Patent Publication Number: US-2004042865-A1

Title: Rotary tool

Description:
[0001] The invention relates to a rotary tool having the characteristics specified in the preamble of claim 1, a drilling or milling cutter in particular.  
       [0002] In a state-of-the art rotary tool disclosed in EP-A-0 296 460 the cutting circle diameter is modified by rotating the cutting element carrier mounted so as to be offset eccentrically from the rotation axis as a function of the torque acting on tool during operation. For this purpose the cutting element carrier is pretensioned by a torsion spring in a first stop position which corresponds to a first cutting circle diameter. Rotation against the action of the torsion spring from this position occurs if the operating torque exceeds a threshold value. This results in automatic setting of different cutting circle diameters for trimming machining processes and for scrubbing, which is carried out with higher operating torque.  
       [0003] DE-U-91 01 149 discloses a generic tool with a locking mechanism by means of which the cutting element carrier may be locked with the head in selected rotary positions which correspond to the desired cutting circle diameter of the cutting edge of the cutting element. The tool disclosed has on one of its ends a tapering mounting shank conforming to DIN (German Industrial Standards) for securing the tool on a metalworking machine, and on the other end the tool is provided with a cutting plate which is mounted in a bracket in the tool resembling a drill rod. The center of the machining diameter of the cutting tools is eccentrically offset from the rotation axis of the tool proper; for the purpose of setting the eccentric offset, diagonal gear elements of the tool holder and of the cutting element carrier are disengaged from the cutting plate, and after rotation about the longitudinal axis of the tool clockwise/counterclockwise, re-engaged with the cutting plate, against the action of a coupling mechanism and accordingly against the force of a pressure spring.  
       [0004] Consequently, the disclosed solution makes it possible, in the case of a rotary tool, not only to adjust the cutting circle diameter between two cutting circle diameters provided for special machining processes, but also rapidly to modify the cutting circle diameter by predetermined adjustment amounts even when small changes are to be made. However, the disclosed solution involves a large number of components which result in correspondingly high space requirements; the unbalanced behavior associated with such components must be overcome in order to achieve good machining accuracies.  
       [0005] In addition, DE-A-33 12 990 discloses provision, in a tool in which a lateral face of a head enclosing a bearing bore is guided on one of the locating faces of the flange of the cutting element carrier, of locking recesses which act in conjunction with a spring-loaded catch element provided in the flange of the cutting element carrier to form rotary catches between cutting element carrier and head, in order thus to adjust the cutting elements held so as to be adjustable to different boring diameters.  
       [0006] On the basis of the generic state of the art the object of the invention is to provide a rotary tool which has a small number of parts and thus may be produced by a simple process and cost-effectively. Another object of the invention is achievement of a low space requirement in order thus to counteract the occurrence of unbalanced conditions generating problems. The object as thus formulated is attained by a rotary tool having the characteristics specified in patent claim 1 as a whole.  
       [0007] In that, as specified in the descriptive portion of claim 1, the cutting element carrier has an opening serving as seat for a cutting plate, which opening extends from the frontal surface of the flange into the bearing journal, and in that means are provided for tensioning the cutting plate, in particular a tightening screw seated in the bearing journal, which screw is accessible from the circumference of the head into the bearing bore when the cutting element carrier is in a selected rotary position, a tool is obtained which is characterized by a low number of components and thus may be produced simply and cost-effectively. Because of the low number of components the structural weight is also low, so that the occurrence of unbalanced conditions creating problems is counteracted to the greatest extent possible.  
       [0008] The value selected for the eccentricity of the adjustment axis in the case of the tool claimed for the invention relative to the tool axis and the value of the radial distance at which the cutting edge of the cutting element is mounted on the cutting element carrier determine the amount of change in the cutting circle diameter per angular unit of rotation of the cutting element carrier relative to the head of the shank. The relationships may be configured by the simplest of means so that a desired precision adjustment of the cutting circle diameter is made on rotation of the cutting element carrier, which is then fixed in the respective rotary position by the locking mechanism against further rotation.  
       [0009] In one advantageous exemplary embodiment the cutting element carrier has for the purpose of forming the rotary bearing on the head of the shank a bearing journal which is mounted in a bearing bore eccentrically relative to the axis of rotation of the shank and suitably rotatably mounted concentrically relative to the head, the cutting edge of the cutting element being mounted eccentrically offset at a radial distance from the axis of the bearing journal.  
       [0010] The tool claimed for the invention may be designed so that the total adjustment range for the cutting circle diameter resulting from rotation of the cutting element carrier over a range of 180° is subdivided into fixed adjustment steps, for example, into adjustment steps of the cutting circle diameter of 0.1 mm or 0.05 mm. A locking mechanism, for example, one in the form of a ball lock, may be provided for this purpose between the cutting element carrier and the head, there being provided on the cutting element carrier a spring-loaded notch ball which may drop into locking recesses which are mounted on the head of the shank so that they effect locking in the rotary steps corresponding to the desired changes in the cutting diameter. 
     
    
    
     [0011] The invention is discussed in detail in what follows on the basis of an exemplary embodiment shown in the drawing, in which  
     [0012]FIG. 1 presents a perspective view of a milling cutter in one exemplary embodiment of the invention;  
     [0013]FIGS. 2 and 3 show views of the milling cutter on different and respectively larger scales and in an exploded perspective view, and  
     [0014]FIG. 4 a top view on an even larger scale of the front end of the head on the tool shank in the exemplary embodiment. 
    
    
     [0015]FIG. 1 presents a general view of the exemplary embodiment in the form of a milling cutter as assembled, the tool shank connectible to a rotary drive (not shown) being identified as  1  and a head opposite it of greater diameter molded on the front end of the shank  1  as  3 . The circular cylindrical head  3  is concentric with the shank  1 , also circularly cylindrical, and the tool rotation axis  5  defined by this shank.  
     [0016] As is to be seen from FIG. 4, the head  3  on the front end of the tool shaft  1  has a bearing bore  7  which is offset eccentrically relative to the rotation axis  5  of the shank  1  at a distance designated as D and which in turn defines the insertion axis  9 . As is also to be seen from FIG. 4, there is in the shank  1  an inner through bore  11  which opens out into the bearing bore  7  of the head  3 , is concentric with the rotation axis  5  of the shank, and forms a flow channel for coolant delivery.  
     [0017] As is to be seen from FIGS. 2 and 3, the bearing bore  7  forms in the head  3  acting in conjunction with a bearing journal  13  a pivot bearing for a cutting element carrier  15  integral with the bearing journal  13 . This carrier has on its end facing the workpiece to be machined a round flange  17  of a diameter greater than that of the bearing journal  13 , this flange  17  having on its front end, that is, the end facing the workpiece to be machined, an opening  19  (FIG. 2) for a cutting plate  21  serving as seat for a cutting element. For the purpose of delivery of coolant to the cutting edge  23  of the cutting plate  21 , the latter has a through bore  25  (FIG. 2) which, by way of the opening  19  in the flange  17  of the cutting element carrier and a following inner bore of the bearing journal  13  (not shown), extends the delivery channel for the coolant by way of the inner bore  11  in the shank  1 .  
     [0018] The cutting plate  21  is secured against rotation in the opening  19  forming its seat by the non-circular shape of the opening  19  adapted to the cutting plate  21  and is fastened axially by means of a locking screw  27  (FIGS. 2 and 3), which is seated in a threaded bore (not shown) of the bearing journal  13  and, as is indicated in FIGS. 2 and 3 by broken lines, is accessible through a radial bore  29  (only indicated in FIG. 2) which is formed in the wall of the head  3  enclosing the bearing bore  7  with the bearing journal  13  and head  3  in a selected rotary position. The bearing journal  13 , in turn, may be fixed in the bearing bore  7  by means of a locking screw  31  which is seated in a threaded bore  33  in the wall of the head  3  enclosing the bearing bore  7  and acts in conjunction with the bearing journal  13 . The latter has incorporated in it a circular groove  35  which is in alignment with the locking screw  31  when the bearing journal  13  has been introduced into the bearing bore  7 . In this configuration the bearing journal  13  is secured in place axially in the bearing bore  7  but is rotatable relative to the head  3  if the locking screw  31  is loosened only to the extent that it still engages the circular groove  35  without exerting a clamping effect.  
     [0019] On the area of transition to the bearing journal  13  the flange  17  of the cutting element carrier  15  forms a locating face  37  positioned in the radial plane; when the tool has been assembled, this locating face  37  is guided on the level edge face  39  of the head  3  delimiting the bearing bore  7  in the rotary movement serving to adjust the cutting circle diameter. Dome-shaped locking recesses  41 , evenly distributed over a range of 180°, as is to be seen from FIGS. 2 and 4, are made in the edge face  39  which, together with a spring-loaded locking ball  43  seated in a spring housing  47  which in turn is seated in a perforation  47  in the flange  17 , permits rotary locking with the locking recesses  41 . In the example illustrated the recesses  41  are arranged so that the rotary movement is divided into ten rotary steps when the cutting element carrier  15  is rotated over the entire range of displacement of 180°.  
     [0020] As FIG. 4 clearly shows, the recesses  41  are distributed at equal distances in a circle concentric with the bearing bore  7  and thus with the insertion axis  9  and eccentric relative to the rotation axis  5 , specifically, in the circle which the locking ball  43  describes during rotation of the bearing journal  13  in the bearing bore  7 . This rotary movement leads to change in the diameter of the cutting circle of the cutting edge  23  of the cutting element  21  if this element is mounted on the cutting element carrier  15  in a position such that the cutting edge  23  is situated eccentrically a certain radial distance from the cutting insertion axis  9 .  
     [0021] If the bearing journal  13  is displaced eccentrically the same distance from the circumference of the flange  17 , the distance by which the bearing bore  7  is displaced eccentrically from the rotation axis  5 , this distance being identified as D in FIG. 4, then, with the cutting element carrier  15  and head  3  in a relative rotary position, the circumference of the flange  17  is concentric with the circumference of the head  3 . This rotary position, which is easily perceived by the user, may then be provided as initial position for the range of adjustment, the circumference of the flange  17  being progressively displaced eccentrically relative to the head  3  as the rotation movement, that is, rotation of the cutting element carrier  15 , progresses.  
     [0022] If continuous rotational adjustment is desired, the spring housing  45  with locking ball  43  may be omitted. Markings which indicate the rotational displacement and simplify adjustment may be provided for this purpose on the circumference of the head  3  and on the circumference of the flange  17 , in place of the rotary locking or as a supplement to it.