Pipe couplings

Claim 1

A pipe coupling comprising an elastomeric bellows having annular end faces adapted to abut corresponding annular flanges of pipes being coupled, said bellows comprising an integral moulded one-piece elastomeric unit having a thick fabric-reinforced internal wall defining a passageway for fluid flowing through the coupling and a thick fabric-reinforced external wall, the external wall being of generally uniform thickness but being thickened in regions adjacent to the end faces; and annular metal plate embedded in the thickend regions of the external wall adjacent the respective end faces at each end of the bellows, each plate lying in a plane substantially parallel to said end faces and being surrounded by fabric-reinforced elastomeric material, each plate further including a plurality of threaded holes aligned with corresponding holes in respective end faces for receiving threaded ends of a bolt or stud such that the end faces may be bolted to the flanges of the pipes being coupled; the internal wall and external wall being spaced apart to form an annular cavity around the passageway, the cavity being fillable with pressurized fluid and a sensing element being positionable in fluid communication with and responsive to pressure within the cavity for providing an alarm output whenever the sensed pressure rises over or falls below predetermined limit values; and wherein the internal and external walls interconnect the annular end faces and each have a portion formed with at least one permanent, preformed, radially outwardly extending arch or corrugation, said portion of said internal wall lying between said annular end faces such that, together with said end faces, said portion provides a zig-zag or folded bellows construction which allows for axial expansion and contraction of the pipes joined by the coupling.