Abstract:
A workholding apparatus comprising a chuck body, first jaw members and second jaw members wherein the second jaw members are shaped to grip a workpiece of a particular geometry. The first and second jaw members are constructed to enable easy, quick and manual replacement of the second jaw members with other second jaw members having different grip shapes so as to enable gripping of workpieces with different geometries.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 61/382,066 filed Sep. 13, 2010 the entire disclosure of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to a workholding apparatus for machine tools. In particular, the workholding apparatus is especially suited for holding various sizes of workpieces on a machine tool transfer device. 
     BACKGROUND OF THE INVENTION 
     In metalworking operations where a workpiece is machined, equipment of some type is necessary to hold the workpiece in position in a machine tool so the machining process can be successfully carried out. This type of equipment is known as “workholding” equipment. 
     It is well known in machining processes for a workpiece to be transported to and/or from the workholding equipment via transfer device. In one known embodiment, workpieces are transferred between a cutter spindle and an auxiliary spindle where another process (e.g. chamfering) may be carried out. One manner of transferring a workpiece between spindles is via a rotary transfer arm. The rotary arm usually comprises a pair of workholding devices (e.g. chucks) that grasp a workpiece during the transfer. Each chuck usually includes a gripper device comprising a plurality (e.g. two or three) of jaws. The form of the grippers is usually one which compliments the form of that portion of workpiece to be gripped. In bevel gear manufacture, for example, different jaw forms or shapes would be required depending upon whether the part being gripped is a bevel pinion or a bevel ring gear as can be appreciated by the artisan. 
     On a machine having a transfer mechanism, a change in the type of workpiece being processed usually requires a change in the type and/or shape of the jaws of the chucks on the transfer mechanisms. Generally, this involves removing of a plurality of bolts to release each jaw from its associated chuck body and replacing the bolts when securing the replacement jaw to the chuck body. Such a task is time consuming, requires one or more tools and presents the possibility of thread damage to the bolts and/or chuck body. 
     It is an object of the present invention to provide a gripping apparatus whereby jaws are quickly and easily exchanged without the need for tools. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a workholding apparatus comprising a chuck body, first jaw members and second jaw members wherein the second jaw members are shaped to grip a workpiece of a particular geometry. The first and second jaw members are constructed to enable easy, quick and manual replacement of the second jaw members with other second jaw members having different grip shapes so as to enable gripping of workpieces with different geometries. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial front view showing two spindles and a rotary transfer arm of a gear manufacturing machine. 
         FIG. 2  illustrates a chuck body with first jaw members thereon. 
         FIG. 3  is a cross-sectional view of the chuck body and first jaw members of  FIG. 2 . 
         FIG. 4  is a perspective view of a first jaw member of the present invention. 
         FIG. 5  is a cross-sectional view of a first jaw member with a closure spring. 
         FIG. 6  is a cross-sectional view of a first jaw member with a closure pin. 
         FIG. 7  illustrates a rotary transfer arm with the chuck body and first jaw members of  FIG. 2 . 
         FIG. 8  shows second jaw members positioned on the apparatus of  FIG. 3  for gripping a pinion. 
         FIG. 9  illustrates a rotary transfer arm with the workholding apparatus of  FIG. 8 . 
         FIG. 10  shows second jaw members positioned on the apparatus of  FIG. 3  for gripping a ring gear. 
         FIG. 11  illustrates a rotary transfer arm with the workholding apparatus of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Before any features and at least one construction of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other constructions and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purposes of description and should not be regarded as limiting. 
       FIG. 1  illustrates a known type of gear cutting machine  2  comprising a transfer arm  4 . Upon the completion of a cutting process, the transfer arm  4  is actuated outwardly (i.e. away from cutter spindle  6  and auxiliary spindle  8 ) from a rest position and rotated to simultaneously grip a cut gear  10  on spindle  6  and a gear blank  12  on auxiliary spindle  8  via jaws  14  (two or more at each end of transfer arm  4 ), withdraw both workpieces from their respective spindles and then rotate (usually about 180 degrees) to bring the blank gear  12  to the work spindle  6  for cutting and the cut gear  10  to auxiliary spindle  8  for chamfering. Inward movement of the transfer arm  4  (i.e. toward the respective spindles) is then effected in order to load the gear blank  12  and cut gear  10  in their respective spindles. Once the workpieces are loaded, the transfer arm  4  returns to a rest position. Replacement of jaws  14  has been by removal of bolts as described above. 
     The inventors have addressed the noted deficiencies of the prior art with the chuck device  20  shown in  FIGS. 2-6 . Preferably, the chuck  20  includes a chuck body  22  comprising at least two opposed linear movable slides  24  that are actuated by known means (e.g. hydraulic, pneumatic, etc.). The chuck body  22  per se is commercially available, such as from Schunk GmbH &amp; Co. KG, for example. 
     According to the invention, a first jaw member  26  is secured via a removable manner to each linear slide  24  such as by a pair of screws  28 . Each first jaw member  26  includes an outer fixed gripping member, such as stop  30 , and an opposed inner gripping member, such as clasp member  32 , movable between an open release position and a closed gripping position. Wall portion  34  and first angular surface  36  of outer fixed stop  30  cooperate with planar surface  38  of first jaw member  26  to define a first groove  40  in each first jaw member  26 . Clasp  32  is pivotable about a pin  42  ( FIG. 5 ) near a first end thereof and is resiliently biased, such as by one or more springs  44 , toward outer fixed stop  30 . The second end of clasp  32  includes second angular surface  46  ( FIG. 3 ) which terminates spaced from planar surface  38  thereby forming second groove  48  in the region between planar surface  38  and the terminus of second angular surface  46 . With respect to the orientation of  FIG. 3 , first angular surface  36  faces generally toward planar surface  38  and second angular surface  46  faces generally away from planar surface  38 . It should be understood that the positions of fixed stop  30  and clasp member  32  on first jaw member  26  may be reversed from the arrangement shown in  FIG. 2 . 
       FIG. 7  shows a transfer arm  4 , of the type shown in  FIG. 1 , having chuck bodies  22  and a pair of first jaw members  26  positioned on each chuck body. It is to be understood that if desired, more than two first jaw members on a chuck body are also contemplated by the present invention. For example, a three jaw chuck may be utilized for gripping and transferring certain types of workpieces. In such an instance, the chuck body  22  would comprise three linear slides  24  circumferentially arranged preferably equidistantly from one another. 
       FIG. 8  illustrates a further element of the present invention, namely, a second jaw member  50  which is insertable into and removable from each first jaw member  26  in a tool-less manner. Second jaw member  50  comprises a first end  51  having a first shoulder  52  which is preferably shaped generally complementary with the shape of first groove  40  and a second shoulder  54  which is preferably shaped generally complementary with the shape of second groove  48 . First shoulder  52  is inserted into first groove  40  followed by sliding the second shoulder  54  along second angled surface  46  until it “snaps” into position in second groove  48  due to the spring action of the clasp member  32 . The second jaw member  50  further preferably includes a key (not shown) on the bottom surface thereof that is insertable into a keyway  39  ( FIG. 2 ) located in the planar surface  38  of first jaw member  26 . 
     Second jaw member  50  also includes a second end  53  which has an end surface shaped so as to conform to the shape of the workpiece that is in contact with the second end  53  when gripped. In  FIG. 8 , the workpiece is a pinion member  56 . Inward movement of slides  24  (toward axis A), which carry first jaw members  26  and second jaw members  50 , results in gripping pinion member  56  while outward movement of slides  24  (away from axis A) results in pinion member  56  being released. 
     It should be noted that if additional holding force is desired for maintaining second jaw member  50  in position on first jaw member  26 , a threaded pin  58  ( FIG. 6 ) with hand tightened knob  60  may be included in addition to, or alternative to, spring member  44 . 
       FIG. 9  shows a transfer arm  4  having the inventive workholding apparatus of  FIG. 8  thereon. Chuck bodies  22 , a pair of first jaw members  26  positioned on each chuck body and a pair of second jaw members  50  positioned on each first jaw member  26  comprise the apparatus for gripping pinion member  56  during transfer between machine spindles. 
     The present invention provides for fast, easy and tool-less changing of the second jaw member in order to grip another workpiece having a different outer geometry. In  FIG. 10 , for example, chuck body  22  and first jaw member  26  are unchanged from those of previous Figures. However, the second jaw member  62 , while having the same first end  51 , first shoulder  52  and second shoulder  54  as previously described, has a differently shaped second end  55  so as to be complementary in shape to the gripping surfaces of a ring gear member  64 . 
     As an example, removing second jaw members  50  ( FIG. 8 ) for replacement by second jaw members  62  ( FIG. 10 ) is accomplished by opening the workholding apparatus  20  by moving slides  24  away from each other (away from axis A), manually removing threaded pin  58 ,  60  if present, manually opening each closure  32  (preferably via a gripping surface such as tabs  33  in  FIG. 4 ) in the direction of arrows  57 , and lifting second jaw member  50  from its position on first jaw member  26 . Second jaw members  62  (or another second jaw member having a different form) may then be inserted into first jaw members  26  and snapped into place as previously described. 
       FIG. 11  shows a transfer arm  4  having the workholding apparatus of  FIG. 10  thereon. Chuck bodies  22 , a pair of first jaw members  26  positioned on each chuck body and a pair of second jaw members  62  positioned on each first jaw member  26  comprise the apparatus for gripping ring gear member  64  during transfer between machine spindles. With reference to  FIGS. 9 and 11 , changing the workholding apparatus of the transfer mechanism  4  from pinion gripping to ring gear gripping is one of removing second jaw member  50  and replacing it with second jaw member  62 . 
     Of course, it can be appreciated that second jaw members having other second end geometries are also contemplated depending upon the form of the particular workpiece being gripped for transfer. 
     While the present invention has been shown as residing on a rotary transfer arm, the present invention is not limited thereto. The inventive workholding apparatus may be utilized in other workpiece transfer arrangements as well as in machining operations other than cutting, for example grinding, honing or other hard finishing operations. Furthermore, while the present invention has been described with respect to workpiece holding, the invention may also be applicable to holding of tools, especially in regard to the exchange of like tools such as when a worn tool is exchanged for a new or sharpened tool. 
     While the invention has been described with reference to preferred embodiments it is to be understood that the invention is not limited to the particulars thereof. The present invention is intended to include modifications which would be apparent to those skilled in the art to which the subject matter pertains without deviating from the spirit and scope of the appended claims.