Extrusion blow molding methods and articles made thereby

Abstract

A process for extrusion blow molding an article, and an extrusion blow-molded article, in which a solid radially outwardly extending flange is blown into the tubular side wall of the article. A circumferentially extending groove is formed in the inner surface of the mold that molds the tubular side wall of the article. A parison of molten thermoplastic material is extruded and the parison is inflated by blowing to blow the parison against the walls of a mold. During inflation, the groove is filled by the molten thermoplastic material. The material that filled the groove forms a solid radially outwardly extending flange molded to the tubular side wall of the article. A portion of the article extending above the flange is severed in a single cutting step to form an article having an outward flange at its top end.

That which is claimed:  
     
         1 . An extrusion blow-molded intermediate article of manufacture for making a container, the intermediate article comprising: 
 a base wall;    a generally tubular side wall having a bottom end joined to the base wall and an opposite top end spaced from the base wall;    a generally tubular accommodation portion extending from the top end of the side wall up to an upper end of the intermediate article; and    a solid, radially outwardly extending flange blow molded so as to integrally join the top end of the side wall and the accommodation portion at a juncture therebetween, the flange extending radially outward of immediately adjacent portions of the side wall and the accommodation portion.    
     
     
         2 . The intermediate article of  claim 1 , wherein at least a portion of the flange has a thickness different from that of the side wall.  
     
     
         3 . The intermediate article of  claim 1 , wherein the flange has a thickness that is uniform in a radial direction of the flange and is different from a thickness of the side wall at the top end thereof.  
     
     
         4 . The intermediate article of  claim 1 , wherein the flange has a thickness that varies in a radial direction of the flange.  
     
     
         5 . The intermediate article of  claim 4 , wherein the flange tapers in thickness in the radial direction.  
     
     
         6 . An extrusion blow-molded container, comprising: 
 a base wall;    a tubular side wall having a bottom end joined to the base wall and an opposite top end defining a container opening; and    a solid flange integrally molded to the top end of the side wall and extending radially outwardly thereof, the flange having a radially outermost edge that is molded by a mold surface during the extrusion blow molding of the container.    
     
     
         7 . The container of  claim 6 , wherein the flange is annular and the molded outermost edge of the flange has a radius that is substantially uniform about a circumference of the flange.  
     
     
         8 . The container of  claim 6 , wherein at least a portion of the flange has a thickness greater than that of the tubular side wall.  
     
     
         9 . The container of  claim 6 , wherein the flange has a thickness that varies in the radial direction.  
     
     
         10 . The container of  claim 9 , wherein the flange tapers in the radial direction.  
     
     
         11 . The container of  claim 6 , wherein the side wall and flange each has a thickness from about 0.01 inch to about 0.06 inch.  
     
     
         12 . The container of  claim 6 , further comprising a metal end closure seamed onto the container, the closure having an outer curled edge interlocked with the flange.  
     
     
         13 . The container of  claim 12 , wherein the container includes a hinge region at a juncture between the tubular side wall and the flange, the hinge region being thinner than the side wall and flange to facilitate rotation of the flange about the hinge region during seaming of the end closure.  
     
     
         14 . The container of  claim 6 , further comprising a flexible membrane end closure sealed onto the flange to hermetically close the container.  
     
     
         15 . An extrusion blow-molded container, comprising: 
 a base wall;    a tubular side wall having a bottom end joined to the base wall and an opposite top end defining a container opening; and    a solid flange integrally molded to the top end of the side wall and extending radially outwardly thereof, the flange being formed by blowing molten thermoplastic material into a groove formed in a side wall inner surface of a blow mold such that the material fills the groove, whereby upper and lower surfaces of the flange comprise molded surfaces that are molded by surfaces of the groove.    
     
     
         16 . The container of  claim 15 , wherein a radially outermost edge of the flange comprises a molded edge that is molded by a surface of the groove, whereby trimming of the outermost edge is unnecessary.  
     
     
         17 . The container of  claim 15 , wherein at least a portion of the flange has a thickness greater than that of the side wall.  
     
     
         18 . The container of  claim 15 , wherein at least a portion of the flange has a thickness less than that of the side wall.  
     
     
         19 . The container of  claim 15 , wherein the flange has a thickness that varies in the radial direction.  
     
     
         20 . The container of  claim 19 , wherein the flange tapers in thickness.  
     
     
         21 . A method for making an extrusion blow-molded article, the method comprising the steps of: 
 extruding a tubular parison of molten thermoplastic material from an annular throat of a die;    enclosing the parison in a mold and closing one end of the parison, the mold having a side wall inner surface encircling a central longitudinal axis of the mold and having a base wall inner surface adjacent the closed end of the parison;    providing a circumferentially extending groove in the side wall inner surface of the mold at a location spaced longitudinally from the base wall inner surface; and    inflating the parison to cause the parison to expand against and conform to the side wall and base wall inner surfaces of the mold to form an article comprising a base wall and a tubular side wall;    wherein during the inflating step the molten thermoplastic material is blown into the groove in the mold such that the groove is substantially entirely filled by the molten material so as to form a solid flange extending radially outwardly from the side wall of the article.    
     
     
         22 . The method of  claim 21 , further comprising the step of removing that portion of the article that extends above the flange.  
     
     
         23 . The method of  claim 21 , wherein the extruding step comprises suddenly enlarging the width of the annular throat of the die when extruding a localized region of the parison corresponding to the groove in the mold to substantially thicken the parison in said localized region so as to provide sufficient molten material to fill the groove.  
     
     
         24 . The method of  claim 23 , wherein the die throat is suddenly enlarged via a rapidly responsive actuator.  
     
     
         25 . The method of  claim 23 , wherein after the localized region of the parison corresponding to the groove is extruded, the die throat is suddenly constricted to extrude an end portion of the parison.  
     
     
         26 . The method of  claim 23 , wherein the die throat width used for extruding said localized region of the parison is at least 5 times the die throat width used for extruding portions of the parison that form the base wall and that portion of the side wall that extends from the base wall to the flange.  
     
     
         27 . The method of  claim 26 , wherein the die throat width used for extruding said localized region of the parison is at least 10 times the die throat width used for extruding the portions of the parison that form the base wall and the portion of the side wall that extends from the base wall to the flange.  
     
     
         28 . The method of  claim 21 , wherein the groove is provided to have a depth in a radial direction corresponding to a desired radial extent of the flange.  
     
     
         29 . The method of  claim 28 , wherein the groove is provided to have a width that is substantially constant in the radial direction, whereby the flange is made to have a radially uniform thickness.  
     
     
         30 . The method of  claim 29 , wherein the groove is provided to have a width greater than a predetermined thickness of the side wall of the article, whereby the flange is made thicker than the side wall.  
     
     
         31 . The method of  claim 29 , wherein the groove is provided to have a width less than a predetermined thickness of the side wall of the article, whereby the flange is made thinner than the side wall.  
     
     
         32 . The method of  claim 28 , wherein the groove is provided to have a width that varies in the radial direction, whereby the flange is made to have a radially varying thickness.  
     
     
         33 . An extrusion blow-molded container, comprising: 
 a base wall;    a tubular side wall having a bottom end joined to the base wall and an opposite top end defining an opening of the container; and    a solid radially outwardly extending flange integrally molded onto the top end of the side wall, at least a portion of the flange having a thickness different from that of the side wall.    
     
     
         34 . The container of  claim 33 , wherein the flange has a thickness that varies in a radial direction of the flange.  
     
     
         35 . The container of  claim 34 , wherein the flange tapers in the radial direction.  
     
     
         36 . The container of  claim 33 , wherein the flange has a thickness that is substantially uniform along a radial direction of the flange.  
     
     
         37 . The container of  claim 31 , wherein the flange is thicker than the side wall.  
     
     
         38 . The container of  claim 36 , wherein the flange is thinner than the side wall.  
     
     
         39 . The container of  claim 36 , wherein the side wall and flange each has a thickness between about 0.01 inch and about 0.06 inch.  
     
     
         40 . A method for making an extrusion blow-molded container, comprising the steps of: 
 providing an intermediate article according to  claim 35;  and    severing the accommodation portion from the tubular side wall and flange, thereby forming a container having the radially outwardly extending flange formed at the top end of the side wall.    
     
     
         41 . The method of  claim 40 , wherein the severing step comprises cutting through the intermediate article in a generally radial direction such that a resulting cut surface is substantially flush with the flange.