Intervalometer For An Illumination System

Abstract

An electrical intervalometer for a battlefield illumination system wherein an electronic impulse fires a flare and also controls the time interval for the firing of subsequent flares with the further ability of interrupting the firing sequence and then resuming firing at the aforementioned time intervals.

Description

BACKGROUND OF THE INVENTION

This invention relates to intervalometers, and more particularly to an intervalometer for a battlefield illumination system.

There has been in the past limitations relating to base perimeter defenses. In one version of an illumination system there were utilized powder initiators for starting the sequence of flares and powder fusing for timing. The system had to be started manually and the interrupt ability was limited. It was necessary to have an operator near the flare package, which emitted a flash and an explosion when a flare was launched. This could pinpoint its location in the dark and could possibly draw hostile fire. There was also a remote danger of an explosion if a malfunction occurred and all of the propellants ignited at once. Also, in the prior art, there are systems which perform a similar function. However, these systems utilize electromechanical devices and powder trains. The present invention is an all-electronic system making it possible to be keyed in electronically with any variety of security devices or area defense systems.

SUMMARY OF THE INVENTION

The present invention is an electronic intervalometer for a battlefield illumination system. In particular, the system provides an electrical impulse to fire a flare and also controls the time intervals for the firing of subsequent flares. The essential components of the system are an intrusion switch latch, an interval clock, a pulse generator, a one-shot multivibrator, a delay circuit and a shift register. In operation, when the intrusion switch latch is triggered, an initial flare is fired; thereafter, flares will be fired automatically at predetermined intervals until the supply of flares is exhausted or the sequence is interrupted.

The illumination system is a flare package which was designed for use with base perimeter defense systems and can be interfaced with those systems. It can also be used without intrusion detection systems; for example, by a sentry in an outpost. When connected to intrusion equipment it can be left unattended. The firing sequence can be manually interrupted in case of a false alarm confirmed, saving the remaining flares. It can also be fired manually, in case the operator suspects an intrusion without an alarm given. The apparatus is completely self-contained.

An object of the present invention is to provide an intervalometer for an illumination system wherein an electrical impulse fires a flare and also controls the time interval for firing subsequent flares.

Another object of the present invention is to provide an intervalometer for an illumination system in which the firing sequence for flares can be manually interrupted.

Yet another object of the present invention is to provide an intervalometer for an illumination system which permits initiation and sequencing for a ground-based ordnance dispenser.

The various features of novelty which characterize this invention are pointed out with particularity in the claims annexed to and forming part of this specification. For a better understanding of the invention, however, its advantages and specific objects obtained with its use, reference should be had to the accompanying drawings and description matter in which is illustrated a preferred embodiment of the invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a preferred embodiment of the flare firing intervalometer system of the present invention;

FIG. 2 shows a diagram in block form of the shift register of FIG. 1;

FIG. 3 shows a schematic diagram of the components of FIG. 1 excluding the shift register and firing circuits; and

FIG. 4 shows a schematic diagram of one of the twelve firing circuits.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Now referring in detail to FIG. 1, there is shown logic power switch 50. Upon closing switch 50, power from power source 51 is supplied to one-shot multivibrator 52, one-shot multivibrator delay 53, and shift register 54. The purpose of one-shot multivibrator delay 53 is to hold the output of one-shot multivibrator 52 to prevent it from triggering shift register 54 during the supply voltage (power) turn-on time.

The second step is to close firing circuit power switch 55. This supplies power from power source 56 to 12 firing circuits represented by block 57. Switch 50 is closed before switch 55 to prevent the firing circuits from being triggered by a transient output from shift register 54 which could occur during supply voltage (power) turn-on. Sequence interrupt switch 58 is a normally closed switch, and local firing switch 59 is normally open. Switch 58 and switch 59 are held in their normal positions by switch covers.

With switches 50 and 55 closed, power is supplied to one-shot multivibrator 52, one-shot multivibrator delay 53, shift register 54, and firing circuits 57. The system is in a standby mode at this point. Intrusion switch latch 60, which is a silicon controlled switch (SCS), PNPN device, acts as a blocking diode until it is triggered, then it acts as a holding relay. When intrusion switch terminals 59a and 59b are shorted either by a remote device connected across to terminals 59c and 59d or by closing local firing switch 59, silicon controlled switch turns on. Power is then supplied to initial pulse generator 61 and interval clock 62. Initial pulse generator 61 triggers one-shot multivibrator 52 which triggers shift register 54 to its first output. The output number one of shift register 54 goes from 0 to -9 volts which triggers firing circuit number one which is contained in block 57. Block 57 includes 12 separate firing circuits, each receives a separate input from shift register 54. The first squib in the flare package is ignited by the number one firing circuit. The silicon controlled switch also provides power to interval clock 62. Thirty seconds after one-shot multivibrator 52 is triggered by initial pulse generator 61, one-shot multivibrator 52 is triggered by interval clock 62. One-shot multivibrator 52 then triggers shift register 54 to its second output, which triggers the second firing circuit in block 57 and fires the second squib. This process will continue until 12 flares have been fired. Shift register 54 will continue to cycle and the intervalometer should be turned off after the 12 flares have been fired.

If it is necessary to interrupt the sequence at any time, the firing can be stopped by momentarily opening switch 58. This commutates the silicon controlled switch and cuts off power to interval clock 62 and initial pulse generator 61. When switch 58 is closed again, the silicon controlled switch will remain turned off until switch 59 is closed again, or terminals 59c and 59d are shorted. The memory is held by shift register 54 as long as switch 50 remains closed.

If, after having been interrupted, the intrusion switch is shorted, or switch 59 is closed, the silicon controlled switch will turn on, causing a flare to be fired immediately by the same sequence as previously explained. The flares will continue to fire at 30-second intervals until the flares are exhausted, or the sequence is interrupted.

Now referring to FIG. 2, which is a block diagram of shift register 54 of FIG. 1, it is comprised of 12-bit shift register 70 and two gated buffers 71 and 72. Shift register 70 is a General Instrument Serial-In Parallel-Out MEM 3012SP. The buffers are General Instrument 6 channel multiplexers, type MEM 2009.

Supply voltage for shift register 70 enters pin N. Supply voltages for buffers 71 and 72 enter pin C and ground is pin X.

When the system is first turned on, that is, when switch 50 of FIG. 1 has been closed and the alarm has not been tripped, the readings are:

Pin C- 24 volts (approx)

Buffers pins 9 to 14, and shift register pin 8a- 23 volts (approx).

If the potential at pin 8a of the shift register is 0 to -2 volts, no data input will result. If the potential exceeds -2 volts, in the negative direction, a data input will result. For the shift register to begin operating a data input voltage must be present at the time a clock pulse is applied at lead 10a of the shift register.

The outputs of the shift register are at zero potential at the beginning of the operation. When the first clock pulse occurs, the shift register takes the data input and shifts it to the first output, pin 7a of the shift register, pin 1b of the output. The reading of the output is approximately -8 volts. The gated buffer takes this output and lowers the potential at pins 14 to 9 of the buffers and pin 8a of the shift register to less than -2 volts. This is the purpose of the gated buffer, that is, to keep one bit at a time in the shift register.

Occasionally, some gates in the buffer differ in drain-to-source resistance (R.sub.D-S ) and allow the potential at pin 8a of the shift register to exceed -2 volts. This allows another bit to enter the shift register and follow the first bit. The second bit will not interfere with the operation of the intervalometer, since the first bit is the one that will fire the flares.

After the first clock pulse, the voltage readings are ##SPC1##

After the second clock pulse, the leading bit moves along and is read at 2b through 12b according to the clock pulse.

Now referring to FIG. 3, there is shown a schematic diagram and the interconnections of the components of FIG. 1 with the exception of firing circuits 57 and shift register 54. The schematic of interval clock 62 is shown as 62a, of initial pulse generator 61 as 61a, intrusion switch latch 60 as 60a, of one-shot multivibrator 52 as 52a, and of one-shot multivibrator delay 53 as 53a. R.sub.4 shown in schematic 62 a is a variable resistor. The nominal 30-second interval can be adjusted by means of R.sub.4 over an adjustment range of .+-. 6 seconds.

Referring to FIG. 4, there is shown the schematic of one of the 12 identical firing circuits included in block 57. The shift register output triggers the circuit through point B. The trigger at the anode gate of silicon controlled switch Qa, a 3N81, turns on the silicon controlled switch. The step waveform is current limited by resistor R.sub.c and differentiated by capacitor C.sub.b. The differentiated pulse turns transistor Q.sub.b, a 2N4305, , on, and the transistor conducts and produces a waveform which has a period of approximately 20 milliseconds. The pulse travels through limiting resistor R.sub.e out through point E, through a cable to the squib and returns through a common line to point D. It is noted that any conventional pulse controlled firing circuit with the proper current capacity may be utilized.

The system of the present invention will fire a flare every 30 seconds after the first immediately fired flare, for a total of 12 flares. The sequence can be interrupted at any time by operating a switch. After the sequence has been interrupted, the system will fire a flare immediately when started again, and also to resume firing at 30-second intervals. This interrupt and restart ability is immediate, even if the 30-second cycle has not passed since the previous flare was fired.

Claims

We claim:

1. An electronic intervalometer for an illumination system comprising an initial pulse generator providing a single initiating pulse output upon receiving actuating power, an interval clock providing a pulse output at preselected time intervals also after receiving actuating power, a one-shot multivibrator receiving said pulse outputs from said initial pulse generator and interval clock, said one-shot multivibrator providing a pulse output for each pulse input, a shift register having an input connected to the output of said one-shot multivibrator, and further having a multiplicity of outputs, each of said shift register outputs providing a firing pulse in sequence in accordance with the receipt of an input pulse, a multiplicity of flare firing circuits, each having an input corresponding to an associated output from said shift register, a first power source, a first switch, connected to said first power source and upon closing thereof operating to supply actuating power to said one-shot multivibrator, and said shift register, a silicon controlled switch acting as a blocking diode until triggered then acting as a holding relay, a second switch, normally closed, interconnecting said silicon switch with said first power source by way of said first switch, and a third switch, normally open, shorting said silicon controlled switch to ground upon closing thereof and thereupon operating to actuate said silicon switch to provide power to said initial pulse generator and said interval clock.

2. An electronic intervalometer as described in claim 1 further including a second power source, and a fourth switch, said fourth switch upon closing thereof supplying power to said flare firing circuits.

3. An electronic intervalometer as described in claim 2 further including means to delay the output pulse from said one-shot multivibrator to said shift register to hold the output of said one-shot multivibrator to prevent triggering said shift register during turn-on time of said power.