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This disclosure relates to fire containment systems for use in household or commercial appliances and, in particular, to a fire containment system for a vented clothes dryer appliance.
A combination clothes washer-dryer appliance is especially suitable for installation and use in tightly confined living spaces such as those in motor homes, yachts, recreation vehicles, and condominiums. Combination washer-dryer appliances are available with either a non-vented condenser dryer or a vented dryer.
A combination washer-non-vented condenser dryer has a closed outer tub constructed with a sealed separate condenser section to enable a drying process. A wash load of clothes is contained in an inner tub or basket that is mounted for rotation inside the outer tub. An air-circulating fan draws air internally from the rear of the outer tub, passes the air over a heating element of a heater box assembly attached to the top of the outer tub, and returns the heated air to the front of the outer tub by way of an inlet through a door seal. Warm air travels through and collects moisture from a wash load tumbling in the basket as it rotates. The hot, moist air extracted from the wash load travels through the condenser section where a cold water stream, at a typical rate of 2 gal/hour (7.57 l/hr), condenses the moisture into water. The water is then pumped out of the appliance through its water discharge hose. Relatively dry air is then drawn back over the heating element to repeat the process. The air-circulating fan, a one shot cut-out or thermal fuse cable, and a thermistor located in the heater box assembly control the air temperature.
A combination washer-vented dryer performs a drying process by means of a water-sealed outer tub, with an exhaust outlet located above a washing high water operating level and at the rear of the outer tub. Outside air enters beneath a blower assembly and is passed over a heating element encased in a cast aluminum heater housing attached to the top of the outer tub. Forced air developed by the blower assembly enters the front of the outer tub through an inlet opening in a door seal. Air circulates through a wash load tumbling in the basket as it rotates inside the outer tub. Moisture-carrying air extracted from the wash load exits the outer tub through an exhaust outlet pipe.
Clothes dryer appliances sold in the United States must meet the UL 2158 Dryer Fire Containment Standard, which entails passing four fire containment tests including static tumbler (drum load fire), dynamic tumbler (drum load fire), static tumbler (base lint fire), and dynamic tumbler (base lint fire) tests. Meeting this UL standard is particularly challenging for vented dryer appliances because they do not operate with a closed air system.
What is needed, therefore, is a fire containment system for vented clothes dryer appliances. What is especially needed is a fire containment system that can be implemented in a commercially available combination clothes washer-vented dryer appliance with minimal structural changes to it.
A preferred embodiment of a fire containment system is implemented in a combination washer-dryer appliance equipped with air-vented exhaust. The fire containment system causes cold water flow through a fire suppression fluid conduit and into an interior space of a tub of the appliance to contain and extinguish a fire burning within the interior space.
The appliance includes a cold water inlet in fluid communication with multiple cold water valve outlets to which different ones of valve actuators are associated. The multiple cold water valve outlets are configured for selective delivery of cold water along associated conduits to the interior space of the tub and are actuatable in response to valve control signals applied to associated ones of the valve actuators.
The fire suppression fluid conduit is connected between one of the multiple cold water valve outlets and a fire suppression fluid inlet positioned in a top portion of the tub to provide a path of cold water flow into the interior space of the tub. A preferred fire suppression fluid conduit is a flexible water hose.
A water-resistant electromechanical switch is set in an aperture formed in and positioned in the top portion of the tub. The electromechanical switch has a heat sensitive surface and is secured in a fluid-tight seal to the tub so that the heat sensitive surface is exposed to the interior of the tub to measure an internal temperature in the interior of the tub. The electromechanical switch has electrical conductors for providing first and second switching states that indicate respective first and second electrical conduction conditions of the electromechanical switch, and the electromechanical switch is characterized by upper and lower temperature thresholds. The first electrical conduction condition represents a presumed presence of fire in the interior space of the tub and is developed in response to a rise in the measured internal temperature above the upper temperature threshold and to a subsequent fall in the measured internal temperature to the lower temperature threshold. The second electrical conduction condition represents a presumed absence of fire in the interior space of the tub and is developed in response to the measured internal temperature when it is below the lower temperature threshold.
A valve control signal applied to the valve actuator associated with the one of the multiple cold water valve outlets connected to the fire suppression fluid inlet actuates the one cold water valve outlet upon occurrence of the first switching state of the electromechanical switch. The valve control signal thereby causes cold water flow through the fire suppression fluid conduit and into the interior space of the tub to contain and extinguish a fire burning within the interior space.
An alternative preferred embodiment of a fire containment system is implemented in a steam-injected dryer appliance. This can be done by actuating cold water flow not to produce steam as intended for use in a normal drying cycle but instead in response to a thermostat measurement of temperature indicating a presumed presence of fire burning within the interior space of the tub.
Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.
With reference to
Valve outlet 18o of hot water valve 18 and valve outlets 30o and 32o of cold water valve 22 deliver separate streams of water to corresponding separate water flow channels of a manifold 36. Hot water delivered from valve outlet 18o and cold water delivered from valve outlet 30o flow through their associated channels of manifold 36 and drop into a formed hopper 38 located at a terminus 40 of manifold 36. Cold water delivered from valve outlet 32o flows through its associated channel of manifold 36 to additive tray 24 and then drops into hopper 38. Manifold 36 replaces separate hoses that were used in earlier model appliances.
Appliance 10 has a wash load front door 42 through which a user accesses an interior space 44 of outer tub 14 to place in a perforated stainless steel drum or basket 46 a load of laundry to be washed and dried. Basket 46 is positioned for rotation about a horizontal axis inside outer tub 14. Basket 46 has in its bottom and side portions an array of mutually spaced apart holes 48 (
Fire containment system 12 includes a flexible, ribbed water delivery hose 58 and a water-resistant thermostat 60 that are fitted with fluid- or water-tight seals into respective apertures or holes 62 and 64 formed in an upper portion 66 of outer tub 14. Water delivery hose 58 is connected between valve outlet 34o of cold water valve 22 and hole 62 in outer tub 14. Valve outlet 34o provides to water delivery hose 58 a strong flow of fire-extinguishing cold water for discharge into outer tub 14 and basket 46 through its holes 48. Water delivery hose 58 functions as a fire suppression fluid conduit. Water delivery hose 58 is positioned at a convenient location on upper portion 66 of outer tub 14 so that water delivered from valve outlet 34o and flowing through water delivery hose 58 sprays directly through proximally situated holes 48 in basket 46 and into interior space 44 of outer tub 14.
Thermostat 60 is an electromechanical switch, preferably a bimetal disk temperature-controlled device, which is set in hole 64 formed in upper portion 66 in proximity to hole 62 where water delivery hose 58 is connected. A preferred thermostat 60 is a 36T series snap-action temperature control of a close on temperature rise type, which is available from Therm-O-Disc, Inc., Mansfield, Ohio, a wholly owned subsidiary of Emerson Electric Co., St. Louis, Mo.
Thermostat 60 is characterized by upper and lower temperature thresholds and produces a control signal in first and second states. The first state of the control signal is indicative of a first or closed circuit electrical conduction condition of thermostat 60. The closed circuit condition of thermostat 60 represents a presumed presence of a fire burning in basket 46 positioned in interior space 44 of outer tub 14 and is developed in response to a rise in the measured internal temperature above the upper temperature threshold and to a subsequent fall in the measured internal temperature to the lower temperature threshold. The second state of the control signal is indicative of a second or open circuit electrical conduction condition of thermostat 60. The open circuit condition of thermostat 60 represents a presumed absence of fire in basket 46 positioned in interior space 44 of outer tub 14 and is developed in response to the measured internal temperature when it is below the lower temperature threshold.
The upper temperature threshold represents a temperature set above a maximum operating temperature limit reached during a normal drying cycle of appliance 10. Setting the upper temperature threshold in this manner provides a safety factor against activating cold water flow through water delivery hose 58 during normal extreme dryer operation. The upper temperature threshold is within a temperature range of between about 90° C. and about 110° C., and preferably at about 105° C.
The lower temperature threshold represents a temperature below the upper temperature threshold by a nominal temperature differential established by thermostat 60. The reason is that the upper temperature threshold of thermostat 60 is set and the nominal temperature differential characteristic of a particular thermostat 60 establishes the lower temperature differential. A suitable thermostat 60 is, therefore, one in which the lower temperature threshold is sufficiently low to indicate cessation of a fire presumed to have been burning in interior space 44 of outer tub 14. The lower temperature threshold is within a temperature range of between about 40° C. and about 53° C., and preferably at about 50° C.
Electric valve actuator 34a and thermostat 60 are connected in electrical series, with a wire 80 connecting a terminal 82 of electric valve actuator 34a to a terminal 84 of thermostat 60. A wire 86 connects a terminal 88 of valve actuator 34a to line wire terminal L, and a wire 90 connects a terminal 92 of thermostat 60 to line wire terminal N. Thermostat 60 opens and closes the electrical circuit between wires 80 and 90 and thereby establishes the first and second states of the control signal applied to valve actuator 34a to control water flow from valve outlet 34o of cold water valve 22.
Delivering the control signal in the first state to valve actuator 34a provides cold water flow from valve outlet 34o, through water delivery hose 58, and into basket 46 and outer tub 14, thereby to contain and douse a fire burning in basket 46 positioned in interior space 44 of outer tub 14. Cold water flow through water delivery hose 58 continues until thermostat 60 measures an internal temperature of interior space 44 of outer tub 14 below the lower temperature threshold, indicating that the fire is presumed to have been extinguished. An internal temperature below the lower temperature threshold causes thermostat 60 to deliver the control signal in the second state to valve actuator 34a to shut off water flow from valve outlet 34o and thereby stop discharge of water into basket 46 and outer tub 14.
Appliance 10 further comprises an overflow feature, which is standard in commercially available high-end combination washer-dryer appliances and includes a main discharge pump 104 operating in conjunction with a pressure switch (not shown). The pressure switch sends a water level signal to discharge pump 104 to actuate it and thereby cause water to drain from outer tub 14 when water filling interior space 44 reaches a predetermined high water level set by the pressure switch. Fire containment system 12 takes advantage of this overflow feature, which prevents a water overflow condition in outer tub 14 when cold water flows through water delivery hose 58 and into basket 46 and outer tub 14 to extinguish a fire burning in basket 46.
There is needed minimal modification of a prior art combination washer-vented dryer appliance to implement fire containment system 12. The modifications of appliance 10 to integrate fire containment system 12 entail only cutting holes 62 and 64 in upper portion 66 of outer tub 14, connecting water delivery hose 58 between valve outlet 34o of cold water valve 34 and hole 62, setting thermostat 60 in hole 64, and connecting wires 80, 86, and 90 as described above.
An inherent disadvantage of fire containment system 12′ is that the cold water delivered by cold water fill valve 30 is discharged from manifold 36 and into the bottom of outer tub 14, not directly from upper portion 66 of outer tub 14, through holes 48 in basket 46, and directly onto the burning clothes and fire. Water flows from inner tub 14 and into basket 46 through its holes 48 as inner tub 14 fills with water. The indirect delivery of water into basket 46 adversely impacts the effectiveness of fire containment system 12′ by appreciably increasing the time for delivery of a sufficient amount of water to douse a fire in basket 46 positioned inside outer tub 14.
It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. For example, a steam-injected dryer appliance can be configured to implement the disclosed fire containment system. This can be done by actuating cold water flow not to produce steam as intended for use in a normal drying cycle but instead in response to a thermostat measurement of temperature indicating a presumed presence of fire burning in the basket. The scope of the present invention should, therefore, be determined only by the following claims.
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