Liquid medicine administration device

A liquid medicine administration device comprising:

• a liquid medicine container filled with liquid medicine, the liquid medicine container including a tip at which is located an opening through which the liquid medicine is discharged during administration of the liquid medicine;
• a gasket positioned inside the liquid medicine container and connected to a plunger, the gasket being movable in the liquid medicine container toward the opening of the liquid medicine container to discharge the liquid medicine through the opening;
• a housing in which is housed the liquid medicine container and the plunger;
• a motor that is operatively connected to the plunger by at least two gears in engagement with one another so that rotational output produced by the motor is applied to the plunger,
• at least one guide wall that engages the plunger to restrict rotation of the plunger so that the rotational output produced by the motor and applied to the plunger by way of the at least two gears results in axial movement of the plunger;
• and
• the at least two gears remaining in engagement with one another when the at least two gears receive torque less than a preset torque;
• and
• the engagement of the at least two gears ending when the at least two gears receive torque equal to or greater than the preset torque.

A method comprising:

• inserting a needle tube into a living body, the needle tube being connected to a liquid medicine container containing liquid medicine so that sliding movement of a gasket connected to a plunger and positioned in the liquid medicine container causes the liquid medicine to flow from the liquid medicine container to the needle tube, the plunger being operatively connected to a motor so that a drive torque produced by the motor is transferred to the plunger to slidably move the gasket;
• operating the motor to produce the drive torque, and transferring the drive torque to the plunger to slidably move the gasket in the liquid medicine container so that the liquid medicine in the liquid medicine container flows from the liquid medicine container to the needle tube, the transferring of the drive torque to the plunger occurring when the drive torque is less than a preset torque;
• and
• stopping the transferring of the drive torque to the plunger when the drive torque is equal to or greater than the preset torque.