US1997676A - X-ray tube - Google Patents

Description

April 3 K. G. CATLIN 1,997,676

X-RAY TUBE Filed Feb. 11, 1935 5 Sheets-Sheet 1 INVENTOR TORNE April 16, 1935. K. G. CATI .IN 1,997,676

. X-RAY TUBE Filed Feb. 11, 1933 5 Sheets-Sheet 5 -mnym INVENTOR Patented Apr. 16, 1935 UNITED STATES PATENT OFFICE 18 Claims.

This invention relates to the class of devices known as X-ray tubes.

The objects of the invention are to enable the use of heavy current, without overheating of the focal spot, to maintain a desired sharp focus and to attain these and other advantages with a relatively simple, inexpensive and practical construction.

In previous endeavors, it has been proposed to make the anticathode as a movable electrode, so as to vary the surface subjected to bombardment of the cathode rays. Possibly, the best example is that form in which the anticathode element is in fact the rotor of an induction motor cooperatively disposed to an electromagnetic stator on the outside of the tube. Such constructions however, necessarily are expensive, have a limited useful life and must be handled and used with care.

The present invention is distinguished in particular from this most successful of the known movable target tubes by being of much simpler and more rugged design and consisting of fewer parts much less likely to get out of order.

The novel features of construction distinguishing the invention from the last-considered and other known prior art, as well as the various new combinations and relations of parts will appear as the specification proceeds.

The drawings accompanying and forming part of the specification illustrate a number of different possible embodiments of the invention, but it will be understood that the structure may be further modified and changed all within the true spirit and broad scope of the invention as expressed in the claims.

Fig. 1 is a broken sectional and partly diagrammatic illustration of a form of the invention in which the anticathode is constructed and mounted for movement after the manner of a pendulum.

Fig.2 is a. vertical sectional view of this form of-tube.

Fig. 3 is a partly broken view illustrating a modification of the pendulum construction.

Figs. 4 and 5 are fragmentary and somewhat diagrammatic front and side illustrations of a modification on the general lines of that first shown.

Fig. 6 is a diagrammatic illustration of a reciprocating electrode form of tube.

.Fig. '7 is a broken diagrammatic illustration of an arcuate pendulum type of the tube.

Figs. 8, 9, 10 are diagrammatic illustrations of an oscillating and two torsional type of pendulum electrode tubes.

Fig. 11 is a diagrammatic representation of a pendulum type of tube with movement to the target indicated as communicated by a magnetic induction system.

Fig. 12 is an enlarged cross-sectional detail of the target as on line l2--l2 of Fig. 11.

Figs. 13 and 14 are views similar to Figs. 11 and 12 illustrative of another form of magneto induction operation.

Fig. 15 is a diagrammatic side representation of a form in which the target is suspended resiliently for the desired movement.

In the several views, the anticathode or target electrode is designated 20, and it is supported in each instance, so that it may have a limited swinging, oscillating or reciprocating movement with respect to the filament or cathode. element 2|.

In Figs. 1, 2 and 3, the target element is an elongated arcuate member suspended by a flexible resilient strip 22, of steel, copper, or the like, secured to a suitable terminal block 23, sealed in the head of the tube structure 24. The tube or envelope is shown in the form of a flattened flasklike structure extended inthe direction of the swinging movement of the pendulum and having a flat supporting base .25, enabling it to be solidly held as by suitable base clamps, such as indicated at 26. 1

The face of the target may be a sheet or layer of tungsten as indicated at 21, and thismay be backed up by a layer 28, of copper or, in. certain cases, by a layer of magnetic material such as iron.

In the first form of the invention, the backing layer is preferably a grade of magnetic iron and in this case, the pendulum movement is initiated by an electromagnet 29, suitably supported on the outside of the tube in the line of movement of the target. To hold the target to swinging movement in a single plane equidistant at all times from the filament, the suspending element 22, may be a ribbon of substantial width,-such as indicated, having a desired degree of transverse stability.

One method of using the first form of tube is to draw the pendulum .up to one side by magnetic attraction and then, after releasing the target to make the exposure through a suitable timer. 7

In Fig. 1, connections for this purpose are illustrated diagrammatically, no attempt being made to show details of the timer and other circuit devices customarily employed in X-ray work.

The connections shown in Fig. l which may be considered primarily illustrative in character involve first a suitable supply for the filament or cathode element, the same being shown as including a variable transformer at 30, which may be connected in a convenient service circuit, such as an ordinary lighting circuit.

The magnet for lifting the pendulum target is supplied with energy from a suitable source indicated at 3i, and the circuit for this magnet is shown as controlled by a hand switch 32, consisting of switch lever 32, which when engaged with its cooperating contact 33, is automatically held in the switch closed relation by a holding magnet 34, in series in the circuit. Part of the magnet circuit is made by switch contacts 35, 36, the latter carried by a spring lever 31, which is equipped with a push button 33. The fixed end of this switch lever is connected in the magnet circuit at 39, and this same end of the switch lever is connected at 40, with the timer 4|. The other side of this timer is connected at 42, 43, with contact 44, positioned for engagement by contact 45, on the other side of the push button lever.

The timer is shown connected through a suitable circuit breaker 46, into the 220 volt circuit 41, working through a variable auto transformer 48, high tension transformer and usually a rectifier 49, into the high tension side of the tube.

The operation will be understood from, the above. Upon closing the magnet circuit at 32, the magnet will draw the target to the side of the tube and hold it there until ready for the exposure. The exposure is controlled by simply operating the push button 38, which acts first to interrupt the circuit through the holding magnet, thus releasing the target and then to close the circuit at 45, 44, through the timer, which thereupon takes control and effects discharge at and for the time for which it has been set, from the filament to the then moving target.

For long exposures, the target may be kept continuously in movement, so as to thereby continuously present successive new focal spots. For the ordinary, shorter exposures, only one swin or a portion of a single swing of the target is sufficient.

The operation of the push button by interrupting the magnet circuit at 35, 36, de-energizes the circuit holdingmagnet 34, thus automatically cutting the target holding magnet out of action, until the magnet circuit has again been purposely restored at the manual switch 32. This prevents magnet 23 from again coming into action upon releasing push button 33, after making the exposure and the timer is usually so constructed as to interrupt its own circuit after the exposure is made. Hence, any subsequent accidental or unintentional operation of the push button will have no effect on the target. Relay 34 also may be used, if desired, to interrupt the timer circuit so that only one exposure can be made for each closing of the hand switch 32.

The pendulum starting magnet may be set in the side of the tube and for instance, be made as a solenoid coil mounted in a re-entrant portion of the tube, into which the target may swing and if continuous motion of the target is desired, automatic contact mechanism may be provided for energizing the magnet coil in synchronism with swinging movements of the pendulum.

Mechanical as well as electrical means may be provided for initiating or maintaining swinging movements of the pendulum. Thus, in the construction illustrated in Fig. 3, a secondary pendulum on the outside of the tube is used to set up the movements of the target pendulum within the tube. This outside pendulum is shown as consisting simply of a pendulum weight 30, properly proportioned to the pendulum within the tube and fixed on the upper end of the pendulum strip 22 which in this case is an upward extension of the internal spring pendulum strip 22.

When the external pendulum 50 is vibrated by hand or by electrical or mechanical means, the target pendulum within the tube will start to oscillate proportionately and, with the target in motion, the exposure circuit may be closed as by means such as shown in Fig. 1.

The form of the invention illustrated in Figs. 4 and 5, is generally similar to that first illustrated. The target however is of circular form and the oscillation may be initiated in this smaller type by simply rocking the tube and then holding it rigid while the exposure is made and the pendulum is in motion. For such purpose, the tube may be mounted for swinging movement in a support, provision being made for stopping and then rigidly holding the tube, such structure involving for example, the pivotal mounting of the tube on the swinging axis of the pendulum and a bell crank or the like for rocking and then securing the tube.

In Fig. 6, the movable target is a reciprocating element in the nature of a rod 5|, carried by a solenoid core 52, operating in coil 53, this target rod being angularly related to the cathode element 2i. Suitable circuit arrangements such as above described, may be used for setting the target into movement and effecting the desired timed exposure while the target is in movement.

The construction shown in Fig. 7, involves a modification of the pendulum type of target first disclosed, in that the cathode rays are reflected from the arcuate end surface 54, instead of from the flat side face of the target, and in that the tube is double-ended and horizontal more like conventional types.

Fig. 8 illustrates a smaller form of tube, such as shown in Fig. 7, with a circular filament type cathode instead of spiral type, focused on the arcuate end face of the target.

Figs. 9 and 10 illustrate torsion type target pendulums involving fiat disc targets 3|, either directly suspended from the torsion pendulum rod 56, as in Fig. 9, or suspended therefrom through the medium of a spiral spring 51, for increasing the amplitude of movement. In these constructions, the target movement may be initiated and/ or maintained by rotating the tube on its axis by mechanical or other means, first in one direction and then in the opposite to store up and release torsional forces in the pendulum.

Figs. 11 to 14 illustrate forms of the invention similar to the first, in which the pendulum action is started by magnetic induction. In Figs. 11 and 12, a coil 53 is located outside the tube in position to induce currents in the body of the target serving by the repulsive action thus set up to swing the target and hence generate the movement desired in the making of the exposures. Fig. 11 also illustrates how the suspension may include a free swinging link at 53, to enable the pendulum to oscillate more easily.

In Fig. 13, a reversed condition is illustrated, the actuating coil being mounted on the pendulum and co-acting with a fixed metallic body 60, outside the tube and which latter, if desired, may have a suitable opposing winding 6|, associated therewith. Flexible leads are indicated as 62, for the coil connections within the tube, thesame being'locat'ed adjacent the swinging axis, of the pendulum strip.

Fig. illustrates a further modification in which the target movement ismade possible by suspending the target element on an extensible and contractible spring 63. In this case, the desired movement may be initiated and/or maintained by reciprocating the tube, by hand or otherwise, and then holding it rigidly, with the pendulum in vertical movement 'while the exposure is being made.

The .vibration or swinging of the target, whether. the motion be oscillatory as in the case of the swinging pendulum construction, or reciprocatory, as in the plunger or spring suspended forms, or rotary as in the case of the torsion pendulum forms, provides a changing surface for the focal spot, enabling heavy current to be employed without burning in the anticathode surface and this is all accomplished in a relatively simple, inexpensive and rugged construction adapted with reasonable use to last indefinitely. The gravity swing or travel of the target gives a desired constancy or regularity of movement and the timer can be controlled to cut in the exposure in the desired period of travel, in the intermediate portions of the swing. The timer thus may continue in control during a plurality of swings, effecting the desired exposure or exposures and in the desired portions of each swing. Various other means may be employed for initiating or maintaining the swinging movement. As one example, the electromagnet may be bipolar and supported directly beneath the arcuate target and shiftable from this position up to one side, so that. when energized, it may be used to magnetically drag the pendulum from the bottom position any desired extent up to one side and then released from such selected position. As another modification, the pendulum may be caught and held by a small latch of magnetic properties, which can be tripped when desired by an electromagnet on the outside of the tube. Also, the. so-called sympathetic vibration effects may be utilized to start the pendulum inside the tube swinging from a like pendulum located outside the tube, alongside the one inside.

What is claimed is:

1. An X-ray device, comprising in combination, an envelope, cathode and anticathode elements. therein and mounted one to swing as a free pendulum with respect to the other and with the anticathode surface constantly in the same relation in respect to the cathode element and means for selectively timing the discharge between the elements to different periods in the swinging of the free pendulum element.

2. An X-ray device, comprising in combination, an envelope, cathode and anticathode elements therein, said anticathode consisting of a suspended freely swinging pendulum having a target surface disposed in the same constant relation to the cathode element in all positions of its pendulum swinging movement.

3. An X-ray device, comprising in combination an envelope, cathode and anticathode elements therein, said anticathode consisting of a suspended freely swinging pendulum having a target surface disposed in the same constant relation to the cathode element in all positions of its movement, means for effecting swinging movements of the pendulum and means for selectively timing the discharge in the course of said swinging movements.

4. An X-ray device, comprising in combina- 5 tion, an envelope, cathode and anticathode elementstherein, said anticathode consisting of a swinging pendulum having a target surface disposed in the same constant relation to the cathode element in all positions of its movement and 10 an electric coil outside the envelope and within the range of influence on the pendulum anticathode inside the envelope.

5. An X-ray tube, comprising an envelope having a neck and a widened base, a pendulum anti- )5 cathode suspended from the neck of the envelope and adapted to swing in the widened base portion of the envelope and a cathode element mounted in the widened base portion of the envelope in cooperative relation to the face of 20 the pendulum anticathode.

6. An X-ray tube, comprising an envelope having a neck and a widened base, a pendulum anticathode suspended from the neck of the envelope and adapted to swing in the widened base portion of the envelope, a cathode element mounted in the widened base portion of the envelope in cooperative relation to the face of the pendulum anticathode and electrical means on the outside of the envelope and cooperating with the anticathode therein to swing the same to one side of the envelope.

7. An X-ray tube, comprising an envelope having a neck and a widened base, a pendulum anticathode suspended from the neck of the envelope and adapted to swing in the widened base portion of the envelope, a cathode element mounted in the widened base portion of the envelope in cooperative relation to the face of the pendulum anticathode, electrical means on the outside of the envelope and cooperating with the anticathode therein to swing the same to one side of the envelope and means for then releasing the pendulum anticathode and for automatically initiating discharge of the tube with the pendulum anticathode in movement.

8. In X-ray apparatus, a target comprising a target element and a spring support strip rigidly secured to said target at one end and rigidly supported at the opposite end, said strip being of substantial width and possessed of sufiicient transverse stability to maintain the target element swinging in a definite fixed path, a cathode focused on said target element and positioned at a continuous fixed distance from said path of movement and an envelope for said target and cathode.

9. In X-ray apparatus, a target comprising a target element and a spring support strip rigidly secured to said target at one end and rigidly sup- 0 ported at the opposite end, said strip being of substantial width and possessed of sufficient transverse stability to maintain the target element swinging in a definite fixed path, a cathode focused on said target element and positioned at a. continuous fixed distance from said path of movement, said target element being elongated in said path of movement to thereby provide a continuous target surface throughout the range of travel afforded by the spring supporting strip and an envelope for said target and cathode.

10. In X-ray apparatus, a target comprising a target element and a spring support strip rigidly secured to said target at one end and rigidly supported at the opposite end, said strip being of submovement and an enclosing tube having a re-' stricted neck supporting the rigidly held end of the spring supporting strip and a widened portion about the path of movement of the target.

11. An X-ray device, comprising a target element having a fiat face and an arcuate face, means supporting said target to swing with said fiat face in a fixed plane and said arcuate face following a definite arc of movement, a cathode focused on said fiat face of the targetand an envelope for said target and cathode.

12. An X-ray device comprising a target element having a fiat face and an arcuate face, means supporting said target to swing with said fiat face in a fixed plane and said arcuate face following a definite arc of movement, a cathode focused on said arcuate face of the target and an envelope for said target and cathode.

13. An X-ray device, comprising a target element having a fiat face and an arcuate face, means supporting said target to swing with said flat face in a fixed plane and said arcuate face following a definite arc of movement, a cathode focused on one of said faces of the target, means for initiating free swinging movement of said target and an envelope for said target and cathode.

14. An X-ray device-comprising an envelope, cathode and anti-cathode elements therein, one mounted to swing as a pendulum with respect to the other and a pendulum outside the envelope constructed and arranged to effect swinging movements of the pendulum element within the envelope.

15. An x-ray device comprising an envelope, cathode and anti-cathode elements therein, a flex-- ible pendulum strip supporting one of said elements to swing as a pendulum within the envelope, an extension to such pendulum strip outside the envelope and a pendulum weight on said outside extension for enabling pendulum movements of said extension to impart swinging movements to the pendulum element within the envelope.

16. An X-ray device comprising an envelope, cathode and anti-cathode elements therein, one mountedto swing as a pendulum with respect to the other, a timer connected to control discharge across said elements in the swing of the pendulum element and means for initiating swinging movement of the pendulum element and substantially simultaneously cutting said timer into control of the discharge of the tube.

17. An X-ray device comprising an envelope, cathode and anti-cathode elements therein, one mounted to swing as a pendulum with respect to the other, a timer connected to control discharge across said elements in the swing of the pendulum element, means for initiating swinging movement of the pendulum element and substantially simultaneously cutting said timer into control of the discharge of the tube, said means including an automatic circuit breaker requiring restoration before again initiating the pendulum movement and timer control.

18. An X-ray device, comprising a vibrating target mounted for free arcuate swinging movement in a definite fixed path, a cathode focused on said target, said target having an arcuate target surface elongated in said path of target movement and an envelope for said swinging target and cathode.

KENNETH G. CA'I'LIN.

Images