US1964454A - Electric relay - Google Patents

Description

June 26, 1934.

ELECTRIC RELAY Filed Jan. 21, 1932 W. D. COCKRELL ET AL Inventors: William D. Cockrell,

Pieter JuchCer;

Their Attorney.

Patented June 26, 1934 ELECTRIC RELAY William D. Cockrell, Schenectady, and Pieter J uohter, ScOtia,

N. Y., assignors to General Electric Company, a corporation of New York Application January 21,

1932, Serial No. 587,944

7 Claims. (01. 250-415) Our invention relates to alternating current relay apparatus including a variable rectifying resistance control element and an electron discharge amplifier and it is the object of our invention to provide an improved form of such apparatus wherein greater sensitivity is obtained. Our invention is particularly applicable to that form of such apparatus in which the control element is a'photo-electric tube, the apparatus operating in response to variations of light reaching the tube.

Our invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a circuit diagram illustrating the preferred form of our invention; and Fig. 2 is a circuit diagram showing a modification.

In the drawing, alternating current for the operation of the apparatus is shown supplied thereto, by way of example, through the transformer 1 having a primary winding 2 and a secondary comprising the three windings 4, 5, and 6. In the arrangement illustrated, winding 4 supplies the control device '7, winding 5 supplies cathode heating current for the electron discharge amplifier 8 and winding 6 supplies current to the output or load circuit of the amplifier. Control device '7 may be any suitable variable rectifying resistance device. In the form illustrated this device is represented as a photo-electric tube which through the leads 9 and 10 is connected with the secondary winding 4 to form a series circuit including the capacitor 11 whose capacitance may, by way of example, be of the order of .0002 mi. and resistor 12 whose resistance may, by way of example, be of the order or" 10 to 20 megohms. The tube '7, it will be noted, is arranged with its cathode connected with the resistor 12. The cathode 14 of the amp ifier 8 connects through the midpoint of winding 5 with the adjustable arm 15 of potentiometer 16 which bridges the winding 4 and is grounded at one end as shown. The output or load circuit of amplifier 8 includes the transformer winding 6 and the winding of the relay 20 connected together in the well known manner. The control grid 17 of amplifier 8 connects with the above-mentionedseries circuit at the point 18 which is between the resistor 12 and the control device 7. This grid connection includes the resistor 19 which, by way of example, may have a value of several megohms.

With the apparatus arranged as shown and as described above the amplifier 8 having a rectifying characteristic permits current to passv in the load circuit only during that half wave, which for convenience will be termed the positive half, which makes the anode positive with respect to the cathode. The winding 4 is wound in the same manner as winding 6 so that the polarity of its ends follows the polarity of the corresponding ends of that winding. It the resistance of the control tube '7 is infinite, that is, if no light is falling upon it, the grid 17 receives no positive charge from winding 4 during the positive half cycle and remains sufliciently negative to render the amplifier 8 inoperative to pass the necessary current to cause the operation of relay 20. When the resistance of tube 7 is lowered as when light falls upon it, the grid 17 is rendered less negative or more positive by an amount proportional to the lowered resistance of tube 7. Thus the amplifier 8 passes current in proportion to the decrease in resistance of 7 or the amount of light falling upon it. During each negative halt cycle when the polarity of winding 4 is reversed, the grid is made positive by reason of its connection through resistors 19 and. 12 and the capacitor 11 with the left hand end of winding 4 which at that time is positive. Since the grid 17 is positive with respect to the cathode 14 a grid current flows through resistors 19 and 12 during the negative half cycle charging the capacitor 11 until the grid and cathode have substantially the same potential. When at the end of this half cycle the current again reverses, the capacitor 11 first discharges through resistor 12 and tube '7, this being possible since the cathode of the tube connects with the resistor 12. Without the resistor 12 the potential of the point 18 with respect to the cathode and consequently that of grid 1'7 would follow the potential of the adjacent plate of the capacitor during the interval of discharge with the result that by the time that the grid potential became sufficiently positive to cause the amplifier to pass current necessary for the operation of relay 20 the current in the alternating current circuit would be well ad vanced in the positive half cycle. We have found that by providing the resistor 12 between capacitor 11 and the point 18 we can cause the amplifier 8 to pass the necessary current earlier in each positive half cycle. The discharge current from the capacitor 11 produces an IR drop in the resistor 12 and thus renders the point 18 and hence grid 1'7 less negative or more positive, however it may be considered, thus causing the amplifier to begin passing current necessary for the opera,-

tion of the relay earlier in each positive half cycle.

When the leads 9 and 10 to the device 7 are long so that there is a relatively large capacitance between the leads and between the cathode lead 9 and ground which capacitances are represented diagrammatically by the dotted capacitors 22 and 23 respectively, we have found it to be desirable to employ the resistor 19 in the grid connection thereby limiting the grid current which charges these leads. When the leads are short, however, the resistor 19 and the ground connection may be omitted.

In the modification illustrated by Fig. 2 the arrangement of apparatus is similar to that shown in Fig. l the principal difference being that the control device 7 is connected between the point 18 and an intermediate point in the secondary winding 6. The apparatus shown in Fig. 2 operates in a manner similar to that already described above in connection with Fig. l and hence a detailed description of this modified form is thought to be unnecessary.

We have chosen the particular embodiments described above as illustrative of our invention and it will be apparent that various other modifications may be made without departing from the spirit and scope of our invention which modifications we aim to cover by the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a source of alternating current, a variable rectifying resistor and a capacitor connected in a ser'es circuit, an electron discharge amplifier operable from said source and having a control grid connected with said series circuit and an impedance in said grid connection for limiting the fiow of grid current which charges said capacitor and the circuit connections of said resistor.

2. In combination, a source of alternating current, a photo-electric tube having capacitative leads and a capacitor connected in a series circuit, an electron discharge amplifier operable from said source and having a control grid connected with said series circuit between the capacitor and the tube and a resistor in said connection for limiting the grid current supplied to the capacitor and to said leads.

rectifying resistor and a resistor in said grid connection.

4. In combination, a transformer having a plurality of secondary windings, a capacitor, a resistor and a photoelectric tube connected in a series circuit with one of said windings, an electron discharge device having a cathode operatively connected with an intermediate point of said one winding and a control grid connected with said series circuit between the resistor and the tube, a resistor in said grid connection and a load device connected with another of said secondary windings in the output circuit of said amplifier.

5. In combination, a source of alternating current, a grid controlled electron discharge amplifier having an anode-cathode circuit connected to be supplied from said source and constructed to pass current during the positive half cycles only of the source, a variable impedance, means for supplying a positive charge to said grid from said source controlled by said impedance during the positive half cycles, means comprising a capacitor for supplying a positive charge to the grid from said source during the negative half cycles and means for producing a voltage drop between the capacitor and the grid.

6. In combination, a source of alternating current, a grid controlled electron discharge amplifier having an anode-cathode circuit connected to be supplied from said source and constructed to pass current during the positive half cycles only of the source, means for supplying a positive charge to said grid from said source during the positive half cycles, a photo-electric device arranged to control the supply of said charge, means including a capacitor for supplying a positive charge to the grid from said source during the negative half cycles and a resistor arranged to produce a voltage drop between the capacitor and the rid.

7. In combination, a transformer having a plurality of secondary windings, a grid controlled electron discharge device having an anode-cathode circuit connected with cne of said windings, a photo-electric tube and a capacitor connected in a series circuit across the other of said windings, a connection between said cathode and an intermediate point of said other winding, a con nection between the grid and said series circuit at a point thereof between the photo-electric tube the capacitor and a resistor in said series circuit between said point and the capacitor.

WILLIAM D. COCKRELL. PIETER JUCHTER.

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