Control of air conditioning apparatus
United States Patent [1 1 Arledge, Jr.  
 [ CONTROL OF AIR CONDITIONING APPARATUS [75] Inventor: Arthur E. Arledge, Ji&#39;., Cazenovia,  
 [73] Assignee: Carrier Corporation, Syracuse, N.Y.  
 [22] Filed: Aug. 2, 1973 21 Appl. No.: 385,023  
 [52] US. Cl. 165/26; 165/35; 165/123 [51] Int. Cl F28f 27/02 [58] Field of Search 165/123, 27, 26, 35, 40, 165/101, 103; 98/38 [56] References Cited UNITED STATES PATENTS 3,034,725 5/1962 Person 98/38 X 3,208,508 9/1965 Bryans et al.... 165/123 X 3,323,584 6/1967 Serratto 165/123 X 3,470,945 10/1969 Schmidt 165/123 X 3,623,542 ll/l97l Fragnito 165/123 X FOREIGN PATENTS OR APPLICATIONS 1,211,137 11/1970 United Kingdom 165/123 [451 Apr. 15, 1975 Primary Examiner-Manuel A. Antonakas Attorney, Agent, or Firm-J. Raymond Curtin; Barry E. Deutsch [57] ABSTRACT An induction type air conditioning unit having a first heat exchanger connected to a source of a relatively cold heat exchange medium and a second heat exchanger connected to a source of a relatively warm heat exchange medium. Dampers are provided to selectively direct the air induced from a space served by the unit through either the first heat exchanger, the second heat exchanger, or through a path bypassing both first and second heat exchangers. The dampers are operatively connected to an inflatable bellows. The inflatable bellows is connected to the source of primary air for the induction unit. The primary air pressure in the inflatable bellows is varied in response to changes. in room temperature to vary the path of flow of the air induced into the induction unit to therebyobtain a desired temperature for air discharged into said space.  
 4 Claims, 5 Drawing Figures PATENTED AF 1 5 i975 SHEET 1 OF 2 FIG.I  
 FIG.2  
 SHEET 2 or g 0m mm mm mm ww mm mm mm 1 CONTROL OF AIR CONDITIONING APPARATUS BACKGROUND OF THE INVENTION This invention relates to air conditioning units. and more particularly to air conditioning units of the induction type.  
  Induction type air conditioning units are well known to those skilled in the art. Such units generally comprise a casing having a plenum provided therein. connected to a source of primary air. The primary air is supplied from a central station at a relatively high velocity and high static pressure. The primary air is discharged from the plenum via nozzles. thereby inducing air from the space. generally known as secondary air. into the mixing chamber of the unit. Generally. a heat exchanger. either connected to a source of either a relatively cold heat exchange medium or connected to a source ofa relatively warm heat exchange medium. defines the flow path entrance for the secondary air into the mixing chamber of the unit. The primary air and the secondary air streams mix within such chamber and are discharged therefrom to provide a desired temperature level in a space conditioned by the unit.  
  Induction type air conditioning units are generally employed in conditioning the air in buildings having many individual spaces or rooms. for example office buildings. schools. and hospitals. Most induction type air conditioning units permit the occupant of an individual room to obtain a desired temperature level therein. without affecting the temperature of air in another room or space in the building.  
  Most induction units have heretofore been employed in two-pipe air conditioning systems. The main disadvantage of such two-pipe air conditioning systems is that the heat exchange medium supplied to the individual induction units is either at a relatively warm temperature or at a relatively cold temperature. Particularly during intermediate seasons. some spaces in the building require heating. whereas other spaces require cooling. Since the temperature of the heat exchange medium is substantially uniform throughout the entire system. some of the occupants will not be able to obtain desired temperature conditions in their respective rooms.  
  In U.S. Pat. No. 3.323.584. there is disclosed an induction type air conditioning unit suitable for use in a four-pipe air conditioning system. The utilization of two heat exchangers having respectively a relatively warm heat exchange medium and a relatively cold heat exchange medium supplied independently thereto. permits individual occupants to obtain desired temperature levels within a wide range. For example. some units may be operated to provide heating. whereas other units may provide cooling. Although. a four-pipe system has the capability to provide extremely comfortable conditions throughout the building regardless of individual occupant preferences. the benefits are offset by the high cost of installing and controlling same. The relatively complex damper mechanisms required to selectively direct the secondary air over the desired heat exchange coil to obtain a desired temperature level has heretofore substantially increased the manufacturing cost of the unit employing the same. In addition, the requisite damper actuators. for example either complex pneumatic or electric control systems. has further increased the cost of manufacturing such a unit. and has additionally increased the cost of installing and operating the individualunits and thus the air conditioning system.  
  In U.S. Pat. No. 3.122.201, there is disclosed an induction type air conditioning unit employing primary air to selectively inflate a bellows to regulate the flow of air either through or about a heat exchange coil. However, the induction unit disclosed in U.S. Pat. No. 3.122.201 may only be employed in a two-pipe air conditioning system.  
 SUMMARY OF THE INVENTION It is therefore an object of the invention to provide an induction type air conditioning unit suitable for utilization in a four-pipe air conditioning system.  
  It is a further object of the present invention to provide an induction unit. suitable for use in a four-pipe system. utilizing primary air as a motivating force for actuating the dampers.  
  It is yet another object of the present invention to provide a novel method of controlling an induction unit employed in a four-pipe air conditioning system.  
  It is still a further object of the present invention to provide a novel method of controlling an induction unit employed in a four-pipe air conditioning system.  
  It is still a further object of the present invention to provide -a novel damper mechanism for selectively directing secondary air induced into an induction type unit through a desired flow path.  
  These and other objects of the present invention are obtained by providing an induction unit having a first heat exchanger defining a first flow path for air induced into an air conditioning unit. The first heat exchanger is connected to a source of a relatively cold heat exchange medium. A second heat exchanger defines a second flow path for the induced air; the second heat exchanger being connected to a source of a relatively warm heat exchange medium. Means define a third flow path for the induced air, said flow path bypassing said first and second heat exchangers. An inflatable bellows is connected to the primary air. the primary air pressure in the bellows varying with changes in temper ature of the space being conditioned. A damper mechanism is connected to the bellows for directing the air through a selected one of said flow paths to obtain desired temperature conditions within the space.  
 BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view, partially broken away. of an air conditioning unit embodying the present invention;  
  FIG. 2 is a schematic representation of a control for the air conditioning unit illustrated in FIG. 1;  
  FIG. 3 is a sectional view of the air conditioning unit of FIG. I in a first operating mode;  
  FIG. 4 is a view similar to FIG. 3 showing the unit in a second operating mode; and  
  FIG. 5 is yet another sectional view of the unit showing a third operating mode.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing. there is shown an air conditioning unit embodying the present invention. In referring to the various figues. like numerals shall refer to like parts.  
  Referring particularly to FIG. 1, there is illustrated an air conditioning unit 10. Unit 10 is of the type known to those familiar with the art as an induction unit. The air conditioning unit includes casing 11 having a plenum chamber 14 contained therein. Plenum chamber 14 is connected via a suitable duct 15 to a source of primary air (not shown). The primary air is supplied to unit 10 at a high velocity and at a high static pressure. The primary air is discharged from plenum 14 via nozzles 16 having nozzle orifices 17. The nozzles operate to discharge the primary air at a relatively high velocity to induce secondary air from the space or room being conditioned into mixing chamber 18 of the unit. The secondary air entering the unit passes thereinto via inlet grill 12. The mixture of secondary and primary air is discharged from the unit into the space via discharge grill or outlet 13.  
  Provided within the unit are first and second heat exchangers 19 and 20. Heat exchanger 19 is connected to a source (not shown) of relatively cold heat exchange medium. for example relatively cold water. which is supplied to the heat exchanger via inlet pipe 21. The heat exchange medium is returned to the source via outlet pipe 22.  
  Heat exchanger 20 is connected to a suitable source (not shown) of a relatively warm heat exchange medium. for example. relatively warm water. Heat exchanger 20 includes an inlet pipe 23 and an outlet pipe 24 for such heat exchange medium. As shall be more fully explained hereinafter. heat exchanger 19 defines a first fluid flow path for the secondary air entering the air conditioning unit; whereas heat exchanger 20 defines a second fluid flow path for the air induced into such unit. The manner in which the air is directed through a selected one of the flow paths or through a third flow path bypassing heat exchangers 19 and 20 shallbe more fully explained hereinafter.  
  Opcratively associated with heat exchangers l9 and 20 are dampers 26 and 27. Dampers 26 and 27 form a portion of the control for directing the air through a selected one of the flow paths. The control further includes an inflatable bellows 25. Plate member 45 is operatively connected to the bellows. the position of the plate being varied in accordance with variations in the inflation of the bellows. Spring 46 supplies a force on plate member 45 in opposition to the force supplied by the bellows.  
  A first link 28 is connected to plate member 45 and is movable therewith. A second link 30 is suitably connected. for example via pin 29. to link 28. The control further includes a third link 31 suitably connected to link 30 via pin 47&#39;. Link 31 includes elongated slots 35 and 36.  
  Damper 26 is associated with heat exchanger 20 having the relatively warm heat exchange medium flowing therethrough. Damper 26 is attached to link 49. the damper being designed to pivot about point 33. Link 49 includes a pin 37. the pin being movably disposed within elongated slot 36 of link 31.  
  Damper 27 is pivotally attached to link 48, the damper being designed to pivot about point 32. Link 48 includes a pin 34, movably provided in elongated slot 35 of link 31. One end ofa tension spring 38 is suitably connected to link 48 and the other end of the spring is connected to link 49.  
  Referring particularly to FIG. 2, there is shown a schematic illustration of a preferred control system for regulating the position of inflatable bellows 25.  
  Primary air from duct 15 is supplied via a filter 39 to a pressure regulator 40. Pressure regulator 40 maintains a constant predetermined downstream pressure regardless of variations in primary air pressure in the duct. Connected downstream of regulator 40 is an orifice 41, which is connected to a bleed-type thermostat 42. The bleed thermostat includes an orifice 44 having a bimetallic element 43 suitably positioned thereover. Inflatable bellows 25 is&#39; connected between orifice 41 and thermostat 42. When the thermostat senses that the room temperature is above a predetermined level. bimetallic element 43 preferably operates to close off orifice 44 to increase the pressure signal to inflatable bellows 25 to thereby expand the bellows. Conversely. when the room temperature falls below a predetermined value. the bimetallic element opens orifice 44 to decrease the pressure signal supplied to bellows 25 to thereby deflate same. The manner in which the control functions to selectively direct the secondary air through a desired flow path to obtain desired temperature conditions in the space shall now be explained.  
 COOLING MODE OPERATION Referring particularly to FIG. 3. the unit is shown as operating in a cooling mode. As noted hereinbefore. when the thermostat senses that the room temperature is above a predetermined value. the primary air pressure signal to inflatable bellows 25 is increased thereby increasing the degree of inflation of the bellows. Plate member 45 is rotated in a counter-clockwise direction as a result of the expansion of bellows 25. Link 28 is likewise rotated in a counter-clockwise direction about.  
 pivot point 46&#39;. Link 30 is thus moved towards the left as viewed in the Figure of the drawing; similarly link 31 moves to the left as viewed in the Figure.  
  The movement of link 31 to the left. moves the right edge of elongated slot 35 into contact with pin 34, thereby causing damper 27 to pivot in a clockwise direction about point 32. The damper thereby assumes the position illustrated in FIG. 3 to permit the secondary air induced into the unit to pass over heat exchange coil 19 in heat transfer relation with the relatively cold heat exchange medium flowing therethrough. to cool the secondary air prior to its mixing with the primary air for eventual discharge into the room or space being conditioned. When the unit is operating in the manner illustrated in FIG. 3, damper 26 is positioned so as to prevent any flow of secondary air across heat exchanger 20 having the relatively warm heat exchange medium flowing therethrough.  
 BYPASS MODE OF OPERATION As the temperature of the air in the room is reduced so as to reach the set point therefore. the thermostat senses such occurrence and bimetallic element 43 partially uncovers orifice 44 to thereby decrease the primary air pressure signal supplied to bellows 25; causing the bellows to partially deflate. Spring 46 provides a force on plate member 45 to cause the member to rotate in a clockwise direction as the bellows deflates. Similarly. link 28 also rotates in a clockwise direction thereby moving links 30 and 31 to the right as viewed in FIG. 4.  
  As link 31 moves to the right. elongated slot 36 moves relative to pin 37 of link 49 so that the pin comes into contact with the left-hand edge of the slot. However. spring 38 provides a force to maintain damper 26 in its blocking position relative to heat exchanger so secondary air flow over the heat exchanger is prevented.  
  As link 31 moves to the right as viewed in FIG. 4. elongated slot 35 moves therewith: however. the slot does not move relative to the pin 34. but rather. the pin moves along with the slot due to the forceproviding by spring 38. Such spring force causes damper 27 to pivot in a counter-clockwise direction about point 32 so the damper moves into a blocking position relative to heat exchanger 19. thereby preventing any flow of induced air thereover.  
  When the dampers are positioned in the manner illus trated in FIG. 4. air induced into the unit via the discharge of primary air flows through a second flow path 47 essentially bypassing both heat exchangers.  
 HEATING MODE OPERATION Referring now to FIG. 5. the unit is illustrated as operating in a heating mode. As the temperature of the room falls below the present onset point level. bimetallic element 43 operates to completely open orifice 44. to bleed substantially the entire primary air pressure signal from bellows to thereby deflate same. Spring 46 supplies a force to rotate plate member 45 in a clockwise direction about point 46&#39;. Link 28 similarly is rotated in a clockwise direction. The movement of link 28 in a further clockwise path causes links 30 and 31 to move further to the right as viewed in FIG. 5.  
  Such movement creates a force at the contact point between pin 37 and elongated slot 36 to overcome the force of spring 38 to cause damper 26 to rotate in a counter-clockwise direction about point 33. Although elongated slot moves relative to pin 34, no further movement of damper 27 is obtained. since the damper is already in abutting or blocking relationship relative to heat exchanger 19.  
  The secondary air induced into the unit thus flows through a third flow path. as defined by heat exchanger 20. since damper 26 has moved from its blocking position relative to such heat exchanger. The induced secondary air will continue to flow over the heat exchanger in heat transfer relation with the relatively warm heat exchange medium passing therethrough until the desired room temperature is obtained. When such room temperature is obtained. the bellows will inflate in the manner described so as to place the unit in its bypass mode as illustrated in FIG. 4.  
  The induction unit in accordance with the present invention can be satisfactorily employed in a four-pipe air conditioning system without requiring costly and complex controls as heretofore required in order to direct the air through the desired flow path to obtain satisfactory temperature conditions within the space being conditioned.  
  While a preferred embodiment of the invention has been described and illustrated. the invention should not be limited thereto. but may be otherwise embodied within the scope of the following claims.  
 I claim:  
 1. A control for determining the flow path of air induced from a space into a mixing chamber of an air conditioning unit by the discharge of primary air within the casing of said unit and having a first heat exchanger connected to a source of a relatively cold heat exchange medium and interposed in a first flow path. a second heat exchange medium and interposed in a first flow path. a second heat exchanger connected to a source of a relatively warm heat exchange medium and interposed in a second flow path and a third flow path bypassing said first and second flow paths. said control comprising:  
 a. an inflatable bellows connected to said source of primary air;  
 b. thermostatic means for sensing the temperature of said space being conditioned for regulating the pressure of said primary air in said inflatable bellows; and  
 c. damper means operatively connected to said inflatable bellows for directing the induced air through one of said flow paths; said damper means including link means connected to said inflatable bellows and first and second dampers pivotally connected to said link means. said first damper being movable relative to said first heat exchanger to selectively open or close the flow path including said first heat exchanger. said second damper being movable relative to said second heat exchanger to selectively open or close the flow path including said second heat exchanger. said first and second dampers in combination operating to selectively open or close said third flow path; said link means including a first link having a pair of elongated slots. said first and second dampers having pins disposed in said slots; as pressure in said bellows increases in response to sensed changes in the temperature in said space. a selected one of said flow path is opened and said other two flow paths are closed. as the pressure in said bellows decreases. at selected second of said flow paths is opened and said other two flow paths are closed. and as the pressure in said bellows further decreases. a selected third of said flow paths is opened and said other two flow paths are closed. to thereby continuously regulate the temperature of air discharged from said unit into said space to maintain the temperature of the air in said space&#39;at a desired level.  
  2. A control in accordance with claim 1 wherein said damper means further includes a plate member operatively connected to said inflatable bellows. spring means supplying a force acting on said plate members in opposition to the force supplied by said inflatable bellows.  
  3. A control in accordance with claim 2 wherein a tension spring is connected at one end to said first damper and is connected at its other end to said second damper.  
  4. A control in accordance with claim I wherein a tension spring is connected at one end to said first damper and is connected at its other end to said second damper.