US3176751A - Heat shield for burner fan - Google Patents

Description

April 6, 1965 R. A. GERLlTz HEAT SHIELD FOR BURNER FAN Filed Oct. 16, 1962 L -PM INVENTOR REUBEN A. GERLlTz,

ATTOIINEYI.

'MSl Patented Apr. 6, 1965 3,176,751 HEAT SHIELD FOR BURNER FAN Reuben A. Gerlitz, Springfield, hio, assigner to Roh- & Myers, Inc., Springeld, Ohio, a corporation of o Fiied Oct. 16, 1962, Ser. No. 230,836 1 Claim. (Cl. 15S-76) This invention relates to a heat shield for a burner fan of a type adapted to be used in ovens, boiler furnaces, and related equipment. In such devices the fan is necessary to provide air for combustion.

In most burner applications, the fan is so located that the direct flame from the burner cannot reach it. However, it has been found that a different location of the motor fan unit results in certain economies of space and increased eiciencies of operation. But this relocation of the fan unit subjects the impeller to the direct flame of the burner, and this has several very undesirable etfects.

In the 4first place, it causes a high rate of heat transfer along the shaft to the fan bearings, creating a bearing life problem. Secondly, it raises the impeller temperature above the maximum allowable for aluminum, and thus requires stainless steel or some other high density ferrous material. Because of the greater precision required, balancing of these heavier impellers is considerably more costly. Thirdly, the uneven temperature distribution over the surface of the impeller subjects it to high thermal stresses, resulting in possible unbalance and/o1` structural failure of the impeller. Finally, the llame may deposit a certain amount of soot on the impeller hub, and this will adversely affect impeller balance.

Accordingly, it is the primary object of my invention to provide a heat shield adapted to be used in a burner fan so located as to be subject to the direct burner ame which will eliminate the above mentioned deleterious effects.

More specifically, it is an object of my invention to provide such a heat shield which will permit the use of aluminum or other conventional low density metals for the impeller fan when the fan is relocated so as to be subjected to the direct flame of the burner, and which will result in more satisfactory performance through longer unit life, more accurate balance of the impeller and reduction of thermal stresses. v

These objects and others described in greater detail in this specification, or those which will become apparent from an examination of the drawings, are accomplished by that certain construction and arrangement of parts of which I shall now describe an exemplary embodiment.

Reference is made to the drawings forming a part of this application, in which like reference characters refer to similar parts throughout the several views, and in which:

FIG. 1 is a longitudinal sectional view of a burner fan and heat shield according to the present invention, and

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. l.

In the practice of my invention, I provide a motor which may be of any suitable size and capacity, and which is fastened to the fan housing 11 as at 12. It will be noted that the fan housing 11 is directly coupled with the duct 13 in which the air is heated by the burner nozzle 14.

The wall between the motor 10 and the fan housing 11 is formed of any suitable insulative material as indicated at 15. And as a further precaution, I also provide the shaft cooler shown at 16.

In the drawings I have shown an elongated motor shaft 17 suitably journaled in bearings (not shown) which mouth inlet shown at 19.

carries the fan or impeller 1S.` The fan unit shown in the Y drawings is largely conventional, and includes a bell It will of course be understood that this arrangement is not a limitation on the invention, which may be used with any desired impeller arrangement or fan unit. The small arrows throughout the drawing indicate the flow of air when the unit is in operation.

It will be noted that as the air leaves the periphery of the impeller, a dead air space is created in the center of the duct adjacent to the impeller hub and behind the burner nozzle 14. As the ilow arrows indicate, there will be considerable movement of hot air and llame into this dead air space adjacent the hub of the impeller, and this results in all of the disadvantages enumerated at the outset of this specification.

To correct this problem, I have provided a heat shield indicated at 20, which effectively prevents the direct burner flame from contacting the hub or blades of the impeller. In the embodiment shown, the shield is shown as having a flange 21 facing toward the hot gases; I have found that this configuration is to be preferred in certain cases, but does not form a limitation on this invention. The heat shield will function equally well if the ange is facing the other way, or even if the heat shield comprises simply atcircular disc. The heat shield is attached to the fan unit by any convenient method, such as the small posts shown at 22.

In burner fan applications involving very high tempera- Y tures stainless steel is to be preferred as the material for construction of the heat shield. For less severe temperatures plain steel or some other material would be equally satisfactory.

Variations and modications within the spirit of the invention will of course occur to the skilled worker in the art. Consequently, I do not intend to limit Imyself except in the manner set forth in the claim which follows.

What is claimed as new and what is desired to be secured by Letters Patent is:

A pressure atomizing burner fan unit of the type wherein the fan impeller is subject to contact with the burner flame, comprising a fan housing having a terminal end and a shaft mounted therein for rotational movement, a motor secured to said housing and driving said shaft, an impeller mounted on said shaft, an air duct connected to the terminal end of said fan housing, a burner in said air duct, and a circular imperforate heat shield means for said impeller, having a radius smaller than the radius of said air duct, said imperforate heat shield means being disposed between said impeller and said burner, and providing an annular passageway between said fan housing and air duct, so that air set in motion by said impeller passes through said annular passage, and by vortex action, scrubs said imperforate shield means to cool the same, so that said impelier is protected from the direct ame and heat of the burner.

References Cited hy the Examiner UNITED STATES PATENTS 1,599,578 9/26 Maze 158-76 g 2,299,154 10/42` Lair.

2,507,006 5/50 Hammell et als. 158-77 2,675,865 4/54 Betzer 15S-4 2,896,933 7/59 Barnes 263-19 Y FOREIGN PATENTS 955,510 6/49 France.

JAMES W. WESTHAVER, Primary Examiner.

MEYER PERLIN, Examiner.

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