Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Layered – stratified traversely of length – or multiphase...
Reexamination Certificate
2001-01-26
2003-12-16
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Layered, stratified traversely of length, or multiphase...
C264S171290, C264S281000
Reexamination Certificate
active
06663808
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to novel thermoplastic pipes which can withstand a varied range of internally generated and/or applied pressures for utilization within, primarily, underground liquid and gas transport systems. Such pipes are improvements over standard metal (i.e., steel, lead, and the like) pipes due to construction costs, shipping costs, implementation costs (particularly underground), modulus strength allowances to compensate for underground movements (i.e., earthquakes and tremors), non-rusting characteristics, and ease in manufacture. Such pipes are preferably reinforced with specific fabric articles that permit a lower thickness of plastic to be utilized than is generally required to withstand high pressure situations. A simplified, potentially on-site production method for producing more uniform, better-performing pipes as well as a specific molding dorn for such a purpose are also contemplated within this invention.
BACKGROUND OF THE INVENTION
Underground transport of liquids and gases has been utilized for many years. Such underground transport has proven to be the most efficient and safest manner in which to transport potentially explosive, flammable, and/or toxic liquids (such as crude oil, for example) and gases (such as methane and propane, as examples) long distances. The principle method followed to provide such long distance underground transport has been through metal tubes and pipes. In the past, the utilization of metals (such as steel, copper, lead, and the like) was effective from cost and raw material supply perspectives. However, with the population growing throughout the world and the necessity for transporting liquids and gases to more remote locations increases, the continued utilization of such metal articles has become more and more difficult for a number of reasons. Initially, the production of such metal tubes and pipes must be undertaken through high-temperature production methods at specific foundries which are normally located a substantial distance from the desired installation site. Such off-site production thus requires transport of cumbersome metal articles to the installation location and then subsequent placement into already-dug channels. These procedures are, again, difficult to follow since metal articles are rather heavy and must be connected together to form the desired pipeline. Additionally, in order to reduce the number of connections between individual pipes, longer metal pipes could be formed, which adds to the complexity with an increase in required welded connections. Further problems associated with metal pipes and tubes include, without limitation, the potential for rusting (which may contaminate the transported liquid or gas), the low threshold of earth-shifting which could cause a break within the pipeline, and the difficulty in replacing worn out metal pipes in sections, again due to the metal pipe weight, metal pipe length, and connection welds. These break problems have proven to be extremely troublesome in certain geographic areas which are susceptible to earthquakes and tremors on a regular basis. When such unexpected quakes have occurred in the past, the metal gas and liquid pipelines have not proven to be flexible enough to withstand the shear forces applied thereto and explosions, leaks, or discontinued supplies to such areas have resulted. These metal articles have remained in use because of their ability to withstand high pressures. Furthermore, although such metal pipes are designed to withstand such high pressures (i.e., above 80 bars, for instance), once a crack develops within the actual metal pipe structure, it has been found that such cracks easily propagate and spread in size and possibly number upon the application of continued high pressure to the same weakened area. In such an instance, failure of the pipe is therefore imminent unless closure is effectuated and repairs or replacements are undertaken.
Although there is a need to produce new pipelines to remote locations around the world, there is also a need to replace the now-deteriorating pipelines already in use. Aging pipelines have recently caused great concern as to the safety of utilizing such old articles. Unexpected explosions have occurred with tragic consequences. Thorough review and replacement of such old metal pipes is thus necessary; however, due to the difficulties in determining the exact sections of such pipelines which require replacement, there is a desire to completely replace old pipelines but following the same exact routes. Again, due to the difficulties noted above, there is a perceived need to develop more reasonable, safer, longer-lasting, easier-to-install, non-rusting, non-crack propagating, and more flexible pipeline materials. To date, there have been some new thermoset or thermoplastic articles which are designed to withstand rather low pressure applications (i.e., 20 bars or below) and which include certain fiber-wound reinforcement materials (including fiberglass, polyaramids, polyesters, polyamides, carbon fibers, and the like). However, the resultant articles do not include specific textile reinforcements (they are fibers wound around specific layers of plastic material) and thus are difficult and rather costly to produce. Furthermore, such fiber-wound materials cannot be easily produced at the pipe installation site again due to the complexity of creating fiber-wound reinforcement articles subsequent to thermoplastic or thermoset layer production. Additionally, with such off-site production, transport and in-ground placement remain a difficult problem. Thus, although some improvements have been provided in the past in relation and in comparison to metal pipes and tubes, there simply is no viable alternative presented to date within the pertinent prior art which accords the underground liquid and gas transport industry a manner of replacing such high pressure metal articles.
Additionally, prior attempts at producing reinforced resinous pipes have uncovered other problems with such final products, most notably non-uniformity in both the thickness of the pipe walls as well as the shape of the pipe itself. With such non-uniformity, limitations as to pressure resistance may occur, particularly due to the weakening of discrete areas of the pipe to a greater degree than the other areas of the same article. In such a situation, even with reinforcements present to provide greater elongation at break for the entire article, there still exists a potential problem with greater stress being placed on the weakest portion of the pipe upon exposure to higher pressures. Thus, a procedure to produce a more uniform thermoplastic, preferably reinforced, pipe article is necessary to provide greater security and more reliable pipes over the lifetime of use of such an article. Since such thermoplastic or thermoset articles do not return to their original shape and/or thickness after pressure stresses have thinned the walls through expansion, again, there is a great need to produce a more uniform article to defend against uneven thinning.
Furthermore, upon utilization of reinforcements, such as without limitation, fiber-wound tapes (such as polyaramids, and the like), textile layers (including, scrim, non-woven, woven, and the like fabrics) in-laid or surrounding at least one layer of resinous material, and the like, it is imperative that effective adhesion be effectuated between the resinous layer and the reinforcement material. In the past, wrapping of fiber-wound material around the target resin has been practiced with the possible inclusion of an adhesion promoter formulation to aid in adhesive effects. Also, since such wrapping must be performed on molten resin to achieve sufficient adhesive characteristics, the cooled resin thus adheres more readily to the already-in-place reinforcement material. However, even with such a procedure, there is no specific guarantee that appreciable amounts of molten resin will effectively enter the interstices of the particular wrapped tape material. Thus, a
Eashoo Mark
Milliken & Company
Moyer Terry T.
Parks William S.
LandOfFree
Method of producing textile reinforced thermoplastic or... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing textile reinforced thermoplastic or..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing textile reinforced thermoplastic or... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3140500