Patent Application
20150033576
The present invention relates to an electrical safety circuit for a completely, quickly and safely de-energizing home appliances, mainly de-energizing a dryer machine when a user inadvertently charges the dryer machine with garments or other articles which are contaminated with solvents, which could lead to a fire risk if said apparatus is left unattended by the user, and further due to the fact that today most garments are made of synthetic materials which are more flammable than garments made of cotton.
As a consequence, the Underwriters Laboratories Inc. (UL), a product safety certificating organization, released a new version of its safety standard for electric clothes dryers listing—Standard UL2158 for Electric Clothes Dryers—wich is in force since march 2013, which have stringent requirements for fire containment in appliances. Accordingly, the present invention provides a de-energizing electrical safety circuit comprising, in a preferred embodiment, a normally open thermostat and two switches as part of its electrical facility, thus reducing the user risks in case of fire, particularly if the user tries to extinguish fire by using water.
It is well known that risky situations exist, especially when the user fails to follow the usage recommendations described in the appliance manuals. Said risky situations can lead to malfunctions of the home appliances or even fire.
This subject is so relevant that, according to a study carried out by the U.S. Department of Homeland Security between 2002 and 2004, (Clothes Dryer Fires in Residential Buildings, Topical Fire Research Series. Vol. 7, issue 1, January 2007), about 15,600 fires that requires firemen intervention are originated either by a wrong installation of the dryer machine or lack of maintenance of the machine by the user. Is estimated that these fires annually cause economic loses by an amount that rises approximately $99 million, in addition to 400 injuries and 15 deaths.
It is noteworthy that 80% of fires caused by misuse of clothes dryer machines occur in residential buildings, including, within this category, single or multifamily homes, mobile homes, hotels and motels, bedroom type residences, grove huts, and the like.
Fire can start mainly when the user inadvertently place in the dryer machine garments or other articles which are contaminated with solvents, this can lead to fire risk if the dryer machine is left unattended by the user, in addition to the fact that, today most garments are made of synthetic materials which are flammable more than garments made of cotton.
As a consequence, in 2009, the Underwriters Laboratories Inc. (UL), a product safety certificating organization, released a new version of its safety standard for the electric clothes dryers listing—Standard UL2158 for Electric Clothes Dryers—which is in force since early 2013, which includes aggressive fire testing that must be successfully passed in order for said dryers machines to be granted with the UL listing. Modifications made to standard UL2158 have as an object the reduction of quantity or severity of fires related to clothes dryers in residential buildings caused by user negligence.
In order to fulfill safety requirements, several tests have been carried out on home clothes dryers, which have allowed determine that arcing (electric arc formation) between cables within the dryers cabinet is as well a factor that can lead to fire on cable sheaths, and extending fire to other dryer areas originating a fabric hanging above the dryers cabinet on fire, wherein the fabric corresponds to clothes left by the user on the dryer's top cover. Tests have demonstrated that this arcing is also a factor that can cause fire to fabric when dust or lint is trapped in the dryer or other items placed on or besides the dryer by the user. The mere use of switches or fuses on the electric facility circuitry of power lines, may not be enough to completely de-energize the dryer's electrical system in order to avoid arcing between powered or energized cables. Further, with the use of power disconnection devices other than fuses, such as the use of thermo magnetic or thermoelectric breakers, mainly when these are aged devices, disconnection can be too slow or, they are not sensible enough to disconnect the dryer's power when an initial arcing between cables occurs. Also, power disconnection devices might not protect against arcing because fire occurs randomly and the power disconnect device does not react to potential fire causes, resulting fire produced whether inside or outside the dryer cabinet.
Accordingly, in order to reduce the fire risk or its severity, and so as to comply with standard UL2158, a number of modifications have been made to clothes dryers. Among the inventions that can be cited in this respect are the following:
U.S. Pat. No. 5,315,765 (1994) by Melvin Holts et al. discloses high efficiency circuitry for a microwave dryer, wherein powered wire lines have each a fuse in circuit connection therewith. A third fuse is connected in circuit with a DC power source. This patent shows these fuses as power limit fuses. There are no teachings about physical location of these fuses within the dryer's cabinet.
U.S. Pat. No. 6,715,216 B1 (2004) by Naom Salameh, et al. provides a clothes dryer with a fire detector therein and a suppressor system that releases a fire suppressor substance in the dryer chamber when a fire condition is detected. Similar to the patent document KR 20060103581 (2006) by Kim Choul Geun, the system described in patent document U.S. Pat. No. 6,715,216 B1 (2004) by Naom Salameh, et al, does not consider power turn off, thus causing that, even though the suppressor substance, proposed in said patent document, is released, said suppressor substance may not be enough for fire extinction because electric power still present in the clothes dryer.
Kim Choul Geun's KR 20060103581 (2006), discloses an apparatus for extinguishing fire that is originated within the dryer. Said apparatus comprises a smoke sensor for fire detection, an extinguisher being a water injection unit, and a control unit, which shuts on and off the extinguisher, according to information received by the sensor. The system described in that patent does not consider power shut off, which can cause the extinguisher apparatus of Kim Choul Geun's patent document KR 20060103581 (2006) not being enough to suppress fire within the clothes dryer.
Patent document US 2010/0192404 (2010) by Antonio Maltese, et al. discloses a clothes dryer including a fire protection system having a control circuit comprising strategic arrangement of temperature-dependent switches which power up a relay upon the detection of excessive heat within the cabinet. The powered relay disconnects power of the electric charge source in order to reduce fire risk within the dryer's cabinet. Power interruption to a relay by means of thermostats allows for the heat to be detected on a plurality of areas within the dryer's cabinet, while disconnecting power of electric source.
Document patent US 2010/0192405 A1 (2010) by Mircea Rosca, teaches a clothes dryer comprising strategic arrangement of temperature dependent switches which de-energize the relay when excessive heat inside the cabinet is detected. The unpowered relay disconnects power to the electric charge source in order to reduce the occurrence of fire risks within the dryer cabinet. Power interruption to a relay by means of thermostats allows for the detection of heat on a plurality of areas within the dryer's cabinet, while power to electric charge source is disconnected.
Both patent document, US 2010/0192404 (2010) and US 2010/0192405 (2010), include a relay in its safety system which, since current is not shut off, it possibly could fail if said relay stabilizes and powers up again the dryer's electric system resulting in an increased fire risk.
Although a number of modifications and improvements that have been made to de-energize dryer machines, there is still a necessity in the art for an efficient de-energizing system, so that when a fire occurs in the electrical facility it will not represent a potential risk to the user.
The present invention provides a de-energizing electrical safety circuit for completely de-energizing, in a Quick, controlled, and safe manner a dryer machine including, in a preferred embodiment, a normally-open thermostat and two electrical switches as part of its electrical facility. By electrical switch it is basically meant a device that allows to shunt or interrupt the electrical current path by means of a circuit, these may include circuit breakers, trips, thermo magnetic breakers, also known as fuses like ceramic fuses, for example. The use of any of these kind of switches will have as an object the reduction of the user risks in case of fire, particularly if said user tries to extinguish fire with water.
In a preferred embodiment of the present invention, said switches will have a capacity of at least 15 amperes.
The de-energizing electrical safety circuit of the present invention comprises placing two switches on the power input of the dryer machine, which at the same time will be connected in parallel to a normally open thermostat. In its preferred embodiment the normally open thermostat will be part of the top bearing assembly, and can be located anywhere on this part. In another embodiment it can be part of the trap duct, and located anywhere on this part. In any of the above embodiments, the location of the normally-open thermostat will allow to the normally-open thermostat, in case of a temperature increase inside the dryer machine, reach its tripping temperature, closing, at the same time the electric circuit which causes a current magnitude that opens the switches; the above having the purpose of avoiding exposure of the user to electrical shocks by completely de-energizing the dryer machine almost immediately.
In a preferred embodiment of the invention, at least one normally-open thermostat can be used, preferably a ceramics type, with a tripping temperature preferably higher than a temperature measured in normal operation or in tests related to the standard UL2158 spanning to a temperature range from 100° C. to 170° C.
For a better understanding of the present invention reference is made to the following drawings, the purpose of which is only illustrative, wherein:
The present invention provides a de-energizing electrical safety circuit in home electric appliances that a potential fire risk, generally caused by user's misuse of said appliances could be present, which in its preferred embodiment will be applied to a dryer machine 10 shown in
Referring to
Located inside the cabinet 11 is a drum 20 installed to rotate around a substantially horizontal shaft. A motor 32 turns the drum 20 around the horizontal shaft, for example by means of a pulley 30 and belt 31. The drum 20 is generally cylindrical in shape, having an outer cylindrical wall 22 and an open end 21 typically comprising a metal ring 23, mechanically joined to the drum 20 for reducing the diameter of the opening 25 of drum 20, thus allowing fitting in a top bearing 24 shown in
Drum 20 includes a drum rear wall 26, rotatably supported inside the cabinet 11 by a support 27. The drum rear wall 26 includes a plurality of holes (not shown) receiving hot air that has been heated by a heater comprising electric heating elements 47 located in the heater housing 17. The heater housing 17 receives ambient air passing through a venting input 28 and to the heater housing 17 around a circular edge 50 of said heater housing 17.
Although the exemplary dryer machine 10 shown in
The air heated by the heater is withdrawn from and into the drum 20 by means of a driving fan 35, which is driven by a second motor, the fan motor 36, in the shown embodiment. In an alternative embodiment, the motor 32 can be used to drive the driving fan 35. The air is withdrawn by the driving fan 35 from the heater housing 17 into, though, and out of the drum 20, through a grid 33 and a screen filter 34. Grid 33 keeps cloth items revolving inside the drum 20 out of contact from the screen filter 34, and away from touching the lint trapped by the screen filter 34 inside the trap duct 40. As air passes through the screen filter 34, it flows through the lower duct portion 41 and air is injected by the fan wheel of the driving fan 35 joined to the fan motor 36 of the dryer machine 10 through an ejection duct 42. In this embodiment, the drum 20 is in airflow communication with the trap duct whose lower duct portion 41 has an exit in airflow communication with the fan wheel of the driving fan 35 and ejection duct 42. The ejection duct 42 passes through the rear wall 13 that commonly connects to a suitable venting (no shown) exhausting air to the exterior.
Once the cloth items have been dried, these can be removed from the drum 20 through the opening 25. Opening 25 is shown closed by a circular window type door 45. The circular window type door 45 has a handle 46 to pivotally open said circular window type door 45 around a hinge 48.
The dryer machine 10 in
With reference to
In reference to
The powered wire input line 66 of the dryer machine 10 together with the neutral input line 65 are respectively connected in electrical circuit with supply or charge powered wired line 70 and neutral line 83, respectively, via control circuit 90 depicted in
Control circuit 90, as shown in
Another important element of the control circuit 91 which is an object of the present invention is the inclusion of at least one temperature-sensing normally-open thermostat 76, connected in electrical circuit preferably between the charge powered wire line 70 and the neutral line 83, as shown in
Referring to
The placement of switches 74, 73 forming part of the control circuit 91 of the de-energizing electrical safety circuit of the present invention, is preferably close to the wiring input opening 71. As shown in
It should be understood that for a gas dryer machine, the amount of power required to power the same is less than that for an electrical dryer machine since the heating is achieved by combustion of natural gas or propane gas, and not by electrical heating elements 47. As a result, wiring for this arrangement typically comprises one powered wire input line 100 and one neutral input line 101 entering into the drum of the gas dryer machine (not shown) and is rated at 120 volts and 15 amps. A power cord (not shown) connected to the gas dryer machine includes a powered wire input line 100, a neutral input line 101 and a grounding wire line (no shown). The grounding wire line (not shown) is grounded to the cabinet (not shown) of the gas dryer machine. A terminal box similar to that shown in
In its preferred embodiment, the normally-open thermostat 76 forming part of the control circuit 91 of the de-energizing electrical safety circuit, being the object of the present invention, is of a ceramics type, nevertheless any other material could be used as well, and it is located preferably as part of the top bearing assembly 24 as depicted in
In the test performed, it is estimated that the de-energizing electrical safety circuit being the object of the present invention allows de-energizing the dryer machine at most in 1 minute.
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 |
|---|---|---|---|
| MX/A/2013/009023 | Aug 2013 | MX | national |
