A clamping assembly for an injection moulding installation includes a rigid, elongated positioning structure and an elongated clamping structure. A fixed platen is rigidly coupled to the positioning structure and articulatedly coupled to a first end portion of the clamping structure. Longitudinal, axially directed sliding bearings are formed integrally with the positioning structure. The assembly further includes a movable platen slidably supported on the bearings for a free, axially directed displacement with respect to the positioning structure towards and away from the fixed platen. A platen drive unit is articulatedly coupled to a second and opposite end portion of the clamping structure and to the movable platen for imparting that displacement to the movable platen.