Patent Publication Number: US-2010119318-A1

Title: Machine Tool Apparatus and Related Methods

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/909,963, filed on Apr. 4, 2007, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to machine tools, and more particularly, to a machine tool apparatus for use in connection with milling machines. 
     BACKGROUND OF THE INVENTION 
     Machining internal features, such as internal keyways, in workpieces is often a difficult and time-consuming process, requiring frequent, and often complex, adjustments to workpieces and to the machine tool or tools employed to machine the features. 
     U.S. Pat. No. 2,475,227 and U.S. Pat. No. 4,923,342 describe various devices intended to facilitate the machining of internal features. However, these devices employ circular cutting blades that are limited in their ability to create specialized features. For instance, forming features with varying depths typically requires one or more blade changes and it can be difficult or impossible to create certain features that do not begin at an edge of the workpiece. Also, the cutting action of the circular blades tends to set up undesirable stresses in the workpiece around the machined feature. 
     U.S. Pat. No. 8,24,322 and U.S. Pat. No. 2,372,913 describe devices in which tooling bits are used instead of circular cutting blades. While the use of tooling bits tends to result in lower stresses in the workpiece, the devices of the &#39;322 and &#39;913 patents are also somewhat limited in the types of features that can be created. For instance, cutting keyways with varying depths, while not necessarily requiring a change of tooling, requires stopping to adjust the position of the workpiece or the tooling, increasing the time required and limiting the complexity of depth variations that are practically achievable. 
     Additionally, none of the devices in the above patents is adapted to take advantage of the capabilities of modern milling machines, which feature chucks having multiple translational and rotational degrees of freedom. For instance, these devices would lack the dimensional stability to reliably machine features when moved in multiple directions. 
     Forming keyways or similar features is often a part of larger milling or machining jobs. Due to the time and difficulty of forming keyways, many machine shops will turn away such jobs even though they can complete the non-keyway related aspects of the job relatively easily. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide a machine tool apparatus that enables complex keyways and other features to be formed more quickly and reliably. It is a further object of the present invention to provide a machine tool apparatus that is adapted utilize the capabilities of modern milling machines and other machine tools to form keyways as well as a range of additional features. 
     According to an embodiment of the present invention, a machine tool apparatus includes a transfer arm assembly and a carriage assembly. The transfer arm assembly includes a housing with a tooling end adapted to carry a tooling bit extending therefrom, a spindle extending from the housing for engagement by a chuck, and at least a first drive shaft for transferring rotational motion from the spindle to the tooling end. The tooling end is adapted to carry the tooling bit for rotation about a tooling axis that is angularly offset from a rotational axis of the first drive shaft. The carriage assembly carries the transfer arm assembly and is adapted to allow translation of the transfer arm assembly in at least two directions. 
     According to an aspect of the present invention, a tooling end adapter includes an adapter housing and an adapter rotation transfer mechanism arranged therein. The adapter has an adapter tooling end adapted to carry an adapter tooling bit extending therefrom and a tooling engagement end adapted to engage the tooling end of the transfer arm assembly housing. The adapter rotation transfer mechanism transfers rotational motion from the tooling engagement end to the adapter tooling end. 
     According to another aspect of the present invention, a method of machining a feature into a workpiece includes arranging a machine tool apparatus on a milling machine bed. The machine tool apparatus includes a transfer arm assembly carried by a carriage assembly allowing translation in at least two directions. The transfer arm assembly has substantially perpendicular first and second drive shafts for transferring rotational motion from a spindle to a tooling end. A tooling bit is inserted into the tooling end, and the spindle is engaged with a milling machine chuck. The workpiece is secured adjacent to the tooling end with a workpiece holding section. The milling machine chuck is rotated to rotate the tooling bit, and the milling machine chuck is moved to move the tooling bit into engagement with the workpiece. 
     These and other objects, aspects and advantages of the present invention will be better understood in view of the drawings and the following detailed description of a preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view of a machine tool apparatus, including a workpiece holding section and a power transmission section, according to an embodiment of the present invention; 
         FIG. 2  is a side view of the workpiece holding section of  FIG. 1 , with components partially cut-away to show details and hidden components shown in broken lines; 
         FIG. 3  is a front view of the power transmission section of  FIG. 1 , including a transfer arm assembly housing formed from connected housing halves; 
         FIG. 4  is a side view of the power transmission section of  FIG. 1 ; 
         FIG. 5  is a side view of one of the housing halves of  FIG. 3 , showing internal details of the transfer arm assembly; 
         FIG. 6  is a perspective view of a workpiece with examples of features machinable with the machine tool apparatus of  FIG. 1 ; 
         FIG. 7  is side view of a tooling end adapter, according to an aspect of the present invention, connected to the transfer arm assembly of the power transmission section of  FIG. 1 , with hidden components shown in broken lines; and 
         FIG. 8  is partially exploded, schematic perspective view of the tooling end adapter of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , according to an embodiment of the present invention, a machine tool apparatus  10  includes a workpiece holding section  12  and a power transfer section  14 . The apparatus  10  further includes a base plate  16  on which the holding section  12  and power transmission section  14  are mounted. References herein to the x-, y-, and z-directions are made relative to the coordinate indications on the Figures. 
     Referring to  FIG. 2 , the workpiece holding section  12  has a stage assembly  20  and a pneumatic clamp assembly  22 . The stage assembly  20  has a v-shaped stage  30  with a first end  32  extending through the pneumatic clamp assembly  22 . A second end  34  of the stage  30  is connected with a z-adjustment plate  36 . A pinion  38  engages a corresponding rack  40  on the plate  36 . A z-adjustment knob  42  is connected coaxially with the pinion  38 . The pinion  38  and knob  42  are rotatably mounted in a block  44  secured to the base plate  16 . For additional stability, the first end  32  of the stage  30  is moveably engaged to another block  46  by plate  48 , rack  50  and pinion  52 . 
     The stage  30  has a slot  54  defined therein. A stopper block  56  is connected with the v-shaped stage  30  by a stopper block adjustment knob  58 . The adjustment knob  58  extends through a portion of the slot  54  and is adjustably threaded into the stopper block  56 . 
     The pneumatic clamp assembly  22  includes a pneumatic cylinder  60  suspended over the first end  32  of the v-shaped stage  30 . The cylinder  60  is connected to a frame  62  secured to the base plate  16 . A clamp  64  is connected to a piston rod  66  extending into the cylinder  60 . Pneumatic lines  68  extend between the cylinder  60  and a pneumatic control valve  70  connected to the frame  62 . An air inlet  72  extends from the valve  70  opposite the pneumatic lines  68  allowing an air supply line (not shown) to be connected with the pneumatic clamp assembly  22 . A control handle  74  is connected to the control valve  70 . 
     Referring to  FIGS. 3 and 4 , the power transfer section  14  includes an xyz carriage assembly  76  carrying a transfer arm assembly  78 . The carriage assembly  76  has y-oriented rails  80  secured to the base plate  16 . Y-oriented linear bearings  82  slidably engage the y-oriented rails  80 . Cross bars  84  overlie the y-oriented rails  80  and are secured to the y-oriented linear bearings  82 . 
     Carriage sidewalls  86  are secured to opposite ends of the cross bars  84  and extend therefrom in the z-direction away from the base plate  16 . Z-oriented rails  90  are connected to the sidewalls  86  facing toward the transfer arm assembly  78 . Z-oriented linear bearings  92  slidably engage the z-oriented rails  90 . The z-oriented linear bearings  92  are secured to side bars  94 . X-oriented linear bearings  98  are also secured to the side bars  94  and slidably engage x-oriented rails  100  connected to the transfer arm assembly  78 . 
     The transfer arm assembly  78  includes a housing  110  formed of housing halves  112 . The housing halves  112  are secured together by a plurality of machine screws  114 . The housing  112  includes a z-oriented portion  120  and a x-oriented portion  122  that meet to form a “T”. A spindle  124  extends from the z-oriented portion  120  through a first cover plate  126 , and a fluid connection line  128  enters the housing  110  in the z-oriented portion  120 . Proximate to the stage assembly  20  (see  FIG. 1 ), the x-oriented portion  122  has a tooling end  130  covered by a second cover plate  132 . A fluid outlet  134  and a tooling bit  136  extend out of the tooling end  130 . 
     Referring to  FIG. 5 , complementary halves of a z-oriented bore  140  and x-oriented bore  142  are defined in the housing halves  112 , so as to extend through respective z- and x-oriented portions  120 ,  122  of the housing  110  when the housing halves  112  are assembled. The bores  140 ,  142  are formed with a plurality of roller bearing seats  144  and thrust bearing seats  146 , as well as gear clearances  148 . Additionally, complementary halves of a tooling bore  150  are defined in the housing halves  112  at the tooling end  130  of the x-oriented portion  122 . 
     A cooling fluid channel  154  is formed in one of the housing halves  112  extending between the fluid connection line  128  and the fluid outlet  134 . The cooling fluid channel  154  is dimensioned to receive a cooling fluid tube  156  therein, with one end attached to the fluid connection line  128  and the other end forming and terminating at the cooling fluid outlet  134 . 
     The transfer arm assembly  78  further includes a z-oriented drive shaft  160 , x-oriented drive shaft  162  and tooling holder  164  accommodated within the z-oriented bore  140 , x-oriented bore  142  and tooling bore  150 , respectively. The spindle  124  forms an upper end of the z-oriented drive shaft and the tooling bit  136  is removably inserted into the tooling holder  164 . 
     Bevel gears  166 , accommodated within the gear clearances  148 , transfer power between the z-oriented drive shaft  160  and the x-oriented drive shaft  162 , and between the x-oriented drive shaft  162  and the tooling holder  164 . A plurality of roller bearings  168  are arranged around the z- and x-oriented drive shafts  160 ,  162  and seat within the roller bearing seats  144 . A plurality of thrust bearings  170  are arranged around the z- and x-oriented drive shafts  160 ,  162  and seat within the thrust bearing seats  146 . Between each pair of thrust bearings  170 , there are respective increased diameter portions  172  of the z- and x-oriented drive shafts  160 ,  162 . A bearing element  176 , preferably an oil-impregnated bushing, needle bearing or the like, is arranged around the tooling holder  164  and seats within the tooling bore  150 . 
     In operation, the machine tool apparatus  10  is arranged on a milling machine bed  200  (see  FIG. 1 ) or other suitable surface. The chuck  204  of the milling machine is attached to the spindle  124  of the transfer arm assembly  78 . An air supply line is connected to the air inlet  72  and the fluid connection line  128  is connected to a fluid supply. An appropriate tooling bit  136  is inserted into the tooling holder  164 . 
     A workpiece  210  (see, for example,  FIG. 6 ) to be keyed is arranged on the stage  30  and butted against the stopper block  56  (see  FIG. 2 ). The stopper block  56  and workpiece  210  are slid into the desired position and the stopper block  56  is set by tightening the stopper block adjustment knob  58 . Final z-adjustments are made to the workpiece  210  by operating the z-adjustment knob  42  to raise or lower the stage  30 . The control handle  70  is operated to port air through the pneumatic lines  68  to the top of, and from the bottom of, the pneumatic cylinder  60 , displacing the piston rod  66  toward the workpiece  210 . The clamp  64  engages the workpiece  210 , holding the workpiece  210  immobile. 
     The milling machine chuck  204  is rotated and this rotation is transferred through the transfer arm assembly  78  to the tooling holder  164  by the z- and x-oriented drive shafts  160 ,  162 , causing the tooling bit  136  to rotate. The milling machine chuck  204  is translated is the desired direction or directions to move the transfer arm assembly  78  and engage the tooling bit  136  with the workpiece  210  for the feature  212  to be machined. Examples of features  212  that are quickly and easily machined using the machine tool apparatus  10  are shown in  FIG. 6 . 
     From the foregoing, it will be appreciated that the machine tool apparatus of the present invention advantageously allows the chuck movement capabilities of modern manual and computer numerical control milling to more quickly and reliably machine a variety of features including, for example, internal and external keyways, splines, gears, blind holes, oil ring grooves, tapered keyways and step keys. For instance, keyways and other features having a variable or step change in depth in the z-direction can be machined without having to reset or adjust the workpiece. 
     Additionally, the carriage assembly  76  enhances the directional stability of the transfer arm assembly  78  during movement and machining. For additional directional stability, the x-, y- and z-oriented rails  80 ,  90  of the xyz carriage assembly  76  can be equipped with locking mechanisms, for instance, computer controlled electromagnetic locks. Prior to commencing, or alternately during, keying, one or more locking mechanisms can be locked. 
     Referring to  FIGS. 7 and 8 , according to an aspect of the present invention, a tooling end adapter  220  is connected to the tooling end of the transfer arm assembly  78  in lieu of a tooling bit. The tooling end adapter  220  includes a housing  222  having a cover  224 . The cover  224  is secured to the housing  222  by a plurality of screws  226 . 
     The housing  222  extends between a tooling engagement end  230 , adapted to engage the tooling end  130  of the transfer arm assembly  78 , and an adapter tooling end  232 , adapted to rotatably carry an adapter tooling bit  234 . The tooling engagement end  230  is secured to the tooling end  130  by a plurality of screws  236 . 
     The tooling engagement end  230  includes a rotatably mounted bit adapter  240  for engagement with the tooling holder  164  of the tooling end  130 . The bit adapter  240  extends through an opening  242  in the cover  224 . The adapter tooling end  232  includes a rotatably mounted adapter tooling holder  244  for holding the adapter tooling bit  234 . 
     An adapter rotation transfer mechanism  246  extends between the tooling engagement end  230  and the adapter tooling end  232  for transferring rotational motion therebetween. The adapter rotation transfer mechanism  246  includes a plurality of intermeshing rotatably mounted gear wheels  248 . 
     The dimensions of adapter tooling end  232  in a plane orthogonal to the x-direction are smaller than the dimensions of the tooling end  130  of the transfer arm assembly. As a result, the tooling end adapter  220  adds flexibility to the apparatus  10  by, for example, allowing internal machining of workpieces with internal clearances insufficient to permit the introduction of the tooling end  130 . 
     Those skilled in the art will appreciate that the present invention is not limited to the embodiment herein shown and described. Instead, various modifications, and adaptations for particular circumstances, are possible within the scope of the invention as herein shown and described. 
     For example, in the embodiment shown, the power transfer section  14  is adapted for compatibility with a vertically-oriented milling machine. However, aspects of the present invention are readily applicable or adaptable for use in connection with horizontally-oriented milling machines and other machine tools capable of engaging a spline and impart rotation motion thereto. For instance, in connection with a horizontally-oriented milling machine, a straight transfer arm assembly with a single drive shaft terminating in a spindle could be employed, rather than the t-shaped transfer arm  78  with dual drive shafts  160 ,  162 . 
     Spindle, as used herein, is not necessarily limited to a rod- or pin-shaped structure, but should be understood to encompass equivalent structures that are engageable by a chuck to impart rotational motion. Similarly, chuck, as used herein, is not necessarily limited to a particular structure, but should be understood to encompass portions of machine tools adapted for engaging other structures to impart rotation thereto. Additionally, while the term machine tool is not necessarily limited to machines designed for working particular materials. 
     Also, the power transmission section  14  can be used in combination with other workpiece holding section, either commonly or separately mounted. For instance, a fixed stage could be employed. As another example, a mechanical vice, hydraulic or electromagnetic clamp could be used instead of the pneumatic clamp assembly  22 . 
     Additionally, although a carriage assembly employing linear bearings and rails have been found to present excellent stability, carriage assemblies employing other mechanisms for supporting relative motion between components, such as other bearing types, could also be employed. Carriage assemblies can also be employed adapted to accommodate other degrees of freedom impartable by machine tools to chucks. 
     Furthermore, adapter rotation transfer mechanisms employing elements other than, or in addition to the plurality of gears  248  are possible within the scope of the present invention. For example, belts, chains or drive shafts could also be employed in connection with a rotation transfer mechanism. 
     The foregoing examples are not an exhaustive list of possible modifications and adaptations. Rather, those skilled in the art will understand that these and other modifications and variations fall within the scope of the present invention as herein shown and described.