Cover for a liquid delivery system having an integrated plunger position detection unit, and corresponding method

Abstract

The sensor is integrated with the sliding cover, providing a liquid delivery system that measures the plunger position while the cover is being removed or installed. [Solution] A slide cover for a liquid delivery device, such as a cap 100 for a pen syringe 200, incorporates a series of sensors, including a first optical sensor 110, which has an output that changes as the plunger 220 of the pen syringe 200 passes through during the operation of removing or attaching the cap 100. This output is used together with the output of at least one additional position sensor 120 to determine the position of the plunger 220 along the cylinder 210 of the liquid delivery device. By monitoring the change in the position of the plunger 220, the amount of medication delivered by the liquid delivery device can be determined, displayed, stored, and / or transmitted to an external device for further data processing or storage.

Description

Technical Field

[0001] Field and Background of the Invention The present invention relates to liquid delivery systems, and more particularly to instruments and methods for measuring the timing and amount of a dose delivered by a pen-injector type drug delivery device and / or for monitoring the amount of drug remaining in the device.

Background Art

[0002] In the field of liquid delivery devices, particularly pen injectors, it is necessary to provide the user with reliable information about the dose of liquid drug already administered.

[0003] Various attempts have been made to add functionality to pen injectors by providing smart caps. As an example, U.S. Patent No. 8,743,662 (Patent Document 1), in which the present invention and the assignee are the same, discloses a smart cap for a pen injector that monitors the time elapsed since the pen injector was last used.

[0004] Another smart cap device has attempted to measure the amount of dispensed drug dose. An example of such a device is U.S. Patent No. 8,817,258 (Patent Document 2). This device requires a wide array of optical sensors extending along the cap.

Summary of the Invention

[0005] The present invention is an instrument in which a sensor is integrated with a slide cover of a liquid delivery system and measures the position of a plunger of the liquid delivery system while the cover is removed or reinstalled.

[0006] According to the teachings of aspects of the present invention, an instrument for use with a liquid delivery system comprising a transparent cylinder for containing a liquid and a plunger that is movable along the axis of the cylinder for discharging the liquid through a discharge port, comprising: (a) a slide cover configured to slidely engage with the cylinder so as to be slidable along the cylinder parallel to the axis from a first position to a second position; and (b)(i) an optical sensor having an optical emitter for emitting radiant energy and an optical receiver for generating a first output representing the amount of radiant energy received by the optical receiver, wherein the optical sensor plunges when the slide cover slides in engagement with the transparent cylinder. An instrument is provided, comprising: (ii) an optical sensor positioned inward such that a first output changes as it passes through the cylinder; and a set of sensors housed in the slide cover so as to move with the slide cover, including (ii) a position sensor positioned to generate a second output representing the current position of the slide cover between a first position and a second position; and (c) a processing system associated with the set of sensors to receive at least the first and second outputs, configured to determine the corresponding current position of the slide cover represented by the second output in response to a variation in the first output representing the optical sensor reaching the plunger, thereby determining the position of the plunger along the cylinder.

[0007] According to a further feature of the present invention, the slide cover is implemented as a cap having a central lumen for receiving the end of a pen syringe having a protruding needle.

[0008] According to a further feature of the present invention, an optical sensor is implemented using a plurality of optical emitters and a plurality of corresponding optical receivers spaced apart around a central lumen, such that at least one pair of optical emitters and optical receivers are not obstructed when used with a pen syringe having an optical obstruction extending along a transparent cylinder parallel to the axis.

[0009] According to a further feature of an aspect of the present invention for a pen syringe having a number of fixed optical obstacles spaced apart along a transparent cylinder, the processing system is configured to (a) process a first output to detect fluctuations representing the passage of the leading edge and trailing edge of the plunger by a first optical sensor; (b) determine the position of the leading edge of the plunger along the cylinder; and (c) determine the position of the trailing edge of the plunger when it is detected that the leading edge of the plunger is approaching a fixed optical obstacle.

[0010] To be used with a pen syringe having an initial plunger position enclosed within an opaque housing, according to a further feature of the present invention, the series of sensors further includes an auxiliary optical sensor having an optical emitter for emitting obliquely radiated energy through the wall of a transparent cylinder toward the surface of the plunger, and an optical receiver for generating an auxiliary output representing the amount of obliquely radiated energy received by the optical receiver.

[0011] A further feature of the present invention also provides a cradle slidably mounted in a central lumen and configured to receive the end of a pen syringe, wherein the slide cover is spring-biased toward a terminal position to engage with the end of the pen syringe when the slide cover is in a first position, and is retractable to move together with the end of the pen syringe as the slide cover slides to a second position.

[0012] According to a further feature of the present invention, a position sensor is associated with a cradle such that a second output represents the current position of the cradle within the central lumen.

[0013] A further feature of the present invention is also provided, which is arranged to bias the cradle toward an end position, and the position sensor includes a load cell arranged to measure the compressive force in the cradle spring.

[0014] A further feature of the present invention is also provided, which is positioned within the slide cover such that the biasing force acting on the cradle corresponds to a combination of the force from the cradle spring and the force from the force adjusting spring, and a load cell is positioned to measure the compressive force in the cradle spring alone.

[0015] According to further features of the present invention, the position sensor is a second optical sensor including an emitter and a receiver.

[0016] According to a further feature of an aspect of the present invention, the second optical sensor is configured to generate a second output representing the current position of the slide cover based on the intensity of the reflected light.

[0017] According to a further feature of the embodiment of the present invention, the position sensor is an electrical sensor that generates a second output as a function of variation in capacitance or inductance between two electrical components whose overlap is variable.

[0018] A further feature of the present invention is also provided, which is positioned relative to the slide cover to operate when the liquid delivery system engages with the instrument, and at least a portion of the instrument has a low-power sleep state that is selectively activated when the microswitch is operated.

[0019] A further feature of the present invention is also provided, which is a non-volatile data storage component associated with the processing system, which is configured to store the previous position of the plunger, compare the current position of the plunger with the previous position, determine whether a liquid has been dispensed, and calculate the amount of liquid dispensed.

[0020] According to a further feature of the present invention, a display unit integrated with the slide cover is also provided, and the processing system is further configured to display data relating to the delivered dosage.

[0021] According to further features of the embodiments of the present invention, a wireless communication subsystem is also provided, which is associated with a processing system and configured to transmit data to an external device.

[0022] According to further features of aspects of the present invention, a pen syringe configured for delivering a measured dose of liquid drug via a needle is also provided, wherein a slide cover is implemented as a cap having a central lumen for receiving the end of the pen syringe containing the needle.

[0023] According to the teachings of aspects of the present invention, also provided is an apparatus for use with a liquid delivery system comprising a transparent cylinder for containing a liquid and a plunger movable along the axis of the cylinder for discharging the liquid through a discharge port, comprising: (a) a slide cover configured to slide-engage with the cylinder so as to be slidable along the cylinder parallel to the axis from a first position to a second position; (b) a series of sensors housed in the slide cover so as to move with the slide cover, comprising at least a first sensor and a second sensor, wherein the first sensor is a plunger sensor that generates a signal, and the plunger sensor is configured to non-contact sense at least a portion of the plunger as the slide cover slides in engagement with the transparent cylinder such that fluctuations in the first signal represent the plunger passing through a defined position along the slide cover; and (c) a processing system associated with the series of sensors to receive the output of the sensors and configured to identify fluctuations in the output of the plunger sensor as the plunger passes through the plunger, and further configured to process the output to derive the position of the plunger along the cylinder.

[0024] According to a further feature of an aspect of the present invention, the second sensor is a position sensor arranged to generate a second output representing the current position of the slide cover between a first position and a second position.

[0025] According to a further feature of the embodiment of the present invention, the first and second sensors are a pair of similar sensors spaced apart along an axis.

[0026] According to the teachings of aspects of the present invention, there is also provided a method for measuring the position of a plunger within a transparent cylinder of a drug delivery device for calculating a drug delivery dosage, the method comprising the following steps: (a) providing a slide cover configured to slidably engage with the cylinder such that it is slidable parallel to the axis of the cylinder from a first position to a second position, the slide cover being provided with a plunger sensor configured to non-contact detect at least a portion of the plunger; (b) sliding the cover along the cylinder and detecting a variation in a first output corresponding to the plunger sensor reaching the plunger; and (c) using the output of at least one additional sensor to determine the position of the cover relative to the cylinder when the plunger sensor reaches the plunger, thereby determining the position of the plunger.

[0027] According to a further feature of aspects of the present invention, the at least one additional sensor is a distance sensor arranged to measure an axial distance between a portion of the slide cover and a portion of the drug delivery device.

[0028] According to a further feature of aspects of the present invention, the plunger sensor is an optical sensor having an optical emitter for emitting radiant energy and an optical receiver for generating a first output representative of the amount of radiant energy received by the optical receiver.

[0029] According to a further feature of aspects of the present invention, the at least one additional sensor is a second optical sensor spaced axially from a first optical sensor and including an optical emitter for emitting radiant energy and an optical receiver for receiving radiant energy, the method further comprising: (a) detecting a variation in the output of the second optical sensor corresponding to the second optical sensor reaching the plunger; and (b) deriving the speed of the sliding motion used to determine the position of the plunger from the time difference between features in the outputs from the two optical sensors. [Invention 1001] (a) A slide cover configured to slidably engage with a cylinder so as to be slidable parallel to the axis along the cylinder from a first position to a second position; (b) (i) An optical sensor and an optical receiver having an optical emitter for emitting radiant energy and generating a first output representing the amount of the radiant energy received by the optical receiver, wherein the optical sensor is disposed in an inward arrangement such that the first output changes as the optical sensor passes through a plunger when the slide cover engages and slides with a transparent cylinder, and (ii) A position sensor disposed to generate a second output representing the current position of the slide cover between the first position and the second position A series of sensors housed in the slide cover so as to move with the slide cover, including; and (c) A processing system associated with the series of sensors so as to receive at least the first output and the second output, configured to determine a corresponding current position of the slide cover represented by the second output in response to a variation in the first output representing the optical sensor reaching the plunger, thereby determining the position of the plunger along the cylinder Including, An instrument for use with a liquid delivery system including a transparent cylinder for containing a liquid and at least a partially opaque plunger movable along the axis of the cylinder for discharging the liquid through a discharge port. [Invention 1002] The instrument of Invention 1001, wherein the slide cover is implemented as a cap having a central lumen for receiving an end of a pen injector having a protruding needle. [Invention 1003] A plurality of optical emitters spaced around the central lumen and a corresponding plurality of optical receivers spaced around the central lumen are used to implement the optical sensor such that at least a pair of the optical emitters and the optical receivers are not blocked when used with a pen injector having an optical obstacle extending parallel to the axis along a transparent cylinder. The instrument of Invention 1002. [Invention 1004] The aforementioned processing system (a) Process the first output to detect fluctuations that indicate the first optical sensor is passing the leading edge and trailing edge of the plunger; (b) Determine the position of the leading edge of the plunger along the cylinder; and (c) When it is detected that the leading edge of the plunger is approaching a fixed optical obstruction, the position of the trailing edge of the plunger is determined. It is structured in such a way. The apparatus of the present invention 1002 for use with a pen syringe having multiple fixed optical obstructions spaced apart along a transparent cylinder. [Invention 1005] The series of sensors further includes an auxiliary optical sensor having an optical emitter for emitting obliquely radiated energy through the wall of a transparent cylinder toward the surface of a plunger, and an optical receiver for generating an auxiliary output representing the amount of obliquely radiated energy received by the optical receiver, The apparatus of the present invention 1002 for use with a pen syringe having an initial plunger position inside an opaque housing. [Invention 1006] A cradle slidably mounted within a central lumen and configured to receive the end of a pen syringe, wherein the slide cover is spring-biased toward a terminal position to engage with the end of the pen syringe when in the first position, and is retractable so as the slide cover slides to a second position to move together with the end of the pen syringe. The apparatus of the present invention 1002 further includes. [Invention 1007] The apparatus of the present invention 1006, wherein the position sensor is associated with a cradle such that the second output represents the current position of the cradle within the central lumen. [Invention 1008] The apparatus of the present invention 1006 further includes a cradle spring positioned to bias the cradle toward an end position, wherein the position sensor includes a load cell positioned to measure the compressive force in the cradle spring. [Invention 1009] The apparatus of the present invention 1008 further includes a force adjusting spring disposed within the slide cover such that the biasing force acting on the cradle corresponds to a combination of the force from the cradle spring and the force from the force adjusting spring, and a load cell is provided to measure the compressive force in the cradle spring alone. [Invention 1010] The apparatus according to any one of the present invention 1001 to 1007, wherein the position sensor is a second optical sensor including an emitter and a receiver. [Invention 1011] The apparatus of the present invention 1010, wherein the second optical sensor is configured to generate the second output representing the current position of the slide cover based on the intensity of reflected light. [Invention 1012] The apparatus according to any of the invention 1001 to 1007, wherein the position sensor is an electrical sensor that generates the second output as a function of variation in capacitance or inductance between two electrical components having a variable overlap. [Invention 1013] The apparatus of the present invention 1001 further includes a microswitch positioned relative to the slide cover to operate when the apparatus is engaged with a liquid delivery system, wherein at least a portion of the apparatus has a low-power sleep state and is selectively activated when the microswitch is operated. [Invention 1014] The apparatus of the present invention 1001 further comprises a non-volatile data storage component associated with the processing system, wherein the processing system is configured to store the previous position of a plunger, compare the current position of the plunger with the previous position, determine whether a liquid has been dispensed, and calculate the amount of liquid dispensed. [Invention 1015] The apparatus of the present invention 1014, further comprising a display unit integrated with the slide cover, wherein the processing system is further configured to display data relating to the delivered dosage. [Invention 1016] The apparatus of the present invention 1001 further includes a wireless communication subsystem associated with the processing system and configured to transmit data to an external device. [Invention 1017] The apparatus of the present invention 1001 further comprises a pen syringe configured for delivering a measured dose of liquid drug via a needle, wherein the slide cover is implemented as a cap having a central lumen for receiving the end of the pen syringe, including the needle. [Invention 1018] (a) A slide cover configured to slide with the cylinder so as to be able to slide along the cylinder parallel to the axis from a first position to a second position; (b) A series of sensors housed in the slide cover so as to move with the slide cover, the first sensor being a plunger sensor that generates a signal, and the plunger sensor being configured to non-contact detect at least a portion of the plunger as the slide cover slides in engagement with the transparent cylinder, such that fluctuations in the first signal represent the plunger passing through a defined position along the slide cover; and (c) A processing system associated with the series of sensors to receive the output of the sensors, configured to identify fluctuations in the output of the plunger sensor as the plunger passes through the plunger, and further configured to process the output to derive the position of the plunger along the cylinder. including, An instrument for use with a liquid delivery system, comprising a transparent cylinder for containing liquid and a plunger movable along the axis of the cylinder for discharging the liquid through a discharge port. [Invention 1019] The apparatus of the present invention 1018, wherein the second sensor is a position sensor arranged to generate a second output representing the current position of the slide cover between the first position and the second position. [Invention 1020] The apparatus of the present invention 1018, wherein the first and second sensors are a pair of similar sensors spaced apart along the axis. [Invention 1021] (a) A slide cover configured to slide-engage with a cylinder so as to be able to slide along the cylinder parallel to the axis of the shaft from a first position to a second position, wherein a plunger sensor configured to non-contact detect at least a portion of the plunger is provided. The process of preparing; (b) A step of sliding the cover along the cylinder and detecting a fluctuation in the first output corresponding to the plunger sensor that reaches the plunger; and (c) The process of using the output of at least one additional sensor to determine the position of the cover relative to the cylinder when the plunger sensor reaches the plunger, thereby determining the position of the plunger. A method for measuring the position of a plunger in a transparent cylinder of a drug delivery device for the purpose of calculating the drug delivery dose. [Invention 1022] The method of the present invention 1021, wherein the at least one additional sensor is a distance sensor positioned to measure the axial distance between the portion of the slide cover and the portion of the drug delivery device. [Invention 1023] The method of the present invention 1021, wherein the plunger sensor is an optical sensor having an optical emitter for emitting radiant energy and an optical receiver for generating a first output representing the amount of said radiant energy received by the optical receiver. [Invention 1024] The at least one additional sensor is a second optical sensor comprising an optical emitter for emitting radiant energy and an optical receiver for receiving the radiant energy, and is positioned axially apart from the first optical sensor. The method is (a) a step of detecting fluctuations in the output of the second optical sensor corresponding to the second optical sensor that reaches the plunger; and (b) A step of deriving the speed of the sliding motion used to determine the position of the plunger from the time difference between the features in the outputs from the two optical sensors. The method of the present invention 1023, further comprising: [Brief explanation of the drawing]

[0030] The present invention is described herein only by reference to the accompanying drawings.

[0031] [Figure 1] This is a schematic diagram of a cap manufactured and operated according to an embodiment of the present invention, used to cap a pen syringe. [Figure 2A] Figure 1 is a schematic isometric view of the cap and pen syringe, with the pen syringe located outside the cap. [Figure 2B] Figure 1 is a schematic isometric view of the cap and pen syringe, with the pen syringe partially inserted into the cap. [Figure 2C] Figure 1 is a schematic isometric view of the cap and pen syringe, with the pen syringe fully inserted into the cap. [Figure 3A] Figure 2B shows a schematic cross-sectional view along the central axis of the cap. [Figure 3B] Figure 2C shows a schematic cross-sectional view along the central axis of the cap. [Figure 3C] This is a magnified view of the area labeled III in Figure 3A. [Figure 4] Figure 4A is a schematic cross-sectional view of an exemplary shape of a pen syringe reservoir; Figures 4B and 4C are cross-sectional views obtained from the optical sensor of Figure 3A, illustrating insertion of the pen syringe reservoir of Figure 4A in two different orientations. [Figure 5] Figures 5A–5D are schematic side views of an exemplary pen syringe showing four plungers in consecutive positions. [Figure 6]Figures 6A to 6D are schematic graphs illustrating the characteristics of the output of the optical sensors in Figures 4B and 4C as a function of the insertion distance of the pen syringe into the cap, corresponding to the plunger position in Figures 5A to 5D, respectively. [Figure 7] Figures 7A and 7B are similar to Figures 3A and 3B, respectively, illustrating embodiments of additional optical sensors. [Figure 8] Figures 8A and 8B are similar to Figures 3A and 3B, showing different embodiments of the position sensor. [Figure 9A] This is a schematic axial cross-sectional view illustrating the operating principle of a further different embodiment of the present invention, shown in a continuous position during the removal of the cap of a pen syringe. [Figure 9B] This is a schematic axial cross-sectional view illustrating the operating principle of a further different embodiment of the present invention, shown in a continuous position during the removal of the cap of a pen syringe. [Figure 9C] This is a schematic axial cross-sectional view illustrating the operating principle of a further different embodiment of the present invention, shown in a continuous position during the removal of the cap of a pen syringe. [Figure 9D] This is a schematic axial cross-sectional view illustrating the operating principle of a further different embodiment of the present invention, shown in a continuous position during the removal of the cap of a pen syringe. [Figure 9E] This is a schematic axial cross-sectional view illustrating the operating principle of a further different embodiment of the present invention, shown in a continuous position during the removal of the cap of a pen syringe. [Figure 10] Figure 10A is a schematic axial cross-sectional view illustrating in more detail an embodiment of the present invention based on the principles shown in Figures 9A to 9E; Figures 10B to 10D are enlarged views of the region in Figure 10A labeled X, shown in a state corresponding to the position in Figures 9A to 9C, respectively. [Modes for carrying out the invention]

[0032] Preferred Embodiment Description The present invention relates to an apparatus and a corresponding method for which a sensor is integrated with a slide cover of a liquid delivery system and for measuring the position of a plunger of the liquid delivery system while the cover is being removed or reattached.

[0033] The principle and operation of the apparatus according to the present invention may be better understood by referring to the drawings and accompanying descriptions.

[0034] Broadly speaking, the present invention utilizes a slide cover, such as a cap for a pen syringe, incorporating a series of sensors including a first optical sensor that operates during the removal and / or installation of the cap and generates a signal that changes as the optical sensor reaches the plunger of the liquid delivery device. This signal is then used in conjunction with the output of at least one additional sensor to determine the position of the plunger along the cylinder of the liquid delivery device. By monitoring the change in plunger position, the amount of medication delivered by the liquid delivery device can be determined, displayed, stored, and / or transmitted to an external device for further data processing or storage.

[0035] Embodiments of the present invention can be broadly divided into two subgroups that all share a common inventive concept. The first subgroup, described herein with reference to Figures 1-8B, uses a position sensor together with a first optical sensor to measure the relative position of the liquid delivery device to the cover when the first optical sensor reaches the plunger. The second subgroup of embodiments illustrated with reference to Figures 9A-10D uses at least one additional optical sensor to determine the speed at which the cover moves relative to the liquid delivery device, thereby deriving the position at which it encounters the plunger.

[0036] Referring here to the drawings, Figures 1–7B illustrate the features of a first instrument, generally denoted 100, which is manufactured and operates according to an embodiment of the present invention as a cap for an injection pen ("pen syringe") 200, the pen syringe 200 having a generally transparent reservoir, which is in the form of a cylinder 210 with a transparent wall 211 for containing liquid, and a plunger 220 (interchangeably referred to herein as the "piston") that is at least partially opaque, movable along the axis of the cylinder 210 to discharge liquid through a discharge port, which is typically implemented as a partition associated with a replaceable injection needle 230.

[0037] The device 100 is formed as a slide cover, here referred to as the cap 100, which is configured to slide with the cylinder 210 so that the cap can slide along the cylinder parallel to the axis from a first position (Figures 2B and 3A) at the start of reattaching the cap to a second position (Figures 2C and 3B) where the cap is fully engaged with the pen syringe 200.

[0038] A series of sensors are housed in the slide cover so as to move with the slide cover. The series of sensors includes an optical sensor 110 having an optical emitter 111 for emitting radiant energy and an optical receiver 112 for generating a first output representing the amount of radiant energy received by the optical receiver. The optical sensor 110 is positioned inward so that the first output changes as the optical sensor 110 passes through the plunger 220 as the slide cover slides in engagement with the transparent cylinder 210.

[0039] The set of sensors also includes a position sensor 120 positioned to generate a second output representing the current position of the slide cover 100 between a first and second position relative to the pen syringe 200. A processing system 122, including at least one processor 124, is associated with the set of sensors to receive sensor outputs. The processing system 122 is configured to respond to fluctuations in the output from optical sensor 110, which indicates that the optical sensor has reached the plunger 220, and to determine the corresponding current position of the cover 100 represented by the output of position sensor 120, thereby determining the position of the plunger 220 along the cylinder 210.

[0040] Therefore, a particular aspect of the present invention provides a characteristic mode of operation in which the plunger position is detected using a sensor that slides along the cylinder 210. By utilizing the relative movement between the cover and the reservoir in the measurement process, accurate measurements can be suitably achieved with a small number of sensors.

[0041] Looking at the features of more detailed embodiments of the present invention, the optical sensor 110 is typically implemented as an emitter / receiver pair 111, 112 facing each other to interact with the liquid delivery device during the sliding motion of the cover. In a preferred example of a cap with a central lumen 101 for receiving the end of a pen syringe, the sensor 110 is typically implemented as a transmissive sensor in which the emitter 111 and receiver 112 are in a facing relationship across the central lumen, most typically along the diameter, so that the intensity of the received light is affected by the portion of the pen syringe inserted between the two elements. For the highest possible measurement accuracy, in certain particularly preferred embodiments, the emitter 111 is configured to produce a narrow beam with minimal spread in the direction parallel to the axis. This may be achieved by a suitable selection of a light source, such as a directional LED or laser diode, and / or by the use of parallel slits arranged perpendicular to the axis of the lumen. Some degree of spread in a plane perpendicular to the axis of the lumen may be advantageous, but is typically not required. The light source may be operated with visible or invisible light of any desired wavelength. In the various embodiments described below in which multiple optical sensors are used, crosstalk between sensors may be avoided by either using a separate wavelength for each sensor (e.g., by adding a bandpass filter, the receiver also becomes wavelength-specific) or by time-division multiplexing in which each sensor emits and detects pulses of light emission within separate periods of the cycle. The sampling rate is preferably at least 100 Hz and typically exceeds 1000 Hz.

[0042] In the case of a pen syringe with a transparent cylindrical reservoir free of optical obstructions, the optical sensor 110 can be implemented substantially as a single emitter / receiver pair 111, 112. In certain cases, however, commercially available pen syringes have various structural support and / or protective structures that partially opaqueize the surface of the transparent cylinder. Therefore, certain corresponding preferred embodiments of the present invention provide solutions for dealing with such obstructions, as will be described below.

[0043] Figure 4A is a schematic cross-sectional view obtained from a cylinder 210 in which two opposing regions of the cylinder wall 211 are covered by a plastic support structure 212 extending along the cylinder parallel to its axis. In this case, a single emitter / receiver pair optical sensor risks failing to detect the plunger depending on the orientation in which the pen syringe is inserted into the cap. According to one option (not shown), features formed on the cap 100, complementary to the asymmetric support structure features of the pen syringe 200, may ensure that the orientation of the cap relative to the pen syringe is one in which the emitter / receiver pair aligns in a straight line with the exposed region of the transparent wall 211 without being obstructed by the support structure 212.

[0044] According to an alternative solution, the optical sensor 110 is implemented with two or more optical emitters 111 spaced around a central lumen, and a corresponding number of optical receivers 112 spaced around a central lumen, as shown in Figures 4B and 4C. As a result, at least one pair of optical emitters and optical receivers are not obstructed regardless of the orientation in which the pen syringe is inserted into the cap. Thus, for example, Figure 4B illustrates the case where the left-right emitter / receiver pair is obstructed by the support structure 212, but the top-bottom emitter / receiver pair is operational, while Figure 4C illustrates the orientation of the pen syringe where the opposite is true.

[0045] In this case, multiple emitter / receiver pairs are preferably positioned at a single axial location along the central lumen and treated as a single sensor used to generate a single output. According to one particularly preferred option, a single output is generated through a preprocessing step performed by the processing system 122, thereby selecting the emitter / receiver pair with the largest dynamic range in that output as the "active" portion of the sensor, while pairs with smaller dynamic ranges are ignored. Other options, such as summing the sensor outputs, may also yield effective results, but are considered less sensitive than the selective use of the output with the largest dynamic range.

[0046] In certain commercially available pen syringes, further types of optical obstructions are present, as illustrated in Figures 5A–5D. In this case, the pen syringe 200 also features, in addition to the longitudinal support structure 212, multiple bridging ribs 213 that subdivide the window to the reservoir to form multiple fixed optical obstructions spaced apart along the transparent cylinder. The position of the tip surface 221 of the plunger 220 can be optically detected when it is on the opposite side of the “window” between the ribs 213, as shown in 5A, 5B, and 5D, but at certain positions, such as in Figure 5C, the tip surface 221 is obscured from view by one or the other rib 213.

[0047] According to one aspect of the present invention, continuity of plunger position measurement is achieved by switching the detection of the leading edge / front 221 and the rear edge / rear 222 of the plunger in such cases. Specifically, the processing system 122 is configured to process the output of the optical sensor 110 to detect fluctuations representing the optical sensor 110 passing through both the leading edge and the rear edge of the plunger (the leading and rear edges viewed from the side are observed as “edges”). During the initial operation, the processor 122 determines the position of the leading edge 221 of the plunger 22 along the cylinder. When the processor 122 determines that the leading edge 221 is approaching one of the fixed optical obstacles 213, the processor switches to determining the plunger position based on the detection of the rear edge 222 of the plunger. Given that the plunger has a constant known length (which can also be determined during measurement while both sides of the plunger are exposed, as in Figure 5B), the position of the leading edge 221 can be accurately determined even while it is hidden from view. Once the leading edge 221 emerges from behind the obstacle, the processing system 122 typically switches to directly determining the position of the front of the plunger again, as shown in Figure 5D. Optionally, if the positions of both the front and rear edges of the plunger are detected, both measurements may be used to improve accuracy and / or for error checking. Whenever either the front or rear edge approaches an obstacle, the processing system switches to using only the unobstructed edge.

[0048] Figures 6A–6D show schematic diagrams of the light emission intensity output I of the optical sensor 110 as a function of the insertion distance d of the pen syringe 200 into the cap 100, corresponding to the states in Figures 5A–5D, respectively. Note that the illustrative signals shown here are for the relatively more complex case of Figures 5A–5D, which includes an optical obstruction in the form of a rib 213. The operation in the simpler case without such obstructions is clearly understood by analogy from these drawings and accompanying descriptions.

[0049] As shown in Figures 6A and 6C, the illustrated graph can be subdivided into regions corresponding to different parts of the pen syringe 200 as it passes through the optical sensor 110. Region A corresponds to the generally unattenuated signal at level I1 before the body of the pen syringe reaches the sensor, which may be slightly affected by the presence of a protruding needle, which may also include a needle cover 231 as shown in some cases. When the internal sliding cradle 160 is used (as described later), this region immediately in front of the pen syringe is typically opaque, and its optical properties become independent of the presence or absence of the needle and cover, which further simplifies the detection process. Region B corresponds to the passage of the solid end of the pen syringe, which results in an optical obstruction and a strong attenuation of the output signal to the corresponding level I4. As the relative motion of the pen syringe 200 and cap 100 continues and the overlap increases, at least one emitter / receiver pair of the optical sensor 110 aligns with the window through the cylinder 210, thus generating a relatively high signal at level I2. Signal I2 is typically slightly lower than I1 due to scattering and / or absorption occurring at the cylinder wall 211 and / or in the liquid. In this example, region C is obscured by a localized signal drop D due to the obstruction 213, after which the signal returns to level I2 in region C, which is a further window portion. Then, as the leading edge 221 of the plunger 220 reaches the optical sensor 110, the signal drops again to I4 until the entire plunger has passed (region P), or, in the case of Figures 5A and 6A, remains hidden for the rest of the motion.

[0050] The position of the front (or rear) end of the plunger is preferably determined by the start of a steep line gradient associated with the corresponding signal change, but other measurement points, such as the signal half-height, may also be used and, when used consistently, may yield good results.

[0051] Figure 6C illustrates the signal corresponding to the state in Figure 5C, where the leading edge 221 cannot be directly found from the optical signal output, and instead its position is calculated based on the measurement of the trailing edge 222, as described above.

[0052] In this specification, the optical sensor 110 is illustrated with reference to the transmission mode, but it should be noted that a reflection mode may also be used, in which the emitter and receiver are located on the same side of the lumen. The resulting signal shape will differ, but all aspects of the processing described herein can be readily adapted to forms that are obvious to those skilled in the art.

[0053] In certain commercially available pen syringes, the plunger's position during the initial stages of movement is within the opaque region of the pen syringe housing, only reaching the exposed transparent portion of the reservoir after some use. Figures 7A and 7B show a modified cap 100, further comprising an auxiliary optical sensor having an optical emitter 113 for radiating obliquely radiated energy through the transparent cylinder wall 211 toward the surface 221 of the plunger and an optical receiver 114 for generating an auxiliary output representing the amount of obliquely radiated energy received by the optical receiver. In this case, the plunger position is typically derived from intensity measurements based on pre-calibration for each given type of pen syringe. Since this measurement method is used only over a small range of positions in the initial stages of the plunger's movement, the measurement can be performed while the pen syringe is stationary after full insertion into the cap, and sufficient accuracy can typically be achieved using a single auxiliary sensor (with multiple emitter / receiver pairs as described above, optionally with reference to Figures 4A-4C).

[0054] It should be noted that, in some cases, it may be possible to find wavelengths of emission that pass through various plastic parts of a device that do not transmit visible light for various optical sensors of the present invention. For example, it has been found that a beam of an 850 nm solid-state laser passes through the plastic support structure of various pen syringes relatively unimpeded, but is strongly attenuated by the device's silicone plunger. One non-limiting example of a suitable optical emitter for such cases is the OPV382 vertical-cavity surface-emitting laser, commercially available from OPTEK Technology Inc. (USA). The use of such wavelengths may eliminate the need for some or all of the solutions described above, with reference to Figures 4B–7B.

[0055] Now looking at additional features of a particular preferred embodiment of the present invention, the instrument 100 may be advantageously provided with a sliding “cradle” 160 slidably mounted within a central lumen 101 configured to receive the end of a pen syringe 200. The term “cradle” as used herein refers to a slider, also called a “slider” herein, which is shaped to receive the end of a pen syringe and suitably accommodates its end in a clearly defined position, regardless of whether the pen syringe is currently connected to a needle adapter with or without a needle cover, or whether it is in a needleless state with its partition contact surface exposed. This is preferably achieved by providing an engagement mechanism radially outward from the mounting area of ​​the needle adapter that engages with the outer circumference of the front end of the reservoir. The cradle 160 is preferably spring-biased by a spring 170 toward a terminal position to engage with the end of the pen syringe when the cap 100 is in a first position, which is at the start of reattaching the cap or the end of removing the cap (Figure 3A), and is retractable against the spring 170 to move with the end of the pen syringe 200 as the cap 100 and pen syringe 200 slide to a second fully engaged position. The placement of the cradle 160 helps maintain a precise straight alignment between the pen syringe 200 and the cap 100 during movement, ensuring smooth and predictable movement of the pen syringe within the cap, which in turn helps improve the accuracy of measurements by the optical sensor 110.

[0056] Now, looking at the position sensor 210, it may be implemented in many different ways, and a wide range of non-limiting examples using different techniques will be described below. In some cases, the presence of the cradle 160 may be advantageously used for the implementation of the position sensor. For example, the position sensor 120 may be advantageously associated with the cradle 160 such that the output of the position sensor represents the current position of the cradle 160 within the central lumen 101. Since the engagement between the end of the pen syringe 200 and the cradle 160 is clearly defined, and the cradle 160 is spring-biased and moves with the pen syringe 200 to maintain its engagement with the pen syringe 200, the position of the cradle 160 can be used as a direct indicator of the position of the pen syringe 200.

[0057] One particularly preferred non-limiting example of the position sensor 120, illustrated in Figures 3A and 3B, utilizes a load cell 171 positioned to measure the compressive force in the spring 170. Since the compressive force on the spring 170 is proportional to the displacement of the spring according to Hooke's Law, the measurement of the force on the load cell can simply be translated into the position of the cradle 160 and, consequently, the position of the pen syringe 200. The processing system 122 is connected to the load cell 171 to read the output of the load cell and translate its output into the position of the pen syringe. The position of the plunger 220 in the cylinder 210 can be derived by processing the signal from the optical sensor 110 to determine when the front (or rear) surface of the plunger is at a predetermined position along the lumen 101, and by determining the corresponding position of the pen syringe 200 at that moment. From the known cylinder bore and the difference in the continuous position of the plunger, the calculated volume of the liquid formulation delivered from the reservoir can be obtained.

[0058] The use of calculations based on Hooke's Law assumes that any dynamic effects occurring during the motion of the spring are negligible. This assumption is typically good, as long as the spring characteristics (mainly mass and spring constant) are such that any internal vibrations of the spring occur at relatively high frequencies compared to the time it takes for the spring to compress or stretch. If any vibrations with known characteristic frequencies of spring vibration are detected in the output signal, these can be excluded by the processor 122.

[0059] The strength of the spring 170 is preferably selected so as to ensure that the load cell operates within its most sensitive range and / or within the range that provides a linear output response. In some cases, this force may be greater than desired for the overall biasing force on the cradle 160, potentially leading to a risk of the pen syringe being unintentionally ejected from the cap, or it may be too small to reliably maintain engagement between the tip of the pen syringe 200 and the cradle 160 while removing the cap. In such cases, the device 100 may include a force-regulating spring (not shown) located within the cap, while the load cell 171 is positioned to measure the compressive force in the cradle spring 170 alone, so that the biasing force acting on the cradle corresponds to a combination of the force from the cradle spring 170 and the force from the force-regulating spring.

[0060] A particularly preferred feature of certain embodiments of the present invention is that the device 100 automatically operates to acquire a dosage reading once per medication cycle, but enters a low-power "sleep" state when not in use. Multiple options may be used to achieve automatic operation. According to the first option illustrated in Figure 3C, a mechanical switch, such as a microswitch 180, is provided to activate the device. The state of the switch 180 is preferably changed as the cradle 160 (which moves with the pen syringe 200) passes the switch button 181. The processing system 122 responds to the change in the state of the switch 180 and activates the device to a measurement mode in which all sensors are operated in the normal manner for measurement. The positioning of the switch 180 as shown herein is particularly suitable for a system configured to perform a measurement during the cap mounting process, i.e., when the pen syringe is inserted into the cap (or, for the purposes of this application, the cap is mounted on the pen syringe). In alternative embodiments described below with reference to Figures 9A-10D, a microswitch is located at the distal end of the cap 100 to activate the system at the start of the cap removal operation. In either case, the device is configured to return to a low-power sleep mode after a given time sufficient to complete the cap attachment or cap removal operation, which is preferably typically within a few seconds. Optionally, processing and display components may remain activated for longer periods to complete all necessary calculations and display the results for a predetermined time, while some components may remain activated for different times depending on their function, as the sensor is stopped for a short time sufficient to complete the movement and associated measurements. Button 131 is typically provided to reactivate the display unit 130 as needed to display the most recent dosage data.

[0061] In an alternative embodiment for achieving recovery from sleep mode without a mechanical microswitch, the load cell 171 itself may be used in low-power mode as an actuation sensor for detecting the start of operation. Typically, the load cell operates on an input voltage and provides an output that is a varying proportion of the input voltage depending on the current load. During normal operation, the load cell 171 is supplied with an operating voltage that typically corresponds to the input power supply voltage from the power supply 128, e.g., 5V, to provide maximum resolution in the output signal. According to this feature of the aspect of the present invention, in sleep mode, the load cell 171 may be operated on a reduced voltage of less than 1V, e.g., 0.5V, and the output voltage is monitored by a low-power circuit that converts small changes in the output voltage into actuation signals to the processing system 122, which then reactivates all relevant components.

[0062] A brief reference to the remaining components illustrated in Figure 1 reveals that the processing system 122 includes at least one processor 124 and a data storage device 126, and preferably a communication subsystem 140. The processing system 122 may be implemented in various ways, using a standard processor chip appropriately configured by software or firmware, or by dedicated hardware, or any combination thereof, in combination with appropriate input and output interfaces necessary for sending and receiving outputs from various sensors and other components of the system. The display unit 130 is typically a display unit for a limited number of digits or alphanumeric information, which typically displays the last delivered dose and the time that dose was delivered. For broader information, display of past records and / or analysis of drug delivery patterns, data is preferably uploaded to an external electronic device via a communication subsystem 140, which may be a wireless communication subsystem by any desired standard such as Bluetooth® or a wired connection interface such as a micro USB connector. The external device may be a user device such as a personal computer (PC) or a mobile communication device (smartphone), or an insulin pump and / or glucose monitoring device. The device may run diabetes management software (e.g., an app). Additionally or alternatively, data may be transmitted to the healthcare provider's networked system. This system may provide additional information, either directly or via an external device, including injection history for a given period, and warnings about empty cartridges, nearly empty cartridges, scheduled injection times, etc.

[0063] The entire device is powered by a power source 128, which may be a number of small batteries, such as button batteries, which may be disposable or rechargeable.

[0064] It should be noted that the load cell-based position measurement described above is only one of several possible techniques for implementing the position sensor 120. Further examples illustrated in Figures 8A and 8B implement the position sensor 120 facing the cradle 160 as an optical sensor utilizing an emitter 121 and receiver 122 mounted within the closed end of the lumen 101 of the cap 100. Most preferably, the end face 161 of the cradle 160 is implemented as a diffuse reflective surface, such as a sheet of white material. The intensity of the light emitted from the emitter 121 to the receiver 122 after reflection from the end face 161 provides an indication of the distance of the surface 161 from the end of the lumen 101. Since the cap is preferably a closed structure that does not transmit ambient light, relatively high-precision distance measurements can be achieved using a predefined lookup table or formula that is optionally and intermittently self-recalibrated based on one or both of two known stationary positions at the furthest end of the cradle 160.

[0065] Since the pen syringe 200 engages with the cradle 160 in a known spatial relationship, measuring the cradle position 160 also results in measuring the position of the pen syringe. As previously described, measurements corresponding to the plunger reaching a predetermined position along the lumen 101 are identified, and then the position of the plunger along the reservoir cylinder is determined. In all other respects, the structure and function of the instruments in Figures 8A and 8B are structurally and functionally similar to those in Figures 2A–7B, with equivalent elements similarly labeled and understandable by analogy.

[0066] The position sensor 120 may, alternatively, be implemented using other optical sensor technologies, including, but not limited to, triangulation techniques and time-of-flight distance measurement techniques, as are well known in the field of distance measurement.

[0067] In addition to the above embodiments of the position sensor 120, various other proximity sensing and linear encoder techniques may be used to implement the functions of one or both of the sensor 110 (which may be more commonly referred to as a "plunger sensor") and the position sensor 120. Other suitable sensing techniques for the position sensor 120 include, but are not limited to, electrical sensors that produce an output as a function of variation in capacitance (e.g., variable overlap of sliding conductors) or induction (e.g., sliding overlap of coils) between two electrical components with variable overlap, and ultrasonic time-of-flight or intensity-based distance sensors.

[0068] If a metallic element can be embedded in the plunger 220 (or its rod), or if the entire rod is made of metal, a linear variable differential transformer (LVDT) sensor can be used instead of the optical sensor 110 to detect the passage of the plunger 220 at a predetermined position along the lumen 101. If an additional metallic reference element is incorporated near the front of the reservoir, the LVDT sensor can perform the functions of both sensors 110 and 120.

[0069] Figures 9A–10D illustrate further embodiments of the instrument 100 as a smart cap for a pen syringe 200, in which the direct measurement of the position of the pen syringe relative to the cap is replaced by a velocity-based calculation. Specifically, during the process of removing the cap from the pen syringe, the user applies a force greater than the threshold force required to securely disengage the cap from the pen syringe, which results in a rapid involuntary movement as the pen syringe and cap separate. This movement closely approximates constant velocity motion over a relevant range of approximately 5 centimeters. This constant velocity can be utilized to measure the plunger position, as will be described below.

[0070] Referring to the schematic diagrams in Figures 9A to 9E, the device 100 here includes a first optical sensor 110a located near the proximal end of the internal lumen 101 and a second optical sensor 110b located elsewhere along the lumen 101. Each optical sensor is implemented in accordance with any or all of the features described above in relation to the sensor 110. The device also preferably includes a microswitch 180 which is actuated by a portion of the pen syringe 200 when the pen syringe is fully engaged with the cap (opening in this case) and switched off (closing in this case) by the initial movement of the pen syringe 200 from its fully engaged position (from Figure 9A to Figure 9B).

[0071] The optical sensor 110b is positioned to produce a variation in output as some optically discriminative feature of the pen syringe passes through it. In the illustrations herein, that feature is the distal end of the pen syringe, which is detected as a transition in position from the state in Figure 9B to the state in Figure 9C. This event can be associated with time t0 or considered to start a timer.

[0072] The optical sensor 110a is positioned proximal to the instrument 100 so as to produce an output variation corresponding to the passage of the plunger, as described in detail above in relation to the sensor 110. This occurs in the transition between states in Figures 9C and 9D, as illustrated here, and is denoted as time t1. As the instrument 100 and the pen syringe 200 move apart, the optically discriminative feature recognized by sensor 110b also passes through sensor 110a, as illustrated in Figure 9E, and is denoted as time t2.

[0073] The processor 122 processes these outputs to derive the aforementioned time and then determines the position of the plunger. The relative velocity of the cap and the pen syringe can be defined based on the distance L between the two optical sensors divided by (t2-t0). The distance between the optically discriminative features of the plunger and the pen syringe is obtained by multiplying time (t2-t1) by velocity.

[0074] Figures 10A to 10D illustrate in more detail the structure that implements the principle described with reference to Figures 9A to 9E, showing the arrangement of the emitters of the microswitch 180 and the optical sensor 110b. Figures 10B to 10D illustrate the sequential positions corresponding to the states in Figures 9A to 9C, respectively.

[0075] In certain cases where it is desirable to leave space for the user to reattach the cap to the pen syringe, with or without the accompanying needle and needle cover, the microswitch 180 and optical sensor 110b may, as will be apparent to those skilled in the art, be advantageously repositioned to work in cooperation with areas of the pen syringe that are unaffected by the presence or absence of the needle adapter and / or cover.

[0076] As described in the context of the preceding embodiments, if appropriate conductive (metallic) components are incorporated into the pen syringe structure both within the plunger / rod assembly and in the distal region of the pen syringe, functionally equivalent embodiments of the invention to those shown in Figures 9A-10D may be implemented using a coil array corresponding to two spaced-apart linear variable differential transformer (LVDT) sensors to determine t0, t1, and t2.

[0077] At this stage, the operation of various embodiments of the present invention and corresponding methods according to the present invention are considered to be clear. Specifically, various embodiments detect the plunger position based on a signal sampled during the relative motion while attaching or removing the cap from the pen syringe. The current plunger position is compared with a previously measured plunger position to determine whether a drug has been administered, and if so, how much. The cap then displays a screen, typically on a display panel 130, which shows the time and amount of the last administered drug.

[0078] Although the present invention is illustrated in the context of a pen syringe, different embodiments of the present invention may be used to determine the delivered dose and / or remaining amount in any context in which a drug or other liquid is delivered by a syringe-type device.

[0079] It is acknowledged that the above description is intended to serve only as an example, and that many other embodiments are possible within the scope of the invention as defined in the appended claims. [Prior art documents] [Patent Documents]

[0080] [Patent Document 1] U.S. Patent No. 8,743,662 [Patent Document 2] U.S. Patent No. 8817258

Claims

1. (a) A slide cover configured to slide-engage with a cylinder so as to be slidable along the cylinder parallel to its axis from a first position to a second position, wherein the slide cover is mounted as a cap having a central lumen for receiving the end of a pen syringe having a protruding needle, a cradle is slidably mounted within the central lumen, the cradle is configured to receive the end of the pen syringe, the cradle is spring-biased toward a terminal position to engage with the end of the pen syringe when the slide cover is in the first position, and is retractable so as to move with the end of the pen syringe as the slide cover slides to the second position, a cradle spring is provided to bias the cradle toward the terminal position, and the end face of the cradle is mounted as a diffuse reflecting surface; (b) A series of sensors housed in the slide cover so as to move with the slide cover, the series of sensors comprising at least a first sensor and a second sensor, the first sensor being a plunger sensor that generates a signal, the plunger sensor being configured to non-contact sense at least a portion of the plunger as the slide cover slides in engagement with a transparent cylinder such that fluctuations of a first signal represent the plunger passing through a defined position along the slide cover, the plunger sensor being an optical sensor having an optical emitter for emitting radiant energy and an optical receiver for generating a first output representing the amount of the radiant energy received by an optical receiver, the optical sensor being configured such that the first output changes as the optical sensor passes the plunger as the slide cover slides in engagement with a transparent cylinder The set of sensors is configured such that the second sensor is inwardly positioned, and the second sensor is mounted within the closed end of the central lumen and includes an emitter and receiver oriented toward the diffuse reflecting surface of the cradle, the second sensor is a position sensor configured to operate independently of the plunger sensor and to generate a second output representing the current position of the slide cover between the first and second positions, the position sensor is configured to determine the distance between the diffuse reflecting surface and the central lumen based on the intensity of the light emitted from the emitter that reaches the receiver after being reflected from the diffuse reflecting surface when the plunger sensor reaches the plunger, thereby determining the position of the slide cover relative to the cylinder, and the position sensor is associated with the cradle such that the second output of the position sensor represents the current position of the cradle within the central lumen; and (c) A processing system associated with the series of sensors to receive the outputs of the series of sensors, wherein the processing system is configured to identify variations in the output of the plunger sensor as the plunger passes a defined position along the slide cover, and the processing system is further configured to process the outputs to derive the position of the plunger along the cylinder. including, An instrument for use with a liquid delivery system, comprising a transparent cylinder for containing liquid and a plunger movable along the axis of the cylinder for discharging the liquid through a discharge port.

2. The plunger is at least partially opaque, The processing system is configured to determine the corresponding current position of the slide cover, represented by the second output, in response to fluctuations in the first output representing the optical sensor reaching the plunger, thereby determining the position of the plunger along the cylinder. The apparatus according to claim 1.

3. The apparatus according to claim 1, wherein the optical sensor is implemented using a plurality of optical emitters and a plurality of corresponding optical receivers spaced apart around a central lumen, such that at least one pair of optical emitters and optical receivers are not obstructed when used with a pen syringe having an optical obstruction extending parallel to the axis along a transparent cylinder.

4. The aforementioned processing system (a) Processing the first output to detect fluctuations that indicate the optical sensor is passing the leading edge and trailing edge of the plunger; (b) Determine the position of the leading edge of the plunger along the cylinder; and (c) When it is detected that the leading edge of the plunger is approaching a fixed optical obstruction, the position of the trailing edge of the plunger is determined. It is structured in such a way. The apparatus according to claim 1, for use with a pen syringe having a plurality of fixed optical obstructions spaced apart along a transparent cylinder.

5. The series of sensors further includes an auxiliary optical sensor having an optical emitter for emitting obliquely radiated energy through the wall of a transparent cylinder toward the surface of a plunger, and an optical receiver for generating an auxiliary output representing the amount of obliquely radiated energy received by the optical receiver, The apparatus according to claim 1, for use with a pen syringe having an initial plunger position inside an opaque housing.

6. The apparatus according to claim 1, wherein the position sensor is associated with a cradle such that the second output represents the current position of the cradle within the central lumen.

7. The apparatus according to claim 1, wherein the second sensor is configured to generate the second output representing the current position of the slide cover based on the intensity of reflected light.

8. The apparatus according to claim 2, further comprising a microswitch positioned relative to the slide cover to operate when the apparatus is engaged with a liquid delivery system, wherein at least a portion of the apparatus has a low-power sleep state and is selectively activated when the microswitch is operated.

9. The apparatus according to claim 2, further comprising a non-volatile data storage component associated with the processing system, wherein the processing system is configured to store the previous position of the plunger, compare the current position of the plunger with the previous position, determine whether a liquid has been dispensed, and calculate the amount of liquid dispensed.

10. The apparatus according to claim 9, further comprising a display unit integrated with the slide cover, wherein the processing system is further configured to display data relating to the delivered dosage.

11. The apparatus according to claim 2, further comprising a pen syringe configured for delivering a measured dose of liquid drug via a needle, wherein the slide cover is implemented as a cap having a central lumen for receiving the end of the pen syringe, including the needle.

12. (A) A step of preparing a slide cover configured to slide-engage with a cylinder so as to be slidable along the cylinder parallel to its axis from a first position to a second position, the slide cover being provided with a plunger sensor configured to non-contact detect at least a portion of the plunger, wherein the slide cover is mounted as a cap having a central lumen for receiving the end of a pen syringe having a protruding needle, a cradle is slidably mounted in the central lumen, the cradle is configured to receive the end of the pen syringe, the cradle is spring-biased toward a terminal position to engage with the end of the pen syringe when the slide cover is in the first position, and as the slide cover slides to the second position, the cradle engages with the end of the pen syringe The process includes the following: the cradle is retractable to move together, a cradle spring is arranged to bias the cradle toward the terminal position, the end face of the cradle is mounted as a diffuse reflecting surface, the plunger sensor is an optical sensor having an optical emitter for emitting radiant energy and an optical receiver for generating a first output representing the amount of the radiant energy received by the optical receiver, the optical sensor is positioned inward such that the first output changes as the optical sensor passes the plunger as the slide cover slides in engagement with a transparent cylinder, the slide cover includes a second sensor mounted within the closed end of the central lumen and oriented toward the diffuse reflecting surface of the cradle; (B) A step of sliding the slide cover along the cylinder and detecting fluctuations in the first output corresponding to the plunger sensor that reaches the plunger; and (C) A position sensor which operates independently of the plunger sensor and is positioned to generate a second output representing the current position of the slide cover between the first position and the second position, and is configured to determine the distance between the diffuse reflecting surface and the central lumen based on the intensity of the light emitted from the emitter that reaches the receiver after being reflected from the diffuse reflecting surface when the plunger sensor reaches the plunger, thereby determining the position of the slide cover relative to the cylinder, wherein the second output of the position sensor is associated with the cradle such that it represents the current position of the cradle in the central lumen, and the position of the plunger is determined by utilizing the second sensor. A method of using the instrument described in claim 1 for measuring the position of a plunger in the transparent cylinder of the instrument for calculating a drug delivery dose, including,

13. (A) A step of preparing a slide cover configured to slide-engage with a cylinder so as to be slidable along the cylinder parallel to its axis from a first position to a second position, the slide cover being provided with a plunger sensor configured to non-contact detect at least a portion of the plunger, wherein the slide cover is mounted as a cap having a central lumen for receiving the end of a pen syringe having a protruding needle, a cradle is slidably mounted in the central lumen, the cradle is configured to receive the end of the pen syringe, the cradle is spring-biased toward a terminal position to engage with the end of the pen syringe when the slide cover is in the first position, and moves together with the end of the pen syringe as the slide cover slides to the second position The process includes a first optical sensor having a cradle spring that is retractable to move, a cradle spring that is arranged to bias the cradle toward the terminal position, the end face of the cradle being mounted as a diffuse reflecting surface, the plunger sensor being a first optical sensor having an optical emitter for emitting radiant energy and an optical receiver for generating a first output representing the amount of the radiant energy received by the optical receiver, the first optical sensor being positioned inward such that the first output changes as the first optical sensor passes the plunger as the slide cover slides in engagement with a transparent cylinder, the slide cover being mounted within the closed end of the central lumen and including a second sensor having an emitter and receiver oriented toward the diffuse reflecting surface of the cradle; (B) A step of sliding the slide cover along the cylinder and detecting fluctuations in the first output corresponding to the plunger sensor that reaches the plunger; and (C) A position sensor which operates independently of the plunger sensor and is positioned to generate a second output representing the current position of the slide cover between the first position and the second position, and is configured to determine the distance between the diffuse reflecting surface and the central lumen based on the intensity of the light emitted from the emitter that reaches the receiver after being reflected from the diffuse reflecting surface when the plunger sensor reaches the plunger, thereby determining the position of the slide cover relative to the cylinder, wherein the second output of the position sensor is associated with the cradle such that it represents the current position of the cradle in the central lumen, and the position of the plunger is determined by utilizing the second sensor. A method of using the instrument described in claim 1 for measuring the position of a plunger in the transparent cylinder of the instrument for calculating a drug delivery dose, including, The method, wherein the plunger sensor is a first optical sensor having an optical emitter for emitting radiant energy and an optical receiver for generating a first output representing the amount of said radiant energy received by the optical receiver.

14. The slide cover includes a third optical sensor comprising an optical emitter for emitting radiant energy and an optical receiver for receiving the radiant energy, wherein the third optical sensor is positioned axially apart from the first optical sensor. The method is (a) a step of detecting a variation in the output of the third optical sensor corresponding to the third optical sensor that reaches the plunger; and (b) A step of deriving the speed of the sliding motion used to determine the position of the plunger from the time difference between the features in the outputs from the first and third optical sensors. The method according to claim 13, further comprising:

Images