Abstract:
A cutting tool having an outer surface with a plurality of inserts connected to a distinct pocket extending generally radially on the outer surface. The cutting inserts are arranged in a helical array on the outer surface in a manner that at least one cutting edge of each cutting insert is spaced in an angular circumferential direction from the pocket of the next adjacent cutting insert. The spacing of the inserts is such that a distinct point on the each one of the one or more cutting edges define part of a layout line having a non-uniform slope.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a helical milling cutter, more particularly to a helical milling cutter having helical arrays of cutting inserts removably attached to seats formed on the cutting tool. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the field of metal cutting, and more particularly metal cutting tool design, it is desirable to develop tools that obtain the most even distribution of cutting loads on a helical cutter during a cutting operation. Optimizing the cutting loads of a cutting tool allow the tool to work more quickly and efficiently. Additionally, it is desirable to optimize the cutting loads to prevent unwanted vibrations or chatter as the cutting tool moves against the work piece. Additionally, the unwanted vibrations can cause breakage of the cutting tool inserts or the body of the tool, which decreases the usable life of the cutting tool and its components and may ruin the work piece. 
         [0003]    One such solution to improving cutting load is described in U.S. Pat. No. 5,083,887. In this solution, the cutting inserts are disposed in a helical array in which the cutting edge of each insert, with respect to the cutting tool, is spaced in a circumferential direction from the seat of the next adjacent insert and is in overlapping relationship in the axial direction with the cutting edge of the next adjacent insert, and the radially extending edges of each insert are in overlapping relationship with the radially extending edges of the adjacent inserts, such that the same point on all the cutting edges of all the inserts from the second row onward in any column comprise a continuous and non-interrupted layout line defining the helical array. The cutting tool described by this invention provides greater percentages of contact between the cutting tool and the work piece throughout the rotation of the tool; however, eliminating unwanted vibrations and improving cutting load is not achieved. In particular, the industry desires improved tools for even better surface finishing, smoother cutting action, reduced vibrations, reduced handling, reduced chattering, more economical cutters, more durable cutters, longer lasting cutters, and more simplistic designs for easier and faster manufacture and insert replacement. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention relates to a cutting tool having an outer surface with a plurality of inserts connected to a distinct pocket extending generally radially on the outer surface. The cutting inserts are arranged in a helical array on the outer surface in a manner that at least one cutting edge of each cutting insert is spaced in an angular circumferential direction from the pocket of the adjacent cutting insert. The spacing of the inserts is such that a distinct point on the each one of the one or more cutting edges define part of a layout line having a non-uniform slope. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Further features of the present invention, as well as the advantages derived therefrom, will become clear from the following detailed description made with reference to the drawings in which: 
           [0006]      FIG. 1  is a projection of cutting inserts in a prior art helical cutting tool; 
           [0007]      FIG. 2  is a projection of cutting inserts illustrating some of the features of the present invention; 
           [0008]      FIG. 3A  is a perspective side view of a cutting tool in accordance with one embodiment of the present invention; 
           [0009]      FIG. 3B  is an end view of a cutting tool in accordance with one embodiment of the present invention; 
           [0010]      FIG. 4A  is an end view of a cutting tool insert placement of a single column in accordance with one embodiment of the present invention; 
           [0011]      FIG. 4B  is a side view of a cutting tool insert placement of a single column in accordance with one embodiment of the present invention; and 
           [0012]      FIG. 5  is an enlarged sectional side view of several cutting tool pockets with the cutting inserts removed. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    Referring now to  FIGS. 2-5  generally and more specifically to  FIG. 3A , a cutting tool  10  is shown. In a preferred embodiment, the cutting tool  10  is a helical milling cutter for use in a milling machine or machining center. Cutting tool  10  has a body  12  with an outer surface  14  that is generally cylindrically shaped and rotates about a rotational axis  16  during operation of the cutting tool  10  as well known in the art. Formed on the outer surface  14  are a number of columns A, B, C, D each having a plurality of cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  connected to the outer surface  14  of the cutting tool  10 . The columns A, B, C, D extend generally parallel to the rotational axis  16 . The columns A, B, C, D include a chip gash or flute that is used for chip removal during a cutting operation. However, the presence or absence of a chip gash or flute is not necessary in order to have a column of inserts formed on the cutting tool  10 , it will be appreciated that certain applications of the present invention benefit from or require a chip gash or flute for chip removal during the cutting process. Another factor in designing cutting tools is the number of columns of cutting inserts used. The cutting tool  10  depicted in  FIGS. 2 and 3A  has four columns A, B, C, D. However, it is within the scope of this invention to have a greater or lesser number of columns depending on the needs of a particular cutting tool design, e.g. insert size, milling cutter diameter, orientation of inserts, etc. It will be appreciated that the present invention can be applied to any cutting tool having a greater or lesser number of columns. 
         [0014]    The cutting inserts are also arranged in rows that generally extend perpendicular to the rotational axis  16  and extend about the circumference of the cutter body  12 . A first row of cutting inserts  22  is located at an axial cutting end  17  of the tool body  12 . A second row of cutting inserts  24 , third row of cutting inserts  26 , fourth row of cutting inserts  28 , fifth row of cutting inserts  30  and sixth row of cutting inserts  32 , etc. are located generally adjacent each other in series along the axial length of the body  12 . The cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  are arranged in a helical array and are each connected to a distinct seat pocket  18  that is formed on and extends generally radial from the outer surface  14 . 
         [0015]    As shown in the drawings the number of inserts in each row is equivalent to the number of columns used in the cutting tool  10 . However a lesser number of inserts can be used such that not every column has to have an insert in each row. The placement of the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  on the outer surface  14  of the cutting tool  10  has an effect on the performance characteristics of the cutting tool  10 . In particular, the angular circumferential placement of the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  and/or pockets  18  along the columns A, B, C, D can affect the factors, such as but not limited to, cutting load, deflection, vibration and cutting edge wear or failure. Additionally, the angular circumferential distance between adjacent pockets  18  and/or cutting inserts within a row also effects factors such as, but not limited to, tool deflection, cutting load, vibration and cutting edge wear or failure. 
         [0016]      FIG. 1  represents a two dimensional schematic view of cutting insert placement on a prior art cutting tool. Like reference numerals differing by  100  are used to represent similar structures to that of the present invention. The cutting tool has four columns A, B, C, D each having a first row of cutting inserts  122 , a second row of cutting inserts  124 , third row of cutting inserts  126 , fourth row of cutting inserts  128 , fifth row of cutting inserts  130  and sixth row of cutting inserts  132  located generally adjacent each other in series from left to right across the page which in application to a cutting tool is along the axial length of the cutter tool body. The distance between distinct points on adjacent columns is what is referred to as a column measurement (CM), which is shown as equal between the columns A, B, C, D. Each column A, B, C, D has a layout line  144  defined as a continuous generally linear line drawn between the same distinct points  146  on each of the cutting inserts  122 ,  124 ,  126 ,  128 ,  130 ,  132 . It will be appreciated that the layout line is an imaginary line formed by interconnecting the same point on each insert, (e.g., the same point on the cutting edge of each insert), or by interconnecting the same point on each pocket  18  of the cutter. As shown in the figures, the slope (e.g. angular circumferential placement of the cutting inserts) is uniform and linear from second, third, fourth, fifth and sixth cutting inserts  124 ,  126 ,  128 ,  130 ,  132 . However, the slope between the first cutting insert  122  and second cutting insert  124  may vary from the other inserts in the column because of the placement of the first cutting insert  122  on the axial cutting end of the cutting tool body. The slope is derived from the row measurement (RM) or angular circumferential distance between rows in the same column. 
         [0017]      FIG. 2  represents a two dimensional schematic view of cutting insert placement of the cutting tool  10  in accordance with one embodiment of the present invention. The distance between distinct points on adjacent columns is what is referred to as a column measurement (CM), which is shown as equal between the columns A, B, C, D. Each column A, B, C, D has a layout line  44  defined as a generally continuous line drawn between the same distinct points  46  on the cutting edge of each of the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32 . As shown in  FIG. 5 , a layout line  244  can also be defined by the same distinct points  246  on the pockets  18  within the same column formed on the tool body  12 . If cutting inserts of uniform size are used then the layout line  244  defined by points on the pockets  18  would generally be the same as the layout line  44  defined by distinct points  46  on the cutting edge of each of the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  in a column. Alternatively, if cutting inserts of non-uniform size are used then a layout line would be formed that is different than a layout line  244  formed using distinct points  246  on the pockets  18 . All of the above mentioned variations are within the scope of this invention. 
         [0018]    Referring back to  FIG. 2 , the slope of the layout line  44  is derived from the row measurement (RM) or angular circumferential distance between rows in the same column. The RM measurement between the distinct points  46  of the inserts of each row  22 ,  24 ,  26 ,  28 ,  30 ,  32  is shown in  FIG. 2 . The slope (e.g. angular circumferential placement of the cutting inserts) of the layout line  44  of the present invention compared to the layout line  144  of the prior art is non-uniform and varies between at least two adjacent inserts within the same column. The variation in the layout line  44  maximizes the operation of the cutting tool by causing the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  of all the columns A, B, C, D to contact the work piece in a manner that minimizes one or more of vibration, tool deflection, cutting load, cutting edge wear and/or failure, etc. by minimizing the difference between minimum and maximum cutting forces as the cutter rotates during the cutting operation. Additionally, there is an improvement in cutting insert load efficiency, usable life is increased and instances of tool body and cutting insert failure are decreased.  FIGS. 3B and 4A  show the RM values between cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  of a single column A, B, C, D.  FIG. 4B  is an end view of the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  of  FIG. 4A  with RM values shown in a three dimensional point of view. The RM value between adjacent inserts in a row is indicative of the angular circumferential distance between two adjacent row inserts in the same column A, B, C, D. 
         [0019]    As indicated above, the slope of the layout line  44 , when inserts of uniform size are used will depend on angular circumferential placement of the bearing face  34  of each pocket  18  along the column. This results in the layout line  44  being the same as the layout line  244 . The position of the bearing face  34  can be controlled by varying a height  42  or distance between bearing faces  34  of adjacent rows within the same column as shown in  FIG. 5 , which is an enlarged two dimensional view of three pockets  18  in the same column A, B, C, D. Each pocket  18  has its respective cutting insert removed, however, the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  if present would be removably connected to a bearing face  34  of the pocket  18  using a suitable fastener as is well known in the art. Referring briefly to  FIG. 3A , one of the pockets  18 ′ has an insert removed and the bearing face  34  having a receiver aperture  36  can be seen. The receiver aperture  36  is configured to receive a fastener  38  that extends through the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  for removably connecting the cutting insert to the bearing face  34 . Each pocket  18  also has a radial wall  40  and axial wall  19 . A height  42  measurement is shown and is defined by the angular circumferential distance between adjacent bearing faces  34  in the same column.  FIG. 5  depicts the height  42  as being two dimensional, however, it is actually a three dimensional measurement because in application the cutting tool body  12  is three dimensional with the pockets  18  being placed about the outer surface  14  of the tool body  12 . 
         [0020]    The angular circumferential placement of the cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  between adjacent inserts in the same column or the same can be adjusted by changing the height  42  between adjacent pockets  18  such that the angular circumferential distance between cutting inserts  22 ,  24 ,  26 ,  28 ,  30 ,  32  is varied causing different RM measurement values between adjacent rows. This has the effect of creating a layout line  44  or layout line  244  (when cutting inserts of uniform size are used) having a varied slope compared to the layout line  144  in a prior art tool as illustrated in  FIG. 1 . 
         [0021]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, 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. 
         [0022]    While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.