US2311725A - X-ray tube - Google Patents

X-ray tube Download PDF

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Publication number
US2311725A
US2311725A US390322A US39032241A US2311725A US 2311725 A US2311725 A US 2311725A US 390322 A US390322 A US 390322A US 39032241 A US39032241 A US 39032241A US 2311725 A US2311725 A US 2311725A
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United States
Prior art keywords
anode
envelope
bearings
support member
pedestal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US390322A
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English (en)
Inventor
Zed J Atlee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric X Ray Corp
Original Assignee
General Electric X Ray Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by General Electric X Ray Corp filed Critical General Electric X Ray Corp
Priority to US390322A priority Critical patent/US2311725A/en
Application granted granted Critical
Publication of US2311725A publication Critical patent/US2311725A/en
Priority to FR943753D priority patent/FR943753A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/24Tubes wherein the point of impact of the cathode ray on the anode or anticathode is movable relative to the surface thereof
    • H01J35/26Tubes wherein the point of impact of the cathode ray on the anode or anticathode is movable relative to the surface thereof by rotation of the anode or anticathode

Definitions

  • This invention relates in general to rotatable devices and has more particular reference to rotatable structures enclosed in sealed envelopes, the invention pertaining especially to an improved rotatable anode structure for use in X-ray tubes.
  • An important object of the present invention is to provide a rotating structure of the character mentioned, having a magnetic brake formed and arranged therein and operable normally to check rotary movement of the device; a further object being to form the braking means as a permanent magnet built into the rotary device and the mounting on which it is carried.
  • Another important object is to provide an improved braking system for controlling the rtation of a rotary anode in an X-ray tube.
  • Another important object resides in providing an improved mounting structure for a rotary de-. vice of the character mentioned; a further ob ject being to form the mounting as a hollow pedestal within which is journaled a turnable spindle carrying the rotatable device, whereby the pedestal may form a stationary mounting for carrying the magnet or other auxiliary equipment in position to co-operate with the rotary device; a
  • Another important object is to provide for the accomplishment of the foregoing in a structure in which the rotary device comprises a tubular skirt portion embracing and enclosing not only the support pedestal but also all of the mechanism and auxiliary equipment mounted thereon.
  • Figure l is a sectional View through an X-ray tube provided with a rotating anode embodying my present invention.
  • Figures 2 and 3 are views taken, respectively, along the lines 22 and 3-3 in Figure l.
  • an X-ray generator ll comprising spaced-apart cathode and anode means l3 and l5 enclosed within a preferably glass envelope IT.
  • the anode I5 is of the rotating type, being turnab y supported for rotation on mounting means l 9 which, in turn, is supported on the envelope l! at one end thereof.
  • the envelope I! has an envelope extension 2! within which the anode I5 is snugly disposed, the envelope having a re-entrant sleeve-like portion 23 forming an annular space 25 between the envelope extension 2! and the re-entrant portion 23.
  • the mounting means I9 comprises a pedestal having a stem-like portion 21 extending outwardly of the envelope and a portion 29 extending within the envelope.
  • the anode I5 is rotatably mounted on the portion 29, which is preferably hollow; and the pedestal is sealed to the envelope at the re-entrant portion 23, which defines an opening in which the pedestal extends.
  • the pedestal is provided with an annular shoulder 3
  • This seal 34 supports the pedestal and the anode thereon in position embraced by the envelope extension 2
  • the hollow pedestal portion 29 defines an axial cavity 35 extending within the pedestal and opening at the end thereof within the envelope, and the anode I5 is journaled on the inwardly extending portions of the pedestal.
  • X-ray generators function to produce X-rays in response to the activation of the anode by electronic action established by the operation of the cathode l3, said electronic action consisting of the impingement of electrons emitted by the cathode upon a target 4
  • Electronic impingement on the target results in the generation of relatively large quantities of heat at the target, which is dissipated thence through the body of the anode l5.
  • the temperature of the X-ray generator, and particularly the anode may be of the order of 500 centigrade and above.
  • X-ray generators are conditioned for operation by exhausting from the envelope substantially al-lgaseous and other impurities byevacuating the envelope, as by means of a molecular exhaust pump, and finally sealing the envelope in evacuated condition.
  • be rotated at high speed in order to minimize the danger of over-heating the target itself at the point of electron impact.
  • Considerable difiiculty is encountered in providing suitable support for the rotating element l5, since it is desirable to support the element in precise alignment for high speed rotation substantially without vibration throughout extended service periods.
  • My present invention includes the provision of means for lubricating the bearings in a manner avoiding the aforesaid difiiculties, so that the device I5 may be supported for high speed, substantially frictionless rotation within the envelope.
  • an X-ray generator remains in operation for but short intervals of time, of the order of a few seconds, sufficient to accomplish the making of X-ray photographs.
  • the anode I5 is first brought to operating speed, as by means of a suitable motor, at which time the tube energizing system connected with the anode and cathode is actuated for the production of X-rays through electronic impingement upon the target 4
  • the tube energizing system is disabled and the anode driving means is de-energized.
  • means is.
  • anode being of appreciable mass and supported on substantially frictionless bearing means, will tend to continue to rotate for an appreciable interval, of the order of several minutes, even after the anode driving means has been de-energized, there being little, if any, braking effect due to windage in the evacuated envelope.
  • the service life of an X-ray tube having a rotating anode depends upon wear in the anode bearings, which is relatively rapid in X-ray tubes in which the bearings are subjected to the excessive heat conditions developed as a result of the operation of the device.
  • the service life of the bearings is further shortened due to the fact that lubrication, in the ordinary sense, cannot be provided where bearings are in operation under the substantial vacuum conditions prevailing in X-ray tubes.
  • I provide not only for adequately lubricating the bearings, but also provide means in the anode structure itself for rapidly braking the anode to stand-still condition in order to reduce coasting time and resultant bearing wear after the termination of the period of useful rotation.
  • 5 comprises a cylindrical body 39 having an open end extending in the annular envelope space 25 in position to encircle the seal 34.
  • the anode thus forms a shield for protecting the seal 34 from deterioration through impingement of stray electrons thereon.
  • the opposite end of. the anode body is enclosed and afiords a mounting for the target 4!.
  • comprises an annular ring of suitable target material, such as tungsten, which is embedded and secured in the preferably copper body of the anode IS.
  • the anode body is formed with a groove 42 at the marginal edge of the end wall of the anode outwardly of the outer edge of the ring 4
  • the ring 44 may comprise a tungsten copper composition and is joined to the outer edge of the target ring 4
  • the strengthening ring 44 preferably comprises a sponge-like mass of tungsten or other suitable material, such as tantalum or molybdenum, characterized by high melting temperature, with a preferably cuprous, tough, crack-resisting alloy filling the pores of said sponge-like mass.
  • I may use a predominantly copper alloy containing a heat hardening constituent, the alloy also permissively and preferably containing a deoxidating medium to promote wetting with tungsten.
  • Any suitable hardening medium such as chromium or cobalt, may be employed as the heat hardening constituent, and I may use beryllium, lithium, boron, calcium, or other suitable wetting agent.
  • a satisfactory alloy formula is:
  • the ring 44 may be made by pressing a homogeneous mixture of tungsten and the copper alloy in powdered condition to form a pressed ring. This ring may then be sintered to form the finished ring of appropriate shape.
  • and 44 may be accomplished as a casting process by pre-forming the target ring 4
  • the material of the ring thus has a coefficient of thermal expansion intermediate that of the target and body so that the tendency for cracking between the target and the body is greatly minimized.
  • the pedestal portion 29 extends within the cylindrical body of the anode and carries anode bearings comprising, in the illustrated embodiment, a pair of roller bearings 43 and 45 in spaced-apart position on the pedestal portion 29.
  • Each bearing comprises an outer race secured preferably in the hollow pedestal, and an inner race secured on and thereby supporting a spindle 41, suitable roller members being conventionally retained between the inner and outer race portions of the bearings.
  • the spindle 41 may, of course, be secured in the bearings in any suitable or preferred fashion, although I have shown the same as being formed with threaded portions receiving clamping nuts for clampingly securing the inner bearing races in spaced relationship on the spindle 41, the outer races of the bearings 43 and 45 being secured. in the cavity 35, the outer race of the hearing 43 being secured in a seat 49 formed near the bottom of the cavity, said race being held in said seat by a spacing tube 5
  • forms a seat for receiving the outer race of the bearing 45, which is held in place by a clamping tube 53 having a flange portion 55 secured to the inner end of the pedestal portion 29 as by means of holding screws 51.
  • the spindle 47 is thus journaled for rotation in the bearings 43 and 45 which are mounted on the pedestal portion 29.
  • the stem 47 has an end formed with a flange 59 outwardly of the open end of the pedestal portion 29.
  • the anode i is secured on said flange 59 by means of an annular mounting frame 6
  • the frame El has an end wall 63 formed with an opening defined by a boss 65 for receiving the end of the stem 41 outwardly of the flange 59, the frame 6
  • comprises cylindrical portions preferably formed integrally with the wall 63 and extending thence outwardly of and encircling the pedestal portion 29, said frame 6
  • I provide for the application thereto of a lubricating medium which has a vapor pressure sufficiently low so that it will not evaporate from the bearing under the conditions of temperature and pressure prevailing within the envelope.
  • a lubricating medium a material such as barium, caesium, strontium, cadmium, chromium, copper, silver, aluminum, iron or nickel, which have a vapor pressure of the order of l0 mm. of mercury at 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.
  • I provide for applying the selected lubricating medium in lm-like form upon the bearings after the same have been assembled in place and the envelope evacuated.
  • the selected material or materials are applied upon the bearing surfaces by vaporizing the same and directing the vaporized material upon the bearing surfaces to be treated, whereby to condense the vapor as a thin film upon the Working surfaces of the bearings.
  • the deposited material forms an alloy with the material of the bearings, which may be any suitable ferrous material, whereby is formed an alloy film having desired lubricating properties.
  • vaporization and delivery of the bearing material upon the surfaces to'be treated may be accomplished in any suitable or preferred manher.
  • 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, as by the passage of an electric current, in order to vaporize the material within the capsule and blow the resulting vapor from the capsule and onto the surfaces to be processed.
  • the bearing material may be formed as a filamentary wire in which the desired lubricating medium is incorporated and vaporized upon the bearing surfaces by passing an electric current through the wire. I prefer, however, in treating bearings for use in X-ray generators, to employ a hollow filamentary wire of iron or nickel containing,
  • a quantity of lubricating material such as barium
  • the hollow wire being weakened by reducing its wall thickness along a side of the wire facing the bearings to be treated.
  • the material therein may be vaporized and vapor products projected through the weakened wall section upon the bearing surfaces.
  • an electrical heating current may be caused to flow through the wire in order to raise the temperature thereof to a point at which the lubricating material therein may be vaporized, and, as heretofore described, expelled through the weakened wall portion of the loops and onto the bearings.
  • the bearings may thus be lubricated, and the quantity of lubricating material applied to each bearing may be regulated by controlling the activating current delivered through each loop.
  • Each loop furthermore, may be supplied with suflicient lubricating medium to enable re-lubrication of the bearings from time to time during the service life of the device.
  • I provide magnetic means on the stationary and rotatable portions of the anode support adapted to function as a magnetic brake.
  • the magnet may, of course, be applied on either one of the relatively rotatable members in position to magnetically influence the other, and, as shown in the drawing, the brake comprises a magnet 8"! fastened on the stationary pedestal in position to magnetically co-operate with a member of magnetic material on the anode, this co-operating member of magnetic material conveniently comprising the anode support frame 6!, which may be formed of steel or other suitable material adapted to form a magnetic circuit with the magnet 81.
  • the magnet 37 comprises a bar of permanently magnetized material characterized by the ability to retain magnetic properties at the operating temperature of the anode.
  • Alnico is a suitable material for the purpose.
  • the permanent magnet 81 is anchored in a slot 89 formed longitudinally in the external surfaces of the pedestal portion 29, suitable fastening straps 9
  • the bar 81 at its opposite ends, is formed to receive the straps 9
  • This magnetic circuit will at all times tend to prevent relative angular movement between the pedestal on which the magnet 81 is clamped and the anode I5 which is secured to the frame 6i. This tendency to prevent relative rotation between the parts, oi course, is not sufficient to prevent rotation of the anode at operating speed when the anode driving motor is in operation. However, as soon as the anode driving motor is disabled, the magnetic brake, afiorded by the permanent magnet 8'! and the cooperating frame iii of magnetic material, will brake the anode to stand-still within a period of the order of a fraction of a minute.
  • the formation of the frame 6! of steel, in combination with the formation of the anode with a cylindrical skirt of cuprous material embracing the frame 6!, enables me to utilize the anode assembly as the rotor of an electric motor having stationary motor windings 99 arranged in annular form and disposed about the envelope extension 2! in which the anode structure is disposed.
  • a rotating electromagnetic effect may be established within the envelope portion 2!, and the anode thus caused to rotate.
  • An X-ray tube having a sealed envelope, a rotary structure in said envelope comprising a support member, a rotary member on said support member, magnetic brake means comprising a permanent magnet on one of said members, and a co-operating element on the other member and forming, with said permanent magnet, a magnetic circuit whereby normally to resist relative angular movement between the support member and the rotary member.
  • An X-ray tube having a sealed envelope, a rotary structure in said envelope comprising a support member, a rotary member on said support member, a permanent magnet on said support member, means on said rotary member and forming a magnetic circuit with said magnet whereby normally to resist relative angular movement between the support member and the rotary member.
  • An X-ray tube having a sealed envelope, a rotary structure in said envelope comprising a support member, a rotary member on said support member, a permanent magnet anchored on one of said members, circuit-forming means anchored on the other member and forming a magnetic circuit with said permanent magnet, and magnet shoes on said permanent magnet and extending to form small gaps with said circuitforming means whereby to establish a magnetic circuit on the support member and on said rotary member tending normally to resist relative angular movement between the members.
  • An X-ray tube having a sealed envelope, a rotary structure in said envelope comprising a support member, means forming a rotary anode member supported on and having hollow portions embracing the support member, said hollow portions being spaced outwardly of the support member, and magnetic brake means comprising a permanent magnet on one of said members and a co-operating element on the other member and forming, with said permanent magnet, a magnetic circuit whereby normally to resist relative angular movement between the support member and the rotary anode member, said permanent magnet and said co-operating element being disposed within the space defined between the support member and the hollow portions of the anode member.
  • An X-ray tube having a sealed envelope, a rotary structure in said envelope comprising a hollow support member for-med with a cavity having an opening, a stem journaled in said cavity and having an end projecting at said opening, a rotatable support frame secured on the projecting end of the stem and having portions, including portions of magnetic material, spaced outwardly of and encircling said support member, a permanent magnet on said support member within said embracing portions of magnetic material, and means forming an anode secured on said rotatable support frame.
  • An X-ray tube having a sealed envelope, a rotary structure in said envelope comprising a support member, rotary means journaled on said support member and having portions, including portions of magnetic material, spaced outwardly of and encircling said support member, said support member being formed with a seat and a permanent magnet secured in said seat in position extending within said embracing portions of magnetic material.

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  • X-Ray Techniques (AREA)
US390322A 1941-04-25 1941-04-25 X-ray tube Expired - Lifetime US2311725A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US390322A US2311725A (en) 1941-04-25 1941-04-25 X-ray tube
FR943753D FR943753A (fr) 1941-04-25 1947-03-20 Perfectionnements aux ancdes tournantes de tubes à rayons chi

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US390322A US2311725A (en) 1941-04-25 1941-04-25 X-ray tube

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Publication Number Publication Date
US2311725A true US2311725A (en) 1943-02-23

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Application Number Title Priority Date Filing Date
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FR (1) FR943753A (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2797350A (en) * 1952-12-01 1957-06-25 Philips Corp X-ray tube
US2812462A (en) * 1953-05-18 1957-11-05 Gen Electric Anode structure
US3502926A (en) * 1967-03-24 1970-03-24 Hitachi Ltd Rotating anode x-ray tube with magnetic damper
EP2701179A3 (fr) * 2012-08-22 2017-06-28 General Electric Company Cible de tube à rayons X présentant une efficacité thermique améliorée et son procédé de fabrication

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2797350A (en) * 1952-12-01 1957-06-25 Philips Corp X-ray tube
US2812462A (en) * 1953-05-18 1957-11-05 Gen Electric Anode structure
US3502926A (en) * 1967-03-24 1970-03-24 Hitachi Ltd Rotating anode x-ray tube with magnetic damper
EP2701179A3 (fr) * 2012-08-22 2017-06-28 General Electric Company Cible de tube à rayons X présentant une efficacité thermique améliorée et son procédé de fabrication

Also Published As

Publication number Publication date
FR943753A (fr) 1949-03-17

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