US2450530A - X-ray rectifying mechanism - Google Patents

Description

Oct. 5, 1948. D. SUSSIN X-RAY RECTIFYING MECHANISM 2 Sheets-Sheet 1 Filed March 21, '1945 @ct. 5, 1948. suss 2,450,530

X-RAY RECTIFYING MECHANISM Filed March 21, 1945 2 Sheets-Sheet :2

Patented Oct. 5, 1948 2,450,530 X-RAY RECTIFYING MECHANISM David Sussin, South Fort Mitchell, Ky., assignor to The Kellcy-Koett Manufacturing Company, Covington, Ky, a corporation of Ohio Application March 21, 1945, Serial No. 583,949

This invention relates to X-ray apparatus and more particularly to an X-ray tube or like vacuum or controlled atmosphere container having a full wave rectification means incorporated or built thereinto.

One of the principal objects of the invention is to provide an X-ray tube or like vacuum or controlled atmospher container having rectification means incorporated or built inside said container and which thus can give full wave rectification, without the use of the noisy, dangerous and cumbersome mechanical rectifiers operating in open air, heretofore sometimes used in conjunction with X-ray tubes, thus maintaining all the advantage in rectification which could be secured from such mechanical rectifiers but without the use of expensiveand bulky electric valvetube bridge circuits which have more generally been used in more recent years.

Still another object is to provide mechanical rectification for X-ray tubes in which full wave pulsating rectified current may be secured with the current to the tube being limited to desired high voltage and undesired low voltage eliminated.

Another object is to provide for rectification means in which proper balance may be readily attained in the rectified voltage with simple and comparatively cheap instrumentalities and the expensively manufactured valve tubes now necessary for proper balance, even under one fixed set of conditions, may be eliminated together with the large containers, a quantity of insulating oil, grid controls to block or make ineifective the undesired low voltage of the X-ray tube current, etc.

Other objects and advantages of the invention will be apparent from the following description and claims and the drawing.

In the drawing, in which like characters of reference designate like parts throughout the several views thereof,

Fig. 1 is a somewhat diagrammatic sectional view, along the line |-l of Fig. 2, through an X- ray tube having parts of the rectifying mechanism enclosed in the tube envelope, with parts shown in elevation for clear understanding of the invention; I

Fig. 2 is a somewhat diagrammatic sectional view, along the line 22 of Fig. 1, looking in the direction of the arrows, with a diagrammatic showing of the transformer and wiring;

Fig. 3 is a sectional view through a modified embodiment of this invention, shownpartly in 14 Claims. (Cl. 250101) section and partly in elevation, somewhat a in Fig. 1, for clearer disclosure;

Fig, 4 is a somewhat diagrammatic sectional view along the line 4-4 of Fig. 3 looking in the direction of the arrows, with a diagrammatic showing of the transformer and wiring; and

Fig. 5 is a diagrammatic view illustrating a rectified pulsating current with only the desired high voltage portions of the current passing to the tube and the undesired low voltage portions eliminated.

It has long been the practice to use alternating current, rectified to be uni-directional, for X-ray tubes. In fact, as is well known, an X-ray tube when cold is self-rectifying as the electron current will pass from the heated filament to the target under the selected operating voltage of the tube during the proper one-half of the wave cycle but on the succeeding half it will notpass in the reverse direction. However thi places a potential strain on the tube, and if the target should become sufficiently heated the electron current would pass in reverse from the target to the filament on such half cycle with unpredictable operating results, with probable damage to the filament, with resulting lack of proper control, and even destruction of the tube itself.

Mechanisms and methods of rectification have long been used in an efiort to secure unidirectional and proper and more efficient use of both halves or sides of the wave cycle. Mechanical rectifiers using discs with spaced contacts, or brushes, and cooperating spaced contacts or terminals for the high Voltage transformer, acting somewhat similar to commutators, were operated by synchronous motors to cause the respective contacts to close in proper phase relation with the unidirectional path provided by the X-ray tube, thereby utilizing both sides of the voltage wave.

While such mechanisms theoretically rectified satisfactorily, in fact they were cumbersome, noisy, presented exposed high voltage, produced high frequency sparks, and were subject to electrical and mechanical weanand deterioration.

Later a bridge circuit utilizing vacuum electronic-rectifier tubes came into use, which eliminated the undesirable features of mechanical rectifiers, as mentioned above; and such has replaced the mechanical rectifier in modern X-ray equipment. But such rectifier tubes are expensive; they occupy considerable space and also require supplementary equipment if the voltage effective during radiography is to be maintained within a predetermined range or above a minimum voltage. Also it must be understood that wherever hot cathode rectifiers are used they must be supplied with power to energize the filament. The supply must be insulated from ground to the same voltage at which the rectifiers themselves are operating, and since they appear in form of small transformers due to the fact their primaries are utilized for control purposes, the primaries must be insulated from the secondaries for full high tension voltage. Such tubes of themselves have no provisions of themselves to suppress or eliminate undesirably low voltage in operation; and balancing such tube arrangements for the voltages used is quite diflicult and requires great nicety in constructing and assembling the tubes into operating arrangements.

In many cases an external metal filter was used with such vacuum rectifier tubes systems as a selector to attenuate some of the undesirable X-rays produced by the low voltage current, thereby attenuating some of the desirably usable rays too. This was done to improve the quality of the selected X-rays desired to be used, while not eliminating them at the sourceproducing them at the X-ray tube target and effecting con trol of the emanating X-rays with a view to eliminating the undesirable portion.

In some instances, as for industrial radiography, a controllable grid bias was used, which produced blocking of the flow of the cathode stream in the X-ray tube, until a suiiiciently high impressed voltage was available to overcome the blocking effect.

The present invention, of which preferred embodiments are disclosed somewhat diagrammatically in the drawing, secures the desirable advantages of rectifying mechanisms as heretofore used, and without the disadvantages thereof; and also secures the desirable results, in radiographic work, which come from the use of a controllable grid bias sometimes included in an X-ray tube and used to block the cathode stream from the filament until the tube current has reached a t e of sufiiciently high voltage to overcome the blocking effect.

It being well recognized that when only the high voltage adjacent the peak of the voltage wave is applied to effect X-radiation from the X-ray tube, there will be produced beams of X- rays of more uniform quality than when the lower voltages in the voltage wave are included, and that the presence of the softer X-rays resulting from the lower voltage will tend to produce less satisfactory radiographs since the softer rays cannot contribute to the primary image but increase the undesirable scattered radiation.

While the controllable grid bias could also be utilized by including a third element in the valve tubes, this has not been done in practice because it would be very costly, as, of course, the valve tubes would have to be perfectly balanced in their characteristics and the amount of grid control used.

Nevertheless, the advantages of usin valve tubes has been such that they displaced mechanical rectifiers in modern X-ray equipment, and generally some form of filter, grid bias or the like is used to insure that the proper radiographic picture will be secured.

In the present invention, the means for elTecting rectifying of the high potential alternating current which supplies the tube circuit comprises rectifyin means sealed within the tube so that the advantages of mechanical rectification may be secured Without the disadvantages here- I the stator 28 carries tofore referred to. As shown in Fig. l, which is a somewhat diagrammatic illustration of an X ray tube constructed in accordance with the present invention, the glass envelope or container IE] is made of the type of glass ordinarily used in good quality X-ray tubes. This tube has sealed into one end a filament I l which is to be heated by the flow of current from a suitable source, in the usual manner, with the heating current brought in through the leads illustrated diagrammatically at l2, the filament and the leads connected thereto being mounted in a member shown diagrammatically in elevation and designated l5 which is properly sealed in the usual manner to the glass envelope of the tube.

The other end of the tube, as shown at 16 receives a synchronous motor which is shown diagrammatically, the stator 28 being shown as mounted upon the outside of the portion 55 and the rotor 2i mounted inside such portion i6 upon a shaft 22, upon which is supported a special roller bearing shown diagrammatically and designated 23, and of a type well known in the industry for supporting a rotating target shaft and which is mounted on a stationary shaft such as 22 extending through the glass wall of the tube and which is so constructed that the shaft 22 and the bearing may be sealed with respect to the shaft opening so tightly that the tube may be evacuated to the very high vacuums which are currently used in X-ray tubes. This form of bearing and method of effecting such sealin is well known in the industry and description thereof is believed unnecessary, the sealing being effected at 24, as diagrammatically shown. The

bearing on the stationary shaft 22 also carries at its inside end one end of a shaft 25 the opposite end of which carries the target 25, which is shown as a frusto-conical member, and which rotates with the shaft 25 and thus permits the bombarded surface of the target to have a substantial path of travel before a succeeding bombardment occurs at the same surface portion, to permit necessary heat distribution and cooling. Target 26 is made of a material of high atomic number, usually tungsten.

Preferably any suitable means for maintaining the synchronous motor in phase may be supplied, for example, the stator 20 may be so mounted that it may be given necessary small angular movements to accomplish this, with means for locking it in proper position, such means being shown diagrammatically and designated by the numeral 27.

The shaft 25, intermediate the target 26 and a disc-like member 39, of material having a high dielectric constant, sufficiently high to adequately insulate against the high voltage from the secondary of the transformer connected to the tube. As shown this member 39 is a corrugated disc, and made of glass or other suitable insulating material, preferably having some resiliency. One of the purposes of the corrugations is to increase the distance across the surface so as to increase the creepage path for the high voltage and the use of such corrugations permits of additional creepage resistance without increasing the diameter of the tube. It is not necessary that the disc be continuous throughout, but a suitable spider-like member or other properly shaped supports for the parts hereinafter described may be used. This disc is connected to the shaft 25 by means of a sleeve 32, preferably of heat insulating material, so that it will rotate with the shaft and if desired the member 30 may be definitely aifixed to the shaft 22 by means of suitable set screws or the like,

The disc 30, or other supporting members, carries two pairs of contactors or shoes those of one pair being designated by the numerals 40, 4| and those of the other pair by the numerals 42, 43. These contactors are carried by the disc 30 and the two members of each pair are 90 from each other and one member of each pair is 180 from the corresponding contactor of the other pair. For example, the contactors or shoes 40, 4| which constitute one pair are 90 from each other as are also the two contactors 42, 43 of the other pair while contactor 48 is 180 from 43 and 4| is 180 from 42. Each pair of contactors is connected by a suitable conductor such as the wires 44 and 45 which connect the pairs 40-4l and 42-43 respectively.

Likewise, the wall or envelope of the tube has sealed therein four contact members which are designated respectively 50, 5|, 52 and 53. As shown the contact members 50 and 52, which are 180 apart, and are sealed into the glass envelope so that the necessary high vacuum or controlled atmosphere may be secured and retained, are connected respectively to the secondary of a high voltage transformer, by means of conductors 55 and 56 respectively, the secondary oi the high voltage transformer being indicated diagrammatically at 51 and connected to ground as indicated diagrammatically at 58. The primary of the transformer is shown diagrammatically as 59. As will be seen the several contactors or shoes 40-43, which are carried by the rotatable disc 30 have lesser angular extent than the stationary sealed contacts 55-53, and by properly proportioning the angular width of the movable contactors 40-43 and the sealed stationary contact members 50-53 the length of time during which these contact members are in actual'contact, during rotation of the disc 30, may be controlled with respect to the current Wave so that they will be in contact only during the high voltage portion of the wave and will thus make effective use in the tube only of the high voltage, with any undesirably low voltage eliminated.

The disc 30, especially if corrugated as shown, may have suificient resiliency to press the contactor in suitable sliding contact with the contact members 50-53; but if desired springs 60, or other suitably resilient means, may be employed to insure the desired pressure between the contactors and contact members.

The contacts 55 and 53 are connected by the conductors 05 and 65 respectively to the target 25 and the filament H, such connections preferably being made inside of the tube envelope. In this manner, as the pairs of contactors 40-4l and 42-43 are carried by the revolving disc to pass by the terminals or contact members 50-52 which are connected to the secondary of the high voltage transformer, the current is rectified and made unidirectional, as diagrammatically illustrated in Fig. 5. And also as illustrated in that figure the relative angular dimensions of the movable contactors and the fixed contact members are such that the rectified or unidirectional current has the lower voltage portions eliminated and the higher voltage portions effective causing the current to travel through the conductors 55 and 66 to provide the rectified high voltage necessary for operation of the tube, with the electron current flowing from the filament H to the target 26.

Because of the parts for rectifying the'current being enclosed inside the tube envelope, the whole operation takes place within said envelope and the noise, sparking, liability to shocks, and other objections to mechanical rectifiers are avoided. As stated the disc 30, or other means supporting the contactors or shoes 40-43 is preferably slightly flexible or provided with suitable springs or other resilient means so that this pressure will cause the stationary and rotating contact members to be held firmly against each other and thus prevent difliculties that arise from such movable contacts in mechanical rectifiers as heretofore used. When made corrugated, as shown to give longer path of travel and therefore prevent creepage across the disc, the corrugations tend to add such flexibility that adequately strong discs of glass, such as makes up the envelope of the tube may also be sufficiently flexible to give this desired firm definite rubbing, sliding contact; but other suitable materials, such as certain of the plastics which have high dielectric constants may be used and readily molded.

Fig. 5 shows diagrammatically the full rectification of the high voltage current, and also those low voltage portions of the wave which are eliminated, the cross-hatched portion representing the part of the wave which is permitted to pass as a result of limitation of the time the contactors and the contact members are in conducting contact with each other.

The full wave rectification is also illustrated diagrammatically in this Fig. 5, the full line showing all of the waves on one side of zero voltage, and the dotted lines showing the portion of the wave which is rectified to give the unidirectional current flow.

The manner in which this is accomplished is also illustrated diagrammatically in Figs. 2 and 4. As shown in Fig. 2 the electrically interconnected contactors 42 and 43 are in contact with the contact members 53 and 52 respectively and, as indicated by the arrows, the current flows from the high voltage secondary of the transformer through the contact member 52 and the contactor 43 along the conductor 45 and contactor 42 and thence through the contact member 53 and theconductor 66 to the tube to cause the electron current flow across the evacuated space in the tube from the heated filament H to the target 26. The other end of the high voltage secondary 51 is connected to the stationary shaft 22 and through the rotating shaft 25 and the bearing and sleeve 23 in which it is mounted for rotation, by the conductor 65 which is connected to the contact member 5|, the cooperating contactor 4|, the interconnecting electrical conductor 44, the contactor 40, the contactor member and back through the outside conductor to the other terminal of the secondary 51 of the transformer.

When the shaft 25 is rotated, by the motor, i. e. into the position shown in Fig. 4, which corresponds to electrical degrees of the high voltage current wave, this will move the contactors 42 and 43 into conducting contact with the contact members 5| and 52 respectively and the contactors 40 and 4| into conducting contact with the contacting members 53 and 50. When in such position, the lower half of the current wave is in effect, tending to flow in the reverse direction from the upper half, and as a result the actual flow of current through the contact members and the several conductors is also the same as indicated by the arrows so that during the period of conducting contact the high voltage part of the 7 .current wave passes likewise through the conductor 66 to the heated filament l l with the same direction of fiow of current within the evacuated tube and on back through the rotating shaft 25 and stationary supporting shaft 22.

In Fig. 3 a different form of X-ray tube is shown, which has a glass envelope with a shaft 1| sealed through the wall thereof and carrying a target '12. This tube also has sealed through the wall thereof a member 15, which carries conductors 76 by means of which low voltage heating current may be carried to the filament 11, this member 75 also having provisions 18 for attachment to the high voltage from the secondary of the transformer as illustrated and described above, and as shown in Fig. 4 in which the contactors are shown as advanced 90 from the positioning thereof as shown in Fig. 2, the various parts thereof being given the same numbers as in Fig. 2 but with each number primed. This particular type of target and filament arrangement for an X-raytube is sufficiently similar to stationary target and heated filament arrangements as used in other X-ray tubes so that this diagrammatic showing is believed entirely adequate.

As shown in this construction of Fig. 3 the glass envelope for the tube is made to provide a cylindrical portion 80, having four contact members 50, 5|, 52 and 53 sealed in the wall thereof and likewise having a rotatable shaft which carries, inside the tube a rotatable disc carrying two pairs of contactors indicated at 4| and 42 43' and connected by conductors in pairs, these parts corresponding in construction and operation to the member 30 and pairs of electrically connected contactors described above. As the construction and mode of operation of this member 30' and the pairs of electrically interconnecting contactors are the same as above described it f is .to .be understood that during rotation of the shaft..25 the current is rectified to be unidirectionaland vwith low voltage eliminated as described above, and also that the X-ray tube is connected in the same manner to the secondary of ,the high voltage transformer, the wires for efiecting this connection being indicated and designated respectively as 56', 66' respectively. The wires 65366 connect the target and heatedfilament to the high voltage. The shaft 22 and the rotating shaft 25 in this construction are not connected to the secondary of the transformer but the contact members-50' and 52 are connected .to this transformer secondary so that the rotating .disc 30' with its pairs of contactors and contact members causes the same rectification as above described and the contactors and othertwo contact members are connected across thetube, to give the same mode of operation.

.As in the case of the form of tube shown in Figs. 1 and 2 the envelope may be highly evacuated, .in which event the operation would be substantially as described above, except that a fixed target is used in place of a rotating target. However, it may be desirable that the rectifying mechanism referred to may operate in a controlled atmosphere of inert gas and also that the pressure of the inert gas may be much higher than the highly evacuated atmosphere used for the X-ray filament and target, or'even increased considerably above atmospheric, in order to aifect the vaporpressure of the metals used for the contactors and other metal parts and thus suppress vaporization of the metal under the influence of heat and the breaking of the electrical current as the disc 83 revolves. As shown, therefore, the envelope'lO is provided with a partition 90, which may be of glass, formed integrally with the glass envelope of the tube, or such other material as may be sufficiently impervious to the passage of gases, Which will be adversely affected by stray X-radiations and which may be fixed, or otherwise tightly sealed, against the inside of the envelope '0 so that the necessary high vacuum, secured by a. controlled highly evacuated atmosphere, may be maintained in the space to one side of this partition 90 for proper operation of the X-ray dis charge members 12 and 11; while the space to the right, in which the parts of the rectifying mechanism are housed may be maintained under much higher pressure, even above atmospheric. The partition 90 is shown as concavo-convex with the convex side toward the right to give greater strength in resisting pressures above atmospheric of the inert gases which may be utilized.

The synchronous motor has a stationary or stator part 20 affixed to the outside of the portion 5% of the envelope for the rectifying mechanism, as shown in Fig. 1 and described above, and like- Wise has a rotor 2| mounted upon a rotatable sleeve having suitable sealing means 24' which sleeve is carried by suitable bearings upon the supporting stationary shaft 22, and which also carries within its inner end the rotatable shaft 25, which construction corresponds to that shown in 1 and described above. In the construction of Figs. 1 and 3 the envelope portion carrying the stationary shaft 22, 22 is doubled back upon itself to permit sufficient flexing or bending due to temperature changes and other operating forces. And the same is true of the portion of the tube through which the support 1 I, for the target, passes in Fig. 3. The partition need not be used if the controlled atmosphere is to be uniform, as in Fig. l; and likewise the portion of the envelope containing the rectifier may be physically separate from the tube without affecting the desirable rectifying operations, that is, the tube may have a continuous envelope in place of thepartition 98 so as to be a self-contained unit and likewise the rectifying mechanism may be a separate self-contained unit having an enclosure portion corresponding to the partition 90,

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. An X-ray tube comprising a high vacuum container, a filament therein, means for effecting controlled heating of said filament, a target, mechanical rectifying means for the high voltage current comprising movable contractors mounted within said container, and means operable from the outside of said container for causing rectifyin movement of said rectifying means.

2. An X-ray tube comprising a high vacuum container, a filament therein, means for effecting controlled heating of said filament, a target, and mechanical rectifying means for the high voltage current including movable contact members mounted within said container, relatively stationary contact members also mounted with in said container, and means for causing rectifying movement of said movable contact members relative to said stationary contact members.

' 3. An X-ray tube comprising a high vacuum container, a filament therein, means for effect ing controlled heating of said filament, a target, and rectifying means comprising contact memers sealed through the Wall of the container substantially diametrically opposite each other and connected to the source of high voltage cur-- rent, diametrically opposed contact members for the rectified current sealed through the wall of the container and spaced a predetermined angular distance from said first contact members, means within the container carrying pairs of contaotors angularly spaced to contact two of said contact members simultaneously, a conducting interconnector between each pair of contaotors, and synchronous means to move pairs of contaotors into rectifying 'contact with the contact members.

4. An X-ray tube comprising a high vacuum container, a filament therein, means for effecting controlled heating of said filament, a target, and rectifying means comprising contact members sealed through the wall of the container substantially diametically opposite each other and connected to the source of high voltage current, diametrically opposed contact members for the rectified current sealed through the wall of the container and spaced a predetermined angular distance from said first contact members, means within the container carrying pairs of contaotors angularly spaced to contact two of said contact members simultaneously for a predetermined part of the wave cycle of the high voltage current, a conducting interconnector between each pair of contaotors, and synchronous means to move pairs of contaotors into rectifying contact with the contact members.

5. An X-ra tube comprising a high vacuum container, 3, filament therein, means for effecting controlled heating of said filament, a target, and rectifying means for the high voltage current mounted within said container and comprising diametrically opposed contact members sealed through said container, a rotatable member inside said container, pairs of electrically connected contaotors carried by said rotatable member, and means operable from outside the container for moving said electrically connected pairs of contaotors into rectifying contact with cooperating contact members.

6. An X-ray tube comprising a high vacuum container, a filament therein, means for efiecting controlled heating of said filament, a target, and rectifying means for the high voltage current mounted within said container and comprising diametrically opposed contact members sealed through said container, a rotatable member inside said container, pairs of electrically connected contactors carried by said rotatable member, and means operable from outside the container for moving said electrically connected pairs of contactors into rectifying contact with cooperating contact members, said contaotors and contact members being of controlled relative angular extent to be in conducting contact for a predetermined part of each high voltage wave cycle of the high voltage current.

'7. An X-ray tube comprising a high vacuum container, 3, filament therein, means for effecting controlled heating of said filament, a target, diametrically opposed contact members sealed through the wall of said container, a stationary shaft sealed through the wall of said container, a synchronous motor comprising a rotor mounted upon said stationary shaft and a stator mount- 10 ed on the outside of said container, a rotatable shaft inside the container and rotatable by said rotor, contaotors within the container moved by said shaft for limited contact with said contact members, said contaotors being arranged in electrically interconnected pairs and angularly spaced with respect to the contact members to bring both pairs of contactors into rectifying contact with the contact members.

8. An X-ray tube comprising a high vacuum container, a filament therein, means for effecting controlled heating of said filament, a target, rectifying means for the high voltage current comprising movable contactors mounted within said container and contact members carried by said container, means operable from the outside of said container for causing rectifying movement of said rectifying means, and resilient means Within said container for effecting positive but substantially frictionless movement of the contactors across said contact members during operation.

9. An X-ray tube comprising a high vacuum container, a filament therein, means for effecting controlled heating of said filament, a target, rectifying means for the high voltage current comprising contact members sealed in the wall of the container and connected to the secondary of a high voltage transformer, a rotatable disc within said container of dielectric constant high enough to insulate against the high voltage current, contaotors carried by said disc and angularly spaced for rectifying contact with the contact members, and means for rotating said disc to effect rectifying contact of the contaotors and contact members.

10. An X-ray tube comprising a high vacuum container, a filament therein, means for effecting controlled heating of said filament, a target rectifying means for the high voltage current comprising contact members sealed in the wall of the container and connected to the secondary of a high voltage transformer, a rotatable member within said container and operated synchronously with the high voltage current, and cont-actors carried thereby and angularly spaced with respect to said contact members, so that upon rotation of said contactor carrying member sequential rectifying contacts will be effected, the surface of said rotatable member being lengthened to increase resistance to current creepage thereacross during operation.

11. An X-ray tube comprising a container having a controlled pressure atmosphere therein, a filament, a target and means for effecting controlled heating of said filament, rectifying means for the high voltage current comprising contact members sealed in the wall of said container and connected to the secondary of a high voltage transformer, rotatable supporting means within said container and operating synchronously with a high voltage current, contaotors carried by said rotatable supporting means and angularly spaced with repect to said contact members, so that upon rotation of said contactor carrying member sequential rectifying contaotors will be effected, the surface of said rotatable member being lengthened to increase resistance to current creepage thereacross during operation.

12. An X-ray tube comprising a high vacuum container, a filament therein, means for effecting controlled heating of said filament, a target, rectifying means for the high voltage current comprising contact members sealed in the wall of said container and connected to the secondary of a high voltage transformer, a rotatable member within said container and operated synchronously with the high voltage current, contactors carried' by said rotatable member and angularly spaced with'respect'to said contact members, and means for resiliently pressing said contactors so that upon rotation of said contactor carrying member sequential rectifying pressure contacts will be efiected, the surface of said rotatable memher being lengthened to increase resistance to current creepage thereacross during operation.

13; For use in connection with an X-ray tube utilizing rectified high Voltage, rectifying means for the high voltage comprisin a container having a controlled pressure atmosphere therein, angularly spaced contactmembers sealed in the wall of said container and'connected with a secondary of a high voltage transformer, a rotatable supporting means within said container and operated synchronously with the contactors carried by said rotatable supporting means and angularly spaced with respect to said contact members, and means for resiliently pressing said contactors radially outwardly relative to the axis of rotation that upon rotation member sequential of said contactor carrying rectifyin pressure contacts will be effected between said contactors and-contact members;

14. For use in connection with an X-ray tube utilizing rectified high voltage, rectifyin means high voltage current,

of said supporting means so for the high voltage comprising a container having a controlled'pressure atmosphere therein, an-

gularly spaced contact members sealed in the wall;

spaced with respect to saidcontact members, and.

resilient means for urging the contactorsradially outwardly relative to the axis of rotation ofsaid' supporting means and into controlled sliding pressure contact with the contact members during rotation so that sequential rectifying contacts will be efiected between said contactors and contact members. DAVID SUSSIN.

REFERENCES CITED The following references are of record in thefile. of this patent:v

UNITED STATES PATENTS Number Name Date 1,251,126 Snook Dec. 25, 1917 1,623,569 Zacher April 5, 1927' 2,250,963 Mutscheller July 29, 1941 2,350,642 Schwarzer June 6,1944

Certificate of Correction Patent No. 2,450,530. October 5, 1948.

DAVID SUSSIN It is hereby certified that errors appear in the above numbered patent requiring correction as follows:

Column 8, line 62, claim 1, for the word contractors read contactors; column 9, line 24, claim 4, for diameticall'y read diametrically; column 10, line 39, claim 10, after target insert a comma;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 8th day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent N 0. 2,450,530. October 5, 1948.

DAVID SUSSIN It is hereby certified that errors appear in the above numbered patent requiring correction as follows: 1

Column 8, line 62, claim 1, for the word contractors read contactors; column 9, line 24, claim 4, for diametically read diametrically; column 10, line 39, claim 10, after target insert a comma;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 8th day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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