WO2002026391A1

WO2002026391A1 - Dispensing chopped reinforcement strand using oriented dispensing nozzles

Info

Publication number: WO2002026391A1
Application number: PCT/EP2001/011155
Authority: WO
Inventors: Michael H. Jander
Original assignee: Owens Corning Composites Sprl
Priority date: 2000-09-29
Filing date: 2001-09-26
Publication date: 2002-04-04
Also published as: AU2002213970A1

Abstract

A method of dispensing reinforcement strands including establishing multiple streams of reinforcement strands (19), and chopping the multiple streams of reinforcement strands into multiple currents of discrete reinforcement fibers (65). Each current of the discrete reinforcement fibers is directed into a dispensing nozzle (66) so that the discrete reinforcement fibers travel along a path extending generally along a longitudinal axis (68) of the nozzle. The nozzles are oriented so that the axes of each of the nozzles converge with respect to each other. A flow of the discrete length reinforcement fibers (70) is dispensed from each of the nozzles onto a collecting surface (16).

Description

DISPENSING CHOPPED REINFORCEMENT STRAND USING ORIENTED DISPENSING NOZZLES

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

This invention pertains to dispensing reinforcement fibers, and particularly in the dispensing of chopped reinforcement fibers to form a reinforced article, or to form a reinforcement mat or preform suitable for reinforcing molded articles, such as structural composites. More particularly, the invention pertains to receiving a continuous length of a reinforcement strand or roving, cutting the reinforcement strand into discrete lengths, and , dispensing the discrete lengths onto a collecting surface.

BACKGROUND OF THE INVENTION

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 programming 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 sprayed up or deposited fibers are dusted with a powdered binder, and compressed with a second perforated mold. Hot air and pressure 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. The requirement for the delivery of reinforcement fibers at such high speeds taxes the ability of the equipment to physically supply the strand at the higher speed. One known solution to this problem of throughput limitations is to supply the input roving strand in two streams of roving material, with each of the two streams being emitted from a nozzle onto the preform screen. While the use of multiple streams has enabled an increase in overall throughput, the use of two dispensing nozzles can inadvertently produce patterning or unevenness in the laying down of discrete length fibers. During the preform making process this unevenness requires the application of additional discrete fibers to even out the layers of fibers on the preform. The necessity of the additional application of fibers is time-consuming, thereby increasing the manufacturing cost of the preform products. It would be advantageous if there could be developed a process and apparatus that would enable the time required for preform manufacturing to be reduced.

SUMMARY OF THE INVENTION

The above objects as well as other objects not specifically enumerated are achieved by a method of dispensing reinforcement strands including establishing multiple streams of reinforcement strands, and chopping the multiple streams of reinforcement strands into multiple currents of discrete reinforcement fibers. Each current of the discrete reinforcement fibers is directed into a dispensing nozzle so that the discrete reinforcement fibers travel along a path extending generally along a longitudinal axis of the nozzle. The nozzles are oriented so that the axes of each of the nozzles converge with respect to each other. A flow of the discrete length reinforcement fibers is dispensed from each of the nozzles onto a collecting surface. According to this invention, there is also provided a method of dispensing reinforcement strands including establishing one or more streams of reinforcement strands, and chopping the one or more streams of reinforcement strands into one or more currents of discrete length reinforcement fibers. Each of the one or more currents of discrete length reinforcement fibers is directed into one or more dispensing nozzles so that the discrete reinforcement fibers travel along paths extending generally along the longitudinal axes of the nozzles. Flows of the discrete length reinforcement fibers are dispensed from the one or more nozzles onto a collecting surface according to a fiber distribution pattern. One or more edge plates are positioned relative to the nozzles to intercept some of the dispensed . fibers, thereby modifying the fiber distribution pattern.

According to this invention, there is also provided apparatus for dispensing reinforcement strands, the apparatus including multiple feeders for moving multiple streams of reinforcement strands, and a chopper for chopping each stream of reinforcement strands into multiple currents of discrete reinforcement fibers. A dispensing nozzle receives the discrete reinforcement fibers and dispenses the discrete reinforcement fibers along a path extending generally along a longitudinal axis of the nozzle, wherein the nozzles are oriented so that the axes of the nozzles converge with respect to each other. A collection surface receives the discrete length reinforcement fibers to form a preform. According to this invention, there is also provided apparatus for dispensing reinforcement strands, the apparatus including one or more feeders for moving one or more streams of reinforcement strands, and a chopper for chopping each stream of reinforcement strands into multiple currents of discrete reinforcement fibers. A dispensing nozzle receives the discrete reinforcement fibers and dispenses the discrete reinforcement fibers along a path extending generally along a longitudinal axis of the nozzle, wherein the nozzles are oriented so that the axes of each of the nozzles converge with respect to each other. A collection surface receives the discrete length reinforcement fibers to form a preform. One or more edge plates are positioned relative to the nozzles to intercept some of the dispensed fibers, thereby modifying the fiber distribution pattern. Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view in perspective illustrating a reinforcement dispenser depositing discrete reinforcement fibers onto a preform molding surface according to the method and apparatus of the invention. Figs. 2A and 2B are schematic cross-sectional of a prior art reinforcement dispenser using two nozzles to direct two flows of discrete length reinforcement fibers onto a collecting surface.

Fig. 3 is a schematic cross-sectional view of a reinforcement dispenser of the invention that uses two focused nozzles to direct two flows of discrete length reinforcement fibers onto a collecting surface.

Fig. 4 is a schematic elevational side view of the reinforcement dispenser of Fig. 3.

Fig. 5 is a schematic elevational view of an embodiment of the reinforcement dispenser of the invention, where the reinforcement dispenser includes edge plate for controlling the distribution of the discrete length fibers onto the screen.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

As shown in Fig. 1, a robotized reinforcement dispenser 10, which includes an articulation arm 12, is positioned to deposit discrete reinforcement fibers 14 onto a collection surface, such as preform molding surface 16. 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. The articulation arm can be provided with a hydraulic system or other similar system to enable the articulation arm to be positioned adjacent or above any portion of the collection surface. The movement of the articulation arm can be controlled by a computer, not shown, according to a predetermined pattern so that a desired pattern of reinforcement fiber is laid down on the collection surface. The chopped reinforcement fiber is dispensed by a dispensing unit 18 mounted at the end of the articulation arm 12.

A continuous reinforcement fiber or strand, such as a roving, not shown in Fig. 1 but indicated at 19 in Fig. 4, is supplied from a source not shown, and is transported to the fiber dispenser and through the articulation arm. The continuous reinforcement fiber is chopped or cut at the end of the articulation arm to produce the discrete length reinforcement fibers. The continuous reinforcement fiber can be any material suitable for reinforcement purposes. A preferred material is assembled glass fiber roving, available from Owens Corning, 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 (monfilament) or a strand comprised of numerous filaments. Typically the invention is used with a glass fiber roving consisting of anywhere from about 2200 to about 4800 tex, where a tex is defined as one gram per 1000 meters of filament. Usually the roving is formed by combining a plurality of strands, with each strand being about 25 to about 100 tex.

As shown in Fig. 2A, a prior art dispensing unit includes a strand dispensing apparatus indicated generally at 20 and a strand supply apparatus indicated generally at 22. The stand supply apparatus includes a plurality of generally parallel feeder tubes 24 that receive streams of reinforcement strands from a strand source, not shown. The strands are channeled by flexible conduits 26 into a strand gathering fixture 28. Each strand gathering fixture receives the output from two of the parallel feeder tubes 24 and two of the flexible conduits 26. Positioned beneath each of the strand fixtures 28 are a pair of feeders, which can be in the form of rotatably mounted pull rolls 30 that cooperate to pull the strands from the strand source and into the strand dispensing apparatus 20. Positioned beneath or downstream from the pull rolls 30 is a chopper 34 that is adapted to engage the strand and chop the stand into discrete length reinforcement fibers 14. A dispensing nozzle 36 receives the discrete length reinforcement fibers 14 from the chopper 34 and dispenses them onto the preform molding surface 16. As shown in Fig. 2B, where there are two dispensing nozzles 36, the accumulation 38 of fibers 14 on the preform 16 is in the form of two distinct mounds or ridges 40, sometimes referred to as laminelles. There is a corresponding low spot or valley 42 between the two ridges 40. The ridges and valleys from such a dispensing apparatus create a patterning or unevenness that is undesirable, and additional deposits of discrete length reinforcement fibers 14 are required to provide the desired uniform accumulation of fibers on the preform surface. As shown in Figs. 3 and 4, the dispensing unit 18 of the invention includes a strand supply apparatus 50 similar to that shown in Fig. 2, and a strand dispensing apparatus 52. The strand supply apparatus 50 includes a plurality of generally parallel feeder tubes 54 that receive streams of reinforcement strands 19 from a strand source, not shown. The advantage of using a plurality of feeder tubes and a plurality of strands is that this enables the strands to be unwound from the strand shipping package at a slower, more manageable speed. The strands are channeled by flexible conduits 56 into a strand gathering fixture 58. Each strand gathering fixture receives the output from two of the parallel feeder tubes 54 and two of the flexible conduits 56. Positioned beneath each of the strand fixtures 58 are a pair of feeders, which can be in the form of rotatably mounted pull rolls 60 that cooperate to pull the strands 19 from the strand source and into the strand dispensing apparatus 50.

Positioned beneath or downstream from the pull rolls 60 is a chopper 64 that is adapted to engage the strand and chop the stand into discrete length reinforcement fibers 14. A dispensing nozzle 66 receives a current 65 of the discrete length reinforcement fibers, partially shown in Fig. 4, from the chopper 64 and dispenses the fibers onto the collection surface, which is preform molding surface 16. As shown, there are two dispensing nozzles 66. Preferably, each current 65 is directed into an associated or dedicated dispensing nozzle 66. High speed downward air flows, not shown, are introduced into the currents 65 to help direct the currents into the nozzles 66.

Each of the dispensing nozzles 66 has a longitudinal axis 68, which for purposes of clarity is shown only in Fig. 5. It can be seen in Fig. 3 that each of the dispensing nozzles 66 dispenses a flow 70 of the discrete length reinforcement fibers along a path extending generally along the longitudinal axes 68 of the nozzles 66. As shown i Fig. 5, the nozzles are oriented at a combined acute angle 72 so that the axes of each of the nozzles converges with respect to each other. Although it is preferable to have both nozzles mounted at an acute angle to the general longitudinal orientation of the dispensing unit 18, it is possible to have the two nozzles oriented at an acute angle to each other with one of the nozzles parallel to the general longitudinal orientation of the dispensing unit 18. The orientation of the two nozzles is configured so that the axes of each of the nozzles converge with respect to each other insures that the flows 70 of dispensed discrete length reinforcement fibers from the two nozzles will be directed toward one another. Preferably, the two flows 70 of discrete length reinforcement fibers converge or intersect to form a combined flow 74. The angle of orientation of the nozzles with respect to each other can be any suitable angle that directs the flows 70 toward each other. Preferably, the nozzles are oriented with respect to each other such that the angle 72 is within the range of from about 2 degrees to about 30 degrees. More preferably, the angle 72 is within the range of from about 5 degrees to about 15 degrees. Figs. 3 and 4 show that two currents 65 of discrete length reinforcement fibers are formed from four streams of reinforcement strands. The two currents 65 are dispensed as two flows 70 of fibers. It is to be understood that multiple currents of discrete reinforcement fibers from multiple streams of reinforcement strands can be chopped into multiple currents of discrete length reinforcement fibers and dispensed by nozzles that are oriented along converging axes.

The fibers of the combined flow 74 collected on the preform screen 16 form an accumulation 78 that does not have significant separate ridges like the ridges 40 (Fig. 2) produced using the reinforcement dispenser of the prior art. Instead, the accumulation 78 has a more uniform, singular coherent shape. Since the ridges and valleys of the prior art fiber distribution are minimized or eliminated, the preform can be made in a significantly shorter time than would be possible using a prior art reinforcement dispenser. For example, in one demonstration a conventional prior art reinforcement dispenser was used to make a preform using glass fibers. The time required for making the preform was about 4 minutes. The same preform was then made using the reinforcement dispenser of the invention. The axes of the two dispensing nozzles were oriented with respect to each other at an angle of about 10 degrees, and the two flows of fibers intersected just above the preform screen. The same preform was made in about 2 minutes using the reinforcement dispenser of the invention, thereby greatly increasing the efficiency of the preform making process. It is to be understood that one possible benefit of the increased distribution efficiency of the invention is that the robotic articulation arm 12 can be moved at a slower lateral speed. The slower robot speed helps eliminate ridges or laminelles and helps provide a more uniform fiber accumulation on the preform. As shown in Fig. 3, the nozzles 66 can be provided with an air escape module 80 that is provided with air escape ports 82 for removal of some of the air traveling with the discrete length reinforcement-fibers moving through the nozzle. Removing some of the air traveling with the fibers prior to the exit of the fibers from the nozzles is advantageous because it reduces the tendency of the fibers and entrained air from bouncing or reflecting from the preform screen 16. Since there is a reduced tendency for reflecting the fibers, the nozzle can be moved closer to the preform, thereby enabling the reinforcement dispenser to more accurately make the preforms. Also, the higher the fiber speed, the greater the peak or ridge of the distribution, that is, the greater the chance for laminelles ridges or laminelles 40. Although only one air escape module 80 is shown, it is to be understood that several of the modules could be used for the removal of more air from the flow of fibers.

In a preferred embodiment of the invention the two fiber flows 70 begin to intersect at a point about 300 to about 400 mm below the nozzles 66, and substantially completely merge within the next 25-50 mm, while still above the preform screen. Although intersection of the flows 70 above the screen is shown, it is to be understood that the nozzles can be oriented so that the two nozzle axes 68 intersect at a point below the preform screen. An optional feature of the invention is the use of one or more edge plates 86 mounted on the nozzle or any other appropriate element of the reinforcement dispenser, as shown in Fig. 5. The edge plates can be positioned so that a distal end 88 of the edge plate 86 extends into the area where the discrete length reinforcement fibers are accumulating on the preform 16. The edge plates intercept or deflect some of the dispensed fibers, thereby modifying the fiber distribution pattern. In one embodiment of the invention, the edge plates confine the fibers to a desired area, thereby enabling the reinforcement dispenser to form more precise accumulations 78. Preferably, the edge plates are pivotally mounted about a hinge 90 so that the edge plates can be folded out of the way, as shown in phantom lines. When mounted on a hinge 90, the edge plate can be moved into and out of position for intercepting the fibers. It is to be understood that the nozzles can be provided with just a single edge plate rather than edge plate for each nozzle. Also, the movement of the edge plate with respect to the nozzle 66 can be provided with a means, such as a motor, not shown, for pivoting the edge plate, and also provided with a controller, not shown, for controlling the pivoting of the edge plate during the preform making process. By using a controlled pivoting edge plate that can be moved relative to the strand dispensing apparatus 52, more precise and intricate patterns of fibers can be developed in the preform.

The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from its scope.

Claims

WHAT IS CLAIMED IS:

1. A method of dispensing reinforcement strands comprising: establishing multiple streams of reinforcement strands (19); chopping the multiple streams of reinforcement strands into multiple currents of discrete reinforcement fibers (65); directing each current of the discrete reinforcement fibers into a dispensing nozzle (66) so that the discrete reinforcement fibers travel along a path extending generally along a longitudinal axis of the nozzle; orienting the nozzles so that the axes (68) of each of the nozzles converge with respect to each other; and dispensing a flow of the discrete length reinforcement fibers (70) from each of the nozzles onto a collecting surface (16).

2. The method of claim 1 in which the collecting surface (16) is a preform screen.

3. The method of claim 1 including orienting the nozzles (66) so that the flows (70) from each of the nozzles intersect to form a combined flow.

4. The method of claim 3 in which the flows (70) intersect at a point above the collecting surface (16).

5. The method of claim 1 including orienting the nozzles (66) so that the axes (68) of each of the nozzles intersect at a point beneath the collecting surface (16).

6. The method of claim 1 in which the step of directing each current (65) into the nozzle (66) is carried out by introducing air into the current.

7. The method of claim 6 including removing a portion of the air traveling within the currents (66) prior to the exit of the fibers (70) from the nozzles (66).

8. The method of claim 1 in which there are two streams of reinforcement strands (19), two dispensing nozzles (66), and two flows of discrete length reinforcement fibers (70) being deposited onto the collecting surface (16).

9. The method of claim 1 in which the axes (68) of the nozzles (66) are oriented with respect to each other at an angle that is within the range of from about 2 degrees to about 30 degrees.

10. The method of claim 1 in which the step of directing the currents of discrete length reinforcement fibers (65) into the dispensing nozzles (66) comprises directing each current of discrete length reinforcement fibers into an associated dispensing nozzle.

11. A method of dispensing reinforcement strands comprising: establishing one or more streams of reinforcement strands (19); chopping the one or more streams of reinforcement strands into one or more currents of discrete length reinforcement fibers (65); directing each of the one or more currents of discrete length reinforcement fibers into one or more dispensing nozzles (66) so that the discrete reinforcement fibers travel along paths extending generally along the longitudinal axes (68) of the nozzles; dispensing flows of the discrete length reinforcement fibers (70) from the one or more nozzles onto a collecting surface (16) according to a fiber distribution pattern; and positioning one or more edge plates (86) relative to the nozzles to intercept some of the dispensed fibers, thereby modifying the fiber distribution pattern.

12. The method of claim 11 in which the interception of some of the dispensed fibers (70) includes deflecting the fibers.

13. The method of claim 11 in which the collecting surface (16) is a preform screen.

14. The method of claim 11 in which there are two streams of reinforcement strands (19), two dispensing nozzles (66), and two flows of discrete length reinforcement fibers (70) being deposited onto the collecting surface (16).

15. The method of claim 11 in which the edge plate (86) is mounted on hinges (90) for movement into and out of position for intercepting the fibers (70).

16. The method of claim 11 including orienting the nozzles (66) so that the axes (68) of each of the nozzles converge with respect to each other.

17. The method of claim 16 in which the axes (68) intersect at a point above the collecting surface (16).

18. The method of claim 16 in which the axes (68) of the nozzles (66) are oriented with respect to each other at an angle that is within the range of from about 2 degrees to about 30 degrees.

19. The method of claim 1 in which the step of directing the currents of discrete length reinforcement fibers (65) into dispensing nozzles (66) comprises directing each current of discrete length reinforcement fibers into an associated dispensing nozzle.

20. Apparatus for dispensing reinforcement strands comprising: multiple feeders (54) for moving multiple streams of reinforcement strands (19); a chopper (64) for chopping each stream of reinforcement strands into multiple currents of discrete reinforcement fibers (65); a dispensing nozzle (66) for receiving the discrete reinforcement fibers and dispensing the discrete reinforcement fibers (70) along a path extending generally along a longitudinal axis (68) of the nozzle, wherein the nozzles are oriented so that the axes of the- nozzles converge with respect to each other; and a collection surface (16) for receiving the discrete length reinforcement fibers to form a preform.

21. The apparatus of claim 20 in which the collecting surface (16) is a preform screen.

22. The apparatus of claim 20 in which the nozzle (66) is provided with air removal ports (82) for removing a portion of the air traveling within the currents (65) prior to the exit of the fibers from the nozzles.

23. The apparatus of claim 20 in which there are two dispensing nozzles (66).

24. The apparatus of claim 20 in which the axes (68) of the nozzles (66) are oriented with respect to each other at an angle that is within the range of from about 2 degrees to about 30 degrees.

25. Apparatus for dispensing reinforcement strands comprising: one or more feeders (54) for moving one or more streams of reinforcement strands

(19); a chopper (64) for chopping each stream of reinforcement strands into multiple currents of discrete reinforcement fibers (65); a dispensing nozzle (66) for receiving the discrete reinforcement fibers and dispensing the discrete reinforcement fibers (70) along a path extending generally along a longitudinal axis (68) of the nozzle, wherein the nozzles are oriented so that the axes of each of the nozzles converge with respect to each other; a collection surface (16) for receiving the discrete length reinforcement fibers to form a preform; and one or more edge plates (86) positioned relative to the nozzles to intercept some of the dispensed fibers, thereby modifying the fiber distribution pattern.

26. The apparatus of claim 25 in which the collection surface (16) is a preform screen.

27. The apparatus of claim 25 in which the nozzle (66) is provided with air removal ports (82) for removing a portion of the air traveling within the currents (65)prior to the exit of the fibers from the nozzles.

28. The apparatus of claim 25 in which there are two dispensing nozzles (66).

29. The apparatus of claim 25 in which the axes (68) of the nozzles (66) are oriented with respect to each other at an angle that is within the range of from about 2 degrees to about 30 degrees.

30. The apparatus of claim 25 in which the edge plate (86) is mounted on hinges (90) for movement into and out of position for intercepting the fibers (70).

31. The apparatus of claim 25 in which the nozzles (66) are oriented so that the axes (68) of each of the nozzles converge with respect to each other.