Patent Publication Number: US-2023144539-A1

Title: Method for molding and forming flip-flop and mold thereof

Description:
BACKGROUND OF THE INVENTION 
     Field of Invention 
     The invention relates to shoemaking technology, and more particularly to a method for molding and forming a flip-flop and a mold thereof. 
     Related Art 
     Flip-flop structurally comprises a sole and a slender V-shaped strap, due to the slender structure of the V-shaped strap, in the conventional technology of using polymer material as a raw material for manufacturing, it is difficult to integrally form the V-shaped strap on the sole in a single molding and forming process, and it is required to adopt different manufacturing processes to make the sole and the V-shaped strap separately, and then the sole and the V-shaped strap are assembled with each other through processing to complete a finished product of the flip-flop. 
     SUMMARY OF THE INVENTION 
     Therefore, a main object of the invention is to provide a method for molding and forming a flip-flop using a polymer raw material as a material, and a slender and elongated V-shaped strap of the flip-flop is integrally formed on a sole through a mold to eliminate an assembly process of secondary processing. 
     In order to achieve the above object, a main technical feature of the method for molding and forming the flip-flop provided by the invention is that when the polymer raw material is filled into a mold chamber space of the mold, the filled raw material is preferentially flowed in a direction of a strap area space used to mold a V-shaped strap portion of the flip-flop to ensure that the slender V-shaped strap portion of the flip-flop can be integrally formed. 
     In order to achieve the above method, the invention further provides a mold for molding and forming a flip-flop comprising a first mold plate and a second mold plate used to form a multi-piece mold body, a mold chamber defined by the first mold plate and the second mold plate overlapping and connecting to each other in a mold clamping state, and three material filling channels separately provided on the first mold plate to communicate with the mold chamber, a polymer raw material externally provided is capable of entering the mold chamber through the material filling channels to be reacted, foamed, molded and formed by the mold chamber into a finished product of the flip-flop. 
     In order to mold the required flip-flop, the mold chamber is divided into a sole area shaped like the flip-flop sole, a strap area shaped like the slender and elongated V-shaped strap of the flip-flop, and three hole-shaped connecting areas communicating with the sole area and the strap area respectively and corresponding to positions of three end points of the V-shape, and an outlet orifice of each of the material filling channels located on a chamber wall of the mold chamber is respectively facing toward each of the three connecting areas, thereby, when the polymer raw material externally provided and pushed by an external force enters the mold chamber through each of the outlet orifices, the polymer raw material entering the mold chamber can be first accumulated in the connecting areas or their adjacent areas due to the above-mentioned relative positions, so that the polymer raw material is capable of smoothly entering a space of the strap area, and the space of the strap area can be fully filled with the polymer raw material. 
     On the other hand, the above disclosed method can also be carried out with the assistance of the technique of back-pressure foaming and forming, that is, before the polymer raw material is filled, a back-pressure gas is filled into the mold chamber of the mold for molding and forming the flip-flop in the mold clamping state, so that inside the mold chamber is filled with the gas with a predetermined pressure value, and then the above-mentioned polymer raw material filling procedure is carried out. After filling of a rated amount of the polymer raw material is completed, the back-pressure gas is vented from the mold while the polymer raw material is foaming, and foaming is completed while the back pressure disappears. 
     Wherein, the mold for molding and forming the flip-flop further comprises at least one gas channel capable of being controlled to open and close to be served as a flow channel for the back-pressure gas to enter and exit the mold chamber. 
     Further, a quantity of the gas channel can be set to more than one, the gas channels can be divided into a first set communicating with the sole area and a second set communicating with the strap area, thereby when the back-pressure gas is vented in the method for molding and forming the flip-flop, the back-pressure gas located in the strap area can be vented first through the second set of the gas channels, so that a back pressure value of the gas in the strap area reduces or reaches a vacuum level, in this way, through a difference in back pressure values between the sole area space and the strap area space, the polymer raw material located in the sole area of a higher pressure value can be pushed to move to the space of the strap area of a lower pressure value to ensure that the strap area can be fully filled with the polymer raw material, and then all the back-pressure gas still remaining in the mold chamber is vented to proceed with foaming. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is flow diagrams of a preferred embodiment of the invention. 
         FIG.  2    is a perspective view of a flip-flop made according to a preferred embodiment of the invention. 
         FIG.  3    is a cross-sectional view of a mold according to a preferred embodiment of the invention. 
         FIG.  4    is a top view of the mold according to a preferred embodiment of the invention. 
         FIG.  5    is a cross-sectional view of the mold provided with gas channels according to a preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIG.  1   , a method  10  for molding and forming a flip-flop provided in a preferred embodiment of the invention is used to manufacture a flip-flop  20  as shown in  FIG.  2   , and is performed by a mold  30  for molding and forming a flip-flop as shown in  FIG.  3   . 
     Please refer to  FIGS.  3  and  4   , the mold  30  for molding and forming the flip-flop is a multi-layer mold, and comprises a first mold plate  31  and a second mold plate  32  with an appropriate thickness respectively, a mold chamber  33  defined by the first mold plate  31  and the second mold plate  32 , and three hole-shaped material filling channels  34 . 
     The first mold plate  31  and the second mold plate  32  are capable of displacing relative to each other between a mold clamping position when overlapping and connecting with each other as shown in  FIG.  3    and a mold opening position when separating and spaced apart from each other under application of an external force, and the first mold plate  31  and the second mold plate  32  located at the mold clamping position jointly define the mold chamber  33  in a closed state between the first mold plate  31  and the second mold plate  32 . 
     The mold chamber  33  has a spatial shape the same as that of the flip-flop  20  as shown in  FIG.  2   , and is divided into a sole area  331  corresponding to a shape of a sole  21  of the flip-flop  20  and located between the first mold plate  31  and the second mold plate  32 , a strap area  332  corresponding to a slender and elongated V-shaped strap  22  of the flip-flop  20  and located in the second mold plate  32 , and three hole-shaped connecting areas  333  corresponding to positions of three end points of a V-shape of the strap area  332  and middle parts thereof and located on the second mold plate  32  to communicate with the sole area  331 . 
     Wherein, in order to facilitate taking out a molded product, the second mold plate  32  used to define the strap area  332  can be composed of a mold body  321  and a mold core  322 ; however, the technical content related to the mold core  322  provided in the mold  30  is a commonly known technical content, and is not the technical feature of the invention, so it will not be redundantly described here; but any person having ordinary skill in the art to which the invention pertains can easily complete the mold structure used to define the mold chamber  33  based on the general knowledge at the time of application of the invention. 
     Each of the material filling channels  34  is respectively disposed on the first mold plate  31 , and an outlet orifice  341  of each of the material filling channels  34  is respectively formed on a chamber wall of the mold chamber  33  to communicate the material filling channels  34  with the mold chamber  33 , and each of the outlet orifices  341  is respectively facing toward each of the connecting areas  333 . 
     Further, a virtual outlet area (a) extending along a hole axis of each of the outlet orifices  341  in a direction of the mold chamber  33  respectively forms an intersection with a virtual connecting area (b) extending along a hole axis of each of the corresponding connecting areas  333  in a direction of the sole area  331  within a spatial boundary of the sole area  331 , and a boundary of the intersection can be further expanded to a coaxial overlapping state as shown in  FIG.  3   . 
     The method  10  for molding and forming the flip-flop using the mold  30  for molding and forming the flip-flop comprises steps of: 
     step A: adopting the mold  30  for molding and forming the flip-flop; 
     step B: as shown in  FIG.  3 (A) , positioning the mold  30  for molding and forming the flip-flop at a mold clamping position; 
     step C: pushing a rated amount of a polymer raw material by an acting force applied externally to converge the polymer raw material at an inlet orifice  342  located on a top side of the first mold plate  31  before entering each of the material filling channels  34  respectively, and then the polymer raw material entering the mold chamber  33  through each of the outlet orifices  341 , by means of corresponding positions between each of the outlet orifices  341  and each of the connecting areas  333 , at the beginning of entering the mold chamber  33 , the polymer raw material being capable of converging in the connecting areas  333  and areas surrounding the connecting areas  333  as shown in  FIG.  3 (B) , so that the polymer raw material entering the mold chamber  33  being capable of flowing toward the strap area  332  through each of the connecting areas  333  before filling the sole area  331  to preferentially fill a space of the strap area  332  fully and then fill the sole area  331  after filling the entire space of the strap area  332  to complete filling of the rated amount of the polymer raw material as shown in  FIG.  3 (C) ; wherein, the technical means used to fill the polymer raw material into the mold chamber  33  can be a conventional filling device; however, the injection technique is a basic technical content generally well-known to those having ordinary skill in the art to which the invention pertains, and is not the technical feature of the invention, so it will not be redundantly described here; and 
     step D: after foaming, molding and forming of the filled polymer raw material in the mold chamber  33  as shown in  FIG.  3 (D) , opening the mold  30  for molding and forming the flip-flop to a mold opening position as shown in  FIG.  3 (E)  before taking out a finished product of the formed flip-flop  20 . 
     Thereby, the method  10  for molding and forming the flip-flop is capable of ensuring that the slender and elongated V-shaped strap  22  and the block-shaped sole  21  of the flip-flop  20  can be integrally molded and formed into a finished product in a single molding to eliminate the need for separate manufacturing and additional assembly processing in the conventional technique, and capable of ensuring a stable quality of the formed flip-flop  20 . 
     In addition, there are two more points that need to be further explained and clarified. 
     Firstly, in the method  10  for molding and forming the flip-flop and the mold  30  for molding and forming the flip-flop, although coaxial configuration between each of the outlet orifices  341  and each of the connecting areas  333  is disclosed as an optimal state, but its industrial use is not limited thereto. As long as an efficacy of the filled polymer raw material being capable of entering the strap area  332  preferentially can be achieved by the guiding the filled polymer raw material through each of the outlet orifices  341  to cause the polymer raw material to be adjacent to each of the connecting areas  333  when entering the mold chamber  33 , such technical means or method or device falls within the scope covered by the technical features of the invention. 
     Secondly, performing of the method  10  for molding and forming the flip-flop can be assisted by adopting the technical means of back-pressure molding. The specific back-pressure molding technical content is already disclosed by the prior art, and therefore, only the parts related to the technical features of the invention will be described hereinafter. 
     As shown in  FIG.  5   , in order to form a back pressure in the mold chamber  33 , the mold  30  needs to have a plurality of gas channels  35  that can be used as gas flow channels, and the gas channels  35  are divided into a first set  35   a  communicating with the sole area  331  and a second set  35   b  communicating with the strap area  332 , and opening and closing of each of the gas channels  35  can be controlled; however, the control technique for opening and closing of the gas channels  35  is a conventional technology, so it will not be repeated here. 
     In the method  10  for molding and forming the flip-flop using the mold  30  shown in  FIG.  5   , a back-pressure gas is filled into the mold chamber  33  through each of the gas channels  35  before performing the step C, a pressure formed by the gas filled into the mold chamber  33  causes a back pressure on the polymer raw material that subsequently enters the mold chamber  33 , and prevents the polymer raw material from foaming during filling. 
     The back pressure is continuously maintained until foaming in the step D, that is, while the polymer raw material of the step D is foamed, the back-pressure gas that causes the back pressure is synchronously vented from the mold chamber  33 , and the polymer raw material can be foamed while the back pressure disappears. 
     Wherein, in addition to the method of venting all the back-pressure gas in a single time as described above, another method of venting in stages can also be used. 
     In the method of venting the back-pressure gas in stages, the gas channels  35  of the second set  35   b  are opened, the back-pressure gas located in the strap area  332  is vented first, and then the back-pressure gas located in the sole area  331  is vented. Due to a time difference of venting, a difference in pressure values is generated between the sole area  331  and the strap area  332 , with the pressure difference, the polymer raw material is pushed from the sole area  331  to the strap area  332  to ensure that the polymer raw material is capable of filling the entire space of the strap area  332  fully to maintain a good quality of a finished product. Wherein, in a step of the first stage of venting the back-pressure gas from the strap area  332 , an extent of a pressure reduction is not limited to achieving a vacuum level of full venting. Even though a part of the back-pressure gas still remains, it is still sufficient to form the above pressure difference to ensure an integrity of the V-shaped strap  22  after molding and forming. 
     It is to be understood that the above description is only the embodiments of the invention and is not used to limit the present invention, and changes in accordance with the concepts of the present invention may be made without departing from the spirit of the present invention. For example, the equivalent effects produced by various transformations, variations, modifications and applications made to the configurations or arrangements shall still fall within the scope covered by the appended claims of the present invention.