Lamp For Producing Colored Flame

Abstract

To provide a desired colored flame for a lamp, our method and lamp provides a safe way of incorporating the metallic chlorides on a portion of the wick, which we pack in a removable covering attached to the exterior of a metal container prior to use. The container has fuel and a wick opening which is covered before use by a closure. In use the closure is removed from the container, and the covering is removed from the wick. An untreated portion of the wick is inserted through the wick opening to the fuel in the bottom of the container. The fuel is then ignited and burns to heat the metallic salts on the portion of the wick extending beyond the wick opening to produce desired colored flame.

Description

Our invention relates to a method and lamp for producing colored flame.

An object of our invention is to provide a method of producing colored flame by incorporating metallic salts in or upon one portion of the wick of a lamp, the other portion of said wick extending into fuel in the lamp, so that upon ignition and burning of the fuel, the burning will heat the metallic salts on the wick to produce a colored flame.

Another object is to provide a lamp for producing desired colored flame, in which fuel is housed in a metal container having a wick opening, a removable closure for closing the opening, and a wick treated on one portion with desired metallic salts, said wick covered by a removable covering and associated with the exterior of said container during transit, storage and shelf life before use, said wick upon removal of its covering and after removal of the closure from the container, having an untreated portion inserted through the wick opening into the fuel at the bottom of the container, and upon the fuel being ignited and burning, the metallic salts on the wick are heated to produce a desired colored flame.

Still another object of our invention is to provide a reasonably safe product for shipment, storage and shelf life which will not deteriorate prior to sale and use.

Our invention also contemplates such other objects, advantages and capabilities as will later more fully appear, and which are inherently possessed by our invention.

While we have shown in the accompanying drawings a preferred embodiment of our invention, yet it is to be understood that the same is susceptible of modification and change without departing from the spirit of our invention .

Referring to the drawings, FIG. 1 is a perspective view of our container in closed position prior to use, partly broken away to show the wick housed in the overcap;

FIG. 2 is a perspective view of our container in open position with the wick ready for use, partly broken away to show the interior; and

FIG. 3 is an elevational view showing the flame of our lamp in use.

Liquid fueled lamps have been used for centuries to provide heat and light and consist essentially of a fuel reservoir, fuel, and a means for burning the liquid fuel so that the burning rate can be controlled. Reservoirs can consist of any container which will hold the liquid fuel without leakage, which will protect the main body of fuel from uncontrolled ignition, and from which fuel can be withdrawn at a controlled rate when ignited. Suitable reservoirs have been made of metal, glass, plastic, ceramics, stone or bone which are totally enclosed except for a small opening through which into the liquid fuel a wick of such material that permits the fuel to rise by capillary action from the reservoir to the outer end of the wick at which point it may be ignited and burned. A secondary, closable opening may be provided for refueling, or refueling may be done through the wick opening.

Historically, liquid fuels have consisted of various oils and organic liquids which when ignited will continue to burn at a controlled rate. Examples of liquid fuels are fats, mineral oils, animal oils, vegetable oils; kerosene, naptha, and other petroleum fractions; and natural or synthetic organic liquids such as alcohols, glycol ethers, esters, ketones, etcetera.

The flame produced by most liquid fuels in wick type lamps is a luminous yellow due to the production of glowing carbon particles in the flame. Fats, oils, and petroleum fractions are volatilized by the flame heat into gases which at flame temperatures break down to form hydrogen and free carbon. High molecular weight organic liquids usually burn with a luminous flame for the same reason, exceptions being polymers of certain low molecular weight materials such as polyethylene. Low molecular weight organic liquids tend to burn with a blue or slightly luminous flame because they are more likely to burn without preliminary decomposition into hydrogen and carbon. Fuels which burn with a luminous flame can be made to burn with a clear blue flame if excess air or oxygen is introduced into the flame (Bunsen burner), but this condition cannot be simply attained in a wick type lamp. For illumination purposes luminous fuels have been favored because they give off more useful light. For heating purposes non-luminous fuels have been favored because they burn with a clean flame which does not introduce noxious fumes into the atmosphere or cause deposits of incompletely burned combustion products onto heated surfaces. Methanol (methyl alcohol) is the most common non-luminous fuel because it is inexpensive and readily available.

Color flames have been deemed desirable for decorative or ornamental purposes, and products have been marketed for the purpose of producing colored flames in burning wood and coal. The natural colors produced by burning wood or coal are typical of luminous flames, yellow to orange with areas of clear blue due to the combustion of carbon monoxide. Sometimes flames of other colors appear due to metallic compounds which occur naturally in wood or coal. Other colors may be added to the luminous flame but it is seen as a mixture with the luminous flame. This added color is produced by the introduction of certain metallic salts which when heated to high temperatures color the flame. The color imparted to flame by certain metallic salts has been the basis for indentifying the metal portion of the salt in qualitative chemical analysis for many years. Lithium salts impart a carmine red color, strontium salts a scarlet, copper salts a blue, barium salts a yellow green, and sodium salts a yellow. There are other metals whose salts give colored flames according to the Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., Cleveland, Ohio, at least as far back as the 1936 edition. The coloring of flame by metallic salts requires that the salt be at a location in the flame where the temperature is high enough to excite the atoms of the metal portion of the salt so that they emit visible radiation, the color of which is peculiar to the metal and the temperature.

We have found that the creation of a flame of relatively pure color can be achieved by introducing a color producing, metal salt at the point of burning of a fuel which burns with a non-luminous or clear blue flame. The salt can be introduced at the point of burning by dissolving the salt in the fuel in which case the evaporation of the fuel as it burns leaves a salt residue at the point of burning. The salt may also be incorporated into the wick at the point of burning, and in this case maximum color is favored by a slight solubility of the salt in the fuel. Methanol is again a favored as a fuel because it can dissolve useful amounts of many salts. The salts to be selected should produce the desired color, be fuel soluble to some extent, of a low order or toxicity (the deadly thallium compounds will produce a green flame), do not corrode the wick so as to require wick adjustment to maintain flame, and do not corrode the lamp reservoir.

When metallic salts are dissolved in methanol for the purpose of producing a colored flame, and when this solution is placed in a liquid fuel lamp and ignited, it will burn initially with a clear blue flame characteristic of methanol, which after a period of one to five minutes, depending upon salt concentration, begins to burn with a desired colored flame as the salts begin to accumulate at the tip of the wick. The delay in developing the flame color after ignition may be a disappointment to one who expects immediate confirmation of the claim for a colored flame. Most of the liquid fueled lamps on the market today for decorative use are formed from steel or aluminum and are designed for use with kerosene. These lamps designed for use with kerosene, a high flash solvent with a flash point in the range of 130.degree.-190.degree.F., may produce small explosions and flaming eruptions when used with methanol fuel which has a flash point of 50.degree.-60.degree.F. Furthermore, these lamps often have insecure covers which spring loose when the lamp is upset and cause a flash fire of considerable intensity. These characteristics of methanol fuels demand that this fuel be used with a lamp specifically designed for use with this fuel so that the fuel and lamp combination will not be an undue fire hazard, will not corrode the lamp so as to cause dangerous leakage of fuel, and will immediately upon ignition produce the desired colored flame.

Given the properties of a methanol solution of metallic salts which will produce a colored flame, it is evident that common metal lamps could not be used successfully unless the fuel were isolated from the lamp or torch reservoir by an inert lining. Inert plastic coatings can be applied to metal reservoirs or containers but are difficult to apply with no imperfections which allow metal attack. Inert plastic bags may be used to protect the reservoir from the fuel but are difficult to attach.

It is our invention that a different and successful approach is to place the metallic salts in the wick rather than in the fuel, keeping the wick outside the lamp until ready for use.

One form of our method is the incorporating the salts in the wick by dipping part or all of the wick into a solution of salts and subsequently removing the solvent by drying. This can be done, but some of the desirable salts tend to absorb atmospheric moisture, and the wick must be bagged in a moistureproof container to prevent the salts from picking up moisture and corroding contacting surfaces. A better approach and one which eliminates the drying operation is to first dip the end of the wick into a molten wax and immediately dipping the wax wetted wick end into a dry, metallic salt powder before the wax hardens. Thus, the salt is placed at the end of the wick where it is needed and held there by the hardened wax which keeps the salts from falling off and which protects the salts from atmospheric moisture. The wax can be colored with a dye to indicate the color of the flame to be expected. The wax to be used should burn with a colorless or pale blue flame so that the initial flame color is not contaminated by the yellow of a luminous flame. Suitable waxes are polyethylene or polyethylene glycol.

While methanol is the fuel of choice, it has a high degree of oral toxicity and under the regulations of the Poison Prevention Packaging Act of 1970, household preparations containing more than 4 percent methanol must be equipped with a child-proof closure as defined in the regulations for the Act. Accordingly, our preferred combination consists of a container 10, preferably metal, with a closable wick opening 11 and filled with methanol 12 or methanol containing certain additives; the closable opening 11 is closed with a screw cap 13 or other suitable closure; a wick 14 one portion or end of which is impregnated with a metallic salt 15 suitable for producing a colored flame 16, and a child-proof overcap 17 of a volume sufficient to contain the entire wick coiled into the overcap when the overcap is secured over the top of the container 10, in accordance with the Regulations of the Poison Prevention Packaging Act of 1970. The overcap which is preferably plastic or plastic lined may also be used as a flame extinguisher when placed tightly over a flaming wick. The overcap 17 may be colored to indicate the desired flame. The wick may also be colored where the metallic salt is added and the wick must be of such material as to cause a rapid rise of fuel by capillary action from the fuel reservoir of the lamp or torch to the end of the wick. The wick material must not be affected by the fuel and must not contribute toward flame color.

The container may be of any desirable size, but generally we have used containers holding from 1/2 pint to 1 gallon of fuel, with one pint the preferred size for patio and garden use of the average household.

The wick is ordinarily 3/4 of an inch in diameter and should be of such a diameter as to fill the wick opening 11 of the container 10 and be long enough to extend from the bottom of the container to above the wick opening to permit the colored flame.

In use, wick 14 is removed from overcap 17 or other suitable covering such as a plastic bag, an untreated end of the wick 14 is inserted through wick opening 11 into fuel 12 at the bottom of the container 10, with the treated upper end extending beyond opening 11. Upon the fuel being ignited and burning, the metallic salt 15 in the wick 14 will be heated immediately to produce a flame of desired true color, and to steadily maintain this true color.

In the course of selecting metallic salts which produce the brightest and most enduring colored flame, we make the following observations.

1. Salts of organic acids are decomposed by the flame heat into high alkaline products such as carbonates, hydroxides and oxides which corrode the cotton wick causing loss of wick and requiring wick extension to maintain flame size.

2. The metallic chlorides are the most desirable salts because they do not cause excessive wick attack, their relatively high volatility results in a bright flame, and they tend to protect the burning wick from afterglow when the flame is extinguished.

3. If the metallic salts are incorporated in the wick, excessive amounts of the salts impede the capillary travel of the fuel to the burning wick end and reduce flame size.

4. Flame color brightness can be enhanced by incorporating limited amounts (5-20 percent) of water into the fuel. This added water increases salt solubility in the fuel, enabling the salt to better migrate to the burning wick end.

5. Maximum flame color is achieved from salts located at the very end of the burning wick because this is the hottest part of the wick. Heat is required to excite the mettallic salts sufficiently for color production.

Other pertinent observations on our invention are:

1. A wick of purest cotton or cellulose is desirable for producing a flame of pure color. Any other suitable material may be used. Sodium salts are commonly found as an impurity in natural products such as raw cotton. Sodium salts are undesirable because they readily produce a bright yellow flame which, while desirable as such, masks out other colors. 2. Boric acid reacts with methanol to produce methyl borate, a compound which burns a green flame. This fact can be used to advantage to produce a green flame. The methyl borate green is faint compared to that produced by copper salts but acts to reinforce the copper green. The unreacted boric acid accumulates on the wick to prevent afterglow. Afterglow is especially undesirable in the presence of copper compounds because the heat of afterglow plus the catalytic effect of copper compounds will convert methanol to the highly obnoxious formaldehyde.

3. The selection of molten wax for a carrier or binder of metallic salts at the wick end was directed by these considerations:

a. The wax should melt in the range of 130.degree.-160.degree.F. so that the handling hazard is minimized and that the wax will air harden quickly.

b. The wax should burn with a non-luminous flame.

c. The wax, when molten, should quickly wet the wick.

d. A polyethylene glycol having an average molecular weight of 6000 meets the foregoing requirements.

The following examples are selected to illustrate our invention:

1. Dipping an end of a pure cotton wick into molten wax (polyethylene glycol having an average molecular weight of 6000) and immediately dipping the wax wetted wick end into powdered lithium salts such as lithium chloride to acquire 0.5 grams. The range of such salt used may extend from 0.1 gram to 1.0 gram. When the other end of the wick extends within a lamp having methanol fuel, and the fuel is ignited and burns said salts are heated to produce a red flame.

2. Using the same method as set forth in example 1, except that potassium salts such as potassium chloride instead of lithium salts such as lithium chloride are used in the same proportions to produce a blue violet flame.

3. To produce a green flame, the same method as set forth in example 1 and in the same proportions used except that a copper salt such as cupric chloride is in place of a lithium salt. We also suggest that instead of the usual methanol fuel, that a fuel consisting of substantially 3 percent boric acid 12 percent water and 85 percent methanol by weight be used to produce and maintain the green flame.

4. To produce a gold flame, the same method set forth in example 1 and in the same proportions as used except that sodium chloride is used as the salt.

5. To produce a rainbow flame of red, yellow, green and blue violet, we proceed to wax an end of the wick as in example 1. We then dip about a quarter of the surface of the wax wetted wick end into lithium chloride to obtain 0.25 grams, rotate the wick a quarter turn and dip this area into sodium chloride to obtain 0.25 grams, rotate the wick another quarter turn and dip this area into cupric chloride to obtain 0.25 grams, rotate the wick another quarter turn and dip this area into potassium chloride to obtain 0.25 grams.

6. Red flame may also be obtained by dipping the wick into molten lithium acetate or other molten lithium salt. In this situation the methanol fuel should contain 0.1 to 1.0 percent by weight of lithium chloride to prevent wick attack by decomposed lithium acetate.

7. A red flame may also be obtained by dipping part or all of the wick into a solution of lithium salts such as lithium chloride, the solution containing a wetting agent to facilitate penetration of the wick by the salt solution. The solution strength and immersion time should be such that the wick when dried contains from 0.5 grams to 5.0 grams of salt.

8. To produce a green flame, the same method and proportions as in example 7, except that the salt is a copper salt such as cupric chloride.

9. To produce a blue violet flame, the same method and proportions as in example 7, except that the only salt used is a potassium salt such as potassium chloride.

10. To produce a gold flame, the same method and proportions as in example 7, except that the only salt used is a sodium salt such as sodium chloride.

11. To produce a red flame, dip the wick end into a molten suspension of a powdered lithium salt such as lithium chloride in polyethylene glycol having an average molecular weight of 6000.

12. To produce a green flame, dip the wick end as in example 11, except that the salt is a copper salt such as cupric chloride instead of lithium chloride.

13. To produce a blue violet flame, dip the wick end as in example 11, except that the salt is a potassium salt such as potassium chloride instead of lithium chloride.

14. To produce a gold flame, dip the wick end as in example 11, except that the salt is a sodium salt such as sodium chloride instead of lithium chloride.

In all of the foregoing examples, an appropriate dye may be added to indicate the flame color produced by the treated wick.

Claims

1. A lamp comprising a container having a non-luminous fuel and a wick opening, a closure for closing the wick opening, a wick, desired metallic chloride incorporated in said wick, an overcap for said wick having means for removable attachment to the exterior of said container during transit, storage and shelf life prior to use, said closure removable from said container, said wick removable from said overcap, so that the lower end of said wick inserted through the wick opening extends into the fuel at the bottom of the container, and its upper end extends beyond the wick opening, so that upon the fuel being ignited and burning heats the

2. The lamp set forth in claim 1, in which the metallic chloride is

4. A lamp comprising a container having a non-luminous fuel and a wick opening, a closure for closing the wick opening, a wick, lithium chloride dissolved in said fuel, an overcap for housing said wick and having means for removable attachment to the exterior of said container during transit, storage and shelf life prior to use, said closure removable from said container, said wick removable from said overcap so that the lower end of said wick inserted through the wick opening extends into the fuel at the bottom of the container, and its upper end extends beyond the wick opening, so that upon the fuel being ignited and burning evaporates leaving a heated deposit of lithium chloride on the wick end to provide a

5. A lamp comprising a container having methanol fuel and a wick opening, a closure for closing the wick opening, a wick, boric acid dissolved in said fuel to form methol borate, an overcap for housing said wick and having means for removable attachment to the exterior of said container during transit, storage and shelf life prior to use, said closure removable from said container, said wick removable from said overcap, so that the lower end of said wick inserted through the wick opening extends into the fuel at the bottom of the container, and its upper end extends beyond the wick opening, so that upon the fuel being ignited and burining heats the methol

6. A lamp comprising a container having a non-luminous fuel and a wick opening, a closure for closing the wick opening, a wick, sodium salts dissolved in said fuel, an overcap for housing said wick and having means for removable attachment to the exterior of said container during transit, storage and shelf life prior to use, said closure removable from said container, said wick removable from said overcap, so that the lower end of said wick inserted through the wick opening extends into the fuel at the bottom of the container, and its upper end extends beyond the wick opening, so that upon the fuel being ignited and burning heats the sodium salts to provide a yellow flame.