Abstract:
A caliper for measuring the size of an object, especially the thickness of an object with non-planar surfaces. After measured, the caliper can be removed from the object without changing the measured value. The caliper includes a scale ruler, a vernier slidably disposed on the scale ruler, a first jaw fixedly connected to the scale ruler and a second jaw pivotally connected to the vernier. In normal state, the second jaw is kept in a position in alignment with and in parallel to the first jaw, whereby the caliper can be used to measure the object in a common manner. After measured, the second jaw is rotated to another position, permitting the caliper to be removed from the measured object.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a vehicle service tool, and more particularly to caliper, which is applicable to, but not limited to, a brake disc for measuring the thickness thereof. 
         [0003]    2. Description of the Related Art 
         [0004]    It is known that a disc brake system includes a brake master cylinder and a brake wheel cylinder. When a driver pedals the brake pedal, via the fluid in the brake master cylinder, the pressure is transmitted to the piston of the brake wheel cylinder on the brake caliper for driving the brake linings to tightly clamp the brake disc. In this case, the rotational speed of the wheel is lowered down under the frictional force against the brake disc so as to achieve the object of braking. 
         [0005]    However, the braking effect is achieved by means of the friction between the brake linings and the brake disc. Therefore, the wear of the contact faces of the brake linings and the brake disc is inevitable. With respect to the brake linings, the wear is relatively obvious and thus it is necessary to periodically replace the brake linings. With respect to the brake disc, the wear is concentrated on a part of the brake disc that contact with brake linings. Referring to  FIG. 3 , the brake disc  50  is only partially worn to form two annular grooves  51  on two faces of the brake disc  50  respectively. It is known that the travel of the brake wheel cylinder is fixed. Therefore, in the case that the brake disc  50  is over-worn and the thickness between the bottom walls of the annular grooves  51  is too thin, the braking performance will be directly affected to threaten the safety in driving. 
         [0006]    According to the conventional technique, the thickness of the brake disc is generally measured by means of a caliper ruler or a micrometer caliper. With respect to the caliper ruler, the measurement jaws can simply attach to a complete plane face so that the caliper ruler can be only used to measure a brand-new brake disc, which has not been used yet. As to a used and worn brake disc with the annular grooves on two faces, the caliper ruler can be hardly used to measure the thickness of the brake disc. With respect to the micrometer caliper, it can be used to measure the thickness of both a brand-new brake disc and a worn brake disc with the annular grooves. However, the measurement value shown by the micrometer caliper only indicates the distance between the shaft and the anvil. As a result, once the distance between the shaft and anvil changes, the shown value will synchronously change. Accordingly, it is necessary for a user to read the brake disc thickness value of the micrometer caliper still connected to the wheel hub in a narrow space and then take off the micrometer from the brake disc. Therefore, it is quite inconvenient to use the micrometer caliper. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore a primary object of the present invention to provide a caliper for measuring the size of an object, especially the thickness of an object with non-planar surfaces. After measured, the caliper can be removed from the object without changing the measured value. 
         [0008]    To achieve the above and other objects, the caliper of the present invention includes: a main body having a scale ruler with a predetermined length, a vernier slidably disposed on the scale ruler and reciprocally displaceable along a length of the scale ruler and a restriction section for locking the vernier on the scale ruler without displacement, one side of the scale ruler being marked with a main scale along the length of the scale ruler, one side of the vernier being marked with a subsidiary scale; and a measurement section including a first jaw fixedly connected to one end of the scale ruler and a second jaw disposed on the vernier in alignment with and in parallel to the first jaw. The distance between the first jaw and the second jaw is variable with the displacement of the vernier along the scale ruler. A first measurement end protrudes from one side of an end of the first jaw, which side is proximal to the second jaw. A second measurement end protrudes from one side of an end of the second jaw, which side is proximal to the first jaw. The caliper is characterized in that the second jaw is pivotally connected to the vernier via a pivot pin and is swingable around the pivot pin between a first position and a second position to change an angle contained between the first and second jaws. The caliper further includes a locating section disposed on the vernier. The locating section has a restriction body movable between a third position and a fourth position. When the restriction body is positioned in the third position, an abutment end of the restriction body is engaged with one side of the second jaw to restrict the second jaw to the first position. When the restriction body is positioned in the fourth position, the abutment end is disengaged from the second jaw, permitting the second jaw to freely swing between the first and second positions. 
         [0009]    The present invention can be best understood through the following description and accompanying drawings, wherein: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective assembled view of a preferred embodiment of the present invention; 
           [0011]      FIG. 2  is a perspective exploded view of the preferred embodiment of the present invention; 
           [0012]      FIG. 3  is a plane view of the preferred embodiment of the present invention, showing that the caliper of the present invention is used to measure the thickness of a brake disc; 
           [0013]      FIG. 4  is a plane view of the preferred embodiment of the present invention, showing that the caliper of the present invention is to be removed from the brake disc after measured; and 
           [0014]      FIG. 5  is a plane view of the preferred embodiment of the present invention, showing that the caliper of the present invention is removed from the brake disc. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Please refer to  FIGS. 1 to 5 . According to a preferred embodiment, the caliper  10  of the present invention includes a main body  20 , a measurement section  30  and a locating section  40 . 
         [0016]    The main body  20  has a scale ruler  21  with a certain length in the form of a rectangular slat and a vernier  22  substantially in the form of a block. The vernier  22  is slidably disposed on the scale ruler  21  and reciprocally linearly displaceable along a length of the scale ruler  21 . A restriction section  23  formed of a bolt is screwed on the vernier  22 . One end of the restriction section  23  can abut against the scale ruler  21  to lock the vernier  22  on the scale ruler  21  without displacement. One side of the scale ruler  21  is marked with a main scale  24 , while one side of the vernier  22  is marked with a subsidiary scale  25  for showing the size data of a measured article. The other side of the scale ruler  21  is recessed to form a slide channel  26  extending along the length of the scale ruler  21 . 
         [0017]    The measurement section  30  includes a first jaw  31  in the form of an elongated bar and a second jaw  33  also in the form of an elongated bar. One end of the first jaw  31  is indirectly fixedly connected to one end of the scale ruler  21  via a fixing seat  32 . The length of the first jaw  31  is normal to the length of the scale ruler  21 . One end of the second jaw  33  is pivotally connected to the vernier  22  in alignment with and in parallel to the first jaw  31 . A distance between the first jaw  31  and the second jaw  33  is variable with the sliding movement of the vernier  22 . In addition, the second jaw  33  is swingable around a pivot pin between a first position and a second position to change an angle contained between the first and second jaws  31 ,  33 . To speak more specifically, when the second jaw  33  is positioned in the first position, the second jaw  33  is in parallel to the first jaw  31 . When the second jay  33  is positioned in the second position, the lengths of the first and second jaws  31 ,  33  contain an acute angle. An arched first measurement end  34  protrudes from one side of the other end of the first jaw  31 , which side is proximal to the second jaw  33 . An arched second measurement end  35  protrudes from one side of the other end of the second jaw  33 , which side is proximal to the first jaw  31 . The first and second measurement ends  34 ,  35  are opposite to each other. A measurement rod  36  with a certain length is slidably inlaid in the slide channel  26 . One end of the measurement rod  36  is fixedly connected to the vernier  22 , whereby the measurement rod  36  is displaceable relative to the scale ruler  21  in parallel to the length of the scale ruler  21  along with the movement of the vernier  22  so as to extend the other end of the measurement rod  36  from the other end of the scale ruler  21 . 
         [0018]    To speak more specifically, the second jaw  33  has an elongated jaw body  331 . One end of the jaw body  331  is pivotally connected to the vernier  22 . A part of an end face of the end of the jaw body  331  is a locating plane face  332 . When the second jaw  33  is positioned in the first position, the locating plane face  332  is attached to an adjacent plane face of the vernier  22 . Another part of the end face of the end of the jaw body  331  is a rotary arched face  333  in adjacency to the locating plane face  332 . The pivot pin pivotally connected between the jaw body  331  and the vernier  22  is positioned at a curvature center of the rotary arched face  333 . Accordingly, when the second jaw  33  is rotated between the first and second positions, the rotary arched face  333  can abut against the vernier  22  in a rolling manner to keep the rotation stable. 
         [0019]    The locating section  40  is disposed on the vernier  22  for elastically normally restricting the second jaw  33  to the first position. The locating section  40  has a restriction body  41  in the form of an elongated plate. The restriction body  41  is pivotally disposed on the vernier  22  and is rotatable around a pivot pin between a third position and a fourth position. An elastic member  42  formed of a spring is sandwiched between the one end of the restriction body  41  and the vernier  22  for providing an elastic force to keep the restriction body  41  in the third position. An engagement notch  43  with a certain depth is formed on one side of the second jaw  33 . The other end of the restriction body  41  is an abutment end  411 , which can be correspondingly engaged in the engagement notch  43 . Accordingly, when the restriction body  41  is positioned in the third position, the abutment end  411  is engaged in the engagement notch  43  and the elastic member  42  provides an elastic force to keep the restriction body  41  in the third position, whereby the second jaw  33  is restricted to the first position. When an external force is applied to the restriction body  41  to offset the elastic force provided by the elastic member  42  and pivotally rotate the restriction body  41  from the third position to the fourth position, the second jaw  33  is released from the restriction and permitted to freely swing between the first and second positions. 
         [0020]    According to the above arrangement, the caliper  10  can be used to measure the thickness of a used brake disk  50  worn with annular grooves. Referring to  FIGS. 3 to 5 , in a common measurement method of a conventional caliper, a user can hold a brake disc  50  between the first and second jaws  31 ,  33  with the opposite first and second measurement ends  34 ,  35  extending into the annular grooves  51  of the worn brake disc  50  in abutment with the bottom walls thereof. In this case, the data shown by the main scale  24  and the subsidiary scale  25  can indicate the value of the thickness of the worn brake disc. 
         [0021]    At this time, in order to facilitate the user&#39;s reading the data shown by the main scale  24  and the subsidiary scale  25 , the vernier  22  is first locked on the scale ruler  21  with the restriction section  23  so as to keep that the measured value unchanged. Then, the user can conveniently manually apply a force to the restriction body  41  for pressing and rotating the restriction body  41  from the third position to the fourth position. Under such circumstance, the second jaw  22  can be freely swung. At this time, the user can apply a force to the second jaw  22  to rotate the second jaw  22  from the first position to the second position to enlarge the angle a contained between the first and second jaws  21 ,  22  and thus enlarge the distance D between the first and second measurement ends  34 ,  35 . In this case, the caliper  10  can be easily removed from the measured brake disc  50 . Accordingly, the user can conveniently read the value shown by the main scale  24  and the subsidiary scale  25 . 
         [0022]    The caliper  10  enables a user to measure the thickness of the brake disc and read the measured value at different times. That is, the user can first measure the thickness of the object in a narrow space and then read the measure value in a wider place. In comparison with the conventional technique, the use of the caliper is much more facilitated. 
         [0023]    In addition, in the field of vehicle service, the measurement rod  36  serves as a measurement tool for measuring such as the depth of tire stripes. Accordingly, the caliper  10  can be more widely applied in the field of vehicle service. 
         [0024]    Furthermore, it should be noted that in the above embodiment, the restriction body  41  of the locating section  40  is pivotally connected to the vernier  22 . In practice, the manner in which the restriction body  41  is connected to the vernier  22  is not limited to the above embodiment. For example, alternatively, the restriction body  41  can be slidably connected to the vernier  22  and movable between the third and fourth positions. This arrangement can achieve the same effect as the first embodiment. 
         [0025]    The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention.