Improved flow regulator

Technical Field

This invention generally relates to a device for regulating the flow of a fluid, particularly a gas, through the device.

Background Art

In heating, ventilating, and air conditioning (HVAC) systems and house exhaust systems, air flow is typically controlled using resistors to slow down the flow of air to and from different points in a building. When one resistor is adjusted, the pressure level throughout the system will change; any change in the system pressure will affect the flow of air past every other resistor. Thus, adjusting a resistor at one point causes "cross-talk" with resistors at other points.

One of the most complex problems confronted by the HVAC industry is controlling air flow through process rooms, such as the clean rooms used in semiconductor integrated-circuit chip manufacturing. Some air exits the process room through process equipment and other work stations with fume hoods. A partial vacuum is usually required in such equipment in order to ensure that noxious fumes do not leak from the process equipment or fume hoods and thereby endanger personnel working nearby. It is frequently important that a constant partial vacuum be maintained in, or a constant flow rate be maintained through, the process equipment in order to minimize defects in the integrated circuit chips being manufactured. The fumes from some process equipment may be prone to condense on regulators mounted between the process equipment and the house exhaust system. Regulators used in such situations must be frequently cleaned and maintained.

The invention is defined in the attached independent claim. Further, preferred features may be found in the sub-claims appended thereto.

The present invention regulates a partial vacuum in a region, such as in a piece of process equipment or a fume hood. The partial vacuum may be with respect to the environment in which the equipment is located, so that the region's pressure is between the pressure of the environment and the pressure of the vacuum source to which the regulator is attached.

The regulator according to the present invention includes a hingedly mounted leaf-piston member having a distal face, exposed to a reference pressure, and a frontal face forming a portion of the conduit wall, the member being hingedly mounted about a pivot point. In a preferred embodiment, the distal face is on top and the frontal face on the bottom of the member. Attached to the member is a gate extending into the passageway so as to variably impede fluid flowing through the passageway at a constriction point. Preferably, the gate is in the form of a grate that is fixedly attached to the member at a point downstream from the pivot point. A fixed grate is mounted immediately adjacent the movable member's grate, so that the two grates form a plurality of constriction points. The gate's impedance on the fluid flow varies as a function of the pressure differential across the member's frontal and distal faces. The gate and the member are mounted so that each moves in a direction transverse to the direction of the fluid through the constriction point.

The regulator uses a restoring torque on the member around the pivot point tending to tend to cause the gate to lessen the impedance on the fluid flow, so that when there is no flow through the passageway the amount that the gate impedes the flow is relatively low. Preferably, the restoring torque is created by the weight of the member upstream of the pivot point. A counterweight may be used in order to create a large enough restoring torque. The counterweight may be mounted on a rail to permit the restoring torque to be easily modified.

To permit easy removal of the member and the gate, the member preferably has a downward-facing groove at the pivot point, so that the member can pivotally rest on a rod fixedly attached to the conduit at the pivot point.

To inhibit the member from vibrating, the regulator includes a dashpot formed with a section of the member and a section of the conduit's fixed portion, the two sections being located immediately adjacent each other. The movable member's section of the dashpot and the fixed portion of the dashpot define a dashpot volume of fluid, which varies as the position of the member varies, but which is always substantially smaller than the volume of fluid in the conduit between the constriction point and the pivot point. The dashpot is preferably vented to the reference pressure and to the plenum.

One embodiment of the regulator includes a bypass channel, into which the gate does not extend, even when the gate is imparting the greatest impedance on the flow, so that a portion of the flow through the passageway bypasses the constriction points defined by the fixed and movable portions. This embodiment preferably includes a variable throttle valve for variably restricting the flow bypassing the constriction points defined by the fixed and movable portions of the impedance means.

Brief Description of the Drawings

<ul id="ul0001" list-style="none" compact="compact"><li>FIG. 1 shows a cross-section of a regulator according to the present invention with little or no flow passing through it.</li><li>FIG. 2 shows a cross-section of the FIG. 1 regulator with sufficient flow to cause the piston member to pivot downward and increase the impedance on the flow through the regulator.</li><li>FIG. 3A shows a cross-section of an alternative embodiment of the regulator with a bypass throttle valve and with little or no flow passing through it, and FIG. 3B shows a detail of FIG. 3A.</li><li>FIG. 4A shows a cross-section of the FIG. 3A embodiment with the bypass throttle valve adjusted and with a significant amount of flow passing through it, and FIG. 4B shows a detail of FIG. 4A..</li><li>FIG. 5 is a graph representing how the flows through the FIGS. 1 and 3 embodiments are regulated.</li></ul>

Description of Specific Embodiments

FIG. 1 shows a preferred embodiment of the present invention. The regulator shown in FIG. 1 is similar in many respects to the regulator shown in Fig. 1 of U.S. Patent No. 5,251,654. Like this earlier regulator, the leaf-piston member <b>5</b> is hingedly mounted, and variations in the pressure differential across the member--between the frontal face <b>52</b> and distal face <b>51</b>--will tend to rotate the member <b>5</b> around the pivot point <b>84.</b> The distal face <b>51</b> is preferably exposed to ambient pressure, and the regulator maintains a constant pressure differential between the ambient pressure (or whatever reference pressure is chosen) and the plenum <b>79,</b> with the plenum pressure being less than the ambient (or reference) pressure.

The FIG. 1 regulator is particularly useful for maintaining a partial vacuum in process equipment, and this is accomplished by attaching the inlet <b>81</b> to the process equipment and attaching the outlet <b>82</b> of the regulator to a vacuum source. In a typical application, air flows from the environment in which the process equipment sits, into and through the process equipment, then through the regulator, and finally to the house exhaust system. The pressure in the environment, the air of which is substantially still, is exposed to the member's distal face <b>51</b> and thereby serves as the reference pressure.

The member <b>5</b> has a gate <b>96</b> attached to it. In the FIG. 1 embodiment, the gate <b>96</b> is a grate having a pair of arms <b>967</b> (only one of which is shown in the cross-section view of FIG. 1) extending downwardly and supporting the ends of the upstream crosspieces <b>961,</b> which collectively form the movable grate. Each of the upstream crosspieces <b>961</b> has immediately adjacent to it a corresponding downstream crosspiece <b>964,</b> which is connected to the sidewalls of the conduit. The downstream crosspieces <b>964</b> form the fixed grate <b>94,</b> which cooperates with the movable grate <b>96</b> to form constriction points, through which the flow passes. These crosspieces perform the same function as the airfoil segments shown in Figs. 5, 6, 7A and 7B of U.S. Patent No. 5,251,654 (referenced hereinabove), and the grates shown in Figs. 1 and 5 of U.S. Patent No.5,320,124; they create a variable impedance on the flow through the regulator. (Different arrangements of the grates are possible; for instance, the fixed grate <b>94</b> may be located upstream of the movable grate <b>96,</b> although it will be appreciated that the arrangement shown in FIG. 1, with the fixed grate <b>96</b> located downstream and the movable grate located closer to the pivot point <b>84,</b> is simpler to construct and disassemble.)

The member <b>5</b> is weighted so that, when there is little or no flow through the regulator, the gate <b>96</b> is pulled all the way up--as shown in FIG. 1--and causes the least impedance. In the preferred embodiment, this is accomplished by a counterweight <b>90</b> mounted on a rail <b>91,</b> along which the counterweight can be moved. The counterweight <b>90</b> is mounted so that it applies a torque on the member <b>5</b> around the pivot point <b>84,</b> opposite of and greater than the torque applied by the gate <b>96</b> and the rest of the member <b>5</b> to the right (as shown in the drawing) of the pivot point <b>84.</b> Thus, the member <b>5</b> has a net torque rotating it into its position of least impedance (the member's highest position). This torque is called the restoring torque. The FIG. 1 regulator also includes a dashpot <b>25</b> located near the pivot point <b>84;</b> the dashpot <b>25</b> is discussed in greater detail below.

FIG. 2 shows the FIG. 1 regulator with sufficient vacuum being applied to its outlet <b>82</b> to cause the member <b>5</b> to rotate down, causing the upstream and downstream crosspieces, <b>961</b> and <b>964,</b> to narrow the constriction points <b>80</b> and increase the impedance on the flow through the conduit. Because the torque being applied by the counterweight <b>90</b> is substantially constant and because the movable crosspieces <b>961</b> move transversely to the fluid flowing through the constriction points <b>80,</b> the regulator is able to maintain a constant pressure differential between the reference pressure exerted on the member's distal face <b>51</b> and the plenum <b>79</b>--once a sufficient vacuum is applied to the outlet <b>82</b> to cause the member to rotate downward, and until the vacuum at the outlet <b>82</b> becomes so great that the member <b>5</b> cannot rotate down any further. The traverse movement of the movable crosspieces <b>961</b> across the constriction points <b>80</b> prevents the movement of the member <b>5</b> from being directly affected by the pressure of the vacuum source, so that the regulator may maintain a constant partial vacuum in the plenum <b>79</b> despite variations in the strength of the vacuum source.

The torque created by the counterweight <b>90</b> can be modified by changing the position of the counterweight <b>90</b> along the rail <b>91.</b> (Of course several counterweights may be used, and each may be mounted on a separate rail.) The further from the pivot point <b>848</b> that the counterweight <b>90</b> is positioned, the greater the torque rotating the member <b>5</b> upwardly and the greater the reference-/plenum-pressure differential maintained by the regulator. The constant pressure differential between the plenum <b>79</b> and the member's distal face <b>51</b> can be used to maintain a substantially constant partial vacuum in the process equipment to which the inlet <b>81</b> is attached, or to maintain a substantially constant flow rate through the device.

The member <b>5</b> rotates up and down in order to compensate for changes in the vacuum source pressure, as well as changes in the reference pressure against distal face <b>51</b> and changes in the restrictions on the flow from the environment, in which the process equipment sits, to the plenum. (An example of a change in the restriction on the flow from the environment to the plenum would be when the doors of the process equipment are opened and closed: opening the doors decreases the amount of restriction on the flow from the environment into the equipment and to the plenum; closing the doors increases the restriction on the flow from the environment into the equipment and the plenum.) In rotating up and down, the member <b>5</b> may become subject to harmonic oscillations, so according to the invention the regulator includes a dashpot <b>25</b> to reduce high-frequency oscillations. The dashpot <b>25</b> may be formed by sections of the member <b>5</b> and the fixed portion of the conduit. A similar dashpot design is shown in the embodiment depicted in FIGS. 3A and 4A. As shown in FIG. 4B, a section <b>92</b> of the member <b>5</b> and a section <b>42</b> of the fixed portion of the conduit together define a dashpot volume <b>29.</b> The size of this volume <b>29</b> is a small fraction of the volume of the plenum <b>79,</b> below the frontal face <b>52</b> of the member <b>5</b>. Because of the small size of the dashpot volume <b>29,</b> quick large changes in the position of the member <b>5</b>--resulting from quick large changes reference-/plenum-pressure differential--would cause enormous changes in the pressure of the gas in the volume <b>29.</b> Thus, the dashpot <b>25</b> tends to slow any quick large movements of the member <b>5</b>. Slow changes in the position of the member <b>5</b>--resulting from slow changes in the reference-/plenum-pressure differential--are not inhibited by the dashpot <b>25</b> because the gas in the dashpot volume <b>29</b> can slowly escape from or flow into the dashpot volume <b>29.</b> The dashpot <b>25</b> is preferably vented at two locations, one location <b>26</b> leading into the reference chamber above the member's distal face <b>52,</b> and the other location <b>27</b> leading into the plenum <b>79.</b> By venting the dashpot volume <b>29</b> to the reference pressure and the plenum pressure, the effect of the dashpot <b>25</b> on the regulator's ability to maintain a constant pressure differential is minimized. (For example, it will be appreciated that if the dashpot volume were exposed to the pressure downstream of the gate-i.e., the vacuum-source pressure--the position of the member could be affected directly by the vacuum-source pressure.) The vents <b>26</b> and <b>27</b> to the dashpot should be very narrow in order to greatly inhibit the flow into and out the dashpot volume <b>29,</b> without preventing flow into and out of the volume <b>29.</b>

The two depicted embodiments, one of which is shown in FIGS. 1 and 2, and the other of which is shown in FIGS. 3A and 4A, have a design that is advantageous for use with "wet" process equipment, i.e., equipment which create fumes that may condense in the regulator. By mounting the piston member <b>5</b> at the top of the regulator, the bottom portion of the regulator may be made solid so that any condensation will be caught at the bottom of the regulator, from where it can be drained. (If the member <b>5</b> were mounted on the bottom of the regulator, condensation could seep through the gaps between the member <b>5</b> and the rest of the conduit walls.)

The design also allows the easy removal of the member/gate structure. The member <b>5</b> has a groove <b>849</b> at the location of the pivot point. The groove <b>849</b> rests on a rod <b>848</b> (preferably a Teflon-coated rod to reduce friction) so that the member can rotate around the pivot point and so that the member/gate structure can be easily removed off of the rod <b>848.</b> This arrangement permits easy access into the inside of the regulator so that the regulator's inside and in particular the movable crosspieces <b>961</b> can be easily cleaned. (Although in the preferred embodiments shown herein, the gate <b>96</b> is fixedly attached to, or is an integral portion of, the member, in alternative embodiments the gate may be hingedly attached to the member. Such an alternative structure makes the regulator somewhat more complicated to disassemble and to clean.)

The embodiment shown in FIGS. 3A and 4A also allows the removal of the fixed crosspieces <b>964,</b> the pivot rod <b>848</b> and the fixed section <b>42</b> of the damper <b>92</b> so that these items may also be easily cleaned. The fixed portion of the conduit includes a removable portion <b>40</b> that can be unfastened and easily removed from the rest of the regulator. It will be appreciated that this embodiment permits the removal and replacement of the entire self-regulating portion of the device, i.e., the member <b>5,</b> the counterweight <b>90</b> and its rail <b>91,</b> the movable grate <b>96</b> (comprising the movable cross pieces <b>961</b> and the gate arms <b>967),</b> the fixed grate <b>94</b> (comprising the fixed crosspieces <b>964</b> and the sidewalls <b>968</b> to which they are attached), the damper <b>25,</b> and the pivot point <b>84.</b> The easy-removal features of the embodiments shown in FIGS. 1-4 permit the important parts regulator to be replaced--while the parts are being repaired or cleaned, for instance--without having to shut down the process equipment for long periods.

The embodiment shown in FIGS. 3A and 4A includes a bypass channel <b>60</b> not found in the FIG. 1 embodiment. The bypass channel <b>60</b> preferably includes an adjustable throttle valve <b>65</b> to variably constrict the bypass channel <b>60.</b> The bypass channel <b>60</b> permits some of the fluid flowing through the regulator to bypass the constriction points <b>80</b> formed by the fixed <b>94</b> and movable <b>96</b> grates. By opening up the bypass throttle valve <b>65,</b> the desired plenum pressure (relative the reference pressure) can be reached more quickly. By closing the bypass throttle valve <b>65</b> (as shown in FIG. 3A), the regulator of FIGS. 3A and 4A can be made to function like the non-bypass regulator shown in FIGS. 1 and 2.

FIG. 5 shows how the relative plenum vacuum strength (in, say, negative inches of water) varies with exhaust vacuum strength (in, say, negative inches of water, as well) in a regulator with a bypass and in a regulator without a bypass. In both cases, as the exhaust vacuum is turned on and increases in strength (i.e., as the exhaust pressure drops), the plenum vacuum also increases (i.e., the plenum pressure drops) until the vacuum in the plenum <b>79</b> is strong enough to overcome the torque applied by the counterweight <b>90</b> on the member <b>5,</b> so as to cause the member <b>5</b> to rotate downwardly and narrow the constriction points <b>80.</b> The narrowing of the constriction points <b>80</b> increases the impedance on the flow between the plenum <b>79</b> and the exhaust (at outlet <b>82).</b> At this point, when the constriction points begin to narrow, a constant plenum vacuum (compared with the reference pressure) is maintained. Because the bypass version of the regulator has less impedance between the plenum <b>79</b> and the exhaust, the desired plenum vacuum is reached more quickly than the non-bypass version of the regulator.

Eventually, the exhaust vacuum strength will increase so much that the member <b>5</b> is pulled down all the way, so that the gate <b>96</b> can impede the flow no further. This point is reached in the bypass version of the regulator more quickly (i.e., at a lower exhaust vacuum strength) than in the non-bypass version of the regulator. Once the member <b>5</b> has moved down as much as possible, the plenum vacuum starts increasing in strength with the exhaust vacuum. Thus, it will be appreciated that opening the bypass throttle valve <b>65</b> causes the region that the regulator maintains a constant pressure--the flat plateau shown on the FIG. 5 graph--to move to lower exhaust vacuums; conversely, closing the bypass throttle valve <b>65</b> causes the region where constant plenum pressure is maintained to move to higher exhaust pressures. The throttle valve <b>65</b> may be adjusted accordingly to set the region of the constant plenum vacuum where (along the axis of increasing exhaust vacuum strength) it will be most beneficial for a given application. As noted above, the position (or the weight) of the counterweight <b>90</b> may be adjusted in order to adjust the desired constant pressure; the greater the torque created by the counterweight <b>90</b> the greater the pressure differential between the plenum <b>79</b> and the reference pressure applied against the member's distal face <b>51.</b>

The new features disclosed herein--in particular, the dashpot <b>26</b> and the bypass channel--can be applied to regulators that regulate the flow from a fluid source to an environment such as that shown in Fig. 5 of U.S. Patent No. 5,255,709. For instance, by connecting the right side of the FIG. 3A embodiment to an HVAC or other air source, adapting the member <b>5</b> (in particular the damper <b>25</b> end of the member) so that the member/gate structure can rotate up instead of down, and reversing the restoring torque, so as to cause the member <b>5</b> to be in its lowest position (and the position causing the least impedance) when there is no flow through the regulator. Such a regulator will maintain a pressure in its plenum that is a constant amount greater than (as opposed to less than, in the case of the FIG. 3A embodiment) the reference--or environment--pressure. Of course, the fixed section <b>42</b> of the dashpot <b>25</b> would have to be over the dashpot's movable section <b>92</b> to permit the member <b>5</b> to rotate properly, but the adapted dashpot could reduce vibration of the member in the manner discussed above. Likewise, the bypass throttle valve <b>65</b> could be adjusted to move the region over which the adapted regulator maintains a constant pressure.