Patch injector

1. A patch injector for parenteral administration of a drug to a drug recipient having a skin surface, the patch injector comprising:

a drug-cartridge module having a drug reservoir with a longitudinal drug-reservoir axis;

a plunger movably disposed in the drug reservoir;

a power-pack module attached to a proximal end of the drug-cartridge module;

a compressed, elastic power element disposed in the power-pack module and coupled to the plunger, the compressed, elastic power element expandable along the longitudinal drug-reservoir axis;

a drug-recipient interface module connected to the power-pack module, the drug-recipient interface module comprising:

a skin-contact surface extending parallel to the longitudinal drug-reservoir axis;

an injection-needle insertion mechanism driven by the compressed, elastic power element and wherein the power-pack module in which the compressed, elastic power element is disposed and the drug-cartridge module are attached to an insertion-mechanism frame pivotably coupled to the skin-contact surface by a pivot offset from the longitudinal drug-reservoir axis;

an injection needle disposed at a distal end of the drug reservoir, the injection needle in fluid communication with the drug reservoir and oriented orthogonal to the drug reservoir and generally toward the skin-contact surface,

characterized in that,

the compressed, elastic power element is configured to displace the plunger distally into the drug reservoir and to move the injection needle toward the skin-contact surface when the compressed, elastic power element expands distally along the longitudinal drug-reservoir axis generating a bending moment in the injection-needle insertion mechanism, wherein a proximal end of the compressed, elastic power element disposed in the power-pack module is fixedly secured to an extension of the skin-contact surface and expansion of the compressed, elastic power element generates the bending moment that rotates the insertion-mechanism frame driving the injection needle toward the skin-contact surface.

2. The patch injector according to claim 1 , further comprising a locking mechanism having an inactive state in which the compressed, elastic power element is maintained in compression and an active state in which the compressed, elastic power element expands along the longitudinal drug-reservoir axis driving the plunger distally into the drug reservoir.

3. The patch injector according to claim 2 , wherein the power-pack module further comprises:

an outer sleeve including a twisting element and a groove with a notch at one end of the twisting element;

an inner sleeve disposed in the outer sleeve, the inner sleeve having an inner-piston lug which extends outwardly through the groove of the outer sleeve and is slideable in the groove,

wherein the inner-piston lug is releasably retained in the notch when the locking mechanism is in the inactive state.

4. The patch injector according to claim 3 , wherein the drug-recipient interface module further comprises an activation switch, wherein a depression of which causes relative rotational movement between the inner and outer sleeves, which releases the inner-piston lug from the notch and allows the compressed, elastic power element to expand along the longitudinal drug-reservoir axis.

5. The patch injector according to claim 1 , wherein the drug-recipient interface module further comprises a needle-protection mechanism having a needle-shield configured to permanently encapsulate the injection needle when the patch injector is removed from the skin surface of the drug recipient.