Abstract:
A two-piece water box assembly includes a water box main body and an inline adapter ring. The water box main body and inline adapter ring define the water box cutting chamber, with the inline adapter ring being positioned between the water box main body and the die plate. The adapter ring is fastened through the die plate to the extruder inlet housing with a first plurality of fastening elements. The water box main body is also coupled to the extruder inlet housing, through apertures in the die plate and inline adapter ring, by a second plurality of fastening elements, preferably less in number than the first plurality of fastening elements. When access to the cutter hub or cutting chamber is necessary for cleaning or otherwise, the water box main body can be removed easily by unfastening the second fastening elements only, while the inline adapter ring remains fixed to the die plate and extruder inlet housing, thus maintaining the seal therewith and the die plate insulation gasket.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to improvements in underwater pelletizers and more particularly to the water box of an underwater pelletizer constructed of a two-piece assembly for improved access to the cutter hub. 
   2. Description of the Prior Art 
   Underwater pelletizers are well known and operate in conjunction with a die plate having multiple orifices through which molten polymer or other extrudable material is extruded from the inlet housing of an extruder into strands, with the orifices terminating at the die face of the die plate. The pelletizer includes a powered rotary cutter having a cutter hub mounted on a shaft with a plurality of blades supported from the cutter hub which move against the die face for shearing the extruded polymer strands into pellets as the polymer (or extrudate) is extruded beyond the die face. A water box having inlet and outlet pipes encloses the die face, cutter hub and blades to form a cutting chamber through which water flows to quench and rigidify the extruded polymer strands, thus enabling the cutting blades to better shear the extruded strands into pellets. The flow of water through the cutting chamber defined by the water box also conveys a slurry of the water and sheared pellets through the outlet pipe to a pellet dewaterer and/or a dryer. The above described underwater pelletizers are disclosed in related U.S. patents including U.S. Pat. Nos. 4,123,207, 4,251,198, 4,621,996, 4,728,276 and 5,059,103, 5,624,688, all owned by the assignee of this invention. 
   Previous water boxes for underwater pelletizers have been made of one piece construction. During the pelletization process, if the polymer or other extrudate strands extruded through the die plate are not properly sheared the polymer strands can “wrap up” around the rotating cutter hub and drive shaft in the water box, and even get into the inlet and outlet pipes. Should cutter hub wrap up occur it has been necessary to separate the water box from the die plate so that the water box can be cleaned. If the pelletizer cannot be rolled back from the die plate, access to the cutter hub is impaired, making cleaning of the water box difficult. As a result, some operators try to clean the water box by taking the cutter hub off from the die plate side of the water box or, worse yet, try to use a towmotor to pull the pelletizer back, damaging the equipment. Therefore, a need exists for a water box that allows easy access to the cutter hub in the event of cutter hub wrap up or other conditions requiring access to the cutter hub or interior of the water box. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a two-piece water box assembly that facilitates operator access to the cutter hub for easier and faster clean up in the event of cutter hub wrap up or other conditions requiring access to the cutter hub or water box interior. 
   Another object of the present invention is to provide a water box with a water box main body and a separate inline adapter or mounting ring secured directly to the die plate and separating the water box main body from the die plate. 
   A further object of the present invention is to provide the water box main body with an inline flange for attachment to the adapter ring that allows the water box main body to be firmly secured to the die plate through the adapter ring, but with fewer connecting elements, thus speeding the water box removal process. 
   Still another object of the present invention is to provide a water box assembly that can be easily disassembled without breaking the seal between the die plate, the insulation ring gasket and the adapter or mounting ring. 
   A still further object of the present invention is to provide a water box assembly having reduced water pressure sealing requirements which can therefore be manufactured less expensively. 
   Yet another object of this invention to be specifically enumerated herein is to provide a water box assembly in accordance with the preceding objects which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide an assembly that will be economically feasible, long lasting and relatively trouble free in operation. 
   In accordance with these and other objects, the water box assembly of the present invention has a multi-piece construction including a water box main body and a water box-to-die plate inline adapter or mounting ring. The water box main body and inline load ring define a cutting chamber between the water inlet and the water and pellet slurry outlet; the inlet and outlet are typically disposed in diametrically opposed relation, such as the water inlet at the bottom of the cutting chamber and the water and pellet slurry outlet at the top. The inline adapter ring is positioned between the water box main body and the die plate, and the adapter ring is separately fastened through the die plate to the extruder inlet housing with a first plurality of fastening elements. The water box main body is then affixed to the inline adapter ring with a second plurality of fastening elements that preferably are fewer in number than the first plurality of fastening elements. 
   When cleaning of the cutter hub or access to the cutting chamber becomes necessary, the water box main body can be easily removed from the inline adapter ring, using the fewer second plurality of fastening elements. Meanwhile, the inline adapter ring remains fixed to the die plate, and extruder inlet housing, thus maintaining its seal therewith. The fixed adapter ring would keep the die insulation ring sealed as well, thus allowing the water box main body to be removed without breaking the seal between the die plate, insulation ring gasket and the adapter ring. 
   The foregoing objects together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of an underwater pelletizer having a conventional one-piece water box fastened to the die plate in accordance with the prior art; 
       FIG. 2  is an exploded perspective view of a two-piece water box assembly constructed in accordance with the present invention; 
       FIGS. 3A–3F  are perspective views of the water box assembly in accordance with the present invention, illustrating the components and assembly thereof; and 
       FIG. 4  is a sectional view of a two-piece water box assembly in accordance with the present invention fastened to the die plate in the same manner as shown for the prior water box in  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Although only one preferred embodiment of the present invention is explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components of this specific embodiment. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiment, specific terminology will be resorted to for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
     FIG. 1  illustrates an underwater pelletizer as disclosed in U.S. Pat. No. 5,624,688, which is hereby incorporated by reference as if fully set forth. The extruder to the pelletizer includes an inlet housing  10  having an inlet passageway  12  for receiving molten polymer or other extrudate from upstream equipment. The molten polymer is diverted outwardly by a nose cone  14  and enters into a plurality of extrusion orifices  16  in a die plate  18 . The die plate  18  is secured to the inlet housing by fastening bolts  20  or the like of the pelletizer, and the die plate is typically provided with heating elements  22  located in cavities  24  in the die plate. The die plate  18  includes a die face  26  of wear resistant material which is adhered onto the die plate. Insulation ring gaskets  28  or an insulation plug are mounted in recess  29  of the die plate. 
   Attached to the housing  10  and die plate  18  is a water box generally designated by reference numeral  30  which includes a cutting chamber  31 , a water circulating inlet passageway  32  and discharge passageway  34  for water and pellets. The water box  30  includes a mounting flange  36  for attaching the water box to the die plate  18  and housing  10 , and a flange  38  at the opposite end thereof having an inclined surface  40  for association with a similar flange on an adapter connected to a drive unit. A drive shaft  42  extends axially through the cutting chamber  31  and supports and drives a cutter assembly generally designated by reference numeral  44 . The cutter assembly  44  includes a cutter hub  46  and a plurality of cutter knives  48  having their cutting edge associated with the die face  26  and the discharge points of the orifices  16 . 
   Another representative underwater pelletizer is disclosed in U.S. Pat. No. 5,059,103 also hereby incorporated by reference as if fully set forth herein. This patent discloses a typical Model 7 pelletizer manufactured by the assignee of this application for which the present invention may be adaptable. 
   As shown in  FIG. 1  of the present drawings, the prior art water box  30  and die plate  18  are attached to the housing  10  by fastening elements  20 . There are typically twelve or more of such fastening elements on most pelletizers, each of which must be removed in order to remove the water box  30 . These fastening elements are often difficult to access if they are close to the inlet and outlet pipes defining the inlet passageway  32  and discharge passageway  34 , respectively. As a result, the size of the pipe that may be used in many water boxes can be limited. 
   The present invention solves this problem through a two-piece water box assembly that reduces the number of fastening elements which must be removed in order to gain access to the cutting chamber for cleaning or other purposes. As illustrated in  FIGS. 2–4 , the two-piece water box assembly of the present invention is generally designated by reference numeral  49  and includes a water box main body generally designated by reference numeral  50 , and an inline adapter or mounting ring generally designated by reference numeral  52 . A die plate, generally designated by reference numeral  56 , is secured between the adapter ring  52  and the flange  54  of the extruder inlet housing  10 . For purposes of description, the water box main body  50  represents the “outer” side of the water box assembly  49 , and the adapter ring  54  represents the “inner” side of such water box assembly. 
   The water box main body  50  includes an inlet pipe  58  and an outlet pipe  60  preferably disposed in diametrically opposed relation and separated by a generally cylindrical chamber housing  62 . The body  50  also includes a mounting flange  64  which extends from an inner periphery of the chamber housing  62  and includes an outer surface  66 , an inner surface  68  and a cylindrical external surface  70 . A plurality of generally circular apertures  72  sized to receive fastening elements  74  extend through the flange  64 . In the preferred embodiment shown, the fastening elements  74  are studs to which nuts  76  are secured to join the water box main body  50  to housing flange  54  through the adapter ring  52  and die plate  56 . 
   The adapter ring  52  is an annular ring member aligned with the main body  50  and having a substantially flat outer face  78  that abuts the inner surface  68  of the flange  64  on the water box main body  50 . Passing through the flat outer face  78  to a generally flat inner face  80  are a first plurality of generally circular apertures  82  sized to receive bolts or fastening elements  84 . The apertures  82  are counter-sunk to receive the heads  86  of the bolts  84  so that, when the bolts  84  are fully inserted, the tops of heads  86  are flush with the outer face  78  or recessed therefrom. 
   The adapter ring  52  also includes a second plurality of generally circular apertures  72 A comparably sized and in alignment with apertures  72  in the main body flange  64  to receive the fastening elements  74 . The first and second pluralities of apertures are preferably of the same size, although apertures  72  are not countersunk. The outer face  78  of the adapter ring  52  is machined to fit in close abutment with the inner surface  68  of the flange  64  so that, when joined, the surfaces are sealed tight and the external cylindrical surface  88  of the adapter ring  52  and the external surface  70  of the flange  64  preferably create a generally uniform cylindrical outer surface. 
   The inlet housing flange  54  also has a cylindrical external surface  90  and a substantially flat outer face  92 . Cut into the face  92  are a plurality of generally circular apertures  72 B sized to receive and hold the base of fastening elements  74  and a plurality of generally circular apertures  83  sized to threadedly receive the bolts  84  therein. In the preferred embodiment shown, there are four fastening elements  74  which are positioned to straddle the horizontal and vertical centerlines of the adapter ring  54  so as to facilitate access to securing nuts  76  on either side of pipes  58  and  60 . 
   The die plate  56  may be of conventional design and includes a substantially flat die face  94 , a substantially flat inner face  96 , a cylindrical external surface  98  and a plurality of extrusion or die orifices  99 . The die plate  56  shown in  FIG. 2  has only four orifices  99 , whereas the plate  56  shown in  FIGS. 3 and 4  have multiple small orifices for forming micropellets. Passing through the inner face  96  and the outer face  94  are a plurality of circular apertures  100  sized to allow fastening elements  74  and fastening elements  84  to pass therethrough. 
   The outer face  92  of the housing flange  54  is machined to is fit in close abutment with the inner face  96  of the die plate  56 , and the inner face  80  of the adapter ring  52  is machined to fit in close abutment with the die face  94  of the die plate  56  so that, when joined together the mating surfaces are tightly sealed and the external surface  90  of the adapter ring  52 , the external surface  98  of the die plate  56  and the external surface  88  of the adapter ring  52  preferably create, along with the external surface  70  of the flange  64 , a uniform cylindrical outer surface. 
     FIGS. 3A–3F  illustrate the assembly of the water box of the present invention. As shown in  FIG. 3A , the studs  74  are rigidly installed in the inlet housing flange  54 , by screw threads or the like. The die plate  56 , which is typically provided with insulation ring gaskets  102  or a solid insulation plug as known by persons of skill in the art, is installed by sliding the same onto the studs  74 , as shown in  FIG. 3B , followed by the adapter ring  52  as shown in  FIG. 3C . The adapter ring  52  is sealingly secured to the die plate  56  and housing inlet flange  54  by installing the fastening elements  84  through holes  82  and  100  and into threaded engagement with apertures  83 . The elements  84  may be embodied as socket head cap screw bolts having head  86  which fit flush with the outer face  78  of the adapter ring  52  as illustrated in  FIG. 3D . The water box main body  50  is then slid onto the studs  74  with the inlet pipe  58  and outlet pipe  60  in a generally vertical orientation, as shown in  FIG. 3E , and nuts  76  are used to tighten the water box main body  50  against the inline adapter ring  52  to complete the installation of the water box assembly as shown in  FIG. 3F . 
   As shown in the embodiment illustrated in  FIGS. 2–4 , the water box main body  50  is connected to the adapter ring, die plate  56  and extruder housing flange  54  by only four fastening elements  74 . In the case of polymer wrap up during the pelletization process, or other reason to access the cutter hub or cutting chamber, only the four fastening elements  74  need to be removed to release the water box. When the water box is pulled from the die plate, the cutter hub and cutting chamber are fully exposed, allowing for faster and easier clean up. At the same time, the inline adapter ring  52  remains tightly and sealingly fastened to the die plate and extruder inlet housing, keeping them sealed. The inline adapter ring also keeps the die insulation ring sealed during water box removal, extending the life of the insulation ring. 
   Further advantages of the two-piece water box assembly include reduced pressure requirements which allow for less expensive construction. Particularly, the inline adapter ring seals against the polymer pressure, such that the water box need only seal against water pressure from the cutting chamber. 
   The water box assembly is preferably intended for use on larger sized pelletizers such as the Model 12, G2 and Model 7, as manufactured by the assignee of the present invention. 
   The foregoing is considered as illustrative only of the principles of the invention. Numerous modifications and changes will readily occur to those skilled in the art. For example, a two-piece water box with a single inline adapter ring, and a water box main body, as disclosed herein, is preferred. However, other multipiece assemblies could be designed to allow easier access to the cutter hub and cutting chamber for clean up and the like. 
   In another embodiment, the adapter ring  52  and flange  64  could have enlarged outer diameters. In such a construction, the fastening elements  74  might be much shorter and extend only through ring  52  and flange  64 , axially outwardly from fasteners  84 , rather than extend all the way into extruder inlet housing flange  54 . Accordingly, the foregoing preferred embodiment is not intended to limit the invention to the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.