US3801258A

US3801258A - Post purge system for gas burners

Info

Publication number: US3801258A
Application number: US00316763A
Authority: US
Inventors: P Mutchler
Original assignee: American Air Filter Co Inc
Current assignee: Allis Chalmers Corp; Daikin Applied Americas Inc
Priority date: 1972-12-20
Filing date: 1972-12-20
Publication date: 1974-04-02
Anticipated expiration: 1991-04-02
Also published as: CA971097A

Abstract

A post purge device for a fuel burning apparatus wherein a fuel pressure sensing means is disposed between and in communication with a main fuel line supplying fuel to a fuel burning apparatus and a diaphragm, the fuel pressure sensing means containing a fluid therein wherein movement of the fluid is determined by the pressure in the fuel line thereby causing movement of the diaphragm in response to the movement of the fluid, the diaphragm being in electrical communication with a combustion air blower wherein a predetermined amount of movement of the diaphragm controls the energization of the combustion air blower.

Description

United States Patent 11 1 Mutchler 1 1 POST PURGE SYSTEM FOR GAS BURNERS [75] Inventor: Paul A. Mutchler, University City,

[73] Assignee: American Air Filter Company, 1nc.,

Louisville, Ky.

22 Filed: Dec. 20, 1972 211 Appl. No.: 316,763

[111 3,801,258 [451 Apr. 2 1974 3,388,862 6/1968 Gabrielson 431/12 X Primary Examiner-Edward G. Favors [57] ABSTRACT A post purge device for a fuel burning apparatus wherein a fuel pressure sensing means is disposed between and in communication with a main fuel line supplying fuel to a fuel burning apparatus and a diaphragm, the fuel pressure sensing means containing a fluid therein wherein movement of the fluid is determined by the pressure in the fuel line thereby causing movement of the diaphragm in response to the movement of the fluid, the diaphragm being in electrical communication with a combustion air blower wherein a predetermined amount of movement of the diaphragm controls the energization of the combustion air blower.

4 Claims, 2 Drawing Figures [52] U.S. Cl. 431/90 [51] Int. Cl F23n l/02 [58] Field of Search... 431/90, 12; 137/100, 101.21

[56] References Cited UNITED STATES PATENTS 2,986,207 5/1961 Scogin 431/90 3,393,965 7/1968 Vaughan.. 431/12 3,522,661 8/1970 Scott r v r 431/2 X 2,976,689 3/1961 Dodds et a1; 137/100 X POST PURGE SYSTEM FOR GAS BURNERS BACKGROUND OF THE INVENTION This invention relates to a post purge system for a gas burner. More particularly, the invention relates to a post purge system for gas burners utilizing a fuel pressure sensing means in combination with a diaphragm, the diaphragm being responsive to the fuel pressure sensing means and in turn being the means for maintaining the actuation of an electrical circuit including a combustion air blower for a burning apparatus after the main fuel gas to the burning apparatus has been closed off.

In the purging of a fuel burning apparatus after the fuel gas has been shut off, many elaborate devices have been provided for operating the apparatus combustion air blower for a preselected period of time as means for purging unburned gas from the apparatus thereby providing avery desirable feature for any gas burning apparatus. Electrically operated timing devices have found wide acceptance as the means for maintaining the combustion air blower in operation after the main fuel gas has been shut down. These timing devices keep the combustion air blower energized for a preselected period of time after a fuel gas supply valve has been fluid 7 therein, fluid 7 being heavier than the fuel gas,

closed off or a pressure sensing means has indicated a fuel gas line pressure below a preselected pressure setting. Thus, for a preselected period of time, the combustion air blower remains in operation thereby purging the fuel burning apparatus. However, most of the arrangements utilizing electrical timing devices are quite expensive and elaborate in their construction.

SUMMARY OF THE INVENTION In the present invention, it is recognized that it is desirable to provide a post purge system for a gas burning apparatus which is inexpensive, durable, and easily installed. Furthermore, it is recognized that it is desirable to provide a post purge system which does not require elaborate electrical timing devices.

The present invention advantageously provides a straightforward arrangement for a post purge system for a fluid fuel burner which is inexpensive, durable and easily constructed. The present invention further provides for the utilization of a fuel pressuresensing means disposed between a main gas line and a diaphragm means, the diaphragm means being responsive through the pressure sensing means to the pressure in the main gas line, the diaphragm being in electrical communication with a combustion air blower to maintain actuation of the combustion air blower circuit after the main gas fuel line has been closed off.

Various other features of the present invention will become obvious to those skilled in the art upon reading the disclosure as set forth hereinafter.

More particularly, the present invention provides a post purge device for a fuel burning apparatus comprising: a main fluid fuel line in communication with a fluid fuel supply and a fuel burning apparatus; a fuel pressure sensing means disposed between the main fuel gas line and a diaphragm means, the fluid pressure sensing means having a first fluid therein responsive to pressure in the fuel gas line, the diaphragm means being operative in response to movement of the first fluid; and, a combustion air blower in electrical communicative relation with the diaphragm means.

It is to be understood that the description of the examples of the present invention given hereinafter are not by way of limitation and various modifications within the scope of the present invention will occur to those skilled in the art upon reading the disclosure as set forth hereinafter.

Referring .to the drawing:

FIG. 1 of the drawing diagrammatically illustrates one preferred apparatus of this invention; and,

FIG. 2 of the drawing diagrammatically illustrates another preferred apparatus of this invention.

The post purge device of the present invention in FIG. 1 includes a combustion air blower l to supply combustion air by means of conduit 2 to a fuel gas burner 3. Fuel gas to fuel gas burner 3 is supplied through conduit 4 which has a branch conduit 5 in communication with a fuel pressure sensing means illustrated as the U-tube 6.

The U-tube 6 defined by

legs

8 and 10, includes a such as, for example, a silicon oil. Leg 8 is in communication with branch conduit 5 and contains the fuel gas in the top portion and fluid 7 in the lower portion. The U-tube 6 further includes a restriction at the bend of the tube 6, the restriction being exemplified as a limiting orifice 9. Limiting orifice 9 is provided so that when the fuel gas pressure in the top of leg 8 is decreasing,

the flow of fluid 7 in the leg 10 is limited in its movement into the leg 8 in equalizing the pressures in the legs '8 and 10. Further description of the flow limiting orifice 9 will be discussed hereinafter.

Leg 10 of the U-tube 6 extends upwardly and communicates with a housing 11 which includes a diaphragm 12 therein. In the space between the top of the fluid 7 and the diaphragm 12 is a fluid l3, fluid 13 being lighter than the fluid 7 in theU-tube 6 and exemplified in the present example as air. The fluid 13 disposed between the fluid 7 and the diaphragm 12 maintains a pressure on the diaphragm 12, the amount of pressure on diaphragm 12 depending upon the level of the fluid 7 in leg 10. Housing 11 further includes an electrical contact switch 14 which is normally open but operable by the movement of a vertically extending rod 25 in response to movement of diaphragm 12. For example, when the diaphragm 12 moves upward, rod 25 urges normally open switch 14 closed and when diaphragm 12 moves downward in response to a decrease of the fluid 13 pressure in U-tube leg 10, rod 25 urges contact switch 14 to an open position. The lines com pleting the circuit between normally open switch 14 for blower 1 and the main power source are line 16 which is connected to the main switch 17 of the main power source and the line 15 disposed between switch 14 and blower 1. Line 18 is an electrical line connecting the combustion air blower l to a circuit within electrical box 24 which, through a plurality of connections (not shown), communicates with the line 19 leading from the box to the main power switch 17, thus completing a circuit including the normally open switch 14, switch 14 being actuated in response to the main fuel gas pressure through the aforementioned U-tube 6. The portion of theelectrical circuit disposed between

lines

18 and 19 may include, for example, safety control devices which open the circuit upon detection of an unsafe condition thereby de-actuating the combustion air blower l.

In the main gas line 4 is a solenoid operated valve 21, a pressure regulator 22, and a main gas supply valve 23. The solenoid operated valve 21 is of any suitable commercial construction. The operation of the solenoid valve 21 is by an electrical circuit (not shown) which is adapted to maintain the valve 21 in an open position during the operation of the gas burner 3. Pressure regulator 22 is included in the main fuel gas conduit line 4 to maintain a preselected pressure on the main gas line whenever the gas burner 3 is in operation. The main gas supply valve 23 is provided to manually control the gas to the gas burner 3.

, Under'normal operations of a burning apparatus, the combustion air blower 1 is energized and supplies combustion air to the burner 3 by way of conduit 2. Fuel gas flow to the burner 3 is maintained through fuel gas conduit 4 with fuel gas under line pressure being in contact with fluid 7 in leg 8. Pressure of the fuel gas on fluid 7 in leg 8 forces the fluid 7 into leg 10 thereby compressing the fluid 13 in leg 10. Diaphragm 12 being operable in relation to the pressure exerted by fluid 13 is maintained in an upwards position due to the pressure exerted by fluid 13 thereby maintaining switch 14 in a closed position through rod 25. Thus, as long as the fuel gas pressure in conduit 4 exceeds a predetermined fuel gas pressure setting, blower 1 will remain energized.

On the shut down and purging of the gas burner 3, the switch which energized the solenoid operated valve 21 is opened thereby closing valve 21. The volume of fuel gas in conduit 4 then decreases causing the fuel gas pressure in the top portion of leg 8 to decrease, the result being the fluid 7 in leg 10 moving into leg 8 replacing the void left by the fuel gas. Thus, the pressure on diaphragm 12 decreases in response to movement of fluid 7. However, the flow limiting orifice 9 restricts the flowof the fluid '7 from leg 10 into leg 8 thereby decreasing the pressure on diaphragm 12 at a rate slower than the decreasing pressure in conduit 4. At a preselected pressure on the diaphragm 12, the diaphragm 12 in combination with rod 25 will move downward a sufficient distance so that at a preselected point, switch 14 opens. Flow limiting orifice 9 having a predetermined opening therein will, determine the post purge time of the blower based upon the decreasing volume in leg 10 simultaneously decreasing pressure on diaphragm 12. If the opening in the orifice 9 is relatively small in comparison with the inside diameter of the U-tube 6, the time for the fluid in leg 10 to move through the orifice 9 and into leg 8 will require a much longer time than if the orifice 9 is relatively large.

FIG. 2 illustrates another preferred embodiment of the present invention including means for maintaining energization of the blower 1 under certain conditions even though switch 14 is open or the blower is disconnected from the circuit including the pressure switch 14. In this example, a second circuit is connected to blower l in parallel with the circuit including line 16 and switch 14. This circuit includes line disposed between switch 17 and blower 1. Line 30 is provided with a manual on-off switch 31 and a normally open contact switch 32, normally open contact switch 32 being operable to a closed position in response to actuation of relay 33. Also provided is a line 34 disposed between switch 14 and blower 1. Line 34 includes a normally closed contact switch 35, normally closed contact switch 35 being operable to an open position in response to actuation of relay 33.

Relay 33 is energized in response to changes in preselected operating conditions. For example, in electronic or amplifying type electrical combustion relays, the power supply to the combustion air blower generally provides line current for auxiliary safety devices which in turn powers the programming system of the combustion relay. Without the relay 33 a feed back situation would exist and an unsafe situation would result whereby the apparatus would continue to operate after the operating switch was satisfied and the burner was to be deactivated.

It will be realized that various changes may be made to the specific embodiment shown and described without departing from the spirit and scope of the present invention.

What is claimed is:

1. A post purge device for a fuel burning apparatus comprising:

a. a main fluid fuel line in communication with a fluid supply and a fuel burning apparatus;

b. a fuel pressure sensing means disposed between said main fluid fuel line and a diaphragm means, said fuel pressure sensing means being a U-tube having two legs with a flow limiting device therein, one leg of said U-tube being in communication with said main fuel gas line and the second leg of said U-tube being in communication with said diaphragm means, said fuel pressure sensing means having afirst fluid therein responsive to pressure in said fluid fuel line, said diaphragm means being opv erative in response to movement of said first fluid;

and,

c. a combustion air blower in electrical communicative relation with said diaphragm means.

2. The post purge device of claim 1, said first fluid being heavier than said fluid fuel, said U-tube having a second fluid in said second leg, said second fluid being lighter than said first fluid and disposed between said first fluid and said diaphragm means. i

3. The post purge device of claim 2 wherein said diaphragm means includes a rod in communication with a normally open switch, said switch being in an electrical circuit which includes said combustion air blower whereby upward movement of said rod in response to said second fluid pressure closes said switch and decrease in said second fluid pressure releases said rod whereby said switch is moved to an open position.

4. The post purge device of claim 1 including means for maintaining said combustion air blower energized under preselected conditions independent of said diaphragm means.

Claims

1. A post purge device for a fuel burning apparatus comprising: a. a main fluid fuel line in communication with a fluid supply and a fuel burning apparatus; b. a fuel pressure sensing means disposed between said main fluid fuel line and a diaphragm means, said fuel pressure sensing means being a U-tube having two legs with a flow limiting device therein, one leg of said U-tube being in communication with said main fuel gas line and the second leg of said U-tube being in communication with said diaphragm means, said fuel pressure sensing means having a first fluid therein responsive to pressure in said fluid fuel line, said diaphragm means being operative in response to movement of said first fluid; and, c. a combustion air blower in electrical communicative relation with said diaphragm means.

2. The post purge device of claim 1, said first fluid being heavier than said fluid fuel, said U-tube having a second fluid in said second leg, said second fluid being lighter than said first fluid and disposed between said first fluid and said diaphragm means.