Medication dispensing apparatus with gear set having drive member accommodating opening

• US 20070191784A1
• Filed: 03/25/2005
• Published: 08/16/2007
• Est. Priority Date: 03/30/2004
• Status: Active Grant

• Current Assignee: Eli Lilly and Company
• Original Assignee: IDEO Product Development, Inc.
• Inventors: Judson, Jared, Jacobs, Alexander
• Granted Patent: US 7,857,791 B2
• Time in Patent Office: Days
• US Class Current: 604/224
• CPC Class Codes: A61M 2205/583 by visual feedback
• CPC Class Codes: A61M 5/31536 Blocking means to immobilize a selected dose, e.g. to administer equal doses
• CPC Class Codes: A61M 5/31555 by purely axial movement of dose setting member, e.g. during setting or filling of a syringe
• CPC Class Codes: A61M 5/31558 using scaling up or down transmissions, e.g. gearbox
• CPC Class Codes: A61M 5/3157 Means providing feedback signals when administration is completed A61M5/20 takes precedence
• CPC Class Codes: A61M 5/31571 Means preventing accidental administration for automatic syringes A61M5/20
• CPC Class Codes: A61M 5/3158 performed by axially moving actuator operated by user, e.g. an injection button
• CPC Class Codes: A61M 5/502 for blocking the piston

Abstract

A medication dispensing apparatus having a gear set (62) to provide a mechanical advantage to the plunging of the apparatus plunger (64). The gear set has a first pinion (114) in meshed engagement with a rack (91) of the plunger, and a second pinion (126) in meshed engagement with a rack (80) of a drive member (68) of the apparatus. The gear set operatively interconnects the plunger and the drive member such that after the plunger is moved relative to the housing (30, 31) in proximal direction to prepare the apparatus for injection, the plunger, when distally moved, causes the drive member to advance in a distal direction to force medication through an outlet, typically provided with an injection needle (40), at the distal end (22) of the apparatus. An opening (130) through one of the pinions accommodates the drive member to allow for a compact apparatus.

Claims

1. A medication dispensing apparatus comprising:

a housing;

a drive member within said housing and movable in a distal direction;

a fluid container defining a medicine-filled reservoir with a movable piston at one end and an outlet at the other end, said piston engageable by said drive member to be advanced toward said outlet when said drive member is moved distally;

a plunger movable relative to said housing from a distal position to a proximal position, said plunger manually pushable relative to said housing in the distal direction to be shifted from said proximal position to said distal position;

means for interconnecting said drive member and said plunger to convert motion of said plunger from said proximal position to said distal position into a lesser amount of motion of said drive member in said distal direction, said interconnecting means including a gear set including a first pinion in meshed engagement with a rack of said plunger and a second pinion in meshed engagement with a rack of said drive member; and

characterized in that at least a portion of said drive member extends through an opening through at least one of said first and second pinions.

2. The medication dispensing apparatus of claim 1 wherein said first pinion comprises said opening, wherein plunger rack engaging teeth of said first pinion are coplanar with said at least a portion of said drive member extending through said opening, whereby said rack engaging teeth do not extend continuously around said first pinion.

3. The medication dispensing apparatus of claim 2 wherein an axis of rolling rotation of said first pinion extends through said opening and is oriented generally perpendicular to said at least a portion of said drive member extending through said opening.

4. The medication dispensing apparatus of claim 1 wherein said plunger rack engaging teeth are arranged with a larger pitch diameter than a pitch diameter of said drive member rack engaging teeth of said first pinion.

5. The medication dispensing apparatus of claim 2 wherein said drive member includes a first part and a second part, said drive member first part movable in a distal direction, said drive member second part clutchably connected to said first part to be moveable relative thereto in a proximal direction but not the distal direction, said second part comprising said rack in meshed engagement with said second pinion, wherein said first part comprises at least a portion of said drive member extending through said opening.

6. The medication dispensing apparatus of claim 5 wherein distal movement of said drive member first part causes advancement of said piston in the same distance and direction, wherein said drive member first part comprises at least one longitudinally extending row of ratchet teeth and said drive member second part comprises a least one pawl that interfits with said at least one longitudinally extending row of ratchet teeth.

7. The medication dispensing apparatus of claim 6 further comprising at least one anti-back up member operably engaging said drive member first part to prevent movement of said drive member first part in a proximal direction within said housing.

8. The medication dispensing apparatus of claim 1 wherein said plunger comprises a first part, a second part, and a biasing element captured in a preloaded state to bias said first and second plunger parts apart, the preload of said preloaded state selected large enough to allow said plunger to properly operate the apparatus without further compression of said biasing element, and wherein said biasing element is compressible prior to apparatus damaging forces being transferred therethrough during initial shifting of said plunger from said proximal position toward said distal position.

9. The medication dispensing apparatus of claim 8 wherein said plunger first part comprises said rack in meshed engagement with said first pinion, wherein said plunger second part is manually pushable relative to said housing, and wherein said biasing element and said first and second plunger parts are selected and configured to allow said plunger second part to be shifted completely to said distal position from said proximal position without distal movement of said plunger first part and with compression of said biasing element.

10. The medication dispensing apparatus of claim 9 wherein said biasing element comprises a coiled spring having a first end that directly engages said plunger first part and a second end that directly engages said plunger second part.

11. The medication dispensing apparatus of claim 1 further comprising means for preventing an injection until the plunger has been manually shifted to said proximal position that corresponds to a fully cocked position.

12. The medication dispensing apparatus of claim 11 wherein said injection preventing means comprises a guide and a follower, said guide axially fixed within said housing and having a proximal end, a distal end, a first travel surface and a second travel surface, said first travel surface interrupted by a plurality of ratchet teeth, said follower comprising a pawl of said plunger, wherein said pawl slides along said first travel surface over said plurality of ratchet teeth during movement of said plunger from said distal position to said fully cocked position, whereby interaction of said ratchet teeth and said pawl limit distal travel of said plunger, and wherein said follower passes said second travel surface during movement of said plunger from said fully cocked position to said distal position.

13. The medication dispensing apparatus of claim 12 wherein said guide is integrally formed with said housing.

14. The medication dispensing apparatus of claim 12 wherein said guide proximal end cams said pawl to shift from said first travel surface to said second travel surface during movement of said plunger from said fully cocked position toward said distal position.

15. The medication dispensing apparatus of claim 12 wherein said pawl snaps against another element to provide an audible indication of the completion of pen cocking when said pawl passes said guide proximal end during movement of said plunger to said fully cocked position.

16. The medication dispensing apparatus of claim 1 wherein said first pinion and said second pinion are corotatable and coaxially arranged within said housing.

17. The medication dispensing apparatus of claim 1 wherein said second pinion comprises a pair of mirror image pinions that are coaxial with and flank said first pinion, and wherein said first and second pinions comprise a one-piece construction.