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|Title:||Medication dispensing apparatus with triple screw threads for mechanical advantage|
|Abstract:||A medication dispensing apparatus that provides a mechanical advantage. During dose preparing, a nut rotating element (410) and a screw element (368) are in a first axial arrangement such that a screwing motion of the nut rotating element and screw element relative to the apparatus housing that moves the elements a first axial distance from a home position screws a nut (364) along a drive member threaded shaft (362) a second axial distance different than the first axial distance. During dose dispensing, the nut rotating element and the screw element are in a second axial arrangement, whereby a screwing motion of the screw element relative to the housing back toward the home position advances a plunger (366) in the distal direction to axially advance the nut and thereby the drive number and a fluid container piston to dispense medicine.|
|Inventor(s):||DeRuntz; Otto Daniel (Dunstable, MA), Focht; Kenneth Allen (Needham, MA), Jacobs; Alexander Thomas (Somerville, MA), Johansen; Elizabeth Whitney (Allston, MA), Jodson; Jared Alden (Topsfield, MA)|
|Assignee:||Eli Lilly and Company (Indianapolis, IN)|
|Filing Date:||Sep 28, 2007|
|Claims:||1. A medication dispensing apparatus comprising: a housing; a drive member rotatably fixed during dose preparing and injecting and axially movable in a distal direction relative to said housing, said drive member including a threaded shaft; a fluid container defining a medicine-filled reservoir with a movable piston at one end and an outlet at the other end, said piston engagable by said drive member to be advanced toward said outlet when said drive member is moved distally; a nut screwable along said drive member threaded shaft; a screw element threadedly engaged with said housing to be screwable relative to said housing; a nut rotating element connected with said nut to be axially movable and rotatably fixed relative thereto, said nut rotating element rotatably fixed with said screw element when said nut rotating element and said screw element are in a first axial arrangement, said nut rotating element rotatable relative to said screw element when said nut rotating element and said screw element are in a second axial arrangement; a nut advancing plunger threadedly engaged with said screw element, said plunger axially movable and rotatably fixed relative to said housing; wherein the threading of said screw element to said housing is of a first lead, the threading of said plunger to said screw element is of a second lead, and the threading of said drive member threaded shaft is of a third lead, and said first lead, said second lead and said third lead are each a different value; wherein during dose preparing, said nut rotating element and said screw element are in said first axial arrangement, whereby a screwing motion of said nut rotating element and screw element relative to said housing screws said nut rotating element and said screw element a first axial distance from a home position, which screwing motion of said nut rotating element screws said nut along said drive member threaded shaft a second axial distance different than said first axial distance; wherein during dose dispensing, said nut rotating element and said screw element are in said second axial arrangement, whereby a screwing motion of said screw element relative to said housing back toward said home position advances said plunger in said distal direction to axially advance said nut and thereby said drive member and said fluid container piston to dispense medicine from said outlet; wherein said nut rotating element comprises a sleeve portion within said screw element and a manually engageable button portion external to said screw element, said sleeve portion and button portion axially and rotatably shiftable as a unit; wherein said button portion comprises a depending lip positioned radially outward of and axially extending distally of a proximal end of said screw element; means for biasing said nut rotating element and said screw element from said second axial arrangement toward said first axial arrangement; wherein said screw element and said nut rotating element comprise interfitting teeth that disengage when said biasing means are overcome to shift said nut rotating element and screw element from said first axial arrangement to said second axial arrangement; wherein said screw element comprises a tubular member having a radially inner surface and a radially outer surface, wherein said outer surface is threaded to said housing, and wherein said inner surface is threaded to said plunger; wherein said nut and said nut rotating element comprise interfitting fingers that share an annular space; wherein said nut and said nut advancing plunger comprise cooperating clicker elements for creating audible indications during dose preparing; wherein said first lead equals a factor M times the third lead, and wherein said second lead equals a factor (M-1) times the third lead; wherein said housing comprises a tubular body portion and a bulkhead portion that are adhesively fixedly secured together, said bulkhead portion including tabs that slidably fit within keyways in said drive member to prevent rotation of said drive member within said housing, wherein said nut advancing plunger is axially movable and rotatably fixed relative to said housing bulkhead portion by at least one lug of said housing bulkhead portion that slidably fits within at least one slot formed in said plunger; wherein said nut advancing plunger includes at least one flange that directly frictionally engages at least one flange of said nut during dose dispensing to resist nut rotation; wherein said screw element serves as a dial and comprises dose indication markings on said radially outer surface; a plurality of teeth on said nut advancing plunger that are engageable with at least one tooth on a portion of said nut rotating element to limit apparatus misuse; clicking means for identifying a dose setting, said clicking means including two sets of longitudinally extending ribs radially projecting from said nut, each set spanning 90.degree. of the nut circumference and centered 180.degree. apart from the other set, said clicking means further including four axially-extending, resilient toothed fingers of said plunger, said toothed fingers centered at 90.degree. intervals around the circumference of said plunger; and means for indicating an end of injection, said indicating means including a resilient arm with a toothed end which projects from and is integrally formed with a proximal face of a bulkhead separately formed and rotatably fixed to said housing, said indicating means further including a detent on an annular, distal face of said screw element which said toothed end of said arm snaps over when said screw element is fully screwed distally into said housing during injecting, and wherein a portion of said bulkhead is abutted by and thereby forms a hard stop for said screw element when said screw element is fully screwed distally into said housing.|
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