Medical device with unidirectionally valved reciprocating piston pump and discrete dose duplication and timing for reciprocating piston pump

Abstract

A medical device including a reservoir, a patient cannula, and a fluid path connecting the reservoir and the patient cannula. The device also includes a first one-way valve, a reciprocating piston mechanism, and a second one-way valve disposed sequentially on the fluid path between the reservoir and the patient cannula.

Description

MEDICAL DEVICE WITH UNIDIRECTIONALLY VALVED RECIPROCATING PISTON PUMP AND DISCRETE DOSE DUPLICATION AND TIMING FOR RECIPROCATING PISTON PUMPCross-Reference to Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application No.63 / 611,924 filed December 19, 2023, which is hereby incorporated by reference in its entirety.Field of the Invention

[0002] The present invention relates to medical devices, and more particularly, a medical device with a reciprocating piston mechanism, and a method of controlling delivery of a total dose of medicament from a medical device with a reciprocating piston mechanism.Background of the Invention

[0003] Typical drug delivery patch pump designs are challenged by the need to achieve small size, low power consumption, accurate delivery, high reliability, and low manufacturing costs. In addition, it is desirable to provide safety features, for example, to prevent runaway dosing.Summary of Embodiments of the Invention

[0004] Accordingly, it is an aspect of the present invention to provide a medical device with increased safety features.

[0005] The foregoing and / or other aspects of the present invention are achieved by providing a medical device. The medical device includes a reservoir, a patient cannula, and a fluid path connecting the reservoir and the patient cannula. The device also includes a first one-way valve, a reciprocating piston mechanism, and a second one-way valve disposed sequentially on the fluid path between the reservoir and the patient cannula.

[0006] The foregoing and / or other aspects of the present invention are also achieved by providing a method of operating a medical device having a reservoir housing a medicament, apatient cannula, a fluid path connecting the reservoir and the patient cannula, and a first one-way valve, a reciprocating piston mechanism, and a second one-way valve disposed sequentially on the fluid path between the reservoir and the patient cannula. The method also includes operating the reciprocating piston mechanism to draw back, thereby closing the second one-way valve via back pressure, and drawing a volume of medicament from the reservoir, through the first oneway valve and into a discrete volume piston chamber. The method also includes operating the reciprocating piston mechanism to push forward, thereby closing the first one-way valve and expelling the volume of medicament through the second one-way valve toward the patient cannula. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0007] The foregoing and / or other aspects of the present invention are also achieved by providing a method of controlling delivery of a total dose of medicament over a time period in a medical device with a controller and a reciprocating pump. The method of controlling delivery also includes dividing the total dose over the time period into equally spaced discrete doses with equal intervals between the discrete doses. The delivery7also includes at a first dosing time, controlling the medical device with the controller to deliver at least two of the doses sequentially without an interval between, and appropriately increasing the interval before a next dosing time. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0008] Additional and / or other aspects and advantages of the present invention will be set forth in the description that follows, or will be apparent from the description, or may be learned by practice of the invention.Brief Description of the Drawings

[0009] The above and / or other aspects and advantages of embodiments of the invention will be more readily appreciated from the following detailed description, taken in conjunction with the accompanying drawings, of which:Fig. 1 is a perspective view of a wearable fluid delivery’ device constructed in accordance with an embodiment of the present invention;Fig. 2 is a block diagram of example components of a fluid delivery’ device in accordance with an embodiment of the present invention;Fig. 3 is a perspective view of wearable fluid delivery device in accordance with another embodiment of the present invention;Fig. 4 is a block diagram of the device of Fig. 3;Fig. 5 is a perspective view of a one-way valve of the device of Fig. 3;Fig. 6 is a cross-sectional view of a manifold of the device of Fig. 3;Figs. 7 and 8 are respective top and perspective views of another embodiment of the present invention;Figs. 9 and 10 are respective top and bottom perspective views of a reciprocating piston mechanism in accordance with another embodiment of the present invention;Figs. 11 and 12 are respective cross-sectional and partial cross-sectional views of the reciprocating piston mechanism of Figs. 9 and 10;Fig. 13 is flow chart of a method in accordance with an embodiment of the present invention;Fig. 14 is a flow chart of another method in accordance with an embodiment of the present invention; andFig. 15 is a visual representation of dosing schemas in accordance with an embodiment of the present invention.Detailed Description of Embodiments of the Present Invention

[0010] Reference will now be made in detail to embodiments of the present invention, which are illustrated in the accompanying drawings, wherein like reference numerals refer to likeelements throughout. The embodiments described herein exemplify, but do not limit, the present invention by referring to the drawings.

[0011] The embodiments are not intended to be mutually exclusive so that the features of one embodiment can be combined with other embodiments as long as they do not contradict each other.

[0012] It will be understood by one skilled in the art that this disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The embodiments herein are capable of other embodiments, and capable of being practiced or carried out in various ways. Phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Tire use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[0013] Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled”" and variations thereof are not restricted to physical or mechanical connections or couplings. Further, terms such as “up,” “down,” “bottom,” “top,” “front,” “rear,” “upper,” “lower,” “upwardly,” “downwardly,” and other orientational descriptors are intended to facilitate the description of the exemplary embodiments of the present invention, and are not intended to limit the structure of the exemplary7embodiments of the present invention to any particular position or orientation. Terms of degree, such as “substantially” or “approximately,” are understood by those skilled in the art to refer to reasonable ranges around and including the given value and ranges outside the given value, for example, general tolerances associated with manufacturing, assembly, and use of the embodiments. The term “substantially,” when referring to a structure or characteristic, includes the characteristic that is mostly or entirely present in the characteristic or structure.

[0014] Fig. 1 is a perspective view of one example of a wearable fluid delivery device 10 constructed in accordance with an example embodiment. As shown in Fig. 1, the medicament delivery device 10 comprises a baseplate 12, a cover 14, and an insertion mechanism 16 in an un-deployed position. The reservoir fluid delivery device 10 can be filled with the fluid (e.g.,medicament or drug) by a user inserting a needle of a filled syringe 36 into a fill port (not shown) provided in the baseplate 12 that has an inlet fluid path from the fill port to the reservoir. It is to be understood that the fluid delivery device 10 can be filled with a fluid (e.g., drug) using different mechanisms and methods.

[0015] Fig. 2 is an illustrative system diagram that illustrates example components in an example medication delivery device 10 having for example, an infusion pump. The medication delivery device 10 can include an electronics sub-system 52 for controlling operations of components in a fluidics sub-system 54 such as the pump 64. A power storage sub-system 50 can include one or more batteries 56, for example, for providing power to components in the electronics and fluidics sub-systems 52 and 54. The fluidics sub-system 54 can comprise, for example, an optional fill port 68 for filling a reservoir 70 (e.g., with medication), although the medication delivery device 10 can be optionally shipped from a manufacture having its reservoir already filled, or can be configured to receive a filled reservoir from a medical professional or user. The medication delivery device 10 also includes an insertion mechanism 74 for deploying a cannula 72 for insertion into an infusion site on a patient’s skin. The fluidics sub-system 54 also has a metering sub-system 62 comprising the pump 64 and a pump actuator 66.

[0016] The pump actuator 66 can be a DC motor and gearbox assembly or other pump driving mechanism for controlling the plunger or piston 30. The microcontroller 58 can be provided with an integrated or separate memory device 76 having computer software instructions for controlling, for example, operation of the pump actuator 66.

[0017] Fig. 3 is a perspective view of wearable fluid delivery device 100 in accordance with another embodiment of the present invention, in which a cover 114 is removed to aid clarity. And Fig. 4 is a block diagram of the device 100. Similar to the embodiment of Figs. 1 and 2, the device 100 includes a baseplate 112 on which one or more batteries 156, a pump 164, a pump actuator 166 (such as a DC motor and gearbox assembly or other pump driving mechanism), an insertion mechanism 174, and a reservoir 170 are mounted. The device 100 also includes a patient cannula 130 (best shown in Figs. 7 and 8), as part of the insertion mechanism 174.

[0018] Preferably, the reservoir 170 is rigid. The reservoir 170 may be unitarily formed from non-metallic and metallic materials, such as polymeric materials, including, but not limited to, thermoplastics, stainless steels or other metallic alloys.

[0019] The reservoir 170 has a stopper or plunger 180 movably disposed therein. According to one embodiment, the stopper is freely movable within the reservoir 170. The stopper 180 is not connected to a driving mechanism that would inhibit the motion of the stopper 180, and the stopper 180 moves within the reservoir as a result of the pressure of the fluid (e.g., medicament) in the reserv oir.

[0020] For example, according to one embodiment, the reservoir 170 is initially filled by a patient or medical professional using a syringe 36 to create volumetric displacement of the delivery fluid. This is achieved by starting the stopper 180 at a distal or front end of the reservoir 170 with a completely empty reservoir 170. The stopper 180 is pushed back by entering fluid that is introduced by the patient via the fill port 168. That is, when the reserv oir 170 is filled by the syringe 36 via the fill port 168, the stopper 180 is driven toward a proximal or rear of the reservoir 170 by the incoming fluid. And, as will be subsequently described in greater detail, as the fluid is pulled from the reservoir by the pump 164, the stopper 180 is pulled toward the front of the reserv oir 170 as a result of the pressure drop due to the removal of the fluid without driving the stopper 180 by an external mechanism.

[0021] The stopper 180 is a sealing member that may be made up of one or several components to create a floating piston face. The plunger 180 may have more than one contact point for sealing along a longitudinal axis of the reservoir 170 to balance forces and prevent tilting of the plunger 180 relative to the reservoir 170. Tire plunger 180 may be unitarily formed from non-metallic and metallic materials, such as polymeric materials, including, but not limited to, thermoplastics, stainless steels or other metallic alloys. The plunger 180 may also have O-ring seals present to achieve a robust sealing joint with the reservoir 170.

[0022] More specifically, the device 100 includes a fluid path 118 connecting the reserv oir 170 and the patient cannula 130. A first one-way valve 120, a reciprocating piston mechanism (or pump) 164, and a second one-way valve 122 are disposed sequentially on the fluid path 118 between the reservoir 170 and the patient cannula 130. Fig. 4 is a block diagram illustrating thesequential disposition of the first one-way valve 120, the reciprocating piston mechanism 164, and the second one-way valve 122 on the fluid path 118. The fluid path 118 includes a proximal fluid path or flow path 124 disposed between the reservoir 170 and the first one-way valve 120, and a distal fluid path or flow path 126 disposed between the second one-way valve 122 and the patient cannula 130 (best shown in Figs. 6 and 7). Each of the one-way valves 120, 122 permits distal flow therethrough, but prevents proximal flow therethrough. That is, the first one-way valve 120 permits fluid to flow distally from the reservoir 170 toward the reciprocating piston mechanism 164, but prevents fluid flowing proximally therethough from the reciprocating piston mechanism 164 toward the reservoir 170. Similarly, the second one-way valve 122 permits fluid to flow distally from the reciprocating piston mechanism 164 toward the patient cannula 130, but prevents fluid from flowing proximally therethough from the patient cannula 130 toward the reciprocating piston mechanism 164.

[0023] According to one embodiment, each of the one-way valves 120, 122, shown for example, in Fig. 5, are designed to achieve minimal volumetric deformation under back pressure while suitably performing the main function of flow control. Each one way valve or one-way check valve 120, 122 may be unitarily formed from non-metallic materials, such as polymeric materials, including, but not limited to, thermoplastics, elastomers, silicones and combinations thereof (e.g., copolymers of thermop lastics / elastomers). The one way valves 120, 122 may be of elastomeric design including, but not limited to, a duckbill valve, umbrella valve, Belleville valve, ball valve, dome valve, cross-slot valve, or any combination of these valves. The one way valves 120, 122 may also be mechanically or electromechanically controlled. As will be subsequently described in greater detail, the one way valves 120, 122 may be supported with a secondary design feature of the fluid path to provide volumetric reduction of dead space within the flow path 118.

[0024] According to one embodiment, as shown, for example, in Fig. 6, the reciprocating piston mechanism 164 includes a reciprocating piston 158 and a discrete volume piston chamber 162. Further, according to one embodiment, the device 100 includes a manifold 160. The manifold 160 houses the first and second one-way valves 120, 122 and at least a portion of the reciprocating piston mechanism 164. The manifold 160 forms the discrete volume pistonchamber 162. Preferably, the reciprocating piston 158 includes a sealing member 161 disposed at the free end thereof to prevent any fluid from escaping around the reciprocating piston 158 from the discrete volume piston chamber 162. The sealing member 161 can be an O-ring or other elastomeric design, which is located and positioned by a rigid body, such as reciprocating piston 158, capable of a stroke length of suitable fluid delivery size.

[0025] The reciprocating piston 158 may be unitarily formed from non-metallic and metallic materials, such as polymeric materials, including, but not limited to, thermoplastics, stainless steels or other metallic alloys. The reciprocating piston 158 may be driven linearly directly with a DC motor connection, or with gearbox force transferring mechanisms, including, but not limited to an eccentric wheel, rack / pinion, or lead screw.

[0026] According to one embodiment, the manifold 160 includes a manifold projection 167 extending into an internal void 171 of the first one-way valve 120 opposite to a fluid flow direction through the first one-way valve 120. Tire manifold projection 167 reduces volumetric deformation of the first one-way valve 120 under back pressure, for example, during a dispense stroke of the reciprocating piston mechanism 164 (i.e., pushing fluid out of the reciprocating mechanism 164 and through the second one-way valve 122 toward the patient cannula 130).

[0027] According to one embodiment, the device 100 also includes an inlet housing 163 securing the first one-way valve 120 in the manifold 160. Additionally, the device 100 includes an outlet housing 165 securing the second one-way valve 122 in the manifold 160. The outlet housing 165 has an outlet housing projection 169 extending into an internal void 173 of the second one-way valve 122 opposite to a fluid flow direction through the second one-way valve 122. The outlet housing projection 169 reduces volumetric deformation of the second one-way valve 122, for example, during an intake or aspirating stroke of the reciprocating piston mechanism 164 (i.e., pulling fluid into the reciprocating mechanism 164 from the reservoir 170 through the first one-way valve 120). The manifold projection 167 and the outlet housing projection 169 are volumetric reduction features.

[0028] The volumetric reduction features 167, 169 are a component of the fluid path that reduces the space within the one way valves 120, 122 where fluid can reside during latent pumping times. These features serve at least two purposes in this novel design. One purpose oftire volumetric reduction features 167, 169 are to reduce a total fluid path volume, thereby reducing the effects of dwell time and minimizing complex flow patterns. Another purpose of the volumetric reduction features 167, 169 is to provide support to the one way check valves 120, 122 in the case of pumping against back pressure. Under this condition, a one way check valve of elastomeric design without volumetric reduction features will be subjected to local deformations, which can negatively affect the dose volume of a full stroke of the reciprocating piston. Embodiments of the present invention solve this issue by limiting the amount of deformation that is capable of occurring. The volumetric reduction features 167, 169 may be unitarily formed from non-metallic and metallic materials, such as polymeric materials, including, but not limited to, thermoplastics, stainless steels or other metallic alloys.

[0029] As shown, for example, in Figs. 3, 7, and 8, the reciprocating piston mechanism 164 can include the reciprocating piston 158, a piston coupler 172 coupled at a first end thereof to the reciprocating piston 158, and coupled at a second end thereof about a driving wheel 174 that has an eccentric driving mount 176. In operation, as the motor 166 rotates or drives the driving wheel 174, which is eccentrically mounted to the motor 166 via the eccentric driving mount 176, the eccentric rotation of the driving wheel 174 and the interaction between the driving wheel 174 and the piston coupler 172 converts the rotation of the motor 166 into reciprocation of the reciprocating piston 158. According to one embodiment, the piston coupler 172 is fixedly coupled to the reciprocating piston 158, which is constrained to move linearly. According to another embodiment, the piston coupler 172 is movably coupled to the reciprocating piston 158.

[0030] The embodiment of Figs. 7 and 8 is substantially similar to the embodiment of Fig. 3, except for the shape and size of the reservoir 170 and the location of the one or more batteries 156.

[0031] Figs. 9 and 10 are respective top and bottom perspective views of a reciprocating piston mechanism 164 in accordance with another embodiment of the present invention, and Figs. 11 and 12 are respective perspective cross-sectional and partial cross-sectional views of the same. In Figs. 9 -12, the motor 166 that drive the driving wheel 174 is omitted to aid clarity, but would be disposed through the throughhole 179 in the upright wall of the baseplate 112, were it depicted.

[0032] As shown, for example, in Figs. 9-12, the reciprocating piston mechanism 164 includes the reciprocating piston 158, the piston coupler 172 coupled at a first end thereof to the reciprocating piston 158, and coupled at a second end thereof to a first end of a link 178. A second end of the link 178 couples with the eccentric driving mount 176 of the driving wheel 174.

[0033] Figs. 9-12 also illustrate the outlet housing 165, the inlet housing 163, and the manifold 160. Additionally illustrated in Figs. 9-12 is a reservoir vial holder 190 for holding a vial reservoir 170. A user or medical professional, as previously noted, can insert such a vial reservoir 170 into the device 100.

[0034] Fig. 13 is flow chart of a method 200 of operating the medical device 100 in accordance with an embodiment of the present invention. In operation of the device 100, the controller or microcontroller 190, like the microcontroller 58, controls the device 100 to perform a first operation 210 to operate the reciprocating piston mechanism 164 to draw back, thereby closing the second one-way valve 122 via back pressure, and drawing a volume of medicament from the reservoir 170, through the first one-way valve 120 and into a discrete volume piston chamber 162. The controller or microcontroller 190 controls the device 100 to perform a second operation 220 to operate the reciprocating piston mechanism 164 to push forward, thereby closing the first one-way valve 120 and expelling the volume of medicament through the second one-way valve 122 toward the patient cannula 130.

[0035] Embodiments of the present invention employ one-way check valves 120, 122 to achieve a unidirectional flow in combination with a reciprocating discrete volume piston chamber 162. Embodiments of the present invention deliver fluids, such as insulin or other hormones, antibiotics, chemotherapy drugs, and pain relievers, from the reservoir 170 to a patient. Check valves 120, 122 reliably control fluid flow. When the check valves 120, 122 are coupled with dead- volume reducing features, the device 100, such as a micro-dosing piston patch pump 100, is capable of withdrawing very small doses from a large volume reservoir 170 using hydraulic advantages, and dispensing the very small doses to a patient.

[0036] A unidirectional flow is achieved by orienting two or more check valves 120, 122 on each side of the reciprocating piston mechanism 164. This orientation makes the distally locatedone way check valve 122 stay closed while the reciprocating piston 158 is aspirating, which opens the proximal one way check valve 120, allowing the piston chamber to fill from the reservoir 170. During the dispense stroke, when the piston 158 advances, the proximal one way check valve 120 is hydraulically closed, while the distal one way check valve 122 opens, allowing fluid to flow to the patient.

[0037] One advantage of embodiments of the present invention is the inlierent safety featur e of preventing runaway doses. The unidirectionally-valved reciprocating piston pump advances and returns the piston 158 along a linear travel path. This design lends itself to having safety features present, such as, but not limited to, a DC motor direction reversal, a limit switch, an encoder, and / or physical hard stops. Embodiments of the present invention are also very adaptable to many size constraints, allowing for the device 100 to remain small.

[0038] One use of the device 100 is to deliver insulin to a patient. Employing a microcontroller 190, the device 100 can deliver serial doses over a time. A dwell time is the time in between doses. Adhesion of insulin to the pump surfaces (sleeve, piston, plug, seals) can occur during dwell times. During a next actuation of the pump 158, some or all of the adhered insulin is wiped or scraped off those surfaces and into the fluid path. Once in the fluid path, the insulin can be exposed to many solid-liquid-air interfaces.

[0039] In related art insulin delivery devices, the medicament delivery cycle has one stroke occurring between dwell times. This means that some of the freshly removed adhered insulin, which should be in a state that is tending towards aggregation, can only make it to the manifold and downstream baseplate geometry, where it will dwell for the next cycle time depending on basal rate. Observation in tests revealed that these two areas have trapped aggregation in them, so it is likely these are nucleation sites for the recently released deformed insulin to start the chain reaction of the aggregati on pathway. Pushing the adhered insulin past these points in the system may prevent that chain reaction from occurring.

[0040] Fig. 14 is a flow chart of a method 300 in accordance with an embodiment of the present invention, and Fig. 15 is a visual representation of dosing schemas in accordance with embodiments of the present invention. More specifically, method 300 is a method of controlling delivery of a total dose of medicament over a time period in a medical device with a controllerand a reciprocating pump, such as device 100. In a first operation 310, the controller or microcontroller 190 divides the total dose over the time period into equally spaced discrete doses with equal intervals between the discrete doses. Then, in a second operation 320, at a first dosing time, the controller or microcontroller 190 controls the medical device 100 to deliver at least two of the doses sequentially without an interval between, and appropriately increases the interval before a next dosing time.

[0041] For example, in Fig. 15, to deliver 30 units of insulin per day, in operation 310, the controller or microcontroller 190 divides the total dose (30 units) over 24 hours to yield 5 pF or 0.5U every’ 24 minutes (first line of the table in Fig. 15). In the first example (shown in the second line of the table in Fig. 15), at a time to deliver the first dose (operation 320), the controller or microcontroller 190 controls the medical device 100 to deliver two of the 5 pL or 0.5U together without an interval in between (delivering 10 pL or 1U), and increases the interval until the next dose to 48 minutes. The controller or microcontroller continues this pattern of delivering two doses together without an interval in between and then waiting 48 minutes to deliver the next two doses.

[0042] Similarly, in the second example (shown in the last line of the table in Fig. 15), at a time to deliver the first dose (operation 320), the controller or microcontroller 190 controls the medical device 100 to deliver three of the 5 pL or 0.5LTtogether without an interval in between (delivering 15 pL or 1.5U), and increases the interval until the next dose to 72 minutes. The controller or microcontroller continues this pattern of delivering three doses together without an interval in between and then waiting 72 minutes to deliver the next three doses.

[0043] Embodiments of this invention use a control system to change the dose structure profile or schema of a discrete dose size, such as delivering twice, or any multiple, of the number of adjoining doses while also waiting twice, or any equal multiple, the amount of time to next dose. The reciprocating piston mechanism, such as reciprocating pump mechanism 164, delivers fluids, such as insulin or other hormones, antibiotics, chemotherapy drugs, and / or pain relievers. Embodiments of the present invention improve the fluid compatibility of a reciprocating piston pump that has a wiping surface that is susceptible to drug adhesion during long dwell times. Software control is an implementation to gain significant mechanical and chemical advantagesfor fluid delivery compatibility. By doing two or more doses back to back, there is not enough time in between these doses for fluid adhesion to occur. This limits the total number of times the reciprocating piston pump can swipe and potentially re-release adhered fluid.

[0044] One advantage of embodiments of the present the invention is the improvement to fluid delivery compatibility. These embodiments reduce total fluid residence in downstream stagnant volumes.

[0045] Although related art discrete volume reciprocating pumps have historically had adhesion issues, the dose structuring solution of embodiments of the present invention reduces the effect of dwell time within the pumping chamber. Related parameters to achieve these embodiments are reciprocating pump chamber volume, downstream volume, and dose rate.

[0046] Although only a few embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. It will be appreciated by those skilled in the art that other changes may also be made to the disclosed embodiments without departing from the scope of the invention. In addition, any of the embodiments, features and / or elements disclosed herein may be combined with one another to form various additional combinations not specifically disclosed, as long as the embodiments, features and / or elements being combined do not contradict each other. All such changes and combinations are considered to be within the scope of the invention as defined by the appended claims and their equivalents.

Claims

What is claimed is:

1. A medical device, comprising: a reservoir; a patient cannula; a fluid path connecting the reservoir and the patient cannula; and a first one-way valve, a reciprocating piston mechanism, and a second one-way valve disposed sequentially on the fluid path between the reservoir and the patient cannula.

2. The medical device according to claim 1, further comprising a stopper movably disposed within the reservoir.

3. The medical device according to claim 2, wherein the stopper is freely movable within the reservoir.

4. The medical device according to claim 2, wherein the reservoir is rigid.

5. The medical device according to claim 2, wherein the stopper is not connected to a driving mechanism.

6. The medical device according to claim 1, wherein the reciprocating piston mechanism comprises a reciprocating piston and a discrete volume piston chamber.

7. Tire medical device according to claim 1, wherein the reciprocating piston mechanism comprises: a reciprocating piston;a piston coupler, coupled at a first end thereof to the reciprocating piston; a link coupled at a first end thereof to a second end of the piston coupler; and a driving wheel having an eccentric driving mount coupled with a second end of the link.8.. The medical device according to claim 7, further comprising a motor driving the driving wheel.

9. The medical device according to claim 7, further comprising a manifold housing the reciprocating piston, the piston coupler, and the first and second one-way valves, the manifold forming a discrete volume piston chamber.

10. The medical device according to claim 1, further comprising a manifold housing the first and second one-way valves and at least a portion of the reciprocating piston mechanism, the manifold forming a discrete volume piston chamber.

11. The medical device according to claim 10, wherein the manifold includes a manifold projection extending into an internal void of the first one-way valve opposite to a fluid flow direction through the first one-way valve to reduce volumetric deformation of the first one-way valve under back pressure.

12. The medical device according to claim 11, further comprising an inlet housing securing the first one-way valve in the manifold.

13. The medical device according to claim 11, further comprising an outlet housing securing the second one-way valve in the manifold and having an outlet housing projection extending into an internal void of the second one-way valve opposite to a fluid flow direction through the second one-way valve to reduce volumetric deformation of the second one-way valve under back pressure.

14. A method of operating a medical device having a reservoir housing a medicament, a patient cannula, a fluid path connecting the reservoir and the patient cannula, and a first one-way valve, a reciprocating piston mechanism, and a second one-way valve disposed sequentially on the fluid path between the reservoir and the patient cannula, the method comprising: operating the reciprocating piston mechanism to draw back, thereby closing the second one-way valve via back pressure, and drawing a volume of medicament from the reservoir, through the first one-way valve and into a discrete volume piston chamber; and operating the reciprocating piston mechanism to push forward, thereby closing the first one-way valve and expelling the volume of medicament through the second one-way valve toward the patient cannula.

15. A method of controlling de lively of a total dose of medicament over a time period in a medical device with a controller and a reciprocating pump, the method comprising: dividing the total dose over the time period into equally spaced discrete doses with equal intervals between the discrete doses; and at a first dosing time, controlling the medical device with the controller to deliver at least two of the doses sequentially without an iiiterval between, and appropriately increasing tire iiiterval before a next dosing time.

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