US2000617A - Electric time fuse - Google Patents

Description

M y 1935- 7 K. SCHAFFLER-GLGSSL 2,000,617

ELECTRIC TIMEFUSE 7 Filed Feb. 21, 1953 vaqg [rm/anion- I ented May 7, 1935 "IED VJVSTAA'TES e 2.000.617 me e TIME FUSE Konra,d Schafller-Gliissl, Vienna, Austriav view, and of which no one can be omitted without impairing the efllcacy of the others. 'I'he inven-' tion relates more particularly to'electric time fuses of the type comprising a charge of a re-.

tarding composition tor the purpose of efiecting the timing.

.One of the above mentioned' measures is the provision of a match head which, while being capable of easy electric ignition, generates, at the last stage of the combustion an intense heat withmuch gas generation and will ensure ignition of the retarding charge even if the latter should be difilcult to ignite. In this respect the intention consists in coating the core of the match head with a layer of. metal powder mixed with an oxygen carrier. a

Reliable ignition of the retarding charge is further ensured according to the invention by enclosing said charge in a cylinder presenting to the match head a tapered end whereon the heat is concentrated.

A further measure essential for the attainment of the object of the invention is the use of a retarding charge which will burn at a slow regular rate and which can be stored without degeneration, and in this respectthe invention consists in forming the charge from iron powder the particles of which are coated with a neutral, readily adhering substance such as chalk or the like, and mixed in coated condition with an oxygen carrier. The attainment of the object of the invention is further conditional onthe provision of an herinetic closure for the different charges so that the internal gas .pressure will remain high and without fluctuations, in order that the combustion or the retarding charge may proceed with the desired speed and regularity. In this respect the invention consists in closing the fuse car.- tridge with a plug of lead or other compressible material and sealing said-plug to the cartridge case and to the leading-in wires by pressing circumierential 5 and substantially. continuous grooves into the case and the plug. Experience has shown that any leakage of gas from the fuse, and consequent reduction ofthe internal pressure, during the combustion of the delaying charge, affects the rate at which the latterburns and consequently upsets the timing of the fuse.

. closing plug 6' and which supply current for ignit- Application February 21, 1933, Serial No. 657,786 a l -In Austria June 17,1932 I 1 j invention relates to an electric timeiuse and has for its object to enhance the reliability of timing and ignition 01' such fusesunder'all; possible working conditions. To'attain this ob- .iect it has been found in practice tosbe essentialto adopt a. combinationof measures which contribute jointly to the achievement of the aim in" The invention isillustrated in the accompany- V ing=drawing which represents a vertical section .oi an electric'time iuse according to the invention. f

' The ruse comprises a cartridge case I contain-f 5 ing amatch head 2 and a retarding .charge 5. The match head is carried by electric leading-in wires 1 which enter the cartridge through a ing the match head. 1

. According to the invention the match head comprises a core of easily ignitable material which immediatelysurrounds the fuse wire, and an outer coating 3 capable of generating an intense heat. The coating consists of a metal powi5 der of iron, aluminium, zinc,.antimon y, zirconi um, or the like mixed with an oxygen carrier in the form of a chlorate or nitrate, for instance potassium chlorate or barium nitrate. A mixture in about equal proportions of metal and oxygen 20 carrier has been shown to give the best results. Several. metals can be usedtogether.

In order to concentrate the heat generated by the match head on the forward end of the retarding charge 5, the thick wall of the surrounding 25 cylinder 4 istapered at the end which faces the match head, as shown in the drawing. By this arrangement the extreme end of the charge will be surrounded by a ring of insulating air, and heat which would otherwise be dissipated through the cylinder I and through the cartridge case, will be available for ensuring a reliable ignition of the retarding charge. v

For the. retarding charge a mixture of iron powder and an oxygen carrier, for instance potas- 5 sium permanganate, is employed. Since the potassium permanganate has a strongly oxidizing influence on the iron which would be detrimental to prolongedstorage and since it also causes the iron to burn too rapidly with considerable heat generation, is necessary to add a neutral substance which will check oxidation and retard the combustion. For this purpose the iron powder is mixed with a phlegmatizing substance," for instance chalk, capable of enclosing and adhering to the iron particles. The iron powder is mixed with the chalk before the oxygen carrier is added. Treated in this manner the iron will be protected from over-rapid oxidation, and 50 the charge will burn slowly anduniiormly, very little heating of the cartridge will'take, place, and

premature ignition of the explosive charge will be prevented. A suitable mixture is obtained case.

finely ground chalk, and 30 parts potassium permanganate Since the speed of the combustion is dependent on the gas pressure in the cartridge, it is essential to maintain the pressure free from fluctuations owing to leakage through the cartridge For'this purpose the closing plug 6, which is made of lead or other compressible material, is hermetically sealed to the cartridge case by pressing circumferential and substantially continuous grooves 8 into cartridge case and plug. 1 This compression of the plug is made so that a simultaneous hermetic sealing of the plug to the leading-in wires 7, will be effected.

I claim:

1. An electric time fuse comprising in combination a fuse case open at one end and closed at the other end, lead-in wires, a plug of yielding material longitudinally traversed by the said lead-in wires and adapted to form a closure of the open end of the saidrcase without any leakage, an electrically fired match head attached to the said wires and coated exteriorly with a mixture of metal powder and an oxygen carrier, a charge of a retarding composition composed of iron particles coated with a neutral phlegmatizing substance and mixed with an oxygen carrier, a shell containing the said retarding composition closely fitting within the said fuse case and having its end nearest to the said match head taperedly reduced in thickness of wall, and a priming charge located between the outer end of the said shell and the closed end of the fuse case, substantially the case.

3. In an electric time fuse as claimed in claim I the said retarding composition consisting of iron} particles coated with chalk and mixed with po-j tassium permanganate. 7

4. In an electric time fuse as claimed in claim 1 20 the said retarding composition consisting of iron particles coated with chalk and mixed with potassium permanganate, these ingredients being used in the proportions of 15:3:30 respectively.

KONRAD SCI-IAFFLER-GL6SSL.

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