US2090582A

US2090582A - X-ray tube

Info

Publication number: US2090582A
Application number: US710432A
Authority: US
Inventors: Harry F Mesick
Original assignee: General Electric X Ray Corp
Current assignee: General Electric X Ray Corp
Priority date: 1934-02-09
Filing date: 1934-02-09
Publication date: 1937-08-17
Anticipated expiration: 1954-08-17
Also published as: BE407782A; GB442324A; FR785412A

Description

H. F. MESICK Aug. 17, 1937.

X-RAY TUBE Filed Feb. 9, 1934 5 Sheets-Sheet l E@ miv.

H. F. MESICK Aug. ll'?, i937.

X-RAY TUBE Filed Feb. 9, 1934 5 Sheets-Sheet 2 ug. il?, 3937. H 5; MESICK 2,090,582

X-RAY TUBE Filed Feb. 9, 1934 5 Sheets-Sheet 3 Fl .Q5

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.. IIB L INVENTOR ORNEY Patented Aug. 17, 1937 UNITED STATES X-RAY TUBE Harry F. Mesick, Chicago, Ill., assigner to General Electric X-Ray Corporation, a corporation of New York Application February 9, 1934, Serial No. 710,432

9 Claims. (Cl. Z50-35) This invention has to do with an X-ray tube in which the area of bombardment or focal spot on the target is constantly shifted by rotating the tube or anode so as to subject an ever changing surface of target material to bombardment during any given X-ray exposure, thus increasing the area subjected to electronic bombardment without increasing the size of the focal spot.

A tube of the type herein described is capable l0 of handling large amounts of energy with a relatively small focal spot, thus making the tube applicable to heavy or fast work where eX- tremely good definition is essential. Tubes of this type constructed previously to this invention contain denite limitations, either as to load capacity or lfocal spot shape, which limit their usefulness. These limitations are avoided in the type of tube constructed by applicant.

The present invention relates further to means u whereby a line focus cathode may be used in a tube of the type described in connection with an anode which is stationary with respect to the tube envelope, and hence is capable of. transmitting heat generated at the focal spot to a radiator exterior to the envelope at a rate to permitl energization of the tube for relatively long periods of time.

The invention has to do further with an X-ray tube, the cathode of which is rotatable within 3U the tube envelope and with reference thereto, but

in which no brushes are used within the envelope.

The invention concerns also novel means for bringing the focal spot in a rotating X-ray tube 3,3 with a line focus cathode into proper position for use of the X-rays emanating therefrom, and for directing them so that their greatest intensity will be in a single direction.

Involve-d in the attaining of these objects are 4U novel means for supporting an X-ray tube, unique means for supporting a cathode in such tube, improved means for causing a tube to rotate, novel electrical connections, unique cooling means, and improved means for holding one element of the tube against rotation.

These objects and such other objects as may hereinafter appear are obtained by the novel construction, unique arrangement and improved combination of elements illustrated in the acgc companying drawing of a tube embodying the subject matter of the invention, hereby made a part of this specication, and in which:

Figure l is a median longitudinal section of an improved Xray tube in which the invention is 55 disclosed;

Figure 2 is a median longitudinal section of the cathode end of the same device on the same plane as Figure 1;

Figure 3 is a median longitudinal section of the anode of the same device on the same plane as 5 Figure 1;

Figure 4 is a cross section of the X-ray tube on line 4-4 of VFigure 1 Y c Figure 5 is a cross section lof the device on line 5--5 of, Figure l; and l0 Figure 6 is a diagram of circuit which may be employed with the present tube.

Like reference characters are used to designate similar parts in the drawings and in the Y following description of such embodiment of the 15 invention.

AThe X-ray tube I0, shown in the several figures, comprises a glass envelope Il of reduced diameter at its anode end, indicatedk I2. An anode I3 in the tube consists of a copper head 20 I3a, and a shank I3b, and has a tungsten face or button I4. The tungsten button I4 is attached to the anode in any manner which produces a good thermal union between such button and the body of the anode. A sleeve I5 is attached, in any desired manner as by means of soldering, to the anode at i6. The sleeve I5 is used to make a tight joint between glass and metal while avoiding the danger of breakage because of the differential expansion and contraction of the materials consequent upon temperature changes.

It is made of relatively thin nickelsteel or some other suitable metal.

The outer end I'I of the sleeve I5 is sealed to a glass cylinder I8 in a manner well known in the 35 art and the cylinder I8, in turn, is sealed at I9 within the reduced portion I2 of the envelope.

The cathode end of the envelope II has a reduced portion 29 into which a cathode stem 2I is sealed as indicated at 22. The cathode stem includes a main cylinder 23 having one end/24 of reduced diameter. A pinch seal 25, through which two wires 23 and 2l pass, closes the reduced section 24, the joint being made secure by means of a ring seal 28.

The inner end of the reduced section 24 of the cathode stem is sealed at 30 to a small sleeve 3I to which there is attached, in any desired manner as by copper brazing, a collar 32. The sleeve 3I is of the same type and similar to the sleeve 50 I5 before mentioned` A center supporting tube 33, made of steel or similar material, is attached to the collar 32 in any desired fashion, as for instance by means of the screws 34. At the inner end of the tube 33 there is a bored out 55 section 35 serving as a receptacle for a split insulator 36 and a collar 31 about said insulator. The insulator 36 supports Within, its center the rod 38. Three set screws penetrate the wall of the tube 33, lock against the collar 31 and urge the split insulators 36 toward one another to lock the inner rod 38 in a selected position. The free end of the rod 38 carries an annular ball bearing 40. The two wires 26 and 21 are atl() tached in` any desired fashion, as for instance, by spot welding, respectively to the cylinder 33 and to the inner rod 38.

On the periphery of the cylinder 33 and near the opposed ends thereof are two annular ball l bearings 4| and 42. Each of these bearings carries a cylinder 43 and 44, respectively, about its periphery.

Attached to the cylinders. 43 and 44, in any desired fashion as by means of the screws 43a and 44a, is an outer cathode supporting cylinder 45.

The inner end of said cylinder 45 carries a focusing cup 46. An opening 41 for the purpose of supporting lament 48 is eccentrically located with respect to the center of the cup 49. Materiall is removed at 49 in the back of the cup 46 on the opposite side of its center or axis in afashion to offset the removal of the material for making the hole 41.

One end of the filament 48is, attached, in any desired fashion as for instance by arc welding, to a support wire 50 which is, in turn, supported in the cathode cup 46 by means of a set screw 5|. The other end of the filament is similarly supported on a support lead 52 which is in turn insulated from the cathode cup by passing the lead through an aperture 53 in the cathode cup I without touching the walls of the aperture, and supporting it between two insulators 54, which are clamped together by means of screws 55 and supported by means of supports 56. The inner end of the wire 52 is fastened in any desired fashion to the outer ring of the ball bearing 49, as shown.

Due to the fact that the ball bearings 4|, 42 and the entire cathode structure must be brought up toa dull red heat during evacuation of the tube, it is necessary to make the bearings out of a self-hardening steel. The term cathode structure appearing in the immediately precedn ing sentence and in the claims refers to the combination of the filament 48, the cathode supporting cylinder 45, and the focusing device 48 in case such a device is employed. Most of the high speed steels are suitable for this work, but applicant has found a high tungsten content steel to be best.

Seal off 62 is what remains of the exhaust constriction after the tube was exhausted and sealed 01T.

A motor for rotating the tube is designated 19, and is connected to the tube by a shaft 10a and a flexible coupling 1| having a heat insulating section 12 of any suitable heat-resisting non-heat vconducting material to prevent passage of heat 65 from the shank of the anode directly into the motor by conduction. One end of the exible coupling 1| is attached -to Vthe motor shaft by a set screw 13, and the other is attached to the anode shank by a set screw 14.

A radiator 15 acts both as a means of radiating the heat generated in the anode and as a fan for circulating air about the exterior ofthe X-ray tube. The radiator 15 consists of an inner sleeve 16 having thereon washers 11 supported by spacers 18. Rings 19 and 80 hold the r fan.

entire structure in assembly. Several of the washers, as indicated at 11a, are notched and portions thereof bent fan-wise to provide bladelike devices for driving air in the manner of a This farming action causes additional air movements about the tube and the rotating washers and increases the radiation Vof heat therefrom. The high tension connection to the anode is through a spring 61 set in a cavity 68 in the end of the anode I3 and bearing on the end of a pin 69 set in the shaft 19a of the motor 10.

Attached to the inner sleeve 16 next to ring is a driving member 8|. The X-ray tube I0 has attached at the reduced portion I2 at the anode end an anode cap 82, which is held in place by cement or in any other suitable manner. In a similar fashion, a cathode cap 831s attached by cement at the reduced section 29 of the cathode end. The anode cap 82 is made preferably of insulating material such as a` phenol condensation product, and carries a steel ring 84 onto which annular ball bearing 85 is attached in any desired fashion, as for example by the keys 8B. Connection is also made between the driving member 8| and the cap 82 as indicated at 82a by screws 92D.

A phenol condensation product insulating tube 81 is fastened at one end to the anode cap 82, as indicated, by screws 88. The insulating tube 81 passes over the entire X-ray tube as shown, and is fastened to the cathode cap by means of screws 89.

From the foregoing it will be seen that the power applied to the shank of the anode I2 is not transmitted through the sleeve I5 but byvmember 8| to anode cap 82 and the anode end of the tube, also to the insulating tube 81, to cathode cap 03, and tothe cathode end of the tube. fashion the placing of undue strain on the relatively fragile sleeve I5 and the joint I1 between it and the glass is avoided.

Cathode cap 83 carries a steel sleeve 90 to which an annular ball bearing 9| is secured by means of a key 92. The outer ends of the two wires 26 and 21 are secured respectively to a slip ring 93 and to a stud 94 at the outer end of the cathode cap 83. Wire 26 passes through a hole in'a lead lining 95 of the cathode cap, thence through a hole in the cap, and is secured to said slip ring 93 by soldering, as shown. Wire 21 leads through an insulator 94a., through lead lining 95 of the cathode cap, and through the cathode cap 83, and is secured to stud 94 by soldering.

It is apparent that if proper supporting means are provided for the annular bearings 85 and 9| and for the motor 10, it is possible to rotate the tube I0. The support for these parts consists of a casing |00. This casing is similar in structure to that described in copending application of Malvern J. Gross, entitled Tube casing, Serial Number 685,867, filed August 19, 1933, assigned to General Electric X-Ray Corporation, a corporation of New York, August 8, 1933, and recorded in Liber H-157, page 235 of the records of titles, and consists essentially of a metallic middle section IOI, into which a supporting cone |02 is screwed as shown. The middle section is telescopically assembled into an X-ray protective cylinder |03 preferably made of lead. This cylinder is provided with an opening |04 through which the beam of useful X-rays passes. of the protective cylinder |93 is an insulating cylinder |85 made of insulating tubing. As the two cylinders |03 and |05 are of greater length In this Inside f V on the outside thereof.

- by screws Bla.

than the center section"llftheyprojectalong ea'ch'side -of the latter and are" surrounded by insulating vsleeves 05 and |01' made of insulating material opaqueto X'rays.

Sleeves |0I', |03, |05, |05 andl'l can beattached to eachother in any manner desired. In the preferred embodiment of the invention, a phenol condensationvproduct cement is used, and serves not only as a goodmechanical bond between the various units but, because of its high insulating qualities, 4also to fill effectively all the joints from an electrical standpoint and prevent the passage of electric current longitudinally of the tube along paths lying in the spaces between the various telescoped sections.

The cathode end of the cylinder |06 is closed by means of a cap l0, which is formed preferably of conducting material and is adapted to be locked onto the sleeve |06 by means of screw threads ||0a, on the cap and ||0b on the sleeve. The cathode-.base rcarries at its end a so-called Edison plug having a center section I2 and a circumferential section ||3. This plug can be fastened to the end piece inv anyy desired fashion, as for instance by means of screws I4. Contact is made from the circumferential section H3 to the slip ring 03v through the medium of a brush contact mechanism IE5. This mechanism consists of a brush ||6 adapted to ride within a guide tube A spring H8V forces 'the'brush into engagement with the ring 03. This spring engages the brush-at one end and at the other end engages the inner surface of the adjusting screw ||9 which closes tube IIT. A pigtail |20 short circuits the spring ||0 to prevent loss of tension therein by heat due to the passage of the current through it.

Center section ||2 of plug has attached to it a stud |2|, a projection of which passes through the center section ||2 and is soldered A spring |23 engages the stud |2| at one end and at' the other` end engages a screw plug |24 which acts as a cap for a tube |25 Within which rides a brush |26. A spring |27 Vengages the plug |24 at one end and at the other end engages brush |25 to urge the latter into Contact with the center stud 94. A pigtail |28. short circuits the spring |21v to prevent loss of temper thereof by heating, due to the passing of current through it.

Thus, if the terminals of the heating circuit are placed at the terminals of the Edison plug, connections are made to the cathode of the tube while the latter rotates, through the medium of the contactl rings `and brush mechanism just described.

At the outer end of cathode supporting cylinder 45 and opposite each other are two lugs 6| of magnetic metal such as iron one hundred eighty degrees apart and fastened to cylinder The insulating sleeve |06 is provided with two oppositely disposed apertures |30 one hundred eighty degrees apart and on aline concentric with the lugs 6|. Through these apertures the retaining magnets 60 pass in as .close proximity as possible to the insulating sleeve |05.V lThe sizes of the apertures |30 and the magnets 60 are such that the magnets can be shifted in the apertures about thelong axis of the tlila...l V.The two magnets eare made preferably of Vsome high permeable material, such as vcobalt steel or other alloy, and are connected together by means of a yoke |3| made preferably of magnetic material. Slot |32 in the yoke |3| cooperates with a screw |33, making it possible to move the two retaining magnets about the longitudinal axis of the tube as a unit.

Movement of the magnets causes corresponding movement of the independently movable cathode structure through the interaction of the lugs 6| with the magnets. By this means it is possible to position accurately the opening 41 in the cathode focusing cap 46 to cause the focal spot of the tube to move about the longitudinal axis of the tube as a center, so as to bring the latter into the desired relation with the opening |04 in the X-ray protective cylinder |03. This is necessary due to variations in the various parts of the bearings, and because the cathode will assume various angles of lag with respect to the magnets 60 incidental to changes in the speed of rotation of the tube from time to time.

At the open end of the sleeve |01 at the anode end of the tube is a motor supporting casing |50. This consists of an open supporting casting |5I, partially cylindrical in shape, and on which the motor 'i0 is fastened by means of screws |52.` A perforated metallic casing |53 is secured to the casting l5! by means of screws |54. The entire unit so formed is attached to the tube casing and held in engagement therewith by means of a ring |55.

To avoid excessive absorption of radiation by the glass walls of envelope the portion of the glass wall which comes between the focal spot and the opening |04 is reduced in thickness as indicated at |60;

The operation of the device which has been described is clear from the foregoing. The tube is adapted to be rotated within its casing by the motor at the anode end of the tube. The driving power of the motor is transmitted to the tube through the external caps and sleeves. the tube is rotated contacts for the high and low tension electric currents are maintained at the outer cathode end of the tube through brushes outside of that tube and thence through the ball bearings within the tube to the cathode and the cathode filament.

The filament current passes from the outside H3 of the Edison plug through brush |16 to the ring contact 93 and wire 26, from there through the tube 33 and the bearings 4| and 42, to the cathode cap to which is grounded one end of the filament. The current then goes through the filament to the rod 52 and through it and the ball bearing 40 to the rod 38. This rod is connected to wire 2 which carries the current to the brush |20 whence it reaches the center contact ||2 of the Edison plug.

The anode high voltage connection is through the electric motor. While the tube and anode are rotated by the motor, the cathode within the tube is kept stationary by the drag of the magnets 60 on the lugs 5|. The position of the magnets can be altered to adjust the cathode, making it possible to keep the focal point on the anode always in the proper place with respect to the opening |535 for X-rays. The cathode remaining stationary and the anode rotating with the rest of the tube, the focal point remains only an instant on any one spot on the anode. Thus a small and line focal point with consequent excellence of definition can be employed for long periods with minimum damage to the anode.

Connections are made to the anode of the tube While Cit by -means of the two wire cables |40. (See Figure 6.) One of these wires is grounded to thesupport casting |5|, and the other connects to one terminal of the motor l0, the other motor terminal'l being also grounded as shown at |4|. The two free ends of the wire |40 connect to the terminals of a secondary |42 of the insulation transformer |43. Primary winding |44 is energized from any suitable source of power, as, for instance, that indicated at |45.

A rheostat |46 is interposed in this primary circuit for the purpose of bringing the motor up to speed slowly and thus avoiding stresses on the various rotating parts of the tube. The lament is energized from a secondary |48 of filament transformer |41 connected to the center contact |22 and the shell ||3 of the cathode terminal of the tube.

'I'he primary |49 of this transformer is energized from any suitable source of power, such as indicated at |45 as shown, a control |6| being interposed in the primary circuit forthe purpose of regulating the amount of energy to the iilament of the tube. A high tension transformerV |62 has at the ends of its secondary |63 connected, one to the secondary |42 of the motor insulation transformer, and the other to the secondary |48 of the lament insulation transformer. The primary |64 is energized from auto transformer |65, which is in turn connected to any suitable source of power, as, for instance, that indicated at |45.

Claims covering broadly the feature of a cathode and an anode, respectively, movably and immovably mounted within the envelope of an X- ray tube together with means for moving the envelope and anode with respect to the cathode are contained in the Ungelenk application, Serial No. 408,587, led November Z0, 1929 and assigned to the same assignee as the present application. Consequently, the claims in the present application are limited to details of the broad invention disclosed-and claimed in the said Ungelenk application.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:

1. In combination, a casing and an X-ray tube containing a lamentary cathode and anode, said cathode and anode being respectively movably and immovably mounted with respect to said tube, rotary bearing members between said tube and casing, means for rotating said tube and an- 0de within said casing while maintaining the cathode stationary, whereby the anode and cathode are moved with respect to one another.

2. In combination, a casing and an X-ray tube containing a lamentary cathode and anode, said cathode and anode being respectively movably and immovably mounted with respect to said tube, rotary bearing'members between said tube and casing, means including an electric motor for rotating said tube within said casing while maintaining the cathode stationary, whereby the anode and cathodev are moved with respect to one another.

3. An X-ray tube having a support, bearing means between said tube and said support allowing rotation of said tube, an anode and a cathode structure immovably and movably mounted respectively with respect to said tube, means for` rotating said tube and anode with respect to said cathode structure, a filament constituting part of said cathode structure, power supply means for said filament, annular ball bearing means supporting said cathode. structure within said tube, other annular ball bearing means electrically insulated from said first mentioned ball bearing means, one race of said rst ball bearing means being electrically connected to one side yof said filament and the other race thereof being electrically connected to one side of said filament power supply means, and one race of said other ball bearing means being electrically connected to the other side of said filament, and the other race thereof being connected to the other side oi said filament power supply means.

4. An X-ray tube having an envelope containing an anode and a cathode structure immovably and movably mounted respectively with respect to said envelope, said anode having a projecting stem and being sealed to said envelope by a sleeve, bearing means allowing rotation of said tube and anode, rotative power means therefor, coupling means between said power means and said anode stem, rotative impulse transmission means between said anode stem and said envelope and removed from said sleeve, and rmeans for holding said cathode structure stationary when the anode and envelope are rotated.

5. In combination, an X-ray tube having an envelope containing an anode and a cathode structure immovably and movably mounted Vrespectively with respect to said envelope, said anode having a projecting stem, bearing means allowing rotation of the envelope and anode and permitting the cathode structure to remain stationary, power means for rotating said tube, means forv holding said cathode'structure sta.- tionary when the anode and envelope are rotated, and heat radiating means attached/to said anode stem and comprising vanes thereabout, parts of said vanes being shaped to cause circulation of air when said anode stem,'vanes and envelope are rotated.

6. In combination, an X-ray tube having an envelope containing an anode and a cathode structure immovably and movably mounted respectively with respect to said envelope, said anode having a projecting stem, bearing means a1- lowing rotation of said tube and anode and permitting the cathode structure to remain stationary, rotative power means to rotate said tube, means for holding said cathode structure stationary when the anode and envelope are rotated, and coupling means comprising heat insulating and resistant material between said rotative power meansand said anode stem.

7. In combination, an X-ray tube having an anode and a cathode structure including a lament, said anode and cathode structure being immovably and movably mounted respectively with respect to said tube, bearing means allowing rotation of said tube and anodefand permitting the cathode structure to remain stationary, means for causing rotation of said tube, means for holding said cathode structure stationary when the anode and envelope are rotated, a source of electrical energy for said filament, a cap over the cathode end of said tube,I contact means on said cap, other contact means on said cap and electrically insulated from'V said rst mentioned contact means, said contact means being electrically connected to the ends of said iilament, a second cap separate from said rst cap, brush means in said second cap and in electrical connection with said contact means, and electrical connectons between said brush means and said source of energy.

8. In combination, a casing and an X-ray tube containing a lamentary cathode and an anode, said cathode and anode being respectively movably and immovably mounted with respect to said tube, rotary bearing means between said tube and casing, means contained within the casing for rotating the tube with respect to the casing, and means for maintaining the cathode stationary whereby the anode and cathode are moved with respect to one another.

9. In combination, an X-ray tube and a support for said tube, said tube containing an anode and a cathode structure including a filament, said anode being xedly secured to said tube, rotatable means for supporting the cathode structure within said tube, and for permitting rotation between the tube and said cathode structure, means for producing relative motion between the tube and the cathode structure, an electrical connection including a rotatable device between one end of said lament and the exterior of said tube, the other end of said lament being connected to said cathode structure, and an electrical connection between said rotatable means and the exterior of said tube whereby current may be supplied to said lament while the tube and the cathode are being rotated With respect to one another.

HARRY F. MESICK.