Abstract:
Disclosed is an alignment tool. A body of the alignment tool fits into a turret block, while a head holds a machine-tool. During the alignment process, the head and body are allowed to move relative to one another in two dimensions perpendicular to an axis of rotation of a spindle. To align the alignment tool, a workpiece is inserted into the spindle. As the workpiece spins, a machine-tool cuts a taper in it. An “empty” alignment tool is brought to bear against the tapered workpiece. The axis of the head of the empty alignment tool, and thus the axis of any machine-tool held by the head, is aligned with the axis of the tapered workpiece and, thus, with the axis of the spindle. Once the machine-tool is aligned with the spindle, the head and body are tightly fastened together to preserve the alignment.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is related generally to machine-tools, and, more particularly, to aligning a machine-tool with a spindle. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a typical small-scale drill press, a drill bit is held in a chuck or collet. The bit is then rotated and brought to bear against a workpiece. A typical lathe is similar, but it rotates the workpiece instead of the machine-tool. In these machines, keeping the machine-tool aligned with the workpiece is important but fairly straightforward. 
         [0003]    The situation changes with the more complex machines used in industry. Often, these machines include a rotating turret disk that holds a number of toolholders. Each toolholder is available to hold one machine-tool. In operation, the turret disk is rotated so that a toolholder holding a machine-tool appropriate for the next machining step is moved into place. The machine-tool is then brought to bear on a workpiece held by a rotating spindle. These multiple-toolholder machines are very useful because they allow an operator, whether a human or a computer, to rapidly switch from one machine-tool to another without having to remove one machine-tool and then insert another. However, the movement of the toolholders into position and then out again has implications for alignment. 
         [0004]    Ideally, once a machine-tool held in a toolholder is properly aligned with the axis of rotation of the spindle that holds the workpiece, this machine-tool can be moved away and back again without affecting the alignment. Reality intervenes, however, and the pressures and vibrations of the working machine, and wear on the machine-tool itself, gradually cause the machine-tool to work out of alignment. This is a well known problem, and for it there exist well known fixes. The primary fix involves expert aligners who come out and fix the alignment of the toolholders. As a job requiring great expertise, this is an expensive process. During the alignment, the multiple-toolholder machine may be out of operation for a significant amount of time. After all that, the machine-tools eventually go out of alignment again, and the expensive and time-consuming process must be repeated. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    In view of the foregoing, the present invention provides an alignment tool and a method for aligning a machine-tool with a spindle. The body of the alignment tool fits into a turret block. The body is attached to a head of the alignment tool. The head holds the actual machine-tool (by means of, for example, a self-centering collet). During the alignment process, the head and body are allowed to move relative to one another in two dimensions perpendicular to the axis of the spindle. Once the axis of the machine-tool is aligned with the axis of the spindle, the head and body are tightly fastened together to preserve the alignment. 
         [0006]    In some embodiments, the head can accommodate machine-tools of various sizes. To further increase the usable range of the alignment tool beyond what one head can accommodate, multiple heads of various sizes can be provided that all work with a given body. 
         [0007]    In a preferred method for aligning the alignment tool, a workpiece is inserted into a spindle. The workpiece is spun, and a machine-tool cuts a taper in it. This step ensures that the axis of rotation of the taper matches the axis of rotation of the spindle. Without removing the now tapered workpiece, an “empty” alignment tool (that is, one not holding a machine-tool) is indexed into position opposite the tapered workpiece. The connection between the alignment tool&#39;s head and body is loosened. The alignment tool is then brought to bear against the tapered workpiece. The taper causes the axis of the head of the alignment tool to match the axis of the taper. The alignment tool&#39;s head and body are then tightly connected. The axis of the head of the alignment tool, and thus the axis of any machine-tool held by the head, now matches the axis of the tapered workpiece and, thus, matches the axis of rotation of the spindle. With the alignment achieved, the tapered workpiece can be removed. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0008]    While the appended claims set forth the features of the present invention with particularity, the invention, together with its objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which: 
           [0009]      FIG. 1  is an assembly drawing of an alignment tool with a collet-accepting head according to the present invention; 
           [0010]      FIG. 2  is an assembly drawing of an alignment tool with a shank-accepting head; 
           [0011]      FIGS. 3A ,  3 B, and  3 C are views of a body of an alignment tool; 
           [0012]      FIG. 3D  is a cross-section of a body of an alignment tool taken along the line A-A of  FIG. 3B ; 
           [0013]      FIG. 4A  is an end view of a collet-accepting head of an alignment tool; 
           [0014]      FIG. 4B  is a cross-section of a collet-accepting head of an alignment tool taken along the line B-B if  FIG. 4A ; 
           [0015]      FIGS. 5A and 5B  are views of a shank-accepting head of an alignment tool; 
           [0016]      FIG. 5C  is a cross-section of a shank-accepting head of an alignment tool taken along the line C-C of  FIG. 5B ; and 
           [0017]      FIG. 6  is a flowchart of a preferred method for aligning a machine-tool with a spindle according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Turning to the drawings, wherein like reference numerals refer to like elements, the present invention is illustrated as being implemented in a suitable environment. The following description is based on embodiments of the invention and should not be taken as limiting the invention with regard to alternative embodiments that are not explicitly described herein. 
         [0019]      FIG. 1  shows an alignment tool  100  according to one embodiment of the present invention. In the figure, the alignment tool  100  is meant to be held by a turret block  102 . As is well known in the art, a rotating turret disk (not shown) may support several turret blocks  102  to allow an operator, whether human or a computer, to rapidly switch from one machine-tool to another. In some of these multiple-toolholder machines, the turret disk rotates about a vertical axis, and the machine is then called a drill press (although it can do much more than drilling). In other machines, the turret disk rotates about a horizontal axis, and the machine is called a milling machine or a lathe. While the illustrations used in this application are mostly directed to a mill, the invention is independent of the orientation of the rotating turret disk. 
         [0020]    The piece of the alignment tool  100  held by the turret block  102  is called the “body”  104 . Attachable to the body  104  is a head  106 . In  FIG. 1 , the head  106  attaches to the body  104  by eight machine screws  108  that fit through holes in the head  106  and screw into the body  104 . As discussed below in reference to  FIG. 4B , the machine screws  108  together form an attachment mechanism that, when loosened for an alignment process, allows the body  104  and head  106  to move relative to one another in two dimensions perpendicular to an axis of a workpiece-holding spindle (not shown). Other attachment mechanisms are possible, such as bolts that pass through both the body  104  and head  106  and are then secured by nuts. 
         [0021]    In the embodiment of  FIG. 1 , a collet  110  is attached to the head  106  by a collect nut  112 . The collet  110  holds a machine-tool (not shown) and centers the machine-tool along an axis of the collet  110 . 
         [0022]    The entire alignment tool  100  from the body  104  to the collect nut  112  can replace a traditional toolholder without having to modify either the turret block  102  or the machine-tools used with it. 
         [0023]      FIG. 2  shows another alignment tool  200  according to a second embodiment of the present invention. This alignment tool  202  does not include the collet  110  of  FIG. 1 . Instead, the body  202  includes a hollow channel (see  FIG. 5C ) that accepts the shank of a machine-tool. 
         [0024]      FIGS. 3A ,  3 B,  3 C, and  3 D illustrate the body  104  of the alignment tools  100 ,  200 .  FIG. 3A  is a side view of the body  104 . The length and diameter of the stem  300  are sized to fit snugly in a turret block  102 . Differently sized bodies  104  can be used with differently sized heads  106 ,  202  to flexibly accommodate a large range of machine-tools in a large range of turret blocks  102 . 
         [0025]      FIG. 3B  shows one face of the body  104 , while  FIG. 3C  shows the other face. The illustrated embodiment includes eight threaded holes  302  to receive the eight machine screws  108  of the attachment mechanism. 
         [0026]    Sectioning the body  104  along line A-A of  FIG. 3B  produces  FIG. 3D . It is clear how, in another embodiment, the threaded holes  302  could be replaced by unthreaded holes drilled through the body  104  to accommodate bolts. The cavity  304  in the middle of the body  104  accepts an end of a machine-tool. 
         [0027]      FIG. 4A  shows a face of the head  106  of the alignment tool  100  of  FIG. 1 . The cross-section of the head  106  in  FIG. 4B  illustrates a number of features of this particular embodiment. The through holes  400  used for attaching this head  106  to the body  104  are countersunk. The countersunk portions are made larger than the heads of the machine screws  108  that fit into them in order to allow freedom of movement of the head  106  relative to the body  104  when the machine screws  108  are not tightened. 
         [0028]    The threads  402  on the outside surface of the head  106  accept the collet nut  112 . The cavity  404  accepts a machine-tool which is held in place by the collet  110 . The angle  406  at the entrance to the cavity  404  may be useful during the alignment process as discussed below. In some embodiments, a value of about  8  degrees works well for this angle  406 . 
         [0029]      FIGS. 5A ,  5 B, and SC illustrate the shank-accepting head  202  of  FIG. 2 . The stem  500  of the head  202  includes at least one threaded hole  502  for securing the shank of a machine-tool. The face view of the shank-accepting head  202  in  FIG. 5B  may be compared to the similar view of the collet head  106  of  FIG. 4A . By making the pattern and size of the through holes  400  identical in both embodiments, a given body  104  of the alignment tool  100 ,  200  can be made to accommodate heads  106 ,  202  of various types and sizes. 
         [0030]    The cross-section in  FIG. 5C  shows clearly the cavity  504  that accepts the shank of a machine-tool. The diameter of this cavity is such as to accept the shank with a close tolerance. Machine screws thread into the one or more holes  502  and press against the shank of the machine-tool to secure its position in the head  202 . Like the angle  406  of the collet head  106 , the angle  506  of the shank-accepting head  202  at the entrance to the cavity  504  may be useful during the alignment process as discussed below. In some embodiments, a value of about  8  degrees works well for this angle  506 . 
         [0031]      FIG. 6  depicts one method for using the alignment tool  100 ,  200  to align a machine-tool with the axis of rotation of a spindle. In drill presses or milling machines with multiple tool holders, a machine-tool is brought to bear on a workpiece held by a rotating spindle. The axis of rotation of the spindle does not change, but the axis of the machine-tool may gradually slip out of alignment with the spindle&#39;s axis. To reset the alignment, the method of  FIG. 6  beings in step  600  by determining the axis of rotation of the spindle. One way to perform this step is by placing a piece of round stock in the spindle and spinning it. A machine-tool is then used to cut a tapered end in the workpiece. Because the taper is made by holding a cutting tool steady while the workpiece is spun by the spindle, the taper is created so that its axis of rotation necessarily matches the axis of rotation of the spindle. 
         [0032]    Leaving the newly tapered workpiece in place in the spindle, a body  104  of an alignment tool  100 ,  200  is attached to a machine-tool turret  102  in step  602 . (It is quite likely that step  602  is performed before step  600 . Usually, the alignment tool  100 ,  200  used throughout the method of  FIG. 6  is the same one used when cutting the taper of step  600 . However, step  602  is explicitly called out because a different alignment tool  100 ,  200  may be used if desired.) 
         [0033]    In step  604 , a head  106 ,  202  is loosely attached to the body  104  of the alignment tool  100 ,  200 . The attachment may be made by the machine screws  108  shown in  FIGS. 1 and 2 . If so, then the machine screws  108  are not fully tightened in this step. They are left loose enough to allow the head  106 ,  202  of the machine-tool  100 ,  200  to move relative to the body  104  in two dimensions perpendicular to the axis of rotation of the spindle. 
         [0034]    In step  606 , the alignment tool  100 ,  200  is brought to bear against the tapered workpiece, still held in the spindle, created in step  600 . Note that the spindle is not rotating at this time. Note also that the alignment tool  100 ,  200  is not holding a machine-tool. Because of this, the cavity in the middle of the alignment tool  100 ,  200  which would normally hold a machine-tool can be placed against the tapered workpiece. In the embodiment of  FIG. 1 , for example, the hole in the centerline of the collet  110  can be placed against the tapered workpiece. Alternatively, the collet  110  and collet nut  112  can be removed and the head  106  can touch the tapered workpiece directly. The angle  406  of the head  106  (see  FIG. 4B ) can then help to bring the tapered workpiece to bear against the head  106 , though the angle  406  is not required for this. In the embodiment of  FIG. 2 , the head  202  is brought to touch the tapered workpiece. The angle  506  of the head  202  (see  FIG. 5C ) can be useful here but is not required. In any case, because the head  106 ,  202  is only loosely attached to the body  104  of the alignment tool  100 ,  200 , the taper of the workpiece can shift the head  106 ,  202  in two dimensions perpendicular to the axis of the taper. Thus, by pushing the alignment tool  100 ,  200  against the tapered workpiece, the center axis of the alignment tool  100 ,  200  is made to match the axis of the tapered workpiece (which is necessarily identical to the rotation axis of the spindle as discussed above). 
         [0035]    In step  608 , without removing the alignment tool  100 ,  200  from its position in contact with the tapered workpiece, the machine screws  108  are tightened to hold the head  106 ,  202  of the alignment tool  100 ,  200  firmly against the body  104 . The alignment tool  100 ,  200 , still firmly mounted in the turret  102 , can then be moved away from the tapered workpiece. 
         [0036]    The tapered workpiece is no longer needed and can be removed. The method ends in step  610  when a machine-tool is placed in the alignment tool  100 ,  200  and tightened. Note what has been achieved by the straightforward method of  FIG. 6 . A workpiece was created with an axis of rotation that matched the (nonvarying) axis of rotation of the spindle. The axis of that tapered workpiece was used to set the axis of the head  106 ,  202  of the alignment tool  100 ,  200 . When a machine-tool is held by the alignment tool  100 ,  200 , its axis matches that of the head  106 ,  202  of the alignment tool  100 ,  200  (because of the collet  110  or the shank-accepting cavity  504 ). In summary, the method of  FIG. 6  quickly and economically ensures that the axis of the machine-tool is aligned with the axis of rotation of the spindle. 
         [0037]    In view of the many possible embodiments to which the principles of the present invention may be applied, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of the invention. Those of skill in the art will recognize that some implementation details, such as the range of sizes of the alignment tools, are determined by specific situations. Therefore, the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof.