Abstract:
The method and system for attenuating or damping the amplitude of vacuum pressure oscillations in a vacuum system uses a flow-modulated damper to disperse and damp high-amplitude vacuum oscillations of a vacuum generator to a degree where fine vacuum control may be achieved for delicate work such as eye surgery.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 61/552,306, filed Oct. 27, 2011. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates generally to a method and system for attenuating or damping the amplitude of vacuum pressure oscillations in a vacuum system, and more particularly, which is self modulating to attenuate or damp high amplitude vacuum pressure oscillations to limit or prevent transmission thereof to sensitive apparatus connected to the system such as instruments and tools. 
       BACKGROUND ART 
       [0003]    The disclosure of U.S. Provisional Application No. 61/552,306, filed Oct. 27, 2011, is hereby incorporated herein in its entirety by reference. 
         [0004]    Vacuum generators that use air or another compressible gas, are well known for parts holding and pick &amp; place applications. Within the design parameters of the vacuum generator, the maximum vacuum level attained is typically controlled by changing the inlet feed pressure of the compressed gas supply. Part release is typically obtained by turning off the inlet air supply to allow ambient air to be drawn through the exhaust nozzle to dissipate vacuum in the downstream system. 
         [0005]    Compressible gas vacuum generators utilize a progression of gas flow nozzles for generating the vacuum. The first nozzle of a vacuum generator is configured to generate deep, maximum vacuum (greater than approximately 90% vacuum) and accomplishes this by increasing inlet air velocity to a sonic level as the feed pressure is increased and the vacuum level deepens. Until sonic velocity is approached, the induced vacuum pressure may exhibit minor low amplitude, low frequency oscillations, but is typically fairly stable overall. 
         [0006]    Because the media is compressible gas, as deeper vacuum levels are attained, it has been observed that within a relatively narrow range of feed air pressures, random rate instability and turbulence within the vacuum generator can cause higher amplitude random rate oscillations in vacuum pressure. This period of instability is often evidenced by exhaust air noises which can be heard as rapid popping or humming or squealing noises. In aeronautical engineering literature this instability/turbulence phenomenon is well documented for aircraft as they break the sound barrier. As a rule, the vacuum generated is proportional to the velocity of the air stream in the first nozzle, and the rapid velocity oscillations have been found to be accompanied by corresponding rapid ripples and spike oscillation in the vacuum level generated, which can exceed 45 mm Hg. peak-to-trough. Because the oscillations often occur at high frequency, they do not register on a bourdon tube style vacuum gauge due to slow response time of those gauges, but can be observed with an oscilloscope. 
         [0007]    For many industrial applications the high frequency, high amplitude vacuum oscillations are not problematic because the work pieces being held or manipulated are robust enough not to be damaged by the oscillations. Also, the attendant vacuum generator exhaust noises are often not noticed or of importance as they may be concealed by the ambient background noise of a manufacturing plant. However, high amplitude vacuum spikes can cause problems for more sensitive applications where the vacuum level must be precisely controlled, such as, but not limited to, applications such as in the medical field in which precision instruments are used and delicate parts or tissue is handled or manipulated. 
         [0008]    Referring to  FIG. 1 , vacuum flow is plotted against vacuum pressure generated by a representative vacuum generator supplied by compressed air at a particular feed pressure. The resulting curve shows that the generator produces high vacuum flow at shallow vacuum levels (near atmospheric pressure) and zero or near zero vacuum or air flow, hereinafter sometimes referred to as “vacuum flow” or “air flow”, at the deepest maximum vacuum level that can be attained in a sealed system. The area under the curve from atmospheric pressure to a particular vacuum level represents the power available to evacuate the volume of a system by the vacuum generator. The curve also shows several areas where irregularities caused by turbulent air flow through the first and second nozzles of the vacuum generator affect the vacuum generation, in particular, reduce it, at about −320 mm Hg. and about −520 mm Hg. 
         [0009]    The objectionable high amplitude vacuum pressure oscillations have been found to develop as vacuum level deepens and approaches its maximum level. This region of  FIG. 1  is magnified to illustrate representative oscillations in the maximum level region, and also comparatively at a shallower vacuum region. In a vacuum generator utilizing two nozzles, this effect is believed to be due to the instability of the air stream passing through the first nozzle as the compressed air is increased to sonic or near-sonic velocity in order to generate a less-than atmospheric pressure (vacuum) in the chamber between the nozzles. The oscillations were found to be most existent near the deepest vacuum, particularly between about −620 and −690 mm Hg. and can have a peak-to-peak amplitude greater than 100 mm Hg., reaching 180 mm Hg. or so. One practical application where this has been found problematic is for supplying vacuum to certain instruments for delicate surgery of the eye which require steady vacuum in this range. 
         [0010]    One known manner to attenuate or damp the transmission of the objectionable high amplitude vacuum pressure oscillations in a vacuum system is to use flow restrictors, such as baffles and the like. However, one shortcoming to this approach is that any flow restriction or restrictions between the nozzles and the vacuum system being evacuated by the vacuum generator will reduce the available power. Any restrictions can also cause system evacuation time to increase and will reduce the responsiveness of the overall system. Fixed flow restrictors such as baffles and the like are also disadvantageous as they are always present and thus do not modulate or vary in effectiveness in response to vacuum demand or the undesirable oscillations as they arise. For some applications such as the above referenced surgical instrument application, it is important that the oscillation damping be self-modulating to provide minimal resistance to vacuum flow throughout the full range of operation of the instruments. 
         [0011]    Although the above description is for a single-stage vacuum generator comprising a first and second nozzle in series, it should be noted that the noted shortcomings also pertain to multi-stage vacuum generators having three or more nozzles in series, and to larger capacity generators where sets of two or more nozzles are placed in parallel to obtain a greater vacuum flow rate. 
         [0012]    Thus, what is sought is a manner of attenuating or damping the amplitude of vacuum pressure oscillations in a vacuum system, and more particularly, which is self modulating to attenuate or damp high amplitude vacuum pressure oscillations to limit or prevent transmission thereof to sensitive apparatus connected to the system such as instruments and tools. 
       SUMMARY OF THE INVENTION 
       [0013]    What is disclosed is a method and system for attenuating or damping the amplitude of vacuum pressure oscillations in a vacuum using or powered system, which is self modulating to attenuate or damp high amplitude vacuum pressure oscillations to limit or prevent transmission thereof to sensitive apparatus of the using device or system such as instruments, tools, and the like. The invention may be integrated with the vacuum source, such as a vacuum generator or the like, or installed anywhere in the vacuum system, line or other flow path between the vacuum source, e.g., vacuum generator, and the using system. 
         [0014]    According to a preferred aspect of the invention, the method and system utilize a flow-modulated damper in a vacuum flow path between a vacuum generator and the vacuum using or powered system, configured and operable to reduce the amplitude of vacuum pressure oscillations conveyed to the vacuum using device or system, e.g., instruments, tools, and other devices thereof, at very low vacuum flow at maximum vacuum, and also under deep vacuum/low flow conditions. The flow-modulated damper is additionally configured to have minimal flow restriction over the full flow range of vacuum produced by a vacuum generator, so that pertinent performance parameters such as, but not limited to, system evacuation time and vent time, are not significantly affected, including under shallow vacuum/high flow conditions. As a result, in the deep and maximum vacuum ranges, as used here being generally in a −550 mm Hg. or higher level, vacuum pressure oscillations are reduced to a level where delicate parts and tissue can be held or manipulated without damage, and at shallower vacuum levels, flow and response are not significantly reduced. As an example of a practical application, in the medical field, and in surgery of the eye in particular, it is important for the surgeon to have precise vacuum pressure and to have deep vacuum delivered to the surgical instruments with minimum amplitude oscillations and good response time. 
         [0015]    In testing, the invention has been shown to reduce the vacuum oscillations by a factor of two-thirds and more in certain of those applications. For example, in a system wherein undamped oscillations can be found at 100 mm Hg. and reach as high as 180 mm Hg. peak to trough amplitude, use of the self-modulating damper of the invention has been found to reduce that amplitude to consistently as low as 20 mm Hg. 
         [0016]    According to another preferred aspect of the invention, the flow-modulated damper can be integrated into a housing that includes the vacuum generator, or it can be integrated into. e.g., plumbed, into a system as a stand-alone component in a vacuum flow path between the vacuum generator and vacuum using or powered device or system. The damper comprises an elongate element or member of a rubber or rubber-like polymer having resilient flexibility and a flat longitudinally extending surface. As a non-limiting example, the member can have a generally rectangular cross sectional shape. The element is constrained at one longitudinal end, and has an opposite free end, which in combination with the resilient flexibility enables it to function in the manner of a tongue. An intermediate portion of the element between the two ends is disposed over a port that connects the vacuum generator with the vacuum using system. The structure surrounding the port preferably forms a substantially flat surface or seat. The element, when in its flat free or unmodulated state, that is, unflexed, it is disposed in a closed position in covering relation to the port and lays against or contacts the seat around the periphery of the port, to form a substantially sealed condition thereabout, except for at least one small vacuum orifice which extend through a peripheral interface between the element and the seat, from the edge of the element to the edge of the port. 
         [0017]    The at least one small vacuum orifice is sufficiently configured in at least size, such that when the element is closed against the seat, it is capable of communicating a low vacuum or air flow level at deep vacuum from a using system connected to the port, but is insufficient in size to permit greater flow without modulating or opening. The shape, size and location of the vacuum orifice or orifices can be configured to provide a desired or metered level of low flow, and can be incorporated into the damper only; into the seat only; or partially in both the damper and the seat. As non-limiting examples, the orifice can be formed in the damper and/or seat by molding or machining. Also, it has been found that neither the orientation or location of the orifice with respect to the vacuum source is critical, which is desirable as it enables using the damper at about any location between a vacuum source and a using device or system, including in a chamber or plenum of a flow path adjacent to the vacuum source or generator or in a line connecting the generator with the using system. Still further, as noted above, the invention utilizes at least one of the small vacuum orifices, and they can be provided in a variety of configurations, as desired or required for a particular application. 
         [0018]    According to another preferred aspect of the invention, when the damper is in the unmodulated or closed position under low flow conditions at deep vacuum, the resilient property of the damper combined with the small size of the vacuum orifice or orifices has been found to substantially damp and limit amplitude of pressure oscillations through the orifice or orifices. This is advantageous, as it enables use of a variety of instruments and tools that are sensitive to or affected by such oscillations and require only minimal vacuum flow under deep vacuum conditions. Also advantageously, obstructions such as baffles or flow restrictors are not required in or about the orifice or orifices for preventing transmission of high amplitude vibrations, either from the vacuum generating side or the using side, such that that vacuum flow and response are not unacceptably affected or degraded under the no or low flow conditions. 
         [0019]    According to another preferred aspect of the invention, the flow-modulating capability is provided or facilitated by the characteristics of the damper, namely, a combination of the restraint of the damper at only one end, its resiliently flexibility, and the presence and configuration of the vacuum orifice or orifices. Essentially, with the damper unmodulated or closed, if flow through the small orifice, or orifices, is inadequate to meet demand, vacuum condition in the port and on the port side of the damper will be different, that is, shallower, than those on the vacuum generator side of the damper. As long as this differential vacuum condition exists, it will exert a resultant force on the damper, in a direction toward the deeper vacuum or lower pressure side, that is, away from the port. When this force is sufficient, the damper will responsively resiliently yield or flex, so as to break contact with at least a portion of the seat about the port and open to a certain extent which will be a function of the differential vacuum condition and characteristics of the damper. The opening of the damper will communicate vacuum flow from the port to at least one portion or region of the periphery of the damper, from where the air will flow toward the region of the lowest or deepest vacuum, generally toward the vacuum generator. 
         [0020]    The configuration and/or composition of the damper is selected such that when the damper is resiliently flexed or modulated, internal stresses will be generated within the damper, urging it to return to the flat or free state (unmodulated). These internal stresses will be in opposition to the external forces exerted by the differential vacuum condition. As a result, when modulated the damper will automatically flex to an extent or position wherein the internal stresses will equal the external forces. Because many factors or condition can change at any time, including, but not limited to, vacuum usage by the using system, generation, temperature and other environmental conditions, external forces exerted against the damper may be very dynamic, and the damper will responsively flex or modulate, in a manner seeking to achieve equilibrium between the external forces and internal stresses acting on it. In this regard, the resilient flexibility of the damper, dimensions and structural features thereof, as well as distance from the port to the constrained end, volume of regions or cavities on both sides of the damper, and port size and configuration, can be selected to achieve desired or required modulation characteristics. As one non-limiting example in this regard, the damper can be of one piece, uniform flat construction. As another example, the damper can include one or more grooves, ribs, or other structural features that will influence the manner of flexure thereof, e.g., more toward the free end verses toward the constrained end, more curvature or less, that can influence modulation characteristics reactive to flow and differential vacuum conditions. 
         [0021]    To explain further, the extent to and manner by which the damper will flex and open will be a function of the construction of the damper, which will be a constant, and the external forces and internal stresses generated by differential vacuum conditions, and flow through the vacuum port. As air (or other gases or vapors) flows between the surface of the damper and the seat or other adjacent surfaces, the surface area of the damper exposed to the shallower vacuum, may be increased, which can flex the damper to a greater extent or in a different manner compared to lesser flow conditions, until equilibrium is reached. If steady flow conditions are present, the damper is operable to maintain a steady flexed position, and the resilient property of the damper enables it to store the energy that it absorbs as the internal stresses, which will then be released to reduce the degree of flexure or return the damper to the flat or closed (unmodulated) condition, which like the flexure, will be a function of the vacuum flow through the damper. As a result, the damper is self modulating in both the opening and closing directions responsive to flow. 
         [0022]    As another preferred aspect of the invention, the self modulating capability and flexure characteristics of the damper can be selected to provide rapid or slow response to dynamic conditions, as desired or required for a particular application. The self modulating characteristics can also be configured to enable the damper to flex to an infinite number of positions between the unmodulated or fully closed or flat position and its fully flexed position responsive to a wide range of flow conditions that can rapidly change. 
         [0023]    As still another feature of the invention, the resilient composition and configuration of the damper enable it to absorb and damp a significant portion of any high amplitude pressure oscillations in proximity thereto, particularly when the damper is open. In regard to configuration, the attachment of the damper at only one end, and its resulting tongue like operability when open, presents a wedge shaped entrance region between the vacuum generating source and the port. This wedge shaped region is bounded on one side by the surface in which the port is located, and on the opposite side by the resiliently flexible damper. This configuration has been found to advantageously damp a substantial portion of any high amplitude pressure oscillations that enter that region, especially at lower flow rates under deeper vacuum conditions when the damper is only partially open and the wedge shaped area is relatively small in extent between the surface of the damper and the opposing surface, such that transmission of the pressure oscillations through the port to the using system or device is reduced markedly under the lower flow conditions, which is a particularly sought after feature for applications wherein sensitive instruments and tools are to be used. 
         [0024]    Thus, the combination of a vacuum generator and flow-modulated damper, are configurable according to the invention to provide a vacuum delivery system responsive to dynamic conditions, that attenuates or damps unwanted pressure disturbances under deep vacuum, no and low flow conditions, to provide steady, high quality vacuum to an instrument or instruments or other vacuum using or operated devices connected to the system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a graphical representation of vacuum level verses vacuum flow rate for a typical vacuum generator of a type capable of providing a range of air or gas flow rates at vacuum levels ranging from shallow to deep; 
           [0026]      FIG. 2  is a perspective view of apparatus of a system of the invention, including a housing with a cover panel removed to reveal a plenum, vacuum generator and flow-modulated damper of the system; 
           [0027]      FIG. 3  is an end view of the housing of  FIG. 2  showing an exhaust port of the system; 
           [0028]      FIG. 4  is a sectional view of the housing, showing elements of the vacuum system, including the vacuum generator and the flow-modulated damper in an unmodulated or closed position which communicates only low levels of vacuum flow (denoted by small arrows) from a using device connected to the system through a small vacuum orifice of the damper; 
           [0029]      FIG. 4A  is a simplified partial fragmentary sectional view of the housing and damper in the unmodulated or closed position, illustrating with arrows external forces exerted thereagainst by a differential vacuum condition; 
           [0030]      FIG. 5  is another sectional view of the housing, vacuum generator, and the flow-modulated damper in a partially open position, representative of the configuration of the system for a higher but still relatively low level of flow, denoted by larger arrows; 
           [0031]      FIG. 5A  is another simplified partial fragmentary sectional view of the housing, showing the damper in the partially open position, illustrating again with arrows external forces exerted thereagainst by a differential vacuum condition resulting from the higher level of flow; 
           [0032]      FIG. 6  is another sectional view of the housing, vacuum generator, and the flow-modulated damper in a more fully open position, representative of the configuration of the system for a still higher level of flow, denoted by still larger arrows; 
           [0033]      FIG. 7  is another sectional view of the housing, vacuum generator, and the flow-modulated damper, showing an alternative embodiment of a vacuum orifice of the damper; 
           [0034]      FIG. 8  is a sectional view of an alternative embodiment of apparatus of the vacuum system of the invention; 
           [0035]      FIG. 9  is a sectional view of another alternative embodiment of apparatus of the vacuum system of the invention; 
           [0036]      FIG. 10  is a plan view of one embodiment of a damper of the invention; 
           [0037]      FIG. 11  is a plan view of another embodiment of a damper of the invention; and; 
           [0038]      FIG. 12  is a graphical representation of vacuum level (pressure) verses vacuum for a vacuum system, illustrating in a first balloon representative undamped amplitude of vacuum pressure oscillations in the deep vacuum range generated during operation of the system, and in a second balloon representative reduction in amplitude of the oscillations achieved using the flow-modulated damper of the invention 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    Referring now to the drawings, wherein preferred embodiments of the invention are illustrated, as discussed above,  FIG. 1  is a graphical representation of vacuum level verses vacuum flow rate for a typical vacuum generator of a type typically utilized for providing vacuum to devices such as, but not limited to, instruments and tools for performing surgery on sensitive tissue such as the human eye. Such instruments commonly require relatively deep vacuum, e.g., more than about −550 mm Hg., at very low flow rates, as well as higher flow rates at shallower vacuum, e.g., under about −500 mm Hg. Three representative levels of vacuum demand are denoted by letters A, B and C. As also discussed above, a common problem encountered when using such sensitive instruments and tools is that disturbances in the vacuum flow commonly generated at deep vacuum conditions can be undesirably transmitted through the vacuum generation system to the instrument or tool. In particular, such disturbances of greatest concern include high amplitude pressure oscillations typically encountered at deep vacuum, low flow conditions, generally denoted by region D. 
         [0040]    Referring also to  FIGS. 2 through 6 , apparatus  20  of a system of the invention for attenuating or damping the amplitude of vacuum pressure oscillations in a vacuum system, is shown. Apparatus  20  includes a flow-modulated damper  22  that is integrated into a housing  24 , along with a vacuum generator  26  including a first nozzle  28  and a second nozzle  30  disposed in a passage through housing  24  between an inlet port  32  that will be connected to a source of pressurized gas, such as air or another suitable gas or a mixture of gases (herein referred to collectively as “air”), and an exhaust port  34  through which the gas will be exhausted from the system. Housing  24  can be formed, for instance, of a suitable substantially rigid material such as a metal or plastics, with the required features molded or machined therein, and can include an optional removable service panel or cover  24 A, as illustrated in  FIG. 2 . Nozzle  28  has a converging internal flow passage through which the pressurized gas (denoted by arrows G in  FIG. 4 , flows, that increases the velocity of the gas stream flowing across a gap  36  between nozzles  28  and  30 , just before the stream enters nozzle  30 . In accordance with Bernoulli&#39;s principle, the gas stream causes a sub-atmospheric pressure (vacuum) in and adjacent plenum or chamber  38  in connection with  36 . The gas stream expands and slows as it passes through nozzle  30  then exhausts to atmosphere through port  34 . 
         [0041]    The flow-modulated damper  22  includes a flexible element  40  preferably constructed of a resiliently flexible material, such as, but not limited to, a rubber or rubber-like polymer material, having a first end  42  constrained at one end in a cavity formed by housing  24  adjacent to chamber  38 , and an opposite second end  44  located in chamber  38 . Second end  44  preferably has an elongate shape with a thin cross section relative to its length, so as to have opposite, longitudinally extending surfaces, at least one of which preferably is flat. Second end  44  in its free state is substantially straight, so as to be capable of conforming to a straight flat surface, when placed in abutment therewith, and is freely flexible, so as to be capable of flexing away from the surface at an acute angle thereto, essentially in the manner of a tongue. The composition and structure of flexible element  40 , including the shape and dimensions of second end  44 , can be selected to provide desired flexibility characteristics for a particular application. 
         [0042]    Referring more particularly to  FIGS. 4 and 4A , second end  44  of element  40  is positioned such that a flat longitudinally extending surface  46  surface thereof, in its free or unmodulated state, is positioned to lay against or abut an internal surface of housing  24  bounding chamber  38 , which serves as a seat  48 . Seat  48  is similarly flat and further extends about one end of a vacuum port  50  of a vacuum flow path of the system. The other end of vacuum port  50  connects with a using system or device  52 , which can comprise, but is not limited to a vacuum powered tool or instrument used for surgery of the eye or the like. 
         [0043]    In the embodiment shown, flexible element  40  is positioned and configured such that in the unmodulated condition or state an intermediate portion of second end  44  is disposed over port  50  and lays against or contacts seat  48  around the periphery of the port, to form a substantially sealed condition thereabout. Second end  44  further includes small vacuum orifices  54 , here on opposite sides of the damper, each of which extends through a peripheral interface between the damper and seat  48  (see  FIGS. 10 and 11  also), from the edge of the damper to at least the edge of the port, to communicate port  50  with chamber  38  in connection with vacuum generator  26 . 
         [0044]    Each vacuum orifice  54  is sized and configured such that when flexible element  40  is unmodulated so as to lay against seat  48 , it is capable of communicating a low vacuum flow level at deep vacuum from a using device or system, represented by system  52  shown connected to port  50 , but is insufficient in size to permit greater flow. To provide this capability it can be observed that the sectional flow area through each vacuum orifice  54  (and collectively through both orifices  54 ) is substantially smaller than a sectional flow area through port  50 . Here, as noted above, each vacuum orifice  54  is located in a side of second end  44  of the damper, to provide a desired or metered level of low vacuum flow from using system  52  under deep vacuum conditions. When flexible element  40  is in the closed position under these conditions, the resilient property combined with the small size of orifices  54  damps and limits transmission of high amplitude pressure oscillations through the orifices without need for obstructions such as baffles or flow restrictors that can reduce responsiveness at low flow conditions. As an example, the configuration of damper  22  shown, which is representative of both of the embodiments shown in  FIGS. 10 and 11 , has been found to reduce the amplitude of oscillations substantially, e.g., down to as low as 20 mm Hg. compared to as greater than 100 mm Hg. Undamped, as illustrated graphically in  FIG. 12 . 
         [0045]    Referring in particular to  FIGS. 4 and 4A , flow-modulated damper  22  is shown with second end  44  of flexible element  40  in a flat position and configuration, that is, unmodulated, abutting or laying against and forming a substantially sealed condition with seat  48  except for the flow communicated therebetween through vacuum orifices  54 . Here, due to this substantially sealed condition, only very low flow, as denoted by the small arrows, or no flow occurs between the using system or device, represented by device  52 , which is representative of flow conditions in the area of the graph of  FIG. 1  denoted by letter A. 
         [0046]    When element  40  is unmodulated or closed, if vacuum flow through orifices  54  is inadequate to meet vacuum demand of the using system or device, pressure in port  50  will increase, that is, the vacuum condition in port  50  will be shallower, than that in chamber  38  on the vacuum generator side of element  40 . This will result in a differential vacuum condition between chamber  38  on one side of element  40 , and port  50  on the other side, which will exert a force on element  40 , in a region of surface  46  generally corresponding to the location and shape of port  50 , in a direction toward the deeper vacuum or lower pressure side, that is, away from port  50 , as denoted by force arrow array  56 . 
         [0047]    Referring more particularly to  FIGS. 5 and 5A , if the differential vacuum condition increases sufficiently, the resulting force acting on element  40  will increase sufficiently to cause element  40  to responsively modulate, by resiliently yielding or flexing, so as to break contact with at least a portion of seat  48  and open to a certain extent, as denoted by numeral  58 . Opening  58  provides a path for vacuum or air flow between surface  46  and seat  48 , from port  50  to at least one portion or region of the periphery of element  40 , from where the air will seek the region of the lowest or deepest vacuum, generally toward vacuum generator  26 , as denoted by the heavier arrows. This flexure is facilitated by the configuration and composition of element  40 . When opening  58  is present, the region of surface  46  of flexible element  40  against which the external forces of the shallower vacuum (higher pressure) condition are exerted will increase, as denoted by enlarged force array  56 A in  FIG. 5A . The forces can vary in degree and location, as a function of the location of opening  58 , level of vacuum flow, velocity thereof, and other factors. This is representative of the position and configuration of flexible element  40  under deep vacuum, low vacuum or air flow conditions as generally identified by region B of the graph of  FIG. 1 . Under these conditions, vacuum oscillations can cause using system or device problems, but the position and configuration of flexible element  40  provide maximum oscillation damping effect while still not restricting vacuum flow. 
         [0048]    As a result of the flexure, internal stresses will develop within flexible element  40 , denoted by arrow  60  (shown externally of the flexible element due to its small size). Internal stresses  60  oppose external forces  58 , and an equilibrium condition therebetween will be reached, with the flexible element being flexed in a corresponding manner reflecting the distribution of forces and internal stresses. The flow conditions may be dynamic to varying extents, or more static. If conditions are dynamic, distribution of forces can vary, such that the shape and/or degree of flexure of flexible element  40  may vary considerably. If conditions are more steady state, flexible element  40  can maintain a more constant flexed shape and/or position. When flexed, the resiliency or elasticity of flexible element  40  enables it to store the energy of internal stresses  60  urging it to return to its flat shape and position. When the flow conditions lessen, the external forces will be reduced, and flexible element will release a corresponding proportion of internal stresses  60  to reduce the degree of flexure thereof and the size of opening  58 . Thus, damper  22  is self modulating in both the opening and closing directions responsive to flow. 
         [0049]    Because many factors or condition can change at any time, including, but not limited to, vacuum usage by the using system or device, generation, temperature and other environmental conditions, external forces  58  exerted against flexible element  40  may be very dynamic, and the flexible element will responsively flex or modulate, in a manner to reach equilibrium between the external forces and internal stresses  60 . 
         [0050]    Referring more particularly to  FIG. 6 , increased flexure of flexible element  40  to a more fully open position is illustrated, responsive to greater vacuum flow from using device  52  to vacuum generator  26 , as denoted by the heavier arrows. Here, the size of opening  58  is significantly larger, and there is greater curvature of flexible element  40 , which is indicative of greater external forces acting on the flexible element resulting from the flow. This is representative of the position and configuration of flexible element  40  under shallow vacuum, high air flow conditions, about as illustrated at location C on the graph of  FIG. 1 . Under these conditions vacuum oscillations are not an issue and the fully or nearly fully open damper  22  causes minimal flow restriction so vacuum flow is maximized and system evacuation time is minimized. 
         [0051]    The resilient flexibility of flexible element  40 , dimensions and structural features thereof, as well as distance of port  50  to constrained end  42 , volume of chamber  38  and port  50 , and the configurations thereof, can be selected to achieve desired or required flow and modulation characteristics. As a non-limiting example, second end  44  of flexible element  40  can be of one piece, uniform flat construction, with the exception of vacuum orifice or orifices  54 , which can be located on only one side of the flexible element, or on two or more sides, to communicate vacuum or air flow from two or more sides of the flexible element. The location of orifice or orifices  54  at an intermediate position between the ends of end  44  of flexible element  40  can also serve to reduce the cross sectional extent thereof, which can facilitate flexure of the flexible element at that location, as will be discussed in reference to  FIGS. 10 and 11  below. Additionally, end  44  can include one or more grooves, ribs, or other structural elements to further influence or change the manner or degree of flexure thereof, e.g., to increase flexure more toward the free end verses toward the constrained end, or to increase or decrease the radius of curvature, to influence modulation characteristics reactive to flow and differential vacuum conditions in a desired manner. 
         [0052]    The resilient composition and configuration of flexible element  40  additionally enable it to absorb and damp a significant portion of any high amplitude pressure oscillations, particularly when the flexible element is unmodulated and closed, or partially modulated and open, as represented in  FIGS. 4 ,  4 A,  5 , and  5 A. In particular, in the unmodulated state, the rubber or rubbery material of element  40  bounds one side of each vacuum orifice  54 , the other side being the seat  48 , such that pressure oscillations are damped or attenuated by impinging the rubber or rubbery surface bounding the orifices  54 . In the partially modulated state, the oscillations are damped first by impinging surface  46  of flexible element  40  which absorbs and attenuates pressure spikes. When the flexible element is open so as to form wedge shaped opening  58 , the pressure spikes are deflected by the geometry of the opening outwardly toward chamber  38  and away from port  50 . As the pressure waves expand outward, the wave amplitude is decreased so the oscillations are effectively dispersed and damped. Additionally, as can be best seen in  FIGS. 4A and 5A , surface  46  extends a significant distance past port  50 . This can be advantageous to provide additional surface area for deflecting, absorbing, and attenuating the pressure spikes. This additional extent can be tailored, as desired or required to achieve desired damping effect. 
         [0053]    In particular with regard to  FIGS. 5 ,  5 A, and  6 , it can be observed that flexible element  40  is oriented and positioned to extend longitudinally toward gap  36  of vacuum generator  26 , and such that the free end of second end  44  of flexible element  40  is disposed closely adjacent to that gap. This is advantageous as it aligns flexible element  40  and wedge shaped opening  58  longitudinally with the most direct vacuum flow path between port  50  and gap  36 , such that pressure waves emanating from gap  36  toward port  50  and entering the wedge shaped opening will be exposed to the maximum damping effect of the invention. 
         [0054]    Referring also to  FIGS. 7 ,  8 , and  9 , several alternative embodiments of apparatus  20  of the invention are shown. In  FIG. 7 , flow-modulated damper  22  is configured slightly differently by locating vacuum orifice or orifices  54  in an edge or lip on the periphery of vacuum port  50 , instead of formed in second end  44  of flexible element  40  as in the embodiment of  FIGS. 4 ,  4 A,  5 , and  5 A. Otherwise, nozzles  28  and  30 , ports  32  and  34  and chamber  38  are configured as discussed above. This location of orifice or orifices  54  provides similar or the same vacuum generation, operation and damping as just explained. 
         [0055]    In the embodiments of the invention of  FIGS. 8 and 9 , flow-modulated damper  22  is contained in an inline housing  62 , which will be connected between a vacuum generator, such as generator  26  of the previous FIGS., and a using system or device, as illustrated by the flow arrows. Housing  62  includes a vacuum generator port  64  and a vacuum port  50  for connection via suitable lines or plumbing to the vacuum generator and the using system, respectively. Flexible element  40  is located in the same relation to vacuum port  50  as in the previous embodiments, but vacuum generator port  64  is in a different location than gap  36  of vacuum generator  26  of the embodiments discussed above, but is still adjacent to the free end of second end  44  of flexible element  40 . Alternatively, port  64  can be located in other surfaces of housing  62 , such as surface  66 , and chamber  38  can be dimensioned differently, as desired or required for achieving sought after vacuum power and/or damping characteristics for a particular application. 
         [0056]    Essentially, the only difference between the embodiments of  FIGS. 8 and 9  is the location of small vacuum orifices  54 , which is in second end  44  of flexible element  40  in  FIG. 8 , and in the edge of housing  62  bounding port  50 . Damper  22  of both embodiments will operate in substantially the same manner as described above, to provide flow-modulated vacuum to the using system or device, while damping transmission of high amplitude pressure oscillations to the using system or device under deep and maximum vacuum and low flow or no flow conditions. 
         [0057]    Referring also to  FIGS. 10 and 11 , alternative embodiments of flexible element  40  are illustrated. First end  42  of the flexible elements is the same for both versions. Both flexible elements include small vacuum orifices  54  in opposite sides of second end  44 . However, in the version of  FIG. 10 , vacuum orifices are separated, such that the flexible element forms a rib  68  that acts to stiffen the flexible element at that location. In contrast, in the version of  FIG. 11 , orifices  54  connect, or extend completely across the flexible element, such that it is more easily flexed at that location, more in the manner of a hinge, whereas the version of  FIG. 10  can be expected to flex in a more curvaceous manner at this location. As a non-limiting example, the more easily flexed version of  FIG. 11  may have more utility or responsiveness at lower differential pressures, or when a greater amount of air or gas flow is desired for a particular differential pressure. 
         [0058]    Referring also to  FIG. 12 , a graphical representation of vacuum level verses vacuum flow for a vacuum system at deep vacuum, low flow, is shown. In the balloon on the left, typical undamped vacuum pressure oscillations under deep vacuum of between about −550 mm Hg. and about −700 mm Hg., and low flow conditions, having a representative peak-to-trough amplitude of about 100 mm Hg., are illustrated. In the balloon on the right, the deep vacuum pressure oscillations are illustrated, damped using a flow-modulating damper of the invention as shown in  FIG. 4 . 
         [0059]    It can be observed in the illustrations of the balloons of  FIG. 12 , that amplitude of the oscillations is reduced to about 20 mm Hg. 
         [0060]    As another advantage of damper  22  of the invention, vacuum orifice or orifices  54  will allow flow in both directions, that is, as vacuum flow from the using system or device to the vacuum chamber or generator, and in the reverse direction, so when the air supply is removed from inlet port  32 , system vacuum will be vented by atmospheric air flowing into port  34 , through nozzle  30  and into chamber  38 , through vacuum orifice or orifices  54  and into vacuum port  50 . 
         [0061]    Here, it should be noted that vacuum orifice  54  is depicted larger than its actual size so as to be easily visible, but in practice will be substantially smaller, its actual size to be determined as a function of vacuum flow requirements of a using device or system and other application parameters. It should also be noted that orifice or orifices  54  can be incorporated completely into flexible element  40 ; completely in seat  48 ; or partially in each, as desired or required for a particular application. Additionally, although vacuum orifices  54  are depicted herein as being located in the side of flexible element  40  or a corresponding location on seat  48 , alternatively, they or an additional orifice  54  can be located in another surfaces of the flexible element or seat, as desired or required for a particular application. 
         [0062]    In light of all the foregoing, it should thus be apparent to those skilled in the art that there has been shown and described a method and system for attenuating or damping the amplitude of vacuum pressure oscillations in a vacuum system using a flow modulated damper. However, it should also be apparent that, within the principles and scope of the invention, many changes are possible and contemplated, including in the details, materials, and arrangements of parts which have been described and illustrated to explain the nature of the invention. Thus, while the foregoing description and discussion addresses certain preferred embodiments or elements of the invention, it should further be understood that concepts of the invention, as based upon the foregoing description and discussion, may be readily incorporated into or employed in other embodiments and constructions without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown, and all changes, modifications, variations, and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is limited only by the claims which follow.