US3545675A - Unit ventilator control system - Google Patents

Description

United States Patent [72] Inventor Wesley L. Taylor 3,220,649 11/1965 Story 236/37 Glenview, Illinois 3,234,955 2/1966 Auger 137/815 [21] App]. No. 631,108 3,279,531 10/1966 Bowles 137/81.5X Filed g f F 7 Primary ExaminerWilliam R. Cline A32 r: gz'g gigigo ggl Attorneyl-lume, Clement, Hume & Lee [45] Patented Dec. 8, 1970' [73] Assignee Powers Regulator Company Skokie, m ABSTRACT: A pure fluid amplifier which projects a laminar a corporation of Delaware by meme power stream and Includes a control section for developing a assignments pressure differential across the projected laminar power stream for a substantial portion of the length of the power stream (preferably a portion of the length of the power stream [54] UNIT VENTILATOR CONTROL SYSTEM at least equal 10 four times the Width 0f the power stream 1 Claim, 23 Drawing Figs 61211551011 orifice) so as to angularly displace the power stream w l e maintaining the power stream laminar at all points in ad- [52] US. Cl 236/38, Vance f the receiver aperture preferably there is a venting 51 I Cl 236/91 236/82; 137/815 region immediately in advance of the receiver aperture which nt. is relieved in all directions in a plane perpendicular to the plane of angular displacement. A system for biasing the Fleld ofsefll'ch I l .5, laminar deflector (or other pressure operated pure am- 236/(Cm1sulted), 38, 82 plifier) by aspirating fluid from the control section in a quanti- References Cited :y substantially equal to the quiescent input flow to the ampliler. A unit ventilator control using a laminar deflector is 2 727 69] lzll i zg l-z STATE? PATENTS shown. A proportional controller using a biased laminar yea eta 236 38 deflector is shown.

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.Q \WN R m w W X W m 1 I X m M W M Q l w mm Q Q a wmmw r \Nk M @w ff Zr/ \mit. U m mwh fl wwm Ad, 3m NW; kg M v A UNIT VENTILATOR CONTROL SYSTEM This application is a continuation-in-part of Pat. application Ser. No. 571,829, filed Aug. 1 l, 1966 and now abandoned.

This invention relates to fluid amplifiers, and more particularly, to pure fluid amplifiers of the type wherein amplification depends upon the influence exerted on a fluid power stream by a controlled fluid pressure gradient provided generally transversely of the direction of flow of the power stream. In practice, the present invention is characterized by a unique manner of providing and influencing a laminar power stream which results in unusually high pressure gain.

The advantages of low cost and increased reliability of pure fluid amplifiers in many applications has sparked considerable development activity in the field. As a result, a number of different types of pure fluid amplifiers have been produced. A general survey of various types of pure fluid amplifiers and their characteristics may be found in the June 24, 1965, issue of Machine Design at pages 153 through 180. Despite this development work, there is presently a need for pure fluid amplifiers capable of high pressure gain, yet smooth proportional action. The present invention responds to this need.

It is well known by those skilled in the art that a fluid power stream can be deflected by a fluid control steam directed against the power stream in a direction generally perpendicular thereto. The power stream deflects through an angle which is related to the energy and momentum of the control stream. In conventional practice, however, the deflected power stream is nonlaminar turbulent for the reason that the interaction of the control stream with the power stream acts to produce or enhance turbulence in the power stream. Indeed, it is indicated in Auger U.S. Pat. No. 3,234,955, that a laminar power stream can be made turbulent by the control stream even though the control stream does not provide sufficient energy to substantially deflect the power stream.

In accordance with the present invention, it has now been found that a laminar power stream of considerable operational length (that is, a laminar power stream which extends a considerable distance from its emission orifice to a receiver port) can be angularly displaced by a pressure gradient acting transversely across the power stream for a substantial portion of length adjacent the emission nozzle, without causing turbulence to occur within the operational length of the power stream. The significance of this attainment is apparent. The deflection of a narrow power stream of considerable length affords greatly enhanced gain. Indeed, pressure gains in excess of I have been achieved in an amplifier according to the present invention with a dead ended receiver and this with smooth proportional action.

It may be noted at this juncture that a pure fluid amplifier according to the present invention makes use of unusually large control ports, a condition which normally would lead one to expect that serious problems of low input impedance and large control pressure losses would ensue. However, while the input impedance does diminish as control port length increases, the no-load pressure gain increases rapidly, and the unexpected result is an amplifier with a very high pressure gain and power gains equal to or better than a typical momentum amplifier.

Accordingly, it is a principal object of the present invention to provide a novel pure fluid amplifier characterized by significantly high pressure gain, yet smooth proportional action. As used herein, the term pressure gain in reference to a single input amplifier means the ratio of change in output receiver pressure to the change in input control pressure. With reference to a dual input and dual output amplifier, this term means the ratio of the change in the difference between two output pressures to the change in the difference between two input control pressures.

Itis another object of the present invention to provide a pure fluid amplifier wherein a laminar power stream of considerable length is angularly displaced without causing turbulence to occur within its operational length.

It is yet another object of the present invention to provide a system for biasing laminar deflectors and other pressureoperated pure fluid amplifiers. As will be seen, the biasing arrangement of the present invention enables the matching of the operating range of a pressure-operated amplifier stage with the operating range of a preceding amplifier stage. For example, it enables the matching of operating points of a pressure-operated amplifier stage with a preceding momentumtype amplifier stage. Moreover, biasing is accomplished in a manner which provides a compensating effect for variations in supply pressure and in a manner which does not work a degradation of gain.

Briefly described, the pure fluid amplifier of the present invention comprises a supply conduit of predetermined parameters and including an emission orifice such that the supply conduit is capable of producing and projecting a laminar stream, means for causing flow of fluid through the supply conduit under a predetermined pressure which is so related to the parameters of the supply conduit as to project a laminar power stream from the supply conduit emission orifice, at least one receiver aperture spaced a predetermined distance from the supply conduit outlet orifice and positioned to normally receive a at least a portion of the projected laminar power stream, and control means for developing a biasing pressure differential across the projected laminar power stream for a substantial portion of the length of the projected power stream without causing a substantial fluid stream velocity component to impinge against the power stream so as to angularly displace the power stream while maintaining the power stream laminar at all points in advance of the receiver aperture. Preferably, the portion of the length of the projected power stream across which the pressure differential is applied is at least equal to four times the dimension of the supply outlet orifice in the plane of angular displacement of the power stream. Further, it is preferable to include means defining a venting region immediately in advance of the receiver aperture, the venting region being relieved in all directions in a plane perpendicular to the plane of angular displacement. A unique and advantageous biasing arrangement for matching the operating range of a laminar deflector or other pressureoperated pure fluid amplifier with the operating range of a source of control pressure signals is achieved by aspirating fluid from the control chamber of the pressure-operated amplifier in volume substantially equal to the quiescent point input flow volume from said source of control pressure signals so that deviations in said input fluid flow volume from said quiescent point volume effect a corresponding change in the control pressure applied to the power stream of the pressureoperated amplifier.

The foregoing and other features and objects of the present invention will become more apparent by reference to the following detailed description taken in conjunction with the appended drawings.

In the drawings:

FIG. 1 is a top plan view of one form of pure fluid amplifier according to the present invention.

FIG. 2 is a top plan view of the pure fluid amplifier of FIG. 1 with the cover plate removed.

FIG. 2A is an enlarged view of a portion of FIG. 2 to aid in explaining the present invention.

FIG. 3 is a cross-sectional view as taken along the line 3-3 in FIG. 1.

FIG. 4 is a cross-sectional view as taken along the line 4-4 in FIG. 2.

FIG. 5 is a cross-sectional view as taken along the line 5-5 in FIG. 2.

FIG. 6 is a graph illustrating the change in the position of the point of turbulence in a projected power stream in relation to the supply pressure in the supply conduit for the purpose of aiding the explanation of the present invention.

FIG. 7 is a graph illustrating the lateral displacement of the extreme end of the laminar power stream in relation to a change in the control pressure in accordance with the principles of the present invention.

FIGS. 8 and 9 are graphs illustrating receiver output pressure versus control pressure as obtained in accordance with the present invention.

FIG. 10 is a graph illustrating a family of curves of receiver output pressure versus control pressure as obtained in accordance with the present invention.

FIG. 11 is a top plan view of another form of a pure fluid amplifier according to the present invention.

FIG. 12 is a top plan view of still another form of pure fluid amplifier according to the present invention.

FIG. 13 is a top plan view of yet another form of pure fluid amplifier in accordance with the present invention.

FIG. 14 is a schematic representation of a unit ventilator system in which a pure fluid amplifier according to the present invention controls a switching action.

FIG. 15 is a top plan view of the pure fluid amplifier and associated valving elements as used in the unit ventilator system of FIG. 14.

FIG. 16 is a cross-sectional view as taken along the line 16-16 ofFIG. 15.

FIG. 17 is a partially schematic, partially cross-sectional representation of a control circuit using a biased pure fluid amplifier according to the present invention.

FIG. 18 is an enlarged view of the third stage pure fluid amplifier in the FIG. 17 control circuit.

FIG. 19 is an enlarged view of the second stage pure fluid amplifier in the FIG. 17 control circuit.

FIGS. 20A, 20B, and 21 are three graphs of performance characteristics of the pressure-operated laminar deflector amplifiers of the control circuit of FIG. 17 arranged to aid in explaining the biasing system of the present invention.

Angular Displacement of a Laminar Power Stream Reference is made to the Auger U.S. Pat. No. 3,234,955. As pointed out therein, the distal end of a projected laminar stream is marked by a point of turbulence beyond which the stream flow is nonlaminar or turbulent and the position of the point of turbulence depends upon the size of the supply conduit outlet orifice from which the laminar stream is projected and upon the magnitude of the static pressure forcing the fluid through the supply conduit. The experimental work of the present inventor indicates that for a given size outlet orifice the position of the point of turbulence" moves downstream very markedly as the static supply pressure is reduced. More specifically, it has been found that with a supply conduit such as shown in FIG. 2 comprising a 0.016 inch square passageway 21 of approximately /2inch length preceded by a %inch diameter stagnation chamber 22, the distance from the datum line d following the control section 23 to the point of turbulence" (not shown) increases rapidly as the static supply pressure decreases, as shown in FIG. 6. The graph of FIG. 6 is approximate and was based on the use of a 0.0l8 inch internal diameter, dead ended probe in lieu ofthe receiver 41 as shown in FIG. 2.

Significantly, it has been found that if one operates well within the region to the left of the curve in FIG. 6, a laminar power stream can be angularly displaced without causing the point of turbulence to advance to a position upstream of the receiver. The result, as will be seen, is greatly enhanced pressure gain.

Referring now more specifically to FIGS. 1 through 5, there is shown one preferred form of pure fluid amplifier 20 according to the present invention. As seen, the amplifier 20 includes a main body member 24 and a cover plate 25 which is secured to the main body member 24 by screws 26.

The main body member 24 is further fabricated to cooperate with the cover plate 25 to define a control section 23 which in the form of the invention shown in FIGS. 1 through 5 comprises a pair of control chambers 31 and 32 disposed on opposite sidesof the laminar power stream 29 in opposing relationship. The wall 33 of the control chamber 23 and the parallel wall 34 cooperate to confine the laminar power stream 28 to its plan of angular displacement so that pressure differential between the control chambers 31 and 32 acts on the laminar power stream much in a manner as though the laminar power stream were a diaphragm separating the control chambers 31 and 32. In this regard, it may be noted that the walls 33 and 34 as shown in FIG. 2 have zero setback from the corresponding edges of the supply conduit outlet orifice 28. However, the walls 33 and 34 may also be in interference with the laminar power stream or be very,slightly set back from the edges of the emission orifice 28.

The downstream sides of the control chambers 31 and 32 are formed by projecting wall elements 35 and 36, respectively, which approach the laminar power stream 29 in opposing directions, each preferably presenting a knife edge toward the laminar power stream 29. As will be discussed further on in this description, it has been found that the spacing between forward edge of the downstream projecting wall element associated with a particular control chamber determines the input impedance of the particular control chamber.

The control chambers 31 and 32 are preferably provided with rather large diameter inlet ports 37 and 38 acting as stagnating chambers which tend to remove momentum from fluid introduced through the respective openings 39 and 40.

The datum line d shown in FIG. 2 marks the downstream termination of the control section 33. It falls along the downstream sides of the projecting wall elements 35 and 36. From this datum line d to the upstream face of the receiver (a distance which will be referred to hereinafter as X distance), there is provided a venting region 43 which is relieved in all directions perpendicular to the plane of angular displacement of the power stream 28. This venting region is important because it enables vented dispersion of the fluid particles which do not enter the receiver port 42, thereby preventing an undesired pressure buildup to occur in the vicinity of the receiver port. The venting provided is gross due to the enlarged wings of the venting region which extend outwardly and rearwardly on both sides of the receiver 41 and to the fact that the cover plate 25 is provided with a cutout 44 completely opening the venting region 43 to atmosphere.

As a matter of clarification, it should be understood that when the power stream is referred to as being laminar at all points in advance of the receiver aperture," it is meant the power stream at all points before it enters the receiver aperture or impinges against the receiver face and does not include dispersion flow of fluid particles which have impinged against the receiver face. Also, in characterizing the power stream as laminar, it is meant that the power stream in its essential integrity as a fluid stream is laminar" as opposed to turbulent. Obviously, this is not intended to exclude the possible presence in some applications of the invention of eddies or turbulence at the side edges of the power stream or interface regions between the power stream and the ambient fluid through which it passes.

The receiver port 42 in the form of the invention shown in FIGS. 1 through 5 is also a square passageway defined by the main body member 24 and the cover plate 25 and is concentrically aligned with the supply conduit outlet orifice 28 as indicated by the center line c. In this form of the invention, the cross-sectional area of the receiver port 42 is smaller than the cross-sectional area of the supply conduit emission orifice 28 so as to enhance the sensitivity of the amplifier. The outlet for the receiver in this form of the n invention is through the bore 45 for one of the screws 26 and, thence, through the opening 46. The screw bore 45 is sufficiently larger than the associated screw 26 to provide an adequate fluid path, and this arrangement reduces the cost of fabrication.

To effect operation of the amplifier shown in FIGS. 1 through 5, the supply conduit opening 27 is connected to a suitable source of fluid under pressure (not shown). The control pressure inlet openings 39 and 40, in turn, are connected respectively to sources of control pressure (not shown), the fluctuations of which relative to one another are to be amplified. In some cases, one or the other of the inlet openings may simply communicate with atmosphere, in which event atmospheric pressure serves as a reference with which pressure fluctuations communicated to the other control pressure inlet opening are compared. The control pressure sources may in some applications present positive pressure conditions (i.e. pressures above atmospheric pressure) and in other applications may present negative or vacuum pressure conditions. The point of importance is that separate pressure conditions are applied to the control sections 31 and 32 through the ports 37 and 38. As previously indicated, the ports 37 and 38 act in the manner of stagnation chambers so that the pressure conditions applied to the control sections 31 and 32 are essentially static pressure conditions. Under these circumstances a pressure differential equal to the differences between the static pressures in the control chambers 31 and 32 is applied transversely across the laminar power stream. It is important to understand that the control chambers are relatively very large in width; in other words, the width dimension L shown in FIG. 2A is appreciably larger than the dimension D, the dimension of the supply conduit emission orifice 28 in the plane of angular deflection of the laminar power stream. In fact, the ratio L/D should be four or greater. Accordingly, the pressure differential is applied to a substantial portion of the length of the laminar power stream. It will be noted that for the length L of the power stream.(the portion of the power stream across which a pressure differential is applied), the power stream is confined by walls 33 and 34 causing the pressure differential to act on the power stream in the manner of a pressure differential acting on a diaphragm. The pressure differential causes an angular displacement of the laminar power stream as illustrated diagrammatically in FIG. 2A. Importantly, this angular displacement occurs without causing the power stream to become nonlaminar or turbulent in the region in advance of the receiver port 42. In other words, the point of turbulence referred to in the Auger US. Pat. No. 3,234,955 may be considered a virtual point located either within or downstream of the receiver port 42. In the present invention, the pressure differential applied across the power stream does not cause this virtual point of turbulence to advance upstream of the receiver port. The angular displacement of the relatively long, narrow power stream without impairing its integrity as a laminar stream is indicated by the graph of FIG. 7. The graph of FIG. 7 is based on tests using the same test structure previously referred to in relation to the graph of FIG. 6. The probe was located an X distance of %inch from the datum line d, and the supply pressure to the supply conduit was inches of water. As shown in FIG. 7, the point of maximum pressure was laterally displaced as control pressure was increased on one side of the power stream, the opposite side of the power stream being exposed to atmosphere. The continued integrity of the power stream as a laminar stream during the displacement represented in FIG. 7 is shown by the fact that the output pressure from the probe decreased very little with power stream displacement. Specifically, the output pressure from the probe at zero relative control pressure was 4.9 inches of water; at a control pressure of 0.02 inches of water, the receiver probe output pressure was 4.8 inches of water; at a control pressure of 0.04 inches of water, the receiver probe output pressure was 4.7 inches of water; at a control pressure of 0.06 inches of water, the receiver probe output pressure was 4.6 inches of water; at a control pressure of 0.08 inches of water, the receiver probe output pressure was 4.5 inches of water; at a control pressure of 0.12 inches of water, the receiver probe output pressure was 4.2 inches of water; and at a control pressure of 0.14 inches of water, the receiver probe output pressure was 3.8 inches of water.

Turning to FIG. 8, there is presented a pair of curves of receiver output pressure versus control pressure. Again, a

0.018 inch internal diameter receiver probe was used. The

supply pressure was 10 inches of water. Curve 8a was produced with an X distance spacing from the datum line at to the receiver probe of Ainch. Curve 8b was produced with an X distance spacing from the datum line at to the receiver probe of inch. Significantly, curve 8a indicated an average gain of approximately with curve 8b indicating an average gain of slightly less than 80. By way of comparison with curve 8b, reference is made to FIG. 9 in which an average gain of approximately 135 is indicated for an X distance spacing of /2inch with a supply pressure of 15 inches of water in lieu of the supply pressure of 10 inches of water used to produce gain V 15 inches of water for curve 10a 12.5 inches of Water for curve 10b 11.2 inches of Water for curve 10 inches of water for curve 10d 8.5 inches of water for curve 10c 7.4 inches of water for curve 10f 5.7 inches of water for curve 10g 4.5 inches of Water for curve 1012.

Again it is seen that the pressure gain is very high. For example, the pressure gain on the linear portion of curve 10a is approximately 100. Moreover, the proportional action is smooth.

Referring now to FIG. 11, there is shown somewhat diagrammatically an additional form of pure fluid amplifiers according to the present invention with-the cover plate removed. The amplifier of FIG. 11 illustrated is arranged for single positive control pressure utilization. Control chamber 132 is designed to apply atmospheric pressure to one side of the laminar power stream while control chamber 131 is adapted to apply positive control pressure signals to the laminar power stream. As in the amplifier of FIGS. 1 through 5, in the amplifier 120 the length of the control section is greater in magnitude than the width D of the power stream emission orifice 128 by at least a factor of four, and the region immediately in advance of the receiver port 142 is relieved in all directions in a plane perpendicular to the plane of angular displacement of the laminar power stream. This region, in turn, is grossly vented to the sides and by a cutout in the cover plate (not shown) like the cutout 44 shown in FIG. 1. It should be noted in FIG. 11 that the forward edge of the wall element 135 is brought up to the quiescent or nonangularly displaced position of the laminar power stream and may in fact be slightly in interference with the laminar power stream. As previously noted, it has been found that in fluid amplifiers according to the present invention, input impedance and control pressure losses associated with a particular control chamber are a function of the spacing between the forward edge of the associated wall elements and the laminar power stream and the pressure condition in the control chamber relative to atmospheric pressure. Accordingly, FIG. 11 illustrates the arrangement for maximum input impedance and minimum control pressure losses for a positive pressure-operated amplifier of the present invention having a given control port width. As the laminar power stream is moved away from the wall element 135 by an increase in positive control pressure in the chamber 131, the input impedance declines somewhat.

Turning to FIG. 12, there is shown another form of pure fluid amplifier 220 according to the present invention. The amplifier 220 is similar to the amplifier 120 of FIG. 11 except that it is designed for single vacuum-control pressure operation. It will be noted that the wall element 235 associated with the control chamber 231 unlike the wall element 135 in FIG. 11 is spaced a finite distance from the nonangularly displaced position of the laminar power stream. The spacing is necessary in order to permit the laminar power stream to be moved toward the control chamber 231 as the magnitude of the control vacuum therein increases. In an application in which maximum possible input impedance is desired, this spacing will be made as small as possible consistent with the desired maximum angular displacement of the laminar power stream. In contrast with the amplifier 120 of FIG. 11, in the amplifier 220 of FIG. 12 the input impedance will generally be at its highest level at the point of maximum angular displacement of laminar power stream and at its lowest level at the quiescent or nonangularly displaced position of the laminar power stream. However, the change in input impedance with angular displacement of the laminar power stream is not as pronounced under vacuum-control pressure operation as under positive-pressure operation but rather tends to remain at a higher level.

FIG. 13 depicts an amplifier 320 according to the present invention which is adapted for dual input control signals and dual receivers. In other respects, the amplifier 320 is similar to those described above. The dual receiver ports 343 and 353 are separated by a splitter 360 which is aligned with the axis of the power stream outlet orifice 328 and which preferably presents a knife edge to the laminar power stream. A change in the pressure differential across the laminar power stream in the control section 323 is amplified as a proportional change in the difference in pressures in the dual receivers. As in the other amplifiers described, the input impedance of either of the control chambers is a function of the instantaneous spacing between the forward edge of the associated downstream wall element and the laminar power stream.

Unit Ventilator Control System Using a Laminar Deflector By way of illustration, there is shown in FIGS. 14 through 16 a utilization ofa pure fluid amplifier according to the present invention to effect control of air dampers in a unit ventilator system. As will be seen, the amplifier in this arrangement serves to sense whether or not the unit ventilator fan is running, and, if it is not running, to cause closure of the outside air dampers to prevent coil freezeup.

Referring to FIG. 14, it is seen that the unit ventilator 400 includes a supply line 401 for supplying air from a conventional source 399 at a predetermined pressure level, p.s.i. for example. The supply line 401 provides supply pressure to a pneumatic room thermostat 402 and to the pneumatic switch 410. A conduit 403 connects the output side of the room thermostat 402 to the input side of an internal pneumatic thermostat 404 disposed in the air stream. The output side of the air stream thermostat 404 is connected by a conduit 405 to the switch input port of the pneumatic switch 410. The outlet port of the switch 410 is connected to a pneumatic motor 406 and to a pressure-responsive coil flow control valve 407 via conduit 408. The motor 406 determines the position of the outside air damper 409 while the valve 407 determines the quantity of flow of heating fluid through the coil 411. The suction side of the fan 413 is connected via conduit 414 to an input control pressure port of the switch 410. With the exception of the pneumatic switch 410 and its interconnections, the structure of the unit ventilator 401 is conventional.

Referring to FIGS. 15 and 16, the switch 410 is depicted. It comprises an assembly 412 fabricated to include a sensing stage 420, a relay stage 470, and a switching stage 480.

The sensing stage 420 consists of a fluid amplifier according to the present invention. It includes a supply conduit comprising a straight line lead-in 422 of sufficient length to assure laminar flow and a passageway 421 which terminates at emission orifice 428. The control section 423 includes a control chamber 431 on one side. The opposite side of the control section 423 is open to atmosphere. The downstream end of the control chamber 431 is formed by the wall element 435. As in the previously described embodiments of the invention, the length of the control section 423 is larger than the width of the outlet orifice 428 by at least a factor of four, and the region immediately in advance of the face of the receiver 441 is relieved in all directions in a plane perpendicular to the plane of angular displacement of the laminar power stream and grossly vented to atmosphere. It will be also noted that the walls 433 and 434 confine the laminar power stream to its plane ofangular displacement.

The output of the receiver 441 is communicated via conduit 451 to a chamber 452 on one side of the diaphragm 453. A chamber 454 on the opposite side of the diaphragm 453 cooperates with the diaphragm 453 to form a portion of the relay stage 470. The chamber 454 is vented to atmosphere by the outlet 455. The diaphragm 453 is connected to a ball member 456 which valves a port 457 adapted to connect the chamber 454 with a conduit 458. The conduit 458 is connected through a restriction 459 to the supply pressure line 401. The ball member 456 is normally biased by a spring 461 into seated position closing the port 457.

The conduit 458 is also connected to a chamber 462 on one side of another diaphragm 463. On the opposite side of the diaphragm 463 there is still another chamber 464 forming a portion of the switching stage 480. The chamber 464 is vented to atmosphere by outlet 465. The diaphragm 464 carries a plate 466 which is adapted to abut against a valving member 467. At one end, the conduit 471 continuously communicates with the chamber 464. At its opposite end, the conduit 471 is in valved communication with a chamber 473. Valving of the conduit 471 is provided by one end of a dumbbell valve member 472. The opposite end of the valve member 472 valves the exterior end of a bore 474. A bias spring 475 urges the valve member 472 into a seated position such that communication between the chamber 473 and the switch inlet port 476 is normally closed. A port 477 connected directly to chamber 473 serves as the switch outlet port which is connected to conduit 408. The inlet port 476 is connected to conduit 405.

In normal operation with the fan 413 operating, a vacuum condition is presented to control chamber 431 of the fluid amplifier comprising sensing stage 420 via conduit 414. In accordance with the principles of the present invention, the laminar power stream projected from the emission orifice 428 is angularly displaced with the result that the pressure level in the receiver 441 and thus in the chamber 452 is substantially atmospheric pressure. With no effective pressure differential across the diaphragm 453, the bias spring 461 maintains the valve member 456 in the relay stage 470 closed so that the chamber 462 is maintained at supply pressure. The diaphragm 463 responds to supply pressure in the chamber 462 by moving the valve member .67 to the right in FIG. 16. This action closes off the path through which chamber 473 and port 477 are otherwise vented and connects port 477 to port 476. In short, the switching stage 480 is caused to function in the manner of a three-way valve, disconnecting outlet port 477 from communication with atmospheric and connecting it instead to switch inlet port. Under these conditions, the room thermostat functions in conventional manner to position the coil control valve 407 and the damper motor 406 to maintain the desired temperature. The air stream thermostat 404 functions in conventional manner to prevent air from being discharged at a temperature below a predetermined minimum temperature (for example, 60 F.) by venting pressure from the control valve 407 and damper motor 406 to gradually open the control valve and gradually close the outside air dampen 409.

When the fan 413 is off, a vacuum is no longer presented to the control chamber 431 of the fluid amplifier section 420. As a result, the laminar power stream is received by the receiver 441 without angular displacement. A pressure equal to several inches of water is thus produced in the receiver 441 and communicated to the chamber 452. This causes deflection of the diaphragm 453 which opens the bore 457. The chamber 462 is thereby vented with the result that in the switch stage 480, the inlet port 476 is closed, and the switch outlet port 477 is vented to atmosphere. Accordingly, the damper motor 406 and the control valve 407 are relieved, causing the air damper 409 to be closed and the control valve 407 to be fully opened for maximum flow of heating fluid. Thus, the coil 411 is protected from freezeup.

Biasing System and its Application in a Controller Turning now to FIG. 17, there is shown a control circuit 501 in which two singlesided-type laminar deflectors 620 and 720 of the present invention are employed as the second and third stages. By single-sided-type," it is meant that the amplifier has a single control signal input and a single output receiver like the amplifiers shown in FIGS. 12 and 13 and previously described. One advantage of single-sided-type amplifiers is that with only a single receiver, the need for a splitter is eliminated thereby increasing the ease of manufacture.

The control circuit 501 is arranged as a proportional controller for maintaining a variable such as temperature at a preselected level or setpoint. A conventional pneumatic thermostat 503 is provided with supply pressure from a conventional regulated source 504 which may, for example, provide pneumatic fluid at 20 p.s.i. The thermostat 503 provides an input signal via restrictor 510 to one control jet chamber 505 of the amplifier 502 which is a differential momentumtype amplifier as distinguished from the pressure-operated laminar deflectors of the present invention. The input variable signal pressure P in chamber 505 varies with sensed temperature within a range, for example, of l to 4 inches of water, to project a control jet from nozzle 505a which varies ac cordingly. The chamber 506 of the amplifier 502 is connected to the regulated source through a restrictor 507 for providing a power stream from nozzle 506a. The other control jet chamber 508 provides a reference signal pressure P for projecting a corresponding control jet from nozzle 506a. The chamber 508 is connected to a conduit 509 which, in turn, is connected through variable restrictor 511 to the regulated source 504 and through variable restrictor 512 to the con troller output conduit 513. The variable restrictor 511 serves as the setpoint adjustment, and the variable restrictor 512 serves as the sensitivity adjustment. The amplifier 502 is vented in front of its receiver 514 by venting conduits 515 and 516. The receiver 514 is connected to the control pressure chamber 631 of the second stage amplifier 620 via conduit 637. In order to provide suitable output characteristics from the amplifier 502, the receiver 514 may be laterally offset with respect to the power stream nozzle.

The second stage amplifier 620 is a single-sided laminar deflector similar to the amplifiers of FIGS. 11 and 12; the control chamber 632 is vented to atmosphere. Like the laminar deflectors previously described, the amplifier 620 includes a supply conduit including a stagnation chamber 622 followed by a passageway 621 which terminates in an emission orifice 628 for projecting a laminar power stream. The region 643 immediately in advance of the receiver 642 is relieved in all directions in a plane perpendicular to the axis of the receiver 642 and vented. The amplifier 620 differs from the amplifiers of FIGS. 11 and 12 in that the receiver 642 is laterally offset toward the control chamber 631. As will be specifically referred to further on, the width of the control chamber 631 is much larger than the width of the emission orifice 628, and the control chamber downstream wall element 635 is setback from the center line of the emission orifice. It will be noted that the stagnation chamber 622 is connected to the supply source 504 through a restrictor 601. The receiver 642 is connected via conduit 737 to the control pressure chamber 731 of the third stage amplifier 720.

The third stage amplifier 720 differs from the second stage amplifier 620 in that the receiver 742 is aligned with the emission orifice 728, the wall element 735 is spaced a lesser distance from the center line of the emission orifice than is the wall element 635, and the width of the emission orifice 728 is slightly smaller than the width of the emission orifice 628. As a general proposition, in a laminar device, it is desirable to make the emission orifice as small as possible consistent with manufacturing capabilities. The reason for making the emission nozzle small is to lower the Reynolds number which is the best available index of a laminar power stream. For example, with a 0.016 inch by 0.016 inch emission orifice and a 10D or 0.l6 inch control chamber width, the maximum working output pressure obtained from the laminar power stream may be l0 inches of water, but if the emission orifice is reduced to 0.010

inch 'by 0.010 inch, a working output pressure from the laminar power stream of 20 inches of water may be obtained. In the controller 501, the amplifier 720 is provided with a 0.0l0 inch by 0.010 inch emission orifice in order to provide the relatively high input pressure required by the pilot valve 517. The supply conduit stagnation chamber 722 of the amplifier 720 is connected via restrictor 701 to the supply source 504. The receiver 742 is connected directly to the pilot valve 517.

The pilot valve 517 preferably has a 30 to 1 pressure ratio. This relative high pressure ratio may be obtained in a small size by using the valving structure described in US. Pat. No. 3,244,l of the present inventor which issued on Apr. 5, 1966. The output conduit 513 from the pilot valve 517 would normally be connected to utilization means such as a motor valve in a hot water-heating conduit.

The biasing portion of the control circuit 501 is formed by a bias conduit 518 which terminates in an outlet orifice 519. A Venturi section 521 is connected to the supply source 504 via a restrictor 522 and conducts a high velocity flow transversely across the orifice 519 into the chamber 523 which is well vented to remain at atmospheric pressure. In the well-known manner of aspirator operation, the high velocity flow through the Venturi section 521 creates a low pressure condition at the outlet of the orifice 519, drawing off fluid from the conduit 513 through the orifice 519. This aspirator arrangement 526 effectively acts as a pressure sink, maintaining a predetermined pressure level in the conduit 513. It is important to note that the conduit 637, and hence the control chamber 631 of the second stage amplifier, are connected to the bias conduit 518 via a restrictor 524.

Referring to FIG. 18, there is shown an enlarged view of the third stage amplifier 720 in FIG. 17 which is a positive pressure-operated laminar deflector. The width of the emission orifice 728 is indicated by the reference character D. The width L of the control section 731 is preferably 10D. The outer edge of the wall element 735 is preferably spaced ID from the center line C of the emission orifice 728. The receiver 742 is coaxial with the emission orifice 728. With the receiver from the preceding fluid amplifier connected to the control chamber 731, the control port pressure is always essentially positive. Accordingly, the input flow comprises a component a which is entrained by the power stream plus a component b which passes between the tip of the wall element 735 and the laminar power stream. As previously noted in reference to FIG. 11, the input impedance of this type of device decreases as the laminar power stream is angularly displaced by increasing control pressure. The input flow will rise appreciably with increasing control pressure in chamber 73 1.

FIG. 19 is an enlarged view of the second stage amplifier 620 in the control circuit of FIG. 17 which is a negative pressure-operated laminar deflector. In normal operation, the pressure in the control chamber 631 is less than atmospheric. The spacing of the tip of the wall element 635 from the emission orifice 628 center line is 2 /zD and L is 10D. The receiver 642 center line R is offset l -%D from the emission orifice center line C. With a negative control pressure input to the control chamber 631, the input control signal flow 0,, into the chamber 631 is determined by the composite of entrainment flow e, return flow f, and reverse flow g between the tip of the wall element 635 and the laminar power stream. In normal operation, the Q flow will be positive, that is, air will be flowing from the conduit 637 into the chamber 631 because the entrainment flow component e will be larger than the sum of the return flow component f and the reverse flow component g. A discussion of the components of flow in a pressure control port generally can be found at pages 50 through 64 of Basic Applied Research in Fluid Power Control" by S. Y. Lee et al. Massachusetts Institute of Technology, Technical Report AFFDL-TR-65-79, dated May, 1965, and distributed by the Clearinghouse for Federal Scientific and Technical Information, Department of Commerce. The negative pressure mode of operation of amplifier 620 is characterized by a generally higher and more stable input impedance than found in positive pressure operation. The input flow magnitude varies much less than in the case of the positive control mode. There is a slight decrease in input flow as the control pressure becomes more negative.

One phenomenon with respect to the negative pressure mode of operation may be noted at this point. If the conduit 637 were obstructed or for other reasons could not supply sufficient fluid into the control chamber 631 to equal the output entrainment flow e, the entrainment flow component e will cause an increasingly negative pressure condition to occur in the control port 631. As the pressure becomes more negative, the laminar power stream is drawn toward the wall element 635 which further restricts the flow component g, increasing the tendency toward a vacuum in the control port 631. In this manner it would be possible for the partial vacuum in the control port 631 to draw the power stream partially into the control port 631 to a point where return flow fequals entrainment flow e. To provide desirable input flow and pressure characteristics in negative pressure operation, the tip of the wall element 635 is spaced farther away from the center line of the emission orifice 628 than in the case of the positive pressure operated amplifier 720. The preferred spacing from the emission orifice 628 center line where the control chamber width is D is from 2D to 3- /D, or, in reference to the control chamber width, the preferred spacing is from 0.2L to 0.35L. Having determined the proper spacing of the tip of wall element 635 from the center line C of the emission orifice 628, the offset of the center line R of the receiver 642 from the center line of the emission orifice 628 is selected to provide desired output flow and pressure performance characteristics.

Referring now to FIGS. 20A, 20B, and 21, the relationship between the performance characteristics of the second stage amplifier 620 and the third stage amplifier 720 is illustrated. In FIG. 21 relating to amplifier 720, a curve h of output pressure in inches of water versus input pressure in inches ofwater, and a curve i of input flow in standard cubic inches per minute (s.c.i.m.) versus input pressure in inches of water are provided. The curves h and i were derived with an amplifier like the amplifier 720 operating with a supply pressure of 1.6 p.s.i. In order for the pilot valve 517 to provide an output pressure range of 3 to p.s.i., the output pressure P, range provided by the amplifier 720 in the particular case represented by FIG. 21 was 4 inches of water to 14 inches of water which, in turn, represented an input control pressure P, range of approximately 0.07 inches of water to 0.14 inches of water. For this range of input control pressures, it is seen from FIG. 21 that the input flow to amplifier 720 is from approximately 1.15 to 1.52 s.c.i.m. Since the input flow to the amplifier 720 is approximately equal to the output flow from the amplifier 620, and the input control pressure to the amplifier 720 is approximately equal to the output pressure from the amplifier 620, two points in and n can be located on FIG. B which is a graph of amplifier 620 output flow versus amplifier 620 output pressure. The graph of FIG. 208 was derived from an amplifier like amplifier 620 operating at a supply pressure of 10 inches of water.

The points m and n in FIG. 20B determine the control pressure P range for the amplifier 620 to provide the proper flow and pressure to the amplifier 720, and the line 0 extending between points m and n can be considered an output load line for amplifier 620. In the present example, it is seen that the control pressure range must be approximately minus 0.047 inches of water to minus 0.056 inches of water. Having determined the control pressure P range from FIG. 20B, the range of input flow Q, to the amplifier 620 control section 631 can be determined from FIG. 20A, which is a graph of input flow 0,, versus control pressure P;,. The curve q in FIG. 20A was derived from an amplifier like amplifier 620 operating at a supply pressure of 10 inches of water.

From the input flow curve q in FIG. 20A, it can be seen that for the given control pressure P, range, the input flow Q, will vary between approximately 0.31 and 0.49 s.c.i.m. The amplifier 502, the aspirator 526, and the restrictor 524 are designedto provide the requisite control pressure range P and attendant input flow O to the amplifier 620. In particular, the aspirator 526 and restrictor 524 provide the biasing means for matching the output operating range of the momentum-type amplifier 502 with the negative pressure operation of the laminar deflector amplifier 620.

In the control circuit of FIG. 17, the opposing control jets from the respective nozzles 505a and 506a determine the angular deflection of the power stream so that a summing point function (P P,) is performed by the momentum-type amplifier 502. In actual operation it would be advantageous to operate a about the point where P =P,, but the no-load output pressure of the amplifier 520 at this point may typically be 10 inches of water, and the control pressure input to the second stage must be much less than this pressure or the amplifier 620 will be overdriven into saturation. As noted above, it is the function of the aspirator 526 and the restrictor 524 to suppress the output of the first stage to bring it within the working range ofthe second stage. This function may be understood by investigating flow ofpneumatic fluid in the conduit 637.

Essentially the flow in conduit 637 is a summation of three possible components. The first component is the output flow Q, from the first stage receiver 514. The second component is the aspirated outflow Q through the restrictor 524, which outflow in general is a function of the difference between the pressure P, in the conduit 637, the pressure P, in the bias conduit 518, and the value of the restrictor 524. The third component of flow is Q the flow into the control chamber 631 of the amplifier 620 from the conduit 637.

As seen from FIG. 208, the aspirator-biased amplifier 620 produces very small load change in the output from the preceding amplifier stage throughout the operating range since the pressure P; in the conduit 637 and the control chamber 631 is very close to zero, the operating range being from minus 0.056 inches of water to minus 0.047 inches of water. Hence, the instantaneous value of the flow Q, into the conduit 637 from the receiver 514 is substantially independent of fluctuations in the pressure P, and may be approximated as where Q, quiescent is the known no-load flow from the receiver 514 when P,=P and K, is a proportionality constant. By no-load flow, it is meant the volume of flow to a pressure region in which the pressure is effectively atmospheric pressure in terms ofits effect on the flow Q,. The flow 0 as previously noted, is a composite of entrainment flow e, return flow f, and reverse flow g shown in FIG. 19. It will be appreciated that the Q flow varies with the angular displacement of the power stream caused by variations in the control pressure P, as shown in FIG. 20A. Assuming operation along a linear segment of the curve q in FIG. 20A, the instantaneous value of the flow 0;, may be approximated as Qa= Qy a a where K, is a proportionality constant and where 0,, is the value of 0 when P is zero (or, for more exact approximation, the value of Q; at the point P =0 on a straight line projected from coincidence with the linear operating range). The flow 0 through the restrictor 524 to the aspirator 526 may be expressed as The flow Q, into the chamber 637 is equal to the output flows Q and 0 Hence, summing the flows,

can be made virtually a constant by making P very large in comparison with P In practice that is what is done. P is given a magnitude on the order of l or 2 p.s.i. while P;,, as seen, is in the range of about 0.05 inches of water. Also, R is made large as possible in practice. Now to set the correct bias for the is approximately equal to Q quiescent, i.e. the flow into the aspirator is made approximately equal to the known noload" quiescent flow from the receiver 514. Hence, this quantity can be subtracted from both sides of the flow summing equation above with the result that amplifier 620, R is adjusted to a value at which Thus, it is seen that the control pressure P and hence, the angular displacement of the power stream in amplifier 620 is a function of the deviations K (P -P in input flow Q and, therefore, a function of the summation (P -P performed by the amplifier 502. By use of the aspirator 526, the operating range of the amplifier 620 has been matched to the operating range of the amplifier 502.

Under certain circumstances such as a radical change in set point, a condition could occur in which the power stream of the first stage amplifier 501 is virtually completely removed from the receiver 514. If this condition lowers P to an extent that the power stream of the amplifier 620 is effectively drawn into the control chamber 631, a control inversion would be produced, resulting in a total controller runaway condition. The possibility of a runaway situation is prevented by properly spacing the tip of the wall element 635 from the center line of the emission orifice 628 as previously described and by correlating the design of the input characteristics of the amplifier 620 so that P will not reach a negative level sufficient to pull the power stream into the control chamber 631.

In typical operation of the controller 501, a temperature set point such as 72 F. is set by adjustment of the variable restrictor 511. A drop in temperature below 72 F. will result an error signal in the form of a change in output pressure from the first stage amplifier 502. This error signal is amplified by the second stage amplifier 620 and by the third stage amplifier 720 and is submitted to the pilot valve 517 to effect an increase in heat output by the heating apparatus. A negative feedback signal from the pilot valve 517 is transmitted to the chamber 508 of the first stage amplifier 502 via the conduit 509 to provide a throttling effect. Adjustment of the variable restrictor 512 enables adjustment of the throttling effect and, hence, sensitivity of the controller. It should be noted that since the effect of the aspirator 526 is determined by supply pressure, the aspirator 526 provides a compensating effect for variations in the pressure level at the supply source 504.

The foregoing description discloses a unique pure fluid amplifier system in which angular displacement of a laminar power stream is achieved providing unusually high pressure gain together with smooth proportional action and versatile impedance matching characteristics. In FIGS. 14 through 16, one form of application of the pure fluid amplifier has been shown. Many other applications will occur to those skilled in the art. The foregoing description also discloses a biasing system for a laminar deflector and other pressure-operated pure fluid amplifiers and the use of the biasing system in a proportional controller.

While specific forms of the present invention have been illustrated and described herein, it is to be understood that this is by way of example only and is not to be construed in any manner as a limitation. It is contemplated that modifications may be made within the scope of the claims without departing from the spirit of the invention.

lclaim:

1. In a unit ventilator adapted to be connected to a source of supply pressure and including a fan, a heating coil, a pneumatically operated control valve for controlling the flow of heating medium through said heating coil, an outside air damper, a pneumatically operated motor for positioning said outside air damper, an external pneumatic thermostat and an internal pneumatic thermostat for producing pressure signals for controlling said heating coil control valve and said damper motor, and valve means for transmitting said pressure signals to said heating coil control valve and said damper motor, the combination therewith comprising:

a. A supply conduit of predetermined parameters and including an emission orifice, said conduit being adapted to produce a laminar fluid stream;

b. Means connecting said supply conduit to said source of supply pressure for effecting flow of fluid through said supply conduit so as to project a laminar fluid power stream from said supply conduit emission orifice;

c. A receiver including at least one receiver aperture spaced a predetermined distance from said supply conduit emission orifice and positioned to normally receive said projected laminar power stream;

d. Control means for applying a biasing pressure differential across said power stream for a predetermined portion of its length for angularly displacing said power stream an amount dependent upon the magnitude of said pressure differential while maintaining said power stream laminar at all points in advance of said receiver aperture, said control means including means confining said power stream to said plane of angular displacement for said predetermined portion of its length, means defining a control chamber extending along one side of said power stream from said supply conduit emission orifice for a distance at least in excess of the dimension of said supply conduit emission orifice in said plane of angular displacement and including a downstream wall which approaches the nonangularly displaced location of said power stream, means for connecting said control chamber to the suction side of said fan so as to apply a vacuum pressure condition to said one side of said power stream when said fan is operating, and means disposed on the opposite side of said power stream from said control chamber for applying atmospheric pressure to said opposite side of said power stream, said biasing pressure differential being the difference in magnitude between said vacuum pressure condition and atmospheric pressure whereby when said fan is operating said power stream is angularly displaced and a low pressure condition exists in said receiver whereas when said fan ceases operating said power stream returns to its nonangularly displaced position causing a high pressure condition to exist in said receiver; and

. Means responsive to the presence of said higher pressure condition in said receiver for causing said valve means to block transmission of said pressure signals to said damper motor and said heating coil control valve and to vent said damper motor and said heating coil control valve so as to close said outside air damper and open said heating coil control valve to prevent coil freezeup.

Patent No.

lnventot-(s) WESLEY L. TAYLOR UNITED STATES PATENT OFFICE Decemher 8 l9l0 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE DRAWINGS:

IN THE SPECIFICATION:

Column 1, line 23,

Column Column Column Column Column Column 10, lines 62, 63,

line 21,

line 62,

line 21,

line 32,

line 20,

"steam" should read -streamdelete first "a" delete "n" "diaphragm 464" should read --diaphragm 463-- "2 -l/2D" should read 2;

"3-1/2D" should read .....3;5D.

delete "a" Signed and sealed this 13th day of Jul 1971 (SEAL) Attest:

EDWARD M.FLETCHER,J'R.

Attesting Officer WILLIAM E. SCHUYLER, J Commissioner of Patent

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