The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 16, 1990
Filed:
Feb. 21, 1989
Alan J Dickinson, Cramlington, GB;
Trevor G Stafford, Whiteley Bay, GB;
British Gas plc, London, GB;
Abstract
First and second members (e.g. pipes, fittings) of cross-linked polyolefinic material such as polyethylene having a melt flow index (MFI) of zero are joined using a third member of polyolefinic material such as polyethylene having a higher MFI e.g. 0.3. The first member 10 and the third member gripped by clamps 18, 20 of a butt fusion machine are pressed against opposite faces of a heater plate which is then withdrawn and the members are pressed together by the clamps. Only the third member is upset to form beads 24, 26. Part of the third member is removed leaving a stub part 16. The second member is joined to the stub's face 36 using the heater plate. The part 16 is upset leaving a thin wafer 48. The two interfaces 30, 50 limit the growth of cracks in the wafer to prevent their propagation through the pipe thickness under hoop stress. The beads are preferably removed at each stage.