DRUG DELIVERY DEVICE WITH ELECTRONIC SYSTEM

Abstract

An electronic system for a drug delivery device is disclosed. The electronic system comprises a dose setting and drive mechanism. The dose setting and drive mechanism comprises a first member and a button module. The dose setting and drive mechanism is configured such that, at least in the dose delivery operation and/or in the dose setting operation, the first member moves relative to the button module. The electronic system has at least a first low power consumption state and a second high power consumption state. A rotation and/or axial movement of the button module relative to the first member generates a movement component of the at least one switch member relative to the button module and the first member, which triggers switching between the first low power consumption state and the second high power consumption state.

Claims

1-15. (canceled)

16. An electronic system for a drug delivery device, the electronic system comprising: a dose setting and drive mechanism configured to perform (i) a dose setting operation for setting a dose to be delivered by the drug delivery device and (ii) a dose delivery operation for delivering the set dose, the dose setting and drive mechanism comprising a first member; and a button module comprising an electronic control unit connected to at least a rotary sensor, a communication unit, and a use detection unit, the communication unit being configured to communicate with another device, the use detection unit having multiple switches comprising a rotational switch and an axial switch, wherein the electronic control unit is configured to control an operation of the electronic system, and has a distal surface facing towards the dose setting and drive mechanism, wherein the button module and the dose setting and drive mechanism are configured such that the first member rotates relative to the button module during the dose delivery operation but does not rotate relative to the button module during the dose setting operation, and the button module moves axially relative to the first member during a transition from the dose setting operation to the dose delivery operation, or when the button module is pressed in a dialled condition of a zero unit dose, wherein the switches comprise at least four contact pads at the distal surface of the electronic control unit and at least two switch members each having at least two corresponding switch contacts defining a first electrical state when one of the switch contacts is not connected to a corresponding contact pad, and a second electrical state when both contact pads of the respective switch members are connected to the corresponding switch contacts, wherein a rotation of the first member relative to the button module generates a movement component of a switch member of the rotational switch relative to the button module and the first member, thereby switching between the first electrical state and the second electrical state which in turn triggers activation of the rotary sensor, wherein an axial movement of the button module relative to the first member generates a movement component of a switch member of the axial switch relative to the button module and the first member, thereby switching between the first and the second electrical states which in turn activates the communication unit.

17. The electronic system according to claim 16, wherein a least one of (i) the movement component generated as a result of the rotation of the first member relative to the button module or (ii) the movement component generated as a result of an axial movement of the button module relative to the first member is an axial movement relative to the button module and the first member.

18. The electronic system according to claim 16, wherein the rotary sensor comprises at least one of a light source with a corresponding optical sensor, an electrical sliding contact, a mechanical switching arrangement, or a magnetic sensor.

19. The electronic system according to claim 16, wherein each switch member comprises at least a respective first elastically deformable switch contact abutting or connected to one of the contact pads, and a respective second elastically deformable switch contact arranged axially offset to the respective first elastically deformable switch contact and spaced from one of the other contact pads.

20. The electronic system according to claim 16, wherein the axial switch is operable by a relative axial displacement of the button module and the first member, wherein the axial switch comprises a switch chassis constraining a switch contact strip comprising elastically deformable switch contacts.

21. The electronic system according to claim 20, wherein the switch contact strip is substantially U-shaped with two legs each forming one of the elastically deformable switch contacts, and wherein the switch contact strip is arranged such that the legs are axially offset to each other.

22. The electronic system according to claim 20, wherein the switch chassis is interposed between a module chassis of the button module and the electronic control unit with an axially extending protrusion of the switch chassis extending towards the first member, such that when the button module moves axially towards the first member, one of the switch contacts is brought into abutment with one of the contact pads.

23. The electronic system according to claim 16, wherein the rotational switch is operable by a relative rotation of the button module and the first member, wherein the rotational switch comprises a rocker constraining a switch contact pressing comprising elastically deformable switch contacts, wherein the rocker is pivotably guided in the button module.

24. The electronic system according to claim 23, wherein the switch contact pressing comprises two contact arms, wherein tips of the two contact arms are axially offset to each other and form elastically deformable switch contacts.

25. The electronic system according to claim 23, wherein the rocker is interposed between a module chassis of the button module and the electronic control unit with a radially extending protrusion of the rocker extending towards the first member, such that when the button module rotates relative to the first member a radial motion of the protrusion of the rocker results in an axial motion at the switch contacts, and results in one of the switch contacts to be brought into abutment with one of the contact pads.

26. The electronic system according to claim 16, wherein the first member is a dial sleeve assembly or a member axially and/or rotationally locked thereto, wherein the first member is rotatable relative to a housing of the dose setting and drive mechanism at least in the dose setting operation, and wherein the button module is axially displaceable relative to the first member and rotationally constrained to the housing at least in the dose delivery operation.

27. The electronic system according to claim 26, wherein the first member is rotatable relative to the housing of the does setting and drive mechanism along a helical path.

28. The electronic system according to claim 25, wherein a switch chassis of the axial switch is interposed between a module chassis of the button module and the electronic control unit with an axially extending protrusion of the switch chassis extending towards the first member, such that when the button module moves axially towards the first member, one of the switch contacts is brought into abutment with one of the contact pads, and wherein the first member comprises an encoder ring having a radial ratchet profile for interaction with the radially extending protrusion of the rocker of the rotational switch, and a proximally facing, ring-shaped running face for interaction with the axially extending protrusion of the switch chassis of the axial switch.

29. The electronic system according to claim 16, wherein the rotary sensor is in a sleeping mode in a first low power consumption state and is configured to be activated to enter a second high power consumption state, with the electronic system being configured such that it is switched from the first low power consumption state into the second high power consumption state by the electronic control unit in response to a signal of the rotational switch, thereby inducing the rotary sensor to initiate a motion detection.

30. The electronic system according to claim 29, wherein the electronic control unit is adapted to switch the rotary sensor into the first low power consumption state in response to a signal indicating that the axial switch is switched from a first electrical state of the axial switch to a second electrical state of the axial switch.

31. The electronic system according to claim 30, wherein the first electrical state of the axial switch is an electrically open circuit state, and the second electrical state of the axial switch is an electrically closed circuit state of the axial switch.

32. The electronic system according to claim 29, wherein the electronic control unit is adapted to generate a failure indicating signal when a difference in rotational positon is detected by the rotary sensor without detection of a state change of the rotational switch, or when a rotational switch state change is received with no corresponding axial switch state change.

33. The electronic system according to claim 16, wherein the communication unit is in a sleeping mode in a first low power consumption state and is configured to be activated to enter a second high power consumption state.

34. The electronic system according to claim 33, wherein the communication unit comprises a wireless communication interface for communicating with another device, with the electronic system being configured such that it is switched from the first low power consumption state into the second high power consumption state by the electronic control unit in response to a signal of the axial switch, thereby inducing the communication unit to initiate a manual synchronization and/or a pairing with another device.

35. A drug delivery device comprising: a electronic system comprising a dose setting and drive mechanism configured to perform (i) a dose setting operation for setting a dose to be delivered by the drug delivery device and (ii) a dose delivery operation for delivering the set dose, the dose setting and drive mechanism comprising a first member; and a button module comprising an electronic control unit connected to at least a rotary sensor, a communication unit, and a use detection unit, the communication unit being configured to communicate with another device, the use detection unit having multiple switches comprising a rotational switch and an axial switch, wherein the electronic control unit is configured to control an operation of the electronic system, and has a distal surface facing towards the dose setting and drive mechanism, wherein the button module and the dose setting and drive mechanism are configured such that the first member rotates relative to the button module during the dose delivery operation but does not rotate relative to the button module during the dose setting operation, and the button module moves axially relative to the first member during a transition from the dose setting operation to the dose delivery operation, or when the button module is pressed in a dialled condition of zero unit dose, wherein the switches comprise at least four contact pads at the distal surface of the electronic control unit and at least two switch members each having at least two corresponding switch contacts defining a first electrical state when one of the switch contacts is not connected to a corresponding contact pad, and a second electrical state when both contact pads of the respective switch members are connected to the corresponding switch contacts, wherein a rotation of the first member relative to the button module generates a movement component of a switch member of the rotational switch relative to the button module and the first member, thereby switching between the first and the second electrical states which in turn triggers activation of the rotary sensor, wherein an axial movement of the button module relative to the first member generates a movement component of a switch member of the axial switch relative to the button module and the first member, thereby switching between the first and the second electrical states which in turn activates the communication unit; and a container receptacle that is permanently or releasably connected to the dose setting and drive mechanism, and adapted to receive a container containing a medicament.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0064] Non-limiting, exemplary embodiments of the disclosure will now be described with reference to the accompanying drawings, in which:

[0065] FIG. 1 shows an embodiment of a drug delivery device;

[0066] FIG. 2a shows a perspective view of an axial switch sub-assembly according to an embodiment of the present disclosure;

[0067] FIG. 2b shows a perspective view of the axial switch sub-assembly during assembly into a module chassis;

[0068] FIG. 2c shows a sectional view of the axial switch sub-assembly during assembly into a module chassis;

[0069] FIG. 2d shows a sectional view of the axial switch sub-assembly during a further assembly step;

[0070] FIG. 2e shows a sectional view of the axial switch sub-assembly and a PCB after assembly into a module chassis;

[0071] FIG. 2f shows a sectional view of the axial switch during use;

[0072] FIG. 2g shows a perspective view of the axial switch during use;

[0073] FIG. 2h shows the contact pad locations on the underside of the PCB;

[0074] FIG. 3a shows a perspective view of a rocker sub-assembly according to an embodiment of the present disclosure;

[0075] FIG. 3b shows a sectional view of the rocker sub-assembly during assembly into a module chassis;

[0076] FIG. 3c shows a bottom view of the rocker sub-assembly during assembly;

[0077] FIG. 3d shows a sectional view of the rocker sub-assembly and a PCB after assembly into a module chassis;

[0078] FIG. 3e shows a top view of the rocker sub-assembly;

[0079] FIG. 3f shows a sectional view of the rocker in a first use position;

[0080] FIG. 3g shows a sectional view of the rocker in a second use position; and

[0081] FIG. 4 illustrates schematically an embodiment of an electronic system for a drug delivery device.

[0082] In the figures, identical elements, identically acting elements or elements of the same kind may be provided with the same reference numerals.

DETAILED DESCRIPTION

[0083] In the following, some embodiments will be described with reference to an insulin injection device. The present disclosure is however not limited to such application and may equally well be deployed with injection devices that are configured to eject other medicaments or drug delivery devices in general, preferably pen-type devices and/or injection devices.

[0084] Embodiments are provided in relation to injection devices, in particular to variable dose injection devices, which record and/or track data on doses delivered thereby. These data may include the size of the selected dose and/or the size of the actually delivered dose, the time and date of administration, the duration of the administration and the like. Features described herein include the arrangement of sensing elements and power management techniques (e.g. to facilitate small batteries and/or to enable efficient power usage).

[0085] Certain embodiments in this document are illustrated with respect to the injection device disclosed in EP 2 890 435 where an injection button and grip (dose setting member or dose setter) are combined. The injection button may provide the user interface member for initiating and/or performing a dose delivery operation of the drug delivery device. The grip or knob may provide the user interface member for initiating and/or performing a dose setting operation. Both devices are of the dial extension type, i.e. their length increases during dose setting. Other injection devices with the same kinematical behaviour of the dial extension and button during dose setting and dose expelling operational mode are known as, for example, the Kwikpen® device marketed by Eli Lilly and the Novopen® 4 device marketed by Novo Nordisk. An application of the general principles to these devices therefore appears straightforward and further explanations will be omitted. However, the general principles of the present disclosure are not limited to that kinematical behaviour. Certain other embodiments may be conceived for application to Sanofi's SoloSTAR® injection device where there are separate injection button and grip components/dose setting members. Thus, there may be two separate user interface members, one for the dose setting operation and one for the dose delivery operation.

[0086] “Distal” is used herein to specify directions, ends or surfaces which are arranged or are to be arranged to face or point towards a dispensing end of the drug delivery device or components thereof and/or point away from, are to be arranged to face away from or face away from the proximal end. On the other hand, “proximal” is used to specify directions, ends or surfaces which are arranged or are to be arranged to face away from or point away from the dispensing end and/or from the distal end of the drug delivery device or components thereof. The distal end may be the end closest to the dispensing and/or furthest away from the proximal end and the proximal end may be the end furthest away from the dispensing end. A proximal surface may face away from the distal end and/or towards the proximal end. A distal surface may face towards the distal end and/or away from the proximal end. The dispensing end may be the needle end where a needle unit is or is to be mounted to the device, for example.

[0087] FIG. 1 is an exploded view of a medicament delivery device or drug delivery device. In this example, the medicament delivery device is an injection device 1, e.g. a pen-type injector, such an injection pen disclosed in EP 2 890 435.

[0088] The injection device 1 of FIG. 1 is an injection pen that comprises a housing 10 and contains a container 14, e.g. an insulin container, or a receptacle for such a container. The container may contain a drug. A needle 15 can be affixed to the container or the receptacle. The container may be a cartridge and the receptacle may be a cartridge holder. The needle is protected by an inner needle cap 16 and either an outer needle cap 17 or another cap 18. An insulin dose to be ejected from injection device 1 can be set, programmed, or ‘dialled in’ by turning a dosage knob or dial grip 12, and a currently programmed or set dose is then displayed via dosage window 13, for instance in multiples of units. The indicia displayed in the window may be provided on a number sleeve or dial sleeve. For example, where the injection device 1 is configured to administer human insulin, the dosage may be displayed in so-called International Units (IU), wherein one IU is the biological equivalent of about 45.5 micrograms of pure crystalline insulin ( 1/22 mg). Other units may be employed in injection devices for delivering analogue insulin or other medicaments. It should be noted that the selected dose may equally well be displayed differently than as shown in the dosage window 13 in FIG. 1.

[0089] The dosage window 13 may be in the form of an aperture in the housing 10, which permits a user to view a limited portion of a dial sleeve assembly 20 that is configured to move when the dial grip 12 is turned, to provide a visual indication of a currently set dose. The dial grip 12 is rotated on a helical path with respect to the housing 10 when setting a dose.

[0090] In this example, the dial grip 12 includes one or more formations to facilitate attachment of a data collection device. Especially, the dial grip 12 may be arranged to attach a button module 11 onto the dial grip 12. As an alternative, the dial grip may comprise such a button module of an electronic system.

[0091] The injection device 1 may be configured so that turning the dial grip 12 causes a mechanical click sound to provide acoustic feedback to a user. In this embodiment, the dial grip 12 also acts as an injection button. When needle 15 is stuck into a skin portion of a patient, and then dial grip 12 and/or the attached button module 11 is pushed in an axial direction, the insulin dose displayed in dosage display window 13 will be ejected from injection device 1. When the needle 15 of injection device 1 remains for a certain time in the skin portion after the dial grip 12 is pushed, the dose is injected into the patient's body. Ejection of the insulin dose may also cause a mechanical click sound, which may be different from the sounds produced when rotating the dial grip 12 during dialing of the dose.

[0092] In this embodiment, during delivery of the insulin dose, the dial grip 12 is returned to its initial position in an axial movement, without rotation, while the dial sleeve assembly 20 is rotated to return to its initial position, e.g. to display a dose of zero units. FIG. 1 shows the injection device 1 in this 0U dialled condition. As noted already, the disclosure is not restricted to insulin but should encompass all drugs in the drug container 14, especially liquid drugs or drug formulations.

[0093] Injection device 1 may be used for several injection processes until either the insulin container 14 is empty or the expiration date of the medicament in the injection device 1 (e.g. 28 days after the first use) is reached. In the case of a reusable device, it is possible to replace the insulin container.

[0094] Furthermore, before using injection device 1 for the first time, it may be necessary to perform a so-called “prime shot” to remove air from insulin container 14 and needle 15, for instance by selecting two units of insulin and pressing dial grip 12 while holding injection device 1 with the needle 15 upwards. For simplicity of presentation, in the following, it will be assumed that the ejected amounts substantially correspond to the injected doses, so that, for instance the amount of medicament ejected from the injection device 1 is equal to the dose received by the user. Nevertheless, differences (e.g. losses) between the ejected amounts and the injected doses may need to be taken into account.

[0095] As explained above, the dial grip 12 also functions as an injection button so that the same component is used for dialling/setting the dose and dispensing/delivering the dose. As an alternative (not shown), a separate injection button may be used which is axially displaceable, at least a limited distance, relative to the dial grip 12 to effect or trigger dose dispensing.

[0096] In the following, an electronic system 100 according to the disclosure will be described with respect to exemplary embodiments and with reference to FIG. 4. The electronic system 100 comprises a dose setting and drive mechanism which may be part of an injection device 1 as depicted in FIG. 1 and an electrical power supply 150, e.g. a rechargeable or non-rechargeable battery, as shown in FIG. 4. The electronic system 100 further comprises an electronic control unit 110, e.g. comprising or consisting or being part of a PCBA, configured to control an operation of the electronic system 100 which has a first state and a second state, wherein the electronic system 100 has an increased electrical power consumption in the second state as compared to the first state. The electronic system 100 further comprises an encoding and motion sensing unit 120, e.g. a rotary sensor, and an electrical use detector unit 130 which is operatively connected to the electronic control unit 110 and which is configured to generate at least a first signal which is indicative that the user performs an operation. An example of such an operation is that the user of the injection device and/or the electronic system enters a manual synchronization or pairing mode of the electronic system 100 and/or that a user starts dose dispensing. The electronic system 100 is configured such that it is switched from the first state into the second state by the electronic control unit 110 in response to said first signal. The electronic system further comprises a communication unit 140 for communicating with another device. When the communication unit 140 is active to perform the manual synchronization or pairing mode, the electronic system 100 is in its second state.

[0097] Although not explicitly depicted, the electronic system 100 may comprise a, preferably permanent and/or non-volatile, storage or memory unit, which may store data related to the operation of the drug delivery device such as dose history data, for example.

[0098] Unless specifically disclosed otherwise in the following, the electronic system 100 may have the functions and may be arranged and/or designed as described in unpublished EP 20315066.9 and EP 20315357.2, the disclosure of which is incorporated herein by reference.

[0099] The present disclosure comprises alternatives for generating the first signal by means of an electrical use detector unit 130. In more detail, the embodiments are based on detecting an axial movement of a first member of the dose setting and drive mechanism with respect to the button module 11.

[0100] A first embodiment is depicted in FIGS. 2a to 2g. This embodiment is directed to an axial switch forming part of a use detection unit 130 of the electronic system 100. The use detection unit 130 is received within the button module 11. The button module 11 may be housed within the dial grip 12 or may be a separate unit attached to the dial grip 12. In the embodiment depicted in FIGS. 2a to 2g, the dial grip 12 has an, e.g. substantially cylindrical, outer shape with a profile allowing gripping and rotating the dial grip 12. The button module 11 is mainly received within the dial grip 12, wherein the dial grip 12 may form an outer housing of the button module 11. The dial grip 12 further houses a module chassis 19 fitted into the dial grip 12 during assembly of the device.

[0101] The dose setting and drive mechanism of the exemplary embodiment depicted in FIGS. 2a to 2g comprises at least a dial sleeve assembly in the form of a ring, e.g. an encoder ring 20, which may be permanently attached to a dial sleeve or number sleeve of the drug delivery device. As an alternative, the encoder ring 20 may be a unitary part of a dial sleeve assembly or number sleeve of the drug delivery device. In an embodiment, the dial sleeve assembly and, thus, the encoder ring 20 rotate and move axially on a helical path together with the button module 11 during dose setting. Further, the dial sleeve assembly and, thus, the encoder ring 20 rotate and move axially on a helical path in an opposite direction during dose delivery, wherein the button module 11 only moves axially such that a relative rotation occurs between the encoder ring 20 and the button module 11. Further, it may be possible to perform a relative axial movement, e.g. a limited axial movement, between the encoder ring 20 and the button module 11, for example for coupling and/or de-coupling the button module 11 or the encoder ring 20 from further components of the dose setting and drive mechanism.

[0102] As shown in FIG. 2a, a potential embodiment of the axial switch comprises a single switch contact strip that is manufactured from stainless steel or beryllium copper etc. sheet or strip.

[0103] The switch contact strip 21 is assembled onto a switch chassis 22 and comprises two elastically deformable arms each having a switch contact 23, 24 at its respective free end.

[0104] The switch chassis 22 constrains the switch contact strip 21 from translation and positions the switch contacts 23, 24 in the correct position for assembly into the button module sub-assembly. As shown in FIG. 2b, the axial switch sub-assembly is initially positioned into the module chassis 19 of the button module sub-assembly. A pin 25 on the switch chassis 22 component protrudes axially through a hole in the module chassis 19.

[0105] As shown in FIG. 2d, the electronic control unit PCBA 110 is assembled onto the module chassis 19 and compresses the axial switch sub-assembly into the final assembly position. The PCB has two exposed metallic pads 26, 27 on the distal surface. In this state the proximal surface of the switch contact 23 is in contact with one of the exposed pads 26 and is connected electronically to the PCB. The compression of the switch contact 23 may provide, e.g. approximately 0.2N, of pre-load, which ensures the switch chassis 22 is biased distally in the module chassis 19. The other switch contact 24 is in clearance to the PCB and the second pad 27 so that it is in a first electrical state (for example electrically open circuit in the depicted embodiment).

[0106] In the dialling state, when the button module 11 is assembled to the rest of the mechanism as shown in FIGS. 2e to 2g, there is axial clearance between the pin 25 and the encoder ring 20 which forms part of the dial sleeve assembly. As shown in FIGS. 2f and 2g, when the button module 11 is pressed it is displaced axially with respect to the dial sleeve assembly, ie. the encoder ring 20. Firstly the clearance between the switch chassis pin 23 and the encoder ring 20 is closed, followed by the switch chassis 22 being lifted to deflect the switch contact 24 proximally and close the clearance between the switch contact 24 and the second contact pad 27 on the PCB. Once this clearance has been closed, the electrical state of the switch is changed (for example to electrically closed in the depicted embodiment). This sequence operates in reverse when the button module 11 is released.

[0107] Thus, opening or closing the electrical contact between a switch contact 23 or 24 with a respective pad 26, 27 of the PCB may be used to wake up the electronic system or may trigger transition into a sleeping mode or other mode with comparably lower power consumption. Thus, the axial switch 23, 24, 26, 27 may be or form part of the electrical use detection unit 130.

[0108] The axial force to close the switch acts on the proximal surface of the encoder ring 20 during dispense, therefore there is a torque loss which acts to increase the dispense force of the injection device. The proximal surface of the encoder ring 20 is arranged as a continuous ring to provide a smooth running face 28 and minimise variation in dispense force. The moving contact occurring between two moulded polymer parts allows a material combination to be selected that maintains a low coefficient of friction at this interface, thus, performance is better than a metal contact sliding on a polymer surface.

[0109] The switch has been arranged such that the electrical change of state of the switch occurs prior to full displacement of the button module 11 which may be required to couple or de-couple further component parts of the dose setting and drive mechanism during the transition from a dose setting mode to a dose deliver mode. It is preferable, to limit the detrimental effect on dispense force, for the axial forces applied by the axial switch to the encoder ring 20 to be minimised. There is accommodation in the deflection of the switch contacts 23, 24 for over-travel of the switch chassis 22 after the switch contact 24 has contacted the second pad 27 of the PCB without the switch chassis 22 interfering with the PCB. This allows the switch to close in all tolerance conditions while maintaining a low reaction force on the proximal surface of the encoder ring 20.

[0110] An additional or alternative electrical use detection unit 130 is described in the following with reference to FIGS. 3a to 3g depicting an embodiment with a rotational switch.

[0111] As shown in FIG. 3a, a potential embodiment of the rotational switch comprises of a single rocker contact pressing 30 that is manufactured from stainless steel or beryllium copper etc. sheet or strip. This rocker contact pressing 30 has two contact arms, the tips of which, in the assembled orientation, are arranged with one more proximal than the other. The tips of the arms each form a respective switch contact 31, 32. The rocker contact pressing 30 is assembled onto a rocker 33 with e.g. two arms 34 for pivotably mounting the rocker 33 into the module chassis 19 as described above or a similar chassis component of the button module 11.

[0112] As shown in FIG. 3b, the rocker sub-assembly is initially positioned into the module chassis 19 of the button module 11 sub-assembly. A tip or radially extending protrusion 35 of the rocker 33 component protrudes through a hole in the module chassis 19. in FIGS. 3a and 3c, the protrusion 35 has the shape of a tooth as will be explained below in more detail. The arms 34 of the rocker 33 form an axle which is clipped into pockets in the module chassis 19, such that radial motion of the protrusion 35 of the rocker 33 results in axial motion at the rocker switch contacts 31, 32.

[0113] When the PCB is assembled onto the module chassis 19 the rocker sub-assembly is compressed into the final assembly position. The PCB has two (further) exposed metallic pads on the bottom surface from which only one pad 36 is visible in FIG. 3d. In the nominal tolerance condition the more proximal of the arms, i.e. the preload arm with switch contact 31, on the rocker is in contact with one of the exposed pads 37 and is connected electronically to the PCB. The compression of the preload arm provides a small pre-load force, which ensures the rocker tip or protrusion 35 is biased radially out of the module chassis 19. The other arm of the rocker 33, i.e. the switching arm with contact 32, is in clearance to the PCB so that it is in a first electrical state (for example electrically open circuit in the depicted embodiment).

[0114] A radial ratchet profile 38 is moulded in the encoder ring 20 which forms part of the dial sleeve assembly. In the dialling state, when the button module 11 is assembled to the rest of the mechanism as shown in FIGS. 3f to 3g, the protrusion 35 of the rocker 33 sits in a root of a ratchet tooth of ratchet profile 38. The switching arm with contact 32 therefore remains in clearance to the PCB.

[0115] When the button module 11 is pressed it is displaced axially with respect to the dial sleeve assembly. The rocker protrusion 35 remains in the same root of a ratchet tooth during this initial axial travel. When dispensing begins, the dial sleeve assembly rotates relative to the button module 11 and the rocker protrusion 35 is pushed radially into the module chassis 19 each time a ratchet tooth on the encoder ring 20 passes the rocker protrusion 35. As shown in FIG. 3g, the rocker sub-assembly rotates about the rocker axle 34, and the contact 32 of the switching arm moves proximally to close the clearance to the second contact pad 36 on the PCB. Once this clearance has been closed, the electrical state of the switch is changed (for example to electrically closed in the depicted embodiment).

[0116] It is possible to invert the arrangement so that the shape of the rocker protrusion 35 defines the cam profile and the ratchet teeth on the inner diameter of the encoder ring 20 become a series of cam followers. Using the rocker protrusion 35 as the driving profile reduces potential variation in the torque loss that may result from inconsistencies in the ratchet teeth profiles. In addition, the alternative arrangement may offer superior robustness since the width and therefore strength of the rocker protrusion 35 can be increased and wear will not be focussed on a single point on the rocker protrusion 35.

[0117] In an alternative, the profile of the encoder ratchet 38 can be optimised to minimise the peak torque loss as a result of deflecting the rocker protrusion 35 radially during dispense. As the rocker protrusion 35 is deflected radially inwards, the deflection induced in the preload and switching arms increases. Consequently, the radial reaction force of the rocker protrusion 35 acting on the encoder ring 20 increases as the rocker protrusion 35 is deflected radially inwards. The ramp profile of the ratchet teeth is configured to maximise the radial deflection induced in the rocker protrusion 35 when the reaction force from it is near a minimum (i.e. when the rocker protrusion 35 has not been significantly deflected). This is embodied as a ratchet ramp profile that varies from near radial at its maximum diameter to tangential or near tangential as it approaches its minimum diameter. In the embodiment described the encoder ring 20 creates a cam profile and the rocker protrusion 35 acts as a cam follower.

[0118] Although the time taken to initialise the encoder system is short, a delay between the start of dispensing and the start of encoding a dispensed dose may have detrimental implications of on accuracy of encoding a dispensed dose. It is possible in very fast dispense events, that the system may dispense 1 or 2 units before the encoder system has had time to initialise, and therefore there could be an error in the reported dose. The system may use Gray code caching (e.g. as described in unpublished EP 20315066.9 and EP20315305.1, the disclosure of which is incorporated herein by reference) to compare the orientation of the dial sleeve assembly at the end of dose, with where it would be expected to be given the stored dial sleeve orientation at the end of the previous dose and the dispense volume recorded by the encoder system. The reported dose volume can then be retrospectively corrected. It is possible to detect and correct an error of up to 3U which is expected to be sufficient for all dispense cases.

[0119] Although described mainly with respect to a drug delivery device having a similar working principle as the device disclosed in EP 2 890 435, the electronic system is applicable to any other type of drug delivery device having component parts performing a relative axial and/or rotational movement in defined conditions or states.

REFERENCE NUMERALS

[0120] 1 device [0121] 10 housing [0122] 11 button module [0123] 12 dial grip [0124] 13 dosage window [0125] 14 container/container receptacle [0126] 15 needle [0127] 16 inner needle cap [0128] 17 outer needle cap [0129] 18 cap [0130] 19 module chassis [0131] 20 encoder ring (dial sleeve assembly) [0132] 21 switch contact strip [0133] 22 switch chassis [0134] 23, 24 switch contact [0135] 25 protrusion (pin) [0136] 26, 27 contact pad [0137] 28 running face [0138] 30 switch contact pressing [0139] 31, 32 switch contact [0140] 33 rocker [0141] 34 arm (axle) [0142] 35 protrusion (tip) [0143] 36, 37 contact pad [0144] 38 ratchet profile [0145] 100 electronic system [0146] 110 electronic control unit (PCBA) [0147] 120 encoding and motion sensing unit [0148] 130 use detection unit [0149] 140 communication unit [0150] 150 electrical power supply