US1825224A

US1825224A - Safety fuse

Info

Publication number: US1825224A
Application number: US432086A
Authority: US
Inventors: Henry E Ellsworth
Original assignee: ENSIGNBICKFORD CO
Current assignee: ENSIGNBICKFORD CO
Priority date: 1930-02-28
Filing date: 1930-02-28
Publication date: 1931-09-29
Anticipated expiration: 1948-09-29
Also published as: GB374032A; FR712281A

Description

Sept. 29, 1931.

By tlorneys,

Patented Sept. 29, 1931 narran stares rarsnrerrics 't HENRY E. ELLSWORTH, OF SIMSBUEY, CONNECTICUT, ASSIGNOR T THE y ENSIGN- BICKFORD CO., OF SIIVISBURY, CONNECTICUT, A CORPORATION' OF CONNECTICUT."

SAFETY FUSE Application filed February 28, 1930. Serial No.l 432,086.

The present invention relates to safety fuse, to products made from or embodying such fuse and to the manner of using ther same.

,- An object of the invention is to provide a new and improved type of weatherproof safety fuse. A further object is to provide safety fuse which may be readily primed with a composition to assist in the easy ignition of the fuse. A still further object is to provide a very slow burning fuse of unliform burning rate. A still further Objectis to employ such fuse cut into short lengths as delay elements for use in electric blasting 15 caps, which delay elements may be vprimed at one end if desired.

According to th-e present invention I accomplish the foregoing and other objects by pioviding safety fuse consisting of a core 2g of inflammable material enclosed Within a fibrous or cellular covering, and the resulting fuse enclosed within a covering of impervious material'.A Preferably the inflammable material is a slow burning powder;

the fibrous covering, a textile which is woven or wrapped around the powder core; the covering of impervious material, a metal such as lead, tin, aluminum or the like,

' which is closely fitted over the textile mate- ,30 rial to reduce to a minimum or` entirely eliminate air spaces between thebutside of the textile covering and the inside of the metallic covering. This fuse can be used in the conventional manner or it may be cut into short lengths and primed with an easily ignitable compound to provide delay elements for velectric blasting caps. Y

The invention will be better understood from the detailed description which follows e0 and the accompanying drawings, wherein Figure l is a longitudinal, diametrical section through a. portion of safety fuse embodying the present invention.

Fig. 2 is a transverse section of the safety fuse taken substantially along the plane of the line 2 2 of Fig. 1.

Fig. 3 is an elevation partly broken away of an application of the safetyV fuse of the present invention to form what is termed a delay element.

.Fig 4l is a longitudinal, diainetrical section of an electric blasting cap Vwhich embodies a delay'element shown' in Fig. 3.

Referring first to Figs. l and 2 of4 the drawings, the safety-fuse consists of alcore A of slow burning powder which is enclosed in a wrapping orcovering Bof textile.

fabric preferably formed ofjute and cotton yarns. The elements A and B inassembled relation constitute what is recognized'in the arts as safety fuse, and the composition of the powder A and the character ofthe covering B may be varied, as desired. Snugly engaging around the covering B is artube Cv of impervious material which is of a relatively non-conibustible character, and one that is capable of having its outer diameter accurately sized for a pur-pose which will presently bemade apparent. Preferably this outer tube Ais formed of lead, but it will be understood -that yit may be formed of other ductile metals or any other substance which may be found to have the requisite characteristics. n

Thesafety fuse A, B, C may be fabricated or manufactured in any manner which is.

found practicable, it being a desirable quality of the fuse that the coating C closely engage the covering B -so that air spaces between said B and C will be reduced to a minimum or entirely eliminated. It is also desirable that the covering B be formed .of a textile which hasa cellular structure so trat airmay be occluded within said cells or between the fibers of the textile material, so that as the powder core burns, the air cells will provide a cooling andY insulating effect which will prevent the melting of the outer coating C, which melting might result in obstructing the propagation yof the burning.

in the production of the-safetyA fuse A, B, C, a powder core A of a suitably slow and uniform burning powder is spun into fuse A, B, by a process similar to that used in making resin-core solder, lead covered cables and the like.

In Fig. 3 there is illustrated what I term a delay element for electric blasting caps, said delay element being formed of a suitable length lof safety fuse, asiillustrated in Fig. l, which pieceof fuse, after being cut to the desired length, and accurately `sized to suitable diameter itisprimed at one end, as shownatD, with 'an easily igiiitable' compound. Theprimin'g compound may be of any desired or preferred compositionfand I have found as a suitable composition foi this purpose a paste gfoi'ined-by dissolving' Celluloid in acetone and mixing therewith ordinary' blacky meal 'powdeiU in the proportion :of twenty pa'rtsfby weight of powder to oneipart of Celluloid. `A vdelay element suoli 'as above described should `iliave the following specilications:

ELS

meltl during burning.

`l. Itmustburii very slowl'yian'd accurate ly-`-in fact, more fslowlyfan'd with Vgreater accuracy' than 'any' safety? fuse? hitherto made for-general use.` f

V52,. AIt must have a uniform and `accurate diameter.

B. It musthave a rigid body which can bezp'ressed into a copper shell, producing a veryclose iit, so that -the ila'sh from the igniter cannot pass between the F fuse element and the' copper tube and Aprodiitey a premature' ignition. The importance of this feature will be *appreciated when one considers-that the 'shortest'elements are only i about one-quarter inch longuaii'd'vthe igniter produces' a veryV4 hot and sudden-flash.

4. It must be easily ignited.

5. It must burn without emission of side sparks or hot gases.

6. 'The metal tubemust Vnot ruptureor '7. 'It shouldbelch'eapf and easy tolmanufacture.

The delay element as shown in Fig'. 3, and having' the characteristicsspecified in the'precedinglparagraph is used in an' electric blasting cap'in the manner illustrated in F ig. ll, wherein the'blasting cap consists of aftube shell E formed of brass, copper voi aluminum within whichthe 'delay element isiitted betweenA a detoiiatingAcompou-nd F intheY 'bottom of the shell an'dvanignition head G fittedLinto the 'outer end-ofthecap. The primingt composition 'Dv of the delay element is spaced from' theelectricy ignition head g Aof the ignition head, and the shell between said element-s isl` for-medfwith 'openings e which provide vents Vfor the gases formed 'in `the burning of the fuse. F or ig'niting the composition g of the ignition head, a pair-ofelecti'ic conductors g joined by a platinum bridge extend through insulating materialg'gfof the ignition head. F or protecting'the ignition head 'g and-the prim- -it will-be apparent that I have deviseda novel type of safety fuse which may be used in' a conventional manner and whicliisparltici'ilarly' useful "in the preparation of delay elements for electric blasting caps.

T hese delay elements can be cheaply and accurately -inadefandprovidean eflicient means of increasing the efficiency of the electric blasting caps ofthe type wherein delayed or properlytimedexplo'sions can be electricallyfsct off.

Vhile I have shown and described what I consider a preferred embodiment 'of-my invention and 'the manner in which 'the sainemay be used, I doV not wish to be limited-to the specfic construction or composition of elements described, since these may be varied'within the scope of one skilled in tlieart without departing from the spirit of my'in'vention.

What I claim is:

l. A Ifuse element consisting of a core" of slow burning powder, cellular material enclosing the powder anda covering of a relatively non-combustible rigid impervious material snugly engaging over the cellular material, said impervious material having an'accurately sized uniform external diameter.

2. A fuse element consisting of 'a core of safety fuse enclosed 4within a ductile tube which is drawn down snugly against 'the onter'surface ofthe safety fuse to reduce to a 'minimum Vairspaces between the fuse and the inner wall of the tube, said ductile tube having an accurately sized external diameter.

The method of forming a fiise element comprising. enclosing safety "fuse withinan imperforate relatively nonecombustible, rigid, impervious material, causing said material to `snugly engage over `said safety fuse and accurately and uniformly sizing4 the' outerdiameter of the enclosing material.

t. The method offorming a fuse element comprising enclosing safety fusewithin an imperforate ductile metal tube aiid then reducing the diameter of the metal tube to lit snugly over the safety'fuse,

For use in blastingV caps or the like, a delay element comprising alength of safety fuse enclosed throughout' its length in afcasing' of relatively non-combustible, rigid, impervious material, the outer diameter `of which isacciirately sized, one end of the fuse being primed with an easily ignitable compound.

6. For use in blasting caps or the like, a delay element comprising a length of safety fuse enclosed throughout its length in a ductile metal tube having a uniform external diameter, the fuse at one end of the tube being primed with an easily ignitable compound.

7. The method of forming delay elements for blasting caps or the like, comprising forming in long lengths, a fuse element having a core of inflammable material, a coating of fibrous material enclosing the inflammable material and an outer coating of impervious relatively non-combustible rigid material, cutting said fuse element into desired lengths and priming one end of each length so obtained with an easily ignitable compound.

8. The method of forming delay elements for blasting caps or the like, comprising forming in long lengths, a fuse element having a core of slow burning powder, accating of textile material enclosing the powder and a metal covering snugly engaging over the textile material, cutting said fuse elementA into desired lengths and priming one end of said lengths of fuse element with an easily ignitable compound.

9. For use in an electric blasting cap comprising a shell having an ignition head at the top and a detonating compound at the bottom, a delay element for positioning between said ignition head and said detonating compound, said delay element comprising a short length of safety fuse snugly enclosed within a metal jacket which is adapted to closely fit the interior of the shell, said delay element being primed at one end with a compound adapted to be ignited by the ignition head of the blasting cap.

10. A delay element comprising a core of inflammable material enclosed within a ductile metal tube, and means between the inflammable material and the tube for preventing the melting or rupturing of the tube during the burning of the inflammable material.

ll. The method of Jformingl delay elements for blasting caps and the like, comprising forming in long lengths a fuse element having a core of inflammable material enclosed within a ductile metal tube, and means between the inflammable material and the tube for preventing melting or rupturing of the tube during the burning of the inflammable material and cutting said fuse element into desired lengths.

In .witness whereof, I have hereunto signed my name.

HENRY E. ELLSVORTH,