US20150033576A1

US20150033576A1 - De-energizing electrical safety circuit

Info

Publication number: US20150033576A1
Application number: US14/451,590
Authority: US
Inventors: Juan Daniel Hernandez Jimenez; Mirian Graciela Vera Tesillos; Luis Alfredo Lucia Mendoza; Jose Alberto Arteaga Hinojosa; Jose Augusto Moreno Escobar; Carlos Alberto Ricardez Macias
Original assignee: Mabe SA de CV
Current assignee: Mabe SA de CV
Priority date: 2013-08-05
Filing date: 2014-08-05
Publication date: 2015-02-05
Also published as: CA2858052A1; MX337950B; MX2013009023A

Abstract

The present invention describes a de-energizing electrical safety circuit for appliances, in particular dryer machines wherein said circuit controls power supplied from a power source, via a power cord comprising a neutral line and at least one live input line connected to a neutral line and at least one charge powered line, respectively. The de-energizing electrical safety circuit comprises at least one normally open thermostat connected to two switches corresponding to a neutral line and a charge powered line; at least one thermostat is mounted within the cabinet external to the drum. The excess heat in the cabinet closes at least one thermostat thus closing the circuit and allowing the power to flow between the neutral line and the charge powered line causing a short circuit in at least one thermostat and then opening the switches and thereby achieving a complete de-energizing of the dryer machine.

Description

FIELD OF THE INVENTION

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.

BACKGROUND OF INVENTION

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.

BRIEF DESCRIPTION OF THE INVENTION

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.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention reference is made to the following drawings, the purpose of which is only illustrative, wherein:

FIG. 1 is a perspective view of an exemplary dryer machine, which can benefit from the present invention.

FIG. 2 is a sectional side view of an exemplary dryer machine that can benefit from the present invention, showing internal and external main components.

FIG. 3 is an isometric view of the drum of the exemplary dryer machine that can benefit from the present invention, showing a top bearing where a thermostat will preferable be located and forming part of the present invention.

FIG. 4 is an external partial view of a rear wall showing the connection of a power cord to an exemplary terminal block of exemplary electrical clothes dryer.

FIG. 5 is an electrical circuit diagram according to the present invention.

FIG. 6 is a perspective view of the cabinet's interior of the exemplary dryer machine showing the switches and partially showing the wiring supplying power to the drum's motor.

FIG. 7 is an electrical schematic diagram for an exemplary dryer machine powered up by one or more electrical heating elements.

FIG. 8 is an electrical schematic diagram for an exemplary gas dryer machine heated by means of a gas heater.

FIG. 9 is a sectional view of the top bearing wherein the thermostat preferred location is shown forming part of the de-energizing electrical safety circuit of the present invention, although said thermostat can be located anywhere on this part.

FIG. 10 is a close-up view of a section of the top bearing showing a thermostat preferred location, although said thermostat can be located anywhere on this piece being part of the de-energizing electrical safety circuit of the present invention, as well as cables that allow communication with switches forming part of the de-energizing electrical safety circuit of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Theoretical Approach

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 FIG. 1.
Referring to FIGS. 1 and 2, an exemplary dryer machine 10 that can be beneficiated by the present invention, is shown. The dryer machine 10 includes a cabinet 11 having a front wall 12, a rear wall 13, a pair of side walls 14, and 15, spaced apart one from another by front wall 12 and rear wall 13, a floor or base 16 and a top cover 18.
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 FIG. 3. Also, said top bearing 24 defines an opening 25 inside the drum 20. Cloth items and other fabrics are loaded inside the drum 20 through the opening 25. A plurality of drum ridges (not shown) are provided inside the drum 20 in order to lift the items and then let them fall again to the bottom of the drum 20 while said drum 20 rotates.
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 FIG. 1 is an electric dryer machine having electrical heating elements 47 which heat ambient air, it should be understood that the dryer machine 10 can be a gas dryer machine, having a gas burner (not shown) for heating ambient air entering the dryer machine 10. The gas burner (not shown) can be located below the drum 20 and includes ducts that extend from the gas burner (not shown) to the drum rear wall 26.
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 FIG. 1, is shown having a control panel 43 with touch or rotating controls 44, allowing the user to control the operation of the dryer machine 10.
With reference to FIGS. 4 and 5, the cable harness circuitry 75 of the dryer machine 10 is shown. Power is supplied to the dryer machine 10 in FIG. 4 from a preferably three phase power source (not shown) through a power cord 51, said power cord 51 has two powered cables 52 and 54, a cable with a neutral current 55, and a ground cable 56. Ground cable 56 is shown connected by a screw 57 to the rear wall 13 of the dryer machine 10. Cables 52, 54, 55, and 66 of power cord 51 are rated for 120/140 volts and 30 amps. Power cord 51 is connected to the rear wall 13 of the dryer machine 10 by a strain cable clamp 58. Powered cables 52 and 54 as well as the neutral cable 55, are connected by screws 60 to separate terminals in the terminal block 61 of the terminal block facility 62. A cover 63 is clamped by a screw 64 to the rear wall 13 to cover the terminal block facility 62. The block terminal 61 is shown installed on the exterior of said rear wall 13.
In reference to FIGS. 4 and 6, a neutral input line 65 of the dryer machine 10 and two powered wire lines 66 and 67 pass through a wiring input opening 71 located on the rear wall 13 of the dryer machine 10. The powered wire lines 66, 67 as well as a neutral entry line 65, are shown in FIG. 4 entering the cabinet 11 of the dryer machine 10 through the input wiring opening 71, and as shown in figure emerging from the input wiring opening 71 into the cabinet 11 of the dryer machine 10.
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 FIG. 5 and control circuit 91 also depicted in FIG. 5. The Charge or supply powered wired lines 70, and 67, together with neutral line 83 are connected in a wiring harness 75, depicted in FIG. 6 to provide power to the electric charge or supply 92 within cabinet 11 of the dryer machine 10, including for example motor 32, fan motor 36, and electrical heating elements 47 of heater housing 17, among others. This electrical charge or supply is shown schematically in FIG. 5. Also, it should be understood that the wiring harness 75 will provide power to an electronic power supply 103 for the electronic components of the dryer machine 10.
Control circuit 90, as shown in FIG. 5, is for controlling the power supply from the power source to the electrical charge 92. The control circuit 91, being an object of the present invention, comprises switches 74, 73 connected in electrical circuit between the powered wire input line 66 and the neutral input line 65 of the dryer machine 10 and corresponding charge powered wire line 70 and neutral line 83 of the dryer machine. So, switches 74, 73 are located between the powered wire input line 66 and the neutral input line 65 in correspondence with their respective charge powered wire line 70 and neutral line 83. Each of the switches 74, 73 comprises contacts 93, 94 and a cut circuit bar 95. Contact 93 corresponds to an end of the input line being either the powered wire input line 66 or the neutral input line 65; similarly contact 94 corresponds to the end of either the charge powered wire line 70 or the neutral line 83. The shorting circuit bar 95 spans the breadth between contacts 93 and 94 joining said contacts in circuit allowing power to flow to the dryer machine 10.
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 FIG. 5. In a preferred embodiment, the normally open thermostat 76 connected in electrical circuit closes in response to the detection of excess of heat inside the dryer machine 10. Typically, the normally open thermostat 76 comprises a bimetal element (not shown) that changes position at a predetermined temperature to close the circuit of the normally open thermostat 76. When the predetermined temperature of the at least one normally-open thermostat 76 (as discussed above, it can be more than one thermostat forming part of the control circuit being an object of the present invention) is reached or exceeded, the normally-open thermostat 76 closes the circuit between charge powered wire line 70 and neutral line 83 causing, within said normally-open thermostat 76 an electric current magnitude, thus opening switches 74, 73 and completely and almost instantly de-energizing the dryer machine 10.
Referring to FIG. 7, the distribution of the power to charges 32, 36, 17, 103 in the drum of the dryer machine is shown. For optimal protection, adjacent or within each space of the dryer machine may be located a normally open thermostat 76; in the preferred embodiment a normally open thermostat 76 has been arranged as an integral element of the top bearing 24 as shown in figures and 10. As shown in FIG. 7, in the event of an excess heat, generally caused by either a lack of maintenance to the dryer machine 10 or in the case of fire, mainly by user negligence, in any of these instances, the normally-open thermostat 76 will close opening in turn switches 74, 73 as shown in the diagram of FIG. 7) corresponding to the circuit between the powered wire input line 66 and its correspondent charge powered wire line 70 as well as the neutral input line 65 with its corresponding neutral line in order to disconnect electric charge from power and ending any operation being carried out by the dryer machine 10.
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 FIG. 6, in order to limit the length of powered wire input line 66 and neutral input line 65 unprotected by the control circuit 91 of the de-energizing electrical safety circuit being the object of the present invention and extending within the cabinet 11 to a short distance. In the event of a fire or excess heat condition, this may limit the amount of wire that may arc due to deterioration of the wires caused by the heat. This serves to reduce the potential risk inside the dryer cabinet 11 of the dryer machine 10.
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 FIG. 4 is used, or alternatively, the power cord is connected directly through a strain relief clamp (not shown) to the gas dryer machine, so that the powered wire input line 100 and the neutral input line 101 of the power cord pass directly through a wire input opening (not shown) into the cabinet of the gas dryer machine. The terminal block of switches similar to that shown in FIG. 6 is located closely adjacent to the wiring input opening so as to minimize the length of unprotected powered wire line of the power cord within the cabinet of the gas dryer machine. A schematic representation of the wiring diagram of such a system is shown in FIG. 8, wherein the powered wire input line 100 and the neutral input line 101 are provided for supplying power to the fan motor 36, the motor 32, the gas burner heater control 102, and the electronic power supply 103. The control relay 91 of the de-energizing electrical safety circuit being the object of the present invention is located in the circuit shown in FIG. 8, to disconnect power to the charge powered wire line 104 and the charges 32, 36, 102, 103.
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 FIG. 9, which can be fastened by any fastening means such as screws, snaps, as shown in FIG. 10. In a preferred embodiment a normally-open thermostat 76 is shown fastened by a screw 79. In another embodiment it could be assembled in the trap duct 40 of the dryer machine 10.
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.

Claims

1. A dryer machine including a cabinet housing a drum and ducts associated therewith for directing air flow into and through the drum of said dryer machine to dry cloth items placed in the drum, wherein said dryer machine further includes a main harness supplying power to an electric charge characterized by:

a) a power cord for supplying power from a power source to an electrical charge in the cabinet, the power cord comprising a neutral input line and at least one powered wire input line entering the cabinet;

b) the electrical charge being connected in circuit with the neutral input line of the power cord and at least one charge powered wire line;

c) a de-energizing electrical safety circuit for controlling the power supply from the power source to the electrical load, the de-energizing electrical safety circuit comprising a control circuit comprising two switches; one switch positioned between the neutral input line and a corresponding neutral line; and the other switch positioned between at least one powered wire input line and a corresponding charge powered wire line; said switches being preset normally closed in order to allow power to flow from the input line to the charge powered wire line or to the neutral line, as the case may be; and

d) the control circuit comprising at least one normally-open bimetal thermostat and mounted within the cabinet connected between the neutral line and at least one charge powered wire line, that upon reaching or exceeding its working temperature closes the circuit between the neutral line and the at least one charge powered wire line thus opening the normally-closed switches in order to disconnect the power between the neutral input line and its corresponding neutral line, as well as the power of the at least one powered wire input line and its corresponding charge powered wire line.

2. The dryer machine according to claim 1, characterized in that:

the de-energizing electrical safety circuit comprises a plurality of thermostats located in different areas of the cabinet and electrically connected in parallel with the switches.

3. The dryer machine according to claim 1, characterized in that:

at least one normally-open thermostat is preferably of a ceramics type, with a tripping temperature preferably higher than a temperature measured in normal operation or in tests regarding to the standard UL2158.

4. The dryer machine according to claim 1, characterized in that:

the terminal block of switches is located adjacent to the wiring input opening located on the rear of the dryer machine.

5. The dryer machine according to claim 1, characterized in that:

at least one normally-opened thermostat can be connected between two powered wire lines.

6. The dryer machine according to claim 1, characterized in that:

The electric charge comprises at least one motor and one electronic power source.

7. The dryer machine according to claim 1, characterized in that:

the time to completely de-energize the dryer machine is at most 1 minute.

8. The dryer machine according to claim 1, characterized in that:

the time to de-energize the dryer machine is 1 minute or less.

9. The dryer machine according to claim 1, characterized in that

the switches, as part of the electrical facility, are switches preferably of a ceramics type with a working capability of at least 30 amperes.