Drug Delivery Device With Multifunctional Bias Structure

Abstract

The present invention provides a drug delivery device comprising a housing (2) extending along a longitudinal axis, a dose dial member (3) being rotatable relative to the housing (2) to set a dose ofdrug to be expelled from an attached reservoir and comprising a first serrated transversal surface (7), a second serrated transversal surface (16) being axially and rotationally fixed with respect tothe housing (2), and being configured for slipping engagement with the first serrated transversal surface (7) in a bi-directional ratchet interface in response to the dose dial member (3) being rotated relative to the housing (2) to increase or decrease the dose, and a dose delivery mechanism for expelling a set dose, the dose delivery mechanism comprising a piston rod (50),a torsion spring (30) for providing energy to drive the piston rod (50), an activation button (8) being axially movable relative to the housing (2) between an inactivated position in which the torsion spring (30) is retained and an activated position in which the torsion spring (30) is released to cause an expelling of the set dose, the activation button (8) being biased towards the inactivated position by a bias structure (40) arranged to act between the dose dial member (3) and the activation button (8), the bias structure (40) thereby further biasing the first serrated transversal surface (7) towards the second serrated transversal surface (16), and a drive member (20) being rotationally biased by the torsion spring (30), wherein the drive member (20) is axially fixed to the activation button (8) and axiallymovable relative to the housing (2) between a dose setting position in which the drive member (20) is rotationally fixed to the dose dial member (3) and a dose expelling position in which the drive member (20) is rotationally freed from the dose dial member (3) and rotationally interlocked with the piston rod (50).

Description

technical field [0001] The present invention relates generally to spring-actuated drug delivery devices, and more particularly to ratchet mechanisms for use in such devices. Background technique [0002] Drug delivery devices, such as injection devices, are widely used to administer liquid drugs to persons in need of therapeutic treatment. Many injection devices are capable of repeatedly setting and injecting fixed or variable volumes of medicament according to the operation of corresponding dose setting mechanisms and dose ejection mechanisms in the device. Some injection devices are adapted to be loaded with a pre-filled medicament reservoir containing a volume sufficient to provide multiple injectable doses of medicament. When the reservoir is empty, the user replaces it with a new one, and thus the injection device can be used repeatedly. Other injection devices are pre-filled when delivered to the user and can only be used until the drug reservoir is emptied, after wh...

AI Technical Summary

Problems solved by technology

[0008] Thus, while an axial ratchet mechanism may be preferred in some designs, prior art solutions are not optimal given the general desire to reduce the amount of waste and manufacturing costs of drug delivery This is particularly evident in the field of delivery devices where, after its drug product has been emptied, the entire product is discarded

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