Abstract:
A gear holding fixture is provided so that the appropriate position upon a gear tooth may be placed in line with an indenting device on testing equipment. The fixture includes a base that supports a movable rack, the rack including a plurality of teeth. The gear being tested is supported upon the movable rack in a way wherein the teeth on the gear intermesh with the teeth on the rack. The fixture also includes a gear axle restraint that is selectively movable depending on whether the gear is being tested or being replaced. The gear axle restraint in a gear testing position abuts an axle that supports the gear and extends along the gear&#39;s axis of rotation. This reduces the gear to only rotational movement. Thus, as the rack is moved incrementally along the base, the teeth on the rack drive the teeth of the gear, causing the gear to rotate.

Description:
BACKGROUND OF THE INVENTION 
   Gears are used in many mechanical applications including motor vehicles. The gear&#39;s teeth are critical areas, subject to the most wear as well as having the greatest propensity to fracture or otherwise fail. It is important that gears are designed to appropriate specifications to avoid such failure, including material size and material quality specifications. 
   One specific material quality important to wear and strength of the gear teeth is hardness. Each gear material has a usual hardness factor, but this may be changed by additional treatment of the material, either locally (i.e. to wear surfaces) or throughout the gear. The usual hardness or the amended hardness of the gear is often tested for accuracy and consistency. A number of hardness tests and apparatus have been developed, most involving the concept of applying multiple loads at a common position using a device that creates a small depression on the material surface. The difference in indentation depth between a minor load applied and a major load applied is reflective of material hardness. 
   The gear or other workpiece must be placed in a stable position that allows the indenting portion of a testing device to access the desired area, and to apply the load repeatedly. The gear or other workpiece must be held so as not to be moved by the application of the minor or major load. U.S. Pat. No. 2,712,754 illustrates a typical fixture used to hold a gear or gear-like object in a position for access by a hardness testing device. Specifically, two wedges engage teeth on generally opposite sides of the gear for support. However, fine adjustments are made using a slidable supporting foot and the degree of adjustment is limited. 
   What is desired is a gear holding fixture that allows for easy adjustment of the position of the gear, thus, allowing hardness testing to be carried out. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention overcomes these and other disadvantages in the prior art. The gear holding fixture of the present invention provides an easily adjustable device so that the appropriate position upon a gear tooth may be placed in line with an indenting device on testing equipment. 
   In accordance with the present invention, the fixture includes a base that supports a movable rack, the rack including a plurality of teeth. The gear being tested is supported upon the movable rack such that the teeth on the gear intermesh with the teeth on the rack. Thus, as the rack is moved, the teeth on the rack drive the teeth of the gear, causing the gear to rotate. 
   The fixture also includes a gear axle restraint that is selectively movable depending on whether the gear is being tested or being replaced and may be adjusted for gears having different diameters. The gear axle restraint in a first or gear testing position abuts an axle that supports the gear and extends along the gear&#39;s axis of rotation. This limits the gear to only rotational movement. In a second or loading/unloading position, the gear axle restraint is moved away from the axle of the gear. The gear may then be removed from the fixture. The gear axle restraint is affixed to a pair of glides which in turn are slidingly engaged with two contoured guides. The guides are each affixed to one of two posts that are in turn affixed to the fixture base. When in the first or test position, the gear is moved into a position of proper alignment by using a crank and screw that, when turned, move the rack incrementally along the surface of the fixture base. 
   These and other features, aspects and advantages of the present invention will be fully described by the following description, appended claims, and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a first perspective view of the gear holding fixture of the present invention; 
       FIG. 2  is a second perspective view of the gear holding fixture of the present invention; 
       FIG. 3  is a front elevational view of the gear holding fixture oriented within a hardness testing apparatus; 
       FIG. 4  is a perspective view of the gear holding fixture represented as a segment of  FIG. 3 , 
       FIG. 5  is a top elevational view of a gear supported within the gear holding fixture of the present invention; 
       FIGS. 6-9  are perspective views showing the steps of loading a gear into the gear holding fixture. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings, specifically  FIGS. 1 and 2 , a preferred gear holding fixture  10  according to the present invention is illustrated. The gear holding fixture  10  includes an adjustable rack  12  and adjustable gear axle restraint  14  that allow different sized gears to be secured and the gear&#39;s tooth position to be easily adjusted. As described in more detail below, the fixture  10  additionally includes a base  16 , two posts  18 ,  20  including guides  22 ,  24 , a gib  26 , a translation screw  28  for moving the rack  12 , and a threaded member  30  and thumb nut  32  for securing the gear axle restraint  14 . 
   Referring to  FIGS. 1 through 5 , the rack  12  is formed from a generally rectangular plate have a plurality of teeth  34  protruding from an upper surface thereof. The teeth  34  are oriented transverse to the length of the rack  12 . An opposite surface of the rack is smooth and slides across the upper surface of the base  16 . The rack side surfaces  36 ,  38  perpendicular to the upper surface are also smooth and slide against the smooth surfaces of the gib  26 . One end surface  40  of the rack  12  defines a threaded aperture  42  into which a translation screw  28  is threadingly received. The threaded aperture  42  has a sufficient depth to allow significant movement of the rack  12  with respect to the translation screw  28  which rotates, but does not move linearly. The opposite end surface  44  is smooth. Preferably, the rack teeth  34  have a uniform pitch matching the pitch of the gear being tested. Accordingly, different racks  12  will be required to test differently pitched gears. 
   The translation screw  28  is a threaded body extending lengthwise along the base  16 . A crank  46  is affixed to an end of the translation screw  28  opposite the rack  12 . The crank  46  includes a central barrel  48  and a t-handle  50  extending therethrough. The crank  46  is pinned or otherwise affixed to the screw  26  for common rotation therewith. 
   Referring to  FIGS. 1 and 2 , the base  16  slidingly supports the rack  12  and is a flat plate. The base  16  has a generally rectangular shape with two beveled corners  52 ,  54  at a first end  56 . The gib  26  extends lengthwise along an upper face  58  of the base  16 . The gib  26  comprises two rectangular blocks  60 ,  62  each defining two apertures, for facilitating attachment to the base  16 . The blocks  60 ,  62  are spaced from one another so as to receive the rack  12  therebetween. 
   A mounting block  64 , which is generally square in shape, is affixed to the second end  57  of the base  16 . The mounting block  64  defines a central aperture  66  in a direction parallel to the length of the base  16  through which the translation screw  28  extends. A nut  124  is positioned adjacent to the mounting block  64  on a side adjacent to the rack  12 . The central hole defined by the nut  124  is aligned with the central aperture  66  within the mounting block. 
   Two posts  18 ,  20  are shown extending perpendicular to a plane defined by the upper surface  58  of the base  16 . The posts  18 ,  20  are generally rectangular in shape, and have one beveled corner at a first end  68 ,  70  opposite the base  16 . The posts  18 ,  20  each define two apertures at a first end  72 ,  74  (adjacent the base) and three additional apertures along an imaginary central axis extending along the length of the posts  18 ,  20 . The posts  18 ,  20  are affixed to the associated side surface of the base  16  by appropriate means, such as the illustrated screws or, optionally, by welding, etc. 
   Two guides  22 ,  24  extend parallel to the two rectangular posts  18 ,  20  and are affixed thereto. Each guide  22 ,  24  includes two notches  76   a ,  76   b  and  78   a ,  78   b  extending along the length of the guide  22 ,  24  on opposite sides, the sides being perpendicular to the face of the post  18 ,  20  to which the guide  22 ,  24  is affixed. Each guide  22  has a length that is generally equivalent to the length of a post  18  minus the thickness of the base  16 . Each guide  22 ,  24  defines three apertures that facilitate attachment to the posts  18 ,  20  via mechanical fasteners. 
   Referring to  FIG. 5 , each glide  80 ,  82  is a rectangular solid including a lengthwise extending channel  84 ,  86  on one side. The channel  84  on glide  80  includes a base wall  88  and two side walls  90 ,  92  and includes two lengthwise projections  94 ,  96 , protruding from opposite channel side walls  90 ,  92 . The projections  94 ,  96  have a shape that matches the inverse shape of the notches  76   a ,  76   b  on the guide  22 . The channel  86  on glide  82  is generally identical to the channel  84  described hereinbefore. 
   Referring to  FIGS. 2 ,  4  and  5 , the gear axle restraint  14  includes two arms  100 ,  102 , a base member  112 , and an adjustment screw system  118 . The arms  100 ,  102  extend lengthwise, parallel to, but laterally displaced from, the rack  12 . Each arm  100 ,  102  is a generally rectangular solid with a height oriented parallel to the length of the posts  19 ,  20 . Each arm  100 ,  102  may have a beveled corner  104 ,  106  at an end opposite the rack  12  and adjacent to the base  16 . Each arm  100 ,  102  includes a V-notch section  108 ,  110  near the end closest to the rack  12 . The notch  108 ,  110  is open downwardly so as to face toward the base  16 . More specifically, the notch  108 ,  110  includes forward and rearward angled surfaces that are linked by a generally horizontal surface as illustrated. Each arm  100 ,  102  defines a plurality of apertures near the center of its length and at the end opposite the rack  12  to facilitate attachment to the base member  112  in a cantilever fashion. 
   The square base member  112  extends between and interconnects the arms  100 ,  102  at the end opposite the rack  12 . The base member  112  defines a number of screw receptacles  114  and a central aperture  116  passing through the base member  112  in a direction perpendicular to the screw receptacles  114  and the arms  100 ,  102 . Screws extend through apertures in the arms  100 ,  102  and into the screw receptacles  114  of the base member  112  to affix the arms to the base member. 
   The adjustment screw system  118  includes a threaded member  30 , thumb nut  32 , thrust washer  120  and compression spring  122 . The threaded member  30  is oriented parallel to the posts  18 ,  20  and perpendicular to the base  16 . One end of the threaded member  30  is supported by the base  16  at an end opposite the mounting block  64  and is located generally in the center of the base&#39;s width. Preferably, the threaded member  30  is threaded through a nut that is welded to the base, and into a threaded hole formed in the base to securely attach the threaded member  30  to the base  16 . The threaded member  30  freely extends through the central aperture  116  defined by the base member  112 . 
   The compression spring  122  fits over and around the threaded member  30  and is located between the base member  112  and the base  16 . The thrust washer  120  and thumb nut  32  fit over the threaded member  30  and are located above the base member  112 . The thumb nut  32  may have a knurled exterior making it easy to grip. 
   Referring to  FIGS. 1 ,  2  and  5 , the gib  26  (i.e., blocks  60 ,  62 ) is affixed to the upper face  58  of the base  16  lengthwise using screws. The rack  12  is supported on the base  16 , between the gib  26  and is allowed to slidingly move, lengthwise along the base  16 . The translation screw  28  is threaded into the aperture  42  in the end  40  of the rack  12 . The opposite end of the translation screw  28  is threaded through the nut  124  and affixed thereto with a pin and passes freely through an aperture  66  in the mounting block  64 . The crank  46  is affixed to the end of the translation screw  28  passing through the mounting block  64  using a pin. As the crank  46  is rotated the rack  12  slides lengthwise along the base  16 . 
   The posts  18 ,  20  are bolted to sides of the base  16  and interior sides of the posts  18 ,  20  point toward the rack  12 . Each guide  22 ,  24  is affixed to an interior side of one of the posts  18 ,  20 . Preferably, an upper end of the guide  22 ,  24  is flush with the upper end of the associated post  18 ,  20 , and the lower end of the guide abuts the base  16 . Each guide  22 ,  24  is bolted to the post  18 ,  20  and is located in the center of the post&#39;s width. Each guide  22 ,  24  slidingly receives one of the glides  80 ,  82 . The projections  94 ,  96  within the channel  84  defined by each glide  80 ,  82  fit within the notches  76   a ,  76   b  and  78   a ,  78   b  defined by the guides  22 ,  24 . Each glide  22 ,  24  is affixed to one of the arms  100 ,  102  of the gear axle restraint  14 , generally at a mid-point of the arm. 
   The gear axle restraint  14  is assembled by bolting each arm  100 ,  102  to an opposite side of the base member  112 . Thus, the notches  108 ,  110  on the arms  100 ,  102  are aligned. The lower end of the threaded member  30  is affixed to the base  16  and the compression spring  122  is placed around the threaded member  30 . The base member  112  of the gear axle restraint  14  is placed over the threaded member  30  which places the spring  122  between the upper surface of the base  16  and the lower surface of the base member  112 . The aperture  116  within the base member  112  allows passage of the threaded member  30 , but not the spring  122 . The thrust washer  120  is placed over the threaded member  30  and against the upper side of the base member  112 . The thumb nut  32  is threaded onto the threaded member  30  and, when tightened, abuts the thrust washer  120 . 
   Referring to  FIGS. 3-4  and  6 - 9 , a gear  150  is selected for testing. If not already including a stub axle  152 , one is chosen from a supply and is placed through a central aperture  154  within the gear  150 . The operator determines how high the gear axle restraint  14  must be raised in order to allow the gear  150  to be placed in a position where the stub axle  152  is aligned with the notches  108 ,  110  in the arms of the gear axle restraint  14 . The thumb nut  32  is rotated allowing the spring  122  to force the base member  112  and arms  100 ,  102  of the gear axle restraint  14  to the proper position. The base member  112  of the gear axle restraint  14  moves along the threaded member  30  and the glides  80 ,  82  move along the guides  22 ,  24  under the influence of spring force. The gear  150  is put in place with its teeth  156  intermeshed with teeth  34  upon the rack  12  and the stub axle  152  aligned with the notches  108 ,  110  on the arms  100 ,  102 . The thumb nut  32  is then rotated in an opposite direction until the arms  100 ,  102  firmly secure the gear  150  in position. However, the gear  150  may still be rotated around its stub axle  152  via movement of the rack  12 , described hereinafter. 
   The appropriate gear tooth  156  to be tested is chosen and the appropriate alignment of that gear tooth  156  is determined to access by the indenter  158  of the hardness tester  160 . Generally, the selected gear tooth  156  is positioned so that the surface thereof being tested is substantially parallel to the base  16 . The crank  46  is moved in either a clockwise or counter clockwise direction to rotate the gear  150  in the necessary direction to place the selected gear tooth in the desired orientation. Movement of the crank  46  causes the translation screw to rotate which in turn causes the rack  12  to move linearly. Preferably, no lock is used to hold the translation screw  28  in place during testing. Although force is applied to the gear during testing, it is not sufficient to rotate the translation screw  28  and, thus, cannot move the rack  12 . Accordingly, application of testing forces will not cause the gear to rotate. 
   The gear  150  is now ready to be tested. If another tooth  156  on the same gear  150  needs to be tested, the gear  150  may be rotated to the appropriate position by turning the crank  46  that moves the rack  12 . When testing is complete, the gear axle restraint  14  is loosened by rotation of the thumb nut  32 . The gear axle restraint  14  may then be raised and the gear  150  removed from the fixture  10 . 
   The posts are shown having a generally rectangular shape, but may be any shape such as rod-like or tubular. To assist in sliding the glides may be equipped with ball or roller bearings secured within a race. The adjustment screw system may be replaced with a pneumatic piston and return spring system. Both or either of the adjustment screw system and crank for moving the rack may be fitted with a stepper motor to allow precise incremental movements. The crank is described as including a T-handle, but may, alternatively, have a handle of any shape, such as a cylinder with a knurled outside surface. 
   The present invention is an improvement over the prior art because it is a compact, fully contained fixture with a flat bottom that may be placed within numerous different hardness testing devices. No loosening of bolts or other stops is required to rotated the gear for desired alignment. Additionally, a large degree of rotational adjustment is allowed due to the length of the rack. 
   Although the invention has been shown and described with reference to certain preferred and alternate embodiments, the invention is not limited to these specific embodiments. Minor variations and insubstantial differences in the various combinations of materials and methods of application may occur to those of ordinary skill in the art while remaining within the scope of the invention as claimed and equivalents.