Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – Work-secured and/or work-guided
Patent
1981-02-23
1982-07-06
Simmons, David A.
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
Work-secured and/or work-guided
156215, 1563042, 1563043, 156503, B65H 800
Patent
active
043381537
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention concerns welding of the plastic lining inside concrete tubing at the joint between adjacent sections of tubing.
BACKGROUND
Some types of concrete tubing such as those intended for use as sewer pipe are provided with plastic lining for protecting the concrete from the effects of material in the pipe. In exemplary embodiments the lining is polyvinyl chloride or other thermoplastic material in the order of two to five millimeters thick. Such tubing may be lined around the entire circumference or around an upper portion of the circumference. The latter embodiment is suitable for sewer pipe where a lower portion of the pipe is protected by immersion in liquid contents of the pipe and only an upper portion is exposed to gases that could damage the concrete.
In either embodiment it is important to seal the plastic lining within adjacent sections of tubing at the butt joint between the sections. In some embodiments a flap of extra plastic is provided at one end of each section of tubing and that flap is lapped over the plastic lining in an adjacent section of pipe and sealed in place. Alternatively, a strip of plastic can be added along the joint overlapping the plastic lining in adjacent sections of tubing. In either embodiment the overlapped portion is preferably heat welded for providing a fluid-tight seal.
It has been the practice to manually weld such plastic linings using a hot air gun or the like for melting the plastic. Such techniques are costly and difficult and can be subject to variable quality. It is therefore desirable to provide a technique for rapidly and reliably welding the joints in plastic lining in concrete tubing or the like. Preferably the technique should be suitable for tubes of a variety of diameters and for either lap joints employing a flap of plastic from one tubing section overlapping the plastic in another section or joints employing an added sealing strip of plastic over the lining in adjacent sections. Preferably the technique is suitable for welding the lining adjacent a butt joint normal to the tubing axis or at a beveled or mitered joint adjacent a change in direction of the tubing.
BRIEF SUMMARY OF THE INVENTION
There is, therefore, provided in practice of this invention an apparatus for welding the plastic lining of tubing comprising a carriage movable inside such tubing along its length. In use the carriage is fixed in position within the tubing at a selected location adjacent a seam to be welded. At least one carrier arm is mounted on the carriage for rotation about an axis coinciding with the axis of the tubing and a welding unit is mounted on an outer end of such a carrier arm remote from the axis of the tubing so as to be near the wall of the tubing. A drive source adjacent the welding unit includes means for engaging the interior of the tubing and self propelling the welding unit and carrier arm around the interior of the tubing. The welding unit and drive are biased outwardly toward the wall of the tubing, and are guided along a welding seam around the tubing, either by a guide wheel in the gap between adjacent pipe ends or by guide rollers engaging a guide ring temporarily clamped in the tubing. Translation of the welding unit along the length of the tubing to remain aligned with the welding seam is accommodated without moving the carriage. Such translation can be accommodated by mounting the welding unit on a pivot arm which can also pivot about an axis extending radially in the tubing. The carrier arm can also be mounted for pivoting about an axis normal to the tube axis so that the welding unit can be guided along a bevel joint.
DRAWINGS
Additional features and advantages of the present invention will be appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 is a semi-schematic end view of welding apparatus constructed according to principles of this invention within a tube illustrated in transvers
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patent: 3516242 (1950-07-01), Munger
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patent: 4054473 (1977-10-01), Ohnstad
patent: 4146419 (1979-03-01), Neidhart
Ameron Inc.
Simmons David A.
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