You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to earth and rock boring apparatus, finding particular utility in the formation of vertical shafts to mines or other subterranean installations. 
     2. Statement of the Prior Art 
     It has been previously known to provide a plurality of drills supported in a casing within a housing pipe and to rotate both the support and pipes while the drills are free to rotate about their axis. Representative of patented art is U.S. Pat. No. 3,945,445. 
     SUMMARY OF THE INVENTION 
     The present invention provides a large diameter earth and rock boring apparatus which eliminates the necessity for driving a drill stem from above ground, and which relies principally upon the mass and weight of the drill assembly for its bore function. The assembly hereof is driven, and is provided with fluid input and exhaust means for evacuation of drilled material. 
     In presently practiced mining procedures, particularly in certain types of long shaft coal mines, it is necessary as the shaft is extended to provide periodic vertical intercept shafts. Conventionally, the intercept shafts are formed by blasting, drilling and excavation in clam shell buckets and the like. This procedure is not only costly and dangerous, but often results in shafts of irregular form having fragmented, unstable side walls. Also, blasting often causes flooding by disruption of adjacent subterranean water sources, and in that event, the shaft walls must be lined with concrete resulting in additional cost. 
     The present invention provides a method and means for the construction of shafts of the type described above, embodying the essential characteristic of pulverization of material to be drilled, combination of the pulverized material with a fluid medium to form a slurry, and pumping of the slurry to the surface for disposal. 
     The apparatus hereof is adapted for operation from the surface thereby avoiding dangers inherent in those devices requiring personnel to be present at the bottom of shaft. 
     The unit hereof comprises a main body section of tubular form, supported for releasable stationary positioning, a casing with a lower hub supporting free wheeling cutters, and fluid input and exhaust means. The rate of drilling is a function of the weight and mass of the cutting elements, and the rate of motion thereof. 
     Other and further objects and advantages of the invention will become apparent to those skilled in the art from a consideration of the following specification when read in conjunction with the annexed drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is an elevational view taken through a section of drilled shaft, showing earth drilling equipment constructed and assembled in accordance with the teachings of this invention, vertically foreshortened; 
     FIG. 2 is a sectional view looking down on the cutting component, of the unit shown in FIG. 1; 
     FIG. 3 is a view similar to FIG. 2, but taken below the drive wheels, and with portions of the base removed for disclosure of details; 
     FIG. 4 is a horizontal cross sectional view taken to show the jack arrangement; 
     FIG. 5 is another sectional view looking down, taken below the base to disclose the fluid input and exhaust means, the cutting elements being shown in phantom lines; 
     FIG. 6 is a foreshortened vertical sectional view taken through the main body tube and casing; and 
     FIGS. 7a through 7d are schematic views showing sequences of operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings in more detail, the invention finds its principal environment of intended utilization in the formation of a substantially vertical shaft 10 in the earth 12. The shaft 10, as it is formed, has an inside wall 14, and drilling occurs at its bottom 16. The bottom is, during drilling, constantly eroded by the action of the apparatus, commencing from the surface 18 to a desired depth or to an intersection with a tunnel or the like. 
     The apparatus hereof is generally identified in the drawing by reference character 20. A principal structural and functional component of the unit 20 is an elongated main body tube 22 which is normally vertically disposed when the unit is in use. The main body tube 22 has upper and lower ends 24, 26, an outer side wall 28, and an inside wall 30 defining a bore 32 (FIG. 6). In FIGS. 1 and 4, it will be observed that a plurality of jack assemblies 34 are fixedly secured on the outer side wall 28, each comprising a fixed lateral sleeve 36 with a extensible and retractable rod 38 projecting from its end remote from the main body tube. The rods are connected at the outer ends to elongated abutment members 40 which extend between and interconnect vertically aligned pairs of the jacks. The jack sleeves 36 are rigidified and reinforced by a series of braces 42 which extend back to the main body tube and between one another of the sleeves. The jacks may be hydraulic or otherwise actuated. 
     Disposed vertically within the main body tube 22 is an elongated, tubular outer casing 44. The casing has a top end portion 46, and an opposite bottom end portion 48, the top and bottom end portions projecting above and below the upper and lower ends 24, 26, respectively, of the main body tube. The casing 44 is rotatably journaled within the bore 32 of the main body tube, as described more fully hereinafter, and has a vertical passageway 50 defined by its interior wall 52. 
     The bottom end portion 48 of the casing is fixedly connected to a horizontal base member 54. The base member is of optional and variable design, but here is shown as of cruciform shape with a central hub 56 with an opening 58 receiving the casing, and having upper and lower sides 60 and 62. The cruciform configuration provides a pair of diametrically opposite cutter arms 64 and 66, and radially spaced, diametrically opposite pair of drive wheel arms 68 and 70 (FIGS. 2 and 3). 
     Fitted within the passageway 50 of the outer casing and inwardly spaced therefrom is a tubular exhaust tube 72. The exhaust tube 72 has a lower intake end 74 which projects, as shown in FIG. 6, below the base member 54, and an upper discharge end 76 with a flange 78 for connection to a suitable conduit. Below said base, the lower intake end 74 is integrally joined to a plurality of scavenging tubes 80. The scavenging tubes are hollow, and in fluid communication with the tube 72, and each has an outer vertically depending leg 82 with an enlarged mouth element 84 at its lower extremity. 
     A fluid input pipe is of reduced diameter relative to the exhaust tube 72, and has a top portion 88 and a bottom portion 90 with an end wall 92. Immediately above the end wall 92, ports 94 are formed in the portion 90 of the pipe 86, and spouts 96 are secured to the pipe about each of said ports. The spouts have downturned nozzles 98 at their ends. 
     Mounted on the upper side 60 of the base member 54 on said cutter arms 64 is a drive motor 100 with an output gear box 102 or other conventional drive conversion mechanism. On each of the drive wheel arms 68 and 70 of the base is a housing 104 for a worm gear drive (not shown), and shafts 106 from the gear box 102 drivingly engage the same. A driven stub axle 108 extends from each of the housings 104, and a drive wheel 110 with a friction tire 112 is secured thereto. The wheels are driven from the motor 100 to rotate the base by frictional contact of the friction tires. The motor may be of the reversible types so that the direction of the rotation of the unit can be changed. 
     A cutter motor 114 is mounted on the drive wheel arm 68 above the base, and has a operatively associated output gear 116. On the extremities of the cutter arms 64 and 66 are housings 118 with side worm gear portions 121. Shafts 120 are engaged at one end with the gear drive 116 and at the opposite end within the worm gear portions 121 in driving relation. Vertical drive cutter axles 122 extend from the housings 118 through the base. The plurality of downwardly and outwardly extending legs 124 are radially spaced on each axle, and the legs have upwardly inclined foot portions 126. 
     The cutting elements 128 hereof each comprises an assembly of disk form plates 130 suitably clamped together in freely rotatable fashion on the respective foot portions 126 of the axles 122. As seen in FIG. 1, the plates are of variable diameter, increasing from inside to out, such that, with the inclination of the foot portions, the peripheral cutting edges of the plates are disposed in contact with the shaft bottom 16. 
     Means 132 on the outer casing 44 and on the main body tube 22 for energizing the drive and cutter motors is provided. The particular means employed is a variable feature of the invention, and various optional power arrangements are contemplated according to energy availability, terrain and the like. In this illustration, the means 132 comprises a housing 134 secured on a base 136 above a collar 138 on the casing. As shown in FIG. 6, the collar is fixedly secured to the casing, as by a weld, but the base 136 is not, and the casing is free to rotate without the plate. An insulater sleeve 140 is attached to the casing within the housing, and a series of annular electrical contacts 142 are placed thereabout in spaced apart relation. A housing mount rod 144 is secured on the main body tube by gusset plates 146 and a slide bushing 148 in an opening 150 in the base 136 permits vertical sliding movement of the rod therein. The rod however prevents rotation of the base and housing with the casing. A power supply cable 152 extends to a power supply and control station (not shown) located on the surface. A series of stationary contacts 154 within the housing are in sliding engagement with annular contacts 142, and suitable electrical wiring 156 is positioned between the casing and the exhaust tube 72. 
     In FIGS. 7a through 7d, it is seen that start up involves initial erection of an above ground frame 158 comprising an outter super structure 160 and interior wall 162. The main body tube 22 is initially positioned within the wall confines and the jack assemblies 34 are extended to bring the abutment members 40 into contact with the walls. The exhaust tube 72 is connected to a pump 164 leading to a slurry discharge site, and the input pipe 86 has a pump 166 supplying fluid from a reservoir or other source. This places the cutting elements 128 on the surface as shown in FIG. 7a. Rotation of the casing, base and cutting elements is then instituted by energization of the drive motor 100 resulting in the frictional contact of the tires 112 of the wheels 110. Fluid is introduced into the cutting area and forms a slurry with excavated material, the slurry being then expelled through the tube 72. In FIG. 7b the drilling has progressed to a point near the vertical downward limit of the casing with respect to the main body tube, and shaft formation has occurred to a first depth. At this point, the jacks 34 are retracted and the main body tube lowered to the position shown in FIG. 7c. The jacks are again extended at this point to bring the abutment member into contact partially with the wall 162 and partially with the shaft 14. FIG. 7d shows completion of this cycle and it will be noted that the process of lowering the tube may continue until the desired drill depth is achieved. 
     It will of course be understood that during operation the cutter drive motors 114 are energized in order to drive the cutters.

Summary:
Earth drilling equipment includes a main body tube with jacks to releasably support it within a drilled shaft, or within an erected start up shaft. An outer casing is rotatably mounted within the main body tube, and carries a horizontal base on which are driven wheels, and vertical shafts which have cutting elements. Means within the casing for fluid input and evacuation within the drill area is provided to form a slurry of the fluid and excavated material for withdrawal through the casing. As drilling continues, the main body tube is lowered into the shaft. 
     The cutting elements include plates with cutting edges mounted on individual axles such that the edges are maintained in cutting relation to the area to be drilled.