Drive assembly for a medicament delivery device

Abstract

A power pack for use with a medicament delivery device is presented having a plunger rod movable along a longitudinal axis; a drive spring operably connected to said plunger rod; a plunger rod sleeve arranged with holding elements for releasably holding said plunger rod with said drive spring in a tensioned state. Signal initiating elements are arranged to said plunger rod; and signal generating elements arranged to cooperate with said signal initiating elements for providing information to a user of a medicament delivery device about the movement of said plunger rod when said plunger rod sleeve has been activated to release said holding elements.

1 . A notification mechanism positioned within a medicament delivery device, where the notification mechanism comprises:
 a tubular proximal part comprising a central opening and an inwardly extending ledge that projects radially into the central opening; and   an assembly comprising a plunger rod and a drive spring, where the assembly is movably positioned within the central opening such that a row of signal initiating elements positioned longitudinally along the assembly slidably engage the inwardly extending ledge, and   wherein the signal initiating elements slidably engage with the inwardly extending ledge during relative axial movement between the assembly and the tubular proximal part such that a tactile or audible signal notification is provided to a user of the medicament delivery device.   
     
     
         2 . The notification mechanism of  claim 1 , wherein the inwardly extending ledge is part of a flexible arm. 
     
     
         3 . The notification mechanism of  claim 2 , wherein the flexible arm generally projects proximally along a longitudinal axis of the assembly. 
     
     
         4 . The notification mechanism of  claim 1 , wherein the tubular proximal part further comprises two inwardly extending ledges diametrically positioned around the central opening such that both inwardly extending ledges project radially into the central opening. 
     
     
         5 . The notification mechanism of  claim 2 , wherein the flexible arm flexes radially outward as the assembly moves in a proximal direction during engagement with the signal initiating elements. 
     
     
         6 . The notification mechanism of  claim 1 , wherein the inwardly extending ledge is formed as an integral part of the tubular proximal part. 
     
     
         7 . The notification mechanism of  claim 1 , wherein the row of signal initiating elements comprise a plurality of alternating recesses and protrusions. 
     
     
         8 . The notification mechanism of  claim 1 , wherein the signal initiating elements are equally spaced in the row to provide a constant notification frequency of the tactile or audible signals. 
     
     
         9 . The notification mechanism of  claim 1 , wherein the signal initiating elements are unequally spaced in the row to provide a variable notification frequency of the tactile or audible notification signals. 
     
     
         10 . The notification mechanism of  claim 9 , wherein the variable notification frequency provides notice to the user that a medicament delivery sequence is progressing. 
     
     
         12 . The notification mechanism of  claim 1 , wherein the inwardly extending ledge is formed at the end of a flexible arm that is shaped to snap into and out of the signal initiating elements during a medicament delivery sequence. 
     
     
         13 . The notification mechanism of  claim 1 , wherein the user is notified at an end of a medicament delivery sequence. 
     
     
         14 . The notification mechanism of  claim 1 , wherein the tubular proximal part is axially fixed relative to the assembly such that the inwardly extending ledge only moves radially outward and radially inwardly as the assembly moves axially in the proximal direction. 
     
     
         15 . The notification mechanism of  claim 1 , wherein the notification mechanism further comprises a spring that causes the relative axial movement between the assembly and the tubular proximal part. 
     
     
         16 . A medicament delivery device comprising:
 an outer housing having a longitudinal axis; and   a notification mechanism comprising:   a tubular proximal part having a central opening and an inwardly extending ledge that projects radially into the central opening; and   an assembly comprising:   a drive spring having a biased state and a released state;   a plunger rod positioned within the central opening; and   a row of signal initiating elements projecting along the longitudinal axis;   wherein engagement of the inwardly extending ledge with assembly during relative axial movement between the assembly and the tubular proximal part produces a tactile or audible signal notification to a user of the medicament delivery device during medicament delivery.