Dose counters for inhalers, inhalers and shafts thereof

摘要

A dose counter for a metered dose inhaler indicates to a user the number of doses of active drug remaining in the medicament canister which is retained within and movable with respect to the body of the inhaler to dispense a dose. The dose counter includes an incremental counting system including a tape winder spool for a tape with incremental tape indicia for counting doses. The incremental counting system includes a main body and an actuator pawl 80 that is arranged to be driven in response to canister motion by the pin 34 and to increment a ratchet wheel 94 by engagement with the teeth of the ratchet. The actuator pawl 80 and ratchet wheel are configured to have predetermined canister fire (left hand figure) and count (right hand figure) configurations in a canister fire sequence. The canister fire configuration is determined by a position of the pawl relative to a datum at which the canister fires medicament. The count configuration is determined by a position of the pawl relative to the datum at which the incremental count system makes an incremental count. The ratchet wheel 94 has a plurality of circumferentially spaced teeth and an associated count pawl 138 (not to be confused with the actuation pawl 80). When in the count configuration, transitioning from the fire configuration, the count pawl 138 has finished riding up along a forward surface 142 of one of the teeth and has resiliently jumped over the tooth into engagement with the back of the next tooth to prevent backing of the count tape wound up on the spool rotated by rotation of the ratchet wheel.