IL32364A - Flare body comprising a wire net - Google Patents

Description

FLARE BODY COMPRISING A WIRE NET ncn ynsn πτικη nix or asbestos, in a suitable manner it is possible to obtain that the flames which are actuated by the air flow swee ing around the flare composition do not cause an ignition of the flare composition at other sections than that facing the grourkl j3y means of the insulation it has been possible to obtain a combustion which if the flare composition consists of a circular cylinder with end faces at right angles to the axis of the cylinder takes -place in axial direction and with substantially constant and equal velocity over the whole burning sur-j face which moves successively in the direction of the axis of the cylinder and which thus is substantially plane and perpen-f iicular to the axis of the cylinder.

The more regular combustion of the flare compositiqn obtained by the use of the insulation has led to an increased Light yield or more correctly an increased total amount of Light during the burning time, but further investigations have !s own that smoke which occurs during the combustion of the fleire o position was developed between the burning surface and the round, that is between the flame and the ground so that the Intended illumi ation of the ground below the flare composition ioes not become as high as expected.

When for various reasons the flare composition together with the surrounding insulation was encased in a sleeve :>r a casing of steel which surrounded the flare composition in substantially the same way as the insulation, i.e. left free Dnly the end surface of the flare composition of the circular ylindrical flare body facing the ground, there was obtained a considerable increase of the total light amount produced; duijing he burning time. The reason therefore seems to depend on the [act that 'by- the combustion of the flare composition in the previously mentioned regular way with the burning surface sub- -Ly (except from oscillations or the like) that indicated by the arrow f. It is obvious that the insulation protects the rear (sections of the flare body from being ignited by the flames (shown by the lines a.

In Fig. 2 there is shown in the same manner as in Fig. 1 the conditions at a flare body with a connection means 3, a flare composition 1 and a surrounding steel casing 5· After a certain burning time it is in this case obtained a re-| siaining edge portion 5a of the steel casing which edge portiorj sxtends beyond the burning flare composition 1 and causes the formation of a fierce flame diagram atically shown by the j)ent lines b. The drag - also in this case the fall-direction I Is indicated by the arrow f - causes a deflection of the outer free end of the fierce flamo and the occurrence of the producea jmoke behind the deflected fierce flame, as is diagrammatically indicated by the dotted line ^. Thus it is clear that by usic a steel casing there is no considerable amount of smoke betweqn he burning flare composition and the flame on one side and t |e ground on the other side. This is the reason of the already mentioned good efficiency or the great total amount of light from flare bodies according to Fig. 2. For the sake of complete less it is pointed out that in Fig. 2 a possible or normally used insulation has not been shown.

As previously mentioned it has been found that a surprising improvement is achieved if instead of a steel casin| there is used a net of metal with a considerable ability to withstand high temperatures, for instance stainless steel. ;It ias been found that by the application of a steel net directly) iround a flare composition and without using an insulation, ;he advantage of a fierce flame, as mentioned in connection with Fig. 2, is obtained and with the produced smoke placed j i behind the fierce flame deflected by the influence of the j drag. This is a very surprising result and the physical condi tions are not fully explained. Thus the following explanation does not in any way restrict the invention but is only mentioned in order to try to give such a good picture of the conj editions as at present is possiblee It is likely that a wire net with, suitable mesh and {wire thickness is not only able to act as a noszle but also may assist the fierce flame, flowing out through the forward opening in the wire net, in drawing secondary air through the meshes of the wire net. The effect hereof is double in that probably a certain turbulence which improves the combustion |arises in the burning zone immediately in front of the end surface of the flare composition, and further the oxygen of the incoming air causes a more complete combustion of the material of the flare composition which in the present case pre-} ferably has deficit of oxygen (relatively to the amount of magnesium in the flare composition) and that for this reason it is achieved a greater total amount of light for a certain [amount or weight of flare composition than if for instance {there is excess of oxygen in the flare composition.

Thus, by the sole use of a wire net a surprising jLmprovement is obtained, but it has been found that there is certain tendency of irregular combustion and a possibility that in spite of the fierce flame a further ignition of the flare composition can occur at for instance the rear portion.

According to a further development of the present Invention the metal wire net is combined with an insulation-mown pe r se , which however can be made comparatively thin.. Άη embodiment of a flare body of this kind is shown in Fig. Li-in which there is a flare composition 1, an ignition device 2 and connection means 3. The flare composition is at the cylinder surface surrounded by metal wire net 6 which by means of an insulation layer ka. is separated from the flare composition 1. This insulating layer a. may be thin. According to a . referred embodiment the metal wire net is moulded into the insulation which thus consists of a first layer Lt-a between the net 6 and the flare composition and a second layer b outside the net 6. Said insulation may consist of the same plastic material with filler in the form of MgO or asbestos, as is already mentioned. In Fig. 3 which, is an end view of the embodiment shown in Fig. l\- it is to bo seen that the- flare body is in the form of a circular cylinder..However, it is to be observed that it is not necessary to use a circular cylinder but also other shapes of cylinders can be used. If considerable irregularities regarding the combustion process can be allowed it is possible also to use other shapes of the flare composition, which however must have a free surface la with an ignitio device 2 so that it can be ignited and burn and leave a usably light flow. However, it ought to be pointed' out that the invention is not limited to flare bodies with the flare composition in the shape of a cylinder or a circular cylinder, although these shapes are the most commonly used« As already mentioned the action of the metal net is especially advantageous in connection with the use of a thin insulation and a flare composition having a deficit of oxygen as regards the oxygen-containing material in the. flare composition in comparison to the amount of magnesium or possibly a substance of another metal or other compounds which forms the Material intended for the combustion.

As an example of the improvement obtained by the (present invention it can be mentioned that by a flare body havj-fLng a diameter of 70 mm and an initial length of 90 mm and a ircular section it has been obtained in using only one plastic insulation a total light yield of about 8 millions candela seconds, while the use of a steel casing or a steel casing in o bination with an insulation - a hitherto much used embodiment - has given an average light yield of about 20-22 milliori candela seconds. :By using .a net of stainless steel- with a dia1-neter of about 0.25-.10 mm and meshes of .1.0-2.0 mm, i.e. orresponding to 1^-18 mesh, it has been obtained values over 30 millions candela seconds. A favourable result has also beerj ahieved by so small meshes as 35 mesh.

No formula for the relationship between the mesh' of the wire net and other factors has been ascertained but it las been found easily. to ascertain the optimal mesh by simple' experiments in each case. It is evident that the already mentioned suction of secondary air through the wire net is presented and that the wire net is more easily choked up at small xie she s while big meshes do not cause, such a nozzle-action of the wire net as intended.

As non-limiting state e-nt it can be mentioned that (for flare bodies with circular cross- section and having a-dia-i neter of 60-100 mm, the optimal values for the wire net nor-nally lie within that field obtained by using a thread having a diameter of 0.25-1.0 mm. and a free mesh of about 1.0-2.0 mni.

It can also be mentioned that except for the already stated advantages by the use of a wire net a further advantage (lies in the fact that the smaller mass of the wire net and the great cooling which a falling wire net is subjected to since the flare composition has finished to burn, makes the risk: for an ignition of the ground where the rest of a flare body falls considerably reduced in comparison with a flare body having a steel casing.

The invention has been described in connection to flare bodies intended to be carried by parachutes, but of course -the invention may also be preferably used for flare bodies used in another way.

Claims (1)

1. WHAT IS CLAIMED A flare body having a flare of a material which produces light by and a material to the combustion and provided with a free approximately plane first end stantially perpendicular to the longitudinal direction of ί the flare composition and with a closed second end characterized in that the outer surface of the flare tion between the first and the second end surfaces is j by a wire net of metal having ability to withstand high peratures arising by the combustion of the flare A flare body according to claim characterized that between the flare composition and the wire net there jis provided a heat insulation in the form of a thin layer of for instance plastic material with a filler of asbestos ί the A flare body according to claim characterized that the wire net at the outer side facing away from the flare composition has a layer of heat insulating preferably of the same material as the heat insulation between wire net and the flare A flare body according to claim characterized in that the wire net is moulded the heat insulation in a way that the wire net has a layer of the insulation at inner as well as at the outer sidee A body according to any of claims 1 characterized in that the wire net consists of stainless A flare body according to any of 1 ac in that the wire net of thread having a diameter of and a free mesh of p mm COHEN ZEDEK SPISBACH Box Attorneys for Applicant insufficientOCRQuality