Patent Grant
8172171
The present invention relates to a doff system and method for enabling dispensing of tows of material such as fibers from a center-pull doff.
In the composites reinforcement industry, and in particular, the fiber side of the industry, where common fibers are glass, carbon, aramid (Kevlar) and the like, there is a need to transition these fibers from their “as-built” state to process dispensing in the most efficient manner. The term “efficient” in this disclosure means both dispensing with the minimum disturbance and in an “untwist fashion”.
In the fiberglass industry in the US, dominated by Owens Corning, PPG, Vetrotex, and FGI, there is a process in which a “doff” of fiberglass is automatically made in a 24 hour-per-day operation. Molten glass in an elevated furnace is allowed to drop naturally through Platinum bushings and is cooled and consolidated into thousands of glass filaments that make up a single “tow”. This tow may have sizing added, but the tow can be traveling at 100 miles per hour as it exits the Platinum bushings.
This tow is in a flattened “wet” state (from sizing solutions) that allow it to be formed into a band as it is automatically wound up onto a temporary mandrel of paper or cardboard sleeve material in a very precise wound pattern. This wound pattern quickly increases from approximately 4-6 inches in inside diameter to approximately 10-11 inches in outside diameter in perhaps 2-3 minutes. A glass doff, when completed may weigh approximately 40 lbs. and have 3 miles of glass tow wound around the temporary cardboard or paper sleeve or inside mandrel.
When a doff is completed in the automatic winding process, a laborer will manually remove the finished 40-lb doff and stack it on a pallet. Once a pallet of wet doffs is completed they will be sent to a large drying operational room, and left to dry the wet sizing for many hours. After a set time the “dry” doffs are removed from the room and they are taken to a final prep-to-ship area. Here a laborer will remove the temporary sleeve from the inside of the doff and may actually discharge manually a layer (or two) of fiberglass that is not fully dry. Shrink wrap will be put on the outside of the doff for handling and shipping and the doff will be stacked onto a pallet for shipping. Doffs produced in this way are known as center-pull doffs, since they require dispensing of tows from the inside to the outside of the doff.
This doff is then sold to a processor such as a pultrusion manufacturer, weaving or stitching manufacturer, or any of about 30 different types of “composite processors” where it is combined with resins and a composite will be formed (this obviously an over-simplified explanation of “processing”). All of these processors remove the fiberglass doff from the shipping pallet and stack the doff onto a shelf, rack, or horizontal surface, and then the manufacturer dispenses a single tow from one doff, along with hundreds, or even thousands of tows from like doffs, and processes all tows in parallel into a composite of some shape and design.
This action is referred to as “Center-Pull”, since the doff by its very nature requires and demands dispensing from the inside outward. The tow is pulled from the inside of the doff and naturally unwinds in a twisted fashion as it pulls out from the inside diameter (ID) of the doff. Much as a coiled hose, being pulled longitudinally from a coiled state, these generally flat bands of fiberglass tows perform the same physical twisting. With every rotation around the inside diameter of the doff, there is exactly one twist that is imparted to the fiberglass band. This natural twist can have detrimental performance attributes when formed in a composite. The location of the twist can provide a localized void as the filaments cannot stretch. Thus the tow bands have edge filaments that must naturally buckle the interior filaments at the location of a twist. This reduces fiber volume and minimized the quantity of filaments that can be consolidated in a given cross sectional area.
Processors of fiber doffs, including fiberglass doffs, have recognized for some time the need for providing untwisted fiber. They therefore have demanded that the fiber manufacturers rewind a manufactured “virgin” center-pull doff. The doff described above is “virgin” because it exists undisturbed following the initial winding from the furnace bushing and the subsequent drying. Filaments as small as 8-13 microns made from these materials can be very prone to fracture when handled or disturbed. In spite of this problem, processors have asked glass manufacturers to rewind these virgin doffs so that the tows can be dispensed in a less twisted or untwisted state.
This rewind process is interesting. This is because the glass manufacturer takes a virgin doff and installs said doff onto an expensive and sophisticated machine, wherein the inside of the doff is mounted onto the machine and then the doff (with Shrink-wrap removed) is spooled and rotated and the tow is rewound onto a spool from outside-to-inside, creating what is known in the industry as a tangent spool. This tangent spool can be used by a processor such as a filament winder to dispense from the outside of the tangent spool in an untwisted tow fashion, to get the desired results in performance from a composite, with zero twist in the tow.
These tangent spools are typically about ½ the weight of a center-pull doff. But the manufacturer will charge anywhere from 5-10 cents per lb. or more to do this rewinding. The processor also knows that after the doff has been rewound into this tangent spool, that this action is one more step in handling the fiber and that it is likely there will be broken filaments and, thus, degraded strength in the sum of all the filaments that make up the tow.
Machines adapted for handling tangent spools include filament winders and tangent pull dispensing tooling. In order to allow a doff to be placed onto such devices, the fiber manufacturer has to rewind the doff onto a tangent-pull cardboard sleeve of the correct diameter accepted by such machines. As stated, it is well-known in the industry that this rewinding of glass fibers creates some loss in performance, as this secondary handling will undoubtedly break fiber-filaments and affect the structural strength of the end product. Additionally, the rewinding requires labor and time, and it is not unusual for a fiber manufacturer to add 5-10 cents per lb. or more, to the price of a rewound spool of glass fiber, over the price of a “virgin” center-pull doff.
In Applicants prior U.S. Pat. No. 7,690,179 (U.S. application Ser. No. 11/771,919 which claims priority from Prov. App. No. 60/945,853), the contents of which are incorporated herein by reference, an untwist device was disclosed using a novel rotating table, activated by a control system, to dispense tows in an untwisted fashion from an original, center-pull doff. This device has been commercialized. However, there are some restrictions and difficulties in locating turntables in manufacturing-process plants.
Embodiments described herein involve a doff system and method in which a virgin, non-rewound center-pull doff of fiberglass or other fiber, is secured to a device which allows the “virgin” glass tows to be dispensed from the outside of the doff in a zero-twist state, exiting the doff in the most undisturbed fashion since the tows were manufactured at the glass furnace bushing discharge. The described embodiments take the variable inside diameter of a center-pull doff and create a means to rotate the doff around its theoretical centerline, simulating a tangent-spool fiber package.
According to one embodiment, a doff core device is provided which simulates the cardboard sleeve of a tangent-pull doff by having a standard or constant internal diameter, but has a variable outer diameter to allow the core device to be secured in the hollow center of center-pull doffs of varying internal diameter. The resultant doff and core assembly or system can be placed onto a filament winder, tangent pull dispensing tooling, or other processors designed to receive the cardboard sleeve of a tangent spool, in place of such a tangent spool.
In one embodiment, the doff core device has a central tubular core of predetermined fixed internal diameter and an outer press bar portion of varying diameter secured to the outside of the core by an adjustment mechanism to allow movement from a compressed, minimum diameter state into expanded states of varying diameter, and can be locked in a selected expanded state. The predetermined internal diameter of the tubular core is selected to allow installation on a filament winder or similar processor designed to dispense fiber from the outside to the inside, in place of a cardboard core onto which a virgin doff of fiber has been rewound after manufacture. The press bar portion in one embodiment comprises a series of spaced longitudinal press bars adjustably mounted on outside of the tubular core via pivoted connecting links pivoted to the respective press bars at one end and to an adjuster nut which is threadably engaged with the tubular core at the opposite end, the adjuster nut and connecting links together comprising the adjustment mechanism. Each press bar extends along the length of the core and has an outer surface configured to press against the inner diameter of a virgin fiberglass doff, i.e. a doff which has not been re-wound subsequent to manufacture. The adjustment mechanism between the tubular core and press bars allows the separation between the core and press bars to be adjusted until the press bars bear against the inner diameter of a virgin doff, and a locking device secures the press bars in the adjusted position.
According to another aspect, a doff method of unwinding fiber tows from the outside of a virgin or center-pull doff without first re-winding onto a cardboard sleeve comprises installing a doff core device of variable outer diameter and constant internal diameter into the cavity or hollow center of a center-pull doff, expanding the doff core device to press against the internal diameter of the doff, and locking the device in the expanded condition. The constant internal diameter of the doff core device is selected to allow installation on processors such as filament winders, tangent pull dispensing tooling, and composite processors designed to accept a cardboard sleeve of a tangent spool, and simulates such a cardboard sleeve onto which fiber tows have been re-wound, thus eliminating the need to re-wind the originally manufactured doff.
Up to now, no such device has existed which can take the variable inside diameter (ID) of a center-pull doff and create a means for rotating said doff around its theoretical centerline, creating a core that simulates a tangent-spool fiber package. The ID of a center-pull doff is variable and can have several tenths of an inch difference in dimensions between a series of shipped center-pull doffs, and the doff core device therefore has an outer diameter which can be varied to fit center-pull doffs over the normal range of IDs encountered in such doffs. The outer press bar portion is configured to have a positive lock on the ID of the center-pull doff. This provides a relatively simple device that can accomplish similar performance outcomes as in the above referenced U.S. Pat. No. 7,690,179 (hereinafter '179 patent).
The doff system and method described herein allows dispensing of virgin fiberglass tows from the outside to the inside of a virgin fiberglass doff, using a device which simulates a tangent spool of a re-wound fiber package. When secured to the doff core device at its center, a center-pull doff can now have a 3 inch or other standard diameter core adapted to the doff's internal diameter, and it is no longer required that the fiber manufacturer has to rewind the doff onto a tangent-pull cardboard sleeve of the correct diameter accepted by such machines.
Certain embodiments as disclosed herein provide for a system and method for unwinding a virgin center-pull fiber doff from the outside to the inside, to avoid the need to re-wind the doff before dispensing material or tow from the doff.
Reference will be made herein to glass filament manufacturing, such as plants that produce multiple glass filaments, also known as fiberglass. However, the advantages disclosed herein may apply to any fiber reinforcement, not only fiberglass, and may also apply to doffs of fiber such a carbon, aramid, co-mingled thermoplastic roving (such as Twintex), thermoplastic fibers, PE fibers, basalt fibers, and the like. Even though the following description refers to a fiberglass process, it should be understood that the doff core device and method described herein applies equally to processing of other fiber materials. The doff core device and method described below may also be used to handle any elongate material that is coiled and needs a temporary core, not only fiber material, and is therefore applicable to other industries and materials which require spooled packaging.
After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention.
Many, if not all of the parts of the doff core device can be made from injected molded plastic, although any suitable material could used to fabricate the shapes, by any suitable process known to those skilled in component manufacturing. As illustrated in
There are four press bars 16 in the assembled device of
The length of doff core device 100 of
Expander nut 24 has right hand, internal threads 110 configured for threaded engagement over the right hand threads 10 of the tubular core 2, while expander nut 22 has left hand, internal threads 111 configured for threaded engagement over the left hand threads 11 at the opposite end of the tubular core. As illustrated in
As noted above, there are eight H-arms or pivoted connecting links 18 in device 100. One H-arm or connecting link is shown in
One of the press bars 16 is illustrated in more detail in
The final part of device 100 is the lock nut 26 which is shown in
One embodiment of a method of securing the doff core device 100 of
In
Once the device is inserted, the user holds one of the press bars 16 with one hand (any one of the four press bars may be held during this step) while rotating tubular core 2 relative to the press bars, such that the expander nut 24 incrementally moves along threads 11 toward the central shoulder 14. In one embodiment, the end of tubular core 2 may be slotted to accept a simple torque wrench, so as to assist the installer in rotating the tubular core relative to the press bars and attached expander nuts.
Several things happen during this step. Not only does expander nut 24 move toward the central shoulder 4, but expander nut 22 also moves inward towards the shoulder 4 due to the rotation of tubular core 2, at the same speed and rate of displacement. At the same time, the H-arms 18 synchronously rotate about their respective pivot connections to the nuts and the press bars, moving the four press bars 16 outboard to expand the device to a larger outer diameter (see
The above movements are all caused by only the manual right hand threading of expander nut 26, by way of rotation of the tubular core, 2. Due to the connections, the left hand threading of expander nut 22 occurs automatically, with no manual torque of the nut 22 required. In other words, the single person installing this expander does not have to physically touch the expander nut 22. By holding a press bar 16 with one hand and rotating the tubular core, all key components of the enabler move linearly. That is, the expander nuts move linearly toward the shoulder 4 of the tubular core and the press bars move linearly outward to contact the center of the center-pull doff.
The installer continues to move the right hand expander nut, by rotating the tubular core 2 with manual torque until the press bars are tight and secure to the inside diameter of the center-pull doff. Now the lock nut 26 is threaded onto the threads 11 at the right hand end of tubular core 2, until it jams with the expander nut 24. Device 100 is now locked in its expanded condition inside the center-pull doff.
The process is complete. The internal core of the tubular core can now be installed on any filament winder equipment, tangent pull dispensing equipment, or composite process equipment, and each of these alternatives is hereinafter referred to as doff processing equipment. Outside tangent fiber can then be dispensed from the thus enabled center pull doff. Once all outside tangent fiber has been dispensed from the outside of the center-pull-doff, the above process can be reversed by first removing the lock nut 26, then holding one of the press bars while rotating tubular core 2 in the opposite direction so that the press bars are retracted inwards as the expander nuts move away from shoulder 4. The device 100 is now ready to be installed in a new center pull doff. Theoretically, the device 100 can be used over and over and the applicants foresee no event that would cause sufficient “wear” or to require an overhaul. Certainly damage may occur due to mishandling or abuse, but there is no reason that the doff core device 100 cannot be a productive component for a manufacturer for many years of operation. The doff core device and installation method described above allow a virgin center pull doff to be installed directly on outside-to-inside unwinding machinery or processing equipment by one person. The doff core device is light weight and inexpensive to manufacture and use, and can be easily handled with no special tools.
Doff core device 100 is easily inserted into the cavity of the center-pull doff and secured in the cavity with a very rapid manual operation by one person. After device 100 is securely installed in a center-pull doff, it can be used as a mounting core to mount the center-pull doff on composite machinery and tooling, allowing a manufacturer to pull the fiber from the outside of a virgin center-pull doff, thus converting the center-pull doff to an “outside-tangent-pull-doff”. This avoids having to re-wind virgin center-pull doffs onto cardboard cores before they can be mounted on such machinery, significantly reducing processing time and expense.
Center-pull doffs can have a range of internal diameters which slightly vary from one another. The doff core device 100 described above has a variable outer diameter and can be adjusted mechanically to be secured in center-pull doffs of varying internal diameters, simply by adjusting the positions of nuts 22, 24 along the threads 10, 11, respectively. Thus, the angular momentum and torque can be transferred from the core 2 to the outside of the now “outside-tangent-pull-doff”, without any slippage, and be balanced. The centerline of the tubular core 2 is concentric with the theoretical center-line of the center-pull doff.
During installation of device 100 in a center-pull doff, press bars 16 press outboard uniformly from the tubular core, 2, with all press bars moving outwardly at the same distance from the tubular core, such that the press bars all contact the inside of the center-pull doff at the same time. The press bars extend parallel to one another along the length of tubular core 2 and are designed to contact with the inside diameter of the center-pull doff along substantially the entire length of the doff.
Once the press bars are moved outward to securely press against the inside of the center-pull doff, lock nut 26 can be securely placed on the tubular core to lock the press bars in position and to resist or prevent the press bars from releasing the internal friction against the inside of the center-pull doff, regardless of the stage of “pay-out” of the fibrous material, either at the beginning of the doff's use (100% fiber availability) to halfway wherein 50% of the fiber on the doff has been pulled tangentially from the outside of the doff, to where the entire doff is nearly expended, wherein 99% or more of the doff has been thoroughly expended and tangentially dispensed. The core device is therefore unlikely to slip relative to center-pull doff when reasonable processing torques are applied to the outside surface of the doff during processing or dispensing of 100% of the doff fiber.
This efficiency gain allows for a superior composite laminate due to undisturbed fibers having their maximum strength and being dispensed in an at least substantially untwisted state, allowing for the greatest fiber volumes and thus the highest strength per unit cross sectional area, with minimum voids.
The doff core device described above is not limited to use in processing fibers, but may be scaled to handle any elongate material that is coiled and needs a temporary core. The device can be made in various sizes, from very large to very small, with each size covering a different range of outer diameters, depending on the application. Several industries and several materials require spooled packaging and there is practically no limit to the possibilities of adapting a simple version of the doff core device and doff method described above for other materials and industries.
The doff core device described above is a low cost device which allows a processor to take a “virgin fiberglass doff”, for example, and dispense that doff in an untwisted fashion from the outside to the inside. This potentially has great benefit to composite processors. They could purchase the lowest cost fiber, i.e. the original center-pull doff (no tangent spools with premium pricing for the rewind effort by the manufacturer), the most “virgin” and undisturbed fiber, convert the center-pull doff to a tangent pull doff by securing the doff core device in the center of the doff, and use the resultant tangent pool doff in the composite process, thus making the composite process less expensive.
The relative dimensions of each of the described components of the doff core device in the embodiment described above, as well as their numbers can be modified in alternative embodiments based on the type of spoolable material and doff dimensions. For example, the device may have more than four or less than four press bars, and the number of pivotal connecting links 18 may be different in other embodiments. The connecting links 18 and expander nuts 22, 23 in other embodiments may also be of different shapes.
The drawings may depict exemplary configurations for the invention, which is done to aid in understanding the features and functionality that can be included in the invention. The invention is not restricted to the illustrated architectures or configurations, but can be implemented using a variety of alternative architectures and configurations. Additionally, although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features and functionality described in one or more of the individual embodiments with which they are described, but instead can be applied, alone or in some combination, to one or more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus the breadth and scope of the present invention, especially in the following claims, should not be limited by any of the above-described exemplary embodiments.
Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as mean “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; and adjectives such as “conventional,” “traditional,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, a group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should also be read as “and/or” unless expressly stated otherwise. Furthermore, although item, elements or components of the disclosure may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated. The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent.
The present application claims the benefit of U.S. provisional pat. App. Ser. No. 61/292,957, filed Jan. 7, 2010, the contents of which are incorporated herein by reference in their entirety.
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| Number | Date | Country | |
|---|---|---|---|
| 61292957 | Jan 2010 | US |
