Pen-type injector
View Patent ↗A pen-type injector is improved so that a user may select a delivery dose of a medicinal product from a multidose cartridge. The injector includes a housing, a cartridge containing the medicinal product retained within the housing, a piston rod, a dose selecting member to select the dose of medicinal product to be expelled, and a drive member to expel the selected dose of the medicinal product. The housing is formed unitary so that the dose selecting member and the drive member are moveably retained within the housing. The injector may include a ratchet associated with an insert to ensure the piston rod only rotates in a single direction through the insert, a button located on the drive member, and a clutch which upon depression of the button prevents rotation between the dose selecting member and the drive member.
1. A drive mechanism for use in a drug delivery device comprising:
a housing;
a dose dial sleeve located in the housing and having a helical track configured to allow the dose dial sleeve to rotate and translate relative to the housing during dose setting and dose delivery;
a drive sleeve releasably connected to the dose dial sleeve and comprising a central receiving area;
a piston rod extending through a threaded circular opening in the housing, where the piston rod has a first end and a second end, where the first end comprises a thread, the second end having a larger diameter than the first end and comprises a U-shaped cross-section having limbs extending longitudinally in a proximal direction, where the limbs are received within the drive sleeve; and
a button of a generally T-shaped configuration comprising a stem provided with a peripheral bead,
wherein the stem of the button is retained within the central receiving area with the peripheral bead being retained in a peripheral recess of the drive sleeve,
wherein the button is able to freely rotate with respect to the drive sleeve.
2. The drive mechanism of claim 1 where a pressure foot is attached to the first end of the piston rod on a first side of a web.
3. The drive mechanism of claim 2 where the pressure foot is reversible.
4. The drive mechanism of claim 1 where a clicker is provided between the dose dial sleeve and the drive sleeve.
5. The drive mechanism of claim 1 where the piston rod has a dual start thread.
6. The drive mechanism of claim 1 further comprising a clutch comprising a plurality of radially extending longitudinally directed teeth, where a radial separation of the teeth corresponds to a unit dose of a medicinal product, where the clutch is configured to releasably and rotationally fix together the dose dial sleeve and the drive sleeve.
7. The drive mechanism of claim 1 , wherein the first end extends through a circular opening in a web that is located in the housing.
8. The drive mechanism of claim 1 where the second end of the piston rod is configured to engage an internal surface of the drive sleeve.