Crystallizing machine

Details Crystallizing machine Crystallizing machine

2000-08-16

2001-10-30

Hiteshew, Felisa (Department: 1765)

Chemical apparatus and process disinfecting, deodorizing, preser

Physical type apparatus

Crystallizer

C422S240000, C422S250100

Reexamination Certificate

active

06309613

ABSTRACT:

TECHNICAL FIELD
This machine relates to a process and apparatus for use in strengthening the finish area of a hollow blow molded container manufactured from a thermoplastic, such as a thermoplastic polyester or a biaxially oriented polyethylene terephthalate resin.
BACKGROUND ART
A hollow blow molded thermoplastic, such as a thermoplastic polyester or a biaxially oriented polyethylene terephthalate resin, “PET”, container, commonly used to contain food or beverage, has excellent physical properties, durability, and a wide range of applications. However, when used in hot-fill applications, certain portions of the container which are not subjected to the biaxial orientation during the blow molding process, such as the neck area seal edge or thread, commonly referred to as the finish area, are found to soften and deform in an undesirable manner because the temperature of the food or beverage fill is often above the glass transition temperature of the plastic. Many methodologies and processes have been tried in attempts to strengthen the neck area of such containers by enhancing the density of the resin and opacifying and whitening the neck due to the crystallization of the thermoplastic resin by heat treating the neck.
Strengthening the neck area of a thermoplastic container greatly increases the craze resistance of the neck area, improves the mechanical rigidity and increases impact resistance, wear resistance, and external pressure resistance of the container. However, a common side effect of such a thermal treatment of the neck area of the container is an undesirable deformation of the neck area, thus leading to problems with capping and sealing the container.
U.S. Pat. No. 4,476,084 provides a solution to the problem of deformation during heat treating by placing a cold die pin or plug into the bore of the neck prior to heating. The cold die pin assists in maintaining the proper size and shape of the neck during the crystallization process. Others have found similar solutions. See, for example, U.S. Pat. Nos. 4,388,356, 4,379,099, 4,572,811, 4,590,021 and 5,261,545. The use of such cold plugs and dies however have led to problems when speed of manufacture is a priority. Inefficient heating, failure to properly position the plug and deformation of the thermoplastic container due to the weight of the plug have commonly been experienced, thereby leading to a further search for a fast, efficient way of crystallizing the neck area of the thermoplastic container.
BRIEF DESCRIPTION OF THE INVENTION
The crystallizing machine and its process of this invention improves upon the efforts of the prior art in many ways. The machine makes use of a preheated plug which is inserted into the mouth or neck of a thermoplastic preform or container, commonly known as a workpiece. While the workpiece is described herein as being a thermoplastic, it is preferable that it be a thermoplastic polyester, and even more preferable that it be polyethylene terephthalate (PET). For the purposes of this description, references will be made to PET workpieces. However, this description is not intended to be limiting on the invention described herein. The workpiece is carried solely in an upright position by the preheated plug through the crystallizing process. The preheated plug assures even and efficient heating when crystallizing the finish area of the workpiece and constrains the shape of the finish area to a predetermined size and shape during the crystallizing process.
The crystallizing machine of the present invention is constructed from modular subassemblies. The first modular subassembly includes the workpiece in-feed and plug preheat operations and incorporates the power source and drive apparatus for the entire machine. The opposed end of the crystallizing machine is constructed of a module or subassembly which operates to provide the turnaround and tensioning for the transport member carrying the workpieces. Positioned between the first modular subassembly and the opposed end modular subassembly are heating and cooling processing modules or subassemblies which can be provided in any number, depending on the size constraints and workpiece quantity restraints desired. The processing modules provide the heating and crystallizing processes for the finish area of the workpiece and the cooling process for the workpiece prior to unloading.
For the purposes of the following description of the preferred embodiment, reference will be had to the following drawings and the crystallizing machine of the present invention will be described as having four subassemblies. However, the description of the invention is not intended to be limiting upon the scope of the claims which follow.


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