EP0818655B1 - Method and device for controlling the size of the flame of a gas cooking apparatus - Google Patents

Description

The invention relates to a device and a corresponding Method for controlled gradual reduction of a burner nozzle of a gas-operated cooking or baking device via a gas supply supplied gas stream Q.

Common cooking or baking devices, for example gas stoves, Gas hobs, gas hobs or gas ovens, have one or more burners in which the gas is mixed with atmospheric oxygen and burned. The gas supply to the burner is via a gas supply line from a gas pipeline network, a gas tank or a gas bottle is supplied with gas. With a city gas pipeline network the feed pressure is approx. 8 mbar; he however, is subject to fluctuations and can reach 4 mbar decline. For cooking and baking equipment operated with camping gas the feed pressure is approx. 50 mbar.

The burners have a burner nozzle that is connected the burner to the gas supply line the relevant, the flow resistance limiting the outflowing gas flow forms and thus the maximum heating power of the Brenners determined. The flow resistance in the gas supply line can usually be neglected become. The maximum heating output of the burner must, however in practical use by the user at the moment required heating power can be reduced. The reducing the heating power must therefore be with the help of a suitable one Control anytime, easily and on a value as close as possible to the desired or required Heat output can be carried out.

To reduce the heating output of the burner, after state of the art conventional continuous Control valves used. By partially closing the Valve is throttled the gas flow and the desired Gas flow rate and thus the desired heating output set. In most cases this is done Manual adjustment of the valves. The setting accuracy the valve is relatively small. Furthermore show such proportional valves also a hysteresis in the control behavior, so the flow rate doesn't just depend on the position of the valve or the display on the associated setting button depends, but also in what direction the valve for setting the desired flow rate is actuated (i.e. opened or closed) and how long the previous adjustment path is.

For this reason, the operator orientates himself in everything Usually not on the scale assigned to the valve, but changes the position of the valve until the desired one Heat output, which is based on the size of the flame or judge the cooking or baking behavior of the dishes can, is achieved. By including this Scale differences compensating operator in the Control of the heating power can be accepted that the setting accuracy and reproducibility of the gas flow are very small and therefore the flame size and the heating output with the same setting of the controller or the scale can be significantly different.

In applications where an automatic or motorized Setting the gas flow is desired it is known to adjust the valves stepper motors too use that are controlled by a control circuit. However, this solution is technically very complex and expensive. The problem also arises here that the proportional or available Valves show hysteresis behavior so that when activated a certain valve position by means of Stepper motor depending on the control direction and control path length Differing gas flows result. So be in these cases also in the respective settings no heat outputs assigned in a reproducible manner achieved.

From document DE 4225789 A1 is a measuring and testing device for the one-time setting and adjustment of a Gas heater known in the two in a row switched gas pressure regulator, a programmable logic controller Control with the necessary for the respective adjustment cases Working characteristics and four pressure gauges provided are. There are also a number of parallel branches provided, each from a series connection a solenoid valve and a reference nozzle. To adjust the gas flow for the adjustment of the Gas heater is only one of the branches open; only in exceptional cases is by optional Parallel connection of several nozzles a certain gas throughput achieved. This known device is technical very complex, so that they are in the context of production control to adjust an adjustable throttle or an adjustable gas device pressure regulator of a gas heater suitable, but not for permanent adjustment the heating capacity of a gas-powered cooking or Baking device by the user.

From the patent US-4,585,161 is a forced draft burner known in which two continuously adjustable Control valves and a balance controller the amount and that Ratio of gas and combustion air can be controlled. To the adjustable control valve in the gas supply another, controllable auxiliary valve connected in parallel. The degrees of opening are controlled by means of a control device of the gas valve and the auxiliary valve to achieve a constant gas flow regulated. There are sensors for this required to measure gas flow rates.

From document CH-303445 is an adjustable gas burner known a gas stove, in which by means of several side-by-side, switchable nozzles one and the same Mixing tube of the gas burner is fed. The single ones Nozzles are turned on and off by a common tap switched off, the intermediate stages by throttling by means of one upstream of the individual nozzles Cross-sectional narrowing can be realized.

A gas regulator is known from document FR-911.892, which is a series of openings with different diameters has, of which at a desired heating level exactly one for the gas flow is opened.

The present invention takes this state into account the technology based the task, a device and a method for controlled reduction of a burner nozzle a gas-powered cooking or baking device to create a gas feed line Q, by means of which the gas flow through the user of the device adjustable in steps reproducible with high accuracy is. After other aspects, it is desirable that the method and the device are technically inexpensive are feasible, easy to use and durable work reliably.

The invention is based on the consideration, a number provide throttle elements, by means of which a through the burner nozzle and the connection pressure given, maximum Gas flow can be reproduced in stages in a defined manner can be reduced. To switch the on and off The function of the respective throttle elements are switching elements to provide the gas flow through each Can turn throttle element on and off. Through the Combination of certain switching elements switched on and off can then achieve a defined reduction in the gas flow be performed or if all throttling elements are open, the maximum gas flow is achieved become.

The idea of the invention can be connected in series of throttle elements in practice.

To achieve the above object in a method and a device of the type mentioned proposed according to the invention that the gas flow Q a Number n of control elements connected in series in the gas supply line passes through, each with a throttle element Throttling the gas stream flowing through it and a Throttle element switching element connected in parallel to Switching a bypass on and off to the throttle element have, and the switching elements optionally, depending on the desired heating output, can be switched on and off. Mixed forms are also possible in which throttle elements connected in parallel as well as in series are.

The control bodies can in principle the function of Switching element and that of the throttle element in one Realize assembly, for example in the form of an electromagnetic actuated binary throttle valve, the has a closed and a throttle position. In this In this case, the control members each comprise a switching element and a throttle element in the sense that they are these elements Realize in a single control at the same time.

In general, however, it will be more advantageous to use the Switching elements and the throttle elements in separate components to realize a high reproducibility of the set gas flow or an inexpensive embodiment to realize. By separating the tax organs into a switching element and a separate throttling element it is possible, depending on suitability, costs, Accuracy, security, etc. for the respective function to use particularly suitable components.

The switching elements are individually by hand, using a respective control device or advantageously by means of a common control device on and off. In the most general case there is a number n of control devices provide with which each switching element can be switched on and off individually. For simplification operation, however, it is particularly advantageous one for the switching elements of a burner nozzle, provide common control device, each has different switching levels to which the by the combination of the switching elements corresponding gradations are assigned to the gas flow. By setting the control device, for example the associated one Controller or by pressing the corresponding step key, a certain switching level is selected, and the Control unit combines the corresponding switching elements to generate the preselected one to be fed to the burner nozzle Gas stream.

In order to create a manageable simple and safe operation option create, it is proposed that the control device an integer number i discrete for the n switching elements Has switching positions, each one Combination of the open and closed positions of the n Switching elements is assigned. The control device can for example a rotary or tap changer, a control panel with buttons assigned to the respective switching positions are, or preferably also a "touch control panel", a switch that can be operated by touch his. In this case, the user does not have to look around the individual control of the individual switching elements to take care of, since the control device the selected switching stage automatically in the appropriate manner in the corresponding Combination of open and closed switching elements implements.

It can be advantageous if the number i of the switching positions the control device is smaller than the number the various realizable with the switching elements Gradations of the gas flow, for example, if not all levels for practical use are necessary. For example, it may be desirable be a fine gradation in the area of advanced cooking, in the other areas, however, a coarser gradation to provide the total number of adjustable levels in to keep practically reasonable limits.

For simple, manageable operation, it is advantageous if the combinations of the open and closed positions of the n switching elements are assigned a sequence of n = 1, 2, 3,..., I consecutive switching positions S _{m of} the control device such that the gas flows Q _m fed to the burner nozzle form an ascending or descending sequence in the respective switching position S _m . In this case, the closest higher or lower heating level is set by increasing or decreasing the switch position, i.e. a monotonous adjustment option is achieved.

According to a preferred feature, it is proposed that the number i of the switching positions of the control device is 2 ⁿ , the switching positions being assigned exactly one of the possible combinations of the open and closed positions of the n switching elements. In this case, the maximum possible number of gradations must be realized. It is particularly advantageous if the sequence of m = 1, 2, 3,..., 2 ⁿ successive switching positions S _{m of} the control device is assigned to the combinations of the open and closed positions of the n switching elements in such a way that the gas flows Q _{m form} an ascending or descending sequence which essentially assumes the values Q _m = Q _max * (m-1) / (2 ⁿ -1). Here, uniform gradations of the heating power are realized by means of the control device for successive switching positions, as known to the user of electronically controllable electric stoves and electric hobs. The above-mentioned requirement with regard to a uniform gradation of the adjustable heating powers will, however, generally be difficult to meet with a series connection of throttle elements.

For technical reasons there is a certain tolerance-based deviation of the set gas flow from the target value, which can however be accepted under practical conditions. Accordingly, it is proposed according to a further advantageous feature is that the maximum deviation of the switching positions S _m assigned sums Q _m of the partial gas streams Q _k from the exact graduation less than ± 20%, preferably less than ± 15%, preferably less than ± 10%, and is particularly preferably less than ± 5%.

The switching elements can in principle in any way are operated, for example mechanically, pneumatically or hydraulic. According to a particularly preferred feature it is proposed that at least one switching element, preferably all switching elements can be actuated electrically.

The switching elements can be in an advantageous embodiment binary solenoid switching valves that are open and have a closed position. Such solenoid valves are known and fulfill those to be placed on them safety requirements. With such solenoid switching valves it is, as is generally the case with electrical actuatable switching elements, for an additional Feature of advantage if that occurring during the switching process Clacking is prevented or dampened. To this Purpose can open the electrical control signal and / or closing the switching element, at least in the area of the switching point, be edge-controlled, so that the switching process is not abrupt. advantageously, is therefore an electrical circuit for gradual Increase and / or decrease the electrical Control current provided.

For a long service life and operational reliability of the invention It is advantageous that the device Carry out switching elements only a few switching cycles, namely only if the setting of the gas flow Q is changed becomes. Therefore, if at all, they are only subject to a very long-term wear.

In more complex embodiments, the flow resistance of the throttle elements in the factory or, if necessary be adjustable by the user. Come for this for example adjustable throttle valves in question a calibration option for setting and adjusting of their choke resistance to a desired value. This can be beneficial if it is on the Achieving a high degree of accuracy of the gradations or of the set partial gas flows arrives, which then through exact setting and exact adjustment of the throttle elements is feasible. According to a preferred one, for the usual accuracy requirements to be set in practice sufficient feature is suggested that one, several or preferably all throttle elements one have predetermined flow resistance. The Throttle elements can be used, for example, as capillaries, capillary tubes, Nozzle or pipe constriction can be realized. These embodiments are with satisfactory accuracy to implement inexpensively.

The advantages of a device and a method according to this invention over the prior art in that by means of known and commercially available components a desired, gradual reduction in gas flow rate a very high degree of reproducibility can be realized so that at the respective Setting the assigned control device reliably the same heating output is achieved. The control the device through controls can with a using inexpensive, commercially available components Control device take place. Another advantage is to see that the invention also exclusively with binary switching elements, i.e. without proportional valves is executable.

It should be noted that pressure fluctuations by the invention are not compensated in the gas supply line and consequently also affect the heating output. The In this respect, invention does not solve the problem in absolute terms reproducible gas flows and heating outputs realize, but solves the problem, a given maximum gas flow in a reproducible way to smaller ones Grading values. If the maximum gas flow is conditional due to network pressure fluctuations, will also change the reduced, graded gas flows accordingly to change. The reproducibility of the setting remains intact. In view of the fact that Network pressure fluctuations only affect the Affect heating power, only gradually and the changes in the heating output due to this accepted the conventionally used tap valves the invention represents a significant improvement compared to the prior art for reproducible, controlled reduction of the gas flow. If necessary the device according to the invention can also with a device that allows fluctuations in gas pressure the gas supply line compensated or reduced, combined become.

The following embodiment of the invention leaves others recognize advantageous features and peculiarities, the based on the schematic representation in the drawing are described and explained in more detail below.

Fig. 1

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung mit drei in Reihe geschalteten Drosselelementen mit Bypass.

It shows:

Fig. 1

is a schematic representation of a device according to the invention with three throttle elements connected in series with bypass.

Fig. 1 shows one of a gas pipeline network, a gas tank or a gas bottle supplied gas supply line 1 for the supply of gas controlled according to the invention to a Burner nozzle 3, which is part of a burner 2, the e.g. built into a gas stove or gas oven can be. Those for gas-powered are not shown Cooking and baking devices usual security elements (Thermocouple and associated solenoid valve) that the When the flame goes out, interrupt the gas flow.

In the embodiment according to FIG. 1 there are three throttle elements 15, 25 and 35 connected in series in the gas supply line 1. The throttle elements 15, 25 and 35 are capillaries, which have a fixed flow resistance exhibit. The choke resistances of the individual choke elements are preferably different. For example, you can be dimensioned so that the burner nozzle 3 of the burner 2 supplied via the burner feed line 5 Gas flow by switching on one throttle element is reduced to 3/4 or 1/2 or 1/4. When switching the gas flow is from two or three throttle elements on one by the product of the above shares given part of the maximum gas flow reduced.

For switching the respective throttle elements on and off these are switching elements 14, 24 and 34 in parallel connected. When opening a switching element, the flows Gas flow unhindered by that acting as a bypass 16, 26, 36 Switching element, so that the associated throttle element does not reduce the gas flow. For example when opening the switching element 24, the throttling the throttle element 25 out of function and the gas flow provided the throttle elements 14 and 34 are closed are throttled only by the throttle elements 15 and 35.

The switching elements 14, 24 and 34 are common Control device 4 controlled by means of which the desired Heating power is adjustable. To switch off of the gas flow is an additional one, in the burner supply line 5 or preferably the gas supply line 1 used Switching valve, which is not shown, required. This can be done, for example, to monitor the Extinguishing the flame uses existing solenoid valve become.

In the illustrated preferred embodiment all three switching elements electrically operable binary Solenoid switching valves that have an open and a closed position have a bypass either one or can be switched off. That independently of each other opening and closing of the solenoid switching valves is controlled by the control device 4.

Claims (14)

1. Device for controlled, step-wise reduction in the gas flow Q fed by way of a gas feed duct (1) to a burner nozzle (3) of a gas-powered cooking or baking appliance, characterised in that it comprises a number n of control elements which are connected in series in the gas feed duct (1) and the control elements each comprise a respective throttle element (15, 25, 35) for throttling the gas flow flowing therethrough and a respective switching element (14, 24, 34), which is connected in parallel with the throttle element (15, 25, 35), for switching on and switching off a bypass (16, 26, 36) to the throttle element (15, 25, 35), the switching elements being selectably switchable on and off in accordance with the respectively selected heating power.
2. Device according to claim 1, characterised in that the switching elements (11, 21, 31, 41; 14, 24, 34) are switchable on and off by means of a common control device (4).
3. Device according to claim 2, characterised in that the control device (4) comprises an integral number i of discrete switching settings, with each of which there is associated a respective combination of the open and closed settings of the n switching elements (11, 21, 31, 41; 14, 24, 34).
4. Device according to claim 3, characterised in that the number i of the switching settings of the control devices (4) amounts to 2ⁿ, wherein exactly one respective one of the possible combinations of the open and closed settings of the n switching elements (11, 21, 31, 41; 14, 24, 34) is associated with each of the switching settings.
5. Device according to claim 4, characterised in that a sequence of m = 1, 2, 3, ..., 2ⁿ of successive switching settings S_m of the control device (4) are associated with the combinations of open and closed settings of the n switching elements (11, 21, 31, 41; 14, 24, 34) in such a manner that the gas flows Q_m fed to the burner nozzle (3) form an ascending or a descending sequence which substantially adopts the value Q_m = Q_max · (m-1)/(2ⁿ-1).
6. Device according to claim 5, characterised in that the maximum deviation of the gas flows Q_m from the precise steps is less than ± 20%, preferably less than ± 15%, preferably less ± 10% and particularly preferably less than ± 5%.
7. Device according to claim 1, characterised in that at least one switching element (11, 21, 31, 41; 14, 24, 34) is constructed as a binary magnetic switching valve.
8. Device according to claim 1, characterised in that it comprises an electric circuit for gradual increase and/or reduction in the electric control current of the switching element (11, 21, 31, 41; 14, 24, 34).
9. Device according to claim 1, characterised in that at least one of the throttle elements (12, 22, 32, 42; 15, 25, 35) comprises a fixedly preset flow resistance.
10. Device according to claim 9, characterised in that the throttle element (12, 22, 32, 42; 15, 25, 35) is constructed as a capillary, capillary tube, nozzle or pipe constriction.
11. Cooking or baking appliance, especially a gas oven, a gas cooking field, a gas cooking hob or a gas baking oven, characterised in that it comprises a device according to one or more of claims 1 to 10.
12. Method for controlled step-wise reduction in the gas flow Q fed by way of a gas feed duct (1) to a burner nozzle (3) of a gas-powered cooking or baking appliance, characterised in that the gas flow Q flows through a number n of control elements connected in series in the gas feed duct (1), the control elements each comprising a respective throttle element (15, 25, 35) for throttling the gas flow flowing therethrough and a respective switching element (14, 24, 34), which is connected in parallel with the throttle element (15, 25, 35), for switching on and off a bypass (16, 26, 36) to the throttle element (15, 25, 35) and the switching elements being selectively switched on and off in accordance with the respectively selected heating power.
13. Method according to claim 12, characterised in that the n switching elements (11, 21, 31, 41; 14, 24, 34) are switched on and off by means of a common control device (4).
14. Method according to claim 13, characterised in that the n switching elements (11, 21, 31, 41) are controlled by a control device (4) which comprises an integral number i of discrete switching settings, with each of which there is associated a respective combination of the opening and closed settings of the n switching elements (11, 21, 31, 41).

Images