BACKGROUND OF THE INVENTION There exist many devices and methods for controlling fluid flows, whether these flow are in open channels or in closed conduits. Areas in which such devices and methods find use include medical, industrial, automotive, aeronautical, sewage treatment and water management, among many others.

Many of these areas require very precise control of small quantities of fluid.

Such areas include medical infusion systems pharmaceuticals production, various vehicle systems. In many of these areas, complex mechanical or electromechanical solutions exist, although attempts have been made to find electromagnetic solutions.

An indication of the state of the art is provided by US Patent No. 3,982,722, entitled "Magnetic Control Valve." This patent describes a fluid control, valve for a fluid system , particularly an air-conditioning system in a vehicle. A flow passage in the system is defined by a "radially flexible tubular member so that the flow area" thereof is variable. Three electromagnets are arranged coaxially about the tubular member, such that an annular space is formed between the electromagnets and the tubular member. Of the three electromagnets, the internal diameter of the middle one is smaller than the diameter of the outer ones, so as to create a constriction in the annular space. A volume of small iron particles is located in the annular space. In order to constrict the flow area of the tubular member, the middle electromagnet is operated so as to attract the iron particles thereto, such that they accumulate in the central area and apply a radially inward force to the tubular member, thereby narrowing the cross-sectional area thereof. The tubular member is allowed to expand when the extreme electromagnets are operated so as to attract the iron particles away from the center.

Disadvantages of the above-described structure include the fact that it provides throttling only of a fluid flow, and that it is incapable of providing high resolution, real time control of a fluid flow.

SUMMARY OF THE INVENTION The present invention seeks to provide apparatus which is capable of changing the dynamic state of fluid flows by selective application of electromagnetic fields to a working member, which is operative to directly influence the fluid flow. The present invention is further capable of providing very high resolution activation of a working member, and is further capable of providing selectable variation in time of the activation of a working member in real time. The present invention is also, due to a minimal number of working parts, highly reliable.

There is thus provided, in accordance with a preferred embodiment of the invention, an electromagnetic flow control apparatus which includes a fluid flow conduit, a magnetic membrane, and a plurality of discrete sources of selectably variable magnetic fields, such as electromagnets, arranged in an ordered array, to drive the membrane in a desired manner to control the flow of fluid in the conduit. The membrane can preferably be driven between two extreme positions wherein the flow of fluid in the conduit is totally unrestricted in the rest position of the membrane and wherein the flow is highly restricted or stopped completely in the maximum deformation of the membrane radially inward.

Further, in accordance with a preferred embodiment of the present invention, the electromagnetic flow control apparatus additionally includes a control device to selectively activate the array of electromagnets so to produce a desired deformation in the magnetic membrane and a desired time variation thereof.

In accordance with a preferred embodiment of the present invention, the flow control apparatus is an integrated fluid flow conduit and electromagnetic control apparatus wherein the magnetic membrane is the body of or is embedded in the fluid flow conduit. In accordance with an alternative embodiment of the present invention, the flow control apparatus encloses an existing fluid flow conduit and controls the fluid flow therein by exerting pressure thereon from without.

In accordance with additional embodiments of the present invention, the flow control apparatus additionally includes a rod member, which may be made of magnetic material, located centrally in the fluid flow conduit along the length of the flow control apparatus. Such a rod can enhance the capability of the flow control apparatus to cut off the flow of fluid in the conduit.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which: Fig. 1 is a schematic cross-sectional view of flow control apparatus, constructed in accordance with a first embodiment of the invention, in which a magnetic membrane is controlled via a single array of electromagnets, only; Fig. 2 is a schematic cross-sectional view of flow control apparatus, constructed in accordance with a second embodiment of the invention, in which a magnetic membrane is controlled via a pair of electromagnet arrays; Figs. 3A, 3B, and 3C are isometric, side-sectional, and cross-sectional views, respectively, of an integrated fluid flow conduit and electromagnetic flow control apparatus constructed in accordance with a third embodiment of the invention; Figs. 4A and 4B are cross-sectional views of the conduit of Figs. 3A, 3B and 3C, in partially closed and fully closed positions, respectively; Fig. 5A is a side-sectional view of a conduit and fluid control apparatus, similar to that of Figs. 3A-4B, but including a rod member extending longitudinally therein; Figs. 5B and 5C are cross-sectional views of the conduit of Fig. 5A, in fully open and fully closed positions, respectively; and Fig. 6A is a side-sectional view of a fluid control apparatus, according to another embodiment of the invention, for use with an existing fluid flow conduit, also shown in the figure; Fig. 6B is a side-sectional view of a fluid control apparatus similar to that in Fig. 6A, with the addition of a protective air cushion around the existing fluid flow conduit.

Fig. 7 is a block diagram of a controller circuit forming part of the apparatus shown in Fig. 1.

Fig. 8 is a block diagram of a driver circuit forming part of the apparatus shown in Fig. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring, now to Figure 1, there is shown, schematically, a fluid flow control device, referred to generally as 10, in accordance with a first embodiment of the present invention. A magnetic membrane 11 is located opposite an array of electromagnets 12. The array may be linear, as in Figure 1, or planar. Electric power from the power supply 14 is distributed among the electromagnets of the array 12 by a controller and driver unit 13 so as to create varying magnetic fields 15 which produce a desired wavelike, dynamic, deformation of the membrane 11' When the membrane is placed within or adjacent to a fluid flow conduit with fluid flowing therein, as shown by arrows 16, the deformation will cause a corresponding variation in the fluid flow characteristic. The use of a plurality of electromagnets 12 and the electronic control thereof to produce electromagnetic fields 15 acting on the membrane element 11 which directly affects the fluid flow, provides high resolution and real time control thereof.

Figures 7 and 8 show block diagrams of examples of controller and driver circuits, respectively, which together may constitute controller and driver unit 13 shown in Figure 1. These circuits, as will be understood by persons skilled in the art, are operative to distribute power to the electromagnets of the array to create the aforementioned varying magnetic fields.

As will be understood by persons skilled in the art, magnetic membrane 11 can have a number of alternative configurations. These may be, in alternative embodiments of the invention, by way of example, any of the following: a single membrane made of a flexible magnetic material, such as polyethylene impregnated with iron filings or with nickel a compound membrane having joined magnetic and non-magnetic Leers iere n the magnetic layer transfers forces resulting from its deformation as described above to the non-magnetic layer a single non-magnetic membrane having magnetic elements embedded therein a single non-magnetic membrane having magnetic elements attached to its surface It will be further understood by persons skilled in the art that such magnetic elements may be permanent magnets or other magnetic material.

In a second embodiment of the present invention, shown schematically in Figure 2, a second array of electromagnets 27, similar to the first array 22, is located opposite the magnetic membrane 21. The use of an additional array provides enhanced spatial and temporal response in the magnetic membrane 21 with resulting enhanced control of the flow of the fluid in the conduit.

As will be understood by persons skilled in the art, the more discrete locations whereat electromagnetic fields can be applied to the magnetic membrane, the greater is the resolution of the control over the deformation thereof.

Referring now to Figures 3A, 3B, and 3C, there is shown, in isometric, side-sectional, and cross-sectional views, respectively, an integrated fluid flow conduit and electromagnetic flow control apparatus, constructed in accordance with a preferred embodiment of the present invention. In this embodiment, a plurality of arrays of electromagnets 32 are arranged cylindrically around a fluid flow conduit 31 whose walls are made of magnetic material. Figure 3C shows the cross-sectional view of the conduit 31 when it is fully open. Figures 4A and 4B, show the conduit 31 when it is partially closed and fully closed, respectively, as a result of the application of suitable magnetic fields via the arrays of electromagnets.

The spatial resolution of the control of the deformation of the fluid flow conduit, together with the time resolution of the control provided by electronic control of the individual electromagnets allows such embodiments of the present invention to impart a wavelike motion to fluid flows along the conduit 31 along its length, as indicated by 11' and 21' in Figures 1 and 2 respectively, so as to drive the flow fluid though the conduit in a peristaltic-like fashion.

Referring now to Figures 5A, 5B, and 5C, there is shown an alternative embodiment of the present invention wherein an integrated fluid flow conduit and electromagnetic flow control apparatus additionally includes a rod 53 running longitudinally in the center of the fluid flow conduit 51. Rod 53 is supported by any suitable mounting elements (not shown). When the magnetic elements 52 are activated to close the fluid flow conduit 51, as shown in Figure 5C, the magnetic membrane wall of the conduit 51 presses against the rod 53, thereby providing a firmer seal to close the conduit to fluid flow. In accordance with a further embodiment of the present invention, the rod 53 may be made of magnetic material in order to enhance the magnetic force for closing the fluid flow in the conduit 51.

In a further preferred embodiment of the present invention, an electromagnetic flow control apparatus 62 is employed in conjunction with an existing fluid flow conduit 61, as shown in Figures 6A and 6B. In this embodiment of the invention, an electromagnetic flow control apparatus 62, including a magnetic membrane 63, is a sleeve-like construction that is placed around a segment of an existing fluid flow conduit 61. The deformation of the magnetic membrane 63 in response to the magnetic fields produced by the apparatus 62 presses on the conduit to control the fluid flow therein. In alternative embodiment of the invention, the electromagnetic flow control apparatus 62 may include a gas-filled cell 65 separating the magnetic membrane 63 from the fluid flow conduit 61 to provide a cushion to protect the conduit from excessive forces.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is limited solely by the claims, which follow.