Improved Metering Mechanism and Injection Device

Abstract

The present invention refers to a metering mechanism for an injection device. The mechanism comprises an actuating element (1) for setting or discharging a dose from the injection device, a piston rod (2) for producing an advance movement for dispensing a dose, a piston rod sleeve (3) in which the piston rod (2) is accommodated such that the piston rod (2) can be non-rotatably connected to the piston rod sleeve (3), and a coupling element (4) with which the actuating element (1) and the piston rod sleeve (3) can be coupled for discharge of the dose set with the actuating element (1) in such a way that a dispensing movement of the actuating element (1) is transmitted to the piston rod (2) by way of the piston rod sleeve (3) connected to the piston rod (2). To prevent underdosage, the piston rod (2) comprises a stop (2c) and the coupling element (4) comprises a counter-stop (4e) which move relative to each other at least during setting of a dose and which abut each other in a maximum dose stop position, thereby preventing further setting of a dose. Further, the present invention refers to an injection device with such a metering mechanism.

Claims

1. A metering mechanism for an injection device, comprising an actuating element (1) for setting or discharging a dose from the injection device, a piston rod (2) for producing an advance movement for dispensing a dose, a piston rod sleeve (3) in which the piston rod (2) is accommodated such that the piston rod (2) can be non-rotatably connected to the piston rod sleeve (3), a coupling element (4) with which the actuating element (1) and the piston rod sleeve (3) can be coupled for discharge of the dose set with the actuating element (1) in such a way that a dispensing movement of the actuating element (1) is transmitted to the piston rod (2) by way of the piston rod sleeve (3) connected to the piston rod (2), wherein the metering mechanism further comprises a reverse rotation prevention element (5) for the piston rod sleeve (3), to permit rotation of the piston rod sleeve (3) in one direction and to block it in the opposite direction, wherein the piston rod (2) can be non-rotatably connected to the piston rod sleeve (3) by means of a coupling sleeve (7) wherein the coupling sleeve (7) can be in engagement with the piston rod sleeve (3) to form a non-rotatable connection between the piston rod (2) and the coupling sleeve (7) and wherein the coupling sleeve (7) can be out of engagement with the piston rod sleeve (3) such that the piston rod (2) is rotatable relative to the piston rod sleeve (3), characterized in that the piston rod (2) comprises a stop (2c) and that the coupling element (4) comprises a counter-stop (4e) which move relative to each other at least during setting of a dose and which abut each other in a maximum dose stop position, thereby preventing further setting of a dose.

2. The metering mechanism according to claim 1, characterized in that the stop (2c) is a radial protrusion integrally formed on the piston rod (2).

3. The metering mechanism according to claim 1 or 2, characterized in that the counter-stop (4e) is a radial protrusion integrally formed on the coupling element (4).

4. The metering mechanism according to any one of the preceding claims, characterized in that the stop (2c) and the counter-stop (4e) move axially towards each other during setting of a dose.

5. The metering mechanism according to any one of the preceding claims, characterized in that upon abutment of the stop (2c) and the counter-stop (4e) prevents further axial displacement of the coupling element (4) in a direction increasing the dose set with the actuating element (1) and permits the dispensing movement of the actuating element (1).

6. The metering mechanism according to any one of the preceding claims, characterized in that the actuating element (1) is coupled to the coupling element (4) such that an axial movement of the actuating element (1) for setting a dose is transmitted to the coupling element (4).

7. The metering mechanism according to one of the preceding claims, characterized in that the coupling element (4) has a coupling member (4a) and the actuating element (1) has a counterpart coupling member which can be coupled or opened relative to each other by an axial or radial displacement of the coupling element (4) relative to the actuating element (1).

8. The metering mechanism according to claims 6 and 7, characterized in that the actuating element (1) comprises a shoulder as the counterpart coupling member and the coupling element (4) comprises a flange (4a) with at least one tooth (4c) as the coupling member arranged such that an axial movement of the actuating element (1) for setting a dose is transmitted to the coupling element (4).

9. The metering mechanism according to claims 7 and 8, characterized in that the coupling member (4a) and the counterpart coupling member are each provided with teeth.

10. The metering mechanism according to any one of the preceding claims, characterized in that the coupling element (4) comprises a tubular portion guided within the piston rod sleeve (3), wherein the tubular portion of the coupling element (4) and the piston rod sleeve (3) comprise ribs and grooves (3d, 4d) preventing relative rotation of the coupling element (4) and the piston rod sleeve (3) and permitting relative axial displacement of the coupling element (4) and the piston rod sleeve (3).

11. The metering mechanism according to one of the preceding claims characterized in that the reverse rotation prevention element (5) and the piston rod sleeve (3) are in engagement by means of a tooth means or a latching means and that the reverse rotation prevention element (5) has a spring arm (5) or is in the form of a spring arm (5a).

12. The metering mechanism according to one of the preceding claims characterized in that the reverse rotation prevention element (5) and the piston rod sleeve (3) are coupled and/or that the reverse rotation prevention element (5) is non-rotatably and axially fixedly connected to a housing (6) of the metering mechanism.

13. The metering mechanism according to one of the preceding claims characterized in that the piston rod (2) is axially displaceable relative to the piston rod sleeve (3) when the coupling sleeve (7) is out of engagement with the piston rod (2).

14. An injection device having a metering mechanism according to one of the preceding claims and comprising a cartridge holder (18) for receiving a cartridge (19) containing a medicament, characterized in that the stop (2c) and the counter-stop (4e) are arranged adapted to the content of the cartridge (19) such that the stop (2c) and the counter-stop (4e) abut each other if the dose set with the actuating element (1) corresponds to the remaining dischargeable content of the cartridge (19).

15. The injection device according to claim 14, characterized in that the coupling sleeve (7) is brought in engagement with the piston rod sleeve (3) by attachment of the cartridge holder (18) and that the coupling sleeve (7) is brought out of engagement with the piston rod sleeve (3) by detachment of the cartridge holder (18).

Description

[0097] Non-limiting, exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0098] FIG. 1 schematically shows an injection device according to the prior art;

[0099] FIG. 2 schematically shows an exploded sectional view of component parts of a metering mechanism according to an embodiment of the present invention;

[0100] FIG. 3 schematically shows a sectional view of the metering mechanism of FIG. 2 in a state permitting setting a dose;

[0101] FIG. 4 schematically shows a sectional view of the metering mechanism of FIG. 2 in a state preventing setting a dose; and

[0102] FIG. 5 schematically shows a further sectional view of an embodiment of an injection device with the metering mechanism of FIG. 2.

[0103] Referring to FIG. 1, there is shown an injection device as disclosed in EP 2 643 036 B1 with a metering mechanism. The metering mechanism comprises an actuating element 1 for setting and delivering a dose. The actuating element 1 has an external thread 1b, which is guided into an internal thread of an internal housing 6 of the metering mechanism. To set a dose, the actuating element 1 is screwed out of the housing 6 while the actuating element 1 is screwed back into the housing 6 to deliver (discharge) a dose. A number sleeve 9 (display sleeve) is arranged axially and rotationally fixed on the actuating element 1, to display the actually set dose in a display window 21a of an outer housing sleeve 21 which coaxially surrounds the housing 6. At a distal end of the external thread 1b, there is a stop cam 1a cooperating with a corresponding counter cam 6a (shown in FIG. 5) of the housing 6 to limit the setting of a maximum dose. In stop contact, the actuating element 1 cannot be unscrewed further out of the housing 6. A further stop cam 6b is provided as a minimum dose stop, typically preventing setting a dose below the dose value zero.

[0104] In the metering mechanism, a piston rod 2 is movably mounted with an external thread 2a for generating a movement for dispensing a dose. At the distal end of the piston rod 2, a pressure foot or flange 11 is rotatably arranged. During the advancing movement of the piston rod 2, the flange 11 abuts a rubber bung, which is movably received in a cartridge 19 in order to deliver a medicament from the injection device. The cartridge 19 is received in a cartridge holder 18. A detachable protective cap 20 is provided for receiving the cartridge holder 18.

[0105] The external thread 2a of the piston rod 2 is in a threaded engagement with an internal thread of a threaded sleeve 12. The threaded sleeve 12 is axially and rotatably constrained to the housing 6 via the outer housing sleeve 21. The threaded sleeve 12 serves to transform a rotational movement of the piston rod 2 in a combined rotational and axial movement of the piston rod 2. A stop cam 2b of the piston rod 2 can come into abutment contact with the threaded sleeve 12 when the cartridge 19 is empty. The distal end of the cartridge holder 18 has a thread 18b to connect a needle unit to the cartridge 19. At the proximal end of the cartridge holder 18 there is an outwardly projecting locking cam 18a which can be brought into engagement with a guide 12a in the threaded sleeve 12 to form a bayonet locking.

[0106] A piston rod sleeve 3 surrounds the piston rod 2 coaxially. A coupling sleeve 7 is provided for coupling the piston rod 2 detachably with the piston rod sleeve 3. For this purpose, the coupling sleeve 7 is rotationally constrained to the piston rod 2, for example by means of a rib 7a provided on an inner surface of the coupling sleeve 7 engaging a longitudinally extending groove 2d (see FIG. 5) of the piston rod 2. Further, longitudinally extending ribs 7b are arranged on an outer surface of the coupling sleeve 7 which engage grooves 3a on an inner surface of the piston rod sleeve 3.

[0107] A coupling element 4 is provided for coupling the actuating element 1 and the piston rod sleeve 3 such that a dose discharging movement of the actuating element 1 can be transmitted to the piston rod 2 via the piston rod sleeve 3 and the coupling sleeve 7. Longitudinally extending ribs 4b are arranged on an inner surface of the coupling element 4 which engage corresponding ribs 3c extending on an outer surface of the piston rod sleeve 3 to provide a rotationally fixed connection between the coupling element 4 and the piston rod sleeve 3. However, due to the rib connection, the coupling element 4 can move axially relative to the piston rod sleeve 3. The coupling element 4 is provided with a coupling element 4a in the form of a flange with a tooth 4c which can engage with a corresponding coupling element, e.g. a ring of teeth (not shown), arranged on an internal shoulder of the actuating element 1.

[0108] A knob 8 is rotatably mounted in the actuating element 1 by means of a snap connection 8a. A spring 13 is disposed within the knob 8 and is supported at the distal end on a flange 4a of the coupling element 4 and at the proximal end on a spring holder 14 which is held in the knob 8.

[0109] The metering mechanism further comprises a reverse rotation prevention element 5 with a spring arm 5a. The reverse rotation prevention element 5 is rotationally and axially fixed to the housing 6. The spring arm 5a engages a toothing 3b on a radially protruding flange of the piston rod sleeve. The spring arm 5a and the toothing 3b are designed such that the piston rod sleeve 3 can only be rotated in one direction relative to the spring arm 5a, namely during dose discharging.

[0110] The coupling sleeve 7, a coupling ring 15, a coupling holder 16 and a clutch spring 17 are mounted in the threaded sleeve 12. At its distal end, the coupling sleeve 7 has an outwardly projecting ring 7c. The coupling ring 15 comprises webs extending in the longitudinal direction which are provided with an annular groove 15a. The ring 7c of the coupling sleeve 7 is axially fixed in the annular groove 15a but free to rotate with respect to the coupling ring 15. A guide cam 15b is arranged at the distal end of the coupling ring 15 for engaging a guide track 16a of the coupling holder 16. The guide track 16a is designed such that the guide cam 15b can be guided with respect to the threaded sleeve 12 during rotation of the coupling ring 15.

[0111] The clutch spring 17 is supported at its proximal end on the threaded sleeve 12 and with its distal end on the coupling holder 16. The coupling holder 16 is axially displaceable and rotatable relative to the threaded sleeve 12, whereas the coupling ring 15 is axially movable but rotationally fixed with respect to the threaded sleeve 12. The cartridge holder 18 has a recess 18c which can engage with a cam 16c of the coupling holder 16. The coupling holder 16 has a projection 16b to be guided in the threaded sleeve for attaching the coupling holder 16 with a cartridge holder 18 in a locking position. An inwardly projecting web 15c is mounted on an inner surface of the coupling ring 15 which is received in a longitudinal groove 12c of the threaded sleeve 12. Due to the guide slot between the coupling holder 16 and the coupling ring 15, a rotation of the coupling holder 16 relative to the threaded sleeve 12 results in an axial movement of the coupling ring 15 (with coupling sleeve 7) relative to the threaded sleeve 12, thereby bringing coupling sleeve 7 in an out of engagement with the piston rod sleeve 3 depending on the direction of rotation of the coupling holder, i.e. depending of attachment or detachment of the cartridge holder 18.

[0112] In order to set the dose with the injection device of FIG. 1, a user rotates actuating element 1 in a first direction such that the actuating element 1 winds out of housing 6 and housing sleeve 21 guided by external thread 1b. Coupling element 4 is axially entrained by actuating element 1 with flange 4a abutting a respective shoulder in actuating element 1. Tooth 4c rides over the teeth in actuating element 1 compressing spring 13. Due to the splined engagement of the coupling element 4 with the piston rod sleeve 3 the coupling element 4 is prevented from rotation by means of reverse rotation prevention element 5 acting on piston rod sleeve 3. With the cartridge holder 18 attached to the threaded sleeve 12, coupling sleeve 7 and engages piston rod sleeve 3 such that the piston rod 2 is prevented from rotating, too. During dose setting a respective dose value printed on the number sleeve 9 is displayed in the window 21a as of the number sleeve 9 rotates together with actuating element 1.

[0113] After a dose has been set, the user may discharge the dose by pushing on knob 8. This compresses spring 13 such that tooth 4c is kept in engagement with the respective teeth of actuating element 1. Further, actuating element 1 is wound back into the housing 6 and housing sleeve 21, wherein rotation of the actuating element 1 is transmitted via the coupling element 4 to the piston rod sleeve 3 and, thus, via coupling sleeve 7 to piston rod 2. Due to the threaded engagement of the piston rod 2 with the threaded sleeve 12, the piston rod 2 translates axially in the distal direction with the flange 11 acting on a bung (not shown) in the cartridge 19.

[0114] With respect to further details of the dose setting and dose discharging operation as well as to exchanging the cartridge 19 and resetting piston rod 2 reference is made to EP 2 643 036 B1.

[0115] Turning now to FIGS. 2 to 5 an embodiment of the present invention is described which is based on the injection device as mentioned above and as disclosed in EP 2 643 036 B1. Like reference numerals are used for components corresponding to components described above with respect to FIG. 1.

[0116] As can be taken from FIG. 2 the piston rod 2 is amended with respect to the piston rod of FIG. 1 in that a flange like stop 2c is provided at the proximal end of the piston rod 2. The position of the stop 2c is chosen such that the stop 2c reaches a distal portion of the piston rod sleeve when the cartridge 19 is nearly empty. The piston rod is an elongate member with an outer thread 2a which is not shown in FIGS. 2 to 5.

[0117] The piston rod sleeve 3 and to the coupling element 4 are both elongate tubular elements which are guided in each other. The coupling element 4 has a tubular portion guided within the piston rod sleeve 3. The piston rod sleeve 3 and the coupling element 4 are amended with respect to FIG. 1 in that the coupling element 4 has a reduced diameter and is arranged within the piston rod sleeve 3 which has an increased diameter. The piston rod sleeve 3 and the coupling element 4 are rotationally constrained to each other by means of external grooves 4d (between ribs) of the coupling element 4 and internal ribs 3d of the piston rod sleeve 3. Relative axial movement between the piston rod sleeve 3 and the coupling element 4 remains possible. A counter-stop 4e is provided at the distal end of coupling element 4 in the form of a radially inwards protruding flange. The length of the coupling element and the position of counter-stop 4e is chosen such that the counter-stop 4e may come in contact with stop 2c when the cartridge 19 is nearly empty but does not interfere with stop 2c when the cartridge 19 is substantially full, i.e. as long as the piston rod 2 is not displaced distally too far.

[0118] In the exemplary embodiment depicted in FIGS. 2 to 4 the piston rod sleeve 3 is provided with an optional inwardly protruding flange 3e forming a guiding portion for of the piston rod 2. With the piston rod 2 being guided in the threaded sleeve 12, in the coupling sleeve 7 and, optionally, in counter-stop 4e of the coupling element 4, the protruding flange 3e may be omitted. The metering mechanism may comprise in addition to the piston rod 2, the piston rod sleeve 3, the coupling element 4 and the coupling sleeve 7 depicted in FIGS. 2 to 4 an actuating element as shown in FIG. 1 and a reverse rotation prevention element as shown in FIG. 1.

[0119] As an alternative to the reverse rotation prevention element 5 shown in FIG. 1, the reverse rotation prevention element may be designed as comprising an, e.g. circumferentially extending, ratchet arm provided on or near the distal flange of the piston rod sleeve 3 wherein the toothing 3b on this flange might be omitted. Such a ratchet arm may interact with teeth or ribs on the inner surface of housing 6 such that rotation of the piston rod sleeve 3 is permitted in one direction (dose discharging) and is blocked in the opposite direction. Further alternatives to the reverse rotation prevention element 5 shown in FIG. 1 may include a ratchet arm provided as an integral part of housing 6 acting on teeth or ribs provided on the piston rod sleeve 3, e.g. on the distal flange.

[0120] In the example depicted in FIG. 1, the coupling sleeve 7 is splined to the piston rod 2 and in threaded engagement with the threaded sleeve 12. As an alternative, the coupling sleeve 7 may be provided with an internal thread engaging the external thread 2a of the piston rod 2 while the piston rod 2 is in splined engagement with sleeve 12 such that rotation of the piston rod 2 with respect to sleeve 12 is prevented but axial displacement of the piston rod 2 with respect to sleeve 12 is permitted. This would result in the piston rod 2 being displaced without rotation when discharging a dose.

[0121] FIG. 3 shows the metering mechanism in a state in which the piston rod 2 is in a retracted (proximal) position such that stop 2c is axially spaced from counter-stop 4e. When a dose is set, e.g. by rotating an actuating element coupled to the coupling element 4, the coupling element 4 is retracted in the proximal direction with respect to piston rod 2 which remains stationary together with piston rod sleeve 3 during dose setting. Rotation of the piston rod sleeve 3 and the piston rod 2 are prevented by the reverse rotation prevention element. The relative axial movement of the coupling element 4 with respect to the piston rod sleeve 3 results in the counter-stop 4e moving axially in the direction towards the stop 2c during dose setting. However, with the piston rod 2 being in its retracted (proximal) position stop 2c does not interfere with counter-stop 4e during dose setting (dose increasing).

[0122] FIG. 4 shows the metering mechanism after several doses have been discharged such that the piston rod 2 with stop 2c is displaced in the distal direction compared to the state depicted in FIG. 3. In addition, a dose is set in the state depicted in FIG. 4 as can be seen from the proximal displacement of the coupling element 4 with counter-stop 4e relative to the piston rod sleeve 3. This is a maximum dose stop position.

[0123] In FIG. 4 the dose set substantially corresponds to the dischargeable amount of medicament in the cartridge 19. In this situation stop 2c abuts counter-stop 4e, thereby preventing further proximal movement of the coupling element 4 with respect to the piston rod 2. As the piston rod 2 is prevented from being retracted in the proximal direction due to the reverse rotation prevention element acting on piston rod sleeve 3, further proximal movement of the coupling element 4 is stopped by this abutment. This results in stopping the dose setting movement of the actuating element which is in axial engagement with the coupling element 4 by means of flange 4c. In other words, stop 2c and counter-stop 4e form a limiter preventing setting of a dose which exceeds the amount of medicament remaining in the cartridge 19.

[0124] In the state depicted in FIG. 4 the set dose can be discharged from the injection device as explained above with respect to FIG. 1 by winding the actuating element back into the mechanism while engaging the coupling between the actuating element and the coupling element 4. This results in a common rotation of the actuating element, the coupling element 4, the piston rod sleeve 3, the coupling sleeve 7 and the piston rod 2. Due to the threaded engagement of the piston rod 2 with the threaded sleeve 12, this rotation drives the piston rod 2 in the distal direction with respect to the threaded sleeve 12 and the piston rod sleeve 3. However, in the state depicted in FIG. 4, it is impossible to increase the set dose. This prevents the risk of an underdosage.

[0125] After discharging the (limited) dose the cartridge 19 may be replaced by the full cartridge if the injection device is a resettable injection device. For this purpose of the cartridge holder 18 is a detached from the threaded sleeve 12 which decouples coupling sleeve 7 from piston rod sleeve 3 as explained in more detail in EP 2 643 036 B1 due to interaction with coupling ring 16 and coupling holder 15. The piston rod 2 can then be pushed back into the position depicted in FIG. 3 guided within the coupling sleeve 7 but without transmitting the rotation of the piston rod 2 to the piston rod sleeve 3. When pushing back the piston rod 2, the stop 2c translates away from the counter-stop 4e, thus again permitting dose setting for the new cartridge.

[0126] FIG. 5 schematically shows a metering mechanism similar to that of FIGS. 2 to 4 implemented into the injection device of FIG. 1 in a sectional view along line X-X in FIG. 3. While the general design and arrangement of the component parts as well as in their interaction is identical to the embodiment depicted in FIGS. 2 to 4, the dimensions of the component parts of the metering mechanism shown in FIG. 5 slightly differs from FIGS. 2 to 4. FIG. 5 shows a groove 2d engaging rib 7a (not shown in FIG. 5) for providing a rotationally fixed guiding of the piston rod 2 in the coupling sleeve 7.

[0127] There metering mechanism with the limiter according to the present invention may be used in resettable (i.e., reusable) devices and in non-resettable (i.e., disposable) devices. Further, the limiter may be used not only in manually driven injection devices as explained with respect to FIGS. 1 to 5 but also in spring driven or spring assisted devices.

REFERENCE NUMERALS

[0128] 1 actuating element [0129] 1a cam [0130] 1b outer thread [0131] 2 piston rod [0132] 2a outer thread [0133] 2b cam [0134] 2c stop [0135] 2d groove [0136] 4 piston rod sleeve [0137] 3a grooves [0138] 3b toothing [0139] 3c ribs [0140] 3d ribs [0141] 3e flange [0142] 4 coupling element [0143] 4a flange [0144] 4b ribs [0145] 4c tooth [0146] 4d groove [0147] 4e counter-stop [0148] 5 reverse rotation prevention element [0149] 5a arm [0150] 6 housing [0151] 6a cam [0152] 6b cam [0153] 7 coupling sleeve [0154] 7a rib [0155] 7b ribs [0156] 7c ring [0157] 8 knob [0158] 8a snap feature [0159] 9 number sleeve [0160] 11 flange [0161] 12 threaded sleeve [0162] 12a guide [0163] 12c groove [0164] 13 spring [0165] 14 spring holder [0166] 15 coupling ring [0167] 15a groove [0168] 15b cam [0169] 15c web [0170] 16 coupling holder [0171] 16a guide track [0172] 16b projection [0173] 16c cam [0174] 17 spring [0175] 18 cartridge holder [0176] 18a cam [0177] 18b thread [0178] 18c recess [0179] 19 cartridge [0180] 20 cap [0181] 21 housing sleeve [0182] 21a window