Patent Publication Number: US-6658204-B2

Title: Door insulator with safety plug

Description:
FIELD OF THE INVENTION 
     The invention relates to water heaters, and more particularly to water heaters having doors that provide access to electrical components mounted within the water heaters. 
     BACKGROUND OF THE INVENTION 
     It is known to provide water heaters with a tank, a jacket that surrounds the tank, and an electrical component, such as a thermostat or a heating element. The electrical component is coupled to the tank and is accessible through an opening in the jacket. The opening of the jacket is typically covered by a removable door. The door is movable between an open position providing access to the opening and a closed position restricting access to the opening. 
     It is also known to provide a polystyrene dam that surrounds the electrical component and that extends between the tank and the jacket to protect the electrical component from the insulating foam while the foam is injected between the tank and the jacket. Thus, the dam at least partially defines the opening. In addition, it is known to insert a polystyrene cap into the opening of the jacket and within the dam to further insulate the tank from the environment. 
     SUMMARY OF THE INVENTION 
     The water heater of the present invention increases safety and decreases the likelihood of electrocution during water heater maintenance by providing a door assembly that selectively opens and closes an electrical circuit providing electricity to an electrical component of the water heater. More specifically, when the door assembly is removed to gain access to the electrical component, the electrical circuit is opened, and when the door assembly is closed, the electrical circuit is closed. 
     The door assembly also eliminates the need for a permanently fixed dam around the electrical component by providing a dam that is moldable to a door of the door assembly. The dam is shaped to closely cover and surround the electrical component and to provide the necessary seal against the tank and jacket during the injection of the insulation foam between the tank and the jacket. The dam may optionally be sprayed or coated with a release agent so that the dam does not bond with the injected insulation, thereby allowing the cover assembly to be removed after the insulation foam cures. 
     In an alternate configuration of the water heater, a conventional foam dam is positioned within an opening in the jacket to protect the electrical component of a water heater from insulating foam during injection of the foam between the tank and the jacket of the water heater. The door assembly includes a ceramic foam insulating cap that is molded to the door and that is insertable in the dam to provide rigidity to the dam and to maintain the shape of the dam under high forces that are generated by injecting a thick layer of insulation between the tank and the jacket. The ceramic foam insulating cap also improves the insulating effect of the door assembly on the water heater. 
    
    
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view illustrating a water heater embodying the invention. 
     FIG. 2 is an enlarged exploded view of a portion of the water heater. 
     FIG. 3 is an enlarged view of a plug of the water heater. 
     FIG. 4 is a rear perspective view illustrating the door assembly of the water heater. 
     FIG. 5 is an enlarged partial cutaway view of a portion of the water heater. 
     FIG. 6 is a cross-section view taken along line  6 — 6  in FIG.  5 . 
     FIG. 7 is a cross-section view taken along line  7 — 7  in FIG.  5 . 
     FIG. 8 is an enlarged exploded view of a portion of a water heater according to another embodiment of the invention. 
     FIG. 9 is an enlarged rear perspective view illustrating a door assembly of the water heater shown in FIG.  8 . 
     FIG. 10 is an enlarged partial cutaway view illustrating a portion of the water heater shown in FIG.  8 . 
     FIG. 11 is a cross-section view taken along line  11 — 11  in FIG.  10 . 
     FIG. 12 is a cross-section view taken along line  12 — 12  in FIG.  10 . 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order. 
     DETAILED DESCRIPTION 
     A water heater  10  embodying the invention is illustrated in the drawings. As shown in FIG. 1, the water heater  10  comprises a tank  12  including an outer surface  14  and an inner surface  16  that defines a water chamber  18 . The water heater  10  also comprises an electrical component  20  such as a thermostat or a heating element, extending at least in part outwardly of the outer surface  14  of the tank  12 . The illustrated water heater  10  is an electric water heater and includes both a thermostat and a heating element. It should be noted that the invention can also be utilized with a gas water heater which includes an electrical component such as a thermostat. 
     The water heater  10  further comprises a jacket  22  surrounding the tank  12 . The jacket  22  includes an outer surface  24  and has an opening  26  that allows access to the electrical component  20  (FIG.  2 ). In the illustrated construction, the opening  26  is rectangular. As shown in FIG. 1, a layer of foam insulating material  28  is located between the tank  12  and the jacket  22 . The manner in which the insulating material  28  is placed between the tank  12  and the jacket  22  is described in greater detail below. 
     The water heater  10  further comprises a door assembly  30  which is removably mounted on the jacket  22  such that the door assembly  30  is movable between an open position (FIG. 2) that allows access to the opening  26  and the electrical component  20 , and a closed position (FIG. 5) that restricts access to the opening  26  and the electrical component  20 . As best shown in FIG. 4, the door assembly  30  includes a door  32 , an insulating cap  34 , and a connecting device, such as electrical conduits  36 . With reference to FIG. 6, the door  32  has an outer flange portion  38  engaging the outer surface  24  of the jacket  22 , a central portion  40  spaced a distance from the outer surface  24  of the jacket  22 , and an intermediate portion  42  which is located between the central portion  40  and the outer flange portion  38 . The door  32  is removably secured to the jacket  22  by a plurality of screws  44  or other suitable fasteners (e.g., bolts, clips, studs, nuts, etc.) extending through holes  46  located in the intermediate portion  42  and the jacket  22 . The door  32  is preferably stamped from sheet metal, such as aluminum or stainless steel. 
     Referring back to FIG. 4, the insulating cap  34  is connected to the central portion  40  of the door  32 . The insulating cap  34  includes an inner surface  48  that is spaced a distance from the door  32 . The insulating cap  34  is preferably molded to the door  32  and is molded from materials that are electrically non-conductive and that are poor thermal conductors. Alternatively, the cap  34  could be a separate piece from the door  32 . 
     With reference to FIGS. 4-6, the insulating cap  34  also includes a socket  54  that contains the conduits  36 . The electrical conduits  36  have portions embedded within the insulating cap  34  and exposed portion within the socket  54 . The conduits  36  are generally parallel to each other and do not extend out of the socket  54 . 
     As shown in FIG. 2, the water heater  10  further comprises a dam  60  within the opening  26  and surrounding the electrical component  20 . The dam  60  extends between the tank  12  and the jacket  22 . The dam  60  is preferably rectangular and fits snugly within the opening  26 . 
     As shown in FIGS. 6 and 7, the dam  60  includes a flexible inner portion  62  sealingly engaging the outer surface  14  of the tank  12 . The inner portion  62  is preferably made of flexible urethane. The dam  60  also includes an outer portion  64  made of expandable polystyrene and fixed to the inner portion  62  by suitable means such as adhesive. The outer portion  64  includes, adjacent the outer end thereof, a lip  66  extending between the door  32  and the jacket  22  (FIG.  6 ). More particularly, the lip  66  extends between the intermediate portion  42  of the door  32  and the outer surface  24  of the jacket  22 , and the lip  66  is compressed between the door  32  and the outer surface  24  of the jacket  22 . The lip  66  consequently sealingly engages the outer surface  24  of the jacket  22  when the door assembly  30  is closed. The outer portion  64  of the dam  60  also includes inner walls  68  that include a shoulder  70  and that define a space containing the electrical component  20 . 
     When the door assembly  30  is in the closed position (FIGS. 1,  4 - 7 ), the inner surface  48  of the insulating cap  34  engages the shoulder  70 , and outer walls  72  of the insulating cap  34  engage the inner walls  68  of the dam  60 . More particularly, the outer walls  72  of the insulating cap  34  are wedged against the inner walls  68  of the dam  60 . The portion of the inner walls  68  that receive the insulating cap  34  are preferably tapered in the direction toward the tank  12  and toward the inside of the dam  60  so that the insulating cap  34  is forced against the dam  30  inner walls  68 . The insulating cap  34  is configured to closely cover the electrical component  20  when the door assembly  30  is in the closed position to maximize the insulating properties of the insulating cap  34 . 
     The water heater  10  includes an electrical circuit (not shown) that is electrically connected to the electrical component  20 . The electrical circuit is also electrically connected to a power source (not shown). The electrical circuit provides electricity to the electrical component  20  when the electrical circuit is closed and does not supply electricity to the electrical component when the electrical circuit is open. 
     As shown in FIGS. 2 and 3, the electrical component  20  includes a hollow plug  74  that extends from the electrical component  20  and that includes four pairs of contacts  76  which are positioned within the plug  74  and connected to the electrical circuit. When the door assembly  30  is closed, as shown in FIGS. 6 and 7, the plug  74  is inserted into the socket  54  such that one of the electrical conduits  36  is inserted between the first and second contacts  76  and the other electrical conduit  36  is inserted between the third and fourth contacts  76 . Connection of the electrical conduit  36  with the contacts  76  of the plug  74  closes the electrical circuit thereby providing electricity to the electrical component  20 . Conversely, when the door assembly  30  is opened, as shown in FIG. 2, the plug  74  is removed from the socket  54  removing the electrical conduit  36  from contact with the contacts  76  so that no electricity is provided to the electrical component  20 . In addition to opening and closing the circuit, the plug  74  and socket  54  arrangement can also be configured to secure the door assembly  30  in the closed position. 
     The present invention is not limited to the plug  74  and socket  54  arrangement of the illustrated embodiment. Rather, other structures known to those skilled in the art can be used to close the electrical circuit when the door assembly  30  is in the closed position, such as, for example, a spring contact. 
     Typically, the electrical circuit will be connected to a 220-volt power source thereby providing 110 volts through a wire  56  connected to the first contact  76  and 110 volts through a wire  58  connected to the second contact  76 . Therefore, to completely disconnect the electrical component from electricity, both wires  56 ,  58  must be disconnected from the electrical component  20 . 
     Disconnecting the electrical component  20  from the power source of the electrical circuit by removing the door assembly  30  is advantageous because it reduces the risk of electrocution when the electrical component  20  is made accessible for adjustment or maintenance. Therefore, the electrical component  20  will not be supplied with electricity when the door assembly  30  is removed. 
     The water heater  10  is assembled as follows. First, the tank  12 , the electrical component  20 , the jacket  22 , and the dam  60  are arranged as described above. Next, the door assembly  30  is secured over the opening  26  so that the lip  66  of the dam  60  is compressed between the door  32  and the jacket  22 . By securing the door assembly  30 , the insulating cap  34  is inserted into the dam  60  and the plug  74  is inserted into the socket  54  as described above. Last, insulating foam  28  is injected between the tank  12  and the jacket  22  and around the dam  60  to provide insulation between the tank  12  and the jacket  22 . Because the dam  60  sealingly engages both the tank  12  and the jacket  22 , the dam  60  keeps substantially all of the foam  28  outside of the cavity  50  and thereby substantially prevents the foam  28  from reaching the electrical component  20 . 
     To enhance the performance and efficiency of the water heater  10 , it has become necessary to increase the thickness of the insulating foam  28  between the tank  12  and the jacket  22 . Increasing the thickness of the insulating foam  28  also increases the pressure that is exerted on the dam  60  and insulating cap  34  by the foam  28  during the injection process. In order for the dam  60  and the insulating cap  34  to withstand this increase in pressure, the insulating cap  34  is preferably molded from a ceramic foam to improve the strength and insulation characteristics of the insulating cap  34 . Specifically, the ceramic foam insulating cap  34  rigidifies the dam  60  and helps the dam  60  to resist the force exerted on the dam  60  by the foam  28  during injection of the foam  28 . 
     An alternative construction of a water heater  110  is illustrated in FIGS. 8-12. In this embodiment of the invention, the water heater  110  includes a door assembly  112  having a door  114 , a dam  116  connected to the door  114 , and a connecting device, such as electrical conduits  36 . The dam  116  replaces the dam  60  and insulating cap  34  arrangement of the water heater  10  illustrated in FIGS. 1-7 and serves the functions of both the dam  60  and the insulating cap  34 . As most of the elements of the water heater  110  remain identical to the water heater  10 , identical reference numerals are used in FIGS. 8-12 to identify features common to both illustrated embodiments, and the description of the common features will not be repeated. 
     As shown in FIG. 9, the dam  116  is connected to the door  114  and includes a concave inner surface  120  that is spaced a distance from the door  114 . The dam  116  includes a rectangular cavity  122  that is recessed from the inner surface  120  toward the door  114  thereby defining a first recessed wall  124 . The dam  116  is preferably molded directly to the door  114 , and preferably molded from ceramic foam or urethane foam. However, the dam  116  can be molded from other materials that are electrically non-conductive, that are poor thermal conductors, and that are substantially rigid to withstand the pressures exerted on the dam  116  during injection of the insulating foam  28 . The dam  116  also includes a socket  54  that is recessed from the first inner surface  120 . 
     The door assembly  112  is movable between the open and closed position and is movable to open and close the electrical circuit in the same manner as described above with respect to the water heater  10 . The cavity  122  is configured to closely cover the electrical component  20  when the door assembly  112  is in the closed position to maximize the insulating properties of the dam  116 . 
     The dam  116  includes a lip  134  extending between the door  114  and the jacket  22 . More particularly, the lip  134  extends between an intermediate portion  42  of the door  114  and the outer surface  24  of the jacket  22 , and the lip  134  is compressed between the door  114  and the outer surface  24  of the jacket  22 . The lip  134  consequently sealingly engages the outer surface  24  of the jacket  22 . 
     The water heater  110  is assembled as follows. First, the tank  12 , the electrical component  20 , and the jacket  22  are arranged as described above. Next, the door assembly  112  is secured over the opening  26  so that the lip  134  of the dam  116  is compressed between the door  114  and the jacket  22 . By securing the door assembly  112  to the jacket  22 , the concave inner surface  120  of the dam  116  snugly engages the outer surface  14  of the tank  12  and the plug  74  is inserted into the socket  54 . Last, insulating foam  28  is injected between the tank  12  and the jacket  22  and around the dam  116  to provide insulation between the tank  12  and the jacket  22 . Because the dam  116  sealingly engages both the tank  12  and the jacket  22 , the dam  116  keeps substantially all of the foam  28  outside of the dam  116  and thereby substantially prevents the foam  28  from reaching the electrical component  20 . In order to prevent the dam  116  from bonding to the injected foam  28 , the dam  116  is coated with a releasing agent prior to injecting the insulating foam  28  so that the door assembly  112  can be opened and the dam  116  can be removed from the jacket  22 .