Abstract:
A continuous and flexible method and apparatus is provided for applying one or more coating materials to internal and/or external portions of a fiber batt to provide edge and surface coating layers on those surfaces of the fiber batt that will be exposed during subsequent use. The invention provides for the coating to be applied selectively all exposed surfaces of a fiber batt and provided internally within the fiber batt for later splitting into opposing edges, thereby improving both the manufacturing process and the consistency and flexibility of the resulting product by reducing or eliminating the need for subsequent manual coating of unfinished edge surfaces.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to a method and apparatus for continuously and selectively applying surface coatings and/or reinforced regions to a fiber batt to form a duct liner, duct wrap, dust board or similar product in which the exposed surfaces are provided with a suitable coating. 
     2. Description of the Prior Art 
     It is a well known to use a layer or batt of fiberglass, polymeric fiber or combination of fibers as an internal liner for sheet metal ductwork in heating, ventilating and air conditioning applications. Such liners insulate the ductwork to maintain the temperature of the air passing through the duct and, during cooling operations, to prevent condensation on exterior surfaces of the duct. These batts, can also can provide efficient sound absorption to control or decrease noise transmission within ductwork or in other applications. Particularly for batts used as duct liners, an interior surface of the liner will be exposed, at least periodically, to high velocity air flow. As a result, various federal, state, local and trade association regulations mandate that such liners meet certain standards. 
     One of the standards the liner must typically meet requires a certain resistance to erosion or degradation caused by the air flow through the duct. Such standard typically require that duct liners shall not break, flake, delaminate or otherwise erode at air flow velocities representing the greater of a specified multiple of the rated velocity or some minimum velocity. In order to accommodate such standards, manufacturers of such duct liners typically coat at least the major surface of the fiber batt that will be exposed to the air with one or more layers of materials that will prevent degradation of the underlying batt. Such layers may comprise a rubber or polymeric material that, when cured, forms a tough protective skin on the treated surface. Similarly, a fabric layer may be attached to the surface either singly or in combination with one or more underlying layers. 
     The coatings used in conjunction with duct liners have included a variety of elastomeric aqueous cross-linkable emulsion compositions such as acrylic emulsions. Typically, these elastomeric cross-linkable compositions are frothed or foamed prior to being applied to the fiber batt or other insulating sheet in order to provide a generally uniform coating on at least one major surface of the insulation. When the coating is heat cured, the emulsion coating composition is heated to a temperature and for a duration sufficient to evaporate the majority of the water and cause the frothed or foamed coating to collapse (i.e., coalesce and lose bubbles from the froth or foam). Heat curing also causes the elastomeric resins to cross link to form a thin protective coating. 
     Examples of such coating processes are provided in U.S. Pat. No. 4,990,370, issued Feb. 5, 1991, On-Line Surface and Edge Coating of Fiber Glass Duct Liner; U.S. Pat. No. 5,211,988, issued May 18, 1993, Method for Preparing a Smooth Surfaced Tough Elastomeric Coated Fibrous Batt; and U.S. Pat. No. 5,487,412, issued Jan. 30, 1996, Glass Fiber Airduct With Coated-Interior Surface Containing a Biocide. An example of a multilayer coating process is provided in U.S. application U.S. Ser. No. 2001/0033926, published Oct. 25, 2001. 
     These duct liners and other insulation products are typically provided by the manufacturers in rolls of approximately 100 feet in length and in a variety standard widths ranging between two and five feet. The duct manufacturers, in turn, attach the duct liner to a sheet metal surface with the coated side exposed and then trims the sheet metal and duct liner combination to standard widths and lengths that are then bent and formed into duct work with the duct liner providing the interior surface. 
     In some instances, however, the edges of the batt are not coated and in other instances, the trimming and forming creates an uncoated edge on the duct liner batt. In such instances, the uncoated surfaces represent areas that would be more prone to erosion, requiring the duct manufacturers and installers to coat or otherwise seal the exposed batt to comply with the relevant standards. Frequently this additional coating was applied during duct manufacturer after the initial forming of the sheet metal to produce a series of L-shaped duct portions. These duct portions can then be stacked to expose the uncoated edges and an adhesive or other sealant composition applied manually using a spray gun, brush, or roller. This practice, however, requires additional labor and handling by the duct manufacturer and can lead to visually unattractive results, varying coating quality, and environmental concerns. Further, such manually applied coatings may not, in fact, be sufficient to satisfy the applicable performance standards. 
     Another alternative is to supply batt users, particularly users such as HVAC duct and vehicle manufacturers, with a wider range finished batt widths to reduce the need for trimming batts to ensure an appropriate fit. This approach, however, complicates the ordering, manufacturing and inventory systems associated with Just-In-Time (JIT) by increasing the number of parts that have to be tracked. 
     SUMMARY OF THE INVENTION 
     The present invention provides a continuous and flexible method and apparatus for applying a coating material to portions of a fiber batt that may become an exposed surface in a subsequent application. The present invention provides for the selective coating of both major surfaces and actual or potential edge surfaces, thereby improving both the manufacturing process and the consistency and flexibility of the resulting product by reducing or eliminating the need for manual coating of unfinished edge surfaces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of the coating application according to a first embodiment of the present invention. 
     FIG. 2 is a schematic view of the coating application according to a second embodiment of the present invention. 
     FIG. 3 is a schematic view of the coating application according to the first embodiment of the present invention. 
     FIGS. 4A-B are cross-sectional views of a resulting fiber batt at the points indicated on FIG.  3 . 
     FIG. 5 is a schematic view of the coating application according to a third embodiment of the present invention. 
     FIG. 6 is a schematic view of the coating application according to the third embodiment of the present invention. 
     FIGS. 7A-B are cross-sectional views of a resulting fiber batt at the points indicated on FIG.  5 . 
     FIGS. 8A-B are cross-sectional views of an alternate fiber batt at the points indicated on FIG.  5 . 
     FIG. 9 is a schematic view of the coating application according to a fourth embodiment of the present invention. 
     FIGS. 10A-C are cross-sectional views of alternate fiber batts according to the fourth embodiment of the present invention. 
     FIG. 11 is a schematic view of the coating application according to a fifth embodiment of the present invention. 
     FIG. 12 is a schematic view of the coating application according to a sixth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1, a first embodiment of the coating application feeds a fiber batt  10  past one or more ejector heads  14  that apply a binder composition  15  to the fiber batt. The binder composition  15  may comprise one or more liquid binder solutions, dry particulate materials or slurries that, under the selected application conditions, can penetrate a desired distance into the fiber batt. Depending on the coating system utilized and the materials selected, the fiber batt, or the individual fibers that comprise the batt, may be treated to improve the effectiveness of the binder coating operation. Such treatments may alter the surface characteristics of the fibers or may simply comprise moistening portions of the fiber batt to improve retention of a particulate coating material within the batt. In the event that a binder solution or slurry is utilized, the coating operation may include a drying step to remove at least the majority of the water or other solvent before actually curing the binder composition. 
     The coating material  15  is applied to selected regions of the upper surface  11  of the fiber batt under conditions that ensure that the coating material is preferably distributed throughout the thickness of the fiber batt in a relatively narrow band. Depending on the characteristics of the fiber batt  10 , such as thickness and open volume, and the coating material  15 , such as viscosity, flowrate, particle size distribution and ejection velocity, a vacuum device  16  may be provided adjacent the rear surface  13  of the fiber batt to assist in the penetration of the coating material through the fiber batt. 
     Although, as shown in FIG. 1, a common vacuum device  16  may serve a number of ejector heads  14 , in the embodiment shown in FIG. 2, each of the ejector heads is associated with a dedicated vacuum device  17  to provide additional control of the penetration of the coating material  15 . As also shown in FIG. 2, the coating material  15  may be applied to the fiber from the rear surface  13 , preferably with a vacuum assist from a vacuum device  17 . The availability of two-sided coating allows full thickness coating of the fiber batt under operating conditions that would preclude a single-sided application from achieving sufficient coating material density throughout the entire thickness of the fiber batt. Such operating conditions may include fiber batts that are thicker and/or denser, more viscous coating compositions, or the need to limit pressure applied to the fiber batt. 
     FIG. 3 illustrates the manufacturing stages of a preferred embodiment of the invention as the fiber batt  10  moves from left to right through the apparatus. As the fiber batt  10  passes under ejector head  14 , a coating material  15  is injected, optionally with vacuum assist  17 , through the thickness of the fiber batt. The impregnated fiber batt passes adjacent one or more heaters  18 ,  19  or through an oven and heated to a temperature sufficient to cure, melt or flow the coating material to form one or more coating layers extending through the fiber batt. In applications utilizing a liquid coating material, additional dryers or evaporators may be arranged after the ejector heads to remove a portion of the solvent, typically water, before the impregnated batt enters the curing operation. After the coating layers have cooled sufficiently, the fiber batt  10  may be split into a number of smaller fiber batts by splitter  20  that separates the fiber batt at the coating layers. 
     In addition to the primary polymer or resin component, typical coating materials used in the present invention may be formulated to vary the elasticity, abrasion resistance, rigidity, density, flammability, water resistance, color, etc. of the resulting coating or film. These coating materials may also include, without limitation, pigments, fillers, fire retardants, organic or inorganic biocides, bactericides, fungicides, viscosity modifiers, water repellents, surfactants and curing catalysts. 
     FIG. 4A illustrates a cross-sectional of a fiber batt  10  in which three coating layers  21  have been formed. FIG. 4B illustrates the same fiber batt  10  after it has passed through splitters  20  that are aligned with each of the coating layers  21  to produce standard size fiber batts  10   a  having coating layers  21   a ,  21   b  on the exposed edges. 
     FIG. 5 illustrates a preferred embodiment of the present invention in which the fiber batt  10 , after the initial injection of the coating material  15  through ejector heads  14 , passes under a second ejector or series of ejectors  22  that deposit a coating material layer  25  on or near the surface  11  of the fiber batt. Again, depending on the coating material and the batt, the second ejector may be provided with a corresponding vacuum device  24  to ensure sufficient penetration of the coating material  23 . Further, although it is preferred that the surface layer  25  is deposited after the interior coating layers  21  have been formed, depending on the materials selected and the intended application, the interior coating layers could also be formed by injecting a coating material or materials through a previously formed surface layer. 
     Although it is generally preferred that the coating material injected into the fiber batt  15  and the coating material applied only near the surface  23  are the same or similar materials, depending on the intended application and the desired properties the coating materials may be quite different and one or both may comprise a mixture of materials. After depositing the surface layer  25 , the impregnated fiber batt is again heated to a temperature sufficient to cure or fuse substantially all of the coating materials that have been added to the fiber batt. One embodiment for the ejector  22  is illustrated in FIG. 6 in which a single broad ejector is used to deposit the coating material  23  on the surface of the fiber batt  10 . 
     FIG. 7A illustrates a cross-sectional of a fiber batt  10  in which three coating layers  21  have been formed through the fiber batt and a surface layer  25  has been formed on or at a main surface  11  of the fiber batt. FIG. 7B illustrates the same fiber batt  10  after it has passed through splitters  20  that are aligned with each of the coating layers  21  to produce standard size fiber batts  10   a  having coating layers  21   a ,  21   b  on the exposed edges and a face layer  25   a  on the main surface. 
     FIG. 8A illustrates a cross-sectional of an alternative fiber batt  10  in which two coating layers  21 , two smaller reinforcing regions,  26   a  and  26   b , and a larger reinforcing region  27 , have been formed through the fiber batt and a surface layer  25  has been formed on or at a main surface  11  of the fiber batt. FIG. 8B illustrates the same fiber batt  10  after it has passed through a splitter  20  that was aligned with each of the coating layers  21  to produce a fiber batt  10   a  having coating layers  21   a ,  21   b  on the exposed edges, a face layer  25   a  on the main surface, and reinforcing regions  26   a-b ,  27  to adjust the mechanical properties of the resulting batt. As will be appreciated, the sizing, spacing, and material(s) used to form the reinforcing regions may be adjusted to provide a wide range of properties in the resulting fiber batt product. 
     FIG. 9 illustrates a fourth embodiment of the invention that incorporates the addition of a non-woven material into the fiber batt coating. As the fiber batt  10  passes under ejector  22 , a layer  25  or pattern  25   a  of one or more coating materials  23  is formed on or near the surface of the fiber batt. A non-woven fabric  28 , typically taken from a roll  27 , is then applied to fiber batt over the layer  25  or pattern  25   a  of the coating material. The contact between the fabric  28  and the coating material may be maintained by a series of rollers  29   a , or other conventional mechanisms (this includes compression in most cases), until the curing has been completed. The fiber batt is then heated to a temperature sufficient to cure or fuse the coating material, thereby attaching the fabric  28  to the fiber batt. 
     FIGS. 10A and 10B illustrate the construction of the resulting fiber batt product with the non-woven fabric  28  forming the outermost layer of the coating. As illustrated in FIG. 10C, additional ejector heads as provided in FIGS. 1-3 and  5  may also be incorporated into the mechanism of FIG. 9 for creating coating layer regions  21  that can be split into coating layers  21   a-b  and thereby seal the edges of the resulting fiber batt product. Alternatively, the non-woven fabric  28  may be replaced, or supplemented, by a film layer, with the laminated structure then being heat set using one or more hot rolls. 
     As illustrated in FIG. 11, a fifth embodiment of the invention provides for the activation of regions of the fiber batt for receiving the coating material. An activator  30  directs an activator stream onto the fiber batt  10  in order to activate the region that is intended to receive the coating material  15 . The particular method of activation will be determined by the particular combination of fiber batt and coating material that will be used. For instance, the activation may be accomplished by heating narrow regions of the fiber batt  10  to increase the adhesion of the coating material on the heated portions of the fibers that comprise the fiber batt. Alternatively, the activation may comprise an adhesive or solvent that will coat portions of the fiber and increase the retention of the coating materials on the coated portions. 
     As illustrated in FIG. 11, an ejector  30  may be used to apply a stream of an activating liquid  31  to the fiber batt  10 . The penetration of the activating liquid  31  into the fiber batt and/or the removal of excess liquid may be assisted by a corresponding vacuum assembly  32  arranged opposite the ejector  30 . 
     In any event, after activating selected regions of the fiber batt  10 , corresponding ejectors  14  are used to apply the coating material to the activated portions of the fiber batt. The impregnated fiber batt is then heated to cure, set or fuse the coating material to form the desired fiber batt product. After the coating layers have cooled sufficiently, the fiber batt  10  may be split into a number of smaller fiber batts by splitter  20  that separates the fiber batt at the coating layers to form a fiber batt product. 
     As illustrated in FIG. 12, both the activator ejectors  30  and the coating material ejectors  14  (not shown) may be arranged to provide activated regions and coating regions both at the edge of the fiber batt  10  and at one or more positions across the width of the fiber batt that can later be split to form edge coating layers. 
     The description and illustrations of the present invention provided above are merely exemplary in nature and it is anticipated that those of ordinary skill in the art will appreciate that many variations of the specific method and apparatus described are possible without departing from the spirit and scope of the invention.