BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a clamshell lathe, and in particular to a mechanism for cutting, beveling, facing and boring the wall of a large diameter work piece. 
     2. Description of the Related Art 
     Clamshell lathes are known in the art. A clamshell lathe generally has a first and second semi-circular segment. The semi-circulars segments are clamped together to form an annular assembly encircling a work piece to be machined. The annular assembly includes a stationary ring, and a rotatable ring abutting the stationary ring. The rotatable ring is made of steel and has a spur gear on its peripheral surface and it is journaled on the bearings to the stationary portion for rotation about a concentrically disposed work piece. A motor drives a spur gear that meshes with the spur gear on the rotatbale right and that rotates the rotatable ring about the concentric work piece. A cutting tool assembly is mounted on the rotatable ring for machining the work piece. 
     The prior art cutting tools, however, have not adequately addressed the need for machining the work piece at an angle, such as may be required in creating a beveled edge on an end of the work piece. Moreover, the cutting tools have been able to incrementally advance in a radial direction against the work piece, the prior art advancing mechanisms incrementally advance the cutting tool upon every revolution of the rotatable ring of the clamshell lathe by the interaction of a star wheel with a stationary ring. The present invention dispenses with the star wheel arrangement and instead uses a tripper mechanism that allows control over the extent of radial displacement of the cutting tool relative to the workpiece being machined. 
     SUMMARY OF THE INVENTION 
     The invention provides a swivel head module which includes an adjustable tool head assembly. The adjustable tool head assembly has a tool for machining the work piece, and is capable of being incrementally advanced in a radial direction against the work piece. Without limitation, the tool may be a steel bit, and abrasive surface, or other type of metal working tool known in the art. Moreover, the adjustable tool head assembly further includes a means for positioning the metal working tool along an x-axis, y-axis and z-axis. A tripper assembly is operatively coupled to the tool head assembly to incrementally urge the tool head against the work piece upon each revolution of the clamshell ring. The tripper assembly incorporates a solenoid that when remotely actuated, selectively controls incremental advancement of the tool against the work piece. 
     The primary advantage of the present invention is that it provides machining of the work piece at any desired angle between 0° and 90°. 
     An additional advantage of the present invention is that it provides an improved means for incrementally urging the cutting tool radially against the work piece from a locator remote from the swivel head module. 
     For a better understanding of the invention, and the advantages obtained in its use, reference should be made to the drawings and the accompanying descriptive material, in which there is illustrated an described a preferred embodiment of the invention representing the best mode known to us for practicing the invention. 
    
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the swivel head module assembly of the present invention; 
         FIG. 2A  illustrates an exploded view of the tool head displacement assembly of the swivel head assembly in accordance with the present invention; 
         FIG. 2B  illustrates an exploded view of the positioning assembly for positioning the tool head displacement assembly along the x-axis and y-axis of the swivel head assembly in accordance with the present invention; 
         FIG. 2C  shows an exploded view of the positioning assembly for positioning the tool head displacement assembly along the z-axis. 
         FIG. 3  shows a perspective view of the tripper assembly used with the swivel head assembly of the present invention; and, 
         FIG. 4  is an exploded view of the tripper assembly of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows the adjustable swivel head assembly  10  having a suitable metal working tool (not shown) at a distal end thereof. The adjustable swivel head assembly  10  includes a tool head displacement assembly  12 , a positioning assembly  14 , and, a translation assembly  16 .  FIG. 2  shows an exploded view of the swivel head assembly  10   
     The tool head displacement assembly  12  includes a feed screw assembly  18  and a housing  20 . The feed screw assembly  18  allows incremental displacement of the tool employed located at the distal end  19  of the assembly  12 . The feed screw assembly  18  has a feed screw  22  ( FIG. 2 ) with a first and a second end  24 ,  26  respectively. A feed nut  28  is translated along the feed screw  22  during rotation of the feed screw. Rotation of the feed screw  22  in a first direction translates the feed nut  28  toward the second end  26  of the feed screw  22 , which in turn translates a bore bar that supports the metal working tool at its free end. Thus, when the feed nut  28  is incrementally translated, the metal working tool is incrementally urged radially against a work piece. 
     A cam arm  30  rotates the feed screw  22  through a one-way clutch in a manner fully described below to translate the feed nut  28 . A plurality of one-way clutch sleeves  32  are disposed on the feed screw  22 . The cam arm  30  has a feed screw aperture  31 , supporting a roller clutch member  33 . It engages the clutch sleeves  32  to rotate the feed screw  22  only in a first radial direction. The roller clutch  33  transmits torque between the cam arm  30  to the feed screw  22  and allows free overrun in the opposite direction. The cam arm  30  can be activated automatically by the translational assembly  16  in a way to be described, or manually by turning swivel head module hand wheel  34 . The swivel head module hand wheel  34  is attached to the first end  24  of the feed screw  22 . The swivel head module hand wheel  34  has a central feed screw hex aperture  36  which captures the first end  24  of the feed screw  22 . A hand wheel handle  38  is coupled to the swivel head module hand wheel  34  to facilitate rotation of the hand wheel  34 . Here, rotation of the swivel head module hand wheel  34  causes rotation of the radial feed screw  22  so that the feed nut  28  is urged against the bore bar  40  slidingly disposed in the housing  20  of the swivel head module  10 . The feed nut  28  is disposed in the housing  20 . Slidingly supporting a bore bar  40  having a free end  42 . The metal working tool is adapted to be is disposed at the free end of the bore bar  40 . The end of the bore bar  40  has a longitudinal groove  40  for receiving a key  43  formed on the swivel housing  44 , allowing the bore bar  40  to slide without rotating in housing  44 . 
     To ensure that the feed screw  22  stays axially, concentrically aligned in the housing  20 , while at the same time facilitating rotation of the feed screw  22 , a tube cap  48  is provided. The tube cap  48  has a central sleeve  50  for guiding the feed screw  22 . A cup bearing  52  and cone bearing  54  cooperate to facilitate rotation of the feed screw  22 . The cup bearing  52  is placed on a opposing side of the sleeve  50  from the cone bearing  54 . 
     To accommodate rotation of the cam arm  30  in the housing  20 , a lower cam bracket  56  and an upper cam bracket  62  when bolted together by fasteners  68  to form a housing for a set of ball bearings  60  and  66  journaling the screw  22 . The cam arm  30  is also contained within the housing formed by the lower cam bracket  56  and an upper cam bracket  62 . 
     The cam arm  30  is activated by the translational assembly  16 . The translational assembly  16  communicates with a tripper assembly  70  (shown in  FIGS. 3 and 4 ) to remotely activate the displacement assembly  12  of the swivel head module  10 . The translation assembly  16  includes a roller bracket assembly  72  coupled to a cam cable  74  at a first end  76  of the cam cable  74 , and to cam arm bracket assembly  78  at a second end  80  of the cam cable  74 . 
     The roller bracket assembly  72  includes a roller  82  coupled to a roller cable bracket  84 . The roller cable bracket has a first and second end  85   a  and  85   b . The roller  82  is threaded into the roller cable bracket  84 . Adjustment screw  86  positions the roller  82  so it contacts ramp  232  in a desired position. The roller cable bracket  84  is slidingly disposed in a roller bracket housing  88 . When the roller  82  intersects with a ramp of the tripper assembly  16 , the roller bracket  84  slides upward in the roller bracket housing  88 . A cable guide  90  is coupled to the roller bracket housing  88 . The first end  76  of the cam cable  74  is coupled to a first clevis  92 . The first clevis  92  is coupled to the second end  85   b  of the roller cable bracket  84 . 
     The cam arm bracket assembly  78  includes a cable bracket  100  having a first and second end  102 ,  104 . The cam cable bracket  100  has a cable plate  106  at its second end  104 . The cable plate  106  has a cable plate aperture  108  which the cam cable  74  passes through. The cam cable bracket  100  further includes a guide weldment  110  with a guide aperture  112  through it. The first end  102  of the cable bracket  100  is coupled to the lower cam bracket  56  by fasteners  103  pass through apertures  105  and into threaded apertures  107  in bracket  56 . 
     The cam arm bracket assembly  78  further includes a second clevis  114  coupled to the second end  80  of the cam cable  74 . The second clevis  114  is coupled to a cam link  116  by a shoulder bolt  118 . The cam link  116  is joined to the cam arm  30  by a further shoulder bolt  120 . 
     A cam spring rod  121  extends from ear  110  to the clevis  114  that connects to the cam arm  30 . The cam rod  121  also includes a cam rod spring  122  which extends from ear  110  to the base portion of clevis  114 , and encircles the cam rod  121 . First and second hex nuts  124 ,  126  connects the cam rod  121  to a clevis  128 . The clevis  128  is secured to the cam arm  30  by a dowel  130  which passes through aligned apertures in the clevis  128  and the cam arm  30 . 
     When the roller  82  runs up a ramp  232  or  234  of the tripper assembly  16 , the roller cable bracket  84  is urged upward. The force is transferred through the cam cable  74  to the cam arm  30 . The cam arm  30  is thereby rotated by an amount determined by the ramp slope, and the torque is transferred to the feed screw  22  via the roller clutch  33 . This in turn urges the facing tool against the work piece. 
     Positioning assembly  14  comprises a pair of triangular steel gussets  132  that support the leg portions of a right angle base plate member  136 . The positioning assembly  14  can position the tool head displacement assembly  12  against the work piece along an x-axis, y-axis and z-axis as indicated by the double headed arrow markings on  FIG. 1 . The x-axis platform  134  includes the base plate  136 , a fixed x-axis slide plate  138  and a movable x-axis saddle  140 . The x-axis slide plate  138  has a pair of opposing gibs  142 ,  144  affixed to the surface  146  of the x-axis slide plate  138 . As observed in  FIG. 1  the first and second opposing gibs  142 ,  144  together form a channel  148  in which an x-axis feed screw  150  is located. X-axis feed screw  150  is journaled in a bearing allowing it to rotate in the channel  148 . A feed nut is threaded on the screw  150  and engages the x-axis saddle  140 . The x-axis saddle  140  has a top surface  156  and a bottom surface (unnumbered) with a first and second saddle legs  158 ,  160 . The saddle legs  158 ,  160  mate to the first and second opposing gibs  142 ,  144  such that when the feed screw  150  is rotated the feed nut translates the saddle  140  along the first and second opposing gibs  142 ,  144 . 
     The y-axis platform  162  is also supported buy the gussets  132  perpendicular to the x-axis platform  136 . The y-axis platform  162  includes a y-axis saddle  164 , a y-axis side plate  166  and a y-axis feed screw  168 . The movable y-axis saddle  164  is bolted to a leg of the member  136  by a plurality of fasteners  170 . Y-axis slide plate  166  has a central channel  172  defined by a pair of parallel gibs  186  and  187 . A y-axis feed screw bracket  178  is attached to an end wall  180  of the y-axis slide plate  166  and supports bearings  181  and  183  used to journal the feed screw  168 . The roller bracket assembly  72  is fastened to the y-feed saddle slide plate  166 . Thus, when the y-axis feed screw is rotated, the base plate  136  supporting the assembly  12  is raised or lowered along the y-axis. 
     The z-axis platform comprises a steel plate  188  bolted atop the x-axis saddle  140 . The z-axis platform  188  has a top surface  190  and a first and second sides  192 ,  194 . A left swivel bracket  200  is bolted to the first side surface  192 , and a right swivel bracket  202  is coupled to the second side surface  194  using socket head cap screws at as  196 . The left and right swivel brackets  200 ,  202  both have swivel lock apertures  204  for containing a swivel housing lock  206 ,  208 . The left and right swivel bracket  200 ,  202  are pivotally coupled to the swivel housing  44 . 
     As seen in  FIG. 2C , the swivel housing locks  206 ,  208  comprise an annular flange  210  surrounding a central circular hub  212 . Hub  212  has a pair of apertures  214  in which a pair of dowels  216  are adapted to be inserted. The swivel lock dowels  216  project into aperture  214  mating swivel housing dowel aperture  222  formed in the swivel housing  44 . Thus, the swivel housing  44  along with the entire housing assembly  12  is also rotated. It is to be noted that the annular flange  210  of the swivel housing locks  206 ,  208  have a plurality of arcuate apertures  224 . Socket head cap screws  226  are inserted into each arcuate aperture  224 . The intersection of the end of the arcuate apertures  224  with the screws  226  acts as a limiter on the rotation of the swivel lock  206 . Additionally, the screws  226  secure the swivel lock  206  into a desired set position so that the assembly  12  will be at a predetermined angle to the work piece. 
     The tripper assembly  70 , shown in  FIGS. 3 and 4 , includes a ramp assembly  230  and a slide assembly  232 , and a solenoid assembly  234 . The ramp assembly  230  cooperates with the roller  82  to activate the translation assembly  16 . The ramp assembly  230  includes a feed ramp  233  coupled to a reverse ramp  234 . The feed ramp  233  has a first end  236  and a second end  238 . The second end  238  of the feed ramp  233  has a feed ramp pivot aperture  240  ( FIG. 4 ). The reverse ramp  234  has a first end  242  and a second end  244 . A pivot notch  246  is located at the first end  242  of the reverse ramp  234 . The pivot notch  246  is adapted to receive a second end  238  of the feed ramp  233 . A reverse ramp pivot aperture  248  is located adjacent the pivot notch  246 . When the second end  238  of the feed ramp  233  is inserted into the pivot notch  246 , the feed ramp pivot aperture  240  is aligned with the reverse ramp pivot aperture  248 . A pivot shoulder screw  250  is inserted into the now aligned feed ramp pivot aperture  240  and reverse ramp pivot aperture  248  to form up and down ramp segments  256 . 
     The ramp assembly  230  further includes a feed adjustment bracket  258 . The feed adjustment bracket  258  includes a base portion  260  having a first and second end  262 ,  264 . An integrally formed stem portion  268  extends perpendicularly from a midpoint of the base portion  260 . The stem  268  has a central oval-shaped aperture  270  and a top feed screw aperture  272  through the top surface  274  and intersecting the oval aperture. A feed adjustment feed screw  276 , having a first and second end  278 ,  280  is inserted through the top of the feed screw aperture  272 . A feed adjustment feed nut  282  is threaded onto the feed adjustment feed screw  276 . When the feed adjustment feed screw  276  is journaled for rotation in the central aperture  272 , the feed adjustment feed nut  282  is translated along the feed adjustment feed screw  276  in the central aperture  270  as the screw is rotated. The feed adjustment feed nut  282  has a feed screw aperture  284  and a pivot connection aperture  286  at right angles to one another. The second end  254  of the pivot shoulder screw  250  is threaded into the pivot connection aperture  286  of the feed adjustment feed nut  282 . Thus, as the feed adjustment feed nut  282  is translated, the angle of the pitch of the ramp  256  is adjusted. The feed adjustment feed screw further includes a bushing  286  located proximate the top opening  272 . A hex nut  288  is coupled to the second end  280  of the feed adjustment feed screw  276 . Feed ramp  233  further includes a feed ramp oval aperture  237  at first end  236 . Reverse ramp  234  includes a reverse ramp oval aperture  245  at second end  244 . A feed ramp shoulder screw  253  passes through the feed ramp oval aperture  237  and is fastened to the first end  262  of the horizontal segment  260  by feed ramp fastener aperture  263 . The reverse ramp  234  is secured to the feed adjustment bracket as well. A ramp feed aperture  251  passes through the oval-shaped reverse feed aperture  245  and is inserted into reverse feed fastener aperture  265 . Reverse feed fastener aperture  265  is disposed on the second end  264  of the horizontal segment  260 . 
     An electrically operated solenoid assembly  234  has a tripper base  290 . The tripper base  290  has a main plate  292  coupled to a u-shaped flange  294 . The u-shaped flange  294  has a first and second flange gibs  296 ,  298 . A solenoid  300  having a reciprocally moveable plunger  302  is disposed on the main plate  292  with the u-shaped flange  294  surrounding the periphery of the solenoid  300 . A front solenoid mount bracket  304  is provided with a central opening  306  to accommodate the projection  302 . A solenoid cover  308  covers the solenoid  300 . A plurality of fasteners  310  secure the solenoid cover  308  to the solenoid mount bracket  304 . 
     The slide assembly  232  includes a slide plate  312  having a front assembly  314 , a back assembly  316  and a first and second side wall  318 ,  320 . The side walls  318 ,  320  combine with the front and back assemblies  314 ,  316  to form a solenoid receiving aperture  322 . The slide plate  312  closely overlays the tripper base  290 . The first and second flange gibs  296 ,  298  are disposed next to the outside surfaces  322  of the first and second side walls  318 ,  320 . Moreover, the first and second end  324 ,  326  of the back segment  316  acts as a limiter on the slide plates  312  ability to slide forward. 
     The front segment  314  has a top surface  328  and a front surface  330 . A push bracket  332  is coupled to the top surface  328  of the front segment  314 . The push bracket  332  is bolted to the front of the tripper slide  312  as shown. 
     The front surface  330  of the slide plate  312  is attached to the feed adjustment bracket  260  again by screw fasteners  344 . The solenoid  300  urges the solenoid plunger  302  against the push bracket  322  thus sliding the slide plate  312  and the feed adjustment bracket  260  into the path of the roller  82  as the assembly  10  orbits the workpiece held in the clamshell. The roller rolls up feed bracket  233 , causing the translation assembly  16  to activate the cam arm  30 , as previously described. Because of the one-way clutch arrangement, the roller descending the ramp  234  does not result in further rotation of the screw  22 . 
     First and second tripper gibs  346 ,  348  are bolted to the top of the solenoid gibs  296 ,  298  respectively as shown in  FIG. 4 . 
     The gibs  346  and  348  each have a boss  356 ,  358  projecting from an upper surface  357 . Spring anchor pegs  363  and  362  are inserted into holes formed in the top surface  328  of the front segment  314  across from the bosses  356  and  358 . Biasing springs  360  and  361  extend between the two bosses and the two spring anchor pegs  362  and  363 . When the solenoid plunger  302  retracts on de-energization of the solenoid, the first and second biasing springs  360 ,  361  urge the slide assembly  312  to return to its home position out of the path of the roller  82  terminating movement of the tool bit relative to the workpiece. 
     This invention has been defined herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment details and operating procedures, can be accomplished without departing from the scope of the invention itself.
A swivel head assembly for a clamshell lathe is provided. The swivel head module includes an adjustable tool head assembly. The adjustable tool head assembly has a tool for machining a work piece, and is capable of being incrementally advanced in a radial direction against the work piece. The swivel head assembly further includes a means for positioning the metal working tool along an x-axis, y-axis, and z-axis. A tripper assembly is operatively coupled to the tool head assembly to incrementally urge the tool head against the work piece upon each revolution of the clamshell ring. The tripper assembly incorporates a solenoid for selectively incrementally advancing the tool against the work piece.