Abstract: An injection molding device for molding shaped bodies of natural or synthetic rubber comprising a heatable mold for shaping and vulcanizing therein the bodies to be molded and an elongated feed duct communicating with the mold via an injection nozzle. Plasticized material is fed into the duct by a plasticizing device and injection is effected by a piston-type injection device, both communicating with the duct. There is provided in the duct a valve which in its closed position blocks ingress of plasticized material into the duct but opens the duct for ingress of the material to be pressed by the injection means into the mold via the nozzle. The valve head is axially displaceable in the duct and mounts a member so dimensioned that in the open position of the valve it fully closes the nozzle opening, thereby pushing any residual plasticized material into the mold and in the closed position is completely withdrawn from the nozzle opening.