US2029436A - X-ray system for reducing steepness of wave front - Google Patents

Description

Feb. 4, 1936.

M. MORRISON X RAY SYSTEM FOR REDUCING STEEPNESS OF WAVE FRONT Filed March 25, 1932 Source INVENTOR MV/VTFO/Vfl M0 3/5 0/ ATTORNEY Patented Feb. 4, 1936 X-RAY SYSTEM FOR REDUCING STEEP- NESS OF WAVE FRONT ration of Delaware Application March 25, 1932, Serial No. 601,071

14 Claims.

This invention relates to X-ray apparatus and particularly to an X-ray system for taking short exposure radiographic pictures.

In systems of this general type high potential heavy current electrical energy is usually employed to energize the X-ray tube for a brief period of time. The apparatus usually employed is a suitable switching means in the high tension circuit to suddenly connect the Y-ray tube to the source of electrical energy and enable the current supplied by the latter to flow between the electrodes of the X-ray tube.

Heretofore in such systems upon closure of the switching means the sudden flow or surge of the high potential heavy currents occasionally causes deleterious results to the tube. This is due primarily to the liberation of gases within the tube itself upon energization by these heavy currents resulting in puncture of the envelope and destruction of the tube. Frequently the emission of electrons from the cathode due to the surge of heavy current is so great that the cathode itself becomes disrupted.

The sudden rush of current through the X-ray tube upon closure of the switching means is initially so great that the rise of the energy from zero to maximum is so rapid as to be analogous to a portion of the wave form having a frequency of the order of millions of cycles per second.

I have found that if the steepness of this wave front, as it is commonly referred to in the art, is materially lessened for a brief period of time regardless of the minuteness thereof and the energy supplied to the tube is permitted to gradually rise the possibilities of destruction of the X-ray tube are obviated.

It is accordingly an object of my invention to provide an X-ray system in which the X-ray tube is suddenly energized by high potential heavy current energy and in which the energy supplied to the latter is permitted to gradually rise in a minute period of time.

Another object of my invention is to provide means associated with the X-ray tube adapted to reduce the steepness of the wave front of the energy supplied to the X-ray tube.

Another object of my invention is to provide an X-ray system for taking short exposure X-ray photographs in which the initial flow of the current from a suitable source is short circuited around the X-ray tube for a minute period of time.

Another object of my invention is to provide an X-ray system for taking short exposure X-ray photographs in which the initial flow of the current from a suitable source is short circuited around the X-ray tube for a minute period of time and the energy supplied to the X-ray tube is permitted to gradually rise in an equally short period of time after expiration of the period of short circuiting of the tube.

A further object of my invention is to provide an X-ray system in which a steep wave front of the energy supplied to the X-ray tube is prevented upon connection of the latter to a source of high potential heavy current energy and to shield the cathode from these heavy currents during the initial surge thereof to prevent deleterious results to the X-ray tube.

Still further objects of my invention will become apparent to those skilled in the art by reference to the accompanying drawing wherein the single figure is a diagrammatic representation of an X-ray system utilizing an embodiment of my invention.

Referring now to the drawing in detail I have shown a suitable source of electrical energy for supplying high potential heavy current electrical energy, such as a high tension transformer 5, the primary winding 6 of which is connected to a suitable source of alternating current of commercial potential by means of a pair of conductors LI and L2. The secondary winding 1 of this high tension transformer is arranged to store uni-directional energy in a pair of condensers 8 and 9 of relatively large capacity during one half wave of the alternating current cycle.

One end of the secondary winding 1 is con nected, by means of a conductor IE, to the condenser 8 through a suitable rectifying valve [2 and the opposite end of the secondary winding is similarly connected by means of a conductor l3 to the condenser 9 through a rectifying valve M. The condensers 8 and 9 are connected by means of a conductor I5 to the mid-point of the secondary winding 1. The thermionic cathodes of the respective rectifying valves l2 and I4 receive heating currents from a suitable source of low tension energy, such for example as batteries or low tension transformers IS, the primary windings of which may be connected to the source of supply LI and L2, if desired.

During alternate half waves of the alternating current cycle the secondary winding 1 will store energy in the condensers 8 and 9 respectively, as is well known in the art. Suitable switching means, such as a mechanically operated switch, shown generally at I1 is arranged to connect this source of high potential heavy current electrical energy to an X-ray tube, such as shown at l8.

Although any suitable switching means, such as a vacuum switch, may be employed with equal facility I have shown a mechanically operated switch which comp-rises a shaft E9, of suitable insulating material journalled in a pair of bearings 29, which in turn are supported by brackets 22 and the shaft is is rotatably operable by means of an insulated handle 23.

A pair of spherical contact terminals 2 and 25 are rigidly secured to the insulated shaft i9 and are rotatable therewith. These contact terminals are connected by means of conductors 23 and 2? to the source of high potential heavy current energy comprising the condensers 8 and 9 respectively. A pair of stationary spherical contact terminals 28 and 29 are positioned in such a manner as to be contacted by the terminals 24 and 25 carried by the insulated shaft l9 upon rotation of the latter.

The contact terminal 28 is connected by means of a conductor 39 to the cathode electrode of the X-ray tube It and the contact terminal 29 is connected by means of a conductor 32 to the anode electrode of the X-ray tube 58. A resistance element 33 is connected in series with the contact terminal 29 and the anode of the X-ray tube for a purpose to be hereinafter more fully set forth.

The cathode of the X-ray tube i8 is arranged to receive heating current from a suitable source,

such as a battery or'a low tension transformer 34, the primary of which may be connected to the source of supply, such as the conductors Li and L2 in the same manner as the source of cathode heating energy IB for the valve rectifiers l2 and M.

A capacitance element, such as a condenser 35, is connected between the conductors 33 and 32 and is thus in electrical shunt or parallel relation with respect to the X-ray tube i8 and the source of energy therefor. A condenser 36 of somewhat larger capacity than the condenser 35 is also connected in a shunt circuit relative to the cathode of the X-ray tube l8 and the source of heating energy therefor. The operation of the system just described for the taking of radiographic pictures is as follows:

Assuming that the switching device H is in the open position as shown in the drawing, a suitable switch, not shown, in series with the primary winding 6 of the high tension transformer 5 is first closed allowing energy to be supplied through the conductors LI and L2 to the primary winding 5. This in turn energizes the secondary winding 1 and during alternate half waves of the alternating current cycle energy will be supplied to the secondary winding through the respective rectifying valves l2 and it to the condensers 8 and 9, respectively. These condensers being of relatively large capacity of the order of a microfarad at a potential of between 75 and 160 kilovolts become completely charged with this voltage. When it is desired to energize the X-ray tube the insulated shaft i9 is rotated by means of the handle 23. This rotation establishes contact between the respective spherical contact members 24 and 28, and 25 and 29, respectively.

The high potential electrical energy stored in the condensers 8 and 9 thus suddenly discharges through the X-ray tube l8. This circuit may be traced from the condenser it through conductor ,26, contact terminals 24 and 23, and conductor 30 to the X-ray tube is, thence back to condenser 9 through conductor 32, resistance element 33, contact terminals 29 and 25, and conductor 27. This sudden surge of the high potential energy,

upon the sudden closing of the switch, would under usual conditions cause a sudden rise of the current from zero to maximum on flowing through the X-ray tube with a resulting wave front analogous to a portion of the wave form of millions of cycles per second which may disrupt the tube.

The purpose, therefore, of the condenser 35 Which is connected in a shunt circuit with the X-ray tube and the high tension source is to prevent the steepness of this wave front. As the resistance of the condenser 35 is much less than that of the X-ray tube to the initial surge of energy, the closure of the switch ll, will cause this condenser to first take a charge, and as the latter tends to reach its maximum capacity the current then flows through the X-ray tube. This condenser 35 is of such capacity that current flows through the X-ray tube before the same reaches its maximum and after the condenser becomes completely charged the entire energy is supplied to the X-ray tube. After the respective condensers 8 and 9 have completely discharged their entire energy the condenser 35 likewise discharges through the X-ray tube.

It can thus be appreciated that upon the initial surge of the energy from the condensers a and 9, upon closure of the switch, the condenser 35 acts for a minute period of time as a short circuit for the X-ray tube.

through the X-ray tube, gradually rising from zero to maximum in an equally minute period of time.

The function of the condenser 35 although operable for a very brief period of time thus reduces the steepness of the wave front of the energy supplied to the tube and the same, although in itself of brief duration, nevertheless gradually rises and obviates the possibilities of deleterious results to the X-ray tube due to the steep wave front of the initial surge.

The condenser device 36 which is connected in shunt circuit with the cathode also receives a portion of the initial energy supplied to the X-ray tube and helps to prevent high voltage from being built up across the filamentary cathode, which would otherwise occur due to the employment of the steep wave front of the energy supplied to the tube as heretofore mentioned. This, therefore, prevents the high potential discharge current, when supplied to the X-ray tube, from injuring the cathode.

The resistance element 33 functions in the high tension circuit as a means for preventing oscillations in the high tension circuit from affecting the supply of energy from the high tension source. Although this resistance element 33 prevents oscillations the primary purpose thereof is to absorb the entire voltage drop in the circuit during the minute period of time when the condenser 35 is receiving the initial surge and is functioning as a short circuit for the energy around the X-ray tube.

There is likewise an IR drop across the re- After the expiration of this period of time the current starts to flow sistance element 33 when the current is flowing through the X-ray tube, but as the current is in the order of hundreds of milliamperes at '75 to kilovolts this drop is immaterial.

It can thus be readily appreciated by those skilled in the art that I have provided an X-ray system for taking short exposure radiographs from a high potential source in which the initial surge of the current is prevented from causing deleterious results to the X-ray tube. Moreover,

the entire period of energization of the X-ray tube is extremely small, but despite the shortness of this period there is an entire absence of steepness of the wave form of the energy supplied to the tube, as the rise thereof is a gradual one from zero to maximum.

Although I have shown and described one specific embodiment of my invention I do not desire to be limited thereto as various other modifications of the same may be made Without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In an X-ray system, the combination with an X-ray tube and a source of high potential electrical energy therefor, of means for connecting said X-ray tube to said source to cause the sudden energization thereof, and means adapted to be connected in parallel with said X-ray tube and said high potential source for retarding the instantaneous supply of the entire energy from said source to said X-ray tube upon the operation of said first mentioned means.

2. In an X-ray system, the combination with an X-ray tube and a source of high potential electrical energy therefor, of means for connecting said X-ray tube to said source to cause the sudden energizatio-n thereof, and means adapted to be connected in parallel with said X-ray tube and said high potential source for retarding the supply of the entire energy of said source to said X-ray tube for a short period of time upon operation of said first mentioned means to reduce the steepness of the wave front of the energy supplied to said X-ray tube.

3. In an X-ray system, the combination with an X-ray tube and a source of high potential electrical energy therefor, of means for connecting said X-ray tube to said source to; cause the sudden energization thereof, and means associated with said X-ray tube and adapted to be connected in parallel with the latter and said source, and arranged to receive a portion of the energy thereof to prevent the entire energy of said source from being initially supplied to said X-ray tube upon the operation of said first mentioned means.

4. In an X-ray system, the combination with an X-ray tube and a source of high potential electrical energy therefor, of means for connecting said X-ray tube to said source to cause the sudden energization thereof, and means connected in parallel with said X-ray tube and the source of energy therefor and energizable with the said X-ray tube upon operation of said first mentioned means to cause said source to gradually energize X-ray tube over a minute period of time in order to reduce the steepness of the wave front of the initial supply of energy to said X-ray tube.

5. In an X-ray system, the combination with an X-ray tube and a source of high potential electrical energy therefor, of means for connecting said X-ray tube to said source to cause the sudden energization thereof, and means for preventing the immediate supply of energy from said high potential source through said X-ray tube upon the operation of said first mentioned means comprising a condenser connected in parallel with said X-ray tube and said high potential source therefor and adapted to become charged by the sudden supply of energy from said source and prohibit the supply thereof to said X-ray tube for a minute period of time to reduce the steepness of the wave front of the energy when the same is initially supplied to said X-ray tube.

6. In an X-ray system, an X-ray tube, a source of high potential electrical energy for energizing said tube, switching means operable to connect said X-ray tube to said source, and a condenser connected in parallel with said X-ray tube and said source and energizable with said tube from said source upon operation of said switching means, said condenser adapted to become charged by the initial supply of energy from said source upon operation of said switching means to cause the energy supplied to said X-ray tube to gradually rise from zero to maximum in a minute period of time.

'7. In an X-ray system, a high tension circuit including an X-ray tube and a source of high potential electrical energy, a second high tension circuit including a capacitance and said source, and switching means common to both of said circuits operable to connect said tube and said capacitance simultaneously to said source to cause said last mentioned circuit containing the capacitance to receive the initial supply of energy from said source and said first mentioned circuit containing the X-ray tube to become energized vith a gradual rise in the energy from zero to maximum in a minute period of time after energization of said second mentioned circuit.

8. In an X-ray system, the combination with an X-ray tube and a source of high potential electrical energy therefor, of means for suddenly connecting said X-ray tube to said source, and means for substantially short-circuiting the supply of energy around said X-ray tube for a period of time in the order of micro-seconds after operation of said first mentioned means, said last mentioned means adapted to become ineffective to short circuit the energy after expiration of said period of time and effective to cause the energy supplied to said X-ray tube to gradually rise from zero to maximum with an absence of a steep wave front in an equally short period of time after operation of said first mentioned means.

9. In an X-ray system, an X-ray tube provided with a cathode to be heated, a source of high potential electrical energy for energizing said tube, a source of low tension energy for supplying heating current to the cathode of said tube, means for suddenly connecting said X-ray tube to said high tension source, means for preventing the supply of the entire energy from said source to said X-ray tube for a short period of time and for causing the supply of energy thereto after the expiration of said period of time, with an absence of steepness in the wave front of the energy supplied to said X-ray tube, and means connected in parallel with the cathode of said X-ray tube and said low tension source to prevent said high tension heavy current source from deleteriously afiecting said cathode upon operation of said first mentioned means.

10. In an X-ray system, an X-ray tube provided with a cathode to be heated, a source of high potential electrical energy for energizing said tube, a source of low-tension energy for supplying heating current to the cathode of said tube, means for suddenly connecting said X-ray tube to said high tension source, means to prevent the sudden fiow of energy from deleteriously aifecting said tube upon operation of said first mentioned means, comprising means connected in parallel with the electrodes of said tube and said source of energy therefor, and adapted to receive the initial flow of energy for a minute period of time to cause the energy supplied to said X-ray tube to gradually rise in an equally short period of time and obviate possibilities of destroying said tube, and means connected in parallel with the cathode of said tube and said low tension heating source therefor, and adapted to receive a portion of the initial supply of energy supplied to said X-ray tube to prevent said high potential energy from causing destruction of said cathode.

11. In an X-ray system, an X-ray tube provided With a cathode to be heated, a source of high potential electrical energy for energizing said tube, a source of low-tension energy for supplying heating current to the cathode of said tube, means for suddenly connecting said X-ray tube to said high tension source, and means to prevent the sudden supply of energy from deleteriously affecting said tube upon operation of said, first mentioned means comprising a condenser connected in parallel with the electrodes of said tube and said high potential source and adapted to receive the initial supply of energy for a minute period of time to cause the energy supplied to said X-ray tube to gradually rise in an equally short period of time and obviate possibilities of destruction of said tube, and a condenser connected in parallel with the cathode of said X- ray tube and said low tension heating source and adapted to receive a portion of the initial supply of energy supplied to said X-ray tube by said high potential source to prevent the high potential heavy current energy from destroying said cathode.

12. In an X-ray system, an X-ray tube provided with a cathode to be heated, a source of high potential electrical energy for energizing said tube, a source of low-tension energy for supplying heating current to the cathode of said tube, means for suddenly connecting said X-ray tube to said high tension source, and means connected in parallel with said cathode and said low tension source and connected to said high tension source to prevent the sudden supply of en ergy therefrom to said X-ray tube from deleteriously affecting said cathode upon operation of said firstementioned means.

13. In an X-ray system, an X-ray tube provided with a cathode to be heated, a source of high potential electrical energy for energizing i said tube, a source of low-tension energy for supplying heating current to the cathode of said tube, means for connecting said X-ray tube to said high tension source to cause the sudden energization thereof, and means connected in parallel with said cathode and the 10W tension heating source therefor and connected to said high tension source to prevent the sudden supply of energy therefrom to said X-ray tube from deleteriously affecting said cathode upon operation of said first mentioned means.

14. In an X-ray system, an X-ray tube provided with a cathode to be heated, a source of high potential electrical energy for energizing said tube, a source of low tension energy for supplying heating current to the cathode of said tube, a switch for connecting said X-ray tube to said high tension source to cause the sudden energization thereof, and a condenser connected in parallel with said cathode and the low tension heating source therefor and connected to said high tension source to prevent the sudden supply of energy therefrom to said X-ray tube from' deleteriously affecting said cathode upon operation of said first mentioned means.

MONTFORD MORRISON,

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