FIELD OF INVENTION

The present invention relates to a drug delivery device.

BACKGROUND

Pen type drug delivery devices have application where regular injection by persons without formal medical training occurs. This is increasingly common among patients having diabetes where self-treatment enables such patients to conduct effective management of their diabetes.

For good or perfect glycemic control, the dose of insulin or insulin glargine has to be adjusted for each individual in accordance with a blood glucose level to be achieved. The present invention relates to injectors, for example hand-held injectors, especially pen-type injectors, that is to injectors of the kind that provide for administration by injection of medicinal products from a multidose cartridge. In particular, the present invention relates to such injectors where a user may set the dose.

A user undertaking self-administration of insulin will commonly need to administer between 1 and 80 International Units.

SUMMARY

According to an aspect of the invention there is provided a drug delivery device comprising: a housing; a cylindrical member rotatably supported within the housing; and a plurality of sensors; wherein: the outer surface of the cylindrical member is provided with a single track, the track forming an encoder and having a plurality of first track segments and a plurality of second track segments arranged along the length of the track which are respectively capable of inducing first and second responses in the sensors; and in each rotational position of the cylindrical member relative to the housing at least one different first track segment is capable of inducing a first response in at least one said sensor, thereby enabling the rotational position of the cylindrical member relative to the housing to be determined.

Advantageously, this enables the absolute rotational position of the cylindrical member relative to the housing to be determined using a single track.

The cylindrical member may be supported within the housing and configured to be rotated relative to the housing and the sensors.

The cylindrical member may be movable along a helical path between a plurality of discrete positions. Preferably, each discrete position is being associated with a specific dose amount.

In each discrete position of the cylindrical member the sensors are respectively capable of having induced therein a first or second response by one said first or second track segment.

In each of the discrete positions of the cylindrical member a unique combination of first and second responses is capable of being induced across the plurality of sensors.

Each discrete position of the sensors along the track may be associated with a unique binary code.

The plurality of sensors may be arranged along a single track. The plurality of sensors may be configured to enable interaction with unique configurations of first and second track segments. Preferably, the plurality of sensors interacts with unique configurations of first and second track segments whenever an increment of insulin is dialled or dispensed.

The device may further comprise a processor configured to determine the rotational position of the cylindrical member relative to the housing by analysing signals output from each of the sensors which correspond with whether a first said response or a second said response is induced in a respective said sensor.

The sensors may each comprise an electrical contact, and the first and second track segments may respectively have lower and higher values of electrical resistance, the first track segments being electrically coupled to one another.

The processor may be configured to cause an electrical signal to be applied to one of the electrical contacts while simultaneously detecting whether any of the other electrical contacts are energised, thereby enabling the rotational position of the cylindrical member relative to the housing to be determined.

The processor may be configured to cause an electrical signal to be applied to each of the first track segments via an additional electrical contact while simultaneously detecting whether any of the other electrical contacts are energised, thereby enabling the rotational position of the cylindrical member relative to the housing to be determined.

Advantageously, this enables the absolute rotational position of the cylindrical member relative to the housing to be directly determined by analysing which of the electrical contacts are energised.

The additional electrical contact may engage a section of the track which electrically couples the first track segments to one another.

The device may further comprise an additional track located adjacent the track forming said encoder, said additional track being electrically conductive and in engagement with a further electrical contact, wherein the processor may be configured to analyse signals from the further electrical contact to determine the operational mode of said device.

Advantageously, this enables whether the device is in dialling mode or drug dispensing mode to be determined.

The device may further comprise a switch configured to electrically couple the two tracks in one operational mode of said device, and to electrically decouple the two tracks in another operational mode of said device.

The device may further comprise a delivery button configured to cause expulsion of a drug from the drug delivery device upon actuation thereof by a user, wherein depression of the delivery button changes a state of the switch.

The sensors may each comprise an optical sensor, and the first and second track segments may respectively comprise differently coloured parts of said track.

The processor may be configured to determine which of said optical sensors are directed towards a first track segment and which of said optical sensors are directed towards a second track segment, thereby enabling the rotational position of the cylindrical member relative to the housing to be determined.

Advantageously, this enables the absolute rotational position of the cylindrical member relative to the housing to be directly determined by analysing which types of track segment the optical sensors are directed towards.

The device may further comprise a sleeve which surrounds at least part of said cylindrical member and which rotates relative to the optical sensors in one operational mode of the device but not in another operational mode of the device, and an additional optical sensor for use in monitoring the rotational position of opaque markings provided on the sleeve in order to determine the mode of operation of the device.

Advantageously, this enables whether the device is in dialling mode or drug dispensing mode to be determined.

The processor may be configured to determine a selected drug dose by searching a lookup table stored in a memory, the lookup table providing a conversion between a rotational position of the cylindrical member relative to the housing and a selected drug dose.

The processor may be configured to determine a delivered drug dose by subtracting a remaining drug dose from the selected drug dose.

