WO2013158963A1

WO2013158963A1 - Ice making machine and method with silver ion sanitation

Info

Publication number: WO2013158963A1
Application number: PCT/US2013/037316
Authority: WO
Inventors: Daryl Gregory Erbs
Original assignee: Manitowoc Foodservice Companies, Llc
Priority date: 2012-04-20
Filing date: 2013-04-19
Publication date: 2013-10-24

Abstract

An ice making machine and method for introducing silver ions into water during sump fill time. An ionization device is controlled to introduce the silver ions based on the volume of the water being delivered to the sump. The resulting ice pieces contain the silver ions so as to prevent contamination due to contact with ice scoops, ice bins, vessels and hands of users.

Description

ICE MAKING MACHINE AND METHOD WITH SILVER

ION SANITATION

FIELD OF THE DISCLOSURE

This disclosure relates to an ice making machine and method with protection from microbial contamination.

BACKGROUND OF THE DISCLOSURE

The antimicrobial properties of silver have been known from ancient times. In recent times, silver ions have been used to disinfect potable water supplies, bottled water and other foods. Silver has also been added to the materials used in food contact surfaces to prevent growth of microorganisms on those surfaces.

Existing commercial ion sanitation systems are designed to release a continuous rate of silver ions into a flow stream by controlling current flow between a cathode and a silver anode. These designs require precise control of the water flow rate through the system, or alternately, setting the ion release rate to correspond to the highest possible flow rate to ensure sufficient silver ion concentration is achieved for sanitation purposes. This leads to excessive ion concentration at the lower range of flow rates that may exceed tolerance limits for silver ions in potable water set by a governmental agency (e.g., the Environmental Protection Agency of the United States). Additional problems involve control of electrical current over the entire range of water conductivity that exists in public and private water supplies.

Ice pieces, for example, cubes, produced by a commercial automatic ice machine are normally free from bacterial and other microbial contamination. However, undesirable and potentially harmful microbial contamination can infect the ice pieces when accumulated in an ice bin or are transported to other use bins or serving vessels, contact with human hands and the surfaces of the bins, scoops, and vessels.

There is a need for an ice making machine and a method that provides antimicrobial protection for ice pieces without the disadvantages of the existing ice making machines.

SUMMARY OF THE DISCLOSURE

According to the ice making machine and method of the present disclosure, controlled levels of silver ions are introduced into a batch of water used to produce ice pieces in an ice making machine, the ice pieces contain a sufficient quantity of silver ions to kill any bacteria or other organisms that are introduced to the surface of the ice pieces through contamination. This allows the ice pieces to disinfect themselves over their lifetime, and serve to disinfect the surfaces of the bin, scoop or other vessels that they contact.

In one embodiment of the ice making machine of the present disclosure, an ice making apparatus makes ice using water in a sump. A water valve is connected in a piping to supply a volume of water to the sump. A silver anode and a cathode are disposed in the piping between the water valve and the sump. An ionization control device controls a voltage applied to the silver anode and the cathode to release a target amount of silver ions into the volume of water when flowing through the piping.

In another embodiment of the ice making machine of the present disclosure, the volume of water is delivered to the sump in a first time interval, and the voltage is applied to the silver anode and the cathode only during a second time interval within and shorter than the first time interval. In another embodiment of the ice making machine of the present disclosure, the target amount of silver ions is released during the second time interval. In another embodiment of the ice making machine of the present disclosure, the second interval begins after a short delay to assure that the water is flowing through the piping.

In another embodiment of the ice making machine of the present disclosure, the voltage is controlled in a range having a high target voltage value and a low target voltage value.

In another embodiment of the ice making machine of the present disclosure, the ionization control device comprises a capacitor, a charging circuit that charges the capacitor to the high target voltage value and a switch that when in a closed condition connects the capacitor to the silver anode and the cathode to discharge the capacitor to the low target voltage value while the silver ions release into the volume of water. In another embodiment of the ice making machine of the present disclosure, the switch, when in an open condition, disconnects the capacitor from the silver anode and the cathode. The charging circuit is operable to charge the capacitor while the switch is in the open condition. In another embodiment of the ice making machine of the present disclosure, a voltage monitor monitors the voltage. A controller has connections to the water valve, the switch and the charging circuit. Prior to a sump fill time, the controller controls the charging circuit to charge the capacitor to the high target voltage value. During the sump fill time, the controller controls the water valve to an open position to allow water to flow in the piping and controls the switch to the closed condition to discharge the capacitor to the low target voltage value. In one embodiment of the method of the present disclosure, sump water of an ice making machine is ionized by:

providing a silver anode and a cathode in a piping;

supplying a volume of water via the piping to a sump of the ice making machine;

controlling a voltage applied to the silver anode and the cathode to release a target amount of silver ions into the volume of water flowing through the piping. In another embodiment of the method of the present disclosure, the volume of water is delivered to the sump in a first time interval, and the voltage is applied to the silver anode and the cathode only during a second time interval within and shorter than the first time interval. In another embodiment of the method of the present disclosure, the target amount of silver ions is released during the second time interval.

In another embodiment of the method of the present disclosure, the second interval begins after a short delay to assure that the water is flowing through the piping.

In another embodiment of the method of the present disclosure, the voltage is controlled in a range having a high target voltage value and a low target voltage value.

In another embodiment of the method of the present disclosure, the method further comprises:

connecting and disconnecting a capacitor to the silver anode and the cathode:

charging a capacitor, while disconnected from the silver anode and the cathode, to the high target voltage value; and discharging the capacitor, while connected to the silver anode and the cathode, to the low target voltage value during a water fill time of the ice making machine while the ions release into the volume of water. In another embodiment of the method of the present disclosure, method further comprises providing a controller that controls the steps of supplying, controlling, connecting and disconnecting, charging and discharging. BRIEF DESCRIPTION OF THE DRAWINGS

Other and further objects, advantages and features of the present disclosure will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure and:

Fig. 1 is a block diagram of an ice making machine of the present disclosure;

Fig. 2 is a block diagram of an ionization control device of the ice- making machine of Fig. 1 ;

Fig. 3 is a circuit diagram of a capacitor charging circuit of the ionization control device of Fig. 2; and Fig. 4 is a flow diagram for the ionization program of the ice making machine of Fig. 1 .

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Fig. 1 , an ice making machine 20 comprises an ice making apparatus 22 and a controller 24. Ice making apparatus 22 comprises an ionization control device 26, a water reservoir (or sump) 28, a refrigeration system 30, a condenser 32, an evaporator 34 and an ice bin 36. Refrigeration system 30 is in fluid communication with condenser 32 and evaporator 34 to provide refrigerant flow during a freeze cycle and hot gas flow during a harvest cycle. During the freeze cycle water is supplied from water reservoir 28 to an ice making surface of evaporator 34, which is cooled by the refrigerant flow to grow ice on the ice making surface. During the harvest cycle the ice making surface is warmed by the hot gas flow to loosen the ice from the ice making surface so that it falls into ice bin 36.

It is contemplated that the activities of ionization control device 26 can be controlled directly by controller 24 or by a microcontroller that is controlled by controller 24. By way of example and completeness of description, the illustrated embodiment is described for an embodiment in which controller 24 directly controls the activities of ionization control device 26. Controller 24 controls the freeze cycle and harvest cycle through connections to various components of ice making machine apparatus 22. These components include ionization control device 26, a water inlet valve 38 and others that are not shown in the drawing. Water inlet valve 38 is located to supply water from a water source 40 via a piping 46 to water reservoir 28 and is connected in electrical circuit with controller 24 via a connection 42. Water inlet valve 38, for example, may be a solenoid controlled valve.

Ionization control device 26 is connected in electrical circuit with controller 24 via a connection 44, a connection 48 and a connection 88. Each of these connections may include one or more separate electrical conductors. Ionization device 26 comprises electrical conductors 64 and 66 that are connected to a silver anode 68 and a cathode 70, respectively. Silver anode 68 and cathode 70 are disposed in spaced apart relation inside a section of piping 46 between water valve 38 and sump 28. When water valve 38 is opened to fill sump 28, ionization control device 26 provides a voltage across silver anode 68 and cathode 70 such that by electrolysis silver ions are introduced into the water flow in piping 46.

Cathode 70 comprises a metallic material, for example, steel.

Controller 24 comprises a processor 50, a memory 52 and an input/output (I/O) unit 54 that are interconnected by a bus 56. A

refrigeration program 58 and an ionization program 60 are stored in memory 52 together with other programs (not shown) needed for processor 50 (e.g., an operating system and utility programs) for the operation of ice making apparatus 22. Memory 54 may be any suitable memory, such as, a random access memory, a read only memory, a plug-in memory (e.g., a flash memory, a disk memory or other plug-in memory) and/or any combination thereof. The plug-in memory may be plugged into controller 24, for example, via a USB port 62. Processor 50 executes refrigeration program 58 to control the components of ice making apparatus 22 to form ice pieces on evaporator 34 during a freeze cycle and to separate the ice pieces from evaporator 34 during a harvest cycle so that they are delivered to ice bin 36. Processor 50 also executes ionization program 60 to operate ionization control device 26 to introduce silver ions into the water flow in piping 46 during a fill time for sump 28. Ionization program 60 may be a separate program as shown in Fig. 1 or incorporated into refrigeration program 58.

Referring to Fig. 2, ionization control device 26 comprises a charging circuit 72 connected to a capacitor 74 which is in turn connected to a switch 76. Switch 76 is connected to electrical conductors 64 and 66. A power supply 78 provides a DC voltage to charging circuit 72 via a switch 84. A voltage monitor 80 is connected to capacitor 74. An output of voltage monitor 80 is connected to an analog to digital (A/D) converter 82 via an electrical conductor 86. Electrical conductor 48 is connected to an output of A/D converter 82. Electrical conductor 44 is connected to switch 76. Power supply 78, charging circuit 72, capacitor 74, voltage monitor 80, A/D converter 82 and electrical conductor 66 are each connected to a voltage reference shown as circuit ground.

Power supply 78 is preferably a switching power supply that converts incoming AC power to ice making machine 20 to a DC voltage that is selected based on the current flow characteristics of silver anode 68 and cathode 70 such that for the lowest conductivity water (de-ionized or reverse osmosis), there is still enough current flow to silver anode 68 to add the required number of silver ions to the water volume that fills sump 28. The selected DC voltage is above a high target voltage value for capacitor 74.

For example, the selected DC voltage is determined by measuring the resistivity of the anode/cathode pair when immersed in the highest resistivity water allowed for use by the ice machine, which represents an upper limit for resistance for the silver ion cell, and determining the maximum water flow rate allowed by the highest flow rate water inlet valve operating at the highest allowed inlet water pressure. The water flow rate can be converted into a required average ion release rate to achieve the target ion concentration in the inlet water flow at this worst case condition. The ion flow rate is directly related to current flow by Coulomb's law. The resulting current flow requirement and maximum resistivity for the cell define the average capacitor voltage required, and the upper voltage target is equal to the average plus one half the working voltage range for the capacitor, with the working voltage range determined by practical considerations of capacitor life and capacitor size. The capacitor voltage rating is selected to safely tolerate the maximum voltage output for the power supply. Voltage monitor 80 comprises a voltage divider of two resistors in series connected across or in parallel with capacitor 74. An electrical conductor 86 is connected to a junction of the two resistors and to an input of A D converter 82. A/D converter 82 provides a digital signal on connection 48 that is proportional to the DC voltage at the junction of the two resistors. The resistance ratio of the two resistors is such that the input voltage to A/D converter 82 is in the 0 to 5 volts range, while the capacitor voltage may be significantly higher than 5 volts DC. The sum of the resistances of the two resistors is relatively large to minimize leakage current from charged capacitor 74.

Switches 76 and 88 may be any suitable switches that can be controlled to switch between an open and a closed condition by controller 24. For example, switches 76 and 84 may be a transistor or other solid state switching device.

Referring to Figs. 1 , 2 and 4, processor 50 executes ionization program 60 to control ionization control device 26 to introduce silver ions into water being delivered to sump 28. At box 100 of Fig. 4, processor 50 commences a charging sequence, which is executed prior to a water fill time. At box 102, processor 50 sends a signal via connection 88 to close switch 84. Current flows from power supply 78 via switch 84 to charging circuit 72 to charge capacitor 74. While capacitor 74 is being charged, switch 76 is open. At box 104, voltage monitor 80 monitors the voltage across capacitor 74 and provides an output signal that is converted to a digital signal by A/D converter 82 and conveyed to controller 24 via connection 48. When the voltage across capacitor 74 attains the high target voltage, processor 50 sends a signal via connection 88 to operate switch 84 to switch from the closed condition to the open condition.

At the start of a fill time for sump 28, processor 50 at box 107 commences a discharge sequence. At box 108, processor 50 sends a signal via connection 42 to control water valve 38 to open so that water begins to flow through the section of piping 46 between water valve 38 and sump 28. After a short time interval, processor 50 at box 1 10 sends a signal via connection 44 to close switch 76 to commence a discharge of capacitor 74 in a discharge circuit that includes electrical connectors 64 and 66, silver anode 68, the water, cathode 70 and circuit ground. The short interval of delay ensures that water has begun to flow between silver anode 68 and cathode 70. Electrical current flow through the water involves an electrolytic release of silver ions into the water. As capacitor 74 discharges, the voltage across capacitor 74 declines from the high target voltage value to a lower target voltage value. Voltage monitor 80 monitors the voltage across capacitor 74. The output of voltage monitor 80 is converted to a digital signal by A/D converter 82 and conveyed via connection 48 to controller 24. Processor 50 at box 1 12 compares the voltage values represented by the digital signals to the lower target voltage value. When the lower target voltage value is reached, processor 50 at box 1 14 sends a signal via connection 44 to open switch 76, which stops the injection of silver ions into water flow through piping 46. At box 1 16 processor 50 determines if the fill time has ended. When the fill time has ended, processor 50 at box 1 18 sends a signal via connection 42 to close water inlet valve 38.

In some embodiments, ice making machine 20 may have the capability of adjusting the water usage for each ice making cycle according to a water quality measure, such as total dissolved solids (TDS) of the water. Controller 24 in these embodiments has the ability to adjust the capacitor voltage accordingly to add an adjusted quantity of silver ions by varying the lower target voltage value for the capacitor at the time the switch 76 is opened to stop the silver ion flow. This feature can also be used in embodiments where the ice making machine has information about the model number of the ice making machine and the batch water volume for that model stored in memory.

Referring to Fig. 3, an exemplary embodiment of charging circuit 72 comprises a transistor 130, a resistor 138, a Zener diode 140 and a pulse width modulator (PWM) 142. Transistor 130 has a base 132, an emitter 134 and a collector 136. Resistor 138 is connected between collector 136 and base 132. Zener diode 140 is connected between base 134 and circuit ground. Emitter 134 is connected to capacitor 74. PWM 142 has an input 144 connected to power supply 78 and an output 146 connected to collector 136 and resistor 138. In operation, prior to a fill time the voltage at emitter 134 is at or about the low target voltage value of capacitor 74 and transistor 130 is off. Power supply 78 is enabled to supply a DC voltage to PWM 142, which converts the DC voltage to a sequence of variable width pulses that have an amplitude approximately equal to the high target voltage value. Base 132, being connected to the junction of resistor 138 and Zener diode 140, is more positive than the low target voltage value such that transistor 130 turns on and off for a time equal to the width of a current pulse. During this time, charging current flows from PWM 142 via collector 136 and emitter 134 to charge capacitor 74. When a pulse width time ends, transistor 130 turns off.

PWM 142 provides a pulse train in which the pulse width varies from wide to narrow as the voltage across capacitor 74 approaches the high target voltage. This allows the voltage to build up rapidly and then to move slowly to the high target voltage so as to avoid over shooting. When the voltage at emitter 134 reaches the high target voltage, emitter 134 is more positive than base 132 and transistor 130 turns off regardless of any further pulses. The pulse train is discontinued by separate feedback control from voltage monitor 80 and controller 24.

The present disclosure having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present disclosure as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1 . An ice making machine comprising:

an ice making apparatus that makes ice using water in a sump;

a water valve connected in a piping to supply a volume of water to said sump;

a silver anode and a cathode anode disposed in said piping between said water valve and said sump; and

an ionization control device that controls a voltage applied to said silver anode and said cathode to release a target amount of silver ions into said volume of water when flowing through said piping.

2. The ice making machine of claim 1 , wherein said volume of water is delivered to said sump in a first time interval, and where said voltage is applied to said silver anode and said cathode only during a second time interval within and shorter than said first time interval.

3. The ice making machine of claim 2, wherein said target amount of silver ions is released during said second time interval.

4. The ice making machine of claim 3, wherein said second interval begins after a short delay to assure that the water is flowing through the piping.

5. The ice making machine of claim 1 , wherein said voltage is controlled in a range having a high target voltage value and a low target voltage value.

6. The ice making machine of claim 5, wherein said ionization control device comprises a capacitor, a charging circuit that charges said capacitor to said high target voltage value and a switch that when in a closed condition connects said capacitor to said silver anode and said cathode to discharge said capacitor to said low target voltage value while said silver ions release into said volume of water.

7. The ice making machine of claim 6, wherein said switch when in an open condition disconnects said capacitor from said silver anode and said cathode, and wherein said charging circuit is operable to charge said capacitor while said switch is in said open condition.

8. The ice making machine of claim 7, further comprising a voltage monitor that monitors said voltage and a controller having connections to said water valve, said switch and said charging circuit, wherein prior to a sump fill time said controller controls said charging circuit to charge said capacitor to said high target voltage value, and wherein during said sump fill time controls said water valve to an open position to allow water to flow in said piping and controls said switch to said closed condition to discharge said capacitor to said low target voltage value.

9. A method for ionizing sump water of an ice making machine

comprising:

providing a silver anode and a cathode in a piping;

supplying a volume of water via said piping to a sump of said ice making machine;

controlling a voltage applied to said silver anode and said cathode to release a target amount of silver ions into said volume of water flowing through said piping.

10. The method of claim 9, wherein said volume of water is delivered to said sump in a first time interval, and where said voltage is applied to said silver anode and said cathode only during a second time interval within and shorter than said first time interval.

1 1 . The method of claim 10, wherein said target amount of silver ions is released during said second time interval.

12. The method of claim 1 1 , wherein said second interval begins after a short delay to assure that the water is flowing through the piping.

13. The method of claim 9, wherein said voltage is controlled in a range having a high target voltage value and a low target voltage value.

14. The method of claim 13, further comprising:

connecting and disconnecting a capacitor to said silver anode and said cathode:

charging a capacitor, while disconnected from said silver anode and said cathode, to said high target voltage value; and

discharging said capacitor, while connected to said silver anode and said cathode, to said low target voltage value during a water fill time of said ice making machine while said ions release into said volume of water.

15. The method of claim 14, further comprising:

providing a controller that controls said steps of supplying, controlling, connecting and disconnecting, charging and discharging.