US1475583A - Variable-current generator - Google Patents

Description

Nov. 27 1923.

c. A. HOXIE VARIABLE CURRENT GENERATOR Filed May 20, 1921 L mmm Inx/ntor-Z Charies A. Hoxie, y M

, His Attorney.

I Patented Nov. V I

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Be it known that I, Cmnms A. Hoxm, a citizen of the United States, residmg at schenectaldly, in the county of Schenectady, State of ew York, have invented certam' new and useful Improvements in Variable-' Current Generators, of which the following is a specification.

Thls invention relates to a method and ap aratus for producing varying currents or vo tages and is articular ly app icable to the reduction of a ternating or pulsating currents or voltages having any desired wave form. "I 2" ,One object of my invention is to provide pe wherein. the amount of current or vo tage produced at any instant'is controlled b a screen placed of light trave ing from a v suita aphotmelectric cell. This screen is provid with specially .formed cut-way or transparent portions and is arthat thelight whichpasses through these ortions and alls upon the photo-electric ce is causedto varyin amanner corresponding to the variation to produce in the current able source to r v g 1 The referre'dform of the apparatus c0n structe in accordance with particularly adapted for the currentsor voltages which vary throu h periodic cycles and it may thus be used or the of current or voltages of ure sine waves. Means are also providedw ereby the frequenc as well as the form of such waves may be c an ed as desired.

Other objects an advantagesof my invention will appear from'the following description taken in connection with the-accompanying drawings, wherein Fig.1 is a diagrammatic view of an apparatus cons structed in accordance with my invention, and'Fig. 2 is a showing in detailof meansfor controlling the passage of light to the photo-electric cell 'so that currentsjqfsine wave form are produced. 3

Referring to Fig. 1 of thedrawing, A represents a'source of light, B a photo.- electric cell and C 'thermionic vacuum tube amplifier. Light from-the source [A passes through a lens 10, ,gpenings in'the dis 11 and screen 12 hereinafter morefully tofbe described and thence to thejcell B. i I

is cell may be conveniently made by condensation over t Iode.

be conveniently, operated at a my invention isproduc'tmn of 18 81. lerill No. 71,280. I

exhausting a tube evaporating within the same a quantity of-metallic otassium which is condensed upon the wa a suitable barrier being provided to revent its I e surface w "ch is intended to act as ,a window. 100 microns of hydrogen are then admitted to the tube and the li ht sensitive potassium tube is 'forme by connecting the tube in series with a resistance of about 10000 ohms to a 500 volt source of potential which will pass about 33 milli-amp'eres through the tube in the form of a bluish discharge. .In this 0peratlon the potassium constitutes the cathsensitiveness may be still further increased by introducing new h drogen and again submitting the tube to] ischargc. Finally the hydrogen is removed and argon gas is ad- Theiresult produced is an increase m the sensitiveness of the, tube. If desired the mitted,- the pressure ofthis varying according to working conditions from 1111010118. Lower pressures are used with higher increases in potentials to give thev tube a greater stability. "Such a tube may potential which is between 50 and 500 volts. If desired toincrease the sensitivity more argon 7 may be admitted. 7

When this cell is placed, in series with a suitable source of potential the current through the cell is dependent upon the quantity of light falling upon the cathodeorthe --area of cathode surface illuminated. While I- have shown and described one form of photo-electric cell, it is clear that other forms may be used.-- I intend that the term photo-electric cell shall apply to a device of this type which is adapted to be included in an electric circuit and has the property of changing the current passing therethrough in proportion to any change in the quantrtyof area of I illumination to which the cell 1s subjected regardless of the rapidwith which the change in illumination is it e ected. The cell-I employ should be aiso substantially free from inductance -or capacity. The screen in the form of invention shown in Fig. 2 isfprovided with-an open-'- ing 14 to ermit passage-of light into the cell B. T e shape-of this opening varies with the term of wave-it is desired to-produce' and in-the present instance is offa form to give a sine wave. The; edges of the openings are each of the form right and left.

of a sine curve. The disc 11 likewise interposed in the girth of light from the source A to the cell is mounted to rotate about anaxis 15 and is adapted to be actuated by a motor 16 which may be controlled to run at any desired speed. The disc 11 in the form shown is provided with a series of openings 17 near its outer edge which are approximately rectangular in form and are spaced apart from one another by a dlstance equal to the width of an opening.

The effect of the rotation of the disc 11 in front of the opening 14 is to cause a beam of light of the form in cross section of one of 15 the openings 17 to pass across the opening 14 at a unlforl'n rate producing a definite variation in the quantity of light entering the cell and a resulting proportional vanation in the current through the cell. In the form shown I have provided a rectangular opening in the disc 11 and a curved opcnin in the screen 12. The same results woul however, be effected by making the opening in the Screen rectangular andathe openings in the disc of the special form to give the desired wave. In connection with the form of openings in the disc and screen it'is to be noted that the desired wave form is determined merely by the quantity of light which enters the cell B from instant to instant. It will thus be seen that various forms of openings will effect this result, the sole condition being that the change in area per unit distance in the direction of motion be thesame. While I have shown the disc 11 provided with openings 17 as a means for causing the light to pass over the opening 14 it iS obvious however that other. means may be employed, such for example as a rotatlng mirror.

The circuit through the cell B includes a battery 18 and a non-inductive resistance 19, this circuit being in electrical connection with the grid 20 of the amplifier C from a point 21 intermediate the resistance 19 and anode 8. The filament 22 is connected to the opposite end of resistance 19 preferably through a few battery c ll 23 to maintain a proper difference of potential between the filament andgrid. In certain cases the potential difi'erence across the terminals of the resistance 19 will be such' as to make the use of these battery cells unnecessary. Included in the plate circuit of the amplifier is a source of current and a non-inductive resistance 24 to the ends of which are connected the terminals 25 and 26. While I have shown as an amplifier a pliotron, it is obvious that other forms of amplifiers may be used, such for example, as a dynatron. In any such case the photo-electric cell will be arranged so as to affect the control circuit of the amplifier.

, From the above it will be seen oration a pulsating voltage of that n opthe desired without appreciable inductance ma netic or electrostatic fields. fiat I A oordance with the shape of the light controllin openings is the use of a photo-electric cell which produces changes in current corresponding strictly to changes in the area illuminated and the use of electric circuits or capacity. Because of the latter feature my device may be employed without danger of interference to neighboring instruments because of stray claim as new and desire to secure by Letters Patent of the United States is:

1. The method of producing voltage or current waves of predetermined form by means of a photo-electric device having a light sensitive cathode which consists in causing the cross sectional area of a beam of light directed on said cathode to undergo variations corresponding to complete cycles of the desired voltage or current waves.

2. The method of producing voltage or current waves of predetermined form by means of a photo-electric device having a light sensitive cathode which consists in directing a beam of light upon said cathode, causing the beam to undergo cycles of variations in cross sectional area corresponding to complete cycles of the voltage or current wave desired, and amplifying said waves.

In a device for producing voltage or current waves having a predetermined definite form, the combination of a photo-electric device, means for directing a beam of light toward said device, and means comprising a pair of cooperating relatively. movable members for varying the cross-sectional area of said beam in accordance with the form of the waves to be produced.

4. In a device for producing voltage or current waves having a predetermined definite form, the combination of a photo-electric device, 'means for directing a-beam of light toward said device, and a pair of relatively movable members arranged in the path of said beam, said members having registerable openings for varying the cross sectional area of said beam in accordance with the desired form of wave to be produced. 125

, 5. A device for producing periodic voltage or current waves having a definite predetermined form comprising a photo-electric device having a light sensitive cathode,

a 'circuit including a source of energy connected to said device, asource of light, means for directing a beam of light from said source onto said cathode, a screen and a rotatable disk each arranged in the path of 5 said .beam of light, said disk having a plurality of substantially rectangular openings therein and said screen having an opening constructed to cooperate with eachgopening in'said disk to permit the passage of said beam and to vary the cross sectional 10 area thereof in proportion to the afnplitude of the instantaneous values of the voltage or current waves to be produced.

In'witnes s whereof I have hereunto set my hand this 18th da. of Max, 1921.

CHA LES HOXIE.

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