Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-09-22
2001-05-08
Lorin, Francis J. (Department: 1775)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S304600, C156S503000, C156S581000, C156S583100, C219S104000, C219S464100
Reexamination Certificate
active
06228204
ABSTRACT:
BACKGROUND OF THE INVENTION
Metal pipe lined with non-metallic material, usually a thermoplastic substance, has been known for considerable time and is in widespread used for handling diverse materials spanning the gamut from corrosive acid to food. Many types of thermoplastics have been used for the liners. For example, polyvinylidene fluoride (PVDF), polypropylene, perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), and polytetrafluoroethylene (PTFE) polymers are typical pipe lining materials.
Joining sections of lined pipe can be done by a variety of methods, including using flanged pipe sections and welding the pipe sections together. It is preferred to weld the pipe liners together in order to form a secure pipe joint which is less likely to leak than a flanged pipe joint.
However, when fluorinated polymeric resins are utilized as lining materials, such as PFA, FEP, and PTFE, conventional welding techniques have proven ineffective, due to, for example, the difficulty in welding melt-processable PFA and FEP to themselves using contact welding techniques, and fusing sintered or ram extruded PTFE to itself due to the lack of adhesion even when heat and pressure are employed. An attempt to overcome the adhesion problems related to joining PTFE articles is described in U.S. Pat. 3,946,136, assigned to Hoechst Aktiengesellschaft. Yet, the '136 patent describes heating the resin from the outside in rather than heating the PTFE surfaces themselves and describes using an oven. Thus, the invention described therein cannot be used in the field. Another attempt to overcome adhesion problems related to joining PTFE articles is described in U.S. Pat. No. 4,073,856, assigned to Resistoflex; however, the '856 patent describes the use of a complicated mold which does not have the capability of being used in the field.
Hot plate welding techniques have been successfully used in the field. However, hot plate welding techniques have been unsuccessful for use in welding fluorinated melt-processable materials, because the fluoropolymeric materials have adhered to the hot plate welding equipment.
Non-contact welding techniques have also been used. Such techniques utilize infrared welding energy sources which heat the exterior and also penetrate the surface and heat the interior of the polymeric article. This non-contact approach overcomes the undesirable adhesion problem of the contact heater; however, this non-contact method allows the polymeric liners to relieve residual stress from the molding process and/or extrusion process, and any additional stresses incurred during the manufacturing process. This stress relieving, associated with the penetrating heat of the infrared source, causes the ends of the liners to geometrically distort, resulting in a less than desirable weld where the liners are joined together. This non-contact method is also difficult to use in the field.
It would be an advance in the art of plastic lined pipe products to provide a simple apparatus and method for welding fluorinated polymeric pipe liners together which is capable of being used in the field.
SUMMARY OF THE INVENTION
In one aspect, the present invention as an apparatus for welding fluoropolymeric pipe liners together comprising: a plate having first and second opposing surfaces, the first and second opposing surfaces facing away from each other; a temperature-resistant coating overlaying at least one of the opposing surfaces; and means for heating the first and second opposing surfaces.
In a second aspect, the present invention is a method for joining first and second fluoropolymeric liners to each other, comprising: contacting the first opposing surface of the aforementioned apparatus to an end of a first fluoropolymeric liner under pressure; contacting the second opposing surface of the aforementioned apparatus to an end of a second fluoropolymeric liner under pressure; removing the apparatus; and pressing the ends of the fluoropolymeric liners together liner under pressure to form a weld.
The present invention provides a simple solution to the problem of welding fluoropolymeric lining materials. The present invention provides an apparatus and a contact method of welding fluoropolymeric liners together which is capable of being used outdoors in the field or indoors where the piping system is to be assembled. The present invention can be used to weld together (1) melt-processable fluorinated polymeric PFA and FEP liners, (2) sintered or ram extruded PTFE liners, and (3) sintered or ram extruded PTFE liners utilizing a melt-processable fluorinated polymeric adhesive layer.
REFERENCES:
patent: 1601029 (1926-09-01), Ligonnet
patent: 2438685 (1948-03-01), Stevens
patent: 2505647 (1950-04-01), Norris
patent: 3013925 (1961-12-01), Larsen
patent: 3207644 (1965-09-01), Hobson, Jr. et al.
patent: 3929541 (1975-12-01), Spears et al.
patent: 4054473 (1977-10-01), Ohnstad
patent: 4283448 (1981-08-01), Bowman
patent: 4484975 (1984-11-01), McElroy
patent: 5124533 (1992-06-01), Dommer et al.
Ewald Jeff A.
Lewis Ray A.
Reinhardt Walther C.
Crane & Co.
Fitzpatrick ,Cella, Harper & Scinto
Lorin Francis J.
LandOfFree
Method and apparatus for welding together fluoropolymer pipe... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for welding together fluoropolymer pipe..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for welding together fluoropolymer pipe... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2437608