US3834856A

US3834856A - Pilot reclamation system for gas-fires forced draft heater

Info

Publication number: US3834856A
Application number: US00393123A
Authority: US
Inventors: L James
Original assignee: Coleman Co Inc
Current assignee: Recreation Vehicle Products Inc
Priority date: 1973-08-30
Filing date: 1973-08-30
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10

Abstract

A pilot reclamation system energizes the combustion air blower of a heater before the pilot flame is completely extinguished from lack of oxygen so that the oxygen supply for the pilot flame is replenished. Sensing means for sensing the temperature of the pilot light is operatively connected to switch means for energizing the combustion air blower. The temperature sensing means includes plunger means which move the switch means to close a circuit for the blower motor when the temperature of the pilot light falls below a predetermined level. When the oxygen supply to the pilot light is replenished and the temperature of the pilot light rises above a predetermined level, the temperature sensing means allows the switch to move to the open position.

Description

United States Patent [191 James 1 Sept. 10,1974

[75] Inventor: Larry S. James, Wichita, Kans.

[73] Assignee: The Coleman Company, Inc.,

Wichita, Kans.

Primary ExaminerCarroll B. Dority, Jr.

[57] ABSTRACT A pilot reclamation system energizes the combustion air blower of a heater before the pilot flame is completely extinguished from lack of oxygen so that the oxygen supply for the pilot flame is replenished. Sensing means for sensing the temperature of the pilot light is operatively connected to switch means for energizing the combustion air blower. The temperature sensing means includes plunger means which move the switch means to close a circuit for the blower motor when the temperature of the pilot light falls below a predetermined level. When the oxygen supply to the pilot light is replenished and the temperature of the pilot light rises above a predetermined level, the temperature sensing means allows the switch to move to the open position.

9 Claims, 5 Drawing Figures PATENIED SEPI 01914 SNEU 2 BF 2 Hes PILOT RECLAMATION SYSTEM FOR GAS-FIRES FORCED DRAFT HEATER BACKGROUND This invention relates to forced draft, gas-fired heaters which make use of a pilot for main valve safety. Such appliances are often equipped with a combustion air blower for supplying combustion air to the area around the gas burner. However, when the heater is not on, i.e., when fuel is not being supplied to the burner and only the pilot light is lit, the combustion air blower is turnedoff. As a result, the area around the pilot light can become filled with combustion products, and insufficient oxygen may be available to sustain the pilot flame. Eventually, the pilot light may be extinguished, and the safety device on the mainfuel valve will shut the valve and prevent further operation of the heater. Before the heater can be used again, the pilot light must be relit.

The likelihood that the pilot light will be extinguished is increased if the heater is positioned in an area which is not supplied with fresh air. For example, heaters for recreational vehicles or mobile homes are frequently designed to fit into tight spacesbelow counters and the like, and such heaters are particularly susceptible to pilot flame outage.

SUMMARY The invention utilizes the combustion air blower to purge the pilot area of combustion products and toreplenish the oxygen supply before the pilot flame is completely extinguished due to lack of oxygen. The necessity of frequent relighting of the pilot light is therefore eliminated. The pilot reclamation system can be combined with a conventional safety'mechanism for the main valve, and the pilot reclamation system cooperates with the safety mechanism insuch a way that the operation of the safety mechanism is not affected. After the pilot light is supplied with oxygen, the blower motor is turned off.

DESCRIPTION OF THE DRAWING The invention will be explained in conjunction with an illustrative embodiment shown in the accompanying drawing, in which:

FIG. I is a front elevational view of a fuel valve equipped with a pilot reclamation system formed in accordance with the invention;

FIG. 2 is a side elevational view, partially broken away, taken along the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary view of the fuel valve similar to FIG. 2 showing the fuel valve in the on position when the pilot light is lit;

FIG. 4 is a fragmentary perspective view of the fuel valve and the pilot reclamation system when the fuel valve is on; and

FIG. 5 is a fragmentary partially schematic view.

DESCRIPTION OF SPECIFIC EMBODIMENT Referring now to FIGS. 1 and 2, thenumeral l0 designates generally a conventional main fuel valve for a gas-fired, forced draft heating appliance. For. example, the gas valve can be used with a furnace or heater for recreational vehicles similar to the furnace shown in US. Pat. No. 3,680,541.

The fuel valve is conventional and need not be described in detail, the particular fuel valve illustrated being manufactured by the Electric Products Division of The Eaton Corporation. The fuel valve includes a body or casing 11 having a fuel passage 12 provided therethrough. A shut-off valve within the casing is movable between an open position in which fuel can flow through the fuel passage 12 and a closed position in which fuel flow is prevented, and the shut-off valve is biased to the closed position.

The shut-off valve can be manually moved to the open position by pushing a plunger 13 to the left as viewed in FIG. 2, and as the shut-off valve is moved to the open position, a disc 14 mounted on a rod 15 is also moved to the left. The rod 15 is connected to the shutoff valve, and the valve can be retained in the on position after the plunger 13 is released by retaining the disc 14 in its extended position illustrated in FIG. 3. For this purpose a lever arm 16 having a cylindrical pin 17 secured thereto is mounted on an L-shaped support bracket 18. The lever arm is secured to the mounting bracket by screw 19 and bolt 20 (FIG. 3), and the bracket is secured to the valve body by screw 21. The support bracket 18 is formed from spring metal to provide a resilient mounting for the lever arm 16, and the spring mounting means biases the lever arm into the position illustrated in FIG. 2 in which the cylindrical pin 17 is below the periphery of the disc 14.

The lever arm 16 can be moved from the lower position of FIG. 2 to the raised position of FIG. 3 by a plunger or piston 23 which is slidably mounted in the valve body and which is movable by a temperature sensing means designated generally by the numeral 24. The temperature-sensing means includes a tubular mercury bulb 26 (FIGS. 1 and 5) which is connected to a bellows 27 by an elongated nietalzcapillary tube 28. The bellows is mounted within a cup-like closure 29 which is secured to the valve body below the piston 23, and the upper surface of the bellows engages the lower end of the piston.

The mercury bulb 26 is filled with mercury, and the bulb is adapted to be positioned adjacent the flame of a pilot light 30 (FIG. 5), which is mounted near burner 31 of the heater. When the pilot light is lit, the mercury within the bulb vaporizes, and the pressure within the bellows increases. The increased pressure within the bellows causes the bellows to expand to urge the piston 23 upwardly.

When the pilot light is to be lit, the plunger 13 is pushed to the left as viewed in FIG. 2 from the position shown in FIG. 2 to the position shown in FIG. 3 to open the shut-off valve within the valve body and to move the disc 14 to the left of the pin 17 which is carried by the lever arm 16. The plunger 13 islmanually retained in the depressed position while the pilot light islit. As the mercury bulb 26 is heated by the pilot flame, the bellows 27 raises the piston 23 which in turn moves the lever arm 16 upwardly about the pivot provided by the spring mounting bracket 18 to the position shown in FIG. 3. In this position the retainingpin 17 is raised to a position behind the disc 14, and the plunger 13 can be released. The disc 14 is retained in theposition illustratedinFlG. 3 by the pin, andthe shutoff valve is held in the open position. Fuel is thusfree to flow through the fuel valve 10 to the burner when the conventional thermostat which is associated with the appliance opens the valve which-supplies fuel-to the burner.

If the pilot light is extinguisheclrfor some reason, the mercury bulb 26 cools, andthe pressure withinthe bellows 27 decreases. Since the spring mounting bracket 18 urges the lever arm 16 into the lowered position illustrated in FIG. 2, the lever arm 16 and the piston 23 will be moved downwardly by the spring mounting bracket 17 as the pressure within the bellows decreases and the bellows contracts. Eventually, the retaining pin 17 will move below the periphery of the disc 14, and the disc 14 and the mounting rod will be moved back to the off position of FIG. 2 by the spring means associated with the shut-off valve. Thereafter, even if the thermostat calls for heat, the shut-off valve will remain closed, and no fuel will flow through the main valve.

The shut-off valve can be opened only by following the foregoing procedure in which plunger 13 is manually depressed and the pilot light is relit.

The foregoing is a description of a typical fuel valve which is equipped with a pilot safety mechanism and which utilizes plunger means actuated by temperaturesensing means to maintain the valve in the open position. When the temperature of the temperature-sensing means drops below a predetermined level due to extinguishment of the pilot flame, the plunger means is allowed to return to an unactuated or off position whereby the shut-off valve is released to return to the off position.

The pilot reclamation system formed in accordance with the invention cooperates with the conventional safety mechanism of a fuel valve to prevent extinguishment of the pilot flame bacause of insufficient oxygen. When the oxygen supply for the pilot flame is less than that needed to support full combustion, the pilot flame will begin to dim, and the temperature of the flame will decrease. This decrease in temperature will be sensed by the temperature-sensing means, and the pilot reclamation system will be actuated by the temperaturesensing means to turn on the motor of the combustion air blower before the temperature-sensing means permits the shut-off valve to be closed. The combustion air blower will supply fresh air to the area of the burner and the pilot light and will purge this area of combustion products so that the pilot flame can burn with full intensity.

An electric switch 34 is mounted by screws 35 (FIG. 1) on a plate 36 which depends from a mounting bracket 37 secured to the valve body. The particular mounting bracket 37 includes a planar upper plate 38 and a bottom plate 39 having a first end portion 39a which is secured to the bottom surface of the upper plate 38, as by spot welding, and a second end portion 39b which is offset downwardly from the upper plate 38 by an intermediate portion 390.

A switch lever arm 41 has one end thereof pivotally secured to the switch 34 at 42, and the other end of the switch lever arm rests on top of the lever arm 16 adjacent the retaining pin 17 (see particularly FIG. 4). The switch lever arm 41 engages a movable switch element 43 which opens and closes the circuit between the terminals of the switch.

A pair of wire leads 44 and 45 are connected to the switch terminals and connect the switch to the circuit of a blower motor 46 illustrated in FIG. 5. If desired,

the switch 34 can be connected in series with a battery saver switch 47 which opens the circuit of the motor if the pilot flame is completely extinguished. The battery saver switch is also operatively connected to the temperature sensing means and, since such a switch is well known in the art, will not be described in detail.

When the pilot flame is extinguished and the lever arm 16 of the valve safety mechanism is in the lowered position illustrated in FIG. 2, the switch lever arm 41 is also in a lowered position in which the switch element 43 is permitted to assume its closed position in which the switch terminals are connected. The switch element 43 is spring-biased to its closed position so that the switch is normally closed. However, even though the switch 34 is closed, the battery saver switch 47 is open, and the blower motor will not be energized.

After the pilot light is lit and the lever arm 16 is moved to its raised position illustrated in FIG. 3, the switch lever arm 41 is pivoted upwardly by the lever arm 16 to move the switch element 43 into its open position in which the circuit between the switch terminals is opened. In this position the blower motor will not be supplied with current through the circuit illustrated in FIG. 5, but another circuit can be provided in parallel to permit the blower motor to be energized when the thermostat calls for fuel to be supplied to the burner. This circuit would be the conventional circuit associated with the thermostat.

When the burner remains off for a period of time and the oxygen in the area of the pilot is consumed, the pilot flame begins to dim. This reduces the temperature of the mercury bulb 26, and the lever arm 16 begins to move downwardly under the influence of the spring mounting bracket 18 as previously described. As the lever arm 16 moves downwardly, the switch lever arm 41 follows the lever arm 16 downwardly, and the switch element 43 is eventually allowed to reach its closed position. The switch is set so that the switch element 43 reaches its closed position prior to the time at which the pilot flame would be completely extinguished, and

the closing of the switch 34 energizes the blower motor 46 so that fresh air is supplied to the area of the pilot. Since the blower is energized before the pilot flame is extinguished, the lever arm 16 is not lowered sufficiently to permit the pin 17 to release the disc 14, and the shut-off valve remains open. When fresh air is supplied to the pilot, the temperature of the pilot flame increases, and the increased heat on the mercury bulb 26 increases the pressure within the bellows and returns the lever arm 16 and the switch lever arm 41 to their raised positions. This again shuts off the blower motor until the pilot flame begins to dim again.

Since the switch 34 should be closed before the lever arm 16 is lowered sufficiently to release the disc 14, it is advantageous to provide adjusting means for adjusting the amount of travel of the lever arm required to permit the switch to close. In the embodiment illustrated, the adjusting means is provided by the mounting bracket 37.

The lower plate 39 of the mounting bracket is formed of spring metal, and the outer end 39b thereof is biased upwardly toward the upper plate 38. The spacing between the upper plate 38 and the outer end 39b of the lower plate can be adjusted by an adjusting screw 49 which is threaded through the upper plate 38 and locked in place by nut 50. Adjustment of the screw 49 causes the switch 34 to pivot with respect to the outer end of the switch lever arm 41 which engages the lever arm 16, and'this varies the distance which the switch lever arm 41 must travel before the switch element 43 is moved from an opened position to a closed position.

Since the switch lever arm 41 follows the lever arm 16 from the raised position to the lowered position in which the shut-off valve is closed, the switch lever arm does not interfere with the operation of the safety mechanism for closing the shut-off valve when the pilot flame is extinguished. The only force which is exerted on the lever arm 16 by the pilot reclamation means is the slight force exerted by the bias of the switch element 43 and the weight of the switch lever arm, and this force increases the tendency of the safety mechanism to move to the off position.

The particular pilot reclamation means shown in the drawing cooperates with the safety mechanism of the main fuel valve. However, the pilot reclamation means can also be provided as a separate system having an independent temperature-sensing means for sensing the temperature of the pilot flame.

Further, although mechanical means have been described for moving the plunger to actuate the switch means of the blower motor circuit, the temperaturesensing means can also be a conventional thermocouple or thermal generator which provides an electric current to a relay. When the pilot flame is burning normally, the thermal generator will energize the relay to maintain the blower motor circuit open. When the temperature of the pilot flame decreases, the current delivered by the thermal generator to the relay decreases. The relay can be selected to close the blower motor circuit when the temperature of the pilot flame falls to a certain lever, thereby energizing the blower motor to purge the pilot area. As the pilot flame and the thermal generator heat up, the relay is again energized to open the blower motor circuit;

While in the foregoing specification detailed descriptions of specific embodiments of the invention were set forth for the purpose of illustration, it is to be understood that many of the details herein given may be varied considerably by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. A pilot reclamation system for a gasfired forced draft heater having burner means, a pilot light adjacent the burner means for igniting the burner means, an air blower for supplying combustion air to the burner means, the air blower having an electric blower motor, and a circuit for supplying electric current to the blower motor, the pilot reclamation system comprising means for sensing the temperature of the pilot light, switch means associated with the temperature-sensing means, the temperature-sensing means moving the switch means to close said circuit when the temperature of the pilot light falls below a predetermined level and moving the switch means to open said circuit when the temperature of the pilot light rises above a predetermined level whereby the air blower supplies air to the area of the burner means when the temperature of the pilot light falls below a predetermined level.

2. The system of claim 1 in which the switch means is an electrical switch having open and closed positions, the temperature-sensing means including movable plunger means for mechanically moving the switch between the open and closed positions.

, 3. The system of claim 1 in which the heater IS equipped with a fuel valve for supplying fuel to the burner means, the temperature-sensing means being associated with the fuel valve and including movable retaining means movable in response to the temperature of the pilot light, shut-off means on the fuel valve movable between an open position in which fuel may flow to the burner means and a closed position in which fuel is shut off from the burner means, the shut-off means being biased to the closed position and being maintained in the open position'by theretaining means when the pilot light is lit, the retaining means being movable to release the shutoff means when the pilot light goes out whereby fuel flow to the burner means is shut off, the switch means being an electrical switch having open and closed positions, lever means engaging the retaining means for movement therewith, the lever means closing the switch before the retaining means releases the shut-off means.

4. The system of claim 3 in which the lever means is adjustable to vary the distance which the retaining means moves before the switch is closed.

5. The system of claim 3 in which the retaining means includes a reciprocably mounted plunger movable between extended and retracted positions and a first lever arm pivotally mounted on the fuel valve and movable between first and second positions, the first lever arm being biased toward the first position, the plunger being engageable with the first lever arm as the plunger moves from the retracted to the extended position to move the first lever arm from the first to the second position, the first lever arm maintaining the shut-off means when the first lever arm is moved to the first position, said lever means for closing the switch including a second lever arm pivotally mounted on the fuel valve and engaging the first lever arm so that the second lever arm is moved by the first lever arm as the first lever arm moves from the first to the second position, the second lever arm maintaining the switch in the open position when the first lever arm is in the second position, the second lever arm permitting the switch to close as the first lever arm moves from the second position toward the first position.

6. Pilot reclamation means for a fuel valve for supplying fuel to a fuel burner, the fuel valve having;

a. shut-off means movable between open and closed positions and being biased toward the closed position,

b. retaining means movable between a first position and a second position and being biased toward the first position, the retaining means being engageable with the shut-off means when the retaining means is in the second position to maintain the shut-off means in the open position and releasing the shutoff means when the retaining means moves toward the first position to close the shut-off means,

c. temperature-sensing means associated with the retaining means and adapted to sense the temperature of a pilot light, the temperature-sensing means including means for moving the retaining means toward the second position as the temperature of the pilot light increases, the retaining means being in the first position when the pilot light is out whereby the retaining means maintains the shut-off means open when the pilot light is lit and permits the shut-off means to close when the pilot light goes out,

the pilot reclamation means comprising d. a switch mounted on the fuel .valve and adapted to be connected to the motor of a combustion air blower for the fuel burner, the switch having a switch element movable between open and closed positions,

e. a switch arm pivotally mounted on the fuel valve and being engageable with the switch element; the switch arm being engaged by the retaining means when the retaining means is in the second position whereby the switch element is maintained in the open position by the switch arm, movement of the retaining means from the second position to the first position permitting movement of the switch arm, movement of the switch arm permitting the switch element to move to the closed position before the retaining means reaches its first position whereby the motor of the combustion air blower will be energized before the pilot light goes out.

7. The structure of claim 6 in which the switch element is biased toward the closed position.

8. The structure of claim 6 in which the retaining means includes a reciprocably mounted plunger movable between extended and retracted positions and a lever arm pivotally mounted on the fuel valve and movable between first and second positions, the lever arm being biased toward the first position, the plunger being engageable with the lever arm as the plunger moves from the retracted to the extended position to move the lever arm from the first to the second position, the lever arm maintaining the shut-off means in the open position when the lever arm is in the second position and releasing the shut-off means when the lever arm is moved to the first position to permit the shut-off means to move to the closed position, the switch arm engaging the lever arm and being movable therewith to open and close the switch.

9. The structure of claim 6 including adjusting means for varying the distance which the switch arm must move before the switch element is moved from the open position to the closed position.

Claims

1. A pilot reclamation system for a gas-fired forced draft heater having burner means, a pilot light adjacent the burner means for igniting the burner means, an air blower for supplying combustion air to the burner means, the air blower having an electric blower motor, and a circuit for supplying electric current to the blower motor, the pilot reclamation system comprising means for sensing the temperature of the pilot light, switch means associated with the temperature-sensing means, the temperature-sensing means moving the switch means to close said circuit when the temperature of the pilot light falls below a predetermined level and moving the switch means to open said circuit when the temperature of the pilot light rises above a predetermined level whereby the air blower supplies air to the area of the burner means when the temperature of the pilot light falls below a predetermined level.

3. The system of claim 1 in which the heater is equipped with a fuel valve for supplying fuel to the burner means, the temperature-sensing means being associated with the fuel valve and including movable retaining means movable in response to the temperature of the pilot light, shut-off means on the fuel valve movable between an open position in which fuel may flow to the burner means and a closed position in which fuel is shut off from the burner means, the shut-off means being biased to the closed position and being maintained in the open position by the retaining means when the pilot light is lit, the retaining means being movable to release the shutoff means when the pilot light goes out whereby fuel flow to the burner means is shut off, the switch means being an electrical switch having open and closed positions, lever means engaging the retaining means for movement therewith, the lever means closing the switch before the retaining means releases the shut-off means.

6. Pilot reclamation means for a fuel valve for supplying fuel to a fuel burner, the fuel valve having; a. shut-off means movable between open and closed positions and being biased toward the closed position, b. retaining means movable between a first position and a second position and being biased toward the first position, the retaining means being engageable with the shut-off means when the retaining means is in the second position to maintain the shut-off means in the open position and releasing the shut-off means when the retaining means moves toward the first position to close the shut-off means, c. temperature-sensing means associated with the retaining means and adapted to sense the temperature of a pilot light, the temperature-sensing means including means for moving the retaining means toward the second position as the temperature of the pilot light increases, the retaining means being in the first position when the pilot light is out whereby the retaining means maintains the shut-off means open when the pilot light is lit and permits the shut-off means to close when the pilot light goes out, the pilot reclamation means comprising d. a switch mounted on the fuel valve and adapted to be connected to the motor of a combustion air blower for the fuel burner, the switch having a switch element movable between open and closed positions, e. a switch arm pivotally mounted on the fuel valve and being engageable with the switch element, the switch arm being engaged by the retaining means when the retaining means is in the second position whereby the switch element is maintained in the open position by the switch arm, movement of the retaining means from the second position to the first position permitting movement of the switch arm, movement of the switch arm permitting the switch element to move to the closed position before the retaining means reaches its first position whereby the motor of the combustion air blower will be energized before the pilot light goes out.