US2650301A - Electric timing device - Google Patents

Description

Aug. 25, 1953 E. B. FARMER 2,650,301

ELECTRIC TIMING DEVICE Filed March 5, 1951 5 1. $0,? 6 f6 LOAD Z AU fizz/em) 'Edward ,5. firmer a W1; imzwwy Patented Aug. 25, 1953 Application March 3, 1951, Serial No. 213,705

8 Claims.

1 This invention deals with electric timing devices of the type wherein the time constant of a reactive network determines the time interval between the closing of a starting switch and the change of conductivity of a vacuum tube Whose control electrode is connected to-th-e timing network.

Previously proposed devices of this type have various defects such as sensitivity to polarity in case of sometimes unavoidableleakage through a starting switch, impossibility of connecting a 'load to a starting terminal, unpredictable firing of the control tube immediatelyupon-operation of the starting component; and a tendency-of tubes of some types to-niisfire in spite of grounding of the negative supply terminal, due to a residual charge on the timing capacitor.

Objects of the present invention are to provide a timing device which avoids the above indicated defects, which does not require standby current for its control tube, which does not require recharging time of the timing capacitor be tween consecutive cycles of operation, which is especially suited for comparatively short adjustable=timing intervals oftheapproxima'te order of between 0.03 to 12 seconds, which isparticularly suitable for operation with energy saving cold-cathode gas tubes, and which is simple-small and inexpensive and yet very accurate, rugged and particularly also versatile as to adaptability to a largevariety of uses including operation-"of spot welders, sequence control, processing-monitoring of machine output and-short"interval-timing applications generally.

In one of its aspects, the timing device according to the invention comprises direct current supply terminals, a normally open starting switch such as the normally open contacts of a starting relay, a vacuum tube ior example of the cold cathode type with anode, cathode and control electrode, a resistor of comparatively high resistance permanently connected between the anode and the cathode of'the'tube, connections for inserting the starting switch in series between the cathode and one of the supply 'terminals, a control relay'which has contacts actuated by a coil, a control capacitor connected between the control electrode and the cathode of the tube, and provisions for charging the con trol capacitor from the supply terminals.

Other features which-can beincorporated according to the invention are a normally closed starting relay contact connected across'the control capacitor; connection of the power relayco'il between a terminal and the-anode of the tube;

incorporation of a rectifying-network for alternating current operation, in a manner particularly suited for the relay circuit; anda safety resistor connecting the normally closed relay contacts across the control capacitor.

Other objects, aspects and features will appear, in additionto those contained in the above statement of the nature and substance including some of the objects of the invention, from the following description of 'a typical practical embodiment illustrating its novel characteristics. This description refers to a drawing in which Fig. 1 is the circuit diagram of an embodiment of the invention; and

Figs. 2, 3 and 4 are simplifieddiagrams illustrating various possibilities of using the timer according to the invention.

In Fig. 1, alternating current supplyterminals are indicated at ta and to. The supply-line is connected to a rectifying networkN with input terminals til, tz'Z, output terminals tel, 7502, rectifier U, protective resistor RI and filter capacitor C'l Connected between the supply terminals is the coil LI of a starting relaySl withnormally open starting contacts s2 and normally-closed safety contacts sl. Contacts 81,32 are-prefererably of themake-be'fore-break type. In series with relay coil L is a starting contactor ss, for example a push button switch. Terminal 't is between starter relay coil-and starter switch.

The anode a of a cold cathode tubeGis connected to terminal tol, through the coil L2 of a powerrelay'S-Z withnormally closed contacts 33 and normally 'open'contacts s4. The cathode 'k is connected to terminal 2 through normally open contacts s2. Between anode a and cathode kare connected-an adjustable potentiometer R2 and the control capacitor Co. This capacitor'is normally-short circuitedthrough contacts-s! and discharge resistor R3. The control electrode e isconnected-to point n between resistor R2 and capacitor C0, through a'limiting resistor'R4. A tube shuntingresistor R5 of comparativelyhigh value is connected across anode a and cathode-k.

The power relay'S2, representing a load impedance, may have any desirable number and type of contacts; a normally closed contact '83 and a normally-open contact 34 are shown by Way of example. A load Z, controlled by "the power relay-or-other tube controlled impedance ableto develop a suitable potential is indicated as connected to the supply terminals through contacts s4.

In .an embodiment :for average purposes, the ratings of theprincipalzelements are as follows:

Resistors:

RI, R3, 50 ohm R2, 10,000 .ohm fixed and .10 .megohm -.po-

tentiometer R4,'R5,56,'000 ohm Capacitors "Cl, 40 mfd. electrolytic Co, .25 mfd.-2.0-mfd. Tube: Cold cathode, type 5823 gas "tube The above described device operates as follows:

When starting switch Ss is closed, coil Ll is energized which in turn closes contacts s2 and applies the direct potential between terminals tol, toZ to anode and cathode of the tube G.

Electrode e is at that time at cathode potential,

having been connected to the cathode through contacts sl. With contacts sl opened and s2 closed by coil LI, the control capacitor Cc begins to charge at a rate determined by potentiometer R2. When the voltage at n reaches the firing potential of tube G, the circuit containing coil L2 of power relay S2 is closed and contacts s3, s4 transferred, completing the timing interval. It is assumed that starting switch Ss is retained closed during the timing cycle, or that an appropriate holding device is provided. It will be understood that electrode .9 loses control of tube G after it has fired, and that the tube and relay S2 are deenergized after S s is opened, so that the circuit is then reset and ready for the next cycle.

The normally closed contact 5! of starting relay SI holds the starting electrode e essentially at cathode potentional during all standby time. This also prevents the control or timing capacitor Cc from picking up charge due to leakage. When starting relay SI is energized by starter switch S8, the short circuit across timing capacitor C is removed and the timing network is instantly connected to line. Since SI operates in about one half cycle and its speed of operation can be made quite constant, it introduces very little error into the timing cycle.

During the standby period, the timing network is isolated from terminal to by normally open contact 82, so that any load connected to to will not affect the timing. The presence of a load on to after closure of 52 does not have any effect.

Aresistor R large enough to prevent power relay $2 from operating when in series therewith was found to eliminate all tendency of tube G to misfire with either line polarity; this feature constitutes an important improvement with regard to certainty of operation.

The discharge resistor R3 goes into effect upon closing of contact s2.

While not absolutely necessary for good opera tion, the use of make-before-break contacts on relay SI prevents a small charge from entering the timing capacitor C0 while the relay contacts transfer, which charge might slightly affect the timing interval.

It will be understood that the device can be operated directly from a direct current supply, when rectifier N can be omitted.

Figs. 2, 3 and 4 indicate various ways in which the device according to Fig. 1 can be connected. In each of these figures, a block T indicates a timer according to Fig. 1, with the terminals and switches identified as in Fig. 1.

With connections according to Fig. 2, the load Zl is deenergized after the time delay, and the load Z2 is energized after the delay.

With connections according to Fig. 3, the load Z is energized at the start, and deenergized at the end of the timing period.

The connection according to Fig. 4 provides a repeat cycle; timer Tl controls the on time whereas timer T2 controls the off time.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications Z and equivalents which fall within the scope of the appended claims.

I claim:

1. A timing device comprising direct current supply terminals; normally open starting contacts; a tube of the gaseous cold cathode type with anode, cathode, and control electrode; a resistor of comparatively high value permanently and free of said control electrode connected between said anode and said cathode; means connecting said starting contacts between said cathode and one of said terminals; a control relay having a coil for closing said starting contacts; a control capacitor connected between the control electrode and cathode of said tube; and means for charging said capacitor from said terminals upon closure of said starting contacts.

2. A timing device comprising direct current supply terminals; a control relay having normally open starting contacts and normally closed contacts and a coil for actuating said contacts; a tube of the gaseous cold cathode type with anode, cathode and control electrode; means connecting said normally open starting contacts between said cathode and one of said terminals; a load impedance in circuit with said anode and cathode; a control capacitor connected between the control electrode and cathode of said tube; means for charging said capacitor from said terminals upon closure of said starting contacts; and means connecting said normally closed con tacts of the control relay across said capacitor.

3. A timing device comprising direct current supply terminals; a control relay having normally open starting contacts and normally closed contacts in make-before-break arrangement and a coil for actuating said contacts; a tube of the gaseous cold cathode type with anode, cathode and control electrode; means connecting said normally open starting contacts between said cathode and one of said terminals; a load impedance connected in circuit with said anode and cathode; a control capacitor connected between the control electrode and cathode of said tube; means for charging said capacitor from said terminals upon closure of said starting contacts; and means connecting said normally closed contacts of the control relay across said capacitor.

4. A timing device comprising direct current supply terminals; a control relay having normally open starting contacts and normally closed contacts and a coil for actuating said contacts; a tube of the gaseous cold cathode type with anode, cathode and control electrode; a resistor of comparatively high rating permanently and free of said electrode connected between said anode and said cathode; means connecting said normally open starting contacts between said cathode and one of said terminals; a load impedance in circuit with said anode and cathode, in series with said resistor with the tube nonconductive; a control capacitor connected between control electrode and cathode of said tube; means for charging said capacitor from said terminals upon closure of said starting contacts; and means connecting said normally closed contacts of the control relay across said capacitor.

5. A timing device comprising supply terminals for connection to an alternating current source; a rectifying network having two input and two output terminals; connections between said supply and said input terminals; a normally open starting switch; a control relay having a set of normally open starting contacts, a set of normally closed safety contacts and a coil connected through said starting switch between said input terminals for actuating said contacts upon closure of said starting switch; a tube of the gaseous cold cathode type with anode, cathode and control electrode; a load impedance in circuit with said anode and cathode; means connecting said normally open starting contacts of said control relay between said cathode and the second output terminal; a control network including a capacitor and resistance means connected in series between said first output terminal and said cathode, with the capacitor on the cathode and the resistor on the output terminal; a resistor leading from the connection between said capacitor and said resistance means to said control electrode; and means connecting said normally closed safety contacts of said control relay across said capacitor.

6. A timing device comprising supply terminals for connection to an alternating current source; a rectifying network having two input and two output terminals; connections between said supply and said input terminals; a normally open starting switch; a control relay having a set of normally open starting contacts, a set of normally closed safety contacts and a coil connected through said starting switch between said input terminals for actuating said contacts upon closure of said starting switch; a tube of the gaseous cold cathode type with anode, cathode and control electrode; a resistor of comparatively high rating permanently and free of said electrode connected between said anode and said cathode; a load impedance in circuit with said anode and cathode, in series with said resistor with the tube nonconductve; means connecting said normally open starting contacts of said control relay between said cathode and the second output terminal; a control network including a capacitor and resistance means connected in series between said first output terminal and said cathode, with the capacitor on the cathode and the resistor on the output terminal; a resistor leading from the connection between said capacitor and said resistance means to said control electrode; and means connecting said normally closed contacts of said control relay across said capacitor.

7. A timing device comprising supply terminals for connection to an alternating current source;

a rectifying network having two input and two output terminals; connections between said supply and said input terminals; a normally open starting switch; a control relay having a set of normally open starting contacts and a set of normally closed safety contacts in make-beforebreak arrangements of said contacts, respectively, and a coil connected through said starting switch between said input terminals, for actuating said contacts upon closure of said starting switch; a tube of the gaseous cold cathode type with anode, cathode and control electrode; a resistor of comparatively high rating permanently and free of said electrode connected between said anode and said cathode; a load impedance in circuit with said anode and cathode, in series with said resistor with the tube nonconductive; means connecting said normally open starting contacts of said control relay between said cathode and the second output terminal; a control network including a capacitor and resistance means connected in series between said first output terminal and said cathode, with the capacitor on the cathode and the resistor on the output terminal; a resistor leading from the connection between said capacitor and said resistance means to said control electrode; and means including a resistor of low resistance connecting said normally closed contacts of said control relay across said capacitor.

8. A timing device comprising direct current supply terminals; a tube of the gaseous cold cathode type with anode, cathode and control electrode; terminals providing for connection of a controlled high impedance means in series with said anode and cathode; a resistor connected permanently and free of said control electrode across said cathode and anode, said resistor having a value sufiiciently high to prevent appreciable voltage drop across said impedance means when said tube is non-conductive with impedance means and resistor in series; and means adapted to connect said anode and said cathode to respective terminals and to bring said control electrode to firing potential.

EDWARD B. FARMER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,552,321 Lea Sept. 1, 1925 2,104,128 Honaman Jan. 4, 1938 2,201,166 Germeshausen May 21, 1940 2,208,241 Bachelet July 16, 1940 2,360,721 Rose Oct. 17, 1944 2,362,769 Parratt Nov. 14, 1944 2,366,060 Schneider Dec. 26, 1944 2,429,451 Cade Oct. 21, 1947

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