Abstract:
A rotation molded particulate collection bottle for a copier/duplicator machine, which is connectable to a particulates separation source, which is not prone to failure under vacuums required in the air circulation systems for copier/duplicator machines and which is rotation molded and has a wall thickness of at least about 0.20 inches.

Description:
RELATED U.S. APPLICATION DATA 
     This application claims the benefit of the disclosure and filing date of U.S. Provisional Application No. 60/239,337 filed Oct. 11, 2000. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a rotation molded particulate copier/printer/duplicator machine collection bottle which is not prone to failure under vacuums required in the air circulation systems for copier/printer/duplicator machines. 
     BACKGROUND OF THE INVENTION 
     In copier/printer/duplicator machines, a photoconductor film is commonly circulated past a primary charger, an imaging section, and a toner application section where a toner is applied to the image created in the imaging section. The photoconductor film is then passed into contact with paper or other transfer medium and the toner image is transferred to the paper, which is subsequently passed through a fuser system to fix the toner image to the receiver. In the operation of such machines it is common practice to withdraw the excess toner by a vacuum suction at selected locations in the machine, such as a brush cleaner used to recondition the photoconductor film after transfer of the toner image to the receiver before passing the film back to the primary charger. The air streams withdrawn are typically withdrawn from the machine by suction and passed to a cyclone separator where particulates are separated from the stream and passed to a particulates collection bottle. The gaseous stream is thereafter passed through a filter and to a blower. 
     The suction required is typically up to about 60 inches of water and it has been found that the commonly used blow molded parts of static dissipative extrusion polyethylene are prone to failure. 
     The blow molding process yields parts with high levels of molded-in stress and wide variations in wall thickness. The additives needed to provide static dissipation and flame retardant properties further reduce the mechanical properties of the base polyethylene resin. The result has been collection bottles that have cracked and allowed vacuum leaks while under the 35 to 50 inches of water vacuum load of the printer and copier cleaning systems. Alternative materials have been investigated for use in the blow molding process to produce more reliable bottles but none have been found. 
     Failures of the bottle by cracking or the like permits the reverse flow of the particulates, which may include toner, back upwardly into the cyclone separator and out of the cyclone separator with the gas. The blower prefilter is not designed to handle particulates in this quantity. As a result air contamination in the vicinity of the machine, and in the machine itself, can result. Such failures at a high frequency are unacceptable and a continuing search has been directed to the development of particulates collection bottles for use with copier/printer/duplicator machines, which are more reliable and are less prone to such failure. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a more reliable collection bottle comprises a rotation molded particulates collection bottle for a copier/printer/duplicator machine comprising a rotation molded container having a top and a bottom, a wall thickness of at least about 0.20 inches and a particulates inlet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of an air distribution system for a copier/printer/duplicator machine; 
     FIG. 2 is a schematic front view of a collection bottle; 
     FIG. 3 is a cross-sectional view of a fib as positioned in a side of the mottle of FIG. 2; 
     FIG. 4 is a side view of the bottle shown in FIG. 2; and, 
     FIG. 5 is a top view of the bottle shown in FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the description of the Figures, the same numbers will be used throughout to refer to the same or similar components. 
     Referring now specifically to FIG. 1, an electrographic process cleaning system  110  is presented of the type configured to have a particle collection container  38 . A vacuum is imposed upon the cleaning system  110 , by a vacuum source  118  for example. In the example presented, the vacuum source  118  also drives the flow of cleaning gas throughout the cleaning system  110 . Although not limited to a particular electrographic process, the invention is particularly useful in an electrographic process that implements a photoconductive film loop and dry toner development, also known as electrophotography. While the exemplary electrographic process cleaning system  110  presented in FIG. 1 is configured in a manner suitable for cleaning dry electrographic toner and paper particles in a film loop electrographic process, it is not intended to limit the invention in such manner. The cleaning system  110  is part of an electrographic marking engine  16 , of which only a portion is shown, broken away at line  18 . 
     The cleaning system  110  comprises a particle separator  116  in fluid communication with the particle collection container  38  via a conduit  120 . The vacuum source  118  is in fluid communication with the particle separator  116  via a vacuum supply conduit  134 . The particle separator  116  is also in fluid communication with a manifold  136  which, in turn, is in fluid communication with a film loop cleaning station (not shown) via a first conduit  138 , a transfer roller cleaning station (not shown) via a second conduit  140 , and a toning station dust collector (not shown) via a third conduit  142 . The vacuum draws waste particles from the film loop cleaning station, transfer roller cleaning station, and the toning station dust collector through the conduits  138 ,  140  and  142 , through the manifold  136 , and into the particle separator  116  where the particles are separated from the flow and drop into the particle collection container  38 . The vacuum source  118  draws the cleaned flow out of the particle separator  116  through conduit  134 . The structure of the film loop cleaning station, transfer roller cleaning station, and toning station dust collector are known in the art. Such apparatus is provided in the Digimaster® 9110 brand digital high volume printer manufactured by Heidelberg Digital L.L.C. of Rochester, N.Y. 
     It is desirable that the particle collection container  38 , also referred to herein as a bottle, be a static dissipative vessel. Accordingly, a static dissipative extrusion grade polyethylene plastic resin has been used to produce bottles by blow molding. These bottles have high levels of molded-in stress and wide variations in wall thickness and have been found to be less reliable than desired. The material additives needed to provide the static dissipation and flame retardant properties also reduce some mechanical properties of the base polyethylene resin. The result has been parts that have cracked and allowed vacuum leaks while under the 35 to 50 inches of water vacuum load of the copier/printer/duplicator cleaning systems, especially under repeated cycles of increased and reduced vacuum. A search for alternative materials has been unsuccessful in developing other materials, which are suitable replacements in the blow molding process to produce reliable parts. Blow molding is a well-known process and is described in Engineering Materials Properties and Selection,@ Fifth Edition, Kenneth G. Budinski, 1966, Prentiss Hall, a Simon and Shuster Company, Upper Saddle River, N.J. 07458, pp. 71-71. 
     It has now been found that more reliable bottles can be produced by a rotation molding process. Rotation molding processes are also well known to those skilled in the art and typically comprise the addition of a pre-measured amount of plastic material in liquid or powder form into a cavity in a mold with the mold then being closed. The amount of material required is determined by the wall thickness desired. 
     The molding machine then moves the mold into an oven where the mold and subsequently the plastic is brought up to the molding temperature. As the mold is heated, it is rotated continuously about its vertical and horizontal axes. A reverse rotation can also be used to fill small intricacies and hidden areas of the mold. This bi-axial rotation brings all the surfaces of the mold into contact with the puddle of plastic material. The mold continues to rotate within the oven until all the plastic material has been picked up by the hot inside surfaces of the cavity. The mold continues to rotate until the plastic material densifies into a uniform layer of melt. 
     While continuing to rotate, the mold is cooled. Air or a mixture of air and water cools the mold and the layer of molten plastic material. This cooling process continues until the plastic part has cooled sufficiently to retain its shape. The mold is then moved to an unloading station where the mold is opened and the part removed. 
     Such processes are well known to those skilled in the art and will not be discussed further. 
     By such processes, parts of greater wall thickness and having greatly reduced molded-in stress levels are possible. Parts produced by this process for use as the collection bottle are desirably at least 0.20 inches in thickness. The rotation-molded parts are also much more uniform in their thickness than the blow molded parts. Further as a result of the process steps, an embedded or molded-in metal insert can be placed in a wall of the rotation molded collection bottles. With the blow molded bottles it was necessary to attach an electrical conductor by the use of a screw and washer to the exterior surface of the collection bottle. 
     It was also found that increasing the thickness of the blow molded parts created unacceptable processing difficulties. It has now been surprisingly found that by rotation molding, parts of a suitable thickness can be produced which are much more reliable. The rotation-molded parts are of a greater thickness than the blow molded parts since the strength of the rotation-molded plastics is less than that of the blow-molded plastics. Since the side-wall thickness can be increased, is more uniform and has a lower internal stress level, it has been found that desirable results can be achieved with rotation-molded bottles. Rotation molded bottles have been successfully tested through cycles of at least 30,000 cycles at repetitive vacuum loads from 0 to 80 inches of water. Desirably the wall thickness is at least 0.20 inches and preferably is greater than 0.210 inches. The rotation molding process allows the ability to increase the wall thickness to handle the vacuum loads. 
     A suitable plastic for the production of the rotation-molded parts is a copolymer polyethylene resin marketed by ROTEC under the trademark ICORENE C517. This resin has a permanent semi-conductivity, low warping and good processing characteristics and a high level of ultraviolet stabilizer. Its permanent anti-static electrical conductivity is over 1,000,000 times more electrically conductive than standard natural rotomolding resin, and it is provided as a black mesh powder (500 microns). The resin typically has the following physical properties: 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 PHYSICAL PROPERTIES 
               
             
          
           
               
                 PROPERTY 
                 TEST METHOD 
                 UNIT 
                 VALUE 
               
               
                   
               
             
          
           
               
                 Melt Index (190_C., 
                 ISO 1133 
                 g/10 min. 
                 6.0 
               
               
                 2.16 kg) 
               
               
                 Density 
                 ISO 1183 
                 g/cm 3   
                 0.934 
               
               
                 Tensile Strength (Yield) 
                   
                 MPa 
                 16 
               
               
                 Tensile Strength (Break) 
                   
                 MPa 
               
               
                 Elongation 
                 ISO R 527 
                 MPa 
               
               
                 Flexural Modulus 
                 ASTM D790 
                 MPa 
                 550 
               
               
                 Hardness 
                 ISO R868 
                 Shore D 
                 55 
               
               
                 Izod Impact Strength 
               
               
                 Instrumented Impact 
                 ISO 6603-2 
                 J/mm 
                 (100% ductile) 
               
               
                 Strength 
                   
                   
                 20 20 18 
               
               
                 −20 C. 0 C. +20 C. 
               
               
                 Vicat Softening Point 
                 ISO 306 A120 
                 _C. 
               
               
                 ESCR (2)   
                 ASTM D1693 
                 Hrs 
               
               
                 Meets FDA 
               
               
                 Requirements 
               
               
                 UV-Stabilized 
                   
                   
                 Yes 
               
               
                   
               
             
          
         
       
     
     The bottles of the present invention also include a metal insert adapted to provide a plastic-metal contact. It is convenient to mold a metal insert into rotation molded collection bottles whereas it is not convenient in the blow molding process. 
     In FIG. 2, a side view of a representative collection bottle is shown. A collection bottle  38  is shown having a top  74  and a bottom  76 . The bottle is of irregular shape to fit a desired application. The bottle includes an inlet  78  having a top  80 . The top is adapted to include a threaded fitting, a shoulder or other types of fittings or the like as required to sealingly couple it to an outlet from a particulates source. Typically ribs  82  are positioned on the wide surfaces of bottle  38  to reduce the tendency of the sides to collapse under the vacuum. As shown, a shoulder  84  is positioned above a lower section  85  of bottle  38  to form a reduced cross-sectional upper section  86 . 
     In FIG. 3, a section of bottle  38  showing a rib  82  is shown. Rib  82  is formed by an arcuate section  90  positioned in a wall  92  of bottle  38 . The rib is shown having an arcuate cross-section  90  but this rib could be any irregularity such as a triangular section, square section, or the like so long as it constitutes an irregularity in the surface of wall  92  sufficient to reduce the flexibility of wall  92 . 
     The corners of bottle  38  are all rounded at rounds  94  so that no squared surfaces are included. 
     In FIG. 4, an end view of bottle  38  is shown. No ribs are shown in this view for simplicity. 
     In FIG. 5, a top view of the bottle of FIG. 2 is shown. In this view, a metal insert  96  is shown positioned on top  74  of bottle  38 . This metal insert is shown with a threaded opening  98  to receive a threaded connector to electrically discharge static currents from bottle  38 . 
     It will be appreciated that bottle  38  can be of substantially any shape, including round, and that the shape shown is representative as designed for a particular application requiring a collection bottle of this shape. The shape of the bottle will vary routinely depending upon the space available for the collection bottle and the like. Such variations are well known to those skilled in the art. By the use of rotation molding to form the bottle, the formed bottle includes less internal stress and has a greater wall thickness and wall uniformity and as produced is much more reliable. 
     As indicated previously it is difficult to produce bottles having a greater wall thickness by blow molding and the blow molded bottles are much more susceptible to flexural failure upon repeated application of the vacuum. 
     Having thus described the invention by reference to certain of its preferred embodiments, it is noted the embodiments described are illustrative rather than limiting in nature and that many variations and modifications are possible within the scope of the present invention.