Abstract:
A tool adapter includes a holder structured to be attached to a machine tool and a tool receiver structured to receive a portion of a rotary cutting tool therein. The tool receiver being mounted in the holder so as to be rotatable to a limited extent. The tool receiver being mounted in the holder so as to be elastically resilient in the axial direction.

Description:
[0001]    This application claims priority to German application 10 2011 102 563.8 filed May 26, 2011, the contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates generally to tool adapters having a holder, which can be attached to a machine tool, and having a tool receiver, in which a tool can be received, in particular a drilling tool, the tool receiver being mounted on the holder so as to be rotatable to a limited extent. 
         [0004]    2. Background Information 
         [0005]    An example tool adapter for which the present invention improves upon is shown in U.S. Pat. No. 6,082,236. Here, the tool receiver is realized as a collar, which is rotatably mounted inside the holder by means of two bearing rings. Vulcanized-in between the outer surface of the tool receiver and the inner surface of the holder there is a rubber bushing, which limits the rotation of the tool receiver relative to the holder. A torque can be transmitted from the holder to the tool receiver via the rubber bushing, while, at the same time, vibrations that occur can be damped. In this way, it is also possible to reduce noise produced during the machining of a workpiece by means of a tool clamped in the tool receiver. 
         [0006]    While useful for damping vibrations to a certain extent, there is still room for improvement in terms of vibration dampening capabilities over conventional tool adaptors. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a tool adapter of the type stated at the outset designed in such a way that improved vibration damping is achieved. 
         [0008]    To achieve such improved vibration damping it is provided, according to the invention, that the tool receiver is mounted on the holder so as to be elastically resilient in the axial direction. This makes it possible also to damp vibrations occurring in the axial direction. 
         [0009]    Preferably, an elastic element is provided between the tool receiver and an end face of the holder, such that the tool receiver is received in the holder so as to be elastically resilient in the axial direction. An elastic element, for example a disk or plate composed of rubber or an elastomer, enables the desired axial resilience to be obtained with little resource expenditure, while, at the same time, enabling a compact structural form to be achieved. 
         [0010]    According to a preferred embodiment, it is provided that the tool receiver is disposed inside an opening of the holder, which opening is open at an end face of the holder. In this way, the tool receiver can be mounted inside the holder with little resource expenditure. 
         [0011]    Preferably, it is provided that the tool receiver is realized as a bushing, which is mounted without play in the opening of the holder. Here, “without play” means a mounting that allows the desired movability in the circumferential direction (i.e. rotatable) and in the axial direction (i.e. displaceable) but, at the same time, ensures precise guiding of the tool receiver in the holder, in particular in respect of the center axis of the tool receiver. In other words, the guiding without play ensures that the tool receiver cannot become tilted or skewed inside the holder. 
         [0012]    According to a preferred embodiment, provided on the end face of the holder there is a clamping element, which presses the tool receiver into the opening. The clamping element, which can be realized, for example, as a bearing contact disk, closes the opening in the axial direction, such that the tool receiver is reliably held inside the holder. 
         [0013]    Preferably, in this case, disposed between the clamping element and the elastic element there is a bearing ring, by means of which the bias of the elastic element can be set. This makes it possible to apply a settable bias to the elastic element, which is responsible for damping in the axial direction, such that the tool adapter can be set to differing vibration frequencies. This can be effected in a technically simple manner, in that bearing rings of differing thicknesses are available, and the bearing ring that is suitable for the respective application is selected. 
         [0014]    According to a preferred embodiment, a torque transmission element is provided, which acts positively between the tool receiver and the holder. This ensures a reliable transmission of torque from the holder to the tool receiver. Preferably, in this case, a damping element is provided, which acts in the circumferential direction between the tool receiver and the holder. The damping element ensures that vibrations acting in the circumferential direction are damped. 
         [0015]    According to a design of the invention, it is provided that the damping element surrounds the torque transmission element in the manner of a ring. Such a design enables vibrations to be damped in both circumferential directions with little resource expenditure, while, at the same time, allowing the axial displacement of the tool receiver relative to the holder that is necessary for damping vibrations acting in the axial direction. 
         [0016]    According to a design of the invention, it is provided that the torque transmission element is fixedly connected to the tool receiver in the circumferential direction and projects into a cutout in the holder whose dimensions, at least in the circumferential direction, are greater than the dimensions of the torque transmission element. Preferably, in this case, the damping element fills the space that remains between the torque transmission element and the edge of the cutout, so as to ensure that the torque transmission element is driven positively in the holder, the damping element being interposed. 
         [0017]    The torque transmission element can be realized in the manner of a feather key, such that elongate side walls are available for the transmission of torque. Preferably, the torque transmission element is arranged so as to be settable, such that the bias exerted upon the damping element can be altered. This makes it possible for the damping characteristic in the circumferential direction also to be set according to the respective applications. 
         [0018]    According to a design of the invention, it is provided in this case that the torque transmission element widens outwardly, such that it can exert a bias upon the damping element in the radial direction. In this way, the bias exerted upon the damping element can be set with little resource expenditure, namely, in that the torque transmission element can assume differing positions on the tool receiver in the radial direction. 
         [0019]    According to a design of the invention, it is provided that the torque transmission element engages in a receiver in the tool receiver. The receiver defines a type of sliding seat, such that the torque transmission element is mechanically fixed in the circumferential direction, but can be set in the radial direction. The torque transmission element in this case is preferably screwed to the tool receiver. In this way, the torque transmission element can be reliably attached to the tool receiver, while, at the same time, it can be set in the radial direction. 
         [0020]    Preferably, a plurality of torque transmission elements are provided, disposed in a distributed manner around the center axis of the tool adapter. For example, three or four torque transmission elements can be disposed at an angle of 120° or 90°, which reduces the load on each individual torque transmission element and increases the total service life of the tool adapter. 
         [0021]    Preferably, it is provided that a sleeve is provided, which surrounds the holder on the outside. The sleeve serves, on the one hand, as protection against soiling and other influences. On the other hand, the sleeve serves as a support, in particular in the region of the torque transmission elements, so as to prevent the damping element from being displaced outward there. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
           [0023]      FIG. 1  shows a sectional view of a tool adapter according to the invention; 
           [0024]      FIG. 2  shows a sectional view of the holder of the tool adapter from  FIG. 1 ; 
           [0025]      FIG. 3  shows a perspective view of the holder of  FIG. 2 ; 
           [0026]      FIG. 4  shows a sectional view of the tool receiver of the tool adapter from  FIG. 1 ; 
           [0027]      FIG. 5  shows a sectional view of the tool receiver of  FIG. 4  with, attached thereto, a torque transmission element, a damping element and an elastic element; 
           [0028]      FIG. 6  shows a section along the plane VI-VI from  FIG. 5 ; and 
           [0029]      FIG. 7  shows an alternative design, in a section along the plane VII-VII from  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    Directional phrases used herein, such as, for example, left, right, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. Identical parts are provided with the same reference number in all drawings. 
         [0031]      FIG. 1  shows a tool adapter  5 , which serves to receive a tool  7 , indicated schematically, in particular a drilling tool. The drilling tool can be clamped in the tool adapter  5  by means of clamping means  8  (which are merely indicated). The tool adapter  5  is provided to be clamped into a machine tool via a connection side  9 , such that the tool  7  can be driven, for example, made to rotate. 
         [0032]    The tool adapter  5  contains a holder  10  (see also  FIGS. 2 and 3 ), which has a generally collar-type form, having a center axis M. The holder  10  is made of metal and, in its interior, has a cylindrical opening, such that a cylindrical inner surface  12  is constituted in the holder  10 . The opening in the holder  10  is delimited, at the end that faces away from the end face, by a base surface  14 , which is aligned perpendicularly in relation to the center axis M. 
         [0033]    Disposed in the wall of the holder  10 , distributed around the circumference, are a plurality of window-type cutouts  16 , which have two lateral surfaces  18  opposite each other in the circumferential direction, and aligned parallel to each other and, perpendicular thereto, short end faces  20 . 
         [0034]    Disposed inside the holder  10  is a tool receiver  22  (see, in particular,  FIGS. 3 and 4 ), which is realized in the form of a collar and inside which the tool  7  can be disposed. The tool receiver  22  is likewise composed of metal, and has a cylindrical outer surface  24  whose dimensions are matched to the dimensions of the inner surface  12  of the holder  10  such that the tool receiver  22  is received without play inside the holder. “Without play” in this case means that the holder  10  defines the alignment of the tool receiver  22  in a precise manner, while, at the same time, the tool receiver can be rotated inside the holder  10 . 
         [0035]    On its outer surface the tool receiver  22  is provided with a plurality of receivers  26  ( FIG. 4 ), which correspond to the cutouts  16  in the holder  10  and in each of which a torque transmission element  28  can be disposed, which is realized so as to be similar to a feather key (see, in particular,  FIG. 5 ). Each torque transmission element  28  thus has an elongate form, whose longitudinal axis extends parallel to the center axis M, the radially inward lying portion engaging substantially without play in the receiver  26  in the tool receiver. For the purpose of fastening the torque transmission elements  28 , respectively two setting screws  30  are provided, which can be screwed into threaded holes  32  in the tool receiver  22 . When in the mounted state, the torque transmission elements  28  are located centrally in the cutouts  16  of the holder  10 , the dimensions of the cutouts  16  being greater than the dimensions of the torque transmission elements  28 . 
         [0036]    For the purpose of damping vibrations in the circumferential direction, a plurality of damping elements  34  ( FIGS. 5-7 ) are provided, which are each disposed around one of the torque transmission elements  28 , and which are composed of rubber or an elastomer. The damping elements  34  are generally realized in the form of a ring, and completely fill the space between the torque transmission elements  28  and the walls  18 ,  20  of the cutouts  16 . Even in their initial state, these damping elements have a certain bias. In addition, this bias can be set by means of the torque transmission elements  28 . 
         [0037]    For this purpose, it is provided that each torque transmission element  28  widens outwardly in the radial direction, in that projecting contact pressure surfaces  36  are provided. These contact pressure surfaces  36  extend around the entire circumference of the torque transmission element  28  and displace the damping element  34  radially inward and both in the circumferential direction and in the axial direction when the damping element is clamped inward in the radial direction, against the tool receiver  22 , by means of the setting screws  30 . The angle of the contact pressure surfaces  36  relative to the radially extending center axis of the torque transmission elements  28  is in the range from 15° to 75°, 45° being preferred. 
         [0038]    To enable a setting to be performed, in the initial state a gap  38  is provided between the underside of the torque transmission element  28  and the base of the receiver  26 . When the setting screws  30  are screwed in further, the gap  38  is reduced, as a result of which the damping element  34  is pressed more firmly against the lateral surfaces  18  and the end faces  20  of the corresponding cutout  16 . As can be seen in  FIG. 7 , shims  50  can also be disposed between the base of the receiver  26  and the torque transmission elements  28 . This enables the bias of the damping elements  34  to be set. 
         [0039]    For the purpose of damping in the axial direction, an elastic element  40  (see  FIGS. 1 and 5 ), realized in the form of a disk or plate, is disposed between the base surface  14  of the opening of the holder  10  and the tool receiver  22 . The elastic element  40  is thickened along its circumference, such that, in combination with a bevel  42  of the tool receiver  22 , a wedge effect is achieved. The elastic element, likewise, is composed of rubber or elastomer. 
         [0040]    Disposed on the end face of the holder  10  there is a clamping element  44 , which is realized as a ring or bearing contact disk. This clamping element is attached to the end face of the holder  10 , so as to be settable, by means of setting screws  46 , the clamping element  44  being supported on the tool receiver  22  via a bearing ring  48 . The setting screws  46  can be used to set the strength of bias of the elastic element  40  on the base surface  14  of the holder  10 . The axial bias is set through differing thicknesses of the bearing ring  48 . 
         [0041]    As can be seen in the sectional view of the alternate embodiment of  FIG. 7  in particular, disposed on the outside of the holder  10  there is a sleeve  47 , which fixedly surrounds the holder. On the one hand, the sleeve  47  prevents soiling from accumulating in the region of the cutouts  16  and the torque transmission elements  28 . On the other hand, the sleeve prevents the damping elements  34  from being displaced radially outward as loads occur. In other words, the sleeve  47  serves as a support for the damping elements  34 . 
         [0042]    When the tool  7  is to be driven, a torque is transmitted from the holder  10  to the tool receiver  22  and from there to the tool  7 . Since the tool receiver  22  is elastically mounted inside the holder  10 , vibrations that occur during machining performed by means of the tool  7  undergo extensive damping. On the one hand, this is effected in the axial direction, owing to the elastic element  40 . On the other hand, vibrations are damped in the circumferential direction, since the tool receiver  22  is coupled to the holder  10  in an elastically resilient manner via the torque transmission elements  28 , which are guided in the receivers  26 , and via the damping elements  34 . A high load capacity and, at the same time, a long service life are ensured because the damping elements are supported over a large area, both on the lateral surfaces  18  in the holder  10  and on the side walls of the torque transmission elements  28 . A particular advantage of the tool adapter  5  described consists in that the bias of the elastic element  40  and of the damping elements  34  can be set. It is thereby possible to set the frequencies at which a particularly high damping is effected. A maximum of vibration damping can thus be achieved for any desired machining, such that there is a maximum reduction of the noise produced during machining. 
         [0043]    As can be seen in  FIG. 7 , the outside of the damping elements  34  can also be oblique, such that they are supported on the holder via an obliquely aligned bearing contact surface. Suitable angles are in the range from 15° to 75°, 45° being preferred. The effect of the oblique bearing contact surface is that the outside of the damping elements is subjected not only to compression, but also to shear, this being advantageous for vibration damping. 
         [0044]    While a specific embodiment of the invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to the details provided herein could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.