Drug delivery device with electromagnetic drive unit

Abstract

The disclosure relates to a drug delivery device having a drive unit includes a stator comprising a plurality of coils consecutively arranged in an axial direction, and an armature axially movable within the stator, the armature including a number of magnets and pole shoes consecutively arranged in the axial direction. A respective pole shoe is arranged between respectively neighbouring magnets. At least one axial end of the armature comprises a terminal pole shoe.

1 - 15 . (canceled) 
     
     
         16 . A method, comprising:
 initiating supply of current through a plurality of coils of a stator to apply a thrust force on an armature, thereby causing a stopper of a drug delivery device to translate distally to dispense a dose of a medicament;   measuring an inductance of a first coil of the plurality of coils;   determining a dispensed dose of the medicament or an amount of medicament remaining in a cartridge based on the measured inductance; and   determining an axial position of the armature within the stator by determining an inductance for each coil of the plurality of coils.   
     
     
         17 . The method according to  claim 16 , wherein initiating the supply of current comprises:
 initiating the supply of current through the plurality of coils such that the armature is advanced axially from an initial position; and   ceasing the supply of current through the plurality of coils such that the armature returns to the initial position.   
     
     
         18 . The method according to  claim 16 , wherein the dispensed dose is determined based on the axial position of the armature within the stator. 
     
     
         19 . The method according to  claim 16 , wherein the inductance determined for each coil of the plurality of coils is determined using a control unit connected to each coil of the plurality of coils. 
     
     
         20 . The method according to  claim 16 , wherein measuring the inductance comprises applying an alternating voltage to the first coil. 
     
     
         21 . The method according to  claim 16 , wherein measuring the inductance comprises applying an alternating current to the first coil. 
     
     
         22 . The method according to  claim 16 , wherein measuring the inductance comprises: connecting the first coil to a capacitor having a capacitance to form a resonator; and determining a resonance frequency of the capacitor. 
     
     
         23 . The method according to  claim 16 , wherein measuring the inductance comprises using a bridge network connected to the first coil. 
     
     
         24 . The method according to  claim 16 , wherein:
 the armature comprises a plurality of magnets and a plurality of pole shoes consecutively arranged in an axial direction;   a respective pole shoe of the plurality of poles shoes is arranged between respectively neighboring magnets of the plurality of magnets; and   at least one axial end of the armature comprises a terminal pole shoe.   
     
     
         25 . The method according to  claim 16 , wherein the thrust force is 20 N. 
     
     
         26 . The method according to  claim 16 , wherein determining the dispensed dose comprises measuring a fluctuation of the inductance of the first coil. 
     
     
         27 . The method according to  claim 16 , wherein:
 the first coil comprises a cylindrical coil, and   the measured inductance is based on a number N of windings, a magnetic field constant λ0, a relative permeability µr, and the internal cross-sectional area A of the cylindrical coil.   
     
     
         28 . The method according to  claim 16 , wherein:
 the first coil comprises a cylindrical coil, and   the measured inductance is based on a number N of windings, a magnetic field constant λ0, a relative permeability µr, an internal cross-sectional area A of the cylindrical coil, and a radius of a winding rW.   
     
     
         29 . The method according to  claim 16 , wherein, to apply the thrust force, the coils of the plurality of coils are supplied with an alternating or pulsed current such that magnetic fields are induced in the coils of the plurality of coils and interact with a static magnetic field generated by one or more magnets of the armature. 
     
     
         30 . The method according to  claim 16 , wherein the inductance of the first coil is measured using a voltage used to apply the thrust force to the armature. 
     
     
         31 . The method according to  claim 16 , wherein the armature moves to a zero position when the coils of the plurality of coils are turned off. 
     
     
         32 . A method, comprising:
 initiating supply of current through a plurality of coils of a stator to apply a thrust force on an armature, thereby causing a stopper of a drug delivery device to translate distally to dispense a dose of a medicament;   measuring an inductance of a coil of the plurality of coils by applying an alternating voltage to the coil; and   determining a dispensed dose of the medicament or an amount of medicament remaining in a cartridge based on the measured inductance.   
     
     
         33 . The method according to  claim 32 , wherein measuring the inductance further comprises determining an amplitude and phase shift of a current in the coil. 
     
     
         34 . The method according to  claim 32 , wherein:
 the armature comprises a plurality of magnets and a plurality of pole shoes consecutively arranged in an axial direction;   a respective pole shoe of the plurality of poles shoes is arranged between respectively neighboring magnets of the plurality of magnets; and   at least one axial end of the armature comprises a terminal pole shoe.   
     
     
         35 . A method, comprising:
 initiating supply of current through a plurality of coils of a stator to apply a thrust force on an armature, thereby causing a stopper of a drug delivery device to translate distally to dispense a dose of a medicament;   measuring an inductance of a coil of the plurality of coils by connecting the coil to a capacitor having a capacitance to form a resonator and determining a resonance frequency of the capacitor; and   determining a dispensed dose of the medicament or an amount of medicament remaining in a cartridge based on the measured inductance.