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Publication numberUS3379266 A
Publication typeGrant
Publication dateApr 23, 1968
Filing dateOct 21, 1965
Priority dateOct 21, 1965
Publication numberUS 3379266 A, US 3379266A, US-A-3379266, US3379266 A, US3379266A
InventorsFletcher Roy W
Original AssigneeRoy W. Fletcher
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Earth boring mechanism with expansion underreamer
US 3379266 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

April 23, 1968 R. w. FLETCHER EARTH BORING MECHANISM WITH EXPANSION UNDERREAMER Filed oct. 21, 1965 United States Patent O 3,379,266 EARTH BORING MECHANHSM WITH EXiANSION UNDERREAMER Roy W. Fletcher, 35 Twin Oaks Ave., San Rafael, Calif. 94901 Filed Oct. 21, 1%5, Ser. No. 499,764 8 Claims. (Cl. F15-285) ABSTRACT F THE DISCLSURE An earth boring mechanism with three rotatively connected telescoping elements, one rotating on a base plate having a threaded footer and slidably supporting a spider, another roating and moving the spider to expand and collapse articulated cutting blades interconnecting the spider and baseplate, and the third element limiting upward movement of the spider and carrying a screw conveyor.

The improved earth boring mechanism comprising the present invention has been designed for use primarily in connection with the boring or drilling of holes in an earth foundation for the erection of concrete columns and the like, the mechanism having associated therewith means whereby an annular torus may be cut in an otherwise cylindrical shaft so that when the wet concrete is poured into the shaft and has become set or hardened, an annular bead or footing, or both, will be provided on the concrete column so that the latter will resist settling under the influence of the weight of an overlying installation such as a stoop, porch or the like. The invention is, however, capable of other uses and earth boring mechanisms embodying the principles of the present invention may be employed in the production of holes, with or without undercuts as desired, regardless of whether such holes be employed for concrete work or otherwise. Irrespective however of the particular use to which the present invention may be put, the essential features thereof are at all times preserved.

Earth boring mechanisms having associated therewith means for effecting bottom cuts in a shaft undergoing boring `are known. However, the present invention affords a novel mechanism which is versatile and more efficient than present day earth boring mechanisms in that it is capable of producing a completed shaft with one or more undercuts therein and without requiring the use of extraneous or auxilliary equipment such as ordinarily is required in connection with known earth boring mechanisms. For example, where conventional earth boring equipment designed for the same purpose `as that of the present invention is concerned, continued boring or cutting operations can not be conducted without frequent removal of the loosened earth and stone. Even where soft clay is concerned, clogging of the cutting blades will take pla-:e unless they are given ample clearance for purposes of rotation by removal of the diggings at frequent intervals. Such removal of the diggings has been accomplished by the use of bucket type lifts, earth ygrabs `and the like but these, when in use, require termination of the digging operation until such time as the shaft undergoing digging has been substantially cleared of excess loose material.

The present invention overcomes this particular limitation that is attendant upon the use of conventional digging mechanisms and, accordingly, it contemplates the provision of an apparatus whereby during actual boring operations the loose diggings are continuously withdrawn from the shaft undergoing boring so that the mechanism may remain in continuous use until such time as the shaft undergoing boring is nearly complete and ful-l shaft depth has been attained. Then, and at the completion of boring operations, and in order to clear the bottom of the shaft of any loose material which otherwise would not be removed rice because boring operations have been terminated, the cutting or boring blades associated with the mechanism are caused to contract upon the loosened material in the manner of an earth grab and, upon withdrawal of the mechanism from the shaft, substantially all of the remaining loose material will be lifted from the shaft with the mechanism. Stated otherwise, whereas conventional boring mechanism requires frequent withdrawal thereof from the shaft undergoing boring for earth removal, the present boring mechanism requires but one removal, and such removal takes place at the termination of boring operations and constitutes the termin-al removal of the mechanism from the scene of operations.

The provision of an earth boring mechanism such as has been briefly outlined above, and possessing the stated advantages, constitutes the principal object of the present invention. A further object of the invention is to provide such an apparatus having associated therewith novel elbow type expansible and contractible cutting blades which are effective on opposite sides of the elbow joint for cutting purposes and vwhich therefore materially enlarge the cutting area available, thereby resulting in la mechanism which will bore a shaft more efliciently and at a faster rate than has heretofore been possible with conventional mechanism.

An additional and important object of the invention is to provide a boring mechanism of this type having associated therewith novel manual control means whereby the mechanism may be operated without requiring 'any particu-lar degree of skill or experience, and which, moreover, requires no `walking lbeam or other steadying inuence for its support during operation thereof.

With these and other objects in view, which will become readily apparent as the following description ensues, the invention consists in the novel construction, combination and arrangement of parts shown in the accompanying single sheet of drawings forming a part of this specification.

In the drawing:

FlG. 1 is a side elevational view, partly in longitudinal section, showing an earth boring mechanism embodying the principles and concept of the present invention;

FIG. 2 is a sectional view taken substantially on the line 2 2 of FIG. l;

FIG. 3 is a sectional view showing a modification of FIG. l as it would appear at the line 3-3 of FIG. l; and

FIG. 4 is an enlarged fragmentary side elevational view, partly in section, illustrating the manner of operation of the earth boring mechanism in the production of a shaft having an undercut footing and also a bead part way down.

Re erring now to the drawings in detail and in particular to FIG. l an earth boring mechanism embodying the present invention has been designated in its entirety at 1G. The mechanism involves in its general organization a main torsion shaft 12, which may be i'i the form of a cylindrical tube, the upper end of which carries a torsion bar 14 by means of which the shaft 12 may be rotated. Carried at the lower end of the shaft 12 is the digging mechanism proper, this mechanism including a series of four radial elbow type cutters 16, each of which comprises an upper cutting blade 18 and a lower cutting blade 2% pivotally connected together as at 22 to provide an elbow joint. The upper ends of the upper blades 18 are pivoted by bolts 24 to a collar or spider 26 which as shown in FIG. 3 has bifurcated radial arms 2S between which the upper ends of the blades 18 extend, or as shown in FIGS. 1 and 4 is received between spaced ears 25 upon the upper ends of blades 18, the bolts 24 in both embodiments passing through the arms 28 and associated blades 18. The lower ends of the lower blades 2t) are pivote-d to a oase plate or spider 30 (FIG. 2)

3 by bolts 32, the spider being welded as at 34 or otherwise fixedly secured to the lower end of the torsion rod 12.

As best seen in FIG. 1, the upper cutting blades 18 are each in the form of an angle bar having a lateral flange provided with a series of cutting teeth 36 which extend upwardly along the blade in the immediate vicinity of the pivotal connection 22 and which project laterally in the direction of rotation of the torsion bar 12. The blades ltl are of relatively narrow design as compared to the lower cutting blades 20 which are relatively wide and are each comprised of a flat plate portion 38 having a series of cutting teeth 40 extending along its leading edge, 4and a marginal flange or rib 42 extending along its trailing edge. Ears 44 are formed on the lower endge of the plate portion 38 and the pivot bolts 32 project through these ears and are threadly received in the spider 30 as clearly shown in FIG. 2.

The underneath side of the spider 30 has welded. or

otherwise secured thereto a generally conical fee-der in the form of an earth boring worm, the functions of which are to provide a centering guide and establish a downward drag on the earth boring mechanism as a whole during digging operations as will be described in greater detail presently.

The upper vertically shiftable spider 26 is carried at the lower end of a sleeve 52 which telescopes with the torsion shaft 12 and an outer sleeve or guard 54 surrounds the sleeve 52. The upper end of the sleeve 52 is welded as at 56 to the torsion bar 14, and carries at its lower end an abutment plate 58 designed for engagement by the spider 26 for limiting the uppermost position of the latter with respect to the torsion bar 12. An elongated vertical slot 60 is formed in one side of the outer sleeve 54 and an operating bar 62 projects radially outwardly through the slot 60 and has its inner end anchored in the vertically shiftable sleeve 52. T he outer sleeve 54 is provided with a relatively short pitch, wide blade, helical screw conveyor or elevator 64 by means of which earth diggings are removed from the shaft undergoing formation, all in a manner that will be described in greater detail subsequently.

In FIG. 4 the versatility of the herein described earth boring mechanism of the present invention has been illustrated, the mechanism being shown in the condition which it assumes near the completion of digging operations in the creation of a shaft which is adapted, when completed, to have poured therein a mass of wet concrete in the formation of a foundation pillar or the like associated with a building construction. For exemplary purposes, the

shaft 70 is shown as being provided with an annular beadlike recess 72 in the medial region thereof, and a lower enlarged base void 74 which. establishes a base footing for the pillar. Otherwise, the shaft 70 is cylindrical as indicated at 76.

Initial digging operations are performed by centering the lower tip of the conical feeder 50 on the surface of the ground or earth at the particular point selected for creation of the shaft 70, and then, with the mechanism in a vertical position, applying downward pressure thereto and rotating the torsion bar 12 in a clockwise direction as viewed in FIGS. 2 and 3. It will be understood, of course, that the operating bar 62 will be positioned near the upper end of the slot 60 in the outer sleeve 54 so that the articulated elbow joints established by the various upper and lower cutting blades 18 and 20 will assume the retracted or almost straightened positions in which they are shown in FIG. 1 wherein a minimum diameter shaft 70 will be created. For any desired larger diameter shaft, the initial position of the operating bar 62 will be appropriately adjusted downwardly from its uppermost posilion.

Continued turning of the torsion bar 12 will apply torque to the lower spider 30, and consequently to the feeder 50 which then will enter the earth and be drawn downwardly therein until Such time as the teeth 40 0H the lower blades 20 encounter the earth. Thereafter, with the conical feeder Stl serving the dual purpose of drawing the entire mechanism downwardly and of loosening the earth in advance of the cutting teeth 40, digging operations will continue until such time as the cutting teeth 40 are completely embedded in the earth and the cuLting teeth 36 on the upper blades 18 reach a level where they too may assist in the digging operation. Further and continued rotation of the torsion bar 12 will be accompanied by a lowering of the mechanism bodily into the earth with loose diggings moving upwardly through the spider 26 and onto the elevator 64. When the helical screw elevator 64 encounters the loosened diggings the loosened diggings will be elevated out of the shaft 7) and be deposited at the rim of the shaft where they may readily be removed. If no adjustment of the operating bar 62 is resorted to during such digging operations, a truly cylindrical shaft 70 will result and, due to the relatively broad expanse of the lower cutting blades 20, as previously described, the four blades will establish, in effect, a cradle which will support most of the diggings therein so that when the mechanism is finally lifted from the shaft, the entrained diggings will be removed from the latter.

,For the creation of a base footing as exemplified by the enlarged void 74 at the lower end of the shaft 70, it is merely necessary for the operator to progressively lower the operating rod 62 during the final digging operations. Initial downward adjustment of this rod 62 will cause the upper spider 26 to move away from the abutment plate 58, thus tending to partially collapse the articulated blade structure 18, Ztl and widen the cutting action of the teeth 40 and 36 so that these blades will cornmence to establish the bell-shaped void '74 at the base of the shaft 70. The screw elevator or conveyor 64, having at this time assumed a lowered position suthcient to engage the diggings in the shaft 70, will, as digging operations are continued, progressively remove digging from the upper regions of the bell-shaped void so that torsional resistance to turning of the mechanism 10 will be considerably relieved.

It is to be noted at this point that whereas during the digging of the cylindrical portion 76 of the shaft 70, both the teeth 40 and the teeth 36 are effective for cutting action, only the teeth 40 are. effective during creation of the bell-shaped void 74. This is due to the fact that during expansion of the articulated blade structure, the upper cutting teeth are directed more radially inwardly toward` the central axis of the boring mechanism 10 away from the wall of the bell formed void.

At such time as the full diameter of the bell-shaped void 74 is completed, the upper spider 26 will come to rest on the lower spider 3) and the blades 18 and 20 will be collapsed upon each other, an approximation of this condition being shown in FIG. 4 where the apparatus is fragmented to show the upper and bottom Walls of the void '74.

At this time, the operating bar 62 will be disposed in the lower regions of the slot 60. `Digging operations may then be discontinued preparatory to lifting the mechanism from the shaft 70.

Removal of the mechanism 10 from the shaft 7G is accomplished by raising the operating bar 62 in the slot 60, thus elevating the upper spider 26 and causing the blades 18 and 20 to become retracted to the positions in which they are shown in FIG. l. During such retraction of the blades, the small amount of diggings remaining in the void 74, i.e., the diggings which lie below the level of the screw elevator 64, are gathered together by the cradle-like action of the four relatively wide blades 20 which compresses these diggings into small proportions so that they may readily pass through the cylindrical portion 76 of the shaft 70 when the mechanism is lifted from the latter. Gathering of the diggings at the extreme bottom region of the void 74 is enhanced by the provision of the ribs 42 which extend along the trailing edges of the blades Ztl. During raising of the operating bar 62 preparatory to removal of the mechanism from the shaft, a slow rotational movement of the torsion bar 12 in a boring direction will cause the diggings to move onto the upper surfaces of the blades 2t) and the ribs 42 will tend to hold these diggings on the blades and prevent such from passing completely over the blades. in this manner a gathering action on the diggings will take place so that upon inward collapse of the blades the aforementioned gathering operation upon the diggings will result for a lift out.

Creation of a bead-forming annulus such as has been shown at 72. may readily be accomplished by proper manipulation of the operating rod 62 during rotation of the torsion shaft l2. A slight downward movement of the rod 62 in the slot et) will distend the cutting blades 18 and 20 to provide the downwardly facing area of the void. When the desired radial extent of the void has been attained, a slight upward movement of the rod 62 will establish the upwardly facing area of such void and the cutting blades will then be restored to their fully retracted positions so that continued rotation of the torsion shaft 12 will effect a continuation of the cylindrical portion 71S of the shaft 7d below the annular void 72. The vertical extent or width of the void, and consequentl of the bead which is to be formed in the concrete column, may be controlled by the duration of time that the operating rod 62 is allowed to remain in its lowered position during the digging operation.

From the above description it ywill be appreciated that the earth boring mechanism lil of the present invention is capable of cutting kerfs of a wide variety of sizes and shapes by proper manipulation of the operating rod 62. Inverted or upright frusto-conical void shapes and compound void shapes consisting of any desired combination of conical or spherical contours are made possible by an appropriate manipulation of the operating bar 62,. An initial application o-f the mechanism to the earth and a terminal Iremoval thereof from the shaft which is formed thereby are adequate to produce a wide variety of shaft shapes without requiring any intervening withdrawals of the mechanism from the shaft undergoing digging.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawing or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. For example, whereas the exemplary form of mechanism shown and described herein is a manually operable mechanism, it is within the purview of the present invention to provide a power-actuated mechanism which operates upon the same basic principles as those described herein. For example, for an effective application of power-initiated torque to the torsion shaft l2, the radial torsioin bar i4 may b'e replaced by a suitable pulley which may be connected by -a belt to the drive pulley of an operating motor. The operating control rod 62 in such a case would be replaced by a suitable fork-shift mechanism, all `within the scope of the present invention. These and other modifications are contemplated within the scope of the appended claims.

What is claimed is:

i. Earth boring mechanism comprising in combination: a central vertical torsion shaft, means carried at the upper end of said shaft whereby the same may be rotated in an earth-boring direction, a base plate xedly secured to the lower end of said shaft and rotatable in unison therewith, a spider vertically slidable on said shaft between said upper and lower ends thereof toward and away from said base plate, sleeve means encompassing said torsion shaft and having an abutment limiting the uppermost portion of the spider, an articulated series of cutting blades operatively connected to the base plate and spider and including a plurality of upper blades having their upper ends pvoted to the spider and a plurality of lower blades having their lower ends pivoted to the base plate, the free end of each upper blade being pivotally connected to the free end of an associated lower blade, thus establishing an articulated elbow joint, said blades being capable of swinging movement in respective vertical planes whereby, upon lowering and raising of the spider, the articulated series of blades are capable of radial expansion and contraction respectively, means reciprocable Within said sleeve means for raising and lowering said spider with respect to said base plate, and a threaded footer lixedly secured to the underneath side of said base plate having a major diameter approximately the same as the base plate for drawing said torsion shaft, and consequentlyv the entire earth boring mechanism downwardly and loosening the earth in advance of said blades during rotation of the torsion shaft in an earth-'boring direction.

2. Earth boring mechanism as set forth in claim 1 and wherein each of said upper and lower cutting blades are provided with a series of cutting teeth thereon which project laterally in the leading direction of rotation of the torsion shaft and in the vicinity of the elbow joints between associated blades.

3. Earth 1boring mechanism as set forth in claim 1 and wherein each of said lower cutting blades is in the form of a flat plate having a series of cutting teeth on the leading edge thereof, the width of said plate in a horizontal direction being of appreciable extent whereby, upon raising of said spider and consequent contraction of the articulated series of blades, said lower blades establish, in effect, an earth supporting cradle by means of which loose earth diggings may be elevated bodily with the mechanism.

4. Earth boring mechanism comprising in combination: a central vertical torsion shaft, means carried at the upper end of said shaft whereby the same may Ibe rotated in an earth-boring direction, a base plate xedly secured to the lower end of said shaft and rotatable in unison therewith, a spider vertically slidable on said shaft between said upper and lower ends thereof toward and away from said `base plate, screw conveyor means above said spider and rotatable with and carried by said torsion shaft limiting the uppermost position of the spider, an articulated series of cutting blades operatively connected to the base plate and spider and including a plurality of upper blades having their upper ends pivoted to the spider and a plurality of lower blades having their lower ends pivoted to the base plate, the free end of each upper blade being pivotally connected to the free end of an associated lower blade, thus establishing an articulated elbow joint, said blades being capable of swinging movement in respective vertical planes whereby, upon lowering and raising of the spider, the articulated series of blades are capable of radial expansion and contraction respectively, a tubular sleeve slidable on said torsion shaft, having its lower end iixedly secured to said spider, and projecting upwardly from the spider, an operating rod projecting laterally from the upper end of said sleeve, said sleeve being movable bodily with the spider between a lowered position wherein it is remote from the upper end of the torsion rod and a raised position wherein it is in close proximity to said upper end, and a threaded footer fixedly secured to the underneath side of said base plate for drawing said torsion shaft, and consequently the entire earth boring mechanism downwardly during rotation of the torsion shaft in an earth-boring direction.

5. Earth boring mechanism as set forth in claim 4, wherein each of said lower cutting blades is in the form of a llat plate having a series of cutting teeth on the leading edge thereof, the width of said plate in a horizontal direction being of appreciable extent whereby, upon raising of said spider and consequent contraction of the articulated series of blades, said lower blades establish, in effect, an earth-supporting cradle by means of which loose earth digeings may be elevated bodily with the mechanism.

Earth boring mechanism as set forth in claim 4,

wherein each of said lower cutting blades is in the form of a iiat plate having a series of cutting teeth on the leading edge thereof and an earth impelling rib on the trailing edge thereof, the width of said plate in a horizontal direction being of appreciable extent whereby, upon raising of said spider and consequent contraction of the articulated series of blades, said lower blades establish, in effect, an earth-confining and supporting cradle by means of which loose earth digvings may be elevated bodily with the mechanism.

7. Earth boring mechanism comprising in combination: a central vertical torsion shaft, an operating member at the upper end of said shaft whereby the same may be rotated in an earth-boring direction, a base plate ixedly secured to the lower end of said shaft and rotatable in unison therewith, a spider vertically slidable on said shaft between said upper and lower ends thereof toward and away from said base plate, an articulated series of cutting blades operatively connected to the base plate and spider and including n plurality of upper blades pivoed at their upper ends to the spider and a plurality of lower blades having their lower ends pivoted to the base plate, the free end of each upper blade being pivoted to the free end of an associated lower blade, thus establishing an articulated elbow joint, said blades being capable of swing movement in respective vertical planes whereby, upon lowering and raising of the spider, the articulated series of blades are capable of radial expansion and contraction respectively, a tubular sleeve slidable on said torsion shaft, having its lower end xedly secured to the spider, and

projecting upwardly from the latter, an operating rod projecting radiaiy from the upper end of said sleeve, said sleeve being movable bodily with the spider between a lowered position wherein said operating rod is remote from said operating member and a raised position wherein it is in close proximity to said operating member, and an outer tubular sleeve encompassing said lirst mentioned tubular sleeve and having its upper end iixcdly secured to the operating member, there being a vertical slot in said outer tubular sleeve through ywhich said operating rod projects.

8. Earth boring mechanism as set forth in claim 7 and including, additionally, a threaded footer xedly secured to the underneath side of said base plate for drawing said torsion shaft, and consequently the entire earth boring mechanism downwardly during rotation of the torsion i shaft in an earth-boring direction.

References Cited UNITED STATES PATENTS 1,970,063 8/1934 Steinman 175--285 X 2,031,353 Z/l936 Woodnuii 175-285 2,176,410 ill/i939 Ruddell 175-285 2,450,223 9/1948 Barbour 175--285 X 2,910,274 lil/1959 Scott 175-285 X 3,077,235 2/1963 Govin 175-285 CHARLES E. OCONNELL, Primary Examiner.

ERNEST R. PURSER, NILE C. BYERS, JR., Examiners.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1970063 *Apr 24, 1933Aug 14, 1934Steinman Frederick WUnderreamer
US2031353 *Aug 16, 1935Feb 18, 1936Ellis Woodruff HarveyUnderreamer
US2176410 *Feb 26, 1938Oct 17, 1939Ruddell Stuart GExpanding auger
US2450223 *Nov 25, 1944Sep 28, 1948Barbour William RWell reaming apparatus
US2910274 *Jun 7, 1956Oct 27, 1959Scott Loren FExcavating apparatus
US3077235 *Aug 3, 1960Feb 12, 1963Salem Tool CoCollapsible mining head
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3598193 *Jan 29, 1970Aug 10, 1971Navenby LtdCutter bits with radially extendable cutter elements
US3757876 *Sep 1, 1971Sep 11, 1973Smith InternationalDrilling and belling apparatus
US4323129 *Feb 25, 1980Apr 6, 1982Cordes William JHole digging apparatus and method
US6575255 *Aug 13, 2001Jun 10, 2003Cdx Gas, LlcPantograph underreamer
US6591922Aug 13, 2001Jul 15, 2003Cdx Gas, LlcPantograph underreamer and method for forming a well bore cavity
US6595301Aug 17, 2001Jul 22, 2003Cdx Gas, LlcSingle-blade underreamer
US6595302Aug 17, 2001Jul 22, 2003Cdx Gas, LlcMulti-blade underreamer
US6644422 *Aug 13, 2001Nov 11, 2003Cdx Gas, L.L.C.Pantograph underreamer
US6722452Feb 19, 2002Apr 20, 2004Cdx Gas, LlcPantograph underreamer
US6851479Jul 17, 2002Feb 8, 2005Cdx Gas, LlcCavity positioning tool and method
US6962216May 31, 2002Nov 8, 2005Cdx Gas, LlcWedge activated underreamer
US6976547Jul 16, 2002Dec 20, 2005Cdx Gas, LlcActuator underreamer
US7007758Feb 7, 2005Mar 7, 2006Cdx Gas, LlcCavity positioning tool and method
US7182157Dec 21, 2004Feb 27, 2007Cdx Gas, LlcEnlarging well bores having tubing therein
US7213644Oct 14, 2003May 8, 2007Cdx Gas, LlcCavity positioning tool and method
US7264048Apr 21, 2003Sep 4, 2007Cdx Gas, LlcSlot cavity
US7434620Mar 27, 2007Oct 14, 2008Cdx Gas, LlcCavity positioning tool and method
US7891441Jun 6, 2007Feb 22, 2011Paul Bernard LeeExpandable downhole tool
US8276690Jan 28, 2011Oct 2, 2012Paul Bernard LeeExpandable downhole tool
DE2422489A1 *May 9, 1974Nov 20, 1975Takechi Komusho KkEarth borer with drill shaft and screw shaped cutting blade - shaft has hub with stops for rotary blades pivot fitted to hub
WO2007144719A2 *Jun 6, 2007Dec 21, 2007Lee Paul BernardExpandable downhole tool
Classifications
U.S. Classification175/285
International ClassificationE21B10/00, E21B10/44, E21B10/32, E21B10/26
Cooperative ClassificationE21B10/44, E21B10/32
European ClassificationE21B10/44, E21B10/32