Abstract:
In the description and drawings a method of forming a fiberglass mat is disclosed. A drum is rotated, a molten fiberglass material is fed through at least one orifice of a furnace while rotating the drum, and the relative position of the orifice with respect to a location on the drum is altered while rotating the drum and feeding the molten fiber glass material through the orifice to build up a fiberglass matt along a traverse length.

Description:
CROSS-REFERENCE TO RELATED DOCUMENTS 
     This Application claims the benefit of Provisional Application Ser. No. 61/233,116 filed Aug. 11, 2009, entitled Method of Forming a Fiberglass Mat, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     This invention pertains to a method of manufacturing a fiberglass mat. 
     2. Description of the Related Art 
     Technology for making a condensed mat of glass fiber strands is known in the art. Such technology includes, for example, the Modigliani process. The Modigliani process is generally described in several patents issued to Modigliani, namely, U.S. Pat. Nos. 2,546,230; 2,609,320 and 2,964,439. Subsequent improvements and variations of the Modigliani process have been made and are known in the art—many of which are described in patents issued subsequent to the Modigliani patents. The aforementioned patents and improvements generally involve a melting furnace feeding molten glass to orifices which discharge fine glass fibers. The fine glass fibers are in turn wrapped circumferentially around a rotating drum. During the deposition of the fibers on the rotating drum, a thermosetting resin may be applied to the surface to hold the fibers at their overlapping junctions between layers. 
     The furnace and/or orifices may move longitudinally back and forth along the rotating drum while the drum remains longitudinally stationary during the assembly process. Alternatively, the furnace and orifices may remain stationary while the drum rotates and moves longitudinally back and forth with respect to the stationary furnace. 
     After a suitable thickness of fibers has been created, the condensed mat may be severed from the drum by, for example, a cut across the mat parallel with the axis of the drum. Thereafter, the condensed mat may be stretched or expanded longitudinally and or latitudinally as desired. 
     SUMMARY 
     Generally, in one aspect, a method of forming a fiberglass mat comprises the steps of rotating a drum, feeding a molten fiberglass material through at least one orifice of a furnace while rotating the drum, and altering the relative position of the orifice with respect to a location on the drum while rotating the drum and feeding the molten fiber glass material through the orifice to build up a fiberglass matt along a traverse length. During at least a portion of building up the fiberglass mat the relative position of the orifice with respect to the location on the drum is moving at a variable speed in a first direction for less than the traverse length then moving at a substantially constant speed in a second direction for less than the traverse length a plurality of times. The first direction is substantially opposite the second direction. 
     In some embodiments the drum is traversable along a drum traverse path substantially parallel with an axis of rotation of the drum. In versions of those embodiments the orifice is traversable along a furnace traverse path substantially parallel with the axis of rotation of the drum. 
     In some embodiments the substantially constant speed is at least three times greater than the maximum speed of the variable speed. In versions of those embodiments the distance of each first direction movement is less than twenty-five percent of the traverse length. In versions of those embodiments the difference in distance between each first direction movement and each second direction movement is less than five percent of the traverse length. In versions of those embodiments the variable speed is sinusoidally variable. 
     Generally, in another aspect, a method of forming a fiberglass mat, comprises the steps of rotating a drum, feeding a molten fiberglass material through at least one orifice of a furnace while rotating the drum, and traversing one of the drum and the furnace back and forth along a traverse path such that a first end thereof moves between a first traverse location and a second traverse location while maintaining the other of the drum and the furnace in a substantially stationary position while rotating the drum and feeding the molten fiber glass material through the orifice to build up the fiberglass mat. The traverse path is generally perpendicular to the rotation of the drum. A plurality of traverses of the first end between the first traverse location and the second traverse location are fiber curl traverses. During at least a portion of movement of the first end between the first traverse location and the second traverse location during the fiber curl traverses the first end is: moving along the traverse path in a first direction from a first location between the first traverse location and the second traverse location, the first location being more proximal the first traverse location than the second traverse location; stopping at a second location between the first traverse location and the second traverse location, the second location being more proximal to the second traverse location than the first location is to the second traverse location; moving along the traverse path in a second direction generally opposite the first direction; stopping at a third location between the first traverse location and the second traverse location, the third location being more proximal to the first traverse location than the second location is to the first traverse location; and moving in the first direction. 
     In some embodiments the third location is between the first location and the second location. 
     In some embodiments the third location is between the first location and the first traverse location. In versions of those embodiments the step of stopping at a fourth location between the first traverse location and the second traverse location more proximal to the second traverse location than the third location is to the second traverse location. In versions of those embodiments the fourth location is between the second location and the second traverse location. In versions of those embodiments the first end of the drum is traversed back and forth along the traverse path between the first traverse location and the second traverse location while maintaining the furnace in a substantially stationary position. 
     Generally, in another aspect, a method of forming a fiberglass mat, comprises the steps of rotating a drum, feeding a molten fiberglass material through at least one orifice of a furnace while rotating the drum, and traversing one of the drum and the furnace back and forth along a traverse path such that a first end thereof moves between a first traverse location and a second traverse location while rotating the drum and feeding the molten fiber glass material through the orifice to build up the fiberglass mat. A plurality of traverses of the first end between the first traverse location and the second traverse location are fiber curl traverses. During a portion of movement of the first end between the first traverse location and the second traverse location during the fiber curl traverses the position of the first end is: moving at a variable speed along the traverse path in a first direction from a first location between the first traverse location and the second traverse location, the first location being more proximal the first traverse location than the second traverse location; stopping at a second location between the first traverse location and the second traverse location, the second location being more proximal to the second traverse location than the first location is to the second traverse location; the distance between the first location and the third location is less than twenty-five percent of the distance between the first traverse location and the second traverse location; moving along the traverse path in a second direction generally opposite the first direction; stopping at a third location between the first traverse location and the second traverse location more proximal to the first traverse location than the second location is to the first traverse location; the distance between the second location and the third location is less than twenty-five percent of the distance between the first traverse location and the second traverse location; and moving at a variable speed in the first direction. 
     In some embodiments movement in the second direction is at a second variable speed distinct from the first variable speed. 
     In some embodiments movement in the second direction is at a substantially constant speed. In versions of those embodiments the third location is between the first location and the first traverse location. In versions of those embodiments the distance between the third location and the first location is less than five percent of the distance between the first traverse location and the second traverse location. In versions of those embodiments the substantially constant speed is at least three times greater than the maximum speed of the variable speed. 
     In some embodiments the distance between the third location and the first location is less than one percent of the distance between the first traverse location and the second traverse location. 
    
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATIONS 
         FIG. 1  is a front view of a stationary furnace and a traversable drum that may be utilized in embodiments of the method of manufacturing a fiberglass mat of the present invention; 
         FIG. 2  is a front view of a traversable furnace and a stationary drum that may be utilized in embodiments of the method of manufacturing a fiberglass mat of the present invention; 
         FIG. 3A  is a graphical depiction of an embodiment of a method of forming a skin layer in a fiberglass mat; 
         FIG. 3B  is a graphical depiction of an embodiment of a method of forming a loft layer in a fiberglass mat; 
         FIG. 4  is a graphical depiction of an embodiment of a method of forming a fiber curl layer in a fiberglass mat; 
         FIG. 5  is a graphical depiction of a second embodiment of a method of forming a fiber curl layer in a fiberglass mat; 
         FIGS. 6A-1  and  6 A- 2  are tables having a plurality of values for three of the lines depicted in the graphical depiction of the second embodiment of a method of forming a fiber curl layer in a fiberglass mat of  FIG. 5 ; 
         FIG. 6B  is a table having a plurality of values for two of the lines depicted in the graphical depiction of the second embodiment of a method of forming a fiber curl layer in a fiberglass mat of  FIG. 5 ; 
         FIG. 7  is a graphical depiction of a third embodiment of a method of forming a fiber curl layer in a fiberglass mat; and 
         FIGS. 8A and 8B  are tables having a plurality of values for each of the lines depicted in the graphical depiction of the third embodiment of a method of forming a fiber curl layer in a fiberglass mat of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” “in communication with” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. 
     Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible. 
     Referring now to  FIG. 1  through  FIGS. 8A and 8B  wherein like numerals refer to like parts, embodiments of a method of manufacturing a fiberglass mat will be described in detail. Referring initially to  FIG. 1 , a furnace  20  and a drum  30  that may be utilized in the embodiments of the method described herein are shown. The furnace  20  may be mounted to a structure in a substantially stationary position. The furnace  20  has a furnace first end  21  and a furnace second end  22 . The furnace  20  has a plurality of orifices  24  provided adjacent the drum  30  through which molten fiberglass material  3  may exit and be deposited onto the drum  30 . The drum  30  has a drum first end  31  and a drum second end  32  and may be traversed along a traverse path generally indicated by a dotted line  5 . The drum  30  may be traversed such that drum first end  31  thereof moves a preselected traverse length between a first drum traverse location  41  and a second drum traverse location  42 . In  FIG. 1  the drum  30  is depicted in solid lines with the first drum end  31  substantially aligned with the first drum traverse location  41 . In  FIG. 1  the drum  30  is also depicted in dotted lines with the first drum end  31  substantially aligned with the second drum traverse location  42 . In some embodiments the drum  30  may be traversed along traverse path  5  by a sprocket and chain drive that may be driven by a variable speed motor controlled by a programmable logic control (PLC). The PLC may in some embodiments replace original eccentric and concentric sprockets in the sprocket and chain drive. In other embodiments the drum  30  may be traversed along traverse path  5  using other technology such as, for example, using a linear drive or using a motor in combination with timing belts. The drum  30  is also rotatable in a direction of rotation indicated generally by arrow  7 . In the depicted embodiment the traverse path  5  is generally parallel with the axis of rotation of the drum  30 . 
     Alternatively, as depicted in  FIG. 2 , the drum  30  may be mounted to a structure in a substantially stationary position. The furnace  20  may be traversed such that the first furnace end thereof moves a preselected traverse length between a first furnace traverse location  141  and a second furnace traverse location  142 . In  FIG. 2  the furnace  20  is depicted in solid lines with the first furnace end  21  substantially aligned with the first furnace traverse location  141 . In  FIG. 2  the furnace  20  is also depicted in dotted lines with the first furnace end  22  substantially aligned with the second furnace traverse location  142 . In some embodiments the furnace  20  may be traversed along a traverse path generally indicated by dotted line  6  by a sprocket and chain drive that may be driven by a variable speed motor controlled by a programmable logic control (PLC). The PLC may replace original eccentric and concentric sprockets in the sprocket and chain drive. In other embodiments the drum  30  may be traversed along traverse path  5  using other technology such as, for example, using a linear drive or using a motor in combination with timing belts. In the depicted embodiment the traverse path  6  is generally parallel with the axis of rotation of the drum  30 . 
     The drum  30 , the furnace  20 , and interaction between the drum  30  and the furnace  20  are shown in  FIGS. 1 and 2  are described herein in detail. One skilled in the art will realize that the embodiments of a method of manufacturing a fiberglass mat described herein may also be utilized with a drum, a furnace, and/or interactions between a drum and a furnace that may vary in one or more respects from those shown in  FIGS. 1 and 2 . For example, in some embodiments both the furnace and the drum may be traversable to build up a fiberglass mat along a traverse length. Also, for example, in some embodiments the traverse length of the drum  30  and/or the furnace  20  may be altered such that less than or more of the drum  30  will be covered with a fiberglass mat. Throughout the remainder of this detailed description it will often be referenced that the first drum end  31  of drum  30  is being traversed between the first traverse location  41  and the second traverse location  42  and that the furnace  20  is remaining substantially stationary. Such description herein is for ease in description only and should not be regarded as limiting. 
     In  FIGS. 3A and 3B , two traditional methods of forming a layer in a fiberglass mat are generally depicted in graphical form. In traditional methods of forming a layer in a fiberglass mat the drum  30  is traversed back and forth from the first traverse location  41  to the second traverse location  42  at either a constant (concentric) or a varying (eccentric) speed. The drum  30  is moving in a single direction only as drum first end  31  traverses from the first traverse location  41  to the second traverse location  42  and drum  30  moves in a single opposite direction as drum first end  31  traverses from the second traverse location  42  to the first traverse location  41 . Typically, a single direction substantially constant speed is used to form skin or backing layers and a variable speed, such as, for example, a sinusoidally variable speed, is used to form lofting layers. 
     Referring particularly to  FIG. 3A , a skin layer traverse as drum first end  31  moves from the first traverse location  41  to the second traverse location  42  and a skin layer traverse as drum first end  31  moves from the second traverse location  42  to the first traverse location  41  is graphically depicted. The left most horizontal location in the graph of  FIG. 3A  represents the positioning of the first traverse location  41 . The right most horizontal location in the graph of  FIG. 3A  represents the positioning of the second traverse location  42 . Skin line  102  tracks the drum first end  31  as the drum  30  moves at a constant speed, causing the drum first end  31  to move from the first traverse location  41  to the second traverse location  42 . The drum  30  then stops (transitioning around a sprocket in some embodiments) as the drum first end  31  reaches the second traverse location  42  and the drum  30  moves in an opposite direction at substantially the same constant speed. This causes the drum first end  31  to move back in the opposite direction to the first traverse location  41 , as represented by skin line  103 . Multiple substantially constant speed traverses of the drum  30 , wherein the drum first end  31  moves back and forth between the first traverse location  41  and the second traverse location  42  may occur while the drum  30  is rotating to achieve a skin layer. 
     Referring particularly to  FIG. 3B , a body layer traverse as drum first end  31  moves from the first traverse location  41  to the second traverse location  42  and a body layer traverse as drum first end  31  moves from the second traverse location  42  to the first traverse location  41  is graphically depicted. The left most horizontal location in the graph of  FIG. 3B  represents the positioning of the first traverse location  41 . The right most horizontal location in the graph of  FIG. 3B  represents the positioning of the second traverse location  42 . Loft line  104  tracks drum first end  31  as the drum  30  moves at a sinusoidally variable speed, causing the drum first end  31  to move from the first traverse location  41  to the second traverse location  42 . The drum  30  then stops (transitioning around a sprocket in some embodiments) and the drum  30  moves in an opposite direction at a sinusoidally variable speed, causing the drum first end to move from the second traverse location  42  back to the first traverse location  41 , as represented by loft line  105 . Multiple variable speed traverses of the drum  30 , wherein the drum first end  31  moves back and forth between the first traverse location  41  and the second traverse location  42 , may occur while the drum  30  is rotating to achieve a loft or body layer. In alternative embodiments of forming a body layer the centerline, the amplitude, phase and/or frequency of loft line  104  and/or loft line  105  may be adjusted. 
     Referring now to  FIG. 4 , a first embodiment of a method of forming a fiber curl layer in a fiberglass mat is depicted in graphical form. The horizontal axis in the graph of  FIG. 4  represents distance, with the left most location in the horizontal axis representing the positioning of the first traverse location  41 . The right most horizontal location in the graph of  FIG. 4  represents the second traverse location  42 . The vertical axis in the graph of  FIG. 4  represents velocity of the drum  30  in the direction of the traverse path  5 . A positive velocity in  FIG. 4  indicates the drum first end  31  is moving in a direction from the first traverse location  41  to the second traverse location  42  and a negative velocity in  FIG. 4  indicates the drum first end  31  is moving in a direction from the second traverse location  42  to the first traverse location  41 . 
     Still referring to  FIG. 4 , line  111  tracks the drum first end  31  as it moves at a sinusoidally variable speed from a location  121  adjacent the first traverse location  41  to a location  122 , where it comes to a stop. Location  122  is more proximal the second traverse location  42  than location  121  is to the second traverse location  42 . Line  112  tracks the drum first end  31  as it is then traversed in an opposite or reverse direction back toward first traverse location  41  at a substantially constant speed to location  123 , where it comes to a stop. It is understood that in some embodiments the drum  30  may not come to an instantaneous stop and instantaneously reverse paths as depicted in the graph of  FIG. 4 , but instead may require a certain distance to come to a complete stop and a certain distance to reverse paths and ramp up to a desired speed. Location  123  is located between location  121  and location  122 . In some embodiments the substantially constant speed movement may be greater than the maximum speed of the variable speed movement in the opposite direction. For example, in some embodiments, the substantially constant speed movement may be approximately four times greater than the maximum speed of the variable speed movement in the opposite direction. Also, for example, in some embodiments, the substantially constant speed movement may be approximately three times greater than the maximum speed of the variable speed movement in the opposite direction. Line  113  tracks the drum first end  31  as it moves at a sinusoidally variable speed from location  123  to a location  124 , where it comes to a stop. Location  124  is more proximal the second traverse location  42  than location  123  is to the second traverse location  42 . Line  114  tracks the drum first end  31  as it is then traversed in an opposite direction back toward first traverse location  41  at a substantially constant speed to location  125 , where it comes to a stop. Location  125  is located between location  122  and location  123 . Line  115  tracks the drum first end  31  as it moves at a sinusoidally variable speed from location  125  to location  126 , where it comes to a stop. 
     Only a portion of a traverse from first traverse location  41  to second traverse location  42  is illustrated in  FIG. 4 . However, it is clear that the pattern depicted in  FIG. 4  of moving the drum  30  in a first direction at a variable speed for less than the traverse length, then moving the drum  30  in an opposite direction at a substantially constant speed for less than the traverse length may be repeated until a full traverse of the drum  30  has been completed, such that the drum first end  31  has moved from the first traverse location  41  to the second traverse location  42 . Moreover, a similar pattern may be followed as the drum  30  continues to traverse in an opposite direction, such that the drum first end  31  moves from the second traverse location  42  to the first traverse location  41 . A plurality of traverses of the drum  30  back and forth, such that drum first end  31  moves back and forth between first traverse location  41  and the second traverse location  42  may be made while repeating the pattern to produce a fiber curl layer. In some embodiments the fiber curl layer created has an open characteristic, has slightly bundled fibers, and has an increased random curl to the fibers when the fiberglass mat is cut off the drum  30  and subsequently expanded. In some embodiments the slight bundling and added curl of the fibers may provide increased strength in the final filter product. 
     In some embodiments of manufacturing a fiberglass mat, a mat may be manufactured that combines the fiber curl layer described herein with other layers. For example, a skin layer as known in the art and described herein, may comprise a first layer of a mat and may be manufactured by traversing the drum  30  back and forth at a substantially constant speed, wherein drum first end  31  is moved back and forth between first traverse location  41  and second traverse location  42  at a substantially constant speed. A fiber curl layer as described herein may comprise a second layer of the mat and may be formed atop the skin layer. Also, for example, a first skin layer as known in the art and described herein, may comprise a first layer of a mat, a fiber curl layer may comprise a second layer of the mat and may be formed atop the first skin layer, and a second skin layer may comprise a third layer of a mat and be formed atop the fiber curl layer. 
     Also, for example, a skin layer as known in the art and described herein, may comprise a first layer of a mat, a loft or body layer as described herein may comprise a second layer of a mat and may be formed atop the skin layer, and a fiber curl layer may comprise a third layer of the mat and may be formed atop the body layer. The loft or body layer may comprise two or more distinct layers. For example, the drum  30  may be traversed back and forth at a first sinusoidally variable speed having a first amplitude a plurality of times, and then may be traversed back and forth at a second sinusoidally variable speed having a second amplitude a plurality of times. The mats described herein may be subsequently expanded and used in various industries such as, for example, the paint air filtration industry. 
     In accordance with embodiments of the method described herein, many variations may be made to the movement of the drum  30  to produce various products that have one or more fiber curl layers having different visual characteristics, different mechanical characteristics, and/or different filter characteristics. For example, in some embodiments when producing a fiber curl layer it is not necessary that certain movements of the drum  30  be at a substantially constant speed. For example, during a single traverse of the drum  30  along a traverse length, wherein drum  31  moves between first traverse location  41  and second traverse location  42 , the drum  30  may be moved in a first direction at a first variable speed for less than the traverse length, then the drum  30  moved in an opposite direction at a second variable speed for less than the traverse length, and this general movement may be repeated until a single traverse of the drum  30  has been completed. The first variable speed and the second variable speed may vary with respect to one another in a number of ways such as, for example, average speed, maximum speed, minimum speed, amplitude, frequency, and/or waveform. 
     Also, for example, in some embodiments one or more variable speed movements may be non-sinusoidal. Also, for example, in some embodiments the centerline, amplitude, phase and/or frequency of the sinusoidal or other variable speed movement may be increased, decreased, and/or varied during one, multiple, or all traverses. Also, for example, the speed of the variable speed movement and/or of the substantially constant speed movement may be increased, decreased, and/or varied during one, multiple, or all traverses. The rotational speed of the drum  30  may also be increased, decreased, and/or varied during one, multiple, or all traverses. Decreasing the drum rotational speed, for example, while keeping other parameters constant may result in a fiber curl layer wherein the fibers are more coarse and the fiber curl layer is more open. Also, for example, cullet or fiberglass throughput through the furnace  20  may be increased, decreased, and/or varied during one, multiple, or all traverses. Also, for example, the amount of any resin applied to the fiberglass mat may be increased, decreased, and/or varied during one, multiple, or all traverses. 
     Referring now to  FIG. 5 , a second embodiment of a method of forming a fiber curl layer in a fiberglass mat is depicted in graphical form. The horizontal axis in the graph of  FIG. 5  represents distance in inches. The left most location of the horizontal axis represents a location where the drum first end  31  is approximately six inches away from the first traverse location  41 . The right most location in the horizontal axis represents a location where the drum first end  31  is approximately twenty-four inches away from the first traverse location  41  and more proximal to the second traverse location  42 . 
     The vertical axis in the graph of  FIG. 5  represents the fiber angle, in degrees, of molten fiberglass strands  3  that are being deposited from the furnace  20  onto the drum  30 . The fiber angle will be dependent on both the traversing speed of the drum  30  and the rotational speed of the drum  30 . As a result, achieving a constant angle does not necessitate traversing of the drum  30  at a constant speed nor does achieving a variable angle necessitate traversing of the drum  30  at a variable speed. The positive fiber angles indicate the drum  30  is traversing in a direction wherein the drum first end  31  is moving from the first traverse location  41  to the second traverse location  42  and the negative fiber angles indicate the drum  30  is traversing in a direction wherein the drum first end  31  is moving from the second traverse location  42  to the first traverse location  41 . 
     Still referring to  FIG. 5 , line  181  tracks the substantially constant fiber angle of fiber being deposited on the drum  30  as the drum first end  31  moves toward the first traverse location  41  from a location  191  to a location  192 , where it comes to a stop. Location  192  is more proximal the first traverse location  41  than location  191  is to the first traverse location  41 . Location  191  is a location where the drum first end  31  is approximately 23.53 inches from the first traverse location  41 . Location  192  is a location where the drum first end  31  is approximately 8.61 inches from first traverse location  41 . In some embodiments the distance between location  191  and location  192  may be approximately one-sixth of the traverse length. 
     Line  182  tracks the variable fiber angle of fiber being deposited on the drum  30  as the drum  30  is then traversed in an opposite or reverse direction wherein drum first end  31  moves back toward the second traverse location  42  at a variable speed to location  193 , where it comes to a stop. Location  193  is located between location  191  and location  192 . Location  193  is a location where the drum first end  31  is approximately 23.05 inches from the first traverse location  41 . Line  183  tracks the substantially constant fiber angle of fiber being deposited on the drum  30  as the drum  30  moves from location  193  to a location  194 , where it comes to a stop. In the embodiment depicted in  FIG. 5 , the fiber angle of line  183  is the same as the fiber angle of line  181 , although line  183  is depicted offset slightly from line  181  for clarity. Location  194  is more proximal the first traverse location  41  than location  193  is to the first traverse location  41 . In some embodiments the distance between location  194  and location  192  may be less than one percent of the traverse length. Location  194  is a location where drum first end  31  is approximately 8.02 inches from the first traverse location  41 . Line  184  tracks the variable fiber angle of fiber being deposited on the drum  30  as the drum first end  31  moves toward the second traverse location  42  from location  194  to a location  195 , where it comes to a stop. Location  195  is a location where the drum first end  31  is approximately 22.47 inches from the first traverse location  41 . Line  185  tracks the tracks the substantially constant fiber angle of fiber being deposited on the drum  30  as the drum first end  31  moves toward the first traverse location  41  from location  195  to location  196 , where it comes to a stop. In the embodiment depicted in  FIG. 5 , the fiber angle of line  185  is the same as the fiber angle of line  181  and line  183 , although line  185  is depicted offset slightly from line  181  and  183  for clarity. Location  196  is a location where the drum first end  31  is approximately 7.43 inches from the first traverse location  41 . In some embodiments the distance between location  196  and location  194  may be less than one percent of the traverse length. 
     The drum  30  is traversing such that the drum first end  31  is moving from the second traverse location  42  toward the traverse location  41  in  FIG. 5 , whereas the drum  30  is traversing from the first traverse location  41  toward the second traverse location  42  in  FIG. 4 . Also, in  FIG. 5  the movement of the drum is progressing across the traverse length when the constant fiber angle is being deposited, whereas in  FIG. 4  the movement of the drum is progressing across the traverse length when the drum  30  is being moved at a variable speed and variable fiber angles are being deposited. 
     Referring now to  FIGS. 6A-1  and  6 A- 2  and  FIG. 6B , tables are shown that correspond to  FIG. 5  and provide a plurality of location and fiber angle values for lines  181 ,  182 ,  183 ,  184 , and  185 . Locations  191 ,  192 ,  193 ,  194 ,  195 , and  196  are also provided in the tables of  FIGS. 6A-1  and  6 A- 2  and  FIG. 6B  for ease in reference. 
     Only a portion of a traverse showing movement of drum first end  31  from second traverse location  42  to first traverse location  41  is illustrated in  FIG. 5  and depicted in table form in  FIGS. 6A-1  and  6 A- 2 . However, it is clear that the pattern depicted in  FIG. 5  and  FIGS. 6A-1  and  6 A- 2  may be repeated until a full traverse of the drum  30  has been completed. Also, it is clear that in some embodiments when the drum first end  31  reaches either the first traverse location  41  or the second traverse location  42 , drum  30  may reverse traversing directions while either a variable or a substantially constant fiber angle continues to be laid. Moreover, in some embodiments the drum  30  may reverse directions multiple times as drum first end  31  is near a traverse location as it continues to progress through a predetermined pattern. For example, assume a substantially constant fiber angle is being laid on the drum  30  as the drum first end  31  approaches the first traverse location  41  moving in a first direction. The substantially constant fiber angle may continue to be laid as the drum first end  31  reaches the first traverse location  41  and moves in a second direction toward the second traverse location  42 . The drum  30  may then come to a stop and move again in the first direction and a variable angle fiber may be laid on the drum  30  as the drum first end  31  approaches the first traverse location  41  moving in the first direction. The variable angle may continue to be laid as the drum first end  31  reaches the first traverse location  41  and moves in the second direction toward the second traverse location  42 . This may occur a plurality of times while the drum first end  31  is proximal to the first traverse location  41  and/or the second traverse location  42 . 
     Referring now to  FIG. 7 , a third embodiment of a method of forming a fiber curl layer in a fiberglass mat is depicted in graphical form. The horizontal axis in the graph of  FIG. 7  represents distance in inches. The left most location of the horizontal axis represents a location where the drum first end  31  is approximately six inches away from the first traverse location  41 . The right most location in the horizontal axis represents a location where the drum first end  31  is approximately seventeen inches away from the first traverse location  41  and more proximal to the second traverse location  42 . 
     The vertical axis in the graph of  FIG. 7  represents the fiber angle, in degrees, of molten fiberglass strands  3  that are being deposited from the furnace  20  onto the drum  30 . The fiber angle will be dependent on both the traversing speed of the drum  30  and the rotational speed of the drum  30 . The positive fiber angles indicate the drum  30  is traversing in a direction wherein the drum first end  31  is moving from the first traverse location  41  to the second traverse location  42  and the negative fiber angles indicate the drum  30  is traversing in a direction wherein the drum first end  31  is moving from the second traverse location  42  to the first traverse location  41 . 
     Still referring to  FIG. 7 , line  281  tracks the substantially constant fiber angle of fiber being deposited on the drum  30  as the drum first end  31  moves toward the first traverse location  41  from a location  291  to a location  292 , where it comes to a stop. Location  292  is more proximal the first traverse location  41  than location  291  is to the first traverse location  41 . Location  291  is a location where the drum first end  31  is approximately 16.02 inches from the first traverse location  41 . Location  292  is a location where the drum first end  31  is approximately 8.34 inches from first traverse location  41 . In some embodiments the distance between location  291  and location  292  may be approximately one-eleventh of the traverse length. 
     Line  282  tracks the variable fiber angle of fiber being deposited on the drum  30  as the drum  30  is then traversed in an opposite or reverse direction wherein drum first end  31  moves back toward the second traverse location  42  at a variable speed to location  293 , where it comes to a stop. Location  293  is located between location  291  and location  292 . Location  293  is a location where the drum first end  31  is approximately 15.43 inches from the first traverse location  41 . Line  283  tracks the substantially constant fiber angle of fiber being deposited on the drum  30  as the drum  30  moves from location  293  to a location  294 , where it comes to a stop. In the embodiment depicted in  FIG. 7 , the fiber angle of line  283  is the same as the fiber angle of line  281 , although line  283  is depicted offset slightly from line  281  for clarity. Location  294  is more proximal the first traverse location  41  than location  293  is to the first traverse location  41 . In some embodiments the distance between location  294  and location  292  may be less than one percent of the traverse length. Location  294  is a location where drum first end  31  is approximately 7.8 inches from the first traverse location  41 . Line  284  tracks the variable fiber angle of fiber being deposited on the drum  30  as the drum first end  31  moves toward the second traverse location  42  from location  294  to a location  295 , where it comes to a stop. Location  295  is a location where the drum first end  31  is approximately 14.84 inches from the first traverse location  41 . 
     The drum  30  is traversing such that the drum first end  31  is moving from the second traverse location  42  toward the traverse location  41  in  FIG. 7  and the movement of the drum is progressing across the traverse length when the constant fiber angle is being deposited. As described herein, in some embodiments when the drum first end  31  reaches either the first traverse location  41  or the second traverse location  42 , drum  30  may reverse traversing directions while either a variable or a substantially constant fiber angle continues to be laid. Moreover, in some embodiments the drum  30  may reverse directions multiple times as drum first end  31  is near a traverse location as it continues to progress through a predetermined pattern. Also, as described herein, in some embodiments the movement of the drum  30  may alternatively or additionally progress across the traverse length when the variable fiber angle is being deposited. 
     In some embodiments whether the drum  30  progresses across the traverse length when the variable angle is being laid or when the constant angle is being laid may be dependent upon a controller&#39;s analysis of a sine wave having X axis values representative of time and having positive and negative Y axis values. The controller may be in electrical communication with the drum  30  and may cause the drum  30  to move in a certain speed and direction. The controller may cause a variable angle to be laid on the drum  30  when the sine wave has positive Y axis values and may cause a constant angle to be laid on the drum  30  when the sine wave has negative Y values. The sine wave may be shifted along the Y axis as desired to thereby alter the amount of constant and variable fiber angle being laid. Thus, the sine wave may be altered to thereby control whether the drum  30  progresses across the traverse length when the variable angle is being laid or when the constant angle is being laid. 
     Referring now to  FIGS. 8A and 8B , a table is shown that corresponds to  FIG. 7  and provides a plurality of location and fiber angle values for lines  281 ,  282 ,  283 , and  284 . Locations  291 ,  292 ,  293 ,  294 , and  295  are also provided in the table of  FIGS. 8A and 8B  for ease in reference. 
     Only a portion of a traverse showing movement of drum first end  31  from second traverse location  42  to first traverse location  41  is illustrated in  FIG. 7  and depicted in table form in  FIGS. 8A and 8B . However, it is clear that the pattern depicted in  FIGS. 7 and 8A  and  8 B may be repeated until a full traverse of the drum  30  has been completed. Also, it is clear that in some embodiments when the drum first end  31  reaches either the first traverse location  41  or the second traverse location  42 , drum  30  may reverse traversing directions while either a variable or a substantially constant fiber angle continues to be laid. Moreover, in some embodiments the drum  30  may reverse directions multiple times as drum first end  31  is near a traverse location as it continues to progress through a predetermined pattern. 
     In some embodiments the method of forming a fiber curl layer in a fiberglass mat may be utilized to form a final fiberglass product having a rigid fiber curl layer on an air entry side of the fiberglass mat, a fiberglass skin layer on an air exit side of the final fiberglass product, and a fiberglass loft layer between the fiber curl layer and the skin layer. In some embodiments the fiber curl layer may be manufactured in accordance with the third embodiment of  FIGS. 7 and 8A  and  8 B. 
     The rigid fiber curl layer may be relatively open and have a number of fibers consistently bundled together to provide rigidity for structural support. The fiber bundles may be in a generally sinusoidal arrangement when the final fiberglass product is created, providing structural support and rigidity along with filtering capacity. 
     In some embodiments the skin layer may have a thickness of approximately one-quarter of an inch. The body layer may comprise two or more distinct layers. For example, a first loft layer may be immediately adjacent the rigid fiber curl layer and be manufactured by traversing the drum  30  back and forth at a first sinusoidally variable speed having a first amplitude a plurality of times. A second loft layer may be immediately adjacent the skin layer and be manufactured by traversing the drum  30  back and forth at a second sinusoidally variable speed a plurality of times. The second sinusoidally variable speed may have an amplitude that is approximately one-half of the amplitude of the first sinusoidally variable speed. The first loft layer may be less dense than the second loft layer and more corrugated than the second loft layer. In some embodiments the skin layer and the first loft layer may have a plurality of fibers of a substantially common first average diameter and the second loft layer and the rigid fiber curl layer may have a plurality of fibers of a substantially common second average diameter. In some of those embodiments the first average diameter may be approximately 38 microns and in some of those embodiments the second average diameter may be approximately 28 microns. 
     The foregoing description has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is understood that while certain forms of the invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims and allowable functional equivalents thereof.