US2507377A - Electron tube timing relay - Google Patents

Description

May 9, 1950 L. H. MATTHIAS 2,507,377

ELECTRON TUBE TIMING RELAY Filed Dec. 11, 1944 2 Sheets-Sheet 1 LYNN l-L MAT'TWAS ZNVEN TOR.

B wzzad A TTORNEY May 9, 1950 L. H. MATTHIAS ELECTRON TUBE TIMING RELAY 2 Sheets-Sheet 2 Filed Dec. 11, 1944 VOLTAGE BA 6WD POTENTIAL.

LYNN HJJIATTHMS INVENTOR.

ATTORNEY Patented May 9, 1950 UNITED STATES PT ENT OFFICE ELECTRON TUBE TIMING RELAY Lynn H. Matthias, Fox Point, Wis., assignor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Application December 11, 1944, Serial No. 567,721

3 Claims. 1

This invention relates to circuit systems comprising electronic devices and in particular pertains to a system employing an electronic valve to accomplish automatically a definite time cycle.

An object of my invention is an electrical circuit for timing to permit the use of component parts of dependability and which parts of themselves carry electric currents to actuate a magnetic relay without amplification.

It is a further object of my invention to provide a simple circuit arrangement of the essential elements, wherein such elements are utilized efficiently and wherein there is a minimum of power loss.

It is a further object of my invention to provide a simple adjustment to vary the time interval required.

It is a further object of my invention to utilize a capacitor as an energy storage device with an arrangement which provides for said capacitor to be charged at a high rate and to a high voltage.

It is still a further object of my invention to produce an electrical timing system wherein repetitive action is secured without any appreciable delay necessary between timing operations and to accomplish thisdesirable feature in a simplified. manner.

A need has long been felt for an electrical timing system which is of few parts of rugged construction, but which system will allow of extreme accuracy. in performance.

My invention is a fulfillment of the above objects and is illustrated in the following description, the accompanying drawings being a part thereof.

Figure l is a circuit arrangement embodying my invention and Figure 2 is a diagrammatic showing of the relation of the important voltages and currents which function in the circuit arrangement of Figure 1.

Referring to Fig. l, a vacuum tube is indicated by VT and comprises in this instance an anode P, a grid G, a filament F and a cathode K.

The timing cycle is effected by the energy stored in the local circuit comprising capacitor Cl and a resistance B3. This local circuit is connected by conductor ill to the grid G. A control relay CR, which in this-instance is equipped with normally open contacts indicated by NO and normally closed contacts indicated by NC, is operable by the current to the aforementioned anode P. A capacitor C2 is connected in parallel with the magnet coil of the control relay. The anode P is connected to the control relay and capacitor as indicated by conductor II.

A transformer T is connected to the incoming power lines as indicated by conductor LI and L2. This transformer T, which supplies power to the circuit system, is arranged with taps as indicated by C, B, A, and l and 2. Taps l and 2 are connected to corresponding taps l and 2' of the filament F of the vacuum tube. Bridged across taps C and A is a resistance composed of resistors Bi and R2 in series with control station S, and conductors l5, l6 and [4. From the storage circuit a conductor I! is connected by means of a variable tap at point D to resistor Tap B of the transformer is connected by means of conductor I3 to the cathode K.

With the circuit connected to the power supply lines at LI and L2 and with switch S open the cathode K of the vacuum tube is heated and an alternating voltage as supplied from taps B to A is applied to the anode of the tube. This voltage would normally cause the tube to conduct current during the half cycle that the anode is positive. However, the voltage-as supplied from taps B to C is 180 electrical degrees out of phase with that from taps B to A, and is applied to the grid G of the tube" through the resistor RI, and capacitor C! and resistor R3 in parallel. The half cycle during which the voltage from B to A is positive the voltage on the-control grid of the tube is negative and consequently no anode current can flow through the tube.

When the voltage from B to A becomes negative the voltage B to C is positiveand since the anode P exercises very little control on the grid, current will flow from the grid G to the cathode K, or rather electrons will flow from the cathode K to the grid G to the capacitor Cl and also through resistor R3 and resistor RI back to the transformer. Resistor R3 is of a comparatively high value and consequently most of the electrons flowing to the grid will flow into the capacitor Cl. The terminal of the capacitor C! thus acquires a negative charge. Since resistor R3 is comparatively high in value very little of'this charge is lost during thecycle'when transformer 3 tap C is negative with respect to B, and consequently the potential across capacitor CI increases during successive half cycles when transformer tap C is positive to very nearly the peak voltage of B to C. When capacitor Cl acquires this potential the current drawn through the grid on subsequent half cycles when tap C is positive is only the amount necessary to provide the charge lost from the capacitor Cl through the shunt resistor R3. Since the potential acquired by the capacitor Cl is negative the control grid voltage is more negative durin positive half cycles of BA and consequently there is even less possibility of anode current through the vacuum tube than when capacitor C! is uncharged. Ca-

pacitor Cl and resistor R3 are of course selected.

so that Cl will acquire the peak potential B to C in a very few half cycles.

Resistors R! and R2 are small in comparison to R3 and thus the voltage from B to D is practically equal to BC during the interval that current flows in the grid cathode circuit to charge Cl. However, when switch S is closed the voltage BD becomes nearly zero, i. e., D is brought to nearly the cathode potential. The grid potential is thus only the potential of the capacitor plus an amount determined by This quantity isusually zero or positive, i. e., of the same sign as BA, the value depending on the timing desired. Thus when switch S is closed the potential ofthe grid with respect to the cathode is initially negative for positive and negative half cycles of BA. The capacitor C! is thus slowly discharged from near the peak value of BC through the resistor R3. As the grid potential approaches zero, current through the anode circuit increases and finally the magnet coil will be energized sufficiently to cause operation of relay OR.

The relation 'of the important voltages and currents which function in the circuit arrangement of Fig. l are shown in Fig. 2. The timing interval is shown as only a few cycles for convenience in representation. Normally the anode current will continue to increase beyond this value to a value limited by the impedance of C2 and control relay CR, the tube characteristics and the voltage BA. The capacitor C2 is used to reduce the impedance of the relay coil. The closing of the relay operates thecontacts NO and NC and completes the timing cycle.

When S is again opened the charging cycle is again repeated and the timer is set for another timing operation which is again initiated by closing switch S.

It will be noted on reference to the description and more particularly to Fig. l the work circuit connected to the cathode K, the anode P and control relay CR is indicated by a heavy line and the work circiut does not include in series any other device such as a resistor or switch. The control circuit which includes the grid, the capacitor Cl and the resistors is in'light lines and carries comparatively small electrical currents.

My invention therefore provides an efiicient electrical system of the work circuit in combination with the pilot circuit.

In a specific application of my invention a timing range of up to thirty seconds was obtained with the values of the component parts as follows: Resistor R5 twenty-four thousand ohms, resistorR2 eighteeen thousand ohms, capacitor Cl two microfarads, resistor R3 ten megohms, capacitor C2 eight microfarads, the resistance of magnet coil of the relay CR is twenty-three hundred ohms, the vacuum tube was of the type 8C5, the potential at BA was two hundred twenty volts and the potential at BC was two hundred twenty volts.

Although the specific application has been given with the three electrode type tube, the multi-electrode type tubes may advantageously be used; gas or vapor filled tubes may also be used.

While this invention has herein been described by reference to one specific embodiment thereof, it is intended that the protection of Letters Patent to be granted hereon be not necessarily limited thereby, the intent being that the protection to be granted extend to the full limit of the inventive advance disclosed herein as defined by the claims hereto appended.

I claim as my invention:

1. An apparatus for timing comprising an electric valve having a cathode, anode and grid;

with a pilot switch in shunt circuit with both the said source of power and said transformer and of such value to reduce potential at said first capacitor terminal to a potential substantially that of said cathode.

2. An apparatus for producing a time delay comprising an electric valve having a cathode, anode and a grid; a capacitor bridged by a re sistor; one terminal of said capacitor connected to said grid; the other terminal of said capacitor connected to a potential divider; an alternating current power source; a transformer connected to said power source to provide opposite instantaneous potential to that of the power source; said potential divider connected in shunt with said transformer and having a switch in series therein; an electric current responsive device connected in series with said anode and cathode and in constant circuit with said source of power; said capacitor and its bridging resistor of appropriate value correlated with said potential divider to provide a time period after the closing of said switch before sufficient current flows through anode and cathode to operate the electric current responsive device.

3. An apparatus for producing a time delay comprising an electric valve having a cathode, anode, and gridyan alternating current power source bridged by the primary of an auto-transformer; said auto-transformer having an added secondary winding; a current responsive device in constant circuit with the anode and that terminal of the power source connected only to the primary of said auto-transformer; a shunt circuit comprising in order a resistor, a voltage dividing resistor with a variable tap, and a switch; said shunt circuit connected to the aforementioned terminal of the power source through said switch, and to the aforementioned added secondary winding through said resistor; a local circuit consisting v of a capacitor bridged by a 5 resistor, one terminal of said local circuit connected to the grid and the opposite terminal of said local circuit connected to the variable tap on said voltage dividing resistor; said cathode connected to said auto-transformer at the point common to the primary and secondary winding,

the whole arranged to energize said current re-f sponsive device a time interval after said switch is closed, said time interval predetermined by the I position of the tap on the voltage dividing resistor.

LYNN H. MATTHIAS.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Stansbury Dec. 1, 1936 Crago May 27, 1941 Schoene Aug. 5, 1941 Pritchard Aug. 11, 1942 Bivens Sept. 26-, 1944 Few Mar. 20, 1945 Few Dec. 7, 1946

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