Abstract:
A gripping device that engages and disengages an inserted workpiece with an essentially perpendicular engagement action thereby eliminating any sliding contact with the workpiece. Such perpendicular and non-sliding engagement is achieved through the action of a plurality of gripping fingers driven by a spherical ball and hinged inside of a chuck housing that guides the fingers in a substantially perpendicular motion relative to the engaged surface during engagement and disengagement. Engagement with a workpiece is achieved by the simple action of compressing a spring retained outer casing and releasing the outer casing once the workpiece has been placed-within the gripping range of the internal fingers.

Description:
FIELD OF THE INVENTION 
     The present invention relates to devices such as chucks for gripping workpieces and more particularly to such devices that are capable of gripping and releasing a workpiece such as a shaft without galling or otherwise marring the surface thereof. 
     BACKGROUND OF THE INVENTION 
     In many manufacturing processes workpiece handling equipment is used to move a part from one location to another or to hold or grip a part during a fabrication operation. In many cases, such as those involving gripping by a shaft during such manipulation, a chuck is used to first grip the shaft, hold the shaft during manipulation and then release the shaft for further fabrication or handling. Chucks commonly used to achieve such gripping rely on a sliding motion during the engagement and disengagement portions of the gripping operation. While such action is generally not a problem, for example, when a drill bit is inserted into a drill and the like, in some situations such sliding engagement is entirely unsatisfactory because the sliding action during engagement and disengagement results in marring, galling or otherwise affecting the surface of the engaged part. Such is the case, for example, in the handling of electric motor armatures and the like during the manufacturing and finishing processes associated with the fabrication of such devices. Even minimal surface damage to the armatures of such devices imparted during manufacture can affect the performance and durability of such devices. 
     Accordingly, the availability of a gripping device such as a chuck that can engage and disengage a workpiece such as an armature without damaging the surface thereof would be of significant benefit to the manufacturer of such devices. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the present invention to provide a gripping device capable of engaging and disengaging a shaft, armature or the like without damaging the surface thereof. 
     It is anther object of the present invention to provide an improved gripping device that can engage and disengage a shaft, armature or the like workpiece without any sliding contact that can adversely affect the surface of the engaged or disengaged shaft, armature or the like workpiece. 
     SUMMARY OF THE INVENTION 
     The present invention provides a gripping device that engages and disengages an inserted workpiece with an entirely perpendicular engagement action thereby totally eliminating any sliding contact with the workpiece. Such perpendicular and non-sliding engagement is achieved through the action of a plurality of gripping fingers driven by a spherical ball and hinged inside of a chuck housing that guides the fingers in a substantially perpendicular motion relative to the engaged surface during engagement and disengagement. Engagement with a workpiece is achieved by the simple action of compressing an outer casing and releasing the outer casing once the workpiece has been placed within the gripping range of the internal fingers. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a preferred embodiment of the gripping device of the present invention in the closed or gripping position. 
     FIG. 2 is a cross-sectional view of a preferred embodiment of the gripping device of the present invention showing all of the essential operating parts for this embodiment. 
     FIG. 3 is an exploded view of a preferred embodiment of the gripping device of the present invention. 
     FIG. 4 is a perspective view of a preferred embodiment of the gripping device of the present invention in the open or releasing position. 
    
    
     DETAILED DESCRIPTION 
     In order to obtain a gripping device that is capable of tightly engaging a workpiece without any sliding motion such as that normally encountered in the use of conventional such gripping devices or chucks, it is necessary that all gripping motion, i.e. all motion by engagement surfaces or members be substantially perpendicular to the workpiece. The gripping device of the present invention achieves such perpendicular movement and consequently eliminates any damage to the gripped workpiece during engagement or disengagement with the gripping device. Such perpendicular movement is obtained through the action of a spherical ball driving against asymmetric recesses in the facing sides of gripping fingers that are slideably mounted within the gripping device. 
     Referring now to FIGS. 2 and 3 that respectively show a random cross-sectional view and an exploded view of one preferred embodiment of the gripping device  10  of the present invention, gripping device  10  comprises: a circular base  12  having a rear wall  22 , an open front  23  and a peripheral wall  25  that together with rear wall  22  define an open interior  27 ; a finger mounting tower  14  including pin slots  16  and finger slots  18 ; a pair of set screws  20  that screw into rear wall  22  of base  12 ; guideposts  24  that are inserted into apertures  21  in peripheral wall  25  and registered apertures  29  (see FIG. 2) in cylindrical finger guide  48 ; a plurality of fingers  26  each having a pin  28  mounted therethrough, a gripping surface  30 , sliding surfaces  32  and  34  and ball receipt recess  36 ; spherical ball  38  contained in spherical ball receipt recesses  36 ; a circular spring  40  that fits into open interior  27  of circular base  12  about and concentric with finger mounting tower  14  about fingers  26 ; a collar  42  that encloses spring  40 , fingers  26 , guide posts  24  and fits moveably about the periphery of wall  25  and includes an aperture  44  for insertion of assembly and ball retention pin  46 ; and finally, cylindrical finger guide  48  having a collar portion  42  and incorporates aperture  50  for receipt of threaded ball retention pin  46  and provides finger bearing surfaces  52  and  54 , the latter being shown only in FIG.  2 . According to the preferred embodiment depicted in FIGS. 1-4 a threaded male connector  64  is provided for attachment of gripping device  10  to an appropriate tool mounting system. 
     In further detail, base  12  contains finger mounting tower  14  that provides horizontal pin slots  16  and vertical finger slots  18  that begin at the interior surface of rear wall  22  and extend to the top of finger mounting tower  14  thereby providing three individual tower sections  14   a ,  14   b  and  14   c . In its assembly, as described in further detail hereinafter, fingers  26  are oriented in finger slots  18  and pins  28  slid into pin slots  16  thereby permitting fingers  26  to slide toward and away from the centerline of base  12  without falling out. 
     Guideposts  24  serve to maintain proper alignment between base  12  and its associated members and cylindrical finger guide  48  and its associated members. Quite clearly, guideposts  24  must fit into apertures  29  in a fashion that permits axial movement of base  12  and cylindrical finger guide  48  relative to one another as described herein. Consequently, apertures  29  must be of a length to accommodate such axial movement. 
     Spherical ball receipt recesses  36  have an elongated shape as best seen in FIG.  2 . Spherical ball receipt recesses  36  are preferably wide at their forward end, that end closest to gripping surfaces  30 , to allow introduction of spherical ball  38  as described below during assembly but have uniformly angled surfaces  62  in their rearward portions, those proximate finger mounting tower  14  so as to permit spherical ball  38  to move rearward toward end wall  22  during operation as described below. While the angle of angled surfaces  32 ,  34 ,  52 ,  54 , and  62  may be varied considerably depending upon the gripping capacity and the size of gripping device  10 , an angle of between about 20 and 40 degrees is generally acceptable with an angle of about 30 degrees being preferred. 
     Spring  40  which, as described hereinafter, provides gripping device  10 &#39;s gripping pressure, may comprise any of a number of conventional spring configurations such as wire coil springs etc, but it is specifically preferred that spring  40  be a continuous spiraling wave spring of the type recognized in the art that applies pressure in a continuous spiraling wave. Such a spring imparts maximum pressure for a given minimal diameter and depth while providing excellent performance for long periods of time during high speed loading and unloading operations. 
     While annular finger guide  48  and collar  42  are depicted in FIG. 3 as separate parts, they may comprise a single assembly if the appropriate bearing surfaces can be provided as described below. Also, as described in connection with the detailed description of spherical ball recesses  36 , surfaces  32  and  34  and  52 ,  54  and  62  may be angled within a wide range depending upon the configuration of gripping device  10 . Quite clearly all of these angles should be of mating proportions to permit smooth and uniform operation of gripping device  10 , and angles of between about 20 and about 40 degrees are acceptable therefor with angles of about 30 degrees being specifically preferred. As will be apparent to the skilled artisan, whatever angle is selected for these various parts, all of the angles should be the same to assure smooth operation of the device. 
     When assembled, gripping device  10 , has the configuration best shown in random cross-section in FIG.  2 . Assembly is accomplished as follows, cylindrical finger guide  48  is inserted into collar  42  so that apertures  44  and  50  are in registration forming a first assembly section. Spring  40  is located in open front  23  inside of and adjacent to peripheral wall  25  and bearing against rear wall  22 . Guideposts  24  are inserted into apertures  21 , the first assembly section described above, oriented facing base  12  and guideposts  24  aligned with apertures  29  therein. The entire assembly is then mechanically compressed, in the direction shown by arrows  58  in FIG. 2, against the force of spring  40 . At sufficient compression, virtually complete compression, such that the rear annular rim  56  of annular finger guide  48  is adjacent to rear wall  22 , fingers  26  are individually inserted such that pins  28  engage pin slots  16  and fingers  26  engage finger slots  18 . Spherical ball  38  is then deposited into ball receipt recesses  36 , ball retention pin  46  is then screwed into registered apertures  44  and  50  and compression pressure released. At this time, sliding surfaces  32  and  34  on fingers  26  are in contact with finger bearing surfaces  52  and  54  and the assembly is complete except for the insertion of set screws  20  into rear wall  22 . The purpose of set screws  20  is determined by their length which must be sufficient to limit the travel of annular finger guide  48  backward, i.e. in the direction of arrows  58  in FIG. 2, beyond a point where fingers  26  could be accidentally or unintentionally removed from the assembly in the reverse of the assembly operation just described. Of course, the removal of set screws  20  is the first step in the intentional disassembly of gripping device  10  for purposes of changing fingers  26  or otherwise servicing the device. Chamfered surface  37  is provided on fingers  26  to provide clearance for tip  60  when fingers  26  are in close proximity in a “tight” gripping situation. 
     In operation, the first assembly comprising collar  42 , cylindrical finger guide  48  and ball retention pin  46  is compressed mechanically or robotically in the direction of arrows  58 . As this action occurs, it will be apparent to the skilled artisan that tip section  60  of ball retention pin  46  will force spherical ball  38  in the direction of arrows  58  causing fingers  26  to be driven apart as, spherical ball  38  engages slanted portions  62  of ball receipt recesses  36 . Simultaneously with such application of force, sliding surfaces  32  and  34  move along finger bearing surfaces  52  and  54 , fingers  26  slide radially in finger slots  18 , and pins  28  slide radially in pin slots  16 . This action results in fingers  26  to move relatively outwardly, i.e. longitudinally, from annular finger guide  48  and associated gripping surfaces  30  to move perpendicularly away from the center line, i.e. radially, of gripping device  10  in the direction indicated by arrows  70  in FIG.  2 . In this configuration presented in FIG. 4, gripping device  10  is in condition for receipt of a workpiece to be inserted between gripping surfaces  30 . Upon release of compression pressure upon spring 40 directed in the direction of arrows  58 , the first assembly comprising cylindrical finger guide  48 , collar  42  and threaded spherical ball retention pin  46  are forced in the direction of arrow  66  in FIG. 1 by the action of spring  40  allowing ball  38  to move forward in recesses  36  while surfaces  52  and  54  bear against surfaces  32  and  34  causing fingers  26  to withdraw into cylindrical finger guide  48  and associated gripping surfaces  30  to collapse perpendicularly upon any workpiece inserted therebetween. Such a configuration, absent a workpiece, is shown in FIG.  1 . 
     Gripping device  10  has been depicted and described according to a preferred embodiment that utilizes three fingers  26 . As will be apparent to the skilled artisan, the basic invention of utilizing a centrally mounted ball to force apart perpendicularly gripping surfaces upon the application of longitudinal pressure could be utilized with as few as two and upwards of three fingers having gripping surfaces capable of engaging a workpiece with gripping surfaces of varying sizes and shapes. Accordingly, all such modifications are intended to be within the scope of the appended claims. 
     As will be further evident to the skilled artisan, a number of variations can be made to the structure described herein to achieve a similar although somewhat result. For example, spring  40  could be located about the exterior of base  12 , if some appropriate mechanism were provided to retain it. In fact, spring  40  could be dispensed with entirely, if some other, but obviously more cumbersome activator for pin  46  were applied externally to the surface of gripping device  10 . The structure of finger mounting tower  14  could be changed to another structure that provides a mechanism for slideably retaining fingers  26 . The essential elements of gripping device  10  are the presence of spherical ball  38  in ball recess  36  and angular recess  62  in fingers  26  and a means such as pin  46  to drive fingers  26  apart in a guided fashion so that gripping surfaces  30  move perpendicularly away from the centerline of gripping device  10  when pin  46  is activated and return to a “closed” position through the application of internally or externally applied pressure in the opposite direction. 
     While gripping device  10  may be fabricated from any acceptable material including but not limited to metals and plastics, conventional tool steel and high strength steels have been found to be fully acceptable materials of construction for high volume and extended use operation with the former being specifically preferred for ease of machining and cost reasons. 
     There has thus been described, a gripping device that by virtue of its design and construction can engage a workpiece inserted therein with a virtually entirely perpendicular engagement motion thereby eliminating any sliding motion and the possibility of any damage to the inserted workpiece. 
     As the invention has been described, it will be apparent to those skilled in the art that the same may be varied in many ways without departing from the spirit and scope of the invention. Any and all such modifications are intended to be within the scope of the appended claims.