LINEAR ACTIVATED MEDICATION DOSING PUMP SYSTEM

Description

BACKGROUND

[0001] Many conventional drug delivery systems, including, for example, wearable drug delivery devices, include a drug container, often referred to as a reservoir, that stores a liquid drug. A liquid drug stored in the reservoir may be delivered to the user by expelling the drug from the reservoir using a driven plunger, for example, a leadscrew driven plunger, see e.g. US 2016 / 0213851 A1, US 2011 / 0073620 A1, US 2015 / 0051487 A1 and US 2003 / 0055380 A1. In present known embodiments, the plunger is typically disposed directly within the reservoir such that the reservoir and the drive comprise a single unit. As result, the reservoir requires a large cross-sectional area, such as to be able to hold the device's entire supply of the drug. The large cross-sectional area has the disadvantage of increasing the minimum dosing increment for a given axial displacement of the plunger. In addition, the larger cross-sectional area requires a larger diameter plunger which leads to more drag and friction on the interior sealing surfaces of the reservoir, thereby increasing the force required to achieve a given pressure and, as a result, requiring a larger, more powerful motor to drive the plunger. A need therefore exists for a configuration which achieves the same effective delivery of the drug, but with a container having a smaller cross-sectional area to overcome the identified deficiencies.BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is a cross-sectional view of the pump chamber of a first embodiment of the invention in which dual plungers are used. FIG. 2 is a schematic view of the pump system of the present invention in a first state in which the pump chamber is empty and the plungers are in a touching, face-to-face configuration. FIG. 3 is a schematic view of the pump system of the present invention in a second state in which the plungers have moved away from each other to draw a liquid from the reservoir into the pump chamber. FIG. 4 is a schematic view of the pump system of the present invention in a third state in which the plungers are moving toward each other to force the liquid from the pump chamber to the patient interface. FIG. 5 is a schematic view of the pump system of the present invention in a fourth state in which all the liquid has been forced from the pump chamber toward the patient interface. FIGS. 6(A-C) show three variations of the pump system of the present invention in which sensors are used to determine the volume of the liquid which has been drawn into the pump chamber. FIG. 7 is a flowchart showing the process by which one or multiple units of the liquid are moved from the reservoir to the patient interface. FIG. 8 is a cross-sectional view of the pump chamber of an example in which a single plunger is used. FIG. 9 is a schematic view of the pump system of Fig. 8 in a first state in which the pump chamber is empty and the plunger is touching the end wall of the pump chamber. FIG. 10 is a schematic view of the pump system of Fig. 8 in a second state in which the plunger has moved away from the end wall to draw a liquid from the reservoir into the pump chamber. FIG. 11 is a schematic view of the pump system of Fig. 8 in a third state in which the plunger is moving toward the end wall to force the liquid from the pump chamber to the patient interface. FIG. 12 is a schematic view of the pump system of Fig. 8 in a fourth state in which all the liquid has been forced from the pump chamber toward the patient interface. FIG. 13 is a flowchart showing the process of the example of Fig. 8 in which one or multiple units of the liquid are moved from the reservoir to the patient interface. DETAILED DESCRIPTION

[0003] The present invention is directed to a pump system as defined in claim 1.

[0004] According to the present invention, the pump chamber has disposed therein a pair of plungers driven by a leadscrew having both left-hand and right-hand threads such that, when the leadscrew rotates in one direction, the plungers move toward each other and, when the leadscrew is rotated in the opposite direction, the plungers move away from each other.

[0005] The first conduit connecting the pump chamber to the reservoir connects to the pump chamber between the plungers, preferably in the middle of the pump chamber. Thereby, the movement of the plungers away from each other creates a negative pressure in the pump chamber which draws the liquid from the reservoir through the first conduit and into the pump chamber. The leadscrew is thus rotated in a direction such as to move the plungers away from each other to draw the liquid into the pump chamber. The liquid is prevented from returning to the reservoir by the one-way valve disposed in the conduit between the reservoir and the pump chamber.

[0006] Once the pump chamber is filled with an appropriate quantity of the liquid, the leadscrew is rotated in a second, opposite direction, thereby driving the plungers toward each other. A second conduit connected to the pump chamber between the plungers connects the pump chamber to a patient interface, typically a needle. Thus, motion of the plungers toward each other causes a movement of the liquid through the second conduit to the patient. The second conduit is also fitted with a one-way valve such that the suction created by the motion of the plungers away from each other to draw the liquid from the reservoir into the pump chamber does not also draw fluids from the patient through the patient interface and into the pump chamber.

[0007] In one embodiment of the invention, the rotation of the leadscrew can be driven by a drive coupled to the leadscrew either directly or via gearing.

[0008] The improved liquid delivery system disclosed herein thus addresses the problems identified in the Background section. By separating the reservoir from the pump chamber, the pump chamber can be configured with a cross-sectional area of any size, preferably small enough to overcome the difficulties associated with the larger diameter cross-sectional areas of conventional, prior art devices.

[0009] FIG. 1 is a cross-sectional view of a first embodiment of the pump chamber 104 of the present invention. Pump chamber 104 consists of an open-ended container comprising sidewall 103 and endcap 105. Sidewall 103 may comprise a tube-like structure having a cross-sectional shape. In some instances, sidewall 103 and endcap 105 may be formed as an integral unit, however, in other instances, sidewall 103 and endcap 105 may be formed separately and joined together. Sidewall 103 and endcap 105 may be composed of, for example, glass, polypropylene or any other bio- or drug-compatible material. In certain embodiments, endcap 105 may be absent, with pump chamber 104 being open at both ends.

[0010] Sidewall 103 has formed therein inlet port 113 and outlet port 117. Inlet port 113 connects, via a conduit, to a reservoir which may hold a quantity of a liquid. Outlet port 117 connects to a patient interface for delivery of the liquid to a patient. Preferably, inlet port 113 and outlet port 117 will be located midway between plungers 106a, 106b, such that when plungers 106a, 106b are in a touching, face-to-face configuration, access to both inlet port 113 and outlet port 117 are fully or partially blocked. This serves as a safety feature to prevent free-flow of the liquid from the reservoir to the patient interface in the event of valve failure. In preferred embodiments of the invention, inlet port 113 and outlet port 117 are located opposite each other along sidewall 103; however, in other embodiments, inlet port 113 and outlet port 117 may be positioned at any convenient location along sidewall 103.

[0011] Disposed within pump chamber 104 are plungers 106a, 106b. In some embodiments, plungers 106a, 106b may be composed of, for example, a butyl rubber or silicon rubber material or any other commonly known drug-compatible material. In other embodiments, plungers 106a, 106b may be composed of a polycarbonate derivative or cyclic olefin polymer (COP), in which case, plungers 106a, 106b may be surrounded by one or more O-rings composed of butyl rubber or silicon rubber. In some embodiments, plungers 106a, 106b are configured with flat facing surfaces. In other embodiments, other shapes may be used but preferably the plungers 106a, 106b will have mating shapes, for example, one concave and one convex, such that when plungers 106a, 106b are together, no volume remains therebetween. The faces of plungers 106a, 106b may be configured with channels to direct the movement of the liquid in a desired direction.

[0012] Plungers 106a, 106b are connected by leadscrew 108. In certain embodiments, leadscrew 108 may be composed of stainless steel, polypropylene, or any other well-known bio- or drug-compatible material. In preferred embodiments, leadscrew 108 comprises both left-handed threading 101a and right-handed threading 101b as an interface with plungers 106a, 106b, such that rotation of leadscrew 108 in a first direction will cause plungers 106a, 106b to move toward each other along the longitudinal axis of pump chamber 104 until touching, and such that rotation of leadscrew 108 in a second, opposite direction will cause plungers 106a, 106b to move away from each other along the longitudinal axis of pump chamber 104.

[0013] FIG. 2 is a schematic representation of the first embodiment of the invention in which a linear-actuated drug dosing system 100 comprises two plungers 106a,106b disposed in pump chamber 104. Reservoir 102 may contain a quantity of a liquid 103, for example, a drug in liquid form. In some embodiments of the invention, reservoir 102 may be rigid, while, in other embodiments, the reservoir 102 may be flexible and collapsible to eliminate the need for a vent in the reservoir to prevent a vacuum performing therein as liquid 103 is drawn from reservoir 102 into pump chamber 104. In some embodiments, reservoir 102 may be composed of high-density polyethylene or, in other embodiments, ACLAR ®< .

[0014] Reservoir 102 is fluidly coupled to pump chamber 104 through inlet port 113 via inlet conduit 112. Likewise, pump chamber 104 is fluidly coupled to a patient interface through outlet port 117 via outlet conduit 116. Inlet conduit 112 and outlet conduit 116 may be composed of, for example, stainless steel or Teflon and may be, for example, tubing of the type of which hypodermic needles are constructed. One-way valve 114 prevents liquid 103, which has entered the pump chamber 104, from returning to reservoir 102. The patient interface may be, for example, a needle, a needle conduit or tubing that can be used as a fluid path to deliver the liquid 103 to a patient. One-way valve 118 prevents fluids from the patient from being drawn into pump chamber 104 as liquid 103 is being drawn into pump chamber 104 from reservoir 102.

[0015] Plungers 106a, 106b are disposed within the pump chamber 104 and may be sealed against the inner surface of sidewall 103 of pump chamber 104. It should be noted that the cross-sectional shape of pump chamber 104 may be any shape, including circular; however, in preferred embodiments, the cross-sectional shape of pump chamber 104 may be any one of a number of non-circular shapes, preferred examples of which are shown as reference number 124 in FIG. 2. The non-circular, cross-sectional shape of pump chamber 104 is desirable to prevent plungers 106a, 106b from rotating within pump chamber 104 when leadscrew 108 is rotated. Non-rotation of plungers 106a, 106b is necessary to enable the movement of the plungers 106a, 106b along the longitudinal axis of pump chamber 104 driven by the rotation of leadscrew 108 as it rotates in either direction.

[0016] Leadscrew 108 may be driven by any one of a number of known methods. In one embodiment, the drive source may be motor 120, which may be coupled to leadscrew 108 via gearing 122. Leadscrew 108 is, in this embodiment of the invention, configured with both left-hand and right-hand threads, as shown in the figure. Thus, rotation of leadscrew 108 in a first direction (e.g. clockwise) will cause plungers 106a, 106b to move toward each other, while rotation of leadscrew 108 in an opposite direction (e.g. counter-clockwise) will cause plungers 106a, 106b to move away from each other.

[0017] Motor 120 may be coupled to leadscrew 108 via gearing 122. In some embodiments of the invention, gearing 122 may be a planetary gear system, but any configuration of coupling between the motor 120 and leadscrew 108 may be used, including a direct connection. Motor 120 may be a continuous motion motor or stepper motor and is preferably controlled by a software-driven controller.

[0018] In alternate embodiments of the invention, a nitinol wire drive (not shown) may be used to drive gearing 122 in lieu of motor 120 and may be coupled to leadscrew 108 via gearing 122.

[0019] FIG. 2 shows the device in a static state, with plungers 106a, 106b shown together. This is a likely state of the device just subsequent to the delivery of one or more units of liquid 103 and in ready state for filling of the pump chamber 104 with additional liquid 103 from reservoir 102.

[0020] FIG. 3 is a schematic diagram showing the process of drawing liquid 103 from reservoir 102 into pump chamber 104. Motor 120 may be activated in a direction such as to cause plungers 106a, 106b to move away from each other as shown by the arrows in pump chamber 104. Movement of plungers 106a, 106b away from each other causes a negative pressure to form in the volume 104a between the plungers 106a, 106b, which serves to draw liquid 103 through conduit 112, into pump chamber 104 and, more specifically, into volume 104a between plungers 106a, 106b. One-way valve 118 prevents fluids from the patient from being drawn through conduit 116 and into volume 104a of pump chamber 104 as plungers 106a, 106b create the negative pressure within volume 104a as they move away from each other.

[0021] Pump chamber 104 may be configured with a vent 107 on end wall 105 of pump chamber 104 to allow air between plunger 106b and end wall 105 of pump chamber 104 to escape as plunger 106b is moved toward end wall 105, and to allow air to enter the space between end wall 105 and plunger 106b when plunger 106b is moved in the opposite direction, away from end wall 105.

[0022] FIG. 4 is a schematic diagram illustrating the process of pumping liquid 103 from volume 104a through conduit 116 to the patient interface. Motor 120 may be rotated in a direction opposite the direction of rotation used to draw liquid 103 into volume 104a such as to move plungers 106a, 106b toward each other as shown by the arrows in FIG. 4, thereby creating a positive pressure within volume 104a. The movement of plungers 106a, 106b toward each other reduces the size of volume 104a and forces liquid 103 into the conduit 116 and out to the patient through the patient interface. One-way valve 114 prevents liquid 103 from returning to reservoir 102 as plungers 106a, 106b move toward each other, ensuring that all of liquid 103 within volume 104a is forced into conduit 116.

[0023] Once plungers 106a, 106b have reached a position where they are touching one another, as shown in FIG. 5, all, or most of liquid 103 within volume 104a will have been forced into conduit 116 to the patient interface. Plungers 106a, 106b do not necessarily need to touch each other to complete a cycle of liquid delivery. However, to reduce the amount of residual liquid within the system, and hence reduce the amount of wasted liquid at the end of usage of system 100, plungers 106a, 106b preferably come into contact at the end of each cycle of liquid delivery, or alternatively, at a final cycle of drug delivery when all or nearly all of liquid drug has been dispensed from reservoir 102. Having plungers 106a, 106b come into contact only at a final cycle of drug delivery will reduce the impact that plungers 106a, 106b have on constituents of the liquid (e.g., molecules of insulin) during each cycle of liquid delivery, thereby prolonging the life or effectiveness of the liquid (e.g., protein molecules within the liquid).

[0024] It should be noted that conduits 112, 116 interface with pump chamber 104 in the volume 104a between plunger 106a, 106b. In preferred embodiments of the invention, conduits 112 and 116 will connect to volume 104a midway between the largest distance that plunger 106a, 106b can travel from each other, or, in other words, at the point where plungers 106a, 106b meet when they are touching each other or at the end of a cycle, such that when plungers 106a, 106b are in the position shown in FIG. 2, both inlet port 113 and outlet port 117 are blocked.

[0025] It should be noted that multiple units of liquid 103 may be drawn into volume 104a at a single time and may be dispensed in separate units to the patient. It is not necessary that volume 104a be emptied each time that a unit of liquid 103 is delivered to the patient.

[0026] It should be further noted that the quantity of liquid 103 drawn into volume 104a is dependent upon the distance between plungers 106a, 106b at their furthest point of travel away from each other. Thus, the quantity of liquid 103 drawn into volume 104a can be controlled by varying the distance between plungers 106a, 106b. Larger distances between plungers 106a, 106b will result in a larger volume 104a and, thus, a larger quantity of liquid 103, while smaller distances will result a smaller volume 104a and a smaller quantity of liquid 103 being drawn into volume 104a.

[0027] One advantage of the dual-plunger design is that the system is balanced axially such that it does not induce a thrust onto the bearing support (i.e. the portion where the leadscrew 108 interfaces with end wall 105 of pump chamber 104. This translates into less frictional losses in the system. One further advantage is that the design prevents the free flow of liquid 103 directly from reservoir 102 to the patient when plungers 106a, 106 block inlet port 113 and outlet port 117. This can be a safety mechanism in the case of an over-pressure situation or if squeezing of the device forces liquid 103 out of reservoir 102.

[0028] Various other methods are possible in this embodiment of the invention for measuring the size of the volume 104a between plungers 106a, 106b, and thus the quantity of liquid 103 which is drawn into volume 104a. In one embodiment of the invention, the size of volume 104a may be determined algorithmically by calculation based on the number of turns of leadscrew 108 and the known distance that plungers 106a, 106b travel based on the determined number of turns. Other embodiments of determining the size of volume 104a utilizing sensors will now be discussed.

[0029] FIG. 6A shows one embodiment using a pressure gauge to calculate a volume change in the pump chamber 104 using the ideal gas law equation PV = nRT. A gas pressure gauge 601 may be configured to interface with pump chamber 104 through vent 107 in end wall 105. Using air pressure in area 602 as measured by pressure gauge 601, the change in the position of the plungers, and thus changes in the quantity of liquid 103 in volume 104a, can be derived from a measurement of the change in air pressure within area 602. The actual quantity of liquid 103 drawn into volume 104a may be further dependent on other factors, for example, the size of conduit 112.

[0030] FIG. 6B shows a second embodiment utilizing a three-segment custom linear encoder using simple analog techniques. In this embodiment, change in the length (length = l 1 + l 2 + l 3 ) of conductive bar or wire 604 can alter its resistance / current and can be calibrated to the position of plunger 106b. The position of plunger 106a can thereafter be inferred from the position of plunger 106b.

[0031] FIG. 6C shows yet another embodiment utilizing an ultrasonic sensor. An ultrasonic source 606 may direct a beam of ultrasonic sound through vent 107. The speed of sound through various media (i.e., air → plastic → aqueous spolution → plastic → air) is known and, as such, based on timing, with the known distance between the ultrasonic source 606 and an ultrasonic detector 608, a quantity of the liquid 103 can be inferred.

[0032] FIG. 7 shows a flowchart showing process 700 for delivery of liquid 103 from the reservoir 102 to the patient interface. The system 100 begins from a start position 702. The start position is preferably the position wherein the plungers 106a, 106b are in a touching, face-to-face configuration such that volume 104a is reduced to virtually zero.

[0033] At block 704, the plungers are moved apart by turning of leadscrew 108 and liquid 103 is drawn from reservoir 102 into the volume 104a between plungers 106a and 106b. At block 706, it is determined whether the desired quantity of liquid 103 has been drawn into volume 104a of pump chamber 104 and, if not, control is returned to block 704, where the plungers 106a, 106b continue to move away from each other until the desired quantity of liquid 103 is present in volume 104a. The determination of whether the desired quantity of liquid 103 has been drawn into volume 104a may be made algorithmically by calculating, for example, the number of turns of leadscrew 108 and its relationship to the size of volume 104a or with the assistance of one of the sensor arrangements shown in FIGS. 6(A-C), or through the use of any other sensor arrangement.

[0034] At block 716 it is determined if it is time for the delivery of the additional units of liquid 103 to the patient. If so, control is sent to block 708 and if not, system 100 loops at decision point 716 until triggered. The delivery of additional units of liquid 103 could be triggered automatically, for example, by a periodic timer, by manual initiation of the delivery by the patient, or by any other means, such as through an analysis of input received from sensors regarding the current condition of the patient.

[0035] At block 708, the movement of plungers 106a, 106b toward each other is initiated by rotation of leadscrew 108 in an opposite direction, such as to force a quantity of liquid 103 from volume 104a and into conduit 116, and from there to the patient interface. At 710 it is determined if the quantity so far delivered to the patient interface comprises the desired quantity and, if not, control returns to 708, where the plungers continue to move toward each other to push a further quantity of liquid 103 to the patient interface. At 710, if the desired quantity of liquid 103 has been delivered to the patient interface, the process is complete at 712.

[0036] At decision point 714, it is determined if the volume 104a is empty, that is, the last quantity of liquid 103 has been delivered to the patient. If volume 104a is empty, control returns to start position 702 and the process repeats with the loading of an additional quantity of liquid 103 from reservoir 102 to volume 104a. If volume 104a is not empty, control returns to decision point 716, where the process loops until the delivery of the next unit of liquid 103 is triggered.

[0037] Note that the end position of the plungers when the pump chamber is empty at block 712 is the same as start position at 702, wherein the plungers are in a touching, face-to-face configuration and are thereby ready to draw the next quantity of liquid 103 into volume 104a.

[0038] The second embodiment of the invention has components similar to the first embodiment in configuration and composition and operates in a similar manner. As such, the description of the second embodiment has been condensed for brevity and like reference numerals have been used for like components.

[0039] FIG. 8 is a cross-sectional view of an example of a pump chamber 104 in which only a single plunger 106 is used. Rotation of leadscrew 108 in a first direction moves plunger 106 toward end wall 105, while movement of the leadscrew 108 in a second, opposite direction moves plunger 106 away from end wall 105. Inlet port 113 and outlet port 117 are preferably located adjacent end wall 105, such that movement of the plunger 106 toward the end wall forces any liquid within the pump chamber 104 into the output conduit 117. Otherwise, the components and materials of the second embodiment of the pump chamber are identical to that of the first embodiment shown in FIG. 1.

[0040] FIG. 9 is a schematic representation of the example of Fig. 8 in which a linear-actuated drug dosing system 100 comprises a single plunger 106 disposed in pump chamber 104.

[0041] Reservoir 102 is fluidly coupled to pump chamber 104 through inlet port 113 via inlet conduit 112. Likewise, pump chamber 104 is fluidly coupled to a patient interface through outlet port 117 via outlet conduit 116. One-way valve 114 prevents liquid 103 which has entered the pump chamber 104, from returning to reservoir 102. One-way valve 118 prevents fluids from the patient from being drawn into pump chamber 104 as liquid 103 as being drawn into pump chamber 104 from reservoir 102.

[0042] Plunger 106 is disposed within the pump chamber 104 and may be sealed against the inner surface sidewall 103 of pump chamber 104. Leadscrew 108 may be driven by any one of a number of known methods. In one embodiment, the drive source may be motor 120, which is coupled to leadscrew 108 via gearing 122. Leadscrew 108 is, in this embodiment of the invention, configured with a single threading, as shown in the figure. Thus, rotation of leadscrew 108 in a first direction (e.g. clockwise) will cause plunger 106 to move toward end wall 105, while rotation of leadscrew 108 in an opposite direction (e.g. counter-clockwise) will cause plunger 106 to move away from end wall 105.

[0043] Motor 120 may be coupled to leadscrew 108 via gearing 122 to drive leadscrew 108 in either rotational direction.

[0044] FIG. 9 shows the device in a static state, with plunger 106 shown adjacent end wall 105 and blocking inlet port 113 and outlet port 117.

[0045] FIG. 10 is a schematic diagram showing the process of drawing liquid 103 from reservoir 102 into pump chamber 104. Motor 120 may be activated in a direction such as to cause plunger 106 to move away from end wall 105 as shown by the arrow in pump chamber 104. Movement of plunger 106 away from end wall 105 causes a negative pressure to form in the volume 104a between the plunger and end wall 105, which serves to draw liquid 103 through conduit 112, into pump chamber 104 and, more specifically, into volume 104a between plunger 106 and end wall 105. One-way valve 118 prevents fluids from the patient from being drawn through conduit 116 and into volume 104a as plunger 106 creates the negative pressure within volume 104a as it moves away from end wall 105.

[0046] FIG. 11 is a schematic diagram illustrating the process of pumping liquid 103 from volume 104a through conduit 116 to the patient interface. Motor 120 may be rotated in a direction opposite the direction of rotation used to draw liquid 103 into volume 104a such as to move plunger 106 toward end wall 105 as shown by the arrow in FIG. 11, thereby creating a positive pressure within volume 104a. The movement of plunger 106 toward end wall 105 reduces the size of volume 104a and forces liquid 103 into the conduit 116 and out to the patient through the patient interface. One-way valve 114 prevents liquid 103 from returning to reservoir 102 as plunger 106 moves toward end wall 105, ensuring that all of liquid 103 within volume 104a is forced into conduit 116.

[0047] Once plunger 106 has reached a position where it is touching end wall 105, as shown in FIG. 12, all, or most of liquid 103 within volume 104a will have been forced into conduit 116 to the patient interface. Plunger 106 does not necessarily need to touch end wall 105 to complete a cycle of liquid delivery. However, to reduce the amount of residual liquid within the system, and hence reduce the amount of wasted liquid at the end of usage of system 100, plunger 106 preferably comes into contact with end wall 105 at the end of each cycle of liquid delivery, or alternatively, at a final cycle of drug delivery when all or nearly all of liquid drug has been dispensed from reservoir 102. Having plunger 106 come into contact with end wall 105 only at a final cycle of drug delivery will reduce the impact that plunger 106 has on constituents of the liquid (e.g., molecules of insulin) during each cycle of liquid delivery, thereby prolonging the life or effectiveness of the liquid (e.g., protein molecules within the liquid).

[0048] It should be noted that conduits 112, 116 must interface with pump chamber 104 in the volume 104a between plunger 106 and end wall 105. In preferred embodiments of the invention, conduits 112 and 116 will connect to volume 104a directly adjacent end wall 105, such that when plunger 106 is in the position shown in FIG. 12, both inlet port 113 and outlet port 117 are blocked.

[0049] FIG. 13 shows a flowchart showing process 1300 for delivery of liquid 103 from the reservoir 102 to the patient interface. The system 100 begins from a start position 1302. The start position is preferably the position wherein plunger 106 is in contact with end wall 105 such that volume 104a is reduced to virtually zero.

[0050] At block 1304, the plunger 106 is moved away from end wall 105 by turning of leadscrew 108 and liquid 103 is drawn from reservoir 102 into the volume 104a between plunger 106 and end wall 105. At block 1306, it is determined whether the desired quantity of liquid 103 has been drawn into volume 104a and, if not, control is returned to block 1304, where the plunger 106 continues to move away from end wall 105 until the desired quantity of liquid 103 is present in volume 104a.

[0051] At block 1316 it is determined if it is time for the delivery of the additional units of liquid 103 to the patient. If so, control is sent to block 1308 and if not, system 100 loops at decision point 1316 until triggered.

[0052] At block 1308, the movement of plunger 106 toward end wall 106 is initiated by rotation of leadscrew 108 in an opposite direction, such as to force a quantity of liquid 103 from volume 104a and into conduit 116, and from there to the patient interface. At 1310 it is determined if the quantity so far delivered to the patient interface comprises the desired quantity and, if not, control returns to 1308, where the plunger 106 continues to move toward end wall 105 to push a further quantity of liquid 103 to the patient interface. At 1310, if the desired quantity of liquid 103 has been delivered to the patient interface, the process is complete at 1312.

[0053] At decision point 1314, it is determined if the volume 104a is empty and, if so, control returns to start position 1302 and the process repeats with the loading of an additional quantity of liquid 103 from reservoir 102 to volume 104a. If volume 104a is not empty, control returns to decision point 1316, where the process loops until the delivery the next unit of liquid 103 is triggered.

[0054] The embodiments described herein provide numerous benefits over existing prior art systems. As will be appreciated by a person of ordinary skill in the art, and, in particular with wearable devices, the comfort of the patient can be enhanced by reducing the size of the device. The above described embodiments accomplish this by allowing for a pump mechanism having a smaller cross-sectional area and, in addition, utilizing non-circular cross-sectional shapes that could, for instance, be provided as a flattened rectangular shape, thereby reducing the profile of the device. In addition, the smaller cross-sectional area of the pump mechanism, in addition to the fact that only a portion of the quantity of liquid in the reservoir is drawn into the pump chamber at any one time, allows for the use of a smaller, less powerful motor to drive the plungers.

Claims

1. A pump system comprising: a pump chamber (104) of which at least one end is open-ended, a leadscrew (108) extending along a longitudinal axis of the pump chamber (104), a first plunger (106a) and a second plunger (106b), an inlet port (113) and an outlet port (117) defined in a sidewall of the pump chamber, wherein the inlet port and outlet port are located in an area of the sidewall between the first and second plungers, a reservoir (102), in fluid communication with the pump chamber via an inlet conduit (112) which is coupled to the inlet port, an inlet one-way valve (114), disposed between the reservoir and the pump chamber, the one-way valve allowing fluid to flow from the reservoir into the pump chamber and preventing fluid from flowing from the pump chamber to the reservoir, a patient interface, in fluid communication with the pump chamber via an outlet conduit which is coupled to the outlet port, an outlet one-way valve (118), disposed between the pump chamber and the patient interface, the one-way valve allowing fluid to flow from the pump chamber to the patient interface and preventing fluid from flowing from the patient interface to the pump chamber, wherein the leadscrew has left-hand and right-hand threads (101a, 101b) defined thereon, wherein the first plunger (106a) is coupled to the leadscrew via the left-hand threads (101a), and wherein the second plunger (106b) is coupled to the leadscrew via the right-hand threads (101b), wherein rotation of the leadscrew (108) in a first direction causes the first and second plungers (106a, 106b) to move toward each other, and wherein rotation of the leadscrew (108) in a second, opposite direction causes the first and second plungers (106a, 106b) to move away from each other, and in that a drive is coupled to the leadscrew for rotating the leadscrew in the first and second directions.

2. The pump system of claim 1, wherein the pump chamber(104) has a non-circular cross-sectional shape.

3. The pump system of claim 1 or 2 wherein the reservoir is collapsible.

4. The pump system of one of the preceding claims, wherein movement of the plungers (106a, 106b) away from each other causes a negative pressure in a space between the plungers (106a, 106b) within the pump chamber, the negative pressure drawing a liquid disposed in the reservoir into the pump chamber through the inlet conduit.

5. The pump system of claim 4, wherein movement of the plungers (106a, 106b) toward each other causes a positive pressure in the space between the plungers (106a, 106b) within the pump chamber (104), the positive pressure forcing the liquid in the pump chamber (104) into the outlet conduit.

6. The pump system of claim 5, wherein the volume of the space between the first and second plungers (106a, 106b) can be algorithmically determined based on the number of turns of the leadscrew.

7. The pump system of claim 5, wherein the volume of the space between the first and second plungers (106a, 106b) can be algorithmically determined based on input from one or more sensors.

8. The pump system of claim 5, wherein one or more units of the liquid may be drawn into the reservoir as the plungers (106a, 106b) move away from each other.

9. The pump system of claim 5, wherein a single unit of the liquid may be sent to the patient interface by movement of the first and second plungers (106a, 106b) to reduce the volume of the space between the first and second plungers by a predetermined amount corresponding to the single unit of the liquid.

10. The pump system of one of the preceding claims, wherein the drive comprises a motor coupled to the leadscrew via one or more gears (122).

11. The pump system of one of claims 1 to 9, wherein the drive comprises a nitinol wire drive coupled to the leadscrew via a gearing (122).