US2751196A

US2751196A - Rotary bit for dry rock drilling

Info

Publication number: US2751196A
Application number: US503292A
Authority: US
Inventors: Smith Belmont Duard
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-04-22
Filing date: 1955-04-22
Publication date: 1956-06-19
Anticipated expiration: 1973-06-19

Description

June 19, 1956 B. D. SMITH 2,751,196 ROTARY BIT FOR DRY ROCK DRILLING Filed April 22, 1955 2 Sheets-Shea t l 2&

INVENTOR ,Be Zmonzfl. Smith,

ATTO E Y June 19, 1956 B. D. SMITH 2,751,196

ROTARY BIT FOR DRY ROCK DRILLING Filed April 22, 1955 2 Sheets-Sheet 2 7 .33 a I 29 i 1 3/ 0 l0 1 22 1 I l/ 20 .2

INVENTOR 2,751,196 ROTARY BIT FOR DRY RGQK DLING Belmont Duard Smith, Eaton, Ohio Application April 22, 1955, Serial No. 503,292 Claims. (Cl. 255-304) This invention relates to rotary rock drilling apparatus, and has for its principal object the provision of an improved drill bit of the rotating cutter type which is especially adapted for use in the dry drilling of rock formations, as for example, in the production of blasting holes in quarrying operations.

The use of rotary cutter bits in the drilling of oil, gas and other deep wells is well known and in such operations the common practice is to cool the cutters and bring the cuttings to the ground surface by means of a flushing liquid or semi-liquidv slush or mud which is pumped down through the drill stem, discharged over or around the cutters, and returned to the surface along with the cuttings through the bore' exteriorly of the stem. The bearings upon which the cutters rotate are protected as well as possible against entry of the cuttings thereto, and in at least some instances provision has been made for supplying a lubricant to them.

In some fields, as in quarrying, the presence of liquid in the bore hole is objectionable and therefore it has been proposed to modify the conventional. oil well practice by using compressed air rather than water or slush as the cooling and flushing fluid. This is feasible since in such operations the bores ordinarily do not extend to depths greater than a few hundred feet and air pressures on the order of from 25 to 100 pounds per square inch are sufficient to bring the cuttings to the surface. In some bits employed in such work, in addition to discharging the air over or around the cutters, the bit has been providedwith ducts whereby a portion of the air may be discharged directly to the cutter bearings for cooling purposes.

The bit of the present invention is basically one of this type. However, it is provided with means whereby a pool. of oil or analogous lubricant may be established within the bit in such position as to be directly actediuporr by the compressed air and thereby constantly forced to: the cutter bearings through the conventional air cooling ducts. The construction is suchthat the lubricant in the pool can be replenished without withdrawing the bit from the bore; for example, as the drilling proceeds before each length of drill stem is added to the string. a small quantity of oil is merely poured into the stem already in the hole and descends along the stern wall by gravity to the pool in the bit. Thus, an adequate supply of lubricant for the cutter-bearings may be maintained with a minimum expenditure of time and effort.

In another aspect of the invention the means for establishing the lubricant pool comprises a tubular member or thimble disposed in the main air passage of the bit body and having a plurality of ports in its lower end for directing jets of air between the rotary cutters, the upper end portion of said thimble projecting upwardly from said main air passage and in conjunction with the peripheral Wall of the bit providing a reservoir in whichthe lubricant pool is established and maintained, and from which the lubricating ducts lead to the cutter bearings. The thimbles may be merely frictionally retained in the bit passage whereby to be readily changeable to 2,751,196 Patented June 19,1956

meet varied operating requirements, or in some instances they'ma'y be permanently securedin place as by welding them to the bit body.

Several embodiments of theinvention are illustrated in the accompanying drawings constituting a part of this specification, in: which like. reference characters designate like parts throughout. the views and in which:

Figure 1 is a' central vertical sectional view of a rotarycutterrock drilling bit embodying one form of the invention;

Fig. 2' is a horizontal"sectional-plan view on the plane indicated by theline 22'in Fig. 1;

Fig. 3 is a fragmentary view similar to Fig. 1 but on a somewhat smaller scale, showing a slightly different form of bit and thimble;

Fig. 4 is a fragmentary view similar to Fig. 3, showing a longer thimble permanently secured inplace;

Fig. 5 is a similar view showing formation of the lubricant reservoir by means of an integral annular flange extending upwardly from the bit body around the air passage;

Fig. 6 is a similar view illustrating application of the invention to a bit having a plurality of air passages through its body; and

Fig 7 is a perspective view of astill further modified form of jet and. reservoir forming element- Referringrmore.particularly to Figs. 1 and 2, the rotaryeutter bitll) there shown comprises a body 11 having the usual tubular thre'aded extension 12 for attachment. to the drilling stem (not; shown). A. plurality of circumferentially spacedlcgs 13 depend from the body 11, each of which is provided. with an inwardly extending coniform boss 14-upon which a toothed cutter element or cone 15 is rotatably mounted by means of. antifriction balls and/ or rollers 16 and 17. Each coniform boss 14 is provided with ducts 18" and'19: which communicate with a duct 20 that extends upwardly through the leg 13 and body 11 to the peripheral portion of the chamber 21 provided by the tubular threaded extension of the bit. The said ducts have heretofore served to conduct a portion of the compressed air supplied tothe chamber 21 to the cutter bearings 16 and: 17 whereby to cool them; and the body 11 has been provided with. an axial passage 22 through which the major portion of the. air has been discharged over. and around the cutters 15-.

While the supplying of air to the cutter bearings may cool them to some extent, the small clearances through which the air must pass. are not conducive to a flow adequate to satisfactorily perform the intended purpose, and in many instances it has been found insufficient to prevent heating and expansion of the parts with resultant seizing or locking of the cutters. Neither does the air prevent wear incident to the metal-to-metal contact of the parts, and all in all the life of the bearings of these prior bits has been relatively short.

To overcome this, in the form of the present invention shown. in Figs. 1 and 2 there is removably disposed in the main air'passage 22' of the bit body a thimble member 25- the'lower closed end of which is located somewhat below the plane of the under face of the body 11' and is provided with a plurality of inclined radially extending" air passages 26. These are of reduced diameter as compared with that of the bore 27 of the thimble, with which they communicate, and they are so disposed as to. direct jets of air from the chamber 21 outwardly and downwardly into the rock bore, preferably between the cutters 15.

The flaring, upper portion 28 of the thimble member extends upwardly into the bit chamber 21 substantially as shown in- Fig 1 and in conjunction with the peripheral wall andbottom. of said chamber provides an annular open-toppedreservoir 29-: in which a pool of oil or similar lubricant 30 may be established and replenished as necessary by merely pouring such lubricant in to the upper end of the drill stem, without withdrawing the drill from the hole. The top surface of the pool is indirect contact with and subject to the pressure of the air supplied to the chamber 21, whereby a forced feed of the lubricant through the

ducts

20, 19 and 18' to the cutter bearings is maintained, thus insuring free rotation of the cutters and lengthened life of the bearings.

The bit shown in Fig. 3 differs slightly from that of Fig. 1 in that the duct 20' instead of communicating with ducts such as 18 and 19 in the bearing boss 14, discharges directly into the clearance between the cutter and said boss. The tubular member 31 shown in Fig. 3 also is slightly different, being tapered throughout its length, and while its upper portion projects into the bit chamber 21 whereby to provide the lubricant reservoir 29 as in the preceding form, its lower end is disposed approximately in the plane of the under face of the body 11. The jet passages 26 also are of relatively smaller diameter than those of Fig. l.

The thimble shown in Fig. 4 is similar to that of Fig. 3 except that it is longer whereby to extend further below the under face of the bit body than either of the forms shown in Figs. 1 and 3, and in addition to the radial jet passages 26 it is provided with an axial passage 26'. This thimble is also indicated as being rigidly secured in place by welding it to the body 11 at 32. It will be obvious from Figs. 1, 3 and 4 that the thimbles may be of varying lengths whereby to discharge the air closer to or farther away from the cutters 15, and that the diameters and arrangements of the jet passages may be varied as necessary or desired to meet various operating conditions. Thus, since the thimbles are readily interchangeable the bits are easily adaptable to various air pressures and to any drilling situations that may be encountered while at the same time retaining the advantageous mode of lubricating the cutter bearings.

In lieu of employing the thimbles or 31 to provide the lubricant reservoir 29, the same result may be attained by means of an annular flange extending upwardly from the body 11 into the bit chamber 21, as shown in Fig. 5.

Some bits, instead of having a single axial air passage 22, are provided with a plurality of smaller passages as shown at 34 in Fig. 6. If these be located sufiiciently close to one another the bit body may be bored out to provide a single axial passage and a thimble inserted therein as in Figs. 1, 3 and 4. If however, the passages 34 are too widely spaced to make this feasible, a tubular nipple 35 may be removably or rigidly disposed in each such passage, as shown in said Fig. 6, whereby to provide the oil reservoir 29.

In Fig. 7 there is illustrated a plug member 36 provided with a plurality of air passages 37 extending through it longitudinally, which may be used in place of the thimbles shown in Figs. 1, 3 and 4.

is added to the string, without withdrawing the bit from the hole as is possible with the present invention, the life of said bearings may easily 'be lengthened by from 100% to 200% over that of unlubricated or mere air-cooled bearings, and thus it is economically feasible to re-tip the cutter teeth two or three times.

Having described several exemplifications of the invention, what is claimed is:

1. A rotary bit for dry rock drilling, comprising a bit body having a chamber in its upper portion for receiving compressed air, and a plurality of cutter elements rotatably carried by its lower portion, the body also being provided with an air passage extending from the chamber to adjacent said cutter elements, and with ducts extending from the chamber to the bearings of the cutter elements; and means extending upwardly from said air passage into the body chamber and in conjunction with portions of the walls of the latter providing an opentopped reservoir adapted to receive lubricant poured into the top of the chamber and thereby provide a lubricant pool the surface of which is subject to direct action of the compressed air in the chamber whereby such lubricant may be forced through said body ducts to the bearings of the cutter elements.

2. A rotary bit for dry rock drilling, comprising a bit body having a chamber in its upper portion for receiving compressed air, and a plurality of cutter elements rotatably carried by its lower portion, the body also being provided with an air passage extending from the chamber to adjacent said cutter elements, and with ducts extending from the chamber to the bearings of the cutter elements; and an air conducting member disposed in said body passage and projecting from the upper end thereof into said chamber in wholly spaced relation to the walls of the latter whereby to form, in conjunction with portions of said chamber walls, an open-topped reservoir 7 adapted to receive lubricant poured into the top of the chamber and thereby provide a pool of lubricant which is subject to direct action of the compressed air in the chamber whereby such lubricant may be forced through said body ducts to the bearings of the cutter elements.

3. A rotary bit for dry rock drilling, comprising a bit body having a chamber in its upper portion for receiving compressed air, and a plurality of cutter elements rotatably carried by its lower portion, the body also being provided with an axial air passage extending from the chamber to adjacent said cutter elements, and with ducts extending from the lower peripheral portion of the chamber to the bearings of the cutter elements; and a tubular air conducting member readily removably disposed in said body passage With its upper portion extending into said chamber whereby, in conjunction with portions of Although the cutters 15 are formed of hardened alloy steel, wear on the cutter teeth unavoidably takes place during use or" the bits and they become shortened and blunted or rounded to such an extent as to materially impair their cutting efliciency. When this occurs it is an accepted practice in the art, if the cutter bearings be still serviceable, to rebuild the teeth with weld metal to substantially their original size and shape, as this can be done at a cost appreciably less than that of a new cutter. It has been found however, that where adequate lubrication of the cutter bearings has not been provided, such bearings usually are so badly worn by the time the cutter teeth need re-building that repair of said teeth is uneconomic since the worn bearings will fail rapidly once the bit is put back into service.

By making proper lubrication of the cutter bearings a mere matter of pouring a half pint or so of oil into the upper end of the drill stern each time a length of stem the walls of the latter, to form an annular open-topped reservoir adapted to receive lubricant poured into the top of the chamber and thus provide a pool of lubricant the surface of which is subject to direct action of the compressed air in the chamber whereby such lubricant may be forced through said body ducts to the bearings of the cutter elements.

4. A rotary bit for dry rock drilling, comprising a bit body having a chamber in its upper portion for receiving compressed air, and a plurality of cutter elements rotatably carried by its lower portion, the body also being provided with an air passage extending from the chamber to adjacent said cutter elements, and with ducts extending from the chamber to the bearings of the cutter elements; and an annular flange concentric with said body passage and extending upwardly therefrom into said chamber and in conjunction with portions of the chamber walls providing an open-topped reservoir adapted to receive lubricant poured into the top of theehamber and thus provide a pool of such lubricant the surface of which is subject to direct pressure of the air in the chamber whereby said lubricant may be forced through said body ducts to the bearings of the cutter elements.

5. A rotary bit for dry roc i drilling, comprising a bit body having a chamber in its upper portion for receiving compressed air, and a plurality of cutter elements rotatably carried by its lower portion, the body also being provided with an air passage extending from the chamber to adjacent said cutter elements, and with ducts extending from the chamber to the bearings of the cutter elements; and an elongated plug member provided with air passages extending longitudinally therethrough, said plug being disposed in said body air passage with its upper end portion projecting therefrom into the body chamber and in conjunction with portions of the chamber walls providing an open-topped reservoir adapted to receive lubricant poured into the top of the chamber and thus provide a pool of such lubricant the surface of which is subject to direct pressure of the air in the chamber whereby said lubricant may be forced through said body ducts to the bearings of the cutter elements.

References Cited in the file of this patent UNITED STATES PATENTS 1,708,288 Wadsworth Apr. 9, 1929 1,816,203 Behnke July 28, 1931 2,661,932 Woods Dec. 8, 1953