Forced air circulation system for a dishwasher

Abstract

There is disclosed a dishwasher incorporating a fan and motor for circulating air downwardly through the wash chamber during the drying cycle. The fan and motor are mounted within the dishwasher door. The fan is of the squirrel cage type with the motor being mounted radially inwardly of the fan blades.

Description

Without exception, presently available dishwashers incorporate means for drying dishes in the wash chamber. Presently used drying techniques appear to fall in one of two categories. The first category involves the use of a resistive heating element disposed in a lower portion of the wash chamber which is energized during the drying cycle. There is accordingly established a convectional air circulation system which flows air upwardly through the wash chamber. With this drying technique, hot humid air is typically exhausted from an upper portion of the wash chamber with relatively cool low humidity air passing into the wash chamber adjacent the bottom thereof. The second category of drying techniques is a forced air circulation system in which a fan is positioned under the tub and forces air upwardly therethrough to exhaust adjacent the top of the wash chamber. In this technique, the circulated air is heated before introduction into the wash chamber and/or heated in the wash chamber. Since the air is relatively hot, there are established natural convection currents upwardly through the wash chamber which supplement the upward forced air circulation.

It has been found that passing air downwardly through the wash chamber during drying in opposition to natural convection currents has a number of advantages as pointed out more fully hereinafter.

Disclosures of general interest are found in U.S. Pat. Nos. 2,608,003; 2,708,230; 3,068,877 and 3,241,563.

It is an object of this invention to provide a forced air circulation system for a dishwasher which incorporates means for passing air downwardly through a heated wash chamber during the drying cycle.

In summary, this invention comprises a dishwasher including a tub and a movable door defining therebetween a wash chamber, the door having inner and outer panels providing therebetween a compartment; an article receiving rack and means mounting the rack for movement into and at least partially out of the wash chamber; means for spraying washing liquid toward the rack; a source for heating air passing through the wash chamber during a drying portion of the operating cycle; and means for passing air downwardly through the wash chamber during the drying portion of the operating cycle including a fan, in the compartment, having an inlet opening to the exterior of the dishwasher and an outlet opening through the inner door panel into the wash chamber at a first predetermined level; a motor drivably connected to the fan; and means for exhausting air from the wash chamber at a second predetermined level below the fan outlet.

IN THE DRAWINGS

FIG. 1 is an isometric view of the exterior of the dishwasher;

FIG. 2 is an enlarged cross sectional view of the dishwasher of FIG. 1 taken substantially along line 2--2 thereof as viewed in the direction indicated by the arrows;

FIG. 3 is a partial front elevational view of the dishwasher door, part of the outer door panel being broken away for clarity of illustration;

FIG. 4 is an isometric view of a fan-motor arrangement utilized as part of this invention; and

FIG. 5 is a cross sectional view of the dishwasher door illustrated in FIG. 3 taken substantially along line 5--5 thereof as viewed in the direction indicated by the arrows.

Referring to FIGS. 1 and 2, there is illustrated a dishwasher 10 comprising as major components a cabinet 12 including a door 14, a tub 16 providing with the door 14 a wash chamber 18, a plurality of racks 20, 22, 24 for receiving articles to be washed, means 26 for spraying washing liquid toward the racks 20, 22, 24, means 28 for heating the wash chamber 18 during the drying cycle, means 30 for circulating air through the wash chamber 18 during the drying cycle and a timer mechanism 32 for controlling the operation of the dishwasher 10.

The cabinet 12 provides a lower front panel 34 generally coplaner with the front of the door 14 and an upstanding flange 36 from which extend a pair of brackets 38. The door 14 is pivotally mounted on the bracket 38 by a pair of pins 40 for movement between a generally horizontal open position and a generally vertical position closing the front of the tub 16. A suitable peripheral gasket 42 seals between the door 14 and the tub 16.

The door 14 comprises an outer door panel 44 and an inner door panel 46 defining therebetween a door compartment 48 housing the timer 32, part of the air circulating means 30, electrical wiring (not shown) and other washing aids such as a detergent dispenser (not shown) or the like.

The tub 16 may be of any suitable design and includes a tub bottom 50 separating the wash chamber 18 from a pump-motor compartment 52. The tub 16 also provides ledges 54 therein for supporting the lower rack 24 for movement between positions in and at least partially out of the wash chamber 18. The tub 16 provides additional ledges (not shown) for supporting the middle rack 22 in the wash chamber 18. Upon outward movement of the middle rack 22, the front wheels 56 thereof drop into load supported position with a rail 58 carried by the lower rack 24. Accordingly, the middle rack 22 is mounted for movement in and at least partially out of the wash chamber 18. The upper rack 20 is mounted for similar movement by a guide-roller arrangement 60.

The spraying means 26 may be of any suitable type and conveniently includes a spray arm 62 mounted for rotation about a central axis in fluid communication with a pump 64 driven by a suitable motor 66. The pump 64 and motor 66 are conveniently sealed against the tub bottom 50 by a rubber boot 68 and annular clamping ring 70. A shield 72 may be provided for protecting the boot 68. Operation of the motor 66 is controlled by the timer 32 in any suitable manner.

The heating means 28 desirably includes a resistive heating element 74 as is now customary in dishwashers. The heating element 74 is energized in response to operation of the timer 32 during the drying cycle.

One advantage of the air circulating system of this invention involves the drying of silverware carried in a receiver or basket 76 mounted on the middle rack 22. Silverware is characteristically closely spaced in the basket 76. Consequently there is a relatively large quantity of water per unit volume of the wash chamber held in the basket 76. If only for this reason, it would be desirable to provide a larger quantity of air passing through the basket 76. There is still another reason why drying of articles in the basket 76 is more difficult than other articles held in the racks 20, 22, 24. If one were to remove a hot wet plate from the dishwasher 10 at the end of the last rinse cycle and place it on a countertop, the plate will dry without artificial circulation. If one were similarly to remove a hot wet silverware piece from the dishwasher 10 and place it on a countertop, the silverware piece will not dry. This phenomenon is apparently dependent on the surface area of the two articles in relation to their heat holding capacity. For these reasons, the most acute area in the wash chamber 18 for drying is the silverware basket 76. The air circulating means 30 is particularly adapted to provide relatively large quantities of low humidity air passing downwardly through the silverware basket 76 while providing sufficient air circulation in the remainder of the wash chamber 18.

To these ends, the air circulating means 30 comprises a fan 78 having a housing 80 providing an inlet 82 opening to the exterior of the dishwasher 10 through louvers in the outer door panel 44 and an outlet 84 opening through the inner door panel 46 to the wash chamber 18.

The fan 78 is of the squirrel cage variety and includes a plurality of circumferentially spaced fan blades 86 mounted on a plate or disc 88 and positioned to provide a radially inward cavity for receiving a motor 90. The motor 90 includes an output shaft 92 secured to the plate 88 in any suitable manner for rotating the fan blades 86 in response to shaft rotation. The shaft 92 is mounted for rotation in any suitable manner, as by a bearing 94 carried by the first compartment 98 and/or by bearings (not shown) internally of the motor 90. As illustrated in FIG. 5, the motor 90 is mounted by a plurality of braces 96 to the fan housing 80. It will accordingly be seen that energization of the motor 90 rotates the shaft 92 thereby rotating the plate 88 and consequently the fan blades 86.

An important feature of the air circulating means 30 is that the motor 90 is nested within the confines of the fan 78. Accordingly, the space required for the fan-motor assembly is no greater than that required by the fan 78 itself. Thus, a conventional 7-inch outer diameter squirrel cage fan can be utilized in this invention without requiring enlargement of the compartment 48. This is of considerable practical importance since any enlargement of the compartment 48 effectively decreases the size of the wash chamber 18 and possibly interferes with the racks 20, 22, 24 therein. Furthermore, the provision of a narrow high capacity fan allows the incorporation of the air circulating means of this invention in a standard dishwasher door.

The fan housing 80 may be of any suitable design and is illustrated as a first compartment 98 enclosing the fan 78 and motor 90 providing a passage 100 into a second compartment 102 providing the outlet 84. The compartment 102 is conveniently configured in much the same manner as the vent now used on production model dishwashers.

Positioned adjacent the fan outlet 84 and connected to the inner door panel 46 is a guard 104. The guard 104 effectively prevents water emitting from the spray arm 62 from passing through the opening 84 into the fan housing 80. The guard 104 may conveniently be configured in a manner quite similar to the vent guards presently used.

The air circulating means 30 also comprises an outlet opening 106 leading from the wash chamber 18 into the door compartment 48. A deflector 108 is positioned inside the wash chamber 18 overlying the opening 106 to prevent water entry into the compartment 48. An outlet opening 110 is provided leading from the door compartment 48 to the exterior of the dishwasher to allow escape of circulated air. The air outlet 110 desirably is to the front of the dishwasher 10 rather than to the side or back thereof for better dissipation of high humidity air. It will be noted that the inlet 84 into the wash chamber 18 is above the silverware basket 76 while the outlet 106 is below the basket 76 to assure downward air movement therethrough.

In operation, the timer 32 terminates the last rinse cycle and manipulates the pump 64 to discharge the last batch of rinse water from the wash chamber 18. The heating element 74 is energized to heat the wash chamber 18 and consequently evaporate water on the articles therein. Energization of the heating element 74 tends to create upward convection currents illustrated by the dashed arrow 112. The motor 90 is energized either continuously or intermittently during the drying cycle. Upon driving of the fan 78, air enters the inlet 82 axially of the fan 78, passes in heat exchange relation to the motor 90, and tangentially discharges from the first compartment 98 into the second compartment 102. Heat exchange between inlet air and the motor 90 acts to heat the circulated air and cool the motor 90. Air exits from the outlet 84 and is diverted both upwardly and downwardly into the wash chamber 18. A substantial part of the fan discharge passes downwardly through the silverware basket 76 and exits through the openings 106, 110 to the exterior of the dishwasher 10. Part of the fan discharge moves further rearwardly of the silverware basket as suggested by the arrow 114. The forced air circulation induced by the fan 78 is sufficient to overcome the upward convection currents indicated by the dashed arrow 112.

The cooperation of the heating element 74 and the air circulation means 30 provides improved drying performance, decreased drying time or a combination thereof. Decreased cost and adequate drying performance and time may be obtained by omitting the heating element 74. The kitchenware and tableware in the dishwasher 10 are rather hot at the end of the wash cycle since hot water has been circulated in the wash chamber 18. The retained heat in the washed articles and in the dishwasher assists in evaporating water from the articles as does the circulating low humidity air. Thus, the retained heat constitutes a source in the wash chamber for heating air passing through the wash chamber.

Claims

I claim:

1. A dishwasher comprising:

a tub and a movable door defining therebetween a wash chamber, the door having inner and outer panels defining therebetween a compartment;

an article receiving rack and means mounting the rack for movement into and at least partially out of the wash chamber;

means for spraying washing liquid toward the rack;

a heat source for heating air passing through the wash chamber during a drying portion of the operating cycle; and

means for diverting air both upwardly and downwardly in the wash chamber during the drying portion of the cycle including

a fan, in the compartment, having an inlet opening to the exterior of the dishwasher and an outlet opening through the inner door panel into the wash chamber at a first elevation;

a motor drivably connected to the fan and nested within the confines of the fan to cause air entering the inlet opening to pass over said motor in heat exchange relationship thereto; and

means for exhausting air from the wash chamber at a second elevation below the first elevation.

2. The dishwasher of claim 1 wherein the rack resides in the wash chamber below the first elevation.

3. The dishwasher of claim 2 further comprising a silverware receiver carried by the rack between the elevations, the receiver being positioned adjacent the inner door panel when the door is closed.

4. The dishwasher of claim 1 wherein the fan inlet opens through the outer door panel.

5. The dishwasher of claim 4 wherein the fan comprises a plurality of circumferentially spaced blades defining a cavity radially inwardly therefrom and means mounting the blades for rotation, the motor at least partially residing in the cavity.

6. The dishwasher of claim 5 wherein the door compartment is generally planer, the blade mounting means mounts the blades for rotation in a plane extending substantially in the plane of the door compartment.