US3311179A - Reamer attachments for earth drilling apparatus - Google Patents

Description

March 28, 1967 J. A. MEREDITH 3,331,379

REAMER ATTACHMENTS FOR EARTH DRILLING APPARATUS Filed Jan. 6, 1964 5 Sheets-$heet l INVENTOR, JOHN A. MEREDiTH A ORNEY March 28, 1967 J. A. MEREDITH 3,311,179

REAMER ATTACHMENTS FOR EARTH DRILLING APPARATUS Filed Jan. 6, 1964 5 sheets-sheet 2 H L 1 I9 50 11 -& 49 8 2g 49 F/6 4 INVENTOR.

JOHN A. MEREDITH BY paw 7% A ORNEY March 28, 1967 J. A. MEREDITH 3,311,179

REAMER ATTACHMENTS FOR EARTH DRILLING APPARATUS Filed Jan. 6, 1964 5 Sheets-Sheet 5 INVENTOR.

JOHN A- MEREDITH ATTORNEY United States Patent The present invention relates to earth drilling apparatus and, more particularly, to equipment and apparatus of the foregoing type that is well adapted for enlarging the size and bore of drill holes.

In recent years powered equipment has been designed and built for the drilling of caisson footings and the like. In addition to the provision of powered apparatus for rotating the drill apparatus, further improvements have been made in the design and construction of the boring tool itself. As the result of the combined advances in technology, it is now possible and economically feasible to provide drilled caisson footings for many different types of building construction. The caissons as installed or cast in place in the earth holes provide secure and stable foundations for buildings of ever increasing size.

The success in the application of drilled footings to smaller structures has indicated the desirability of adapting the same construction techniques to larger structures. This has required the provision of heavier and larger equipment for drilling holes of ever increasing diameter and of similarly increased depth. The resultant changes in the power driving equipment and in its capability to drill holes of larger diameter and deeper extent have made it possible through provision of the present apparatus to facilitate the installation of massive structures of considerable military and defense importance.

The combination of the larger power driving equipment and the attachments described herein now makes it possible to drill holes in earth structures of sufficient diameter and depth to receive intercontinental ballistic missile launch facilities. V/ith such equipment all necessary earth work for the installation of such facilities can be accomplished expeditiously and economically.

Accordingly, while the general objective of the present invention has been to provide attachments and equipment that will facilitate the drilling of large caisson holes, a companion objective has been to provide such equipment that would facilitate the installation of missile launching facilities with a consequent saving in time and money.

Specific objects of the present invention are the provision of earth auger attachments adapted to enlarge and ream previously drilled holes so that openings of larger diameter and depth may be provided without exceeding the torque and driving capabilities of conventional earth auger equipment.

A further object of the invention is the provision of reamer attachments specifically adapted to ream and undercut an earth structure to provide an enlarged footing or collar in spaced position along the vertical extent of the drilled hole.

Another object of the invention is to provide attach ments for earth auger driving apparatus which will facilitate the drilling of earth openings peculiarly well adapted to the installation of missile launch facilities.

Further and additional objects of the present invention will be apparent from the appended description and drawings, in which FIG. 1 is a top plan view in partial broken section showing construction details of an under-reamer attachment made in accordance with the present invention,

FIG. 2 is a side elevation showing further features of the attachment illustrated in FIG. 1,

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FIG. 3 is a top plan view illustrating the configuration of a reamer attachment for earth auger equipment,

FIG. 4 is a side elevation in partial section showing additional details in the construction of said reamer attachment,

FIG. 5 is a side sectional elevation illustrating progressive steps in the digging of a missile launching facility,

FIG. 6 is a side elevation showing the under-reamer techniques used in connection with such construction, and

FIG. 7 is a perspective view and diagram of said reamer attachment.

Briefly stated, the present invention provides reamer and under-reamer attachments for earth auger equipment so that the hole size capacity of even the largest present day earth drilling equipment may be extended. In general, separate embodiments of the invention are shown which are specifically provided for the purpose of reaming a drilled opening to a larger size and, separately, for underreaming the sides of a previously drilled or reamed hole to provide a bell footing or collar for such hole. The reamer attachment provides outrigger arms and supports for a plurality of cutters which are disposed to progressively engage the walls of earth surrounding a previously drilled hole as necessary to enlarge the bore of such hole while accurately maintaining the location of such hole. The under-reamer is provided with adjustable support means whereby the effective horizontal extension of the cutting apparatus may be progressively changed to provide an under-reamed footing or collar for a previously drilled and reamed opening.

Before explanation of the details of specific embodiments of the invention, it is believed advisable to first disclose the nature of a typical cycle of operation. A representative step process is discernible from a study of FIGURES 5 and 6. Here it will be seen that an earth structure 11 has first been drilled with a conventional auger 16 to provide a hole 12 which is of the largest diameter possible within the torque and depth capacity of a drilling apparatus 14. The hole 12 usually will be drilled through use of a conventional screw flight type of auger 16 which is for descriptive purposes shown at the bottom of hole 12 in FIGURE 5. Necessarily, such auger 16 will ordinarily be removed from the hole by the retraction of the kelly bar 17 upon completion of the initial bore 12.

After completion of such initial bore 12, the reamer attachment 18, as more fully illustrated in FIGURES 3 and 4, will be positioned on the kelly bar 17, and the size of the drilled opening will be enlarged first by the lower cutters 19 and thereafter by the upper cutters 21 until the enlarged hole or opening 22 ha been obtained. Use of the reamer attachment will be continued until the buildup of loosened earth products in the lower hole 12 stops the further progress of such operations. Thereafter, the auger attachment 16 or other clean-out apparatus may again be placed on the equipment to clean out the accumulated debris at the bottom of hole 12. The reamer attach-ment 18 will thereafter be again placed on the kelly bar 17, and the reaming function will be continued. Actually, in some instances the dirt hoisting and carrying capacity of the reamer 18 may itself 'be utilized to raise the loosened earth out of the bottom of the hole.

By proper interchange of attachments the full depth of an enlar ed hole 22 may be completed. Thereafter, operations may be continued with the under-reamer attachment 23 shown diagrammatically in FIGURE 6 and in detail in FIGURES 1 and 2 so that the hole 22 may be provided with an enlarged hell or footing 24 and, if desired, a top or intermediate collar portion 26. In the use of this under-reamer apparatus the cutter arms 27 and the associated cutter bits thereon will be retracted until the under-reamer 23 is at the bottom of the previously drilled hole 22. Thereafter, the arms 27 will be progressively extended until the desired enlarged diameter has been attained. Subsequent rotation and raising of the under-reamer will then cut the desired bell footing 24 or collar 26. Upon removal of all of the loosened materials a finished opening of large diameter having top and bottom collars and footings of increased size and diameter will be obtained.

For the purpose of establishing relationships in size as necessary for a further understanding of the nature and function of the apparatus to be herein described, it should be noted that the drilled holes 12 .may through use of present designs and equipment be on the order of ten feet in diameter and up to eighty-five feet deep. The reamer attachment 18 can efiiciently enlarge the size of the hole 12 to provide an opening 22 that is fourteen feet in diameter and of the described depth. The presently described under-reamer 23 can thereafter enlarge the derived hole or opening 22 to provide collar and footing sections of sixteen foot diameter.

The detailed features of preferred embodiments of the generally described reamer and under-reamer apparatus are shown respectively in FIGURES 3, 4 and 7, and 1 and 2. The reamer attachment 18, as shown in FIGURES 3, 4 and 7, is a massive structure of rigid construction providing a strong frame 28 made up of a plurality of elements which, in general, radiate from a central kelly socket 29 to deliver the torque forces exerted by the kelly bar outwardly to the various cutter elements. Specifically, the kelly socket 29 is a vertically disposed hollow element of square cross-section adapted to receive the kelly bar 17 or kelly bar extension of earth auger apparatus. In conventional manner a hole 31 is provided so that a pin may be placed through the kelly bar and socket 19 to hold the two element in assembled relation.

The general frame structure 28 of the reamer 18 extends radially outwardly from the kelly bar socket 29 and includes the use of lower cross bars 33. These cross bars are preferably wide flange beams, and in the apparatus previously described are of approximately 14 inch size. The lower cross bar 33 provide support for a circular guide ring 34 which is provided with an outer tapered surface and which is preferably of a size to engage and be guided by the sidewalls of a previously drilled hole, such as the illustrated hole 12 shown in FIGURE 5.

A guide ring 36 is disposed above guide ring 34 to likewise engage the slightly reamed sidewall of the hole so that the entire reamer 18 is provided with an initial hole guiding contact which tends to prevent the entire reamer apparatus from deviating from the central bore of the originally provided hole 12.

As shown in FIGURES 4 and 7, the upper and lower guide rings 36 and 34 provide support for connecting elements 37 disposed in quadrant positions about the kelly socket 29. These connecting elements 37 are disposed along the tapered contour defined by the upper and lower guide rings 36 and 34 and further provide support for cutter bit sockets 38 and the associated cutter bits 39. These cutter bits 39 extend outwardly from the sockets 38 to engage the earth walls as necessary to cut the tapered surface. In connection with the positioning of these cutter bits 39, it should be noted that the sockets and bits are disposed at various positions along the substantially vertical extent of the supports 37 so that the bits at one quadrant position are not at the same level a those in a following quadrant position. Accordingly, each bit will cut a distinctive and separate path as the reamer 18 is rotated. The cutter bits 39 in position between the lower and upper guide rings 34 and 36 cut a pilot bore in the earth structure having a regularly tapered surface. The degree of outwardly disposed angle for such taper is relatively limited so that an excessive cutting load will not be imposed on any specific cutter bit 39. With diminished cutting load a near true and accurate pilot bore may be obtained.

After attainment of the desired pilot bore, a heavier cuttlng function may be carried out by successive extensions on the reamer apparatus 18 with little danger of deviating from the true bore of the original hole 12. Preferably the desired extension cuts are made in stepped arrangement to avoid excessive loadings on the reamer 18, the kelly bar 17 and on the drive apparatus itself. FIGURES 3, 4 and 7 illustrate a reamer attachment 1% in which at least two separate extensions are provided. A first or intermediate extension 41 is disposed in radial position intermediate the position for the second or top extension 42. Accordingly, as the apparatus is rotated the cutter bits 19 of the intermediate extension will be cutting at a position ninety degrees out-of-phase with respect to the cutter bits 21 of the top extension. As in the previous instance, it should likewise be noted that the separate cutter bits 39 of the cutter group 19 are again in out-of-line position with respect to the corresponding cutter bits 19 in the diametrically opposed group at the same intermediate extension level. This is the same dispersed cutter bit pattern as that utilized in connection with the pilot bore section and in the top extension.

The upwardly and outwardly directed angular position for the cutter bits on the intermediate and top extensions is similar but of considerably greater degree than the taper angle for the pilot bore section. Because of the increased angle, the intermediate and top extensions account for the major enlargement in the diameter of the drilled and reamed holes. Since the cutters for the intermediate extension, disposed at diametrically opposed positions, are at a lesser radial distance than the top extension cutters, and since it is desirable to balance the cutting load about the circumference of the reamer attachment 18, the radial cutting width of the intermediate extension is slightly greater than that for the top extension which will be cutting earth at a greater distance away from the central kelly bar. Regulation of the number, placement and radial distance of the separate cutter bits on the intermediate and top extensions, respectively, can effectively balance the torque loading on the reamer attachment 18 notwithstanding the ninety degree relative positioning for said intermediate and top extensions.

The step arrangement of the intermediate and top extensions has been found preferable to a single tapered disposition for the cutter bits for several reasons. First the stepped arrangement makes it possible to provide additional guide elements at both the point of departure and the point of finish for each individual taper. These guide elements help to preserve the desired direction of bore for the apparatus. The guide elements for the top and intermediate extensions may be of full circular extent, but the segmental arc elements 46 and 47, as shown, are preferred.

In addition to the provision of improved guide functrons, the stepped arrangement for the tapered extensions provides a better result due to the inherent nature of earth structures themselves. The stepped cutting arrangement makes it easier for the cutter bits to break away larger segments of bedded earth structures, and, accordmgly, the cutting action proceeds at a faster pace.

The actual placement and bracing of the intermediate and top extensions utilizes main supports 48 and 49 joined to the kelly socket 29 and into other frame or frame support members, such as the guide elements 46 and 47. Cross braces 50 are also used to support the elements 46 and 47 in the desired circular arrangement.

Since it is often necessary for attendant personnel to be lowered into the hole as the digging proceeds, a deck plate 52 may be provided above and across the lower cross bars 33. This provides a platform when it becomes necessary to change the cutter bits or when inspection at thebottom of the hole is required for other purposes.

While the use of intermediate and top extensions has been shown, it is true that where the required enlargement of the hole is not of the relative proportion described, a single extension level could be used. Necessarily, the cutting load disposed on opposite sides of the pilot bore should be equalized, and, accordingly, a balanced arrangement of extension elements should be used. A balanced arrangement will assure proper alignment of the bore and will also make it possible to maintain somewhat equal torque forces with respect to the central location of the kelly bar. While the primary function of the reamer attachment 18 is to cut and loosen materials from the wall of the previously drilled opening so such loosened materials will fall to the bottom of the opening, it has been found that a considerable quantity of removed materials can accumulate above the bottom deck 52 of the reamer 18. These materials can be hoisted out of the hole and thrown off the reamer by the rotation thereof. Ordinarily the loosened materials which accumulate in the bottom of the hole 12 will be subsequently removed therefrom through use of an auger flight 16 or a bucket auger whenever such accumulated materials block the further downward progress of the reaming operations.

When the enlarged hole 22 has been completed to the full desired depth, the derived hole may be used for numerous purposes. In many instances it is desirable, however, to provide an even further enlarged opening in spaced positions along the vertical extent of the hole. In the construction of missile silos as well as in the construction of building footings, improved structural or foundation characteristics may be expected through provision of a bell footing at the bottom of the drilled and reamed hole. Such enlarged bell at the bottom of the hole can, of course, provide an increased area of contact for the distribution of the load carried by a structural member formed in the drilled hole. Similarly, it is often desirable to provide an enlarged cross-section or collar ad acent the top of the drilled hole or at some other location along the vertical extent thereof.

In the construction of the described missile silo a lower bell footing and an upper collar have been desired. FIG- URES 1 and 2 show and disclose a type of under-reamer 23 that has been found useful in the digging of such bell footing and collar structures. Here an under-reamer 23 1s preferably built with a cross-shaped frame structure made up of radially disposed arms 61 joined to the kelly bar socket 62 and extending at ninety degree positions therefrom. The outer ends of the arms 61 provide support for a segmental guide surface 63, which is preferably of size corresponding to the diameter of the finished and reamed hole 22. A top plate 64 interconnects such guide surface 63 and the top of the cross bars 61. In addition to providing brace support for the guide surface 63, the top plate 64 cooperatively with an arm 66 provides support for a pivot pin 67. A cutter arm 27 is adapted for pivoting movement about such pin 67. A plurality of holes 69 are provided through the top surface of the plate 64. Cutter arm 27 is of such length that it will extend beyond the guide face 63 when the cutter is disposed in aligned radial position with respect to the arms 61. At other angular positions about the pivot 67 the cutter arm 27 will extend a different distance past the guide surface 63 or may be retracted inwardly therefrom. Such changes in the extension of the cutter arm 27 may be made by the placement of a pin 71 in a selected hole 69. If the pin 71 is placed in a hole such as that illustrated, the cutter arm 27 will be backed up against the pin when the under-reamer is rotated in the direction shown by the arrow. Since the cutter arm 27 is free to move pivotally except as such movement is blocked or limited by the pin 71, reverse rotation of the under-reamer 23 will be accompanied by the retraction of the cutter arm so that the entire assembly may be removed through the previously reamed hole.

As in the prior instance, the top plate 64 and the plates 72 disposed above cross braces 70 provide convenient walkways for personnel. In the operation of the underreamer for digging a bell extension at the bottom of a drilled and reamed hole 22, the cutter arms 27 will be retracted to a position radially inside of the guide surfaces 63. The entire under-reamer 23 will then be lowered by extension of the kelly bar to the bottom of the hole. Attendant personnel can then place the stop pins 71 in corresponding holes 69, and subsequently rotation of the under-reamer 23 will gradually bring the cutter bars 27 up against such stop pins 71. To maintain balance the diametrically opposed bars 27 should be extended the same distance while bars and cutters on the adjacent following assemblies may be at different radial positions to provide a progressive cut. The outward movement of the cutter bars 27 results from an interaction between the earth structure and the cutter bits 73 on the cutter bars 27. When all of the cutter bars have come to an extended position against their respective pins 71, the pins can be reset successively until the full desired extension for the cutter bars 27 has been obtained. After the cutter bars are fully extended, the kelly bar can be extended or retracted as it is rotated so that the teeth 73 will cut and remove earth to provide the desired bell structure. When the full out has been completed, reverse rotation will free the cutter bars by moving them to a retracted position so the under-reamer may be removed through the previously reamed hole 22. Since this operation in effect undercuts the earth structure, the efiiciency of dirt removal is quite good. It has been found, however, that it is again advisable to have the cutter bits disposed in non-following positions so that each bit cuts a separate and distinct path. As previously mentioned, the desired non-following pattern may be obtained by different placement of the pins 71 on adjacent assemblies or by changing the cutter bit placement pattern on separate cutter bars 27.

While separate embodiments of the invention have been shown and described, it should be apparent that the invention is susceptible to various modifications and changes. All such modifications and changes as come within the scope of the present claims are deemed to be a part of this invention.

I claim:

1. A reamer attachment for earth drilling apparatus adapted for enlarging the diameter of pilot holes or openings that have been previously drilled to substantially the full torque capacity of the drilling apparatus through use of conventional auger attachments carried and rotated by the kelly bar of such earth drilling apparatus, comprising a vertically disposed kelly socket for the reception of the kelly bar of such earth drilling apparatus, a cross frame joined to said kelly socket, guide members circumferentially disposed on the outer extremities of said cross frame and adapted to engage the walls of said previously drilled pilot holes or openings, cutter bits disposed adjacent said guide members in non-following position each with respect to the cutter bit circumferentially next adjacent thereto for slightly enlarging the bore diameter of said pilot hole and to provide a guide bore in said earth structure, extension arms extending radially outwardly past said first cutter bits at circumferentially spaced positions, and cutters on said extension arms disposed for cutting and reaming an opening of substantially increased diameter, said cutters being likewise disposed in non-following position each with respect to the cutters circumferentially next adjacent thereto whereby each of said cutter bits and cutters will engage, cut and remove a portion of earth wall to progressively ream and enlarge said original pilot opening and guide bore.

2. A reamer attachment for earth drilling apparatus adapted for enlarging the diameter of pilot holes or openings that have been previously drilled to substantially the full torque capacity of the drilling apparatus through use of conventional auger attachments carried and rotated by the kelly bar of such earth drilling apparatus, comprising a vertically disposed kelly socket for the reception of the kelly bar of such earth drilling apparatus, a cross frame joined to said kelly socket, guide members circumferentially disposed on the outer extremities of said cross frame and adapted to engage the walls of said previously drilled pilot holes or openings, cutter bits disposed adjacent said guide members in non-following posi tion each with respect to the cutter bit circumferentially next adjacent thereto for slightly enlarging the bore diameter of said pilot hole and to provide a guide bore in said earth structure, intermediate extension arms extending radially outwardly past said first cutter bits at circumferentially spaced positions, cutters on said intermediate extension arms disposed for cutting and reaming an opening of substantially increased diameter, upper extension arms extending radially outwardly past the circumferential limits of said intermediate extension arms, and cutters on said upper extension disposed for cutting and reaming an opening of diameter greater than that cut by said intermediate extension, said cutters being likewise disposed in non-following position each with respect to the cutter circumferentially next adjacent thereto whereby each of said cutter bits and cutters will engage, cut and remove a portion of earth wall to progressively ream and enlarge said original pilot opening and guide bore.

3. A reamer attachment for earth drilling apparatus adapted for enlarging the diameter of pilot holes or openings that have been previously drilled to substantially the full torque capacity of the drilling apparatus through use of conventional auger attachments carried and rotated by the kelly bar of such earth drilling apparatus, comprising a vertically disposed kelly socket for the reception of the kelly bar of such earth drilling apparatus, a cross frame joined to said kelly socket, guide members circumferentially disposed on the outer extremities of said cross frame and adapted to engage the walls of said previously drilled pilot holes or openings, cutter bits disposed adjacent said guide members in non-following position each with respect to the cutter bit circumferentially next adjacent thereto for slightly enlarging the bore diameter of said pilot hole and to provide a guide bore in said earth structure, diametrically opposed intermediate extension arms extending radially outwardly past said first cutter bits, diametrically opposed upper extension arms extending radially outward past said intermediate extension arms at circumferential positions away from said intermediate extension arrns, and cutters on said extension arms disposed for cutting and reaming openings of successively increased diameter, all of said cutters being likewise disposed in non-following position each with respect to the cutters circumferentially next adjacent thereto whereby each of said cutters and cutter bits will engage, cut and remove a portion of earth wal' to progressively ream and enlarge said original pilot opening and guide bore.

4. A reamer attachment for earth drilling apparatus adapted for enlarging the diameter of pilot holes or openings that have been previously drilled to substantially the full torque capacity of the drilling apparatus through use of conventional auger attachments carried and rotated by the kelly bar of such earth drilling apparatus, comprising a vertically disposed kelly socket for the reception of the kelly bar of such earth drilling apparatus, a cross frame joined to said kelly socket, guide members circumferentially disposed on the outer extremities of said cross frame and adapted to engage the walls of said previously drilled pilot holes or openings, cutter bits disposed adjacent said guide members in non-following position each with respect to the cutter bit circumferentially next adjacent thereto for slightly enlarging the bore diameter of said pilot hole and to provide a guide bore in said earth structure, diametrically opposed intermediate extension arms extending radially outwardly past said first cutter bits, diametrically opposed upper extension arms extending radially outward past said intermediate extension arms at circumferential positions away from said intermediate extension arms, cutters on said extension arms disposed for cutting and reaming openings of successively increased diameter, all of said cutters being likewise disposed in non-following position each with respect to the cutters circumferentially next adjacent thereto whereby each of said cutters and cutter bits will engage, cut and remove a portion of earth wall to progressively ream and enlarge said original pilot opening and guide bore, and said cutters on said intermediate and upper extension arms being of proper number and radial position to balance the torque forces of the diametrically opposed and circumferentially following positions.

References Cited by the Examiner UNITED STATES PATENTS 883,137 3/1908 Karns 17'5-384 892,849 7/1908 Karns 175-384 X 1,172,065 2/1916 Sletten et al. 175-391 X 1,436,890 11/1922 Mathews 175-263 X 1,667,155 3/1927 Higdon 175263 2,684,834 7/1954 Miller et al. 175-53 2,843,362 7/1958 Degen 175385 X 2,960,312 11/1960 Kandle 175391 X 3,011,567 12/1961 Turner 175--53 3,077,235 2/1963 Govin 175391 X CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

R. E. FAVREAU, Assistant Examiner.

Claims (1)

1. A REAMER ATTACHMENT FOR EARTH DRILLING APPARATUS ADAPTED FOR ENLARGING THE DIAMETER OF PILOT HOLES OR OPENINGS THAT HAVE BEEN PREVIOUSLY DRILLED TO SUBSTANTIALLY THE FULL TORQUE CAPACITY OF THE DRILLING APPARATUS THROUGH USE OF CONVENTIONAL AUGER ATTACHMENTS CARRIED AND ROTATED BY THE KELLY BAR OF SUCH EARTH DRILLING APPARATUS, COMPRISING A VERTICALLY DISPOSED KELLY SOCKET FOR THE RECEPTION OF THE KELLY BAR OF SUCH EARTH DRILLING APPARATUS, A CROSS FRAME JOINED TO SAID KELLY SOCKET, GUIDE MEMBERS CIRCUMFERENTIALLY DISPOSED ON THE OUTER EXTREMITIES OF SAID CROSS FRAME AND ADAPTED TO ENGAGE THE WALLS OF SAID PREVIOUSLY DRILLED PILOT HOLES OR OPENINGS, CUTTER BITS DISPOSED ADJACENT SAID GUIDE MEMBERS IN NON-FOLLOWING POSITION EACH WITH RESPECT TO THE CUTTER BIT CIRCUMFERENTIALLY NEXT ADJACENT THERETO FOR SLIGHTLY ENLARGING THE BORE DIAMETER OF SAID PILOT HOLE AND TO PROVIDE A GUIDE BORE IN SAID EARTH STRUCTURE, EXTENSION ARMS EXTENDING RADIALLY OUTWARDLY PAST SAID FIRST CUTTER BITS AT CIRCUMFERENTIALLY SPACED POSITIONS, AND CUTTERS ON SAID EXTENSION ARMS DISPOSED FOR CUTTING AND REAMING AN OPENING OF SUBSTANTIALLY INCREASED DIAMETER, SAID CUTTERS BEING LIKEWISE DISPOSED IN NON-FOLLOWING POSITION EACH WITH RESPECT TO THE CUTTERS CIRCUMFERENTIALLY NEXT ADJACENT THERETO WHEREBY EACH OF SAID CUTTER BITS AND CUTTERS WILL ENGAGE, CUT AND REMOVE A PORTION OF EARTH WALL TO PROGRESSIVELY REAM AND ENLARGE SAID ORIGINAL PILOT OPENING AND GUIDE BORE.

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