the disclosure relates to a system for injecting a thermoplastic material in the fluid state , including : a dispenser adapted to be maintained at an injection temperature higher than the temperature limit at which the material is in a fluid state ; an injection nozzle defining at least one portion of a transition passage ; a stopper mounted inside the transition passage so as to slide between a blocking position and an opening position thereof ; and control means for alternately sliding the stopper , wherein the control means comprises a jack with a rod parallel to the sliding direction of the stopper , and which is secured in an offset manner on the dispenser via a flattened beam , and a lever arranged so as to tilt about an axis so as to transmit the movements of the jack rod to the stopper .