GB2422770A

GB2422770A - Electric boiler

Info

Publication number: GB2422770A
Application number: GB0502570A
Authority: GB
Inventors: Chow Hung
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-02-08
Filing date: 2005-02-08
Publication date: 2006-08-09
Also published as: GB0502570D0

Abstract

The boiler includes a body 1, a liquid container 10, a base portion 6, a handle 11, and a cover 12. An electro-thermal plate 2 and a thermal sensor 5, such as a thermistor, are provided at the bottom of the container and are electrically connected to each other. A temperature setting device is provided for setting the required liquid temperature. A control circuit operates the electro-thermal plate through processing signals from the thermal sensor and temperature setting device. The control circuit is electrically connected to the thermal sensor, the electro-thermal plate, and the temperature setting device. The control circuit may include a CPU, a relay switch control circuit, and an LED display unit.

Description

1 2422770

ELECTRIC BOILER

The invention relates to an electric appliance, particularly to an electric boiler with which the temperature of a liquid to be heated is adjustable and the liquid can be maintained at a set temperature.

Technical Background

Electric boilers, for example kettles and urns, are known to operate in such a manner that, when the liquid is heated to reach a fixed temperature, a control circuit will automatically switch off power to the vessel. As a result, the conventional vessels cannot meet the requirement that the liquid is regulated to or held at a temperature selected from a range of temperatures, thus leading to an unnecessary waste of energy.

Summary of the Utility Model

The object of the present invention is to provide an electric boiler in which the temperature of the liquid to be heated can be set freely and the liquid in the boiler can be maintained at the set temperature.

The present invention provides an electric boiler comprising a body, a container for receiving a liquid to be heated and an electro-thermal plate disposed within the body, the boiler further comprising: a temperature setting device for setting a temperature of the liquid; a thermal sensor disposed at the inner surface of a bottom face of the container and electrically connected to the electro-thermal plate; and a control circuit for operating the electro-thermal plate through processing an electrical signal received from the thermal sensor and the temperature set by the temperature setting device, the control circuit being electrically connected to the thermal sensor, the electro- thermal plate, and the temperature setting device respectively.

According to the invention, a thermal sensor is provided to contact the liquid, and detect the temperature accurately and promptly. With the electric boiler of the invention the temperature of a liquid to be heated can be set freely within a range of temperatures according to a specific requirement, and the boiler can keep the liquid to or at a desired temperature.

Brief Description of the Drawings

Fig. 1 shows a perspective view of a configuration of an embodiment according to the invention; Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1; Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1; Fig. 4 is an exploded view of an electric boiler according to the utility model; Fig. 5 is a block diagram of an electric boiler according to the utility model.

Description of Preferred Embodiments

The present invention will now be described below with reference to the drawings.

An electric boiler according to the present invention will now be described with reference to Figs 1 to 4. The electric boiler comprises a body 1, a base portion 6, a handle 11 and a cover 12. As shown in Figs 2 and 4, the body 1 includes a container 10 for holding a liquid to be heated, and an electro-thermal plate 2, provided at the bottom of the container 10. The electro-thermal plate 2 is mounted within the body 1 through a bottom cover 4 and springs 22. A sealing ring 21 is disposed between the body and the electro-thermal plate 2.

A thermal sensor 5 is provided at the inner surface of the bottom face of the container 1 so as to contact a liquid to be heated in the container. The sensor 5 is fixed to the plate 2 by a fastener 51 and a bolt 52, and electrically connected to the plate 2. In one embodiment, the thermal sensor 5 comprises a thermistor RT. A small sealing ring 53 is provided for thermally and electrically insulating the thermal sensor 5 from the electro-thermal plate 2. Electrodes of the thermal sensor 5 are connected with a CPU at a printed circuit board (PCB) 9 through a connector 54 provided at a bracket 23 fixed to the electro- thermal plate 2. A temperature controller 3 having an electric switch circuit is also provided at the bracket 23 and is connected with the PCB 9 for controlling the temperature of the liquid to be heated.

A display 61 for showing the temperature set, a knob 62 for setting a temperature and a switching button 63 are provided at the base portion 6. The PCB 9 is mounted within the base portion 6 by bolts. A base plate 7 is mounted at the bottom of the base portion 6. A transformer 91 is mounted on the base plate 7 through a pad 92.

An opening 70 is configured at the center of the base plate 7 for mounting a wire wrapping board 8. A power supply line 81 is connected to the board 8.

As shown in Fig. 5, a control unit of the boiler according to the invention includes a rectifier circuit 100 for converting the AC power into the DC power supply, a CPU 101 for comparing the temperature detected by the sensor 5 with the temperature set by users via a knob 62 and outputting control signals according to the result of the comparison, a temperature setting device 102 for setting the temperature to which it is desired to heat the liquid, an LED display unit 103, and an electric switching circuit 104.

The control unit of the invention will now be described in more detail with reference to Fig. 6. The rectifier circuit 100 comprises a transformer T for lowering the voltage of the input AC, and a bridge rectifier circuit composed of diodes Dl -D4 for outputting DC power supply VCC (for example, l2V DC) to a relay K. The rectifier circuit 100 further comprises a voltage regulator circuit U2, such as 78L05, for receiving the power supply VCC and outputting DC voltage VDD to the CPU 101 and the LED display unit 103 composed of light emitting diodes.

The CPU 101, for example, a PlC 16C57 of 4.0MHz, enters standby state when power is supplied to the boiler. After the switch SWI/SW2 (corresponding to the switching button 63 in Fig. 4) is turned on, a high voltage is generated from the pin RB2 or RB3 of the CPU 101, enabling the comparing of the temperature detected by the thermal sensor 5 with the preset temperature.

The thermistor RT is connected with its electrodes to pins RA 1 and RA2 of the CPU 101. When the CPU 101 determines by comparing the signal output from the electrodes of the thermistor RT with the stored value that the detected temperature is lower than the temperature set by the user, it outputs a higher voltage from its RB4 pin to the base of a transistor Q14 to turn it on, and thus drive the relay K to be closed. The AC power is then applied through the relay K so as to be supplied to the electro-thermal plate 2 and cause it to heat up. When the CPU 101 determines that the detected temperature is equal to or higher than the set temperature, its pin RB4 outputs a lower voltage to power off the electro-thermal plate 2.

The resistance of the thermistor R of the thermal sensor 5 changes with the temperature of the heated liquid, which affects the speed of discharge of a capacitor CO (for example, a 0.1 j.iF/ 1 6V capacitor). The thermal sensor 5 of the utility model is sensitive to the change in temperature. Therefore, the control circuit may control the power supplied to the electro-thermal plate 2 so as to be operable to control the temperature according to the temperature set by the user.

The temperature setting device 102 comprises the knob 62 as shown in Fig. 4 and an encoder (HEADER 3) which outputs encoded digital signals based on the temperature set by the knob 62. Pins 1 and 3 of the encoder are connected to pins RB1 and RBO of the CPU 101 respectively. The CPU 1010, upon receiving the digital signals output from the encoder, changes the set temperature stored therein, and outputs control signals via pins RCORC6 and RB5-RB6, to refresh the temperature displayed on the LED display unit 103.

The electronic switching circuit 104 of the temperature controller 3 comprises the relay K, the transistor Q14 and the diode D2. Two electrodes of the diode D2 are connected respectively to the two ends of the winding of the relay K for protecting it and improving its sensitivity.

Preferably, the pin RC7 of the CPU 101 is connected to one end of the displaying switch SW3 through a resistor RO. Thus, the CPU 101 controls the LED display unit 103 to display the temperature in Fahrenheit when the displaying switch SW3 is connected to the ground, and display the temperature in Centigrade when the displaying switch SW3 is connected to the power supply VDD.

Claims

CLAIMS: 1. An electric boiler comprising a body (1), a container (10) for

receiving a liquid to be heated and an electro-thermal plate (2) disposed within the body, characterised in that, said boiler further comprises: a temperature setting device (102) for setting a temperature of the liquid; a thermal sensor (5) disposed at the inner surface of a bottom face of the container and electrically connected to the electro-thermal plate (2); and a control circuit for operating the electro-thermal plate (2) through processing an electrical signal received from the thermal sensor (5) and processing a signal indicative of the temperature set by the temperature setting device (102), the control circuit being electrically connected to the thermal sensor (5), the electro-thermal plate (2) and the temperature setting device (102) respectively.
2. The electric boiler of claim 1, wherein the thennal sensor (5) comprises a thermistor contacting the liquid.
3. The electric boiler of claim 1 or 2, wherein the control circuit comprises: a CPU (101) for processing a signal received from the thermal sensor (5) in terms of the temperature set by the temperature setting device (102), and outputting a control signal; and a relay switch control circuit for controlling power supplied to the electro- thermal plate (2) according to the control signal output from the CPU (101).
4. The electric boiler of claim 3, further comprising an LED display unit controlled by the CPU (101).
5. The electric boiler of claim 4, further comprising a displaying switch (SW3), operable to control the LED display unit (103) to display the temperature set based on a signal received from the CPU.
6. The electric boiler of any of claims 1 to 5, wherein an insulating material is provided between the boiler body (1) and the electro-thermal plate (2), and between the thermal sensor (5) and the electro-thermal plate (2), respectively.
7. The electric boiler of any of claims 1 to 5, wherein the temperature setting device (102) comprises a knob (62) for setting a temperature, and an encoder for outputting to the CPU (101) digital signals based on the temperature set by the knob (62).