US 3896827 A
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.
Claims available in
Description (OCR text may contain errors)
United States Patent Robinson July 29, 1975 1 1 DISH MACHINE MONITORING OF TIME, 3.18.2,440 5/1965 Widegren 58/145 R TEMPERATURE ALKALINITY AND 3,406,695 10/1968 Perl 134/58 D 3,490,467 1/1970 GOI'C 6181.... 134/18 PRESSURE PARAMETERS 1127.376 5/1972 Pickup 417/477 Inventor: Norman R. Robinson, 6902 Brighton Dr., Dublin, Calif. 94566 Filed: Aug. 31, 1973 Appl. No.: 393,345
US. Cl. 134/10; 134/18; 134/25 A; 134/56 D; 417/477 Int. Cl. B08b 3/10 Field of Search 134/18, 10, 25 A. 25 R, 134/29, 30, 32, 57 D, 58 D, 72, 56 D, 48; 417/474, 477; 58/145 R References Cited UNITED STATES PATENTS Low 134/57 D Meeker et a1 134/48 X Primary Examiner-S. Leon Bashore Assistant Examiner-Richard V. Fisher Attorney, Agent, or Firm-Limbach, Limbach & Sutton  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.
13 Claims, 4 Drawing Figures PATENTEU JUL2 9197.5
SHEET PATENTED JUL 2 9 I975 SHEET FIE:-
DISH MACHINE MONITORING OF TIME, TEMPERATURE, ALKALINITY, AND PRESSURE PARAMETERS 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 operatorinitiated steps. For example, with most commercial dishwashing machines the operator must close drain valves; open fill valves and till 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. I 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. 7
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. I 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 I4, 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 detergentcontaining 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 CI-IB 38. The timer 20 is installed in control box (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 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 l.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 pressureresponsive 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 dishactuation. 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.
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 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,
5 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.