Fluent material handling – with receiver or receiver coacting mea – Plural filling means – Diverse flow manifold
Reexamination Certificate
1999-03-31
2001-04-17
Douglas, Steven O. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Plural filling means
Diverse flow manifold
C425S572000
Reexamination Certificate
active
06216752
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to vacuum assisted resin transfer molding (VARTM) fabrication, and more particularly to a gravity feed resin delivery system.
BACKGROUND OF THE INVENTION
Vacuum assisted resin transfer molding (VARTM) and related processes and techniques have been widely used to fabricate relatively large fiber-reinforced composite articles. Such articles may include coach chassis for busses and trailers and fiber glass boat hulls, for example.
In general, the VARTM process includes the distribution of dry, fiber strips, plies or mats about the surface of a female mold to form a fiber lay-up of a desired thickness. The fiber strips or plies may take the form of a cloth or sheet of fibers of glass, carbon or other suitable material. In addition, one or more rigid core layers may be included. The core layers may be formed of a solid foam material or balsa wood. The core layers may be sandwiched between the fiber plies to form a fiber/core composite lay-up or laminate.
A flexible, fluid impermeable bag, sheet or covering is positioned atop the exposed lay-up and sealed about the periphery thereof. A relative vacuum is drawn between the mold and the bag, thereby causing the bag to compress against the fiber lay-up. A chemically catalyzed liquid resin is introduced into the evacuated bagged mold through a series of resin supply lines or conduits. A multitude of individual resin supply lines may be used so as to facilitate distributed wetting or infusion of the liquid resin about the fiber lay-up. The vacuum source and resin supply lines are strategically positioned relative to one another in a manner which encourages controlled wetting. In this respect, the vacuum source may be applied at one side of the fiber lay-up and the resin introduced at an opposing side, and thus tending to cause the resin to be pulled across and wet portions of the fiber lay-up therebetween.
Underwetting and overwetting of the fiber lay-up are particularly problematic, as such conditions may result in unacceptable structural weaknesses and deficiencies of the resultant article. In addition, nonuniform resin distribution may also result in unacceptable structural weaknesses and deficiencies of the resultant article.
Some of the contemporary techniques for facilitating more uniformed or homogeneous resin distribution include the use of redundant resin delivery apparatus. As such, when fabricating large structures, often several dozen individual resin reservoirs or pumping systems may surround the mold surface. Each of the resin reservoirs are then connected to lengthy resin supply lines to selective localized resin application areas or zones about the mold surface. While these techniques enhance the distribution of resin about the fiber lay-up, such a techniques results in undue inefficient multiplicity of the resin delivery apparatus. Operators must monitor the many resin delivery apparatus subcomponents which increases the time and skill requirements in order to fabricate a resultant article to desired quality control standards. For example, in the event one of the resin supply reservoirs runs dry during the fabrication process, the entire resultant reinforced resin part is often scrapped. While such labor intensive steps and equipment intensive processes, including inspection tasks, may result in a structure which conforms to desired mechanical requirements, such a process so limits the production efficiency so as to make the process economically nonfeasible.
In addition, as mentioned above, the contemporary resin distribution techniques require a multitude of lengthy resin supply lines about the mold surface. Such supply lines are distributed about the surrounding floor surface and create a physical tripping hazard.
As such, based upon the foregoing, there exists a need in the art for an improved device for enhancing ans simplifying resin distribution in comparison to the prior art.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a simple gravity feed resin delivery system for VARTM fabrication of large fiber-reinforced resin structures formed upon a mold surface. The system is provided with a resin source for dispensing catalyzed liquid resin. A resin manifold is disposed above the mold surface. The resin manifold has a manifold inlet port for receiving the resin from the resin source. The resin manifold further has a plurality of manifold outlet ports lengthwise distributed there along for draining resin therethrough. The system is further provided with a plurality of resin infusion lines which extend between the resin manifold to adjacent the mold surface. Each of the resin infusion lines are in fluid communication with a respective manifold outlet port for receiving resin drained therethrough.
In the preferred embodiment of the present invention, the resin manifold is a generally elongate tubular structure which extends substantially along the mold surface. In this respect, the resin manifold is preferably formed cardboard tubing and the resin outlet ports are generally circular apertures which may be simply formed therein by drilling or puncturing the resin manifold. The resin infusion lines are cooperatively sized to mate with the resin outlet ports via insertion therethrough in sealed communication therewith.
The present invention for the delivery of resin during VARTM fabrication presents numerous advantages not found in the related prior art. In particular, the system takes full advantage of gravity for distributing resin from the resin manifold to the various resin infusion lines. Thus, only a single resin pump is required for large resin structures. In addition, due to the relatively close proximity of the resin manifold to the mold surface (i.e., directly above), the attached resin infusion lines are relatively short. As such, this tends to improve worker safety, minimizes material costs and improves part quality. Further, it is contemplated that undue redundancy within the resin delivery system is mitigated because there is provided a single central resin manifold. Thus, a multiplicity of catalyzed resin reservoirs or buckets is avoided which are typically employed in the art.
Advantageously, it is contemplated that the resin manifold may be formed of readily available inexpensive cardboard tubing. Furthermore, the manifold inlet and outlets may easily be formed therein via simple drilling or punching fabrication steps. Thus, the resin manifold may be considered economically disposable. Whereas, other more expensive prior art manifold apparatus may have to undergo flushing or cleaning steps for reuse.
As such, the present invention represents an advance in the art.
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Anderson Terry J.
Douglas Steven O.
Hoch, Jr. Karl J.
Northrop Grumman Corporation
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