GB2440939A

GB2440939A - Cutting head provided with a retractable threading means

Info

Publication number: GB2440939A
Application number: GB0607612A
Authority: GB
Inventors: Lewis Stansfield
Original assignee: Compagnie du Sol SARL
Current assignee: Compagnie du Sol SARL
Priority date: 2006-04-18
Filing date: 2006-04-18
Publication date: 2008-02-20
Anticipated expiration: 2026-04-18
Also published as: GB2440939B; GB0607612D0

Abstract

A cutting head comprising: <UL ST=" Ò "> <LI>an upper part (22) comprising: a cylindrical body (30) and an extension (28) extending downwardly from said cylindrical body; <LI>a lower hollow cylindrical part (24) provided with an external flight (36), said extension sliding within said lower part; <LI>means (38) for connecting in rotation said two parts and for limiting the sliding of the extension within the lower part between a retracted mutual position and an extended mutual position; <LI>a threading tooth (40) movably mounted close to the lower end of the lower part; <LI>means (42) for moving said tooth between a retracted position and an extended position; and <LI>control means (44) mounted at the lower end of said extension for cooperating with said moving means so that when said two parts are in abutment, said tooth is maintained in its retracted position and when said two parts are in their mutual extended position, said tooth is in its extended position. </UL>

Description

CUTTING HEAD PROVIDED WITH THREADING MEANS

The present invention relates to a cutting head provided with threading means for cutting an internal thread inside the wall of a bored pile shaft, said shaft being preferably, but not necessarily, bored in clay or similar soil. This cutting head is connected to a normal string of flight augers during piling operations.

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 or tooth which has a fixed position with respect to the flight of the tool. 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.

In other tools provided with threading means, the threading tooth can be moved from a retracted position to an operating extended position.

In the European Patent application 1 471 187 in the name of Compagnie du Sol, the threading tooth is maintained in its retracted position when the drilling tool is rotated in a first direction and the threading tooth is moved to its extended position when the drilling tool is rotated in the opposite direction.

An object of the present invention is to provide a cutting head which is equipped with a threading tooth which can be moved from its retracted position to its extended position irrespective of the direction of rotation of the cutting head and wherein the tooth is safely moved to its extended position and maintained in this position during the whole upwardly movement of the cutting head to cut a helical slot in the wall of the shaft.

To achieve this object, according to the present invention, the cutting head comprises: an upper part comprising: a cylindrical body provided with an external flight and an extension extending downwardly from said cylindrical body; : . a lower hollow cylindrical part provided with an external flight, said extension being adapted to slide within said lower hollow cylindrical *G4I part; connecting means for connecting in rotation said upper and lower parts, and for limiting the sliding of the extension within the lower part between a retracted mutual position wherein the lower end of the upper part is in abutment with the upper end of the lower part, and an extended mutual position wherein the distance between the lower end of the upper part and the upper end of the lower part is limited to a predetermined value; tooth means movably mounted close to the lower end of the lower part; moving means for moving said tooth means between a retracted position wherein said tooth means do not extend beyond the side of the flight and an extended position wherein said tooth means extend beyond the side of the flight; and control means mounted at the lower end of said extension for cooperating with said moving means so that when said upper and lower parts are in abutment, said tooth means are maintained in their retracted position and when said upper and lower parts are in their mutual extended position, said tooth means are in their expanded position.

It will be understood that, during the downwards movement of the cutting head corresponding to the boring of the pile, the upper part of the tool is pressed in abutment against the upper end of the lower part by the strength opposed by the soil to be cut. Then, the threading tooth is S. maintained in its retracted position. By contrast, when the cutting head is moved upwardly, the vertical traction applied to the upper part of the cutting head combined with the resisting effect of the soil on the flight of the lower part of the cutting head, move the upper and lower parts of the cutting head into their mutual extended position. As a result, the threading tooth is moved to its extended position and maintained in this position.

Preferably, the tooth means are moved in translation in a radial direction with respect to the longitudinal axis of the cutting head.

However, in a variant, the tooth means could be rotated about an axis secured to the flight of the cutting head between a retracted position and an extended position.

In a preferred embodiment, the moving means comprise a tubular guide secured to the lower part of the head and radially extending and a piston movable within said tubular guide and having a first end secured to said tooth means, and a second end for cooperating with said control means.

Preferably, the control means are adapted to convert the vertical movement of the extension from the retracted position to the extended position of the upper and lower parts into a movement of translation of said control means, and consequently of the tooth means.

Also advantageously, the moving means further comprise return means to move said tooth means from their extended position to their retracted position when said upper and lower parts are in their mutual retracted position.

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

-figures 1 and 2 show the whole cutting head when the threading tooth is in its retracted position and in its extended position; : * -figure 3 is a vertical sectional view of the whole cutting head; -figure 4 is a vertical view of the upper part and the connecting part of the cutting head in their retracted position; -figure 5 is a vertical sectional view according to line A-A of.

figure 4; -figure 6 is a horizontal sectional view according to line B-B of figure 4; -figure 7 is a vertical view of the upper part and of the upper portion of the lower part of the cutting head in an extended position; -figure 8 is a vertical sectional view according to line C-C of figure 7; -figure 9 is a perspective view of the lower portion of the lower part of the cutting head; -figure 10 is a view identical to figure 9, but partially cut; and -figure 11 is a vertical sectional view of the lower portion of the lower part of the cutting head.

Referring firstly to figures 1 to 3, the main parts of the cutting head 20 will be described.

The cutting head 20 comprises an upper part 22 and a lower part 24. The upper end 22a of the upper part 22 is provided with connection means 26 for connection to a normal string of flight auger. The lower end 22b of the upper part is downwardly extended by a tubular extension 28. The upper part 22 is formed by a tubular body 30 and a flight 32.

The lower part 24 has the general shape of a cylindrical hallow stem 34 provided with a flight 36. The extension 28 of the upper part 22 is slidely mounted within the hollow stem 34 of the lower part 24.

The lower part 24 of the cutting head 20 is connected to the upper part 22 by connecting means 38. The purpose of the connecting means 38 is to secure in rotation the upper part 22 and the lower part 24: s.' and to allow a limited relative movement of translation along the common axis of the parts 22 and 24 between the two parts of the cutting head.

The lower end 24a of the lower part 24 of the cutting head is * equipped with a movable threading tooth 40. The threading tooth is., connected to moving means 42 to move the threading tooth 40. **, The lower end 28a of the tubular extension 28 of the upper part 22 is provided with control means 44.

The control means 44 cooperate with the moving means 42. As it will be explained in more details hereinafter, when the upper part 22 of the cutting head 20 is in abutment against the upper end 24b of the lower part 24, the threading tooth 40 is allowed to be in a retracted position as shown in figure 1. This situation corresponds to the downward movement of the cutting head. When the upper part 22 and the lower part 24 are in a mutual extended position as shown in figure 2, the control means 44 act on the moving means 42 to move the threading tooth into its extended position and to maintain it in this position. This situation corresponds to an upward movement of the cutting head.

Referring now to figures 4 to 8, a preferred embodiment of the connecting means 38 will be described in detail.

As already explained the purpose of the connecting means is to secure in rotation the upper part 22 and the lower part 24 while permitting a vertical translation movement of a limited length between the upper and lower parts 22 and 24.

As shown in figure 5 or 8, the upper end 34a of the hollow stem 34 is secured to a female hexagonal drive box 46. The lower end 22b of the upper part 22 is secured to the upper end 48a of a male hexagonal drive 48. The lower end 48b of the male hexagonal drive 48 is secured to the upper end 28b of the extension 28.

The cooperation of the female drive box 46 with the male drive 48 connects the upper and lower parts in rotation. : :..

The upper end 46a of the female drive box 46 is provided with a retaining ring 50 secured to the drive box 46 and projecting out of the inner wall 46c of the drive box 46. The outer wall 48c of the male drive 48 is provided with a shoulder 52 which can cooperate with the retaining.*, ring 50.

When the upper part 22 is relatively moved apart from the lower part 24, the length of the movement is limited by the cooperation of the ring 50 and the shoulder 52 as shown in figure 8.

Referring now to figures 9 to 11, a preferred embodiment of the moving means 42 and of the control means 44 will be described.

Close to the lower end 24a of the lower part 24, a protected volume 54 is limited by a helix 56 of the flight 36, a lateral wall or skirt 58 and a bottom plate 59. Within this protected volume 54, a guide tube 60 having a horizontal axis is secured to the stem 34 of the lower part 24.

This tube extends radially with respect to the longitudinal axis XX' of the stem 34. A piston 62 is slidely mounted within the tube 60. The threading tooth 40 is secured to a first end 62a of the piston. The second end 62b of the piston 62 has the shape of an inclined surface 64.

The lower end of the stem 34 is provided with a vertical slot 66 through which a control member having the shape of wedge 68 can be moved vertically. The wedge 68 is secured on the outer surface of the lower end of the extension 28. Due to the inclined surface 64 and the wedge 68, a vertical movement of the extension 28 of the upper part 22 transmits a horizontal movement to the threading tooth 40. When the wedge 68 does not cooperate with the inclined surface 64 of the piston 62, a return system comprising a lever 70, connected to the piston 62, and a tension spring 72 causes the retraction of the threading tooth 40.

The operation of the cutting head provided with the threading tooth is as follows: When the cutting head 20 is moved downwardly and rotated to: ..

bore the shaft in the ground, the upper part 22 is in abutment against the lower part 24 or, more precisely, the bottom of the male hexagonal drive 48 is in contact with the bottom of the female hexagonal drive box 46. The extension 28 is retracted into the stem 34 of the lower part * 24 and the wedge 68 does not act against the inclined surface 64 of the piston 62. The threading tooth 40 is maintained in its retracted position by the return system 70, 72. As a result, no helical slot is cut within the inner wall of the shaft.

When the cutting head 20 is moved upwardly, the upper and lower parts 22 and 24 are in a mutual extended position limited by the cooperation of the shoulder 52 and the ring 50. The wedge 68 is in an upper position and acts on the inclined surface 64 of the piston 62 and it moves the piston 62. As a result, the threading tooth 40 is moved in its extended position and it is maintained in this position as long as an upward traction is applied to the upper part 22 of the cutting head. During the lift of the cutting head, a helical slot or thread is cut within the inner wall of the shaft or bore.

It is to be underlined that the position of the threading tooth does not depend of the direction of rotation of the cutting head.

Claims

CLAIMS

1. A cutting head comprising: * an upper part comprising: a cylindrical body provided with an external flight and an extension extending downwardly from said cylindrical body; * a lower hollow cylindrical part provided with an external flight, said extension being adapted to slide within said lower hollow cylindrical part; : *.

* connecting means for connecting in rotation said upper and lower parts and for limiting the sliding of the extension within the lower part between a retracted mutual position wherein the lower end of the upper part is in abutment with the upper end of the lower part, and an extended mutual position wherein the distance between the lower end of the upper part and the upper end of the lower part is limited to a predetermined value; * tooth means movably mounted close to the lower end of the lower part; * moving means for moving said tooth means between a retracted position wherein said tooth means do not extend beyond the side of the flight and an extended position wherein said tooth means extend beyond the side of the flight; and * control means mounted at the lower end of said extension for cooperating with said moving means so that when said upper and lower parts are in abutment, said tooth means are maintained in their retracted position and when said upper and lower parts are in their mutual extended position, said tooth means are in their extended position.

2. A cutting head according to claim 1, wherein said tooth means are moved in translation in a radial direction.

3. A cutting head according to claim 2, wherein said moving means comprise a tubular guide secured to the lower part and radially extending, and a piston movable within said tubular guide and having a first end secured to said tooth means, and a second end for cooperating with said control means.

4. A cutting head according to claim 3, wherein said control means are adapted to convert the movement of the extension from the retracted position to the extended position of the upper and lower parts into a movement of translation of said control means. : :..

5. A cutting head according to claim 3 or 4, wherein said moving means further comprise returning means to move said tooth means from their extended position to their retracted position when said upper and lower parts are in their mutual retracted position.

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