US 9,808,581 B2
Plunger retraction for leak prevention in injection device
Jerry Marshall, Oxford (GB); and Jakub Tomaszewski, Woodstock (GB)
Assigned to OWEN MUMFORD LIMITED, Woodstock (GB)
Appl. No. 14/910,389
Filed by OWEN MUMFORD LIMITED, Woodstock (GB)
PCT Filed Jul. 2, 2014, PCT No. PCT/GB2014/052007
§ 371(c)(1), (2) Date Feb. 5, 2016,
PCT Pub. No. WO2015/036729, PCT Pub. Date Mar. 19, 2015.
Claims priority of application No. 1316079.1 (GB), filed on Sep. 10, 2013.
Prior Publication US 2016/0175536 A1, Jun. 23, 2016
Int. Cl. A61M 5/315 (2006.01); A61M 5/20 (2006.01)
CPC A61M 5/31566 (2013.01) [A61M 5/20 (2013.01); A61M 5/31585 (2013.01); A61M 5/3156 (2013.01); A61M 5/31511 (2013.01); A61M 5/31513 (2013.01); A61M 5/31515 (2013.01); A61M 5/31535 (2013.01); A61M 5/31553 (2013.01); A61M 2005/2026 (2013.01)] 5 Claims
OG exemplary drawing
 
1. An injection device comprising:
a main housing;
a plunger comprising a leadscrew and a cap attached to the leadscrew such that, in use, the cap engages a bung of a cartridge containing medicament;
a drive gear within the housing and engaging with a said leadscrew such that rotation of the drive gear drives the plunger axially through the housing towards the bung; and
a release trigger comprising a locking ring having generally axially extending teeth for engaging with corresponding teeth on the drive gear, the release trigger being generally axially movable between an engaged position in which the generally axially extending teeth of the locking ring and the corresponding teeth on the drive gear are engaged so as to prevent rotation of the drive gear relative to the housing, and a disengaged position in which the generally axially extending teeth of the locking ring and the corresponding teeth on the drive gear are disengaged so as to enable rotation of the drive gear;
wherein the teeth of the locking ring and teeth of the drive gear have a screw pitch so that axial movement of the trigger between the disengaged position and the engaged position causes counter-rotation of the drive gear so as to retract the plunger away from the bung.