Drug delivery device

Abstract

A drug delivery device having a housing containing a gas generator controlled by an electronic controller. The gas generator generates gas into a reciprocable chamber, whereby reciprocation of the chamber causes a lever to reciprocate a pawl, and this action causes a ratchet to undergo incremental advancement. The device may also be provided with manual control for delivering a bolus dose of drug when necessary.

1 . A drug delivery device comprising:
 a housing containing a drug reservoir;   means for facilitating expulsion of drug from the drug reservoir;   a mechanism in communication with the facilitation means, operable to undergo incremental advancement and thereby drive the drug from the reservoir;   a member operatively associated with the mechanism to cause the incremental advancement of the mechanism as the member moves in a first direction; and gas generating means located within the housing and operable to expand in a chamber, the member being in transmission relation to the chamber, whereby the member is driven by the movement of the chamber to advance the mechanism and thereby drive the drug from the reservoir in incremental fashion.   
     
     
         2 . The drug delivery device according to  claim 1 , wherein the mechanism in communication with the facilitation means comprises a ratchet. 
     
     
         3 . The drug delivery device according to  claim 1 , wherein the member moves in a reciprocable fashion. 
     
     
         4 . The drug delivery device according to  claim 3 , wherein the movement of the reciprocable member causes the stepwise advancement of the mechanism. 
     
     
         5 . The drug delivery device according  claim 3 , wherein the member is connected to a wall of the chamber, whereby the reciprocable movement of the member is driven by the expansion and contraction of the chamber. 
     
     
         6 . The drug delivery device according to  claim 1 , wherein the chamber is elastically biased to revert to a contracted state, and wherein a venting means is provided to enable contraction of the chamber after gas generation has expanded the chamber. 
     
     
         7 . The drug delivery device according to  claim 6 , wherein the venting means is passive and allows escape of gas therethrough when the chamber is pressurised relative to atmospheric pressure. 
     
     
         8 . The drug delivery device according to  claim 7 , wherein the gas generator is adapted to generate gas at a rate higher than the rate at which venting occurs, whereby when the gas generator is active, the chamber becomes pressurised and expands, and when the gas generator is inactive, the venting means causes depressurisation and contraction of the chamber. 
     
     
         9 . The drug delivery device according to  claim 7 , wherein the venting means comprises a permeable or semi-permeable member. 
     
     
         10 . The drug delivery device according to  claim 9 , wherein the member is a silicone membrane. 
     
     
         11 . The drug delivery device according to  claim 1 , wherein the mechanism is caused to advance as the chamber undergoes expansion. 
     
     
         12 . The drug delivery device according to  claim 1 , wherein the mechanism is caused to advance as the chamber undergoes contraction. 
     
     
         13 . The drug delivery device according to  claim 1 , wherein the member comprises a lever extending between the chamber and the mechanism. 
     
     
         14 . The drug delivery device according to  claim 1 , wherein the mechanism comprises a rigid ratchet element having spaced formations on a surface thereof. 
     
     
         15 . The drug delivery device according to  claim 14 , wherein the formations have a sawtooth cross section. 
     
     
         16 . The drug delivery device according  claim 14 , wherein the formations are grooves on a surface of the rigid ratchet element. 
     
     
         17 . The drug delivery device according to  claim 14 , wherein the mechanism includes a pawl carried on the member, the pawl being adapted to make ratcheting engagement with the formations on the rigid ratchet element. 
     
     
         18 . The drug delivery device according to  claim 17 , wherein the pawl is resiliently biased against the formations on the rigid ratchet element. 
     
     
         19 . The drug delivery device according to  claim 18 , wherein the pawl is in the form of a substantially flat spring an end of which bears against the formations on the rigid ratchet element. 
     
     
         20 . The drug delivery device according to  claim 18 , wherein the formations are regularly spaced along the rigid ratchet element, and wherein the pawl comprises a pair of pawl members resiliently biased against the rigid ratchet element at different points along the length of the rigid ratchet element, the axial distance between the pair of pawl members being different to the axial distance between successive formations. 
     
     
         21 .- 55 . (canceled)