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A drive mechanism for delivery of infusion medium a coil capable of being electrically activated to provide an electromagnetic field. The coil surrounds a piston channel extending in an axial direction. An armature is located adjacent the coil, on one side of the axial channel. The armature is movea

A drive mechanism for delivery of infusion medium a coil capable of being electrically activated to provide an electromagnetic field. The coil surrounds a piston channel extending in an axial direction. An armature is located adjacent the coil, on one side of the axial channel. The armature is moveable toward a forward position, in response to the electromagnetic field produced by activation of the coil. A piston is located within the piston channel and is moveable axially within the 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. The armature may be configured with a reduced diameter by including a coil cup for supporting the coil including a shelf portion defining at least a portion of a pole surface of the coil cup.

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What is claimed is: 1. A drive mechanism for an infusion device, the drive mechanism comprising: a first housing having an inlet, the first housing defining an interior volume for receiving fluidic media from the inlet, the interior volume having a width dimension; a coil arranged to be selectively

What is claimed is: 1. A drive mechanism for an infusion device, the drive mechanism comprising: a first housing having an inlet, the first housing defining an interior volume for receiving fluidic media from the inlet, the interior volume having a width dimension; a coil arranged to be selectively energized; an armature moveable in the interior volume of the first housing at least between a retracted position and an advanced position in response to energizing the coil, the armature having a first pair of pole surfaces; a coil housing containing the coil, the coil housing composed of a magnetizable material and providing a second pair of pole surfaces in a magnetic flux path with the first pair of pole surfaces when the coil is energized; a second housing containing the coil housing, the second housing defining a piston channel extending through at least a portion of the second housing; a piston moveable along the piston channel in conjunction with movement of the armature at least between a retracted position and an advanced position to convey fluidic media from the interior volume of the first housing and out the piston channel in a case where the interior volume of the first housing contains fluidic media and the coil is energized to move the armature and the piston to the advanced position, the piston channel having a length dimension along which the piston moves between the retracted position and the advanced position; and a barrier member arranged between the armature and the coil housing, the barrier member defining an opening through which the piston extends into the piston channel, the opening having a width dimension that is less than the width dimension of the interior volume, the width dimension of the opening and the width dimension of the interior volume transverse the length dimension of the piston channel; wherein the armature comprises an armature body having a cavity and a magnetic material located within the cavity. 2. The drive mechanism as recited in claim 1, wherein the armature body is composed of a material having a lower magnetic permeability relative to the magnetic material. 3. The drive mechanism as recited in claim 2, wherein the armature body is composed of at least one of titanium, stainless steel, biocompatible plastic, ceramic, and glass. 4. The drive mechanism as recited in claim 2, wherein the armature body is composed of a non-ferritic stainless steel. 5. The drive mechanism as recited in claim 1, wherein the magnetic material comprises at least one of a ferrous material and a ferritic stainless steel material. 6. The drive mechanism as recited in claim 1, further comprising: a cover provided over the cavity of the armature body to cover the magnetic material located within the cavity. 7. The drive mechanism as recited in claim 6, wherein the cover comprises a foil material. 8. The drive mechanism as recited in claim 1, the armature comprising a cover for inhibiting the magnetic material from contacting fluidic media in the interior volume of the first housing. 9. The drive mechanism as recited in claim 1, wherein the magnetic material located within the cavity completes a flux path when the coil is energized. 10. The drive mechanism as recited in claim 9, the armature comprising a cover for inhibiting the magnetic material from contacting fluidic media in the interior volume of the first housing when the coil is energized. 11. The drive mechanism as recited in claim 10, wherein the cover comprises a foil material. 12. The drive mechanism as recited in claim 1, wherein the first pole surfaces face the same direction. 13. A method for making a drive mechanism for an infusion device, the method comprising: providing a first housing having an inlet, the first housing defining an interior volume for receiving fluidic media from the inlet, the interior volume having a width dimension; arranging a coil to be selectively energized; supporting an armature for movement in the interior volume of the first housing at least between a retracted position and an advanced position in response to energizing the coil, the armature having an armature body and a first pair of pole surfaces; containing the coil in a coil housing composed of a magnetizable material; providing a second housing containing the coil housing, the second housing defining a piston channel extending through at least a portion of the second housing supporting a piston in the piston channel for movement in conjunction with movement of the armature in response to energizing the coil to convey fluidic media from the interior volume of the first housing and out the piston channel in a case where the interior volume of the first housing contains fluidic media and the coil is energized to move the armature and the piston to the advanced position, the piston channel having a length dimension along which the piston moves between the retracted position and the advanced position; arranging the coil housing such that a second pair of pole surfaces on the coil housing are in a magnetic flux path with the first pair of pole surfaces when the coil is energized; arranging a barrier member between the armature and the coil housing, the barrier member defining an opening through which the piston extends into the piston channel, the opening having a width dimension that is less than the width dimension of the interior volume, the width dimension of the opening and the width dimension of the interior volume transverse the length dimension of the piston channel; and supporting a magnetic material within a cavity in the armature body for completing the flux path when the coil is energized. 14. The method as recited in claim 13, wherein supporting an armature comprises supporting an armature having an armature body composed of a material having a lower magnetic permeability relative to the magnetic material. 15. The method as recited in claim 13, wherein supporting an armature comprises supporting an armature having an armature body composed of at least one of titanium, stainless steel, biocompatible plastic, ceramic, and glass. 16. The method as recited in claim 13, wherein supporting an armature comprises supporting an armature having an armature body composed of a non-ferritic stainless steel. 17. The method as recited in claim 13, wherein supporting a magnetic material comprises supporting at least one of a ferrous material and ferritic stainless steel material. 18. The method as recited in claim 13, further comprising: covering the magnetic material with a cover provided over the cavity of the armature body. 19. The method as recited in claim 13, further comprising: covering the magnetic material with a foil disposed over the cavity of the armature body. 20. The method as recited in claim 13, further comprising: covering the magnetic material with a cover that inhibits the magnetic material from contacting fluidic media in the interior volume of the first housing. 21. The drive mechanism as recited in claim 13, wherein supporting an armature comprises supporting an armature with the first pole surfaces facing the same direction. 22. The drive mechanism as recited in claim 1, the piston channel extending completely through the coil housing. 23. The drive mechanism as recited in claim 1, the piston having a fluid channel extending through an axial length of the piston, the fluid channel for conveying fluidic media from the interior volume of the first housing. 24. The drive mechanism as recited in claim 23, wherein the fluid channel extends though the armature and the piston. 25. The drive mechanism as recited in claim 1, the magnetic material having a portion extending toward the coil housing such that the portion is closer to the coil housing than a remaining portion of the magnetic material. 26. The drive mechanism as recited in claim 1, wherein the cavity and the magnetic material are annularly shaped. 27. The drive mechanism as recited in claim 1, wherein a portion of the armature extends through the magnetic material. 28. The drive mechanism as recited in claim 1, wherein a portion of the armature is surrounded by the magnetic material. 29. The drive mechanism as recited in claim 1, further comprising: a bias member arranged in the piston channel to impart a force on the armature toward the retracted position. 30. The drive mechanism as recited in claim 29, the bias member configured to move the piston and armature to the retracted position when the coil is not energized. 31. The drive mechanism as recited in claim 29, wherein the bias member comprises a spring. 32. The drive mechanism as recited in claim 29, the second housing having a ridge portion defining a portion of the piston channel, the ridge portion for supporting the bias member in the piston channel. 33. The drive mechanism as recited in claim 1, the piston arranged such that a side surface extending along an entire length of the piston faces the inner surface of the second housing, the side surface of the piston in contact with the fluidic media being conveyed by the piston from the interior volume of the first housing. 34. The drive mechanism as recited in claim 33, the piston moveable in an axial direction, the axial direction parallel with the side surface of the piston. 35. The drive mechanism as recited in claim 1, wherein the inlet of the first housing is laterally offset from the piston channel. 36. The drive mechanism as recited in claim 35, wherein the inlet of the first housing extends in a direction that is non-parallel with a direction in which the piston channel extends. 37. The drive mechanism as recited in claim 1, wherein the inlet of the first housing is in fluid communication with the interior volume of the first housing in a case where the armature and the piston are in the retracted position. 38. The drive mechanism as recited in claim 1, wherein the inlet of the first housing is in fluid communication with the piston channel in a case where the armature and the piston are in the retracted position. 39. The drive mechanism as recited in claim 1, wherein the coil housing has a width dimension that is transverse the length dimension of the piston channel; and wherein the width dimension of the interior volume is at least as great as the width dimension of the coil housing. 40. The drive mechanism as recited in claim 1, wherein the opening of the barrier member has a length dimension that is less than the width dimension of the opening of the barrier member. 41. The drive mechanism as recited in claim 1, wherein the coil housing has a width dimension that is transverse the length dimension of the piston channel; wherein the first pair of pole surface has a width dimension that is transverse the length dimension of the piston channel; wherein the barrier member has a width dimension that is transverse the length dimension of the piston channel and is at least as great as the width dimension of the coil housing and the width dimension of the first pair of pole surfaces of the armature; and wherein the barrier member has a thickness that is less than the width dimension of the barrier member. 42. The drive mechanism as recited in claim 1, wherein the armature has a width dimension that is transverse the length dimension of the piston channel and is greater than the width dimension of the opening of the barrier member.