GAS-AIR RATIO CONTROL VALVE FOR GAS BURNERS

Abstract: An operating rod (7) which can be moved forward and backward is provided with a primary air flow rate regulating valve (A), a secondary air flow rate regulating valve (B) and a raw gas flow rate regulating valve (G). This can increase and decrease the degrees of opening of the valve by moving the operating rod (7) forward and backward. In each of these valves, the inner surface of a valve body or a valve box can be tapered. The operating rod can also be vertically moved. The raw gas can be mixed with the primary air by sending the former in countercurrent to the flow of the latter.

Description: - GENERAL TECHNICAL FIELD - This invention relates to a gas-air ratio control valve device which is used in a gas burner and adapted to properly control the feeding ratio of a primary air, a secondary air and a raw gas to the gas burner and which is chiefly used in a gas-type hot water supply system. - BACKGROUND ART - In a gas burner, it is necessary to secure a most appropriate proportion between a raw gas flow rate and an air flow rate in order to obtain a complete combustion. To this end, heretofore, a primary air and a secondary air which were to be fed to a gas burner were controlled by properly varying the number of rotation of a centrifual blower or reducing the aperture of an air intake port of on air blower by means of an electronic control circuit or the like, and the raw gas which was to be fed to the gas burner was regulated in flow rate by increasing or decreasing the degree of the opening degree of a gas delivery valve. However, according to such control means as mentioned, although there was no problem when the gas burner was at high load combustion, if a pressure change (an external factor, a rush of wind, etc.) should occur at the exhaust port side of the gas burner when the gas burner was at low load combustion, it had the shortcomings in that the flame of the gas burner was blown out, that carbon monoxide was generated, or that a back phenomenon of a flame was taken place and as a result, that a proper combustion was difficult to obtain. Furthermore, the conventional control method had the shortcoming in that since the ratio of a secondary air with respect to a primary air was impossible to control, the generation of a combustion noise was difficult to restrain. Especially known it is from DE-A-1 751 255, on which the pre-characterizing portion of claim 1 is based, that a gas flow rate control valve and an air flow rate control valve are arranged on the same aixs, which is the symmetry axis of the entrance for introducing air as well as burner gas into the burning chamber of a furnace. Valve member of the air flow rate control valve and valve member of the burner gas flow rate control valve are connected with a single operating rod, which is reason that both valve members being actuated simultaneously by the operating rod according to the forward and backward movement respectively. Just one gas entrance and one air entrance are parts of the device and air and gas will be mixed when entering the furnace to be burned in the furnace. From FR-A-654 600 it appears that a rod at it's opposite ends is provided with a gas flow ratio control valve and an air flow ratio control valve, respectively, for simultaneous operation by the rod. It is therefore an object of the present invent ion to provide a gas-air ratio control valve for gas burners, in which such shortcomings as inherent in the prior art as mentioned can be overcome, the flame of a gas burner is not blown out even if a pressure change (an external factor, a rush of wind etc.) is taken at an exhaust port side of the gas burner, a carbon monoxide is generated, the back phenomenon of a flame can be prevented from being taken place, and as a result, a proper combustion can be obtained. - DISCLOSURE OF THE INVENTION - The present invention comprises a burner portion and a control portion for controlling a raw gas flow rate, a primary air flow rate and a secondary air flow rate; said control portion being provided with a primary air chamber, a secondary air chamber and a raw gas chamber, said primary air chamber, secondary air chamber and raw gas chamber being communicated with said burner portion; said control portion being provided with an operating rod which is able to move forward and backward, said control portion being also provided with a raw gas flow rate control valve portion, a primary air flow rate control valve portion and a secondary air flow rate control valve portion which are opened and closed according to the forward and backward movement of the operating rod; said various valves being operated according to the forward and backward movement of said operating rod by means of a suitable actuator, so that the primary air flow rate flowed into said primary air chamber, the secondary air flow rate flowed into said secondary air chamber and the raw gas flow rate flowed into said raw gas chamber are controlled. By virtue of the foregoing arrangement, if the operating rod is moved forward and backward by the actuator, the raw gas flow rate control valve portion, the primary air flow rate control valve portion and the secondary air flow rate control portion can be interlocked without varying the pressure of the air-fuel mixture (a mixture of the primary air and the raw gas) which is to be fed to the gas burner. In this invention, at the time when the raw gas flow rate control valve portion and the air flow rate control valve portion are to be constructed, if an annular valve seat which is secured to the valve box and a valve body which is secured to the operating rod, are concentrically arranged and if either an inner wall surface of the valve seat or the external wall surface of the valve body is formed in a tapered shape, the air ratio can be controlled simply by varying the angle of the taper of the external wall surface of the valve body. In this invention, if only the raw gas control valve portion and primary air control valve portion are provided to the control portion and if the secondary air is freely fed to the gas burner portion, the structure of the control portion becomes simple. Furthermore, at the time when this invention is to be constituted, if a basic barrel is provided with an air chamber and a raw gas chamber, and if the basic barrel is disposed in the vertical direction, and if the basic barrel is designed in such a manner as to be communicated with a gas burner through an opening at an upper end of the basic barrel, and if the basic barrel is formed at its side wall with an air window so that the air chamber is communicated with outside the basic barrel, and if the basic barrel is formed with a raw gas inlet port so that a raw gas generated in the raw gas chamber can be introduced therein, and if the basis barrel is provided at its axial center with an operating rod which is able to move forward and backward and if a raw gas flow rate control valve and an air flow rate control valve, which are opened and closed according to the forward and backward movement of the operating rod, are symmetrically disposed by serving the axial center of the basic barrel as the point of symmetry, and if the control valve is activated according to the forward and backward movement of the operating rod in the vertical direction by a suitable actuator, so that the control valve is actuated to control a primary air flow rate flowing from the air chamber to the gas burner portion and to control a raw gas flaw rate flowing from the raw gas chamber to the gas burner portion, the air-fuel mixture discharged from the air outlet port of the control portion can easily be equalized because the air-fuel mixture flow rate which is to be fed to the control portion is controlled. Furthermore, at the time when the present invention is to be constituted, in a gas-air ratio control valve for gas burners, in which a fixed barrel is disposed generally at the center of a basic barrel in the vertical direction, a primary air chamber being disPosed between the fixed barrel and the basic barrel, the interior of the fixed barrel being served as a raw gas chamber, the basic barrel being formed at an upper end thereof with an opening and is communicated with a gas burner portion through the opening, the basic barrel being formed at a side wall thereof with an air window so that the primary air chamber is communicated with outside the basic barrel, the basic barrel being formed with a raw gas introducing passage so that a raw gas can be introduced into the raw gas chamber, the fixed barrel being provided with a reciprocation barrel as such that the reciprocation barrel can be moved forward and backward, the reciprocation barrel being further provided with a raw gas flow passage, the reciprocation barrel being moved forward and backward in the vertical direction by a suitable means thereby to actuate the primary air flow rate control valve portion and the raw gas flow rate control valve so that a primary air flow rate flowing from the primary air chamber to the gas burner portion is controlled and so that a raw gas flow rate flowing from the raw gas chamber and converging with the primary air through the raw gas flow passage is controlled, if the raw gas passage of the fixing barrel is opened up at the primary air chamber and if the opening is faced opposite with the flowing direction of the primary air, the raw gas flowed into the primary air chamber causes a turbulence together with the primary air and as a result, the raw gas can be uniformly mixed in a short flow passage. Still further, at the time when the present invention is to be constituted, in a gas-air ratio control valve for gas burners which includes a gas burner and a ratio control valve for controlling an air-fuel mixture flow rate which is to be fed to the gas burner, the ratio control valve being provided with an air inlet part and a raw gas inlet port, the air inlet port being provided with an air blower, the raw gas inlet port being connected with a raw gas pipe through an electromagnetic valve, so that a pressure air is fed to the ratio control valve by means of activation of the air blower and so that a raw gas is fed to the ratio control valve through the raw gas pipe, the air blower being provided with an air pressure detecting means and the raw gas pipe being provided with a gas pressure detecting means, these detecting means being set with a set value so that the electromagnetic valve is closed when the air pressure of the air blower or the raw gas pressure of the raw gas pipe becomes other value than the set value, that is, the air blower being provided with an air pressure detecting means and the raw gas pipe being provided with a gas pressure detecting means, these detecting means being set with a set value so that the electromagnetic valve is closed when the air pressure of the air blower or the raw gas pressure of the raw gas pipe becomes other value than the set value. Accordingly, raw gas and combusting air are fed to the flow rate control valve always under a predetermined pressure. - BRIEF DESCRIPTION OF THE DRAWINGS - Fig. 1 is a sectional view of a first embodiment; Fig. 2 is a sectional view of a second embodiment; Fig. 3 is a sectional view of a third embodiment; Fig. 4 is a sectional view of a fourth embodiment; Fig. 5 is a sectional view of a fifth embodiment; Figs. 6 through 8 show a sixth embodiment, in which Fig. 6 is a front sectional view, Fig. 7 is a right side view, and Fig. 8 is a plan view; Fig. 9 is a front sectional view of a seventh embodiment; Figs. 10 through 12 show an eighth embodiment, in which Fig. 10 is a front sectional view, Fig. 11 is a plan view, and Fig. 12 is a right side view; Figs. 13 and 14 show a ninth embodiment, in which Fig. 13 is a front sectional view, and Fig. 14 is a plan view; Fig. 15 is a front sectional view of a tenth embodiment; Fig. 16 is a sectional view when viewed from the front; Figs. 17 through 20 show a twelfth embodiment, in which Fig. 17 is a front sectional view, Fig. 18 is a sectional view taken along line XVIII-XVIII of Fig. 17, Fig. 19 is side sectional view, and Fig. 20 is a cut-away perspective view of an important portion showing the arranging state of a secondary air flow rate control valve; and Fig. 21 is a sectional view of a thirteenth embodiment. - Best Mode for Carrying Out the Invention - In order to describe the present invention in more detail, the invention will be described with reference to the accompanying drawings. Fig. 1 shows a first embodiment. In Fig. 1, 1 denotes a burner portion of a gas type hot water supplying system, and 2 denotes a control portion for controlling a raw gas flow rate, a primary air flow rate and a secondary air flow rate which are to be fed to the burner portion 1. The burner portion 1 and the control portion 2 are integrally formed through a casing 3. The control portion 2 will be described next. 31 denotes an air inlet port which is integral with the control portion 2. The air inlet port 31 is connected with an outlet port 4 of an air blower 4. 5 denotes a supporting barrel which is fitted to the side of the casing 3. The supporting barrel 5 is opened up within the casing 3, the interior thereof functioning as a raw gas chamber 51. 52 denotes a raw gas introducing passage which is formed in the supporting barrel 5. The raw gas introducing passage 52 is adapted to introduce a raw gas from outside into the raw gas chamber 51. 6 denotes a cylindrical valve box member which is fitted into the supporting barrel 5. The rear end of the valve box member 6 is thrusted through the supporting barrel 5. 61 denotes a nut which is engaged with a projecting portion of the valve box member 6 to form a so-called double nut structure for securing the valve box member 6. 62 denotes an annular valve seat which is secured to the front end port of the valve box member 6. The function of the valve seat 62 will be described afterward. 63 denotes a shaft hole formed in a right end portion (in Fig. 1) of the valve box member 6, and 7 denotes an operating rod which is reciprocally movably inserted into the shaft hole 63. 71 denotes a valve body which is integral with an intermediate portion of the operating rod 7. The external wall surface of the valve body 71 is tapered and forms a raw gas flow rate control valve G of the present invention together with the annular valve seat 62. The opening area of the raw gas flow rate control valve G is increased and decreased according to the reciprocal movement of the operating rod 7 thereby to control the flow rate of a raw gas passed. Next, 32 denotes a partition wall which is secured to the case 3. The partition wall 32 partitions the interior of the case 3 into a primary air chamber 321 and a secondary air chamber 322. 33 denotes an annular valve seat which is fitted to the partition wall 32. The internal wall surface of the valve seat 33 is tapered. 8 denotes a reciprocal barrel which is reciprocally movably fitted into the supporting barrel 6. The reciprocal barrel 8 is secured to a left end of the operating rod 7 and is reciprocally moved according to the reciprocal movement of the operating rod 7. 81 denotes a dish-shaped valve body which is integral with a right end of the reciprocal barrel 8. The valve body 81 constitutes a primary air control valve A together with the valve seat 33. The primary air flow rate control valve A increases or decreases its opening area according to the reciprocal movement of the operating rod 7, thereby to control a primary air flow rate which is to be flowed into the primary air chamber 321. 811 denotes a raw gas discharging passage which is radially formed in the valve body 81. The raw gas discharging passage 811 (Fig.3) causes the interior of the reciprocal barrel 8 to be communicated with the primary air chamber 321 to discharge a raw gas into the primary air chamber 321. The raw gas flawed into the primary air chamber 321 is mixed with a primary air in the primary air chamber 321. Next, 9 denotes a fixed barrel which is secured to the case 3. The fixed barrel 9 partitions the interior of the case 3 into a compression air chamber 91 and the secondary air chamber 322. 92 denotes a valve barrel which is integral with a projecting portion of the valve body 81 through a connecting piece 911. The valve barrel 92 is reciprocally movably fitted into the fixed barrel 9. The reciprocal movement of the valve barrel 92 increases or decreases the opening area between the partition wall 32. and the valve barrel 92. That is, the valve barrel 92 and the fixed barrel 9 constitute a secondary air flow rate control valve B of the present invention and control a secondary air flow rate, which is to be flowed into the secondary air chamber 322, according to the reciprocal movement of the operating rod 7. 921 denotes a return spring for returning the operating rod 7 into its original state. Furthermore, the burner portion 1 will be described. In the figure, 11 denotes a head plate of a burner. The inner side of the burner head plate 11 is communicated with the primary air chamber 321 of the control portion 2. 111, 111, ... denote flame holes formed in the burner head plate 11. The flame holes 111, 111, ... are adapted to discharge an air-fuel mixture outside the burner head plate 11. The air-fuel mixture discharged constitutes, when ignited, an internal flame L. 12 denotes a secondary air pipe, which is disposed to an upper location of the burner head plate 11. The secondary air pipe 12 is communicated with the secondary air chamber 322 of the control portion 2. 121, 121, ... denote tiny holes which are formed in the secondary air pipe 12. The tiny holes 121, 121, ... are adapted to discharge a secondary air to the upper part of the internal flame L. The secondary air discharged assists the combustion of the air-fuel mixture and forms an external flame H at an upper part of the internal flame L. 13 denotes a heat exchanger which disposed to an upper part of the external flame H. The heat exchanger 13 is adapted to heat water until it becomes a hot water. Next, the operation of the above-mentioned embodiment will be described. If the operating rod 7 is moved in the left direction, i.e, pushed in by a suitable actuator, the opening areas of the raw gas flow rate control valve G, the primary air flaw rate control valve A and the secondary air flow rate control valve B became large. Due to the foregoing, the air-fuel mixture and the secondary air which are to be fed to the burner portion 1 are increased. And, when the operation of the actuator is over, the operating rod 7 is restored to its original state by means of the function of a return spring 921. Fig. 2 shows a second embodiment. In the example of the second embodiment, the supporting barrel 5 and the valve seat of the primary air flow rate control valve A are integral with the case 3. Also, the valve body 71 of the raw gas flaw rate control valve G and the valve body 81 of the primary air flow rate control valve A in this embodiment are contacted with each other and fitted to the outer periphery of the operating rod 7 and then held between the retaining pin 711 and the compression spring 712. Fig. 3 shows a third embodiment. In the example of the third embodiment, the tapered surface of the valve seat 81 of the primary air flow rate control valve A and the valve body 71 of the raw gas control valve G is in the reversed inclination as those of the first and the second embodiments. Due to the foregoing, when the operating rod 7 is moved in the right direction, i.e., withdrawn, the opening areas of the raw gas flow rate control valve G, the primary air flow rate control valve A and the secondary air flow rate control valve B become large. Fig. 4 shows a fourth embodiment. In the example of the fourth embodiment, an outer wall surface of the valve body 81 of the secondary air flow rate control valve B is tapered. Also, the operating rod 7 is secured to the valve body 81 and, when moved in the right direction (in the direction as shown by an arrow in the figure), the raw gas flow rate control valve G, the primary air flow rate control valve A and the secondary air flow rate control valve B are opened. In the example of the fifth embodiment according to Fig. 5, a gas flow-in pipe and the operating rod 7 penetrate the blast pipe 42 of the air blower 4. In this embodiment, when the operating rod 7 is moved in the upward direction, i.e., pushed in, the raw gas flow rate control valve G, the primary air flow rate control valve A and the secondary air flow rate control valve B are opened. In the above-mentioned embodiments, the actuator used is of the type which is actuated, for example, by variation of pressure, temperature, etc. of water which is to be fed to a heat exchanger. Figs. 6 through 8 show a sixth embodiment. In the example of this embodiment, the raw gas chamber 51 is independent of a primary air chamber 331 in the control portion 2, and the raw gas and the primary air are mixed together after they flowed out of the control portion 2. Fig. 9 shows a seventh embodiment. In the example of this embodiment, the invention is applied to a blast-type burner. In the figure, 11a denotes a burner, and 111a denotes a flame hole of the burner 11a. 16a denotes an air chamber which is formed below the burner 11a. This air chamber 16a communicates with a combustion air chamber 333 for the control portion 2. 15a denotes a fuel pipe which is formed at an upper nor lion of the air chamber 16a. This fuel pipe 15a communicates with the raw chamber 51 of the control portion 2. 151a denotes a nozzle which is formed at the fuel pipe 15a. This nozzle 151a jets a raw gas toward the burner 11a for supplying. C denotes an air flow rate control valve. Figs. 10 through 12 show an eighth embodiment. In the example of this embodiment, the secondary air is not controlled in the control portion 2. In Fig. 10, 811 denotes a guide plate which is adapted to equalize the pressure of the air-fuel mixture which is to be fed to the gas burner portion 1. Fig. 13 and Fig. 14 show a ninth embodiment. In the example of this embodiment, since the taper of the valve portions A and G is formed in the opposite direction to that of the eighth embodiment, the operating rod 7 is moved back and forth in the opposite direction in order to obtain the same motion as that of the eighth embodiment. Fig. 15 shows a tenth embodiment. In the example of this embodiment, the operating rod 7 is vertically moved back and forth and a solenoid 8 is used as an actuator. The operation of this embodiment will be described. When an electric current flows into the solenoid 8, an iron core 83 and hence an operating rod 57 are moved in the vertical direction, and the opening areas of the raw gas flow rate control valve G and the primary air flow rate control valve A become large. Due to the foregoing, an air-fuel flow rate which is to be fed to a gas burner portion (not shown) is increased and as a result, the combustion quantity of heat is increased. And, when the flowing of the electric current into the solenoid 8 is stopped, the iron core 83 and thus the operating rod 7 are energized by a spring (not shown) and moved downward, and the opening areas of the raw gas flow rate control valve G and the primary air flow rate control valve A become small . Due to the foregoing, the air-fuel mixture which is to be fed to the gas burner portion (not shown) is decreased and as a result, the combustion quantity of heat is decreased and restored to its original state. In the figures, the basic barrel 55 corresponds to the case. Similarly, 53 denotes an air window. Fig. 16 denotes an eleventh embodiment. In the example of this embodiment, a primary air nozzle 821 is opened in such a manner as to face with the flow of a primary air. Figs. 17 through 20 show a twelfth embodiment. Fig. 21 shows a thirteenth embodiment. In this embodiment, R denotes means for detecting the number of rotation (means for detecting the pressure of a combustion air of this invention) which is adapted to detest the number of rotation of an air blasting fan. Similarly, P denotes a raw gas pipe which is connected to a raw gas inlet port 52 of the ratio control valve 2. E denotes an electromagnetic valve which is disposed at the raw gas pipe P, V denotes a governor which is disposed at a downstream side of the electromagnetic valve E, and S denotes a pressure switch (corresponding to the means for detecting the gas pressure of this invention) which is disposed at a downstream side of the governor V. The number of rotation detecting means R and the pressure switch S are established in set values, and when the number of rotation of the air blasting fan and the pressure of the raw gas become something other than the set values, the electromagnetic valve E is closed. As for the combustion air pressure detecting means, a pressure switch may be used. - Possibility for Industrial Use - As described in the foregoing, a gas-air ratio control valve for gas burners according to the present invention is useful as means for controlling the feeding of a combustion air and raw gas to a gas burner, and particularly, it is suitable for the use in a gas-type hot water supplying system.

Claims: A gas-air ratio control valve device for gas burners comprising a burner portion (1) and a control portion (2) for controlling a raw gas flow rate and an air flow rate; said control portion being provided with a raw gas chamber (51) and an air chamber (321) communicating with said burner portion, respectively; said control valve device being included in said control portion (2) being provided with an operating rod (7) which is axially movable in a forward and backward direction and is connected to a suitable actuator; said control valve device (2) further being provided with a raw gas flow rate control valve (G) and an air flow rate control valve (A) being actuated by the movement of the operating rod (7) to control the raw gas flow rate into said raw gas chamber (51) and an air flow rate into said air chamber (321); characterized in that the valve body (71) of said gas flow rate control valve (G) and the valve body (33) of said air flow rate control valve (A), which is a first air flow rate control valve, are arranged on the same shaft together with the valve body (92) of a second air flow rate control valve (B), the first air flow rate control valve (A) controlling air flow rate to a first air chamber (321) connected with the raw gas chamber (51) and to be to connect to the burner portion (1), the second air flow rate control valve (B) controlling air flow rate to a second air chamber (322) connect to the burner portion (1) separately. A control valve device according to claim 1, characterized in that each of the valves (A,B,G) comprises an annular valve seat (33,62). A control valve device according to claim 1 or claim 2, characterized in that the valve seat (62) of the raw gas flow rate valve (G) is secured to a valve box (6) and a valve body (71) secured to said operating rod (7), said valve box (6) and said valve body (71) being arranged concentrically in a valve casing (3) whereby either an inner wall surface of said valve seat (62) or an external wall surface of said valve body (71) is formed in a tapered shape. A control valve device according to one of claims 1 to 3, characterized in that said two air chambers (321,322) and the raw gas chamber are arranged concentrically to the same axis of the valve casing (3). A control valve device according to claims 1 to 4, characterized in that said primary air chamber (321) is separated from said raw gas chamber (51) but communicated with it by raw gas discharging passages (811). A control valve device according to claims 1 to 5, characterized in that a basic barrel is provided with an air chamber and a raw gas chamber, and the basic barrel is disposed in the vertical direction; said basic barrel communicating with a gas burner through an opening formed at an upper end thereof; said basic barrel being formed at its side wall with an air window so that the air chamber is communicating with outside the basic barrel; said basic barrel being formed with a raw gas inlet port so that a raw gas generated in said raw gas chamber can be introduced therein; said basic barrel being provided at its axial center with said operating rod and said raw gas flow rate control valve and said air flow rate control valve symmetrically disposed by serving the axial center of said basic barrel as the point of symmetry. A control valve device according to claim 6, characterized in that a fixing barrel is disposed generally at the center of said basic barrel in the vertical direction, a space between said fixing barrel and said basic barrel serving as a primary air chamber and the interior of said fixing barrel serving as a raw gas chamber; said fixing barrel being provided with a reciprocation barrel as such that said reciprocation barrel can be moved forward and backward, and said reciprocation barrel further being provided with a raw gas flow passage; said reciprocation barrel being moved forward and backward in the vertical direction by a suitable means thereby actuating said primary air flow rate control valve and said raw gas flow rate control valve so that a primary air flow rate from said primary air chamber to said gas burner portion is controlled and so that a raw gas flow rate flowing from said raw gas chamber and converging with said primary air through said raw gas flow passage is controlled; wherein said raw gas flow passage of said fixing barrel is opened up at said primary air chamber and said opening is faced opposite with the flowing direction of said primary air. A control valve device according to claims 1 to 7, including a gas burner and a ratio control valve for controlling an air-fuel mixture flowing rate which is to be fed to said gas burner and said ratio control valve being provided with an air inlet port and a raw gas inlet port, said air inlet port being provided with an air blower, said raw gas inlet port being connected with a raw gas pipe through an electromagnetic valve by means of activation of said air blower and so that a raw gas is fed to said ratio control valve through said raw gas pipe; characterized in that said air blower is provided with an air pressure detecting means and said raw gas pipe is provided with a gas pressure detecting means, these detecting means being set with a set value so that said electromagnetic valve is closed when air pressure of said air blower or raw gas pressure of said raw gas pipe differs from the set value. A control valve device according to claim 8, characterized in that said air pressure detecting means comprises means for detecting the number of rotation of a rotating fan of an air blower.

Inventors: FURUHASHI TOSHIO EIKEN K K K N, HASEGAWA MAKOTO EIKEN K K K NA, FURUHASHI, TOSHIO EIKEN K.K.K. NAI, HASEGAWA, MAKOTO EIKEN K.K.K.NAI
Applicants: EIKEN IND, EIKEN KOUGYO KABUSHIKI KAISHA
Application year: 1988
Main classification: F23N1
IPC codes: F23D14, F23N1