US2578557A - Electric timing device - Google Patents

Description

Dec. 11, 1951 L, A, KlNG ELECTRIC TIMING DEVICE lFiled Jan. 25, 1946 INVENTOR [UU/5 A. K//G ATTORNEY S SSS SEQ h. E\ W5S SQ Patented Dec. 11, 1951 ELECTRIC TIMING DEVICE Louis A. King,

Haddonfeld, N. J., assigner to Radio Corporation of America, a corporation of `Delaware Application January 25, 1946, Serial No.643,362 3 Claims. (Cl. -250-27) This invention relates to electric timing devices.

An object of the invention is to provide an electronic timing device which will produce an automatically cycled operation for ultra short time periods below 0.1 second, and is suitable for use with industrial type power apparatus.

Another object is to produce simply and accurately short timing intervals for periods ranging in duration from 0.001 second to 0.5 second.

A further object is to provide an electronic timing device employing a multi-dial decade capacitor unit for selecting time intervals between 0.001 second and 0.5 second in stepsof 0.001 second, and in which an output pulse (voltage or current) having sharp edges Aand of preselected time duration may be .produced by the operation of a switch, with an accuracy of calibration and repeatacality within approximately 5% of the selected time .interval independently lof normally varying operating conditions and electron tube replacements.

Still another object is to provide an electric timer capable of producing electrical pulses of accurately timed durations ranging from milliseconds to tenthsof a second, suitable for controlling a power oscillation generator in industrial heating equipment.

Existing mechanical type timing devices constitute timed relays and have a minimum timed interval of 0.2 second at which the accuracy is `very poor. It is for this reason that there is great need for a non-mechanical electronic timer to operate in the millisecond range.

The present invention provides a highly accurate, simple and compact electrical timing system Ahaving a wider range of usefulness than previously known arrangements.

A description of the invention follows in conjunction with a drawing whose single gure illustrates a preferred embodiment.

Referring to the drawing in more detail, there is shown an electrical timing device comprising a twin triode vacuum tube V controlled by the operation of a keying relay K whose relay winding is connected to terminals M and N. These terminals M and N are coupled to suitable key or switch mechanism and energysource (not shown) for Lfurnishing energizing current to the winding of relay K whenever it is desired to operate the timing device.

Vacuum tube V comprises two triode electrode 4sections X and Y. The 'anode of the Y section 'is supplied with positive polarizing, potential of 150 volts relative to the cathode through resistor R6. The anode of the .X triode section issupplied with positive `polarizing potential through the resistor R1 via leads I3 and I4, whether switch S5 is closed for voltage feed tc the utilization circuit, or whether switch S5 is opened for current feed to the utilization circuit. In the latter case, the ,positive polarizing potential will be supplied through the current operated device of the utilization circuit (not shown). This utilization circuit, by way of example only, may be an electronic keyer circuit for controlling a power oscillator such as may be employed in industrial heating equipment. Resistor R1 is of considerably smaller value than resistor R5. The grid of electrode section X is coupled to its cathode through resistor R8, while the grid of electrode section Y is coupled to its cathode through resistors R4 and R5. It will thus be seen that both triode electrode sections of vacuum tube V have a common cathode resistor R5.

A source of constant voltage supply l5 has its positive terminal connected to the anodes of the twin triode tube V through resistors RS and R1, and its negative terminal connected to the vcathodes of this tube through resistor R5. y.'Ihis constant voltage source l5 may be any conventional .power supply circuit having a voltage :regulator tube and supplying, by way of example, voltage of volts to the anodes of tube V relative to the cathodes. Connected across the terminals of the voltage supply l5 are shown a pair of series connected resistors R2 and R3. The junction point of these two resistors is connected to contact I rof the relay K. Contact 2 of relay K is connected to the grid of the Y electrode section. The armature of relay K is connected to one side of condenser C whose other side is connected to resistor R5 and to the negative terminal of the constant voltage supply. Resistor R2 has a considerably greater resistance than resistor R3, while resistor R4 has a considerably greater resistance than resistor R5.

In one embodiment of the invention successvvfully tried out in practice, resistor R2 was 80,000 ohms, resistor R3 was 20,000 ohms, resistor .R4 was 330,000 ohms, resistor R5 was 3,000 ohms, resister R6 was 100,000 ohms, resistor R1 was 15,000 ohms, resistor R0 was 452,000 ohms, and capacitor C hada value of .001'microfarad- Thepotential Aacross the voltage supply I5 Awas 150 volts.

In circuit with the electrodes of twin triode tube V there is shown a capacitor decade unit |00 Vhaving `three dials Si, S2 and S3. This capacitor decade unit controls the time duration of the .pulse `produced by .the :timing deviceover periods 'ranging :from .0.001 second tov0.5 second. There are three groups of condensers suitably labeled tenths of a second, hundredths of a second and milliseconds (thousandths of a second). Under control of dial SI are nine equal value condensers CI to C9 each capable of causing the timing device to produce a pulse of 0.001 second duration. Under control of dial S2 are nine equal value condensers CIU to CIB each capable of causing the timing device to produce a pulse of 0.01 second duration. Under control of dial S3 are four equal value condensers CIS to C22 each capable of causing the timing device to produce a pulse of 0.1 second duration. Dials Si and S2 can each be turned to cover any one of tensettings reading to 9, while dial S3 can be turned to cover any one of ve settings reading 0 to 5. The setting of any one dial to a particular number will cause a corresponding number of condensers in its particular group to be arranged in electrically parallel relation.

rIhe condensers in the three groups are eiectively arranged in electrically parallel relation by means of connections I0 and Il, depending upon the setting of the dials. The equivalent capacitance of the decade unit is shown by the dotted line capacitor 8 shown connected between the anode of the Y electrode section of tube V and the grid of the X electrode section of tube V. The reading of the capacitor decade unit for the particular positions of the dials Si, S2 and S3 shown in the drawing is 0.27 '1 second.

Output from the timing device is obtained from terminals A, B and C. Ii an output voltage pulse is desired, terminals A and B are utilized, and terminals B and C short-circuited by means of switch S5. It will thus be seen that terminals A and B are effectively connected across resistor R1 by virtue of leads l2 and i3. If an output pulse of current is desired, then switch S is opened and terminals B and C are utilized. The current operated device (not shown) will then be connected in series with resistor R1 through lead I3. These output pulses have steep leading and trailing edges.

When the electronic timing device of the invention is at rest, relay K will be in the position shown in which the armature engages contact l. In this position there will be a flow of current through section X of tube V which causes a voltage to be developed across common cathode resistor R5 of a magnitude sufficient to bias the Y electrode section to cut-off. By way of example, the voltage drop across resistor R5 due to ilow of current through electrode section X, may be about 15 volts. By way of explanation, it may be stated that when the constant voltage supply is rst turned on, there is a tendency for current to flow through both the X and Y electrode sections of tube V, but this tendency is overcome by the flow of current through the X section which produces a negative bias on the grid of the Y section, due to the flow of current through resistor R5 o sufficient magnitude to bias the Y section beyond cut-oil. It should be noted, at this time, that the grid of the X electrode section is at cathode potential by virtue of resistor R8.

In this condition, wherein the armature of the relay K engages contact l, the capacitor C will charge up to the full value of the voltage drop across R3, amounting to 37.5 volts.

The capacity between the grid of the X section and the anode of the Y section is charged up to a value equal to the potential drop across the anode and cathode of the Y electrode section, and.

this potential drop amounts to about 135 volts. This 135 volt value is the difference between 150 volts supplied by the voltage supply I5 and the 15 volt drop across resistor R5 caused by the ow of current therethrough, due to conduction in the X electrode section. This particular capacity between the grid of the X section and the anode of the Y section is made up of the capacitor decade unit 103 whose equivalent capacitance is indicated by dotted line capacitor 8.

The voltage drop across resistor R1 is '18 volts, assuming switch S5 between leads I3 and i4 to be closed. As stated above, resistor R1 is of considerably lower resistance than R6, and the reason for this is to ena-ble sufficient current to ilow through the X electrode section and through resistor R5 to bias the Y electrode section beyond cut-off.

In order to reduce the output voltage across resistor R1, from the 78 volts value to Zero, for an interval which is predetermined by the setting of the capacitor decade unit |00, the relay K is energized by current applied to terminals M and N in order to cause the armature of this relay to engage contact number 2. When the armature of relay K engages Contact number 2, the condenser C is connected to the grid of the Y electrode section and discharges through resistor R4, thus producing a momentary positive pulse on the grid of the Y electrode section of sufficient magnitude to cause the Y electrode section to conduct. When the Y electrode section conducts, the anode-cathode voltage of this electrode section is reduced from a value of 135 volts to the normally conductive drop through the Y electrode section. The drop in voltage across resistor R6 during the time the Y electrode section conducts is about 86 volts, due to the high resistance of resistor R6, while the voltage drop through the Y electrode section itself is about 62 volts.

At the instant the Y electrode section starts to conduct, the grid of the X electrode section is biased negatively by an amount sufficient to cut off the flow of current from the X electrode section, due to the 135 volt charge on the capacitor decade unit |05. With the values of the various elements assumed above, the grid of the X section is biased negatively relative to its cathode by an amount of about '12 volts, which is the voltage drop across resistor R8.

It should be noted at this time that when the Y electrode section conducts, the Voltage drop across resistor R5 is about 2.6 volts as compared to the 15 volt drop across this same resistor when the X electrode section is conducting.

During the time the Y electrode section con-- ducts and the X electrode section is biased beyond cut-01T, the output voltage across resistor R1 is zero. The changes in voltage across resister R1 are instantaneous in comparison to the time interval range used in the capacitor decade.

As the charge on the capacitor decade leaks off through resistor R8 and the electrodes of the conducting Y electrode section, the grid potential on the X electrode section is reduced until such time as the X electrode section again begins to conduct and cause current to flow through resistor R5 of amagnitude suiicient to bias theY electrode section to cut-ofi. The time interval of cut-oi of the X electrode section is determined by the setting of the capacitor decade unit li). It will thus be observed that electrode Sections X and Y are connected in a self-restoring trigger circuit having one degree of electrical stability.

If it is assumed that the dial settings of the capacitor decade unitare as shownin the drawing, then output voltage obtainable from ,termi-- nals A and B connected across resistor R1 (assuming switch S is closed) is out ofi for a time interval of .277 second. If, by way of 4further illustration, it is desired. to out 01T the output voltage for a time interval or" .125 second,then this is achieved by setting the dial S3 to .1, or the rst contact associated with this dial, setting the dial S2 to .02 corresponding to the second contact associated with this dial, and setting dial Si to point .005 corresponding to the 5th contact associated with this last dial. In practice, dials Sl, S2 and S3 are rotatable through anarc of a circle to cover `the different settings associated therewith.

In the event itgis desired to obtain current feed from the timing device of the invention rather than voltage feed, then switch S5 is opened and the utilization circuit connected to the output terminals B and C with the current operated dcvice of the utilization circuit (not shown) in circuit with the C output terminal.

Connected across resistor R3, there is provided an interlock switch S4 which is used to short circuit resistor R8 during changes in the time interval settings of the capacitor decade in order to prevent false operation (cut off of the X electrode section) due to the charging current on add-ed capacitors inthe decade unit idil. The capacitor decade |00 is provided with a door which must be opened to `provide access to the dials Si, S2, S3. When the door of the capacitor decade is open, the interlock switch Slt operates to short circuit resistor R8. The control between the interlock switch Sd and the door of the capacitor decade v,|00 is represented by dot and dash line Mil.

The timing device of the invention operates to produce a single interruption of output voltage or current regardless of whether relay K makes momentary or sustained contact with contact member 2. However, it is necessary for the armature of relay K to be restored to engage contact I and then move again to engage contact 2 before another cycle of operations of the timing device can be initiated.

An advantage of the present invention lies in the fact that the input and output circuits are relatively independent of each other; that is, isolated, so that there is no reaction from the output to the input except through the very small and inconsequential interelectrode capacity of the vacuum tube V. The timing device of the invention is characterized by very sharp changes in output voltage from a positive to a zero value.

The utilization circuit connected to the timing device of the invention may comprise an electronic keyer or relay which may close the grid circuit of a high power oscillation generator for very short intervals of time, in response to the pulses produced by the timing device in order to produce short pulses of radio frequency energy in the output of this generator. As an example only, the high power generator controlled by the electronic keyer or relay may be of the order of 50 kilowatts and higher for use in industrial heating applications.

What is claimed is:

l. An electrical timing system comprising first and second electric tube electrode structures each having an anode, and a grid, cathode means for supplying electrons to said structures, a source of unidirectional current supply, a resistor connecting the anode of said rst electrode structure to the positive terminal of said source, a resistor 'of .considerably lower value than :said rst resistor connecting :the anode of said second structure to said positive terminal, a common cathode resistor for said electrode structures connected between the negative terminal of said source and said cathode means, a resistor connected between the grid of said rst tube and that end of said common cathode resistor farthest removed from said cathode means, a resistor connected lbetween the grid of said second tube and the other end of said common cathode resistor, a switch hav-ing an armature and a pair of contacts, a connection from one of said contacts to said source, a connection from the other contact `to the grid oisaid rst structure, a condenser connecting the armature of said switch to a point on said-common cathode resistor removed `from Vsaid `cathode means, whereby said second structure conducts `and biases said rst structure to cut-oit when said armature engages said one contact, andthe current passing conditions of said structures are reversed at least momentarily when said armature engages said other contact, a capacitor decade unit connected between the anode of said first electrode structure and the grid of said second electrode structure, said decade unit comprising three groups of condensers each of which has a dial in circuit therewith, the condensers in one group being calibrated in tenths of a second, the condensers in the second group being calibrated in hundredths of a second land the condensers of the third group being calibrated in -thousandths of a second, the dial settings of said decade unit determining the time duration of the output pulse obtainable from said timing system, the timing intervalsselectable by said decade unit ranging in duration from 0.001 second to 0.5 second, and an output circuit connected to the anode resistor of said second structure.

2. An electrical timing system comprising a self-restoring trigger circuit having rst and second vacuum tube electrode structures each including an anode and a grid, cathode means for supplying electrons to said structures, a source of constant voltage of the order of volts direct current, a resistor of the order of 100,000 ohms connecting the anode of said rst structure to the positive terminal of said source, a resistor of the order of 15,000 ohms connecting the anode of said second structure to said positive terminal, a common cathode resistor of the order of 3000 ohms connected between the negative terminal of said source and said cathode means, a resistor of the order of 330,000 ohms connecting the grid of said rst structure to the end of said cathode resistor which is connected to said negative terminal, a resistor of the order of 452,000 ohms connecting the grid of said second structure to said cathode means, a switch having an armature and a pair of contacts, a resistor network, connected across said source of constant voltage and comprising two resistors in series one of which has a value of the order of 80,000 ohms and the other of a value of the order of 20,000 ohms, a connection from one of said contacts to the junction point of Said last two resistors, a connection from the other contact to the grid of said rst structure, a condenser of the order of .001 microiarad connecting the armature of said switch to said negative terminal, an adjustable capacitor arrangement connected between the anode of said rst structure and the grid of said second structure, said capacitor arrangement including a plurality of groups of condensers and individual dials for said groups, and connections for coupling certain ones of said condensers in parallel in dependence upon the setting of said dials, and an output circuit coupled to the anode resistor of said second structure.

3. An electrical timing System comprising a self-restoring trigger circuit having first and second electronic tube electrode structures each including an anode, and a grid, cathode means for supplying electrons to said structures, a source of unidirectional current supply, a resistor counecting the anode of said rst electrode struc ture to the positive terminal of said source, a resistor of considerably lower value than said first resistor connecting the anode of said second structure to said positive terminal, a common cathode resistor for said electrode structures connected between the negative terminal of said source and said cathode means, a resistor connected between the grid of said rst tube electrode structure and that end of said common cathode resistor farthest removed from said cathode means, a resistor connected between the grid oi said second tube electrode structure and the other end of said common cathode resistor, a switch having an armature and a pair of contacts, a connection from one of said contacts to a terminal of said source, a connection from the other Contact to the grid of said rst structure, a condenser connecting the armature of saii switch to a point on said common cathode resistor removed from said cathode means, whereby said second structure conducts and biases said first structure to cut-oil when said armature engages said one contact, and the current passing conditions of said structures are reversed at least momentarily when said armature engages said other contact, an adjustable capacitor unit located within a housing and connected between the anode of said first electrode structure and the grid of said second electrode structure, said capacitor unit including a plurality of groups of condensers arranged in parallel with means for operatively selecting one or more condensers in each group, the effective Value of said capacitor unit determining the time duration of the output pulse from said timing system, an interlock switch coupled across the resistive grid connection of said Second electrode structure and controlled by a door in the housing of said adjustable capacitor unit for shorting said last resistive grid connection whenever it is desired to vary the effective value of said capacitor unit, and an output circuit connected to the anode resistor of said second structure.

LOUIS A. KING.

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

UNITED STATES PATENTS Number Name Date 1,251,440 Sultzer Dec. 25, 1917 2,185,363 White Jan. 2, 1940 2,404,553 Wales July 23, 1945 2,405,237 Ruhlig Aug. 6, 1946 2,416,328 Labin Feb. 25, 1947 2,432,453 Skellett Dec. 9, 1947 2,432,516 Doba Dec, 16, 1947 2,444,036 Crost June 29, .1948 2,457,062 Moore Dec. 21, 1948 FOREIGN PATENTS Number Country Date 529,526 Great Britain Nov. 22, 1940 538,440 Great Britain Aug. 5, 1941

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