Patent Publication Number: US-2005121234-A1

Title: Drilling machine having rotary tools

Description:
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.  
     BACKGROUND OF THE INVENTION  
      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.  
       FIG. 1  shows a drilling vehicle  10  constituted mainly by a platform  12  equipped with a jib  14  having a drilling machine  16  suspended from its top end  14   a  by means of cables  18 . The drilling machine  16  comprises a frame  20  with two pairs of rotary drilling tools or cutters  22  and  24  mounted at its bottom end. Each pair of drilling tools  22  or  24  is constituted by two drilling tools  26  and  28 , as can be seen more clearly in  FIG. 3 , the drilling tools being rotatably mounted about axes which usually coincide, the common axis being referenced  30 . Furthermore, the two pairs of tools have parallel axes of rotation. More precisely, each pair of tools is rotatably mounted in a support plate  32  secured to the bottom end  20   a  of the frame of the drilling 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  FIG. 3 , the presence of the support plate  32  between the drilling tools  26  and  28  of a same pair leaves a gap e between the action zones of the drilling tools on the cutting face  40 . The gap  39  leads to a ridge  42  being formed in the cutting face. In addition, the plate  32  presents an edge  32   a  that is usually semi-circular, semi-oval, or polygonal in shape.  
      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  32   a  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.  
     OBJECTS AND SUMMARY OF THE INVENTION  
      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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      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:  
       FIG. 1 , described above, is an overall view of a drilling vehicle;  
       FIG. 2 , described above, is a view showing the bottom portion of the drilling machine, with a portion of a pair of drilling tools being removed;  
       FIG. 3 , described above, is a simplified side view showing a pair of drilling tools and their action on the cutting face;  
       FIG. 4  is a side view of the support assembly for supporting the drilling tools equipped with nozzles for producing high-pressure jets;  
       FIG. 4A  is a view of a detail of  FIG. 4  showing the supply of the jet-producing nozzles.  
       FIG. 4B  is a detail view of  FIG. 4A  showing the structure of a nozzle;  
       FIG. 5  is a perspective view of the edge of the support assembly constituting an improved embodiment of the invention;  
       FIG. 5A  is a side view showing the edge of the support element;  
       FIG. 6  is a view from below showing a variant embodiment of the edge of the support element; and  
       FIG. 6A  is a section view on line A-A of  FIG. 6 . 
    
    
     MORE DETAILED DESCRIPTION  
      A preferred embodiment of the invention is described below with reference firstly to  FIGS. 4, 4A , and  4 B.  
       FIG. 4  shows the plate  32  fixed onto the bottom end of the frame  20   a  of the drilling machine, and onto which plate the pair of tools  26 ,  28  are mounted and supported. The plate includes a central recess  50  for mounting motors and drums carrying the drilling elements. The figure shows the supply lines  52  for supplying liquid under pressure to the drive motors of the drilling tools. In simplified manner,  FIG. 4  shows nozzles such as  54  for creating very high pressure jets of liquid which are provided in the edge  32   a  of the plate  32  facing the cutting face  40 , and more precisely the ridge  42 . The nozzles therefore produce jets  56  of liquid under pressure that are directed towards the ridge over its entire length, i.e. its extent along the direction that is perpendicular to the plane of  FIG. 3 .  
      As shown in  FIG. 4A , the nozzles  54  are preferably supplied by supply lines such as  57 , formed in the thickness of the plate  32 . The nozzle supply lines  57  are connected to hydraulic supply hoses  58  mounted in parallel with the main supply hoses for powering the hydraulic motors.  
      As shown more clearly in  FIG. 4B , the nozzles  54  are mounted inside the plate  32  in such a manner that their outlets  54   a  are set back from the bottom edges  32   a  of the plate  32 . For this purpose, holes  58  are pierced in the edge of the plate  32  to enable the high-pressure jets delivered by the nozzles  54  to be expelled.  
      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  FIGS. 5 and 5 A. In this improved embodiment, in order to break up the ridge, the high pressure jets are accompanied by a mechanical bending effect on the ridge.  
      To achieve this result, the bottom edge  32   a  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  32   a  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  32   a  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.  
       FIGS. 6 and 6 A show a variant embodiment of the parts enabling bending force to be applied to the ridge  42 .  
      In this embodiment, the prismatic parts  70  fixed on the edge  32   a  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.