TECHNICAL FIELD

The present invention is related to a cooking appliance adapted to a cooktop, particularly a glass ceramic cooktop.

PRIOR ART

Different solutions to solve or minimize the initial heating times of the radiant elements of a radiant heater are known in the state of the art. Attempts to minimize the initial heating time by means of additional radiant elements operating at higher powers for a short time period generate a high temperature which conflicts with the maximum temperature at which a safety device of the radiant focal point switches off the radiant element to keep the radiant plate safe. EP0886459A2 discloses a radiant heater where in a first step the temperature of the glass ceramic cooking hob is allowed to exceed a predetermined continuous safe level for a predetermined maximum time period and such that a predetermined temporary safe temperature level, greater than the predetermined continuous safe level, is not exceeded, and where in a second step the heater is regulated according to the controlled temperature to achieve a temperature of the glass ceramic cooking hob selected in a range reaching up to the predetermined continuous safe temperature level.

EP233375A describes a radiant heater having a first radiant element and a second radiant element with their corresponding control elements. During the initial heating time (less than 20 seconds), both radiant elements are connected in parallel, and they are subsequently connected in series. A timer controls the duration of the heating phase and subsequently opens and closes the corresponding switches. ES1069307U discloses a radiant heater comprising a main radiant element and an auxiliary radiant element both arranged on the insulating base, defining a main heating area and an auxiliary heating area, respectively. The radiant heater comprises a main temperature limiting device including a sensor element arranged on the main heating element, the main temperature limiting device being connected to the main heating element and to the auxiliary heating element. On the other hand, the radiant heater comprises an auxiliary temperature limiting device associated with the auxiliary heating element and connected in series with the main temperature limiting device, the temperature for disconnecting the auxiliary temperature limiting device being substantially greater than the temperature for disconnecting the temperature limiting device arranged on the main heating element. If an excessive overheating occurs in the auxiliary heating area which has not been detected by the main temperature limiting device associated with the main heating element, said overheating will be detected by the auxiliary temperature limiting device which will safely disconnect the auxiliary heating element.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a cooking appliance adapted to a cooktop according to the claims.

The cooking appliance comprises at least one radiant heater comprising an insulating base, a resistance fixed on said insulating base, each end of the resistance being fixed to a respective terminal, and safety means connected to one of the terminals and suitable for disconnecting the resistance when a limit temperature is detected.

The resistance comprises a third terminal demarcating a first part and a second part of the resistance. Furthermore, the cooking appliance comprises a switch connected to the third terminal and arranged in parallel to the second part of the resistance.

A cooking appliance which can quickly heat the content of the container arranged on the radiant heater without reaching the limit temperature after which the radiant heater is disconnected is thus obtained, the cooking appliance having a simple and optimized configuration with a single resistance. These and other advantages and features of the invention will become apparent in view of the drawings and the detailed description of the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 is a plan view of a first embodiment of the cooking appliance according to the invention.

Figure 2 shows an electrical circuit diagram of the cooking appliance shown in Figure 1 .

Figure 3 is a plan view of a second embodiment of the cooking appliance according to the invention. Figure 4 shows an electrical circuit diagram of the cooking appliance shown in Figure 3.

DETAILED DISCLOSURE OF THE INVENTION

Figures 1 and 3 show a cooking appliance according to the invention comprising a radiant heater 1 suitable for a non-depicted glass ceramic cooktop. The radiant heater comprises a metal cover 2 shaped like a cylindrical container, a substantially cylindrical insulating base 3 made of a thermally and electrically insulating material fitted on the bottom of the cover 2, a resistance 4 inserted in the insulating base 3, a peripheral insulating ring 5 supported on the insulating base 3 and contacting the inner surface of the cooktop, and a safety device 6 connected to a non-depicted control. In other non-depicted embodiments, the peripheral insulating ring 5 and the insulating base 3 can form a single piece. The safety device 6 is a temperature limiting device known in the state of the art so it is not considered necessary to describe it in detail. The objective of said temperature limiting device 6 is to limit the temperature reached by the radiant heater 1 to prevent damaging the cooktop, and to also prolong the service life of said radiant heater 1 , such that it cannot exceed a pre-established limit temperature during operation. To that end, the temperature limiting device 6 comprises a sensor element 7 diametrically traversing the insulating ring 5, extending over the entire insulating base 3 above the resistance 4, an insulating support 8 which is fixed to the outside of the metal cover 2 by known fixing means, and a safety switch 9 schematically depicted in Figure 2 housed inside the support 8 and connected to the sensor element 7.

In the embodiments shown in Figures 1 and 3, the resistance 4 is arranged helically wound, each end of the resistance 4 being connected to a respective terminal 12, 13. The two terminals 12, 13 are arranged coupled in a support 17 which is fixed to the cover 2. The two terminals 12, 13 traverse the cover 2 as well as the insulating ring 5. One of the terminals 12, 13 is further arranged connected to the temperature limiting device 6.

The resistance 4 according to the invention comprises a third terminal 14 demarcating a first part 4a and a second part 4b of the resistance 4, said third terminal 14 being suitable for being powered for a predetermined heating time. The third terminal 14 is arranged coupled in the support 17 together with the first terminal 12 and second terminal 13. The third terminal 14 traverses the cover 2 as well as the insulating ring 5, the terminals 12, 13, 14 being arranged substantially parallel to one another.

In the embodiments shown in Figures 1 and 3, the first terminal 12 is arranged coupled to the free end of the second part 4b of the resistance 4, whereas the second terminal 13 is arranged coupled to the free end of the first part 4a of the resistance 4.

The cooking appliance comprises control means suitable for controlling the operation of the radiant heater 1 . The control means thus comprise a control switch 21 depicted in Figures 2 and 4, whereby they provide or cut off power supply to/from the radiant heater 1 , and a switch 15 suitable for changing over the connection between the first part 4a and the second part 4b of the resistance 4. The change-over switch 15 is arranged connected to the third terminal 14 and arranged in parallel to the second part 4b of the resistance 4.

In the first embodiment of the invention shown in Figures 1 and 2, the safety device 6 is arranged connected to the first terminal 12 such that both the second part 4b of the resistance 4 and the safety device 6 are arranged in parallel to the change-over switch 15. Initially, once the control means have enabled the radiant heater 1 through the control switches 21 , the control means keep the switch 15 closed, only powering the first part 4a of the resistance 4 through the second terminal 13 for the predetermined heating time at maximum power in order to quickly heat (booster mode) the content of a container arranged on the radiant heater 1 . The predetermined heating time is established between about 1 minute and about 10 minutes. In one embodiment of the invention, the predetermined heating time is about 4 minutes. During this predetermined time, the radiant heater 1 quickly heats the content of the container at the rated power without the temperature limiting device 6 acting, cutting off the power supply to the resistance 4. Once the predetermined heating time has lapsed, the control means act on the switch 15 connected to the third terminal 14 opening it, such that the resistance 4 is powered through the first terminal 12 and the second terminal 13, both the first part 4a and the second part 4b being energized, therefore reducing the power consumed by the radiant heater 1 .

In the second embodiment of the invention shown in Figures 3 and 4, the safety device 6 is connected to the second terminal 13 such that both the first part 4a of the resistance 4 and the safety device 6 are arranged in series with the change- over switch 15. Initially, once the control switches 21 are operated, the control means keep the switch 15 closed for the predetermined heating time such that only the first part 4a is energized for the predetermined heating time at maximum power in order to quickly heat (booster function) the content of a container arranged on the radiant heater 1 . The predetermined heating time is established between about 1 minute and about 10 minutes. In one embodiment of the invention, the predetermined heating time is about 4 minutes. During this predetermined time, the radiant heater 1 quickly heats the content of the container at the rated power. If the temperature measured by the temperature limiting device 6 reaches the cut-off temperature value of said limiting device 6, said temperature limiting device 6 would act, cutting off the power supply to the resistance 4 through the safety switch 9. Once the predetermined heating time has lapsed, the control powers the resistance 4 through the first terminal 12 and the second terminal 13 such that the entire resistance 4, i.e., both the first part 4a and the second part 4b, is energized, therefore reducing the power consumed by the radiant heater 1 .

In both embodiments, the first part 4a of the resistance 4 is disposed helically wound in the central part of the radiant heater 1 , whereas the second part 4b of the resistance 4 is arranged substantially concentric to the first part 4a in the outer periphery of the first part 4a. The first part 4a and the second part 4b are arranged connected in series forming a single resistance 4. The first part 4a of the resistance 4 is larger than the second part 4b of the resistance 4. Once the predetermined heating time has lapsed and the entire resistance 4 is powered, the power consumed by the radiant heater 1 decreases between about 10% and about 50% with respect to the value thereof in booster mode. In the embodiment shown in Figure 1 , the second part 4b comprises a helical turn.