Abstract:
A manifold is connected between an extruder and the associated die assembly to supply plastic flow to the die. The output from the extruder is split into multiple passages in which each manifold passage supplies plastic flow to an extrusion passage within the die assembly. An adjustable throttle valve is positioned within each manifold passage to regulate the flow volume through the manifold passage, thereby controlling the output of the die assembly. An adjustment mechanism is constructed having a lever arm actuated by a screw to provide movement of a spring biased part of the valve to open and close a valve seat against a valve stem.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an assembly for regulating the volume of flow of molten plastic material from an extruder to a die having multiple flow passages. 
   2. Brief Description of Related Developments 
   In certain circumstances it is necessary to supply multiple passages of an extrusion die with molten plastic material. This is accomplished in many instances by providing separate extruders for the inlet of each of the multiple passages. This may be cumbersome where there are closely adjacent multiple passages and unnecessary where several of the flow passages are intended to use the same material. 
   It is an object of this invention to provide an inlet manifold connected to a single extruder which is constructed to split the outflow of the extruder into multiple extrusion passages of an extrusion die assembly. 
   Multiple passages are generally used to feed multiple extrusion channels which extrude separate products, concentric layers, or other configurations. In such circumstances, it is sometimes difficult to maintain an even flow volume in adjacent passages because of uneven temperature distribution and other factors. This may result in an imbalance in output. This imbalance can cause problems in post extrusion processing. 
   It is the purpose of this invention to provide a manifold which divides a single feed flow into multiple channels and includes an adjustable throttle valve to regulate the flow volume in the extrusion passages supplied by the extruder. A manifold of this type is described in U.S. Pat. No. 6,971,865 which issued on Dec. 6, 2005, the disclosure of which is incorporated herein in its entirety. 
   It is another purpose of this invention to construct a means for conveniently adjusting the valve position to accurately regulate the flow of plastic. 
   SUMMARY OF THE INVENTION 
   An input manifold is constructed with an inlet for receiving molten plastic material from an extruder. The inlet splits the flow into several flow passages, at least two, to supply flowing plastic to the extrusion passages of a die assembly. The extrusion passages direct the flowing plastic to the die outlets of the assembly. The manifold is constructed having spaced adjacent upstream and downstream sections. The manifold sections have aligned passages for receiving and transmitting the flowing plastic. Each passage of the downstream section is constructed with a stationery valve stem positioned along the axis of the passage and having a conically shaped upstream facing surface. 
   A valve body is constructed to be mounted in each of the passages and includes an axial channel. The valve body is mounted to slidably engage the aligned passages of both the upstream and downstream sections, thereby bridging the gap between the manifold sections. The downstream end of the valve body channel is constructed with a conical valve seat to receive the upstream facing surface of the valve stem. The valve body slides within the manifold to adjust the valve opening, thereby regulating the flow of plastic in the passages. The outer surface of each of the valve bodies is constructed with a flange for engaging a bias spring. The bias spring is constrained between the valve body flange and a portion of the manifold to exert a force on the valve body tending to move the valve body into the open position. 
   The downstream manifold section may be attached to the die assembly by screws with the valve stems in place within the manifold section passages. The valve bodies are assembled by positioning the valve body assembly so that the valve bodies fit into the passages of the downstream manifold section. The upstream manifold section is positioned to receive the valve bodies. 
   In order to adjust the position of the valve bodies relative to the valve seat, a lever arm is mounted in the manifold for pivotal movement about a fulcrum positioned intermediate its length. An inner portion of the lever arm engages the valve body flange to cause axial movement of the valve body against the bias spring. Axial movement of the valve body will adjust the clearance between the valve stem and the valve seat and thereby regulate the flow volume in a particular passage. The adjustment levers are actuated by screws located at the outer end of the adjustment lever. The screws extend through the lever and engage a portion of the manifold to provide a pivot force tending to rotate the inner end of the lever against the bias spring in the throttling direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The manifold assembly of this invention is explained in more detail below with reference to the accompanying drawing, in which: 
       FIG. 1  is a sectional view of an extrusion die using an adjustable inlet manifold; and 
       FIG. 2   a  is an enlarged sectional view of the manifold of  FIG. 1  showing an embodiment of the adjustment mechanism of this application; and 
       FIG. 2   b  is an enlarged sectional view of the valve mechanism shown in  FIG. 2   a;    
       FIG. 3   a  is a sectional view of a Belleville washer stack, as used in an embodiment of the manifold of  FIG. 1 ; 
       FIG. 3   b  is a sectional view of a Belleville alternative washer stack, as used in an embodiment of the manifold of  FIG. 1 ; and 
       FIG. 3   c  is a top view of the Belleville washer stack of  FIGS. 3   a  and  3   b.    
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   To illustrate the construction of this invention, an extrusion system  101  is shown in  FIG. 1 . The system  101  consists of extruders (not shown) having feeds  102  and  103  which supply molten plastic to die assembly  104 . In die assembly  104  extrusion passages A and B carry molten plastic to die element  105  where it exits as a multilayered tubular product. Extrusion passages A and B may be fed by a single extruder (not shown). The extrusion system  101  can take many different forms having two or more passages to be supplied by a single extruder, for example, in an embodiment where products are not coaxially layered products, but products that are extruded side by side. In order to provide multiple flows from a single extruder feed  102 , in particular the two flows in the embodiment shown in  FIG. 1 , an input manifold  106  is constructed with an inlet  107  for receiving molten plastic material from extruder feed  102 . The inlet  107  splits the flow into a pair of flow passages  108  and  109 . Flow passages  108  and  109  are connected to supply flowing plastic to the extrusion passages A and B of die assembly  104 . The plastic flow joins in die element  105  to form a multilayered extruded tubular product. Plastic flow through the manifold is from the upstream feed  102  downstream towards the die element  105  as shown by arrows F. 
   The manifold  106  is constructed of sections  110 , and  111  through which the flow passages  108  and  109  extend. The upstream section  110  connects to extruder feed  102  at inlet  107  and serves to divide the flow of plastic into two streams in passages  108  and  109 . The manifold sections  110  and  111  are connected by means of a pair of valve bodies  112  and  113 , which, as shown in  FIG. 2   a , are mounted for sliding motion within the portions of flow passages  108  and  109  that are contained within the downstream manifold section  111 . Aligned openings to flow passages  108  and  109  are formed at the interface surface  115  of upstream manifold section  110  and downstream manifold section  111  to receive valve bodies  112  and  113 . Valve bodies  112  and  113  have drilled flow passages axially extending through the length of the valve bodies to connect the adjoining portions of manifold flow passages  108  and  109 . 
   As best shown in  FIG. 2   b , the portions of the passages  108  and  109  within the downstream portion of manifold section  111  contain stationery valve stems  116  and  117  positioned along the axis of the respective passage. The valve bodies and valve stems combine to form valve assemblies  130  to provide an adjustable throttle action to the plastic flow with in the passages  108  and  109 . 
   The valve assembly  130  of passage  108 , as shown in  FIGS. 2   a  and  2   b , consists of a valve body  112  and a valve stem  116 . Valve body  112  is constructed with a conical seat portion  118  and valve stem  116  is constructed with conically shaped upstream facing surface  120 . Valve body  113  of passage  109  is constructed identically having a seat portion  119  and similarly valve stem  117  would have an engaging surface  121 . The bodies and stems are positioned in the passages  108  and  109  in axially alignment and are mounted for relative sliding motion within the passages. The relative motion provides an adjustable throttling of the plastic flow in the respective passage. To adjust the flow of plastic within the passages  108  and  109 , the valve bodies  112  and  113  are moved axially relative to their respective valve seats  116  and  117 . To actuate this motion an adjustment mechanism  129  is provided. Adjustment mechanism  129  consists of a valve body flange  131 , lever  132 , adjustment screw  133  and spring  134 . 
   Valve body flange  131  is constructed in valve bodies  112  and  113  and extends radially outward to provide a surface to capture spring  134  and to engage the inner end  135  of lever  132 . 
   A pair of levers  132  is mounted on downstream manifold section  111  for pivotal motion about a fulcrum formed by attachment pin  136 . Pin  136  is positioned centrally on the lever  132  with inner and outer portions of lever  132  extending on either side of pin  136 . The inner end of lever  132  engages an upper surface of flange  131  and provides a force on the valve bodies tending to move the valve bodies axially against spring  134 . As shown in the figures, motion of the valve bodies  112  and  113  downward tends to close the valve elements and restrict the flow of plastic in the flow passages  108  and  109 . Upward motion will tend to separate the valve elements and open the passages. It should be noticed that the movements of the valve action can be oriented in most any direction depending on the packaging requirement of a particular extrusion application. 
   A spring  134  is mounted to engage the lower surface of flange  131  and exert a force that biases the valve bodies  112  and  113  towards the opening direction. As shown, clockwise pivotal motion of lever  132  will oppose the motion of spring  134 . Spring  134  may be constructed as a coil spring in one embodiment. In another embodiment spring  134  may be constructed as shown in  FIGS. 3   a ,  3   b , and  3   c . In the embodiment of  FIG. 3 , spring  134  consists of a stack of multiple Belleville washers  140  and  141  stacked in axial alignment with the dimpled surface of the spring either parallel, as shown in  FIG. 3   a , or opposing as shown in  FIG. 3   b . This type of washer is generally disc shaped with an aperture at its center, as shown in  FIG. 3   c . The disc is dimpled to provide an axial resilience at a predetermined spring force, as is well known. Although the stack is illustrated for simplicity as a stack of dual spring washers, a person skilled in the art could stack more layers of washers, depending on the performance desired. 
   In order to position the valve bodies  112  and  113  to accommodate the desired flow requirements, adjustment screw  133  is mounted through a transverse bore  137  in the outer end  138  of lever  132 . Transverse bore  137  is threaded to engage screw  133  and allow for movement of screw  133  through lever  132 . As shown in  FIG. 2 , screw  133  extends through lever  132  to abut a surface on manifold section  111 . Rotation of screw  133  will tend to pivot lever  132  about pin  136  and move inner end  135  upward or downward. This motion is transmitted through flange  131  to cause axial movement of the valve bodies  112  and  113  with or against spring  134 . Screw  133  may be adjusted by any appropriate drive means such as a wrench, screw driver, or other means depending on the drive configuration of the screw. 
   In this manner a means of providing multiple flow passages from a single plastic feed is constructed having a convenient mechanism for accurately adjusting the flow rate in the multiple flow passages independently. 
   In the above description, it should be understood that the die assemblies shown are for illustration only and do not form part of this invention which can be used in a wide variety of applications in which there is a need to provide a regulated flow from a single extruder to multiple extrusion channels.