Patent Publication Number: US-9833576-B2

Title: Rotary sensor module with axial switch

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. §371 National Stage application of International Application PCT/EP2014/053220 (published as WO 2014/128156), filed Feb. 19, 2014, which claims priority to European Patent Application 13155802.5, filed Feb. 19, 2013; this application claims priority under 35 U.S.C. §119 to U.S. Provisional Application 61/767,818; filed Feb. 22, 2013. 
    
    
     The present invention relates to devices, assemblies and systems adapted for capturing information in respect of both rotational movement and axial movement. In a specific aspect the invention addresses issues relating to electronic dose data capturing in and for a drug delivery device. 
     BACKGROUND OF THE INVENTION 
     In the disclosure of the present invention reference is mostly made to the treatment of diabetes by delivery of insulin using a drug delivery device, 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 pre-filled 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, from 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&#39;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&#39;s decision making with respect to future medication. Accordingly, it may be desirable to automate the logging of ejection information from medication delivery systems. 
     Correspondingly, a number of injection devices with a dose monitoring/acquisition feature has been provided, see e.g. in US 2009/0318865, WO 2010/052275 and U.S. Pat. No. 7,008,399. However, most devices of today are without it. 
     Having regard to the above, it is an object of the present invention to provide a drug delivery device as well as components and assemblies therefore which cost-effectively and reliably allows detection and storage of dose data related to use of a drug delivery device. It is a further object to provide such components and assemblies which could be used also in other applications having the same types of input. 
     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 aspect of the invention a sensor assembly is provided comprising first and second portions, the first portion comprising a first rotary sensor part, the first rotary sensor part comprising a surface with a plurality of individual electrically conducting sensor areas arranged in a pattern, and the second portion comprising a second rotary sensor part arranged rotationally relative to the first portion thereby defining an axis of rotation, the second rotary sensor part comprising a plurality of contact structures adapted to be in contact with conducting sensor areas on the first sensor rotary part. At least a portion of the contact structures are configured to engage and connect different sensor areas as the first and second part of the rotary sensor rotate relative to each, the created connections being indicative of a rotational position between the first and second portions, however, at least one of the contact structures is an actuatable contact structure being axially moveable (i.e. as defined by the axis of rotation) relative to the first portion and having a connected position in which the actuatable contact structure is in contact with a sensor area and a dis-connected position in which the actuatable contact structure is not in contact with a sensor area. The sensor assembly further comprises actuator means for axially moving the at least one actuatable contact structure between the connected and the dis-connected position. When it is defined that the actuatable contact structure is axially moveable relative to the first portion, this definition covers that any or both of the two structures are moved relative to a reference. 
     Such an arrangement allows a rotary sensor assembly to be incorporated cost-effectively in a given apparatus in which it is desirable to combine a rotary sensor with an axially actuated contact in a compact and cost-effective way, e.g. for electric and electronic appliances in different technical fields, e.g. the medical, laboratory or automotive field. The contact provided by an axially actuatable contact structure may for short be denoted an “axial switch”. 
     The second rotary sensor part may be in the form of a metallic disc member comprising a plurality of integrally formed flexible arms forming the contact structures, at least one of the flexible arms ( 333 ) being axially moveable to thereby form the actuatable contact structure. The sensor assembly may be provided with electronic circuitry adapted to determine a rotational position between the first and second portions based on a given pattern of contact positions. The determination of rotation may be in the form of detection of incremental rotation (i.e. counting), absolute determination within a given number of degrees, or absolutely within a full rotation. The circuitry will typically comprise a processor in the form of a microprocessor, microcontroller or CPU which may be of a general purpose design or be specifically designed for the actual device. 
     In an exemplary embodiment the sensor assembly is provided in combination with a housing, with the first portion being arranged rotationally relative to the housing, and the second portion being arranged non-rotationally relative to the housing, and with at least one of the first and second portions being arranged axially moveable relative to the housing, the actuator means being arranged between the housing and the second portion. The actuator means could be in the form of a mechanical connection formed between the housing and the flexible switch arm, whereby relative axial movement between the housing and the flexible switch arm moves the switch contact between the connected and dis-connected positions. 
     In an exemplary application the rotary sensor assembly can be incorporated cost-effectively and reliably in a drug delivery device comprising a rotational member which rotates corresponding to a set and/or expelled dose and which also comprises an a component providing an axial displacement during operation of the device, the axial displacement being indicative of a change of state of the device relative for the detection of a set or expelled dose. For example, the axial movement may be related to the actuation of a release member which releases a drug expelling mechanism. The sensor assembly may be implemented with corresponding effect in other devices in which a sensor providing rotational and axial detection in a cost-effective way is relevant. 
     Correspondingly, in an exemplary embodiment a drug delivery device is provided comprising a sensor assembly as described above, the drug delivery device further comprising a housing, a drug-filled cartridge or means for receiving a drug-filled cartridge, and drug expelling means, the cartridge comprising an axially displaceable piston and a distal outlet portion. The drug expelling means comprises dose setting means allowing a user to set a dose of drug to be expelled, an axially displaceable piston rod adapted to move the piston of a cartridge in a distal direction to thereby expel drug from the cartridge, a rotational member adapted to rotate corresponding to a set and/or expelled dose, and an axially moveable actuation member adapted to actuate the drug expelling means to thereby expel the set dose of drug. In such an arrangement the first and second rotary sensor parts rotate relative to each other during setting and/or expelling of a dose of drug, and the actuatable contact structure is actuated between its two positions when the actuation member is moved axially. 
     The first portion of the sensor assembly may be mounted to and rotate with the rotational member, the first portion comprising electronic circuitry adapted to estimate an amount of expelled drug based on detection of rotational movement between the first and second portions corresponding to a set and/or expelled dose. The rotational member may be adapted to move axially between an initial and an actuated position, the first portion of the sensor assembly being mounted to move axially with the rotational member. Also the second portion may be mounted to move axially with the rotational member. For such a design the inherent movements of the rotational member can be detected simple and effectively by the sensor assembly of the present invention. 
     The electronic circuitry may be provided with logging means adapted to create a log for dose amounts of drug expelled from a cartridge by the drug expelling means, the dose amounts being calculated based on relative rotation between the first and second rotary sensor parts during setting and/or expelling of a dose of drug. The electronic circuitry may be provided with transmitter means adapted to transmit stored data to an external receiver. Alternatively or in addition, the first portion may comprise a display which may be controlled to be turned off during rotation of the first portion. 
     In a specific embodiment of the invention a drug delivery device is provided comprising a housing, a drug-filled cartridge or means for receiving a drug-filled cartridge, and drug expelling means, the cartridge comprising an axially displaceable piston and a distal outlet portion. The drug expelling means comprises dose setting means allowing a user to set a dose of drug to be expelled, an axially displaceable piston rod adapted to move the piston of a cartridge in a distal direction to thereby expel drug from the cartridge, a rotational member adapted to rotate corresponding to a set and/or expelled dose, and an axially moveable actuation member adapted to actuate the drug expelling means to thereby expel the set dose of drug. The drug delivery device further comprises sensor means adapted to detect a set and/or an expelled dose, comprising (i) a first portion comprising a first rotary sensor part, the first rotary sensor part comprising a surface with a plurality of individual electrically conducting sensor areas arranged in a pattern, and (ii) a second portion comprising a second rotary sensor part arranged rotationally relative to the first portion, the second rotary sensor part comprising a plurality of contact structures adapted to be in contact with conducting sensor areas on the first sensor rotary part. At least a portion of the contact structures are configured to engage and connect different sensor areas as the first and second part of the rotary sensor rotate relative to each, the created connections being indicative of a rotational position between the first and second portions. At least one of the contact structures is an actuatable contact structure being axially moveable relative to the first portion and having a connected position in which the actuatable contact structure is in contact with a sensor area and a dis-connected position in which the actuatable contact structure is not in contact with a sensor area. The first and second rotary sensor parts rotate relative to each other during setting and/or expelling of a dose of drug, and the at least one actuatable contact structure is actuated between its two positions when the actuation member is moved axially. 
     The electronic circuitry may be adapted to determine a rotational position between the first and second portions based on a given pattern of created connections, the electronic circuitry comprising logging means adapted to create a log for dose amounts of drug expelled from a cartridge by the drug expelling means, wherein the dose amounts are calculated based on relative rotation between the first and second rotary sensor parts during setting and/or expelling of a dose of drug. The drug delivery device may comprise additional features as described above. 
     As used herein, the term “drug” is meant to encompass any flowable medicine formulation 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 containing one or more drug agents. The drug may be a single drug compound or a premixed or co-formulated multiple drug compounds drug agent from a single reservoir. Representative drugs include pharmaceuticals such as peptides (e.g. insulins, insulin containing drugs, GLP-1 containing drugs as well as derivatives thereof), proteins, and hormones, biologically derived or active agents, hormonal and gene based agents, nutritional formulas and other substances in both solid (dispensed) or liquid form. In the description of the exemplary embodiments reference will be made to the use of insulin and GLP-1 containing drugs, this including analogues thereof as well as combinations with one or more other drugs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention will be further described with reference to the drawings, wherein 
         FIGS. 1 and 2  show a front-loaded drug delivery device with respectively without a drug cartridge mounted, 
         FIG. 3  shows in an exploded view a drug delivery device subassembly comprising a logging module, 
         FIG. 4  shows an exploded view of the logging module of  FIG. 3 , 
         FIGS. 5 and 6  show first respectively second rotary sensor parts of the module of  FIG. 3 , 
         FIG. 7  shows the logging module of  FIG. 4  in an assembled state, 
         FIG. 8  shows a cross-sectional view of the subassembly of  FIG. 3  in an assembled state, 
         FIGS. 9A-9C  show operation of an axial switch of the logging module in different operational states, 
         FIG. 10  shows a drug delivery pen provided with a logging module and in communication with a smartphone, and 
         FIG. 11  shows in an exploded view a display assembly. 
     
    
    
     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 components could be provided as unitary components, e.g. manufactured as a single injection moulded part. The terms “assembly” and “subassembly” do not imply that the described components necessarily can be assembled to provide a unitary or functional assembly or subassembly during a given assembly procedure but is merely used to describe components grouped together as being functionally more closely related. 
     Referring to  FIG. 1  a pen-formed drug delivery device  100  will be described. The device represents a “generic” drug delivery device providing an example of a device in combination with which embodiments of the present invention is intended to be used, such a device comprising a rotational member adapted to rotate corresponding to a set and/or expelled dose of drug. 
     More specifically, the pen device comprises a cap part (not shown) and a main part having a proximal body or drive assembly portion  120  with a housing  121  in which a drug expelling mechanism is arranged or integrated, and a distal cartridge holder portion in which a drug-filled transparent cartridge  180  with a distal needle-penetrable septum can be arranged and retained in place by a cartridge holder  110  attached to the proximal portion, the cartridge holder having openings allowing a portion of the cartridge to be inspected. The cartridge may for example contain an insulin, GLP-1 or growth hormone formulation. The device is designed to be loaded by the user with a new cartridge through a distal receiving opening in the cartridge holder, the cartridge being provided with a piston driven by a piston rod  128  forming part of the expelling mechanism. A proximal-most rotatable dose ring member  125  serves to manually set a desired dose of drug shown in display window  126  and which can then be expelled when the release button  127  is actuated. Depending on the type of expelling mechanism embodied in the drug delivery device, the expelling mechanism may comprise a spring 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 ring member and the release button moves proximally during dose setting corresponding to the set dose size, and then moved distally by the user to expel the set dose. The cartridge is provided with distal coupling means in the form of a needle hub mount  182  having, in the shown example, an external thread  185  adapted to engage an inner thread of a corresponding hub of a needle assembly. In alternative embodiments the thread may be combined with or replaced by other connection means, e.g. a bayonet coupling. 
     The cartridge holder comprises a distal opening adapted to receive a cartridge. More specifically, the cartridge holder comprises an outer rotatable tube member  170  operated by the user to control movement of gripping means to thereby open and close gripping shoulders  145  configured to grip and hold a cartridge.  FIG. 2  shows the device with the cartridge removed and the gripping shoulders in their un-locked “open” position in which a cartridge can be removed and a new inserted. 
     As appears,  FIG. 1  shows a drug delivery device of the front-loaded type in which a cartridge is inserted through a distal opening in the cartridge holder which in non-removable attached to the main part of the device, however, the drug delivery device may alternatively comprise a cartridge holder adapted to be removed from the device main portion and in which a cartridge is received and removed through the proximal opening. 
     With reference to  FIG. 3  a subassembly  200  for a drug delivery device will be described, the subassembly comprising a logging module in combination with parts of the drug delivery device being directly functionally related to the incorporation and operation of logging unit. More specifically, the subassembly comprises an electronically controlled logging module  300 , an inner tube member  210 , a generally cylindrical inner housing member  220 , a dial ring member  230  and a button assembly comprising a button ring  240 , a button window  241  and a button spring  242 . The inner housing member is configured to be arranged inside an outer housing member providing the exterior of the drug delivery device. 
     The different components of the logging module  300  are shown in  FIG. 4 . More specifically, the logging module comprises a housing member  310  having a barrel-shaped proximal main portion  311  with a distally extending tube portion  312 , a mounting foil member  313 , a disc-formed first rotary sensor part  320  onto which a first connector  329  is to be mounted, a disc-formed second rotary sensor part  330 , a rotary sensor holder  339  with a lateral projection  337 , a flexible PCB  340  folded in a multi-layered stack and onto which a second connector  349  is to be mounted, a battery  345  and battery clip  346 , a number of mounting rings  350 ,  351 ,  352 , an antenna  360 , an LCD  370  and an LCD frame  371 . Alternatively an OLED or another desirable display technology could be used. On the PCB electronic circuitry components are mounted, e.g. micro-controller, display driver, memory and wireless communication means. As will be described below in greater detail the first rotary sensor part  320  comprises a plurality of arc-formed discreet contact areas, and the second rotary sensor part  330  comprises a plurality of flexible contact arms of which one provides an axial switch having a laterally extending projection  334 . 
       FIG. 5  shows the first rotary sensor part  320  comprising a ring-formed disc formed from circuit board material and on which a number of contact areas (or segments) has been plated on forming three concentric rings, an inner, an intermediate and an outer ring. In the shown embodiment the inner ring is a single contact segments  321  used as ground (i.e. reference), the intermediate ring comprises four discrete arch-formed position contact segments  322  arranged with a certain circumferential distance there between, and the outer ring comprises three discrete arch-formed switch contact segments  323  arranged with only a small circumferential gap there between, the segments being individually connected to a given contact terminal of the multi-terminal connector  329  mounted on the rear (proximal) face of the disc. If a given segment is not connected to a terminal it can be considered a passive segment. 
     The second rotary sensor part  330  shown in  FIG. 6  is in the form of a metallic disc comprising a number of flexible arc-formed contact arms protruding proximally, the distal end of each contact arm comprising a dome-formed contact point  335  (facing downwards in the figure) adapted to create a galvanic connection with a given contact segment. The contact arms are arranged corresponding to the three concentric rings of the first rotary sensor part. More specifically, the second rotary sensor part comprises two inner contact arms  331 , three intermediate contact arms  332  and two outer contact arms  333 . 
     In this way a given pair of contact arms provides a combined contact structure adapted to create electric contact between two contact segments. In the shown embodiment the two inner ground contact arms  331  are provided to be in contact with the single ground contact segment  321  of the inner concentric ring, the three position contact arms  332  are provided to create contact with the four position contact segments  322  of the intermediate concentric ring, and the two outer switch contact arms  333  are provided to be in contact with the three switch contact segments  323  of the outer concentric ring, the outer switch contact arms carrying a laterally extending projection  334 . Indeed, for the intermediate and outer contact arms the rotational position between the two sensor parts will determine which contact segment is engaged with a given contact arm. The two outer switch contact arms  333  are in the shown embodiment used to provide redundancy for the axial switch, however, in cooperation with the switch contact segments of the outer ring they could additionally be used to provide rotational information. 
     The second rotary sensor part further comprises a gripping part  336  adapted to engage the projection  337  on the rotary sensor holder  339  to prevent rotational movement there between. 
     In the shown embodiment the intermediate arms and contact segments provide the rotary sensor contacts whereas the outer arms and contact segments provide an axial switch as will be described in greater detail below. 
     The four position contact segments  322  represent in combination with the ground segment four position contacts having an “off” state when not connected by the ground contact arms  331  and any of the position contact arms, and an “on” state when connected by the ground contact arms and a given position contact arm. 
     For a given rotational position the electrically connected arms create a number of “on” galvanic contacts between given pairs of contact segments, other non-connected areas representing an “off” contact condition. The shown rotary sensor has a resolution of 15 degrees, i.e. 24 steps for a full rotation, such that for each 15 degrees of rotation a pre-determined change in which of the individual position rotary contacts are on and off is created. As each of the shown contact segments is connected to the electronic circuitry  340  it is possible to determine the relative rotational position between the two rotary sensor parts. 
       FIG. 7  shows the logging module  300  in an assembled state. The flexible PCB  340  with its mounted components and the antenna have been mounted in a sandwich configuration with the mounting rings  350 ,  351 ,  352  providing the required spacing and attachment via e.g. gluing or adhesives, the battery  345  being attached to the PCB via battery clip  346 . The PCB sandwich is mounted with a “tongue” threaded through a distal opening in the housing  311  button portion and held in place with adhesive mounting foil member  325  (see  FIG. 4 ) during assembly. The first rotary sensor part  320  is mounted non-rotationally on the tube portion  312  and connected to the PCB via the connectors  329 ,  349 . The second rotary sensor part  330  is mounted non-rotationally and axially fixed on the rotary sensor holder  339  which is mounted rotationally free but axially fixed on the tube portion  312 . By this arrangement the flexible rotary sensor arms are held in sliding contact with the contact surfaces. The LCD  370  is mounted on top of the PCB sandwich which together is held in place in the housing barrel by the display frame  371  which is permanently attached to the housing by e.g. welding. As appears, in this way an electronic logging module is provided comprising a distally arranged rotatable sensor part. As shown in  FIG. 4  the housing main portion  311  comprises a circumferential distal flange  313  with a number of proximally projecting teeth  314  and a circumferential proximal groove  315 . The tube portion  312  is provided with distal snap connectors  316  adapted to engage corresponding openings  211  in the inner tube member  210 . 
       FIG. 8  shows a cross-sectional view of the subassembly  200  in an assembled state. The term “subassembly” does not imply that the shown parts necessary are assembled to provide a subassembly as shown and which can be used in an assembly process for a given drug delivery device. In contrast, the shown logging module of  FIG. 7  may be provided in the shown form as a “real” subassembly. Referring to the parts shown in  FIGS. 3 and 4 , the inner tube member  210  is connected rotationally and axially locked to the distal tube portion  312  of the logging module. This arrangement is mainly for the purpose of moulding and subsequent assembly. The dial ring member  230  is mounted on the proximal portion of the housing member  220  on which it is allowed to freely rotate but not move axially. The dial ring member  230  comprises an inner circumferential coupling flange  231  with a plurality of distally facing teeth adapted to engage the proximally facing teeth  314  of the logging module to thereby rotationally lock the two components during engagement. The housing member  220  comprises first and second openings or cut-outs  221 ,  222  (see  FIG. 3 ) adapted to engage respectively the rotary sensor holder lateral projection  337  and the axial switch lateral projection  334 , this ensuring non-rotational engagement between the second rotary sensor part and the housing yet allows axial movement. 
     The button  240  with the window  241  attached is mounted on the module housing in gripping engagement with the circumferential groove  315 , this allowing the button to rotate relative to the module housing. The axially compressed button assembly spring  242  is arranged in the circumferential gap between the module housing and the dial ring member and held in place between a distally facing ring portion of the button ring and the proximally facing portion of the coupling flange. In this way the spring provides an axial force biasing the module proximally into non-rotational engagement with the dial ring member  230  via the coupling flange, however, when a distally directed force is applied to the module via the button the module can be moved distally and thereby out of the rotational coupling with the dial ring member, this allowing the logging module main housing to rotate relative to the dial ring member. 
     As indicated above, the shown rotary sensor comprises an axial switch, this switch serving to detect an axial position of the logging module relative to (here) the housing member  220 . More specifically,  FIG. 9A  shows the logging module  300  biased into an initial proximal position by the button spring  242 ,  FIG. 9B  shows the logging module in an intermediate position in which it has been moved distally by the distance H 1 , and  FIG. 9C  shows the logging module in an actuated distal position in which it has been moved distally by the distance H 2 . In all three states the axial switch lateral projection  334  is positioned in the corresponding housing opening  221  and rotationally locked to the housing via the rotary sensor holder  339 . As appears, in  FIG. 9A  the switch projection  334  engages a proximal edge of the opening and the flexible switch arm  333  with the contact point  335  is thereby held out of contact with the first rotary sensor part  320 , in  FIG. 9B  the switch projection  334  still engages the proximal edge of the opening, however, the logging module has been moved distally and thereby the first rotary sensor part  320  has been moved into contact with the switch arm  333 , this bringing the axial switch into an “on” state detectable by the logging module circuitry, and in  FIG. 9C  the logging module has been moved further distally to its actuated distal position. The switch projection  334  has been moved out of engagement with the proximal edge of the opening, the axial switch thus remaining in its “on” state. In an exemplary embodiment the axial movement between the different positions may be e.g. 1.5 mm, this ensuring that the expelling mode is safely registered by the axial switch before the dosing mechanism is actually released. The axial switch could also be used to control the functioning of the logging module when no dose has been set, see below. 
     The parts of the subassembly  200 , apart from module  300 , as shown in  FIG. 3  represent “generic” parts of a drug expelling mechanism having properties which are relevant for the implementation of embodiments of the present invention. More specifically, the shown module  300  is adapted to be implemented in a drug delivery device having a housing, dose setting means allowing a user to set a dose of drug to be expelled, and a rotational member adapted to rotate corresponding to a set and/or expelled dose. In the shown subassembly the inner tube member  210  represents a “generic” rotational member. 
     Although not part of the present invention, in the following a short description of a drug expelling mechanism into which the shown inner tube member  210  could be integrated will be described. When setting a dose to be expelled the user rotates the dial ring member  230  and thereby the inner tube member  210  to a given rotational position representing a desired dose, this straining a torsional spring member arranged around the tube member and attached at its proximal end to a housing proximal portion and at its distal end to the tube member distal portion. A ratchet coupling arranged at the distal end of the inner tube member serves to hold the now rotationally biased tube member in the set position. A scale drum is coupled to and rotates with the tube member, the scale drum having a threaded connection with the housing (e.g. threads  226  in  FIG. 3 ) whereby a spirally arranged series of numeric values is moved relative to a window in the housing (e.g. opening  225  in  FIG. 3 ), the shown number indicating the presently set dose. To release the set and loaded mechanism the user pushes a proximal release button whereby the inner tube member is moved distally. By this action the ratchet coupling (serving as a release member) is released and the inner tube member is moved into engagement, directly or indirectly, with a rotational drive member, the drive member being arranged to rotate a piston rod which due to a threaded engagement with the housing is moved distally to thereby the set dose. As the tube member rotates backwards, thereby driving the piston rod distally, also the scale drum is rotated backwards and reaches its initial “zero” position together with the tube member. This kind of mechanism is known from e.g. the FlexTouch® drug delivery pen device marketed by Novo Nordisk for the injection of e.g. insulin formulations. 
     As appears, in the described exemplary mechanism the inner tube member  210  (to which the main portion of the logging module  300  is rigidly mounted) rotates relative to the housing  220  during both setting and expelling of a given dose. As the second rotary sensor part  330  is rotationally locked to the housing, also the two rotary sensor parts  320 ,  330  rotate relative to each other during both setting and expelling of a given dose. As this is merely an exemplary mechanism, other mechanisms can be envisaged in which a given member rotates only during setting or expelling. 
     This said, in the shown embodiment the logging module is adapted to detect rotation in both directions corresponding to a set dose and an expelled dose. In the shown embodiment the logging module is further provided with an axial switch allowing the module to detect whether the mechanism is in the setting or expelling mode, however, this is an optional feature. In the shown embodiment the code pattern has a step “resolution” of 15 degrees of rotations which for a given drug formulation and delivery device combination may correspond to 1 unit (IU) of insulin. Indeed, for a drug formulation having the double concentration a 7.5 degree rotary resolution would be necessary to register dose steps corresponding to 1 IU of insulin. The rotary sensor comprising the rotary contacts and the associated electronic circuitry could be designed to detect the amount of rotation using a number of designs, e.g. each 15 degrees increment may be counted, or a given position may be detected absolutely within sectors of e.g. 120 or 360 degrees, a counter registering the number of completed sectors. Such a counter could be implemented using the switch arms and outer contact areas described with reference to  FIGS. 5 and 6 . With a “counting” design it is important that the first increment is registered, however, modern electronics can be operated in a low-power “on” state avoiding the delay normally associated with a wake-up change of state from a “sleep” state to an “on” state. 
     In an exemplary embodiment the rotary sensor is designed to count the number of steps during setting and to count down the number of steps during expelling, with the expelling steps being registered in the log as the dose being expelled. By counting in both directions proper registering and functioning of the logging module can be assured to a high degree. As a given dose of drug, especially if large, may be divided and injected with a given pause, the logging module may be programmed to log two dose amounts expelled within a given time window, e.g. 15 minutes, as one dose. 
     The logging module may be configured to store and show data in different ways. To many users the time since last dose and the size of that dose are the most important values. To other users and/or a medical practitioner an overview of the entire log for a given period, e.g. a week or a month, may be of importance. To allow such an overview the logging module may be provided with output means allowing the dose log to be transferred, e.g. by NFC transfer, to an external display device, e.g. a smartphone or computer for better graphic overview, see below. 
     To ensure that the full dose is expelled the logging module may be set up to display the last expelled dose only when the expelling mechanism has been returned to zero. Otherwise a given “half” dose will be stored in the log but not displayed. For example, if a dose of 40 IU is dialled and 20 IU are expelled immediately thereafter the display will not show data for that delivery. To have the dose shown in the display the user may expel the remaining dose and the combined dose of 40 IU together with a time stamp will be shown in the display. Alternatively the user may dial the expelling mechanism back to zero and the display will show 20 IU, or the user may dial the expelling mechanism back to 10 IU and expel the 10 IU and the display will show 30 IU. Indeed, for the expelled amounts to be combined the two (or more) doses will have to be expelled within the above-described time window, e.g. 15 minutes. Otherwise only the last portion of the dose will display, the first portion being stored merely as an entry in the log. 
     The display can be configured to show data in different formats. For example, the display  411  of  FIG. 10  is a two-line display in which time is shown using a HH:MM:SS stop watch design, this providing that the time since the last dose expelled from the device can be shown with a running second counter allowing a user to easily identify the shown information as a counting time value. After 24 hours the display may continue to display time in the HH:MM:SS format or change to a day and hour format. 
     To save energy the display will turn off after a pre-determined amount of time, e.g. 30 seconds. To turn on the display again the user may e.g. press the button thereby using the axial switch to turn on the display, or the display may be turned on when the dose dial is turned away from and then back to zero. 
     A user may desire to check the dose log directly on the module display. Toggling through the dose log could also be controlled by the axial switch, e.g. two fast pushes on the button  412  will bring the module into log display mode, each consecutive push on the button recalling the next log entry. The module may leave the log display mode automatically after a given amount of time, or the user may bring the module into normal display mode by e.g. dialling back and forth as described above. As an alternative, the electronic module may be provided with other types of input means, e.g. a motion sensor which would allow a user to turn on the display by shaking or tapping, or a touch sensor integrated in the display as is well known from e.g. smartphones which would allow a user to turn on the display by swiping a finger across the display. 
       FIG. 10  shows a drug delivery pen  400  provided with a logging module  410  as described above and arranged next to a smartphone  430  configured to receive logging data from the logging module via wireless communication, e.g. NFC. As appears, the logging module is provided with a display configured to indicate the size of the last dose and the time since the last dose using the stopwatch display mode. 
     In order to communicate with the logging module the smartphone has been provided with specific “insulin diary” software. When the software is activated to initiate data transfer the smartphone NFC transmitter will transmit specific code which will wake up any nearby logging module which will then retransmit a unique code identifying the specific module. If a specific code is received for the first time the user is asked to confirm pairing and is asked to select from a list the given drug that should be associated with the given logging module, e.g. “Mix 30” as shown. In this way the smartphone can create an insulin diary covering more than one drug. In the described simple “manual” set-up the user has to ensure that a correct cartridge, e.g. with Mix 30 insulin, is loaded in a drug delivery pen which has been associated with that type of drug. Indeed, other set-ups can be envisaged, e.g. a given pen may be (mechanically) coded to only accept a given type of cartridge with the designated type of drug, or the pen and logging module may be provided with the ability to identify different types of cartridges and thus types of drug. 
     In the shown embodiment log data from a logging module associated with a Mix 30 insulin has been transferred. In the exemplary user interface the user can toggle back and forth between different day views, each day view showing the different amounts of drug delivered together with a real time value. In  FIG. 10  on a given day  431  first and second amounts  432  of Mix 30 has been delivered with the time and amount shown for each delivery. 
     In the embodiment of  FIG. 7  the LCD has been attached to the PCB using traditional ACF (Anisotropic Conductive Film) bonding, however, in  FIG. 11  an alternative solution for attaching the LCD to a PCB is shown. More specifically,  FIG. 11  shows in an exploded view a display assembly  500  comprising a PCB  510  with a flexible connector  511 , a curved elastomeric connector  520  (e.g. a Zebra® connector), a segmented LCD (e.g. numeric or dot-matrix)  530 , a mounting ring  540  and a housing ring  550 . The LCD comprises a connector array with a plurality of connectors arranged in a first curved configuration a long at a part of the curved circumferential portion, e.g. 300 degrees, and the PCB comprises a corresponding connector array having a plurality of connectors arranged in a second curved configuration corresponding at least in part to the first curved configuration. The curved elastomeric connector is adapted to establish a plurality of electrical connections between the connectors of the two connector arrays when the LCD, the PCB and the elastomeric connector is arranged in conducting contact. In an assembled state the housing ring is attached to the PCB thereby holding the remaining components into forced engagement with each other. 
     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.