Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – By means advancing along terrain and guiding pipe or cable...
Reexamination Certificate
1999-12-23
2002-07-16
Will, Thomas B. (Department: 3673)
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
By means advancing along terrain and guiding pipe or cable...
C405S154100, C405S156000, C405S177000, C242S557000, C242S566000, C242S595100, C242S615200
Reexamination Certificate
active
06419424
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to transporting, unwinding and reforming a pipe and, more particularly, to an improved trailer for transporting a pipe coil, straightening and rerounding the pipe, and assisting in unwinding the pipe for laying in a trench.
BACKGROUND OF THE INVENTION
Fluid natural resources are commonly supplied through underground piping. A particularly prevalent use of such pipe is in the natural gas industry. In recent decades, an industry-wide shift has been made away from the use of metal piping, which generally proved unreliable due to corrosion in the underground environment, and toward more reliable types of plastic piping. Initially, this pipe was formed of polyvinyl chloride (PVC) or the like. While the PVC pipe is corrosion resistant, other significant problems were presented by its use. First of all, the inherent rigidity of PVC pipe (also known as “stick pipe”) dictates that it is available only in singular, elongate sections. Thus, to create a continuous underground pipeline, the on-site chemical or heat fusion of the ends of adjoining pipe sections is necessary. As should be appreciated, this operation is time consuming, labor intensive and requires specialized chemical or heat welding techniques and highly skilled workers to precisely complete the fusion.
To meet this need and overcome the aforementioned difficulties, there has been a recent shift away from the use of PVC pipe and toward the use of pipe made from other, more durable, flexible polymeric materials, such as, for example, polyethylene. One great advantage resulting from this advancement is the ability to store and deliver the pipe in coils comprised of several hundred, or even thousands, of feet of pipe. This of course makes substantially continuous pipe laying possible with only a few, infrequent interruptions to permit a worker to fuse the ends of adjoining coils together. Thus, as is now widely recognized throughout the industry, flexible polyethylene coil pipe results in a significant time savings over the prior art stick pipe laying operation, reduces the incidence of joint defects or failure due to the low number of fusion sites, and is also more durable in the underground environment.
Notwithstanding these vast improvements over the prior art metal and PVC piping, the use of flexible coil pipe is not without limitations. Perhaps the most significant limitation is the absence of an effective device for both transporting the coil to the work site and assisting in laying the pipe from the coil into a trench. Indeed, most minor repair jobs or branch lines require only one coil of pipe, or a portion of a coil, for completion. In these incidences, it is even more desirable to provide a device for efficiently transporting the coil from place to place, as well as to complete the pipe laying as necessary, without the need for support equipment.
Also, we have found that virtually all prior art transportation devices rely on a reel or spool to support the coil on the trailer or other vehicle. This arrangement is troublesome for several reasons. First of all, to avoid the additional expense associated with selling pipe pre-wound on such reels, the coil must be loaded onto the reel by the pipe laying contractor. As should be appreciated, this extra operation requires a significant amount of effort and time. The troublesome nature of the use of reels is compounded when it is considered that flexible pipe comes pre-coiled in a number of different diameters, depending on the size (cross-sectional diameter) of the pipe. Thus, in some prior art devices in order to accommodate the various diameters of coil, a number of different size reels must be made available by the manufacturer. Additionally, it has been our experience that reels tend to allow the coil to shift back and forth in an uncontrolled fashion, especially when the end of the pipe approaches. This increases the chance that the coil can become tangled or hung up on the reel and cause deleterious binding, which of course requires substantial downtime to correct.
And inherent problem characterizing the use of flexible plastic pipe is the tendency of the pipe itself to change shape when it is formed into the coil, especially after resting in a coiled position for an extended time. More particularly, the bending into the coil causes the pipe to assume a degree of curvature in the longitudinal direction, as well as an ovalness in cross-section. This deformation is sometimes referred to as “coil set.” As can readily be appreciated, the curvature and ovalness makes the pipe difficult to control during unwinding. Such flexible pipe has a good memory and, thus, there is a tendency for the pipe to backlash to the original coiled position and maintain its oval shape during unwinding. Obviously, to make the pipe lay in the trench, it must be straightened, and to maintain the maximum cross sectional area it must be rerounded. If the pipe is not so properly and accurately reformed, this coil set would make it difficult to mate the ends of two adjoining coils of pipe for fusion. This is because the ends to be mated would tend to be at a slight angle to each other, and they would likely have slightly different degrees of roundness.
There have been attempts in the past to successfully combine straightening and rerounding of plastic pipe as it is being unwound from the reel or the like in analogous applications. For example, in U.S. Pat. No. 4,095,437 to Cox, an apparatus is provided having a plurality of opposed roller pairs alternatively mounted in upright and transverse positions to contact and straighten/reround pipe. Another example is shown in U.S. Pat. No. 4,527,639 to Dickinson, III, et al., which discloses a device for removing the curvature and ovalness from drill pipe that extends through a curved passage in a bore hole that changes directions.
A more recently proposed apparatus particularly tailored for use with flexible coils of polyethylene pipe is described in U.S. Pat. No. 5,676,009 to Bright et al. and assigned to Chevron. The ′009 patent provides for a combined straightener and rerounder device that is towed behind a truck carrying a pipe coil. The device includes a set of straightener rollers to first remove the curvature, and then a set of side pressure rollers to remove the ovalness from the pipe. Although straightening and rerounding is achieved, other noteworthy limitations create problems. First of all, because the straightener/rerounder device remains in a fixed position behind the trailer, it can not track the pipe unwinding from the coil. This shortcoming can lead to the creation of deleterious pinch points and binding as the pipe is pulled from the periphery of the coil to the center fixed inlet of the device. In addition, loading of the pipe into the straightener requires a significant amount of time and effort. One or more workers must wrestle the end of the pipe and insert is over and under offset straightener rollers and then through separate rerounder rollers. It should also be recognized that the device does not itself carry the pipe coil and, thus this results in having to have a support a piece of equipment (truck or separate trailer) remain at the work site during the pipe laying operation.
Therefore, as should be appreciated from reviewing the foregoing description of the prior art, a need is identified for an improved trailer that both transports a coil of pipe to a work site and assists in laying the pipe from the coil into a trench. The trailer would eliminate the need for a reel or spool for supporting the coil, yet should provide proper support for the coil to ensure smooth rotation during the pipe laying operation. Adaptability for use with different diameters of coils would also be provided. In addition, the trailer would permit loading of the coil in an efficient and substantially effortless manner. To remove curvature and ovalness from the pipe unwinding from the coil, an improved on-board straightener/rerounder would also be provided that tracks the pipe during unwinding to
Boggs Franklin S.
Null Robert L.
Ronk Robert L.
Waller Kendrall P.
King and Schickli PLLC
Lee Jong-Suk
Null's Machine & Mfg., Inc.
Will Thomas B.
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