Abstract:
A restriction sensor system for identifying the existence of blockages in exhaust conduits of clothes dryers. The restriction sensor system may include a pressure sensing device having a body configured to be coupled to an exhaust conduit of a clothes dryer. The pressure sensing device may be capable of determining changes in air pressure in the exhaust conduit. Once the air pressure present in the exhaust conduit exceeds a threshold air pressure, the pressure sensing device may send a signal to an indicator to generate an alarm, which may be a visual alarm or audible alarm, or both.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention is directed generally to clothes dryers, and more particularly, to safety systems for clothes dryers.  
         BACKGROUND  
         [0002]    Conventional clothes dryers are constructed of a tumbler configured to hold clothes, a motor for rotating the tumbler, a heating element for heating air, a fan for blowing the heated air across the clothes while the clothes are in the tumbler, and an exhaust conduit for venting the heated air from the dryer. The heating element may be electric or gas powered. Because a close dryer includes a heating element, there always exists the chance of fire. Conventional clothes dryers include many different safety devices for reducing the likelihood of a fire. For instance, a conventional clothes dryer often includes a lint screen for removing lint from the air coming from a tumbler. The lint screen is often placed in an easily accessible location, such as in a slot in a top surface of the clothes dryer, and covers an exhaust conduit where the conduit leaves the tumbler. The lint screen collects lint from the air that has been picked up from the clothing in the tumbler. Most, if not all, manufacturers of clothes dryers recommend that lint screens be cleaned after each load of clothes is dried. Otherwise, an unacceptable amount of lint may build up on the lint screen and pose a fire hazard and prevent efficient operation.  
           [0003]    Clothes dryers also typically contain heat sensors, such as thermocouples, for preventing dryers from overheating and causing fires. Most clothes dryers position a thermocouple proximate to a heating element of the clothes dryer. In this position, the thermocouple is capable of monitoring the area surrounding the heating element and can be used to determine whether the air surrounding the heating element is exceeding a predetermined threshold temperature. If the air becomes too hot, the thermocouple breaks a circuit, which thereby turns the dryer off and prevents the dryer from operating. The temperature of the air surrounding the heating element is monitored because the air surrounding the heating element often becomes too hot for safe operation when an exhaust conduit contains a blockage. Blockages in the exhaust conduits are dangerous because the blockages can cause the heating element to overheat and ignite lint near the heating element.  
           [0004]    Many exhaust hoses for clothes dryers are incorrectly installed such that the exhaust hoses have internal diameters that are too small or are restrained. Such configurations accelerate lint collection on inside surfaces of the exhaust hoses, which may eventually result in partial or total blockage of the exhaust conduit. Such accumulation of lint may occur relatively quickly or over a longer period, such as a few years, and may go unnoticed by a homeowner. Such conditions are extremely dangerous.  
           [0005]    While the conventional configuration of locating a thermocouple proximate to heating elements in a dryer has undoubtedly prevented many fires, dryers having this configuration remain susceptible to fires. In fact, dryers remain one of the most dangerous household appliances. Thus, a need exists for a system for improving the safety of clothes dryers.  
         SUMMARY OF THE INVENTION  
         [0006]    This invention relates to a restriction sensor system usable with a clothes dryer for identifying blockages in an exhaust conduit downstream of a lint screen in an effort to prevent dangerous conditions and fires. The blockages may be found in the exhaust conduit located inside of or outside of a clothes dryer. The restriction sensor system may include a pressure sensing device for sensing the air pressure in an exhaust conduit of a clothes dryer downstream of a lint screen and creating an alert message when the air pressure on the exhaust conduit exceeds a pre-established threshold air pressure. The pressure sensing device may be formed from a body configured to be coupled to an exhaust conduit of a clothes dryer and may have at least one cavity for containing a diaphragm. The pressure sensing device may also include a diaphragm capable of reacting to relatively small changes in air pressure in the exhaust conduit. The pressure sensing device may also include a sensor for sensing the reactions of the diaphragm. In one embodiment, the sensor may be coupled to the diaphragm. The pressure sensing device may also include an orifice in the body for admitting a gas, such as air, from the exhaust conduit into the cavity of the pressure sensing device.  
           [0007]    The restriction sensor system may also include one or more indicators for indicating that the pressure sensing device has identified that the air pressure in the exhaust conduit of the clothes dryer has exceeded a threshold air pressure. The indicator may be capable of generating a visual alert or an audible alert, or both. The indicator may be configured to be attached to a control panel of a clothes dryer or in another location on a clothes dryer.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.  
         [0009]    [0009]FIG. 1 is a perspective view with a partial cut away of a clothes dryer having a restriction sensor system.  
         [0010]    [0010]FIG. 2 is a perspective view of a pressure sensing device usable in the restriction sensor system of FIG. 1.  
         [0011]    [0011]FIG. 3 is an exploded view of the pressure sensing device of FIG. 2.  
         [0012]    [0012]FIG. 4 is a perspective view of another embodiment of a pressure sensing device.  
         [0013]    [0013]FIG. 5 is a side view of another embodiment of a pressure sensing device.  
         [0014]    [0014]FIG. 6 is a top view of the pressure sensing device shown in FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    As shown in FIGS.  1 - 4 , this invention is a restriction sensor system  10  for use with an exhaust system  12  of a clothes dryer  14 . Restriction sensor system  10  may be capable of determining whether an exhaust conduit  16  downstream of a lint screen contains a blockage, which could potentially cause unsafe conditions and lead to a fire. Exhaust conduit  16  may include portions of the exhaust system located inside of or outside of clothes dryer  14 , or both. Restriction sensor system  10  may include a pressure sensing device  18  and an indicator  20  for indicating that pressure sensing device  18  has sensed an air pressure exceeding a threshold pressure in exhaust conduit  16  of clothes dryer  14 .  
         [0016]    Pressure sensing device  18  may be capable of determining whether the air pressure in exhaust conduit  16  has exceeded a threshold air pressure, which may indicate that a blockage exists. In one embodiment, pressure sensing device  18  may be a differential pressure monitoring device, as available from Veris Industries in Portland, Oreg. and shown in FIGS. 5 and 6. Exhaust conduit  16  is a conduit downstream of a lint screen, or if a dryer does not contain a lint screen, exhaust conduit  16  is a conduit extending from tumbler  36  to an exit port venting air from clothes dryer  14 . Pressure sensing device  18  may be formed from a body  22  configured to fit into exhaust conduit  16 . Body  22  may contain one or more cavities  24  for containing a diaphragm, as shown in FIG. 3. In at least one embodiment, a diaphragm  26  is positioned in cavity  24 . Diaphragm  26  may be positioned so that a plane  27  in which diaphragm  26  rests is generally orthogonal to a general direction in which air is flowing and striking diaphragm  26 . Diaphragm  26  may be a thin film capable of reacting to small changes in pressure.  
         [0017]    Cavity  24  may be in communication with one or more orifices  28  in body  22 . Orifice  28  may admit air found in exhaust conduit  16 , into cavity  24 . In another embodiment, orifice  28  may be coupled to a conduit  29  for admitting air found in exhaust conduit  16 . Orifice  28  may have any size appropriate for admitting a gas into cavity  24 . Orifice  28  is configured to inhibit contamination by lint or other debris. In one embodiment, orifice  28  and conduit  29  may form a pitot tube or static tube.  
         [0018]    Body  22  may also have a sensor  30  coupled to diaphragm  26 . Sensor  30  may be capable of sensing changes in position of diaphragm  26  that may be caused by changes in pressure in exhaust conduit  16 . Sensor  30  may also be capable of measuring strain in diaphragm  26 . Sensor  30  may be formed from solid-state feedback circuitry.  
         [0019]    Body  22  may further include a fin  32 , as shown in FIG. 4, housing orifice  28 . Fin  32  may be coupled to a bottom side  40  of body  22 . Fin  32  may be sized to accommodate orifice  28  and may have an aerodynamically efficient exterior surface. Fin  32  may include a curved edge  42  extending from the bottom side  40  of body  22  to orifice  28 . In another embodiment, body  32  may not include fin  32 , but instead include only conduit  29 , as shown in FIG. 2. Conduit  29  may have any size appropriate for admitting air into cavity  24 . In one embodiment, restriction sensor system  10  may be configured to position orifice  10  in exhaust conduit  16  so that orifice  28  faces downstream. However, this invention is not limited to positioning orifice  28  in this position. Rather, in another embodiment, restriction sensor system  10  may be positioned so that orifice  28  faces upstream.  
         [0020]    Pressure sensing device  18  may include one or more indicators  20  for indicating that the exhaust conduit  16  has undergone an increase in air pressure that may be caused by, for instance and not by way of limitation, a blockage in exhaust conduit  16 . Indicator  20  may emit a visual alert or an audible alert, or both. Indicator  20  may be a light emitting device (LED) or other visually alerting device. Indicator  20  may also be a speaker, buzzer, or other noise making device. Indicator  20  may be configured to be attached to a control panel  34  of clothes dryer  14 . Indicator  20  may be coupled to sensor  30  using one or more electricity conducting wires  38 . Wires  38  may be connected to connectors  44 .  
         [0021]    In another embodiment, restriction sensor system  10  may include pressure sensing device  18  including diaphragm  26 , as shown in FIGS. 5 and 6, that is configured to be coupled to exhaust conduit  16  of clothes dryer  14  using a conduit rather than coupling the pressure sensing device  18  directly to exhaust conduit  16 . Diaphragm  26  may be a diaphragm having model number RSS-495 that is available from Cleveland Controls of Cleveland, Ohio. The conduit may be coupled to diaphragm  26  at an inlet  35  using connection mechanisms such as, but not limited to, barbs and other devices. The conduit may be mounted directly to a port in exhaust conduit  16 . Alternatively, the conduit may be mounted a device or have an end with a fin  32 . In this embodiment, restriction sensor system  10  may also include sensor  30  in communication with diaphragm  26  and one or more indicators  20  for indicating the pressure in exhaust conduit  16  of clothes dryer  14 . Sensor  30  may be, but is not limited to, a snap-acting switch.  
         [0022]    Restriction sensor system  10  is capable of being installed on any clothes dryer with little modification during a manufacturing process or after a clothes dryer has been completely assembled. The clothes dryer may have a tumbler  36  for containing clothes, a heating element for heating air, a fan for blowing air across the clothes in tumbler  36 , an exhaust conduit  16  for removing heated air, a control panel  34 , and a motor for rotating tumbler  36 . Pressure sensing device  18  may be coupled to exhaust conduit  16  downstream of either a lint screen, or if the clothes dryer does not have a lint screen, down stream of the point at which exhaust conduit  16  couples to tumbler  36 .  
         [0023]    During operation of clothes dryer  14 , lint and other debris is collected with a lint screen. However, lint and other debris often pass through the lint screen and collects in exhaust conduit  16 . Accumulation of lint and other debris in exhaust conduit  16  is a fire hazard. When clothes dryer  14  is operating, air pressure develops in exhaust conduit  16 . As debris collects in clothes dryer  14 , the air pressure in exhaust conduit  16  increases. As the air pressure increases, diaphragm  26  reacts to the change in air pressure. Sensor  30  senses the reaction of diaphragm  26 . When the air pressure in exhaust conduit  16  exceeds a threshold pressure, sensor  30  causes indicator  20  to indicate that exhaust conduit  16  exceeds the threshold pressure. An increase in air pressure in the exhaust system of a clothes dryer may be caused by an increase in lint accumulation.  
         [0024]    Indicator  20  may indicate that an air pressure in excess of a threshold air pressure has been observed by producing a blinking light, a light that is continuously turned on, a noise, such as, but not limited to, a buzzer, a voice that may give instructions on how to check the exhaust conduit, or others. In one embodiment, after sensor  30  determines that a threshold air pressure has been exceeded, indicator  20  remains actuated at all times when clothes dryer  14  is in use until the air pressure subsides to a level beneath the threshold air pressure. The threshold air pressure will vary depending on numerous factors, such as, but not limited to, the diameter of exhaust conduit  16 , the length of exhaust conduit  16 , the presence or absence of a cover on the end of exhaust conduit  16  and other factors. As a result, the threshold air pressure may vary.  
         [0025]    The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.