KR20070030722A - Device for heating liquids - Google Patents

Abstract

The present invention relates to a liquid container (1), at least one electrical heating element (3) connected to the liquid container for heating the liquid (2) contained in the liquid container, and to detect the boiling temperature of the liquid in the liquid container. One or more boiling sensors (7) connected to the inner side of the liquid container, one or more overheat sensors (11) thermally connected to the electrical heating element, and heating elements, boiling sensors and overheat sensors are disposed so that the power supplied to the heating element is boiling The present invention relates to a liquid heating device including an electric circuit to be blocked by a sensor and an overheat sensor.

The time controlled electrical switch is positioned parallel to the boiling sensor in the electrical circuit to bypass the boiling sensor for a determined time interval regardless of the state of the boiling sensor upon activation of the heating element.

Liquid burner

Description

Liquid Heating Device {DEVICE FOR HEATING LIQUIDS}

The present invention relates to a liquid heating device according to the front end of claim 1.

Kitchen equipment, laboratory equipment, rice cookers, water kettles, and electric water kettles and liquid heaters typically include temperature sensing electrical circuits to control the heating process or protect the device from overheating, in addition to heating elements for heating liquids. do. The temperature sensing electrical circuit can, for example, switch off the heating element when the heated liquid reaches a predetermined desired temperature. Another example of the use of a temperature sensing electrical circuit is to prevent the heating element from overheating, for example when switching on the appliance without a liquid capable of transferring heat.

British patent GB 2 153 190 describes a method of manufacturing a device for heating water. The heating element described herein is a substrate provided with an electrically insulating material on which a heater track is screen printed. The apparatus is provided with a first temperature sensor for sensing steam and a second sensor for sensing a "boiling dry" condition. In another embodiment, the second sensor may be disposed adjacent the heater track above the heating element. Thermistors are proposed as sensors.

An alternative, often applied to water kettles, for example with thermistor-shaped sensors, is a bimetal switch thermally connected to the heating element and thus can be used as a safety measure against overheating. The bimetal switch is for example to switch off the heating element when the temperature of the heating element exceeds a determined value or when the heated liquid boils.

It is an object of the present invention to provide a liquid heating device and heating element which can be operated at a desired moment in a reliable manner in contrast to the prior art.

The invention is characterized in that for this purpose, a time-controlled electrical switch for bypassing the boiling sensor during operation of the heating element for a determined time interval regardless of the state of the boiling sensor is arranged in parallel in the electrical circuit with the boiling sensor. One type of device is provided. This provides the user of the device with the option of heating the liquid for a determined time (actually short), for example a few seconds if the boiling sensor prevents the heating element from switching on because of the too high temperature. This may occur, for example, after the heating element has been switched off because the liquid in the vessel is boiling. After the heating element is switched off and activated, the boiling sensor remains hot for a while. Updated switch-on of the heating element is not possible immediately because of the relatively high temperature of the boiling sensor. The bimetal switch returns only if the thermistor is sufficiently cooled with the activation of the heating element enabled or after sufficient cooling the thermistor obtains a resistance value at which the heating element can be activated. The activation of the activated overheat sensor may not be interrupted by a time controlled electrical switch. Therefore, time-controlled electrical switches placed parallel to the overheat sensor should be avoided. Deactivation of the overheat sensor can occur after dangerous conditions such as when the device is heated to too high a temperature.

In a preferred embodiment, the time controlled electrical switch can be operated manually or at least switched on. The user of the water jug can, for example, cause the water to be cut off again without the boiling sensor blocking it after switching on because the water is heated to the boiling point. This is actually advantageous because the user usually wants to use boiled water immediately after boiling. When the boiling temperature is reached in normal use, the kettle will switch off, so it will take some time before the user can use the water kettle. Cooling of the boiled liquid can meanwhile be blocked with the device according to the invention. For safety reasons, the electrical switch can bypass the boiling sensor only for a determined period of time (under time control). Permanent bypassing results in, for example, a "boiling dry" state of the heating element.

In a preferred embodiment, the boiling sensors and the time-controlled electrical switches placed in parallel are arranged in the first power supply circuit and thus the relay located in the second circuit including the heating circuit is activated. The use of separate power circuits ensures easy compliance with the approval regulations required by the device. Here, an overheat sensor may also be included in the first power supply circuit and may also supply the first and second power supply circuits having separate power supply means or having different voltage levels. Conversely, it is also possible to connect the same voltage source to both power supply circuits.

It may also be desirable if both the boiling sensor or the overheat sensor include more than one thermistor. Thermistors are temperature sensing electrical resistors such as NTC and PTC resistors that can be obtained, for example, in many variations. Thermistors are, for example, more powerful than bimetal switches. An important difference from bimetallic switches is that the thermistors do not contain any moving parts that are essential for operation. Thermistors can have a smaller size. Two features allow the device to be designed more freely. The device according to the invention with one or more thermistors is relatively very simple and inexpensive. Another advantage of applying a thermistor is that the thermistor's switching time can be very short. The short switching time has the advantage that the device runs fast (and therefore relatively safe). Thermistors also have the advantage of operating at low voltages and low amperes; This need (and indeed what is desired) is not integrated into the main current circuit. Another advantage of thermistors operating at low voltages and low amperes is that they can be made very light and therefore they can also operate with very short time delays (low mass inertia). Short delays during switching (short switching time) significantly reduce overheating (eg blown fuses). Short time delays are also called "small time constants."

Conversely, it is also possible to use small bimetal switches that do not need to be integrated into the main current circuit as well. Thermistors (or small bimetallic switches) are not included in the main current circuit to allow free design of the devices to be integrated. Another advantage of applying a thermistor is that it can apply so-called multitrack elements. The thermistors can thus be applied, for example in pairs, with a plurality of surfaces of the heating element. Thus, the heating element as a whole is not protected but is of smaller size on separate parts of the heating element. This is found faster and more accurately.

In addition to thermistors or bimetal switches, for example, electrical components such as leakage current switches, leakage current sensors, resistors, electrical fuses and electric light sources, meters, integrated circuits (ICs), and other components may also be included in the electrical circuits. .

It is desirable if the boiling sensor is thermally connected within the liquid container at a position higher than the determined maximum liquid height of the liquid container. The boiling sensor detects the vapor temperature of the liquid phase and thereby avoids interruption of the power supply when non-homogeneous temperature fluctuations occur in the heated liquid. The vapor comes into contact with the sensor, which increases the temperature of the sensor and detects the boiling temperature. The temperature of the liquid phase rises only when the liquid boils and therefore a relatively large amount of steam is generated. The above technical measurement has the advantage that a relatively less accurate and inexpensive sensor can be used for detecting liquid boiling temperature detection.

In a non-limiting preferred embodiment, the boiling sensor is located in a chamber connected to the liquid container for communication with the liquid container where the chamber is above the maximum liquid height. The boiling sensor will substantially measure the vapor temperature of the liquid phase in this manner. Since the boiling sensor is in the chamber, boiling point detection is more reliable than outside the chamber. Outside, it is not accurate to detect temperature fluctuations and boiling of liquids.

This is desirable when the boiling sensor is shielded from the liquid container by the medium density method. On the other hand, this prevents the adverse effect of the liquid in the vessel on the boiling sensor and the electronic circuit connected thereto. On the other hand, material from the boiling sensor prevents contaminants from entering the liquid container (eg through clothing or dissolved) to contaminate the liquid. Even if the boiling sensor is shielded with a splashproof plate or the boiling sensor is located in a tubular or capsule-like cover, the boiling sensor is designed to be shielded by integrating the boiling sensor in the liquid container wall line. Intermediate dense materials used for shielding may include, for example, plastics, metals or ceramics.

In a particularly non-limiting preferred embodiment of the invention, the boiling sensor is located outside the liquid container, and the boiling sensor is in thermal contact with the inner side of the liquid container via the thermal conductor. The thermal conductor may be in the form of a wire or strip, for example, preferably made of a metal such as copper or aluminum. The thermal conductor may be partially covered with a thermal insulation layer, for example in the form of a strip, package, tube or sleeve. This makes the heat conduction more efficient to the boiling sensor through the heat insulator and prevents heat from conducting directly to the heat conductor through the wall of the liquid container. The use of thermal conductors allows the free design of the device according to the invention since the sensor does not need to be located at the measuring position and can therefore be arranged at various positions. The insertion of thermal conductors also provides an improved option for protecting the boiling sensor from the adverse effects of liquids or liquid vapors.

It is preferred if the device is provided with means for limiting the electrical power supplied to the heating element. This provides an extra safety mechanism in addition to protection by the overheat sensor. The power-limiting means can be, for example, a fuse, a leak switch or other commercial power-limiting electronic component.

In a non-limiting preferred embodiment, the means for limiting the power supplied to the heating element comprises additional power supply means which operate overheating and are connected to the heating element. For example, it is possible here to face plug pins which are connected to heating elements (e.g. circuits arranged by printing techniques) via insulating material that melts at a determined temperature. When the insulating material melts, the heating element melts and contact is achieved.

A boiling sensor connected to the inner side of the liquid container for detection of the boiling temperature of the liquid in the liquid container may be placed in a portion of the liquid container located above the liquid. Conversely, when the temperature of the boiling sensor increases rapidly due to turbulent flow, the boiling sensor may be placed in the liquid such that the temperature of the boiling sensor rises later than the temperature of the liquid until boiling. 1095161)

The invention may become more apparent below with reference to some non-limiting examples.

1 is a cross-sectional view of a device according to the invention.

2 is a cross-sectional view of an alternative embodiment of the device according to the invention wherein the boiling sensor is located outside the liquid container.

3 is a circuit diagram for the application of the device according to the invention.

4 is a schematic representation of another alternative circuit diagram for the application of the device according to the invention.

1 shows a preferred embodiment of a liquid heating device according to the invention.

The apparatus is provided with a liquid container 1 in which a liquid 2 to be heated can be accommodated. The device is also provided with a heating element 3 in thermal contact with a liquid 2 which is heated in this case via a heat conductor 4 which is a metal plate. The semi-open chamber 5, in which the holes 6 are formed, through which the vapor from the liquid 2 can enter the chamber 5, is placed above the intended maximum filling level of the liquid container 1 (indicated by dashed line M). . Thermistor 7 (or instead of bimetal switch 7) serving as a boiling sensor is located in chamber 5. The intermediate dense layer 8 is arranged around the thermistor 7 to protect the thermistor 7 from the reaction of steam. Thermistor 7 is connected to the electrical circuit 10 by electrical wiring 9. The heating element 3 is thermally connected to a second thermistor 11 which functions as an overheat sensor. The overheat sensor is likewise connected to the electrical circuit 10. The electrical circuit 10 supplies power to the heating element 3 from the power supply 12 via a base plate 14 releasably connected to the device. Base plate 14 is connected to an external power source 12 and makes electrical contact with corresponding reverse contact points A and B disposed at the bottom of the device when the device is positioned on the base plate 14. Electrical contact points A 'and B' are formed. The electrical circuit 10 cuts off the power supply to the heating element 3 by turning off the on / off switch 13 when the boiling sensor 7 detects hot vapor from the boiling liquid 2. If it is desired to heat or boil the liquid 2, the on / off switch 13 can be turned on by the user. When the liquid 2 reaches the boiling temperature, the vapor of the released liquid heats the boiling sensor 7 to detect the boiling of the liquid 2. Power supplied to the heating element 3 is cut off when the overheat sensor 11 detects overheating. This can occur for example when the device is turned on using the switch 13 without the liquid 2 present in the liquid container 1. Since the heating element 3 cannot transfer any heat to the liquid 2, the temperature rises until the overheat sensor 11 reaches a determined (overheating) temperature, and the electrical circuit 10 causes the switch 13 to turn off. It is turned off to block the power supply to the heating element 3. It is clear that the controlled overheating temperature is higher than the boiling temperature of the liquid 2 to be heated. If the liquid 2 to be heated is for example water, the boiling sensor 7 turns off the superheating element 3 when it is heated for a while by steam having an overheating temperature of 90-100 ° C. Superheat temperatures are generally between 250 and 300. The switch 15, in which the temperature connection is made in which the boiling sensor 7 is bypassed, is arranged in parallel with the boiling sensor 7. If the boiling sensor 7 is activated by heat, the heating element 3 can still be powered. The switch 15 is a time control switch that closes for a determined time after the moment of activation and then opens (automatically) again afterwards. Immediately after the boiling of the liquid 2 is stopped by the boiling sensor 7, the liquid can be heated once again (by boiling) by operating the switch 15.

2 is a schematic diagram of a second preferred embodiment according to the present invention. The liquid container 21 contains the liquid 22 to be heated. The liquid 22 is heated by a plurality of heating elements 24 printed under the heat conducting plate 23. The heat conduction plate 23 prevents the liquid 22 to be heated from being in direct contact with the heating element 2. The conducting plate 23 also distributes heat and allows effective heat transfer from the heating element 24 to the liquid 22.

In a non-limiting preferred embodiment, thermistor 25 functioning as an overheat sensor is in direct thermal contact with the heating element 24 such that a change in temperature of the heating element 24 can be detected quickly. The second sensor 26 functions as a boiling sensor and lies outside the liquid container 21. The second sensor 26 is in thermal contact with the liquid container 21 via the thermal conductor 27. The outer end 28 of the thermal conductor 27 is above the maximum filling level M of the liquid container 21 at the measuring position. The thermal conductor 27 is covered over a portion of its length with a thermal insulation sleeve 29 that prevents heat from being transferred directly from the liquid 22 to the thermal conductor 27 through the side wall of the liquid container 21. . The outer end of the thermal conductor 27 is partially shielded with a splash resistant plate 30 which is etched at an angle towards the liquid 22 to drain the condensed water. Due to the positioning of the chamber as such, the outer end of the thermal conductor 27 is heated by steam above the maximum filling level M. According to the invention the time control switch 40 is in parallel with the sensor 26 so as to be able to temporarily neutralize the operation of the sensor 26, especially when the sensor 26 makes the activation of the heating element 24 impossible. Is placed.

3 is a schematic diagram of an electrical circuit applied in an apparatus according to the invention. Included in the circuit diagram is a switch 31 in which the user manually closes the power supply circuit so that the device is in operation.

Coils 32 are arranged in the circuit that generate a magnetic field that is connected to the switch 31 and holds the switch 31 in the 'on' position during the current flow. The switch 31 (momentary relay switch, relay by hand operation) is commercially available in many variations. When the power supply circuit is closed, current flows through the element 33. Heating element 33 appears in the circuit as a resistor.

The coil 32, in this case the boiling sensor 34 and the overheat sensor 35 (also a PTC resistor) formed by the PTC resistor, are connected in parallel with the heating element 33. The overheat sensor 35 is in thermal contact with the heating element 33. Both the boiling sensor 34 and the overheat sensor 35 are PTC resistors which obtain a greater electrical resistance when heated. Now, when the sum of the resistances of the boiling sensor 34 and the overheat sensor 35 reaches a resistance value determined by heating of one of the two thermistors, the current through the coil 32 in series with the thermistor is too small to generate The magnetic field will not be strong enough to hold the switch 31 in the 'on' position. The switch 31 is in the 'off' position by an opposing force, for example a mechanical spring mechanism. Accordingly, the power supplied to the heating element 33 is cut off and the heating of the liquid or the overheating of the heating element 33 is stopped. If the mechanism inadvertently fails in case of overheating, then heating element 33 is provided with a weakened area in which in case of overheating or electrical overload in a second safe way, the overheating is thus blocked. If the boiling sensor 34 (due to the relatively high temperature) makes the activation of the heating element temporary while the intention to activate the heating element 33 is nevertheless, this temporarily disables the time controlled electrical switch 37. By closing it is possible.

4 is a schematic diagram of another alternative circuit 50 of the device according to the invention. The boiling sensor 52, the overheat sensor 53, and the coil 59 of the relay 55 are disposed in the first power supply circuit 51. The time control switch 54 is positioned in parallel with the boiling sensor 52 so that the operation of the boiling sensor 52 can be temporarily stopped. The first power supply circuit 51 operates a relay 55 in which the contact means 60 located in the second power supply circuit 56 can be operated. The heating element 57 is included in the second power supply circuit 56 such that the activation or deactivation of the heating element 57 can be adjusted by manipulating the relay 55. The heating element 57 is in thermal contact with the overheat sensor 53 (indicated by dashed line 58). Referring also to FIGS. 1 and 3, the influence of the energized coil 59 may enable the relay 55 to switch permanently to the main current of the heating element 57. If the control current word then falls, the coil 59 of the relay 55 loses voltage and the main current through the heating element 57 is switched off.

Thus, the control is no longer enforced when the temperature drops; Momentary operation of the switch is then necessary for this purpose.

Claims (13)

-Liquid containers (1, 21), One or more electrical heating elements 3, 24, 33, 57 connected to the liquid containers 1, 21 for heating the liquids 2, 22 contained in the liquid containers 1, 21, One or more boiling sensors 7, 26, 34, 52 connected to the inner side of the liquid containers 1, 21 for detecting the boiling temperature of the liquids 2, 22 in the liquid containers 1, 21. , One or more overheat sensors 11, 25, 35, 53 thermally connected to the electrical heating elements 3, 24, 33, 57, and Heating elements 3, 24, 33, 57, boiling sensors 7, 26, 34, 52 and overheat sensors 11, 25, 35, 53 are arranged to the heating elements 3, 24, 33, 57. In a liquid heating device comprising an electric circuit for allowing the power supplied to be blocked by the boiling sensor (7, 26, 34, 52) and the overheat sensor (11, 25, 35, 53), Located parallel to the boiling sensors 7, 26, 34, 52 in the electrical circuit, regardless of the state of the boiling sensors 7, 26, 34, 52 upon activation of the heating elements 3, 24, 33, 57. Liquid heating apparatus characterized by a time controlled electrical switch (15, 37, 40, 54) bypassing the boiling sensor (7, 26, 34, 52) for a determined time interval. 2. Liquid heating apparatus according to claim 1, characterized in that the time controlled electrical switch (15, 37, 40, 54) can be operated manually. 3. The coil (59) according to claim 1 or 2, wherein the boiling sensors (7, 26, 34, 52), the time-controlled electrical switches (15, 37, 40, 54) and the relay (55) of the relay (55) To activate the switching contact means 60 of the relay 55 which is arranged in the first power supply circuit 51 and thus in the second power supply circuit 56 in which the heating elements 3, 24, 33, 57 are included. Liquid heater. 4. Liquid heating apparatus according to claim 3, wherein an overheat sensor (11, 25, 35, 53) is included in the first power supply circuit (51). The liquid heating device according to any one of the preceding claims, wherein the boiling sensor (7, 26, 34, 52) and the overheat sensor (11, 25, 35, 53) both comprise at least one thermistor. 6. A liquid heating apparatus according to claim 5, wherein said at least one thermistor is a PTC resistor. 7. Liquid heating apparatus according to claim 5 or 6, wherein said at least one thermistor is an NTC resistor. The inner side of the liquid container (1, 21) according to any one of the preceding claims, wherein the boiling sensor (7, 26, 34, 52) is above the maximum liquid level (M) of the liquid container (1, 21). Liquid heater characterized in that it is thermally connected.  9. The liquid according to claim 8, wherein the boiling sensors (7, 26, 34, 52) are located in a chamber (5) connected to the liquid containers (1, 21) so that the chamber (5) is a liquid above the maximum liquid level (M). Liquid heater characterized in that it communicates with the vessel (1, 21). The liquid heating device according to claim 1, wherein the boiling sensor (7, 26, 34, 52) is shielded from the liquid container (1, 21) by means of medium density. The method of claim 1, wherein the boiling sensors 7, 26, 34, 52 are located outside the liquid containers 1, 21 and thermally in contact with the interior of the liquid containers 1, 21 via a thermal conductor 27. Liquid heating apparatus characterized in that the contact. Liquid heating according to any one of the preceding claims, characterized in that a switching contact means (60) operating by overheating is included in the power supply circuit (56) and power is supplied to the heating elements (3, 24, 33, 57). Device. The boiling sensor 7, 26, according to claim 1, connected to an inner side of the liquid container 1, 21 for the detection of the boiling temperature of the liquid 2, 22 in the liquid container 1, 21. 34, 52, characterized in that the liquid heating device is located in a part of the liquid container (1, 21) located above the liquid (2, 22).

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