Abstract:
A rotatable tool includes a shank rotatable about a longitudinal axis, a drawbar mounted to an axial front end of the shank, and a cutting head mounted to an axial front end of the drawbar. The shank and the drawbar include mutually engageable screw threads which impart an axial displacement of the drawbar relative to the shank. The cutting head and the drawbar include mutually engageable serrations for transferring axial force therebetween. The serrations are axially spaced from one another and extend transversely relative to the axis.

Description:
[0001]     The present application claims priority under 35 U.S.C. § 119 to Patent Application Serial No. 0402039-2 filed in Sweden on Aug. 19, 2004.  
       TECHNICAL FIELD OF THE INVENTION  
       [0002]     The present invention relates to a rotatable tool, which comprises a shank, a cutting head and a drawbar, the shank and the drawbar having cooperating members for imparting to the drawbar and the shank a displacement in relation to each other in the axial direction of the tool, and that the cutting head and the drawbar have cooperating engagement members for the transfer of forces in the axial direction of the tool. The invention also separately relates to a cutting head and a drawbar.  
       STATE OF THE ART  
       [0003]     By EP 0 776 719, a rotary tool for cutting machining is previously known, the tool comprising an exchangeable cutting head, a shank as well as a connecting piece. Transfer of force in the axial direction between the cutting head and the connecting piece takes place by a pin of the cutting head cooperating with a groove of the connecting piece. The connecting piece also has an external thread, which is in engagement with an internal thread of the shank. The shank has a generally cone-shaped seat, which is intended to co-operate with conical parts of the cutting head and the connecting piece. Upon rotation of the connecting piece in relation to the shank, an axial displacement of the connecting piece in relation to the shank will take place, and via the pin/groove coupling, the cutting head is pulled into the seat of the shank.  
         [0004]     By SE-A-0200852-2 (U.S. Publication 2003/0210963), a rotary tool is previously known where a connecting piece has a recess defined by axially slotted walls. A male part of a cutting part is intended to be received in the recess. The walls are externally conical and cooperate with a conical seat when the connecting piece is displaced axially in relation to a shank included in the tool. Upon the axial displacement, the male part is clamped in the recess. According to a preferred embodiment, the recess has members for jointly rotating the male part when rotating the tool.  
       OBJECTS AND FEATURES OF THE INVENTION  
       [0005]     A primary object of the present invention is to provide a rotatable tool, in which the cutting head is exchangeable in an exceptionally user-friendly way.  
         [0006]     Another object of the present invention is to improve the stability of the cutting head in relation to the shank.  
         [0007]     At least the primary object of the present invention is realised by means of a rotatable tool which comprises a shank, a drawbar, and a cutting head. The shank is rotatable about a longitudinal axis. The drawbar is mounted to an axial front end of the shank, and the cutting head is mounted to an axial front end of the drawbar. The shank and the drawbar include mutually engageable displacement members for imparting an axial displacement of the drawbar relative to the shank. The cutting head and the drawbar include mutually engageable force transfer members for transferring forces therebetween in the axial direction. The force transfer members include serrations extending transversely relative to the axis.  
         [0008]     The invention also pertains to a cutting head for rotation about a center axis of rotation, the cutting head including an axially forward cutting end and an axially rearward engagement portion comprising axially spaced serrations extending transversely relative to the axis.  
         [0009]     Another aspect of the invention relates to a drawbar which defines a longitudinal axis of rotation and which includes an axial rear portion adapted to be anchored in a shank. An axially forward end of the drawbar includes an engagement portion adapted to receive a cutting head and including axially spaced serrations which extend transversely relative to the axis. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     Below, preferred embodiments of the invention will be described, reference being made to the appended drawings, where:  
         [0011]      FIG. 1  shows a side view of a first embodiment of a tool according to the present invention;  
         [0012]      FIG. 2  shows a perspective view of the tool according to  FIG. 1 ;  
         [0013]      FIG. 3  shows a perspective view of a cutting head included in the tool according to the present invention;  
         [0014]      FIG. 4  shows a side view of the cutting head according to  FIG. 3 ;  
         [0015]      FIG. 5  shows a side view of the cutting head when this has been rotated 90° around a centre axis C-C in comparison with  FIG. 4 ;  
         [0016]      FIG. 6  shows a perspective view of a drawbar included in the tool according to the present invention;  
         [0017]      FIG. 7  shows a side view of the drawbar according to  FIG. 6 ;  
         [0018]      FIG. 8  shows a side view of the drawbar when this has been rotated 90° around a centre axis C-C in comparison with  FIG. 7 ;  
         [0019]      FIG. 9  shows a side view of a shank included in the tool according to the present invention, certain hidden parts of the shank having been made visible;  
         [0020]      FIG. 10  shows a section in the axial direction through the tool according to  FIG. 1 ;  
         [0021]      FIG. 10A  shows an enlarged detail of  FIG. 10 ;  
         [0022]      FIG. 11  shows a section in the axial direction through the tool according to  FIG. 1 , but the section is taken in a plane that is rotated by 90° in comparison with the section according to  FIG. 10 ;  
         [0023]      FIG. 11A  shows an enlarged detail of  FIG. 11 ;  
         [0024]      FIG. 12  shows a side view of a cutting head and a drawbar according to an alternative embodiment;  
         [0025]      FIG. 13  shows an exploded view in perspective of an alternative embodiment of a tool according to the present invention; and  
         [0026]      FIG. 14  shows an exploded side view of the alternative embodiment of the tool. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0027]     The embodiment shown in  FIGS. 1 and 2  of a tool  1  according to the present invention consists of an end mill. The milling cutter according to  FIGS. 1 and 2  comprises a shank  3  and a cutting head  5 . The line C-C defines the axial center direction of the shank  3 , of the cutting head  5  and of the entire milling cutter as well as the rotation axis of the milling cutter.  
         [0028]     In  FIGS. 3-5  the cutting head  5  is shown, which accordingly can be mounted exchangeably in the shank  3 . The cutting head  5  has an axial center direction C-C, which coincides with the axial center direction C-C of the milling cutter when the cutting head  5  is mounted in the shank  3 . For that purpose, the cutting head  5  has a male-shaped, first engagement portion  7 , which is shaped basically as a truncated cone with two diametrically opposite material portions removed. Thereby, two generally parallel, planar, first side surfaces  9  are formed, which are provided with first linear serrations  10 . In the embodiment illustrated in  FIGS. 3-5 , the first serrations consist of a plurality of uniform, straight and parallel ridges separated by grooves. The side surfaces  9  have an extension in the axial direction C-C of the cutting head  5  and are facing away from each other. As is seen in  FIGS. 4 and 5 , the longitudinal direction of the serrations  10  generally has an extension transverse to the axial direction C-C of the cutting head  5 , more precisely perpendicular to the axial direction C-C of the cutting head  5 .  
         [0029]     However, the side surfaces  9  are not situated along the entire height of the first engagement portion  7 . This entails that farthest away from the free end of the first engagement portion  7 , there is formed a continuous first guide surface  8 , of limited height, which accordingly extends around the entire circumference of the engagement portion  7 . The first guide surface  8  has the same conicity as the rest of the engagement portion  7 .  
         [0030]     The cutting head  5  also comprises a chip-removing portion  11 , and an intermediate portion  12  forming a transition portion between the first engagement portion  7  and the chip-removing portion  11 . The intermediate portion  12  is provided with a key recess  13 .  
         [0031]     In the area of the connection of the first engagement portion  7  to the intermediate portion  12 , there is formed a continuous, first support surface  14 , running around the entire circumference of the cutting head  5 , which surface generally has an extension perpendicular to the axial direction C-C of the cutting head  5 . The first support surface  14  extends radially out from the first guide surface  8 . This first support surface  14  is intended to come into abutment against the open end of the shank  3 , adjacent to the seat of the shank  3 , see below.  
         [0032]     In  FIGS. 6-8 , a drawbar  20  is shown, which is included in the milling cutter according to the present invention. The drawbar  20  comprises a female-shaped, second engagement portion  21  and an externally threaded (male screw thread) anchoring portion  22 . The axial center direction of the drawbar  20  is defined by the dash-dotted line C-C, see  FIG. 7 . The second engagement portion  21  comprises two generally parallel, planar, second side surfaces  23  and a bottom surface  24  connecting the side surfaces  23 . The side surfaces  23  are facing each other and have an extension in the axial direction C-C of the drawbar  20 . The two parallel side surfaces  23  are provided with second serrations  25 , which have a longitudinal direction extending transverse to the axial direction C-C of the drawbar  20 , more precisely perpendicular to the axial direction C-C. The second serrations also consist of a plurality of uniform, straight and parallel ridges being separated by grooves. Thus, the first serrations  10  of the cutting head  5  can mate with the second linear serrations  25  of the drawbar  20 , by the ridges of one of said serrations engaging the grooves of the other of said serrations and vice versa for the transfer of forces in the axial direction C-C. Furthermore, the longitudinal direction of the serrations is to be understood as the longitudinal direction of the ridges and grooves making up the serrations.  
         [0033]     The second engagement portion  21  has an external shape that constitutes a part of a circular cylinder. In the embodiment illustrated, the external thread  26  presented by the anchoring portion  22  has an extension along the entire length of the anchoring portion  22 .  
         [0034]     As is most clearly seen in  FIG. 7 , at the free end of the anchoring portion  22 , the drawbar  20  is provided with a key recess  27 , by means of which the drawbar  20  can be rotated by access from the end of the shank  3  that is facing away from a seat  30  of the shank  3 , see  FIG. 9 .  
         [0035]     Thus, the shank  3  shown in  FIG. 9  is provided with a seat  30 , which mainly has a circular cylindrical shape. However, in the area of the open end of the seat  30 , a conical second guide surface  31  is formed, which has a limited extension in the axial center direction C-C of the shank. In the area of the open end of the seat  30 , a second support surface  32  is also formed, which is situated in a plane transverse to the axial direction C-C and intended to co-operate with the first support surface  14  of the cutting head  5 . The shank  3  also comprises an internal thread (female screw thread)  33 , which is situated adjacent to the inner end of the seat  30 .  
         [0036]     In  FIGS. 10, 10A ,  11 ,  11 A, it is seen how the different components included in the tool are mounted and co-operate with each other. Thus, the external thread  26  of the drawbar  20  has been brought into engagement with the internal thread  33  of the shank  3 . While the female-shaped engagement portion  21  still is outside the free end of the shank  3 , the cutting head  5  is mounted in the drawbar  20 . That is effected by bringing the male-shaped engagement portion  7  of the cutting head  5  into cooperation with the female-shaped engagement portion  21  of the drawbar  20 . In order to execute this, the male-shaped engagement portion  7  is inserted from the side into the female-shaped engagement portion  21 . Thereby, each of the two parallel, first side surfaces  9  of the male-shaped engagement portion  7  will be oriented directly opposite an appurtenant second, side surface  23  of the drawbar  20 , which surfaces  23  form a transversely open slot.  
         [0037]     By rotating the cutting head  5  around the centre axis C-C, suitably by means of a key cooperating with the key recess  13 , the drawbar  20  will also be rotated. At a certain direction of rotation, this means that the external thread  26  of the anchoring portion  22  is threaded into the internal thread  33  of the shank  3  to produce an axial displacement of the drawbar into the shank. The rotation of the cutting head  5  also means that the external limiting surfaces of the engagement portions  7  and  21  are received in the seat  30  of the shank  3 . When this takes place, a stronger engagement between the male-shaped engagement portion  7  of the cutting head  5  and the female-shaped engagement portion  21  of the drawbar  20  will also arise.  
         [0038]     When the external surface of the female-shaped engagement portion  21  contacts the seat  30  of the shank  3 , a clamping of the male-shaped engagement portion  7  in the female-shaped engagement portion  21  will take place. By the presence of the first and second serrations  10  and  25 , respectively, an exceptionally stable joint between the cutting head  5  and the drawbar  20  is provided. Upon continued rotation of the cutting head  5 , the first guide surface  8  will come into co-operation with the second guide surface  31  of the seat  30  in the shank  3 , see  FIG. 11A , this abutment being effected in the area of the open end of the seat  3 .  
         [0039]     As is particularly seen in  FIG. 11A , there is a certain play between the main part of the male-shaped engagement portion  7  and the seat  30 . Thereby, it is guaranteed that there will be a satisfactory guiding between the guide surfaces  8 ,  31  in the area of the open end of the seat  30 .  
         [0040]     When the cutting head  5  has assumed the final position thereof in the shank  3 , also the first support surface  14  of the cutting head  5  has come into abutment against the second support surface  32  of the shank  3 . The co-operation of the first guide surface  8  with the second guide surface  31  and the mutual co-operation of the support surfaces  14 ,  32  are important functions in order to make the clamping of the cutting head  5  in the shank  3  sufficiently stable. In that connection, it should be particularly pointed out that, according to a preferred embodiment, the diameter generated by the first guide surface  8  is somewhat larger than the diameter generated by the second guide surface  31 . Since the guide surfaces  8 ,  31  are conical, the diameters are compared in sections that are perpendicular to the axial direction C-C and located at the same distance from the plane that contains the support surface  14  and  32 , respectively. As for the stability, of course also the cooperating serrations  10  and  25  of the respective engagement portion  7 ,  21  contribute.  
         [0041]     In  FIGS. 12-14 , an alternative embodiment of a tool  101  according to the present invention is shown. Correspondingly, as in the above-described tool, it comprises a shank  3 , a cutting head  105  and a drawbar  120 . As is indicated by the reference designation, the shank  3  may be identical with the shank shown above in  FIG. 9 . The cutting head  105  is provided with a first engagement portion  107 , an intermediate portion  112  and a chip-removing portion  111 . The first engagement portion  107  has a planar, first side surface  109 , which is provided with first serrations  110 , which generally have an extension in the longitudinal direction thereof transverse to the axial center direction C-C of the tool. The first engagement portion  107  has an external shape that constitutes a part of a truncated cone. Adjacent to the intermediate portion  112 , the cutting head  105  is provided with a guide surface  108  as well as a first support surface  114 , see  FIG. 12 . Both the guide surface  108  and the first support surface  114  extend around the entire circumference of the cutting head. The first support surface  114  extends radially out from the guide surface  108 . The guide surface has a conicity that coincides with the conicity of the external surface of the first engagement portion  107 .  
         [0042]     The intermediate portion  112  is provided with a key recess  113 . The chip-removing portion ill is only schematically shown in  FIGS. 11-13 .  
         [0043]     The drawbar  120  comprises a second engagement portion  121  and an externally threaded anchoring portion  122 . The axial center direction of the drawbar  120  is defined by the dash-dotted line C-C, see  FIG. 12 . The second engagement portion  121  comprises a planar, second side surface  123 , which is provided with second serrations  125 , which have a longitudinal direction that extends transverse to the axial center direction C-C of the drawbar  120 , more precisely perpendicular to the axial center direction C-C. The second engagement portion  121  has an external shape that constitutes a part of a truncated cone. Correspondingly, as in the above-described embodiment, the anchoring portion  122  has an external thread  126 .  
         [0044]     When mounting the cutting head  105  in the shank  3 , the two engagement portions  107  and  121  are brought into engagement with each other, this being effected when the draw-bar  120  is only partly inserted in the shank  3 , see  FIGS. 12 and 13 . When the two engagement portions  107  and  121  are in engagement with each other, the serrations  110  and  125  of the respective engagement portion are in contact with each other. Upon simultaneous rotation of the two engagement portions  107 ,  121  in a certain direction, the engagement portions  107  and  121  of both the drawbar  120  and the cutting head  105  will be displaced down into the seat  30  of the shank  3 . When the cutting head  105  is in principle entirely inserted in the seat  30 , the guide surface  108  will come into co-operation with the seat  30  and the first support surface  114  will come into abutment against the second support surface  31  of the shank  3 .  
         [0045]     Generally, it applies for the milling cutter according to the present invention that the side surfaces  9 ,  23 ;  109 ,  123  should be provided with at least two serrations.  
         [0000]     Feasible Modifications of the Invention  
         [0046]     According to the present invention, the serrations arranged on a side surface of the engagement members do not need to be identical as regards the dimensions thereof. They may also have varying mutual distance, whereby erroneous mounting of the cutting head on the drawbar is prevented.  
         [0047]     As has been pointed out above, the serrations  10  and  25  of the side surfaces  9  and  23 , respectively, have a longitudinal direction that extends transverse to the axial direction C-C. By this expression, it is to be appreciated that the longitudinal direction of the serrations  10 ,  25  does not need to be perpendicular to the axial direction C-C but may be angled a few degrees.  
         [0048]     Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.