DE2343833A1 - Electric hot-plate - has a glass-like or ceramic plate with at least one heater below it pressed to the plate - Google Patents

Abstract

The hot plate includes a temperature sensor, parallel to the ceramic plate. The sensor is in the form of an expansion rod passing through the heaters and operating a temperature limiting switch in the heater area. The sensor is placed between the heating elements and insulation in the supporting plate for the heaters. The straight sensor lies on a diameter of a round heater unit. It may be provided directly on the underside of a spiral tubular heater. The working and safety contacts are both mounted on a spring clip arrangement on a common bracket.

Description

Dipl.-Ing. EI DEN El ER Dipl.-Chern. Dr. RUFF Dipl.-Ing. J. BEIER

7 STUTTGART 1 Neckarstrasse 50 Telephone CO711} 22 7O 51

Aug. 23, 1973 - JB / Va

Applicant: EGO Elektro-Geräte Blanc tu Fischer 7519 Oberderdingen / Wiirtt.

A 14 919 A 14 920

Electric cooker

The invention relates to an electric cooking appliance with an upper made of vitreous or ceramic material Plate and at least one heating unit arranged therebelow with a carrier shell and arranged therein and heating elements pressed against the glass ceramic plate and with a temperature sensor lying parallel to the glass ceramic plate.

Such an electric cooking appliance is from the German Offenlegungsschrift 2 205 132 became known. Thereby exist the heating elements made of spirally wound flexible ear

radiators with an essentially triangular cross-section, which are pressed against the glass ceramic plate from below,! / location are two ring-shaped areas of heating elements

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Poeteoheckkonto Stuttgart 42O3O Dresdner Bank Stuttgart Account 9 Oll 341

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provided, between which a turn remains free. In this lies a spiral turn of a tubular temperature sensor, which is designed as an electrical sensor, ie as a result of an inserted resistance wire or some other material that changes its conductance significantly under the influence of temperature, a Jj ¹ UhIersignal is generated which is in an electrical or electronic switching or Control device can be used. Although this allows very good regulation, it should be noted that the switching or control device for evaluating the electrical sensor signal is relatively complex. It must also be attached to the electric cooker in an area that has a relatively low temperature, especially when electronic components are used. This is often difficult with very flat installation units, since electronic components can only withstand 80 ° C.

As is well known, the temperature of a glass ceramic plate must must be monitored particularly carefully, as these do not overtemperature tolerates. In addition, the heating elements and thus the underside of the glass ceramic require very high temperatures in order to bring sufficient power through the insulating glass ceramic plate also other very reliable and relatively simple switching and control devices such as hydraulic controllers. The hydraulic fluid would have such temperatures no longer easily tolerated.

The object of the invention is therefore the aforementioned electric cooking appliance with respect to the limitation of the highest To improve the temperatures occurring so that no costly, remote from the heating unit to be arranged una temperature-sensitive switching or control devices are more necessary.

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This task is achieved according to the invention in that the temperature sensor is designed as a rod-shaped mechanical expansion member on which the glass ceramic plate facing away from the side of the heating elements runs along transversely through the Ileizeinheit and one as a temperature limiter Acting switch for heating the heating elements operated, which is arranged in the area of the heating unit is.

Εε it has always been assumed that the glass ceramic plate, which works with a working temperature just below the temperature that leads to damage, only can be properly monitored by a l <\ ihler -de-r rests directly on its underside. Amazingly, it has been shown that with a rod-shaped temperature sensor, which runs at a relatively large distance from the glass ceramic plate and even below the relatively close adjacent heating elements, a very effective temperature limitation of the maximum temperature for the Glass ceramic plate can be created. Tests have shown that it is even possible to use the temperature limiter to be used as a working regulator by. without any other temperature control the heating unit only with energy control is operated, d. H. the heating unit is heated so high that it is constantly controlled by the temperature limiter during operation is switched on and off.

The function of the temperature limiter is so excellent that with a proper cooking with a pot standing on it, an overall output of 84 % is achieved (ie the heating unit was switched on 84% of the time and was switched on 16% of the time by the Temperature limiter switched off), would be the worst

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Trap with a poorly fitting and reflective pot that does poorly on performance, a relative one Duty cycle (relative power consumption) of only 30% was achieved. The temperatures on the glass ceramic plate in the range between 500 ° and 600 ° were reduced to a few . 10 ° kept constant exactly. Also an attempt with a displaced saucepan, i. H. with a decrease in performance only in one Part of the heated cooking surface could still be a very good one good regulation can be achieved without impermissible temperatures in the area not covered by the saucepan occurred.

Further advantages and features emerge from the subclaims and the description in connection with the drawings. Some embodiments of the invention are shown in FIG the drawing and are explained in more detail below. Show it

Fig. 1 is a section through a temperature limiter which is used in a Electric cooking appliance according to the invention is suitable,

FIG. 2 shows an enlarged detail from FIG. 1,

3 shows a plan view of a heating unit with a temperature limiter according to FIGS. 1 and 2,

Fig. 4- an echematic section along the line IV - IV in Fig. 3 and

Fig. 5 is a schematic circuit diagram.

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0FNGiNAiI

The one in Pig. Temperature limiter 11 shown in 1 and 2 is also in the application filed on the same day by the same applicant with the title "temperature limiter" described. It has a housing 12 and one attached to it Temperature sensor 13, which is designed as a thermal expansion element. For example, it consists of a tubular stainless steel sleeve 14 attached to its lower end is connected to a central rod 15, if necessary via an adjusting screw 42. The rod 15 can be made of ceramic material that has a very low has thermal expansion coefficient, during that of the sleeve 14 is greater.

In the housing 12 of the temperature limiter 11 is a rocker 16 in the form of a two-armed lever around an axis pivotally arranged. One arm of the rocker 16 presses on the rod 15 j while the other arm on a pressure rod rests, which protrudes through an opening in a carrier 44 made of insulating material, which on its from the Rocker 16 carries a snap switch 56 in a recess on the side facing away from it. This snap switch has a Snap spring 47, the two bent spring parts of which are attached to an abutment. 46 support, which is like an L-shaped, is formed via a leaf spring mounted lever 45 and with its part remote from the support on Carrier is attached. The lever 45 is supported by the üruckstab 19 from, and he can thus actuate the snap switch in the opening direction by pressing upward in the drawing. A normally open contact 26 is at one end the snap spring 47 is arranged. The mating contact for this is attached to the carrier 44 and is electrically connected to a terminal 2? tied together. At the other end of the snap spring is a Arranged safety contact 28, which cooperates with a mating contact on the housing opposite this

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is mounted insulated and electrically connected to a terminal 29.

The actual switching mechanism can be seen particularly in FIG. 2, which shows a working position of the snap switch shows. In the switching spring 47 of the switching mechanism are made of thin spring material through two incisions existing switching spring two outer continuous connecting parts and two spring parts 49, 50 separated, of which the spring part 49 on the side of the safety contact. 28 is and actuated while the spring part 50 belongs to the actuation of the normally open contact 26 and on the side of which is arranged. The spring parts are * in Usually bent out in an arc upwards and supported with their facing one another also as Cutting 51 designated ends in cutting edge bearings 52, which are designed as notches on two opposite sides of the arm 46. Ide cutting edge bearing 52 for the spring parts 49 and 50 are at different points on the arm 46, in the example shown here Blade bearing for the spring part 50 for the working contact 26 higher, i.e. h, more about the equilibrium or snap position facing, lies as the cutting edge bearing for the spring part 49 which actuates the safety contact 28.

The switching spring 47 with its contacts 26 and 28 is freely supported, i. H. she is only through in her position • Installation of their contacts 26, 28 on the corresponding mating contacts and held by supporting their spring parts in the abutments in part 46. The contact distance at The open contact is in the working contact 26 by a stop 55 provided on the insulating material carrier 44 limited to a relatively low value, while it can be very large in the case of safety contact 28.

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From the schematic circuit diagram of FIG. 5 it can be seen that that the contacts 26 and 28 are connected in series, the snap spring 47 in the usual way conducting tasks takes over, and that the entire temperature limiter 11 electrically in series with two heating resistors 33, 33 'connected in parallel with one another, one in Pig. 2 shown Heating unit 34 of the electric cooker and with an adjustable controller 35 is connected. Via the temperature limiter 11 "so flows from the network connection 36 of the Electricity supplied to heating unit 34. The controller 35 can be any controller, but preferably an energy controller, which enables a stepless power supply to the heating resistors 33 »33 '. · "*"

The temperature limiter 1T according to FIGS. 1 and 2 works as follows:

Normally the contacts 26 and 28 are closed, and when the heating resistors 33 »33 'are switched on by means of the controller 35, current flows through these contacts and heats the heating unit 34. The sleeve 14 expands more than the rod 15 with a smaller thermal expansion coefficient, so that the rocker 16 is pivoted clockwise and presses on the lever 45 via the push rod 19, whereby the arm 46, as can be seen in FIG is moved laterally towards the safety contact 28. When the blade bearing 52 for the spring part 50 comes over its snap point, the switching spring 47 snaps around on the side of the normally open contact 26, and the normally open contact 26 lifts off its counter contact 53 and rests against the stop 55 of the angle lever 45 downwards, and the contact 26 closes again when the snap point for the spring part is exceeded.

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This is the normal functional sequence that takes place each time the limit temperature is reached. It will each time, as can be seen from Fig. 2, the snap spring 47 in its longitudinal direction, d. H. across the contacts, moved back and forth, not only when switching, but also for each one below the switching point, caused by different temperatures at the sensor 13 Move. This prevents the welding or sticking of the safety contact 28, so that this also is ready for use if it has not been used for years.

If now the working contact 26 has not opened due to welding or gluing, although the cutting edge bearing 52 for the spring part 50 has long migrated over the snap point, the angle lever is pivoted further by further expansion of the sleeve 14, and the arm 4b moves so far upwards, until the cutting edge bearing 52 for the spring part 49 also comes over the snap point, so that the safety contact 28 then opens. As a result of its large contact distance, the snap spring 47 comes into a position from which it is not returned to its original position even if the element 1 $ cools down. This phenomenon occurs because the spring parts 49, 50, the one. Exercise spring action on the part 46 downwards, which counteracted the force of the spring 4j, now no longer have this spring action or to a greatly reduced extent. Together with the dimensioning of the other resilient parts in the switch, the contact blocks and the design of the cutting edge bearings, the snap spring is dimensioned such that this self-retention occurs when the safety contact 28 is in the open position. So there is an advantageous effect that when

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If the safety contact responds, the hotplate can only be put back into operation when the temperature limiter is repaired and the normally open contact 26 is working again.

In Figs. 3 and 4, a heating unit is shown schematically, in which a temperature limiter 11 according to FIGS. 1 and 2 is used. An electric cooker 100 shown in Fig. 4 is indicated with a wall, has an upper plate 101 made of heat-resistant and in particular Thermal shock-resistant, glass-like or ceramic material, a so-called glass ceramic. Under this plate a plurality of heating units 102 are arranged which, like scTiematic indicated by a spring 103 sui the underside the glass ceramic plate are pressed and delimit a hotplate there. The heating units 102 are ready-to-install and units that can be easily dismantled as a whole. Your heating elements, which are arranged relatively firmly in the carrier shell 33 '33' consist of spirally wound tubular heating elements with an approximately triangular cross-section, which are quite flexible in themselves. Lie heating units are in German Offenlegungsschrift 2 205 132 described in more detail. The top the heating elements 33> S5 'is therefore very well connected to the Underside of the glass ceramic plate 101-pressed that the lateral flanges of a support shell 105 »in which the heating elements are arranged, pressed via an elastic intermediate layer 106 to the underside of the glass ceramic plate will. This results in so much leeway that the heating elements even with a rather rigid arrangement within firmly pressed against the carrier shell. The carrier shell has an essentially circular shape and a centering one in the middle and a point of application for the impression forming the spring force.

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The heating elements 33, 33 'are in the example shown designed as two spirally wound hanging sections lying one inside the other, which, however, as can be seen from FIG are connected in parallel. They can also be connected in series. The heating elements can can also be spirally wound from a continuous tubular heating element, in which case a division into two ring areas can be omitted.

Below the heating elements 33} 33 'and above one off The temperature sensor protrudes from the highly heat-resistant insulating material 107 and corrugated aluminum foil 108 13 through the "heating unit 102" parallel to the glass ceramic plate. As can be seen from FIG. it extends in the direction of a diameter, i. H. he goes through the center. It's in the carrier shell 105 held at its beginning and end. This makes all areas of the heating unit as even as possible sensed by the temperature sensor 13. However, it can also be arranged slightly offset from the center, for example to leave space for a temperature sensor 109, indicated schematically in dashed lines in FIG. 5, which controls the controller 35, which in this case is not designed as an energy regulator, but as a temperature regulator. So a certain performance adjustment to the different working conditions could already be achieved from the controller, so that the temperature limiter 11 then only needs to act as an upper limit.

As already mentioned, the temperature limiter 11 works despite the relatively large distance from the glass ceramic plate and the heating elements in between. Above all, the time lag is also great small amount. It has a simple and robust structure,

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and to the heating unit only two supply lines are necessary, in one of which the temperature limiter is switched on is. The temperature limiter is located directly on the heating unit and does not need a separate one Connections and no separate installation. It is insensitive to temperature and is both mechanical and electrical very reliable. Due to its arrangement below the heating elements, it becomes as close as possible to the heating elements occupying area of the hotplate does not require a largely unheated area for the sensor, so that a higher Heat throughput is possible at the same temperature.

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Claims (1)

A 14 919/20 - 12 - Expectations Electric cooking appliance with an upper plate made of vitreous or ceramic material and at least one heating unit arranged underneath with a support shell and heating elements arranged therein and pressed against the glass ceramic plate and with a temperature sensor lying parallel to the glass ceramic plate, characterized in that the temperature sensor (13) _as; a rod-shaped, mechanical expansion member is formed at which the glass ceramic plate (101) side away from the heating elements (33, 33 ') along transversely through the heating unit (102) therethrough extending and acting as a temperature limiter (11) switch (26) for heating the heating elements (33> 33 '), which is arranged in the area of the heating unit (102). 2. Electric cooking appliance according to claim 1, characterized in that that the temperature sensor (13) between the heating elements and an insulation introduced into the carrier bar (105) (107, 108) runs, 3 · Electric cooking appliance according to claim 1 or 2, characterized in that that the straight temperature sensor (13) is arranged almost on a diameter of the round heating unit (102) let. M- ,. Dry cooking appliance according to claims 1 to 3 * characterized in that four temperature sensors (13) are immediate. attacking on the underside of the spirally wound, Ala tubular heating element formed heating elements (33 »33 ') is arranged. 509815/0471 5. Electric cooking appliance according to one of claims 1 to 4, characterized · characterized in that in the temperature limiter one of the Temperature sensor (13) actuatable safety contact (28) is provided, which is significantly exceeded when the the set temperature causes the power supply to be switched off. 6. Electric cooker according to claim 5> characterized in that that the safety contact (28) switches off permanently after the set temperature has been exceeded once of the electric cooker causes. 7. Electric cooking appliance according to one of claims 1 to 6, characterized characterized in that the temperature sensor (13) is a known expansion member with a sleeve (14) and a Rod (15) made of materials with different thermal expansion sko efficient en is provided. 8. Electric cooking appliance according to claim 7 »characterized in that the temperature sensor (13) via an actuating linkage, which consists of a two-armed rocker (16) and a push rod (19) on the actuator (25, 45) for the Contacts (26, 28) acts. 9. Electric cooking appliance according to one of claims 5 to 8, characterized in that work and safety contact (26, 28) are designed as snap contacts with different basic settings. 10. Electric cooking appliance according to claim 9 »characterized in that that working and safety contacts (26, 28) can be actuated by a common snap spring (47). 509815/0471