EP2509477A2

EP2509477A2 - Deep-fryer and method for deep-frying food

Info

Publication number: EP2509477A2
Application number: EP10798640A
Authority: EP
Inventors: Gerardus Adrianus Van Loon
Original assignee: Princess Household Appliances BV
Current assignee: Princess Household Appliances BV
Priority date: 2009-12-09
Filing date: 2010-12-09
Publication date: 2012-10-17
Also published as: WO2011071383A3; WO2011071383A2; NL2003927C2

Abstract

The invention relates to a deep- fryer (1), comprising a fryer pot (3) for a deep-frying medium, such as an oil, and heating means (6, 20) thermally coupled to the fryer pot (3), comprising a heating element (6) connected to a source of electrical energy via a thermostat (16) thermally coupled to the fryer pot (3), wherein the deep- fryer (1) comprises a manually controllable control circuit (7) for temporarily connecting at least a part of the heating means (6, 20) directly to the source of electrical energy. A user of the deep- fryer (1) can thus additionally heat the deep-frying medium temporarily. The temperature of the deep-frying medium is then temporarily not determined by the thermostat (16) because this is bypassed. The finally deep-fried food will hereby be deep- fried at a temperature which differs to lesser extent from the desired deep-frying temperature.

Description

Deep-fryer and method for deep-frying food

The invention relates to a deep-fryer. The invention also relates to a method for deep- frying food.

Deep-frying food, such as for instance french fries, snacks and fish, is a known and widely used method of preparing food. Use is usually made for this purpose of a deep- fryer, comprising: a fryer pot for a deep-frying medium, such as an oil, heating means thermally coupled to the fryer pot, comprising a heating element connected to a source of electrical energy via a thermostat thermally coupled to the fryer pot. For deep-frying of food the deep-frying medium is brought to a desired deep-frying temperature, after which the food to be deep-fried is placed in the deep-frying medium and, after a desired frying time, is once again removed from the deep-frying medium. A drawback of this known deep-fryer and this known method for deep-frying food is that, once the food for deep-frying has been placed in the deep-frying medium, the temperature of the deep-frying medium will fall below the desired deep-frying temperature since the temperature of the food for deep-frying is generally substantially lower than the deep-frying medium which has been brought to the desired temperature. This is because such food usually comes from a freezer or refrigerator. The heating element connected to the source of electrical energy via the thermostat thermally coupled to the fryer pot will require some time to bring the deep-frying medium back to the desired deep-frying temperature. At least temporarily deep-frying food below the desired deep-frying temperature may result in deep-frying medium being undesirably taken up into the food, whereby the food can become fatter and less healthy, and in an adverse effect on the taste, for instance because the food is less crispy than desired.

For this purpose US-A-6058 245 comprises a deep-fryer comprising a fryer pot for a deep-frying medium, such as an oil, a first heating element which is thermally coupled to the fryer pot and which can be connected to a source of electrical energy via a thermostat thermally coupled to the fryer pot, and a second heating element thermally coupled to the fryer pot. In this prior art deep-fryer the second heating element is connected to a second thermostat. When a large quantity of food for deep-frying is therefore placed in the fryer pot, it takes some time before the two heating elements are switched on, so that the above stated problem is not solved.

There is therefore a need for a deep-fryer and for such a method in which this drawback is obviated.

The invention provides for this purpose a deep-fryer of the above stated type, wherein the second heating element can be temporarily connected directly to the source of electrical energy by a manually operated control circuit.

A heating element is hereby added which can be directly connected to the source of electrical energy only by the control circuit, this is also structurally simple and provides an increased electric power for temporarily bringing the deep-frying medium above the desired temperature. This is because the heating element connected to the source of electrical energy via the control circuit and the heating element connected to the source of electrical energy via the thermostat are both heated by the electric current flowing through the elements. This heating element connected to the source of electrical energy via the thermostat will after all be activated since the thermostat will detect that the temperature of the deep-fiying medium has fallen below the desired temperature because relatively cold food has been placed into the deep-frying medium.

If a user forgets to operate the manually operated control circuit such that the at least one part of the heating means is no longer directly connected to the source of electrical energy, the at least one part of the heating means will continue to heat the deep-frying medium. Not only can this have an adverse effect on the food for deep-frying, but deep- frying food at too high a temperature may after all result in burning of particularly outer parts of food and insufficient cooking of particularly inner parts of the food, and may also result in dangerous situations and even fire hazard. In an advantageous embodiment the control circuit therefore comprises a controllable time switch which is adapted, when operated, to temporarily connect the at least one part of the heating means directly to the source of electrical energy. This reduces the risk of the temperature of the deep- frying medium becoming undesirably or even dangerously high, since after a period of time determined by the time switch the at least one part of the heating means is no longer connected to the source of electrical energy.

According to another embodiment, the control circuit is adapted, when operated, to temporarily connect the first heating element directly to the source of electrical energy. The influence of the thermostat on the first heating element is hereby disabled, so that the increase in the temperature of the deep-frying fat as a result of the second heating element being switched on does not result in the first heating element being switched off.

In a further embodiment the time switch is adapted to block operation for a

predetermined period of time after switch-off. This further reduces the risk of an undesired rise in the temperature of the deep-frying medium. If the time switch can only be operated again after a predetermined period of time, the deep-frying medium will after all have cooled to a lower temperature before the at least one part of the heating means is once again directly connected to the source of electrical energy. This increases the safety of the deep-fryer.

The time switch can be embodied in diverse ways. The time switch can thus be a digitally embodied time switch. The time switch particularly comprises a thermal switch which is thermally coupled to a resistor which is connected for conducting a current heating the thermal switch when the thermal switch is closed. Such a thermal switch is heated when a current heating the switch flows through the switch. If the temperature in the switch rises above a predetermined temperature, the switch will interrupt the circuit. This increases the safety of the deep-fryer.

The thermal switch preferably comprises a bimetal. A bimetal is a structurally simple and reliable form of a temperature-sensitive switch. In another embodiment the thermal switch is provided with at least two contacts, one of which is connected to the heating means and the other to the resistor. The thermal switch can hereby be operated independently of the thermostat by a user of the deep- fryer without the thermal time switch closing the circuit after cooling and thereby temporarily connecting at least a part of the heating means directly to the source of electrical energy in repeated and undesirable manner.

In yet another embodiment the deep-fryer comprises a thermal protection coupled to the fryer pot. A safe deep-fryer is hereby obtained in that the thermal protection is activated if the fryer pot exceeds a predetermined temperature. Irrespective of which part of the heating means heats the deep-frying medium, i.e. the heating element connected to the source of electrical energy via the thermostat thermally coupled to the fryer pot and/or the part of the heating means which can be temporarily connected directly to the source of electrical energy, the thermal protection coupled to the fryer pot will interrupt the circuit with which the heating means can be connected to the source of electrical energy.

The present invention will be elucidated hereinbelow with reference to the

accompanying, non-limitative figures, in which:

Figure 1 is a schematic perspective view of a deep-fryer according to the present invention;

Figure 2 is a view corresponding to figure 1 in which a heating element is shown; Figure 3 is a circuit diagram of a first embodiment of a circuit of the deep-fryer according to the present invention; and

Figure 4 is a circuit diagram of a second embodiment of a circuit of the deep-fryer according to the present invention.

A deep-fryer designated in its entirety with 1 is shown with reference to figure 1. Deep- fryer 1 comprises a housing constructed from plastic wall parts 2, in which is situated a fryer pot 3 manufactured from metal for holding a deep-frying medium such as an oil. A deep-frying basket for holding food is placed in fryer pot 3. Deep-frying basket 4 comprises a handle 5 for gripping of deep-frying basket 4 by a user. Deep-frying basket 4 can be positioned between position in which deep-frying basket 4 is situated substantially in the deep-frying medium (as shown here) and the food is deep-fried in heated deep-frying medium, and a position in which deep-frying basket 4 is situated substantially outside fryer pot 3, in which the deep-fried food can for instance drain. Figure 2 shows deep-fryer 1 of figure 1 , wherein a heating element 6 is shown in broken lines. A spacer 13 is connected to heating element 6 to hold the heating element at a distance from a bottom part 14 of fryer pot 3. Not only is the deep-frying medium hereby heated more effectively, heating element 6 being surrounded by deep-frying medium whereby the heat radiated in multiple directions by heating element 6 heats the deep-frying medium, but a so-called 'cold zone' is also created, where residues such as fried food accumulate without being burnt further by the hot deep-frying medium.

Figure 2 also shows that deep-fryer 1 comprises an on/off switch 9, two indicator lights 10, 11, a push button 12 and a control knob 5 for a thermostat switch. Deep-fryer 1 can be connected to the mains by means of a mains lead 8.

Figure 3 shows circuit 7 of deep- fryer 1. The circuit comprises two connecting points 5a, 15b and an earth point 15c to which mains lead 8 is connected. Connecting point i 5a is connected to one side of on/off switch 9, while the other side of this on/off switch 9 is connected to heating element 6 embodied as resistor via a thermostat 16 thermally coupled to the fryer pot. The thermostat preferably takes a controllable form. The other side of heating element 6 is connected to connecting point 15b via a safety thermostat 19. The indicator light in the form of a LED 17 provided with a series resistance 17a is connected in parallel to the heating element. This lamp serves to indicate whether the heating element is switched on. An indicator light in the form of a LED 10 with a series resistance 10a is further connected in parallel to thermostat 16. This lamp indicates when the thermostat is switched off and the oil present in the pot has reached its desired temperature.

According to the invention the circuit is provided with a time switch designated in its entirety with 12. This time switch 12 is formed in the present exemplary embodiment by a bipolar thermal switch 12a, 12b and a resistor 12c thermally coupled to this switch 12a, 12b. Thermal switch 12a, 12b can also be switched on manually. The series connection of first switch contacts 12a and resistor 12c is connected in parallel to indicator light 17 so that the circuit operates independently of thermostat 16. Second switch contacts 12b are connected between the connecting point between first switch contacts 12a and resistor 12c on the one hand and the connecting point between heating element 6 and thermostat 1 on the other. It will otherwise be apparent that a switch provided with three contacts could be used instead of a bipolar switch. Finally, an indicator light in the form a LED 18 and a series resistance 18a is connected in parallel to resistor 12c. Lamp 18 indicates that time switch 12 is switched on. The operation of this time switch 12 is as follows: when this switch 12 is switched on, contacts 12a and 12b will be closed. A current will hereby begin to flow through resistor 12c, which heats this resistor. Lamp 18 is also turned on. A current will also flow through heating element 6 irrespective of the switching position of thermostat 16. The desired effect according to the invention is hereby achieved. After a time resistor 12c will be heated such that it heats the thermally sensitive switch contacts 12a and causes these contacts to open, together with contacts 12b. The initial situation is hereby restored in which thermostat 16 determines switching on and off of heating element 6. A particular effect of this circuit is that reactivation of the time switch is not possible until it has sufficiently cooled. This prevents heating element 6 being switched on for a long time independently of the thermostat, which could result in dangerous situations.

Figure 4 shows another embodiment of circuit 7. This circuit 7 differs from that shown in figure 3 in that a second heating element 20 is provided. The first, original heating element 6 is also connected for control only by thermostat 1 . Second heating element 20 is connected for control only by time switch 12a, 12b, 12c. Although the

embodiment shown here makes use of a bipolar time switch, it is likewise possible to make use of a single-pole time switch 12a, 12c, wherein contact pair 12b and the associated switch contacts are omitted. The series connection of the first pair of contacts 12a of this time switch 12, resistor 12c of this time switch 12 and second heating element 20 is connected in parallel to indicator light 17 so that the circuit acts independently of thermostat 16.

Because resistor 12c is also thermally coupled in this embodiment to the thermally sensitive switch contacts 12a, which can otherwise be embodied as bimetal as in the previous embodiment, once the thermal switch has been closed current will flow through resistor 12c which heats this resistor and, after a time, heats switch 12a and causes it to open. An embodiment is thus obtained wherein the fryer pot is also additionally heated for a period of time in order to compensate cooling caused by deep- frying of cold products. In the present case an additional heating element is used so that extra power can be supplied and a better compensation obtained.

It will otherwise be apparent that numerous circuits differing from the circuits shown above fall within the scope of protection of the invention as defined by the claims.

Claims

1. Deep-fryer, comprising:

a fryer pot for a deep-frying medium, such as an oil;

- a first heating element which is thermally coupled to the fryer pot and which can be connected to a source of electrical energy via a thermostat thermally coupled to the fryer pot; and

a second heating element thermally coupled to the fryer pot; characterized in that the second heating element can be temporarily connected directly to the source of electrical energy by a manually operated control circuit.

2. Deep-fryer as claimed in claim 1 , characterized in that the control circuit comprises a controllable time switch which is adapted, when operated, to temporarily connect at least the second heating element directly to the source of electrical energy.

3. Deep-fryer as claimed in claim 2, characterized in that the control circuit is adapted, when operated, to temporarily connect the first heating element directly to the source of electrical energy.

4. Deep-fryer as claimed in claim 2 or 3, characterized in that the time switch is adapted to block operation for a predetermined period of time after switch-off.

5. Deep-fryer as claimed in claim 2, 3 or 4, characterized in that the time switch comprises a thermal switch which is thermally coupled to a resistor which is connected for conducting a current heating the thermal switch only when the thermal switch is closed.

6. Deep-fryer as claimed in claim 5, characterized in that the thermal switch comprises a bimetal.

7. Deep-fryer as claimed in claim 5 or 6, characterized in that the thermal switch is provided with at least two contacts, one of which is connected to the heating means and the other to the resistor thermally connected to the thermal switch.

8. Deep-fryer as claimed in claim 5 or 6, characterized in that the resistor thermally connected to the thermal switch is incorporated in the bimetal.

9. Deep-fryer as claimed in any of the foregoing claims, characterized in that the deep-fryer comprises a thermal protection coupled thermally to the fryer pot independently of the thermostat and the control circuit for the purpose of switching off the heating elements when a temperature is exceeded.

10. Method for deep-frying food, comprising of:

- bringing deep-frying medium, such as oil, to a desired deep-frying temperature; introducing food for deep-frying into the deep-frying medium; and

taking deep-fried food out of the deep-frying medium after a desired time, characterized in that prior to introducing food for deep-frying into the deep-frying medium the deep-frying medium is temporarily additionally heated.