Infusion device and driving mechanism for same

• US 7,131,967 B2
• Filed: 02/19/2003
• Issued: 11/07/2006
• Est. Priority Date: 09/07/2001
• Status: Expired due to Term

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Bosley, Robert W., Gray, John F.
• Primary Examiner(s): Sirmons, Kevin C.
• Assistant Examiner(s): Huh, Benjamin
• Application Number:
  US10/369,242
• Publication Number:
  US 20030135160A1
• Time in Patent Office: 1,357 Days
• Field of Search: 604/890.1, 604/811.1, 604/131, 604/93.01, 604/151, 604/152, 417415-417, 417/44.1, 417/45, 417/44.11, 128/DIG.12
• 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. A coil surrounds a piston channel. An armature is located adjacent the coil. The armature is moveable toward a forward position in response to the electromagnetic field produced by activation of the coil. A piston located within the piston channel is moveable within the channel to a forward position in response to movement of the armature. The armature and piston are moved toward a retracted position when the coil is not energized. In the retracted position, a piston chamber formed between the piston and a valve member is filled with infusion medium. As the piston is moved to its forward position, piston chamber volume is reduced and pressure within the piston chamber increases and moves the valve member into an open position. Medium from the piston chamber is then discharged into an outlet chamber.

Claims

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

at least one coil winding around a piston channel, the piston channel having an inlet end and an outlet end for communication of infusion medium from the inlet end and out through the outlet end;

a magnetic return path structure surrounding the piston channel and providing a portion of at least one magnetic return path for said at least one coil;

a piston located within the piston channel and moveable axially within the piston channel in response to energization of said at least one coil; and

an armature disposed adjacent said at least one coil, on one side of the piston channel, to provide a further portion of said at least one magnetic return path, the armature having two annular pole faces, wherein both annular pole faces face a same axial direction.

2. The drive mechanism as recited in claim 1, further including an inlet for receiving infusion medium, the inlet in fluid flow communication with the inlet end of the piston channel.

3. The drive mechanism as recited in claim 1, wherein said at least one coil is entirely wound around the piston channel.

4. The drive mechanism of claim 1, 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;

and

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.

5. 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.

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

7. 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 piston channel.

8. 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.

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

an outlet in flow communication with the outlet end of the piston channel, for discharging infusion medium from the piston channel.

10. The drive mechanism of claim 1, wherein the two annular pole faces are concentric.

11. The drive mechanism of claim 10, wherein the two annular pole faces comprise an inner pole face and an outer pole face, wherein the inner pole face has a width greater than a width of the outer pole face.

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

at least one coil surrounding a piston channel, the piston channel having an inlet end and an outlet end for communication of infusion medium from the inlet end and out through the outlet end;

a magnetic return path structure surrounding the piston channel and providing a portion of at least one magnetic return path for said at least one coil;

a piston located within the piston channel and moveable axially within the piston channel in response to energization of said at least one coil; and

an armature disposed adjacent said at least one coil, on one side of the piston channel, to provide a further portion of said at least one magnetic return path, the armature having two pole faces, wherein each pole face is directed substantially axially with respect to the piston channel,

wherein said at least one coil includes a coil having windings which surround the piston channel, and

wherein said magnetic return path structure includes 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 central channel surrounded by the inner wall, the central 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 two pole faces of the armature to provide an electromagnetic flux path upon electrical activation of the coil.

13. The drive mechanism as recited in claim 12, 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 includes radial struts for conducting electromagnetic flux in a radial direction.

14. The drive mechanism as recited in claim 13, wherein the radial struts are made of a magnetizable material.

15. The drive mechanism as recited in claim 14, wherein the two pole faces of the armature comprise 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.

16. The drive mechanism as recited in claim 15, wherein the radial struts couple the inner and outer pole surfaces of the armature.

17. The drive mechanism as recited in claim 15, wherein the armature further has apertures between the radial struts.

18. The drive mechanism as recited in claim 15, wherein at least one of the inner and outer pole surfaces of the armature are textured.

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

at least one coil having windings surrounding a piston channel, the piston channel having an inlet end and an outlet end for communication of infusion medium from the inlet end and out through the outlet end, wherein the at least one coil is capable of being electrically activated to provide an electromagnetic field;

a magnetic return path structure surrounding the piston channel and providing a portion of at least one magnetic return path for said at least one coil;

a piston located within the piston channel and moveable axially within the piston channel in response to energization of said at least one coil; and

an armature disposed adjacent said at least one coil, on one side of the piston channel, to provide a further portion of said at least one magnetic return path, the armature having two pole faces within at least one magnetic return path, wherein each pole face is directed substantially axially with respect to the piston channel;

wherein said magnetic return path structure includes 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 central channel surrounded by the inner wall, the central 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 two pole faces of the armature to provide an electromagnetic flux path upon electrical activation of the coil;

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

wherein the armature includes radial struts for conducting electromagnetic flux in a radial direction;

wherein the two pole faces of the armature comprise 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; and

wherein the inner pole surface of the armature is spaced from the inner wall of the coil cup by a first gap and the outer pole surface of the armature is spaced from the outer wall of the coil cup by a second gap when the coil is not electrically activated, and wherein the second gap is larger than the first gap.

20. A method for making an infusion medium delivery device, the method comprising:

providing at least one coil winding around a piston channel, the piston channel having an inlet end and an outlet end for communication of infusion medium from the inlet end and out through the outlet end;

providing a piston through the piston channel and moveable axially within the piston channel in response to energization of said at least one coil;

providing a magnetic return path structure surrounding the piston channel and providing a portion of at least one magnetic return path for said at least one coil; and

providing an armature disposed adjacent said at least one coil, on one side of the piston channel, to provide a further portion of said at least one magnetic return path, the armature having two annular pole faces, wherein both annular pole faces face a same axial direction.

21. The method as recited in claim 20, further including providing an inlet for receiving infusion medium, the inlet in fluid flow communication with the inlet end of the piston channel.

22. The method as recited in claim 20, wherein said at least one coil is entirely wound around the piston channel.

23. The drive mechanism of claim 20, further comprising:

providing an outlet in flow communication with the outlet end of the piston channel, for discharging infusion medium from the piston channel.

24. The method of claim 20, wherein the two annular pole faces are concentric.

25. The method of claim 24, wherein the two annular pole faces comprise an inner pole face and an outer pole face, wherein the inner pole face has a width greater than a width of the outer pole face.

26. The method as recited in claim 20, further including:

providing an outlet chamber in flow communication with the outlet end of the piston channel, the outlet chamber disposed adjacent the at least one coil, on the opposite side of the piston channel relative to the armature, for receiving infusion medium from the channel;

providing a valve member moveable between open and closed positions to selectively allow and inhibit fluid flow from the piston channel, the valve member being moveable in response to axial movement of the piston within the piston channel; and

providing an outlet port in flow communication with the outlet chamber.

27. The method as recited in claim 26, wherein the valve member is located within the outlet chamber.

28. A method for making an infusion medium delivery device, the method comprising:

providing at least one coil surrounding a piston channel, the piston channel having an inlet end and an outlet end for communication of infusion medium from the inlet end and out through the outlet end;

providing a piston through the piston channel and moveable axially within the piston channel in response to energization of said at least one coil;

providing a magnetic return path structure surrounding the piston channel and providing a portion of at least one magnetic return path for said at least one coil; and

providing an armature disposed adjacent said at least one coil, on one side of the piston channel, to provide a further portion of said at least one magnetic return path, the armature having two pole faces, wherein each pole face is directed substantially axially with respect to the piston channel,

wherein providing said magnetic return path structure includes providing a coil cup composed of a magnetizable material and 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 central channel surrounded by the inner wall, the central 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 two pole faces of the armature to provide an electromagnetic flux path upon electrical activation of the coil.

29. The method as recited in claim 28, wherein providing an armature having two pole faces includes providing an armature having 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 wall of the coil cup, and outer pole surface of the armature faces the outer pole surface of the outer wall of the coil cup.

30. The method as recited in claim 29, wherein the armature includes radial struts for conducting electromagnetic flux in a radial direction.

31. A method for delivery of infusion medium comprising:

providing at least one coil winding around a piston channel, the piston channel having an inlet end and an outlet end for communication of infusion medium from the inlet end and out through the outlet end;

providing a piston through the piston channel and moveable axially within the piston channel in response to energization of said at least one coil;

providing a magnetic return path structure surrounding the piston channel and providing a portion of at least one magnetic return path for said at least one coil;

providing an armature disposed adjacent said at least one coil, on one side of the piston channel, to provide a further portion of said at least one magnetic return path, the armature having two annular pole faces, wherein both annular pole faces face a same axial direction;

providing an outlet chamber in flow communication with the outlet end of the piston channel, the outlet chamber disposed adjacent the at least one coil, on the opposite side of the piston channel relative to the armature, for receiving infusion medium from the piston channel;

providing a valve member moveable between open and closed positions to selectively allow and inhibit fluid flow from the piston channel, the valve member being moveable in response to axial movement of the piston within the piston channel;

providing an outlet port in flow communication with the outlet chamber;

receiving infusion medium through the inlet;

urging the piston and armature toward a retracted position to form a piston chamber between one end of the piston and the valve member;

filling the piston chamber with the infusion medium by passing a volume of the infusion medium received on an armature side of the coil from the inlet through the piston channel to the piston; and

electrically activating the coil to provide an electromagnetic field to move the armature and piston toward a forward position to deliver a volume of infusion medium through the outlet port.

32. The method as recited in claim 31, further including:

moving the piston toward the forward position under the force of the electromagnetic field to compress a volume of the piston chamber and force the valve member to an open position;

discharging the infusion medium from the piston chamber, through the open valve member and into the outlet chamber, upon the piston being moved to the forward position; and

delivering the infusion medium discharged from the outlet chamber through the outlet port.

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 winding around the piston channel;

a magnetic return path structure surrounding the piston channel and providing a portion of at least one magnetic return path for the coil;

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 a pair of annular pole surfaces, both annular pole surfaces facing a same axial direction.

34. The drive mechanism of claim 33, wherein the armature further comprises radial struts for conducting electromagnetic flux between the pair of annular pole surfaces in a radial direction.

35. The drive mechanism of claim 33, wherein the pair of annular pole surfaces are concentric.

36. The drive mechanism of claim 35, wherein the pair of annular pole surfaces comprise an inner pole surface and an outer pole surface, wherein the inner pole surface has a width greater than a width of the outer pole surface.