US1626687A - X-ray-tube radiator - Google Patents

Description

May 3, 1927-. 1,626,687

M. MORRISON X-RAY TUBE RADIATOR Filed March 4 1922 15' 4 INVENTOR; 1 MONTF'ORD MORRISON ATTORNEY Patented May 3, 1927.

UNITED STATES I ;oFF1cE.

PATEN MONTFORD MORRISON, OF NEW YORK, N. Y.

x-mv-runn RADIATOR.

Application filed March 4,

. ploying particles moving at a high velocity,

impinging thereon.

the electrode with which such'pa'rticles collide becomes heated abovea red heat, owing to the energy imparted to it by the particles,

This phenomenon is especially true of X-ray devices wherein electrons strike an electrode at a velocity of the order of miles per second. Witha continuous stream of high-velocity particles .bombarding an electrode, it is apparent that the'temperature of the latter will progressively increase unless special means are provided to conduct heat from the bombarded electrode at a rate faster than that at which it is receiving energy in the form of heat.

In the operation of tubes which function by bombardment of an electrode and in which the latter is thereby heated to a high temperature, the heating of such electrode is frequently the limiting feature as to the duration of time which the device may be operated, continuouslly. As the electrode is progressively heate and approaches its melting point, it is sometimes necessary to discontinue the operation of the device to allow the temperature of the electrode to fall practically to room temperature. However such devices are frequently operated too long, with the result that the electrode melts, the usefulness of the device being thus terminated.

It will, therefore, be appreciated that in such devices coolin means are very desirable in order to exten the time during which uch devices may be continuously operated. In an X-ray tube, the over-heating of the target or anode not only jeopardizes the integrity of the latter but gives rise to the generation of X-rays in parts of the tube not designed for that purpose; this is due to the fact that at least part of the anode may become heated to 'an electron-emitting temperature whereby electrons are withdrawn therefrom and impinge on other parts of the tube such as the normal cathode from which undesirable X-rays thereon emanate.

Considering that alternatingcurrent is applied to self-rectifying tubes and that an X- ray tube utilizes only one-half of every cycle, it will be appreciated that the emission of tron emitting temperature.

. Cooling means such as 1922. Serial No. misc.

electrons from the excessively heated-anode not onl means the loss of approximately one-hal the energy required to operate the tube but isalso very objectionable in that it gives rise to X-rays that are uncontrolled and are therefore potentiall injurious or detrimental. the anode or target to an electron emitting temperature destroys the rectifying property of a tube designed to be self-rectifying.

For self-rectifying tubes, therefore, it is necessary to keep the target below an elec- To accomplish this, an efficient cooling device or radiator is required.

radiators and circulating liquids have in the past been used to counteract the tem erature normall result ing in electrodes su ject to bnmbard ment by high velocity particles. Such means how ever, have not proven entirely satisfactory either because they have been cumbersome or too complicated or have not been uniformly efiicient in all positions.

. The necessity for uniform efficiency of the radiator specially when applied to X-ray tubes used by dentists physicians will be appreciated when it is considered that the In other wor s, heating of tube must be adjusted for use in various positions. One type of radiator heretofore commonl used has been of such construction that a fairly, satisfactory efliciency is secured A special object of the invention is the provision of a radiator for an X-ray tube which shall have substantially the same efficiency in all positions in which it is desired to use it.

Other objects may be inferred from a reading of the following specification.

My invention will be explained in connection with one embodiment thereof and as applied to the cooling of an X-ray tube.

' radiator to the anode of an X-ray tube.

Y of the bulb.

radiator consists and the size, area, andv backed by In Fig. 1 is shown the usual form of X- ray tube 2 comprising a glass bulb 3 having oppositely extending arms 4 and 5 into which are sealed respectively a cathode 7 adapted to be heated to incandescence and an anode or target 8 from which -rays emanate. The anode 8 is given a comparatively lar e mass and may consist of a face plate 9 of refractory metal such as tungsten a metal 10 of good heat conductivity such as copper, the latter having comparatively large cross section and extending through the end of the neck 5 to the outside It is obvious that a portion of the anode 8 is constructed of a metal of good heat conductivity and given a large cross section for the purpose of dissipating the heat as rapidly as practicable. These factors alone, however, are not sutficient to keep the target below an electron-emitting temperature if the tube is run for more than a rather short time.

To efiect a more rapid dissipation of heat than is afforded by the construction of the anode itself, a radiator 11 is attached to the outer end 12 of the anode 8. This radiator preferably consists of metal of good heat conductivity such as copper and may consist of one or more plates or fins 14 of area sufiicient to effect the desired result.

The nature of the material ofwhich the number of its plates are not the only factors which demand consideration when the nullator is to be. employed on an X-ray tube.

It is found that the position of the fins or plates relative to the position of the tube and to each other are important considerations in the construction of efficient radiators and these factors constitute features of this invention.

It has been found that when the radiator is constructed and properly positioned with respect to the X-ray tube according to this invention a more rapid dissipation of the heat from the anode may be effected than with previous types of radiators. To accomplish this the radiator should be so constructed as to secure the best possible circulation. of air through and around it to efiect the dissipation of heat by convection.

Fig. 1 is an ele- This may be accomplished by so disposipig the plates or fins 14 with res ect to the ray tube and to each other t at there may always be afforded a vertical passage by which the air may pass through the radiator. It will'be appreciated that such a construction allows the best natural draft to pass through the radiator. To this end the plates 14 are so disposed with respect to the tube that their planes are parallel or substantially parallel to the axis of the tube, so that they may be vertical for any position in which the tube is to be used. They are therefore parallel with respect to each other as shown in Fig. 2, from which it will be seen from Fig. 2 that a vertical passage for the air currents is afforded when the tube is in a horizontal position.

,Referring now to Fig. 3, the radiator 11 is shown in the position taken when the longitudinal axis of the tube is in a vertical position. It will be seen from this view that the open spacing of the discs or plates at the end to which they are attached to the X-raytube provides in this position also a Vertical passage for the air currents which are to cool the radiator. From the parallel disposition of the plates and the open vertical passages existing for all positions of the radiator when the plates are vertical, it will be appreciated that an et'ficient circulation of the air will take place when the X- ray tube is in any position in a given plane.

The plates of the radiator may be attached to the outer end of the anode 8 in any practical manner such, for instance, as by in-- sertion into slots provided in the outer fanshaped end 12 of the anode 8, as shown in Fig. 4.

Referring to Fig. 5, the plates of the radiator may also be secured to a stem 15 provided at its outer end with a tapered aperture or recess 16. In this construction the exposed end 12 of the anode may be tapered so that the stem 15 of the radiator may be frictionally secured to the electrode by the disposition of the shank 17 of the stem 15 over the tapered end of the anode. The advantage of employing this construction lies in the fact that when the position of the tube is changed from one plane to another the radiator maybe adjusted so that the plates thereof are maintained in a vertical plane.

While I have herein'described one embodiment of my invention in X-ray tube lurality of plates spaced apart, said ing a plates ing disposed in planes substantially conductivity and arranged substantlally,

parallel to the axis of the tube, and to one another, whereby they may be disposed in substantially vertical planes when the tube is used in various ositions.

3. An X-ray tu e comprising an evacuated vessel, a cathode and an anode therein, a radiator thermally connected with the anode and comprising a plurality of metal plates or fins extending therefrom, spaced apart and substantially parallel to the axis of the tube.

4. An X-ray tube comprising an evacuated envelope, a plurahty o electrodes therein, a radiator in thermal relation with one of said electrodes and comprising a plurality of metallic plates extending away from the tube, space apart and arranged substantially parallel with the axis of the tube and with each other, whereby the tube may be used in various positions with the plates arranged in substantially vertical planes, for the eflicient dissipation of heat therefrom. v

5. A radiator for an X-ray tube compris ing a stem and a plurality of vanes projecting therefrom, said vanes being disposed in parallelism to each other and to the axis of said stem and having their exterior surfaces unobstructed, whereby air currents may freely circulate thereover.

6. A radiator for an X-ray tube comprising a stem and at least one plate projectin therefrom and parallel to the axis of sai stem, said plate having its surfaces unobstructed and extending on-each side of the axis of said stem, whereby air currents may freely circulate thereover. g

7 A radiator for X-ray tubes comprising a stem, a plurality of vanes projecting therefrom and arranged in parallelism to each other and to the axis of said stem, said plates having their surfaces unobstructed, whereby air currents may freely circulate thereover and means for securing said radiator to an ob'ect.

n testimony whereof, I have hereunto subscribed my name this 27th day of February, 1922.

MONTFORD MORRISON.

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