Dose setting mechanism and drug delivery device with ratchet mechanism

A dose setting mechanism comprising:

• a first element and a second element, the first element being moveable with respect to the second element;
• the first element comprising a sleeve-shaped main body coupled to the second element by a threaded connection comprising a helical thread, and
• a ratchet mechanism coupling the first element to the second element and allowing motion of the first element with respect to the second element from a first position to a second position only in a first direction while preventing motion of the first element with respect to the second element in a second direction that is opposite to the first direction,
• wherein the ratchet mechanism comprises a ratchet feature including a plurality of teeth comprised by one of the first element and the second element and a pawl that is comprised by the other one of the first element and the second element,
• wherein the teeth are arranged in a line between a first pawl position and a second pawl position, and the pawl is configured to move along the teeth from the first pawl position to the second pawl position when the first element moves with respect to the second element from the first position of the first element to the second position of the first element, and
• wherein the first element is movable with respect to the second element in the second direction from the second position of the first element into the first position of the first element only after passing the second position of the first element in the first direction.

A drug delivery device comprising:

• a dose setting mechanism comprising:
• a first element and a second element, the first element being moveable with respect to the second element, the first element comprising a sleeve-shaped main body coupled to the second element by a threaded connection;
• and
• a ratchet mechanism coupling the first element to the second element and allowing motion of the first element with respect to the second element from a first position to a second position only in a first direction while preventing motion of the first element with respect to the second element in a second direction that is opposite to the first direction,
• wherein the ratchet mechanism comprises a ratchet feature including a plurality of teeth comprised by one of the first element and the second element and a pawl that is comprised by the other one of the first element and the second element,
• wherein the teeth are arranged in a line between a first pawl position and a second pawl position, and the pawl is configured to move along the teeth from the first pawl position to the second pawl position when the first element moves with respect to the second element from the first position of the first element to the second position of the first element,
• wherein the first element is movable with respect to the second element in the second direction from the second position of the first element to the first position of the first element only after the first element passes the second position of the first element in the first direction, wherein when the first element is in the second position, the pawl is beyond the plurality of teeth and the pawl is disengaged from the teeth;
• a housing, the first element being arranged within the housing such that at least a portion of the first element is visible through an aperture in the housing, and the second element being interposed between the housing and the first element and in threaded engagement with the first element such that rotation of the first element causes an axial displacement of the second element;
• a dose selector operable to set a dose by rotation relative to the housing;
• and
• a piston rod coupled to the housing and to a drive sleeve such that rotation of the drive sleeve relative to the housing causes the piston rod to translate relative to the housing.