US1233137A - X-ray system. - Google Patents

Description

H. C. SNOOK.

X-RAY SYSTEM.

APPLICATION FILED APR. 13. 1909. RENEWED NOV. 9.191s.- l @7 Patented July 10,1917.

2 SHEETS-SHEET l- W mm 3 4" I SSHEET 2.

Patented July 10, 1917.

Mm m NQQ Q 5 W3 APPLICATION FILED APR-1'3, 1909- RENEWED NOV- 9. 1916.

mam? strength than air,

x-nnr SYSTEM.

1,233,137. Application filed April 13, 1909, Serial No. 489,551.

To all whom it may concern:

Be it known that LHoMan CLYDE SNOOK, a citizen of the United States, residing in the city of Philadelphia, county of Philadelphia, and State of Pennsylvania, have invented a certain new and useful Improvement in X-Ray Systems, of which the following is a specification.

My' invention relates to a system and apparatus for delivering high potential unidirectional current to an X-ray tube or other translating device, or to a consumption circuit.

My invention resides in a system and apparatus involving and carrying forward'the principles described and claimed in my Letters Patent of the United States No. 954,056 and N '0. 1,131,870. i

My invention resides in a system and ap paratus involving a switch for rectifying high potential alternating currents for general use, and particularly for the excitation of X-ray tubes, whereby substantially all or any desired smaller part of each half current wave in a 'single phase system or a large or other suitable fraction of each half wave in a poly'phase system is delivered to the X-ray tube or other translating device or circuit, and all of the half waves delivered in the same direction. And in my system and apparatus the high potential rectifying switch is of small dimensions considering the potentials involved and its relatively moving contacts are submerged in a. medium having far greater dielectric such as oil, a compressed air or other gas, etc. 7

My invention resides in an X-ray system in which the resistance of the X-ray tube circuit is maintained substantially constant and is devoid of resistance pulsations such as have been caused in prior systems by air gaps varying in length; and my invention resides in an X-ray system in which connection from the X-ray tube toJthe means delivering high potential impulses is through a rectifying switch and a' path of unvarying resistance, the resistance through and between the' cooperating rectifying switch con-, tacts being practically constant for all relative positions of those contacts.

My, system herein described is similar to the polyphase system described in my aforesaid Patent'No. 1,131,870, in that the high potential energy of olyphase current is transmitted as uni-directional uninterrupt- Specification of Letters Yatent.

Patented July 10, 1917. Renewed November 9, 1916. Serial No. 130,476.

ed high potential energy to the consumption or work circuit. And in my presentsystem the advantages as .to lar to those of the system of my said prior application, in that the digging or pitting of the target or anti-cathode, with a given mean energy, is reduced, fluctuation in X-ray tubes are simivacuum is also reduced-and greater uniform ity of rays procured.

In the system herein described, however, there is a further advantage, in that fluctuations in resistance in the consumption or work circuit are substantially suppressed, because in-the switching apparatus actual engagement takes place between the relatively moving contacts, air gaps being avoided, as above described.

I accordingly believe myself to be the first to deliver to a.work .or consumption circuit uni-directional high tension current, that is, current at voltages higher than five thousand or ten thousand volts upward to more than one without substantial fluctuation of resistance of the consumption circuit, particularly when the consumption circuit contains a vacuum or X-ray tube, and when, the energy delivered to the is'either single or polyphase current, and when polyphase current, causing delivery of uninterrupted uni-directional current to the consumption circuit.

My invention resides also in other fea-. tures hereinafter described and claimed.

For an illustration ofsom'e of the forms my invention may take, reference is to be had to the accompanying drawings, in which: v h Figure 1 is a diagrammatic view illustrating the apparatus and circuit arrangements of my system involving a rectifying switch such as shown in Figs.- 3 and .4. a Fig. 2 is a diagrammatic view illustrating my apparatus" and system involving a modified form of rectifying switch, such, for 6X1 Fig. 4:

alternating curis a horizontal sectional view, partly in plan,-taken on the'line 2- 2, Flg. 3, and

looking in'the' direction of the arrows.

Fig. 5 1s a fragmentary. view of a modihundred thousand volts,

switching. mechanism- 3 is a vertical elevational view, partly I high potenmember of the prollO -- adjustable resistances {1, preferably non-in- 7 ductive resistance 22.

ductive, to the pr1mariesp ,p and p of the -'threephase transformer T having the high potential secondaries 8 ,8 and 8 here shown 0 as Y connected and having their common terminal connected tolearth 6 by conductor 5. The three'transformer secondaries have their other'terminals connected through the high" frequency choke coils D with the brushes .7, 8-, and 9 which bear respectively. upon. the three slip rings 10, 11, and 12 of the high potentialrectifying switch E such as. shown in Figs, 3 and 4. The slip ring 10 connects by conductor 13 with the con-- ducting arcs 14; the slip ring 11 connects by conductor 15 with the conducting arcs 16; and'the slip ring 12 connects by conductor 17 with the conducting; arcs 18.

In .the arrangement shown, a pair of roller brushes 19, 19 is disposed substantially at right 'angles to a similar pair of brushes 20, 20*. The distance between the points of contact of the roller brushes of each pair is substantiallfequal to the width of the in: sulation 21, between neighboring conducting -segments or arcs 14', 16, 18, and should preferably be notgreaterithan the width of the; insulation 21. And it is desirable that the width of the insulation 21 between con ducting arcs or segments should not begreater than the circumferential width or angular extent of the conducting ar'cs or segments themselves. And 'theroller brushes of. each pair are not in direct electrical com- .munication'with each other. but are "conmated by a high inductive or high non-inserves to minimize current flow between the two-brushes to which it'is connected during the timethat those brushes are in contact withdifi'erent conducting arcs or segments.

And from points at substantially the middle,

of the high inductances or non-inductive resistances 22 extend the conductors 23 and 24 to the two terminals of an X-ray tube or- I other translating device" X, an ammeter'F;

"medium of slip-rings, and a .pair of col if desired, intervening in one of these conductors as 24.

In the system just described stationary windings in which polyphase E. M. FLs. are, induced or developed are connected to ro-' tating contact segments or arcs through the lectors cooperates with the contact segments I sumption circuit.

The resistance 22 or arcs to take off unidirectional current.

' Here one mechanical'cycle of the rectifying "switch E corresponds with two electrical cycles. 1

The apparatus may also be arranged with connections from the stationary windings to stationary contact arcs or segments the brushes-or collectors then becoming the rotating members.

And, if four collectors be used instead of two as shown, and three neighboring arcs connected to three slip rings, the cross con nections between the conducting arcs or segments need not be used with two electrical cycles to one mechanical cycle, opposing pairs of collectors being in 'such case connected together.

The rotating element of the rectifying switch E is driven in synchronism with'the current which it rectifies, and by preference by amechanical connection with the rotating member of the source orgenerator G which delivers the alternating current to the transformerT, which preferably has very small magnetic leakage.

The switch E rectifies-thecurrent in each of the three phases so that there are in effect overlapping half waves in the con- These overlapping half waves then cause -in the circuit of the tube X unidirectional impulses-of a frequency triple the frequency of one-half cycle supplied by the transformer T. And this triple frequency current has a potential or voltage which is higher than the voltage of any one of the secondaries 8 ,8 or s.

- While the arcs or segments 14, 16 and 18 may be less than 60 mechanical degrees or 120 electrical degrees in extent,. yet the period of contact with each are or segment, because each pair of brushes constitutes separate contacts connected through a high inductance or high resistance, is substantially equal to a time corresponding with 120 electrical degrees- In' Fig. 3 is shown the inverted rotary R or a generator G of the current delivered to the transformer T. This generator or converter is supported ,by the bracket 25 upon the plate or member 26 preferably of insulating material, which is in turn su ported on any suitable device. or member 2 Extending through a bushing 28 in the member 26 is the shaft 29 upon, which is secured the insulatingmaterial 30, such as hard rubber. Upon the member 30' are mounted the slip rings 10, 11-, and 12 which are connected by conductors 13, 15"and 17, as shown in Fig. 1, (and extending through the mass 30) with the conducting arcs or segments 14, 16 and 1'8, respectively, which, as before stated, are

separated by insulation 21,'Which may consist of blocks of mica or other suitable maments and secured in the mass 30 of insulating material. Upon the slip. rings 10, 11, and 12 bear the brushes, preferably roller brushes, 7, 8, and 9, as shown, such brushes being supported by 31 depending from the plate or member 26 and connected at their bottom. by a yoke 32 having at its center a bearing 33 for the lower end of the shaft 29. This shaft is directly coupled to the shaft 34 of the generator or converter R, an insulating coupling 35 intervening.

Adapted tocontact the conducting arcs or segments 14, 16 and 18 are the pairs of roller contacts 19, 19"and 20,20 each pair being supported upon an insulating member 36 resiliently mounted by a leaf spring 37 upon the support 38 held in position upon the vertical insulating members 31; Springs 39 press inwardly upon the members 36 to cause the roller brushes to maintain physical contact with the conducting segments or arcs 14, 16 and 18 and their intervening insulation 21, the springs 39 bearing at their outer ends agamst'the inner walls of the tank or casing 40 supported by the plate or member 36 and containing oil to a level' above all of the slip rings, conducting arcs or segments, and their cooperating brushes or collectors.

- Or the chamber formed by the tank or inclosure 40 may be air or gas tight and may contain any suitable gas or other material having a greater disruptive voltage than air, air or gas under pressure being available when suitable.

By the arrangement shown the system disclosed in Fig. 1 may be used with a high potential rectifying switch occupying'a minimum of space or volume and yet operating satisfactorily to rectify the alternating current of high potential, as, for example, from 50,000 to 150,000 volts.

In Fig. 2, the primaries of the-- transformer T and the rotary converter or gen-' erator R or-G are not shown. The secondaries s 8 and s are the same as shown in Fig. 1 and are connected through the high frequency inductances D with roller or other brushes of a rectifying switch H comprising the three disks to, tv and 0.0 of insulating material capable of withstanding the high potentials involved, there being one of these insulating disks for each phase of the transformer secondary current. The transformer in this case again is preferably of a type having very small magnetic leakage. Set into the insulating disk w is a conducting are 41 which extends entirely through the disk w and has an exposed face on each side of the disk. On one side of the disk, the front, for example, are arranged the four roller brushes or other contacting devices 42 all electrically connected together and to a terminal of the secondary .9 On the other side of the disk, the rear, for exthe insulating members I both connected to ample, are the two pairs of opposed roller brushes or similar contacting devices, one pair 43, 43 electr'icallyconnected to the conductor 23, and a similar pair 44, 44 disposed at right angles to the first pair and both electrically connected to the conductor 24, the conductors 23 and 24 being tht consumption circuit including the X-ray tube X, or other suitable translating device, an ammeter F as shown being included in such circuit. The three disks w Q0 403 are all mechanically connected to and driven by a shaft 29,

preferably mechanically connected to the converter or generator R or G such as'shown in Figs. 1 and 3. p

The second disk 'w has a conducting are 45 .set in, but this arc is in a different angular positlon with respect to the driving shaft than the are 41 "of the disk w. And with disk w are associated four roller brushes or contacting. devices 46 on the front side all connected together and to the terminal of the secondary 8 On the rear the opposing pair of similar contacting devices 47 are electrically connected to the conductor 23; while the pair 48v disposed at-right angles to the pair 47 are also electrically connected to the conductor 24. And finally, in the,case of disk 'w we have a third conducting are 49 set in and cooperating with the four roller or other contacting devices 50 on the front side, all connected to a terminal of the secondary s and the opposed pair51 on the rear side connected to the conductor 23, and the second pair 52, at right angles, the conductor 24. As here shown each of the conducting arcs 41-, 45 and 49 has an angular or circumferential I extent of substantially degrees corresponding with substantially 120 electrical degrees, and each is shifted with respect to the other substantially 60 mechanical degrees or 120 electrical degrees.

When in operation, the shaft 29, as shown in Fig. 5, is rotated by the shaft of the converter or generator R or Gthus carrying the conducting arcs 41, 45 and 49 around in synchronism and thus closing circuit between opposed contacts or rollers and bringing the consumption circuit 23 and 24 into communication with the secondaries of the transformer T in a certain order of succession and at certain relative times'so that to said consumption circuit there is delivered high potential unidirectional current.

The switch H rect'ifies the current in each of the three phases so that there are, in effect, in the consumption circuit overlap-. ping half waves. These overlapping half waves then cause in the consumption circuit half waves of the three different phases, and

unidirectional impulses ofa frequency triple the frequency of one half cycle supplied by the transformer T. And this triple frequency current has a potential or voltage which is higher than the voltage of any one of'the secondaries s 8 or 8 f -The inserted conducting arcs, as 41, 45, and 49, may be slightly less than 60 mechani cal degrees or 120 electrical degrees in extent,

but'they should be made substantially 60 mechanical degrees or 120 electrical degrees in extent for a three phase system.

As seenfrom Fig. 6-, the hereinbefore described switching mechanisms. rectify the current of each phase, so that thereare the overlapping half waves a, I), 0, a, Z), and c, of which a, b and 0 represent the positive a, b and 0' represent the turned over negative half waves. The. sw tch relations are such that each transformer secondary is in .circuit, for each half wave for a time corresponding with the length 01. There results a then in the circuit of the tube X a fluctuating current of frequency triple the frequency of a half cycle of one phase supplied by the transformer T, this triple frequency current being represented by the curve e in the upper part of Fig. 6. This curve is obtained by adding the prdinates of those parts of the curves below for-and during such'periods as theditferent phases are. ac: tivelyin circuit as controlled by the switching mechanism. 'It will be noted that the minimum potential impressed upon the' ter- -minals of tube represented by the, distance f, is greater than the potential of any I 1 one of the secondaries of the transformer T.

This curve shows that the tube X is constantly subjected to a potential whose mini mum is f which is always greater than the potential deliver-ed by any one phase of the transformer T, and thisminimum potential f is sufficient to excite the tube X.

This minimum potential f'occurs at a moment or instant when the-secondary delivering the current wave a is in series with the other-two secondaries in parallel with-each other. Accordingly, theord-inate f is equal curve 0 plus the ordinate at the intersection to the sum of the maximum ordinate of of the half waves a and 6 directly below the maximum of the curve c A maximum of understood that mysystem and rectifying apparatus are adaptable also to a single any number employ an air gap in the rectifying switch and do not employ a resistance which is synchronously varied. By my system substantially all of each half of the current waves, in a single phase system, or a large fraction in polyphase systems, ofboth signs, are impressed upon the consumption circuit, and with small magnetic leakage in the transformer and by a mechanical connection between the rotating member of the rectify-- ing switch and the rotatable member of the current producer, current in inverse direction in the consumption circuit is avoided, and in the case of an X-ray tube circuit, inverse discharge in the tube is prevented, thus resulting in the preventionof reduction of intensity of excitation of the tube and also in theprevention of shortening of life of the tube. -And from the fact that the resistance of thetube circuit, exclusive of the tube itself, is constant, a s attained by the rectifying switch described, or from the additional fact of the low magnetic leakage of the transformer cooperating with the advantages-produced by the rectifying switch, the

strength of the current through the 'X-ray I tube varies only 'with the variation of the resistance of the tube itself.

While I utilize an alternating current, I' do not utilize only small fractions or the crests of the current waves, though such may be used, but I preferably employ substantially all of each current wave, in a single phase system, and do not suppress the current waves of one sign. And with a polyphase alternating current I do not utilize a small fraction only of a current wave, though such may be used, but I employ all the waves of bothsigns, and preferably utilize that fraction of each half wave, symmetricallycn either side of thefmaXimum voltage, w ich is found by dividingtwo by the number of phases in the alternating current supply.

'Thus, in a three phase system, I use twothirds of each half wave. And, in any case, I do not employ an air gap or a varyl g resistance, but by the contacting devices shown and described, without any sparking, or variation in resistance, I bring the X-ray tubeinto perfectly definite electrical connection with the wave source at a definite time.

I do not herein specifically claim subject matter of Fig. 2, but. claim the same in my divisional application Serial Number 141,072,

'filed January 8, 1917'. \Vhat I claim is;

1. The combination with a source of high potentialalternating current, ofan X-ray tube, synchronous switching means for rectifying the current delivered to said tube and to said tube is reduced.

for connecting said tube with said source comprising'relatively movable ing successively into engagement with each other, a resistance periodically bridging neighboring contacts,

tw'een-saidtube and said source of current,

whereby fluctuation 1n the energy delivered 2 The combination with potential tube, of

a source of high alternating current, of an X-ray a synchronous rectifying switch comprising-relativelymovable brushes and contacts, a brush comprising separated contacts and a. resistance connecting said sepa' rated contacts, said separated brush con.- tacts simultaneously periodically engaging neighboring switch contacts, said resistance,

' brushes and contacts forming a continuous uninterrupted connection ,between source of current and said 'X-ray tube, whereby fluctuation in the energy delivered to said tube is reduced.

sumption circuithaving continuous uninter through said contacts, brushes and resistance. 4.--Thecomb1nation with a plurality of" tenti al rectifying switch windings as a H 3. The combmat'on with windings delivering high potential polyphase current, of

a consumption circuit, a synchronous recti- 1 fying switch intervening between said windings and said consumptionicircuit, said rectifying switch comprising relatively movable contacts and brushes coming into engagement with each other, and means for introducing resistance between successivephase terminal of said consumption circuit is transferred from one to another-of said phase windings, a terminal of said conrupted connection with said windings windings delivering high potential polyphase current, an X-ray tube, and a high poconnected to said windings and to said X-ray 'tube and delivering to' said" X-ray tube uninterruptedcurrent in one direction only, said switch having relatively movable contacts coming into engagement with each other mainta1ning continuous connection between said X- tial polyphase current, of an X-ray a high potential rectifying switch passing ray tube and said windings'through a path of unvarying resistance, whereby for a given" mean of' energy delivered to said tube the maximum thereof and resultant destructive efiect upon said tube and variations in the rays are reduced.

5. The combination with a plurality of stationary windings delivering high potentube, and

through .said X-ray tube in one direction only uninterrupted current'from all the half waves of said polyphase current, said switch having relatively movable contacts coming into engagement with each other maintaining continuous connection'between said X- contacts comwinding said resistance afiording continuous uninterrupted connection begaging sets of contacts, said .gular relations with ray tube and said windings through a path of unvarying resistance.

6. The combination with a stationary delivering high potential alternating current, of a consumption circuit, a high potential translating device in said circuit,

switching mechanism connecting said wind-- ing with said circuit, conducting arcs and brushes coming into engagement with said arcs, said brushes comprising contacts having diiferent angular relations with said arcs,-aconductor of high resistance connecting said brushcontacts, and a circuit connection to said conductor.

7. The combination with a plurality of windings delivering high potential polyphase current, of a high potential rectifying switch comprising relatively moving and enan X-ray tube traversed always in the same direction by energy delivered by said windings through said contacts, the resistance of the path through and between said sets of contacts remaining substantially constant for all relative positions of said contacts.

8. The combination with stationary windings delivering high potential polyphase current, of an X-rav tube, a high potential switch intervening between 'said windings and said tube and comprising relatively rotatable contacts and brushes'engaging each other, said brushes comprising contacts so spaced that one of said brush contacts makes connection with one of said first named contacts atfsubstantially the same instant an other-of said brush contacts makes connecti'onwith the neXt succeeding of said first 10. A high potential rectifying switch comprising conducting arcs or segments and cooperating brushes, the brushes comprising contacts engaging and having different ansaid arcs or segments,.a symmetrically acting resistance connecting said contacts together,

ances, and a source of polyphase high potential current delivering energy always in the same direction through said tube through said rectifying switch,

an X-ray tube hav- 'ing its terminals connected to said resistsaid X-ray tube con- .ti'nuously connected through said resistances, contacts and arcs or segments with said source through a path of unvarying 'resist ance. 1

11. A system of X-ray tube excitation comprising a source of high potential polyphase current, an X-ray tube, switching mechanism operating in synchronism with said'current delivering uninterrupted uni-- directional current to said tube, said switching mechanism comprising relatively movablev segments and brushes engaging each other and maintaining continuous uninterrupted connection between said X-ray tube and 'saidsour'ce of current through solid conductors, whereby resistance pulsations in the circuit of said tube external to said tube are prevented.

12. A system of X-ray tube excitation comprising a source of high potential polyphase current, an X-ray tube, synchronous switching mechanism delivering uni-directional uninterrupted current from said source to said tube, said switchin mechanism comprising relatively rotating segvment's and brushes engaging each other, said said rectifying switch comprising relatively lso movable contacts and brushes, a brush com- -'prising separated contacts and a resistance connecting said separated contacts, said separated brush contacts simultaneously peri odically engaging neighboring switch contacts, said resistance, brushes and contacts forming a continuous uninterrupted c0nnec tion between said source of current and said X-ray tube, whereby fluctuation in the energy delivered'to said tube is reduced.

14. The combination with a generator of polyphase alternating current, of means for transforming said current to high potential polyphase current, an X-ray ,tube, a high potential-polyphase rectifying switch whose rotatable member is mechanically connected with the rotating member of said generator, said rectifying switch comprising relatively movable brushes and contacts, a brush comprising separated contacts and a resistance.

connecting said separated contacts, said separated brush contacts simultaneously periodically engaging neighboring switch conwhereby fluctuation in the tacts, s'aid'resistance, brushes and contacts forming a continuous uninterrupted connection between said source of current and said X-ray tube, whereby fluctuation in the energy delivered to said tube is reduced and "short circuitinglbetween different phases is prevented.

15. The combination with a generator of alternating current, of a transformer for stepping saidcurrent up to high potential, an X-ray tube, a rectifying switch whose rotatable member is mechanically connected with the rotating element of said generator, saidgenerator producing a plurality of electrical cycles for each revolution of the rotatable member of said switch, said rectifying switch comprising relatively movable contacts and brushes, a brush comprising separated contacts and a resistance connecting said separated contacts, said separated brush contacts simultaneously periodically engaging neighboring switch contacts, said resistance, brushes and contacts forming a continuous uninterrupted connection between said source of current and said X-ray tube, energy delivered to said tube is reduced.

16. The combination with a generator of polyphase alternating current, of means for.

transforming said current to high-potential polyphase current, an X-ray tube, a high potential polyphase rectifying switch whose rotatable member is mechanically connected with the rotating member of said generator,

said generator producing a plurality of electrical cycles for each revolution of'tlie rotatable member of said switch, said rec tifying switch comprising, relatively inovable brushes and contacts, a brush comprising separated contacts and a resistance connecting said separated contacts, said separated brush contacts simultaneously periodically engaging neighboring switch contacts, said" resistance, brushes and contacts forming a continuous uninterrupted connection between said source of current and said X-ray tube, whereby fluctuation in the energy delivered to said tube is reduced and short circuiting' between different phases is prevented.

17. The combination with a source of .high potential alternating current, of an X-ray tube, of a synchronous rectifying switch comprising relatively movable brushes and contacts, a brush comprising separated contacts and a resistance connecting said separated contacts, 'said separated brush contacts simultaneously periodically engaging neighboring switch contacts, and -a medium having greater dielectric strcngth than that of air submerging said brush and switch contacts, said resistance, brushes and contacts forming a continuous uninterrupted connection be-.

tween said source of current and said X-ray tube, whereby fluctuation in the energy delivered to said tube is reduced.

18. The combination with a source of high potential fluctuating current, of an X-ray tube, means for connecting said tube with said source and for rectifying the current delivered to said tube comprising relatively movable contacts coming successively into engagement with each other, a mass of material having greater dielectric strength than air in which saidmovable contacts are inclosed, and current restraining means cocperating with said contacts affording continuous uninterrupted nection between said tube and said source of current, whereby fluctuation in the energy delivered to. said tube is reduced.

19. The combination with a source of high potential fluctuating current, of an X-ray tube,- synchronous switching means for rectifying the current delivered to said tube andfor continuously connecting said tube with said source comprising'relatively movable contacts coming successively into engagement with each other, a mass of material having air in which said contacts are submerged,

a resistance periodically bridging; neigh boring contacts, said resistance affording f continuous uninterrupted connection between said tube and said source of current, whereby fluctuation. in the energy delivered to said tube is reduced;

20. The combination with current, of a transformer netic leakage delivering current at high higher dielectric strength than a source" of having. small magpotential, an X-ray tube, means r'or connecting said X-ray tube with said, transformer and for rectifying the current delivered thereby to said tube comprising relatively movable contacts coming success'ively into engagement with each other, and current restraining means cooperating with said contacts afiording continuous uninterrupted connection between said tube and said transformenwhereby fluctuation in the energy delivered to said tube is reduced.

21. The combination with a source of current, of a transformer having small magnetic leakage delivering current at high potential, an X-ray tube, means for connecting said X-ray tube with said transformer and for rectifying the current delivered thereby to saidgtube comprising rel-- atively movable contacts coming successively into engagement with each other,and

current restraining 'meansncocperating with said contacts afi'ording continuous uninterrupted connection between said tube and said transformer, whereby fluctuation in r the energy delivered to said tube is reduced,

said contacts being in engagement witheach other during a large part of the potential wave which causes passage of current therethrough.

In testimony whereof I have hereunto .aflixed mysignature in the presence of the two subscribing witnesses.

, HOMER CLYDE SNOOK. WitnesSesz A. E, S'rrnnBocK,

E. T. MoGALL.

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