Drive mechanism for drug delivery pumps with integrated status indication
A drive mechanism includes a housing, a piston adapted to impart movement to a plunger seal within a drug container, a plurality of biasing members disposed in parallel, and a retainer. The biasing members are disposed to release energy to cause movement of the piston from a retracted first position to the extended second position, the piston bearing against the plunger seal to dispense medicine. The retainer is disposed to maintain the biasing members in the energized position and to release the biasing members to permit the piston to dispense the medicine. The drive mechanism may also include an end-of-dose indicator to identify at least one of when the sleeve assembly is disposed subjacent a window in the housing, the relative motion of the sleeve assembly with reference to the window or another reference component, the stoppage of such motion, and the rated or change of rate of motion.
1. A drug pump drive mechanism for use in cooperation with a drug container including a plunger seal, the drive mechanism comprising:
a drive housing including an axis, the housing further including a window,
a piston disposed for movement from at least a retracted first position to an extended second position along said axis, the piston adapted to impart movement to the plunger seal within the drug container,
at least one biasing member disposed and adapted to move from an energized first position to a deenergized second position as a result of the release of energy, the biasing member being disposed to cause movement of the piston from the retracted first position to the extended second position as the biasing member moves from the energized first position to the deenergized second position,
a retainer, the retainer being moveable between a retaining first position and a releasing second position, the retainer disposed to maintain the biasing member in the energized first position when the retainer is in the retaining first position, and to release the biasing member from the first energized position when the retainer moves to the releasing second position,
a sleeve assembly disposed at least partially within the drive housing, at least a portion of the sleeve assembly being adapted to move along said axis with the piston, at least a portion of the sleeve assembly being visible through said window when the piston is one of the retracted first position or the extended second position, the sleeve assembly not being visible through said window when the piston is in the other of the retracted first position or the extended second position, and
an end-of-dose indicator disposed substantially adjacent the window, the end-of-dose indicator being adapted to identify at least one of when the sleeve assembly is disposed subjacent the window and when the sleeve assembly is not disposed subjacent the window.
2. The drug pump drive mechanism as claimed in claim 1 further including the sleeve assembly disposed about the at least one biasing member.
3. The drug pump drive mechanism as claimed in claim 1 wherein the sleeve assembly includes a plurality of telescoping sleeves.
4. The drug pump drive mechanism as claimed in claim 1 wherein the at least one biasing member includes at least one of a tension spring or a compression spring.
5. The drug pump drive mechanism as claimed in claim 1 including at least two biasing members, the sleeve assembly being disposed about the at least two biasing members.
6. The drug pump drive mechanism as claimed in claim 1 wherein the at least one biasing member includes a pair of compression springs.
7. The drug pump drive mechanism as claimed in claim 6 wherein the compression springs are concentrically disposed.
8. The drug pump drive mechanism as claimed in claim 1 wherein the end-of-dose indicator includes a sensor disposed to sense at least one of when the sleeve assembly is disposed subjacent the window and when the sleeve assembly is not disposed subjacent the window.
9. The drug pump drive mechanism as claimed in claim 8 wherein the sensor is at least one of a mechanical sensor, an electrical sensor, an ultrasonic sensor, a capacitive sensor, a magnetic sensor, or an optical sensor.
10. The drug pump drive mechanism as claimed m claim 9 wherein the sensor is a mechanical sensor disposed to bear against the sleeve assembly when the sleeve assembly is disposed subjacent the window.
11. The drug pump drive mechanism as claimed in claim 10 wherein the sleeve assembly has a trailing edge, and the mechanical sensor is disposed in a first position bearing against the sleeve assembly when the piston is in the retracted first position and a triggered second position when the trailing edge of the sleeve assembly moves axially past the window.
12. The drug pump drive mechanism as claimed in claim 11 wherein the sensor is adapted to be electrically connected to a power and control system associated with the drug pump.
13. The drug pump drive mechanism as claimed in claim 1 wherein the retainer engages at least a portion of the piston to retain the piston in its retracted position when the retainer is in its retaining first position.
14. The drug pump drive mechanism as claimed m claim 13 wherein the piston includes a locking groove and the retainer is at least partially received within the locking groove to retain the piston in its retracted first position when the retainer is in its retaining first position.
15. The drug pump drive mechanism as claimed in claim 1 including a plurality of biasing members disposed in parallel.