Dishwasher Drying System

Abstract

A domestic dishwasher drying system in which heated moist air is withdrawn from the upper portion of the tub by a blower which also draws cooling air over the motor driving the blower and pump, the moist heated air and the motor cooling air being mixed and passed through a duct for discharge into the room space at the lower front of the dishwasher. A water tap is provided at the outlet of the tub which prevents the withdrawal of air during washing and rinsing operations in the dishwasher.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to the art of drying systems for domestic dishwashers.

2. Description of the Prior Art

The prior art patents of which we are aware and in which in a domestic dishwasher air is moved into or out of the tub with a forced air system are U.S. Pat. Nos. 3,397,708; 3,241,563; 3,126,898; 3,126,024; 3,103,227; and 2,674,249. In the arrangements of the first two, fourth and sixth listed patents, the air is forced into the tub during the drying operation. In the arrangements of the other two patents, air is withdrawn from the lower portion of the tub and is mixed with air heated by the motor in the space below the dishwasher tub.

It is our view that our system provides advantages in certain respects over the two patents mentioned in which air is withdrawn from the tub and which are considered closest in concept to a system in accordance with our invention.

SUMMARY OF THE INVENTION

In accordance with our invention, the arrangement includes a tub with heating means in the lower portion energized at least during the drying operation, means defining an air inlet through the tub adjacent the lower edge of the tub door, means in the upper portion of one of the vertical walls of the tub defining an air outlet from the tub, with the outlet means including means for trapping water to substantially block the outlet from the tub during washing and rinse operations and for releasing the water block during a drying operation, an electric motor driven blower having a suction and pressure side means for channeling air in heat exchange relation past the motor to the suction side of the blower, duct means connecting the air outlet for the tub to the suction side of the blower, and discharge duct means leading from the pressure side of the blower to the room space at the lower front of the dishwasher. Thus during a drying operation, the blower draws both moist air from the tub and heated air from the motor and discharges the comingled air through the discharge duct means. The arrangement according to the invention also contemplates that the water inlet opening to the tub be located in the upper portion of the tub so that following the drying operation, ventilating air can enter the tub through the air inlet and leave by way of at least the opening through which water is admitted to the tub.

DRAWING DESCRIPTION

FIG. 1 is a partly schematic side elevational view of an undercounter dishwasher provided with a drying system according to the invention;

FIG. 2 is an isometric view of the motor-blower-pump assembly for the dishwasher;

FIG. 3 is a partly broken view of the interior of the blower; and

FIG. 4 is a vertical section corresponding to one taken along the line IV--IV of FIG. 1 and illustrating the air outlet arrangement for the tub including the water trap.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, the undercounter domestic dishwasher illustrated is shown in a typical location installed below a kitchen counter top 10. The tub is conventional in the sense of including opposite side and rear walls 12 and 14, respectively, a bottom sump 16 and an open front face 18 adapted to be closed by a door 20 hinged adjacent its lower edge, as is conventional. The sump contains an electric resistance heater 22 adapted to be energized at least during a dish drying operation. The dishwasher includes the usual conventional components such as controls including a timer which controls a cycle including wash, rinse and dry operations, dish racks, water drain arrangement, and the water inlet control arrangement, for example. As such are not a part of the invention, they are not shown. However, the location of the water inlet 23 in the upper portion of the tub on the wall opposite that wall facing the viewer in FIG. 1 is shown. In accordance with conventional practice, the water inlet opening 23 to the tub is in communication with atmosphere through the conventional air gap provided in the water inlet arrangement for the dishwasher.

Referring now to FIGS. 2 and 3 as well as FIG. 1, a motor-air blower-water pump assembly generally designated 24 is supported below the bottom sump wall 16 of the tub. This assembly is mounted in generally canted relation to the planes of the vertical walls of the tub as is perhaps best seen in FIG. 1. The shaft 26 (FIG. 3) of the motor 28 drives both the air blower 30 and the water pump 32 arranged in successive series relation at the one end of the motor. The water return inlet for the pump is designated 34 while the pump recirculation outlet is designated 36. As is conventional, in a recirculation mode the water which accumulates in the sump is drawn into the inlet 34 and forced up through the outlet 36 into water distributing means (not shown) located within the tub. In a drain mode, the water drawn into inlet 34 is pumped out a drain outlet (not shown).

The housing of the motor 28 includes air inlet openings 38 through which air flows into and past the motor in heat exchange relation. The end of the motor housing 28 opposite the viewer in FIG. 2 is provided with openings therein which permits the heat exchange air to pass therethrough and through a large circular opening in the side wall 40 of the blower. A fragmentary portion of this blower wall 40, and a portion of the edge of the large opening 42 through which the heat exchange air from the motor passes to the eye of the centrifugal blower 44 are shown in FIG. 3.

Referring to FIG. 3, the blower 30 includes a casing 46 of generally scroll shape in outline including an opposite end wall 48, only part of which is seen through the arc-shaped opening 50 provided in a partition 52 which is spaced from and generally parallel to the end wall 48. This arrangement is provided so that air may be drawn into the eye of the impeller 44 both through the usual location, which is the opening 42 aligned with the axis of the blower, and from a peripheral location on the scroll. At this peripheral location there is a hollow connection 54 through which air is received from the tub, as will be explained later. The air which is admitted through the connection 54 flows as indicated by the arrows in FIG. 3 into the space between the end wall 48 and the partition 52, and is then drawn into the eye of the impeller through the arc-shaped opening 50 and through a series of openings 56 in the back plate 58 of the impeller. The outlet connection from the blower is designated 60.

The suction side of the blower is connected to the tub air outlet generally designated 62 by a hose or duct 64 which extends from the air outlet to the blower connection 54. An opening 66 is provided in the upper portion of the side wall 12 of the tub. A fitting 68 is secured to the inside face of the wall 12 to prevent water from being thrown directly through the opening 66 by the water distributing means in the tub. The fitting includes a lower water trap portion 70 which holds water thrown at the side wall by the water distributing means during wash and rinse operations. The trap includes a leak hole 72 in its bottom through which the water 74 accumulated in the trap drains continuously during the wash and rinse operations. However, the hole 72 is sized so that the trap maintains a water level, as shown, by the continual addition of water flung about by the water distributing means.

On the exterior side of the wall 12, a connecting fitting 76 is provided to which the duct 64 is connected. In some models, it is desirable to provide a pressure relief hole 78 in the exterior connector so that the suction pressure induced by the blower is not sufficient that the water 74 bubbles and the air seal provided thereby is lost. The size of the pressure relief opening 78, if it is needed at all, is dependent upon the suction pressure developed by the blower in the air outlet plenum, relative to the head of water in the trap 70. So long as the machine cycle is in a washing or rinsing operation during which water is being flung about, the trap will prevent air from leaving the tub. This is of course desirable since loss of air would also result in loss of heat from the tub and the water therein. When the machine goes into a dry operation, and no water is being flung about the tub, the water in the trap drains through the hole 72 and then air can exit through the outlet means in the path indicated by the dash line arrows in FIG. 4.

During the drying operation, the heater 22 is energized to facilitate the drying. Accordingly, the tub contains moist hot air during the drying operation. Air is admitted into the tub through an air inlet 80 (FIG. 1) formed in the lower portion of the door 20 and provided with suitable baffles to prevent the passage of water outwardly therethrough during a washing and rinsing operation. Thus the admission of room air from in front of the machine and into the lower portion where it is heated and rises by convection results in a naturally convective flow toward the upper portion the tub. The air outlet means 62 is located in the upper portion of the tub (i.e., above the middle of the tub with respect to its height). Since the suction side of the blower is connected to the air outlet means, a small volume of air is constantly being withdrawn from the tub during the drying operation and drawn into the blower 30. At the same time, a much larger quantity of air is being drawn to the suction side of the blower in heat exchange relation through the motor 28. The relatively small quantity of hot moist air from the tub, and the heated air drawn past the motor, is comingled as it passes through the blower and is directed out of the blower outlet 60 through the discharge duct 82 connected to the outlet. This discharge duct is preferably of a material which absorbs vibration, such a a soft plastic foam, which also gives it the property of some sound absorption. This duct leads to the lower front of the dishwasher where an elbow 84 directs it downwardly through an opening in the horizontal wall of the toe panel 86. Thus, this comingled heated moist air from the tub, and the heated air from the motor is carried out from underneath the tub and discharged into the room air space at the lower front of the dishwasher. This is considered highly preferable to simply discharging this air into the total space underlying the tub where the heat could cause motor temperature rise problems, as well as the moisture would tend to condense upon cooler surfaces thereabout.

The significance of the location of the water inlet opening 23 in the upper portion of the tub wall relates to obtaining a ventilating air flow through the tub after the drying operation is terminated. Under some conditions, the air inside the tub at the end of a drying operation is still somewhat moist. Since at the end of a drying operation the walls of the tub cool down faster than the dishes and utensils in the tub, moisture will condense first upon these walls to the degree that it is present. This can give an impression that an inadequate drying job has not been done on the dishes. By virtue of the ventilation through the inlet 80 and out the water inlet 23 at this time, the relative humidity of the air in the tub is reduced more quickly.

The rate at which warm moist air is drawn from the upper portion of the tub by the blower, relative to the rate at which dry air is drawn in heat exchange relation past the motor, when a heating element 22 of typical wattage rating is used, is relatively small. When using a heating element of approximately 700 to 750 watts, in a tub of ordinary size, it is believed that drawing air at a rate falling at a range of about 2 to 7 CFM provides satisfactory operation. The rate at which cooling air is drawn past the motor of course depends upon the character of the motor itself, but this rate in one commercial device which we envisage employing the invention may be in the order of, say, 50 CFM.

With the arrangement as disclosed, there is little if any visible moist air exiting from the dishwasher during a drying operation. This is of course because it is being forced out at a substantial velocity, and the warm, moist air from the tub is highly diluted by the warm, dry air drawn past the motor.

Claims

We claim:

1. In a domestic undercounter dishwasher including a tub and having a heater in the lower part thereof adapted to be energized at least during a drying operation following washing and rinsing operations, a drying system therefor including:

a motor driven blower below said tub;

means for admitting room air into the lower portion of said tub;

means for drawing warm, moist air from the upper portion of said tub to said blower, and for drawing dry air in heat exchange relation past said motor to said blower, and mixing said moist air and said dry air and conveying all of said mixed air from said blower through a separate discharge duct having an outlet at the lower front of said dishwasher in communication with the room space in which said dishwasher is located, and

water trap means for blocking the withdrawal of air from the upper portion of said tub during washing and rinsing operations.

2. In a dishwasher according to claim 1 wherein:

said warm moist air constitutes a minor portion of the total of said mixed air.

3. In a dishwasher having a cycle including wash, rinse, and dry operations:

a tub including opposite and rear side walls and having an open front face;

a door on the open front face of said tub;

a heating element in the lower portion of said tub energized at least during said drying operation;

means defining an air inlet to said tub adjacent the lower edge of said door;

means in the upper portion of one of said side walls defining an air outlet from said tub, said air outlet means includes means for trapping water to substantially block said outlet from said tub during wash and rinse operations, and for releasing said water to unblock said air outlet during a drying operation;

a blower having a suction and a pressure side;

an electric motor driving said blower;

means for channeling air in heat exchange relation past said motor to the suction side of said blower;

means conecting said air outlet means for said tub to the suction side of said blower;

discharge duct means having an inlet end connected to said pressure side of said blower, and an outlet end in communication with the room space in front of said dishwasher so that the air discharged from said blower is directed into the room in front of said dishwasher; and

said blower operating during said dry operation to draw both moist warm air from said tub and heated air from said motor and discharging all of said comingled air through said discharge duct outlet.

4. In a dishwasher according to claim 3 wherein

said water trapping means includes a reservoir in which water is accumulated during washing and rinsing operations, said reservoir including a leak port therein to permit said water to drain therefrom at the conclusion of said operations.

5. In a dishwasher according to claim 4 wherein

said air outlet means includes a pressure relief opening on the downstream side of said reservoir, relative to the direction of air flow through said air outlet means.

6. In a dishwasher according to claim 3 wherein:

said dishwasher includes a water inlet opening, placing the interior of the tub in communication with the exterior, in the upper portion of one of said side walls of said tub.