Abstract:
A method and apparatus is provided to transport parisons from the extrusion die to a second location. The parison is extruded and a collar means is provided to contact the parison near its upper end and create a holding geometry whereby the parison is retained by the collar means without pinching the parison. The parison is then transported vertically or horizontally to the mold unit without closing or pinching the parison. The holding geometry is created by slightly deforming the parison wall near the collar means. The parison is therefore transported to the second location, for example a mold unit, instead of moving the mold unit, to the parison.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application is a continuation of U.S. application Ser. No. 08/919,887, filed Aug. 28, 1997 now abandoned, which is a continuation of U.S. application Ser. No. 08/337,274, now abandoned, filed Nov. 10, 1994 which claims priority from United Kingdom Application No. 9323267.6, filed Nov. 11, 1993. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to a method and apparatus for making hollow plastic products, and more particularly to a method and apparatus for transporting the parison of molten plastic to the mold units without pinching the parison. 
     BACKGROUND OF THE INVENTION 
     It is well known in the art to make hollow plastic products such as containers or other like products using the extrusion blow-molding process. In the extrusion blow-molding process, plastic in a melted state is introduced into a mold. The molten plastic is generally extruded into a cylindrically-shaped tube or hose referred to as a parison. The mold is closed and the interior of the mold is then pressurized to force the melted plastic onto the interior walls of the mold, which is then allowed to cool so that the plastic solidifies. The end product is a hollow plastic product having the shape of the interior of the mold. In some applications, such as the production of fuel tanks for automobiles, the parisons may be 8 feet or more in length. 
     In the extrusion blow-molding process, the parison is formed by pressing the melted plastic through a die in one of two ways, either by the accumulator method or by the continuous extrusion method. In the accumulator method, a hydraulic means intermittently forces the melted plastic through the die to form the parisons. In the continuous method, the melted plastic flows continuously through the die to form the parison. 
     Previously, only small and mid-size plastic hollow products could be produced using the continuous extrusion blow-molding method. Recent developments in the art of blow-molding have allowed the production of larger sized products using the continuous method. In order to produce the larger containers, however, correspondingly larger equipment is required. As well, the parison must be correspondingly larger in diameter and length. 
     For this reason, two different versions of the continuous extrusion blow-molding process are known. In the first version, the die is located above the mold unit and the parison is transported vertically down into the mold unit. The disadvantage with this version of the method is that the equipment is very tall where large products are to be produced. In some applications, the equipment can be as high as 40 to 45 feet. Therefore, much taller buildings are required to house the equipment. 
     A further disadvantage of the vertical transportation version of the continuous process is that the parison must be carried into the mold unit, which is now done by pinching the upper end of the parison, separating it from the die and lowering it into the mold unit. This pinching and vertical movement, however, often causes the larger sized parisons to collapse or flatten onto each other. That is, the pinching of the upper end causes the parison wall to collapse throughout the entire length of the parison rather than the parison retaining its generally cylindrical shape. This creates further difficulties in the overall manufacturing process since the lower end of the parison closes, thereby preventing the parison from being located properly in the mold area. By “pinching” it is meant that the wall of the parison is closed. 
     The second version of the continuous extrusion process includes shuttling of the machine clamping units. In this method, at least two mold units mounted on individual clamping units are used for each parison-forming die. The die is typically located between the two or more mold units, and the clamping units are each moved in turn under the die so the mold units can receive the parison. Thus, this method requires a substantial amount of floor space in order to operate the equipment and accommodate the two or more clamping units. As well, the clamping units used for larger products can be very heavy (up to 100,000 lbs each), therefore they must be mounted on moving steel frame structures with drives and rails. This, of course, makes the equipment relatively very expensive. As well, the power consumption required to accelerate, move and stop the units is great. 
     Various devices for carrying parisons are disclosed in the art. In U.S. Pat. No. 3,000,051, a method and apparatus for manufacturing hollow articles from melted plastic tubes (i.e. parisons) is disclosed. Also disclosed is a method and apparatus for handling a heated, vertically extruded tube or rod of thermal plastic material prior to enclosing the tube into a mold. The parison is extruded between two vertically-spaced pairs of horizontally aligned holding members. The two lower holding members are provided in opposed vertical surfaces with identical tube-engaging notches having a generally tapered configuration. The parison is extruded and the bottom tube holding members are moved toward each other until they abut. At that point, the cooperating notches define an aperture that is somewhat smaller than the diameter of the extruded parison so that the lower portions of the parison are grasped with sufficient firmness by the holding members to provide vertical support for the parison. On the other hand, the top pair of tube holding members also have tube engaging notches, but the aperture defined by the top tube holding members is slightly larger than the diameter of the parison so that the top holding members do not engage the parison wall. Therefore, only the bottom pair of tube holding members actually engage and vertically support the parison. The top tube holding members do not engage the parison wall. As well, the parison is only moved vertically from the extruder to the mold; there is no mention of the holding members being capable of moving the parison horizontally. 
     U.S. Pat. No. 4,153,408 discloses a gripping device for holding the parison, and a method for extrusion blowing hollow articles in which the parison is transferred from the extrusion die to a blow mold by means of the gripper device. The gripper device includes gripper jaws that grip the parison as it issues from the extruder. The gripper jaws move in scissor-like fashion so that the top of the parison is pinched by the gripper jaws. Therefore, this gripper device requires the parison to be pinched in order to be retained within the gripping device. 
     U.S. Pat. No. 4,761,130 discloses a method and apparatus for blow-molding square-shaped articles. The parison must be pinched at both ends. U.S Pat. No. 4,770,839 also discloses a blow-molding method in which the parison must be pinched. 
     The present invention eliminates the disadvantages of the prior art, and of the vertical transportation and shuttling versions of the continuous extrusion blow-molding process known so far. The present invention provides a parison carrying device that carries the parison to the mold unit without moving the mold units themselves, without requiring the mold unit to be located immediately under the die and without pinching the parison. The parison carrying device of the present invention includes a collar means that retains the parison without pinching the parison wall thus minimizing the likelihood of the parison collapsing. The present invention also provides means for closing the upper end of the parison without necessarily pinching the parison wall in applications where the interior of the parison is pressurized prior to the mold closing. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a method is provided for transporting a parison from an extrusion die to a second location, the parison having an upper end and an outside wall, comprising the steps of: 
     a) vertically extruding the parison from the die; 
     b) providing a collar means having an inner face capable of contacting the outside wall near the upper end of the parison; 
     c) creating a holding geometry between the collar means and the parison by contacting the inner face with the outside wall, whereby the parison is retained by the collar means without pinching the parison; 
     d) separating the parison from the die without pinching the parison; and 
     e) transporting the parison to the second location by moving the collar means without pinching the parison. 
     According to another aspect of the present invention, a method is provided for transporting a cylindrically-shaped parison from a die to a mold unit, the parison having an upper end and inside and outside walls, comprising the steps of: 
     a) extruding the parison from the die; 
     b) providing a collar means having an inner face capable of contacting the outside wall near the upper end of the parison, the inner face including notches; 
     c) providing a disc-shaped core member disposed adjacent the die such that the core member is located inside the cylindrical parison during extrusion of the parison from the die and the peripheral face of the core member contacts the inside wall, the core member having a plurality of inner passages extending radially outwardly from the core member and terminating at the peripheral face of the core member; 
     d) applying pressure in the inner passages such that the parison wall contacting the peripheral face is forced into the notches to create a holding geometry between the collar means and the parison such that the parison is retained by the collar means without pinching the parison; 
     e) separating the parison from the die without pinching the parison; and 
     f) transporting the parison to the mold unit by moving the collar means without pinching the parison. 
     According to a further aspect of the present invention, a method is provided for transporting a cylindrically-shaped parison from a die to a mold unit, the parison having an upper end and inside and outside walls, comprising the steps of: 
     a) extruding the parison from the die; 
     b) providing a collar means having a slanted inner face capable of contacting the outside wall near the upper end of the parison; 
     c) providing a disc-shaped core member disposed adjacent the die such that the core member is located inside the parison during extrusion of the parison, the core member having a peripheral face that contacts the inside wall of the parison during extrusion, the peripheral face being slanted in a direction opposite to the slanted inner face of the collar means such that the peripheral and inner faces cooperate with each other; 
     d) contacting the collar means with the outside wall to trap the parison between the cooperating peripheral and inner faces to create a holding geometry between the collar means and the parison such that the parison is retained by the collar means without pinching the parison; 
     e) separating the parison from the die without pinching the parison; and 
     f) transporting the parison to the mold unit by moving the collar means without pinching the parison. 
     According to yet a further aspect of the present invention, a method is provided for transporting a cylindrically-shaped parison from a die to a mold unit, the parison having an upper end and inside and outside walls, comprising the steps of: 
     a) extruding the parison from the die; 
     b) providing a collar means having an inner face and two slidably mounted elements on the inner face defining a notch, the inner face capable of contacting the outside wall near the upper end of the parison; 
     c) contacting the inner face with the outside wall; 
     d) slidably moving the elements toward each other to trap a portion of the parison in the notch defined by the elements and create an annular ridge around the parison, thereby creating a holding geometry between the collar means and the parison such that the parison is retained by the collar means without pinching the parison; 
     e) separating the parison from the die without pinching the parison; and 
     f) transporting the parison to the mold unit by moving the collar means without pinching the parison. 
     According to yet a further aspect of the present invention, an apparatus is provided for transporting a cylindrically-shaped parison from an extrusion die to a second location, the parison being vertically extruded from the die and having an upper end and an outside wall, comprising: 
     a) collar means having an inner face capable of contacting the outside wall near the upper end of the parison; 
     b) means associated with the collar means for bringing the inner face into contact with the outside wall to create a holding geometry between the inner face and the parison such that the parison is retained by the collar means without pinching the parison; and 
     c) means for moving the parison away from the die thereby separating the parison from the die without pinching the parison and for transporting the parison to the second location by moving the collar means without pinching the parison. 
     According to yet a further aspect of the present invention, an apparatus is provided for transporting a cylindrically-shaped parison from an extrusion die to a second location, the parison being vertically extruded from the die and having an upper end and inside and outside walls, comprising: 
     a) collar means having an inner face capable of contacting the outside wall near the upper end of the parison; 
     b) a plurality of notches on the inner face; 
     c) a disc-shaped core member disposed adjacent the die such that the core member is located inside the cylindrical parison during extrusion of the parison and the peripheral face of the core member contacts the inside wall; 
     d) a plurality of inner passages in the core member extending radially outwardly from the core member and terminating at the peripheral face of the core member and opposite the notches; 
     e) means associated with the collar means for bringing the inner face into contact with the outside wall; 
     f) means for applying pressure in the passages such that the parison contacting the peripheral face is forced against the notches to create a holding geometry between the collar means and the parison such that the parison is retained by the collar means without pinching the parison; and 
     g) means for moving the parison away from the die thereby separating the parison from the die without pinching the parison and for transporting the parison to the second location by moving the collar means without pinching the parison. 
     According to yet a further aspect of the present invention, an apparatus is provided for transporting a cylindrically-shaped parison from an extrusion die to a second location, the parison being vertically extruded from the die and having an upper end and inside and outside walls, comprising: 
     a) collar means having a slanted inner face capable of contacting the outside wall near the upper end of the parison; 
     b) notches on the inner face; 
     c) a disc-shaped core member disposed adjacent the die such that the core member is located inside the cylindrical parison during extrusion of the parison, the core member having a peripheral face that contacts the inside wall; 
     d) the peripheral face being slanted in a direction opposite to the inner face of the collar means such that the peripheral and inner faces cooperate with each other; 
     e) means associated with the collar means for bringing the inner face into contact with the outside wall to trap the parison between the cooperating peripheral and inner faces; and 
     f) means for moving the parison away from the die thereby separating the parison from the die without pinching the parison and for transporting the parison to the second location by moving the collar means without pinching the parison. 
     According to yet a further aspect of the present invention, an apparatus is provided for transporting a cylindrically-shaped parison from an extrusion die to a second location, the parison being vertically extruded from the die and having an upper end and inside and outside walls, comprising: 
     a) collar means having an inner face capable of contacting the outside wall near the upper end of the parison; 
     b) two slidably mounted elements on the inner face defining a notch between them; 
     c) means associated with the collar means for bringing the inner face into contact with the outside wall; 
     d) means for slidably moving the elements toward each other to trap a portion of the parison in the notch defined by the elements and create an annular ridge around the outside of the parison, thereby retaining the parison in the collar means; and 
     e) means for moving the parison away from the die thereby separating the parison from the die without pinching the parison and for transporting the parison to the second location by moving the collar means without pinching the parison. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described in detail with reference to the accompanying drawings, in which like numerals denote like parts in the several views, and in which: 
     FIG. 1 is a schematic drawing showing in a general way the method and apparatus of the present invention; 
     FIGS. 2A-2C show the vacuum method embodiment of the parison carrying device of the present invention; 
     FIGS. 3A-3C show the pressure method embodiment of the parison carrying device of the present invention; 
     FIGS. 4A-4C show the mechanically pressing method of the parison carrying device of the present invention; 
     FIGS. 5A-5C show a further embodiment of the parison carrying device of the present invention; 
     FIGS. 6A-6C show the direct closing of the open end of the parison by the parison carrying device; 
     FIGS. 7A-7C show the closing of the open end of the parison by a separate closing mechanism disposed on the parison carrying device; 
     FIGS. 8A-8D show the closing of the open end of the parison by a lid or lid segments disposed on the parison carrying device; 
     FIGS. 9A-9B show the closing of the open end of the parison by a plunger; 
     FIG. 10 shows an embodiment of the parison carrying device of the present invention in which the collar means has a round shape; 
     FIG. 11 shows an embodiment of the parison carrying device of the present invention in which the collar means has a square shape; 
     FIG. 12 shows an embodiment of the parison carrying device of the present invention in which the collar means has a rectangular shape; 
     FIG. 13 shows an embodiment of the parison carrying device of the present invention in which the collar means has an oval shape; 
     FIG. 14 shows an embodiment of the parison carrying device of the present invention in which the collar means has N-corners; 
     FIG. 15 shows an embodiment of the parison carrying device of the present invention in which the collar means has a hexagonal shape; and 
     FIGS. 16A-16C illustrate the opening and closing movements of the collar means of the parison carrying device of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, one embodiment of the process of the present invention is illustrated in a general way. A generally cylindrically-shaped parison  10  is shown formed by passage of melted plastic through a die  12 . The parison  10  is formed generally in the shape of a cylinder, but other shapes may also be used. Two mold units  11  and  13  are shown located on either side of die  12 . Mold units  11  and  13  remain stationary. The parison carrying device of the present invention (not shown in FIG. 1) carries parisons to each of mold units  11  and  13  where the parisons are formed by the molds into finished hollow products. Thus, in the process of the present invention, the parison  10  is moved to the mold units  11  and  13  rather than the mold units  11  and  13  moving to the parison  10 . As well, the die  12  need not be located immediately above a mold unit, thus having the advantage of decreasing the overall height of the equipment. Accordingly, many of the disadvantages of the prior art are eliminated. 
     In FIGS. 2A to  2 C, there is shown a cross-sectional view of the parison  10  being formed by passage of melted plastic through die  12 . The parison  10  is preferably cylindrical in shape. The parison carrying device of the present invention grasps and retains the parison  10 , separates the parison  10  from the die  12  without pinching the parison  10  and transports the parison  10  to a mold unit (not shown) also without pinching the parison  10 . 
     The parison carrying device of the present invention allows the parison  10  to be separated from the die  12  and carried to the mold unit without pinching the parison  10 , and therefore, without causing the inside of the parison  10  to be closed separation of the parison from the die. The parison carrying device of the present invention does so by providing a stabilizing collar around parison  10  which causes the parison wall  18  in the area of the collar to deform and create a holding geometry whereby the parison  10  is retained by the parison carrying device. The parison wall  18  in the area of the collar is thus firmly retained by the collar, allowing the parison  10  to be separated from the die and carried to the mold unit without pinching. 
     In the embodiment illustrated in FIGS. 2A to  2 C, the parison carrying device of the present invention includes two or more collar means  14  that are initially separated from the parison  10  as shown in FIG.  2 A. When the required length of parison  10  has been extruded from the die  12  and is ready to be separated from the die  12  and carried to the mold unit, collar means  14  are moved towards the parison  10  in the directions of arrows  20  until they are around the parison  10 . The interior of each of collar means  14  includes a cavity  16  in which a vacuum is applied by known means. The cavity  16  extends to the inner face  19  of collar means  14  and terminates at notch  21 . As collar means  14  contact the parison wall  18  (FIG. 2B) the vacuum applied in cavity  16  causes the parison wall  18  in the area of collar means  14  to be deformed and “sucked” into notch  21 . The portion of the parison wall  18  that is so sucked into notch  21  is retained therein. This action of the collar means  14  on the parison wall  18  creates a holding geometry that retains the parison wall  18  in the collar means  14 . Once the holding geometry on parison wall  18  is formed, the parison carrying device is able to hold and retain the parison  10  without pinching of the parison walls  18 . 
     Therefore, in this first embodiment of the parison carrying device of the present invention, collar means  14  first move in the direction of arrows  20  as shown in FIG. 2A until the inner face  19  is in contact with the parison wall  18 . Once the parison wall  18  is retained by the collar means  14 , as described above, the parison carrying device moves in the direction of arrows  22  in FIG.  2 B. Since the parison  10  is retained within the parison carrying device, parison  10  also moves in the direction of arrows  22 , thereby separating and removing parison  10  from die  12  without pinching the parison wall  18 . To facilitate separation of the parison  10 , the die  12  may optionally be provided with a rod  23  disposed within the opening  25  of the die  12 . Rod  23  can be moved (typically by a hydraulic piston which not shown) so that the opening  25  is closed, thereby cutting the parison  10  from the molten plastic in the die  12  and separating it from the die  12 . The parison  10  is then carried by the parison carrying device to one of mold units  11  or  13  (not shown in FIGS. 2A to  2 C) for processing into a hollow product, such as an automobile fuel tank. Since parison  10  is not pinched when it is separated from die  12  or transported to the mold unit, it is unlikely to collapse or flatten over its entire length, thus making it easy to ensure that parison  10  is properly placed within the mold unit. 
     FIGS. 3A-3C show in cross-sectional view a second embodiment of the parison carrying device of the present invention, namely the use of pressure rather than vacuum. In this embodiment, the parison carrying device includes at least two second collar means  30 . Second collar means  30  differ from collar means  14  of FIGS. 2A to  2 C in that second collar means  30  do not have a cavity  16  in which vacuum is applied, although second collar means  30  have a notch  31  similar to the notch  21  of collar means  14 . 
     As shown in FIG. 3A, parison  10  is formed by die  12 . Second collar means  30  are initially separated from parison wall  18 . When the required length of parison  10  is extruded and the parison  10  is to be separated from die  12 , second collar means  30  are moved towards the parison wall  18  in the direction of arrows  32  until second collar means  30  contact the parison wall  18 . 
     The parison carrying device illustrated in FIGS. 3A to  3 C includes a core member  34  disposed adjacent to the opening of die  12 . Core  34  comprises a series of inner passage ways  36  including passages that extend radially from the centre of core  34  and terminate at the peripheral face of core  34 . As better illustrated in FIG. 3B, once second collar means  30  are around parison wall  18 , increased pressure is applied in passage ways  36  of core  34 . Since the passage ways  36  extend radially through the core member  34  and terminate opposite notch  31  of second collar members  34 , the increased pressure within passage ways  36  causes the parison wall  18  to be “pushed” against second collar means  30  and into notch  31 . The portion of the parison wall  18  in the notch  31  is retained therein, thus the internal pressure within passage ways  36  forces the parison wall  18  to form the holding geometry in second collar means  30 . 
     Once the holding geometry is formed within second collar means  30 , the parison carrying device is moved in the direction of arrow  38 , thereby separating and removing parison  10  from die  12  without pinching parison wall  18 . Parison  10  can then be transported to the mold units also without pinching thereby alleviating the risk of the parison  10  flattening and collapsing onto itself. 
     A third embodiment of the parison carrying device of the present invention is illustrated in FIGS. 4A-4C. This third embodiment uses a mechanically pressing method for creating the holding geometry on parison wall  18 . In FIG. 4A, parison  10  is shown being formed by die  12 . In this embodiment of the present invention, a core  40  is disposed adjacent the opening of die  12 . Core  40  includes slanting annular face  42 . The parison carrying device shown in FIGS. 4A to  4 C comprises at least two third collar means  46  also having slanted faces  47  corresponding to annular face  42 . As shown in FIG. 4B, when third collar means  46  are moved to contact parison wall  18 , the portion of the parison wall  18  in the area of third collar means  46  is trapped between annular face  42  and the corresponding slanting faces  47  on third collar means  46 . This creates the holding geometry for parison wall  18 , thereby retaining parison  10  in the parison carrying device. 
     In FIG. 4C, the parison carrying device is shown moving in the direction of arrow  48 . As such, parison  10  is separated and removed from die  12  without pinching of the parison wall  18 . 
     A fourth embodiment is illustrated in FIG. 5A to  5 C. FIG. 5A is a close up view of a collar means  49   a . On the inner face of collar means  49   a  is a notch  49   b  defined by two slidably mounted elements  49   c  and  49   d . Parison wall  18  is shown after collar means  49   a  was placed in contact with the parison  10  and a portion of parison wall  18  forced into notch  49   b  by one of the methods shown in FIGS. 2A-2C or FIGS. 3A-3C. 
     Once parison wall  18  is in notch  49   b , elements  49   c  and  49   d  are moved in the direction of arrows  49   e  and  49   f , respectively, as shown in FIG.  5 B. The portion of parison wall  18  within notch  49   b  is thereby squeezed between elements  49   c  and  49   d . The result is an annular ridge  49   g  of the parison wall  18  circling around parison  10 . The annular ridge  49   g  is retained in the notch  49   b , thereby forming a holding geometry allowing parison  10  to be carried securely by the parison carrying device. This fourth embodiment of the parison carrying device is useful for bigger, heavier parisons as the holding geometry created provides a firmer hold on the parison  10 . 
     Therefore, the four embodiments of the parison carrying device of the present invention illustrated in FIGS. 2 to  5  create a holding geometry of various sizes and shapes on the portion of the parison  10  in the area of the collar means. The holding geometry is, in essence, a pocket of parison wall  18  formed near the upper end of parison  10  which allows parison  10  to be retained by the collar means without pinching the parison  10 . Therefore, the parison carrying device of the present invention allows the upper end of the parison  10  to remain opened (that is, not pinched), while at the same time, providing a strong retaining grip on the parison  10  for carrying it to the mold area. 
     For a large number of products made using the extrusion blow molding process, it is required that the parison, once it is located in the mold unit, be pressurized prior to closing of the mold unit. Typically, the parison is pressurized to pressures of about 1.5 to 2 psi. As such, the upper end of the parison, which remains open when the parison carrying device of the present invention is used, must be closed so that the parison can be suitably pressurized. 
     FIGS. 6 to  9  illustrate various embodiments of the present invention that allow for the parison&#39;s open upper end to be closed for pre-inflation purposes. In the specific embodiment shown in FIGS. 6A-6C, the parison carrying device itself closes the upper end of parison  10 . It will be understood that the present invention does not require that the upper end of the parison  10  be closed as shown in FIG. 6C, but rather the embodiment of FIG. 6C is merely an example. As shown in FIG. 6A, the parison carrying device is initially generally square-shaped although other geometric pivoting arm configurations can be used. The parison carrying device comprises two support arms  50  and  52 , each having two pinching arms pivotally connected thereto. Parison  10  is separated from a die (not shown) and carried to a mold unit (not shown) by moving support arms  50  towards parison  10 , thereby causing the free ends of the pinching arms to contact each other. As such, the parison wall  18  is forced to take the shape defined by the four pinching arms, namely a square shape. The pinching arms act like the collar means described above so as to create a holding geometry to retain parison  10  therein. Thus, parison  10  can then be carried to the mold without pinching, thereby reducing the likelihood of total collapse of parison  10 . 
     Once parison  10  is properly located in the mold unit, support arms  50  and  52  are moved closer, causing the two pinching arms on each of support arms  50  or  52  to straighten, thereby pinching the upper end of parison  10  by bringing the parison wall  18  together. As such, the upper end of parison  10  is closed allowing for the interior of parison  10  to be pressurized. The problems associated with the premature collapse of the parison are eliminated because parison  10  is already properly located in the mold unit prior to pinching of its upper end. If total collapse occurs, the result is insignificant since the parison  10  is already properly located in the mold unit. 
     In the embodiment shown in FIG. 7A-7C, the pinching mechanism is separate from the parison carrying device itself. The parison carrying device comprises two collar means  60  and  62 , which can be any of the collar means described with reference to FIGS. 2 to  5  above. Disposed above collar means  60  and  62  are pinching blocks  64  and  66 . As seen in FIG. 7B, collar means  60  and  62  are brought together around the parison  10  in a manner similar to that described in either of FIGS. 2 to  5  above. Once a holding geometry is created by collar means  60  and  62  and parison  10  is retained within collar means  60  and  62 , parison  10  is separated from the die, carried to the mold unit and properly located therein. Pinching blocks  64  and  66  are then moved in the direction of arrows  68  as shown in FIG. 7C until the inside surfaces of parison wall  18  come together and close the upper end of parison  10 . As can be seen from FIG. 7C, collar means  60  and  62  retain their original shape in contrast to the embodiment of FIG.  6 . 
     FIGS. 8A-8D show a further embodiment of the parison carrying device of the present invention. In this embodiment, a lid or lid segments are used to close the upper end of parison  10 . The parison carrying device comprises two collar means  70  and  72  of the type described with reference to FIGS. 2 to  5 . Pivotally connected to either one of the collar means  70  or  72  is a lid  74 . The parison carrying device illustrated in FIGS. 8A to  8 D functions essentially like the parison carrying device described with reference to FIG. 2 to  5  above. Once collar means  70  and  72  are in place and parison  10  is retained therein as shown in FIG. 8B, the parison  10  can be separated from the die. Lid  74  can then be pivoted about its pivot axis until lid  74  covers the opening at the upper end of parison  10  as shown in FIG.  8 C. Suitable locking means may be added to keep lid  74  in place when the parison  10  is pressurized, although this may not be necessary because of the relatively small pressures used in the pre-inflation stage. 
     FIG. 8D is a cross-sectional view of parison  10  at its upper end. Parison  10  is retained by collar means  70  and  72 , thereby keeping the upper end of parison  10  open. Lid  74  is then pivoted about its pivot axis  76  in the direction of arrows  78  until lid  74  comes to rest at the top of the parison  10  and closes the open end of the parison  10 . In contrast to the closing mechanisms of the embodiments in FIG. 6 and 7, parison  10  is not pinched in this case, thus lid  74  can be moved to its closing position at any time after parison  10  is removed from the die. In the embodiments of FIG. 6 and 7, the parison  10  is preferably first properly located in the mold unit prior to closing the upper end by pinching to avoid the likelihood of total collapse of the parison. 
     A fourth embodiment of the closing means for the parison carrying device of the present invention is illustrated in FIGS. 9A and 9B. In this embodiment, a plunger  80  and associated support  82  are used. Once the parison  10  has been removed from the mold cavity, and while it is being retained by the parison carrying device  84 , the plunger  80  is moved in the direction of arrow  86  until it is inserted into the open upper end of the parison  10 . As such, the upper end of parison  10  is thereby closed allowing for pressure build-up in the parison  10 . Again, since the parison  10  is not pinched, the upper end can be closed before the parison is properly located in the mold. 
     It will be understood that the parison carrying device of the present invention is not limited to any of the shapes illustrated in FIGS. 2 to  9  above. For example, the parison carrying device of the present invention can comprise collar means of varying sizes shapes, and pivotion pinching configurations, including the following examples: 
     FIG.  10 : round or circular shape; 
     FIG.  11 : square or diamond shape; 
     FIG.  12 : rectangular shape; 
     FIG.  13 : oval shape; 
     FIG.  14 : a polygon having N-corners; and 
     FIG.  15 : hexagonal shape. 
     One of the important aspects of the examples illustrated in FIGS. 10 to  15  is that the collar means assist in creating a holding geometry near the upper end of the parison allowing the parison to be retained therein without pinching. The parison can then be separated from the die and transported to the mold unit. 
     Furthermore, the movement of the parison carrying device of the present invention is not limited to linear movement. For example, in FIG. 16A, two circular collar means  90  and  92  are shown as capable of moving in a linear manner in the direction of arrows  94  and  96 , respectively. In FIG. 16B, collar means  98  and  100  are also circular in shape, however, collar means  98  and  100  do not move in a linear direction, but rather pivot about a pivot point  102 . Thus, collar means  98  and  100  swing in the direction of arrows  104  and  106 , respectively, until they are around the parison. 
     In FIG. 16C, a combination of the linear and pivotal movements are shown. Collar means  108  and  110  move linearly in the directions of arrows  112  and  11   4 , respectively, and also pivot about pivot points  116  and  118 , respectively, so that collar means  108  and  110  swing in the directions of arrows  120  and  122 . 
     In summary of this disclosure, the parison carrying device of the present invention includes collar means that assist in creating a holding geometry near the upper end of the parison that allows the parison to be retained within the carrying device without pinching the parison wall. The parison can then be separated from the die and transported to the mold unit. The mold unit can thus be stationary and need not be located immediately below the die. As well, the present invention provides means for closing the open end of the parison in applications where a pressure must be built up within the parison prior to the mold closing. 
     Modifications and alterations are possible and all such modifications and alterations are within the sphere and scope of the present invention as described herein.