An injection device for delivering a liquid composition, comprising a generally elongated housing (2), arranged to hold an exchangeable cartridge (3) containing the liquid composition. The housing comprises a drive device, and a plunger rod (5) connected with the drive device and connected to a plunger within the cartridge, when the cartridge is held at the housing, for driving the plunger within the cartridge. The plunger comprises a rod connector (7) connected with a front end portion (8) of the plunger rod. The rod connector has an entrance opening defined by wall sections of the rod connector, the width of the entrance opening being smaller than the width of the front end portion. The width of a rod portion adjacent to and rear of the front end portion at the most corresponds to the width of the entrance opening. The wall sections are resilient for enabling the front end portion to pass the entrance opening upon exerting an opening force on the wall sections. The rod connector comprises a rod stop portion, wherein there is a longitudinal play between the plunger rod on one hand and the entrance opening and the rod stop portion on the other hand, thereby enabling the front end portion to move back and forth between the entrance opening and the rod stop portion without moving the plunger.Un dispositivo de inyección para suministrar una composición líquida, que comprende un alojamiento generalmente alargado (2), dispuesto para sostener un cartucho intercambiable (3) que contiene la composición líquida； el alojamiento comprende un dispositivo de impulso y una varilla de émbolo (5) conectada con el dispositivo de impulso y conectada con un émbolo dentro del cartucho, cuando el cartucho se sostiene en el alojamiento, para impulsar el émbolo dentro del cartucho； el émbolo comprende un conector de varilla (7) conectado con una porción de extremo frontal (8) de la varilla de émbolo； el conector de varilla tiene una abertura de entrada definida por secciones de pared del
