Abstract: The present invention relates to a device for pushing and pulling an accessory instrument of a manufacturing plant, such as a clamp for a metallic mould, by means of a chain driven by a hydraulic actuator having a vertical cylinder. One end of the chain is supported by a case which houses the chain. The chain is driven by one of more sprockets engaging the chain at and rotatably supported by a movable part of the cylinder.

Abstract: A work-clamp pallet of the exchangeable type for facilitating changing of works and intended for use with a machine tool of either the vertical or horizontal type with its base block provided with a plurality of hydraulic clamping devices and also with a special shut-off valve for shutting down its oil path. It is so arranged that its oil path may be shut down after supplying the hydraulic clamping devices with a set level of hydraulic pressure. This hydraulic pressure is maintained for a long time without any supplementary feeding of hydraulic pressure for the clamping devices to be kept in the clamping condition. When this work-clamp pallet is used, it is possible to change workpieces on the work-clamp pallet at a work-changing station outside the work table of the machine tool. The work-clamp pallet with workpieces clamped in position can then be transferred onto the machine tool to carry out the machining operations.