Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – For press shaping surface
Reexamination Certificate
1999-09-10
2002-09-10
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
For press shaping surface
C425S522000, C425S526000, C249S079000, C249S102000
Reexamination Certificate
active
06447281
ABSTRACT:
FIELD OF THE INVENTION
The invention relates in general to stretch blow mold machinery. More particularly, the invention relates to an improved stretch blow mold shell, and a shell holder assembly therefor in which the shell holder is constructed and arranged to be mounted to one of a pair of pivoting clamp brackets used to pivotably close an opposed pair of the mold shells on themselves for use in defining a bottle cavity during usage thereof on a stretch blow mold machine.
BACKGROUND OF THE INVENTION
The use of stretch blow mold machinery is well known. Stretch blow mold machines offer the advantage of quickly and economically producing a wide variety of bottle shapes and sizes commonly used throughout a great number of consumer markets. These include longneck beverage bottles, wide mouth bottles, as well as a wide variety of soft drink and juice bottles, for example, ranging in size from approximately half liter up to 5 liters.
The use of rotating stretch blow mold machines constructed to have a rotating central frame member, or carousel, which rotates about a fixed or stationary central frame member is well known. A plurality of radially spaced bottle forming stations are typically stationed along the circumference of the carousel, each bottle forming station comprising a pair of opposed and pivotably affixed clamp brackets constructed to move from an open into a closed position, and back, in timed relationship with the rotation of the framework during machine operation.
In the known machines, a pair of shell holders, which may be identical or may differ from one another, but which, however, are substantially uniform in size and shape with respect to one another will be separately received within each respective one of the clamp brackets pivotably affixed to the blow mold machine carousel. These shell holders are fastened to the clamp brackets by a plurality of threaded fasteners, and may also be provided with cooling channels defined therein so that cooling water may be passed therethrough in the effort to regulate the interior surface temperature of a separate one of the blow mold shells fastened thereto and carried thereon, and which are used to define the bottle forming cavity which will form the bottle, or other object, during usage of the machine.
Each blow mold station thus also includes a pair of blow mold shell halves. These blow mold shell halves are typically identical, such that a symmetrical bottle, or other article, will be formed during the stretch blow mold process. Each mold shell is fastened to a respective one of the shell holders such that the completed bottle forming station will have a pair of opposed clamp brackets which are pivotably affixed to one another, much in the fashion as disclosed in U.S. Pat. No. 5,326,250 entitled “Opening and Closing Mechanism for Portfolio Blowing and Blowing Stretching Mold” issued Jul. 5, 1994 in the name of inventor Doudement, and as well as in U.S. Pat. No. 5,683,729 entitled “Apparatus for Making Containers by Blow Moulding Plastic Parisons” issued to Nov. 11, 1997 in the name of inventor Valles; a shell holder fastened to each respective clamp bracket; and in turn a mold shell half affixed to the shell holder by suitable means. Common methods of attaching these shell halves to the shell holders include the use of predefined cavities formed within the shell holder within which the shell is placed and then held in position by a keeper plate or plates fastened to the shell holder, or by passing fasteners directly through the shell and into the shell holder.
Current rotating stretch blow mold machines are capable of producing up to 50,000 articles per hour, based on the size of the articles being produced, for example half liter bottles as opposed to five liter bottles. However, an advantageous feature of certain stretch blow mold machines, and particularly those manufactured by Sidel, S.A. of Le Havre, France, and its U.S. subsidiary Sidel, Inc., is that through the use of a modular design, for example modular mold shell halves, and modular shell holders, it is possible to use one rotating blow mold machine in conjunction with several sets of shell holders, and mold shells, to produce a wide variety of bottles, for example, using only one machine. This greatly reduces machine costs, and increases operating efficiencies for stretch blow mold bottle producers. However, the change-over from molding bottles of one size to bottles of another size can be quite time consuming due to the amount of time required to remove and replace the shell holders from each pair of clamp brackets about the periphery of the machine, as well as removing and replacing the shells from the respective shell holders.
Another disadvantage of the known types of blow mold shells and shell holders is the manner in which the blow mold shell is cooled during the bottle formation process. As known to those of skill in the art, when using a PET (polyethylene terephthalate) preform, also known as a parison, it is desirable to maintain the temperature of the neck and/or threaded neck portion of the bottle at a cooler temperature than the remaining portion of the preform during the stretch blow mold process such that a sufficient amount of structural strength and rigidity is provided at the neck so that it may be used to safely convey the bottle along a packaging line, for example, whereupon the bottle is filled and then sealed/capped, and carried at its neck for being packaged and shipped. Thus, it is desirable to maintain a thicker wall section at the neck portion of the bottle, as well as at the base portion, for the purposes of lending structural rigidity to the bottle.
A cooling circuit, therefore, may be integrally defined within the neck or upper portion of the shell halves to cool the neck portion of the PET container as it is being formed, and which may also be used to cool the sidewall portion of the shell, although there is only one cooling circuit in these known constructions. The wall section of the bottle, on the other hand, which extends between the neck and base, will typically be molded in a thinner section between the neck and base in that as the bottle is empty the sidewall does not need to have a great deal of strength. Once the bottle is formed, all that is required is a sufficient amount of strength along the sidewall of the bottle to ensure that the bottle does not collapse while being handled, nor rupture once it is filled with the appropriate fluid. As known to those in the art, once the fluid is constrained within the bottle, the fluid itself acts as a constrained load carrying column which will support its own weight, so long as sufficient sidewall strength exists within the container sidewall to ensure it will not rupture.
Thus, it is desirable to mold bottles and other articles with as thin a wall section as possible, as the cost of the plastic PET material is the largest part of the expense in making bottles in the stretch blow mold process. As it is desirable to reduce the per unit costs of each bottle produced, it is desirable to precisely and separately control the temperature of the sidewall of the preform/shell as the bottle is formed to be able to provide the minimal amount of PET material required to form the bottle by keeping the sidewall warmer/hotter than the neck or base portions, for example.
In order to attempt to control the temperature of the sidewall portion of the shell/bottle, a cooling channel is drilled or otherwise defined within the shell holder, which channel will extend in the lengthwise direction of the holder and be positioned as closely as possible to the sidewall of the mold shell in order to try to cool the interior surface of the mold shell during the stretch blow mold process. Although this type of construction has proven to be adequate for high volume strength blow mold bottle production, the problem persists that a thicker wall section is formed because of the inability to separately control the temperature of the sidewall portion of the mold shell with respect to the neck portion thereof, whi
Alston & Bird LLP
Davis Robert
Sidel, Inc.
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