US Patent 7172404 Molding insert for molding machines

The invention relates to the production of multi-layered concrete moulded bodies in a moulding machine comprising a moulding insert having a plurality of mould cavities. Relief structures are arranged in the lateral walls of the mould cavities and are dimensioned in such a way that projections formed on the moulded body when the filled concrete material is compacted engage in the relief structures, thereby creating sufficient retaining force for compensating the net weight of the moulded body and enabling the moulded bodied to be extracted from the mould cavities as a result of additional demoulding forces and causing elastic deformation of the projections without any material being cut off from the projections.