Pipe connector device

A pipe connector comprises a tubular pin member having a frustoconical outer surface and a tubular box member having a frustoconical inner surface corresponding to the outer surface of the pin member and which overlies the frustoconical surface of the pin member when the members are fully engaged. The members are provided with inter-engageable annular projections and grooves on the said peripheral surfaces for axially locking the members together when they are fully engaged together. The projections and grooves are spaced apart along the surfaces. The inner tubular surface of the pin member and an outer tubular surface of the box member each include at least one of a recess and/or a protrusion/radially enlarged section which reduces and/or increases the thickness of the tubular wall along the length of the associated member so as to balance the displacement of the members at different points along the length thereof under injection pressure.