US2006563A - Discharge device - Google Patents

Description

July 2, 1935. N, H. STEWART DISCHARGE DEVICE Filed Sept. 50, 1955 INVENTOR /v. H. Tfn/AFT BY7 71 n ATTORNEY iff Patented July 2, 1935 DISCHARGE DEYICE Nelson f H. Stewart,y Verona,l `N. J., assignor to Westinghouse Lamp Company, a corporation of Pennsylvania Application September 30, 1933, Serial No. 691,575

v 1 claim. (ol. 25o- 35) :This invention relates toelectric discharge" devices and more particularly to devices of this character employed" inthe X-rayfield and commonly termed .X-'ray tubes.

l5 cific aspect the invention is directed to an improved construction in X-ray tubes of the type disclosed inthe VUnited Statespatent toNelson H. Stewart-which patent Was 'issued on August 1,1933 and bears thenumber 1,920,606. f

ing an elongated envelope having an anode, a cathode ,and an `Xray screening means Ytherein. rThescreen houses the target end of the.

anode .and lthe cathode to screen o-ut undesirable X-rays. The screen 'is composed of nickel-iron and is relatively heavy.v Because-ofthe weight of thefscreenit has'been necessary toprovide means for supporting the same within the tube. Heretofore, for this purpose, it has been pro-r posed to employ ka plurality of plates and conducting Wires. The conducting wires'A served to aid in the supporting of the screen as well as providing a conductingpath for the current to be supplied to the cathode. These wires-were sealeddirectly in said envelope, forming a glassto-metall Wireseal and vextended exteriorly and interiorlyof Asaid envelope. The interior pore tionsof said 'wires were mechanically connected to saidscreen and 'electrically connected tothe cathode.,

Was nota commercially feasible construction because the entire weight of the screen is carried by 'the seals. In normal Vtransportatio'n and when subjected rto the shocks incident to manipulation and operationthesealssometimes fractured because the glass was strained at the seals. In order to prevent said screen from striking the side wall rof the envelope there are provided a' plurality of resilient plates located betweenr the screen and envelope. So that the screen might not be totally supported bysaid seals and by the frictional engagement of said screen andenvelope with the resilient plates, at least one of the plates has an vupstanding ear with an opening therein through Which'projects a ynipple on the interiorl of said envelope. The resilient plate, Whose ear surrounds said nipple, supports said plate to maintain the screen from sliding longitudinally in said tube.

, Although' Vthe aforesaidy arrangement has served the purpose of supporting the screen, tubes of this construction have not always been satisfactory for other reasons and, in addition, manufacturing difficulties were encountered in production. q Generally, the nipple. 'is formed by merely heating the evacuated bulb, .containingy the internal parts, at afrestricted area just opposite the opening in the ear of the resilient f plate. 'In some casesjthe glass is heated too In its more spe-y Said-patentdiscloses an X-rayY tube compris-` The' screen, solely Ysupported Aby, said wires,

highly'at this area or,'fo'r some other reason,

the heated glass is drawn inandV bubblessothat.`

it is readily pierced. Even when the nipple'is properly formed, that portion of the glass which. has been heated has its internal structure" changed. As a consequence itiisv strainedfat that point*` and may crack upon cooling 'or .in u

normal manipulation, transportation or operation. Of course annealing thev glass after the nipple is formed suggests itself as a solution,"

but it is not commercially feasible becauseit is too diicult to carry out when the nipple hasta,

vacuum on one side. l

In order to eliminate these physical shortcom` ings inherent in the tubes heretofore manufac-' tured, I have developedthe following invention. Briefly stated, the invention comprises the elimination of a Wire-to-glassfseal to support the screen and also the elimination of the vitreous teat or nipple for supporting the screen. For this purpose, I employ one or more copper thimbles ring-sealed tolthe envelope and connected to said screen for supportingthefsame.

An object of my invention is to provide an electric discharge device whose heavy elements are supported by a ring seal to renderv them more rugged and so that shrinkage during manufacturing is considerably reduced. Q

Another object of my inventionv is to provide an electric discharge device containing no glass-'-v to-wire seals, but onlyring seals.

Another object of my invention is to` provide an X-ray tube that is more `rugged than those heretofore produced. Y

VA still further object of my "invention is to provide an'X-ray tube Whose Yheavy screen'issupported by a ring seal. f

These and other objects of my invention may bereadily ascertainedfrom the following speci-l iicationA and drawing wherein,

Figure `1 represents a longitudinal cross sectional view With some of the parts inl elevation having a body'portion Ilv of generally cylindricalv form with a hemispherical portion l2 atone end and a reentrant tube I 3V at its other end. vr'This ree'ntrarit tube I3 extends upwardly into'the lbody portion, and has a copper sleeve `or sup"-r` port coupling I4 Vhermeticallyv sealed thereto. An anode extension-I5 is secured toand'car?v ried by: said coupling I4. An anode I6` is locat-.V ed within -the envelope :and-is also?v carried ,by

said support coupling I4. Intermediate the lower end of the anode I6 and the coupling I4 is a thimble shield II whose lower end extends below the seal between the coupling I4 and the reentrant tube I3.

Fusedly ring-sealed to the inner wall of the envelope I0 is a vitreous tubular cylinder I8 extending upwardly in the envelope. ode I6 is surrounded by said cylinder or sleeve I8. A plurality of resilient plates I9 bear against the outer surface of the anode and the inner surface of the sleeve I8 to partially support the anode and to absorb mechanical shocks.

Disposed around and having its interior wall spaced from the free end of the anode I6 is an X-ray screen composed of nickel-iron and consisting of a cylindrical portion 20 and a top plate 22 secured to each other in any convement manner. The X-ray screen houses the free end of the anode and a cathode 23 together with its'focusing cup 24.

According to my invention I provide a novel means for supporting said screen, which means may also serve as the conductors of electricity for the cathode 23. My novel means comprises essentially the employment of a cap or thimble having its free circular edge ring-sealed by fusion to a small cylindrical section extending from the wall ofthe envelope. This type of construction permits the construction of more rugged X-ray tubes and also lowers the manufacturing costs because it reduces the percentage of tubes whose envelopes had to be discarded and the parts reassembled when the old type of support was employed.

In carrying out my invention, the upper end of the 'cylindrical portion II of the envelope has a pair of diametrically disposed short outwardly extending small cylindrical vitreous sleeves 25 and 26. United to the outer ends of said sleeves 25 and 26 by fusion are, respectively, short reentrant vitreous tubular sleeves 2'| and 28. The free ends of these sleeves 2'I Vand 28 are spaced l a slight distance from the inner walls of the sleeves 25 and 26. `A thimble or cap 29 composed of copper or the like is secured to each of said sleeves 21 and 28 and to the X-ray screen to properly support the latter.

As illustrated, the thimbles or caps 29 may be of any desired shape. The rims of the caps or thimbles 29 are tapered downwardly towards the free edges. The caps 29 are secured to the short tubular sleeves 21 and 28 by a simple fusion process so that the joint between the glass and metal shall be a hermetic and air-tight seal. Integrally united to the base of the caps 29 are conducting rods 30 and 3| which may be of the same composition as the cap per se. The rods 30 extend outwardly from said caps and the rods 3I are located within said envelope.

A cap, having rods 30 and 3 I, may be machined out of a single piece of metal. The outer or free ends of the rods 3| are threaded. Inverted J- shaped rigid supports 33 and 34 are secured onto the inner rods 3 I. 'Ihe outer portion of the elongated arms of the members 33 and 34 are also screw threaded. The screw threaded portion of the rod 34 is threadedly secured to a threaded opening 35 in the top plate of the X-ray screen member.

An opening diametrically disposed with relation-to the opening 35 has an insulating bushing 36.1ocated therein. Passing through said bushing which insulates the same from the X-ray The ani screen member is the threaded portion of the rod 33. A nut 3'I is screwed onto each of the outermost ends of the rods 33 and 34. The outer ends of the cathode 23 are secured to the outer ends of the rods 33 and 34. 'Ihus the rods 33 Vand 34 act as supports for both the screen member and the cathode.

In order that the entire weight of the X-ray screen member Yneed not be carried by the caps 29 and also in order that the tube shall be further protected from mechanical shocks, I provide a plurality of spaced resilient plates 39. These plates 39 are of the type disclosed by A. C. Blakeman in his copending application Serial No. 560,738 filed September 2, 1931 and assigned to the same assignee as the present invention. The plates 39 are spaced around the screen land bear against the outer surface of the screen'and the inner wall of the envelope.V With my construction and especially because I use the thimbles or caps 29, I need not employ a resilient plate having an upstanding ear with an opening therein tting around a vitreous nipple in the envelope. As a matter of fact with the construction shown in Figure l, it is not necessary that I employ a resilient plate having an upstanding ear.

However, it is within the purview of my invention to employ a resilient plate having an upstandjng ear. Sometimes I may desire to substitute a flexible member for the members 33 and 34. When this is a prerequisite or desirable, I employ a structurev such as shown in Figure 2. For the members 33 and 34 shown in Figure l, I may substitute flexible members such as 40, secured respectively to the rods 38 and 3| and associated with the screen in the same manner as the rods 33 and 34. One of the resilient plates 39 may have an ear 42 with its opening fitting over the rod 3| to prevent excess longitudinal displacement of said screen. If I desire, I may have an ear on each of two resilient plates, with the openings in said ears fitting respectively over the rods 30 and 3| and mounted on an insulator 43, as shown. Contact caps 44 t over the outwardly extending vitreous sleeves and are sealed with a basing cement 45 and soldered to the outwardly extending rods 30.

Although I have described my invention withI some particularity it is not to be limited to the exact construction shown and described, but only by the prior art.

What is claimed is:

An X-ray tube comprising an elongated vitreous-envelope, an anode, a cathode and an X-ray screen therein, said envelope consisting of a body portion, a reentrant tube in the lower end of said body portion, a hemispherical portion at the upper end of said body portion, a pair of diametrically opposed vitreous tubular sections integral with said body portion and extending therefrom, a short reentrant vitreous tube integral with each section, a plurality of metallic caps carried by said reentrant tubes, each of said reentrant tubes having one of said caps ring-sealed thereto, said anode electrically connected to one of said caps, a cathode electrically connected to said other caps, means connected to said screen and one of said caps for supporting said screen, and a plurality of resilient plates bearing against the outer surface of said screen and the inner surface of said envelope to also support said screen and protect the envelope from mechanical shocks.

NELSON H. STEWART. i

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