US2428884A - Electric blasting cap - Google Patents

Electric blasting cap Download PDF

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Publication number
US2428884A
US2428884A US439339A US43933942A US2428884A US 2428884 A US2428884 A US 2428884A US 439339 A US439339 A US 439339A US 43933942 A US43933942 A US 43933942A US 2428884 A US2428884 A US 2428884A
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United States
Prior art keywords
shell
plug
cap
fins
caps
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Expired - Lifetime
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US439339A
Inventor
Edward K Lefren
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Hercules Powder Co
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Hercules Powder Co
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Priority to US439339A priority Critical patent/US2428884A/en
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Publication of US2428884A publication Critical patent/US2428884A/en
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Application status is Expired - Lifetime legal-status Critical

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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42AMMUNITION; BLASTING
    • F42BEXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
    • F42B3/00Blasting cartridges, i.e. case and explosive
    • F42B3/10Initiators therefor
    • F42B3/103Mounting initiator heads in initiators; Sealing-plugs

Description

Get. 14, 1194? E. K. LEFREN ELECTRI C BLASTING CAP Filed April 1'7, 1942 INVENTOR. EDWARD If. LEFREN 2,428,884 ELECTRIC BLASTING CAP Edward K. Lefren, Kingston, N. Y., assignor to Hercules Powder Company, Wilmington, DeL, a corporation of Delaware Application April 17, 1942, Serial No. 439,339 3 Claims. (Cl. 102-28) This invention relates to electric blasting caps and electric firing devices and, more particularly, to a new and improved electric blasting cap which is provided with means adapted to facilitate assembly of the parts in a moistureproof relationship.

lhe various prior art blasting devices such as electric blasting caps, electric delay caps, and the like, normally contain a plug which either slips loosely into the cap and is then sealed therein by means of asphalt, or the like, or is sealed therein by means of crimping the shell into the plug itself. By these methods, caps can be made moistureproof, but oftentimes due to temperature changes and various external reasons, the caps do not maintain their moistureproofness. In the prior devices, the manufacture'of moistureproof caps is complicated and time consuming. Each of the known caps in order to be'made moistureproof requires a plurality of assembling operations.

The known caps which are supposedly waterproof are designed to include an explosive charge in the closed end of a bronze shell and an ignition assembly adjacent to the explosive charge which consists of a pair of lead wires electrically connected by means of a resistance wire and held in-position by means of a plug. This ignition assembly, in the majority of instances, is inserted loosely into the cap' and sealing means superimposed thereon. In some instances, the plug is inserted into the cap and the cap shell erimped into the plug.

The above described known methods of pro.- ducing moistureproof caps have met with commercial success but it has often been found that the caps so produced do' not perform entirely satisfactorily since some few of these caps may lack complete moistureproofness. The caps which do not remain moistureproof may cause trouble in firing various explosive shots and are therefore undesirable. The moistureproofness of the caps may be seriously affected by hot storage conditions because moistureproofing material such as asphalt tends to flow under a hot storage condition and either to exude out of the top of the cap or leak past the plug down into the explosive. Either type of flowage produces an unsatisfactory cap. In some instances, caps do not withstand cold storage because the moistureproofing agent may harden and become brittle and pull away from the shellunder low temperature conditions and thereby allow moisture to enter the shell. Prior art caps in which moistureproofing is effected by the use of asphalt are undesirably long. Thdse in which the moisture resistance is produced by crimping the shell into the plug are somewhat shorter but the crimping operation isdiflicult to control and some types of plugs must be heated to enable the shell to be crimped into the plug.

Therefore, it is an object of this invention to provide an electric blasting cap having a combination lock and sealing means adapted to facilitate assembly of the cap and protect the cap against the entrance of moisture.

Another object is to provide a plug having resilient means adapted to permit quick assembly of the plug and shell, secure the plug in operating position with the shell, and seal the shell against the entrance of moisture.

Nore specifically, it is an object to provide the plug of the ignition assembly with spaced resilient fins adapted to facilitate assembly of the parts, secure the ignition assembly in operating position, and seal the cap againstthe entrance of moisture.

Generally described, the electric blasting cap of the present invention comprises a shell preferably of copper, bronze, or aluminum having an explosive charge in the closed end and having superimposed upon this explosive charge an ignition assembly comprising a dielectric plug having a pair of leg wires therethrough in dielectric relation with one another, and a'resistance wire electrically connecting the terminal ends of these leg wires. The ignition assembly plug is provided with resilient fin-like members sufiiciently larger than the inside diameter of the blasting cap shell so that when the assembly is moved to operating position with the shell, the members are compressed against the inner surface of the shell thereby forming a barrier against the entrance of moisture into the shell. The fin-like members are also bent upwardly out of normal alignment and in this position act as a locking means for holding the assembly in operating position within the shell.

A preferred embodiment of the invention has been chosen for purposes of illustration and de ing cap comprising an ignition assembly I and a blasting cap shell 2. The ignition assembly I comprises a pair of insulated leg wires 3 molded or otherwise inserted into a body portion of plug 4 each of which terminates at the lower end of the plu to form a terminal member or wire 5. These terminal wires are electrically connected by means of a bridge wire 6. The plug 4 may be made of rubber, resin, or any other suitable hard or soft dielectric material.

A combination moisture seal and locking means 7 in the form of fins I are carried by the plug 4. These fins may be cast as an integral part of the plug 4 or may be separate units secured in any suitable manner thereto. Where the plug 4 is made of a. rubber material, it is preferred to cast the fins and plug as an integral unit. Where the plug is made of a hard material as, for example, a thermoplastic or thermosetting resin, it is preferred to make the fins in separate units of any suitable resilient material and then secure these units on the plug in any convenient manner as by cementing. v

The fins are formed with a substantially brcad base tapering outwardly therefrom toward a relatively narrow rim portion. Formed in this manner, the fins are more resilient in their peripheral portion than at their base portion and in this way act to provide the desired moisture seal and locking effects.

The lower portion of the shell 2 is provided with an explosive charge which may comprise a base charge 8 and a priming charg 9. The base charge 8 may be tetryl, pentaerythritol-tetranitrate, nitrostarch or the like and the priming charge may be lead azide, diazo-dinitrophenol, mercury fulminate or the like either alone or admixed with an oxidizing agent such as potassium chlorate, barium nitrate, lead dioxide or the like. The priming charge 9 is placed in the cap in a loose condition so that the bridge wire 6 may be easily moved into the charge as the plug is positioned in the shell. This invention is applicable to caps containing any arrangement of explosive charge, for example, single charge, or charges with ignition mixtures superimposed thereon.

The upper end of the shell, which is shown slightly greater in diameter than the lower end, but which may be straight sided (not shown) if desirable, receives the plug together with the fins in tight fitting relationship. As the plug 4 is moved into the shell, the fins I which are diametrically larger than the inside diameter of the upper end of the shell, are compressed inwardly and moved upwardly out of normal alignment. After the plug has been moved into the position shown in Fig. 2, the fins operate to provide a barrier against the entrance of moisture into the shell. The fins also act to lock the ignitionassembly in operative position by reason of the fact that in' addition to the normal tight fitting relationship between the fins and shell, the fins tend to move into normal alignment during any outward movement of the plug which movement causes still greater compression of the fins and therefore effects a still tighter fit between the fins and the shell which tighter fit then tends to prevent this outward movement of the plug relative to the shell.

Other ignition assemblies operable in accordance with this invention are those of the cavity type, the bead type or the match head type.

The fins 1 may be modified to produce a locking and moisture sealing eflect. For example, a continuous helix may extend from the lower end of the body portion 4 to the upper end thereof and terminate in a sealing member similar to the upper fin shown in the drawings. The fins may be peripherally-disposed about the body portion 4 out of horizontal alignment and the desired looking and sealing results obtained. Other modifications are obvious from this disclosure.

From the foregoing description, it will be obvious that the objects of this invention have been accomplished by providing a blasting cap which is simple, efiicient and economical to manufacture, which is provided with means adapted to facilitate assembly of the parts, to provide a moisture seal and lock the parts in operating position.

What I claim and desire to protect by Letters Patent is:

1. An electric blasting cap which comprises a loaded tubular shell having a. dielectric ignition assembly plug disposed therein comprising a body portion having a pair of leg wires extendin in spaced dielectric relationship therethrough with the terminal ends of said pair of leg wires extending from said body portion being connected by a bridge wire, and at least one resilient finl ke member outwardly and peripherally disposed about said body portion, said finlike member being formed with a relatively broad base portion adjacent to said body portion and tapering outwardly therefrom toward a relatively narrow peripheral portion more resilient than said base and body portions, said peripheral portion being diametrically larger than the inside diameter of the upper end of said tubular shell prior to insertion into the shell.

2. An electric blasting cap which comprises a loaded tubular shell having a dielectric ignition assembly plug disposed therein comprising a resilient body portion having a pair of leg wires extending in spaced dielectric relationship therethrough with the terminal ends of said pair of leg Wires extending from said body portion being connected by a bridge wire, and at least one resilient finlike member outwardly and peripherally disposed about said body portion, said finlike member being formed with a relatively broad base portion adjacent to said body portion and tapering outwardly therefrom toward a relatively narrow peripheral portion more resilient than said base and body portions, said peripheral portion being diametrically larger than the inside diameter of the upper end of said tubular shell prior to insertion into the shell.

3. An electric blasting cap which comprises a loaded tubular shell having a dielectric ignition assembly plug disposed therein comprising a resilient body portion having a pair of leg wires extending in spaced dielectric relationship therethrough with the terminal ends of said pair of leg wires extending from said body portion being connected by a bridge wire, and a plurality of resilient finlike members outwardly and peripherally disposed about said body portion and in spaced parallel relationship with each other, said finlike members being formed with a relatively broad base portion adjacent to said body portion and tapering outwardly therefrom toward a relatively narrow peripheral portion more resilient than said base and body portions,-said peripheral portion being diametrically larger than the inside diameter of the upper end of said tubular shell prior to insertion into the shell.

EDWARD K.

REFERENCES @ITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Number Switzerland July 4, 1906

US439339A 1942-04-17 1942-04-17 Electric blasting cap Expired - Lifetime US2428884A (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2660118A (en) * 1949-08-19 1953-11-24 Olin Ind Inc Blasting cap
US2695562A (en) * 1950-08-14 1954-11-30 Olin Mathieson Blasting cap and method of making same
US2695563A (en) * 1951-09-27 1954-11-30 Olin Mathieson Electric blasting cap
US3041973A (en) * 1959-03-27 1962-07-03 Benjamin F Sanders Recoverable tamping plug
US3984623A (en) * 1974-10-23 1976-10-05 Worden Owen W Cable splice housing
US4270455A (en) * 1979-01-02 1981-06-02 Atlas Powder Company Blasting cap booster assembly
US4825764A (en) * 1986-02-24 1989-05-02 Ruggieri Connecting device between a firing fuse of a pyrotechnic product and an igniter
US4887919A (en) * 1985-01-08 1989-12-19 Skf (U.K) Limited Preventing movement of an article along a shaft or bore

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US408096A (en) * 1889-07-30 Territory
CH37332A (en) * 1906-06-04 1907-05-31 Weibel Mulisch Josef grafting
US1306641A (en) * 1919-06-10 Gas-shell and the like
US1503420A (en) * 1923-06-02 1924-07-29 Hutton Ernest Blasting gun
GB246727A (en) * 1925-07-15 1926-02-04 Thomas Campbell Futers Improvements in and relating to the construction of detonators
US1577539A (en) * 1922-08-28 1926-03-23 Polk Alexander Hamilton Dispensing device
FR40035E (en) * 1931-03-27 1932-03-21 Closure for containers with dropper pipette using dropper
US2083733A (en) * 1934-02-28 1937-06-15 Safety Mining Co Anchoring means
US2129439A (en) * 1934-12-18 1938-09-06 Cardox Corp Anchoring means
US2178723A (en) * 1936-11-03 1939-11-07 Forsyth Peter Mcgill Detonator

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US408096A (en) * 1889-07-30 Territory
US1306641A (en) * 1919-06-10 Gas-shell and the like
CH37332A (en) * 1906-06-04 1907-05-31 Weibel Mulisch Josef grafting
US1577539A (en) * 1922-08-28 1926-03-23 Polk Alexander Hamilton Dispensing device
US1503420A (en) * 1923-06-02 1924-07-29 Hutton Ernest Blasting gun
GB246727A (en) * 1925-07-15 1926-02-04 Thomas Campbell Futers Improvements in and relating to the construction of detonators
FR40035E (en) * 1931-03-27 1932-03-21 Closure for containers with dropper pipette using dropper
US2083733A (en) * 1934-02-28 1937-06-15 Safety Mining Co Anchoring means
US2129439A (en) * 1934-12-18 1938-09-06 Cardox Corp Anchoring means
US2178723A (en) * 1936-11-03 1939-11-07 Forsyth Peter Mcgill Detonator

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2660118A (en) * 1949-08-19 1953-11-24 Olin Ind Inc Blasting cap
US2695562A (en) * 1950-08-14 1954-11-30 Olin Mathieson Blasting cap and method of making same
US2695563A (en) * 1951-09-27 1954-11-30 Olin Mathieson Electric blasting cap
US3041973A (en) * 1959-03-27 1962-07-03 Benjamin F Sanders Recoverable tamping plug
US3984623A (en) * 1974-10-23 1976-10-05 Worden Owen W Cable splice housing
US4270455A (en) * 1979-01-02 1981-06-02 Atlas Powder Company Blasting cap booster assembly
US4887919A (en) * 1985-01-08 1989-12-19 Skf (U.K) Limited Preventing movement of an article along a shaft or bore
US4948320A (en) * 1985-01-08 1990-08-14 Skf (U K) Limited Preventing movement of an article along a shaft or bore
US4825764A (en) * 1986-02-24 1989-05-02 Ruggieri Connecting device between a firing fuse of a pyrotechnic product and an igniter

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