Abstract:
A gas burner for cooking areas includes a lower part and an upper part. The upper part has gas repulsion ducts with gas outlet openings for gas flames. The upper part is rotatably mounted on the lower part by a compressed-air bearing configured to apply a compressed-air cushion to pneumatically lift the upper part off the lower part for allowing contactless turning of the upper part in relation to the lower part about an axis of rotation. The gas repulsion ducts are formed to drive the upper part in relation to the lower part about the axis of rotation by gas flowing through the gas repulsion ducts at positive pressure. Such a configuration makes it possible to evenly distribute the heat of the flames in the periphery of the burner and to minimize minimum gas burner output by using less flames.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of copending International Application No. PCT/EP99/05713, filed Aug. 6, 1999, which designated the United States. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention lies in the field of household appliances. The invention relates to a gas burner for cooking areas. 
     A gas burner is disclosed in European Patent EP 0 415 049 B1. The burner includes a lower part seated on an upper part and in which gas outlet openings for gas flames are formed. Connected centrally to the underside of the lower part is a feed pipe for the feeding of combustion gas and primary air. 
     Prior art gas burners on the market produce a static flame pattern. The minimum output that can be set is relatively high and is concentrated on small areas in the region of the flames. Such concentration often leads to food burning in a pot that is standing on the gas burner, even when the minimum output is set. The gas flames cannot be made unlimitedly as small as desired, but instead go out below a minimum size, required for maintaining the burning state. 
     U.S. Pat. No. 2,646,788 discloses a gas burner in which the upper part can rotate on the lower part. An additional drive mechanism is required for the driving of the upper part. French Patent No. FR 1 535 256 A describes a gas burner in which the upper part is mounted in the lower part by a perpendicularly disposed spindle. The upper part is able to rotate on the lower part due to horizontally disposed gas outlet openings. The disadvantages of these solutions are not only very complex constructions, in particular, in the case of the mounting or the drive in the U.S. specification, but also that they aim for a maximum burner output, which is based on a better surface area distribution. Such distribution is not possible with these solutions to minimize the burner output, for example, when keeping food warm. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a gas burner for cooking areas that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that distributes the heat of a gas burner over as large a surface area as possible, in particular, when set to the minimum output. Furthermore, the invention is intended to provide a possible way of further minimizing the smallest possible output of gas burners. 
     With the foregoing and other objects in view, there is provided, in accordance with the invention, a gas burner for cooking areas, including a lower part, and an upper part having gas repulsion ducts with gas outlet openings for gas flames, the upper part rotatably mounted on the lower part by a compressed-air bearing configured to apply a compressed-air cushion to pneumatically lift the upper part off the lower part for allowing contactless turning of the upper part in relation to the lower part about an axis of rotation, the gas repulsion ducts being formed to drive the upper part in relation to the lower part about the axis of rotation by gas flowing through the gas repulsion ducts at positive pressure. 
     The gas burner according to the invention has the advantages that it distributes the heat produced by its gas flames under a pot or other utensil more evenly over a larger surface area than the prior art gas burners, in particular, when set to the minimum output (gas burner set to the smallest possible flame size), and that it can be set to a smaller minimum output than prior art gas burners. 
     The gas burner according to the invention is preferably configured such that, when set to the minimum output, only a very small number of individual gas flames are produced. According to the invention, only one to five individual gas flames are preferably provided. These gas flames are set in rotation at low speed, preferably in the range between 20 and 100 rpm. Such rotation achieves the effect that, because of the reduced number of gas flames, the overall output of the burner is reduced, although the length of the individual flame may well be greater than in the case of prior art gas burners. The rotation has the effect that the heat is evenly distributed under a pot or other utensil that is standing on the gas burner. 
     In accordance with another feature of the invention, the axis of rotation is a vertical axis of rotation. 
     In accordance with a further feature of the invention, the gas repulsion ducts are formed to drive the upper part in relation to the lower part in a circumferential direction. 
     In accordance with an added feature of the invention, the gas repulsion ducts are curved and have side walls pointing in a circumferential direction to be driven by the gas flowing at positive pressure about the axis of rotation. 
     In accordance with an additional feature of the invention, the gas repulsion ducts are turbine blade-shaped. 
     In accordance with yet another feature of the invention, the upper part has an outer circumference, the gas repulsion ducts have downstream end portions with gas outlet openings at the outer circumference, and the openings are directed in a circumferential direction and counter to a direction of rotation of the upper part to produce a gas repulsion from emerging gas for driving the upper part about the axis of rotation. 
     In accordance with yet an added feature of the invention, the gas repulsion ducts open downward toward the lower part, the upper part has lands between the gas repulsion ducts, and the lands are configured to support the upper part on the lower part. 
     In accordance with yet an additional feature of the invention, the gas repulsion ducts form the compressed-air bearing. 
     In accordance with again another feature of the invention, the gas repulsion ducts have radially inner, upstream beginnings and downstream ends with gas outlet openings for gas flames, and including a duct disposed in or in a vicinity of the axis of rotation for feeding one of combustion gas and a mixture of combustion gas and air, the duct fluidically connected to the beginnings. 
     In accordance with again an added feature of the invention, the gas outlet openings are disposed in a horizontal plane, the gas repulsion ducts have downstream outlets disposed in another horizontal plane, the gas repulsion ducts have upstream portions, and including a duct for feeding one of combustion gas and a mixture of combustion gas and air, and another duct for feeding air at a positive pressure with respect to the surroundings, the gas outlet openings being fluidically connected with the duct and the upstream portions being fluidically connected with the another duct. 
     In accordance with again an additional feature of the invention, there is provided a compressed-air source for feeding air at a pressure above atmospheric pressure to the gas repulsion ducts. 
     In accordance with a concomitant feature of the invention, the upper part has an increasingly reduced diameter in a downward direction at a region of the gas repulsion ducts, the lower part has a depression having another increasingly reduced diameter in the downward direction matched to the diameter, and the region protrudes into the depression. 
     Other features that are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a gas burner for cooking areas, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view through a lower part and an upper part seated on the lower part of a gas burner according to the invention in a switched-off state; 
     FIG. 2 is a cross-sectional view through the gas burner of FIG. 1 in a switched-on state; 
     FIG. 3 is a bottom plan view of the upper part of the gas burner of FIGS. 1 and 2; 
     FIG. 4 is a cross-sectional view through a lower part and an upper part seated on the lower part of a further embodiment of a gas burner according to the invention in a switched-off state; 
     FIG. 5 is a cross-sectional view through the gas burner of FIG. 4 in a switched-on state; and 
     FIG. 6 is a bottom plan view of the upper part of the gas burner of FIGS.  4  and  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In all the figures of the drawing, sub-features and integral parts that correspond to one another bear the same reference symbol in each case. 
     Referring now to the figures of the drawings in detail and first, particularly to FIGS. 1,  2 , and  3  thereof, there is shown a gas burner according to the invention for cooking areas having a lower part  2  and an upper part  6  (burner cover) rotatably disposed about a vertical axis of rotation  4 . On the underside of the upper part  6  gas repulsion ducts  8  are formed such that the upper part  6  can be driven in relation to the lower part  2  in the circumferential direction about the axis of rotation  4  by high-pressure gas that flows essentially radially outward from the vicinity of the axis of rotation  4  through the gas repulsion ducts  8  and, at the downstream ends of which, leaves from gas outlet openings  10 . The gas can be ignited at the openings  10  to form gas flames. 
     As the view from below of the upper part  6  in FIG. 3 shows, the gas repulsion ducts  8  have a curved shape and side walls pointing in the circumferential direction in the manner of turbine blades, so that they can be driven by the gas flowing at positive pressure about the axis of rotation  4  in the direction of an arrow  14 . The gas repulsion ducts  8  need not be limited to the shape shown in the figures. 
     At the outer circumference of the upper part  6 , the downstream end portions of the gas repulsion ducts  8  and their gas outlet openings  10  are directed in the circumferential direction counter to the direction of rotation  14 , preferably approximately tangentially, in order that gas emerging from the gas outlet openings  10  drives the upper part  6  about the axis of rotation  4  (repulsion effect). 
     The gas repulsion ducts  8  formed in the upper part  6  are open downward toward the lower part  2  and the lands  16  between the gas repulsion ducts  8  can be placed on the lower part  2  to support the upper part on the lower part. 
     The mixture of combustion gas and primary air flowing through the gas repulsion ducts  8  is at such a high pressure that it can lift the upper part  6  off the lower part  2  by a few tenths of a millimeter or a few millimeters and turn it about the axis of rotation  4 . The mixture of combustion gas and primary air under positive pressure forms between the upper part a-d the lower part a gas cushion, on which the upper part  6  rotates contactlessly on the lower part  2 . Consequently, he gas repulsion ducts  8  form a compressed-air bearing. FIG. 1 shows the lower and upper parts  2 ,  6  in a switched-off state, and FIG. 2 shows the parts  2 ,  6  in a switched-on state. 
     The radially inner, upstream ends of the gas repulsion ducts  8  are located above a vertical duct  18  axially disposed with respect to the axis of rotation  4 . The duct  18  can be fed combustion gas  20  through a gas tap  22  that is capable of being opened and closed to a greater or lesser extent by an operating element  24  on an operating panel of a gas cooker, and through a mixing chamber  25 . At the same time, primary air  26  is fed by a blower  28  through the mixing chamber  25  at approximately the same pressure as the combustion gas  20  to the central duct  18 . The gas flames  30  of the mixture of combustion gas and primary air can induct secondary air  32  from their surroundings to improve the combustion. 
     The rotation of the upper part  6  in relation to the non-rotating lower part  2  and the individual gas flames  30  are produced in the following way. Under the gas burner, the combustion gas  20  and the primary air  26  are mixed with the primary air  26  being fed to the mixing chamber  25  at approximately the same pressure as the combustion gas  20 . The pressure for the primary air  26  can be generated by the blower  28  or another suitable device and, if appropriate, can be set. 
     The mixture of combustion gas and primary air flows to the burner head, made of the lower part  2  and the upper part  6 , where it lifts the upper part  6  (burner cover) slightly off the lower part  2 , so that the upper part  6  is floating on the gas-air cushion. 
     The upper part  6  has on its underside grooves that form the gas repulsion ducts  8 . After the mixture of combustion gas and air has been formed, the tangentially deflected gas streams form individual flames  30  that rotate about the axis of rotation  4 . 
     At settings to relatively great burner outputs and at full burn, the rotating upper part  6  (burner cover) lifts off further from the lower part, so that a closed flame ring can form. 
     Depending on the form and shape of the gas repulsion ducts  8 , the upper part  6  is driven for rotation about the axis of rotation  4  only by the repulsion of the gases flowing out of them downstream and/or by the gas acting in a turbine-like manner on the side walls of the gas repulsion ducts. 
     In the further embodiment according to FIGS. 4,  5  and  6 , the same principle is applied as in the embodiment according to FIGS. 1,  2  and  3 , but with the difference that only air at positive pressure is fed to the gas repulsion ducts, without combustion gas, or with only a small proportion of combustion gas, and that the combustion gas is fed to separate gas outlet openings, at which the gas flames are ignited. FIG. 4 shows the lower and upper parts  102 ,  106  in a switched-off state, and FIG. 5 shows the parts  102 ,  106  in a switched-on state. 
     In FIGS. 4,  5 , and  6 , an upper part  106  is rotatably disposed about a vertical axis of rotation  4  on a lower part  102 . Gas repulsion ducts  108  are formed in the upper part  106  such that compressed air  27  flowing through them at positive pressure turns the upper part  106  in relation to the lower part  102  about the axis of rotation  4 . The lower part  102  is disposed in a non-rotating manner. 
     According to FIG. 6, the gas repulsion ducts  108  have a curved shape and side walls pointing in the circumferential direction in the manner of turbine blades. The gas repulsion ducts  8  need not be limited to the shape shown in the figures, so long as the compressed air flowing along the ducts  108  at positive pressure drives the ducts  108  about the axis of rotation  4 . At the outer circumference of the upper part  106 , where the ducts  108  have their air outlet openings  31 , the downstream end portions of the gas repulsion ducts  108  are directed approximately tangentially in the circumferential direction counter to the direction of rotation  114 , so that compressed air leaving them drives the upper part  106  about the axis of rotation  14  in relation to the non-rotating lower part  102  by a repulsion effect. 
     In the cross-section shown in FIGS. 4 and 5, the upper part  106  has on its underside, in the region of its gas repulsion ducts  108 , a lower hemisphere form. The hemisphere region protrudes into a matching hemispherical recess of the lower part  102 . 
     The hemisphere region of the upper part  106  is hollow. The hollow space  35  is provided at the upper end, directly above the air outlet openings  31  for compressed air  27  of the gas repulsion ducts  108 . The hollow space  35  has gas outlet openings  33  for combustion gas  20  or a mixture of combustion gas and primary air for forming at least one individual gas flame  30 . The compressed air of the air outlet openings  31  can be fed as secondary air to the gas flames  30 . The air outlet openings  31 , configured in a ring, lie in a horizontal plane located below another horizontal plane in which the gas outlet openings  33  are configure in a ring. 
     The combustion air  20  or a mixture of combustion air  20  and primary air (corresponding to primary air  26  from FIG. 2) is fed to the hollow space  35  of the upper part  106  through a pipe  37  that is disposed axially with respect to the axis of rotation  4 . The pipe  37  is connected to the lower part  102  and protrudes into the hollow space  35 . The pipe  37  is provided in the hollow space  35  with stops  39  that limit the vertical lifting-off distance of the upper part  106  from the lower part  102 . 
     According to FIGS. 4 and 5, the lower part  102  may include a lower body  103  and an upper body  105 . In this case, it is expedient to pass the compressed air  27  from a compressed-air source  28 , for example, a blower, in the separating plane  41  through an annular duct  107  around the axis of rotation  4  to an axially parallel air duct  109  and from the air duct  109  into the hollow space  35 . Consequently, the compressed air  27  forms a “seal” in the separating plane  41  for sealing off combustion gas that is flowing from an axial duct  21  in the lower body  103  into the pipe  37 . 
     In the embodiment according to FIGS. 4,  5  and  6 , only a compressed-air stream lifts the upper part  106 . A small part of the compressed-air stream serves in the separating plane  41  for sealing off with respect to the combustion gas  20  and, if appropriate, can also be admixed with the combustion gas  20  as primary air, for example, through a gap in the separating plane  41 . The other, far greater part of the compressed air  27  serves not only for lifting and rotating the upper part  106  (burner cover) but also for supplying the gas flames  30  with secondary air. One particular advantage of the embodiment is that the lifting and the rotational speed of the upper part  106  are independent of the amount of combustion gas fed per unit of time and can be set or controlled independently of the combustion gas. The compressed air  27  is intended for lifting and rotating the upper part  106  and can be used as secondary air independent of the geometry of the cooktop formed by the gas burner. 
     The “gas- or air-cushion bearing” can, according to another embodiment, be configured as a hydrostatic bearing or hydrodynamic bearing, as are disclosed in the prior art for other technical fields.