Abstract:
An eccentric work piece holder supports a work piece in alignment during rotary operations. First-, second- and third aligning members, associated with the rotary axis of a rotary unit, provides pivoting movements relative to the rotary axis while bearing the work piece. These pivoting movements of the aligning members enable the work piece to be aligned during rotary operations.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is related to U.S. application Ser. No. 10/320,868, filed Dec. 17, 2002, by Stephen C. Meissner, et al., and entitled, “Method Of Alignably Supporting A Work Piece For Rotary Movements.” 

   FIELD OF THE INVENTION 
   The invention relates generally to the field of work piece alignment, and in particular to work piece alignment on turning machines. More specifically, the invention relates to work piece alignment on turning machines to remove radial misalignment (runout) between the work piece and the rotary axis. 
   BACKGROUND OF THE INVENTION 
   In turning machines, such as lathes, ultra-precision grinders, and single point diamond turning machines, the work piece must be lined up exactly with the rotary axis to which it is attached. If the work piece is not aligned correctly at the beginning of the operation, precision and accuracy of the finished piece is compromised. The movements of the cutting tool are set precisely to coincide with the alignment of the rotary axis of the toolholder, and therefore, the work piece must be lined up exactly with the rotary axis of the toolholder for the machining operation to be successful. 
   Runout, characterized by uneven off-center motion, occurs when the alignment of the work piece is not present or not perfect. This results in machining errors on the work piece, and also adds more wear to the cutting tool. Since the motion is uneven, the edge of the tool is not worn evenly. Alignment must remain precise during the work operation. 
   Traditional removal of radial runout consists of mounting a work piece on either a vacuum or magnetic chuck, and tapping the work piece in the opposite direction of offset until radial runout is reduced to a satisfactory level as measured with an indicating device. Alignment in this traditional manner requires a high level of skill to achieve a reduction in radial runout efficiently. Relocation of the work piece by tapping it back and forth may result in adjustment overshoot and further misalignment in other directions, thus requiring additional alignment. These steps cost time and energy and often results in frustration 
   There have been numerous prior art attempts to resolve the aforementioned problems. To solve the problem of runout, some devices depend on elaborate designs for both the toolholder and the work piece that are costly to manufacture. In other developments, the alignment may be adjusted by very complicated arrangements: pre-alignment bores and meshed tooth sets (PCT No. WO 99/42238 issued to Kevin J. Bisset on Aug. 26, 1999); jaws connected to drives with gear trains (U.S. Pat. No. 4,718,682 issued to Antun Zilic et al. on Jan. 12, 1988); jaws, motors, and a clutch (U.S. Pat. No. 4,209,180 issued to Mario Bertorello on Jun. 24, 1980); and piston and ball lock assemblies (U.S. Pat. No. 6,375,398 issued to Jack R. Gaudreau et al. on Apr. 23, 2002). 
   Other attempts to address this problem include devices that require a particular tool end working with a particular toolholder to secure the alignment. Most of them require a shank and collet with a cylindrical shaped housing to accept the tool end. Such devices are disclosed in: U.S. Pat. No. 3,790,182 issued to Robert H. Schuman on Feb. 5, 1974; U.S. Pat. No. 3,599,996 issued to Donald G. Holt on Aug. 17, 1971; U.S. Pat. No. 5,882,015 issued to Ronald L. McPherson on Mar. 16, 1999; and U.S. Pat. No. 6,375,398 issued to Jack R. Gaudreau et al. on Apr. 23, 2002. Misalignment and runout can be controlled only if the toolholder and tool ends are manufactured exactly as described in these patents. Different types of work pieces with different tool ends would not be acceptable. 
   The size of most of the devices cited in the aforementioned patents cannot be adjusted significantly. Because of the mechanisms built into the toolholder or the tool end, reducing the size of the device would be difficult if not impossible. (See, for example, the devices as depicted in U.S. Pat. No. 4,718,682 issued to Antun Zilic et al. and U.S. Pat. No. 4,209,180 issued to Mario Bertorello.) These devices cannot be made significantly smaller. 
   Skilled artisans will appreciate that there are other devices made for specialized purposes and, although effective for their specialties, offer no versatility. The device disclosed in U.S. Pat. No. 4,209,180 (Bertorello), for instance, is made for large, heavy machining operations. Moreover, devices disclosed in U.S. Pat. No. 3,595,591 issued to Roland G. Koch et al. on Jul. 27, 1971 and U.S. Pat. No. 5,882,015 (McPherson) are floating toolholders, focused on machines that complete precise holes or threads. 
   One skilled in the art will appreciate that a device, like the one described in U.S. Pat. No. 4,583,432 issued to Michael W. Bricker on Apr. 22, 1986, for instance, involves the completion of a two-step process to set the alignment. In the first step, it is required to set the coarse adjustment and then set the precise adjustment by turning four fine adjustment screws in appropriate sequential rotation. Such process steps add complexity and time consuming adjustment to such an alignment operation. 
   Another device as described in PCT No. WO 99/10785 issued to Patrick Boland, et al. on Mar. 4, 1999, requires a CNC computer to align the work piece accurately. 
   Therefore, a need persists in the art for an eccentric toolholder that allows for radial offsets to be separated along two perpendicular axes, which may then be independently adjusted for precise alignment. The toolholder of the invention eliminates run-out and can be used for many different types of work pieces. Moreover, the toolholder is relatively compact and easily manufactured. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a work piece holder device that maintains the work piece in alignment during rotary movements. 
   Another object of the invention is to provide a work piece holder that compensates for work piece run-out during operation. 
   Yet another object of the invention is to provide a method of aligning a work piece during rotary operations. 
   It is a feature of the invention that aligning members, structurally associated along the rotary axis of a rotary unit, holds a work piece aligned relative to the rotary axis in response to pivotal movements of the aligning members during operation. 
   To accomplish the aforementioned objects, advantages and features of the invention, there is provided, in one aspect of the invention, an eccentric work piece holder adaptable to a rotary unit having a rotary axis for rotating a work piece during operation. A first aligning member is fixedly mounted on the rotary axis of the rotary unit. A second aligning member is mounted for substantially X-directional pivotal movements along the rotary axis. The second aligning member is arranged adjacent to the first aligning member. A third aligning member, being arranged nearest adjacent to the second aligning member, has a bore opening for holding the work piece. The third aligning member is mounted for substantially Y-directional pivotal movement along the rotary axis. Rotary movement of the first-, second- and third aligning members along the rotary axis causes the work piece secured in the third aligning member to align relative to the rotary axis in response to pivotable movements of the second aligning member in the substantially X direction and pivotable movements of the third aligning member in the substantially Y direction, thereby compensating for work piece runout in the X and Y directions. 
   In another aspect of the invention, a method of making an eccentric work piece holder involves the steps of providing a plurality of associated aligning members, one of said plurality of aligning members providing means for holding a work piece, as described above. Means is provided for enabling each one of the plurality of associated aligning members to pivot along a rotary axis in one direction in response to a corresponding directional run-out of the work piece. Fixedly adjusting the position of the work piece relative to the rotary axis after the work piece run-out has been compensated for. 
   The present invention has the following advantages: In applications where concentric alignment is needed between a rotary axis and a cylindrical part, the disclosed device provides a means for quick and precise removal of radial runout by allowing eccentric adjustment along two perpendicular axes. The device is compact and lightweight consisting of only three small disks or plates, thus providing advantage for applications that have weight limitations and/or space constraints. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein: 
       FIG. 1  is an isometric view of the assembled eccentric toolholder shown holding a cylindrical part and mounted to a circular disk representing the rotary axis of a machine tool; 
       FIG. 2  is an isometric exploded view of the eccentric toolholder showing the three components of the invention along with a cylindrical part; 
       FIG. 3  is an illustration of the first disk of the assembly; 
       FIG. 4  is an illustration of the second disk of the assembly; 
       FIG. 5  is an illustration of the third disk of the assembly; 
       FIG. 6  is an isometric view of the first disk mounted to a circular disk representing the rotary axis of a machine tool; 
       FIG. 7  is a front view of the first disk mounted to a circular disk representing the rotary axis of a machine tool; 
       FIG. 8  is an isometric view of the second disk mounted to the first disk, which is mounted to a circular disk representing the rotary axis of a machine tool; 
       FIG. 9  is a front view of the assembly consisting of the first and second disks mounted to a circular disk representing the rotary axis of a machine tool, with the second disk rotated slightly to the left of the first disk&#39;s center; 
       FIG. 10  is a front view of the assembly consisting of the first and second disks mounted to a circular disk representing the rotary axis of a machine tool, with the second disk concentrically aligned with the first disk; 
       FIG. 11  is a front view of the assembly consisting of the first and second disks mounted to a circular disk representing the rotary axis of a machine tool, with the second disk rotated slightly to the right of the first disk&#39;s center; 
       FIG. 12  is an isometric view of the third disk mounted to the assembly of the first disk and second disk, which is mounted to a circular disk representing the rotary axis of a machine tool; 
       FIG. 13  is a front view of the assembly consisting of the first, second, and third disks mounted to a circular disk representing the rotary axis of a machine tool, with the third disk rotated slightly above the second disk&#39;s center; 
       FIG. 14  is a front view of the assembly consisting of the first, second, and third disks mounted to a circular disk representing the rotary axis of a machine tool, with the third disk concentrically aligned with the first and second disks; and 
       FIG. 15  is a front view of the assembly consisting of the first, second, and third disks mounted to a circular disk representing the rotary axis of a machine tool, with the third disk rotated slightly below the second disk&#39;s center. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Turning now to the drawings, and in particular to  FIGS. 1 and 2 , the eccentric work piece holder  100  of the invention is illustrated. Broadly defined, eccentric work piece holder  100  is adaptable to a rotary unit (not shown). Rotary unit has a rotary axis  4  for rotating the work piece  5  during operation. A first aligning member  1  is fixedly mounted on the rotary axis  4  of the rotary unit. A second aligning member  2  is mounted for substantially X-directional pivotal movements along the rotary axis  4 . The second aligning member  2  is arranged adjacent to the first aligning member  1 . A third aligning member  3 , being arranged nearest adjacent to the second aligning member  2 , has a bore opening  13  for holding the work piece  5 . Further, a third aligning member  3  is mounted for substantially Y-directional pivotal movement along the rotary axis  4 . Rotary movement of the first-, second- and third aligning members  1 ,  2 ,  3 , respectively, along the rotary axis  4  causes the work piece  5 , secured in the third aligning member  3 , to align relative to the rotary axis  4  in response to pivotable movements of the second aligning member  2  in the substantially X direction and pivotable movements of the third aligning member  3  in the substantially Y direction, thereby compensating for work piece runout in the X and Y directions. 
   Eccentric work piece holder  100  provides adjustment capability that allows radial runout between rotary axis  4  and work piece  5  to be removed via translations along two perpendicular axes, as described below. The present invention may be applied to work piece holding on turning machines to remove radial misalignment (runout) between the work piece  5  and the rotary axis  4 . The operating principle behind the eccentric work piece holder  100  of the invention relies on the ability to move a work piece  5  along radial trajectories that lie in planes perpendicular to the cylindrical axis of the selected rotary mount. In reducing radial runout to within sub-micron dimensions, radial trajectories become nearly linear at the point of axis intersection. This phenomenon allows precise removal of radial runout, separating adjustment into two mutually perpendicular axes. 
   Referring again to  FIGS. 1 and 2 , more particularly, the eccentric toolholder  100 , assembled and attached to the rotary axis  4  of a turning machine (not shown), is illustrated. The work piece  5  is fastened securely within the third aligning member  3 . Moreover, third aligning member  3  is secured to the second aligning member  2 . Second aligning member  2  is secured to the first aligning member  1 . First aligning member  1  is mounted securely to rotary axis  4 . According to  FIG. 2 , an exploded view of the eccentric toolholder  100  depicts preferred securing and adjustment features. Preferably, first aligning member  1  is secured to the rotary axis  4  via three fasteners using mounting holes  6 . Further, second aligning member  2  pivots about mid-pivot point  7  through mid-pivot counter bore  8 . Further, third aligning member  3  pivots about top-pivot point  12  (hidden in this view, shown in FIGS.  4  and  8 - 11 ) through top-pivot counter bore  11 . Work piece  5  is positioned into third aligning member bore opening  13  and secured into third aligning member  3  via several fasteners acting through radial tapped holes  9 . Fasteners are not shown for clarity. 
   Referring to  FIGS. 3 ,  4 , and  5 , an unobstructed view of each aligning member  1 ,  2 ,  3  is illustrated. According to  FIG. 3 , first aligning member  1 , is stationary and consists of three mounting holes  6  for mounting to the rotary axis  4  of a machine tool. This first aligning member  1  is also provided with a mid-pivot point  7  for the first point of rotation of the second aligning member  2 . According to  FIG. 4 , second aligning member  2  has two holes, one clearance mid-pivot counter bore  8  and one tapped top-pivot point  12  offset by substantially 90 degrees. The mid-pivot counter bore  8  aligns with the mid-pivot point  7  in the first aligning member  1  and is fitted with a fastening member (not shown) that allows rotation of the second aligning member  2  when loosened. According to  FIG. 5 , the third aligning member  3  has a centrally located opening  13  to hold a cylindrical work piece  5 . In addition, the third aligning member  3  contains two holes, one clearance top-pivot counter bore  11  and one clearance mid-pivot adjustment hole  10  offset by 90 degrees. The top-pivot counter bore  11  aligns with the tapped top-pivot point  12  in the second aligning member  2  and is fitted with a fastening member (not shown) that allows rotation of the third aligning member  3  when loosened. The mid-pivot adjustment hole  10  allows access to the fastening member (not shown) in the second aligning member  2 . 
   Referring to  FIGS. 6 and 7 , in operation, the first aligning member  1  is aligned to be concentric with the rotary axis  4  to which it is mounted. Both the second aligning member  2  and third aligning member  3  are then attached with their respective fastening members—loosely aligned to be concentric with the first aligning member  1 . A cylindrical work piece  5  is then mounted rigidly in the third aligning member  3  using any manner of holding, including clamping, on the body diameter with set screws driven normal to the cylindrical surface through radial tapped holes  9  in the third aligning member  3 . Alignment is pursued while rotating the mounted assembly in the machine tool with an indicator measuring run out on the cylindrical work piece  5  held. Run out is first eliminated in a direction aligned with the single degree-of-freedom (dof) dictated by the movement of the second aligning member  2 . As depicted in  FIG. 9 , the first degree-of-freedom is shown to be along the horizontal plane—allowing movement from side to side. 
   Referring to  FIG. 8 , the attachment of second aligning member  2  to first aligning member  1  is illustrated. The preferred attachment is accomplished via a fastener (not shown) that passes through mid-pivot counter bore  8  in second aligning member  2  and the mid pivot point  7  of first aligning member  1 . 
   Referring to  FIGS. 9 ,  10 , and  11 , various locations are illustrated of the second aligning member  2  while rotating about mid-pivot counter bore  8 , providing a representation of motion indicating side-to-side movement. Using half the indicator measurement of total run out for the cylindrical work piece  5  in the horizontal plane, the second aligning member  2  would be adjusted by loosening the fastener at mid-pivot counter bore  8  and then moving the second aligning member  2  in the proper direction by this offset amount and refastening. The refastening step negates the run-out in this first degree-of-freedom direction. Run out is then eliminated in a direction perpendicular to the first degree-of-freedom, dictated by the third aligning member  3 . According to  FIG. 13 , the second degree-of-freedom is shown to be along the vertical plane allowing movement up-and-down. 
   Referring to  FIG. 12 , the attachment of third aligning member  3  which contains work piece  5  to second aligning member  2  is illustrated. The preferred attachment is accomplished via a fastener (not shown) that passes through top-pivot counter bore  11  in third aligning member  3  and the top pivot point  12  of second aligning member  2 . 
   Referring to  FIGS. 13 ,  14 , and  15 , various locations of the third aligning member  3  while rotating about top-pivot counter bore  11  are illustrated. This provides the pivotal movement of third aligning member  3  along the vertical axis. Similar to the first degree-of-freedom adjustment, using half the indicator measurement of total run out for the cylindrical work piece  5  in the vertical plane, the third aligning member  3  would be adjusted by loosening the fastener at top-pivot counter bore  11  and moving the third aligning member  3  in the proper direction by this offset amount and refastening, negating the run-out in this second degree-of-freedom direction. Once both first and second degree-of-freedom adjustments are made, run out is eliminated. This device allows elimination of run-out between two cylindrical parts. 
   The invention has been described with reference to a preferred embodiment. However, a person of ordinary skill in the art can effect variations and modifications without departing from the scope of the invention. 
   Parts List 
   
       
         1  first aligning member 
         2  second aligning member 
         3  third aligning member 
         4  rotary axis 
         5  work piece 
         6  mounting holes 
         7  mid-pivot point 
         8  mid-pivot counter bore 
         9  radial tapped holes 
         10  mid-pivot adjustment hole 
         11  top-pivot counter bore 
         12  top-pivot point 
         13  third aligning member bore opening 
         100  eccentric work piece holder