SE1651014A1 - Infusion Pump - Google Patents

Abstract

An infusion pump is disclosed, which comprises a housing including a first housing unit and a second housing unit, a chamber located at least partially in the first housing unit, an outlet, an outlet valve between the chamber and the outlet, an inlet, and an inlet valve between the inlet and the chamber. At least one of the outlet valve and the inlet valve is arranged between the first housing unit and the second housing unit. A method for providing such an infusion pump is also disclosed.

Description

lO lnfusion Pump Field of the lnventionThis invention pertains in general to the field of infusion pumps, such as ambulatory infusion pumps that may be devised for application in micro infusion therapies. More particularly, theinvention relates to an infusion pump, which comprises a housing including a first housing unit and asecond housing unit, a chamber located at least partially in the first housing unit, an outlet, an outletvalve betvveen the chamber and the outlet, an inlet, and an inlet valve between the inlet and thechamber. At least one of the outlet valve and the inlet valve may comprise a spherical valve memberand a valve seat member arranged between the first housing unit and the second housing unit. Thevalve and at least one of the first housing unit and the second housing unit may be made of differentmaterials. The valve may be made at least partially of a metallic material and the housing may bemade of a non-metallic material, such as plastic. The invention also pertains to a method forproviding the infusion pump.

Background of the lnvention Ambulatory infusion pumps may be used for infusion therapy of liquid medicaments ornutrients, such as for diabetes care or pain management. The devices are designed for continuousdelivery of small precise amounts of the liquid. The ambulatory infusion pumps are operated byinteracting with the infusion pump via a user interface including a display and buttons formanipulating the infusion pump. The devices are normally battery powered and include variouselectronics, and a pumping unit. The liquid is contained in a reservoir. Since the user normallycarries the device around the clock, it is desired that the device is small and light. Many times that isnot the case due to the type of pump unit used and the requirements for a user interface, whichrestricts the possibilities to design a device that is convenient to carry and simple to operate. Thedesign is dictated by the technology rather than user needs. However, due to the small amounts ofliquid being administrated, designing a reliable pump unit that that does not dictate the designoptions for the device is challenging.

One example of an ambulatory infusion pump is the insulin pump. This micro infusionpump has evolved from a manual syringe. Most insulin pumps available on the marked are simply anatomized syringe comprising a cylindrical container and a piston. Movement of the piston in smallincrements relative the cylindrical container is effected by a small step motor in order to deliver apredefined amount of insulin at predetermined time intervals, which simulates a '“continuous” deliveryof insulin. The amount of insulin delivered in each incremental movement of the piston can be about0.00025-0.00050 ml or 0.25-0.50 mm3.

The piston pumps are relatively bulky. The housing for the pump needs space for the fullstroke of the piston, which is essentially twice the entire length of the cylindrical container for the lO medicament. The cylindrical container has only one outlet, such that the container needs to be filledor replaced after a single stroke of the piston. Devices containing this type of technology tend to bebulky, square and inconvenient for the user. The devices are designed around the technology,including the pump unit, battery and display, making them fairly bulky and inconvenient for the userto carry. The pump unit offers few options to design a user-friendlier device.

Another example of an infusion pump is for administration of a medicament for painmanagement or for nutrients. Such pumps may deliver medication or nutrients from either a cassettetype of tube arrangement or from an administration type of tube arrangement. Such pumps include areusable control module detachably coupled to a pressure plate at a top surface of a disposable fluidreservoir cassette. Fluid is pumped from the cassette by the reusable control module when thecassette is coupled to the control module. These types of pumps tend to be less precise, makingthem unsuitable for administration of minute amounts of liquid, such as insulin.

Still other examples of infusion pumps comprise a flow material reservoir wherein the liquidis pressurized. The liquid is contained in a compressible container or bag, and air around thecontainer or bag is pressurized. These devices require complex and expensive sensors to measurethe volume of the flow material reservoir and/or the volume of flow material dispersed from theinfusion pump.

Hence, an improved infusion pump, and components useable for such an improvedinfusion pump, would be advantageous and in particular allowing for improved robustness, increasedflexibility, cost-effectiveness, and/or reduced complexity would be advantageous.

Summary of the lnvention Accordingly, embodiments of the present invention preferably seek to mitigate, alleviate oreliminate one or more deficiencies, disadvantages or issues in the art, such as the above-identified,singly or in any combination by providing an infusion pump, and a method for providing such aninfusion pump, according to the appended patent claims.

Embodiments include an infusion pump comprising a housing including a first housing unitand a second housing unit, a chamber located at least partially in the first housing unit, an outlet, anoutlet valve between the chamber and the outlet, an inlet, and an inlet valve between the inlet andthe chamber. At least one of the outlet valve and the inlet valve is arranged between the first housingunit and the second housing unit.

At least one of the outlet valve and the inlet valve may comprise a spherical valve memberand a valve seat member. The valve seat member and at least one of the first housing unit and thesecond housing unit may be made of different materials.

The valve seat member may be made of a metallic material. Additionally or alternatively,the valve seat member may comprise a valve seat having a radius corresponding to a radius of the lO spherical valve member. The first housing unit may comprise a recess for receiving at least a portionof the valve seat member. The first housing unit may be made of a non-metallic material.

The first housing unit and the second housing unit may be made of the same material andtogether form a space for enclosing at least one of the outlet valve and the inlet valve. The valve seatmember may comprise a recess, in which the spherical valve member is at least partially arranged.

The first housing unit may comprise a recess sized for receiving at least a portion of thesecond housing unit. The first housing unit may be joined to the second housing unit. ln some embodiments, a spring member is arranged to bias the spherical valve membertowards a valve seat of the valve seat member.

The spring member may comprise a disc spring, such as a spiral disc spring. The springmember may comprise a rim arranged at least partially around a circumference of the spherical valvemember. The rim may be ring shaped and arranged completely around the circumference ofspherical valve member. ln some embodiments, the rim forms a seal betvveen the valve seatmember and at least one of the first housing unit and the second housing unit.

A spring element of the spring member is formed by at least one slit in a center portion ofthe spring member.

The spherical valve member may be arranged at least partially between the valve seatmember and the rim. A pressure component of the spring member, which may form a seat for thespherical valve member, may be connected to the rim via the spring element, be arranged inabutment with the spherical valve member and be biased towards and moveable relative the valveseat.

The rim of the spring member may be arranged at a ledge of at least one of the firsthousing unit and the second housing unit, or the valve seat member, wherein a height of the ledge islower than a thickness of the rim in an uncompressed state. The rim may be compressed by thevalve seat member when the second housing unit is arranged relative the first housing unit in anassembled state. ln some embodiments, a reservoir for a liquid medicament or a nutrient is arranged in fluidcommunication with the inlet of the infusion pump according to embodiments of the invention. ln some embodiments, a disc spring is arranged between the valve seat member and atleast one of the first housing unit and the second housing unit of the infusion pump according toembodiments of the invention.

Embodiments includes a method for providing an infusion pump, comprising providing afirst housing unit having a chamber located therein, providing a second housing unit having an inletand an outlet, providing an outlet valve, providing an inlet valve, arranging the outlet valve betweenthe chamber and the outlet in at least one space formed by the first housing unit and the secondhousing unit, and arranging the inlet valve between the inlet and the chamber in said at least onespace formed by the first housing unit and the second housing unit. lO Further embodiments of the invention are defined in the dependent claims.

Embodiments of the invention provide for producing the valve and the housing as separatecomponents using different manufacturing techniques, each being optimal for producing therespective component. The valve may be produced using a high precision production technique,such milling. The housing has lower requirements on the precision of the production technique, andcan thus be produced with another production technique, such as by injection molding or casting,that is less expensive. Hence, the overall production cost of the infusion pump may be loweredcompared to producing the housing and the valve using the production technique required forsufficient accuracy of the valve.

Embodiments of the invention also provide a less complex and more flexible infusion pumpthat accurately can deliver minute volumes of liquid. Embodiments provide for precision that issufficient for use as an insulin pump. Embodiments provide an insulin pump with a chamber that issmaller than the reservoir in which the liquid to be administered is contained. Embodiments have aninlet valve and an outlet valve to the chamber, which provide for pressurizing the liquid in thechamber but not in the reservoir. lnstead, the design allows for using the same components of thepump for refilling the chamber with liquid from the reservoir and for pressurizing the liquid in thechamber. This allows for reduced complexity. Also, the chamber and the reservoir can be separated,which offers increased flexibility to design a user-friendly ambulatory infusion pump that is lessdependent on the technology. The chamber can be made much smaller with a fixed shape, whereasthe reservoir from which the liquid is drawn can have an arbitrary shape, such as adapted to theexterior chassis of the device. The chassis can in turn be designed with the user needs in mindrather than being dictated by the pump technology. The device can for example be designed fordifferent user groups, such as for men, women, kids etc. with different designs of the chassis wherethe reservoirs for different user groups have different shapes in order to accommodate requirementson the chassis design. Yet, the design of the infusion pump unit with the chamber may be fixed, butdue to its small size it does not impair the flexibility and design options for the chassis. Furthermore,embodiments provide for reduced complexity that provide for overall simplified production withassociated reduced manufacturing costs. Embodiments of the invention contribute to make theinfusion pump precise for delivery of minute amounts of liquid, such as various aspects of valvesand/or disc springs for an inlet and/or an outlet to/from the chamber. Such embodiments may formseparate inventions, but each contribute and combine to the reduced complexity and increasedflexibility of the infusion pump of the present invention. For example, the valve is particularly usefulfor an infusion pump, wherein minute amounts of a liquid are delivered. The chamber of the pump forpressurizing the liquid can be made smaller than is previously known since using the valve allows forrefilling the chamber. A smaller chamber allows for a smaller diameter of a piston for pressurizing theliquid, which in turn means that the accuracy of the infusion pump is improved. The piston can simply lO travel a longer distance for each delivery of liquid compared to previously know infusion pumps witha single stroke, which must have a larger diameter to deliver the same amount. A longer travel iseasier to control, allowing for improved accuracy. lt should be emphasized that the term “comprises/comprising” when used in thisspecification is taken to specify the presence of stated features, integers, steps or components butdoes not preclude the presence or addition of one or more other features, integers, steps,components or groups thereof.

Brief Description of the Drawings These and other aspects, features and advantages of which embodiments of the inventionare capable of will be apparent and elucidated from the following description of embodiments of thepresent invention, reference being made to the accompanying drawings, in which Fig. 1 is a cross-sectional view of an embodiment of the infusion pump; Fig. 2 is a cross-sectional view of an embodiment of the valve; Fig. 3 is a cross-sectional view of an embodiment of an inlet valve and an outlet valve eacharranged in a recesses of the first housing unit and the second housing unit; Fig. 4 is an exploded view of an embodiment of the infusion pump: Fig. 5 is a perspective view of an embodiment of a spring member; Fig. 6 is a top view of an embodiment of a spring member; Fig. 7 is a cross-sectional view of a valve with an inlet connected to a reservoir; Fig. 8a is a cross sectional view of a pre-assembled valve; and Fig. 8b is a perspective view of a pre-assembled valve.

Description of Embodiments Specific embodiments of the invention will now be described with reference to theaccompanying drawings. This invention may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein; rather, these embodimentsare provided so that this disclosure will be thorough and complete, and will fully convey the scope ofthe invention to those skilled in the art. The terminology used in the detailed description of theembodiments illustrated in the accompanying drawings is not intended to be limiting of the invention.ln the drawings, like numbers refer to like elements.

The following description focuses on embodiments of the present invention applicable asan ambulatory infusion pump, such as an insulin pump. However, it will be appreciated that theinvention is not limited to this application but may be applied for administration of other liquidmedicaments, liquid pain management and/or nutrient. lt is particularly useful for incrementaladministration of minute amounts of liquid, such as about 0.00010-00050 ml in each step. lO Fig. 1 illustrates components of embodiments of an infusion pump unit, which will bereferred to as an infusion pump in the following. The infusion pump comprises a housing 1. ln theembodiment of Fig. 1, the housing comprises a first housing unit 2 and a second housing unit 3. Achamber 4 is located at least partially in the first housing unit 2. The housing 1 includes an out|et 5,and an in|et 6. An out|et valve 7 may be arranged between the chamber 4 and the out|et 5. An in|etvalve 8 may be arranged between the in|et 6 and the chamber 4.

Fig. 2 illustrates a valve 10, which may be used as the out|et valve 7 and/or the in|et valve8. The valve 10 comprises a spherical valve member 11, and a valve seat member 12. The valveseat member 12 has a first recess 13. The first recess 13 may extend from a first end of the valveseat member 12, which preferably is cylindrical, towards an opposing second end. The first recess13 may have a depth that is slightly smaller than a diameter of the spherical valve member 11, whichmay be used for biasing the spherical valve member 11 towards a valve seat 14 of the valve seatmember 12, as will be discussed below. ln other embodiments, such as illustrated in Figs. 8a-8b, thespherical valve member 11 is fully contained in the valve seat member 12. The first recess 13 has adiameter slightly larger than the diameter of the spherical valve member 11. The spherical valvemember 11 can freely move within the first recess 13 in the axial direction of the valve 10. However,the spherical valve member 11 can substantially not move within the first recess 13 in the radialdirection of the valve 10. Hence, the spherical valve member 11 may be centered within the firstrecess 13. A slight space betvveen the recess 13 and the spherical valve member 11 allows liquid topass when pressurized, whereby the spherical valve member 11 moves in the axial direction of thevalve to provide clearance from the valve seat 14. The valve seat member 12 has a second recess15 from the second end, opposing the first end, of the valve seat member 12. The second recess 15is preferably cylindrical. The second recess 15 is co-axial with the first recess 13 and has a diameterthat is smaller than the diameter of the first recess 13. Hence, the valve seat 14 may have adiameter corresponding to a diameter of the spherical valve member 11, which is not the maximumdiameter of the spherical valve member 11. The first diameter may be in the range of 1 .5-3 mm. Thesecond diameter may be in the range of 1-2 mm.

The valve seat 14 is formed by an edge at the intersection of the first recess 13 and thesecond recess 15. The edge forms a surface against which a portion of the spherical valve member11 may be seated in a closed position of the valve. The edge may have a chamfer. The chamfer mayhave a curvature, which is substantially complementary in shape to the curvature of an outer surfaceof the spherical valve member 11. Hence, the surface contact between the spherical valve member11 and the valve seat 14 may be increased. An increased surface contact is useful in applicationswherein the amount of liquid to administered is small and thus the compression in the chamber 4 foreach increment of a piston 16 is low, such as for delivery of insulin. The increased surface contactimproves the tightness of the valve, particularly in delivery of small amounts of liquid. lO The spherical valve member 11 may be centered with the first recess 13 and the secondrecess 15, i.e. the center of the spherical valve member 11 is coaxial with the first recess 13 and thesecond recess 15 in the closed position. Since the diameter of the spherical valve member 11 islarger than the diameter of the second recess 15, a portion of the spherical valve member 11extends into the second recess 15. The diameter and/or the length of the second recess 15 is/aredimensioned such that the portion of the spherical valve member 11 located therein does not reachthe second end of the valve 10.

Returning to Fig. 1, at least one of the outlet valve 7 and the inlet valve 8 comprises aspherical valve member 11a, 11b, and a valve seat member 12a, 12b arranged between the firsthousing unit 2 and the second housing unit 3. The valve 10 of Fig. 2 may be as used as the outletvalve 7 and/or the inlet valve 8, respectfully. Hence, for embodiments of the outlet valve 7 and/or theinlet valve 8, reference is made to the embodiments illustrated in Fig. 2. The piston 16 may bearranged in the chamber 4, such as illustrated in Fig. 2. The piston 16 may be a reciprocating piston16 for pressuring liquid contained in the chamber 4. The piston 16 may have a circumferential recess17 at its distal end for receiving a seal, such as an o-ring, for sealing between the chamber 4 and thepiston 16. ln a fon/vard stroke, the piston pressurizes the liquid in the chamber 4 when movedtowards the valves 7, 8, which closes the inlet valve 8 and/or opens the outlet valve 7. ln a backwardstroke the piston 16 is moved away from the valves 7, 8, which closes the outlet valve 7 and/oropens the inlet valve 8 and the chamber 4 is refilled with liquid. Hence, the inlet valve 8 and outletvalve 7 may co-operate to prevent pressurizing the reservoir for the liquid and a back-flow of liquidalready delivered via the outlet. As such, the piston can be made smaller compared to the prior art,allowing for increased precision for delivering the same amount of liquid in a single step. ln some embodiments, the valve seat member 12 and at least one of the first housing unit2 and the second housing unit 3 are made of different materials. For example, the first housing unit 2and/or the second housing unit 3 may be made of a medical grade plastic material. The medicalgrade plastic material may have properties such that the housing unit may be sterilized, e.g. by hotor cold sterilization, and meet FDA (Federal Drug Administration) and USP (United StatesPharmacopeia) classifications, such as for containing liquid medical medicaments and nutrients.Such plastic materials are generally available as such and will not further discussed herein. Thevalve seat member 12 may be made of a metallic material, such as a surgical steel, for exampleaustenitic 316 stainless steel or martensitic 440 or 420 stainless steel. Such metallic materials aregenerally available as such and will not further discussed herein. Providing the housing 1 and thevalve seat member 12 in different materials provide for producing an infusion pump that is applicablefor low pressures, and thus for delivery of small amounts of liquids in a single step, efficiently withhigh precision. Components of the infusion pump that are not critical for the accuracy of the infusionpump, such as the first housing unit 2, the second housing unit 3, and/or the piston 16 may be madein a material that can be produced in high volumes, such as by injection molding or casting, quickly lO and thus efficiently and at low cost. However, such materials and/or production processes may nothave sufficient accuracy and/or be elastic making them unsuitable for achieving the accuracyrequired in certain applications, such as for administration of the amount of liquid involved e.g. foradministration of insulin. The valve seat member 12 may be made of a material that is suitable forhigher precision and/or producing using different technology than that of the housing 1. Suchmaterial may e.g. be a plastic material, for example the metallic material mentioned above. Plasticmaterials may be processed using one or several processing techniques, such as milling, turning,and/or punching, and using tools for successively increased accuracy of the components. Thereby,an interface between the valve seat member 12 and the spherical valve member 11 can be providedwith higher accuracy compared to providing this interface directly in any of the housing units 2, 3made of an elastic material. This is particularly useful in applications where the pressure in thechamber 4 for administrating the liquid is low. ln applications where pressures in the chamber 4 arehigher, the accuracy between the valve seat 14 and the spherical component is less critical. Withhigh enough pressures, the valve seat 14 may be formed directly in the material of the housing 1,even if that is an elastic material. The valve seat member 12 forms an intermediate componentincreasing the accuracy of the interface between the valve seat 14 and the spherical valve member11. Accuracy in this context means that the surface of the valve seat 14 and the outer surface of thespherical valve member 11 should be sufficiently smooth that liquid may not pass the interface evenwhen the piston 16 is moved a short distance within the chamber 4, such as in the range of 0,005-0.015 mm in each in increment of the piston 16. The diameter of the chamber may be in the range of4-8 mm. The maximum length of the chamber for containing liquid may be in the range of 4-20 mm.Hence, the chamber may as well as the infusion pump as such may be made compact.

Fig. 1 illustrates the first housing unit 2 and the second housing unit 3, which may beprovided separate from the valve members 7, 8. The housing comprises at least one recess 20a,20b that forms a space for receiving at least one valve member 7, 8. ln this embodiment, a firstrecess 20a is provided for receiving the outlet valve member 7. A second recess 20b is provided forreceiving the inlet valve 8. The first recess 20a and the second recess 20b may be sized such thatthe valves 7, 8 are received snugly therein in, for example in a press or friction fit. Hence, a seal isformed between the each recess 20a, 20b and the respective valve 7, 8. Thus, the recess 20a, 20bmay have an inner dimension substantially corresponding to an outer dimension of the valve seatmember 12a, 12b, whereby an outer surface of at least one of the outlet valve 7 and the inlet valve 8is enclosed by each recess 20a, 20b. ln some embodiments, the space formed by the recess 20a, 20b is provided partially in thefirst housing unit 2 and partially in the second housing unit 3. This provides, e.g., for efficientassembly of the infusion pump. For example, about 1/3 to 2/3, such as about 1/2, of the recess maybe formed in the first housing unit 2 and about 2/3 to 1/3, such as 1/2, of the recess may be formedin the second housing unit 3. Hence, the valve 7, 8 may first be arranged in the recess of the first lO housing unit 2, and then the second housing unit 3 is inserted into another recess at the distal end ofthe first housing unit 2, which is slightly larger in diameter than the recess in which the valve isarranged. Hence, the second housing unit 3 may form a plug, also illustrated in Fig. 4, receivedwithin the first housing unit 2 and may be positioned at least partially between the valve 7, 8 and adistal end of the housing 1, such as the distal end of the first housing unit 2. This provides forproviding a seal betvveen the first housing unit 2 and the second housing unit 3. Furthermore, the firsthousing unit 2 may be joined to the second housing unit 3 such that the valve 7, 8 is fully enclosedand the housing units 2, 3 may not disassemble and are liquid tight. Furthermore, a joint may beformed between the first housing unit 2 and the second housing unit 3, e.g. by an adhesive and/or byheat fusion of the material of the housing units 2, 3. At least one seal, such as an o-ring, may beprovided in at least one recess of the valve seat member 12 and in abutment with the recess of thehousing 1. ln the illustrated embodiment, a first seal is arranged between the valve seat member 12and the first housing member 2, and a second seal is provided between the valve seat member 12and the second housing unit 3. An end of the second housing unit 3 is arranged between the seals inthe axial direction of the housing 1 and within the first housing unit 2. Hence, efficient sealing isprovided at the same time as the housing units 2, 3 and the valve 10 are easy to assemble. ln some embodiments, the first housing unit 2 and the second housing unit 3 are made ofthe same material. This provides for efficient production of these components, as described above,in a plastic material. lt also provides for efficiently forming the joint, such as described above.

Fig. 3, illustrates embodiments of at least one spring member 30a, 30b that may bearranged within the housing 1 and in fluid communication with the chamber, such as between thefirst housing unit 2 and the second housing unit 3, illustrated e.g. also in Fig. 4. Each spring member30a, 30b may be arranged to bias the spherical valve member 11a, 11b towards the valve seat 14 ofeach valve seat member 12a, 12b. A spring member 30a, 30b may be required when the amount ofliquid that is administrated is small, i.e. when the length movement of the piston 16 is small for eachincrement, such as described above, whereby the pressure in the chamber 4 is equally small. Suchbiasing in not required for higher pressures and larger amounts of liquids being delivered each timeof delivery. ln the embodiment of Fig. 3, the spring member 30a, 30b comprises a disc spring. The discspring may be made of a plastic material, wherein the shape of the disc spring provides the requiredflexibility for biasing of the spherical valve member 11. ln other embodiments, the spring member30a, 30b is made of an elastic material, wherein the elastic properties of the spring member providethe flexibility of the spring element for the required biasing force.

Fig. 4 illustrates an embodiment of the infusion pump, including the housing with the firsthousing unit 2a. As illustrated, the first housing unit 2a may include a plurality of guide members atits proximal end for guiding the piston 16 during its reciprocating movement. The guide membersextend substantially in the longitudinal axis of the first housing unit 2a. The piston 16a has mating lO protrusions extending substantially perpendicular to its Iongitudinal axis. Each protrusion is slidablyreceived betvveen a pair of guide members. Hence, guiding reciprocating movement of the piston 16within the chamber along the Iongitudinal axis is provided for. An o-ring 50e is arrangedcircumferentially around the piston 16a at the circumferential recess 17. The valve seat members12a, 12b may be arranged within the housing, such as within the first housing unit 2. ln thisembodiment, each valve seat member 12a, 12b has a single circumferential recess for receiving aseal member 50a, 50c, such as an o-ring. The spherical valve members 11a, 11b may be arrangedas described above. The spring members 30a, 30b may be arranged as described with regard toeach of the embodiments described herein. ln the embodiment of Fig. 4, the valve seat member 12a, 12b is arranged at a recess of thefirst housing unit 2a. The second housing unit 3a, 3b forms a plug. ln the illustrated embodiment, therecess of the first housing unit 2a for each valve seat member 12a, 12b has a uniform diameter.Hence, a first plug 3a is provided for valve seat member 12a, and a second plug 3b is provided forthe second valve seat member 12b. The diameter of the plugs 3a, 3b may correspond to thediameter of the valve seat members 12a, 12b, and may this be provided in the recesses between thevalve seat members 12a, 12b and the distal end of the first housing unit 2a. Each plug 3a, 3b has athrough hole that forms the inlet and the outlet, respectively. A seal member 50b, 50d, such as an o-ring, may be arranged in a circumferential recess in the plug 3a, 3b, which provides a seal betweenthe first housing unit 2a, and the second housing unit 3a, 3b. The first plug 3a may be connected to afluid conduit, such as a hose of an infusion set. Hence, a fluid tight conduit is provided between thechamber and the outlet of the infusion pump. Similarly, the second plug 3b may be connected to orform part of a reservoir, e.g. as illustrated in Fig. 7. Hence a fluid tight conduit is provided betweenthe reservoir and the chamber. The embodiment of Fig. 4 provides for a production process that issimplified by providing multiple components with uniform diameters, which also facilitates theassembly process. ln other embodiments, the first and the second plug 3a, 3b are provided as a single unit,such as illustrated in Figs. 1 and 3, and arranged relative the first housing unit 2a. Each plug 3a, 3bmay form the purpose to secure the valve seat members 12a, 12b within the first housing unit 2, 2a.Additionally or alternatively, each plug may provide a seal, e.g. using the seal member 50b, 50d,between the first housing unit 2a and the second housing unit 3a, 3b. Hence, the tightness in thecommunication path from the inlet, via the chamber, to the outlet is further enhanced compared tohaving a single seal member only at the valve seat member 12a, 12b. ln still other embodiments, the housing only comprises the first housing unit 2, 2a. Thevalve seat members 12a, 12b may be arranged in a recess of the first housing unit, such asdescribed above, and provide the inlet and the outlet, respectively. The embodiment of Fig. 4 mayalso be combined with the other embodiments described herein, e.g. with regard to the spring lO 11 members 30a, 30b, the seal members 50a-50d, and the first housing unit 2 and the second housingunit 3.

Figs. 5-6 illustrate embodiments of the spring member 130, 230 that comprises a rim 131,231 such as a circumferential rim. The rim 131, 231 may be arranged at least partially around thespherical valve member 11, such as i||ustrated in Fig. 3. The spring member 130, 230 may have apressure component 132, 232 that is arranged at the center of the spring member 130, 230, and thatmay be arranged in abutment with the spherical valve member 11. Hence, the pressure component132, 232 may form a seat for the spherical valve member 11. The pressure component 132, 232may abut the spherical valve member 11 coaxially with recesses 14, 15 of the valve seat member12. A spring element 133, 233 connects the pressure component to the rim 131, 231. The springmember 130, 230 may be generally disc shaped. Hence, the rim 131, 231, the pressure component132, 232, and the spring member 130, 230, may be provided in a single plane. As such, the springmember 131, 230 may form a disc spring. Furthermore, the spring member 130, 230 may be formedfrom a single piece of material.

The spring member 130, 230 can be used for a valve 10 that is efficient to assemble whilebeing useful for delivery of small amounts of liquid where the pressure provided by the piston 16 isnot sufficient for providing a tight interface betvveen the valve seat 14 and the spherical valvemember 11. Particularly, the embodiments of Fig. 5-6 provide for applying a small pressure, such asa few hg, to the spherical valve member 11. Such small pressures are difficult to provide with ahelical spring having subsequent turns in separate planes. Furthermore, a disc shaped springmember is easy to assemble with the valve seat member 12a, 12b, such as will be discussed below.

Figs. 5 and 6 illustrate embodiments where the rim 131, 231 is arranged completely arounda the spring member 131, 231, such as circumferentially around the spring member 131. Hence, itmay also be provided circumferentially around an end of the valve seat component 12, such as isi||ustrated in Figs 8a-8b.

The rim 131, 231 may form a seal between the valve seat member 12 and at least one ofthe first housing unit 2 and the second housing unit 3, such as when the rim 131, 231 is provided inan elastic material. For the outlet valve 7, the rim 131, 231 may be arranged between the valve seatmember 30a and the first housing unit 2. For the inlet valve 8, the rim 131, 231 may be arrangedbetween the valve seat member 30b and the second housing unit 3. ln the embodiments of Figs. 5, the spring element 133 is formed by at least one slit in anelastic element. The rim 131 may be provided circumferentially around the slit 133. The springmember 130 may be cylindrical, such as disc shaped. The elastic element may provide a seal, suchas by the rim that encircles the at least one slit. The spring member 130 and the seal member maybe formed as a single component. A central portion of the spring member 130 may form the pressurecomponent 132. The pressure provided by the spring member 130 may e.g. be adjusted by the typeof material of the spring element 133, the thickness of the material, and the number and/or shape of lO 12 the at least one slit. The at least one slit may also be arranged for efficient flow of liquid passing thespherical valve member 11. ln this embodiment, three slits are arranged in a triangular patter, with apiece of material separating the vertices of the triangle. Hence, the pressure component 132 isprovided at the center of the triangular slit pattern. ln other embodiments, the at least one slit 133 is semi-circular. Alternatively or additionally,the slit may be straight extending from one side of the rim 131 to the other side of the rim 131. Astraight slit allows for uniform pressure applied on a spherical valve member 11, which in turnprovides for accuracy, particularly for delivery of small amounts of liquid. The number of and/orlength/width of the slits provided may be selected depending on pressures, amount of liquid to bedelivered, biasing force, the material of the spring member 30 etc. For example, the length may be inthe range of 0.5-4 mm.

The embodiment of Fig. 6 illustrates a spring member in the form of a disc spring, whichmay be used for a valve of an infusion pump as discussed above. The disc spring comprises the rim231, the spring element 233, and the pressure component 232 in the center of the disc spring. Thepressure component 232 forms in this embodiment a circumferential seat. The spring element 233 isarranged around the circumferential seat, and the rim 231, the spring element 233, and thecircumferential seat are arranged in a single plane. ln the illustrated embodiment, the rim 231 is ring-shaped, the spring element 233 is spiralwinding and extends from the rim 231 to the circumferential seat. The spring element 233 may havea plurality of circumferential turns. The thickness of the spring element 233 may be smaller than thewidth of each turn or the pattern such that the force exerted by the spring element 233 issubstantially in the axial direction of the spring member 230. Furthermore, the circumferential seat issubstantially circular. ln this embodiment, the helically shaped spring element 233 has a first endconnected to the rim 231, and a second free end. The last turn of the helically shaped spring element233 forms the circumferential seat. ln other embodiments, the circumferential seat is ring shaped, towhich the second end of the spring element 233 is connected. Furthermore, in other embodiments,the rim 233 is formed by the last turn of a winding spring element. Hence, the entire spring element233 may be winding in a single plane. At least a first turn may form the rim 231, and a last turn mayform the circumferential seat. Betvveen the rim 231 and the circumferential seat 233, there may bedistances between each turn at least when assembled in the valve, such that liquid is allowed topass. ln the embodiment of Fig. 6, the spring element 233 is formed by at least one slit 234extending from the rim 231 to a center section of the spring member 230. Again, the rim 231 may beprovided circumferentially around the slit 234. The spring member 230 may be cylindrical, such asdisc shaped. A central portion of the spring member 230 may form the pressure component 232. Thepressure provided by the spring member 230 may e.g. be adjusted by the type of material of thespring member 230, the thickness of the material, and the number and/or shape of the at least one lO 13 slit. The spring member 230 may be made of a metallic material, such as spring steel. The at leastone slit 234 may also be arranged for efficient flow of liquid passing the spherical valve member 11.ln this embodiment, the slit 234 is a spiral slit that forms a spiral spring element 233. The springelement may form one or several turns. ln the illustrated embodiment, the spring element formsalmost four turns, but may be in the range of 3-6 turns. The thickness of the spring member 230, thewidth of the spring element 233, and the shape of the spring element 233 may adjust the springcoefficient of the spring member 230. ln the illustrated embodiment, the spring element 233 ends adistance in the radial direction from the center of the spring member 230. The last turn of the springelement 233 at the center of the spring member may form a substantially circular ridge that forms thepressure component 232. The ridge may have a diameter that is smaller than the maximum diameterof the spherical valve member 11 such that a pressure is applied around the spherical valve member11, as is illustrated in Fig. 8a. ln other embodiments, the spring element 233 connects the rim 231 tothe pressure component 232 in the form of a ring shaped element with a diameter that is smallerthan the maximum diameter of the spherical valve member 11. ln still other embodiments, thepressure component 232 is a plate arranged at the center of the spring member 230. ln other embodiments, the at least one slit 234 forms a meandering pattern betvveen therim 231 and the pressure component 232. ln still other embodiments, the at least one slit 234 formsa cell structure betvveen the rim 231 and the pressure component 232.

The spring member 130, 230 may be arranged to bias the spherical valve member 11towards the valve seat 14. The pressure component 132, 232 may be biased towards the sphericalvalve member 11 by fixing the rim 131, 231 in an appropriate position relative the spherical valvemember. For example, the rim 131, 232 may be arranged between the valve 11 and the first housingunit 2 and/or the second housing unit 3, and the pressure component to abut the spherical valvemember 11 with a desired biasing force towards the valve seat 14. The at least one slit 133, 143allows for movement of the spherical valve member 11 and for liquid to pass through the springmember 130, 230.

As is illustrated in Fig. 2, the rim 130 may be arranged at a ledge 40 of the recess 20a, 20bof the housing 1. For example, the ledge 40 may have a width that substantially corresponds to awidth of the end of the valve seat member 12 at its first recess 13. The rim 131, 231 may be fixedbetvveen the housing 1 and the valve seat member 12a, 12b by applying a pressure to the valve seatmember 12a, 12b, such as by applying a pressure to the second housing unit 3 when assembledwith the first housing unit 2. Hence, efficient assembly of the spring member 30 is provided for.Furthermore, the efficiency may be further improved by providing a seal with the spring member 30.

A height of the ledge 40 in the longitudinal direction of the valve seat member 11 may beshorter than a thickness of the rim 131. This ascertains that a pressure may be applied to the springmember 130, 230 when the valve seat member is assembled in the housing 1. Furthermore, if thespring member 130 is an elastic spring member the height of the ledge 40 may be shorter than the lO 14 thickness of the rim 131 in an uncompressed state. ln Fig. 2, the rim 131 is illustrated in itsuncompressed state for illustration purposes such that the ledge 40 and the rim 131 overlap.However, the rim would be compressed when the components are assembled. When thecomponents are assembled, the valve seat member 11 is assembled in the housing 1 such that itabuts the ledge 40, whereby the rim 131 is compressed a predefined amount, which may provide asea|. At the same time, the pressure component 132 is biased towards the spherica| valve member11 providing a sea| betvveen the spherica| valve member 11 and the valve seat 14. The sameprinciple for providing biasing applies even if the spring member 130, 230 is provided in a non-elasticmaterial, such as the embodiment of Fig. 6. For example, the valve seat member 12 may compressthe rim 31 when the second housing unit 3 is arranged relative the first housing unit 2 in anassembled state.

As can be seen in Figs. 3 and 4, at least one sea| member 50a, 50b may be providedbetvveen the first housing unit 2, 2a and the valve seat member 12a of the outlet valve 7.Correspondingly, at least one sea| 50c, 50d may be provided betvveen the second housing unit 3 andthe valve seat member 12b of the inlet valve 8, or the betvveen the first housing unit 2a and thesecond housing unit 3a, 3b as described with regard to Fig. 4 Fig. 4, such as has been describedabove.

The infusion pump is described above with the outlet valve 7 and the inlet valve 8. Theoutlet valve 7 and the inlet valve 8 may be identical, but oriented differently in the housing 1. Theoutlet valve 7 is arranged with its spherica| valve member 11a towards the outlet 5. The inlet valve 8may be arranged with its spherica| valve member 11b towards the inlet 6. The outlet 5 and the inlet 6may be provided in at least one of the first housing unit 2 and the second housing unit 3. ln theembodiments of Figs. 1 and 4, the inlet 6 is provided entirely in the second housing unit 3, whereasthe outlet 5 is formed partially in the first housing unit 2 and partially in the second housing unit 3. ln some embodiments, the valve seat member 11a of the outlet valve 7 and the valve seatmember 11b of the inlet valve 8 are provided as a single unit. The first recess 13 and the secondrecess 15 are provided in a single component, such as a disc shaped element, for each of the outletvalve 7 and the inlet valve 8. This provides for efficient assembly of the infusion pump, wherein thenumber of components is reduced. A single component may comprise both an inlet valve seatmember and an outlet valve seat member. For such an arrangement, a sea| may be provided oneach side of the single component, which comprises a spring member for biasing the spherica| valvemember 11a, 11b on each side. A sea| may also be shaped for sealing between the outlet 5 and/orinlet 6 and the single component, which may be formed as an integral unit with the spring member,wherein efficient assembly of the infusion pump is provided for.

Embodiments provide a combined sea| and spring member. ln some examples, suchembodiments are used with an infusion pump according to the invention. The combined sea| and lO spring member may be arranged between the valve seat member 11 and at least one of the firsthousing unit 2 and the second housing unit 3 of the infusion pump.

Embodiments provide a method for providing an infusion pump according to theembodiments described above. The method comprises providing the first housing unit 2, whichcomprises at least a portion of the chamber 4 located therein. Also, the second housing unit 3, whichmay have the outlet 5 and/or the inlet 6, is provided. Furthermore, the outlet valve 7, which mayinclude a first spherical valve member 11a and a first valve seat member 12a, may be provided. Theinlet valve 8, which may include a second spherical valve member 12a and a second valve seatmember 11b may, be provided. The outlet valve 7 may be arranged between the chamber 4 and theoutlet 5 in a first space formed by the first housing unit 2 and the second housing unit 3, such asdescribed above. The inlet valve 8 may be arranged between the inlet 6 and the chamber 4 in asecond space formed by the first housing unit 2 and the second housing unit 3, such as describedabove. ln the embodiments described above, the housing 1 is described as comprising a firsthousing unit 2 and a second housing unit 3 that are provided as separate units that are assembledafter the valves 7, 8 are arranged in the first housing unit 2. ln other embodiments, the housing ismade as a single unit, such as by molding the housing 1 around the other components, for examplethe outlet valve 7 and inlet valve 8. ln some embodiments, the infusion pump comprises the housing 1, the chamber 4 locatedin the housing 1, the outlet 5, the outlet valve 7 between the chamber 4 and the outlet 5, the inlet 6,and the inlet valve 8 between the inlet 6 and the chamber 4. At least one of the outlet valve 7 and theinlet valve 8 may comprise a spherical valve member 11a, 11b and a valve seat member 12a, 12b,arranged in the housing. The spring member 30 may be arranged in the housing 1 and to bias thespherical valve member 11a, 11b towards the valve seat 14 of the valve seat member 12a, 12b. Thespring member 30, 130, 230 may be arranged as has been described above with regard to theembodiments of Figs. 1-6. These embodiments are particularly useful for embodiments of theinfusion pump wherein the pressure provided within the chamber 4 is low, and the amount of liquiddistributed by moving the piston 16 within the chamber 4 is small. For example, the piston 16 mayonly move a fraction of the length of the chamber 4 for delivery of a predefined amount of the liquid,such as 0.00010-00050 ml. Thus, the build up of pressure is low when liquid is ejected from thechamber 4. When the chamber 4 is to be re-filled, the piston 16 may traveller with a complete stroke,possibly even faster than when the liquid is ejected. Therefore, depending on the distance and/orspeed the piston is travelling for delivery of a predefined amount of liquid, it may be desired to biasthe spherical valve member 11b for the inlet valve 8. However, it may not be required to bias thespherical valve member 11a for the outlet valve 7. ln other embodiments, the piston 16 moves slowlyduring the inlet phase, wherein it may be desired also to bias the spherical valve member 11a for theoutlet valve 7. ln still other embodiment, such as described above with regard to Figs. 1-6, it may be lO 16 desired that neither the spherical valve member 11a for the outlet valve 7 nor the spherical valvemember 11b for the inlet valve 8 are biased.

The spring member 30, 130, 230 may be configured as has been described above withregard to Figs. 1-6, and be arranged in the housing 1, such as described above with relative to thefirst housing unit 2 and the second housing unit 3. The spring member 30, 130, 230 may be formedas a single integral component providing a seal, such as described above, and may thus be acomponent made of an elastic material. Alternatively, the seal and the spring member 30, 130, 230are provided as separate components.

The spring member 30, 130, 230 may comprise the rim 131, 231 as described above. Therim 131, 231 may be arranged at a ledge 40, also as described above. ln embodiments using the spring member 30, the housing 1 may be made in the samematerial as the valve seat member 11, such as described above. ln other embodiments, the valveseat member 11 and at least one of the first housing unit 2 and the second housing unit 3 are madeof different materials, such as described above. The spring member 30, 130, 230 may be made of athird material, that is more elastic than the material of the housing.

The spherical valve member may be made of an plastic material, such as a metallic or aceramic material.

Fig. 7 illustrates the inlet 6 of the infusion pump according to the embodiments describedabove arranged in fluid communication with a reservoir for a liquid medicament or a nutrient. Whennot othen/vise described, aspects described with reference to the valve 10 and its arrangement withinthe housing 1 of the infusion pump, such aspects are applicable to any of the outlet valve 7 and theinlet valve 8. The reservoir may have an arbitrary shape and may be collapsible.

Still alternative embodiments provide a method for providing an infusion pump. Suchalternative methods includes providing a housing comprising a chamber 4, an outlet 5, and an inlet 6;providing an outlet valve 7 comprising a first spherical valve member 11a and a first valve seatmember 12a, which comprises a first valve seat 14; providing an inlet valve comprising a secondspherical valve member 11b and a second valve seat member 12b, which comprises a second valveseat 14; providing at least one spring member 30, 130, 230; arranging the outlet valve 7 between thechamber 4 and the outlet 5; arranging the inlet valve 8 betvveen the chamber 4 and the inlet 6;biasing at least one of the first spherical valve member 11a towards the first valve seat 12a and thesecond spherical valve member 11b towards the second valve seat 12b using said at least onespring member 30, 130, 230.

The method may comprise arranging the spring member 30, 130, 230 as has beendescribed above with regard to Figs. 1-7. ln still other embodiments, the valve 10 may be provided as a pre-assembled componentthat may be produced and tested separately before assembly with the other components of theinfusion pump. lO 17 Figs. 8a-8b illustrates embodiments of a pre-assembled valve 410 that comprises aspherical valve member 11, a valve seat member 12, and a spring member 230. The spring membermay be seated at a ledge 413 formed at a proximal end of a recess 414 at one end of the valve seatmember 12. The spherical valve member 11 is arranged at least partially betvveen the ledge 413 andthe valve seat 14. The valve seat 14 may be arranged at a distal end of the recess 414. A smallportion of the spherical valve member 11 extends betvveen the end of the valve seat member 12 andthe ledge 413 such that it is biased towards the valve seat 14, as has been discussed before. Thediameter of the recess 414 at its proximal end may be slightly smaller than the remaining portion ofthe recess towards the ledge 413, whereby at least one flange 415 is provided at the proximal end ofthe valve seat member 12. The flange 415 may extend towards the central longitudinal axis of therecess 414 and have a minimum diameter slightly smaller than a maximum diameter of the springmember 230. Hence, the spring member may be secured in the recess 414 betvveen the ledge 413and the flange 415. The spring member 230 is illustrated as spiral, but may have other shapes asdiscussed above. ln the illustrated embodiments, the valve seat member 12 has two circumferentialrecesses for receiving seal members 50a, 50b (not illustrated), such as o-rings, to seal against thefirst and/or the second housing member 2, 3, such as described above. ln other embodiments one,more than two, or no such recesses are provided. Providing the valve 410 as a pre-assembledcomponent provides for efficient assembly of the infusion pump. The valve 410 may be a criticalcomponent for the functioning of the infusion pump. Hence, when provided as a separatecomponent, it may be quality tested before assembly with the other components. That means thatonly approved valves are assembled with the other components. Hence, the scrap compared toperforming the quality testing after assembly with the housing components may be reduced. Hence,an overall more efficient assembly of the infusion pump is provided for. Furthermore, it may beproduced with productions techniques, such as milling, which is more accurate than productiontechniques used for the housing.

The infusion pump of the embodiments of presented above may be contained in aninfusion pump device, such as an insulin pump. The piston 16 may be connected to a motor, such asa step motor or a piezo motor, which is controlled by various electronics and one or severalcontrollers. The motor may move the piston 16 in at least one step for delivery of a pre-definedamount of liquid, such as a fraction of a unit of insulin. The length of movement of the piston isdependent on the size of the chamber 4, which is fixed, and the amount to be delivered, which isvariable. The amount to be delivered may be set in a user interface, and controller software maycontrol the length of travel of the piston 14. The controller software may also be configured to controlamount of liquid in the chamber 4, in order to re-fill the chamber 4 at defined intervals, such as whena particular amount of liquid has been delivered betvveen tvvo-refills of the chamber 4, or when aminimum amount of liquid in the chamber 4 has been reached. lO 18 As will be apparent, the features and attributes of the specific embodiments disclosedabove may be combined in different ways to form additional embodiments, all of which fall within thescope of the present disclosure.

Conditional language used herein, such as, among others, “can,” “cou|d,” “might,” “may,”“e.g.,” and the like, unless specifically stated othen/vise, or othen/vise understood within the contextas used, is generally intended to convey that certain embodiments include, while other embodimentsdo not include, certain features, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are in any way required for one ormore embodiments or that one or more embodiments necessarily include logic for deciding, with orwithout author input or prompting, whether these features, elements and/or states are included or areto be performed in any particular embodiment.

Any process descriptions, elements, or blocks in the flow diagrams described herein and/ordepicted in the attached figures should be understood as potentially representing modules,segments, or portions of code which include one or more executable instructions for implementingspecific logical functions or steps in the process. Alternate implementations are included within thescope of the embodiments described herein in which elements or functions may be deleted,executed out of order from that shown or discussed, including substantially concurrently or in reverseorder, depending on the functionality involved, as would be understood by those skilled in the art.

The present invention has been described above with reference to specific embodiments.However, other embodiments than the above described are equally possible within the scope of theinvention. Different method steps than those described above may be provided within the scope ofthe invention. The different features and steps of the invention may be combined in othercombinations than those described. The scope of the invention is only limited by the appendedpatent claims.

Claims (15)

1. An infusion pump, comprising housing including a first housing unit and a second housing unit; a chamber located at least partially in the first housing unit; an outlet; an outlet valve between the chamber and the outlet; an inlet; and an inlet valve betvveen the inlet and the chamber; wherein at least one of the outlet valve and the inlet valve is arranged betvveen the first housing unit and the second housing unit.

2. The infusion pump according to claim 1, wherein at least one of the outlet valveand the inlet valve comprises a spherical valve member and a valve seat member, and thevalve seat member and at least one of the first housing unit and the second housing unit aremade of different materials.

3. The infusion pump according to claim 2, wherein the valve seat member ismade of a metallic material and comprises a valve seat having a radius corresponding to aradius of the spherical valve member, and the first housing unit comprises a recess forreceiving at least a portion of the valve seat member, the first housing unit being made of anon-metallic material.

4. The infusion pump according to claim 2 or 3, wherein the first housing unit andthe second housing unit are made of the same material and together form a space forenclosing at least one of the outlet valve and the inlet valve, and wherein the valve seatmember comprises a recess, in which the spherical valve member is at least partiallyarranged.

5. The infusion pump according to claim 4, wherein the first housing unit comprisesa recess sized for receiving at least a portion of the second housing unit, and wherein the firsthousing unit is joined to the second housing unit.

6. The infusion pump according to claim 4 or 5, further comprising a springmember arranged to bias the spherical valve member towards a valve seat of the valve seatmember. lO

7. The infusion pump according to claim 6, wherein the spring member comprisesa disc spring, such as a spiral disc spring.

8. The infusion pump according to claim 6 or 7, wherein the spring membercomprises a rim arranged at least partially around a circumference of the spherical valvemember.

9. The infusion pump according to claim 8, wherein the rim is ring shaped andarranged completely around the circumference of spherical valve member, and wherein therim forms a seal between the valve seat member and at least one of the first housing unit andthe second housing unit.

10. The infusion pump according to any of claims 8 to 9, wherein a spring elementof the spring member is formed by at least one slit in a center portion of the spring member.

11. The infusion pump according to any of claims 8 to 10, wherein the sphericalvalve member is arranged at least partially between the valve seat member and the rim, andwherein a pressure component of the spring member connected to the rim via a springelement and arranged in abutment with the spherical valve member is biased towards andmoveable relative the valve seat.

12. The infusion pump according to claim 10 or 11, wherein the rim of the springmember is arranged at a ledge of at least one of the first housing unit and the second housingunit, wherein a height of the ledge is lower than a thickness of the rim in an uncompressedstate, and wherein the rim is compressed by the valve seat member when the second housingunit is arranged relative the first housing unit in an assembled state.

13. A reservoir for a liquid medicament or a nutrient arranged in fluidcommunication with the inlet of the infusion pump according to any of the previous claims.

14. A disc spring arranged between a valve seat member of at least one of theoutlet valve and the inlet valve and at least one of the first housing unit and the secondhousing unit of the infusion pump of any of claims 1 to 12.

15. A method for providing an infusion pump, comprisingproviding a first housing unit having a chamber located therein;providing a second housing unit having an inlet and an outlet; lO providing an outlet valve; providing an inlet valve; arranging the outlet valve between the chamber and the outlet in at least onespace formed by the first housing unit and the second housing unit; and arranging the inlet valve between the inlet and the chamber in said at least onespace formed by the first housing unit and the second housing unit.