Abstract:
The present invention includes a device and a method of applying a coating to a web. The preferred device comprises a feed nozzle coupled to a stiffener coupled to a spring coupled to a position/force adjuster. The feed nozzle comprises a fluid reservoir, a feed pipe, a metering surface, end seals and a back seal. The stiffener spring, as the frame deflects and polymer covered rolls deform, permits the rotation of the feed nozzle so a proper geometry is maintained, permitting increased control and a wider film thickness control range for a specific nozzle shape. This device permits greater film thickness control, ability to process at much higher speeds than currently achievable, and a wider range of film thickness. This device permits coatings to be applied at much wider ranges of rheological characteristics. Coatings can be applied at higher percent solids with improved characteristics. Multiple feed nozzles provide rapid product changeover for greater equipment utilization and higher productivity.

Description:
STATEMENT OF RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. application Ser. No. 678,228, filed Oct. 2, 2000, now U.S. Pat. No. 6,656,529, issued Dec. 2, 2003, which is a continuation of U.S. Appl. No. PCT/US99/10819 designating the United States, filed May 18, 1999, and from U.S. Provisional application 60/086,047, filed May 19, 1998, which are hereby incorporated by reference. 
     
    
     
       BACKGROUND  
         [0002]    The present invention relates to systems for applying coatings under pressure to a web of material. A variety of coatings may be used, such as, but not restricted to, solvent- or water-based coatings, and the web may be made of a variety of materials, such as, but not restricted to, steel, aluminum, textiles, paper or film. U.S. Pat. No. 5,743,964 “Pankake” is an example of prior art roll coating.  
           [0003]    The primary known technology for application of film in the range of 1 milligram per square inch to 30+milligrams per square inch of fluid on a substrate at speeds greater than 250 feet per minute involves a process known as roll coating. This involves picking up a fluid out of an open pan with a pick-up roll or feeding the fluid by gravity into a top nip. (A nip is the pinch point between rollers.) The fluid is then transferred from that roll to the next or is transmitted through a nip to the next roll. Eventually, the fluid is transferred from a roll to the web.  
           [0004]    Another approach commonly used for applying fluid to a substrate involves the use of a die or slot. This process is normally limited to speeds up to approximately 200 feet per minute. The fluid may be deposited onto a roll for transfer to the substrate or directly onto the substrate with this method.  
           [0005]    Coating being picked up out of a pan, sprayed, or nip fed is exposed to ambient conditions and the atmosphere. This permits dry out or skinning-over and evaporation of volatiles that contribute to product variability and environmental pollution, foaming, and splashing. Numerous other defects are also associated with unstable or uncontrolled fluid dynamics that occur at the entry point of the roll into the fluid contained in the pan, the exit point of the roll out of the fluid in the pan, or at the nip point. Some of these defects are often labeled as skips, seashore, ribbing, blisters, voids, shinnies, or splotching. The fluid picked up out of a pan is susceptible to being slung from the roll ends, creating a safety hazard, product defects, and a mess.  
           [0006]    The appearance and thickness of the applied fluid is governed by a very complex relationship between the equipment configuration, equipment settings, and the fluid characteristics. Some of these variables include the number of rolls, direction of rotation of the rolls, roll material, roll finish, roll diameter, roll hardness, roll geometry, nip pressures, fluid viscosity, and fluid rheology. The relationships of all of these variables in the roll coatings process today provide a relatively small window for successful application of a specific fluid at a specific thickness. Fluids are very often applied at viscosities of 10 to 500 centistokes, depending on the desired applied film thickness. This requires the addition of large volumes of solvents or carrier fluid in many cases. The evaporation of these large volumes of solvents into the atmosphere is very undesirable from an environmental standpoint. Also, since the solvents evaporate from the open pan during the process, the characteristics of the coating are constantly changing during the process, making it very difficult to control the process.  
           [0007]    The set-up of the above process must also be done in a way to achieve the desired film thickness while minimizing an appearance defect known as ribbing in the roll coating process. Typically, fluids are reduced in viscosity, and long flow-out zones are provided. These flow-out zones permit the ribs to be leveled out.  
           [0008]    The use of open pans also creates major limitations to rapid, repeatable product changes. Typically, a product change for a pan feed system requires to between 10 minutes and several hours. To achieve product changes in less than 30 minutes usually requires additional investments of millions of dollars in capital equipment and labor intensive activities on major web processing lines.  
           [0009]    As will be seen from the subsequent description of the preferred embodiments of the present invention, these and other limitations and shortcomings of the prior art are overcome by the present invention.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention includes a device for and a method of-applying a coating to a material web such as, but not restricted to, a sheet of steel, aluminum, textile, paper, or film. An elongated feed nozzle is used to feed coating material under pressure. The pressure may be supplied by gravity or by a low pressure pump. The feed nozzle seals-up against either the web or a roll. The feed nozzle includes a fluid reservoir, a metering surface, end seals (end closures) and a back seal. The fluid reservoir, in conjunction with the end seals and the back seal, forms a cavity which contains the fluid as it is being fed through the feed nozzle. This avoids all the problems of having the coating in open trays. The present invention further provides a mechanism for rotating one nozzle out of the operating position and another nozzle into operating position, permitting a very quick change of coatings. With this arrangement, the nozzle that is off-line can be cleaned and prepared while the on-line nozzle is operating. The present invention also provides a support spring, which supports the nozzle and provides automatic position adjustment of the nozzle in response to the amount of force being exerted by the nozzle. The preferred embodiment also provides a nozzle contact angle adjustment mechanism, a mechanism to adjust the profile of the metering surface, a feed nozzle force sensor, a feed nozzle cleaning assembly, and an applicator roll cleaning assembly. A stiffener is used to make the metering surface rigid. The stiffener can be integral with the feed nozzle, or a separate stiffener can be attached to the feed nozzle. A preferred embodiment permits feed nozzle force control and contact surface angle control to be operated independently of one another, which cannot be achieved with die or slot coating. These technologies require precise control of clearances. The support spring, as the frame deflects and polymer covered rolls deform, permits the rotation of the feed nozzle to maintain a proper geometry, permitting increased control and a wider film thickness control range for a specific nozzle shape. The additional dynamic actuators of nozzle force and metering surface add new quality, speed and film thickness capability to web coating. Dynamic feed nozzle force control can be accomplished independent of reservoir cavity pressure and metering surface contact angle.  
           [0011]    The feed nozzle and support frame can include a profile adjustment device to control the bending or profile across the feed nozzle bar, permitting variable coating thickness profiles or correcting variable thickness profiles across the web with this feed system. While the profile control of the housing or support is manual in the prototype described herein, the control can be done via hydraulic cylinders, stepper motors, pneumatic cylinders, manual linkages, etc. The profile control is not limited to the aforementioned but may be done in any manner that will permit controlled and repeatable flexing of the member.  
           [0012]    Control of pressurized coating and coating build-up at ends of the feed bar is accomplished by means of an end seal in the feed nozzle bar. The end seal may have several different configurations.  
           [0013]    The back seal may be made of any flexible blade compatible with the coating being applied that will seal and remain sealed against the surface being coated without causing damage. Examples of suitable materials include, but are not restricted to aluminum, steel, and plastic. 
       
    
    
     DESCRIPTION OF THE DRAWING  
       [0014]    [0014]FIG. 1 is a rear perspective view of one example of a coating machine made in accordance with the present invention;  
         [0015]    [0015]FIG. 2 is a broken-away side view of the machine of FIG. 1;  
         [0016]    [0016]FIG. 3 is a schematic side view showing the web to be coated travelling through the machine of FIG. 1;  
         [0017]    [0017]FIG. 4 is a broken-away front perspective view of the feed nozzle and its related support mechanism of the machine of FIG. 1;  
         [0018]    [0018]FIG. 5 is a perspective view of the feed nozzle of FIG. 4;  
         [0019]    [0019]FIG. 6 is a perspective view of the base of the feed nozzle support mechanism of FIG. 4;  
         [0020]    [0020]FIG. 7 is the same view as FIG. 6, but with the feed nozzle moved forward;  
         [0021]    [0021]FIG. 8 is a broken-away sectional view of the base of FIG. 7;  
         [0022]    [0022]FIG. 9 is a side sectional view taken through the feed nozzle of FIG. 1;  
         [0023]    [0023]FIG. 9A is a side view showing the feed nozzle of FIG. 9;  
         [0024]    [0024]FIG. 9B is the same view as. FIG. 9, but with the profile of the feed nozzle having been adjusted;  
         [0025]    [0025]FIG. 9C is a broken-away top view of the connection between the feed nozzle and stiffener of FIG. 9B;  
         [0026]    [0026]FIG. 10 is a view taken along the line  10 - 10  of FIG. 5;  
         [0027]    [0027]FIG. 10A is a broken-away perspective view, similar to that of FIG. 10, but showing an alternate flexible, labyrinth type end seal;  
         [0028]    [0028]FIG. 10B is an end view of the embodiment of FIG. 10A;  
         [0029]    [0029]FIG. 10C is a front view taken along line  10 C- 10 C of the embodiment of FIG. 10A;  
         [0030]    [0030]FIG. 11 is a broken-away perspective view of the feed nozzle, stiffener member, and feed pipes of FIG. 1;  
         [0031]    [0031]FIG. 12 is a broken-away view taken along the line  12 - 12  of FIG. 5;  
         [0032]    [0032]FIG. 13 is a schematic side view showing the nozzle, roll, and nozzle cleaner of FIG. 1;  
         [0033]    [0033]FIG. 14 is a broken-away section view showing one end of the mounting block, stiffener, and feed nozzle of FIG. 1;  
         [0034]    [0034]FIG. 15 is a view taken along the line  15 - 15  of FIG. 1;  
         [0035]    [0035]FIG. 16 is a schematic side view of a roll cleaning mechanism made in accordance with the present invention;  
         [0036]    [0036]FIG. 17 is a schematic side view of an alternative embodiment of a manner in which a web of material could be coated by the machine of FIG. 1;  
         [0037]    [0037]FIG. 18 is a schematic side view of a second alternative embodiment of a manner in which a web of material could be coated by the machine of FIG. 1; and  
         [0038]    [0038]FIG. 19 is a schematic side view of a third alternative embodiment of a manner in which a web of material could be coated by the machine of FIG. 1. 
     
    
     DETAILED DESCRIPTION  
       [0039]    FIGS.  1 - 16  show a first preferred embodiment of a system  10  for coating a web of material made in accordance with the present invention. (FIGS.  10 A- 10 C show an alternate embodiment using a different type of seal.) The system  10  includes a stationary base  12 , and left and right movable roller support and nozzle support frames  14 ,  16  mounted on the base  12 . The left and right sides of this system  10  are essentially mirror images of each other. Each of the movable frames  14 ,  16  is mounted on a linear bearing arrangement  18 , as shown in FIGS.  6 - 8 , and the position of each movable frame member  14 ,  16  is controlled by a stepper motor, as will be explained in more detail later. Left and right springs  22  are mounted on the left and right nozzle support frames  16 . Mounting blocks  23  are bolted to their respective springs  22 . In this preferred embodiment, the springs  22  are leaf springs, although other types of springs could be used. One end of each spring  22  is bolted onto an upwardly-projecting arm portion  28  of its respective nozzle support frame  16  by means of bolts  30 . As seen in FIG. 1, the springs  22  permit the nozzle to rotate counterclockwise about a point above the nozzle contact point. A sensor  32  is mounted on each of the support frames  14 ,  16  to measure the force being applied by and to the respective frame.  14 ,  16 .  
         [0040]    Looking at the details in FIGS. 14 and 15, it can be seen that left and right sleeves  67  are keyed by keys  25  to their respective spherical bearings  26  in the mounting blocks  23 . A stiffener beam  24  is mounted on the sleeves  67  by means of bearings  27 . Locking rings  69  are clamped onto their respective sleeves  67  by means of screws  71 , so the locking rings  69 , sleeves  67 , and spherical bearings  26  are all fixed together. The stiffener beam  24  is locked to the locking rings  69  by means of one set of locking bolts  76  or  78 , which fit into respective recesses in the locking rings  69 , as shown in FIG. 15. It will be noted that the holes which receive the second set of locking bolts  78  are angularly offset so that the stiffener beam  24  is in a slightly different angular position when the second set of locking bolts  78  is, used. In order to rotate the stiffener beam  24  relative to the sleeves  67 , the bolts  76  or  78  are retracted until they clear the locking collar  69 , the stiffener beam  24  is rotated  180  degrees, and the respective set of bolts  76  or  78  is then inserted again into the locking collar  69 . While this locking mechanism is shown in the prototype, it will be understood that various known types of rotating and locking mechanisms could be used. The feed pipes  68  are fixed at their other ends to the stiffener beam  24 , as shown in FIG. 11, so the feed pipes  68  rotate with the stiffener beam  24  relative to the fixed sleeves  67 .  
         [0041]    The stiffener beam  24  has first and, second opposed, substantially flat walls  34 ,  36  (see FIG. 2), and a feed nozzle  38  is mounted on each of those walls. The feed nozzles  38  are mounted opposite each other, with one inverted relative to the other so they can be selectively rotated into operating position by rotating the stiffener beam  24  as described above.  
         [0042]    Referring to FIG. 9, each feed nozzle  38  includes a reservoir made up of a rear wall  40 , a top wall  42 , projecting forward from the rear wall  40 , and defining a metering surface  44  at its front edge, a bottom wall  46 , and a front wall  48 , comprising a flexible back seal. The leading edge of the feed bar or nozzle  38  is sealed using the back seal  48 . This back seal  48  is made of a flexible material that runs the full width of the feed nozzle  38 . The blade  48  rests against the substrate or applicator roll  57 . Contact pressure (sealing pressure) can be developed several different ways. The methods include mechanical deflection or stressing of the back seal  48 , deflection of the back seal  48  against the applicator roll  57  or substrate  72  with internal pressure in the feed nozzle, or a combination of the two. The back seal  48  terminates below the metering surface  44 , leaving a gap  50  between the back seal  48  and the metering surface  44 , through which coating  52  flows during operation of the system.  
         [0043]    The downstream edge or application metering surface  44  of the feed nozzle  38  is shaped specifically to provide the desired thickness and appearance characteristics for the specific substrate or roll and fluid. It may be flat, rounded, grooved, or any number of shapes. Generally the metering surface  44  is tapered to provide a wider gap at the lower edge  54  (the leading edge where the roller enters) and a narrower gap at the upper edge  56 , the downstream edge where the roller leaves the nozzle  38 . As will be explained in more detail later, the metering surface  44  is shaped to provide the desired coating characteristics through hydrodynamic effects along the length of the roll/substrate and metering nip. Harder surfaces or thicker coatings may require a concave shape, while softer surfaces and thicker coatings may use flat or convex metering surface  44  contours.  
         [0044]    The ends of the feed nozzle  38  are sealed to the roll  57  (or substrate  72 ) by the end seals  58  to ensure the inside of the feed nozzle  38  remains evenly pressurized across its entire width. The end seals  58  may-be a labyrinth design seal as shown, or they may be mechanically contacting seals or pressurized fluid seals depending on the lubricity of the coating. The gap  50  between the back seal  48 , the metering surface  44 , and the end seals  58  is bridged by the roll  57  (or substrate  72 ). Fluid in the nozzle or feed bar  38  first contacts the roll  57  (or substrate  72 ) as the surface of the roll  57  passes the top of the back seal  48 , and the thickness of the coating fluid on the roll  57  (or substrate  72 ) is determined by the gap between the metering surface  44  and the roll as well as by the viscosity of the fluid and the hydrodynamics as the roll rotates past the metering surface  44 .  
         [0045]    The left and right end seals  58  are shown best in FIGS. 9A and 10 (and an alternative type of end seal  58 A is shown in FIGS. 10A, 10B; and  10 C and is described later). The end seals  58  follow the contour of the roll  57  and have a V shape, including inner and outer walls  60 ,  62 , which are joined together at the back and top and are open at the front and bottom. The roll  57  extends beyond the outer walls  62  of the left and right end seals  58 , so there is a seal between the roll  57  (or substrate  72 ) and the nozzle  38  so that only the desired amount of coating that passes between the roll  57  (or substrate) and the upper edge  56  of the metering surface  44  leaves the nozzle  38 . Any coating that may carry over beyond the inner walls  60  of the end seals is scraped off at the upper apex  64  of the end seal and is stopped by the outer wall  62 , draining down through the lower opening  66  of the end seal  58 . The end seal  58  effectively uses hydrodynamics or a labyrinth effect to seal the ends of the pressurized feed bar or nozzle  38 , without damaging the application surface. The end seal is designed to accommodate changing angles of the nozzle relative to the roll  57  and various surface shapes of the roll  57  or, if the coating is applied directly to the web  72 , the end seal  58  will also accommodate different surface shapes of the web surface. Extending along below each nozzle  38  is a catch trough  66 , which catches any coating that may escape past the back seal  48  or past the end seals  58 .  
         [0046]    The contour of the labyrinth end seal  58  should be shaped to provide a clearance equal to the desired film thickness between the roll  57  (or substrate  72 ) and the seal  58  at the apex  64  of the seal  58 . This clearance should transition smoothly such that, at a point lined up with the trailing edge of the back seal  48 , the clearance between the end seal  58  and the roll  57  (or substrate  72 ) is approximately 0.001″ to 0.008″.  
         [0047]    An alternative preferred embodiment for a labyrinth style end seal  58 A is shown in FIGS. 10A, 10B, and  10 C. The seal  58 A includes generally parallel inner and outer walls  60 A,  62 A respectively, and these walls  60 A,  62 A converge at an apex  64  near the trailing edge of the metering surface  44 . The spacing between the walls  60 A,  62 A forms a pocket  65 A, which may have a width of a few thousands of an inch or greater. The depth and spacing of the pocket  65 A is optimized for the specific coating, roll  57  (or substrate  72 ) deflection rate, and speed, to achieve a wetted exit roll  57  (or substrate  72 ), While not permitting enough fluid out to create excessive leakage or slinging of the fluid. The top surface of the inner and outer walls  60 A,  62 A preferably has a slight slope (in the range of 2 degrees to 10 degrees from the horizontal), sloping toward the inner pocket  65 A, which may improve the wetting characteristics. The intent is to have the pocket  65 A full of the coating fluid such that it is able to wet the roll  57  (or substrate  72 ), but not enough to have the pocket  65 A under substantial pressure so as to cause spraying or slinging of the coating fluid beyond the end seal  58  or  58 A.  
         [0048]    A labyrinth end seal  58 ,  58 A may be flexible or rigid. If the roll  57  (or substrate  72 ) deflects by more than approximately 0.003″ across the product range, then a deflectable, self-correcting end seal  58 A should be considered. The end seal  58 A depicted in FIGS.  10 A- 10 C is designed to provide deflection of the end seal  58 A to permit usage with a deflectable roll  57  (or substrate  72 ). The end seal  58 A is deflectable by virtue of the fact that it mounts onto the nozzle  38  by means of a relatively thin and flexible bracket  67  which compensates for the deflection of the roll  57  (or substrate  72 ). The deflection required of the end seal  58 A can be calculated using standard engineering design practices, and it should be designed to match the deflection rate of the roll  57  (or substrate  72 ) that can be measured directly.  
         [0049]    Each of the feed nozzles  38  is coupled to and reinforced by a stiffener  24  (See FIG. 11). In this embodiment, the stiffener  24  includes two walls,  34 ,  36 . The stiffener beam  24  in this embodiment is a fabricated beam that also houses the feed pipes  68 , which feed coating to the nozzles  38 . The profile of the metering surface  44  of the feed bar or nozzle  38  may be adjusted in order to vary the coating thickness across the width of the web  72  or in order to make the thickness constant by adjusting the position of the metering surface  44  relative to the stiffener  24 . As shown in FIGS. 9B and 9C, the stiffener  24  has many stiffener frame pulling apertures  96  and stiffener frame pusher threaded apertures  98  along its length. In the reservoir, there are corresponding feed nozzle pulling threaded apertures  100  and feed nozzle pusher surfaces  102 . Adjacent to each stiffener clearance  96  is a feeder nozzle pulling threaded aperture  100 . Bolts  104  are inserted through the desired apertures to selectively pull the reservoir towards the stiffener  24  and to push the reservoir away from the stiffener at various positions to achieve the desired profile. It should be noted that, while the reservoir and metering surface are relatively rigid, the stiffener  24  is even more rigid, and this jacking and pulling can achieve slight distortions of the metering surface  44  to achieve the desired profile. While the bolts  104  are currently adjusted manually, it is understood that they may alternatively be adjusted automatically by electro-mechanical or other known means.  
         [0050]    In order to feed pressurized coating to the nozzles  38 , there are left and right feed pipes  68 , projecting out the left and right ends of the stiffener beam  24  along the axis of rotation of the stiffener beam  24 . Each feed pipe  68  bends and extends to its respective nozzle  38 . As shown in FIGS. 5 and 12, there are aligned openings  70  through each surface  34 ,  36  of the stiffener beam  24  and through the respective rear wall  40  of the respective reservoir, which permit coating fluid to pass through the feed pipes  68 , through the aligned openings  70 , and into the respective reservoir of the nozzle  38 . (Only one nozzle  38  will be receiving coating at any given time, because the other nozzle  38  will be inverted and will not be in operating position. However, a nozzle  38  that is out of operating position may be receiving cleaning fluid through its respective feed pipe  68 , as will be explained later.)  
         [0051]    Coating material is piped under pressure through a respective feed pipe  68  to a respective nozzle  38 . In this preferred embodiment, the coating is pumped into a constant head tank, and the head of the coating fluid in the tank maintains a constant operating pressure. There is also a tank of cleaning fluid, and, by switching valves and rotating a cleaning assembly into place, as will be described later, cleaning fluid can be circulated through a nozzle  38  to clean the nozzle.  
         [0052]    Adjacent to the nozzle  38  which is in the forward, operating position, is the roll  57 . In this preferred embodiment, the roll  57  preferably is an applicator roll, which picks up coating from the nozzle  38  and then transfers the coating to a moving web  72  of material rotating over an adjacent backup roll  74 . This arrangement is shown schematically in FIG. 3. FIGS. 17, 18, and  19  show alternative arrangements. In FIG. 17, the web  72  of material to be coated passes between the nozzle  38  and the roll  57 , so the web  72  is coated directly by the nozzle  38 , and the roll  57  functions as a back-up roll. In FIG. 18, the web  72  passes over the roll  57 , which picks up coating from the nozzle  38  and transfers the coating to the web  72 . In FIG. 19, the web  72  passes between two nozzles  38  and each side of the web  72  is coated directly by a nozzle  38 .  
         [0053]    There are various sensors and control mechanisms for controlling the relative positions between the metering surface  44  and the roll  57  and the amount of force applied by the metering surface  44 , which will be described later.  
         [0054]    The stiffener beam  24  is supported by support bearings  26 , which are coupled to the support springs  22  through the mounting blocks  23  (See FIG. 14). Each support spring  22  is fixed at one end to one of the nozzle support frame members  16 , which, as described above, is mounted for linear motion along the base  12 . There is a force sensor  32  mounted on each of the nozzle support frame members  16 , and there is a force sensor  32  mounted on each of the roll support frame members  14 . The position of each of the frame members  14 ,  16 , is controlled by a motor  20 , which rotates a threaded shaft  106 , which pushes and pulls its respective frame member  14 , 16  along a linear track  108 , where it is supported by linear bearings  110 . Thus, the motors  20  control the relative positions of the nozzle  38  and the roll  57 , setting the gap between the metering surface  44  and the roll  57  and controlling the force exerted by the nozzle  38  on the roll  57 . In this preferred embodiment, the motors  20  are stepper motors. However, other kinds of motors may be used, such as servo motors and hydraulic servos. The motors  20  may be controlled in response to a central controller, which receives signals from the force sensors  32 , thereby controlling the force with which the coating fluid is applied to the roller  57 . While the feed nozzle force sensor  32  is shown as being mounted on the frame  16 , it may be incorporated into the support spring  22 , may be mounted under the support spring  22 , or may be incorporated into the feed nozzle slide position/force adjuster linear bearing arrangement  18 . The stiffener  24  may be integral with the feed nozzle  38 . However, in this preferred embodiment, the stiffener  24  is a separate member, which permits adjustment of the profile of the feed nozzle  38 , as was explained above. While stepper motors  20  are used in this embodiment, other control mechanisms, such as hydraulic motors, hydraulic cylinders, and hand cranks could be used instead.  
         [0055]    By mounting the feed nozzle  38  on the support springs  22 , an additional adjustment is provided. As the fluid pressure builds up between the feed nozzle  38  and the roll  57 , the springs  22  extend, causing the stiffener  24  and the on-line feed nozzle  38  to rotate slightly up and away from the roll  57 , and, as the fluid pressure is reduced, the springs  22  retract, rotating the feed bar  38  back downwardly and closer to the roll  57 , so that a proper metering gap is maintained at the metering surface  44 . In this preferred embodiment, the springs  22  are leaf springs having a thickness and arcuate shape designed to maintain the desired metering gap for a particular fluid. It is expected that various types and shapes of springs will be used depending upon the desired thickness and the characteristics of the coating fluid to be used.  
         [0056]    By adjusting the shape of the reservoir cavity, the heat build up from the turbulence of the coating material can be controlled. The opening  70  from the feed pipe into the nozzle  38  is tapered to minimize turbulence (See FIG. 12). As the ratio of reservoir cavity cross sectional area to the exposed surface being coated increases, more heat is added to the coating due to turbulence.  
         [0057]    As was explained earlier, FIGS. 14 and 15 show a mounting arrangement which permits the stiffener beam  24  to be rotated 180 degrees from first to second operating positions. In the first operating position, one of the nozzles  38  is on-line, and, in the second operating position, the beam  24  is rotated 180 degrees from the first position, thereby putting the second nozzle  38  into operating position. While one example of the mechanism for mounting and rotating the stiffener beam  24  is shown here, many other mechanical or electro-mechanical arrangements could be used. For example, a rotating handle and gearing could be used to control the angular position of the stiffener beam  24  relative to the sleeve  67 .  
         [0058]    Contact force, reservoir cavity pressure, shape of the metering surface and contact angle are all control actuators. These actuators provide a wide operating control window and can be operated manually or can be fully automated and dynamically controlled via mathematical algorithms or product feedback. In the present embodiment, the bolts  76 ,  78  are controlled manually.  
         [0059]    The pressure feed coating application system  10  enables complete control of the fluid through the application process. Pre-filtered and conditioned fluid is applied under pressure directly to the web  72  or to the applicator roll  57 . Thus, there is no opportunity for the phenomena that create foam, skips, voids, shinnies, splotching, or slings to develop. The fluid is not open to the atmosphere, therefore the fluid cannot skin-over or dry-out. By keeping the coating fluid contained and by controlling the shape of the nozzle, the nozzle pressure, nozzle angle, relative positions of the nozzle  38  and roll  57 , and the roll hardness, it is possible to provide precise control of the film thickness. Defects associated with unstable or uncontrolled fluid dynamics are eliminated. Coatings may be applied using this equipment at high speeds of over 250 feet per minute with very good appearance (no ribs) at a much wider range of fluid viscosities than was previously possible.  
         [0060]    [0060]FIG. 17 shows the pressure feed coating application assembly  10  applying coating fluid from the nozzle  38  directly to the product web  72 . Applying the coating from the nozzle to an applicator roll for transfer to the product or applying directly from the nozzle to the product provide significant improvements over conventional two and three roll coating systems. Application of pre-metered coating to the applicator roll eliminates the need for using a second or third roll. Improved product characteristics can be achieved with one roll using this method.  
         [0061]    Under certain circumstances, it may be advantageous to use this system to apply coating to a roll one removed from an applicator roll. This roll may be operated in either the forward or reverse direction. This system still provides many advantages over conventional two or three roll, Roll Coating Systems.  
         [0062]    The pressure feed coating application feed system  10  feeds pressurized coating into the sealed feed bar  38  with pressurized fluid against the roll or substrate as opposed to designed clearances used in die, slot and curtain application systems.  
         [0063]    In the preferred embodiment of the present invention, the materials of construction of the stiffener beam and nozzle would typically be metal, usually steel or aluminum.  
         [0064]    [0064]FIGS. 1 and 13 illustrate a feed nozzle cleaning assembly  82 , which is shifted into position by the cylinder  84  to enclose the feed nozzle  38  that is off line. The feed nozzle cleaning assembly  82  includes a cover  86 , which seals against the stiffener  24  and against the bottom wall  46  of the feed nozzle  38 , enclosing the feed nozzle  38 . Cleaning fluid is circulated through the respective feed pipe  68 , through the feed nozzle  38 , is caught in the cover  86 , and is recirculated. Cleaning fluid is also sprayed through cleaning nozzles  87  in the cover  86  to clean the feed nozzle  38 . In normal operation, the off-line nozzle  38  will be cleaned while an on-line nozzle remains in service, as shown in FIG. 13.  
         [0065]    [0065]FIG. 16 illustrates an applicator roll cleaning assembly  88 , which is a means of cleaning the applicator roll  57 . In the preferred embodiment of the present invention, the cleaning assembly  88  includes a cleaning blade  90  mounted on an arm  91 , which is coupled to a cleaning blade actuator (not shown), which causes the cleaning blade arm  91  to pivot about the axis  92 . The roll cleaning assembly  88  also includes cleaning nozzles  94 , which spray cleaning fluid on the roll  57 . While this means of cleaning the applicator roll  57  is manual, it will be obvious to anyone skilled in the art that it could readily be converted to an automated cleaning system. The present design provides the space and layout that permits the use of such a cleaning system, which could not be used in prior art coating systems.  
         [0066]    It will be obvious to those skilled in the art that modifications and additions may be made to the embodiments described above without departing from the scope of the present invention.