Dishwasher With Soil Detecting Means

Abstract

Provision is made in an automatic timer controlled dishwashing machine for detecting soil particles carried in washing liquid within the machine and reacting thereto by effecting the nature of the operational program of the machine whereby dishes in the machine are subjected to additional rinsing action. The invention includes a mechanical sensing device adapted to sense and react to the presence of soil by electrically signaling the machine's timer control to thereby alter the normal operational program of the machine.

Description

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates generally to washing appliances and more specifically pertains to an article washing machine such as a dishwasher wherein soiled items are stored for washing within a chamber and the washing action includes contacting the items with washing liquid to effect removal of soil therefrom.

II. The Prior Art

The conventional domestic dishwashing machine has a timer control adapted to automatically complete a series of steps in accordance with a predetermined program to cleanse soiled dishes and similar items and render them ready for re-use. In the typical dishwasher the soiled items are subjected to a series of washing and rinsing steps, followed ordinarily by a drying step. This series of steps constitutes an operational cycle or predetermined program of operation that is automatically conducted and controlled by the timer. The timer is usually of the type having a rotatable shaft with cams mounted thereon to sequentially actuate switches in circuit with various electrical components of the machine. For each washing or rinsing step of the program, fresh water is brought into the machine and recirculated over items stored in the wash chamber, after which the water is drained out of the chamber and then fresh water is introduced for the next step. The washer step usually involves the automatic dispensing of detergent into the water which is then recirculatd over the soiled items for a time generally exceeding the time of recirculation during the rinsing step. Liquid recirculation during the shorter rinsing step will generally utilize fresh incoming water without the addition of any detergent or washing additives thereto. The typical operational program may comprise several successive, relatively short, rinse steps followed by a longer wash step. The wash step may then be followed by one or more final rinse steps. Since the machine is drained after each step and fresh water is introduced for each successive step, particles of food soil suspended in the recirculated liquid is less for each successive step. Ideally, the liquid utilized in the final rise step of the operational cycle will contain few or no soil particles. However, this, of course, depends to some extent on the number of items being washed and the amount and characteristics of the soil on the items when they are placed in the machine.

There is a direct relationship between the amount of soil carried in the recirculated liquid in a dishwashing machine and the degree of cleanliness of the dishes in the machine. To increase the efficiency of a dishwashing machine it would be desirable to have a means incorporated in the machine for detecting or sensing the presence of soil particles in the recirculated liquid in the dishwashing machine and reacting to the presence of excessive soil particles by altering the machine's operational cycle or program such that the dishes are subjected to additional washing and rinsing action.

It is recognized that the possibility of sensing the condition of liquid in a washing appliance and providing for means to react to the condition to effect the operation of the machine has been appreciated in the prior art. For example, U.S. Pat. No. 3,114,253 issued Dec. 17, 1963, to Morey et al, and assigned to the assignee of the present invention, teaches the use of a light sensitive resistor to sense cloudiness or turbidity of washing liquid in a washing machine. This particular approach has not been found to be practical in attaining the desired effect in a dishwashing machine, particularly where the cloudiness of washing liquid and its ability to pass light therethrough varies considerably in accordance with the nature of the food particles on dishes to be washed and the type of treating agents added during the operational cycle of the machine to facilitate the cleansing action.

SUMMARY OF THE INVENTION

The present invention may be broadly summarized as relating to the provision of a detecting means in a dishwashing machine capable of reacting to the presence of food soil particles suspending in washing liquid within the machine. The detecting means is employed in the type of dishwasher having an automatic timer control and wherein soiled items such as dishes and the like are stored in a chamber and are therein contacted with liquid for at least one predetermined time interval to effect the cleaning thereof during the machine's operational cycle. The machine preferably has means therewith for directing the liquid that has contacted the soiled items through a flow path having a comparatively narrow channel area or constriction therealong. The detecting means senses a partial restriction of the narrow channel area by food soil particles and initiates a reaction that causes a change in the program or operational cycle of the washing machine whereby the dishes are subjected to further cleaning action by liquid contact. In the preferred embodiment the detection of soil particles causes the operational cycle of the machine to be altered such that time usually taken for a final drying step is reduced and one or more rinse steps occur prior to a shortened drying step to assure a comparatively cleaner condition of the items in the machine.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevational view of the lower portion of an automatic dishwashing machine incorporating a device for detecting and reacting to the presence of soil particles in the washing liquid in the machine in accordance with the present invention;

FIG. 2 is an enlarged side elevational view of the detecting device first shown in FIG. 1, here having portions thereof illustrated in vertical section;

FIG. 3 is a fragmentary view of the device as shown in FIG. 2 with components thereof repositioned in accordance with the operation of the present invention;

FIG. 4 is an elevational view of the device as shown in FIG. 2 taken from the right end thereof; and

FIG. 5 is a schematic representation of the electrical circuitry for the dishwasher shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 there is shown an automatic dishwashing machine 10 having a housing or cabinet 12 defining a wash chamber 14. The dishwasher is of the front loading type having a closure or door 16 permitting access to the chamber and a rack 18 slidably mounted therein. Mounted within the wash chamber 14 is a rotatable spray arm 20 having spaced apart orifices 22 along the upper surfaces thereof for discharging washing liquid upwardly over dishes and other items stored for washing in the rack 18. The spray arm 20 has a hollow body in liquid flow communication with a pedestal 24 that receives a pressurized flow of liquid from a pump 26 disposed below the bottom 28 of the wash chamber 14. The bottom 28 has a sump 30 for receiving accumulated liquid from the lower portion of the wash chamber 14 and conducting it through a conduit 32 to the intake side of the pump 26. The pump 26 is driven by an electric motor 34 in circuit with a timer control switch (not shown). within the housing of the pump 26 is a solenoid operated valve (not shown) adapted to be movable between two positions. In one position the valve disposes the pump for recirculation of liquid received from the sump 30 whereby it is pumped upwardly through the pedestal 24 and outwardly through the spray arm 20. In its other position the valve is disposed such that the pump conducts liquid received from the sump 30 outwardly through a drain line 36 for discharge from the dishwashing machine into the household sewage system. It will be noted that the drain line 36 leads to an intake port 38 of a soil sensing or detecting device 40.

The dishwasher 10 is prepared for operation by opening the door 16 and placing soiled dishes or other items in the rack 18. The dishwasher has a detergent cup (not shown) in which detergent may be placed for automatic timer controlled dispensing later during the operational cycle of the machine. When the items to be washed are in place within the chamber 14 the door 16 is closed and the timer control is advanced to its start position by the machine operator. The timer control then conducts the machine through the programmed sequence of steps. The first step, usually a rinse step, involves introducing hot water into the wash chamber 14. To accomplish this, the timer control actuates a solenoid operated water inlet valve (not shown), and the water accumulates in the lower portion of the wash chamber 14. When the water has reached a predetermined level in the wash chamber 14, the motor 34 is automatically actuated to drive the pump 26 whereby the water in the wash chamber 14 flows downwardly through the sump 30 and the conduit 32 and is then pumped upwardly through the spray arm 20. The spray arm 20 is of the reactive type whereby the liquid stream from one of its discharge ports imparts a counterimpetus against the outer end of the spray arm nd causes it to rotate while it distributes streams of liquid upwardly over the dishes in the rack 18. The rinse step continues by pumped recirculation of the water for a predetermined period of time after which the timer control causes the previously mentioned drain valve in the pump housing 26 to change position whereby continued pumping directs the accumulated liquid from the wash chamber 14 outwardly through the drain hose 36. The pumped liquid moves through the device 40, as will be hereafter described in more detail, and outwardly from the machine by means of a drain hose 86 to the household sewage system.

Thereafter, the machine may perform a second rinse step or, alternatively, depending upon the timer control program, a wash step that is similar to the rinse step heretofore described but involves the automatic dispensing of detergent into the water in the wash chamber 14 to provide a washing solution for recirculation over the dishes in the rack 18. Then, depending upon the program, the normal operational cycle may further include an additional wash step or several final rinse steps followed by a drying step. The drying step may utilize an electrical resistance heating element 19 and vent means to and from the chamber (not shown) for providing connection currents to dry the dishes stored in the rack 18.

The device 40 mounted within the cabinet 12 of the dishwasher 10 in FIG. 1 is a presently preferred embodiment of detecting or sensing means for sensing and reacting to the presence of food soil particles in liquid being pumped out of the wash chamber 14 of the machine 10. The device 40 acts to sense small quantities of soil in the liquid within the dishwasher 10. The device 40 reacts to the sensing of such soil particles by causing an electrical signal to be transmitted to the timer control of the dishwasher whereby additional steps of wash or rinse time or exchange of liquid in the machine occur to further clean the items stored in the machine.

More specifically, with reference to FIG. 2, washing liquid having soil particles emulsified or suspended therein enters a casing or cylinder 42 defining a flow area 43 and flows through a small annular gap 44 between the edge of a reciprocal member or piston 46 and the cylinder side wall 48. The pump 26 serves as a means of pressurizing the drain flow to the area 43 whereby a build up of soil in the annular gap 44 causes a pressure differential across the piston 46 which forces the piston rearwardly (to the right as viewed in FIG. 2). As a function of its rearward movement, the piston 46 actuates a switch 50. The circuitry of the machine is such that actuation of the switch 50 causes the dishwashing machine 10 to function in an alternative mode as compared to that which would have occurred if the switch 50 had not been actuated. It is preferred that the device 40 be provided with means to prevent the sensing action of the device except at a specific point in the operational cycle of the machine 10. The sensing preferably occurs just before the machine 10 would normally begin the drying step of its operational cycle. Then, if presence of soil particles in the recirculating liquid of the rinse step just preceding the drying step is sensed by the device 40, the retraction of the piston 46 and actuation of the switch 50 automatically alters the operational program whereby one or more full rinse steps occur before commencement of the drying step.

As illustrated in FIGS. 2 and 3, the piston 46 of the device 40 is adapted for reciprocation and includes a horizontally elongated stem or body portion 52 having a dish-like face portion 54 occupying the chamber or cylinder 42 defined by the cylindrical side walls 48, a front wall 56, and a back wall 58. The stem 52 of the piston 46 extends through an opening 60 in the back wall 58 and has a flexible annular diaphragm 62 at an intermediate point therealong for sealing the back wall opening 60 whereby liquid entering the cylinder 42 through the inlet 38 can only exit through a downwardly projecting outlet 64. It should be noted that the piston 46 is guided for horizontal reciprocation by means of a guide bar 66 that is a lateral extension of the cylinder front wall 56.

The stem 52 of the piston 46 is carried between upper and lower rotatable members or rollers 68 and 70 (see FIG. 4). The downwardly facing surface of the stem 52 is substantially straight whereby it tracks against the lower roller 70 and causes the roller 70 to rotate about an axle 72 constituting a stationary axis. Whereas the lower roller 70 is journalled to rotate about the axle 72, the upper, slightly smaller roller 68 is journaled to rotate about a vertically movable axis 74. Slots 75 are provided in a support frame member 76 to allow the vertical movement (see FIG. 4). The axle 74 is thus movable, with the roller 68 thereon, a short distance upwardly while maintaining its horizontal disposition. Thus, when the piston 46 retracts, a hump portion 77 of the stem 52 serves to cam the roller 68 upwardly from a position shown in FIG. 2 to that shown in FIG. 3. As the roller 68 moves upwardly it bears against a pivotal rod or arm 78 extends from the switch 50. The switch 50, which is open when the piston 46 is in the forward disposition shown in FIG. 2, is caused to close by movement of the arm 78 upwardly to the position shown in FIG. 3. The downwardly facing side of the piston stem 52 has a tooth-like projection 80 for engaging a slot 82 (see FIG. 3) in a bimetal element 84 whereby the piston 46 is held in the retracted position except when the bimetal element 84 is caused to flex downwardly to the position shown in dotted lines in FIG. 2. The bimetal element is well known as an electrical triggering device and comprises two flat pieces of metal having respectively different coefficients of expansion. The metal pieces are laminated together with an insulator therebetween and adapted to conduct current therethrough. The resistance to the current causes the metal to heat such that the element temporarily flexes in response to current conducted therethrough.

Having described the major elements of the sensing device 40, the sensing action thereof may now be considered. During the "pump out" or draining of washing liquid at the termination of the rinse step immediately preceding the drying step in the operational cycle of the dishwasher 10, the piston 46 of the device 40 is disposed as shown in FIG. 2 whereby liquid pumped through drain line 36 will enter the inlet 38 and flow through the annular gap 44 defined by the edge of the piston face portion 54 and the adjacent cylinder wall 48. The size of the gap 44 is preferably such that reasonably clean rinse water will bypass the piston 46 and move through the chamber or cylinder 42 and outwardly through the outlet 64 and be drained out of the machine 10 through a drain conduit 86. Food particles carried in the liquid and pumped therewith into the chamber 42 will tend to accumulate across the annular gap 44. When the accumulated soil blocks the area of the gap 44 sufficiently, the increase in liquid pressure against the piston face portion 54 causes the piston 46 to retract from the sensing position of FIG. 2 to the retracted position shown in FIG. 3.

The sensitivity of the piston to react is preferably adjustable within reasonable parameters. For this purpose the hump portion 77 on the piston stem 52 may be provided with a substantially sharp drop-off forming a lip 88 which must pass under the upper roller 68 when the piston 46 retracts. The upper roller 68 is provided with an adjustable biasing means (see FIG. 4) for urging it normally downwardly against the piston stem 52. The force moving the piston 46 rearwardly must be sufficient to overcome the biasing means and push the roller 68 upwardly. Adjustment of the biasing force holding the roller downwardly provides a means of controlling and setting the sensitivity of the piston's reaction to fluid pressure against its face portion. As shown in FIG. 4, springs 85 serve as the biasing means, and the sensitivity of the device is variable in accordance with the selected spring tension.

In the typical automatic dishwasher, the various operating components such as the water inlet valve and the electric motor driving the recirculating pump are controlled in proper sequence by the timer control. The conventional timer control comprises a synchronous motor having a cylinder or a series of abutting discs turning in unison on the motor shaft whereby peripheral camming surfaces actuate electrical switches to open and close in a desired sequence. FIG. 5 schematically illustrates a circuitry incorporating the present invention including a timer motor 90 having cams 92,94,96,98 and 100 that respectively actuate switches 102, 104, 106, 108 and 110. The circuitry shown in FIG. 5 also includes a switch 112 which is an interlock safety switch that is closed by the action of closing the door 16 to the washing chamber 14 of the maching 10 (see FIG. 1).

The combination of components for the dishwasher 10 are shown in FIG. 5. There is the substantially high wattage heating element 19 (see also FIG. 1) for generating heat to the washing chamber 14 during the drying step of the operational cycle, a solenoid operated water valve 116, a solenoid operated drain valve 118 (contained in the housing of the pump 26 in FIG. 1), and the motor 34 for driving the pump 26. The bimetal element 84 shown in FIGS. 2 and 3 is also represented schematically in FIG. 5. Current to the machine is provided through lines L.sub.1 and L.sub.2.

With continued reference to FIG. 5, the dishwasher is started in its operational cycle by manipulation of a control knob 120. The control knob 120 is rotated a few degrees to turn the shaft of the motor 90 whereby cam 92 causes switch 102 to close. It is assumed at this stage that the door to the dishwasher has been closed whereby the interlock switch 112 is also closed. As timer motor 90 continues to operate, its advancing shaft causes cam 94 to move switch 104 to complete the circuit through contact 122. Simultaneously, with the movement of cam 94, cam 98 causes switch 108 to complete the circuit through contact 124 to the water valve 116. The water-fill operation continues for a predetermined time period terminated by movement of cam 98 to cause switch 108 to assume a neutral or open position intermediate the contacts 124 and 126. Simultaneously, cam 100 causes switch 110 to close and energize motor 34 to drive the pump in its recirculation mode. Such recirculation of the liquid within the machine constitutes the preliminary rinse step of the operational cycle.

The additional rinse steps and wash steps are sequentially accomplished by the various cams operating the proper switches. The wash step differs from the rinse step by the automatic dispensing of detergent (by means now shown) into the recirculating liquid. At the end of each rinse or wash step, the cam 98 causes switch 108 to actuate the drain valve 118 whereby continued operation of the pump 34 causes the liquid in the machine to flow out through drain line 36, through the cylinder 42 of the device 40 and thence out of the machine to the household sewage line.

During the dishwasher operation the occurrence of the first pump-out of liquid from the machine at the end of the preliminary rinse step actuates the device 40 whereby the switch 50 is closed. Soil carried in the liquid being drained may sufficiently block the gap 44 in the device 40 to crease a pressure differential against the piston 46 whereby it is caused to move to the retracted position shown in FIG. 3. The bimetal element 84 serves as a holding means; it engages the tooth-Like projection 80 of the piston stem 12 whereby the piston 46 is held in the retracted position.

For the last rinse step of the operational cycle, the switch 106 is closed by cam 96 whereby the bimetal element 84 is placed in series with the chamber heating element 19. The bimetal element 84 then acts to release the piston 46. It heats and flexes away from the tooth-like projection 80 such that the piston 46 is forced to move to the sensing or operative position shown in FIG. 2. The force of the biased roller 68 against the hump-like portion 77 of the piston stem 52 pushes the piston 46 from its retracted position to its operative position once the bimetal 84 has released the piston. The arm 78 of the switch 50 (FIG. 2) has means (not shown) for biasing it normally downwardly such that the switch 50 opens when the piston 46 advances to the position shown in FIG. 2. Then, if soil in the liquid being drained through the device 40 at the end of the last rinse step actuates the device 40 such that the piston is pushed to its retracted position, the switch 50 is thereby closed. Closing of the switch 50 shunts the switch 104 that would normally complete a circuit through contact 128 to initiate the drying step at the end of the operational cycle. With the switch 50 closed, the circuitry of the machine is disposed to operate for additional rinsing. Continued advancement of the timer control will sequentially actuate the water valve 116, the motor 34, and the drain valve 118 to accomplish an additional rinse step.

By the proper combination of cams and switches in the timer control two or more rinses could occur in the event that the device 40 sensed the presence of sufficient soil in the last rinse step of the normal operational cycle of the machine and closed the swtich 50. These additional rinses would occur during time that would normally have been used for part of the drying step in the normal operational cycle. The length of the normal drying step can be such that utilization of a part of its time period for one or two additional relatively short rinse steps will not materially effect the combination of the dried dishes at the end of the machine's operation.

In accordance with the circuitry illustrated in FIG. 5, the switches 108 and 110 controlling the water valve, drain valve, and pump motor will operate during the last portion of the operational cycle of the machine whether or not the device 40 senses and reacts to residual soil particles in the drainage liquid from the last normal rinse step. In the normal situation wherein the device 40 would not be actuated by the presence of residual soil particles in the drainage liquid, the switch 108 and 110 are mechanically cam-operated during the drying step at the end of the normal operational cycle but do not energize the water valve 116, the drain valve 118, or the motor 34 due to the fact that switch 50 remains open whereby current is not conducted to these components.

The device 40 heretofore described operates a soil detecting means that is automatically self-cleaning. When the piston 46 is retracted, drainage flow through the flow area 43 serves to carry away soil particles therefrom and sweep them out of the device 40.

Claims

I claim:

1. A soil sensing means for a washing apparatus having a wash chamber for holding articles to be washed, the washing apparatus further having liquid inlet means for the wash chamber, liquid draining means for the wash chamber, pumping means for circulating liquid through the wash chamber, and a timer means for controlling the operational interaction of the liquid inlet means, liquid draining means, and pumping means; said soil sensing means comprising;

reciprocal means for varying the cross-sectional flow area of the liquid draining means, said reciprocal means being disposeable to a sensing position wherein the cross-sectional flow area of the liquid draining means is substantially restricted and a retracted position wherein the cross-sectional flow area of the liquid draining means is substantially unrestricted, said reciprocal means being urged from said sensing position to said retracted position upon a predetermined increase in pressure in the liquid draining means resulting from further restriction of the cross-sectional flow area of the liquid draining means by entrained soil particles, and the timer means being responsive to said reciprocal means upon said reciprocal means being urged to said retracted position so that additional washing for the articles in the wash chamber is provided.

2. The invention as defined within claim 1 wherein said soil sensing means is disposed within the liquid draining means.

3. The invention as defined within claim 1 further including switch means responsive to movement of said reciprocal means, and said switch means being in electrical circuit with the timer means so that the timer means is responsive to said reciprocal means upon said reciprocal means being urged to said retracted position.

4. The invention as defined in claim 2 wherein said sensing means further comprises a casing means for carrying liquid flow therethrough with said reciprocal means being disposed within said casing means, whereby the substantially restricted cross-sectional flow area of the liquid draining means is the space between the edge of said reciprocal means and the inside surface of said casing means when said reciprocal means is in said sensing position.

5. The invention as defined in claim 4 further including biasing means for normally biasing said reciprocal means toward said sensing position.

6. The invention of claim 5 further including holding means for holding said reciprocal means in said retracted position for a predetermined period of time.

7. The invention as defined in claim 6 further including releasing means for releasing said holding means.

8. The invention as defined in claim 7 wherein said releasing means includes an electrical resistance element.