Drill Bit With Pivoting Cutting Portion

Abstract

An adapter comprising an upper part and a lower part hingedly interconnected by a bolt disposed excentrically to a drill string axis carries a drill bit at the lower end of the lower part. The adapter and bit is carried through a tubular casing so that the bit and lower part are below the casing. The string is rotated so that the bit and lower part swings out and undercuts the casing.

Description

This invention relates to a drilling equipment consisting of a rotatable drill bit, a drill string which carries said drill bit, and a casing tube string which follows the drill bit down into the hole. Such equipments are used with advantage for drilling operations where it is desired to drill into bedrock without first having to remove the overlying deposits of earth, clay, stone and other loose formations. The invention is particularly suitable for water well drilling, where it is often desired to insert a casing tube through the overburden down to bedrock, and sometimes a distance into bedrock, in order to prevent the hole from collapsing and/or to seal off the well from contaminated surface water. The casing string may have a length of a few meters to several 10s of meters. The expression "drill string" in the specification and claims should be given a wide interpretation so that it covers a single drill rod or tube, a train of drill rods or tubes interconnected by screw threaded portions, couplings, sleeves, or equivalent elements, and also a tube or train of tubes carrying a so called "down the hole drill" or a rotary drill at the bit end. The drilling equipment according to the invention is substantially characterized by this that the drill bit is attached to an adapter which consists of an upper part which is centrically guided by the casing tube and a lower part which is connected to the upper part by a hinge-like connection and onto which the drill bit is attached in such a manner as to permit the bit and the lower part to swing out below the casing tube on an axis which is parallel to the axis of the drill string to a position which is excentric relative to the axis of the drill string so that the bit may drill a hole of a sufficiently large diameter to provide space for the casing tubes. After having drilled through the loose formations with the equipment according to the invention onto and sometimes also a distance into bedrock the drill string with the adapter and the bit may be withdrawn through the casing tube. The tube may sometimes be cemented in place by pouring grouting in the hole in order to obtain a solid and sealed connection between the casing tube and the drilled hole. Thereafter, the adapter is removed from the drill string and a drill bit is connected directly to the lower end of a rod or a down the hole machine forming part of the drill string, and drilling in the rock through the casing tube string is continued to the desired depth. For ordinary water well drilling no other equipment is required in addition to an ordinary percussion drilling equipment that the special adapter and sometimes some means for pressing down the casing tubes into the hole. In many cases the casing tubes will follow the bit down into the hole by its own weight, whereas in other cases it may be required to attach a clamp or a similar device to the drill string in order to transfer feed pressure to the string of casing tubes from the feeding mechanism of the drill.

Two embodiments of percussion drilling equipments according to the invention are illustrated by way of example on the enclosed drawings.

FIG. 1 is a longitudinal section of a drill hole and a casing tube disposed therein and with the drill string, adapter and bit in side view.

FIG. 2 is a similar view in which, however, the flushing channels are indicated in dotted lines.

FIG. 3 and 4 are cross sections on line III--III in FIG. 2 and show the adapter with its lower part in excentric and centric positions.

FIG. 5 is a view similar to FIG. 1 of drilling equipment in which the drill string has a down the hole drill at the lower end.

FIG. 6 is a view similar to FIG. 2 of the embodiment of FIG. 5.

The drilling equipment illustrated in FIGS. 1-4 on the drawings consists of a drill string 1, which may comprise a single drill rod or a set of drill rods coupled together with suitable coupling sleeves or directly to each other. The drill string is powered by a suitable drill (not illustrated) which in this case should be a heavy percussion drill with powerful rotation means. The lower threaded portion 2 of the drill string 1 is screwed into an adapter which consists of an upper part 3 and a lower part 4, both of which are in essence cylindrically shaped with a diameter somewhat less than the inner diameter of a casing tube 5, which depending upon the circumstances may consist of a single tube or a string of tubes connected together with suitable couplings or sockets or threaded directly into each other. The lower part 4 is coupled to the upper part 3 in a hinge-like manner by means of a bolt 6, which extends through a hole drilled excentrically through the upper part 3 and the lower part 4, parallel to the rotational axis of the drill string 7, which is also the central axis of the casing tube 5. The upper part 3 and the lower part 4 cooperate by means of abutments 8 and 9 partially defined by axially extending abutment faces 10 and 11, respectively, which are formed in such a manner that when the drill string has been moved through the casing tube so far that the lower part 4 is situated below the casing tube, then the lower part 4 may swing out to the position illustrated in FIGS. 1-3. A suitable water well drill bit 12 provided with tungsten carbide inserts is connected to the lower part 4 by means of a threaded sleeve 13 which is threaded into the bit 12 as well as into the lower part 4 of the adapter. Flushing fluid is supplied to the drill bit through a flushing channel 14 in the drill string which communicates with a flushing channel 15 in the upper part 3, which again communicates with a flushing channel 16 in the lower part 4 through a transfer channel 17. The flushing channel 16 which is provided in the socket 13 communicates with the flushing channels 18 in the drill bit. During drilling most of the cuttings will normally be flushed out through the space 19 between the upper part 3 and the inner wall of the casing tube 5, and will be expelled from the hole at the upper end of the casing tube.

During drilling the drill string 1 with the adapter 3, 4 and the drill bit 12 is inserted into the casing tube 5 until the bit and the lower part 4 is located outside of the lower end of the casing tube, as shown in FIGS. 1 and 2. Because of the rotation of the drill string the lower part 4 and the drill bit 12 will swing out so that the bit drills a hole 20 with a diameter which is larger than the outer diameter of the casing tube 5 and preferably a diameter which is so large that the coupling sleeves of the casing tubes may also pass into the hole. When the drilling equipment has been driven down to bedrock and sometimes a distance into bedrock, the rotation of the drill is reversed which causes the lower part 4 and the drill bit 12 to swing back to a central position as related to the upper part 3 and the drill string 1. The drill string with the adapter and the drill bit may then be pulled out of the casing tube. If desired, the bottom portion of the casing tube may now be solidly connected to bedrock by means of grouting in order to obtain a sealing between the casing tube and the rock. Thereafter, the adapter 3, 4 is removed from the drill string, the drill bit 12 is fitted directly to the drill string 1 and drilling in rock is continued through the casing tube to the desired depth.

In some cases it may be required to submit the casing tube to blows from below in order to remove it out of the hole and this can be achieved by means of the lower part 4 of the adapter. Instead of the abutments 8 and 9 which are shown on the drawings, one may mount a pin on one part of the adapter and make a corresponding recess in the other part so that the lower part may swing out to a certain desired angle relative to the upper part. By making the pin as an excentric and by providing it with suitable locking means, one may in a simple manner vary the desired swing-out angle and thereby also the hole diameter. Instead of a percussion drill and a percussion bit, one may also make use of a rotary drill with a suitable drill bit, e.g., a roller bit with one or several rollers such as a tricone bit.

In the embodiment of FIGS. 5 and 6 the lower end of the drill string comprises a down the hole drill 21 which in conventional manner is fitted to the end of a rotary tube string (not illustrated) through which working fluid such as compressed air is supplied to the down the hole drill for reciprocating the piston 22 to deliver impacts to a shank 23 and for supplying flushing fluid through a tube 24 and a passage 25 in the shank. The shank 23 is splined and arranged so that it can be rotated in conventional way by rotation of the down the hole drill 21. The shank 23 is screwed into a threaded socket 26 at the upper part 30 of the adapter which has a bore 27 communicating with the channel 15 in the upper part 30 and channels 16, 17, 18 in the lower adapter part 4 and bit 12 which are identical with the embodiment of FIGS. 1-4. The upper and lower parts 30 and 4 are hingedly connected by a bolt 6 in similar way as illustrated in FIG. 1. The upper part 30 may have additional channels 28 leading from the bore 27 to the outside of upper part 30 and axial or helical external grooves 29 for passage of cuttings and flushing fluid. The part 30 may be made integral with the shank 23 in which case the bolt 6 may be replaced by a stud bolt or screw which is screw threaded into the upper part 30. The adapter of FIGS. 5-6 operates in the same way as the adapter in FIGS. 1-4 and when drilling has been carried on through overburden to a desired depth the drill string including the down the hole drill is lifted through the casing 5 and the adapter 30, 4, bit 12 and shank 23 is replaced by a conventional down the hole bit which can pass through the casing 5 and drilling is continued through the now stationary casing 5.

The above described drilling equipments illustrated on the drawings should be considered as examples only which in several details may be modified within the scope of the claims.

Claims

I claim:

1. A drilling equipment consisting of a rotating drill bit, a drill string which carries said drill bit, and a casing tube string which follows the drill bit down into the hole, characterized in that the drill bit is attached to an adapter which consists of an upper part which is centrally attached to the drill string and centrally guided by the casing tube, a lower part which is connected to the upper part by a hinge-like connection and onto which the bit is attached in such a manner as to permit the bit and the lower part to partake of a rotatable traverse between prescribed limits about an axis which is parallel to the axis of the drill string so as to establish cutting and withdrawal positions for said drill bit, and cooperating depending and upstanding abutting surfaces on said upper and lower parts to provide said prescribed limits for said rotatable traverse.

2. A drilling equipment according to claim 1, wherein the upper part and the lower part of the adapter are provided with cooperating abutments, which are arranged so as to permit the lower part to swing out a certain angle as related to the upper part.

3. A drilling equipment according to claim 2, wherein a flushing channel is provided in the upper part which communicates with a flushing channel in the lower part when said part is swung out sideways and leads further to a flushing channel in the drill bit.

4. A drilling equipment according to claim 3, wherein the upper part is connected to the lower part by hinge-like means comprising a bolt which extends through an axially drilled hole in the upper and the lower parts of the adapter, said hole extending parallel to the axis of the drill string.

5. A drilling equipment according to claim 4, wherein the upper part is made in two pieces one of which forms the shank to fit in a down the hole machine and the other accomodating a bolt for hingedly connecting said other piece to the lower part.

6. A drilling equipment according to claim 5, wherein the upper part has passages for conveying flushing medium to the lower part and to the free exterior surface of the upper part.

7. A drilling equipment comprising an adapter arranged to be attached to a drill string movable within a casing tube string concentric with said drill string and said casing tube string to be guided by the latter, and a member carrying a percussion hard metal insert and carried by said adapter and movable relative to the adapter between an abutment defining one extreme position in which said member is concentric with the adapter and retractable through said tube string and an abutment defining a second extreme position in which the member is eccentric relative the adapter and said hard metal insert is disposed in position to undercut the tube string, said abutments being cooperating depending and upstanding surfaces on said member and said adapter.

8. A drilling equipment consisting of an adapter arranged to be attached to a drill string movable within a casing tube string concentric with said drill string and said casing tube string to be guided by the latter, a member carrying a percussion hard metal bit and carried by said adapter journalled relative to the adapter on an axis parallel to the axis of the adapter from one extreme position in which said member and the bit are concentric with the adapter and retractable through said tube string to a second extreme position in which the member is eccentric relative the adapter and said bit is disposed in a position to undercut the tube string, and flushing medium passages having continuous communication with each other through said member and bit only when said member is in said eccentric position.

9. A drilling equipment consisting of rotating percussion drill bit means, a drill string which carries said drill bit means, and a casing tube string which follows the drill bit means down into a hole, characterized in that the drill bit means is carried by an adapter which consists of an upper part centrally attached to the drill string and centrally guided by the casing tube string and having a stepped lower end portion, a single lower part having a stepped upper end portion movably mounted on said upper part to be displaced thereon from a central position in which it may pass into the casing tube string to an offset position in which said drill bit means is capable of undercutting the casing tube string, and said stepped portions comprising angularly abutting axial surfaces confining said movement between said central position and said offset position and axially abutting transverse end surfaces cooperating to transmit percussion energy to the bit means from the drill string.

10. A drilling equipment according to claim 9, in which the lower part is journalled on the upper part on an axis offset from the central axis of the drill string and the casing tube string.