Abstract:
A sealed bottle, a sealing method and an apparatus for blow molded aseptic bottles are disclosed. A sealing tool, having two integral blades, laterally displaces one side against the opposing side of an inflated parison. The sealing tools forms a seal which includes of a pair of indentations in collapsed portion of the parison, and a build-up material forming a dam therebetween.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to blow molded sealed aseptic bottles, a method for blow molding sealed aseptic bottles and an apparatus for sealing blow molding aseptic bottles. 
     Conventional aseptic bottles are blow molded using high pressure sterile air. The high pressure sterile air is vented and then the bottles are either sealed in the mold or the molded bottles are filled and sealed immediately after being molded so as to assure the sterility of the bottles and their contents. Often it is not practical to fill freshly molded sterile bottles. For example, there may be a time interval or travel distance between the blow molding operation and the filling operation. 
     Sealing blow molded aseptic bottles in the mold has met with limited success, requiring complicated tooling and processing and resulting in bottles that are fragile and prone to failure during transportation/storage prior to filling. Thus, there is a need for a simplified seal for aseptic bottles that is more rugged and employs less complex tooling. A rugged, simplified seal for aseptic bottles will assure that it can be stored for a sufficient period of time without damage to the seal or distortion to the aseptic bottle. 
     In achieving the above objectives and overcoming the limitations of the prior art, the present invention provides a sealing apparatus for blow molded bottles which includes a pair of mold halves that define a bottle cavity, first and second dome cavities and a passageway connecting the dome cavities. A sealing is removably mounted through one of the mold halves and is movable so as to be extended into the passageway. The tool includes a pair of spaced apart blades formed on its distal end. In a retracted position, the tool and its blades are substantially withdrawn from the passageway. In an extended position, the blades of the tool extend partway across the passageway to compress a portion of a blow molded parison therein and form a seal in which the vestiges of the pinch line are eliminated. In the seal achieved with the present invention, the two layers of the polymeric material become molecularly joined forming what is referred to herein as a molecular seal. 
     In another aspect, the present invention provides a bottle which includes a body portion formed with a first dome connected to a second dome by a collapsed passageway. The collapsed passageway forms a seal having one side of the passageway displaced laterally against the opposing side, thereby being collapsed, and further having defined therein, a pair of adjacent indentations in the thermoplastic resin. 
     In its final aspect, the present invention provides a method for forming a sealed, unfilled hollow aseptic container from a parison of thermoplastic material. The method includes the steps of introducing a molten parison between a pair of open mold halves, closing the mold halves to capture the parison in a mold cavity having the shape of a container; flowing pressurized air into the interior of the captured parison to expand the walls of the parison against the mold cavity thereby forming an expanded parison in the shape of the mold cavity; reducing the pressure within the expanded parison; and collapsing a portion of the expanded parison and forming at least one molecular seal in the collapsed portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various advantages of the present invention will become apparent to one skilled in the art upon reading the following specification and by reference to the drawings which include: 
         FIG. 1  is a cross-sectional view of a pair of open mold halves with a sealing tool according to the present invention; 
         FIG. 2  is a cross-sectional view, prior to sealing, of a blow molded aseptic bottle located within the mold prior to sealing; 
         FIG. 3  is a cross-sectional view similar to  FIG. 2  of a sealed aseptic bottle; 
         FIG. 4  is an enlarged view of the extended tool for sealing the aseptic bottle; 
         FIG. 5  is a side view of the sealing tool according to the present invention; 
         FIG. 6  is a side sectional view of an upper portion of the mold half with the sealing tool; 
         FIG. 7  is a perspective view of the tool in  FIG. 6 ; and 
         FIG. 8  is a sectional view of a sealed aseptic bottle according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, extrusion blow molded plastic container bottles  30  are typically made from high density polyethylene resin although other suitable resins can be used. In forming such a bottle  30 , a parison  12  of hot sterile resin is extruded between an open pair of complimentary mold halves  14 ,  16  as shown in  FIG. 1 . The mold halves include surfaces defining a bottle cavity  18 , blow dome recess  20  and spin dome recess  22 . A blow channel  24  connects the blow dome recess  20  to the spin dome recess  22 . The spin dome recess  22  is formed immediately above the bottle cavity  18 . 
     When the molds  14 ,  16  are closed and the parison is blow molded, as shown in  FIG. 2 , the cavity  18 , recesses  20 ,  22  and channel  24  in the mold halves  14 ,  16  form the inflated parison  12  into a bottle  30  that includes an integral spin dome  32  and blow dome  34 , the blow dome  34  located above the spin dome  32  and being connected thereto by a blow passage  33 . One mold half  14  includes a blow needle passage  26  which extends to the blow dome cavity  20 . A needle (not shown), connected to a source of sterile blow air through an appropriate valving system, is coupled to a drive mechanism that moves the needle back and forth between a retracted position and an extended position. In the extended position, the needle tip pierces into the parison  12  within the blow dome cavity  20 . The bottle  30  and associated structures are then blow molded and the pressurized blow air is exhausted, reducing the pressure in the mold to a negative pressure (about negative 10–20 inches of water). 
     Once reaching the appropriate negative pressure, a sealing tool  49 , which is mounted in the cavity in a passageway  51  in the mold half  14 , is moved by a drive (not illustrated) to engage the blow passage  33  and seal the bottle  30  above the spin dome  32 , as shown in  FIGS. 3 and 4 . The sealing tool  49  includes a bar  50  having a pair of integral blades  52 ,  54  which, when actuated, are extended into the material forming the blow passage  33 . The passageway  51 , within which the sealing tool  49  is mounted, locates the tool  49  at a right angle to the blow passage  30 . The blades  52 ,  54  are integrally formed with the sealing tool  49 , extend through ports  44 ,  46  in the end of passage  51 , and are longitudinally spaced apart along the blow channel  24  to assure the formation of a seal according to this invention. 
     The sealing tool  49  is reciprocally driven by a drive mechanism  27 , which can be pneumatic, electric or mechanical. The bar  50  itself is formed of a round shaft with the two sealing blades  52 ,  54  extending in a parallel but spaced apart relationship from its distal end. In the retracted position, the sealing tool  49  does not extend into the blow channel  24 , but the tips  56 ,  58  of the blades  52 ,  54  are positioned in the ports  44 ,  46  adjacent to the blow channel  24 . The tips  56 ,  58  preferably do not extend past the surface forming the blow channel  24  adjacent to the tool  49  when the sealing tool  49  is in the retracted position. 
     As mentioned above, sterile blow air inflates the parison  12  against the walls of the mold halves  14 ,  16 . The mold halves  14 ,  16  are cooled by water so that the skin of the inflated hot plastic in the cavities is quickly cooled to begin hardening and forming the blow dome  34 , spin dome  32 , blow passage  33  and bottle  30 . While thermoplastic resin is a good insulator and it does not lose heat quickly, the surfaces forming in the blow channel  24  may optionally be fitted with heat retention inserts or plates to reduce the heat transfer from the blow channel  24  and aid in sealing of the blow passage  33 . 
     As stated before, the sealing tool  49  is not actuated until there has been an appropriate reduction of pressure within the blown plastic body. The extension of the sealing tool  49  causes the sealing blades  52 ,  54  to protrude from the ports  44 ,  46  and enter the blow channel  24 , pushing the thermoplastic resin of one side of the blow passage  33  toward the other side thereof. The tool  49  and blades  52 ,  54  continued to be advanced and cause the opposing sides of the blow passage  33  to collapse and adhere together forming a seal. With the sides of the blow passage  33  collapsed upon one another, the tool  49  is still further advanced until the blades  52 ,  54  protrude into the material now forming the collapsed blow passage  33 ′. This additional penetration eliminates or minimizes the existence of a pinch line between the opposing sides of the collapsed blow passage  33 ′ and results in the material adjacent to this penetration being molecularly joined to create what is herein referred to as a “molecular seal  57 ” with a dam  59  of material built-up therebetween. This greatly enhances the integrity of the seal  90  and is best seen in  FIGS. 3 ,  4  and  8 . 
     As seen in  FIG. 5 , the tips  56 ,  58  of the sealing blades  52 ,  54 , respectively, are chamfered  60 ,  62  with a small, flat land  61  located centrally on each end. The lands  61  and chamfers  60  help force the material displacement during the extension of the sealing tool  49  and penetration of the blades  52 ,  54  into the material. The dam  59  is formed by pushing material of the collapsing blow passage  33  into the area between the blades  52 ,  54  as the tips of the blades  52 ,  54  penetrate the collapsed passageway  33 ′. The sealing tool  49  is left in the extended position until the collapsed and compressed molten plastic has cooled to the point where the tool  49  can be withdrawn without damage to the newly formed seals. Once the seals are formed, the sealing tool  49  is retracted back to the position shown in  FIG. 2 , the mold halves  14 ,  16  separate and the bottle  30  is removed from the mold cavity. 
     With the seal  90  is formed, the blow dome  34  can be removed without affecting the integrity of the seal  90  of the bottle  30 . This reduces the potential of sending bacteria, molds and yeast, which might be present in the blow dome  34 , to the filling system. 
     The step by step molding of bottle  30  from a sterile thermoplastic resin through an extrusion blow molding operation will now be described. The parison  12  is extruded between open mold halves  14 ,  16 , as shown in  FIG. 1 . The mold halves are closed to capture a portion of the parison  12  within the bottle cavity  18 , the spin dome recess  22 , blow dome recess  24  and the blow channel  24 . Upon closing, the mating surfaces of the mold halves  14 ,  16 , cause the formation of flash  45  integral with the captured parison  12 . 
     Once the mold halves  14 ,  16  have closed, the blow needle is extended through channel  26  into the cavity formed by the blow dome recess  24  until it punctures the confined parison. Sterile blow air, at a pressure of approximately 80–120 pounds per square inch, is caused to flow through the needle and into the parison  12  to inflate the parison against the surfaces of the mold halves  14 ,  16  to form the blow dome  34 , the spin dome  32 , the blow channel  33  and the bottle  30 , all having a common interior. The blow air holds the expanded plastic in intimate contact with the walls of mold halves  14 ,  16  causing the plastic to begin to cool. The entire outer surface or skin of the bottle  30  and associated structures cools below the melt temperature of the thermoplastic resin and begins to harden. 
     During cooling of the plastic in the mold, the trapped blow air in the interior is heated by the plastic to about 200° to 250° F. Following cooling and setting of the bottle skin, the blow needle is withdrawn and the confined, pressurized and hot blow air is vented quickly, preferably to the atmosphere. At the same time, a valve (not shown) is opened and a large volume of pressurized air flows through a venturi (not shown). The remaining air flows rapidly out of the bottle interior. 
     Venting of the pressurized blow air from the bottle  30  in this manner reduces the pressure in the bottle interior to atmospheric pressure. Immediately after the pressure in the bottle falls to atmospheric pressure, the venturi quickly draws air from the interior of the bottle into the venturi and out to atmosphere, which reduces the pressure in the bottle below atmospheric pressure. Thus, the pressure in the bottle interior is at a pressure in the range of about a negative 10 to 25 inches of water. Those skilled in the art will recognize that pressure provided for in the bottle will depend on the specifics of the particular bottle including bottle thickness, geometry and parison temperature. Once the pressure of the interior of the bottle  30  is at the desired negative pressure, the sealing tool  49 , as shown in  FIG. 4 , is actuated to extend the blades  52 ,  54  into the blow passage  33 . 
     The tips  56 ,  58  of the blades  52 ,  54 , respectively, first engage one side of the blow passage  33  and force the softened plastic material into sealing engagement with the material of the opposite side of the blow passage  33 . The chamfered tips  56 ,  58  force the still formable thermoplastic resin into welded engagement with the layer of plastic on the opposite side of the blow passage  33  so as to form a seal. Further extension of the blades  52 ,  54  across the blow channel  24  and into contact with collapsed blow passage  33 ′ causes penetration of the tips  56 ,  58  into the collapsed blow passage  33 ′. This penetration compresses the material and is to a depth in the material which eliminates or significantly reduces the presence of a pinch line between the opposing surfaces of the collapsed blow passage  33 ′, resulting in molecular seals  57  being formed. Upper and lower pinch lines  70 ,  72  can be seen in  FIGS. 3 ,  4  and  8  and are notably absent where penetration of the blades  52 ,  54  has occurred. Between the seals  57  a dam  59  of material is built-up as the chamfers  60  on the tips of the blades  52 ,  54  push material laterally during penetration. Optionally, the thickness of the parison may be increased in the vacinity of the blow channel  24  to provide additional thermoplastic resin for forming the seal. 
     As mentioned above, the mold halves  14 ,  16  may optionally have insulating inserts along the surfaces defining the blow channel  24 , such inserts may be used in order to prevent the thermoplastic resin of the blow passage  33  from being cooled too quickly below the molding temperature of the resin. 
     Those skilled in the art will recognize that in the extended position of the tool  49 , the tips  56 ,  58  push on or through the surface of the collapsed passage  33 ′ by limiting the stroke of the tool  49 . Depth of penetration  50  so as to form the indentations  74 ,  76  will depend on the specifics of a given application including the material type, molding temperature and thickness of expanded parison walls in the blow passage  33  area. 
     Once the seal  90  is formed, the sealing tool  49  is retracted to its initial position, the mold halves separate and the bottle  30  is ejected from the mold cavities  14 ,  16 . As one skilled in the art will appreciate, the flash  45  and blow dome  34  can then be removed without affecting the integrity of the seal  90 . 
     While the above preferred embodiment illustrates the invention, it is understood that this invention is capable of modification and therefore the invention is not limited to the precise detail set forth but falls within the changes and alterations that fall within the purview of the following claims.