotor mounted coaxially of said spindle, a coaxial tubular bearing sleeve in said rotor, means securing said sleeve against axial movement relative to said rotor, a slope-type outer ball bearing race in said sleeve opposite said inner race, a plurality of ball bearings between said inner and outer race, and a second snap ring engaged within a groove in said sleeve and engaging said outer race to prevent movement thereof relative to said sleeve in a direction opposite to the face of said outer race whereby said rotor is secured upon said spindle.

14. An electron tube having an evacuated envelope and a rotatable electrode in said envelope, a mounting for said electrode comprising a spindle extending inwardly of said envelope, bearing means for supporting said electrode on said spindle including a slope-type inner ball bearing race on said spindle having a bearing surface facing away from the free end of said spindle, a snap ring fixed in a groove in said spindle and opera-tively engaging said inner race to secure the same against move ment toward said free spindle end, a tubular electrode rotor mounted coaxially of said spindle, a slope-type outer ball bearing race mounted in said rotor, a plurality of ball bearings between said inner and outer races, means on said rotor securing said outer race against movement relative to the rotor in a direction opposite to its face, and resilient means acting between said spindle and rotor to urge said rotor in the direction of said free end of said spindle whereby said races are urged into snug engagement with said ball bearings.

15. An electron tube having an evacuated envelope and a rotatable electrode in said envelope, a mounting for said electrode comprising a spindle extending inwardly of said envelope, a pair of slope-type inner ball bearing races on said spindle mounted with their bearing surfaces facing away from one another, one of said races being mounted adjacent the free end of said spindle and the second being spaced therefrom, a snap ring fixed in a groove in said spindle and operatively engaging said second race to secure the same against movement toward said free end, spring means for biasing said one race toward said free end, a cup-shaped electrode rotor mounted coaxially'of said spindle with the closed end of said rotor adjacent said free spindle end, a coaxial tubular bearing sleeve in said rotor, means securing said sleeve against axial movement relative to said rotor, a pair of slope-type outer ball bearing races in said sleeve, one opposite each of said inner races, a plurality of ball bearings between each pair of said inner and outer races, the outer race opposite said one inner race abut-ting against said closed rotor end, and a second snap ring engaged within a groove in said sleeve and engaging the outer race opposite said second inner race to prevent movement of said last mentioned outer race relatively away from said closed rotor end whereby said rotor is secured upon said spindle.

References Cited in the file of this patent UNITED STATES PATENTS 892,866 Moonen July 7, 1908 1,400,001 Rider Dec. 13, 1921 2,230,857 Atlee Feb. 4, 1941 2,274,865 Machlett Mar. 3, 1942 2,648,025 Agule Aug. 4, 1953

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