US3047209A - Air flow control systems - Google Patents

Description

puff-vu `luly 31, 1962 Filed Aug. 13, 1959 M. w. PATRICK 3,047,209

AIR FLOW CONTROL SYSTEMS 2 Sheets-Sheet 1 BY Qf/f ATTORNEY` July 31, 1962 M. w. PATRICK 3,047,209

AIR FLOW CONTROL SYSTEMS Filed Aug. 13, 1959 2 Sheets-Sheet 2 5T- O 46 I A 5K 66 l| 64 ll l I I M68 46! 1'| I I In v T b rllllllllllllllllllllll INVENTOR /lf/MM/ /f/Irf/af BY Wwf@ ATTORNEY` This invention relates to air ow control systems and more particularly to systems for controlling the amount of air delivered by the blower in a forced air domestic heating and cooling system.

One of the diiculties encountered in the operation of forced hot air systems is the tendency of the system t deliver substantial volumes of relatively cold air to the space to be heated, particularly at the start of the blower cycle. Under such conditions the cold ail within the duct system and the plenum chamber is forced into the room of the dwelling thus causing cold drafts and often lowering the temperature of the room. Also in the interests of efficiency and to prevent overheating the furnace room, the blower should not be stopped immediately upon the cessation of operation of the burner. Under these conditions a similar although not so severe effect is. produced since in most systems the air continues to be delivered at full volume despite a substantial drop in its temperature.

In recognition of these difliculties, it has been proposed to modulate the flow of air to reduce the volume of air delivered by the blower when the blower is started and as it continues to deliver cooler air after the burner is shut of. One such proposal is described and claimed in United States Patent Re. 24,421. However it has been found that this unit tends to lag the system with the result that the volume of air is unduly restricted during the starting cycle and excessive air is permitted to flow while the blower continues to run after the burner has been shut off. Also, transient conditions may result in partial flow restriction even when the burner and blower have been operating at normal temperature for some time.

It is accordingly the principal purpose and object of the present invention to provide improved systems for controlling the volume of air delivered by a blower associated with a forced air heating system which effectively prevents the delivery of objectionable amounts of -cold air into the room to be heated under all operating conditions.

It is also an object of the present invention to provide improved control systems for blowers which assure the delivery of the full rated capacity of the blower at all times when the blower is operating normally and delivering air at a temperature above a preselected minimum temperature or during the cooling cycle.

It is .a further object of the present invention to provide improved control systems for blowers which are positive and reliable in operation, which are of relatively simple construction and which may be installed readily in existing systems as well as in new equipment.

It is an additional object of the invention to provide improved systems and apparatus for controlling the output of a blower associated with. a combined forced air heating and cooling unit which functions effectively during both the heating and cooling cycles without the attention of the operator.

In accomplishing these and' other objects there is provided a temperature sensitive element for positioning an air flow control vane in the discharge throat of a blower, a heater element to modulate the action of the temperature sensitive element and` a novel control circuit for regulating the operation of the heater element .automatically during the heating and cooling cycles, these. ele- -nited States VParana ice ments cooperating to produce an overall system efficiency not heretofore obtainable.

Additional objects and advantages of the present invention will become apparent as the description proceeds in connection with the accompanying drawings in which:

FIGURE l is a side elevation of a blower incorporattrical circuit forming a part of the present invention;

FIGURES 4 and 5 are enlarged fragmentary elevations of the apparatus shown in FIGURES l and 2, respectively;

FGURE 6 is a fragmentary elevation of the heater element forming a part of the present invention; and y FIGURE 7 is a fragmentary section taken along line '7 7 of FIGURE 6.

Referringnow more particularly to the drawings, the blower assembly indicated generally at 20 is of theV centrifugal type and is provided with a rotor 22 which draws air in through inlet openings 24 in the side walls 26 and 23 of the blower housing and discharges it through the' throat 3d.

In .accordance with conventional practice, the blower assembly 20 will be mounted in the fan compartment of a furnace with the inlet openings 2d connected to the cold air return ducts and the discharge throat 30 directing air over `the heat exchanger and thence through supply ducts to the rooms or other spaces to be heated. Since this arrangement is entirely conventional, the furnace heat exchanger, plenum chamber and associated ducts have been omitted. However for further details of a typical installation, reference may be had lto Reissue Patent 24,421 issued January 28, 1958, for Blower Discharge Volume Control.

When the system is adapted for cooling, the evaporator coils will be placed in the furnace plenum chamber in accordance with conventional practice.

The blower rotor 22 is `driven at a constant speed by an electric motor 32, preferably by a belt drive 34. The output of the blower is controlled by a restrictor vane assembly indicated generally at 36 which is preferably of the same construction as that shown in aforesaid Reissue Patent 124,421. The restrictor vane 36 is non-rotatably secured to a pivot shaft 38 rotatably mounted in the opposite side walls 26 and 28 of the blower housing. One end of the Vane pivot shaft 38 projects outwardly beyond the blower side wall 26 into a box-like housing 40 detachably secured to the side wall 26. Adjustably secured by bolts 42 to a side wall 44 of the housing lil is one end of a coiled bi-metallic spring 46. The flattened opposite end 43 of the spring 46 extends through a slot in the pro-` jecting portion of the Vane pivot shaft 38. The vbi-metallic spring 46 is so arranged that when it is heated it is effective to move the vane 36 in a counterclockwise direction as viewed in FIGURE 4 to dispose the vane in the position shown in FIGURE 4 where it permits substantially unrestricted flow of air through the discharge'throat 3i) of the blower. When the spring 46 is cooled, it is effective to move the vane in the opposite direction to the position shown in FIGURE l, its movement in this direction being limited by. contact of an adjustable stop member Sil with the blower housing.

As more fully explained in the aforesaid Reissue Patent 24,421, the vane assembly 36, because of its position in the discharge throat 30 of the blower, is capable of reducing the output of the blower to a fraction of thefull blower capacity.

A strip heater assembly indicated generally at l52 is disposed in close surface contact with substantially theentire length of the bi-metallic spring 46. As shown in FIGURES 6 and 7, the strip heater assembly ocmprises a length of wire 54 such as Chromel-A resistance wire encased in a wrapping of berglass tape 56. The ends of the envelope formed by the tape 56 are closed and reinforced by a fiberglass wrapping 58. The fiberglass tape 56 is preferably provided with a silicon thermo-setting adhesive to permit its rapid, easy and permanent attachment to the surface of the bi-metallic spring 46.

Mounted on the side Wall 6l) of the casing member 40 is a micro-switch 62 which is normally closed and is opened when an actuating button 64 on its upper surface is slightly depressed. A switch actuator 66 is non-rotatably secured to the projecting portion of the vane pivot arm 33 and is provided with an arm 68 which is operative to depress lthe switch button 64 when the restrictor vane 36 is in its fully open position as shown in FIGURE 4.

The energization of the strip heater asembly 52 is controlled by `the circuit which is shown in simplified form in FIGURE 3, to which detailed reference will now be be made. The blower motor 32 is connected to 1'10 v. leads 70 and 72 through a conventional thermostatic switch 74. In accordance with conventional practice, the switch 74 is mounted on the furnace plenum chamber and is set to close when the temperature of the air in the plenum chamber rises to a predetermined value, for example 110" to 120 F. The burner control apparatus indicated generally at 76 is connected to 24 v. circuit leads 78 and 80 through a two-way thermostatic switch 82 mounted in the space served by the furnace. Thus, when the temperature of the room or other space to be heated falls below a pre-set level, the switch 82 closes, starting the burner which, after a relatively short period of time, raises the temperature in the furnace plenum chamber to a level which closes the thermostatic switch 74 and the blower begins to operate.

When the blower first begins to operate, the air in the duct system between the furnace and the space to be heated is cold. If this air is forced rapidly into the room, it produces unpleasant cold drafts. It is for this reason that the restrictor vane 36 occupies its position of maximum flow restriction when the blower begins tol operate. The rate at which the cold air is forced into the room is greatly reduced and the objectionable drafts are substantially eliminated. However it is also important to remove the restriction from the throat of the blower as soon as possible to permit delivery of the full rated capacity of the blower as soon as the cold air is exhausted from the duct system and it is for this purpose that the unique combination of the bi-metallic strip 46, the strip heater 52 and the associated control is provided.

With continuing reference to FIGURE 3, the strip heater 52 is controlled by the thermostatic switch 74, the micro-switch 62, and a normally open relay switch 84 which is closed whenever the burner circuit is actauted upon closure of the thermostatic switch S2. Since switch 62 is normally closed, the strip heater 52 will be energized immediately when the thermostatic switch 74 closes after the burner has begun to operate. Accordingly when the blower begins to operate, the strip heater 52 is energized and the ibimetal strip 46 immediately begins to move the vane 36 from its initial full restricting position thus gradually increasing the air flow delivered by the blower. This air ow change is gradual and thus the air temperature at the room diffusers is held relativelyconstant while the discharge velocity increases. When the room thermostat 82 is satisfied, the burner control 76 s de-energized and the relay contacts 84 are allowed to open thus deenergizing the strip heater 52.

However the blower 32 continues to run as long as the thermostatic switch 74 is closed, that is as long as the temperature in the plenum chamber is above the off setting. During this time the bi-metallic strip 46 cools and gradually closes the vane 36 and 4thus modulates the air flow from a maximum at the end of the `furnace cycle to a minimum at the end of the blower cycle.

When the system is adapted for cooling as well as heating the compressor motor 86 is switched on and oi by a normally open relay 88 in a 220 v. circuit 90. A second normally open relay 92 having contacts 93 and 94 in the circuit for the heater 52 and the blower motor 32, respectively, in connected in parallel with relay 84 and switch 74, respectively. Thus when thermostat 82 is closed in the cool position, the compressor motor 86, the strip heater 52 and the blower motor 32 will be energized simultaneously.

When either the combustion device or the compressor is operating, .the strip heater `52 is supplied with pulses of power just sufficient to maintain it in the full open position. This is accomplished by the use of the switch actuator 68 which in the full open position of the vane depresses the button 64 in the microswitch 62 thus opening the switch, momentarily breaking the circuit to the strip heater. The slight cooling of the bi-metal spring 46 retracts the actuator 63 slightly thus permitting the microswitch 62 to close and again applying power to the strip heater 52 thus maintaining the bi-metallic strip in relatively the same position and without an excessive amount of stored heat. Thus both the danger of overheating of the bi-metallic strip and waste of an excessive amount of power is avoided by the provision and utiliza-tion of the switch 62.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come wtihin the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters IPatent is:

l. Apparatus for regulating the output of a forced hot air heating system comprising a blower for delivering warm air to the space to be heated, a vane pivotally mounted in the discharge throat of said blower for movement betwen a flow restricting position and a non-restircting position, a bi-metallic coil spring having one end rigid with said blower and the other end operably connected to said vane and arranged to move said vane toward said non-restricting position when said spring is heated and to move said vane to said restricting position when said spring is cooled, a heater element for selectively heating said spring, and means for energizing said heater element when said blower is initially energized.

2. The combination according to claim l wherein said heater element comprises a strip heater in close surface contact with said bi-metallic spring.

3. Apparatus for regulating the output of a forced hot air heating system comprising a blower for delivering warm air to the space to be heated, a vane pivotally mounted in the discharge throat of said blower for movement between a flow restricting position and a non-restricting position., a temperature sensitive element operably connected to said vane and arranged to move said vane toward said non-restricting position when said element is heated and to move said vane to said ow restricting position when said element is cooled, a heater element for selectively heating said temperature sensitive element, means for energizing said heater element when said blower is initially energized, and means to temporarily de-energize said heater element when said vane reaches said nonrestricting position.

4. Apparatus for regulating the output of a forced hot air heating system comprising a blower for delivering air to the space to be heated, a vane pivotally mounted in the discharge throat -of said blower for movement between a flow restricting position and a non-restricting position, a temperature sensitive element operably connected to said vane and arranged to move said vane toward said non-restricting position when said element is heated and to move said vane to said flow restricting position when said element is cooled, a heater element for selectively heating said temperature sensitive element, an electrical circuit for energizing said heater element when said blower is initially energized, a normally closed switch in said electrical circuit, and means responsive to movement of said vane to said non-restricting position to open said switch and temporarily cle-energize said heater.

5. Apparatus for regulating the output of a forced hot air heating system comprising a blower for delivering =air to the space to be heated, a vane pivotally mounted in the discharge throat of said blower for movement between a How restricting position and a non-restricting position, a coiled bi-metallic spring having one end rigid with the blower and the Iopposite end operably connected to said vane and arranged to move said vane toward said nonrestricting position when said element is heated and to move said vane toward said ow restricting position when said element is cooled, a strip heater coi-led in close surface contact with at least a portion of said loi-metallic spring, an electrical circuit `for selectively energizing said strip heater, a normally closed switch in said circuit and a switch operator carried by said vane and operable to open said switch to temporarily de-energize said heater when said vane reaches said non-restricted position.

6. Apparatus for regulating the output of a forced air system for heating or cooling a space comprising a blower for delivering air to said space, a vane pivotally mounted in the discharge throat of said -blower for movement be-v i tween a ilow restricting position and a non-restricting i position when said element is cooled, a heater element for selectively heating said temperature sensitive element, `and means for energizing said heater element when said blower is initially energized.

References Cited in the tile of this patent UNITED STATES PATENTS Re.24,421 Patrick Jan. 28, 1958 2,292,082 Miller Aug. 4, 1942 v2,385,096 zMcCollum Sept. 18,1945 2,413,150 McReynolds Dec. 24, 1946 2,428,751 Foulds Oct. 7, 1947 2,537,121 Copping Ian. 9, 1951 2,686,661 Gillick et al Aug. 17, 1954 2,693,914 v Payne Nov. 9, 1954 2,721,704 Patrick 06h25, 1955 2,751,152 Ellenberlger June 19, 1956 2,769,312 Harrold et al Nov. 6, 1956 2,793,811 Caselman May '28, 1957 2,865,610 Sparrow Dec. 23, 1958 2,905,790 Markham Sept. 22, 1959

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