US2648526A - Rotary earth boring bit - Google Patents

Description

Aug. 11, 1953 G. H. LANCHESTER ROTARY EARTH BORING BIT Filed Oct. 6, 194'? INVENTOR George Herbert Lonchester ATTORNE YS Patented Aug. 11 1953 UNITED STATES PATENT OFFICE ROTARY EARTH BORING BIT Application October 6, 1947, Serial No. 778,183 In Great Britain April 9, 1946 2 Claims. 1

This invention relates to improvements in rotary earth boring bits and has more particular reference to the type of bit for well drilling wherein multiple abrading or cutting wheels are rotated under pressure upon the work surface as the drill bit descends, and wherein a mud flush is led to the working face and the cutting tool in its rotation excavates to its full diameter, the flush removing the eroded material.

Heretofore earth boring bits for oil wells and the like as set out above and particularly those of the multiple cutter head type have been fashioned by dividing the bit stock into as many sections as the number of cutters, each section carrying a stub axle and each such axle a cutting tool. Equally each such cutting tool is provided with looking ball races and thrust roller bearings wherein the locking balls are inserted through passage ways extending from the exterior perimeter to the race.

The provision of ball entrances to the cutting tool races tends to weaken the cross section of the stub axle, and the closure wall of each passage is continuously in abrasive contact with the wall of the well being drilled.

The object of the present invention is to provide a multiple cutter bit wherein a divided cutter head is avoided with an increase of strength and rigidity and wherein both ball and roller races are provided, the said balls for the bearings being introduced at the time of assembly without rollway passages for their entrance. A further object of the invention is the easy removal and replacement of all or any of the cutters without disassembly of the whole cutter head or bit.

The invention consists in a rotary earth boring bit having a single piece housing centrally cored with threaded connection spigot and tapering sides, said housing accommodating a series of upwardly converging stationary stub shafts, all said shafts being secured within said housing by a single locking member, each said shaft carrying an angularly disposed stub axle, said axle carrying a toothed cutter cone rotatably mounted thereon but positionally locked thereto, and adapted to abrasively contact the work surface upon rotation of the bit.

The invention is further characterized by means for circulating the lubricating flush that is brought to the work surface and its return flow, said flush being introduced above the cone cutters and means for rotatably locking the cutter cones upon the stub axles and sealing the bearings against entry of dirt.

The races for'the balls of the ball bearings in the conical and toothed cutters are turned to running size but the entrance rims are left a few thousandths of an inch less than the diameter for admission of the balls. The roller paths are turned to exact size and provision made for a sealing ring or rings. To assemble the bearings the axles with the balls and rollers are placed in position for entry and a cramping force applied from back to front.

The conical and toothed cutter is now heated externally by any convenient means causing expansion of the cutter shells until the balls pass the previously undersized rims and snap into the race, at which point the heating means and cramps are withdrawn and the cutter shape in cooling regains its intentional dimensions. When the balls are entering within the respective races the movement of the stub axle to nest within the cutter shell also simultaneously locates the journal rollers which are axially disposed and tends to close the cutter shell base upon the sealin ring or rings. A locating spigot formed at the end of the stub axle enters a recess or socket in the cutter shell nose which aligns the interengaging parts and has the further benefit of producing a relatively even thickness of cutter shell which is important for expansion under heat when assembling the ball races, and for heat treatment when hardening.

In order that the invention shall be more fully understood and described, reference is made to the accompanying drawings wherein a three cutter wheel assembly is shown and wherein:

Fig. 1 is a part sectional elevation of the assembled drill bit with three toothed conical cutters,

Fig. 2 is a vertical elevation of stub shaft and axle m,

Fig. 3 is a vertical elevation of stub shaft and axle y,

Fig. 4 is a vertical part elevation of stub shaft for stub axle 2,

Fig. 5 is a plan of the bit head at line A-B, Fig. 1, and

Fig. 6 is a fragmentary front elevation showing one of the stub shafts and its squared shoulders.

Referring to the drawings, and particularly to Fig. 1, the drill bit head I is formed as a steel housing internally cored at 2 and formed with jointing shoulder 3, and normal screw thread and tapering coupling spigot 4. The housing has a grooved cylindrical skirt 5, and an upwardly tapering grooved contour above said skirt. The

housing I is bored angularly as at 6 to accommodate the three stationary stub shafts .r, y, and a, each said shaft having incised ports I for mud flush circulation to the cutting face from the passage 2, the latter in a known manner being in fluid circuit with a tubular drill string (not shown). The stub shafts m, y and z are held from downward displacement by the threaded bolt 8, whose head is accommodated in a recess 9 in the housing I. The shank of the bolt engages grooves I in the shafts a: and :l/ but is threaded into a screwed aperture II in shaft 2. This assembly rigidly locks the shafts :c, y, :c, in their upper parts but each said shaft is provided with squared shoulders 12 which respectively engage rectangular sided bearing seats l3 in the housing :I The operative lower end of the shafts :r, y, 2 have curved back shields I4 and an led emen ions I5 of the shafts, said extensions carrying angled stub axles l6. Each stub axle l6 carries a boss H for seating a sealing ring IS, a roller path 19 and roller race seat 20 and below the latter a ball race 2 [,each stub ax-le terminating in a locating spigot 22. Disposedu-pon the stub axles are the cutter wheels 23. Said cutter wheels are formed as conical members of hardened steel, the angle of disposition of the stub axle to the common axis of the bit being such that the taper of the conical cutter used gives a substantially horizontal contact or that of a flattened cone of the cutter wheel teeth 24 to the rock or earth drilled. In the form shown stub shaft 2 carries a cutter wheel 23 having a terminal cutter tooth or cone "bit 24a which projects beyond the axial center w of the drill bit. The object of this is to prevent conical piping at the well center face and obviate an undue side thrust when boring very hard rock such as porphyry. The rows of teeth 24 of the several cutting heads 23 are staggered the one in relation to its neighbors at cross planes where interference or jamming would A otherwise occur at the lower series of toothed rings as shown in Fig. 1. Hence neither of the cutting wheels on stub axles of shafts :c and y areprovided with terminal cone bit teeth similar to tooth 24a, while the outermost toothed ring 241) whose wear and stress is the greatest is clear of any contact with its neighbor wheels and are made of stout section and longer length of face. Ihe interior of the cutter wheel conical shells are each provided with a socket 25 for spigot 22 a ball race 26 for the balls 21, the rim 28 of said race being turned to be less in diameter by say =7 or 8 thousandths of an inch than the outermost limits of a confining circle of the assembled balls. The remaining part of the cutter wheel interior has a truly turned roller path 29 and a recess 30 for the sealing ring 18, the back of the cutter shell just contacting the shoulder of the part 15 of stub shaft m, y, z.

The operation of the invention is as follows: Assuming the parts to be assembled as above described the drill bit as a whole is threaded to the tubular drill tube string and the bit and string lowered into operative position. The pressure due to gravity of the bit upon the working surface is adjusted by the operator. The mud lubricating flush is pumped under pressure down the string tube and enters the drill bit through the core tube 2, passes through the passages TI and is fed to the cutting tools through three equi-spaced tubular ports 31, the return circuit of the flush being external of the drill bit and through the passages between the core cutters past the tapering sides of the bit housing 1, and through the annular passage existing between the well wall and drilling tube string to the ground surface. the cutting drill bit is then rotated and the teeth 24 cut or abrade the earth or rock surface and the respective toothed cutter cones are free to revolve. In some cases the teeth of the cutter cones 24 may be angled to increase drag contact with the surface, and are preferably tipped with tungsten carbide, or other like hard and wear-resisting material. Since the teeth of one cutter are staggered in relation to the others the whole circular area of the work surface is traversed and the tooth 24a removes the center, this tooth under revolution of the whole cutter cone exerting the maximum abrasive force. Although the invention has been described as applied to a three cutter head bit, the invention is equally satisfactory with a two cutter head or four.

According to the invention any one of the cutters and its stub shaft may be removed and replaced without the slightest difficulty or great loss of time. To achieve this the bolt 8 is withdrawn, the particular stub shaft removed, a new one inserted and the bolt 8 replaced. This method of replacement is of great advantage over some types of multiple cutter drill bits wherein the housing is in the form of a multiple series of coupled parts each of which is an independent entity requiring exact alignment with the other-s in reassembly.

It will be understood that once the cutter cones 23 are in position upon the stub axles, the stub shaft 9; or y or z and its stub axle I6 are in locked relationship and cannot come adrift, the only means of removing and replacing the cutter cones 23 being to heat the cone about the ball race 26 and rim e. g. by electrical means, and then pull the cone from its axle I 6.

I claim:

1. A rotary earth boring bit comprising a shank with at least three bores converging upwardly from the base thereof and with a bore extending transversely of said shank near the upper ends of said converging bores, said transverse bore fully intersecting one of said converging bores and partially intersecting each of the remaining converging bores, a stationary stub shaft remov ably mounted in each of said converging bores, an angularly disposed stub axle secured to the lower end of each stub shaft, a rotary cutter cone mounted on each stub axle, and a single locking member adapted to be secured in said transverse bore to look all said stub shafts in their respective bores, said single locking member having a threaded end, the stub shaft in said fully intersected bore being formed with a threaded transverse hole adapted to receive the threaded end of said locking member, and the remaining stub shafts each being formed with a peripheral lock ing recess to receive and fit around the body of the locking member in said transverse bore.

2. A rotary earth boring bit comprising a shank formed with at least three bores converging up.- wardly from the base thereof and with a bore ex? tending transversely of said shank near the upper ends of said converging bores, a stationary stub shaft removably mounted in each of said upwardly extending bores, each said stub shaft being formed near its upper end with a locking recess, an angularly disposed stub axle secured to the lower end of each said stub shaft, a rotary cutter cone mounted on each said stub axle, and a single locking member adapted to be secured in said transverse bore in locking relationship with the locking recesses in said stub shafts, and thereby to look all said stub shafts in their respective 5 bores, in which the shank is provided with a centrally located mudfiush passage extending from its upper end to the upper end of the converging bores, in which each stationary stub shaft is provided with a mudfiush passage extending from its upper end, Where it communicates with the mudflush passage in the shank, to a point about ha1f way down the length of the stub shaft, and. in which the shank is further provided with an additional mudflush passage for each stub shaft, said additional mudfiush passages extending up- Wardly from the lower end of said shank to communicate each with the lower end of one of said mudflush passages in said stub shafts, the lower ends of said additional mudfiush passages terminating just above said rotary cutters.

GEORGE HERBERT LANCHESTER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 829,634 Decker Aug. 28, 1906 Number Number

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