US3141410A - Blasting initiator - Google Patents

Description

July 21, 1964 R. P. GUNDLACH ETAL 3,141,410

BLASTING INITIATOR Filed Feb. 8, 1962 FIGA Br f'/ .4/

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States York Filed Feb. S, 1962, Ser. No. 174,345 7 Claims. (Cl. 102-24) The present invention pertains to initiators, and more specifically, to initiators which are relatively insensitivel to impact, friction and burning and yet are very effective in achieving high order detonation.

This is a continuation-in-part of application, Serial No. 20,376, filed Apr. 6, 1960, now abandoned.

An initiator is a relatively small compact explosive composition that is used to detonate a larger or main body explosive such as the ammonium nitrate-oil mixture. The initiator sets up the last step in the chain reaction of setting off a large body of explosive. The detonation process proceeds through the following stages: detonating cord, booster, initiator and main body explosives, each stage rendering a larger explosive force than the preceding stage and each subsequent stage requiring the larger explosive force to detonate it. Initiators heretofore known have had the disadvantages of requiring considerable tedium in the application of a booster or the attachment of the primersuch as detonating cordat the point of use.

Therefore, it is an object of the present invention to provide an initiator having, and a mode of making it with, a built-in booster, but which is relatively insensitive, except in purposeful detonation, and which is safe to handle.

Further objects will appear from the detailed description taken in connection with the drawings in which:

FIGURE l is a top view of the initiator; and

FIGURE 2 is a cross-sectional view of the initiator.

According to the present invention, the initiator consists of a block of a suitable explosive composition molded into a container and having cast in situ therein a short cylinder of large size detonating cord to serve as a booster element. During the casting of the composition, there is maintained therein two passageways passing vertically through the composition. The booster element is cast in situ within the explosive composition in such a manner that its ends are exposed at at least one of the vertical passageways. When the initiator is to be detonated, a smaller size detonating cord is passed through one or both of the vertical passageways and secured in position. When the detonating cord is detonated and the detonation wave reaches the booster element, the booster element will detonate thereby detonating the initiator.

Referring now to the drawings, a block of explosive 1 is cast in situ within a suitable container 2 formed of paper, or other suitable material. The container 2 has a base 3, in which there is a pair of spaced apertures 7. The explosive composition may be, and usually is, selected so as to have detonation characteristics which will detonate the main body of a blasting agent. Where the blasting agent is a common one such as the well-known ammonium nitrate-oil mixture, the explosive element 1 is preferably composed according to any one of the following examples:

(A) An explosive composition containing 50% TNT (trinitrotoluene) and 50% PETN (pentaerythritol tetranitrate).

(B) Composition B-containing 60% RDX (cyclotrimethylenetrinitramine), 38% TNT (trinitrotoluene) and 2% eeswax.

. PETN) therein.

(C) An explosive composition containing 98% RDX and 2% beeswax.

The shape of the explosive block 1 depends upon the shape of the container, but is preferably a cylinder on the order of three inches in diameter and two inches in axial dimension. The molding may be accomplished either by melting and pouring the explosive, or by pressing plastic granules into cohesion. Ineither event, during the casting operation, a pair of steel pins (not shown) project upwardly from a suitable base (not shown) through apertures 7 to a position above the level of the top of container 2. Hence, the pins protrude through what will subsequently become the block of explosive, and when the pins are withdrawn, they will leave open passageways 4 through the block 1. Preferably prior to the beginning of the molding operation, a booster 5 is wedged endwise between the 1aforesaid pins. The booster 5 preferably consists of a short cylinder cut from a length of large size detonating cord, as, for example, Primacord winch is 0.4 inch in diameter, and having 400 grains of pentaerythritol tetranitrate (hereinafter referred to as PETN) per foot. If desired, however, the container 2 may be partially filled with the explosive composition before the booster 5 is wedged between the pins. In either event, the container Z is filled, or substantially filled, with explosive composition, so as to completely envelop booster 5, except at the ends which are adjacent the aforesaid pins, and which, when the pins are removed, will be exposed on the interior of passageways 4. Booster element 5 is thus cast in situ in block l. When the explosive composition has set solid, the container 2 and its contents are removed from the pins and lid 6 applied thereto.

The passageways 4 are of such size as to accommodate a strand of detonating cord of the size and character used for setting off an explosion from a remote point. Typical of such detonating cord is a plastic or braided tube, 0.2 inch in diameter, containing 50 grains per foot of PETN, and having a detonation rate of 20,000 feet per second. The detonating cord, from which the short cylinder forming booster element 5 is cut, is of similar construction, except that it is larger in diameter, and contains, for example, 400 grains of PETN per foot.

The booster element 5, however, may have a variety of shapes and sizes since these are not vultimately important in the overall operating ability of the initiator. The important features, rather, reside in the positioning of the booster element within the initiator and the content or amount of explosive material (such as RDX or We have found that about 15 grains of the explosive material is necessarily present in the booster element to obtain detonation. However, numerous tests have been run, showing that a booster element containing about 50 grains of explosive material renders the initiator 100% reliable, while still maintaining a high safety factor; therefore, the preferred amount of explosive material present in the booster element should be about 50 grains. It is believed that any more than about 60 grains of the explosive material would be uneconomical, however, the present invention is inclusive of such amounts.

Initiators having booster elements molded in situ containing about 50 grains of explosive material, have successfully survived numerous safety tests which are well known to those skilled in the art, such as the pendulum swing, the block drop and burning tests, with no detonations resulting therefrom.

The following specific examples are representative of the initiators of the present invention, but the invention is not deemed to be limited thereby.

. 3 Example I A 11/2 inch piece of 400 grain Primacord (400 grains of PETN per foot) .4 inch in diameter was molded in situ in a block of Composition B. The resulting initiator had a diameter of about 3 inches. Initiators of this type have a 100% reliability whenl purposely detonated, while not being detonated by any of the safety test procedures above stated.

Example II A cardboard tube .4 x 1.5 containing 3.3 grams (about 51 grains) of RDX was molded in situ in a block of Cornposition E. The resulting initiator had a diameter of about 3 inches. Initiators of this type have a 100% reliability when purposely detonated, and possess a high safety factor in that they were not detonated by any of the safety test procedures above stated.

Example III A one inch piece of 400 grain Primacord (about 34 grains of PETN) was molded in situ on a block of Cornposition B. The resulting initiator had a diameter of about 2 inches. lnitiators of this type have an 80 plus percent reliability with a high safety factor as above described.

In order to prevent the loss of PETN at the cut ends of the booster element 5, suitable caps 8 of paper, plastic, or any other material which does not interfere with the transmission of the explosive wave from the small detonating cord to the booster, may be applied.

The steel pins which form openings 4 in the cast block are preferably coated with a suitable mold release composition, in order to facilitate vtheir removal after the explosive composition has solidified and set.

In the use of the device for detonating blasting charges, the lid 6 is first removed, and a strand of detonating cord, approximately 0.2 inches in diameter as aforesaid, is threaded through one or both openings 4, and suitably affixed. The last-mentioned detonating cord will be of suiicient length to extend to the remote point at which it is to be detonated, and the container 2 will be planted in a position such as to detonate the blasting charge.

From the foregoing description, it is evident that the invention is not limited to the details of construction shown in the specic embodiments, and so it is further apparent that operable substitutions for the explosive composition may be readily made without departing from the present invention. It is therefore understood that the invention is not limited to the specic details shown and described.

Many changes in and modifications of the construction described may be made without departing from the spirit of our invention or sacrificing its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. An initiator comprising a molded block of explosive composition having cast in situ therein an encased cylinder of explosive material in an amount within the range of about l to about 60 grains, said cylinder having its ends each adjacent to a Vertical passageway passing through the molded block, wherein said cylinder is located entirely between said passageways, and said passageways having a size such as to accommodate a standard strand of detonating cord.

2. An initiator comprising a molded block of Composition B having cast in situ therein an encased cylinder of PETN in an amount within the range of about l5 to about 60 grains, said cylinder having its ends each adjacent to a vertical passageway passing through the molded block, wherein said cylinder is located entirely between said passageways, and said passageways having a size such as to accommodate a standard strand of detonating Cord.

3. An initiator comprising a molded block of explosive composition having cast in situ therein an encased cylinlinder of RDX in an amount within the range of about 15 to about 60 grains, said cylinder having its ends each adjacent to a vertical passageway passing through the molded block, wherein said cylinder is located entirely between said passageways, and said passageways having a size such as to accommodate a standard strand of detonating cord.

4. An initiator comprising a molded block of Composition B having cast in situ therein an encased cylinder of RDX inV anY amount with the range of about 15 to about 60 grains, said cylinder having its ends each adjacent to a vertical passageway passing through the molded block, wherein said cylinder is located entirely between said passageways, and said passageways having a size such as to accommodate a standard strand of detonating cord.

5. An initiator comprising a molded block of explosive composition having cast in situ therein an encased cylinder of PETN in an amount within the range of about 15 to about 60 grains, said cylinder havings its ends each adjacent to a vertical passageway passing through the molded block, wherein said cylinder is located entirely between said passageways, and said passageways having a size such as to accommodate a standard strand of detonating cord.

6. An 'initiator comprising a molded block of Composition B having cast in situ therein an encased cylinder of PETN in an amount of about 50 grains, said cylinder having its ends each adjacent to a vertical passageway passing through the molded block, wherein said cylinder is located entirely between said passageways, and said passageways having a size such as to accommodate a standard strand of detonating cord.

7. An initiator comprising a molded block of Composition B having cast in situ therein an encased cylinder of RDX in an amount of about 50 grains, said cylinder having its ends each adjacent to a vertical passageway passing through the molded block, wherein said cylinder is located entirely between said passageways, and said passageways having a size such as to accommodate a standard strand of detonating cord.

References Cited in the iile of this patent UNITED STATES PATENTS 2,709,407 Lowe May 31, 1955 2,775,200 Guenter Dec. 25, 1956 2,913,982 Hayes Nov. 24, 1959 2,944,485 Ely et al July 12, 1960 3,037,452 Cook et al. June 5, 1962 3,037,453 Cook et al. June 5, 1962` Le.. .e

Claims (1)

1. AN INITIATOR COMPRISING A MOLDED BLOCK OF EXPLOSIVE COMPOSITION HAVING CAST IN SITU THEREIN AN ENCASED CYLINDER OF EXPLOSIVE MATERIAL IN AN AMOUNT WITHIN THE RANGE OF ABOUT 15 TO ABOUT 60 GRAINS, SAID CYLINDER HAVING ITS ENDS EACH ADJACENT TO A VERTICAL PASSAGEWAY PASSING THROUGH THE MOLDED BLOCK, WHEREIN SAID CYLINDER IS LO-

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