US2943673A - Flame thrower - Google Patents

Description

July 5, 1960 Filed May 27, 1945' c. HICKMAN 2,943,673

FLAME THROWER 2 Sheets-Sheet 1 CLARENCE N. HICKMAN Lg-M SW @AwKM W July 5, 1960 2,943,673

FLAME THROWER Filed May 27, 1945 ZS heetS-Sheet 2 CLARENCE N. HICKMAN 4 M S. W

Unite FLAlVIE THROWER Filed Mar. 27, 1945, Ser. No. 585,183

Claims. (Cl. 158-28) The invention described herein may be manufactured and used by or for the Government, for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a pressure system suitable for flame throwers, and more particularly to a multiple unit gas pressure generator arrangement for expelling an incendiary mixture from a closed reservoir.

In flame throwing apparatus, it is desirable that the stream of combustible liquid be projected by high pressures of the order of 400 psi. to obtain as much range as possible. It is also desirable that the gas pressure used to project the stream of combustible liquid be'fairly steady in order to avoid loss of range by falling pressures as the supply of combustible liquids diminish. Flame throwing apparatus usually includes a closed reservoir containing a supply of a combustible or incendiary liquid.

mixture, a nozzle connected to the reservoir, and a source of pressure such as nitrogen for expelling the combustible mixture from the reservoir through the nozzle.

As a result of my studies and experiments in the development of propellants for rockets, I have determined that the burning of propellant compositions, such as double-base powders, may be utilized as a source of gas under pressure suitable for expelling a combustible mixture from a closed reservoir. I have found that such propellant compositions may be used with safety to generate desired gas pressures within flame throwing apparatus. The proper selection and ignition of a series of relatively small amounts of rocket-type propellant compositions within the reservoir of flame throwing apparatus results in the generation of gas pressures which promote eflicient and controlled expulsion of incendiary liquid mixtures.

An important object of this invention is the provision of a flame thrower wherein a plurality of propellant charges are used to discharge an inflammable liquid under pressure through a nozzle.

A more specific object of this invention is the provision of a flame thrower wherein a plurality of electrically ignited rocket motors are used to discharge an inflammable liquid under pressure through a discharge nozzle, the rocket motors serving to build up discharge pressures in a container holding the inflammable liquid, and after the ignition of the first rocket motor, the remaining rocket motors, each being ignited in series, as soon as the discharge pressure in the container produced by the preceding rocket motor drops to a predetermined value.

Other objects of my invention will in part be obvious, and will in part appear hereinafter.

For a more complete understanding of the nature and scope of this invention, reference may be had to the following detailed description thereof, wherein:

Fig. l is a partly diagrammatic view showing a flame thrower including its control system, forming one embodimerit of the invention;

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Fig. 2 is an elevational view, partly in section, showing in detail the construction of a rocket motor unit that may be used in the embodiment shown in Fig. l; and

Fig. 3 is a fragmentary end elevational view of the unit shown in Fig. 2.

Referring to Fig. 1 of the drawing, a reservoir is indicated by the numeral 10'. The reservoir 10 is provided with a nozzle 11 through which a combustible or incendiary liquid mixture 12 is ejected against a desired target. Where the flame throwing apparatus is airborne by an airplane or the like, the nozzle 11 is directed oppositely to the direction of flight, The nozzle 11 may be provided with a blowout closure disc 13 retaining the combustible mixture 12 within the reservoir 10 until the apparatus is placed in operation. A valve or other suitable closure means (not shown) may be used in place of the blowout disc 13. The combustible mixture 12 fills the reservoir 10 to approximately the level indicated by numeral 14 p-rovidinga free space 15 within the reservoir above the combustible mixture, 1

The pressure generator assembly includes a closed housing 16 secured in the end of the reservoir 10 and an external electrical circuit for igniting units of combustible powder within the housing. The inner end of the housing 16 is provided with an upstanding outlet goose neck 17 extending into the free space 15 above the combustible mixture 12. A plurality of tubular rocket-type motors 18 are mounted within the housing 16. Each motor 18 encloses a grain or grains of combustible powder 19 suitably supported within the motor tube and provided with an electric igniter connected to the external electrical circuit. The powder 19 may be, for example, in the form of discs of double-base powder or may be in, the form of small cylinders of extruded double-base powder. The outlet neck 17 of the housing 16 is provided with a closure or blowout disc 20 which prevents access of the combustible incendiary mixture to the interior of the housing 16. A screen or trap 21 is secured within the housing 16 between the motors 18 and the outlet neck 17 to prevent burning powder from being swept into the reservoir 10 through outlet 17. A pressure relief safety outlet 28 extends from space 15 to the outside of reservoir 10 and is provided with a blowout disc 29 Referring particularly to Figs. 2 and 3 for a detailed description of the rocket motor unit, it will be seen that the cylindrical housing 16 contains sixteen rocket motors 18 symmetrically arranged in two concentric circles. The outer circle contains eleven motors and the inner circle contains five. The motors 18 are supported in a circular block 40 provided with a number of bolts 41 in its outer periphery for attaching it securely to the container 10 (Fig. 1);

Each rocket motor 18 comprises a tubular section 42 which, for the greater part of its length, is filled with powder grains 19 separated by collars 43. Each of the motors 18 is provided with a discharge nozzle 44 at its outlet end. The nozzles 44 are provided with outwardly directed discharge openings 45, and are closed with plugs 46. The tubular sections 42 abut against the support block 40 and are retained in place by sleeves 50. One section of each sleeve 50 is screwed into the end of a. tube 42 while the other section is screwed into the block 40. The rear end of each rocket motor 18 is closed by a plug 51 provided with a hexhead 52, a threaded section 53, and a sleeve section 54 telescopically fitting in the sleeve 50, as shown. Holes 55 are drilled in the plugs 51 to accommodate ignition wires for firing the rocket motors 18.

The electrical circuit for igniting the powder 19 in motors 18 includes a magnetic step switch 22, a pulser 30, a switch 31, a pressure controlled switch 23, a battery 24, and a manually operated actuating switch 25. The switch 23 is hydrostatically controlled by a Sylphon hydrostat 26 responsive to changes in pressure within the reservoir and is electrically insulated from reservoir 10. Switch 23 is preferably a micro-transfer switch so that the hydrostat 26 need not be a part of the electrical circuit. The step switch 22 includes a plurality of contacts 33 connected to the igniters of motors 18, and has an electromagnet 27 for shifting the switch arm 34 progressively from one contact 33 to the next, each time the magnet circuit is closed by the pulser 30. The switch 31 opens each time the step switch magnet 27 operates.

The pulser 30 is preferably operated by a motor 32 to intermittently open and close the circuit from the battery 24 through switch 25 to the micro-switch 23 to the step switch magnet 27. The pulser 30 also intermittently opens and closes the circuit from the battery 24 through switch 25 through switch 31 to step switch 22 to the igniters of the motors 18. The pulser 30 is operated at a speed to open and close these circuits about five times per second.

The mode of operation of the above described embodiment of my invention will now be given. Outlet nozzle 11 is initially closed by a blowout disc 13, safety outlet 28 is closed by a blowout disc 29, and the outlet neck 17 of housing 16 is closed by a blowout disc 20. The reservoir 10 is filled with a combustible or incendiary mixture 12, such as gasoline, thickened gasoline, or the like, to the level indicated by numeral 14. The initial pressure within the reservoir 10 is approximately atmospheric permitting the Sylphon 26 to maintain switch 23 in the upper closed position as illustrated, connecting the switch 22 with the pulser 30. When it is desired to generate pressure within the space to expel the mixture 12 outwardly through the nozzle 11 at a target, the key switch is manually closed. Closure of the switch 25 completes an electrical circuit from the battery 24 through pulser through switches 23 and 31 to switch 22 and thence to the igniter for one of the motors 18, the other side of the said igniter being grounded. An igniter being thus energized ignites the powder 19 in one of the motors 18. As the first unit or units of powder burn, the products of combustion build up a gas pressure within housing 16 causing blowout plug 20 to be ejected from outlet 17 causing a gas pressure to build up in space 15. This gas pressure causes the incendiary mixture 12 to force blowout disc 13 from outlet nozzle 11, and then forces the mixture to be expelled from the apparatus under high pressure. The expelled mixture may be ignited as it leaves the nozzle 11 by any suitable means provided on the nozzle, such ignition means not being a part of my present invention.

The pressure produced in space 15 by the burning of a unit or units of powder 19 within housing 16 causes the Sylphon 26 to move to an extended position breaking the circuit to the electromagnet 27 of step switch 22. Switch 22 shifts to the next contact when a decrease in pressure in reservoir 10 to about 350 psi. due to expulsion of some of mixture 12 causes the Sylphon 26 to shift switch 23 back again to the closed position illustrated, and the igniter of the next motor 18 is then energized. The burning of powder in the second motor 18 provides additional products of combustion to maintain the desired gas pressure in space 15 for the continued expulsion of mixture 12. The gas pressure generating cycle is repeated successively until all the powder units of the plurality of motors 18 are ignited and burned. The screen or trap 21 within the housing 16 prevents burning powder particles from being swept into the reservoir 10 through outlet 17. The outlet 28 serves as a safety device to relieve excess pressure in space 15, the blowout disc 29 being mounted to open in case the pressure in space 15 exceeds an allowable maximum pressure. The safety outlet thereby prevents damage to the reservoir and prevents the rupture of the reservoir which obviously might be extremely dangerous.

The products of combustion from the burning of powder 19 are not such as to ignite the incendiary mixture within the reservoir 10, chiefly because of lack of oxygen necessary to support combustion. The powder screen 21 prevents ignited powder particles from reaching the combustible mixture.

The apparatus illustrated may be made with any desired number of powder combustion motors 18. Sixteen motors 13 each containing two five-inch sticks of inch diameter powder are adequate to generate enough gas pressure to completely empty a 200 gallon reservoir at delivery pressures of the order of 400 pounds per square inch through a nozzle of 10 square inches in about 2 seconds.

The ignition arrangement providing successive ignition of a plurality of pressure generators in response to the pressure within reservoir 10 serves to maintain a reasonably constant pressure over the incendiary mixture thereby promoting a steady eflicient expulsion of the mixture through nozzle 11. If desired, the motors 18 may be ignited in groups at the start and the end of the expulsion process.

The flame throwing apparatus illustrated and described is particularly suitable for use on airplanes because of its light weight and simple actuating mechanism. Numerous variations and modifications of the embodiment illustrated will be readily apparent to those skilled in the art, the bounds of my invention being defined by the spirit and scope of the following claims.

I claim:

1. In a pressure generating assembly for use in expelling fiuid from a reservoir, the combination comprising a housing having an outlet adapted to be positioned in said reservoir, a plurality of rocket motors having outlet nozzles and being charged with combustible powder within said housing, an igniter adapted to be energized by an electric current for each of said powder units, and an electric circuit system for progressively firing each of said igniters by passing an electric current through said igniters and including a circuit breaker adapted to be opened and closed by changes in pressure in said reservoir.

2. In a pressure generating assembly for use in expelling fluid from a reservoir, the combination comprising a housing having an outlet adapted to be positioned in said reservoir, a plurality of combustible powder, rocket motors having a gas outlet nozzle within said housing, an igniter adapted to be fired by passing an electrical current therethrough for each of said powder motors, and an electrical circuit including a battery and an intermittently operated step switch for progressively energizing each of said igniters.

3. In a pressure generating assembly for use in expelling fluid from a reservoir, the combination comprising a housing having an outlet adapted to be positioned in said reservoir, a plurality of rocket motors having a discharge outlet in said housing and being charged with combustible powder, an igniter adapted to be fired by passing an electric current therethrough for each of said powder units, and an electrical circuit means operatively connected to said igniter and including a source of electricity, at pressure responsive circuit breaker adapted to be connected to the interior of said reservoir for making and breaking the flow of electricity from said source, and an intermittently operated step switch for successively connecting said igniters to said source of electricity to ignite said powder units progressively.

4. In a pressure generating assembly for use in expelling fluid from a reservoir, the combination comprising a housing having an outlet adapted to be positioned in said reservoir, a'rocket motor in said housing having a gas discharge outlet adapted to discharge the gaseous products of combustion within said housing and being charged with combustible powder, a screen between said powder unit and said housing outlet, and an igniter for energizing References Cited in the file of this patent g plowder r m f 1 UNITED STATES PATENTS n a pressure genera mg assem y or use 1n expe ling fluid from a reservoir, the combination comprising a 1 gggai "A S housing having an outlet adapted to be positioned in said 5 1304710 Seidler 1919 reservoir, a blowout disc normally closing said outlet, a fly/6:797 Case May 1921 rocket motor having a gas discharge outlet within said 463,518 Thomas July 1923 housing and being charged with combustible powder hav- 7 15 Gammeter Oct 9, 1 ing an igniter adapted to be fired by passing an electric 2,107,313 Urquhart Feb. 8, 1938 current therethrough for energizing said rocket motor. 10 2,253,601 Armstrong Aug. 26, 1941

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