Dry powder inhaler

An inhaler, comprising

• a housing,
• a mouthpiece through which a dose of medicament is inhaled by a user,
• a blister strip having a plurality of blisters, each blister containing, at least initially, a dose of medicament for inhalation by a user,
• a blister opening assembly for facilitating withdrawal of medicament from a target blister of the blister strip,
• an actuator mechanism operable to sequentially move each blister into alignment with the blister opening assembly so as to become said target blister,
• the housing comprising a first blister compartment for storing an unopened portion of the blister strip as a first coil, a second blister compartment for receiving an opened portion of the blister strip and coiling it into a second coil, and a movable dividing wall separating the first and second blister compartments,
• the movable dividing wall being displaced progressively during successive actuations of the inhaler, thereby causing the volume of the first blister compartment to decrease progressively and the volume of the second blister compartment to increase progressively,
• the inhaler further comprising
• a first arcuate supporting surface which is disposed in, or forms part of, the first blister compartment within the housing for supporting at least a portion of the first coil,
• wherein a radius of the first arcuate supporting surface matches the radius of the first coil, at a stage in the life of the inhaler, when the diameter of the first coil is at a maximum and
• a blister strip guide rib positioned in the second blister compartment for controlling the direction of the used blister strip as it enters the second blister compartment, with a section of the used blister strip passing between the guide rib and an internal surface of the housing during successive actuations of the inhaler, wherein the blister strip has a height a when it is located in the second blister compartment and the guide rib is spaced apart from the internal surface of the housing by distance b to form a channel through which the section of the blister strip passes, wherein the section of the blister strip passing between the guide rib and the internal surface of the housing does not include a blister bowl which contained the dose of medicament before the blister was opened,
• characterized in that the blister height a as the section of the blister strip passes through the channel is greater than the distance b of the channel.