US2830793A - Drill bit - Google Patents

Description

E. `E. KEEsE DRILL BIT April 15, 1958 5 Sheets-Sheet 1 INVENTOR M E e m z w .a M h.

W.. M M z ...f mam Filed March 29. 1954 E. E. KEESE April 15, 1958 I INVE OR I flliwslf. Keese dM/w, w wzwy ATTORNEYS April 15, 1958 E. E. KEEsE 2,830,79`3

INVE Elia/sKeese NTOR BY I ATTORNEYS United States Patent F DRILL BIT Elias E. Keese, Dallas County, Tex., assignor to Teas Instruments Incorporated, Dallas, Tex., a corporanon of Delaware Application March 29, 1954, Serial No. 419,271

3 Claims. (Cl. 255-61) This invention relates to a drill bit and more particularly to a drill bit for use in seismic surveying in those sections of the country in which the low Velocity, unconsolidated surface layer of the earth is comprised of mud, clay, or other comparatively soft formations.

In seismic surveying, a customary practice has been drilling a shot hole through the low velocity surface layer of the earth, or the weathered layer as it is more commonly known, in order to locate the seismic wave generating source at or slightly into the consolidated earth layer. The reason for this admittedly expensive and time-consuming practice is that invariably the quality of the record of underground reflections is improved and in many instances, is the difference between recognizable and non-recognizable reflections. In geographical locales where the weathered layer to be penetrated consists of mnd, clay, or other comparatively soft formations, standard drilling equipment and methods have been modified to meet the special considerations involved. Thus, for example, light weight tubing can be used because no hard formations are encountered in drilling the shot holes to a suilicient depth to locate the wave source in contact with the consolidated earth layer. Because it may be necessary to use the same shot hole for subsequent shots, it is advantageous to leave the tubing in the shot hole until all shots have been fired; the reason being that the shot hole would in all probability completely close after firing the first shot if the tubing were prematurely removed.

One of the first methods developed for drilling holes of this Character made use of lightweight tubing threaded on either end to allow Sections to be added to the drill string. In the practice of this method no drill bit was used with the first or lower tubing section. Instead, the lower end of the first drill stem section was cut and bent to form cutting edges and water passages for a drilling fiuid. To drill the hole, this initial vsection was rotated and fiuid pumped through the drill tubing accomplishing the function of removing the cuttings, thus allowing the section to penetrate into the earth. Other Sections were threaded onto the drill section as the drilling progressed into the ground until the hole reached the required depth. When the explosive charge Was lowered into the tubing 'and fired, the tubing being of lightweight material belledout or expanded preventing its withdrawal from the hole. Although this method was satisfactory in obtaining seismic reflections from underground layers,.it was undflff Patenfed Apr. 15, 13583 'ice is` drilled by this method, the tubing is' removed sufiiciently to allow a long tamping rod to be inserted into the tubing and knock the hit off, leaving the drill tubing free of obstructions. The seismic charges are then placed into the hole beneath the tubing and fired with the consequent result that the tubing remains undamaged and can be completely salvaged from the shot hole. Although slightly more economical, relatively speaking, than the first-mentioned method, this method is still uneconomical because its practice necessarily results lin the loss of a drill bit for every hole. It has a further disadvantage in that should the hole close below the tubing after a shot is fired and it becomes necessary to fire additional shots to obtain satisfactory records, the hole cannot be re-drilled without pulling the tubing and replacing the drill bit.

It is apparent from the foregoing description that although producing satisfactory seismic exploration results, both methods are uneconornical in that some equipment must be left in the hole. Accordingly, it is the primary objective of this invention to provide a novel method for drilling a shot hole which allows the seismic charge to freely pass to the bottom of the hole and yet permits the tubing as well as the drill bit to be salvaged from the hole after the explosive charge or charges are detonated.

As a secondary but equally important objective, is the provision of a drill bit of unique Character which may be used in carrying out the novel method.

Closely associated with this secondary objective is the ability of the drill bit to re-drill a hole should it close after the first or any subsequent charge is fired, same susceptible of being accomplished without removing the tubing from the hole and replacing the bit.

lt is another objective of this invention to disclose a simply and ruggedly constructed bit that can be reused indefinitely for this type of drilling, with provisions for easy replacement of worn or unsuitable parts.

It is still a further object of this invention to provide a drill bit which can be economically constructed from standard, easily producible and identical components.

Other and further objects of the present invention will become apparent and the above enumerated objects clarified when considered along with the description of the p drawings in which:

Figure 1 is a side elevation in perspective of the drill bit in condition for drilling together with a coupling for attaching the drill bit to a drill stem;

Figure 2 is an end view of the drill bit looking in an upward' direction;

Figure 3 is a perspective view of the drill bit with the cuttingl edges spread to allow passage of the charge to the bottom of the hole;

Figure 4 shows an alternate method of construction for the cutter blade support pipe;

Figure 5 represents a modification of the drill bit of j Figure 1;v and economical because only the top section of tubing or at .lugs welded to the tubing. The bit .may also be of the type that is held in place by ashear pin. After the hole Figure 6 represents a modification .of the drill bit of IFigure 5.

. is separated from the other by a distance slightly greater than the width of the cutter blades to allow each blade to swing freely when supported in position. Cutter blade 18, shaped generally as a rectangle to present a straight edge in contact with the side wall of the hole to be drilled but beveled on the interior edge by the removal of two trianguw lar areas of metal, is inserted between brackets 12 and 13 and hinged in position by means of pin 19 inserted through holes drilled in the brackets and the cutter blade. To provide for more effective cutting, blade 18 is curved in the direction of rotation as will be evident from an inspection of Figure 2 and the edge in contact with the bottom of the hole is ground to present a straight line cutting edge. A segmental piece of metal 20 whose arc subtends an angle of slightly less than l20 at the center of a circle and whose radius is equal to the mean radius of pipe is integrally attached at approximately right angles to the cutter blade 18. Identical in all respects to cutter blade 18, blade 21 is supported in hinged connection with brackets 14 and by pin 22 and cutter blade 24 is supported in hinged connection with brackets 16 and 17 by means of pin 25. Closure segments 23 and 26, identical to closure segment 20, are attached at right 'angles to cutter blades 21 and 24 respectively.

To bring the hinged cutter blades together for the most effective drilling, several additional features are provided. First, between each pair of brackets, notches 27, 28 and 29 are cut into the lower circumference of pipe 10 with a width equal to the distance separating the bracket pairs. These notches not only allow the -cutter blades to swing inward without binding against pipe 10 but carry the bending moment caused by the force on the 'blades during the drilling operation instead of the hinge brackets. Toward the lower end of each cutter blade, holes 33, 34 and 35 are drilled into blades 18, 21 and 24 respectively and a small diameter wire 36 passed through each hole to secure the blades in the closed position. As can be most clearly seen in Figure 2, when the blades are in the closed position, the lower end of pipe 10 is completely closed by the 'segments 20, 23, and 26 except for three approximately triangular openings 30, 31 and 32 along the front side of each cutter blade. The purpose of these openings is to provide a high Velocity passage through the drill bit and allow the drilling fluid to keep the cutting side of the blades clean as well as pick up the drill bit cuttings and float them to the surface.

To begin drilling Operations, the drill bit is connected with the drill tubing by means of a connector indicated -generally by the numeral 60 in Figure 1. A standard threaded pipe coupling 61 is welded to a section of light weight threaded drill tubing 62 and engages with the threaded end 11 of pipe 10. The hole is then drilled into the ground by rotating the drill tubing and adding sections until the desired depth has been reaohed.

At this point, the entire drill stem is pulled out of the hole a suflicient distance to prevent damage to the cutter blades from an explosive charge to be placed at the bottom of the hole. A long tamping rod is then inserted into the drill tubing to break the small diameter wire 36 and force the cutter blades and their associated closure segments to 'swing outward and into the side walls of the hole, the bevelled inner edges of the blades assisting the tamping rod in this spreading operation. Thus, as shown in Figure 3, a clear passage through the drill bit is provided when the blades are spread for the introduction of an explosive charge into the hole, or any other equipment for that matter. After the first shot, additional charge-s can be lowered through the drill tubing and bit as necessary and the tubing withdrawn each time to a safe distance above the charge with the tubing still being available to maintain the drill hole above the shot open for any subsequent charges. Should the drill hole'become too shallow after successive explosions, the hole may be redrilled by raising the tubing slightly so that the pressure of the side walls above the blades forces the blades inward to the closed position and then lowering the tubing to the bottom and rotating as before. vIt should be recognized, however, that the bit is stilleffective in redrilling Operations eventhough the cutter blades do not completely close 'at first since the blades have a tendency to move inward as pressure is applied to the bit.

The cutter blade pipe support section described above in connection with Figures 1 and 2 may 'be taken from a piece of pipe and the hanger brackets welded in place alongside appropriately located notches or the entire support section cast in a single operation. Another very suitable method for forming this section is illustrated in Figure 4 wherein a series of identical castings are made with an arc length of l20 at the desired radiu-s and a pair of brackets spaced relatively and adjacent to a longitudinal slot form an integral part of each casting. When three of these identicl Sections, designated as 10a, 10h and 10a, are brought together and welded longitudinally along each seam, a cutter blade support section will be formed identical to that shown in Figures 1 and 2. It is to be noted further that the cutter blades and closure segments are also identical to each other and can be cast vas a single piece. Thus, with three parts of each of two basic castings, a drill bit as disclosed can be formed.

A modification of the three cutter blade drill bit of Figures 1 and 2 is shown in Figure 5. In this figure, a cutter blade section 40, plain on both ends, is formed with two pairs of diametrically opposite brackets, 41 and 42 and 43 and another not shown. Blade 44 with its associated closure segment 46 is supported from brackets 41 and 42 by pin 45 and an identical blade 47 is supported from the opposite pair of brackets by pin 48. The notches 49 and 50 permit the blades to be brought together across the lower end of pipe 40 and when thus closed, high Velocity drilling fluid passages are formed by the closure segments one of which is indicated by the numeral 51. This drill bit is suitable for use in the softer of the formations as each blade handles a larger portion of the drill hole material. Another feature of the bit is shown by the plain upper end of pipe 40. This allows the bit to be welded to the drill tubing instead of using a threaded connection or 'alternately, to be threaded as required for use with the various non-standard pipe threads commonly found in the field.

Figure 6 is identical in all respects to Figure 5 except for the construction of the cutter blades 44 and 47. Blades 44 and 47 are shown constructed with a two step cutting edge as indicated by the numerals 44a and 44b and 47a and 47b. The stepped blade is used for drilling in comparatively hard formations where the bite taken by a straight cutting edge causes an undue stress on the drill bit, the remainder of the drill string, and driving equipment. It is apparent, of course, that the stepped-blade construction can be used with the drill bit of Figures l and 2 where the character of the formation warrants its use.

Although the present invention has been disclosed with I reference to particular embodiments, nevertheless various modifications and changes which are obvious to one skilled in the art are within the spirit, scope and contemplation of the inventive thoughts expressed herein.

What is clairned is:

. 1. A drill bit comprising an annular body, a plurality of blades circumferentially arranged about the exterior of said body to depend therefrom with the cutting edges of said blades being positioned below an end of said body, means pivoting said blades to said body, said pivoting means having its pivot axis exterior to the wall of said body, said body being provided with longitudinal slots adjacent the respective blades to permit said blades to swing into and out of said body, each of said blades having its inner edge slanted with respect to the axis of said body, said inner edge extending from the wall of said body into and across the interior thereof, and breakable means holding said blades together.

2. A drill bit comprising an annular body, a plurality of blades circumferentially arranged about the exterior 'of said body to depend therefrom with the cutting edges of said blades being positioned below an end of said body,

' means pivoting said blades to said body, said pivot means 'having its pivot axis exten'or to the wall of said body,

said body being provided with longtudinal slots adjacent the respective blades to permit said blades to swing into and out of said body, a separate plate attached to each of said blades underlying one end of said body to cover a portion of the bore of the body between the blade to which the plate is attached and an adjacent second blade, leaving a small part of the bore uncovered adjacent to the said second blade, and breakable means holding said blades together.

3. A drll bit as recited in claim 2 Wherein said pivoting means comprise a separate lug for each blade mounted on the outside of said annular body and pivot means carried by said lug to which the separate blade is attached, and wherein said plates are pie shaped.

References Cited in the file of this patent UNITED STATES PATENTS Davis Inne 3, Fullilove Apr. 4, Rutherford et al Mar. 23, Cramer Dec. 3, Abegg Aug. 26, Anderson Oct. 20, Church July 27, Prassel Feb. 7, Vincent Mar. 6, Baker et al July 7, Kammerer Dec. 22, Ellis Ian. 12,

Monaghan Apr. 3,

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