Air conditioning apparatus

Abstract

Air conditioning apparatus ventilates room air with environmental air after the environmental air has been filtered, heated and humidified to appropriate levels. Environmental air is drawn into an intake duct, is passed successively through an air filter, an electric filament heater and is humidified by directing the air stream through a moving evaporator belt which is saturated with water from a water tank which is automatically controlled by a humidistat. The humidity level and temperature are automatically maintained by means of the humidistat and air temperature sensor.

Description

The present invention relates to room air conditioning apparatus and in particular to air conditioning apparatus operative to automatically render and maintain room air temperature at preselected temperature and humidity levels.

The equilibrium vapor pressure of any substance increases more and more rapidly as the temperature thereof is increased. The equilibrium vapor pressure of water ranges from 0.1 mm of mercury at -40.degree.C (i.e., over ice) to about 55 mm of mercury at 40.degree.C. The pressure of water vapor in the air, however, is usually less than the equilibrium value, the existing vapor pressure usually being described by the relative humidity, i.e., the fraction it forms with the equilibrium value at the existing temperature. Thus, in a cold climate, air that is saturated or less than saturated at, for example, 15.degree.F is brought indoors and heated to 75.degree.F, whereupon without change in its actual moisture content, its relative humidity becomes extremely low. Such low humidity is hard on the respiratory passages of the human body, particularly when they double as speech organs, so that it is important to add moisture to heated room air in the wintertime.

It is therefore an object of the present invention to provide an air conditioner operative to automatically ventilate, heat and humidify room air with environmental air to maintain the room air at preselected temperature and relative humidity levels.

It is a further object of the present invention to provide an air conditioner of the character just described, which is compact, economical to manufacture and adaptable for easy installation in a double-hung window.

In accordance with the present invention there is provided an air conditioning apparatus comprising a housing including an air inlet duct, a humidifier chamber, blower means and an air discharge duct. The air inlet duct has an air inlet part for communication with the ambient atmosphere and an outlet opening communicating with the humidifier chamber. An air filter for trapping dirt particles from the ambient atmosphere is fixedly positioned in the air inlet duct downstream from the air inlet port and an electric air heater is fixedly positioned in the air inlet duct downstream from the air filter. Disposed within the humidifier chamber is a tank containing liquid and an endless liquid-transport belt rotatably mounted on a pair of vertically spaced rollers for rotating the belt with flat face thereof parallel to the inlet duct outlet opening. The endless belt has an upper portion facing the inlet opening and a lower portion immersed in the liquid in the tank.

Electric motor means are connected to at least one of the rollers to rotatably transport the endless belt successively into immersion with the liquid and past the inlet duct outlet opinion to impart moisture to the air stream exiting through the inlet duct outlet opening. Blower means are located downstream of the humidifying chamber for drawing ambient air through the air inlet duct and through the liquid transport belt. An air discharge duct is located downstream of the blower means. Air temperature sensing means and humidity sensing means are located in the discharge duct for detecting the temperature and humidity of air passing through the discharge duct. Control means are operative in response to the air temperature sensing means and humidity sensing means for actuating and de-actuating the electric air heater and the electric motor means driving the rollers to maintain the temperature and humidity of the air stream in the discharge duct respectively at preselected levels.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a pictorial representation of an air conditioning apparatus constructed in accordance with the principles of the present invention in a preferred embodiment thereof;

FIG. 2 is a sectional view of the apparatus of FIG. 1 taken along line 2--2;

FIG. 3 is a sectional view taken along the line 3--3;

FIG. 4 is a graph of relative humidity at which visible condensation will appear on the inside surface of a window pane at 70.degree.F room air temperature for various environmental air temperature; and

FIG. 5 is an electrical schematic diagram of the air temperature controller circuit of the present invention.

Referring in detail to the drawings, and in particular to FIG. 1 thereof, an air conditioning apparatus constructed in accordance with the principles of the present invention and for installation in the conventional double-hung window is designated by the numeral 10. Air conditioner 10 comprises an air inlet duct 12 rectangular in cross section having a downwardly-open throat portion 14 at the forward end thereof for communication with the environmental air outside of the house. An air filter 16 is slidably retained in a pair of vertical slots 18 and 20 fixedly mounted in sidewalls 22 and 24 of duct 12. Air filter 16 comprises a thin rectangular frame 26 enclosing air filter material such as industrial urethane open cell foam 28. A thin rectangular aperture 29 extends transversely across the width of duct top wall 30 to receive air filter 16 and to allow filter 16 to be slidably received downwardly in filter slots 18 and 20 whereupon the bottom edge of filter frame 26 comes to rest upon duct bottom wall 32. A slot cover 34 forms a substantially air-tight seal over aperture 29 once air filter 16 has been inserted into duct 12.

An electric filament heater unit 36 is fixedly mounted between duct top and bottom walls 30 and 32, spaced slightly behind air filter 16. Heater unit 36 comprises a pair of epoxy glass heater frames 33, 35 mounted back-to-back in an aluminum frame 37. Each of epoxy glass frames 33, 35 is divided into three openings to form three sections 33a, 33b, 33c, 35a, 35b, 35c. Approximately 10 feet of 0.010 inch diameter nichrome heater wire 38 having a resistance of about 6.66 ohms/ft is strung across the frame openings on metal standoffs located along the epoxy glass heater frames 33, 35 to form three heater screens 38a, 38b, 38c of fairly small mesh interposed across the air flow path, to form a total resistive load of 11 ohms.

Air inlet duct 12 opens into a humdifying chamber 46 bounded by sidewalls 48 and 50 extending from duct sidewalls 22 and 24 respectively. A water tank 52 in the form of a box-like housing 54 extends below humidifying chamber 46 is partially filled with water 56 and is provided with a water level gauge 55. Water tank housing 54 comprises front and rear walls 58, 60, bottom wall 62 and sidewalls 64 and 66. An endless evaporator belt 68 is mounted on top and bottom rollers 70, 72 which are horizontally mounted in a separate frame 21 located in humidifier chamber 46, with top roller 70 mounted across the upper ends of the frame sidewalls 21a and 21b and bottom roller 72 mounted across the lower ends thereof which is immersed in the water 56. The provision of a separate belt frame 21 permits the removal thereof from humidifier chamber 46 for cleaning or replacement. A suitable material for belt 68 may be that known as industrial urethane open cell foam material similar to air filter material 28 but of larger void area.

Water tank housing 54 is closed at its upper end by means of a top wall 74 which defines a belt opening 76 between the free edge thereof and the rear end of duct bottom wall 32.

An electrical air blower 88 which comprises a centrifugal fan 89 with tangential blades 90 is mounted in blower housing 86 which includes a scroll-shaped duct wall 92 tangentially fixed to tank top wall 74 and blower housing front wall 84. Blower housing 86 at its front end opens into humidifier chamber 46 and into discharge duct 82 at its upper end.

Discharge duct 82 is pivotally mounted to front wall 84 of blower housing 86 by means of hinges 101 whereby discharge duct 82 can be pivoted to the open position depicted by phantom outline 103 to permit access to the interior thereof and blower housing 86. A baffle 99 is provided to direct the air flow produced by blower 88 into discharge duct 82.

Humidifier chamber 46 is bounded at its top end by the underside of discharge duct wall 78 and by front wall 80 which includes a shoulder portion 80a for supporting duct wall 78. Duct wall 78 terminates at its lower end in an angle portion 49 which rests on and overhangs the top edge of blower housing wall 51.

An air temperature sensor 87 in the form of a thermistor is located in discharge duct 82 just below grilled air discharge outlet 96. A control panel 90 provided with control buttons and dials for setting the desired air quality characteristics is secured to front wall 93 of discharge duct 82. Thus, dial 92 sets the humidity level, dial 94 sets the speed of evaporator belt 68, buttons 95 control air inlet shutter assembly 85 which controls the movment of air inlet port shutter 15 via cable linkage 109, dial 98 sets the desired air temperature at discharge outlet 96 and indicator light 97 indicating whether evaporator belt 68 is moving or has stopped. The electronic sensing and control circuitry for accomplishing the functions controlled by dials 92, 94, 98 are located in a rectangular housing 100 which is secured to the inside of duct front wall 93.

In operation, unit 10 is installed in a room window by resting the underside of inlet duct 12, i.e., bottom wall 32, on the window sash (not shown) and allowing water tank housing 54 to overhang the window sill along the wall adjacent to the window. Bottom wall 32 is provided with a shoulder 17 to clear the storm window frame (not shown) which is commonly found in windows. When electrical power is applied to blower 88, a negative air pressure, i.e., suction pressure, is created in inlet duct 12, and humidifying chamber 46, i.e., upstream from blower 88, thereby drawing environmental air into air inlet port 13. Air inlet duct 12 is provided with air inlet port shutter 15 to control the flow of environmental air into inlet duct 12, and which as mentioned above is opened and closed manually by means of a cable linkage 85.

The air flow, whose path is indicated by dashed line 19, continues from the mouth of inlet port 13 through duct 12 and through air filter 16 where the air filtration process takes place, namely the removal of relatively small particles of dirt and dust from the air. The smaller the size of the open cells in the air filter foam material 28, the better the filtration capabilities of filter 16. The smallness of the size of the foam material open cells will be limited by the air moving capabilities of blower 88, i.e., its ability to overcome the air flow impedance path through air filter foam material 28.

The location of air filter 16 upstream from heater unit 36 and humidifier chamber 46 is significant in that air borne dust or dirt particles are thereby removed from the air stream before the air reaches the heating elements of heater unit 36 and evaporator belt 68. Otherwise, air-borne dirt particles in the air stream would tend to foul the heating elements 38 and would also cause the creation of unpleasant odors in addition to increasing the resistance of the heat transfer path from heating elements 38 to the air stream. Because the air filter material 28 comprises open cell foam material it can be easily cleaned by using an ordinary household portable vacuum cleaner after removing filter 16 from air inlet duct 12, without disturbing the installation of unit 10.

After passing through air filter 16, the air flow continues through heater unit 36 which is operative to raise the temperature of the air passing therethrough as measured by air temperature sensor 87 to a temperature corresponding to the setting of air temperature dial 98. The air stream then passes through evaporator belt 68 which is saturated with water that has been picked up as belt 68 passes through the water 56 in water tank 52.

The elements of air conditioner 10 which accomplish the air heating and temperature control of the air stream are respectively heater unit 36 and the proportional controller which includes air temperature sensing thermistor 87. The proportional controller may advantageously constitute a "phase voltage firing" controller 83 which is operative to maintain a relatively fixed discharged air temperature at discharge outlet 82 within the temperature range available at temperature control dial 98, typically 60.degree.F - 75.degree.F, regardless of changes in either the environmental air temperature or the flow rate of the air stream. Thus, by way of example, for a fixed air flow rate of 30 - 40 CFM, the proportional controller can maintain a discharge air temperature of 70.degree.F for environmental air temperatures ranging from 70.degree.F - -20.degree.F. It is appreciated that instead of the "phase voltage firing" controller just described, a "zero voltage firing" proportional controller may be utilized, which although not capable of maintaining the discharge air temperature as precisely as the "phase voltage firing" controller, may nevertheless be desirable where radio frequency interference may be a serious problem.

Continuous air humidification sensing and control for the air flow in humidifier chamber 46 is accomplished in the following manner. Humidification sensing of the air stream in discharge duct 82 may be accomplished by using materials which exhibit a change in some parameter thereof which has a known relationship with the relative humidity level of the air stream. Such materials are of two kinds, firstly the dimensional type which are particularly suitable for on-off control of the parameter which governs the evaporation rate, and secondly, material which when coupled with a displacement transducer which produces a continuous electrical output for the continuous control of the evaporation rate parameter, i.e., the relative humidity level. The latter electrical parameter change type materials are best suited for the continuous or proportional type control of the relative humidity control parameter, in which case, signal converters are ordinarily required to convert the output of the humidification sensor to an electrical signal suitable for control purposes.

The nylon tape in humidistat 81 expands and contracts in response to an increase and decrease respectively in the humidity of the air passing therethrough. The expansion and contraction of the nylon tape is operative in response to a particular humidity setting of humidistat control dial 92, to actuate the on-off switch (not shown) which supplies electrical power to evaporator belt drive motor 69.

The principles of the present invention described herein are based upon the use of an on-off humidity sensing and control system. Thus, an on-off type of humidistat 81 which comprises a humidity sensor 79 of nylon tape may be employed to control the amount of moisture to be imparted to the air stream in humidifier chamber 46 in conjunction with a graph showing maximum allowable relative humidity vs. environmental air temperature such as the graph shown in FIG. 4 to determine the maximum allowable relative humidity for the air discharged from discharge outlet 96. A suitable humidistat 81 for such purpose is the Humidity Controller Type 46B1192-2 sold by Honeywell, Inc.

The operating procedure of unit 10 will now be described for the case of overnight use. The user, having determined the approximate overnight low of the environmental air temperature, examines the maximum allowable relative humidity reading from the above-mentioned graph of maximum allowable relative humdity vs. environmental temperature curve. He then sets humidistat control dial 92 to the relative humidity level corresponding to the environmental air temperature and sets belt speed control dial 94 to its maximum setting. Power to unit 10 is them provided by actuating unit on-off switch 57 and belt drive on-off indicator light 97 is observed. If indicator light 97 remains continuously on, this would be an indication that the humidification process is operating at its maximum capacity and that the relative humidity of the discharge air is not greater than that set by humidistat control dial 92. If, however, indicator light 97 lights up intermittently, this would indicate that the relative humidity of the discharge air is greater than the relative humidity setting of humidistat control dial 92, calling for manual correction by reducing the speed of evaporation belt 68 by adjusting dial 94 in successive small steps until belt drive indicator light 97 remains continuously on, indicating that the discharge air relative humidity has not exceeded the setting of humidistat control dial 92.

Referring to FIG. 5 the air temperature controller circuit for controlling the temperature of air flow in discharge duct 82 is shown in schematic form. The three heater screens 38a, 38b and 38c appear as six resistive elements 38a.sub.1, 38a.sub.2, 38b.sub.1, 38b.sub.2, 38c.sub.1 and 38c.sub.3 connected in parallel with a total resistive load of 11 ohms. This resistive circuit 38 is connected at one end to one electrode 104 a Triac 102 which has another electrode 106 thereof jointly connected to zero-crossing Triac drive circuit terminals 4 and 5 and a gate electrode 108 connected to terminal 7 of Triac driver circuit 83. Thermistor 87 comprises one leg of a bridge circuit including resistors, 110, 112, 114, 116 and 118 whereby the junction of thermistor 87 and resistor 110 is connected to terminal 2 of Triac driver circuit 83, the junction of resistors 112 and 116 is connected to terminal 1, and the junction of resistors 114 and 118 is connected to terminal 3 of Triac driver circuit 83. Additionally a capacitor 120 is connected across resistor 110 and thermistor 87, a capacitor 122 is connected across terminals 6 and 8 of Triac driver circuit 83 and resistor 124 is connected between terminal 6 of Triac driver circuit 83 and the other end of resistive heater circuit 38. The air temperature controller circuit of FIG. 5 is connected to a standard 120 volts A.C. power source 130 by leads 126 and 128 which are respectively connected to terminals 4 and 5 of Triac driver circuit 83 and the other end of heater circuit 38.

In operation, Triac driver circuit 83 is operative to compare the voltage produced across thermistor 87 corresponding to the measured air temperature with a preselected voltage corresponding to the desired air temperature as determined by air temperature control dial 98. If the thermistor voltage is less than the reference voltage, a control voltage signal is produced at Triac driver circuit terminal 7 which is applied to gating electrode 108 of Triac 102 causing Triac 102 to fire and thereby connect heater circuit 38 to power source 130 to cause heater 38 to heat the air stream in discharge duct 82. The resultant increase in the temperature of the air flow is discharge duct 82 is reflected in a corresponding increase in the voltage across thermistor 83 and when the air temperature increases to above the preselected level the voltage signal terminal 7 of Triac driver circuit 83 ceases and Triac 102 presents an open circuit across its electrodes 104 and 106 thereby deenergizing heater circuit 38.

In addition to using unit 10 on a continuous basis as just described, unit 10 may be employed for short periods of time in a conventional humidifier mode for the purpose of raising the relative humidity level of the room air just prior to ventilating, by making slight modifications (not shown) in the design of unit 10. For such operation, a second inlet port would be provided just upstream of air filter 16 as well as a two-speed motor (not shown) for driving blower 88. In this mode of operation, humidistat dial 92 and evaporator belt dial 94 are set to their maximum settings respectively. Air inlet port 14 is closed while the above-mentioned second inlet port (not shown) is opened and blower 88 is turned on to its high speed operation.

Although the invention has been described with reference to particular embodiments thereof, it is to be understood that such embodiments are merely illustrative of the application of the principles of the invention. Numerous modifications may be made therein and other arrangements may be devised without departing from the spirit and scope of the invention.

Claims

1. Air conditioning apparatus comprising a housing including an air inlet duct, a humidifier chamber, an air discharge duct and enclosing blower means for drawing air through said air inlet duct, said humidifier chamber and said air discharge duct, said air inlet duct having an air inlet port for communication with the ambient air and an outlet opening communicating with said humidifier chamber, an air filter for trapping dirt particles present in the ambient air fixedly positioned in said air inlet duct downstream from said air inlet port, an electric air heater fixedly positioned in said air inlet duct downstream from said air filter, a tank containing liquid disposed within said humidifier chamber, an endless liquid-transport belt rotatably mounted on a pair of vertically spaced rollers for rotating said belt with the flat face thereof parallel to said inlet duct opening, said endless belt having an upper portion thereof facing said inlet duct outlet opening and having a lower portion thereof immersed in said liquid, electric motor means connected to at least one of said rollers whereby said motor means when actuated drives said rollers to rotatably transport said endless belt successively into immersion in said liquid and past said inlet duct outlet opening to impart moisture to the air stream exiting through said inlet duct outlet opening, blower means located downstream of said humidifying chamber for drawing ambient air through said air inlet duct and through said liquid-transport belt, an air discharge duct located downstream of said blower means, air temperature sensing means and humidity sensing means located in said air discharge duct for detecting the temperature and humidity of air passing through said discharge duct, control means operative in response to said air temperature sensing means and humidity sensing means for actuating and de-actuating said electric air heater and said electric motor means driving said rollers to maintain the temperature and humidity of the air stream in said discharge duct respectively at preselected levels, a shutter pivotally mounted in said air inlet port for opening and closing said air inlet port, shutter control means on the front face of said housing and a cable linkage connecting said shutter to said shutter control means whereby actuation of said shutter control means is operative

2. Apparatus as defined in claim 1 wherein said liquid-transport belt

3. Apparatus as defined in claim 1 wherein said blower means comprises a tangential blower having its intake communicating with said humidifying

4. Apparatus as defined in claim 1 wherein said air temperature sensing

5. Apparatus as defined in claim 4 wherein said humidity sensing means

6. Apparatus as defined in claim 4 wherein said control means comprises a resistor bridge circuit including said thermistor, gating means having one of its main electrodes connected to said electric heater and another of its main electrodes adaptable for connection to an A.C. power source, and a gating means driver circuit having its input connected to said resistor bridge circuit and to the other of said gating means main electrodes, said driver circuit having its output connected to the gate electrode of said

7. Apparatus as defined in claim 6 wherein said gating means comprises a triac.