Heat shield for burner fan

April 6, 1965 r. a. gerlitz 3,176,751

HEAT SHIELD FOR BURNER FAN Filed Oct. 16, 1962

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ATTORNEYS.

United States Patent Office

3,176,751

Patented Apr. 6, 1965 .: ¹

3,176,751

HEAT SHIELD FOR BURNER FAN Reuben A. Gerlitz, Springfield, Ohio, assignor to Robbins &amp; Myers, Inc., Springfield, Ohio, a corporation of Ohio 6

Filed Oct. 16, 1962, Ser. No. 230,836

Claim. (CI. 158—76)

This invention relates to a heat shield for a burner fan of a type adapted to be used in ovens, boiler furnaces, io 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 15 motor fan unit results in certain economies of space and increased efficiencies 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 effects.

In the first place, it causes a high rate of heat transfer 20 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, bal- 25 ancing 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/or structural failure of the impeller. Finally, the flame may 30 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 flame 35 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 40 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. 45

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. CO

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 ⁵⁵fan and heat shield according to the present invention, and

FIG. 2 is a cross-sectional view taken along line 2—2 of FIG. 1.

In the practice of my invention, I provide a motor 19 which may be of any suitable size and capacity, and θθ 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 ⁶⁵11 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 carries the fan or impeller 18. The fan Unit shown in the drawings is largely conventional, and includes a bell mouth inlet shown at 19. 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 flow arrows indicate, there will be considerable movement of hot air and flame 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 flange is facing the other way, or even if the heat shield comprises simply a circular 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 temperatures 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 modifications within the spirit of the invention will of course occur to the skilled worker in the art. Consequently, I do not intend to limit myself except in the manner set forth in the claim which follows.