System for conserving energy and washing agents in a dishwasher

In an electrically energized commercial dishwasher machine having at least one washing section followed by a rinse section and having a conveyor for conveying dishes through the various sections in sequence, a timing element is set to cause the machine to automatically shut off after running for a predetermined time period slightly longer than the time required for the conveyor to convey dishes through all the various sections of the machine. The timing element is reset to cause the machine to continue to run for a new such predetermined time period whenever a signal from a sensor indicates the presence of dishes in the rinse section.

FIELD OF THE INVENTION 
This invention is in the field of commercial dishwasher machines as used in 
restaurants, hotels, motels, hospitals and other establishments or 
institutions in which large numbers of dishes, cups, saucers, platters, 
bowls, knives, forks, spoons, etc. are washed repeatedly. Such dishwasher 
machines are of two types: (1) rack type, (2) continuous conveyor belt 
type as will be described more fully further below. This invention relates 
to method and system for conserving energy, water and washing compounds in 
commercial dishwasher machines of either type and of any large commercial 
size. 
BACKGROUND OF THE INVENTION 
In most restaurants, hotels, motels, hospitals and other establishments or 
institutions in which large numbers of dishes, etc. and eating utensils 
are repeatedly washed in large commercial dishwasher machines, the 
electricity and hot water being consumed by the dishwasher machine are not 
metered to the machine itself. The dishwasher personnel who are working in 
the kitchen are usually very busy handling the dishes, etc. and the 
utensils for three meals a day. These personnel do not pay much attention 
to the dishwasher machine itself so long as it is operating 
satisfactorily. They do not wish to be bothered with turning the 
dishwasher machine on-and-off during a working day. In many instances, in 
my personal observation, the dishwasher personnel will turn on the 
dishwasher machine at the beginning of a working day, and then they turn 
the machine off at the end of the working day. The management of the 
institution is usually not aware of the consumption of electricity and hot 
water occurring in the dishwasher machine itself, because these are not 
separately metered to the dishwasher machine. In fact, the electricity and 
hot water for the kitchen may not be separately metered from the 
institution as a whole. Thus, it is difficult for management effectively 
to determine whether or not excessive amounts of electric energy, hot 
water and washing compound are being consumed by the dishwasher machine. 
In a test which I carried out in a restaurant, the consumption of washing 
compound was actually reduced to approximately one-third during one entire 
week by employing the present invention. The electricity and hot water to 
the machine involved were not metered, but the conclusion seems logical 
that the consumption of electricity and hot water were also reduced 
approximately to one-third. Also, it is logical to conclude that the wear 
and tear on the dishwasher machine were reduced to approximately 
one-third. It is my estimate that today in New York City a large 
dishwasher machine running continuously each day that the restaurant is 
open for business and in which the hot water in the power wash and power 
rinse stations is electrically heated and the hot water in the final rinse 
station is electrically boosted in temperature to more than 180.degree. F. 
will consume $10,000 to $20,000 of electrical power in one year, and 
possibly even more. 
SUMMARY OF THE INVENTION 
The problems of excessive consumption of electricity, hot water and washing 
compound are advantageously overcome by the method and system of the 
present invention. 
Advantageously, the machine is automatically shut off whenever a sensor in 
the final rinse station of the dishwasher signals that the rinse station 
is empty. An adjustable time delay is associated with this final rinse 
station sensor and it can be set to a predetermined time delay as may be 
desired, depending upon the through-put time of the machine for assuring 
that the machine has completely emptied itself of dishes and implements 
before the automatic shut off occurs. 
A key-actuated switch in this system enables the machine to be returned to 
its normal manual control mode at any time desired by the management, for 
example when maintenance is to be performed on the system or in the event 
of malfunction of the energy conserving system. Therefore, the management 
is assured that the dishwasher machine itself is never rendered 
non-useable by this energy conserving system, since the dishwasher machine 
can be immediately returned to its manual control mode by flipping a key 
actuated switch at any time. 
In accordance with another feature of this invention the conventional 
"STOP" switch of the dishwasher machine is not over-ridden by this energy 
conserving system. Thus, the machine can be stopped immediately whenever 
the "STOP" switch is actuated. 
It is an object of the present invention to conserve electrical energy, hot 
water, and dishwashing compound in commercial dishwasher machines of the 
rack type and of the continuous conveyor belt type. A rack type dishwasher 
machine is one in which the dishes and implements are loaded into portable 
racks. These racks are pushed through the dishwasher machine by a 
reciprocating conveyor bar having a plurality of ratchet fingers (often 
called "feed dogs") which project up to engage the bottom of the racks 
during the forward stroke of the conveyor bar for pushing the racks 
forward in the machine a predetermined distance equal to the forward 
stroke of the conveyor bar. During the return stroke of the conveyor bar 
these feed dogs retract and slide back beneath the racks without moving 
the racks backward. 
A continuous conveyor belt type of dishwasher machine has a conveyor made 
of pivotally interconnected links in the manner of a wide chain belt, with 
spaced upwardly projecting elements for supporting dishes in upstanding 
position, i.e. resting on one edge between the elements, for augmenting 
drain-off of the dishes during washing in the machine. This conveyor belt 
moves forward continuously through the machine. 
As used in the specification and claims, the term "dishes" is used 
generically to include dishes, cups, saucers, platters, plates, bowls, 
glasses, mugs, pitchers, trays, and the like. The term "implements" is 
used generically in the specification and claims to include knives, forks, 
spoons, spreaders, ladles, and the like. 
As used in the specification and claims, the term "conveyor" is used 
generically to include a continuous motion conveyor and an intermittent 
motion conveyor and is used generically to include a conveyor having a 
belt as the conveying means and a conveyor having movable racks which are 
moved as the conveyor means. 
As used herein the term "food service utensils" is used generically to 
include both "dishes" and "implements.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Referring to FIG. 1, there is shown a commercial dishwasher machine 10 
including three bays or sections, namely, a power driven pre-wash section 
12, a power driven main wash section 14, and a hot rinse section 16. A 
conveyor 18 extends from an entrance end 20 of the machine through these 
three sections of the machine for conveying dishes and implements through 
these three sections in sequence for washing and rinsing them. Then the 
conveyor conveys the washed and rinsed dishes and implements out the exit 
end 21. This conveyor 18 may be a rack-type conveyor or a belt-type 
conveyor, depending upon whether the machine 10 is an intermittent motion 
rack-type of machine or a continuous motion belt type of machine. 
As explained in the introduction, a rack type dishwasher machine is one in 
which the dishes and implements are loaded into portable racks. These 
racks are pushed through the dishwasher machine by a reciprocating 
conveyor bar having a plurality of ratchet fingers (often called "feed 
dogs") which project up to engage the bottom of the racks during the 
forward stroke of the conveyor bar for pushing the racks forward in the 
machine a predetermined distance equal to the forward stroke of the 
conveyor bar. During the return stroke of the conveyor bar these feed dogs 
retract and slide back beneath the racks without moving the racks 
backward. Also, as explained in the introduction, a continuous conveyor 
belt type of dishwasher machine has a conveyor made of pivotally 
interconnected links in the manner of a wide chain belt, with spaced 
upwardly projecting elements for supporting dishes in upstanding position, 
i.e. resting on one edge between the elements, for augmenting drain-off of 
the dishes during washing in the machine. Such a conveyor belt moves 
forward continuously through the machine. 
The present invention is applicable to both types of commercial dishwasher 
machines; however, for purposes of illustration, it is assumed that this 
is a rack-type of machine, with the dishes and implements being loaded 
into manually portable racks 22 which are slid through the machine 10 on a 
pair of spaced tracks 24 (FIG. 3) by the conveyor 18. A conveyor drive 
motor 26, usually a three-phase alternating current (AC) induction motor, 
operates the conveyor 18 through an appropriate drive mechanism 28 as is 
known in the commercial dishwasher art. This conveyor drive mechanism 28 
usually incorporates an overload-responsive friction-slip clutch which 
will slip whenever the conveyor 18 encounters an unduly large impedance 
against moving. The motor 26 is energized through a relay, and this relay 
is tripped open when the overload-responsive clutch begins to slip, as is 
known in the commercial dishwasher machine art. 
The dishwasher machine 10 is equipped with a conventional control panel 30 
including a start button 31 for normally starting operation of the machine 
and a stop button of a normally closed switch 32 which immediately stops 
operation of the machine whenever this stop button is depressed, 
regardless of the stage of operation of the machine at the instant when 
this stop button is actuated. It is among the advantages of the 
conservation method and system of this invention that they do not 
interfere with the operability of this stop button. Therefore, the machine 
10 can be stopped immediately at any time by pressing the stop button 32. 
The pre-wash section 12 includes a tank 34 at the bottom of this section 
for holding hot water containing a dishwashing compound. A motor 36 drives 
a pump 38 for recirculating this water from the tank 34 for washing the 
dishes and implements in this pre-wash section 12. There is an electrical 
heater incorporated in the machine for keeping the water hot in the tank 
34. Whenever the machine 10 is running, hot water is continuously added to 
the tank 34. 
As the water is added to the tank 34 through a solenoid valve 39, a washing 
compound is automatically metered into the incoming hot water by 
conventional metering equipment, as known in the art. The tank 34 has an 
overflow weir leading into a sewer line connection, so that the water 
level in this tank cannot exceed the overflow setting. This prewash 
section 12 usually includes a removable screen (not shown) located above 
the tank 34 for catching lumps of food material that have been washed from 
the dishes and implements. In order to provide access into the prewash 
section, there is a removable door 40. 
From the above discussion, it will be understood that the motor 36 and pump 
38 are running whenever the machine 10 is running. Moreover, hot water is 
continuously being added into the tank 34, together with a washing 
compound whenever the machine is running. Therefore, unnecessary operation 
of this machine inevitably involves the consumption of hot water, washing 
compound and energy for heating the incoming water to the desired 
relatively high temperature and for energizing the pump motor 38, plus the 
energy for energizing the conveyor motor 36. In some cases, sewerage 
charges are involved, depending upon the quantity of water being 
discharged into the sewer line. 
Inviting attention to the main wash section 14, there is a similar tank 44 
located at the bottom of this section for holding the hot wash water which 
also contains a washing compound. It is to be understood that the hot 
water in the tank 44 is kept separated from the water in the tank 34, and 
there are suitable internal baffles and curtains between the sections 12 
and 14 for the purpose of isolating these two sections while permitting 
the conveyed racks containing dishes and implements to travel along the 
conveyor 18. 
Whenever the machine 10 is running, hot water passing through a solenoid 
valve 49 is continuously added to this tank 44 into which washing compound 
is metered. The motor 46 and pump 48 serve to recirculate the hot water 
from the tank 44 for washing dishes and implements in section 14. A 
removable door 42 provides access into the main wash section 14. 
Consequently, whenever the machine 10 is running, this section also 
consumes hot water, washing compound and electrical energy for heating the 
incoming water, and for energizing the pump motor 46. 
In the rinse section 16, the hot water is not recirculated. It is 
electrically heated to assure that the rinse water has a temperature above 
a minimum of 180.degree. F. A rinse compound is automatically metered into 
the incoming rinse water for causing the dishes and implements to dry 
sparkling clean without streaking. 
A solenoid valve 50 allows the hot rinse water to be sprayed over the 
dishes and implements in the rinse section whenever this solenoid valve 50 
is electrically energized. 
As shown in FIG. 3, there is a sensor switch 52 operated by a cam 54 which 
is actuated whenever a rack 22 is present in the rinse section. This 
sensor switch and cam 54 are conventionally included in the machine 10 for 
energizing the solenoid valve 50 whenever a rack 22 is resident in this 
rinse section 16. It is among the advantages of the invention that this 
method and system enable use of the existing sensor 54 and sensor-actuated 
switch 52 for conserving hot water, energy and washing compound. 
In FIG. 2 is shown a conservation control system 100 embodying this 
invention for saving hot water, washing compound and electrical energy in 
the operation of the dishwasher machine 10. This system is included in a 
cabinet 58 which may be mounted on the machine 10 or on a wall or building 
support column, or other permanent structure located conveniently near to 
the machine 10. In FIG. 1 the conservation control cabinet 58 is shown 
mounted on the wall near the entrance 20 of the washer machine 10. 
The power supply terminals of the dishwasher machine are shown at 60 and 61 
for connection to a suitable source 62 of electrical power, for example, a 
60-cycle 120 volt AC outlet. The existing stop switch of the dishwasher 32 
is located in the lead from the so-called "hot" terminal 61, the other 
terminal 60 being the neutral lead, as indicated by the "ground" symbol. 
The conservation control system 100 includes seven terminals 71 through 77, 
respectively, for making external connections, as will be explained as 
this description proceeds. The terminal 71 is connected to the neutral 
(ground side) 60 of the electrical supply for the dishwasher machine 10. 
The conservation control system 100 includes six relays 90, 91, 92, 93, 94 
and 95, respectively, for providing various control functions, as will be 
explained. In addition, there is an elapsed time registering clock 96 
which is turned "on" whenever the washer machine is running. This clock 96 
tells the operator the cumulative length of time that the machine has been 
running. By periodically reading this clock, the management can determine 
the extent to which the dishwasher 10 has been running since the previous 
reading. 
The relay 95 is a "TIMING OFF" relay which automatically turns "off" after 
a predetermined time period. At the time of installation of this system 
100, the relay 95 is pre-set by the installer for a time period which is 
slightly longer than the length of time required for the conveyor 18 to 
convey a given food service utensil from the entrance 20 to the exit 21 of 
the machine 10. In other words, this relay 95 is pre-set for a time period 
slightly longer than that required for the machine to complete one full 
washing cycle. For example, this timing relay 95 may be pre-set for a time 
period approximately 5% longer than the time required for the machine 10 
to complete one full cycle of washing operation. 
Conventionally, a commercial dishwasher machine, such as the machine 10, 
has a conveyor 18 which advances the food service utensils through the 
machine at an average of approximately 3.5 to 4 feet per minute. 
Therefore, if the machine 10 is approximately ten feet long from entrance 
20 to exit 21, a full washing cycle duration is approximately 2.5 to 2.9 
minutes. In such a case, the timing off relay 95 would be pre-set for a 
time period from approximately 2.6 to 3.0 minutes, depending upon the 
particular full washing cycle duration of the specific machine involved. 
This timing relay is enclosed and arranged in the cabinet 58 so that it 
cannot be readjusted by the machine operator. 
The relay 94 is also a timing relay, except that it is a "TIMING ON" relay 
which is arranged to turn "on" after a predetermined time period which is 
set by the installer. The time period for this relay 94 is somewhat 
shorter than the time period for relay 95. In other words, relay 94 will 
turn "on" a short time interval, for example, twenty seconds, before the 
relay 95 turns "off." The purpose of this timing on relay 94 is to alert 
the operator that the machine will soon automatically stop running. 
Therefore, the machine should be loaded quickly if there are further 
dishes and implements remaining to be washed. The terminal 3 of this relay 
94 is connected to a horn 82 and a signal light 104 for providing a short 
"beep" tone as well as flashing the signal light, when the timing relay 94 
turns "on." 
In order to install this system 100 in the washer 10, the "hot" lead 64 of 
the dishwasher is disconnected from the terminal 66 of the stop switch 32. 
Instead, this hot lead 64 is connected to the terminal 74 of this 
conservation control system. This hot lead 64 of the dishwasher machine is 
indicated by "X" at several places in FIG. 2. Then, the terminal 73 of 
this system is connected to the terminal 66 of the stop switch 32. 
Terminals 72 and 75 of the system 100 are connected into the power control 
relay 80 of the conveyor motor 26. As discussed above, the conveyor motor 
26 is conventionally supplied with 3-phase AC electrical power through the 
relay 80. This relay contains three sets of contacts for controlling the 
electrical power to be supplied to the motor 26. There is a fourth set of 
contacts in this relay 80, and the terminals 72 and 75 are connected to 
this fourth set of contacts. Thus, a circuit is completed between 
terminals 72 and 75 whenever the conveyor motor is energized by actuation 
of the motor relay 80. 
These terminals 72 and 75 are connected to the switch terminals 87 and 88 
of a double-pole, double-throw key switch 86 which can only be operated by 
the proper key. When the switch arms are turned up to the contacts 85 and 
89, the switch 86 is set for "MANUAL" operation. When the switch arms are 
turned down to the contacts 87 and 88, this switch is set for automatic 
"CONSERVATION" operation by employing the system 100. 
The purpose of this key switch 86 is to enable the machine 10 to be 
returned to its customary manual control operation in the event that the 
control system 100 might malfunction. Consequently, the management of the 
installation where the washer machine 10 is located is assured that this 
system 100 will not cause any loss of operation, because the management 
can immediately turn the key switch if the operator reports any 
malfunction in this system 100. By tracing the circuit path 
66-73-69-111-68-86-85-65-113-74-64 involving the switch contact 85 and its 
associated switch arm, the reader will see that when the key switch is set 
for MANUAL operation, the terminal 66 of the stop switch 32 is directly 
connected to the terminal 74 of the system and to the "hot" power lead 64 
of the washer. Consequently, the system 100 is completely by-passed, and 
the washer 10 will run in its conventional manner. 
The terminal 76 of this conserving system 100 is connected to the 
controlled side of the start switch 31 of the washer. Thus, terminal 8 of 
the start relay 90 is energized whenever the start switch on the machine 
is closed. 
The terminal 77 of this system is connected to the controlled side of the 
rinse-sensor-actuated switch 52. Thus, the terminal 77 becomes energized 
whenever the rinse is operating, and a signal light 101 is turned "on" 
which indicated to the operator that the rinse section of the washer is 
operating. As shown in FIG. 1, this signal light 101, as well as the other 
signal lights 102, 103, 104 and 105 are located on the front panel of the 
cabinet 58. Energization of this terminal 77 also serves to energize the 
terminal 1 of the conveyor control relay 92. 
The conservation control cabinet 58 conveniently includes a start switch 84 
associated with the timing off relay 95 so that the operator can manually 
start the machine by pressing either the usual start switch 31 or this 
second start switch 84. 
In operation when the start switch 31 is closed, a circuit is completed 
from the electrical supply terminal 61 to terminal 8 of the start relay 
90, thereby feeding power to terminal 5 which is connected by a lead 110 
to the terminal 7 of the "RUN" relay 91 for energizing the relay winding 
of which the other terminal 2 is connected to the neutral (ground) lead 
112. Thus, energization of this RUN relay 91 causes its arms to engage 
contacts 6 and 3, thereby completing a circuit from the hot lead 111 
through terminals 1 and 3 to the lead 113 which is connected with the 
machine supply terminal 74. Consequently, power is now supplied from 
terminal 73 through leads 69 and 111, and through the terminals 1 and 3 of 
the RUN relay 91 to the supply terminal 74 of the washer, thereby placing 
the washer in its normal running operation. 
Since the dishwasher is now running, the relay 80 for the conveyor motor is 
closed, providing a connection between terminals 72 and 75. Consequently, 
electrical power is fed from the terminal 73 through the leads 69, 111, 
68, key switch terminal 87, terminal 75, contacts in motor relay 80, 
terminal 72, key switch terminal 88 and lead 114 to terminl 7 of 
"CONVEYOR" relay 92. Thus, the winding of the CONVEYOR relay 92 is 
energized for closing a circuit to the relay terminal 6 to energize the 
signal lamp 103 for indicating to the operator that the conveyor is 
running. 
If, for any reason, the conveyor motor relay 80 is deenergized, the winding 
of CONVEYOR relay 92 becomes deenergized, thereby turning off the signal 
lamp 103, while turning on the signal lamp 102 to indicate to the operator 
that the conveyor has become stopped, possibly as the result of a jammed 
rack 22. 
Assuming that the dishwasher is running normally, a rack 22 will enter the 
rinse section 16, actuating the switch 52 for operating the rinse solenoid 
valve. Through terminal 77 and lead 115 the closure of switch 52 also 
energizes the terminal 1 of CONVEYOR relay 92. Since the conveyor is 
operating, the relay arm is making contact with the terminal 3 for closing 
a circuit through a lead 116 from this terminal 3 over to terminal 7 of 
the "TIMING CONTROL" relay 93. Consequently, the right hand relay arm of 
this TIMING CONTROL relay 93 is separated from its contact 4 and no 
electricity can flow through the lead 117 to terminal 7 of the TIMING ON 
relay 94. Therefore, whenever the rinse sensor switch 52 is closed the 
TIMING ON relay is deenergized to become returned to the beginning of its 
time measuring period. 
Whenever the conveyor motor relay 80 is closed, the TIMING OFF relay begins 
its measuring period, because the conservation system terminal 75 is 
connected through a lead 118a to the winding of the relay 95 for 
energizing this relay winding whenever the conveyor motor begins running. 
Therefore, the washer will automatically be shut off by the TIMING OFF 
relay 95 at the end of its pre-set time limit, unless the rinse sensor 
switch 52 becomes actuated during the pre-set measured time period. 
Whenever the rinse switch 52 causes the TIMING CONTROL relay 93 to 
deenergize the TIMING ON relay 94, it also completes a circuit from the 
lead 119 through relay terminals 8 and 6 of relay 93 to the lead 120. In 
other words, actuation of the TIMING CONTROL relay 93 serves to complete a 
circuit between the leads 119 and 120 which, in effect, is the same as 
occurs when the start switch 84 is closed. 
As shown in FIG. 4, in a washer machine in which the conveyor 18 is of the 
belt type, the rinse sensor switch 52 is controlled by a so-called 
whip-type of switch actuator 122. This whip-type actuator 122 includes a 
pivotally mounted horizontal rod which extends across the machine at a 
sufficiently high elevation that the rod 124 will clear all utensils 
conveyed by the conveyor 18. 
There are multiple legs 126 secured to the rod 124 and extending down from 
this rod so that these legs are swung forwardly when food service utensils 
are conveyed beneath the actuator 122, thereby closing the switch 52 for 
energizing the rinse solenoid valve. Actuation of this switch 52 produces 
the other desirable conservation control action by the system 100 by 
virtue of connecting the system terminal 77 to the control side of this 
rinse switch 52 in FIG. 4. 
It is to be understood that the pump motors 36 and 46 are three phase 
induction motors each of which has a control relay for energizing it 
whenever the washer machine 10 is running. The relays for these pump 
motors as well as the relay 80 for the conveyor motor 26 are customarily 
located in the control cabinet 30 of the washer 10. In order to employ the 
present invention it is not necessary to make any additional connections 
to these conventional pump motor relays, and so they are not shown in FIG. 
2. 
Thus, advantageously, the conservation control system 100 and the method 
automatically causes the washer machine 10 to run sufficiently long to 
complete a full cycle of washing whenever the rinse sensor switch 52 is 
actuated. However, if there are no dishes or implements within the washer, 
then the machine 10 is automatically turned off at the end of the pre-set 
time period as established by the TIMING OFF relay 95. 
A suitable TIMING ON relay 94 is commercially available under the 
designation Cramer Solid State Timer, Model 390A, which can be pre-set at 
any point over a range from 3 to 300 seconds. 
An appropriate TIMING OFF relay 95 can be obtained commercially from 
National Control Corporation of Lombard, Ill., having a range of 
adjustment from 1.8 to 180 seconds. 
A practical CLOCK 96 is a running meter available from ENM Company, of 
Chicago, Ill. 
From the foregoing description it will be appreciated that the particular 
machine 10 as shown and the sensor arrangements as shown in FIGS. 3 and 4 
are illustrative and are provided by way of example and are not intended 
as limitations. Also, FIG. 2 shows the conservation system of the present 
invention as hard wired circuit. It will be understood by those skilled in 
the art that the various timing, signalling and control functions as 
described can be equivalently performed by a microprocessor. However, it 
is my preference to employ circuit components as shown because a very 
rugged system 100 is thereby obtained, in view of the fact that the 
ambient conditions around a commercial dishwasher machine are often humid 
and warm. 
This invention is not limited to the examples shown but is intended to be 
interpreted and understood to the full scope of the following claims.