Patent ID: 9381305
Filing Date: 2016-07-05
CPC Classification: A61M

Claim Text:
1. A medical device comprising: a dose delivery mechanism comprising a piston rod, the piston rod having a screw thread being located a first distance near a piston and a further screw thread located at a second distance from the piston, where the second distance is greater than the first distance and the piston rod rotates during dose delivery; a lock nut and a piston rod nut of the mechanism, where one of the lock nut or the piston rod nut is threadedly engaged with the piston rod; a coupling device configured to cause the lock nut and the piston rod nut to engage each other to prevent relative rotation between them; a spring arranged in contact with at least one of the lock nut and the piston rod nut and tending to engage or disengage the lock nut and the piston rod nut; and the spring being a wave spring or wave washer.