US2972475A

US2972475A - Air intake apparatus

Info

Publication number: US2972475A
Application number: US754340A
Authority: US
Inventors: Homer K Monroe
Original assignee: AEROVENT FAN CO Inc
Current assignee: AEROVENT FAN CO Inc
Priority date: 1958-08-11
Filing date: 1958-08-11
Publication date: 1961-02-21
Anticipated expiration: 1978-02-21

Description

Feb. 21, 1961 H. K. MONROE 2,972,475

AIR INTAKE APPARATUS Filed Aug. 11, 1958 I HOMER K- MONROE 33 BY ATTORNEYS United States Patent AIR INTAKE APPARATUS Homer K. Monroe, Piqua, Ohio, assignor to Aerovent Fan Co., Inc., Piqua, Ohio, a corporation of Ohio Filed Aug. 11, 1958, Ser. No. 754,340

4 Claims. (Cl. 26319) This invention relates to improvements in air preheater and more specifically to improvements in air makeup apparatus for use in building structures employing exhaust fans.

The utilization of exhaust fans to maintain the air within a building in adequate condition requires that there be a suitable supply of incoming air to take the place of the air exhausted. The operation of exhaust fans with an inadequate supply of incoming air results in a negative pressure situation within the building structure or in leakage from the outside air into the building, making heating difiicult. It is therefore desirable to supply to areas utilizing exhaust fans a suitable quantity of preheated air to maintain normal pressures within the building at a desired temperature.

This invention contemplates the provision of an improved air intake unit which is compact, has the major components thereof within a single housing, and is readily installed within a wall opening or the like of a building structure.

The invention particularly contemplates the provision of a gas fired, pre-heater air-intake unit in which the housing of the unit encloses the burner and air-gas premixer and which pre-mixer is suitably direct coupled to the burner, both the pre-mixer and the proportioning valve being within the airstream passing through the unit.

In the practice of a preferred embodiment of the invention a propeller type fan positioned Within an outlet of a housing draws air through an inlet of the housing and propels the air through the outlet. The air outlet communicates with the interior of a building, the air of which is to be maintained heated.

The housing in the usual arrangement is mounted on a wall of a building and the inlet to the housing is in direct communication with the outside atmosphere. The fan is driven by an electric motor over which the air drawn through the inlet passes and the fan and motor shaft are preferably directly connected without intermediate power transmission means. Between the fan and the air inlet a gas burner is positioned to heat the incoming air.

The gas burner is suitably complete in a peripheral sense, that is, itis formed as' an annulus and has a relatively large central opening. Suitably the gas burner is simply a conduit having a peripheral dimension such that it is 'somewhat less than the overall diameter of the propeller fan. To provide protection for the electric motor, when the motor is co-axial with the fan and burner, a shield in the form of a duct is extended from the motor through the central opening of the burner. This arrangement-serves not only to prevent hot air from contacting the motor, but in addition provides a flow of cool air through the duct to the motor.

A combustible gas-air mixture is supplied to the burne conduit from a pre-mixer having a centrifugal blower to propel the mixture under pressure throughout the burner conduit. j i

This pre-mixer in the arrangement of this invention is 2,972,475 Patented Feb. 21, 1961.

2. provided within the housing; in addition the pre-mixer is directly coupled to the burner. Usually it is necessary with such pre-mixers, to prevent burner backfire into the pre-mixer, to connect the outlet of the centrifugal blower to the burner conduit through gas diverting bafiles.

In the present arrangement the propeller fan action creates in the area forwardly of the burner a pressure, which is low relative to the gas pressure within the conduit; consequently there is no tendency, either on starting the burner, or in general operation, for a backfire to the blower to occur. Further the positioning of the pre-' mixer within the housing and the cooling of the premixer arrangement by air passing inwardly of the housing to the burner makes for compactness and economy of space.

The burner itself is in close proximity to the fan, but not so close that the fan heats unduly. With most applications the burner is toward the air inlet from the fan a distance of about one-half to a full fan diameter. Further the burner is of somewhat smaller periphery than the fan, that is, about to of the fan dimension. With this arrangement, and with the fan and burner co-axial, the fan tips are not heated to excess; that is, the hottest portion of the air passing through the burner is in contact'with the fan well inwardly of the fan tips. Under such conditions the central portion of the fan and the fan driving motor are relatively cool.

To operate such gas fired apparatusitis customary to initiate the burner action at a low firing rate; this is the condition under which backfiring may occur and is due to the tendency for a partial vacuum to buildup in the conduit connecting the pr'e-mixer to the burner. However, with the propeller fan of this invention pos1- tioned forwardly or on the air'outlet side of the burner, the fan tends to assist the flow of combustible gas from the pre-mixer to the burner and the tendency towards backfire is eliminated. A

The operation of the fan itself,lthe burner itself and the pre-mixer are conventional and customary controls are employed to govern system operation.

The improvements specifically contemplated by the invention include: (a) the positioning of the propeller fan on the air outlet side of the burner; (b) the mounting of the fan motor co-axial. with the fan and'burner and the protection of the motor from the heated air occasioned by the burner operation; (0) the provision of the" pre mixer within the housing and in direct connectionwith the burner; and'(d) the inclusion of a proportioning valve within the housing in conjunction with the premixer.

The invention will be more fully understood by reference to the following detailed description and accompanying drawing wherein:

Figure 1 is a perspective view, partially in section, and with parts broken away, illustrating the apparatus of invention positioned on a wall of a building;

Figure 2 is a fragmentary elevational view of a portion of the structure of Figure 1; and

Figure 3 is a schematic view illustrating an arrangement of some components of Figure l.

Referring to the drawing, the numeral 1 designates a housing in the form of a longitudinally extending casing which is mounted on a wall 3 of a building structure. The housing has an air inlet opening 5 communicating with the exterior of the building through the rearward portion of the housing indicated at 7. Forwardly in the housing at 9 there is provided a shutterin an air-outlet opening, which is arranged to be opened and closed. in order that when the unit of invention is not in operation cold air will not pass from the atmosphere into the building.

ments of the shutter in unison and a frame 13 bounds the shutter. Inwardly of the shutter and designated by the numeral 15 is a propeller type fan having a circumferentially extending shroud 17, g

The fan is mounted on a shaft -19 of an electric motor 21. Accordingly driving of the fan by the' motor 'dravis air from the air inlet to the outlet in which the shutter 9 is positioned. The motor21is provided .witha shield 23 in the form of a. duct which. extends .rearwardlyfrorn the fan towards the air inlet. This duct is effective to shield the motor from radiantheat.

An air-gaspre-mixer of the Centrifugal blower .type .is designated at 25 and driven by motor26 and isassociated with a proportioning valve a=rrangementl27 and .a modulating motor 29. i i

A gas-carrying conduit 31 is provided externally of the housing with a pilot solenoid valve 33, which itself communicates with a conduit 35. The numeral 39 designates a safety shutofi valve and a pressure gauge connection is indicated at 41. i

Through this arrangement gas may be supplied to the interior of the housing through the conduit portion 31 to mix with the air drawn in at .43. As will be .noted from Figures land 2 the outlet of the centrifugal blower arrangement is directly connected to an annular extension burner conduit 45 having burner outlets 46. The burner is closely positioned adjacent the flame ,rod 47 and supports a pilot 49 in housing 50.

Further, the burner, as may be readily noted from Figure ,l, is annular in form and is positioned toward the air inlet from the fan 15. Suitably the distance between the burner and fan is about one fan diameter, butshould be suflicient such that the fan does not become unduly heated. Further, the burner is slightly smaller in periphery than the fan itself, so that the heated .air passing over the burner strikes the fan inwardly of the fan blade tips. The .shield or duct23 over the motor extends rearwardly through the opening of the .annular burner, and ,accordingly receives'cool air drawn through the outlet 5, which air passes over the motor 21 and maintains the motor 21 cool. This direct connection to .the burner conduit, which is indicated at 51in Figures 1 and 2, ,isan important feature, for the arrangement provides for compactness and efliciency in the apparatus.

In this connection it is to be noted that customarily in the initial starting of the pre-mixer, the centrifugal action of the pre-mixer is such that the gas-air mixture tends to follow an upper course through the outlet conduitzof the pre-mixer as indicated in the zone A in Figure i Thus, in the .area belowthe zone A there tends to .be a vacuum pressure due ..to theflow .of gas through the zone A. Accordingly the .fiame .emanating from the burner opening '46 then normally tends to be drawn back into the conduit portion 51, resulting in a backfire.

In the present instance, however, due to the positioning the centrifugal fan forwardly of the burner, the pressure on the fan side of the burner openings would always be such that the flame and the gases of combustion which produce the flame would tend to-be drawn outwardly through the burner opening and not reversely into the conduit portion 51.

Referring .now to Figure 3, it will -be noted that the modulating motor 29 -is' in controlled relation with the air inlet through control rod 53. Further, the pilot 49 has an airinletatSS providing good air mixing with the gas passingto the pilot from the solenoid valve 33.

Also, as shown .in Figure-3', there is provided at 57 a.valve.fitting and at 59 apressure regulator, a main gas cock being indicated at 61. {The numeral 63 in Figure 3 designates a high pressure gas cutoff, whilethe numeral 65 indicates a low pressure :gas cutoff-these usual attanggliims 11 9 q together "through nector 67 and communicating'withthe mainline thr n -T-q9 n.ector e9.

To operate the device the fan motor is started and action is initiated. The pilot is ignited by a spark from a spark plug 70 (Figure l) in the conventional manner and occasions ignition of the gas flowing from the pilot burner. The flame rod 47 senses the presence of the pilot flame and controls the operation of the apparatus thereafter, as is customary in practice, that is, by control of operation of the main gas valve or safety shut-off valve 39. However, it is to be noted that no backfiring occurs due to the arrangement of the components. Further, it is to .be noted that the components remain cool due to their positioning. Thus the proportioning valve, the pre-mixer and the motor which drives the fan, all have a cool unit of air directed toward them from the inlet. Suitably at the inlet a thermostat 81 is provided.

The inclusion of the components within the housing in the manner described provides for a most compact unit. Further, :the annular arrangement of the burner provides for heating the air in a most eflicient manner without unduly heating the fan blades. This burner .as constructed is substantially rectangular, havingcurved corner portions for the sake of convenience in assembly. However, the burner could be completely circular if ,so desired.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. .In an air supply unit, the improvementwhich ,cornprises the combination of a longitudinally extending casing having an air inlet rearwardly in the.,casing and an air outlet forwardly in the casing, a propeller type fan within the casing adjacentthe air outlet-arrangedto pro pel air from the air inlet throughthe casing to the air outlet, a gas burner conduit which is complete in a peripheral sense and which lies in a plane parallel to that .ofsaid fan and which conduit has a central opening therethrough, said ,gas burner conduit having an axis which is coaxial with the propeller fan, and said gas burner conduit being spaced from the fan toward the air inlet, said burner conduit comprising an annular shaped extension conduit arranged in the interior of said casing and around said axis, said extension conduit being spaced rearwardly of said fan and toward said air inlet whereby ,air drawn in through said air inlet flows over said burner and is heated and then propelled by said fan through said outlet, said extension conduit having gas burner ports disposed outwardly of the ,said axis at a distance of about one-third to five-sixths of the propeller fan radius so that ,hot air passing through the burner is in contact .withthe fan well inwardlyof the fan tips, said ports of said burner fronting toward the fan, an electric motor connected to the fan for the driving of the fan and positioned betweenthe fan and burner conduit .and shielded from the heat of the burner, and an air gas pre-mixer directly connected to the gasburner conduit rearwardly of the burner conduit toward the air inlet for feeding a combustible mixture to the burner conduit.

2. Inan air supply unit, thecombination of a longitudinally extending casing havingan air inlet rearwardly in the casing andan air outlet forwardly in the casing, a propeller'fan within the casing adjacent the air outlet arranged to propel air th'roughtthe casing fromthe inlet to the said air outlet, a gas burner disposed between the fan and air inlet and over which air flows and is heated by said gas burner in the passage of .air from the inlet to the fan and outlet, said gas burner comprising an annular shaped extension conduit arranged in the interior of said casing and spaced rearwardly of .said fan toward said air inlet, whereby air drawn in through said air inlet flows over said burner and is heated and then propelled by said fan through said outlet, said burner having gas burner ports fronting toward the said propeller fan, means for driving said propeller fan, an air-gas pre-mixer in the casing directly connected to the gas burner for feeding a combustible mixture to the gas burner, said pre-mixer being positioned rearwardly of the burner toward the air inlet so that air flowing to the fan and outlet from the inlet flows over said premixer, and means for driving said pre-mixer.

3. In an air supply unit, the combination of a longitudinally extending casing having an air inlet rearwardly .in the casing and an air outlet forwardly in the casing,

a propeller fan comprising a hub and attached fan blades within the casing adjacent the air outlet arranged to propel air through the casing from the inlet to the said air outlet, a gas burner disposed between the fan and air inlet and over which air flows and is heated by said burner in the passage of air from the inlet to the fan and outlet, said gas burner comprising an extension conduit which is circled about in said casing rearwardly of said fan, said burner conduit being spaced between said fan and said air inlet, whereby air passing over the burner conduit is heated and strikes said fan inwardly of the tips of said fan blades, said burner conduit having ports fronting toward the said propeller fan, means for driving said propeller fan, an air-gas pre-mixer in the casing directly connected to the gas burner for feeding a combustible mixture to the gas burner, said premixer being positioned rearwardly of the burner toward the air inlet so that air flowing to the fan and outlet from the inlet flows over said pre-mixer, and means within the casing rearwardly of the burner toward the air inlet for driving said air-gas pro-mixer.

4. In an air supply unit for providing make-up air to within a building, in combination, a longitudinally extending casing having an air inlet rearwardly in the casing and an air outlet forwardly in the casing, a propeller type fan within the casing forwardly adjacent the air outlet arranged to propel air through the casing from the air inlet to the said air outlet, a gas burner conduit which is circled about within said casing rearwardly of the fan and forwardly of said air inlet, said encircled burner conduit lying in a plane substantially parallel to a plane in which said propeller type fan lies, said burner conduit having a central axial opening therethrough and also having a plurality of ports fronting on said fan, an electric motor in said casing substantially co-axial with the fan and burner conduit, said electric motor being connected with said fan for driving of the fan and said electric motor having a shield therearound in the form of a duct extending from forwardly of the burner conduit toward the air inlet rearwardly through the said central axial opening beyond the said burner conduit toward said air inlet, a gas-air pre-mixer within the casing on the air inlet side of the burner conduit and directly connected to the burner conduit for feeding a combustible mixture to the burner conduit, a proportioning valve within the casing on the air inlet side of a combustible mixture to said pre-mixer, and an electric motor in the casing for driving said pre-mixer, said latter the burner connected with said pre-mixer for supplying motor being positioned on the air inlet side of said burner conduit and over which latter said electric motor air flows in passage to said burner conduit and air outlet.

References Cited in the file of this patent UNITED STATES PATENTS 684,458 Porter Oct. 15, 1901 1,958,331 Bell May 8, 1934 2,046,660 Spencer July 7, 1936 2,137,682 Fisher Nov. 22, 1938 2,412,990 Kruse Dec. 24, 1946 2,460,983 Hess Feb. 8, 1949 2,832,580 Hess Apr. 29, 1958 OTHER REFERENCES Pages 178 and 179 of Trinks Industrial Furnaces, vol. H, 2nd edition 1942, published by John Wiley 8: Sons Inc., New York, N.Y.

UNITED STATES PATENT OFFICE QEHHCATIN 1 CORRECTION Patent No, 2 972 475 February 21 1961 Homer K. Monroe ears in the above numbered pat- It is hereby certified that error app Patent should read as en't requiring correction and that the said Letters corrected below.

Column 6 line :21 strike out "the burner connected with said pre mixer for supplying" and insert the same after "air inlet side of in line 18 same column.

Signed and sealed this 8th day of August 1961.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer- DAVID L. LADD Commissioner of Patents