Abstract:
A mechanism retains an asymmetric work piece in a fixed orientation during a machining process on diversely positioned surfaces falling on multiple work piece axes. The mechanism includes a body having an upper surface forming an elongated V-shaped groove, a planar lower surface spaced from the upper surface, and a through passage extending between the upper and lower surfaces. A fastener includes an elongated shaft which extends within said passage, and has an upper end emerging within the V-shaped groove for engaging the work piece, and a lower end extending below and configured to abut the lower surface to maintain the shaft under tensile loading. A plurality of discrete mechanisms can be commonly mounted on a machining table in a spaced-apart relationship with the V-shaped grooves in axial alignment to support a single super elongated work piece. The fastener can be axially advanced or retarded to vary tensile loading.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to work holding devices employed in manufacturing processes in general and to V-block type work holding devices employed in manufacturing processes in particular. 
       BACKGROUND 
       [0002]    V-block type work holding devices have been employed in the machine tool industry for more than a century. They are typically employed for holding parts for machining or inspection. Typically, an elongated “V” groove configuration is machined or ground centrally in a block which has a provision for accommodating a horse shoe style clamp to secure the work piece within a V-groove. More advanced designs enable the V-block to be held on up to five sides. Nevertheless, the prior art suffers from numerous shortcomings which include low holding/clamping strength, marred work pieces, deformed fasteners/guides, a large profile interfering with associated machine tools, and a generalized lack of versatility. 
         [0003]    One known V-fixture provides a “strap” device for securing a work piece in an inverted orientation. The strap itself is secured by screws into threaded lands on either side of the V-groove. The relative inaccessibility of the work piece in this type of jig limits the cutting tool to cross-drilling applications. Another V-fixture features a V-block having a tangent contact drill guide being vertically adjustable by legs straddling either side of the V-block. Screws on either side of the V-block secure the position. This prevents turning the V-block on its side for additional operations. Additionally, the straps cannot exert any significant clamping force on the work piece by the nature of its design. 
         [0004]    Another V-block configuration employs threaded holes on the lands on either side of the V-block to secure and position a V-shaped work holding clamp. The threads do not extend through the V-block and limit work holding to the V-shaped cavity. Additionally, the clamp has a high profile which may interfere with machining operations. Furthermore, small diameter work pieces are located at the bottom of the V-shaped cavity, making it even less accessible to a cutting tool. Also, the mechanism will not permit the V-block to be held on the clamping side. 
         [0005]    A similar device features a block having a single central V-shaped cavity and a flat base with threaded holes in lands adjacent to the V-shaped cavity. The ends of an “I” shaped tangent plate are secured to the V-block. A liner is disposed within the V-shaped cavity. This design lacks guide pins secured in the tangent clamp plate or a counter bore feature to recess the securing screws permitting turning of the fixture on any side. Additionally, the threaded holes are not threaded completely through the V-block, which limits the tool to holding the work within the V-shaped cavity. 
         [0006]    Yet another device includes a universal angle self-adjusting V-block work piece holder including a rectangular base supporting two separate upright inverted W&#39;s that run parallel to each other along the longer sides of the rectangular base. A channel of constant width runs laterally between the two opposing vertically positioned W&#39;s. Four holes located at the apex of each peak are used as insertion points for two hexagonal screws with smooth cylindrical shafts. These shafts provide a sufficient axle for rotation of the pivoting panels to which they are attached from a through aperture extending from a ridge at the bottom of each panel. The extending portions of the separated pivotal panels are thin enough to slip between the lateral channel, and swivel when attached between the two vertical walls by the cylinder shafts. Each panel is therefore allowed movement independent of the other. Thus, the holder supports a work piece at a variety of predetermined angular orientations during the machining process. 
       SUMMARY 
       [0007]    The present disclosure describes a compact V-block fixture configured to precisely locate and hold a complex shaped, asymmetrical work piece such as a rotor die part for machining about virtually the entire peripheral outer surface of the work piece without having to re-set the work piece with the V-block fixture midway through the machining process. In application, the V-block fixture is bolted to a machining table and the work piece is non-adjustably bolted to the V-block fixture from below whereby the fastener(s) is/are not exposed and does/do not interfere with the machining process. The compact nature of the V-block fixture provides substantially 360° circumferential access clearance for machining the work piece. The work piece is non-adjustably bolted to the V-block fixture to ensure unit-to-unit repeatability. 
         [0008]    According to an embodiment of the disclosure, a mechanism for retaining a work piece in a fixed orientation during a machining process on diversely positioned surfaces falling on multiple work piece axes includes a body portion having an upper surface with an elongated V-shaped groove formed therein, a planar lower surface spaced from the upper surface, and a through passage extending between the upper and lower surfaces. A fastener portion includes an elongated shaft disposed within the through passage having an upper end emerging within the V-shaped groove and configured to engage a work piece aligned therewith and a lower end extending below and configured to abut the lower surface and to maintain the elongated shaft under tensile loading. 
         [0009]    According to another embodiment of the disclosure, a mechanism for retaining an elongated work piece in a fixed orientation during a machining process on diversely positioned surfaces falling on multiple work piece axes includes two or more longitudinally spaced apart V-block fixtures commonly affixed to a machining table, each including a fastener portion having an upper end separately engaging a work piece at spaced points there along. 
         [0010]    According to yet another embodiment of the disclosure, a method for retaining a work piece in a fixed orientation during a machining process on diversely positioned surfaces falling on multiple work piece axes, includes the steps of providing a body portion of a V-block fixture having an upper surface with an elongated V-shaped groove formed therein, a planar lower surface spaced from the upper surface, and a through passage extending between the upper and lower surfaces, providing a fastener portion of a V-block fixture including an elongated shaft disposed within the through passage, wherein the elongated shaft has an upper end emerging within the V-shaped groove and is configured to engage a work piece aligned therewith and a lower end extending below and configured to abut the lower surface and to maintain the elongated shaft under tensile loading. The method further includes the steps providing a work piece with an outwardly opening recess formed therein, aligning the work piece with the V-shaped groove, aligning the work piece outwardly opening recess with the upper end of the elongated shaft, and extending the upper end of the elongated shaft within said outwardly opening recess to establish engagement there between and to establish/maintain tensile loading of the shaft. 
         [0011]    These and other features and advantages of the disclosure will become apparent upon reading the following specification, which, along with the drawings, describes alternative embodiments of the disclosure in detail. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present apparatus will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0013]      FIG. 1  is perspective view of a rotor V-block secured to a machine table and supporting a complex shaped work piece (e.g., rotor die); 
           [0014]      FIG. 2  is a broken end plan view of the V-block, machine table and work piece of  FIG. 1 , wherein the outer surface envelope of the work piece is simplified; 
           [0015]      FIG. 3  is a broken side plan view of the V-block, machine table and work piece of  FIG. 1 , wherein the outer surface envelope of the work piece is simplified; 
           [0016]      FIG. 4  is a cross-sectional view of the assembled V-block, machine table and work piece of  FIG. 2  taken along line  4 - 4  of  FIG. 3 ; 
           [0017]      FIG. 5  is a broken, end plan view of the V-groove portion of the V-block of  FIG. 2  illustrating selected details on an enlarged scale; and 
           [0018]      FIG. 6  is a broken side plan view of an assembled V-block, machine table and work piece similar to  FIG. 3 , wherein multiple (e.g., two) similar spaced-apart V-blocks are simultaneously employed to secure a single super elongated work piece. 
           [0019]    Although the drawings represent embodiments of the present apparatus and method, the drawings are not necessarily to scale and certain features may be exaggerated in order to illustrate and explain the present disclosure. The exemplification set forth herein illustrates embodiments of the apparatus and method, in varied forms, and such exemplification is not to be construed as limiting the scope of the present apparatus and method in any manner. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    In the following Detailed Description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. In this regard, directional terminology, such as “top”, “bottom”, “front”, “back”, “leading”, “trailing”, etc. is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Furthermore, the axes (e.g., ±X, ±Y, and ±Z axes) are referenced on the drawings to provide a relative directional sense only. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. 
         [0021]    The present disclosure describes a compact V-block fixture, formed of hardened tool steel and configured to precisely locate and hold a rotor die part for machining In application, the V-block fixture is bolted to a machine table and the rotor die part is bolted to the V-block fixture. The compact nature of the V-block fixture provides access clearance for machining the rotor die part without repositioning or resetting it on the V-block fixture during the machining process. The rotor die part is non-adjustably bolted to the V-block fixture to ensure unit-to-unit repeatability. 
         [0022]    The compact V-block fixture of the present disclosure serves to locate the rotor die part in a planned location for part setup. The design specifications of the rotor die part define the precise location of the V-block fixture within the host computer aided design (e.g., cad) system. The “cutter line” creator also includes the V-block fixture and rotor die part in the cad system to check for potential machining collisions (e.g., interferences). This permits positioning of the fixture to ensure adequate clearance of machining of the rotor die part. 
         [0023]    Previous fixtures tended to be too large for smaller parts and did not provide a specified planned location for part setup. Such fixtures lacked adequate clearance for the machining process. Slotted bolt holes in the fixture employed for clamping the part to the fixture permitted a range of locations, frequently resulting in piece to piece variances. The present disclosure is substantially more compact and allows ample clearance for machining all of the critical diversely positioned surfaces of the rotor die part falling on multiple work piece axes with a single setup. A precise line-to-line slip-fit of the fastener (e.g., bolt) within a host retainer passageway ensures overall precision in the machining process. 
         [0024]    Referring to  FIG. 1 , a rotor die part (e.g., work piece)  10  is illustrated mounted to a V-block fixture (e.g., retaining mechanism)  12  which, in turn, is mounted to a planar surface  14  of a machining table  16 . The overall assembly is identified by reference numeral  18 . 
         [0025]    The rotor die part  10  includes an active die portion  20 , a mid-portion  22  and a base portion  24  arranged in an elongated configuration along longitudinal axis Y (e.g., a first principle axis). The rotor die part  10  has a complex shape which is asymmetrical in all three principle axes (e.g., X, Y and Z axes) and forms varied irregular surfaces which can only be accessed, for machining purposes, along one of said principle axes or an intermediate (e.g., offset vector intermediate the X and Y axes, the X and Z axes, the Y and Z axes or the X, Y and Z axes). The rotor die part  10  is preferably monolithically formed from a single piece of hardened steel. The V-block fixture  12  includes a body portion  26  preferably monolithically formed from a single piece of D2tool steel material (i.e., a discrete body portion) which has been fully hardened. The body portion  26  of the V-block fixture  12  includes a base portion  28  affixed to the machining table  16  by a pair of threaded fasteners (e.g., bolts and nuts)  30 , or other suitable fasteners, and an upper portion  32  extending vertically from the base portion  26  along vertical axis Z. Base portion  28  forms an opposed pair of laterally extending cooperating feet  34 . Each foot  34  has a slot  36  for receiving the shank of a respective threaded fastener  30 . 
         [0026]    For purposes of providing non-limiting definition and to enable clear understanding of the present disclosure, “longitudinal” means parallel to the direction of the Y axis, “lateral” means parallel to the direction of the X axis, and “vertical” means parallel to the direction of the Z axis. 
         [0027]    The rotor die part  10  has a number of diversely positioned surfaces which fall on or transect multiple axes. By way of example, the active die portion  20  of the rotor die part  10  has an asymmetrical outer surface detail  38  in the form of a circumferentially segmented, tapered cone converging longitudinally along the −Y axis. Furthermore, the active die portion  20  of the rotor die part  10  has a number of complex, irregularly shaped details  40 ,  42 ,  44 , and  46 , each requiring precision machining and surface finishing. Also, the mid-portion  22  of the rotor die part  10  has a number of complex, irregularly shaped details  48 ,  50 ,  52 ,  54 ,  56  and  58 , each requiring precision machining and surface finishing. Similarly, the base portion  24  of the rotor die part  10  has a number of complex, irregularly shaped details  58 ,  60 ,  62  and  64 , each requiring precision machining and surface finishing. The details  38 - 64  highlighted herein are merely examples. 
         [0028]    Although a multi-axis milling machine is capable of being programmed to fabricate each of the individual details  38 - 64  et seq separately, doing so with a single rotor die part  10 -V-block fixture  12  setup was heretofore not practical. The compact structure of the V-block fixture  12 , particularly its relatively small dimension in the longitudinal direction (e.g., Y axis), exposes all of the details  38 - 64  to a machine tool head (not illustrated) without risking contact between the V-block fixture  12  and the machine tool head during the machining process. Restated, all external surface areas (e.g., details  38 - 64 ) of the rotor die part  10  are accessible to a cutting head of a multi-axis milling machine approaching the rotor die part  10  along one or a combination of the ±X, ±Y and ±Z axes, without interfering with the V-block fixture  12 . 
         [0029]    Referring to  FIGS. 2 ,  3 ,  4  and  5 , the assembly  18  of  FIG. 1  is depicted in varying perspectives, and is identical in all material respects to the assembly  18  of  FIG. 1 , with the sole exception that the rotor die part  10  in  FIGS. 2 ,  3  and  4  is illustrated as a simple solid cylinder, for the sake of simplicity. By definition, the rotor die part  10  is configured along a first principle axis extending parallel to the Y axis, a second principle axis extending parallel to the X axis and a third principle axis extending parallel to the Z axis. As illustrated in  FIGS. 2 ,  3 ,  4  and  5 , the rotor die part  10  is elongated along the first principle axis. 
         [0030]    As best seen in  FIG. 3 , the mid-portion  22  of the rotor die part  10  is longitudinally and laterally centered over the V-block structure  12 , with the active die portion  20  of the rotor die part  10  extending, in cantilever fashion, along the −Y axis, and the base portion  24  of the rotor die part  10  extending, in cantilever fashion, along the +Y axis. Although the rotor die part  10  is depicted with the center of mass/geometrical center aligned with the vertical axis Z, it is contemplated that the rotor die part  10  can be mounted to the V-block fixture  12  geometrically offset along the ±Y axis. Furthermore, the designation of the rotor die part  10  as including an active portion  20 , a mid-portion  22  and a base portion  24  is considered as arbitrary and included herein for the sake of clarity only. For example, it is contemplated that the entire axial (e.g., Y axis) length of the rotor die part  10  can function as an active die portion. Accordingly, the designation of the rotor die part  10  as including am active portion  20 , a mid-portion  22  and a base portion  24  is not to be considered as limiting. 
         [0031]    The body portion  26  of the V-block fixture  12  defines an upper surface  66  with an elongated V-shaped groove  68  formed therein oriented along the Y axis. A generally rectangular elongated recess  70  is formed along the nadir  72  of the V-shaped groove  68  also extends along the Y axis. The rectangular elongated recess  70  aligned with the nadir  72  of the V-shaped groove  68  ensures a localized clearance from the rotor die part  10  and enables removal of any chaff and cutting oil accumulated during the machining process. 
         [0032]    A generally rectangular longitudinally directed opening  74  extends through the base portion  28  of body portion  26  of the V-block fixture  12  laterally intermediate the two feet  34  and centered beneath the nadir  72  of the V-shaped groove  68 . The opening  74  defines opposed side walls  76  and  78  and a ceiling (e.g., planar lower surface)  80  transitioning at each longitudinal end thereof in stress-relieving bevels  82 ,  84  and  86 , respectively. 
         [0033]    The ceiling  80  is vertically spaced below the upper surface  66  of the upper portion  32  of the V-block fixture  12 . A vertically extending through passage  88  extends between the ceiling  80  and the upper surface  66 , having an upper opening  90  centered longitudinally and laterally with both the V-shaped groove  68  and the elongated recess  70 . The vertically extending through passage  88  has a lower opening  92  centered longitudinally and laterally with the ceiling (e.g., lower surface)  80 . 
         [0034]    As best illustrated in  FIGS. 2 and 4 , a fastener portion  94  of the V-block fixture  12  includes an elongated shaft  96  disposed within the through passage  88 , preferably in a slip-fit relationship. The fastener portion  94  is preferably monolithically formed from a single (i.e., discrete) piece of fully hardened steel. The elongated shaft  96  has an upper end  98  emerging through the upper opening  90  and extending into the V-shaped groove  68 . The elongated shaft  96  has a lower end  100  emerging through the lower opening  92  and extending into the longitudinal opening  74  in the base portion  28  of the body portion  26  of the V-block fixture  12 . The lower end  100  of the fastener portion  94  terminates in an enlarged head portion  102  forming a thrust surface  104  on an upper surface thereof bearing against the ceiling  80  through an intermediate washer/bushing  106 . This structure constitutes an adjustable abutment feature. The enlarged head portion  102  forms engagement surfaces  108 , such as hexagonally arranged flats, adapted for cooperating engagement with a tool (e.g., hand tool) to apply torque to the fastener portion  94 . In the embodiment illustrated herein, the fastener portion  94  essentially constitutes a bolt having external threads extending along its shank formed of fully hardened tool steel. The through passage  88  is illustrated as being tubular in shape with a smooth i.d. (e.g., inside diameter) surface dimensioned in a slip-fit relationship with the threaded shank of the bolt. It is further contemplated that two or more fastener portions  94  can be employed with a single V-block fixture  12 . 
         [0035]    Alternatively, the fastener portion  94  of the V-block fixture  12  can constitute an elongated shaft  96  with external threads formed at the upper end  98  configured to engage mating threads formed in the blind bore  110  in the rotor die part  10  and external threads formed at the lower end  100  for receiving a mating nut/thrust washer combination for bearing against the ceiling  80  of the longitudinal opening  74  of the base portion  28  of the body portion  26  of the V-block fixture  12  to establish tensile loading of the shaft. This alternative configuration essentially constitutes a threaded stud. 
         [0036]    As best illustrated in  FIGS. 3 and 4 , the upper end  98  of the elongated shaft  96  of the fastener portion  94  extends vertically above the upper surface  66  of the V-block fixture  12 . The rotor die part  10  has an internally threaded blind bore  110  externally accessible through an opening  112  in a preformed region  114  of a peripheral outer surface of the mid-portion  22  of the rotor die part  10 . The preformed region  114  is shaped to nest within the V-shaped groove  68  of V-block fixture  12  ensuring intimate line-to-line or surface-to-surface contact between the outer peripheral surface of the rotor die part  10  and the upper surface  66  of the V-block fixture  12 . 
         [0037]    The longitudinal opening  74  in the base portion  28  of the body portion  26  of the V-block fixture  12  provides external access to the enlarged head portion  102  of the fastener portion  94  of the V-block fixture  12  via a suitable tool, such as a hand wrench, for assembling and disassembling the V-block fixture  12 -rotor die part  10 -machining table  16  construct and increasing/decreasing the tensile loading of the elongated shaft  96  of the fastener portion  94  insitu (i.e., in a fully assembled condition). 
         [0038]    As best illustrated in  FIGS. 1 and 3 , the body portion  26  of the V-block fixture  12  includes a number (e.g., an opposed pair) of threaded blind bores  116  (only one is illustrated), each configured to releasably receive a lift point attachment such as an O-ring. Multiple symmetrically distributed lift points about the center of mass of the V-block fixture  12 , either alone or in combination with the rotor die part  10  enable precision lifting, horizontal translation and placement, such as with an overhead hoist, without creating swaying or angular/off axis perturbations. 
         [0039]    The method of the present disclosure is employed by selecting/designing a blank for the rotor die part  10  having a mid-portion  22  with a preformed region  114  suitable for mounting on the V-block fixture  12 . Next, the threaded blind bore  110  is formed in the preformed region  114 . The preformed region  114  of the rotor die part  10  blank is then nested within the V-shaped groove  68  of the V-block fixture  12  with the through passage  88  of the V-block fixture  12  axially aligned with the threaded blind bore  110  of the rotor die part  10  blank. 
         [0040]    The elongated shaft  96  of the fastener portion  94  of the V-block fixture  12  is then advanced axially until the external threads of the elongated shaft  96  engage the internal threads of the blind bore  110 . A tool (not illustrated) then applies torque to the enlarged head portion  102  of the fastener portion  94  of the V-block fixture  12 , causing the fastener portion  94  to advance axially until the thrust surface  104  of the enlarged head portion  102  abuts the ceiling  80  of the base portion  28  of the body portion  26  of the V-block fixture  12 . Additional torque is then applied to the enlarged head portion  102  until a predetermined tensile level is established in the elongated shaft  96  of the fastener portion  94  of the V-block fixture  12 . 
         [0041]    In a separate step, the V-block fixture  12 , alone or with the rotor die part  10  pre-mounted thereto, is securely affixed to the associated machining table  16  using the threaded fasteners  30 . Once the feet  34  of the V-block fixture  12  are pre-positioned on the planar surface  14  of the machining table  16 , the V-block fixture  12  can be positionally adjusted along the Y axis, as indicated by arrow  120 , placing the V-block fixture  12  in a final design-intent position. Lastly, the V-block fixture  12  is affixed to the machining table  16  by the threaded fasteners  30  or other suitable devices. 
         [0042]    Once mounted, machining of the entire exposed outer surface of the rotor die part  10 , with the sole exception of the preformed region  114 , including all details  30 - 64  can inter alia take place without the need for interim repositioning of the rotor die part  10 . 
         [0043]    Referring to  FIG. 6 , an elongated rotor die part (e.g., work piece)  10 ′ is illustrated mounted to a pair of V-block fixtures (e.g., retaining mechanisms)  12  which, in turn, are mounted to a planar surface  14 ′ of a common machining table  16 ′. The overall assembly is identified by reference numeral  18 ′, and is identical in all material respects to the embodiment described in connection with  FIGS. 1-5 , unless described otherwise. 
         [0044]    The pair of V-block fixtures  12  are longitudinally spaced apart, as indicated by an arrow  118 , sufficiently to ensure machining of the entire exposed outer surface of the rotor die part  10 ′, with the sole exception of the preformed regions  114 ′ associated with the two V-block fixtures  12 , without the need for interim repositioning of the rotor die part  10 ′. 
         [0045]    It is to be understood that the present apparatus and method has been described with reference to specific embodiments and variations to provide the features and advantages previously described and that the embodiments are susceptible of modification as will be apparent to those skilled in the art. 
         [0046]    Furthermore, it is contemplated that many alternative, common inexpensive materials can be employed to construct the basis constituent components. Accordingly, the forgoing is not to be construed in a limiting sense. 
         [0047]    The present apparatus and method has been described in an illustrative manner, and it is to be understood that the terminology, which has been used is intended to be in the nature of words of description rather than of limitation. 
         [0048]    Obviously, many modifications and variations of the present disclosure are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for illustrative purposes and convenience and are not in any way limiting, the present apparatus and method, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents, may be practiced otherwise than is specifically described.