Patent Application
20180100251
None.
This invention relates generally to the field of reinforcing fibers and more particularly to a process and apparatus for spreading a multiple filament tow into a spread web by subjecting the multiple filament tow to a cyclical high velocity impact with the spreading rollers which result in spreading of the tow band.
In the composites industry, a tow is an untwisted bundle of continuous filaments, and it refers to man-made fibers, particularly carbon fibers. Tows are designated by the number of fibers they contain. For example, a 12K tow contains about 12,000 fibers. Multiple filament tows are often used for producing fiber reinforced plastic materials. Examples of such fibers are carbon, glass, and aramids. Such fibers have low mass and a relatively high tensile strength in their longitudinal direction. These fibers are often embedded in a plastic matrix with a matrix resin for producing such products as golf clubs, fishing rods, automotive components, and aeronautical applications.
Such fibers are generally supplied from the manufacturer in the form of multiple filament tows which are wound into a spool for handling on traditional textile equipment.
It has been found desirable to lessen the density of such tows for ease of resin impregnation, lessen expense by utilizing heavier tows and spreading to result in similar products obtained by lighter tows, and produce thinner density materials to reduce weight materials. Various prior art devices and processes have been carried out for spreading such tows to reduce the density thereof.
This invention is directed to a process of spreading a multiple filament tow so as to both reduce the density and the costs thereof per unit of area. Conventional methods for spreading fiber involve running the fibers over multiple stationary spreading bars, generating high tensions during the process. However, for delicate fibers such as carbon fiber, the high tension and friction generated during the process result in broken filaments which degrade the properties of the carbon fiber. This new process is carried out with a unique apparatus which subjects the tow to a high speed, high frequency contact between the tow and rollers causing the tow to spread. The relatively low tension required in this process prevents excessive damage to the filaments while the cyclical impact between the rollers and tow induce the spreading effect.
The tow to be spread is passed through a series of rotating discs which are driven in unison and each of which have four rollers thereon about which the tow progresses. The rollers located on the disc are concentrically located about two separate diameters such that the distance between the first and third roller is greater than the distance between the second and fourth roller. Additionally, the rollers of adjacent discs are offset from one another by up to 90°. This offset is responsible for the periodical slack generated of the tow passing there through, which produces the cyclical high impact contact between the roller and the tow. The inlet tension is controlled by a tensioning creel having a spool thereon from which the tow is unwound. Additional tension and vibration control is brought about by dancing rollers which can be either free rolling or load bearing.
Various other advantages and features of this invention will be apparent from the following detailed description given with reference to the various figures of drawing.
According to this invention, it has been found that a multiple filament tow may be spread to lower the density and unit cost by a unique process carried out by the apparatus of this invention.
The tow 1 is then fed to a series of driven discs 17, 19, and 21. These discs will be further discussed infra. Upon leaving the last disc 21 the tow is subject to additional tension control by dancing roller 23. The dancing rollers 15 and 23 have illustrated in phantom the amplitudes of movement associated with the damping activity. The tow 1 is pulled through a series of driven rollers 25 which pull the tow 1 through the rotating discs and associated rollers. A speed controller 27 controls the speed of the driven rollers 25. At this point the multi-filament tow has been spread to a desired degree and is thus wound upon a take-up winder for removal and further processing.
Referring to
Referring to disc 19 which is adjacent to disc 17 and disc 21, disc 19 offset from the position of the adjacent rollers by 90°. This amount of offset may be varied between zero and 90° with the greater spreading effect occurring at 90°.
It can be appreciated that multiple discs may be provided to carry out the process of this invention. The greater the number of discs, the greater the spreading effect. Additionally, the rollers 31, 33, 35, and 37 may be free to rotate, or may be locked in position to add a greater tensioning effect upon multi-filament tow 1. It should be noted that once the multiple filament tow 1 has passed through all of the discs and rollers, that a spread multi-filament tow 1′ is the resulted product.
Referring to
It is thus seen that the process and apparatus of this invention provide a unique spread multiple filament tow in a simple and efficient manner. As the foregoing description has been exemplary in nature, it is to be construed by the spirit and scope of the following appended Claims.
