Why do dishwashers reverse the rotation of the motor

Not very good results. Drain Solenoid: Not all dishwashers have drain solenoids. If this solenoid fails to operate the dishwasher will be stuck in ether the wash or drain mode.

Most often the dishwasher will be unable to drain. The picture on the right is a defective solenoid; notice the melted black plastic on its metal plunger post. Thermostat: A thermostat is used to measure the amount or heat presentin the water of the dishwasher. Some dishwashers may have several thermostats, which are almost always single temperature bimetal switches.

Most newer dishwashers designs have reduced water-heating ability to conserve electricity and comply with energy star standards. Therefore it is more important than ever that the water heater be set to a temperature level that will compensate for this temperature reduction.

Save the water in a bucket and use it in the washer or to water your plants. Soil Sensor: Some dishwashers use a soil sensor, actually called a turbidity sensor to monitor the amount of soil the wash water. Technologies like this are another benefit to solid-state timers. Motor: The motor converts electric energy supplied by the timer into rotational motion.

This rotational motion is used to spin an impeller, which pushes water up into and out of spray arms. There are many different motors styles but they can all be categorized into two main groups, single directional and reversing.

Single direction motors will use a separate drain pump motor or a drain solenoid to reroute water out through the drain system. The motor may also spin a grinding blade that will pulverize any debris rinsed from the dishes into smaller pieces able to easily pass through the drain system. Dishwasher Repair Videos. Most modern drain pumps are usually magnetically driven. A rotating magnetic field is created, causing a small paddle wheel inside the dishwasher pump to spin pushing water out through the drain system.

Tip: Sometimes become jammed by small items like bone fragments or toothpicks. Objects can also break a blade of the paddle wheel off reducing its ability to move water. Door Switch: Dishwashers use a series of door switches to control electrical flow to other components, the switches close allowing current to flow when the door is sealed.

In most cases the switches are located on both the right and left side of the latch within the dishwashers door. Tip: Sometimes the small actuator that inserts into the latch will become slightly bent not engaging some or all of these switches fully; the result is no dishwasher operation because the dishwasher thinks that the door is open. Slightly adjusting the door switch actuator to apply more pressure may help.

Issuance of the liquid from one of the propelling orifices urges rotation of the casing in one direction about the axis, while issuance of liquid from the other urges reverse rotation of the casing. The arm passageway is divided into an inlet portion connected to the casing liquid inlet opening and two outlet portions which have a common intersection with the passageway inlet portion and extend from opposite sides thereof to a respective one of the propelling orifices.

A pair of air inlet ports are provided in the casing arm and are connected by separate conduits to the opposite sides of the passageway inlet portion adjacent the intersection. The air conduits have a considerably smaller cross-section than the liquid passageway portions. Control means including a cam-actuated valve plate rotatably mounted on the casing arm are provided for selectively opening and closing the air inlet ports to allow aspiration of air through only one of the ports at one time and thus direct the liquid toward one of the propelling orifices and away from the other whereby direction of rotation of the casing about the axis can be reversed.

Background of the invention This invention relates to automatic dishwashers. More particularly it relates to a reversing spray head assembly for an automatic dishwasher. Many automatic dishwashers have a spray head assenibly comprising a hollow casing supported for rotation about an axis transverse to its major plane.

A plurality of orifices are provided in the casing and wash fluid fed into the casing under pressure by a pump issues from certain of the orifices to generate a vigorous spray action. Others of the orifices are located at the outer ends of a pair of arms that extend outwardly in opposite directions from the axis of rotation and are employed as jet propelling orifices to rotate the casing about the axis. A typical dishwasher spray head assembly of this type is illustrated in U. Patent No.

Cushing, and assigned to the General Electric Company, assignee of the present invention. In such presently known assemblies, the jet propelling orifices provide for rotation of the casing in only one direction. While this unidirectional rotation of the spray head casing helps to distribute the spray about the dishwasher wash charnber, it is possible because the rotation is unidirectional to miss certain portions of the soiled articles contained within the wash chamber.

Hence, it would be desirable to periodically reverse the rotation of the spray head casing 3,, IPatented June 3, in order to more thoroughly distribute the spray to the soiled articles.

Preferably, the control fluid is aspirated air and the casing is provided with at least one additional orifice for issuing the liquid to generate a washing action within the wash chamber. Brief description of the drawings The present invention is illustrated in the accompanying drawings, wherein:. FIGURE 1 is an elevational view, partly cut away to show details, of an automatic dishwasher employing the present invention;. Description of the preferred embodiment Referring now to the drawings and particularlyto FIGURE 1 thereof, there is illustrated an automatic dishwasher 10 having an outer cabinet 11 defining therein a wash chamber Disposed within the wash chamber 12 are dish-supporting racks 13 and 14 which are adapted to receive and support dishes or other articles tobe washed within the wash chamber A closure member or door 15 is provided in one wall of the cabinet 11', pivotal about a hinge means 16 to provide access to the wash chamber When the door is pivoted downwardly, the rack 13 can be at least partially withdrawn from the wash chamber The rack 13 is mounted by means of a slide and roller system 17 provided at each side of the rack 13 and slidably supporting the rack 13 from the inner wall of the cabinet Similarly, the rack 14 can be at least partially withdrawn from the wash chamber 12 by means of a roller 18, which rides upon a surface '19 provided at each side of the cabinet The lower extremity of the wash chamber 12 is detined by a bottom wall 20 which gradually slopes to a low point 21 near the center of the dishwasher.

Disposed ybelow the low point 21 is a sump 22 which may be formed integrally with the bottom wall or which may be a separate element secured to the bottom wall An electric motor not shown includes a drive shaft 3 rotatable within the housing in opposite first and second directions. Pumps 6, 7 include respective impellers 4, 5 keyed or otherwise fixed to shaft 3 to rotate therewith in the opposite first and second directions. Pumps 6, 7 are separated by means of a partition 8 within the housing.

Thus, this results in an integral pump unit construction having the two pumps 6, 7 within a single enclosure and operable by a single drive source. It particularly is contemplated that the pump unit of the present invention is employable with a dishwasher not shown wherein pump 6 is connected to a water discharge circuit for discharging water from a sump of the dishwasher and wherein pump 7 is connected to a water circulating circuit for circulating water to a spraying structure to spray dishes or other articles to be cleaned within the dishwasher.

Impeller 4 of discharge pump 6 is of the peripheral outflow type, known in the art, and capable of pumping fluid, such as dirty dishwasher fluid, from a suction side indicated in FIG. On the other hand, circulating pump 7 is a centrifugal pump and its impeller 5 is shaped as shown in FIGS. That is, impeller 5 is provided with a plurality of blades 12 which are oriented forwardly with respect to the second direction of rotation of shaft 3.

This second direction of rotation is indicated in FIG. Attention is directed to the fact that the inlets and outlets or suction sides and delivery sides of the two pumps are indicated only schematically in FIG.

However, it is intended that such structural arrangements be conventional and clearly would be understood by one skilled in the art. Centrifugal pumps provided with impellers having forwarding oriented blades, i.

It particularly is to be noted that such "action" centrifugal pumps have not in the past been employed in operations wherein their impellers are rotated in the reverse direction, i. However, contrary to such prior understanding and uses, the pump unit of the present invention has the surprising effect that energy consumption of the centrifugal pump 7 is particularly reduced when its impeller 5 is rotated in direction 11, i.

In fact, it has been experimentally determined that when drive shaft 3 is rotated in first direction 11, i. Such overall energy consumption is also particularly reduced due to the known characteristics of the peripheral outflow pump 6. On the other hand, the centrifugal pump 7, of the action type in accordance with the present invention, maintains a high yield even when it is pumping, i. In the preferred application of the pump unit of the present invention in a dishwasher, during this phase the discharge pump 6 substantially intakes air only, so that its energy consumption is particularly low.

Thus, even during a water circulating phase, i. As a result, due to the particular combination of pumps 6, 7 and the particular configuration of impeller 5, it is possible to correspondingly downsize the reversible electric motor, including the overall dimensions thereof.

In this connection, the overall dimensions of the pump unit further can be reduced, compared with known such pump units, due to the intrinsic characteristics of centrifugal pump 7 having an impeller of the action type.

Thus, it is known that, under the same conditions with regard to rotation speed and hydraulic head, the diameter of the impeller and therefore the overall dimensions of a pump of the centrifugal type having forward-oriented blades are less than those of a centrifugal pump of the radial type having backward-oriented blades.

Furthermore, hydraulic noise and vibrations occurring in the pump unit according to the present invention are reduced to the same extent as is avoidance of wasted energy consumption. In accordance with a further feature of the present invention, the partition 8 has therethrough a calibrated opening 14 that permanently connects the pump chambers of pumps 6, 7.

Particularly, opening 14 is an annular opening defined around a hub 15 that is common to both impellers 4, 5 and that extends through partition 8. Particularly, opening 14 is predetermined or calibrated with respect to the size of hub 15 and with respect to the designed operating parameters of the pump unit to provide that fluid flow between the two pump chambers always will be in a single direction, i.

This is achieved due to the combined action of the two pumps. Thus, when the impellers 4, 5 are rotated in the direction indicated by arrow 13, a flux or flow of fluid through opening 14 from pump 7 to pump 6 is caused by a strong hydraulic head at centrifugal pump 7. On the other hand, when the impellers are rotated in the opposite direction 11, the same flux or flow of liquid through opening 14 from pump 7 to pump 6 is produced by the suction effect of the peripheral outflow pump 6, only a low hydraulic head being present at centrifugal pump 7.

As a consequence of the above advantageous feature of the present invention, particularly when the pump unit is incorporated into a dishwasher, soiled water cannot flow through opening 14 from the water discharge circuit connected with pump 6 to the water circulating circuit connected with pump 7.