Recyclable medication dispensing device

• US 6,221,046 B1
• Filed: 07/09/1996
• Issued: 04/24/2001
• Est. Priority Date: 03/07/1995
• Status: Expired due to Term

• Current Assignee: Eli Lilly and Company
• Original Assignee: Eli Lilly and Company
• Inventors: Hodge, Andrew, Hixson, Dave, Burroughs, Andrew
• Primary Examiner(s): Seidel, Richard K.
• Assistant Examiner(s): Hayes, Michael J
• Application Number:
  US08/678,528
• Time in Patent Office: 1,750 Days
• Field of Search: 604/207, 604/208, 604/209, 604/210, 604/211, 604/181, 604/186, 604/187, 604/232, 604/224, 604/218, 604/220, 604/228, 604/229, 604/71, 604/72, 604/404, 604/246, 222/309, 222/390, 222/391
• US Class Current: 604/153
• CPC Class Codes: A61M 2205/581 by audible feedback
• CPC Class Codes: A61M 2205/582 by tactile feedback
• CPC Class Codes: A61M 5/24 Ampoule syringes, i.e. syringes with needle for use in combination with replaceable ampoules or carpules, e.g. automatic ampoules or carpules A61J1/06
• CPC Class Codes: A61M 5/31535 Means improving security or handling thereof, e.g. blocking means, means preventing insufficient dosing, means allowing correction of overset dose
• CPC Class Codes: A61M 5/31541 Means preventing setting of a dose beyond the amount remaining in the cartridge
• CPC Class Codes: A61M 5/31551 including axial movement of dose setting member
• CPC Class Codes: A61M 5/31556 Accuracy improving means
• CPC Class Codes: A61M 5/3156 using volume steps only adjustable in discrete intervals, i.e. individually distinct intervals
• 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 5/31593 Multi-dose, i.e. individually set dose repeatedly administered from the same medicament reservoir

Abstract

A multi-use medication dispensing pen made of a plastic material that is recyclable after the contents of the medication cartridge have been exhausted. The pen is made of a minimal number of parts, which include a housing, a dial mechanism, a generally cylindrical button assembly located within the proximal end of the dial mechanism, an internally threaded nut, and an externally threaded leadscrew. The pen is arranged so that the dial mechanism must be rotated to the zero-dose position prior to setting a dose. The pen includes a lockout mechanism that prevents the dial mechanism from being inadvertently depressed during dosing. The pen further includes a mechanism that limits the maximum dosage that can be dialed up and a mechanism that prevents the user from dialing up a dosage greater than that remaining in the cartridge.

Claims

1. A medication injection pen having a distal end and a proximal end, said pen comprising:

a housing defining an interior space;

a cartridge mounted within said housing interior space near said distal end and including a piston, an exit and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably and axially shiftably mounted to said housing proximally of said cartridge, said dial mechanism having a dose-setting axial position and an end-of-injection axial position, said dial mechanism having a surface rotatably engaged with said nut when said dial mechanism is in said dose-setting axial position whereby rotation of said dial mechanism relative to said housing causes said nut to rotate relative to said drive stem to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut during injection to thereby drive said drive stem distally, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position for said dial mechanism and said nut;

said housing including at least one lock element engageable with a mating lock element on said nut when said nut is in said end-of-injection axial position, whereby rotation of said nut is inhibited in said end-of-injection position, rotation of said dial mechanism in said dose setting position transmitting sufficient torque to said nut to disengage said lock elements, wherein said at least one lock element comprises at least one rib disposed on an inner surface of said housing and said mating lock element comprises at least one prong which rotationally engages said at least one rib when said dial mechanism is in said end-of-injection axial position to thereby inhibit inadvertent rotation of said nut, rotation of said dial in said dose-setting position providing sufficient torque to force said at least one prong out of engagement with said at least one rib to thereby allow said nut to rotate about and axially translate along said drive stem.

2. A medication injection pen having a distal end and a proximal end, said pen comprising:

a housing defining an interior space;

a cartridge mounted within said housing interior near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably and axially shiftably mounted to said housing proximally of said cartridge, said dial mechanism having a dose-setting axial position and an end-of-injection axial position, said dial mechanism having a surface rotatably engaged with said nut when said dial mechanism is in said dose-setting axial position whereby rotation of said dial mechanism relative to said housing causes said nut to rotate relative to said drive stem to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut during injection to thereby drive said drive stem distally, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position for said dial mechanism and said nut;

said housing including at least one lock element engageable with a mating lock element on said nut when said nut is in said end-of-injection axial position, whereby rotation of said nut is inhibited in said end-of-injection position, rotation of said dial mechanism in said dose setting position transmitting sufficient torque to said nut to disengage said lock elements, wherein said housing further includes an end-of-injection bulkhead, said bulkhead disposed on said housing adjacent said end-of-injection position of said nut, said nut being provided with at least one engagement surface at a distal end thereof, said engagement surface axially engaging said bulkhead when an injection is complete to thereby prevent further telescopic insertion of said dial mechanism into said housing.

3. The pen of claim 2 wherein said bulkhead includes a plurality of tangs which engage a plurality of ratchet teeth provided along a longitudinal axis of said drive stem to allow movement of said drive stem with respect to said housing only in the direction of said distal end of said pen, a damping compound being provided between said tangs and said ratchet teeth to provide relatively slow, smooth, and quiet movement of said drive stem through said housing.

4. A medication injection pen having a distal end and a proximal end, said pen comprising:

a housing defining an interior space;

a cartridge mounted within said housing interior near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably and axially shiftably mounted to said housing proximally of said cartridge, said dial mechanism having a dose-setting axial position and an end-of-injection axial position, said dial mechanism having a surface rotatably engaged with said nut when said dial mechanism is in said dose-setting axial position whereby rotation of said dial mechanism relative to said housing causes said nut to rotate relative to said drive stem to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut during injection to thereby drive said drive stem distally, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position for said dial mechanism and said nut;

said housing including at least one lock element engageable with a mating lock element on said nut when said nut is in said end-of-injection axial position, whereby rotation of said nut is inhibited in said end-of-injection position, rotation of said dial mechanism in said dose setting position transmitting sufficient torque to said nut to disengage said lock elements, wherein said dial mechanism further includes a first outwardly projecting thread and a second outwardly projecting thread wherein said second thread includes two projections divided by a keyway, said housing further including a threaded surface defined by a helical land and a helical groove about an inner circumference thereof, a distal portion of said helical land including a first gap and a second gap, said second gap divided by a projecting key, axial proximal retraction of said dial mechanism relative to said housing being prevented in all rotational positions of said dial mechanism except where said first thread is aligned with said first gap and said second thread and keyway are aligned with said second gap and key.

5. A medication injection pen having a distal end and a proximal end, said pen comprising:

a housing defining an interior space;

a cartridge mounted within said housing interior space near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

means for maintaining said drive stem in contact with said piston by preventing axial retraction of said drive stem away from said piston;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably mounted to said housing distally of said cartridge, said dial mechanism axially shiftable between a relatively proximal dose setting axial position and a relatively distal end-of-injection axial position, said dial mechanism having a first surface rotatably engaged with said nut by axially shifting said dial mechanism to said dose setting axial position whereby rotation of said dial mechanism relative to said housing causes said nut to rotate relative to said drive stem to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut by axially shifting said dial mechanism from said dose setting position to said end-of-injection position to thereby drive said drive stem distally and discharge a selected dosage of said injectable medication, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position, axially shifting said dial assembly to said end-of-injection position rotationally disengaging said dial mechanism first surface and said nut, wherein said nut includes at least one prong which rotationally engages at least one rib provided on an inner surface of said housing when said dial mechanism is in said end-of-injection position to thereby inhibit inadvertent rotation of said nut, rotation of said dial mechanism when said dial mechanism is in said dose-setting position providing sufficient torque to force said at least one prong out of engagement with said at least one rib to thereby allow said nut to rotate about and axially translate along said drive stem.

6. A medication injection pen having a distal end and a proximal end, said pen comprising:

a housing defining an interior space;

a cartridge mounted within said housing interior near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

means for maintaining said drive stem in contact with said piston by preventing axial retraction of said drive stem away from said piston;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatable mounted to said housing distally of said cartridge, said dial mechanism axially shiftable between a relatively proximal dose setting axial position and a relatively distal end-of-injection axial position, said dial mechanism having a first surface rotatably engaged with said nut by axially shifting said dial mechanism to said dose setting axial position whereby rotation of said dial mechanism relative to said housing causes said nut to rotate relative to said drive stem to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut by axially shifting said dial mechanism from said dose setting position to said end-of-injection position to thereby drive said drive stem distally and discharge a selected dosage of said injectable medication, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position, axially shifting said dial assembly to said end-of-injection position rotationally disengaging said dial mechanism first surface and said nut, wherein said housing further includes an end-of-injection bulkhead, said bulkhead disposed on said housing adjacent said end-of-injection position of said nut, said nut being provided with at least one engagement surface at a distal end thereof, said engagement surface axially engaging said bulkhead when an injection is complete to thereby prevent further telescopic insertion of said dial mechanism into said housing.

7. The pen of claim 6, wherein said bulkhead includes a plurality of tangs which engage a plurality of ratchet teeth provided along a longitudinal axis of said drive stem to allow movement of said drive stem with respect to said housing only in the direction of said distal end of said apparatus, a damping compound being provided between said ratchet teeth and said tangs to provide relatively slow, smooth, and quiet movement of said drive stem through said housing.

8. A medication injection pen having a distal end and a proximal end, said pen comprising:

a housing defining an interior space;

a cartridge mounted within said housing interior near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

means for maintaining said drive stem in contact with said piston by preventing axial retraction of said drive stem away from said piston;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably mounted to said housing distally of said cartridge, said dial mechanism axially shiftable between a relatively proximal dose setting axial position and a relatively distal end-of-injection axial position, said dial mechanism having a first surface rotatably engaged with said nut by axially shifting said dial mechanism to said dose setting axial position whereby rotation of said dial mechanism relative to said housing causes said nut to rotate relative to said drive stem to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut by axially shifting said dial mechanism from said dose setting position to said end-of-injection position to thereby drive said drive stem distally and discharge a selected dosage of said injectable medication, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position, axially shifting said dial assembly to said end-of-injection position rotationally disengaging said dial mechanism first surface and said nut, wherein said dosage setting dial mechanism further includes a first outwardly projecting thread and a second outwardly projecting thread wherein said second thread includes two projections divided by a keyway, said housing further including a threaded surface defined by a helical land and a helical groove about an inner circumference thereof, a distal portion of said helical land including a first gap and a second gap, said second gap divided by a projecting key, axial proximal retraction of said dial mechanism relative to said housing being prevented in all rotational positions of said dial mechanism except where said first thread is aligned with said first gap and said second thread and keyway are aligned with said second gap and key.

9. A medication injection pen having a distal end and a proximal end, said pen comprising:

a generally hollow housing including a groove disposed in a plane oriented perpendicular to an axis of said housing and disposed on an inner surface of said housing and a helically threaded surface disposed on an inner portion of said housing;

a cartridge mounted within said housing near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably and axially shiftably mounted to said housing proximally of said cartridge, said dial mechanism having a dose setting axial position and an end-of-injection axial position, said dial mechanism having a surface rotatably engaged with said nut and a thread surface engaged with said helically threaded surface of said housing when said dial assembly is in said dose setting axial position, whereby rotation of said dial mechanism relative to said housing in said dose setting position causes said nut to rotate relative to said drive stem and said dial assembly to move axially proximally to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut during injection to thereby drive said drive stem distally, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position; and

an end-of-injection click finger disposed on said dial mechanism, said click finger elastically deformable relative to said dial mechanism, said click finger snapping into said housing groove when said dial mechanism is in said end-of-injection position, wherein said nut includes at least one prong which rotationally engages at least one rib provided on an inner surface of said housing when said dial mechanism is in said end-of-injection position to thereby inhibit inadvertent rotation of said nut, rotation of said dial mechanism in said dose-setting position providing sufficient torque to force said at least one prong out of engagement with said at least one rib to thereby allow said nut to rotate about and axially translate along said drive stem.

10. A medication injection pen having a distal end and a proximal end, said pen comprising:

a generally hollow housing including a groove disposed in a plane oriented perpendicular to an axis of said housing and disposed on an inner surface of said housing and a helically threaded surface disposed on an inner portion of said housing;

a cartridge mounted within said housing near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably and axially shiftably mounted to said housing proximally of said cartridge, said dial mechanism having a dose setting axial position and an end-of-injection axial position, said dial mechanism having a surface rotatably engaged with said nut and a thread surface engaged with said helically threaded surface of said housing when said dial assembly is in said dose setting axial position, whereby rotation of said dial mechanism relative to said housing in said dose setting position causes said nut to rotate relative to said drive stem and said dial assembly to move axially proximally to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut during injection to thereby drive said drive stem distally a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position; and

an end-of-injection click finger disposed on said dial mechanism, said click finger elastically deformable relative to said dial mechanism, said click finger snapping into said housing groove when said dial mechanism is in said end-of-injection position, wherein said housing further includes an end-of-injection bulkhead, said bulkhead disposed on said housing adjacent said end-of-injection position of said nut, said nut being provided with at least one engagement surface at a distal end thereof, said engagement surface axially engaging said bulkhead when an injection is complete to thereby prevent further telescopic insertion of said dial mechanism into said housing.

11. The pen of claim 10, wherein said bulkhead includes a plurality of tangs which engage a plurality of ratchet teeth provided along a longitudinal axis of said drive stem to allow movement of said drive stem with respect to said housing only in the direction of said distal end of said apparatus, a damping compound being provided between said ratchet teeth and said housing tangs to provide relatively slow, smooth, and quiet movement of said drive stem through said housing.

12. A medication injection pen having a distal end and a proximal end, said pen comprising:

a generally hollow housing including a groove disposed in a plane oriented perpendicular to an axis of said housing and disposed on an inner surface of said housing and a helically threaded surface disposed on an inner portion of said housing;

a cartridge mounted within said housing near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing interior in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

a rotatable threaded nut threadingly disposed on said drive stem;

a dosage setting dial mechanism rotatably and axially shiftably mounted to said housing proximally of said cartridge, said dial mechanism having a dose setting axial position and an end-of-injection axial position, said dial mechanism having a surface rotatably engaged with said nut and a thread surface engaged with said helically threaded surface of said housing when said dial assembly is in said dose setting axial position, whereby rotation of said dial mechanism relative to said housing in said dose setting position causes said nut to rotate relative to said drive stem and said dial assembly to move axially proximally to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut during injection to thereby drive said drive stem distally, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position; and

an end-of-injection click finger disposed on said dial mechanism, said click finger elastically deformable relative to said dial mechanism, said click finger snapping into said housing groove when said dial mechanism is in said end-of-injection position, wherein said dosage setting dial mechanism further includes a first outwardly projecting thread and a second outwardly projecting thread wherein said second thread includes two projections divided by a keyway, said housing further including a threaded surface defined by a helical land and a helical groove about an inner circumference thereof, a distal portion of said helical land including a first gap and a second gap, said second gap divided by a projecting key, said axial proximal retraction of said dial mechanism relative to said housing being prevented in all rotational positions of said dial mechanism except where said first thread is aligned with said first gap and said second thread and keyway are aligned with said second gap and key.

13. A medication injection pen having a distal end and a proximal end, said pen comprising:

a generally hollow housing including a helical groove disposed on an inner circumference thereof near said proximal end;

a cartridge mounted within said housing near said distal end and including a piston, an exit, and an injectable medication between said piston and said exit;

a threaded drive stem mounted within said housing in axial alignment with said cartridge, said drive stem axially moveable through said cartridge for driving said piston and ejecting said medication from said cartridge;

a rotatable threaded nut threading disposed on said drive stem;

a dosage setting dial mechanism rotatably, axially shiftably mounted to said housing proximally of said cartridge, said dial mechanism having a dose setting axial position and an end-of-injection axial position, said dial mechanism having a surface rotatably engaged with said nut when said dial mechanism is in said dose setting axial position whereby rotation of said dial mechanism relative to said housing causes said nut to rotate relative to said drive stem to thereby set a dose, said dial mechanism having a second surface axially engaged with said nut during injection to thereby drive said drive stem distally, a distal limit of travel of said axially engaged dial mechanism and said nut relative to said housing defining said end-of-injection position, said dial mechanism including first and second threads on an outer circumference thereof, said threads being threadingly engageable with said housing helical groove and resiliently deformable radially inwardly and outwardly relative to said dial mechanism; and

a button telescopically received in a proximal end of said dial mechanism, said button having a distal end having a first circumferential step and a second circumferential step, said first step having a enlarged diameter, said second step having a larger diameter than said first step, said first step engaging and biasing said deformable threads outward into engagement with said helical groove and thereby preventing said dial mechanism from non-rotationally axially advancing relative to said housing with said first step engaged with said deformable threads, said second step engaging said dial mechanism to prevent said button from being fully retracted out of said pen, said button adapted to be telescopically axially advanced within said dial mechanism to thereby move said first step out of engagement with said deformable threads to thereby allow said threads to deform inward and out of engagement with said helical groove, said dial mechanism thereby being non-rotationally axially advanceable relative to said housing with said first step disengaged from said deformable threads.

14. The pen of claim 13, wherein said button further includes a third enlarged diameter portion between said first step and said proximal end, said third enlarged diameter portion engaging an elastically deformable and inwardly ramped surface on said dial mechanism, said ramped surface deforming outward when said button is depressed to allow for an injection, said ramped surface biasing said button toward said proximal end of said pen when said button is not depressed.

15. The pen of claim 13, wherein said second thread is divided by a keyway, and said housing helical groove includes a first gap and a second gap, said second gap divided by a projecting key, said axial proximal retraction of said dial mechanism relative to said housing being prevented in all rotational positions of said dial mechanism except where said first thread is aligned with said first gap and said second thread and keyway are aligned with said second gap and key.

16. The pen of claim 13 wherein said nut includes at least one prong which rotationally engages at least one rib provided on an inner surface of said housing when said pen is in said non-dose setting position to thereby inhibit inadvertent rotation of said nut, rotation of said dial mechanism in said dose-setting position providing sufficient torque to force said at least one prong out of engagement with said at least one rib to thereby allow said nut to rotate about and axially translate along said drive stem.

17. The pen of claim 13, wherein said nut includes a plurality of clutch teeth disposed on an outer surface thereof, said nut being telescopingly received within said dial mechanism when said dial mechanism is in said dose-setting position, said clutch teeth rotationally engaging a plurality of receiving splines provided on an inner surface of said dial mechanism when said dial mechanism is in said dose-setting position, said dial mechanism being telescopingly inserted into said housing when being moved to said end-of-injection position and thereby causing said receiving splines to become disengaged from said clutch teeth when said dial mechanism is in said end-of-injection position.

18. The pen of claim 13, wherein said housing further includes a centering ring around an inner circumference thereof and about a distal end of said dial mechanism to maintain proper alignment of said dial mechanism within said housing.

19. The pen of claim 13, wherein said drive stem further includes a helical thread about its exterior and a stop disposed near a proximal end of said stem, said nut having a surface positioned to rotationally engage said stop when said nut has reached a predetermined axial position on said drive stem and thereby prevent further proximal movement of said drive stem.

20. The pen of claim 13, wherein said housing further includes an end-of-injection bulkhead, said bulkhead disposed on said housing adjacent said end-of-injection position of said nut, said nut being provided with at least one engagement surface at a distal end thereof, said engagement surface axially engaging said bulkhead when an injection is complete to thereby prevent further telescopic insertion of said dial mechanism into said housing.

21. The pen of claim 20, wherein said bulkhead includes a plurality of tangs which engage a plurality of ratchet teeth provided along a longitudinal axis of said drive stem to allow movement of said drive stem with respect to said housing only in the direction of said distal end of said apparatus, a damping compound being provided between said ratchet teeth and said tangs to provide relatively slow, smooth, and quiet movement of said drive stem through said housing.

22. The pen of claim 13 wherein said housing is comprised of two semicylindrical plastic portions having longitudinal edges, said longitudinal edges being aligned and ultrasonically welded together to form a cylinder.

23. The pen of claim 13 wherein said housing further includes a circular groove about an inner circumference thereof, and said dial mechanism includes

an end-of-injection click finger, said click finger elastically deformable relative to said dosage setting dial, said click finger snapping into said housing circular groove when an injection is complete to provide the user with an audible indication thereof.