Patent Publication Number: US-2007116797-A1

Title: Ejector pin and injection mold with the ejector pin

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an ejector pin and an injection mold with the ejector pin, and more particularly to an ejector pin with eccentric mechanism for avoiding the rotation of the ejector pin.  
      2. The Related Art  
      An ejector pin is used to push the product out of the mold. As shown in  FIG. 8  and  FIG. 9 , a first conventional ejector pin  10   a  includes a pin shaft  12   a  and a pinhead  14   a  located on one end of the pin shaft  12   a.  The other end of the pin shaft  12   a  is flat. The pin shaft  12   a  and the pinhead  14   a  are cylinder and have the same axle center ◯ 1 . Because the ejector pin  10   a  easily rotates around the axle center ◯ 1 , the ejector pin  10   a  is usually used in the condition that the surface of the product is flat. While the surface of the product is curved, the flat end of the pin shaft  12   a  injures the product and must be made into curved shape coupled to the surface of the product. Meantime, the ejector pin  10   a  must be fixed in the mold to avoid the surface of the product hurt by the rotation of the ejector pin  10   a.    
      As shown in  FIG. 10  and  FIG. 11 , a second conventional self-fixed ejector pin  10   b  is improved from the ejector pin  10   a.  The flat end of the pin shaft  12   b  is made into ramp to match to the surface of the product. A D-shape head  14   b  is grinded from the cylinder pinhead  14   a . The pin shaft  12   b  and the D-shape head  14   b  have the same axle center ◯ 2 .  
      Referring to  FIG. 12  and  FIG. 13 , in order to fix the self-fixed ejector pin  10   b  in the mold, a special cavity  16   b  of football field shape must be milled in the mold to receive the D-shape head  14   b.  Through the mating of the D-shape head  14   b  and the special cavity  16   b,  the rotation of the self-fixed ejector pin  10   b  is avoided. But the special cavity  16   b  is difficult to be formed by milling. After a round hole is milled it requires moving the mill cutter back and forth for several times to form the special cavity  16   b.  This complex procedure wastes a lot of time and increases the cost.  
     SUMMARY OF THE INVENTION  
      Accordingly, an object of the present invention is to provide an ejector pin comprising a pin shaft and a pinhead located on one end of the pin shaft. The pin shaft and the pinhead are cylinder and have different axle centers. The caliber of the pinhead is bigger than that of the pin shaft. Because the pinhead is cylinder, the process of the production is simplified and the cost is reduced.  
      Another object of the present invention is to provide an injection mold with the ejector pin. The injection mold comprises a first fixed board, a female mold bellow the first fixed board, a female core located in the female mold, a male mold bellow the female mold, a male core located in the male mold, a mold housing formed between the female core and the male core, a second fixed board bellow the male mold, a pair of side boards fixed between the second fixed board and the male mold, a cavity formed between the side boards, a first pushing board located in the cavity defined by the side boards, and a second pushing board fixed bellow the first pushing board. The first pushing board defines a head-received cavity at the bottom and a shaft hole stretching from the top potion of the first pushing board to the bottom communicating with the head-received cavity. The pin shaft hole and the head-received cavity are eccentric and coupled with the pin shaft and the pinhead. The eccentric ejector pin and the eccentric pin shaft hole and head-received cavity are easy to be manufactured. When the ejector pin pushes the product out of the mold housing, any rotation of the ejector pin is avoided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which:  
       FIG. 1  is a perspective view of an injection mold with an ejector pin in accordance with the present invention;  
       FIG. 2  is a perspective view of the ejector pin in accordance with a first embodiment of the present invention;  
       FIG. 3  is a side view of the ejection pin while fixed in the injection mold in accordance with the first embodiment of the present invention;  
       FIG. 4  is a top view of the ejector pin which is fixed in the injection mold, showing that the pin shaft and the pinhead are eccentric;  
       FIG. 5  is the side view of the ejector pin while fixed in the injection mold in accordance with a second embodiment of the present invention;  
       FIG. 6  is the top view of the second embodiment of the ejector pin which is fixed in the injection mold, showing that the pin shaft and the pinhead are eccentric;  
       FIG. 7  is an enlarged view of the potion VII in  FIG. 1 ;  
       FIG. 8  is a front view of a first conventional ejector pin;  
       FIG. 9  is the top plane view of the conventional ejector pin shown in  FIG. 8 ;  
       FIG. 10  is the front view of a second conventional self-fixed ejector pin;  
       FIG. 11  is the top plane view of the second conventional self-fixed ejector pin shown in  FIG. 10 ;  
       FIG. 12  is the side view of the second conventional self-fixed pin which is fixed in the injection mold;  
       FIG. 13  is the top view of the second conventional self-fixed ejector pin fixed in the injection mold. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      For facilitating understanding, like components are designated by like reference numerals throughout the various embodiments of the invention as shown in the attached drawings.  
      Now referring to  FIG. 1 , which shows a cross-section view of a injection mold  100  with an ejector pin  10  in accordance with the present invention. The injection mold  100  includes a first fixed board  20 , a female mold  30  fixed bellow the first fixed board  20 , a female core  32  located in the female mold  30 , a male mold  40  located bellow the female mold  30 , a male core  42  located in the male mold  40 , a second fixed board  50  fixed bellow the male mold  40  and a plurality of side boards  44  fixed between the male mold  40  and the second fixed board  50 . The side boards  44 , the male mold  40  and the second fixed board  50  define a cavity which receives a first pushing board  62  and a second pushing board  64 . The second pushing board  64  is fixed bellow the first pushing board  62 . A plurality of locating pins  72  are fixed on the first pushing board  62 . Each locating pin  72  has a spring  74  and stretches into a hole (not shown) formed in the male mold  40 .  
      While the female mold  30  is closed with the male mold  40 , a mold housing (not shown) is formed between the female core  32  and the male core  42  to hold a product  200 . The ejector pin  10  is fixed in the first pushing board  62  and stretches through the male mold  40  to the mold housing. While the injection mold  100  is open, the first pushing board  62  and the second pushing board  64  slide up and down in the cavity. Accordingly, the ejector pin  10  is driven up and down. Then the product  200  is pushed out of the mold housing.  
       FIG. 2  shows a first embodiment of the ejector pin  10  of the present invention. The ejector pin  10  includes a pin shaft  12  and a pinhead  14  located at bottom end of the pin shaft  12 . The pin shaft  12  and the pinhead  14  are cylinder and have different axle centers. The caliber of the pinhead  14  is bigger than that of the pin shaft  12 . The top portion of the pin shaft  12  is a ramp surface to contact with the surface of the product  200 .  
       FIGS. 3-4  show the ejector pin  10  fixed in the first pushing board  62 . The pinhead  14  and the pin shaft  12  are eccentrically arranged and have different axle centers. That is, the projection of the pin shaft  12  forms a circle ◯ 3  on the pinhead  14 . The circle ◯ 3  is seated in the circle ◯ 4  formed by the pinhead  14 . The circles ◯ 3  and ◯ 4  are eccentric circles and the circles ◯ 3  is enclosed in the circles ◯ 4 . The circles ◯ 3  and ◯ 4  have no portion to contact with each other.  
      As shown in  FIGS. 5-6 , there is a second embodiment of an ejector pin  10  of the present invention. The ejector pin  10  includes a pin shaft  12 ′ and a pinhead  14 ′ located at bottom end of the pin shaft  12 ′. The pinhead  14 ′ and the pin shaft  12 ′ are eccentrically arranged and have different axle centers. The projection of the pin shaft  12 ′ forms a circle ◯′ 3  and the projection of the pinhead  14 ′ forms a circle ◯′ 4 . The circle ◯′ 3  is located in the circle ◯′ 4 . The circle ◯′ 3  and ◯′ 4  are eccentric circles and tangent with each other. That is, the projections of the pin shaft  12 ′ and the pinhead  14 ′ form a pair of tangent circles ◯′ 3  and ◯′ 4 .  
      As shown in  FIG. 7 , the first pushing board  62  defines at least one head-receiving cavity  65  at the bottom and a shaft hole  66  which is extends from the head-receiving cavity  65 . The head-receiving cavity  65  is a cylinder in according to the shape and size of the pinhead  14 . The shaft hole  66  is a cylinder in according to the shape and size of the pin shaft  12 . That is, the head-receiving cavity  65  and the shaft hole  66  are eccentrically arranged. The shaft hole  66  extends through the first pushing board  62  and communicates with the head-receiving cavity  65 . The shaft hole  66  and the head-receiving cavity  65  have different axle centers in according to the axle centers of the pin shaft  12  and the pinhead  14 . Therefore, the ejector pin  10  is inserted in the cavity  65  and the shaft hole  66  for fixing the ejector pin  10  in the injection mold  100 .  
      While assembling, the pin shaft  12  is inserted into the shaft hole  66  from the bottom of the first pushing board  62 . When the injection mold  100  is close, the pin shaft  12  extends through the male mold  40  and the male core  42  to the mold housing. The pinhead  14  locates in the head-receiving cavity  65 . Because of the different axle centers of the shaft hole  66  and the head-receiving cavity  65  the ejector pin  10  is fixed there without rotation. Then, the second pushing board  64  is fixed bellow the first pushing board  62 . When the mold is open, the first and second pushing boards  62  and  64  slide up and down and drive the ejector pin  10  to push the product  200  out of the mold housing.  
      In this invention, both the pin shaft  12  and the pinhead  14  are designed as a cylinder. It can be easily manufactured by only one step. Comparing with the complex process of the conventional self-fixed ejector pin  10   b,  the pin shaft  12  of the present invention is simple and easy to achieve. It doesn&#39;t need to grind the cylinder pinhead  14  into D shape. Accordingly, in order to form the head-receiving cavity  65 , it only needs to mill a cylinder cavity according to the shape of the pinhead  14 . It avoid the complex process of moving the mill cutter in the cavity back and forth for several times to form a football field shape.  
      The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.