The present invention relates to a clothes dryer and, more particularly, to the strategic placement of temperature-dependent switches within the dryer cabinet which switches operate to disconnect power to the electrical wiring in the dryer and to reduce the risk of fire occurring in the dryer cabinet.
Clothes dryers typically circulate heated air through a rotating drum in order to remove the moisture from wet clothing placed therein. There has been a concern with respect to the build up of excess heat in the drum or in some areas of the dryer cabinet which can potentially cause a fire to occur in the dryer drum or within the cabinet itself.
U.S. Pat. No. 6,655,047 issued to Miller, II discloses a fire detection means which emits a signal that can trigger an electrical disconnect means in response to the signal. The electrical disconnect means de-energises the heat source and blower of the dryer. The disconnect means may comprise a fails-open relay, a switch or normally open solenoid valves. In a gas dryer, it may comprise normally closed solenoid valves. The electrical disconnect means can be located between the power cord and the source of electrical power to the dryer, within the dryer enclosure, within the main breaker box supplying power to the dryer, or within any of the other components receiving electrical power in the vicinity of the dryer. The detectors may also be located along the ventilation or exhaust path.
U.S. Pat. No. 6,715,216 issued to Salameh et al. teaches temperature detectors that can signal a controller to deactivate the heater, the motor and the blower when a fire condition is detected. The temperature detector may comprise a normally open bi-metal thermostat that can be positioned adjacent the drying chamber, such as at the inlet and the outlet of the drying chamber. The temperature detector sends a signal to the controller when a set point at the location of the detector has been reached or exceeded. It appears that some power must reach the dryer to run the controller even after a fire is detected.
Neither of U.S. Pat. No. 6,655,047 and U.S. Pat. No. 6,715,216 teaches the energization of a relay by thermostats to disconnect power to the dryer circuitry. Further, neither of these two documents teaches the strategic placement of the thermostats within the dryer cabinet in order to have fire protection means in specific areas of the dryer in which excess heat may accumulate.
As a result of testing done on domestic clothes dryers, it has been determined that excess heat may accumulate within the dryer cabinet, which can cause fires to occur within the dryer cabinet. The mere use of temperature detectors in dryer cabinet may not be sufficient to reduce the risk of fire due to excess heat accumulation. Further, the use of power disconnect devices external to the cabinet may be too slow or not sufficiently sensitive to disconnect power from the dryer when a fire condition is initially detected. Systems which require a signal to be sent to a control center which then disconnects power to the dryer are complex and may also have slow response times in the event of a fire detection. Further, such systems may supply power to the control center even after a fire is detected and power is disconnected from the components. Consequently there is a need in domestic clothes dryers to provide for a sensitive means of power disconnection to the dryer electrical load such that these high heat areas are strategically targeted for protection that results in a power disconnect to the electrical wiring in the cabinet.
The present invention relates to a clothes dryer and, more particularly, to the strategic placement of temperature-dependent switches which energize a relay upon detection of excess heat within the cabinet. The energized relay in turn disconnects power to the electrical load to reduce the risk of fire occurring in the dryer cabinet. The interruption of power to a relay using thermostats allows heat to be readily detected in one or possibly a plurality of areas within the dryer cabinet, while disconnecting power to the electrical load.
It is important to disconnect power to the clothes dryer electrical load in the event of a fire in the cabinet of the dryer to diminish the chances of a fire spreading outside of the dryer cabinet. Further, the disconnection of power during a fire condition may prevent arcing caused by heat damaged wires. Hence, it is advantageous to have as many potentially high heat areas in the cabinet protected in order to prevent the initiation of a fire condition.
In accordance with one embodiment of the present invention there is provided a clothes dryer comprising a cabinet and a dryer drum mounted within the cabinet. The dryer has ducting associated therewith for directing air flow into and through the dryer drum to dry clothing articles placed in the drum. The dryer further comprises a power cord for supplying power from a power source to an electrical load in the cabinet. The power cord comprises a cord neutral wire line and at least one entry live wire line which pass into the cabinet. The electrical load is connected in circuit with the power cord neutral wire line and at least one load live wire line. The dryer further comprises a control circuit for controlling the supply of power from the power source to the electrical load. The control circuit comprises a relay which comprises a switch positioned between the at least one entry live wire line and a corresponding load live wire line. The switch is normally biased closed to allow power to flow from the live wire entry line to the corresponding load live wire line. The relay comprises an electromagnet which, when energized opens the normally closed switch to disconnect power between the live wire entry line and the corresponding load live wire line . The dryer further comprises an electromagnet control circuit connected in circuit between at least one of the entry live wire lines and the cord neutral line. The electromagnetic control circuit comprises at least one temperature-sensing thermostat mounted within the cabinet external of the drum and associated ducting, the at least one temperature-sensing thermostat being normally open and closing in response to excessive heat in the cabinet. Power is normally disconnected from the electromagnet control circuit to de-energize the electromagnet to close the switch. Power flows through the electromagnet control circuit when the temperature sensing thermostat closes in response to excessive heat in the cabinet thereby energizing the electromagnet and opening the switch.
In an alternative embodiment of the present invention, the power cord is electrically connected to a terminal box mounted on the wall of the cabinet. One of the terminal box and the power cord has a cord neutral wire line and at least one entry live wire line. The neutral line is connected in electrical circuit with the electrical load.
In another alternative embodiment of the present invention, the electromagnet control circuit comprises a plurality of thermostats located in different areas of the cabinet and electrically connected in parallel. This arrangement provides the advantages wherein a plurality of locations within the cabinet may be protected simultaneously and only one of the temperature-dependent switches may be required to close to energise the relay to disconnect the electrical load from the power source.
In another embodiment, the cabinet further comprises a wiring entry opening through which the power cord neutral wire line and the at least one entry live wire line pass into the cabinet. The relay may be located adjacent the wiring entry opening. This permits power to be disconnected from the dryer at the point of entry of the power cord into the dryer. It is well known that a fire condition may cause damage to the wire coating protecting wires from short circuits. Short circuits have the potential to increase the risk of a fire condition. By disconnecting power at the point of entry, potential further damage caused by shorts along the power supply line are reduced or are avoided. The electrical load may comprise at least one motor and an electronic power supply.
For a more thorough understanding of the nature and objects of the present invention reference may be had, by way of example, to the accompanying diagrammatic drawings in which:
The present invention relates to a clothes dryer and, more particularly, to the strategic placement of temperature-dependent switches which connect power to a relay, upon detection of excess heat within the dryer cabinet. The connected relay in turn disconnects power to the electrical load to reduce the risk of fire occurring in the dryer cabinet.
Referring to
Within the cabinet 12 is a drum or container 26 mounted for rotation around a substantially horizontal axis. A motor 44 rotates the drum 26 about the horizontal axis through, for example, a pulley 40 and a belt 42. The drum 26 is generally cylindrical in shape, has an outer cylindrical wall 28, and has an open end 27 that typically comprises a metal ring 29 attached by welding to the drum 26 for reducing the diameter of the opening of the drum 26 to match a front bulkhead wall or front bearing 30. The bearing 30 further defines an opening 32 into the drum 26. Clothing articles and other fabrics are loaded into the drum 26 through the opening 32. A plurality of tumbling ribs (not shown in figures) are provided within the drum 26 to lift the articles and then allow them to tumble back to the bottom of the drum as the drum rotates.
The drum 26 includes a drum rear wall 34 rotatably supported within the main housing 12 by bearing 35. The drum rear wall 34 includes a plurality of holes (not shown) that receive hot air that has been heated by a heater comprising electrical heating elements 64 (
Although the exemplary clothes dryer 10 shown in
Air heated by the heater is drawn into and from the drum 26 by a blower fan 48 which is also driven by a second motor 49 in the embodiment shown. In an alternative embodiment, motor 44 may be used to drive blower fan 48. Air is drawn by the blower fan 48 from the heater housing 22, into, through and out of the drum 26, through a grill 45 and screen filter 46. Grill 45 keeps clothing articles tumbling in the drum 26 from contacting the filter 46 and touching the lint trapped by the filter 46 within the trap duct 50. As the air passes through the screen filter 46, it flows through lower duct portion 51 and is blown by blower wheel 48 attached to motor 49 out of the clothes dryer 10 through an exhaust duct 52. In this embodiment, the drum 26 is in air flow communication with the trap duct 50 whose lower duct portion 51 has an outlet that is in air flow communication with the blower wheel 48 and the exhaust duct 52. The exhaust duct 52 passes through the rear panel 16 and is usually connected to suitable venting (not shown) that vents the air outdoors.
After the clothing articles have been dried, they may be removed from the drum 26 via the opening 32. Opening 32 is shown closed by a window or port-hole like door 60. Door 60 has a handle 62 for pivotally opening the door about hinge 65.
The dryer 10 is shown to have a control panel 54 with touch and or dial controls 56 that permit the user to control operation of dryer 10.
Referring to
In
Control circuit 117, as shown in
Referring still to
Referring to
During the operation of the dryer 10, heat may accumulate in excess in areas within the dryer cabinet 12. Heat may be caused, for example, by the operation of the motor 44 or the heating elements 64. Spaces within the cabinet 12 that are prone to excessive heat accumulation or to a fire condition are determined through testing. For optimal protection, adjacent or within each space may be located a thermostat 112. Accordingly, although a plurality of thermostats 112 are shown in
The placement of the relay 104 is preferably close to the wiring entry opening 100. As shown in
It should be understood that for a gas dryer, the amount of power to the dryer is reduced since the heating is achieved by combustion of natural gas or propane gas, and not by electrical heating elements. As a result, wiring for this arrangement typically comprises one power line and one neutral line entering into the dryer drum and rated at 120V and 15 Amps. A power cord connected to the dryer includes a power line, a neutral line and a grounding wire line. The grounding wire is grounded to the chassis or cabinet 12 of the clothes dryer 10. A terminal box is used similar to that shown in
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the scope of the present invention as disclosed herein.
Number | Date | Country | Kind |
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2,651,546 | Jan 2009 | CA | national |
This application is related to the US patent application entitled “CLOTHES DRYER FIRE SAFEGUARD CIRCUIT WITH DE-ENERGIZED RELAY CUTOFFS” (Dkt. No. CWC-274), U.S. Ser. No. ______ filed _______, commonly assigned to Mabe Canada, Inc.