In the present state of the known art, numerous types of BUTTERFLY VALVES exist which are intended to be connected to piping by flanges, screwthreads or welding. But the recent development of pipes made from plastics material, for example polyvinyl chloride or P.V.C. and tubes made from fibrocement, makes Butterfly Valvesintended to be connected to these pipes very desirable and it is the object of the invention to fulfil this new need.

Furthermore, the invention relates to a butterfly valve which is liquid-tight both against leakages of liquid conveyed in the pipe and against the entry of external fluid, for example to prevent the pollution of drinking water by underground water which is always suspect.

The invention also relates to a butterfly valve whose metal casing is completely covered internally and externally with a polymer in order to prevent corrosion on the one hand and the pollution of the liquid conveyed on the other hand.

Finally, the invention also relates to a butterfly valve whose positioning and removal are easy and quick, without having to touch the piping, which is a considerable advantage especially when said piping is buried.

Consequently, the Butterfly Valves according to the invention comprises a metal casing rough-cast with holes passing therethrough and covered internally and externally with elastomer filling said holes and a butterfly member in the form of a disc with two spherical segments of coated metal or reinforced plastics, mounted on two splined half-shafts rotating in bearings which are preferably self-lubricating. The butterfly valve according to the invention may comprise male and/female connecting-pieces gripping the piping by fitting or by adhesives or by couplings and the double seal is ensured by the annular lips of said elastomer, namely lips having a steep side opposite the inside of the piping and at least one lip having a steep side opposite the outside of the piping.

According to another feature of the invention, the butterfly valve may co-operate with a sleeve and a cylindrical spacing member housed in a sleeve sliding on the pipework and locked. After unlocking, sliding of the sleeve on the pipework releases the spacer member and the valve and sleeve may be released by sliding.

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