Abstract:
A mounting attachment for a penetrating tool such as a drilling head on a machine with a machining shaft includes a support provided with means for coupling to a machine; a tool holder provided with means for fixing a tool; means for axially guiding the tool holder relative to the support; means for linking in rotation the tool holder and the support; and elastically deformable suspension means for suspending the tool holder from the support, the suspension means allowing axial translation and self-sustaining reciprocating or vibrating axial movements of the tool holder resulting from a controlled displacement of the support with respect to a workpiece.

Description:
This application is a continuation of International Application No. PCT/FR98/01454, filed Jul. 7, 1998 and designating the U.S. This PCT application is incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to the field of operations of machining workpieces, such as making drillings, particularly very deep drillings. 
     DESCRIPTION OF THE RELATED ART 
     Drilling machines are known which comprise a mechanism designed, as the drilling head advances, to bring about forced reciprocating movements over a predetermined stroke, these forced movements causing the thickness of the chip to vary, allowing it to break up and thus making it easier to remove. In spite of these advantages, such mechanisms are complicated, bulky and expensive. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a penetrating-tool mounting attachment of a particularly simple structure which makes it possible to bring about reciprocating movements of the tool as it advances. 
     The attachment for mounting on a machine a penetrating tool such as a drilling head, having a machining axis, comprises, according to the invention, a support equipped with means of coupling it to a machine, a tool holder provided with means for attaching a tool, means for axially guiding the tool holder with respect to the support, means for rotationally connecting the tool holder and the support, and elastically deformable means for connecting the tool holder and the support in terms of axial translation, the said elastically deformable means of connection in axial translation being dimensioned such as to produce self-sustained reciprocating or vibrating axial movements of the tool holder during the controlled relative advance of the support with respect to the workpiece. 
     According to the invention, the mounting attachment may advantageously comprise means for adjusting the stiffness of the said elastically deformable means of connection in axial translation. 
     According to an alternative form of the invention, the said guide means comprise two axially deformable annular plates comprising an inner part and an outer part which are connected respectively to the support and to the tool holder and which are joined together by non-radial branches. 
     According to one alternative form of the invention, the said guide means comprise a ball-type slideway. 
     According to another alternative form of the invention, the said elastically deformable connecting means comprise at least one spring leaf arranged in a radial plane, which is fixed at two points spaced along its length to, on the one hand, the support and, on the other hand, the tool holder. 
     According to a preferred alternative form of the invention, the said elastically deformable means of connection in axial translation comprise two spring leaves arranged parallel to each other in a radial plane and one on each side of the axis, the said leaves being fixed to, on the one hand, the support and, on the other hand, the tool holder, at a mid-point and at two points spaced from this mid-point on each side thereof in the direction of their length, respectively. 
     According to the invention, means are preferably provided for adjusting the distance between the said points of attachment of the said spring leaf or leaves. 
     According to another alternative form of the invention, the said elastically deformable means of connection in axial translation comprise at least one essentially cylindrical spring. 
     According to the invention, the said cylindrical spring may advantageously comprise a cylinder which, in its wall, has offset openings so as to form peripheral portions which are elastically deformable in the axial direction. 
     According to the invention, the ends of the said cylindrical spring are preferably fixed to the support and to the tool holder, respectively. 
     According to the invention, the support preferably comprises a cylindrical part for coupling to the machine, extended by a cylindrical part into which the tool holder at least partially extends. 
     According to the invention, in an alternative form, the mounting attachment comprises means for conveying fluid to the tool, comprising a duct running axially through the support, a duct running axially through the tool holder and a pipe connecting the said ducts and which is axially deformable or flexible. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The present invention will be better understood from studying attachments for mounting on a machine a penetrating tool such as a drilling head, which are described by way of nonlimiting examples with reference to the drawing, in which: 
     FIG. 1 depicts a side view in elevation of a first mounting attachment according to the invention; 
     FIG. 2 depicts a view from beneath, from the tool end, of the mounting attachment of FIG. 1; 
     FIG. 3 depicts a radial section on III—III of the aforementioned mounting attachment, identified in FIGS. 1 and 5; 
     FIG. 4 depicts an axial section on IV—IV of the aforementioned mounting attachment, in the plane of FIG.  1  and identified in FIG. 3; 
     FIG. 5 depicts an axial section on V—V of the aforementioned mounting attachment, at right angles to the cutting plane of FIG. 4, identified in FIGS. 1 and 3; 
     FIG. 6 depicts an axial section through a second mounting attachment according to the present invention; 
     and FIG. 7 depicts an axial section through a spring of the mounting attachment of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 to  5 , it may be seen that these depict an attachment, identified overall by reference  1 , for mounting a penetrating tool consisting of a drilling head  2  on a machine  3  with a vertical machining axis. 
     The drilling head  1  comprises an axial support identified overall by the reference  4 , which comprises a cylindrical part  5  engaged in a bore  6  of a chuck  7  of the machine  3  and immobilized in this bore  6  by a radial screw  8 . 
     The support  4  further comprises a cylindrical part  9  which extends the cylindrical part  5  downwards, which is of larger diameter than this cylindrical part  5  and which is connected to the latter by a radial disk  10 . This cylindrical part  9  comprises, essentially at its center, two opposed large openings  11  and two opposed flats  12  which are formed in the remaining upper parts over the openings  11 . 
     Secured against the flats  12 , via screws  13 , are the vertical branches  14  of angle brackets  15 , the horizontal branches  16  of which extend through the upper part of the openings  11  of the cylindrical part  9 , the undersides of these branches  16  having aligned slideways  16   a.    
     The mounting attachment  1  further comprises an axial tool holder  17  which comprises a cylinder  17   a  which runs axially inside the cylindrical part  9  of the support  4  some distance from its wall. 
     The upper part and the lower part of the cylinder  17   a  are connected to the upper part and to the lower part of the cylindrical part  9  of the support  4  on each side of the openings  11 , by suspension and axial-guidance disks  18 . 
     The disks  18  exhibit inner rings  19  fixed axially against shoulders  20  of the cylinder  17   a , by virtue of nuts  21 , and outer rings  22  fixed axially in the cylindrical part  9  of the support  4 , between a shoulder  23  of this cylindrical part  9  and axial screws  24 , via cylindrical spacer pieces  25  and  26 . The intermediate spacer piece  25  having opposed openings  25   a  which correspond to the opposed openings  11  of the cylindrical part  9 . Furthermore, the lower rings  19  and the outer rings  22  of the disks  18  are connected by branches  27  which do not run radially, their ends being angularly offset by about 60°. 
     The mounting attachment  1  further comprises two spring leaves  28  which run parallel to each other in a radial plane, one on each side of the cylinder  17   a  of the tool holder  17  and underneath the branches  16  of the angle brackets  15 . 
     The central parts of the leaves  28  are engaged in opposed lateral slits  29  in the cylinder  17   a  of the tool holder  17 . On each side of and at a distance from their central part, the leaves  28  are secured to the slideways  16   a  of the angle brackets  16  by sliders  30  and screws  31 , so that they are adjustable in their lengthwise direction. 
     The upper sides of the slits  29  of the cylinder  17   a  are V-shaped so that they have a point  32  against which the leaves  28  rest. Furthermore, the cylinder  17   a  of the tool holder  17  has axial counterbores  33  which open into the slits  29  via their undersides and in which are arranged bearing fingers  34  held in these counterbores  33  by a peripheral ring  35  surrounding the cylinder  17   a.    
     Screws  36  engaged at an angle in the cylinder  17   a  of the tool holder  17  rest against inclined undersides  37  of the fingers  34 . The screws  36  allow the fingers  34  to be shifted upward so that their rounded upper ends  37   a  rest against the leaves  28  and press these against the tops  32  of the slits  29 . Thus, the central parts of the leaves  28  are trapped axially, by point contact, between the tops  32  and the fingers  34 . 
     The screws  31  of the slideways  16  and the screws  36  are accessible through the openings  11  and  25   a.    
     Furthermore, the lower part of the cylinder  17   a  of the tool holder  17  has an axial bore  38  in which the upper part of the drilling head  2  is attached, using a binding screw  39 . 
     Finally, the chuck  7  of the machine  3 , the cylindrical part  5  of the support  4  and the tool holder  17  have axial passages  40 ,  41  and  42 . The axial passage  42  in the support  4  and the axial passage  42  in the tool holder  17 , which are some distance apart, are connected by a flexible serpentine pipe  43 . Thus, the passage  40  in the chuck  7 , the serpentine pipe  43  and the axial passage  42  in the tool holder  17  constitute a duct for conveying a fluid to an axial passage  44  in the drilling head  2 . 
     The mounting attachment  1  which has just been described can be used as follows. 
     When the chuck  7  of the machine  3  and the support  4  which is connected to it move with respect to a workpiece, not depicted, that is to be drilled, under the effect of means for the controlled and constant advance of the machine  3 , the drilling forces are transmitted to the tool holder  17  by the spring leaves  28 . The guide disks  18  and the serpentine coil  43  are constructed in such a way as to be able to deform in such a way that their deformations have no appreciable influence on the said forces. 
     The forces associated with the penetration of the drilling head causes the spring leaves  28  to flex about the tops  32  of the slits  29  and about the opposed fingers  24  as far as the sliders  30 . 
     As the stiffness of the spring leaves  28  and the position of the sliders  30  along the slideways  16   a  are well chosen, a phenomenon of self-sustained vibration causing reciprocating axial movements or axial oscillations of the drilling head  2  can therefore occur during the controlled advance of the support  4 , and may advantageously be synchronized with the relative rotation of the drilling head  2  with respect to the workpiece that is to be drilled. 
     These reciprocating movements which are self-sustaining as the drilling head  2  advances may cause a variation in the thickness of the chip or chips formed. 
     Insofar as the retreating movement of the drilling head  2  with respect to the advance of the support  4  is such that its cutting edge or edges approach, reach, or pass beyond the surface machined by them, this variation in thickness may be such that the chips break up intermittently. 
     Thus, it may be far easier for the chips to be removed, particularly under the effect of the fluid conveyed through the attachment  1  and the drilling head  2 . 
     Furthermore, particularly when drilling to a great depth, the self-sustaining axial oscillations or reciprocating axial movements of the drilling head  2  may, with or without the breaking-up of the chip or chips formed, allow any vibrations, particularly axial and/or transverse vibrations, of the drilling head with respect to the workpiece, to be absorbed, at least in part. 
     In consequence, the mounting attachment  1  makes it possible to improve the straightness of the drillings, reduce drill wear and improve the quality of the internal surface of the holes. 
     Referring now to FIGS. 6 and 7, it may be seen that a simplified drilling head has been depicted, identified in general using the reference  45 , which comprises a support  46  and a tool holder  47 . 
     The support  46  has a cylindrical part  48  engaged in a bore  49  of a chuck  50  of a machine  51  and a cylindrical part  52  which extends the cylindrical part  48  and which has a slightly larger diameter. The tool holder  47  is in the form of a cylinder engaged inside and some distance from the cylindrical part  52  of the support  46 . 
     Placed between the lower part of the tool holder  48  and the lower part of the cylindrical part  52  of the support  46  is a ball-type slideway  53  allowing the tool holder  47  to be guided axially with respect to the support  46 . 
     The upper part of the tool holder  47  has a reduced diameter creating a shoulder  54 . Placed between this shoulder  54  and the bottom  55  of the cylindrical part  52  of the support  46  is a spring  56  in the form of a cylinder. The upper part of this spring  56  is fixed to the upper part of the cylindrical part  52  of the support  56  by radial screws  57  and the lower part of the spring  56  is connected to the tool holder  47  by radial screws  58 . 
     The tool holder  47  has a bore  59  in which a drill head  60  is secured. 
     As in the previous example, the chuck  50 , the cylindrical part  52  of the support  46 , the tool holder  47  and the drilling head  60  have a pipe for conveying a fluid, the duct in the support  46  and the duct in the tool holder  47  being connected, as before, by a serpentine coil  61 . 
     Referring more specifically to FIG. 7, it may be seen that the cylindrical spring  56  is constructed from a cylinder, in the wall of which oblong openings  62  are machined in the peripheral direction, these openings being offset from one another in such a way as to form peripheral portions  68  which can be deformed elastically in the axial direction. 
     The mounting attachment  45  which has just been described with reference to FIGS. 6 and 7 works in the same way as the mounting attachment  1  described with reference to FIGS. 1 to  5 . 
     Thus, the forces of the penetration of the drilling head  60  on the workpiece during the controlled advance of the support  46  with respect to the workpiece, not depicted, are achieved via a cylindrical spring  56 , without the ball-type slideway  53  and the serpentine coil  61  having an appreciable influence on these forces. 
     The rotational forces are taken up by the screws  57  and  58  and by the cylindrical spring  56  in its peripheral direction. The axial forces are transmitted by the cylindrical spring  56 , particularly by its inner portions  63 . 
     To the extent that the dimensions and openings  62  of the spring  56  are correctly selected, self-sustaining reciprocating vibrating movements or axial oscillations of the drilling head can occur during the controlled advance of the support  46 .