Abstract:
In the field of helical bladed rotors, and their sealing assemblies an improved upstream seal for mixer rotors is provided. It includes a bushing-like visco sleeve subassembly, a sleeve shaped metallic liner positioned abutting the visco sleeve; a sleeve-like, visco seal having first and second peripheries, an L-shaped packing seat retainer, all configured to provide a single annular shaped inner chamber in which a single, rope-like packing component serves to minimize hardening of the packing assembly by minimizing feed particulate material leaking into the upstream visco seal.

Description:
This is an examinable patent application under Section 111(a) submitted for a formal filing receipt. 
     1. Field of the Invention 
     The present invention lies in the field of helical bladed, rotors and their sealing assemblies on the drive end of the rotors serving as continuous mixers for plastic materials. 
     2. Background of the Invention 
     The present invention relates to the operating problems encountered with sealing arrangements for a rotatable shaft, like a helical rotor. During rotor turning, a sealing pressure is built up and maintained in the molten materials as enclosed within the annular clearances provided between the rotors and the surrounding barrel by means of the helical ridges moving within the mixer. The current practice for a drive end journal, or rotor pilot component, requires a packing gland seal means to effect a compression on the packing component itself, so that its seals against an outer wear sleeve. The currently accepted sealing means is effective for only a relatively short time. This occurs because the particulate feed materials, and in their thermoplastic forms, work their way into the seal assembly itself. This then serves to harden the packing component, eventually to the extent that it appreciably stiffens, and the packing will no longer seat tightly against the wear sleeve. The positive air pressure in the mixer will cause the leaking of particulates to flow through the impaired sealing means, creating mixer site contamination, impacting worker cleanliness, and risking operating safety. 
     Accordingly, it is a principal object of the invention to provide a visco sealing means in which particulate and molten materials do not bleed through the sealing means so as to generate site contamination. 
     It is another object to maintain the required sealing pressure at desired speeds of helical rotor rotation. 
     Yet another object of the invention is to eliminate any air pressure leakage from the mixing cylinder upon startup until the working area is loaded with molten material and/or particularly feed. 
     A still further object of the invention is to reduce seal area wear and packing seals degeneration so as to extend the operational range for a given sealing means assembly. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is now provided a continuous mixer apparatus adapted for commingling of particulate thermoplastic materials of varying polymeric compositions, and having a mixer barrel, at least one main rotor with a helical profile body section at one end thereof, a driven journal located at the opposite end thereof, a drive end rotor plate, a drive end packing seal retainer, and a packing gland seal means, the improvement in the packing gland seal means which comprises: a bushing-like, visco sleeve assembly having a cylindrical inner surface being provided with an integral continuous, first peripheral annular ridge located proximal to the one longitudinal end of the sleeve assembly, which one end is distal from the helical profile body; a generally sleeve-shaped, metallic liner positioned adjacent the inner periphery ridge of the assembly; a sleeve-like, circular visco seal, being stepped-down intermediate the ends thereof, having first and second cylindrical peripheries, with the lesser diameter, periphery seal being located distal from the helical profile body section and with the larger diameter periphery seal being provided with a visco seal threading, and with the sleeve assembly and circular visco seal defining an annulus-type inner chamber there between; a single, rope-like first packing component positioned about the visco seal periphery and abutting the annular ridge of the sleeve subassembly; and the packing seal retainer being L-shaped and positioned adjacent the sleeve subassembly and also abutting and compressing laterally the first packing component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a conventional compact processor for plastic particulate materials comprising a unitized particulate mixing and extrusion system, wherein particulate plastics are mixed, liquified and the resulting molten materials are pelletized for later molding into useful articles; 
     FIG. 2 is an enlarged, vertical view of the processor of FIG. 1, taken along lines  2 — 2  in FIG. 1, depicting a parallel set of material mixing assembly rotors, positioned within the compact processor of FIG. 1; 
     FIG. 3 is a broken away, enlarged vertical view of the drive and assembly of the mixing components of a processor of FIG. 1, wherein a drive end, prior art, packing gland seal configuration is depicted; 
     FIG. 4 is another broken out, enlarged vertical sectional view of the drive end, packing gland seal means configuration but now of the present invention; 
     FIGS. 5A and 5B are side elevation, and end elevational, views, respectively, of the visco sleeve assembly bushing of the present invention, as employed on the present visco assembly of FIG. 4; 
     FIGS. 6A and 6B are side elevation and end elevation views, respectively, of the sleeve-like, circular sealing component of the present invention for the left hand rotor of FIG. 2; 
     FIGS. 7A and 7B are side elevation, and end elevation, views, respectively, of the packing seal of the present invention; 
     FIG. 8 is an exploded perspective view, illustrating the several components, both standard and novel, which comprises the improved drive end, visco seal assembly of the present invention; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 1, there is shown a compact processor  20  for plastic materials and comprising a unitized mixing and extrusion system that allows a user to customize mixing and extrusion of plastic materials being processed. This unitized processor system comprises a two-rotor, continuous mixer  22  mounted on an upper level  23  of a framework  24 . Plastic materials, fillers, additives, colorants, and the like, as desired by the user, namely various ingredients desired to be mixed with plastic materials, are introduced into a feed entrance (sometimes called a “feed throat”) of the continuous mixer  22 , as indicated by an arrow  26 . The resulting molten plastic materials flow by gravity down from the continuous mixer  22  like a molten “rope”, descending within a vertical chute  28 , into a hot-feed extruder  30 . The output from the extruder  30  issues through an extruder head  32  adapted to have various types of an extrusion device  33  mounted thereon, as may be desired by the user. 
     For driving the two rotors in the mixer  22 , there is shown a suitable drive system  34 , for example, such as a d.c. drive motor  35  arranged with suitable feedback speed and torque controls, as known in the art, for turning the mixer rotors preferably at predetermined constant speed. This motor  35  is coupled to a suitable speed-reducer  36 , for example such as an all helical gear, speed-reducer with two output shafts coupled to two three-piece rotors for rotating the two rotors in opposite directions about their respective longitudinal axes. In this illustrative example, the two rotors are turned in opposite directions at the even/or ratio rates. 
     The mixer  22  includes a drive end frame  38  (also called a “drive bearing housing assembly”) for rotatably supporting a drive end journal (not seen in FIG.  1 ). This drive end frame  38  and its journal will be described in detail later. The mixer includes a driven end frame  39  “which may be called the “water end frame” and also may be called “driven bearing housing assembly”) for rotatably supporting a driven end journal (not seen in FIG.  1 ). The driven end, frame  39 , and its journal, also will be described in detail later. Mounted between drive and driven end frames  38 ,  39  is a mixer chamber barrel, or housing  40 , including an upper half  41  and a lower half  42 . 
     For driving an extruder feed screw  44  (FIG. 1) in the hot-fed extruder  30 , there is shown an electric motor  46  mounted on a base  48  of framework  24 . This motor  46  is coupled through a suitable speed-reducer transmission  50  to the extruder screw  44 . 
     Looking to top plan view of FIG. 2, with upper barrel half  41  removed, there is shown a pair of parallel rotors,  60 L/R, both positioned horizontally within housing  40 , and which are denominated left and right hand mixing rotors, respectively. The left-hand, longitudinal ends of the mixing rotors are mounted conventionally in journals at the drive end, frame  38 , while the drive ends each have a packing seal assembly, generally  52 L/R, respectively, to be described, in connection with FIG. 4, et seq. The other longitudinal ends of the paired rotors are mounted in driven ends of the housing frames,  39 L/R (FIG.  1 ). 
     Reference will now be made to FIG. 3 to describe a state of the prior art device regarding drive end, packing seal assemblies, employable in connection with the compact processor for plastic materials, schematically seen in FIGS. 1 &amp; 2. Axially mounted to the drive end  38  of right hand, helical rotor  60 R is the drive end, packing seal assembly, generally  52 R. It comprises: an inner, collar-like. wear sleeve  66 ; an L-shaped, packing seal retainer  68 ; a bushing-like, packing housing  70 ; and an alignment ring  72 , which separates three rope-like, packing components,  74 A,  74 B, and  74 C; the subassembly  78  at the free outer end comprises rotor plate  80 ; and associated bolts and washers,  76 A, B, C which clamp that describes parts in a working relation; the horizontal flanged element  68 F of seal retainer  68  is biased inwardly, via its lock nut  82  against the set of rope packings  74 . These serve to expand same radially against the circular periphery of wear sleeve  66 . 
     Experience has shown that the particulate material, while in process, infiltrates into the just-described sealing arrangement, thereby hardening this packing set, generally  74 A/ 74 B. This progresses to the extent that they will not properly seal against wear sleeve  66 . This time developing defect causes feed particulate to leak about the wearing sleeve  66  periphery. When the leakage contamination levels reach appreciable levels, the mixer must be shut down, and all the just-described packing seal elements are disassembled, so as to permit replacement of the three rope packing rings, the intermediate alignment ring and the wear sleeve. 
     Looking now to the vertical sectional view of FIG. 4, a structurally modified and improved visco sealing assembly of the present invention is depicted. Several of the components are continued modified, such as the rotor plate  80 A, and the seal retainer  68 A, but the alignment ring  72  is now omitted. The sleeve assembly  70 A, the wear sleeve  66 A, and the packing component  88 A themselves, are significantly reconfigured for superior visco sealing. Sleeve assembly  70 A is now provided along its inner circumferential surface with an integral, continuous peripheral ridge  90 , which ridge is located quite proximal to the longitudinal end, of sleeve assembly sidewall  86 S, and is distal from the adjoining right hand, rotor  60 R/L flanged end  89 . A second circular, axially projecting ridge  94  is provided upon the sleeve assembly sidewall  86 S, and is contiguous (conjoined) with the inner peripheral ridge  90  thereof. 
     An annular chamber  96  of squared cross section, is defined by bushing-like, sleeve assembly  70 A; ridge  94 ; ridge  90 , wear sleeve  66 A, and packing seal retainer  68 A. These elements provide the functional recess for a single rope packing component,  88 A. Offset, but linearly aligned with chamber  96 , is the annular chamber  87 A of an elongate rectangular cross section defined by the opposing circumferential periphery of sleeve assembly  70 A and drive end visco seal wear sleeve  66 A. This annulus-shaped recess  87 A accommodates the metal liner  102  of the present invention, which liner demonstrates prolonged effectiveness during mixing and extrusion. The novel heat resistant, liner  102  of the present invention is preferably composed of bronze. 
     The side and end elevational view of FIGS.  5 A/B, depict the dimensions of the somewhat modified bushing-like, sleeve assembly  70 A with sleeve  102  in place; while the side and end elevation views of FIGS.  6 A/B depict the right hand, visco wear sleeve seal  66 A. Note that the inwardly oriented, circular ridge  90  on bushing  70 A provides lateral support to the inward edge of sleeve liner  102 . The sleeve seal  66 A has a peripherally threaded segment ( 66 T) proximal to the one longitudinal end. This latter sleeve component is known in the art as a standard element for visco seals, which was described in expired U.S. Pat. No. 3,963,247, of Jun. 15, 1976 to Nommensen. 
     In the end elevational view and side elevational view of FIGS. 7A and 7B, the circular, ring-like, configuration resilient of packing  88 A is depicted. 
     Looking now to the exploded perspective view of FIG. 8, which depicts all of the operative components aligned pre-assembly, opposing lower edge,  103 , of seal retainer  68 A, has a set screw  104 , which screw serves to retain packing  88 A in abutting relationship with inward oriented, circular ridge  90  of sleeve assembly  70 A with grease fitting  71 A. 
     Two diametrically opposed, squared notches,  106 L/R, are provided in the circular rim  106  of drive end visco sleeve  66 A which extends outwardly of the one longitudinal end. These serve to key the alignment of the sealing component within the drive end subassembly  52 L (right hand rotor shown) of FIG.  2 . 
     Selected spaced-apart sealing elements, to wit, L-shaped seal retainer  68 A, bushing-like sleeve assembly  70 A, dual circumference, visco seal  66 A, and rope packing  88 A, comprise the modified elements of the drive end, improved visco seal means of the present invention.