Abstract:
A vent for a dishwasher provides a valve with dual actuation, either to be electrically actuated according to a cycle of the dishwasher so as to close during periods of high noise generation, typically the wash cycle, and opened during the dry cycle, or to be actuated independently of the cycle under pressure differences such as may be caused by interruption of the dishwasher cycle and opening and closing of the dishwasher door such as may cause a pressure surge as the introduced cool air is rapidly heated in the interior of the dishwasher.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     BACKGROUND OF THE INVENTION 
     The present invention relates to automatic dishwashing machines (dishwashers) and in particular to a dishwasher providing for low noise operation. 
     Dishwashers, such as those found in many homes, provide a closable chamber holding one or more racks into which eating utensils and cookware may be placed for cleaning. The chamber may include a door, opening to the front of the chamber to allow easy loading and unloading of the chamber, and closing, during a washing cycle, to prevent the escape of water which is sprayed within the volume of the chamber to wash the items placed in the racks. 
     Upon completion of the washing cycle, a drying cycle is initiated in which water is drained from the enclosure and moist air is discharged through an upper vent. Cool air pulled into the chamber through a lower vent rapidly dries the heated dishes. 
     Dishwashers can be quite noisy during the washing cycle, the noise coming from the agitated water, movement of the dishes, and the dishwasher mechanism of the water pump and motor. Some of this noise can be reduced by properly shrouding the chamber and dishwasher mechanism with sound absorbing materials. Nevertheless, a considerable amount of noise can still escape from even a properly shrouded chamber through the vents. Even a small vent area can allow a significant amount of noise to escape by diffraction. 
     One method of reducing noise escaping through the vent is to construct a vent which may close during the washing cycle and then open once the agitated water and pumping action has ceased to allow for proper drying of the dishes. Unfortunately, such closable vents can create a problem when the user interrupts the washing cycle to add a forgotten item for cleaning. When the dishwasher door is opened to insert the additional item, the chamber&#39;s volume of heated, moist air is replaced by colder air from the room. When the dishwasher door is reclosed, the hot dishes, racks and walls of the dishwasher together with the agitating hot water quickly heat the cold air causing it to expand. This expansion can force water from the dishwasher out through the door leading the user to believe the dishwasher has malfunctioned. 
     BRIEF SUMMARY OF THE INVENTION 
     The present inventors have recognized that a low noise vent for a dishwasher can be produced by properly combining an electrically actuated valve with a pressure actuated valve. The electrically actuated valve may be closed during the washing cycle and opened during the drying cycle, whereas the pressure actuated valve may provide relief of the surge pressure generated when the wash cycle is interrupted and started again. 
     Importantly, the pressure actuated valve may respond at an arbitrary time in the washing cycle independent of the cycle timer of the dishwasher while the electrically actuated valve may respond during the drying cycle when no triggering change in pressure occurs. 
     Specifically, then, the present invention provides a noise reducing vent for use with a dishwasher, the vent having an electrically actuated valve positioned to block passage of air from the sealable volume of the dishwasher to the outside of the dishwasher in a closed state and to allow the passage of air from the sealable volume to the outside of the dishwasher in an open state, the electrically actuated valve moving between the open and closed state in response to an electrical signal. The electrically actuated valve is combined with a pressure actuated valve positioned to block the passage of air from the sealable volume to the outside of the dishwasher in a closed state and to allow the passage of air from the sealable volume to outside the dishwasher in an open state, the pressure actuated valve moving from the closed to the open state in response to a predetermined excess of air pressure in the sealed volume over the air pressure outside the dishwasher. 
     It thus is one object of the invention to provide a vent that can be closed to reduce noise emitted from a dishwasher in response to normal cycle timing of the dishwasher and yet which prevents over-pressure of the sealed volume of the dishwasher such as may occur after interruptions of the washing cycle when the door of the dishwasher is opened. 
     The electrically actuated valve may employ a wax motor moving a valve element to cover or uncover an aperture leading between the sealable volume and outside of the dishwasher. 
     Thus it is another object of the invention to permit the use of an inexpensive yet slower wax motor for opening and closing the valve during the expected changes between cycles of the dishwasher while allowing response to extremely fast and unexpected pressure fluctuations caused by interruption of the washing cycle. 
     The predetermined pressure at which the pressure-actuated valve is triggered may be set to less than one inch of water. 
     Thus it is another object of the invention to provide a vent which actuates to rapidly suppress low surge pressures that might otherwise be sufficient to expel water from water traps that are used in some dishwashers to block air inlet vents during the washing cycle. 
     The pressure-actuated valve may be a caged ball seatable against a circular aperture leading between the sealable volume and the outside of the dishwasher. Alternatively, the pressure-actuated valve may include at least one flap hinged to movably cover an aperture leading between the sealable volume and outside the dishwasher. 
     Thus it is another object of the invention to provide extremely simple and robust valve mechanisms that may be pressure actuated at very low pressures. 
     The vent may include a common housing providing a first opening to the sealable volume and a second opening to outside the dishwasher, the first and second openings separated by a wall having a first and second aperture, each associated with one of the electrically actuated valves and pressure-actuated valves. 
     Thus it is another object of the invention to provide an integral vent unit such as may be mounted in the door of the dishwasher or the like. 
     The housing may include a second wall opposed to the first aperture having a third aperture therein and the electrically actuated valve may include a flexible boot having a valve surface sized to block the first aperture when the electrically actuated valve is actuated to block the first aperture, the flexible boot having side walls extending from the valve surface to an edge attached at the third aperture. 
     Thus it is another object of the invention to provide an electrically actuated valve that may be shielded from all contact material from the sealable volume of the dishwasher. 
     The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration, a preferred embodiment of the invention. Such embodiment does not necessary represent the full scope of the invention, however, and reference must be made to the claims herein for interpreting the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified perspective view of a residential dishwasher showing the flow of cold and hot air into and out of the dishwasher when the washing cycle is interrupted and showing a vent path through the dishwasher door; 
     FIG. 2 is a graph plotting pressure versus time after a closing of the door of a dishwasher after interrupting of the washing cycle of the dishwasher of FIG. 1 with the vent path closed to reduce noise and further showing resultant surge pressure as is reduced by the present invention; 
     FIG. 3 is a perspective cutaway view of a first embodiment of the present invention showing a housing providing a first aperture separating the inside and outside of the dishwasher, the first aperture provided with a ball and cage valve in an open state, the housing also providing a second aperture for use with an electrically actuated valve not shown in FIG. 3; 
     FIG. 4 is a cross-section along line  4 — 4  of FIG. 3 showing the electrically actuated valve as may be positioned on the second aperture of FIG. 3 per the present invention; 
     FIGS. 5 a  and  5   b  are alternative embodiments of the pressure actuated valve of FIG. 3 in which an elastomeric flap is used to cover apertures leading between the inside and outside of the dishwasher, FIG. 5 a  showing the valve in the closed state and FIG. 5 b  showing the valve in the open state; 
     FIG. 6 is a fragmentary figure similar to FIG. 3 showing an alternative embodiment with integrated pressure and electrically actuated valves; and 
     FIG. 7 is a fragmentary cross-sectional along line  7 — 7  of FIG. 6 showing operation of the alternative embodiment of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, a dishwasher  10  includes a generally rectangular cabinet  12  open at the front but sealable by a hinged door  14  at that opening to define an enclosed volume  16 . The volume  16  may hold one or more racks  18  to support dishes  20  or other items to be washed. The door  14  may include a vent  22  allowing passage of steam and air from the enclosed volume  16  to the outside of the dishwasher  10  as indicated by arrow  24 . 
     Referring now to FIGS. 1 and 2, when the door  14  of the dishwasher  10  is opened as shown in FIG. 1 after initiation of the dishwashing cycle, heated air  26  escapes from the volume  16  to be replaced by cooled air  28  from the room. As shown in FIG. 2, when the door  14  is closed again at time to and if the vent  22  is closed to reduce sound level outside of the dishwasher  10 , then a rapid pressure spike  30  occurs caused by the heating of the air held within the enclosed volume  16  by the already warmed dishes  20  and walls of the volume  16 . At time t 1 , when agitation of hot water is resumed, the pressure rises to a spike  32  that may be sufficient to force water from the volume  16  past the door  14 . 
     Referring now to FIG. 3 for this reason, the present invention provides a vent  22 , having a housing  34  such as may be a generally rectangular, parallelepiped having a first opening  36  communicating with the sealable volume  16  of the dishwasher  10  to allow the passage of air and steam  38  into the housing  34 . A second opening  40  in the housing  34  communicates directly with the air outside of the dishwasher  10  allowing the passage of air and steam  38  from the housing  34  out to the outside air. 
     Dividing the interior volume of the housing  34  is a wall  42  such as may be positioned horizontally and which has two apertures  44  and  46  cut therein. Air and steam  38  flowing into the first opening  36  must pass through one of apertures  44  and  46  so as to continue and flow out through opening  40 . 
     A ring-shaped valve seat  47  encircles aperture  44 . On the top edge of the valve seat a lightweight ball  48  may rest. The upper half of the ball is encircled by a cylindrical cage  50  preventing the ball from moving substantially off of the axis of the valve seat  47 . 
     When the pressure of the air within the volume  16  of the dishwasher  10  is substantially equal to or less than the ambient pressure, the ball  48  rests on the valve seat  47  sealing aperture  44  and preventing the escape of sound through the aperture  44 . Alternatively, when the pressure within the volume  16  rises such as in pressure spike  30  and  32  shown in FIG. 2, the ball rises allowing passage of air and steam  38  through aperture  44 . 
     The size and weight of the ball  48  and the area of the valve seat  47  may be adjusted so that this pressure threshold occurs at approximately one inch of water. Accordingly, referring again to FIG. 2, the pressure spikes  30  and  32  are reduced to levels  31  and  33  insufficient to eject water from the volume  16  of the dishwasher  10 . Instead, pressurized air and steam  38  will overcome the weight of the ball  48  and pass through the aperture  44  to escape out opening  40 . 
     Referring now to FIGS. 3 and 4, positioned across from the wall  42  and aperture  46 , is parallel wall  51  having an aperture  52  coaxial with aperture  46 . Wall  51  serves to support electrically actuated valve  54  (shown only in FIG.  4 ). The electrically actuated valve  54  includes a flexible boot  56  having a generally planar valve surface  58  sized to block the aperture  46  when the valve surface  58  is pressed against aperture  46  thereby obstructing the flow of air and steam  38 . The valve surface  58  is pressed against aperture  46  (or withdrawn therefrom) by a plunger  60  fitting within the boot  56  and adjacent to an inner side of valve surface  58  opposite the aperture  46 . The plunger  60  in turn connects to a shaft  62  of a wax motor  64 . Operating according to well-known principals, the wax motor  64  moves the shaft  62  toward the aperture  46  when electrical current is conducted through terminals  66  of the wax motor  64  to heat an internal element (not shown), melt a contained wax material causing expansion of that material against the shaft  62 . The terminals  66  are connected to a cycle timer (not shown) of conventional design to provide current during the wash cycle and thereby to close the aperture  46  during that time of high noise generation. It will be understood from this description that an inverted logic may also be used in which the presence of current from the cycle timer opens the aperture  46  or wherein a bi-state mechanism is adapted where current alternately opens then closes the aperture  46 . 
     The boot  56  has upwardly extending sidewalls  68  terminating at a radially extending flange  70 , the latter which fits into a depressed rim  72  ringing the aperture  52 . 
     It will be understood that the depressed rim  72  is not required and that flange  70  could sit on top of wall  51 . A corresponding flange plate  74  on the wax motor  64  sandwiches the flange  70  between the depressed rim  72  and the flange plate  74  sealing the boot against the wall  51  and protecting the wax motor  64  from water and steam  38 . The flange plate  74  also serves to support the wax motor  64  against the wall  51 . 
     Referring to FIGS. 5 a  and  5   b , the pressure actuated valve need not be limited to the ball and cage design shown in FIG. 3 but may include generally any well known pressure actuated valve including diaphragm, umbrella, and flapper valves known in the art. In one such alternative embodiment, aperture  44  is separated into two portions  44   a  and  44   b  as divided by diametric support bar  80 . An elastomeric flap  82  is attached at its center to the diametric support bar  80  to extend over the apertures  44   a  and  44   b  and in a relaxed state to lie horizontally atop wall  42  sealing in noise. Pressure from air and steam  38  above a designated threshold, as shown in FIG. 5 b , causes an upward flexing of the edges of the elastomeric flap  82  away from the apertures  44   a  and  44   b  allowing passage of air and steam therethrough. The weight and elasticity of the flap  82  and the area of the apertures  44   a  and  44   b  may be adjusted so as to provide an arbitrary pressure threshold for opening and the necessary clear aperture when the flap  82  does open. The ability to subdivide the aperture  46  allows great flexibility in the selection of different elastomeric interior materials. 
     Referring now to FIGS. 6 and 7 in an alternative embodiment, the separate pressure actuated valve formed by ball  48  and valve seat  47 , operating to open and close aperture  44 , and electrically actuated valve  54  operating to open and close aperture  46 , (all shown in FIG. 3) may be combined so that only a single aperture  90  is cut within wall  42  providing a single path through wall  42  between openings  36  and  40 . 
     The aperture  90  may be covered by a generally rectangular flap  92  lying in a closed state atop wall  42  over aperture  90  and hinged at one end by knuckle  94  supported by horizontally opposed pintels  96  so that the flap  92  may rotate about the knuckle  94  and rise away from aperture  90  under the same excess pressure conditions that lift ball  48  from valve seat  47  (shown in FIG.  3 ). In this regard, the weight of the flap  92  is adjusted to provide for similar pressure relief as provided by ball  48  and seat  47  or flap  82  and aperture  44 . 
     Extending oppositely from knuckle  94  away from flap  92  is a hook  98  curving upward from wall  42  so as to be behind downwardly extending finger  100  attached to shaft  102  of wax motor  104 . When current is not provided to the wax motor  104 , the downward finger  100  moves from a first position  103  to a second position l 05  engaging hook  98  to raise flap  92  away from aperture  90 . When the wax motor  104  receives current, the downward extending finger  100  returns to the first position  103  in which hook  98  does not engage downward finger  100  allowing for the full range of motion of the flap  92  between open and closed state. 
     Thus, it will be understood that in the first position  103 , the flap  92  is free to move in response to pressure but in the second position, the flap is raised away from aperture  90  independent of any excess pressure but in response to the removal of the electrical signal from the dishwasher timer. 
     As will be understood in the art, the wax motor  104  may be replaced with other electrical actuators including but not limited to solenoids and motors and that the signal from the dishwasher may be either a current or lack of current as is necessary for correct operation of the vent  22 . 
     The above description has been that of a preferred embodiment of the present invention, it will occur to those that practice the art that many modifications may be made without departing from the spirit and scope of the invention. In order to apprise the public of the various embodiments that may fall within the scope of the invention, the following claims are made.