Patent Publication Number: US-2009219015-A1

Title: Apparatus for measuring kinetic parameters of punch

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to measuring apparatuses, and particularly to an apparatus and method for measuring kinetic parameters of a punch during press molding. 
     2. Description of Related Art 
     In a typical press molding machine, a punch is used to insert into and engage with molding die, so as to make through holes or blind holes in a workpiece. Initially, the workpiece is placed on a molding surface of molding die having a predetermined concave shape. Next, the workpiece is pressed by a punch having a shape corresponding to the concaved portion. Often the punch may be displaced along the molding surface of the molding die during press molding. As a result, the accuracy of the press-molded product may be affected. 
     What is needed is an apparatus and method for determining the position of the punch during press molding. 
     SUMMARY 
     An exemplary apparatus and method for measuring kinetic parameters of a machining tool within a press molding machine includes two magnets and two electrical conductors attached to a machining tool. The two magnets are fixed for producing two magnetic fields that are at an angle to each other. The two electrical conductors are connected to a controller to form two closed loops respectively. Each electrical conductor is located in a corresponding magnetic field and is unparallel to the direction of the corresponding magnetic field. Upon the condition that the machining tool deviates from its axial path, voltages are induced across the two electrical conductors. The controller receives the induced voltages, and determines a velocity of the machining tool&#39;s deviation from the axial path. 
     Other novel features and advantages will become more apparent from the following detailed description of preferred and exemplary embodiment when taken in conjunction with the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of an apparatus for measuring kinetic parameters of a punch in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  is a schematic view of two conductive wires in two magnetic fields which are respectively produced by two magnets of  FIG. 1 ; and 
         FIG. 3  is a schematic view showing the relationship between a moving direction of the punch, and field directions of the magnetic fields of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an apparatus for measuring kinetic parameters of a punch  30  within a press molding machine is used to accurately determine the position of the punch  30 . The apparatus, in accordance with an exemplary embodiment of the present invention, includes a fixing device  10  made of nonconductive material, a pair of U-shaped magnets  22  and  24  and a pair of conductive wires ab and cd. 
     The fixing device  10  has a hollow cylindrical main body  16  for receiving the punch  30 , two rectangular projecting portions  12  and  14  protruding from the main body  16 . The conductive wires ab and cd are embedded in the projecting portions  12  and  14  respectively. The projecting portion  12  is perpendicular to the projecting portion  14 . In this exemplary embodiment, the conductive wires ab and cd are parallel to the axial direction of the punch  30 . The magnet  22  has a north pole  220 , a south pole  222 , and a bottom part  224  connecting the north pole  220  to the south pole  222  to form a recess. The magnet  24  has a north pole  240 , a south pole  242 , and a bottom part  244  connecting the north pole  240  to the south pole  242  to form another recess. In this exemplary embodiment, the magnets  22  and  24  are suspended firmly from a ceiling of a worktable of the press molding machine maintained in a fixed position. The projecting portions  12  and  14  are non-contactingly located in the recesses of the magnets  22  and  24  respectively and move with the punch  30 . North poles  220 ,  240  of the magnets  22  and  24  face each other. 
     Referring to  FIG. 1  and  FIG. 2 , the magnets  22  and  24  are configured for producing two uniform magnetic fields B 1  and B 2  that are perpendicular to each other. The conductive wire ab is located within the magnetic field B 1 , and the conductive wire cd is located within the magnetic field B 2 . The conductive wires ab and cd are arranged to be perpendicular to their respective magnetic field lies. Two ends of the conductive wire ab are connected to an AD converter  40  to form a closed loop. Two ends of the conductive wire cd are connected to an AD converter  50  to form another closed loop. The AD converters  40  and  50  are both electronically connected to a controller  60  of the press molding machine. The AD converters  40 ,  50  may be fixed in or on one of the fixing device  10  and the press molding machine. 
     In use, when the punch  30  moves along its path, it may deviate from its axial direction, the conductive wires ab and cd move in the magnetic fields B 1  and B 2  respectively, and voltages are induced across the wires ab and cd. The AD converters  40  and  50  convert the voltages from analog values to digital values, respectively. The controller  60  receives the digital values of the voltages and calculates the kinetic velocity of the conductive wires ab and cd. 
     Referring to  FIG. 3 , a plane coordinate system is defined. In the present embodiment the magnets are set to produce magnetic fields B 2  and B 1  which perpendicular to each other. The x-axis and y-axis are parallel to the directions of the magnetic fields B 2  and B 1  respectively. Defining that the speed of the punch  30  deviation from it&#39;s axial direction is v, v is made of a x-axis component vx and a y-axis component vy. The values of the two components vx and vy are determined according to the following equations: 
     
       
         
           
               
             
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     Wherein: 
     E1 and E2 are respectively the strength of the magnetic fields B 1  and B 2   
     L1 and L2 are respectively the length of the conductive wires ab and cd that are inside and perpendicular to the magnetic fields B 1  and B 2   
     α is the angle between a deviating direction of the punch  30  and the direction of the magnetic field B 1   
     β is the angle between the deviating direction of the punch  30  and the direction of the magnetic field B 2   
     e1 and e2 are the digital values of the induced voltages received by the controller  60 . 
     In this exemplary embodiment, the equations pre-set in the controller  60  can be changed according to the user&#39;s needs. Given that the magnets are offset by ninety degrees, β is equal to 90°−α (graphic example shown in  FIG. 3 ). In an alternative embodiment, the two end of each of the conductive wires ab and cd can be connected to the controller  60 , which receive the induced voltages without going through the AD converters  40  and  50 . Also in other embodiments, the angle between the magnets can be set at any angle. 
     The displacements of the punch  30  along the x-axis and y-axis can be calculated by the controller  60  according to the x-axis component vx and the y-axis component vy respectively. The position of the punch  30  and a workpiece to be punched by the press molding machine can be adjusted by the controller  60  according to the displacements of the punch  30  along the x-axis and y-axis respectively. Therefore, the press molding machine works more accurately. 
     The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.