US1655637A - X-ray apparatus - Google Patents

Description

JanIlO, 1928.

F. 3. SMITH X-RAY APPARATUS Filed Dec; 8, 1926 vvm I NV EN TOR A TTORNEY.

Patented Jan. 10, 1928.

UNITED STATES g 1,655,637 PATENT OFFICE.

JERANKLIN s. smrn, or BROOKLYN, new YORK, .assrenon- 'ro rnonucrs rno'rno- 'IION CORPORATION, A oonrona'rron or DELAWARE.

X-RAY APPARATUS.

Application filed December 8, 1926. Serial No. 153,283.

This invention relates to X-ray apparatus and systems and more particularly to X-ray apparatus adapted to operate at very high potentials. i

One of the objects of thisinvention is to provide an X-ray apparatus and system which will be of simple and thoroughly practical construction and arrangement and capable of highly eiiicient action when in use. Another object is to provide apparatus of the above-mentioned character in which a high voltage X-ray tube may be dependably and reliably operated while at the same time the safeguarding of auxiliary apparatus against such high voltages may be achieved in a simple and thoroughly effective manner. Another object is to provide an X-ray system and apparatus in which, while the initial source of potentialis an alternating one, the X-ray tube may be associated with a uni-directional high potential and hence associated with a uni-directional current, free from substantial variations or fluctuations and of substantial steadiness, all without endangering or over-stressing the rectifying device employed. Another object of this invention is to provide a systom of the above-mentioned character in which uni-lateral valves, such as kenotrons, may be safely employed in conjunction with a plurality of appropriate condensers for appropriately charging the latter from the alternating source of high potential, while preventing the impression upon the rectifying valve itself of either the full potential applied to the X-ray tube itself or of a potential in excess of what the rectifying valve may itself safely withstand. Another object is to provide an X-ray apparatus and system of the above-mentioned type which will be well adapted to meet the varying conditions of hard practical use. Other ob jects will be in part obvious or in part pointed out hereinafter.

i The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be here- -rafter described and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing in. which is shown one of various possible embodiments of my invention,

Figure 1 is a diagrammatic representation of the circuits and apparatus, certain mechanical features being shown in elevation;

I Figure 2 is an end view of certain of the mechanical features of the high tension switch of Figure 1, as viewed along the line 2-2 of Figure 1, and I Figure 3 is a sectional view as seen along the line 3-3 of Figure 2. I

Similar reference characters refer to similar parts throughout the several views of the drawing. a

As conducive to a clearer understanding of certain features of this invention, it may at this point he noted that in certain uses of the X-ray tube the characteristics of the latter when operated at very high potentials are desired to be made use of; while X-ray tubes can be made to operate under and withstand relatively high potentials, in order to achievein practice the advantages of such characteristics of the X-ray tube, yet the application of such relatively high potentials to the. tube gives rise to certain serious difliculties and disadvantages in the apparatus associated with the X-ray tube and by or through which it is energized at,

this high potential. Such of these advantageous characteristicsof the X-ray tube as above outlined may be conveniently made of practical use where the X-ray tube is connected so that. its immediatesource of energy comprises two condensers connected in series, one of which is charged during the half-cycle of; an appropriate high tension alternating current and the next one is charged at the succeeding half-cycle of the same high potential current. .An advantage of such an arrangement resides in the fact that the condensers thus, in series, provide an appropriate high tension for energizing the X-ray tube while, for charging the condensers, and individually, a potential substantially only half of that normally applied to the X-ray tube need be employed. Such an arrangement is usually carried out in practice by the employment of uni-directional valves, conveniently of the hot cath ode or thermionic type, for example; these valves insure the charging of the respective condensers during the appropriate half cycles of the alternating potential applied thereto and, being uni-directional, also insure against the discharge of one condenser while the other is being charged.

But such a circuit arrangement, while achieving a number of desirable advantages has the very serious disadvantage that the rectifying or uni-directional valve or valves become subjected to the full potential applied to the X-ray tube and either the potential applied to the X-ray tube must be therefore and necessarily limited to one which the rectifying valves themselves can withstand and thus the desired Cl12ILaCtQI'IS tics of the iii-ray tube become unattainable, or the rectifying valves become over-stressed, rapidly and quickly break down, and thus destroyed. A dominant aim of this invention is to provide an X-ray system and apparatus in which fullest advantage of the characteristics of a very high potential X- ray tube may be taken while at the same time eliminating in a thoroughly practical way such defects, limitations and disadvantages as have just been pointed out, and in which the Xray tube may be energized with a unidirectional potential and current of substantial steadiness and free from substantial variations, even though the initial source of energy is an alternating current source of the usual commercial character.

Referring now to the drawing and more particularly to Figure 1, there is shown at 10 an X-ray tube having a cathode 11 conveniently of the filament type and an appropriate anode 12 for coaction therewith; the cathode 11 may be supplied with heating current through any appropriate source as, for example, by means of a suitable trans former indicated generally at 13. Two suitable condensers 14: and 15 are connected in series through a conductor 16 and these condensers 1a and 15 are in turn connected by the conductors 17 and 18 to the cathode 11 and anode 12 respectively of the X-ray tube 10. If, therefore, each condenser is individually charged from an appropriate source, the potential applied to the X-ray tube 10 will be substantially the sum of the potentials across the charged condensers.

The condensers 14. and 10 are arranged to be charger simultaneously from preferably the same source of potential, and the latter takes the form of a transformer having a primary winding 19 and a secondary winding 20, the midpoint 21 of which is connected by conductor 22 to the conductor 16 which connects the condensers 14; and 15 in series; the mid-point 21 of the secondary winding 20 may be grounded as by grounding the conductor 22 at G. The transformer 19-20 has such a ratio of transformation that the potential across each ofthe halves 20 and 20" of the winding 20 is appropriate for suitably charging individually the condensers 14 and 15; the primary winding 19 may be energized from any suitable source of alternating potential.

One terminal of the secondary winding 20 is connected to the movable switch member 23 of a synchronously driven switching apparatus generally indicated at 24; this synchronously operated mechanism 24 preferably includes, in addition to the movable switch member or electrode 23 another electrode 25 similar substantially to the electrode 23. These two electrodes 23 and 25, each carrying a switch blade 23 and 25* respectively, are connected to a synchronous motor 26 through the shaft 27 and 28 re spectively, the latter being suitably insulated or preferably of an insulating material so as to isolate the synchronous motor 26 from the conductive parts of the switching mechanism 24. Moreover, the electrodes 23 and 25 are so related to each other that the switching blades 28 and 25 thereof are spaced about 180 one from the other as viewed in the plane of rotation of the blades.

Coacting with the blade member 28 are two fixed electrodes 29and 30, also spaced 180.apart in the plane of rotation of the switch blade 23 and coacting with the switch blade 25 are two fixed electrodes 31 and 32, also spaced 180 in the plane of rotation of the switch blade The fixed electrodes 29, 30, 31 and 32 are spherical and the electrodes 23 and 25, connected. to the shafts 27 and 28 respectively, are of a generally cylindrical form with curved or substantially hemi-spherical ends. The blade members 23 and 25*, which may be made integrally with their respective rotatable electrodes 23 and 25, are of a radial extent sullicient to just about clear their respective coacting fixed electrodes and are moreover given a shape substai'itially like that further illustrated in Figures 2 and 3.

From Figures 2 and 3 in which one of these switch blades.- as the blade 23, is further illustrated, it will be seen that the blade 23 is shaped to provide an arcuate end portion. 23 of an extent in the direction of the plane of rotation thereof sufficient to insure the closure of the associated high tension circuit for a sufficient length of time, and this particular shape, in coaction with the spherical or curved exposed coacting faces of the fixed electrodes. achieves the prompt commencement and subsequent prompt cessation of the arcing over the high tension current and moreover in a manner relatively noiselessly. But in order further to diminish the noise of the apparatus, the switch blades are given a shape in crosssection, as will be more clearly seen from Figure 3. which is substantially stream-line and is effective to reduce to a minimum the air disturbances due to the speed of rotation of the switch blade. and thereby brings aloput a like reduction in the resultant noise.

As above noted, one of the terminals of the secondary winding 20 is connected as by conductor 33 to the rotatable electrode lid 23 of the synchronous switching mechanism 24; assuming the parts to be momentarily in the position illustrated in the drawing, which position willbe assumed at substantially the peak of the half-cycle of potential effective in the secondary winding 20, there will. be seen to be completed a charging circuit for the condenser 14, substantially as followsz-From the mid-point 21 of the secondary winding 20 (or the righthand terminal of the left-hand half 20' of the secondary winding 20), conductor 22, conductor 16, condenser 14, cathode 34 of a kenotron 35,ianode 36 of the kenotron 35, conductor 37, fixed electrode 29, switch blade 23 and movable switch electrode 23, conductor, 33 to the left-hand terminal of the half 20" of the secondary winding 20. The electron flow of charging current through the condenser 14 will thus be seen to be in the direction in which the charging circuit has just been traced, as will be clear from the direction of the electron flow from the cathode 34 to the anode 36 of the kenotron 35; accordingly, the electron flow of charging current into the condenser 14 will be seen to be in the direction from the right to the left as the circuit of Figure 1 is viewed in the drawing. The condenser 14 will therefore be receiving a charge at the peak of the potential of one half-cycle of the energy output of the secondary of the transformer 1.9-20, and the potential ofthe condenser 14 is thus raised, on being charged, toone that is commensurate with if not entirely equal to the potential across the half 20 of the secondary winding 20. 'At the same time, however, and during substantially the peak of the same halfcycle, there hasbeen closed by theswitching apparatus 24 a charging circuit for the condenser 15, substantially as follows :,From the right-hand terminal of the right-hand half 20 of the secondary winding 20, conductor 38, movable switch electrode 25 and switch blade 25", fixed'electrode 32, conductor 39, cathode 40 of a kenotron 41, anode 42 of the kenotron 41, thence through condenser 15, conductor 16, conductor 22 to the mid-point 21 of the secondary winding 20 and thence to the left-hand terminal of the right-hand half 20 of the secondary 20. The electron flow of charging current through the condenser 15 will thus be seen to be in the direction in which the charging circuit has just been traced, as will be clear from the direction of the electron flow from the cathode 40 to the anode 42 of the keno" tron 41; accordingly the electro-nflow of charging current into the condenser 15 will be seen. to be in the direction from therighti to the left as the circuit of Figure 1 is viewed in the drawing.

Both condensers 14 and 15 thus receive a charge; and the charging current and the resultant potential across the individual condensers 14 and 15 will be in the direction in which the charging circuits have been traced hereinabove; the potential effective across the electrodes 11 and 12 of the X-ray tube 10 will therefore be seen to be the sum of the potentials across the condensers 14 and 15 and the X-ray tube will be excited at this correspondingly high potential.

Bearing in mind thatthe switch blades 23 and 25' are rotating, it will be noted that the arcuate end portion of each blade (as is clearly shown in Figure 2 at 23 with respect to the switch blade 23') permits the above-described charging circuits to remain closed for a sufficient length of time to per.- mit the condensers to receive an adequate charge, and this occurs throughout an ap propriate portion of the peak of the poten tial half-wave active in the secondary winding 20 of the transformer 19-20, active at the time.

By the time the next half-cycle occurs,

and this next half-cycle, as will be readily understood, will bring about a reversal in polarity of the transformer secondary 20, the synchronous motor 26 will have rotated the switch electrodes 23 and 25 throughout 180, the switch blades 23 and 25' being thereby removed from coacting relation with respect to the electrodes 29 and 32 and being positioned for'coaction with the electrodes 30 and 31.

In this latter position of the synchronous switching apparatus 24, two new charging circuits for the condensers 14 and 15 are completed, each through a kenotron, and each circuit completed in such a way that the condensers 14 and 15 are charged in the same direction as they were before.

More specially, the charging circuit for the condenser 14, thus completed, will be seen to be substantially as follows :-from the mid-point 21 of the secondary winding 20 (this corresponding to left-hand terminal ofthe right-hand half 20 of the secondary winding 20), conductor 22, conductor 16, condenser 14, cathode 34 of kenotron anode 36 of kenotron 35, conductor 37, conductor43, fixed electrode 31, switch blade 25*, and its associated rotatable electrode 25, conductor 38 and thence to the right-hand terminal of the half 20 of the secondary winding 20. The charging of the condenser 14 and the raising of its potential during this succeeding half cycle thusproceeds. The electron flow of charging current into the condenser 14 will thus be seen to be in the direction in which the charging circuit has just been traced, as will be clear from the direction of the electron flow fromthc cathode 34 to the anode of the henotron 35; accordingly, the electron flow of chargingcurrent into the condenser 14 will be seen to be in the direction fromthe right to the left as llll) the circuit of Figure 1 is viewed in the drawing.

And as noted above, the condenser is at the same time receiving a charge, the charging circuit therefor being substantially as follows: from the left-hand terminal of the left-hand half of the secondary windin g 20, conductor 33, rotatable electrode 23 and its associated switch, blade 23, fixed electrode 3 conductor conductor 39, cathode of henotron 41, anode 42 of kenot-ron 41, thence through the condenser 15, conductor 16, conductor 22, and thence to the mid-point 21 of secondary winding 20 (this point 21 being the right-hand terminal of the left-hand half 20 of the secondary winding 20). The electron flow of charging current through the condenser 15 will be seen to be in the direction in'which the charging circuit has just been traced, as will be clear from the direction of the electron iiow from the cathode 40 to the anode 42 of kenotron 41; accordingly, the electron flow of charging current into the condenser 15 will be seen to be in the direction from the right to the left as the circuit of Figure 1 is viewed in the drawing. Thus, it will be seen that the condensers 14 and 15, as successive half cycles and corresponding reversals in the potential effective in the secondary winding 20 occur, are charged in the same direction and thus there is made effective across the terminals of the serially connected condensers 14 and 15 potentials, additive values of which are always in the same direction and thus appropriate for exciting the X-ray tube 10.

The operations above described in connection with two successive half cycles, are of course repeated and in each instance of charge of the condensers, a rectifying valve insures the charging of each condenser in appropriate direction and moreover in such a manner as to achieve the manifold advantages of the lrenotron in substantially smoothing out and maintaining free from substantial variations the total potential across the two condensers 14 and 15 and hence the potential available for exciting the X-ray tube 10. Moreover, the two serially connected condensers will be seen to be charged simultaneously at-each half-wave of the source of alternating poten tial, thus bringing about such a rapid succession of charges to the two condensers that the potential exciting the X-ray tube 10 is further steadied and greater uniformity and smoothness thereof achieved. The X-ray tube 10 will thus be seen to be subjected to an energizing potential which is substantially constant and unidirectional, due to the ubOVQ-(lOSCllbQfl smoothing-out action of both the kenotrons and the condenser; the electron flow of current energizing the X-ray tube 10 will take place in the following Circuit and in the direction in which the circuit is traced :-Condenser 14, conductor 16, condenser 15, conductor 17, filament cathode 11 of the X-ray tube 10, anode 12, and by way of conductor 18 back to the condenser 14. l/Vhile the electron flow of charging current into or through the condensers 14 or 15 takes place, as hereinbefore described, in the direction from the right to the left as the diagram of Figure 1 is viewed in the drawing, the electron flow of discharge current out of the condensers and through the X-ray tube 10 takes place in the reverse direction and hence in the direction in which the X- ray tube energizing circuit has'justcbeen traced.

The rectifying devices 35 and 41 may take any appropriate form but, as already hereinabove indicated, a number of thoroughly practical advantages are achieved when these devices are of the kind known as keno trons; these kenotrons 35 and 41 may have their filament type of cathodes 34 and 42 respectively supplied with heating current from any suitable source, preferably the transformers 45 and 46 respectively.

As hereinbefore noted, the electrodes of the synchronous switching mechanism 24 are of predetermined shape; these electrodes are so spaced and the radii of their various curved surfaces so chosen that eachfixed electrode with its associated rotatable electrode forms a circuit-controlling device which is substantially corona-less in action and moreover, so that together they havev a capacitance, when related to each other as are the members 23 and 30, for example, of Figure 1, equivalent to or preferably less than the capacity of a henotron. This feature makes it possible to avoid such a distribution of voltage drops in any-of the circuits as will cause a voltage drop across the kenotron in the circuit greater than half the Voltage across the capacitance of the kenotron and the capacitance in series therewith of the spaced electrodes of the switching mechanism; in this manner, as will be made clearer hereinafter, the kenotron is safeguarded against overstressing and possible resultant breakage thereof.

For example, assuming the parts to be in the posit-ion shown in Figure 1, and assuming that the condensers 14 and 15 have been charged during the preceding half-cycle and are receiving a charge during the succeeding half-cycle represented by the positioning of the parts as shown in Figure 1, there will have been established a circuit in' which the potential of one of the condensers and the potential of one-half of the secondary winding (its polarity now reversed) would be additive; thus, for example, there is established a circuit.substantially as follows from the left-hand terminal of the left-hand half 20 of the secondary winding" 20, conductor 38, the capacitance between electrode 23 .andelectrode 30, conductor 44, conductor 39, cathode 40 of kenotron 41, anode 42 of kenotron 41, condenser 15, conductor 16, conductor 22 and thence to the right-hand terminal of the left-hand half 20 of the secondaryiwinding 20. In this circuit, the 'poten' tial of the half 20 of the secondary winding tron '41 could'not Withstand; it wouldtherefore become over-stressed, and destroyed. But because of the relation in value of the capacitance between the electrode 23 and electrode" with respect to the capacitance of the kenotron 41, this additive potential becomes distributed with respect to these two capacitances 'in'such a manner that a potential no greater than ha'lf of this additive potential is impressed across the kenotron 41. Such a potential, however, the kenotron 41 can safely withstand.

tential which the kenotron'41 can'withstand -By way of illustration, and as further conducive to a clearer understanding of these features of my invention, it might be assumed, for example, that the limiting po'- sa-fely'is 100 kv. Eachcondenser 14 and'1 5 may thus be charged at substantially-this potential so that the available potential for operating the X-ray tube 10 is approximately or substantially 200 Withj-these assumptions, and bearing in mind the circuit above"clescribed, the condenser 15, charged during the preceding half-cycle, is brought to apot-'enti-al in the neighborhood of 100 kv' and this potential is active in one direction;

the potential across the hair 20 of the secondary Winding 20, now reversed as to polarity, will'be in the neighborhood of l00 kv l', and with respect to the charged 'con-' denser 15, will be active in the same direction as the potential across the latter. Across the electrode 23 and the anode 42 (the latter of the kenotron 41) therefore, there will be active a potential equivalent to the sum of these two potentials, namely, 200 kv.- But this high-potential, bearingin mind that it i This capacitance, however, being proportioned as hereinbefore noted, with respect to the capacitance of the kenotron 41, prevents the inverse distribution of condenser potentials taking place in such relative proportions that the kenotron41 becomes overstressed.

It will thus be seen that the limiting voltage which the, kenotron can safely withstand need no longer limit the potentials appliedto the X-ray tube itself, and need not therefore limit the action and characteristics of the latter. Moreover, it will be seen that the many advantages of utilizing a uni lateral valve may be effectively achieved, and moreover, with apparatus not only vof effective safeguarding actionbut also capable of rugged and inexpensive construction. It will therefore be seen that there has been provided in this invention a system andflap paratus in which the several objects hereinbefore noted, as well as many thoroughly practical advantages are successfully achieved. i

As many possible embodiments may be made of the above invention, and as many changes might'be made in the embodiment above set forth, it is to be understood thatall preted asil'lustrative and not in a limiting sense.

I claim:

- 1. In apparatus of the character described,

matter hereinbefo're set forth or shown in l the accompanying drawing is to be inter in combination, an X-ray tube, two serially,

connected condensers bridged across said tube for energizingthe latter, a transformer having ahigh tension winding, the latter having its midpoint connected intermediate of'said two condensers, a rectifying valve, one for each of said condensers and through which the latter'may be charged from said high tension winding, and synchronously operativemeans for connecting one terminal of the high tension-winding to the circuit in which is included one of said valves and one of saidcondensers and for interposing a capacity reactan'ce between the. said terminal of-the high tension winding and the circuit in which the'other' valve and other condenser is included and for connecting the other termmalof the lngh tension winding'to' said last-mentioned circuit and for interposing a capacity reactance' between the first-mentioned terminal of the high tension winding and said last-mentioned circuit.

2. In apparatus of the character described, in combination, an X-ray tube, two serially connected condensers bridged across said tube for energizing the latter, a trans former'having a high tension winding, the latter having its midpoint connected intermediate of said two condensers, a rectifying valve, one for each of said condensers and through which the latter may be charged from said high tension winding, and a synchronously operative switching mechanisin, said mechanism including two insulated rotating circuit-controlling members each in connection with one terminal of said high tension winding and each coacting with a pair of fixed electrodes, one electrode of each pair being connected in the circuit in which is included one of said condensers and one oi said valves and the other electrodes of said pairs being connected to the circuit in which is included the other condenser and the other kenotron.

3. In apparatus ot the character described, in combination. an X-ray tube, two

serially connected condensers bridged across said tube for energizing the latterca transformer having a high tension winding, the latter having its midpoint connected intermediate of said two condensers,a rectifying valve, one for each of said condensers and through which the latter may be charged from said high tension winding, and a synchronously operative switching mechanism, said mechanism including two in sulated rotating circuit-controlling members each in connection with one terminal ot said high tension winding and each coacting with a pair of fixed electrodes, one electrode of each pair being connected in the circuit in which is included one of said condensers and one of said valves and the other electrodes of said pairs being connected to the circuit in which is included the other condenser and the other valve, said circuit-controlling members and their respective coacting electrodes being shaped and proportioned so that, when related to each other for circuitopening operation, they form a capacity reactance the capacity of which is equal to or less than the capacity of one of said valves. 4:. In apparatus of the character described,v

in combination, two serially connected condensers, a uni-lateral valve for each con denser and through which the latter maybe charged, a source of relatively high alternating potential for charging saidcondensers, and synchronously operative switching mechanism for reversing, during each half cycle, the connection of said source to said condensers, whereby said condensers are simultaneously charged in the same direction and through said valves during each half cycle, said switching mechanism being adapted to interpose a gap in the circuit in whichis'et fective the potential across one condenser and active in one direction and the potential of said source active in a direction to be additive thereto and in which circuit is included the valve associated with the other condenser, whereby said last-mentioned valve is safeguarded against the cumulative effect of said last-mentioned two potentials.

In apparatus of the character described, in combination, two serially connected condensers, a uni-lateral valve, for each condenser and through which the latter may be charged, a source of relatively high alternating potential for charging said condensers, and synchronously operative switching mechanism for reversing, during each half cycle, the connection of said source tosaid condensers, whereby said condensers are simul taneously charged in the same direction and through. said valves during each half cycle, and means whereby said switching mechanism interposes a capacitance in the circuit in which is effective the potential across one of said condensers in one direction and the potential of said source in a direction to be additive thereto and in which is included the valve associated with the other condenser,

from saidother condenser and connecting it to charge said first-mentioned condenser, said mechanism being adapted to interpose a gap in the circuit in which is included one of said condensers, the source of potential removed from the circuit of said last-mentioned condenser, and the valve associated with the other condenser.

In testimony whereof, I have signed my name to this specification this 4th day of December, 1926.

FRANKLIN S. SMITH.

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