US 2597641 A
Description (OCR text may contain errors)
y 20, 1952 E. H. HULL ET AL 2,597,641
PRESSURE-OPERATED STARTING DEVICE Filed Dec. 5, 1945 Inventors: Edwin Hull, Arthur F. Winslow,
Patented May 20, 1952 UNITED STATES PATENT OFFICE PRESSURE-OPERATED STARTING DEVICE Edwin H. Hull, Schenectady, and Arthur F. Winslow, Scotia, N. Y., assignors to General Electric Company, a corporation of New York Application December 3, 1945, Serial No. 632,548
Claims. (Cl. 102-39) bustion of a powder charge is employed for starting from rest or powering devices, such as gyroscopes, single stroke pistonand cylinder-devices, electric circuit breakers, and, in general, devices which are intended to be put into operation in a fraction of a second or. are intended to be run for short periods. Such devices are subject to damage if the burning of the charge occurs with too great violence.
In accordance with our present invention we have provided a novel combination of large-sized, slow-burning powder pellets in combination with externally afiixed discrete, small grains of fasterburning powder. In accordance with a feature of our invention, we have provided a combustion device for burning such pellets in combination with means for restraining movement thereof when ignited.
Apparatus embodying our invention is illustrated: by the accompanying drawing in which Fig. l is a vertical section of an ignition and combustion device; Fig. 2 is an enlarged sectional view of the combustion chamber showing a charge in operative position; and Figs. 3 to 6 illustrate modified powder pellets.
The apparatus shown in Fig. 1 comprises a channel-shaped combustion chamber I which is connected by a conduit 2 to a device 3 which is to be rapidly energized by gas under pressure. As such device may assume various forms, and itself is not a part of the present invention, it has been merely indicated in the drawing. The conduit 2 terminates in a conical perforated diaphragm 4, herein termed a grate, providing spaces through which the gaseous combustion products enter the conduit 2. Above the grate is located a frangible diaphragm 5 which is ruptured if excessive pressure should be generated, thereby venting the excess pressure into a relief conduit 6. The diaphragm 5, which may consist of steel, or brass, or any non-brittle metal, is provided with a depressed ring-shaped channel I which weakens the resistance to excessive internal pressure of the diaphragm. Exessive internal pressure will cause the diaphragm to bulge and finally to be ruptured at a region inwardly spaced from the edge of the restraining wall of the conduit 6.
Into the combustion chamber communicatingwith the conduit 2 through the orifices of the grate is inserted a cartridge 8 which may consist of a 12-gauge standard brass case having a crimped end 8 and containing propellant pellets 9 of combustion material. The pellets 9 may consist of a single base" smokeless cannon powder and, in general, of a colloidal nitrocellulose, or may consist of a double base smokeless powder, such as cordite, comprising mixtures of nitrocellulose and nitroglycerine. The pellets also may consist of nitrocellulose powders, either single or doube base, mixed with other ingredients such as oxidizers and metals. The pellets may consist of the so-called rocket powders which are mixtures "of tars or rubbers with oxidizing agents, such as perchlorates of ammonium or potassium, and a plasticizer.
The pellets of propellant, smokeless powder burn at the rate of about .2 inch per second per thousand pound pressure per square inch of surface, the rate of burningincreasing with the pressure at about the .9 power. If such pellets were packed in a cartridge in direct contact with an ignition means, such as a primer, a too sudden burning of the pellets with accompanying gasification might result in damage to the apparatus.
. Uncontrolled ignition is one of the major difficulties in using large-grained smokeless powder.
The usual ignition method is to use a burst of flame from a charge of black powder or other ignition device. Uneven ignition of the powder grains or pellets often results from such ignition due to the geometry of the grains, method of packing in the container, etc.
When the pellets are coated as described hereinafter, all of the pellets are ignited on all surfaces in a short finite time in a repeatable manner.
If the powder pellets were allowed to come into direct contact with the primer, they might be split by the primer explosion. If the powder pellets were allowed any freedom of motion inside the cartridge or combustion chamber, they might be blown against the grate and be split, resulting in too rapid combustion as well as damaging of the grate.
In accordance with a feature of our invention, the pellets 9 are urged into contact with the grate 4 by a spring I0 which is partly compressed against the end wall II when the cartridge is inserted, and urges the pellets against the crimped end 8 of the cartridge. A breech plug I2 holds the cartridge in place and compresses the spring upon insertion of the cartridge, as shown in Fig.
1. In a perforation of the wall I I of the cartridge is inserted a percussion cap l3 (Fig. 2). A firing pin l4 explodes the cap when the firing pin is struck at its exterior end.
In Fig. 1 is shown a magnetically released spring-operated hammer mechanism l5 for striking the firing pin. A magnet l6 trips the latch 11 when the energizing circuit i8 is closed, as by the operation of a push button 25. The spring-operated latch II, when released, trips the hammer 15 which is set under spring tension, as indicated. The hammer strikes the firing pin 14 and causes it to detonate the percussion cap l3. The blast of flame from the exploding cap l3 ignites the fuel pellets 9.
As shown in the drawing, pellets 9 are coated with small grains of a faster-burning, more easily ignited powder. The igniting grains adhering to the surface of the powder pellet, which are indicated in the drawing by stippling, are distributed over the surface of the pellet. The grains may consist of an easily ignitible substance such as conventional pyro-technic ignitors. They may consist, for example, of ordinary black powder, modified black powder, of a mixture of an organic oxygen-bearing substance and a suitable quick-burning fuel, of a fibrous form of nitrocellulose or semi-colloidal nitrocellulose commonly called blank fire, smokeless powder, or of a very finely divided colloidal nitrocellulose (smokeless powder). The .relatively massive, dense powder pellets 9 are. provided with a frosting of adhering grains of the faster-burning powder. Adhesion of the grains to the powder pellets is insured by coating the pellets with an ignitible adhesive, such as cellulose nitrate dissolved in a volatile solvent, as, for example, aeetone, or the large grains may be dipped in acetone to provide a sticky surface. Upon partial evaporation of the solvent, the still sticky pellets have the quick-burning powder grains applied in any suitable manner. The exterior frosting of quick-burning powder starts combustion of the slower-burning, less-ignitible large pellets even though they are positioned at some distance from the igniter cap 13. In some cases it is desirable to provide a single hollow combustion pellet of greater length, as shown in Fig. 3, in place of a plurality of pellets, as shown in Fig. 2. The powder stick shown in Fig. 3 has a longitudinal aperture as indicated.
In other cases it is desirable that combustion of a massive powder grain should be regulated so that combustion occurs at part of its surface only. In Fig. 4 are shown in section two powder pellets 20, 2! placed end-to-end. The side surfaces are coated with a flame-excluding material 22 which may consist of conventional friction tape. The end surfaces are uncoated. Grains 23 of fast-burning powder, such as above described, are affixed upon the external surfaces of the ends of the pellets 20, 2| and upon the exterior'exposed surface of the tape. If the grains 23;are ignited, as by a percussion cap, suchas shown in Fig. 2, they act as a fuse to carry the ignition to the exposed end surfaces of the pellets 20, 21 which are consumed endwise only, thereby slowing down their combustion.
The pellet 24, Fig. 5, is coated with ignitionexcluding material, such as a suitable tape, except for-one exposed end surface. Grains of fastburning, easily ignitible powder are affixed upon the entire exterior surface but ignite the pellet only at its exposed end surface. In Fig.6 a pellet of powder is shown which is coated with ignitionexcluding material except for an end surface which is the only surface coated with grains of fast-burning powder. This coated surface will become ignited by the cap 13 to which it is juxtaposed in a cartridge, the remaining surfaces being shielded from ignition.
Regardless of the number or shape of the combustion pellets, they should be held fixedly against the grate, as by a compressed spring 10. A closure pad 19 of nitrocellulose, or other suitable combustible material, preferably is interposed between the grate and the combustible pellet or pellets. In some cases the grate may be omitted, as when the cartridge is to be used for propelling a projectile (not shown).
In order to obtain the best efiiciency, it is desirable to have the combustion chamber volume relatively small and to employ high pressures of the order of 15,000 to 25,000 pounds per square inch. Three solid pellets of smokeless powder, such as shown in Fig. 2, about 0.672 to 0.675 inch in diameter and having a total length of 1.9 to 2.2 inches, are desirable for use with a nozzle having a throat diameter of about 0.05 inch. The combustion of the charge delivers gas at a pressure within the specified range over a period of about 0.2 to 0.3 second. If a somewhat lower pressure range of about 10,000 to 15,000 pounds per square inch is desired, an elongated, apertured, cylindrical stick of smokeless powder is desirable. Such a stick, which is shown in Fig. 3, may have a diameter of about 0.672 to 0.675 inch and an aperture of about 0.082 inch.
What we claim as new and desire to secure by Letters Patent of the United States is:
1. A massive pellet of projectile-propellant powder, a flame-excluding layer of material covering part of the surface of said pellet and closely adjacent, discrete grains of fasterburning powder affixed to surfaces of said pellet including the entire outer surface of said flameexcluding layer.
2. A cartridge consisting of a casing which is open-ended and crimped at one extremity and is closed at the opposite extremity, a propellant charge therein, a primer and means between said primer and said propellant charge for urging said charge against the crimped end of said casing.
33. A cartridge comprising a tubular casing having at one extremity an end wall having an orifice, an ignition cap mounted in said orifice, said casing being open at the opposite extremity and provided with an abutment, a propellant charge in said casing and a spring mounted in said casing adjacent said end wall for urging said charge against said abutment.
4. A starting device for apparatus intended to be put into motion quickly comprising the combination of a combustion chamber having a volume so restricted that the combustion in about 0.2 to 0.3 second of three pellets of smokeless powder each having a diameter of about 0.672 to 0.675 inch and a total length of about 1.9 to 2.2 inch will produce thereingas at a pressure in the range of about 15,000 to 25,000 pounds'per square inch,.an open-work grate at one end of said chamber, means for urging a powder pellet against said grate, and independent means for igniting said pellet located at the opposite end of said chamber.
5. The combination of a combustion chamber, a grate at one end of the chamber, a pellet of propellant material in said chamber, one end of which is held in contact with saidgrate by a spring interposed between the other end of said pellet and the opposite end of said chamber and means for igniting said pellet, said igniting means being located at said opposite end of said chamber. 5
EDWIN H. HULL. ARTHUR F. WINSLOW.
REFERENCES CITED The following references are of record in the 10 file of this patent:
UNITED STATES PATENTS Number Number Germany Aug. 5, 1930