Gas cooking equipment and method for producing gas cooking equipment

A control system for adjusting the heat output of at least one gas burner. The control system including at least one control organ in a gas main line feeding the gas burner for adjusting the gas throughput supplied to the gas burner nozzle. The control system further including at least one secondary line in parallel with the control organ with a shut-off organ for opening and closing the secondary line. The secondary line having a lower flow resistance than the flow resistance in the control organ line.

The present invention relates to gas cooking equipment and a method for producing the same. The gas cooking equipment has at least one gas burner and a control system for adjusting the heat output of the gas burner. The control system further has at least one control organ in a gas main leading to the gas burner which adjusts a gas throughput supplied to a burner nozzle and at least one secondary line running parallel to the control organ with an allocated shut-off organ for opening and closing the secondary line.

A generic cooking apparatus having a valve control arrangement in a gas supply pipe to a gas burner is known from EP 0 818 655. In the valve control arrangement the gas supply pipe branches into a number of part gas pipes switched in parallel, which are connected to the burner nozzle. A control valve for switching on and off the part gas stream flowing therethrough and a choke element for throttling the part gas stream flowing therethrough are arranged in each part gas pipe. A defined reduction of the gas flow can be implemented by combining certain switching elements which have been switched on and switched off. The maximum gas flow is achieved when all the choke elements are open.

The object of the present invention is to provide gas cooking equipment or a method for producing gas cooking equipment with at least one gas burner whose control system allows reliable operation of the burner.

The present invention provides gas cooking equipment having at least one secondary line switched in parallel to a control organ with the secondary line having a flow resistance which restricts the gas throughput in the secondary line. Said flow resistance is constructed as lower than the flow resistance formed by the burner nozzle. A pressure loss in the gas flow through the secondary line is thus substantially reduced. The substantially reduced pressure loss when the secondary line is open results in an improved primary air intake in the area of the burner nozzle. The flame formation at the gas burner is therefore substantially more reliable at high gas flow rates.

The flow resistance in the secondary line can be determined in various ways. In a simple realisation of the invention from the point of view of production technology, the determining flow resistance which restricts the gas throughput is determined by the smallest transmission cross-section in the secondary line. The smallest transmission cross-section in the secondary line is thus larger than the transmission cross-section of the burner nozzle.

It is advantageous if the secondary line is only opened to adjust the maximum gas throughput during operation of cooking equipment. The secondary line is therefore not used to adjust the part gas throughputs. In this case, the flow resistance in the secondary line can be reduced to a negligible amount compared with the flow resistance in the gas main. Thus, regardless of whether the control organ arranged in the gas main is opened or closed, the maximum gas throughput is always set when the secondary line is open.

The control system can preferably have a number of control lines switched in parallel to one another with corresponding control or regulating organs. These branch off the gas main and can each supply a part gas throughput to the burner nozzle. Compared to conventional gas taps, no hysteresis effects are obtained with such a control system. The control lines switched in parallel make it possible to adjust the part gas throughput substantially more accurately. The maximum gas throughput is set when all the control lines of the control system are opened. In this case, however, the pressure loss in the control system is substantially higher than that when a conventional completely opened gas tap is used. In this control system in particular, the pressure loss at maximum gas throughput can be effectively reduced by the secondary line according to the invention.

A control valve with an associated control choke can be provided in each of the control lines as shut-off or regulating organs. The control choke is used to restrict the gas throughput to a part gas throughput. In contrast to a proportional valve with continuous adjustment, the control valve merely has one closed and one opened position.

In order to reduce the flow resistance in the secondary line, the number of inserts in the secondary line, possibly the number of shut-off, control or regulating organs, is restricted to merely one unthrottled shut-off organ.

For reasons of space it is advantageous if the control lines are brought together in a housing, for example, a valve block. The secondary line can advantageously be integrated in the housing of the control system. Assembly of the control elements or choke elements at the works is simplified if the choke elements are inserted in mounting openings of the control lines in the housing of the control system such that they can be removed.

In a particularly simple method of manufacturing the control system from the production technology point of view, a conventional valve block having a number of control lines is first manufactured. Choke elements are inserted in the control lines, with the exception of at least one control line. The unthrottled control line forms the secondary line according to the invention.

Instead of a choke element, the mounting opening of the unthrottled control line can be closed by a non-throttling closure element. Alternatively, a choke element can be mounted in the unthrottled control lines of the valve block, the transmission cross-section of said choke element being larger than the transmission cross-section of the burner nozzle. From the production technology point of view, it is especially advantageous if the mounting opening in the unthrottled control line is completely dispensed with when manufacturing the valve block.

A gas burner1belonging to a gas cooking apparatus is shown highly schematically inFIG. 1. Said gas burner is connected via a gas main3to a gas pipe network. A control system5is arranged in the gas main3. A gas throughput to the gas burner1is adjusted by means of the control system5according to a desired heat output of the gas burner1. Not shown are the usual safety elements for the gas cooking equipment such as a thermocouple and a relevant magnetic valve for shutting down the gas burner for safety when a flame goes out.

The control system5has three control lines7,9,11switched in parallel and a secondary line13switched in parallel thereto. Both the control lines7,9,11and the secondary line13branch off from the gas main3and then combine again to form a burner intake pipe15. Said intake pipe opens into a burner nozzle14. An electrically actuated magnetic control valve is arranged in each of these lines7,9,11,13. The magnetic control valves17can be switched from a closed position into an open position and can be controlled by means of an electronic control device21via signal leads19. A user can adjust heat output stages of the gas burner1via the control device21. As is described subsequently with reference toFIG. 2, a part gas throughput Q1to Q7Up to a maximum gas throughput Q8can be adjusted according to the selected heat output stage.

The control device21can control the magnetic control valves17independently of one another. The magnetic valves17arranged in the control lines7,9,11are followed by choke elements23,25,27. The diameter d1of each choke element23,25,27indicated inFIG. 6determines its transmission cross-section. The diameters d1in the control lines7,9,11are designed as substantially smaller than a transmission cross-section of the burner nozzle14. Thus, in the present case the diameter of the burner nozzle14is about 0.5 mm. The choke diameter d1of the choke elements23,25,27lies between 0.1 and 0.3 mm.

Unlike the control lines7,9,11, the secondary line13is unthrottled. As a result, the flow resistance in the unthrottled secondary line13is reduced as far as possible. Compared to the control lines7,9,11, the pressure loss by the open secondary line13is negligible. When the secondary line13is open, the maximum gas throughput Q8is thus passed through the secondary line13without greater loss of pressure. In order to reduce the flow resistance, the transmission cross-section in the secondary line13is made substantially larger than the transmission cross-section of the burner nozzle14.

The transmission cross-sections of the choke elements23,25,27are designed at the works. In the present case, when the control lines7,9,11are open, about 65% of the maximum gas throughput is supplied to the burner nozzle14. In this case, the first choke element23transmits about 20%, the second choke element25transmits about 24% and the third choke element27transmits about 30% of the maximum gas throughput. By combining the open and closed positions of the magnetic valves17in the three control lines, eight (i.e., 23) heat output stages with the different part gas throughputs 0 and Q1to Q7are obtained by means of the three control lines7,9,11. The heat output stages can be adjusted by means of the electronic control device21. The part gas throughputs Q1to Q7are obtained from the flow characteristic of the control system5shown inFIG. 2. If the user selects the eighth heat output stage, the electronic control device21opens the magnetic valve17in the secondary line13. The maximum gas throughput Q8to the burner nozzle14is thereby set.

According to the flow characteristic inFIG. 2, the part gas throughputs Q1to Q7of the heat output stages1to7increase almost linearly up to about 62%. After the magnetic valve17in the secondary line13has been switched to the open position, an over-proportional jump of the heat output takes place from Q7to the maximum gas throughput Q8. The over-proportional increase from the part gas throughput Q7to the maximum gas throughput Q8yields approximately an exponential profile of the flow characteristic. Such an exponential profile is especially advantageous from the application technology point of view.

The design configuration of the control system5is explained in the followingFIGS. 3 to 6. Consequently, both the control lines7,9,11and also the secondary line13are integrated in a housing33formed as a compact valve block. The valve block33made of plastic has a hemispherical inlet connection35on one side when viewed from the side. Said valve block sits in positive contact on an outer circumference of the gas main3constructed as a pipe. The gas main3is pressed in a gastight fashion onto the inlet connection35by means of retaining clips which are not shown. An outlet connection37is constructed on the valve block33opposite to the inlet connection35. The burner intake pipe15is inserted in a gastight fashion in the outlet connection37. Four magnetic valve heads39of the magnetic valves17are further mounted in the valve block33according toFIG. 3. The choke elements23,25,27are shown inserted in the valve block on the opposite side.

FIG. 4shows a side sectional view of the valve block33. The area of the inlet connection35,37is shown in a first sectional plane X. The central area of the valve block33between the inlet and outlet connection35,37is shown parallel thereto in a second sectional plane Y. The area of the outlet connection37is shown in a third sectional plane Z. It can be deduced fromFIG. 4that horizontal blind holes41,43oppositely directed to one another run in the valve block33. Said holes each open into the inlet connection35and into the outlet connection37of the valve block33and are aligned parallel to one another. The control lines7,9,11connect the blind inlet hole41to the blind outlet hole43.

In detail each of the control lines7,9,11has a valve channel45. The valve channel45runs perpendicular to the horizontal blind holes41,43. One end of the valve channel45opens into a circular recess51which is worked into the valve block33. The circular recess51forms a valve seat for a valve disk53of the magnetic valve head39, as indicated by the dashed lines inFIG. 4. In addition, a small-diameter first transmission channel55, which leads to the blind inlet hole41, opens into the recessed valve seat51as shown inFIGS. 5 and 6. At the same time, the valve channel45is in communication with the blind outlet hole43by means of a second transmission channel57. Each of the control lines7,9,11running between the blind holes41,43is consequently formed by the first transmission channel55, the valve channel45and the second transmission channel57.

In the closed position of the magnetic valves17the valve disk53of the magnetic valve heads39lies on the recessed valve seat51. The valve channel45of the corresponding control line is thereby closed whereby the control line as such is closed. In the open position of the magnetic valve17the valve disk55is not in contact with the valve seat51. In this case, the corresponding control line is open.

Opposite to the recessed valve seat51each of the valve channels45opens into a mounting opening59. The choke elements23,25,27can be mounted in the mounting opening59, as is indicated inFIG. 6. According toFIG. 6, the choke element25is constructed as an insert nozzle. Said nozzle can be screwed into the mounting opening59of the valve channel45.

The configuration of the secondary line13in the valve block33is explained with reference toFIG. 5. Like the control lines7,9,11the secondary line13runs inside the valve block33. The secondary line13is formed in accordance with the control lines by the first transmission channel55, the valve channel45and the second transmission channel57. Unlike the control lines, however, the secondary line13is unthrottled, i.e., no insert nozzle25is arranged in the secondary line13. The largest possible transmission cross-section in the secondary line13is thereby achieved. In the secondary line the flow resistance which restricts the gas throughput is formed by the first transmission channel55. The diameter d2of the transmission channel55is about 1.5 to 2 mm. The diameter d2of the first transmission channel55is thus considerably larger than the diameter of the burner nozzle14.

Instead of an insert nozzle, a closure element61is inserted in the mounting opening59of the secondary line13according toFIG. 5. This closes the mounting opening59without throttling the secondary line13. Alternatively thereto, the closure element61can be omitted if the mounting opening is completely dispensed with in the secondary line13when the valve block33is manufactured at the works. In this case, the secondary line13is closed in the area of the mounting openings59in the valve block33without the secondary line13being throttled.

With the present control system it is also possible to achieve small continuous heat outputs at the gas burner1by cyclically switching on and off the magnetic valves17of the control lines7,9,11. It is advantageous that re-ignition can take place reliably at any pre-set heat output with the control system5.

Heat output stages