GB839743A - Improvements in or relating to pipe joints - Google Patents

Abstract

839,743. Pipe joints. EVERED & CO. Ltd. July 2, 1956 [July 2, 1955; Dec. 3, 1955; Dec. 10, 1955; Dec. 20, 1955; May 17, 1956], Nos. 19188/55, 34667/55, 35525/55, 36419/55 and 15349/56. Class 99(1). In a method of making an end-to-end joint between pipes 26, 27 of thermoplastic material, such as polyethylene or polyvinyl chloride, heat is supplied to the end portions of the pipes while those ends are confined between inner and outer sleeves 10, 14 and the pipes are pressed axially towards each other to cause the end portions to become joined through a fused fluid-tight union 30 of thermoplastic material which is then caused or permitted to cool or harden. As shown, the thin-walled inner sleeve 10, Fig. 3, is made of brass, copper, stainless steel, or fabric woven from glass fibres impregnated with a silicone or polyester resin, and is formed with a central, circumferential rib 11 ; alternatively, a separate moulded ring 12, Fig. 2, of thermoplastic material adherent to the sleeve is employed, an inward deformation 13 being produced in the wall of the sleeve. The outer sleeve 14 of metal, ceramic or heat-resisting glass is formed with a central, internal flange 17, adjacent each end face 21 of which is a keying recess 20, and internal, bevelled or bell-mouthed end portions 15. Indicator holes 25 which are formed in the wall of the sleeve 14 and open into the recesses 20 are so dimensioned that expulsion of fluent thermoplastic material therethrough occurs only when temperature and pressure conditions have been established in the material of the pipes to produce the fused union 30. The material displaced by the flange 17 and filling the recesses 20 provide resistance to tensile forces applied to the pipes, and the joint is relieved of torsional stresses by the provision of axially-extending keyways in the surface portions 15, 16 of the outer sleeve. To indicate that sufficient heat has been supplied to the outer sleeve at least one band 31 of a material, such as " Thermindex" (Registered Trade Mark), which undergoes a change in appearance at a predetermined temperature is applied to the sleeve. The end faces 21 and the inner face 18 of the flange intersect in sharp edges 23 to promote displacement of part of the pipe material into the keying recesses 20 the volume of which is not greater than the reduction in passageway volume produced by the flange. In a modification, the outer sleeve 14 is provided with a self-contained heating means comprising combustible fuel in the form of a wound filament 32, Fig. 5, protected by removable sheet metal covers 33, 34. In a further modification, the tubular, metal outer sleeve 14 is formed with an inwardly-projecting channelsection flange flanked on either side by an annular channel functioning in the same manner as the recesses 20. In making the joint, heat may be applied to the end portions of the pipes by pre-heating the outer sleeve before introducing the pipes between the sleeves, or the outer sleeve may be heated after insertion of the pipes between the sleeves ; the pipes may be warmed prior to passage thereof between the sleeves. Cooling of the joint may take place as a result of natural cooling in the atmosphere, and this process can be accelerated by subjecting the outer sleeve to a cooling fluid such as air or water, or by applying a wet cloth to the joint. According to the first Provisional Specification, the outer surface of the inner sleeve tapers from the middle of the sleeve towards the ends thereof, and the outer sleeve may be formed in separable portions, and removed upon completion of the joint. In the second Provisional Specification, it is stated that the heating means may be ignited by a fuse and be in the form of powder, blocks or tablets retained in position by a perforated housing. Also, the heating means may be in the form of a slug located within the inner sleeve or the inner part of a non-thermoplastic, e.g. metal, pipe to which a thermoplastic pipe is to be joined, ash or residue left after burning of the fuel being removed prior to assembly of the pipes, or by flushing, brushing or otherwise cleaning of the joined pipes internally. Liquid fuel may be used and retained in position around the outer sleeve by providing a porous carrier of incombustible material bounded by heat-conserving material. One of the pipes may be of metal or a non-thermoplastic, non-metallic material, and heated before or after two pipes are brought into contact, the material of a thermoplastic pipe interengaging in keying formations in the non- thermoplastic pipe. The third Provisional Specification describes an inner sleeve formed of compressed or compacted sodium chloride, starch or sugar and dissolved in water or other liquid, the reinforcement of the sleeve after dissolution thereof being left in granular or divided form or filaments removable by flushing. Keying formations such as ribs of saw-tooth section arc provided externally of the inner sleeve. According to the fifth Provisional Specification, the outer sleeve is provided internally with rectilinear or helical grooves of quickpitch form, or internal intersecting threaded formations of opposite hand to produce diamond-shaped projections, and the inner and outer sleeves are of moulded synthetic resin containing a heat-resisting silicone. Speci - fications 839,744 and 839,745 are referred to.