Abstract:
A plunger for use in forming parisons during the manufacture of glass containers having a biased open valve therein.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is directed to a plunger for use in forming parisons during the manufacture of glass containers with individual section (I.S.) machines. 
   2. Description of Related Art 
   A well-established process for manufacturing glass containers is known as the “blow-and-blow” process. In the “blow-and-blow” process, a gob of molten glass is introduced and partially shaped or molded into an object called a parison, which eventually will be formed into a glass container. The parison is formed by a blowing operation in a mold. The gob is introduced into the mold positioned over a plunger which acts to form the neck region of the parison. A vacuum is provided below the gob to urge the gob into the neck and around the plunger. The plunger is then withdrawn creating a space into which air is blown to expand the gob to the shape of the mold cavity. Thereafter, the shaped gob or parison is transferred to a finishing mold for a further blowing operation to form the parison into a container. Details of a suitable mechanism for plunger cycling are disclosed, for example, in U.S. Pat. No. 5,358,543 entitled “Air Tube Structure in a Glass Container Forming Machine”. The details of a suitable mechanism for connecting either a vacuum or blowing air to a piston for transfer through the plunger to the blank mold is described in U.S. Pat. No. 5,876,475 entitled “Glass Container Forming Process and Equipment”. Both of these patents are incorporated herein by reference. 
   SUMMARY OF THE INVENTION 
   Briefly, according to the present invention, there is provided a plunger for being attached to a piston that inserts and withdraws the plunger from the neck region of a blank mold during the manufacture of a parison for forming glass containers in the blow-and-blow process. The plunger comprises a hollow cylindrical body, the lower end of which engages the piston. A radial flange extends from the exterior of the cylindrical body, preferably spaced from the lower end of the hollow cylindrical body. A nose portion is attached or integral with the upper end of the hollow cylindrical body and is configured for insertion in the neck region of the blank mold. A shoulder is defined between the nose portion and the hollow cylindrical body. One or more passages extend between the interior of the hollow cylindrical body and the shoulder. The nose portion has a hollow interior opening onto a valve seat at the upper end thereof. One or more passages extend between the interior of the hollow cylindrical body and the hollow interior of the nose portion. A guide bore extends between the interior of the hollow cylindrical body and the hollow interior of the nose portion. A valve stopper has a stem positioned within the bore such that in the valve&#39;s most downward position the valve stopper rests in the valve seat. A high temperature spring is coiled around the valve stem for urging the stopper away from the valve seat. A mechanism such as a snap ring is positioned at the lower end of the valve stem for restraining the maximum upward movement of the valve stem. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and other objects and advantages will become clear from the following detailed description made with reference to the drawings in which: 
       FIG. 1  is a section view of a portion of the plunger cylinder assembly, neck ring, and parison mold of an I.S. machine with the plunger in the full-up position prior to seating of the gob in the neck ring; 
       FIG. 2  is a section view similar to  FIG. 1 , with the plunger in the full-up position with the gob shown entering the neck region; 
       FIG. 3  is a section view similar to  FIG. 1 , with the plunger in the full-up position after seating of the gob in the neck ring; 
       FIG. 4  is a section view similar to  FIG. 2  with the plunger in the blow position; 
       FIG. 5A  is a section view of an alternate embodiment of the plunger; and  FIG. 5B  is a section view taken along lines VA—VA of FIG.  5 A. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Directing attention to  FIGS. 1  to  4 , details of a plunger cylinder assembly are illustrated. A blank or parison mold  10  is positioned over a neck ring  11 . A plunger cylinder assembly  20  moves a plunger  12  in and out of the opening in the neck ring  11 . An element known in the art as a thimble  13  slides over the plunger  12  and moves up and down independently of the plunger  12  to abut the bottom of the neck ring  11  during certain stages of the parison forming process. The function of a plunger cylinder assembly is principally to position the plunger  12  and thimble  13  in one of three positions, namely, “full-up”, “blow”, and “full-down”. 
   Referring to  FIG. 1 , the plunger  12  is placed in the full-up position wherein it enters the neck ring  11  for the formation of the neck of the parison as a gob of molten glass flows into the space between the neck ring  11  and the upper end or nose of the plunger  12 . At this position, the thimble  13 , which slides outside of the plunger  12 , bears upon the underside of the neck ring  11 . In this position, a vacuum is pulled through passages  15 ,  16 , and  19  in the plunger  12 , neck ring  11 , and the lower end of the parison mold  10  to draw the gob into the neck and mold  10 . The neck ring  11  often is configured to form threads on the exterior of the neck of the parison and container. 
   Referring to  FIG. 2 , the plunger is shown in the full-up position and the gob has just reached the neck region and rests on the top surface of the valve head. The vacuum can still be drawn on the neck region. Referring to  FIG. 3 , the plunger remains in the full-up position and the gob has pushed the valve closed and has filled the neck region. 
   Referring to  FIG. 4 , the plunger  12  is placed in the blow position wherein it is partially withdrawn from the neck ring leaving a space or bubble in the bottom of the gob into which air may be forced to blow the gob into contact with the walls of the mold forming the parision. 
   The plunger  12  may be positioned in the full-down or retracted position, wherein the plunger  12  is moved further away from the neck and the thimble  13  is pulled back away from the neck ring  11 . In this position, after the mold has been separated from the neck ring  11 , the formed parison can be carried away from the plunger cylinder by the neck ring  11  to the final container forming apparatus. 
   Of particular interest for the subject invention are the plunger  12  and the associated details. As previously discussed, the molten gob is introduced within the blank mold  10  to form a parison  18  which conforms to the mold within the neck region  14 . The neck region  14  is comprised of the neck contour wall and the nose of the plunger  12 . 
   As previously mentioned, a molten gob of glass may be urged within the blank mold  10  by a vacuum generated at the bottom of the blank mold. The arrangement is for drawing the molten gob into the blank mold utilizing a vacuum comprising passages  15  within the plunger  12 , passages  16  within the neck region  14 , and passages  19  within the blank mold  10 . In particular, the plunger  12  has a hollow interior and passages extending therethrough whereby vacuum generated from below the plunger  12  is transferred to the mold. Mold passages  19  extend into the interior of the blank mold  10  while gaps produced by the outer diameter of the plunger  12  being smaller than the inner diameter at the base of the neck ring  11  thereby create a small gap around the perimeter of the plunger  12  to provide vacuum access. In prior art assemblies, the vacuum was only communicated with the interior of the blank mold by the above-described passages and gap. 
   The plunger  12 , according to the present invention, comprises a hollow cylindrical body  21 , the lower end  22  of which is provided with a structure  23  for attaching the plunger to a piston adapter  17 . The adapter, in turn, is connected to the piston. Preferably and traditionally, the cylindrical body  21  has a circular section perpendicular to the axis thereof. Other cross sections, such as a regular polygon cross section, would be acceptable. As illustrated in the drawings, the structure  23  for attaching the plunger  12  to the piston  17  adapter is a groove for receiving balls  24  held in radial bores in the upper end of the piston  17 . A suitable structure is described in detail in allowed U.S. patent application Ser. No. 09/713,724 entitled “Quick Change Connector for Plunger for Glass Container Forming Process and Equipment.” Traditional connectors between the plunger and piston, such as removable clamps, are also suitable structures for attaching the plunger to the piston. 
   A radial flange  25  extends from the exterior of cylindrical body  21 , preferably spaced from the lower end. The purpose of the flange is to engage the thimble  13  to limit the upward-most travel of the plunger relative to the thimble as shown in  FIGS. 1  to  4 . 
   A nose portion  28  attached to the upper end of the hollow cylindrical body  21  is configured for insertion in the neck region  14  of the neck ring  11 . The length and configuration of the nose portion depends upon the configuration of the neck of the bottle being made. For example, a wine bottle requires a long neck to accept the full length of the cork. Bottles with threaded necks require a much shorter neck. Because the maximum diameter of the nose portion of the plunger where it joins the cylindrical body is less than the diameter of the cylindrical body, a shoulder  29  is defined between the nose portion and the hollow cylindrical body. Preferably and typically, the surface of the nose portion  28  is a surface of revolution that has an axis that is coaxial with the axis of the hollow cylindrical body  21 . One or more passages  15  extend between the interior of the hollow cylindrical body  21  and the shoulder. Normally, at least four such passages are equally spaced around the cylindrical body. The nose portion has a hollow interior  31  opening onto a valve seat  32  at the upper end thereof. The valve seat  32  is tapered so as not to hold debris passed therethrough. The hollow interior  31  of the nose portion and the hollow interior of the cylindrical body  21  are separated by a wall  34  except for the passages and guide bore next described. 
   One or more passages  35  extend between the interior of the hollow cylindrical body and the hollow interior  31  of the nose portion. The purpose of these passages is to conduct the blown air or the seating vacuum to the neck region of the necking ring through the valve seat  32 . Preferably, the upper ends of the passages  35  widen out in a funnel shape to ensure that when a vacuum is pulled through the valve seat, no debris drawn down from the mold will be captured in the hollow interior of the nose portion. Most preferably, the upper ends of the funnel-shaped entrances to the passages  35  overlap in a manner to eliminate any surface upon which debris can lodge. 
   A guide bore  33  extends between the interior of the hollow cylindrical body and the hollow interior of the nose portion. Preferably, the guide bore has an axis that is coaxial with the axis of the hollow cylindrical body  21  and the nose portion  28 . 
   A valve stopper  40  has a tapered underside configured to rest snugly in the valve seat  32  at the upper end of the nose portion. A valve stem  41  attached to the valve stopper is positioned within guide bore  33  such that in its most downward position, the valve stopper rests in the valve seat and in its most upward position, the valve stem extends into the interior of the hollow cylindrical body. According to one embodiment, the upper surface of the valve stopper is coated with a material  45  having a heat-conductivity less than the metal from which the stopper and valve stem are formed. This reduced the length of the reheat period following withdrawal of the nose portion of the plunger and before the blow. 
   A high temperature spring  42 , for example, made of Inconel, is coiled around the valve stem for urging the stopper away from the valve seat. At one end, the spring  42  abuts the underside of the stopper  40  and at the other end, it abuts the wall  34  separating the hollow interior of the nose portion from the hollow interior of the cylindrical body. The passages  35  direct a flow of air along the spring and valve stem during the blowing operation that serves to cool both the spring and the valve stem. An attachment on the lower end of the valve stem, such as a snap ring  44 , restrains the maximum upward movement of the valve stem. 
   During the time a vacuum is being pulled to draw down the molten gob of glass, the spring causes the valve stopper to unseat as shown in FIG.  1 . As the gob is drawn into the necking ring, it presses the valve closed as shown in FIG.  3 . When the nose portion is withdrawn from the gob leaving a space or bubble, the valve is urged open again as shown in FIG.  4 . Hence, the drawing of the vacuum does not simply depend upon the passages in the neck ring and the gap between the plunger and neck ring. Because of the speed with which the gob enters the blank mold and the rate at which the red-hot gob heats the air that it contacts, the gob has a tendency to be repelled as it enters the mold. This problem is overcome by the plunger as described herein. Moreover, the blowing of the parison to the blank mold walls is facilitated by the open valve. 
   Referring to  FIG. 5A , an alternate embodiment of the plunger is shown in which the valve stopper has a cylindrical shape with a diameter just less than the diameter of the hollow interior opening of the nose portion so that the valve stopper can be withdrawn within the nose portion. The downward travel of the valve stopper is limited by the wings  41 A extending from the valve stem, as illustrated in  FIG. 5B , coming to rest upon the upper surface of wall  34 . This embodiment is intended for especially narrow bottle necks. 
   Having thus described my invention in the detail and particularity required by the Patent Laws what is desired protected by Letters Patent is set forth in the following claims.