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  Continuous filament mat and method of makingUSPTO Application #: 20060135017Title: Continuous filament mat and method of making Abstract: The present invention provides an improved method of forming continuous filament mat (CFM) at greater through-put while maintaining or improving product quality by use of a synchronized draw process. The synchronized draw process provides CFM having improved weight variation, structure and tensile strength is capable of operating at increased mat line speed. CFM produced may have controlled mat density, MD density variation, CM density variation, MD tensile strength and CM tensile strength by controlling the period, frequency and interval of the deposited fiber strands. Using the synchronization technology of the present invention it is possible to control the tensile strength ratio (MD/CD) to meet a specific customer need by adjusting the LFR, frequency, period, and line speed. The method of the present invention provides for increasing the throughput of specialized and costly CFM manufacturing equipment without substantial expenditure. (end of abstract) Agent: Owens Corning - Granville, OH, US Inventors: Jeng Lin, Eugene V. Galloway, Frank Peel, Axel Larsen USPTO Applicaton #: 20060135017 - Class: 442327000 (USPTO) Related Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Nonwoven Fabric (i.e., Nonwoven Strand Or Fiber Material) The Patent Description & Claims data below is from USPTO Patent Application 20060135017. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION [0001] The present invention relates to an improved continuous filament mat (CFM) having improved weight variation along the length of the mat and a method of making such a mat. BACKGROUND OF THE INVENTION [0002] Continuous Filament Mat (CFM) is a continuous reinforcement fiber, non-woven mat containing a resin compatible binder. CFM is used with polyester, vinyl esters urethanes and other compatible resin systems. It includes continuous fibers randomly oriented in multiple layers with a suitable bonding resin and typically contains a silane coupling agent. CFM is particularly suitable for compression molded electrical and non-electrical laminates, as well as for use in pultrusion processes or any process in which a smooth surface is desired. CFM is used in many fiberglass reinforced plastic (FRP) structural applications such as: compression molding, infusion molding, filament winding, pultrusion, reaction injection molding (RIM), resin transfer molding (RTM), and vacuum bagging. The finished molded products have high equiaxial strengths. Typical products are marine railings, window frames, boat parts, high voltage transformers and corrosion resistant pipes. CFM may also be combined with a woven roving to make a combination mat that has superior processability and structural properties. The reinforcing filaments typically thermoplastic fibers such as glass or polymeric fibers; however, any fiber such as carbon and aramid fibers may be used. For the purposes of the present application, the invention will be described using glass fibers as an example. [0003] Compression molding is a mass production method where molding compounds and other resin glass combinations are compressed in matched metal tools located between platens in a press. Typically, pressures of 150 lbs/in.sup.2 and temperatures between 265.degree. F. (130.degree. C.) and 340.degree. F. (170.degree. C.) are used to achieve cycle times of 2-3 minutes. Molding compounds of a thermoset resin, chopped roving, fillers and a catalyst are used in sheet molding compound (SMC). SMC is placed in the tool and covered with a layer of CFM to produce a Class A surface on parts such as automotive body panels, appliance housings and composite doors, [0004] Infusion molding processes such as vacuum assisted resin transfer molding (VARTM) use a single-sided mold that is covered with CFM and other reinforcements and sealed with a flexible vacuum bag or film. A vacuum is drawn on the space between the mold and the seal containing the reinforcements, and a thermoset resin is allowed to infiltrate the reinforcements. The resin flows through the reinforcements and cures to form the finished composite. Large high reinforcement content structural composite parts can be produced to make parts such as boat hulls and windmill blades. [0005] Pultrusion is a continuous process for making lightweight lineal profiles such as reinforcing rods, I-beams and tubing. Pultruded parts incorporate a variety of reinforcements ranging from TYPE 30 single-end roving (available from Owens Corning of Toledo, Ohio), bulky roving, surfacing veils, CFM and woven glass fabrics. After the reinforcement is impregnated with resin, the material is pulled through a heated die that gives it a cross-sectional shape, and is then cured to create the composite profile. [0006] Resin Transfer Molding (RTM) is a liquid molding process where a thermosetting resin is injected into a closed mold cavity to make moderate volume semi-structural or appearance parts. CFM, fabrics, multi-end preform rovings, veils, chopped strand mat and directed fiber preforms can be used in resin transfer molding as reinforcements. In RTM, the dry fiber reinforcement is placed in the bottom half of matching molds, the mold is closed and sealed, and then resin is slowly pumped into the mold. The resin wets through the reinforcement fibers and solidifies to form a composite part such as semi-truck parts and electrical cabinets. The molding pressure is typically lower in RTM than in the compression molding process, therefore, tooling and equipment capital costs are lower than high volume compression molding, but higher than open molding processes. [0007] Vacuum bagging is used to tightly consolidate composites used in windmills, aerospace parts and other applications. Materials that are pre-impregnated with resin are typically laminated with vacuum bagging. The components include a film or fabric, breather medium and plastic film that is applied in sequence on top of a laminate stack in an airtight mold. Air between the mold and film is extracted with a vacuum pump, resulting in a positive-pressure force. This compression forces air and excess resin from the composite laminate or components. Vacuum bagging is also used in conjunction with other processes such as infusion molding and wet lay-up. [0008] CFM is formed by reciprocally depositing continuous reinforcing filaments across the width of a moving conveyor. Typically, a CFM line includes 6-20 fiber draw positions from a source that randomly deposit the fibers across the width of the conveyor. The fiber draw positions may include an idler wheel, a pull wheel and an oscillating finger wheel within the pull wheel. Fibers are drawn from the fiber source, around the idler wheel and over the pull wheel. The oscillating finger wheel penetrates the pull wheel to determine the angle at which the fibers are thrown from the wheel and hence, the position across the width of the conveyor. As the finger wheel oscillates, the fibers are deposited on the conveyor in a saw-tooth pattern having defined period (P). The fibers are thrown from the pull wheel faster than the fibers traverse the width of the conveyor so that the fibers form loops on the conveyor. As shown in EQ. 1, the loop formation ratio (LFR) is proportional to the pull speed (S.sub.p) of the fibers divided by the throw length (L) and the frequency (f). As shown in EQ. 2, the period (P) is proportional to the mat line speed S.sub.ml, divided by the frequency (f). LFR = S p / ( 2 .times. Lf ) ( 1 ) P = S ml / f ( 2 ) [0009] In prior art CFM processes each draw position deposits the fibers independently of the other draw positions in the line. FIG. 1A shows a graph of the relative weight verses the location in the machine direction of a CFM mat produced on a 12 draw position line at a frequency of 60 oscillations per minute (OPM), a line speed of 33 feet per minute (FPM), and a period of 6.5 inches. The peak to valley weight variation along the length of the mat ranges from 8-18 % by weight. [0010] As the LFR approaches 10, the fibers are deposited in random loops on the collection conveyor. With a decreasing LFR, the loops become less random and the fibers tend to lie transverse to the length of the collection conveyor. At an LFR of 3.25 a distinct transverse array becomes visible and at a LFR of less than about 2.5 the fibers are substantially transverse to the collection conveyor. A high LFR is preferred in CFM because the random loop pattern increases the tensile strength of the mat. A lower LFR provides a mat having a higher tensile strength in the cross-machine direction and a decreased tensile strength in the machine direction. [0011] In the prior art CFM processes, weight distribution in the mat was related to the mat line speed (S.sub.ml) and period. Increased mat line speed increased the variation in weight distribution. In order to control the variation, frequency (f) was increased; however, with increased frequency the loop formation ratio decreases and hence the fibers are deposited on the collection conveyor in relatively straight arrays rather than being deposited in loops. In the prior art processes, a period in excess of about 180 mm causes a standard deviation of the weight of the mat in the machine direction to increase above about 2.2, which a variation that is not acceptable for use in a number of composite fabrication processes. Since an increased mat line speed (S.sub.ml) increases the oscillation period (P), the maximum line speed is governed by the weight distribution acceptable for use in the composite fabrication process. [0012] FIG. 1A shows the weight distribution in the machine direction of CFM manufactured in accordance with the prior art process. The CFM line includes 12 draw positions each operating at random, the frequency (f) is 60 OPM with a line speed of 33 FPM with a period of 6.5 in. The mat is built up from the 12 draw positions which are independent of one another and provide a peak to valley variation in weight that ranges from 8% to 18%. This variation in weight is increased when fiber draw positions are taken off-line due to equipment failures or for maintenance. [0013] The limitations on frequency (f), LFR and mat line speed (S.sub.ml) prevent the prior art CFM process from producing mat having a suitable tensile strength at commercially desirable high speeds. New technologies in the composite glass industry, such as gas-oxygen fired furnaces, have increased the melting capacity of furnaces used to produce glass fibers. The increased melting capacity has created a bottleneck in the production line at the CFM line. Additional CFM lines require substantial capital and it is desired to utilize the additional melting capacity while avoiding the capital cost of building new fiber forming and CFM lines. SUMMARY OF THE INVENTION [0014] The present invention provides an improved method of forming continuous filament mat at greater through-put while maintaining or improving product quality by use of a synchronized draw process. The synchronized draw process provides CFM having improved weight variation is capable of operating at increased mat line speed (S.sub.ml) and provides CFM having improved structure and tensile strength. [0015] The synchronized draw process may be performed on a standard CFM line with little additional hardware and hence at low cost. The additions to the CFM line include a master PLC 50 that is in communication with forming position 12 via PLC linkage 52. The synchronized draw process may also include a master encoder 54 downstream from the forming position 12 to provide conveyor speed and position data to the master PLC 50 so that the forming position 12 may be individually controlled. BRIEF DESCRIPTION OF THE DRAWING [0016] FIG. 1A is a graphical representation of the weight distribution in the machine direction of CFM manufactured in accordance with a prior art process. [0017] FIG. 1B is a graphical representation of the weight distribution in the machine direction of CFM manufactured in accordance with one aspect of the present invention. [0018] FIG. 2 is an elevation view of a forming position of the present invention including an oscillating servo drive. [0019] FIG. 3 is a schematic view of the CFM line of the present invention including a master PLC in communication with forming position via PLC linkage. [0020] FIG. 4A and 4B are of the profile of fibers deposited on a forming conveyor in the manufacture of a CFM in accordance with the present invention. Continue reading... Full patent description for Continuous filament mat and method of making Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Continuous filament mat and method of making patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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