Method and apparatus for joining thermoplastic line elements
US4334146A · kind A · utility
Inventor
Key dates
| Filing date | Dec 28, 1979 |
| Grant date | Jun 8, 1982 |
| Priority date | — |
| Expiry date | Dec 28, 1999 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C66/9674
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Electric welding sleeves used more particularly with larger pipe diameters have a heating wire winding which is under compressive stress due to the shrinkage of the sleeve member. This compressive stress and the elongation of the resistance heating wire occurring during the welding process can lead to a lateral displacement and contact with adjacent turns. The welding apparatus (4) used for welding such sleeves obviates these difficulties in that the overall welding time of the electric welding sleeve (15) is subdivided into a preheating time and a welding time. During the preheating time a partial power is used and during the welding time the full welding power. If the welding power is taken from an alternating current system the welding process can start with half the power by arranging a diode (8) in the welding circuit (2) and at the end of the preheating time the diode is bridged by a switching stage (10).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.