Patent Application
20170014015
A conventional automated dishwasher includes either a hinged or sliding door that selectively provides access to a treating chamber in which dishes are placed for treatment according to an automatic cycle of operation. Some doors may be provided with a window through which the treating chamber may be visible from an exterior of the dishwasher. The window provides an additional component in the dishwasher which must be provided within the dishwasher in such a manner as to minimize the leakage of fluid from the treating chamber to other parts of the dishwasher or to the exterior of the dishwasher.
An embodiment of the invention relates to a dishwasher comprising a treating chamber for receiving dishes for treatment according to a cycle of operation and a door assembly selectively moveable to close an access opening to the treating chamber, the door assembly comprising a door panel having a window opening, a spacer provided between confronting inner surfaces of first and second window panes, and a peripheral frame supporting the first and second window panes within the window opening.
In the drawings:
A door assembly 20 may be movably mounted to the dishwasher 10 for movement between opened and closed positions to selectively open and close the open face 18 of the tub 14. Thus, the door assembly 20 provides accessibility to the treating chamber 16 for the loading and unloading of dishes or other washable items. When the door assembly 20 is closed, user access to the treating chamber 16 may be prevented, whereas user access to the treating chamber 16 may be permitted when the door assembly 20 is open. The door assembly 20 may be hingedly connected with the chassis 12 or slidingly attached to a drawer slide system to selectively provide access to the treating chamber 16.
Additional features, such as a liquid supply and circulation system 22, including one or more liquid supply and drain conduits, sprayers and/or pumps, a control system 24 including one or more controllers and a user interface, one or more dish racks 26, and any other alternative or additional features used in a conventional automatic dishwasher may also be provided in the dishwasher 10 without deviating from the scope of the invention.
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The peripheral frame 62 has a generally “C-shaped” interior cross-section that receives the spacer 74, the peripheral edge 70c, 72c, and at least a portion of the outer surface 70b, 72b of the exterior and interior window panes 70, 72 adjacent the spacer 74 and peripheral edges 70c, 72c and extends about the perimeter of the spacer 74 and peripheral edges 70c, 72c. The peripheral frame 62 can include opposing exterior and interior legs 90 and 92, respectively, connected by a horizontal leg 94. The exterior leg 90 can be in the form of a trim bezel. The interior leg 92 can include an inwardly extending flange 96 extending about at least a portion of the perimeter of the peripheral frame 62. The peripheral frame 62 can further include a depending leg 98 extending away from the “C-shaped” portion of the peripheral frame 62 adjacent the inner face 46 of the interior door panel 42 and configured to seal with the interior door panel 42 through the seal 78, which can be in the form of a sealant and/or a gasket.
Still referring to
The process 200 begins with assembling the spacer 74 and the edge seal element 76 between the confronting inner surfaces 70a, 72a of the exterior and interior window frames 70, 72 at 202. Assembling the spacer 74 and edge seal element 76 with the exterior and interior window frames 70, 72 can include the application of one or more sealants between the components. For example, a sealant can be provided between the spacer 74 and the edge seal element 76 and/or between the inner surfaces 70a, 72a and the spacer 74 and/or the edge seal element 76. Non-limiting examples of suitable types of sealants include silicone, a butyl rubber based sealant, a polyisobutylene sealant, and combinations thereof.
At 204, the peripheral frame 62 can be overmolded about the periphery of the assembled spacer 74 and peripheral edges 70c, 72c of the exterior and interior window panes 70, 72 in an injection molding process to encapsulate the assembled window panes 70, 72 and spacer 74. During the injection molding process, the spacer 74 provides support to the exterior and interior window panes 70, 72 to prevent the window panes 70, 72 from being damaged due to the molding pressure. The material forming the spacer 74 as well as the dimensions of the spacer 74 can be configured to provide sufficient support for the window panes 70, 72 during the injection molding process. In addition, the location and number of gates, i.e. the openings through which the molten polymeric material is injected into the mold cavity, can be selected to maintain the pressure on the window panes 70, 72 during the injection molding process below the yield point of the spacer 74. As used herein, yield point refers to the point at which plastic deformation begins in the stress-strain curve for the materials used to form the spacer 74. For example, gates can be provided at or adjacent the corners of the peripheral frame 62 and/or near the thickest portion of the peripheral frame 62, which in the embodiment of
At 206 at least a partial melt weld (also referred to as a melt bond, fusion weld, or fusion bond) can be formed between adjacent portions of the peripheral frame 62 and the spacer 74 around at least a portion of the periphery of the peripheral frame 62 and the spacer 74 to form a seal about the peripheral edges 70c, 72c of the window panes 70, 72. The materials forming the peripheral frame 62 and the spacer 74 can be selected such that a bond is formed between adjacent portions of the peripheral frame 62 and the spacer 74 during the overmolding process at 204. The bond between the peripheral frame 62 and the spacer 74 can be formed in a melt or fusion welding process in which a molecular bond is generated between two compatible thermoplastic materials when heat is used to melt or soften the polymer at the interface to enable polymer intermolecular diffusion across the interface and polymer chain entanglements to form a melt weld.
To facilitate the formation of at least a partial melt weld between the adjacent portions of the peripheral frame 62 and the spacer 74, the materials forming the peripheral frame 62 and the spacer 74 include a compatible base polymeric resin which may be the same or different. Several factors can affect the degree of welding between the materials forming the peripheral frame 62 and the spacer 74, non-limiting examples of which include the polymer structure, melt temperature, melt index (flow), and modulus of elasticity (stiffness) of the base resin. Generally, compatible materials will have a melt temperature difference within about 22° C. of each other and/or similar molecular groups. Additional parameters that can affect the degree of welding include interfacial pressure, time, and the degree of interfacial contact between the materials forming the bond.
In a preferred embodiment, the peripheral frame 62 and the spacer 74 are made from the same base resin, preferably a polypropylene-based resin. When both the peripheral frame 62 and the spacer 74 are made from a polypropylene-based resin, the amount of force required to separate the peripheral frame 62 and the spacer 74 is greater than the amount of force required when the peripheral frame 62 is made from a nylon-based material and the spacer 74 is made from a polypropylene-based material. In one example, the amount of force required to separate the peripheral frame is made from a nylon-based material and a spacer made from a polypropylene-based material was such that the peripheral frame and spacer could be separated by hand, whereas when the peripheral frame and spacer were both made from a polypropylene-based material which were at least partially melt welded, the amount of force required to separate the peripheral frame and spacer was on the order of 600-1000 lbs. The increase in separation force can provide an indication of the strength of the seal between the peripheral frame and spacer.
In the preferred embodiment, one or both of the peripheral frame 62 and the spacer 74 are made from a material that includes a polypropylene-based resin and one more additives, including a filler. The filler can be used to increase the strength of the peripheral frame 62 and the spacer 74, which may be the same or different in the peripheral frame 62 and the spacer 74. During the overmolding process of 204, the spacer 74 must be configured to support the exterior and interior window panes 70, 72 and withstand the pressure applied by the injected polymeric melt. However, increasing amounts of filler can decrease the degree of welding between materials. Thus, the amount of filler present in the spacer 74 can be selected so as to balance the requirements of strength necessary to withstand the molding pressures and provide a bond between the peripheral frame 62 and the spacer 74 having the desired strength. In an exemplary embodiment, the peripheral frame 62 is made from a material including a polypropylene-based resin and having about 10-50% by weight (wt. %) filler and the spacer 74 is made from a material including a polypropylene-based resin and having a filler loading of about 10-50 wt. %. In one example, the peripheral frame 62 includes a 20 wt. % filler loading and the spacer 74 includes a 30 wt. % filler loading. Non-limiting examples of suitable fillers include fiberglass, minerals, glass, mica, calcium carbonate, sand, quartz, carbon black, nanotubes, glass spheres, and talc.
The base resin for the peripheral frame 62 and the spacer 74 are also preferably selected to be compatible with the environment inside the dishwasher treating chamber 16. During a cycle of operation, the components of the dishwasher 10 in fluid contact with the treating chamber 16 can be exposed to a variety of treating agents and debris and variations in temperature and moisture. Polypropylene-based resins have been found to be satisfactorily compatible with the conditions inside the treating chamber 16. Alternative resins, such as polyvinylchloride, while they may exhibit acceptable bond strength between the peripheral frame 62 and the spacer 74 when used in forming the peripheral frame 62 and the spacer 74, are generally not satisfactorily compatible with the conditions inside the treating chamber 16. For example, polyvinylchloride can be damaged by repeated exposure to detergent, in some cases.
The base resin for the peripheral frame 62 and the spacer 74 can also be selected to have similar coefficients of thermal expansion. In use in the dishwasher 10, during a cycle of operation, the components exposed to the treating chamber 16 will experience variations in temperature and moisture during the cycle of operation. If the coefficient of thermal expansion of the materials used in the peripheral frame 62 and spacer 74 are too dissimilar, stress may be applied to the bonds between the peripheral frame 62 and spacer 74, potentially weakening the seal formed around the window panes 70, 72. In a preferred embodiment, the material used to form peripheral frame 62 has a coefficient of thermal expansion within 10% or less, preferably 5% or less, of the coefficient of thermal expansion of the material used to form the spacer 74. The amount of filler used in either or both the materials used to form the peripheral frame 62 and the spacer 74 can be used up to a loading level of about 50 wt. % to facilitate the adjusting the coefficient of thermal expansion for each material to a value that is within 10% and/or that is compatible with the environment within the dishwasher 10 during a cycle of operation.
The process 200 can also include an optional additional step to promote adhesion between the peripheral frame 62 and the spacer 74 at 208. In one example, at least the outer face of the head 84b of the spacer 74 can be provided with an adhesion promoter to facilitate the formation of a melt weld between adjacent faces of the peripheral frame 62 and the spacer 74. Non-limiting examples of an adhesion promoter includes Primer 94, available from 3M™, Loctite® 793™ Prism® Primer, available from Henkel. Alternatively, or additionally, the outer face of the head 84b can be treated to provide a texture or grain to the spacer 74. Non-limiting examples of treatments to add texture or grain include vapor honing, in which the outer face of the head 84b is subjected to a vapor to disrupt the surface, a chemical etching process, such as acid etching, dry or wet abrasive blasting, or a chemical mold etching process. In an exemplary embodiment, the spacer 74 can be provided with a surface roughness in the range of 0.1-0.3 micrometers.
The encapsulation of the window assembly 40 by the peripheral frame 62 and the formation of at least a partial melt weld between adjacent portions of the peripheral frame 62 and the spacer 74 is provided to form a seal about the peripheral edges 70c, 72c of the exterior and interior window panes 70, 72 to seal the chamber 80 from the exterior environment, particularly the environment within the treating chamber 16. During the overmolding process 204, the molten polymeric resin molds around the portions of the outer surfaces 70b, 72b and peripheral edges 70c, 72c of the exterior and interior window panes 70, 72 adjacent the bezel 90 and interior leg 92 and forms a mechanical bond between these adjacent components as the polymeric resin shrinks and cools. The melt weld between adjacent portions of the peripheral frame 62 and the spacer 74 provides an additional seal around the peripheral edges 70c, 72c of the exterior and interior window panes 70, 72.
During use of the dishwasher 10, water, treating chemistry, and debris can come into contact with any of the components of the dishwasher 10 in fluid communication with the treating chamber 16. If the window assembly 40 is not adequately sealed, liquid, and any materials carried by the liquid, such as food debris, can leak into the chamber 80 between the exterior and interior window panes 70, 72, and form an undesirable film or sludge within the chamber 80 over time, which may become visible to the consumer. Even if the liquid evaporates within the chamber 80, debris, such as food debris or dissolved salts carried by the liquid, will remain and can build up over time. In some cases, the liquid may even leak to an exterior of the dishwasher 10. The encapsulation of the window assembly 40 by the peripheral frame 62 and the formation of at least a partial melt weld between adjacent portions of the peripheral frame 62 and the spacer 74 is provided to form a seal about the peripheral edges 70c, 72c of the exterior and interior window panes 70, 72 to inhibit leakage around and into the window assembly 40.
Still referring to
The window assembly 340 can be encapsulated by the peripheral frame 362 in a manner similar to that described above for the window assembly 40 and peripheral frame 62 according to the process 200 of
The door assembly 20 described herein includes a window assembly 40, 340 formed with first and second window panes that define an intervening sealed chamber. In a traditional door assembly in which two separate panels are individually attached, one to the exterior door panel and the other to the interior door panel, humidity and condensation may occur between the panels, which is difficult to prevent. The window assemblies 40, 340 described herein form a sealed chamber that minimizes the likelihood of moisture and debris entering the space between the first and second window panes that could obscure the view through the window assemblies 40, 340 or build-up over time.
To the extent not already described, the different features and structures of the various embodiments of the invention may be used in combination with each other as desired. For example, one or more of the features illustrated and/or described with respect to one of the window assemblies 40, 340 may be used with or combined with one or more features illustrated and/or described with respect to the other of the window assemblies 40, 340. That one feature may not be illustrated in all of the embodiments is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different embodiments may be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described.
While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing disclosure and drawings without departing from the spirit of the invention which is defined in the appended claims.
