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  Cigarette lighter with improved safety propertiesUSPTO Application #: 20060024630Title: Cigarette lighter with improved safety properties Abstract: A cigarette lighter with improved safety property includes a combustion chamber formed as a receptacle in which a cigarette to be lit is inserted. The receptacle is formed of three concentric vented tubes. The combustion chamber is shaped and dimensioned in a manner to completely envelop the flame produced in the combustion chamber, and to prevent any objects with dimensions larger than diameter of a cigarette to be received in the combustion chamber. A flame stabilizer is secured in the inner tube of the receptacle unit at a predetermined distance from the burner in order to limit the insertion of the cigarette and to prevent the unwanted extinction of the flame if the cigarette is inserted too close to the source of the flame. (end of abstract) Agent: Rosenberg, Klein & Lee - Ellicott City, MD, US Inventors: Justin Wade Williamson, Andre W. Marshall, James G. Quintiere USPTO Applicaton #: 20060024630 - Class: 431254000 (USPTO) Related Patent Categories: Combustion, Electrical Or Mechanical Igniter Correlated With Burner Feed The Patent Description & Claims data below is from USPTO Patent Application 20060024630. Brief Patent Description - Full Patent Description - Patent Application Claims
REFERENCE TO RELATED APPLICATIONS [0001] This Utility Patent Application is based on Provisional Patent Application No. 60/592,876 filed Jul. 30, 2004. FIELD OF THE INVENTION [0002] The present invention relates to cigarette lighters and more in particular, to systems for improving fire safety considerations of cigarette lighters. [0003] In overall concept, the present invention relates to a cigarette lighter which generates a flame completely enveloped within the combustion chamber of the cigarette lighter, whereby the cigarette being lit is brought into contact with the flame within the combustion chamber. [0004] Further, the present invention relates to a cigarette lighter equipped with a receptacle designed according to the geometry of a cigarette such that only objects of similar geometry or smaller than a cigarette may be inserted into the receptacle. In this manner, the cigarette lighter provides local heating to the cigarette, and as the result, reduced heating to objects surrounding the cigarette lighter. [0005] The present invention further relates to a cigarette lighter which includes an elongated combustion chamber receiving the cigarette to be ignited, which includes a plurality of concentric stainless steel tubes designed to improve the flame characteristics, temperature distribution, as well as ignition propensity of the cigarette lighter. [0006] Still further, the present invention relates to a cigarette lighter having a flame recession acting as a medium to absorb energy from the flame within the recession while increasing the distance between the flame source and the exit of the hot gases. The flame recession completely contains the flame, thus making it less enticing to curious children, and further significantly improves exit gas properties. BACKGROUND OF THE INVENTION [0007] Small flames, such as those found in candles, matches, cigarette/utility lighters and the incipient fire pose a significant fire hazard. These small flames can release enough thermal energy to cause unwanted ignition and sustain burning. Small ignition sources are dangerous and may produce a fire that may remain unnoticed for a significant period of time. Of these small sources, candles are most commonly recognized as fire hazards. The National Fire Protection Association (NFPA) recognizes this risk and has published a fact sheet with safety tips for using candles in the home. Other small ignition sources include matches and cigarette lighters. Cigarette lighter flames produce a high risk of ignition and therefore need special consideration. [0008] The current standard for improving safety of lighters focuses on adding mechanical child safety features to lighters. These additional mechanical child safety features however do nothing to resolve the unwanted ignition propensity of the lighter flame. [0009] Existing mechanical safety features provided for cigarette lighters are cumbersome and are often bypassed in order to improve ease of use. These "child safety" features are intended to inhibit use of the lighter by persons who lack the motor skills and understanding to operate the lighter. Studies conducted by the National Association of State Fire Marshals (NASFM), such as the Juvenile Firesetter Program, have shown that these features are insufficient for reducing unwanted ignition by juveniles ages 4 to 16. Additionally, the American Society for Testing and Materials (ASTM) standard for regulation of cigarette lighters, ASTM F400-00, is qualitative in nature with respect to unwanted ignition propensity and does not characterize the increased hazard of many new cigarette lighter designs. The NASFM has recognized that there is a need for detailed thermal characterization of cigarette lighters in order to determine the ignition propensity and methods for reducing the ignition propensity. [0010] There is very little previous work characterizing the ignition hazard from cigarette lighters. However, previous work on the thermal behavior of fire plumes may be applied to cigarette lighters with appropriate scaling. Some studies have characterized the gas temperature above a fire source, heat transfer to surfaces above a fire source, ignition of materials with external heating, and transition to turbulence in plumes. [0011] Temperature profiles are a key thermal characteristic of fire flows as they are indicative of the heating potential of the flow. Lighter nozzles that produce higher plume temperatures correspondingly have a higher risk of ignition than those with lower temperatures assuming comparable velocities. Morton et al. previously determined the centerline velocity and temperature distributions in a turbulent plume issuing from a point source (Morton B. R., et al., "Turbulent Gravitational Convection from Maintained and Instantaneous Sources", Proceedings of the Royal Society of London, Series A, V. 234, pp. 1-23, 1956). Morton, et al. found that the centerline temperature decay along the plume axis followed a (-5/3) power law: T - T .infin. T .infin. = 5 .times. Q 6 .times. .alpha. .times. ( 9 10 .times. .alpha. .times. .times. Q ) - 1 / 3 .times. z - 5 / 3 ( 1 ) where T is the centerline plume temperature, T.sub..infin. is the ambient temperature, Q is the energy release rate of the flame, .alpha. is the plume entrainment coefficient constant experimentally found to be 0.11, and z is the characteristic height above the source, based on integral analysis of the turbulent plume equations. [0012] McCaffrey, et al. measured the centerline temperature decay along the plume axis above fire sources (McCafrrey, B. T., et al., "Purely Buoyant Diffusion Flames: Some Experimental Results", Center for Fire Research, National Engineering Laboratory, National Bureau of Standards, No. NBSIR 79-1910, 1979). McCaffrey, et al. found that the temperature decayed according to the same theoretical power law in the plume zone sufficiently far from the source. They also identified a flame zone with constant temperature and an intermittent zone where the temperature decayed inversely with position along the plume axis. Flows from cigarette lighter flames are rarely turbulent near the source. Thus it is important to observe the laminar characteristics and compare them to classical laminar theories for appropriate analysis. The laminar plume equations were solved by Fujii using similarity analysis (Fujii, T. I., "Theory of Steady Laminar Natural Convection Above a Horizontal Line Heat Source and a Point of Heat and Mass Transfer", Vol. 6, pp. 597-606, 1963). Fujii's laminar analysis predicted that centerline temperatures should decay inversely with position above the plume. The flow generated by cigarette lighters can be considered a forced flow, especially in cases where the fuel is premixed with air. Morton, et al. has investigated plumes generated by a steady release of mass, momentum and buoyancy, analytically illustrating the difference between forced plumes and purely buoyant plumes. The results of this analysis shows that forced plumes decay similarly to a jet in the near field with (-1) power law decay and transitioning to plume decay in the far field with an offset. [0013] Transition to turbulence has been studied extensively for vertical plumes. Determining if and where this turbulence occurs is of great importance to scaling data in the flows produced by cigarette lighter flames since the flow is initially laminar which eventually transitions to turbulent flow. Krishnamurthy et al. and Jiang et al. have studied buoyant flows adjacent to a vertical surface using experimental and modeling approaches respectively (Krishnamurthy, R., and Gebhart, B., "An Experimental Study of Transition to Turbulence in Vertical Mixed Convection Flows", Journal of Heat Transfer, Vol. 111, pp. 121-130, 1989; and Jiang, X., and Luo, K. H., "Dynamics and Structure of Transitional Buoyant Jet Diffusion Flames with Side-Wall Effects", Combustion and Flame, Vol. 133, pp. 29-45, 2003). [0014] This geometry is of particular interest for convective heating of the side wall as the convective heating coefficient has a strong dependence on the level of turbulence. Bejan and Kimura et al. have studied free buoyant plumes, and provide a fundamental method for determining the transition to turbulence (Bejan, A., Convection Heat Transfer, Ch. 6, John Wiley and Sons, New York, pp. 202-223, 1983; and Kimura, S., and Bejan, A., "Mechanism for Transition to Turbulence in Buoyant Plume Flow", International Journal of Heat and Mass Transfer, Vol. 26, pp. 1515-1532, 1983). Using the instability analysis prescribed by Kimura et al., a predictor of the transition to turbulence can be predicted by z.sub.t.about.Q.sup.-1/2, where z.sub.t is the turbulent transition height and Q is the energy release rate of the flame. Similarly, a critical Rayleigh number approach, Ra q = gz ir 2 .times. Q . ( avk ) air .times. T .infin. .ltoreq. 10 10 , ( 2 ) where g is the gravitational constant, z.sub.ir is the height for transition to turbulence, and (avk).sub.air are the thermal diffusivity, kinematic viscosity, and conductivity of air respectively, can be used as described by Bejan. [0015] Heat transfer to horizontal surfaces above large fire sources has also been studied extensively. This configuration has been used for studying heat loading on ceilings and other objects above fires. Heat transfer to a horizontal surface results from plume impingement and the formation of a wall jet traveling radially outward below the horizontal surface. In this study, heat flux was used as a metric for ignition propensity of the source. Alpert determined an analytical solution from integral analysis for ceiling jet temperatures, velocities, and jet thicknesses (Alpert, R. L., "Fire Induced Turbulent Ceiling Jet", Factory Mutual Research Corporation, FMC 19722-2, 1971). He was able to determine a local heat flux to the ceiling from the theory that he developed for ceiling jets. He found a dimensionless heat flux: .xi.=q''H.sup.2/{dot over (Q)} (3) where q'' is the incident heat flux, and H is the ceiling height, from his turbulent heat transfer analysis. Veldman et al. and Faeth et al. conducted experiments for ceiling jet heat transfer (Veldman, C. C., Kubota, T., and Zukoski, E. E., "An Experimental Investigation of the Heat Transfer from a Buoyant Gas Plume to a Horizontal Ceiling--Part 1. Unobstructed Ceiling", Center for Fire Research, National Engineering Laboratory, National Bureau of Standards, No. NBS-GCR-77-97, 1975; and Faeth, G. M. and You, H. Z., "An Investigation of Fire Impingement on a Horizontal Ceiling", Center for Fire Research, National Engineering Laboratory, National Bureau of Standards, No. NBS-GCR-81-304 (1981). They found significant scatter in the heat flux data with only limited agreement with the Alpert's ceiling jet theory. They attributed the scatter to other phenomena that may be important to the ceiling heat transfer including radiation effects. [0016] Chow and Motevalli have performed numerical studies of the ceiling jet to characterize the velocity and temperature profile of the flow as a function of the radius (Chow, W. K., "Numerical Studies on the Transient Behaviour of a Fire Plume and Ceiling Jet", Mathematical and Computer Modeling, Vol. 17, pp. 71-79, 1993; and Motevalli, V., "Numerical Prediction of Ceiling Jet Temperature Profiles During Ceiling Heating Using Empirical Velocity Profiles and Turbulent Continuity and Energy Equations", Fire Safety Journal, Vol. 22, pp. 125-144, 1994). These profiles are useful for calculating heat flux to a ceiling surface, however, the studies do not evaluate the steady state solution for a thermally thin ceiling. Motevalli, et al. has investigated the small scale steady state case (Motevalli, V., and Marks, C. H., "Transient and Steady State Study of Small-Scale, Fire-Induced Unconfined Ceiling Jets", 5.sup.th AIAA/ASME Thermophysical and Heat Transfer Conferences, ed. Quintiere, J. G. and Cooper, L. Y., American Society of Mechanical Engineers, New York, pp. 49-61, 1990). This study illustrates that there is a negligible difference between the transient and the steady state ceiling jet flow however, it does not characterize heat transfer to the ceiling. [0017] The ability of a cigarette lighter to ignite thin materials is of particular interest in determining the devices safety performance. Unfortunately, much of the ignition research conducted has focused on thermally thick or semi-infinite solids. Relatively little work has been done with thermally thin solids. [0018] Drysdale has discussed the theory behind ignition of thermally thin slabs based on the solution of the differential one-dimensional heat conduction equation, showing that regardless of the mode of heat transfer, ignition time is directly proportional to the thermal capacity per unit area (.tau.pc) where .tau. is the thickness, p is the density and c is the specific heat of the ignition material (Drysdale, D. D., An Introduction to Fire Dynamics, Second Edition, Ch. 6, John Wiley and Sons, New York, pp. 193-232, 1998). [0019] Studies performed by Zhou, et al., Thomson, et al., Atreya, et al., and Moghtaderi, et al., discuss methods for determining critical heat fluxes and temperatures for ignition of various materials under several different heating conditions. These studies used piloted ignition and thermally thick materials (Zhou, Y. Y., Walther, D. C., and Fernandez-Pello, A. C., "Numerical Analysis of Piloted Ignition of Polymeric Materials", Combustion and Flame, Vol. 131, pp. 147-158, 2002; Thomson, H. W., Drysdale, D. D., and Beyler, C. L., "An Experimental Evaluation of Critical Temperature as a Criterion for Piloted Ignition", Fire Safety Journal, Vol. 13, pp. 185-196, 1988; Atreya, A., and Wichman, I. S., "Heat and Mass Transfer During Piloted Ignition of Cellulosic Solids", Journal of Heat Transfer, Vol. 111, pp. 719-725, 1989; and Mohgtaderi, B., Novozhilov, V., Fletcher, D. F., and Kent, J. H., "A New Correlation for Bench-Scale Piloted Ignition Data of Wood", Fire Safety Journal, Vol. 29, pp. 41-59, 1997). [0020] Nelson, et al. performed a study of thermally thin solids in the cone calorimeter illustrating that the critical heat flux can be determined graphically by from 1/t.sub.ig versus the incident heat flux, q'', where t.sub.ig is the time to ignition (Nelson, M. I., Brindley, J., and McIntosh, A. C., "Ignition Properties of Thermally Thin Materials in the Cone Calorimeter: A Critical Mass Flux Model", Combustion Science and Technology, Vols. 113-114, pp. 221-241, 1996). [0021] Although extensive studies regarding the characterization of flames have been performed which are discussed in previous paragraphs, still further investigations have been found to be needed in order to design a cigarette lighter with satisfactory safety properties. Continue reading... Full patent description for Cigarette lighter with improved safety properties Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Cigarette lighter with improved safety properties 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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