US2148372A

US2148372A - Offset tricone bit

Info

Publication number: US2148372A
Application number: US70080A
Authority: US
Inventors: Lewis E Garfield
Original assignee: Hughes Tool Co
Current assignee: Hughes Tool Co
Priority date: 1936-03-21
Filing date: 1936-03-21
Publication date: 1939-02-21
Anticipated expiration: 1956-02-21

Description

Feb. 21, 1939. 1.. E. GARFIELD 2,148,372

OFFSET TRICONE BIT Filed March 21, 1956 2 Sheds-Sheet 1 Lewis 25' Garfield INVENTOR.

A TTORNEYS.

Patented Feb. 21, 1939 UNITED STATES PATENT OFFICE.

This invention relates Lewis E. Garfield, Houston,

Tex., assignor to poration of Texas Application -March 21, 1936, Serial No. 70,080

2 Claims.

to well drills of the.

cone type where the cutters are approximately conical in shape and surround the ends of the shafts upon which they are mounted.

The use of three cones upon such a well drill,

while a fairly recent development, has now become quite common in the oil fields. These cones have previously been set upon the head of the drill with the axes of the cutters pointing radially toward the longitudinal axis of the drill head and of the well bore.

When so mounted,

the cutters have a true rolling action upon the well bottom provided the apex of the cone lies on such axis. is efiicient in its action.

Such a cone runs smoothly and It has a disadvantage,

however, that it does not cut so rapidly as it should.

It is an object of this invention to increase the speed of drilling with a three cone bit by oifsetting the axes of the cones from a radial position relative to the head, so that the cutting teeth have more of a scraping action in rolling upon the well bottom.

It is a further object, where the rows of teeth forward advancing side and thus enable the drill to be introduced into the hole more easily and without wear upon the cutter or bearings.

I also aim to position the cutters so that the thrust in drilling will be delivered more uniformly upon the bearings best formed and positioned to carry the thrust.

In the drawings herewith Fig. 1 is a side elevation of a well drill embodying the invention.

Fig. 2 is a bottom plan view of the cutters alone, positioned as they Fig. 3 is a diagram illu are in operation. strating the position of the cutters relative the axis of the hole.

Fig. 4 is a broken section showing the relative positions of the cutter teeth where the cutter axes are not offset but the teeth interflt.

Fig. 5 is a similar s change. produced in the by offsetting cutters wher cutters interfit.

ection illustrating the positions of the teeth e the teeth on adjacent The manner in which the cutters are mounted for operation is seen in Fig. 1, where the bit head I has an upwardly tapered shank 2 and three downwardly projecting legs 3. Upon these legs are the three cones 4 so mounted that their 5 apices converge toward the center of the head.

As will be seen in Fig. 2 the teeth upon each cutter are formed in circumferential rows 5 around the tapered periphery of the cone. While the cutters are called cones, in practice they are not truly conical. The teeth 5 adjacent the base are on a different taper than are the teeth on the remainder of the cutter; The rows of teeth on the forward tapered zone are formed in rows offset. longitudinally of the cone from it corresponding rows on the adjacent cutters. Hence each cutter is formed to mate with the other two cones. The cutters may be spaced apart, as shown in Fig. 2, or they may be set close together so that the teeth on one cutter 29 may interfit between the rows of teeth on both adjacent cutters as shown in Figs. 4 and 5.

To give the cutting teeth a more effective cutting action, I incline the axis of each cutter in a direction forwardly and outwardly from the axis of the hole as the bit head is rotated in drilling. In Fig. 3, the cutter ,4 has its axis 1 set so that it lies tangent to an imaginary circle 9 about the longitudinal axis 6 of the wall, the walls of which are indicated by the circle I0. 30 The length of the 'radius of the circle 9 may vary from 1% of an inch to 1 inches, the. good eifect of offsetting being obtained within these limits. The radius of the hole is shown by lines 8 for purposes of more clearly indicating the movement of the cutter axis from its ordinary radial position.

When the cutters are thus positioned, it will be seen that the base, or largest diameter, ll of the cutter contacts with the wall of the hole 40 at its forward advancing side and not at the central portion of the base, as heretofore. This has the effect of giving the cutter a rolling contact with the wall of the hole as the cutter is moved downwardly in the well, as where it is being introduced into the well. This prevents the scraping of the base of the cone on the wall of the well and the consequent clogging and wear previously experienced with prior bits of this character.

Further the rows of teeth on the cutter have a longitudinal component of thrust at the forward end as will be understood from Fig. 3. As the cutter is moved around the well bottom A by the rotation of the drill, it will roll on the bottom but will also have a thrust in the direction of the cutter axis I. This will not only give the cutting teeth a scraping action in rolling but will exert a force upon the cutter toward the base. This force together with the upward thrust of the formation will produce a component thrust which is effectively taken up by the usual roller bearings.

Where the teeth on adjacent cutters interflt, as shown in Figs. 4 and 5, I also obtain another marked advantage. Where the cutters are set with their axes radial instead of offset as described, the rows of teeth on adjacent cutters interflt as shown in Fig. 4. It will be seen that the space between adjacent rows of teeth on each cutter must be wide enough to mate with two rows of teeth, one on each of the adjacent cutters. To provide this space it is necessary to make the teeth, or rather the rows of teeth, narrow. For as the teeth out tracks in concentric circles on the well bottom, and the cones have their apices converging on the same center, there must be room between adjacent rows of teeth on each cutter for two rows of teeth to pass. That is, one row of teeth on the cutter preceding and one row on the following cutter.

Where the cutters are offset, however, the effeet is to move the rows of teeth on each cutter farther forward relative to the corresponding rows of teeth on the following cutter and to the rear relative to the corresponding rows on the preceding cutter.

This can be understood with reference to the diagrammatic illustrations in Figs. 4 and 5. These two figures are top plan sectional views, as contrasted with the showing in Fig. 3, which is a bottom plan view. In Fig. 4 the axes of the cutters 4 are radial relative to the axis of the hole. Refer to the row of teeth indicated at l2 on one of the cutters. In Fig. 4 this row of teeth is closely adjacent the row l3 on the following cutter and is adjacent the row I 4 on the preceding cutter. In Fig. 5 the cutter axis 1 of each cutter has been offset from the center as described relative to Fig. 3. This throws the row of teeth' l2 rearwardly relative to the row I3 on the following cutter and forwardly away from the row 14 on the preceding cutter. This effect is exaggerated by the fact that the row of teeth l3 on the following cutter has also been thrown away from row l2 by its being also offset. The neteffect of this offsetting of the cutter axes is to throw the rowsof teeth on adjacent cutters further toward the middle of the spacesbetween the rows of teeth on adjacent cutters and thus allow more clearance. I am thus enabled to make the teethwider as indicated in the shading IS on the teeth in Fig. 5, and still have plenty of room for the teeth on adjacent cones to intermesh in operation. The bottom of the hole is thus more effectively cut. There are no circles of uncut bottom between the tracks out by the rows of teeth on adjacent cutters. The teeth are stronger and cut longer before becoming worn out.

As has been previously pointed out, the offsetting of the cones gives a better cutting action of the teeth due to their scraping or ploughing action on the bottom. The load upon the bearings in operation is more uniformly distributed.

There is a more markedoutward thrust which keeps the cutters forced outwardly to cut the wall of the holeand prevent locking of the cutters. Also the rows of teeth can be made wider even where they do not interflt on adjacent cutters. Each row of teeth is more than half as wide as the space between corresponding rows of teeth on adjacent cutters. The bottom of the hole is thus more effectively cut by the drill. Where the teeth of the cutters are interfltting a complete overlapping of the tracks of the rows of teeth on the well bottom can be obtained, thus assuring efficient and rapid action of the drill. Cutters thus mounted show a marked increase in speed of drilling. In addition to this superior performance in drilling, the drill can be more easily inserted into the well because of the rolling action of the cutters on the wall of the hole as the drill is lowered.

What I claim is:

1. In a well drill, a head rotatable on a central longitudinal axis, three approximately conical shaped cutters on the forward end thereof, the axis of each cutter being offset to the forward side of the longitudinal axis of the drill as the drill is rotated, teeth on said cutters arranged in rows circumferentially about the same, the rows of teeth on each cutter interfitting between the rows of teeth on each adjacent cutter, said teeth being more than half as wide as the space between the corresponding rows of teeth adjacent cutters.

2. A three cone well drill having the axes of the cones pointed at the apex forwardly and outwardly from the longitudinal axis of the well bore as said cones are rolled about the bottom of the well, circumferential rows of teeth on said I cones, said teeth on each cutter being offset relative to the corresponding rows of teeth on adjacent cutters, the offsetting of the cutter axes acting to permit greater width of teeth in adjacent rows.

LEWIS E. GARFIELD.