Abstract:
A method for elongating a foil, comprising steps of: providing an injection molding device, the injection molding device comprising a male mold having a projecting part protruding and a female mold defining a cavity; transmitting the foil into the injection molding device and between the male and female molds; clamping the male and female molds to form a molding space, the molding space being separated into a first airproof space adjacent to the female mold and a second airproof space adjacent to the male mold by the foil; vacuuming the first airproof space to suck the foil toward the first airproof space; and inputting thermal medium into the second airproof space to press the foil to cling to the inner surface of the cavity of the female mold.

Description:
[0001]    Relevant subject matter is disclosed in the co-pending U.S. patent applications (Attorney Docket Nos. US14020, US14022, US14023, US14024) filed on the same date and entitled “INJECTION MOLDING DEVICE”, “METHOD FOR MANUFACTURING A FOIL DECORATED MOLDING”, “VALVE DEVICE OF INJECTION MOLDING DEVICE”, “INJECTION MOLDING DEVICE”, respectively, which are assigned to the same assignee with this patent application. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method for elongating a foil in an injection molding device. 
         [0004]    2. Description of Related Art 
         [0005]    Conventionally, various kinds of methods for manufacturing a foil decorated molding, which is molded by an injection molding process and has a transfer layer removed from a substrate foil of a transfer foil and placed on the surface of the molding after the transfer foil is inserted into cavities in an injection mold, have been known in the art. Since the use of the method requires an alignment of the transfer foil along a cavity-forming face of the mold, the transfer foil is preheated before the injection molding process so as to be easily aligned along the cavity-forming face of the mold where the cavity-forming face thereof is greatly recessed or projected from a parting face of the mold. 
         [0006]    A traditional injection molding method includes transferring a heater between the male mold and the female mold to heat the foil before matching the molds, and removing the heater after the foil is heated. However, because of the need for the heater and the space it occupies, cost and volume of the injection mold is increased. 
         [0007]    What is needed is to provide an effective method for elongating a foil in an injection molding device. 
       SUMMARY 
       [0008]    In one embodiment, a method for elongating a foil, comprising steps of: providing an injection molding device, the injection molding device comprising a male mold having a projecting part protruding and a female mold defining a cavity; transmitting the foil into the injection molding device and between the male and female molds; clamping the male and female molds to form a molding space, the molding space being separated into a first airproof space adjacent to the female mold and a second airproof space adjacent to the male mold by the foil; vacuuming the first airproof space to suck the foil toward the first airproof space; and inputting thermal medium into the second airproof space to press the foil to cling to the inner surface of the cavity of the female mold. 
         [0009]    Other advantages and novel features of the present invention will become more apparent from the following detailed description of an embodiment when taken in conjunction with the accompanying drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a cross-sectional view of an injection molding device actualizing a method for elongating a foil in accordance with an embodiment of the present invention, the injection molding device including a male mold and a female mold; 
           [0011]      FIG. 2  is a cross-sectional view of the female mold, similar to  FIG. 1 ; 
           [0012]      FIGS. 3 and 4  are enlarged, partially cutaway views of the male mold of  FIG. 1 , showing two using states respectively; 
           [0013]      FIG. 5  is a cross-sectional view of the female mold of  FIG. 1 , but showing the foil extending into the cavity of the female mold; 
           [0014]      FIG. 6  is similar to  FIG. 1 , but showing the foil extending along an inner surface of the cavity of the female mold and the male and female molds matched together; 
           [0015]      FIG. 7  is similar to  FIG. 6 , but showing a state after injection; and 
           [0016]      FIG. 8  is a flow chart of the method for elongating the foil. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Referring to  FIG. 1 , an injection molding device actualizing a method for elongating a foil in accordance with an embodiment of the present invention is provided for elongating a foil  100 . The injection molding device includes a transport  10 , a mold including a male mold  20  and a female mold  30 , a plurality of pressing members  40 , and a thermal medium source  90 . 
         [0018]    The male mold  20  forms a projecting part  21  protruding toward the female mold  30 . A plurality of air discharging holes  23  is defined in the male mold  20  around the projecting part  21  and extending from a side, facing the female mold  30 , of the male mold  20  to an opposite side of the male mold  20 . A pressure release valve  80  is connected to each air discharging hole  23 . The pressure release valve  80  is adjustable according to need during molding. A plurality of receiving slots  25  is defined in the male mold  20  in vicinity of edges of the male mold  20 . A plurality of hermetic rings  27  is received in the corresponding receiving slots  25 . 
         [0019]    Referring to  FIG. 2 , the female mold  30  defines a cavity  31  therein. The cavity  31  includes a bottom surface A 3 , a first side surface A 1  extending from an edge of the bottom surface A 3  and a second side surface A 2  extending from an opposite edge of the bottom surface A 3  to a surface that faces the male mold  20 , with an opening formed on the corresponding surface of the female mold  30 . A length of the opening of the cavity  31  is L. A plurality of air discharging holes  32  is defined in the male mold  20  and extending from a side, facing the male mold  20 , of the female mold  30  to an opposite side of the female mold  30 . At least two of the air discharging holes  32  extend from the bottom surface A 3  of the cavity  31  to the corresponding side of the female mold  30  opposite to the male mold  20 . Each air discharging hole  32  is connected to a vacuum pump at the side of the female mold  30  opposite to the male mold  20 . A plurality of hermetic rings  33  is attached to the female mold  30  adjacent to an edge of the female mold  30 . 
         [0020]    Referring also to  FIGS. 3 and 4 , the male mold  20  defines a plurality of channels  29  therein extending from a side, facing the female mold  30 , of the projecting part  21  to a side of the male mold  20  opposite to the female mold  30 . Each channel  29  includes a bell-mouthed recessed portion  291  defined in the projecting part  21  with a large end thereof in the surface facing the female mold  30 , of the projecting part  21 , a conduit  295  defined in the male mold  20  communicating with a small end of the recessed portion  291 , and an L-shaped slender duct  296  with one end communicating with the conduit  295  and the other end passing through the surface opposite to the female mold  30 , of the male mold  20 . A block  298  protrudes in from one end opposite to the recessed portion  291 , of the conduit  295 . One end of a pipe  91  is connected to the end opposite to the female mold  30 , of each slender duct  296 , and the other end of the pipe  91  is connected to the thermal medium source  90 . A through hole is defined in the block  298 . 
         [0021]    A plug  70  is attached in each channel  29 . The plug  70  includes a taper-shaped obturating portion  71  for obturating the recessed portion  291  of the channel  29 , and a pole  73  extending from a small end of the obturating portion  71 . The pole  73  extends through the through hole of the block  298 . A fastening member  75  is fixed to a distal end of the pole  73 . A resilient member  79 , such as a spring, fits about the pole  73  and is resiliently located between the block  298  and the fastening member  75 . 
         [0022]    The thermal medium source  90  has thermal medium contained therein, such as thermal liquid or high-pressure gas. In this embodiment, the thermal medium is thermal high-pressure gas. The thermal medium is capable of being heated by an electric heater or an infrared ray heater (IR heater). 
         [0023]    The transport  10  includes two transporting rollers  13  and two guiding rollers  15  positioned at two opposite ends of the mold respectively, for transporting the foil  100  into the mold. The foil  100  includes a base layer, and a printed layer attached to the base layer and having printed patterns or characters. 
         [0024]    Referring also to  FIG. 8 , the method includes the following steps. The foil  100  is transported into the mold between the male and female molds  20 ,  30 . The male, female molds  20 ,  30 , and the pressing members  40  are clamped together to form a molding space among an inner surface of the cavity  31  of the female mold  30 , the projecting portion  21  of the male mold  20 , and parts around the projecting portion  21 . The pressing members  40  are received in the corresponding receiving slots  25  of the male mold  20 , and press the corresponding hermetic rings  27 ,  33  to airproof the molding space. The molding space is separated into a first airproof space adjacent to the female mold  30  and a second airproof space adjacent to the male mold  20  by the foil  100 . The vacuum pump is connected to the air discharging holes  32  of the female mold  30  to vacuumize the first airproof space, thus the foil  100  is sucked toward the first airproof space, as shown in  FIG. 5 . The pressure release valve  80  is shut, and the value of the pressure release valve  80  is predetermined according to the molding condition. The thermal medium source  90  inputs heated gas to the channels  29  via the pipes  91 . The plugs  70  are driven by the heated gas to move toward the female mold  30 , therefore the channels  29  open. The heated gas is blown into the second airproof space to press the foil  100  to cling to the inner surface of the cavity  31  of the female mold  30 . The foil  100  is intenerated by the heated gas to cling to the inner surface of the cavity  31  easily, as shown in  FIG. 6 . 
         [0025]    Referring also to  FIG. 7 , molten resin is injected through an injection opening defined in the male mold  20  into the molding space. The molten resin presses the plugs  70  into the corresponding channels  29  against resistance of the corresponding resilient members  79 . The heated gas in the second airproof space is released via the air discharging holes  23  of the male mold  20  when the pressure in the molding space is greater than the predetermined value of the pressure release valve  80 . The molten resin is cooled to form a mold body. The mold is opened, with the male mold  20  being separated from the female mold  30 . The base layer of the foil  100  is released from the mold body. Thus, the printed layer of the foil  100  is attached to a surface of the mold body. 
         [0026]    In this embodiment, the injection molding device is used for elongating the foil  100  between the male and female molds  20 ,  30  by exhausting air from the cavity  31  via the air discharge holes  32  of the female mold  30  and pressurizing the foil  100  via the heated gas. For example, a length of the first side surface A 1  is a 1 , a length of the second side surface A 2  is a 2 , and a length of the bottom surface A 3  is a 3 , when the first, second, and bottom surface A 1 , A 2 , A 3  of the cavity  31  and the length L accord with an expressional a 1 +a 2 +a 3 &gt;=(1+20%)*L, the foil  100  is capable of being elongated for suiting the cavity  31  of the female mold  30 . 
         [0027]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.