Tubular burner

Abstract

A flame hole member of a tubular burner has a front plate and a rear plate both of sheet metal make. The front plate has a first flame hole in the central portion of the front plate, and a plurality of second flame holes located around a periphery of the first flame hole, each of the second flame holes being of a slit shape in a width below a quenching distance. The rear plate has a first ventilation hole in the central portion of the rear plate, and a plurality of second ventilation holes of smaller diameter than the first ventilation hole, each of the second ventilation holes being located around a periphery of the first ventilation hole. At least one of the rear plate and the front plate is provided with a cylindrical section for introducing into the first flame hole.

What is claimed is: 
     
         1 . A tubular burner comprising:
 a mixing tube inclusive of an inlet port, at a rear end thereof, into which a fuel gas and primary air flow, a venturi section having a smaller diameter than a diameter of the inlet port, and a tapered tube section having a gradually larger diameter from the venturi section toward a front of the mixing tube; and   a flame hole member having a plurality of flame holes and being adapted to be fitted into a front end region of the mixing tube such that a mixture of the fuel gas and primary air is ejected through the flame holes for combustion,   the flame hole member being made up of a front plate of sheet metal make, and a rear plate of sheet metal make located behind the front plate,   the front plate having a first flame hole in a central portion of the front plate, and a plurality of second flame holes located around a periphery of the first flame hole, each of the second flame holes being of a slit shape in a width below a quenching distance,   the rear plate having a first ventilation hole in a central portion of the rear plate, and a plurality of second ventilation holes of smaller diameter than the first ventilation hole, each of the second ventilation holes being located around a periphery of the first ventilation hole,   at least one of the rear plate and the front plate having disposed therein a cylindrical section for introducing into the first flame hole the mixture of the fuel gas and primary air flowing into the first ventilation hole.   
     
     
         2 . The tubular burner according to  claim 1 , wherein a rear region of the cylindrical section is gradually reduced in diameter from the first ventilation hole forward, and wherein the cylindrical section in front of the rear region is formed into a cylindrical shape of smaller diameter than the first ventilation hole. 
     
     
         3 . The tubular burner according to  claim 1 , wherein a length of the cylindrical section is equivalent to a longitudinal distance between the rear plate and the front plate. 
     
     
         4 . The tubular burner according to  claim 1 , wherein the cylindrical section is disposed in the rear plate, and wherein a diameter of the first flame hole is larger than an inner diameter at the front end of the cylindrical section. 
     
     
         5 . The tubular burner according to  claim 1 ,
 wherein the second flame holes are of slit shape elongated in a radial direction of the front plate,   wherein a plurality of inner second flame holes are formed in a portion, closer to the first flame hole, of the front plate at a circumferentially equal pitch, and   wherein a plurality of outer second flame holes are formed while being circumferentially deviated by half a pitch from the inner second flame holes so that the outer second flame holes are located between: such an intermediate portion in the front plate as is located in a diametrically inner end and a diametrically outer end of the inner second flame holes; and such a portion in the front plate as is located diametrically outward of the diametrically outer end of the inner second flame holes.   
     
     
         6 . The tubular burner according to  claim 2 ,
 wherein the second flame holes are of slit shape elongated in a radial direction of the front plate,   wherein a plurality of inner second flame holes are formed in a portion, closer to the first flame hole, of the front plate at a circumferentially equal pitch, and   wherein a plurality of outer second flame holes are formed while being circumferentially deviated by half a pitch from the inner second flame holes so that the outer second flame holes are located between: such an intermediate portion in the front plate as is located in a diametrically inner end and a diametrically outer end of the inner second flame holes; and such a portion in the front plate as is located diametrically outward of the diametrically outer end of the inner second flame holes.   
     
     
         7 . The tubular burner according to  claim 3 ,
 wherein the second flame holes are of slit shape elongated in a radial direction of the front plate,   wherein a plurality of inner second flame holes are formed in a portion, closer to the first flame hole, of the front plate at a circumferentially equal pitch, and   wherein a plurality of outer second flame holes are formed while being circumferentially deviated by half a pitch from the inner second flame holes so that the outer second flame holes are located between: such an intermediate portion in the front plate as is located in a diametrically inner end and a diametrically outer end of the inner second flame holes; and such a portion in the front plate as is located diametrically outward of the diametrically outer end of the inner second flame holes.   
     
     
         8 . The tubular burner according to  claim 4 ,
 wherein the second flame holes are of slit shape elongated in a radial direction of the front plate,   wherein a plurality of inner second flame holes are formed in a portion, closer to the first flame hole, of the front plate at a circumferentially equal pitch, and   wherein a plurality of outer second flame holes are formed while being circumferentially deviated by half a pitch from the inner second flame holes so that the outer second flame holes are located between: such an intermediate portion in the front plate as is located in a diametrically inner end and a diametrically outer end of the inner second flame holes; and such a portion in the front plate as is located diametrically outward of the diametrically outer end of the inner second flame holes.