coupling 24 is cupshaped and has a square extension 47 which is arranged to be engaged in a recess 32 in an extension 33 formed on the moulding box 2 a pinion 35 which is slidable in a slot 34 is fastened on the piston rod 30 the pinion 35 meshes with a rack 36 the rack 36 is part of a piston 37 fig3 of a double action cylinder 38 the length of the rack 36 is such that the moulding box 2 can be turned 180 u00b0 at the side of the apparatus 1 a rail conveyor truck 39 of a rail conveyor is shown in fig1 this rail conveyor truck has a vacuum pipe 40 which by means of a coupling 42 can be connected to the moulding box 2 a pin 41 also provided on the rail conveyor truck 39 serves to centre the moulding box 2 the moulding box 2 consists of a frame 44 fig2 on which two projections 32 43 are formed in the interior of the frame an evacuation passage is provided for evacuating sand introduced into the frame the coupling 23 cooperates with the projection 43 the coupling 23 is connected to the vacuum pipe 28 and serves to evacuate the moulding box 2 the projection 43 provided on the moulding box is closed by means of a non return valve consisting of a spring 45 and a ball 46 the non return valve comes into operation when the moulding box 2 has been deposited on the rail.