Patent Application
20050121234
The present invention provides a drilling machine of the type comprising a frame, and at least one pair of rotary drilling tools mounted on the frame, the rotary drilling tools presenting substantially the same axis of rotation.
A particular example of that type of known machine, usually referred to as a “cutter”, is described below with reference to accompanying FIGS. 1 to 3, in order to better understand the problems that can arise from using such a machine.
The drilling vehicle also includes a flexible hose 34 associated with suction orifices 36 and with a suction pump 38 for sucking up the cuttings resulting from the action of the drilling tools. The drilling machine also includes hydraulic supply hoses for hydraulically powering the motors driving the pairs of rotary tools 22 and 24.
As can be seen more clearly in
It should be understood that while the pairs of drilling tools are being actuated, the formation of the ridge 42 opposes or hinders progress of the drilling tool, especially if the ground that is being drilled is relatively hard.
The ridge 42 typically presents a height of about 250 millimeters (mm) and a width of about 70 mm. The bottom edge 32a of the plate 32 exerts a compression force on the top of the ridge, said bottom edge being a portion of a surface that is cylindrical (in the broad sense of the term) with generator lines that are parallel to the axis of rotation of the tools. As a result of the bumping of the machine, lateral parasitic forces induce bending and shearing forces which tend to cause the ridge to rupture.
With very hard rocks, the reaction of the ridge against the drilling machine can take up a large fraction, or even all, of the thrust force exerted by the weight of the machine, thereby limiting the effectiveness of the rotary drilling tools corresponding.
An object of the present invention is to provide a drilling machine of the above-mentioned type which makes it possible to improve the progressive disintegration of the ridge so as to improve the overall effectiveness of the drilling machine, in particular when drilling hard ground.
The invention achieves this object by providing a drilling machine comprising a frame; at least one pair of rotary drilling tools having substantially the same axis of rotation; and a support assembly secured to the frame and supporting said pair of tools in rotation, said support assembly presenting an edge facing the cutting face and extending between the tools of said pair of tools, said machine further comprising means mounted on said support assembly for creating at least one jet of liquid at very high pressure directed towards the cutting face between the action zones of said pair of tools; whereby said jet of liquid at very high pressure breaks up the ridge which forms in the cutting face between the action zones of said pair of rotary tools.
It should be understood that by means of the presence of the very high pressure jet(s) of liquid which is/are directed towards the ridge, breaking up of said ridge is improved very substantially compared to the sole compression action of the edge of the support assembly for the rotary tools. Improved breaking up of the ridge tends to improve the overall effectiveness of the tool.
The jet-creation means preferably comprise at least one nozzle supplied with very high pressure liquid, and opening out into said edge of the support assembly.
In an improved embodiment of the invention, said edge of the above-defined drilling machine presents, at least over a portion of its length, a face that is not symmetrical about said mid-plane, whereby said asymmetrical face exerts a bending force on the ridge formed between the action zones of said pair of tools, so as to break up said ridge.
It should be understood that as a result of at least one portion of the edge of the support assembly presenting a face that is not symmetrical about the mid-plane of the support element, i.e. about the drilling direction facing the ridge which tends to form between the rotary tools of a same pair, mechanical bending action is exerted on the ridge by the face because of its orientation, which is more favorable to disintegration than a compression action since, as indicated above, the ridge is weaker in bending than in compression.
The term “face of a portion of the rim” of the support element refers equally to a surface that is plane as to a surface that is skew.
It should also be understood that in this improved embodiment, the disintegration of the ridge results from combining the action of the very high pressure jets, and the mechanical bending action of the inclined edge of the support assembly on the ridge.
Other characteristics and advantages of the invention appear better on reading the following description of several embodiments of the invention given by way of non-limiting example.
The description refers to the accompanying figures in which:
A preferred embodiment of the invention is described below with reference firstly to
As shown in
As shown more clearly in
The pressure of the liquid serving to create the jets preferably lies in the range 100 mega pascals (MPa) to 200 MPa.
It should thus be understood that by means of the presence of the jets created by the nozzles 54, it is possible to cause the ridge 42 to disintegrate as fast as it is being formed, in particular if the ground that is being drilled is hard.
An improved embodiment of the drilling machine is described below with reference to
To achieve this result, the bottom edge 32a of the plate 32 is no longer constituted by a cylindrical surface having generator lines that are perpendicular to the drilling direction, but by a succession of preferably alternating faces that are not symmetrical about the mid-plane P, P′ of the plate 32. The faces can consist of plane surfaces or skew surfaces. To do this, prism-shaped elements such as 60 are preferably fixed on the edge proper 32a of the plate 32, each of said elements presenting an active face 62 which forms an angle relative to the drilling direction F, which angle lies in the range 30° to 60°, and is preferably equal to 45°. The prismatic elements 60 are also preferably disposed in alternation about the mid-plane P, P′ of the plate 32 in such a manner that the active faces 62 are alternately on opposite sides of the mid-plane P, P′. By means of their sloping faces 62, the prismatic parts exert on the ridge, a force that is not perpendicular to the top of the ridge, but that is inclined relative to said ridge, thereby enabling a bending force to be applied to the ridge, tending to disintegrate it.
The nozzles 54 are thus mounted in the prismatic parts 60, and the supply lines extend into said parts.
It should thus be understood that the ridge breaks up as a result of the combination of the hydraulic action of the jets created by the nozzles 54, and the mechanical action of the sloping faces 62 of the prismatic parts 60 mounted on the edge 32a of the plate 32. A further improvement is thus obtained in breaking up the ridge that appears in the cutting face, and thus an overall improvement in the effectiveness of the drilling machine, in particular when the ground is very hard.
In this embodiment, the prismatic parts 70 fixed on the edge 32a of the plate 32 have a trapezoidal right section having an active small base 72 of small size.
The longitudinal axes x, x′ of the parts 70 form an angle b relative to with the mid-plane P, P′ of the plate 32. The angle b lies in the range 30° to 60°, for example.
In the above description, consideration is given to a drilling machine, usually referred to as a “cutter”. The invention can very well be applied to other machines so long as the machine includes at least one pair of rotary tools whose action on the cutting face leads to a ridge being formed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 03/13460 | Nov 2003 | FR | national |
