A nozzle for injecting a viscous fluid, such as a molten plastic and a non-viscous fluid, such as a gas, includes a nozzle body having an inlet end, a discharge end and a flow passage for viscous fluid extending from the inlet end to the discharge end. A shut off valve device is provided for reciprocating in the nozzle body flow passage to control the flow of viscous fluid through the nozzle body discharge end. The shut off valve device includes a valve body and a non-viscous fluid flow passage provided in the valve body. A baffle device is located in the non-viscous fluid flow passage of the shut off valve for retarding a flow of viscous fluid in the non-viscous flow passage.