US2103335A

US2103335A - X-ray tube

Info

Publication number: US2103335A
Application number: US614124A
Authority: US
Inventors: Jr Harry F Mesick; Malvern J Gross
Original assignee: General Electric X Ray Corp
Current assignee: General Electric X Ray Corp
Priority date: 1932-05-28
Filing date: 1932-05-28
Publication date: 1937-12-28
Anticipated expiration: 1954-12-28
Also published as: FR756143A; GB420438A

Description

Dec. 28, 1937. H. F. MEslcK, JR., r- T AL X-RAY TUBE Filed May 28, 1932 2 sheets-,Sheet 1f' HmzRY F mamon JR MALVERN J. @Ross n on u i Sie um. mi A Dec. 2s, l192.7.

H. F. MESICK. JR., El' AL X-RAY TUBE 2 Sheets-Sheet 2 Filed May 28, 1932 FICq. C

nannllll/ H meer F. meslck .1a. mnu/ERM J. G2055 INVENTORS ATTORN EY Patented Dec. 28,V 1937 UNITED STAT-Es X-RAY TUBE Harry F. Mesick, Jr; and Malvern J. Gross, Chicago, lll., assignors to General Electric X-Ray. Corporation, Chicago, Ill., a corporation of New York Application May 28, 193Z,.Serial No. 614,124.

24 Claims.

This invention has to do with an IX-ray` tube and relates particularly to improvements with-Y in such a tube and a casing therefor.

Up to the present time it has vbeen the practice of the manufacturers of X-ray tubes to fabricate A external casings for tubes in a mannery that order, to send the casing as well as the tube to the manufacturer. Because oijrindentations or the like accumulated in the casing during use, during shipment, or by damage during its removal from the tube, usually it has been necessary to replacev the casingras well as repair or replace the tube.

Another object of the presentrinvention is to" provide an easily demountable casing for an X- ray tube which casing has means for measurably placing a window therein in Xed relationship with the focal spot or spots upon the anode of the tube.

Another' object of the present invention is toprovide for an X-ray tube, a casing having a window with a lead jacket adjacent thereto to absorb all but the useful cone of X-rays, there being insulating sleeves impregnated with a salt of a metal of high molecular weight extendingy from the lead jacket as an additional protection from other than the useful X-rays.

Still another object of the present invention is 'to provide a casing for an X-ray tube and having means for an adjustable mounting of the tube.

Another object ci the present invention is to provide a casing for an X-ray tube and to which may be attached either a water reservoir or a cooler of the radiator type for the purpose of cooling the tube anode.

Another object of the present invention is to provide a casing for an X-ray tube and from which the tube is capable of delivering X-rays of a relatively loW penetrating power.

Another object of the present invention is to provide a cathode in an X-ray tube having a multiplicity of laments suitable for independent (Cl. Z50-34) energization whereby different intensities and` elds of usefulness may berobtained. r Y

Anotherobject of the present inventionisthe provisiony within the structure of acasing for an X-ray tube, of means for insulating from exposed metallic parts of the tube an'drcasing the-relectrical charges which accumulatetuponthetube walls. Y

- Still another object of the present invention is to provide within the structure of a'detachable X-ray tube casing a sleeve `of high dielectric eATENT i oFPlCl:

strength and of low X-ray absorption qualities whereby to: insulate any metallic supporting means from the tube and to permitof the `ready passage ofthe useful field of X-rays therethrough without an aperture being formed inf the casing.

Other objects of thepresent invention arethe provision of: v

A metallic supporting member within acasing Meansiinterposedy within the filament circuits n of an X-ray tube for standardizing filament excitation characteristics. i v y An electrical conductive sleeve within vthe structure of a casing for anX-ray tube for distributing electrical charges inherently accumulated by such a tube and for improving the operation of thetube'.

These, and other desirable objects which are obtained by the novel construction, unique arrangement, and improved combination of the parts comprising the invention, will be made apparent in the following description when read in conjunction with the .accompanying drawings, hereby made a part of this specification, disclosing one embodiment of the invention,Y and wherein like reference characters indicate similar parts and in whichzy Y Y Figure l is a longitudinal section ofk an X-ray tube and casing incorporating the invention, the tube having waterv cooling means;

Figure 2 is an elevation, partly in longitudinal section, of a tube similar to that shown in Figure 1 but with air cooling;

Figure 3 is a perspective view of the glass portion of a tube to be enclosedby the c asings illustrated in Figures 1 and 2; l

Figure 4 is an enlarged sectional view of the cathode end of an X-ray tube showing in detail parts of the structure;

Figure 5 is a sectional view of an X-ray tube incorporating the invention and taken on the line 5-5 of Figure 4;

Figure 6 is a perspective View of the unassembled parts comprising the cathode end of the tube;

Figure 7 is a diametric section of a tube taken on the broken line 'I-'I of Figure 1; and

Figure 8 is an enlarged fragmentary sectional view of the tube casing shown in Figures 1 and 2.

Attention is first directed to Figures 1 and 2 and particularly to an anode Ill having a head II at the inner end of a hollow shank I2. Upon the diagonal face of the head II is a tungsten target I3. Y

A sleeve I5, preferably made of nickel steel, is copper brazed or otherwise suitably secured to an auxiliary ring I5a. which is soldered or otherwise attached to the anode as indicated at IB. The left end of the sleeve I5, Figure 1, is turned down and a glass cylinder I1 is attached at I8, in accordance with modern practice. The anode and cylinder I'I are then sealed into a cylindrical outer tube I9, shown in perspective in Figure 3, the seal being indicated at 20.

Ring I5a is preferably made of steel, but any metal which can be brazed and'soldered may be substituted therefor. The sleeve I5 is Van alloy of steel and nickel, with approximately forty-two per cent nickel. If this sleeve I5 be secured directy to the copper anode by silver-copper solder, the sleeve is attacked by the solder when heated to high temperatures. Small cracks are thereby effected in the sleeve where this solder of high melting point comes in contact therewith. Consequently, a tube' so constructed is defective due to these cracks and soon becomes useless.

When solder of a lower melting temperature is used, the zinc or similar metal which forms a. part of the solder distills at the operating `temperature of the anode and collects upon the glass walls of the tube in the form of a thin metal coating to affect the operating characteristics ofthe tube. 'I'he steel ring Ilia is not attacked by the silver-copper solder and thus provides a serviceable coupling between the sleeve I5 and the solder of high melting point, the latter not having the tendency to vaporize, due to the absence of zinc-or similar material, as does a solder of lower melting point. There is no action, therefore, to form a deposit vupon the tube walls. The structure thus described permits the use of a solder of high melting point which permits the anode to be run at higher temperature thus increasing the normal energy capacity of the tube. Consequently, since the solder does not come into contact with the nickel-steel sleeve I5, the objectionable formation of cracks in the sleeve is precluded.

One of the requirements within the structure of an X-ray tube for prolonging its life and stabilizing its operating characteristics is the provision of a greater distance between the walls of the tube adjacent to the bombarded end of the anode than at a position near the supported end thereof. This structure is to prevent stray and reflected electrons from the anode from getting back onto the glass in the anode arm thereby unbalancing the voltage distribution along the glass and causing excessive bombardment thereof, with the resultant heat and fluorescence of the glass. The conventional glass shell for an X-ray tube has an enlarged portion about the bombarded end of the anode to meet this desired requirement.

In the case of the present tube which has a truly cylindrical wall, the shape of the anode It is altered to provide the desired space relationship between the anode and the wall. It will be Vobserved in Figure 1 that the anode III! increases in diameter as the point of `seal with the ring I5@ is approached from the extended end of the head II.

This tapering coniguration' of the anode makes the present form of tube with the cylindrical wall equivalent in operation and life to that of the more complicated form of wall with an enlarged central portion. Even if a cylindrical tube, which is made as eiective as the ordinary shaped tube by the tapering of the anode, was not especially desirable becauseV adaptable to a removable sleeve casing to be described later in this specification, the cylindrical tube has still another advantage of being less unwieldy than the ordinary tube.

A cathode 2, shown in detail in Figures 4 and 5, consists of a focusing cup 22 having two apertures 23 and 24.- Two leads 21, preferably of molybdenum, are screwed into tapped holes 28 in the base oi cupr22. The

filaments

25 and 26 are attached to center leads `29s and 3G, respectively, in any desi1"edfashion as by binding with wire Si and arc welding. The outer ends of the ilaments extend as

leads

33 and 34 and are carried through holes in the focusing cup and attached to the outer edge of the focusing cup as indicatedV at 35. VNickel brazing has provento be a satisfactory method of making the connection at 35. The two center leads 29 and 3) are ness so that it may yieldingly engage the glass v cylinder 43 for support.

Attached to the glass cylinder 43 and sealed thereto, as at 44, so as to extend therewithin is a pinch seal 45, sealing three wires 415, 41 and i8 in a manner well known in the art. One end ci the wire 4G is attached to the free end of the wire 30, preferably by spotwelding, as shown at In the same fashion the free ends of the wires?? and 29 are attached to Wires 48 and 4l'.

Interpos'ed between sections of the wires lit and t8' are two standardizing resistances 45a and 41a which may be made in any desired fashion as by using coils of resistance wires suitably insulated. In the particular construction illustrated, the resistances 46a and lila vare open coils of relatively stifiresistance wire'such as an alloy of nickel and chromium and are covered by a glass tube. These coils 46a and Ma are used to compensate for inherent differences in different types of cathode filaments to permit their excitation fiom a source of power of standard characteristics.

A definite order of operation is followed in the assembly of the cathode. The two filaments after being roughly positioned are accurately adjusted by means of a depth gauge and the screws locked up tightly to keep them in a selected position. After this, joints 49 are made and the sleeve 4I is screwed into place on the focusing cup 22, the focusing cup being held stationary and the sleeve 39,. revolved until the desired position is obtained. The cathode structure is thensealed into the cylinder i9 at circular joinder 5B. At this end, aprotruding section is formed pursuant to the process of evacuating the tube. K

After having been given certain tests, the tube, as assembled to this stage, is supplied with a cap 53 on its cathode end. The cap 53 is attached tc the glass in any desired manner, as by means of litharge-and glycerin, by plaster of Paris, or by a Bakelite compound.

Attached to the cap 53 is a selector switch 54 shown more in detail in Figure 6. The three leads 45, LZ1 and i8 are carried back to this selector switch to make contact respectively with contact 54a, contact 55 and center stud 56, the latter named parts being carriedrby an insulating disc 5.1.

The disc 51 is secured tothe sleeve 53 by a plurality of screws 58. Center stud 55 is electrically connected to the sleeve 53 by means of a contact strip 5e shown in dotted outline. The contact 59 is for the purpose only of preventing static discharges from the stud 55 and across the edge of the insulating disc 51 to the sleeve 53. A cupshaped contact member 68 serves as a medium for connecting either spring 54a or spring 55 to one side of the circuit for energizing the iilament in the manner hereinafter described.

The circuit for energizingV the filament is connected to the X-ray tube by means of a plug Sil. One side of the circuit is carried on a shell di and the other side is carried by a center contact 52. The shell 6| is mechanically and electrically connected to a meta-l disc 63 (an electrical conductor), by means of screws Ell. This metalv disc 63 carries an indexing stud 65 which engages a hole 65 in the dielectric disc 51 for the purpose of holding discs 63 and 51 in Ya selected fixed into a slot to limit the rotative movement of the contact cup El! to the curvilinear dimensions of the slot 15. Contact is then mad-e betweenV the disc 63 and the contact cup 68 by engagement of their two opposing surfaces 1| and 12 when the two members are in assembled position.

The contact member 53 is then at the same potential as the .side of the electric circuit connected to the shell 6|, and. when it is in a position so that stud 59 is at one end of the slot 15, it electrically connects the shell 6| to the contact 55. When in the other position, it connects the shell to the contact 54a and hence toy the inner end of filaments or 25 by means of the wires 4B and 41.

The outer ends of the fila-ments 'are grounded to the cup 22 and thus are electrically lconnected to the support wires 21 and the lead i8 which is connected to center stud as previously described. The stud 55 passes through a hole 15 in the contact plate 68 and through a center hole 15 in the disc 53 from which it is insulated by means of an insulating bushing 1E. A nut E1 coacts with threads upon the stud 56V and the end of the bushing 1S to hold the disc 63 in vassembly With the cap 53. Nut 11 is provided with a boss 18 onto which contact spring 1S seats. The other end of spring 19 is attached about a boss 80, which forms a part of the center contact 52. In this manner, the electric circuit is completed from stud 56 to contact 52 to formthe return circuit from the outer ends of both filaments.

After the sleeve 53 has been attached to the end of the cylindrical tube, the

wires

46, 41 and 68 are drawnthrough suitable apertures'in the insulating disc 51 and secured respectively to the contacts 54a and 55 and to the center stud 5.6.

` When the plug 62 is screwed into a proper socket for supplying electrical energy to the tube, the metal cup 68 will be at one potential and the center stud 56, the focusing cup 22, the

filaments

25 and 26, and the contacts 54a andn55will be at a potential different than that of the cup @8.

In theange of the member 63 is an oblong A aperture 68a through which indicating figures upon the periphery of the disc 63 may be'viewed. Byturning the cup 58 in a clockwiseVV direction with reference from the cathode end of the tube,

and as limited by the pin 68 abutting an end ofthe aperture 1|),A the piece 68h within the cup 68 -will be carried into contact with the electrode V Y Elia to close the electric circuit through the Y.

filament 26. Concurrently the aperture 68a is carried over the indicia upon the periphery of collar. |50. lA second and complemental 'collar |5| screws upon the threaded shoulder lta. collar |5| is drilled and tapped for receiving a set screw |52. V from the collar |5| providedwithv a radial slot |54.andrapertures |53. iA v The description'up to this point covers the vacuum tube properiand the parts` permanently attached thereto. Where tube replacementsare The The threadedV shoulder.` |50a projects longitudinally ofthe tubefrom thel 'I'here is a flange |53 projecting necessary, the outer casing now to bev described is retained by the user and only the above'rdescribed parts'are sent to the manufacturer for repair.-

If a tubeis beyond the state of practical repair,VV

an entirely new tube may be obtained by the owner of the worn out tube to fit into the' outer sleeve. or casing which he still possesses. this way, i. e., by the use of interchangeable and replaceable vacuum tubes in a single outer casing,

the cost of replacements is substantially reduced, i

retained by the user. l y y The casing proper consists of anV insulating Yas only one portion of the assembly need be re-V j placed, theotherv portion of the assembly 'being sleeve 9D, which' is immediately about the center of the glass cylinder le. Sleeve 9|! can be made of any desired linsulating materialhaving' low f n member 92a surrounds the sleeve 5| and is`secured to it by insulating varnish orother suitable material. The member 92a includes a sleeve 93, the center portion of which isV ribbed as shown at 94 for heat dissipation in a manner to be later described. Said central Vrnerr'iber V93 has two anges S5.

. A passageior the useful beamrof X-rays is proy .integral to the ring |51.

vided by a window aperture 91 bounded by an internally threaded cylinder 98 into which various devices, such as diaphragms, and the like, may be secured by a nut 99. there is no window in the sleeve 90.

Two tapered insulating sleeves or sections,

and Il, are suitably chamfered and notched to t snugly over the sleeves 90 and 9| and beneath the respective flanges 95. Pins 95d anchored within the flanges 95 project into notches ||l0a and |0|a within the ends of the sections |09 and |0| so that the sections will be denitely arranged axially with reference to the window 91. An insulating varnish or shellac may be used for attaching the sleeves |00 and |0| to the sleeves 90 and 9| to assist the tight t used to hold the parts in place.

The sections |00 and |ll| are made of an insulating material, such as a phenol condensation product, glass, hard rubber, or a similar product whichhas been impregnated with a salt of high molecular weight for the purpose of rendering the combination impervious to the passage of indirect X-rays from within the tube.

In the manufacture of the tubeproper which includes the anode, cathode, the glass cylinder I9, the cap 53 and switch assembly attached thereto, the collar |50 and the index ring |5|, it is not always possible to make the cylinder I9 of exact standard length. Variation occurs where the end of the tube is sealed off at Therefore, it becomes necessary to make the means for attaching the casing and tube one to another of an adjustable nature for the -casing is of a standard size and length.

The anode and cathode are set within the tube with the cathode filament and the target I3 of the anode in a definite standard spaced relationship with reference to each other. Later, the cap 53, collar |59 and ring |5| are set upon the ends of the tube. The ring l5| is advanced upon the collar |50 until its inner face is a selected distance from the anode target.

The ring |5I, in addition to being spaced at a denite predetermined distance from the anode target, is also selectively alined with the anode axially. Tightening the set screw |52 insures the maintenance of the desired position of the ring |5i. The ring as held by the set screw |52 is in such a position that the pin |55 when inserted into the slot |54 will position the Window 91 of the casing in radial alinement with the useful ileld of X-rays as deected from the anode target.

The sleeves 93, |00 and |0| are of a standard length, and the notches |000. and |0|a are of a depth to receive the pins 95a in a manner allowing the ends of the outer sleeves to abut solidly It will be noted that against the ends of. the intermediate sleeve 93. It follows that the overall longitudinal dimension of the casing is denitely xed. There is no telescopic motion relative any of the parts forming the casing. Instead, the casing is a rigid accurately fabricated member.

There is a standard known distance between the left end of the sleeve I0 Figure l, and the center of the window 91. The collar |5| is advanced upon the collar |50 until the distance between the inner face of the flange |53 and the center of the anode target is equal to the distance between the left end of the sleeve |0| and the center of the window 91. By screwing the flanged ring |51 to draw the said end of the sleeve I|J| against the inner face of the ange |53 with the pin |55 seated in the notch |50, the window 91 will be squarely alined with the conical X-ray eld to emanate from the target I3.

Adjustment to accommodate the slight discrepancy in tube lengths is had at the cathode end of the tube after the casing has been thus accurately iitted to the tube from the anode end. It will be recalled that the anged ring |5| slidingly engages the cap 53. lIhe ring, therefore, can with equal eiiicacy engage the cap at any section along the part of greater diameter. Never is there such a disparity of dimensions in the tube that the ring IBI will fail to register some place upon the enlarged section of the cap 53.

An examination of the iiange |53 will reveal that said flange has a thinned section. The material of the ange |53 is resilient so that there may be a slight axial movement of the tube relative to the casing, the cap 53 being free to slide within the anged ring |5| to accommodate such a movement. This flexible mounting for the tube is addedprotection therefor, and cushions the effect of any accidental blows which might Without such cushioning be detrimental to the tube.

In the above described manner, a certain and simple method is provided for the assembly of a vacuum tube in the casing and for the alinement of the focal spot, both axially and radially of the casing for the passage of useful X-rays through an opening in the outerV casing, in com.- bination with cushioning means for absorbing shocks due to rough handling. Ap'ertures |58 provide for ventilation within the casing and assist to-cool the tube. The cooling of the tube is further assisted by the sleeve 93, which has a ribbed section 94 as previously described, to promote the dissipation of heat into the surrounding air.

*The simplicity of. the casing makes it practical for a user to retain an outer casing in the event of damage to the vacuum tube and for the manufacturer of the Ytube to'ship to the user for replacement only a vacuum tube. Hence, a highly economical and p ractical method of tube repair is possible.

To further provide a greater possible exibility of the present X-ray tube the anode has been designed so that it can be cooled either by water or air at the option of the user. As noted, the anode of the tube is hollow and projects beyond the end of the casing. The collar |50 is threaded near its outer end to render it applicable for the coupling thereto of a cooling unit.

When the anode is to be cooled by means of Water, the connections are made as sho-wn in Figures land 8, in which the member is a baiile the operation of which is more fully described in a patent to Jesse L. Worden, No. 1,972,414, issued September 4, 1934. The baille is held in position ltube.

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

1. The combination with an X-ray tube, of a demountable casing comprising an inner continuous, imperforate sleeve of insulating material transparent to X-light, a centrally disposed housing member of X-ray absorbing material about said transparent insulating sleeve, and end housing sleeves of insulating X-ray absorbing material engaging said centrally disposed member, there being a window for a beamo-f X-light in said centrally disposed housing member.

2. An X-ray tube having an envelope and provided with an anode and cathode, there being a fitting at one end of said tube, in cornbination with a casing for said tube held in demountable assembly with respect to said fitting and having a window providing an outlet for X-light in juxtaposition to the bombarded area of the anode, said casing comprising aninner sleeve of insulating material transparent to X- light and surrounding the envelope of said tube,

an outer sleeve of X-ray absorbing material about i sembly with respect to one of said fittings and said envelope, said casing comprising a jacket of insulating material surrounding the tube approximate the anode and cathode thereof to add dielectric strength to the envelope, a second jacket of metallic X-ray absorbing material of less longitudinal extent than and disposed about said insulating sleeve, there being a window in said metallic sleeve for the escape of a beam of useful X-light, and end members intermediate said metallic sleeve and said end fittings and of an insulating material impregnated with a salt of high molecular weight.

4. The X-ray tube and housing described in claim 3, and in which said metallic sleeve is surrounded by a second metallic sleeve to which the end members are attached, there being a window in said second metallic sleeve registering with the window in said first referred to metallic sleeve.

5. An X-ray tube comprising a generally cylindrical envelope having an anode and a cathode disposed therein away from its ends, in combination with a sleeve of insulating material transparent to X-light completely encircling said envelope and extending from the median line toward the ends a distance greater thanthe space between the anode and cathode a metallic sleeve surrounding said insulating sleeve and having a window in juxtaposition to said anode for the passage of a beam of useful X-light, said metallic sleeve being of less longitudinal extent in respect to said envelope than said insulating sleeve, a second metallic sleeve about said first named metallic sleeve and having a window registering with the window in said first mentioned metallic sleeve, and insulating end members opaque to X-light extending from said second mentioned metallic sleeve to the ends of said envelope.

6. In an X-ray tube, an anode having a flange selectively positioned longitudinally thereof, there being a guide means on said flange and said flange being rotatably adjustable on said anode to position said guide means radially of said tube, a cathode in said tube, a casing including a window and having guide means at one end thereof cooperating with the guide means on said llange, said casing being adapted to t around said tube with the Vend thereof in abutment with said ange Vfor selectively disposing said window longitudinally with respect to a useful beam of X-light from said tube, and with said guide means in alignment tofix the position of said window radially of such useful X-ray beam.

7. For use with an X-ray tube having an envelope and an anode and a cathode therein, a casing adapted to telescope longitudinally thereof and comprising a portion of electrically con- Y ducting material opaque to X-light for equalizing electrostatic charges induced on the envelope by the potentials of the anode and cathode, said casing having a window therethrough for the passage of a beam of useful X-light, and a sleeve of electrical insulating material of great dielectric strength and transparent to X-light, said sleeve being within said opaque portion and in axial alignment therewith, and being wider than the diameter of said window and across said WindoW.

8. The combination with an X-ray tube having an anode extending outwardly of the tube, of a demountable casing comprising anV inner continuous sleeve of insulating material transparent to X-light, a centrally disposed housing member of X-ray absorbing material about the insulating sleeve, said housing member having a window through which a beam of X-light may be projected outwardly of said casing, and end closures for said casing comprising sleeves of insulating and X-ray absorbing material secured to the centrally disposed member, one of said sleeves having a closure at its end through which said anode may extend out of the casing.

9. The combination with an X-ray tube having an anode extending outwardly of the tube, of a demountable casing comprising an inner continuous sleeve of insulating material transparent to X-light, a centrally disposed housing member of X-ray absorbing material about the insulating sleeve, said housing member having a window through which a beam of X-light may be projected outwardly of said housing, end closures for said housing comprising sleeves of insulating and X-ray absorbing material secured to the centrally disposed member, one of said sleeves having a closure at its end through which said anode may extend out of the casing, said anode having a cavity opening outwardly of said casing and means connected on the projecting end of the anode for circulating a cooling medium within said cavity.

10. An X-ray tube comprising a cylindrical envelope of material relatively transparent to X-light and of substantially uniform diameter and wall thickness throughout its extent, an anode having a portion forming a substantially point source of X-light for projection through the walls of said envelope, a demountable casing around said envelope comprising an inner continuous, imperforate sleeve of insulating material transparent to X-light, a centrally 'disposed housing member of X-ray absorbing material about the insulating sleeve, said housing member having a window, end housing sleeves of insulating, X-ray absorbing material secured to said housing member in position enclosing the opposed ends of the envelope, the walls of said envelope being ground to produce a thin spot opposite said housing member, the remaining walls of the envelope being relatively thick in order to impede the passage of X-light therethrough except at said thin spot at which minimum impedance to the passage of X-light is afforded.

11. The combination with an X-ray tube, of a demountable casing comprising anV inner continuous, imperforate sleeve of insulating material transparent to X-light and a housing comprising a centrally disposed housing member of X-ray absorbing material about said insulating sleeve, said housing member having a window through which X-light may be projected from the X-ray tube and iin-like heat dissipating means on the outer surface of said housing member, and said casing comprising end housing sleeves of insulating X-ray absorbing material secured to said centrally disposed member. Y

12. The combination with an X-ray tub adapted when energized to provide a substantially point source of X-light, of a demountable casing for said tube comprising an inner continuous, imperforate sleeve of insulating material transparent to X-light and a sectional housing comprising a centrally disposed housing member of X-ray absorbent material disposed about the transparent insulating sleeve, and having a window through which X-light from said point source may be projected, and end housingsleeves of insulating X-ray absorbent material secured to said centrally disposed housing member and extending oppositely to enclose the opposed ends of said X-ray tube, said X-ray tube and casing being formed with co-operating means aording an index for registering said point source with said window as and when the X-ray tube is assembled in the casing.

13. The combination as set forth in claim 1 wherein the sleeve of insulating material extends at its opposite ends outwardly of said centrally disposed housing member and within the end housing sleeves.

14. The Vcombination of an X-ray tube having an anode and a cathode in a suitable envelope from which a beam of useful X-rays is projected from said anode in a direction normal to the axis oi" the envelope, an inner sleeve of insulating material transparent to said X-rays encircling the tube between said anode and cathode and extending longitudinally thereof toward the ends of the tube, an outer sleeveof X-ray absorbing material extending over said inner sleeve and to the ends of the tube, said outer sleeve comprising a section of X-ray absorbentmetal at the median portion of the envelope having an opening therein, a metallic sleeve enclosing this median section and being provided with an X-ray transmitting window in registry with the opening in said section, and X-ray absorbing end members extending from the outer sleeve toward the ends of the tube and cap'members cooperating with said end members to enclose the ends of the tube.

15. In an X-ray apparatus the combination of an X-ray tube having an envelope with an anode and cathode therein, adjustable guide means on the anode, a casing for said tube, said casing having a window therein adapted to be disposed adjacent said anode for transmitting a beam of X-rays, index means on said casing for cooperating with the guide means on the anode to aline the window in said casing with said anode when said casing and tube are assembled.

16. In an X-ray apparatus, the combination of an X-ray tube having an venvelope with an anode and cathode therein, and a unitary casing adapted to telescope thereover, said casing comprising a metallic sleeve for equalizing electrostatic charges induced on the renvelope by the potentials of the anode and cathode, an electrical insulating sleeve intermediatethe metallic sleeve and the envelope for fortifying the dielectric strength of said tube, said metallic sleeve beingV of an X-ray absorptive'material andhaving a window for the passage of useful X-rays and said insulating sleeve being of X-ray transparent material and extending entirely across said window.

17. An X-ray apparatus comprising in combination an X-ray tube having Aan envelope with an anode and a cathode therein, a casing of material opaque to X-rays and having a window ytherein enclosing said tube, .an adjustable guide means on said envelope abutting an end of said casing, said guide means being adapted to be adjusted axially of the tube to aV distance from the face of the anode equal to the distance between said abutting end of the casing and said window,an indexing means on the abutting end of said'casingand cooperating withV said guide means to selectively position the window of said casing in respect to the anode of said tube whereby tubesvhaving envelopes of slightly different dimensions may b interchanged within the casing.

. 18. An X-ray tube comprising a cylindrical envelope of material relatively transparent to X- light and of substantially uniform diameter and wall thickness throughout its extent, an anode having a Yportion forming a substantially point source of X-light for projection through the wallV of said envelope, a demountable casing around said envelope comprising an inner continuous sleeve of insulating material transparent to X- light, a centrally disposed housing member of X- ray absorbing material about Ythe insulating sleeve, said housing member having a Window and end housing sleeves of insulating, X-ray absorbing material secured to said housing member in position enclosing the opposed ends of theY envelope, the Wall of' said envelope having a thin spot opposite said housing member, said thin spot being formed by removing a curved portion of the cylindrical envelope from the outer surface thereof, said removed portion having a crescent-like cross sectional coniiguration in a. plane normal to the axis of the cylindrical envelope and the remaining portion of the Wall of the envelope being relatively thick in order to impede the of said envelope, a demountable casing around saidA envelope comprising anvinner continuous sleeve of insulating material transparent to X- light, a centrally disposed housing member of X- ray absorbing material about the insulating sleeve, said housing member having a window and end housing sleeves of insulating X-ray absorbing material secured to said housing memberY in position enclosing the opposed ends of the envelope, the wall of said envelope being ground to produce a thin spot opposite said housing member, the remaining portion of the wall of the envelope being relatively thick in order to impede the passage of X-light therethrough except at said thin spot at which minimum impedance to the passage of X-light is afforded, and said envelope and the casing being formed with cooperating means providing an index for .registering a thin spot of the envelope with the Window of said housing member as and when the parts are assembled.

20. An X-ray tube having a cylindrical envelope and a casing enclosing said envelope, said casing comprising laminations of electrically insulatory and non-insulatcry material, certain of said laminations of the casing being opaque to X-light and having a Window for the emission of a beam of useful X-light and another lamination being closely circumjacent said envelope and of a dielectric material transparent to X-light, said dielectric lamination having a continuous extension across the window formed in the opaque laminations through which extension the beam of useful X-light is projected.

21. X-ray apparatus comprising the combination of an X-ray tubeahaving an envelope With an anode and a cathode therein, guiding and fastening means on said anode selectively adjustable radially and longitudinally of said tube, a casing telescoping the Whole length of said tube and having parts complemental to said guiding and fastening means, said casing having a Window transparent to X-light, said guiding and fastening means and the comp-lemental parts of said casing being adapted to close one end of said tube and to be operatively connected one to the other only when said Window is proximate the X-light emitting face of said anode and is disposed radially of said envelope to pass the most intense beam of X-light projected from` said anode, and a cap member cooperating with the end of said casing opposite said guiding and fastening means to enclose the other end of said tube.

22. X-ray apparatus comprising in combination an X-ray tube having an envelope generally cylindrical in configuration With an anode and a cathode axially disposed therein, guiding and fastening means on said anode adjacent one end of said tube a predetermined distance from the focal spot of said anode and positioned in predetermined radial relationship to the emitting face of said anode, a cylindrical casing extending longitudinally of said tube, a cap cooperating with said casing to enclose the end of said tube opposite said guiding and fastening means', said casing having an X-ray transmitting Window, and means on said casing adapted to cooperate With said guiding and fastening means to enclose the first mentioned end of said tube, said last mentioned means being adapted to engage said guiding and fastening means only when said X-ray transmitting window is proximate the emitting face of said' anode and is disposed radially thereof to permit the passage of the most intense X-ray beams radiating from said anode face.

l23. A11 X-ray tube having an envelope, a casing closely circumjacent said envelope, said casing comprising laminations of insulatory, and non-insulatory material, certain of said laminations of the casing being opaque to X-light and having a Window for emission of a beam of useful X-light and another lamination being of a dielectric material transparent to X-light and through which the beam of useful X-light is projected, clamping means having a pair of split collars encircling said casing proximate said Window, means for controlling the frictional contact of said pair of split collars with said casing, and a support for said clamping means.

24. In X-ray apparatus, the combination of an Xray tube having an anode and a cathode and a glass envelope in the form of a cylinder surrounding said anode and cathode and to Which said anode and said cathode are sealed, and a casing adapted to surround said envelope, said casing comprising an insulating cylinder in close proximity to the glass envelope proximate the anode and the cathode of the tube for fortifying the dielectric strength of the envelope, a metallic sleeve surrounding a portion of the insulating cylinder for equalizing the electrostatic charges induced on the envelope by the potentials of the anode and the cathode, and a heat dissipating sleeve surrounding said metallic sleeve, said heat dissipating sleeve .and said metallic sleeve having openings therethrough for the passage of a useful beam of X-rays, and said heat dissipating sleeve being of metal and comprising outwardly projecting spaced apart fins.

HARRY F. MESICK, JR. MALVERN J. GROSS.