Abstract:
The crisscross fulcrum according to the present invention is formed as a continuous member by fabricating one elastic member in the form of a plate. Therefore, the rocking fulcrum member can be obtained as a precise fulcrum member at a low cost with reduced variations in the spring characteristic and can be easily assembled. Additionally, in the present invention, it is preferable that a heat treatment should be performed on the crisscross spring formed by fabricating the one elastic member in the form of a plate. By the heat treatment performed after fabricating for forming the crisscross spring, the spring characteristic is improved.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a rocking fulcrum member and, more particularly, to a crisscross-spring-type rocking fulcrum member used in a lever-type detector or the like. 
   2. Description of the Related Art 
   In lever-type detectors or the like, a finger arm having a contactor attached to its tip is supported on a rocking fulcrum so as to be able to seesaw. The detector detects the amount of movement of the finger arm when the contactor is in contact with a work. 
   Examples of rocking fulcrum members used in such detectors are an elastic fulcrum such as shown in  FIG. 7C , an L-shaped spring fulcrum such as shown in  FIG. 7B , a bearing (not shown) and crisscross spring fulcrums such as shown in  FIG. 7A . Elastic fulcrums are capable of operating with accuracy but can be used only in a case where the measurement range is narrow because they have only restricted swing angles. 
   L-shaped spring fulcrums are low-priced and are being widely used but have a drawback in that the fulcrum center is shifted with a swinging movement and cannot be suitably used as a precise fulcrum member. Bearing fulcrums can have any swing angle but need periodical replacement because their accuracy is reduced due to wear. 
   Crisscross spring fulcrums include those formed by disposing two plate springs so that the plate springs cross each other as shown on the left-hand side of  FIG. 7A , and those integrally formed by being cut by wire cutting as shown on the right-hand side of  FIG. 7A . The latter have sufficient rigidity and high accuracy during repeated use and can therefore be suitably used as a precise fulcrum. 
   A crisscross spring fulcrum such as shown on the left-hand side of  FIG. 7A  is fixed by screwing opposite ends of the two plate springs to members or by welding the opposite ends to the members. A method of die-casting a crisscross spring base member and embedding the opposite ends of the two plate springs in the crisscross spring base member at the time of casting is also used (see, for example, WO 98/20297 pamphlet). 
   A crisscross spring fulcrum having two plate springs welded to grooves in a cylindrical housing has also been proposed (see, for example, U.S. Pat. No. 3,807,029). 
   In assembly of the above-described crisscross spring fulcrum member fixed by screwing opposite ends of the two plate springs to members has problems that a considerably long time is required for assembly and variations in spring characteristic occur due to assembly errors. The crisscross spring fulcrum having two plate springs embedded in a crisscross spring base member by die casting as described in WO 98/20297 pamphlet and the crisscross spring fulcrum having two plate springs fixed to a base member by welding as described in U.S. Pat. No. 3,807,029 have a problem that a considerably long time is required for fabricating and the assembly and manufacturing costs are high and another problem that the plate springs are heated at a high temperature at the time of welding or die casting to degrade the spring characteristic. 
   The crisscross spring fulcrum integrally formed by cutting using wire cutting electrodischarge machining also has a problem that a considerably long time is required for fabricating and the manufacturing cost is high and another problem that the characteristic of the spring degrades with time due to microcracks caused by machining. 
   SUMMARY OF THE INVENTION 
   In view of the above-described circumstances, an object of the present invention is to provide a rocking fulcrum member having a crisscross spring fulcrum, capable of being manufactured at a low cost with reduced variations in the spring characteristic, and capable of being easily assembled. 
   To achieve the above-described object, according to a first aspect of the present invention, there is provided a rocking fulcrum member, comprising: a first elastic plate portion and a second elastic plate portion placed on planes intersecting each other to form a crisscross spring, wherein each of the first elastic plate portion and the second elastic plate portion has extensions from its one end and the other end in its longitudinal direction; the extension from the one end of the first elastic plate portion is bent at an acute angle from the first elastic plate portion, while the extension from the other end of the first elastic plate portion is bent at an obtuse angle from the first elastic plate portion; the extension from the one end of the second elastic plate portion is bent at an obtuse angle from the second elastic plate portion, while the extension from the other end of the second elastic plate portion is bent at an acute angle from the second elastic plate portion; the extension from the one end of the first elastic plate portion and the extension from the one end of the second elastic plate portion are formed as one continuous member on one plane; the extension from the other end of the first elastic plate portion and the extension from the other end of the second elastic plate portion are formed as one continuous member on one plane; and the first elastic plate portion, the extension from the one end of the first elastic plate portion, the extension from the other end of the first elastic plate portion, the second elastic plate portion, the extension from the one end of the second elastic plate portion and the extension from the other end of the second elastic plate portion are a continuous member formed by fabricating one elastic member in the form of a plate. 
   In the first aspect of the present invention, it is preferable that a width of the first elastic plate portion and a width of the second elastic plate portion should be equal to each other. 
   To achieve the above-described object, according to a second aspect of the present invention, there is provided a rocking fulcrum member, comprising: a first elastic plate portion, a second elastic plate portion and a third elastic plate portion, the first elastic plate portion and the third elastic plate portion being placed parallel to each other on one plane, the second elastic plate portion being placed between the first elastic plate portion and the third elastic plate portion, the first elastic plate portion, the third elastic plate portion and the second elastic plate portion being placed on planes intersecting each other to form a crisscross spring, wherein each of the first elastic plate portion, the second elastic plate portion and the third elastic plate portion has extensions from its one end and the other end in its longitudinal direction; the extension from the one end of the first elastic plate portion is bent at an acute angle from the first elastic plate portion, while the extension from the other end of the first elastic plate portion is bent at an obtuse angle from the first elastic plate portion; the extension from the one end of the second elastic plate portion is bent at an obtuse angle from the second elastic plate portion, while the extension from the other end of the second elastic plate portion is bent at an acute angle from the second elastic plate portion; the extension from the one end of the third elastic plate portion is bent at an acute angle from the third elastic plate portion, while the extension from the other end of the third elastic plate portion is bent at an obtuse angle from the third elastic plate portion; the extension from the one end of the first elastic plate portion, the extension from the one end of the second elastic plate portion and the extension from the one end of the third elastic plate portion are formed as one continuous member on one plane; the extension from the other end of the first elastic plate portion, the extension from the other end of the second elastic plate portion and the extension from the other end of the third elastic plate portion are formed as one continuous member on one plane; and the first elastic plate portion, the extension from the one end of the first elastic plate portion, the extension from the other end of the first elastic plate portion, the second elastic plate portion, the extension from the one end of the second elastic plate portion, the extension from the other end of the second elastic plate portion, the third elastic plate portion, the extension from the one end of the third elastic plate portion and the extension from the other end of the third elastic plate portion are a continuous member formed by fabricating one elastic member in the form of a plate. 
   In the second aspect of the present invention, it is preferable that sum of a width of the first elastic plate portion and a width of the third elastic plate portion should be equal to a width of the second elastic plate portion. 
   In the first or the second aspect of the present invention, it is preferable that an attachment hole for attachment of a member should be formed in each of the continuous member on one plane in which the extension from the one end of each elastic plate portion is formed and the continuous member on one plane in which the extension from the other end of each elastic plate portion is formed. 
   According to the present invention, the crisscross fulcrum is formed as a continuous member by fabricating one elastic member in the form of a plate. Therefore, the rocking fulcrum member can be obtained as a precise fulcrum member at a low cost with reduced variations in the spring characteristic and can be easily assembled. 
   In the first or the second aspect of the present invention, it is preferable that a heat treatment should be performed on the crisscross spring formed by fabricating the one elastic member in the form of a plate. By the heat treatment performed after fabricating for forming the crisscross spring, the spring characteristic is improved. 
   As described above, the crisscross fulcrum in the rocking fulcrum member of the present invention is formed as a continuous member by fabricating one elastic member in the form of a plate and, therefore, the rocking fulcrum member can be obtained as a precise fulcrum member at a low cost with reduced variations in the spring characteristic and can be easily assembled. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a rocking fulcrum member according to an embodiment of the present invention; 
       FIG. 2  is a side view of the rocking fulcrum member according to the embodiment of the present invention; 
       FIG. 3  is a plan view of the rocking fulcrum member before forming; 
       FIG. 4  is a perspective view of an example of a modification of the embodiment; 
       FIG. 5  is a plan view of the rocking fulcrum member in the modification of the embodiment before forming; 
       FIG. 6  is a sectional side view of an example of an application of the rocking fulcrum member of the present invention; and 
       FIGS. 7A to 7C  are perspective views of conventional rocking fulcrum members. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A preferred embodiment of a rocking fulcrum member in accordance with the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same portions or components are indicated by the same reference numerals or symbols. 
     FIG. 1  is a perspective view of an embodiment of a rocking fulcrum member in accordance with the present invention, and  FIG. 2  is a side view of the embodiment. As shown in  FIGS. 1 and 2 , the rocking fulcrum member  10  has a first elastic plate portion  10 A and a second elastic plate portion  10 B. The surfaces of the first elastic plate portion  10 A and the second elastic plate portion  10 B cross each other at right angles to form a crisscross spring  11 . 
   An extension  10 C from one end of the first elastic plate portion  10 A is bent at 45° from the first elastic plate portion  10 A, while an extension  10 D from the other end of the first elastic plate portion  10 A is bent at 135° from the first elastic plate portion  10 A. 
   An extension  10 E from one end of the second elastic plate portion  10 B is bent at 135° from the second elastic plate portion  10 B, while an extension  10 F from the other end of the second elastic plate portion  10 B is bent at 45° from the second elastic plate portion  10 B. 
   The extension  10 C from one end of the first elastic plate portion and the extension  10 E from one end of the second elastic plate portion are formed integrally with each other to form one L-shaped flat plate, and the extension  10 D from the other end of the first elastic plate portion and the extension  10 F from the other end of the second elastic plate portion are also formed integrally with each other to form one L-shaped flat plate. Three attachment holes  10 G for attachment of a member are formed in each L-shaped flat plate. 
   In the rocking fulcrum member  10  having the above-described structure, the L-shaped flat plate portions are parallel to each other in a no-load condition. When a force is applied to the L-shaped flat plate portions in such a direction that the L-shaped flat plate portions are brought closer to each other or moved away from each other, rocking on the crisscross fulcrum formed by the first elastic plate portion  10 A and the second elastic plate portion  10 B is caused. 
   The rocking fulcrum member  10  is integrally formed into a state shown in  FIGS. 1 and 2  from one elastic plate member  50  shown in  FIG. 3 . A large-size elastic plate member is first punched with a punching press to form the elastic plate member  50 , six attachment holes  10 G and a central slit  50 A, and the elastic plate member  50  is thereafter press-formed so as to be bent through predetermined angles at positions indicated by dotted lines in  FIG. 3 . A heat treatment is performed on the formed member to improve the spring characteristic. 
   The width L 1  of the first elastic plate portion and the width L 2  of the second elastic plate portion are equal to each other and the precise crisscross spring fulcrum is formed in a torsion-free condition. 
     FIG. 4  is a perspective view showing an example of a modification of the embodiment of the rocking fulcrum member in accordance with the present invention. A rocking fulcrum member  20  has a first elastic plate portion  20 A, a second elastic plate portion  20 B and a third elastic plate portion  20 H. The first elastic plate portion  20 A and the third elastic plate portion  20 H are placed parallel to each other with a certain spacing provided therebetween. The second elastic plate portion  20 B is placed between the first elastic plate portion  20 A and the third elastic plate portion  20 H. 
   The surfaces of the first elastic plate portion  20 A, the third elastic plate portion  20 H and the second elastic plate portion  20 B cross each other at right angles to form a crisscross spring  21 . 
   An extension  20 C from one end of the first elastic plate portion  20 A is bent at 45° from the first elastic plate portion  20 A, while an extension  20 D from the other end of the first elastic plate portion  20 A is bent at 135° from the first elastic plate portion  20 A. 
   An extension  20 E from one end of the second elastic plate portion  20 B is bent at 135° from the second elastic plate portion  20 B, while an extension  20 F from the other end of the second elastic plate portion  20 B is bent at 45° from the second elastic plate portion  20 B. 
   Further, an extension  20 J from one end of the third elastic plate portion  20 H is bent at 45° from the third elastic plate portion  20 H, while an extension  20 K (shown in  FIG. 5  referred to below) from the other end of the third elastic plate portion  20 H is bent at 135° from the third elastic plate portion  20 H. 
   The extension  20 C from one end of the first elastic plate portion, the extension  20 E from one end of the second elastic plate portion and the extension  20 J from one end of the third elastic plate portion are formed integrally with each other to form one generally concave flat plate, and the extension  20 D from the other end of the first elastic plate portion, the extension  20 F from the other end of the second elastic plate portion and the extension  20 K from the third elastic plate portion are also formed integrally with each other to form one generally convex flat plate. Four attachment holes  20 G for attachment of a member in the concave flat plate, and three attachment holes  20 G for attachment of a member in the convex flat plate are formed. 
   In the rocking fulcrum member  20  having the above-described structure, the generally concave flat plate portions and the generally convex flat plate portions are parallel to each other in a no-load condition, as are the corresponding portions of the above-described rocking fulcrum member  10 . When a force is applied to the generally concave flat plate portions in such a direction that the generally convex flat plate portions are brought closer to each other or moved away from each other, rocking on the crisscross fulcrum formed by the first elastic plate portion  20 A, the third elastic plate portion  20 H and the second elastic plate portion  20 B is caused. 
   The rocking fulcrum member  20  is integrally formed into a state shown in  FIG. 4  from one elastic plate member  60  shown in  FIG. 5 , as is the above-described rocking fulcrum member  10 . A large-size elastic plate member is first punched with a punching press to form the elastic plate member  60 , seven attachment holes  20 G and two central slits  60 A, and the elastic plate member  60  is thereafter press-formed so as to be bent through predetermined angles at positions indicated by dotted lines in  FIG. 5 . A heat treatment is performed on the formed member to improve the spring characteristic. 
   The width L 3  of the first elastic plate portion and the width L 5  of the third elastic plate portion are equal to each other and the sum of the width L 3  of the first elastic plate portion and the width L 5  of the third elastic plate portion is equal to the width L 4  of the second elastic plate portion. The precise crisscross fulcrum is formed in a torsion-free condition. 
     FIG. 6  shows an example of an application of the rocking fulcrum member  10  in accordance with the present invention to a rocking fulcrum for a measuring head  80 . In the measuring head  80 , one of the L-shaped flat plate portions of the rocking fulcrum member  10  is screwed to a measuring head body  81  by using the three attachment holes  10 G and an attachment plate  82  having three threaded holes, as shown in  FIG. 6 . 
   An arm member  83  is screwed to the other L-shaped flat plate portion of the rocking fulcrum member  10  by using another attachment plate  82 . A finger  84  is attached to a fore end of the arm member  83 . A contactor  85  is attached to a tip of the finger  84 . A core  86  of a differential transformer is attached to a rear end of the arm member  83 . A coil  87  of the differential transformer is attached to the measuring head body  81 . 
   A compression coil spring  88  is provided between the measuring head body  81  and the arm member  83  to apply a measuring pressure to the contactor  85 . A stopper screw provided in the measuring head body  81  is used to set a rocking lower end of the arm member  83 . 
   In the measuring head  80  having the above-described structure, the arm member  83  seesaws on the crisscross spring fulcrum formed by the rocking fulcrum member  10 . The amount of movement of the contactor  85  when the contactor  85  is in contact with a work is detected with the differential transformer, thus making an accurate measurement. 
   The rocking fulcrum member  10  is a press-formed crisscross spring fulcrum member integrally formed as described above. Therefore, the rocking fulcrum member  10  can be manufactured at a low cost and easily mounted, are free from variations in crisscross spring fulcrum characteristic due to variations in the mounted state and can be suitably used as a precise rocking fulcrum. 
   In the above-described embodiment, the crisscross spring in which the surfaces of the first elastic plate spring portion  10 A and the second elastic plate spring portion  10 B cross each other at right angles is formed. In the example of modification of the embodiment, the crisscross spring in which the surfaces of the first elastic plate spring portion  20 A, the third elastic plate spring portion  20 H and the second elastic plate spring portion  20 B cross each other at right angles is formed. However, the crossing angle between these portions in the arrangement of the present invention may be different from 90°.