Patent Abstract:
A home appliance includes a panel forming one of a tub, drum, and a housing for the appliance. The panel includes a first metal layer, a second metal layer, and a viscoelastic layer between, and spanning the entireties of, the first and second metal layers. The viscoelastic layer is configured such that the panel exhibits a composite loss factor of at least 0.05. The panel therefore forms appliance structure with integral noise attenuation, which improves upon the prior art by reducing the number of parts and manufacturing steps necessary for add-on noise attenuators. Furthermore, since the viscoelastic layer spans the entirety of the metal layers, noise attenuation is continuous across the panel, unlike many prior art noise attenuators which provide only localized noise attenuation.

Full Description:
TECHNICAL FIELD  
       [0001]     This invention relates to home appliances including a panel with two metal layers and a viscoelastic layer therebetween spanning the entirety of both metal layers such that the panel exhibits a composite loss factor of at least 0.05.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many home appliances include components that produce significant amounts of noise and vibration. For example, a household dishwasher includes an electric motor that drives a water pump, which produces noise and vibration. The pump forces water at high velocity through nozzles into a chamber, where the water acts on plates, glassware, etc., and contacts the inner surface of the chamber. When the water impacts the plates, glassware, and inner surface of the chamber, it produces unwanted noise and vibration.  
         [0003]     Household clothes washing machines typically include a drum for containing clothes and water, and a motor to rotate the drum. The rotation of the drum produces significant noise and vibration, especially at high speeds during a rinse cycle and when the clothes are arranged so as to produce an unbalanced load. Household clothes dryers typically include a drum rotatable about a horizontal axis. The clothes tumble inside the drum, producing a significant amount of noise and vibration.  
         [0004]     Prior art attempts to attenuate the noise and vibration produced by household appliances involve significant costs and disadvantages. For example, mastic PSAs are asphaltic patches that contain a pressure-sensitive adhesive (PSA) used to attach the patch to the appliance structure (such as a tub or housing). Heat activated mastic patches are typically placed on horizontal metal surfaces and bond to the surface with heat over a period of time. Mastics are typically nonrecyclable.  
         [0005]     Metal or foil patches may include a pressure sensitive adhesive attached to a layer of metal foil or a metal sheet. The force requirements to adhere the metal or foil patch varies from light hand pressure to several hundred pounds, requiring the use of a machine or tool.  
         [0006]     Mastic PSAs, heat activated mastic patches, and metal or foil patches require additional labor and equipment to install, result in acoustic variation from article to article because of variation in placement location, and have only localized damping coverage limited to the area covered by the damping material.  
         [0007]     Spray-on bitumen may be applied to the structure of a home appliance. The bitumen must be baked in order to cure, and may require multiple applications to achieve the desired coating thickness. The bitumen is nonrecyclable, may require additional labor and/or equipment to install, involves increased energy costs due to the baking process, and results in unwanted fumes during application and curing.  
         [0008]     Felt/fiber patches or blankets may be applied to metal appliance structures, requiring fasteners, additional labor, and inferior noise, vibration, and harshness characteristics. Foams may also be applied to metal appliance structure, typically by being sprayed on. Foams may also be injection molded in a die into the desired shape. Foams require additional labor and/or equipment and result in only localized damping coverage.  
         [0009]     Accordingly, prior art attempts to reduce the noise, vibration, and harshness of home appliances are labor-intensive, increase cost, and provide damping only in the area in which they are applied.  
       SUMMARY OF THE INVENTION  
       [0010]     A home appliance is provided that includes a panel forming at least a portion of the appliance. The panel has two metal layers and a viscoelastic layer therebetween spanning the entirety of both metal layers. The viscoelastic layer is configured such that the panel exhibits a composite loss factor of at least 0.05.  
         [0011]     According to one aspect of the invention, the panel at least partially defines a tub for a dishwasher and exhibits a composite loss factor of at least 0.05 between 40° F. and 150° F. to attenuate noise incurred by the spray action of water on the tub. According to another aspect of the invention, the panel at least partially forms a housing or tub of a clothes washing machine and exhibits a composite loss factor of at least 0.05 between 40° F. and 150° F. According to yet another aspect of the invention, the panel forms at least a portion of a drum or housing of a clothes dryer and exhibits a composite loss factor of at least 0.05 between 80° F. and 250° F.  
         [0012]     The panel provides noise attenuation at every point on its surface, as opposed to the prior art, which provides only localized noise attenuation. The panel also provides noise attenuation that is integral to the structure of the appliance, which results in a reduction of parts and manufacturing steps compared to the prior art. The panel is also recyclable.  
         [0013]     According to yet another aspect of the invention, one of the metal layers has a metal composition different from the other metal layer, enabling improved aesthetics on one side of the panel while optimizing cost, strength, or other characteristics on the other side of the panel.  
         [0014]     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a schematic, cross-sectional view of a laminated panel structure;  
         [0016]      FIG. 2  is a schematic, perspective view of a dishwasher including a tub having the laminated panel structure of  FIG. 1 ;  
         [0017]      FIG. 3  is a graph depicting the relationship between composite loss factor and temperature for two exemplary formulations of the viscoelastic layer of the laminated panel of  FIG. 1 ;  
         [0018]      FIG. 4  is a schematic, perspective view of a washing machine including a tub and housing having the laminated panel structure of  FIG. 1 ; and  
         [0019]      FIG. 5  is a schematic, perspective view of a clothes dryer including a drum and housing having the laminated panel structure of  FIG. 1 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Referring to  FIG. 1 , a cross-section of a panel  10  is schematically depicted. The panel  10  is a laminated sheet structure which includes a first metal layer  14  and a second metal layer  18 . A viscoelastic layer  22  is disposed between, and spans the entirety of, the first metal layer  14  and the second metal layer  18 . Referring to  FIG. 2 , a portion of a dishwasher  26  is schematically depicted. The dishwasher  26  includes a tub  30  having five generally planar sides  34 A-E. Sides  34 A,  34 B, and  34 C are formed from a single panel  10 A that is bent at creases  38 A,  38 B. Side  34 D is formed by panel  10 B, and side  34 E is formed by panel  10 C. Panels  10 B and  10 C are connected to panel  10 A such that the sides  34 A-E define a dishwashing chamber  42  having an opening  46 . As shown in  FIG. 2 , panel  10 A defines two flanges on opposite sides of opening  46 . A door (not shown) is pivotably connected with respect to the tub  30  to selectively obstruct and seal the opening  46 . Those skilled in the art will recognize a variety of methods for operatively connecting panels  10 B and  10 C to panel  10 A, such as welding, mechanical fasteners such as bolts, adhesive bonding, etc.  
         [0021]     The dishwasher  26  also includes a spray arm  50  with a plurality of holes or nozzles  54  thereon within the chamber  42 . A pump  58  is in fluid communication with the nozzles  54  and is configured to selectively supply pressurized water to the chamber  42  through the nozzles  54 . The nozzles  54  are directed generally upward to spray water on dishes, glassware, etc., on racks (not shown) within the chamber  42 , as understood by those skilled in the art. Some of the spray from the nozzles  54  will impact the inner surface  62  of the tub  30 . In prior art tubs, the spray impacting the tub causes excessive noise and vibration, which is particularly undesirable when the dishwasher is used in homes.  
         [0022]     Panels  10 A,  10 B, and  10 C are entirely formed of the laminated panel structure shown at  10  in  FIG. 1 . Thus, one side of each panel  10 A,  10 B,  10 C is formed of a respective first metal layer, the other side of each panel  10 A,  10 B,  10 C is formed of a respective second metal layer, and each first metal layer is separated from the corresponding second metal layer by a viscoelastic layer that spans the entirety of the respective first and second metal layers.  
         [0023]     Referring again to  FIG. 1 , it may be desirable for the metal layers  14 ,  18  to have different metal compositions. For example, the first metal layer  14  may be aluminum, stainless steel, etc., to provide the inner surface of the tub with an aesthetically pleasing appearance, and the second metal layer  18  may be hot dip galvanized steel to provide the panel with strength at low cost. Furthermore, it may be desirable for the metal layers  14 ,  18  to have different thicknesses. For example, the first metal layer  14  may be thinner than the second metal layer  18 ; thus, for example, if the first metal layer  14  is aluminum or stainless steel and the second metal layer  18  is steel, the second metal layer may be thicker than the first metal layer so that less aluminum or stainless steel is employed in the construction of the panel  10 , with resultant cost savings.  
         [0024]     Referring to  FIG. 3 , the relationship between composite loss factor and temperature for two exemplary viscoelastic layer formulations are schematically depicted. Line  66  depicts the composite loss factor of a panel with a first viscoelastic layer formulation as a function of temperature. With the first viscoelastic layer formulation, the panel exhibits a composite loss factor of approximately 0.01 at 0° F., 0.40 at approximately 70° F., and approximately 0.06 at 200° F. Furthermore, with the first viscoelastic layer formulation, the panel exhibits a composite loss factor of at least 0.05 (i.e., 5 percent) at all temperatures between approximately 40° F. and approximately 220° F., and the panel exhibits a composite loss factor of at least 0.10 (i.e., 10 percent) at all temperatures between approximately 55° F. and approximately 160° F., as shown by line  66 .  
         [0025]     Line  70  depicts the composite loss factor of a panel with a second viscoelastic layer formulation as a function of temperature. With the second viscoelastic layer formulation, the panel exhibits a composite loss factor of approximately 0.02 at 50° F., 0.40 at approximately 160° F., and approximately 0.20 at 200° F. Furthermore, with the second viscoelastic layer formulation, the panel exhibits a composite loss factor of at least 0.05 at all temperatures between approximately 80° F. and approximately 280° F., and the panel exhibits a composite loss factor of at least 0.10 at all temperatures between approximately 110° F. and approximately 250° F., as shown by line  70 .  
         [0026]     Referring again to  FIGS. 1 and 2 , the viscoelastic layer  22  is the first viscoelastic layer formulation such that the composite loss factor of the panels  10 A,  10 B,  10 C is a function of temperature as shown by line  66  of  FIG. 3 , which provides superior noise attenuation under dishwasher operating conditions. Since the laminated panel structure shown in  FIG. 1  is coextensive with the entire tub  30 , noise attenuation is provided at every point on the inner surface  62  of the chamber  42 .  
         [0027]     Referring to  FIG. 4 , a clothes washing machine  74  is schematically depicted. The washing machine  74  includes a housing  78  defined by one or more panels  10 D. The housing  78  defines a compartment  86  containing a generally cylindrical outer tub  90  and an inner tub  94  (sometimes referred to as a “basket”) disposed within the outer tub  90 . The inner tub  94  defines a plurality of holes  98 , and an agitator  102  is disposed within the inner tub  94 . A motor  106  is operatively connected to the inner tub  94  to selectively cause the rotation thereof with respect to the outer tub  90 , and to cause movement of the agitator  102 , as understood by those skilled in the art. In operation, the inner tub  94  is filled with clothes through an opening covered by lid  108 , and the outer tub  90  is filled with water, which also fills the inner tub  94  through holes  98 . The motor  106  drives the agitator  102  during a wash cycle, and the motor  106  rotates the inner tub  94  to remove water from the clothes contained therein. A control panel  112  is provided to control the operation of the machine.  
         [0028]     The housing  78  and the outer tub  90  are formed entirely by the laminated panel structure depicted in  FIG. 1 , and include the first viscoelastic layer formulation such that the composite loss factor of the housing  78  and outer tub  90  is a function of temperature as shown by line  66  of  FIG. 3 , which provides superior noise attenuation under clothes washing machine operating conditions.  
         [0029]     Referring to  FIG. 5 , a clothes dryer  116  is schematically depicted. The clothes dryer  116  includes a housing  120  defining a compartment  124 . A drum  128  is located within the compartment  124  and defines a generally cylindrical chamber  132  for containing clothes (not shown). The chamber  132  is accessible through an opening in the housing  120  obstructed by door  134 . A motor  136  is operatively connected to the drum  128  to cause the rotation thereof. The rotation of the drum causes clothes contained therein to tumble, and heat is applied to facilitate drying, as understood by those skilled in the art. Within the scope of the claimed invention, a “generally cylindrical” chamber may or may not include paddles extending radially inward to assist movement of the clothes. The drum  128  and the housing  120  are formed entirely of the laminated panel structure depicted in  FIG. 1 , and the viscoelastic layer is characterized by the second viscoelastic layer formulation such that the composite loss factor of the drum  128  and housing  120  is a function of temperature as shown by line  70  in  FIG. 3 , which provides superior noise attenuation for clothes dryer operating conditions. A control panel  140  controls the operation of the dryer  116 .  
         [0030]     In an alternative embodiment, the panels  10 A,  10 B,  10 C of  FIG. 2 , the housing  78  and tub  90  of  FIG. 4 , and the housing  120  and drum  128  of  FIG. 5  are characterized by a composite loss factor of at least 0.05 at all temperatures between 40° F. and 200° F.  
         [0031]     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.

Technology Classification (CPC): 3