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WO2007141225A1 - Contact free axial position determination of a moving element in a medication delivery device - Google Patents

Contact free axial position determination of a moving element in a medication delivery device Download PDF

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Publication number
WO2007141225A1
WO2007141225A1 PCT/EP2007/055430 EP2007055430W WO2007141225A1 WO 2007141225 A1 WO2007141225 A1 WO 2007141225A1 EP 2007055430 W EP2007055430 W EP 2007055430W WO 2007141225 A1 WO2007141225 A1 WO 2007141225A1
Authority
WO
WIPO (PCT)
Prior art keywords
delivery device
medication delivery
electrode
transmitter
movably mounted
Prior art date
Application number
PCT/EP2007/055430
Other languages
French (fr)
Inventor
VON Bodo MÜNCHOW
Preben Nielsen
Peter Grønning NIELSEN
Original Assignee
Novo Nordisk A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Novo Nordisk A/S filed Critical Novo Nordisk A/S
Publication of WO2007141225A1 publication Critical patent/WO2007141225A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance
    • G01D5/241—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance by relative movement of capacitor electrodes
    • G01D5/2412—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance by relative movement of capacitor electrodes by varying overlap
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
    • A61M5/178—Syringes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/50—General characteristics of the apparatus with microprocessors or computers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/60—General characteristics of the apparatus with identification means
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2205/00—General characteristics of the apparatus
    • A61M2205/60—General characteristics of the apparatus with identification means
    • A61M2205/6027—Electric-conductive bridges closing detection circuits, with or without identifying elements, e.g. resistances, zener-diodes

Definitions

  • the present invention relates to an arrangement and a method for determining an axial position of a movably mounted member in a medication delivery device.
  • the present invention relates to an arrangement that is essentially insensitive to non-axial movements and which, at the same time, takes up a minimum amount of space.
  • US 4,420,754 discloses a system for measuring the relative movement between two elements, such as the scale and slide of a hand-held measuring instrument.
  • the system includes the provision of a number of groups of supply electrodes on the slide, each of the electrodes in each group being supplied from a respective one of a multiple number of output signals from a signal generator so that all of the supply electrodes are furnished with voltages according to a cyclic pattern, the slide also having at least one receiving electrode which feeds a signal processing unit.
  • the scale is provided with an electronic pattern comprising internally galvanically connected parts, one being a detecting part, located close to the area where the supply electrodes of the slide are moved, the other of the two parts being a transferring part which is located close to the area where the receiving electrode of the slide is moved.
  • the movement of the slide along the scale generates a signal from the receiving electrode which is derived from the signals from at least two adjacent supply electrodes and the position of the slide is determined by a signal processing unit which identifies the amplitude ratio of
  • US 6,329,813 discloses an inductive absolute position sensor applying at least one magnetic field generator that generates a first changing magnetic flux in a first flux region.
  • a plurality of coupling loops have a first plurality of coupling loop portions spaced at an interval related to a first wavelength along a measuring axis and a second plurality of coupling loop portions spaced at an interval related to a second wavelength along a measuring axis.
  • One of the first plurality of coupling loop portions and the second plurality of coupling loop portions are inductively coupled to a first changing magnetic flux from a transmitter winding in a first flux region to generate a second changing magnetic flux outside the first flux region in the other of the first plurality of coupling loop portions and the second plurality of coupling loop portions.
  • a magnetic flux sensor is positioned outside the first flux region and is responsive to the second changing magnetic flux to generate a position-dependent output signal.
  • the output signal varies at the first or second wavelength of the corresponding other of the first plurality of coupling loop portions and the second plurality of coupling loop portions that generates the second changing magnetic flux.
  • US 2004/0207385 relates to a device for detecting the position of a rotor relative to a stator, wherein at least one electrode is arranged on the rotor and at least one electrode is arranged on the stator, such that the electrodes at least partially overlap in at least one rotational position of the rotor relative to the stator.
  • US 2004/0207385 further relates to a method for measuring the rotational position of a rotor comprising at least one rotor electrode relative to a stator comprising at least one stator electrode, wherein the rotational position is detected using a capacitive coupling between the rotor electrode and the stator electrode.
  • US 2004/0207385 relates to the determining of angular positions between two objects such as between a rotatably mounted rotor and a stationary stator. It is a disadvantage of the arrangement suggested in US 2004/0207385 that the emitters and receivers are position in a manner where they take up an unnecessary amount of space. For compact systems the solution suggested by US 2004/0207385 is not applicable.
  • a medication delivery device for expelling set doses of medicament
  • the medication delivery device comprising a position determining arrangement for detecting absolute axial positions of a movably mounted member arranged movably relative to a first member within the medication delivery device, the position determining arrangement comprising
  • a reflector electrode associated with an exterior surface part of the movably mounted member, the reflector electrode of the movably mounted member being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode.
  • the term “associated” is defined to encompass embodiments where one or more of the electrodes is/are arranged on respective surface parts of the medical delivery device, thus being formed onto respective interior and exterior surface parts of the medication delivery device. Also, “associated” is defined to encompass electrodes being formed so as to be embedded in the relevant members of the device, such as in electrically non-conducting material such as polymeric material. Still, within the context of the present invention, “associated” encompasses embodiments where intermediary and separate members may be arranged between reflector electrode(s) and opposing electrodes. Furthermore, the electrodes may be formed integrally in the relevant members of the device by disposing electrically conducting particles, such as nano-particles into specific areas of the relevant members whereby these areas then constitutes the electrodes.
  • the first member may be fixedly arranged with respect to the housing of the medication delivery device, or alternatively constitute a housing part.
  • the above-mentioned transmitter/ receiver/ reflector arrangement may be implemented once in the medication delivery device.
  • the above-mentioned transmitter/receiver/reflector arrangement may be implemented a plurality of times in the medication delivery device.
  • a single medication delivery device may comprise a plurality of axially arranged position determining arrangements. By incorporating a plurality of position determining arrangements in a single medication delivery device higher stability, increased signal levels etc. may be obtained.
  • At least one of the transmitter electrodes, the receiver electrode or the reflector electrode may be cylindrically-shaped.
  • cylindrically-shaped is meant that one or some of the electrodes form an essentially unbroken path 360 degrees around the respective surfaces of the medication delivery device.
  • one or some electrodes extend essentially 360 degrees.
  • electrodes may be discontinued such that one or some of the electrodes may be open at one or several places.
  • a given electrode such as for example a transmitter electrode, may be constituted by a single or a plurality of electrodes.
  • the transmitter electrodes, the receiver electrode and the reflector electrode are all cylindrically-shaped.
  • some or all of the electrodes may be formed as ring shaped electrodes having a short dimension in the axial direction, such as less than 3 mm.
  • this symmetric (rotational) arrangement of electrodes the output signal from the system becomes essentially insensitive to non-axial displacement/movements, such as radial movements, of the movably mounted member.
  • other cross-sectional profiles such as elliptical, rectangular, quadratic etc, are also applicable.
  • a dielectric layer may be disposed on each or some of the electrodes. Particularly, in applications where the spacing between coaxially arranged electrodes are small, an nonconducting electric layer may be arranged on the surface of one or more of the electrodes opposing other respective electrodes.
  • the medication delivery device may further comprise a first signal generator arranged to generate a first time varying signal and apply this first time varying signal to the first transmitter electrode.
  • a second signal generator may be arranged to generate a second time varying signal and apply this second time varying signal to the second transmitter electrode.
  • the first and second signal generators are constituted by a single electronic circuit.
  • the first and second time varying signals may have a fundamental frequency within the range 1-100 kHz. In case of PWM-generated time varying signals the fundamental frequencies of the first and second time varying signals may be around 10 kHz, with peak-to-peak amplitudes of around 1 V. However, peak-to-peak amplitudes within the range 0.1-10 V are also applicable.
  • the movably mounted member may be adapted to perform a combined rotational and translational movement relative to the housing of the medication delivery device. Alternatively, the movably mounted member may be adapted to perform a translational movement relative to the housing of the medication delivery device.
  • the electrical coupling between transmitter electrodes and the reflector electrode may comprise a capacitive coupling.
  • the electrical coupling between the receiver electrode and the reflector electrode may comprise a capacitive coupling.
  • the receiver electrode may, in an axial direction of the medication delivery device, be arranged between the first and second transmitter electrodes.
  • the arrangement of electrodes on the interior surface parts of the housing may be a transmitter- receiver-transmitter arrangement.
  • the present invention relates to a method for determining absolute axial positions of a movably mounted member arranged within a medication delivery device, the positions being determined relative to a housing of the medication delivery device, the method comprising the steps of
  • the reflector electrode of the movably mounted member being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode
  • the first and second transmitter signals may be approximately 180 degrees out of phase, and they may have a fundamental frequency within the range 1-100 kHz.
  • the fundamental frequencies of the first and second time varying signals may be around 10 kHz, with peak-to-peak amplitudes of around 1 V. However, peak-to-peak amplitudes within the range 0.1-10 V are also applicable.
  • the output signal from the receiver electrode may vary in a linear manner as a function of the axial position of movably mounted member.
  • the output signal may be zero.
  • the output signal may vary in a linear manner until the movably mounted member reaches one of its end position. At these end positions the output signal takes the value ⁇ X volts.
  • the electrical coupling between transmitter electrodes and the reflector electrode may comprise a capacitive coupling.
  • the electrical coupling between the receiver electrode and the reflector electrode may comprise a capacitive coupling.
  • the present invention relates to a medication delivery device for expelling set doses of medicament, the medication delivery device comprising a position determining arrangement for detecting absolute axial positions of a movably mounted member arranged within the medication delivery device, the position determining arrangement comprising
  • a reflector electrode being movably mounted relative the receiver electrode, the reflector electrode being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode.
  • the transmitter and receiver electrodes may be arranged on the movably mounted member optionally with some additional electronics, such as a signal generator, a signal processor etc, whereas the reflector electrode may be arranged on the housing of the medication delivery device.
  • the present invention relates to a method for determining absolute axial positions of a movably mounted member arranged within a medication delivery device, the positions being determined relative to a housing of the medication delivery device, the method comprising the steps of - providing a first and a second transmitter electrode fixedly arranged relative to each other,
  • a reflector electrode being movably mounted relative the receiver electrode, the reflector electrode being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode, and
  • the transmitter and receiver electrodes may be arranged on the movably mounted member optionally with some additional electronics, such as a signal generator, a signal processor etc, whereas the reflector electrode may be arranged on the housing of the medication delivery device.
  • Fig. 1 and 2 show a movably mounted member in a centre position and in a near-end upper position, respectively
  • Fig. 3 shows a radially displaced member in a medication delivery device
  • Fig. 4 shows a skewed member in a medication delivery device.
  • Fig. 5 shows a cross sectional view of an alternative embodiment of the invention.
  • the present invention relates to a medication delivery device comprising an arrangement for determining an absolute axial position of a movably mounted member relative to a housing of the medication delivery device.
  • the arrangement is implemented to take up minimum space within the medication delivery device.
  • Fig. 1 the principle of the present invention is depicted.
  • an axially movable mounted member 2 is arranged in a housing 1 of a medication delivery device.
  • a pair of transmitter electrodes 3, 4 and a receiver electrode 5 are arranged on interior surface parts of the housing 1 of the medication delivery device.
  • the transmitter electrodes and the receiver electrode are provided as cylindrical or near-cylindrical electrodes extending 360 degrees or nearly 360 degrees.
  • the receiver electrode 5 is arranged between the two transmitter electrodes 3, 4. The distance between transmitter electrode 3 and receiver electrode 5 equals the distance between transmitter electrode 4 and receiver electrode 5.
  • the movably mounted member 2 has a reflector electrode 6 arranged on an exterior surface thereof.
  • the reflector electrode is formed as a cylindrical or a near-cylindrical shaped electrode extending 360 degrees or nearly 360 degrees around the movably mounted member.
  • Fig. 1 the movably mounted member 2 is illustrated in its central position. Since the two transmitter electrodes 3, 4 are provided with the same time varying signal, but 180 degrees out of phase, and the signal from the receiver electrode 5 is rectified in a syncron detector/rectifier which is synchronous with the signals provided to transmitter electrodes 3, 4, a zero volt output signal is provided when the movably mounted member 2 is in its central position.
  • the output signal DC signal
  • the output signal may vary accordingly in a linear manner.
  • the output signal may vary linearly as a function of the axial position of the movably mounted member between the two end positions.
  • the output signal may alternatively vary in a non-linear manner depending on the configuration of associated control electronics and the shapes of the electrodes.
  • the transmitter electrodes and receiver electrode are arranged in a symmetric arrangement along the axial direction of the housing of the medication delivery device, the influence of non-axial movements, such as a radial displacement of the movably mounted member, twisting and/or bending of the movably mounted member, is essentially avoided.
  • the number of transmitter electrodes can be larger that to. If N denotes the number of applied transmitter electrodes, the signals supplied to the transmitter electrodes are 360/N out of phase. Additional reflector and receiver electrodes must be applied as well.
  • Fig. 2 shows a situation where the movably mounted member 2 has been displaced towards the upper end of the medication delivery device. As previously mentioned such a displacement generates a non-zero DC output signal.
  • Figs. 3 and 4 illustrate a radial displacement and tilting of the moveably mounted member 2, respectively.
  • the output signal from the arrangement is, however, not influenced by the radial displacement as illustrated in Fig. 3.
  • the output signal influenced in case the movably mounted member is skewed or tilted away from the intended axial symmetric position as illustrated if Fig. 4.
  • Fig. 5 shows a cross sectional view of an alternative embodiment specially adapted to be used in a medication delivery device such as an injection pen where several elements are to be accommodated coaxially inside the moveably mounted member 2.
  • the moveably mounted member 2 is a cylindrical hollow member of tubular form in which additional elements (not shown) are able to slide axially relative to the moveably mounted member 2.
  • the tubular element is provided with a coaxially disposed inner tubular member 7 formed of a metal in order to shield the sensing electrodes 3-6 from internal metallic parts which may be provided inside the inner tubular member 7.
  • a dielectric layer 8 may be disposed between the inner tubular member 7 and the reflector electrode 6 in order to keep the reflector electrode electrically isolated from the inner tubular member 7.
  • the axial length of the dielectric layer 8 is preferably at least the length of the reflector electrode 6.
  • the inner tubular member 7 is arranged so that the tubular member axially overlaps all electrodes 3, 4 and 5 in each position the moveably mounted member 2 is allowed to take. In this manner, the tubular member 7 acts as a shield against internal metallic parts which otherwise may influence the position sensing.
  • the sensor arrangement according to the invention may be designed to provide sensor signals corresponding to a continuous range of axial positions. Also the sensor arrangement may be designed to sense between two or more distinct axial positions, so as to provide a switch.

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Abstract

The present invention relates to a medication delivery device for expelling set doses of medicament, the medication delivery device comprising a position determining arrangement for detecting absolute axial positions of a movably mounted member arranged within the medication delivery device, the position determining arrangement comprising first and second transmitter electrodes arranged on interior surface parts of a housing of the medication delivery device, a receiver electrode arranged on an interior surface part of the housing of the medication delivery device, and a reflector electrode arranged on an exterior surface part of the movably mounted member, the electrode of the movably mounted member being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode.

Description

CONTACT FREE AXIAL POSITION DETERMINATION OF A MOVING ELEMENT IN A MEDICATION DELIVERY DEVICE
FIELD OF THE INVENTION
The present invention relates to an arrangement and a method for determining an axial position of a movably mounted member in a medication delivery device. In particular, the present invention relates to an arrangement that is essentially insensitive to non-axial movements and which, at the same time, takes up a minimum amount of space.
BACKGROUND OF THE INVENTION
US 4,420,754 discloses a system for measuring the relative movement between two elements, such as the scale and slide of a hand-held measuring instrument. The system includes the provision of a number of groups of supply electrodes on the slide, each of the electrodes in each group being supplied from a respective one of a multiple number of output signals from a signal generator so that all of the supply electrodes are furnished with voltages according to a cyclic pattern, the slide also having at least one receiving electrode which feeds a signal processing unit. The scale is provided with an electronic pattern comprising internally galvanically connected parts, one being a detecting part, located close to the area where the supply electrodes of the slide are moved, the other of the two parts being a transferring part which is located close to the area where the receiving electrode of the slide is moved. The movement of the slide along the scale generates a signal from the receiving electrode which is derived from the signals from at least two adjacent supply electrodes and the position of the slide is determined by a signal processing unit which identifies the amplitude ratio of the received signals.
US 6,329,813 discloses an inductive absolute position sensor applying at least one magnetic field generator that generates a first changing magnetic flux in a first flux region. A plurality of coupling loops have a first plurality of coupling loop portions spaced at an interval related to a first wavelength along a measuring axis and a second plurality of coupling loop portions spaced at an interval related to a second wavelength along a measuring axis. One of the first plurality of coupling loop portions and the second plurality of coupling loop portions are inductively coupled to a first changing magnetic flux from a transmitter winding in a first flux region to generate a second changing magnetic flux outside the first flux region in the other of the first plurality of coupling loop portions and the second plurality of coupling loop portions. A magnetic flux sensor is positioned outside the first flux region and is responsive to the second changing magnetic flux to generate a position-dependent output signal. The output signal varies at the first or second wavelength of the corresponding other of the first plurality of coupling loop portions and the second plurality of coupling loop portions that generates the second changing magnetic flux.
The rather complicated arrangements suggested in both US 4,420,754 and US 6,329,813 are adapted for determining linear translations between two objects.
US 2004/0207385 relates to a device for detecting the position of a rotor relative to a stator, wherein at least one electrode is arranged on the rotor and at least one electrode is arranged on the stator, such that the electrodes at least partially overlap in at least one rotational position of the rotor relative to the stator. US 2004/0207385 further relates to a method for measuring the rotational position of a rotor comprising at least one rotor electrode relative to a stator comprising at least one stator electrode, wherein the rotational position is detected using a capacitive coupling between the rotor electrode and the stator electrode.
US 2004/0207385 relates to the determining of angular positions between two objects such as between a rotatably mounted rotor and a stationary stator. It is a disadvantage of the arrangement suggested in US 2004/0207385 that the emitters and receivers are position in a manner where they take up an unnecessary amount of space. For compact systems the solution suggested by US 2004/0207385 is not applicable.
Furthermore, the arrangement suggested in US 2004/0207385 is not adapted for contact free and absolute position determination. As depicted in figures 8 and 9 of US 2004/0207385 and the corresponding text in paragraphs 0053 and 0054 additional components such as force sensors or electrical resistors are required if absolute measurements are to be performed. Thus, it is a disadvantage of the arrangement suggested in 2004/0207385 that absolute measurements cannot be performed without the adding of contact requiring elements, such as force sensors and electrical resistors - the latter being implemented as a voltage divider.
It is an object of the present invention to provide a space saving arrangement for measuring an absolute axial position of a movably mounted member in a medication delivery device.
It is a further object of the present invention to provide a space saving arrangement for measuring an absolute axial position of a movably mounted member in a medication delivery device, the arrangement being essentially insensitive to non-axial movements of the movably mounted member. SYMMARY OF THE INVENTION
The above-mentioned objects are complied with by providing, in a first aspect, a medication delivery device for expelling set doses of medicament, the medication delivery device comprising a position determining arrangement for detecting absolute axial positions of a movably mounted member arranged movably relative to a first member within the medication delivery device, the position determining arrangement comprising
- a first transmitter electrode associated with a first interior surface part of a first member of the medication delivery device,
- a second transmitter electrode associated with a second interior surface part of the first member of the medication delivery device,
- a receiver electrode associated with an interior surface part of the first member of the medication delivery device, and
- a reflector electrode associated with an exterior surface part of the movably mounted member, the reflector electrode of the movably mounted member being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode.
Within the context of the present invention, the term "associated" is defined to encompass embodiments where one or more of the electrodes is/are arranged on respective surface parts of the medical delivery device, thus being formed onto respective interior and exterior surface parts of the medication delivery device. Also, "associated" is defined to encompass electrodes being formed so as to be embedded in the relevant members of the device, such as in electrically non-conducting material such as polymeric material. Still, within the context of the present invention, "associated" encompasses embodiments where intermediary and separate members may be arranged between reflector electrode(s) and opposing electrodes. Furthermore, the electrodes may be formed integrally in the relevant members of the device by disposing electrically conducting particles, such as nano-particles into specific areas of the relevant members whereby these areas then constitutes the electrodes.
The first member may be fixedly arranged with respect to the housing of the medication delivery device, or alternatively constitute a housing part.
The above-mentioned transmitter/ receiver/ reflector arrangement may be implemented once in the medication delivery device. Alternatively, the above-mentioned transmitter/receiver/reflector arrangement may be implemented a plurality of times in the medication delivery device. Thus, a single medication delivery device may comprise a plurality of axially arranged position determining arrangements. By incorporating a plurality of position determining arrangements in a single medication delivery device higher stability, increased signal levels etc. may be obtained.
At least one of the transmitter electrodes, the receiver electrode or the reflector electrode may be cylindrically-shaped. By cylindrically-shaped is meant that one or some of the electrodes form an essentially unbroken path 360 degrees around the respective surfaces of the medication delivery device. Thus, seen from the centre of the medication delivery device, one or some electrodes extend essentially 360 degrees. By essentially is meant that electrodes may be discontinued such that one or some of the electrodes may be open at one or several places. Thus, a given electrode, such as for example a transmitter electrode, may be constituted by a single or a plurality of electrodes. Alternatively, the transmitter electrodes, the receiver electrode and the reflector electrode are all cylindrically-shaped. Still alternatively, some or all of the electrodes may be formed as ring shaped electrodes having a short dimension in the axial direction, such as less than 3 mm. By applying this symmetric (rotational) arrangement of electrodes the output signal from the system becomes essentially insensitive to non-axial displacement/movements, such as radial movements, of the movably mounted member. However, other cross-sectional profiles, such as elliptical, rectangular, quadratic etc, are also applicable.
A dielectric layer may be disposed on each or some of the electrodes. Particularly, in applications where the spacing between coaxially arranged electrodes are small, an nonconducting electric layer may be arranged on the surface of one or more of the electrodes opposing other respective electrodes.
The medication delivery device may further comprise a first signal generator arranged to generate a first time varying signal and apply this first time varying signal to the first transmitter electrode. Furthermore, a second signal generator may be arranged to generate a second time varying signal and apply this second time varying signal to the second transmitter electrode. Preferably, the first and second signal generators are constituted by a single electronic circuit. The first and second time varying signals may have a fundamental frequency within the range 1-100 kHz. In case of PWM-generated time varying signals the fundamental frequencies of the first and second time varying signals may be around 10 kHz, with peak-to-peak amplitudes of around 1 V. However, peak-to-peak amplitudes within the range 0.1-10 V are also applicable. The movably mounted member may be adapted to perform a combined rotational and translational movement relative to the housing of the medication delivery device. Alternatively, the movably mounted member may be adapted to perform a translational movement relative to the housing of the medication delivery device.
The electrical coupling between transmitter electrodes and the reflector electrode may comprise a capacitive coupling. Similarly, the electrical coupling between the receiver electrode and the reflector electrode may comprise a capacitive coupling.
In one embodiment the receiver electrode may, in an axial direction of the medication delivery device, be arranged between the first and second transmitter electrodes. Thus, the arrangement of electrodes on the interior surface parts of the housing may be a transmitter- receiver-transmitter arrangement.
In a second aspect, the present invention relates to a method for determining absolute axial positions of a movably mounted member arranged within a medication delivery device, the positions being determined relative to a housing of the medication delivery device, the method comprising the steps of
- providing a first transmitter electrode associated with a first interior surface part of a housing of the medication delivery device,
- providing a second transmitter electrode associated with a second interior surface part of the housing of the medication delivery device,
- providing a receiver electrode associated with an interior surface part of the housing of the medication delivery device,
- providing a reflector electrode associated with an exterior surface part of the movably mounted member, the reflector electrode of the movably mounted member being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode, and
- providing first and second transmitter signals to respective ones of first and second transmitter electrodes, and determining the axial position of the movably mounted member from a detected output signal from the receiver electrode. The first and second transmitter signals may be approximately 180 degrees out of phase, and they may have a fundamental frequency within the range 1-100 kHz. In case of PWM- generated signals the fundamental frequencies of the first and second time varying signals may be around 10 kHz, with peak-to-peak amplitudes of around 1 V. However, peak-to-peak amplitudes within the range 0.1-10 V are also applicable.
The output signal from the receiver electrode may vary in a linear manner as a function of the axial position of movably mounted member. Thus, with the movably mounted member positioned in a centre position the output signal may be zero. As the movably mounted member is displaced towards the ends of its moving range the output signal may vary in a linear manner until the movably mounted member reaches one of its end position. At these end positions the output signal takes the value ± X volts.
The electrical coupling between transmitter electrodes and the reflector electrode may comprise a capacitive coupling. Similarly, the electrical coupling between the receiver electrode and the reflector electrode may comprise a capacitive coupling.
In a third aspect, the present invention relates to a medication delivery device for expelling set doses of medicament, the medication delivery device comprising a position determining arrangement for detecting absolute axial positions of a movably mounted member arranged within the medication delivery device, the position determining arrangement comprising
- a first and a second transmitter electrode fixedly arranged relative to each other,
- a receiver electrode fixedly arranged relative to the transmitter electrodes, and
- a reflector electrode being movably mounted relative the receiver electrode, the reflector electrode being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode.
Thus, according to this aspect of the present invention the transmitter and receiver electrodes may be arranged on the movably mounted member optionally with some additional electronics, such as a signal generator, a signal processor etc, whereas the reflector electrode may be arranged on the housing of the medication delivery device.
In a fourth aspect, the present invention relates to a method for determining absolute axial positions of a movably mounted member arranged within a medication delivery device, the positions being determined relative to a housing of the medication delivery device, the method comprising the steps of - providing a first and a second transmitter electrode fixedly arranged relative to each other,
- providing a receiver electrode fixedly arranged relative to the transmitter electrodes,
- providing a reflector electrode being movably mounted relative the receiver electrode, the reflector electrode being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode, and
- providing first and second transmitter signals to respective ones of first and second transmitter electrodes, and determining the axial position of the movably mounted member from a detected output signal from the receiver electrode.
As with the third aspect of the present invention the transmitter and receiver electrodes may be arranged on the movably mounted member optionally with some additional electronics, such as a signal generator, a signal processor etc, whereas the reflector electrode may be arranged on the housing of the medication delivery device.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be explained with reference to the accompanying figures, wherein
Fig. 1 and 2 show a movably mounted member in a centre position and in a near-end upper position, respectively,
Fig. 3 shows a radially displaced member in a medication delivery device, and
Fig. 4 shows a skewed member in a medication delivery device.
Fig. 5 shows a cross sectional view of an alternative embodiment of the invention.
While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. DETAILED DESCRIPTION OF THE INVENTION
In its broadest aspect the present invention relates to a medication delivery device comprising an arrangement for determining an absolute axial position of a movably mounted member relative to a housing of the medication delivery device. The arrangement is implemented to take up minimum space within the medication delivery device.
In Fig. 1 the principle of the present invention is depicted. As seen, an axially movable mounted member 2 is arranged in a housing 1 of a medication delivery device. On interior surface parts of the housing 1 of the medication delivery device a pair of transmitter electrodes 3, 4 and a receiver electrode 5 are arranged. In order to be essentially insensitive to non-axial movements the transmitter electrodes and the receiver electrode are provided as cylindrical or near-cylindrical electrodes extending 360 degrees or nearly 360 degrees. As seen, the receiver electrode 5 is arranged between the two transmitter electrodes 3, 4. The distance between transmitter electrode 3 and receiver electrode 5 equals the distance between transmitter electrode 4 and receiver electrode 5.
Still referring to Fig. 1, the movably mounted member 2 has a reflector electrode 6 arranged on an exterior surface thereof. In order to be essentially insensitive to non-axial movements the reflector electrode is formed as a cylindrical or a near-cylindrical shaped electrode extending 360 degrees or nearly 360 degrees around the movably mounted member.
In Fig. 1 the movably mounted member 2 is illustrated in its central position. Since the two transmitter electrodes 3, 4 are provided with the same time varying signal, but 180 degrees out of phase, and the signal from the receiver electrode 5 is rectified in a syncron detector/rectifier which is synchronous with the signals provided to transmitter electrodes 3, 4, a zero volt output signal is provided when the movably mounted member 2 is in its central position. When the movably mounted member is displaced towards one of the axial end positions the output signal (DC signal) may vary accordingly in a linear manner. Thus, with the movably mounted member positioned at one end position an output signal of +X Volt is generated whereas an output signal of -X Volt is generated when of the movably mounted member is positioned at the opposite end position. As already mentioned the output signal may vary linearly as a function of the axial position of the movably mounted member between the two end positions. The output signal may alternatively vary in a non-linear manner depending on the configuration of associated control electronics and the shapes of the electrodes.
Since the transmitter electrodes and receiver electrode are arranged in a symmetric arrangement along the axial direction of the housing of the medication delivery device, the influence of non-axial movements, such as a radial displacement of the movably mounted member, twisting and/or bending of the movably mounted member, is essentially avoided.
It should be noted that the number of transmitter electrodes can be larger that to. If N denotes the number of applied transmitter electrodes, the signals supplied to the transmitter electrodes are 360/N out of phase. Additional reflector and receiver electrodes must be applied as well.
Fig. 2 shows a situation where the movably mounted member 2 has been displaced towards the upper end of the medication delivery device. As previously mentioned such a displacement generates a non-zero DC output signal.
Figs. 3 and 4 illustrate a radial displacement and tilting of the moveably mounted member 2, respectively. The output signal from the arrangement is, however, not influenced by the radial displacement as illustrated in Fig. 3. Nor is the output signal influenced in case the movably mounted member is skewed or tilted away from the intended axial symmetric position as illustrated if Fig. 4.
Fig. 5 shows a cross sectional view of an alternative embodiment specially adapted to be used in a medication delivery device such as an injection pen where several elements are to be accommodated coaxially inside the moveably mounted member 2. Here the moveably mounted member 2 is a cylindrical hollow member of tubular form in which additional elements (not shown) are able to slide axially relative to the moveably mounted member 2. In the depicted embodiment the tubular element is provided with a coaxially disposed inner tubular member 7 formed of a metal in order to shield the sensing electrodes 3-6 from internal metallic parts which may be provided inside the inner tubular member 7. In addition, a dielectric layer 8 may be disposed between the inner tubular member 7 and the reflector electrode 6 in order to keep the reflector electrode electrically isolated from the inner tubular member 7. The axial length of the dielectric layer 8 is preferably at least the length of the reflector electrode 6. The inner tubular member 7 is arranged so that the tubular member axially overlaps all electrodes 3, 4 and 5 in each position the moveably mounted member 2 is allowed to take. In this manner, the tubular member 7 acts as a shield against internal metallic parts which otherwise may influence the position sensing.
The sensor arrangement according to the invention may be designed to provide sensor signals corresponding to a continuous range of axial positions. Also the sensor arrangement may be designed to sense between two or more distinct axial positions, so as to provide a switch.

Claims

1. A medication delivery device for expelling set doses of medicament, the medication delivery device comprising a position determining arrangement for detecting absolute axial positions of a movably mounted member arranged within the medication delivery device, the position determining arrangement comprising
- a first transmitter electrode associated with a first interior surface part of a housing of the medication delivery device,
- a second transmitter electrode associated with a second interior surface part of the housing of the medication delivery device,
- a receiver electrode associated with an interior surface part of the housing of the medication delivery device, and
- a reflector electrode associated with an exterior surface part of the movably mounted member, the reflector electrode of the movably mounted member being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode.
2. A medication delivery device according to claim 1, wherein at least one of the transmitter electrodes, the receiver electrode or the reflector electrode is cylindrically-shaped.
3. A medication delivery device according to claim 1, wherein the transmitter electrodes, the receiver electrode and the reflector electrode are cylindrically-shaped.
4. A medication delivery device according to any of claims 1-3, further comprising a first signal generator arranged to generate a first time varying signal and apply this first time varying signal to the first transmitter electrode.
5. A medication delivery device according to any of claims 1-4, further comprising a second signal generator arranged to generate a second time varying signal and apply this second time varying signal to the second transmitter electrode.
6. A medication delivery device according to claim 5, wherein the first and second signal generators are constituted by a single electronic circuit.
7. A medication delivery device according to any of the preceding claims, wherein the movably mounted member is adapted to perform a combined rotational and translational movement relative to the housing of the medication delivery device.
8. A medication delivery device according to any of claims 1-6, wherein the movably mounted member is adapted to perform a translational movement relative to the housing of the medication delivery device.
9. A medication delivery device according to any of the preceding claims, wherein the electrical coupling between transmitter electrodes and the reflector electrode comprises a capacitive coupling.
10. A medication delivery device according to any of the preceding claims, wherein the electrical coupling between the receiver electrode and the reflector electrode comprises a capacitive coupling.
11. A medication delivery device according to any of the preceding claims, wherein the receiver electrode is arranged between the first and second transmitter electrodes.
12. A method for determining absolute axial positions of a movably mounted member arranged within a medication delivery device, the positions being determined relative to a housing of the medication delivery device, the method comprising the steps of
- providing a first transmitter electrode associated with a first interior surface part of the medication delivery device,
- providing a second transmitter electrode associated with a second interior surface part of the medication delivery device,
- providing a receiver electrode associated with an interior surface part of the medication delivery device,
- providing a reflector electrode associated with an exterior surface part of the movably mounted member, the reflector electrode of the movably mounted member being adapted to electrically couple to at least one of the transmitter electrodes and to the receiver electrode, and - providing first and second transmitter signals to respective ones of first and second transmitter electrodes, and determining the axial position of the movably mounted member from a detected output signal from the receiver electrode.
13. A method according to claim 12, wherein the first and second transmitter signals are approximately 180 degrees out of phase.
14. A method according to claim 12 or 13, wherein the output signal from the receiver electrode varies in a linear manner as a function of the axial position of movably mounted member.
15. A method according to any of claims 12-14, wherein the electrical coupling between transmitter electrodes and the reflector electrode comprises a capacitive coupling.
16. A method according to any of claims 12-15, wherein the electrical coupling between the receiver electrode and the reflector electrode comprises a capacitive coupling.
PCT/EP2007/055430 2006-06-02 2007-06-01 Contact free axial position determination of a moving element in a medication delivery device WO2007141225A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP06011469.1 2006-06-02
EP06011469 2006-06-02

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2078981A1 (en) 2008-01-10 2009-07-15 Dialog Imaging Systems GmbH Lens positioning system
WO2010088973A1 (en) * 2009-02-06 2010-08-12 Shl Group Ab Medicament delivery device with electronic dose sensor
EP2327431A1 (en) 2009-11-25 2011-06-01 Letcat Aktiebolag Medical delivery device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0336022A1 (en) * 1988-04-08 1989-10-11 SCHUT'S IM- & EXPORTHANDEL B.V. Capacitive displacement meter
US20040207385A1 (en) * 2001-07-09 2004-10-21 Simone Gafner Position detection

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0336022A1 (en) * 1988-04-08 1989-10-11 SCHUT'S IM- & EXPORTHANDEL B.V. Capacitive displacement meter
US20040207385A1 (en) * 2001-07-09 2004-10-21 Simone Gafner Position detection

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2078981A1 (en) 2008-01-10 2009-07-15 Dialog Imaging Systems GmbH Lens positioning system
US8363324B2 (en) 2008-01-10 2013-01-29 Digital Imaging Systems Gmbh Lens positioning system
WO2010088973A1 (en) * 2009-02-06 2010-08-12 Shl Group Ab Medicament delivery device with electronic dose sensor
US8529520B2 (en) 2009-02-06 2013-09-10 Shl Group Ab Medicament delivery device with electronic dose sensor
EP2327431A1 (en) 2009-11-25 2011-06-01 Letcat Aktiebolag Medical delivery device
WO2011064299A1 (en) 2009-11-25 2011-06-03 Letcat Aktiebolag Medical delivery device

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