Air shot mechanism for electronic injection devices

An injection device comprising:

• a cartridge of medicament;
• a drive mechanism configured to expel medicament from the cartridge;
• an electronic control unit that actuates the drive mechanism;
• a means for setting a desired dose to be expelled from the cartridge;
• and
• wherein the control mechanism is configured so that at the request of a user the drive mechanism is actuated to expel an a predetermined air shot dose from the cartridge, without the need for the user to select the size of the air shot dose.

A method for priming and injecting a dose of medication from an electronic injection device having an electronic control unit and a drive mechanism for expelling medicament contained within the device, the method comprising:

• a. pressing a button to send a signal to an electronic control mechanism to prime the device by expelling a predetermined air-shot dose;
• b. actuating the drive mechanism, upon receipt of the signal from step a, to expel a predetermined air shot dose from the cartridge, wherein the size of the dose is automatically, without user intervention, determined by the electronic control unit;
• c. setting a predetermined dose of medication to inject;
• d. injecting the predetermined dose of medication;
• and
• wherein steps a and b may be performed before or after step c but wherein steps a-c are performed prior to step d;
• and
• wherein the method of steps a-d are repeated.

A medication delivery device comprising:

• a. a cartridge containing a medication;
• b. an electronic control unit;
• c. a plurality of buttons connected to the electronic control unit so that a user may interface with the electronic control unit;
• d. a motorized drive mechanism for expelling medication from the cartridge;
• e. wherein the electronic control unit is configured to accept a dose size from the user and to control the motorized drive mechanism to expel the dose from the cartridge upon receipt of a dosing instruction from the user;
• and
• f. wherein the controller is configured to prime the device prior to injecting the user selected dose, by receiving a command from the user, wherein the command is sent to the control by the user pressing one of the buttons, and wherein the priming occurs by expelling a pro-selected non-user settable air shot dose.

An electronic injection device, comprising:

• a housing containing an electronic circuit into which the size of a set dose can be inputted by operation of dose setting means,
• an injection button that can be operated to inject a set dose,
• an ampoule from which the set of medicine can be pressed out through a needle mounted at the distal end of the ampoule by an electrical driven motor when the injection button is operated,
• further comprising a means for driving out a pre-set small air-shot dose from the cartridge with the aid of the motor upon receipt of an air-shot signal from said circuit.

An electronically controlled motorized injection device comprising:

• a motorized drive means for expelling medication from the device;
• a first circuit for inputting a user selected dose size to be expelled;
• a second circuit for priming the device to expel a small predetermined non-adjustable air shot dose;
• a third circuit for driving the motorized drive means to expel either the air shot dose or the user selected dose.