Forced air/gas burner and baking oven incorporating same

Abstract

A ribbon gas burner for use in a baking oven has a row of gas apertures disposed between two rows of air apertures through which air is forced under pressure. The streams of air issuing from the two rows of air apertures are inclined inwardly towards the gas stream, thereby lengthening the ribbon flame produced by the burner and improving the uniformity of heating within the band oven.

What is claimed is: 
     
       1. A baking oven comprising: a housing having walls defining a chamber;   transport means for moving articles to be baked through the chamber; and   a plurality of gas burners mounted within the chamber and spaced from one another, at least one of the gas burners comprising:   a gas supply conduit;   walls defining an elongate gas plenum communicating with the gas supply conduit, and also defining a row of gas apertures spaced from one another along the length of the gas plenum and extending .Iadd.parallel to one another .Iaddend.from the gas plenum to the external surface of the gas burner, such that gas issuing from these gas apertures will burn to produce a .Iadd.substantially planar .Iaddend.flame extending along the length of the gas burner;   an air supply conduit; and   walls defining at least one air plenum communicating with the air supply conduit, and also defining two rows of air apertures extending from the at least one air plenum to the external surface of the gas burner, the two rows of air apertures being disposed on opposed sides of the row of gas apertures, .Iadd.the air apertures in each row extending parallel to one another, .Iaddend.the two rows of air apertures being directed towards the .[.row of gas apertures.]. .Iadd.plane of the gas flame at equal angles in the range of about 10° to about 30° to this plane but from opposed sides of this plane .Iaddend.such that .Iadd.the two jets of .Iaddend.air issuing from the two rows of apertures will impinge .Iadd.symmetrically .Iaddend.upon the flame .[.produced by the gas issuing from the row of gas apertures.]. .Iadd.from opposed sides thereof .Iaddend.and lengthen this flame.   
     
     
       2. An oven according to claim 1 wherein the transport means comprises a belt conveyor extending through the chamber. 
     
     
       3. An oven according to claim 2 wherein the gas burners are disposed with the elongate gas and air plena extending approximately perpendicular to the direction of movement of the conveyor. 
     
     
       4. An oven according to claim 3 wherein the belt conveyor provides a substantially horizontal surface for carrying the articles to be baked, and wherein the gas burners lie approximately parallel to, and above and below, this horizontal surface. 
     
     
       5. An oven according to claim 1 wherein the walls defining the gas plenum comprise an elongate hollow tube, and a strip of the surface of the tube running along the length of the tube is formed from a mesh, the apertures in the strip of mesh constituting the row of gas apertures. 
     
     
       6. An oven according to claim 1 wherein a removable plate is provided in the housing adjacent one end of the at least one gas burner, said plate having a gas inlet aperture, an air inlet aperture and an igniter power inlet aperture passing therethrough, and a transparent window formed therein, the gas supply conduit extends from the gas inlet aperture to the gas plenum, the air supply conduit extends from the air inlet aperture to the air plenum, an igniter is provided adjacent the gas plenum for igniting gas issuing from the apertures in the gas plenum and means for carrying power are provided extending from the igniter power inlet aperture to the igniter. 
     
     
       7. A process for baking dough goods, which process comprises: transporting the dough goods through a baking oven provided with a plurality of gas burners each having a row of gas apertures.Iadd., the row of gas apertures extending parallel to one another.Iaddend.;   supplying gas to the gas burners, whereby a stream of gas passes through the gas apertures and burns adjacent the gas burner .Iadd.to produce a substantially planar flame extending along the length of the gas burner.Iaddend.; and   in at least one of the gas burners, directing two streams of air from opposed sides of the flame produced by the burning gas inwardly towards the flame, .[.each stream.]. .Iadd.the two streams .Iaddend.of air being directed at .[.an.]. .Iadd.equal .Iaddend.acute .[∠]. .Iadd.angles in the range of about 10° to about 30° .Iaddend.to the .[.direction.]. .Iadd.plane .Iaddend.of the gas .[.issuing from the gas apertures.]. .Iadd.flame but from opposed sides of this plane.Iaddend., thereby causing the streams of air to impinge upon and lengthen the flame.   
     
     
       8. A process according to claim 7 wherein the dough goods are transported through the baking oven on a belt conveyor. 
     
     
       9. A process according to claim 7 wherein the gas apertures, and hence the flame, extend approximately perpendicular to the direction of movement of the conveyor. 
     
     
       10. A process according to claim 9 wherein the dough goods are transported on a substantially horizontal surface of the belt conveyor and the gas burners lie approximately parallel to, and above and below, the horizontal surface. 
     
     
       11. A process according to claim 7 wherein the at least one gas burner comprises an elongate hollow tube, and a strip of the surface of the tube running along the length of the tube is formed from a mesh, the apertures in the strip of mesh constituting the gas apertures of the gas burner. .[. 
     
     
       12.  A process according to claim 7 wherein the acute angles between the directions of the gas and air streams are each in the range of about 10° to about 30°..]. .[.13. A process according to claim 12 
     
     
        wherein the acute angles are substantially equal to one another..]. 14. A gas burner for producing a ribbon flame, the gas burner comprising walls defining an elongate gas plenum having the form of an elongate cylinder and also defining a row of gas apertures .Iadd.extending parallel to one another and .Iaddend.through which gas can issue from the gas plenum and burn to produce a .Iadd.substantially planar .Iaddend.ribbon flame, and walls defining at least one air plenum and also defining two rows of air apertures through which air can issue from the air plenum, the air apertures being disposed on opposed sides of the row of gas apertures, the two rows of air apertures being arranged to produce two streams of air inclined inwardly toward the .Iadd.plane of the .Iaddend.gas .[.issuing from the row of gas apertures with the streams of air being directed at acute angles to the stream of gas.]. .Iadd.flame at equal angles in the range of about 10° to about 30° to this plane but from opposed sides of this plane such that the two jets of air issuing from the two rows of air apertures will impinge symmetrically upon the flame from opposed sides thereof and lengthen this flame.Iaddend., said walls defining said air plenum further defining a part-cylindrical recess partially surrounding the cylindrical gas plenum, and a pair of surfaces lying on opposed sides of the row of gas apertures and each lying approximately in a plane including the axis of the cylindrical gas plenum, the angle between the planes of the pair of surfaces which includes the row of gas apertures being an obtuse angle, one of the two rows of air apertures being formed in each of the pair of surfaces. .[.15. A gas burner according to claim 14 wherein the acute angles are each in the range of about 10° to about 30°..]. .[.16. A gas burner according to claim 14 wherein the acute angles are substantially equal to 
     
     
        one another..]. 17. A baking oven comprising: a housing having walls defining a chamber;   transport means for moving articles to be baked through the chamber; and   a plurality of gas burners mounted within the chamber and spaced from one another, at least one of the gas burners comprising:   a gas supply conduit;   walls defining an elongate gas plenum communicating with the gas supply conduit, and also defining a row of gas apertures spaced from one another along the length of the gas plenum and extending .Iadd.parallel to one another .Iaddend.from the gas plenum to the external surface of the gas burner, such that gas issuing from these apertures will burn to produce a .Iadd.substantially planar .Iaddend.flame extending along the length of the gas plenum, the gas plenum having the form of an elongate cylinder;   an air supply conduit; and   walls defining at least one air plenum communicating with the air supply conduit, and two rows of air apertures extending from the air plenum to the external surface of the gas burner, the two rows of air apertures being disposed on opposed sides of the row of gas apertures, .[.and.]. .Iadd.the air apertures in each row extending parallel to one another, the walls .Iaddend.also defining a part-cylindrical recess partially surrounding the cylindrical gas plenum, and a pair of surfaces lying on opposed sides of the row of gas apertures, with each surface lying approximately in a plane including the axis of the cylindrical gas plenum, the angle between the planes of the pair of surfaces which includes row of apertures being an obtuse angle, one of the two rows of air apertures being formed in each of said pair of surfaces, and the two rows of air apertures being directed towards the .[.row of gas apertures.]. .Iadd.plane of the gas flame at equal angles in the range of about 10° to about 30° to this plane but from opposed sides of this plane .Iaddend.such that .Iadd.the two jets of .Iaddend.air issuing from the two rows of air apertures will impinge .Iadd.symmetrically .Iaddend.upon the flame .[.produced by the gas issuing from the row of gas apertures.]. .Iadd.from opposed sides thereof .Iaddend.and lengthen this   
     
     
        flame. 18. An oven according to claim 17 wherein the obtuse angle is in the range of about 120° to about 160°, .Iadd.and .Iaddend.the rows of air apertures extend substantially normal to the pair of surfaces .[.and the row of gas apertures lies substantially in the 
     
     
        plane bisecting the obtuse angle.].. 19. An oven according to claim 18 wherein a strip of the surface of the elongate cylinder running along the length of the elongate cylinder is formed from a metal mesh, the apertures 
     
     
        in the strip of mesh constituting the row of gas apertures. 20. A process for baking dough goods, which process comprises the steps of: transporting the dough goods through a baking oven provided with a plurality of gas burners, each .Iadd.burner .Iaddend.having walls defining an elongate cylindrical gas plenum and .Iadd.also defining a row of .Iaddend.gas apertures .Iadd.extending parallel to one another and through which gas can issue from the gas plenum and burn to produce a substantially planar ribbon flame.Iaddend., and walls defining an air plenum.[.,.]. .Iadd.and .Iaddend.two rows of air apertures from which can issue two streams of air, .Iadd.from the air plenum, the air apertures being disposed on opposed sides of the row of gas apertures, the two rows of air apertures being arranged to produce two streams of air inclined inwardly toward the plane of the gas flame at equal angles in the range of about 10° to about 30° to this plane but from opposed sides of this plane such that the two jets of air issuing from the two rows of air apertures will impinge symmetrically upon the flame from opposed sides thereof, the walls also defining .Iaddend.a part-cylindrical recess partially surrounding the cylindrical gas plenum, and a pair of surfaces lying on opposed sides of the row of gas apertures in the gas plenum and each lying approximately in a plane including the axis of the cylindrical gas plenum, the angle between the planes of the pair of surfaces which includes the row of gas apertures being an obtuse angle, and one of the two rows of air apertures being formed in each of the pair of surfaces;   supplying gas to the gas burners, .[.whereby a stream of gas passes through the gas apertures and burns adjacent the gas burner.]. .Iadd.thereby causing the gas to pass through the gas apertures and form the flame.Iaddend.; and   .[.in at least one of the gas burners, directing two streams of air from opposed sides of the flame produced by the burning gas inwardly towards the flame, each stream of air being directed at an acute angle to the direction of the gas issuing from the gas apertures,.]. .Iadd.supplying air to the air plena of the gas burners, .Iaddend.thereby causing the   
     
     
        streams of air to impinge upon and lengthen the flame. 21. A process according to claim 20, wherein the obtuse angle is in the range of about 120° to 160° .[.,.]. .Iadd.and .Iaddend.the rows of apertures in the gas plenum extend substantially normal to the pair of surfaces.[.and the row of apertures in the gas burner lie substantially in 
     
     
        the plane bisecting the obtuse angle.].. 22. A process according to claim 20 wherein the air is supplied to the air plenum under a pressure in the 
     
     
        range of about 2 to about 8 kPa. 23. A baking oven comprising: a housing having walls defining a chamber;   transport means for moving articles to be baked through the chamber, said transport means comprising a belt conveyor extending through the chamber; and   a plurality of gas burners mounted within the chamber and spaced from one another, at least one of the gas burners comprising:   a gas supply conduit;   an elongate hollow tube defining an elongate gas plenum communicating with the gas supply conduit, said tube containing a row of gas apertures spaced from one another along the length of the gas plenum and extending .Iadd.parallel to one another .Iaddend.from the gas plenum to the external surface of the tube, such that gas issuing from these gas apertures will burn to produce a .Iadd.substantially planar .Iaddend.flame extending along the length of the gas plenum;   an air supply conduit; and   walls defining at least one air plenum communicating with the air supply conduit, and two rows of air apertures extending from the air plenum to the external surface of the gas burner, the two rows of air apertures being disposed on opposed sides of the row of gas apertures, .[.and.]. .Iadd.the air apertures in each row extending parallel to one another, said walls .Iaddend.also defining a part-cylindrical recess partially surrounding the cylindrical gas plenum, and a pair of surfaces lying on opposed sides of the row of gas apertures, with each surface lying approximately in a plane including the axis of the cylindrical gas plenum, the angle between the planes of the pair of surfaces which includes the row of apertures being an obtuse angle, one of the two rows of air apertures being formed in each of said pair of surfaces, and the two rows of air apertures being directed towards the .[.row of gas apertures.]. .Iadd.plane of the gas flame at equal angles in the range of about 10° to about 30° to this plane but from opposed sides of this plane .Iaddend.such that .Iadd.the two jets of .Iaddend.air issuing from the two rows of air apertures will impinge .Iadd.symmetrically .Iaddend.upon the flame .[.produced by the gas issuing from the row of gas apertures.]. .Iadd.from opposed sides thereof .Iaddend.and lengthen this   
     
     
        flame. 24. An oven according to claim 23 wherein a removable plate is provided in the housing adjacent one end of the at least one gas burner, said plate having a gas inlet aperture, an air inlet aperture and an igniter power inlet aperture passing therethrough, and a transparent window formed therein, the gas supply conduit extends from the gas inlet aperture to the gas plenum, the air supply conduit extends from the air inlet aperture to the air plenum, an igniter is provided adjacent the gas plenum for igniting gas issuing from the apertures in the gas plenum and means for carrying power are provided extending from the igniter power inlet aperture to the igniter.