FIELD OF THE INVENTION

The present invention relates to electric water heaters, and more particularly to an instant electrode water heater that is compact and provides hot water at a substantially high speed and efficiency.

BACKGROUND OF THE INVENTION

Due to high - and further increasing - energy costs, there is an increasing demand in energy efficient electric water heaters. In particular, there is an increasing demand in instant - or on- demand - electric water heaters that heat water only when hot water is being used. Since the instant electric water heaters are more energy efficient and use less space than storage tank electric water heaters, they are preferred for various household and industrial applications such as, for example, showers, and appliances such as, for example, coffee makers, dish washers, and washing machines.

Most prior art tankless water heater systems use resistance type electric heating elements to heat the water. A major disadvantage of tankless water heater systems utilizing resistance type electric heating elements is that the elements themselves have substantial thermal mass and thermal resistance, substantially reducing the speed the water is heated, especially when the water flow is started. Since the water must flow through the heater before the heating element is activated and the heating element requires time to heat the water, there is first cold water flowing out of the heater, which is particularly a disadvantage in applications without a drain such as, for example, coffee makers.

The alternative to using heating elements for heating the water is to pass an electric current through the water by passing it between two electrodes between which an AC voltage exists, known as Direct Electrical Resistance (DER) heating. Unfortunately, existing instant electrode water heaters have numerous disadvantages: they are highly complex, rendering them expensive to manufacture and difficult to implement in a compact fashion; the hot water temperature is difficult to control; and, they have a relatively high lifetime cost since the complete heater has to be replaced when the electrodes are no longer functional due to corrosion and/or mineral deposition.

It is desirable to provide an instant electrode water heater that is simple and compact.

It is also desirable to provide an instant electrode water heater that provides hot water at a substantially high start-up speed and efficiency.

It is also desirable to provide an instant electrode water heater that enables substantially accurate control of the hot water temperature.

It is also desirable to provide an instant electrode water heater that enables simple replacement of the electrodes.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide an instant electrode water heater that is simple and compact.

Another object of the present invention is to provide an instant electrode water heater that provides hot water at a substantially high start-up speed and efficiency.

Another object of the present invention is to provide an instant electrode water heater that enables substantially accurate control of the hot water temperature.

Another object of the present invention is to provide an instant electrode water heater that enables simple replacement of the electrodes.

According to one aspect of the present invention, there is provided an instant electrode water. The instant electrode water heater comprises a housing for containing water therein with the housing having a water inlet and a water outlet. A plurality of electrode plates is disposed inside the housing. The electrode plates are placed such that the electrode plates are oriented parallel to each other and have a predetermined distance between two successive electrode plates for directing water received at the water inlet through successive channels, with each channel being formed by two successive electrode plates, to the water outlet. A plurality of electric contacts is disposed in the housing such that each electric contact is in a touching relationship with a respective electrode plate for providing AC electric power thereto. Electric control circuitry is connected to the electric contacts for controllably providing electric power thereto.

According to the aspect of the present invention, there is provided an instant electrode water heater. The instant electrode water heater comprises a housing having a water inlet and a water outlet and forms a cavity therebetween. An electrode cartridge having a plurality of electrodes therein is removably disposed in the cavity. A cover is removably mounted to the housing in a water sealed fashion for covering the cavity with the electrode cartridge disposed therein. Electric control circuitry is connected to the electrodes for controllably providing AC electric power thereto.

According to the aspect of the present invention, there is provided an instant electrode water heater. The instant electrode water heater comprises a housing having a water inlet and a water outlet and forms a cavity therebetween. A plurality of electrodes is disposed in the cavity.

Electric control circuitry is connected to the electrodes for controllably providing AC electric power thereto. The electric control circuitry comprises current sense circuitry for providing a current sense signal indicative of an electric power usage of the electrodes. A microcontroller is connected to the current sense circuitry, an AC electric power supply, and a user interface. The microcontroller determines supply of the AC electric power to the electrodes in dependence upon the current sense signal and the user input signal and provides a supply control signal indicative of the supply of the AC electric power to the electrodes to the AC electric power supply.

The advantage of the present invention is that it provides an instant electrode water heater that is simple and compact. A further advantage of the present invention is that it provides an instant electrode water heater that provides hot water at a substantially high start-up speed and efficiency.

A further advantage of the present invention is to provide an instant electrode water heater that enables substantially accurate control of the hot water temperature.

A further advantage of the present invention is to provide an instant electrode water heater that enables simple replacement of the electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention is described below with reference to the accompanying drawings, in which:

Figures la and lb are simplified block diagrams illustrating perspective front views of an instant electrode water heater according to a preferred embodiment of the invention;

Figure lc is a simplified block diagram illustrating a perspective rear view of the instant electrode water heater according to a preferred embodiment of the invention;

Figure Id is a simplified block diagram illustrating a cross-sectional view of the electrode cartridge of the instant electrode water heater according to a preferred embodiment of the invention;

Figure le is a simplified block diagram illustrating a front view of an electrode of the instant electrode water heater according to a preferred embodiment of the invention;

Figures If to lh are simplified block diagram illustrating cross-sectional views of details of the instant electrode water heater according to a preferred embodiment of the invention; Figure li is a simplified block diagram illustrating a cross-sectional view of the electrode cartridge of the instant electrode water heater according to a preferred embodiment of the invention;

Figure lk is a simplified block diagram illustrating a cross-sectional view of the housing of the instant electrode water heater according to a preferred embodiment of the invention;

Figures 11 and lm are simplified block diagrams illustrating a top view and a side view of a heat sink element of the instant electrode water heater according to a preferred embodiment of the invention;

Figures 2a and 2b are simplified block diagrams illustrating an electric control circuitry of the instant electrode water heater according to a preferred embodiment of the invention;

Figures 2c to 2i are simplified block diagrams illustrating components of the electric control circuitry of the instant electrode water heater according to a preferred embodiment of the invention;

Figure 3a is a simplified block diagram illustrating a side view of an instant electrode water heater according to another preferred embodiment of the invention; and,

Figures 3b and 3c are simplified block diagrams illustrating perspective views of a quick connect mechanism of the instant electrode water heater according to the other preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described.

While the description of the preferred embodiments hereinbelow is with reference to a wall mounted instant electrode water heater for providing hot water to, for example, a shower or tap, it will become evident to those skilled in the art that the embodiments of the invention are not limited thereto, but are also adaptable for use in appliances such as, for example, coffee makers, dish washers, and washing machines.

Referring to Figures la to lm, an instant electrode water heater 100 according to a preferred embodiment of the invention is provided. The instant electrode water heater 100 comprises an electrically non-conductive housing 102 forming a cavity 112 between water inlet 150.1 and water outlet 150.2. Preferably, the housing 102 is mounted to - or forms a single unit with - wall mounting plate 106, which may be mounted to wall 10 in a conventional manner - using, for example, screw fasteners - after connecting water inlet port 126.1 and water outlet port 126.2 to a waterline and electrical port 128 to an electrical supply, as illustrated in Figures la and lb. It is noted that the electrical supply should be surge protected using a fuse or circuit breaker.

Preferably, electrodes 130 are contained in electrode cartridge 114 with the same being removably disposed in the cavity 1 12. Cover 104 is removably mounted to the housing 102 - using, for example, conventional easy to open/close fasteners such as spring latches or magnetic latches 108 - for covering the cavity 112 with the electrode cartridge 114 disposed therein in a water sealed fashion using for example, an O-ring seal 120 interacting with a respective sealing surface 122. The electrode cartridge 1 14, for example, comprises a cartridge housing having a bottom wall and sidewalls which, in concert with the cover 104, substantially completely enclose the electrodes 130. Inlet opening 116.1 and outlet opening 116.2 disposed in the sidewalls such that they align with the respective water inlet 150.1 and water outlet 150.2 of the cavity 112 when the electrode cartridge 1 14 is properly disposed therein, as illustrated in Figures lb and Id. The substantially complete enclosure of the electrodes 130 in the housing of the electrode cartridge 1 14 protects the electrodes during handling of the electrode cartridge 1 14 by a user when removed from a protective packaging and inserted into the cavity 112, as well as facilitates the proper insertion of the same. Handling and insertion of the electrode cartridge 114 is further facilitated by providing the electrode cartridge 1 14 and the cover 104 as a single unit.

AC electric power is provided to the electrodes 130 via electric cover connector elements 118 disposed in the cover 104 such as, for example, banana plugs or pin plugs, disposed in the cover 104 which are removably mated with respective electric housing connector elements 162 such as, for example, banana jacks or pin jacks disposed in the housing 102 and connected to electric control circuitry 170 disposed in control housing 124 mounted, for example, to the wall mounting plate 106, as illustrated in Figures lb, Id, li, and lk. The electric control circuitry 170 receives AC electric power from electrical port 128 connected to an electrical supply and controllably provides AC electric power to the electrodes 130. Preferably, the electric control circuitry 170 comprises current sense circuitry for providing a current sense signal indicative of an electric power usage of the electrodes 130 and a microcontroller connected to the current sense circuitry and user interface 1 10 such as, for example, a dial or touch screen enabling the user to set a desire hot water temperature. The microcontroller then determines the supply of the AC electric power to the electrodes 130 in dependence upon the current sense signal and the user input signal received from the user interface 110. A preferred embodiment of the electric control circuitry 170 will be described hereinbelow.

Preferably, a cover sensor 164 such as, for example, a Hall Effect sensor is disposed in the housing 102 for providing a cover sensor signal indicating if the cover 104 or, preferably, the spring latch is opened or closed to the microcontroller, as illustrated in Figure lk. If the cover sensor signal is indicative of the cover/latch being opened, the microcontroller stops provision of the AC electrical power to the electric housing connector elements 162 until the cover sensor signal is indicative of the cover/latch being closed in order to protect the user from electric shock when replacing the electrode cartridge 1 14. Optionally, a solenoid valve 154 connected to the electric control circuitry 170 is disposed between the water inlet port 126.1 and the water inlet 150.1. If the cover sensor signal is indicative of the cover/latch being opened, the microcontroller provides a signal to the solenoid valve 154 to shut off the water flow to the water inlet 150.1 until the cover sensor signal is indicative of the cover/latch being closed in order to enable the user to replace the electrode cartridge 1 14 without shutting off the water supply. Further optionally, the solenoid valve 154 is used to control the water flow to the water inlet 150.1 , for example, to reduce the same when a desired hot water temperature cannot be achieved.

Optionally, the electric control circuitry 170 is adapted for sensing a resistance of the electrodes 130 and for providing a message, for example, displayed on user interface 1 10 when the sensed resistance is indicative of a need for replacing the electrode cartridge 1 14.

Further optionally, the electrode cartridge 1 14 is one of a set of different electrode cartridges 1 14 with the electrodes 130 thereof being adapted for heating water having different conductivity. For example, the electrodes 130 are adapted to different water conductivities by changing the distance DE between the electrodes 130 and/or the size - length LE and width WE - of the electrodes 130, as well as the number of the electrodes 130. With the electric control circuitry 170 being adapted for providing AC electric power to the electrodes 130 of any one of the set of different electrode cartridges 1 14, the instant electrode water heater 100 is easily adapted for heating water having specific water conductivity, enabling high speed and efficiency. For example, a user provides a water sample for testing the conductivity to his/her retailer of the water heater and can then purchase the appropriate electrode cartridge 1 14 in dependence upon the test result. This can be done prior purchasing the instant electrode water heater 100, as well as during the lifetime of thereof, for example, when purchasing a replacement electrode cartridge 1 14 in order to adapt to changes in the water conductivity.

Preferably, the electrodes 130 are provided as a plurality of electrode plates 130 - having a predetermined length LE, width WE , and thickness TE - disposed inside the electrode cartridge 1 14, as illustrated in Figures Id and le. The electrode plates 130 are placed such that they are oriented parallel to each other having a predetermined distance DE between two successive electrode plates 130 for directing water received at the water inlet opening 1 16.1 through successive channels with each channel formed by two successive electrode plates 130 to the water outlet opening 1 16.2 with the water being directed to flow in opposite direction in any two successive channels, as indicated by the block arrows in Figure Id. For example, each electrode plate 130 comprises an aperture 132 - such as, for example, a circular aperture having a predetermined diameter DA - disposed in one end portion thereof for enabling the water to flow therethrough and wherein the apertures 132 are disposed in opposite end portions of any two successive electrode plates 130. Alternatively, the apertures 132 are replaced by cut-outs in the end portions of the electrode plates 130 or channels disposed in the cartridge housing.

The electrode plates 130 are secured to the electrode cartridge 114 such that the electrode plates 130 are enabled to vibrate in substantially all directions during provision of the AC electric power, which is achieved, for example, by accommodating the electrode plates 130 in respective grooves 134 disposed in the bottom and/or sidewalls of the electrode cartridge 114, with the grooves having a predetermined width WG which is greater than the thickness TE of the respective electrode plates 130 and a predetermined depth DG which is sufficient for securing the respective electrode plates 130 while vibrating, as illustrated in Figure If. The AC electric power is provided to each of the electrode plates 130 using respective electric contacts disposed in the housing such that each electric contact is in a touching relationship with a respective electrode plate 130. The electric contacts are provided, for example, as pins 140 in contact with the upper end of the electrode plate 130 with a compression spring 142 interposed between electric contact plate 144 disposed in the cover 104 and the pin 140 to ensure electric contact while also enabling the electrode plate 130 to vibrate, as illustrated in Figure lg. Alternatively, the electric contacts are provided using spring clips 148 mounted to the cover 104, as illustrated in Figure lh.

Further alternatively, the electric contacts are disposed in the bottom with the electrode plates 130 placed thereupon and touching contact being ensured by placing a flexible material such as, for example, a foam insert between the top of the electrode plates 130 and the cover 104.

The electric contacts are connected to a neutral wire 146.1 and a live wire 146.2 in

communication with the neutral electric cover connector element 118.1 and the live electric cover connector element 1 18.2, respectively, such that the electrode plates 130 are connected to neutral AC and live AC in an alternating fashion, as illustrated in Figure li.

The housing 102, the cover 104, and the housing of the electrode cartridge 114 are made of a heat resistant and electrically non-conductive material, preferably, a plastic material such as, for example, Acetal using standard plastic molding techniques. Preferably, the electrode plates 130 are made of graphite, manufacturing and installation of which is facilitated by the simple shape of the electrode plates 130 and the touching contact for provision of the electric power.

Alternatively, the electrode plates 130 are made of another electrically conductive material such as, for example, aluminum, stainless steel, or brass. Further alternatively, the electrode plates 130 have a different shape such as, for example, a circular shape to conform with a cylindrical housing.

The electrode plates 130 as described hereinabove provide a relatively large amount of electric power - large electrode surface area in contact with the water - to a relatively small amount of water - small channels between the electrode plates 130 - compared to conventional instant electric water heaters, enabling a substantially compact instant electric water heater having a substantially high start-up speed and efficiency.

In an example implementation, 10 electrode plates 130 having length LE = 57mm, width WE - 51mm, and spaced at distance DE = 1.5mm are employed to heat 4.51/min of water by 40° C using 240V at 40-45A supply power.

Optionally, the electrode cartridge 1 14 is omitted and the electrode plates 130 are directly disposed in the housing 102.

It is noted that the cartridge assembly may also be implemented with other shapes, arrangements of the electrodes, as well as connecting mechanisms for providing the electric power thereto.

Further optionally, the electric control circuitry 170 disposed, for example, on a Printed Circuit Board (PCB), is cooled using a heatsink element 166 in thermal contact with the PCB, as illustrated in figures 11 and lm. The heatsink element 166 comprises a block made of a thermally conductive material such as, for example, copper, having channels 168.1 and 168.3 disposed therein for transmitting water therethrough. The channel 168.1 is connected to the channel 1 8.3 via conduit 168.2 forming a loop which is connected to the water inlet in order to use the cold inlet water prior provision to the water inlet 150.1. A layer 172 of thermally conducting but electrically insulating material is interposed between the heatsink element 166 and the electric control circuitry 170. The layer 172 may be omitted if the PCB is a surface-mount type PCB or the heatsink element 166 is made of an electrically insulating material.

Referring to Figures 2a to 2i, an electric control circuitry 170 for controlling the instant electrode water heater 100 according to a preferred embodiment of the invention is provided. The electric control circuitry 170 comprises current sense and power supply circuitry 170 A, connected to the electrodes 130 via in/port 174 and supply power via supply port 176 in communication with electrical port 128. The current sense and power supply circuitry 170 A provides a current sense signal indicative of an electric power usage of the electrodes 130 and a microcontroller 170B connected to the current sense circuitry and user interface 110 such as, for example, a dial or touch screen via port 178, enabling the user to set a desire hot water temperature. The

microcontroller then controls the supply of the AC electric power to the electrodes 130 in dependence upon the current sense signal and the user input signal received from the user interface 1 10.

The current sense and power supply circuitry 170A preferably comprises to following

components, as illustrated in Figures 2b to 2i:

• Rectifier 170A.2 transforms AC voltage into rectified DC voltage;

• Current sensor 170A.3 uses a low resistance resistor to drop some voltage off the rectified DC voltage dependent on the power usage of the electrodes 130 and provides two differential voltages having a difference proportional to the electrical power usage of the electrodes 130;

• H-Bridge 170.4 uses a network of 4 Insulated-Gate Bipolar Transistors (IGBTs) to invert the input rectified DC voltage from the current sensor into a custom AC voltage waveform dependent on the programming of the microcontroller 170B;

• Gate driver 170 A.5 drives the gates of the IGBTs in the H-Bridge 170A.4 dependent on a digital Pulse- Width Modulation (PWM) signal from the microcontroller 170B;

• Current sense amplifier 170A.6 takes the two differential voltages from the current sensor 170A.3 and amplifies the difference which is measured by the microcontroller 170B; and,

• Power supply 170A.1 takes the AC supply voltage and provides 12V and 3.3V output voltages to run the circuitry.

Microcontroller 170B drives the gate driver 170 A.5 and reads the voltage output from the current sense amplifier 170A.6 and regulates the power provided to the electrodes 130 based on the voltage output from the current sense amplifier to achieve a set power based on the user input signal or preprogrammed into the microcontroller 170B. The microcontroller is, for example, a suitable off-the-shelf Field-Programmable Gate Array (FPGA) as well as the other components are also off-the-shelf components assembled on a PCB using standard technology.

Optionally, the microcontroller 170B is connected to: the cover sensor 164 via port 180; the solenoid valve 154 via port 182; inlet water temperature sensor 156 via port 184; outlet water temperature sensor 158 via port 186; water flow sensor 160 via port 188; and, water conductivity sensor 161 via port 190.

For example, the microcontroller 170B receives a cover sensor signal indicating if the cover 104 or the spring latch 108 is opened or closed to the microcontroller 170B. If the cover sensor signal is indicative of the cover/latch being opened, the microcontroller 170B stops provision of the AC electrical power to the electric housing connector elements 162 until the cover sensor signal is indicative of the cover/latch being closed in order to protect the user from electric shock when replacing the electrode cartridge 114. The microcontroller 170B may also send a signal to the solenoid valve 154 to shut off the water flow if the cover sensor signal is indicative of the cover/latch being opened. Furthermore, the microcontroller 170B may receive one or more signals indicative of the inlet water temperature, the outlet water temperature, the water flow rate, and the water conductivity in order to, for example: determine the start/stop and the amount of electrical power provide to the electrodes 130 based thereon in addition to the current sense signal to achieve a set hot water temperature; determine if the electrodes 130 need to be replaced and provide a message to the user interface 110 indicative thereof; determine one of the set of different electrode cartridges 114 in dependence upon the provided electrical power and provide a message to the user interface 1 10 indicative thereof; adjust the provision of electrical power to the electrodes 130 to changes in the water conductivity or to shut off the electrical power if the changes are greater than a predetermined threshold; adjust the provision of electrical power to changes in resistance of the electrodes 130; and, reduce the water flow if a set hot water temperature cannot be achieved.

As is evident to one skilled in the art, the electric control circuitry 170 may also be adapted for controlling other designs of instant electrode water heaters than the instant electrode water heater 100.

Alternatively, the current sense and power supply circuitry 170 A described hereinabove is replaced by circuitry using a TRIode for Alternating Current (TRIAC) for sensing the AC voltages and regulate the provision of electrical power to the electrodes using Phase Controlled Dimming. While the TRIAC based circuitry is somewhat simpler it is less efficient, in particular, if not water-cooled.

Referring to Figures 3a to 3c, an instant electrode water heater 200 according to another preferred embodiment of the invention is provided. Here, the instant electrode water heater 200 comprises a housing 202 having water inlet port 206A for receiving cold inlet water, water outlet port 208A for providing the heated water, and electrical port 204A. The water inlet port 206A comprises a quick connector element for being easily mated with a respective wall connector element 206B and the electrical port 204A comprises a standard electrical plug for being easily mated with a respective wall outlet 204B. The water inlet port 206A and the electrical port 204 A are place in proximity to each other such they are simultaneously mated with their respective counterparts 206B, 204B. Preferably, the wall connector element 206B comprises a shut off mechanism for shutting off the water flow when the water inlet port 206A is disconnected therefrom. Further preferably, the wall outlet 204B also comprises a shut off mechanism for shutting off the electric power supply when the electrical port 204A is disconnected therefrom.

It is noted that the instant electrode water heater 200 may be implemented with the electrode plates 130 and/or the cartridge assembly as well as with various other designs of instant electrode water heaters.

The present invention has been described herein with regard to preferred embodiments. However, it will be obvious to persons skilled in the art that a number of variations and mod ⁱ f ⁱ cat ⁱ ons can be made without departing from the scope of the invention as described herein.