Abstract:
A rock drilling tool includes a drilling head provided with a cutting body and a helix arranged between the drilling head and a shaft. The cutting body extends continuously over a nominal diameter of the rock drilling tool and has an inner region configured as a centering tip and an outer region bordering the centering tip in the radial direction. The outer region is offset towards the rear in relation to the centering tip in the active direction of the rock drilling tool. The centering tip is configured as a pyramid or a truncated pyramid and has pyramidal edges with lateral surfaces located therebetween. At least one lateral surface of the centering tip is configured as a cavity.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2010/067980, filed on Nov. 23, 2010, which claims the benefit of priority to Serial Nos. DE 10 2009 060 856.7, filed on Dec. 30, 2009; DE 10 2010 017 987.6, filed on Apr. 21, 2010; and DE 10 2010 041 238.4, filed on Sep. 23, 2010 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The disclosure relates to a rock drilling tool for the rotational percussive machining of concrete, rock, masonry and such materials. 
     DE 102 08 630 A1 makes known a rock drilling tool for rotational percussive machining of concrete, rock, masonry and such materials, the rock drilling tool including a drill head which includes a cutting body, and a helix arranged between the drill head and a shaft, wherein the cutting body extends in an uninterrupted manner over a nominal diameter of the rock drilling tool, wherein the cutting body includes an inner region realized as a centering tip and an outer region adjoining the centering tip in the radial direction, wherein the outer region is set back in the effective direction of the rock drilling tool in relation to the centering tip, wherein the centering tip is realized as a pyramid or as a truncated pyramid and has pyramidal edges, wherein side surfaces lie between the pyramidal edges and wherein a tip of the pyramid or of the truncated pyramid is passed through by a longitudinal center axis of the drilling tool. 
     The object underlying the disclosure is to create a rock drilling tool, the material removal rate of which is increased in the region of its centering tip. 
     This object is achieved through the characteristic features of the disclosure. Advantageous and expedient further developments are provided in the sub-claims. 
     SUMMARY 
     The disclosure relates to a rock drilling tool for rotational percussive machining of concrete, rock, masonry and such materials, where at least one side surface of the centering tip, which is realized as a pyramid or a truncated pyramid, is formed as a cavity. This means that in the region of a pyramidal edge adjoining the cavity, the centering tip obtains more aggressive drilling and percussion power as the pyramidal edge recedes into the cavity more deeply in opposition to the effective direction of the rock drilling tool than is the case with a comparable centering tip with planar side surfaces. The core of the disclosure, consequently, is an increase in aggressiveness or in penetration of a rock drilling tool for rotational percussive operation, which—retaining a proven basic geometry—is obtained by the targeted conversion of at least one selected planar surface of the basic geometry into a cavity. By designing at least one side surface of the centering tip, realized as a pyramid or a truncated pyramid, as a cavity, it is possible to achieve a smaller negative rake angle or a smaller wedge angle in the region of a pyramidal edge and thus to increase the efficiency of the rock drilling tool at the centering tip with regard to percussive destruction and with regard to the stripping action. Consequently, the core of the disclosure is a rock drilling tool which is developed on the basis of proven rock drilling tools by means of targeted material removal in the region of the centering tip. 
     As claimed in the disclosure, it is provided that at least two adjacent side surfaces of the centering tip are realized in each case as a cavity. This means that in the region of the pyramidal edge at which the two cavities merge into each other, compared to a rock drilling tool with planar surfaces between the pyramidal edges, there is a main or secondary cutting edge, the negative rake angle of which is made smaller and the clearance angle of which is made larger, such that the main or secondary cutting edge—when viewed in section—has a reduced wedge angle and as a result has an increased action in percussion and in rotation. 
     As an alternative to this, the disclosure provides that all the side surfaces of the centering tip are realized in each case as a cavity. This means that the advantages mentioned in the preceding paragraph are produced at all the main and secondary cutting edges. 
     The disclosure also provides that a wedge is formed in the region of the pyramidal edge of the centering tip lying between two cavities, the wedge surfaces of which wedge being formed by surface portions of the adjacent cavities, wherein a wedge angle of the wedge is smaller than a wedge angle of a centering tip with planar side surfaces. These types of wedges form, in each case, main or secondary cutting edges of the centering tip and serve for increased material removal. 
     In addition, the disclosure provides that a cavity lying in front of the pyramidal edge in the direction of rotation of the rock drilling tool is realized as a face cavity and a cavity lying behind the pyramidal edge in the direction of rotation of the rock drilling tool is realized as a flank cavity, wherein the face cavity ascends more steeply toward the pyramidal edge than the flank cavity. This means that a wedge or a main or secondary cutting edge is obtained where the amount of negative rake angle is less than half the wedge angle and is consequently aggressive and sturdy. 
     The disclosure also provides that the base of the pyramid is realized in particular as a polygon with an odd number of corners or in particular as a polygon with an even number of corners. Polygons with an even number of corners are suitable, in particular, as bases for centering tips with four or six pyramidal edges which are symmetrical with respect to a plane which is passed through by the longitudinal center axis of the rock drilling tool. Polygons with an odd number of corners are suitable, in particular, for centering tips with five, seven or more pyramidal edges where the orientation of the pyramidal edges is not dependent on an orientation of the outer cutting edges. 
     The disclosure also provides that at least one of the cavities deepens in the direction of a center of gravity of the centering tip. This means that a rock drill with increased power is created with a cutting body for which less cemented carbide is necessary compared to a rock drill with a cutting body with planar surfaces. 
     In addition, the disclosure provides that at least two of the pyramidal edges are realized as inner cutting edges and are formed, in particular, as an uninterrupted continuation of the outer cutting edges of the cutting body. Positioning the inner cutting edges of the centering tip and the outer cutting edges of the outer region of the cutting body in this manner creates a cutting body which is optimized in particular also for cutting both in a transition region between the centering tip and the outer region of the cutting body and consequently has a good stripping performance and in particular runs smoothly also in the exclusively rotating mode, which is used sometimes when spot-drilling. 
     In addition, the disclosure provides for at least one of the pyramidal edges, between its root and the tip of the pyramid or of the truncated pyramid, to have a development where the pyramidal edge extends in particular in a curved and/or in particular in a buckled manner along at least one portion keeping the gradient constant with respect to the longitudinal axis. Such a development of the pyramidal edge at a constant angle with respect to the longitudinal axis of the rock drilling tool makes it possible, for example, to realize the pyramidal edge as an inner cutting edge which is curved in a crescent-shaped manner and, when viewed in top view onto the drill head or in the direction of the longitudinal axis of the rock drilling tool, approximates the tip of the pyramid or of the truncated pyramid along a curved path. 
     The disclosure additionally provides for at least one of the pyramidal edges between its root and the tip of the pyramid or of the truncated pyramid, to have a development where the pyramidal edge of the pyramid extends along at least one portion in particular with increasing gradient with respect to the longitudinal axis or in particular with reducing gradient with respect to the longitudinal axis or in particular with erratic change in the gradient with respect to the longitudinal axis. Such a development of the pyramidal edge with a reducing angle with respect to the longitudinal axis of the rock drilling tool or with an increasing angle with respect to the longitudinal axis of the rock drilling tool or with an erratically increasing or reducing angle with respect to the longitudinal axis of the rock drilling tool, makes it possible, for example, to realize a buckle-shaped, sturdy centering tip in the case of an increasing angle or an acute, very aggressive centering tip in the case of a reducing angle. 
     As claimed in the disclosure, an overlapping of the developments of the pyramidal edges described in the two preceding sections is also provided. In this case, it is provided in particular to realize at least two pyramidal edges realized in a mirror-symmetrical manner with respect to the longitudinal axis, in a curved manner and with reducing gradient with respect to the longitudinal axis. Developing the pyramidal edges in such a manner creates a sturdy tip which is realized as a percussive cone. 
     Finally, the disclosure also provides that the cavity is realized, in particular, by two planar surfaces or in particular by several planar surfaces. Using this type of simple geometry, the advantages as claimed in the disclosure can be achieved in a simple and cost-efficient manner. 
     As claimed in the disclosure, it is also provided that the cavity is realized in a buckle-free and curved manner between adjacent pyramidal edges. In the case of rock drilling tools realized in this manner, the cutting body can be cleaned simply after use as the cutting body is free of set back edges. The possibility of cleaning the cutting body of the rock drilling tool in a rapid and successful manner propels its user to care and monitor the rock drill. This means in the end that accidents are prevented and, in addition, ensures constant high quality of the bores as a result. 
     In addition, the disclosure provides that the outer cutting edges, which are formed outside the centering tip by the coinciding of a face and a flank, have a curved development, and, when viewed in the direction of the longitudinal axis, are curved in opposition to a direction of rotation of the drilling tool. The blade-shaped cutting edge achieves an improved entrainment of the drillings about the longitudinal axis or axis of rotation of the rock drilling tool. The improved entrainment leads to more drillings being supplied to the discharge grooves and consequently to a reduction in the amount of drillings which accumulate between the bore hole wall and the rock drilling tool and impair the drilling operation. 
     As claimed in the disclosure, a radially outwardly diverging development of part surfaces of the side surfaces is provided, the part surfaces defining in each case the first and the second outer cutting edge to the side. This means that the radially outwardly increasing cutting forces can be better absorbed by the cutting body. 
     The disclosure also provides that at least one contour line of the centering tip, which specifies a contour in the direction of the longitudinal axis, forms an octagon, where the inner angles enclosed between the consecutive side edges are, in an alternating manner, more than 180° and less than 180°. Such geometry leads to a tip which penetrates in an optimum manner into the rock or the concrete during percussion by its volume, which is reduced compared to a four-sided pyramid, and at the same time has a good cutting and stripping performance by means of its pyramidal edges which are enhanced in comparison with a four-sided pyramid. 
     Finally, the disclosure provides that a diameter of the centering tip is dimensioned in proportion to the nominal diameter of the drill and the diameter of the centering tip is realized in particular between ⅙ and 3/6 of the nominal diameter and preferably approximately ⅓ of the nominal diameter. A solid design of the centering tip in this manner leads to higher stability and nevertheless has a high removal performance due to the special development. 
     In terms of the disclosure, the term a cutting body includes both inserts which are embedded between continuations of the helix and form the drill head with the same, and also solid cemented carbide heads which are fastened in an obtuse manner on the helix and form the entire drill head. Centering tips which are inserted in a separate manner are not cutting bodies within the terms of the disclosure. 
     In the terms of the disclosure, a cavity is a concave surface which runs between two pyramidal edges of the centering tip, the centering tip being realized as a pyramid or a truncated pyramid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details of the disclosure are described in the drawing by way of the schematically represented exemplary embodiments, in which: 
         FIG. 1   a  to  1   p : show different views and sections of a rock drilling tool as claimed in the disclosure and the cutting body thereof; 
         FIGS. 2   a  to  2   k : show a cutting body realized as an insert for a second rock drilling tool as claimed in the disclosure; 
         FIGS. 3   a  to  10   e : show eight further design variants of a cutting body realized as an insert or as a solid cemented carbide head for rock drilling tools as claimed in the disclosure; 
         FIG. 11   a  to  11   f : show further views and sections of the cutting body shown in  FIGS. 1   a  to  1   p  and 
         FIGS. 12 to 14 : shows top views onto two further schematically represented rock drilling tools. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1   a  shows a top view in the direction of a longitudinal axis L of a rock drilling tool  1  as claimed in the disclosure. A drill head  2  of the rock drilling tool  1  includes a cutting body  3 , which is realized as an insert  4 . The insert  4  is held between continuations  5 ,  6  of a helix  7 . In addition, two pilot cutting bodies  8 ,  9  are embedded into the continuations  5 ,  6  which are components of the drill head  2 . 
       FIG. 1   b  shows a perspective view of the rock drilling tool  1  shown in  FIG. 1   a . The further development of the helix  7  and a shaft  10  connecting to the helix are shown by way of the broken lines. 
       FIG. 1   c  shows a side view of the rock drilling tool  1  from the arrow direction  1   c  indicated in  FIG. 1   a . In this view it can be seen how the insert  4  extends over a nominal diameter N of the rock drilling tool  1  running transversely with respect to the longitudinal axis L. 
       FIG. 1   d  shows a further side view of the rock drilling tool  1 , as is produced when the representation of  FIG. 1   a  is looked at from an arrow direction  1   d . It can be seen in  FIG. 1   d  how a centering tip  11 , which is arranged in an inner region  12  of the cutting body  3  or of the insert  4 , projects in an effective direction W of the rock drilling tool  1  beyond an outer region  13  of the cutting body  3  or of the insert  4 . To understand this better, reference is made here to  FIG. 1   e  which shows the rock drilling tool  1  corresponding to the representation of  FIG. 1   a , however the centering tip  11  is shown cut off. The inner region  12  extends over a diameter di which is a maximum of 40% of the nominal diameter N. The outer region  13  is assembled from two part regions  13   a  and  13   b  which abut against the inner region  12  in the direction of the development of the nominal diameter N. 
       FIG. 1   f  now shows a top view of the cutting body  3  or the insert  4  on its own without the continuations, the pilot cutting bodies, the helix and the shaft. The representations  1   g  and  1   h  shows side views of the insert  4  from the arrow directions Ig and Ih indicated in  FIG. 1   f .  FIG. 1   i  shows a section through the  FIG. 1   h  corresponding to the line of intersection Ii-Ii.  FIG. 1   j  shows a perspective view of the insert  4 . It can be seen in particular from looking at  FIGS. 1   h ,  1   i  and  1   j  together that the centering tip  11  forming the inner region  12  is realized as a pyramid  14  which has four pyramidal edges  15   a  to  15   d  which converge in a tip  16  of the pyramid  14 . Between the pyramidal edges  15   a  and  15   b  or  15   c  and  15   d  it is possible to see subsidiary lines  17   a  to  17   d  which have a ray-like development with reference to the tip  16  of the pyramid  14 . Said subsidiary lines  17   a  to  17   d  indicate in a simplified manner a concavely curved shape of side surfaces  18   a  and  18   d , which lie between the pyramidal edges  15   a  and  15   b  or  15   c  and  15   d . The side surfaces  18   a ,  18   c  are consequently realized as cavities  19   a ,  19   c . As can be seen when looking at  FIGS. 1   h ,  1   i ,  1   j  and  1   g  together, the pyramidal edges  15   b  and  15   d  have a buckled development. A first, lower portion  20   a  of the pyramidal edge  15   b  has a first angle W 1  with respect to the longitudinal axis L. A second portion  20   b  of the pyramidal edge  15   b  has a second angle W 2  with respect to the longitudinal axis L. The first angle W 1  is smaller than the second angle W 2 . This is shown in a schematic diagram SK associated with  FIG. 1   j . Consequently the pyramidal edge  15   b  extends in its upper portion  20   b  in a flatter manner than in its lower portion  20   a . The pyramidal edge  15   d  extends in a mirror-symmetrical manner with respect to the pyramidal edge  15   b  with reference to the longitudinal axis L and has a corresponding development. Said buckling-away development of the pyramidal edge  15   b  is caused by side surfaces  18   b  and  18   d , which lie between the pyramidal edges  15   d  and  15   c  or  15   d  and  15   a , being assembled in each case by two differently orientated part surfaces  21   a ,  21   b  or  22   a ,  22   b.    
     The description is continued by way of  FIGS. 1   k  and  1   l ,  FIG. 1   k  being an enlarged representation of  FIG. 1   h , in which further cutting developments are shown and  FIG. 11  showing a section through the  FIG. 1   k  corresponding to the line of intersection IL-IL. As can be seen in  FIG. 11 , outer cutting edges  23 ,  24  of the cutting body  4 , which extend over part regions  13   a ,  13   b  of the outer region  13  in the direction of the inner region  12 , are continued in an uninterrupted manner by means of the pyramidal edges  15   a  and  15   c  toward a tip  16  shown cut-off in  FIG. 11 . In this case, the pyramidal edges  15   a  and  15   c  form inner cutting edges  25 ,  26 , which have the function of main cutting edges  27 ,  28 . The cavities  19   a  and  19   c , which lie in front of the inner cutting edges  25 ,  26  in a direction of rotation w of the insert  4 , form so-called face cavities  29 ,  30 , through the form of which the inner cutting edges  25 ,  26  maintain a small negative rake angle which is between 10° and 45° and preferably is approximately 30°. Flanks  31 ,  32  of the inner cutting edges  25 ,  26  are formed by the part surfaces  21   b  and  22   b  of the side surfaces  18   b  and  18   d . Consequently, wedges  33 ,  34  are formed in the region of the pyramidal edges  15   a  and  15   c , the wedge  33  being formed by the cavity  19   a  and the part surface  22   b , which coincide in the pyramidal edge  15   a  and the wedge  34  being formed by the cavity  19   c  and the part surface  21   b , which coincide in the pyramidal edge  15   c . Corresponding to the above-described development of the cavities  19   a  and  19   c , the wedges  33  and  34  have wedge angles which are reduced by at least 30% compared to wedge angles of a pyramid where the side surfaces are realized as planar surfaces. In the region of the pyramidal edges  15   b  and  15   d , further wedges  35  and  36  are formed, the form of which is determined by the cavity  19   a  and the lateral surface  18   b  or by the cavity  19   c  and the side surface  18   d , which coincide at the pyramidal edges  15   b  and  15   d . Said wedges  35 ,  36  which—as can be seen in  FIG. 1   k —are set back in relation to the wedges  33  and  34  in opposition to the effective direction W, have their destructive action in particular during the percussive movement of the rock drilling tool. It can also be seen in  FIG. 1   k  how the cavity  19   a  is curved in a concave manner in the direction of a point of gravity S of the pyramid  14 . A broken line shows a base side  37  of the pyramid  14  which extends from a root F 15   a  of the pyramidal edge  15   a  to a root  15   b  of the pyramidal edge  15   b . The development of the base side  37  is curved as a result of the cavity-like design of the side surface  18   a . In a corresponding manner, a base surface G 14  of the pyramid  14 —as is shown in a schematic manner by the broken lines in FIG.  11 —is realized as rectangle V 14  between the roots F 15   a , F 15   b , F 15   c  and F 15   d  of the pyramidal edges  15   a  to  15   d , the base sides  37  to  40  extending in a curved manner corresponding to the curvature of the side surfaces  18   a  to  18   d.    
       FIG. 1   m  shows the insert  4  corresponding to the cutting development  1   m - 1   m  shown in  FIG. 1   k . The line of cut  1   m - 1   m  extends below the centering tip  14 . 
       FIG. 1   n  shows an enlarged representation of  FIG. 1   f , in which the cutting developments Io-Io and Ip-Ip of the representations of the insert  4  shown in  FIGS. 1   o  and  1   p  are indicated. 
       FIG. 1   o  shows the cavity  19   c  which ascends toward the pyramidal edge  15   c . In addition, the section shows that the tip  16  of the pyramid  14  is realized as a cone  41  in order to be able to withstand better the percussive loads. 
     The sectional representation  1   p  once again shows the curved form of the cavity  19   a.    
       FIGS. 2   a  to  2   k  show a further cutting body  3  which is realized as insert  4  for a second rock drilling tool as claimed in the disclosure. The insert  4  is divided into an inner region  12  and an outer region  13 , the inner region  12  being defined by a centering tip  11 , to which the outer region  13  connects by way of its part regions  13   a  and  13   b . The insert  4  extends over a nominal diameter N, a diameter di of the inner region  12  is a maximum of 40% of the nominal diameter N. 
       FIG. 2   a  shows a top view onto the insert  4 .  FIGS. 2   b  and  2   c  show side views of the insert  4  from the arrow directions IIb and IIc indicated in  FIG. 2   a .  FIG. 2   d  shows a top view onto the insert  4  with a centering tip  11  shown in a sectioned manner.  FIG. 2   e  shows a perspective view of the insert  4 . 
     As can be seen in particular from  FIG. 2   d , the centering tip  11  is realized as a pyramid  14 , which has six pyramidal edges  42   a  to  42   f , which extend from roots F 42   a  to F 42   f  to a tip  16 —see  FIG. 2   a —of the pyramid  14 . All the side surfaces  18   a  to  18   f  between the pyramidal edges are realized as cavities  43   a  to  43   f . A concave curvature of all the cavities  43   a  to  43   f  toward a longitudinal center axis L of the insert  4  or of the rock drilling tool can be seen from the cutting edges visible in  FIG. 2   d . When viewed in the direction of rotation w, each cavity  43   a  to  43   f  forms a face cavity  44  for the following pyramidal edge and a flank cavity  45  for the preceding pyramidal edge. In the region of the pyramidal edges  18   a  to  18   f , the pyramid  14  consequently has six wedges  46   a  to  46   f , which are each formed by surface portions of the cavities  43   a  to  43   f  which coincide in the respective pyramidal edge  18   a  to  18   f . As inner cutting edges  25 ,  26 , the wedges  46   a  and  46   d  form a seamless continuation of the outer cutting edges  23  and  24 . Two main cutting edges  27  and  28 , which extend over the insert  4 , are consequently formed by the outer cutting edges  23  and  24  as well as the inner cutting edges  25  and  26 . The centering tip  11  or the pyramid  14  projects beyond the outer region  13  of the insert  14  in the effective direction W. It can be seen in particular from  FIGS. 2   c  and  2   f  how the wedges  46   b ,  46   c ,  46   e  and  46   f  form centrally arranged secondary cutting edges  47 . Through the development of the side surfaces  18   a  to  18   f , in the direction of rotation w of the insert  4  a face  48  is formed in front of each pyramidal edge  42   a  to  42   f  and a flank  49  is formed behind each pyramidal edge  42   a  to  42   f .  FIG. 2   e  shows some faces  48  and some of the flanks  49  by way of example. 
       FIG. 2   f  shows a top view onto the insert  4  which corresponds to the representation in  FIG. 2   a . The cutting developments IIg-IIg, IIh-IIh, IIi-IIi, IIj-IIj and IIk-IIk for the sectional  FIGS. 2   g ,  2   h ,  2   i ,  2   j  and  2   k  are shown in this top view. 
     The symmetrical design of the centering tip  11  or of the pyramid  14  with respect to the longitudinal axis L can be seen in  FIG. 2   g . The cavities  43   a ,  43   b  and  43   c  with their concavely curved form can be seen in  FIG. 2   h .  FIG. 2   i  shows, as  FIG. 2   g , the symmetrical development of the centering tip  11  or of the pyramid  14 .  FIG. 11  shows the symmetrical development of the pyramidal edges  42   c  and  42   f  with reference to the longitudinal axis L. Finally,  FIG. 2   k  shows a section, from which it can be seen how the cavities  43   c  and  43   d  ascend toward the pyramidal edge  42   d  and form a flank  49  and a face  48 . 
     Applicable to the eight further design variants of insert  4  for rock drilling tools shown in  FIGS. 3   a  to  10   e , is that the figure referenced by a in each case represents a top view onto the insert, the figures referenced by b and c in each case represent side views of the insert shown, the figure referenced by d in each case shows a top view of the insert with a sectioned tip and the figure referenced by e in each case shows a perspective view of the respective figure. In addition, applicable to all eight exemplary embodiments is that a centering tip  14  realized as a pyramid  14  is arranged in an inner region  12  and an outer region  13 , which consists of two part regions  13   a  and  13   b , connects to the inner region  12 . 
     In the case of the inserts  4  shown in  FIGS. 3   a  to  6   e , the pyramids  14  each have a rectangular base surface G 14  and, in a corresponding manner, four pyramidal edges  15   a  to  15   d , which run to a tip  16  of the pyramid. The pyramidal edges  15   a  to  15   d  are connected by four side surfaces  18   a  to  18   d.    
     In the case of the insert  4  shown in  FIGS. 3   a  to  3   e , the side surface  18   d  is realized as a cavity  19   d . This means that the pyramidal edge  15   d  has integrally formed thereon an enhanced face  48 , which has a negative rake angle which is smaller numerically than the further faces  48  formed by the planar side surfaces  18   a ,  18   b  and  18   c.    
     In the case of the insert  4  shown in  FIGS. 4   a  to  4   e , the side surfaces  18   a  and  18   c  are realized as cavities  19   a  and  19   c . This means that the pyramidal edges  15   a  and  15   c  have integrally formed thereon an enhanced face  48  which has a negative rake angle which is smaller numerically than the further faces  48  formed by the planar side surfaces  18   b  and  18   d.    
     The description relating to  FIGS. 4   a  to  4   e  relates to the insert  4  shown in  FIGS. 5   a  to  5   e , the centering tip  11  being integrated completely into the insert  4  in the design variants of  FIGS. 4   a  to  4   e  and protruding in an effective direction W in the design variants of  FIGS. 5   a  to  5   e.    
     In the case of the insert  4  shown in  FIGS. 6   a  to  6   e , the side surfaces  18   a  to  18   d  are realized as a cavity  19   a  to  19   d . This means that all the pyramidal edges  15   a  to  15   d  have integrally formed thereon an enhanced face  48 , which has a negative rake angle which is numerically smaller than faces formed by planar side surfaces (not present here). 
     In the case of the insert  4  shown in  FIGS. 7   a  to  7   e , this is a design variant which is similar to the first design variant shown in  FIG. 1   a  and following pages. 
     In the case of the insert  4  shown in  FIGS. 8   a  to  8   e , this is a design variant which is similar to the second design variant shown in  FIG. 2   a  and following pages. 
     The design variants shown in  FIGS. 9   a  to  9   e  and  10   a  to  10   e  differ from the previously described design variants in particular in that the cutting bodies  4  thereof in the inner region  12  have a width B 12  which is greater than a width B 13  of the outer region  13  of the cutting body  4 . 
       FIGS. 11   a  to  11   f  shows further views and sections of the cutting body  3  shown in  FIGS. 1   a  to  1   p .  FIG. 11   a  shows a side view of the cutting body  3  in which the development of a section through the cutting body  3  shown in  FIG. 11   b  is provided. The section XIb-XIb extends through the pyramidal edges  15   a  and  15   c , which as inner cutting edges  25 ,  26  form a portion of the main cutting edges  27  and  28 . It can be seen in the sectional view of  FIG. 11   b  how the pyramidal edges  15   a  and  15   c  extend in a symmetrical manner with respect to the longitudinal axis L of the cutting body  3  and merge into the outer cutting edges  23 ,  24  of the outer region  13  by means of shoulders  50 ,  51 . In addition,  FIG. 11   b  shows the nominal diameter N of the insert  3  once again. A diameter DZ of the centering tip  11  is approximately between ⅙ and 3/6 of the nominal diameter N and in the exemplary embodiment shown is approximately ⅓ of the nominal diameter N.  FIG. 11   c  shows two cutting developments which intersect the cutting body  3  along the pyramidal edges  15   b  and  15   d , which form the secondary cutting edges  52 ,  53 . Said pyramidal edges  15   b  and  15   d  are also realized in a symmetrical manner with respect to the longitudinal axis L. Finally,  FIG. 11   f  shows a view of the detail of the centering tip  11 . In this case, to clarify the geometrical form of the centering tip  11  contour lines HL are indicated for the cavity  19   a , said contour lines circling the centering tip  11  at a constant depth, depths being measured in the direction of the development of the longitudinal axis L. 
       FIG. 12  shows a schematic representation of a top view onto a design variant of a rock drilling tool  1  as claimed in the disclosure. The rock drilling tool  1  includes a cutting body  3  which is realized as an insert  4  and is inserted into a slot  54  which is realized in a helix  7  of the rock drilling tool  1 . The cutting body  3  has a centering tip  11  with a pyramid  14  with four pyramidal edges  15   a  to  15   d . In this case, the pyramidal edges  15   a  and  15   c  are components of two main cutting edges  27 ,  28 , which extend from a tip  16  radially outward over the cutting body  3 . Side surfaces  18   a  to  18   d , which extend between the pyramidal edges  15   a  to  15   d , are realized as cavities  19   a  to  19   d . The topography of the centering tip  11  is made clear by means of several contour lines HL. When viewed in the direction of a longitudinal axis L of the rock drilling tool  1  which is perpendicular to the drawing plane, all the contour lines HL of the centering tip  11  form in each case octagons AE, the adjacent edges K 1  to K 8  of which enclose with one another in an alternating manner inner angles W 10 , W 13 , W 15  and W 17  which are more than 180° and angles W 12 , W 14 , W 16  and W 18  which are less than 180°. For better perceptibility, the centering tip  11  is shown in an enlarged manner in  FIG. 13  with a contour line HL. Three variants are shown in  FIG. 12  for the development of outer cutting edges  23  and  24 . Continuous lines show a radial development of the cutting edges  23  and  24 . A broken line shows a development of the cutting edges  23  and  24  where the cutting edges  23  and  24  have a curved development and, when viewed in the direction of the longitudinal axis, are curved in opposition to a direction of rotation w of the rock drilling tool  1 , the cutting edges  23  and  24  again having a radial development toward the outer surfaces of the AF 1  and AF 2  of the cutting body  3 . Dot-dash lines indicate the development of the cutting edges  23  and  24  in a third design variant where the cutting edges  23  and  24  extend in a curved manner from the pyramid  14  as far as up to the outer surfaces AF 1  and AF 2  and are curved in opposition to the direction of rotation w of the rock drilling tool  1 . 
       FIG. 14  shows a schematic representation of a top view onto a further design variant as claimed in the disclosure of a rock drilling tool  1  with a cutting body  3 . Regarding the design of the centering tip  11  and the development of the outer cutting edges  23  and  24 , reference is made to the description relating to  FIGS. 12 and 13 . The cutting body  3  is defined between outer surfaces AF 1  and AF 2  by side surfaces  55 ,  56 , the first side surface  55  merging into a face  23   a  of the first cutting edge  23  and a flank  24   b  of the second cutting edge  24  and the second side surface  56  merging into a flank  23   b  of the first cutting edge  23  and a face  24   a  of the second cutting edge  24  and the side surfaces  55 ,  56  in the region of the first cutting edge  23  and in the region of the second cutting edge  24 , when viewed in the direction of the longitudinal axis L of the rock drilling tool  1 , which is perpendicular to the drawing plane, have a diverging development radially outward with respect to each other. Part surfaces  55   a  and  56   b  of the side surfaces  55  and  56 , which merge into the flank  23   a  and the face  23   b  of the first cutting edge  23 , enclose an angle W 23 , which is between 10° and 40°. Part surfaces  56   a  and  55   b  of the side surfaces  55  and  56 , which merge into the flank  24   a  and the face  24   b  of the second cutting edge  24 , enclose an angle W 24 , which is between 10° and 40°.