Patent Publication Number: US-2012025431-A1

Title: High-pressure bottle-blowing process and apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to methods and equipment used for high-pressure bottle blowing. More particularly, the present invention relates to a high-pressure bottle-blowing process and apparatus that are applicable to manufacturing of plastic containers, wherein the container such molded has precise threads and a bottom formed with a right-angle or acute-angle connecting rim. 
     2. Description of Related Art 
     Cosmetic products retailed, such as nail enamel, mascara and liquid eye liner, are mainly contained in plastic containers made through high-pressure bottle blowing. For example, U.S. Pat. No. 6,059,474 issued to the applicant of the present application has disclosed a multi-purpose nail enamel applicator that incorporates a pen head for drawing and a brush member for painting. The container has a decorative cap sleeved onto its closed bottom end for facilitating its stable stand. In another embodiment of the patent, two said cosmetic containers are connected through a connecting ring so that cosmetic products for different purposes or of different colors can be carried conveniently. 
     Conventionally, the cosmetic container is formed by blowing a preform under high pressure and high temperature. The preform is to be provided with a threaded end for coupling an upper cap, and an opposite end as the closed bottom end. However, in the traditional manufacturing method, for smooth bottle-blowing process and mold-releasing process, it is difficult to provide the bottom end with threads, and thus the bottom end can only engage the decorative cap or the connecting ring by means of a close-fit or wedge mechanism. As the close-fit or wedge mechanism is limited in providing firm combination, when an external force is applied between the cosmetic containers or between its bottom end and the combined decorative cap or the connecting ring, the close-fit or wedge mechanism tends to be broken and cause uncoupling of the components. 
     A considerable approach to remedying the problem may be provision thread-based combination between the bottom end of the cosmetic container and the decorative cap or the connecting ring because it is known that thread-based combination is superior to the close-fit or wedge mechanism in engagement. However, the current bottle-blowing process, as mentioned above, only provides one threaded end to a bottle, which is the one for coupling the upper cap and will encounter some problems when trying to form the bottom end with threads. First, when blown and inflated, the bottom end of the preform is unlikely to loyally inherit the shape of the threaded portion on the surface of the mold because the threads of the threaded portion are too fine for the preform to copy the shape through the bottle-molding process. Second, since each of the threads is a depressed part with a sharp point, bubbles may easily exist between the preform and the mode, leading to defective or even absent threads. 
     In addition, also because of the problem of shaping in the bottle-blowing process and mold-releasing process, the container typically has all its corners and edges formed as a chamfered. This can even highlight the weakness of the close-fit or wedge mechanism because when the bottom end combined with the decorative cap or the connecting ring, the chamfered edge is more likely to slide along and eventually disengage from the decorative cap or the connecting ring under external force, and is less effective in positioning the bottom end as compared with a non-chamfered, square edge. 
     To sum up, only when the problems about the chamfered edges/corners and the defect and absence of threads from the bottom end are overcome, the firm combination between the components of the container can be ensured. 
     SUMMARY OF THE INVENTION 
     In view of the shortcomings of the prior-at device, the present invention herein provides a high-pressure bottle-blowing process. 
     According to the present invention, the high-pressure bottle-blowing process comprises steps of:
         a. providing at least one preform to a molding device;   b. closing a first mold half and a second mold half of the molding device to form a mold cavity between the first mold half and the second mold half for accommodating the preform therein;   c. providing a high-pressure gas to blow and form the preform into a semi-finished container;   d. pushing a movable block below the mold cavity toward the mold cavity to indent the semi-finished container and form the semi-finished container with a bottom so as to shape a finished container; and   e. releasing the finished container from the molding device.       

     In the step (d), the movable block is configured to move vertically in a through hole below the mold cavity so that when rising, the movable block pushes the convex bottom upward to work with the high-pressure gas and make the convex bottom partially extend inward the threading groove, so as to provide the semi-finished container with a threaded portion corresponding to the threading groove. 
     One objective of the present invention is to provide the above-described high-pressure bottle-blowing process, wherein by using the movable block to push the semi-finished container upward, the plastic material is partially pushed backward to form the bottom with a flat surface or a concave surface, so that the bottom is bordered with the periphery of the finished container by a right-angle or acute-angle connecting rim, which allows firmer combination between the components of the container as compared with a container made through he prior-art process. 
     Another objective of the present invention is to provide the above-described high-pressure bottle-blowing process, wherein by using the movable block to push the semi-finished container upward, the plastic material actually fills the threading groove, so that the threaded portion is formed with evener and more precise threads as compared with a container made through he prior-art process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as well as a preferred mode of use, further objectives and advantages thereof will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic drawing of a high-pressure bottle-blowing apparatus according to the present invention; 
         FIG. 2  is a schematic drawing of a molding unit of the present invention; 
         FIGS. 3 and 4  illustrate motion of the molding unit of the present invention; 
         FIG. 5  is a partial, enlarged view of  FIG. 4 ; 
         FIG. 6  also illustrates motion of the molding unit of the present invention; and 
         FIG. 7  is a partial, enlarged view of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a bottle-making machine primarily comprises a material feeding unit  10 , a material injecting unit and a molding unit  30 . The present invention makes improvement on the molding unit  30  and is applicable to manufacturing of plastic containers made of, for example, PET (Polyethylene terephthalate). 
     In manufacturing, plastic grains are introduced from the material feeding unit  10  and then heated to become melted by a heating device  11 . Then the melted material is delivered to the material injecting unit  20  for making preforms. The preforms  40  are transported by a holding device  21  to an output conveyer  22 , and the output conveyer  22  sends the preforms  40  to the molding unit  30  for bottle blowing. The formed preform  40  has a cap-connecting threaded section  41  and a bottle body  42 . While the above configuration is illustrated, it is appreciated by people skilled in the art that any of the existing method for making preforms is usable in the present invention. Since the processes for material-feeding, material injection and formation of preforms are known and not features of the present invention, further discussion is omitted herein. 
     As can be seen in  FIG. 1  and  FIG. 2 , the molding unit  30  includes a molding device  31 , a plurality of first power cylinders  32 , at least one second power cylinder  33 , and a bottle-blowing device (not shown). The molding device  31  comprises a mold set  34  and at least one movable block  35 . The mold set  34  is composed of a pair of symmetrical mold halves, namely a first mold half  341  and a second mold half  342 . The first mold half  341  and the second mold half  342  are driven by the first power cylinders  32 , respectively, so that the first mold half  341  and the second mold half  342  can be drawn together or separated. 
     The first mold half  341  has at least one first recess  343  and the second mold half  342  has at least one second recess  344 . When the first mold half  341  and the second mold half  342  are drawn together, a mold cavity  36  defined by the first recess  343  and the second recess  344  is formed between the first mold half  341  and the second mold half  342  (as shown in  FIG. 4 ), for accommodating a said preform  40 . The mold cavity  36  is communicated to the exterior of the mold set  34  at upper and lower ends thereof. A through hole  361  is formed at the lower end of the mold cavity  36 . From its upper end, the mold cavity is formed successively a cap-connecting thread corresponding section  362 , a bottle-body receiving section  363  and a thread-forming section  364 . The thread-forming section  364  adjacent to the through hole  361  is provided with at least one threading groove  365 . 
     The movable block  35  deposited between the first mold half  341  and the second mold half  342  is driven by the second power cylinder  33  to move vertically in the through hole  361 . It is to be noted that the number of the movable block  35  is not limited and only subject to the number of the mold cavity  36 . The bottle-blowing device provides a high-pressure gas for performing bottle blowing. 
     Referring to  FIG. 3  and  FIG. 4 , the preform  40  is set in a preform seat (not shown) and transported to the molding device  31 . Afterward, the first mold half  341  and the second mold half  342  are drawn together to such confine the preform  40  in the mold cavity  36  that the cap-connecting threaded section  41  is aligned with the cap-connecting thread corresponding section  362  and the bottle body  42  is aligned with the bottle-body receiving section  363 . After the preform  40  is properly positioned, the bottle-blowing device introduces a high-pressure gas into the preform  40  in the mold cavity  36 . 
     Referring to  FIG. 4  and  FIG. 5 , the preform  40  subject to the high-pressure gas has the bottle body  42  inflated and formed conforming to the profiles of the bottle-body receiving section  363  and the thread-forming section  364  so as to become a container  50  with a convex bottom  51 , which is a semi-finished container at this time. Since the high-pressure gas, when reaching the thread-forming section  364 , makes the preform  40  inflated directly downward, the threading groove  365  is not fully filled by the material of the preform  40 , so that a to-be-filled space  37  is left between the bottle body  42  and the threading groove  365 . 
     Referring to  FIG. 6  and  FIG. 7 , after the preform  40  is inflated into the semi-finished container  50 , the movable block  35  is driven by the second power cylinder  33  to rise from the through hole  361  for pushing the convex bottom  51  upward. As a result, the convex bottom  51  has the material partially pushed backward to form a bottom  52  at the lower end of the container  50 . The pressure of the high-pressure gas presented in the container  50  resists the pushed backward material of the convex bottom  51 . Thus, the material of the convex bottom  51 , under the interaction of the up-going force and the down-going force, is forced to expand into the threading groove  365  and fill the to-be-filled space  37 , thereby forming a threaded portion  53  on the container corresponding to the threading groove  365 . 
     From the aforementioned operation it is learned that when the movable block  35  upward pushes the semi-finished container  50 , the bottom  52  is formed at the lower end of the finished container  50  with a flat surface or a concave surface. Consequently, the bottom  52  is bordered with the periphery of the finished container  50  by a right-angle or acute-angle connecting rim. Meantime, the threaded portion  53  is formed with even and precise threads. Thus, the finished container  50  is significantly improved in quality and appearance. Besides, the finished container  50  may be further mounted with a decorative cap (not shown) around the bottom  52  in the manner that the threaded portion  53  couples the decorative cap through matching threads and the non-chamfered edge of the bottom  52 . The resultant combination is therefore firm and secure against departing under unintentional external force or impact. In virtue of the synergistic effect contributed by the bottom  52  and the threaded portion  53 , the finished container  50  and the decorative cap can be combined with enhanced firmness. 
     The present invention has been described with reference to the preferred embodiment and it is understood that the embodiment is not intended to limit the scope of the present invention. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present invention should be encompassed by the appended claims.