MX2011012974A

MX2011012974A - Pump with disc-shaped cavity.

Info

Publication number: MX2011012974A
Application number: MX2011012974A
Authority: MX
Inventors: Richard Janse Van Rensburg; Justin Rorke Buckland; Stuart Andrew Hatfield; James Edward Mccrone
Original assignee: The Technology Partnership Plc
Priority date: 2009-06-03
Filing date: 2009-06-03
Publication date: 2012-01-20
Also published as: JP2012528981A; CN102459899B; AU2016200869A1; BRPI0924510A2; RU2011153727A; AU2009347422B2; AU2016200869B2; CA2764334C; EP2438302B1; JP5623515B2; BRPI0924510B1; CA2764334A1; RU2511832C2; CN102459899A; AU2009347422A1; SG176225A1; EP2438302A1; BRPI0924510B8; WO2010139918A1

Abstract

A pump having a substantially cylindrical shape and defining a cavity formed by a side wall closed at both ends by end walls wherein the cavity contains a fluid is disclosed. The pump further comprises an actuator operatively associated with at least one of the end walls to cause an oscillatory motion of the driven end wall to generate displacement oscillations of the driven end wall within the cavity. The pump further comprises an isolator operatively associated with a peripheral portion of the driven end wall to reduce dampening of the displacement oscillations. The pump further comprises a valve for controlling the flow of fluid through the valve. The valve has first and second plates with offsetting apertures and a sidewall disposed between the plates around the perimeter of the plates to form a cavity in fluid communication with the apertures. The valve further comprises a flap disposed and moveable between the first and second plates and having apertures substantially offset from the apertures of one plate and substantially aligned with the apertures of the other plate. The flap is motivated between the two plates in response to a change in direction of the differential pressure of fluid across the valve.

Description

PUMP WITH CAVITY IN DISC FORM DESCRIPTION OF THE INVENTION The illustrative embodiments of the invention generally relate to a pump for fluid, and more specifically, to a pump having a substantially disc-shaped cavity having substantially circular end walls and a side wall and a valve for controlling the flow of fluid through the pump.

The generation of high amplitude pressure oscillations in closed cavities has received significant attention in the thermo-acoustic and pump type compressor fields. Recent developments in nonlinear acoustics have allowed the generation of pressure waves with higher amplitudes than previously thought possible.

It is known to use acoustic resonance to achieve pumping of fluid from defined inputs and outputs. This can be achieved by using a cylindrical cavity with an acoustic impeller at one end, which drives an acoustic standing wave. In such a cylindrical cavity, the acoustic pressure wave has limited amplitude. Different cross-sectional cavities, such as horn cone, and bulb, have been used to achieve high amplitude pressure oscillations that therefore significantly increase the pumping effect. In such high amplitude waves the non-linear mechanisms with energy dissipation have been suppressed. However, high-amplitude acoustic resonance has not been employed within disc-shaped cavities in which radial pressure oscillations are excited until recently. International Patent Application No. PCT / GB2006 / 001487, published as WO2006 / 111775 (Application v 487), discloses a pump having a substantially disc-shaped cavity with a high aspect ratio, ie the ratio of the radius of the cavity at the height of the cavity.

Such a pump has a substantially cylindrical cavity comprising a side wall closed at each end by end walls. The pump also comprises an actuator that drives any of the end walls to oscillate in a direction substantially perpendicular to the surface of the driven end wall. The spatial profile of the movement of the driven end wall is described as correlated with the spatial profile of the fluid pressure oscillations within the cavity, a state described herein as a correlation mode. When the pump has a correlated mode, the work done by the actuator in the fluid in the cavity is constructively added throughout the end driven wall surface, thereby improving the amplitude of the pressure oscillation in the cavity and providing efficiency of pumping high. In a pump which has no correlated mode there may be areas of the end wall in which the work done by the end wall in the fluid reduces rather than improving the amplitude of the fluid pressure oscillation in the fluid within the cavity . Therefore, the useful work done by the actuator in the fluid is reduced and the pump becomes less efficient. The efficiency of a pump in a correlated manner depends on the interconnection between the driven end wall and the side wall. To maintain the efficiency of such a pump it is desirable to structure the interconnection so as not to diminish or dampen the movement of the driven end wall thereby mitigating any reduction in the amplitude of the fluid pressure oscillations within the cavity.

Such pumps also require a valve to control the flow of fluid through the pump and, more specifically, a valve that is capable of operating at high frequencies. Conventional valves typically operate at low frequencies below 500 Hz for a variety of applications. For example, many conventional compressors typically operate at 50 or 60 Hz. Linear resonance compressors known in the art operate between 150 and 350 Hz. Nevertheless, many portable electronic devices including medical devices require pumps to supply positive pressure or provide a vacuum that is relatively small in size and it is advantageous for such pumps to be inaudible in operation to provide a discrete operation. To achieve these goals, pumps must operate at very high frequencies that require valves capable of operating at around 20 kHz and higher which are not commonly available. To operate at these high frequencies, the valve must be responsive to high frequency oscillatory pressure that can be rectified to create a net flow of fluid through the pump.

According to one embodiment of the invention, the actuator of the pump described above causes an oscillatory movement of the driven side wall ("displacement oscillations") in a direction substantially perpendicular to the end wall or substantially parallel to the longitudinal axis of the cavity. cylindrical, hereinafter referred to as "axial oscillations" of the driven end wall within the cavity. Axial oscillations of the driven end wall generate substantially proportional "pressure oscillations" of fluid within the cavity which creates a radial pressure distribution approaching that of a Bessel function of the first type as described in the '487 Application which is incorporated for reference herein, such oscillations referred to herein as "radial oscillations" of the fluid pressure within the cavity. A portion of the end wall driven between the actuator and the side wall provides an interconnection with the side wall of the pump that decreases the damping of the displacement oscillations to mitigate any reduction in pressure oscillations within the cavity, that portion will be referred to herein as an "isolator". Illustrative embodiments of the insulator are operatively associated with the peripheral portion of the driven end wall to reduce the damping of displacement oscillations.

According to another embodiment of the invention, a pump comprises a pump body having a substantially cylindrical shape defining a cavity formed by a side wall closed at both ends by substantially circular end walls, at least one of the end walls is an end driven wall having a central portion and a peripheral portion adjacent to the side wall, in which the cavity contains fluid when in use. The pump further comprises an actuator operatively associated with the central portion of the end wall driven to cause an oscillatory movement of the end wall driven in a direction substantially perpendicular thereto with a maximum amplitude through the center of the driven end wall, thereby displacement oscillations of the driven end wall are generated when it is in use. The pump further comprises an isolator operatively associated with the peripheral portion of the end wall driven to reduce the damping of the displacement oscillations caused by the connection of the end wall with the side wall of the cavity. The pump further comprises a first opening disposed at the center of one of the end walls, and a second opening disposed at any other location in the pump body, in which the displacement oscillations generate radial oscillations of fluid pressure within the pump body cavity which causes fluid flow through the openings.

According to still another embodiment of the invention, the pump comprises a valve arranged in either the first or second opening to control the flow of fluid through the pump. The valve comprises a first plate having openings that extend generally perpendicular therethrough and a second plate also having openings extending generally perpendicular therethrough, wherein the openings of the second plate are substantially compensated of the openings in the first plate. The valve further comprises a side wall disposed between the first and second plates, wherein the side wall is closed around the perimeter of the first and second plates to form a cavity between the first and second plates in fluid communication with the openings of the body. first and second plates. The valve further comprises a hinge disposed and movable between the first and second plates, wherein the hinge has substantially compensated openings of the openings of the first plate and substantially aligned with the openings of the second plate. The hinge is motivated between the first and second plates in response to a change in direction of the differential pressure of the fluid through the valve.

Other objects, features, and advantages of the illustrative embodiments are described herein and will become apparent with reference to the drawings and detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A to 1C show a schematic cross-sectional visa of a first pump according to an illustrative embodiment of the inventions that provides a positive pressure, a graph of the displacement oscillations of the driven end wall of the pump, and a graph of fluid pressure oscillations within the pump cavity.

Figure 2 shows a schematic top view of the first pump of Figure 1A.

Figure 3 shows a schematic cross-sectional view of a second pump according to an illustrative embodiment of the inventions which provides a negative pressure.

Figure 4 shows a schematic cross-sectional view of a third pump according to an illustrative embodiment of the invention having a frusto-conical base.

Figure 5 shows a schematic cross-sectional view of a fourth pump according to another illustrative embodiment of the invention that includes two actuators.

Figure 6A shows a schematic cross-sectional view of the pump of Figure 3 and Figure 6B shows a graph of fluid pressure oscillations within the pump as shown in FIGURE 1C.

Figure 6C shows a schematic cross-sectional view of an illustrative embodiment of a valve used in Figure 3.

Figure 7A shows a schematic cross-sectional view of an illustrative embodiment of a valve in a closed position, and Figure 7B shows an exploded view of the valve of Figure 7A taken along line 7B- 7B in Figure 7D.

Figure 7C shows a diagrammatic perspective view of the valve of Figure 7B.

Figure 7D shows a schematic top view of the valve of Figure 7B.

Figure 8A shows a schematic cross-sectional view of the valve in Figure 7B in an open position when fluid flows through the valve.

Figure 8B shows a schematic cross-sectional view of the valve in Figure 7B in transition between the open and closed positions.

Figure 9A shows a graph of an oscillatory differential pressure applied across the valve of Figure 7B according to an illustrative embodiment.

Figure 9B shows a graph of an operating cycle of the valve of Figure 7B between an open and closed position.

Figure 10 shows a schematic cross-sectional view of a portion of the valve of Figure 7B in the closed position according to an illustrative embodiment.

Figure 11A shows a schematic cross-sectional view of a modified version of the valve of Figure 7B having release openings.

Figure 11B shows a schematic cross-sectional view of a portion of the valve in Figure 11A.

Figure 12A shows a schematic cross-sectional view of two valves of Figure 7B, one of which is reversed to allow fluid flow in the opposite direction of the other according to an illustrative embodiment.

Figure 12B shows a schematic top view of the valves shown in Figure 12A.

Figure 12C shows a graph of the operating cycles of the valves of Figure 12A between an open and closed position.

Figure 13 shows a schematic cross-sectional view of the bidirectional valve having two valve portions that allow fluid flow in opposite directions with both valve portions having a normally closed position according to an illustrative embodiment.

Figure 14 shows a schematic top view of the bidirectional valves of Figure 13.

Figure 15 shows a schematic cross-sectional view of a bidirectional valve having two valve portions that allow fluid flow in opposite directions with one valve portion having a normally closed position and the other having a normally open position according to to an illustrative modality.

In the following detailed description of several illustrative embodiments, reference is made to the accompanying drawings which form a part hereof, and in which specific preferred embodiments in which the invention can be practiced are shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be used and that structural, mechanical, electrical and chemical-logical changes may be enhanced without departing from the spirit or scope of the invention. . To avoid details that are not necessary to allow those skilled in the art to practice the embodiments described herein, the description may omit certain information known to those skilled in the art. The following detailed description, therefore, should not be taken in a limiting sense, and the scope of the illustrative embodiments is defined only by the appended claims.

Figure 1A is a schematic cross-sectional view of a pump 10 according to an illustrative embodiment of the invention. Referring also to Figure IB, the pump 10 comprises a pump body having a substantially cylindrical shape including a cylindrical wall 19 closed at one end by a base 18 and closed at the other end by an end plate 17 and an insulator 30 in the form of a ring disposed between the end plate 17 and the other end of the cylindrical wall 19 of the pump body. The cylindrical wall 19 and base 18 can be a simple component that comprises the pump body and can be mounted to other components or systems. The internal surfaces of the cylindrical wall 19, the base 18, the end plate 17, and the insulator 30 form a cavity 11 inside the pump 10 in which the cavity 11 comprises a side wall 14 closed at both ends by the walls 12. and 13 extreme. The end wall 13 is the inner surface of the base 18 and the side wall 14 is the inner surface of the cylindrical wall 19. The end wall 12 comprises a central portion corresponding to the inner surface of the end plate 17 and a peripheral portion corresponding to the inner surface of the insulator 30. Although the cavity 11 is substantially circular in shape, the cavity 11 may also be elliptical or another way. The base 18 and the cylindrical wall 19 of the pump body can be formed from any suitable rigid material including, without limitation, metal, ceramic, glass, or plastic including, without limitation, injection molded plastic.

The pump 10 also comprises a piezoelectric disk 20 operatively connected to the end plate 17 to form an actuator 40 which is operatively associated with the central portion of the end wall 12 by the end plate 17. The piezoelectric disc 20 does not require the formation of a piezoelectric material, but may be formed of any vibrationally active electrically active material such as, for example, an electrostrictive or magnetostrictive material. The end plate 17 preferably has a curvature rigidity similar to that of the piezoelectric disc 20 of an electrically inactive material such as metal or ceramic. When the piezoelectric disk 20 is energized by an electric current, the actuator 40 expands and contracts in a radial direction relative to the longitudinal axis of the cavity 11 which causes the end plate 17 to bend, thereby inducing axial deflection of the end wall 12 in a direction substantially perpendicular to the end wall 12. The end plate 17 can also alternatively be formed from electrically active material such as, for example, a piezoelectric, magnetostrictive, or electrostrictive material. In another embodiment, the piezoelectric disk 20 can be replaced by a device in a force transmission relationship with the end wall 12 such as, for example, a mechanical, magnetic or electrostatic device, in which the end wall 12 can be formed as a layer of electrically inactive or passive material driven towards oscillation by such a device (not shown) in the same manner as described above The pump 10 further comprises at least two openings extending from the cavity 11 to the exterior of the pump 10, in which at least one of the first openings may contain a valve for controlling the flow of fluid through the opening. Although the opening containing a valve can be located in any position in the cavity 11 where the actuator 40 generates a pressure differential as described below in more detail, a preferred embodiment of the pump 10 comprises an opening with a valve located at approximately the center of any of the 12, 13 extreme walls. The pump 10 shown in Figures 1A and IB comprises a primary opening 16 which extends from the cavity 11 through the base 18 of the pump body through the center of the end wall 13 and contains a valve 46. The valve 46 is mounted within the primary opening 16 and allows fluid flow in a direction as indicated by the arrow so as to function as an outlet for the pump 10. The second opening 15 can be located at any position within the cavity 11. other than the location of the opening 16 with the valve 46. In a preferred embodiment of the pump 10, the second opening is disposed between the center of any of the end walls 12, 13 and the side wall 14. The embodiment of the pump 10 shown in Figures 1A and IB comprises two secondary openings 15 extending from the cavity 11 through the actuator 40 which is disposed between the center of the end wall 12 and the side wall 14.

Although the secondary openings 15 do not have a valve in this embodiment of the pump 10, they may also have a valve to improve the performance if necessary. In this embodiment of the pump 10, the primary opening 16 has a valve so that the fluid is absorbed in the cavity 11 of the pump 10 through the secondary openings 15 and is pumped out of the cavity 11 through the opening. 16 primary as indicated by the arrows to provide a positive pressure in the primary opening 16.

Referring now to Figure 3, the pump 10 of Figure 1 is shown with an alternative configuration of the primary opening 16. More specifically, the valve 46 'in the primary opening 16' is inverted so that the fluid is absorbed in the cavity 11 through the primary opening 16 'and is expelled from the cavity 11 through the secondary openings 15 as shown in FIG. indicated by the arrows, thereby providing suction or a source of reduced pressure in the primary opening 16 '. The term "reduced pressure" as used herein generally refers to a pressure less than the ambient pressure where the pump 10 is located. Although the terms "vacuum" and "negative pressure" can be used to describe the reduced pressure, the current pressure reduction can be significantly less than the pressure reduction normally associated with a full vacuum. The pressure is "negative" in the sense that it is a gauge pressure, that is, the pressure is reduced below the ambient atmospheric pressure. Unless stated otherwise, the pressure values stipulated herein are gauge pressures. References to increases in reduced pressure typically refer to a decrease in absolute pressure, while decreases in reduced pressure typically refer to an increase in absolute pressure.

Referring now to Figure 4, a pump 70 is shown according to another illustrative embodiment of the invention. The pump 70 is substantially similar to the pump 10 of Figure 1 except that the pump body has a base 18 'having a top surface forming the end wall 13' which is frusto-conical in shape. Accordingly, the height of the cavity 11 varies from the height in the side wall 14 to a smaller height between the end walls 12, 13 'in the center of the walls 12, 13 'extreme. The frusto-conical shape of the end wall 13 'intensifies the pressure in the center of the cavity 11 where the height of the cavity 11 is small relative to the pressure in the side wall 14 of the cavity 11 where the height of the cavity 11 it is bigger. Therefore, when comparing the cylindrical and frusto-conical cavities 11 having equal central pressure amplitudes, it is apparent that the frusto-conical cavity 11 will generally have a smaller pressure amplitude at positions away from the center of the cavity 11: Increasing height of the cavity 11 acts to reduce the amplitude of the pressure wave. As the viscous and thermal energy losses experienced during fluid oscillations in the cavity 11 increase with the amplitude of the oscillations, it is advantageous for the efficiency of the pump 70 to reduce the amplitude of the pressure oscillations away from the center of the cavity 11 by using a frusto-conical cavity design 11. In an illustrative embodiment of the pump 70 where the diameter of the cavity 11 is about 20 mm, the height of the cavity 11 in the side wall 14 is about 1.0 mm tapered at a height in the center of the end wall 13 ' of approximately 0.3 mm. Any of the end walls 12, 13 or both end walls 12, 13 can have a frusto-conical shape.

Referring now to Figure 4, a pump 70 is shown according to another illustrative embodiment of the invention. The pump 70 is substantially similar to the pump 10 of Figure 1 except that the pump body has a base 18 'having a top surface forming the end wall 13' which is frusto-conical in shape. Accordingly, the height of the cavity 11 varies from the height in the side wall 14 to a lower height between the end walls 12, 13 'in the center of the end walls 12, 13'. The frusto-conical shape of the extreme wall 13 'intensifies the pressure in the center of the cavity 11 where the height of the cavity 11 is less relative to the pressure in the side wall 14 of the cavity 11 where the height of the cavity 11 is greater. Therefore, when comparing 11 cylindrical and frusto-conical cavities having equal central pressure amplitudes, it is apparent that the frusto-conical cavity 11 will generally have a smaller pressure amplitude at positions away from the center of the cavity 11: the height in Increase in cavity 11 acts to reduce the amplitude of the pressure wave. As the viscous and thermal energy losses experienced during the oscillations of the fluid in the cavity 11 both increase with the amplitude of said oscillations, it is advantageous for the efficiency of the pump 70 to reduce the amplitude of the pressure oscillations away from the center of the cavity 11 when employing a frusto-conical cavity design 11. In an illustrative embodiment of the pump 70 where the diameter of the cavity 11 is approximately 20 mm, the height of the cavity 11 in the side wall 14 is approximately 1.0 mm tapering to a height in the center of the wall 13 'Extreme of approximately 0.3 mm. Any of the end walls 12, 13 or both walls 12, 13 may have a frusto-conical shape.

Referring now to Figure 5, a pump 60 is shown according to another illustrative embodiment of the invention. The pump 60 is substantially similar to the pump 10 of the Figure except that it includes a second actuator 62 that replaces the base 18 of the pump body. The actuator 62 comprises a second disc 64 and a ring-shaped isolator 66 disposed between the disc 64 and the side wall 14. The pump 60 also comprises a second piezoelectric disk 68 operatively connected to the disk 64 to form the actuator 62. The actuator 62 is operatively associated with the end wall 13 which comprises the internal surfaces of the disk 64 and insulator 66. The second actuator 62 it also generates an oscillatory movement of the end wall 13 in a direction substantially perpendicular to the end wall 13 in a manner similar to the actuator 40 with respect to the end wall 12 as described above. When the actuators 40, 62 are activated, control circuits (not shown) are provided to coordinate the axial displacement oscillations of the actuators. It is preferable that the actuators are driven at the same frequency and approximately out of phase, that is, so that the centers of the end walls 12, 13 move first toward each other and then separate.

The dimensions of the pumps described herein should preferably satisfy certain inequalities with respect to the ratio between the height (h) of the cavity 11 and the radius (r) of the cavity which is the distance from the longitudinal axis of the cavity 11 to the side wall 14. These equations are as follows: r / h > 1.2; Y h2 / r > 4x10"10 meters In one embodiment of the invention, the ratio of the cavity radius to the cavity height (r / h) is between plus or minus 10 and plus or minus 50 when the fluid within the cavity 11 is a gas. In this example, the volume of the cavity 11 may be less than about 10ml. Additionally, the ratio of h 2 / r is preferably within a range between about 10"3 and about 10" 6 meters where the fluid in operation is a gas as opposed to a liquid.

In one embodiment of the invention, the secondary openings 15 are located where the amplitude of the pressure oscillations within the cavity 11 is close to zero, that is, the "nodal" points of the pressure oscillations. Where the cavity 11 is cylindrical, the radial dependence of the pressure oscillation can be approximated by a Bessel function of the first type and the radial node of the lowest order pressure oscillation within the cavity 11 occurs at a distance of approximately 0.63r ± 0.2r from the center of the end wall 12 or the longitudinal axis of the cavity 11. Therefore, the secondary openings 15 are preferably located at a radial distance (a) from the center of the end walls 12, 13, where (a) ) * 0.63r ± 0.2r, that is, close to the nodal points of the pressure oscillations.

Additionally, the pumps described herein should preferably satisfy the following inequality in relation to the radius (r) of cavity and frequency (f) of operation which is the frequency at which the actuator 40 vibrates to generate the axial displacement of the 12 extreme wall. The inequality equation is as follows: = r = r) [Equation 1] 2?? Go to wherein the speed of sound in the fluid in operation within the cavity 11 (c) can range from a slow speed (cs) of about 115 m / s and a fast speed (Cf) equal to about 1,970 m / s as is expressed in the previous equation, and k0 is a constant (k0 = 3.83). The frequency of the oscillatory movement of the actuator 40 is preferably approximately equal to the lowest resonant frequency of radial pressure oscillations in the cavity 11, but may be within 20% thereof. The lower resonant frequency of radial pressure oscillations in the cavity 11 is preferably greater than 500 Hz.

With reference now to the pump 10 in operation, the piezoelectric disk 20 is energized to expand and contract in a radial direction towards the end plate 17 which causes the actuator 40 to curve, which induces an axial displacement of the end wall 12 driven in a direction substantially perpendicular to the extreme driven wall 12. The actuator 40 is operatively associated with the central portion of the end wall 12 as described above so that oscillations of axial displacement of the actuator cause oscillations of axial displacement along the surface of the end wall 12 with maximum amplitudes of oscillations. , that is, oscillations of anti-node displacement, in more or less the center of the extreme wall. Referring back to Figure 1A, the displacement oscillations and resulting pressure oscillations of the pump 10 as generally described above are shown more specifically in Figures IB and 1C, respectively. The phase relationship between displacement oscillations and pressure oscillations may vary, and a particular phase relationship should not be implied by any figure.

Figure IB shows a possible displacement profile illustrating the axial oscillation of the extreme driven wall 12 of the cavity 11. The curved line and solid arrow represent the displacement of the end wall 12 driven at a point in time, and the line Curved dotted represents the displacement of the extreme wall 12 driven a half cycle later. The displacement as shown in this figure and in the other figures is exaggerated. Because the actuator 40 is not rigidly mounted on its perimeter, rather suspended by the insulator 30, the actuator 40 is free to oscillate around its center of mass in its fundamental mode. In this fundamental mode, the amplitude of the displacement oscillations of the actuator 40 is substantially zero at an annular displacement node 22 located between the center of the end wall 12 and the side wall 14. The amplitudes of the displacement oscillations at other points on the end wall 12 have amplitudes greater than zero as represented by the vertical arrows. An anti-node 21 of central displacement exists near the center of the actuator 40 and the anti-node 21 'of peripheral displacement exists near the perimeter of the actuator 40.

Figure 1C shows a possible pressure oscillation profile illustrating the pressure oscillation within the cavity 11 resulting from the axial displacement oscillations shown in Figure IB. The curved line and solid arrows represent the pressure at a point in time, and the dotted curved line represents the pressure a half cycle later. In this mode and modes of higher order, the amplitude of the pressure oscillations has an anti-node 23 of central pressure near the center of the cavity 11 and an anti-node 24 of peripheral pressure near the side wall 14 of the cavity 11. The amplitude of the pressure oscillations is substantially zero at the annular pressure node 25 between the central pressure anti-node 23 and the peripheral pressure anti-node 24. For a cylindrical cavity the radial dependence of the amplitude of the pressure oscillations in the cavity 11 can be approximated by a Bessel function of the first type. The pressure oscillations described above result from the radial movement of the fluid in the cavity 11, and will be referred to as the "radial pressure oscillations" of the fluid within the cavity 11 as distinguished from the axial displacement oscillations of the actuator 40.

With further reference to Figures IB and 1C, it can be seen that the radial dependence of the amplitude of the axial displacement oscillations of the actuator 40 (the "shape mode" of the actuator 40) must approach a Bessel function of the first type to correlate more closely the radial dependence of the amplitude of the desired pressure oscillations in the cavity 11 (the "mode of shape" of the pressure oscillation). By not rigidly mounting the actuator on its perimeter and allowing it to vibrate more freely around its center of mass, the shape mode of the displacement oscillations substantially correlates the shape mode of the pressure oscillations in the cavity 11, thus both the correlation of form mode or, in a simpler way, correlation mode is achieved. Although the correlation mode may not always be perfect in this regard, the axial displacement oscillations of the actuator 40 and the corresponding pressure oscillations in the cavity 11 have substantially the same relative phase throughout the entire surface of the actuator 40 in which the radial position of the annular pressure node 25 of the pressure oscillations in the cavity 11 and the radial position of the annular displacement node 22 of the axial displacement oscillations of the actuator 40 are substantially coincident.

As the actuator 40 vibrates around its center of mass, the radial position of the annular displacement node 22 will necessarily be located within the radius of the actuator 40 when the actuator 40 vibrates in its fundamental mode as illustrated in Figure IB. Therefore, to ensure that the annular displacement node 22 is coincident with the annular pressure node 25, the radius of the actuator (racC) should preferably be greater than the radius of the annular pressure node 25 to optimize the correlation mode. By assuming again that the pressure oscillation in the cavity 11 approaches a Bessel function of the first type, the radius of the annular pressure node 25 can be about 0.63 radius from the center of the end wall 13 to the wall 14 lateral, that is, the radius of the cavity 11 (r) as shown in Figure 1A. Accordingly, the radius of the actuator 40 (ract) should preferably satisfy the following inequality: racC > 0.63r.

The insulator 30 may be a flexible membrane which allows the edge of the actuator 40 to move more freely as described above by bending and stretching in response to the vibration of the actuator 40 as shown by the displacement of the peripheral displacement oscillations 21 'in FIG. Figure IB. The flexible membrane overcomes the potential damping effects of the side wall 14 on the actuator 40 by providing a low mechanical impedance support between the actuator 40 and the cylindrical wall 19 of the pump 10 whereby the damping of the axial oscillations is reduced of the oscillations 21 'of peripheral displacement of the actuator 40. Essentially, the flexible membrane 31 minimizes the energy that is transferred from the actuator 40 to the side wall 14, which remains substantially stationary. Accordingly, the annular displacement node 22 will remain substantially aligned with the annular pressure node 25 to maintain the correlation mode condition of the pump 10. Therefore, the axial displacement oscillations of the extreme driven wall 12 continue to generate efficiently oscillations of the pressure within the cavity 11 from the central pressure anti-node 23 to the peripheral pressure anti-node 24 in the side wall 14 as shown in Figure 1C.

Figure 6A shows a schematic cross-sectional view of the pump of Figure 3 and Figure 6B a graph of the fluid pressure oscillations within the pump as shown in Figure 1C. Valve 46 '(like valve 46) allows the fluid to flow only in one direction as described above. The valve 46 'can be a check valve or any other valve that allows the fluid to flow only in one direction. Some types of valves can regulate fluid flow by alternating between an open and closed position. For such valves to operate at the high frequencies generated by the actuator 40, the valves 46 and 46 'must have an extremely fast response time such that they can open and close on a time scale significantly shorter than the scale of time of pressure variation. One embodiment of the valves 46 and 46 'accomplishes this by employing an extremely light flap valve which has low inertia and therefore can move rapidly in response to changes in relative pressure throughout the valve structure.

With reference to Figures 7A-D such a flap valve, the valve 110 is shown according to an illustrative embodiment. The valve 110 comprises a substantially cylindrical wall 112 which is ring-shaped and closed at one end by a retaining plate 114 and at the other end by a sealing plate 116. The inner surface of the wall 112, the retaining plate 114, and the sealing plate 116 form a cavity 115 within the valve 110. The valve 110 further comprises a substantially circular hinge 117 disposed between the retainer plate 114 and the plate 114. sealing plate 116, but adjacent to sealing plate 116. The hinge 117 may be disposed adjacent the retention plate 114 in an alternative embodiment as will be described in more detail below, and in this regard the hinge 117 is considered to be "predisposed" against either the sealing plate 116 or the plate. 114 retention. The peripheral portion of the hinge 117 is sandwiched between the sealing plate 16 and the ring-shaped wall 112 so that the movement of the hinge 117 is restricted in the plane substantially perpendicular to the surface of the hinge 117. The movement of the hinge 117 in such a plane can also be restricted by the peripheral portion of the hinge 117 which is attached directly to either the sealing plate 116 or the wall 112, or by the hinge 117 being a closed fit within the wall 112 in the form of ring, in alternative modalities. The remainder of the hinge 117 is sufficiently flexible and movable in a direction substantially perpendicular to the surface of the hinge 117, so that a force applied to any surface of the hinge 117 motivates the hinge 117 between the sealing plate 116 and the plate 114. retention.

The retaining plate 114 and the sealing plate 116 both have holes 118 and 120, respectively, which extend through each plate. The hinge 117 also has holes 122 that are generally aligned with the holes 118 of the retainer plate 114 to provide a passage through which the fluid can flow as indicated by the arrows 124 dotted in Figures 6C and 8A. The holes 122 in the hinge 117 may also be partially aligned, i.e. having only a partial overlap, with the holes 118 in the retaining plate 114. Although the holes 118, 120, 122 are shown to be substantially of uniform size and shape, these can be of different diameters or even of different shapes without limiting the scope of the invention. In one embodiment of the invention, the holes 118 and 120 form an alternating pattern over the entire surface of the plates as shown by the solid and dotted circles, respectively, in Figure 7D. In other modalities, the holes 118, 120, 122 can be arranged in different patterns without effecting the operation of the valve 10 with respect to the operation of the individual pairs of the holes 118, 120, 122 as illustrated by individual sets of dotted arrows 124. The pattern of holes 118, 120, 122 can be designed to increase or decrease the number of holes to control the total flow of fluid through the valve 110 as required. For example, the number of holes 118, 120, 122 can be increased to reduce the flow resistance of the valve 110 to increase the total flow rate of the valve 110.

When no force is applied to any surface of the hinge 117 to overcome the predisposition of the hinge 117, the valve 110 is in a "normally closed" position because the hinge 117 is disposed adjacent to the sealing plate 116 where the holes 122 of the hinge are misaligned or not aligned with the holes 118 of the sealing plate 116. In this "normally closed" position, the fluid flow through the sealing plate 116 is substantially blocked or covered by the non-perforated portions of the hinge 117 as shown in Figures 7A and 7B. When pressure is applied against either side of the hinge 117 which overcomes the predisposition of the hinge 117 and motivates the hinge 117 away from the sealing plate 116 towards the retaining plate 114 as shown in Figures 6C and 8A, the valve 110 moves from the normally closed position to an "open" position for a period of time, an opening time delay (T0) allows the fluid to flow in the direction indicated by the dotted arrows 124. When the pressure changes direction as shown in Figure 8B, the hinge 117 will be motivated back to the sealing plate 116 to the normally closed position. When this happens, the fluid will flow for a short period of time, a closing time delay (Tc), in the opposite direction as indicated by the arrows 132 dotted until the hinge 117 seals the holes 120 of the plate 116 of sealing to substantially block the flow of fluid through the sealing plate 116 as shown in Figure 7B. In other embodiments of the invention, the flap 117 may be biased against the retainer plate 114 with the holes 118, 122 aligned in a "normally open" position. In this embodiment, positive pressure against hinge 117 will be required to motivate flap 117 in a "closed" position. It should be noted that the terms "sealed" and "blocked" as used herein in connection with valve operation are intended to include cases in which a substantial (but incomplete) seal or block occurs, such that the resistance of Flow of the valve is greater in the "closed" position than in the "open" position.

The operation of the valve 110 is a function of the change in direction of the differential pressure (?) Of the fluid through the valve 110. In Figure 7B, the differential pressure has been assigned a negative value (- ?? ) as indicated by the arrow pointing downwards. When the differential pressure has a negative value (- ??), the fluid pressure at the outer surface of the retaining plate 114 is greater than the fluid pressure at the surface of the sealing plate 116. This negative differential pressure (- ??) drives the hinge 117 in the fully closed position as described above where the hinge 117 is pressed against the sealing plate 116 to block the holes 120 in the sealing plate 116, thereby the flow of fluid through the valve 110 is substantially prevented. When the differential pressure across the valve 110 is reversed to become a positive differential pressure (+?) as indicated by the arrow pointing upwards in the Figure 8A; the hinge 117 is driven away from the sealing plate 116 and towards the holding plate 114 in the open position. When the differential pressure has a positive value (+?), The fluid pressure on the outer surface of the sealing plate 116 is greater than the fluid pressure on the outer surface of the retaining plate 114. In the open position, the movement of the hinge 117 unlocks the holes 120 of the sealing plate 116 so that the fluid may be able to flow through them and through the aligned holes 122 and 118 of the hinge 117 and holding plate 114, respectively, as indicated by dotted arrows 124.

When the differential pressure across the valve 110 changes back to a negative differential pressure (- ??) as indicated by the arrow pointing downward in Figure 8B, the fluid begins to flow in the opposite direction through the valve 110 as indicated by the dotted arrows 132, which forces the hinge 117 to return to the closed position shown in Figure 7B. In Figure 8B, the fluid pressure between the hinge 117 and the sealing plate 116 is less than the fluid pressure between the hinge 117 and the retaining plate 114. Therefore, the hinge 117 experiences a net force, represented by the arrows 138, which accelerates the hinge 117 towards the sealing plate 116 to close the valve 110. In this way, the changing differential pressure cycles of the valve 110 between the closed and open positions based on the direction (i.e., positive or negative) of the differential pressure through the valve 110. It should be understood that the hinge 117 can be biased against the retaining plate 114 in an open position when it is not apply differential pressure through the valve 110, that is, the valve 110 can then be in a "normally open" position.

With reference again to Figure 6A, the valve 110 is disposed within the primary opening 46 'of the pump 10 so that the fluid is absorbed in the cavity 11 through the primary opening 46' and is expelled from the cavity 11 through the secondary openings 15 as indicated by the solid arrows, whereby a source of reduced pressure is provided in the primary opening 46 'of the pump 10. The flow of fluid through the primary opening 46' as indicated by the solid arrow pointing upwards corresponds to the fluid flow through the holes 118, 120 of the valve 110 as indicated by the dotted arrows 126 that also point upwards. As indicated above, the operation of the valve 110 is a function of the change of direction of a differential pressure (??) of the fluid over the entire surface of the valve holding plate 114 for this embodiment of a pressure pump. negative. The differential pressure (??) is assumed to be substantially uniform over the entire surface of the retaining plate 114 because the diameter of the retaining plate 114 is small relative to the wavelength of the pressure oscillations in the cavity 115 and in addition because the valve 110 is located in the primary opening 46 'near the center of the cavity 115 where the amplitude of the central pressure anti-node 71 is relatively constant. When the differential pressure across the valve 110 is reversed to become positive differential pressure (+?) As shown in Figures 6C and 8A, the predisposed hinge 117 is motivated away from the sealing plate 116 against the plate 114. of retention in the open position. In this position, the movement of the flap 117 unlocks the holes 120 of the sealing plate 116 so as to allow the fluid to flow through them and through the aligned holes 118 of the retainer plate 114 and the holes. 122 of the hinge 117 as indicated by the 124 dotted arrows. When the differential pressure changes back to the negative differential pressure (- ??), the fluid begins to flow in the opposite direction through the valve 110 (see Figure 8B), which forces the hinge 117 to return to the closed position (see Figure 7B). Therefore, as the pressure oscillations in the cavity 11 alternate the valve 110 between the normally closed and open positions, the pump 160 provides a reduced pressure every half cycle when the valve 110 is in the open position.

The differential pressure (??) is assumed to be substantially uniform throughout the entire surface of the retaining plate 114 because it corresponds to the central pressure anti-node 71 as described above, therefore it is a good approximation in that there is no spatial variation in the pressure through the valve 110. While in practice the time dependence of the pressure through the valve can be approximately sinusoidal, in the In the following analysis it should be assumed that the values of the differential pressure (??) between the positive differential pressure (+ ??) and the negative differential pressure (- ??) can be represented by a square wave over the period of time of positive pressure (Tp +) and the negative pressure time period (Tp.) Of the square wave, respectively, as shown in Figure 9A. As the differential pressure (??) alternates the valve 110 between normally closed and open positions, the pump 10 provides a reduced pressure every half cycle when the valve 110 is in the open position subjected to the opening time delay (TD ) and the closing time delay (Tc) as also described above and shown in Figure 9B. When the differential pressure through the valve 110 is initially negative with the valve 110 closed (see Figure 7A) and reversed to become a positive differential pressure (+?), The predisposed hinge 117 is motivated away from the plate 116 of sealing towards the holding plate 114 in the open position (see Figure 7B) after the opening time delay (T0). In this position, the movement of the flap 117 unlocks the holes 120 of the sealing plate 116 so as to allow the fluid to flow through them and through the aligned holes 118 of the retainer plate 114 and the holes. 122 of the hinge 117 as indicated by the dotted arrows 124, whereby a source of reduced pressure is provided outside the primary opening 46 'of the pump 10 during an opening time period (T0). When the differential pressure through the valve 110 changes back to the negative differential pressure (- ??), the fluid begins to flow in the opposite direction through the valve 110 (see Figure 7C) which forces the hinge 117 back to the closed position after the closing time delay (Tc). Valve 110 remains closed for the remainder of the half cycle or closing time period (Tc).

The retaining plate 114 and the sealing plate 116 must be strong enough to withstand the fluid pressure oscillations to which they are subjected without significant mechanical deformation. The retaining plate 114 and the sealing plate 116 can be formed from any suitable rigid material such as glass, silicone, ceramic, or metal. The holes 118, 120 in the retaining plate 114 and the sealing plate 116 can be formed by any suitable process including etching to chemical etching, laser machining, mechanical drilling, blasting with pulverized material, and stamping. In one embodiment, the retaining plate 114 and the sealing plate 116 are formed from steel sheet of between 10 and 200 microns thick, and the holes 118, 120 therein are formed by etching to the chemical etching. The hinge 117 can be formed from any light material, such as metal film or polymer. In one embodiment, when fluid pressure oscillations of 20 kHz or greater are presented either on the side 134 of the retainer plate or on the side 136 of the sealing plate, the hinge 117 can be formed from a sheet of thin polymer between 1 miera and 20 microns thick. For example, the hinge 117 can be formed from polyethylene terephthalate (PET) or a liquid crystal polymer film about 3 microns thick.

To obtain an order of magnitude estimate for the maximum mass per unit area of the hinge '117 according to one embodiment of the invention, again it is assumed that the pressure oscillation through the valve 110 is a square wave as it is shown in Figure 9A and that the full pressure differential descends throughout the hinge 117. Assuming further that the hinge 117 moves as a rigid body, the acceleration of the hinge 117 away from the closed position when the differential pressure is Invests from the negative to the positive value can be expressed as follows: [Equation 2] where x is the position of the hinge 117, p represents the acceleration of the hinge 117, P is the amplitude of the oscillatory pressure wave, and m is the mass per unit area of the hinge 117. By integrating this expression to find the distance, d, traveled by the hinge 117 in a time 7, throws the following: [Equation 3] This expression can be used to estimate the opening time delay (TD) and the closing time delay (Tc), in each case from the pressure reversal point.

In one embodiment of the invention, the hinge 117 must travel the distance between the retaining plate 114 and the sealing plate 116, the valve spacing (vgap) is the perpendicular distance between the two plates, within a shorter period of time that around a quarter (25%) of the time period of the differential pressure oscillation that drives the movement of the hinge 117, that is, the time period of the square wave (tpres) of approach. Based on this approach and the previous equations, the mass per unit area of the hinge 117 (m) is subject to the following inequality: p t 2 P 1 m < , or alternatively m < - [Equation 4] 2dm, 16 2cigap \ 6j- where dgap is the gap separation, ie, the valve spacing (vgap) minus the thickness of the flap 117, and / is the frequency of the applied differential pressure oscillation (as illustrated in Figure 10). In one embodiment, P can be 15 kPa, / can be 20kHz, and dgap can be 25 microns, indicating that the mass per unit area of the hinge 117 (m) must be less than about 60 grams per meter square. By converting the mass per unit area of the hinge 117 (m), the thickness of the hinge 117 is subject to the following inequality: [Equation 5] 2dgtp 16 2 Pftap where pfiap is the density of the material of the hinge 117. When applying a density of material typical for a polymer (for example, of about 1400 kg / m 3), the thickness of the hinge 117 according to this embodiment is less than about 45 microns for the operation of the valve 110 under the above conditions. Because the square wave shown in Figure 9A generally overestimates the sinusoidal oscillatory pressure waveform through valve 110, and also because only a proportion of the pressure difference applied through valve 110 will act as an acceleration pressure difference in the hinge 117, the initial acceleration of the hinge 117 will be less than previously estimated and the opening time delay (T0) in practice will be higher. Therefore, the limit in the hinge thickness derived above is as an upper limit, and in practice, to compensate for the decreased acceleration of the hinge 117, the thickness of the hinge 117 can be reduced to satisfy the inequality of Equation 5 The hinge 117 is thinner to accelerate faster to ensure that the opening time delay (Tc) is less than about one quarter (25%) of the time period of the differential pressure oscillation (tpres).

Minimizing the pressure drop incurred as air flows through valve 110 is important to maximize valve performance as it affects both the maximum flow rate and the stopping pressure that can be achieved. Reducing the size of the valve spacing (vgap) between the plates or the diameter of the holes 118, 120 in the plates increases the flow resistance and increases the pressure drop through the valve 110. According to another embodiment of In the invention, the following analysis employing steady-state flow equations to approximate the flow resistance through the valve 110 can be used to improve the operation of the valve 110. The pressure drop for the flow through an orifice 118 or 120 on any plate can be estimated by using the Hagan-Pousille equation: na 'h, .ok where μ is the dynamic viscosity of fluid, q is the flow rate through the orifice, tpiate is the plate thickness, and dhoie is the orifice diameter.

When the valve 110 is in the open position as shown in Figure 7B, the flow of fluid through the gap between the hinge 117 and the sealing plate 116 (the same value as the dgap gap of the hinge) will propagate. generally radially through the separation to a first approach after leaving the hole 120 in the sealing plate 116 before contracting radially within the hole 118 in the retaining plate 114. If the pattern of the holes 118, 120 in both plates is a square arrangement with a sealing length, s, between the holes 118 of the retaining plate 114 and the holes 120 of the sealing plate 116 as shown in the Figures 7B and 7D, the pressure drop through the cavity 115 of the valve 110 can be approximated by the following equation: ( 2\ 7 ln 2 + 1 [Equation 7] V Therefore, the total pressure drop (approximately Apga + 2 * Aphoie) can be very sensitive to changes in the diameter of the holes 118, 120 and the gap dgap of the hinge between the hinge 117 and the sealing plate 116. It should be noted that a smaller hinge gap dgap which may be desirable to minimize the opening time delay (T0) and the closing time delay (Tc) of the valve 110, may increase the pressure drop significantly. According to the above equation, reducing the gap dgap of hinge from 25 microns to 20 microns doubled the loss of pressure. In many practical embodiments of the valve, it is this exchange between response time and pressure drop that determines the optimal hinge gap dgap between the hinge 117 and the sealing plate 116. In one embodiment, the optimal hinge gap dgap falls within an approximate rate of between 5 microns and about 150 microns.

In establishing the diameter of the holes 120 in the sealing plate 116, consideration must be given both to maintaining the tension experienced by the hinge 117 within acceptable limits during the operation of the valve 110 (such tension is reduced by the use of a diameter smaller for the holes 120 of the sealing plate 116) and to ensure that the pressure drop through the holes 120 does not dominate the total pressure drop through the valve 110. With regard to the latter consideration, a comparison between the above equations 6 and 7 for the orifice pressure drops and separation they give a minimum diameter for the orifices 120 in which the orifice pressure drop is approximately equal to the valve separation pressure drop. This calculation establishes a lower limit on the desirable diameter of the holes 120 mentioned above whose diameter the orifice pressure drop quickly becomes negligently small.

With respect to the previous consideration in relation to the tension experienced by the hinge 117 in operation, Figure 10 illustrates a portion of the valve 110 of Figure 7B in the normally closed position. In this position, the hinge 117 is subjected to tension as the hinge 117 seals and locks the hole 120 in the sealing plate 116 which causes the hinge 117 to deform into the shape of a dimple extending into the opening of the hinge. holes 120 as illustrated. The level of tension in the hinge 117 in this configuration increases with the diameter of the holes 120 in the sealing plate 116 for a given hinge thickness 117. The hinge material 117 will tend to fracture more easily if the diameter of the holes 120 is too large, thus leading to the failure of the valve 110. To reduce the likelihood that the material of the hinge 117 will fracture, the diameter of the orifice 120 can be reduced to limit the stress experienced by the hinge 117 in operation at a level which is below the fatigue stress of the hinge material 117.

The maximum stress experienced by the hinge material 117 in operation can be estimated by using the following two equations: mmrL = K and + K (? [Equation 8] Et4 t t) and [Equation 9] where rhoie is the radius of the hole 120 of the plate 116 sealing, t is the thickness of the hinge 117, and is the deflection of the hinge 117 in the center of the hole 120, Apma is the maximum pressure difference experienced by the hinge 117 when it is sealed, E is the Module of Young of the hinge material 117, yia K4 are constants dependent on the details of the boundary conditions and the Poisson's ratio of the hinge 117. For a given hinge material 117 and hole geometry 120, the equation can be solved for the deformation, y, and then the result is used in equation 9 to calculate the voltage. For values of y < < t, the cubic and square terms y / t in equations 8 and 9 respectively become small and these equations are simplified to correlate the small plate deflection theory. Simplifying these equations results in the maximum stress being proportional to the radius of the holes 120 squared and inversely proportional to the square thickness of the hinge 117. For values of y > > For hinges that do not have flexural rigidity, the cubic and square terms y / t in the two equations become more significant so that the maximum voltage becomes proportional to the radius of the hole 120 to the power 2/3 and inversely proportional to the thickness from the hinge 117 to the power 2/3.

In one embodiment of the invention, the hinge 117 is formed from a thin polymer sheet, such as Mylar with a Poisson ratio of 0.38, and is fixed to the sealing plate 116 at the edge of the holes 120. The constants Kx to K4 can be estimated as 6.23, 3.04, 4.68 and 1.73, respectively. When using these values in Equations 8 and 9 and assuming that the thickness of the hinge 117 is around 3 microns with a Young's Modulus of 4.3 GPa under a pressure difference of 500 mbar, the deflection (y) of the hinge 117 will be approximately lum for a hole radius of 0.06 mm, around 4μ ?? for an orifice radius of 0.1 mm, and around 8um for an orifice radius of 0.15 mm. The maximum tensions under these conditions will be 16, 34 and 43 MPa, respectively. Considering the high number of stress cycles applied to the hinge 117 during the operation of the valve 110, the maximum stress per cycle tolerated by the hinge 117 must be significantly less than the performance voltage of the hinge material 117 to reduce the possibility of the hinge 117 suffering from a fatigue fracture, especially in the dimple portion of the hinge 117 which extends into the holes 120. Based on the fatigue data compiled for a high number of cycles it has been determined that the The actual performance of the hinge material 117 should be at least four times greater than the tension applied to the hinge material 117 (e.g. 16, 34 and 43 MPa as previously calculated). Therefore, the material of the hinge 117 must have a yield stress as high as 150 MPa to minimize the likelihood of such fractures for a maximum orifice diameter in this case of about 200 microns.

Reducing the diameter of the holes 120 beyond this point may be desirable since it also reduces the tension of the hinge 117 and has no significant effect on the valve flow resistance until the diameter of the holes 120 approaches the same size that separation dgap of hinge. Additionally, the reduction in the diameter of the holes 120 allows inclusions of an increased number of holes 120 per unit area of the surface of the valve 110 for one or a given sealing lengths. Nevertheless, the size of the diameter of the holes 120 can be limited, at least in part, by the manner in which the plates of the valve 110 were manufactured. For example, chemical etching limits the diameter of the holes 120 to be greater than about the thickness of the plates to achieve repeatable and controllable chemical etching results. In one embodiment, the holes 120 in the sealing plate 116 are between about 20 microns and about 500 microns in diameter. In another embodiment, the retaining plate 114 and the sealing plate 116 is formed from steel sheet about 100 microns thick, and the holes 118, 120 are about 150 microns in diameter. In this embodiment, valve flap 117 is formed from polyethylene terephthalate (PET) and is about 3 microns thick. The valve spacing (vga) between the sealing plate 116 and the retaining plate 114 is about 25 microns.

Figures 11A and 11B illustrate yet another embodiment of the valve 110, valve 310, comprising release holes 318 extending through the retainer plate 114 between the holes 118 in the retainer plate 114. The release holes 322 facilitate the acceleration of the hinge 117 away from the retaining plate 114 when the differential pressure across the valve 310 changes direction, thereby further reducing the response time of the valve 310, i.e. reduces the closing time delay (Tc). As the differential pressure changes sign and the reverse flow begins (as illustrated by dotted arrows 322), the fluid pressure between the hinge 117 and the sealing plate 112 decreases and then the hinge 117 moves away from the holding plate 114 towards the sealing plate 116. The release holes 318 expose the outer surface 317 of the hinge 117 in contact with the retaining plate 114 to the pressure differential acting to close the valve 310. Also, the release holes 318 reduce the distance 360 that the fluid must penetrate. between retaining plate 114 and hinge 117 to release hinge 117 from retaining plate 114 as illustrated in Figure 11B. The release holes 318 may have a different diameter than the other holes 118, 120 in the valve plates. In Figures 11A and 11B, the retaining plate 114 acts to limit movement of the flap 117 and to support the flap 117 in the open position while having a reduced surface contact area with the surface 317 of the flap 117.

Figures 12A and 12B show two valves 110 as shown in Figure 7A where one valve 410 is oriented in the same position as the valve 110 of Figure 7A and the other valve 420 is inverted or reversed with the retention plate 114 on the underside and the sealing plate 116 on the upper side. The valves 410, 420 operate as described above with respect to the valve 110 of Figures 7A-7C and 8A-8B, but with the air flows in opposite directions as indicated by the arrow 412 dotted for the valve 410 and arrow 422 dotted valve 420 where one valve acts as an inlet valve and the other acts as an outlet valve. Figure 12C shows a graph of the operation cycle of valves 410, 420 between a closed and open position that are modulated by the square-wave cycle of the pressure differential (??) as illustrated by dotted lines (see Figures 9A and 9B). The graph shows a half cycle for each of the valves 410, 420 as each one opens from the closed position. When the differential pressure across the valve 410 is initially negative and reversed to become positive differential pressure (+?), The valve 410 opens as described above and is shown by the graph 414 with fluid flowing in the indicated direction by arrow 412. However, when the differential pressure across valve 420 is initially positive and reversed to become negative differential pressure (- ??), valve 420 opens as described above and as shown by the graph 424 with fluid flowing in the opposite direction as indicated by the arrow 422. Accordingly, the combination of the valves 410, 420 functions as a bi-directional valve allowing the flow of fluid in both directions in response to the cycle of the differential pressure (??) . The valves 410, 420 can be conveniently mounted to each other within the primary opening 46 'of the pump 10 to provide fluid flow in the direction indicated by the solid arrow in the primary opening 46' as shown in Figure 6A for one half cycle, and then in the opposite direction (not shown) for the half cycle opposite.

Figures 13 and 14 show yet another embodiment of the 410 valves, 420 of Figure 12A in which two valves 510, 520 corresponding to valves 410, 420, respectively, are formed within a single structure 505. Essentially, the two valves 510, 520 share a common wall or divider barrier 540 which in this case is formed as part of the wall 112, although other constructions may be possible. When the differential pressure through the valve 510 is initially negative and reversed to become positive differential pressure (+?), The valve 510 opens from its normally closed position with the fluid flowing in the direction indicated by the arrow 512 However, when the differential pressure across the valve 520 is initially positive and reversed to become a negative differential pressure (- ??), the valve 520 opens from its normally closed position with fluid flowing in the opposite direction As indicated by arrow 522. Accordingly, the combination of valves 510, 520 functions as a bidirectional valve that allows fluid flow in both directions in response to the differential pressure cycle (??).

Figure 15 shows still another embodiment of a bi-directional valve 555 having a similar structure as the bidirectional valve 505 of Figure 14. The bidirectional valve 551 is also formed within a simple structure having two 510, 530 valves that share a wall common or barrier 560 divider which is also formed as part of the wall 112. The valve 510 operates in the same manner as described above with the hinge 117 shown in the normally closed position blocking the holes 20 as also described above . However, the bidirectional valve 550 has a simple hinge 117 having a first hinge portion 117A inside the valve 510 and a second hinge portion 117B within the valve 530. The second hinge portion 117B is biased against the plate 516 and comprises orifices 522 which are aligned with the holes 120 of the plate 516 instead of the holes 118 of the plate 514 unlike the valves described above. Essentially, the valve 130 is predisposed by the flap portion 117B in a normally open position as distinguished from a normally closed position of other valves described above. Therefore, the combination of valves 510, 530 functions as a bidirectional valve that allows fluid flow in both directions in response to the differential pressure cycle (??) with the two valves opening and closing in alternate cycles.

It should be apparent from the foregoing that an invention having significant advantages has been provided. Although the invention is shown in only a few of its forms, not only is it limited but it is susceptible to several changes and modifications without departing from the spirit of the same.

Claims

CLAIMS 1. A pump characterized because it comprises: a pump body having a substantially cylindrical shape defining a cavity for containing a fluid, the cavity is formed by a side wall closed at both ends by substantially circular end walls, at least one of the end walls is an end wall driven having a central portion and a peripheral portion extending radially outwardly from the central portion of the driven end wall; an actuator operatively associated with the central portion of the end wall driven to cause an oscillatory movement of the driven end wall, whereby displacement oscillations of the driven end wall are generated in a direction substantially perpendicular thereto with an annular node between the center of the extreme driven wall and the side wall when in use; an isolator operatively associated with the peripheral portion of the driven end wall to reduce the damping of the displacement oscillations; a first opening disposed at any location in the cavity other than the location of the annular node and extending through the pump body; a second opening disposed at any location in the pump body different from the location of the first opening and extending through the pump body; Y , a hinge valve disposed in at least one of the first openings and second openings; wherein the displacement oscillations generate corresponding radial pressure oscillations of the fluid within the cavity of the pump body causing the fluid to flow through the first and second openings when in use. 2. The pump according to claim 1, characterized in that the ratio of the radius (r) of the cavity extends from the longitudinal axis of the cavity to the side wall at the height of the side wall of the cavity (h) is greater than 1.23. The pump according to claim 2, characterized in that the height (h) of the cavity and the radius (r) of the cavity are further related by the following equation: h2 / r > 4x10 ~ 10 meters. 4. The pump according to claim 2, characterized in that the second opening is arranged in one of the end walls at a distance of about 0.63 (r) ± 0.2 (r) from the center of the end wall. 5. The pump according to claim 2, characterized in that the actuator drives the end wall associated therewith to cause oscillatory movement at a frequency (f). 6. The pump according to claim 2, characterized in that the actuator drives the end wall associated therewith to cause an oscillatory movement at a frequency (f) in which the radius (r) is related to the frequency (f) by the following equation: k «cs < k0cf where cs ~ 115 m / s, cr ~ l 970 m / s, and k0 = 3.83. 7. The pump according to claim 1, characterized in that the lowest resonant frequency of the radial pressure oscillations is greater than about 500 Hz. 8. The pump according to claim 1, characterized in that the frequency of the displacement oscillations of the driven end wall is approximately equal to the lowest resonant frequency of the radial pressure oscillations. 9. The pump according to claim 1, characterized in that the frequency of the displacement oscillations of the driven end wall is within 20% of the lowest resonant frequency of the radial pressure oscillations. 10. The pump according to claim 1, characterized in that the displacement oscillations of the driven end wall are correlated in shape to the radial pressure oscillations. 11. The pump in accordance with the claim 1, characterized in that the valve allows the fluid to flow through the cavity substantially in one direction. 12. The pump in accordance with the claim 2, characterized in that the ratio is between about 10 and about 50 when the fluid in use within the cavity is a gas. 13. The pump according to claim 3, characterized in that the ratio of h 2 / r is between about 10"3 meters and about 10" 6 meters when the fluid in use within the cavity is a gas. 14. The pump according to claim 2, characterized in that the volume of the cavity is less than about 10 ml. 15. The pump according to claim 1, further characterized in that it comprises: a second actuator operatively associated with the central portion of the other end wall to cause an oscillatory movement of the end wall in a direction substantially perpendicular to it; Y a second insulator operatively associated with the peripheral portion of the end wall to reduce the damping of the oscillatory movement of the end wall by the side wall within the cavity. 16. The pump in accordance with the claim 1, characterized in that the actuator comprises a piezoelectric component for causing oscillatory movement. 17. The pump according to claim 1, characterized in that the actuator comprises a magnetostrictive component to provide the oscillatory movement. 18. The pump in accordance with the claim 2, "characterized in that the radius of the actuator is greater than or equal to 0.63 (r). 19. The pump according to claim 18, characterized in that the radius of the actuator is less than or equal to the radius of the cavity (r). 20. A pump characterized because it comprises: a pump body having a substantially cylindrical cavity having a side wall closed by two end surfaces to contain a fluid, the cavity having a height (h) and a radius (r), in which the ratio of the spokes (r) at height (h) is greater than about 1.2; an actuator operatively associated with a central portion of an end surface and adapted to cause an oscillatory movement of the end surface with an annular node between the center of the end surface and the side wall when used; an isolator operatively associated with a peripheral portion of the end surface to reduce the damping of the oscillatory movement; a first valve opening disposed at any location in the cavity other than the location of the annular node and extending through the pump body; a second valve opening disposed at any location on the pump body different from the location of the first opening and extending through the pump body; Y a hinge valve disposed in at least one of the first valve openings and second valve openings to allow fluid to flow through the cavity when in use. 21. The pump according to claim 20, characterized in that the flapper valve comprises: a first plate having openings that extend generally perpendicular through the first plate; a second plate having first openings extending generally perpendicular through the second plate, the first openings being substantially offset from the openings of the first plate; a spacer disposed between the first plate and the second plate to form a cavity therebetween in fluid communication with the openings of the first plate and the first openings of the second plate; Y a hinge disposed and movable between the first plate and the second plate, the hinge has substantially compensated openings of the openings of the first plate and substantially aligned with the first openings of the second plate; whereby the hinge is motivated between the first and second plates in response to a change in direction of the differential pressure of the fluid through the flapper valve. 22. The pump according to claim 21, characterized in that the second plate comprises second openings that extend generally perpendicular through the second plate and are separated between the first openings of the second plate, whereby the second openings are compensated of the openings of the hinge. 23. The pump according to claim 21, characterized in that the hinge is arranged adjacent to the first or second plates in a first position when the differential pressure is substantially zero and is movable to another of the first and second plates in a second position. when a differential pressure is applied, whereby the hinge is motivated from the first position to the second position in response to a change in direction of the differential pressure of the fluid through the flap valve and back to the first position in response to an inversion in the direction of the differential pressure of the fluid. 24. The pump in accordance with the claim 23, characterized in that the hinge is disposed adjacent to the second plate in a normally open position, whereby the fluid flows through the hinge valve when the hinge is in the first position and the fluid flow is blocked by the Hinge valve when the hinge is in the second position. 25. The pump in accordance with the claim 24, characterized in that the second plate also comprises second openings that extend generally perpendicular through the second plate and are spaced between the first openings of the second plate, whereby the second openings are offset from the openings of the hinge when it is in the second position. 26. The pump according to claim 23, characterized in that the hinge is arranged adjacent to the first plate in a normally closed position, whereby the flow of fluid is blocked by the hinge valve when the hinge is in the first position and the fluid flows through the flap valve when the hinge is in the second position. 27. The pump in accordance with the claim 26, characterized in that the second plate further comprises second openings extending generally perpendicular through the second plate and are spaced between the first openings of the second plate, whereby the second openings are offset from the openings of the hinge when it is in the second position. 28. The pump according to claim 21, characterized in that the first and second plates are formed from substantially rigid material selected from the group consisting of metal, plastic, silicone, and glass. 29. The pump according to claim 28, characterized in that the metal is steel having a thickness between about 100 and about 200 microns. 30. The pump according to claim 21, characterized in that the hinge and either one of the first or second plates are separated by a distance between about 5 microns and about 150 microns when the hinge is arranged adjacent to the other plate. 31. The pump according to claim 30, characterized in that the hinge is formed from a polymer having a thickness of about 3 microns and the distance between the hinge and any of the first and second plates is about 15 microns and about 50 microns when the hinge is arranged adjacent to the other plate. 32. The pump according to claim 21, characterized in that the hinge is formed from a light weight material selected from the group consisting of a polymer and metal. 33. The pump in accordance with the claim 32, characterized in that the lightweight material is a polymer having a thickness of less than about 20 microns. 34. The pump in accordance with the claim 33, characterized in that the polymer is polyethylene terephthalate having a thickness of about 3 microns. 35. The pump according to claim 33, characterized in that the polymer is a liquid crystal film having a thickness of about 3 microns. 36. The pump according to claim 21, characterized in that the openings in the first plate are less than about 500 microns in diameter. 37. The pump according to claim 21, characterized in that the hinge is formed from a polymer having a thickness of about 3 microns and the openings in the first plate are less than about 150 microns in diameter. 38. The pump according to claim 21, characterized in that the first and second plates are formed from steel having a thickness of about 100 microns, and wherein the openings of the first plate, the first openings of the second plates, and the openings of the hinge are about 150 microns in diameter, and wherein the hinge is formed from a polymer film having a thickness of about 3 microns. 39. The pump in accordance with the claim 21, characterized in that the change in direction of the differential pressure oscillates at a frequency of greater than about 20 kHz. 40. The pump according to claim 39, characterized in that the hinge has a response time delay of less than about twenty-five percent of the time period of the differential pressure oscillations. 41. The pump according to claim 21, characterized in that the first and second plates, the spacer, and the hinge comprise a first valve portion, and the hinge valve further comprises a second valve portion comprising: a first plate having openings that extend generally perpendicular through the first plate; a second plate having first openings extending generally perpendicular through the second plate, the first openings being substantially offset from the openings of the first plate; a spacer disposed between the first plate and the second plates to form a cavity therebetween in fluid communication with the openings of the first plate and the first openings of the second plate; Y a hinge disposed and movable between the first plate and second plate, the hinge has substantially compensated openings of the openings of the first plate and substantially aligned with the first openings of the second plate; whereby the hinge is motivated between the first and second plates in response to a change in direction of the differential pressure of the fluid through the flapper valve; Y wherein the first and second valve portions are oriented with respect to the differential pressure to allow the fluid through the two portions of the valve in opposite directions in response to the cycle of differential pressure of the fluid through the valve. 42. The pump in accordance with the claim 41, characterized in that the hinge of each valve portion is arranged adjacent to either one of the first and second plates in a first position when the differential pressure is substantially zero and movable to another of the first and second plates in a second position when a differential pressure is applied, whereby each of the hinges is motivated from the first position to the second position in response to a change in direction of the differential pressure of the fluid through the flap valve and back to the first position in response to a reversal of direction of the differential pressure of the fluid. 43. The pump according to claim 41, characterized in that the first and second valve portions are oriented in opposite directions with respect to the differential pressure, and the hinge of each valve portion is disposed adjacent to the second plate in a normally open position. , whereby fluid flows through each valve portion when the hinges are in the first position and the fluid flow is blocked by the valve portions when the hinges are in the second position. 44. The pump according to claim 41, characterized in that the first and second valve portions are oriented in opposite directions with respect to the differential pressure, and the hinge of each valve portion is arranged adjacent to the first plate in a normally closed position. , whereby the fluid flow is blocked by the valve portions when the hinges are in the first position and the fluid flows through the valve portions when the hinges are in the second position. 45. The pump according to claim 41, characterized in that the first and second valve portions are oriented in opposite directions with respect to the differential pressure, the hinge of the first valve portion is disposed adjacent the first plate of a normally closed position. whereby the fluid flow is blocked by the first valve portion when the hinge is in the first position and the fluid flows through the first valve portion when the hinge is in the second position, and the hinge of the valve is in the second position. the second valve portion is disposed adjacent the second plate in a normally open position whereby the fluid flows through the second valve portion when the hinge is in the first position and the fluid flow is blocked by the second valve portion when the hinge is in the second position. 46. The pump according to claim 20, characterized in that the oscillatory movement generates oscillations of radial pressure of the fluid within the cavity which causes the fluid to flow through the first opening and the second opening. 47. The pump according to claim 46, characterized in that the lowest resonant frequency of the radial pressure oscillations is greater than about 500 Hz. 48. The pump according to claim 46, characterized in that the frequency of the oscillatory movement is approximately equal to the lowest resonance frequency of the radial pressure oscillations. 49. The pump according to claim 46, characterized in that the frequency of the oscillatory movement is within 20% of the lowest resonant frequency of the radial pressure oscillations. 50. The pump according to claim 46, characterized in that the oscillatory movement is correlated in shape to the radial pressure oscillations. 51. The pump according to claim 20, characterized in that the height (h) of the cavity and the radius (r) of the cavity are further related by the following equation: h2 / r > 4x10"10 meters. 52. The pump according to claim 20, characterized in that the actuator drives the end surface of the cavity associated therewith to cause oscillatory movement at a frequency (f) where the radius (r) is related to the frequency (f) by the following equation: 2 P? 2 P? where cs ~ 1 15 m / s, c, ~ 1970 m / s, and k0 = 3.83. 53. The pump in accordance with the claim 20, characterized in that the radius of the actuator is greater than or equal to 0. 63 (r). 54. The pump according to claim 53, characterized in that the radius of the actuator is less than or equal to the radius of the cavity (r). 55. The pump according to claim 20, characterized in that the second valve opening is arranged on one of the end surfaces at a distance of about 0.63 (r) ± 0.2 (r) from the center of the end surface. 56. The pump according to claim 20, characterized in that the valve allows the fluid to flow through the cavity in substantially one direction. 57. The pump according to claim 20, characterized in that the ratio is within the range of about 10 and about 50 when the fluid in use within the cavity is a gas. 58. The pump according to claim 20, characterized in that the ratio of h 2 / r is between about 10 ~ 3 meters and about 10"6 meters when the fluid in use within the cavity is a gas. 59. The pump according to claim 20, characterized in that the volume of the cavity is less than about 10 ml. 60. The pump in accordance with the claim 20, further characterized because it comprises: a second actuator operatively associated with a central portion of the other end surface of the cavity to cause an oscillatory movement of the end surface; Y a second insulator operatively associated with a peripheral portion of the end surface to reduce the damping of the oscillatory movement. 61. The pump according to claim 20, characterized in that the actuator comprises a piezoelectric component for causing oscillatory movement. 62. The pump according to claim 20, characterized in that the actuator comprises a magnetostrictive component to provide the oscillatory movement. 63. The pump according to claim 20, characterized in that one of the end surfaces of the cavity has a frusto-conical shape wherein the height (h) of the cavity varies from a first height around the center of an end surface to a second height adjacent to the side wall smaller than the first height. 64. The pump according to claim 20, characterized in that one of the end surfaces of the cavity has a frusto-conical shape in which the height (h) of the cavity increases from a first height around the center of an end surface to a second height adjacent to the side wall. 65. The pump according to claim 64, characterized in that the ratio of the first height to the second height is not less than about 50%. 66. The pump according to claim 20, characterized in that the flapper valve is a bi-directional valve for controlling fluid flow in two directions, the bidirectional valve comprises at least two valve portions for controlling the fluid flow, each portion of Valve comprises: a first plate having openings that extend generally perpendicular through the first plate; a second plate having openings that extend generally perpendicular through the second plate, the first openings being theirs partially offset from the openings of the first plates; a spacer disposed between the first plate and the second plates to form a cavity therebetween in fluid communication with the openings of the first plate and the openings of the second plate; Y a hinge disposed and movable between the first and second plates, the hinge has substantially compensated openings of the openings of the first plate and substantially aligned with the openings of the second plate; whereby the hinge is motivated between the first and second plates in response to the change in direction of the differential pressure of the fluid through the valve; Y wherein the first and second valve portions are oriented with respect to the differential pressure to allow the fluid to flow through the two portions of the valve in opposite directions in response to the cycle of differential pressure of the fluid through the valve. 67. The bidirectional valve according to claim 66, characterized in that the hinge of each valve portion is arranged adjacent to any of the first and second plates in a first position when the differential pressure is substantially zero and movable to another first and second plates in a second position when differential pressure is applied, whereby each hinge is motivated from the first position to the second position in response to a change in direction of the differential pressure of the fluid through the valve and back to the first position in response to an inversion in the direction of the differential pressure of the fluid.