US3026041A - Conditioned air distribution - Google Patents

Description

March 20, 1962 A. P. JENTOFT Filed May 6, 1960 -PNEUMATIC FLOW CONTROLLER 3| 4; Sheets-Sheet 1 I I 5 2| I Z "I l 5, {/20 l 2 I 11 I L8. I 1 l q I PNEUMATIC I blg E 25 I THERMOSTAT I I 23 I I l I3 I L I PRIOR f ART THERMOSTAT PRESSURE HIGH STATIC AIR PRESSURE IN FLOW HOT AIR INLET HOT All-7 D o 0 [NORMAL RA N65! THERMOSTAT PRESSURE INVENTOR.

ARTHUR P. JENTOFT BY 6 I March 20, 1962 A. P. JENTOFT CONDITIONED AIR DISTRIBUTION 4 Sheets-Sheet 2 Filed May 6, 1960 PNEUMATIC FLOW CONTROLLER n y MO M UR u m PT NORMAL RANGEI THERMOSTAT PRESSURE INVENTOR.

ARTHUR P. JEN TOF'I A TORNEY March 20, 1962 A. P. JENTOFT 3,026,041

CONDITIONED AIR DISTRIBUTION Filed May 6, 1960 4 Sheets-Sheet 3 3| PNEUMATIC FLOW CONTROLLER PNEUMATIC THERMOSTAT LOW LOW STATIC STATIC AIR PRESSURE IN AIR PRESSURE IN FLOW HOT AIR FLOW HOT AIR NLET \wm/n INLET \HOTA/R 0 Q O [NORMAL RANGE! O I/VOl-PMAL RANGEI THERMOSTAT PRESSURE THERMOSTAT PRESSURE INVENTOR.

ARTHUR P. JENTOFT BY 4 fl.

ATTORNEY Filed May 6, 1960 A. P. JENTOFT CONDITIONED AIR DISTRIBUTION 4 Sheets-Sheet 4 GQ QT 3| PNEUMATIC FLOW CONTROLLER 34 f F A 4 H PNEUMATIC 1:; i9 THERMOSTAT 14 INVENTOR.

ARTHUR P. JENTOFT T R EY United States Patent Office 3,026,041 Patented Mar. 20, 1952 3,026,041 CONDITIONED AIR DISTRIBUTION Arthur P. Jentoft, Wexford, Pa., assignor to H. H. Robertson Company Filed May 6, 1960, Ser. No. 27,411 3 Claims. (Cl. 23613) This invention relates to air conditioning systems and more particularly to a method and apparatus for automatic regulation of room temperature and inlet volume of air flow in a two stream air conditioning system.

Air conditioning systems employing two separate streams of air, hot and cold, are well known in the art. See, for example, US. Patent 2,729,429. Such air conditioning systems operate by providing separate streams of air which are distributed throughout a building for blending prior to discharge into the rooms of the building. One of these streams is maintained at a temperature substantially above the temperature which it is desired to maintain within the rooms. The other stream is maintained at a temperature which is substantially below the temperature which it is desired to maintain in the rooms. By independently throttling the two streams, a resultant blended stream of conditioned air can be provided for discharge into the rooms at a blended temperature which will maintain the desired conditions within the rooms of the building. Good ventilation practice dictates that the conditioned air should be supplied to the individual rooms at a substantially constant volume of flow.

For a clear understanding of the present invention and of problems presented by two stream conditioned air systems, reference should be had to the accompanying drawings in which:

FIGURE 1 is a schematic illustration of a prior art mixer box having automatic controls suitable for normal operation of two-stream air conditioning systems;

FIGURE 2 is a graphical representation of the normal operation of the mixer box illustrated in FIGURE 1;

FIGURE 3 is a graphical illustration of one defect which is inherent in the operation of the prior art mixer box shown in FIGURE 1;

FIGURE 4 is a schematic illustration of a mixer box according to one embodiment of the present invention which offsets the inherent defect illustrated in FIGURE 3;

FIGURE 5 is a cross-section illustration of a shuttle valve which is shown schematically in FIGURE 4;

FIGURE 6 is a graphical illustration showing the results achieved by operation of the mixer box of FIG- URE 4;

FIGURE 7 is a graphical illustration showing another defect which is inherent in the operation of the prior art mixer box of FIGURE 1;

FIGURE 8 is a schematic illustration of an alternative embodiment of the present invention which ofisets the inherent defect illustrated in FIGURE 7;

FIGURE 9 is a cross-section illustration of a shuttle valve which is illustrated schematically in FIGURE 8;

FIGURE 10 is a graphical illustration showing the results achieved by the operation of the mixer box of FIG- URE 8; and

FIGURE 11 is a schematic illustration of a preferred embodiment of the mixer box of this invention including the features ah'eady shown in FIGURES 4 and 8.

Every room, group of rooms or portion of a single room in a building may be considered as a relatively confined zone for the purposes of air conditioning. A continuous supply of conditioned air is introduced into each room (control zone) and a corresponding quantity of air is removed from the room (control zone) for dissipation or reconditioning and recirculation.

As shown in FIGURE 1, an individual room or control zone is indicated by the numeral 10.

Two streams of conditioned air are provided throughout the building and are represented by the numerals 11 (cold air inlet) and 12 (hot air inlet). The two air inlets communicate with amixer box 13 which is shown in cross-section. A pair ofpartitions 14, 15 extend across the cavity of themixer box 13 and divided the cavity into aninlet blending chamber 16, amixing chamber 17 and adistribution chamber 18. Thepartition 14 separates theinlet blending chamber 16 from themixing chamber 17 and has a plurality ofdirectional mixing vanes 19 which create some turbulence as air passes through theportion 14 to provide a uniformly mixed stream of blended air. Thepartition 15 separates themixing chamber 17 from thedistribution chamber 18 and has aperforate plate 20 through which air may experience streamline flow. Theperforate plate 26 may be a screen, perforated sheet, netting, mesh and the like.Imperforate plates 21 are provided in a slidable mounting in which they may be extended or retracted to'regulate the cross-sectional area of theperforate plate 21 to regulate the flow of air therethrough.

A pair of pneumatically controlledvalves 22, 23 is provided in the cold air inlet 11 and thehot air inlet 12 respectively to throttle the fioWs of air issuing into theinlet blending chamber 16. Air is discharged from theinlets 11 and 12 into theinlet blending chamber 16 whence it passes between thevanes 19 for uniformity of mixing within themixing chamber 17. Uniformly blended air passes through the perforate plate 213 into thedistribution chamber 18 whence it is discharged into the control zone 10 throughconduits 24, 25.Additional conduits 26 may be provided to discharge additional air to other rooms or to different locations of the same room. The entire air discharge from thedistribution chamber 18 enters the control zone albeit several different rooms may reeive the discharge.

Anexit conduit 27 is provided to withdraw air from the control zone 10 for dissipation or reconditioning and recirculation.

Apneumatic thermostat 28 is maintained within the control zone 10 for continuous observation of the temperature therein. A supply stream of pressurized air is introduced into thethermostat 28 through asupply conduit 29. Thethermostat 28 regulates the pressure of the supply air, usually by bleeding a portion of the air, according to the deviation of the actual temperature within the control Zone 10 from a predetermined temperature setting of thethermostat 28. Thus a temperature regulated pressure of the throttled supply air is introduced into a conduit 36 which communicates with and operates the pneumatically controlledvalve 23 in thehot air inlet 12. Normally the supply air in theconduit 29 is maintained at a pressure of about 17 to 20 pounds per square inch. The temperature regulated pressure in theconduit 30 normally has a range of about 5 pounds per square inch, that is, from about 8 pounds per square inch to about 13 pounds per square inch. Hereinafter any conduit which confines the temperature regulated pressure and which extends between thethermostat 28 and any other element in the system will be identified as the thermostat conduit.

When the temperature Within the control zone It) is below the predetermined value, the temperature regulated pressure in thethermostat conduit 30 is reduced; when the temperature in the control zone 10 is above the predetermined value, the temperature regulated pressure in thethermostat conduit 30 is increased. The pneumaticallyresponsive valve 23 operates to be opened when confronted with relatively low pressures and to be closed when confronted with relatively high pressures. Thus the amount of hot air issuing fromhot air inlet 12 into theinlet blending chamber 16 is controlled in response to deviations of the actual temperature within thecontrol zone 19 from a predetermined value.

A substantially constant volume discharge of blended conditioned air into thedistribution chamber 18 is achieved by means of a pneumatic flow controller such as adifferential pressure regulator 31. It will be observed that the perforate plate 24) in thebaflie 15 serves as a flow measuring orifice. A pair of staticpressure sensing tape 32, 33 is provided to observe the static pressure on each side of thebaffie 15 and to transmit these static pressures to thedifferential pressure regulator 31. So long as a constant volume of air passes through theperforate plate 20, a predetermined constant pressure differential will exist between thepressure taps 32, 33. If the volume of air passing through the perforate plate 24) exceeds the predetermined value, the pressure differential existing between thepressure taps 32, 33 will increase. Similarly if the volume of air passing through the perforate plate 2i) is less than the predetermined value, the pressure diflferential existing between thepressure taps 32, 33 will decrease. Accordingly thedifferential pressure regulator 31 serves to regulate a supply of pressurized air from aconduit 34, usually by bleeding a portion of the air, in response to deviations in the observed difierential pressure from a predetermined constant value. Thus a flow regulated pressure of the throttled supply air is introduced into aconduit 35. Hereinafter any conduit which confines the flow regulated pressure and which extends between thedifferential pressure regulator 31 and any other element in the system will be identified as a pressure regulator conduit. If the observed differential pressure is greater than the predetermined value, the flow regulated pressure maintained in the pressure regulatedconduit 35 increases. It the observed differential pressure is less than the predetermined value, the flow regulated pressure maintained in thepressure regulator conduit 35 is decreased.

Theperforate plate 20 serves principally to promote a uniform flow of air from the mixingchamber 17 to the distribution chamber in order that the pressure diiierential existing between thechambers 17 and 18 may be accurately measured by suitable pressure differential measuring apparatus. Thepressure regulator conduit 35 communicates with and operates the pneumatically controlledvalve 22 in the cold air inlet 11. Normally the range of the flow regulated pressure maintained within thepressure regulator conduit 35 will be about 5 pounds per square inch, that is, from about 3 pounds per square inch to about 8 pounds per square inch. High air pressures in thepressure regulator conduit 35 tend to close the pneumatically controlledvalve 22. Low air pressures in thepressure regulator conduit 35 tend to open the pneumatically controlledvalve 22.

It is thus apparent that the how of hot air from thehot air inlet 12 is regulated in response to thethermostat 28 in such manner that greater quantities of hot air will be discharged into theinlet blending chamber 16 when the actual temperature in the control Zone is below the predetermined temperature setting. The amount of cold air discharged into theinlet blending chamber 16 from the cold air inlet 11 will be sufiicient so that the combination of the hot air and cold air which passes through theperforate plate 20 is a predetermined volume.

The normal operation of the system illustrated in FIGURE 1 can be described by the graphical representation shown in FIGURE 2. The vertical axis represents the flow of air from each of the twoinlets 11, 12. An arrow A indicates the predetermined constant volume of air which is desired in the control zone It The horizontal axis indicates the temperature regulated pressure (thermostat pressure) maintained within the temperature regulated conduit 39. It will be observed that increasing thermostat pressure results in a decreased volume of hot air entering into theinlet blending charnher 16. The amount of cold air discharged into theinlet blending chamber 16 is supplementarily dependent upon the amount of hot air and is such that the summation of the cold air and the hot air is equal to the predetermined constant volume which is indicated by the arrow A. The arrow B indicates the flow of hot air which is achieved when the pneumatically controlledvalve 23 is fully opened with a normal static pressure being maintained in thehot air inlet 12. The arrow C indicates that there is no hot air admitted into theinlet blending chamber 16 when the pneumatically controlledvalve 23 is completely closed, corresponding to a high temperature regulated pressure appearing within the conduit 3%). Under normal operatin conditions, the system illustrated in FIGURE 1 will perform entirely within the normal range indicated in FIGURE 2. That is, some quantity of air will be admitted into theinlet blending chamber 16 from each of theinlets 11 and 12.

The system illustrated in FIGURE 1 exhibits inherent defects in two circumstances:

Circumstance ].When the control zone 10 is cold and a high static pressure exists in thehot air inlet 12.

Circumstance 2.When the control zone iii is cold and a low static pressure exists in thehot air inlet 12.

According to the present invention, mixer box controls are presented which overcome the inherent defects in the two described circumstances. To offset circumstance 1, a shuttle valve is provided in the thermostat conduit which permits the differential pressure regulator to override the thermostat as the control parameter for the pneumatically controlled valve in the hot air inlet. To compensate for circumstance 2, a shuttle valve is provided in the pressure regulator conduit which causes closure of the pneumatically controlled valve in the cold air inlet in respose to pressurized supply air when the thermostat pressure falls below its normal operating range.

The principal obiect of this invention is to provide a mixer box and controls therefor which will automatically regulate the flow of air from a two-stream air conditioning system to maintain a predetermined temperature within a control zone while providing ventilation at a substantially constant volume rate.

A further object of this invention is to provide a mixer box and control system therefor to regulate the flow or" air from a two-stream air conditioning system regardless of the static pressure fluctuations in the streams.

These and other objects and advantages of the present invention will become apparent from the following detailed description.

Circumstance I.When the control zone 10 is cold and a high static pressure exists in thehot air inlet 12.

Consider the system shown in FIGURE 1 when the control zone 10 is cold, i.e., at a temperature below tr e predetermined temperature. Decreased temperature regulated pressure in thethermostat conduit 30 will cause the pneumatically controlledvalve 23 to move to fully open position. If, at this time, the static pressure within thehot air inlet 12 is excessive, it is possible that the hot air issuing into theinlet blending chamber 16 has a greater volume than the predetermined volume which is controlled by thedifferential pressure regulator 31. Accordingly the pressure taps 32, 33 will sense an excessive differential pressure; hence an increasing flow regulated pressure will appear in thepressure regulator conduit 35 to cause the pneumatically controlledvalve 22 to close completely. Thedifferential pressure regulator 31 at that point has fully compensated the dependent variable which it controls yet has not limited the volume of air flowing through theperforate plate 20 to the predetermined value. The result is as shown in FIGURE 3 where it appears from the arrow D that the flow of cold air has been terminated yet the total flow, representing exclusively hot air, exceeds the predetermined value (indicated by the arrow A) as shown by the shadedarea 34. Thus when circumstance 1 develops, an excessive volume of air is introduced into thecontrol zone 18 through theconduits 24, 25.

The embodiment of this invention illustrated in FIG- URE 4 avoids the difi'iculties just described with reference to circumstance l. The essential elements of FIG- URE 4 are the same as those illustrated in FIGURE 1 and corresponding numerals refer to corresponding elements.

Ashuttle valve 40 is provided having two inlet connections and one outlet connection. Athermostat conduit 30a connects thethermostat 28 with one of the inlet connections of theshuttle valve 40. Apressure regulator conduit 41 extends from thepressure regulator conduit 35 to the other inlet connection of theshuttle valve 49. A pneumaticvalve operating conduit 42 connects the outlet of theshuttle valve 40 with the pneumatically controlledvalve 23.

Theshuttle valve 40 is more clearly illustrated in FIG- URE 5. Essentially theshuttle valve 49 is formed from two casinghalves 43 and 44 which are joined together by means ofbolts 45. Aflexible diaphragm 46 separates the casing halves 43 and 44. Cavities in each of the casing halves 43 and 44 form a right hand chamber 47 and a left hand chamber 48 separated by theflexible diaphragm 46. Aconduit 49 is provided in thecasing half 43 for communication between the thermostat conduit 39a and the right hand chamber 47. Aconduit 50 is provided in thecasing half 44 for communicating between thepressure regulator conduit 41 and the left hand chamber 48. Aconduit 51 extends through both of the casing halves 43, 44 and communicates between the right hand chamber 47 and the pneumaticvalve operating conduit 42. A threadedneedle adjustment screw 52 extends through thecasing half 43 to provide an adjustable restriction in theconduit 51. Aconduit 53 is provided in thecasing half 44 between the left hand chamber 48 and the pneumaticvalve operating conduit 42. Acentral boss 54, 55 extends inwardly from each of the casing halves 43, 44 respectively.

It will be apparent that the air pressure of the thermostat conduit 33a is presented in the right hand chamber 47 through theconduit 49 whereas the air pressure of the pressure reulator conduit 41 is presented in the left hand chamber 48 through theconduit 50. Under normal operating conditions, the pressure in the right hand chamber 47 will exceed the pressure in the left hand chamber 48 and consequently thediaphragm 46 will be displaced to the left to cover the chamber openings of theconduits 50, 53 which are presented in the left hand chamber 48 in theboss 55. Accordingly theconduits 49, 51 will be in communication with the right hand chamber 47 and the air pressure of the thermostat conduit 3% will be transmitted through theconduit 49, the right hand chamber 47, theconduit 51 to the pneumaticvalve operating conduit 42. In effect, under normal operating conditions, there is a direct conduit connection between thethermostat 28 and the pneumatically controlledvalve 23 and hence the system shown in FIGURE 4 normally functions exactly as the system shown in FIGURE 1.

However when circumstance l is presented, i.e., the temperature within thecontrol zone 16 is below the predetermined value and a high static pressure exists in thehot air inlet 12, the inherent defect illustrated in FIG- URE 3 is ofiset by the apparatus shown in FIGURE 4. The defect is offset in the following manner. Because of the low temperature existing in the control zone 10, the air pressure in the thermostat conduit 34a is a low value tending to open the pneumatically controlledvalve 23 to a maximum open position. Similarly the air pressure in thepressure regulator conduit 35 is a maximum tending to close the pneumatically operatedvalve 22. Once the pneumatically operatedvalve 22 is fully closed, thedifferential pressure regulator 31 will continue to increase the air pressure in thepressure regulator conduit 35 in an effort to correct for the excessive differential pressure which is being sensed through the pressure taps 32, 33. The further increasing pressure is transmitted through theconduit 41 into theshuttle valve 40 through theconduit 50. When the pressure in theleft hand chamber 43 exceeds the pressure in the right hand chamber 47, thediaphragm 46 moves from left to right covering theboss 54 and opening theboss 55, Thus the increased pressure from theconduit 41 is transmitted through the conduit 5% into the left hand chamber 48 through the conduit 5;: to the pneumaticvalve operating conduit 42 where it exerts a pressure against the pneumatically operatedvalve 23 tending to cause it to move toward a closed position until only the predetermined volume of air is issuing through theperforate plate 20.

Normal operation is restored when the static pressure in thehot air inlet 12 is reduced to a normal value or when the temperature in the control zone 10 rises to a value closer to the predetermined value. If the static pressure in thehot air inlet 12 decreases to a normal value, the air issuing from theconduit 12 into theinlet blending chamber 16 will be less than the predetermined value and the air pressure in thepressure regulator conduits 35 and 41 will decrease to allow thediaphragm 46 to move against theboss 55 as in normal operation. Alternatively a closer approach to the predetermined temperature in the control zone 1% will result in an increase in the air pressure in thethermostat conduit 30a which will cause thediaphragm 46 to move against theboss 55 and at the same time exert a closing tendency through the pneumaticvalve operating conduit 42 against the pneumatically operatedvalve 23.

The correction achieved by the system illustrated in FIGURE 4 is shown graphically in FIGURE 6. When the flow of cold air has been terminated completely (see the arrow D), theshuttle valve 40 automatically switches the control parameter from the thermostat to the differential pressure regulator so that the desired volume of air, as indicated by the arrow A, is not exceeded.

A typical situation which might create circumstance 1 would be presented when an individual within the control zone 10 opens a window or a door in cold weather to allow a substantial quantity of cold air to enter the control zone 10 and create a decrease in the actual temperature therein. If this situation should develop at a time when an excessive static pressure appears in thehot air inlet 12, circumstance 1 would be presented.

Circumstance 2.When the control zone 10 is cold and a low static pressure exists in thehot air inlet 12.

Referring once again to the apparatus shown in FIG- URE l, in this circumstance thethermostat 28 develops an increasing temperature regulated pressure in the thermostat conduit 39 causing the pneumatically operatedvalve 23 to open to a full position. Because of the inadequate static pressure in thehot air inlet 12, less than the predetermined total volume of air is discharged from thehot air inlet 12 into theinlet blending chamber 16. Accordingly thedifferential pressure regulator 31 reduces the flow regulated pressure in thepressure regulator conduit 35 causing the pneumatically operatedvalve 22 to move in an open position. As a result, a blend of air from the cold air inlet 11 and thehot air inlet 12 is introduced into theinlet blending chamber 16 and thence through the mixingchamber 17 to thedistribution chamber 18 and into the control zone 1% despite the fact that the control zone 10 already is at a temperature below the predetermined value.

This condition is illustrated graphically in FIGURE 7 where the arrow E indicates the maximum flow of hot air attainable with a fully openedvalve 23. Because the value indicated by the arrow B is less than the predeterined value indicated by the arrow A, a quantity of cold air indicated by the shaded area 61 will enter the control Zone 10.

According to a further embodiment of the present invention as illustrated in FIGURE 8, the difiiculties described as circumstance 2 can be obviated. The elements of the mixer box shown in FIGURE 8 are essentially the same as those shown in FIGURE 1. merals are employed to indicate corresponding elements.

. The principal change is the provision of ashuttle valve 62 having twoinlet ports 63, 64, oneoutlet port 65, and onecontrol port 66. A source of supply air is introduced into aconduit 67 to theinlet port 63. Thepressure regulator conduit 35a joins thedifferential pressure regulator 31 with theinlet port 64. Avalve operating conduit 68 joins theoutlet port 65 with the pneumatically operatedvalve 22. A shuttlevalve operating conduit 69 connects thethermostat conduit 30 with the shuttle valve operatinginlet port 66.

Theshuttle valve 62 is more fully illustrated in FIG- URE 9.

Thevalve 62 comprises ahollow casing 70 having aninternal chamber 71 and the previously mentionedinlet ports 63, 64 andoutlet port 65. Anannular boss 72 is provided externally of thecasing 70 surrounding aplunger port 73 which extends through thecasing 70. A resilient diaphragm 74 is secured across the outer surface of theannular boss 72 by peripheral sealing of a cover plate 75. The diaphragm 74 comprises the common wall of twochambers 76 and 77 which are respectively a shuttlevalve operating chamber 76 and avent chamber 77. The shuttlevalve operating port 66 appears in the cover plate 75. Secured to the diaphragm 74 is aflat metal plate 78 and, mounted normally thereto, an operatingplunger 79 which extends through theplunger port 73. A bleed port 88, opening to the atmosphere, extends through theannular boss 72 from thevent chamber 77.

Within theshuttle valve chamber 71 and pivotally mounted about a pin 81 is aflapper 82 suitably formed from a fiat piece of metal and having at its extreme end a pair ofpads 83, 84 of rubber or similar resilient material. A normally compressedspring 85 is positioned with relation to theflapper 82 to exert a force tending to cause counterclockwise movement of theflapper 32 whereby thepad 83 covers thetip 86 of thepressure regulator conduit 35a and thepad 84 is displaced from thetip 87 of thesupply air conduit 67. Opposing the counterclockwise force presented by the normally compressedspring 85 is theplunger 79 which bears against theflapper 82 exerting a clockwise force about the pivot pin 81. The force exerted by theplunger 79 is determined by the pressure maintained within the operatingchamber 76, i.e., the pressure within thethermostat conduit 69.

Normally the pressure in the operatingchamber 76 is sufficient to cause theplunger 7 to overcome the resiliency of the normally compressedspring 85 whereby, under normal conditions, thepad 84 is compressed against thetip 87 of thesupply air conduit 67 so that a direct flow passageway is provided from the pressureregulator con duit 35a through itstip 86 and into the pneumatic controlledvalve operating conduit 68. When the temperature regulated pressure in thethermostat conduit 69 falls below a predetermined value, theresilient spring 85 causes counterclockwise movement of theflapper 82 whereby thesupply air conduit 67 is free to introduce its pressure directly into theconduit 68. The pressure of the air in thesupply conduit 67 is at all times in excess of that appearing in thepressure regulator conduit 35a. Under normal conditions the supply air conduit pressure will be from about 17 to 20 pounds per square inch. The pressure in the how regulatedpressure regulator conduit 35a will have a range of about pounds per square inch, for example from about 3 to about 8 pounds per square inch. Since the normal range of pressures in the thermostat conduits 3t), 69 is from about 8 to 13 pounds per square inch, theresilient spring 85 produces counterclockwise movement of theflapper 82 only when the pressure in the operatingchamber 76 falls below about 8 pounds per Corresponding nusquare inch. The spring tension of the spring is adjusted to the lower pressure of the operating range of the pressures in thethermostat conduit 30.

Returning to FIGURE 8, it will be observed that the system operates satisfactorily under circumstance 2. That is, under normal conditions, the system shown in FIG- URE 8 performs exactly as the system shown in FIG- URE '1.

Where, however, the low pressure maintained in thethermostat conduit 30 results in a fully openedvalve 23, that same low pressure will activate theshuttle valve 62 whereby the supply air from theconduit 67 will be introduced into theconduit 68 to operate the pneumatically controlledvalve 22. By virtue of its normal pressure of 17 to 20 pounds per square inch, the pressure from thesupply air conduit 67 will cause the pneumatically controlledvalve 22 to close completely.

Accordingly the characteristics of the system illustrated in FIGURE 8 can be graphically represented as shown in FIGURE 10. When the temperature regulated pressure from the thermostat decreases to a value below its normal operating range, the pneumatically controlledvalve 23 becomes fully opened and, with a constant static pressure existing in thehot air inlet 12, the resulting air flow through thehot air inlet 12 will be constant as shown by the arrow F. Because of the postulated low static pressure in thehot air inlet 12, the flow of air therefrom at fully opened position is less than the predetermined flow of air as indicated by the arrow A. Nevertheless, because the thermostatic pressure is below its normal range, the further inflow of cold air is prevented and exclusively hot air is introduced into theinlet blending chamber 16. Admittedly the total flow of air from the system shown in FIGURE 8 does not, in this one isolated circumstance, have a constant value.

A typical situation giving rise to the circumstance 2 occurs in the early morning in buildings which have been mantained at lower than normal temperatures throughout the preceding evening during which the building was relatively unoccupied. In the early morning, every room or control zone 10 presents a temperature below the predetermined value and accordingly every room or control zone requires substantial quantities of hot air until the predetermined temperature is attained. Because of the universal demand upon the hot air supply, certain periods of low duct pressure may occur in thehot air inlets 12 through the inability of the hot air supply system to provide the peak load requirements. Thus the system illustrated in FIGURE 8 compensates for a problem which occurs daily in the operation of dual duct air conditioning systems.

Having now described its elements the preferred embodiment of the present invention may now be quickly illustrated by reference to FIGURE 11. The apparatus shown in FIGURE 11 embodies that previously shown in FIGURES 4 and 8., Corresponding numerals are employed to indicate corresponding elements.

As shown in FIGURE 11, both theshuttle valve 40 and theshuttle valve 62 are included in the preferred embodiment. The system shown in FIGURE 11 operates exactly, with respect to theshuttle valve 40, as the system illustrated in FIGURE 4. The system, with respect to theshuttle valve 62, operates exactly as that shown in FIG- URE 8. Theconduit 30a joins thethermostat 28 with theshuttle valve 46. In the preferred embodiment, the shuttlevalve operating conduit 69 joins thethermostat conduit 30a with the operatingport 66 of theshuttle valve 62. Similarly the pressureregulator conduit conduit 35a joins thedifierential pressure regulator 31 with theinlet port 64 of theshuttle valve 62. In the preferred embodiment thepressure regulator conduit 41 joins thepressure regulator conduit 35a with the inlet port of theshuttle valve 40.

According to the provisions of the patent statutes, I have explained the principle, preferred embodiment and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In an air conditioning mixing and distributing box having a hot air inlet, a cold air inlet and at least one outlet conduit for discharging a blended stream of conditioned air into a relatively confined zone, a fluid pressure operated valve in each of said inlet conduits, a source of supply air under pressure, flow responsive means adapted to control the pressure of a first supply air source as aflow regulated pressure in accordance with the flow rate of said blended air stream, temperature responsive means within said relatively confined zone adapted to control the pressure of a second supply air source as a temperature regulated pressure in accordance with the temperature existing within said relatively confined zone, shuttle valve means having two fluid inlets and one fluid outlet adapted to communicate the said fluid outlet with that fluid inlet having the greater static pressure, conduit means communicating the said temperature regulated pressure and the said flow regulated pressure respectively to the said two fluid inlets and for connecting the said fluid outlet to the said fluid pressure operated valve in the said hot air inlet, and conduit means communicating said flow regulated pressure to said fluid operated valve in said cold air inlet.

2. In an air conditioning mixing and distributing box having a hot air inlet, a cold air inlet and at least one outlet conduit for discharging a blended stream of conditioned air into a relatively confined zone, a fluid pressure operated valve in each of said inlet conduits, a source of supply air under premure, flow responsive means adapted to control the pressure of a first supply air source as a flow regulates pressure in accordance with the flow rate of said blended air stream, temperature responsive means within said relatively confined zone adapted to control the pressure of a second supply air source as a temperature regulated pressure in accordance with the temperature existing within said relatively confined zone, conduit means communicating the said temperature regulated pressure to the said fluid pressure operated valve in the said hot air inlet, shuttle valve means having two inlet ports and one outlet port, means within said shuttle valve means responsive to the pressure of said temperature regulated pressure to communicate said outlet port with only one of said inlet ports, conduit means connecting a third supply air source to one of said inlet ports and communicating said flow regulated pressure to the other of said fluid inlet ports and for connecting said outlet port to said fluid operated valve in said cold air inlet.

3. In an air conditioning mixing and distributing box having a hot air inlet, a cold air inlet and at least one outlet conduit for discharging a blended stream of conditioned air into a relatively confined zone, a fluid pressure operated valve in each of said inlet conduits, a source of supply air under pressure, flow responsive means adapted to control the pressure of a first supply air source as a flow regulated pressure in accordance with the flow rate of said blended air stream, temperature responsive means Within said relatively confined zone adapted to control the pressure of a second supply air source as a temperature regulated pressure in accordance with the temperature ex isting within said relatively confined zone, first shuttle valve means having two fluid inlets and one fluid outlet adapted to communicate the said fluid outlet with that fluid inlet having the greater static pressure, conduit means communicating the said temperature regulated pressure and the said flow regulated pressure respectively to the said two fluid inlets and for connecting the said fiuid outlet to the said fluid pressure operated valve in the said hot air inlet, second shuttle valve means having two inlet ports and one outlet port, means within said second shuttle valve means responsive to the pressure of said temperature regulated pressure to communicate said outlet port with only one of said inlet ports, conduit means connecting a third supply air source to one of said inlet ports and communicating said flow regulated pressure to the other of said fluid inlet ports and for connecting said outlet port to said fluid operated valve in said cold air inlet.

References Cited in the file of this patent UNITED STATES PATENTS 2,793,812 McDonald May 28, 1957 2,815,915 Salerno Dec. 10, 1957 2,821,343 Payne Ian. 28, 1958 Disclaimer 3,026,04L-Arthur P. J entoft, Wexford, Pa. CONDITIONED AIR DISTRIBUTION. Patent dated Mar. 20, 1962. Disclaimer filed Sept. 13, 1962, by the assignee, H. H. Robertson Company. Hereb enters this disclaimer to claim 1 of said patent.

Gazette October 25, 1962.]

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