US Patent 7416402 Sprue bushing anti-drool device

An anti-drool mechanism suitable for use in an injection molding system is provided herein. An injection molding machine includes a retractable machine nozzle for injecting a melt stream into a manifold. Between the machine nozzle and the manifold is an anti-drool mechanism, which includes a melt passage and a fixed pin disposed within the melt passage. The fixed pin is sized so that the melt stream will flow around the pin. The fixed pin has a head portion configured to engage with the machine nozzle and includes a first sealing surface. An actuated shut-off collar is also disposed within the melt passage, surrounding the pin, and includes a second sealing surface configured to cut off the flow of the melt stream when in contact with the first sealing surface.