STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable 
   INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
   Not Applicable 
   CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a multi-purpose drilling tool. 
   2. Description of the Related Art 
   Publication DE 31 23 048 A1 makes known a universal drill that includes a boring head with a hard-metal plate, a shank attached thereto, and a clamping shank. The universal drill is designed for machining hard and slightly hard materials; percussive motion must not take place during drilling. The disadvantage of this type of drill is that, although it is suited for machining concrete, masonry and similar hard materials, the fact that it is limited to rotary operation means the rapid progress typically made in machining these types of materials does not occur, with the result that the acceptance of a drill of this type among professional users is low. 
   Furthermore, publication U.S. Pat. No. 5,172,775 makes known a drill with a drill bit insert that is also designed exclusively for a rotary application. 
   BRIEF SUMMARY OF THE INVENTION 
   The object of the present invention is to provide a multi-purpose drilling tool that is suited for use in the rotating drilling mode to machine, via chip-removal, materials such as wood, metal and plastic, and impact-sensitive materials such as tiles and roofing tiles, and for use in the rotary-impacting drilling mode to drill concrete, stone and bricks. 
   This object is attained, according to the present invention, based on the features of the definition of the species in claim  1  by the characterizing features of claim  1 . Advantageous further developments are stated in the subclaims. 
   The present invention is based on the basic idea of achieving a symbiosis between a drill designed exclusively for rotary application and a drill designed for a rotary-impacting application to provide the craftsman with a tool that reduces the number of drill bit changes and the number of drill bits one must have on hand, thereby saving working time that is lost when drill bits must be replaced, located or identified. The multi-purpose drilling tool according to the present invention has a cutting element with faces, flanks and cutting edges, a rake angle (γ) with γ≧0° being provided for at least one part of the face, and a lip clearance angle (α) of 5°≦α≦15° and, in particular, α≈10°, being provided. A drill of this type for universal application is optimally designed for machining the most diverse types of materials in the rotary and rotary-impacting mode, since the selected rake angle is also suitable for use to machine long-chipping materials, and since the large wedge angle makes the cutting lip adequately stable for impacting work. Rake angles (γ) of 0° to 10° are provided in particular. 
   In addition, according to the present invention, the cutting edge is oriented toward a longitudinal drill bit axis. The convergent profile of the cutting edges results in the required centering of the multi-purpose drilling tool for pilot drilling and during the drilling operation itself. At the same time, the slender design in the region of the longitudinal drill bit axis makes it easier for the multi-purpose drilling tool to penetrate the material. 
   According to the present invention, it is also provided to vary the profile of the cutting edge in the direction of the longitudinal drill bit axis by superposing on it a curved and/or arched and/or zigzag profile. As a result, it is possible to influence the geometry of the flank that also serves as the striking surface and to design it optimally for the loads to be incurred. 
   The present invention further provides a point angle (β) of 110° to 130° and preferably approximately β=120°, which is formed by the cutting edges. With a point angle of this type, it is possible to perform clean pilot drilling with the drill bit tip while keeping the resultant radial forces low. 
   According to the present invention, it is provided to allow the cutting edges to transition into each other via a chisel edge. As a result, low susceptibility to wear of the hard-metal plate in the region of the longitudinal drill bit axis is ensured during rotary-impacting operation in particular, since the flanks of the chisel edge approximately form a point angle that corresponds to the point angle of the cutting lips. 
   According to an embodiment of the present invention, it is provided to allow the cutting edges to transition into each other without forming a chisel edge. A cutting point of this type enables, in particular, highly-exact pilot drilling when the tool is operated in the drilling mode. When the material for the cutting element is selected accordingly, adequate stability is still ensured during rotary-impacting operation when the intended point angle is used. 
   In addition, according to the present invention, the face is positioned with a slight slant relative to a longitudinal mid-plane, and the face is allowed to transition into the lateral surface via a transition surface configured in the shape of a channel. As a result, it is possible to design the cutting element based on simple, basic geometry and to easily create the desired profile of the face and the cutting edge. 
   According to the present invention, the lateral surface and the face meet at a straight transition edge, the transition edge being oriented parallel with a longitudinal axis of the multi-purpose drilling tool or extending at an acute angle with this longitudinal axis. The ratio of the size of the lateral surface to the face can be influenced by the different profiles. In particular, by using an inclined profile of the transition edge, it is possible to push chips or drill cuttings produced in the region of the drill bit tip radially outwardly on the path along the longitudinal drill bit axis with the aid of the channel produced via this profile. 
   According to the present invention, the cutting edge is extended past the chisel edge and/or the punctiform cutting point, this extension transitioning into the lateral surface on the other side of a transversal mid-plane and having an arched shape in particular. 
   According to the present invention, the face is configured as a flat surface that has a uniform rake angle γ. As a result, it is possible to design the geometry of the drill bit insert required for the multi-purpose drilling tool in a particularly easy manner and to forego a cost-intensive, complex shaping procedure. 
   Finally, according to one embodiment of the present invention, the face is formed by at least two flat partial surfaces that have different rake angles, a first partial surface with a rake angle γ≧0° being provided in a radially outwardly located region of the drill bit insert of the multi-purpose drilling tool and, a second partial surface being provided in a region located directly around the longitudinal mid-axis of the multi-purpose drilling tool, the second partial surface having a negative rake angle γ&lt;0°. As a result, it is possible to realize a face with a rake angle ≧0° in a radially outwardly located region of the drill bit insert and still design a short chisel edge or a point without having to forgo the stable design of the drill bit insert. 


   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     Further details of the present invention are described in the drawing with reference to schematically depicted exemplary embodiments. 
       FIG. 1  Shows a perspective side view of a cutting element of a not-shown multi-purpose drilling tool, 
       FIG. 2   a  Shows a side view of a further cutting element of a further not-shown multi-purpose drilling tool, 
       FIG. 2   b  Shows an underside view of the cutting element shown in  FIG. 2   a,    
       FIG. 2   c  Shows a further side view of the cutting element shown in  FIG. 2   a,    
       FIG. 2   d  Shows a top view of the cutting element shown in  FIG. 2   a,    
       FIG. 3   a  Shows a side view of a multi-purpose drilling tool according to the present invention, 
       FIG. 3   b  Shows a top view of the multi-purpose drilling tool shown in  FIG. 4   a,    
       FIG. 3   c  Shows an enlarged detained view of the multi-purpose drilling tool shown in  FIG. 4   a,    
       FIG. 3   d  Shows a view of the depiction in  FIG. 4   c , from an arrow direction IVd, 
       FIGS. 4   a - 4   c  Show an embodiment of a drill bit insert with a shortened chisel edge, in three views, 
       FIGS. 5   a - 5   c  Show a further embodiment of a drill bit insert without a chisel edge, in three views, and 
       FIGS. 6   a - 6   d  Show eight embodiments of the profile of the cutting edges. 
   


   DETAILED DESCRIPTION OF THE INVENTION 
   A perspective side view of a cutting element  1  of a not-shown multi-purpose drilling tool is shown in  FIG. 1 . Cutting element  1  is embedded in a not-shown boring head that transitions into a not-shown drill twist which, in turn, transitions into a not-shown clamping shank. The clamping shank can be designed cylindrical in shape or as a system insertion end and, in particular, as an “SDS-Plus clamping shank” or the like, and enables, in particular, both rotary and rotary-impacting operation of the multi-purpose drilling tool. 
   Cutting element  1  is formed essentially by two cutting lips  3  and  4  located centrosymmetrically to a longitudinal drill bit axis  2 . The description below is limited largely to cutting lip  3 , with cutting lip  4  having the same configuration. Cutting element  1  is limited laterally by two longitudinal sides  5 ,  6  and two transverse sides  7 ,  8 . Cutting lip  3  is formed essentially by a face  9  which forms a part of longitudinal side  5 , and a flank  10 , face  9  and flank  10  transitioning into each other at a cutting edge  11 . Face  9  has a rake angle γ=0° with a parallel line PL or a leading edge  25  that extends parallel to longitudinal axis  2 . Flank  10  has a lip clearance angle α=10° with a plane EXY positioned perpendicularly to longitudinal axis  2 . This results in a wedge angle β 2 =80° enclosed between face  9  and flank  10  which provides a high level of stability to cutting lip  3  against striking from a direction z′, because cutting edge  11  is still supported in an optimal manner despite the fact that a negative rake angle—which is typical with cutting elements used for impact drilling—is not present. Cutting edges  11  and  12  enclose a point angle β=118°. Flanks  10 ,  13  of cutting lips  3  and  4  meet at a chisel edge  14 , which also joins cutting edges  11  and  12 . Chisel edge  14  is divided in the middle by longitudinal drill bit axis  2 . Cutting edge  11  also has an extension  15  with which it is extended, with an arched shape, past chisel edge  14  into the region of cutting lip  4  to a lateral surface  16  and meets two edges, namely an edge FS formed by flank  13  and lateral surface  16 , and edge SS formed by lateral surface  16 , face  9  and a transition surface  19  located between the two. Due to the profile of cutting edge  11  and its extension  15 , longitudinal side  5  formed by aforementioned surfaces  9 ,  16  and  19  is not configured as a plane, since face  9  recedes relative to a plane E 16  defined by lateral surface  16 . Cutting edge  11  and face  9  extend toward plane E 16  at a taper angle λ=7°. This means cutting element  1  tapers from a width SH to a width SQ from transverse side  7  toward longitudinal drill bit axis  2  in the region of cutting lip  3 . The ratio of SH to SQ is in the range of 0.25×SH≦SQ≦0.9×SH, and it is provided in particular that width SH tapers to SQ=0.5×SH. A lateral surface  17  extends parallel to a longitudinal mid-plane EYZ, and cutting edge  11  extends toward longitudinal mid-plane EYZ or longitudinal drill bit axis  2  at a taper angle λ. According to a not-shown embodiment, it is provided that lateral surface  17  also extends toward longitudinal drill bit axis  2 . 
   The dashed lines labelled “G” outline a simple geometric body, out of which cutting element  1  is formed, e.g., via chip-removing machining. 
   An embodiment of the profile of edge SS is depicted using edge SSB indicated by the dashed-dotted line. Edge SS, which defines the transition between lateral surface  16  and face  9  extends parallel to longitudinal drill bit axis  2 . Face  9  forms a planar surface  18  and transitions into lateral surface  16  via a transition surface  19  which is concave for the distance of nearly a quadrant and extends parallel to edge SS. Planar surface  18  and transition surface  19  meet at an edge  20 . In contrast, edge SSB extends with an incline relative to longitudinal drill bit axis  2 . This results in a planar surface  18 ′ having a smaller surface area and a transition surface configured in the shape of a channel  19 ′ which also extends at an angle. Due to the reduction in size of planar surface  18 ′ formed by face  9 , an enlarged lateral surface  16  results. According to a not-shown embodiment, curved profiles of edge SSB are also provided, edge SSB preferably extending in plane E 16  of lateral surface  16 . A transverse mid-plane EXZ extends through the longitudinal drill bit axis perpendicularly to longitudinal mid-plane EYZ. 
   A side view of a transverse side  7  of a hard-metal drill bit insert  1  of a not-shown multi-purpose drilling tool is shown in  FIG. 2   a . Hard-metal drill bit insert  1  is limited by an underside  22  and longitudinal sides  5 ,  6  with lateral sides  16 ,  17 . Transverse side  7  transitions into a flank  10  which rises toward a chisel edge  14 . A cutting edge  11  follows the same course. Where cutting edge  11  meets chisel edge  14 , it transitions into an extension  15  and, together with extension  15  and an edge SSB, limits a face  9 . An extension  23  of a second cutting edge  12  ( FIG. 2   c ) is shown to the left of a longitudinal drill bit axis  2 , extension  23  extending toward a lateral surface  17 . Also shown in  FIG. 2   a  are the main angles of a cutting lip  3  formed by flank  10 , face  9  and cutting edge  11 . The angles are a rake angle γ=0° between a line PL which is parallel to longitudinal drill bit axis  2  and face  9 , a lip clearance angle α=10° between a plane EXY extending perpendicularly to longitudinal drill bit axis  2  and flank  10 , and a wedge angle β 2 =80° enclosed by face  9  and flank  10 . 
     FIG. 2   b  shows a top view of underside  22  of cutting element  1 . Extensions of lateral surfaces  16  and  17  are indicated with dashed lines which show that faces  9  and  24  are oriented toward longitudinal drill bit axis  2 . 
     FIG. 2   c  shows a view of longitudinal side  6  of cutting element  1  shown in  FIGS. 2   a  and  2   b . Edge SSB, where lateral surface  16  transitions into face  9  has a profile that approximately corresponds to that of edge SSB in  FIG. 1 . Lateral surface  16  expands into the region of cutting lip  3 . A flank  13 , a cutting edge  12  and a leading edge  26  of a second cutting lip  4  are shown. Of cutting lip  3 , only cutting edge  11 , face  9  and a leading edge  25  can be seen. 
     FIG. 2   d  shows a top view of cutting element  1  shown in  FIG. 2   c . As is the case with  FIG. 1 , a longitudinal mid-plane EYZ and a transversal mid-plane EXZ are also shown here. Lateral surfaces  16 ,  17  extend parallel to longitudinal mid-plane EYZ, and cutting edges  11 ,  12  and faces  9 ,  24  extend toward longitudinal mid-plane EYZ. An extension  15  of cutting edge  9  extends past transversal mid-plane EXZ to lateral surface  16  and is therefore located in the y-direction on the other side of an intersection Z which is an imaginary extension of chisel edge  14  with lateral surface  16 . This also applies, in an analogous manner, for an extension of cutting edge  12 . In other words, chisel edge  14  defines a plane E 14  positioned perpendicularly in the plane of the drawing. With regard for cutting edges  11  and  12 , they transition into lateral surfaces  16  and  17  on the other side of plane E 14 . Leading edges  25 ,  26  have the greatest radial distance from the longitudinal drill bit axis.  FIG. 2   d  also shows, with configurations  1  and  11 , two different variations of an alternative design of the lateral surfaces which also result in a relatively short chisel edge  14  with a good centering effect. 
     FIG. 3   a  shows a side view of a multi-purpose drilling tool  27  with a boring head  28  that supports a cutting element  1  and transitions into a drill twist  29 . The drill twist transitions into a clamping shank  30 . 
     FIG. 3   b  shows a top view of multi-purpose drilling tool  27  shown in  FIG. 3   a . Drill bit insert  1  defines a nominal diameter DN. Faces  9 ,  24  transition into flutes  31  and  32  in drill twist  29 . 
     FIG. 3   c  shows a detained view of multi-purpose drilling tool  27  shown in  FIG. 3   a . Boring head  28  is composed of two prolongations  33 ,  34  of drill twist  29  (refer also to  FIG. 3   d ) which hold cutting element  1  in the region of lateral surfaces  16 ,  17 . Faces  9  and  24  are not covered by prolongations  33  and  34  in a lower region  35  close to an underside  22  of multi-purpose drilling tool  1 , either, and they transition directly into flutes  31  and  32 . As a result, there is an unobstructed path along which chips and/or drill cuttings can be carried away. 
     FIG. 3   d  shows the detained view shown in  FIG. 3   c  in a view rotated by 90°. The lateral embedding of cutting element  1  between projections formed by prolongations  33 ,  34  is also shown in this view. 
     FIGS. 4   a  through  4   c  show an embodiment of a drill bit insert  1  with a shortened chisel edge  14 , in three views. It is designed largely similar to the drill bit inserts shown in the preceding Figures. Chisel edge  14  is shortened as compared with the drill bit insert shown in  FIGS. 2   a  through  2   d . This shortening of chisel edge  14  is formed via a polished face in the region of a drill tip  36 . The polished face subdivides a face  9  and  24  into two partial faces  9   a ,  9   b  and  24   a ,  24   b . First partial faces  9   a ,  24   a  form a much larger surface than the two partial surfaces  9   b ,  24   b  configured in the region of drill tip  36 . The first partial surfaces  9   a ,  24   a  have a rake angle γ=0°, and the second partial surfaces  9   b ,  24   b  have a negative rake angle γ≈35°. Subdividing faces  9  and  24  into two planar partial surfaces  9   a ,  9   b  and  24   a ,  24   b  with different rake angles also results in a polygonal profile of cutting edge  11  and  12 . This means, a taper angle λ of cutting edge  12  of a longitudinal mid-plane EYZ increases abruptly toward a longitudinal drill bit axis  2 , from λ≈7° to λ≈18°. 
     FIGS. 5   a  through  5   c  show a further embodiment of a drill bit insert  1 , in three views. It is designed largely analogously to the drill bit inserts shown in the preceding Figures, but it does not have a chisel edge. It has a point  37  instead, at which flanks  10 ,  13  and faces  9 ,  24  meet to form a point. Tip  37  is formed via a polished face in the region of a drill tip  36 . The polished face subdivides a face  9  and  24  into two partial faces  9   a ,  9   b  and  24   a ,  24   b . First partial faces  9   a ,  24   a  form a much larger surface than the two partial surfaces  9   b ,  24   b  configured in the region of drill tip  36 . The first partial surfaces  9   a ,  24   a  have a rake angle γ=0°, and the second partial surfaces  9   b ,  24   b  have a negative rake angle γ≈40°. Subdividing faces  9  and  24  into two planar partial surfaces  9   a ,  9   b  and  24   a ,  24   b  with different rake angles γ also results in a polygonal profile of cutting edge  11  and  12 . This means, a taper angle λ of cutting edge  12  of a longitudinal mid-plane EYZ increases abruptly toward a longitudinal drill bit axis  2 , from λ≈7° to λ≈23°. 
     FIGS. 6   a  through  6   d  show eight embodiments of the profile of a cutting edge  11  and  12  in a top view of cutting elements. The embodiments are indicated in depictions as shown in  FIG. 2   d.    
     FIG. 6   a  shows a cutting edge  11  on a cutting element  1 , cutting edge  11  extending toward a chisel edge  14  in a sinusoidal manner and initially approaching a longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 .  FIG. 6   a  also shows a cutting edge  12  that extends toward chisel edge  14  with a zigzag pattern, cutting edge  12  initially approaching longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 . 
     FIG. 6   b  shows a cutting edge  11  on a cutting element  1 , cutting edge  11  extending toward a chisel edge  14  in a sinusoidal manner and initially moving away from a longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 .  FIG. 6   b  also shows a cutting edge  12  that extends toward chisel edge  14  with a zigzag pattern, cutting edge  12  initially moving away from longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 . 
     FIG. 6   c  shows a cutting edge  11  on a cutting element  1 , cutting edge  11  extending toward a chisel edge  14  in an arched manner and initially moving away from a longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 .  FIG. 6   c  also shows a cutting edge  12  that extends toward chisel edge  14  with an angled pattern, cutting edge  12  initially moving away from longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 . 
     FIG. 6   d  shows a cutting edge  11  on a cutting element  1 , cutting edge  11  extending toward a chisel edge  14  in an arched manner and initially approaching a longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 .  FIG. 6   d  also shows a cutting edge  12  that extends toward chisel edge  14  with an angled pattern, cutting edge  12  initially approaching longitudinal mid-plane EYZ in a radially outwardly located region of cutting element  1 . 
   The present invention is not limited to the exemplary embodiments shown or described. Rather, it includes further developments of the present invention within the scope of patent claims. Feasible materials for the cutting element include, in particular, hard metal, PKD or ceramic. 
   REFERENCE NUMERALS 
   
       
         1  Cutting element 
         2  Longitudinal drill bit axis 
         3 ,  4  Cutting lip 
         5 ,  6  Longitudinal side 
         7 ,  8  Transverse side 
         9  Face of  3   
         9   a ,  9   b  First and/or second partial face of  9   
         10  Flank of  3   
         11  Cutting edge of  3   
         12  Cutting edge of  4   
         13  Flank of  4   
         14  Chisel edge 
         15  Extension of  9   
         16 ,  17  Lateral surface 
         18 ,  18 ′ Planar surface 
         19 ,  19 ′ Transition surface between  16  and  18   
         20  Transition edge in  9  with SS 
         21  Transition edge in  9  with SSB 
         22  Underside 
         23  Extension of  12   
         24  Face of  4   
         24   a ,  24   b  First and/or second partial face of  24   
         25 , 26  Leading edge 
         27  Multi-purpose drilling tool 
         28  Boring head 
         29  Drill twist 
         30  Clamping shank 
         31 ,  32  Flute of  29   
         33 ,  34  Prolongation of  29   
         35  Lower region of  9  and/or  24   
         36  Drill tip 
         37  Tip 
       α Lip clearance angle 
       β Point angle 
       β 2  Wedge angle 
       γ Rake angle 
       λ Taper angle 
       DN Nominal diameter of  27   
       E 14  Plane defined by  14   
       E 16  Plane defined by  16   
       EXY Plane perpendicular to  2   
       EXZ Transversal mid-plane 
       EYZ Longitudinal mid-plane 
       FS Edge between  13  and  16   
       G Outline of geometric bodies 
       SH Width of  1  at  7   
       SS Edge between  16  and  9   
       SSB Variation of edge between  16  and  9   
       SQ Width of  1  at  14   
       Z Intersection of  14  and  16
The present invention relates to a multi-purpose drilling tool with a boring head, a drill twist connected thereto and a downstream clamping shank, a cutting element ( 1) being provided on the working side of the boring head. The cutting element ( 1) has a face ( 9, 24) with a rake angle (g) having a value of g>=0deg b, the cutting element ( 1) having a flank ( 10, 13) with a lip clearance angle (a) having a value of 5deg<=a<=15deg and, in particular, a10deg.