Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-06-30
2001-11-27
Silbaugh, Jan H. (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S224000, C156S245000, C156S258000, C156S274200, C156S304200, C156S304300, C156S304600, C264S138000, C264S152000, C264S249000, C264S449000, C264SDIG004, C285S021200
Reexamination Certificate
active
06322653
ABSTRACT:
This invention relates to a method for joining together thermoplastics pipes made by spiral winding of a hollow profile with mainly rectangular cross section and by welding together the wound rounds located beside each other.
In joining together of spiral wound pipes, a lot of problems are encountered, either as a consequence of the irregular form of the pipe end with an open profile end, or due to a straightly cut pipe end with an end surface having, over most of the periphery of the pipe, a groove-formed recess passing into the helically extending channel of the profile.
In accordance with previously known methods, the joining together of spirally wound pipes has been carried out either by extruder welding from the inside of the pipe, or by pipe sleeve joints. All of these previously known methods tend to require relatively much work. Extruder welding also requires a relatively complicated equipment and the pipe sleeve joints often lead to problems with leaking seams.
The objective of the present invention is to eliminate these problems. This is achieved by using a method characterized by the following stages:
cutting of the profile in the end of the pipe along the inside of that side wall fastened to the nearest preceding wound round and with a section that cuts the end of the profile in a right or an obtuse angle, of equal size for all the pipe ends that are to be joined together,
closing the holes in the cut profile ends and preparation of the pipe end surfaces along the entire periphery,
positioning two pipes aligned with each other so that the cut profile ends are axially offset,
inserting a disc-formed welding ring, matching with the inner and outer diameters of the pipe, in the slot between said two pipes, which welding ring comprises at least one loop of a resistance wire covered by a thermoplastics sleeve,
centering the two pipes with an inner and an outer root support around the seam,
pressing the pipe ends against each other,
connecting the resistance wire of the welding ring to a current source in order to heat the thermoplastics material in the welding ring and the pipe ends so that the thermoplastics material melts down and forms a welding seam,
cooling the welding seam,
removing the root support and other accessories from the welded pipe, and
cutting off the connecting wires of the welding ring.
Using this method, an elegant and simple way to join together spiral wound pipes is provided, resulting in nice, tight, and secure seams. When the outer profile is cut using the method described above, a pipe end is obtained with a double wall thickness, and this will, to a sufficient degree, maintain its rigidity even under the heating process with the welding ring, thus ensuring that a sufficient pressure force can be maintained between the end surfaces of both of the pipes to be joined together.
Other characteristics of the invention will become evident by studying the attached, dependent claims
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Andtbacka Anders
Blomqvist Gunnar
Slotte Stefan
Connolly Bove & Lodge & Hutz LLP
OY Kwh Pipe AB
Silbaugh Jan H.
Staicovici Stefan
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