US3699373A - X-ray tube with electrically conductive bearing bypass - Google Patents

X-ray tube with electrically conductive bearing bypass Download PDF

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Publication number
US3699373A
US3699373A US159235A US3699373DA US3699373A US 3699373 A US3699373 A US 3699373A US 159235 A US159235 A US 159235A US 3699373D A US3699373D A US 3699373DA US 3699373 A US3699373 A US 3699373A
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Prior art keywords
shaft
ray tube
bearings
set forth
contact
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Expired - Lifetime
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US159235A
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English (en)
Inventor
William P Holland
Robert E Azud
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Varian Medical Systems Inc
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Machlett Laboratories Inc
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Assigned to VARIAN ASSOCIATES, INC., A DE CORP. reassignment VARIAN ASSOCIATES, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: MACHLETT LABORATORIES
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08—Anodes; Anti cathodes
    • H01J35/10—Rotary anodes; Arrangements for rotating anodes; Cooling rotary anodes
    • H01J35/101—Arrangements for rotating anodes, e.g. supporting means, means for greasing, means for sealing the axle or means for shielding or protecting the driving
    • H01J35/1017—Bearings for rotating anodes
    • H01J35/1024—Rolling bearings

Definitions

  • a present state of the art rotating anode X-ray tube embodies ananode structure which comprises essen tially a target which is affixed to or mounted on a shaft supported byv the inner races of ball bearings. Also affixed to the shaft concentrically therewith is a skirtlike rotor which becomes a section of an induction motor cathode causes current to flow through the shaft, the
  • Such a rotating anode structure is operated in a high vacuum environment of the order of Torr andat high temperature which, at the bearings, may reach up to 600C.
  • the particular construction of known conventional rotating anode tubes utilizes bearing structures which carry electrical current between the rotating and the stationary elements of thetube. Since the hearings, in addition to their mechanical requirements, must perform as electrical conductors for passing power, possibly as high as 100 KW, through the anode circuit, this presents serious problems.
  • the environmental conditions do not permit the use of conven tional organic lubricants and solid lubricating techniques must be used, thereby imposing extreme limitationson bearing performance in terms of life and audible noise. Numerous investigators have demonstrated the deleterious effects of electrical current through ball bearings due to arcing phenomena when making and breaking contacts. These effects impose further influences of surface degradation on bearings, leading to shorter life and increased noise.
  • the present invention includes an auxiliary contact interposed between the target shaft and the stationary anode support structure of the tube for providing an efficient highly electrically conductive path therebetween so that current need not flow through the conventional bearings.
  • a contact is" a springloaded device having a minimum of friction so as to reduce high stress points and subsequent wear at the contact surface.
  • the device furthermore is structured to avoid any responseby the contact device'to eccentric motion of the target shaft or any centrifugal forces acting upon the contact device, either of which might lead to stress points and wear at the contact surfaces.
  • Such undesirable wear produces undesirable wear particle generation and/or seizure when wear particles migrate into the support bearings.
  • the present invention further includes the utilization of a wear particle trap insert which presents a labyrinth barrier to any wear particles generated by the novel bypass contact device.
  • This barrier confines any such particles to an area preceding the load or support. bearings, thereby preventing migration of the particles and consequent ultimate damage to the bearings or other tube elements.
  • FIG. 1 is an elevational view partly in axial section of a rotating anode tube having inner race rotation and embodying a preferred form of this invention
  • FIG. 2 is an enlarged sectional view of the bypass contact structure shown in the tube of FIG. 1;
  • FIGS. 3-5 are sectional views of modified forms of bypass contact devices which may be used with the tube of FIG. 1;
  • FIG. 6 is an axial sectional view of a rotating anode tube having outer race rotation and including a form of the present invention.
  • the rotating anode X-ray tube shown in FIG. 1 comprises an evacuated envelope 10 containing within one end portion thereof a cathode structure 12 which is suitably mounted upon supporting structure 14 sealed to the end of the envelope and which is adapted to be supplied with filament power by means of externally extending leads 16 as is well known.
  • the opposite end of the envelope has an axially extending hollow neck portion 18 with a reentrant end 20 to the termination of which is sealed one end of a Kovar collar 22.
  • the opposite end of the collar 22 is sealed to the circumference of a tubular-shaped bearing housing 24 which has a solid reduced-diameter end portion 26 extending exteriorly of the envelope within reentrant portion 20 for cooling purposes and for providing means for applying anode potential to the tube in a well-known manner.
  • Bearing housing 24 is provided on its inner surface with a circumferential shoulder 28 on which rests one side of an annular outer bearing race 30 of a first bearend of atubular spacer or cylinder 34 which is fitted within the housing and which is engaged at its other end by an outer race 36 of a second bearing 38.
  • These bearings and spacer form an assembly which is held in place at one end by set screws 40 which extend through the walls of housing 24 adjacent the exposed end of race 36.
  • Balls 42 and an inner race 44 complete the bearing unit 38, the race 44 being mounted in a circumferentially grooved area of a shaft 46, preferably of steel, which extends axially of the tube within housing 24 and spaced therefrom as shown.
  • the lower end of shaft 46 has a portion 47 of reduced diameter on which a nut 45 is threaded into engagement with the inner race 43 of bearing 32 for holding the bearing-spacer assembly in place.
  • the inner end of shaft 46 is threadably or otherwise connected to a head 48 which is bolted or otherwise fixed to the inner end of a hollow skirtlike rotor 50.
  • Rotor 50 encircles the bearing support housing 24 in spaced relation thereto within the envelope portion 18.
  • the interior of the envelope is evacuated to the order of 10' Torr.
  • the target 52 becomes extremely hot, which heat is transmitted through hub 54 into head 48 and shaft 46 to the bearings which sometimes assume temperatures as high as 600C. Therefore, in conventional X-ray tubes of this type the environmental conditions do not permit the use of conventional organic lubricants for the bearings. Solid lubricants must be utilized, thereby imposing extreme limitations on the bearing performance in terms oflife and noise.
  • additional or auxiliary electrical contact means is provided, as will be described, so that nonconductive materials may be used for the bearings and the lubricant.
  • the bearings may be made of a refractory oxide, ceramic, silicate or nitride or the like, certain of which possess physical requirements which are better suited to X- ray tube bearing requirements from a life and noise viewpoint when the requirement of electrical conductivity does not exist.
  • An example of an especially convenient nonconductive lubricant is molydisulphide.
  • the auxiliary electrical connection mentioned above may take one of several forms but will preferably be structured as shown in FIGS. 1 and 2.
  • the lower end portion of bearing support 24 is solid and thus seals the lower end of the cavity 56 within which the shaft 46 projects. Such a solid area of support 24 also seals off the vacuumized envelope.
  • Conductively affixed to the support 24 within the lower end of the cavity 56 is a ring or disc 58 to which is fixed one end of a leaf spring 60.
  • the free end of the leaf spring 60 projects toward the adjacent end of shaft 46 and carries a contact button 62 which is disposed in engagement with an insert 64 fixed in the extreme end of shaft portion 47.
  • the pressure of the contact spring upon the shaft will function to take up some of the undesirable play in the bearings, reducing noise. Additionally, the contact device provides a more efficient path for exit of heat from the shaft toward the bearing support and skirt than is possible through the bearings.
  • a further significant feature is the inclusion of a wear particle trap 66 which presents a labyrinth barrier to the wear particles generated by the button-insert contact.
  • the trap 66 comprises a short hollow cylinder or collar 68 which extends axially within cavity 56 from the ring or disc 58 to a point or level beyond the button-insert contact, at which level the end of the cylinder has an inwardly turned flange portion 70 the inner periphery of which relatively closely encircles the nut as shown clearly in FIG. 2. This barrier confines the wear particles to an area preceding the load bearings, thereby preventing migration to the bearings and ultimate damage.
  • the inner end of the cavity 56 in support 24 contains a retaining ring 72 on which is seated a ball bearing assembly 74 including a first race 76 and a second race 78with balls or rollers therebetween.
  • the adjacent reduced diameter end portion 47 of shaft 46 and nut 45 thereon are slightly spaced from race 78 but are electrically connected to it by a coiled contact pressure spring 80, the lower end of which rests in a spring retainer 82 carried by race 78, with its upper end engaging a flanged portion of nut 45.
  • the retaining ring 72 on race 76 may be of selected thickness to control pressure of the spring 80 upon the nut and shaft, and also is provided with an inwardly directed flange portion 84 which encircles the second race 78 to trap wear particles from this bearing in a localized area.
  • a modified sliding contact device is illustrated in FIG. 5 and comprises a flat-faced silver insert 88 in the extreme end of portion 47 of shaft 46 which is used as the contact of the rotating shaft 46.
  • the extreme inner end of the cavity 56 is provided with an axial bore 90 within which is slidably mounted a contact pin 92 which has its inner end engaged by a coiled spring 94 which is confined within the bore and urges the pin 92 into engagement with the insert 88.
  • a contact pin 92 In a structure of this type limited axial constraint is imposed on the pin 92 and permits it to form its own wear path.
  • a wear particle trap 94 is located in the base of the cavity 56 and has a flanged portion closely encircling the nut 45 to prevent wear particles from migrating into the support bearings.
  • FIG. 6 there is shown a rotating anode tube wherein the anode is supported in a somewhat different manner than in the structure of FIG. 1.
  • the anode 100 has a hub 102 fixed to one end of skirt 104.
  • a coaxial cylindrical bearing support 108 connected by relatively small annular areas to the skirt to reduce the amount of heat which is transmitted by the skirt into the support 108.
  • Support 108 carries a pair of spaced bearing races 110 and 112 which are fixed thereto and support ball bearings ll4-l16 respectively which rotate about the circumference ofa fixed shaft 118.
  • shaft 118 is spaced from the ad jacent inner end. surface of the skirt 104 while its lower end is provided with a reduced diameter end portion 120 which is threaded into a blocklike terminal 122 extending out the end of the tube envelope and sealed thereto as by collar 124.
  • the cavity 106 becomes a compartment 126 within which the selected bypass contact structure is mounted.
  • the selected bypass contact structure is mounted.
  • contact structure may take the form illustrated in FIG. 2 wherein a leaf spring device 128 is mounted in the base of the compartment and'carries a silver contact button 130 which engages the polished or hard-coated end of the shaft 118, the exposed surface of an insert 132 therein, or a hardening coating on said surface.
  • bypass contact structures may be employed with the anode structure of FIG. 6 such as the structures shown in FIGS. 35, in accordance with this invention.
  • a particle trap 134 also may be employed,as shown.
  • a novel bearing bypass for electrical current I flow in a rotating anode X-ray tube whereby the support bearings may be conveniently made of nonconductive material, as well as the lubricant therefor.
  • Such a bearing bypass as described will provide improved electrical current flow through the tubes anode. circuit and permit reduction in overall tube noise.
  • An X-ray tube of the rotating anode type comprising an envelope containing an anode structure and a cathode structure in spaced cooperative relation, the anode structure including an X-ray generating target and a member supported for rotation with said target, a fixed support member mounted on said envelope, bearings between said rotatable member and said support member, and an electrical contact device electrically interconnecting said rotatable member and said support member for providing electrical conduction therebetween independent of and in bypass relation to' said bearings.
  • An X-ray tube comprising an envelope containing an anode structure and a cathode structure in spaced cooperative relation, the anode structure including an X-ray generating target, a shaft connected at one end to the target, a cylindrical support fixed to said envelope and projecting coaxially in encircling relation to said shaft, bearings rotatably connecting said shaft to said support, and an electrical contact device electrically interconnecting said shaft and said support for providing electrical conduction therebetween independent of and in bypass relation to said bearings.
  • An X-ray tube as set forth in claim 10 wherein said contact device comprises a rotating bearing located with a first race thereof in firm abutting relation against said shaft and with a second race spaced from said support, and spring means is located between said second race and said support for resiliently electrically connecting same.
  • An X-ray tube comprising an envelope containing an anode structure and a cathode structure in spaced cooperative relation, the anode structure including an X-ray generating target, a hollow cylindrical member connected at one end to the target, a shaft fixed to the envelope and extending coaxially within said member, bearings between said shaft and member whereby said member and target are rotatably supported by said shaft, and an electrical contact device electrically interconnecting said member and said shaft for providing electrical conduction therebetween independent of and in bypass relation to said bearings.

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  • X-Ray Techniques (AREA)
US159235A 1971-07-02 1971-07-02 X-ray tube with electrically conductive bearing bypass Expired - Lifetime US3699373A (en)

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US15923571A 1971-07-02 1971-07-02

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CH (1) CH545537A (enrdf_load_html_response)
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4187442A (en) * 1978-09-05 1980-02-05 General Electric Company Rotating anode X-ray tube with improved thermal capacity
FR2475799A1 (fr) * 1980-02-07 1981-08-14 Siemens Ag Tube a rayons x a anode tournante
US4326144A (en) * 1979-04-03 1982-04-20 Siemens Aktiengesellschaft Rotating anode x-ray tube
EP0184664A1 (de) * 1984-11-10 1986-06-18 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. Wärmeableitung von rotierenden Bauteilen in Raumfluggeräten
US4866748A (en) * 1988-08-15 1989-09-12 Varian Associates, Inc. Rotor structure brazed joint
US4969172A (en) * 1988-08-15 1990-11-06 Machlett Labs. Inc. X-ray tube rotor structure
US5308172A (en) * 1993-07-19 1994-05-03 General Electric Company Bearing assembly
US6295338B1 (en) * 1999-10-28 2001-09-25 Marconi Medical Systems, Inc. Oil cooled bearing assembly
US20090129548A1 (en) * 2006-04-04 2009-05-21 Wolfgang Kaika Bearing unit for rotary anodes of x-ray tubes

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117739023B (zh) * 2024-02-20 2024-04-23 无锡市宇寿医疗器械有限公司 一种高性能双极液态金属球管轴承

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3634870A (en) * 1970-03-03 1972-01-11 Machlett Lab Inc Rotating anode for x-ray generator

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3634870A (en) * 1970-03-03 1972-01-11 Machlett Lab Inc Rotating anode for x-ray generator

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4187442A (en) * 1978-09-05 1980-02-05 General Electric Company Rotating anode X-ray tube with improved thermal capacity
US4326144A (en) * 1979-04-03 1982-04-20 Siemens Aktiengesellschaft Rotating anode x-ray tube
FR2475799A1 (fr) * 1980-02-07 1981-08-14 Siemens Ag Tube a rayons x a anode tournante
EP0184664A1 (de) * 1984-11-10 1986-06-18 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. Wärmeableitung von rotierenden Bauteilen in Raumfluggeräten
US4866748A (en) * 1988-08-15 1989-09-12 Varian Associates, Inc. Rotor structure brazed joint
US4969172A (en) * 1988-08-15 1990-11-06 Machlett Labs. Inc. X-ray tube rotor structure
US5308172A (en) * 1993-07-19 1994-05-03 General Electric Company Bearing assembly
US6295338B1 (en) * 1999-10-28 2001-09-25 Marconi Medical Systems, Inc. Oil cooled bearing assembly
US20090129548A1 (en) * 2006-04-04 2009-05-21 Wolfgang Kaika Bearing unit for rotary anodes of x-ray tubes
US7970104B2 (en) * 2006-04-04 2011-06-28 Paul Mueller Gmbh & Co. Kg Unternehmensbeteiligungen Bearing unit for rotary anodes of X-ray tubes
TWI398896B (zh) * 2006-04-04 2013-06-11 Ｘ射線管旋轉陽極之軸承單元
KR101383420B1 (ko) * 2006-04-04 2014-04-08 파울 뮬러 게엠베하 앤드 코 카게 운테르네멘스베테리군겐 Ｘ－레이 튜브의 회전 애노드를 위한 베어링 유닛

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GB1364175A (en) 1974-08-21

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Owner name: VARIAN ASSOCIATES, INC., A DE CORP., STATELESS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:MACHLETT LABORATORIES;REEL/FRAME:005060/0761

Effective date: 19890129