Abstract:
An apparatus for releasably holding a tubular toolholder shank by axially reciprocating a lock rod between a locked and unlocked position. Compression balls following a helical path on a torque nut are used to retract a compression sleeve, which in turn compresses springs against the lock rod to move the lock rod into the locked position. As a result, a repeatable lock rod force is possible with a pre-determined and self limiting rotation of the torque nut. The same helical groove may be used to advance the compression sleeve against the lock rod to urge the toolholder from the base member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to tooling for machining operations and, more particularly, directed to a toolholder assembly for precisely locating a toolholder at a selected location within the toolholder assembly during a machining operation. 
     2. Description of The Related Art 
     Minimizing the down time of a machine tool in a production environment is critical to the success of a machining facility. Historically, one major contribution to such down time was the time needed to change damaged or worn out cutting tools used by the machine tool. A cutting tool is held by a toolholder, which is typically mounted within a tool support member secured to a machine tool. When the cutting tool must be replaced, the entire toolholder with the cutting tool attached thereto is removed from the support member. A number of couplings are designed to permit quick connecting and disconnecting of the toolholder to and from the tool support member to expedite the tool changing process. One such device is described in U.S. Pat. No. 4,736,659 entitled “Toolholder Assembly for Holding a Toolholder Shank.” This patent is co-owned by the Assignee of the present application and is hereby incorporated by reference. The toolholder assembly described in that patent utilizes two locking balls which are urged radially outwardly within a tool support member to engage apertures on the shank of a toolholder. While this arrangement is efficient and permits a toolholder to be removed or secured to a tool support member in a short amount of time, the design of this arrangement may limit its application to tool support members having radial access. Many industrial applications require the use of a tool support member having rear access. 
     U.S. Pat. No. 5,279,194 entitled “Ball Lock Assembly Without a Canister” is owned by the Assignee of the present application and is hereby incorporated by reference. While this assembly provides for rear access, actuation of the lock rod therein is achieved through multiple rotations of the torque nut and it is difficult to apply a given pull-back force. 
     In addition to a tool support member having rear access for actuation, a further object of the subject invention is to provide a repeatable maximum pull-back force on the lock rod with a minimum rotation of a rear end torque nut. 
     SUMMARY OF THE INVENTION 
     An apparatus for releasably holding a tubular toolholder shank has a base member with a forwardly facing surface and a bore intersecting the forwardly facing surface. The bore extends rearwardly therefrom along a longitudinal axis for receiving the toolholder shank. A lock rod with a forward and rearward end is rotationally restrained about the longitudinal axis and is movable within the base member in a rearward and forward reciprocating motion for pulling the toolholder shank rearwardly within the bore into a locked position and for releasing the toolholder shank from the bore to an unlocked position. A torque nut is rotatively mounted to the base member and operable upon the rearward end of the lock rod to provide the rearward and forward reciprocating motion of the lock rod. The torque nut has a segment with an outer surface and has one of an aperture extending within the outer surface or a groove extending at least partially around the outer surface. At least a portion of the groove is angled relative to the longitudinal axis. A compression sleeve is engaged by the torque nut through at least one compression member and resiliently engages the lock rod. The compression sleeve has the other of an aperture extending within the sleeve or a groove extending at least partially around the sleeve. The aperture is aligned with the associated groove and the at least one compression member is positioned within the groove and within the aperture, such that when the torque nut is rotated in one direction, the at least one compression member and compression sleeve are displaced axially rearward within the base and, when the torque nut is rotated in the opposite direction, the at least one compression member and compression sleeve are displaced axially forward within the base. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as other features and advantages of the invention, will become apparent upon consideration of the detailed descriptions in connection with the several drawings in which: 
         FIG. 1  is a cross-sectional view of the toolholder assembly in accordance with the subject invention, whereby the lock rod is in the released position and the toolholder is not secured within the base member; 
         FIG. 2  is a cross-sectional view of the toolholder assembly, whereby the lock rod is in the locked position and the toolholder is secured within the base member; 
         FIG. 3  is cross-sectional view along lines  3 - 3  in  FIG. 1 , illustrating the manner by which the lock rod is rotationally restrained within the base member; 
         FIG. 4  is a schematic of the relationship between the torque nut compression ball and compression sleeve illustrating a straight helical groove on the outer surface of the torque nut and its relationship with the compression ball and compression sleeve, wherein the compression sleeve is illustrated in the released position; 
         FIG. 4A  is a cross-sectional view of the schematic of  FIG. 4  viewed along arrows “ 4 - 4 ”; 
         FIG. 5  is a sketch similar to that illustrated in  FIG. 4 , however, now the torque nut is rotated such that the compression sleeve is in the locked position; 
         FIG. 6  is a sketch illustrating the groove in the compression sleeve and the compression ball in a aperture in the outer surface of the torque nut, whereby, once again, the compression sleeve is in the released position; 
         FIG. 7  illustrates a sketch similar to that in  FIG. 6 , however, now with the torque nut rotated such that the compression sleeve is in the locked position; 
         FIG. 8  illustrates a sketch similar to that of  FIG. 4 , however, the groove on the outer surface of the torque nut now includes segments of different orientations to assist in releasing the toolholder from the base member, wherein the compression sleeve is illustrated in the released position; 
         FIG. 8A  is a cross-sectional view of the schematic of  FIG. 8  viewed along arrows “ 8 - 8 ”; 
         FIG. 9  is a sketch similar to that of  FIG. 8 , however, now the torque nut has been rotated such that the compression sleeve is in the locked position; 
         FIG. 10  is a graph of displacement vs. rotation for the arrangements illustrated in  FIGS. 4 and 5  and  FIGS. 6 and 7 ; and 
         FIG. 11  is a graph of a displacement vs. rotation representative of the displacement vs. rotation for the arrangement illustrated in  FIGS. 8 and 9 . 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Directing attention to  FIG. 1 , the goal of the toolholder assembly  10  is to move a lock rod  15  back and forth along a longitudinal axis  17  within a base member  20  to secure a toolholder  22  within the base member  20  ( FIG. 2 ) or to eject the toolholder  22  from the base member  20  ( FIG. 1 ). 
     The base member  20  has a forwardly facing surface  27  and a bore  30  intersecting with the forwardly facing surface  27  and extending rearwardly therefrom along the longitudinal axis  17  for receiving the toolholder shank  25  of the toolholder  22 . As illustrated in  FIG. 1 , the toolholder shank  25  may freely move in and out of the bore  30 . 
     The lock rod  15  has a forward end  32  and a rearward end  34 . As will be explained in the discussion of  FIG. 3 , the lock rod is rotationally restrained about the longitudinal axis  17 . The lock rod  15  is movable within the base member  20  in a rearward and forward reciprocating motion for pulling the toolholder shank  25  rearwardly within the bore  30  into the locked position, as illustrated in  FIG. 2 , and for releasing the toolholder shank  25  from the bore  30  to the unlocked position illustrated in  FIG. 1 . 
     A torque nut  35  is rotatively mounted to the base member  20  and operable upon the rearward end  34  of the lock rod  15  to provide the rearward and forward reciprocating motion of the lock rod  15 . The torque nut  35  has a segment  37  with an outer surface  40 . A groove  45  ( FIG. 4 ) extends at least partially around the outer surface  40  and, wherein, at least a portion of the groove  45  is angled relative to a line  47  perpendicular to the longitudinal axis  17  to form an angle a. A compression sleeve  50  is engaged by the torque nut through at least one compression member  52 . Additionally, the compression sleeve  50  resiliently engages the lock rod  15  ( FIG. 1 ). In particular, the lock rod  15  has a pull-back shoulder  54  extending radially outward, while the compression sleeve  50  has a shoulder  56  extending radially inward, and the opposing faces of the lock rod shoulder  54  and compression sleeve shoulder  56  capture and compress a set of springs  58  positioned about the lock rod  15 . The springs  58  may be Belleville washers, as illustrated. The compression sleeve  50  has an aperture  60  extending therethrough to accommodate the compression member  52  which, as illustrated, is a ball. It should be noted that there are two compression members  52 , illustrated in  FIG. 1  and  FIG. 2 , and each has an associated groove  45 . However, only one compression member  52  and groove  45  set will be discussed, with the understanding that the other set is similar. 
     When the aperture  60  ( FIG. 1  and  FIG. 4 ) is aligned with the associated groove  45  and the compression member  52  is positioned within both the groove  45  and the aperture  60  ( FIG. 1  and  FIG. 4 ), then, when the torque nut  35  is rotated in one direction, the compression member  52  and the compression sleeve  50  are displaced axially forward within the base member  20 , as illustrated in  FIG. 1 , and when the torque nut  35  is rotated in the opposite direction, the compression member  52  and the compression sleeve  50  are displaced axially rearward within the base  20 , as illustrated in  FIG. 2  and  FIG. 5 . 
     As illustrated in  FIGS. 4 and 5 , the groove  45  is in the outer surface  40  of the torque nut  35  and the aperture  60  extends through the wall  62  of the compression sleeve  50 . 
     As illustrated in an alternative embodiment, in  FIGS. 6 and 7 , it is entirely possible for the aperture  60 A to exist within the outer surface  40  of the torque nut  35 , while the groove  45 A extends within the wall  62  of the compression sleeve  50 . 
     The purpose of this toolholder assembly  10  is to secure the toolholder  22  within the base member  20 . Although the manner by which the lock rod  15  engages the toolholder  22  is not the focus of the subject invention, this mechanism will be described to assist in understanding the overall operation of the toolholder assembly  10 , with the understanding that this portion of the toolholder assembly may be modified to accommodate other toolholders. 
     Directing attention to  FIG. 1 , the toolholder  22  has a rearwardly facing abutment surface  64  and the toolholder shank  25  is tubular with a shank wall  66  extending rearwardly from the toolholder  22 . Within the shank wall  66  are spaced perforations  68  and within the spaced perforations  68  may be forwardly facing concave contact surfaces  70 . 
     The toolholder assembly  10  illustrated in  FIG. 1  is typical of a toolholder used for non-rotating tooling such as a lathe. However, it should be understood that the toolholder assembly  10  may have attached to it any one of a variety of tools that may be associated with either non-rotating or rotating applications. 
     As previously mentioned, the base member  20  has a forwardly facing surface  27  and a bore  30 . Within the bore  30 , extending through the base member  20 , is a stub  72  which extends into the bore  30  of the base member  20 . A stub bore  75  extends longitudinally through the stub  72  and the lock rod  15  is slideably mounted within the stub bore  75 . 
     Toward the forward end  32  of the lock rod  15  are depressions  77  which may be aligned with radial apertures  79  extending through the stub  72  into the stub bore  75 . When the lock rod  15  is moved to the right, locking elements  80  positioned within the apertures  79  of the sub  72  and within the depressions  77  of the lock rod  15  are urged radially outwardly. 
       FIG. 1  shows the toolholder  22  removed from the base member  20 . To secure the toolholder  22  within the base  20 , the lock rod  15  must be positioned such that the locking elements  80  are within the depressions  77  and recessed within the radial apertures  79 . In this orientation, the locking elements  80  are clear of the perforations  68  within the shank  25  of the toolholder  22  and, therefore, the tubular shank  25  of the toolholder may be inserted into the bore  30 . 
     As shown in  FIG. 2 , with the toolholder  22  positioned within the bore  30 , the lock rod  15  may be pulled to the right, away from the toolholder  22 , such that the locking elements  80  are displaced radially outwardly from the depression  77  onto ramps  82 , thereby causing the locking elements  80  to penetrate the perforations  68  and contact the forwardly facing concave contact surface  70  of the toolholder shank  25 . When the lock rod  15  is retracted to the right, the toolholder  22  is urged within the base member  20  and the rearwardly facing abutment face  64  of the toolholder  22  contacts the forwardly facing abutment surface  27  of the base member  20 . This action of the lock rod  15  secures the toolholder  22  within the base member  20 . 
     To release the toolholder  22  from the base member  20 , the lock rod  15  is urged to the left toward the toolholder  22 . In such a manner, the locking elements  80  are urged within the radial apertures  79  and depressions  77  so that adequate clearance is provided and the toolholder  22  may be removed from the base member  20  as shown in  FIG. 1 . 
     When the toolholder  22  is locked within the base member  20 , there may exist elastic deformation of the base member  20 , thereby creating high frictional forces retaining the toolholder  22  within the base member  20 . To release the toolholder  22 , the lock rod  15  is extended at the forward end of the base member  20  such that the lock rod  15  protrudes beyond the stub  72  ( FIG. 5 ) and contacts an impact area  84 , thereby ejecting the toolholder  22  from the base member  20 . Therefore, by moving the lock rod  15 , the toolholder  22  may be secured or released within the base member  20 , thereby providing for quick change of the toolholder  22 . 
     As mentioned, this mechanism for securing the toolholder  22  within the base member  20  is not part of the subject invention, but is described only to enhance the understanding of the operation of the subject invention. It should be appreciated that the subject invention may be applied to toolholders and lock rods having different geometries than that described herein. 
     The invention is directed to the mechanism of reciprocating the lock rod  15  by using a predetermined rotation of the torque nut  35  to pull the lock rod  15  back with a repeatable force and, furthermore, to rotate the torque nut  35  in the opposite direction to advance the lock rod  15  to bump off the toolholder  22  from the base member  20 . 
     Directing attention to  FIGS. 1 and 2 , the mechanics for securing the toolholder  22  within the base member  20  will be described. Beginning in the arrangement illustrated in  FIG. 1 , whereby the locking elements  80  are recessed within the depressions  77  and the toolholder  22  is free to move in and out of the base member bore  30 , the torque nut  35  is rotated in, for example, a clockwise fashion. The compression members  52  are positioned within the apertures  60  of the compression sleeve  50 . Furthermore, the compression members  52  are captured between the inner wall  90  of the base member  20  and the groove  45  on the outer surface  40  of the torque nut  35 . As illustrated in  FIGS. 4 and 5 , the groove  45  has a helical configuration such that, when the torque nut  35  is rotated, the compression member  52  follows the groove and is moved from left to right. Because the compression member  52  is captured within the aperture  60  of the compression sleeve  50 , as the compression member  52  moves from left to right, so does the compression sleeve  50 . The shoulder  56  ( FIG. 1 ) of the compression sleeve  50  compresses the springs  58  against the shoulder  54  of the lock rod  15 , thereby urging the lock rod  15  from the left to the right, as illustrated in  FIG. 2 . As a note, the lock rod shoulder  54  is part of an end cap  92  that may be threadably secured to the end  34  of the lock rod  15 . As the compression sleeve  50  moves further to the right, the springs  58  continue to apply a force to the shoulder  54  of the lock rod  15  and move the lock rod further to the right. The motion of the compression member  52  within the groove  45  is illustrated in  FIGS. 4 and 5 , wherein  FIG. 4  illustrates the compression member  52  in its forward most position corresponding with the arrangement in  FIG. 1 , while  FIG. 5  illustrates the compression member  52  in its rearward most position consistent with the arrangement illustrated in  FIG. 2 . There is a breakout section  95  illustrated in  FIGS. 4 and 5 , and this is a non-functional portion that is intended only for manufacturing to permit an end mill to enter the outer surface  40  of the torque nut  35  and to machine the groove  45 . This breakout section  95  is also illustrated in  FIG. 1 . 
     Redirecting attention to  FIG. 4 , at least a portion of the groove  45  is angled with respect to a line  47 , perpendicular to the longitudinal axis  17  and it is this angular orientation coupled with rotation of the torque nut  35  that causes the compression member  52  to move the compression sleeve  50  along the longitudinal axis  17 . As illustrated in  FIG. 4 , the groove  45  may be helical with respect to the longitudinal axis  17 . It is of particular note that the entire range of travel for the compression member  52 , from the forward most position illustrated in  FIG. 1 , to the rearward most position illustrated in  FIG. 2 , is achieved by rotation of the torque nut  35  in an amount less than 180 degrees about the longitudinal axis  17 . In particular, directing attention to  FIG. 4A , which is a sectional view of the torque nut segment  37  along lines  4 A- 4 A in  FIG. 4 , the compression member  52  may be moved between the two ends of the groove  45  with a rotation of the torque nut  35  of 132 degrees. Not only does this provide a predetermined range of rotation of the torque nut  35  to engage or disengage the toolholder  22 , but furthermore, the pull-back force applied to the lock rod  15  is predetermined and is repeatable This occurs because the springs  58  are compressed by the longitudinal travel of the compression sleeve  50 , which itself is limited by the travel of the compression member  52  within the groove  45 . 
     Directing attention to  FIG. 4 , a single groove  45  is used to move the compression member  52  to the left or to the right. The groove  45  illustrated in  FIG. 4  forms an angle A with the line  47  perpendicular to the longitudinal axis of between 12 and 22 degrees and preferably forms angle A of approximately 17 degrees. The determination of this angle is based upon the desired compression provided by the compression members  52  upon the lock rod  15  and the desired torque that must be imparted to the torque nut  35  to achieve such a compression. In the arrangement illustrated in  FIG. 4 , the same angle A is used to pull back the lock rod  15  and to move the lock rod from right to left, and, as will be discussed, to bump off the toolholder  15  from the base member  20 . 
     For purposes of discussion, when the compression member  52  follows the groove  45  to move the compression sleeve  50  to the right, the angle A of the groove  45  will define a pull-back pitch. When the compression member  52  follows the groove  45  and moves the compression sleeve  50  from right to left, the angle A will define a bump-off pitch. As will be discussed with respect to the angle of the groove  45 , the force needed to bump off the toolholder  22  from the base member  20  may be greater than the force required to pull back the lock rod  15  to lock the toolholder  22  within the base member  20 . 
     Directing attention again to  FIGS. 1 and 2 , the lock rod  15  has a range of motion along the longitudinal axis  17  including a bump-off region  100  defined by the area where the forward end  32  of the lock rod  15  ( FIG. 1 ) occupies a portion of the same space as the toolholder  22  would occupy in the locked position ( FIG. 2 ). As a result, with the toolholder  22  in the locked position within the base member  20 , the lock rod  15  may be advanced to the left ( FIG. 1 ) to contact the impact area  84  of the toolholder to forcibly push the toolholder  22  from the base member  20 . As illustrated in  FIG. 4 , since the groove has a constant angle A, the pull-back pitch of the groove  45  is identical to the bump-off pitch of the groove. The groove  45  extends around the cylindrical outer surface  40  of the torque nut  35  and, as a result, the angle A actually defines a helical angle about the outer surface  40 . 
     It should be appreciated that the bump-off region  100  ( FIG. 1 ) is relatively small and, therefore, the motion of the lock rod  15  to eject the toolholder  22  from the base member  20  may also be relatively small. However, depending upon the force of the resilient interference fit with which the toolholder  32  is mounted within the base member  20 , the force required to eject the toolholder  22  may be greater. As a result, while the same groove angle A used for the pull-back section to retain the lock rod  15  within the base member  20  may be used in the opposite direction to eject the toolholder  22 , it may be preferable to change the groove angle A in the bump-off region  100 . 
       FIGS. 8 and 9  illustrate a groove  45  having a pull-back section  105  and a bump-off section  108  with a transition section  110 , therebetween. As previously discussed, the pull-back section  105  is generally helical and forms and angle A with a line  47  perpendicular to the longitudinal axis  17 . However, for the bump-off section  108 , it is desirable to produce a greater longitudinal force for a given rotation of the torque nut  35  and, as a result, the bump-off section  108  extends along a groove  145  whose center line forms an angle B relative to the line perpendicular to the longitudinal axis  17  of between 5 and 15 degrees and preferably, 10 degrees. By providing a smaller angle, then, for the same torque applied to the torque nut  35 , a greater longitudinal force is generated to eject the toolholder  22  from the base member  20 . 
     Directing attention to  FIG. 2 , it should be appreciated that the torque applied to the torque nut  35  should extend the locking elements  80  radially outward to fully engage the toolholder  22 . On the other hand, to release the toolholder  22 , the torque nut  35  is rotated in the opposite direction and once the locking elements  80  begin to fall within the depressions  77 , the force to move the lock rod  15  to the left is minimal until the forward end  32  of the lock rod  15  encounters the impact area  84  of the toolholder  22 . At that point, the lock rod  15  must apply a greater force to the impact area  84  of the toolholder  22  to bump off the toolholder  22  from the base member  20 . However, between the release of the compression members  52  and the bump-off, the forces that must be applied to the lock rod  15  are minimal. As a result, the transition segment  110  ( FIG. 8 ) of groove  45  may have a fairly aggressive angle to advance the lock rod  15  a larger distance for a given rotation. Nevertheless, once the compression member  52  advances the lock rod  15  far enough to contact the impact area  84 , then the smaller angle B associated with the bump-off section  108  will permit the application of the same torque to produce a greater longitudinal force to enhance bumping off the toolholder  22 . The bump-off section ( 108 ) has a bump-off pitch with an angle B relative to a line  47  perpendicular to the longitudinal axis of between 12 and 22 degrees and preferably 17 degrees. 
       FIGS. 10 and 11  illustrate different displacements of the lock rod  15  for the same rotation of the torque nut  35 . In particular, the constant angle A in  FIG. 4  will produce a displacement of the lock rod  15  similar to that illustrated in  FIG. 10 . When the torque nut  35  is at the “unlocked” position ( FIGS. 1 and 4 ), there is no displacement of the lock rod  15  as shown at the “ 0 - 0 ” coordinate in  FIG. 10 . As the torque nut  35  is rotated, the lock rod  15  is displaced in a linear fashion until the rotation is limited by the groove  45  design. As shown in  FIG. 10 , the torque nut  35  rotation is limited to 132 degrees. 
     However, as previously mentioned, the bump-off region may require forces higher than those needed to lock the toolholder  22  within the base member  20 . The graph in  FIG. 11  represents the displacement of the lock rod  15  when the groove  45  illustrated in  FIG. 8  is utilized. Moving from the upper right of the graph in  FIG. 11 , which represents the “locked” position, as the torque nut  35  is rotated from the locked position, the locking element  80  travels along the pull-back section  105  and enters the transition segment  110  and then the bump-off section  108 . Here the angle of the groove  45  changes such that, for the same torque nut  35  rotation, the lock rod  15  is displaced a smaller amount. This produces a “wedging” effect providing a greater longitudinal force suitable to more easily eject the toolholder  22  from the base member  20 . It should be noted that the composite arrangement of the pull-back section  105 , transition segment  110  and the bump-off section  108 , represented in  FIG. 11 , permits the lock rod  15  to travel its entire range with a rotation that is less than the rotation required for the “straight” groove  45 , represented by  FIG. 10 . 
     While discussed herein are helical angles that are constant, it should be appreciated that other non-helical grooves may be utilized to improve the efficiency of the torque nut  35  rotation for different lock rod  15  configurations. 
     Unlike the pull-back sequence where the shoulder  56  ( FIG. 2 ) of the compression sleeve  50  engages the springs  58  to act against the shoulder  54  of the lock rod  15 , causing the lock rod  15  to move to the right, during the bump-off sequence, the compression sleeve  50  ( FIG. 1 ) is moved to the left and encounters the lock rod bump-off shoulder  55  and urges the bump-off shoulder  55  to the left, which in turn urges the lock rod  15  to the left to eject the toolholder.  FIG. 2  illustrates the bump-off shoulder  55  with the lock rod  15  in the locked position, while  FIG. 1  illustrates the bump-off shoulder  55  contacted by the compression sleeve  50  and urged to the left so that the forward end  32  of the lock rod  15  contacts the impact area  84  and ejects the toolholder  22 . 
     The lock rod  15  illustrated herein is designed to be held non-rotatable about the longitudinal axis  17 .  FIG. 3  illustrates a cross-sectional view of the base member  20  along lines “ 3 - 3 ” in  FIG. 2 . Of particular note, the lock rod bump-off shoulder  55  is non-circular and fits within a non-circular passageway  112  within the bore  30  of the base member  20 . Through this mechanism, the lock rod is rotationally restrained about but movable along the longitudinal axis  17 . 
     It should be noted that the toolholder assembly  10  is activated by the torque nut  35  from the rearward end of the base member  20 . Furthermore, the torque nut  35  may have a hexagonal end, such that it may be accessible using commercially available tools. In order to maximize the efficiency of the spring compression, the springs  58  may be pre-loaded between the pull-back shoulder  54  of the lock rod  15  and the shoulder  56  of the compression sleeve  50 . 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. The presently preferred embodiments described herein are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.