Device for administering an injectable product

1. A device for administering an injectable product, comprising:

a) a housing,

b) a displaceably mounted product container accommodated by the housing, the product container containing the injectable product retained between an outlet and a plunger mounted therein so that the plunger can be displaced in a forward-drive direction in order to dispense the product,

c) a plunger rod comprising a first end that acts on the plunger in the forward-drive direction and a second end opposite the first end, the second end comprising a widening that retains the plunger rod in a retained position in a retaining engagement, and

d) a spring acting on the plunger rod in the forward-drive direction, wherein the plunger rod is held releasably in the retained position in the retaining engagement against the force of the spring, and wherein the spring projects into the container substantially as far as the plunger in the retained position.

2. A device as claimed in claim 1 , wherein the plunger rod has a ram, the ram pushing against the plunger in the forward-drive direction to dispense the product.

3. A device as claimed in claim 2 , wherein the ram forms a foremost end face of the plunger rod in the forward-drive direction.

4. A device as claimed in claim 1 , wherein the plunger rod surrounds the spring.

5. A device as claimed in claim 4 , wherein the plunger rod is a sleeve and the spring is supported on a shoulder which projects inwardly on a front end of the sleeve in the forward-drive direction and forms the foremost end face of the plunger rod.

6. A device as claimed in claim 4 , wherein the plunger rod widening comprises a retaining shoulder extending at an angle with respect to the forward-drive direction with a directional component parallel with and a directional component perpendicular to the forward-drive direction.

7. A device as claimed in claim 4 , wherein the plunger rod is a sleeve structure made from a semi-finished product by a plastic forming process.

8. A device as claimed in claim 4 , wherein the plunger rod is formed as a single piece.

9. A device as claimed in claim 4 , wherein a metallic material is used to make the plunger rod.

10. A device as claimed in claim 4 , wherein the plunger rod is a deep-drawn part.

11. A device as claimed in claim 4 , wherein the plunger rod is produced from a tubular piece by forming at least one end of the tubular piece.

12. A device as claimed in claim 1 , further comprising a support structure which supports the product container so that the container is displaceable in the forward-drive direction.

13. A device as claimed in claim 12 , wherein the support structure forms a support for the spring.

14. A device as claimed in claim 12 , wherein the housing supports the support structure so that the support structure is displaceable in the direction opposite the forward-drive direction.

15. A device as claimed in claim 12 , wherein the plunger rod is in the retaining engagement with the support structure.

16. A device as claimed in claim 1 , wherein the plunger rod widening comprises a retaining shoulder and the device comprises a complementary shoulder fixed so that it can not be displaced in the forward-drive direction, at least when the plunger rod is in the retained position.

17. A device as claimed in claim 16 , wherein the retaining shoulder and the complementary shoulder are in direct contact with one another in the retaining engagement.

18. The device according to claim 16 , wherein a transmitting device causes the retaining engagement between the retaining shoulder and the complementary shoulder.

19. A device as claimed in claim 18 , wherein a blocking mechanism is provided, which blocks one of the retaining shoulder and complementary shoulder in the retaining engagement.

20. A device for administering an injectable product, comprising a housing, a displaceably mounted product container associated with the housing, a plunger in the container for retaining the injectable product in the product container and so that the plunger can be displaced in a forward-drive direction to administer the product, a plunger rod having a first end acting on the plunger in the forward-drive direction and a second end opposite the first end having a widening by which the plunger rod is held in a releasable retained position, and a spring acting on the plunger rod in the forward-drive direction, the plunger rod releasably held in the retained position in a retaining engagement against the force of the spring, wherein the spring projects into the container substantially as far as the plunger in the retained position.

21. A device for administering an injectable product, comprising:

a) a housing,

b) a displaceably mounted product container accommodated by the housing, the product container containing the injectable product retained between an outlet and a plunger mounted therein so that the plunger can be displaced in a forward-drive direction in order to dispense the product,

c) a plunger rod having a first end acting on the plunger in the forward-drive direction and a second end opposite the first end having an axial, open funnel shape widening in a direction opposite to the forward-drive direction,

d) a spring acting on the plunger rod in the forward-drive direction, wherein the plunger rod is held releasably by the axial, open funnel shape in a retained position in a retaining engagement against the force of the spring, and wherein the spring projects into the container substantially as far as the plunger in the retained position, and

e) a cannula cover disposed on a distal end of the container over an injection cannula.

22. A device as claimed in claim 21 , wherein the cannula cover comprises an axially flexible rubber sleeve.

23. A device as claimed in claim 22 , wherein the cannula cover restricts penetration depth of the injection cannula during dispensement of the product.