Abstract:
A pilot burner safety device of a gas combustion apparatus for shutting down a gas supply valve automatically at poor oxygen condition, includes an air intaking air means for intaking into a gas supplying passage, a heat detecting means mounted adjacent to the flame nozzle and an intaking control means mounted adjacent to the flame nozzle for controlling an air volume through the air intaking means by detecting flame temperature at the flame nozzle, and an air control means including a shape memory alloy which closes the halves of the air intaking means as a first step and opens the whole of the air intaking means at a heated condition, thereby avoiding nonignition phenomena at the initial ignition, and achieving a firing in one ignition operation.

Description:
BACKGROUND OF INVENTION 
     The invention is related to providing a pilot burner safety device of a gas combustion apparatus for shutting down a gas supply valve automatically at poor oxygen condition, particularly to providing a pilot burner safety device for enhancing reliability during initial ignition operation, in which this safety device has means of automatically controlling the air volume taken in through an intaking hole preventing the occurrence of a flame lifting phenomena, which that at initialized firing excessive air volume adversely influences the mixed gas intended to be at a certain theoretical concentration rate, so that it diminishes the speed of a combustion process to below that of a mixed gas flow. 
     Nowadays, houses tend to be sealed with the result that indoor ventilation has deteriorated unless there is forced ventilation. Nevertheless, if an open-type instant heater and an indoor convection type heater, etc. are used indoors, it induces a poor oxygen environment, which could cause a person inside to be poisoned by carbon monoxide. 
     Japan Laid Open Patent Publication No. Sho 57-60113 describes a safety device, preventing accidents caused by a long operation. This device detects the state of a flame heat generated by a flame lifting at poor oxygen conditions during the combustion operation of a main burner. If the detected heat is below the predetermined temperature, it cuts off the electromagnetic force at a gas supply valve through a control circuit to stop the gas supply. 
     In other words, the flame is formed away from the flame nozzle in a pilot burner, or spaced away in a predetermined distance from the thermocouple adjacent to the flame nozzle, so that the thermocouple is not heated and shuts off the electromagnetic force at the electromagnetic gas supply valve stopping the gas supply, and thereby extinguishing the main burner. 
     As described below in detail, a pilot burner includes the body, which is perforated through the inner center portion thereof to form a gas supplying passage. Into the gas supplying passage there is a nozzle fitted for jetting gas supplied from a storage vessel. An air supply hole is pierced at a predetermined position along the way of the gas supplying passage of a pilot burner. Therefore, gas from the nozzle is mixed at the predetermined rate with air taken in from the air intaking hole, and the mixed gas is jetted at the flame nozzle located at the front end of a pilot burner to generate the flame at firing. 
     However, in the pilot burner, the size of the air supply hole is determined to supply necessary air for a normal combustion condition, and through the hole, air is fed in excess over the air volume required for initialized firing. At this time the speed of a mixed gas flow is greater than that of a combustion process, after which a flame is formed away from the flame nozzle of a pilot burner, or a flame lifting phenomena such as that which occurs in a poor oxygen condition happens. Therefore, the heat of a flame is not transferred to the thermocouple adjacent to the flame nozzle, with the result that the electromagnetic force at the valve is shut off. Whereby the electromagnetic gas supply valve is closed when it should be opened. This occurs frequently. The nonignition phenomena cause the user to go through the ignition step several times. Due to it, it may inconvenience a user with unsatisfactory results. The nonignition phenomena occurring at initial firing may result from excess air volume over the desired air volume at initiation 
     So, the air intaking hole is sized to intake an air volume, rendering the safety device inoperative and not preventing an accident that could result from a poor carbon environment. 
     In view of the foregoing, it is the object of this invention to provide a pilot burner safety device of a gas combustion apparatus having a safety aspect of automatically, controlling the intaking air volume required for firing in accordance with the initial ignition or normal combustion operation automatically and then stopping supply gas at poor oxygen condition, and preventing the nonignition phenomena at initial ignition, to achive a firing at the first ignition operation. 
     BRIEF SUMMARY OF INVENTION 
     In the first preferred embodiment of the present invention, the safety device comprises an air intaking air means for intaking into a gas supplying passage, a heat detecting means mounted adjacent to the flame nozzle, and an air intaking control means mounted adjacent to the flame nozzle for controlling an air volume through the air intaking means by detecting flame temperature at the flame nozzle, and an air intaking control means including a shape memory alloy which closes the air intaking means to air flow as a first step, and then opens the air intaking means air hole at a heated condition. 
     In the second preferred embodiment of the present invention, the safety device comprises an air intaking means for inhaling air into a gas supply passage, a heat detecting means mounted adjacent to the flame nozzle, a temperature detecting means for detecting temperature at the combustion portion or the gas exhaust portion and an air intaking control means mounted on the bottom portion of the flame nozzle to control an air volume of the air intaking means by detecting the temperature at the combustion portion or the gas exhaust portion. The air taking control means includes a bellows shape changing its length by an expansion or contraction of material in the temperature detecting means the, by which means air intaking means is closed by half at a first step and is opened wholly at a heated condition. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The present invention will be described in detail by reference to the accompanying drawings, in which: 
     FIG. 1 is a plan view of one example of the pilot burner with an air intaking apparatus in the first preferred embodiment. 
     FIG. 2 (A) is a cross section taken on line A--A&#39; in FIG. 1 at initial firing. 
     FIG. 2 (B) is a cross section taken on line A--A&#39; in FIG. 1 at normal firing. 
     FIG. 3 is a plan view of another example of the pilot burner with an air intaking apparatus in the second preferred embodiment at initial firing. 
     FIG. 4 is a plan view of another example of the pilot burner with air intaking apparatus in the second preferred embodiment at normal firing. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 and FIG. 2 are views illustrating the first preferred embodiment. 
     Body 1 of a pilot burner is provided with gas supplying passage 11 perforated at the inner center thereof throughout its longitudinal length. At the front end of body 1 there is flame nozzle 11A installed, and at the rear end of body 1 there is gas supplying tube 12 connected. Air supplying hole 11B is pierced on gas supplying passage 11 of body 1. 
     Heat detecting means 13 is mounted at the one end of body 1 close to the front of flame nozzle 11A in a position reaching the flame, so that it opens or closes an electromagnetic gas supplying valve 20 operated by an electromagnetic operator 21. The electromagnetic gas supplying valve 20 receives a signal corresponding to the complete or incomplete combustion of flame at flame nozzle 11A, resulting in flow or flow cut off of gas supply with respect to the main burner. Fittings 22, 24 couple valve 20 to a supply of fuel gas 26. 
     An air intaking control means 2 is installed in body 1 for adjusting an air intaking volume according to opening or closing air supplying hole 11B mentioned above. Air intaking control means 2 is made of a shape memory alloy of two metal pieces being attached face to face to each other, in which two metal pieces are different in expansion coefficient according to their own temperature change from each other. The body of air intaking control means 2 is in the form of a cross, so that fixed strips 21A and 21B are horizontally mounted on both sides and opening/closing portion 22 of the opening/closing air intaking hole 11B is placed on one side of the remainder acrossing the line of fixed strips. Fixed strip 21A and 21B is fixed to surrounding plate 3 with screws 4A, 4B acrossing the longitudinal direction of body 1. A proper size of air intaking hole 11B is formed at an initial firing by the opening/closing portion 22. The heat corresponding to the complete or incomplete combustion of flame from flame nozzle 11A is transferred to air intaking control means 2. Air intaking control means 2 closed halves of air intaking hole 11B as illustrated in FIG. 2A at an initial firing. Air intaking control means 2 opens air intaking hole 11B as illustrated in FIG. 2B during a normal combustion operation as the opening/closing portion 22 is deflected upward by a flame heat from nozzle 11A. 
     In other words, air intaking hole 11B is half closed by opening/closing portion 22 at initial firing, so that air less volume is inhaled than that of air available during a normal combustion operation as illustrated in FIG. 2A. 
     While an ignition device (not shown) is being operated, the flame generated near the pilot burner (not shown) ignites flame nozzle 11A at an initial firing and then a firing starts. At this time, since air is fed in a small volume dependent upon maintaining a greater speed of mixed gas flow than that during a combustion process, it completely prevents the flame lifting phenomena or a flame forming away from flame nozzle 11A. Heat detecting means 13 exposed to heat, will cause a gas supplying valve to open (not shown) wholly. This control action enhances reliability as it can completely prevent nonignition due to a discontinuance of gas. 
     At normal combustion, opening/closing portion 22, described in FIG. 2B in part, is bent upwards resulting in intaking hole 11B being wide open and allowing an air volume required for a normal firing. 
     Moreover, owing to the influence applied from the external environment or the stopping operation associated therewith, the firing of the combustion portion is stopped, while opening/closing portion 22 in the air intaking control means comes back in the former state and waits for the following ignition step. 
     As set forth hereinabove, the first preferred embodiment of present invention provides a pilot burner safety device. It operates with the air intaking control means to change its own configuration by a detecting means detecting a firing and extinguishing state, and controls variably air intaking volume through an air intaking hole of the pilot burner according to initial or normal firing. Particularly at initial firing, it prevents the flame from spacing away from the flame nozzle of the pilot burner, detects the firing at a thermocouple with certainty, and supplies a gas steadily to prevent completely a nonignition phenomena. It enhances the reliability to ignite with a first time ignition operation. 
     FIG. 3 and FIG. 4 are views illustrating the second preferred embodiment. 
     The second embodiment is provided with body 1 having air supplying hole 11B that is the same as above first preferred embodiment, heat detecting means 13 that is the same as above first preferred embodiment, and air intaking control means 3 that controls a volume of intaking air fed through an air intaking hole according to a supply nozzle&#39;s longitudinal movement. 
     The body of air intaking control means 3 is made in the form of a bellows, in which material 8A filled in heat detecting means 8, which will be described later, expands and contracts in its length in accordance with an expansion and contraction of the body. The front end of the air intaking control means is fixed with thread member 5A, 5B. The rear end contacts with fixing component 6 which is threadedly coupled at the end of gas supplying nozzle 10 which moves through gas supplying passage 11 of body 1, with result that gas supplying nozzle 10 cooperates with air intaking control means 3 in harmony. 
     Heat detecting means 8 is provided with a hollow tube type closure body, in which material 8A filled therein, expands and contacts in its length in according with the heat change. The material is made of solid and liquid having an excellent characteristic to expands and contract as it is converted into the gas phase when heated. Also heat detecting means 8 is installed near a passage of the combustion portion and exhaust portion exhausting a combustion gas to detect the operating situation for a combustor so, that the extinguishing and firing conditions for the combustion portion are detected at extinguishing or firing. Therefore, connecting member 7 in the form of the capillary tube is connected between heat detecting means 8 and air intaking control means 3. 
     As material 8A in heat detecting means 8 is gets hot, material 8A expands so that material 8A is fed through connecting member 7 into air intaking control means 3, whereby air intaking control means 3 expands in its length. 
     On the contrary, as heat detecting means 8 gets cold, material 8A having been fed into air intaking control means 3 by the heat-expansion is contracted, with the result that material 8A is returned to heat detecting means 8 through connecting member 7 and air intaking control means 3 comes back in the former state. In other words, air intake hole 11B is closed in part by opening/closing portion 22 at an initial firing, so that less volume of air than that of air available during a normal combustion operation is inhaled therethrough as illustrated in FIG. 3. It enhances the reliability to completely prevent the nonignition due to a flame lifting phenomena. 
     Also at normal combustion, gas supplying nozzle 10 comes backward like shown in FIG. 4, with the result that it opens intaking hole 11B completely and feeds an air volume required for normal firing. Moreover, owing to the influence applied from the external environment or the stopping operation associated therewith, the firing of the combustion portion is stopped, while gas supplying nozzle 10 in air intaking control means 3 comes back in the former state and waits for the following ignition step. 
     As set forth hereinabove, the second preferred embodiment of present invention provides a pilot burner safety device. Gas supplying nozzle 10 moves backward/forward with the air intaking control means in harmony to change its own configuration by a detecting means detecting a firing and extinguishing state, from which an effect is taken in connection with the first preferred embodiment.