US2881790A - Stack draft responsive fuel flow control - Google Patents

Description

United States Patent STACK DRAFT RESPONSIVE FUEL FLOW CONTROL Lourdes V. McCarty, Milwaukee, Wis., assignor, by mesne assignments, to Controls Company of America, Schiller Park, 11]., a corporation of Delaware Application October 3, 1955, Serial No. 537,964 Claims. (Cl. 137-389) This invention relates to an oil flow control which increases the flow rate when the burner draft increases.

It is desirable to have oil flow to a burner properly proportioned to the draft whether the draft be natural or forced. If the flow' is so proportioned, the fire will be clean at all times. A simple control providing these results has not heretofore been attained and the object of this invention is to provide such a control.

Another object is to provide a simple control of the type described which can be readily designed for diiferent flow characteristics for the same draft.

The present device employs the stack draft as an indication of the draft. This has two distinct advantages. The stack draft is an accurate measure of the draft under natural or forced draft conditions and, furthermore, takes into account the change in draft as the stack gases heat Other objects and advantages'will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings in which:

Fig. 1 is a top plan view of one form of control embodying the invention;

Fig. 2 is a vertical section of the control as indicated by line 2-2 on Fig. 1; and

Fig. 3 is a vertical section of the tubular fulcrum showing its vent to the air space under the inverted pan.

Referring now to the drawings in detail, the casing is provided with an inlet 12 and an outlet 14. The inlet valve 16 is biased away from seat 18 by compressed spring 20 acting upwardly against the stem shoulder 22. The spring 20 holds the valve in contact with pin 24 threadably mounted in bushing 26 in the inverted panlike member 28. The inverted pan 28 is pivotally mounted on the shaft 30 mounted between the opposed sides of the casing. One end of the shaft is provided with a central bore 32 and longitudinal slots 34 opening to the space under the pan-like member 28. The bored end of shaft 30 is brought through the side of casing 10 and conduit 36 is connected thereto while the other end of the conduit is mounted within the stack of the burner supplied by the present fuel control. Therefore, pressure variations in the stack are communicated to the underside of pan 28 through conduit 36, bore 32 and slots 34.

The axis of shaft 30 is the pivot axis for the pan and since the axis of the pan is off center, it is obvious that the weight of the pan will bear down to the right of the pivot axis and would tend to allow valve 16 to open to its fullest under the influence of compressed spring 20. The weight or downward force exerted by pan 28 about the pivot axis is supported or opposed by float 38 connected to the pan by means of stud 40 threaded into bushing 42 carried by the pan. It will be obvious that this arrangement will permit valve 16 to regulate the flow into the casing to maintain a constant level so long as the displacement of the float 38 remains constant.

Flow to the outlet travels up through orifice 44 into the well-like chamber 46 and out through conduit 48.

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Conduit 48 would, in most instances, be provided with a suitable metering stem which might be manually or automatically operated. Details such as this have no bearing on the present invention since the present invention is related primarily to the means of varying the head on the outlet and no valve need be shown in the present instance to illustrate the manner in which the head will be varied.

The stack pressure is communicated to the chamber under pan 28 defined by the liquid in the casing, the pan and the peripheral flange of the pan depending into the liquid. The stack pressure is below atmospheric and, therefore, subjecting the underside of pan 28 to stack pressure results in atmospheric pressure exerting an increased force on the pan, which increases the weight or force necessary to be supported or opposed by float 38. Thus, the displacement of float 38 increases as the vacuum in the stack increases and, of course, the float will sink further into the liquid resulting in opening the inlet valve and obtaining a higher liquid level. The greater the vacuum in the stack, the higher will be the liquid level in the casing 10 and hence the greater will be the liquid head on the outlet which, of course, results in increased flow through the outlet.

All stacks have a vacuum within the stack (when the burner is operating) whether the draft be natural or forced. In addition to being useful in connection with natural or forced draft burners, the present arrangement has an additional advantage in that employing the stack draft to regulate the head on the outlet (and thus the flow to the burner) provides an accurate indicia of the capability of the burner to handle an increased flow. Thus, when starting up from a cold start with a cold stack, the burner is unable to properly burn the amount of oil which it will handle with case after the stack has been heated sufficiently to create the full draft. Under these conditions, the present control will increase the oil level gradually as the vacuum in the stack increases. The rate of oil flow can be selected so that the combustion will not be sooty at any time. It might be said that the present control regulates the flow to the burner in accordance with the readiness or ability of the burner to handle the flow.

It will be appreciated that the amount of oil level change in the casing for a given draft can be changed by changing the ratio of the area and the leverage of the float to the area and the leverage of the pan. While the present structure is shown with the float positioned under the pan (this obviously best utilizes the space) it will be appreciated that the float could be located outside the pan. Similarly, the outlet valve location can be varied and the outlet valve arrangement can be changed to any desired form without departing from the spirit of this invention.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. A fuel control comprising a casing having an inlet and an outlet, a valve for the inlet, an inverted panlike member mounted in the casing for movement about a horizontal axis and connected to said valve to actuate the valve, a float carried by the member under said member so the valve is actuated to maintain a level in the casing determined by the buoyancy of the float, and conduit means communicating withthe underside of the member and adapted for connection to the stack of a burner so the reduced pressure under the member will 3 submerge the float and the valve is opened to raise the level wi thin the casing. f

2. A liquid fuel control comprising, a casing having an inlet and an outlet, a yalve for ,the inlet, an inverted member having its edges depending into the liquid in the fcasing to define a chamber under the member above the liquid level and mounted in the casing -for movement about ahorizontalaxis, the member" being connected to the valve so the weight of the member acting about said axis tends to. openthe valve, .21 float connected to the member and supporting the weight thereof, and a conduit communicating with said chamber and adapted for connection to the stack of a burner so the stack vacuum acts to reduce the chamber pressure and atmospheric pressure acting on the member increases thejweight sup.

ported by 'thc1fl0at and thereby increases the float displacement to increase the'flevel ,in the casing and the liquid head on the outlet.

3. A fuel control according .to claim .2 in which the conduit comprises the pivotal mounting for the member. 4. A fuel control according to claim 2 in which the float is positioned under the'member.

5. A fuel control comprising a casing having an inlet and an outlet, a'"valve"'fo'r' regulating flow through the inlet, a float connected to the valve for regulating movement thereof, means including a member pivotally mounted'in said casing and connected between said valve and said float for varying thedisplacement of said float in response to pressure variations at a remote location, said means also including a chamber defined partially by said member, the member'being adapted to be sealed by liquid in the casing to define therewith an enclosed cham ber, conduit means ,ror subjecting said chamber to pressure variations at' ja'remote 'location, reduction of the pressure within the chamber causing atmospheric pressure to exert an increased force on the member which, in turn, increases the eff e ctiye weight supported by the float.

References Cited in the file of this patent UNITED STATES PATENTS 1,6 45,443 Meyers Oct. 11, 19 27 1,667,314 Gilmore et al; Apr.t24, 1928 2,747,601 Quist May 29, 1956 2,774,314 Schneider Dec. 18, 19 56

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