Operating head with phased fluid delivery

An operating head assembly comprising a non-rotatable body, a power driven, rotary head journaled in said body and thereby having an axis of rotation, and a fluid distribution system, a fluid input duct means incorporated in said fluid distribution system and connecting said body with said for head for continuous feed of fluid thereto as said head, in use, rotates relatively to said body, a plurality of delivery jet nozzles located at respective positions on said head, manifold means including at least one duct in said head for passing said fluid to said jet nozzles, a plurality of valve units carried in said head, a shut-off valve incorporated in each of said valve units, each said shut-off valve being biassed, in use, to a closed position, an hydraulic power operated actuating means, to open or close said duct(s) leading to said jet(s) in a respective angular sector of said actuating means being constituted by a plunger type actuator operable to displace said shut-off valve from said closed position, a plurality of hydraulic power ducts located equiangularly around said head on a common pitch circule, an annular radial face provided on said head, said hydraulic power ducts at one end thereof emerging at said annular radial face, an annular radial face of said body located in close proximity to said annular radial face of said head, a plurality of seal formations located in said annular radial face of said body about the same pitch circle, an annular radial face provided on said head, said hydraulic power ducts at one end thereof emerging at said annular radial face of said body located in close proximity to said annular radial face of said head, a plurality of seal formations located in said annular radial face of said body about the same pitch as said hydraulic power ducts so as to be co-operable therewith for the transmission of hydraulic power between said body and said head, and automatic timing means including drive input means of said body of said assembly operable for selective transmission of hydraulic power to said plunger type actuators of said valve units individually by way of said hydraulic power ducts co-acting with said seal formations as said head rotates, said timing means being controllable so that said fluid is supplied to said jet nozzles as they pass sequentially through a pre-selectable angular sector determined by the direction in which said head assembly is being displaced.