Dose mechanism for an injection device for limiting a dose setting corresponding to the amount of medicament left

• US 8,920,383 B2
• Filed: 07/17/2006
• Issued: 12/30/2014
• Est. Priority Date: 07/27/2005
• Status: Active Grant

• Current Assignee: Novo Nordisk A/S
• Original Assignee: Novo Nordisk A/S
• Inventors: Enggaard, Christian Peter, Moller, Claus Schmidt, Markussen, Tom Hede
• Primary Examiner(s): Sirmons, Kevin C
• Assistant Examiner(s): Hall, Deanna K
• Application Number:
  US11/996,409
• Publication Number:
  US 20080243087A1
• Time in Patent Office: 3,088 Days
• Field of Search: 604/181, 604/187, 604207-211, 604218-231
• US Class Current: 604/207
• CPC Class Codes: A61M 2005/202 cocking means, e.g. to bias the main drive spring of an injector
• CPC Class Codes: A61M 2005/3151 by friction
• CPC Class Codes: A61M 5/20 Automatic syringes, e.g. with automatically actuated piston rod, with automatic needle injection, filling automatically A61M5/142 , A61M5/46 take precedence; hypodermic projectiles F42B12/54
• CPC Class Codes: A61M 5/31505 Integral with the syringe barrel, i.e. connected to the barrel so as to make up a single complete piece or unit
• CPC Class Codes: A61M 5/31526 by means of stepwise axial movements, e.g. ratchet mechanisms or detents
• CPC Class Codes: A61M 5/31528 by means of rotational movements, e.g. screw-thread mechanisms
• CPC Class Codes: A61M 5/31541 Means preventing setting of a dose beyond the amount remaining in the cartridge
• CPC Class Codes: A61M 5/31551 including axial movement of dose setting member
• CPC Class Codes: A61M 5/31553 without axial movement of dose setting member
• CPC Class Codes: A61M 5/3156 using volume steps only adjustable in discrete intervals, i.e. individually distinct intervals
• CPC Class Codes: A61M 5/31571 Means preventing accidental administration for automatic syringes A61M5/20
• CPC Class Codes: A61M 5/31583 based on rotational translation, i.e. movement of piston rod is caused by relative rotation between the user activated actuator and the piston rod
• CPC Class Codes: A61M 5/31586 performed by rotationally moving or pivoted actuator, e.g. an injection lever or handle
• CPC Class Codes: A61M 5/31593 Multi-dose, i.e. individually set dose repeatedly administered from the same medicament reservoir

Abstract

A mechanism for preventing setting of a dose, which exceeds the amount of a medicament in a reservoir in an injection device. The device comprises a threaded piston rod, a limiter and a driver. The three elements are arranged such that during dose setting, the limiter is moved towards an end-of-contend position, wherein dose setting is limited. The invention comprises an accumulative and a non-accumulative embodiment. The invention further relates to a mechanism for prevention ejection of a dose exceeding the set dose.

Claims

1. A mechanism for preventing setting of a dose which exceeds the amount of a medicament in a reservoir in an injection device, wherein a dose is set by rotating a dose setting member of a dose setting mechanism, the mechanism comprising:

a piston rod having a threaded outer surface, wherein the piston rod rotates and translates axially forward during expelling of medication from the reservoir;

a limiter that prevents the setting of a dose which exceeds the amount of medication in a reservoir in the device, the limiter defining a passage for the piston rod;

a driver defining a passage for the limiter, the driver being coupled to the dose setting member such that rotation of the dose setting member during dose setting causes the driver to rotate; and

wherein the limiter is coupled to the driver and the piston rod such that relative rotation between the driver and the piston rod during dose setting causes the limiter to move towards a stopping position.

2. A mechanism according to claim 1, further comprising a housing defining a passage for the piston rod, the passage having a threaded inner surface for engagement with the threaded outer surface of the piston rod, the housing being arranged with respect to the piston rod such that rotation of the piston rod in relation to the housing causes the piston rod to be displaced relative to the housing in a longitudinal direction.

3. A mechanism according to claim 1, further comprising a locking means for locking the piston rod against rotation in at least one direction relative to the housing.

4. A mechanism according to claim 1, wherein:

the limiter has a threaded outer surface and is rotationally retained in relation to the piston rod; and

the passage of the driver has a threaded inner surface for engagement with the threaded outer surface of the limiter.

5. A mechanism according to claim 1, wherein the limiter comprises a first engaging surface adapted to engage a corresponding second engaging surface of the driver.

6. A mechanism according to claim 1, wherein the limiter comprises a plurality of teeth adapted to engage corresponding teeth of the housing and/or the driver when the limiter is in the stopping position.

7. A mechanism according to claim 1, wherein:

the passage of the limiter has a threaded inner surface for engagement with the threaded outer surface of the piston rod; and

the driver is rotationally retained in relation to the limiter.

8. A mechanism according to claim 1, wherein the limiter comprises a first engaging surface adapted to engage a corresponding second engaging surface of the piston rod.

9. A mechanism according to claim 5, wherein the threaded outer surface of the piston rod comprises the first engaging surface and the threaded inner surface of the driver comprises the second engaging surface.

10. A mechanism according to claim 1, further comprising a ratchet mechanism interconnecting the driver and the housing.

11. A mechanism according to claim 10, wherein the ratchet mechanism comprises a first and a second part, the first part being coupled to the driver and the second part being adapted to be locked for rotation relative to the housing by means of the locking means.

12. A mechanism according to claim 10, further comprising an ejection assisting system for providing an ejection force for assisting an operator during ejection.

13. A syringe device according to claim 12, wherein the ejection assisting system comprises a spring which is strained when the dose setting member is rotated during dose setting.