US3614928A - Cast high explosive primer - Google Patents
Cast high explosive primer Download PDFInfo
- Publication number
- US3614928A US3614928A US806406A US3614928DA US3614928A US 3614928 A US3614928 A US 3614928A US 806406 A US806406 A US 806406A US 3614928D A US3614928D A US 3614928DA US 3614928 A US3614928 A US 3614928A
- Authority
- US
- United States
- Prior art keywords
- explosive
- cast
- detonating fuse
- primer
- high explosive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F42—AMMUNITION; BLASTING
- F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
- F42B3/00—Blasting cartridges, i.e. case and explosive
- F42B3/10—Initiators therefor
Definitions
- the cut ends of the resulting loop of detonating fuse are then imbedded in a cup of molten high explosive so that, upon cooling, the loop with surrounding sleeve protrudes from the surface of the cast explosive, forming an assembly which is useful in attaching a connecting piece of detonating fuse or in positioning a blasting cap or electric detonator so that the end containing the base charge is maintained in firm physical contact with both the detonating fuse and the surface of the cast high explosive.
- Blasting explosives are ordinarily manufactured and packaged in a form in which they are not sensitive to the impacts and friction which can occur in the normal course of transportation and placement of charges.
- the cheapest and probably most commonly used blasting explosives at the present time are based on ammonium nitrate and a small percentage of a suitable fuel, such as a high-boiling petroleum distillate or a finey divided carbonaceous substance or oxidizable metal.
- a suitable fuel such as a high-boiling petroleum distillate or a finey divided carbonaceous substance or oxidizable metal.
- the maximum detonation velocity of the common ammonium nitrate explosive is not very high, somewhere between 3,000 and 4,000 meters per second, whereas the common high explosive high velocities within the range of about 6,000 to 8,000 meters per second.
- Primers, or boosters, as they are sometimes called, are customarily made of a major quantity of a high explosive and an initiating quantity of detonating fuse or PETN and with some provision for attaching thereto a detonating fuse, electric detonator or blasting cap.
- the combination of detonator and primer is designed to produce a compression wave of sufficient amplitude and total energy that it will travel through and initiate the entire charge of ammonium nitrate explosive. Since the primer is composed of expensive ingredients, it is necessary that this device be designed to operate efiiciently, with the minimum quantity of high explosive.
- high efiiciency in a primer is obtained by producing a substantially simultaneous detonation of all of the explosive ingredients of both detonators and primer, so that the pressure peaks add together to increase the amplitude of the compression wave.
- This objective is not readily accomplished and for this reason improvement of the design of primers is continuously sought by the manufacturers of these devices.
- Some of the most eflicient primers in use at the present time either require tedious hand labor in assembly, or are excessively bulky, having been cheapened by extending the high explosive with grains of blasting powder or other lower cost ingredients.
- FIG. 1 is a longitudinal cross-sectional 'view through the center of the body of cast explosive in the primer, showing the location of the ends of a length of detonating fuse imbedded in the cast solid explosive.
- FIG. 2 is an overall view of the primer with an electric detonator positioned for use.
- a length of detonating fuse such as primacord or cordtex is cut and doubled to form a loop 1.
- a flexible sleeve 2 which may be obtained by cutting oif a short length of flexible plastic tubing.
- the flexible sleeve is then placed in a clamp which holds the fuse and sleeve assembly in a stationary position after the cut ends of the fuse are immersed in molten high explosive contained in a cup-like container 3.
- a solid mass of cast high explosive 4 is obtained with the ends of the detonating fuse firmly imbedded therein and having an exposed upper surface 5.
- the exposed upper surface of cast explosive is important so that when a detonator 6 is placed in position, as shown in FIG.
- the flexible sleeve is also essential to efficient functioning of the primer, as it provides a means to hold a detonator in close physical contact with both the detonating fuse and the cast explosive.
- the flexible sleeve also provides a means for quickly forming a tight knot between the end of a piece of detonating fuse and the fuse loop on the primer, if this is the chosen means of detonation.
- a primer in a specific embodiment of this invention consists of a cylindrical cup approximately 50 mm. high and 50 mm. in diameter filled with cast pentolite (50 percent PETN, 50 percent TNT) in which is imbedded both ends of a piece of SO-grain primacord about 205 mm. in length, doubled into a loop and passed through a sleeve consisting of a 25 mm. length of polyethylene tubing having an inside diameter of about 13 mm.
- the performance of this primer compared favorably with commercial primers containing more than twice as much high explosive.
- EXAMPLE 3 A primer containing one-fourth pound of cast pentolite was constructed as shown in FIG. 1 and to it was attached an electric detonator as shown in FIG. 2. The primer was placed on top of a mild steel plate of one-half inch thickness and was detonated, resulting in perforation of the plate, the hole being round and approximately the same size as the primer. A conventional one-third pound pentolite primer was equipped with an electric detonator, placed on the plate and fired, producing only a dent in the plate. It was necessary to use a three-fourth pound conventional type primer in order to perforate the plate.
- EXAMPLE 4 A series of cast primers was prepared as shown in FIG. 1, with decreasing amounts of cast pentolite in the same size cup. The smallest quantity used filled the cup to a depth of only one-fourth inch. The ends of the detonating fuse were lowered to the bottom of the cup so as to obtain secure irnbedding in the molten explosive. All of the primers in the series detonated successfully. Upon comparison with commercial cast pentolite primers with a hole through the center for a loosely threaded piece of detonating fuse, it was found that when the primer was shorter than three inches, detonation with the same size 4 fuse was not reliable. This was attributed to poor physical contact between the two explosives.
- the preferred shape of the body of cast high explosive in the primers of this invention is a cylinder in which the height is approximately equal to diameter.
- the flexible sleeve which is essential for obtaining good contact between detonator, cast explosive and detonating fuse, may be made of a variety of materials. Although flexible plastic tubing is preferred, a short length of coiled wire or thin metal tubing may be used. If metal tubingis employed for this purpose, it is necessary to round off the edges of the metal at the ends of the sleeve so they will not chafe or cut the loop of detonating fuse.
- the length of the loop of detonating fuse be shorter than the length of the electric detonator which will be used.
- the Wire leads can be passed down under the loop so that when placed under tension the detonator will be forced down against the exposed surface of the cast explosive, rather than pulled away from it.
- a primer for detonating ammonium nitrate explosive charges comprising a body of solid cast high explosive having imbedded therein both ends of a length of detonating fuse, said length of fuse being formed into a loop outside the body of cast high explosive and encircled by a movable flexible tubular sleeve.
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Connections Effected By Soldering, Adhesion, Or Permanent Deformation (AREA)
- Fuses (AREA)
Abstract
Description
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US80640669A | 1969-03-12 | 1969-03-12 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3614928A true US3614928A (en) | 1971-10-26 |
Family
ID=25193975
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US806406A Expired - Lifetime US3614928A (en) | 1969-03-12 | 1969-03-12 | Cast high explosive primer |
Country Status (1)
Country | Link |
---|---|
US (1) | US3614928A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3878785A (en) * | 1971-12-01 | 1975-04-22 | Nitro Nobel Ab | Propagation device and initiation system for low energy fuses |
EP0083165A2 (en) * | 1981-12-28 | 1983-07-06 | E.I. Du Pont De Nemours And Company | Non-electric blasting assembly |
US5747722A (en) * | 1996-01-11 | 1998-05-05 | The Ensign-Bickford Company | Detonators having multiple-line input leads |
US6006671A (en) * | 1995-02-24 | 1999-12-28 | Yunan; Malak Elias | Hybrid shock tube/LEDC system for initiating explosives |
-
1969
- 1969-03-12 US US806406A patent/US3614928A/en not_active Expired - Lifetime
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3878785A (en) * | 1971-12-01 | 1975-04-22 | Nitro Nobel Ab | Propagation device and initiation system for low energy fuses |
EP0083165A2 (en) * | 1981-12-28 | 1983-07-06 | E.I. Du Pont De Nemours And Company | Non-electric blasting assembly |
EP0083165A3 (en) * | 1981-12-28 | 1984-05-30 | E.I. Du Pont De Nemours And Company | Non-electric blasting assembly |
US6006671A (en) * | 1995-02-24 | 1999-12-28 | Yunan; Malak Elias | Hybrid shock tube/LEDC system for initiating explosives |
US5747722A (en) * | 1996-01-11 | 1998-05-05 | The Ensign-Bickford Company | Detonators having multiple-line input leads |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: THERMEX ENERGY CORPORATION 13601 PRESTON ROAD DALL Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:GULF OIL CORPORATION;REEL/FRAME:004354/0001 Effective date: 19841114 |
|
AS | Assignment |
Owner name: GENERAL ELECTRIC CREDIT CORPORATION 100 GALLERIA P Free format text: SECURITY INTEREST;ASSIGNOR:THERMEX ENERGY CORPORATION;REEL/FRAME:004362/0093 Effective date: 19841114 |
|
AS | Assignment |
Owner name: THERMEX ENERGY CORPORATION, TEXAS Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:GENERAL ELECTRIC CAPITAL CORPORATION;REEL/FRAME:005424/0260 Effective date: 19900606 |