Abstract:
A method for making a screw member for plate member fastener is disclosed to include the step of preparing a metal element subject to a predetermined size and then processing the metal element through a cold extrusion forging operation to form a head at one end, a connection portion at an opposite end and a shank between the head and the connection portion, the step of processing the connection portion through a thread rolling operation to form threads around the periphery, the step of processing the threads to form a stop end edge at one side in proximity to the shank, and the step of finishing the final product.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention: 
         [0002]    The present invention relates to a plate member fastener fabrication method and more particularly, to a method for making a screw member for plate member fastener that raises reliability of the use of the plate member fastener. 
         [0003]    2. Description of the Related Art: 
         [0004]    When fastening plate members together, a positioning screw formed of a knob, a ring and a screw nail is usually used. During installation, the screw nail and the ring are secured to the first plate member, and then the knob is rotated to drive the screw nail into the second plate member, and then a hand tool is used to fasten tight the screw nail, affixing the first and second plate members together. This plate member joining method can be used in a machine tool to join plate members together. 
         [0005]    The power drive or speed-adjustment unit of a machine tool is provided inside the housing. To facilitate repair of the machine tool or adjustment of the output speed of the machine tool, a detachable plate member is usually provided at the housing of the power drive or speed-adjustment unit. Screw bolts are commonly used to fasten the movable plate member to the housing. When unfastening screw bolts to dismount a movable plate member from the housing, the associating lock nuts may fall from the screw bolts. 
         [0006]    There is known a plate member fastener comprised of a cap, a screw member, a spring member and a locating base for joining two metal plate members together. After fixation of the locating base of the plate member fastener to a through hole on a first plate member, the screw member is threaded into a screw hole on a second plate member to secure the first plate member and the second plate member together. Because the locating base of the plate member fastener is kept secured to the first plate member after removal of the first plate member from the second plate member, the plate member fastener will not be missed by accident. According to this design, the screw member A, as shown in  FIG. 9 , has a head A 1 , a shank A 2  perpendicularly extended from the center of the bottom side of the head A 1  and a connection portion A 3  axially extended from the bottom end of the shank A 2  remote from the head A 1 . The connection portion A 3  has an outer thread A 31  spirally extending around the periphery. The outer thread A 31  has a reduced end portion A 311 . During installation, the outer thread A 31  of the connection portion A 3  is threaded into the screw hole on the second metal plate member (not shown). When the reduced end portion A 311  of the outer thread A 31  reaches the inner thread of the screw hole of the second metal plate member, the first metal plate member and the second metal plate member are firmly secured together. If the operator continuously rotates the head A 1  of the screw member A at this time, the reduced end portion A 311  of the outer thread A 31  will be threaded into the screw hole of the second metal plate member, causing the screw member A to be stuck in the screw hole of the second metal plate member. Therefore, when threading the screw member A into the screw hole of the second metal plate member, the rotary driving force must be properly controlled to avoid overthreading. 
         [0007]    Further, the reduced end portion A 311  of the outer thread A 31  slopes in one direction. When the spring member is sleeved onto the screw member A and stopped between the reduced end portion A 311  of the outer thread A 31  and the bottom side of the head A 1 , the spring member may bias. When the screw member A, the cap and the locating base are assembled, the cap and the locating base may be not kept in perfect alignment. Small deviation of the component parts may increase the difficulty of the installation of the plate member fastener. 
         [0008]    Accordingly, there is a strong need for plate member fastener that overcomes the aforementioned and other deleterious effects of the prior art plate member fastener. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a method for the fabrication of a screw member for plate member fastener, which facilitates mounting and dismounting of the plate member fastener, avoiding overthreading during installation. 
         [0010]    A screw member fabrication method in accordance with the present invention includes the steps of (a) preparing a metal element subject to a predetermined size, and then processing the metal element through a cold extrusion forging operation to form a head at one end, a connection portion at an opposite end and a shank between said head and said connection portion, (b) processing the connection portion through a thread rolling operation to form threads around the periphery of the connection portion, (c) processing threads to form a stop end edge at one side in proximity to the shank, and (d) finishing the final product. When the screw member is used in a plate member fastener and threaded through a mounting through hole on a first metal plate member into a corresponding screw hole of a second metal plate member to secure the first metal plate member and the second metal plate member together, the stop end edge of the screw member avoids overthreading, preventing sticking of the screw member in the second metal plate member. 
         [0011]    Further, the stop end edge is a flat edge extending in direction perpendicular to the axis of the screw member. When the screw member is used in a plate member fastener and a spring member is sleeved onto the screw member and stopped between the bottom side of the head and stop end edge of the screw member, the screw member will not be forced to bias and can be accurately threaded into the screw hole of the second metal plate member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is an exploded view of the plate member fastener in accordance with the present invention. 
           [0013]      FIG. 2  is a flow chart of the present invention showing the fabrication of a screw member for plate member fastener in accordance with the present invention. 
           [0014]      FIG. 3  is a schematic sectional view, showing a metal element set in forging dies of a forging machine according to the present invention. 
           [0015]      FIG. 4  is a schematic sectional view of the present invention, showing the thread rolling operation (I). 
           [0016]      FIG. 5  is a schematic sectional view of the present invention, showing the thread rolling operation (II). 
           [0017]      FIG. 6  is side view of a finished screw member according to the present invention. 
           [0018]      FIG. 7  is an exploded view in sectional elevation of the present invention, showing the cap molded on the head of the screw member. 
           [0019]      FIG. 8  is a sectional view of the present invention, showing the plate member fastener fastened to two metal plate members. 
           [0020]      FIG. 9  is a side view of a screw member for plate member fastener according to the prior art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    Referring to  FIGS. 1 and 7 , a plate member fastener in accordance with the present invention comprises a cap  1 , a screw member  2 , a barrel  3 , and a spring member  4 . 
         [0022]    The cap  1  is a hollow member having a center opening  10  axially extending through the top and bottom sides for receiving the barrel  3 , the screw member  2  and the spring member  4 , a serrated inside retaining portion  11  arranged around the inside wall near the top side for retaining the engagement portion  211  of the screw member  2 , and a grip  12  located on the periphery at the top side for gripping by hand. 
         [0023]    The screw member  2  is a metal member having a head  21 , an engagement portion  211  formed on the periphery of the head  21  for engagement with the serrated inside retaining portion  11  of the cap  1 , a shank  22  perpendicularly extended from the center of the bottom wall of the head  21  and terminating in a connection tip  23 , threads  231  spirally arranged around the periphery of the connection tip  23  and defining a stop end edge  2311  at a proximal side relative to the shank  22 , and a tool groove  24  located on the top wall of the head  21 . Further, the tool groove  24  can be a Phillipes groove, keystone groove, asterisk groove or hex groove. 
         [0024]    The barrel  3  is a hollow cylindrical metal member having an inside accommodation space  30  extending through top and bottom sides thereof, a step  31  located on the inside around the inside accommodation space  30 , a locating groove  32  extending around the inside wall inside the inside accommodation space  30  and abutted against the bottom side of the step  31 , a bottom extension tube  33  axially forwardly extended from the bottom side of the barrel  3 , and a bonding edge  331  defined on the bottom side of the barrel  3  around the bottom extension tube  33 . Further, a retainer ring  34  is secured to the periphery of the shank  22  of the screw member  2  and positioned in the locating groove  32  inside the inside accommodation space  30 . 
         [0025]    The spring member  4  is sleeved onto the screw member  2 , having a deformable coiled body  41  surrounding the shank  22  of the screw member  2  and two end portions  42  respective disposed at the two distal ends of the deformable coiled body  41 . 
         [0026]    Referring to FIGS.  2 , 3   4 ,  5  and  6 , the screw member  2  is made of a metal element  5  that can be a steel, iron or stainless steel ingot. 
         [0027]    The screw member  2  is made subject to the following steps:
     100  Prepare a metal element  5  subject to a predetermined size.     101  Process the metal element  5  through a cold extrusion forging operation to form the desired head  21 , shank  22  and connection portion  23 .     102  Process the connection portion  23  through a thread rolling operation to form the desired threads  231 .     103  Process the threads  231  to form the desired stop edge  2311  at one side in proximity to the shank  22 .     104  Finish the desired screw member  2 .   
 
         [0033]    The metal element  5  is extruded into the desired length and width through a cold extrusion operation, and then processed through a cold forging process to form the desired head  21 , shank  22  and connection portion  23 . The cold extrusion forging operation is described hereinafter. After extrusion through a cold extrusion operation, the metal element  5  is put in between an upper die  61  and a bottom die  62  of a forging machine  6 , and then forged to form the desired shank  22  and connection portion  23 , and then a hammer forging die  63  is attached to one end of the metal element  5  outside the upper die  61  and the bottom die  62  and hammered to forge the respective end of the metal element  5  into the desired head  21 . Thereafter, the shape-formed metal element  5  thus obtained is put in between the thread rolling faces  7111  and  7121  of the two flat thread rolling dies  711  and  712  of a first thread rolling die set  71  of a thread rolling machine  7 , and then the two flat thread rolling dies  711  and  712  are reciprocated relative to each other to force the respective thread rolling faces  7111  and  7121  against the connection portion  23 , thereby forming a semi-finished screw member  2  having the desired threads  231  around the periphery of the connection portion  23 . Thereafter, the semi-finished screw member  2  thus obtained is put in between the thread rolling faces  7211  and  7221  of the two flat thread rolling dies  721  and  722  of a second thread rolling die set  72  of the thread rolling machine  7  wherein one flat thread rolling dies  721  has a top mounting groove  7213  located on the top wall  7210  thereof and an end edge-forming block  7212  affixed to the top mounting groove  7213  with a flat end edge-forming face  7214  thereof suspending in the thread rolling face  7211 , and then the two flat thread rolling dies  721  and  722  of the second thread rolling die set  72  are reciprocated relative to each other to force the respective thread rolling faces  7211  and  7221  against the connection portion  23 , causing the flat end edge-forming face  7214  to cut the end portion  2311  of the last thread  231  of the semi-finished screw member  2  so that a finished screw member  2  having the desired stop end edge  2311  at the end of the set of threads  231  in proximity to the shank  22  is thus obtained. When the screw member  2  is threaded into the screw hole  821  of a second metal plate member  82  during the use of the plate member fastener to secure a first metal plate member  81  to the second metal plate member  82 , the stop end edge  2311  will be stopped against the inner threads  8211  to prohibit forward rotation, avoiding overthreading of the screw member  2  (see  FIG. 8 ). Further, the flat end edge-forming face  7214  may be directly formed integral with the thread rolling face  7211  of the flat thread rolling die  721 , or the end edge-forming block  7212  may be separately made and then inserted into the flat thread rolling die  721 . 
         [0034]    Referring to  FIG. 7 , the screw member  2  made subject to the aforesaid fabrication method is fastened to the cap  1 , and then the spring member  4  is sleeved onto the screw member  2 , and then the retainer ring  34  is fastened to the screw member  2  to secure the barrel  3  to the screw member  2  in the cap  1 . 
         [0035]    Further, the cap  1  can be directly molded on the head  21  of the screw member  2  with over-molding technology. After molding, the engagement portion  211  of the head  21  of the screw member  21  that can be formed of a series of barbs, teeth or protruding ribs is formed integral with the serrated inside retaining portion  11  of the cap  1 . Thereafter, the spring member  4  is inserted into the center opening  10  of the cap  1  to sleeve the deformable coiled body  41 , and then the barrel  3  is inserted into the center opening  10  of the cap  1  to have the screw member  2  and the spring member  4  be accommodated in the inside accommodation space  30  and the two end portions  42  of the spring member  4  be respectively stopped the bottom side of the head  21  of the screw member  2  and the step  31  of the barrel  3 . Further, the retainer ring  34  is fastened to the periphery of the shank  22  of the screw member  2  and positioned in the locating groove  32  inside the barrel  3 . 
         [0036]    Referring to  FIG. 8 , during application of the present invention to fasten a set of metal plate members  8 , an automatic installation machine is used to pick up the plate member fastener and then to insert the bottom extension tube  33  of the barrel  3  of the plate member fastener into the mounting through hole  811  of the first metal plate member  81  and to attach the bonding edge  331  of the barrel  3  to the solder paste  812  that was applied to the border area of the mounting through hole  811  of the first metal plate member  81 , and then a reflow soldering process is applied to have the barrel  3  be bonded to the first metal plate  81 . 
         [0037]    After installation of the barrel  3  in the first metal plate member  81 , attach the first metal plate member  81  to the second metal plate member  82  to aim the screw member  2  at the screw hole  821  of the second metal plate member  82 , and then force the cap  1  downwards and rotate the cap  1  to drive the outer thread  231  of the screw member  2  into the screw hole  821  of the second metal plate member  82 , and then attach a hand tool (for example, screwdriver) to the tool groove  24  of the screw member  2  and rotate the hand tool to tighten up the connection between the screw member  2  and the second metal plate member  82 . Thus, the first metal plate member  81  and the second metal plate member  82  are firmly secured together by the plate member fastener. By means of the effect of the stop end edge  2311 , the invention avoids overthreading of the screw member  2  and facilitates disconnection of the first metal plate member  81  from the second metal plate member  82 . 
         [0038]    Further, the stop end edge  2311  of the screw member  2  is a flat edge extending in direction perpendicular to the axis of the screw member  2 . Thus, when the spring member  4  is received in the barrel  1  and the two end portions  42  are respectively stopped at the bottom side of the head  21  and stop end edge  2311  of the screw member  2 , the screw member  2  will not be forced to bias and can be accurately threaded into the screw hole  821  of the second metal plate member  82 . 
         [0039]    While the present disclosure has been described with reference to one exemplary embodiment, it will be understood that the description of the exemplary embodiment is not a limitation of the invention. 
         [0040]    Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.