Mechanical automatic injection pen

A mechanical automatic injection pen is used to install a needle assembly with a medicine to perform an injection operation, the mechanical automatic injection ped comprising:

• a first assembly, comprises:
• a first pipe includes an opposite first end and a second end;
• a pulling assembly, which is movable inserted into the first pipe along an axis from the first end of the first pipe, and one end of the pulling assembly includes an opening hole;
• a push rod, which is inserted into the first pipe and the pulling assembly from the second end of the first pipe along the axis, and one end of the push rod away from the needle assembly through the opening hole;
• a locking assembly, coupled to the second end of the first pipe, the locking member is used to lock the push rod;
• a first elastic assembly, the two ends of the first elastic assembly are in contact with the first pipe and the pulling assembly respectively;
• and
• a second elastic assembly, the two ends of the second elastic assembly are in contact with the first pipe and the push rod;
• and
• a second assembly, combined with the first assembly along the axis to form a receiving space for installing the needle assembly, the second assembly comprises:
• a second pipe, coupled to the second end of the first pipe;
• and
• an actuating assembly, inserted through the second pipe, and one end of the actuating assembly is in contact with the locking assembly;
• wherein, the locking assembly is actuated by the actuating assembly to release a locked state of the push rod, so that the push rod moves toward the needle assembly along the axis through the second elastic assembly to push the medicine to perform an injection operation;
• when the injection operation is completed, the pulling assembly moves along the axis toward a direction away from the second pipe by an external force, thereby gradually driving the push rod to return to the position before the injection operation, so that the push rod is locked by the locking assembly again, and the pulling assembly is returned to the position before it is moved by the external force through the first elastic assembly.