EP0233038A2

EP0233038A2 - Down-the-hole-drill

Info

Publication number: EP0233038A2
Application number: EP87300928A
Authority: EP
Inventors: David William Paul; David Stanley Williams
Original assignee: Boart International Ltd
Current assignee: Boart International Ltd
Priority date: 1986-02-03
Filing date: 1987-02-03
Publication date: 1987-08-19
Also published as: AU6807387A; NO870405L; NO870405D0; FI870444A0; FI870444A; EP0233038A3; AU581800B2

Abstract

A down-the-hole drill is hydraulically powered with air flushing. The rotation motor (16) is on the drill string (10) and rotates a percussion hammer (20) to which the drill bit is chucked. Hydraulic fluid flows in umbilicals (11) clipped into grooves on the sides of the drill rods. The shuttle valve (26) for the hammer is in line with the piston (25).

Description

BACKGROUND TO THE INVENTION

This invention relates to a down-the-hole drill.
In conventional down-the-hole drilling the drilling machine is pneumatically operated with compressed air supplying the energy for percussion as well as acting as the flushing fluid for cuttings formed during drilling. The percussion device is at the bottom of a drill string which conveys compressed air and which is rotated on surface.
Hydraulic percussive machines have been developed - see U.S. patents Nos. 3,887,619; 3,701,386; 4,179,983; 4,020,746 and 4,430,926. However, none of these prior proposals deal with down-the-hole drilling.
There have been proposals (see US patent No. 4 463 814 and SA Patent No. 78/6583) to have both the percussion device and the rotation motor down the hole. In this kind of device thrust is applied by hydraulically clamping the apparatus in a hole and thrusting the percussion drill also by hydraulic means. Power is supplied by means of an electric cable. In the case of the US patent flushing fluid is passed to the apparatus through an umbilical linking it to the surface while in the case of the South Africa patent, the drill hole is filled with a fluid such as water. In both cases water is a basic requirement. In addition an umbilical may be broken more readily than a conventional drill string. Such a break could lead to the loss of drilling time and even of the apparatus which is down the hole.
An apparatus has already been proposed which has a drilling head comprising independently powered percussive and rotation devices, the head being attached to a tubular drill string and power for at least one of the devices being fed along umbilicals externally of or within the drill string. It was proposed that a hydraulic motor drive a shaft which has splines engaged with the chuck of the percussion motor to cause the chuck to rotate and hence cause the drilling bit to rotate. The problem was that the percussion apparatus had to be arranged concentrically around the shaft which drives the chuck which is virtually impossible in the space available in the average diameter drill hole.

SUMMARY OF THE INVENTION

According to the invention a down-the-hole drill comprises a drill string and percussion and rotation devices at the lower end of the drill string characterised in that the percussion device is a hammer to which a drill bit is chucked and having an upwardly extending shank, and the rotation device is a rotation motor in the lower end of the drill string and in driving engagement with the shank.
The hammer and the rotation motor are preferably hydraulically powered and hydraulic fluid passes to them through a circuit allowing free flow to hammer and flow to the rotation device only when a predetermined condition has been attained.
If, as is usual, reciprocation of the hammer is controlled by a shuttle valve, the valve is and operates in line with the hammer axis.
The invention also provides that hydraulic fluid be passed down to the lower end of the drill string and up the drill string along hoses accommodated in grooves down the sides of the drill string.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows the layout, largely in section of a down-the-hole drilling apparatus towards the bottom of its length;
Figure 2 is a section on the line 2-2 in Figure 1; and
Figure 3 is a hydraulic flow diagram of the apparatus.

DESCRIPTION OF AN EMBODIMENT

Figure 1 shows the lower end 10 of a drill which carries a pair of hoses 11 in rubber lined grooves down its side - see Figure 2. In the centre there is a pipe 12. The hoses 11 carry hydraulic fluid and the pipe 12 carries compressed air for flushing.
The end 10 connects with a tubular section 14 which carries a low pressure accumulator 15 on the return side of the hydraulic system and a rotary hydraulic motor 16. The shaft 17 of the motor 16 is attached to a splined sleeve 18 which is in driving engagement with an extension 19 on a shank 20 of a percussion hammer. The sleeve 18 and the extension 19 form a liquid swivel for connecting annular grooves 21 and 22 to feed bores 23 and 24 for the hammer.
The hammer has a piston 25 which is caused to reciprocate in a conventional manner in conjunction with a shuttle valve 26 as described in the above mentioned patents. However in this case the shuttle valve 26 is in line with the piston 25 and not beside it or extending transversely to it is with the above mentioned patents. The piston 25 and the shuttle valve 26 are contained in a tubular housing 27 which rotates with a seal 28 against the section 14.
The housing 27 also carries a chuck 28 to which is chucked a button bit 29 in the usual manner.
Ducts (not shown) bypass the various parts to pass air down the centre of the button bit to the bottom of the hole being drilled.
The housing 27 also contains a high pressure accumulator 30. The hoses 11 connect with the various hydraulic components along bores in the thicknesses of the sections and so on for hydraulic fluid to be fed to and returned from those components. Many of these connections are not shown in Figure 1 as a matter of convenience. The full hydraulic circuit is shown in Figure 3 in which components described above have the same reference numbers as they were given above.
A hydraulic pump 31 on surface draws hydraulic fluid from a tank 32 and pumps it to a control valve 33. A hose 11 feeds the fluid down the drill hole. At the bottom of the drill string the feed splits to pass first to the shuttle valve 26 and the piston 25. Hydraulic fluid returns via the low pressure accumulator 15 and a hose 11 to tank 32 after passing through a filter 35.
Second the feed passes to a pressure reducing flow control valve 34 controlling the hydraulic motor 16. The valve 34 ensures that the hammer is not starved of feed by the motor 16.
In operation a valve (not shown) at the surface admits compressed air to the pipe 12 while the valve 33 admits hydraulic fluid to the hammer and motor. First the hammer will start up, next the motor 16 and drilling is then in full swing. The rate of flushing is controlled by controlling the flow of compressed air while the drilling rate is controlled by operating the valve 33.

Claims

1. A down-the-hole drill comprising a drill string and percussion and rotation devices at the lower end of the drill string characterised in that the percussion device is a hammer to which a drill bit is chucked and having an upwardly extending shank, and the rotation device is a rotation motor in the lower end of the drill string and in driving engagement with the shank.

2. The drill claimed in claim 1 in which the hammer and the rotation motor are hydraulically powered and hydraulic fluid passes to them through a circuit allowing free flow to the hammer and flow to the rotation device only when a predetermined condition has been attained.

3. The drill claimed in claim 2 in which reciprocation of the hammer is controlled by a shuttle valve which is and operates in line with the hammer axis.

4. The drill claimed in either one of claims 2 or 3 in which the hydraulic fluid is passed down to the lower end of the drill string and up the drill string along hoses accommodated in grooves down the sides of the drill string.