Needle-less injector

An actuator in combination with a cartridge to form a needle-less injector, comprising:

• (a) said cartridge being prefilled with a liquid to be injected in a subject, said cartridge comprising,
• (i) a liquid outlet and a free piston inward of the liquid outlet in contact with the liquid;
• (ii) a separately held plurality of components which are to be mixed with one another prior to injection;
• and
• (iii) a mixing member for mixing the plurality of components with one another, wherein the plurality of compartments are separated by at least one partition and said cartridge further has a penetrating member so mounted therein as to be movable to a mixing position in which it penetrates the partition;
• and
• (b) said actuator comprising:
• (i) a housing adapted to be connected with the cartridge;
• (ii) impact member mounted within said housing inward of the free piston so as to be movable from a first position toward the liquid outlet to strike the free piston and to continue to move the free piston toward the liquid outlet whereby a dose of the liquid is expelled through the liquid outlet in the cartridge, said impact member further comprising a mixing means being movable toward the liquid outlet for striking the mixing member, said mixing means in striking said mixing member being further operable to move the penetrating member to the mixing position whereby the plurality of components are mixed with one another;
• (iii) a sealed chamber within said housing prefilled with pressurized gas and connected with said impact member such that said pressurized gas constantly exerts a force on said impact member when said impact member is in said first position to normally urge said impact member toward the liquid outlet;
• and
• (iv) a latch within said housing for engaging said impact member to prevent movement of the impact member toward the liquid outlet in response to said force exerted by said pressurized gas, and being movable to a firing position for permitting such movement.

A method of injecting a dose of liquid in a subject using

• an injector including a cartridge prefilled with the liquid and having a liquid outlet and a free piston in contact with the liquid,
• an impact member movable from a first position behind the free piston to first strike said free piston and then to continue to move the piston toward said liquid outlet to expel a dose of liquid through said liquid outlet;
• a chamber prefilled with pressurized gas which constantly contacts and exerts a force on said impact member in said first position to urge said impact member towards said piston
• a latch movable from a restraining position, in which said latch engages and prevents movement of the said impact member in response to the force exerted by the gas, to a firing position, in which said latch does not engage said impact member and permits such movement;
• (ii) causing said latch to move from said restraining position said method comprising the steps of to said firing position, whereby said impact member moves toward the liquid outlet, strikes said free piston, and continues to move said piston toward the liquid outlet to expel a single dose of said liquid.