Infusion device and driving mechanism for same

• US 6,997,921 B2
• Filed: 12/27/2001
• Issued: 02/14/2006
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Bosley, Robert W., Gray, John F.
• Primary Examiner(s): Hayes, Michael J.
• Application Number:
  US10/033,722
• Publication Number:
  US 20030050624A1
• Time in Patent Office: 1,510 Days
• Field of Search: 604/890.1, 604/891.1, 604/131, 604/151, 604/152, 604/93.01
• US Class Current: 604/891.1
• CPC Class Codes: A61M 5/14216 Reciprocating piston type
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: F04B 17/042 the solenoid motor being separated from the fluid flow
• CPC Class Codes: F04B 53/1032 Spring-actuated disc valves F04B53/1022, F04B53/103 take precedence

Abstract

A drive mechanism for delivery of infusion medium has a coil and an armature moveable toward a forward position, in response to the electromagnetic field produced by activation of the coil. A piston is moveable axially within a piston channel to a forward position, in response to movement of the armature to its forward position. The armature and piston are moved toward a retracted position, when the coil is not energized. In the retracted position of the piston, a piston chamber is formed between the piston and a valve member and is filled with infusion medium. As the piston is moved to its forward position, the piston chamber volume is reduced and pressure within the piston chamber increases to a point where the pressure moves the valve member into an open position through an outlet.

Claims

1. A drive mechanism for delivery of infusion medium comprising:

an inlet for receiving infusion medium;

a piston channel for communication of infusion medium received by the inlet;

a coil surrounding the piston channel;

a piston located within the piston channel and moveable axially within the piston channel to drive infusion medium into the piston channel; and

an armature disposed adjacent the coil, on one side of the piston channel, the armature having a pair of pole surfaces and also having radial struts for conducting electromagnetic flux between the pole surfaces in a radial direction;

wherein a clearance between the piston and the piston channel causes a volume of the infusion medium for refilling the piston channel to be greater than a volume of the infusion medium backflowing through the piston channel.

2. A drive mechanism as recited in claim 1, further comprising a coil cup composed of a magnetizable material, the coil cup having:

a generally annular inner wall;

a generally annular outer wall;

a generally annular interior between the inner and outer walls, the annular interior containing the coil; and

a piston channel surrounded by the inner wall, the piston channel of the coil cup being substantially coaxial with the coil;

wherein the inner wall has one end defining an inner pole surface and the outer wall has a second end defining an outer pole surface, the inner and outer pole surfaces acting with the armature to provide an electromagnetic flux path upon electrical activation of the coil.

3. A drive mechanism as recited in claim 2, further comprising a housing having a generally annular cavity containing the coil cup, the housing further having a central channel defining the piston channel.

4. A drive mechanism as recited in claim 3, wherein the housing is open on one side to the generally annular cavity and has a further cavity disposed on the opposite side, the further cavity defining an outlet chamber.

5. A drive mechanism as recited in claim 3, wherein the coil cup is secured to the housing by a friction fit of the coil cup within the generally annular cavity of the housing.

6. A drive mechanism as recited in claim 2, further comprising:

a housing having an interior cavity containing the coil cup, the housing further having a central channel defining the piston channel, the housing being open on one side to the interior cavity; and

a cover member disposed over the open side of the housing, the cover member defining an interior volume in which the armature is moveably disposed;

wherein said inlet is in flow communication with the interior volume of the cover member.

7. A drive mechanism as recited in claim 6, further comprising means for urging the armature in an axial direction toward the cover member toward a retracted position, wherein the cover member includes at least one stop surface for contacting the armature in the retracted position.

8. A drive mechanism as recited in claim 7, wherein the means for urging comprises a spring.

9. A drive mechanism as recited in claim 7, wherein the means for urging comprises a magnet disposed within the cover member.

10. A drive mechanism as recited in claim 2, further comprising:

a housing having a cavity containing the coil cup, the housing having a central channel that defines the piston channel, the housing having a further cavity disposed on one end of the piston channel, wherein the further cavity defines an outlet chamber;

a valve member moveable between open and closed positions to selectively open and close one end of the piston channel to the outlet chamber; and

a valve spring for urging the valve member in the closed position;

wherein the valve member and valve spring are located within the further cavity defining the outlet chamber.

11. A drive mechanism as recited in claim 1, further comprising means for urging the armature and piston to move in an axial direction away from the outlet chamber.

12. A drive mechanism as recited in claim 11, wherein the means for urging comprises a spring.

13. A drive mechanism as recited in claim 11, wherein the means for urging comprises a magnet.

14. A drive mechanism as recited in claim 1, further comprising a valve member moveable between open and closed positions to selectively allow and inhibit fluid flow between the inlet and the outlet, the valve member being moveable in response to axial movement of the piston within the piston channel.

15. A drive mechanism as recited in claim 1, further comprising a valve member moveable between open and closed positions to selectively open and close one end of the piston channel to an outlet chamber, the valve member being moveable in response to axial movement of the piston within the piston channel.

16. A drive mechanism as recited in claim 15, wherein the piston is moveable in the axial direction of the channel between a retracted position and a forward position, wherein the valve member is located in the closed position when the piston is in the retracted position and wherein the valve member is moved to the open position when the piston is moved to the forward position.

17. A drive mechanism as recited in claim 15, wherein the piston is moveable in the axial direction of the piston channel between a retracted position and a forward position such that, upon the piston being in the retracted position, a volume is defined between the piston and the valve member for receiving infusion medium through the piston channel and, upon the piston thereafter being moved toward the forward position, the volume between the piston and the valve member decreases to increase infusion medium pressure within the volume, force the valve member to the open position and discharge infusion medium into an outlet chamber.

18. A drive mechanism as recited in claim 1, further comprising a housing containing the coil and an outlet chamber, the housing having at least one fluid flow damping means or accumulator disposed in a flow path between the outlet chamber and the outlet, for reducing flow pressure variations.

19. A drive mechanism as recited in claim 18, wherein said at least one damping means comprises at least one compressible member disposed within the flow path.

20. A drive mechanism as recited in claim 18, wherein said at least one damping means comprises at least one chamber containing at least one compressible pillow.

21. A drive mechanism as recited in claim 18, wherein said at least one damping means comprises a plurality of chambers, each containing at least one compressible pillow.

22. A drive mechanism as recited in claim 1, further comprising:

a valve member moveable between open and closed positions to selectively open and close one end of the piston channel to an outlet chamber; and

a valve spring for urging the valve member in the closed position;

wherein the valve member and valve spring are located within the outlet chamber.

23. A drive mechanism as recited in claim 1, wherein the piston and armature are composed of a single, unitary structure.

24. A drive mechanism as recited in claim 23, wherein the piston has two ends spaced apart in the axial direction and a flow passage extending in the axial direction from one end of the piston to the other end of the piston.

25. A drive mechanism as recited in claim 1, wherein the piston and armature are composed of separable structures and are moveable independent of each other.

26. A drive mechanism as recited in claim 1, further comprising:

a valve member moveable between open and closed positions to selectively open and close one end of the piston channel to an outlet chamber, the valve member being moveable in response to axial movement of the piston within the piston channel;

wherein the piston has two ends spaced apart in the axial direction and a flow passage extending in the axial direction from one end of the piston to the other end of the piston; and

wherein the piston is moveable in the axial direction of the channel between a retracted position and a forward position such that, upon the piston being in the retracted position, a volume is defined between the piston and the valve member for receiving infusion medium through the passage in the piston and, upon the piston thereafter being moved toward the forward position, the volume between the piston and the valve member decreases to increase infusion medium pressure within the volume, force the valve member to the open position and discharge infusion medium into the outlet chamber.

27. The drive mechanism of claim 1, wherein the volume of the infusion medium for refilling the piston channel is about 1 to 4 times greater than the volume of the infusion medium backflowing through the piston channel.

28. The drive mechanism of claim 1, wherein a ratio of a diameter of the piston to a diameter of the piston channel is within a range of about 0.990 to about 0.995.

29. The drive mechanism of claim 1, wherein the clearance between the piston and the piston channel averages about 250 microinches.

30. The drive mechanism of claim 1, further comprising:

a valve member being moveable in response to axial movement of the piston within the piston channel,

wherein a clearance between the piston and the piston channel is sufficient to restrict the infusion medium within the piston channel such that pressure on the infusion medium caused by movement of the piston opens the valve member.

31. The drive mechanism of claim 1, further comprising:

an outlet chamber disposed adjacent the coil, on the opposite side of the piston channel relative to the armature for receiving infusion medium from the channel; and

an outlet in flow communication with the outlet chamber, for discharging infusion medium from the outlet chamber.

32. A drive mechanism for delivery of infusion medium comprising:

an inlet for receiving infusion medium;

a piston channel for communication of infusion medium received by the inlet;

a coil surrounding the piston channel;

a piston located within the piston channel and moveable axially within the piston channel to drive infusion medium into the piston channel; and

an armature disposed adjacent the coil, on one side of the piston channel,

wherein a clearance between the piston and the piston channel causes a volume of the infusion medium for refilling the piston channel to be greater than a volume of the infusion medium backflowing through the piston channel;

wherein the coil is capable of being electrically activated to provide an electromagnetic field;

wherein the armature is moveable toward the coil, in response to the electromagnetic field produced by an activation of the coil; and

wherein the armature comprises radial struts for conducting electromagnetic flux in a radial direction.

33. A drive mechanism for delivery of infusion medium comprising:

an inlet for receiving infusion medium;

a piston channel for communication of infusion medium received by the inlet;

a coil surrounding the piston channel;

a piston located within the piston channel and moveable axially within the piston channel to drive infusion medium into the piston channel; and

an armature disposed adjacent the coil, on one side of the piston channel,

wherein a clearance between the piston and the piston channel causes a volume of the infusion medium for refilling the piston channel to be greater than a volume of the infusion medium backflowing through the piston channel;

wherein the armature has an annular inner pole surface and an annular outer pole surface, each made of a magnetizable material, wherein the inner pole surface of the armature faces the inner pole surface of the inner coil cup wall, and outer pole surface of the armature faces the outer pole surface of the outer coil cup wall.

34. A drive mechanism as recited in claim 33, wherein the armature further has a plurality of radial struts made of magnetizable material coupling the inner and outer pole surfaces of the armature.

35. A drive mechanism as recited in claim 34, wherein the armature further has apertures between the radial struts.

36. A drive mechanism as recited in claim 33, wherein at least one of the inner and outer pole surfaces of the armature are textured.

37. A drive mechanism as recited in claim 33, wherein the inner pole surface of the armature is spaced from the inner cup wall by a first gap and the outer pole surface is spaced from the outer cup wall by a second gap when the coil is not electrically activated, and wherein the second gap is larger than the first gap.

38. A drive mechanism for delivery of infusion medium comprising:

an inlet for receiving infusion medium;

at least one coil capable of being electrically activated to provide an electromagnetic field, the at least one coil surrounding an axial piston channel that provides a passage for communication of infusion medium received by the inlet;

an armature disposed adjacent the coil, on one side of the axial piston channel and moveable in a first direction relative to the coil, in response to the electromagnetic field produced by an activation of the coil, the armature having a pair of pole surfaces and also having radial struts for conducting electromagnetic flux between the pole surfaces in a radial direction; and

a piston located within the piston channel and moveable axially within the channel in the first direction, in response to movement of the armature,

wherein a clearance between the piston and the piston channel causes a volume of infusion medium for refilling the piston channel to be greater than a volume of infusion medium backflowing through the piston channel.

39. The drive mechanism of claim 38, further comprising:

an outlet chamber disposed adjacent the coil, on the opposite side of the piston channel relative to the armature for receiving infusion medium from the piston channel, upon movement of the piston in the first direction; and

an outlet in flow communication with the outlet chamber, for discharging infusion medium from the outlet chamber.

40. An infusion device for delivering infusion medium, the device comprising:

a housing having an outlet through which infusion medium may be discharged;

a reservoir disposed within the housing, for containing a volume of infusion medium;

a control circuit for providing drive control signals;

a drive mechanism disposed within the housing, for driving infusion medium from the reservoir and out the outlet, in response to drive control signals from the control circuit; and

a power source disposed within the housing, for providing power to the control circuit and drive mechanism;

wherein the drive mechanism comprises;

an inlet for receiving infusion medium from the reservoir;

at least one coil capable of being electrically activated to provide an electromagnetic field in response to a signal from the control circuit, the at least one coil surrounding an axial piston channel that provides a passage for communication of infusion medium received by the inlet;

an armature disposed adjacent the coil, on one side of the axial channel and moveable in a first direction relative to the coil, in response to the electromagnetic field produced by an activation of the coil, the armature having a pair of pole surfaces and also having radial struts for conducting electromagnetic flux between the pole surfaces in a radial direction; and

a piston located within the piston channel of the coil and moveable axially within the channel in the first direction, in response to movement of the armature,

wherein a clearance between the piston and the piston channel causes a volume of infusion medium for refilling the piston channel to be greater than a volume of infusion medium backflowing through the piston channel.

41. The infusion device of claim 40, wherein the drive mechanism further comprises:

an outlet chamber disposed adjacent the coil, on the opposite side of the piston channel relative to the armature for receiving infusion medium from the piston channel, upon movement of the piston in the first direction; and

an outlet port in flow communication with the outlet chamber and the housing outlet, for discharging medium from the outlet chamber, through the housing outlet.

42. A drive mechanism for delivery of infusion medium comprising:

an inlet for receiving infusion medium;

a piston channel for communication of infusion medium received by the inlet;

a coil surrounding the piston channel;

a piston located within the piston channel and moveable axially within the piston channel to drive infusion medium into the piston channel;

an armature disposed adjacent the coil, on one side of the piston channel;

an outlet chamber disposed adjacent the coil, on the opposite side of the piston channel relative to the armature for receiving infusion medium from the channel; and

an outlet in flow communication with the outlet chamber, for discharging infusion medium from the outlet chamber,

wherein the coil is capable of being electrically activated to provide an electromagnetic field;

wherein the armature is moveable toward the coil, in response to the electromagnetic field produced by an activation of the coil; and

wherein the armature comprises radial struts for conducting electromagnetic flux in a radial direction.

43. A drive mechanism for delivery of infusion medium comprising:

an inlet for receiving infusion medium;

a piston channel for communication of infusion medium received by the inlet;

a coil surrounding the piston channel;

a piston located within the piston channel and moveable axially within the piston channel to drive infusion medium into the piston channel;

a coil cup containing the coil, the coil cup having an inner pole surface and an outer pole surface;

an armature disposed adjacent the coil, on one side of the piston channel;

an outlet chamber disposed adjacent the coil, on the opposite side of the piston channel relative to the armature for receiving infusion medium from the channel; and

an outlet in flow communication with the outlet chamber, for discharging infusion medium from the outlet chamber,

wherein the armature has an annular inner pole surface and an annular outer pole surface, each made of a magnetizable material, and

wherein the inner pole surface of the armature faces the inner pole surface of the coil cup, and the outer pole surface of the armature faces the outer pole surface of the coil cup.