GB2400869A - Threading apparatus - Google Patents

Abstract

Threading apparatus (30, figure 1) for creating a threaded groove (58, figure 6) in a wall (37, figure 6) defining a pile shaft 39 comprises a rotatable cutting means (38, figure 1) with cutting tools 52, 54 which moves between a retracted non-cutting position and an extended cutting position, and control means 56, 58 for controlling the extension and retraction of the cutting tools 52, 54, which is dependent upon the direction of rotation.

Description

D.caP-rc The present invention relates to a threading equipment for

cutting an internal thread inside a previously bored pile shaft, said shaft being preferably, but not necessarily, bored in clay or similar soil.

When making concrete piles in the soil it is advantageous to limit the diameter of the pile shaft to be bored. Indeed, when the diameter of the pile shaft is reduced, the cost of the drilling operation is lowered.

However, the bearing capacity of the concrete pile greatly depends on the diameter of the pile. A technique to increase the bearing capacity of a pile of a given diameter is to make a thread or a helical slot in the internal wall of the pile shaft. When the pile shaft is filled with concrete to obtain the pile, the thread or helical slot is also filled with concrete.

EP 1 277 887 in the name of Compagnie du Sol describes a drilling tool which is provided with a cutter. This cutter projects outside the lower end of the flight of this tool. When the tool is rotated and lifted the cutter makes a helical slot or thread in the inner wall of the pile shaft bored by the drilling tool itself. However, this technique is only usable when the tool is of the horizontal displacement type.

An object of the present invention is to provide equipment or apparatus which permits the cutting of an internal thread-like groove inside a previously bored pile shaft, especially when the pile shaft is bored in clay or similar soil.

The invention provides threading equipment for cutting a thread in the wall of a pile shaft, the threading equipment comprising: - a displaceable assembly comprising an upper section including at least one cutting means and control means to move said at least one cutting means from a retracted position, wherein said at least one cutting means is disposed radially inwardly of said wall and an extended position, wherein said at least one cutting means projects into said wall of the pile shaft; - means for controlling the vertical displacement speed of said displaceable assembly; and - means for controlling the rotation speed and the sense of rotation of said assembly about its vertical axis, whereby when in said extended position said at least one cutting means is arranged to cut at least one thread in said wall of the pile shaft, said at least one thread having a controlled pitch along a controlled length of said pile shaft.

It will be understood that during downward displacement of the displaceable assembly within the pile shaft, the at least one cutting means is in its retracted position. When the assembly reaches the bottom of the shaft the at least one cutting means is moved to its extended position. Then the displaceable assembly is raised and rotated whereby the at least one cutting means makes a thread-like or helical slot in the wall of the pile shaft.

Preferably, the displaceable assembly further comprises a lower section secured to the upper section, said lower section comprising a cylindrical container for receiving the soil cuttings.

Advantageously, the displaceable assembly is fixed at the lower end of the driving rods. When the driving rods are rotated in a first direction the cutting member is in its retracted position and when the driving rods are rotated in a second direction the cutting member is in its extended cutting, or active, position.

The pitch of the thread and the length of the thread can be predetermined by controlling the rotation speed and vertical displacement speed of the displaceable assembly.

Also advantageously, the displaceable assembly is provided with means, for example drag plates, to create a friction force between the displaceable assembly and the wall of the pile shaft whereby the sense of rotation of the driving rods can efficiently move the cutting member from its retracted position to its extended position.

Other features or advantages of the present invention will appear clearer on reading the following description of embodiments of the invention given by way of non-limiting example.

The description refers to the drawings in which:

- Fig. 1 is a simplified view of a first embodiment of the threading equipment; - Figs. 2 and 3 are simplified vertical sectional views of the threading equipment showing the cutting members in their retracted and extended positions; - Figs. 4A and 4B are detailed horizontal views of a second embodiment of the threading equipment showing the cutting members in their extended and retracted positions; - Fig. 5 is a vertical sectional view of the second embodiment of the threading equipment; - Fig. 6 is an example of a pile obtained by using the threading equipment; and Fig. 7 shows a cutting tool adapted to be used with the threading equipment.

Referring firstly to Fig. 1, the main parts of a first embodiment of the threading equipment will be described.

The threading equipment comprises a piling rig 10 provided with a vertical mast 12. The upper end 12a of the mast is equipped with two pulleys 14, 16 for a cable 18. The mast 12 also forms a vertical guide for a movable rotary drive box 20. The rotary drive box 20 can be moved along the whole length of the mast 12. The equipment further comprises a set of driving rods or Kelly bar 22. The Kelly bar consists of a plurality of steel tubes which are locked one to the other. The upper end 22a of the Kelly bar is secured to an end of the cable 18. As a result, the up and down vertical movement of the Kelly bar is controlled by the cable.

The Kelly bar 22 passes through the rotary drive box 20 and the box applies a rotative torque to the Kelly bar 22. However, the Kelly bar can be vertically moved with respect to the box 20.

The lower end 22b of the Kelly bar or of the driving rods is connected to a threading apparatus, or displaceable assembly, 30. The threading apparatus 30 preferably comprises an upper section 32 and a lower section 34 which are interconnected. The upper section 32 will be described in greater detail hereinafter. The lower section 34 is in the form of a cylindrical container, or bucket, 36 for catching the clay or soil cuttings as they fall from the upper section 32 which consists of cutting means 38 (Fig 1) adapted to cut a thread or helical slot in the internal wall 37 of a previously bored pile shaft 39.

The equipment further comprises speed transducers (not shown) to measure the vertical displacement speed and the rotational speed of the driving rods 22.

Referring now to Figs 2 and 3, the lower section 34 consists of the cylindrical container 36, which has a cylindrical lateral wall 40, a bottom, 42 and an open upper end 44.

The bottom 42 is secured to a rotating control axis 46 (Fig 3), the upper end of which is connected by a linking member 48 to the lower end of the driving rods 22.

The cutting means 38 comprises two cutting tools 52,54 diametrically opposed about the vertical control axis 46. Each cutting tool is linked to the axis 46 by a control mechanism 56,58. The control mechanism is designed so that each cutting tool 52,54 can be moved, in a plane substantially perpendicular to the axis 46, between a retracted position shown in Fig 3 and an extended position shown in Fig 2. More precisely, when the axis is rotated in the direction of arrow Fl (Fig 2), the cutting tools are moved to their extended position and when the axis 46 is rotated in the direction of arrow F2 (Fig 3), the cutting tools are moved to their retracted position.

When the displaceable assembly 30 is moved downwardly in the pile shaft 39 the driving rods 22 are rotated in the direction F2 so that the cutting tools 52,54 are maintained in their retracted position. When the displaceable assembly 30 reaches the bottom of the shaft 39 the rods 22 are rotated in the direction F1 so that the cutting tools 52,54 are moved and maintained in their extended position. Then the displaceable assembly 30 is lifted while the vertical and rotational speeds are controlled so that the cutting tools 52,54 each cut a thread-like helical slot in the wall 37 of the pile shaft 39. The thread has a pitch which is defined by the vertical and rotational speeds. This pitch can be varied along the length of the pile shaft. The thread can extend only along a lower portion of the shaft. The displaceable assembly 30 is rotated in the direction F2 when the thread is terminated.

The soil cuttings fall into the cylindrical container 36. The thread can be formed in one or several sections depending on the capacity of the container 36. As previously explained, the threading apparatus can have no lower section, i.e. no bucket.

Fig. 6 shows a shaft 39, the wall 37 of which is provided with a threadlike or helical slot 58 produced by one of the cutting tools 52,54. The shape of the slot is defined by the shape of the cutting tool 52,54. With two diametrically opposed cutting tools, such as the cutting tools 52,54, a double helical slot is obtained.

Referring to Figs 4A, 4B and 5, a second, preferred embodiment of the threading apparatus, or displaceable assembly, 62 comprises means to create a friction force between the threading apparatus and the wall 37 of the pile shaft. This friction force causes the actual movement of the cutting members with respect to the frame of the equipment between their extended and retracted positions.

The threading apparatus 62 comprises two diametrically disposed cutting systems 64,66 and a cylindrical container 36 (Fig 5). These two cutting systems are identical, so only the cutting system 64 will be described.

The cutting system 64 is connected with a vertical drive tube 68, which is attached to the lower end 22b of the Kelly bar 22, secured to the drive tube 68 by a drive bracket 70, secured to the drive tube 68. Linking levers 72 have a first end 72a which is pivotally mounted on an end 70a of the drive bracket 70. The second end 72b of the linking levers 72 is pivotally mounted on the median, or central, portion 74a of a cutting frame 74. In a horizontal plane, the cutting frame 74 has the shape of an arc of a circle. A first end 74b of the cutting frame 74 is pivotally mounted at the ends of upper drag brackets 76. The upper drag brackets 76 are secured to a drag tube 78 which is mounted around the outside of the drive tube 68. The drag tube 78 can rotate around the drive tube 68, thus allowing the drag brackets 76 to rotate relative to the drive brackets 70.

Lower drag brackets 77 are also secured to the drag tube 78. Ends of the lower drag brackets 77 are connected with a drag plate 80. The drag plate has the general shape of a portion of cylinder and is mounted on the drag brackets 77 by means of a biasing spring 82.

The second end 74C of the cutting frame 74 is provided with a tool holder 84 for receiving the cutting tool or cutting teeth 86. The cutting tool 86 projects outside the external face of the cutting frame 74. As shown in Fig 5, the drag plate 80 is disposed below the cutting tool 86.

The drag plate 80 is positioned so as to be in firm contact with the inner wall 37 of the shaft under the effect of the biasing spring 82 when the threading apparatus 62 is introduced into the upper end of the pile shaft.

Due to the friction force created between the drag plate 80 and the wall of the shaft, when the drive tube 68 is rotated in a counter-clockwise direction (Fig. 4B) the drive bracket 70 is also rotated and the cutting frame 74 is pivoted about the end 76b of the drag bracket 76, towards the inner part of the threading apparatus 62 by means of the linking lever 72. Consequently, the cutting tool 86 is moved to and retained in its retracted position.

Also due to the friction force, when the drive tube 68 is rotated in the clockwise direction (Fig 4A), the drive bracket 70 is also rotated. The rotation of the drive bracket 70 produces an outward pivotal movement of the cutting frame 74 about its ends 74b by means of the linking lever 72. Consequently, the cutting tool 86 is moved to its extended position. Moreover, when the cutting tool 86 begins to bite into the soil, it will provide additional resistance to rotation to keep it in the extended to its maximum radial extent.

When the thread has been completed or the cylindrical container 36 has been filled with soil cuttings, the threading apparatus 62 is rotated in a counter-clockwise direction to retract the cutting tools 86, thus allowing it to be removed from the pile shaft.

Typically, the threading equipment is lifted 800 mm for each rotation, thereby forming a double helix with a pitch of 800 mm and a distance between two threads of 400 mm. q

Claims (13)

1. Threading equipment for cutting a thread in the wall of a pile shaft, the threading equipment comprising: - a displaceable assembly comprising an upper section including at least one cutting means and control means to move said at least one cutting means from a retracted position, wherein said at least one cutting means is disposed radially inwardly of said wall and an extended position, wherein said at least one cutting means projects into said wall of the pile shaft; - means for controlling the vertical displacement speed of said displaceable assembly; and - means for controlling the rotation speed and the sense of rotation of said assembly about its vertical axis, whereby when in said extended position said at least one cutting means is arranged to cut at least one thread in said wall of the pile shaft, said at least one thread having a controlled pitch along a controlled length of said pile shaft.

2. Threading equipment as claimed in claim 1, wherein said displaceable assembly further comprises a lower section connected to said upper section, said lower section comprising a cylindrical container.

3. Threading equipment as claimed in claim 1 or 2, wherein said means for controlling the vertical displacement of said displaceable assembly and means for controlling the speed of rotation and sense of rotation of said displaceable assembly comprises: - a plurality of driving rods, said displaceable assembly being connected to the lower end of said rods; means for rotating said rods at a controlled speed in a clockwise direction and counter-clockwise direction; and - means for vertically moving said rods at a controlled speed. q

4. Threading equipment as claimed in claim 1, 2 or 3, wherein said control means comprises means for creating a friction force between said upper section and said wall of said pile shaft.

5. Threading equipment as claimed in claim 4, wherein said means for creating a friction force includes at least two moveable drag plates biased by two biasing means.

6. Threading equipment as claimed in claim 4 when dependent on claim 3, wherein said control means further comprises mechanical linking means having a first end connected to said at least one cutting means and a second end Cinematically connected to said lower ends of said driving rods, the arrangement being such that said at least one cutting means is in its extended position when said driving rods are rotated in one of said clockwise and counter-clockwise directions and in its retracted position when said driving rods are rotated in the other of said clockwise and counter-clockwise directions.

7. Threading equipment as claimed in claim 6, wherein said mechanical linking means comprises: - a drive tube secured to said driving rods; - a drag tube mounted around said drive tube; - a support member for supporting the or a said cutting means and having a first end secured to said drive tube, said cutting means being secured to said support member at a place distinct from said first end; - a drive bracket secured to said drive tube; and - a lever member having a first end pivotally mounted at the end of said bracket and a second end pivotally mounted on said support member at a place distinct from said first end.

IN

8. Threading equipment as claimed in claim 7, wherein said means for creating a friction force comprises two drag brackets secured to said drag tube and two drag plates, each drag plate being mounted at the end of a drag bracket by means of biasing springs.

9. Threading equipment as claimed in any one of the preceding claims, wherein said at least one cutting means is a cutter the active end of which has in vertical section the shape of the profile of the thread to be cut in the surface of the shaft.

10. Threading equipment as claimed in any one of the preceding claims, wherein said at least one cutting means is moved, between its retracted and extended position, within a plane substantially perpendicular to the longitudinal axis of the displaceable assembly.

11. Threading equipment according to any one of the preceding claims, comprising two said cutting means disposed diametrically opposite one another.

12. Apparatus for cutting a thread-like groove in a wall defining a pile shaft, said apparatus comprising a rotatable cutting portion comprising cutting means movable between a retracted non-cutting position and an extended cutting position and means for controllably moving said cutting means between said cutting and non-cutting positions according to the direction of rotation of said cutting position.

13. Apparatus for cutting a thread-like groove in a wall defining a pile shaft substantially as herein described with reference to the drawings.