An injector for introducing different liquid products of a rubber mixture into a chamber of an internal mixer in which the injector is mounted, the injector comprising: - a cylindrical housing of a predetermined length between an injection end and an opposite end of the injector, the housing comprising an injection conduit dedicated to the flow of a liquid product to form the mixture, the injection conduit extending between an outlet of the injection conduit, which is coextensive with the injection end of the housing , and an opposite inlet , and the injection conduit comprising a seat defined adjacent to the outlet ; - a valve disposed in the injection conduit that meters a corresponding liquid product, the valve comprising a longitudinal stem that extends between a tail disposed adjacent the inlet of the injection conduit and a head disposed adjacent the seat of the injection conduit; - a return spring disposed around the stem of the valve that controls a sliding movement of the valve relative to the injection conduit between a closed position, where the head engages the seat and blocks the outlet of the injection conduit , and an open position, where the head no longer engages the seat and unblocks the outlet of the injection conduit ; - an injection device integrated with the housing and comprising a supply conduit that delivers a liquid product to a corresponding injection conduit from a reservoir in which the liquid product is stored, each supply conduit being arranged perpendicularly to a corresponding injection conduit to introduce the liquid product to the inlet of the injection conduit ; the injector is characterized in that - the housing comprises at least two injection conduits and in that - a temperature control circuit is inside the injector . - a cylindrical housing of a predetermined length between an injection end and an opposite end of the injector, the housing comprising an injection conduit dedicated to the flow of a liquid product to form the mixture, the injection conduit extending between an outlet of the injection conduit, which is coextensive with the injection end of the housing , and an opposite inlet , and the injection conduit comprising a seat defined adjacent to the outlet ; - a valve disposed in the injection conduit that meters a corresponding liquid product, the valve comprising a longitudinal stem that extends between a tail disposed adjacent the inlet of the injection conduit and a head disposed adjacent the seat of the injection conduit; - a return spring disposed around the stem of the valve that controls a sliding movement of the valve relative to the injection conduit between a closed position, where the head engages the seat and blocks the outlet of the injection conduit , and an open position, where the head no longer engages the seat and unblocks the outlet of the injection conduit ; - an injection device integrated with the housing and comprising a supply conduit that delivers a liquid product to a corresponding injection conduit from a reservoir in which the liquid product is stored, each supply conduit being arranged perpendicularly to a corresponding injection conduit to introduce the liquid product to the inlet of the injection conduit ; the injector is characterized in that - the housing comprises at least two injection conduits and in that - a temperature control circuit is inside the injector . <EOS>