HEATING PLATE

A heating plate includes a thermally conductive, electrically insulating main board on whose surface an electrically-conductive heat-generating circuit and an outer insulating layer are layered. The heat-generating circuit is formed by connecting one first electrically-conductive layer and one second electrically-conductive layer that are arranged in different directions. The first and second electrically-conductive layers are overlapped to form an overlapping area. The heat-generating circuit has at least two electrically-conductive segments exposed outside the outer insulating layer. Thereby, when the electrically-conductive segments receive incoming current, the electrically-conductive heat-generating circuit can generate heat rapidly, and the heat can be transmitted to the main board through the thermally-conductive insulating layer. The overlapping area formed at each turning point along the electrically-conductive heat-generating circuit is more capable of load bearing so that the electrically-conductive heat-generating circuit is unlikely to be damaged at the turning point.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1throughFIG. 3, according to the present invention, a heating plate comprises a main board1, an electrically-conductive heat-generating circuit30and an outer electrically-insulating layer40.

The main board1may be made of a material that is thermally conductive and electrically insulating. In one embodiment, the main board1is a glass board. Alternatively, the main board1, as shown inFIG. 2, is composed of a thermally-conductive board10and a thermally-conductive electrically-insulating layer20deposited on the top of the thermally-conductive board10. Therein, the thermally-conductive board10may be at least one of a stainless steel board, a metal board and a sintered metal board, and the thermally-conductive electrically-insulating layer20is a glass glaze layer. The main board1may be fixed to the exterior of a boiler or a liquid container by means of, for example, screwing, embedding or soldering.

The electrically-conductive heat-generating circuit30is deposited on the external surface of the thermally-conductive electrically-insulating layer20, and is composed of at least one first electrically-conductive layer31and at least one second electrically-conductive layer32. Where the first and second electrically-conductive layers31,32joint are formed with overlapping areas33that are constructed from the stacked first and second electrically-conductive layers31,32(as shown inFIG. 4). The electrically-conductive heat-generating circuit30has at least two electrically-conductive segment34.

The outer electrically-insulating layer40is deposited on the external surface of the electrically-conductive heat-generating circuit30, for sandwiching the electrically-conductive heat-generating circuit30between the thermally-conductive electrically-insulating layer20and the outer electrically-insulating layer40. The outer electrically-insulating layer40may be a layer of glass glaze. Therein, the electrically-conductive segment34is at least partially exposed outside the outer electrically-insulating layer40, for an electrically-conductive member35to connect thereto (as shown inFIG. 5).

In one preferred embodiment, the main board1is a rectangular board having a pair of first edges11and a pair of second edges12. The first electrically-conductive layer31is arranged on the external surface of the thermally-conductive electrically-insulating layer20in a first direction a, while the second electrically-conductive layer32is arranged on the external surface of the thermally-conductive electrically-insulating layer20in a second direction b. Therein, the first direction a is parallel to the first edges11, and the second direction b is parallel to the second edges12, so that the first and second directions a, b are orthogonal to each other. As a result, the first and second electrically-conductive layers31,32jointly form the electrically-conductive heat-generating circuit30with a continuous S-shaped pattern. Moreover, the electrically-conductive heat-generating circuit30has at least one rounded corner36at its turning points.

The thermally-conductive electrically-insulating layer20, the electrically-conductive heat-generating circuit30and the outer electrically-insulating layer40may be successively formed on the thermally-conductive board10through a vacuum screen-printing process and baked respectively, so as to firmly bounded with the thermally-conductive board10.

In use, referring toFIG. 1andFIG. 5, when electric current is input to the electrically-conductive heat-generating circuit30through the electrically-conductive member35, the resistance of the electrically-conductive heat-generating circuit30converts the current into heat. Then the heat generated by the electrically-conductive heat-generating circuit30is transmitted to the main board1through the thermally-conductive electrically-insulating layer20, for the main board1to heat any article to be heated. The disclosed heating plate thus has the advantages of quick heating response and fast actuation of the electrically-conductive heat-generating circuit30. The heating rate at the surface of the heat-generating circuit is up to 250-300° C./s, being superior to the traditional electrothermal-alloy devices. As shown in Table 1 below, in an experiment where the same current (220V, 10 A) was applied to a conventional electrothermal-alloy device (i.e. heating rod) and the disclosed heating plate to heat 1,000 cc of water into steam, the disclosed heating plate exhibited a heat efficiency much higher than that of the conventional electrothermal-alloy device, demonstrating that the disclosed heating plate is more advantageous than the conventional electrothermal-alloy device when fast heating is required.

Additionally, in the disclosed heating plate, the thermally-conductive electrically-insulating layer20, the electrically-conductive heat-generating circuit30and the outer electrically-insulating layer40are closely affixed to the main board1, so the strong binding between the main board1and the functional layers provides the benefits of high mechanical strength and excellent resistant to vibration and thermal shock. In addition, the electrically-conductive heat-generating circuit30is well supported by the main board1, so the heat generated during the heating process can be conducted to the main board1quickly, without the risk of high temperature embrittlement as occurring in electrothermal-alloy devices and the risk of deformation or collapse caused by weak support or improper installation.

The disclosed main board1may be further fixed to the exterior of a boiler or a liquid container by means of, for example, screwing, embedding or soldering. Accordingly, the heating plate is isolated from the liquid to be heated, and less likely to oxidize, thereby having long service life. In addition, since the electrically-conductive heat-generating circuit30is sandwiched between the main board1and the outer electrically-insulating layer40, it is relatively isolated from the atmosphere and can have its service life lengthened to more than then thousand hours.

As shown inFIG. 3andFIG. 4, according to the present invention, the first electrically-conductive layer31and the second electrically-conductive layer32jointly form the electrically-conductive heat-generating circuit30that has a continuous S-shaped pattern, and has every point where the circuit veers formed with the thickened overlapping area33, so as to effectively prevent the turning points from being burned out by concentrated current, thereby providing the electrically-conductive heat-generating circuit30with increased current carrying ability. Similarly, as shown inFIG. 1, the electrically-conductive heat-generating circuit30may have its turning points formed as rounded corners36, which can help reduce current concentration at the turning points as compared to traditional right-angle corners.