Feed box for pilger mill - has double piston, part controlling the mandrel, part running in auxiliary chamber

摘要

Feed box for pilgrim rolling mills includes a double piston, the first section of which is adjacent on the piston which controls the mandrel and runs in the return chamber of the piston, the chamber being fed with air. The second section of the double piston runs in an auxiliary chamber bounded by an annular wall and the base of the cylinder, and divided into two parts. The first part of the auxiliary chamber communicates with a source of compressed air at variable pressure; the second part can be fed with oil or other liquid from a reservoir. Communication between the oil reservoir and the second chamber can be intercepted by a holding valve while the air pressure in the first part of the auxiliary chamber is controlled so as to permit rolling. The maximum pressure to be reached in the return air pressure chamber after return of the piston running in the chamber can be pre-defined, while maintaining safety levels and while allowing for irregular running due to operator error or to error arising due to incidents occurring during rolling. The control is obtd. without the aid of expensive equipment.