EP0563561B1 - Superimposing drilling bit - Google Patents

Description

The present invention relates to a drill bit for overlay drilling with a head provided with hard metal pins or the like and a shaft supporting the head, the shaft having means for torsionally rigid connection to a driven inner pipe string, the drill bit having at least one flushing agent line, the head having a plurality of symmetrical Has recesses distributed over its circumference and wherein swivel bits are arranged in the recesses such that they come to lie within the drill bit diameter in the swiveled-in state and protrude in the drill bit diameter.

For a variety of reasons, the trend and necessity in sewer and pipeline construction are increasingly increasing from the open construction to the closed construction, which requires the use of ever new and powerful drilling methods and drilling tools. The Imloch hammer, which was originally designed for use in a quarry, is becoming increasingly important thanks to its excellent drilling performance and its possible uses, even in extreme ground conditions.

Two different paths are used in the prior art for overlay drilling. On the one hand, drilling devices for overlay drilling are known, which use a drilling fluid with a An outer tube linkage carrying a ring drill bit, an inner tube linkage running in the outer tube linkage and carrying a central solid drill bit and provided with a first rotary drive rotating the inner tube linkage and a second rotary drive rotating the outer tube linkage, both linkages being mounted on a driven feed device (DE-C-2 924 393 ). On the other hand, it is known to use eccentric drilling devices. A known eccentric drilling device is described in DE-C 3 024 102. Here, the eccentric drill bit is eccentrically clamped at the end of the outer pipe string in order to obtain a drilling diameter which is larger than the outer diameter of the outer pipe string. After releasing the tension, the eccentric drill bit with the inner pipe rod can be pulled back through the outer pipe rod.

In any case, a drill hole is produced during the overlay drilling, the diameter of which is larger than the outside diameter of the piping to be introduced. The piping is expediently designed as an outer pipe string of the respective drilling device, the ring drill bit carried by the outer pipe string being lost in the case of the device described above as the first alternative, at least in the production of blind holes. In any case, the distance between the outer pipe string and the actual pipe head must always be kept relatively small in order to prevent premature escalation in the borehole wall. To discharge the cuttings, a suitable flushing agent such as air or a water / oil emulsion is discharged deep down - preferably through the inner pipe string. The drilling mud, consisting of cuttings and detergent, is flushed out of the borehole through the annular space between the inner pipe string and the outer pipe string.

Both of the above-mentioned alternative devices for overlay drilling, which have been described in more detail above, suffer from disadvantages in some respects, so that the concentric arrangement of the ring and solid drill bit always results in very high wear, especially of the ring drill bit. Furthermore, the - often lost - ring drill bits are expensive to manufacture, since extremely hard materials have to be used because it is no longer possible to change them during the drilling operation. When using eccentric drill bits, there are relatively large deviations in directional accuracy and only low cutting performance is possible.

From the generic GB-A-2 132 252 a in the hammer or deep hole hammer drill bit is known, which can accommodate additional drill bits with special shafts and tangential locks in the actual drill head for extension bores. The drill bit heads can be designed concentrically or eccentrically. In the case of the eccentric design, the drill bit shaft is designed so that its rotational movement is fixed in the cylindrical receptacle by appropriate stops. It can quickly be seen that due to the special design of the drill bit shaft and receptacle, the manufacturing effort for this known drill bit is extremely high. This is due in particular to the universal applicability with regard to concentric and eccentric drill bits.

The invention is therefore based on the object of designing and developing a drill bit of the type mentioned above in such a way that the drill bit, in particular for replacement, is always removed from the borehole again and yet a large overcut can be achieved.

This object is achieved in that the side walls of the recesses form a stop for the swivel crowns and that the hard metal pins are arranged in the region between the recesses distributed over the entire diameter of the drill bit. In this way, a secure stop is achieved for the swivel crown pivoted into the working position without additional design effort.

The solution according to the invention also has economic advantages, since the individual swivel bits - in contrast to the ring drill bit which can no longer be replaced - can be replaced quickly and easily. This possible reduction in tool life can result in considerable savings in material selection.

As already mentioned, the recesses for the swivel crowns are distributed symmetrically over the circumference of the head. It is advantageous that each swivel crown is provided with an eccentrically arranged shaft and that it has a plurality of receiving bores in the region of the recesses for receiving the shafts of the individual swivel crowns. Here again it is expedient that the receiving bores and / or the swivel crowns have means for a mutual connection. This is particularly important because the drill bit with the swivel bits arranged on it must be recovered from the drill hole. It has proven to be particularly advantageous if each receiving bore in the drill bit has an annular groove and each swivel bit has a widening corresponding to the groove in the region of its shaft. In terms of production technology, it is particularly advantageous if the widening is designed as a spring ring arranged in the groove provided on the shaft of each Schwenbkkrone.

According to a further teaching of the invention, the flushing agent line branches in the shaft of the drill bit to the individual recesses for the swivel bits. It has been found that it is not necessary to also provide the swivel crowns with their own detergent lines if the detergent lines end in the region of the individual recesses. It is advantageous here if the openings of the flushing agent lines are arranged in the recesses in such a way that they are covered by the pivoted-in swivel crowns. It is expedient if, according to a further embodiment of the invention, each recess has two rinsing bores which end in the central rinsing agent line located in the shaft and whose openings to the outside, ie are directed in the swivel direction of each swivel crown. In this embodiment according to the invention, not only is sufficient cooling of the drilling tool and flushing of the cuttings achieved, but the pressure of the flushing agent supports the pivoting out of the borehole caused primarily by frictional engagement of the cutting attachments of the swivel crowns. In addition, the area of the recesses always remains free of drilling mud, etc., so that the swivel crowns can be reliably pivoted into the recesses by rotating the inner boring bar by a small amount in the direction opposite to the drilling direction.

It is also advantageous that, in a further embodiment of the invention, the cutting surface of each swivel crown is chamfered in the region of the largest drill diameter when the swivel crowns are swiveled out, that is to say in the edge region of the "enlarged" drill diameter. This configuration has a favorable influence on the stress distribution in the borehole wall, so that unwanted extrusion can also be avoided in this way.

Fig. 1

eine erfindungsgemäße Bohrkrone mit drei ausgeschwenkten Schwenkkronen in perspektivischer Ansicht,

Fig. 2

eine Aufsicht derselben Bohrkrone, wobei jedoch eine der drei Schwenkkronen im eingeschwenkten Zustand gezeigt ist,

Fig. 3

einen Längsschnitt durch die erfindungsgemäße Bohrkrone entlang der Linie III-III aus Figur 2 ohne Schwenkkronen,

Fig. 4

einen Schnitt durch die erfindungsgemäße Bohrkrone entlang der Linie IV-IV gemäß Figur 3 und

Fig. 5

einen Längsschnitt durch eine der zur erfindungsgemäßen Bohrkrone gehörenden Schwenkkronen.

The invention is explained in more detail below with the aid of a drawing representing an exemplary embodiment. Show in the drawing

Fig. 1

a drill bit according to the invention with three swiveled-out swivel bits in a perspective view,

Fig. 2

a top view of the same drill bit, but showing one of the three swivel bits in the swiveled-in state,

Fig. 3

3 shows a longitudinal section through the drill bit according to the invention along the line III-III from FIG. 2 without swivel bits,

Fig. 4

a section through the drill bit according to the invention along the line IV-IV according to Figure 3 and

Fig. 5

a longitudinal section through one of the swivel bits belonging to the drill bit according to the invention.

The figures show a drill bit consisting primarily of a head 1 and a shaft 2 for overlay drilling. The head 1 of the drill bit according to the invention is provided with hard metal pins 3 in a known manner. The shaft 2 is connected in a rotationally rigid manner to a driven and not shown inner tube linkage, a recess 4 being indicated in FIG. 3.

In the interior of the drill bit according to the invention, a flushing agent line 5 runs through the shaft 2 and the head 1 and is supplied with flushing agent for flushing out the cuttings from a flushing agent line running in the inner pipe string.

According to the invention, the head 1 has a plurality of recesses 6 arranged symmetrically over its circumference. In the illustrated and preferred embodiment, three recesses 6 are provided, in which swivel crowns 7 are arranged such that they come to lie within the drill bit diameter in the swiveled-in state and in project the swung-out state by a predetermined amount beyond the drill bit diameter. While all three swivel crowns 7 are shown in the swung-out state in FIG. 1, one of the three swivel crowns 7 is shown in its position pivoted into the recess 6 in FIG. The embodiment shown relates to a small version of the drill bit according to the invention, in this case the drill head diameter is 88 mm, and in the swung-out state of the swivel bit 7, drilling is carried out with an "expanded" drill diameter of 124 mm. It is easy to see that larger versions allow a correspondingly higher number of swivel crowns 7.

In a further embodiment of the invention, each swivel crown 7 is provided with an eccentrically arranged shaft 8 and the drill bit in the region of its recesses 6 has a plurality of receiving bores 9 for receiving the shafts 8 of the individual swivel crowns 7, as can be seen particularly clearly from FIGS. 3 and 5 .

For a secure connection from the head 1 of the drill bit to the individual swivel crowns 7, the receiving bores and the swivel crowns 7 have means for a mutual connection. In the exemplary embodiment, each receiving bore 9 in the drill bit is provided with an annular groove 10 and each swivel bit 7 on its shaft 8 with a widening corresponding to the groove 10. It is expedient if the widening is designed as a spring ring 11 arranged in the groove 10 provided on the shaft 8. In order to ensure a defined swiveling out of the individual swivel crowns 7, as a means for Limitation of the swiveled-out swivel crowns 7, the side walls 12 delimiting the recess 6, as can be seen particularly clearly from FIGS. 1 and 2. In the illustrated embodiment, the hard metal pins 3 are distributed symmetrically on the head 1 and the three swivel crowns 7. However, it can be advantageous to arrange the hard metal pins 3 asymmetrically, in particular on the swivel crowns. It is particularly expedient that each swivel crown 7 is provided with a bevelled cutting surface 14 in the region of the largest drilling diameter when the swivel crowns 7 are swiveled out, as can be seen from FIG.

Finally, it can be seen from the figures that the openings 13 of the detergent lines 5 are arranged in the recesses 6 in such a way that they are covered by the pivoted-in swivel crowns 7. In particular, FIG. 4 shows that each recess 6 has two flushing bores 5A and 5B, which end in the central flushing agent line 5 located in the shaft 2 and whose openings 13 point outwards, ie in the pivoting direction of each swivel crown 7. For this purpose, it is necessary that the flushing agent line 5 branches in the shaft 2 of the drill bit to the individual recesses 6 for the swivel bits 7, as can be clearly seen in FIG.

Reference number list

1

head

2nd

shaft

3rd

Tungsten carbide pin

4th

Recess

5

Detergent line

5A

Detergent line

5B

Detergent line

6

Recess

7

Swivel crown

8th

shaft

9

Location hole

10th

Groove

11

Spring washer

12th

Side wall

13

opening

14

Cutting surface

Claims (9)

1. A superimposing drilling bit having a head (1) provided with hard metal pins (3) or the like and a shaft (2) supporting the head (1); the shaft (2) having means for connection rigid against torsion to a driven inner tube string; the drilling bit having at least one flushing agent line (5); the head (1) being formed with a plurality of recesses (6) disposed symmetrically distributed over its periphery; and pivoting bits (7) being so disposed in the recesses (6) that in the inwardly pivoted state the bits occupy a position inside the drilling bit diameter and in the outwardly pivoted state project by a given amount beyond the drilling bit diameter, characterized in that the side walls (12) of the recesses (6) form a stop for the pivoting bits (7) in the zone between the recesses (6) the hard metal pins (3) are disposed distributed over the whole diameter of the drilling bit.
2. A drilling bit according to claim 1, characterized in that each pivoting bit (7) has an eccentrically disposed shaft (8) and in the zone of their recesses (6) the drilling bit has a number of receiving bores (9) to receive the shafts (8) of the individual pivoting bits (7).
3. A drilling bit according to claims 1 or 2, characterized in that the receiving bores (9) and/or the pivoting bits (7) have means (10, 11) for connection to one another.
4. A drilling bit according to claims 2 and 3, characterized in that each receiving bore (9) in the drilling bit is formed with an annular groove (10), and the shaft (8) of each pivoting bit (7) is formed with a widened portion corresponding to the groove (10).
5. A drilling bit according to claim 4, characterized in that the widening portion takes the form of a spring ring (11) disposed in the groove (10) with which the shaft (8) is formed.
6. A drilling bit according to one of claims 1 to 5,
   characterized in that the flushing agent line (5) in the shaft (2) of the drilling bit branches to the individual recesses (6) for the pivoting bits (7).
7. A drilling bit according to claim 6, characterized in that the openings (13) of the flushing agent lines (5) are so disposed in the recesses (6) that they are covered by the inwardly pivoted pivoting bits (7).
8. A drilling bit according to claims 6 or 7, characterized in that each recess (6) has two flushing bores (5A, 5B) which terminate in the central flushing agent line (5) situated in the shaft (2) and whose openings (13) point outwardly - i.e. in the pivoting direction of each pivoting bit (7).
9. A drilling bit according to one of claims 1 to 8, characterized in that in the zone of the maximum drilling diameter with the pivoting bits (7) pivoted outwardly, each pivoting bit (7) has a chamfered cutting face (14).

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