An expanding pipe stopper for inserting within a pipe comprises two rigid circular plates 10,14 substantially the same diameter adapted to be inserted wholly within a bore of the pipe. An outwardly expandable annular flexible seal 18 is provided between adjacent peripheral surfaces 12,16 of the two plates 10,14 so as to be capable of projecting radially therefrom. The stopper includes a spigot 20 fixed to the centre 22 of one of said plate 10, extending through a central hole 24 in the other of said plates 14. A collar 28 is connected to the spigot 20 on that side of the other plate 14 remote from the one plate 10. Cam means 32 are pivotable about an axis 34 on the collar 28 radially offset from the centre-line 35 of the spigot 20 and disposed in a plane perpendicular to the line by a lever 36 fixed to the cam means 32, between one position, in which the plates 10,14 do not compress the seal 18 to force it into engagement with the bore of the pipe, and another position, in which the cam means 32 forces the plates 10,14 relatively towards each other so as to compress the seal 18 and thus expand it outwardly to engage in sealing contact with the bore of the pipe. A member 46 is fixed to the collar 28 and is adapted to contact the bore of the pipe so as to provide a reactive force to tilting of the stopper out of its operative position perpendicular to the axis of the pipe. An annular wear plate 48 is interposed between the cam means 32 and the other plate 14.
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