Abstract:
A servo motor driven tapping unit for in die installation has a tap holder pitch adapter assembly mounted for removal while the unit is in the die to facilitate tap and pitch adapter replacement. In one embodiment, the tap holder pitch adapter assembly extends transversely to the servo motor axis, and is offset in another embodiment.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation-in-part of U.S. Ser. No. 09/917,202, filed Jul. 27, 2001, now U.S. Pat. No. 6,547,496. 
     
    
     
       BACKGROUND INVENTION  
         [0002]    This invention concerns tapping devices for forming threads in workpieces. Tapping is often necessary in manufacturing metal servo motor tapping unit for parts, and there have previously been developed in die tapping units to carry out tapping when the part is also been formed. It has long been the practice to operate such tapping units with the die press motion, as described for example in U.S. Pat. No. 5,173,015, and in U.S. patent application Publication No. 2002/0102142 and U.S. Pat. No. 6,547,496 issued from the parent application of the present application.  
           [0003]    An in-die tapping unit which is operated by the press motion has certain disadvantages caused by the fact that presses are usually crank driven with a sinusoidal velocity. Since a tap has a maximum speed at which it can be used, and this cannot be greater than the peak press velocity, tapping is carried out for most of the cycle more slowly than would otherwise be possible. Also, the timing of the tapping is tied to the press motion, limiting flexibility in designing the process.  
           [0004]    It has thus been proposed to use an electric servo motor to drive in die tapping unit to maximize the speed with which the tapping can be completed. Other advantages are the ease of tapping in various directions, and of executing tapping at any time during the press cycle.  
           [0005]    Changing taps must be done frequently due to limited tap life, and when using a servo motor tap drive, changing taps has often required substantial down time due to the need to disassemble or remove the complete tapping units from the press in order to change a tap.  
           [0006]    This problem is further exacerbated by the need to change pitch adapters having mating threads which control the rate of advance of the tap during tapping. These adapters must also be changed when changing tap sizes, and often this requires removal of the entire unit and disassembly in order to replace the pitch adapter.  
           [0007]    It is the object of the present invention to provide an electro servo motor driven in die tapping unit which allows quick and easy replacement of taps and pitch adapters without the need to disassemble or remove the entire tapping unit.  
         SUMMARY OF THE INVENTION  
         [0008]    The above recited objects and other objects which will become apparent upon a reading of the following specification and claims are achieved by an in die servo motor tapping unit which includes an electric servo motor and an attached housing for a tap holder and pitch adapter assembly in which the assembly is easily removable from the servo motor components and housing with the servo motor and components still in the die. The tap holder and pitch adapter assembly includes a tap drive gear driven by a servo motor output gear which tap unit is not coaxial with the servo motor output shaft and gear.  
           [0009]    The tap drive gear is rotatably mounted in a housing mounted to the servo motor, the gear fixed to a hub to rotate the same when the servo motor is energized. The hub slidably receives a tap holder pitch adapter assembly which is also keyed to thereto establish a rotary connection.  
           [0010]    The tap holder pitch adapter assembly is held within the hub by an external cover piece which is detachably fixed to a housing secured to the servo motor. The hub is keyed to an element of the tap holder pitch adapter assembly to allow sliding removal of the assembly from the hub when the cover piece is detached. This allows easier and quicker replacement of the tap or the pitch adapter elements when required. The tap holder pitch adapter assembly in two alternative versions may be mounted offset from the servo motor or at right angles respectively so as to allow removal of the top holder pitch adapter assembly from different directions. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a die having a servo motor tapping unit according to the invention in position thereon.  
         [0012]    [0012]FIG. 2 is a side elevational view of the die shown in FIG. 1.  
         [0013]    [0013]FIG. 3 is a partially exploded view of the servo motor tapping unit shown in FIGS. 1 and 2.  
         [0014]    [0014]FIG. 4 is a fragmentary elevational view of the servo motor tapping unit of FIG. 3 shown in partial section.  
         [0015]    [0015]FIG. 5 is a perspective view of a second embodiment of the servo motor tapping unit according to the invention.  
         [0016]    [0016]FIG. 6 is a partially exploded perspective view of the servo motor tapping unit shown in FIG. 5.  
         [0017]    [0017]FIG. 7 is a fragmentary elevational view of FIGS. 5 and 6, shown in partial section. 
     
    
     DETAILED DESCRIPTION  
       [0018]    In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.  
         [0019]    [0019]FIGS. 1 and 2 show a die assembly  10  including a spaced apart top plate  12  and bottom plate  14  adapted to be mounted in a press. The top plate  12  and bottom  14  plate are mounted on four guide posts  16  to guide movement together and apart induced by press motion in this manner well known in the art.  
         [0020]    The die assembly  10  may have various progressive tooling mounted thereon acting on a workpiece W introduced therein, such as a punch swaging die set  18 , and a cut off die set  20 , operated by motion of the plates  12 ,  14 .  
         [0021]    A servo motor tapping unit  22  is positioned within the die plates  12 ,  14  by suitable mounting means (not shown).  
         [0022]    [0022]FIGS. 3 and 4 show further details of the servo motor tapping unit  20 , which includes an electrical servo motor  24  having a tap mounting assembly including a housing  26  affixed to one end of the servo motor  24 . A connector box  28  allows connection of electrical and control cables (not shown).  
         [0023]    The housing  26  provides support for a shaft extension  30  attached to servo motor output shaft  36  and bearings  32 ,  34  supporting the shaft extension  30 .  
         [0024]    The shaft extension  30  has a bevel gear  38  attached thereto meshed with a second bevel gear  40  attached to a hub sleeve  42  rotatable about an axis transverse to the axis of the servo motor  24 .  
         [0025]    The hub sleeve  42  is slidably keyed to a body portion  44  of a holder pitch adapter assembly  44 , which also includes a collet  48  for releasably receiving the shank of a tap  50 .  
         [0026]    An adapter socket  52  is integral with the body portion  44  and has a threaded socket  54  receiving a threaded shank  56  of a replaceable externally threaded pitch adapter plug  58 .  
         [0027]    The pitch adapter plug  58  in turn is engaged with an internally threaded pitch adapter sleeve  60 . The pitch of the engaged threads is matched to the pitch of the tap  50 .  
         [0028]    The pitch adapter sleeve  60  is keyed to a fixed outer sleeve  62  press fitted into a bore in an exterior plate cover piece  64  detachably fixed to the housing  26 . A snap ring  61  limits the downward movement of the adapter sleeve  60  to insure that the adapter plug  58  and attached components are driven axially down when rotated.  
         [0029]    A safety spring  66  is interposed between the inside of the plate cover piece  64  and the upper end of the adapter sleeve  60 .  
         [0030]    A boss  68  is affixed to the housing having a bore into which the tap  50  is recessed when retracted. A Delrin™ ring  70  prevents entry of dirt into the housing.  
         [0031]    When the servo motor  24  is energized, the gear  38  is driven to drive gear  40 , which rotates hub sleeve  42  affixed thereto.  
         [0032]    The hub sleeve  42  in turn rotates the tap holder  46  and tap  50  received therein.  
         [0033]    The pitch adapter plug  58  is also rotated, causing the attached tap holder  46  to advance axially as tapping proceeds. The adapter sleeve  60  is held rotationally stationary by the keyed connection to the fixed outer sleeve  62  and axially by the snap ring  61 .  
         [0034]    If the tap  50  cannot advance as due to the absence of a hole in the workpiece W, the safety spring  66  is compressed to allow the adapter sleeve  60  to instead move up to prevent breakage of the parts.  
         [0035]    If the tap  50  is inaccessible in the die, the plate cover piece  64  can be detached and the outer sleeve  62 , adapter sleeve  60 , pitch adapter plug  50 , and tap holder  46 , and tap  50  are slid out as a unit, as indicated in FIG. 3. This allows convenient replacement of the tap  50  and also changing the pitch adapter plug  58  and sleeve  42 , with only minimal effort and time required.  
         [0036]    FIGS.  5 - 7  show a second embodiment of the invention in which the tap mounting assembly including a housing  64  offsets the tap  66  from the axis of a servo motor  68 .  
         [0037]    The servo motor  68  has an output shaft  72  which has a pinion gear  74  affixed thereto driving an idler gear  76  which in turn drives a tap driver gear  78  affixed to a hub sleeve rotatably supported in the housing  64 .  
         [0038]    The hub sleeve  80  is keyed to pitch adapter  82  having an externally threaded extension  84  threadably engaged with an internally threaded cover cap piece  86  detachably affixed to the housing  64 .  
         [0039]    A tap holder sleeve  88  is slidably received in the pitch adapter  82  and slidably keyed thereto to be rotated when the pitch adapter  82  is rotated. A snap ring  83  acts as an axial stop, limiting axial movement of the tap holder  88  downwardly as shown in FIG. 7 under the urging of a safety spring.  
         [0040]    A taper grip collet  90  of a well known type threaded into an end bore  92  of the tap holder sleeve  88  is used to grip the tap  66  for retention therein upon being wrenched tight.  
         [0041]    The tap holder sleeve  88  has a stepped outside diameter creating a shoulder engaged with one end of the safety spring  94 , the other end engaging an internal step in the pitch adapter  82 .  
         [0042]    The tap square shank end  96  is received in a square hole formed in the inside of the tap holder sleeve  88  to establish a positive rotary connection and also to be advanced and retracted axially therewith.  
         [0043]    When gear  78  is rotated by the servo motor  68 , pitch adapter  82  is also rotated, the threaded engagement with the stationary cap cover piece  86  causing axial advance of the tap holder sleeve  88  down to rotate and advance the tap  66  in order to tap a hole in a workpiece (not shown). Reverse rotation backs the tap  66  out of the now threaded hole.  
         [0044]    If the tap  66  or pitch adapter components  82 ,  86  need to be changed, the pitch adapter cap screws  96  are removed, and the tap holder pitch adapter assembly lifted out, as shown in FIG. 6, without removal of the servo motor  68  or housing  64 .  
         [0045]    If the tap  66  cannot be advanced, the tap holder sleeve  88  will be driven up against the bias of the safety spring  94  to avoid breakage.  
         [0046]    Thus, a servo motor tapping unit has been provided which allows quick replacement of taps and pitch adapters.