GB1596308A

GB1596308A - Anchor hole drilling

Info

Publication number: GB1596308A
Application number: GB45823/77A
Authority: GB
Original assignee: WEAVER AND HURT Ltd
Current assignee: WEAVER AND HURT Ltd
Priority date: 1978-05-17
Filing date: 1978-05-17
Publication date: 1981-08-26

Description

(54) AN IMPROVEMENT IN OR RELATING TO ANCHOR HOLE DRILLING (71) We, WEAVER AND HURT LIMITED. of 71 Saltergate, Chesterfield, in the County of Derby, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to anchor hole drilling and has for its object to provide an improvement therein.

Anchor holes are drilled, for example, for anchoring support cables for bridges, and the forming of such holes has always been a problem. A hole must first be drilled to the depth required and various means have previously been adopted for enlarging a lower part of the hole so that when the hole has subsequently been filled with concrete (with the support cable extending to the bottom of the hole) a plug of concrete has been formed on the cable in the region of the enlarged portion of the hole and this has constituted an anchor which has prevented the cable from being pulled from the hole when a load has been applied to it.

According to the invention, there is provided a tool for use in anchor hole drilling, that is to say for enlarging a portion of a previously drilled hole, the tool including an upper body part for connection to a lowermost end of a drill "string", a lower body part drivably connected to said upper body part but capable of movement towards or away from the latter by a telescopic connection, at least two pairs of reamer "wings" pivotally connected together and pivotally connected to said upper and lower body parts such that when said upper and lower body parts are caused to move one towards the other they cause the pairs of reamer "wings" to pivot radially outwards, an auger member depending from the lower body part and arranged to pack down the hole material displaced by the reamer "wings", and a foot member carried at the lower end of the auger member for bearing against the bottom of the previously drilled hole. The telescopic connection between the upper body part and the lower body part may be constituted by a length of square section shaft. In this case the length of square section shaft may be welded to the lower body part but be a close sliding fit through a square shaped aperture in a portion of the upper body part.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which: Fig. 1 is a perspective view of a tool embodying the invention, Fig. 2 is a scrap view illustrating in an operative condition a part of the tool to a somewhat larger scale than Fig. 1, Fig. 3 is a view of that same part but in an inoperative condition, and Fig. 4 is a view of a different part of the tool which will presently be referred to.

Referring now to the drawings, the tool there illustrated for enlarging a portion of a previously drilled hole includes an upper body part 10 provided with an internally screwthreaded portion 12 for connection to a lowermost end of a drill "string". The tool also includes a lower body part 14 drivably connected to said upper body part but capable of movement towards or away from the latter by a telescopic connection. The telescopic connection can be seen in Figs. 2 and 3 to be constituted by a length of square section shaft 16 which is welded to the lower body part 14 but which is a close sliding fit through a square shaped aperture in a portion 18 of the upper body part. The square section shaft has a pair of abutment members 17 welded in position on its opposite sides, substantially midway of its length as shown in Fig. 3, and these will be referred to presently.In addition, as best seen in Fig. 3, the four side surfaces of the square section shaft have axially extending half round grooves 19 for a purpose which will presently be explained.

Two pairs of reamer "wings" 20, 22 are pivotally connected together by respective pivot pins 24 and pivotally connected to said upper and lower body parts by respective pivot pins 26 and 28. The reamer "wings" are provided with teeth 30 as shown and at their ends which are pivotally connected to the upper and lower body parts they are a close sliding fit in respective slots 32.

An auger member 34 depends from the lower body part but it will be seen that the vane element 36 of the auger extends in an anti-clockwise direction around its central shaft 38. A foot member generally indicated 40 is carried at the lower end of the auger member and, as best seen in Fig. 4, the foot member includes a shaft portion 42 provided at a lower end with a pronged foot element 44 and provided at its upper end with a bearing housing 46 within which a lowermost end portion of the shaft 38 of the auger member is rotatably mounted in ball bearings 48.

The arrangement is such that when a borehole has been drilled, for example a 6" diameter bore to a depth of perphaps 80 or 90 feet, the tool just described can be used to ream out a portion near the bottom of the bore to 14 or 15 inches (which when it has been filled with concrete will provide a very strong anchor). To ream out the portion near the bottom of the bore, the tool is connected to the lowermost end of the drill "string" on which the rock drill has previously been connected and the tool is then lowered down the hole as the "string" is simultaneously driven in a clockwise sense when viewed from above (as during the previous rock drilling operation). It will be understood that the tool is lowered down the hole with the reamer "wings" in the inoperative condition in which they are shown in Fig. 3.When the tool reaches the bottom of the hole, the pronged foot element 44 will "bottom" in the bore and continued downward pressure on the tool, i.e.

the weight of the drill "string", will cause the reamer "wings" 20, 22 to open out so that in that region the bore is reamed out.

(It will be understood that the presence of the abutment members 17 flanking the square section shaft 16 prevents the reamer "wings" from folding quite flat against said shaft so that the downward pressure from the drill string causes the "wings" to open).

During the reaming out operation compressed air delivered to the upper body part can issue from apertures provided by the grooves 19 for air flushing. Material dislodged during the reaming operation falls onto the auger member and the latter packs it downwards towards the bottom of the bore hole. This can continue until the aubutment members 17 flanking the square section shaft 16 abut against tfie upper body part 10. The tool can then be extracted from the borehole, the reamer "wings" being automatically caused to fold almost flat against the square section shaft 16 as shown in Fig. 3 to allow its extraction as soon as the drill "string" starts to lift.

Thus there is provided a tool which has been found to be particularly advantageous in use. However, various modifications may be made without departing from the scope of the invention. For example, the tool could be provided with more than two pairs of reamer "wings", particularly if the tool is designed for enlarging a relatively large diameter borehole because the body parts of the tool can then be made of a larger diameter. It will also be understood that if the tool is provided with a number of different shaft portions 42 and pronged foot elements 44 which can be used selectively, a number of enlarged portions can be reamed out in a previously drilled borehole at varying depths depending on the lengths of the shaft.

portions 42.

Furthermore, it will be understood that the conventional method of flushing the hole clear of cuttings is to use water, but that the tool described above enables the user to ream the hole dry. However, if the drilling conditions required wet flush the tool will be capable of taking water and still pass the cuttings down below the reamed area. This also applies using compressed air.

In a modification of the tool just described the foot member 40 has been devoid of ball bearings or of a pronged foot element, being constituted merely by a metal ball end arranged to "bottom" in the drilled hole. (This has been a safeguard against grit and dirt having entered the ball bearings and caused them to fail).

WHAT WE CLAIM IS: 1. A tool for use in anchor hole drilling, that is to say for enlarging a portion of a previously drilled hole, the tool including an upper body part for connection to a lowermost end of a drill "string", a lower body part drivably connected to said upper body part but capable of movement towards or away from the latter by a telescopic conneo tion, at least two pairs of reamer "wings" pivotally connected together and pivotally connected to said upper and lower body parts such that when said upper and lower body parts are caused to move one towards the other they cause the pairs of reamer "wings" to pivot radially outwards, an auger member depending from the lower body part and arranged to pack down the hole material displaced by the reamer "wings", and a foot member carried at the lower end of the auger member for bearing against the bottom of the previously drilled hole.

2. A tool according to claim 1, in which the telescopic connection between the upper body part and the lower body part is constituted by a length of square section shaft.

3. A tool according to claim 2, in which the length of square section shaft is welded to the lower body part but is a close sliding

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. are provided with teeth 30 as shown and at their ends which are pivotally connected to the upper and lower body parts they are a close sliding fit in respective slots 32. An auger member 34 depends from the lower body part but it will be seen that the vane element 36 of the auger extends in an anti-clockwise direction around its central shaft 38. A foot member generally indicated 40 is carried at the lower end of the auger member and, as best seen in Fig. 4, the foot member includes a shaft portion 42 provided at a lower end with a pronged foot element 44 and provided at its upper end with a bearing housing 46 within which a lowermost end portion of the shaft 38 of the auger member is rotatably mounted in ball bearings 48. The arrangement is such that when a borehole has been drilled, for example a 6" diameter bore to a depth of perphaps 80 or 90 feet, the tool just described can be used to ream out a portion near the bottom of the bore to 14 or 15 inches (which when it has been filled with concrete will provide a very strong anchor). To ream out the portion near the bottom of the bore, the tool is connected to the lowermost end of the drill "string" on which the rock drill has previously been connected and the tool is then lowered down the hole as the "string" is simultaneously driven in a clockwise sense when viewed from above (as during the previous rock drilling operation). It will be understood that the tool is lowered down the hole with the reamer "wings" in the inoperative condition in which they are shown in Fig. 3.When the tool reaches the bottom of the hole, the pronged foot element 44 will "bottom" in the bore and continued downward pressure on the tool, i.e. the weight of the drill "string", will cause the reamer "wings" 20, 22 to open out so that in that region the bore is reamed out. (It will be understood that the presence of the abutment members 17 flanking the square section shaft 16 prevents the reamer "wings" from folding quite flat against said shaft so that the downward pressure from the drill string causes the "wings" to open). During the reaming out operation compressed air delivered to the upper body part can issue from apertures provided by the grooves 19 for air flushing. Material dislodged during the reaming operation falls onto the auger member and the latter packs it downwards towards the bottom of the bore hole. This can continue until the aubutment members 17 flanking the square section shaft 16 abut against tfie upper body part 10. The tool can then be extracted from the borehole, the reamer "wings" being automatically caused to fold almost flat against the square section shaft 16 as shown in Fig. 3 to allow its extraction as soon as the drill "string" starts to lift. Thus there is provided a tool which has been found to be particularly advantageous in use. However, various modifications may be made without departing from the scope of the invention. For example, the tool could be provided with more than two pairs of reamer "wings", particularly if the tool is designed for enlarging a relatively large diameter borehole because the body parts of the tool can then be made of a larger diameter. It will also be understood that if the tool is provided with a number of different shaft portions 42 and pronged foot elements 44 which can be used selectively, a number of enlarged portions can be reamed out in a previously drilled borehole at varying depths depending on the lengths of the shaft. portions 42. Furthermore, it will be understood that the conventional method of flushing the hole clear of cuttings is to use water, but that the tool described above enables the user to ream the hole dry. However, if the drilling conditions required wet flush the tool will be capable of taking water and still pass the cuttings down below the reamed area. This also applies using compressed air. In a modification of the tool just described the foot member 40 has been devoid of ball bearings or of a pronged foot element, being constituted merely by a metal ball end arranged to "bottom" in the drilled hole. (This has been a safeguard against grit and dirt having entered the ball bearings and caused them to fail). WHAT WE CLAIM IS:

1. A tool for use in anchor hole drilling, that is to say for enlarging a portion of a previously drilled hole, the tool including an upper body part for connection to a lowermost end of a drill "string", a lower body part drivably connected to said upper body part but capable of movement towards or away from the latter by a telescopic conneo tion, at least two pairs of reamer "wings" pivotally connected together and pivotally connected to said upper and lower body parts such that when said upper and lower body parts are caused to move one towards the other they cause the pairs of reamer "wings" to pivot radially outwards, an auger member depending from the lower body part and arranged to pack down the hole material displaced by the reamer "wings", and a foot member carried at the lower end of the auger member for bearing against the bottom of the previously drilled hole.

fit through a square shaped aperture in a portion of the upper body part.

4. A tool for use in anchor hoie drilling, that is to say for enlarging a portion of a previously drilled hole, the tool being constructed, arranged and adapted to be used substantially as hereinbefore described with reference to and as illustrated by the acccompaying drawings.