Patent Publication Number: US-2009236302-A1

Title: Finish Portion For Plastic Preform and Container and Method of Making

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of packaging, and more specifically to preforms for making plastic containers, plastic containers and methods for making such plastic containers. 
     2. Description of the Related Technology 
     It is well known to manufacture plastic containers by injection molding preforms of plastic, such as PET, and blow-molding the preforms in a mold cavity using a stretch blow molding process. After molding, the resulting preforms are discharged from the mold and are typically packaged for shipment to another location for filling with a consumer product such as a beverage. After filling, the containers are capped, boxed and palletized for distribution to the ultimate consumer. 
     At the blow molding location, preforms are customarily fed in single file to a feeding mechanism which transfers the preforms to a conveyor which spaces them from one another and advances them in an open loop path through a pre-heat oven. In order to facilitate handling by such transfer mechanisms, the preforms are typically molded so as to have one or more transfer beads or recesses that may be gripped by the transfer mechanism. One type of transfer mechanism uses chain-type conveyors in the pre-heat oven to engage the preforms at their neck finishes while they are being heated. Sidel of Le Havre France, manufactures a rotary preform transfer device which grips the preheated preforms about their necks and transfers them into the blow mold. The device rotates much like a star-wheel, about a vertical axis, but has claw-like gripping elements which grip the preform about its neck finish and advance it in an arcuate path to a like gripper associated with the blow mold. The gripper on the rotary transfer device is designed to release the preform only after the blow-mold gripper has actually gripped the preform. As a result, the preform is always under positive control as it transits through the pre-heat oven and the blow-mold apparatus 
     The preforms are conveyed by the transfer mechanism to a preheating oven and are heated to a predetermined temperature by various means, such as radiant heaters. After the preforms are heated to the desired temperature, usually near the glass transition temperature (Tg) of the particular plastic from which the preform is molded, the preform is transferred into a blow-mold cavity. In what is known as the stretch blow molding process, the preform is forcibly expanded by means of compressed air into the shape of the mold cavity while simultaneously being subjected to axial stretching in order to effect biaxial orientation of the container. After a brief residence period in the mold, the resulting blown container is discharged from the mold for and is shipped or conveyed to another location for filling. 
     Unfortunately, certain types of preforms may have a shape that is incompatible with common transfer mechanisms, making it difficult or impossible for the transfer mechanism to reliably grip the purchasing structure of the preform and convey the preform to its intended destination. In addition, aesthetic concerns may limit placement of purchasing structure on the preform. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a preform, container and method of making a container that optimize gripping of the preform by a transfer mechanism and that provides a container assembly that is aesthetically attractive. 
     In order to achieve the above and other objects of the invention, a plastic preform according to one aspect of the invention may include a main body portion; and a threaded finish portion, the threaded finish portion having an outer surface and an inner surface, the threaded finish portion further comprising: a proximal end that is unitary with the main body portion; an opposite distal end; at least one thread defined on the outer surface; and a gripping indentation defined in the outer surface, the gripping indentation being longitudinally positioned between the thread and the opposite distal end. 
     According to a second aspect of the invention, a plastic container may include a main body portion; and a threaded finish portion, the threaded finish portion having an outer surface and an inner surface, the threaded finish portion further comprising: a proximal end that is unitary with the main body portion; an opposite distal end; at least one thread defined on the outer surface; and a gripping indentation defined in the outer surface, the gripping indentation being longitudinally positioned between the thread and the opposite distal end. 
     A method of making a plastic container according to a third aspect of the invention may include steps of providing a preform having a threaded finish portion that has at least one external thread and a gripping indentation that is located between the external thread and a distal end of the preform; engaging the preform with a transfer apparatus; and blow molding a container using the preform. 
     These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary side elevational view showing a preform that is constructed according to a preferred embodiment of the invention; 
         FIG. 2  is a cross-sectional view taken along lines  2 - 2  in  FIG. 1 ; 
         FIG. 3  is a fragmentary side elevational view showing a container that is constructed according to a preferred embodiment of the invention; 
         FIG. 4  is a cross-sectional view taken along lines  4 - 4  in  FIG. 1 ; and 
         FIG. 5  is a flowchart depicting a method that is performed according to a preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to  FIG. 1 , a plastic preform  10  that is constructed according to a preferred embodiment of the invention is preferably fabricated from a plastic material, most preferably polyethylene terephthalate or PET. Plastic preform  10  includes a main body portion  12  and a threaded finish portion  14  that has an outer surface  16  and an inner surface  18 , which is best shown in  FIG. 4 . 
     As is best shown in  FIGS. 1 and 4 , plastic preform  10  is constructed so as to further include a proximal end  20  that is unitary with the main body portion  12  and an opposite, distal end  22  that preferably includes a sealing surface to seal against an inside of a closure in conventional fashion. 
     At least one thread  24  is preferably defined on the outer surface  16  of the threaded finish portion  14 . In the illustrated embodiment, the threaded finish portion  14  is provided with a plurality of a external threads  24 , which are of the type that are configured to meet with a conventional metallic lug type closure. However, any conventional type of external threading could be used within the scope of the invention. For example, continuous helical threads could be provided, or helical threads having interruptions defined therein for venting purposes could be used. 
     At least one gripping indentation  26  is preferably defined in the outer surface  16  of the threaded finish portion  14  in a location that is longitudinally positioned between the thread  24  and the opposite, distal end  22  of the threaded finish portion  14 . In the preferred embodiment, there is one such gripping indentation  26  defined in the outer surface  16 . It preferably has an annular shape and it preferably extends about an entire circumference of the outer surface  16  of the threaded finish portion  14 . 
     As is schematically depicted in  FIG. 4 , gripping indentation  26  preferably has a depth DG that is within a range of about 0.015 inches to about 0.040 inches. Gripping indentation  26  preferably includes a substantially flat lower surface  28 , a first side wall  30  that is located on a distal end of the substantially flat lower surface  28  and a second side wall  32  that is located on a proximal end of the substantially flat lower surface  28 . 
     The substantially flat lower surface  28  preferably has a longitudinal dimension L G  that is within a range of about 0.085 inches to about 0.125 inches. 
     The first side wall  30  preferably is shaped to have a uniform longitudinal cross-section about an entire rotation of the threaded finish portion  14 , and preferably forms an angle α 1  with respect to a plane that is perpendicular to the substantially flat lower surface  28  that is within a range of about 0° to about 20°. 
     The second side wall  32  is shaped so it that it also has a uniform longitudinal cross-section about an entire rotation of the threaded finish portion  14 , and preferably forms an angle α 2  with respect to a plane that is perpendicular to the substantially flat lower surface  28  that is within a range of about 0° to about 80°. 
     A longitudinal dimension L d  between the gripping indentation  26  and the distal end  22  of the threaded finish portion  14  is preferably within a range of about 0.04 inches to about 0.25 inches. 
     The flat portion  28  of the gripping indentation  26  preferably is substantially cylindrical in shape and defines an internal radius R G  that is within a range of about 0.75 inches to about 1.25 inches. 
     A method that is performed according to a preferred embodiment of the invention is schematically depicted in  FIG. 5 . A preform corresponding to that described above is first provided, and then is engaged with a transfer apparatus that engages the preform at the gripping indentation. Preferably, the preform is engaged so that the flat portion  28  of the gripping indentation  26  is contacted. The transfer apparatus conveys the preform to a blow molding station where it is blow molded into a container  40 , which is shown in  FIG. 3 . 
     The container  40  includes a main body portion  42  and a threaded finish portion that is substantially identical to the threaded finish portion described above with reference to the plastic preform  10 . 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.