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  Method for ignition of an oil burner and electronic ignition circuitry for oil burnersUSPTO Application #: 20050214703Title: Method for ignition of an oil burner and electronic ignition circuitry for oil burners Abstract: A method for ignition of an oil burner and electronic ignition circuitry for oil burners. Electronic ignition circuit for oil burners, for generating temporally spaced sparks. The electronic circuitry comprises circuitry for producing temporally spaced sparks with a spacing not corresponding to a half-period of the AC mains frequency or of a multiple of the AC mains frequency. The circuitry may be used in a method for ignition of an oil burner forming part of an oil burner system, where said oil burner comprises electronic circuitry for producing a first sequence of temporally spaced sparks for ignition of the oil. According to the method, the electronic circuitry is adjusted to subsequently produce a second sequence of temporally spaced sparks if it is detected that the ignition results in acoustic resonance in the oil burner system using said first sequence of temporally spaced sparks. (end of abstract)
Agent: Mccormick, Paulding & Huber LLP - Hartford, CT, US Inventor: Lars Andreasen USPTO Applicaton #: 20050214703 - Class: 431002000 (USPTO) Related Patent Categories: Combustion, Process Of Combustion Or Burner Operation The Patent Description & Claims data below is from USPTO Patent Application 20050214703. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Patent Application No. PCT/DK02/00269 filed on Apr. 25, 2002. FIELD OF THE INVENTION [0002] The present invention relates to a method for ignition of an oil burner forming part of an oil burner system, where said oil burner comprises electronic circuitry for producing a first sequence of temporally spaced sparks for ignition of the oil, as well as to electronic ignition circuitry for oil burners, for generating temporally spaced sparks. BACKGROUND OF THE INVENTION [0003] In the oil burners typically for heating in single-family houses, electric ignition is employed. [0004] In such burners a blower creates an airflow into which the oil is sprayed through a spray nozzle to form an oil mist in the airflow. In order to ignite the oil an ignition spark gap is located in the vicinity of, but not too close to the spray nozzle. Typically the spark gap is located downstream from the blower and the spray nozzle with respect to the airflow. The distance from the spray nozzle to the spark gap in the direction of the airflow is, however, quite small, e.g. approximately 1-2 mm. The spray nozzle and the spark gap are usually off-set slightly in the direction across the airflow, so as to prevent the oil mist from reaching the electrodes of the spark gap. Other arrangements are of course possible. In particular, the spark gap could be located upstream from the spray nozzle. [0005] On the other hand the spark gap must be located close enough to the spray nozzle to allow the arc formed in the spark gap to actually reach the oil mist and ignite it. When the arc is formed between the electrodes of the spark gap it will be deformed inter alia by the airflow so as to extend downstream into the oil mist. [0006] As already stated, the present invention in particular relates to high voltage high frequency ignition. In FIG. 1 a known electronic circuit for producing the arc is shown. The circuit comprises a spark gap G connected to the secondary of a high voltage high frequency transformer T1. The electronic circuit incorporates an oscillator circuit R1, R2, R3, R4, C3, C4, C5, C6, DZ1, DZ2, TR1 and T1. It should be noticed that the transformer T1 is coupled with the basis of the transistor TR1, so as to provide the feedback needed for the oscillator. [0007] The electronic circuit further comprises a half-wave rectifier circuit D1, C2 rectifying the 50 Hz AC mains supply, as well as noise suppression circuitry L1, C1, R5, R6, the details of which are not considered relevant for the present invention and will not be described in further detail. The 50 Hz AC mains is fed to the circuit as single phase AC on the terminals F and 0. [0008] The oscillator is fed with the half-wave rectified current from the half-wave rectifier, and thus produces 50 high frequency bursts to the high frequency transformer T1 per second, whereby 50 sparks are generated in the gap G per second. [0009] Though a prior art ignition unit with the above circuit has worked well over a number of years, it has been known that under certain circumstances acoustical resonance problems related to the ignition of the oil in the burner system occur. These problems have been increasing over recent years. [0010] These acoustical problems occur in situations where the combustion has reached a self-sustaining state. The repeated occurrence of the ignition spark will influence the combustion, thereby creating flame fronts that will cause pressure pulses, rising and falling with 50 Hz, corresponding to the AC mains frequency. [0011] If, in the above situation, it happens that these 50 Hz pressure pulses coincide with a resonance frequency of the system, e.g. of the Helmholz resonator formed mainly by the combustion chamber and the exhaust duct or of individual parts of the system, the system may be unacceptably noisy producing an annoying howling whenever ignition occur during combustion. In winter this may happen several times per hour, eg. 10 to 15 times. [0012] Since the frequency at which resonance occurs often relate to the Helmholz resonator formed by the combustion chamber and the exhaust duct, the situations where this happens may not easily be predicted, as oil burner systems are often so as to include exhaust ducts in the form of existing chimneys. Thus, the noise problem is rarely discovered until the oil burner unit is fully installed. Moreover, if a new oil burner unit is bought, and installed with an existing exhaust duct, such as a brick chimney, it may be both complicated and costly to overcome the problem, as it involves detuning the system. [0013] Also in recent years oil burner units have been reduced in size and weight. Those reductions have been accompanied with an increase in resonance problems on burner systems. Ways of avoiding and eliminating the problems are investigated intensely by the burner unit providers. [0014] It is the object of the present invention to overcome this acoustic resonance problem in a simple, cost-efficient and versatile manner. SUMMARY OF THE INVENTION [0015] According to a first aspect of the present invention this object is achieved by a method according to the opening paragraph, wherein the electronic circuitry is modified to subsequently produce a second sequence of temporally spaced sparks if it is detected that the ignition results in acoustic resonance in the oil burner system using said first sequence of temporally spaced sparks. [0016] According to a second aspect of the present invention this object is achieved by electronic ignition circuitry according to the opening paragraph, wherein the electronic circuitry comprises circuitry for producing temporally spaced sparks with a spacing not corresponding to a half-period of the AC mains frequency or of a multiple of the AC mains frequency. [0017] By the use of the method or the electronic ignition circuitry of the present invention, the frequency with which the ignition sparks occur in an oil burner may efficiently be de-tuned or de-correlated from the natural resonance frequency of the oil burner system, thereby preventing the unwanted resonance noise. [0018] In a first preferred embodiment of the first aspect of the invention, the electronic circuitry is modified to produce the second sequence by suppressing some of the sparks in the first sequence. [0019] Removing some of the sparks is an efficient way of preventing the build-up of resonance, which may moreover be realised in a cost-efficient way using the electronic ignition circuitry according to the second aspect of the invention. [0020] In particular it has been found advantageous when the electronic circuitry is modified to suppress a unit fraction of the sparks in the first sequence, to suppress all but a unit fraction of the sparks in the first sequence, or to suppress a simple proper fraction of the sparks in the first sequence. Continue reading... Full patent description for Method for ignition of an oil burner and electronic ignition circuitry for oil burners Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method for ignition of an oil burner and electronic ignition circuitry for oil burners patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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