US3453496A - Fire control intervalometer - Google Patents

Description

July l J. B. WRIGHT ET AL .A FIRE CONTROL INTERVALOMETER Filed March 28, 1968 IOP-gw h @Zan-uhm mmc James B.Wright Joy F. Honeycutt,

INVENTORS.

mowlw ATToRNEys United sees Patent o U.S. Cl. 317-80 5 Claims ABSTRACT OF THE DISCLOSURE A solid state controlled, electromechanical intervalometer which furnishes a preselected number of output pulses at a predetermined rate in response to an input command. The intervalometer has three `basic sections in its operation: (l) a control circuit, which initiates the vring and reset circuits and visually indicates the condition of the device at all times, (2) an oscillator circuit, which consists of relays and contacts for furnishing preselected output pulses and (3) a timing circuit, which consists of five individual time functions for the output pulses.

Dedicaory clause The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any roy alty thereon.

Background of the invention This invention relates in general to controlled timing of pulses for an airborne fire control device, and more particularly to an intervalometer for preselecting a number of ring pulses with controlled intervals for firing rocket pairs in ripple re.

Summary of the invention The present invention comprises means for furnishing a preselected number of output pulses at a preselected rate in response to an input command. This operation controls the number of rocket pairs tired when a fire cornmand button is pressed. The intervalometer will automatically tire the number of preselected pairs of rockets in sequence and then shut-off until an operator releases and then recloses the lire command button for another ripple of ring. The circuit can be preset to re l, 2, 3, 4, 6 or twenty-four rocket pairs or can be stopped at anytime in the selected cycle by releasing the fire command button. A digital counter coil keeps a running total of the number of rocket pairs red, allowing the aircraft operator to know the condition of the intervalometer at all times. The intervalometer has three basic sections in its operation: (l) a control circuit, which initiates the ring and reset circuits and visually indicates the condition of the device at all times, (2) an oscillator circuit, which consists of relays and contacts for furnishing preselected output pulses and (3) a timing circuit, which consists of ve individual time functions for controlling the number of output pulses furnished for ring rocket motor squibs.

It is an object of the present invention to provide a novel means of controlling the ring rate and num-ber of rockets tired by a fire control intervalometer.

It is another object of the present invention to provide automatic tiring means for ring rockets in a number of preselected pairs.

It is a further object of the present invention to provide a means for liring all rockets in a bank sequentially or to terminate ring of the rockets anytime in the cycle.

Other objects will be readily appreciated and the invention may be better understood by reference to the 3,453,496 Patented July 1, 1969 ice Brief description of the drawing The figure is a schematic diagram of the intervalometer of the present invention.

Detailed description of the drawing Refer now to the figure for a description of the circuit of the intervalometer. The intervalometer is contained in two units. One unit is located in a rocket armament panel 70fand the other unit is a stepping switch coil and its related contacts located in step switch unit 80. The armament panel 70 contains oscillator and timing circuits and various indicators of the control circuit. The step switch unit contains stepping switch 90, stepping switch coil 14 and its relay contacts along with arming relay coil 12. The condition of the intervalometer can Ibe visually observed on the front of the rocket armament panel at all times by an operator. Located on the front of the rocket Iarmament panel is a counter (not shown) that is actuated by counter coil 22 each time oscillator action fires a rocket pair, a safe lamp DS4, an arm lamp DSS, a zero lamp DS6 indicating the location of the stepping switch 90 in the zero position, and a `selector switch 30 that is manually set by an operator to tire a selected number of rocket pairs when fire command button 28 is pressed. Selector switch 30 can choose l, 2, 3, 4, 6 and twenty-four rocket pairs to be fired when the re command button is pressed. The counter indicates the number of ring pulses generated by the intervalometer, corresponding to the number of rocket pairs fired. Counter coil 22 is pulsed each time relay contact 20a cycles due to action of oscillator coil 20. Resistor R14 provides transient suppression for the counter coil.

The circuit is shown in the safe position as denoted by switch 52 being closed on the safe contact thereof. Switch 52 is directly connected to a positive voltage source at terminal 10. Lead 60 by-passes switch 52 and furnishes the positive voltage to one side of push-button 62 where a press-to-test check of lamps DS4, DSS and DS6 can be made in which burned out lamp elements can be replaced before the intervalometer goes into operation. When switch 52 is closed on the armed contact, arming relay coil 12 is activated by connecting the positive voltage source at terminal 10` to ground 50, through arming relay coil 12. When arming relay coil 12 is activated, relay contact 12a closes and relay Contact 12b opens, respectively connecting positive voltage source at terminal 10 to armed lamp DSS and disconnecting the positive voltage source from safe lamp DS4, thus lighting lamp DSS and turning lamp DS4 off. This gives the operator a visual indication of the intervalometer being in an armed condition. With relay contact 12a closed, the positive voltage source is available to the rocket ring circuits. The voltage is connected to the anode of rectifier CR3 and to one side of relay contact 20a. Relay contact 20a is controlled by oscillator relay coil 20, which will be discussed later.

A description of the control circuit, oscillator and timing or gating circuits will now be given` When re switch 28 is pressed, a positive voltage source, present at terminal 10, is connected on one 4side of fire relay coil 16 and timing relay coil 18. The other side of lire relay coil 16 is connected to ground `50, thus energizing the tire relay coil. Timing relay coil 18 will remain de-energized until SCRI is tired by timing out of the timing circuit, through rectier CRS, or when stepping switch reaches the zero position, indicating that all the rocket pairs have been fired. With re relay coil 16 energized, relay contacts 16a and 16C close, connecting the positive voltage present at terminal 10, through closed relay contact 12a,

rectifier CR3', closed relay contacts 16a, 18a and 20'b to ground S through stepping -switch coil 14 and to a wiper arm of stepping switch y90 through closed relay contact 16C. When stepping switch coil 14 is energized, stepping switch 90 cocks toward one of twenty-four sets of stepping switch contacts that are connected to twentyfour rocket motor squibs 92. With stepping switch coil 14 energized, switch interrupter contact 14a closes, energizing oscillator relay coil 20 from positive voltage source through closed relay contact 12a, CR3, closed contacts 16a, 18a and 14a. When oscillator relay coil 20 is energized, relay contact b opens, de-energizing stepping switch coil 14. Stepping switch 90 advances and interrupter contact 14a opens, de-energizing oscillator relay coil 20, completing one cycle of oscillation. This arrangement provides maximum oif time in stepping switch coil 14 'and stepping switch 90 duty cycle which aids in the accuracy of the number of rockets fired. This is because the signal to stop firing must yarrive while the stepping switch coil is de-energized, since the stepping switch advances on dropout of its coil rather than on pickup. The oscillator is free-running as long as the re command exists, and the timing circuit has not fired, opening the positive voltage supply. The frequency of oscillation is determined by the length of time that the dropout of oscillator relay coil 20 is delayed. The oscillator supplies a 6 cycle per second pulse to the stepping switch coil and to the rocket motor squibs 92. This time delay is determined by the oscillator relay coil 20 in parallel with resistor R9 and capacitor C4 which are in parallel with resistor R16 and potentiometer R15. When voltage from the positive voltage Source is applied on the hot side of the parallel network, oscillator coil 20 is energized. When the positive voltage source is removed from the hot side of the parallel network by oscillator action, oscillator relay coil 20 is held energized for a short time due to the charge stored on capacitor C4. Capacitor C4 will discharge through resistor R9, oscillator relay coil 20, resistor R16 and potentiometer R15. Potentiometer R15 allows this discharge time to be trimmed in order to adjust oscillator frequency.

The oscillator circuit consists of oscillator relay coil 20 and its set of contacts `and stepping switch coil 14 and its interrupter contacts. if the operator desires all twentyfour rocket pairs to be red, he can set the selector knob on the rocket armament panel to 24 (corresponding to the position of selector switch 30 as shown in the figure) and thus shorting the input to unijunction transistor Q1, allowing the oscillator to oscillate at 6 cycles per second until the zero position of the stepping switch 90 contacts is reached. Capacitor CS and resistor R10 form a differentiator which generates a positive pulse from terminal 10 through cam operated contact 90a, closed when stepping switch 90 arrives at the zero position. The positive pulse goes through rectier CR6 to ire silicon controlled rectifier SCR1, energizing timing relay coil 18 and opening relay contact 18a, stopping the oscillator. Diode CR2 provides a discharge path for capacitor C5. When light DS6 is lit, it indicates the location of the stepping switch wiper arm as being in the zero position. When the positive step input from the diierentiator is applied to the gate of SCR1, ring 'SCR1 into conduction, its anode voltage is essentially at ground potential, along with the side of timing relay coil 18` opposite the positive voltage source. With timing relay coil 18 activated, relay contact 18a opens the positive line to the oscillator circuit. Resistor R13 .and diode CRI compose a voltage regulator which prevents noise on the aircraft voltage supply from falsely triggering the timing circuit off.

The timing circuit allows for selection of six different numbers of rocket pairs, as desired, to be red on each ripple of tire. This is accomplished by firing uni-junction transistor Q1 with the voltage stored on capacitor C2. Capacitor C2 and serially connected resistors R7, R6, RS, R4 and R12 form RC time functions for operation of the timing circuit. Potentiometer R11 is used as a trimmer to oiset resistor tolerance variations. The six terminals of selector switch 30 are used to connect the six individual time functions `at the input of unijunction transistor Q1. Resistor R8, Zener diode CR4 and capacitor `C3 form a voltage regulator which provides a constant D-C voltage reference for the RC timers. Resistor R3 and normally closed contact 16b serve as a bleeder path to remove any stored charge from capacitor C2 when fire switch 28 is released. Resistor R1 furnishes temperature stabilization for transistor Q1. When unijunction transistor Q1 is red, a signal developed across resistor R2 is coupled to the gate of silicon controlled rectifier SCR1, through rectier CRS, -ring SCR1 and activating timing relay coil 18 and opening relay contact 18a. Capacitor C1 is initially charged and dumps additional energy into the circuit when the unijunction transistor fires to insure a gating on of SCR1. Thus, when a time equal to the RC time constant selected by selector switch 30 has lapsed, the number of 6 cycles per second pulses furnished by the oscillator has fired that many rocket pairs. An example is that of firing 6 rocket pairs by moving selector switch 30 to terminal 6 and, thus, connecting resistors R7, R6, RS, R4, R11 and R12 in series with capacitor C2. The time function of the serial connection of the above resistors and capacitor C2 is equal to one second, allowing 6 pulses to =be furnished by the oscillator to -re 6 rocket pairs. After SCR1 is fired, its anode voltage is essentially at ground potential, causing timing relay coil 1,8 to energize. When timing relay coil 18 is energized, relay contact 18a opens the positive line to the oscillator and oscillation ceases.

A cycle of ripple re will now be explained taking a ripple of 6 rocket pairs to be iired as an example. An operator can press push-button 62 for a press-to-test check to see that lights DS4, DSS, and DS6 are not burned out. When it is found that all bulbs are burning, switch 52 is switched to it-s armed contact, energizing arming relay coil 12, closing relay contact 12a and opening relay contact 12b. Arm lamp DSS will light by a positive voltage applied thereto and to the anode of rectifier CR3. A selector knob on the front of the rocket armament panel is connected to selector switch 30 and its wiper arm is positioned on terminal 6, representing a ripple of `6 rocket pairs to be tired. The intervalometer is now ready to control ripple firing of 6 rocket pairs when an operator presses re switch 28.

When fire switch 28 is pressed, lire relay coil 16 is immediately activated by positive voltage source 10 being connected through the coil to ground 50, while timing relay coil 18 is not connected to ground and thus remains deactivated. With re relay coil 16 activated, relay contacts 16a and 16C close and 16b opens. Relay contact 16C connects positive voltage source 10 to a wiper arm of stepping switch 90. Relay contact 16a connects positive voltage source 10 through rectifier CR3, contacts 16a, 18a and 20b to ground 50, through stepping switch coil 14. Stepping switch coil 14 is activated, closing relay contact 14a which applies positive voltage source 10 to one side of a parallel network including oscillator coil 20 and resistor R9 and capacitor C4 in parallel with resistor R16 and potentiometer R15. Contacts 90a, 90b and 90C are activated by a cam when stepping switch reaches a zero position and the action resulting will be explained later. With positive voltage source 10` connected to ground 50 through oscillator relay coil 20, the oscillator coil will be activated, thus closing relay contact 20a and opening relay contact 20b. When relay contact 20a closes, positive voltage source 10 is applied to counter coil 22. When relay contact 20b opens, positive voltage source 10 is removed from stepping switch coil 14, thus deactivating the stepping switch coil and opening relay Contact 14a. With relay contact 14a opened, positive voltage source 10 is removed from the parallel network including oscillator relay coil 20, and relay contacts 20a and 20b open and close again simultaneously. When positive voltage source is removed from counter coil 22, one count is digitally recorded and stepping switch coil 14 is activated to begin another cycle of oscillation.

Each time stepping switch coil 14 is activated the wiper arm of stepping switch 90 cocks and upon deactivation the wiper arm advances One of the twenty-four rocket motor squibs 92 will fire on advance of the wiper arm to the contact connected thereto. These oscillations and subsequent rocket motor squib firings will continue until a gating circuit activates timing relay coil 18, and thus removes the positive voltage source 10 from the oscillator circuit.

With oscillations of 6 pulses per second and 6 rocket motor squibs desired to be fired, the oscillator circuit will need to ybe activated for one second. As stated above, selector switch wiper arm was positioned on terminal 6 to obtain controlled firing of 6 rocket pairs. Positive voltage source 10 is connected to the timing function, consisting of resistors R8, R12, R11, R4, R5, R6 and R7 and capacitor C2, through rectifier CR3 and relay contacts 16a and 18a as long as relay contacts 16a and 18a are closed. Only two occurrences will interrupt this continuity. One is for the operator to release fire switch 28 and deactivates fire relay coil 16 before the 1 second of time elapses or for the 1 second of time to elapse and a charge at the input of unijunction transistor Q1 to become large enough to fire the unijunction transistor. When the operator keeps fire switch 28 connected for the 1 second, or more, then relay contact 18a will open, removing positive voltage source 10 from the oscillator circuit. A voltage developed across resistor R2 is coupled to the gate of silicon controlled rectifier SCRI, through rectifier CRS, firing SCRl and activating timing relay coil 18. Another means of firing silicon controlled rectifier SCRI is by a positive pulse connected to its gate through rectifier CR6 connected to the junction of resistor R10 and capacitor C5, where a positive pulse is formed when contact 90a closes.

The intervalometer can -be reset to the stepping switch zero position at any time by placing switch 52 in the safe position and pressing reset switch 26. Cam operated contacts 90a, 90b and 90e are as shown in FIGURE l when stepping switch 90 is in the zero position. However, when resetting back to the zero position, contact 90C will be cl-osed and contacts 90a and 90bv will be opened. When reset button 26 is closed, a positive voltage from terminal 10 will `be connected to one side of stepping switch coil 14 through closed contacts 90e and 20b, thus activating stepping switch coil 14 and closing relay contact 14a. With relay contact 14a closed, positive voltage from terminal 10 is applied to one side of oscillator coil 20, through closed contacts 90e and 14a. Oscillator relay coil 20 will be activated and relay contact 20b opened, removing the positive voltage from stepping switch coil 14, thus opening relay contact 14a. When relay contact 14a opens, the positive voltage is removed from one side of oscillator coil 20, deactivating the oscillator coil and reclosing relay contact 20b, and thus applying the positive voltage to one side of stepping switch coil 14 again. This cycle is repeated with stepping switch 90 advancing on a set of contacts each oscillation until the wiper arm moves to the zero position where a cam will close contacts 90a and 90b and will open contact 90C. Zero lamp DSG will light, giving the operator an indication that stepping switch 90 wiper arm is in the zero position.

The foregoing is considered as illustrative only of the principles of the invention. While a specific embodiment of the invention has been shown and described, other embodiments may be obvious to one skilled in the art, in light of this disclosure. The invention should be limited in scope only by the following claims.

We claim:

1. A fire control intervalometer comprising: an oscillator means; a power supply means, said oscillator means being free running with said power supply means connected thereto and generating a plurality of evenly spaced output pulses; a multistage stepping switch circuit means having a plurality of output contacts and a relay controlled input for sequential connection with said plurality of output contacts; a plurality of rocket motor squibs with inputs to said plurality of rocket motor squibs being connected to said plurality of output contacts of said stepping switch circuit means; a gating means, said gating means connected between said oscillator circuit and said multistage stepping switch circuit means for selectively passing a limited number of said plurality of output pulses from oscillator means to said relay controlled input to said multistage stepping switch circuit means; and a control circuit means comprising a firing and reset means and visual indicating means for indicati-ng the condition of Said fire control intervalometer at all times, said firing means connecting said power supply means to said oscillator means for generating said plurality of evenly spaced output pulses that relay switch said multistage stepping switch circuit means for supplying a plurality of sequential pulses from said output contacts of said multistage stepping switch circuit means to said plurality of rocket motor squibs.

2. A fire control intervalometer as set forth in claim 1 wherein said gating means comprises a plurality of time functions and a selector switch means having a plurality of fixed terminals and a movable wiper arm whereby said selector switch wiper arm is manually positionable on each of said fixed terminals to selectively choose the value of each of said time functions, said time functions being connected between said power supply means and ground for timing out said power supply means from said oscillator means and stopping said plurality of output pulses from said oscillator means to said multistage stepping switch and said plurality of rocket motor squibs.

3. A fire control intervalometer as set forth in claim 2 wherein said gating means further comprises a unijunction transistor having its input connected to said time functions.

4. A tire control intervalometer as set forth in claim 3 wherein each of said time functions corresponds to one of said selector switch fixed terminals where an additional resistor is placed in series with resistor-capacitor time functions for extending the time of build up for the input voltage to said unijunction transistor firing level.

5. A re control intervalometer as set forth in claim 4 wherein said gating means further comprises a control diode for controlling a silicon controlled rectifier that in turn controls a timing relay coil and said silicon controlled rectifier lhaving a gate that is connected to an output of said unijunction transistor for gating said silicon controlled rectifier on an activating said timing relay coil said unijunction transistor fires thus opening a relay contact to said oscillator means from said power source.

References Cited UNITED STATES PATENTS 3,311,788 3/1967 Paige 317-80 3,312,869 4/1967 Werner 317-80 3,316,451 4/1967 Silberman 317-80 3,133,231 5/1964 Faie et al 317-80 3,396,628 8/1968 Nash 89-1.814

VOLODYMYR Y. MAYEWSKY, Primary Examiner.

U.S. Cl. X.R.

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