Title:
Flare system
United States Patent 3888177


Abstract:
A flare system is produced which comprises a flare composition having at st two primary i.e. predominant color emitters which produce one apparent color and a filter which will eliminate the wavelength of at least one of the emitted colors, such that the burning flare appears to be an identical color of an ordinary state of the art flare to the naked eye whereas when viewed through a filter a completely different color will appear.



Inventors:
TYROLER JESSE F
Application Number:
05/443161
Publication Date:
06/10/1975
Filing Date:
02/15/1974
Assignee:
The United States of America as represented by the Secretary of the Army (Washington, DC)
Primary Class:
Other Classes:
149/19.91, 149/116, 356/417
International Classes:
C06B33/00; C06C15/00; F21K5/00; F42B4/26; (IPC1-7): F42B4/26; G01J3/48
Field of Search:
356/87,176,178,186,187,190 250
View Patent Images:
US Patent References:
3755680FLAME COLOR SIGNATURE APPARATUS1973-08-28Smith et al.
3706611N/A1972-12-19Hastings
3667850N/A1972-06-06Smith et al.
3327124Method for facilitating the identification of icbm nose cones and for discriminating against decoys by spectral analysis1967-06-20Plum



Primary Examiner:
Hubler, Malcolm F.
Assistant Examiner:
Buczinski S. C.
Attorney, Agent or Firm:
Edelberg, Nathan Gibson Robert Erkkila Victor P. A.
Parent Case Data:


This is a division of application Ser. No. 195,880 filed Nov. 4, 1971, now abandoned.
Claims:
I claim

1. A method for discriminating between visible, apparently identically colored flares, wherein a polyemitter flare composition has at least two predominant color emitters which in combination produce a visible color apparently identical when viewed with the eye to that produced by another flare composition having a different predominant color emitter which comprises viewing the ignited flare compositions through a filter capable of eliminating the spectral wavelength of at least one of the predominant color emitters of the polyemitter flare composition, such that when viewed with the eye through the filter the polyemitter composition has a different color than the other flare composition.

2. The method of claim 1, wherein the polyemitter flare composition consists essentially of barium nitrate emitting green spectral wavelengths essentially between 0.51 and 0.53 micron and strontium nitrate emitting red spectral wavelengths essentially between 0.60 and 0.68 micron, and the other flare composition consists essentially of sodium nitrate emitting yellow spectral wavelengths essentially between 0.56 and 0.61 micron, both flares producing substantially the same visible yellow color, and wherein the filter transmits spectral wavelengths above 0.53 micron but eliminates spectral wavelengths of 0.53 micron and below, whereby when viewed through the filter the polyemitter composition appears red and the other composition appears yellow.

3. The method of claim 1, wherein the other flare composition has a single predominant color emitter.

4. The method of claim 2 wherein the polyemitter flare composition consists of the following constituents:

Description:
BACKGROUND OF THE INVENTION

In the past surface flares of various colors have been used to outline friendly troop positions when air support was required. This enabled the pilots to identify the front line positions of friendly troops and reduced the possibility of bombing or strafing friendly troops. To counter this enemy forces soon learned to ignite similarly colored flares which succeeded in confusing the pilots and rendered air support ineffectual. To solve this problem I have invented a special flare system which comprises a flare composition having at least two primary i.e. predominant color emitters which in combination will produce a colored flame matching the color of ordinary colored flares to the naked eye and a filter which will eliminate at least one of the primary colors such that the color of the flame is different when viewed through the filter than the color of the ordinary flare.

In a physical sense, color is determined by the wavelength(s) or spectral energy distribution contained in a light beam. In principle, it is possible to produce any color by a suitable combination of three primary colors, one from the middle of the visible spectrum (green) and one from either end (blue-violet and red). Proper proportions of red and green light will produce yellow and if the proper amount of blue-violet light is added, white light is produced. Elements used to color pyrotechnic flames for military uses are strotium, producing red; barium, producing green; and sodium, producing yellow. Copper (blue or green) has also been used. Lithium (red), boron (green), thallium (green), rubidum (red), and cesium (blue), are also strong color producers but their use is not practical because of cost, toxicity, or nature of their compounds.

Color intensifiers which are mainly chlorinated organic compounds, e.g. hexachloroethane (C2 CL6), hexachlorobenzene (C6 CL6), dechlorane (C10 CL12) and polyvinylchloride (CH2 --CHCL), are used to increase the color in the pyrotechnic flame.

It is therefore an object of this invention to provide a flare system comprising a pyrotechnic composition with at least two color emitters and a filter which will eliminate at least one of the colors emitted.

Another object is to provide a flare system which will provide a means for determining enemy and friendly forces.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description.

DESCRIPTION OF THE INVENTION

According to my invention a new flare system is introduced which comprises a special flare composition and optical filter. The flare composition when ignited appears to the naked eye to be one distinctive color but in reality is a combination of primary colors produced by at least two different color emitters in the pyrotechnic composition. The desired color is obtained by the judicious selection of color emitters in proportion to one another. The filter is chosen to block or absorb at least one of the colors so that the ignited pyrotechnic composition when viewed through the filter will emit a different color than the one emitted to the naked eye.

Specifically a flare composition and filter are introduced below as an example of an operative flare system.

______________________________________ Compound Parts By Weight ______________________________________ Barium Nitrate 30 Strontium Nitrate 13 Potassium Perchlorate 9 Magnesium - Atomized 50/100 15 Magnesium - Atomized 30/50 15 Dechlorane (C10 CL12) 12 Vinyl Alcohol Acetate Resin * 4 ______________________________________ * A copolymer of polyvinyl alcohol (18%) and polyvinyl acetate (82%)

The above ingredients are added together and mixed in a circular blending pan with a heavy muller wheel. After the mixing is complete the composition is loaded into a flare canister of desired size. The igniting means may be one conventional to the art such as a squib initiator.

The composition when ignited will burn with a yellow flame such as the one produced by a standard military flare which employs sodium nitrate as a color emitter. This result is due to the hue produced when the red (strontium nitrate) and green (barium nitrate) emitters are combined.

The filter chosen for the above composition is a Corning C.S. 3-67. The Corning C.S. 3-67 is a sharp cutoff filter described by its transmission curves shown in FIGS. 1 and 2.

FIGS. 1 and 2 represent a spectral distribution of a standard yellow (Na) and the example flare composition (Ba and Sr) respectively. The green color region has a spectral energy wavelength between 0.50 and 0.53 microns, the yellow region between 0.56 and 0.61 microns and the red region between 0.60 and 0.68 microns.

More particularly FIG. 1 is a curve of a standard (NaNO3) flare with its energy peak in the yellow (0.56 - 0.61) region. By transmitting this emitted spectral energy through a Corning 3-67 glass filter (as represented by the dotted line in FIG. 1) the yellow region is transmitted unhindered leaving the flare its original yellow color.

In the special flare illustrated in FIG. 2 however, the filter eliminates the green region (0.51 - 0.53) produced by the barium so that all that remains is the red region (0.60 - 0.68). Unfiltered, the green region and red region combine to produce a yellow color very closely matching the color of the pure yellow flare to the naked eye.

Although the example above involves a red-green color emitter composition, it is evident that other color combinations together with selected filters are available to practice my invention.

Thusly, through the practice of my invention a flare system is produced which will create the capability of discrimination between enemy and friendly flares. This system (both flare composition and filter) will provide a means of coding a flare color to avoid duplication by the enemy.

I wish it to be understood that I do not desire to be limited to the exact detail of construction shown and described for obvious modification will occur to a person skilled in the art.