Injection device providing automatic needle retraction

An injection device comprising:

• a body incorporating a syringe cartridge, the syringe cartridge containing a medicament to be injected, including a needle through which the medicment can be injected, and being positioned within the body such that the syringe cartridge can be displaced back and forth within the body;
• a bias mechanism configured to exert a first force against the syringe cartridge, which first force works to maintain the syringe cartridge in a retracted position within the syringe body;
• a drive mechanism comprising an energy source, a drive member, a compound plunger,
• and a decoupling mechanism, wherein the compound plunger includes an outer plunger forming a reservoir, a hydraulic fluid contained within the reservoir, a hydraulic orifice, and an inner plunger positioned within at least partially within the outer plunger, the drive mechanism being configured such that, upon actuation, the energy source, drive member, compound plunger, and decoupling mechanism function together to effect automatic extension of the needle of the syringe cartridge from the body of the injection device, automatic delivery of a desired dose the medicament from the syringe cartridge, and automatic retraction of the needle after delivery of the desired dose of the medicament.

An injection device comprising:

• a body incorporating a syringe cartridge, the syringe cartridge containing a medicament to be injected, including a needle through which the medicment can be injected, and being positioned within the body such that the syringe cartridge can be displaced back and forth within the body;
• a bias mechanism configured to exert a first force against the syringe cartridge, which first force works to maintain the syringe cartridge in a retracted position within the syringe body;
• a drive mechanism comprising an energy source, a drive member, a compound plunger,
• and a decoupling mechanism, wherein the compound plunger includes an outer plunger forming a first reservoir, a hydraulic fluid contained within the first reservoir, a hydraulic orifice sized to prevent escape of the hydraulic fluid from the first reservoir by capillary action, and an inner plunger positioned within at least partially within the outer plunger, the drive mechanism being configured such that, upon actuation, the energy source, drive member, compound plunger, and decoupling mechanism function together to effect automatic extension of the needle of the syringe cartridge from the body of the injection device, automatic delivery of a desired dose the medicament from the syringe cartridge, and automatic retraction of the needle after delivery of the desired dose of the medicament.

An injection device comprising:

• a body incorporating a syringe cartridge, the syringe cartridge containing a medicament to be injected, including a needle through which the medicment can be injected, and being positioned within the body such that the syringe cartridge can be displaced back and forth within the body;
• a bias mechanism configured to exert a first force against the syringe cartridge, which first force works to maintain the syringe cartridge in a retracted position within the syringe body;
• a drive mechanism comprising an energy source, a drive member, a compound plunger, and a decoupling mechanism, wherein the compound plunger includes an outer plunger forming a first reservoir, a hydraulic fluid contained within the first reservoir, a hydraulic orifice sized to prevent escape of the hydraulic fluid from the first reservoir by capillary action, and an inner plunger positioned within at least partially within the outer plunger, the inner plunger being positioned and configured such that, as the drive mechanism operates, the inner plunger acts against the hydraulic fluid and the hydraulic fluid is expelled from the first reservoir through the hydraulic orifice;
• and
• a second reservoir configured to contain the hydraulic fluid expelled from the first reservoir, the second reservoir being formed between an outer surface of the outer plunger, an inner surface of he syringe cartridge, a sealing member included on an outer surface of the outer plunger, and a piston positioned within the syringe cartridge, wherein the sealing member is disposed around the outer surface of the outer plunger such that the sealing member forms a seal that is slidable relative to the outer plunger and to the syringe cartridge.