Rotary Percussive Drill And Method

Abstract

A rotary percussive drill has relatively movable inner and outer concentric drill pipes and a down-the-hole hammer that acts on the inner pipe near the cutting bits. The impact of the hammer is transmitted by an external shoulder on the inner drill to an internal shoulder on the inner drill to an internal shoulder on the outer drill adjacent the bits.

Description

The present invention relates to rotary earth drills such as those for penetrating overburden and the like, and is of particular application to rotary percussive drills having relatively movable inner and outer drill pipes.

Known drilling apparatus of this type suffers from the disadvantage that the inner and outer cutters cannot be simultaneously and equally loaded by a percussion hammer. Down-the-hole hammers of types known heretofore act only on the inner drill bit of the inner drill pipe, which thus tends to lead the outer drill pipe. Loading the outer drill pipe by means of a percussion hammer disposed above ground has the disadvantage that the impacts must be transmitted over the entire length of the outer drill pipe, so that relatively little energy from the blows is usefully applied to the outer drill bit.

It is accordingly an object of the present invention to improve the efficiency of drilling apparatus of the present type by the simultaneous and uniform loading of the inner and outer drill bits by means of a down-the-hole percussion hammer.

Another object of the present invention is the provision of drilling apparatus which is readily adapted to be modified so as to function not only in loose soil or overburden, but also in hard rock, and to provide methods for carrying out the corresponding drilling operations.

Finally, it is an object of the present invention to provide apparatus as described above, which will be relatively simple and inexpensive to manufacture, easy to operate, and rugged and durable in use.

Briefly, the present invention achieves these objects by providing a percussion member which is disposed between the down-the-hole hammer and the internal drill bit, the percussion member providing radially outwardly extending downwardly facing percussion shoulders which bear on radially inwardly extending upwardly facing percussion shoulders on the outer drill bit. The percussive blows are thus transmitted both to the inner and to the outer drill bits. This percussion member is screw-threadedly attached to the inner drill bit. The inner drill pipe transmits air or water that passes through ports in the inner drill bit to flush away the cuttings, which are transmitted back up through channels in the inner bit and percussion member.

The inner and outer drills rotate and advance together through overburden or other relatively loose ground formations. When solid rock is encountered, however, the inner drill is replaced with one that has no percussion member and that passes downwardly through the outer drill to form a bore hole, while the outer drill is held stationary.

Other objects, features and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a fragmentary elevational view, partly in cross section, of the lower part of drilling apparatus according to the present invention;

FIG. 2 is a bottom plan view of the structure shown in FIG. 1;

FIG. 3 is an enlarged fragmentary cross-sectional view of the outer drill bit of the present invention;

FIG. 4 is an exploded elevational view of the percussion member and inner drill bit of the present invention; and

FIG. 5 is a bottom plan view of the structure shown in FIG. 4.

Referring now to the drawings in greater detail, there is shown drilling apparatus according to the present invention, comprising an outer drill pipe 1, an inner drill pipe 2, an annular outer drill bit 3, an inner drill bit 4, and a conventional down-the-hole hammer 5. Outer drill bit 3 is screw-threadedly connected to outer drill pipe 1 at 6. Hammer 5 is disposed at the lower end of inner drill pipe 2. A percussion member 7 is secured to hammer 5 in non-rotatable relation thereto but has limited axial sliding movement relative to hammer 5.

Referring now to FIG. 4, the percussion member 7 is shown there in greater detail as having a splined shank 8 insertable in hammer 5, shank 8 having a flat 9 thereon; and at its lower end, member 7 has an externally screw-threaded shank 10 receivable in a correspondingly screw-threaded recess in inner drill bit 4.

Percussion member 7 has radially outwardly extending shoulder means adjacent its lower end, that terminate downwardly in downwardly facing percussion shoulders 11. Shoulders 11 rest on and are adapted to strike corresponding upwardly facing radially inwardly extending shoulders 12 on drill bit 3. Shoulders 12 may be continuous or spaced apart about a circle.

Inner drill bit 4 has several ports 13 for air or water for flushing away cuttings. Ports 13 communicate with a continuous axial bore 14 that extends through percussion member 7 and up through the inner drill pipe. Circumferentially spaced vertical recesses 15 about the outer edges of percussion member 7 provide return passageways for the flushing fluid and are in alignment with corresponding recesses on drill bit 4 when screw-threaded shank 10 is tightened into drill bit 4. The flushing material then passes upwardly in the usual manner between the inner and outer drill pipes. This return passageway also provides a discharge passageway for the working medium discharged from hammer 5.

During penetration of the soil or overburden, outer and inner pipes 1 and 2 are rotated together by conventional rotary power means (not shown) while being simultaneously loaded by hammer 5 whose impacts are transmitted not only to drill bit 4 but by the novel structure just recited also to drill bit 3. The path of transmission of the blows is thus as short as possible.

When hard rock is reached, the inner drill pipe 2 with hammer 5 and percussion member 7 and inner drill bit 4 is withdrawn upwardly and outer drill pipe 1 is left in place to support the loose soil or rock but is not rotated. There is then inserted an internal drilling cutter (not shown) which passes through the internal aperture 20 of outer drill bit 3, only this replacement inner cutter being driven downwardly by rotation and percussion through the rock. Outer drill pipe 1 remains stationary and the replacement cutter passes downwardly therethrough because it includes no percussion member 7 and because its outer diameter, including the outer diameter of hammer 5, is less than the internal diameter of aperture 20. The inner or replacement cutter can then be withdrawn to enable the bore hole thus formed to be employed for its intended purpose, such as blasting or the like.

After the rock has been traversed, then drilling with the assembly shown in the drawings can be resumed.

From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved.

Although the present invention has been described and illustrated in connection with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

Claims

Having described my invention, I claim:

1. A drilling apparatus comprising an outer drill pipe having an outer drill, an inner drill pipe having an inner drill bit and a down-the-hole hammer to transmit percussive shocks to said inner drill bit, and a percussion member disposed between said hammer and said inner drill bit, said percussion member having portions thereof striking said outer drill bit thereby to transmit percussive shocks also to said outer drill bit, said hammer having an external diameter which is smaller than the least internal diameter of said outer pipe and outer drill bit, thus enabling said inner drill bit to be replaced with another inner drill bit of an outside diameter smaller than the inside diameter of said outer drill pipe and bit to penetrate hard formations with said first drill pipe and said another inner drill bit while maintaining said outer drill pipe and bit stationary.

2. Apparatus as claimed in claim 1, said portions of said percussion member comprising downwardly facing radially outwardly extending shoulder means on said percussion member overlying and contacting upwardly facing radially inwardly extending shoulder means on said outer drill bit.

3. Apparatus as claimed in claim 1, and a screw-threaded connection between said inner drill bit and said percussion member whereby said inner drill bit and percussion member are detachably interconnected.

4. Apparatus as claimed in claim 1, said inner drill bit having a plurality of ports therethrough for the passage of fluid for flushing cuttings from the drill face, said percussion member having an axial bore therethrough that communicates with said ports.