Rich-Lean Burner

Abstract

A rich-lean burner with a lean flame port, a blind clearance, and a rich flame port has: a burner main body with a pair of burner-main-body side plates on both lateral sides thereof; a burner cap with a burner-cap side plate covering the burner main body from at least one lateral outside thereof; and a straightening member with straightening plates to divide the lean flame port into laterally disposed zones. Upper ends of the burner-main-body side plates are below upper ends of the burner-cap side plate and of the straightening plates. The straightening member has a partition plate which is located laterally outside an outer straightening plate contiguous to the blind clearance and which extends upward beyond the burner-main-body side plates. The blind clearance is defined between the partition plate and the outer straightening plate, and the rich flame port is defined between the partition plate and the burner-cap side plate.

Description

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a rich-lean burner having on an upper end portion thereof a lean flame port which is extended in a back-and-forth direction (hereinafter referred to as a “longitudinal” direction) in order to eject a lean fuel/air mixture which is leaner in fuel concentration than a theoretical fuel/air ratio; a blind clearance which is located on at least one right-and-left side (hereinafter referred to as a “lateral” side) of the lean flame port and which is free from ejection of a fuel/air mixture; and a rich flame port which is located on a lateral outside of the blind clearance so as to eject a rich fuel/air mixture which is richer in fuel concentration than the theoretical fuel/air ratio.

2. Background Art

As this kind of rich-lean burner, there is known one having as its constitutional elements: a burner main body including a pair of side plates laterally lying opposite to each other; a burner cap having a side plate covering the burner main body from outside of at least one lateral side (the side in which the rich flame port is disposed) of the burner main body; and a straightening member which is mounted between both the side plates of the burner main body and which has a plurality of straightening plates to divide the lean flame port into a plurality of lateral zones. And the rich-lean burner is conventionally arranged such that: an upper end of each of the side plates of the burner main body is located on the same height as the upper end of the side plates of the burner cap and the upper end of each of the straightening plates; that, among a plurality of straightening plates of the straightening member, a blind clearance is defined between an outer straightening plate that lies next to the blind clearance and the side plate of the burner main body; and that a rich flame port is defined between the side plate of the burner main body and the side plate of the burner cap (see, e.g., JP-A-2007-285536).

Since the zones defining the lean flame port and the rich flame port are subjected to a high temperature, the burner main body, the burner cap, and the straightening member are made of a stainless steel (SUS)-based material (according to Japanese Industrial Standards, JIS) which is superior in resistivity to a high temperature. However, that portion of the burner main body which is subjected to a high temperature is limited to an upper end of the side plate. Therefore, it will be a problem in cost reduction to make the entire burner main body of an expensive SUS-based material.

SUMMARY

Problems that the Invention is to Solve

In view of the above points, this invention has a problem of providing a rich-lean burner in which the burner main body has eliminated the necessity of being made of a material superior in high-temperature durability, thereby attaining a cost reduction.

Means for Solving the Problems

In order to solve the above problem, this invention is a rich-lean burner comprising, on an upper end portion thereof a lean flame port longitudinally extended to eject a lean fuel/air mixture which is leaner in fuel concentration than a theoretical fuel/air ratio; a blind clearance located on at least one lateral side of the lean flame port, the blind clearance being free from ejection of a fuel/air mixture; and a rich flame port located laterally outside the blind clearance thereby ejecting a rich fuel/air mixture which is richer in fuel concentration than the theoretical fuel/air ratio. The rich-lean burner includes constitutional elements of a burner main body having a pair of burner-main-body side plates lying opposite to each other on both lateral sides of the burner main body; a burner cap having a burner-cap side plate covering the burner main body from at least one lateral outside thereof and a straightening member mounted between both the burner-main-body side plates and having a plurality of straightening plates to divide the lean flame port into a plurality of laterally disposed zones. An upper end of each of the burner-main-body side plates is below an upper end of the burner-cap side plate and an upper end of each of the straightening plates. The straightening member has a partition plate located laterally outside an outer straightening plate, among the plurality of straightening plates, that is contiguous to the blind clearance, the partition plate extending upward beyond the burner-main-body side plates. The blind clearance is defined between the partition plate and the outer straightening plate, and the rich flame port is defined between the partition plate and the burner-cap side plate.

According to the arrangement of this invention, the upper end of each of the burner-main-body side plates is located below the upper end of the burner-cap side plate and the upper end of the straightening plates. Therefore, the burner main body is not subjected to heating to such a high temperature. It follows that the burner main body needs not be made of a material that is superior in high-temperature durability.

The straightening member preferably further comprises straightening-member bridge portions arranged at a plurality of longitudinally separate positions, each of the bridge portions connecting an upper end of the partition plate and an upper end of the outer straightening plate. According to this arrangement, the straightening-member bridge portions serve the purpose of a support so that the lateral positional deviation of the partition plates due to aged deterioration can be restricted. Therefore, there can be effectively prevented the deterioration in combustibility as a consequence of lateral changes in the widths of the rich flame port and the blind clearance due to lateral deviation of the partition plate.

The straightening member preferably further comprises constricted (or gathered) portions at longitudinally separated positions that coincide with each of the bridge portions. The constricted portions are arranged by laterally bringing the plurality of straightening plates into intimate contact with one another, thereby longitudinally dividing the lean flame port. According to this arrangement, the thermal effect by the flames to be generated at the lean flame port onto the bridge portions can be reduced, whereby the durability of the bridge portions is improved.

The burner cap preferably comprises: a pair of side plates to cover the burner main body from an outside of laterally one side and from an outside of laterally opposite side; and burner-cap bridge portions disposed at a plurality of longitudinal positions to connect upper ends of both the side plates. Each of the burner-cap bridge portions is disposed at longitudinal positions coinciding with each of the straightening-member bridge portions in contact with a top of each of the straightening-member bridge portions. According to this arrangement, the burner-cap bridge portion is cooled as a result of heat sink to the straightening-member bridge portions which are maintained at a relatively low temperature. As a result, the durability of the burner-cap bridge portions can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rich-lean burner according to an embodiment of this invention.

FIG. 2 is a sectional view taken along the line II-II in FIG. 1.

FIG. 3 is an exploded perspective view of a rich-lean burner according to an embodiment of this invention.

FIG. 4 is a cut-away perspective view of an essential portion of a rich-lean burner according to an embodiment of this invention.

FIG. 5 is a cut-away perspective view of an essential portion of a rich-lean burner according to a second embodiment of this invention.

FIG. 6 is a sectional view of an essential portion of a rich-lean burner according to a third embodiment of this invention.

FIG. 7 is a sectional view of an essential portion of a rich-lean burner according to a fourth embodiment of this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, reference numeral 1 denotes a rich-lean burner according to an embodiment of this invention. The rich-lean burner 1 has on an upper end portion thereof: a lean flame port 2 extended in a longitudinal (i.e., back-and-forth) direction and ejecting a lean fuel/air mixture which is leaner in fuel concentration than a theoretical fuel/air ratio; a pair of blind clearances 4, 4 (i.e., a clearance with lower end being closed to passage) located on both lateral sides of the lean flame port 2 and free from ejection of a fuel/air mixture; and a pair of rich flame ports 3, 3 each of which is located on a lateral outside of the blind clearance 4 on lateral one side of the lean flame port 2 and is located on a lateral outside of the blind clearance 4 on the lateral opposite side of the lean flame port 2, the pair of rich flame ports ejecting a rich fuel/air mixture that is richer in fuel concentration than the theoretical fuel/air ratio.

With reference also to FIG. 3, the rich-lean burner 1 is made up of the constitutional elements of: a burner main body 5 having a pair of side plates 51, 51 which lie laterally (i.e., right and left) opposite to each other; a burner cap 6 which has a pair of side plates 61, 61 to cover the burner main body 5 from one lateral outside, and from the other lateral outside, of the burner main body 5; and a straightening member 7 which is mounted between both the side plates 51, 51 of the burner main body 5 and which has a plurality of straightening plates for dividing the lean flame port 2 into a plurality of laterally disposed zones. Note that the side plates 51, 51 of the burner main body 5 are also referred to as “burner-main-body side plates” and that the side plates 61, 61 of the burner cap 6 are also referred to as “burner-cap side plate(s)” to clarify the two kinds of “side plates.”

Both the side plates 51, 51 of the burner main body 5 are formed by bending a single piece of plate into the shape of a principal rafter along a bending line which is the bottom edge of the burner main body 5. The burner main body 5 is provided, by press-forming both the side plates 51, 51: with a lean fuel/air mixing tube portion 52 which extends forward from an inlet port 52a which opens in a lower and rear end of the burner main body 5; and with a lean fuel/air mixture passage portion 53 which introduces the lean fuel/air mixture from the lean fuel/air mixing tube portion 52 into the lean flame port 2. An area of opening of the inlet port 52a of the lean fuel/air mixing tube portion 52 is relatively large. A relatively large amount of primary air flows into the lean fuel/air mixing tube portion 52 together with the fuel gas from a lean gas nozzle (not illustrated) that lies to face the inlet port 52a, whereby a lean fuel/air mixture is generated. The lean fuel/air mixture passage portion 53 is extended from the front end of the lean fuel/air mixing tube portion 52 upward so as to expand in the longitudinal direction.

In a portion between the lean fuel/air mixing tube portion 52 and the lean fuel/air mixture passage portion 53 of the burner main body 5, there is provided a rich fuel/air mixture passage portion 54 which is formed by press-forming both the side plates 51, 51. The rich fuel/air mixture passage portion 54 extends slightly forward from an inlet port 54a which opens at a rear end of the burner main body 5, and is terminated. At a front side surface of the rich fuel/air mixture passage portion 54, there are provided outlet openings 54b. An area of opening of the inlet port 54a of the rich fuel/air mixing tube portion 54 is relatively small. A relatively small amount of primary air flows into the rich fuel/air mixing tube portion 54 together with the fuel gas from a rich gas nozzle (not illustrated) that faces opposite to the inlet port 54a, whereby a rich fuel/air mixture is generated.

The rich fuel/air mixture ejected from the outlet openings 54b of the rich fuel/air mixture passage portion 54 is introduced into each of the rich flame ports 3 through a rich fuel/air mixture passage portion 62 to be defined between each of the side plates 51 of the burner main body 5 and each of the side plates 61 of the burner cap 6. At a plurality of positions distributed in the longitudinal direction in an upper portion of each of the side plates 61 of the burner cap 6, there are formed recessed portions 63 which divide the rich flame ports 3 in a longitudinal direction.

The straightening member 7 has a pair of inner straightening plates 71in located on a laterally inside, and a pair of outer straightening plates 71out located on laterally both sides. The straightening member 7 further has constricted (or gathered) portions 72 which bring the inner straightening plates 71in and the outer straightening plates 71out laterally into intimate contact with one another, thereby dividing the lean flame port 2 into a plurality of longitudinally divided constricted portions 72. In addition, the respective inner straightening plate 71in and the adjacent outer straightening plate 71out are connected together by means of folded joint portions 73 which are disposed at a plurality of longitudinal positions at a bottom end of the straightening plates 71in, 71out.

By the way, in this embodiment, an arrangement is made as shown in FIGS. 2 and 4, i.e., that each of the side plates 51 of the burner main body 5 is formed such that the upper end of each of the side plates 51 is located below the upper end of each of the side plates 61 of the burner cap 6 and the upper end of each of the straightening plates 71in, 71out. On the other hand, the straightening member 7 is provided with a pair of partition plates 74, 74 which are located laterally outside both the outer straightening plates 71out, 71out and which extend upward beyond each of the side plates 51, 51 in a state of being in close contact, without a gap, with an inner surface on an upper end of each of the side plates 51, 51 of the burner main body 5. It is thus so arranged that each of the rich flame ports 3 is defined between each of the partition plates 74 and each of the side plates 61 of the burner cap 6.

In addition, near the upper end of each of the side plates 51 of the burner main body 5, there are formed dented portions 55 which are dented laterally inward to approach each of the outer straightening plates 71 of the straightening member 7. Into the gap between the dented portions 55 and the respective outer straightening plates 71out, there is inserted a lower end portion of each of the partition plates 74 so as to clog or close the gap. It is thus so arranged that each of the blind clearances 4 is defined between each of the partition plates 74 and each of the outer straightening plates 71out.

In the above-mentioned arrangement, the burner cap 6 and the straightening member 7 are subjected to heating by the flames (rich flames) to be generated in the rich flame ports 3 and by the flames (lean flames) to be generated in the lean flame ports 2, respectively. They must therefore be made of a material such as stainless steel SUS430, etc. according to JIS, which is superior in resistivity to high temperature. On the other hand, since each of the side plates 51 of the burner main body 5 is arranged such that the upper ends of the side plates 51 are below the partition plates 74 whose upper ends define the rich flame ports 3, the side plates 51 do not rise to a considerably high temperature. Therefore, the burner main body 5 that constitutes the majority of the rich-lean burner 1 needs not be made of a material that is superior in resistivity to high temperature. Instead, the burner main body 5 may be made of a relatively inexpensive material of “SA1D” grade or the like which corresponds to aluminized steel according to JIS G3314—SA1D (drawing quality), thereby contributing to the cost reduction.

In addition, according to this embodiment, there are provided bridge portions 75 which connect an upper end of each of the partition plates 74 and an upper end of each of the outer straightening plates 71out at a plurality of longitudinal positions of the straightening member 7. According to this arrangement, the bridge portions 75 serve the purpose of supports so that the lateral deviation of the partition plates 74 due to aged deterioration thereof can be prevented. Therefore, the combustibility can be effectively prevented from deteriorating as a result of changes in lateral widths of the rich flame ports 3 or the blind clearances 4 due to lateral deviation of the partition plates 74.

Still furthermore, according to this embodiment, at such longitudinally separated positions of the straightening member 7 as will coincide with each of the bridge portions 75, there are provided the constricted portions 72 that longitudinally divide the lean flame port 2. According to this arrangement, the bridge portions 75 are located at the positions at which the lean flame port 2 is divided. As a result, the thermal effect on the bridge portions 75 by the lean flames can be reduced, thereby improving the durability of the bridge portions 75.

In addition, the burner cap 6 has bridge portions 64, at a plurality of longitudinal positions, which connect together the upper ends of both the side plates 61, 61. Each of the bridge portions 64 of the burner cap 6 (also referred to as “burner-cap bridge portions”) is disposed at longitudinal positions that coincide with the respective bridge portions 75 of the straightening member 7 (also referred to as “straightening-member bridge portions) such that the burner-cap bridge portion 64 comes into contact with the upper surface of the straightening-member bridge portion 75. According to this arrangement, that bridge portion 64 of the burner cap 6 which is heated by the rich flames to a high temperature is cooled by the heat sink to the straightening-member bridge portion 75 which is maintained at a relatively low temperature. As a result, the durability of the bridge portions 64 of the burner cap 6 is also improved.

In a second embodiment as shown in FIG. 5, the bridge portion 75 which connects the upper end of each of the partition plates 74 and the upper end of each of the outer straightening plates 7 lout is not provided. Instead, there may be employed an arrangement in which each of the outer straightening plates 71out and each of the partition plates 74 are connected together at folded connecting portions 76 which are provided at a plurality of longitudinal lower end positions.

Furthermore, in a third embodiment as shown in FIG. 6, the following arrangement is employed in which the side plate 61 on laterally one side (right side as seen in FIG. 6) of the burner cap 6 is overlapped with the partition plate 74 on the right side of the straightening member 7, whereby the right-side rich flame port 3 may be eliminated. In this case, a similar rich-lean burner 1 is provided on the right side thereof in parallel with each other. And the rich flame port 3 on the left side of the latter (right-side) rich-lean burner 1 is arranged to be in close contact with the blind clearance 4 on the right side of the former (left-side as seen in FIG. 6) rich-lean burner 1.

Still furthermore, according to a fourth embodiment as shown in FIG. 7, it is possible to eliminate not only the rich flame port 3 on the laterally one side (right side as seen in FIG. 7), but also the right-side blind clearance 4, the side plate 61 on the right side of the burner cap 6, and the partition plate 74 on the right side of the straightening member 7. In this case, a similar rich-lean burner 1 is disposed on the right side of the rich-lean burner 1 in parallel with each other. Between the outer straightening plate 71out on the right side of the straightening member 7 of the former rich-lean burner 1, and the side plate 61 on the left side of the burner cap 6 of the latter rich-lean burner 1, there is defined a blind clearance 4′ which is located between the lean flame port 2 of the former rich-lean burner 1 and the rich flame port 3 of the latter rich-lean burner 1.

Claims

1. A rich-lean burner comprising, on an upper end portion thereof: a lean flame port longitudinally extended to eject a lean fuel/air mixture which is leaner in fuel concentration than a theoretical fuel/air ratio; a blind clearance located on at least one lateral side of the lean flame port, the blind clearance being free from ejection of a fuel/air mixture; and a rich flame port located laterally outside the blind clearance thereby ejecting a rich fuel/air mixture which is richer in fuel concentration than the theoretical fuel/air ratio, the rich-lean burner including constitutional elements of: a burner main body having a pair of burner-main-body side plates lying opposite to each other on both lateral sides of the burner main body; a burner cap having a burner-cap side plate covering the burner main body from at least one lateral outside thereof; and a straightening member mounted between both the burner-main-body side plates and having a plurality of straightening plates to divide the lean flame port into a plurality of laterally disposed zones,characterized in: that an upper end of each of the burner-main-body side plates is below an upper end of the burner-cap side plate and an upper end of each of the straightening plates; that the straightening member has a partition plate located laterally outside an outer straightening plate, among the plurality of straightening plates, that is contiguous to the blind clearance, the partition plate extending upward beyond the burner-main-body side plates, that the blind clearance is defined between the partition plate, and the outer straightening plate; and that the rich flame port is defined between the partition plate and the burner-cap side plate.

2. The rich-lean burner according to claim 1, wherein the straightening member further comprises bridge portions arranged at a plurality of longitudinally separate positions, each of the bridge portions connecting an upper end of the partition plate and an upper end of the outer straightening plate.

3. The rich-lean burner according to claim 2, wherein the straightening member further comprises constricted portions at longitudinally separated positions that coincide with the bridge portions, the constricted portions being arranged by laterally bringing the plurality of straightening plates into intimate contact with one another, thereby longitudinally dividing the lean flame port.

4. The rich-lean burner according to claim 3, wherein the burner cap comprises: a pair of side plates to cover the burner main body from an outside of laterally one side and from an outside of laterally opposite side; and bridge portions disposed at a plurality of longitudinal positions to connect upper ends of both the side plates, wherein each of the burner-cap bridge portions is disposed at longitudinal positions coinciding with each of the straightening-member bridge portions in contact with a top of each of the straightening-member bridge portions.