PERFECCIONAMIENTOS EN LAS TORRETAS PORTAHERRAMIENTAS REVOL- VER

摘要

A transfer valve for controlling an hydraulic copying attachment for a machine tool is of the kind in which a tracer is provided by a valve member 4 which is sealingly slidable axially in a cylindrical bore 3 in a valve casing 2 and has annular pilot shoulders 8 sealingly engaging said bore, the casing 2 being formed with fluid ducts 6 opening into the bore 3 by way of individual pilot orifices 7 each shaped to resemble a buttonhole extending peripherally of the cylindrical bore 3 and having opposing edges 7a, 7b, of predetermined concave curvature as viewed normal to the axis of the bore. The shoulders 8 and the buttonhole-shaped orifices 7 co-operate with one another as the valve member 4 moves to define the pilot gaps 9 and control the supply of fluid to the copying attachment with a predetermined gradualness.