Drill Assembly

Abstract

Drill assembly for making a hole into a soil or rock which arrangement comprises a pilot bit (10) drilling the middle part of the hole and a ring bit (1) drilling the outer circle of the hole in which case in the drilling situation the ring bit (1) is adjusted around the pilot bit (10) and rotary movement and drilling impacts are directed from the pilot bit (10) to the ring bit (1) with the help of the mentioned surfaces (4-6);(7-9),(15, 16) adjusted between the bits and conveying power and that the ring bit (1) can be removed around the pilot bit (10) and can be installed to it and that further a coupling ring (2) belongs around the ring bit (1) in order to join a casing pipe, which can be pulled to the drilled hole, to the ring bit (1) with the help of the mentioned coupling ring. The coupling ring. (2) is adjusted around the periphery of the ring bit (1) in such a way that of the parts (13) taking part in the locking of the coupling ring (2) at least two are located at the different sides of the line (L) when the arrangement is assembled which line runs essentially through the middle point of the surface (5) conveying the rotation of the ring bit (1).

Description

Invention relates to a drill assembly for making a hole into a soil or rock which assembly comprises a pilot bit drilling the middle part of the hole and a ring bit drilling the outer circle of the hole in which case in the drilling situation the ring bit is adjusted around the pilot bit and rotary movement and drilling impacts are directed from the pilot bit to the ring bit with the help of the mentioned surfaces adjusted between the bits and conveying the impacts and that the ring bit can be removed around the pilot bit and can be installed to it and that further a coupling ring which can be locked to the ring bit belongs around the ring bit in order to join a casing pipe, which is to be pulled into the drilled hole, to the ring bit through the mentioned coupling ring.

A drill assembly according to the above mentioned preamble is previously known for example from the publication WO 2004/057148 in which the shown ring bit is relatively long in the axial direction because the upper part of the ring bit comprises first a flange part comprising spikes made of for example hard metal. After the flange part there is a a casing part to which a groove has first been formed and after that locking hole formations with the help of which the ring bit is locked to the pilot bit. Also a cutter shoe is relatively long in the axial direction when the cutter shoe is adjusted to exceed essentially in the axial direction both the groove and the locking hole forms located at the casing part of the ring bit. Also the body of the pilot bit is long in the axial direction and the length required by the counter forms adjusted to the locking hole forms of the ring bit is only a small part of it, less than a quarter.

With the drill assembly according to the invention significant improvements can be achieved to the existing prior art according to the publication WO 2004/057148 when as a result of the invention as short ring bit as possible can be constructed. It is characteristic of the invention that the coupling ring is adjusted around the periphery of the ring bit in such a way that of the parts taking part in the reciprocal locking of the coupling ring and the ring bit at least two are located at different sides of the line L when the arrangement is assembled which line runs essentially through the middle point of the surface conveying the rotation of the ring bit.

The advantage of the invention is the fact that the size of the ring bit becomes essentially shorter in the axial direction thanks to the new locating and installation way of the coupling ring. Similarly the length needed for the coupling ring becomes shorter. The thickness of the cylinder part of the ring bit must however be of a certain size due to hard metal installations in which case the thickness of the cylinder part allows the formation of grooves at the outer surface of the ring bit for the attachment of the coupling ring. In some cases even one groove is enough for the coupling ring but two or even several grooves still do not increase too much the length of the coupling ring. The coupling ring is installed most advantageously by shrinking or welding on top of the ring bit. In addition to that the flushing groove becomes shorter when the ring bit becomes shorter in which case the throttling caused by the flushing stream and occurring in the pneumatic line of the drilling diminishes and the drilling speed increases. When the parts taking part in the locking of the coupling ring, for example shoulder rings, are located in the way according to the invention in relation to the hole forms of the ring bit, enough unbroken groove length stays at the ring bit as counter surfaces for the shoulder rings of the coupling ring in spite of the hole forms of the ring bit.

In the following the invention is described more detailed by referring to the accompanying drawings in which

FIG. 1 shows a ring bit according to the invention and a coupling ring as a cut view.

FIG. 2 shows the position of a coupling ring in relation to the ring bit.

FIG. 3 shows a pilot bit as a side view.

FIG. 4 shows the grooves of a bayonet locking formed to the ring bit.

In the FIG. 1 there is a ring bit 1 which has a cylindrical body. The front part of the body comprises a flange part 14 forming an extension which flange part has a length h2 in the axial direction and to which flange part hard metal spikes 13 are attached. The cylinder part directed in the back from the flange part 14 comprises two grooves 12 at its outer surface to which grooves a coupling ring 2 is attached in such a way that ring overhangs 13 of the inner surface of the coupling ring are located into the mentioned grooves 12. The cylinder part of the ring bit 1 also has hole forms in order to lock it to the counter forms of the pilot bit in such a known way. The hole forms comprise surfaces conveying impacts in the axial direction, such as surfaces 4 and 6 and surfaces 5 conveying rotation.

The surface 4 has lift, especially a surface with a constant lift. This cylinder part located behind the flange part 14 of the ring bit 1 comprises essentially only counter forms 12 for the ring overhangs of the coupling ring 2 and counter forms 4-6; 5; 16; 17 of the locking forms 7-9 of the pilot bit 10.

The above mentioned hole forms 4 - 6 are located at the same place at the cylinder part of the ring bit 1 as the coupling ring 2. The coupling ring 2 has a length hl in the axial direction. The hole forms 4-6 require length from the cylinder part essentially the same amount than the coupling ring 2 does. The ring bit 1 will thus have a short construction in the axial direction. The hole forms 4-6 go through the cylinder part of the ring bit. Due to this the grooves 12 in the ring bit are not necessarily continuous grooves around the cylinder part.

In the FIG. 3 a pilot bit 10 is shown which has locking hole forms 7-9 in a such known way as a counter form to the hole forms of the ring bit 1. One has been able to shorten the length of the cross-die head of the pilot bit 10 compared to the previous cross-die heads by using the ring bit and the coupling ring according to the invention.

In the FIG. 4 a hole form for the bayonet locking is shown in the ring bit. There is a vertical groove 18 at the inner surface of the ring bit 1 and at the end of it there is a horizontal part 17. A protruding piece, for example quadrangular, located at the side of the pilot bit moves in this solution first to the end of a vertical groove 18 in a such known way and with a reversion of the pilot bit moves against the surface 5 located at the end of a horizontal groove 17 and functions as the part which conveys the rotation of the pilot bit to the ring bit. Also this piece can convey impacts to the ring bit in its locking position by conveying impacts onto the surface 16 of the ring bit 1. In this case the depths of the grooves 17 and 18 are less than the wall thickness of the ring bit 1.

Claims

1. Drill assembly for making a hole into a soil or rock which assembly comprises a pilot bit (10) drilling the middle part of the hole and a ring bit (1) drilling the outer circle of the hole in which case in the drilling situation the ring bit (1) is adjusted around the pilot bit (10) and rotary movement and drilling impacts are directed from the pilot bit (10) to the ring bit (1) with the help of the mentioned surfaces (4-6);(7-9);(15, 16) adjusted between the bits and conveying power and that the ring bit (1) can be removed around the pilot bit (10) and can be installed to it and that further a coupling ring (2), which can be locked to the ring bit (1), belongs around the ring bit (1) in order to join a casing pipe, which can be pulled into the drilled hole, to the ring bit (1) with the help of the mentioned coupling ring, characterized in that the coupling ring (2) is adjusted around the periphery of the ring bit (1) in such a way that of the parts (13) taking part in the reciprocal locking of the coupling ring (2) and the ring bit (1) at least two are located at different sides of the line (L) when the arrangement is assembled which line runs essentially through the middle point of the surface (5) conveying the rotation of the ring bit (1).

2. Drill assembly according to the claim 1, characterized in that the ring bit (1) comprises at least two annular grooves (12) at the outer circle in which annular grooves the parts taking part in the locking, like shoulder rings (13), and which are located at the inner surface of the coupling ring (2) are adjusted to rotate and move in a limited way in the axial direction of the drill.

3. Drill assembly according to the claim 1, characterized in that the back part (periphery part) of the flange part (14) of the ring bit (1) comprises essentially only the counter forms (12) of the locking forms (13) of the coupling ring (2) and the counter forms (46); (5, 16, 17) of the locking forms (7-9) of the pilot bit (10).

4. Drill assembly according to the claim 1, characterized in that the surfaces (4-6);(7-9); (5, 16) of the bits (1); (10) sometimes conveying force and impacts are essentially at that part of the cylinder part of the ring bit (1) which begins from the flange part (14) and ends to the trail edge of the ring bit (1).

5. Drill assembly according to the claim 1, characterized in that the inner surface of the ring bit (1) is even without the forms which diverge from it towards the pilot bit (10).

6. Drill assembly according to the claim 1, characterized in that the counter parts (4-6) of the locking forms (7-9) formed to the pilot bit (10) and located at the periphery part of the ring bit (1) are forms which are directed through the periphery part of the ring bit (1).

7. Drill assembly according to the claim 1, characterized in that the counter forms (5, 16, 17) of the locking forms formed to the pilot bit (10) and located at the periphery part of the ring bit (1) are surfaces and grooves formed to the periphery part of the ring bit (1), to its inner surface which surfaces and grooves do not penetrate the wall of the periphery part.

8. Drill assembly according to the claim 1, characterized in that the surface located at the periphery part of the ring bit (1) and receiving impacts from the pilot bit (10) is a surface with a lift (4).