WO2017114769A1 - Accessory device with mounting feature - Google Patents

Abstract

An add-on device (200) configured to be releasably attached to a drug delivery device (100) comprising a visual identifier (102) at a specified position, and adapted to determine, when mounted to a drug delivery device housing, an amount of rotation of the indicator member relative to the housing. The add-on device comprises mounting means (230), a memory in which a reference representation of the visual identifier is stored, a camera (221) adapted to capture an image of the visual identifier, and a processor adapted to perform an image analysis comparing a captured image with the stored reference. The add-on device is adapted to perform a mounting position check comprising: capturing an image, performing an image analysis to determine if the captured image comprises the visual identifier, and indicating an error state if the captured image does not comprise the visual identifier.

Description

ACCESSORY DEVICE WITH MOUNTING FEATURE

The present invention generally relates to medical devices for which the generation, collecting and storing of data are relevant. In specific embodiments the invention relates to devices and systems for capturing and organizing drug delivery dose data in a reliable and user- friendly way.

BACKGROUND OF THE INVENTION

In the disclosure of the present invention reference is mostly made to drug delivery devices comprising a threaded piston rod driven by a rotating drive member, such devices being used e.g. in the treatment of diabetes by delivery of insulin, however, this is only an exemplary use of the present invention.

Drug Injection devices have greatly improved the lives of patients who must self-administer drugs and biological agents. Drug Injection devices may take many forms, including simple disposable devices that are little more than an ampoule with an injection means or they may be durable devices adapted to be used with prefilled cartridges. Regardless of their form and type, they have proven to be great aids in assisting patients to self-administer injectable drugs and biological agents. They also greatly assist care givers in administering injectable medicines to those incapable of performing self-injections.

Performing the necessary insulin injection at the right time and in the right size is essential for managing diabetes, i.e. compliance with the specified insulin regimen is important. In order to make it possible for medical personnel to determine the effectiveness of a prescribed dosage pattern, diabetes patients are encouraged to keep a log of the size and time of each injection. However, such logs are normally kept in handwritten notebooks, and the logged information may not be easily uploaded to a computer for data processing. Furthermore, as only events, which are noted by the patient, are logged, the note book system requires that the patient remembers to log each injection, if the logged information is to have any value in the treatment of the patient's disease. A missing or erroneous record in the log results in a misleading picture of the injection history and thus a misleading basis for the medical personnel's decision making with respect to future medication. Accordingly, it may be desirable to automate the logging of injection information from medication delivery systems.

Though some injection devices integrate this monitoring/acquisition mechanism into the de- vice itself, e.g. as disclosed in US 2009/0318865 and WO 2010/052275, most devices of today are without it. The most widely used devices are purely mechanical devices being either durable or prefilled. The latter devices are to be discarded after being emptied and so inexpensive that it is not cost-effective to build-in electronic data acquisition functionality in the device it-self. Addressing this problem a number of solutions have been proposed which would help a user to generate, collect and distribute data indicative of the use of a given medical device.

For example, US 2015/0005713 describes an electronic supplementary device (or "add-on module") adapted to be releasably attached to a drug delivery device of the pen type. The device includes a camera and is configured to perform optical character recognition (OCR) on captured images from a rotating scale drum visible through a dosage window on the drug delivery device, thereby to determine a dose of medicament that has been dialled into the drug delivery device. The device further comprises a photometer allowing the type of drug delivery device and thus the type of drug to be determined. Similar devices are disclosed in WO 2013/120776 and WO 2014/1 1 1337. A further external device for a pen device is shown in WO 2014/161952. As the external device is designed to detect signals or events originating from the device to which it is attached it is important that the two devices are correctly positioned relatively to each other to ensure proper operation and prevent incorrect measurements. Having regard to the above, it is an object of the present invention to provide devices and methods allowing secure, easy and cost-effective operation of a drug delivery assembly comprising a user-mountable device. It is a specific object of the present invention to provide devices and methods allowing secure, easy and cost-effective mounting of a user-mountable device on a drug delivery device.

DISCLOSURE OF THE INVENTION

In the disclosure of the present invention, embodiments and aspects will be described which will address one or more of the above objects or which will address objects apparent from the below disclosure as well as from the description of exemplary embodiments.

Thus, in a first general aspect of the invention an add-on device configured to be releasably attached to a drug delivery device is provided, the add-on device comprising image sensor circuitry adapted to identify a drug delivery device visual identifier and determine on the basis of image analysis if the add-on device is positioned in a pre-defined mounting position on the drug delivery device. In a first more specific aspect an add-on device configured to be releasably attached to a drug delivery device is provided. Such a drug delivery device comprises a drug reservoir or a compartment for receiving a drug reservoir, drug expelling means comprising a dose setting member allowing a user to set a dose amount of drug to be expelled, an indicator member adapted to rotate relative to the housing during dose setting and/or dose expelling corresponding to an axis of rotation, the amount of rotation corresponding to the dose set and/or amount of drug expelled from a reservoir by the expelling means, the indicator member having an initial rotational position, a housing comprising an opening allowing a user to observe a portion of the indicator member, the opening being surrounded by an edge formed by the housing, a visual identifier having a pre-defined location and orientation, and a pattern arranged circumferentially or helically on the indicator member, the pattern comprising a plurality of indicia, the currently observable indicia indicating to a user the size of a currently set dose amount of drug to be expelled. The add-on device is adapted to determine, when mounted to a drug delivery device housing, an expelled dose amount. The add-on device comprises mounting means adapted to releasably mount the add-on device to the drug delivery device in a predetermined position and orientation, capturing means adapted to capture an image of the visual identifier, a memory in which a reference representation of the visual identifier is stored, the reference representation corresponding to an image captured by the capturing means with the add-on device mounted on the drug delivery device in the predetermined position and orientation, and a processor adapted to perform an image analysis comparing a captured image with the stored reference representation of the visual identifier. The add-on device is adapted to perform a mounting position check comprising the steps of capturing an image, performing an image analysis to determine if the captured image comprises the visual identifier, and indicating an error state if the captured image does not comprise the visual identifier.

By this arrangement an image capture-based add-on device is provided which in a simple and cost-effective way ensures to a high degree that the add-on device has been correctly mounted on a corresponding drug delivery device.

The add-on device may be provided with a mounting switch adapted to detect that the addon device is attached to a drug delivery device, this allowing the image check to be performed when the mounting switch is actuated. In addition to the initial position check when the add-on device is mounted on the pen body, the position may be checked and confirmed each time a picture is captured, this allowing to detect if the add-on device has become loose during operation, e.g. when dropped on the floor. In an exemplary embodiment the stored reference representation of the visual identifier corresponds to at least a portion of the edge surrounding the opening allowing a user to view a portion of the scale drum. In this context "the edge" may comprise a portion of the housing edge per se as well as the portion of the scale drum arranged in the vicinity thereof, the two structures forming a visual identifier. To enhance contrast of the edge the scale drum may be manufactured in e.g. a light colour and the housing in a dark colour.

The drug delivery device pattern may comprise an initial pattern portion observable by the user when the indicator member is positioned in the initial rotational position, the initial pattern portion comprising a check pattern. Correspondingly, in an alternative embodiment the stored reference representation of the visual identifier corresponds to at least a portion of the check pattern on the indicator member, this allowing the add-on device to fully cover the housing. Indeed, this would require that the indicator member is positioned in the initial rota- tional position when the mounting position check is performed.

The image capture means (camera) may be designed to capture an image of only a portion of the indicator member observable in the opening. The processor may be adapted to calculate an expelled dose amount based on determined rotational positions of the indicator member, and store in the memory the calculated dose amount to create a log. The amount of rotation of the indicator member relative to the housing may be determined using image capture from the indicator member and subsequent processor image analysis.

In exemplary embodiments the above-described add-on device is provided in combination with a drug delivery device as described above. In such a drug delivery device the pattern may comprise a code, e.g. an indicia comprising an embedded code in the form of a micro- pattern. The code may form part of the initial image portion. Correspondingly, the capturing means may be adapted to capture an image of the code, with the processor being adapted to extract data from the captured code.

The pattern arranged on the indicator member may form a dosing pattern comprising a plurality of pattern portions, each pattern portion being arranged corresponding to a position on the indicator member. Correspondingly, a reference representation of the dosing pattern may be stored in the memory, each part of the stored dosing pattern being correlated with a rota- tional position of the indicator member, with the processor being adapted to perform a best- match analysis between a captured image and the stored reference representation to thereby determine the rotational position of the indicator member. A plurality of reference dosing pattern representations may be stored in the memory, the add-on device being settable to utilize a given reference dosing pattern representation. For example, the drug delivery device may comprise a drug identifier, the add-on device being adapted to capture the drug identifier and select a thereto corresponding reference dosing pattern representation.

In a second general aspect of the invention an add-on device configured to be releasably attached to a drug delivery device is provided, the drug delivery device comprising a housing with an exterior surface, the add-on device being adapted to determine, when mounted to a drug delivery device housing, an expelled dose amount. The add-on device comprises cap- turing means arranged to capture, with the add-on mounted on the drug delivery device, an image of a portion of the drug delivery device which is not covered by the add-on device.

By this arrangement it is possible for the add-on device to retrieve information provided on the outer surface of a drug delivery device, e.g. on a label, without obscuring the information from the user.

The add-on device of the second general aspect may be provided in combination with a drug delivery device adapted to expel a set dose amount of a drug, the drug delivery device comprising a housing with an exterior surface, the exterior surface comprising a visual identifier. The add-on device comprises mounting means adapted to releasably mount the add-on device to the drug delivery device in a predetermined position and orientation in which it does not cover the visual identifier, the capturing means being arranged to capture, with the addon device mounted on the drug delivery device, an image comprising at least a portion of the visual identifier.

The combination may be adapted to identify a pre-defined visual identifier in a captured image, and enter an operational state when the pre-defined visual identifier is identified. Alternatively, the add-on device may be adapted to identify a plurality of pre-defined visual identifiers in a captured image, and enter a corresponding operational state when the pre-defined visual identifier is identified. The add-on device may be adapted to determine an expelled dose amount when mounted to a drug delivery device housing and when in the operational state.

As used herein, the term "insulin" is meant to encompass any drug-containing flowable medi- cine capable of being 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 which has a blood glucose controlling effect, e.g. human insulin and analogues thereof as well as non- insulins such as GLP-1 and analogues thereof. In the description of exemplary embodiments reference will be made to the use of insulin, however, the described module could also be used to create logs for other types of drug, e.g. growth hormone.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the invention will be described with reference to the drawings, wherein fig. 1A shows a pen device,

fig. 1 B shows the pen device of fig. 1 A with the pen cap removed,

fig. 2 shows in an exploded view the components of the pen device of fig. 1 A,

figs. 3A and 3B show in sectional views an expelling mechanism in two states,

fig. 4 shows a schematic representation of an add-on device,

fig. 5 shows an add-on device mounted on the housing of a drug delivery device,

fig. 6 shows a first scale drum in an initial position,

fig. 7 shows a scale drum reference representation,

fig. 8 shows an image capture from a scale drum,

fig. 9 shows cross correlation of the fig. 8 image portion to the reference representation, fig. 10 shows a matched portion of the reference representation,

fig. 1 1 shows a second scale drum in an initial position, and

fig. 12 shows a system comprising a drug delivery device and an add-on device. In the figures like structures are mainly identified by like reference numerals.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

When in the following terms such as "upper" and "lower", "right" and "left", "horizontal" and "vertical" or similar relative expressions are used, these only refer to the appended figures and not necessarily to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as their relative dimensions are intended to serve illustrative purposes only. When the term member or element is used for a given component it generally indicates that in the described embodiment the component is a unitary component, however, the same member or element may alternatively comprise a number of sub-components just as two or more of the described compo- nents could be provided as unitary components, e.g. manufactured as a single injection moulded part. The term "assembly" does not imply that the described components necessarily can be assembled to provide a unitary or functional assembly during a given assembly procedure but is merely used to describe components grouped together as being functionally more closely related.

Before turning to embodiments of the present invention per se, an example of a prefilled drug delivery will be described, such a device providing the basis for the exemplary embodiments of the present invention. Although the pen-formed drug delivery device 100 shown in figs. 1-3 may represent a "generic" drug delivery device, the actually shown device is a FlexTouch® prefilled drug delivery pen as manufactured and sold by Novo Nordisk A/S, Bagsvaerd, Denmark.

The pen device 100 comprises a cap part 107 and a main part having a proximal body or drive assembly portion with a housing 101 in which a drug expelling mechanism is arranged or integrated, and a distal cartridge holder portion in which a drug-filled transparent cartridge 1 13 with a distal needle-penetrable septum is arranged and retained in place by a nonremovable cartridge holder attached to the proximal portion, the cartridge holder having openings allowing a portion of the cartridge to be inspected as well as distal coupling means 1 15 allowing a needle assembly to be releasably mounted. The cartridge is provided with a piston driven by a piston rod forming part of the expelling mechanism and may for example contain an insulin, GLP-1 or growth hormone formulation. A proximal-most rotatable dose setting member 180 serves to manually set a desired dose of drug shown in display window 102 and which can then be expelled when the button 190 is actuated. The window is surrounded by a chamfered edge portion 109 and a dose pointer 109P. Depending on the type of expelling mechanism embodied in the drug delivery device, the expelling mechanism may comprise a spring as in the shown embodiment which is strained during dose setting and then released to drive the piston rod when the release button is actuated. Alternatively the expelling mechanism may be fully manual in which case the dose member and the actuation button moves proximally during dose setting corresponding to the set dose size, and then is moved distally by the user to expel the set dose, e.g. as in a FlexPen® manufactured and sold by Novo Nordisk A/S. Although fig. 1 shows a drug delivery device of the prefilled type, i.e. it is supplied with a pre- mounted cartridge and is to be discarded when the cartridge has been emptied, in alternative embodiments the drug delivery device may be designed to allow a loaded cartridge to be re- placed, e.g. in the form of a "rear-loaded" drug delivery device in which the cartridge holder is adapted to be removed from the device main portion, or alternatively in the form of a "front- loaded" device in which a cartridge is inserted through a distal opening in the cartridge holder which is non-removable attached to the main part of the device. As the invention relates to electronic circuitry adapted to interact with a drug delivery device, an exemplary embodiment of such a device will be described for better understanding of the invention.

Fig. 2 shows an exploded view of the pen-formed drug delivery device 100 shown in fig. 1 . More specifically, the pen comprises a tubular housing 101 with a window opening 102 and onto which a cartridge holder 1 10 is fixedly mounted, a drug-filled cartridge 1 13 being arranged in the cartridge holder. The cartridge holder is provided with distal coupling means 1 15 allowing a needle assembly 1 16 to be releasable mounted, proximal coupling means in the form of two opposed protrusions 1 1 1 allowing a cap 107 to be releasable mounted cover- ing the cartridge holder and a mounted needle assembly, as well as a protrusion 1 12 preventing the pen from rolling on e.g. a table top. In the housing distal end a nut element 125 is fixedly mounted, the nut element comprising a central threaded bore 126, and in the housing proximal end a spring base member 108 with a central opening is fixedly mounted. A drive system comprises a threaded piston rod 120 having two opposed longitudinal grooves and being received in the nut element threaded bore, a ring-formed piston rod drive element 130 rotationally arranged in the housing, and a ring-formed clutch element 140 which is in rotational engagement with the drive element (see below), the engagement allowing axial movement of the clutch element. The clutch element is provided with outer spline elements 141 adapted to engage corresponding splines 104 (see fig. 3B) on the housing inner surface, this allowing the clutch element to be moved between a rotationally locked proximal position, in which the splines are in engagement, and a rotationally free distal position in which the splines are out of engagement. As just mentioned, in both positions the clutch element is rotationally locked to the drive element. The drive element comprises a central bore with two opposed protrusions 131 in engagement with the grooves on the piston rod whereby rotation of the drive element results in rotation and thereby distal axial movement of the piston rod due to the threaded engagement between the piston rod and the nut element. The drive ele- ment further comprises a pair of opposed circumferentially extending flexible ratchet arms 135 adapted to engage corresponding ratchet teeth 105 arranged on the housing inner surface. The drive element and the clutch element comprise cooperating coupling structures ro- tationally locking them together but allowing the clutch element to be moved axially, this al- lowing the clutch element to be moved axially to its distal position in which it is allowed to rotate, thereby transmitting rotational movement from the dial system (see below) to the drive system. The interaction between the clutch element, the drive element and the housing will be shown and described in greater detail with reference to figs. 3A and 3B. On the piston rod an end-of-content (EOC) member 128 is threadedly mounted and on the distal end a washer 127 is rotationally mounted. The EOC member comprises a pair of opposed radial projections 129 for engagement with the reset tube (see below).

The dial system comprises a ratchet tube 150, a reset tube 160, a scale drum 170 with an outer helically arranged pattern forming a row of dose indicia, a user-operated dial member 180 for setting a dose of drug to be expelled, a release button 190 and a torque spring 155 (see fig. 3). The reset tube is mounted axially locked inside the ratchet tube but is allowed to rotate a few degrees (see below). The reset tube comprises on its inner surface two opposed longitudinal grooves 169 adapted to engage the radial projections 129 of the EOC member, whereby the EOC can be rotated by the reset tube but is allowed to move axially. The clutch element is mounted axially locked on the outer distal end portion of the ratchet tube 150, this providing that the ratchet tube can be moved axially in and out of rotational engagement with the housing via the clutch element. The dial member 180 is mounted axially locked but rotationally free on the housing proximal end, the dial ring being under normal operation rotation- ally locked to the reset tube (see below), whereby rotation of dial ring results in a corresponding rotation of the reset tube and thereby 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 the thereto mounted reset tube. The scale drum 170 is arranged in the circumferential space between the ratchet tube and the housing, the drum be- ing rotationally locked to the ratchet tube via cooperating longitudinal splines 151 , 171 and being in rotational threaded engagement with the inner surface of the housing via cooperating thread structures 103, 173, whereby the row of numerals passes the window opening 102 in the housing when the drum is rotated relative to the housing by the ratchet tube. The torque spring is arranged in the circumferential space between the ratchet tube and the reset tube and is at its proximal end secured to the spring base member 108 and at its distal end to the ratchet tube, whereby the spring is strained when the ratchet tube is rotated relative to the housing by rotation of the dial member. A ratchet mechanism with a flexible ratchet arm 152 is provided between the ratchet tube and the clutch element, the latter being provided with an inner circumferential teeth structures 142, each tooth providing a ratchet stop such that the ratchet tube is held in the position to which it is rotated by a user via the reset tube when a dose is set. In order to allow a set dose to be reduced a ratchet release mechanism 162 is provided on the reset tube and acting on the ratchet tube, this allowing a set dose to be reduced by one or more ratchet increments by turning the dial member in the opposite direction, the release mechanism being actuated when the reset tube is rotated the above- described few degrees relative to the ratchet tube.

Having described the different components of the expelling mechanism and their functional relationship, operation of the mechanism will be described next with reference mainly to figs. 3A and 3B. The pen mechanism can be considered as two interacting systems, a dose system and a dial system, this as described above. During dose setting the dial mechanism rotates and the torsion spring is loaded. The dose mechanism is locked to the housing and cannot move. When the push button is pushed down, the dose mechanism is released from the housing and due to the engagement to the dial system, the torsion spring will now rotate back the dial system to the starting point and rotate the dose system along with it.

The central part of the dose mechanism is the piston rod 120, the actual displacement of the plunger being performed by the piston rod. During dose delivery, the piston rod is rotated by the drive element 130 and due to the threaded interaction with the nut element 125 which is fixed to the housing, the piston rod moves forward in the distal direction. Between the rubber piston and the piston rod, the piston washer 127 is placed which serves as an axial bearing for the rotating piston rod and evens out the pressure on the rubber piston. As the piston rod has a non-circular cross section where the piston rod drive element engages with the piston rod, the drive element is locked rotationally to the piston rod, but free to move along the pis- ton rod axis. Consequently, rotation of the drive element results in a linear forwards movement of the piston. The drive element is provided with small ratchet arms 134 which prevent the drive element from rotating clockwise (seen from the push button end). Due to the engagement with the drive element, the piston rod can thus only move forwards. During dose delivery, the drive element rotates anti-clockwise and the ratchet arms 135 provide the user with small clicks due to the engagement with the ratchet teeth 105, e.g. one click per unit of insulin expelled. Turning to the dial system, the dose is set and reset by turning the dial member 180. When turning the dial, the reset tube 160, the EOC member 128, the ratchet tube 150 and the scale drum 170 all turn with it. As the ratchet tube is connected to the distal end of the torque spring 155, the spring is loaded. During dose setting, the arm 152 of the ratchet performs a dial click for each unit dialled due to the interaction with the inner teeth structure 142 of the clutch element. In the shown embodiment the clutch element is provided with 24 ratchet stops providing 24 clicks (increments) for a full 360 degrees rotation relative to the housing. The spring is preloaded during assembly which enables the mechanism to deliver both small and large doses within an acceptable speed interval. As the scale drum is rotationally engaged with the ratchet tube, but movable in the axial direction and the scale drum is in threaded engagement with the housing, the scale drum will move in a helical pattern when the dial system is turned, the number corresponding to the set dose being shown in the housing window 102.

The ratchet 152, 142 between the ratchet tube and the clutch element 140 prevents the spring from turning back the parts. During resetting, the reset tube moves the ratchet arm 152, thereby releasing the ratchet click by click, one click corresponding to one unit IU of insulin in the described embodiment. More specifically, when the dial member is turned clock- wise, the reset tube simply rotates the ratchet tube allowing the arm of the ratchet to freely interact with the teeth structures 142 in the clutch element. When the dial member is turned counter-clockwise, the reset tube interacts directly with the ratchet click arm forcing the click arm towards the centre of the pen away from the teeth in the clutch, thus allowing the click arm on the ratchet to move "one click" backwards due to torque caused by the loaded spring.

To deliver a set dose, the push button 190 is pushed in the distal direction by the user as shown in fig. 3B. The reset tube 160 decouples from the dial member and subsequently the clutch element 140 disengages the housing splines 104. Now the dial mechanism returns to "zero" together with the drive element 130, this leading to a dose of drug being expelled. It is possible to stop and start a dose at any time by releasing or pushing the push button at any time during drug delivery. A dose of less than 5 IU normally cannot be paused, since the rubber piston is compressed very quickly leading to a compression of the rubber piston and subsequently delivery of insulin when the piston returns to the original dimensions. The EOC feature prevents the user from setting a larger dose than left in the cartridge. The EOC member 128 is rotationally locked to the reset tube, which makes the EOC member ro- tate during dose setting, resetting and dose delivery, during which it can be moved axially back and forth following the thread of the piston rod. When it reaches the proximal end of the piston rod a stop is provided, this preventing all the connected parts, including the dial member, from being rotated further in the dose setting direction, i.e. the now set dose corre- sponds to the remaining drug content in the cartridge.

The scale drum 170 is provided with a distal stop surface 174 adapted to engage a corresponding stop surface on the housing inner surface, this providing a maximum dose stop for the scale drum preventing all the connected parts, including the dial member, from being ro- tated further in the dose setting direction. In the shown embodiment the maximum dose is set to 80 IU. Correspondingly, the scale drum is provided with a proximal stop surface adapted to engage a corresponding stop surface on the spring base member, this preventing all the connected parts, including the dial member, from being rotated further in the dose expelling direction, thereby providing a "zero" stop for the entire expelling mechanism.

To prevent accidental over-dosage in case something should fail in the dialling mechanism allowing the scale drum to move beyond its zero-position, the EOC member serves to provide a security system. More specifically, in an initial state with a full cartridge the EOC member is positioned in a distal-most axial position in contact with the drive element. After a given dose has been expelled the EOC member will again be positioned in contact with the drive element. Correspondingly, the EOC member will lock against the drive element in case the mechanism tries to deliver a dose beyond the zero-position. Due to tolerances and flexibility of the different parts of the mechanism the EOC will travel a short distance allowing a small "over dose" of drug to be expelled, e.g. 3-5 IU of insulin.

The expelling mechanism further comprises an end-of-dose (EOD) click feature providing a distinct feedback at the end of an expelled dose informing the user that the full amount of drug has been expelled. More specifically, the EOD function is made by the interaction between the spring base and the scale drum. When the scale drum returns to zero, a small click arm 106 on the spring base is forced backwards by the progressing scale drum. Just before "zero" the arm is released and the arm hits a countersunk surface on the scale drum.

The shown mechanism is further provided with a torque limiter in order to protect the mechanism from overload applied by the user via the dial member. This feature is provided by the interface between the dial member and the reset tube which as described above are rota- tionally locked to each other. More specifically, the dial member is provided with a circumfer- ential inner teeth structure 181 engaging a number of corresponding teeth arranged on a flexible carrier portion 161 of the reset tube. The reset tube teeth are designed to transmit a torque of a given specified maximum size, e.g. 150-300 Nmm, above which the flexible carrier portion and the teeth will bend inwards and make the dial member turn without rotating the rest of the dial mechanism. Thus, the mechanism inside the pen cannot be stressed at a higher load than the torque limiter transmits through the teeth.

Having described the working principles of a mechanical drug delivery device, embodiments of the present invention will be described.

Fig. 4 shows a schematic representation of an add-on device 200 in a state where it has been mounted on the housing 101 of a drug delivery device 100 of the above-described pen type. The add-on device is adapted to determine the amount of drug expelled from the drug delivery device during an expelling event, i.e. the subcutaneous injection of a dose of drug. In the shown embodiment determination of an expelled dose of drug is based on determination of scale drum position at the beginning and at the end of the expelling event. To determine the rotational position of the scale drum the dose numerals as seen in the display window 102 may be captured and used, this allowing an unmodified pen device to be used. Actual determination of scale drum position may be performed using e.g. template matching or opti- cal character recognition (OCR). Alternatively a dedicated code pattern may be provided on the scale drum as disclosed in e.g. WO 2013/004843.

The add-on device comprises a housing 201 in which are arranged electronic circuitry 210 powered by an energy source 21 1. The electronic circuitry is connected to and interacts with a light source 220 adapted to illuminate at least a portion of the scale drum 170 seen in the window 102, a capture (camera) device 221 adapted to capture image data from the scale drum, a mounting switch 230 adapted to engage the pen housing 101 , a display 240 and user input means in the form of one or more buttons 250. In the shown embodiment a further activity switch 235 adapted to engage the dose setting member 180 is provided. Alternatively or in addition an acoustic sensor may be provided to detect specific sounds generated by the expelling mechanism during dose setting and dose expelling. The electronic circuitry 210 will typically comprise controller means, e.g. in the form of a generic microprocessor or an ASIC, ROM and RAM memory providing storage for imbedded program code and data, a display controller and a wireless transmitter/receiver. The add-on device further comprises mounting means (not shown) adapted to releasably mount and securely hold and position the add-on device on the pen housing. For the shown embodiment the add-on device covers the display window for which reason the current dose size shown in the display window has to be captured and displayed on the electronic display 240. Alternatively, the add-on device may be designed to allow the user to view the display window.

The coupling means may be in the form of e.g. a bore allowing the add-on device to slide in place on the pen body, flexible gripping structures allowing the add-on device to be mounted in a perpendicular direction, or locking means which has to be operated by the user, e.g. a hinged latch member or a sliding member. In order to securely hold and position the add-on device on the pen housing the add-on device may be provided with positioning means adapted to engage a corresponding positioning structure on the pen body. The positioning structure may be in the form of an existing structure provided for a different purpose, e.g. the window opening, or a specific mounting structure, e.g. one or more indents provided on the pen body.

As scale drum position and thus dose size determination is based on image capturing and subsequent processing of the captured image data, it is important that the add-on device is correctly positioned in its intended operational position on the drug delivery device. In addition to the above-described coupling and positioning means designed to provide a user- recognisable engagement, e.g. by an ensuring "click", the add-on device 200 is provided with a mounting switch 230, e.g. a mechanical micro switch, which is actuated from an off-state to an on-state when the add-on device is mounted on the pen housing.

Fig. 5 shows an add-on device 300 in a state where it has been mounted on the housing 101 of a drug delivery device of the above-described pen type. The device as shown is intended primarily to illustrate how an add-on device can be positioned on a pen device allowing a camera device (not shown) to capture images of the scale drum as presented in the housing display window 102. Correspondingly, portions of the add-on device have been removed.

The add-on device 300 as shown comprises a housing 301 with a cavity 305 having a lower opening adapted to be positioned over and in alignment with the housing display window 102. The opening is surrounded by a positioning structure in the form of a downwardly pro- truding lip portion 306 adapted to precisely engage and grip the chamfered edge portion 109 of the display opening, this ensuring that the add-on device can be correctly positioned on the pen housing. As will be explained in greater detail below the lip portion does not fully cover the edge portion surrounding the window opening. The add-on device further comprises a user-operatable locking member 360. The locking member may be designed to prevent locking until the add-on device is correctly positioned on the pen housing with the lip portion seated in the housing display opening. The mounting switch may be arranged to be actuated when the locking member is actuated to its fully closed position.

In addition to these positioning and detection means a further positioning check feature is incorporated in the shown add-on device in accordance with an aspect of the invention. More specifically, when the mounting switch is actuated the add-on device will perform a camera- based position check. As mentioned above, the add-on device does not fully cover the housing window edge surrounding the visible portion of the scale drum. Correspondingly, such an edge portion could be used as a visual identifier to provide a position check structure (or check pattern) to check the position of the camera device and thus the mounting position of the add-on device on the pen device, e.g. by template-matching a captured initial image with a stored representation of the check pattern. To enhance contrast of the edge the scale drum may be manufactured in a light colour and the housing in a dark colour, e.g. in white respectively dark blue as used for a FlexTouch from Novo Nordisk A/S. Alternatively or in addition an associated window structure such as the pointer 109P could be used as a check struc- ture. As a further alternative or in addition the visual identifier could incorporate markings in one or more colours. The visual identifier may be arranged to in a way where the image focusing and possible shadow and parallax errors can be handled effectively by the image capturing system. When the correct positioning has been verified the captured image may be used to determine scale drum position and display the corresponding dose value on the elec- ironically controlled display.

In addition to the initial position check when the add-on device is mounted on the pen body, the position may be checked and confirmed each time a picture is capture, this allowing to detect if the add-on device has become loose during operation, e.g. when dropped on the floor.

In an alternative embodiment the add-on device may be designed to fully cover the pen housing edge portion. Based on the fact that the scale drum can be arranged in a well- defined initial zero position relative to the pen housing the indicia provided on the scale drum surface corresponding to the initial position, i.e. the initial pattern, will also be arranged in a well-defined initial position. As shown in fig. 6, apart from the "0" indicia on the scale drum 170 in the initial position most pen devices have additional unique indicia markings indicating the zero position, e.g. a pair of opposed arrows 175. The initial pattern or a portion thereof can then be used to define a check pattern. This combination of a well-defined scale drum initial position and a corresponding unique check pattern can be used to precisely check the position of the camera device and thus the mounting position of the add-on device on the pen device, e.g. by template-matching a captured image with a stored representation of the check pattern.

The above concept may be implemented in a number of ways. For example, the instructions may specify that the user should ensure that the dose is set to zero before mounting the addon device. When the add-on device is mounted on the pen housing the mounting switch will be actuated from the off- to the on-state and the controller may then perform an initial position test by capturing an image of the scale drum and perform a template-match with the stored image of the zero position. If the two images correspond sufficiently to each other an ΌΚ" or similar message may be shown on the display. If the two images do not correspond to each other an error message may be displayed, e.g. like "check mounting" or "set dose to zero". Indeed, in case the pen window cannot be seen the user has to be aware that the zero position corresponds to the dose dial being turned e.g. fully counter clock-wise. After having adjusted the dose setting the user may have to mount the add-on device again or may have to actuate the input button 250.

Alternatively the mounting check may be less automated, e.g. after the mounting switch has been activated the display may show "dose set to zero?" which then has to be confirmed by actuating the input button 250.

The above-described mounting check may be performed each time the add-on device is powered on. Power-on may be manual, e.g. the input button is actuated prior to setting a dose, or it may be based on automatic detection of a dose being set. In the shown embodiment the latter is achieved by a switch 235 engaging the fine line gripping pattern on the dose setting dial 180. When the dial starts rotating this is registered by the switch and the add-on device is powered on.

An addition to the above-described position check, the camera is controlled to capture images during operation of the pen device. In the shown embodiment the currently set dose can- not be seen in the pen display window 102 but instead the electronic display 240 is controlled to display the corresponding value. Control of the display may be based on e.g. template- matching, OCR, pixel-to-pixel image transfer, counting of indices, reading of embedded codes or mechanical detection. When it is detected by image analysis or switch input, e.g. from the activity switch 235, that the scale drum does no longer move the set dose size is captured and stored. If the dose size is adjusted a new set dose value is stored. When the user actuates the release button 190 the spring-driven expelling mechanism rotates the scale drum backwards with a relatively well-defined speed which can be detected by the camera used to determine that an expelling event and not a dose reset event is taking place. When the dose has been fully expelled or the expelling is paused by the user, this is correspondingly detected by use of the camera. If the zero position has been reached, e.g. detected as de- scribed above, the stored dose value becomes the expelled dose size which can then be stored in the memory together with a time stamp to create a log entry. If the zero position has not been reached the add-on device may be programmed to allow the remaining dose to be expelled within a pre-set amount of time. If the dose is not fully expelled within this time frame either the partial expelled dose may be calculated or a "no dose captured" message may be shown on the display.

As mentioned above, the scale drum position may be determined by template-matching with a stored representation of the entire scale drum surface image. Correspondingly, fig. 7 illustrates a template image 215 of the whole scale-drum, obtained by concatenating parts of successive images from a film where the scale-drum moves from position 80 to position 0. The template image is used as a reference when to determine the position of a specific image. The pixel position (horizontal axis in the above figure) corresponds to the drum position (in degrees, IU or other units). As an example, fig. 8 shows an image 216 of the scale-drum window where the position corresponds to 10 IU, the rectangle 217 illustrating the area that is used for position detection. Fig. 9 then shows the cross correlation of the rectangle image portion to the reference 1 15 as a function 1 18 of pixel position. Searching for the peak reveals a best match at pixel position 341 , corresponding to the cut 1 19 from the reference image as shown in fig. 10. The reference image at this pixel offset was taken when the scale drum was in a position 9.8 IU.

Prefilled drug delivery devices, e.g. of the type described above with reference to figs. 1-3, will often be used as a platform device to be used in combination with different types of drugs, e.g. different types of drugs per se or the same type of drug in different concentrations as is the case for the FlexTouch and FlexPro family of devices from Novo Nordisk A/S. For different concentrations of the same drug the scale drum will typically be different just as for different types of drug the units of measurement may be different, e.g. "mg" for GLP-1 drugs instead of "IU" for insulin, resulting in a different scale drum. Correspondingly, if an add-on device can be mounted on drug delivery devices utilized for different types or concentrations of drug it is necessary that a given add-on device can only be used in combination with the drug for which it is intended (e.g. fast or long acting insulin) or, alternatively, adapt itself to the actual drug or concentration if necessary.

As disclosed in e.g. WO 2013/050535 a drug delivery device may be provided with an identifier allowing a corresponding add-on dose logging device to identify the type of device and thus the type of drug. The identifier may e.g. be a colour or a code.

Thus, according to a further aspect of the invention an identifier concept is provided which in a simple, user friendly and cost-effective way allows a camera-based add-on device to identify a given type of drug delivery device, the drug delivery device and the add-on device being provided with a corresponding identifier and means for capturing the information imbedded therein.

Turning to fig. 1 1 the initial or zero position image portion of an alternative scale drum 470 is shown through a housing display opening 102. As the scale drum 470 shown in fig. 6 the initial pattern portion comprises indicia in the form of a "0", a pair of opposed arrow pointers 475, a first increment line pointer 476 for 1 IU and a second increment line pointer 477 for 2 IU. The first increment line pointer 476 is provided with a micro-pattern in form of a 2D barcode from which the embedded data can be retrieved when a captured image is processed. As the code is embedded in a portion of the scale drum image arranged visible when the scale drum is in the initial zero position, data capture can be performed as part of the above- described mounting check. Alternatively, the code may be embedded in any of the increment line pointers.

The 2D barcode can be printed on the scale drum member using the same printing technology as used for the other indicia, e.g. laser printing or ink-jet printing, and will hardly be recog- nisable to the user during normal use of the device. Alternatively, the code may not be "hidden" but printed as an additional image component, e.g. in the form of a 2D barcode.

If the embedded code is formed in a portion of the initial pattern portion which forms a check pattern then indeed the image analysis has to take the potential variability provided by the code patterns into account. The embedded code may in addition to basic information such as the type of drug and the concentration also contain inform in respect of e.g. expiry date and batch code. A given addon device may be adapted to be used with only a single type of drug. If the embedded code is formed as part of the initial pattern it will require the scale drum to be in the zero position in order to allow the add-on device to determine the specific drug and concentration.

Correspondingly, if the code for a specific drug and concentration is not identified the add-on device will show or indicate an error state or ask for the scale drum to be set to zero. Alternatively, e.g. when the add-on device is mounted on a pen device, in which a dose of drug has already been set, the add-on device may be designed to register when such a dose is expelled and then subsequently determine the type of pen device when the scale drum returns to zero.

If a given add-on device is adapted to be used with two or more types of drug, the code will allow the add-on device to choose the corresponding operational mode. For example, if determination of scale drum position is based on image matching the corresponding scale drum template image of the two or more stored template images will be selected.

Fig. 12 shows a system adapted to implement another aspect of the present invention, the system comprising a pre-filled drug delivery pen device 500 of the type described with reference to figs. 1 and 2 above, and an add-on logging device 600 adapted to be mounted on the pen device housing 801.

The pen device housing 501 is provided with a label 502 which in the shown embodiment comprises a visual identifier 505 in the form of a barcode, e.g. a linear barcode or as shown a matrix (2D) barcode. The label may be a standard label comprising such a barcode or the label may be optimized for the present invention. The add-on device 600 is adapted to be mounted on the pen device in a pre-defined rotational and axial position and comprises a mounting sensor adapted to detect that the add-on device has been correctly mounted. In the shown embodiment the add-on device is similar to the type shown in fig. 4 and thus adapted to be mounted proximally on the pen body covering the display opening. On the dis- tally facing portion the add-on device is provided with a camera 605 arranged to capture an image of the pen housing surface comprising the visual identifier 505. The add-on device is adapted to identify a pre-defined visual identifier in a captured image, and enter an operational state when the pre-defined visual identifier is identified. Alternative- ly, the add-on device may be adapted to identify a plurality of pre-defined visual identifiers in a captured image, and enter a corresponding operational state when the pre-defined visual identifier is identified. The add-on device is adapted to determine an expelled dose amount when mounted to a drug delivery device housing and when in the operational state.

In the above description of exemplary embodiments, the different structures and means providing the described functionality for the different components have been described to a degree to which the concept of the present invention will be apparent to the skilled reader. The detailed construction and specification for the different components are considered the object of a normal design procedure performed by the skilled person along the lines set out in the present specification.

Claims

1. An add-on device configured to be releasably attached to a drug delivery device, the drug delivery device comprising: - a drug reservoir or a compartment for receiving a drug reservoir,

drug expelling means comprising a dose setting member allowing a user to set a dose amount of drug to be expelled,

an indicator member adapted to rotate relative to the housing during dose setting and/or dose expelling corresponding to an axis of rotation, the amount of rotation corre- sponding to the dose set and/or amount of drug expelled from a reservoir by the expelling means, the indicator member having an initial rotational position,

a housing comprising an opening allowing a user to observe a portion of the indicator member, the opening being surrounded by an edge formed by the housing,

a visual identifier having a pre-defined location and orientation,

- a pattern arranged circumferentially or helically on the indicator member, the pattern comprising a plurality of indicia, the currently observable indicia indicating to a user the size of a currently set dose amount of drug to be expelled, the add-on device being adapted to determine, when mounted to a drug delivery device housing, an expelled dose amount, the add-on device comprising: mounting means adapted to releasably mount the add-on device to the drug delivery device in a predetermined position and orientation,

capturing means adapted to capture an image of the visual identifier,

- a memory in which a reference representation of the visual identifier is stored, the reference representation corresponding to an image captured by the capturing means with the add-on device mounted on the drug delivery device in the predetermined position and orientation, and

a processor adapted to perform an image analysis comparing a captured image with the stored reference representation of the visual identifier, wherein the add-on device is adapted to perform a mounting position check comprising: capture an image,

perform an image analysis to determine if the captured image comprises the visual identifier, and

indicate an error state if the captured image does not comprise the visual identifier.

2. An add-on device as in claim 1 , further comprising:

a mounting switch adapted to detect that the add-on device is attached to a drug delivery device,

- wherein the mounting position check is performed when the mounting switch is actuated.

3. An add-on device as in claim 1 or 2, wherein the stored reference representation of the visual identifier corresponds to at least a portion of the opening edge (109) or an associ- ated pointer structure (109P).

4. An add-on device as in claim 1 or 2, wherein:

the pattern comprises an initial pattern portion observable by the user when the indicator member is positioned in the initial rotational position, the initial pattern portion compris- ing a check pattern, and

the stored reference representation of the visual identifier corresponds to at least a portion of the check pattern.

5. An add-on device as in any of claims 1-4, wherein only an image of a portion of the indicator member observable in the opening is captured.

6. An add-on device as in any of claims 1-5, wherein the processor is adapted to:

calculate an expelled dose amount based on determined rotational positions of the indicator member, and

- store in the memory the calculated dose amount to create a log.

7. An add-on device as in any of claims 1-6, wherein the amount of rotation of the indicator member relative to the housing is determined using image capture from the indicator member and subsequent processor image analysis.

8. An add-on device as in claim 7, wherein an image position check is performed when an image is captured for position determination.

9. An add-on device as in any of claims 1-8 in combination with a drug delivery device, the drug delivery device comprising: a drug reservoir or a compartment for receiving a drug reservoir,

drug expelling means comprising a dose setting member allowing a user to set a dose amount of drug to be expelled,

an indicator member adapted to rotate relative to the housing during dose setting and/or dose expelling corresponding to an axis of rotation, the amount of rotation corresponding to the dose set and/or amount of drug expelled from a reservoir by the expelling means, the indicator member having an initial rotational position,

a housing comprising an opening allowing a user to observe a portion of the indicator member, the opening being surrounded by an edge formed by the housing,

- a visual identifier having a pre-defined location and orientation,

a pattern arranged circumferentially or helically on the indicator member, the pattern comprising a plurality of indicia, the currently observable indicia indicating to a user the size of a currently set dose amount of drug to be expelled,

10. A combination as in claim 9, wherein:

the pattern comprises an embedded code,

the capturing means is adapted to capture an image of the code, and

the processor is adapted to extract data from the captured code.

1 1 . A combination as in claim 10, wherein the embedded code is comprised in the initial pattern portion.

12. A combination as in claim 10 or 1 1 , wherein the pattern comprises an indicia comprising the embedded code in the form of a micro-pattern.

13. A combination as in any of claims 9-12, wherein: the pattern arranged on the indicator member forms a dosing pattern comprising a plurality of pattern portions, each pattern portion being arranged corresponding to a position on the indicator member,

a reference representation of the dosing pattern is stored in the memory, each part of the stored dosing pattern being correlated with a rotational position of the indicator member, and

the processor is adapted to perform a best-match analysis between a captured im- age and the stored reference representation to thereby determine the rotational position of the indicator member.

14. A combination as in claim 13, wherein a plurality of reference dosing pattern representations are stored in the memory, the add-on device being settable to utilize a given reference dosing pattern representation.

15. A combination as in claim 14, wherein the drug delivery device comprises a drug identifier, the add-on device being adapted to capture the drug identifier and select a thereto corresponding reference dosing pattern representation.

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