# US 12,485,229 B2 · Reusable torsion spring driven injection device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,485,229 B2 - Document ID: US12485229B2 - Status: Granted - Kind: B2 - Application number: 18/014,661 - Filed: 2021-07-12 - Published: 2023-08-10 - Granted: 2025-12-02 - Earliest claimed: 2020-07-15 - Assignees: Novo Nordisk A/S - Applicants: Novo Nordisk A/S - Inventors: Nikolaj Eusebius Jakobsen; Ebbe Kiilerich; Lee Higson - Web page: https://patentgrep.com/patent/US12485229B2 ## CPC - A61M 5/31543: {piston rod reset means, i.e. means for causing or facilitating retraction of piston rod to its starting position during cartridge change} - A61M 5/31551: {including axial movement of dose setting member} - A61M 5/20: Automatic syringes, e.g. with automatically actuated piston rod, with automatic needle injection, filling automatically (A61M5/142 takes precedence) - A61M 5/31585: {the component being manually operated or triggered by an axially moving actuator operated by user, e.g. an axially movable injection button} - A61M 2005/2407: {from the rear} - A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)} ## Abstract The invention relates to an injection device wherein the drive element transferring rotation to the piston rod is divided into two elements which are able to move axially in relation to each other such that the drive mechanism can be released to allow the user to reset the piston rod and change the cartridge. ## Claims ### Claim 1 A reusable torsion spring driven injection device for expelling doses of a liquid drug from a loaded cartridge, comprising: a piston rod having an outer surface with an outer thread extending helically in a longitudinal direction and which outer surface further is provided with a longitudinal extending engagement surface such that the outer surface of the piston rod has a non-circular cross section, a housing structure comprising: a base part comprising a torsion spring driven expelling mechanism for driving the piston rod axially, and a removable cartridge holder part holding the cartridge and releasable connectable to the base part, wherein the torsion spring driven expelling mechanism comprises: a rotatable piston rod driver engaging the engagement surface of the piston rod such that rotation of the rotatable piston rod driver is transmitted to a similar rotation of the piston rod, an internal thread associated with the housing structure and engaging the outer thread on the piston rod such that the piston rod is moved helically when rotated, and a strained torsion spring holding a torque for rotating the rotatable piston rod driver during dose expelling, and wherein, the rotatable piston rod driver comprises an outer element and an inner element releasable coupled together, the outer element being maintained stationary during dose setting and rotated by the torque of the torsion spring during dose expelling, and the inner element being axially movable relatively to the outer element between a first uncoupled position and a second coupled position, the first uncoupled position being a position wherein the inner element is uncoupled from the outer element such that the inner element is rotatable independently of the outer element, and the second coupled position being a position wherein the inner element is coupled to the outer element to follow rotation of the outer element, and wherein a movable element operable connected to the inner element is axially movable to move the inner element axially from the first uncoupled position to the second coupled position. ### Claim 2 (depends on 1) The reusable torsion spring driven injection device according to claim 1, wherein the movable element and the inner element move in unison. ### Claim 3 (depends on 1) The reusable torsion spring driven injection device according to claim 1, wherein the inner element is moved distally into the first uncoupled position by spring structure. ### Claim 4 (depends on 1) The reusable torsion spring driven injection device according to claim 1, wherein the movable element and the inner element is moved proximally into the second coupled position by engagement with the cartridge holder part. ### Claim 5 (depends on 1, 2, 3) The reusable torsion spring driven injection device according to claim 1, 2 or 3, wherein the movable element and the inner element is moved proximally into the second coupled position by engagement with the cartridge. ### Claim 6 (depends on 1) The reusable torsion spring driven injection device according to claim 1, wherein the movable element is a sleeve which is telescopically movable in relation to the housing structure. ### Claim 7 (depends on 6) The reusable torsion spring driven injection device according to claim 6, wherein the sleeve slides axially on the outside of the housing structure. ### Claim 8 (depends on 6) The reusable torsion spring driven injection device according to claim 6, wherein the sleeve is connected to the inner element. ### Claim 9 (depends on 6) The reusable torsion spring driven injection device according to claim 6, wherein the sleeve abuts the cartridge holder part when mounted. ### Claim 10 (depends on 6) The reusable torsion spring driven injection device according to claim 6, wherein a compression spring is encompassed between the sleeve and housing structure urging the sleeve in the distal direction. ### Claim 11 (depends on 5) The reusable torsion spring driven injection device according to claim 5, wherein the movable element is connected to the inner element via an inner ring. ### Claim 12 (depends on 11) The reusable torsion spring driven injection device according to claim 11, wherein the spring structure is encompassed between the movable element and a nut member secured in the base part of the housing structure. ### Claim 13 (depends on 12) The reusable torsion spring driven injection device according to claim 12, wherein the nut member carries the inner thread for the piston rod. ### Claim 14 (depends on 12) The reusable torsion spring driven injection device according to claim 12, wherein the movable element is provided with axial legs operating through openings in the nut member.