Abstract:
A method of scrap reduction in a wheel blow-molding device includes the steps of upwardly extruding a parison and gripping a top end of the parison in a portion of a first mold coupled to the wheel blow-molding device. Then, the parison is enclosed in a second mold coupled to the wheel blow-molding device that follows the first mold. Next, the parison is cut such that a gap in the parison is created.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to scrap reduction in blow molding, and more particularly to scrap reduction in a wheel blow molding device.  
         [0003]     2. Related Art  
         [0004]     Wheel blow molding devices typically have of a series of molds arranged on a wheel revolving around a central pivot. As an empty mold approaches an extruded parison, it closes around the parison, pinching off or cutting the parison. Once the mold is closed, a blow needle is inserted into the mold to inflate the parison into the mold. As the mold continues to revolve around the pivot, the product in the mold cools and hardens, and falls out when the mold opens. The process repeats for the series of molds arranged on the wheel.  
         [0005]     When the product or container to be formed is smaller than the mold, a large amount of scrap, or flash, is created because the parison is traditionally as long as the mold.  
         [0006]     What is needed then is a method that reduces the scrap generated in a wheel blow molding device when the product being produced is significantly shorter than the mold is long.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     Embodiments of the present invention provide a mold for and a method of reducing scrap production in a wheel blow-molding device. An end of an extruded parison portion is gripped by a portion of a leading mold, while the remainder of the parison portion is enclosed in a following mold. The parison portion is cut at a length appropriate for the container being molded, instead of leaving the parison portion as long as the mold body. The mold halves may be in contact with each other in the mold portion where no parts of the container are to be formed.  
         [0008]     In an exemplary embodiment, the present invention may be a method of scrap reduction in a wheel blow-molding device, comprising: upwardly extruding a parison; gripping a top end of the parison in a portion of a first mold coupled to the wheel blow-molding device; enclosing the parison in a second mold coupled to the wheel blow-molding device and following the first mold; and cutting the parison, such that a gap in the parison is created.  
         [0009]     An another exemplary embodiment, the present invention may be a mold for scrap reduction in a wheel blow-molding device, the mold comprising: a first half and a second half, each half having a rotation direction and a transverse direction perpendicular to the rotation direction, each half having: a cavity, adapted to receive a first parison; a parison gap region adjacent to the cavity in the rotation direction; and a parison gripping region adjacent to the parison gap region, adapted to grip an end of a second parison; wherein when the first and second mold halves are coupled, the parison gap regions of the first and second mold halves are in contact with one another and are adapted to prevent the first parison from being blown into the parison gap region.  
         [0010]     Further objectives and advantages, as well as the structure and function of preferred embodiments will become apparent from a consideration of the description, drawings, and examples. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.  
         [0012]      FIG. 1  depicts an exemplary embodiment of a method according to the present invention;  
         [0013]      FIG. 2  depicts an exemplary embodiment of a mold and a wheel blow molding device according to the present invention;  
         [0014]      FIG. 3  depicts an exemplary embodiment of a parison extrusion device according to the present invention; and  
         [0015]      FIG. 4  depicts an exemplary embodiment of the parison extrusion device shown in  FIG. 3  cutting a parison, according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     Embodiments of the invention are discussed in detail below. In describing embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention. All references cited herein are incorporated by reference as if each had been individually incorporated.  
         [0017]      FIG. 1  is a flowchart illustrating an exemplary embodiment of a method of the present invention.  FIG. 2  illustrates an exemplary embodiment of an apparatus  202  used to execute the method. The apparatus  202  comprises a series of molds  204   a ,  204   b  (collectively  204 ) disposed radially around a central pivot in a wheel. A parison extrusion apparatus (not shown) is disposed in proximity to the side of the wheel where the molds  204  are moving upward away from the floor (as indicated by arrow  206 ), so that extruded parison (e.g.,  200 ) may be inserted into or enclosed by the molds. The use of the term “upward” is not meant to limit the invention, but may instead be a direction relative to the turning of the wheel.  
         [0018]     The method of the invention may occur cyclically as any one particular mold completes a revolution about the central pivot. In block  102 , mold  204   a  is closing on a previously extruded parison portion and grips a short portion of a next parison portion in a parison gripping portion  210   a . In block  104 , as the wheel continues to rotate, mold  204   a  pulls the next parison portion upward, e.g., in the direction of arrow  206 , and the next parison portion is extruded in a generally upward direction between the two halves of the next mold  204   b . When the parison portion between the mold halves of mold  204   b  covers the length of the cavity  208 , the parison is cut, in block  106 . The parison may extend slightly beyond the end of the cavity to create a tail flash  216 . In block  108 , extrusion of the parison stops for a period of time equivalent to the passing of the gap region  212 , while the mold  204   b  closes on the parison portion. In block  110 , extrusion of the parison resumes at a time sufficient to allow a short portion of the newly extruded parison to be gripped in the parison gripping portion  210  of closing mold  204   b . A blow needle is inserted into mold  204   b  and a container is blow-molded into the mold  204   b  in block  112 . As the mold  204   b  completes a revolution, the mold  204   b  opens and the container falls or is ejected from the mold in block  114 . The process repeats as mold  204   b  closes over a new parison portion and begins a new revolution.  
         [0019]      FIGS. 3 and 4  illustrate an exemplary parison extrusion apparatus in an extruding and a cutting position, respectively. The parison extrusion apparatus includes a bushing  302  forming a die gap  304 , and a die pin  306 . The position of the die pin  306  in the die gap  304  determines the thickness of the parison by controlling the size of the opening through which the parison is extruded. As  FIG. 4  shows, the parison may be cut by closing the die gap  304  completely. In an exemplary embodiment, the die pin  306  moves upward very rapidly to make contact with the bushing  302  when cutting the parison, but does not distort the bushing orifice. The internal angular relationship between the internal sides of the bushing  302  and the sides of the die pin  306  may vary from what is depicted in the figures.  
         [0020]     While the method described above can be practiced with conventional molds for wheel blow molding devices, the best results in scrap savings may be achieved with a modified mold as seen in  FIG. 2 . In an exemplary embodiment, a mold  204  for scrap reduction in a wheel blow-molding device includes two halves. When the two halves are joined, they form a cavity  208  to receive a parison. Following the cavity, from the perspective of the direction of motion, is a parison gap region  212 . In the parison gap region  212 , the two halves of the mold are in substantial contact with each other. The parison gap region  212  prevents the creation of scrap when the parison in the mold is blown. In conventional molds, a thin cavity is needed in this portion of the mold to accommodate the scrap of the parison. In an exemplary embodiment, the parison gap region  212  may include a small tail flash region  216  directly adjacent to the cavity  208  to allow the formation of a tail flash on the container. The base of the mold  204  includes a parison gripper  210  adjacent to the parison gap region  212 . Parison gripper  210  is adapted to grip the end of a parison. One mold half further contains an opening  214  adapted to receive a blow needle for introducing blow air into the mold.  
         [0021]     By providing parison gap region  212  and cutting the parison as discussed above, a significant reduction in parison waste can be achieved. By properly coordinating the cutting of the parison and the period for which no parison is extruded, little or no parison is provided to parison gap region  212 , thus reducing parison waste.  
         [0022]     The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the present invention. All examples presented are representative and non-limiting. The above-described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.