The spring core consists of at least two opposite side parts with several connecting elements (4) between them. Several elastic shaped parts are provided to enclose at least in part the connecting elements. Several spacer elements (3) determine the distance between the adjoining shaped parts at least in one direction. The spring core as above is then enclosed by a cover which is divided to allow the core to be cleaned or changed. The cover can be divided by a slide fastener or a touch and close fastener on its narrow side. The shaped parts have variable hardness and variable elasticity. They can have different heights and different widths. The spacer elements between the shaped parts can have different sizes so that higher stressed parts of the mattress can be provided with closer together shaped parts.
