Abstract:
A cutting tool for breaking or excavating machines, comprising: a tool body,a main tip ( 1 ), and a plurality of ancillary tips ( 3 ), wherein the ancillary tips ( 3 ) comprises a plurality of tapered cutting tips ( 7 ) or a plurality of cutting edges ( 8 ) for breaking operation; and the ancillary tips ( 3 ) are disposed on the tool body ( 2 ) around the main bit tip ( 1 ). The cutting tool for breaking or excavating machines of the invention is capable of increasing and elongating the wear resistance capability without sacrifice its penetrating ability so as to extend the service life of the bit, as well as increase its working efficiency and safety.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority benefits to Chinese Patent Application No. 200810079978.6 filed Dec. 9, 2008, the contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to cutting bits for wall breaking, tunneling, trenching, coal mining, and road milling machines, and more particularly to a tool comprising more than one ancillary cutting tip in additions to a main cutting tip. 
         [0004]    2. Description of the Related Art 
         [0005]    Most popular conventional bits for breaking or excavating machines are generally comprised of an alloy steel bit body and a carbide alloy bit tip. The carbide alloy bit tip is welded to the head of the bit body using soldering technology. During cutting or breaking, the head of the cutter undergoes strong stresses and is subjected to friction. Thus, the bit body around the carbide alloy bit tip will progressively wear out, generally resulting in the falling off of and catastrophic failure of the bit tip. In underground coal mining application, sparks are created when the tool collides with the rock. Spark must be reduced or eliminated for safety reasons. Various technologies have been developed to elongate the service lifetime of the tool, while trying to improve the safety and penetrating ability thereof. Currently, a majority of cutting bits adopts the three structures shown in  FIGS. 1-3 . Still, 85 percent failures of the tools adopting the above mentioned designs are due to a fall-off of the carbide tip, resulting from a wear out of the steel body. 
         [0006]    German Patent DE19821147A1 discloses a cutting tool design ( FIG. 4 ). The design suggests installing wear-resistant elements around the main cutting tip. However, the design is not optimized, and there is still much room for improvement. Although the design reduces the wear out of the steel body to some extent, it also shows the following weaknesses:
       The front area disposed toward the working direction has to be widened to accommodate the additional wear resistant elements. The shoulder of the bits with such arrangement becomes wide and square, which brings about the problem of heavy pounding and high power consumption.   The flat top surface of the claimed cylindrical wear resistant body also increases resistance against the tool during work. In addition, the sharp right-angled edges of the wear resistant elements are fragile and break easily in collision with the material to be removed. The breakage diminishes the protection effect of the elements.   The necessary length of the wear resistant body, as well as radius to height ratio of the cylindrical wear resistant element, have not been elucidated or optimized. From what is illustrated in the drawings, the radius to height ratio of the cylindrical wear resistant element is very close to 1:1. Obviously, elements with such a configuration can only provide only limited protection to the square part of the tool shoulder. However, in practical working conditions, the entire front part of the tool is often buried beneath the material to be removed. The material to be removed will wear against the front part of the tool, including the metal around and beneath the bottom of the wear resistant element. In this case, the short fat wear resistant element will rapidly lose support and fall out due to wear out of the surrounding metal (see  FIG. 13 ). As a result, such configuration actually cannot provide lasting protection for the steel tool body.       
 
         [0010]    There have been other solutions adopting slimmer and longer wear resistant elements than the above mentioned German patent. However, these solutions can only prolong the service life to a limited extend, while they do not give satisfying results life respect to the problems discussed above. 
       SUMMARY OF THE INVENTION 
       [0011]    Therefore, it is one objective of the present invention to provide a bit tool for breaking or excavating machines capable of increasing the wear resistance capability without sacrificing its penetrating ability so as to extend the service lifetime of the bit, as well as increase its working efficiency and safety. 
         [0012]    To achieve the above objective, there is provided a cutting bit for breaking or excavating machines, comprising: a tool body; a main tip; and a plurality of ancillary tips, the ancillary tips comprising a plurality of tapered cutting tips or a plurality of cutting edges for breaking operation; and the ancillary tips being disposed on the tool body around the main bit tip. 
         [0013]    In certain embodiments of the present invention, the cutting tips of the ancillary tips are in shape of a cone, a frustum, a semi-ellipsoid or a dome, e.g., a spherical dome, with the sectional area of the ancillary tips becoming smaller along their axis. 
         [0014]    In certain embodiments of the present invention, the cutting edges of the ancillary tips are single-wedge or multiple-wedge. 
         [0015]    In certain embodiments of the present invention, the ends of the cutting tips are installed above the front surface of the tool body. 
         [0016]    In certain embodiments of the present invention, the ends of the cutting edge are installed above or flush with the front surface of the tool body. 
         [0017]    In certain embodiments of the present invention, the ratio between the ancillary tips radius and length is in the range of between 1:1.5 and 1:5. 
         [0018]    In certain embodiments of the present invention, between 3 and 50 ancillary tips are installed around the main tip. 
         [0019]    In certain embodiments of the present invention, between 6 and 20 ancillary tips are installed around the main tip. 
         [0020]    In certain embodiments of the present invention, the buried length of the ancillary tip is more than one third of the length of the main tip. 
         [0021]    In certain embodiments of the present invention, the buried length of the ancillary tip is more than one third of the maximum diameter of the main tip. 
         [0022]    In certain embodiments of the present invention, the buried parts of the ancillary tips body are in shape of a cylinder, a cone, or a truncated cone. 
         [0023]    In certain embodiments of the present invention, the main tip is made of a first material; the ancillary tips are made of a second material; the tool body is made of a third material; and the first material is harder than the third material; and the second material is harder than the third material. 
         [0024]    The present invention provides the following solution for the buried length of the ancillary tips:
       a) For tools with plug-type main tip, the buried length of the ancillary tips must be more than one third of that of the main tip.   b) For tools with cap-type main tip, the buried length of the ancillary tips must be more than one third of the maximum diameter of the main tip.       
 
         [0027]    The ancillary tips in the present invention constitute an essentially different concept from the wear resistant element described in DE19821147A1. The wear resistant elements in DE19821147A1 are provided mainly in order to provide limited protection to the square part of the tool shoulder. Meanwhile, the notch formed during cutting can, to some extend, help in rotating the tool before it falls out. However, in DE19821147A1 not much attention was paid to the side effects brought about by the extended shoulder area, which is necessary to accommodate the cylindrical element. For example, the widened shoulder part causes turbulent flow of power and pounding vibration of the machine. 
         [0028]    In DE19821147A1 and CN 200610102129.9, a flat shoulder is necessary to accommodate the wear resistant elements. This flat shoulder can cause a large resistant force against the cutting tool during its operation. The increased resistant force is harmful. Firstly, it will overload the machine, thus causing extra impact and vibration, which is likely to damage the machine. Secondly, it will increase the power consumption. Thirdly, it will produce vast easily flammable coal dust, thus reducing safety. The ancillary tips of this invention provide ideal solution to these problems. The tapered ancillary tips are engaged in cutting work together with the main tip. The tapered tip cuts through the bulk material without causing extra resistant force. Under the same working conditions, the energy consumption of a machine equipped with the tool of this invention is only 50% of the energy consumption of a machine equipped with a tool described in DE19821147A1 or CN 200610102129.9. 
         [0029]    The ancillary tips of the present invention do not have a cylindrical or conical body. The top surface pointed to the working direction is not flat. Rather, the ancillary tips are in the shape of a cylinder with tapered tip, a dome, a cone, a wedge, a mushroom, or the like. The ancillary tips not only act as passive wear resistant member, but also are actively involved in breaking the material to be removed. 
         [0030]    Comparison tests were carried out between embodiments of the present invention and those described in DE19821147A1 and CN 200610102129.9. The results of test shown below indicate that the former have obvious advantage over the latter. 
         [0031]    Conditions of coal mine tests: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Coal seam hardness f = 6. 
                 Mining depth: 0.6 m 
               
               
                   
                 Mining height: 4 m 
                 Shearer haulage speed: 7.7 m/min 
               
               
                   
                 Working face length: 100 m 
                 Shearer drum speed: 28 rpm 
               
               
                   
                   
               
             
          
         
       
     
         [0032]    Normally, a miner uses a traditional single tipped tool. Because coal seams are relatively hard, the tool consumption is large. The traditional tools cannot survive a workload of cutting through a full working face having 100 m in length. On average, 89 bits will be consumed in an 8 hours shift. The average output is about 2000 T per shift. 400 pieces of tools of each type were provided to a coal miner for test. 
         [0033]    1. Comparison Test of Tools Described DE19821147A1: 
         [0034]    Single tipped tools were replaced by the tools constructed according to DE19821147A1. As soon as the shearer was started, the monitoring system indicated the machine was working in an overloaded condition. The tool caused great resistance due to a widened shoulder area. The tools could not penetrate into the coal bulk smoothly; instead, the tools stroke the bulk like hammer. The pounding effect caused heavy coal dust and great vibration of the shearer. The machine operator had to shut off the shearer. In order to carry on the test, the operator had to readjust the shearer working parameters as follows: shearer haulage speed was slowed down to: 4.0 m/min; shearer drum speed was lowered to 19 rpm; and the mining depth remained at 0.6 m. The test was carried on by sacrificing the working efficiency. After the adjustment, the operator managed to maneuver the shearer working at the limit below overloading. Although the wear resistant elements provided some extent of protection to the tool body, they started to suffer breakage soon after start of operation. Some of the wear resistant members started to fall off after the shearer worked though 95 m along the working face. The main tips started to drop out after 120 m. Then the machine had to be stopped for tool replacement. The test lasted 4 working shifts (32 hours). Totally, 276 pieces of tools had to be changed, that is 69 pieces had to be changed every working shift, on average. During the test, coal production output was about 2100 T every working shift. 
         [0035]    2. Comparison Test of Tools According to CN 200610102129.9 
         [0036]    After replacing the tools prepared according to DE19821147A1 with those described in CN 200610102129.9, the shearer operator restored the parameter as follows: shearer haulage speed at 7.7 m/min; shearer drum speed at 28 rpm; the mining depth remained at 0.6 m. At the initial stage, the similar problem appeared as in the previous test. The operator had to readjust the machine the same way as in the previous test, that is, shearer haulage speed was slowed down to: 4.0 m/min; shearer drum speed was lowered to 19 rpm; and the mining depth remained at 0.6 m. Similar to the former test, the wear resistant elements started to suffer breakage soon after operation. However, the elements were held strongly in position because they were embedded deeper into the tool body. As the front tool body around the wear resistant element has worn out, the tool front shoulder disappeared and the tool front became slimmer. When the shearer reached 80 m along the working face, the operator noticed that the working load decreased due to the better penetrating performance of tool. Then the operator restored the parameter to normal settings as follows: shearer haulage speed at 7.7 m/min; shearer drum speed at 28 rpm; the mining depth remained at 0.6 m. A few wear resistant members started to fall off after the shearer fed in 160 m along the working face. Main tips started to drop out after 200 m. Then the machine had to be stopped for tool replacement. The test lasted 4 working shifts (32 hours). Totally, 220 pieces of tools had to be changed, that is 55 pieces had to be changed every working shift in average. During the test, coal production output is about 2350 T every working shift. 
         [0037]    Although this test gives a better result than the previous test, ancillary tips, which can actively get engaged in cutting operation, were adopted for further comparison test. 
         [0038]    3. Comparison Test of Tools According to Present Invention: 
         [0039]    The operator installed the tools of the present invention on the same shearer and started test. The shearer parameters were set as follows: shearer haulage speed at 7.7 m/min; shearer drum speed at 28 rpm; the mining depth remained at 0.6 m. As soon as the test started, the operator noticed the machine was working under rated load. The operator thought it was the result of the sharper tool contour and high penetrating capability. So, the working parameters were set up to as follows: shearer haulage speed at 12.8 m/min; shearer drum speed at 28 rpm; the mining depth remained at 0.6 m. After the adjustment, the machine worked without any overloading. 
         [0040]    During the test, the ancillary tips performed much better than the positive wear resistant elements in the previous tests. They actively got involved in cutting working and provided superior protection to the tool body. Few breakage of the ancillary tips occurred due to impact during their service life. No ancillary tip fell off until the shearer reached 280 m along the working face. Main tips started to drop out only after 350 m. The test lasted 4 working shift (32 hours). Totally, 52 pieces of tools had to be changed during the test, that is, 13 pieces had to be changed every working shift in average. During the test, coal production output is about 3500 T every working shift. 
         [0041]    The following table summarizes the comparison test results: 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Consumption 
                 Consumption 
                   
               
               
                   
                 per working 
                 per ton 
                 Maintenance 
               
               
                   
                 shift 
                 of coal output 
                 downtime 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Single tipped tool 
                 89 pcs 
                 0.045 pcs/ton 
                 120 min/shift  
               
               
                 DE19821147A1 tool 
                 69 pcs 
                 0.033 pcs/ton 
                 90 min/shift 
               
               
                 CN200610102129.9 tool 
                 55 pcs 
                 0.023 pcs/ton 
                 75 min/shift 
               
               
                 Tool of present invention 
                 13 pcs 
                 0.004 pcs/ton 
                 18 min/shift 
               
               
                   
               
             
          
         
       
     
         [0042]    As can be seen from the test result, the present invention has vastly extended the tool service lifetime. At the same time it remarkably improved efficiency of the cutting operation. 
         [0043]    In this invention, ancillary tips can be made of hard material having a lower propensity for incendiary spark production during a cutting operation than the steel of the shank. This arrangement reduces the contact area between material to be removed and steel body, thus reducing the likelihood of producing a spark during mining or excavation operations, in particular in underground coal mining. 
         [0044]    As described before, a wear resistant member can help to rotate the tool during its operation. But if a member fails often, using it has only a limited effect. Ancillary tips of this invention stay in position for a much longer period of time and can help to rotate the tool in operation all through its extended service lifetime. 
         [0045]    In underground coal mining, one of the major safety problems is heavy coal dust, which can be trapped within the mine and is readily ignitable. Disadvantageously, the equipment used in coal mining can generate sparks and thus cause fires or explosion. Therefore, it is important that all appropriate steps be taken to minimize or eliminate the production of sparks. In this invention, ancillary tips can be made of hard material having a lower propensity for incendiary spark production during a cutting operation than the steel of the shank. In addition, the tapered ancillary tips can be installed above the shoulder surface, so that the coal bulk can be crashed before it comes into touch with the steel tool body. This arrangement reduce the contact area between material to be removed and steel body, thus reduced likelihood of producing a spark during mining or excavation operations, in particular in underground coal mining. 
         [0046]    Another advantage of this invention is that the concept of ancillary tips makes it possible to realized equal-strength design of the main tip and the cutting tool body. By adjusting the configuration of the ancillary tip, including the tip contour, its length and diameter, the main tip can be held for much longer time before losing support and falling off due to wear out of the steel tool body. 
         [0047]    The advantages of the present invention can be summarized as follows:
       1. The ancillary tips are actively engaged in the cutting operation; this can not only provide better protection to the steel, but also help in reducing the cutting force.   2. The ancillary tips ensure longer and more reliable tool rotation throughout its service life.   3. The ancillary tips vastly extend service life of the tool.   4. The tools in this invention reduce likelihood of producing sparks during mining or excavation operations, and increase safety in underground coal mining.   5. The tools in this invention realize equal-strength design, which helps in making full use of the resources, especially the precious hard metals.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0053]      FIG. 1  is a structural view of a conventional cutting tool with a plug type main tip; 
           [0054]      FIG. 2  is a structural view of a conventional cutting tool with a mushroom type main tip; 
           [0055]      FIG. 3  is a structural view of a conventional cutting tool with a cap type main tip; 
           [0056]      FIG. 4  is a structural view of a conventional cutting tool with wear resistant elements; 
           [0057]      FIGS. 5 and 6  are structural views of cutting tools installed with cone-tipped ancillary tips according to one embodiment of the present invention, wherein the ancillary cone tips raise above the steel body; 
           [0058]      FIG. 7  is a structural views of a bit body installed with double-wedge ancillary tips according to one embodiment of the present invention, wherein the cutting edges of the ancillary tips raise above the steel body; 
           [0059]      FIGS. 8 and 9  are structural views of a cutting tool installed with single-wedge ancillary tips according to another embodiment of the present invention; 
           [0060]      FIG. 10  is a structural view of a cutting tool installed with single-wedge ancillary tips according to another embodiment of the present invention; 
           [0061]      FIG. 11  is a structural view of a cutting tool installed with cone-tipped ancillary tips according to another embodiment of the present invention, wherein the ancillary cone tips raise above the steel body; 
           [0062]      FIG. 12  is a comparison drawing showing the different protection effect between the cutting tool of the present invention and a cutting tool according to DE19821147A1 during the initial cutting stage of a cutting test; 
           [0063]      FIG. 13  is a comparison drawing showing the different protection effect between cutting tool of the present invention and a cutting tool according to DE19821147A1 during a cutting test; 
           [0064]      FIGS. 14-16  show other embodiments of cone-tip ancillary tips of the present invention; 
           [0065]      FIGS. 17 and 18  illustrate other embodiments of single-wedge ancillary tips of the present invention; and 
           [0066]      FIG. 19  illustrates another embodiments of double-wedge ancillary tips of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0067]    As shown in the drawings, the cutting tools of this invention, comprise: a main carbide alloy main bit tip  1  and a bit body  2 , wherein a plurality of smaller ancillary cutting tips  3  is installed on the bit body around the main carbide alloy bit tip  1 . The sectional area of one end of the ancillary tip  3  becomes progressively smaller along its axis. The tapered profile of the tip  3  forms a plurality of cutting tips  7  or cutting edges  8 . The cutting edges  8  are provided in the form of a single-wedged cylinder or a double-wedged cylinder. In the case of cutting tool adopting cutting tips  7 , the cutting tips  7  can be positioned above the front surface  5  of the tool, so that it can be engaged in cutting operation from the very start. Similarly, in the case when a tip  3  with cutting edges  8  is used, the edges  8  can be positioned either above the front surface  5  of the tool or flush with the surface  5 . In the later case, a smoother tool profile is achieved. 
         [0068]    In present invention, the ratio between the radius of the ancillary tips d and the length H is in the range of between 1:1.5 and 1:5. Between 3 and 50 pieces of ancillary tips  3  can be installed around the main tip  1 . For tools with plug-type main tip  1  as shown in  FIGS. 5 and 7 , the buried length of the ancillary tips must be more than one third of that of the main tip. For tools with cap-type main tip  1  as shown in  FIGS. 9-11 , the buried length of the ancillary tips must be more than one third of the dimension of the maximum diameter D of the main tip. 
         [0069]    The term “buried portion”, as used herein with respect to ancillary tips, is the portion of the ancillary tip which are disposed below the external surface of the bit body (as opposed to protruding above the external surface of the bit body). The term “buried length”, as used herein with respect to ancillary tips, is a length of the buried portion of the ancillary tip. 
         [0070]    The ancillary tips in the present invention are not simply in the form of a cylindrical or conical body. The top surface pointed to the working direction is not flat; instead, the cutting tip or the cutting edge is formed. The ancillary tips are in the shape of a cylinder with tapered tip, a dome, a cone, a wedge, a mushroom, or the like, as shown in  FIGS. 14 to 19 . The ancillary tips not only act as passive wear resistant members, but also get actively involved in breaking the material to be removed. 
         [0071]    In DE19821147A1 and CN 200610102129.9, a flat shoulder  6  of the cutting tool is necessary to accommodate the wear resistant elements. This flat shoulder can cause great resistant force against the cutting tool during its operation. This increased resistant force is harmful, as described above. 
         [0072]    In this invention, ancillary tips can be made of a hard material having a lower propensity for incendiary spark production during a cutting operation than the steel of the shank. This arrangement reduces the contact area between material to be removed and steel body, thus reducing the likelihood of producing a spark during mining or excavation operations, particularly in underground coal mining. 
         [0073]    In certain embodiments of the present invention, the number of the ancillary tips  3  installed on the bit body  2  around the main bit tip  1  is in the range of between 3 and 50, and optimally, in the range of between 6 and 20. 
         [0074]    In present invention, there is provided a solution to the ratio between the radius of ancillary tips d and length H, which is in range of between 1:1.5 and 1:5, and optimally, in the range from between 1:2 and 1:4. The specific ratio can be decided according to other factors, such as the type of the main tip. 
         [0075]    In choosing the length of the ancillary tips, following solutions are provided: (a) for tools with plug-type main tip  1  as shown in  FIGS. 5 and 7 , the buried length of the ancillary tips must be more than one third of that of the main tip; in practical application, the bottom of the ancillary tips should be arranged at more or less the same level as main tip; and (b) for tools with cap-type main tip  1  as shown in  FIGS. 9-11 , the buried length of the ancillary tips must be more than one third of the dimension of the maximum diameter D of the main tip. For example, if the bottom of the plug type main tip  1  is 15 mm down into the tool front surface  5 , according to this invention, the preferable length of the ancillary tips should be between about 10 mm and about 16 mm, and the diameter of the ancillary tips should be preferably about 5 mm. 
         [0076]    In the case of a tool with a cap type main tip as shown in  FIGS. 7 and 11 , the length of the ancillary tips H shall be more than ⅓ of the bottom diameter D of the main tip. More particularly, when D is 22 mm, the length of the ancillary tips should be more than 7 mm and the diameter of the ancillary tips should preferably between about 3 mm and 5.5 mm. This definition overcomes problems encountered with wear resistant element described in DE19821147A1. While DE19821147A1 did not provide a detailed illustration of the wear resistant element, it can be inferred from the provided drawings that the element is fat and short, and the main purpose thereof is to protect the square part of the tool shoulder. Nevertheless, in practical working conditions, the entire top part of the tool is often buried beneath the material to be removed. The material to be removed will wear against the thorough top part of the tool, including the metal around and beneath the bottom of the wear resistant element. In this case, the short fat wear resistant element will quickly lose the support and fall out due to wear of the surround metal. Thus, such configuration actually cannot provide lasting protection for the steel tool body. 
         [0077]    In practical operation, the advantage of the ancillary tips are more obvious, because the tapered tip can help to break the material to be removed before it contacts the steel body, so that it further slows down the wear process. The typical wearing pattern of the cutting tool is disclosed in promotional materials of tool suppliers, all the disclosed tests are a good proof of the advantages of this invention which provides slimmer and longer ancillary tips. In one test carried out, a cutting tool of this invention is installed with a 22 mm diameter plug tip and 8 ancillary tips. The diameter of the ancillary tips is 6 mm and its length is 18 mm. The tool can still provide satisfactory service even after 15 mm of ancillary tips have been consumed. The service life was extended by 2 to 4 times. If the short fat element of prior art had been installed, it would have fallen off soon after the steel around it was worn out. 
         [0078]      FIGS. 5-11  show a cutting tool installed with different forms of ancillary tips. The ancillary tips  3  in this invention not only resist the wear against the steel body, but their tapered front end is also actively engaged in cutting operation. The other advantage is that the tapered ancillary tips make it possible to produce the cutting tool into a very sharp shape. For example, the tapered front of the ancillary tips in  FIG. 10  vastly diminishes the square shoulder of a tool, as shown in  FIG. 4 , which adopts cylindrical wear resistant element. The sharpness of such a tool is essential. In practical operation in underground coal mine, the blunt front of the tool shown in  FIG. 4  actually collides with the coal bulk like a hammer, as shown in the field test. The cutting effect is greatly weakened. The tool fails to penetrate into the coal bulk smoothly, instead, the hammering effect causes such heavy dust and strong vibration of the machine, that operation has to be stopped. After installing tools according to this invention to take the place of the blunt tools, the machine started to work smoothly with much higher feeding speed and lower vibrations. The improved tool of this invention can boost the working efficiency, reduce dust production, and improve the safety of the operation. In extreme cases, where penetration ability of the tool is emphasized, the shoulder of the tool can be totally removed using the concept of the present invention, as shown in  FIG. 10 . 
         [0079]    The ancillary tips in the present invention constitute an essentially different concept from the wear resistant element described in the DE19821147A1. The wear resistant elements  4  in DE19821147A1 are provided mainly in order to provide limited protection to the square part of the tool shoulder  6 . Meanwhile the notch formed during cutting can, to some extent, help in rotating the tool before it falls out. However, DE19821147A1 does not pay much attention to the side effects brought about by the extended shoulder area, which is necessary to accommodate the cylindrical element. For example, the widened shoulder part of the machine causes turbulent flow of the power and pounding vibrations. 
         [0080]      FIGS. 14 to 16  show examples of possible embodiment of the ancillary tips  3 . The dome cutting tip  7  and cone cutting tip  7  allow the ancillary tips to get involved in the cutting operation. They are no longer passive wear resistant members. In addition, these contours get rid of the fragile square edge of simple cylindrical elements of prior art. 
         [0081]    In  FIGS. 17 to 19 , the cutting edges  8  are made from a cylindrical body by removing a portion of the top part of the element. An obtuse angle cutting edge is formed. The obtuse angle cutting edge is stronger than a right angle edge used heretofore in terms of resisting breakage under impact. At the same time, the sloped surface formed can help to eliminate the square, wide shoulder of the tool. The wedged ancillary tips  3  can be installed as shown in  FIGS. 7 and 10 , with its cutting edge raised a little higher above the front surface  5  of the cutting tool. The tip can also be installed as shown in  FIGS. 8 and 9 , with its slope flush with the front surface  5  of the tool so as to realize a smother profile. As shown in  FIGS. 7-10 , the tools with ancillary tips are produced into much shaper contour, which will improve the penetration ability of the tool. 
         [0082]    As mentioned above, a typical wearing pattern of the cutting tool has been described in product brochures and electronic publications of the existing tool producers.  FIGS. 12 and 13  show a typical wear out pattern for a cutting tool. Specifically, for comparison, each sectional view shows a typical wear out pattern of a conventional tool in the left half and a typical wear out pattern of a tool according to this invention in the right half of the drawing. The outermost dotted line shows a profile of an unused tool. The inner solid line  9  shows a typical front contour of a heavily worn out tool before failure. A wear resistant element  4  of invention DE19821147A1 and the ancillary tips  3  of the present invention are put in position to give a clearer comparison of their actual protection effect.  FIG. 12  is a comparison drawing at the initial working stage, while  FIG. 13  is a drawing nearly close to the tool failure. As can be seen from the drawings, the short fat wear resistant element  4  will fall off soon after the steel on the shoulder of the tool. However, the ancillary tips  3  can stay in position for a longer period of time. 
         [0083]    The ancillary tips  3  can be in shape of a sheet, a rectangular parallelepiped, etc. The tapered end of the ancillary tips can be in shape of a multihedral prism, a bi-conical polyhedron, etc. 
         [0084]    This invention is not to be limited to the specific embodiments disclosed herein and modifications for various applications and other embodiments are intended to be included within the scope of the appended claims. While this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and following claims. 
         [0085]    All publications and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application mentioned in this specification was specifically and individually indicated to be incorporated by reference.