Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including application of internal fluid pressure to hollow...
Reexamination Certificate
2002-03-13
2004-03-30
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including application of internal fluid pressure to hollow...
C264S535000, C264S537000, C425S525000, C425S526000, C425S533000, C425S534000, C425S537000, C425S538000
Reexamination Certificate
active
06713013
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for the preparation of preforms and hollow articles in single-row and multi-row preform and blow molds, respectively, and to an apparatus therefor. The invention represents an improvement in applicant's prior U.S. Pat. No. 6,217,819 entitled Universal Single Row and Multi Row Insert Stretch Blow Molding Method and Apparatus Therefor. More particularly, the present invention relates to a method and apparatus, wherein during a preform mold opening stroke an entering tray unit collects and removes molten preforms from the molding area. This end is attained by means of a robotic gripper assembly which lifts the preforms either out of the tray unit or from a preform reheat unit, transfers the preforms through different processing phases, adding internal and external components during the transformation into hollow articles, and returns to a waiting position outside the preform molding and tray unit or preform reheat unit.
2. Brief Description of the Prior Art
Heretofore, in conventional prior art molding machines, known as the one-step method, preforms, also called parisons, are injected into a preform mold and transferred by their neck splits which are mounted beneath a horizontal transfer plate in an intermittent rotary motion into a temperature control station, also called conditioning station, an orientation blow molding or stretch blow molding station and a molded product removing or ejection station producing hollow articles in single and double row molds, respectively., as described in U.S. Pat. Nos. 4,946,367, 4,731,011 both to Nissei ASB and Pat. No. 4,457,689 to Aoki respectively. The advantage of this method is that the preforms being held in an upright position can be precisely heat profiled internally with entering touch or conditioning rods. The drawback of this method is that the molten preforms are required to reside in the conditioning station as long it takes to inject and cool the preforms in the preceeding injection station. Heat pots emanating radiant heat are needed to maintain the proper stretch blow temperature, which adversely effects the programmed temperature profiling by the touch or conditioning rods. A technique for overcoming such limitations is described in U.S. Pat. No. 4,941,816 to Aoki U.S. Pat. Nos. 5,062,787 and 5,364,585 both to Aoki Technical Laboratory and U.S. Pat. No. 5,403,177 to Jomar wherein the injected preforms are directly heat conditioned in the preform mold and then immediately transferred into the stretch blow mold. The drawback of this method is that the preform molds are tailored to a specific hollow article geometry. This reduces the number of different hollow article shapes that can be stretch blown from the same preform shape. Unfortunately, such machines also evidence certain limitations, namely in the difficulty of mold interchangeability due to different swing radii and stack heights, the lack of built in automatic oriented discharge and costly neck splits and neck split holders which are required for each station. The vertical clamping forces applied to the neck splits in the preform molds versus the horizontal clamping forces in the blow molds being mounted onto a common rotary plate causes premature wear and tear to the aligning neck split seats. The rotary plates and the machine beds are required to be laid out for the higher clamping forces in the injection station. As a result, the added inertia of the heavy construction and large swing radii of the transfer plates lengthens the dead time of mold open index and mold close, thereby increasing the overall cycle times. Efforts to reduce dry cycle times have been made, as for example, by replacing the rotary tables through closed circuit conveying devices as described in U.S. Pat. No. 4,895,509 To Giacobbe-Magic and U.S. Pat. No. 5,213,822 to Nissei ASB. However, once again, costly support jaws or neck mold sets mounted on slide guides, are required for each station linked together to transfer the preforms and containers through the forming phases in a rectilinear motion in equal distances and equal time intervals. In the rotary-type and chain-link-type method, all phases of preform molding, conditioning, stretch blowing, and discharging are also interdependent due to a common transfer movement. The larger the number and size of transfer components, especially expensive neck splits, for each processing station leads to longer mold changeover times and higher tooling costs. The more machine component weight needs to be transferred, so resulting in slower dry cycles, and thus longer overall cycles.
The industry has recognized these limitations and has also recognized that containers can be conditioned, stretch blown, and discharged in a fraction of the time that it takes to mold the preforms. This discovery has led to a method and apparatus for injection stretch blow molding as described in U.S. Pat. No. 5,468,443 to Nissei ASB wherein a larger number of injection molding stations produce preforms to be conveyed to a lesser number of stretch blow molding stations. The drawback of this method and apparatus is that it requires neck split moving means for supporting and conveying costly neck splits adapted to hold-neck portions of each preform used to mold the hollow articles through all preform molding, conditioning, blow molding, and ejection stations.
Refinements of the aforementioned patent, U.S. Pat. No. 5,468,443 to Nissei ASB are described in U.S. Pat. No. 4,793,960 to Husky, U.S. Pat. Nos. 5,753,279, 5,744,176 and 6,247,916 all to Nissei ASB as well as brochures of Gerosa's Satellite GE system, SIG's Ecomax injection stretch blow molding machine and HUSKY's Index SB system are also known as one and a half step methods wherein molded preforms are first inverted to be released onto carrier members of a circular transfer conveying system. The inverted preforms are then indexed through a reheating section to assure that the first fraction of molded preforms enters the blow mold station with the same temperature profile as the following fractions of simultaneously molded preforms. Once the preforms are stretch blown into final hollow articles, they are inverted again to release them in an upright position. The limitations of these disclosures resides in the fact that the molten preforms are being inverted to be put onto a multitude of neck-size-dependent carrier members. During the inverting process the outside walls of the preforms touch water cooled transfer tubes in an uncontrolled manner, which tends to alter their thermal profile, so leading to uneven wall distributions in the finished hollow articles. The carrier members create a heatsink below the neck areas and, therefore, the reverted preforms need to be excessively heated in the shoulder area, which with long preforms may lead to bending during the intermittent transfer movements. The residence time of each fraction of preforms before entering the reheat oven banks is longer than each following fraction while the residence time in the reheat oven banks is the same for each preform fraction which enters the blow molds consecutively. The bottom up stretch blow molding method reverses the temperature profile of the preforms in the longitudinal direction. The bottom area of the preforms is hotter due to the chimney effect, which leads to preform-sagging and thinner bottoms and heavier shoulders in the hollow articles. Energy consuming cooling fans are installed to overcome this drawback. Preferential heating zones radiate onto the already hot preform outside walls for the production of oval hollow articles. This heat treatment of vertical section of the body of the preform is practiced successfully in so called two-step or reheat stretch blow molding processes because the preforms enter the heating sections at room temperature closely spaced and allow long oven residence times, as disclosed in U.S. Pat. No. 5,681,521 to Sidel and U.S. Pat. No. 6,287,507 to Corpoplast. A second inverting device is needed to rel
Fink Edward M.
McDowell Suzanne E.
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