Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1993-10-26
1995-07-11
Maki, Steven D.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
15624422, 1563042, 1563045, 1563046, 1563099, 285284, 285330, B29C 6530, B29C 6542
Patent
active
054317622
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for joining spirally wound thermoplastic pipes of a hole profile together.
According to earlier methods, the joining-together of spirally wound pipes of the above-mentioned type usually occurred by means of extruder welding from the outer and inner side of the pipe. Since pipes of very large diameters, 2 m or more, are often concerned, this previously known technique causes considerable technical problems, and it is simultaneously very time-consuming. It was very diffucult to reach a satisfactory final result by means of the previously known technique.
The object of the present invention is to eliminate these problems, which is achieved by means of a method, which is characterized by the following steps: smooth step-formed surface, step-formed gap is formed between the end surfaces, to about 100.degree. C., smoothing organ cooperating therewith inside the pipes to be joined together, two end surfaces, as well as joining place after cooling.
The remaining characteristics of the invention will be apparent from the following description.
The invention will next be described in more detail with reference to the accompanying drawing, wherein
FIG. 1 shows the joining-together of two spirally wound pipes according to the present invention, seen from the outside in a radial direction, and
FIG. 2 shows the joining-together of FIG. 1, seen in an axial direction.
The joining-together of spirally wound thermoplastic pipes 1, 2 made of a hole profile occurs according to the invention as follows. The ends of the two thermoplastic pipes 1, 2 to be joined together are worked such that an end opening of the corresponding hole profile is closed and two smooth step-formed end surfaces 3, 4, which fit together, are obtained, whereafter the two pipes are placed end against end and set such that a uniformly wide step-formed gap (a gap having a step) forms between the end surfaces 3 and 4. The gap width is to be fitted according to the radial dimension of the hole profile, of which the spirally wound pipe 1, 2 is comprised. In connection with the most usual pipe dimensions, the gap width varies in the range of 10-40 mm. A stainless steel band 5 is applied over the gap between the two thermoplastic pipes 1, 2 and is heated to about 100.degree. C. In order to avoid that the melted thermoplastic material will adhere to the steel band 5, it is preferably teflon coated. An extruder 6 with a rotating extruder head 7 and a cooled slide and smoothing organ 8 cooperating therewith are applied inside the pipes 1, 2 to be joined together. The end surfaces 3, 4 are heated e.g. with warm air coming from a warm-air blower 12. A weld seam of melted thermoplastic 9 is extruded into the gap between the two end surfaces 3, 4, whereby the slide and smoothing organ 8 brings about the fact that the melted thermoplastic 9 completely fills the gap and a weld pressure is obtained. In this way, a weld seam with a smooth inner surface is formed. After the extrusion of the whole gap is completed, the heating of the steel band 5 is stopped and the extruded thermoplastic seam is cooled, whereafter the steel band 5 is removed from the joining place. A very smoooth seam may then be observed, which is nearly invisible to the naked eye.
According to a preferred embodiment, the heating of the steel band 5 occurs electrically, preferably by short-circuiting.
For setting the temperature of the steel band 5 to the desired level, it may preferably be provided with a temperature sensor coupled to a regulating circuit, which is arranged to regulate the electricity supply to the steel band. That is, the steel band is provided with a temperature sensor and a regulating circuit maintains the temperature of the steel band at a desired level, based upon readings from the temperature sensor.
The joining place, after the steel band 5 has been applied, has preferably to be surrounded with an insulation layer, as well as a felt cloth 10, which is in turn surrounded with a rubber sleeve 11, which prevents moisture and wetness from coming into c
REFERENCES:
patent: Re24801 (1960-03-01), Kaminsky
patent: 828516 (1906-08-01), Schroder
patent: 2220545 (1940-11-01), Reinhardt
patent: 3022209 (1962-02-01), Campbell
patent: 3030246 (1962-04-01), Westlake
patent: 3126306 (1964-03-01), Sherman
patent: 4338153 (1982-06-01), Zimmerman
patent: 5009737 (1991-04-01), Lescaut
patent: 5099888 (1992-03-01), Valls
Maki Steven D.
OY Kwh Pipe AB
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