Patent Abstract:
An apparatus for coating an article where the apparatus includes an applicator, a conveyor for sequentially transporting a plurality of articles to the roller and a metering bar positioned against the applicator to meter a predetermined amount of coating composition to the applicator for transfer to an article transported to said applicator by the conveyor.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention is directed to coating articles.  
           [0002]    A roll of pressure sensitive adhesive tape is often prepared by applying a pressure sensitive adhesive composition to a backing and then winding the backing on a cylindrical core to form the roll of tape. The edge face of the roll of tape often includes exposed pressure sensitive adhesive, which renders the edge face tacky. In addition, when the tape is wound upon a cylindrical core to form a roll, uneven winding may occur which may cause variations in the edge face surface.  
           [0003]    Multiple rolls of pressure sensitive adhesive tape are often packaged in a stack. When rolls of pressure sensitive adhesive tape are stacked on top of one another they tend to block, i.e., stick together. Blocking tends to increase in frequency and degree over time and at elevated temperatures, e.g., above room temperature. The edge face of a roll of tape may also stick to its packaging, which can make removal of the roll of tape from the packaging difficult. Electrical tape, for example, which is often sold in plastic containers, tends to stick to the plastic walls of the container. The tacky nature of the edge face also tends to pick up dust, dirt and other particulate debris from the environment.  
           [0004]    A number of methods have been developed to protect the edge face of a roll of adhesive tape or detackify the exposed adhesive on the edge face. One common method involves placing a sheet of paper in contact with the edge face, e.g., between two rolls of tape. Another method involves coating the edge face of a roll of tape with very small glass beads. The glass beads tend to fall off the roll, which can cause contamination or damage to manufacturing processes and machinery. Other methods include applying a detackifying agent to the edge of a strip of tape using a sponge or a cloth prior to winding the strip of tape upon a cylindrical core to form a roll.  
         SUMMARY  
         [0005]    In one aspect, the invention features an apparatus for coating an article, the apparatus comprising an applicator, a conveyor for sequentially transporting a plurality of articles to the applicator and a metering bar positioned against the applicator to meter a predetermined amount of coating composition to the applicator for transfer to an article transported to the applicator by the conveyor. In one embodiment, the applicator includes a roller having a durometer of no greater than about 55 Shore A. In another embodiment, the coating apparatus is capable of applying a substantially uniform layer of coating composition on a plurality of articles having different dimensions.  
           [0006]    In some embodiments, the end of the metering bar positioned against the roller has a radius of at least about 2.5 mm. In other embodiments, the end of the metering bar positioned against the roller has a radius of at least about 4.0 mm. In another embodiment, the metering bar exerts a force of at least about 35 g/cm width against the applicator. In some embodiments, the metering bar exerts a force of from about 45 g/cm width to about 900 g/cm width against the applicator.  
           [0007]    In one embodiment, the conveyor is positioned relative to the applicator such that the applicator is capable of coating the edge face of a roll of tape disposed between the conveyor and the applicator. In one embodiment, the applicator is a roller. In other embodiments, the applicator is an endless belt.  
           [0008]    In other embodiments, the apparatus further includes a second applicator and a second metering bar positioned against the second applicator to meter a predetermined amount of coating composition to the second applicator, the second applicator being positioned to receive an article from the conveyor. In one embodiment, the first applicator is a roller and the second applicator is a roller. In other embodiments, the first applicator includes an endless belt. In some embodiments, the second applicator includes an endless belt.  
           [0009]    In another embodiment, the apparatus is capable of substantially simultaneously transferring a coating composition from the first applicator to a first side of an article, and transferring a coating composition from the second applicator to a second side of the article opposite the first side of the article. In some embodiments, the article is a roll of tape and the apparatus is capable of substantially simultaneously transferring a coating composition from the first applicator to a first edge face of a roll of tape and transferring a coating composition from the second applicator to a second edge face of the roll of tape opposite the first edge face of the roll of tape.  
           [0010]    In one embodiment, the first applicator and the second applicator are positioned to maintain an article between the first applicator and the second applicator.  
           [0011]    In another aspect, the invention features a system for manufacturing coated articles, the system including a first station comprising a coating apparatus that includes an applicator, a conveyor capable of sequentially transporting a plurality of articles to the applicator, and a metering bar positioned against the applicator to meter a predetermined amount of coating composition to the applicator for transfer to an article transported to the applicator by the conveyor, and a second station for solidifying the coating composition disposed on the article.  
           [0012]    In some embodiments, the applicator includes a roller. In other embodiments, the applicator includes an endless belt.  
           [0013]    In another embodiment, the conveyor is capable of transporting a coated article to the second station.  
           [0014]    In other embodiments, the system further includes a second conveyor capable of transporting a coated article from the first station to the second station. In one embodiment, the system further includes a second conveyor comprising a first endless belt and a second endless belt, the second conveyor being positioned to transport a coated article to the second station. In some embodiments, the system further includes a second applicator positioned to receive an article from the conveyor, and a second metering bar positioned against the second applicator to meter a predetermined amount of coating composition to the second applicator. In another embodiment, the system further includes a second applicator positioned opposite the first applicator, and a second metering bar positioned against the second applicator to meter a predetermined amount of coating composition to the second applicator. In one embodiment, the system further includes a second conveyor positioned to transport a coated article to the second station. In another embodiment, the system further includes a second conveyor comprising a first endless belt and a second endless belt, the second conveyor being positioned to transport a coated article to the second station. In one embodiment, the second conveyor is capable of transporting a coated article between the first endless belt and the second endless belt.  
           [0015]    In some embodiments, the second station includes a source of radiation. In one embodiment, the source of radiation is capable of generating radiation selected from the group consisting of ultraviolet radiation and electron beam radiation. In other embodiments, the solidifying includes curing. In yet other embodiments, the solidifying includes drying.  
           [0016]    In another aspect, the invention features a method of coating an article using a coating apparatus comprising an applicator, a conveyor for transporting an article the applicator, and a metering bar positioned against the applicator to meter a predetermined amount of coating composition to the applicator, the method including applying a liquid coating composition to the applicator and transferring the coating composition from the applicator to the article. In some embodiments, the coating composition has a viscosity of at least about 15 cps. In other embodiments, the coating composition has a viscosity of at least about 19 cps. In one embodiment, the method further includes curing the coated composition. In another embodiment, the method further includes drying the coated composition  
           [0017]    In some aspects, the invention features a method of coating the edge face of a roll of tape using a coating apparatus that includes an applicator, a conveyor for transporting a roll of tape to the applicator, and a metering bar positioned against the applicator to meter a predetermined amount of coating composition to the applicator, the method including applying a liquid coating composition to the applicator, and transferring the coating composition from the applicator to the edge face of the roll of tape. In one embodiment, the composition has a viscosity of at least about 15 cps. In other embodiments, the composition has a viscosity of at least about 19 cps.  
           [0018]    In some embodiments, the end of the metering bar positioned against the applicator has a radius of at least about 3 mm. In other embodiments, the end of the metering bar positioned against the applicator has a radius of at least about 4 mm. In one embodiment, the metering bar exerts a force of at least about 35 g/cm width against the applicator. In other embodiments, the metering bar exerts a force of from about 45 g/cm width to about 900 g/cm width against the applicator.  
           [0019]    In another embodiment, the conveyor is positioned relative to the applicator such that the applicator is capable of coating the edge face of a roll of tape disposed between the conveyor and the applicator. In one embodiment, the method further includes a second applicator positioned to receive an article from the conveyor, and a second metering bar positioned against the second applicator to meter a predetermined amount of coating composition to the second applicator.  
           [0020]    In some embodiments, the method further includes a second applicator positioned opposite the first applicator, and a second metering bar positioned against the second applicator to meter a predetermined amount of coating composition to the second applicator.  
           [0021]    In one embodiment, the method further includes curing the composition coated on the edge face. In other embodiments, the method further includes drying the composition coated on the edge face.  
           [0022]    In some embodiments, the method further includes substantially simultaneously transferring a coating composition to a first side of an article and a second side of the article opposite the first side of the article. In one embodiment, the article is a roll of tape and the method further includes substantially simultaneously transferring a coating composition to a first edge face of the roll of tape and a second edge face of the roll of tape.  
           [0023]    In other aspects, the invention features an apparatus for coating an article, where the apparatus includes an applicator roller, a conveyor for sequentially transporting a plurality of articles to the roller and a metering bar positioned against the roller to meter a predetermined amount of coating composition to the roller for transfer to an article positioned between the roller and the conveyor.  
           [0024]    The coating apparatus is capable of applying a reproducible coating weight to the surface of a series of articles upon each revolution of the applicator roller. The coating apparatus is well suited to coating the edge face of a roll of tape. The coating apparatus can coat articles that are spaced at irregular intervals on the conveyor that feeds the articles into the apparatus, i.e., the interval between articles to be coated can be varied. The apparatus is also well suited to applying a coating to a number of articles each having a surface to be coated that differs in dimension from the previous article.  
           [0025]    The coating apparatus is constructed such that when an article is not available for coating, the liquid coating composition is not transferred from the roller. The coating apparatus is also capable of controlling the amount of coating composition applied to the roller such that overcoating, i.e., applying coating composition to surfaces other than the target surface, does not occur. In the case of rolls of tape, for example, the coating apparatus is capable of coating surface variations present at the edge face of the roll of tape, while avoiding coating the vertical surfaces of the roll of tape such as the cylindrical core of the roll and the exposed backing of the roll.  
           [0026]    Other features and advantages will be apparent from the following description of the preferred embodiments thereof, and from the claims. In the figures, like numbers are used to represent like elements. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    [0027]FIG. 1 is a side view of a coating apparatus.  
         [0028]    [0028]FIG. 2 is a side view of the metering bar of the coating apparatus of FIG. 1.  
         [0029]    [0029]FIG. 3 is a perspective view of the metering bar of FIG. 2.  
         [0030]    [0030]FIG. 4 is a perspective view of a roll of tape.  
         [0031]    [0031]FIG. 5 is a side view of a coating apparatus according to a second embodiment.  
         [0032]    [0032]FIG. 6 is a top view of the coating apparatus of FIG. 5.  
         [0033]    [0033]FIG. 7 is a side view of a coating apparatus according to a third embodiment.  
         [0034]    [0034]FIG. 8 is a front perspective view of the metering bar and applicator roller of the coating apparatus of FIG. 7.  
         [0035]    [0035]FIG. 9 is a front view of the metering bar of FIG. 8.  
         [0036]    [0036]FIG. 10 is a side view of a second embodiment of a metering bar.  
         [0037]    [0037]FIG. 11 is a perspective view of a third embodiment of a metering bar.  
         [0038]    [0038]FIG. 12 is a side view of a coating apparatus that includes an endless belt. 
     
    
     DETAILED DESCRIPTION  
       [0039]    The coating apparatus is suitable for coating a variety of articles including articles having a variety of different shapes and sizes. For ease of description, however, the coating apparatus is described herein with respect to coating the edge face of a roll of tape.  
         [0040]    FIGS.  1 - 4  illustrate a coating apparatus  10  for applying a liquid coating composition  24  on an edge face  16  of a roll of tape  14 . The coating apparatus  10  includes an applicator  18  in the form of a roller, a metering bar  22  in contact with the applicator roller  18  and a conveyor  26 . The metering bar  22  is positioned such that an edge  33  of the metering bar  26  bears on the surface of the applicator roller  18 . The metering bar  22  and applicator roller  18  combine to define a trough  42 , which receives the liquid coating composition  24 . The force with which the metering bar presses against the applicator roller  18  and the angle at which the arcuate end portion  31  of the metering bar  22  contacts the applicator roller  18  control the amount of coating composition  24  that is carried by the applicator roller  18  as it rotates past the metering bar  22  in a counter clock wise direction.  
         [0041]    The conveyor  26  is positioned beneath the applicator roller  18  at a vertical distance from the applicator roller  18  sufficient to permit a roll of tape  14  positioned with an edge face  16  in contact with the conveyor  26  to pass between the applicator roller  18  and the conveyor  26 . As the conveyor  26  moves, it transports a roll of tape  14  to the applicator roller  18 . As the leading edge of the roll of tape  14  enters the coating station  54 , the applicator roller  18  contacts the edge face  16  and transfers a layer  12  of coating composition  24  to the edge face  16 . The rotation of the applicator roller  18  in a counter clockwise direction provides fresh coating composition  24  to the edge face  16  as it travels through the coating station  54 .  
         [0042]    The liquid composition  24  is applied to the edge face  16  at a predetermined coating weight to provide a coating thickness “X” on the roll of tape. Suitable coating weights will vary depending upon factors related to the roll of tape including, e.g., the composition of the adhesive, the coating weight of the adhesive and the backing of the roll of tape and the surface variations on the edge face of the roll of tape. The apparatus  10  is capable of applying the liquid composition  24  to the edge face  16  without applying the composition to the interior of the central cylinder  32  or the major surface of the exposed backing  30  of the roll of tape  14 .  
         [0043]    Suitable applicator roller materials are conformable to the surface of the article being coated. The roller can include a single material extending through the body of the roller or multiple layers of material. Preferably the exposed roller material is sufficiently conformable to apply a substantially uniform layer of coating composition on a surface having height variations. The roller can also be constructed to include one material or a number of layers of the same or different material. Roller constructions that include multiple layers preferably have a conformable outer surface layer. The applicator roller can be made from a variety of materials including, e.g., nitrile rubber, vinyl modified nitrile rubbers, and urethane. The density of the applicator roller can also vary from a solid to a porous foam construction having open cell pores, closed cell pores, or a combination thereof. Useful rollers have a hardness of from about 12 Shore A to about 55 Shore A, preferably about 24 Shore A.  
         [0044]    Alternately, the applicator can be an endless belt. FIG. 12 illustrates a coating apparatus  110  that includes an endless belt  118  that travels around two rotating pulleys  120 ,  124 . A metering bar  122  applies a pressure against the endless belt  118 . A coating composition  24  is fed to the nip between the metering bar  122  and the endless belt  118 . As the endless belt  118  moves it transports coating composition  24  and applies coating composition  24  to an edge face  116  of a roll of tape  114 , which is brought into position under the endless belt  118  by conveyor  126 .  
         [0045]    The metering bar  22  is a bar that is capable of controlling the amount of coating composition applied to the applicator roller  18  such that each revolution of the applicator roller carries substantially the same amount of coating composition for transfer to the article to be coated. A number of suitable metering bar constructions are available including, e.g., a doctor blade, a doctor blade that includes a gap (e.g., an adjustable gap) as shown, e.g., in FIG. 8, and a doctor blade that includes a rotatable rod as shown, e.g., in FIG. 11. The portion of the metering bar positioned against the applicator can have a smooth or patterned surface.  
         [0046]    The metering bar  22  of FIGS.  1 - 3  is in the form of a doctor blade having an arcuate end portion  31 . The arcuate end portion  31  is positioned and exerts a force against the applicator roller  18  during the coating process. The arcuate end portion  31  is defined by a radius “R.” The radius “R” of the doctor blade  22  can be used to alter the coating weight applied to the edge face  16  of the roll of tape  14 . Increasing the radius of the arcuate end portion  31  of the doctor blade  22  can cause an increase in the hydraulic force at the nip between the doctor blade  22  and the applicator roller  18 , which causes an increase in the coating weight applied to the edge face  16  of the roll of tape  14 . Decreasing the radius R of the arcuate end portion  31  of the doctor blade  22  can decrease the coating weight applied to the edge face  16  of the roll of tape  14 . Preferably the doctor blade has a radius of at least 2.5 mm, more preferably at least about 3 mm, most preferably from about 2.5 mm to about 80 mm.  
         [0047]    The force exerted by the metering bar  22  against the applicator roller  18  can also alter the coating weight of the composition applied to the surface of the edge face. Increasing the force, for example, decreases the coating weight and decreasing the force increases the coating weight. Preferably the force exerted by the metering bar is from 0.25 lb/inch width to about 5.0 lb/inch width of the metering bar.  
         [0048]    The coating apparatus can be used to transfer coating compositions having a wide range of viscosities including compositions having a viscosity of from about 15 centipoise (cps) to greater than 10,000 cps.  
         [0049]    The coating apparatus can be constructed such that the applicator roller rotates continuously. The applicator roller can be connected to a motor capable of controlling the rotation as well as the rotation speed of the roller. When a roll of tape is not present in the coating position, the applicator roller can continue rotating without depositing the coating composition.  
         [0050]    [0050]FIGS. 5 and 6 illustrate a second embodiment of a coating apparatus  40 , which is part of a coating process that includes a coating station  54  and a finishing station  38 . The coating apparatus  40  includes a second roller  52  positioned opposite the first roller  18  to enable simultaneous coating of the first and second edge faces  16 ,  56  of the roll of tape  14 . The second roller  52  is also conformable to the surface variations present on edge face  56  and includes a conformable outer layer  60 . As roller  52  rotates clockwise about its axis a metering bar  22   a  meters a predetermined amount of liquid composition  24  to the second roller  52 .  
         [0051]    A conveyor  46  feeds a roll of tape  14  into the space between the rollers  18 ,  52 . The movement of the first roller  18  in a counter clockwise direction and the second roller  52  in a clockwise direction causes the roll of tape  14  to be taken up by and passed between the two rollers  18 ,  52 . The rollers  18 ,  52  then transfer a layer  12  of liquid coating composition  24  to the opposite edge faces  16 ,  56  of the roll of tape  14  while simultaneously advancing the roll of tape  14  to the transport conveyors  34 ,  36 .  
         [0052]    The roll of tape  14  leaves the coating apparatus  40  via transport conveyors  34 ,  36 , which include two endless belts  62 ,  64  traveling around rotating pulleys  70 . The transport conveyors  34 ,  36  grip the roll of tape  14  as it exits from between the rollers  18 ,  52 . The transport conveyors  34 ,  36  maintain the roll of tape  14  between them by friction. The roll of tape  14  is preferably maintained in a level position as it is transported from the coating station  54 , past the blocking panel  66  and to a finishing station  38  by the transport conveyors  34 ,  36 . The blocking panel  66  can block radiation, e.g., light or heat, transmitted from the finishing station  38  from reaching the coating station  54 . As the roll of tape  14  passes through the finishing station  38  the layers  12  of coating composition  24  on the edge faces  16 ,  56  of the roll of tape  14  are treated, e.g., exposed to radiation  68  for a period sufficient to cure the layers  12  of coating composition  24  in the case of a curable coating composition or dried (e.g., by heat or air) in the case of a water-based or solvent-based coating composition. The roll of tape  14  is then transported out of the finishing station  38  to conveyor  48  for further processing including, e.g., packaging.  
         [0053]    The coating apparatus is suitable for coating a variety of compositions including, e.g., solid (e.g., hot melt and radiation curable compositions), aqueous-based and solvent-based compositions. The coating apparatus can coat compositions having a wide range of viscosities and is well suited to coating compositions having a viscosity from about 15 cps to about 15,000 cps, preferably no greater than about 10,000 cps, most preferably no greater than about 5,000 cps.  
         [0054]    The coating apparatus is also suitable for coating a variety of articles having varying shapes and dimensions including, e.g., piece parts.  
         [0055]    Other embodiments are within the claims. FIGS.  7 - 9 , for example, illustrate a coating apparatus  72  that includes a metering bar  74  in the form of a doctor blade  74  that includes a gap  76  in contact with applicator roller  78 . The gap  76  meters the amount of coating composition  24  that is applied to the applicator roller  78 . A gap doctor blade  74  is capable of applying a greater volume of coating composition to the applicator roller  18  relative to a doctor blade without a gap. A gap doctor blade is particularly useful for coating aqueous-based compositions.  
         [0056]    [0056]FIG. 10 illustrates a metering bar  80  that includes an arcuate portion  82  defined by radius “R 1 ” and having a straight edge. In use, the arcuate portion  82  of the metering bar  80  is in contact with the applicator roller  18 .  
         [0057]    [0057]FIG. 11 illustrates a metering bar  86  that includes a rotatable rod  88  disposed in the applicator-contacting end  90  of the metering bar  86 . The rod  88  is capable of rotating about its longitudinal axis L. The rod  88  can be rotated at predetermined speeds, at predetermined intervals and in predetermined directions, to provide various functions including, e.g., refreshing the arcuate surface available for contact with the applicator, and cleansing the nip between the rod and the applicator. Cleansing the nip and refreshing the arcuate surface can help remove tracks and streaks formed on the applicator roller. The rotatable rod  88  is preferably a hard, dense material including, e.g., metal (e.g., steel, iron or aluminum and alloys thereof) and plastic.

Technology Classification (CPC): 8