US2149798A - Well-drilling bit - Google Patents

Description

March 7, 1939. w 5;, STARKEY 2,149,798

WELL-DRILLING BIT Filed June 27, 1936 ATTORNEY5 Patented Mar. 7, 1939 UNITED STATES PATENT OFFICE WELL-DRILLING BIT Application June 27,

Claims.

My invention relates to well-drilling heads or bits and has for its object the production of a bit which will drill more rapidly in substantially all forms of material and which will be more durable 5 than other bits of which I am aware. A further object of my invention is to produce a bit which will embody no relatively moving parts and which will therefore be free from bearing surfaces subject to excessive wear.

In carrying out my invention, I form the bit as a series of end milling cutters of gradually increasing diameter from the lower end of the bit to the top, these cutters preferably being formed by independent rings held in place on a suitable core which is attached to the lower end of the drill face of each of these rings are provided with an annular series of cutting teeth; and the lowermost.

ring has associated with it a central insert adapt ed to break up the core left by the teeth of that ring. The core upon which the several rings are mounted is hollow and is supplied through the drill pipe with water under relatively high pressure, such water preferably discharging from the which is located at the lower end of the bit and others of which are located intermediate the height of the bit.

The accompanying drawing illustrates my invention: Fig. 1 is a vertical axial section through a complete drill bit embodying my invention; Fig. 2 is a bottom plan view of the lowermost cutter; and Fig. 3 is a side elevation of such lowermost cutter. 1 As shown in the drawing the body ll] of the bit consists of a single piece of metal, conveniently a casting, and has at its upper end an axially extending boss H provided exteriorly with screw threads for engagement with a coupling l2 by which thehead is connected to the lower end of the drill pipe I3. Below the boss H, the head has an annular flange l5 and below this flange a series of steps of gradually decreasing diameter toward the bottom of the body. As shown, there are five of such steps, l6, l1. l8, l9, and 20, but the number may vary.

Upon each of the steps l6, l1; l8, l9, and there is mounted an annular cutting element, such cutting elements being des gnated in the 50 drawing by the reference numerals 2|, 22, 23. 24. and 25. A sixth annular cutting element 26 is disposed at the extreme bottom of the body l0 and has an upwardly extending boss 21 provided exteriorly with screw threads by means of which it is retained in place on the body. Each of the interior of the core through ports at least one of 1936, Serial No. 87,601

cutting elements has an axial thickness a few thousandths of an inch greater than the efiective width of itsassociated step and an external diameter greater than the diameter of the step next above it, so that by the action of the screw threads on the boss 21 the lowermost cutting element 26 can be rotated to clamp all the cutting elements in place.

Each of the cutting elements is provided with an annular series of cutting teeth extending vertically across the cylindrical face of the cutting element and inwardly along the bottom face thereof at least to a point within the circumference of the cutting element next below. The base diameter of the upper cutting element 2| is preferably not less than the diameter of the flange l5, so that the flange IE will not interfere with the movement of thecuttings passing upwardly through the spaces between the teeth of that cutting element.

Rotation of each cutting element on the body to is prevented by any suitable means, the means shown comprising one or more keys 30 associated with each cutting element.

To break up the core which would otherwise be left by the lowermost of the annular cutting elements 26, I mount in such cutting element an insert 32 having a pair of cutting edges which slope outwardlyand upwardly from its center and have their upper ends above the plane of the cutting edges of the teeth on the lower cutting element 26. Conveniently, the insert 32 is of flat stock the edges of which are received in diametrically opposite key-ways in the bore 33 of the cutter 26. To prevent the insert from dropping out of its seat, its upper end may be formed with two outwardly projecting ears 34 overlying the upper end of the boss 21, as is clear from Fig. 1.

The body I0 of the head is hollow and receives water under pressure through the drill pipe l3. At least a part of this water is expelled downwardly between the sides of the insert'32 and the wallof the bore 33, which bore desirably tapers ciiihferentlal p tch of the teeth of all cutting elements will u d approximately the same. As a result of this, all the teeth of one cutting element can not be in alinement with all the teeth of the cutting elements above and below it; and to prevent interference with the free upward flow of water and the cuttings suspended. therein, I flnd it desirable, at least in the case of the larger cutting elements below the uppermost cutting element 2|, to provide an annular groove 36 along the outer upper edge of each cutting element. These various grooves 36 provide for any circumferential movement of water or cuttings that may be necessary to permit them to enter into the spaces between the teeth of the next higher cutting element.

I find in practice that itis difficult if not impossible to secure an adequate flow of water through the relatively small bore 33 in the lowermost cutter 26, and I therefore provide for the emergence of water from the interior ofthe body III at a level above the lower end of the bit. To this end one of the steps on the body I0, shown in the drawing as the step I9, has a width materially greater than the thickness of its associated. cutter 24, and above the cutter 24 the annular wall of the body It! is drilled radially for the reception of nozzle-bushings38. These bushings project outwardly beyond the annular wall of the head-body into a ring 40 which is mounted on the step l9 above the cutter 24. The lower end .of the ring 40 is received in a countcrbore in a second ring 4| which rests upon the cutter 24 and which is clamped between the ring 40 and the cutter 24 by the clamping action of the screw threads on the boss 21 of the lowermost cutter26. The ring 40 projects radially outwardly only a slight distance, if any, beyond the outer ends of the bushings 38, but the second ring 4i is of materially larger external diameter and has its upper face dished, to provide an outwardly and upwardly sloping surface 42. Water emerging outwardly through the nozzles 38 impinges upon the surface 42 and is deflected upwardly against the lower surface of the cutting element 23. By imparting an upward component to the waterdischarged through the nozzles 38, I am enabled to prevent such water from interfering with upward flow of the water which is discharged through the bore 33 of the lowermost cutting element 26.

When a drill head as described is in use, the

teeth on the lower surfaces of the various cutting end cutting teeth of the cutting element next above.

It is to be noted that the spaces between the teeth on the outer and bottom faces of the cutting elements form the sole passages for the water which is discharged from the interior of the body. As a result, such water is compelled to flow in substantial contact with all the cutting edges and tends to carry away immediately all particles which those cutting edges dislodge. Further, all recesseson the outer surface of the head are water passages, and there are no pockets in which the cuttings can collect. Since the aggregate cross-sectional area of thewater passages, even in the case of the largest cutting element, is materially less than that of the annular space above the flange 15, the water passing the cutting edges is maintained under high pressure which is effective to dislodge any rock fragments or other material that would otherwise tend to collect between the teeth.

If all the end cutting teeth of each cutter were in the same plane, the total downwardly directed thrust on the head would be divided equally between all the teeth. To prevent the necessity for an excessive downwardly directed thrust when the head is cutting through hard material, therefore, I prefer to arrange the end teeth of each cutting element so that some of them extend a short distance downwardly beyond the remainder. This is indicated in exaggerated form in Fig. 3, where the lowermost cutting element 26 is shown as having nine teeth three of which, equally spaced, project downwardly beyond the other six. Preferably, these teeth are made as hard as possible, as by facing them with tungsten carbide or some other suitable substance of a type which stands up well under an abrasive cutting action. The proportionate number of cutting teeth on each cutting element which thus project beyond the others may vary, but I have found it convenient to use the proportions indicated in Figs. 2 and 3-in the case of the cutter 26-namely, one long tooth for each two short teeth. I

The distance by which the long teeth project beyond the short teeth should be some-distance intermediate between the depth of cut taken by each tooth in hard material and the depth of cut taken in soft material. I find in practice that while in excessively hard rock each tooth may feed only a few thousandths of an inch each tooth, in soft material, may feed as much as 1' 5 of an inch, and I therefore prefer to have the long teeth project approximately 0.010 inch below the short teeth. In excessively hard rock, the longteeth will do all the cutting, although the shorter teeth may aid in breaking up chips which the longer teeth dislodge. In soft material, all the teeth may cut, although the depth of the outv of the longer teeth will be slightly greater than that of the shorter teeth.

I claim as my invention:

1. In a drill head, a cutting element screwthreadedly mounted at the lower end of said head, said cutting element having an annular series of end cutting teeth and an axial bore extending through it and constituting a fluid passage, and a removable member of flat stock disposed in said passage and dividing it longitudinally, said bore being provided with key-ways receiving the edges of said member, said member'having at its lower end a generally diametrically extending cutting edge located at least in part above the cutting edges of the teeth on said cutting element.

2. In a drill head, a cutting element screwthreadedly mounted at the lower end of said head, said cutting element having an annular series of end cutting teeth and an axial bore extending through it and constituting a fluid passage, and a removable member of fiat stock disposed in said passage and dividing it longitudinally, said bore being provided ,with key-ways receiving the edges of said member, said member having at its lower end a generally diametrically extending cutting edge.

3. In a drill head, a body having an annular flange and below such flange a series of annular steps decreasing in diameter toward the lower end of the body, an annular element mounted on each of said steps,"each oi. such elements having an external diameter greater than the internal diameter of the element next above it, each of said elements projecting downwardly below the end of the associated step to engage the element next below, some of said elements being provided respectively with annular series of cutting teeth. and a clamping member having an external diameter greater than the internal diameter of the annular element immediately above it and also having an upwardly projecting axial boss screwthreadedly received in said body at the lower end thereof, said clamping member having an annular series of cutting teeth.

4. In a drill head, a body having an annular flange and below such flange a series of annular steps decreasing in diameter toward the lower end of the body, an annular element mounted on each of said steps, each or siwh elements having an external diameter greater than the internal diameter of the element next above it, each of said elements projecting downwardly below the end of the associated step to engage the element next below, some of said elements being provided respectively with an annular series of cutting teeth, and a clamping member having an external diameter greater than the internal diameter of v means associated with the lowermost cutting element for breaking up the core left by its annular series of end cutting teeth, said head being hollow and provided with a water-discharge opening at the bottom of the head and with one or more additional water-discharge openings at a point intermediate the lowermost and uppermost cutting elements, said head also having means for deflecting upwardly water discharged from said additional openings.

WILLIAM 'CARLETON STARKEY.

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