Abstract:
A jet type coater with a nozzle orifice is provided with an adjustable, internal filter or screen in the head of the coater. The filter has orifices or slots which are formed by relatively movable members and is adjustable to a size smaller than that of the nozzle orifice, to keep the nozzle orifice unclogged and functioning. The internal filter is also easily clearable on the run without shutdown and cleanable with coating liquid and/or water.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an internal filter for a fountain type, jet type or other type coater which ejects coating through an orifice or slot and a method of use. More particularly, the invention relates to an adjustable or clearable filter and its method of use, the adjustable filter being clearable, on the run, and cleanable, as necessary, to ensure unrestricted performance of the coater.  
           [0002]    Also, filtering of the coating, in a manner adjustable to be set at a filter orifice or slot sizing smaller than that of the coater nozzle orifice to ensure not clogging (partial or total blockage) of the coater nozzle orifice is provided, as is an adjustable or clearable filtering method.  
         PRIOR ART  
         [0003]    Fountain type and jet type coaters are known. Also, filtering of an extrusion type coating, such as a magnetic solution for forming a magnetic recording tape or the like, is known. It is also known to place a filter externally of, but closely adjacent to and upstream of, the coater. It is also known to place a fixed type screen within a coater. All these filters and screens have had the disadvantage of becoming plugged and requiring cleaning or replacement, often necessitating shutting down of the processing line, be it a coater line or a paper making line with coaters thereon. Even where these prior art filters could be replaced on the run, the usually presented additional flow paths are still capable of generating/causing additional coater clots or agglomerations.  
         BRIEF SUMMARY OF THE PRESENT INVENTION  
         [0004]    According to the present invention there is provided a method or process for operating a jet coater or other type coater for coating a paper web which applies a flow or a jet coating liquid through an orifice or nozzle onto a moving surface to coat a web of paper, comprising the steps of admitting the coating into a coating head of the jet or other type coater under pressure, passing the coating through an internal filter or screen within the coater, filtering the coating with the internal filter, and forcing the filtered coating out in a jet through a nozzle orifice onto a moving surface for coating paper. The coater nozzle or orifice is of the type that, if unfiltered coating is applied, it is subject, generally due to its small (narrow) size, to occasional plugging or clogging, at least partially, somewhere along its length (cross machine direction).  
           [0005]    Still further according to the present invention there is provided a jet or other type coater which applies a jet or flow of coating liquid onto a moving surface be it initially a roll surface or the paper web directly to coat the paper web, comprising a coater head, the coater head having an entrance for the admission of coating liquid under pressure and a nozzle or restricting orifice therein for application of coating onto the moving surface, a screen or filter within said coater head located between said entrance and said nozzle orifice for filtering the coating liquid after passing through said entrance and before reaching the nozzle orifice, whereby coating agglomerates or clots which may be contained in the coating liquid are filtered out by the filter before reaching the coating nozzle orifice and preventing nozzle orifice blockage, the screen or filter being clearable, on the run, and cleanable, as necessary. The filter or screen comprises relatively movable portions, defining the screen or filter openings and may be cleared by moving the portions relative to one another. For convenience, this relative motion may be caused by means outside the coater itself The screen size opening can also be adjusted to accommodate different size nozzle openings by moving the defining portions relative to one another. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a cross sectional view through, in this instance, a jet type applicator or coater showing the clearable, adjustable filter or screen of the present invention positioned within of the head of the jet coater, upstream of a nozzle orifice thereof  
         [0007]    [0007]FIG. 2 is a cross sectional view through the filter portion of the coater taken along line  2 - 2  of FIG. 1 showing the filter slots in nearly a closed position.  
         [0008]    [0008]FIG. 2A is a partial cross sectional view of a portion of the filter but showing the slots in a full open position taken on  2 A- 2 A at FIG. 3.  
         [0009]    [0009]FIG. 2B is a partial view similar to FIG. 2A but showing slots  26 C and D formed at an angle in the plate  32 C and wall  28 C.  
         [0010]    [0010]FIG. 3 is a cross sectional view through the filter taken along line  3 - 3  of FIG. 1.  
         [0011]    [0011]FIG. 3A is a partial cross sectional view similar to FIG. 3 of a portion of the filter but showing the slots in a full open position.  
         [0012]    [0012]FIG. 4 is a cross sectional view through the head of the jet coater showing an alternative position for the adjustable filter or screen in a metering chamber of the head of the jet coater, upstream of the nozzle orifice thereof.  
         [0013]    [0013]FIG. 5 is a schematic elevational view of another web coating apparatus showing the present invention in jet coater for coating but one side of a web, and the related structures of the coating apparatus.  
         [0014]    [0014]FIG. 6 is a schematic elevational view of yet another web coating apparatus, known as a film press, for coating both sides of a downrunning web.  
         [0015]    [0015]FIG. 7 is a schematic elevational view of a further web coating apparatus with a down running web coating but one side thereof.  
         [0016]    [0016]FIG. 8 is a schematic elevational view of another film press for coating both sides of a up running web. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]    Referring now to the drawings in greater detail, there is illustrated therein a coater  12  having a screen or filter therein, in this instance, an adjustable or clearable filter  10  of the present invention internal of the jet type coater  12 .  
         [0018]    As shown in FIGS. 1 and 4, the filter  10  is positioned internally within a head  14  of the jet coater  12 , at a suitable position between an entrance  16  (shown in dotted lines) on one end into the support beam  15  for the head  14  through which coating is received under high pressure and a coating application exit  18  which is typically referred to as a jet nozzle orifice  18  within a nozzle portion  20  of the head  14 . A flush out exit  22  (shown in solid line) is on the opposite end of entrance  16  for flushing the reservoir or distribution header  23  formed within the beam  15 .  
         [0019]    The adjustable or clearable filter  10  can, for example, as shown, be incorporated into a flushable distribution header  23  of the head  14 , or can be alternatively elsewhere positioned, such as within a metering channel  24  of the head  14 , downstream of the distribution header  23  for clearability, on the run, and cleanability, as necessary.  
         [0020]    The first embodiment of filter  10 , illustrated in FIGS. 1 through 3A in detail, is incorporated with and forms a part of the distribution header  23 . Here, a plurality of slots  26 A and B are machined through a wall area  28  of the distribution header  23  adjacent the metering channel  24 . Over this slotted wall area  28  is movably positioned a slotted plate  32  which coacts with the slotted wall area  28 , creating the adjustable filtering or screen openings of the filter  10 .  
         [0021]    In a preferred embodiment, it is believed that machining of the slots  26 A and B of the filter  10  is best accomplished when the plate  32  is engaged over the distribution header wall area  28 , with the slots  26 A and B being machined through both structures, i.e., the plate  32  and the wall area  28 , simultaneously, to assure accuracy and precision of alignment of the slots  26 A and B thereof.  
         [0022]    The moveable plate  32  may be held or engaged to the distribution header wall area  28  using any suitable engagement means  34 , such as, for example, through use of clamping strips or retaining bars  36 , secured to the wall area  28  by cap screws  38  or the like. The retaining bars  36  can be full length or be segmented and spaced uniformly across the width of the distribution header. Of course as mentioned above, other retaining means could also be used.  
         [0023]    A primary reason for placing the filter  10  at an entrance  36  into the metering channel  24 , is to position the filter  10  as close as possible to the nozzle orifice  18 . In this position, it is believed that more agglomerates in the coating may be screened out or filtered than is possible with filters in a more remote upstream position. A second reason is to provide a filter  10  which can be cleared, on the run, and cleaned, as necessary, to remove any coating agglomerates trapped therein by as simple a manner as possible.  
         [0024]    In this respect, the distribution header  23 , in the form of a reservoir or chamber is flushable, with high pressure flushing or washing cleaning the filter  10  from the inside out, such washing being accomplished on the run. It is to be understood that supply of extra coating from opening  16  to opening  22  will flush the filter. Alternatively, the filter  10  can also be cleaned from the outside in, by removing or opening an exterior nozzle wall  40 , allowing access to the filter  10  to hose it off with say water. For example, this wall may be pivotally mounted on the beam  15  to be operable.  
         [0025]    It will be understood by those skilled in the art that such clearing on the run with coating liquid may produce sections of defectively coated paper which may be marked and slabbed off during further processing or pulping if necessary.  
         [0026]    Turning now to the more detailed views of the filter  10  provided in FIGS. 2 and 3, it will be understood that the moveable plate  32  slides along an elongate axis thereof extending across the web  100  (FIG. 1) in a cross machine direction such that the material of the plate  32  between the slots  26 A therein can be made to overlie a desired area of the cooperating slots  26 B in the wall area  28  of the distribution header  23 , allowing for adjustability of the size of the opening formed by the cooperating slots  26 A and B, the wall area  28  and the plate  32 . In FIGS. 2 and 3, these slots  26 A and B are aligned to be nearly closed, and in FIGS. 2A and 3A these slots  26 A and B are fully opened.  
         [0027]    Thus, the degree of relative movement between the plate  32  and the slotted wall area  28  determines the size of opening formed and of the particles which are allowed or not allowed to pass therethrough. It should be understood that any size opening between fully opened and fully closed could be achieved. As shown in FIG. 2B, to minimize any peaking at slots, and valleys between slots, the slots  26 C and  32 C and slot  26 D formed in wall area  28 C could be formed at an angle say of anywhere from 45° to 10°.  
         [0028]    It is preferred to select the size of the slots  26 A and B to a size slightly smaller than the maximum width dimension of the nozzle orifice  18  likely to be run, the size of which may also be made adjustable in some coater heads. While running then if needed, the actual overlap of slots  26 A and B can be selected to be slightly smaller than the dimension of the nozzle actually being run. This assumes that the nozzle width can actually be adjusted. Should the nozzle orifice width be fixed then possible the slot size for  26 A and B could be selected to be of a smaller width.  
         [0029]    With a smaller size to the filter slot  26 A and B, any coating agglomerates would effectively be collected by the filter  10 , rather than being allowed to reach and then plugging the nozzle orifice  18 , as it is known that a plugged or partially plugged nozzle orifice  18  causes skip coat on a paper web  106  (see FIG. 5).  
         [0030]    In a preferred embodiment, the clearance between the moveable plate  32  and the retaining bar(s)  36  is preferably 0.010-0.015 inch, as the nozzle orifice  18  is typically open more than 0.030 inch.  
         [0031]    With respect to the filter slots  26 A and B, these slots may be in a size range of approximately 0.500×1.500 inches, with the entrance and exits to the slots  26 A and B being chamfered, as best illustrated by the numerals  33  and  35  in FIG. 3, to enhance the flow of coating medium therethrough and to minimize pressure losses.  
         [0032]    In a preferred embodiment, the slots  26 A and B are spaced apart approximately 1.000 inch, center to center, with a length of the filter slots  26 A and B being approximately 1.25 to 2.0 times the length of the nozzle  20 , though this should not be construed as limiting. The percentage of filter slot width to orifice slot width is in the range of 83% to 98%. For example, an orifice slot width range of 0.030 inches to 0.058 inches results in a filter, slot range of 0.025 inches to 0.051 inches respectively.  
         [0033]    In FIGS. 2 and 3, an end wall  44  of the head  14  is shown and a rod  46  is shown extending through this end wall  44 , the rod  46  being formed integral with or connected to the moveable plate  32 . This rod  46  can be engaged to any suitable moving means (not shown), such an hydraulic cylinder, motorized screwjack, or other suitable device in a manner to cause the moveable plate  32  to move along its elongate axis until a desired filter slot  26  size is achieved. Stop means  48 , such as lock or jamb nuts  48 , are used to control the available degree of plate movement by coaction with a bracket  50 , defined below. It is preferred to set the overlap of slots  26 A and B to a size 0.001-0.005 inch width smaller than the size of the width of the nozzle orifice  18  while filtering is being accomplished, with the slots  26  being set to a fully open position (FIGS. 2A and 3A) for cleaning and flushing or clearing.  
         [0034]    A bracket  50  is proposed for use in limiting the motion of the moveable plate  32 , the bracket  50  being engaged to the end wall  44  by exemplary cap screws  52  in the illustrations. It should be understood, however, that any other suitable means such as positioning bolts or screws or the like could be utilized to limit plate  32  movement, so the exemplary embodiment shown should not be construed as limiting.  
         [0035]    It will also be understood that a seal  54 , such as a compression packing ring  55 , may be used to seal a space  56  between the rod  46  and the end wall  44  through which the rod  46  passes against possible coating leakage therethrough.  
         [0036]    Also, in FIG. 2, the slots  26 A and B are best shown in the barely open position thereof, whereas in FIGS. 2A and 3A, a fully open position of the slots  26 A and B is illustrated. It should be understood that the filtering position could be anywhere in between but closer to that shown in FIG. 3A and in FIG. 2. If desired, an automated control system can be provided to control the movement of the rod  46  and/or the slot  26  size.  
         [0037]    Turning now to FIG. 4, the further embodiment positioning the filter  10 ′ in the metering channel  24 , is illustrated. As noted, parts similar to those shown in FIGS.  1 - 3 , and FIG. 4 are primed, that is  10  is shown as  10 ′. When the filter  10 ′ is positioned thusly, the entire filter can be cleaned by hosing off the filter  10 ′ after opening the exterior nozzle wall  40 ′. Again, the header beam  15 ′ forms on its interior a reservoir  23 ′ which has a plurality of openings  25 ′ extending across the width of the coater  12 ′ which permit flow of coating out of the header.  
         [0038]    In this second embodiment, a first plate  58  serves as a stationary member while a second, movable plate  60  serves as a moveable member, with action and functionality similar to that of the filter  10  of FIGS.  1  to  3 A.  
         [0039]    In this second embodiment, support bars  62  extending upwardly from a bottom wall  64  of the metering channel  24 ′, support the filter  10 ′ within the metering channel  24 ′ with cap screws  66  illustrated as the securement means  66  of choice, although bolts or other screws or other structure could be used as well. These support bars  62  can be continuous in form along the width of the head  14 ′, but may be intermittently relieved across the width of the head  14 ′ to provide a reduction in friction between the filter plates  58  and  60 , easing the setting thereof to form a slot  26 A′ and B′ of desired size. The support bars  62  have spaced openings  67  to allow for draining the metering channel when the nozzle wall  40 ′ is opened for cleaning and a seal  69  to close the area when operating.  
         [0040]    It is seen here also, that the metering channel  24 ′ decreases in width toward the nozzle orifice  18 ′, with the filter  10 ′ being positioned upstream thereof, in a wider area  70  of the metering channel  24 ′.  
         [0041]    Also, as a method of clearing any obstruction at the nozzle orifice  18  or  18 ′, either filter  10  or  10 ′ may be closed off completely for a very short interval and then fully opened, to provide a pressure pulse to the nozzle orifice  18  or  18 ′ to dislodge any agglomerate matter producing an obstruction thereof.  
         [0042]    By way of environment for the coater  12  and the filter  10  and method disclosed herein, FIGS.  5  to  8  are presented. In FIG. 5, a web  106  is supported and transported by a roll surface  100  of a roll  102 . This Figure shows that the jet coater  12  is used to apply or jet the just filtered coating onto the web  106 , which film of coating is then doctored by doctor means  108  from the paper web  106  to the desired coat weight. It should be understood that the doctor means may be either a blade or a roll.  
         [0043]    [0043]FIG. 6 is also presented. It shows two jet coaters  12 ′ that are used to spray a jet or curtain of the just filtered coating onto surfaces of rolls  102 ′ and  103 ′ to form a film, which film is doctored to the desired thickness by doctors  108 ′. This film of desired thickness on each of rolls  102 ′ and  103 ′ is transferred to web  106 ′ as it passes through the nip between rolls  104 ′ and  105 ′. The web continues on for further processing, such as drying and eventually forms a paper roll. Again, the doctoring could be by blade, smooth or grooved rod.  
         [0044]    Again, FIG. 7 shows the present invention incorporated into the coater  112  having a jet applicator  118  and a doctoring unit (shown here with a doctor roll  120 ). It being understood that a blade could also be substituted, which coats one side of the web  122  running in a downward direction between two rolls  124  and  126 . The coater  112  incorporates a filter structure and method of the present invention.  
         [0045]    [0045]FIG. 8 shows two coaters  130  and  132  having filters of the present invention with doctors  134  and  136  (in these instances rolls) used to coat both sides of an up running web  140  running between the nip of two rolls  142  and  144 .  
         [0046]    As noted herein, roll rotation and web travel direction are indicated by arrows or arrowheads shown in the respective rolls and webs.  
         [0047]    As described above, the coater and adjustable and/or internal filter therein and method disclosed herein provide a number of advantages, some of which are inherent in the invention and others of which are set forth above. Also, modifications may be proposed without departing from the teachings herein. Accordingly, the scope of the invention is only to be limited as necessitated by the accompanying claims. It should be understood that these claims cover the structure and steps disclosed therein and equivalent structure and steps.