Abstract:
The present invention discloses an apparatus for detecting spring stiffness which comprises a universal material testing machine, a loading beam of the universal material testing machine, a fixing rod of bracket for Belleville spring deformation detection, a movable clamping rod of bracket for Belleville spring deformation detection, a dial gauge, etc.

Description:
TECHNICAL FIELD 
     The present invention relates to a stiffness detecting apparatus. 
     BACKGROUND OF THE INVENTION 
     Belleville spring has a conical disk shape, which plays unique functions different from conventional springs. Major characteristics of Belleville spring include higher load carrying capacity, shorter stroke, smaller space required, convenience in combined using, easy repair and replacement as well as higher security and lower cost. Accordingly, Belleville spring is suitable for being used in sophisticated heavy machinery occupying smaller space and bearing higher load. The optimal working range of the Belleville spring is from 10% to 75% of its maximum compression stroke. 
     The design, purchase and replacement of the Belleville spring are dependent upon its stiffness. Therefore, it is significant to detect the stiffness of the Belleville spring. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an apparatus for detecting stiffness of Belleville spring. 
     The apparatus for detecting stiffness of Belleville spring comprises: a universal material testing machine, a loading beam of the universal material testing machine, a first fixing rod of bracket for Belleville spring deformation detection, a first movable clamping rod of bracket for Belleville spring deformation detection, a first dial gauge, a loading linkage, a spherical squeezing head, a second dial gauge, a cup-shaped loading barrel, a Belleville spring, a guide base, a second movable clamping rod of bracket for Belleville spring deformation detection, and a second fixing rod of bracket for Belleville spring deformation detection. 
     The guide base is placed on the table portion of the universal material testing machine, with the axis of the guide base coincident with that of the loading beam of the universal material testing machine. The guide base is a shaft with stepped structure and smooth surface. 
     The Belleville spring is placed on the guide base. By adjusting the relative position of the Belleville spring in relation to the guide base, the axis of the Belleville spring is made coincident with that of the guide base. 
     The cup-shaped loading barrel is placed on the Belleville spring. As a cylinder with stepped structure, the cup-shaped loading barrel is provided with a spherical recess at the center of its bottom surface, which mates with the spherical squeezing head to eliminate biased loading. 
     One end of the loading linkage is coupled to the loading beam of the universal material testing machine by means of thread connection, and the other end is coupled to the spherical squeezing head also by means of thread connection. 
     The first fixing rod of bracket for Belleville spring deformation detection and the second fixing rod of bracket for Belleville spring deformation detection are symmetrically fixed on the table portion of the universal material testing machine respectively at two sides of the guide base. 
     The first movable clamping rod of bracket for Belleville spring deformation detection is mounted on the first fixing rod of bracket for Belleville spring deformation detection. The first dial gauge is then clamped on the first movable clamping rod of bracket for Belleville spring deformation detection. By adjusting the first fixing rod of bracket for Belleville spring deformation detection, the first movable clamping rod of bracket for Belleville spring deformation detection and the first dial gauge, the first dial gauge is put into good contact with the outer surface of the bottom of the cup-shaped loading barrel and is kept with a pre-compression of 1-2 mm. 
     The second movable clamping rod of bracket for Belleville spring deformation detection is mounted on the second fixing rod of bracket for Belleville spring deformation detection. Then, the second dial gauge is clamped on the second movable clamping rod of bracket for Belleville spring deformation detection. By adjusting the second movable clamping rod of bracket for Belleville spring deformation detection, the second fixing rod of bracket for Belleville spring deformation detection and the second dial gauge, the second dial gauge is put into good contact with the outer surface of the bottom of the cup-shaped loading barrel and is kept with a pre-compression of 1-2 mm. 
     Load is applied by means of the loading beam of the universal material testing machine, which is then transmitted onto the cup-shaped loading barrel via the loading linkage and the spherical squeezing head, then evenly onto the Belleville spring via the cup-shaped loading barrel. The deformation amount of the Belleville spring is obtained by readings of the first dial gauge and the second dial gauge. At the same time, the value of force exerted by the universal material testing machine is recorded. The stiffness value of the Belleville spring could be calculated by introducing the deformation amount value and the force value into calculation formulas. 
     The present invention employs the universal material testing machine as a force loading source, and load is exerted onto the Belleville spring through the spherical loading device. Two symmetrically placed dial gauges are used to detect the deformation amount of the Belleville spring in order to check on whether biased loading is provided by the loading device. If the readings of said two symmetrically placed dial gauges are different, there must be biased force loading. Under this circumstance, it is imperative to adjust such force transmission devices as the Belleville spring and the guide barrel, until the biased loading is eliminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural schematic view of an apparatus for detecting spring stiffness of the present invention. 
         FIG. 2  is a structural schematic view of the cup-shaped loading barrel of the apparatus for detecting spring stiffness of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The apparatus for detecting Belleville spring stiffness will be described in detail in conjunction with the drawings. 
     The apparatus for detecting Belleville spring stiffness comprises: a universal material testing machine  1 , a loading beam  2  of the universal material testing machine, a first fixing rod of bracket for Belleville spring deformation detection  3 , a first movable clamping rod of bracket for Belleville spring deformation detection  4 , a first dial gauge  5 , a loading linkage  6 , a spherical squeezing head  7 , a second dial gauge  8 , a cup-shaped loading barrel  9 , a Belleville spring  10 , a guide base  11 , a second movable clamping rod of bracket for Belleville spring deformation detection  12 , and a second fixing rod of bracket for Belleville spring deformation detection  13 . 
     The guide base  11  is placed on the table portion of the universal material testing machine  1 , with the axis of the guide base  11  coincident with that of the loading beam  2  of the universal material testing machine. The guide base  11  is a shaft with stepped structure and smooth surface. 
     Belleville spring  10  is placed on the guide base  11 . By adjusting the relative position of the Belleville spring  10  in relation to the guide base  11 , the axis of the Belleville spring  10  is made coincident with that of the guide base  11 . 
     The cup-shaped loading barrel  9  is placed on the Belleville spring  10 . As a cylinder with stepped structure, the cup-shaped loading barrel  9  is provided with a spherical recess at the center of its bottom surface, which mates with the spherical squeezing head  7  to eliminate biased loading. 
     One end of the loading linkage  6  is coupled to the loading beam  2  of the universal material testing machine by means of thread connection, and the other end is coupled to the spherical squeezing head  7  also by means of thread connection. 
     The first fixing rod of bracket for Belleville spring deformation detection  3  and the second fixing rod of bracket for Belleville spring deformation detection  13  are symmetrically fixed on the table portion of the universal material testing machine at two sides of the guide base  11 . 
     The first movable clamping rod of bracket for Belleville spring deformation detection  4  is mounted on the first fixing rod of bracket for Belleville spring deformation detection  3 . The first dial gauge  5  is then clamped on the first movable clamping rod of bracket for Belleville spring deformation detection  4 . By adjusting the first fixing rod of bracket for Belleville spring deformation detection  3 , the first movable clamping rod of bracket for Belleville spring deformation detection  4  and the first dial gauge  5 , the first dial gauge  5  is put into good contact with the outer surface of the bottom of the cup-shaped loading barrel  9  and is kept with a pre-compression of 1-2 mm. 
     The second movable clamping rod of bracket for Belleville spring deformation detection  12  is mounted on the second fixing rod of bracket for Belleville spring deformation detection  13 . Then, the second dial gauge  8  is clamped on the second movable clamping rod of bracket for Belleville spring deformation detection  12 . By adjusting the second movable clamping rod of bracket for Belleville spring deformation detection  12 , the second fixing rod of bracket for Belleville spring deformation detection  13  and the second dial gauge  8 , the second dial gauge  8  is put into good contact with the outer surface of the bottom of the cup-shaped loading barrel  9  and is kept with a pre-compression of 1-2 mm. 
     Load is applied by means of the loading beam  2  of the universal material testing machine  1 , which is then transmitted onto the cup-shaped loading barrel  9  via the loading linkage  6  and the spherical squeezing head  7 , then evenly onto the Belleville spring  10  via the cup-shaped loading barrel  9 . The deformation amount of the Belleville spring  10  is obtained by readings of the first dial gauge  5  and the second dial gauge  8 . At the same time, the value of force exerted by the universal material testing machine  1  is recorded. The stiffness value of the Belleville spring could be calculated by introducing the deformation amount value and the force value into calculation formulas.