BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to movable cooking appliances or cooking trays including structure which is adapted to be placed on a worktop of kitchen furniture or inside a cooking oven (collectively referred to as a cooking unit), and includes a heating element and releasable connector means for making electrical connection with power supply connector means. With the term “movable” we mean any kind of cooking and heating appliance which can be plugged or unplugged to a fixed support, whatever such support is.
Description of the Related Art
The above kind of cooking appliances or cooking accessories are well known in the art. An example is shown in U.S. Pat. No. 5,272,317. With the known appliances the heating element is an electrical resistance heater connected, for instance, to a shelf or tray adapted to be introduced into an oven cavity. The use of electrical resistance heaters has been replaced by more efficient induction heating elements which, despite a higher complexity and cost (mainly due to the complex electronic driving circuit), allow the induction heating elements to reach a desired temperature in a shorter time and with a lower energy consumption. One compromise would be to design an induction cooking appliance or accessory without a built-in electronic driving circuit, and integrating this in kitchen furniture or cooking appliance (such as a traditional oven or an induction oven). By adopting this solution it is important to assure a safe and reliable connection between the “fixed” electronic driving circuit and the movable induction cooking appliance or accessory.
Prior art connectors that are in use generally have terminals with equal length. The design of these connectors doesn't implement any further safety feature that guarantees power supply cut-off when the user is extracting the removable tray with an induction heater while the tray is working. This abnormal procedure may happen during the use of the oven and this can cause a potential risk of electric arcing at the power terminals and potential breakdown of the insulated gate bipolar transistor (IGBT) associated with the electronic driving circuit of the heating element.
SUMMARY OF THE INVENTION
The present invention is mainly focused on the problem of assuring safe and reliable insertion and extraction of a releasable connector means for connecting an induction tray, for instance, into an oven cavity. The present invention also addresses a tray including an induction element being plugged into or unplugged from the socket of a power supply connector means located inside an oven cavity in a safe manner. It is therefore an object of the present invention to provide a solution to the above concerns.
The present invention is focused on the design of a connector that is to be used to connect an induction tray into a socket of an oven cavity or other type of support used for the tray. In a preferred embodiment of the invention, the connector has five male terminals, including two for the power connection (i.e., supplying an induction heating coil), two for the temperature sensor connection (that allows a reading of temperature sensor placed in the coil centre of the induction heating element for safety reasons) and one a ground connection (that guarantees electrical safety for the user). The design of the connector according to the invention enables a safer and more reliable insertion and extraction of the male plug of the induction heating tray whenever the user uses it as an accessory inside an oven or on a kitchen worktop.
BRIEF DESCRIPTION OF THE DRAWINGS
Further advantages and features according to the present invention will be clear from the following detailed description, with reference to the attached drawings in which:
FIG. 1 is a schematic view of an oven according to the present invention;
FIG. 2 is a schematic view detailing the male and female terminals of a plug connector of the oven of FIG. 1, according to a first embodiment of the invention and in a first configuration of use;
FIG. 3 is a schematic view similar to FIG. 2, showing the terminals in a second configuration of use;
FIG. 4 is a schematic view similar to FIG. 2, showing the terminals in a third configuration;
FIG. 5 is a schematic view similar to FIG. 2, showing the terminals in a fourth configuration;
FIG. 6 is a schematic view detailing the male and female terminals of the plug connector an oven of FIG. 1, according to a second embodiment of the invention;
FIG. 7 is a variant of the embodiment shown in FIG. 6;
FIG. 8 is a schematic view detailing the male and female terminals of a plug connector of the oven of FIG. 1, according to a third embodiment of the invention and in an unplugged configuration;
FIG. 9 is a schematic view similar to FIG. 8 in a plugged configuration;
FIG. 10 is a schematic view detailing the male and female terminals of a plug connector according to a fourth embodiment of the present invention;
FIG. 11 is a schematic view of the male terminals of a plug connector in accordance with a further embodiment of the present invention;
FIG. 12 is a schematic view of the male terminals of a plug connector in accordance with yet a further embodiment of the present invention;
FIG. 13 is a schematic view detailing the male and female terminals of a plug connector of the oven of FIG. 1, according to another embodiment of the invention, in a partially unplugged position; and
FIG. 14 is a schematic view similar to FIG. 13, in a plugged position.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to the drawings, an induction oven having a cabinet 10 is shown in FIG. 1, the oven cabinet 10 defining a cooking cavity 10a where an induction tray 12 can be inserted and pulled out. The tray 12 has a double layer main body structure made of non-ferromagnetic material, such as aluminium, and includes an embedded induction heating element or coil (indicated at 36 in FIGS. 11 and 12) with a temperature sensor (depicted at 34 in FIG. 11). On a rear side 12a of the tray 12 there is a plug connector 14 for the electrical connection of tray 12 with a socket connector 16 placed on a rear wall 11 of the oven cavity 10a. In the following, we indicate with reference C the overall power connector assembly of the present invention, including the plug or male connector 14 supported by the tray 12 and the socket or female connector 16 supported by the oven.
As noted previously, with known connectors, the design is not able to provide good safety as it doesn't implement any extra feature which lets the power board cut off the power before male plug extraction. Because of this, extraction of the induction tray 12 without cutting off the power supply to tray 12 may cause safety problems for the customer and reliability problems for the oven.
According to a first embodiment of the present invention depicted in FIG. 1, the design of connector C presents assemblies of five male terminals and associated female terminals which make up a total of five connections. Two sets of the terminals 18 provide power connections, two sets of the terminals 20 are for the temperature sensor connection and one set including terminal 22 is for the ground connection. As shown in the embodiment of FIG. 2, the ground terminal 22 has the greatest length, the sensor terminals 20 (equal to each other in length) are the shortest ones and the power terminals 18 (equal to each other in length) have an intermediate length between the lengths of the ground terminal 22 and of the sensor terminals 20. This design enables the ground terminal 22 to connect first during insertion of plug 14, and to disconnect last during extraction of the plug 14, guaranteeing safety electrical discharge through ground terminal 22 in case there might be a discharge between induction coil 36 (again depicted in FIGS. 11 and 12) and aluminium plates of the tray 12, thus eliminating the electrical risks for the user. FIGS. 2, 3, 4 and 5 show different positions of the male-female connector C: FIG. 2 shows a complete insertion of the plug 14 with all terminals having complete electrical contact; FIG. 3 shows a partial extraction of male plug 14 with ground 22 and power terminals 18 yet in contact; FIG. 4 shows a configuration in which only ground 22 remains in contact; and FIG. 5 shows full extraction, i.e., all terminals are not in contact with socket connector 16. As illustrated in FIG. 3, during extraction of the male plug 14, the sensor terminals 20 lose electrical contact first since they have the shortest length. Once this happens, a power board indicated at P senses the connection as an open-circuit and automatically cuts off the power to the tray 12 before the power terminals are actually disconnected (as they are still in contact with the female sockets due to their longer terminals).
According to a second embodiment of the invention depicted in FIG. 6, inside the female plug 16 there is a switch 24 that is electrically closed by the ground plug 22 when inserting the male plug 14. This circuit is connected to power board P of the oven. The switch 24 can be of any kind. For instance, it can be a mechanical switch (that is in physical contact with the terminals) or it can be a proximity switch (that doesn't need a physical contact), such as a reed switch 40 shown in FIGS. 13 and 14. This switch mechanism 24 can be short-circuited and open-circuited, distinguishing the cases between complete male plug insertion and not complete insertion, respectively. As can be seen in FIG. 6, the extraction of the male plug 14 from the female socket 16 including mechanical switch 24 causes the opening of the circuit, sending therefore a signal to the power board P to interrupt the power supply to the tray 12 before the power terminals 18 are disconnected.
It is clear that the position of the mechanical switch 24 (in FIG. 6 it is positioned close to the ground terminal 22) can vary and can be applied to any other terminal. However, it must be placed in a way that the mechanical switch 24 opens before the power terminals 18 are completely extracted, in order to allow the power board P to cut off the power before the connector 14 is fully extracted from female plug 16 (safety power cut-off).
FIG. 7 shows a connector C which is slightly different from the one shown in FIG. 6, and where the length of the terminals 18, 20 and 22 are similar to the one shown in FIG. 2. In this embodiment, the ground terminal 22 remains the longest for safety precaution as already explained. If the switch 24 is a reed switch, the terminal involved has to be made of permanent magnetic material.
A further embodiment of the present invention is shown in FIGS. 8 and 9, where the male plug 14 has terminals of identical lengths and a female socket 16 with a mechanical switch mechanism 26. This mechanism 26 comprises a metal piece 26a hinged to one of the temperature sensor female terminals 20 via a spring 26b. When the male plug 14 is not inserted (FIG. 8), the metal piece 26a contacts both terminals 20 of sensor 34, short-circuiting them. The power board P senses that temperature sensor terminals 20 are short circuited and it doesn't supply power to induction tray 12. Otherwise, when the male plug 14 is inserted (FIG. 9), the metal piece 26a doesn't contact both terminals 20 and therefore the power board P supplies power to the induction tray 12 as it senses that the male plug 14 is fully inserted and there is no safety issue.
The embodiment shown in FIG. 10 has all five terminals 18, 20, 22 mentioned above at equal length, and it presents in addition a sixth terminal 30b (associated with an additional plug 30a) which is made of another material such as ceramic or plastic and which has a greater length than other terminals. This sixth terminal 30b turns on and off the electrical connection by a mechanical switch 32 during insertion and extraction, respectively.
The embodiment shown in FIG. 11 has the aim of reducing the number of terminals or to avoid the need of adding extra sensor terminals. Reducing the number of terminals would provide a cost saving and easier connection in addition to space saving inside the oven. More specifically, the male plug 14 in this embodiment has four terminals consisting of one ground terminal 22, two power terminals 18 and one single terminal 20 for a temperature sensor indicated with reference 34 in FIG. 11, while the induction coil is schematically indicated with reference 36. According to this embodiment, in order to save material and space, it is possible to use the ground terminal 22 as the second sensor terminal. This embodiment has the ground terminal 22 with the greatest length, the sensor single terminal 20 with the shortest length and the power terminals 18 in between these two lengths as in the first above embodiment. The power board P should be designed for reading the sensor signal with an isolated signal-conditioning circuit, as it is referenced with the oven ground which is isolated with respect to the power supplier in any appliance by default.
In the further embodiment shown in FIG. 12, the five terminals of the previous embodiment 18, 20 and 22 are maintained and an extra temperature sensor 38 is added that will still use the ground as a reference level. This can also be extended to three readings using three terminals and a ground terminal, and so on. Increasing the number of temperature readings enables a better control of the induction heater temperature, and using the ground terminal provides a savings from the number of terminals needed. The power board P should be designed for reading the sensor signal with an isolated signal-conditioning circuit in this embodiment, as well.
Even if in the above embodiments the plug connector 14 is shown as supported by the induction tray 12, it is clear that such a plug connector can be supported by the rear oven wall 11 and the socket connector 16 can be supported by the tray 12 as well.
Patent Grant
10054316
