Replaceable drill bit for rotary drilling of bore holes
[4 1 Apr. 29, 1975 United States Patent [1 1 Harding X XX wo an 5 5 7Q7RD 5 55 .7 .77 m M Q w nm eCdB b mn n \mW O aaCa BGDKB 9 7-5667 99999 03474 -47 64 89406 .1 56876 9 795 38906 [22] Filed: Aug. 23, 1972 Primary Examiner-Geo V. Larkin [21] Appl- 283,192 Attorney. Agent, or Firm-David H Wilson [57] ABSTRACT A rotary drill bit which is releasably attachable to a string of drill pipe and is insertable and retrievable through the drill pipe thus eliminating the costly and EZlb 9/26 [52] U S Cl [51] Int. [58] Field of Search time consuming operation of raising and lowering the string of drill pipe when it becomes necessary to change drill bits.  
 References Cited UNITED STATES PATENTS 862,381 Bennerscheidt........1.v......... 175/258 1.142.460 175/257 15 Claims, 6 Drawing Figures REPLACEABLE DRILL BIT FOR ROTARY DRILLING OF BORE HOLES DESCRIPTION OF THE PRIOR ART string of drill pipe from the bore hole each time the bit [0 must be replaced or inspected.  
  Previous to the development of retrievable rotary bits there had been two main methods of drilling. The most common method utilized a bit which was attached to a string of drill pipe being rotated. This method had the advantage of being able to exert pressure on the bit to increase the speed of the drilling operation. However, when the bit became dull it was necessary to remove the string of drill pipe to change the bit. As the depth of the bore hole increased, this operation became porportionately more costly in terms of loss of drilling time.  
  The second method utilized a bit suspended by cable. The advantage to this method was the savings in time during the removal and reinsertion in comparison with the method incorporating a string of drill pipe. The chief disadvantage was a lack of means for exerting pressure on the bit, the only pressure being the weight of the bit itself.  
  In order to overcome the disadvantages of the two methods, many types of retrievable rotary bits were developed which employed collapsing cutters. Usually though, the retracting and extending mechanisms are quite complex and the large number of parts utilized decreases reliability. This is particularly true since the bit must function in a hostile environment of rock, mud and water.  
 SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved rotary bit of the type capable of being in serted and removed through a string of drill pipe.  
  Another object of the invention is to eliminate the time-consuming round trip of the drill pipe to change the rotary bits with a resultant reduction in time and money during drilling of the bore holes.  
  A further object of the invention is to positively engage the rotary bit cutter members in their outwardly expanded position to prevent any radial forces applied during the drilling operation from forcing the cutter members inwardly.  
  Another object of the invention is to provide a rotary bit of the type indicated through which sufficient fluid can be passed to facilitate removal of cuttings and to clean and cool the bit cutters.  
  A further object of the invention is to provide a rotary bit with a cutter member arrangement that centers the bit in the bore hole, eliminates back pressure at the center of the hole and increases the drilling speed.  
 BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become readily apparent to those skilled in the art from reading the following detailed description of an embodiment of the invention when considered in the light of the accompanying drawings, in which:  
  FIG. I is a fragmentary longitudinal sectional view of the drill pipe exposing a portion of the rotary bit disposed at the bottom of a bore hole;  
  FIG. 2 is an enlarged fragmentary longitudinal sectional view through the drill pipe taken along line 22 of FIG. 3 with portions of the rotary bit shown in side elevation, and being in a locked condition;  
  FIG. 3 is a cross-sectional view taken along line 33 in FIG. 2 with the rotary bit shown;  
  FIG. 4 is a longitudinal sectional view through the drill pipe with the rotary bit shown in side elevation in an unlocked position;  
  FIG. 5 is a view similar to the view of FIG. 2 showing a modified form of the invention; and  
  FIG. 6 is an enlarged fragmentary sectional view showing a spring loaded pin in an alternate embodiment of the present invention.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings there is shown a rotary bit of the type which may be inserted and retrieved through a string of drill pipe. The present invention relates to improvements in the locking and release mechanism by which the rotary bit is engaged to or disengaged from the end of a string of drill pipe. While all the drawings reflect two pairs of cutters this is only for purposes of illustration and should not be construed as a limitation in respect of the present invention. The well drilling industry has found that in terms of efficiency and strength. assemblies of two or three pairs of cutters are preferred. However, the operation of the locking and release mechanism does not depend upon the number of cutters utilized.  
  Referring to FIG. 1, there is shown the present invention as designated by a rotary bit 10 attached to the end ofa string of drill pipe 12 at the bottom of a bore hole. The upper end of the drill pipe is connected to a source of motive power which rotates the string of drill pipe causing cutters 14, I6, [8, and 20 to rotate about their respective axes cutting away the material below them. Fluid. which may be air, water or a special cutting mud. enters the rotary bit 10 under pressure through hose 22 from the surface and exits near the cutters. The streams of fluid not only clean and cool the cutter teeth but they also remove the loose cuttings by forcing them to the surface between the side of the bore hole and the string of drill pipe.  
  In some drilling operations the drill pipe itself is left in the bore hole as a casing to prevent collapse of the walls and a blockage of the hole. In other cases it is preferred to use a separate casing 24 as shown in FIG. I which does not rotate with the drill pipe and is inserted as the drilling progresses. The construction of the present invention permits it to be utilized with either method of drilling.  
  To enable the rotary bit 10 to be raised and lowered cables 26, 28, and 30 are attached and extend through the string of drill pipe to the surface. For purposes which will be explained later cables 28 and 30 pass through and are connected to a ring 32 and cable 26 passes through the center of the ring allowing this cable to move independent of any movement in the cables 28 and 30.  
  FIG. 2 is a more detailed longitudinal section showing portions of the rotary bit in side elevation, the bit being locked into position at the end of the drill pipe 12. The rotary bit is comprised of a wedge 34 and a surrounding cutter assembly 36. The wedge has a conical nose section 38 to which is attached the cable 26. As was previously mentioned this cable allows the wedge to be raised and lowered independent of the cutter assembly or the drill pipe. Also contained in the nose section are inlets for the fluid carried by hose 22. Inlet 40 is connected to a passage 42 which passes longitudinally through the body of the wedge and has an outlet 44 between cutters l6 and 18. There is a similar passage (not shown) on the opposite side of the wedge. Thus fluid under pressure is introduced into the bore holes and turbulence is created which cleans and cools the cutter teeth and increases the efficiency of the cutting action. The position of the outlets is representative only and their location and number will depend upon the number of cutters utilized and the fluid pressure available.  
  The cutter assembly 36 has a cylindrical body 46 with a circular hole 48 in the center large enough to accommodate the upper portion of the wedge which is slidably movable therein. As was previously disclosed, the cutter assembly has the ends of cables 28 and 30 at&#39; tached to its upper surface and the cables 28 and 30 have opposite ends; which extend to the top of the bore hole.  
  The cutter assembly body 46 also has a pair of pins 50 and 52 which are free to move in holes opposite each other and are extensible beyond the exterior side wall of the cutter assembly body 46. The pins 50 and 52 function as extensible latching means for latching the cutter assembly to the lower end of the drill pipe l2. These holes are perpendicular to the longitudinal axis of the body. When the wedge is in place, as shown, the pins are forced outwardly into slidable engagement with radially expanding groove means 54 and 56 formed in the interior wall of the hollow cylindrical body of the lower end of the drill pipe 12. The length of the pins is slightly less than the distance from the wall of the groove to the wall of the cylindrical portion 58 of the wedge 34 when it is adjacent the pins 50 and 52. This allows the wedge to move freely when the pins are adjacent the cylindrical portion 58 of the wedge. The grooves also have a taper along the lower edge which discourages accumulation of foreign material so that the movement of the pins is not inhibited. Referring for the moment to FIG. 3, the pins 50 and 52 rest against the ends of gooves 54 and 56 and as drill pipe 12 is rotated in a clockwise direction the cutter assembly body 46 will be driven in rotation with it by the pins 50 and 52.  
  Referring to FIG. 2, pivotally attached to the cutter assembly body 46 at pivot points 60 and 62 are cutter arms 64 and 66. Attached to the opposite end of the cutter arms are cutters l4 and which are free to rotate about their respective axes. These cutters, along with cutters l6 and 18, are ofa form and a construction well known in the well drilling industry and disclosure of their design is not essential to the operation of the present invention. It is sufficient to relate that the position of cutters 16 and I8 tends to center the rotary bit while cutters l4 and 20 define the diameter of the bore hole.  
  Each of the arms has a key section 68 and 70 which mates with a continuous groove 72 in the wall of the drill pipe 12. As gooves 54 and 56, the groove 72 is provided with a taper along its lower edge to inhibit the buildup of foreign matter which might prevent disengagement of the keys from the slot. As drilling progresses, pressure on the cutters is transmitted to the cutter arms and thereby to pivot points 60 and 62 and pins 50 and 52. The keys 68 and relieve this pressure by transmitting it instead to the walls of the drill pipe. The end of the drill pipe 12 is angled to match a similar angle on cutter arms 64 and 66 which also transmits cutting pressure to the pipe walls.  
  In certain drilling situations there may be a resistance to the cutting action of the cutters l6 and I8 sufficient to prevent the wedge 34 from turning with the cutter assembly 36 and drill pipe 12 as they are rotated. To ensure proper rotation of the wedge the cylindrical portion 58 could be tapered not shown) from the diameter at the bottom of the conical nose section 38 to a larger diameter at the bottom of the cylindrical portion 58 to a dimension which would force pins 50 and 52 against the walls of grooves 54 and 56 thus inhibiting relative rotational movement between the wedge and the cutter assembly. Disengagement would be achieved by dropping a weight down cable 26 to force the wedge from between the pins.  
  An alternative form of the invention is illustrated in FIG. 5 wherein similar structural elements are designated with primed reference numerals. Instead of tapering cylindrical portion 58&#39;, it may be provided with a pair of vertical slots 76 and 78 having a width slightly greater than the diameter of the pins 50&#39; and 52&#39; which would engage the ends of pins 50&#39; and 52&#39; much as the horizontal grooves 54&#39; and 56&#39; engage their opposite ends. The pins then would prevent relative rotation between the cutter assembly 36&#39; and the wedge 34&#39;.  
  Referring to FIG. 4, the rotary bit is shown at an intermediate position in the drill pipe. To attain this position, the string of drill pipe is raised several feet. Then the wedge 34 is lowered by cable 26 and when the conical section 38 is adjacent pins 50 and 52 the pins are free to move inwardly until they clear the inside wall of the drill pipe. This inward movement may be accomplished by numerous means to retract such as spring means for spring loading the pins or magnetic means such as the conical section 38 of the wedge so that it will magnetically attract and draw the pins out of the grooves 54 and 56 toward the center of the cutter assembly body 46. For example, if the conical section 38 is magnetized and the pins 50 and 52 are made from a ferrous metal, the pins 50 and 52 will be magnetically attracted to the conical section 38 as the wedge and the cutter assembly 36 move apart to draw the pins 50 and 52 from the grooves 54 and 56. As a further aid, if the drill pipe 12 and the cutter assembly 36 are rotated in opposite directions with respect to one another, drill pipe counterclockwise and cutter assembly clockwise, the pins 50 and 52 will follow the contour of grooves 54 and 56 and be moved inwardly.  
  FIG. 6 is an enlarged fragmentary sectional view showing a spring loaded pin in an alternate embodiment of the present invention. Elements similar to elements of FIGS. 2 and 5 are designed with double primed reference numerals. For example, the drill pipe 12&#39;&#39; is similar to the drill pipe 12 of FIG. 2 and the drill pipe 12 of FIG. 5. Referring to FIG. 6, there is shown a spring loaded pin 52&#34; having the end portion adjacent cylindrical portion 58&#34; of the wedge of a larger diameter than the body thereof to provide a shoulder against which one end of spring 80 may rest. The cutter assembly body 46&#34; of the cutter assembly is provided with a hole having the end portion adjacent circular hole 48&#34; of a slightly larger diameter than the larger diameter end portion of pin 52&#34; and having the end portion adjacent groove 56&#34; of drill pipe 12&#34; of a slightly larger diameter than the smaller diameter body of pin 52&#34; whereby pin 52&#34; is slidably movable in such hole. The junction of the different diameter hole end portions also forms a shoulder against which the opposite end of spring 80 may rest. In the extended position, as shown in FIG. 6, pin 52&#34; engages groove 56 while compressing spring 80. When the wedge is lowered so that conical nose section 38, shown in H6. 2, is adjacent the larger end portion of pins 52&#34;, spring 80 will tend to expand, forcing pin 52&#34; to disengage from groove 56&#34;. The unconstrained length of the spring 80 should be sufficient to force the end of the pin 52&#34; from the groove 56&#34; so that the pin 52&#34; will clear the inner wall of the drill pipe 12&#34; as the drill bit is raised and lowered.  
  As the wedge is lowered further the cutter arms 64 and 66 are free to pivot toward the center of the cutter assembly until the keys 68 and 70 disengage from groove 72 in the drill pipe wall. The cutter assembly 36 may now be raised by the cables 28 and 30 and the wedge 34 can be raised by the cable 26 as shown in FIG. 4. Now the cutter assembly and the wedge can be raised through the string of drill pipe to the top of the well where they are replaced.  
  As a further aid to the disengagement of the rotary bit from the drill pipe, a difference in the angle of taper may be employed at the points where the cutter arms abut the angled end of the drill pipe and where the wedge abuts the cutter arms. A difference, for example one degree, between the surfaces would tend to force the wedge in a downward direction and force the cutter arms inwardly.  
  After replacing the rotary bit it is lowered through the drill pipe to its previous position. An upward pressure is applied to wedge 34 through cable 26 so that cutter arms 64 and 66 are pivoted outwardly and keys 68 and 70 engage groove 72 in the drill pipe wall. Next, the cutter assembly and wedge are rotated in a counterclockwise direction while the upward pressure applied to conical nose 38 forces the conical nose upward which in turn forces the pins 50 and 52 in an outward direction until the pins engage grooves 54 and 56 and finally contact the ends of these slots allowing the wedge 34 to move upward into the locked position as shown in FIG. 2. Now the string of drill pipe is lowered to the bottom of the bore hole and drilling can be resumed.  
  It is to be understood that if precise vertical positioning of the cutter assembly at the bottom of the drill pipe is desired the invention may take the form illustrated in FIG. 5 without departing from its basic concept. The upper portion of the cutter assembly 36&#39; has a lip 74 with a tapered bottom edge. The lower end of the drill pipe 12 is of a smaller diameter than the diameter at the cutter assembly lip so that as the cutter assembly is lowered through the drill pipe the lip will contact the drill pipe where its diameter decreases. Thus, when the lip 74 of the cutter assembly 34&#39; contacts the decreased diameter portion of the drill pipe 12&#39; pins 50&#39; and 52 are directly opposite grooves 54&#39; and 56&#39;. Then the wedge 34 is moved to lock the cutter assembly to the drill pipe as described above.  
  As shown in the drawings, cutters l4 and 20 are attached to the cutter arms and they face cutters l6 and 18 which are attached to the wedge. The conventional drill bit has the cutters arranged so that they rotate about the center of the bore hole and do not actually cut the material at the center but rather break it away. This produces a pressure point which requires a corresponding downward pressure on the bit assembly. The cutter arrangement of the present invention eliminates the uncut material by providing cutting surfaces across the diameter of the hole. The cutters on the wedge also center the drill bit to prevent side forces which tend to force the bit off the drilling path. These advantages also increase the cutting speed of the assembly. The cutters may also be replaced by stationary teeth which in no way would change the operation of the invention.  
  in accordance with the provisions of the patent statutes, I have explained the principle and mode of operation of my invention and have illustrated and described what now consider to represent its best embodiment. However, it must be understood that within the spirit and scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.  
 What I claim is:  
  1. In a bore hole drilling system including a rotatable string of drill pipe and a retrievable drill bit the improvement comprising means for attaching the bit to the lower end of the drill pipe, said attaching means including:  
 a hollow cylindrical body having a radially expanding groove means in the interior wall thereof;  
 an extensible latching means affixed to said bit slidably engaging the groove means in the interior wall of said body; and  
 a wedge slidably movable in said bit for contact with said extensible latching means to effect the movement of said extensible latching means.  
  2. The system according to claim I wherein said extensible latching means includes a movable pin radially disposed from the longitudinal axis of said bit and slidably movable in said bit having one end adjacent the longitudinal axis of said bit for contact with said wedge and the other end adjacent an exterior side wall of said bit wherein said pin is extensible beyond said exterior side wall for slidable engagement with said groove means.  
  3. The system according to claim 1 wherein said radially expanding groove means includes at least two radially expanding grooves in the interior wall of said body.  
  4. The system according to claim 3 wherein said extensible latching means includes a least two pins radially disposed from the longitudinal axis of said bit and slidably movable in said bit, each having one end adjacent the longitudinal axis of said bit for contact with said wedge and the other end adjacent an exterior side wall of said bit wherein said pins are extensible beyond said exterior side wall for slidable engagement with said groove means.  
  5. The system according to claim 2 wherein said extensible latching means includes means to retract said movable pin.  
  6. The system according to claim 5 wherein said means to retract includes spring means.  
  7. The system according to claim 5 wherein said means to retract includes magnetic means.  
 8. The system according to claim 1 wherein said hollow cylindrical body is the lower end of said drill pipe.  
  9. The system according to claim 1 including a circumferential groove means in the interior wall of said body and a means pivotally affixed to said bit for engaging said circumferential groove means in the interior wall of said body.  
  10. The system according to claim 9 wherein said means for engaging includes a key section pivotally affixed to said bit.  
  ll. The system according to claim 9 wherein said means for engaging includes at least two key sections pivotally affixed to said bit.  
 12. The system according to claim 9 wherein said wedge is slidably movable in said bit to effect the pivotal movement of said means for engaging.  
  13. The system according to claim 9 wherein said hollow cylindrical body is the lower end of said drill pipe.  
  14. The system according to claim 12 wherein the cutters of said bit are attached to said means for engaging and to said wedge.  
  15. The system according to claim 14 wherein said cutters include rotatable cutters having cutting surfaces extending substantially across the diameter of the bore hole.  
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