Abstract:
A tool assembly affording a wider range of adjustment of machining diameter, comprises a boring bar and a tool cartridge supporting a cutting tip and attached to the boring bar. The tool cartridge chassis is pivotably attached via a pin within a recess formed in boring bar; an adjustment screw is provided to a first side of the pivot axis, the screw being threaded into the cartridge chassis and situated in abutment with a surface of the bar. A compression spring is provided to a second side of the pivot axis, interposed between the boring bar and the cartridge chassis. Appreciable pivotal motion can be imparted to the cartridge chassis by loosening or tightening the adjustment screw. Adjustments can be made automatically by providing a draw-bar.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a tool assembly comprising a tool body such as a boring bar, and an adjustable machining tool cartridge attached thereto that provides improved adjustment of the cutting diameter of the tool assembly.  
         BACKGROUND OF THE INVENTION  
         [0002]    A cutaway view of a conventional tool assembly is depicted in FIGS. 4 and 5. The cutting end of a boring bar  1  is illustrated, the other end of the boring bar being understood to be attached to the main shaft of a boring machine or CNC machine via a tapered shank or the like. Boring bar  1  is provided over an area thereof with a recess  3  having a flat side wall  5  and bottom wall  7 .  
           [0003]    A tool cartridge  9  comprises a cartridge chassis  11 ; the chassis is fixed to boring bar  1  by means of a clamping screw  15  threaded into a screw hole  13  formed in the boring bar. Into cartridge chassis  11  is threaded in the axial direction an adjustment screw  17 ; rotation of this screw in the extending direction fills the space between the cartridge chassis and the end wall  6  of the recess while at the same time supporting chassis  11  with strong force from the end wall.  
           [0004]    Cartridge chassis  11  has a cutting tip  19  mounted thereto by a known method. Cartridge chassis  11  is provided, in proximity to the distal end thereof, with an adjustment screw  21  threaded into a screw hole in chassis  11 , this adjustment screw being positioned so as to abut the side walls  5  of recess  3 .  
           [0005]    With this known design, advancing adjustment screw  21  causes cartridge chassis  11  to undergo elastic deformation whereby the outmost end of the cutting tip undergoes radial outward-directed displacement, allowing the machining diameter for the boring operation to be changed.  
           [0006]    With the conventional tool cartridge  9  described above, since the machining diameter is changed via elastic deformation, the scope of adjustment thereof is naturally limited; typically, machining diameter can be adjusted between about 0.1 and 0.4 mm, with larger tool cartridges designed for greater elastic deformation giving a range of about 0.5 to 0.7 mm. Accordingly, there is a need for a tool cartridge affording a wider range of adjustment of machining diameter in order to meet dimensional requirements for various workpieces using an existing tool cartridge mounted on the boring bar or other similar tool.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to a tool assembly comprising a tool body, for example a boring bar or the like, and a tool cartridge supporting a cutting tip and attached to the tool body that overcomes the limitations of the prior art and provides improved adjustment of cutting tip edge position. This invention may be beneficially used in mills, multiple action tools, boring bars and other tools known in the art.  
           [0008]    An object of the present invention is to provide a tool assembly comprising a tool body, such as a boring bar, a tool cartridge having a chassis and supporting a cutting tip, a pivot secured to the tool body for engaging the tool cartridge, an adjustment means, and a spring means, wherein the tool cartridge chassis is pivotably attached to the tool body, the adjustment means is positioned to a first side of the pivot and in abutment with a surface of the tool body, and the spring means positioned on a second side of the pivot is interposed between the tool body and the chassis.  
           [0009]    It is a further object of the invention to provide an adjustment means for transmitting force to a portion of the cartridge chassis so as to impart a radial outward-directed rotational force thereto positioned on a first side of the pivot and a spring means for imparting to the cartridge chassis a rotational force in the direction opposite the first rotational force positioned on a second side of the pivot. It is a further object that the adjustment means and the spring means allow fine adjustment of positioning of a cutting tip on the chassis through control of the chassis&#39; rotation about the pivot.  
           [0010]    A further object of the present invention is to provide a boring bar wherein the chassis of the tool cartridge is pivotably attached within a recess formed in the boring bar; an adjustment screw is provided to a first side of the pivot axis, being threaded into the cartridge chassis and situated in abutment with a surface of the cutting bar; and a tensioning device, such as a compression spring, is provided to a second side of the pivot axis, interposed between the boring bar and cartridge chassis. With this design, appreciable pivotal motion can be imparted to the cartridge chassis by loosening or tightening the adjustment screw, thereby providing a wider range of adjustment than the prior art.  
           [0011]    Another object of the present invention is to provide a tool body, for example a boring bar wherein the chassis of the tool cartridge is pivotably attached within a recess formed in the boring bar and is actuated by a draw-bar. The draw-bar displaceable in the lengthwise direction is provided to the interior of the boring bar for adjusting tool cartridge position. This draw-bar is provided, to a first side of the pivot axis of the cartridge chassis, with a main cam action device for transmitting force to a portion of the cartridge chassis so as to impart radial outward-directed rotational force thereto; a tensioning device, such as a compression spring, for imparting to the cartridge chassis rotational force in the direction opposite the previous rotational force is provided to a second side of the pivot axis; and the pivoting position of the cartridge chassis is adjustable by means of adjustment of the longitudinal position of the draw-bar in relation to the boring bar. With this design, tool cartridge pivoting position can be adjusted automatically over a wide range. A further object of the invention is to provide a tensioning device, such as a compression spring, interposed between the boring bar and cartridge chassis, thus providing a simple design. A yet further object of the invention is fine adjustment of cartridge chassis pivoting position made via an adjustment means such as a screw, cam, wedge, and the like, whether mechanical, hydraulic or pneumatic.  
           [0012]    Alternatively, another further object of the invention is to provide a compression spring interposed between the draw-bar and the cartridge chassis. The draw-bar includes an auxiliary cam action device whereby the degree of compression of the compression spring between the auxiliary cam action device and the cartridge chassis remains unchanged irrespective of the pivoting position of the cartridge chassis imparted by the main cam action device. Thus, the force produced by the compression spring remains constant regardless of the pivoting position of the cartridge chassis so that the degree of change in position of the cutting tip due to centrifugal force is unaffected by the pivoting position of the cartridge chassis.  
           [0013]    A further object of the invention is to provide a follower rod provided between the main cam action device and the cartridge chassis; and an adjustment screw threaded into the cartridge chassis so as to abut the follower rod.  
           [0014]    It is a yet further object of the invention to provide a boring bar wherein the recess is a groove formed coextensive with the lengthwise extension of the boring bar so as to have two side walls, and the cartridge chassis is pivotably supported by a pin supported on the two side walls. This arrangement provides reliable pivotal support.  
         DESCRIPTION OF THE PREFERRED EMBODIMENTS  
         [0015]    A tool assembly pertaining to a first embodiment of the invention is depicted in FIGS. 1 and 2, and comprises a boring bar  31  and a tool cartridge  39 . Boring bar  31  has a recess  33 . In this embodiment, the recess takes the form of a groove with two side walls  35  for tightly accommodating tool cartridge  39 , while allowing pivotal movement of the cartridge about a pivot axis. A pin  37  extends transversely through recess  33 , and will be understood to be removably secured to the boring bar  31 . The cartridge chassis  41  of the tool cartridge is provided with a hole through which the pin passes thereby movably attaching tool cartridge  39  to the boring bar.  
           [0016]    Pin  37  fits the hole tightly so as to allow cartridge chassis  41  to pivot about pin  37  without play. That is, the fit of pin  37  in the hole is such that movement of the chassis in relation to the pin is substantially limited to rotation of the chassis about the pin. Cartridge chassis  41  has a curved rear edge  43  to facilitate pivoting and a distal edge  47  close to the terminal end  32  of the boring bar  31 . In proximity to the distal edge  47  of cartridge chassis  41 , adjustment screw  51  is threaded into a screw hole provided in the cartridge chassis. The distal end  52  of the adjustment screw  51  abuts a face of the boring bar  31 . A cutting tip  49  is mounted on cartridge chassis  41  by a known method analogous to that in the prior art example. The tip is mounted in a depression  40  in the cartridge chassis  41 . In a further embodiment, the cutting edge of the cutting tip is positioned substantially in the center across the width of recess  33 .  
           [0017]    Towards the rear of cartridge chassis  41 , boring bar  31  is provided with a spring accommodating hole  53 . A powerful compression spring  55  is accommodated within this hole so as to press down against the rear section  45  of the cartridge chassis. Alternatively, the spring accommodating hole may be provided in the cartridge chassis  41 . In that case, a plate spring or the like is preferred so as to reduce the overall length of spring  55 . Alternatively, other tensioning devices known in the art may be utilized. In any event, the compression spring is interposed between the rear section of the cartridge chassis and boring bar  31 . With the arrangement described above, when adjustment screw  51  is loosened, that is withdrawn along the screw hole, tool cartridge  39  is energized by compression spring  55  and pivots in the clockwise direction, as viewed in FIG. 1, from the neutral position depicted in FIG. 1. Whereas, when the adjustment screw  51  is tightened, that is advanced along the screw hole, it causes the tool cartridge to pivot in the counterclockwise direction as viewed in FIG. 1, affording an extremely broad range of adjustment for the cutting edge of cutting tip  49 . That is, loosening adjustment screw  51  adjusts cutting tip  49  inward creating a smaller boring radius, while tightening adjustment screw  51  adjusts cutting tip  49  outward creating a larger boring radius. The forces produced by the strong tensioning device and the adjustment screw afford support adequate to withstand machining resistance over the entire range of adjustment.  
           [0018]    [0018]FIG. 3 depicts a tool assembly according to another embodiment of the invention, and comprises a boring bar  61  and a tool cartridge  69 . According to the present embodiment displacement of the edge of the tip is carried out automatically. For this purpose a bore  59  coextensive with the center axis of boring bar  61  is provided, and a draw-bar  60  slidable in the lengthwise direction of the boring bar is provided within the bore  59 . The draw-bar  60  is driven by a drive unit, not shown, under the control of the control unit of the boring machine in a manner for driving draw bars that is well known in the art.  
           [0019]    Apart from the parts described below, the arrangement of tool cartridge  69  is basically the same as that depicted in FIGS. 1 and 2, so discussion of the parts that are the same is omitted here and the preceding description thereof in relation to FIGS. 1 &amp; 2 is hereby incorporated by reference with regard to FIG. 3.  
           [0020]    A radial hole  82  is provided in boring bar  61  at the location of adjustment screw  81 , and a follower rod  83  is slidably arranged within this hole. Draw-bar  60  is provided with main cam action device  84 . Moving draw-bar  60  in the lengthwise direction, with reference to the boring bar, causes the tool cartridge  69  to pivot about pin  67  allowing the radial position of the edge of the cutting tip to be changed.  
           [0021]    A feature of the present embodiment is that the force produced by compression spring  73  remains unchanged regardless of the pivoting position of tool cartridge  69 , thereby allowing better control of cutting edge position. It has been established that the position of the cutting tip edge during the machining operation is determined by the outward pushing force exerted on the adjustment screw  81  by the main cam action device  84 , the force of the compression spring  73 , the centrifugal force, and force directed radially inward from the workpiece; thus, any change in compression spring force can produce a change in cutting tip edge position. Allowing a change in spring force produces a change in the relationship between spring force and the tendency for tool cartridge  69  to pivot about pin  67  with centrifugal force produced as the boring bar turns, making accurate prediction of cutting tip edge position impossible. The problem of variable spring force is solved by means of the present embodiment wherein draw-bar  60  is provided with auxiliary cam action device  85  allowing radially inward movement of spring  73 . Alternatively, other tensioning devices known in the art may be employed  
           [0022]    In FIG. 3, spring  73  takes the form of a stack of a plurality of plate springs accommodated within a spring accommodation hole  65  in tool cartridge  69 . A spring retainer  89  having a follower rod  87  interposed between draw-bar  60  and spring  73 . The profiles of the two cam action devices  84 ,  85  fulfill the following relationship.  
           D1:D2=L1:L2  
           [0023]    where D1 is displacement of follower rod  83 , D2 is displacement of follower rod  87  (D1 and D2 are mutually opposing directions), L1 is the distance from the center of pin  67  to adjustment screw  81 , and L2 is distance from the center of pin  67  to of follower rod  87 . Here, compression spring  73  is accommodated within tool cartridge  69 , but where boring bar  61  has sufficient thickness, accommodation thereof within the boring bar is also possible.  
           [0024]    Alternatively, compression spring  73  may be compressed between boring bar  61  and tool cartridge  69 , as in the example depicted in FIG. 1. In this case, the force produced by the compression spring will change, although automatic adjustment of machining diameter will be afforded.  
           [0025]    An advantage of the preceding embodiments is the ability to make fine adjustments via the adjustment screw  81 ; however, automatic adjustment by the draw-bar  60  is not an essential element, it being possible for follower rod  83  to contact tool cartridge  69  directly.  
           [0026]    According to the present embodiment, a portion of the mechanism for driving the tool cartridge  69  is accommodated within the boring bar  61 , and as the mechanism consists simply of a draw-bar located in the center of the boring bar and a corresponding mechanism interposed between it and the tool cartridge, one or more additional elements identical to tool cartridge  69  or having designs based on the same principle may be provided. In FIG. 3, such an additional tool cartridge is denoted by symbol  91 . While, tool cartridge  91  is shown diagrammatically, it will be readily understood that the cutting tip is arranged facing the direction of rotation of boring bar  61 . It is also possible to provide two tool cartridges spaced apart in the diametrical or lengthwise direction or three or more thereof arranged at equidistant intervals in the circumferential direction.  
           [0027]    By employing a plurality of tool cartridges in this way, fine cutting pitch can be achieved with larger boring bar feed. The positions of the edges of this plurality of tool cartridges can be adjusted via the common draw bar.  
           [0028]    According to the present embodiment, edge position can be adjusted automatically over a wide range, allowing the workpiece to be rough finished to certain dimensions during the forward stroke of the boring bar and then precision finished to different dimensions during the return stroke. Where a plurality of tool cartridges is employed, the tool cartridge equipped with a cutting tip for precision finish machining can be moved into the desired radial position during the precision finish stroke. It is also possible to machine a hole to certain dimensions during the first stroke and to then machine a larger hole partway during the second stroke. In either case, the need to re-clamp the workpiece, such as is ordinarily required when subjecting a number of workpieces to a first operation and then again to a second operation, is obviated, preventing off-centering during the transition from the first operation to the second operation, so as to afford precision machining. Since there is no need to change tool cartridges, mispositioning is prevented and the need for a test operation after attaching a new cartridge, as with conventional tool cartridges, is obviated.  
           [0029]    In FIG. 3, the position of the cutting tip of the additional tool cartridge  91  with respect to the lengthwise extension of boring bar  61  is shown as being the same as that of tool cartridge  69 , but the invention is not limited to such an arrangement. The additional tool cartridge  91  may be arranged to the rear of tool cartridge  69 . In this case, precision finish machining can be accomplished with the cutting tip of additional tool cartridge  91  while the cutting tip of tool cartridge  69  performs rough finish machining during the first forward stroke of boring bar  61 . In this case it is not necessary for additional tool cartridge  91  to be identical to tool cartridge  69 , and the profile of the draw-bar  60  cam action device for tool cartridge  91  can differ from that for tool cartridge  69 .  
           [0030]    Another mechanism for adjusting the radial position of the cutting tip via the drawbar known in the art is placement of the member supporting the cutting tip in direct contact with the cam action device of the draw-bar to assure that it does not undergo displacement in the radial direction, thereby completely eliminating the possibility of fluctuation in machining dimension due to deformation of the compression spring  73  employed in the present invention (as in Registered Utility Model 25329476, for example); such a mechanism can be provided in such a way that the cutting tip supported thereby is located to the rear of the cutting tips of tool cartridges  69  and  91  of the present invention, and used for precision finish machining, while using tool cartridges  69  and  91  for rough finish machining exclusively. It this case, the profiles of the corresponding cam action devices for each cutting tip will be selected so as to allow the draw-bar to be used in common. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]    [0031]FIG. 1 is a sectional view of a tool assembly according to a first embodiment of the invention taken on line  1 - 1  in FIG. 2.  
         [0032]    [0032]FIG. 2 is a sectional view of the tool assembly of FIG. 1 taken on line  2 - 2  in FIG. 1.  
         [0033]    [0033]FIG. 3 is a sectional view of a tool assembly according to another embodiment of the invention showing a sectional view corresponding to FIG. 1.  
         [0034]    [0034]FIG. 4 is a top plan view of a tool assembly showing a tool cartridge according to the prior art.  
         [0035]    [0035]FIG. 5 is a side view of the prior art tool assembly of FIG. 4.