Dose log assembly with rotational transmission features

Abstract

An add-on device comprising a housing, a dose setting assembly, and a dose release assembly with a sensor assembly mounted within the housing. The dose setting assembly comprises a gripping member adapted to non-rotationally engage a dose setting member of the pen device, and an add-on dose setting member rotationally coupled to both the housing outer surface and the gripping member, allowing the gripping member to rotate at least 360 degrees. The sensor assembly is non-rotationally coupled to the housing and is axially movable relative to the housing between a proximal position and a distal position to engage and actuate a release member of the pen device when moved distally.

Description

[Technical field]

[0001] The present invention relates generally to medical devices for efficient and reliable detection of an expelled dose. [Background technology]

[0002] Although the present disclosure primarily refers to drug delivery devices used to treat diabetes, for example by subcutaneous delivery of insulin, this is merely an exemplary use of the invention.

[0003] Drug delivery devices for subcutaneous injection have greatly improved the lives of patients who must self-administer drugs and biological agents. Such drug delivery devices may take many forms, including simple disposable devices that are little more than ampoules with injection means, or may be durable devices adapted to be used with pre-filled cartridges. Regardless of their form and type, these drug injection devices have proven to be of great help in assisting patients to self-administer injectable drugs and biological agents. They also greatly assist caregivers in administering injectable medicines to people who are unable to perform self-injections. A common type of drug delivery device allows the user to set the desired dose size of the drug to be delivered. In the case of a typical mechanical device, the dose setting means is in the form of a rotatable dose setting or dial member, allowing the user to set (or "dial") the desired dose size, which is then expelled from the device.

[0004] Taking the required insulin injections at the correct time and with the correct size is essential to managing diabetes, i.e., adhering to a prescribed insulin regimen is important. To allow a medical professional to determine the effectiveness of a prescribed dosage pattern, a diabetic patient is encouraged to log the size and time of each injection. However, such logs are usually kept in handwritten notebooks, and the logged information may not be easily uploaded to a computer for data processing. Furthermore, since only events noted by the patient are logged, the note system requires the patient to remember to log each injection if the logged information is of any value in treating the patient's disease. Missing or incorrect records in the log will result in an incorrect picture of the injection history, which in turn will result in an incorrect basis for the medical professional's decision-making regarding future drug treatments. Therefore, it may be desirable to automate the logging of injection information from a pharmaceutical delivery system.

[0005] Some injection devices integrate this monitoring / acquisition mechanism into the device itself, as disclosed, for example, in U.S. Pat. No. 5,399,323 and U.S. Pat. No. 5,523,633, while most devices as of today do not. The most widely used devices are purely mechanical devices that are either durable or pre-filled. The latter devices are cheap because they are discarded after they are emptied, and it is not cost-effective to build electronic data acquisition capabilities into the device itself. To address this issue, several solutions have been proposed that would help users generate, collect, and distribute data indicative of the use of a given medical device.

[0006] For example, US Pat. No. 5,399,663 describes in a first embodiment an electronic auxiliary device (also called an "add-on module" or "add-on device") adapted to be releasably attached to a pen-type drug delivery device. The device includes a camera and is configured to perform optical character recognition (OCR) on an image captured from a rotating scale drum visible through a dose window on the drug delivery device, thereby determining the dose of the medicament dialed into the drug delivery device. US Pat. No. 5,399,663 discloses an electronic auxiliary device adapted to be releasably attached to a pen-type drug delivery device. The device includes a camera and is configured to determine the scale drum value based on the OCR. In order to properly determine the size of the dispensed dose, the auxiliary device further comprises additional electromechanical sensor means for determining whether the dose size is set, modified or delivered. A further external device for a pen-type device is shown in US Pat. No. 5,399,663.

[0007] US Patent No. 6,399,633 discloses a drug delivery device with a dose log sensor circuit integrated into a dose button. During dose setting, the dose button is rotationally locked to the dose setting screw and therefore moves axially therewith in the proximal direction when the dose is set. Once the set dose is expelled, the user moves the button, and thus the screw, distally, thereby expelling the set dose. During the distal movement, a rotational clutch between the dose button and the screw is released, allowing the screw to rotate, while the dose button is rotationally fixed by the user's finger, and the relative rotation between the sensor circuit and the screw allows the size of the expelled dose to be determined.

[0008] Nos. 5,993,313 and 5,993,326 disclose an add-on dose logging device for a pen-type drug delivery device, comprising a sensor means adapted to capture the amount of rotation of a magnetic member disposed within the drug delivery device, the amount of rotation of the magnetic member corresponding to the amount of drug expelled from the reservoir by the drug delivery device. During dose setting, the sensor means is coupled to and rotates with the outer dose setting member, and these two components are rotationally decoupled during dose expulsion to prevent transmission of rotation from the dose setting means to the sensor means.

[0009] The add-on devices disclosed in US Pat. No. 5,993,336 and US Pat. No. 5,993,355 comprise an electronic sensor module which is rotationally coupled to both the external and internal dose setting members of a pen-based medication delivery device during dose setting, whereby rotation of the external dose setting member is transmitted to the internal dose setting member via the sensor module. However, it is important that the sensor module does not rotate during dose ejection, and therefore the add-on device is provided with a mechanism for rotationally decoupling the sensor module from the external dose setting member when a dose release button is actuated to eject the set dose.

[0010] This decoupling mechanism adds both complexity, expense, and volume to the add-on dose log device, so a simplified design would be desirable. Therefore, in view of the above, it is an object of the present invention to provide devices, assemblies, and methods that allow for efficient, reliable, and accurate capture of the dispensed dose based on a determination of the amount of rotation for a given indicator component or structure.

[0011] Furthermore, if the sensor module rotates relative to the exterior of the logging device during dose setting, it is difficult to provide an indication or other visual communication means on the exterior surface of the device. Accordingly, it is a further object of the present invention to provide an arrangement in which the sensor module does not rotate during operation, thereby allowing an indication or indicator to be provided cost effectively. The present devices, assemblies and methods may relate to add-on devices adapted to be releasably mounted on a medication delivery device, as well as sensor arrangements formed integrally with a given medication delivery device. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Patent Publication No. US2009 / 0318865 [Patent Document 2] International Publication No. 2010 / 052275 [Patent Document 3] International Publication No. 2014 / 037331 [Patent Document 4] International Publication No. 2014 / 020008 [Patent Document 5] International Publication No. 2014 / 161952 [Patent Document 6] International Publication No. 2020 / 176317 [Patent Document 7] International Publication No. 2019 / 057911 [Patent Document 8] International Publication No. 2019 / 162235 Summary of the Invention

[0013] The present disclosure describes embodiments and aspects that address one or more of the above objects or that address objects apparent from the following disclosure as well as from the description of exemplary embodiments.

[0014] As can be seen from the above descriptions of the known add-on devices from WO 2019 / 057911 and WO 2019 / 162235, the sensor module is not actually rotationally locked relative to the ejection mechanism during dose ejection, but is merely prevented from being rotationally influenced from the outside.

[0015] The present invention is based on the realisation that an arrangement in which the sensor module is rotationally locked to the drug delivery device (but axially movable) both during dose setting and dose ejection allows previous coupling arrangements to be omitted, which may provide a simplified design.

[0016] Thus, in a first general aspect of the invention there is provided an add-on device adapted to be releasably mounted on a drug delivery device comprising a housing, a drug reservoir or means for receiving a drug reservoir, drug ejection means comprising a rotatable dose setting member enabling a user to set a dose of drug to be ejected, a proximally arranged release member actuatable between a proximal position and a distal position, the proximal position enabling the dose to be set and the distal position enabling the drug ejection means to eject the set dose, and an indicator adapted to move during ejection of the dose, the amount of movement indicating the size of the ejected dose. The add-on device comprises an add-on dose setting assembly and an add-on dose release assembly, the add-on dose release assembly comprising a generally tubular add-on housing defining a reference axis, the add-on housing comprising a distal opening adapted to receive a proximal portion of a medication delivery device and releasably attachable to the medication delivery device housing, the add-on housing comprising an interior space and an exterior surface, and a sensor assembly disposed within the interior of the tubular add-on housing and directly or indirectly non-rotationally but axially movably coupled thereto, the sensor assembly operable to detect an amount of rotation of the indicator during ejection of a dose. The add-on dose setting assembly comprises a gripping member rotationally disposed within the interior of the add-on housing and adapted to non-rotationally engage with the dose setting member, and an add-on dose setting member rotationally coupled to an exterior surface of the tubular housing. The add-on dose setting member is coupled to the gripping member allowing the gripping member to rotate at least 360 degrees, and the sensor assembly is axially movable between proximal and distal positions relative to the add-on housing such that when moved distally the sensor assembly engages and actuates the release member when the add-on device is mounted on the drug delivery device.

[0017] This arrangement rotationally locks the sensor module to the medication delivery device during both dose setting and dose ejection, thereby preventing significant rotational movement of the sensor module during dose ejection. Furthermore, such an arrangement allows for simple and cost-effective provision of, for example, an electronically controlled visual indicator, should such a feature be desirable.

[0018] In an exemplary embodiment, the add-on housing comprises one or more lateral openings. The gripping member comprises a circumferential outer gear wheel portion having a first diameter and the add-on dose setting member comprises a circumferential inner gear wheel portion having a second, larger diameter. The circumferential outer gear wheel portion and the circumferential inner gear wheel portion directly or indirectly engage with each other corresponding to the lateral openings, whereby rotation of the dose setting member provides rotation of the gripping member and thus the dose setting member of the medication delivery device.

[0019] In an exemplary embodiment, the axis of rotation of the dose setting member is radially offset from the axis of rotation of the gripping member, which enables the circumferential outer gear wheel portion and the circumferential inner gear wheel portion to engage with each other corresponding to the lateral openings, thereby forming an internal spur gear.

[0020] Alternatively, a transmission gear assembly comprising at least one gear wheel may be disposed corresponding to the lateral opening, and the circumferential outer gear wheel portion and the circumferential inner gear wheel portion engage with each other via the transmission gear assembly. The transmission gear assembly may comprise one or more transmission gear wheels, just as one or more transmission gear assemblies may be provided.

[0021] In an exemplary embodiment, the add-on device further comprises a circumferential flexible cam belt disposed through one or more lateral openings (which may each be in the form of a pair of lateral openings adjacent to one another) and comprising (i) an inner toothed surface disposed to engage with an outer gear wheel portion of the gripping member and (ii) an outer toothed surface disposed to engage with an inner gear wheel portion of the add-on dose setting member. The flexible cam belt is held in engagement with the gripping member at one or more first positions and in contact with the add-on dose setting member at one or more second positions, such that rotation of the add-on dose setting member is transmitted to the gripping member via the flexible cam belt.

[0022] In a further exemplary embodiment, the add-on dose release assembly comprises a crown member disposed inside the add-on housing. The crown member comprises a plurality of coupling fingers adapted to non-rotationally engage with the add-on housing, each finger having an engaged state and a disengaged state engaged with the add-on housing. The gripping member comprises at least one bridge portion adapted to pass between the add-on housing and the one or more coupling fingers in the disengaged state, the gripping member being non-rotationally coupled to the add-on dose setting member via the bridge portion(s). The control structure is non-rotationally disposed relative to the add-on dose setting member and engages with the coupling fingers to move the coupling fingers between the engaged state and the disengaged state, thereby allowing the bridge portion(s) to pass the coupling fingers as the control structure and the gripping member rotate relative to the crown member.

[0023] The coupling fingers may extend axially and may be adapted to move radially between engaged and disengaged states, and the add-on housing may include a plurality of receiving structures each adapted to receive a given coupling finger in coupling engagement.

[0024] The control structure may comprise a circumferential guide track and each coupling finger may comprise a free end received in the guide track such that the coupling fingers move radially into and out of engagement with the add-on housing when the control structure is rotating together with the add-on dose setting member. The coupling fingers may be in the form of flexible fingers carried by a ring structure.

[0025] The control structure may be disposed proximal to and connected to the bridge portion(s) with the guide track facing distally. The control structure may be in the form of a separate member attached to one or more bridge portions or may be integrally formed with the gripping member.

[0026] In yet a further embodiment, the add-on dose setting member comprises a first circumferential toothed portion and the gripping member comprises a second circumferential toothed portion. The add-on device further comprises a transfer ring arranged at an inclined angle with respect to a plane perpendicular to the reference axis, the transfer ring comprising (i) a first circumferential transfer toothed portion engaged with the first toothed portion of the add-on dose setting member and (ii) a second circumferential transfer toothed portion engaged with the second toothed portion of the gripping member, whereby a rotation of the dose setting member provides a rotation of the gripping member via the inclined transfer ring.

[0027] The add-on device may be provided in a combined assembly with the drug delivery device disclosed above.

[0028] In the above-described embodiments, the add-on dose release assembly may further comprise a proximally facing user-actuatable add-on dose release member coupled to the sensor assembly and for axial movement therewith.

[0029] In a further aspect of the present invention, an integrated drug delivery device having an integrated sensor assembly is provided.

[0030] In an exemplary embodiment, the integrated drug delivery device comprises a housing defining a reference axis, a drug reservoir or means for receiving a drug reservoir, a drug ejection means comprising an inner dose setting member adapted to rotate to set a dose, an inner release member actuatable between a proximal position and a distal position, the proximal position allowing the dose to be set and the distal position allowing the drug ejection means to eject the set dose, and an indicator adapted to rotate during ejection of the dose, the amount of rotation indicating a size of the ejected dose. The integrated drug delivery device further comprises a sensor assembly disposed within the housing and directly or indirectly non-rotatably but axially movably coupled thereto, the sensor assembly operable to detect an amount of rotation of the indicator during ejection of the dose. The integrated drug delivery device further comprises a user dose setting member coupled to the housing and adapted to rotate to set a dose, the user dose setting member rotationally coupled to the inner dose setting member to enable the gripping member to rotate at least 360 degrees, and the sensor assembly is axially movable by a user between a proximal position and a distal position relative to the housing so as to engage and actuate the inner release member when moved distally.

[0031] The housing may comprise one or more lateral openings, the inner dose setting member comprises a circumferential outer gear wheel portion having a first diameter and the user dose setting member comprises a circumferential inner gear wheel portion having a second, larger diameter, the circumferential outer gear wheel portion and the circumferential inner gear wheel portion directly or indirectly engage with each other corresponding to the lateral openings, whereby rotation of the dose setting member provides rotation of the gripping member.

[0032] Alternatively, the integrated drug delivery device further comprises a crown member disposed inside the housing and a control structure. The crown member comprises a plurality of coupling fingers adapted to non-rotationally engage with the housing, each finger having an engaged state and a disengaged state engaged with the add-on housing, the inner dose setting member comprises at least one bridge portion adapted to pass between the housing and the one or more coupling fingers in the disengaged state, the inner dose setting member being non-rotationally coupled to the user dose setting member via the bridge portion(s). The control structure is non-rotationally coupled to the user dose setting member and engages with the coupling fingers to control the coupling fingers between the engaged state and the disengaged state, thereby allowing the bridge portion(s) to pass the coupling fingers as the control structure and the inner dose setting member rotate relative to the crown member.

[0033] The integrated drug delivery device may be further modified in accordance with the exemplary embodiments above on the add-on sensor device.

[0034] In a specific embodiment, the indicator comprises a plurality of dipole magnets, and the sensor means comprises a plurality of magnetometers non-rotationally disposed relative to the housing in a mounted state and adapted to determine magnetic field values ​​from the plurality of dipole magnets, and processor means configured to determine a rotational position and / or rotational movement of the indicator based on measurements from the plurality of magnetometers.

[0035] As used herein, the term drug is intended to encompass any drug-containing flowable pharmaceutical product that can be passed through a delivery means such as a cannula or hollow needle in a controlled manner, such as a liquid, solution, gel, or fine suspension, and that has a glycemic control effect, e.g., human insulin and its analogs, as well as non-insulins such as GLP-1 and its analogs. Although the description of the exemplary embodiment refers to the use of insulin, the described sensor assembly can also be used to log other types of drugs (e.g., growth hormone).

[0036] In the following, embodiments of the invention will be described with reference to the drawings. [Brief description of the drawings]

[0037] [Figure 1A] FIG. 1A shows a pen-based device. [Figure 1B] FIG. 1B shows the pen device of FIG. 1A with the pen cap removed. [Diagram 2] FIG. 2 shows an exploded view of the components of the pen device of FIG. 1A. [Figure 3A-3B] 3A and 3B show cross-sectional views of the ejection mechanism in two states. [Figure 4A-4B] 4A and 4B show schematic diagrams of an add-on device and a drug delivery device. [Figure 5A-5B] 5A and 5B respectively show an exemplary drug delivery device and a corresponding add-on device adapted to be mounted thereon, as shown in FIG. 4B. [Figure 6] FIG. 6 shows a schematic diagram of a system comprising three concentric tubular members. [Figure 7] FIG. 7 shows a schematic diagram of the inner spur gear connection between the inner and outer members of FIG. [Figure 8A-8B] 8A and 8B show in exploded view the components of a first embodiment of an add-on dose log device with an internal spur gear connection. [Figure 9] FIG. 9 shows the electronic sensor module mounted within the dose release member. [Figure 10] FIG. 10 shows in partial cutaway view the add-on device of FIG. 8A without the sensor module. [Figure 11] FIG. 11 shows in partial cutaway view the add-on device of FIG. 8A with a sensor module. [Figure 12] FIG. 12 shows the add-on device of FIG. 8A in cross-sectional view. [Figure 13]FIG. 13 shows the add-on device of FIG. 8A in an assembled state in combination with a drug delivery device. [Figure 14] FIG. 14 shows a schematic diagram of an alternative gear connection between the inner and outer members of FIG. [Figure 15] FIG. 15 shows a schematic diagram of a second embodiment of the transmission connection between the inner and outer members of FIG. [Figure 16A-16B] 16A and 16B show, in exploded view, components of a third embodiment of an add-on dose log device comprising a dynamic transmission member. [Figure 17] FIG. 17 shows the components of the add-on dose log device of FIG. 16A in an assembled state. [Figure 18] FIG. 18 shows a guide track member of the add-on dose log device of FIG. 16A. [Figure 19] FIG. 19 shows the add-on device of FIG. 16A in a partial cutaway view. [Figure 20] FIG. 20 shows an alternative configuration of the dynamic transmission member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] In these figures, like structures are primarily identified by like reference numbers.

[0039] When terms such as "upper" and "lower", "right" and "left", "horizontal" and "vertical", or similar relative expressions are used below, they merely refer to the attached figures and do not necessarily show the actual situation of use. The figures shown are schematic, so that the configuration of different structures as well as their relative dimensions are intended to serve illustration purposes only. When the term member or element is used for a given component, this generally indicates that this component is an integral component in the described embodiment, but alternatively the same member or element may include several subcomponents, just as two or more of the described components may be provided as an integral component, for example, manufactured as a single injection molded part. The term "assembly" does not imply that the described components may necessarily be assembled to provide an integral or functional assembly during a given assembly procedure, but is used merely to describe components that are grouped together as more closely related functionally.

[0040] Before turning to embodiments of the invention itself, one example of a pre-filled drug delivery device is described, which provides a basis for exemplary embodiments of the invention. The pen-type drug delivery device 100 shown in Figures 1-3 may represent a "generic" drug delivery device, and the device shown is the FlexTouch® pre-filled drug delivery pen manufactured and sold by Novo Nordisk A / S (Bagsvaerd, Denmark).

[0041] The pen device 100 comprises a main part having a cap part 107, a proximal body or drive assembly part having a housing 101 in which a drug ejection mechanism is disposed or integrated, and a distal cartridge holder part in which a drug-filled transparent cartridge 113 having a distal needle-penetrable septum is disposed and held in place by a non-removable cartridge holder attached to the proximal part, the cartridge holder having an opening allowing a portion of the cartridge to be inspected, as well as a distal connection means 115 allowing a needle assembly to be releasably attached. The cartridge is provided with a piston driven by a piston rod forming part of the ejection mechanism, and may contain, for example, insulin, GLP-1 or growth hormone preparations. A proximal-most rotatable dose setting member 180 having several axially oriented grooves 188 serves to manually set a desired dose of drug which is shown in the display window 102 and which can then be ejected when a button 190 is actuated. As will become clear from the following description, the axially oriented grooves 188 shown may be referred to as "drive grooves". The dose setting member 180 has a generally cylindrical outer surface 181 (i.e. the dose setting member may be slightly tapered) which in the embodiment shown is textured by providing a plurality of axially oriented micro grooves to improve finger grip during dose setting. The window is in the form of an opening in the housing surrounded by the chamfered edge portion 109 and the dose pointer 109P, the window allowing a portion of the helically rotatable indicator member 170 (scale drum) to be observed. Depending on the type of ejection mechanism embodied in the medication delivery device, the ejection mechanism may comprise a spring which deforms during dose setting and is subsequently released when the release button is actuated to drive the piston rod, as seen in the embodiment shown.Alternatively, the ejection mechanism may be entirely manual, in which case the dose member and actuation button move proximally during dose setting corresponding to the set dose size, and are then moved distally by the user to eject the set dose, as seen, for example, in the FlexPen® manufactured and sold by Novo Nordisk A / S.

[0042] Although Figure 1 shows a pre-filled type drug delivery device, i.e. a drug delivery device that is supplied with a pre-loaded cartridge which is discarded when the cartridge is emptied, in alternative embodiments the drug delivery device may be designed to allow the loaded cartridge to be replaced, for example in the form of a "rear-loading" drug delivery device in which the cartridge holder is adapted to be removed from the main part of the device, or alternatively in the form of a "front-loading" device in which the cartridge is inserted into a cartridge holder which is permanently attached to the main part of the device through a distal opening.

[0043] Since the present invention relates to electronic circuits adapted to interact with drug delivery devices, for a better understanding of the invention, exemplary embodiments of such devices will be described.

[0044] Figure 2 shows an exploded view of the pen-type drug delivery device 100 shown in Figure 1. More specifically, the pen comprises a tubular housing 101 having a window opening 102, onto which a cartridge holder 110 is fixedly mounted, with a drug-filled cartridge 113 disposed within the cartridge holder. The cartridge holder is provided with distal connection means 115 allowing a needle assembly 116 to be releasably mounted thereon, and proximal connection means in the form of two opposed projections 111 allowing a cap 107 to be releasably mounted over the cartridge holder and the mounted needle assembly, and projections 112 preventing the pen from rolling, such as on a table. Fixedly mounted to the housing distal end is a nut element 125, which is provided with a central threaded bore 126, and fixedly mounted to the housing proximal end is a spring base member 108 having a central opening. The drive system comprises a threaded piston rod 120 having two opposing longitudinal grooves and received in a threaded bore of the nut element, a ring-shaped piston rod drive element 130 rotationally arranged in the housing, and a ring-shaped clutch element 140 in rotational engagement with the drive element (see below), which engagement allows axial movement of the clutch element. The clutch element is provided with an external spline element 141 adapted to engage with a corresponding spline 104 (see FIG. 3B) on the inner surface of the housing, which allows the clutch element to move between a rotationally locked proximal position in which the splines are engaged and a rotationally free distal position in which the splines are disengaged. As just mentioned, in both these positions the clutch element is rotationally locked to the drive element. The drive element has a central bore with two opposing protrusions 131 that engage grooves on the piston rod such that, due to the threaded engagement between the piston rod and the nut element, rotation of the drive element results in rotation of the piston rod, and thereby distal axial movement.The drive element further comprises a pair of opposed circumferentially extending flexible ratchet arms 135 adapted to engage corresponding ratchet teeth 105 disposed on the housing inner surface. The drive element and clutch element comprise cooperating coupling structure that rotationally locks them together but allows the clutch element to move axially, thereby allowing the clutch element to move axially to its distal position where it can rotate, thereby transmitting rotational movement from the dial system (see below) to the drive system. The interaction between the clutch element, drive element and housing is shown and described in more detail with reference to Figures 3A and 3B.

[0045] Threaded onto the piston rod is an end-of-content (EOC) member 128 which is rotationally mounted on its distal end with a washer 127. The EOC member includes a pair of opposed radial projections 129 for engagement with the reset tube (see below).

[0046] The dial system comprises a ratchet tube 150, a reset tube 160, a scale drum 170 with an externally helically arranged pattern forming a row indicating the dose, a dial member 180 operated by the user for setting the dose of the drug to be expelled, a release button 190 and a torque spring 155 (see FIG. 3). The dial member is provided with a circumferential inner tooth structure 181 that engages with a number of corresponding outer teeth 161 arranged on the reset tube, thereby providing a dial coupling that is engaged when the reset tube is in a proximal position during dose setting and disengaged when the reset tube moves distally during dose expulsion. The reset tube is axially mounted in a locked manner inside the ratchet tube, but can rotate a few degrees (see below). The reset tube comprises on its inner surface two opposing longitudinal grooves 169 adapted to engage with the radial projections 129 of the EOC member, so that the EOC can rotate with the reset tube, but can also move axially. The clutch element is axially locked and mounted on the outer distal end portion of the ratchet tube 150, allowing the ratchet tube to move axially in and out of rotational engagement with the housing via the clutch element. The dial member 180 is axially locked and mounted but rotationally free on the housing proximal end, and the dial ring is rotationally locked to the reset tube under normal operation (see below), such that rotation of the dial ring results in corresponding rotation of the reset tube 160, which in turn results in corresponding rotation of the ratchet tube. The release button 190 is axially locked to the reset tube, but is free to rotate. A return spring 195 provides a proximally directed force on the button and to the reset tube mounted thereto.A scale drum 170 is disposed in the circumferential space between the ratchet tube and the housing, the drum being rotationally locked to the ratchet tube via cooperating longitudinal splines 151, 171 and in rotational threaded engagement with an inner surface of the housing via cooperating thread formations 103, 173 such that a row of numbers passes through a window opening 102 in the housing when the drum is rotated relative to the housing by the ratchet tube. A torque spring is disposed in the circumferential space between the ratchet tube and the reset tube and is secured at its proximal end to the spring base member 108 and at its distal end to the ratchet tube such that the spring deforms when the ratchet tube is rotated relative to the housing by rotation of the dial member. A ratchet mechanism having a flexible ratchet arm 152 is provided between the ratchet tube and the clutch element, which is provided with a circumferential internal tooth arrangement 142, each tooth providing a ratchet stop, such that the ratchet tube is held in the position to which it has been rotated by the user via the reset tube when the dose has been set. To allow the set dose to be reduced, a ratchet release mechanism 162 is provided on the reset tube, which acts on the ratchet tube, thereby allowing the set dose to be reduced by one or more ratchet notches by pivoting the dial member in the opposite direction, the release mechanism being actuated when the reset tube has been rotated the aforementioned number of degrees relative to the ratchet tube.

[0047] Having described the different components of the ejection mechanism and their functional relationships, the operation of the mechanism will now be described, mainly with reference to Figures 3A and 3B.

[0048] The pen mechanism can be considered as two interacting systems, the dose system and the dial system, as described above. During dose setting, the dial mechanism rotates and loads the torsion spring. The dose mechanism is locked in the housing and cannot move. When the push button is pressed, the dose mechanism is released from the housing and due to its engagement with the dial system, at this point the torsion spring rotates the dial system back to the starting point and with it the dose system.

[0049] The central part of the dose mechanism is the piston rod 120, by which the actual displacement of the plunger is performed. During dose delivery, the piston rod is rotated by the drive element 130, which moves the piston rod forward in the distal direction due to threaded interaction with a nut element 125 fixed to the housing. Between the rubber piston and the piston rod, a piston washer 127 is arranged, which acts as an axial bearing for the rotating piston rod and equalizes the pressure on the rubber piston. The piston rod has a non-circular cross section, which allows the piston rod drive element to engage with the piston rod, so that the drive element is rotationally locked to the piston rod but is free to move along the piston rod axis. As a result, rotation of the drive element results in a linear forward movement of the piston. The drive element is provided with a small ratchet arm 134 that prevents the drive element from rotating clockwise (as viewed from the push button end). Thus, due to engagement with the drive element, the piston rod can only move forward. During dose delivery, the drive element rotates counterclockwise and the ratchet arm 135 provides a small click sound to the user due to engagement with the ratchet teeth 105, for example one click per unit of insulin expelled.

[0050] With reference to the dial system, the dose is set and reset by turning the dial member 180. When the dial is turned, the reset tube 160, EOC member 128, ratchet tube 150, and scale drum 170 all turn with the dial because the dial linkage is in an engaged state. The ratchet tube is connected to the distal end of the torque spring 155, which loads the spring. During dose setting, the ratchet arm 152 provides a dial click for each increment the dial is turned by interaction with the internal tooth structure 142 of the clutch element. In the embodiment shown, the clutch element is provided with 24 ratchet stops that provide 24 clicks (notches) for a full 360 degree rotation relative to the housing. The spring is preloaded during assembly, which allows the mechanism to deliver both low and high doses within acceptable speed intervals. The scale drum is rotationally engaged with the ratchet tube but is axially movable, and the scale drum is threadedly engaged with the housing so that as the dial system is turned the scale drum moves in a spiral pattern and a number corresponding to the set dose is shown in the housing window 102.

[0051] The ratchet 152, 142 between the ratchet tube and the clutch element 140 prevents the spring from pivoting back the parts. During reset, the reset tube moves the ratchet arm 152, thereby releasing the ratchet with each click, one click corresponding to one IU in the described embodiment. More specifically, when the dial member pivots clockwise, the reset tube simply rotates the ratchet tube, allowing the arm of the ratchet to freely interact with the tooth structure 142 in the clutch element. When the dial member pivots counterclockwise, the reset tube directly interacts with the ratchet click arm, pushing the click arm towards the center of the pen and away from the teeth in the clutch, and pushing the click arm away from the teeth in the clutch towards the center of the pen, thus allowing the click arm on the ratchet to move backwards "one click" due to the torque created by the loaded spring.

[0052] To deliver the set dose, the push button 190 is pushed distally by the user, as shown in FIG. 3B. The dial couplings 161, 181 disengage, the reset tube 160 disengages from the dial member, and then the clutch element 140 disengages from the housing spline 104. At this point, the dial mechanism returns to "zero" together with the drive element 130, which results in the expulsion of a dose of drug. It is possible to stop and start the dose at any time during drug delivery by releasing or pressing the push button. Doses below 5 IU usually cannot be suspended, since too rapid compression of the rubber piston leads to compression of the rubber piston, which then delivers insulin when the piston returns to its original dimensions.

[0053] The EOC feature prevents the user from setting a dose larger than the dose remaining in the cartridge. The EOC member 128 is rotationally locked to the reset tube, which allows it to rotate during dose setting, resetting and dose delivery while moving axially back and forth following the threads of the piston rod threads. When it reaches the proximal end of the piston rod, a stop is provided, which prevents further rotation of all connected parts, including the dial member, in the dose setting direction, i.e., at this point the set dose corresponds to the remaining drug content in the cartridge.

[0054] The scale drum 170 is provided with a distal stop surface 174 adapted to engage a corresponding stop surface on the housing inner surface, thereby providing a maximum dose stop for the scale drum and preventing further rotation of all connected parts, including the dial member, in the dose setting direction. In the embodiment shown, the maximum dose is set at 80 IU. Accordingly, the scale drum is provided with a proximal stop surface adapted to engage a corresponding stop surface on the spring base member, thereby preventing further rotation of all connected parts, including the dial member, in the dose ejection direction, thereby providing a "zero" stop for the entire ejection mechanism.

[0055] The EOC member functions to provide a security system to prevent accidental overdosing in case any obstruction in the dial mechanism allows the scale drum to move beyond the zero position. More specifically, in the initial state with a full cartridge, the EOC member is positioned in its most distal axial position in contact with the drive element. After a given dose has been expelled, the EOC member is again positioned in contact with the drive element. Accordingly, the EOC member locks against the drive element in case the mechanism attempts to deliver a dose beyond the zero position. Due to the tolerances and flexibility of the various parts of the mechanism, the EOC may advance a small distance, expelling a small "overdose" of medication (e.g., 3-5 IU of insulin).

[0056] The ejection mechanism further comprises an end of dose (EOD) click function that provides a distinct audible feedback at the end of the ejected dose to inform the user that the entire amount of medication has been ejected. More specifically, the EOD function is performed by an interaction between the spring base and the scale drum. As the scale drum returns to zero, a small click arm 106 on the spring base is forced backwards by the advancing scale drum. Just before "zero" the arm is released and it strikes a countersunk surface on the scale drum.

[0057] The mechanism shown is further provided with a torque limiter to protect the mechanism from overloads applied by the user via the dial member. This function is provided by the interface between the dial member and the reset tube, which are rotationally locked to each other as described above. More specifically, the dial member is provided with a circumferential inner tooth structure 181 that engages with several corresponding outer teeth 161, which are arranged on the flexible carrier part of the reset tube. The reset tube teeth are designed to transmit a given specified maximum size of torque, for example 150-300 Nmm, above which the flexible carrier part and the teeth bend inwards, allowing the dial member to pivot without rotating the rest of the dial mechanism. The inner mechanism of the pen is therefore not stressed with loads higher than what the torque limiter transmits via the teeth.

[0058] Having described the operating principles of the mechanical drug delivery device, embodiments of the present invention will now be described.

[0059] 4A and 4B show schematic diagrams of a first assembly of a pen-type pre-filled drug delivery device 200 and an add-on dose log device 300 adapted therefor. The add-on device is adapted to be mounted on a proximal end portion of the pen device housing, which is provided with a dose setting means and a dose releasing means 380 that, in the mounted state, cover corresponding means on the pen device, as shown in FIG. 4B. In the embodiment shown, the add-on device comprises a coupling part 385 adapted to be axially mounted and rotationally locked on the drug delivery housing. The add-on device comprises a rotatable dose setting member 380, which is directly or indirectly coupled to the pen dose setting member during dose setting, such that the rotational movement of the add-on dose setting member is transferred to the pen dose setting member 280 in either direction. In order to reduce external influences during dose ejection and dose sizing, the outer add-on dose setting member 380 may be rotationally decoupled from the pen dose setting member 280 during dose release and dose ejection. The add-on device further comprises a dose release member 390 which is capable of moving distally thereby actuating the pen release member 290.

[0060] 5A and 5B, a specific prior art embodiment of an add-on dose log device 500 adapted to be mounted on a pen-type drug delivery device 400 is shown, which essentially corresponds to the FlexTouch® pre-filled drug delivery pen, the add-on dose log device shown being branded as "Dialoq®". The add-on device 500 essentially corresponds to the add-on dose log device 300 described above and therefore comprises a housing part 585 adapted to be axially mounted and rotationally locked on the drug delivery housing via a releasable coupling means 586, the housing being provided with a window 587 allowing the pen scale drum 470 to be observed during dose setting. The add-on device comprises a rotatable dose setting member 580 coupled to the pen dose setting member 480 during dose setting, such that rotational movement of the add-on dose setting member is transferred to the pen dose setting member via the coupling groove 488 in either direction. The add-on device further comprises a dose release member 590 which is capable of moving distally thereby actuating the pen release member 490.

[0061] To determine the dose size of the expelled medication, the pen device may be provided with a magnetic identifier adapted to rotate during dose expulsion, and the add-on device may be provided with a sensor circuit that allows the amount of rotation to be captured and thereby the expelled dose size to be determined. Some embodiments based on this concept are disclosed and described in detail in WO 2019 / 162235, which is incorporated herein by reference.

[0062] In summary, the add-on device disclosed in WO 2019 / 162235 comprises an outer assembly releasably attachable to a medication delivery device housing and an inner assembly. The outer assembly comprises an add-on dose setting member 580 and an add-on release member 590 axially movable relative to the add-on dose setting member between a dose setting state and a dose ejection state. The inner assembly comprises an inner dose setting member adapted to engage with the dose setting member 480, a sensor means adapted to detect the amount of rotation of the indicator during the ejection of a dose, and an actuator coupled to the add-on release member and axially movable relative to the inner dose setting member between a proximal position and a distal position, the actuator adapted to engage and actuate the release member 490 of the pen device when moved distally. For example, a sensor circuit in the form of an electronic module may form part of the actuator (and thus move axially with it) and be non-rotationally coupled to the inner dose setting member to prevent rotation during the ejection of a dose. The sensor circuitry is typically awakened from a sleep state when a user actuates the add-on release member 590 causing axial movement.

[0063] This decoupling mechanism adds both complexity, cost and volume to the add-on dose log device and therefore a simplified design would be desirable. Also, as mentioned above, the present invention is based on the recognition that an arrangement in which the sensor module is rotationally locked to the drug delivery device (but axially movable) during both dose setting and dose ejection may allow the coupling arrangement to be omitted, thereby providing a simplified and / or more compact design.

[0064] Accordingly, in the following exemplary embodiments, there is provided ensuring that the sensor module is rotationally locked to the drug delivery device / assembly (but axially movable) during both dose setting and dose ejection.

[0065] In a mechanical system, components must refer to each other, and this means here that the orientation and / or position of the components follows in some manner other components in the system. An add-on device of the type disclosed in WO 2019 / 162235 essentially comprises a housing immovably mounted on the pen housing, an inner dose setting coupling member rotationally coupled to the pen dose setting member, and a rotatable outer dose setting member that allows the user to set a dose, i.e. the rotation of the outer dose setting member is transmitted to the inner dose setting member. Such a system can be compared to three tubes 601, 602, 603 with increasing diameters assembled one to the other, as illustrated in FIG. 6.

[0066] The challenge in the system illustrated in Figure 6 is therefore to reference the outer layer to the inner layer through the intermediate layer, in other words to ensure that the tubes rotate when the outer tube rotates, without the need for an electronic module. At first glance this would appear to require the inner tube to have a rigid connection to the outer tube through the intermediate tube, but once the outer tube rotates more than 360 degrees a circumferential slit or opening would be required in the intermediate layer, which would effectively split the intermediate tube in two.

[0067] In a first exemplary embodiment, a rotational coupling mechanism is provided between the inner and outer dose setting members through an opening in the add-on housing (corresponding to the middle layer in FIG. 6), allowing both the inner and outer dose setting members to rotate at least 360 degrees.

[0068] More specifically, and as shown diagrammatically in FIG. 7, an internal spur gear connection is provided between the inner dose setting member 611 and the outer dose setting member 613, the larger diameter outer dose setting member having a circumferential inner gear toothing that engages with a circumferential outer gear toothing on the smaller diameter inner dose setting member. The outer dose setting member is coaxially and rotationally arranged on a cylindrical portion of the add-on housing 612, and the inner dose setting member is rotationally but axially offset arranged inside the tubular housing, these two gears mesh with each other through an opening / slot in the add-on housing. As can be seen, the offset arrangement of the inner dose setting member allows the add-on housing to expand both proximally and distally relative to the gear connection between the two dose setting members. In this way, the distal housing portion can be used to non-rotationally engage with the pen body housing, and the proximal housing portion can be used to accommodate an electronic sensor unit axially movable but non-rotationally coupled to the housing, thereby providing a non-rotational coupling between the sensor module and the pen housing. Since the inner dose setting member is adapted to engage with the pen dose setting member and must therefore be arranged coaxially with the add-on device mounted on the pen device, it must be mounted axially offset on the pen housing.

[0069] 8A, 8B and 9-13, a specific embodiment of an add-on device 700 with an internal spur gear connection between the inner and outer dose setting members will be described.

[0070] More specifically, the add-on device comprises a tubular housing member 710 having a proximal opening 711, a distal opening 712 adapted to receive not only the proximal end of the pen device but also a lateral opening 713, a tubular outer dose setting (dial) member 720, a tubular inner dose setting member 730 adapted to engage with (grasp) the pen dose setting member, a sensor module 740 having a proximal switch 741, a button member 750 adapted to accommodate the sensor module, a switch return spring 760, and (optionally) a button member / sensor module return spring.

[0071] The housing member 710 further comprises a circumferential outer raised structure 714 at a distal end adapted to engage with an outer dose setting member 720, a circumferential inner receiving means adapted to engage with an inner dose setting member 730, an inner stop 716 adapted to engage with a button member 750 and an axial guide means 717. The housing member further comprises a releasable locking means 718 which allows the add-on device to be mounted on the pen housing in an axially as well as axially locked manner.

[0072] The tubular outer dose setting member 720 has a generally smooth inner surface adapted to rotate on the tubular outer surface of the housing, a distal circumferential inner groove 721 adapted to rotationally engage with an outer raised structure of the housing, a distal inner gear toothed portion 722 adapted to engage with the inner dose setting member 730, and an inwardly protruding proximal flange 725 adapted to provide an axial stop for the button member 750.

[0073] The tubular inner dose setting member 730 comprises a distal outer gear toothed portion 732 adapted to engage with an inner gear toothed portion on the outer dose setting member and a proximal portion having several inwardly protruding flexible coupling arms 738 adapted to non-rotationally engage with corresponding coupling structures on the pen dose setting member. The inner dose setting member is adapted to be axially locked but rotationally free mounted within the housing member 710. As the inner dose setting member is adapted to grip the pen dose setting member, it can also be referred to as a gripping member.

[0074] The button member 750 comprises a generally flat proximal button portion 751 and several distally protruding rib structures 752 that provide a cage structure adapted to rotationally lockingly receive and retain a sensor module, as shown in Figure 10. The ribs are adapted to non-rotationally engage the housing 710 and the button member is axially movable between a distal stop provided by the housing and a proximal stop provided by the outer dose setting member flange 725.

[0075] The sensor module 740 has a generally cylindrical configuration and is adapted to be non-rotationally mounted within the button cage structure with a small amount of axial slack, allowing a switch return spring 760 to be disposed between the switch and the flat button portion to ensure that the sensor module returns to its distal position within the cage structure after activation. In one use situation, the distal surface of the sensor module is adapted to engage with a pen release button, allowing the button member to activate the sensor module switch (see below). Details of the sensor circuitry contained within the sensor module are not relevant in the context of the present invention, but are described in detail, for example, in WO 2019 / 162235.

[0076] A return spring (not shown) for the button member may be disposed between the button member and the spring support surface of the housing to ensure that the button member is biased towards its proximal-most position. If no return spring is provided, the button member is free to move axially, but when mounted on the pen device it becomes essentially held axially in a predetermined position between the pen release button and the proximal stop 725 of the button member.

[0077] Figures 11 and 12 show an inner dose setting member 730 disposed within a housing member 710 and in geared engagement with an outer dose setting member 720, as well as a button member 750 rotationally locked and disposed within the housing member. In Figure 12, a sensor module 740 is shown disposed within the button member.

[0078] 12 shows the assembled add-on device in cross section, revealing the axially offset placement of the sensor module within the housing. In the embodiment shown, a narrow gap is provided between the sensor module and the housing, which would allow one or more small diameter return springs to be disposed within the gap.

[0079] In one use scenario, referring to Fig. 13, a user mounts the add-on device 700 onto the proximal end of a corresponding pen based medication delivery device 400, and the releasable add-on locking means 718 engages with a corresponding locking knob 408 on the pen housing 410, whereby the pen dose setting member 480 is received within the inner dose setting member 730. Depending on the design of the latter two members, they may become rotationally locked during the mounting action, or as in this embodiment, subsequently when the user starts to set a dose and the flexible coupling arm 738 non-rotationally engages with a corresponding coupling groove 488 on the pen dose setting member.

[0080] To set a dose, the user rotates the outer add-on dose setting member 720, and thus the inner dose setting member, until the desired dose size is indicated in the pen display window. During the initial rotation of the inner dose setting member, the flexible linkage arm 738 slides on the pen dose setting member until the arm non-rotationally engages with a corresponding axially oriented linkage groove 488 on the pen dose setting member. As can be seen, due to the different diameters of these two gear rings, a slight transmission is provided between the outer and inner dose setting members, which in most cases is not apparent to the user.

[0081] Once the desired dose is set, the user actuates the dose release button 740, which causes the sensor module to move into engagement with the pen release button. The pen release button is biased towards its proximal position by the pen button spring, and the switch return spring 750 is dimensioned to activate the sensor switch, thus allowing the pen release button to begin to move distally, thereby turning on the sensor module before releasing the spring-loaded ejection mechanism. During dose ejection, the sensor module determines the amount of rotation of an indicator element, e.g., a magnet as seen in this embodiment, and thus the ejected dose.

[0082] Once the set dose has been expelled or if the user wishes to pause the injection, the user releases pressure on the dose release button, causing the button return spring to return the button member to its initial position using the sensor module.

[0083] In Fig. 14 an alternative configuration of the first embodiment is shown in which an additional inclined transfer wheel 790 supported by an inner housing support 791 allows for a coaxial arrangement of an inner dose setting member 793 and an outer dose setting member 792. The transfer wheel comprises a circumferential outer gear toothed portion 794 engaged with a circumferential inner gear toothed portion 797 of the outer dose setting member, as well as a distally facing circumferential angular gear toothed portion 795 engaged with a proximally facing circumferential angular gear toothed portion 796 on the inner dose setting member. In such a design, the housing support 791 would form a structure capable of supporting the electronic module.

[0084] 15, a second exemplary embodiment of a coupling mechanism 800 is described that allows the inner and outer dose setting members to rotate together. Similar to the first exemplary embodiment, the concept is to provide a connection through the housing wall at the distal level of the sensor module.

[0085] Instead of an internal spur gear arrangement with an offset inner dose setting member, Figure 15 shows diagrammatically a solution in which the rotational connection between the outer dose setting member 820 and the inner dose setting member 830 is provided by a double-sided flexible cam belt 840 with an outer toothed portion 841 and an inner toothed portion 842, and is screwed through a pair of opposing openings in the add-on housing member 810.

[0086] More specifically, the housing member 810 includes a pair of opposing openings, each pair including two openings 813 with a portion of the wall 812 therebetween, providing an outer cam belt support surface as well as an inner support surface for the inner dose setting member. The remaining wall portion 815 provides an inner cam belt support surface as well as an outer support surface for the outer dose setting member.

[0087] The outer dose setting member 820 has a circumferential inner toothed portion 822 adapted to engage with an outer toothed portion 841 on the cam belt, and the inner dose setting member 830 has a circumferential outer toothed portion 832 adapted to engage with an inner toothed portion 842 on the cam belt.

[0088] As shown in FIG. 15 in an assembled state, a portion of the cam belt positioned on the outside of the housing engages with the inner toothed surface of the outer dose setting member, and a portion of the cam belt positioned on the inside of the housing engages with the outer toothed surface of the inner dose setting member.

[0089] As can be seen, the cam belt design provides an axially symmetrical design, as compared to the first exemplary embodiment, which includes an internal spur gear connection and provides an axially asymmetrical design. Otherwise, the cam belt coupling can be integrated into a given add-on dose log device in essentially the same manner as described for the first exemplary embodiment. That is, the internal spur gear arrangement can be provided with an externally symmetrical design.

[0090] In an alternative configuration (not shown), the cam belt is disposed through a pair of lateral openings having an inner toothed portion of the cam belt which engages a larger portion of the outer toothed portion of the inner dose setting member.

[0091] In a further alternative configuration (not shown), the cam belt is replaced by one or more transmission gear assemblies, each assembly comprising one or more gear wheels. For example, a single transmission gear wheel provides reversal of rotational direction from the outer dose setting member to the inner dose setting member, while two transmission gear wheels in series ensure rotational movement of the two dose setting members in the same direction. Alternatively, two gear wheels of different diameters may be arranged on a common axis and rotate together, which gear wheels engage with the inner and outer dose setting members, respectively.

[0092] 16A, 16B and 17-19, a third exemplary embodiment of a coupling mechanism that allows the inner and outer dose setting members to rotate together is described. While in the first and second exemplary embodiments, the concept is to provide a connection through the housing at a distal level of the sensor module, in the third exemplary embodiment, the concept is to create a connection between the proximal and distal parts of the inner dose setting member that allows the rotational input to "pass" through the electronic module.

[0093] More specifically, the add-on device 900 comprises a tubular housing member 910 having a proximal opening 911 and a distal opening 912 adapted to receive the proximal end of the pen device 400, an outer dose setting member 920, a tubular inner dose setting member 930 adapted to engage with the pen dose setting member, a sensor module 940 having a proximal switch 941, a module housing 950 adapted to accommodate the sensor module, an actuation rod 960, a finger member 970 having a plurality of flexible fingers 971 adapted to non-rotationally engage with the housing, a guide plate 980 non-rotationally coupled to the finger member, a roof member 935, a dose release button 990 axially coupled to the module housing, and a button return spring 999. Figure 17 shows the core components that, in an assembled state, allow the electronic module to be non-rotationally mounted within the housing 900.

[0094] The housing member 910 comprises a circumferential outer raised structure 914 at a proximal end adapted to engage with an outer dose setting member 920, and a circumferential inner array of axially disposed finger grooves 915 adapted to engage with individual fingers of a finger member 970. The housing member further comprises releasable locking means 918 that allows the add-on device to be mounted on the pen housing 400 in an axially as well as rotationally locked manner.

[0095] The outer dose setting member 920 has a generally smooth inner surface adapted to rotate on the tubular outer surface of the housing, a distal circumferential inner groove 924 adapted to rotationally engage with the outer raised structure of the housing, and a guide track 925 for non-rotationally engaging with the inner dose setting member 930 (via the roof member 935), the guide track having a proximal ridge 926 adapted to provide an axial stop for the button member 990.

[0096] The tubular inner dose setting member 930 comprises a pair of opposing partial circumferential finger openings 931 that divide the inner dose setting member into a proximal portion and a distal portion (see below), these two portions being connected by a bridge portion 932 between the openings. The proximal portion is in the form of a roof member 935 adapted to connect to the distal portion via the bridge portion, the roof member comprising a central opening 936 and a distally facing guide track 937 for the fingers 971 of the finger members 970. The guide track and its functional relationship with the finger members will be explained in more detail below. The distal portion comprises a number of inwardly projecting flexible linking arms 938 adapted to non-rotationally engage with corresponding linking structures 488 on the pen dose setting member 480. The inner dose setting member is adapted to be axially locked but rotationally free mounted within the housing member 910.

[0097] The module housing 950 comprises a proximal non-circular central opening 955 adapted to receive the actuation rod 970 and several distally projecting rib structures 952 providing a cage structure adapted to rotationally lock and receive and hold the sensor module 940. The actuation rod 960 has a non-circular cross-section that allows it to be non-rotationally mounted through a correspondingly formed opening 955 in the module housing and a proximal coupling means 965 (here a ball coupling) for axially locked engagement with the dose release button 990. The module housing is axially movable between proximal and distal positions relative to the inner dose setting member. The actuation rod 960 can move axially a small amount relative to the cage structure to allow the module switch to be actuated.

[0098] The sensor module 940 has a generally cylindrical configuration and is adapted to be non-rotationally mounted within the cage structure of the module housing. In one use scenario, a distal surface of the sensor module is adapted to engage the pen release button 490, which allows actuation of a sensor module switch 941 (see below). In the embodiment shown, the switch is in the form of a dome switch that provides a biasing force on an actuation rod.

[0099] The finger member 970 includes a ring portion 972 having a plurality of proximally extending flexible fingers 971, each finger having a lateral projection 975 adapted to be received within a corresponding finger groove 915 of the housing, and a free end 977 adapted to be received within a guide track 937 of the roof member.

[0100] The guide plate 980 includes a plurality of outer radial guide slots 981 each adapted to receive and guide a corresponding flexible finger 971. In the embodiment shown, the guide plate is axially supported on inner protrusions on the respective fingers. The guide plate further includes a central opening 985 configured to non-rotationally receive the actuation rod 960.

[0101] The dose release button 990 comprises a circumferential flange portion 991 adapted to engage with a guide track 925 provided by the outer dose setting member. A distal stop surface is provided by the roof member. The dose release button further comprises a ball linkage socket 995 for engaging with the ball linkage 965 of the actuation rod, allowing bidirectional axial force, and therefore movement, to be transmitted to the electronic module. A button return spring 999 ensures that the dose release button is biased towards its proximal position.

[0102] Having described the individual components of the second exemplary embodiment of the add-on module and their relationships, a more detailed description of the functionality will now be provided.

[0103] The central component of the second embodiment is a finger element 970 that ensures that the sensor module 940 can be non-rotationally coupled to the housing member 910. Essentially, the finger member is non-rotationally coupled to the housing by means of a plurality of fingers 971, 975 that engage with finger grooves 915 of the housing. At the same time, however, a rotating inner dose setting member 930 is disposed between the finger member and the housing member.

[0104] To allow for such inconsistent disposition, a pair of opposing "dynamic gaps" are created between the finger members and the housing members. More specifically, as shown in FIG. 17, at a given rotational position of the finger members, only a portion of the fingers, e.g., 50%, are engaged with the finger grooves through finger openings 931 in the inner dose setting member 930, while corresponding to bridge portions 932, the fingers move radially inwardly out of engagement with the finger grooves, thereby allowing the bridge portions to pass through the finger members. As mentioned above, the proximal free ends 977 of the individual fingers are received within guide tracks 937 of the roof portion of the inner dose setting member, which are designed to allow corresponding to bridge portions to allow the flexible fingers 971 to move inwardly out of engagement with the finger grooves 915 of the housing. As the guide track and bridge portion rotate together (functionally being the same component structure), the fingers move inward to allow the bridge portion to pass, and then move outward to again engage the finger grooves in the housing when the bridge portion has passed. The slots 981 in the guide plate ensure that the fingers move in and out essentially only radially.

[0105] In this way, a certain number of fingers, e.g., 50%, are always engaged with the housing member, thereby ensuring that the finger members (and thus the electronic module) are non-rotationally and "dynamically" mounted within the housing member.

[0106] In one use scenario, the user mounts the add-on device 900 onto the proximal end of the corresponding pen medication delivery device 400 in locked engagement, whereby the pen dose setting member 480 is received within the inner dose setting member 930. Depending on the design of these two members, they may become rotationally locked during the mounting action or, as in this embodiment, when the user subsequently begins to set a dose.

[0107] To set a dose, the user rotates the outer add-on dose setting member 920, and thus the inner dose setting member, until the desired dose size is indicated in the pen display window. As described above, during dose setting, the individual fingers 971 of the finger member disengage and reengage, thereby allowing the bridge portion 932 of the inner dose setting member to pass. During initial rotation of the inner dose setting member, the flexible linkage arm 938 slides on the pen dose setting member until the arm non-rotationally engages with a corresponding axially oriented linkage groove 488 on the pen dose setting member.

[0108] Once the desired dose is set, the user actuates the dose release button 990, which causes the sensor module 940 to move into engagement with the pen release button 490. The pen release button 490 is biased towards its proximal position by the pen button spring, and the dome switch 941 is dimensioned to allow the sensor switch to be actuated, thus turning on the sensor module before the pen release button begins to move distally and subsequently releases the spring-loaded ejection mechanism. During dose ejection, the sensor module determines the amount of rotation of an indicator element, e.g., a magnet as seen in this embodiment, and thus the ejected dose.

[0109] Once the set dose has been expelled or if the user wishes to pause the injection, the user releases pressure on the dose release button, which causes the button return spring 999 to return the dose release button 990 to its initial position using the sensor module.

[0110] 20, an alternative configuration of finger member 1070 is shown. While finger member 970 described above had multiple radially flexible fingers, this alternative configuration comprises several axially movable fingers 1071 connected to a central hub 1072 via flexible hinges 1074. When implemented within a specific add-on device, the housing structure engages and disengages with the fingers in a manner similar to that seen in the above-described third exemplary embodiment of the add-on log device, where the guide tracks are adapted for axial movement instead of radial movement.

[0111] In the above description of the exemplary embodiments, different structures and means for providing the described functionality for the different components have been described to an extent that the concept of the invention is clear to the skilled reader. The detailed construction and specification for the different components are considered to be the subject of a normal design procedure performed by a person skilled in the art along the lines set out in this specification.

Claims

1. An add-on device (700, 900) adapted to be releasably mounted on a drug delivery device (400), said drug delivery device comprising: a device housing (410); a drug reservoir or means for receiving a drug reservoir, - drug ejection means comprising a rotatable dose setting member (480) allowing the user to set the dose of drug to be ejected; - a proximally disposed release member (490) actuatable between a proximal position and a distal position, said proximal position allowing a dose to be set and said distal position allowing said drug ejection means to eject the set dose; an indicator adapted to move during the ejection of a dose, the amount of movement being indicative of the size of said ejected dose; The add-on device, - an add-on dose release assembly; - an add-on dose setting assembly, said add-on dose release assembly comprising: - a generally tubular add-on housing (710, 910) defining a reference axis, said add-on housing comprising a distal opening adapted to receive a proximal portion of said medication delivery device and releasably attachable to said medication delivery device housing in a rotationally and axially locked position relative to said device housing, said add-on housing comprising an interior space and an exterior surface; a sensor assembly (740, 940) disposed inside said tubular add-on housing and directly or indirectly non-rotationally but axially movably coupled thereto, said sensor assembly (740, 940) operable to detect an amount of rotation of said indicator during dose ejection; The add-on dose setting assembly comprises: a gripping member (730, 930) arranged rotationally inside said add-on housing and adapted to engage non-rotationally with said dose setting member (480); an add-on dose setting member (720, 920) rotationally connected to the outer surface of the tubular housing, - said add-on dose setting member is connected to said gripping member and allows said gripping member to rotate at least 360 degrees; - an add-on device (700, 900), wherein the sensor assembly is axially movable between a proximal position and a distal position relative to the add-on housing such that, when the add-on device is mounted on the drug delivery device, the sensor assembly engages and actuates the release member when moved distally.

2. - said add-on housing comprises one or more lateral openings (713, 813), - said gripping member comprises a circumferential outer gear wheel portion (732, 832) having a first diameter, - said add-on dose setting member comprises a circumferential inner gear wheel portion (722, 822) having a second, larger diameter, - said outer circumferential gear wheel portion and said inner circumferential gear wheel portion directly or indirectly engage with one another corresponding to a lateral opening; The add-on device according to claim 1 , whereby rotation of the dose setting member provides rotation of the gripping member.

3. - the axis of rotation of the dose setting member is radially offset from the axis of rotation of the gripping member, The add-on device according to claim 2, wherein said circumferential outer gear wheel portion (732) and said circumferential inner gear wheel portion (722) engage with each other corresponding to a lateral opening to form an internal spur gear.

4. a transmission gear assembly comprising at least one gear wheel arranged corresponding to the lateral opening; The add-on device of claim 2 , wherein the circumferential outer gear wheel portion and the circumferential inner gear wheel portion engage each other via the transmission gear assembly.

5. - a circumferentially flexible cam belt (840) disposed through the lateral opening (813); and (i) an internal toothed surface (842) disposed to engage the outer gear wheel portion (832) of the gripping member; (ii) an outer toothed surface (841) arranged to engage with the inner gear wheel portion (822) of the add-on dose setting member; the flexible cam belt is held in engagement with the gripping member at one or more first positions and in contact with the add-on dose setting member at one or more second positions; The add-on device according to claim 2 , whereby rotation of the add-on dose setting member is transmitted to the gripping member via the flexible cam belt.

6. - said add-on dose release assembly comprises a crown member (970) disposed inside said add-on housing; - said crown member comprises a plurality of coupling fingers (971) adapted to non-rotationally engage with said add-on housing (910), each finger having an engaged state and a disengaged state engaged with said add-on housing; - the gripping member (930) comprises at least one bridge portion (932) adapted to pass between the add-on housing and one or more coupling fingers in a disengaged state, the gripping member being non-rotationally coupled to the add-on dose setting member via the bridge portion(s); and - an add-on device as described in claim 1, wherein a control structure (935) is non-rotationally connected to the add-on dose setting member (920) and engages with the connecting fingers (971) to move the connecting fingers between the engaged state and the disengaged state, thereby allowing the bridge portion(s) to pass through the connecting fingers as the control structure and the gripping member rotate relative to the crown member.

7. - said coupling fingers extend axially and are adapted to move radially between said engaged and disengaged states; The add-on device according to claim 6, wherein the add-on housing comprises a plurality of receiving structures (915) each adapted to receive in coupling engagement a given coupling finger (971, 975).

8. - said control structure (935) comprises a circumferential guide track (937); each connecting finger comprises a free end (977) received in said guide track, The add-on device of claim 7 , whereby the coupling fingers move radially into and out of engagement with the add-on housing when the control structure rotates together with the add-on dose setting member.

9. The add-on device of claim 8, wherein the control structure (935) is disposed proximally of and connected to the bridge portion(s), and the guide track faces distally.

10. - said add-on dose setting member (792) comprises a first circumferential toothed portion (797), - said gripping member (793) comprises a second circumferential toothing (796), The add-on device, a transfer ring (790) arranged at an oblique angle with respect to a plane perpendicular to said reference axis, (i) a first circumferential transmission toothed portion (794) engaged with the first toothed portion (797) of the add-on dose setting member; (ii) a transfer ring (790) comprising a second circumferential transfer toothed portion (795) engaged with the second toothed portion (796) of the gripping member; The add-on device of claim 1 , whereby rotation of the dose setting member provides rotation of the gripping member via the tilted transmission ring.

11. An add-on device (700, 900) according to any one of claims 1 to 10 in combination with a drug delivery device (400) according to claim 1.

12. said add-on dose release assembly comprising: An add-on device according to any one of claims 1 to 11, further comprising a proximally directed user-actuatable add-on release member (750, 990) coupled to and axially moving with the sensor assembly (740, 940).

13. 1. An integrated drug delivery device comprising: a housing defining a reference axis; a drug reservoir or means for receiving a drug reservoir, - a drug discharge means, - an inner dose setting member adapted to rotate to set a dose; an inner release member actuatable between a proximal position and a distal position, said proximal position allowing a dose to be set and said distal position allowing said drug ejection means to eject the set dose; - a drug ejection means comprising an indicator adapted to rotate during the ejection of a dose, the amount of rotation indicating the size of said ejected dose; - a sensor assembly disposed within said housing and directly or indirectly non-rotatably but axially movably coupled thereto, said sensor assembly being operable to detect an amount of rotation of said indicator during dose ejection; a user dose setting member coupled to said housing and adapted to rotate to set a dose; - said user dose setting member is rotationally connected to said inner dose setting member, allowing said inner dose setting member to rotate at least 360 degrees; - an integrated drug delivery device, wherein the sensor assembly is axially movable by the user between a proximal position and a distal position relative to the housing so as to engage and actuate the inner release member when moved distally.

14. - said housing comprises one or more lateral openings, - said inner dose setting member comprises a circumferential outer gear wheel portion having a first diameter, - said user dose setting member comprises a circumferential inner gear wheel portion having a second, larger diameter; - said outer circumferential gear wheel portion and said inner circumferential gear wheel portion directly or indirectly engage with one another corresponding to a lateral opening; The integrated drug delivery device of claim 13, whereby rotation of the dose setting member provides rotation of the gripping member.

15. a crown member disposed within said housing; a control structure; - the crown member comprises a plurality of interlocking fingers adapted to non-rotationally engage the housing, each finger having an engaged state and a disengaged state engaged with the add-on housing; - the inner dose setting member comprises at least one bridge portion adapted to pass between the housing and one or more coupling fingers in a disengaged state, the inner dose setting member being non-rotationally coupled to the user dose setting member via the bridge portion(s); - The integrated drug delivery device of claim 13, wherein the control structure is non-rotationally connected to the user dose setting member and engages with the connecting fingers to control the connecting fingers between the engaged state and the disengaged state, thereby allowing the bridge portion(s) to pass through the connecting fingers as the control structure and the inner dose setting member rotate relative to the crown member.

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