EP0087511A1 - Control device for an electrical cooking plate - Google Patents

Abstract

The device contains a thermally operating, clocking power control device (also known as an energy controller), an additional switch (25) connected in series to the control heating (24) thereof, and a temperature switch (15) arranged on the electric cooking plate and acted upon by its heat. The additional switch (25), which is operated by the adjustment shaft (27) of the power control device (21), is opened in an upper power adjustment range so that, when the electric cooking plate is connected, the total power is connected unclocked because the control heating (24) receives no current. After the temperature switch (15) responds, the power control device operates in a clocking manner according to its adjustment. <IMAGE>

Description

The invention relates to a control device for an electric hotplate according to the preamble of claim 1.

- From DE-PS 23 10 867 (= GB-PS 14 70 296) a control device for an electric hotplate with an adjustable, clocking power control device has become known, in which a purely time-dependent thermal timer, which can be switched on separately from the hotplate setting by pressing a button , increased power is released for parboiling by rendering the power control device ineffective during the parboiling phase in such a way that it releases its power unimpeded. For this purpose, the control heating of the thermal power control device is switched off. However, this control device is complex, among other things because of the multi-stage timer switch, which is complex, and the operation by means of a separate push-button operation is not very sensible. It is therefore established been that in practice the acceleration due to increased power is often not used.

It is also generally known in electric hotplates to switch off all or part of the heating by means of a temperature limiter in order to protect the hotplate and its surroundings against excess temperature when, for example, the hotplate runs empty.

The object of the invention is to provide a control device which is easy and sensible to operate, which has a further reduced manufacturing or assembly expenditure and which releases an increased parboiling performance (so-called "parboiling automatic").

This object is achieved by the characterizing part of claim 1.

In the area in which automatic pre-heating is provided, and this is preferably a medium and the higher power range, the power control device is initially rendered ineffective, for example by being switched off by a manually operable additional contact (preferably by switching off the control heating if it is concerned) is a thermally operating, clocking power control device). Only _" when the hotplate has reached a certain temperature does the temperature switch attached to it switch on the power control device again so that it then passes on the power set thereon in a reduced manner. During the heating-up phase, the control device released the power undiminished.

The temperature switch is preferably designed in this way and arranged that it does not switch on again after it has been switched off during the continued operation of the electric cooking plate in the cooking or roasting area. This can preferably be achieved in that the temperature switch is a slow-acting temperature limiter with a relatively large switching hysteresis of preferably over 10 K (preferably about 20 K) in the range from 390 K (120 ° C) as the upper and about 370 K (100 °) C) is the lower response temperature. Such a temperature limiter can be constructed according to DE-PS 11 23 059 and is very simple to manufacture and reliable. Due to the preferred arrangement in the unheated middle zone of the electric hotplate, it has a relatively low and inertial heat coupling to the hotplate, so that it with a certain. The time delay switches off and does not switch on again during normal cooking and roasting. Since the hotplate temperature is also dependent to a certain extent on the decrease in output, ie the amount and temperature of the food, the temperature switch also takes the food conditions into account to a certain extent and thus creates a duration that is adapted to the respective food to a certain extent, ie automatically controlled heating phase.

This heating phase is preferably provided in the cooking and roasting area of the power control device, but not in the heating area. The location of these areas depends on the size, type and maximum output of the hotplate. As a guideline, however, it can be assumed that in the heating range, in which the heating phase is not normally provided, the power setting is so low that the temperature of the food does not rise above 100 ° C (373 K).

The control device is both for hot plates with Cast body and essentially closed flat cooking surface usable, as well as for heating glass ceramic plates or other hot plates, which can be controlled by power control devices, preferably clocked power control devices. It can also be used for hot plates with one or more heating conductors. In the case of a hotplate with at least two heating resistors, the temperature switch can contain a changeover contact and, when activated, one of the heating conductors can be switched off and the control heating of the power control unit switched on. This makes a second or two-stage temperature limiter unnecessary even with a hotplate with a relatively high total output, because then after the heating phase, in which both heating conductors are switched on, one heating conductor is switched off. The remaining power is sufficient to continue all cooking and roasting after the parboil. For this purpose, the heating conductor switched off by the changeover contact should have such a power that the remaining power enables cooking or roasting to continue without overheating the electric hotplate when idling. The corresponding power distribution depends on the type, power and size of the electric hotplate, but is usually 40 to 45% of the total power for conventional electric hotplates (for example, with 200W total power 850W can be switched off and 1150W remaining).

In order to improve the precise controllability of even low powers, the control heating of the power control device can be preceded by a diode which can be switched off manually in the lower power range in an upper power range. This version is in detail described in DE-AS 26 25 715 (US 4 206 344), to which reference is expressly made here. Their arrangement is easily compatible with the control device according to the invention. As described in the mentioned publication, it can be bridged by a separate switch. However, in an advantageous embodiment of the invention, it is also possible to switch the diode into a circuit leading from the temperature switch for control heating of the power control device. In this case, the diode is switched on automatically when the temperature switch responds, so that it is switched on in the entire cooking and roasting area, and the cooking phase has ended. In contrast, the diode is not connected upstream in the heating range and thus refines the adjustability of low powers. The diode also causes a deliberate kink in the characteristic curve, which not only makes the setting in the lower power range more precise, but also finer with respect to the setting shaft than in the upper power range.

The version in which the additional contact is actuated by a common setting and switching shaft for switching on and setting the power of the power control unit is particularly preferred. When the control device is operated, an increased parboiling power is therefore always released in the intended areas (cooking and roasting area) without special operating measures being necessary. This results in a very effective control that is well adapted to the needs of practice. Due to the reaction of the food to the cooking time, it is also not necessary. selective operability see that is hardly used in practice. By coupling the temperature switch to the temperature of the hotplate and the food to be cooked to a greater or lesser extent, the reaction of the food to be cooked, ie the actual conditions, can be adapted to the requirements. Instead of the temperature limiter described above, which does not switch on again due to its large switching hysteresis and thus has a good and sufficient effect with the least manufacturing outlay, any other type of temperature switch can be used as a temperature switch, in particular those which have a switch-off delay. It would also be conceivable to use a temperature switch which, due to a large contact gap on its snap switch, does not spring back into the starting position after the one-time response and is only mechanically brought back to the starting position when the setting shaft is in the zero position.

It is also an advantage of the invention that conventional power control devices, usually referred to as energy controllers, can be used if a simple additional contact is assigned to them. This can preferably be done in that the additional contact is contained in an attachment switch housing to the power control unit, which is saddled on the operating side of the power control unit and whose housing is penetrated by the common setting shaft.

• Figur 1 bis 4 schematische Schaltbilder von Ausführungsbeispielen von Steuereinrichtungen mit den zugehörigen Elektrokochplatten und
• Figur 5 eine perspektivische Ansicht einer Steuereinrichtung.

The invention is explained in more detail below with the aid of a few exemplary embodiments. Certain advantageous combinations are used in the exemplary embodiments shown. To reduce the number of examples, however, the other combinations of features are not shown and described in detail, although they may also be advantageous. The drawing shows:

• 1 to 4 are schematic circuit diagrams of exemplary embodiments of control devices with the associated electric hotplates and
• Figure 5 is a perspective view of a control device.

In Figure 1, an electric hot plate 11 with two heating resistors 12, 13 is shown schematically. It can be a conventional hotplate with a cast body and heating resistors inserted into grooves on the underside by means of an investment material, which occupy a heated ring area of the hotplate. In the unheated middle zone 14 there is a temperature switch 15, the bimetal 16 of which actuates a snap switch 17, which in the present example is designed as a changeover switch.

In the illustrated, not actuated, ie "cold" position, the snap switch 17 connects a feed line 18 to the hotplate with the heating resistor 12, while in the position not shown, which the switch assumes after its response as a result of temperature increase, the feed line 18 also has an additional the main supply lines 18, 19 provided line 20 is connected between the electric hotplate 11 and the power control unit 21. The temperature switch can be of any construction be art, for example as described in DE-PS 11 23 059, to which reference is made. The temperature switch 15 can be set in such a way that it switches over at a temperature on the hotplate surface on which the cooking vessels are placed of approximately 390 K (120 ° C.) when it is heated up, while switching it on again after cooling only below approx 370 K (100 ° C) takes place. The corresponding temperatures at the temperature switch itself will of course be significantly higher than the specified temperatures. However, they depend on the type of hotplate and the attachment of the temperature switch and can be easily determined based on the above information. The hysteresis, which prevents restarting when the temperature drops, does not necessarily have to be present in the temperature switch itself. If a low-hysteresis temperature switch is fitted accordingly, the structure and temperature conditions in the hotplate itself can ensure that the temperature at the temperature switch after heating up, even when the power supplied is reduced due to a lower setting of the power control unit (but in the cooking or roasting area), the response temperature no longer falls below.

The power control unit 21, which is removed from the electric hotplate and is only connected to it by an electrical connection, is constructed in a conventional manner and can be used according to DE-PS 26 25 716 (US Pat. No. 4,206,344), referred to in the previous explanation will correspond. It has a switch 22 which is opened or closed by a bimetal 23, which is heated by a control heater 24. The control bimetal 24 is connected in parallel to the consumer heating resistors 12, 13, which are also connected in parallel, behind the switch 22, so that the control heater 24 is switched on and off together with the consumers. In the line branch 26 leading to the control heater 24 there is an additional contact 25 via which the control heater 24 can be switched on and off. This switch is bridged by the switch 17 of the temperature switch 15 and the connection 20 if the switch 17 exceeds its response temperature has switched.

The degree of exposure of the bimetal to the switch 22, i.e. the power setting of the power control unit and the opening and closing of the additional contact 25, as well as a possible, not shown, double-pole network separation are carried out from a common setting shaft 27, which can be actuated from a setting button 28.

The additional switch 25 is actuated via a curve or the like, which is set up in such a way that the switch in the lower setting range of the power control device (heating range with a hotplate surface temperature below 370 K (100 ° C.)) is closed, while it is in the middle range above and the upper power range (cooking and roasting area) is open.

• Nach dem Einschalten der Elektrokochplatte am [instellknopf 28 sind die Schalter 22 und 25 geschlossen. Der Schalter 17 des Temperaturschalters befindet sich in der in Figur 1 dargestellten Stellung. Dementsprechend sind beide Heizwiderstände 12, 13 eingeschaltet und werden entsprechend der eingestellten niedrigen Leistung taktend mit Strom versorgt, indem in bekannter Weise das von der Steuerbeheizung 24 aufgeheizte Bimetall 23 den Schalter 22 öffnet und ihn nach Abkühlung wieder schließt.

The function is then as follows:

• After switching on the electric hotplate on the [adjustable button 28, the switches 22 and 25 are closed. The switch 17 of the temperature switch is in the position shown in Figure 1. Accordingly, both heating resistors 12, 13 are switched on and are clocked with current in accordance with the set low power by the bimetal 23 heated by the control heater 24 opening the switch 22 and closing it again after cooling.

With a setting in the cooking or roasting area, the switch 25 is opened and thus the control heater 24 is de-energized, so that via the closed switch 22 both heating resistors 12, 13 are switched on without clocking with undiminished power and heat the hotplate at maximum speed. After this boil-up phase with the highest output, the switch 17 of the temperature switch switches depending on the hotplate heating (and thus also depending on the power consumption), so that the control heater 24 in turn receives power and the power control device now continues cooking or frying power in a clocked manner Form according to the setting of the power control unit. The temperature switch 15 does not switch back during further operation. so that this function is retained until the original status is restored after the hob is switched off.

During the further cooking or roasting, ie after the switch 17 has been switched over, only the heating resistor 13 is switched on, which is sufficient for normal operation. This deliberate reduction in performance ensures that the hotplate is given if it does not require an additional overheating protection switch, which, however, could be connected in series with the heating resistor 13 if desired. The residual power represented by the heating resistor 13 in the order of 55 to 60% (approx. 1150 W with a total power of 2000 W) can be tolerated by an electric hotplate of the type described as idle power if it is forgotten to switch it off.

The embodiment shown in Figure 2 is identical to that in Figure 1 except for the fact that in the line branch 26 'of the control heater 24, a diode 30 is connected in series with the control heater, which can however be bridged by a switch 41. This switch, like the switch 25, can be actuated by the setting shaft 27, namely it is closed in the lower power range of the power control device 21 and opened in an upper area. In the example shown, these areas do not have to match the areas defined by the switch 25.

This arrangement causes the control heating resistor 24 to receive twice as much power at lower powers than in the upper power range. Due to the faster heating of the bimetal in the lower power range, it is possible to achieve shorter "on times" and thus also to achieve lower power settings, that is to say a lower relative duty cycle. In the upper power range, on the other hand, it takes longer to heat the bimetal, so that there is a good adaptation to longer relative switch-on times. It also results in a Desired characteristic curve kink, which enables a finer setting in the lower area.

The embodiment according to FIG. 3 differs from that according to FIG. 1 in that the diode 30 is switched on in the line 20 'between the switch 17 and the control heating resistor 24. The diode is therefore always active when the temperature switch 15 has responded, i.e. in the entire cooking and roasting area, while it is ineffective in the heating area when switch 25 is closed. In this case, the areas in which the diode is connected upstream and in which a parboiling phase takes place coincide with one another. Compared to FIG. 2, the switch 41 is saved, which, however, just like the switch 25, only. had to be designed for the low current of a few watts flowing through the control heating resistor.

FIG. 4 shows an embodiment in which the electric hotplate 11 'has only one heating resistor 31, which consumes the total power of the hotplate. Such a design with only one heating resistor is also used in radiators which are provided for heating glass ceramic plates or as direct contact or radiant heaters. In this case, a temperature switch 15 'is arranged in the area of influence of the hotplate heating and optionally also of the cooking material, which need only have a simple switch 17' instead of the switch 17 in FIG. 1, with the power control device 21 and the switch 25 being of the same design the function is the same as in FIG. 1, with the only difference that both in the heating phase and in the subsequent further cooking and roasting area, only one heating resistor 31 remains undiminished or clocked is switched.

In this embodiment in particular, it is advantageous to provide an additional temperature limiter 42 which secures the hotplate 11 'against upper temperatures by switching off the single heating resistor, which can also be in the form of a plurality of heating resistors connected in series or in parallel, when its response temperature is exceeded. A temperature limiter which is relatively low in hysteresis and is well coupled to the heating of the electric hotplate is preferably used here, which is set to a temperature above 300 ° C. (570 K). A temperature limiter can be used which is constructed and arranged according to DE-PS 24 22 629 (US-PS 4 135 081) or DE-OS 30 27 998 (US-Serial No. 285 144, filed on July 20, 1981) to which express reference is made.

FIG. 5 shows the perspective view of a power control unit 21, which is accommodated in a block-like plastic housing with its bimetal heating ventilated by air slots 32. On the rear side 33, which is remote from the operator, there are connecting plugs 34 and optionally the diode 30, which is mounted on the switch 31, which is actuated by the rear shaft end of the setting shaft 27, by the power control device 21 and a housing 35, saddled on the operating side, for the additional switch 25 protrudes through. The flat housing 35 of this front-mounted switch can accommodate a switching cam plugged onto the setting shaft 27 and the switch 25 designed as a simple resilient contact tab. The saddling can be done by snapping or screwing onto the housing of the energy regulator 21, and the electrical connections can be made internally directly through plug contacts.

Claims (10)

1. Control device for an electric hotplate (11) with at least one heating resistor (12, 13, 31), which contains an adjustable power control device (21), which is so ineffective during a heating phase that the power is released unimpeded, characterized in that a temperature switch (15) acted upon by the heat of the electric hotplate (11) makes the power control device (21) effective when it responds. 2. Control device according to claim 1, characterized in that the heating phase in a medium and higher power range, preferably in the cooking and roasting area, of the power control device (21), but not in the heating area. 3. Control device according to claim 1 or 2, characterized in that the power control device can be switched off by a manually operable additional switch, which preferably switches the control heating (24) of the thermally operating clocked, essentially continuously adjustable power control device (2.1) and which in particular in a header -Switch housing (35) to the power control unit (21) is included, which is saddled on the operating side of the power control unit (21) on the housing and is penetrated by a common setting shaft (27). 4. Control device according to one of the preceding claims, characterized in that the entire power of the electric hotplate (11) is switched on unimpeded during the heating phase. 5. Control device according to one of the preceding claims, characterized in that the temperature switch (15) is designed and arranged so that it does not turn on again after switching off during continued operation of the electric hotplate (11) in the cooking or roasting area. 6. Control device according to one of the preceding claims, characterized in that the temperature switch (15) is a slow working temperature limiter with a switching hysteresis of over 10 °, preferably at about 20 °. 7. Control device according to one of the preceding claims, characterized in that the temperature switch (15) contains a changeover contact (17) which, in the case of a hotplate (11) with at least two heating resistors (12, 13), responds to one of the heating conductors (12). off and the control heating (24) of the power control unit (21) switches on, preferably the heating conductor (12) switched off by the changeover contact (17) having a power of preferably 40 to 45% of the total power of the electric hotplate (11) that the remaining one Remaining power allows you to continue cooking or roasting without overheating the electric hotplate (11) when idling. 8. Control device according to one of the preceding claims, characterized in that the control heating (24) of the power control device (21) is connected upstream in a higher power range, a diode (30) which can be switched off manually in the lower power range and which is preferably connected to one of the temperature switches (15). current branch (20 ') leading to the control heating (24) of the power control unit (21). 9. Control device according to one of the preceding claims, characterized in that the additional switch (25) can be actuated by a common setting and switching shaft (27) for switching on and setting the power of the power control device (21). 10. Control device according to one of the preceding claims, characterized in that in particular in the case of an electric hotplate (11 ') with only one heating resistor (31) in addition to the temperature switch (15, 15') Higher temperature values than the temperature switch (15, 15 ') responding, preferably low-hysteresis, well-connected to the heating of the hotplate (11, 11') temperature limiter (42) is provided, which the heating resistor (s) (12, 13, 31) against upper temperatures backs up.

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