Patent Application
20070029434
This invention relates to an apparatus and method for manufacturing constant-width tow fibers (“tow” or “towpreg”), which are preferably resin-impregnated.
There are a number of challenges involved in manufacturing a constant-width towpreg. Conventional processes of manufacturing a resin-impregnated towpreg require that the towpreg be oscillated back and forth for spooling onto a core of a spool. As a result of handling the towpreg in this way, one of the problems is that that the resin-impregnated fiber tow tends to vary its width, particularly because it is oscillated back and forth for spooling onto the core. The present invention avoids most of the problems that typically tend to vary the tow width.
An embodiment of this invention is an apparatus for winding a towpreg, comprising a spool winding machine comprising a rod-shaped body for mounting a core of a spool, wherein the core is shuttled on the rod-shaped body to allow the towpreg to maintain a straight path substantially normal to an axis of the rod-shaped body. The apparatus could further comprise a spool shuttling carriage. The apparatus could further comprise a towpreg delivery head. The apparatus could further comprise a grooved roller that allows control of a width of the towpreg. The apparatus could further comprise a towpreg cooling device. The apparatus wherein the towpreg cooling device is a towpreg cooling tunnel. Preferably, the towpreg cooling device is a towpreg chiller. The apparatus could further comprise a towpreg width measurement device. The apparatus could further comprise a towpreg speed regulation device for regulating a travel speed of the towpreg. Preferably, the grooved roller has a groove of a desired width and rotates in a direction of travel of the towpreg at a rotational speed resulting in a surface speed at the groove that is slower than the travel speed of the towpreg.
Another embodiment is a method for winding a towpreg, comprising impregnating the towpreg with a resin and winding the towpreg on a core of a spool while simultaneously shuttling the core on a rod-shaped body to allow the towpreg to maintain a straight path substantially normal to an axis of the rod-shaped body.
One of the features of the spool winder of this invention is that the packaging spool core is shuttled back and forth on a rod-shaped body, e.g., a spline-type support shaft, in a pattern-controlled motion, allowing the fiber to proceed in a straight-line substantially normal to the axis of the rod-shaped body, through the impregnation and spooling process. This facilitates accurate width control of the product, an important benefit for material that is to be used in precise fiber placement operations.
In a preferred embodiment of the towpreg process of this invention, fibers are brought from a creel through an impregnation zone. Once impregnated with resin, the towpreg is shaped to a desired width by passing the towpreg over one or more grooved rollers, with the grooved rollers rotating in the direction of fiber travel, but at a slightly slower surface speed than the travel speed of the towpreg. This differential speed provides the benefits that one could achieve by passing the towpreg over a fixed bar for width control of the towpreg, but further provides a self-cleaning feature that is absent in a fixed bar due to the rotation of the grooved rollers. Optionally, the towpreg could be passed over and under a number of fixed impregnating bars to assist impregnation of the resin between the fibers of the towpreg and, at the same time over the grooved rollers to establish a width in accordance with the dimension of the grooves of the grooved rollers.
With the towpreg at a desired width after being impregnated with resin and traversing through the groove of the grooved rollers, in one embodiment the towpreg then passes through a refrigerated tunnel where its temperature is lowed by air convection. This chilling step substantially fixes or freezes the towpreg width as it goes into the next stage of the process which could be a puller. The puller could include two or more relatively large rotating drums having grooves and sidewalls. The rotating drums could be liquid chilled and could pull the towpreg through the entire process up to the location of the rotating drums. Sidewalls on the rotating drum grooves fix the final width of the towpreg by restricting width-expansion due to fiber tension normal forces.
Variations of the preferred embodiment of this embodiment of the claimed apparatus could include a tow sizing unit, tow width measurement unit, tow heating unit, flattening/guide rollers, tow sizing wheel and pressure roller and cooling devices as those disclosed in U.S. Pat. No. 5,397,523, which is incorporated in entirety herein by reference.
The claimed apparatus could potentially be used for any fiber including glass, carbon, aramid, boron, ceramic, and basalt. With shape variations in the drum and roller grooves, the towpreg cross-section may be varied from a rectangular to an oval, each of various dimensions.
The spool winder itself could be a programmable filament-winding machine that is programmed to rotate the spool winder in a particular winding configuration. In the preferred embodiment of this invention, the oscillating carriage of the winder does not move the delivery head of the towpreg, but rather it shuttles the towpreg spool core back and forth on a spline. Shuttling of the spool core allows the towpreg to maintain a straight path. An axial stationary rotating eye head orients the fiber band properly for winding it on the traversing core.
A diagram of the apparatus of the preferred embodiment of this invention is shown in
(A) Width-control impregnation rollers: Heated and rotating at a slower surface speed than that of the fiber travel.
(B) Towpreg cooling tunnel: Air refrigerated and thermostatically controlled with fans to create air turbulence for increase heat transfer.
(C) Towpreg chiller/puller and fiber-length measurement: Puller has width and shape control grooves. Length measurement is accomplished with the attachment of a revolution counter or encoder.
(D) Laser micrometer tow-width measurement and/or mass measurement with commercially available gamma or beta gage mass measurement systems and data logging.
(E) Machine take-up speed-regulation dancer wheel to maintain tow tension between puller and winder.
(F) Rotating eye delivery head to orient the fiber at a proper angle for helical winding at the spool.
(G) Spool winding machine and splined shaft spindles for traversing core spooling. Multiple spindles may be used by incorporating a slip-clutch drive to all but the master spindle, to maintain tension in all spooling.
(H) Spool shuttling carriage controlled by a winding pattern for a programmed helical or circumferential wind.
Test Methods and Results
Controlled tow properties include tow width, height, density, and fiber resin ratio. Quality issues include non-wrinkling of the fibers and non-breaking of the fibers in the process. These various properties are measured by the following tests:
E) Width of the towpreg is measured with a laser micrometer and the resultant data may be recorded and analyzed. Typical data from quality control procedures is listed in the table below:
This application claims benefit from U.S. Provisional Application No. 60/641,749, filed Jan. 7, 2005, entitled “FIXED-WIDTH TOWPREG APPARATUS AND PROCESS,” which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60641749 | Jan 2005 | US |
