US1872016A - Surface mining - Google Patents

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Search Room C?? 1&2372961@ Aug. 16, 1932.

R. H. sHERwoQD ET AL SURFACE MINING Filed July 28, 1950 5 Sheets-Sheet All@ 16, 1932- R. H. sHERwooD ET AL. 1,872,016

SURFACE MINING Filed July 28, 1950 3 Sheets-Sheet 2 Aug. 16, 1932. R. |z. SHERWOOD ET AL 1,872,016

SURFACE MINING Filed July 28, 1950 3 Sheets-Sheet 3 Patented Aug. 16, 1932 ROBERT I-I. SHERWOOD, OF INDIANAPOLIS,

PATENT OFFICE AND WILLIAM I-I. STEWART, OF IIINTON,

INDIANA, ASSIGNORS TO ALLENDALE MANUFACTURING COMPANY, INC., OF INDIAN- APOLIS, INDIANA, A CORPORATION OF INDIANA SURFACE MINING Application led July 28,

Our invention relates to surface mining, especially of coal.

The object of the invention is to simplify such surface mining, and to lessen its cost; and particularly to simplify and lessen the cost of the loosening explosions, such as those which loosen the overburden, preparatory to the removal of material by the stripping machinery, and to make such explosions more satisfactory, more reliable, more uniformly distributed, and more accurately controlled. y

In carrying out our invention, as applied for example in the strip mining of coal, we

use a stripping shovel7 a coal-loading shovel,

and coal-carrying cars in the now well-known way. In order to make it economically possible for the stripping shovel to strip the overburden, the latter is loosened by explosions.

Prior to our invention, the explosive for the loosening explosions in surface mining has been put in the bottoms of vertical holes, drilled from the natural surface of the ground. This often made it necessary to use the higher types of explosives, both toconcentrate the explosive force at the bottoms of the holes and because of diiiculty encountered with some explosives from water which seeped into the vertical holes and filled the bottom parts thereof. The cost of drilling these deep vertical holes has been a very material factor in the cost of surface mining, especially when the overburden has included hard-rock strata; and if the overburden included easy-fiowng material, such as mud or quick sand, the cost of the vertical holes rose enormously, on account of the expense necessary for casing them and for loading the explosive with the casings in place.

In accordance with our invention, we drill long substantially horizontal holes for the loosening` explosive, as into the overburden bank, near the base thereof in the strip mining of coal; and thus provide a series of long horizontal holes which substantially parallel the coal stratum if coal is being mined, and which may be filled to a large extent with explosive to form a horizontal grille- Work of explosive which is more effective to 1930. Serial No. 471,142.

lift and loosen the overlying material. By having the holes horizontal, the strata of rock and easy-flowing material, and the difficulties resultant therefrom, may be avoided. Because these holes are horizontal, or may even slope slightly upward, there is little or no tendency for water to collect in them to any depth. For these reasons, it becomes possible to use a cheaper and less dangerous explosive, such as black powder. In addition, by enlarging the inner ends of the horizontal holes, as by small preliminary explosions, and filling with explosive both these enlargements and a considerable length of the stems of the horizontal holes which lead to said enlargements, a horizontal grillework of explosive, somewhat concentrated at the inner ends of the holes but also underlying -the whole section of material to be loosened,

is obtained; and this greatly increases the effectiveness of the ultimate loosening explosion, which is desirably of the explosive in a group of holes simultaneously, and lessens the amount of explosive necessary for a given loosening effect. As a result, the cost of producing the loosening explosions, which in the strip mining of coal normally amounts to about twenty-five per cent (25%) of the whole cost, is materially reduced, by from a third to a half. This reduces the tota-l cost of the surface mining; and the resultant cost of the product to the ultimate consumer.

The accompanying drawings illustrate my invention: Fig. l is a generalized vertical cross-section through a strip mine for coal, including the mechanism for drilling the horizontal holes for the explosive; Fig. 2 is a fragmentary plan of the strip mine shown in Fig. 1, and shows the stripping shovel, the coal-loading shovel, the relation of the strata of coal to the steam shovels and to the overburden and the spoil bank, and the arrangement of long horizontal holes and the drilling mechanism therefor; Fig. 3 is an enlarged side elevation of the drilling mechanism for the long explosive-containing holes; Fig. 4. is a plan of the drilling mechanism of Fig. 3; Fig. 5 is a. group of fragmentary views showing disassembled a group of parts that go to make up the drill; Fig. 6 is a front elevai l a 5 (-7 of Fig. 3; Fig. 8 is a section substaiitially on the line 8-8 of Fig. 3; Fig. 9 is a section substantially on the line 9-9 of Fig. 7; Fig. 10 is a fragmentary view showing the chuck for the drill of Fig. 5; and Fig. 11 is 0 an enlaiged fragmentary vertical section through one of the explosive holes, somewhat shortened longitudinally of the hole over the proportions that would obtain in actual practice to show the packing of the hole with ex- 5 plosive.

We will describe our invention, example, in connection with the ing of coal.

The coa-l stratum that is obtained in the by way of strip minstrip mining of coal lies beneath a generally horizontal stratified overburden 16 which is usually not over fifty (50) feet thick and varies in accordance with the local geology. The overburden usually includes one or more strata 16 of generally firm rock, and sometimes strata of sand, mud, and dirt, sometimes witli embedded rocks and boulders 17; and at the bottom usually has a layer of shale or slate 18, which .is relatively soft, directly overlying the coal.

The stripping shovel 20, usually mounted on its own caterpillars 21, travels on the stratum of coal 15, in a gully of its own making between the overburden bank on one side 5 and a spoil bank 22 on the other side; and

removes the overburden from one side of such gully and deposits the dirt thus removed upon the spoil bank at the other side thereof as it travels slowly along such gully. By thus re- 49 moving the overburden, it exposes the stratum 15 of coal. The exposed coal of the coal-stratum 15 is removed by a coal-loading shovel 25, also traveling on its own caterpillars 26; and this coal-loading shovel follows the stripping shovel along the gully and loads the coal into cars 27 which travel on a track 28 that is laid on the exposed. coal 15 and leads to the usual tipple.

So far this is standard construction in the strip mining of coal.

In order that the stripping shovel 20 may be able to remove the overburden 16, it is essential, at least from an economical standpoint, that such overburden be first loosened by explosions within it, but preferably is at least in large part, and desirably substantially wholly, left in place in the overburden bank so that it will not fiow or fall down into the gully and interfere with operations there. In order to obtain such loosening, we drill into the overburden bank 16 a series of long horizontal holes 30. These long horizontal holes are near the bottom of the overburden, and usually in the stratum of relatively soft shale or slate 18 and within from one to three feet of the top of the coal-stratuin 15. We prefer that they extend lengthwise into the overburden bank for a distance nearly or quite equal to the height of the bank usuall from tei; (1o) to forty (4o) no precise length of hole is essential) and for an overburden of fifty (50) feetdepth We have found that a spacing of from fifteen (15). to twenty-fw@ (25) feet between successive holes gives Satisfactory results. Of C0uIse, the length o f the holes and the spac ings between holes varies with the nature and height of the overburden.

When the long horizontal holes 30 have been drilled, we have found that it is desirable to. detonate small explosive charges (springing charges) within them at their 'inner ends, to produce enlargements 31 at such inner ends, in which the bulk of the final explosive may be placed.

After the enlargements 31 have been made, such enlargements and part of the stems of the long horizontal holes 30 which respectively lead to them are filled with a suitable explosive 32, which may be ordinary black powder. (See Fig. 11.) After such filling the outer ends of the holes are plugged, as with clay Before the plugging, and iiideed before the filling with powder, a suit* able detonator 34 is put in place in the hole for detonating the chargeof powder 32 when desired. When a sufiicient number of holes 30 have been drilled and charged, the charges in them may be exploded simultaneously, which effectively produces a loosening and breaking up of the overburden 16 which that series of holes underlies, but leaves most and usually all of it in substantially its original location, without any subsequent washing down into the gully, so that the stripping shovel may then remove that loosened overburden from that overburden bank and transfer it to the spoil bank 22.

In order to drill the holes 30, we use the drill mechanism shown in Figs. 3 to 10 inclusive. This drill mechanism consists of a frame 40 having two parallel rails 41 which form a track upon which a carriage 42 may travel toward and from the overburden bank. The frame 40 is put substantially perpendicular to the bank, and rests on the exposed coal stratum 15 in line with the hole 30 which it is desired to drill. The carriage 42 has wheels or rollers 42 by which it travels on the rails 41, and has parts such as fingers 42" Which underlie the heads of the rails 41 to prevent the carriage from tilting.

On the carriage 42 is a drill-driving motor 43, usually an electric motor, which is connected by gears 44 to a drill-shaft 45 also suitably mounted on the carriage in supporting,r trunnions 46 fixed to such carriage. Fixed on that end of the drill-shaft 45 opposite the gears 44 is a drill-chuck 47, shown as a collar, between which and the trunnion 46 is feet, (although Q52, Manno.

stamane a ict HARvEsnNG desirably a thrust bearing 48. The end of the drill-chuck 47 receives the shank 49 of a drill 50.

This drill is made in sections. There are a plurality of sections 51, each desirably having a rectangular shank 52 projecting from both ends of it; and a plurality of coupling sections 53 having correspondingly rectangular holes 54 in its ends for receiving the rectangular shanks 52. The rectangular shanks 52 correspond in general to the shank 49. Any number of sections 51 and 53 may be used to build up a drill-stem of any length; and this drillstem may be lengthened as the depth of the hole is increased, by inserting more sections 51 and 53. At the working end of the drill there is a drilling section 55, which has a hole 54 which may receive one shank 52 of the adjacent drill-section 51. That end of the drilling section 55 opposite the hole 54 is provided with removable and replaceable cutting claws 56, which drill the hole 30 somewhat larger than the outside diameter of the drill-stem, as is clear from Fig. 5. This particular drilling section 55 with its claws 56 is not our invention, but is already known, and is called a moles-foot drill. The various sections 51, 53, and 55 of the drill are held together, and the drill as a whole is held in the drill-chuck 47, by one or more Cotter pins 57 at the various joints. The several sections 51, 53, and 55 are provided with one or more helical or screw-conveyor iianges 58, for feeding rearward along the drill and out of the hole 30 the earth and stone which the drilling section 55 has cut loose. These flanges 58 also serve to guide the drill. The drill is thus a sectional auger drill.

In the horizontal plane of the drill shaft 45 the carriage 42 is provided at each side with an eye 60, to which is attached one end of a cable 61. Each cable 61 extends forward from its eye 6() to a pulley 62 carried in an upright 63 at the forward end of the frame 40, and thence rearward to a winding drum 64. The two winding drums 64 for the two cables 61 are on a cross-shaft 65, which may be manually turned, as by a crank 66. The cross-shaft 65 carries a third winding drum 67, around which extends a third `cable 68 in the opposite direction from the way the cables extend around the drums 64. The cable 68 extends from the drum 67 to the rear of the carriage 42. Thus by turning the crank 66 in opposite directions, the carriage 42 may' be moved either forward or backward.

Desirably the cross-shaft 65 is provided with a ratchet wheel 69` co-operating with a pawl 70. which permits free turning of the cross-shaft in the direction necessary to feed the carriage 42 forward. The pawl 70 must be thrown out of engagement with the ratchet 67 in order to move the carriage 42 rearward.

ref,

Because the drill is necessarily so long, it is desirable to provide a guiding and supporting bracket for it at one or more intermediate points. For this purpose, we provide a U-shaped bracket 71 mounted on a cross-bar 72 which is attached at its ends to the two uprights 63 at the forward end 0f the frame 40, as is clear from Fig. 6. A second and smilar guiding bracket 74 may be provided on a forward extension 75 of the frame.

In drilling 4a hole 30, the frame 40 is set in line with the desired hole, and a suitable number of sections 51 and 53 are attached to the 'drill-shaft 45 and have a drilling section 55 at their ends. The operator feeds the carriage forward by the crank 66, to force the drill 50 against and into the overburden near the bottom thereof; and the motor 43 rotates the drill as the operator thus feeds it forward. The operator feels the resistance offered by the shale or slate to the advance of the drill, and varies his feeding pressure on the crank 66 accordingly.

When the carriage 42 is advanced to the end of the frame 40, the drill is stopped, the carriage 42 is withdrawn to the rear end of the frame 40, additional sections 51 and 53 are inserted, and the drilling operation is resumed as before. This is continued until the desired depth of hole is obtained.

7e claim as our invention:

1. The method of strip-mining coal which is covered by an overburden bank containing a rock stratum, which consists in drilling into the overburden bank near the base thereof and below the rock stratum a series of long substantially horizontal holes substantially paralleling such base, putting explosive charges in said holes, firing those charges to lift the material of the overburden bank to loosen it While leaving it at least largely in place and to fragmentize such rock stratum, removing the loosened and fragmentized material directly from the overburden bank to a spoil bank, and then removing the coal that is uncovered by the removal of the overburden bank.

2. The method of exposing a coal seam covered by a generally horizontally stratified overburden including one or more strata of irm rock, which comprises drilling into the face of the overburden bank a series of long holes located above and generally parallel to the upper face of the coal seam and below a stratum of firm rock, placing explosive charges in said holes, firing such charges to lift the material in the overburden to loosen it and fragmentize thestratum of firm rock above said holes, and then directly removing the loosened and fragmentized overburden material.

3. The method of loosening material in a generally horizontally stratified bank containing solid rock masses and relatively soft l material, Which comprises drilling into the face of the bank near the base thereof and in the relatively soft material a series of holes generally parallel to the stratification, said holes having a length approximating the height of the bank, placing explosive charges in said holes, and firing said charges to lift the bank material to loosen it.

4. The method of loosening material in a generally horizontally stratified bank containing solid rock masses and relatively soft material, which comprises drilling into the face of the bank near the base thereof and in the relatively soft material v.a series of holes generally parallel to the stratiiication, placing explosive charges in said holes, and firing said charges to lift the bank material to loosen it.

5. The method of loosening material in a generally horizontally stratified bank Containing a stratum of firm rock, which comprises placing a plurality of explosive charges beneath said rock stratum While leaving it imperforate, and simultaneously firing said charges to lift the overburden to loosen it and fragmentize said rock-stratum.

6. The method of loosening material in a generally horizontally stratified bank containing a stratum of firm rock, which comprises placing a plurality of explosive charges beneath said rock stratum While leaving it imperforate, and tiring said charges to lift the overburden to loosen it and fragmentize said rock-stratum.

7. The method set forth in claim 2 With the addition of a step of exploding springing charges in said holes before placing the main explosive charges therein.

8. The invention set forth in claim 4 With the addition of the step of exploding springing charges in said holes before placing the main explosive charges therein.

9. The method of exposing a coal seam covered by a generally horizontally stratified overburden including a stratum of shale or slate located closely above the coal seam, which method comprises drilling a series of holes into said stratum of shale or slate from the face of the overburden bank, said holes extending generally parallel to the coal seam, placing explosive charges in said holes, firing such charges to lift the material in the overburden bank to loosen it and fragmentize the stratum of shale or slate, and then directly removing the loosened and fragmentized overburden material.

In Witness whereof, We have hereunto set our hands at Indianapolis, Indiana, this 19th day of July, A. D. one thousand nine hundred and thirty.

ROBERT I-I. SHERWOOD. WILLIAM H. STEWART.

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