Abstract:
A tool for the machining of workpiece surfaces includes at least one adjustable, geometrically defined cutting edge. The tool additionally includes an adjusting device for the adjusting of the distance of the cutting edge to the central axis of tool. The adjusting device has a drive shaft that acts on an adjusting slide via a gearbox, which determines the distance of cutting edge from the central axis of tool. The adjusting slide may be a round slide arranged eccentrically to the central axis of tool. The gearbox may have a high reduction and may directly act on the adjusting slide.

Description:
FIELD 
     The present teachings generally relate to a tool for machining workpiece surfaces. 
     BACKGROUND 
     Tools of the type mentioned here are known. They have at least one adjustable, geometrically defined cutting edge, in addition to an adjusting device, with which the distance of the cutting edge from the central axis of the workpiece can be adjusted. The adjusting device comprises a drive that acts on the adjusting slide via a gearbox, which determines the distance of the cutting edge from the central axis of the workpiece. The adjusting slide is arranged eccentrically to the central axis of the workpiece and designed as a round slide, i.e., the adjusting slide is rotated for the adjustment of the distance of the cutting edge to the central axis of the workpiece, so that a cutting edge that is attached to an adjusting slide is displaced in such a way that the distance to the central axis of the workpiece is changed. 
     The disadvantage of this tool is that the adjustment of the cutting edge cannot take place with specifically high precision, because the adjusting slide is changed by means of a spur gear in its position. Defects in the gear teeth, such as the spacing between the gear teeth or play between the interactive spur gears directly interfere with the positioning of the cutting edge. The latter may also not be precisely adjusted due to the defect. 
     The task of the invention is thus to develop a tool for machining workpiece surfaces of the type mentioned here, in which this disadvantage does not exist in this fashion. 
     SUMMARY 
     In order to solve this task, a tool is proposed that has an adjustable, geometrically defined cutting edge, which is adjustable by means of an adjusting device. In this manner, the distance of the cutting edge to the central axis of the tool may be predetermined. The adjusting device has a drive, which acts on a gearbox via at least one spur gear. This directly affects the position of the adjusting slide, thus the distance of the geometrically defined cutting edge to the central axis of the workpiece. Thus, a spur gear is no longer envisioned between the gearbox and the adjusting slide, contrary to the known solution, so that here also, no spacing and/or play defect can occur. Due to the fact that the gearbox has a high gear reduction, defects during the transfer of a torque from the drive via spur gears to the gearbox corresponding to the gear reduction of the gearbox are reduced. In this manner, it is possible, despite gear tooth defects that can never be completely avoided, to guarantee a very precise positioning of the cutting edge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is further explained below by means of the drawing. Shown are: 
         FIG. 1A  schematic diagram of a lateral view of the tool 
         FIG. 2  Another simplified schematic diagram of a lateral view of a tool, whereby the tool is rotated 90° with respect to  FIG. 1 , and 
         FIG. 3  A schematic diagram of a front view of a tool with various positions of a cutting edge. 
     
    
    
     DETAILED DESCRIPTION 
     The schematic diagram according to  FIG. 1  shows a tool  1  that may be connected via a shaft  3 , which is only indicated here, to a spindle of a tool machine or with interfaces, adapters or the like. On the side  5  opposite the shaft  3 , a geometrically defined cutting edge  7  is indicated. This may be part of the tool or a cutting tip plate that is fastened to tool  1  in a suitable manner. It is possible to also envision a suitable tool holder, such as a magazine or the like. 
     The main body  9  of tool  1  comprises, for example, a drive  11  designed as an electric motor, which can be controlled via a suitable control system  13 , whereby drive  11  can be switched on and off as and the speed and the rotating direction of the driven shaft  15  of drive  11  can be predetermined. An initial spur gear  17  is attached torque proof to the free end of the driven shaft  15 . The rotation of the initial spur gear  17  is transmitted in a suitable manner to a second spur gear  19 . A transmitting device  21  lies outside the image plane according to  FIG. 1 , which will be explained in greater detail below. 
     The second spur gear is attached torque proof to the end of a drive shaft  23 , which transmits a rotation and a torque of the second spur gear  19  to a gearbox  25 . This is characterized preferably by a high speed reduction. 
     Here planetary gears or, in particular, also a harmonic drive gearbox can be used. With gearbox  25  illustrated here, it is envisioned that a rotary motion introduced via the drive shaft  23  in gearbox  25  is transmitted to housing cap  27  of gearbox  25 . It appears in the process that this rotates with a much smaller rotational speed than drive shaft  23 . If the second spur gear  19  of drive  11  rotates at a given rotating angle, housing cap  27  rotates only at a very much smaller rotating angle corresponding to the gear reduction of gearbox  25 . 
     Drive  11  and gearbox  25  are components of an adjusting device  29 , which furthermore still comprises an adjusting slide  31 . It can be seen from the schematic diagram that gearbox  25  acts directly on the adjusting slide  31 . Here it is envisioned that the adjusting slide is directly connected to the drive, which is designated here as housing cap  27 . A rotation of housing cap  27  thus directly produces a rotation of the adjusting slide  31  designed as a rotating round slide, whereby a rotation of housing cap  27  1:1 is transmitted to adjusting slide  31 . 
     It is clear that a rotation produced by drive  11  is transmitted to gearbox  25  of spur gear  17  via transmitting device  21  and via the second spur gear  19 . The latter is connected torque proof to drive shaft  23 , which introduces a rotary motion of the second spur gear  19  in gearbox  25 . Tolerances have an effect on the path between drive  11  and drive shaft  23  during the manufacturing on both the drive itself and spur gears  17  and  19  as well as transmitting device  21 . These defects are strongly reduced by gearbox  25 . A given rotating angle at the entry of gearbox  25 , thus on drive shaft  23 , produces a much smaller rotating angle corresponding to the gear reduction of the gearbox at its exit, i.e., housing cap  27 . Rotating angle defects that occurred in the area between drive  11  and drive shaft  23  are likewise reduced corresponding to the gear reduction of gearbox  25  and thus produce a very much smaller rotating angle defect at the exit side of the gearbox, i.e., housing cap  27 . 
     It is critical that that no more spur gears be interconnected between housing cap  27  and adjusting slide  31 , whose manufacturing tolerances could distort the rotating angle of housing cap  27 . In fact, a given rotating angle of housing cap  27  leads directly to a rotation of the adjusting slide  31  designed as a round slide. The resulting gear reduction in gearbox  25  of a rotating angle defect in the area of the drive shaft  23  is thus maintained unaltered during the rotating displacement of adjusting slide  31 . 
     The distance of cutting edge  7  to central axis  33  of tool  1  is adjusted by means of the adjusting device  29 . In order to produce a change of this distance by a rotation of adjusting slide  31 , its rotating axis  35  is shifted parallel to central axis  33 ; adjusting slide  31  is thus arranged eccentrically in the main body  9  of tool  1 . At the same time, the second spur gear  19  is also arranged coaxially to rotating axis  35  and thus eccentrically to the central axis of tool  1 . With the embodiment selected here, gearbox  25  thus also lies eccentrically to central axis  33  and coaxially to rotating axis  35 . 
       FIG. 2  shows a schematic diagram of the components of the tool  1  illustrated in  FIG. 1 , i.e., drive  11 , its driven shaft  15  as well as the first spur gear  17 . Transmitting device  21  is clearly visible here, because the components of tool  1  are clearly rotated 90° with respect to the illustration in  FIG. 1 . Transmitting device  21  has an initial first pinion gear  37  that meshes with the first spur gear  17 , which acts on a second pinion gear  41  via a transfer shaft  39 . This meshes with the second spur gear  19 . 
     Depending upon the arrangement of transmitting device  21 , thus after the selection of the diameter of the first spur gear  17 , of the first pinion gear  37 , of the second pinion gear  41  and of the second spur gear  19 , a desired gearbox ratio may be predetermined. 
     It is clear here that a rotation of driven shaft  15  of drive  11  by means of the transmitting device  21  leads to a rotation of drive shaft  23 , which is introduced in gearbox  25 . Here, this is also configured as high-reduction gearing. A rotation of the drive shaft  23  also leads to a rotation of the housing cap  27 , whereby the rotating direction of housing cap  27  is opposite to that of drive shaft  23 , if the gearbox  25  is configured as a harmonic drive gearbox or planetary gears. 
     After reading the explanations, it is evident that a rotation of driven shaft  15  leads to a rotation of housing cap  27 . At the same time, a rotation of the first spur gear  17  by means of the transmitting device  21  is transmitted to the second spur gear  19 . The rotating angle of the first spur gear  17  is very greatly reduced by gearbox  25 , so that a very much smaller rotating angle is produced for housing cap  27 . The speed reduction of the gearbox also leads to the defect in the gear tooth system between the first spur gear  17  and the second pinion gear  37  as well as between the second pinion gear  41  and the second spur gear  19  are correspondingly “reduced”, or diminished. In other words: Defects in the gear teeth between spur gear  17  and  19  and in transmitting device  21  are substantially reduced by gearbox  25  and, for all intents and purposes, no longer affect the adjustment of cutting tip plate  7  connected via an adjusting slide  31  to housing cap  27 . 
     Transmitting device  21  illustrated in  FIG. 2  may also be modified:  FIG. 2  illustrates that the first and second spur gears  17  and  19  mesh with the first and second pinion gears  37  and  41 . It is also conceivable that, instead of the spur gears and pinion gears, pulleys are used and a rotation of the first spur gear  17  is transmitted to the first pinion gear  37  by means of a belt. At the same time, for the second spur gear  19  on the other hand, a spur gear may again be used or, likewise, a belt pulley. This also applies to the second pinion gear  41 . 
     Also, it must still be indicated, that spur gears  17  and  19  are here only approximately commensurately designed as an example. Spur gears with different diameters may also be used here. 
     In addition, it is possible to design the first and/or second spur gear  17 ,  19  as a hollow gear with internal teeth and correspondingly, the first and/or second pinion gear,  37 ,  41  can be meshed within this hollow gear. 
     Another modification of the transmitting device  21  may designed, in which the first spur gear  17  is designed substantially smaller and meshes with a second spur gear  19  designed as an hollow gear whose diameter is greater than that of the first spur gear  17 . The eccentric misalignment may thus also be realized by means of a single-stage gearbox with internal teeth. 
     Finally, it should still be indicated that transmitting device  21  may also be realized by a multi-stage gearbox. 
       FIG. 3  shows a schematic diagram of tool  1  from the front, thus on side  5 , lying opposite the shaft  3 . The illustration shows a cutting edge  7 , which is a component of a cutting tip plate  43 , in various positions. According to the rotating position of the adjusting slide  31 , cutting edge  7  is arranged at a more or less great distance to the central axis  33  of tool  1 . 
     Below to the right, beneath a horizontal diameter line D 1 , cutting edge  7  is arranged here at a distance to rotating axis  33 . With a corresponding layout of tool  1 , this may, for example, be selected in such a way that a borehole machined with a cutting edge  7  has a diameter of approx. 38.0. 
     If adjusting slide  31  is designed as a rotating slide valve rotates in the direction of arrow  45 , thus counterclockwise, so that, with a corresponding layout of working spindle  1 , cutting edge  7  is at a distance from central axis of tool  1 , with the machining of a borehole by means of tool  1 , a diameter of approx. 41.5 mm is produced. If adjusting slide  31  further rotates counterclockwise in the direction of arrow  45 , so that it lies just in front of the perpendicular diameter line D 2 , a diameter of approx. 48.0 mm is produced when the borehole is machined by means of tool  1 . 
     If, finally, adjusting slide  31  is rotated in such a way that cutting edge  7  is lined up with the graduation of D 2 , then a diameter of 48.23 mm is produced when the borehole is machined by means of tool  1 . 
     It is clear here, that the adjustment of the diameter of tool  1  depends upon a rotation of adjusting slide  31 . Rotating angle defects thus lead to a deviation of the set diameter of tool  1  from the target diameter. As explained above, rotating angle defects between drive  11  and the entrance of gearbox  25 , thus at its drive shaft  23 , are strongly reduced by gearbox  25 . In other words, the reduction of gearbox  25  reduces an existing rotating angle defect at the entrance of the gearbox in such a way that it practically no longer has any effect at the exit of the gearbox and thus on housing cap  27 . Thus, the rotating angle appears to correspond exactly to the rotating angle of rotating slide valve  31  of housing cap  27 . As a result, the advantage of using this tool  1  described herein is obtainable, because gearbox  25  has a high reduction and directly acts on adjusting slide  31 , thus without any interconnections of further spur gears or the like. 
     The difference between the smallest and the largest indicated borehole diameter depends upon how great the distance between central axis  33  of tool  1  and rotating angle  35  of adjusting slide  31  is. The greater the distance “e” is, so much greater the difference of both indicated diameters is. 
     The change of the diameter of a borehole by means of tool  1  is exclusively produced by a rotary motion of the adjusting slide  31 . The result is that a sealing of the tool in an easy manner is possible. It requires only the use of rotating seals. Losses can be reduced to a minimum by means of antifriction bearings, so that no slide bearings are used. 
     With the rotation of adjusting slide  31 , a once balanced tool  1  remains balanced: With diameter adjustment, no centers of mass/gravity actually move, so very high machining speeds are possible. Moreover, the balancing of the tool is likewise relatively easy. 
     From the explanations, it appears that all of the backlashes occurring up to gearbox  25  are reduced with the reduction factor of gearbox  25 . The disengaging of drive  11 , thus the angle adjustment of the first spur gear  17 , is increased by the reduction. In addition, it appears that with a higher reduction of gearbox  25 , also with small motors, that are used as drive  11 , high torque can be produced during the displacement of adjusting slide  31 . 
     To increase the precision of the tool, so-called pre-stressed and thus spur gears free of play can be used. 
     By means of a suitable control of drive  11  by means of the control system  13 , the distance of cutting edge  7  from the central axis  33  of the tool can be changed during the machining of a borehole surface. It is thus possible to produce boreholes with a contour, such as chamfering, annular grooves, undercuts, conical boreholes and the like.