Coal Mine Shooting Plug

FIELD OF THE INVENTION AND SUMMARY OF THE PRIOR ART

Known forms of blasting, bore-hole loading, and tamping plugs are evidenced by the following U.S. Pat. Nos., all of which disclose various means for expanding the plug within a drilled hole. Reichert (158,126, issued Dec. 22, 1874) and Swingle (993,907, issued May 30, 1911) each illustrating threaded means for expanding the plug; Heitzman (2,007,568, issued July 9, 1935) and Crater (2,296,504, issued Sept. 22, 1942) each show wedge-type expanding means; and the Kihlstrom patent (3,208,381, issued Sept. 28, 1965) discloses a conically-shaped insert forced into place by successive packaged explosives.

Among the objects and advantages of our invention are the following:

1. To provide a magnetically-attracted insert for the plug so that it may be recovered by magnetically "searching" the blasted area, or, magnetically recovered when the mined material is washed or similarly fluid-treated.

2. To provide sealing means to seal the perimeter of the plug in the blast hole.

3. To provide a steel ball within a sealed chamber within the plug, and pressurize the interior of the chamber.

4. To provide a concussion cup at the end of the plug facing the charge to assist in preventing the blast from escaping past the plug and out the drilled hole.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

FIG. 1 is a partly sectional view of a charge and plug inserted in a drilled hole.

FIG. 2 is a similarly sectional view taken generally along line 2--2 in FIG. 1 showing various parts of the plug in cross-section.

FIG. 3 is a cross-sectional view taken approximately along the line 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view taken approximately along the line 4--4 of FIG. 2.

FIG. 5 is a partial view showing the chamber enclosing the steel ball being filled with air.

FIG. 6 is an exploded perspective view of the plug.

The drilled hole for the charge 12, the fuse 14, and the plug 16 is indicated by reference numeral 10 with the plug being generally the same size as the dynamite 12 and closely fitting the hole 10. In FIG. 2, the three major parts of the plug are denoted as the forward plug portion 18, the central portion 30, and the rearmost portion 36. The forward portion 18 includes a generally hemispherical concussion cup 20, hollow chamber 24 covered with a self-sealing rubber composition 26, similar to that used in automotive tires, and an entrapped steel ball 22 in chamber 24.

Central portion 30 has a reduced end nose 32 telescoped into and adhesively secured to forward portion 18 as at 28. Conically-shaped expanding or wedging means 36, having an enlarged, generally hemispherically-shaped tip 38 is mated into the conical open end bore 31 of central portion 30 which has slits 44--44 wherein which roughly divide the rearward portion of central portion 30 into four segments. The inner end of the bore 31 includes an enlarged, hemispherically-shaped recess 34 which receives and retains the wedge 36 in assembled relation to the central portion 30 with the length of the recess 34 being greater than tip 38 to enable the wedge 36 to be driven inwardly to its innermost position as illustrated in FIG. 2. A rubber band 40, or similar elastic means, is seated in a groove 42 which surrounds 30, passes through the slits 44; and, as viewed in FIG. 2 is between the portions 36 and 38 of the expanding means.

As viewed in FIG. 5, with the chamber 24 coated with self-sealing rubber (similar to that used in vehicular tires), and the parts 18 and 30 adhesively secured together, air hose 48, with the needle 46 is inserted into the chamber 24, and chamber 24 is filled with air well above atmospheric pressure. The needle is then withdrawn and the plug 16 is inserted into the hole 10 and wedge 36 driven inwardly.

All of the materials used in the plug are resilient and will be inherently fireproof, or treated to become fireproof, before final assembly. After the explosive charge has been inserted in the drilled hole, the plug inserted and seated, the fuse is ready for ignition. The force of the explosion will cause longitudinal compression of the plug and radial expansion of the relatively thin resilient wall of chamber 24, thus effectively sealing the hole 10 so that the explosion force and gases will be retained in the hole until the blast dislodges the surrounding material.

After the explosion occurs, the entire plug is usually recovered intact. Recovery of the plug may be obtained by passing a magnet adjacent the broken coal and/or minerals. Other magnetic means may be associated with the conveying means or tipple for the blasted materials, or, magnetic means may be associated with washing, or other fluid treatment, to recover the plug. The recovery feature alone is estimated to save over one-third of the blasting and plugging costs in a given coal mine.

In addition to the recovery features, the interrelationships of the concussion cup 20, pressurized and expandible chamber 24, and expanding means 36-38, combine to provide a more effective blast, in which more loose coal is recovered for a given size explosive charge, and less gaseous material escapes around the plug than in the more conventional devices.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.