A Pen-Shaped Torsion Spring Driven Injection Device

摘要

The invention relates to a pen-shaped torsion spring driven injection device for apportioning set dose of a liquid drug. A piston rod having an external thread is driven forward by a rotatable piston rod guide engaging the piston rod. The piston rod guide is rotated by a torsion spring encompassed between the housing and the piston rod guide. A scale drum having a thread engaging the external thread of the piston rod is provided, and the scale drum is rotated up and down the piston rod by a proximal located rotatable dose setting member cooperating with the scale drum. The scale drum thus move helically when rotated as the piston rod is held inrotatable during dose setting.

主权项

1. A pen-shaped torsion spring driven injection device for apportioning set dose of a liquid drug comprising:
A housing having a window, A piston rod having an external thread, A rotatable piston rod guide engaging and driving the piston rod during dose expelling, A torsion spring for rotating the piston rod guide, A rotatable scale drum having a thread engaging the external thread of the piston rod and carrying a plurality of indicia viewable through the window of the housing, A rotatable dose setting member cooperating with the scale drum such that rotation of the dose setting member during dose setting is transformed to a rotation of the scale drum, and whereinthe piston rod is held inrotatable during dose setting whereby the scale drum rotates helically on the external thread of the piston rod.