Patent Publication Number: US-2005142311-A1

Title: Finish assembly for a plastic container or preform

Description:
The present invention is directed to finishes for plastic containers or preforms, to preform assemblies for blow molding plastic containers, to plastic containers blow molded from such preform assemblies, and to methods of making such finishes, preform assemblies and containers.  
     BACKGROUND AND SUMMARY OF THE INVENTION  
      In the manufacture of plastic containers, it is conventional to injection mold or compression mold a container preform having a body and a finish with one or more external threads or other closure attachment means. The preform finish typically is molded to its final geometry, while the body of the preform subsequently is blow molded to the desired geometry of the container body. The preform may be of monolayer construction, or may be of multilayer construction in which one or more intermediate layers in the preform body may or may not extend into the finish area of the preform. U.S. Pat. Nos. 4,609,516, 4,710,118 and 4,954,376 illustrate injection molding of multilayer container preforms.  
      Molding the finish portion of the container as part of the preform presents a number of problems. For example, when the preforms are formed by injection molding, the plastic material typically is injected into a mold cavity at the closed end of the preform body, so that the material must flow along the sides of the preform cavity into the area in which the finish is molded. The finish typically requires more accurate and stable dimensioning than the body of the preform, which can limit the cycle time of the molding process. Furthermore, the finish portion of the preform is of the same material as at least the outer layers of the preform body, which limits the ability to obtain the most desirable characteristics at the finish. When the preform is of polyester construction, such as polyethylene terephthalate (PET), the finish portion of the preform can be wholly or partially crystallized to improve the operating characteristics of the finish area, particularly in hot-fill container applications. However, the requirement that the finish be of the same material as at least the outer layers of the preform body (in a multilayer preform) still limits the design capabilities of preform manufacture.  
      U.S. application Ser. Nos. 10/351,671, 10/375,376, 10/375,758 and 10/403,415, assigned to the assignee of the present application, disclose finish assemblies for preforms and containers in which the preform neck has an external flange around its open end, and a separate plastic finish ring is assembled over the preform neck in abutment with the external flange. The finish ring has one or more external threads or other means for securement of a closure, and can be of a plastic construction different from the plastic construction of the preform. The preform body and neck may be of thin plastic construction. However, liquid that spills on the finish during filling of the container can flow between the finish ring and the preform flange, and collect between the finish ring and the preform neck. Such fluid is unsightly and can encourage the growth of mold. It is a general object of the present invention to provide a finish assembly for a plastic preform or container, a method of making a plastic preform or container, and a preform assembly that reduce or eliminate the likelihood of leakage of fluid between the finish ring and the preform/container neck.  
      A method of making a preform assembly for blow molding a container, in accordance with a first aspect of the present invention, includes providing a plastic preform having a body with a closed end and a neck extending from the body. The neck has an open end and a radially outwardly extending flange surrounding the open end. The flange has an open axially facing channel adjacent to the outer surface of the neck. A finish ring has an annular body, an outer surface with at least one external thread, bead or other means for securing a closure, and an annular lip extending axially from the body. The finish ring is assembled to the preform until the ring abuts the flange, such that the finish ring is received over the outer surface of the neck and the annular lip is received in the neck flange channel to seal the finish ring against the flange. In the preferred embodiments of the invention, the channel in the flange is formed in part by a radially inwardly and axially facing conical surface, and the lip on the finish ring has a radially outwardly and axially facing conical surface in facing engagement with the radially inwardly facing conical surface on the flange to seal the finish ring against the flange and retard or prevent entry of liquid between the finish ring and the neck of the preform.  
      A finish assembly for a plastic container or preform in accordance with a second aspect of the invention includes a plastic neck having an open end surrounded by an external flange. The flange has an open axially facing channel adjacent to the outer surface of the neck. A plastic finish ring has an annular body, an inner surface opposed to the outer surface of the neck, an outer surface with at least one external thread, bead or other means for attachment of a closure, and an annular lip extending axially into the channel. In the preferred embodiments of the invention, the channel is formed in part by a radially inwardly and axially facing conical surface on the flange, and the lip has a radially outwardly and axially facing conical surface in facing engagement with the radially inwardly facing conical surface on the flange to seal the finish ring against the flange against entry of liquid between the finish ring and the neck.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention, together with additional objects, features, advantages and aspects thereof, will be best understood from the following description, the appended claims and the accompanying drawings, in which:  
       FIG. 1  is an elevational view of a preform assembly in accordance with one presently preferred embodiment of the invention;  
       FIG. 2  is an exploded perspective view of the preform assembly illustrated in  FIG. 1 ;  
       FIG. 3  is a fragmentary sectional view taken substantially along the line  3 - 3  in  FIG. 1 ;  
       FIG. 3A  is a fragmentary sectional view on an enlarged scale of the upper end of the preform neck illustrated in  FIG. 3 ;  
       FIG. 3B  is a fragmentary sectional view on an enlarged scale of the upper end of the finish ring illustrated in  FIG. 3 ;  
       FIGS. 4 and 5  are fragmentary sectional views that are similar to that of  FIG. 3  but illustrate respective modified embodiments of the invention; and  
       FIG. 6  is a partially sectioned elevational view of a blow molded plastic container in accordance with another aspect of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIGS. 1-3B  illustrate a preform assembly  10  in accordance with one presently preferred embodiment of the invention as including a preform  12  having a finish ring  14  assembled thereto. Preform  12  includes a body  16  with a closed lower end  18  and an integrally formed neck  20  with an external flange  22  extending radially outwardly from the open end of the neck. Neck  20  preferably is of cylindrical construction, and flange  22  preferably is circumferentially continuous and perpendicular to the axis of neck  20 . An open channel  24  ( FIGS. 3 and 3 A) is formed on the undersurface of flange  22 , such as by being molded into the flange or formed in the flange in a post-molding operation. As best seen in  FIG. 3A , channel  24  has a radially outwardly facing surface  26  that preferably is a continuation of the radially outwardly facing surface  28  of preform neck  20 , an axially facing annular undersurface  30  adjacent to surface  26 , and a generally radially inwardly and axially facing surface  32  extending from the radially outer edge of surface  30 . Surface  32  preferably is of conical construction. Surfaces  26 ,  30  and  32  are circumferentially continuous, and preferably are coaxial with the axis of neck  20  and with each other. Conical surface  32  preferably is at an angle of about 30° to the axis of preform neck  20 . Annular undersurface  30  preferably lies in a plane perpendicular to the axis of neck  20 .  
      Finish ring  14  preferably is of molded plastic construction, having an annular body  34  with an integrally formed axially extending lip  36 . Ring body  34  and lip  36  preferably are circumferentially continuous. Lip  36  has an inner surface  38  ( FIG. 3B ) preferably formed as an extension of the inner surface  40  of ring body  34 , both preferably being cylindrical. Lip  36  also has an axially facing end surface  42 , which preferably lies in a plane perpendicular to the axis of ring  14 , and a radially outwardly and axially facing conical surface  44  that extends from the outer edge of surface  42 . Conical surface  44  preferably is complementary to surface  32  on preform flange  22 , preferably at an angle of about 30°. A second axially facing surface  46 , which may be parallel to or angled with respect to surface  42 , extends from conical surface  44  to the radially outer surface  48  of ring body  34 . Ring body  34  also includes at least one external thread, bead or other means  50  for securing a closure to the final container ( FIG. 6 ). In the exemplary embodiments illustrated in the drawings, ring body  34  also includes an annular bead  52  for engagement by tamper-indicating means on the closure, and a support flange  54  to facilitate subsequent handling of the preform and container.  
      Preform  12  preferably is formed in a compression or injection molding operation. Finish ring  14 , which preferably is itself formed in a suitable plastic molding operation, is assembled over the closed end of the preform so that the radially inner surface  40  of preform body  34  is in close sliding engagement with the outer surface  28   b  of preform neck  20 . The above-noted pending applications disclose various techniques for assembling finish ring  14  over neck  20  and securing the finish ring to the neck, such as by interference press fit. The assembly of finish ring  14  over preform neck  20  continues until lip  36  on finish ring  14  is received within channel  24  on preform neck flange  22  and conical surfaces  44 ,  32  are brought into abutting facing engagement. Such abutting facing engagement of surfaces  44 ,  32  helps prevent any flow of liquid between the opposing surfaces of the finish ring and the preform neck. The axial dimension of channel  24  preferably is coordinated with the axial dimension of finish ring lip  36  so that there is a gap  56  ( FIG. 3 ) between preform neck flange  22  and neck ring surface  46  in assembly, which helps ensure that surfaces  44 ,  32  are in seating engagement.  
       FIGS. 4 and 5  illustrate preform assemblies  60 ,  62  in accordance with respective modified embodiments of the invention. Reference numerals in  FIGS. 4 and 5  that are identical to those in  FIGS. 1-3B  indicate identical or related components. The primary difference between preform assembly  60  in  FIG. 4  and preform assembly  10  in  FIGS. 1-3  is that preform flange  22   a  and/or finish ring lip  36   a  is dimensioned so that there is axially abutting engagement between the axially facing surfaces  30 ,  33  ( FIG. 3A ) on flange  22   a  and surfaces  42 ,  46  ( FIG. 3B ) on neck ring  14   a . In other words, the neck flange and/or the neck ring lip is dimensioned to eliminate gap  56  in  FIG. 3 . There can be a gap between surfaces  30 ,  42  ( FIGS. 3A and 3B ) in the embodiment of  FIG. 4 . In  FIG. 5 , neck flange  22   b  has an axially facing channel in which conical surface  32   b  extends to the outer edge of the flange, and conical surface  44   b  on neck ring lip  36   b  extends to the outer surface of the neck ring, which is to say that axially facing surfaces  33  ( FIG. 3A ) and  46  ( FIG. 3B ) are eliminated.  FIG. 6  illustrates a container  64  that includes a body  16   a  blow molded from body  16  of preform  12  ( FIGS. 1 and 2 ), and a finish assembly  66  in accordance with any of the embodiments illustrated in  FIGS. 1-5 .  
      There have thus been disclosed a method of making a preform assembly, a finish assembly for a plastic container or preform, and a preform assembly that fully satisfy all of the objects and aims previously set forth. The invention has been disclosed in conjunction with several exemplary presently preferred embodiments, and a number of additional modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to person of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.