US1309494A - Edsta spat - Google Patents

Description

R. VARLEY.

X-RAY SYSTEM.

APPLICATION FILED MAR. 1a. 1915.

1 $09,494, Patented July 8, 1919.

Witnwow: W 7 Wm 71/ v W 2 UNITED STATES PATENT OFFICE.

VABLEY, OI BNGLEWOOD; NEW JERSEY.

x-mr sys'rmr,

To all whom it may concern.

Be it known that I' Rrcmno VARLEY, a citizen of the United States, residing at Englewood, in the county of Ber en and State of New J ersey have inven certain new and useful Improvements in X-Ray Systems, of which the following is a full, clear, and exact description. i

This invention relates to a system for producing currents of high frequency, density and potential suitable for X-rays and analogous purposes, the object bein the provision of apparatus by which an -ray tube ma be excited by currents of com aratively hig density, at a maximum e ciency of conversion, with apparatus of low cost caable of operation either direct from existing service circuits or from an alternator, a motor generator or other converting machine of small cost, size and output, and without the use of current rectifiers or other moving parts of a complex nature and requiring appreciable power in their operation.

The improved system comprises a transformer capable of producin in the secondary circuit, currents of hig electro-motive force coincident with comparatively high amperage, in combination with a source of alternating current and means whereby the half waves of one polarity only of the current supplied will e effective in producing current in the secondary of the transformer, to the end that only unidirectional currents will charge the tube. The invention contemplates the use of a transformer in which the magnetic flux is normally largely sup ressed in that limb of the core upon whic the secondary is located while substantially all of the flux is periodically permitted to become suddenly active in that limb, at which periods the sudden surging of the restrained flux induces an instantaneous extraordinary high electromotive force in the secondary circuit capable of jumping a wide gap between the electrodes of the tube. Due to this comparatively high electromotive force I am able to use a secondary coil of comparatively few turns and low resistance w ich affords a comparatively large number of milliamperes of current in the secondary circuit and a discharge in the tube of correspondingly greater density and power of fpenetration.

In the accompanying drawings,

Figure 1 is a diagrammatic view of en- Specification or letters Patent- Patented July 8, 1919.

Application fled larch 18, 1815. Serial No. 15,270.

:uits and apparatus embodying my invenion;

F g. 2 is a similar view of a modification .of the invention, and

of alternating current, which may be eithera motor'generator or arotary converter, in e ther case delivering current from the slip rings g, to the primary circuit 1, 2 throu a pole changing switch 3. T is a trans ormer having a core t in the form of a substantially closed magnetic circuit. On one s1de or limb of this core is a coil 4, here- 1n after called the primary coil, connected with the rimary circuit wires 1, 2, while upon anot er part or limb of the core is located a coil 5, hereinafter referred to asthe secondary coil, of a com aratively larger number of turns and of fi ner wire than is 1n the prlmary coil, and connected in circuit with the wires 6, 7 which are connected, or to be connected, with the respective and proper terminals of an X-ray tube R. Upon the'same limb of the transformer core with the secondary, is another winding 8 havin the function of a choke coil and referre tohereinafter as the choke coil. The circuit of this coil is normally closed through a spring tongue 9 resting against a contact stop 10, the ton e being mounted in a position to be struc and forced away from the contact 10 by a cam disk 11 mounted upon or to be driven by, the shaft of the supply machine G, the contact at 10 being broken once during each rotation of the cam.

Assuming that the generator G delivers a sine wave current such as plotted in Fig. 3, the primary coil- 4 will be correspondingly symmetrically energized setting up a magnetic flux in the transformer core t. Choke coil 8 being normally shortwcircuited at 10 effectually acts as a'choke upon the travel of lines of force through that part of the core under the choke coil and secondary coil windings. Rotation of the cam 11 in synchronous relationship with the generator causes the sudden opening of the circuit of coil 8 at a suitable point in the current wave. Opening of the circuit of coil 8,-as stated, causes a disruptive discharge of current of high voltage to take lace 1n the secondary coil 5 in circuit with t e tube. When the circuit of coil 8 is opened a magnetic surge of great intensity and speed occurs through the entire core of the transformat. A high voltage is immediately built up in the secondary coil 5 sufficiently to instantly bridge or break down the gap between the electrodes of the tube. However, the discharge thus formed is not merely instantaneous but continues as long as the circuit of coil 8 is open. Upon the establishment of the discharge current flows in the secondary circuit an the am ere turns of the-secondary coil take the p ace, in their effect, of the ampere turns of the coil 8. The choking effect is controlled by the are or discharge in the tube, which assumes, by reason of its establishment in the circuit of coil 5, a rheostatic function, for the voltage across the a itself is sustained by the flux change w ic in turn, is controlled by the amperage of the discharge across the gap in the tube. Therefore with a certain changing of flux in the core, pref-- d erably partial y sustained by the active source, increase of gap resistance decreases the current flow across the gap, allowing increase of flux and so reciprocal increase of gap voltage, thus tending to current maintenance and stability. The s stem therefore operates to instantaneousl reak down the resistance of the gap in t e tube with a high voltage and a current of high milliamperes, as compared with a Ruhmkorff coil of equal watt intake.

Preferably, the nerator G is one which delivers one comp ete wave consisting of a positive and a negative impulse, at each rotation and the interrupting cam is so placed upon the shaft of the generator or geared thereto, that it will 0 en the contact at 10 during only one of t e im ulses, say the positive, in each rotation an allow the contacts to remain closed during the other or negative impulse and the remainder of the rotation, as illustrated in Fig.3, where the full lines of the curve indicate approximately the periods during which contacts 10 are open and the dotted lines the eriods during which they are closed. In this manner only unidirectional currents are induced in the secondary circuit, which is necessary for the production of the x rays and the use of current rectifiers with their attendant complication and consumption of power is eliminated. And while only the current impulses of one polarity of the generator, are utilized, this is compensated for by the fact that the peculiar method of transforming affords the greater electro-motive forceand renders it possible to obtain a greater amperage with a given resistance of secondary circuit.

It is obvious that a multipolar nerator or other source at G may be used w ich will yield more than one impulse of a certain olarity at-each rotation. For instance, a

our-pole machine would give two positive and two negative impulses. In such case the cam 11 preferabl would be provided with two projections iametrically opposite each other and adapted to open contact 10 during each positive or each ne ative wave, as the case may be. The poe changing switch 3 is to be used at starting in case the discharge in the tube does not happen to be in the right direction. The cam 11 is small and light ahd entails little or no expenditure of power to operate it so that the converting machine G will not be burdened by its presence on the shaft.

Instead of the mechanical circuit opener for the choke coil circuit, I may, and in fact prefer to, use an electro-magnetic device and thereby dispense with all rotating parts and the requirement of motor power at the point where the tube is to be operated. Such a system is illustrated in Fig. 2 wherein P'inicates a polarized relay of which 12 is the vibrating armature located between poles 13, 13 on which are wound differentially the usual electro-magnetic coils. These coils have been shown as permanently connected in series with the primary circuit of the transformer, which circuit may be suplied from service mains 14, 1'5 and control ed by manual switch 16. They may, however, be connected in parallel with said circuit. The armature of the relay is given a slight bias toward a contact stop 17 by a light spring 18 assisting the normal magnetic bias. The normal polarity of the coils 13 and armature s is as indicated in Fig. 2. When there is a flow of current through the coils 13 in one direction the normal polarity remains unchanged and the armature s is drawn with a force, additional to that of the spring 18, against the contact stop 17. The opposite p ase. of the current will reverse the polarity of the coils 13, causing the armature to be moved to the left, away from the stop 17. Armature 12 and contact 17 are the terminals of the choke coil circuit so that the movements of the armature 12 due to alternations in the primary circuit serve to open and close the circuit of the choke coil and perform the same functions as the cam 11 and spring blade 9 in the system of Fig. 1. The tension of spring 18 is such as to insure the rompt closure of the choke circuit immediately before the point of zero potential in the wave is reached.

The opening of the choke circuit at 17 is delayed slightly but not materially by this spring but such delay is advantageous in a sense, making the surge of lines more pronounced when the choke circuit is opened nearer the peak of the wave. The exact points in the half wave of opening and closing the choke circuit may be adjusted in any convenient way, as by regulating the tension of the spring in the system of Fig. 2, while in Fig. 1 different lengths of cam on disk 11 can be used. When sudden and excessive wide gap, the opening may occur later or nearer the peak of the wave and when longer duration of the discharge is required the opening may occur earlier. An average serviceable location and duration for the in Fig. 3. Under some conditions of structure and operation, objectionable arcing may occur at the contacts which control the choke coil circuit, in which case it may be found desirable to connect a condenser 19 across the contacts 10 in Fig. 1 or 19 in Fig. 2'. Other plans for suppressing the arc may also be adopted, such as maintaining the relay in a sealed chamber containing air or gas under pressure, or a non-oxidizing gas which will prevent destruction of the contacts.

With the apparatus herein described X ray operations can be performed with the greatest convenience. This is especially true with the system which comprises the polarrectifiers and all rotating parts which add to the complexity and expense of other systerms. 1 it may be remarked that While the cam disk 11 is a light and simple piece of apparatus requiring almost negligible power to drive it, nevertheless it may be dispensed opening period is indicated by the full lines Y with and a polarized relay inserted in the primary circuit 1, 2 and thus relieve the mechanical generator of such slight load as the disk entails.

I claim:

1. In an electric system, the combination of a source of alternating current, a transformer supplied thereby, a choke coil associated with the core of the transformer, and an electro-magnetic device actuated by the primary current of thetransformer and controlling thecircuit of the choke coil.

In connection with the system of Fig.

'2. In an electric system, the combination of a source of alternating current, a transformer supplied thereby, a choke coil associated with the core of the transformer and a polarized relay in the primary circuit of the transformer and controlling the circuit of the choke coil.

In Witness whereof I subscribe my signa ture, in the presence of two wltnesses.

RICHARD VARLEY.

Witnesses WALDO M. CHAPIN, JosnPH A. BUoKLnY.

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