Clutch assembly with a blocking system for a medical injection device

1. A clutch assembly with a blocking system for a medical injection device, the clutch assembly comprising: a clutch sleeve located in a tubular housing, wherein the rotation of the clutch sleeve in a first direction arms the injection device for delivery of a defined dose of a medicament contained in a container and the rotation of the clutch sleeve in a second direction causes delivery of the dose, wherein a first ratchet sleeve is mounted on the clutch sleeve, the first ratchet sleeve being rotatable in two directions and cooperating with a second ratchet sleeve which is mounted on the first ratchet sleeve, the second ratchet sleeve being rotatable only in one direction, the housing has an internal toothed ring, the first ratchet sleeve has at least one ratchet, and the second ratchet sleeve has an internal toothed ring and at least one ratchet, the toothed rings have their teeth directed in mutually opposite directions and the ratchets are directed in mutually opposite directions, the at least one ratchet of the first ratchet sleeve cooperates with the toothed ring of the second ratchet sleeve, the at least one ratchet of the second ratchet sleeve cooperates with the toothed ring of the housing, wherein during arming of the device the first ratchet sleeve is stationary in relation to the second ratchet sleeve, the second ratchet sleeve is turned in relation to the housing in said first direction by one tooth of the ring, and during delivery of a dose the second ratchet sleeve is stationary in relation to the housing while the first ratchet sleeve is turned in relation to the second ratchet sleeve in said second direction by one tooth of the ring, and wherein the second ratchet sleeve and the housing have blocking means for preventing the arming of the device when an insufficient volume of the medicament remains in the container, by blocking the rotation of the second ratchet sleeve in relation to the housing.

2. The clutch assembly according to claim 1 , wherein, the clutch sleeve and the first ratchet sleeve are provided with guiding means which during the rotation of the clutch sleeve by a first angle in both directions allow the rotation of the clutch sleeve in relation to the first ratchet sleeve, the first angle being less than 360 degrees.

3. The clutch assembly according to claim 2 , wherein, said guiding means are constituted by at least one rib formed on the outside of the clutch sleeve and at least one internally facing guiding projection of the first ratchet sleeve, the guiding projection defining at least one free space enabling the at least one rib to move within when the clutch sleeve rotates in relation to the first ratchet sleeve.

4. The clutch assembly according to claim 2 , wherein, said guiding means are constituted by at least one rib formed on the outside of the clutch sleeve and an end part of the first ratchet sleeve, the end part having a reduced diameter and having a recess defining at least one free space enabling the at least one rib to move within when the clutch sleeve rotates in relation to the first ratchet sleeve.

5. The clutch assembly according to claim 1 , wherein, each of the ratchet sleeves has two mutually opposite ratchets respectively.

6. The clutch assembly according to claim 3 , wherein, the clutch sleeve has two mutually opposite ribs and the first ratchet sleeve has two mutually opposite guiding projections defining two free spaces.

7. The clutch assembly according to claim 2 , wherein, said guiding means allow the rotation of the clutch sleeve in relation to the first ratchet sleeve within said first angle and their joint rotation within a second angle that is necessary to negotiate one tooth of the toothed rings, the sum of the first and second angles constituting an angle required to arm the injection device.

8. The clutch assembly according to claim 1 , wherein, the blocking means for blocking the rotation of the second ratchet sleeve in relation to the housing are constituted by a blocking projection on the inside of the housing for abutment with a projection located on the outside of the second ratchet sleeve.

9. The clutch assembly according to claim 1 , wherein, the clutch sleeve, the first ratchet sleeve and the second ratchet sleeve are non-translatable axially.

10. The clutch assembly according to claim 1 , wherein, a scale is printed on the outside surface of the second ratchet sleeve, the scale indicating a number of delivered and/or left to be delivered doses of the medicament and the scale being visible to a user through a window in the housing.