Method and Apparatus for Forming Blow Molded Vessels

Abstract

Methods and apparatus for molding a vessel, such as a bottle, with a high quality sealing surface are described herein. In one embodiment, a stepped blow pin can be used to form the sealing surface of a bottle. A stepped blow pin can include a body with a distal end and a proximal end. The blow pin can include a first region that includes a first diameter and a first engagement surface. The blow pin can further include a second region that includes a second diameter. The second region can be positioned between the first region and the distal end. A transition section can be positioned between the first region and second region. The blow pin can also include a top surface position at the proximal end, and a bottom surface positioned at the distal end.

What is claimed is: 
     
         1 . A stepped blow pin comprising:
 at least two regions; a first region for forming a bottle sealing surface with a first diameter, and   a second region positioned below the first region and having a second and greater diameter.   
     
     
         2 . The stepped blow pin of  claim 1 , wherein the first diameter of the first region and the second diameter of the second region vary between 0.001 inches and 0.030 inches. 
     
     
         3 . The stepped blow pin of  claim 1 , wherein the first region that forms the bottle sealing surface has a diameter of 0.586 inches and the second region of the blow pin has a diameter of 0.594 inches. 
     
     
         4 . The stepped blow pin of  claim 1  further comprising an air passage through which air can be injected into a parison. 
     
     
         5 . The stepped blow pin of  claim 1 , wherein the at least two regions have a circular or oval cross section. 
     
     
         6 . A stepped blow pin for forming a high quality sealing surface on an extrusion blow molded vessel comprising:
 a body having a proximal end and a distal end;   an air passage through which air can be injected;   a top surface positioned at the proximal end;   a bottom surface positioned at the distal end;   an upper and a lower region disposed along the cylindrical body with differing outer diameters; where the upper region includes a seal forming surface region;   a first and a second transition region; where the first transition region is disposed between the upper and lower region, and the second transition region is disposed between the lower region and the bottom surface.   
     
     
         7 . The stepped blow pin of  claim 6 , wherein the lower region has a greater diameter compared to the upper region. 
     
     
         8 . The stepped blow pin of  claim 6 , wherein the seal forming surface region is configured to engage a cap sealing surface of a mold cavity. 
     
     
         9 . The stepped blow pin of  claim 6 , wherein the seal forming surface region has a surface finish of SPI A-2 or higher. 
     
     
         10 . The stepped blow pin of  claim 6 , wherein the first and second transition regions are selected from a group comprising a beveled surface, a chamfered surface, a sloping surface, a slant surface or square shaped or combinations thereof. 
     
     
         11 . The stepped blow pin of  claim 10 , wherein the first and second transition region is a beveled surface. 
     
     
         12 . The stepped blow pin of  claim 6  further comprising:
 a shoulder positioned between the proximal end and the upper region, the shoulder including a molding surface that is perpendicular to the body of the blow pin, and 
 a beveled surface that transitions the shoulder to the upper region of the cylindrical body. 
 
     
     
         13 . A stepped blow pin for forming a high quality sealing surface on a extrusion blow molded vessel comprising:
 a cylindrical body having a proximal end and a distal end;   an air passage through which air can be injected;   a top surface positioned at the proximal end;   a bottom surface positioned at the distal end;   an upper region, a middle region and a lower region disposed along the cylindrical body with differing outer diameters; where the upper region includes a seal forming surface region;   a first and a second transition region; where the first transition region is disposed between the upper and middle region and the second transition region is disposed between the middle region and the lower region.   
     
     
         14 . The stepped blow pin of  claim 13 , wherein the upper region and lower region have a smaller outer diameter. 
     
     
         15 . The stepped blow pin of  claim 13 , wherein the middle region has a greater outer diameter compared to the outer diameter of the upper and lower regions. 
     
     
         16 . The stepped blow pin of  claim 15 , wherein the middle region has a diameter between about 0.001 inches and about 0.030 inches greater that the outer diameter of the upper and lower regions. 
     
     
         17 . The stepped blow pin of  claim 15 , wherein the middle region has a diameter between about 0.003 inches and about 0.010 inches greater that the outer diameter of the upper and lower regions. 
     
     
         18 . The stepped blow pin of  claim 13  further comprising:
 a shoulder positioned between the proximal end and the upper region, the shoulder including a molding surface that is perpendicular to the body of the blow pin, and 
 a beveled surface that transitions the shoulder to the upper region of the cylindrical body. 
 
     
     
         19 . The stepped blow pin of  claim 13 , wherein the seal forming surface region has a surface finish of SPI A-3 or higher. 
     
     
         20 . A stepped blow pin for forming a high quality sealing surface on a extrusion blow molded vessel comprising:
 a cylindrical body having an upper region, a middle region, a lower region, a top surface disposed at a proximal end and a bottom surface disposed at a distal end;   an air passage through which air can be injected;   a seal forming surface region disposed between the upper and middle regions; where the seal forming surface region and the lower region have equal outer diameter, which is different from an outer diameter of the upper and middle region;   a first transition region disposed between the upper region and the seal forming surface region;   a second transition region disposed between the seal forming surface region and the middle region;   a third transition region disposed between the middle region and the lower region; and   a fourth transition disposed between the lower region and the bottom surface.   
     
     
         21 . The stepped blow pin of  claim 20 , wherein the seal forming surface region and the lower region have a smaller diameter compared to the outer diameter of the upper and middle regions. 
     
     
         22 . The stepped blow pin of  claim 20 , wherein the upper and middle region each have a diameter between about 0.001 inches and about 0.030 inches greater than each of the outer diameter of the seal forming surface region and lower region. 
     
     
         23 . The stepped blow pin of  claim 20 , wherein the seal forming surface region has a surface finish of SPI A-3 or higher. 
     
     
         24 . The stepped blow pin of  claim 20 , wherein the first, second, third and fourth transition regions are selected from a group comprising a beveled surface, a chamfered surface, a sloping surface, a slant surface or square shaped or combinations thereof. 
     
     
         25 . The stepped blow pin of  claim 20  further comprising:
 a shoulder positioned between the proximal end and the upper region, the shoulder including a molding surface that is perpendicular to the body of the blow pin, and 
 a beveled surface that transitions the shoulder to the upper region of the cylindrical body.