GB2172315A

GB2172315A - Expandable-contractable drilling device

Info

Publication number: GB2172315A
Application number: GB08500129A
Authority: GB
Inventors: Lam Ming Luen
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-01-04
Filing date: 1985-01-04
Publication date: 1986-09-17
Also published as: GB8500129D0

Abstract

This invention relates to a dual stage expansion-contraction drill device. The device can be used for ground-anchoring and other engineering works. In more detail, the device according to the invention comprises a drilling unit 1 and a reaming unit 2, the reaming unit 2 including at least one retractable reaming blade 6,7 for enlarging at least a portion of a hole formed by the drilling unit. The blades 6,7 are biased to their expanded condition by spring 5. <IMAGE>

Description

SPECIFICATION An expandable-contractable drilling device The Technical Background of the Invention This invention relates to an expansion-contraction drilling device and, more particularly, to a dual stage expansion-contraction drilling device. The drilling device according to this invention is especially useful, for example, for drilling in the field of ground-anchoring in the building and civil engineering industry as well as in the mining industry.

At present, existing drilling devices employ one drill bit which drills cylindrical holes of the same diameter as the drill bit. Such cylindrical holes are not entirely satisfactory when a strong ground anchorage is required. In order to produce a strong ground anchorage, it is highly desirable for the blind end of a hole to be enlarged so that, in cross-section. the hole resembles an inverted "T", namely

shape. Considered slightly differently, it is desirable to drill a small diameter hole nearer to the surface and bigger diameter hole remote from the surface. Previously, these holes have to be drilled twice. A smaller hole is first drilled and, thereafter, the base or blind end of the hole is later enlarged.Such a procedure is very time consuming and it is an object of the present invention to provide a drilling device which can drill

shaped holes in only one operation.

According to one aspect of the present invention, an expandable-contractable drilling unit comprises a drilling unit and a reaming unit for enlarging at least a portion of a hole formed by the drilling unit.

According to another aspect of the present invention, an expandable-contractable drilling unit comprises a drilling unit and a reaming unit, the reaming unit including at least one retractable reaming blade for enlarging at least a portion of a hole formed by the drilling unit.

Preferably, the reaming unit comprises a body and means for biasing the or each reaming blade into a non-retracted and reaming position.

The biasing means may take the form of an energy storing means such as a spring. Alternatively the biasing means may be pneumatic or hydraulic.

The invention also includes a method of forming a hole having at least one portion of diameter greater than that of another portion, the method comprising the steps of (a) forming a hole having a first diameter; (b) feeding a sleeve into the hole to support a part of the wall of the hole; (c) passing a device according to the present invention through the sleeve until at least the reaming unit is clear of the sleeve, and (d) applying rotary motion to the said device whereby the reaming blades form a hole of larger diameter than the outer diameter of the hole formed in step (a).

Conveniently, the sleeve is in the form of a hollow pile which forms the hole of step (a) and has a bore for receiving the said device.

The reaming unit which obtains power from the biasing means or alternatively the energy storing means is always in a ready-to-operate state. With the combination of steel pipe and adopting a certain systematic working procedure, this drilling unit will result in shaped holes.

BRIEF DESCRIPTION OF THE DRA WINGS Figure 1 is a part sectional-part external view of the dual stage expansion-contraction drilling device according to the invention; Figure 2 is a view of the device taken in the direction of arrow A of Fig. 1; Figure 3 is a cross-section taken along line Ill-Ill of Fig. 2, and Figure 4 shows a step-by-step method of forming a hole using the device shown in Figs.

1, 2 and 3, the steps comprising: a. piling or drilling a steel pipe into the ground; b. inserting the device of Figs. 1 to 3 into the steel pipe; c. reaming bigger hole beyond the end of the pipe using the device of Figs. 1 to 3; d. withdrawing the device out of the hole; e. putting down grout-pipe into the bottom of the hole and then flushing; f. inserting the stressing cable and then grouting, and g. withdrawing the grout-pipe, followed by the steel pipe.

DETAILED DESCRIPTION OF THE INVENTION A dual stage expandable and contractable drilling device as shown in Fig. 1 has a drilling unit 1 and a reaming unit 2. The drilling unit 1 may take the form of an ordinary drill bit having a pilot bit 9 connected to a bottom adaptor sleeve 8 by a tapered pipe thread.

The front of the reaming unit 2 is connected to the bottom adaptor sleeve 8 of the drilling unit 1, whereas the rear of the reaming unit 2 is connected to drill-rod (not shown) by a top adaptor sleeve 13.

The reaming unit 2 includes a cylindrical reaming-body 14, a biasing means or energy storing unit 5, reaming-blades 6,7, the top adaptor sleeve 13, a bottom shoe 4, a top cap 3, a pin shaft 10 and flushing holes 12.

The biasing means or energy storing unit 5 serves to bias the two or more reaming blades into an extended or non-retracted position. The biasing means may be a compression spring but, if desired, the biasing force may be produced hydraulically using a hydraulic motor or ram. Alternatively the biasing force may be produced pneumatically.

The reaming unit 2 is shown as having two blades but a greater number of blades may be used, and, for longevity, the blades may have tungsten carbide tips.

Ther energy storing unit 5 and the reaming blades 6, 7 are disposed within or carried by the elongated and generally cylindrical reaming body 14.

The reaming blades 6, 7 are mounted in the ream-body 14 through slot 15 formed in the reaming-body 14. The slot 15 can be parallelsided having a length and cross-section at width a little greater than the corresponding dimensions of the reaming blades 6, 7. A hinge pin 10 is mounted in a through hole drilled perpendicular to the slot 15 and serves as a hinge pin for the reaming blades.

The energy storing unit 5 is mounted in a bore formed inside the reaming-body 14. The ends of the enrgy storing unit 5 are connected to the bottom shoe 4 and the top cap 3, respectively. The top cap 3 has a male thread to fit in the female thread of the reaming-body 14. The bottom shoe 4 is usually pressed downwardly (in Fig. 1) by the spring 5. The energy storing unit 5 is usually compressed to provide a biasing force so that the reaming blades 6, 7 are always in an expanded position. On the other hand, when retracting the reaming blades 6, 7, the top cap can assist the reaming blades 6, 7 to overcome the biasing force from the energy storing unit 5 and the reaming blades 6, 7 will rotate about the pin shaft 10 until the outside diameter assumed by the blades is smaller than the pilot bit 9.The biasing force of the energy storing unit 5 should not be so great that, when the reamer blades 6, 7 are pressed inwardly by hand, the energy storing unit 5 cannot be compressed further so that the reaming blades 6, 7 can be contracted into the slot 15.

The reaming blades 6, 7 are ordinarily kept in expanded condition, and the reaming blades 6, 7 are partiaily extended to the outside of the ream-body 14 so that they can normally ascribe a round circle bigger than the outside diameter of the pilot bit 9. When the reaming blades 6, 7 are in working condition, they turn and move forward to cut the rock or other material to enlare the hole. The shape of the reaming blades 6, 7, is such that they can ream holes and can also easily compress the spring 5 so that it achieves a smaller outside diameter than the pilot bit 9. When the reaming blades 6, 7 are in the expanded condition, the angle of the front edge of the blades 6, 7 is 90 degrees to the direction of the forward movement and the back edge is 60 degrees, as shown in Fig. 1.

The drilling unit 1 and the reaming unit 2 of the dual stage expansion-contraction drilling device of this invention have flushing holes 12 in which flushing liquid flow from the top and thence through the ream-body 14 and finally flow out of the device at the front of the pilot bit 9.

The dual stage expansion-contraction drilling device of the invention is mainly used to drill

shaped holes in the ground anchor site. The method of drilling a

shaped hole, which can be seen in Fig. 4, is firstly to pile a length of steel pipe into the ground.

The inside diameter or outside diameter of the steel pipe does not need to be of exact size.

The diameter of the small hole at the upper part of the

shaped hole is the outside diameter of the steel pipe and the bigger hole at the lower part of the

shaped hole is the outside diameter of the reaming blades 6, 7. Then the diameter of the pilot bit 9 of the dual stage expansion-contraction drilling device is smaller than or equal to the inside diameter of the steel pipe. Work is started by contracting the reaming blades 6, 7 and inserting the device into the steel pipe. The blades 6, 7 are prevented from expanding by the steel pipe.

The pilot bit 9 drills from the top of the steel pipe to the bottom of the steel pipe. The reaming blades 6, 7 follow through and will protrude from the pipe at the end of the pipe.

Thereafter, the reaming blades 6, 7 start to ream the hole until the required depth is achieved. When the drilling device is withdrawn, the reaming blades 6, 7 will come into contact with the end of the pipe and owing to the shape of the blades 6, 7, the withdrawal force and the reaction from the wall of the steel pipe, the reaming blades 6, 7 are angularly displaced inwardly to enter into the steel pipe. When they are out of the pipe, the reaming blades 6, 7 will, naturally, under the biasing force exerted by the energy storing unit 5, go back into its expanded position.

Although specific reference has been made to use of the device according to the present invention to holes of inverted "T" cross-section, the device may be used to form holes with enlarged portions disposed at different positions along the axial extent of a pilot hole.

Such enlarged portions can be formed by firstly inserting the steel pipe a limited distance into, for example, the ground, reaming, withdrawing the device into the steel pipe, forcing the steel pipe further into the ground, and repeating the reaming step as required.

Claims

1. An expandable-contractable dulling device comprising a dulling unit and a reaming unit for enlarging at least a portion of a hole formed by the drilling unit.

2. An expandable-contractable dulling device comprising a drilling unit and a reaming unit, the reaming unit including at least one retractable reaming blade for enlarging at least a portion of a hole formed by the dulling unit.

3. A device according to claim 2 wherein the reaming unit comprises a body and means for biasing the or each retractable blade into a non-retracted position.

4. A device according to claim 3 wherein the means for biasing each retractable blade into a non-retractable position is a spring.

5. A device according to any one of claims 3 or 4 wherein the reaming body includes at least one flushing hole.

6. A device according to any one of claims 2 to 5, including two diametrically opposed retractable reaming blades.

7. A device according to any one of claims 2 to 6, wherein each retractable reaming blade is retractable to ascribe a circle having a diameter less than that ascribed by the drill unit.

8. A device according to any one of claims 2 to 7, wherein each reaming blade is shaped to permit ease of retractability into the reaming body.

9. A device according to claim 8 as dependent upon any one of claims 3 to 7, wherein each reaming blade includes a shoulder such that upon movement of the reaming unit against an abutment, each blade is displaced into a retracted position within the reaming body against the biasing force.

10. An expandable-contractable drilling device constructed and arranged substantially as hereinbefore described with reference to and as shown in Figs. 1, 2 and 3 of the accompanying drawings.

11. A method of forming a hole having at least one protion of diameter greater than that of another portion, the method comprising the steps of: a. forming a hole having a first diameter; b. feeding a sleeve into the hole to support a part of the wall of the hole; c. passing a device according to any one of claims 1 to 9 through the sleeve until at least the reaming unit is clear of the sleeve, and d. applying rotary motion to the said device whereby the reaming blades form a hole of larger diameter than the outer diameter of the hole formed in step a.

12. A method according to claim 11, modified in that the sleeve is in the form of a hollow pile which forms the hole of step a, and has a bore for receiving the said device.

13. A method of forming a hole having at least one portion of diameter greater than that of another portion substantially as hereinbefore described and with reference to Fig. 4 of the accompanying drawings.