HK1088375B - Bit assembly - Google Patents

Description

Drill bit assembly

Technical Field

The present invention relates to a drill bit assembly for a drilling device working with percussion and rotation in combination or with rotation only, such drill bit assembly comprising: a pilot bit at the center of the wellbore; a ring bit connected with the pilot bit for drilling an outer ring; a surface for transmitting percussive forces and/or rotational motion between the pilot bit and the ring bit. The drill bit assembly also includes a combination for placing the protective sleeve into a borehole being drilled.

Background

In the prior art, british patent specification 959955 describes a drilling apparatus like the one described above with a medium bit and a ring bit, in which the ring bit is cited to be lockable to the medium bit with a bayonet connection. On the inner surface of the ring bit are provided a number of longitudinal grooves, and also a number of transverse grooves ending at some point, along which the brackets of the middle bit first extend when the ring bit is mounted to the middle bit, and finally, the rotation between the bits, the brackets reaching the end of the transverse grooves. The longitudinal grooves simultaneously act as passages for the flushing medium.

A similar bayonet locking between bits is known from the subsequent finnish patent specification FI-96518, even though in this embodiment the longitudinal bayonet locking grooves function as flushing channels.

A disadvantage of this bayonet locking is that the inner surface of the ring bit must be machined in two separate directions, or alternatively, the inner surface must be machined such that the socket must be oriented towards the centre of the ring bit. It is not possible to make the inner surface of the ring bit a straight cylindrical surface. Furthermore, in connection with the above-mentioned solution, difficulties arise in returning the middle bit together with the locked ring bit into the borehole during drilling. With such a reassembly it is not possible to find out when longitudinal movement occurs in the bayonet lock, nor when it is a suitable moment for the bit to lock in rotation. This is difficult in deep drilled holes, often drilling is started in situations where the bayonet locking is not well done.

Disclosure of Invention

In order to overcome the above-mentioned disadvantages between the ring bit and the pilot bit, a new embodiment has been developed, which is characterized in that in this bit assembly, a structure for preventing rotational and axial movement between the ring bit and the pilot bit is provided at the trailing edge of the ring bit liner, so that said structure is located at a portion of the ring bit liner having a diameter larger than the diameter Ds of the inner surface, on which inner surface no groove is present, and a locking projection on the pilot bit is adapted to cooperate with a recess on the liner of the portion opposite to the projection, which engages the liner wall, said recess having a surface portion capable of transmitting rotational forces to the ring bit and an adjacent surface portion capable of transmitting forces to pull the ring bit out of the borehole.

An advantage of the drill bit assembly according to the invention is that it is easy to machine the ring bit or the corresponding medium bit, i.e. the pilot bit, since in this case, for example, the inner surface of the ring bit is a cylindrical surface without grooves or brackets. Annular grooves and shapes must be made on the outer surface of the pilot bit, but machining on the outer surface of such a workpiece is easy. It is necessary to produce a shape in the liner portion of the ring bit, but this production uses a usual production method in terms of its characteristics. The pilot bit may be pulled out of the borehole during drilling and reinstallation, and in an embodiment according to the invention will be positively guided to its position relative to the ring bit as long as the direction of rotation is correct. The opposite surfaces transmitting the impact force are inclined to push the pilot bit axially towards and into the ring bit, thus locking the segments to each other. The ring bit and the protection sleeve may be pulled out of the borehole by a pilot bit, for example, by simultaneously rotating the pilot bit in a locking direction.

Drawings

FIG. 1 is a side view showing the top end of the drilling apparatus.

Figure 2 shows the top end of the drilling device and shows a cross-section of the protective casing and the drill casing.

Figure 3 shows the drilling apparatus with the ring bit and pilot bit exploded apart.

FIG. 4 shows another locking method

Figure 5 shows a perspective view of a ring bit.

Detailed Description

The invention is described below with reference to the accompanying drawings.

Fig. 1 shows a drilling installation comprising: pilot bit, otherwise known as medium bit 1; a ring bit 2; the most distal drill casing 9 and the protection casing 10.

Figure 2 shows more precisely the construction of the drilling device, in which the liner 5, the inner surface of the barrel ring bit, is machined with the pitch 6 and recess 3, 4 shapes. The pilot bit 1, which is partly inside the ring bit, has a change in diameter behind the liner 5 of the ring bit 2, i.e. in the portion 14, so that the outer diameter is increased. The leading edge of this portion 14 is provided with a counter-shape 7 which is form-fit to the backing portion 5 of the ring bit 2. The solution for pulling apart the protection sleeve 10 is also shown in the sectional view of fig. 2, drawn with the drill sleeve 9, the protection sleeve 10, the middle drill bit 11, the weld seam 16 and the impact shoulder 12 of the pilot drill bit 1.

In order to discharge drilling waste from the front of the drill bit with flushing medium, a channel 13 is provided. The channels are elongate grooves in the face of the pilot bit 1. There is neither a groove nor a shape in the inner surface of the ring bit 2 in connection with the action of the flushing channel 13.

In fig. 3, a split ring bit 2 is shown, the ring bit 2 having an inner diameter Ds. The inner surface of which is a smooth, rotationally cut barrel-shaped surface. In the liner 5 of the ring bit 2, there are 3 locking assemblies between the bit 1 and the bit 2. The assembly comprises a pitch angle shaped part 6 and, very suitably, a recess shaped part having a counter surface 4 at least for rotational power and a counter surface for pulling force, the latter for pulling the ring bit backwards out of the borehole. The angled portion 6 also serves to transmit impacts and forces in the drilling direction. The pilot bit 1 transmits rotary power to the ring bit 2. In one embodiment, an impact force is applied to the drill bit 1, which impact force is transmitted by the drill bit 1 to the ring bit 2 via the surface 6. The impact force can be transmitted entirely by the form of an inclination, in other words, by the tilting action. The presumption is that the entry of the pilot bit 1 into the ring bit 2 forces the bits to lock with each other. The extension of the angled portion 6 may also be a non-angled portion 15. The angled portion 6, although transmitting the percussive force, transmits the percussive force to the ring bit 2 causing it to rotate to the right, in other words, locking the bits to each other.

The pilot bit 1 has correspondingly a rake-shaped portion 8 and a projection 7 which can be brought into engagement with the recesses 3, 4 only by rotation of the pilot bit 1. In the horizontal drilling position, by reinstalling the pilot bit 1, it must be pushed slightly through the drill rod. In the vertical drilling position, the pilot bit 1 and the drill rod are easily interlocked by their own weight with the ring bit 2 of the pilot bit 1. The setting action must immediately cause the pilot bit 1 to be set into the ring bit 2 or to be separated from the ring bit 2 when the pilot bit 1 is set into the borehole, even if the ring bit 2 is rotated a little at the same time.

In prior bayonet locking embodiments, the ring bit turning with rotation may prevent locking and, accordingly, may successfully disengage.

All the percussive forces transmitted from the pilot bit 1 to the ring bit 2 fall on the rear edge of the liner of the ring bit 2, so that a bit like the back surface can be used.

The recess shapes 3, 4, 15 may be rounded or made curved, so that the projections may also be rounded or similar. The recess shape 3, 4, 15 may be angular, comprising straight parts, and correspondingly the protrusions are also angular. Fig. 4 shows a notch shape and a projection solution, in which the axial play of the projection 7 is small. In this case, the entire trailing edge of the ring bit 2 is also inclined, in other words, is of a pitch angle shape. The position of the flushing channel is completely independent of the blocking elements 3, 4, 7, since, in general, they are located further away from the central line of the drilling device than the flushing channel 13.

Figure 5 is an oblique view of the ring bit 2, where it can be seen that the smooth cylindrical surface, which functions as the inner surface, and the recess shape of the liner 5 has impact force transmitting surfaces 3, 4, 15 and 6.

Claims (5)

1. A drill bit assembly for use with a drilling apparatus that operates with percussion and rotation in combination or with rotation only, the drill bit assembly comprising: a pilot bit (1) for drilling the central part of the borehole; a ring bit (2) connected to the pilot bit for drilling an outer ring; means between the pilot bit (1) and the ring bit (2) for transmitting percussive and/or rotary motion from the pilot bit to the surface of the ring bit, the bit assembly further comprising a combination for placing a protective sleeve into a borehole being drilled, characterized in that in the drill bit assembly, a structure for preventing rotation and axial movement between the pilot bit (1) and the ring bit (2) is provided at the rear edge of the ring bit liner (5), whereby said structure is located at a portion of a diameter greater than the diameter (Ds) of the inner surface of said ring bit without grooves, and a locking projection (7) of a pilot bit (1) can be mounted to said liner (5) having an opposite notch shape (3, 4, 15), for engagement of the protrusion (7) with the liner (5), the recess shape comprising the following surfaces: a surface portion (4) which can transmit a rotational movement force to the ring bit (2); a surface portion (3) adjacent to the surface member (4) is adapted to transmit a force for pulling the ring bit out of the borehole.

2. A drill bit assembly according to claim 1, characterized in that the pilot bit (1) has a change in diameter at the portion (14) which change takes place after the ring bit (2) as seen in the drilling direction, the leading edge (14) of said portion comprising a shape (7) adapted to cooperate with the surface portion (3, 4) on the liner portion (5) of the ring bit (2).

3. A drill bit assembly according to claim 1, characterized in that the shape of the liner portion (5) of the ring bit (2) comprises a rake-shaped portion (6) and surface portions (3, 4) forming closed grooves connecting the pilot bit (1) with the ring bit (2).

4. A drill bit assembly according to claim 1, characterized in that the rear edge of the ring bit (2) lining (5) comprises at least one angled section (6) and one or several sections (15) without angle, said sections being the only surfaces receiving impacts from the pilot bit (1).

5. A drill bit assembly according to claim 1, characterized in that a plurality of rake-shaped portions (6) and a plurality of recesses (3, 4) are arranged in the backing portion (5) of the ring bit (2).