US2818532A - Single action timing circuit - Google Patents

Description

Dec. 31, 1957 M. 1.. AITEL v 2,818,532

SINGLE ACTION-TIMING xgcurr Filed Nov. 1, 1955 2 Sheefns-Sheet 1 INVENTOR. Mm; L. AITELI ATTORNEY 1957 M. L. AlTEL 2,818,532

SINGLE ACTION TIMING CIRCUIT Filed Nov. 1. 1955 2 Sheets-Sheet 2 IN V EN TOR.

? [4 6. M05 L-AITELI ATTORNEY SINGLE ACTION TIMING CIRCUIT Moe Lawrence Aitel, Haddon Heights, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November 1, 1955, Serial No. 544,228

17 Claims. (Cl. 315-234) This invention relates to timing circuit devices, and more particularly to a single action timing circuit.

It is often desirable to have a work circuit that operates for a predetermined period of time, or that starts after a predetermined delay. Such circuits find application in photography, electronics, material handling, etc. Various applications of such circuits in these fields include, for example, timing exposures in photography; in electronic circuits, applying anode current a fixed time after connecting cathode heaters, and, in material handling, utilizing the weight or movement of an object to trigger an operation of preset time duration.

It is often advantageous to have the timing circuit operate through a given time interval substantially inde pendent of the time duration of the triggering impulse. Further, it is often desirable that the circuit remain in a quiescent or inoperative condition at the end of the given interval until the trigger is released or reset, without any other resetting action being required.

Circuits of the prior art have accomplished one or more of these results by using many resistors, capacitors, vacuum or gas filled tubes, relays, and other circuit components. Attempts at simplification of the circuits and the consequent reduction in the number of elements often have resulted in the sacrifice of one or more of the features of activation independent of trigger duration, single action operation, or reset by the reset of the trigger.

Accordingly, it is an object of this invention to provide an improved variable timing circuit for control purposes that is simpler than the circuits of the prior art.

Another object of the invention is to provide an improved timing circuit that will operate only once when triggered.

It is a further object of this invention to provide an improved, single action timing circuit wherein the interval timed may be readily varied.

A still further object of the present invention is to provide an improved timing circuit that will operate for a fixed time interval substantially independent of the time duration of the trigger influence.

An additional object of this invention is to provide an improved, single action timing circuit that will be reset only upon release of the trigger.

Circuits embodying the present invention have three operating states, which may be termed dwell, working, and quiescent states. Initially, the circuit may be in a dwell state in which the trigger is set. Actuation of the trigger during the dwell state initiates the second, or working, state. At the conclusion of the timing interval, the circuit assumes a quiescent state which resembles the first state except that the circuit will not work again until the trigger is released or reset.

According to the present invention, a resistor and capacitor in series are connected in parallel with a thyratron or other multi-element, gas-filled tube with the capacitor on the cathode side of the parallel circuit. The control electrode or grid is, coupled to the junction of the resistor and capacitor and is connected to a negative potential source. During the dwell state, a trigger impulse causes the control grid to be disconnected from the negative potential source, thereby starting the timed interval, which constitutes the working state. The capacitor then charges toward the potential of the thyratron anode. The circuit parameters determine the charging time for the capacitor. The end of the timed interval and the working state occurs when the grid is sufficiently raised in potential to fire the tube, and the circuit enters its quiescent state. Releasing the trigger extinguishes the tube and resets the circuit to the dwell state. A relay is included in the anode circuit. The one set of relay contacts may control the grid bias. In one form of the invention, a second set of relay contacts may be used to prevent premature termination of the timed interval should the trigger be released during the Working interval.

The timing circuit may operate an external work circuit by connecting a load through the relay contacts. Alternatively, the relay may energize a work system mechanically. Should an electrical signal be desired, a suitable impedance may be included in the timing circuit to provide a pulse, or a signal of desired level or waveform for the duration of the working state.

The novel features of the invention, as well as the invention itself, both as to its organization and method of operation, will best be understood from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 is a diagram of a circuit embodying one form of the present invention;

Fig. 2 is an alternate form of the circuit of Fig. 1 in which the relay winding is not included in the charging circuit;

Fig. 3 is a modification of the embodiment of Fig. l, in which an additional relay contact switch is included in the relay to prevent premature termination of the working period;

Fig. 4 is an alternate form of a circuit including the invention in which an additional relay contact switch is added to the circuit of Fig. 2 for a like purpose;

Fig. 5 is a further embodiment of the present invention in which the relay is energized only during the Working period;

Fig. 6 is an alternate form of the circuit of Fig. 5 in which a bias is applied to the relay toprevent energization thereof while the thyratron is conducting; and

Fig. 7 is a voltage divider network which may be used in the circuit of Fig. 6.

A common reference potential to which all voltage levels are referred is indicated by the conventional ground symbol 14. Sources of potential are indicated by conventional battery symbols appropriately connected, although any suitable source of power may be used.

In the circuit of Fig. 1., one terminal of the winding of a relay 10 is connected to the positive terminal of a source of potential 12, the negative terminal of which is connected to ground 14. The other terminal of the winding of the relay 10 is connected to ground 14 through a trigger switch 16. Also connected to the relay 10, in a circuit parallel with the trigger switch 16, is the anode 18 of a thyratron 20. The thyratron cathode 22 is connected to ground 14. The thyratron grid 24 is connected to ground 14 through a capacitor 26. The negative termimat of a bias potential source 28 is connected through a contact switch 30 controlled by the relay 10 and a switch current limiting resistor 32 to the thyratron grid 24 at. the junction with the capacitor 26. The positive terminal. of the bias source 28 is connected to ground 14. A variable resistor 34 in series with a fixed resistor 36 connects the grid 24 to the anode 18. The anode to cathode circuit of the thyratron 20 comprises the parallel 3 combination of the switch 16 and the series combination of the resistors 34, 36 and the capacitor 26.

In operation, the relay is normally energized in the dwell state by current flow from the positive source 12, through the relay 10 winding, and thence through the trigger switch 16 to ground 14. The thyratron 20 has its anode 18 and cathode 22 at ground potential because of the short circuit path through the trigger switch 16. The thyratron grid 24 is biased to a negative value by the negative source 28 and the capacitor 26 is charged to that negative value. The combined resistance of the fixed resistor 36 and the variable resistor 34 is very large, that is, ten times as large or more, compared to the resistance of the resistor 32 alone.

The trigger switch 16 may be of any suitable type, such as a relay responsive switch which may he opened 1n response to a trigger impulse from an external source (not shown). When the switch 16 is opened, the relay 10 is de-energized, thus starting the working period. The closed relay contact 30 opens, disconnecting the thyratron grid 24 from the negative source 28. At the same time, the potential of the anode 18 of the thyratron 20 rises to the value of the positive source 12. The capacitor 26 is now charged toward the potential of the positive terminal of the source 12 through the combined resistors 34 and 36 and the winding of the relay 10 which, of course, also has some resistance. The time constant of the combination of the relay winding, the fixed resistor 36, and the capacitor 26 largely determines the minimum charging time for the capacitor 26. The variable resistor 34 may be adjusted to vary the time interval by varying the total resistance of the resistor-capacitor combination. The thyratron grid 24 potential rises as the capacitor 26 is charged and, when the potential of the grid 24 is sufficiently positive, the thyratron 20 is fired. The relay 10, now a part of the anode circuit of the thyratron 20, is energized. The relay contact switch 30 is now closed by the energized relay 10, thereby terminating the dwell state. The negative source 28 is then reconnected to the thyratron grid 24 and capacitor 26, the capacitor 26 again charging to the bias voltage. The thyratron will continue to conduct, leaving the circuit in the quiescent state, until the trigger switch 16 is closed, thereby once again connecting the thyratron cathode 22 to the thyratron anode 18.

In the circuit of Fig. 2, the resistors 34 and 36 are connected directly to the positive source 12, eliminating the relay winding 10 from the charging circuit. However, the operation of the circuit is sufiiciently similar to that described above for the circuit of Fig. 1 so that further description is unnecessary for those skilled in the art.

A premature closing of the trigger switch 16 in the circuits of Fig. 1 and Fig. 2 will re-energize the relay 10 before the predetermined time interval has elapsed. Thus, in efiect, the working state is prematurely terminated. In some applications, this efifect is undesirable. This effect may be avoided by the circuits of Figs. 3 and 4 which include a second contact switch 38 which is controlled by the relay 10. In each of these circuits, this second relay switch 38 is placed in series with the trigger switch 16. The contact switch 38 remains open during the time that the relay 10 is de-energized. Hence, reclosing the trigger switch 16 before the completion of the timed interval has no eltect on the circuit.

In Fig. 5, an alternative form of the invention is shown in which a relay operates only during the timed working interval. The relay 10 is placed in parallel with the thyratron 20 and an additional resistor 40 is added in series with this parallel combination. Preferably, the resistance of resistor 40 is of the same order (has a value within a factor of ten) of the resistance of the winding of the relay 10. Both these values should be great enough so that the voltage across the relay 10, when the thyratron 20 is non-conductive, is sufficient for reliable firing of'the thyratron, and the operating voltage of the thyratron, when conductive, is too low to mamtain the relay 10 energized. In the circuit of Fig. 5, the parallel circuit of the trigger switch 16 with the relay contact switch 38 connects the resistor 40 to the positive source 12. In the dwell state, the switches 16 and 38 are opened and current flows from the positive source 12 through a circuit which includes the fixed resistor 36, the variable resistor 34, the current limiting resistor 32, and the normally-closed relay contact 30 to the negative source 28. The thyratron grid 24, as before, is connected to ground 14 through the capacitor 26, to the source of negative supply 28 through the resistor 32 and the switch 30, and, through the series resistors 34 and 36, to the positive source 12. Therefore, in the dwell state of the circuit, the capacitor 26 is charged to the negative potential and the circuit is ready for operation. Closing the trigger switch 16 provides a shunt path for the current flow through the resistor 40 and the relay 10. The relay 10 is thus energized and the contact switch 38 closes. The contact switch 30 opens and the capacitor 26 starts to charge toward the positive potential level through the resistors 34 and 36. The thyratron grid 24 becomes more positive during the working time interval, which is terminated by the firing of the thyratron 20. The impedance of the thyratron 20 is sufliciently low to shunt the current away from the relay 10. Current flow in the relay 10 is then insufficient to maintain energization thereof. The relay 10 therefore becomes de-energized. Relay contacts 30 thereupon close and contacts 38 open. The circuit is now in the quiescent state, the relay 10 being de-energized. When the trigger switch 16 is re-opened, the thyratron 20 is open-circuited and thus extinguished.

During conduction of the thyratron 20, the current flow through the relay 10 must be kept sufficiently small to prevent energization of the relay 10. Rather than rely upon the relative values of the resistance of the relay winding 10, the resistor 40, and the thyratron 20, a source of positive supply 42 may be introduced into the circuit between the relay 10 and ground 14, as shown in Fig. 6. This source of supply 42 acts to oppose any current flow through the relay 10.

Fig. 7 is a diagram of a voltage divider circuit which may be used to replace the source of supply 42 in the circuit of Fig. 6. A resistor 50 is tapped at the junction 46' to produce a potential equivalent to that of the potential source 42 and may be introduced into the circuit of Fig. 6 at the junction 46. Similarly, the resistor 50 may be connected at the positive supply side by connecting the junction 44' of Fig. 7 to the junction 44 of Fig. 6.

In one form of the embodiment of Fig. 1, the circuit components had the following illustrative values: These values are advisory only and any person skilled in the art should be able to select components of values suitable for any particular application. In this one form of the circuit, the fixed resistor 36 had a value of .13 mcgohrn. The variable resistor 34 had a range from 0 to 2.5 megohms. The positive voltage of the source 12 was forty-eight volts and the negative voltage of the source 28 was 22.5 volts. The capacitor 26 had a value of 1 fd. With a four-element gas-filled thyratron commercially available and designated as 2D21, the time interval varied from 50 milliseconds to one second by adjustments of the variable resistor.

As may be seen, a simple, inexpensive circuit has been described which, in one form, will interrupt the operation of a relay for a predetermined time period or, in another form, will energize a relay for a predetermined time period, and which will insure one and only one operation for each actuation of the trigger.

What is claimed is:

1. A relay circuit comprising a series circuit of a resistor and a capacitor, a gas tube connected in parallel with said series circuit and having a cathode, an anode,

and a control element connected to apoint in said series circuit between said resistor and capacitor, a relay having a winding connected in series 'with'said gas tube,

means for applying a bias voltage to said control element comprising a second resistor having one terminal connected to said control element, a first switch under control of said relay and in series with said second resistor, and a second switch connected between said cathode and anode.

2. A relay circuit comprising a series circuit of a resistor and a capacitor connected at a junction; a thyratron in parallel with said series circuit and having an anode, a control grid connected to said junction, and a cathode; a relay having a winding with two terminals, one of said relay winding terminals being connected to the said thyratron anode; a switch responsive to said relay and having two terminals; means for applying a voltage bias to said thyratron grid including a second resistor connected between said junction and one, of said switch terminals; and a second switch connected to initiate current flow through said relay winding when said second switch is closed. 1

3. A relay circuit comprising a series circuit of a resistor and a capacitor connected at a junction; a thyratron in parallel with said series circuit and having an anode, a control grid connected to said junction, and a cathode; means providing an anode to cathode circuit for said thyratron; a relay having a winding with two terminals, one of said relay winding terminals being connected in the said thyratron anode to cathode circuit; a switch responsive to said relay and having two terminals; means for applying a voltage bias to said thyratron grid including a second resistor connected between said junction and one of said switch terminals; and a second switch connected in said anode to cathode circuit.

4. A relay circuit comprising a relay including a winding having one terminal for connection to a source of power and a second terminal, a switch controlled by said relay and having a pair of terminals, a parallel circuit connected to said relay winding second terminal, said parallel circuit comprising a thyratron having an anode, a cathode, and a control grid, a series circuit including a resistor and a capacitor connected at a junction and further connected to said thyratron grid at said junction, and a second switch having two terminals, one of said second switch terminals being connected to said cathode and the other of said second switch terminals being connected to said relay winding second terminal, and means to apply a voltage bias to said thyratron grid including a second resistor connected between one of said relay control-led switch terminals and said junction.

5. A relay circuit comprising a relay including a winding having one terminal for connection to a source of power and a second terminal, a switch responsive to said relay and having a pair of terminals, a parallel network connected to said relay winding second terminal; said parallel network having first, second and third junctions and including a thyratron having an anode connected to said first junction, a cathode connected to said second junction, and a control grid connected to said third junction, a series circuit between said first and second junctions including a first resistor and a capacitor connected together to provide said third junction, and a second switch having two terminals, one of said second switch terminals being connected to said first junction and the other of said second switch terminals being connected to said second junction, and means for applying a voltage bias to said thyratron grid including a second resistor connected between said third junction and one of said pair of switch terminals.

6. A circuit as claimed in claim 5 wherein said series circuit resistor includes a first resistor portion having a fixed resistance and a second resistor portion having a variable resistance, said second resistor portion being connected between said first resistor portion and said third junction.

7'. A circuit as claimed in claim 6 characterized by the addition of a third switch responsive to said relay and also having two terminals, one of said third switch terminals being connected to said first junction and the other of said third switch terminals being connected to the said one of said second switch terminals whereby said third switch is interposed between said first junction and the said second switch.

8. A relay circuit comprising a first series circuit having first, second, and third junctions and including resistor means and capacitor means serially connected to each other at said third junction, a first parallel circuit having two branches, one of which includes a thyratron having an anode, a cathode, and a control grid and the other of which includes switch means for connecting said thyratron anode and said thyratron cathode, a relay including a winding, second switch means responsive to said relay, and means to apply a biasing voltage, said relay winding being connected in series with said first parallel circuit to provide a second series circuit, said second series circuit being connected in parallel relation with said first series circuit at said first and second junctions to provide a second parallel circuit, said thyratron control grid being connected to said third junction, and said means for applying a biasing voltage including said second switch means and a resistor also connected to said third junction.

9. A relay circuit according to claim 8 wherein said relay winding has a pair of terminals one of which is connected to said first junction and the other of which is connected to said first parallel circuit.

10. A circuit as claimed in claim 8 wherein said resistor means includes a first resistor portion having a fixed resistance and a second resistor portion having a variable resistance, said second resistor portion being connected between said first resistor portion and said third junction.

11. A circuit as claimed in claim 10 characterized by the addition of a third switch means responsive to said relay and interposed between said first switch means and said one branch of the said first parallel circuit.

12. A relay circuit comprising a relay including a winding having two terminals, a thyratron having an anode, a cathode, and a control grid, first and second switch means responsive to said relay, a third switch means, a first series circuit, a second series circuit, and means to apply a bias; said first series circuit having first, second and third junctions and including a first resistor and a capacitor connected together at said third junction, said control grid being also connected to said third junction; said first resistor and said capacitor being connected between said first and second junctions; said second series circuit being connected in parallel with said first series circuit at said first and second junctions and including (1) said first and third switch means connected in parallel, (2) a second resistor serially connected between said parallel switch combination and said thyratron anode, and (3) a parallel combination of said thyratron and said relay, one of said relay winding terminals being connected to the said thyratron anode and the other of said relay winding terminals being connected to the said thyratron cathode; and said means to apply a bias including a third resistor serially connected between said third junction and said second switch means.

13. A circuit as claimed in claim 12 wherein said first series circuit first resistor includes a first resistor portion having a fixed resistance and a second resistor portion having a variable resistance, said second resistor portion being interposed between said first resistor portion and said third junction.

14. A relay circuit comprising a first parallel branch, a second parallel branch, said first and second parallel branches having first and second junctions in common and said first parallel branch having a third junction, and first means for applying a bias; said first parallel branch comprising a first series circuit connected between said first and second junctions and including a first resistor and a capacitor connected to each other at said third junction; said second parallel branch comprising a second series circuit connected between said first and second junctions and including, in series, a second resistor, a first and a second switch means connected in parallel, and a parallel combination, said parallel combination comprising two arms, one arm including a thyratron having an anode, a cathode, and a control grid connected to said third junction, the other of said arms including, in series, a relay having a winding controlling said second switch means, and a second means for applying a bias; and said first means for applying a bias including a third switch means responsive to said relay and a third resistor connected between said third junction and said third switch means.

15. A circuit as claimed in claim 14 wherein said first parallel branch first resistor includes a first resistor portion having a fixed resistance and a second resistor portion having a variable resistance, and said second resistor portionbeing interposed between said first resistor portion and said third junction.

16. A relay circuit including a relay having a winding and a thyratron having an anode, a cathode, and a control grid, said relay being connected between said anode and said cathode, a first switch means for connecting said anode to a source of power, a series circuit connected to said cathode, said series circuit comprising a capacitor and a resistor joined at a junction, said control grid being connected to said junction, and a means to apply a bias to said control grid connected at said junction and including a second resistor and a switch means controlled by said relay.

17. A relay circuit comprising a series circuit of a resistor and a capacitor connected at a junction; a thyratron in parallel with said series circuit and having an anode, a control grid connected to said junction, and a cathode; means providing anode to cathode circuits for said thyratron; a relay having a winding with two terminals, one of said relay winding terminals being connected in one of said thyratron anode to cathode circuits; a switch responsive to said relay and having two terminals; means for applying a voltage bias to said thyratron grid including a second resistor connected between said junction and one of said switch terminals; and a second switch connected in one of said anode to cathode circuits.

.No references cited.

Images