A device for the moulding of thermoplastic containers by blowing comprises a mould (1) with two half-moulds (2, 3), each having a support (5, 6) and a mould block (7, 8) between which, in one half-mould, a compensating chamber (20) is defined, with elastic return means (26) and abutment means (27) being interposed, which are combined in unitary assemblies (35) each comprising: a bore (36) passing through the support and receiving a pin (38) having one end (39) fastened to the mould block and a first radial shoulder (40) against which bears the end (E) of a sleeve (46) screwed in the bore and having an outer head (47) capped by an axially displaceable housing (49), with the elastic return means being interposed, which are preloaded by a nut (53) screwed on the free end of the pin against a second radial shoulder (54) of the pin, at the same time pushing the housing.