US2891761A - Air prover - Google Patents

Description

June23, 1959 y, MCCAVVIRTY 2,891,761

AIR PROVER Filed Oct. 11. 1955 OIL LEVEL 8. I I 7 INVENTOR.

Louaoes V. MCARN ATTORNEY United States Patent AIR PROVER Lourdes V. McCarty, Milwaukee, Wis., assignor, by mesne assignments, to Controls Company of America, Schiller Park, Ill., a corporation of Delaware Application October 11, 1955, Serial No. 539,800

7 Claims. (Cl. 251-62) This invention relates to an air prover control which is employed in connection with forced draft pot-type oil burners to prevent flow of oil to the burner in absence of the full draft necessary to burn the oil.

The object of this invention is to provide a simple control which may be used in connection with any of a wide variety of constant level valves commonly employed in connection with forced draft pot-type burners in order to prevent the full oil flow to the burner when the draft is insufficient to support combustion of the full flow.

Forced draft pot-type burners require a forced air supply to burn the full oil flow properly. If for any reason the blower supplying the air to the burner should fail to deliver the minimum amount of air required for proper combustion, the usual controls will continue to provide the full oil flow which results in sooty combustion. Therefore, it is desirable to reduce the oil flow when the blower is not operating properly. Devices designed to prevent flow under such conditions are generally known as air provers and such air provers as have heretofore been available have generally been an integral part of the constant level control which regulates or meters the oil to the burner. The present control, on the other hand, is a simple device which can be employed in connection with any of the usual controls and is interposed between the constant level control and the burner and acts as an overriding control in that it will prevent the full oil flow from the constant level valve to the pot if the draft is not up to the minimum requirements.

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:

The single figure shows a vertical section through the present control together with a schematic representation of a constant level valve and a forced draft pot-type burner. Y Y The present air prover 10 is "placed in the oil 'supply line between constant level valve 12 and pot-type burner 14. Thus, the constant'level valve outlet 15 is connected toconduit 16 which is connected to inlet 18 of air'prover casing 20. The air prover casing is mounted so that the maximum liquid level in'the casing will line up with'the constantly maintained oil level in control valve 12 and the maximum level position in combustion pot 22 approximately as shown in the drawing; The'air prover outlet 24 supplies oilto pipe '26 which leads to combustion 'pot 22.

Flow between the air prover inlet 18 and outlet 24 is regulated by a valve carried by the inverted cup 28. The valve comprises a slot in the lower end of tube 32. When the cup 28 is in the position shown in solid lines in the drawings, the slot does not communicate with the interior of the casing 20 and no oil flows through the slot.

When the draft pressure in air supply chamber 34 of the burner increases when the blower is operated, the pressure is communicated to the underside of cup 28 through tube 36 which passes through the casing 20 and terminates under the cup 28 well above the maximum 1iq-. uid level in casing 20. When the pressure under cup 28 increases sufficiently to overcome the weight of the cup and valve tube 32 fixed thereto at 38, the cup will rise to the position shown in dotted lines in the drawing to raise slot 30 so that oil can flow from the interior of the casing through openings 40 in guide sleeve 42. It willbe noted that the upper end of sleeve 42 is turned in at 44 to guide the upper end of tube 32. The sleeve also car-' ries a filler block 46, mounted on the sleeve by hairpin cotters 48, to reduce the volume of oil above the outlet valve. The cup 28 can rise freely since the upper portion of casing 10 is vented at 49 and the upward movement of the cup is limited by contact of the top of valve tube 32 with the underside of the casing cover.

From the above it will be appreciated that when there is no draft provided to the pot-type burner, the slot 30 will be positioned as shown in the drawings where no flow can take place through the slot. Therefore, even if the constant level valve 12 has been set, either manually or automatically, to provide for full flow to thepot, no flow will occur through the slot 39. The small orifice 50 is provided to permit the maximum flow which can be burned in the pot without a forced draft and without encountering a sooty condition. It will be noted thatthe orifice 50 communicates with the inlet at all times. This orifice additionally serves to permit pilot flow (if used) from the constant level valve to pass through 'the air prover 10 at all times.

When the draft is established at the pot, the cup 28 will rise when the pressure under the cup is sufficient to lift the weight of the cup and the tubular valve stem 32 carried by the cup. As the pressure builds up under the cup, the oil level under the cup will be depressed an amount corresponding to the pressure head of the draft. The oil thus expelled would, of course, rise outside the cup, but as will be pointed out hereinafter, this volume of oil is not very great and in fact the level under the cup frequently does not come up to the level in the constant level valve under normal operating conditions even though there is no draft supplied to the pot at the time. When the cup 28 rises, it will expose slot 30 to the interior of the casing 20 and permit oil flow through the slot to the burner.

When the constant level valve 12 is providing pilot flow only, the level in casing 20 does not rise much above orifice 50 since orifice 50 is large enough to pass the pilot flow rate quite readily. Therefore, when the flow'rate is increased and the draft is established, there may be a sudden spurt of oil passed by the air prover as the pressure under the cup acts on the orifice 50. This may be'followed. by a short interruption in all flow while the oil flow from the constant level valve makes up the level in the air prover. While this occurs the can or cup 28 will raise the valve to permit the full flow from the constant level valve 12 to pass through the slot 30 and to the burner. When the fan stops operation and the pressure under the culp 28 decreases, the cup moves down to close off slot 30 and prevent any flow from the constant level valve even though the constant levelvalve may be set. to pass the full flow rate. The only flow which can occur if the constant level valve is still providing oil above pilot rate is that passed by orifice 59. If the constant level valve is set back so as to provide only a pilot flow, any accumulated oil in the casing 20 will continue to pass out through orifice 50 giving a flame greater than pilot until an equilibrium condition has been reached at which the pilot flame will continue.

From the above it will be obvious that the filler 46 serves a very useful purpose in decreasing what might be termed the lag time in the air prover upon the start or completion of a full flow condition. Thus, if the volume occupied by filler 46 represented oil which had to be burned on completion of an on cycle, it would take considerably longer for the present control to decrease the flow rate to pilot and this would, in many cases, result in a considerable overshoot of the temperature. The filler need not be solid as shown but could be a cup-like arrangement somewhat on the order of a ring mold and would not have to be closed at its open upper end since even if it filled with oil, there would be an effective occupancy of that volume.

The present control can be readily modified to meet a number of diiTerent conditions. For example, the draft pressure required for a particular burner can be easily matched by placing annular weights on the top of cup 28. If it is desired to have on or off operation only, the orifice 50 could be eliminated from stem 32 so that when the air pressure under the cup dropped to atmospheric all flow would be cut off. In such a case any pilot flow desired could be provided the burner through a separate conduit which would by-pass the air prover.

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. An oil control device, comprising, a casing having an inlet and an outlet and adapted to contain liquid above the level of the outlet, means for maintaining liquid in said casing at substantially a constant level above said outlet, an inverted cup-like member having its open end depending below the liquid level, a valve operatively connected to the member and cooperating with the outlet to control flow of liquid from the casing, conduit means adapted for connection to an air pressure source and communicating with the underside of the member above the liquid level so an increase in pressure under the member sufficient to overcome the weight of the member will raise the member, said valve being opened and closed in response to air pressure at the underside of the member above the liquid level, the liquid flowing from said inlet to said outlet and the liquid in said casing being one and the same.

2. An oil control device according to claim 1 in which the valve is connected directly to the member centrally of the member, guide means for the valve, and means carried by the guide means for displacing a major portion of the liquid volume under said member.

3. An oil control device according to claim 1 including a restricted orifice for passing oil at a low flow rate when the valve is closed.

4. An oil control device, comprising, a casing having an inlet and an outlet, means for maintaining liquid in said casing at substantially a constant level above said outlet, 21 valve for controlling flow of liquid from the casing through the outlet, an inverted cup operatively connected to the valve so it normally biases the valve closed, means for introducing a pressure above atmospheric under the cup, the bottom edge of the cup being below the surface of liquid in the casing so a pressure above atmospheric pressure under the cup acts to lift the cup and open the valve, the liquid flowing from said inlet to said outlet and the liquid in the casing being one and the same' 5. An oil control device comprising, a casing having an inlet and an outlet and adapted to contain liquid above the level of the outlet, means for maintaining liquid in said casing at substantially a constant level above said outlet, an inverted cup-like member in said casing, means for sealing said cup-like member to provide an air-tight chamber on the underside of said cup-like member, a valve operatively connected to the member and cooperating with the outlet to control flow of the liquid from the casing, conduit means adapted for connection to an air pressure source and communicating with said air-tight chamber so an increase in pressure under the member suflicient to overcome the weight of the member will raise the member, said valve being opened when the member is raised and closed when the member is lowered in response to air pressure on the underside of said cup-like member, the liquid flowing from said inlet to said outlet and the liquid in said casing being one and the same, and a vent for said casing outlet to atmosphere.

6. An oil control device according to claim 5 in which said sealing means comprises the bottom edge of the member depending below the surface of liquid in the casing.

7. An oil control device, comprising, a casing having an inlet and an outlet and adapted to contain liquid above the level of the outlet, means for maintaining liquid in said casing at substantially a constant level above said outlet, an inverted cup-like member having its open end depending below the liquid level, a valve cooperating with the outlet to control flow of liquid from the casing, means including a tube-like member for operatively connecting said valve with said cup-like member and for venting said casing outlet to atmosphere, conduit means adapted for connection to an air pressure source and communicating with the underside of the member above the liquidlevel so an increase in pressure under the member sufficient to overcome the weight of the member will raise the member, said valve being opened when the member is raised and closed when the member is lowered in response to air pressure on the underside of said cup-like member above the liquid level, the liquid flowing from said inlet to said outlet and the liquid in said casing being one and the same.

References Cited in the file of this patent UNITED STATES PATENTS 804,908 Williams Nov. 21, 1905 1,115,244 Reynolds Oct. 27, 1914 1,411,402 Blackstone Apr. 4, 1922 1,687,349 Quart Oct. 9, 1928 1,957,490 Davis May 8, 1934 2,122,866 Lippold July 5, 1938 2,169,462 DeGrace Aug. 15, 1939 2,367,038 Martin Ian. 9., 1945 2,529,942 Holthouse Nov. 14, 1950 2,726,675 Bohler Dec. 13, 1955 2,747,601 Quist May 29, 1956 FOREIGN PATENTS 429,338 France of 1911 231,027 Great Britain of 1925

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