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1. WO2020136124 - DRUG RESERVOIR FOR SEPARATE STORAGE OF SUBSTANCES

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[ EN ]

CLAIMS

1. A drug reservoir (1) comprising:

- a reservoir body (2) extending between an outlet end (4) and a proximal end (7),

- a front piston (8) arranged in a pre-use position within the reservoir body (2) between the outlet end (4) and the proximal end (7),

- a rear piston (9) arranged within the reservoir body (2) between the front piston (8) and the proximal end (7),

- a distal chamber (10) defined by the outlet end (4), a first portion of the reservoir body (2), and the front piston (8), the distal chamber (10) holding first contents (18),

- a proximal chamber (11) defined by the front piston (8), a second portion of the res ervoir body (2), and the rear piston (9), the proximal chamber (11) holding second contents (12, 19) comprising a proximal liquid volume (19), and

- bypass means (3) allowing fluid flow past the front piston (8) in an advanced position of the front piston (8) in the reservoir body (2),

wherein the second contents (12, 19) further comprises a proximal gas volume (12) lying within a volume range having a predetermined minimum value.

2. A drug reservoir according to claim 1 , wherein the predetermined minimum value is 15mI.

3. A drug reservoir according to claim 1 , wherein the volume range is a predetermined closed volume range.

4. A drug reservoir according to claim 3, wherein the predetermined closed volume range is [15mI; 200mI]

5. A drug reservoir according to claim 3, wherein the predetermined closed volume range is [20mI; 50mI]

6. A drug reservoir according to any of the preceding claims, wherein the first contents (18) comprises a distal liquid volume and a distal gas volume, and wherein the distal gas volume is smaller than the proximal gas volume (12).

7. A drug reservoir according to any of the preceding claims, wherein the proximal gas vol ume (12) comprises air.

8. A drug reservoir according to any of claims 1 - 6, wherein the proximal gas volume (12) comprises an inert gas.

9. A drug reservoir according to any of the preceding claims, further comprising a hollow needle (5) fixedly arranged at the outlet end (4) and fluidly connected with the distal cham ber (10).

10. A drug delivery device (20) comprising:

- a drug reservoir (1) according to any of the preceding claims, and

- a dose expelling structure for pressurising the proximal chamber (11), the dose ex pelling structure comprising an actuatable piston rod (30) adapted to transfer an ex pelling force to the rear piston (9).

11. A drug delivery device according to claim 10, further comprising a housing (21) extend ing along a reference axis, wherein the dose expelling structure is powered by a spring member (65) operatively coupled with the piston rod (30) and adapted to store energy re leasable to urge the piston rod (30) towards the outlet end (4).

12. A drug delivery device according to claim 11 , further comprising:

- a retention structure (24, 26, 27) which when enabled retains the spring member (65) in a tensioned state, and

- a sleeve member (50) extending axially along a portion of the housing (21) and com prising a release structure (51 , 53),

wherein the sleeve member (50) is configured for proximal displacement relative to the housing (21) and the retention structure (24, 26, 27) from a first position in which the reten tion structure (24, 26, 27) is enabled to a second position in which the retention structure (24, 26, 27) is disabled by the release structure (51 , 53) and stored energy consequently is released from the spring member (65).

13. A method of filling a drug reservoir (1) comprising a generally cylindrical main body (2) with a bypass section (3), a closed outlet end (4), and an open end (7), the method compris ing:

(i) arranging the drug reservoir (1) at least substantially vertically with the open end (7) facing upward,

(ii) introducing a first liquid volume (18) into the drug reservoir (1) through the open end (7) such that a first interior portion of the generally cylindrical main body (2), including the bypass section (3), is covered by liquid in a vertical position of the drug reservoir (1) where the open end (7) faces upward,

(iii) in a first sub-atmospheric pressure environment (100) inserting a first piston (8) into the generally cylindrical main body (2) to a first piston position at least substantially adjoining the free surface of the first liquid volume (18), thereby establishing a front chamber (10) holding the first liquid volume (18),

(iv) introducing a second liquid volume (19) into the drug reservoir (1) through the open end (7), and

(v) in a second sub-atmospheric pressure environment (200) of a surrounding gas in serting a second piston (9) into the generally cylindrical main body (2) to a second piston position, thereby establishing a rear chamber (11), where the second piston position is determined such that the rear chamber (11) holds the second liquid vol- ume (19) and a rear chamber gas volume (12) lying within a volume range having a predetermined minimum value.