Automatic air cut-off for burners

2,111,484

March 15, 1938.

J. C. WOODSON

AUTOMATIC AIR CUT-OFF FOR BURNERS Filed Aug. 19, 1936

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INVENTOR

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Patented Mar. 15, 1938

2,111,484

UNITED STATES PATENT OFFICE

2,111,484 AUTOMATIC AIR CUT-OFF FOR BURNERS James C. Woodson, Cleveland, Ohio, assignor to Lee Wilson, Cleveland, Ohio Application August 19, 1936, Serial No. 96,806 2 Claims. (Cl. 158—119)

This invention relates to a fuel burner and, in particular,. to a device for automatically controlling the amount of air supplied to support combustion.

Radiant tubes heated by combustion gases passing therethrough have proved highly successful for general heating applications, such as the annealing furnace described and claimed in United States patent to Wilson No. 1,952,402. It 10 has been found, however, that when such apparatus is operated at a relatively low rate, the in- . duction of air through the radiant tubes caused by natural draft abstracts an excessive amount of heat and prevents efficient operation.

It is an object of my invention to provide means for preventing the induction of excessive amounts Of cold air through radiant heating tubes, and the resulting loss of heat. In accordance with my invention, I provide a movable 20 valve or closure member for restricting the inflow of air to the burner when operating under low fuel pressures. The closure member may conveniently take the form of a cup adapted to abut, with its edge a flange plate extending from 25 the inspirator tube usually incorporated in fuel burners to¹ induce air for combustion thereinto. Fuel is supplied to the inspirator by a nozzle, and I mount the cup or closure on the nozzle for movement relative thereto. An expansible cham30 ber subject to the pressure of the fuel in the nozzle serves to move the cup to the position in which it permits free induction of air, when the fuel pressure is at a maximum. At lower fuel pressures, the cup moves to partially or complete35 ly closed position under the influence of a closing spring.

A preferred form of the invention and a modification thereof are illustrated in the accompanying drawing to which reference is made for a 40 complete understanding of the invention. In the drawing,

Fig. 1 is a longitudinal sectional view through the device of my invention, parts being shown in elevation; and

Fig. 2 is a similar view of a modification.

An inspirator tube I having a Venturi throat 2 is adapted to deliver a combustible mixture of fuel and air to a heat exchange tube (not shown) for combustion therein. The end of the inSpira50 tor I projects a short distance into the heat exchange tube. A flange plate 3 is secured to the inspirator tube and has ah opening in alinement with the Venturi throat thereof. An end plate · is connected to the flange plate 3 by means of 55 tie rods 5 and has a central opening through which a threaded sleeve 6 extends, being secured thereto by bolts 1 extending through ears 8 formed on the sleeve. A fuel-supply connection 9 is threaded into the outer end. of the sleeve 6.

A nipple i 0 is threaded into the inner end of the 5 sleeve 6 and carries a nozzle 11 being connected thereto by a coupling 12. The nozzle il has a tip 13 with a central bore 14 which is adapted to deliver a jet of fuel into the throat of the inspirator tube I when fuel under pressure is de- 10 livered to the connection 9.

A cup 15 having a cylindrical side wall 16 and a rear wall 17 is adapted to engage the flange plate 3 with its edge. The cup 15 is disposed coaxially with the nozzle 11, the wall ί 1 thereof 15 having an opening 18 through which the nozzle extends. The edge of the cup 15 is normally urged against the plate 3 by a compression spring 19 disposed between a washer 20 backed up by a nut 2 i threaded on the nipple 10 and the rear wall 20 11 of the cup 15. A collar 22 extending around the opening 18 in the rear wall 17 of the cup 15 provides a seat for the spring 19.

A plate or disc 23 is secured on the nozzle 11, having a hole through which the nozzle extends. 25 Coaxial bellows 24 and 25 are secured at opposite ends to the plate 23 and the wall 17 of the cup 15. These bellows define an annular expansible chamber. The nozzle 11 has a port 26 in alinement with a radial passage 27 in the plate 30 23. An axial passage 20 in the latter intersecting the radial passage admits fuel from the nozzle 11 to the annular chamber defined by the bellows.

It will be apparent from the foregoing de- 35 scription that when the fuel supplied to the nozzle 11 is under sufficient pressure, the bellows 24 and 25 will extend against the pressure of the spring (9, and move the cup 15 away from the flange plate 3. Air for combustion may then be in- 40 duced into the inspirator I through the space between the plate 3 and the edge of the cup 15. The size of this space and the amount of air induced therethrough will vary with the pressure under which the fuel is supplied. This is deter- 45 mined by the setting of the burner-control valve (not shown). On a decrease in the fuel pressure resulting from partial closing of the control valve, for example, the spring 19 will partially collapse the bellows 24 and 26 And cause the edge of the 50 cup 15 to move toward the plate 3, thus restricting the induction of air into the inspirator tube in accordance with the decreased fuel pressure. When the control valve is entirely closed, the edge of the cup 15 will engage the plate 3 and 55

2,111,484 entirely cut off flow of air through the inspirator and heat exchange tube which would, otherwise result from the natural draft due to the heated condition of the radiant tube.

Fig. 2 illustrates a modification In which several elements are the same as those of Fig. 1, or similar thereto, and these have been designated by the same reference numerals. The device of •Fig. 2 includes a nozzle II' on which a disc 23' is mounted. A valve or closure member in the form of a cup 15' is movably mounted on the nozzle 11, a bellows 25' having one end secured to the disc 23', and the other end to the rear wall of the cup 15'. Another bellows 24'has one end attached to the rear wall of the cup 15' and the other end to the nozzle 11'. The bellows 24' merely provides a seal between the cup 15' and the nozzle II, and does not affect the expansion of the bellows 25' under the pressure of the fluid fuel. Ports 26' in the tube 11' admit fuel from the nozzle to the space within the bellows.

The operation of the device of Fig. 2 is similar to that of the apparatus shown in Fig. 1, and no additional explanation thereof is necessary.

It will be clear from the above description that my invention provides a simple and comparatively inexpensive device for automatically controlling the amount of air induced into a radiant tube for combustion therein, in accord30 ance with the pressure under which the fuel is supplied and, therefore, the amount of fuel available for combustion. The apparatus serves not only to proportion the amount of air induced to the amount of fuel available, so as to obtain effl35 cient combustion at all times, but prevents the loss of heat resulting from the induction of an excessive amount of cold air through the heated radiant tube.

Although I have illustrated and described but 40 one preferred embodiment of the Invention, and a modification thereof, it will be understood that changes in the exact details of construction herein disclosed may be made without departing from the spirit of the Invention or the scope of the appended claims.