Stock material or miscellaneous articles – Hollow or container type article – Glass – ceramic – or sintered – fused – fired – or calcined metal...
Reexamination Certificate
1999-06-14
2004-08-10
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Glass, ceramic, or sintered, fused, fired, or calcined metal...
C428S084000, C428S034500, C428S034600, C428S034700, C428S035700, C428S036300, C428S036900, C428S036910, C138S172000, C138S174000
Reexamination Certificate
active
06773773
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the manufacture of fiber reinforced thermoplastic pipe lengths and more particularly to a novel continuous processing means for the manufacture of these articles.
The fiber reinforcement of pipe members formed with both thermoset and thermoplastic organic polymers has already gained wide commercial acceptance attributable to affording high strength and stiffness per unit weight when compared to pipe fabrication with the conventional materials previously used for transporting various fluids such as concrete, steel and the like. A variety of fabrication procedures are also well known to produce the composite pipe member with continuous fiber filaments which are commonly applied to the outer pipe surface. In one example, a tension winding process is commercially employed whereby a thermoplastic pipe or coupler member is rotated on a mandrel while the reinforcing fiber is being applied under heat and tension. The fiber tension during winding or wrapping around the underlying thermoplastic member provides a compaction force therebetween to secure thermal bonding of the fibers after the heating has melted or softened the outer surface of the thermoplastic material. This process has been found limited to relatively high fiber angles with respect to the longitudinal axis of the pipe or coupler member, typically greater than 15 degrees because the radial component of the fiber tension provides this compaction force. While tension winding can be augmented with a use of compaction roller means to increase the radial compaction force, the resulting low fiber angles produce undesirable fiber build-up at the mandrel ends since the continuous fibers being applied cannot be cut for a restart of the filament winding process. A further need to apply relatively high pressure as well as provide mandrel rotation during said tension winding process requires robust and expensive mandrels together with significant mandrel handling labor. In a different manufacturing process for the production of reinforced plastic pipe members, continuous glass fibers in a thermoset epoxy matrix are employed. Still other manufacturers produce a reinforced thermoplastic pipe construction having the thermoplastic pipe member as an innerlayer which is surrounded by various outerlayers of the reinforcement material. For example, one such manufacturer surrounds the thermoplastic liner with a fiberglass layer in an epoxy resin matrix and provides an exterior protective layer thereover of a still different fiber material which is again contained in an organic polymer matrix. Using thermoset polymers in the reinforcement of a thermoplastic pipe member frequently creates additional manufacturing problems. The curing required of these polymers occasions contamination as well as time delay and these materials are not recyclable.
Another complex reinforced thermoplastic pipe construction is disclosed in U.S. Pat. No. 4,850,395. As therein described, a core member of thermoplastic material is wound with an inner aramid fiber layer while being covered with still additional tape and metal outer layers. Such end product is understandably found to be both cumbersome and expensive to manufacture. In U.S. Pat. No. 4,469,138 there is disclosed polypropylene pipe lengths reinforced by simply mixing discrete carbon fibers in the starting polymer composition. The resulting product lacks the mechanical strength afforded with continuous fiber reinforcement as well as lacks the ability to orient continuous fibers in a predetermined spatial direction for maximum effectiveness in withstanding applied stress when the pipe member is in service. In the latter regard, such controlled directional orientation of the continuous fiber component in the reinforced thermoplastic pipe member enables the fiber placement to be fixed for such maximum effectiveness since the fiber materials being employed are generally stronger than the thermoplastic polymers forming the pipe member. The fiber reinforced end product is thereby only as strong as the spatial direction of the applied fibers with respect to the direction of the external stress when applied to said reinforced pipe member. Thus, when the fiber reinforced pipe member is stressed by internal fluid pressures in the direction of the fiber placement, the applied load is withstood primarily by the included fibers and the strength of said pipe member is at maximum value. Conversely, when the composite member is stressed in a perpendicular direction to the fiber direction, the applied force must necessarily be resisted primarily by the polymer pipe member so that pipe strength is at a minimum. From such consideration and a further analysis of the expected stress during pipe service employing recognized shell theory calculations, it has been determined that certain installations of the present fiber reinforced thermoplastic pipe members dictate a fiber orientation in the hoop direction whereas dissimilar pipe installations require the fiber direction to be oriented at lesser angles with respect to the longitudinal axis of the reinforced pipe member.
A still more arduous method for reinforcement of a thermoplastic pipe member is disclosed in U.S. Pat. No. 4,347,090 which employs a fabric sleeve applied about the pipe member for this purpose. The method requires an inner liner to be filled with liquid which is then heated causing said liner to expand as well as become partially molten for thermal bonding to an overlying glass fabric layer. An outermost layer comprising a thermoset resin impregnated glass cloth completes the reinforcement. Such final product and its method of fabrication are understandably both complex and expensive.
In U.S. Pat. No. 4,770,442 there is also disclosed a rather complex electrofusion type coupler being employed to join synthetic resin pipe lengths together. Said coupler member employs a cylindrical thermoplastic sleeve which includes a metal heating wire being disposed adjacent the inside surface while being reinforced on the outside surface with a winding or covering formed with a material composition exhibiting a lower thermal expansion than that of the thermoplastic sleeve material. Such reinforcement is said to limit any outward radial expansion of the composite sleeve during subsequent thermal bonding of said member to the pipe lengths being joined together by this means.
It is an important object of the present invention, therefore, to provide a more effective means for the fiber reinforcement of a thermoplastic pipe member in a continuous manner.
It is another important object of the present invention to provide a novel fiber reinforced thermoplastic pipe member having the fiber placement physically incorporated therein so as to better resist the applied stress encountered during use in a significantly improved manner.
Still another important object of the present invention is to provide a novel method for continuous fabrication of a fiber reinforced thermoplastic pipe member.
A still further important object of the present invention is to provide novel apparatus means for the continuous fabrication of a fiber reinforced thermoplastic pipe member.
These and still further objects of the present invention will become more apparent upon considering the following more detailed description of the present invention.
SUMMARY OF THE INVENTION
It has been discovered, surprisingly, that fiber reinforcement of a thermoplastic pipe length can be carried out more effectively in a continuous manner by reversing the customary relative rotation between the fiber when applied and the pipe member. More particularly, the processing procedure of the present invention continuously moves the pipe length in a linear direction without rotation while wrapping a plurality of continuous juxtapositioned reinforcement fibers formed with a material composition selected from the group consisting of ceramics, metals, carbon and organic polymers in an unbonded condition about the outer surface of said moving pipe member in a predetermined spa
ADC Acquisition Company
Chevalier Alicia
McDevitt John F.
Nolan Sandra M.
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