Needle valve nozzle for injection molding plastics has a mechanism to prevent needle rotation during needle adjustment

摘要

An adjuster for setting the position of the valve needle(18) has a mechanism to prevent rotation of the needle around its longitudinal axis during an axial adjustment movement. Rotation prevention is particularly suited to needles with a profiled, in particular a rotationally asymmetric shape relative to the needle axis. A valve needle holder(10), which forms part of the rotation prevention system acts in conjunction with an operating piston(6) and an adjusting spindle(38) which engages a thread in the piston to allow axial adjustment. The valve needle holder has a rotationally asymmetric outer shape relative to the needle axis and forms part of the anti-rotation mechanism which is guided in a rotationally asymmetric bore. Rotation is prevented by a multi-sided head(13) and a securing disc(21) on the operating piston forms the securing mechanism. Teeth around an opening in the disc allow the multi-sided head to be inserted in different positions and prevent rotation of the head and valve holder. In a design variation the valve needle holder has guiding pins at the sides and the operating piston has a bore with longitudinal grooves. The holder is guided in the bore and the guiding pins slide along the grooves to prevent rotation of the adjuster spindle. A holding disc with an internal thread is screwed into the bore and a locking disc with projections and in contact with the holding disc engages in the grooves. A lock nut is screwed either into the internal thread of the holding disc or onto the adjuster spindle. The locking disc is thus clamped between the holding disc and lock nut and the adjuster spindle is screwed into the internal thread of the holding disc. Independent claims are included for: a) an injection molding unit with heated manifold system and injection nozzles, at least one of which has the claimed design; b) a needle shut-off valve for an injection nozzle.