METHOD FOR DISPENSING RESINATED REINFORCEMENT FIBERS

Abstract: A method for dispensing reinforcement fibers to make a preform or laminate includes winding a continuous length of a reinforcement fiber (16) into coils (28) around a form (52) having a longitudinal axis, moving the coils axially with respect to the form to engage a cutter (60), cutting the coils to form discrete length reinforcement fibers (64), applying a resinous material to the discrete fibers, and dispensing the discrete length reinforcement fibers (78).

Description: METHOD FOR DISPENSING RESINATED REINFORCEMENT FIBERS TECHNICAL FIELD This invention pertains to dispensing reinforcement fibers, particularly in the manufacture of a preform suitable for reinforcing molded articles, such as structural composites. More particularly, the invention pertains to receiving a continuous length of a reinforcement fiber, cutting the reinforcement fiber into discrete lengths, and dispensing the discrete lengths onto a collecting surface. BACKGROUND Structural composites and other reinforced molded articles are commonly made by resin transfer molding and structural resin injection molding. These molding processes have been made more efficient by pre-forming the reinforcement fibers into a reinforcement layer or mat, which is the approximate shape and size of the molded article, prior to inserting the reinforcements into the mold. To be acceptable for production at an industrial level, a fast preforming process is required. In the manufacture of preforms, a common practice is to supply a continuous length of reinforcement strand or fiber to a chopper, which chops the continuous fiber into many discrete length fibers, and deposits the discrete length fibers onto a collection surface. This process can be used to make preforms in an automated manner by mounting the reinforcement dispenser for movement over the collection surface, and prograniming the movement of the dispenser to apply the reinforcement fibers in a predetermined, desired pattern. The reinforcement dispenser can be robotized or automated, and such reinforcement fiber dispensers are known art for such uses as making preforms for large structural parts, as in the auto industry, for example. Typically, the preforms are dusted with a powdered binder, and placed into a mold. The heat and pressure of the mold sets the binder, producing a preform of reinforcement fibers which can be stored and shipped to the ultimate molding customer which applies resin to the preform and molds the resinated preform to make a reinforced product, typically using a resin injection process. The process of cutting continuous reinforcement fibers into discrete lengths of reinforcement fibers is useful in the manufacture of laminates as well as in the manufacture of preforms. Dispensers of reinforcement fibers for the manufacture of laminates can also be adapted to be moveable and programmable. As the technical requirements for reinforcement products increases, new methods for dispensing and laying down reinforcement fibers are required. One requirement is that the reinforcement fibers be delivered at faster speeds than used previously. Another requirement is mat me reinforcement fibers be laid down in a predetermined orientation. The advancement in the preform making technology enabling a moveable and programmable reinforcement fiber dispenser has led to requirements for very sophisticated fiber patterns and orientations. Preforms can be designed with specific amounts and orientations of reinforcement fibers to improve the strength of the molded product precisely at the weakest or most stressed location of the product to be molded. Because of this new sophistication, there often is a requirement that the fibers be laid onto the collecting surface in a closely spaced, parallel arrangement. Efforts to deliver closely spaced, generally parallel fibers have not been successful, especially at the high speeds necessary for commercially successful operations. When typical strand chopper nozzles are operated at a faster speed, the resulting discrete reinforcement fibers cannot be successfully laid down in a parallel, closely spaced orientation. The fibers are directed toward the collecting surface in a direction generally perpendicular to the collection surface, and this procedure does not tend to leave the fibers generally parallel and closely spaced. Further, typical nozzle dispensing devices use an air flow to guide the reinforcement fiber into engagement with the chopper blade, and to dispense the discrete fibers after cutting, thereby introducing turbulence to the preform collection surface. It is clear that improvements in cutting continuous reinforcement fibers into discrete lengths and dispensing them in a closely spaced, generally parallel arrangement would be desirable. DISCLOSURE OF INVENTION There has now been developed a method and apparatus for dispensing reinforcement fibers which overcome the disadvantages of previously developed methods. The method of the invention winds the continuous reinforcement fiber around a form, such as a cylinder or a pair of rods, to form loops or coils. The coils are then slid or moved axially of the form where the coils engage a cutter. The coils are cut into discrete length fibers, and they are dispensed in a generally parallel, closely spaced arrangement. The method of the invention enables the input speed of the continuous fiber to increase, while still delivering the discrete reinforcement fibers in an orientation generally parallel to the collection surface. According to this invention, there is provided a method for dispensing reinforcement fibers comprising winding a continuous length of a reinforcement fiber into coils around a form having a longitudinal axis, moving the coils axially with respect to the form to engage a cutter, cutting the coils to form discrete length reinforcement fibers, and dispensing the discrete length reinforcement fibers. Generally, the discrete length reinforcement fibers are dispensed in an axial direction with respect to the form, although they could be dispensed in another direction by means of an air jet or baffle if desired. The method of the invention enables the discrete length reinforcement fibers to be dispensed relatively parallel to each other. If the collection surface is generally horizontal, the discrete length reinforcement fibers can be dispensed generally parallel to the collecting surface. In a specific embodiment, the discrete length reinforcement fibers are oriented generally perpendicular to the axis of the form as they are dispensed. In a specific embodiment of the invention, the form around which the continuous reinforcement fiber is wound to form the coils comprises two or more rods. The form can also be a cylinder around which the continuous reinforcement fiber is wound into coils. In another embodiment, the form is a conical member around which the continuous reinforcement fiber is wound into coils. In yet another embodiment of the invention, the cutter is a knife blade. The cutter can be adapted to cut each coil once to make a single discrete length reinforcement from each loop, or two or more cutters can be used to make two or more discrete length reinforcements from each loop. A guide can be used to direct the discrete length reinforcements so that they are dispensed generally parallel to each other. In a preferred embodiment of the invention, the movement of the coils axially with respect to the form to engage the cutter is accomplished by engaging the coils with a helical surface, which may be one or more helical springs which rotate relative to the coils. In yet another embodiment of the invention, the discrete length fibers are resinated prior to being dispensed. According to this invention, there is also provided apparatus for dispensing reinforcement fibers comprising a form having a longitudinal axis, a winder for winding a continuous length of a reinforcement fiber into coils around the form, a cutter for cutting the coils to form discrete length reinforcement fibers, a coil mover for moving the coils axially with respect to the form to engage the cutter and dispense the discrete length reinforcement fibers. BRIEF DESCRIPTION OF DRAWINGS * Figure 1 is a schematic view in perspective illustrating a reinforcement dispenser depositing discrete reinforcement fibers onto a preform molding surface. Figure 2 is a schematic cross-sectional view in elevation of the reinforcement dispenser for dispensing reinforcement fibers according to the invention, with the helical spring removed for clarity. Figure 3 is a schematic cross-sectional view in elevation of a portion of the reinforcement dispenser of Fig. 2, showing the helical spring. Figure 4 is a cross-sectional plan view taken along line 4-4 of Fig. 3. Figure 5 is a cross-sectional view in elevation taken along line 5-5 of Fig. 4. Figure 6 is a schematic cross-sectional view in elevation of an alternative apparatus for carrying out the method of the invention. Figure 7 is a schematic cross-sectional view in elevation of yet another apparatus for carrying out the method of the invention. Figure 8 is a schematic partially cut away plan view of apparatus for applying resin to the discrete fibers according to the method of the invention. Figure 9 is a cross-sectional view in elevation of the apparatus of Figure 8. taken along line 9-9. Figure 10 is an exploded cross-sectional view in elevation of the apparatus of Figure 9, taken along line 10-10. REST MODE FOR CARRYING OUT THE INVENTION As shown in Fig. 1, a robotized reinforcement dispenser 10 is positioned to deposit discrete reinforcement fibers 12 onto a collection surface, such as preform molding surface 14. Typically the preform molding surface is a screen. The reinforcement dispenser need not be robotized or automated, and could even be stationary with the collection surface being moveable. A source of vacuum is usually positioned beneath the screen to facilitate the preform making process. Continuous reinforcement fiber 16, supplied from a source not shown, is transported to the fiber dispenser where the continuous reinforcement fiber is chopped or cut to produce the discrete length reinforcement fibers. The continuous reinforcement fiber can be any material suitable for reinforcement purposes. A preferred material is Type 30® glass fibers, available from Owens-Coming Fiberglas Corporation, Toledo, Ohio, although other mineral fibers and organic fibers, such as polyester, Kevlar® and carbon fibers, can be used with the invention. It is to be understood that the continuous fiber can be a single filament (monofilament) or a strand comprised of numerous filaments. As shown in Fig. 2, the continuous reinforcement fiber is fed into the dispenser by means of feed wheels 20, which also act to reduce the tendency of fiber twist to migrate upstream toward the continuous reinforcement source. The continuous fiber is then fed along the outer surface of a rotating member, such as rotor 22. The rotor can be mounted for rotation by any suitable means, such as by motor 24. Positioned downstream from the rotor is a form around which the continuous reinforcement fiber is wound by the rotating action of the rotor. The form can be of any shape suitable for receiving the windings of the continuous reinforcement fiber. In the embodiment shown in Fig. 2, the form comprises a pair of rods 26 around which the continuous reinforcement fiber is wound into a series of generally parallel loops or coils 28. The form (or rods 26) is not shown as moving, but it has a longitudinal axis 30, which may also be colinear with the axis of revolution of the rotor. It is to be understood that in an alternative design the form (i.e., the rods) could be rotated, and the rotor could be stationary. In this arrangement the same result of winding the continuous reinforcement fiber into coils around the form would be provided. Also, both the form and the rotor could be mounted for rotation, and could be rotated at different rates to enable the continuous fiber to be wound around the form to create the coils. Once the coils are positioned around the form, the coils are moved down stream, axially of the form (to the left in Fig. 2). Any means can be used to move the coils axially with respect to the form. As shown in Fig. 3, the coils can be moved downstream by the action of a helical surface, such as helical spring 32. For purposes of illustration the helical spring is not shown in Fig. 2. The helical spring is mounted for rotation by any suitable means, such as spring shaft 34. Rotation of the helical spring causes the surface of the spring to engage the coils of the continuous fiber and to urge the coils axially with respect to the form. Another means to move the coils axially with respect to the form is a vibrational system which vibrates the rods and uses gravity to cause the coils to move downwardly. As the coils are moved axially with respect to the form, they are engaged by a cutter which makes one or more cuts in each loop or coil 28. The cutter can be of any type capable of severing the continuous reinforcement fiber into discrete lengths of fibers 12. Examples of cutters include heating devices and lasers. As shown in Figs. 3-5, the cutter can be a knife mounted on the form itself, such as knives 36 mounted on each of the rods 26. Positioned adjacent the knives are cot rolls or cots 38 which act to press the continuous reinforcement fiber sharply into the knife to insure cutting rather than merely dragging the fiber across the knife. Cots used with cutters are well known, and can be of any suitable material. The cots can be mounted for rotation if desired. As shown in Fig. 5, after the coils 28 are cut by the knife, they travel downwardly as discrete lengths of fibers 12. In order to insure that the discrete lengths of fibers are laid down in a generally parallel, closely spaced fashion on the preform molding surface, a guide, such as plates 40 can be used. The plates help align the discrete length fibers, and insure that they are dispensed in a controlled, uniform manner. Preferably, the discrete length fibers are dispensed in an axial direction with respect to the rods, but baffles or air jets could be used to dispense the discrete length fibers in other directions. Since the discrete length fibers are formed by cutting the coils, they are oriented generally perpendicular to the axis of the form as they are dispensed, and are generally parallel to the preform molding surface 14. Although the form around which the continuous reinforcement fiber 16 is wound is shown in Figs. 2-5 as a pair of rods 26, the form can be of other configurations. For example, the form can be three generally parallel rods. The form could be a cylinder. The form could also be a conical member, as shown in Fig. 6. Conical member 42 is mounted for rotation, by means not shown, positioned downstream from rotor 22. The rotor is rotated to distribute the continuous reinforcement fiber 16 into coils 28 wrapped around the conical member. The coils are engaged or grabbed by any suitable means, such as a conveyor or belt 44 and pulled or moved axially with respect to the form, i.e., the conical member. Positioned opposite the belt is a cutter, which can be in the form of a cutter wheel 46 and a cot wheel 48. As the coils are pulled axially with respect to the conical member by the belt (to the left, as shown in Fig. 6), the coils will be cut to form discrete length fibers 12. The method of dispensing discrete length fibers using two knives, as shown in Figs. 2-5, results in two discrete fibers for each of the coils 28. Using only one knife, as shown in Fig. 6, results in only one discrete fiber for each coil. In such a case, it may be advantageous for the fiber handling apparatus, such as modified guide plates, not shown, to be adapted to open up the discrete length fibers after cutting, and align them in a generally parallel orientation. As shown in Fig. 7, the form around which the continuous reinforcement fiber 16 is to be wound can be a pair of rotating helical screws 50. The coils 28 are wound around the helical screws by the rotor 22. The rotating action of the helical screws forces the coils to move axially with respect to the form, i.e., the helical screws, and into engagement with the knife 36. Although two knives are shown in Fig. 7, one knife could be used. The knives cut the coils into discrete lengths of fibers which are dispensed in an axial direction with respect to the form (helical screws). As shown in Figs. 8, 9 and 10, the discrete length reinforcement fibers can be resinated before they are dispensed. The continuous reinforcement fiber 16 is fed into the dispenser and then fed along the outer surface of the rotating rotor 22. The continuous fiber is wound into coils 28 around the form 52, which can be of any shape suitable for receiving the windings of the continuous reinforcement fiber. The form has a longitudinal axis 30, which may also be colinear with the axis of revolution of the rotor. Once the coils are positioned around the form, the coils are moved downstream, axially of the form (to the right in Figs. 8 and 9). The coils are moved downstream by the action of top and bottom conveyor belts 54 and 55, respectively, which are positioned on both sides of a wedge shaped merge plate 58, as shown most clearly in Fig. 9. The top conveyor 54 does not extend across the whole width of the form 52, and is positioned between two knife blades in the form of knife wheels 60 (only one of which is shown in Fig. 8). The knife wheels pinch the coils 28 against cot rolls 62 to cut the coils into discrete length reinforcement fibers 64. These discrete fibers are moved in the downstream direction as two streams of discrete fibers by the action of the top and bottom conveyor belts 54 and 55, which hold the discrete fibers in contact with the upper and lower surfaces 56 and 57, respectively, of wedge shaped merge plate 58. The two streams of discrete fibers 64 merge at the downstream end of the merge plate to form a combined stream of discrete fibers moving axially with respect to the form, and oriented generally perpendicularly to the axis of the form. At the downstream end of the merge plate 58 is a resin plate 66 having a resin surface 68. The discrete fibers are moved along the resin surface by the action of two relatively wide outer belts 70 and 72, and a narrow inner belt 74. The discrete fibers could also be moved by any other suitable means, such as a wheel or plurality of wheels, not shown. As the fibers move along the resin surface, they are oriented generally perpendicularly to the axial direction 30. The beginning edge of the inner belt 74 is downstream from the begiiuiing edges of the two outer belts to avoid interference with the top conveyor belt 54. As the three belts 70, 72 and 74 move the discrete fibers along the resin surface 68, resin is applied to the fibers by injecting the resin through a slot 76 in the resin plate 66 to create resinated fibers 78. The preferred resin is a liquid, although resin in a powder form may also be applied. The resin is supplied to the slot 76 by means of a resin conduit 80 from a source, not shown. Although a slot is shown, the resin can be injected through any suitable opening in the resin surface. As can be seen in Fig. 10, the slot has a length considerably smaller than the length of the discrete fibers 64. The liquid resin is initially applied to the discrete fibers at a central portion 82 of each fiber, and flows or spreads toward the end portions 84 of the fibers as the fibers are moved downstream along the resin surface. By applying the resin under pressure at the central portion and causing the resin to flow, the air surrounding the fibers can be removed, thereby assuring that all of the fibers are coated with resin and that there are no air pockets. The resin injected into the discrete fibers can be a thermoset resin, such as a polyester, epoxy, phenolic or polyurethane resin. The resin can also be a thermoplastic such as Nyrim® resin or others. The discrete fibers can be glass fibers having a weight within the range of from about 300 to about 4800 g/km, and a diameter within the range of from about 8 to about 30 microns. For a roving of 2400 g/km and a diameter of 17 microns, the output would range from about 0.1 to about 5 kg glass fibers per minute, with a total output (resin and glass) within the range of from about 0.2 to about 15 kg per minute. It will be evident from the foregoing that various modifications can be made to this invention. Such, however, are considered as being within the scope of the invention. INDUSTRIAL APPLICABILITY The invention can be useful in making preforms, prepregs and SMC, suitable for molding processes and in making reinforced laminates.

Claims: CLAIMS 1. A method for dispensing reinforcement fibers comprising winding a continuous length of a reinforcement fiber into coils around a form having a longitudinal axis, moving the coils in an axial direction with respect to the form to engage a cutter, cutting the coils to form discrete length reinforcement fibers, applying a resinous material to the discrete fibers, and dispensing the resinated discrete fibers. 2. The method of claim 1 in which the resin is a liquid resin. 3. The method of claim 1 including moving the discrete fibers along a resin surface, and applying the resin to the discrete fibers by introducing the resin through an opening in the resin surface. 4. The method of claim 3 in which the opening is a slot through which the resin is introduced. 5. The method of claim 4 in which the slot has a length which is less than the length of the discrete fibers, and in which the resin spreads from a central portion of the discrete fibers to the end portions of the discrete fibers as the discrete fibers move along the resin surface. 6. The method of claim 3 including moving the discrete fibers along the resin surface with a conveyor. 7. The method of claim 1 in which the step of moving the discrete fibers moves them in an axial direction with respect to the form. 8. The method of claim 7 in which the discrete fibers are oriented generally perpendicularly to the axial direction during the step of moving the discrete fibers along the resin surface. 9. A method for dispensing reinforcement fibers comprising winding a continuous length of a reinforcement fiber into coils around a form having a longitudinal axis, moving the coils in an axial direction with respect to the form to engage a cutter, cutting the coils to form discrete length reinforcement fibers, moving the discrete fibers along a resin surface, applying a liquid resin to the discrete fibers by introducing the resin through an opening in the resin surface, and dispensing the resinated discrete fibers. 10. The method of claim 9 in which the opening is a slot through which the resin is introduced, and the slot has a length which is less than the length of the discrete fibers, and in which the resin spreads from a central portion of the discrete fibers to the end portions of the discrete fibers as the discrete fibers move along the resin surface. 11. The method of claim 9 including moving the discrete fibers along the resin surface with a conveyor. 12. The method of claim 10 in which the step of moving the discrete fibers moves them in an axial direction with respect to the form. 13. The method of claim 1 1 in which the discrete fibers are oriented generally perpendicularly to the axial direction during the step of moving the discrete fibers along the resin surface. 14. The method of claim 13 in which the cutter is a knife blade, and in which the cutter cuts each coil into at least two discrete fibers. 15. A method for dispensing reinforcement fibers comprising winding a continuous length of a reinforcement fiber into coils around a form having a longitudinal axis, moving the coils in an axial direction with respect to the form to engage a cutter, cutting each of the coils to form two streams of discrete length reinforcement fibers, moving the streams of discrete fibers in the axial direction and in contact with the upper and lower surfaces of a wedge-shaped plate, merging the two streams of discrete fibers to form a combined stream of discrete fibers, applying a resinous material to the combined stream of discrete fibers, and dispensing the resinated discrete fibers. 16. The method of claim 15 in which the moving of the stream of the discrete fibers along the upper wedge surface is accomplished by a conveyor, and the moving of the stream of the discrete fibers along the lower wedge surface is accomplished by a conveyor. 17. The method of claim 15 including moving the combined stream of discrete fibers along a resin surface, and applying the resin to the discrete fibers by introducing the resin through a slot in the resin surface. 18. The method of claim 17 in which the slot has a length which is less than the length of the discrete fibers, and in which the resin spreads from a central portion of the discrete fibers to the end portions of the discrete fibers as the discrete fibers move along the resin surface. 19. The method of claim 18 in which the moving of the stream of the discrete fibers along the upper wedge surface is accomplished by a conveyor, and the moving of the stream of the discrete fibers along the lower wedge surface is accomplished by a conveyor. 20. The method of claim 19 in which in which the discrete fibers in the combined stream are oriented generally perpendicularly to the axial direction during the step of moving the combined stream, and in which the combined stream of discrete fibers is moved in an axial direction with respect to the form during the step of moving the combined stream.

Inventors: JANDER MICHAEL J, JANDER, MICHAEL, J.
Applicants: OWENS CORNING S A NV, N.V. OWENS-CORNING S.A.
Application year: 1997
Main classification: B29B11
IPC codes: B29B11, B29C70, B65H54