Drug delivery device with means for determining expelled dose

Abstract

The present invention provides a drug delivery device (1) of the type in which a piston rod (10, 110) extends along a reference axis and is forced to rotate in an expelling direction about the reference axis during a dose expelling event to cause an expelling of drug from a drug reservoir (30, 130), and a resilient ratchet element (12) is operatively coupled with the piston rod (10, 110) and undergoes a deflecting motion comprising elastic deformation and recovery in response to an expelling of a predetermined dose increment, which deflecting motion occasions a velocity fluctuation of the piston rod (10, 110), comprising: a rotator module (50, 150) operatively coupled with the piston rod (10, 110) and configured to rotate about the reference axis against a rotation resisting force in response to a rotation of the piston rod (10, 110) in the expelling direction, the rotator module (50, 150) comprising a sensor system (70, 71; 170, 183; 270, 183) for monitoring a torque transferred by the piston rod (10, 110) during the dose expelling event, wherein the sensor system (70, 71; 170, 183; 270, 183) is configured to, from the monitored torque, identify occurrences of velocity fluctuation of the piston rod (10, 110) attributable to the deflecting motion of the resilient ratchet element 15 (12).

Description

technical field [0001] The present invention relates generally to drug delivery devices, and more particularly to medical injection devices having means for sizing an expelled dose. Background technique [0002] In diabetes care, segmental parenteral drug administration performed using traditional vial and syringe systems is increasingly being replaced by administration using pen injection devices. Pen injection devices are particularly convenient because they allow the user to perform dose injections from pre-filled drug reservoirs without having to manually transfer a specific dose from one reservoir (vial) to another (syringe) first. [0003] There are two main types of pen injection devices available, durable injection devices that are capable of delivering one or more drug doses from pre-filled cartridges that can be loaded into the device prior to use at a cost of The other is a single-use injection device, which is capable of delivering one or more drug doses from a ...

AI Technical Summary

Problems solved by technology

[0010] Although the above solutions enable automatic recording of expelled doses, they do require additional parts in the system which the user has to handle and which suffers in both physical appearance and weight distribution when attached to the pen injection device. Leads to an apparent asymmetry that some users find undesirable

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