US2479274A - Timing circuit - Google Patents

Description

Aug. 16, 1949.

H. M. SIMONS TIMING CIRCUIT Filed Jan. 4, 1946 g 613 Amp" -/7W4%W Patented Aug. 16, 1949 TIBHNG CIRCUIT Harry M. Simons, Langhorne, Pa., assignor to Gage B. Ellis, Langhorne, Pa.

Application January 4, 1946, Serial No. 639,121

2 Claims.

This invention relates to timing circuits and more particularly to a timing circuit for effectin operation of a device for a predetermined time interval in response to an initiating electrical signal which may be of very short duration. In its more limited aspect, the invention relates to an alarm or indicating system in which an indicating device is operated for a predetermined time interval in response to an initiating signal.

The principal object of the invention is to provide a timing circuit which will initiate operation of a device in response to a signal and which will maintain operation of said device for a predetermined time interval.

Another object of the invention is to provide such a timing circuit which is self-restoring so that it will automatically respond to a later signal or any number of successive signals.

A further object of the invention is to provide a timing circuit which will operate a device intermittently as long as a signal persists.

Still another object of the invention is to provide a timing circuit which is adapted to control the operation of a device according to the condition of an electronic control tube, and in which said tube is controlled both by an initiating signal and by a timing means so as to efiect operation of said device for a predetermined time interval in response to the signal.

A further object of the invention is to provide a timing circuit of the stated character which is adapted to delay the operation of the electronic control tube until the cathode thereof reaches its normal operating temperature, thereby preventing damage due to premature operation.

A further object of the invention is to provide a novel alarm or indicating circuit having the desirable features hereinafter described.

A further object of the invention is to provide an alarm system employing power relays which are not subject to the inherent objections of sensitive relays.

Other objects and features of the invention will be apparent from the following detailed description.

Since the invention is primarily intended for embodiment in an alarm system, it will be described with specific reference thereto. However, it is to be understood that the invention is not thus limited but is applicable in any instance in which it is desired to operate a device for a predetermined time interval in response to an initiating signal.

The invention may be fully understood by reference to the accompanying drawing, the single figure of which is a schemati diagram of an alarm system embodying the novel timing circuit of the present invention.

In the case of an alarm system, it is usually desired to operate an audible indicating device, as represented by the electrically operable hell I In a broad sense, however, the bell I is representative of any electrically-operable device which it is desired to operate for a predetermined time interval in response to an initiating signal. Th operating circuit for the bell l comprises a suitable energizing source, such as the battery 2, and the contacts 3 and 4 of a relay 5. A switch 20. may be provided in said circuit. The energization of this circuit is controlled by the timing circuit of this invention presently to be described. Preferably, the relay 5 is provided with a second set of contacts 6 and I which control an energizing circuit for an indicating lamp 8, the energizing current being derived from a suitable source connected to the input terminals 9. It will be apparent that the lamp 8 is a visual indicating device which is operated at the same time that the bell l is operated. The contacts of relay 5 are open when the relay is energized, and they close when the relay is deenergized.

The timing circuit provided by the present invention employs an electronic control tube In, which is preferably a hot-cathode, gas-filled tube, such as a thyratron. Further, this tube is preferably of the tetrode type (e. g. type 2050) having its second or auxiliar grid connected directly to its cathode as illustrated. The tube I0 is A. C. operated and derives its plate voltage from a transformer l I whose primary winding I2 is connected to a suitable alternating current source. It is characteristic of such an A. C. operated gas tube that the control grid thereof is enabled to render the tube conductive or nonconductive, depending on the potential applied to the control grid, since the plate voltage passes through zero value during its successive cycles. The plate or anode of tube In is connected to the upper end of the transformer secondary winding l3 through the winding of a relay I4, and also through the winding of relay 5, the two relay windings being in series in the plate circuit of the tube. The purpose of relay M will be explained later. The plate circuit may be readily traced through conductor IS, the winding Of relay l 4, connection IS, the winding of relay 5, and connection H. The cathode of tube I0 is connected to a point on the secondary winding l3 by way of connection l8.

The tube I is normally rendered conductive by a bias voltage applied thereto through an adjustable voltage divider comprising resistors I9 and 20. The left end of resistor I9 is connected to a regulated D. C. supply source, while the right end of resistor I9 is connected to an adjustable tap 2i on resistor 20. By proper adjustment of the tap, the tube is rendered normally conduc-, tive but becomes non-conductive in response to a signal applied to its control grid. The relays 5.v and I4 are normally energized and are thus shown in the illustration. To prevent chatter of the relays, their windings are shunted by condensers. 22 and 23 respectively.

The initiating signal, which must have aneg-a- 7 tive potential and which is supplied from some suitable source (not shown) by way of terminal 24, renders the tube Ill non-conductive so as tode-energize relay and-thus cause operation of the device I. a resistance-capacitance combination comprising, condenser 25 and resistors 26 and 21, the'resistors being normally in parallel through the normally closed contacts 28 and 29 of relay I4. The re-' sistance-capacitance combination 2526-21 has a predetermined time constant so that the operating signal must be of a predetermined speed. The importance of this will be seen later. Upon application of an operating signal, even though it may be of very short duration, the control grid of tube I 9 is driven negative by the voltage which builds up during the charging'of condenser 25. The tube In is thus rendered non-conductive,

thereby de-energizingboth of the relays 5 and I4 and initiating operation of device I The tube I0 is maintained non-conductive for a predetermined timeinterval by the timing arrangement now to be described.

A diode rectifier tube 38 is provided, and while this tube is preferably of double diode form with its dual elements tied together, it will be treated as a single diode for the purpose of this discussion. The cathode of tube 30 is connectedto the lower end of the transformer secondary winding I3 by Way of connection 3|. A resistor 32 is connected between the anode of tube 30 and contact 330i relay I4. A condenser 34, which constitutes a timing element as will be seen later, is connected between the anode of tube 30 and contact 35 of relay I4. normally closed as illustrated. A contact 36 which is engaged by contact 35 when relay I4 is tie-energized, is connected to one end of a filter resistor 31 by way of connection 38. The opposite end of resistor 31 is connected to one end of resistor 27, the other end of which is grounded. The junction point 39 of resistors 21 and 3! is connected to the junction point 40 of filter resistors M and 42. A by-pass condenser 43 is shunted about resistor 21. In addition to the previously mentioned filtering elements, a filter resistance 44 and condenser 45 are connected between the anode of diode 30 and ground.

Normally contacts 35 and 36 are disengaged from one another, as illustrated, and the timing condenser 34 is completely discharged, being included in a discharge circuit comprising discharging resistor 32 and the closed relay contacts 33 and 35. When an initiating signal arrives, relay I4 is de-energized as previously described, and contacts 29 and 35 move out of engagement with contacts 28 and 33, and contact 35 engages contact 36. Condenser 25 commences to discharge through resistor 26 at a predetermined rate. Thus the application of the signal is interrupted The initiating signal is applied to The contacts 33 and 35 are but, at the same time, condenser 34 is connected to the right-hand end of resistor 31. Consequently, a pulsating current flows from the diode rectifier 30 through condenser 34 and through resistors 3'! and 21. The control grid of tube I0 is thus kept negatively charged, maintaining the tube non-conductive. The timing condenser 34 charges at a predetermined rate, and the negative voltage on the control grid of tube It decreases accordingly. After a predetermined time interval which is dependent on the charging rate of condenser 34, the potential on the control grid of tube It will have risen sufiiciently to permit the tube to become conductive. When this occurs, the relays 5 and I4 are again energized, and the operation of device I is interrupted. The engagement of contact 35 with contact 33 completes the discharging circuit for condenser 34, which discharges through resistor 32. At the same time, contacts 28 and 29 are re-engaged, so that the circuit is ready to receive a subsequent initiating signal. Thus the circuit automatically restores itself to its normal signal-receptive condition.

From the foregoing description, it will be seen that the device I is rendered operative by rendering the control tube II] non-conductive in response to an initiating signal, and the operation of device I is interrupted after a predetermined time interval by the timing arrangement which renders the tube It! conductive.

The timing arrangement also serves to prevent initial operation of tube Ill until its cathode reaches normal operating temperature. If the system is inoperative for any reason and is rendered operative, the timing arrangement will maintain the grid of tube I 0 negative and will prevent operation of the tube for an interval suificient to permit the cathode to reach its normal operating temperature. This is important because premature operation of the tube would damage its cathode.

The importance of the time delay combination 25-2 62l may now be seen. As previously mentioned, this combination has a predetermined time constant during charging of condenser 25, but since the condenser discharges through resistor 26 alone, the time constant is difierent during discharge. By judicious selection of the time constants, the system may be made to respond only to signals of predetermined speed, and it may be caused to operate a number of times in response to a strong signal which places a strong charge on the condenser 25.

One contemplated use of the system is to actuate an alarm device in response to capacity changes of an antenna caused by the presence of a person or object in a certain area. A suitable capacity-responsive system for this purpose is disclosed in a copending application, Serial No. 639,123, filed January 4, 1946. When the present system is thus used, it may be caused to operate once in response to the approach of a person and several times in responseto a persons touching the antenna. This is made possible by the time delay combination above described. Furthermore, the system will not operate in response to very slow changes in capacity due to natural causes.

It may be desired to have the alarm or indicating device I and its operating relay located at a position remote from the rest of the apparatus. Thus the controlling apparatus may be mounted on a main chassis at one location, while the alarm device I and its operating relay may be mounted on a chassis at a remote location. To prevent tampering, each chassis may be disposed within a container or casing, and one or more switches 46 may be arranged on the respective casings so as to set off the alarm in the event of tampering. It will also be seen that the alarm will be set off if the connections l5, l6 and I! are opened, shortcircuited or grounded.

It may be desired to have a tell-tale indicator at each location. For this purpose, lamps 41 and 48, which may be neon pilot lamps, are serially connected along with a resistor 49 in shunt with the relay windings. Since the shunt path through the lamps 41 and 48 has very high resistance, it will not interfere with the operation of the relays.

Switches 56 and 5| may be provided to turn off the relay and indicator circuits while making adjustments or when the system is out of operation. These switches may be controlled together by means of a pick-proof lock and key.

Switch 2a may be used for final control of the system, to be turned on only when the lamps l! and 48 indicate that the system is ready for operation. This switch may also be operated by a pick-proof lock and key.

From the foregoing description, it will be seen that the invention provides a novel timing circuit which is capable of general use where it is desired to operate a device for a predetermined time interval in response to an initiating signal, and which is particularly adapted for operation of an alarm device.

While a preferred embodiment of the invention has been illustrated and described, it will be apparent that various modifications and other embodiments are possible without departing from the scope of the invention as defined in the appended claims.

I claim:

1. A timing circuit for controlling the operation of a device in response to an initiating signal, comprising a normally conductive grid-controlled electron tube for controlling said device, a relay controlled by said tube, a condenser adapted to receive an initiating signal, a resistor connected to said condenser, a second resistor connected to the grid of said tube and connectable to said condenser in parallel relation with said first resistor through contacts of said relay, whereby to establish a negative potential on the grid of said tube to render the tube non-conductive in response to said signal, a timing condenser connectable to said second resistor through contacts of relay, means for applying a negative potential to said grid through said timing condenser and for charging said timing condenser through said second resistor, whereby a negative potential is maintained on the grid of said tube for a predetermined time interval, and a discharging resistor connectable across said timing condenser through contacts on said relay.

2. A timing circuit according to claim 1, wherein said relay is energized when said tube is conductive, and the first and last-mentioned contacts of the relay are closed when it is energized while the second-mentioned contacts are closed when the relay is deenergized.

HARRY M. SIMONS.

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

UNITED STATES PATENTS Number Name Date 1,818,018 Stocker Aug. 11, 1931 1,921,461 Garstang Aug. 8, 1933 2,003,992 Cockrell June 4, 1935 2,061,011 Vingerhoets Nov. 17, 1936 2,165,048 Gulliksen July 4, 1939 2,321,662 Dodd June 15, 1943 2,366,060 Schneider Dec. 26, 1944 2,379,262 Terry June 26, 1945

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