Patent ID: 7753660

Claim:
An infusion device apparatus for delivering a medication fluid, the apparatus comprising: a housing; an inlet in the housing for receiving the fluid; an outlet in the housing for discharging the fluid; a piston channel within the housing through which the fluid flows from the inlet to the outlet; and an actuator positioned within the housing and moveable between a retracted position and a forward position, the actuator defining a piston chamber for storing fluid received through the inlet when the actuator is in the retracted position, the actuator driving the fluid stored in the piston chamber toward the outlet when the actuator transitions from the retracted position to the forward position, the actuator comprising: an armature; and a piston having an overall length along an axial direction and having an inlet end and an outlet end, the piston coupled to the armature and axially moveable within the piston channel with the armature, the housing having defined therein a first fluid chamber above the piston channel, and the housing having defined therein a second fluid chamber below the piston channel, the first fluid chamber in fluid communication with the inlet and the inlet end of the piston located in the first fluid chamber, the second fluid chamber in fluid communication with the outlet and the outlet end of the piston being in fluid communication with the second fluid chamber, and the piston having a groove in an outer surface from its inlet end to its outlet end to form a flow path between the first fluid chamber and the second fluid chamber for conducting fluid from the inlet to the outlet, wherein the groove is a helical groove around the piston.