IL27242A

IL27242A - Primerless explosive charge

Info

Publication number: IL27242A
Application number: IL27242A
Authority: IL
Original assignee: Usm Corp
Priority date: 1966-02-01
Filing date: 1967-01-11
Publication date: 1971-12-29
Also published as: BE693087A; DE1646330B2; DE1646330C3; GB1171338A; SE379038B; US3372643A; NL145483B; NL6701530A; FR1509565A; CH443999A; DE1646330A1; ES336661A1

Description

Primerless deflagrating charge CORPORATION invention relates to low formed and more particularly to a pellet or capsule for providing operating energy to a device upon its impact ignition and deflagration The invention is herein illustrated for use in manually explosively actuated hut is not necessarily thus it being recognized that various modifications may be desirable to alter the potential energy of a given charge or its rate of or to suit a particular ignition There is considerable need for a low and relatively stable explosive as energy source for various for instance portable tools for driving Hitherto a sensitive primer has been commonly used to initiate or the charge has been ignited by electrical or a rise in temperature effected by the compression of air or air with specially added gases or Such alternate approaches generally fail to provide simple means for or afford inexpensive energy compared to the use of a system employing impact ignition of low explosive in a substantially closed While there are a number of known and available low explosives for gunpowder and nitrated cellulose wherein the nitrogen content does not exceed about by it is important that the low especially for industrial be available in a easily handled that it be at least relatively perform uniformly over a wide range of prevailing tem eratures with redictable ener release and that it In the light of the foregoing it is a primary object of this invention to provide a charge of low explosive which is adapted to be safely yet easily deflagrated by a controlled impact and which shall have the favorable attributes above Another object of the invention is to provide this preferred charge in an advantageous form facilitating its ignition and further object of the invention is to provide a low explosive capsule requiring minimal energy to obtain its and which charge is entirely that will leave substantially no residue other than the gases evolved in d To these and in accordance with a feature of the present fibrous nitrated cellulose having a nitrogen content on the order of by weight is compacted and molded to an advantageous pellet shape from commercially available powdered the pellet retaining a porosity such that its density comes within the range of to grams per and having a thinner internal portion adapted to be crushed by impact to facilitate ignition and hence deflagration of the entire molded A further feature of the invention resides in providing a pellet molded of nitrocellulose as just described wherein the thinner portion mentioned is a central recessed web having the shape and size substantiall corresponding to the surface of a firing pin whereby the latter is enabled to initiate ignition by occludin within the ellet a predetermined limited amount Another feature of the invention as herein shown consists in the of a cellulose pellet of the type its base constituting the web thinner tha its surrounding cylindrical wall and having a slightly preferably central portion adapted to receive energy from a firing pin in a localized initial ignition invention is illustrated with reference to the accompanying in t is a perspective view of an exemplary molded pellet consisting of a low 2 is a diametric section of the shown in 1 and indicating not in true a thickened igniter and 3 is a diametric section of a modified explosive Referring first to 1 and there is shown a capsule or pellet low explosive having special merit when employed to supply energy to a for instance a fastener driving is meant that class of explosive materials which upon progressively burn or and the definition is intended to exclude those more highly sensitive explosive materials which have their ignition characterised as a phenomenon which occurs much more violently and at about the speed of sound or roughly times faster than usual In the form of the explosive charge shown in 1 and 2 the pellet has a generally cylindrical or body and a thinner base or The entire exclusive of any or various diluents and is molded from a nitrocellulose fibre powder having a nitrogen content in the range of from to by It is essential of course to take preventive precaution against premature explosion of any suoh but the fibrous cellulose powder while in the normal atmosphere of a room and in reasonably dry condition may be safely compacted to mold it into conveniently useful Ignition of a low explosive charge may be effected by direct mechanical impact therewith thus avoiding any for using a primer or other complex ignition and rendering an explosively actuated suck as a fastener more and Of particular so thoro is the fact that the relatively obdurate low explosive to be ignited by impact must be substantially confined so that only a limited amount of trapped preferably some surrounding and some within the charge is available for aiding ignition and insuring that gas then evolved builds up pressure conducive to deflagrating the entire explosive Accordingly the pellet 10 is desirably molded in a configuration to constitute an obturating liner for an ignition cavity wherein the explosive is to be the pellet shown in presuming a generally cylindrical ignition cavity of substantially corresponding A male forming die is selected to correspond substantially in shape and size at its central portion with a firing pin a protrusion on such a expected to be and would compact the charge material thus providing a central bore or recess in the pellet which is ultimately used to entrap a predetermined volume of air aiding in ignition ensuing In order to enable the formed charge to be ignited with only moderate impact the thin base has a thickened central igniter portion in this is raised to approximately double the thickness surrounding the portion This configuration is effected by a suitable corresponding recess in the end of the male The reduced central portion is shown as a truncated cone having a tapered wall 20 extending at about a angle between the base and the raised igniter or reduced central area adapted to be struck by a firing By way of example one pellet configuration according to the invention and adapted for use in a stud 9 driving tool has an outside diameter of approximately an inside diameter of approximately 4 an overall thickness of about 3 a minimum base thickness of about to mm and a raised igniter portion of about to Since it is probable that the mechanics which facilitates impact ignition of low explosive is assisted by air entrapped between the molded nitrocellulose fibres the molding process shoul compact the powder to the preferred form still retain a suitable range of pellet density for nitrocellulose fibre having a nitrogen content on the order of by weight being the order of about grams to grams per cubic for Solid has a density of per the raised igniter portion may be more porous and be expected entrap slightly more air than in the surrounding such entrapped air being advantageously available together with air compressed about the igniter portion in this critical locality for chemical decomposition when the pin kinetic energy absorbed in frictlonally crushing and initiating ignition in a space then enclosed by the pin end and the inside walls of the Referring now to a variant form of pellet 30 of low preferably having substantially the same chemical composition as referred to is provided intermediate height with a web having a thickness which is less than that of the surrouni ing wall with which it is web 32 may have a centrally thickened igniter portion shown in corresponding to that at 18 in 1 and but need not have such a This is because it is a feature of the configuration being described that its general symmetry and duplicate upper and lower face portions 34 avoid the problem of orienting each molded charge 30 to insure that one or the other face of the web 32 will pellet 30 probably not as precise as that attained with the pellet for most its precision is adequate though the molding dies will not be quite as simple and slightly greater kinetic energy may be needed in the firing Operation of the molded pellets described essentially the In impacting the web or the igniter portion in a percussion cavity of a tool or device to be explosively the firing pin moving axially in a pellet crushes the nitrocellulose fibres er has been received in the closely pellet walls forming the recess The body of the pellet 10 or 30 is adapted to closely fit the percussion cavity so that gas pressure generated will not prematurely displace the pellet or blow it It is believed that the impact action of the firing pin other equivalent striker closely fitting the recess 6 on the pellet is concomitant with an adiabatio pressure in the trapped and entrapped It has been ascertained from trials that given a certain potential the ignition facilitated by the provision of the reduced igniter portion 18 for localizing pellet the molded composition and structure of the charge as described is found to be economical and Its corrosive effect on steel commonly used is If the external walls of the pellet may be treated to shed water and 9 insufficientOCRQuality

Claims

1. . A primerless deflagrating charge for use in an explosively actuated device, said charge comprising a compacted body of nitrocellulose fibres having substantially interconnected interstitial spaces between the fibres defining continuous burning surfaces, said charge having a density less than 1.6 grams per cc. yet more than about 0,6 gram per cc, the compacted body of nitrocellulose fibres being in the shape of an annular pellet having a central recess adapted to serve as an igniter, the bottom of said recess being defined by a wall having a thickness less than that of the surrounding wall.

2. · A charge according to Claim 1, wherein the nitrogen in the nitrocellulose fibre is within the range of 12.75 to 13·75$# by weight.

3. A charge according to Claim 1 or 2, wherein the pellet is cylindrical and has an inner bore the bottom of which is determined by the igniter portion, the surface of said bore being smooth to cooperate in closely fitting relation with an impacting means.

4. A charge according to Claim 1, 2 or 3» wherein the igniter portion constitutes a closure for a cylindrical recess in the pellet.

5. A charge according to any one of the preceding claims wherein the igniter portion is thickened in one part thereof to facilitate initial ignition.

6. A charge according to Claim 4, wherein the igniter portion provides a flat external base for the pellet and has a central raised intex'nal part adapted to be initially impacted. 7« A charge according to any one of the preceding Claims, wherein the igniter portion is formed centrally as a truncated cone. For the Applicants DR. R3E I HOLD COHN AND PARTNERS