US2421991A - Electric control circuits - Google Patents

Description

June 10, 1947. I c. A. CARRIERE 2,421,991

ELECTRIC CONTROL CIRCUIT Filed June 26, 1944 Inventor: Cecil A. Cavrier,

H is Attorney.

Patented June 10, 1947 ELECTRIC CONTROL CIRCUITS Cecil A. Carriere, Schenectady, N. Y.,

assignor to General Electric Company, a corporation of New York Application June 26, 1944, Serial No. 542,166 l 6 Claims.

My invention relates to electric control circuits and more particularly to improved electronic time delay circuits.

It is an object of my invention to provide a new and improved electric control circuit.

It is another object of my invention to provide a new and improved electronic time delay circuit.

It is a further object of my invention to provide a new and improved electronic time delay relay particularly adapted for controlling a load circuit having appreciable energy requirements.

In accordance with the illustrated embodiment of my invention, I have illustrated an electronic time delay relay for effecting the energization of the operating solenoid of a solenoid valve for a predetermined interval of time after closure of an initiating switch. The time interval is de-- termined by the decay of voltage across a circuit including a capacitor connected in the control member circuit of an electric valve having an anode and cathode connected in series with the solenoid and across an alternating current supply circuit. The capacitor is charged from the voltage supply through an electric valve and a resistor. The time constant of the charging circuit is small so that the capacitor charges to the voltage of the supply in a very short interval of time. The capacitor is connected in the control member circuit of the electric valve in the charging circuit so that this valve is maintained nonconducting for at least the interval of the time delay so that the initiating switch, which controls the application of voltage to the charging circuit, may be closed for any interval ranging from a momentary closure to the full duration of the timing interval without altering the duration of the timing interval or the instant at which the timing interval is initiated.

For a better understandin of my invention, reference may be had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. The single figure of the drawing diagrammatically illustrates an embodiment of my invention as applied to a system for effecting energization of a load circuit for a predetermined interval of time after the operation of an initiating switch.

Referring to the drawing, a load circuit, such asthe operating coil l of a solenoid valve 2, is connected for energization from an alternating current supply circuit 3 under the control of an electric discharge device 4. The electric discharge device may be any of the types well known in the art, and, as illustrated, comprises an anode 5, a cathode 6, and a control member or grid 1. These electrodes are mounted within an envelope containing an ionizable medium, such as a gas or a vapor. The operating coil I of the solenoid valve 2 is connected in series with the anodecathode circuit of electric valve 4, resistors 8 and 9, and across the alternating current supply line 3. The resistor 8 is short circuited by a normally closed contact l0 controlled by the solenoid I and is inserted in circuit with the coil l, upon energization thereof, to decrease the energiZing current. An electric valve H, preferably also of the gas filled type, is connected across the terminals of the operating coil of the solenoid l and is poled oppositely with respect to the electric valve 4 to provide a path for current flow upon reversal of voltage across the terminals of the operating coil. This provides for smoother flow of energizing current through the coil 1 from the alternating current source. The electric valve ll operates as a diode with the control member thereof connected with the anode through a resistor l2.

The energization of the control member I of electric valve 4 is accomplished by a control circuit including an electric valve I3, a capacitor l4 and a supply of alternating current voltage including a transformer l5. The transformer I5 is provided with a primary winding l6 connected for energization from the alternating current supply lines 3, and with a pair of secondary windings l1 and i8. Voltage dividing resistors l9 and 20 are connected in series with a normally open initiating switch 2| and across winding H to provide a supply of alternating voltage for the anode-cathode circuit of electric valve l3. The capacitor M with a series current limiting resistor 22 is connected in series with the anodecathode circuit of electric valve [3 and across resistor l9 and an adjustable portion of resistor 20 to provide a charging circuit for capacitor l4 controlled by the conduction of valve l3 in response to closure of the operating switch 2|. An adjustable resistor 23 connected in parallel with the capacitor l4 and series resistor 22 establishes a discharge circuit for the timing capacitor M. The resistor 23 is of large magnitude compared with resistor 22 so that capacitor l4 may be charged in a very small interval of time compared with the timing interval as determined by the discharge of capacitor l4 through resistors 22 and 23. A dephased component of alternating voltage for energizing the control member of valve I3 is provided by a series connected resistor 24 and capacitor 25 energized from the transformer secondary winding i8. The control member of the valve 23 is connected with the cathode thereof through a circuit including a current limiting resistor 25, the capacitor 25 and the resistor 23. As a result of this connection there is supplied to the control member of valve 3 the component of alternating voltage appearing across capacitor 25 and the voltage across resistor 23 in the discharge circuit of capacitor it. As will be described later, the voltage across capacitor 25 lags the voltage of the anode of valve 3 to render the valve conducting at an early point in the positive anode voltage following closure of initiatin switch 2!. Capacitor It immediately charges to the full voltage of the charging circuit and maintains electric valve 13 non-conducting for succeeding half cycles of the supply circuit independently of the operating position of the initiating switch 2!.

The voltage of the control member or grid '5 of electric valve 3' is energized by the resultant of three voltages including a negative component of voltage provided by the self-biasing component including a parallel resistor 2'! and capacitor 28, the voltage of resistor 23 as determined by the voltage of capacitor #4 and an alternating current hold-oi? voltage provided by the portion of the winding 5'! below the intermediate terminal 29 which is connected with the cathode of the electric valve through conductor 39. A single-pole, double-throw switch 35 is connected in the circuit of the control member between the self-biasing circuit and resistor which mat be employed to connect the control member of valve l to the cathode thereof th ough a conductor 32 to energize the solenoid i continuously from the alternating current source 3 inde centiently of the control circuit including electric valve l A brief consideration of the operation of the illustrated embodiment of my invention will pr vide a better understanding of the features and advantages characterizing my invention. When it is desired to effect energization of the solenoid 5 for a predetermined interval of time, the initiatswitch 2! is closed. Immediately upon closure of the switch, the alternating voltage appearing across the lower portion of the voltage dividing resistor 28 and resistor 53 is impressed on the anode-cathode circuit of electric valve 13. The electric valve 53 is rendered conductive in the early portion of the first positive half wave of anode voltage because of the lagging component of alternating voltage impressed on the control member by capacitor 25. Since the resister 22 is small and the time constant of the charging circuit of capacitor It is short, the capacitor 54 reaches the full peak value of volt age impressed on the anode-cathode circuit of the electric valve in a small portion of a half cycle. As soon as the capacitor M becomes charged, it impresses a positive voltage component on control member l of electric valve sufficient to overcome the voltage components impressed on this control member by the selfbiasing circuit and the lower portion of winding l? to render valve 3 conducting and initiate a period of energization of solenoid l. Following each half cycle of conduction by electric valve 5, the voltage across the terminals of the winding of the solenoid reverses and energizing current continues to flow through the shunt path established by electric valve ii. The duration of the energization of solenoid l is determined by the interval required for capacitor M to discharge through resistor 23 sufiiciently to render the voltage of control member 1 less positive than the critical voltage. The duration of the interval may be adjusted by adjusting the position of the movable contact of voltage dividing resistor 20 or adjusting the effective magnitude of resistor 23. As previously mentioned, the voltage of resistor 23 also appears in the circuit of the control member of electric valve 13 as a negative voltage to maintain this valve nonconducting fter the first half cycle of conduction for a period at least as great as the timin interval, so that the moment of initiation and the duration of the timing interval are independent of the length of time that the initiating switch is closed. This double function of the capacitor I4 in controlling both the electric valves 4 and [3 contributes to the simplicity and eifectiveness of the illustrated embodiment of my invention.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

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

1. An alternating current supply circuit, an electric valve having an anode, a cathode and a control member, a load circuit, means connecting said load circuit in series with the anode-cathode circuit of said electric valve and for energization from said supply circuit, an excitation circuit for controlling the energization of said control member includin means for impressing a voltage on said control member tending to maintain said valve nonconducting, means for impressing a transient voltage on said control member to render said valve conducting for a predetermined interval and including a capacitor and a resistor connected in parallel therewith for establishing a discharge circuit for said capacitor, means for charging said capacitor including a second electric valve having a control member, and means for connecting said capacitor in the cathode-tocontrol member circuit of said second electric valve to prevent conduction by said second electric valve during the timin interval and after initial charge of said capacitor.

2. A. supply circuit, an electric valve having an anode, a cathode and a control member, a load circuit, means connecting said load circuit in series with the anode-cathode circuit of said electric valve and for energizaticn from said supply circuit, means for energizing said control member to efiect conduction of current from said supply circuit by said electric valve for a predetermined interval including means for impressa voltage on said control member tending to maintain said valve non-conducting, means for impressing a transient voltage on said control member for overcoming the effect of said first mentions voltage for a predetermined interval including a capacitor having charging and dischargin circuits, said discharging circuit includ- Eng a re lstor connected in circuit with said control member, said che g circuit including a supply of alternating current voltage and a second electric valve of the gas-filled type having a control member, means for impressing a voltage component on the controi member of said second electric valve to render said valve conducting,

means connecting said capacitance in the control member circuit of said second electric valve to prevent conduction of said second electric valve after the initial hall cycle of conduction during which said capacitor is charged, and initiating means for initiating an interval of energization of said load circuit including a switch for controlling the application of alternating current to the anode-cathode circuit of said second electric valve.

3. In combination, a capacitor, a supply of alternating current voltage, an electric valve including an anode, a cathode and a control me ber, meal s for connecting said capacitor in c cult with said supply of alternating current voltage and the anode-cathode circuit oi said electric valve to establish a charging circuit for said capacitor, a discharge circuit for capacitor including a resistance element connected in par allel with said capacitor, a second electric valve including a control ineinioer, means for impressing a voltage on said control member tending to maintain said sec d electric valve nonconductive, for irnnressing a voltage on the con-- trol member of said second electric valve dependent upon the charge on said capacitor and having a polarity tending to render said second electric valve conductive, and means connecting said capacitor in circuit with the control member of said first electric valve to maintain said first electric valve nonconduct 'ng for at least the interval of conduction of said second electric valve, the time constant of char. rig circuit being suiliciently short to permit full. charging of said capacitor durin v a portion of a half cycle of voltage or" current supply.

l. A sunply circuit, an electric valve having an anode, a cathode and a control member, means for energizing control member to eiiect con. duction of current from supply circuit by the anodevcathode circuit of said electric valve for a predetermined interval including means for impressing a voltage on control member te to maintain said valve nonconducting, means for impressing a transient voltage on said control member for overcoming the efiect of said first mentioned voltage for a predetermined interval including a capacitor having charging and discharging circuits, said discharging circuit including resistor connected in circuit with said control member, said charging circuit including a supply of alternating current voltage and a second electric valve of the gas-filled type hav a control member, means for impressing a voltage component on the control member of said second electric valve to render said valve conductive, and means connecting said capacitance in the control member circuit of said second electric valve to prevent conduction of said second electric valve for a predetermined interval after charging of said capacitor.

d tion, a capacitor, a supply of :it voltage, an electric valve inac, a cathode and a control meroior connecting said capacitor in cirh supply of alternating current voltand the anode-cathode circuit of said elecging circuit for said capacitor, a discharge circi t for said capacitor inclrdin a resistance element connected in parlel v th s capaci or, a second electric valve a control member, means for impressd control member tending to d electric valve nonconducesring a voltage on the corn second electric valve dependson the charge of canacitor and having arity tens to render second electric valve con "llCtiVQ, and connecting said capa itor in circuit with the control member of electric valve to maintain said first valve nonconducting for at least the inf conducti n of said second electric valve.

o. ialternating current circuit, a first electric v e having an anode, a cathode and a control member, means connecting the anodeca cde circuit or" said first electric valve for enc atioi from supply circuit, an excitation circuit for controlling the energization of said control member including means for impressing a voltage on control member tending to lid first valve nonconducting, means a transient voltage on said cor1- pacitor iscnarge circuit therefor, means for charging capacitor including a second electric valve having a control member, and means for cc. necting said capacitor in the cathode cwontrol member circuit oi said second 40 lectric valve to prevent conduction by sec- CECIL A. CARRIERE.

USS Ql'ifllli r The following references are record the 00 file 0-: this patent:

UNITED STATES PATENTS Number Name Date 2,280,944 Hall Apr. 23, 19 12 2,132,264 King Oct. 4, 1938 2,397,629 Clark Jan. 5, 1943 2,616,147 LaPierre et al Oct. 1, 1935 2,0902% Noble Aug. 17, 1937 1,946,615 Demarest Feb. 13, 1934

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