| 摘要 |
A pipeline crawler mechanism for increasing the effective length of smaller-diameter gas main which can be inserted into an existing larger-diameter gas main utilizing the techniques described in U.S. Pat. Nos. 3,845,789 and 4,090,534. The mechanism for extending the length of such an insertion includes two self-centering carriers for insertion into the larger-diameter gas main. Each carrier includes an apparatus for attaching a semirigid rod to it so that the carrier may be pushed into the larger-diameter gas main section to a distance determined by the flexibility, weight, etc., of the rod. Each carrier includes a coupler. One coupler includes a male member and the other includes a female member. When the carriers approach each other from opposite ends of the larger-diameter main section upon which an insertion is being conducted, the couplers automatically couple, permitting both carriers and both lengths of the semirigid fiberglass rod to be pulled back toward one end of the larger-diameter main section. Since the length and flexibility of the rod generally determines the maximum length of main section upon which an insertion can be conducted at once, the length of main section upon which an insertion can be conducted at one time is effectively doubled using the crawler.
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