Extraction system for preparing a beverage from a cartridge using a fluid injected under pressure into the said cartridge and comprising: - a cartridge comprising: a beverage delivery wall which can be perforated under the effect of the pressure of the fluid within the cartridge, a wall for injecting the fluid into the cartridge, a nip region, - an extraction device intended to accept the said cartridge and comprising: an injection cage comprising fluid injection means (62, 70), and a cartridge support comprising perforating means (12, 60) for perforating the delivery wall of the cartridge under the effect of the pressure of the fluid in the cartridge; the said injection cage and the said cartridge support being arranged in such a way as to be moved relative to one another by a closure device which closes them around the cartridge prior to injection, and to trap the cartridge in the said nip region, wherein the injection cage comprises a base and a closure piston unit which is mounted so that it can move axially with respect to the said base; the said closure piston unit can move relative to the base under the effect of the pressure of the fluid against the nip region of the cartridge in order to generate clamping forces that prevent the injection cage and the cartridge support from opening up relative to one another as the system is pressurized, wherein the injection cage comprises an internal extraction cavity of a shape designed to at least partially accept the cartridge, wherein the cavity comprises at least one fluid supply duct and possibly at least one opening element, wherein the injection cage comprises a pressure chamber, characterized in that the pressure chamber at rest is substantially entirely occupied by an elastic thrusting means. - a cartridge comprising: a beverage delivery wall which can be perforated under the effect of the pressure of the fluid within the cartridge, a wall for injecting the fluid into the cartridge, a nip region, a beverage delivery wall which can be perforated under the effect of the pressure of the fluid within the cartridge, a wall for injecting the fluid into the cartridge, a nip region, - an extraction device intended to accept the said cartridge and comprising: an injection cage comprising fluid injection means (62, 70), and a cartridge support comprising perforating means (12, 60) for perforating the delivery wall of the cartridge under the effect of the pressure of the fluid in the cartridge; the said injection cage and the said cartridge support being arranged in such a way as to be moved relative to one another by a closure device which closes them around the cartridge prior to injection, and to trap the cartridge in the said nip region, wherein the injection cage comprises a base and a closure piston unit which is mounted so that it can move axially with respect to the said base; the said closure piston unit can move relative to the base under the effect of the pressure of the fluid against the nip region of the cartridge in order to generate clamping forces that prevent the injection cage and the cartridge support from opening up relative to one another as the system is pressurized, wherein the injection cage comprises an internal extraction cavity of a shape designed to at least partially accept the cartridge, wherein the cavity comprises at least one fluid supply duct and possibly at least one opening element, wherein the injection cage comprises a pressure chamber, characterized in that the pressure chamber at rest is substantially entirely occupied by an elastic thrusting means. an injection cage comprising fluid injection means (62, 70), and a cartridge support comprising perforating means (12, 60) for perforating the delivery wall of the cartridge under the effect of the pressure of the fluid in the cartridge; the said injection cage and the said cartridge support being arranged in such a way as to be moved relative to one another by a closure device which closes them around the cartridge prior to injection, and to trap the cartridge in the said nip region, wherein the injection cage comprises a base and a closure piston unit which is mounted so that it can move axially with respect to the said base; the said closure piston unit can move relative to the base under the effect of the pressure of the fluid against the nip region of the cartridge in order to generate clamping forces that prevent the injection cage and the cartridge support from opening up relative to one another as the system is pressurized, wherein the injection cage comprises an internal extraction cavity of a shape designed to at least partially accept the cartridge, wherein the cavity comprises at least one fluid supply duct and possibly at least one opening element, wherein the injection cage comprises a pressure chamber, characterized in that the pressure chamber at rest is substantially entirely occupied by an elastic thrusting means.