Patent Publication Number: US-7591329-B2

Title: Auger with a movable gouge for making a borehole

Description:
BACKGROUND OF THE INVENTION 
     For making a bored pile or a cast-in-place pile, it is usual to make use of a tool such as an auger that serves to dig a cylindrical excavation in the ground corresponding to the dimensions of the pile that is to be made, and that also serves to raise the excavated material. Often, the auger is fitted with a dip tube that is mounted to slide in the hollow core of the auger and that serves, while the auger is being raised, to inject progressively into the borehole the concrete or grout that is to form the pile. 
     The forces that can be absorbed by a bored or cast-in-place pile depend firstly on its diameter and secondly on the coefficient of friction that exists between the outer wall of the pile and the inside wall of the borehole. 
     Increasing the diameter of the pile leads to an increase in the cost of boring and above all to an increase of the quantity of grout or concrete that needs to be used to make the pile. It can thus be understood that in order to increase the effectiveness of the pile it is advantageous to increase the coefficient of friction between the pile and the ground. To do this, it is known to use a gouge to form a helical groove in the inside wall of the borehole, and subsequently, like the remainder of the borehole, the groove will be filled with the concrete or the grout so as to form a helical rib penetrating into the ground. 
     This is shown in accompanying  FIG. 1 , where reference  10  designates the cylindrical borehole, reference  12  the inside wall of the borehole, and reference  14  the helical groove formed in the wall  12  of the borehole. In this figure, there can also be seen the pile  16  with its helical rib  18  penetrating into the ground S. 
     To make the helical groove in the wall of the borehole, it is common practice to fit the bottom end of the blade or “flight” of the auger with a tooth that is used as a gouge. In certain circumstances, the gouge is stationary, i.e. it forms a groove both when the auger is going down and when it is going up. That is described in European patent EP 1 277 877 in the name of Compagnie du Sol. In order to obtain high quality for this groove, i.e. effective compacting of the walls of the rib, it is necessary in particular to control accurately the speed of rotation and the linear displacement of the auger as it goes down, and above all as it comes back up. 
     To simplify those operations, proposals have been made to use an auger fitted with a retractable gouge that projects beyond the flight of the auger for the purpose of making the groove only while the auger is rising. In general, the movable gouge is caused to be extended merely by reversing the direction of rotation of the auger. One such solution is described in EP 1 471 187 in the name of Compagnie du Sol. Such a solution presents the advantage of being simple, but in some circumstances it presents the drawback of not being certain to extend the gouge for the purpose of making the helical groove. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an auger fitted with a movable gouge in which it can be ensured that the gouge is extended effectively while the auger is rising in a manner that is reliable with the gouge being maintained in this position. According to the invention, in order to achieve this object, the auger comprises:
         a core;   at least one helical blade mounted on the outside face of the core and extending over at least a substantial fraction of the length of the core;   a movable cutter gouge suitable for taking up an active position in which the gouge projects outside the volume defined by the periphery of the blade and a retracted position in which it is disposed inside said volume; and   displacement means for displacing said gouge from its retracted position to its active position;       

     wherein:
         said core of the auger is hollow; and   said displacement means comprise:
           an additional member mounted to move in said core in translation and/or in rotation and disposed at least at the bottom end of said core; and   control means for causing said gouge to be displaced from its retracted position to its active position in response to said additional member moving relative to at least the bottom portion of said hollow core.   
               

     It will be understood that the movable gouge is moved from its retracted position to its active or extended position by the additional member moving in translation or rotation. Thus, while the auger is being raised, the gouge is extended into its active position in a manner that is very reliable. 
     In a first configuration, said additional member is a tubular element extending over the entire length of the core of the auger and having a top end connected to a pipe for feeding a slurry under pressure and whose bottom end is provided with at least one orifice for enabling the slurry to be injected into the borehole. 
     In a first embodiment, said tubular element is movable in translation in said core, and said control means cause the gouge to be displaced from its retracted position to its active position in response to the movement in translation of said tubular element. 
     In a second embodiment, said tubular element is movable in rotation in said core, and said control means cause the gouge to be displaced from its retraced position to its active position in response to said tubular element turning. 
     In this first configuration, said tubular element is a dip tube which is movable in translation in said hollow core between a retracted position in which the bottom end of the dip tube closes the bottom end of the core of the auger, and an extended position in which the bottom end of the dip tube projects from the bottom end of the auger. 
     In a second configuration, said additional member is a tube segment mounted to be movable in translation and/or in rotation in the hollow core of the auger, at its bottom end. 
     In a third embodiment, said tube segment is mounted to move in translation inside the core of the auger, and said control means cause the gouge to be displaced from its retracted position to its active position in response to the displacement of the tube segment. 
     In a fourth embodiment, said tube segment is movable in rotation inside the core of the auger, and said control means cause the gouge to be displaced from its retracted position to its active position in response to the movement in rotation of said tube portion. 
     In a fifth embodiment, the core of said auger comprises a top portion and a bottom portion that is movable in translation relative to said top portion over a predetermined length, said gouge being mounted on said bottom portion, said additional member comprises a tubular part secured to the bottom end of the top portion of said core and penetrating inside said bottom portion of the hollow core, and said control means are mounted on said tubular part in such a manner that displacement of said bottom portion of the core in translation relative to said tubular part causes the gouge to be displaced from its retracted position to its active position. 
    
    
     
       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 as non-limiting examples. The description refers to the accompanying figures, in which: 
         FIG. 1 , described above, is a vertical section through a bored pile obtained using an auger with a gouge; 
         FIG. 2  is an elevation view of a boring machine assembly including an auger with a movable gouge; 
         FIGS. 3A and 3B  show the bottom end of an auger fitted with a dip tube corresponding to a first embodiment of the invention; 
         FIG. 4  is a view from beneath showing the bottom end of the core of the auger in the first embodiment of the invention; 
         FIG. 5  shows the control circuit for controlling the movable gouge in the first embodiment of the invention; 
         FIG. 6  shows the bottom end of the auger in a second embodiment of the invention; 
         FIG. 7  is a simplified plan view of the  FIG. 6  auger; 
         FIGS. 8A and 8B  are section views on line XI-XI of  FIG. 6  showing the gouge in its “extended” position and in its “retracted” position; 
         FIG. 9  is a vertical section view of the bottom end of the auger in a variant of the first embodiment of the invention; 
         FIGS. 10A and 10B  are fragmentary perspective views of the bottom portion of the  FIG. 9  auger showing the movable gouge in its two positions; 
         FIGS. 11A and 11B  show the bottom end of the auger in a third embodiment of the invention; 
         FIG. 12  shows the bottom end of the auger in a fourth embodiment of the invention; 
         FIG. 13  is an elevation view of a fifth embodiment of the invention; 
         FIG. 14  is a side view of the fifth embodiment of the invention; 
         FIG. 15  is a vertical section view of the fifth embodiment of the invention; 
         FIG. 16  is an elevation view of the top portion of the cutter head in the retracted position in a fifth embodiment of the invention; 
         FIG. 17  is a vertical section view on line A-A of  FIG. 16 ; 
         FIG. 18  is a horizontal section view on line B-B of  FIG. 16 ; 
         FIG. 19  is a view similar to that of  FIG. 16 , the cutter head being in its extended position; 
         FIG. 20  is a vertical section view on line C-C of  FIG. 19 ; 
         FIG. 21  is a perspective view of the bottom portion of the cutter head; 
         FIG. 22  is a view analogous to  FIG. 21 , but partially cut away; and 
         FIG. 23  is a vertical section view of the bottom end of the cutter head. 
     
    
    
     MORE DETAILED DESCRIPTION 
     With reference initially to  FIG. 2 , there follows a description of the boring machine assembly including the gouge-carrying auger. In this figure, there can be seen a platform  20  with a hinged guide mast  22  with control means symbolized by actuators  24 . A carriage  26  can move along the guide mast  22 , the carriage carrying a drive head  28  for setting the auger  30  into rotation. The carriage  26  can be moved along the mast  22  by means that are not shown. It is thus possible to control both the speed of rotation of the auger using the rotary drive head  28  and also to control the linear displacement speed of the auger by controlling the displacement of the carriage  26  relative the mast  22 . 
     The auger  30  is constituted by a hollow cylindrical core  32  and by two helical blades or “flights”  34  and  36  that are angularly offset by 180°. The core  32  is terminated by a pointed tip  35 . The leading edges  34   a  and  36   a  of the flights are fitted with teeth such as  38 . 
     Naturally, it would not go beyond the invention for the auger to have a single helical flight or for the auger to have one helical flight extending along its entire height and a second helical flight extending over its end portion close to its tip  35 . 
     In the description below with reference to  FIGS. 3A to 10B , a first embodiment of the invention is described in which the additional member is a tubular part that extends over the entire length of the core of the auger, and that is preferably a dip tube. 
     Dip-tube-fitted augers are boring machines that are well known and that are described in particular in French patent application No. 2 807 455 in the name of the Applicant, which should be considered as forming an integral portion of the present description. Under such circumstances, the auger has a hollow core in which a “dip” tube can move in translation, the top end of the dip tube being connected by a hose to a source of grout or cement or more generally a slurry, and the bottom end can project from the bottom end of the auger to allow the grout or the concrete to be injected through orifices into the borehole made using the auger. The dip tube can be moved in translation relative to the auger, e.g. with the help of actuators mounted on the rotary drive head of the auger, and as a general rule the dip tube can also be moved in rotation about its longitudinal axis relative to the auger. 
     In the first embodiment of the invention, the drive means of the movable gouge are controlled by the dip tube moving in translation relative to the auger. 
       FIGS. 3A and 3B  shows the bottom portion of the auger  30  with its core  32 , its flights  34  and  36 , and its pivotally-mounted gouge  42 . A dip tube  100  is slidably mounted in the hollow core  32  and the bottom end of the dip tube is closed by a conically-shaped tip  102 . The dip tube has a plurality of orifices  104  to allow the grout or the cement to escape. When the dip tube  100  is in its raised position inside the core of the auger  32 , the dip tube and the auger are constrained to rotate together. For this purpose, the bottom face  32   a  of the core  32  of the auger is provided with notches such as  106  suitable for co-operating with studs  108  provided at the periphery of the bottom end of the dip tube, i.e. immediately above its end  102 . Thus, in the raised position, the auger and the dip tube are constrained to rotate together. In contrast, when the dip tube is in its extended position in order to allow concrete, cement, or grout to be injected, the bottom end of the dip tube  100  occupies a position such that the orifices  104  are disengaged, and naturally the studs  108  are moved out from the notches  106 . 
     In this first embodiment shown in  FIGS. 3A and 3B , moving pistons such as  110  are mounted in the notches  106 . As can be seen more clearly in  FIG. 4 , the end  32   a  of the core of the auger may have four notches  106 , each notch having two moving pistons  110  mounted therein. 
     It will be understood that when the dip tube is in its retracted position, as shown in  FIG. 3B , the studs  108  penetrate into the notches  106  and push back the pistons  110 . In contrast, when the dip tube is in its extended position, no action is exerted on a piston  110 . It is this absence of action on the pistons  110  that is used for controlling the pivoting of the moving gouge  42 . 
     As shown better in  FIG. 5 , each piston  110  is constituted by a rod  112  suitable for receiving drive from the studs  108  via a first end  112 , while its second end  112   b  co-operates with a return spring  114 . The rod  112  is associated with a piston  116  mounted to move in a cylindrical enclosure  118  filled with an incompressible liquid. The piston  116  subdivides the cylinder  118  into two respective chambers  120  and  122 . Each chamber is connected by a duct  124 ,  126  to a respective control actuator  128 ,  130 . The control actuators  128  and  130  act on the opposite sides of a pivot axis  44  of the gouge  42  so as to bring said gouge respectively into its extended position or into its retracted position. 
     It will be understood that when the dip tube is in its retracted position ( FIG. 3B ), the studs  108  act on the end  112 A of the rod  112 , thus firstly compressing the return spring  114  and secondly feeding incompressible liquid to the actuator  128 , thereby bringing the gouge  42  into its retracted position. In contrast, when the dip tube is caused to be extended relative to the auger ( FIG. 3A ), the studs cease to act on the end  112 A of the rod  112 , which is then driven by the return spring  114  so as to expel the incompressible liquid from the chamber  120  towards the actuator  130 , thereby bringing the gouge  42  into its extended position, with the gouge being held in this position by the return spring  114 . 
       FIGS. 6 ,  7 , and  8  show a second embodiment of the invention. In this embodiment, use is made of rotary movement of the dip tube relative to the auger for the purpose of controlling the movable gouge drive means. At the rotary drive head of the auger  30 , an additional motor  140  is provided, that enables rotary drive to be imparted to the dip tube  100  relative to the core  32  of the auger. More precisely, this capacity for rotation is limited by two abutments  142  and  144  formed at the top end of the core  32  of the auger and by an extension  146  secured to the outside face at the top end  100   a  of the dip tube. By turning about its longitudinal axis, the dip tube  100  can be brought into a first position in which the extension  146  is in contact with the abutment  142 , or into a second position in which the extension  146  is in contact with the second abutment  144 . 
     As shown more clearly in  FIG. 6 , in the vicinity of its bottom end, the dip tube  100  has a portion  150  set back from its outside wall  100   b , which portion is also visible in  FIGS. 8A and 8B . This set-back portion  150  constitutes a cam that can be turned about the longitudinal axis X-X′ of the dip tube and of the core  32  of the auger. Two pushers  152  and  154  are mounted level with the movable gouge  42 , the pushers being movable in translation in holes  156  and  158  formed through the core  32  of the auger. The first ends of the pushers are in contact with the outside face of the dip tube  100  while their other ends are in contact with the control portion of the movable gouge on either side of its pivot axis  44 . 
     In the first angular position of the dip tube  100 , the pusher  152  is in contact with the outside wall  100   b  of the dip tube, while the pusher  154  is in contact with the setback  150 , thus bringing the movable gouge  42  into the extended position ( FIG. 8A ). In contrast, in the second angular position, it is the first pusher  152  that is in contact with the setback  150 , while the second pusher  154  is in contact with the outside wall  100   b  of the dip tube  100 . This holds the gouge  42  in its retracted position. 
     With reference now to  FIGS. 9 ,  10 A, and  10 B, there follows a description of a variant of the first embodiment of the invention. 
     To control the displacements of the movable gouge  42 , use is made of the movement in vertical translation of the dip tube  100  relative to the core of the auger  32 . The control member is constituted essentially by a ring  160  with teeth occupying part of its circumference. The ring surrounds the tip tube  100  is and is free to rotate relative thereto, but is prevented from moving in vertical translation relative to the dip tube. The ring  160  is secured to a control finger  162  which penetrates into a helical slot  164  formed in the corresponding portion of the dip tube and constituting a cam. In reality, in order to take account of the length of the stroke of the dip tube relative to the core of the auger, the helical slot formed in the dip tube is preceded by a vertical slot which therefore has no effect on the ring. The toothed portion of the rotary ring  162  co-operates with a control portion  42   a  of the movable groove  42 , which control portion is likewise toothed. The meshing between the toothed portion of the ring  162  and the control portion  42   a  of the gouge  42  takes place through a slot  166  formed in the bottom portion of the hollow core  32  of the auger. 
     It will be understood that when the dip tube  100  is moved in the vertical direction relative to the core of the auger, the helical slot  164  acts as a cam causing the control finger  162  to turn in one direction or the other and thus turning the partially-toothed ring  162 . When the ring turns it drives the movable gouge  42  to turn about its own axis  42  so as to bring it either into the retraced position as shown in  FIG. 10A  or into the extended position as shown in  FIG. 10B . 
     As in the first embodiment, a rotation sensor can be mounted on the pivot axis  44  of the gouge  42 . The signal delivered by the sensor is conveyed to the control assembly of the auger and serves to verify that the gouge  42  does indeed occupy the desired position. 
     Nevertheless, in these two embodiments, it is preferable to use the displacement (in rotation or in translation) of the dip tube relative to the core of the auger to detect whether the gouge  42  has indeed been brought into its extended position. These movements are easily detected at the top end of the auger. 
     With reference to  FIGS. 11A and 11B  there follows a description of a third embodiment of the invention. It corresponds to the auger  30  not being fitted with a tubular element extending along the entire length of the core of the auger. The grout or concrete is then injected into the borehole by feeding the hollow core  32  of the auger therewith. 
     In this embodiment, the bottom end of the auger is fitted with a movable part  170  constituted by a segment of tube  172  of length that is short relative to the length of the auger and closed at its bottom end by an end wall  174  of conical shape forming the pointed tip of the auger. The tube segment  172  is free to move in translation in the hollow core of the auger and is provided with orifices  176  through which the grout or concrete exits. In addition, when the movable part  170  is in the retracted position inside the auger, the movable part is constrained to rotate together therewith by studs  178  and notches  180  formed in the bottom edge of the core  32  of the auger. 
     During downward movement of the auger, corresponding to digging the borehole, the movable part  170  is held retracted inside the core of the auger ( FIG. 11A ). In contrast, when the auger is raised and a grout or concrete is injected into its hollow core, the pressure of the material on the movable part  170  and also the action of the surrounding ground causes the movable part  170  to move in translation relative to the core of the auger, with the amplitude of this relative movement being limited, for example, by abutments (not shown in the figures). This is shown in  FIG. 11B . 
     This result can also be obtained by interposing a spring between the core of the auger and the movable part. While the auger is moving downwards, the spring is compressed. When the upward movement is started, the spring can expand and cause the movable part to be extended. 
     This relative movement in translation serves to control the pivoting of the gouge  42  via drive means that are represented symbolically by reference  181 . 
     The control means may be of the type shown in  FIGS. 6 to 8  (hydraulic) or of the type shown in  FIGS. 9 and 10  (mechanical), with the tube segment  172  of the movable part replacing the dip tube. 
       FIG. 12  shows a fourth embodiment of the invention. 
     In this embodiment, the auger  30  is fitted with a movable part  170  that is mounted to slide in the hollow  32  of the auger. The difference relative to the third embodiment consists in the fact that the outside face of the tube portion  172  and the bottom end of the inside face of the hollow core  32  of the auger has complementary portions in relief  182  suitable for converting the movement in translation of the movable part  170  relative to the core of the auger when the auger rises, into a movement in rotation. It is this movement that is used to control the displacement of the gouge  42 . 
     The control means represented by reference  184  may then be of the type shown in  FIGS. 6 and 8 , with the tube segment  172  replacing the dip tube. 
     In the embodiment described with reference to  FIGS. 3 to 12 , the movable gouge is caused to turn in order to go from its retracted position to its extended or active position. It will nevertheless be understood that by making modifications within the competence of the person skilled in the art, the control means could be arranged so that the movable gouge is caused to move in translation in a direction that is radial relative to the axis of the core of the auger. 
     With reference below to  FIGS. 13 to 23 , there follows a description of a fifth embodiment of the invention. 
     In this embodiment, the auger is constituted by a cutter head  220  mounted at the bottom end of a string of hollow rods, these rods being provided with respective external helical blades or “flights”. The description below relates essentially to the cutter head  220  that serves to cause the gouge  240  to move. As explained below, the gouge is moved in translation along a radial direction that is substantially orthogonal to the longitudinal axis of the cutter head  220 . Nevertheless, it will readily be understood that by a simple modification within the competence of the person skilled in the art, this movement could be a pivoting movement about an axis associated with the cutter head. 
     The cutter head  220  comprises an top portion  222  and a bottom portion  224 . The top end  222   a  of the cutter head is connected to a string of flight rods by connection means  226 . The bottom end  222   b  of the top portion is extended downwards by a tubular extension  228 . The top portion  222  is constituted by a cylindrical body  230  and a flight  232 . 
     The bottom portion  224  is generally in the form of a cylindrical hollow rod  234  provided with a flight  236 . The extension  228  of the bottom portion  222  is slidably mounted in the hollow rod  224  of the bottom portion  224 . 
     The bottom portion  224  is connected to the top portion  222  by connection means  238 . The connection means  238  constrain the portions  222  and  224  in rotation while allowing the portions  222  and  224  to perform relative movement in translation over a limited amplitude. 
     The bottom end  224   a  of the bottom portion  224  is provided with a movable gouge (or cutter tooth)  240 . The gouge  240  is connected to displacement means  242  for displacing the gouge. 
     The bottom end  228   a  of the tubular extension  228  is provided with control means  244 . 
     The control means  244  co-operate with the displacement means  242 . 
     As explained in greater detail below, when the top portion  222  bears against the top end  224   b  of the bottom portion, the gouge  240  is in its retracted position as shown in  FIG. 13 . This corresponds to the auger moving downwards. When the top portion  222  and the bottom portion  224  are spaced apart, as shown in  FIG. 14 , then the control means  244  act on the displacement means  242  to move the gouge  240  into its extended position and to hold it there. This corresponds to the auger being moved upwards. 
     With reference below to  FIGS. 16 to 20 , there follows a description of a preferred embodiment of the connection means  238 . 
     As shown in  FIGS. 16 to 20 , the top end  234   a  of the hollow rod  234  is secured to a hexagonal female connection box  246 . The bottom end  222   b  of the top portion  222  is secured to the top portion  248   a  of a hexagonal male drive member  248 . The bottom end  248   b  of the male member  248  is secured to the top end  228   b  of the extension  228 . The male and female members  246  are constrained to rotate together. 
     The top end  246   a  of the female member is provided with a retaining ring  250  secured to the female drive box  246  and projects out from the inside wall  246   c  of the drive box  246 . The outer wall  248   c  of the male member  248  is provided with a shoulder  252  that co-operates with the retaining ring  250 . 
     When the top portion  222  is spaced apart from the bottom portion  224 , the amplitude of the displacement is limited by co-operation between the ring  250  and the shoulder  252 . 
     With reference below to  FIGS. 21 to 23 , there follows a description of a preferred embodiment of the control and displacement means  242 ,  244 . 
     Close to the bottom end  224   a  of the bottom portion, a protected volume  254  is defined by the helix  256  of the flight, by a side wall  258 , and by a bottom plate  259 . In the volume  254 , a horizontal-axis guide tube  260  is secured to the rod  234  of the bottom portion  224 . The tube  260  extends radially. A piston  262  is mounted to slide in the tube. The gouge  240  is secured to a first end  262   a  of the piston. The second end of the piston is in the form of an inclined surface  264 . 
     The bottom end of the rod  234  is provided with a slot  266  in which a wedge-shaped control member  268  can move vertically. The wedge  268  is secured on the bottom end of the extension  228 . Vertical displacement of the extension  228  is converted into horizontal movement of the gouge  240  by co-operation between the surface  264  and the wedge  268 . When the wedge  268  does not co-operate with the surface  264 , a return system constituted by a lever  270  connected to the piston  262  and a return spring  272  causes the gouge  240  to be retracted. 
     The operation of this fifth embodiment of the invention is as follows: 
     When the cutter head  220  is moving downwards and in rotation to dig the borehole, the top portion  222  bears against the bottom portion  224 . The extension  228  is in its low position in the rod  234  of the bottom portion  224 , and the wedge  268  does not act on the inclined surface  264 . The gouge  240  is held in its retracted position. 
     When the cutter head  220  is moving upwards, the top and bottom portions  222  and  224  are spaced apart from each other. The wedge  268  occupies a high position and acts on the inclined surface  264  of the piston  262 . The gouge  240  is then taken to its extended position and it is held in this position so long as traction is exerted on the top portion  222  of the cutter head.