BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a capacitive sensor core, and in particular to a capacitive sensor core with flexible hinge. The present invention also relates to an angular displacement sensor, an adjustable digital display caliper, a lever gauge and a micrometer which have the capacitive sensor core with flexible hinge. 
         [0002]    In the mechanical manufacturing, digital display measuring devices are normally used to measure the precise angle, horizontal degree and obliquity. The core component of these devices may consist of mechanisms such as mechanical levers, gears, or sleeves, and the mechanism converts a measurement to a relative displacement between the main grid plate and the minor grid plate. However, since manufacturing errors, clearance of assembling and transmission of the levers, gears or sleeves exist, the clearance between the transmission components such as levers, gears and sleeves can not be removed even if the fit dimension is small and the assembling method is precise. In the precise measurement, even a small clearance may affect the measuring result greatly. 
       SUMMARY OF THE INVENTION 
       [0003]    Having outlined the state of the prior art and its attendant shortages, it is an object of the present invention to provide a capacitive sensor core with flexible hinge, which avoids the clearance between the transmission components such as levers, gears and sleeves. 
         [0004]    The above object of the present invention is achieved by the following technical solutions: 
         [0005]    A capacitive sensor core with flexible hinge, comprises: a main grid plate; a minor grid plate; and a mechanism for converting a measurement to a relative displacement between the main grid plate and the minor grid plate; wherein the mechanism comprises a stationary arm and an active arm, the minor grid plate and the main grid plate are respectively mounted on a driven portion of the active arm and the stationary arm, the stationary arm is connected to the active arm by a flexible hinge; the flexible hinge comprises at least two supporting spring leaves, each supporting spring leaf is connected to the stationary arm at one end, and the other end of the supporting spring leaf is connected to the active arm; each supporting spring leaf is vertical to the main grid plate and the minor grid plate. 
         [0006]    The flexible hinge between the active arm and the stationary arm has two possible structures: 
         [0007]    1. The flexible hinge between the active arm and the stationary arm comprises the intersected supporting spring leaves, the active arm is rotated around the intersection of the supporting spring leaves as the rotation center with respect to the stationary arm, the main grid plate mounted on the stationary arm and the minor grid plate mounted on the driven portion of the active arm are the main grid plate and the minor grid plate of a capacitive angular movement sensor. 
         [0008]    Preferably, the hinged portions of the active arm and the stationary arm are parallel with respect to each other in transverse direction, the minor grid plate on the driven portion of the active arm and the main grid plate on the stationary arm are parallel with respect to each other in longitudinal direction above the hinged portions of the active arm and the stationary arm; straight slots in diagonal direction are provided on the upper front portion or lower front portion of the hinged portion of the stationary arm and on the lower front portion or front portion of the active arm, and these two slots are vertical to the main grid plate and the minor grid plate; straight slots in diagonal direction are also provided on the lower back portion or upper back portion of the hinged portion of the stationary arm and on the upper back portion or lower back portion of the hinged portion of the active arm, and these two slots are also vertical to the main grid plate and the minor grid plate; the two ends of a supporting spring leaf are inserted in the straight slot on the upper front portion or lower front portion of the hinged portion of the stationary arm and the straight slot on the lower front portion or upper front portion of the hinged portion of the active arm respectively; the two ends of another supporting spring leaf are inserted in the straight slot on the upper back portion or lower back portion of the hinged portion of the stationary arm and the straight slot on the lower back portion or upper back portion of the hinged portion of the active arm respectively; a line passing through the intersection point of the supporting spring leaves and vertical to the main sensor grid plate and minor sensor grid plate is the virtual axis of rotation of the active arm with respect to the stationary arm. Comparing with the rotation pivot of mechanical lever, the rotation center of flexible hinge has no fit clearance, and the moving of the driving end completely synchronize with the moving of the driven portion. 
         [0009]    Preferably, the upper and lower ends of the hinged portion of the active arm are both mounted with a horizontal pilot pin, these two horizontal pilot pins are parallel and located in a longitudinal plane, and correspondingly pin holes for receiving the pilot pins are provided on the hinged portion of the stationary arm. Horizontal dynamometric springs are connected between the stationary arm and the active arm at positions above and below the two pilot pins. 
         [0010]    Embodiments of measuring device utilizing the capacitive angular movement sensor core with flexible hinge are as follows: 
         [0011]    (1)A capacitive angular movement sensor, comprises:
       a capacitive sensor core with flexible hinge, comprising a main grid plate, a minor grid plate and a mechanism for converting a measurement to a relative displacement between the main grid plate and the minor grid plate;   wherein the mechanism a stationary device and an active device, the minor grid plate and the main grid plate are respectively mounted on a driven portion of the active device and the stationary device, the stationary device is connected to the active device by a flexible hinge; the active device is mounted on the stationary device via the flexible hinge that is used as supporting device to form a lever-like mechanism, the active device is rotated around the rotation center of the flexible hinge as the rotation center of the lever-like mechanism with respect to the stationary device, the main grid plate mounted on the stationary device and the minor grid plate mounted on the driven portion of the active device are the main grid plate and the minor grid plate of a capacitive angular movement sensor, the flexible hinge comprises at least two supporting spring leaves, each supporting spring leaf is connected to the stationary device at one end, and the other end of the supporting spring leaf is connected to the active device; each supporting spring leaf is vertical to the main grid plate and the minor grid plate; the flexible hinge between the active arm and the stationary arm comprises the intersected supporting spring leaves, the active arm is rotated around the intersection of the supporting spring leaves as the rotation center with respect to the stationary arm, the main grid plate mounted on the stationary arm and the minor grid plate mounted on the driven portion of the active arm are the main grid plate and the minor grid plate of a capacitive angular movement sensor.       
 
         [0014]    Preferably, the hinged portions of the active arm and the stationary arm are parallel with respect to each other in transverse direction, the minor grid plate on the driven portion of the active arm and the main grid plate on the stationary arm are parallel with respect to each other in longitudinal direction above the hinged portions of the active arm and the stationary arm; straight slots in diagonal direction are provided on the upper front portion or lower front portion of the hinged portion of the stationary arm and on the lower front portion or upper front portion of the active arm, and these two slots are vertical to the main grid plate and the minor grid plate; straight slots in diagonal direction are also provided on the lower back portion or upper back portion of the hinged portion of the stationary arm and on the upper back portion or lower back portion of the hinged portion of the active arm, and these two slots are also vertical to the main grid plate and the minor grid plate; the two ends of a supporting spring leaf are inserted in the straight slot on the upper front portion or lower front portion of the hinged portion of the stationary arm and the straight slot on the lower front portion or upper front portion of the hinged portion of the active arm respectively; the two ends of another supporting spring leaf are inserted in the straight slot on the upper back portion or lower back portion of the hinged portion of the stationary arm and the straight slot on the lower back portion or upper back portion of the hinged portion of the active arm respectively; a line passing through the intersection point of the supporting spring leaves and vertical to the main sensor grid plate and minor sensor grid plate is the virtual axis of rotation of the active arm with respect to the stationary arm; a measuring arm inclined towards the stationary arm is connected to the lower portion of the hinged portion of the active arm, a horizontal measuring pin is located at the end of the measuring arm, the hinged portion of the stationary arm is connected with a vertical supporting arm, a cam is mounted on a cam shaft on the end of the vertical supporting arm, the cam shaft is parallel to the measuring pin, and the measuring pin leans on the surface of the cam. 
         [0015]    Preferably, the upper and lower ends of the hinged portion of the active arm are both mounted with a horizontal pilot pin, these two horizontal pilot pins are parallel and located in a longitudinal plane, and correspondingly pin holes for receiving the pilot pins  8  are provided on the hinged portion of the stationary arm. 
         [0016]    Preferably, horizontal dynamometric springs are connected between the stationary arm and the active arm at positions above and below the two pilot pins. 
         [0017]    (2)An adjustable digital caliper, comprises:
       a capacitive sensor core with flexible hinge, comprising a main grid plate, a minor grid plate and a mechanism for converting a measurement to a relative movement between the main grid plate and the minor grid plate;   wherein the mechanism comprises a stationary arm and an active arm, the minor grid plate and the main grid plate are respectively mounted on a driven portion of the active arm and the stationary arm, the stationary arm is connected to the active arm by a flexible hinge; the flexible hinge comprises at least two supporting spring leaves, each supporting spring leaf is connected to the stationary arm at one end, and the other end of the supporting spring leaf is connected to the active arm; each supporting spring leaf is vertical to the main grid plate and the minor grid plate; the flexible hinge between the active arm and the stationary arm comprises the intersected supporting spring leaves, the active arm is rotated around the intersection of the supporting spring leaves as the rotation center with respect to the stationary arm, the main grid plate mounted on the stationary arm and the minor grid plate mounted on the driven portion of the active arm are the main grid plate and the minor grid plate of a capacitive angular movement sensor..       
 
         [0020]    Preferably, the hinged portions of the active arm and the stationary arm are parallel with respect to each other in transverse direction, the minor grid plate on the driven portion of the active arm and the main grid plate on the stationary arm are parallel with respect to each other in longitudinal direction above the hinged portions of the active arm and the stationary arm; straight slots in diagonal direction are provided on the upper front portion or lower front portion of the hinged portion of the stationary arm and on the lower front portion or upper front portion of the active arm, and these two slots are vertical to the main grid plate and the minor grid plate; straight slots in diagonal direction are also provided on the lower back portion or upper back portion of the hinged portion of the stationary arm and on the upper back portion or lower back portion of the hinged portion of the active arm, and these two slots are also vertical to the main grid plate and the minor grid plate; the two ends of a supporting spring leaf are inserted in the straight slot on the upper front portion or lower front portion of the hinged portion of the stationary arm and the straight slot on the lower front portion or upper front portion of the hinged portion of the active arm respectively; the two ends of another supporting spring leaf are inserted in the straight slot on the upper back portion or lower back portion of the hinged portion of the stationary arm and the straight slot on the lower back portion or upper back portion of the hinged portion of the active arm respectively; a line passing through the intersection point of the supporting spring leaves and vertical to the main sensor grid plate and minor sensor grid plate is the virtual axis of rotation of the active arm with respect to the stationary arm; the lower portion of the hinged portion of the active arm is connected with a vertical active measuring arm, an open-bottom frame is arranged on the other side of the hinged portion of the stationary arm, two gliding guide bars in parallel are provided in the rectangular frame, pilot holes for respectively receiving the gliding guide bars are provided on the upper end of the vertical stationary measuring arm, a bolt for adjusting measuring range is cooperated with the inner thread on the upper end of the stationary measuring arm, the bolt is of self-locking function, the measuring surface on the lower end of the stationary measuring arm faces and is parallel to the measuring surface on the lower end of the active measuring arm and is vertical to the main grid plate and the minor grid plate. 
         [0021]    Preferably, the upper end of the hinged portion and the lower end of the stationary arm are provided with at least one horizontal pilot pin, the pilot pin is inserted into a corresponding pin hole on the active arm. 
         [0022]    Preferably, a dynamometric spring is provided horizontally above the pilot pin and below the main grid plate, the dynamometric spring leans on the active arm. 
         [0023]    Preferably, the active arm is further mounted horizontally with a lifting screw above the dynamometric spring and below the minor grid plate. 
         [0024]    Preferably, the measuring surface of the active measuring arm is further provided with a cylindrical measuring head that is capable to swing slightly. 
         [0025]    (3)A lever gauge, comprises:
       a capacitive sensor core with flexible hinge, comprising a main grid plate, a minor grid plate and a mechanism for converting a measurement to a relative movement between the main grid plate and the minor grid plate;   wherein the mechanism comprises a stationary device and an active device, the minor grid plate and the main grid plate are respectively mounted on a driven portion of the active device and the stationary device, the stationary device is connected to the active device by a flexible hinge; the stationary device is a stationary frame, the active device is an active arm, the stationary frame is disposed vertically, the active arm is disposed vertically inside the stationary frame, the minor grid plate mounted on the driven portion of the active arm and the main grid plate mounted in the stationary frame are parallel in longitudinal direction; a seat for the supporting spring leaf is provided on the lower end of the active arm outside the stationary frame; an inclined straight slot is provided on the bottom of the stationary frame on the left side of the opening, and an inclined straight slot is provided on the top left portion of the seat, and these two straight slots are vertical to the main grid plate and the minor grid plate; an inclined straight slot is provided on the bottom of the stationary frame on the right side of the opening, and an inclined straight slot is provided on the top right portion of the seat, and these two straight slots are vertical to the main grid plate and the minor grid plate; the two ends of the two supporting spring leaves are respectively inserted in the straight slots on the stationary frame and the straight slots on the seat, the obliquity of the two supporting spring leaves which intersect inside the seat is identical, and the intersecting line of the two supporting spring leaves is vertical to the main grid plate and the minor grid plate and is the virtual rotation axis of the active arm with respect to the stationary frame; the seat is further hinged with a base for the measuring head, the bottom of the base is connected to the measuring stick having a spherical head.       
 
         [0028]    Preferably, the base is hinged to the seat. An orientation wheel for the active arm is mounted in the stationary frame, the orientation wheel is of a groove for movably receiving the active arm, and the direction of the groove on the orientation wheel is the same as the swinging direction of the active arm. 
         [0029]    Preferably, a pressing plate that is rotated around a shaft is further mounted inside the stationary frame, a pin on the upper end of the pressing plate and a pin on the lower end of the pressing plate lean on the two sides of the active arm respectively, an end of a measuring spring is connected to the pin on one side of the active arm, and the other end of the measuring spring is connected to the inner surface of the stationary frame on the other side of the active arm. Positioning cams at an upper left position and another lower right position are arranged respectively on the two sides of the longitudinal portion of the active arm, and contacted with the outer edge of the pressing plate. 
         [0030]    2. The flexible hinge between the active arm and the stationary arm comprises the supporting spring leaves that are symmetrically arranged, the active arm performs linear movement with respect to the stationary arm according to the symmetry central line of the supporting spring leaves, the main grid plate mounted on the stationary arm and the minor grid plate mounted on the driven portion of the active arm are the main grid plate and the minor grid plate of a linear displacement capacitive sensor. 
         [0031]    Measuring device utilizing the linear displacement capacitive sensor core with flexible hinge may be as follows: 
         [0032]    A micrometer, comprises:
       a capacitive sensor core with flexible hinge, comprising a main grid plate, a minor grid plate and a mechanism for converting a measurement to a relative movement between the main grid plate and the minor grid plate;   wherein the mechanism comprises a stationary device and an active device, the minor grid plate and the main grid plate are respectively mounted on a driven portion of the active device and the stationary device, the stationary device is connected to the active device by a flexible hinge; the flexible hinge comprises at least two supporting spring leaves, each supporting spring leaf is connected to the stationary device at one end, and the other end of the supporting spring leaf is connected to the active device; each supporting spring leaf is vertical to the main grid plate and the minor grid plate; the active device performs a straight-line reciprocating movement up and down with respect to the stationary device, the main grid plate and the minor grid plate respectively mounted on the stationary device and the active device are the main grid plate and the minor grid plate of a linear displacement capacitive sensor.       
 
         [0035]    Preferably, the active device is connected to the stationary device via the flexible hinge, and performs linear movement with respect to the stationary device according to the symmetry central line of the flexible hinge. 
         [0036]    Preferably, the supporting spring leaf is of an angled shape or arc shape, and located symmetrically on the two sides of the active device. 
         [0037]    Preferably, the stationary device and the active device are a circular casing and an active arm respectively, the main grid plate is mounted in the center of the circular casing, the bottom of the circular casing behind the main grid plate is mounted with a vertical guide sleeve, the pilot pin is received in the guide sleeve and the two ends of the pilot pin are exposed out of the guide sleeve, the active device is connected to the stationary device via the flexible hinge, the pilot pin and the guide sleeve form a guide device which performs linear movement with respect to the circular casing according to the symmetry central line of the flexible hinge, the front surface of the main grid plate is mounted with the vertical active arm, a minor grid plate  4  is mounted on a surface of the active arm facing the main grid plate, the upper end of the active arm is connected to the upper end of the pilot pin via transverse connecting element; a straight slot inclined towards the bottom left side is provided on the left side of the body below the main grid plate, a straight slot inclined towards the bottom right side from outside to inside is provided on the right side of the body below the main grid plate; a straight slot inclined towards the top right side is provided on the left side of the connecting element, a straight slot inclined towards the top left side is provided on the right side of the connecting piece, all the straight slots are vertical to the main grid plate and the minor grid plate; angled supporting spring leaves are provided on the two sides of the main grid plate, the two ends of each supporting spring leaf are inserted to the straight slots on the connecting element and the main grid plate on the same side, the two supporting spring leaves form a rhombus, the lower end of the active arm is connected vertically with a measuring stick and the measuring stick extends through a mounting hole on the bottom of the circular casing and is exposed out of the circular casing, and the measuring stick has a tapered measuring head on the end. 
         [0038]    Preferably, each supporting spring leaf is broken at the folded position where a left sliding piece and a right sliding piece are arranged, the supporting spring leaves are received in the straight slots on the left and right sliding pieces. 
         [0039]    Preferably, a lower sleeve is mounted on the measuring stick; the upper end of the lower sleeve is mounted in the mounting hole on the bottom of the circular casing. 
         [0040]    In the capacitive sensor core with flexible hinge, the angular displacement sensor, the adjustable digital display caliper, the lever gauge and the micrometer, two pairs of the main grid plate and the minor grid plate are mounted on the stationary arm and the active arm, one pair is the main grid plate and the minor grid plate of a calibration sensor, and ½ pitch of the calibration sensor is the measuring range, and the other pair is the main grid plate and the minor grid plate of a measuring sensor. 
         [0041]    Advantages of the present invention are as follows: 
         [0042]    1. the supporting point of the lever is a flexible element, which ensures no clearance, no friction, free lubricant, high precision and high stability of movement transmission, and accidental error will not occur in the measuring system; 
         [0043]    2. the main grid pate and the minor grid plate of the capacitive sensor are mounted on the active arm and the stationary arm, which is of a very simple structure; 
         [0044]    3. the distinguish rate and measuring precision of the sensor may be improved conveniently by changing the lever ratio of the lever; 
         [0045]    4. the output data of the sensor may be transmitted to the computer which may correct the measuring error and set the functions conveniently. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0046]      FIG. 1A  is a schematic view of a capacitive sensor core with flexible hinge according to an embodiment of the present invention; 
           [0047]      FIG. 1B  is a front view of the capacitive sensor shown in  FIG. 1A ; 
           [0048]      FIG. 2A  is a schematic view of a capacitive angular movement sensor with flexible hinge according to an embodiment of the present invention; 
           [0049]      FIG. 2B  is a front view of the sensor shown in  FIG. 2B ; 
           [0050]      FIG. 3A  is a schematic view of an adjustable digital caliper according to an embodiment of the present invention; 
           [0051]      FIG. 3B  is a front view of the adjustable digital caliper shown in  FIG. 3A ; 
           [0052]      FIG. 3C  is a left view of the adjustable digital caliper shown in  FIG. 3B ; 
           [0053]      FIG. 4A  is a schematic view of a lever gauge according to an embodiment of the present invention; 
           [0054]      FIG. 4B  is a front view of the lever gauge shown in  FIG. 4A ; 
           [0055]      FIG. 4C  is a sectional view of the lever gauge shown in  FIG. 4B  taking along the line D-D; 
           [0056]      FIG. 5A  is a schematic view of a micrometer according to an embodiment of the present invention; 
           [0057]      FIG. 5B  is a front view of the micrometer shown in  FIG. 4A ; 
           [0058]      FIG. 5C  is a sectional view of the micrometer shown in  FIG. 5B  taking along the line E-E. 
       
    
    
       [0059]      1 : stationary arm;  1 - 1 : stationary frame;  1 - 2 : circular casing;  2 : active arm;  3 : main grid plate;  4  minor grid plate;  5  dynamometric spring;  6  gliding guide bar;  7  supporting spring leaf;  8  pilot pin;  9  measuring pin;  10  lifting screw;  11  bolt for adjusting measuring range;  12  cam;  13  cylindrical measuring head;  14  seat for the supporting spring leaf;  15  base for the measuring head;  16  measuring stick;  17  stationary measuring arm;  18  orientation wheel for the active arm;  19  pressing plate;  20  pin;  21  positioning cam;  22  guide pin;  23  sliding piece;  24  lower sleeve. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0060]    A first embodiment of a capacitive sensor core with flexible hinge is shown in  FIG. 1 . In the capacitive sensor core with flexible hinge, the stationary device is a stationary arm  1 , and the active device is an active arm  2 . The stationary arm  1  comprises a hinged portion on the horizontal position and a driven portion on the vertical position. The driven portion is connected to the rear portion of the top of the hinged portion by a vertical rod. The active arm  2  comprises a hinged portion on the horizontal position and a driven portion on the vertical position. The driven portion is connected to the front portion of the top of the hinged portion. During the assembling of the capacitive sensor core, the hinged portion of the stationary arm is mounted oppositely with respect to the hinged portion of the active arm, while the driven portion of the stationary arm is also mounted oppositely with respect to the driven portion of the active arm. The driven portion of the stationary arm is mounted with a main grid plate  3 , and the driven portion of the active arm is mounted with a minor grid plate  4 . The lower portion of the front of the hinged portion of the active arm is connected to the measuring stick that is oblique towards the hinged portion of the stationary arm, and the measuring stick is provided with a measuring pin  9  at its end on the horizontal position. 
         [0061]    The hinged portion of the stationary arm and the corresponding hinged portion of the active arm are connected with each other by intersected supporting spring leaves  7 , the detailed connection way of which is as follows: 
         [0062]    A straight slot that is inclined towards the top left side from outside to inside is provided on the top of the front of the hinged portion of the stationary arm. The straight slot is vertical to the main grid plate  3  and the minor grid plate  4 . A straight slot that is inclined towards the bottom right side from outside to inside is provided on the bottom of the front of the hinged portion of the active arm, this straight slot is also vertical to the main grid plate  3  and the minor grid plate  4 , and the straight slot on the hinged portion of the stationary arm and the straight slot on the hinged portion of the active arm are on the same diagonal line. The two ends of a supporting spring leaf are inserted in the above two straight slots respectively which ensure the supporting spring leaf  7  to be vertical to the main grid plate  3  and the minor grid plate  4 . 
         [0063]    A straight slot that is inclined towards the bottom left side from outside to inside is provided on the bottom of the back of the hinged portion of the stationary arm, and the straight slot is vertical to the main grid plate  3  and the minor grid plate  4 . A straight slot that is inclined towards the top right side from outside to inside is provided on the top of the back of the hinged portion of the active arm, and this straight slot is also vertical to the main grid plate  3  and the minor grid plate  4 , and the straight slot on the hinged portion of the stationary arm and the straight slot on the hinged portion of the active arm are on the same diagonal line. The two ends of another supporting spring leaf are inserted in the above two straight slots respectively which ensure the supporting spring leaf  7  to be vertical to the main grid plate  3  and the minor grid plate  4 . 
         [0064]    The supporting spring leaves  7  which are on two different planes are intersectingly connected to the stationary arm  1  and the active arm  2  and form flexible hinge levers, and a line passing through the intersection point of the supporting spring leaves  7  and vertical to the main sensor grid plate  3  and minor sensor grid plate  4  is the virtual axis of rotation of the active arm  2  with respect to the stationary arm  1 . 
         [0065]    The upper and lower ends of the middle portion of the hinged portion of the active arm are both mounted with a horizontal pilot pin  8 . These two horizontal pilot pins  8  are located in a longitudinal plane, and correspondingly pin holes for receiving the pilot pins  8  are provided on the hinged portion of the stationary arm. A horizontal dynamometric spring  5  is connected between the hinged portion of the stationary arm and the vertical rod on the top of the hinged portion of the active arm. Similarly, a horizontal dynamometric spring  5  is connected between the hinged portion of the stationary arm and the vertical rod on the bottom of the hinged portion of the active arm. 
         [0066]    As a second embodiment, a capacitive angular movement sensor with flexible hinge utilizes the capacitive sensor core with flexible hinge shown in  FIG. 1 . Referring to  FIG. 2 , in the capacitive angular movement sensor, a cam  12  is mounted on the capacitive sensor core with flexible hinge as shown in  FIG. 1 , wherein the vertical rod of the hinged portion of the stationary arm is extended, and a pin that is at the same horizontal line as the measuring pin  9  on the measuring stick of the hinged portion of the active arm is provided horizontally on the end of the vertical rod. The cam  12  is mounted on the pin on the end of the vertical rod, and the measuring pin  9  leans on the surface of the cam  12 . 
         [0067]    A third embodiment is an adjustable digital caliper which also utilizes the capacitive sensor core with flexible hinge as shown in  FIG. 1 . As shown in  FIG. 3 , the stationary device and the active device are a bar-like stationary arm  1  and a bar-like active arm  2  respectively. The stationary arm  1  comprises a hinged portion on the horizontal position and a driven portion on the vertical position. The driven portion of the stationary arm is connected to the front portion of the top of the hinged portion of the stationary arm. The active arm  2  comprises a hinged portion on the horizontal position and a driven portion on the vertical position. The driven portion of the active arm is connected to the back portion of the top of the hinged portion of the active arm. During the assembling of the adjustable digital caliper, the hinged portion of the stationary arm is mounted oppositely with respect to the hinged portion of the active arm, while the driven portion of the stationary arm is also mounted oppositely with respect to the driven portion of the active arm. The driven portion of the stationary arm is mounted with a main grid plate  3 , and the driven portion of the active arm is mounted with a minor grid plate  4 . The lower portion of the hinged portion of the active arm is connected with a vertical active measuring arm. 
         [0068]    The hinged portion of the stationary arm and the corresponding hinged portion of the active arm are connected with each other by intersected supporting spring leaves  7 , the detailed connection way of which is as follows: 
         [0069]    A straight slot that is inclined towards the bottom left side from outside to inside is provided on the lower front portion of the hinged portion of the stationary arm, and this straight slot is vertical to the main grid plate  3  and the minor grid plate  4 . A straight slot that is inclined towards the top right side from outside to inside is provided on the top of the front of the hinged portion of the active arm, this straight slot is also vertical to the main grid plate  3  and the minor grid plate  4 . These two straight slots are on the same diagonal line. The two ends of a supporting spring leaf  7  are inserted in the above two straight slots respectively, and the supporting spring leaf  7  is vertical to the main grid plate  3  and the minor grid plate  4  after assembling. 
         [0070]    A straight slot that is inclined towards the top left side from outside to inside is provided on the top of the back of the hinged portion of the stationary arm  1 , and the straight slot is vertical to the main grid plate  3  and the minor grid plate  4 . A straight slot that is inclined towards the bottom right side from outside to inside is provided on the lower portion of the back of the hinged portion of the active arm  2 , and this straight slot is also vertical to the main grid plate  3  and the minor grid plate  4 . These two straight slots are on the same diagonal line. The two ends of another supporting spring leaf  7  are inserted in the above two straight slots respectively, and the supporting spring leaf  7  is vertical to the main grid plate  3  and the minor grid plate  4  after assembling. 
         [0071]    The supporting spring leaves  7  which are on two different planes are intersectingly connected to the stationary arm  1  and the active arm  2  respectively and form flexible hinge levers, and a line passing through the intersection point of the supporting spring leaves  7  and vertical to the main sensor grid plate  3  and minor sensor grid plate  4  is the virtual axis of rotation of the active arm  2  with respect to the stationary arm  1 . 
         [0072]    An L-shaped bracket is connected to the outer side of the hinged portion of the stationary arm, and an open-bottom rectangular frame is formed by the L-shaped bracket and the hinged portion of the stationary arm. Two gliding guide bars  6  in parallel are provided in the rectangular frame. Pilot holes for respectively receiving the gliding guide bars  6  are provided on the upper end of the vertical stationary measuring arm  17 , and the measuring surface on the lower end of the stationary measuring arm  17  faces to the measuring surface on the lower end of the active measuring arm. A bolt for adjusting measuring range  11  is further provided between the two gliding guide bars  6 . The bolt for adjusting measuring range  11  extends horizontally into the rectangular frame from outside, and cooperates with the threaded hole in the upper end of the stationary measuring arm  17 . A locking screw is mounted on the rectangular frame, and after the stationary measuring arm  17  is moved to a desired position, the bolt for adjusting measuring range  11  can be locked by the locking screw to stop rotating, so that the stationary measuring arm  17  is locked in position. 
         [0073]    An end of the lower gliding guide bar  6  travels through the hinged portion of the stationary arm and then is received in the pilot hole on the hinged portion of the active arm. The position of the pilot hole for receiving the gliding guide bar  6  is lower than the positions of intersected supporting spring leaves  7 . Another pilot pin  8  is provided horizontally on the stationary arm  1  at a position higher than the positions of the intersected supporting spring leaves  7 . The pilot pin  8  extends into a corresponding pilot hole on the active arm  2 . The stationary arm  1  is further provided horizontally with a dynamometric spring  5  above the pilot pin  8 , and another end of the dynamometric spring  5  leans against the opposite active arm  2 . The active arm  2  is further mounted horizontally with a lifting screw  10  above the dynamometric spring  5 . The measuring surface of the active measuring arm is further provided with a cylindrical measuring head  13  that is capable to swing slightly on the supporting shaft. 
         [0074]    A fourth embodiment is a lever gauge which also utilizes the capacitive sensor core with flexible hinge. As shown in  FIG. 4 , the stationary device and the active device are a stationary frame  1 - 1  and a T-shaped active arm  2  respectively. The stationary frame  1 - 1  is provided with an opening on the bottom, and the longitudinal portion of the active arm  2  is mounted vertically in the stationary frame  1 - 1 , and its lower end is exposed out of the opening on the bottom of the stationary frame  1 - 1 , and the transverse portion on the upper end of the active arm  2  faces to the main grid plate  3  in the stationary frame  1 - 1 . The minor grid plate  4  corresponding to the main grid plate  3  is mounted on the transverse portion on the upper end of the active arm  2 . A straight slot which is inclined towards top left side and a straight slot which is inclined towards top right side are provided on two sides of the opening of the bottom of stationary frame  1 - 1  respectively. The straight slots which have the same gradient are vertical to the main grid plate  3  and the minor grid plate  4 . A seat  14  for the supporting spring leaf is provided on the end of the longitudinal portion of the active arm  2  outside the stationary frame  1 - 1 . Two straight slots corresponding to the gradient of the above two straight slots are provided on the left and right sides of the seat  14 , and these two straight slots are also vertical to the main grid plate  3  and the minor grid plate  4 , and have the same gradient as the above two straight slots. 
         [0075]    Two ends of two supporting spring leaves  7  which are arranged in one plane are respectively inserted into the straight slots corresponding to the seat  14 , and form an intersection within the seat  14 , and the intersecting line of the supporting spring leaves  7  are vertical to the main grid plate  3  and the minor grid plate  4 . The intersecting line is the virtual rotation axis of the stationary frame  1 - 1 . The seat  14  is further hinged with a base  15  for the measuring head; the bottom of the base  15  is connected to the measuring stick  16  which is of a spherical head. 
         [0076]    An orientation wheel  18  for the active arm is mounted in the stationary frame  1 - 1  via supporting shaft, and located on the right side of the longitudinal portion of the active arm  2 . The orientation wheel  8  is of a groove for movably receiving the longitudinal portion of the active arm  2 . 
         [0077]    A pressing plate  19  that is rotated around a shaft is further mounted inside the stationary frame  1 - 1 , and located behind the longitudinal portion of the active arm  2 . A pin on the upper end of the pressing plate  19  and a stress application spring pin on the lower end of the pressing plate  19  lean on the two sides of the longitudinal portion of the active arm  2  respectively. An end of a measuring spring  5  is connected to the pin  20  on the lower end of the pressing plate  19 , and the other end of the measuring spring  5  is connected to the inner surface of the stationary frame  1 - 1  at the left side of the longitudinal portion of the active arm  2 , in order to maintain the measuring spring  5  to be horizontal. Positioning cams  21  at an upper left position and another lower right position are arranged respectively on the two sides of the longitudinal portion of the active arm  2 , and contacted with the outer edge of the pressing plate  19 . 
         [0078]    A fifth embodiment is a micrometer which also utilizes the capacitive sensor core with flexible hinge. As shown in  FIG. 5 , the stationary device and the active device are a circular casing  1 - 2  and a bar-like active arm  2  respectively. A rectangular main grid plate  3  is mounted inside the circular casing  1 - 2 . The front surface of the main grid plate  3  is mounted with the vertical active arm  2 . A minor grid plate  4  is mounted on a surface of the active arm  2  facing the main grid plate  3 . The bottom of the circular casing  1 - 2  behind the main grid plate  3  is mounted with a vertical guide sleeve, the pilot pin  22  is received in the guide sleeve and the two ends of the pilot pin  22  are exposed out of the guide sleeve. The upper end of the active arm  2  is connected to the upper end of the pilot pin  22  via transverse connecting element. The lower end of the active arm  2  is connected vertically with a measuring stick  16 , and the measuring stick  16  extends through a mounting hole on the bottom of the circular casing  1 - 2  and is exposed out of the circular casing  1 - 2 . The measuring stick  16  has a tapered measuring head on its end. 
         [0079]    A left sliding piece  23  and a right sliding piece  23  are arranged equidistantly on the two sides of the main grid plate  3 . A straight slot inclined towards the bottom left side and a straight slot inclined towards the bottom right side from outside to inside are provided respectively on the two lower sides of the body below the main grid plate  3 , and these straight slots are vertical to the main grid plate  3  and the minor grid plate  4 . A straight slot inclined towards the top left side and a straight slot inclined towards the top right side from outside to inside are provided respectively on the two upper sides of the connecting piece on the top of the active arm  2 . Two pairs of intersected straight slots are respectively provided in the left and right sliding piece  23 , and these straight slots are respectively corresponding to the straight slots on the body and the connecting piece below the main grid plate  3 . The ends of four supporting spring leaves  7  are received in the above straight slots, and are in the same plane and vertical to the main grid plate  3  and the minor grid plate  4 , and form a rhombus. 
         [0080]    It should be emphasized that the above-described embodiments of the present invention, particularly, any preferred embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.
A capacitive sensor core with flexible hinge is disclosed. The capacitive sensor core comprises a main grid plate ( 3), an auxiliary grid plate ( 4), and a mechanical structure transferring the measuring quantity to the displacement between the main grid plate ( 3) and the auxiliary grid plate ( 4), the mechanical structure includes a stationary means and a moving means, the auxiliary grid plate( 4) and the main grid plate ( 3) are fixed to the driven portion of the moving means and the corresponding position of the stationary means respectively, the stationary means and the moving means are connected through a flexible hinge; the flexible hinge consists of at least two supporting spring leafs ( 7), one end of each of the supporting spring leaf s( 7) is connected to the stationary means, the other end is connected to the moving means; the plane of each of the supporting spring leaf s ( 7) is perpendicular to the planes of the main and auxiliary grid plates( 3, 4). A flexible hinge lever capacitance angular displacement sensor, an adjustable digital display caliper, a lever gauge and a micrometer are equipped with the cassette mechanism of flexible hinge capacitance sensor.