WO2007143992A1

WO2007143992A1 - A pump

Info

Publication number: WO2007143992A1
Application number: PCT/DK2007/000281
Authority: WO
Inventors: Peter Gravesen; René Bøgelund NYBERG
Original assignee: Danfoss A/S
Priority date: 2006-06-12
Filing date: 2007-06-12
Publication date: 2007-12-21

Abstract

The invention provides a membrane pump e.g. for a mini or micro channel system. The pump has a fluid conduit from an inlet through a displacement chamber with a variable volume to an outlet. The conduit is formed in a first component, and a displacement actuation structure adapted to affect volume change of the displacement chamber as well as an upstream and a downstream valve structure adapted force the fluid in one direction are separated from the fluid and detachably attachable to an outer surface of a first component which forms the fluid conduit. The invention therefore facilitate a simple and reliable pump of which some components can be reused while one component which is contaminated by the pumped fluid, can be disposed of.

Description

A PUMP

INTRODUCTION

The invention relates to a membrane pump with an inlet, an outlet and a membrane which defines a displacement chamber with a variable volume. The pump further comprises an upstream valve structure adapted to restrict a fluid flow from the displacement chamber to the inlet, and a downstream valve structure adapted to restrict a fluid flow from the outlet to the displacement chamber. More particularly, the invention relates to a mini or micro channel pump.

BACKGROUND OF THE INVENTION

US 6,796,215 discloses a membrane pump with a membrane which delimits a conveying space. A pump drive provides an oscillating movement of the membrane whereby a fluid is sucked from a suction side and delivered to a pressure side. The disclosed pump has a relatively complex structure requiring extensive machining and accuracy during manufacturing. Furthermore, the disclosed pump is not suitable for a micro channel system. Also US 6,572,566 discloses a pump for moving liquid through a channel by means of pressure and underpressure.

A micromachined peristaltic pump is disclosed in us 6,007,309. Again, the disclosed pump requires extensive machining and would typically not be suitable e.g. in connection with disposable "one time" use. Another pump with a stretchable membrane is disclosed in US 6,948,918. Again, the disclosed pump is expensive and relatively complicated to produce. DESCRIPTION OF THE INVENTION

It is an object of embodiments of the present invention to provide a membrane pump which is simple and reliable, and which facilitates one time use. According to a first aspect, the invention provides a pump wherein the upstream valve structure, the downstream valve structure and the displacement actuation structure are separated from the fluid and wherein these structures are detachably attachable to an outer surface of a first component which first component forms the fluid conduit.

Since the upstream valve structure, the downstream valve structure and the displacement actuation structure are detachably attachable to the first component and since they are separated from the fluid, the first component could be disposable while the valve and displacement structures could be used several times. Accordingly, the pump according to the invention facilitates a simple and reliable design with reuse of certain parts and disposal of other parts.

"Fluid conduit' is any kind of channel enabling a flow of a fluid, e.g. a liquid medium. The inlet and outlet are any kind of openings into and out of the channel, respectively, and the displacement chamber has a volume which can be varied. When the volume is increased, the fluid is sucked from the inlet and into the chamber. During this first pumping step, the downstream valve structure restricts flow of fluid from the outlet to the chamber. In a subsequent, second, pumping step, the volume is decreased whereby the liquid is displaced out of the chamber and out through the outlet. During the second pumping step, the upstream valve structure restricts a fluid flow from the chamber and out through the inlet.

The displacement chamber could be formed by an elastically deformable wall, and the deformation of the wall could be caused by any kind of displacement actuation structure capable of deforming the wall either by direct contact or by providing a pressure difference across the wall.

The upstream valve structure could be a passive structure which is operated by a pressure difference so that the conduit is essentially unaffected by the upstream valve structure when the pressure in the inlet is higher than the pressure in the displacement chamber, i.e. during the first pumping step. In the second pumping step, i.e. when the fluid is subsequently pumped out of the displacement chamber, the pressure in the chamber increases, and the increase activates the upstream valve structure which restricts flow backwardly towards the inlet. By the word "restrict" is meant that the flow resistance is increased or that flow is completely prevented. The upstream valve structure could also be an active structure which is operated electrically or mechanically based on the movement of the displacement actuation structure or based on movement of the wall of the displacement chamber. An active structure may comprise magnetically operated valves or electrically operated actuators which deform the conduit and thereby restricts fluid flow through the conduit. The same applies with respect to the downstream valve structure which could be passive and leave the conduit essentially unaffected when the pressure in the outlet is lower than the pressure in the displacement chamber and to restrict the flow, when the volume of the displacement chamber increases during the filling of the chamber with fluid from the inlet and the pressure in the chamber thus decreases. The downstream valve structure could also, in accordance with the upstream valve structure, be actively controlled based on volume changes of the displacement chamber.

In order to simplify manufacturing and thus to facilitate low cost manufacturing, or small dimensions of the pump, the fluid conduit could be formed between a base and a membrane which is more flexible than the base. By "more flexible" is meant elastically deformable by use of less force than what would have been required to elastically deform the base, if the base is elastically deformable at all.

The base could e.g. be a relatively rigid plate e.g. of silicon, glass, plastic etc and the conduit could be formed as a groove or depression in an upper surface of the base. The membrane is subsequently attached to the upper surface to cover the groove. The membrane may form the outer surface of the first component to which the valve and displacement actuation structures are detachably attached. The membrane may, however, also be covered at least partly by a top layer which is less flexible than the membrane. The top layer may comprise an aperture pattern exposing a surface portion of the membrane towards the valve structures and towards the displacement actuation structure. The top layer may further comprise attachment means, e.g. screw threaded holes etc. for attachment of the valve structures and the displacement actuation structure. In the last mentioned embodiment, the membrane is sandwiched between the base and the top layers. The base and top could be made from the same material and e.g. in essentially the same thickness. Preferably, the outer surface of the first component is an essentially planar surface.

Preferably, the fluid is isolated in the conduit between the inlet and the outlet so that only the first component is in contact with the fluid in question. Accordingly, the fluid conduit may preferably extend uninterruptedly between the inlet and the outlet. The valve and pump actuation structures preferably operate directly on the outer surface of the membrane by deforming the membrane at various contact portions of the membrane.

A passive valve structure can be provided by a lever arm which is pivotally hinged at a hinge point. The lever arm comprises a first contact portion at which the lever arm is pushed by the outer surface of the membrane and a second contact portion at which the lever arm pushes against the outer surface of the membrane.

In the upstream valve structure, the first and second contact portions of the lever arm are located on opposite sides of the hinge point so that, when the first portion is moved upwardly, away from the conduit, the second portion is moved downwardly towards and into the conduit thereby limiting fluid flow in the conduit.

In the downstream valve structure, the first and second contact portions are on the same side of the hinge point so that, when the first portion is moved upwardly, away from the conduit, the second portion is also moved upwardly out of the conduit thereby increasing a fluid flow in the conduit.

The ratio between the pressure which is applied by the membrane onto the lever arm and the corresponding pressure applied by the lever arm onto the membrane can be adjusted by adjustment of the length from the hinge point to each of the first and second contact points or by selecting different flexibilities for different portions of the membrane, i.e. at the corresponding two contact portions of the membrane, or by allowing different sized areas of the membrane to deflect inwardly and outwardly, respectively. The last mentioned different sized areas can be achieved by the aforementioned top layer in which the aperture sizes at the two contact portions could be of different size.

The lever arm of the downstream valve structure may preferably be biased towards a closed position wherein the second portion is moved into the conduit when the first portion is not influenced by the membrane, and the lever arm of the upstream valve structure may preferably be biased towards an open position wherein the second portion is only moved into the conduit when the first portion is influenced by the membrane. The displacement actuation structure may preferably be formed in one component with the valve structures, and this single component could be detachably attached to the first component e.g. by use of screws, rivets etc or by use of a strap of an elastically deformable material or similar means which bias the single component against the outer surface of the first component.

DETAILED DESCRIPTION OF THE INVENTION

In the following, a preferred embodiment of the invention will be described in further details with reference to the drawing in which:

Fig. 1 illustrates a pump according to the invention in an "open state",

Fig. 2, illustrates a pump according to the invention in a "closed state",

Fig. 3 and 4 illustrate a downstream valve structure in further details, and

Figs. 5 and 6 illustrate an upstream valve structure in further details,

Referring to Figs. 1 and 2, the pump 1 comprises a first component 2 consisting of a base, a membrane, and a top layer (shown in further details in Fig. 3). The pump is adapted for pumping a fluid in a flow direction indicated by the arrow 3 from an inlet 4 to an outlet 5. The pump comprises a fluid conduit 6 extending from the inlet to the outlet. Between the inlet and outlet, the conduit forms a displacement chamber 7. A displacement actuation structure 8 is adapted to affect volume change of the displacement chamber 7. In Fig. 1 , the pump is illustrated in a situation wherein the actuation structure is drawn backwardly to increase the volume of the chamber and thereby to cause a flow of a fluid from the inlet 4 to the chamber 7. The pump comprises an upstream valve structure 9 which is adapted to restrict a fluid flow from the displacement chamber to the inlet 4 when the fluid is pumped out of the displacement chamber 7, c.f. Fig. 2. In Fig. 1 , the upstream valve structure is in an open state wherein fluid is allowed to flow from the inlet to the displacement chamber. The pump further comprises a downstream valve structure 10 adapted to restrict a fluid flow from the outlet 5 to the displacement chamber 7 when the chamber 7 receives fluid from the inlet.

As shown, the upstream valve structure 9, the downstream valve structure 10 and the displacement actuation structure 8 are separated from the fluid. Since all of the structures operate on an outer surface of the membrane, all three structures may be detachably attached to the outer surface of the first component 2. The displacement actuation structure 8 operates on the chamber 7 formed by an enlarged opening in the top layer, which opening exposes the membrane towards the displacement actuation structure. In a similar manner, the upstream valve structure 9 cooperates with the membrane through first and second enlarged openings 11 , 13 in the top layer, and the downstream valve structure 10 cooperates with the membrane through first and second enlarged openings 12, 14 in the top layer.

Figs. 3 and 4 illustrate in further details the downstream portion of the pump with the downstream valve structure 10. As indicated, the valve structure comprises a cantilever 12 which is pivotally hinged at the hinge point 15 and comprises a portion 16 which is pushed upwardly by the membrane when the pressure increases and a portion 17 which in its normally closed state pushes against the membrane and thus restricts a fluid flow towards the outlet. When the pressure in the conduit increases, the cantilever is lifted by the relatively large surface area 12 whereby the portion 18 is lifted away from the membrane, and the flow resistance towards flow between the chamber 7 and the outlet 5 decreases. The valve is biased towards the normally closed configuration by the spring 19. As it readily appears, the valve is controlled by a pressure difference between pressure in the conduit and ambient pressure.

Fig. 3 illustrates the 3 layer sandwich structure with a rigid base plate 20, a more flexible membrane 21 and a top layer 22 in which an aperture pattern exposes an upper surface of the membrane towards the displacement actuation structure 8 and towards the valve structures 9, 10.

Figs. 5 and 6 illustrate in further details the upstream portion of the pump in which the cantilever 23 is pivotally hinged at the hinge point 24. One end 25 of the cantilever is pushed upwardly when the membrane deforms upwardly due to an increasing pressure in the conduit while the other end 26 is pressed downwardly onto the membrane and thereby restricts the flow of fluid from the chamber 7 towards the inlet 4 when the volume of the chamber is decreased.

Claims

1. A membrane pump for pumping a fluid, the pump comprising:

- a fluid conduit from an inlet through a displacement chamber with a variable volume to an outlet,

- a displacement actuation structure adapted to affect volume change of the displacement chamber,

- an upstream valve structure adapted to restrict a fluid flow from the displacement chamber to the inlet, and

- a downstream valve structure adapted to restrict a fluid flow from the outlet to the displacement chamber,

characterized in that the upstream valve structure, the downstream valve structure and the displacement actuation structure are separated from the fluid and that they are detachably attachable to an outer surface of a first component which forms the fluid conduit .

2. A pump according to claim 1 , wherein the fluid conduit is formed between a base and a membrane which is flexible relative to the base, the first component comprising an outer surface to which the upstream valve structure, the downstream valve structure and the displacement actuation structure is detachably attachable.

3. A pump according to claims 1-2, wherein the fluid conduit extends uninterruptedly between the inlet and the outlet.

4. A pump according to any of the preceding claims, wherein the membrane forms the outer surface.

5. A pump according to claims 1-3, wherein a top layer which is less flexible than the membrane forms the outer surface.

6. A pump according to claim 5, wherein the top layer comprises an aperture pattern exposing a surface portion of the membrane towards the valve structures and the displacement actuation structure.

7. A pump according to any of the preceding claims, wherein the displacement actuation structure is adapted to displace the membrane by providing a pressure differential across the membrane.

8. A pump according to any of the preceding claims, wherein at least one of the upstream and downstream valve structures is a passive structure which restricts the fluid flow based on a pressure in the conduit.

9. A pump according to claim 8, wherein each passive structure restricts the flow based on a pressure difference between pressure in the conduit and a pressure of an ambient space.

10. A pump according to any of the preceding claims, wherein the upstream valve structure comprises a lever arm with first and second contact portions operating on the outer surface on opposite sides of a hinge point so that, when the first portion is moved upwardly, away from the conduit, the second portion is moved downwardly towards and into the conduit thereby restricting fluid flow in the conduit.

11. A pump according to claim 10, wherein the lever arm is biased towards an open position wherein the second portion is moved out of the conduit when the first portion is not influenced by the membrane.

12. A pump according to any of the preceding claims, wherein the downstream valve structure comprises a lever arm with first and second contact portions operating on the outer surface on the same side of a hinge point so that, when the first portion is moved upwardly, away from the conduit, the second portion also moved upwardly out of the conduit thereby increasing a fluid flow in the conduit.

13. A pump according to claim 12, wherein the lever arm is biased towards a closed position wherein the second portion is moved into the conduit when the first portion is not influenced by the membrane.

14. A pump according to any of the preceding claims, wherein the outer surface is essentially plane.

15. A pump according to any of the preceding claims, wherein the valve structures are formed in one component.

16. A pump according to claim 14, wherein the displacement actuation structure is formed in one component with the valve structures.