U.S. patent number 3,896,827 [Application Number 05/393,345] was granted by the patent office on 1975-07-29 for dish machine monitoring of time, temperature, alkalinity, and pressure parameters.
Invention is credited to Norman R. Robinson.
United States Patent |
3,896,827 |
Robinson |
July 29, 1975 |
Dish machine monitoring of time, temperature, alkalinity, and
pressure parameters
Abstract
A dishwasher control system for automatically recording the
duration of machine operation to determine cost of supplies,
service and use. Machine operation is commenced by sensing the
pressure of dishes and stopped automatically at the end of the
cycle. During operation, the wash water is continuously sampled and
checked for low temperature, low detergent and low pressure.
Inventors: |
Robinson; Norman R. (Dublin,
CA) |
Family
ID: |
23554311 |
Appl.
No.: |
05/393,345 |
Filed: |
August 31, 1973 |
Current U.S.
Class: |
134/10; 134/25.2;
134/18; 134/56D; 417/477.13 |
Current CPC
Class: |
A47L
15/4427 (20130101); A47L 15/0044 (20130101); A47L
15/0055 (20130101); A47L 15/0049 (20130101); A47L
15/241 (20130101); A47L 2501/07 (20130101); A47L
2501/26 (20130101); A47L 2401/12 (20130101); A47L
2401/14 (20130101); A47L 2401/11 (20130101) |
Current International
Class: |
A47L
15/44 (20060101); A47L 15/42 (20060101); B08b
003/10 () |
Field of
Search: |
;134/18,10,25A,25R,29,30,32,57D,58D,72,56D,48 ;417/474,477
;58/145R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bashore; S. Leon
Assistant Examiner: Fisher; Richard V.
Attorney, Agent or Firm: Limbach, Limbach & Sutton
Claims
I claim:
1. In a method of controlling continuous automatic dishwasher
operation wherein the dishes are transported through a device
comprising at least a washing station and a rinse station and
dishwashing additives are automatically introduced into circulating
dish washing liquid which contacts dishes at said washing station,
the improvement comprising commencing washing operation by
mechanically sensing presence of dishes to be washed, stopping
operation of the device at the conclusion of rinsing, measuring and
recording the duration of operation of the device, continuously
sampling the circulating dish washing liquid during operation of
the device to automatically determine:
1. the temperature and signalling when a temperature is determined
to be below a predetermined value,
2. alkalinity and adding dish washing additives to the circulating
water when alkalinity is determined to be below a predetermined
value, and
3. pressure and signalling when pressure falls below a
predetermined value.
2. A method as in claim 1 wherein said predetermined temperature
value is 150.degree. F. the predetermined pressure value is
three-fourths psi and the predetermined alkalinity value is 0.7
percent concentration by volume.
3. A method as in claim 1 wherein the device has a fill line, the
step of automatically signalling the presence of flow pressure in
the fill line during machine operation.
4. A method as in claim 1 wherein dish washing additives to be
introduced into the liquid are in containers, the steps of
automatically sensing and signalling the depletion of additive
supply in said containers.
5. A method as in claim 1 wherein dishwashing additives are
automatically blended into the sample of circulating dish washing
liquid as needed before the sample is returned to the main flow of
circulating liquid.
6. A method as in claim 5 wherein the automatic blending varies the
relative proportion of additives depending on water conditions and
use needs.
7. A method as in claim 1 wherein dish machine operation is
prevented except when wash water heaters are in operation.
8. In a control system for a dishwashing machine, at least one
water spray station, a conveyor for dishes, and a recirculating
pump to recirculate wash water, the improvement comprising
1. means for energizing the control system and starting the
dishwashing cycle when dishes are ready for washing,
2. means for sensing water pressure and signal means, responsive to
said means for sensing, operable when pressure falls below a
predetermined level during operation of the control system,
3. means for testing level of washing additive in the wash water,
means responsive to said testing means to add washing additive to
wash water when below a predetermined level,
4. temperature sensing means for detecting a temperature below a
predetermined level and signal means responsive to said temperature
sensing means to alert the operator to the low temperature
condition,
5. switch means turning off the dishwashing machine at the close of
each cycle.
9. A system as in claim 8 including measuring means responsive to
the means for energizing the control system and to said switch
means, whereby said measuring means measures the duration of
operation of the dishwashing machine.
10. A system as in claim 8 wherein the dishwashing machine has a
fill line, the improvement comprising pressure sensitive means in
said fill line to detect the flow of water in said line and signal
means to alert the machine operator to the flow of water in the
fill line.
11. A system as in claim 8 including multiple sources for dish
washing additives and flexible tubes for passing additives from
each of the multiple sources to the dishwashing machine, the
improvement comprising pump means engaging said flexible tubes to
pump the additives, said pump means having a rotating driven shaft,
a wheel rotatably mounted on said shaft, two or more rods extending
parallel to said shaft from the periphery of said wheel, each of
said flexible tubes passing over said rods, and tension means for
placing the length of flexible tube from each source passing over
said rods under tension, whereby the contents within the tubes are
pumped as the rods peristaltically stretch said tubes upon rotation
of the wheel about the shaft.
12. A system as in claim 11 wherein the tubes downstream of said
pump means enter a mixing manifold comprising an inlet chamber, a
venturi throat and an exit chamber communicating to the dishwashing
machine, whereby additives flowing from said pump means are
accelerated through the venturi throat.
13. In a control system for a dish washing machine having a fill
line, a loading station, at least one water spray station, a water
heater, a dish conveyor, a recirculating pump and recirculating
water, the improvement comprising
1. control means for commencing operation of the dish machine
responsive to the presence of dishes at the loading station,
2. time measuring means to determine the duration of operation of
the dish washing machine,
3. temperature responsive means communicating with recirculating
water for determining low temperature,
4. a first pressure responsive means in said fill line for
determining the presence of water in the fill line,
5. a second pressure responsive means in said recirculating pump
for determining low pressure,
6. peristaltic pump means for blending additives into a line
communicating with said recirculating water to restore conductivity
above a predetermined level, and
7. a conductivity responsive means communicating with said
recirculating water activating said peristaltic pump when
conductivity is low.
Description
BACKGROUND OF THE INVENTION
Commercial dishwashing machines are widely used in restaurants and
hotels. These machines avoid the requirement for operators handling
dishes and contacting detergents against their skin and they
operate much more rapidly than manual systems. But commercial
machines usually require a number of operator-initiated steps. For
example, with most commercial dishwashing machines the operator
must close drain valves; open fill valves and fill the tanks to the
proper level; install accessories, such as scrap trays and divider
curtains; close inspection doors; turn on tank heaters; and turn on
pumps and conveyor. After carrying out all of these steps, the
operator then proceeds to wash the dishes by inserting racks filled
with dishes or by loading and unloading a continuous belt.
Most commercial dishwashing machines have dispensing systems
associated with them to provide detergent to the machines at proper
concentration. The wash water is monitored to provide a check on
conductance of the alkaline solution. When the detergent level, as
measured by alkalinity, falls below a predetermined level, the
dispenser systems automatically add the necessary dishwashing
additives. However, the dishwashing operator must keep the
dispensing system stocked with detergents and additives and must be
trained in the operation of the dispensing system as well as the
dishwashing machine.
Previous dispensing systems are designed to add detergent and
additives during the wash cycle whenever alkalinity is low.
Occasionally the drain valve to the dishwashing machine is
inadvertently left open and detergent-containing water is passed to
waste. The addition of fresh water to restore the water level
dilutes the detergent. Fresh detergent is added at each wash cycle
because the conductance measure indicates that the detergent level
is low. If the conductance measuring device is not immersed in
water because of low water level, it will signal "low charge" and
cause more detergent to be added.
Another common problem with existing dishwashing machines is that
they tend to be operated over greater periods of time than are
necessary. In many installations, the machine is turned on in the
morning with the first breakfast dishwashing and remains in
continuous operation until the last dishwashing operation after
dinner. During this entire time, the immersion heaters are on to
maintain the water temperature at the desired level. Continuous
operation of the heaters tends to waste considerable electricity
and raise the ambient temperature levels in the dishwashing room.
Similarly, bearings, motors and other moving parts tend to have a
shorter useful life when the machine is continuously operated.
It is an object of the present invention to provide a dishwashing
machine control system that will reduce the time of operation to
that essential for cleaning of dishes; that will dispense
dishwashing additives in amounts necessary only for the efficient
operation of the machine; and that will prevent most of the
operator-caused waste and inefficiency currently found in the
operation of dishwashing machines.
SUMMARY OF THE INVENTION
The present invention involves a method and apparatus for
controlling the operation of automatic dishwashers by commencing
operation only when dishes to be washed are present at the loading
station and stopping the operation of the dishwashing machine at
the conclusion of the measured cycle as the dishes reach the unload
station. The apparatus measures and records the duration of
operation of the dish machine as a check upon the efficient
operation of the machine and as the basis for charging for the use
of the system. Circulating dishwashing water is continuously tested
during operation of this machine for temperature, alkalinity and
pressure. The temperature test provides a convenient check on
whether the wash water is hot enough for proper cleaning and as a
check upon malfunction of the heater system. Alkalinity provides a
convenient check on whether soil removal capacity of the
circulating liquid is adequate. Testing for pressure determines
whether the cleaning action of the dishwashing water is
satisfactory, since the presence of large amounts of protein in the
wash water tends to create high foam levels reducing the cleaning
effectiveness of the liquid, even when it has adequate detergent
levels. Pressure determination also senses whether there is a low
water level condition in the tank or an open or leaking drain
valve. The system may also include sensors for an open fill line to
prevent waste of water and excessive dilution of detergent and for
indicating low supply levels. Where any of the frequently recurring
problems with automatic dishwashers occurs, the system
automatically signals and sounds an alarm for operator
correction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing of a conventional commercial
dishwashing machine.
FIG. 2 is a perspective view of the control box used for operating
the conventional dishwashing machine according to the present
invention.
FIG. 3 is a detail cross-section of the blending device of the
invention.
FIG. 4 is a plan view of the exterior of the control box.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
There are a wide variety of commercial dishwashing machines
available today having many configurations. Many features are
common to the usual machines as to the arrangement of washing
stations and operation. FIG. 1 schematically illustrates the
typical dishwashing machine.
The dishwashing machine comprises a housing 11 through which a
conveyor means 12 passes. Conveyor means 12 is illustrated as a
continuous belt, but other transport means, such as a reciprocating
rod with pawls engageable on specially made racks, are sometimes
used to transport dishes through the housing 11. The machine shown
is divided into several stations, including a loading station 13, a
pre-wash or scrapper station 14, a wash station 16, a power rinse
station 17, a final rinse station 18 and an unload station 19.
Dishes are placed on the conveyor means 12 at station 13 either
directly or in racks designed for use with the particular device.
In the present invention, it is desirable to commence operation of
the dishwashing machine by sensing the presence of dishes to be
washed at station 13. Normally, commercial dishwashing machines
have no such sensing devices built in and must be manually started
by the operator. I prefer a trip switch 15 conveniently located to
be actuated upon placing racks of dishes or the dishes themselves
on the conveyor means 12. While a trip switch 15 is convenient,
other mechanical sensing devices may be used such as
electromagnetic sensors, weight-sensing means, etc. Activation of
the sensing device starts the dishwashing cycle, including
operation of the conveyor 12 and the recirculating pump presently
to be described. Trip switch 15 also causes timer 20 (FIG. 2) to
operate.
Dishes to be washed first enter scrapper station 14 in which a
large flow of water from spray heads 21 and 22 flush large pieces
of food from the surface of dishes to wet the surfaces and to
remove debris. Not all commercial dishwashers have a pre-wash or
scrapper station 14, in which case the dishes proceed immediately
into the wash station 16. Each of the stations has a tank for
receiving water recovered from the spray heads and appropriate
means for removing contaminated water and recirculating relatively
clean water to the extent possible. Since the functions of scrapper
station 14, power rinse station 17 and final rinse station 18 form
no part of the present invention, detailed description and
illustration of these stations is here omitted.
After large particles are removed at scrapper station 14, the
dishes pass on conveyor 12 into wash station 16. There, the dishes
are sprayed with detergent-containing water from heads 23 and 24.
To conserve detergent, it is recirculated by means of recirculating
pump 26. Pump 26 is located beneath the water level 27 in tank 28
of station 16. Pump 26 has an inlet 29 and an outlet 31 which
forces water to spray heads 23 and 24 through pipes 32 and 33. Tank
28 has a fill line 36 for fresh water inlet and a drain line 37 for
removing waste water, both with appropriate valves (not shown) for
inlet and outlet of water.
Detergent and other appropriate dishwashing additives are stored
remote from the dishwashing machine. As illustrated in FIG. 1, a
typical dishwashing machine has a container 38 for detergent,
container 39 for chlorinated additive 39, and perhaps a container
41 for wetting agent or other additives. Of course, any number of
additives may be provided, either more or less than the three
illustrated in FIG. 1. Each container 38, 39 and 41 has associated
piping 42, 43 and 44 for supplying the additives to the tank 28, as
by gravity. The typical dishwashing machine has valve means (not
shown) for providing the appropriate amount of each additive to the
liquid in the tank.
Following washing at station 16, conveyor 12 moves the dishes into
power rinse station 17 where relatively clean rinse water is
sprayed on the dishes from spray heads 46 and 47.
In the embodiment illustrated, there is an additional final rinse
station 18. While all dishwashing machines usually have a wash
station 16 and a final rise station 18, larger machines ordinarily
have scrapper station 14 and power rinse station 17 in addition. In
final rise station 18, a second rinse is sprayed from heads 48 and
49 onto the dishes. Frequently, the rinse water in station 18
contains a wetting agent, such as a nonionic surfactant, to promote
sheeting and smooth drying of the dishes. The rinse additive may
contain some alcohol to promote quick drying. Such additives may be
introduced to final rinse heads 48 and 49 from one of more
containers 51 through appropriate piping 52 and the necessary
metering means, valves, pumps, etc. (not shown).
After the final rinse station 18, conveyor 12 passes the dishes to
discharge station 19 where the dishes are unloaded. When the dishes
reach station 19 the machine will turn off and conclude the cycle.
The machine is turned off by operation of a timer 20 (FIG. 2). The
timer is reset by the trip switch or other means sensing the
presence of dishes at station 13. The timer then runs for the exact
period of time for which the dish machine cycle is designed. Timer
20 is variable to run for any duration of cycle that commercial
dish machines have. An example of a suitable timer 20 is that made
by AMF Corporation, Potter and Brumfield Div. under the designation
CHB 38. The timer 20 is installed in control box 125 (FIG. 1),
which may be locked to prevent access by the operators. Timer 20 is
set at the time of original installation of the control system to
coincide with the normal cycle of the dish machine. Some existing
machines remain in continuous operation until the operator switches
the device off. According to the present invention, it is important
to automatically turn the device off at the conclusion of the cycle
because the time of operation of the machine is measured and
recorded to determine the cost of operation of the system.
Aside from the importance of having a recorded knowledge of the
duration of operation of the device for efficient operation of the
machine and management time studies, it is convenient to service
the machines according to time. While presently available
commercial dishwashing machines are frequently serviced by
businesses other than the owner of the machines, payment for the
service of providing detergents and supplies to the machine is
presently on the basis of materials used, maintenance calls, etc.
The present invention has particular importance in permitting
service of dishwashing machines by supplying repairs, detergents,
training, etc. charged for exclusively on the basis of time of
operation of the machine. Such a method of charging is more
economical and equitable to the owner of the machine and avoids the
risk of substantial losses of detergents and damage to the machine
where operator error occurs, such as by leaving the drain valve
open or other errors described above. The risk of detergent loss,
control system failure, etc. is shifted to the service organization
from the owner.
FIGS. 2, 3 and 4 illustrate the control system of the present
invention. FIG. 2 shows the interior of the control system of the
present invention. A sample of dishwashing water is taken from the
circulating liquid at station 16. Preferably, the sample is taken
by tapping a one-eighth inch hole in the outlet manifold 31 of pump
26 (FIG. 1). The hole may conveniently be connected to a PVC tube
which passes to mixing manifold 56 (FIG. 2). Sample water taken
from a line at the exit end of the circulating pump or elsewhere is
fed through line 57 into mixing manifold 56 and returned to tank 28
of washing station 16 through exit line 58. Preferably, sample
water passes through the control system shown in FIG. 2 through
line 57 and returns via line 58 during the entire time of operation
of the circulating pump in the wash tank. All dishwashing additives
are introduced at the mixing manifold 56, thereby requiring only an
inlet line 57 and outlet line 58 connecting the control system to
the dishwashing machine. Even though any number of additives may be
introduced into the dishwashing liquid, all such additive lines
lead only to the control box shown in FIG. 2 and need not be
connected to the dishwashing machine itself.
Thermostat 59 has an electrode inserted into mixing manifold 56 for
determining temperature. The probe of the thermostat 59 also serves
as one electrode for determination of conductivity of the solution
in mixing manifold 56 for alkalinity determination. Wire 61 is
connected to sensitivity circuit 62. Wire 63, also connected to the
sensitivity circuit 62, leads to a second electrode 64 inserted
into mixing manifold 56. Sensitivity circuit 62 measure the
conductance and, when alkalinity falls below a predetermined level,
introduces detergent additives by activating the pump 66.
Sensitivity circuit 62 consists of means to amplify the
conductivity signal across the detergent solution in manifold 56
between the two electrodes and, if the signal is weak, switching on
the pump. When conductivity is restored and signal strength
increases, circuit 62 turns off pump 66. In practice, I use an
amplifier and control circuit consisting of a transistorized gate
and a potentiometer to adjust the circuit to the desired
concentration at which a relay activates the detergent pump 66. Any
other suitable means for determining conductivity and commencing
pump operation when a low alkalinity condition exists may be
substituted.
Conductivity circuit 62 commences operation of pump 66 when the
level of conductivity falls below the predetermined level.
Sensitivity circuit 62 is connected to pump 66 by appropriate
switch means and wires (not shown).
Pump 66 is a peristaltic pump. Sensitivity circuit 62 commences
operation of a small motor (not shown) which rotates drive shaft 67
to which wheel 68 is attached.
Wheel 68 has three rods attached to its periphery to mark the
corners of an equilateral triangle. The three rods 71, 72 and 73
serve to pump dishwashing additives into mixing manifold 56. FIG. 2
shows three rods, but any suitable number of two or more rods may
be affixed to the wheel 68. Rods 71, 72 and 73 may conveniently be
made of nylon or other suitable material. Lines 74, 75, 76 carry
appropriate dishwashing additives from containers 38, 39 and 41.
These three lines are made of flexible tubing, such as one-fourth
inch diameter polyvinyl chloride. Line 74 is attached to
replaceable tube 77 by means of appropriate connector 78. Line 77
is designed to be detachable from line 74 for replacement with a
similar line of different diameter. In this manner, the relative
proportions of dishwashing additives may easily be varied by the
simple expedient of substituting tubes of greater or lesser
diameter, depending upon the volume of the particular additive
desired. Similarly, tubes 78 and 79 are detachably connected to
lines 75 and 76, respectively, to permit substitution of greater or
lesser diameter tubing in order to enlarge or restrict the volume
of additives to be introduced into mixing manifold 56 from each
line. Line 77 passes through grommet 81 in a hole through plate 82
and passes around rods 73, 72 and 71 before passing out through
plate 82 by means of grommet 83. Tube 77 then terminates and is
detachably connected to line 84 by means of a suitable connector
86, to permit easy substitution of line 77 with a tubing of
different diameter. Line 84, also of flexible tubing, is then
passed to mixing manifold 56 and enters through fitting 87.
Similarly, flexible tube 77 comes from another source of
dishwashing additive which may be incompatible with the first and
is detachably connected to line 78. Line 78 passes through grommet
88 in a hole in plate 89 and then passes around rods 72, 73 and 71
before leaving the pump through grommet 91 in another hole in plate
89. Tube 78 is detachably connected to line 92 in the manner
similar to connector 78. Line 92 then passes to mixing manifold 56
and enters through fitting 93.
Likewise line 76 is detachably connected to line 79 which, in turn,
passes through grommet 94, around rods 72, 73, 71, and then exits
the pump through grommet 95 in a hole in plate 89. Line 79 is
detachably connected to line 96 which passes to mixing manifold 56
and enters through fitting 97.
In operation, peristaltic pump 66 rotates around shaft 67 to force
the contents of tubes 77, 78 and 79 into mixing manifold 56. It
will be observed that clockwise rotation of pump 66 in FIG. 2
stretches each tube as each of rods 71, 72 and 73 pass to a maximum
distance from the respective grommets in plates 82 and 89, thereby
forcing the liquid dishwashing additives contained in the tubes
into mixing manifold 56. Pump 66 efficiently meters additives to
the manifold with a minimum of moving parts in an extremely simple
manner.
Sensitivity circuit 62 and all control circuits are also controlled
by timer 20 so that they are operative only while the dish machine
is operating. Otherwise, the sensing devices will have to have a
standby position for periods when recirculating pumps and other
dish machine parts are not working. It is convenient to have the
timer control the operation of the dish machine and its control
system at precisely the same periods.
While not shown in FIG. 2, the control box may conveniently contain
means for determining the existence of flow pressure in the fill
line to the washing machine. This may be accomplished conveniently
by having a flexible plastic tubing from the fill line to a
pressure switch located in the control box. A pressure switch
designated M3218-4 manufactured by the Hobbs Division of
Stewart-Warner Corp. of Chicago, Illinois, has been found to be
highly satisfactory for this purpose. The pressure switch may be
electrically connected to the alarm system on the face of the
control box as shown in FIG. 4. When the pressure switch senses the
presence of water flowing in the fill line and the system is
operating a light will be turned on on the front of the control
box. Alternatively, the pressure switch may be located at the fill
line itself, rather than in the control box, and electrically
connected with the light on the face of the control box to indicate
water flowing in the fill line. The pressure setting for activating
the switch is variable between one-fourth to thirty pounds per
square inch. I prefer to set the pressure for switch activation at
between one-half and three-fourths psi.
In those installations where rinse water additive is to be
introduced at final rinse station 18, the control box may also
contain a feed line from the final rinse additive storage 51 into
the final rinse heads 48 and 49. A separate pressure sensitive
switch (not shown) activates pump 100 (FIG. 2) which feeds
additives into line 52 (FIG. 1). Suitable timers and circuitry are
well known to those skilled in the art for pumping rinse water
additives into station 18. One acceptable pump is a motor driven
positive displacement injection pump manufactured by Plex Chemical
Co., Union City, California.
FIG. 3 is a cross section of mixing manifold 56 illustrated in FIG.
2. Additive-containing wash water from tank 28 (FIG. 1) is taken
off through sample line 57 at the outlet from pump 26. Referring to
FIG. 3, line 57 preferably has a filter 101 to remove large
particles from the sample water entering mixing manifold 56.
Pressure switch 102 senses, through plastic tube 103, the presence
of water flowing in line 57. When water stops flowing in line 57 or
a low pressure condition occurs while pump 26 is running, pressure
switch 102 activates an alarm system. The alarm system consists of
a light on the face of the control panel (FIG. 4) as well as a bell
to call immediate attention to the operator that water is not being
pumped by pump 26. Lack of pressure in line 57 indicates that there
is no water in tank 28 or that excessive foam in tank 28 is such
that pump 26 is unable to maintain the water pressure required for
efficient operation of the dishwashing machine. Pressure switch 102
is electrically connected through wires 106 and 107 to the bell and
light alarm system. The alarm does not sound when the machine is
turned off, but only when the wash cycle is operating in station
16. Sample water in line 57 enters mixing manifold 56 through
fitting 108 into port 109 and into chamber 111. In chamber 111, the
sample water is tested for temperature and alkalinity. Thermostat
59 functions to measure the temperature and switch on a signal
light when the temperature of sample water falls below a
predetermined level. Conveniently, that level is 150.degree. F. The
probe 112 of thermostat 59 also functions as the anode for
determining alkalinity. Probe 112 is connected by wire 61 to a
sensitivity circuit previously described. The electrode 64 extends
into chamber 111 through fitting 113. Electrode 64 is connected to
a sensitivity circuit through wire 63 in order to measure
alkalinity.
When alkalinity falls below a predetermine level, such as a
concentration of approximately 0.7 percent by volume, the
sensitivity circuit 62 commences operation of peristaltic pump 66
and additive ingredients enter mixing manifold 56 through lines 96,
92 and 84. The potentiometer in circuit 62 may be adjusted to any
desired concentration for operation of pump 66 as conditions in the
particular dishmachine warrant. In practice, I find concentration
between 0.5 and 1.5 percent by volume to be suitable for most
dishwashing conditions. Concentration is determined chemically and
circuit 62 set at the time of installation to the desired value at
which pump operation commences.
Chamber 111 of mixing manifold 56 empties into venturi channel 116
which then passes through exit fitting 117 at the bottom of the
manifold and through line 58 back to the wash tank 28. Venturi
channel 116 has tapered sides to provide a slight acceleration of
sample water passing through it to provide a slight suction on
additive feed lines 96, 92 and 84. The suction in venturi channel
116 serves only to drain lines from the peristaltic pump 66 in the
event of failure of any of the tubes associated therewith.
Introduction of the additives to the sample line is accomplished by
means of the pump. However, when a tube such as tube 77, for
example (FIG. 2), breaks through long flexing in the pump, any
additive in the tube 77 on the upstream side from pump 66 will
drain by gravity back to the storage tank for the additive through
line 74. On the other hand, assume that a break occurs on the
downstream side of tube 77 from the pump rods. The small amount of
additive in line 77 and associated line 84 downstream from the
break would drain back into the control box were it not for venturi
channel 116. Even a small amount of many detergent additives is
sufficient to cause considerable corrosion hazard to personnel and
damage to parts of the control box. As a result of venturi channel
116, sufficient suction is provided in the sample line downstream
from the pump 66 to enable any dishwashing additives to be drained
from broken tubes without draining into the cabinet of the control
box.
In order to take maximum use of the venturi effect in channel 116,
lines 96, 92 and 84 empty into the channel just below the minimum
diameter through ports 121, 122 and 123.
FIG. 4 is the cover of a sheet metal box 125 which conveniently
houses the control system at a location convenient for the operator
of the dishwashing machine. The cover of the closed box is shown in
FIG. 4 to have lights responsive to the various conditions
requiring attention of the operator. Light 126 is responsive to the
pressure-sensitive means and is appropriately designated. Light 127
is connected to the temperature-responsive means and serves to
light up when low temperature is indicated. Light 128 is turned on
when the fill line is in use by means of the pressure-responsive
switch in the fill line. The operator will know to turn off the
fill line by the existence of light 128. I also prefer to install
an audible signal, such as a buzzer, in addition to the light 128.
Light 129 turns on when the supply of dishwashing additives is
below the desired level. The operator will take the necessary steps
to replenish the supply of dishwashing additives. In practice, this
is done by contacting the service representative who provides
detergents to the control system. Light 130 turns on when the
dishwasher is turned on to activate the heating system. Heaters or
gas burners are used for raising the temperature of the wash water
as in conventional machines. Unfortunately, dish machines are
designed to have the operator turn on the water heaters separately
from the pumps and conveyors. Operators frequently leave the water
heaters off and wash with luke-warm water because the dishes are
too hot to handle under normal operation. This is a common operator
failure which is avoided in this system by preventing machine
operation except when the heaters are on. Light 130 indicates the
machine is in an idle condition with hot water and awaiting
dish-actuation. Light 130 also serves to prevent the heaters
remaining on all night when the operator goes home.
FIG. 4 also shows an elapsed running time meter 131 which records
the number of hours of accrued operation of the dishwasher for
complying with maintenance schedules and for charging for use of
the system and products in those instances where the service of the
control system of the dishwashing machine is provided by someone
other then the owner of the machine. The meter is wired to timer 20
to record the total operation of the timer which coincides with the
operation of the dish machine. If the timer is set for a period
longer than the dish machine cycle, the customer unnecessarily pays
for added time. If the timer is set for a shorter period, then the
cycle will not be completed and the dishes will not reach unload
station 19.
Finally, FIG. 4 shows a lock 132 for providing security to the
control system and preventing access to the system except by
authorized persons, usually those associated with the business of
maintenance and supply of detergents, rather than the operators
whose errors frequently have given rise to the problems sought to
be solved by the present invention.
The foregoing specific embodiments are simply exemplary of the
different types of apparatus that may be used to control the
functions of a dishwashing machine. Other forms of apparatus may be
used to perform the control functions specified in the attached
claims. The control system provides a safe, efficient and automatic
operation essentially free of manual operations by an operator of
the dishwashing machine.
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