Patent Description:
Hypodermic syringes are widely used to deliver fluids to the body. It is known to have hypodermic syringes applicable for manual operation. However, auto injectors, such as electronic auto injectors, have been developed and are widely used to aid the administering of fluid or medicaments to the body.

To avoid relying on users correctly performing certain tasks, it is of increasing interest that the auto injector automatically carries out as much as possible of the injection process.

However, for safety of the user, it is of continuous desire that such auto injector prevents adverse use, securing or facilitating that the medicament is given appropriately, and that erroneous usage, or results of erroneous usage, e.g. incorrect dosage or transmission of infections, is prevented or reduced.

It is of further importance to enable precise control of the amount of medicament being injected and/or absorbed by the tissue. Thus, it is of increasing interest to decrease the risk of medicament leaking or being spilled, and furthermore also to decrease the amount of residual medicament in the cartridge following end of injection.

The plunger force may often be limited in order to avoid back-flush of medicament during injection, i.e. that medicament flows backwards around the stopper as oppose to being expelled through the needle. Other objectives might also motivate for plunger force limitation, e.g. for preventing medicament leakage or even to prevent breakage of a cartridge structure. <CIT> discloses an auto-injector according to the state of the art.

Despite the known solutions there is a need for an auto injector for optimizing dosing accuracy, such as by decreasing residual medicament following injection, and preventing medicament leakage, such as through or around an end stopper of the cartridge.

Accordingly, an auto injector for administering a medicament is disclosed. The auto injector comprising: a housing, a cartridge receiver, a drive module, a resistance sensor, and a processing unit.

The cartridge receiver is configured to receive a cartridge comprising a first stopper.

The drive module is coupled to move, such as advance, a plunger rod between a retracted plunger rod position and an extended plunger rod position. The plunger rod is configured to move, such as advance, the first stopper.

The resistance sensor is configured to provide a resistance signal indicative of resistance against movement of the plunger rod.

The processing unit is coupled to the drive module. The processing unit is coupled to the resistance sensor.

The processing unit is configured to: control the drive module to move, such as advance, the plunger rod towards the extended plunger rod position with a plunger rod speed; determine plunger rod position; receive the resistance signal; and control the drive module to adjust movement of the plunger rod if the resistance signal is indicative of resistance against movement of the plunger rod above a high resistance threshold.

The high resistance threshold is based on the plunger rod position.

The housing may accommodate one or more of the cartridge receiver, the drive module, the resistance sensor and the processing unit.

The auto injector also comprises a cartridge comprising the first stopper, wherein the cartridge is configured to be received in the cartridge receiver.

Also disclosed is a method for controlling an auto injector, said method not forming part of the invention. The method comprises:
receiving a cartridge comprising a first stopper; moving a plunger rod towards an extended plunger rod position with a plunger rod speed; determining plunger rod position; receiving a resistance signal indicative of resistance against movement of the plunger rod; and adjusting movement of the plunger rod if the resistance signal is indicative of resistance against movement of the plunger rod above a high resistance threshold, wherein the high resistance threshold is based on the plunger rod position.

It is an advantage of the present disclosure that it provides a way of optimizing dosing accuracy through more fully emptying a drug cartridge during injection by applying more force to the stopper(s) - and maintain such elevated force over a period of time - thereby forcing deformation/compression of the stopper to better contact with (fill out) the interior cartridge shoulder area and thereby press out residual drug sitting here. Additionally, the disclosed approach also provides an improved medicament utilization as less medicament may be wasted from each cartridge.

Plunger rod speed may further be optimized, e.g. leading to an optimization of the time of the injection procedure, e.g. time needed to inject the medicament and/or in preparing for injection.

It is a further advantage of the present disclosure, that patient safety is increased, e.g. by decreasing the risk of incorrect dosage of medicament.

Furthermore, the present disclosure provides the advantage of allowing for improved precision of medicament usage, and allowing for reducing the amount of medicament not being used. Thus, a further advantage of the present disclosure is that cost of not used medicament may be reduced.

The high resistance threshold is based on the plunger rod position. The high resistance threshold is a first high resistance threshold and a second high resistance threshold and/or third high resistance threshold.

The processing unit is configured to determine the high resistance threshold based on the plunger rod position.

The high resistance threshold is a first high resistance threshold when the plunger rod position is between the retracted plunger rod position and a first plunger rod position. The high resistance threshold is a second high resistance threshold when the plunger rod position is between a second plunger rod position and the extended plunger rod position.

The second high resistance threshold is higher than the first high resistance threshold. When the second high resistance threshold corresponds to an extended plunger rod position at the end of the injection of the medicament, the high resistance threshold is higher in order to ensure effective emptying of the cartridge without the risk of leakage at the stoppers or the septum at the end of injection because of the lower needle flow resistance contribution to the pressure in the cartridge.

The first high resistance threshold may be between <NUM>-<NUM> N, such as <NUM> N, <NUM> N, <NUM> N, <NUM> N, <NUM> N, <NUM> N, or <NUM> N. In an example, the first high resistance threshold is <NUM> N. The second high resistance threshold may be between <NUM>-<NUM> N, such as between <NUM>-<NUM> N, or such as between <NUM>-<NUM> N, or such as <NUM> N, <NUM> N, <NUM> N, <NUM> N, or <NUM> N. In an example, the second high resistance threshold is <NUM> N.

The high resistance threshold may be a third high resistance threshold when the plunger rod position is between the first plunger rod position and the second plunger rod position. The high resistance threshold may be the third high resistance threshold when the plunger rod position is at a third plunger rod position. The third plunger rod position may be between the first plunger rod position and the second plunger rod position.

The third high resistance threshold may be higher than the first high resistance threshold. The third high resistance threshold may be lower than the second high resistance threshold. The third high resistance threshold may be between the first high resistance threshold and the second high resistance threshold.

The high resistance threshold, e.g. the third high resistance threshold, may be increasing as the plunger rod position is moved from the first plunger rod position to the second plunger rod position.

The distance between the extended plunger rod position and the first plunger rod position may be between <NUM>-<NUM>, such as <NUM>.

The distance between the retracted plunger rod position and the first plunger rod position may be between <NUM>-<NUM>.

The distance between the retracted plunger rod position and the first plunger rod position may be between <NUM>-<NUM>, such as <NUM>, <NUM>, or <NUM>.

The auto injector may comprise a code sensor. The code sensor may be configured to read a cartridge code feature, such as a cartridge code feature of the cartridge and/or attached to the cartridge. The code sensor may be configured to transmit a code signal indicative of the cartridge code feature. The code sensor may be configured to read the cartridge code feature in a plurality of positions. The cartridge code sensor may be movable. The cartridge code sensor may comprise a plurality of sensors, such as a plurality of transmitters and/or receivers.

The code sensor may comprise an optical sensor. The code sensor may comprise an optical sensor comprising a transmitter and a receiver, such as a light transmitter and a light receiver. The code sensor may be configured to read the cartridge code feature. The code sensor may be configured to read QR codes, bar codes, colour codes, and/or any combination hereof.

The processing unit may be coupled to the code sensor. The processing unit may be configured to receive from the code sensor a code signal indicative of the cartridge code feature. The processing unit may be configured to determine a plunger rod position, such as the first plunger rod position and/or the second plunger rod position, based on the code signal.

The resistance sensor may be configured to measure pressure and/or force applied to a plunger rod front end of the plunger rod. The plunger rod front end may be configured to engage with the first stopper of the cartridge. The resistance sensor may be configured to measure pressure and/or force between the plunger rod and the stopper. For example, the resistance sensor may comprise a pressure transducer and/or a force transducer on the plunger rod front end. The plunger rod may comprise the resistance sensor.

Alternatively or additionally, The resistance sensor may be configured to determine electrical current through the drive module, and/or configured to determine electrical power consumed by the drive module. For example, the resistance sensor may be configured to measure electrical resistance, electrical current, and/or electrical voltage of the drive module. The resistance sensor may comprise an electrical resistance sensor, an electrical current sensor, and/or an electrical voltage sensor. The resistance signal may be based on electrical power consumed by the drive module, such as on the determined electrical power consumed by the drive module. The resistance signal may be based on electrical current through the drive module, such as on the measured electrical current through the drive module. The drive module may comprise the resistance sensor.

Instead of applying a dedicated force sensor, e.g. due to cost and architectural complexity of applying such a force sensor between a plunger and a cartridge stopper, a practical way to monitor equivalent plunger force and/or resistance may be through monitoring the current through the drive module, such as through the motor of the drive module. For electromechanical systems, this will correlate well to output force. The force acting upon an inductor inside a magnetic field can be expressed as F=B*I*I, where B is the magnetic field strength, I is the inductor current and I is the length of the inductor in the magnetic field.

The auto injector may be an electronic auto injector. The auto injector may comprise a battery. The housing may accommodate the battery. The battery may be a rechargeable battery. For example, the battery may be a Li-ion battery or a NiCd battery or a NiMH battery. The battery may be configured to be charged by connection of a charger.

The drive module may comprise one or more electrical elements. The drive module may be configured to receive electrical power from the battery. The drive module may be electrically connected to the battery for receiving electrical power. The drive module may comprise a motor, such as an electro-mechanical motor, such as a DC motor, e.g. a DC motor with or without brushes. The drive module may comprise a solenoid motor. The drive module may comprise a shape memory metal engine. The drive module may comprise an arrangement of springs configured to actuate the plunger rod. The drive module may comprise a pressurized gas configured to actuate the plunger rod.

The cartridge, e.g. a cartridge compartment of the cartridge, may comprise medicament. The movement of the first stopper may be to expel medicament from the cartridge, such as from the cartridge compartment, through a cartridge outlet and/or to expel air from the cartridge, such as from the cartridge compartment, through the cartridge outlet.

The plunger rod position, such as a present plunger rod position, such as the plunger rod position at a specific moment in time, may be determined, e.g. by the processing unit. The plunger rod position may be determined based on detection from a sensor, such as a plunger rod position sensor.

The auto injector may comprise the plunger rod position sensor. The plunger rod position sensor may be configured to detect the position of the plunger rod and/or the position of the first stopper. The drive module may comprise the plunger rod position sensor.

The Auto Injector may comprise a tachometer. The plunger rod position sensor may comprise the tachometer. The plunger rod position sensor may be a tachometer. The tachometer may be configured to count the revolutions of the drive module, such as a motor of the drive module, such as the revolutions of the drive module from a set point, such as a point wherein the position of the plunger rod is known, such as the retracted plunger rod position, such as a fully retracted position of the plunger rod. The count of revolutions of the drive module may be used to determine the plunger rod position, i.e. the position of the plunger rod at a specific moment in time.

The tachometer may be configured to provide a tachometer signal indicative of a count of revolutions of the drive module. The processing unit may be coupled to the tachometer. The processing unit may be configured to receive the tachometer signal. The processing unit may be configured to determine the present plunger rod position based on the tachometer signal.

The processing unit may be coupled to the plunger rod position sensor. The processing unit may receive from the plunger rod position sensor a first plunger rod position sensor signal, such as the tachometer signal, indicative of the count of revolutions of the drive module. The processing unit may determine the position of the plunger rod based on the first plunger rod position sensor signal, e.g. the tachometer signal. The processing unit may receive a second plunger rod position sensor signal, e.g. from the plunger rod position sensor, indicative of the plunger rod being in a known position, such as in the retracted plunger rod position, such as a fully retracted position. The processing unit may be configured to determine the position of the plunger rod based on the first plunger rod position sensor signal, e.g. the tachometer signal, and the second plunger rod position sensor signal. The processing unit may be configured to determine the plunger rod position based on the tachometer signal and the retracted plunger rod position. For example, the processing unit may be configured to determine the plunger rod position based on the number of revolutions of the drive module since the plunger rod was in the retracted plunger rod position.

Adjusting the movement of the plunger rod may comprise decreasing the plunger rod speed.

Adjusting the movement of the plunger rod may comprise stopping the movement of the plunger rod.

Adjusting the movement of the plunger rod may comprise preventing movement of the plunger rod towards the retracted plunger rod position for a dwell time. Alternatively or additionally, adjusting the movement of the plunger rod may comprise maintaining the position of the plunger rod for a dwell time. Preventing retraction or movement towards the retracted plunger rod position may prevent back flow of medicament due to lowering of the pressure inside the cartridge.

Adjusting the movement of the plunger rod may comprise moving the plunger rod to the retracted plunger rod position. For example, the plunger rod may be moved to the retracted plunger rod position after the dwell time.

Adjusting the movement of the plunger rod may comprise gradually decreasing the plunger rod speed, stopping the plunger rod speed, preventing movement of the plunger rod towards the retracted plunger rod position, and moving the plunger rod to the retracted plunger rod position after the dwell time.

The movement of the plunger rod may be readjusted after adjusting the movement of the plunger rod. The processing unit may be configured to control the drive module to readjust the movement of the plunger rod after adjusting the movement of the plunger rod. For example, the movement of the plunger rod may be readjusted after adjusting the movement of the plunger rod if the resistance against movement of the plunger rod is below the high resistance threshold. The processing unit may be configured to control the drive module to readjust the movement of the plunger rod after adjusting the movement of the plunger rod, if the resistance signal is indicative of resistance against movement of the plunger rod below the high resistance threshold. Readjusting the movement of the plunger rod may comprise increasing the plunger rod speed.

The plunger rod speed may be varied. For example, the plunger rod speed may be based on the plunger rod position. The plunger rod speed may be a first plunger rod speed when the plunger rod position is between the retracted plunger rod position and a fourth plunger rod position. The plunger rod speed may be a second plunger rod speed when the plunger rod position is between a fifth plunger rod position and the extended plunger rod position. The second plunger rod speed may be lower than the first plunger rod speed. Alternatively, the second plunger rod speed may be higher than the first plunger rod speed. The processing unit may be configured to determine the plunger rod speed, e.g. based on the plunger rod position.

The fourth plunger rod position may be the first plunger rod position. The fifth plunger rod position may be the second plunger rod position. The first plunger rod position and the second plunger rod position may be the same plunger rod position. The fourth plunger rod position and the fifth plunger rod position may be the same plunger rod position.

The cartridge, such as the cartridge configured to be received by the auto injector, such as by the cartridge receiver of the auto injector, may have a cartridge outlet at a first cartridge end. The cartridge may comprise a cartridge back face, e.g. at the second cartridge end, such as opposite the cartridge outlet. The cartridge back face may comprise a cartridge back end opening. The cartridge back end opening may provide access for a plunger rod, such as the plunger rod of the auto injector, to the first stopper.

The cartridge compartment may contain a medicament. The cartridge outlet may be configured for fluid communication with the cartridge compartment, e.g. at the first cartridge end. The cartridge may be configured to expel medicament through the cartridge outlet. The cartridge outlet may be configured to be coupled with a needle, such as a hypodermic needle, to provide the medicament to be expelled through the needle.

The first stopper of the cartridge may be movable inside the cartridge compartment. The cartridge may comprise a second stopper movable inside the cartridge compartment. The second stopper may be between the first stopper and the cartridge outlet. The cartridge may comprise a third stopper movable inside the cartridge compartment. The third stopper may be between the second stopper and the cartridge outlet. The first stopper, the second stopper, and/or the third stopper may be movable inside the cartridge compartment towards the cartridge outlet, e.g. in a first stopper direction, such as towards a first cartridge end. For example, the medicament may be expelled through the cartridge outlet upon movement of the first stopper, the second stopper, and/or the third stopper, e.g. in the first stopper direction and/or towards the cartridge outlet.

The cartridge may be a dual chamber cartridge. The cartridge compartment may have a first cartridge subcompartment and a second cartridge subcompartment. The first cartridge subcompartment may be between the first stopper and the second stopper. The second cartridge subcompartment may be between the second stopper and the cartridge outlet and/or the third stopper.

The first cartridge subcompartment may contain a first medicament component of the medicament. The second cartridge subcompartment may contain a second medicament component of the medicament. Each of the first medicament component and/or second medicament component may be a powder composition, a fluid, a liquid, a gel, a gas, and/or any combination thereof. The first medicament component and/or the second medicament component may be solute, such as a powder composition. The first medicament component and/or the second medicament component may be a solvent, such as a fluid composition, such as a liquid composition. The second medicament component may be a powder composition and the first medicament component may be a fluid composition, e.g. water or ethanol or saline solution or buffer solution or preservative solution. The second medicament component may be a solute. The first medicament component may be a solvent. It is envisaged that the medicament may be any medicament being injectable via a hypodermic needle, for example after reconstitution of the medicament. The medicament may be a growth hormone. The medicament may be human growth hormone. The medicament may be a depot version, such as a long-acting version, of human growth hormone. The second medicament component may be a powder composition of human growth hormone. The cartridge may have a bypass section, e.g. for providing fluid communication between the first cartridge subcompartment and the second cartridge subcompartment, e.g. when the second stopper is positioned in the bypass section. The cartridge may have a plurality of bypass sections providing fluid communication between neighbouring cartridge subcompartments, e.g. when a stopper separating the neighbouring cartridge subcompartment is positioned in the respective bypass section. The disclosed auto injector may be a reusable auto injector. A reusable auto injector may be especially useful when the cartridge comprises a plurality of subcompartments. For example an auto injector for a multi compartment or multi chamber cartridge may be more advanced, and therefore it may be beneficial to allow the auto injector to be used more than one time. For example, the auto injector may provide automated processes for mixing medicament components, such as for mixing medicament components initially provided in different subcompartments of the cartridge.

It is envisaged that any embodiments or elements as described in connection with any one aspect may be used with any other aspects or embodiments, mutatis mutandis.

The above and other features and advantages of the present invention will become readily apparent to those skilled in the art by the following detailed description of exemplary embodiments thereof with reference to the attached drawings, in which:.

Like elements may, thus, not be described in detail with respect to the description of each figure.

<FIG> illustrates an exemplary auto injector <NUM>. The auto injector <NUM> may be configured for administering a medicament. The auto injector <NUM> may be an electronic auto injector. The auto injector <NUM> comprises a housing <NUM>. The auto injector <NUM> comprises a cartridge receiver <NUM>. The cartridge receiver is configured to receive a cartridge and/or a cartridge assembly comprising a cartridge. The cartridge may contain the medicament. The cartridge receiver <NUM> has a cartridge receiver opening <NUM>. The cartridge receiver <NUM> is configured to receive the cartridge and/or the cartridge assembly through the cartridge receiver opening <NUM> in a cartridge receiving direction <NUM> along a longitudinal axis L.

The auto injector <NUM> may comprise a user interface <NUM>, as illustrated. The auto injector <NUM> comprises a trigger member, such as a contact member <NUM>. The contact member <NUM> may be configured to be pressed against an injection site. The contact member <NUM> may be movable in the cartridge receiving direction <NUM>, relative to the housing, if pressed against the injection site. The contact member <NUM> may be part of the user interface <NUM>.

The user interface <NUM> may comprise a first input member <NUM> as illustrated, e.g. a button. The first input member <NUM> may provide for a user input from a user. For example, the first input member <NUM> may be used for receiving a push from a user to proceed to a next step.

The user interface <NUM> may comprise a first output member <NUM> as illustrated, e.g. a plurality of LEDs. The first output member <NUM> may provide for a user output to a user. The user interface <NUM> may comprise a second output member (not shown), e.g. a speaker. The second output member may be configured to provide audible output to the user. For example, the first output member <NUM> and/or the second output member may be used to indicate a step in the procedure to the user and/or to indicate an error message.

<FIG> illustrates an exemplary system <NUM>. The system <NUM> comprises an auto injector <NUM>, as described in relation to <FIG>, and an exemplary cartridge <NUM> received in the cartridge receiver <NUM>. The cartridge <NUM> comprises a first stopper (not shown). The cartridge <NUM> is shown with a needle cover <NUM>. The needle cover <NUM> may extend out of the contact member <NUM>, as shown, to allow removal of the needle cover <NUM> from the cartridge <NUM>.

<FIG> schematically illustrates an exemplary cartridge <NUM>, such as a cartridge <NUM> being configured to be received in the cartridge receiver of an auto injector, such as the auto injector described in relation to previous figures.

The cartridge <NUM> comprises a cartridge compartment <NUM>. The cartridge compartment <NUM> may be configured for containing a medicament. The cartridge <NUM> has a first end <NUM> and a second end <NUM>. The cartridge <NUM> comprises a cartridge outlet <NUM> at a first cartridge end <NUM>. The cartridge may be configured to expel medicament through the cartridge outlet <NUM>.

The cartridge comprises a first stopper <NUM> movable inside the cartridge compartment <NUM>, e.g. in a first stopper direction <NUM>, e.g. towards the first cartridge end <NUM>. For example, the medicament may be expelled through the cartridge outlet <NUM> upon movement of the first stopper <NUM> in the first stopper direction <NUM>. The cartridge <NUM> comprises a cartridge back face <NUM> at the second cartridge end <NUM>. The cartridge back face <NUM> comprises a cartridge back end opening for providing access to the first stopper <NUM> for a plunger rod.

As illustrated, the cartridge <NUM> may be a dual chamber cartridge. Hence, the cartridge <NUM> comprises a second stopper <NUM> movable inside the cartridge compartment <NUM>, e.g. in the first stopper direction <NUM>, e.g. towards the first cartridge end <NUM>. The cartridge compartment <NUM> comprises a first cartridge subcompartment <NUM> and a second cartridge subcompartment <NUM>. The first cartridge subcompartment <NUM> is between the first stopper <NUM> and the second stopper <NUM>. The first cartridge subcompartment <NUM> may comprise a liquid, such as sterile water or a buffer solution. The second cartridge subcompartment <NUM> is between the second stopper <NUM> and the cartridge outlet <NUM>. The second cartridge subcompartment <NUM> may comprise a medicament, such as a dry medicament, such as a medicament dried by lyophilization. The cartridge <NUM> comprises a bypass section <NUM> for providing fluid communication between the first cartridge subcompartment <NUM> and the second cartridge subcompartment <NUM>. The bypass section <NUM> provides fluid communication between the first cartridge subcompartment <NUM> and the second cartridge subcompartment <NUM> when the second stopper <NUM> is positioned in the bypass section <NUM>.

<FIG> illustrates an exemplary system <NUM>. The system <NUM> comprises an auto injector <NUM>, as described, for example, in relation to <FIG>, and an exemplary cartridge assembly <NUM>. The cartridge assembly <NUM> comprises a cartridge <NUM> with a cartridge compartment <NUM>, a needle assembly <NUM>, and an optional cartridge code feature <NUM>. The cartridge assembly <NUM> is, in the illustrated example, received in the auto injector <NUM>.

The cartridge assembly <NUM> comprises a cartridge holder <NUM>. The cartridge holder is configured for retention of the cartridge <NUM> in the cartridge receiver <NUM> of the auto injector <NUM>. The cartridge holder <NUM> comprises a cartridge retention member <NUM>. The cartridge retention member engages with the cartridge receiver <NUM> for reception of the cartridge <NUM> and the cartridge assembly <NUM> in the cartridge receiver.

The needle assembly <NUM> comprises a needle <NUM> and a needle hub <NUM>. The needle assembly <NUM> is attached to the cartridge <NUM>, e.g. by the needle hub <NUM> having a cartridge holder coupling portion <NUM>, e.g. a threaded coupling portion, being in engagement with a needle assembly coupling portion <NUM> of the cartridge holder <NUM>. The needle <NUM> extends through the cartridge outlet <NUM> of the cartridge <NUM>. The cartridge outlet <NUM> may be blocked by a resilient sealing being penetrated by the needle <NUM>, when the needle assembly <NUM> is attached to the cartridge <NUM>.

The auto injector <NUM> comprises an optional code sensor <NUM> configured to read the cartridge code feature <NUM>. When the cartridge assembly <NUM> is inserted, as shown, the cartridge code feature <NUM> is lined up with the code sensor <NUM>.

The auto injector <NUM> comprises a plunger rod <NUM>. The plunger rod <NUM> is configured to advance a first stopper of the cartridge <NUM>. The plunger rod <NUM> comprises an outer plunger rod <NUM> with an inner thread, and an inner plunger rod <NUM> with an outer thread. The thread of the inner plunger rod <NUM> is in engagement with the thread of the outer plunger rod <NUM>. The outer plunger rod <NUM> is prevented from rotating relative to the housing of the auto injector. The movement of the plunger rod <NUM> comprises rotation of the inner plunger rod <NUM>. The rotation of the inner plunger rod <NUM> results in translational movement of the outer plunger rod <NUM>, due to the outer plunger rod <NUM> being rotationally restricted. The outer plunger rod <NUM>, when moved translationally in the first stopper direction <NUM>, is configured to abut the first stopper of the cartridge <NUM>, and to move the first stopper in the first stopper direction <NUM>.

The drive module <NUM> is coupled to actuate the plunger rod <NUM>. The drive module <NUM> is electrically connected to a battery for receiving electrical power. The drive module <NUM> comprises a motor <NUM>, such as an electro-mechanical motor, such as a DC motor. The drive module <NUM> comprises a transmission <NUM> for coupling the motor <NUM> to the inner plunger rod <NUM> of the plunger rod <NUM>.

Although the example shown comprises a motor <NUM>, which may be an electro-mechanical motor, it will be readily understood that the auto injector <NUM> may be realised having an alternative drive module, such as comprising a solenoid motor, a shape memory metal engine, an arrangement of springs and/or a pressurized gas configured to actuate the plunger rod <NUM>.

The auto injector <NUM> comprises a plunger rod position sensor <NUM>. The plunger rod position sensor <NUM> is configured to detect the position of the plunger rod <NUM>. In the illustrated example, the plunger rod position sensor <NUM> comprises a tachometer configured to count/detect the revolutions of the motor <NUM>. Thus, the position of the plunger rod <NUM> may be determined. The plunger rod position sensor <NUM> may, based on the detection of the position of the plunger rod <NUM>, detect the expelling of medicament and/or air in the cartridge compartment. The position of the plunger rod <NUM> is indicative of the position of the first stopper <NUM> of the cartridge <NUM>.

<FIG> shows a block diagram of an exemplary auto injector <NUM>. The auto injector <NUM> comprises a plurality of sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, a processing unit <NUM>, a drive module <NUM>, and a user interface <NUM>. The sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are coupled to the processing unit <NUM>. The user interface <NUM> is coupled to the processing unit <NUM>. The processing unit is coupled to the drive module <NUM>.

The processing unit <NUM> receives signals from the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the user interface <NUM>. The processing unit <NUM> is configured to control the drive module <NUM>. The processing unit <NUM> may control the drive module <NUM> based on one or more of the received signals from the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the user interface <NUM>.

The auto injector <NUM> comprises an orientation sensor <NUM>. The orientation sensor <NUM> is configured to provide an orientation signal indicative of the orientation of a cartridge received in the auto injector <NUM>. For example, the orientation sensor <NUM> may be configured to detect the orientation of the auto injector <NUM>. The orientation of the cartridge may be determined based on the orientation of the auto injector <NUM>. The orientation sensor <NUM> may be configured to detect the direction of gravity. For example, the orientation sensor <NUM> may comprise an accelerometer.

The processing unit <NUM> is coupled to the orientation sensor <NUM>. The processing unit <NUM> is configured to receive the orientation signal. The processing unit <NUM> may determine the orientation of the cartridge based on the orientation signal. The processing unit <NUM> may control the drive module <NUM> based on the orientation signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to move a plunger rod based on the orientation signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to move the plunger rod towards an extended plunger rod position only if the cartridge outlet is pointing upwards. Alternatively or additionally, the processing unit <NUM> may provide user output via the user interface <NUM> based on the orientation signal.

The auto injector <NUM> comprises a code sensor <NUM>. The code sensor <NUM> is configured to read a cartridge code feature. The code sensor <NUM> is configured to provide a code signal indicative of a cartridge code feature. For example, the code sensor may be configured to read/detect a colour code.

The processing unit <NUM> is coupled to the code sensor <NUM>. The processing unit <NUM> is configured to receive the code signal. The processing unit <NUM> may determine the cartridge code feature of the cartridge assembly based on the code signal. The processing unit <NUM> may be configured to determine a first plunger rod position and/or a second plunger rod position based on the code signal. The processing unit <NUM> may control the drive module <NUM> based on the code signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to move the plunger rod towards the extended plunger rod position based on the code signal. Alternatively or additionally, the processing unit <NUM> may provide user output via the user interface <NUM> based on the code signal.

The auto injector <NUM> comprises a plunger rod position sensor <NUM>. The plunger rod position sensor <NUM> is configured to detect the position of the plunger rod of the auto injector <NUM>, and provide a plunger rod position sensor signal indicative of the position of the plunger rod. The plunger rod position sensor <NUM> may comprise a tachometer coupled to the drive module <NUM>.

The processing unit <NUM> is coupled to the plunger rod position sensor <NUM>. The processing unit <NUM> is configured to receive the plunger rod position sensor signal. The processing unit <NUM> may determine the position of the plunger rod based on the plunger rod position sensor signal. The processing unit <NUM> may control the drive module <NUM> based on the plunger rod position sensor signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to start, stop or continue movement of the plunger rod based on the plunger rod position sensor signal. For example, the processing unit <NUM> may be configured to determine a plunger rod position based on the plunger rod position sensor signal. Alternatively or additionally, the processing unit <NUM> may provide user output via the user interface <NUM> based on the plunger rod position sensor signal.

The processing unit <NUM> is coupled to the cartridge sensor <NUM>. The processing unit <NUM> is configured to receive the cartridge sensor signal. The processing unit <NUM> may control the drive module <NUM> based on the cartridge sensor signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to start movement of the plunger rod if a cartridge assembly is received, and/or only if a cartridge assembly is received. Alternatively or additionally, the processing unit <NUM> may provide user output via the user interface <NUM> based on the cartridge sensor signal.

The code sensor <NUM> and the cartridge sensor <NUM> may be the same sensor, e.g. the code sensor <NUM> may be configured to detect reception of a cartridge assembly and subsequently read the cartridge code feature.

The auto injector <NUM> comprises a needle sensor <NUM>. The needle sensor <NUM> is configured to detect a needle, and/or a needle assembly, and/or a needle cover of a needle assembly, of the cartridge assembly, when the cartridge assembly is received in the auto injector <NUM>. The needle sensor <NUM> provides a needle signal indicative of the presence of a needle, and/or a needle assembly, and/or a needle cover of a needle assembly, of the cartridge assembly.

The processing unit <NUM> is coupled to the needle sensor <NUM>. The processing unit <NUM> is configured to receive the needle signal. The processing unit <NUM> may control the drive module <NUM> based on the needle signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to start movement of the plunger rod only if a needle is present, and/or only if a needle cover is not present, such as removed. Detection of a needle cover may be indicative of a needle being present. The processing unit <NUM> may be configured to control the drive module <NUM> to start only if a needle cover has been detected, and afterwards removed. Alternatively or additionally, the processing unit <NUM> may provide user output via the user interface <NUM> based on the needle signal.

The auto injector <NUM> comprises a temperature sensor <NUM>. The temperature sensor <NUM> is configured to detect a temperature, such as a temperature of the auto injector and/or of the cartridge and/or of the medicament. The temperature sensor <NUM> is configured to provide a temperature signal indicative of the temperature.

The processing unit <NUM> is coupled to the temperature sensor <NUM>. The processing unit <NUM> is configured to receive the temperature signal. The processing unit <NUM> may be configured to determine the temperature, such as the temperature of the auto injector and/or of the cartridge and/or of the medicament based on the temperature signal. The processing unit <NUM> may control the drive module <NUM> based on the temperature signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to move the plunger rod towards the extended plunger rod position based on the temperature signal. Alternatively or additionally, the processing unit <NUM> may provide user output via the user interface <NUM> based on the temperature signal.

The auto injector <NUM> comprises a resistance sensor <NUM>. The resistance sensor <NUM> is configured to detect resistance against movement of the plunger rod of the auto injector <NUM>. The resistance sensor <NUM> may be configured to detect resistance against movement of the plunger rod based on measurements of the drive module <NUM>. For example, the resistance sensor <NUM> may be configured to detect the electrical current of a motor of the drive module <NUM>. For example, the resistance sensor <NUM> may be configured to determine the electrical current through the drive module. Alternatively or additionally, the resistance sensor <NUM> may be configured to measure pressure and/or force applied to a plunger rod front end of the plunger rod. The resistance sensor <NUM> is configured to provide a resistance signal indicative of resistance against movement of the plunger rod.

The processing unit <NUM> is coupled to the resistance sensor <NUM>. The processing unit <NUM> is configured to receive the resistance signal. The processing unit <NUM> may be configured to determine the resistance against movement of the plunger rod based on the resistance signal. The processing unit <NUM> may control the drive module <NUM> based on the resistance signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to adjust movement of the plunger rod based on the resistance signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to start, stop or continue movement of the plunger rod based on the resistance signal.

Movement of the plunger rod results in a plunger rod speed. The processing unit <NUM> may be configured to determine the plunger rod speed. The processing unit <NUM> may be configured to control the drive module <NUM> to adjust, such as readjust, the movement of the plunger rod, if the resistance signal is indicative of resistance against movement of the plunger rod above a high resistance threshold. The processing unit <NUM> may further be configured to control the drive module <NUM> to adjust, such as readjust, the movement of the plunger rod, wherein adjusting the movement of the plunger rod may comprise increasing or decreasing the plunger rod speed. Alternatively or additionally, the processing unit <NUM> may provide user output via the user interface <NUM> based on the resistance signal. The high resistance threshold may be based on the plunger rod position. The processing unit <NUM> may be configured to determine the high resistance threshold, e.g. based on the plunger rod position. The processing unit <NUM> may be configured to determine the high resistance threshold based on the plunger rod position sensor signal, e.g. received from the plunger rod position sensor <NUM>.

The auto injector <NUM> is illustrated comprising all of the above mentioned sensors. However, alternatively, the auto injector may comprise only one or any combination of one or more of the above mentioned sensors.

The auto injector comprises a user interface <NUM>. The user interface <NUM> may comprise one or more input members, e.g. a first input member, for receiving a user input. The user interface is configured to provide a user input signal indicative of the received user input.

The processing unit <NUM> is coupled to the user interface <NUM>. The processing unit <NUM> is configured to receive the user input signal. The processing unit <NUM> may control the drive module <NUM> based on the user input signal. For example, the processing unit <NUM> may be configured to control the drive module <NUM> to move the plunger rod towards the extended plunger rod position based on the user input signal.

The auto injector comprises a housing <NUM> accommodating the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, processing unit <NUM>, user interface <NUM> and drive module <NUM>.

<FIG> schematically illustrates a system <NUM> comprising an exemplary auto injector <NUM> with an inserted cartridge assembly comprising a cartridge <NUM> and a needle assembly <NUM>. The auto injector <NUM> as shown in <FIG> illustrates different ways of implementing sensing of plunger rod position and resistance against movement of the plunger rod.

The plunger rod comprises an outer plunger rod <NUM> with an inner thread, and an inner plunger rod <NUM> with an outer thread. The thread of the inner plunger rod <NUM> is in engagement with the thread of the outer plunger rod <NUM>. The outer plunger rod <NUM> is prevented from rotating relative to the housing <NUM> of the auto injector <NUM>. Rotation of the inner plunger rod <NUM> results in translational movement of the outer plunger rod <NUM>, due to the outer plunger rod <NUM> being rotationally restricted. The outer plunger rod <NUM>, when moved translationally in the first stopper direction <NUM>, is configured to abut the first stopper <NUM> of the cartridge <NUM>, and to move the first stopper in the first stopper direction <NUM>. The plunger rod front end <NUM> is configured to abut the first stopper <NUM>.

A motor <NUM> is coupled to drive the plunger rod via a transmission <NUM>. The motor <NUM> rotates a first part of the transmission <NUM>, which rotates a second part of the transmission <NUM>, which is coupled to rotate the inner plunger rod <NUM>.

The motor <NUM> is controlled by a processing unit <NUM>. The auto injector <NUM>, such as the motor <NUM> and/or the processing unit <NUM>, is powered by a battery <NUM>, such as a rechargeable battery.

Position of the plunger rod, such as the position of the outer plunger rod <NUM> and/or the position of the plunger rod front end <NUM>, may be determined by one or more position sensors 26a, 26b, 26c. For example, as illustrated, the plunger rod position may be determined by a position sensor 26a configured to sense position through a linear sensor coupled to the plunger rod, such as the outer plunger rod <NUM>. Alternatively or additionally, as also illustrated, the plunger rod position may be determined by a position sensor 26b, such as a tachometer, configured to count/detect the revolutions of the motor <NUM>. Alternatively or additionally, as also illustrated, the plunger rod position may be determined by a position sensor 26c, such as a tachometer, configured to count/detect the revolutions of the transmission <NUM> and/or a part of the transmission <NUM>.

Resistance against movement of the plunger rod may be determined by one or more resistance sensors 34a, 34b, 34c, 34d. For example, as illustrated the resistance against movement of the plunger rod may be determined by a resistance sensor, such as a force sensor, 34a positioned in front of the cartridge <NUM>, when the plunger rod advances the first stopper <NUM>, the cartridge will press against the sensor 34a. Alternatively or additionally, as also illustrated, the resistance against movement of the plunger rod may be determined by a resistance sensor, such as a force sensor, 34b positioned on the plunger rod front end <NUM>. Alternatively or additionally, as also illustrated, the resistance against movement of the plunger rod may be determined by a resistance sensor, such as a force sensor, 34c positioned to sense the reaction force from the plunger rod on first stopper <NUM>, e.g. the sensor 34c may be positioned behind the inner plunger rod <NUM>. Alternatively or additionally, as also illustrated, the resistance against movement of the plunger rod may be determined by a resistance sensor 34d configured to measure/detect the amount of current and/or power drawn by the motor <NUM>.

<FIG> shows a resistance graph <NUM> illustrating a high resistance threshold depending on stopper position/plunger rod position, such as the high resistance threshold and the plunger rod position as described in relation to previous figures, and/or the stopper position associated with the plunger rod position as described in relation to previous figures. A plunger rod <NUM> is configured to move the first stopper <NUM>, thus the position of the first stopper <NUM> is determined by the position of the plunger rod <NUM>. Therefore, the position of the first stopper <NUM> may be corresponding to a position of the plunger rod <NUM>. The plunger rod position may designate a plunger rod front end, such as the part of the plunger rod making contact with the first stopper <NUM>.

The resistance graph <NUM> has a first axis 1200X indicating stopper position/plunger rod position and a second axis 1200Y indicating resistance. Solid and dashed lines illustrate different examples of how the high resistance threshold may vary depending on stopper position/plunger rod position.

<FIG> illustrates a plunger rod <NUM> and a cartridge <NUM> with a first stopper <NUM> in situations of corresponding exemplary plunger rod positions explained in the following. <FIG> shows the plunger rod <NUM> being in a retracted plunger rod position <NUM>. <FIG> shows the plunger rod <NUM> being in a position between the retracted plunger rod position <NUM> and a first plunger rod position <NUM>. The first stopper <NUM> has been moved accordingly. <FIG> shows the plunger rod <NUM> being in the first plunger rod position <NUM>. The first stopper <NUM> has been moved accordingly to a first stopper position. <FIG> shows the plunger rod <NUM> being in a second plunger rod position <NUM>. The first stopper <NUM> has been moved accordingly to a second stopper position. <FIG> shows the plunger rod <NUM> being in a position between the second plunger rod position <NUM> and an extended plunger rod position <NUM>. The first stopper <NUM> has been moved accordingly. The plunger rod position illustrated in <FIG> may be the extended plunger rod position <NUM>.

As illustrated by the graph in <FIG>, the high resistance threshold may be a first high resistance threshold <NUM> when the plunger rod position is between the retracted plunger rod position <NUM> and the first plunger rod position <NUM>. The high resistance threshold may be a second high resistance threshold <NUM> when the plunger rod position is between the second plunger rod position <NUM> and the extended plunger rod position <NUM>.

The second high resistance threshold <NUM> may be higher than the first high resistance threshold <NUM>. For example, the first high resistance threshold <NUM> may between <NUM>-<NUM> N, such as <NUM> N, <NUM> N, <NUM> N, <NUM> N, <NUM> N, <NUM> N, or <NUM> N. For example, the second high resistance threshold <NUM> may be between <NUM>-<NUM> N, such as between <NUM>-<NUM> N, or such as between <NUM>-<NUM> N, or such as <NUM> N, <NUM> N, <NUM> N, <NUM> N, or <NUM> N.

As illustrated by the solid line, the high resistance threshold may be the second high resistance threshold <NUM> when the plunger rod position is between the first plunger rod position <NUM> and the extended plunger rod position <NUM>. Alternatively or additionally, the high resistance threshold may be a third high resistance threshold <NUM> when the plunger rod position is between the first plunger rod position <NUM> and the second plunger rod position <NUM>, such as when the plunger rod position is at a third plunger rod position <NUM>. The third high resistance threshold <NUM> may be higher than the first high resistance threshold <NUM>. The third high resistance threshold <NUM> may be lower than the second high resistance threshold <NUM>.

The high resistance threshold may be increasing as a function of the plunger rod position. For example, as illustrated, the high resistance threshold may be increasing as the plunger rod is moved from the first plunger rod position <NUM> to the second plunger rod position <NUM>. The solid and dashed lines illustrate exemplary ways the high resistance threshold may increase as the plunger rod is moved from the first plunger rod position <NUM> to the second plunger rod position <NUM>. A first slope <NUM> illustrates a step-change increase. A second slope <NUM> illustrates a non-linear increase. A third slope <NUM> illustrates a linear increase.

<FIG> shows an exemplary trace T of resistance R against movement of the plunger rod dependent on the position of the plunger rod P. The plunger rod is moved from a retracted position <NUM> to an extended position <NUM>. In the beginning of the movement, the resistance against movement of the plunger rod is constant Ex1, e.g. the plunger rod does not yet push a stopper. Afterwards, a plunger rod front end of the plunger rod abuts a first stopper of the cartridge, and the resistance against movement of the plunger rod increases Ex2. The increased resistance is caused by the resistance against movement of the first stopper, e.g. due to frictional force. The resistance may decrease slightly after the first stopper has started moving, as illustrated. When the plunger rod approaches the extended plunger rod position <NUM>, the resistance may increase again Ex3, e.g. due to the first stopper approaching an end of the cartridge.

The trace T is an example of resistance against plunger rod movement when the cartridge received is a new and/or unused and/or normal cartridge. Other situations, such as situations wherein the cartridge received is apparently flawed, are exemplified by additional exemplary trace, T1.

Trace T1 illustrates an exemplary situation wherein the resistance against movement increases above a first high resistance threshold <NUM>, e.g. before the plunger rod position has passed the first plunger rod position <NUM>. Such situation may for example indicate that the first stopper is blocked from moving, e.g. the cartridge may be flawed. Following such situation, the plunger rod may be retracted to the retracted position and an error message may be provided through a user interface.

At a certain plunger rod position, such as the first plunger rod position <NUM>, the high resistance threshold may be changed, e.g. in order to allow for a higher resistance before aborting the movement of the plunger rod. As illustrated, at the end of the forward movement of the plunger rod, the resistance R increases, e.g. at the second plunger rod position <NUM>, to a resistance above the first high resistance threshold <NUM>. However, since the high resistance threshold at the second plunger rod position is a second high resistance threshold <NUM>, the movement of the plunger rod is continued. Eventually, as illustrated, the resistance against movement may reach the second high resistance threshold <NUM>, e.g. between the second plunger rod position and the extended plunger rod position <NUM>, and the movement of the plunger rod may be stopped.

The thresholds, such as the first high resistance threshold <NUM> and/or the second high resistance threshold <NUM> may be individually determined for the cartridge received. For example, a processing unit may be configured to determine one or more of the thresholds, based on a cartridge code feature of the cartridge and/or cartridge assembly received.

<FIG> shows a speed graph <NUM> illustrating a plunger rod speed depending on stopper position/plunger rod position, such as the plunger rod speed and the plunger rod position as described in relation to previous figures, and/or the stopper position associated with the plunger rod position as described in relation to previous figures. A plunger rod <NUM> is configured to move the first stopper <NUM>, thus the position of the first stopper is determined by the position of the plunger rod <NUM>. Therefore, the position of the first stopper may be corresponding to a position of the plunger rod <NUM>. The plunger rod position may designate a plunger rod front end, such as the part of the plunger rod making contact with the first stopper <NUM>.

The speed graph <NUM> has a first axis 1300X indicating stopper position/plunger rod position and a second axis 1300Y indicating speed, such as plunger rod speed. Solid and dashed lines illustrate different examples of how plunger rod speed may vary depending on stopper position/plunger rod position.

<FIG> illustrate a plunger rod <NUM> and a cartridge <NUM> with a first stopper <NUM> in situations of corresponding exemplary plunger rod positions explained in the following. <FIG> shows the plunger rod <NUM> being in a position between a retracted plunger rod position <NUM> and a fourth plunger rod position <NUM>. <FIG> shows the plunger rod <NUM> being in the fourth plunger rod position <NUM>. The first stopper <NUM> has been moved accordingly to a fourth stopper position. <FIG> shows the plunger rod <NUM> being in a fifth plunger rod position <NUM>. The first stopper <NUM> has been moved accordingly to a fifth stopper position. <FIG> shows the plunger rod <NUM> being in a position between the fifth plunger rod position <NUM> and an extended plunger rod position <NUM>. The first stopper <NUM> has been moved accordingly. The plunger rod position illustrated in <FIG> may be the extended plunger rod position <NUM>.

As illustrated by the graph in <FIG>, the plunger rod speed may be based on the plunger rod position. For example, the plunger rod speed may be a first plunger rod speed <NUM> when the plunger rod position is between the retracted plunger rod position <NUM> and the fourth plunger rod position <NUM>. The plunger rod speed may be a second plunger rod speed <NUM> when the plunger rod position is between the fifth plunger rod position <NUM> and the extended plunger rod position <NUM>. The second plunger rod speed <NUM> may be lower than the first plunger rod speed <NUM>. Alternatively, the second plunger rod speed <NUM> may be higher than the first plunger rod speed <NUM> in order to effectively empty the cartridge.

A plunger rod position may coincide with another plunger rod position. For example, the fourth plunger rod position <NUM> may be the first plunger rod position <NUM> as mentioned in relation to <FIG>. The fifth plunger rod position <NUM> may be the second plunger rod position <NUM> as mentioned in relation to <FIG>.

The plunger rod speed may be decreasing as a function of the plunger rod position. For example, the plunger rod speed may be decreasing as the plunger rod is moved from the fourth plunger rod position <NUM> to the fifth plunger rod position <NUM>. The solid line illustrates an exemplary linear decrease of the plunger rod speed as the plunger rod is moved from the fourth plunger rod position <NUM> to the fifth plunger rod position <NUM>. Other examples may be non-linear decrease and step-change decrease as exemplified by the dashed lines.

<FIG> shows a flow chart of an exemplary method <NUM> for operating and/or controlling an auto injector, such as the auto injector as described in relation to previous figures.

The method <NUM> comprises receiving <NUM> a cartridge comprising a first stopper; moving <NUM> a plunger rod towards an extended plunger rod position; determining <NUM> plunger rod position; receiving a resistance signal <NUM>; and adjusting <NUM> the movement of the plunger rod.

Receiving <NUM> the cartridge may comprise receiving the cartridge in a cartridge receiver of the auto injector.

Moving <NUM> the plunger rod may comprise moving the plunger rod from a retracted plunger rod position. Moving <NUM> the plunger rod may comprise moving the plunger rod in a first plunger rod direction.

Determining <NUM> plunger rod position may be determined by a processing unit of the auto injector. Determining <NUM> plunger rod position may be based on detection from a sensor, such as a plunger rod position sensor, e.g. comprising a tachometer.

Receiving a resistance signal <NUM> may comprise receiving the resistance signal from a resistance sensor. The resistance signal may be indicative of resistance against movement of the plunger rod, such as movement towards the extended plunger rod position, such as movement in the first plunger rod direction.

Adjusting <NUM> the movement may comprise stopping the movement of the plunger rod. Alternatively or additionally, adjusting <NUM> the movement may comprise preventing movement of the plunger rod towards the retracted plunger rod position for a dwell time, e.g. in order to prevent back flow of medicament. Alternatively or additionally, adjusting <NUM> the movement may comprise maintaining the position of the plunger rod for a dwell time, e.g. in order to prevent back flow of medicament. Alternatively or additionally, adjusting <NUM> the movement may comprise moving the plunger rod to the retracted plunger rod position. Alternatively or additionally, adjusting <NUM> the movement may comprise decreasing the plunger rod speed.

Adjusting <NUM> the movement of the plunger rod may be based on the resistance signal. For example, the movement of the plunger rod may be adjusted such that the resistance is held below a high resistance threshold. Adjusting <NUM> the movement of the plunger rod may comprise adjusting the movement of the plunger rod if the resistance signal is indicative of resistance against movement of the plunger rod above a high resistance threshold. The high resistance threshold may be based on the plunger rod position, e.g. the high resistance threshold may be a first high resistance threshold when the plunger rod position is within a one range, and a second high resistance threshold when the plunger rod position is within a second range.

Steps of the exemplary method <NUM>, e. g the steps of moving <NUM> a plunger rod; determining <NUM> plunger rod position; receiving a resistance signal <NUM>; and adjusting <NUM> the movement of the plunger rod, may be controlled by a processing unit, such as the processing unit of the auto injector.

<FIG> shows a flow chart of an exemplary method <NUM> for moving the plunger rod of an auto injector.

Initially, the plunger rod is moved <NUM>, e.g. with a first plunger rod speed, e.g. in a first plunger rod direction.

The resistance against the movement of the plunger rod is monitored, such as continuously monitored. By a first resistance criterion <NUM>, it is determined whether resistance against movement of the plunger rod exceeds a second high resistance threshold. If the resistance against movement of the plunger rod does not exceed the second high resistance threshold (first resistance criterion <NUM> is answered no), by a second resistance criterion <NUM>, it is determined whether resistance against movement of the plunger rod exceeds a first high resistance threshold. If the resistance against movement of the plunger rod does not exceed the first high resistance threshold (second resistance criterion <NUM> is answered no), the movement of the plunger rod is continued <NUM>. The first plunger threshold may be lower than the second high resistance threshold.

The position of the plunger rod is monitored, such as continuously monitored. If the resistance against movement of the plunger rod does exceed the first high resistance threshold (second resistance criterion <NUM> is answered yes), by a first position criterion <NUM>, it is determined whether the plunger rod has reached and/or passed a predetermined plunger rod position, such as a first plunger rod position, a second plunger rod position, a third plunger rod position, a fourth plunger rod position and/or a fifth plunger rod position (see e.g. <FIG> and <FIG> for exemplary positions). If the plunger rod position has reached and/or passed the predetermined plunger rod position (first position criterion <NUM> is answered yes), the movement of the plunger rod is continued <NUM>. Thus, the first high resistance threshold may be exceeded if the plunger rod has reached and/or passed the predetermined plunger rod position.

If the plunger rod position has not reached and/or passed the predetermined plunger rod position (first position criterion <NUM> is answered no), the movement of the plunger rod is stopped <NUM>, and an error may be communicated to the user, e.g. via a user interface. Thus, an error may be assumed if the first high resistance threshold is exceeded before the plunger rod has reached and/or passed the predetermined plunger rod position.

If the resistance against movement of the plunger rod does exceed the second high resistance threshold (first resistance criterion <NUM> is answered yes), the movement of the plunger rod is stopped <NUM> and end of injection may be assumed. In stopping <NUM> the movement of the plunger rod, the plunger rod may be locked in its position for a dwell time, e.g. to prevent a sudden drop in pressure in the cartridge, e.g. to prevent back flow of medicament.

Initially, the plunger rod is moved <NUM> with a first plunger rod speed, e.g. in a first plunger rod direction.

The resistance against the movement of the plunger rod is monitored, such as continuously monitored. By a first resistance criterion <NUM>, it is determined whether resistance against movement of the plunger rod exceeds a first high resistance threshold. If the resistance against movement of the plunger rod does exceed the first high resistance threshold (first resistance criterion <NUM> is answered yes), the movement of the plunger rod is stopped <NUM> and an error may be communicated to the user, e.g. via a user interface.

The position of the plunger rod is monitored, such as continuously monitored. If the resistance against movement of the plunger rod does not exceed the first high resistance threshold (first resistance criterion <NUM> is answered no), by a first position criterion <NUM>, it is determined whether the plunger rod has reached and/or passed a predetermined plunger rod position, such as a first plunger rod position, a second plunger rod position, a third plunger rod position, a fourth plunger rod position and/or a fifth plunger rod position (see e.g. <FIG> and <FIG> for exemplary positions). If the plunger rod position has not reached and/or passed the predetermined plunger rod position (first position criterion <NUM> is answered no), the movement of the plunger rod is continued <NUM> with the first plunger rod speed.

If the plunger rod position has reached and/or passed the predetermined plunger rod position (first position criterion <NUM> is answered yes), the plunger rod is moved <NUM> with a second plunger rod speed, e.g. in the first plunger rod direction. The second plunger rod speed may be lower than the first plunger rod speed. By lowering the plunger rod speed, the amount of medicament needing to be forced though the needle per time, is reduced, thereby reducing the amount of force needed to advance the stopper.

By a second resistance criterion <NUM>, it is determined whether resistance against movement of the plunger rod exceeds a second high resistance threshold. If the resistance against movement of the plunger rod does not exceed the second high resistance threshold (second resistance criterion <NUM> is answered no), the movement of the plunger rod is continued <NUM> with the second plunger rod speed.

If the resistance against movement of the plunger rod does exceed the second high resistance threshold (second resistance criterion <NUM> is answered yes), the movement of the plunger rod is stopped <NUM> and end of injection may be assumed. In stopping <NUM> the movement of the plunger rod, the plunger rod may be locked in its position for a dwell time, e.g. to prevent a sudden drop in pressure in the cartridge, e.g. to prevent back flow of medicament.

The resistance against the movement of the plunger rod is monitored, such as continuously monitored. By a resistance criterion <NUM>, it is determined whether resistance against movement of the plunger rod exceeds a high resistance threshold, such as a first high resistance threshold and/or a second high resistance threshold.

If the resistance against movement of the plunger rod does not exceed the high resistance threshold (resistance criterion <NUM> is answered no), the speed of the movement of the plunger rod is increased <NUM>.

If the resistance against movement of the plunger rod does exceed the high resistance threshold (resistance criterion <NUM> is answered yes), it is determined by a speed criteria <NUM> whether the plunger rod speed is zero, i.e. the plunger rod is not moving.

If the plunger rod speed is not zero (speed criteria <NUM> is answered no) the plunger rod speed is reduced <NUM>. If the plunger rod speed is zero (speed criteria <NUM> is answered yes) the process is stopped <NUM>. In stopping <NUM>, the plunger rod may be locked in its position for a dwell time, e.g. to prevent a sudden drop in pressure in the cartridge, e.g. to prevent back flow of medicament.

The high resistance threshold of resistance criterion <NUM> may be determined based on the position of the plunger rod. The plunger rod position may also be used to determine whether in stopping <NUM> the process, the medicament has been expelled sufficiently and/or an error caused the process to stop too early. A corresponding message may be provided to the user, e.g. via the user interface.

By the method <NUM>, the speed is adjusted to be as high as possible without exceeding the resistance thresholds.

The resistance against the movement of the plunger rod is monitored, such as continuously monitored. By a first resistance criterion <NUM>, it is determined whether resistance against movement of the plunger rod exceeds a first high resistance threshold.

If the resistance against movement of the plunger rod does not exceed the first high resistance threshold (first resistance criterion <NUM> is answered no), the speed of the movement of the plunger rod is increased <NUM>.

The position of the plunger rod is monitored, such as continuously monitored. If the resistance against movement of the plunger rod does exceed the first high resistance threshold (first resistance criterion <NUM> is answered yes), by a first position criterion <NUM>, it is determined whether the plunger rod has reached and/or passed a predetermined plunger rod position, such as a first plunger rod position, a second plunger rod position, a third plunger rod position, a fourth plunger rod position and/or a fifth plunger rod position (see e.g. <FIG> and <FIG> for exemplary positions).

If the plunger rod position has not reached and/or passed the predetermined plunger rod position (first position criterion <NUM> is answered no), the speed of the movement of the plunger rod is decreased <NUM>.

If the plunger rod position has reached and/or passed the predetermined plunger rod position (first position criterion <NUM> is answered yes), the movement of the plunger rod may be continued. Thus, the first high resistance threshold may be exceeded if the plunger rod has reached and/or passed the predetermined plunger rod position. In this case, by a second resistance criterion <NUM>, it is determined whether resistance against movement of the plunger rod exceeds a second high resistance threshold.

If the resistance against movement of the plunger rod does not exceed the second high resistance threshold (second resistance criterion <NUM> is answered no), the speed of the movement of the plunger rod is increased <NUM>.

If the resistance against movement of the plunger rod does exceed the second high resistance threshold (second resistance criterion <NUM> is answered yes), it is determined by a speed criteria <NUM> whether the plunger rod speed is zero, i.e. the plunger rod is not moving.

If the plunger rod speed is not zero (speed criteria <NUM> is answered no) the plunger rod speed is reduced <NUM>. If the plunger rod speed is zero (speed criteria <NUM> is answered yes) the process is stopped <NUM>. In stopping <NUM>, the plunger rod may be locked in its position for a dwell time, e.g. to prevent a sudden drop in pressure in the cartridge, e.g. to prevent back flow of medicament. In stopping <NUM> end of injection may be assumed.

Claim 1:
An auto-injector (<NUM>) for administering a medicament, comprising:
- a housing (<NUM>);
- a cartridge receiver (<NUM>) configured to receive a cartridge (<NUM>) comprising a first stopper (<NUM>);
- a cartridge (<NUM>) comprising a first stopper (<NUM>), wherein the cartridge (<NUM>) is configured to be received in the cartridge receiver (<NUM>);
- a drive module (<NUM>) coupled to move a plunger rod (<NUM>) between a retracted plunger rod position (<NUM>) and an extended plunger rod position (<NUM>) at the end of the injection of the medicament, the plunger rod (<NUM>) being configured to move the first stopper (<NUM>);
- a resistance sensor (<NUM>) configured to provide a resistance signal indicative of resistance against movement of the plunger rod (<NUM>); and
- a processing unit (<NUM>) coupled to the drive module (<NUM>) and to the resistance sensor (<NUM>),
the processing unit (<NUM>) being configured to:
- control the drive module (<NUM>) to move the plunger rod (<NUM>) towards the extended plunger rod position (<NUM>) with a plunger rod speed;
- determine the plunger rod position;
- receive the resistance signal; and control the drive module (<NUM>) to adjust movement of the plunger rod (<NUM>) if the resistance signal is indicative of resistance against movement of the plunger rod (<NUM>) above a high resistance threshold, wherein the high resistance threshold is based on the plunger rod position, and wherein adjusting the movement of the plunger rod (<NUM>) comprises stopping the movement of the plunger rod (<NUM>);
characterized in that
the high resistance threshold is a first high resistance threshold (<NUM>) when the plunger rod position is between the retracted plunger rod position (<NUM>) and a first plunger rod position (<NUM>), and the high resistance threshold is a second high resistance threshold (<NUM>) when the plunger rod position is between a second plunger rod position (<NUM>) and the extended plunger rod position, and wherein the second high resistance threshold (<NUM>) is higher than the first high resistance threshold (<NUM>).