Abstract:
A parallel power chuck for clamping two ends of a shaft or similar workpiece for machining using two centering mechanisms. The centering mechanisms independently operate from a single internal actuation mechanism and clamp each end of the shaft regardless of shaft size from end to end. The internal actuation mechanism further equalizes applied clamping force after compensating for size variation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    None. 
       BACKGROUND OF THE INVENTION 
       [0002]    I. Field of the Invention 
         [0003]    The present disclosure relates generally to a power chuck. In particular, the present disclosure is directed to a parallel power chuck having side by side centering mechanisms in a single assembly to clamp a workpiece on both ends with very high centering accuracy. 
         [0004]    II. Description of the Prior Art 
         [0005]    In machines that operate on a rotating workpiece, such as lathes and the like, the workpiece is typically held in a chuck to rotate the workpiece relative to a tool (such as a blade) so that the tool can operate on the workpiece. The chuck, which is comprised of multiple movable or adjustable jaws, exerts a force on the workpiece to secure or clamp the workpiece in the chuck between the jaws. 
         [0006]    Conventionally, power or force-actuated chucks include a chuck body mounted upon a head stock spindle of a machine tool. The chucks generally carry a plurality of chuck jaws which are radially displaceable in respective guides inwardly and outwardly, respectively, to engage a workpiece or to disengage therefrom. The jaws are actuated by an axially displaceable piston within the chuck body. Typically, each jaw includes a wedge which corresponds with a cooperating wedge on the piston whereby as the wedge surfaces engage in the axial direction, the jaws move in radial and circumferential directions in their respective guides. 
         [0007]    Many cylindrical (for example) workpieces need to be machined while in parallel relation (e.g. to the bed or like of a machine tool). The current industry method for machining these types of pieces is to load the shaft into a so-called fixed vee-block and clamp down over the top of the shaft. However, the use of a vee-block does not accommodate for piece variation. In other words, a shaft with a high limit part diameter on one side will rest higher in the vee-block than the low limit diameter on the other side. The result is that the center line of the shaft, or the position of the workpiece that is to be machined, will be off center. 
         [0008]    Accordingly, it is a general object of this disclosure to provide a power chuck that will maintain the same centerline regardless of workpiece size variation. 
         [0009]    It is another general object of this disclosure to provide a power chuck assembly that utilizes two jaw centering mechanisms side by side, or in parallel, in a single unit to clamp a shaft or similar workpiece on both ends with very high centering accuracy. 
         [0010]    It is a more specific object of this disclosure to provide a power chuck assembly that utilizes two parallel jaw centering mechanisms that independently compensate for variations in workpiece size. 
         [0011]    It is another more specific object of this disclosure to provide a power chuck assembly that utilizes two parallel two-jaw centering mechanisms that equalize the clamping force exerted by each set of jaws on the workpiece after compensating for workpiece size variations. 
         [0012]    These and other objects, features and advantages of this disclosure will be clearly understood through a consideration of the following detailed description. 
       SUMMARY OF THE INVENTION 
       [0013]    According to an embodiment of the present invention, there is provided a parallel power chuck for clamping portions of a workpiece. The chuck having an assembly housing with a front face and a centerline. A first set of jaws is radially displaceable, perpendicular to the centerline and clamps a first portion of the workpiece, while a second set of jaws is adjacent the first set and also radially displaceable, perpendicular to the centerline and clamps a second portion of the workpiece. 
         [0014]    There is also provided a parallel power chuck for clamping portions of a workpiece, the chuck having an assembly housing with an axis through a front face. A primary axial movement member is rotatably coupled to a stabilizing member inside the housing. A pair of secondary axial movement members are also rotatably coupled to the stabilizing member and are further operatively coupled to a set of radially moveable jaws, relative said face, for clamping portions of the workpiece whereby the rotatable couplings of the stabilizing member enable independent clamping of the portions of the workpiece. 
         [0015]    There is further provided a parallel power chuck for clamping two ends of a generally cylindrical workpiece. The chuck having an assembly housing with an axis through a front face. A collar is positioned within the housing for coupling the assembly to a driver for axial movement. A primary spheroidal joint couples the collar to an actuator and secondary spheroidal joints couple respective wedge bolts to the actuator. The wedge bolts are then operatively coupled to respective sets of radially movable jaws relative the front face of the chuck. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The present disclosure will be more fully understood by reference to the following detailed description of one or more preferred embodiments when read in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the views and in which: 
           [0017]      FIG. 1  is a perspective view of a parallel power chuck assembly according to the principles of an embodiment of the present disclosure. 
           [0018]      FIG. 2  is a top plan view of the parallel power chuck assembly of  FIG. 1 . 
           [0019]      FIG. 3  is a cross-sectional view of the parallel power chuck assembly taken along line  3 - 3  of  FIG. 2 . 
           [0020]      FIG. 4  is a cross-sectional view of the parallel power chuck assembly taken along lines  4 - 4  of  FIG. 2 . 
           [0021]      FIG. 5  is a perspective view of the parallel power chuck assembly of  FIG. 1  adapted to receive a noncylindrical workpiece. 
           [0022]      FIG. 6  is a top plan view of the parallel power chuck assembly of  FIG. 5 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the disclosure, its application or use. 
         [0024]    With reference now to the drawings, and in particular  FIGS. 1 and 2 , a parallel power chuck assembly  10  includes a housing subassembly  12  for housing two parallel sets of chuck components side by side. By way of example, these chuck components can be an industry standard, such as ITW-Forkardt 2QLC-LS-250, a more conventional Buck™ chuck jaw and wedge profile, a lever mechanism chuck, or a chuck of a more custom design. In any event, the components include a first set of master jaws  14 A,  14 B and an adjacent second set of master jaws  16 A,  16 B. These cooperating sets of master jaws are designed to clamp on a portion of a workpiece that is parallel to the chuck face  18  on a centerline  20 . When the chuck is actuated, the jaws  14 ,  16  will stroke towards centerline  20  to clamp and load the workpiece and then, after the machining is completed, away from the centerline  20  to unload the workpiece. 
         [0025]    The subassembly  12  is mounted to a backplate  22  which can then be mounted to a spindle adaptor  24 , in the case of a machine lathe, or on a milling machine. Whether the chuck is rotated for machining of the workpiece on the same centerline as the spindle rotation, or the chuck is mounted and the machines cutting tools are rotated, the parallel chuck provides for high centering accuracy regardless of the variation of workpiece shaft size from one end to the other. 
         [0026]    For example, if the shaft of a workpiece has a diameter of 1.000+/−0.005″, the jaws  14 ,  16  must have the ability to clamp on the entire part range of 1.005−0.995″ diameter. In a worst case scenario, the first set of jaws  14  may have to grip on a 1.005″ diameter and the second set of jaws  16  may have to grip on a 0.995″ diameter. In this case, the first set of jaws  14  will clamp the 1.005″ diameter first, and then internal actuator must then compensate to allow the second set of jaws  16  to continue to stroke inward until they clamp the 0.995″ diameter. Once the mechanism compensates and both ends of the shaft are clamped, the mechanism then equalizes the clamping forces of both jaws  14 ,  16 . 
         [0027]    The preceding generalized summary will now be more particularly detailed with regard to  FIGS. 3 and 4  and the use of the parallel power chuck on a spindle, wherein  FIG. 3  is a cross-sectional view of the power chuck assembly taken along lines  3 - 3  of  FIG. 2  and  FIG. 4  is a cross-sectional view of the power chuck assembly taken along lines  4 - 4  of  FIG. 2 . Turning first to  FIG. 3 , the spindle adapter mounts the parallel power chuck onto a lathe (not shown) and the hydraulic cylinder of the lathe is connected to the chuck via a thread in the inner diameter  30  of a primary axial movement member or drawbolt lock collar  32 . As will be described herein, it is this connection which actuates the entire mechanism because a drawbolt  34  is also threaded into the drawbolt lock collar  32 . 
         [0028]    The drawbolt  34  extends axially thru a stabilizer plate or actuator  36  and a drawbolt washer  38  thereby creating a spherical radius mating surface  40  between the drawbolt  34  and the drawbolt washer  38 . This spherical radius mating surface  40  creates a primary spheroidal joint and allows the actuator  36  to rotate, barring any further encumbrances, at almost any angle about the center axis  42  of the parallel power chuck  10 . Accordingly, when the hydraulic cylinder is energized and the drawbolt lock collar  32  is pushed axially, it also pushes the drawbolt  34  which pushes the drawbolt washer  38  and actuator  36  via the flanged face  44  of the drawbolt lock collar  32 . 
         [0029]    Actuator  36  extends to both sides of the housing subassembly  12  and connects to each of the spherical bearing  46 A of the first jaws  14  and the spherical bearing  46 B of the second jaws  16 . This connection creates another spherical radius mating surface  48  between the bearing  46  and the actuator  36 . This spherical radius mating surface  48  creates a secondary spheroidal joint and allows the actuator  36  to rotate, barring any further encumbrances, at almost any angle about the center axis  50 A,  50 B of the spherical bearing  46 . 
         [0030]    The spherical bearings  46 A,  46 B are connected to secondary axial movement members or wedge bolts  52 A,  52 B thru a threaded connection ( 74 A,  74 B). The wedge bolts  52 A and  52 B extend thru a respective chuck connector  54 A,  54 B whereby, the shoulder  56 A,  56 B of the wedge bolt  52 A,  52 B mates with the counter bore face  58 A,  58 B of the chuck connector  54 A,  54 B. The chuck connector  54 A,  54 B is connected to a wedge  60 A,  60 B thru a threaded connection ( 80 A,  80 B). Accordingly, when the drawbolt lock collar  32  is pushed or pulled axially, it will move all connecting component parts, drawbolt  34 , drawbolt washer  38 , actuator  36 , spherical bearing  46 , wedge bolt  52 , chuck connector  54  and wedge  60  in the same direction. 
         [0031]    Turning now to  FIG. 4  and the movements of the jaws  14 . This cross-sectional view depicts the spherical bearing  46 A, the wedge bolt  52 A and the chuck connector  54 A in the center of the view, directly on the center axis  70  of the wedge bolt. The wedge  60 A has an angle  72 , which is preferably at 22°, but will depend upon particular chuck design needs. In any event, the wedge  60 A is connected to the master jaw  14  thru a conventional tee-slot connection at the 22° wedge angle. The interaction between the wedge  60 A and the master jaw  14  are well known and understood in the field of power chucks and will not be detailed herein. For purposes of this disclosure, when the drawbolt lock collar is pushed by the hydraulic cylinder, all of the mating components are also pushed as previously discussed. When wedge  60 A is pushed, it pushes master jaws  14 , and therefore clamping jaws (infra) outward  76  and in the open position. Similarly, when the drawbolt lock collar is pulled by the hydraulic cylinder, all of the mating components are also pulled so when the wedge  60 A is pulled, it pulls master jaws  14  and therefore clamping jaws (infra) inward  78  to the clamping position. 
         [0032]    Referring now to  FIGS. 5 and 6 , the parallel power chuck will now be shown and described as it clamps a non-cylindrical workpiece  100  having a shaft on the left, or a first shaft  102 , and a shaft on the right, or a second shaft  104 . In this particular example, the master jaws  14 ,  16  are coupled to a set of clamping jaws  106 A,  106 B and  108 A,  108 B via bolts  110 , although other forms of clamping jaws can be used. Following the sequence as described in the previous sections, when the drawbolt lock collar  32  is pushed or pulled, it will move clamping jaws  106  and  108  inward or outward through the internal mechanism. If the left and right shafts of the workpiece to be clamped are not equally sized, the parallel power chuck has the ability to compensate and eventually applies an equal clamping force to both shafts. 
         [0033]    Following the previously described example for workpiece  100 , the first shaft  102  will have the 1.005″ diameter and the second shaft  104  will have the 0.995″ diameter. During the clamping cycle, drawbolt lock collar  32  is pulled downward via the hydraulic cylinder, and when the clamping jaws  106  have clamped the 1.005″ diameter part on the left side of the shaft, then clamping jaws  106 , master jaws  14 , wedge  60 A, wedge bolt  52 A and spherical bearing  46 A all stop moving on the left side of the chuck. However, as the actuator  36  pivots around the center axis  50 A of the spherical bearing  46 A on the left side of the chuck, the lock collar  32  continues to pull the drawbolt  34 , drawbolt washer  38  and thus the continued movement of clamping jaws  108 , master jaws  16 , wedge  60 B, wedge bolt  62 B and spherical bearing  46 B on the right side of the chuck. The spherical radius mating surfaces  40  and  48  allow for concurrent pivoting of the actuator  36  at the drawbolt and the spherical bearings thereby compensating for the different sized left  102  and right  104  shafts of the workpiece  100 . This compensation allows clamping jaws  108  to continue to move inward until they clamp the 0.995″ diameter on the right side of the shaft. 
         [0034]    After both clamping jaws  106 ,  108  have clamped the workpiece  100 , the internal pivoting mechanism becomes static. Although the actuator  36  will now be on a slight angle due to the compensation, the spherical mating surfaces  40  and  48  allow the pulling force of the drawbolt lock collar  32  to be equally distributed between clamping jaws  106  and clamping jaws  108 . The compensation for unequal shaft diameters ensures a true centering of the workpiece, while the equalization ensures the uniform application of clamping force throughout the workpiece. 
         [0035]    The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom. Accordingly, while one or more particular embodiments of the disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the invention if its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the present disclosure.