Patent Publication Number: US-2010124581-A1

Title: Injection mold with workpiece trimming edge

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure generally relates to injection molds and, particularly, to an injection mold with a knockout pin having a trimming edge. 
     2. Description of Related Art 
     Injection molding has advantages of low cost, short molding time, simplicity, and ease of forming products with irregular, complex shapes. Injection molds are popular in many manufacturing industries. 
     Referring to  FIG. 6 , a frequently used injection mold  10  is shown. The injection mold  10  includes a fixed half  11 , a movable half  12 , a mold base  13 , and an ejector mechanism  14 . The mold base  13  supports the fixed half  11 , the movable half  12  and the ejector mechanism  14 . The fixed half  11  includes a fixed mold  111 , and the movable half  12  includes a movable mold  121 . When clamping the injection mold  10 , the movable half  12  is coupled to the fixed half  11 , and thus a cavity  151  is formed by the fixed mold  111  and the movable mold  121 . The ejector mechanism  14  includes an ejector retention plate  141  and a plurality of ejector pins  142 . The ejector pins  142  are fixed to the ejector retention plate  141  and moved by the ejector retention plate  141 . To ensure evenness of a surface of the injection molded product, the injection mold  10  includes a gate  152  parallel to the ejector direction and a runner  153  connecting to the gate  152  and admitting molten material therethrough. 
     Referring also to  FIG. 7 , during unclamping of the injection mold  10 , the movable half  12  is separated from the fixed half  11 . The injection molded product and unwanted portions formed in the gate  152  are ejected by the ejector pins  142  driven by the ejector retention plate  141 . 
     Typically, the excess material formed in the gate  152 , i.e., the unwanted portions, is removed manually or by machine. This costs manpower or machine power, and extends the manufacturing time and elevates the cost of the product. 
     Therefore, an injection mold that can overcome the described limitations is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the frequently used injection mold and the injection mold of embodiments of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, and all the views are schematic. 
         FIG. 1  is a cross-section of a first embodiment of an injection mold, shown in a clamped state, and showing a molded product in the injection mold. 
         FIG. 2  is an enlarged view of a region II of the injection mold of  FIG. 1 . 
         FIG. 3  is similar to  FIG. 1 , but showing the injection mold in a separated state. 
         FIG. 4  is a series of views showing a process of the injection mold of  FIG. 1  trimming excess material formed in a gate of the injection mold during molding of a product. 
         FIG. 5  is similar to  FIG. 2 , but showing parts of a second embodiment of an injection mold, and showing a molded product in the injection mold. 
         FIG. 6  is a cross-section of a frequently used injection mold, shown in a clamped state. 
         FIG. 7  is similar to  FIG. 6 , but showing the injection mold in a separated state. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1  and  FIG. 2 , a first embodiment of an injection mold  20  is shown. The injection mold  20  includes a fixed half  21 , a movable half  22 , a mold base  23 , and an ejector mechanism  24 . The mold base  23  supports the fixed half  21 , the movable half  22  and the ejector mechanism  24 . The fixed half  21  and the movable half  22  cooperatively form a cavity  25 . The ejector mechanism  24  is disposed between the fixed half  21  and the movable half  22 . 
     The fixed half  21  includes a fixed plate  211 , a fixed mold  212 , and an injection system  213 . The fixed plate  211  includes a receptacle  214  to receive the fixed mold  212 . The fixed mold  212  includes a molding surface (not labeled) facing the movable half  22 , and the molding surface includes a first cavity surface  215  and a first runner surface  216 . The injection system  213  runs through the fixed plate  211  and the fixed mold  212 , and communicates with the first runner surface  216 . 
     The movable half  22  includes a movable plate  221 , and a movable mold  222  received in the movable plate  221 . The movable mold  222  includes a second cavity surface  223 , a second runner surface  224 , and a gate  225 . The first cavity surface  215  and the second cavity surface  223  cooperatively form the cavity  25 , and the first runner surface  216  and the second runner surface  224  cooperatively form a runner  26 . The runner  26  communicates with the injection system  213 . The gate  225  is a channel extending from the second cavity surface  223  to the interior of the movable mold  222 . Top and bottom ends of the gate  225  communicate with the cavity  25  and with the runner  26 , respectively. 
     The ejector mechanism  24  includes a first ejector retention plate  241 , a second ejector retention plate  242 , a knockout pin  243 , a gate pin  244 , and a runner pin  245 . The first ejector retention plate  241  defines a sliding slot  246 . The ejector mechanism  24  further includes a slider  247  slidably received in the sliding slot  246 , and a plurality of fasteners  249 . One end of the runner pin  245  is fixed to the first ejector retention plate  241  via one fastener  249 , and an opposite end of the runner pin  245  extends towards the runner  26 . One end of the gate pin  244  is fixed to the first ejector retention plate  241  via one fastener  249 , and the other end of the gate pin  244  runs through the movable half  22  and extends towards the gate  225 . One end of the knockout pin  243  hinges on the slider  247 , and the other end of the knockout pin  243  runs through the movable half  22  and extends adjacent to the cavity  25  and the top end of the gate  225 . The gate pin  244  and the runner pin  245  are substantially parallel to a moving direction of the movable half  22 . The knockout pin  243  is oblique to the gate pin  244 . In the illustrated embodiment, an angle defined between the knockout pin  243  and the gate pin  244  is α. The knockout pin  243  includes a trimming edge  248  adjacent to the top end of the gate  225 . More particularly, a top face of the knockout pin  243  including an end thereof at the trimming edge  248  is coplanar with the second cavity surface  223 . The trimming edge  248  abuts a junction where the second cavity surface  223  adjoins a left-hand sidewall of the gate  225 . In the illustrated embodiment, such junction is also an edge. 
     Referring also to  FIG. 3 , in use, the injection mold  20  is clamped and molten material is injected into the injection system  213 . The molten material flows through the runner  26 , the gate  225 , and fills the cavity  25 . The molten material is cooled to solidify, thus forming a product  28 . The product  28  is connected to excess material  27  formed in the gate  225 . 
     Referring also to  FIG. 4 , the movable half  22  is moved to separate from the fixed half  21 . Then the ejector mechanism  24  ejects the product  28  from the movable half  22 . In detail, the first ejector retention plate  241  moves upward, and the slider  247  slides horizontally along the sliding slot  246  while the knockout pin  243  gradually moves upward. The second ejector retention plate  242  drives the gate pin  244  after the first ejector retention plate  241  drives the knockout pin  243 . A moving direction of the product  28  relative to the knockout pin  243  is oblique, because the knockout pin  243  is oblique to the moving direction of the movable half  22 . Therefore, during such moving, the trimming edge  248  cuts the excess material  27  from the product  28 . To obtain maximum quality, the angle α is about 10° to about 30°, and preferably about 15°. 
     In detail, after the movable half  22  is separated from the fixed half  21 , the first ejector retention plate  241  drives the knockout pin  243  and the runner pin  245 . The runner pin  245  biases solidified material in the runner  26  from the product  28  and the movable mold  222 . The angled movement of the knockout pin  243  gradually moves the trimming edge  248  to a root of the excess material  27 , which is finally cut from the product  28  accordingly. During movement of the knockout pin  243 , the sliding slot  246  allows the slider  247  to slide therein. The second ejector retention plate  242  moves the gate pin  244  to completely eject the excess material  27  from the gate  225 . 
     The injection mold  20  with the trimming edge  248  trims the excess material  27  from the product  28  during release of the product  28  from the injection mold  20 . Accordingly, the process is simplified, the manufacturing time is shortened, and manpower and costs are reduced. Consequently, manufacturing efficiency is improved. In addition, the trimmed surface of the product  28  is smooth, improving the final quality of the product  28 . 
     Referring to  FIG. 5 , a second embodiment of an injection mold  30  is shown. The injection mold  30  differs from the injection mold  20  of the first embodiment only in that a second cavity surface  323  of a movable half  32  includes a protrusion  328 , which protrudes into a cavity  35 . The protrusion  328  is directly adjacent to a top end of a gate  325 . In particular, a left-hand side face of the protrusion  328  is integrally coplanar with a right-hand sidewall of the gate  325 . The protrusion  328  and a knockout pin  343  are at opposite sides of the gate  325 . The knockout pin  343  includes a trimming edge  348 . 
     Since the second cavity surface  323  includes the protrusion  328 , a product  38  formed in the cavity includes a depression (not labeled) adjacent to the gate  325 . When the trimming edge  348  trims excess material formed in the gate  325  from the product  38 , an end of the excess material is extruded into the depression, and resistance exerted on the trimming edge  348  during trimming is reduced. Therefore trimming the excess material is easier, a trimmed surface of the product  38  is smoother, and a working lifetime of the trimming edge  348  is longer. 
     Alternatively, the injection mold  20  (or  30 ) may include more than one gate  225  (or  325 ) and more than one knockout pin  243  (or  343 ). In other alternative embodiments, the first ejector retention plate  241  may omit the slider  247 . In such cases, a bottom end of the knockout pin  243  slides horizontally in the sliding slot  246 . 
     Finally, while various embodiments have been described and illustrated, the disclosure is not to be construed as being limited thereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the disclosure as defined by the appended claims.