WO2002035062A1

WO2002035062A1 - Method of rock drilling

Info

Publication number: WO2002035062A1
Application number: PCT/SE2001/002271
Authority: WO
Inventors: Åke EKLÖF
Original assignee: Atlas Copco Rock Drills AB
Current assignee: Epiroc Rock Drills AB
Priority date: 2000-10-26
Filing date: 2001-10-18
Publication date: 2002-05-02
Anticipated expiration: 2003-04-26
Also published as: SE0003881D0; SE516968C2; SE0003881L; AU2001296155A1

Abstract

Method of rock drilling with a percussion rock drilling machine (2) to which a drill string (18) comprising parts (31, 32, 33, 19) screwed together is connected. In order to obtain efficient loosening of the screw joints and reduced drilling time the feed force is reduced at a predetermined distance (37) from a predetermined hole bottom (36) at the same time as the drill string (18) is exerted to impacts with substantially unchanged strength until the drill hole has been completed.

Description

Method of rock drilling

The present invention relates to a method of rock drilling with a percussive rock drilling machine to which a drill string comprising parts screwed together is connected.

According to previously known technique when drilling with high torque on the drill string one often obtains strong tightening of the screw joints in the drill string. In order to loosen these screw joints one lets the hammer device continue to impact the drill string after the drill hole has been completed in order to to shake loose the screw joints. This causes large loads on the drill rig, feed beam, drilling machine and drill steel. Furthermore it takes some time.

The present invention, which is defined in the subsequent claim, aims at achieving a method where the loads on the drilling equipment is reduced at the same time as the productivity of the drilling process is increased. This is achieved by reducing the feed force on the drill string at a predetermined distance from the intended bottom of the drill hole at the same time as the percussive power is substantially maintained until the drill hole has been completed. Through this it is achieved that the screw joints can easily be loosened directly after the drill hole has been completed. In certain particularly difficult situations the invention can advantageously be used in connection with completion of drilling with each individual drill rod to loosen the joint between the shank adapter and the drill string in order to easily add a drill rod to the drill string.

An embodiment of the invention is described below with reference to the accompanying drawing which schematically shows a rock drilling device in which the method according to the invention is used.

The device shown in the drawing comprises a feed beam 1 which is intended to be carried by a not shown drill rig in the usual way. A rock drilling machine 2 is arranged on a slide 21 which is movable along tthe feed beam 1 in the usual way. A drill string 18 comprising a shank adapter 31, one or more drill rods 32, 33 and a drill bit 19 is connected to the rock drilling machine 2. The shank adapter, the drill rods and the drill bit form parts of the drill string. Displacement of the rock drilling machine occurs with the aid of a pressure medium cylinder 3 and a feed line 7. In practice, not shown, there is also a feed line for return feeding of the rock drilling machine. The pressure medium cylinder 3 has a first end 4 which is fixedly connected to the feed beam 1 and a second end 5 which is movable relative to the feed beam. In the shown example it is the piston rod 12 of the pressure medium cylinder 3 which is fixedly connected to the feed beam. One can also turn the pressure medium cylinder 3 so that the movable end 5 is arranged on the piston rod 12. The movable end 5 of the pressure medium cylinder 3 carries a sheave 6. The feed line 7 which is passed over the sheave 6 is with one end fixed on the feed beam 1 and with the other end connected with the slide 21 of the rock drilling machine 2. With this arrangement the rock drilling machine 2 is driven along the feed beam 1 with twice the speed of the movable end 5 of the pressure medium cylinder 3. The rock drilling device is provided with a hose reel marked by means of a suppor 13, and a drill support at the middle of the drill string 18, marked by means of a support 14. This means that the hose reel and the drill support are driven along the feed beam 1 with the same speed as the movable end 5 of the pressure medium cylinder 3 in the usual way. Supports 13,14 are provided with points 9,10 between which a further line 8 is arranged. This further line is passed, one or several turns, about a wheel 17 on a measuring device 11 which is fixedly arranged on the feed beam 1. The measuring device 11 produces pulses corresponding to the displacement of the rock drilling machine 2 along the fed beam 1. Since the measuring cables are connected to a socket 22 on the measuring device 11 the measuring cables are fixedly arranged relative to the feed beam 1 and are thus not exerted to the loads of vibrating pressure medium hoses. The position of the rock drilling machine 2 along the feed beam 1 is measured by counting of the pulses from the measuring device 1 1 in the control unit 35 the inlet 41 of which is connected with the socket 22. The control unit 35 is arranged to keep track of where the drill bit 19 is also when extending or shortening the drill string 18. The pressure medium cylinder 3 is provided with connections 42,43 for pressure medium. As indicated by conductors 44,45 the pressure medium supply to connections 42,43 is controlled by the control unit 35. By means of conductor 46 it is marked that the control unit 35 also controls the hammer device of the rock drillin machine 2 and rotation of the drill string 18. When drilling one should drill to a predetermined hole bottom 36. This is done by driving the rock drilling machine 2 toward the ground 34 and by rotation of the drill string 18 and exerting it to imacts in direction toward the ground. When drilling one uses one or more drill rods 32,33 connected to the shank adapter 31. The position of the drill bit 19 is measured and stored in the control unit 35. The value stored in the control unit is used to calculate the remaining distance to the hole bottom 36. When the drill bit 19 is situated at a predetermined distance 37 from the hole bottom 36 the feed force on the drill bit is reduced by restricting the supply of pressure medium to connection 42. During the final phase of the drilling the impact force against the drill string 18 is maintained substantially unchanged.

Claims

Claim:

1. Method of rock drilling with a percussive rock drilling machine (2), to which a drill string (18) comprising parts (31,32,33,19) screwed together is connected, comprising driving the rock drilling machine (2) toward a ground (34), rotating the drill string (18) and exerting the drill string (18) to impacts in direction toward the ground (34), c h a r a c t e r i z e d in that the displacement of the rock drilling machine (2) toward the ground (34) is measured and stored in a control unit (35), that the value stored in the control unit is used for determining the remaining distance to a hole bottom (36) and that the force by means of which the rock drilling machine (2) is driven toward the ground (34) at a predetermined distance (37) from the hole bottom (36) is reduced at the same time as the drill string (18) is exerted to impacts with substantially unchanged strength.