BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to drill bits for providing holes in earth formations for wells, blast holes and the like. It is more particularly directed to rotary drill bits for use in relatively hard earth formations which may also be abrasive in nature, such as taconite or the like. One of the problems associated with drill bits of the class of drilling activities in which my invention finds substantial advantageous use, is concerned with economics, not only in the cost of labor for running drilling equipment, but in the cost of the drilling equipment itself, including the expendable drilling bits. My invention provides an improved economic advantage, when considering the factors set forth above, and others, in that it provides a substantially longer life, may be easier to fabricate of available components and is reliable in operation.

2. Description of the Prior Art

The following is a list of prior art patents noted in the course of an investigation concerning the subject matter of this application;

    ______________________________________
    U.S. Pat. No. Inventor     Date of Issue
    ______________________________________
    3,193,028     Radzimovsky  7/6/65
    3,251,634     Dareing      5/17/66
    3,344,870     Morris       10/3/67
    3,461,983     Hudson et al 8/19/69
    3,572,452     Winberg      3/30/71
    3,628,616     Neilson      12/21/71
    3,866,695     Jackson      2/18/75
    3,921,735     Dysart       11/25/75
    3,952,815     Dysart       4/27/76
    2,126,035     Reed         8/9/38
    2,126,040     Reed         8/9/38
    2,177,333     Reed         10/24/39
    2,673,128     Reed         3/23/54
    2,664,322     Boice        12/29/53
    2,690,935     Alexander    10/5/54
    2,719,026     Boice        9/27/55
    4,013,325     Rear         3/22/77
    4,140,189     Garner       2/20/79
    4,183,417     Levefelt     1/15/80
    ______________________________________

A plurality of anti-friction roller and ball bearings are disposed intermediate the complementary configured and disposed bearing grooves and surfaces described above in connection with journals 15 and cones 13 and include a plurality of axial roller bearing members 50, a plurality of radially disposed thrust roller bearing members 51, a plurality of retainer-ball bearing members 52 and a plurality of roller bearing members 53. Thrust roller bearings 51 of FIG. 2 are shown having a tapered configuration and it may be noted that a floating spacer ring 54 is disposed at the radially inward periphery of the rollers and that the radially outward ends of rollers 51 are provided with a convex configuration.

The seals to be placed in grooves 20 and 21 are indicated as seal 60 which may be described as an inner seal and which is preferably comprised of an elastomer resilient material that is slightly compressed when in the assembled position shown so that its outer peripheral surface is in sliding frictional and sealing engagement with surface 46 on cones 13 and the inner portions provide a sealing non-rotating contact with the bottom and sides of seal groove 20 in journals 15. The outer seal is indicated generally by reference character 64 and is preferably comprised of a continuous metallic ring of material that is in non-sliding engagement with seal surface 46 on cones 13 and is in sliding frictional engagement with the sides of seal groove 21 in journals 15. It may thus be observed and understood that seal 60 provides a form of pressure responsive seal while seal 64 provides a labyrinth type of seal. The combination of seals 60 and 64 serves to prevent the escape of lubricant from the inside of cones 13 and the inner ends of journals 15 while providing an adequate barrier to prevent the entry of any foreign material, such as drilling debris, into the lubricant containing portions of journals 15 and cones 13.

FIG. 3 illustrates a further embodiment of my invention in which inner seal 60 is shown comprised of a large O-ring 61 that extends outwardly of inner groove 20 and a pair of smaller O-rings 62 and 63 that are disposed adjacent the bottom sides of groove 20. O-rings 62 and 63 may be of lesser hardness with respect to O-ring 61. FIG. 3 further indicates a relocation of lubricant fitting 29 for adding lubricant to the inside of cones 13, as may be required.

It may be noted that the radius of ball-retainer race groove 18 in journals 15 may be related to the radius of retainer-ball bearings 52 whereby the radius of groove 18 is 0.52 times the radius of retainer-balls 52.

The combination and sub-combinations of elements set forth above provide an improved drill bit of the anti-friction bearing type in which the individual elements may be dimensioned to closer tolerances to thereby allow the use of larger carbide, or the like, cutting elements on cones 13 as well at to provide a vastly increased life and economic advantage.

OPERATION OF THE ILLUSTRATED EMBODIMENTS

With the above elements in mind, and assuming that legs 12, having cones 13 in operative disposition, have been assembled to form a body 11, a drill bit 10 is assembled to the end of a drill string. Lubrication is applied to lubricant fitting 29 disposed in air duct 22, extending through the side of legs 12, and is supplied to the interior of cones 13 around journals 15 until the pressure relief valve allows lubricant to flow through duct 30 and seal groove 21 and to appear at the outer periphery of recess 40 in cones 13 adjacent legs 12. The appropriate drive mechanism for the rotary drill stem is started and air is supplied through the interior of the drill stem to air ducts 22 in journals 12. Part of the air flows through duct 22, over lubricant fitting 29, and outwardly through the outer periphery of legs 12 and through branch 23 to radial air groove 47 in cones 13 and therefrom radially outwardly through the interface between legs 12 and the outer surface of cones 13 the rest flows through jet nozzles. As downward pressure is applied to the drill stem, drill bit 10 comes into contact with the earth's formation and commences to drill by rolling cones 13 over the substances encountered. The work performed in breaking up the earth, rock and the like, generates a substantial amount of heat and causes the lubricant on the interior of cones 13 to expand and thereby increase its pressure. It may be appreciated that part of the heat generated is carried out and emitted laterally of legs 12 as the air under pressure circulates through the ducts and nozzles in body 11.

As the temperature of the grease increases, the pressure within cones 13 increases to a level, determined by the characteristics of relief valves 31 in relief duct 30 in journals 15. When the predetermined pressure is exceeded, lubricant is allowed to escape and is conducted outwardly through duct 30 to the bottom of seal groove 21 in journals 15. This provides a lubrication function for outer seal 64 as well as to prevent the application of undue destructive pressure forces to inner seal 60.

The air under pressure supplied to the interface between the outer end of cones 13 or radial air groove 47 in cones 13 is allowed to expand radially outwardly between journals 15 and the outer end of cones 13 to inhibit the flow of drilling debris into cones 13.

It may also be noted that the tapered thrust roller bearings 51 illustrated in FIG. 2 will provide a "true-line" rolling contact that may contribute further to the longevity of the drill bit under working conditions. Similarly, the larger radius of ball bearing retainer race groove 18 over the size of retainer ball bearings 52 provides a further longevity of effective life of drill bit 10.

When it becomes necessary to supply additional lubricant to the interior of cones 13, it may be appreciated that the flow of the cooling and cleaning air through air duct 22, over lubricant fitting 29, prevents the accumulation of drilling debris so as to allow ready access to the fitting.