Abstract:
A measuring device, includes a guiding rail, a sliding unit levitatedly slidably engaged with the guiding rail, and a measuring unit fixed to the sliding unit and comprising at least one clock gauge mounted thereto.

Description:
BACKGROUND  
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to measuring devices, especially to a measuring device for detecting parallelism. 
         [0003]    2. Description of Related Art 
         [0004]    For mechanical equipment such as used for machining, parallelism of some of its parts may need to be frequently adjusted in order to ensure quality performance. For example, a high-precision machine includes a main body having a high-precision threaded shaft, a high-precision slideway, and a fiducial line. It is required that parallelism between the threaded shaft and the fiducial line, and parallelism between the slideway and the fiducial line must be within 0.005 mm, thus frequent checks and adjustments must be made. 
         [0005]    Typically, the threaded shaft and slideway of the main body are measured in three-dimensions by a measuring device, then adjusted with other tools according to the result. However, the main body must first be disassembled from the machine then placed in the measuring device, which is inconvenient, especially when the machine is a heavy one. Furthermore, the cost of the measuring device is high. 
         [0006]    What is desired, therefore, is a more efficient cost-effective measuring device. 
       SUMMARY 
       [0007]    An exemplary measuring device includes a guiding rail, a sliding unit levitatedly slidably engaged with the guiding rail, and a measuring unit fixed to the sliding unit and comprising at least one clock gauge mounted thereto. 
         [0008]    Other advantages and novel features will become more apparent from the following detailed description of embodiment when taken in conjunction with the accompanying drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is an exploded, isometric view of a measuring device in accordance with an embodiment of the present invention together with an object to be measured; and 
           [0010]      FIG. 2  is an assembled, isometric view of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Referring to  FIGS. 1 and 2 , a to-be-measured device  1  includes an adjustable threaded shaft  3  and two adjustable slideways  5 . Tolerances of parallelism of the threaded shaft  3  and the adjustable slideways  5  are 0.005 mm. A measuring device  10  in accordance with an embodiment of the present invention includes a guiding rail  20 , a sliding unit  30  slidably mounted to the guiding rail  20 , and a measuring unit  40  fixed to the sliding unit  30 . 
         [0012]    Because high measuring accuracy is required, high linearity of the guiding rail  20  is required, and linearity of a working face of the guiding rail  20  is limited to be within 0.003 mm. The guiding rail  20  is made of materials with high hardness and chemically inert property, wherein the high hardness prevents the guiding rail  20  from distorting in use, and the chemically inert property prevents surface accuracy of the guiding rail  20  from being reduced because of damage caused by chemical reactions, such as oxidation. The material of the guiding rail  20  can be marble, granite and so on. 
         [0013]    The sliding unit  30  is slidingly engaged on the guiding rail  20  with little or no friction therebetween to ensure measuring accuracy. Economically, in the present embodiment, the sliding unit  30  is an air bearing, but in other embodiments the frictionless engagement may be accomplished via known magnetic levitation, or electrostatic levitation with metal embedded in the guiding rail  20  for generating static charges or electromagnetic field. 
         [0014]    The measuring unit  40  includes a fixing bracket  41  secured to the sliding unit  30  via a plurality of fasteners, and a plurality of probes mounted the fixing bracket  41 . The probes are, or are connected to gauges with indicating means such as clock gauges, thus enabling an operator to detect and determine amount of deflection of the probes. In the embodiment, two clock gauges  43  are respectively mounted to ends of the fixing bracket  41 , and a clock gauge group  45  including a plurality of clock gauges is mounted to a middle portion of the fixing bracket  41 . 
         [0015]    In use, two fiducial blocks  7  are set on the to-be-measured device  1  beforehand. A sidewall of the guiding rail  20  of the measuring device  10  is propped up to the two fiducial blocks  7 , and then the guiding rail  20  is secured to the to-be-measured device  1 . Thus, when the sliding unit  30  slides along the guiding rail  20 , it is considered that the sliding unit  30  slides along a fiducial line. Tolerances of parallelism of the threaded shaft  3  and the slideways  5  of the to-be-measured device  1  relative to the fiducial line must be limited within 0.005 mm respectively. The clock gauges  43  are respectively used to measure the slideways  5 . The clock gauge group  45  measures the threaded shaft  3  from different directions. When the sliding unit  30  is slid along the guiding rail  20 , probes of all the clock gauges respectively move along the slideways  5  and the threaded shaft  3  of the to-be-measured device  1  respectively, such that detecting information is gotten from the clock gauges. Then the slideways  5  and the threaded shaft  3  can be adjusted according to the detecting information to meet the requirement of parallelism. 
         [0016]    Furthermore, it can be understood that the present measuring device  10  can also be used to detect accuracy of linearity, surface roughness, and so on. 
         [0017]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and they will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.