US 3429390 A
Description (OCR text may contain errors)
Feb. 25, 1969 F. 1.. BENNETT EARTH-DRILLING BITS Sheet Filed May 19, 1967 INVENTOR Fred L. Bennett fi a fi Y ATTORNEYS Feb. 25, 1969 F. L. BENNETT 3,429,390
EARTH-DRILLING BITS Filed May.l9. 1967 Sheet 3 of 5 INVENTOR Fred L. Bennett ATTORNEYS Feb. 25, 1969 Filed May 19, 1967 F. L. BENNETT EARTH-DRILLING BITS Sheet 39 I ff INVENTOR Fred L. Bennett ATTORNEYS F. L. BENNETT Feb. 25, 1969 EARTH-DRILLING BITS Sheet 4 015 Filed May 19, 1967 Fl 6. l 7
F I G. I l
INVENTOR Y 7 Fred L. Bennett I, d I v BY W 4 I ATTORNEYS v Feb. 25, 1969 F. L. BENNETT 3,429,390
EARTH-DRILLING BITS Filed May 19, 1967 Sheet 5 of s INVENTOR Fred L. Bennett ATTORNEYS 3,429,390 EARTH-DRILLIN G BITS Fred L. Bennett, Clarksville, Ark., assignor to Supercussion Drills, Inc., San Antonio, Tex., a corporation of Texas Filed May 19, 1967, Ser. No. 639,792
US. Cl. 175343 10 Claims Int. Cl. E21b 9/08; E21c 13/02 ABSTRACT OF THE DISCLOSURE Earth-drilling bits having flat conical drilling faces inclined at an angle to the axis of the drill hole with nontracking drilling elements, means for holding only a portion of the periphery of the bit against the wall of the drill hole, having a unique gyratory movement and unique bearing and sealing means and being particularly adapted for use with percussion and turbine types of drilling rigs.
BACKGROUND OF THE INVENTION Field of the invention The invention was made to answer the need for an earth-drilling bit particularly adapted with bearing and structure sufficiently rugged for use with percussion and turbine types of drilling rigs, Previous bits have not been able to Withstand either heavy impact forces of percussion type drilling rigs or the rotational speeds of turbine type rigs.
Description the prior art No prior art is known except the several US. patents issued to Zublin, the members of which are not known.
SUMMARY OF THE INVENTION The invention relates to earth-drilling bits having angularly-disposed gyratory bit members with relatively flat conical drilling faces with a multiplicity of unequallyspaced drilling elements thereon, the bit members regressing slowly as the bits are rotated or, in other words progressing slowly in the opposite direction to the direction of rotation of the entire bit, with which any type of drilling fluid may be used and which are especially adapted for use with percussion and turbine types of drilling rigs. The various forms of the invention include novel lubricant seals, heavy impact and bit-load bearings means for selectively enhancing the flow of drilling fluid through the bit or terminating the flow to hold the drill string full of drilling fluid under pressure. The bits have stand-off means for holding only a portion of the periphery of the bit member against the wall of the drill hole so that the bits drill bore holes larger in diameter than the bits themselves.
A construction designed to carry out the invention will be hereinafter described, together with other features of the invention.
The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, wherein examples of the invention are shown.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical, longitudinal, sectional view of an earth-drilling bit constructed in accordance with the invention and showing a form thereof adapted to selective enhancing the flow of drilling fluid through the bit, showing the enhancing means closed,
FIG. 2 is a vertical, longitudinal, sectional, fragmentary view of the bit of FIG. 1, showing the enhancing means open,
nited States Patent 0 3,429,395 Patented Feb. 25, 1969 FIG. 3 is a view in perspective of the core of the flowenhancing means,
FIG. 4 is a bottom plan view of the bit,
FIG. 5 is a horizontal, cross-sectional view taken on the line 5-5 of FIG. 1,
FIG. 6 is a vertical, longitudinal, sectional fragmentary view of a modification of the bit showing the valve means for holding pressure in the drill string, the valve means being open,
FIG. 7 is a view similar to FIG. 6, the valve means being closed,
FIG. 8 is a bottom plan view of the valve means of FIGS. 6 and 7,
FIG. 9 is a vertical, longitudinal, sectional view of a further modification of the invention in which the anvil or body member of the bit is isolated percussion-wise from the bit case and the drilling string,
FIG. 10 is a horizontal, cross-sectional view taken on the line 1010 of FIG. 9,
FIG. 11 is a vertical, longitudinal, sectional view of yet another modification of the invention showing unique stabilizing bearings,
FIG. 12 is a horizontal, cross-sectional view taken on the respective line 1212 of FIG. 11,
FIG. 13 is a vertical, longitudinal, sectional view of still another modification of the invention showing structures 'for utilizing thrust bearings in the bits to any desired extent and novel lubricant seals for protecting the bearings,
FIG. 14 is a horizontal, cross-sectional view taken on the line 14-14 of FIG. 13,
FIG. 15 is a bottom plan view of the bit of FIG. 13,
FIG. 16 is a vertical, longitudinal, sectional, fragmentary view of a modified form of the thrust bearings of the bit of FIG. 13,
FIG. 17 is a vertical, longitudinal sectional, fragmentary view of a further modification of the thrust bearings of the bit of FIG. 17, and
FIG. 18 is a horizontal cross-sectional view taken on the line 1818 of FIG. 17.
DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, in FIG. 1 there is shown a form of the invention particularly adapted for use with percussiontype drilling rigs in which a percussion hammer 10 is reciprocated vertically in a percussion tool case 11 in order to impact with great force, rapidly and forcefully, upon the upper end of an anvil 12 constituting the upper end of the earth-drilling bit. The percussion tool itself is not shown but is of a type known in this art in which the function of the percussion tool is dependent upon a creation of back pressure upon the drilling fluid, which may be air, natural gas, drilling mud or any other suitable or desirable type of drilling fluid and upon the downward flow of which, under pressure through the flow passage 13 of the hammer 10 and the flow passage 14 of the anvil 12, the percussion tool is dependent for operation. Upon removal of such back pressure on the drilling fluid, the percussion tool ceases to function, and the hammering or delivery of percussion strokes is stopped.
The anvil 12 constitutes the upper end of a drill body member 15 and is in the form of an upstanding screw threaded pin 16 screw-threadedly connected to the lower end of the case 11 which, in turn, is connected to the lower end of the drill string (not shown). The body member 15 is shouldered at 17 for abutment with the lower end of the case, and below the shoulder 17, the body member 15 carries a plurality of external, radially outwardly-extending stand-oft members 18, preferably hardfaced for engagement with the wall of the drill hole to hold the body member 15 centered therein. The stand- 3 off members may be shoes, rollers or any other suitable or desirable type of structure which will function to center the body member in the drill bore.
The body member is provided on its lower end with a reduced, cylindrical pin 19, eccentrically oifset with respect to the axis of the body member, and extending downwardly at an angle to the longitudinal axis of the body member, which angle may be on the order of magnitude of 35 or greater or lesser.
A downwardly flared drill bit member 20 is provided with a cylindrical socket 21 at its upper end for receiving the pin 19, the bit member being held on the pin by an annulus of retaining balls 22 engaging in a hardened race 23, of semicircular cross section, formed in the wall of the socket 21 intermediate its end, and in a hardened race 24 of vertically elongated semicircular cross section formed at a corresponding elevation on the outer periphery of the pin 19.
The annulus of the retaining balls 22 is inserted into the two races through a radial opening 25 in the bit member aligned with the race 23 and closed by a screw threaded pin 26 after the bearing balls have been placed in position. The vertically elongated configuration of the race 24 permits limited reciprocal movement of the bit member 20 upon the pin 19.
The body member 15 has a downwardly facing shoulder 27 surrounding the upper end of the pin 19, and a hardened race 28 is provided therein complementary with a similar race 29 formed in the upper end of the bit member. An annulus of thrust bearing balls 30 is received in the two races. Further, the lower extremity of the pin 19 is cut away at its margin to form a hardened race 31, and the bottom of the socket 21 is cut away at its margin to form a hardened race 32. An annulus of suitable thrust bearing balls 33 are received in the races 31 and 32.
The bit member has a valve core or member 33 extending axially and upwardly from the bottom of the socket 21, the upper end of the valve member 33 being beveled or chamfered, the lower portion of the member 34 being surrounded by an annular drilling fluid flow passage 35 from which a plurality of rectilinear flow passages 36 extend angularly and downwardly to the drilling face 37 of the bit member and register with flow grooves 38 extending radially outwardly from the passages 36 to the outer periphery of the drilling face, the grooves being notched upwardly at their outer ends as shown at 39.
The drilling face 37, and this is true of all forms of the invention, is approximately flat, approximately flat as used herein meaning an absolutely flat face or one that has the shape of an almost flat, downwardly facing cone, the apex angle of the cone being of the order of 25 or more. The drilling face carries a multiplicity of irregularly spaced drilling elements which may have the form of hard metal inserts 40 having hemispherically shaped lower drilling faces 41. As shown in FIG. 4, the
grooves 38 divide the drilling face 37 into sectors, and the drilling elements 40 are irregularly spaced, either radially or circumferentially in each of the sectors with respect to the other sectors. Thus, as the drilling elements revolve over the bottom of the bore hole, they are prevented from tracking one "another in a gear-like action, and more effective and eflicient action is obtained.
The stand-off members 18 and the angular and offset disposition of the bit member, cause only a portion of the periphery of the drilling face from engaging the wall of the well bore, so that only a sector of possibly 20 to circumferentially, extent of the drilling face is drilling at any one time. The bit member and the drilling face thereof is less in diameter than the bore hole which it drills, but the gyratory movement of the drill member as it drills causes the entire drilling face to be employed for drilling in successive sectors and to drill a bore hole having a bottom of a slightly conical shape when a flat or only slightly conical drilling face is employed and a flat face when a slightly more conical drilling face is used.
This conical shape of the drill bore bottom, as shown at 37' in FIG. 1, functions also to aid in urging the bit toward one side of the bore hole. The bit member is necessarily of less diameter than the bore hole since otherwise the drilling face, being inclined, would drill at diametically opposite points and the desired drilling action would not be achieved.
If the drill string and thus the case 11 and body member 15 is revolved in one direction, by reason of the angle and offset position of the bit member the latter is caused to turn or progress in the opposite direction at a somewhat slower rate, possibly at the rate of 1 revolution to each l040 revolutions of the drill string. In this manner, the bit member undergoes a gyratory action, revolving slowly over the bottom of the bore hole, drilling all portions of the bottom of the bore hole with all portions of the drilling face under whatever load may be applied to the bit through the drill string as well as the quite sizable percussion impact delivered by the hammer 10.
The drilling fluid flow passage 14 extends downwardly through the body 15 into the bit 19 and opens into one side of an enlarged cylindrical flow passage 42 extending downwardly to the lower end of the bit 19 in registry with the annular flow passage 35. Valve means 43 in the form of a cylindrical spool, as shown in FIG. 3 is axially movable in the passage 42 and loosely confined therein by the snap rings 44 and 45 so as to be capable of undergoing limited axial movement in the flow passage 42. The valve member 43 has a rather large axial flow passage 46 surrounded by a number of somewhat smaller longitudinal flow passages 47, the flow passage 46 being of less diameter than the valve member 34. As noted, hereinabove, the type of percussion tool with which the particular bit shown in FIG. 1 is to be used if for operation on the existence of back pressure on the drilling fluid and will cease operating when such back pressure is removed. The structure of the modification of FIG. 1 which achieves this function in that when weight from the drill string is applied to the body member 15 and the pin member 19 is in its downwardmost position in the socket 21, the valve member 34 will engage and close off the center passage 46 of the valve member 43, as shown in FIG. 1, and drilling fluid will be passing only through the relatively restricted passages 47, thereby creating the necessary back pressure. When, however, the drill string is lifted, the bit member 20 drops upon the pin 19 into the position shown in FIG. 2, allowing the valve member 34 to disengage from the valve 43, opening the passage 46 to the flow of drilling fluid, thereby removing the back pressure and causing the percussion tool to cease functioning. Thus, the percussion tool may be placed in and out of operation at will by raising and lowering the drilling string.
It is sometimes desirable to be able to close off the drilling fluid in the drill string when drilling is momentarily halted for any reason, especially when gas such as air or natural gas is being employed at a relatively high pressure as the drilling fluid. If gas is being employed as the drilling fluid under a pressure of 500-1000 pounds per square inch, the loss of this gas under pressure when drilling is halted would necessitate a considerable period of time and expenditure of energy to build up the pressure when drilling is resumed. Drilling systems of this type normally have a back-pressure valve at the top of the drill string, but there is nothing to prevent the escape of the drilling fluid under pressure at the lower end of the drill string. The structure shown in FIGS. 6 and 7 makes provision for closing off the string and includes a cylindrical spool 48 which replaces the spool 43 in the flow passage 42 and has a snug sliding fit therein. The spool 48 is held in the passage 42 by upper and lower snap rings 49 and 50 and is provided with an axial bore 51 with a valve seat 52 at its upper end. A fluted valve core 53 is slidably positioned in the bore 51 formed with a plurality of longitudinal flow passage grooves 54 in its outer face through which the drilling fluid may pass and which also function to provide a back pressure on the drilling fluid. The valve core has a valve face 55 at its upper end adapted to engage the valve seat 52 and normally held spaced thereabove by the engagement of the valve means 34 when the body member and the bit member are collapsed on one another in drilling position, as shown in FIG. 6. When, however, the drill string is lifted, and the body member and bit member separate partially, as shown in FIG. 7, the valve member 34 moves downwardly permitting the valve face 55 to engage the valve seat 52, thus closing off the lower end of the drill string and trapping the drilling fluid under pressure in the interior thereof. Thus, when drilling is resumed, it is not necessary to build up the pressure of the drilling fluid again, and the needless and expensive expenditure of time and energy is avoided.
In the previously described forms of the invention, the hammer 10, although of appreciable mass, is required to deliver its impact strokes against the mass of not only the anvil 16 and the body and bit members but also against the mass of the case 11 and the entire drill string which is connected thereto. It is much more desirable to apply the impact blows of the hammer against only the body and bit members so that much greater forces are delivered to the drilling face of the bit, and such a structure is shown in FIGS. 9 and 10.
In this form of the invention, which is substantially identical to those previously described, except that the spools 43 and 48 are omitted, the upper end of the body member 15 is not connected directly to the case 11, but instead, it is reduced in diameter and formed into an upstanding cylindrical shank 44 slidably received in an externally screwthreaded sleeve 56, which, in turn, is screw threadedly connected to the case 11. At the upper end of the sleeve 56 are suitable sealing and/or bearing rings 57 and 58, above which is a split retaining ring 59 having an inwardly directed annular flange 60 received in a circumferential groove 61 in the upper end of the shank 55 to retain the shank 55 within the sleeve 56. The ring 59 is connected in any suitable fashion to the case 11, and the groove 61 is of greater axial length than the flange 60 so as to permit limited axial move ment of the shank 55 within the sleeve 56. Any suitable back pressure or flow restricting means 62 is removably positioned at the upper end of the drilling fluid flow passage 63 of the shank 55. For getting rotation from the sleeve 56 to the shank 55 and the body member 15, the two elements are splined together by a numeral of cylindrical elements 64 received in recesses 65 and 66 cut in the shank and sleeve, respectively, the recesses being of greater length than the elements 64 so as to permit relative longitudinal movement between the shank and the sleeve.
With this structure, the impact blows of the hammer are directed only to the shank 55, the body member 15 and the bit member 20, and since the bit assembly can move relative to the case and the drill string such impacts are not transmitted to the drilling string so that their force is directed solely to the drilling assembly for more effective and eflicient drilling.
It may be desirable in some instances to provide a small angular flow passage 67 leading from the drilling fluid flow passage 63 or any of the other drilling fluid flow passages into the space at the upper end of the bit member inwardly of the bearing balls 30 to provide lubrication and/or cleaning of the several bearings.
An alternate structure of the bit is shown in FIG. 11 in which an annulus of vertical needle bearings 68 and 69 are situated at the upper and lower ends of the pin 19, respectively, for stabilizing the bit member upon the pin, it being noted that either or both of the needle bearings 68 and 69 may be employed, and that the lower bearing balls 33 are shifted inwardly toward the flow passage 14', or may be omitted entirely.
A preferred form of the invention is shown in FIGS. 13, 14 and 15 in which the grooves 38 are omitted, and only a plurality of upwardly inclined peripheral notches 70, equivalent to the cut away portions 38 of the bit shown in FIG. 1, are provided in the outer margin of the drilling face 71.
The body member 72 has an angularly directed flow passage 73' opening downwardly into a counter bored socket 74 formed eccentrically of the body member 72 and extending angularly to the longitudinal axis thereof. An annular groove 75 is formed in the top of the uppermost and narrowest portion 76 of the socket 74 and receives a grease sealing ring 77 having in its upper and lower faces V-shaped sealing grooves 78 to provide chevron-type lubricant seals.
Below the uppermost portion 76, the socket 74 is enlarged at 79 to receive an annulus of vertical needle-type, stabilizing bearings 80, and the retaining balls 22 are provided therebeneath for retaining the bit member in the socket 74 as previously described.
Below the retaining balls 22, the socket 74 is further enlarged to form a downwardly facing shoulder 81 receiving a bearing ring 82, dual roller bearings 83 and a lower bearing ring 84. Therebelow, the socket is further enlarged at 85 to receive needle-type stabilizing bearings 86 and is formed with a second recess 87 which receives a lubricant retaining ring 88 substantially identical to the sealing ring 77. A suitable lubricant may be introduced into the space between the seals 77 and 88 through the passage 25 and retained therein by the seals and the screw-threaded pin 26. It is noted that the lubricant in the bearing area and the drilling fluid externally of the bit will equalize in pressure through the threads of the screw-threaded plug 26.
The bit member 89 has its exterior stairstepped upwardly having a first shoulder 90 underlying the lower end of the body member 72, a firs-t cylindrical face 91 engaging the sealing ring 88, a second upwardly facing shoulder 92 underlying and supporting the bearings 86, a second cylindrical face 93 engaging the bearings 86, a third upwardly facing shoulder 94 underlying the bearing ring 84, a third cylindrical face 95 adjoining the bearings members 82, 83 and 84 and recessed to receive the retaining balls 22, Above the retaining balls 22 the upper portion of the bit member, which now constitutes an upstanding shank 96, is formed with a further upwardly facing shoulder 97 underlying and supporting the bearings 80 and a further face 98 engaging the bearings 80 and the sealing ring 77. It is quite obvious that the shoulders 81 and 94 may be spaced apart as far as desired so as to accommodate any desired number of thrust bearings superposed therebetween.
The bearings 82, 83 and 84 may be replaced with a metal to metal bearing as shown in FIG. 16. In a metal to metal bearing, the metals must be different or at least, different alloys, thus, assuming the body and bit members to be alloy steels, the upper metallic bearing ring 99 could be formed of tool steel and the lower bearing ring 100 formed of bronze, with grooved faces for the reception and passage of lubricating material. At the beginning the sliding or bearing faces would be between the rings 99 and 100, but as these abutting faces wore and galled the bearing face would shift either to the ring 99 and the shoulder 81 or to the ring 100 and the shoulder 94. When the first of these faces was worn and galled, the bearing then passes to the other of said pairs of faces. By this means the equivalent of three bearings is obtained with the bearing function passing successively from one pair of faces to the next. Of course, more than two of the bearing rings may be used.
The configuration of the drilling elements or inserts 101 in this form of the bit is somewhat modified and a specific example thereof is shown in FIG. 15. In this particular configuration there are eight of the peripheral notches 70 spaced equally around the circumference of the face 71 with eight peripheral drilling inserts 102 spaced equally around the margin of the drilling face, one between each pair of notches. inwardly of the inserts 102 are four drilling inserts 103 radially aligned with the inserts 102 and inwardly thereof three inserts 104 spaced radially inwardly of certain of the inserts 103. A single insert 105 is positioned inwardly of the inserts 104 and one single drilling insert positioned centrally of the drilling face with four drilling fluid flow passages 107 extending through the drilling face 71 intermediate the pairs of the notches 70. Obviously greater or lesser numbers of the drilling inserts may be used, and different configurations or spacings employed.
It is readily apparent that this configuration provides the largest number of cutting inserts at the edge of the drill hole where most of the drilling is to be done with progressively fewer inserts radially inwardly to the center of the bit to accommodate the successively decreasing areas of the bore hole to be drilled, The relatively sparse number of drilling inserts provides uncluttered spaces through which the drilling fluid readily flows to the notches 70, sweeping over the surface being drilled and keeping both it and the drilling face clear of drill material.
The body member 72 has on its periphery above the lower end thereof a plurality of standoff means 108 disposed at an angle, for instance, 45 with respect to the longitudinal axis of the bit, the standoff means 108 being spaced apart to provide fluid flow passages therebetween. The standoff means may be arranged in any desired pattern. The standoff means may be hard-faced guide shoes, rollers or any other suitable structure. In addition, standotf rollers (not shown) could be provided in the body member 72 above the standoff means 108.
A final form of the bit is shown in FIG. 17 this form of the bit being substantially identical to that shown in FIG. 13, but the bearings 82, 83 and 84 being replaced by one or more superposed ball bearings 109 which function as thrust bearings.
Various changes and modifications in the methods and products outlined and disclosed herein may be made within the scope of the claims appended hereto without departing from the spirit of the invention.
What I claim and desire to secure by Letters Patent is:
1. An earth-drilling bit including a bit body member a drill bit member connected to the body member, one of the members having a shank, the other of the members having a socket receiving the shank, said body member and said bit member vertically reciprocable with respect to one another, said body member and said bit member having registering drilling fluid flow passages, the bit member having a single one-piece drilling face and being rotatably mounted on the body member, the bit member having its longitudinal axis inclined with respect to the longitudinal axis of the body member and having an approximately flat drilling face, a drilling fluid flow member carried by one of said members having at least one drilling fluid flow-restricting passage and at least one drilling fluid flow-enhancing passage, valve means carried by the other member registering with the flow-enhancing passage for closing the same when the members are collapsed upon one another so as to permit the flowrestricting passage to restrict the flow of the drilling fluid and for opening the flow-enhancing passage when the members are moved apart to enhance the flow of the drilling fluid, and stand-off members on the outer surface of the body member for holding one portion only of the periphery of the bit member against the wall of the drill hole whereby the drilling face of the bit is smaller in diameter than the hole it drills.
2. An earth-drilling bit as set forth in claim 1 wherein the shank is on the bit member and the socket is on the body member.
3. An earth-drilling bit as set forth in claim 1 wherein the shank is on the bit member and the socket is on the body member, the shank and socket having shoulders facing each other, and a plurality of thrust bearing members confined between the shoulders.
4. An earth-drilling bit as set forth in claim 1 and lubricant sealing rings between the upper and lower extremities of the shank and socket, each sealing ring having V-shaped chevron-type sealing grooves in its upper and lower faces.
5. An earth-drilling bit as set forth in claim 1 wherein the drilling face of the bit member is divided into circumferential sections and carries a multiplicity of earthdrilling elements, the drilling elements of the sections being spaced apart on the drilling face by differing degrees whereby the earth-drilling elements do not track one another as the bit revolves.
6. An earth-drilling bit as set forth in claim 1 and vertically-disposed annuli of needle stabilizer bearings between the upper and lower extremities of the shank and socket.
7. An earth-drilling bit as set forth in claim 1 and circumferentially-spaced upwardly-inclined notches about the periphery of the drilling face.
8. An earth-drilling bit as set forth in claim 1 and circumferentially-spaced upwardly-inclined notches about the periphery of the drilling face, a first peripheral set of drilling elements on the drilling face, one between each pair of notches, a second set of a lesser number of drilling elements spaced radially inwardly of the first set, a third set of a still lesser number of drilling elements spaced radially inwardly of the second set, at least one drilling element spaced radially inwardly of the third set, and at least one drilling element positioned centrally of the drilling face.
9. An earth-drilling bit as set forth in claim 1, and thrust bearings between the body member and the bit member comprising at least a pair of flat superposed rings formed of metals dissimilar to each other and to the metal or metals of which the body member and bit member are formed,
10. An earth-drilling bit including a bit body member, a drill bit member connected to the body member, one of the members having a shank, the other of the members having a socket receiving the shank, said body member and said bit member vertically reciprocable with respect to one another, said body member and said bit member having registering drilling fluid flow passages, the bit member having a single one-piece drilling face and being rotatably mounted on the body member, the bit member having its longitudinal axis inclined with respect to the longitudinal axis of the body member and having an approximately flat drilling face, valve means carried by one of the members for moving between two positions for permitting flow of the drilling fluid in one position and shutting off flow of the drilling fluid in the other position, valve accuating means on the other member for opening the valve means when the members are collapsed upon one another and for closing the valve means when the members are moved apart, and stand-off members on the outer surface of the body member for holding one portion only of the periphery of the bit member against the wall of the drill hole whereby the drilling face of the bit is smaller in diameter than the hole it drills.
References Cited UNITED STATES PATENTS 1,254,267 1/1918 Pickin -376 1,334,632 3/1920 Pickin 175-376 X 1,784,476 12/1930 Zublin 175376 X 1,945,240 1/1934 Tupica 175-376 X 2,013,839 9/1935 Pickin 175376 X 2,154,032 4/1939 Catland 175-376 X 2,207,188 7/1940 Zublin 175376 X 2,598,518 5/1952 Dufilho 175376 X NILE C. BYERS, JR., Primary Examiner.