Abstract:
A coordinate measuring machine has a horizontal rail defining an X-axis, a vertical rail movable along the horizontal rail defining a Z-axis, and a horizontal arm orthogonally situated relative to said X and Z axis defining a Y axis. Pairs of opposed track surfaces integral with the rails are engaged by pairs of wheels for rolling movement of the axes relative to each other. Biasing means such as coil springs urge the wheels of each of the pairs into contact with the opposed track surfaces in order to accurately maintain desired orthogonal relationships between the axes.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to coordinate measuring machines. More specifically, the invention relates to an improved coordinate measuring system especially adaptable for auto body repair.  
         BACKGROUND OF THE INVENTION  
         [0002]    Coordinate measuring machines are used for measurement of auto bodies during repair as described in my U.S. Pat. Nos. 4,683,663 and 5,621,978. Such devices have also been used for dimensional inspection of work pieces such as models or machine parts, for example, in preparation of new product mock-up models or for measurement of machine parts during manufacturing operations. Such devices have been used in producing molds, dies, and fixtures from blueprints or CAD/CAM data with a high degree of accuracy.  
           [0003]    The devices shown in my above-mentioned patents have proved successful in practice. However, a need has existed for improvements of the devices particularly as to retention of the desired angular positioning of measurement arms if subjected to incidental impact during use or after extended periods of wear.  
         SUMMARY OF THE INVENTION  
         [0004]    In accordance with the present invention, an improved coordinate measuring device is provided. In accordance with an important aspect of the invention, the configurations illustrated in my earlier patents are modified to introduce biasing of the measurement arm supporting wheels which support and permit movement of the coordinate arms along supporting rails. As a result, the supported measuring arms are resiliently urged into firm contact with the surfaces upon which they travel.  
           [0005]    In accordance with a further aspect of the invention, the biasing forces are provided by a simple device such as a compression spring. In accordance, a further related aspect of the preferred biasing device is a coiled metal spring of commonly available configuration.  
           [0006]    In accordance with the invention, a coordinate measuring device especially adaptable for use of auto body repair is provided which is imparted with improved dimensional stability. In accordance with yet a further aspect, if flexing of the measuring arms occurred, the biasing forcing provided in accordance with the invention insure return of the arms to their desired original position.  
           [0007]    Briefly, the invention provides a coordinate measuring machine which has a horizontal rail defining an X-axis, a vertical rail movable along the horizontal rail defining a Z-axis, and a horizontal arm orthogonally situated relative to said X and Z axis defining a Y axis. Pairs of opposed track surfaces integral with the rails are engaged by pairs of wheels for rolling movement of the axes relative to each other. Biasing means such as coil springs urge the wheels of each of the pairs into contact with the opposed track surfaces in order to accurately maintain desired orthogonal relationships between the axes.  
           [0008]    Further objects, advantages and aspects of the invention will be apparent from the following detailed description and accompanying drawings wherein: 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is an isometric view, with parts cut away and shown in cross-section of a coordinate measuring device of the present invention;  
         [0010]    [0010]FIG. 2 is a side elevational view of a coordinate-measuring machine of the present invention;  
         [0011]    [0011]FIG. 3 is an enlarged cross-sectional view taken through a measuring arm and supporting rail of the device of FIG. 2; and,  
         [0012]    [0012]FIG. 4 is a fragmentary elevational view with parts broken away to show interior details taken along line  4 - 4  of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    Referring more specifically to the drawings, a coordinate measuring machine is indicated generally by numeral  10 . As best seen in FIGS. 1 and 2, a horizontal rail  12  if provided in order to permit movement in the X direction.  
         [0014]    A vertical rail  14  is provided in order to allow movement of the device in the Z direction. A horizontal rail  16  is orthogonally oriented relative to rails  12  and  14  and is provided for movement of the device in the Y direction. A pointer  18  is usually positioned on the distal end of rail  16  in order to locate a point on a work piece indicated by phantom lines and by numeral  20 .  
         [0015]    The position of each of arms  14  and  16  relative to a starting point can be indicated by means of linear position marking provided along each of the arms, is desired. They can also be indicated by means of extendable-retractable measuring tapes as described in my U.S. Pat. No. 4,683,663. However, as disclosed in my subsequent U.S. Pat. No. 5,621,978, the positions are preferably determined using a microprocessor  24  to which electronic signals are provided by encoding devices  26 ,  28  and  30  located on each of the axes of the coordinate measuring machine. Further details regarding the encoding devices are described and shown in my U.S. Pat. No. 5,621,978, the disclosure of which is incorporated herein by reference.  
         [0016]    As seen in FIGS. 1 and 2, rail  12  which defines the X axis is horizontally positioned and is provided with a pair of V-shaped convex projecting surfaces  36  and  38 . The convex surfaces  36  and  38  are engaged by two or more pairs of lower and upper supporting wheels  39 ,  41  and  40 ,  42 . These pairs of wheels provide a means for supporting the vertical arm  14  for easy rolling movement along the X-axis defined by rail  12 . An encoder  26  transmits electrical signals to a microprocessor  24  for the purpose of providing readings which indicate the precise position of the coordinate measuring device along the X-axis.  
         [0017]    A support housing  50  is provided with pairs of wheels  55 ,  56  and  57 ,  58  which enable rolling movement upwardly and downwardly of the housing  50 , and arm  16  supported thereby, along the Z axis defined by vertical rail  14 .  
         [0018]    Vertical rail  14  is provided with convex surfaces  52  and  54  on its opposite sides. The surfaces  52  and  54  are engaged by concavely surfaced wheels  56 ,  58  and  55 ,  57  rotably mounted to the housing  50  on opposite sides of rail  14 . Housing  50  can be counter balanced by means of a weight located within vertical arm  14  in the same manner in my U.S. Pat. No. 4,683,663, the disclosure of which is incorporated by reference. Housing  50  can, thus, be easily moved up and down along vertical arm  14  and will stay in selected positions thereon.  
         [0019]    Rail  16  is provided with projecting convex surfaces  64  and  66  which provide tracts along its upper and lower surfaces. In the preferred embodiment, the projecting convex surfaces extend centrally along arm  16 . Pairs of concavely surfaced wheels  68 ,  69  and  70 ,  71  engage the upper and lower convex surfaces  64  and  66 , respectively. The mounting device  74  of conventional design secures pointer  18  to the distal end of arm  16 . Mounting device  74  can either be of a stationary type or an extendable-retractable type driven by a servo motor if desired. In the preferred embodiment, rails  12 ,  14  and  16  are all formed of extruded and anodized aluminum. Such shape can accurately be machined to form the projecting concave track surfaces  64 ,  66 , or  36 ,  38 , or  52 ,  54 .  
         [0020]    Referring the FIGS. 3 and 4, it will be seen that the pairs of wheels  40  and  42  are biased into firm engagement with the convex tract members  36  and  38  by means of a biasing spring  80 . Spring  80  is fitted in a slot  82  formed in a plate  15  which supports vertical arm  14 . Spring  80  in its preferred form is a coiled compression spring as shown and is positioned between the lower end of slot  82  and a shaft  84  which supports wheel  42 . A bolt  83  tapped threaded into a central opening in the end of shaft  84  holds the assembly together. A similar shaft  85  holds the wheel  40  in position on plate  15 . Rectangular plates  86  and  88  serve as washers to enclose the opposite sides of the slot  82  and thereby retain the spring  80  in its desired position. By virtue of the forces biasing the wheels  40  and  46  away from each other, the supporting wheels firmly engage the convex rails  36  and  38 . Notably, in the event tilting forces are inadvertently applied against the vertical support  14 , the biasing forces supplied by springs  80  will tend to return the vertical member  14  to its precise vertical orientation. A similar spring  80  is also provided to bias the second pair of wheels  39 ,  41  away from each other so that they are also urged into firm contact with tracks  36  and  38 .  
         [0021]    Similar springs can be provided within slots formed in housing  50  in order to bias the wheels  55  and  57  into engagement with tracks  54 . Also similar springs may be employed to bias the pairs of wheels  68 ,  70  and  69 , 71  into firm engagement with tracks  64  and  66 . It will be understood, that, if desired, the device can be configured so that only one or two of the X, Y or Z axes are provided with biasing forces. However, in order to produce a device having optimum accuracy, all three axes can be provided with biasing forces as shown.  
         [0022]    Also seen in FIG. 1 is a toothed track  34  used for accurate engagement of a toothed wheel connected to encoder  28  in order to achieve accurate position readings for the device. Similar tracks can be provided for engagement of similar wheels connected to encoders  26  and  30 .  
         [0023]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.