WO2009031018A2

WO2009031018A2 - Check valve for a medical device

Info

Publication number: WO2009031018A2
Application number: PCT/IB2008/002305
Authority: WO
Inventors: Alice Ravizza; Marco Goldoni
Original assignee: Haemotronic Advanced Medical Technologies SpA
Current assignee: Haemotronic Advanced Medical Technologies SpA
Priority date: 2007-09-05
Filing date: 2008-09-05
Publication date: 2009-03-12
Anticipated expiration: 2010-03-05
Also published as: ITVR20070126A1; WO2009031018A3

Abstract

A check valve for a medical device comprising: an inlet duct (2); an outlet duct (1); a membrane (3); a compartment (4) for housing said disc membrane (3); a plurality of protuberances (9) inside the compartment (4) and configured to define a support for the disc membrane (3) when the valve is open, the disc membrane (3) being housed in a floating manner inside the compartment (4) so as to divide the compartment (4) into an inlet compartment (5) and an outlet compartment (6).

Description

"CHECK VALVE FOR A MEDICAL DEVICE"

TECHNICAL FIELD

The present • invention refers to a selective valve for regulating the flow inside a hydraulic circuit, in particular for medical applications.

BACKGROUND ART

Different types of flow regulation valves are known, in particular check valves permit the flow in an anterograde direction in the hydraulic circuit which comprises the valve but ideally prevent the flow in the retrograde direction.

Various types of check valves are known, for example duckbill check valves consist of two coplanar lips which in the non- deformed position are ideally adjacent, thus completely blocking the aperture for passage of the flow. Said lips are moved away from each other by an anterograde flow, thus forming an aperture for the passage of said anterograde flow, whereas in the presence of a retrograde flow with sufficient flow rate, due to the elastic properties of their component material, said lips move back again until they adhere to each other and block the aperture.

Said valves in the state of the art have the characteristic of not being completely sealed in the non-deformed position; furthermore a retrograde flow with sufficient flow rate can burst the valve, turning the lips inside out, thus making the valve totally ineffective. Duckbill valves are generally used in extracorporeal fluid circuits, such as circuits for the infusion of drugs or solutions or for extracorporeal blood circulation.

Another type of check valve known in the state of the art is the umbrella valve; said valve consists of a stem coaxial with the axis of the aperture for passage of the fluid and a cap perpendicular to the axis of the aperture . The stem is held in place by a retaining ring also coaxial with the aperture, on which the edges of the cap rest . In the case of an anterograde flow, the fluid in transit passes into the coaxial channel formed by the compartment between the retaining ring and the valve stem; the pressure created on the edges of the cap raises said edges from their seat thus permitting the formation of an aperture for passage of the fluid in an anterograde direction. In the case of a retrograde flow, the edges of the cap are pushed by the pressure created on them against the retaining ring, thus completely blocking the aperture. The intrinsic characteristics of said valves are the high opening pressure and the considerable obstacle to the flow presented by the narrowing of the aperture due to the presence of the retaining ring and the valve stem.

A third type of check valve commonly used is the plane umbrella valve. Said valve consists of a plate or disc positioned square to the axis of the aperture for passage of the fluid and a system for retaining said plate or disc; various systems for retaining said plate are known in the state of the art such as rings, cages, rotation pins, springs etc. In the case of an anterograde flow, as a result of the pressure developed on the plate by the moving fluid, the plate performs the rototranslation permitted by the connected retaining system thus opening an aperture for passage of the fluid. In the case of a retrograde flow, the pressure of the fluid and/or the action of the moving parts of the retaining mechanism (e.g. spring) act on the plate causing it to close the aperture for passage of the fluid. Said valves have the intrinsic characteristic of presenting a considerable obstacle to the flow, consequently causing a high pressure drop and turbulence; in applications involving blood, said characteristics increase the risk of formation of clots.

Said plane umbrella valves provided with retaining systems such as the cages are normally applied to the human body and are not extracorporeal.

DISCLOSURE OF INVENTION The object of the present invention is to produce a check valve which allows selection of the type of fluid passing through and selection of the flow direction.

A further object of the present invention is to produce a check valve suited to extracorporeal applications and suitable for maintaining the closed position also in the presence of corpuscles or clots transported by the fluid flowing inside it.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, it will be further described with reference to the accompanying figures, in particular: figure 1 is a schematic axial section of a check valve according to the present invention in an open position; figure 2 is an axial section of the valve of figure 1 in a closed position; figure 3 is an axial section of a second embodiment of the present invention; and figure 4 is an enlarged view from below of a component of figure 3.

BEST MODE FOR CARRYING OUT THE INVENTION

The valve object of the present invention consists of an inlet duct (2) which lets the fluid into the valve, an outlet duct

(1) which allows the fluid to flow out of the valve, a disc membrane (3) which performs the selective function of the present invention, and a compartment (4) housing said disc membrane (3) shaped so as to allow said disc membrane to perform a translating movement. In particular, the disc membrane (3), as illustrated in the figures, is floating inside the compartment (4) .

The inlet duct (2) leads to the section of the compartment (4) called inlet compartment (6) ; the wall (8) of the inlet compartment (6) containing the outflow end of the inlet duct (2) is curved and the outflow end of the inlet duct (2) is in the centre of said curved wall (8) .

The outlet duct (1) leads to the section of the compartment (4) called outlet compartment (5) ; the wall (7) of the outlet compartment (5) containing the intake end of the outlet duct

(1) is provided with protuberances (9) arranged so as to form channels converging towards the centre of said wall (7) and the intake end of the inlet channel (1) is located at the convergence of said channels .

According to the present invention, the disc membrane (3) is floating in the sense that it has no portion rigidly connected either to the wall (7) or to the wall (8) . The compartment (4) housing the disc membrane (3) is divided by said membrane into two areas called inlet compartment (6) and outlet compartment (5) . The compartment itself (4) is shaped so as to permit translation of the disc membrane (3) only in the direction parallel to the axis of the anterograde flow, i.e. from a position of proximity to the protuberances (9) of the wall (7) to a position of proximity to the wall (8) and vice versa.

The membrane (3) consists of an essentially flat disc made of flexible material with diameter comparable to the diameter of the wall (7) ; the physical characteristics of flexibility of the component material of the disc membrane (3) allow it to deform into a concave shape when the membrane adheres to the wall (8) .

Since the disc membrane (3) has a diameter comparable with that of the wall (7) and adheres in the closing position to the wall (8) , there is a large contact area in the closed position. According to a preferred embodiment, the disc membrane (3) has a diameter at least double than that of the internal diameter of the inlet duct (2) .

In the case of an anterograde flow (see fig. 1) passing inside the valve, the disc membrane (3) is positioned near the protuberances (9) of the wall (7) and has the shape of an undeformed disc; the fluid therefore passes through the inlet duct to the inlet compartment (6) and from the latter to the outlet compartment (5) lapping the edges of the membrane and subsequently flowing out of the compartment (5) to the outlet channel (1) via the channels formed by the protuberances (9) . In the case of an anterograde flow the valve is therefore open.

In the case of retrograde flow with sufficient mass transit in the unit of time (see figure 2) the valve adheres to the wall

(8) and deforms into a concave shape; the membrane therefore blocks the inlet duct (2) and the fluid is retained inside the valve and consequently interrupted. In the case of a retrograde flow the valve is therefore closed.

The translation from the open position to the closed position is performed selectively according to the mass of fluid passing inside the valve in the unit of time. In fact, the disc membrane has an inertia and a greater force is required to overcome said inertia and permit translation from the open position to the closed position of the membrane. Said force is developed by the fluid passing through.

It follows that, all other conditions being equal, there is a minimum retrograde flow passing through in the unit of time

(therefore a flow rate) which overcomes the inertia of the membrane and cause the valve to close. Said flow rate is called "activation flow rate" and, when the fluid passing through is known, it depends on the chemical-physical and dimensional characteristics of the membrane. In said situation, the valve permits selection of the retrograde flows. In said situation furthermore the membrane, when applied to the selection of blood flows, permits a certain quantity of retrograde flow, thus reducing the probability of clot formation.

Vice versa, when the flow rate of the flow passing through is known, the activation flow rate depends on the specific gravity of the fluid itself. In said situation, the membrane allows selection of the type of fluid passing through.

With the membrane construction technique, therefore, the dimensions and chemical-physical characteristics of the membrane can be designed so as to perform the envisaged selective action on the type of fluid or type of flow, as required.

The construction technique further permits construction of the valve in parts that can be assembled subsequently thus permitting the insertion of flexible membranes with different characteristics, maintaining the housing unchanged and therefore reducing the production costs of the various valve models.

The construction technique furthermore provides for construction of the valve with sterilisable materials with one or more of the techniques known in the state of the art . Said materials are furthermore suitable for undergoing other post- production treatments such as micro-coating or coating of the aperture .

The valve is designed for disposable use.

Furthermore, the valve according to the present invention ensures operation without obstructions, for example clots, since it has a simple structure without surfaces or elements to which said clots can adhere, thus affecting the seal of the disc membrane (3) when the valve is closed.

In fact, the opening condition is guaranteed by the presence of the protuberances (9) . The closing condition is guaranteed by the deformability of the membrane which in the closed condition reproduces the form of the wall (8) since it adheres to the latter.

A clot may be larger than the radial clearance with which the disc membrane (3) is fitted inside the compartment (4) .

In this case, the membrane modifies its position since it is floating and furthermore can deform locally along its edge to permit passage of the corpuscle towards the outlet duct (1) .

According to a preferred embodiment, the protuberances (9) can have a flattened shape and mid planes substantially radial with respect to the axis of the outlet duct (1) . In this way, they offer a minimum surface for adhesion of the clots.

The protuberances (9) are fewer than eight, preferably fewer than four, even more preferably 3. This provides the smoothest possible passage for the clots and the disc membrane (3) can deform easily on its edge. The protuberances (9) can be either axially symmetrical or non-axially symmetrical. For example, there are 3 protuberances (9) , two of which are symmetrical with respect to a plane passing through the third and through the axis of the outlet duct (1) (see figure 4) . Preferably, the two symmetrical protuberances (9) are arranged on the opposite side to the non- symmetrical protuberance with respect to the outlet duct (1) . Furthermore, the two symmetrical protuberances (9) are angularly spaced from each other by an angle narrower than the one defined by each protuberance with the non- symmetrical protuberance (9) .

According to an alternative embodiment, the wall (8) has the form of a truncated cone (figure 3) .

The valve can be used in extracorporeal fluid circuits such as a blood transfusion circuit for adults or children, a circuit for the infusion of drugs or solutions in general and in particular of heparin. Said circuits require tubes having different diameters. The valve can be connected to said tubes either by directly modifying the geometry of the inlet ducts

(2) and outlet ducts (1) or by means of connection fittings.

Claims

1. A check valve for a medical device comprising: an inlet duct (2) ; an outlet duct (1) ; a membrane (3) ; a compartment (4) housing said disc membrane (3) ; a plurality of protuberances (9) inside the compartment (4) configured to define a support for the disc membrane (3) when the valve is open, the disc membrane (3) being housed in a floating manner inside the compartment (4) so as to divide the compartment (4) into an inlet compartment (5) and an outlet compartment (6) .

2. The valve as claimed in claim 1 CHARACTERISED IN THAT said membrane (3) is flexible.

3. The valve as claimed in any one of the preceding claims CHARACTERISED IN THAT it comprises a first wall (7) crosswise to the outlet duct (1) and partially delimiting the outlet compartment (5) and a second wall (8) crosswise to the inlet duct (2) and partially delimiting the inlet compartment (6) , and in that the compartment (4) housing the disc membrane (3) is configured so as to permit the movement of the membrane (3) between the first wall (7) and the second wall (8) .

4. The valve as claimed in claim 3, CHARACTERISED IN THAT the second wall (8) is tapered.

5. The valve as claimed in any one of the claims 3 or 4 CHARACTERISED IN THAT the protuberances extend from the wall (7) in the outlet compartment (5) to define channels and the intake end of the outlet duct (1) is located at the confluence of said channels .

6. The valve as claimed in any one of the claims from 3 to 5 CHAACTERISED IN THAT in the "closed" position the membrane (3) is deformed and adheres to the curvature of the wall (8) of the inlet compartment (6) so as to block the inlet duct (2) and prevent the retrograde flow.

7. The valve as claimed in any one of the claims from 3 to 6 CHARACTERISED IN THAT the membrane (3) passes from an "open" position to a "closed" position translating inside the housing compartment (4) towards the wall (8) of the inlet compartment (6) subsequently deforming until it adheres to the curvature of said wall (8) so as to block the inlet duct (2) and prevent the retrograde flow.

8. The valve as claimed in any one of the preceding claims CHARACTERISED IN THAT the passage from the "open" position to the "closed" position is selectively activated by a predefined quantity of fluid mass passing through said valve in the unit of time called "activation flow rate" .

9. The valve as claimed in any one of the preceding claims CHARACTERISED IN THAT said "activation flow rate" depends on the chemical-physical and dimensional characteristics of the membrane (3) .

10. The valve as claimed in any one of the preceding claims CHARACTERISED IN THAT the passage from the "open" position to the "closed" position is selectively activated, all other conditions being equal, by the specific gravity of the fluid passing through, thus permitting selection of the type of fluid passing through.

11. The valve as claimed in any one of the preceding claims CHARACTERISED IN THAT the passage from the "open" position to the "closed" position is selectively activated, all other conditions being equal, by the velocity of the fluid passing through, thus permitting selection of the retrograde flows.

12. The valve as claimed in any one of the preceding claims CHARACTERISED IN THAT said valve can be sterilised according to one of the methods known in the state of the art and can undergo other post-production treatments.

13. The valve as claimed in any one of the preceding claims CHARACTERISED IN THAT it is disposable.

14. An extracorporeal medical device CHARACTERISED IN THAT it comprises a valve as claimed in any one of the preceding claims.