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Publication numberUS3836805 A
Publication typeGrant
Publication dateSep 17, 1974
Filing dateMay 21, 1973
Priority dateMay 21, 1973
Also published asDE2422166A1, DE2422166B2, DE2422166C3
Publication numberUS 3836805 A, US 3836805A, US-A-3836805, US3836805 A, US3836805A
InventorsKok P
Original AssigneePhilips Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Rotating anode x-ray tube
US 3836805 A
Abstract
A rotating anode x-ray tube employing a generally cylindrical anode which is axially moveable relative to the cathode so that the focal spot traverses a spiral path as the anode rotates and moves axially. The axial displacement of the anode can be controlled by the temperature of the focal spot, i.e. by measuring the light emitted from the focal spot area.
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Description  (OCR text may contain errors)

United States Patent [191 Kok Sept. 17, 1974 [54] ROTATING ANODE X-RAY TUBE 3,398,307 8/1968 Brown et al. 313/60 [75] Inventor: Pieter W. Kok, Trumbell, Conn. Primary ExamineFJohfi Kominski [73] Assignee: North American Philips Assistant Examiner-Darwin R. Hostetter Corporation, New York, NY. Attorney, Agent, or Firm-Frank R. Trifari; Carl P. 22 Filed: May 21, 1973 Stemhauser [21] Appl. No.: 362,423 [57] ABSTRACT A rotating anode x-ray tube employing a generally cy- [52] U.S. Cl. 313/60, 313/330 lindrieal ano which is axially moveable relative to [51] Int. Cl. H01j 35/10 th ath d s that the fo al spot traverses a spiral [5 8] Field of Search 313/60 path as h anode rotat s and moves axially The axial displacement of the anode can be controlled by the [56] References Cited temperature of the focal spot, ie by measuring the UNITED STATES PATENTS light emitted from the focal spot area.

2,926,270 2/1960 Zunick 313/60 10 Claims, 1 Drawing Figure y. lo 9 5 2o l------ 7| I15 I17 If Q. we i n. I 7 f j a 2 a "II'IIIIII'";

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ROTATING ANODE X-RAY TUBE The invention relates to a rotating anode x-ray tube in which the anode is axially displaceable to thereby increase the loadability of the focal spot by increasing the cooling surface.

It has been proposed to increase the unit area loading of the anode of an x-ray tube, and thereby increase the x-ray output, by forced cooling of the anode, by rotating the anode, and by a combination of such expedients. It has also been proposed to oscillate a rotating target effectively to increase the amount of fresh metal presented to the electron beam per target revolution as described in US. Pat. No. 2,926,270.

It is an object of the present invention to substantially increase the unit area loading of a rotary anode x-ray tube without resort to forced cooling.

It is another object of the invention to increase the cooling surface of a rotary anode x-ray tube while maintaining a small focal spot.

These and further objects of the invention will appear as the specification progresses.

Broadly stated, the invention relates to a rotary anode x-ray tube employing a generally cylindrical, preferrably cup-shaped anode which is axially displaceable during exposure which increases the cooling surface because the focal track becomes a spiral on a cylindrical drum. The axial displacement can be controlled by the temperature of the focal spot, for instance by measuring the light emitted from the focal spot area on the inside of the cup. The light emitted from the inside of the cup may be detected and converted into an electrical signal which may be amplified and used to drive the motor which controls the axial movement of the anode.

The invention will be described with reference to the accompanying drawing which shows a single, exemplary embodiment of a rotary anode tube according to the invention.

The x-ray tube as shown in drawing includes a generally cylindrical evacuated envelope 1 having an end portion with a metal wall 2 sealed to the remainder of the envelope by a metal-to-glass seal 3 and provided with an x-ray permeable window 4 through which xrays generated within the tube are transmitted.

Mounted for rotation within the envelope is a cupshaped anode 5 having a generally cylindrical outer surface. A cathode cup 6 is positioned opposite the outer cylindrical surface of the cup-shaped anode and is energized by a filament 7 to produce a beam of electrons which impinges on the anode surface and forms a'focal spot 7 visible through the window 4.

Anode 5 is secured to a shaft 8 which is connected to a rotor 9 driven by a stator 10 mounted externally of the envelope. Rotor 9 is mounted for rotation on an axial slide 11 by radial bearings 12.

Axial slide 11 in turn is mounted on a stationary shaft 13 for axial movement by axial bearings 14 and is moved by a rack 15 which forms part of the inner surface ofthe slide and a pinion l6 driven by an axial drive rotor 17. The stationary shaft 13 is sealed in the end of the envelope so that the envelope may be evacuated.

In operation the anode 5 is driven by rotor 9 and presents a continually fresh surface to the impinging beam thus minimizing local heating where the electron beam impinges and forms the focal spot. However. due to thermal lag, the temperature of path described by the focal spot increases-with each revolution thus limiting the loading of the anode.

In order to increase the loading, the anode is moved axially by driving the axial slide 9. This causes the focal spot to describe a spiral on the outer surface of the anode which increases the path length and thus reduces the anode temperature rise due to thermal lag.

To further control the rate at which the anode temperature uses, and thus increase the loadability, the metal end cap 2 is provided with a small window 20 through which the inner surface of the cup-shaped anode can be viewed by a light detector 18 which produces an electrical signal 19 proportional to the intensity of the light emitted by the focal spot 7. This signal is amplified by amplifier 19 and is used to control the axial drive motor 17. Thus, as the anode temperature rises, the light emitted by the focal spot will increase which will increase the signal applied to the axial drive motor causing the anode to be moved axially in response to the increased loading.

Sometimes anodes crack and portions hit the tube window and may leave the shield. The proposed construction provides a metal shield around the anode and the x-ray window is not in the path of an anode part driven by a centrifugal force outside the shield.

What I claim is:

1. An x-ray tube comprising an evacuated envelope, a generally cylindrical anode rotatable about a given axis within said envelope and moveable longitudinally therealong, a cathode for producing an electron beam which impinges on the surface of said anode forming a focal spot thereon where x-ray are generated which emerge from said envelope through an x-ray permeable window therein, means for rotating said anode and means for moving said anode longitudinally along said axis in response to the temperature at the focal spot to thereby present a fresh surface of the anode to the electron beam for producing the focal spot.

2. An x-ray tube as claimed in claim 1 in which the focal spot moves in a spiral path in response to movement of the anode.

3. An x-ray tube as claimed in claim 1 in which the anode is cup-shaped and the cathode faces the outer surface of the cup.

4. An x-ray tube as claimed in claim 3 in which the anode is connected to a rotor which rotates about an axially moveable slide.

5. An x-ray tube as claimed in claim 4 in which the slide is moved by an axial drive mechanism which is actuated by means responsive to the focal spot temperature.

6. An x-ray tube as claimed in claim 5 in which the means responsive to the focal spot temperature is a member responsive to light emitted from the focal spot area inside the cup-shaped anode.

7. An x-ray tube as claimed in claim 5 in which the slide is coupled to the axial drive mechanism through a rack and pinion, the pinion being fixed by positioned and the rack being mounted on said slide.

8. An x-ray tube as claimed in claim 7 in which the rotor is journalled for rotation about the slide.

9. An x-ray tube as claimed in claim 8 in which the slide and rotor are mounted on said shaft by bearing means.

10. An x-ray tube as claimed in claim 9, in which said envelope includes an uninterrupted metal shield around the anode providing better safety from anode explosions.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2926270 *Dec 30, 1957Feb 23, 1960Gen ElectricRotating anode x-ray tube
US3398307 *Aug 25, 1966Aug 20, 1968Varian AssociatesElectron beam chi-ray generator with rotatable target movable along axis of rotation
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3942059 *Jun 12, 1974Mar 2, 1976Compagnie Generale De RadiologieHigh power X-ray tube
US4107563 *Apr 6, 1977Aug 15, 1978Emi LimitedX-ray generating tubes
US4162420 *Jun 5, 1978Jul 24, 1979Grady John KX-ray tube having rotatable and reciprocable anode
US4399551 *Sep 29, 1980Aug 16, 1983Grady John KX-Ray tube having rotatable transversely oscillatory anode
US4417171 *Oct 15, 1981Nov 22, 1983Siemens AktiengesellschaftRotary anode x-ray tube
US4523327 *Jan 5, 1983Jun 11, 1985The United States Of America As Represented By The Secretary Of The Air ForceMulti-color X-ray line source
US4675891 *Jun 25, 1985Jun 23, 1987Thomson-CgrX-ray apparatus with focus position control
US5592525 *Nov 30, 1994Jan 7, 1997General Electric CompanyAn x-ray tube
US6154521 *Oct 26, 1998Nov 28, 2000Picker International, Inc.Gyrating anode x-ray tube
US7305063Jul 15, 2004Dec 4, 2007Koninklijke Philips Electronics N.V.Cylindrical x-ray tube for computed tomography imaging
US7394891 *Aug 25, 2006Jul 1, 2008Noriyoshi Sakabe And Kiwake SakabeX-ray generating method and X-ray generating apparatus
US7751530 *Sep 17, 2007Jul 6, 2010General Electric CompanyHigh flux X-ray target and assembly
US7852987May 18, 2009Dec 14, 2010King Fahd University Of Petroleum And MineralsX-ray tube having a rotating and linearly translating anode
US7949100Mar 15, 2007May 24, 2011Koninklijke Philips Electronics N.V.Dual-colour pyrometric measurement of X-ray focal spot temperature
US8184774Apr 14, 2011May 22, 2012Koninklijke Philips Electronics N.V.Dual-color pyrometric measurement of X-ray focal spot temperature
US8259905Jul 22, 2010Sep 4, 2012King Fahd University Of Petroleum And MineralsX-ray tube having a rotating and linearly translating anode
US8654924Nov 19, 2009Feb 18, 2014Koninklijke Philips N.V.X-ray tube with target temperature sensor
CN100543918CSep 14, 2006Sep 23, 2009坂部知平;坂部贵和子X-ray generating method and x-ray generating apparatus
DE102012203807A1 *Mar 12, 2012Sep 12, 2013Siemens AktiengesellschaftX-ray tube for use in mammography system, has units for rotation of sheath surface around cylinder longitudinal axis, and units for simultaneous translational movement of sheath surface in direction of cylinder longitudinal axis
EP0030453A1 *Dec 3, 1980Jun 17, 1981Pfizer Inc.Rotating anode-type X-ray tube and method of generating an X-ray beam
WO2009136349A2May 4, 2009Nov 12, 2009Philips Intellectual Property & Standards GmbhX-Ray Examination System with Integrated Actuator Means for Performing Translational and/or Rotational Disuplacement Movements of at Least One X-Radiation Emitting Anode's Focal Spot Relative to a Stationary Reference Position and Means for Compensating Resulting Parallel and/or Angular Shifts of the Emitted X-Ray Beams
Classifications
U.S. Classification378/126, 378/93, 378/144, 250/205
International ClassificationH01J35/10, H01J35/28, H01J35/00, H01J35/24
Cooperative ClassificationH01J35/24, H01J35/10, H01J35/28
European ClassificationH01J35/10, H01J35/24, H01J35/28