Technical field

The invention relates to a sprayer operating with a flame jet, by the aid of which different powder metals can be melt and applied as a coating on a properly pre¬ pared surfaceβ The apparatus has a spray head for feeding the powder delivered by a carrying substance, e.g. air, into the flame jet; in the body of the spray head bore-row are to be found for emitting and guiding the mixture of combustible gas to the combustion space of the flame _*

Background art

Applying powders in a melt state onto surfaces - in particular metal surfaces - represents a well known method So e.g. the HU-PS 159 923 discloses a method of this type for applying and preparing a coating. In course of said method the flame required for melting is produced by using a mixture of acetylene and oxygen or acetylene and air. Powder - e.g. aluminium powder - is blown by means of pressurised air along a plane between two slabshaped flame tending to each other and melt inbetween, thereafter the melt powder is applied onto the surface to be coated by using pressurized air.

The disadvantage of said method and apparatus, respect¬ ively, lies in that acetylene is most expensive, energy exploitation is uneconomical, in addition, quality of coating obtained by the method and apparatus does not meet requirements.

A process and an apparatus are also known which use PB-gas or natural gas as combustible gas. The disadvantage of this solution lies in that in order to prevent lateral

deflection of the powder jet discharged in a slab-shape form the spraying head and thus to eliminate powder losses, slab-shaped cold air- e s are directed onto the powder jet. In order to prevent powder losses to the desired extent, a considerable quantity of cold air is required decreasing considerably the temperature of the flame needed for melting the powder, resulting in a lower efficiency of powder .meltingβ As a consequence of the significant quantity of cold air energy required for melting increases considerably, stability of the melting flame decreases. Flame stability is further deteriorated by the fact that structural design of the spray head of known apparatuses does not exclude arrival of the air streams coming from different lateral directions and of uncontrollable intensity at the melting flame _*

Disclosure of Invention

The task of the invention is to develop a powder sprayer operating"with a flame jet, with which the flame for melting the powders wanted to be melted and applied can be easily produced and maintained, in addition, energy content of the required combustible gas - compared to known solutions - can be exploited in a far _. better procen ual ratio, geometric shape and dimensions of the flame are constant and ideal, accordingly shape and dimensions o the powder jet can be also ideally selected; the- roductio costs of the apparatus are low, structural design is simpl at the same time required maintenance is minimal _*

In accordance with the invention the task set is solved by providing a powder sprayer operating with a flame jet, having a spray head feeding the powder delivered by a

carrying substance, e.g. air, into the flame jet, in the body of the spray head rows of bores are to be found emitting and guiding the mixture of combustible gases to the combustion space of the flame. The apparatus according to the invention can be characterized in that unilaterally and/or multilaterally arranged sideplates and/or enclplates extending over the sprayer head body on the side facing the flame combustion space, formed similarly as teeth of a comb and confining the flame space, are fixed - preferab welded - in a heat-conductive -manner to the side lying practically perpendicularly to the surface of the sprayer head body, which incorporates the row of bores emitting the combustible gas needed for flame maintenance.

V/ith the apparatus according to the invention it is con- sidered as advantageous, if between the end of the pipe introducing the combustible gas and discharging into the spray head body and the bores of the rows of bores emittin the combustible gas, a system of bores is formed, allowin _g» the flow the combustible gas in the inside of the spray- head body along a closed path, at an angle of at least

360°.

In the spray head body, the system of bores leading the combustible gas to bores of the row of bores consists essentially of bore-tracts interconnected orthogonally. One or more sideplates and/or endplates can be made of a heat-proof material, so e.g. chrome steel, the outer surface of which can be optionally coated with thermal insulation _*

V/ith a preferred embodiment of the invention the part of the sideplate and/or enάplate extending over the

spray head body toward the combustion space is bent out¬ wards from the plane of the side surface of the spray head body _*

Brief Description of Drawings The powder spraying apparatus operating with a flame jet according to the invention will be described in details by the way of examples illustrated in the accompanying drawings wherein

Pig. 1 shows the sche stical side-view of a preferred embodiment of the apparatus according to the in¬ vention; Fig. 2 shows ^" the schematical top-view of the apparatus according to figure 1; Fig. 3 shows the frontal view of the apparatus in enlarg scale _*

Best Mode of Carrying Out the Invention

The apparatus consists of two main parts, the spray head 1 and the pipeline-system 2 leading the combustible gas and the powder, as well as air or oxygen needed for combustion to the spray head 1.

•The spray head body 3 of the spray head 1 can be prepared - in a well known manner - of a material of good thermal conductivity, e.g. bronze. The pipe 4 leading the combusti gas into the body of the spray head 3, as well as the nozz pipe 5 of flattened shape and having a tapered cross-secti carrying the powdered material, e.g. aluminium powder intended to melt and to apply on a given surface, are conn ed in a sealed manner to the back-side of the spray head body 3 _* Pressurized air is streaming through the nozzle pipe 5 towards the spray head body 3 _> which is partly de-

livering the powder to be melt, partly it delivers a part of the oxygen needed for the combustion of the combustible gas.

As a continuation of the nozzle pipe 5, in the spray head body 3 the narrow groove 6 is formed, extending nearly in full length of the spray head body 3, on both sides of whi - in a manner known per se - a row 7 of bores consisting of bores arranged side-by-side, is formed. The bores of th rows 7 of bores are arranged so, as to be convergent to th flame space 8 in front of the spray head body 3, while the axes thereof are intersecting in the middle-plane, in the symmetry-plane of the groove β _*

Inside the spray head body 3, between the discharge openin of the pipe 4 and the bores of the rows 7 of bores there is a bore system 9 interconnecting said bores, while the system consists of bore-tracts connected essentially ortho gonally _* Separate bore-tracts are leading from the dischar opening of the pipe 4 to the single rows 7 of bores _*

The system 9 of bores allows to flow the combustible gas into the rows of bores, when pressurized air and powder are flowing to the groove 6 and therethrough to the flame space 8 _*

On both sides of the spray head body 3 running parallel with the rows 7 of bores a heat-conductive sideplate 10 each - preferably made of chrome-nickel steel - is fixed, e.g. welded, in a dissipation heat transferring manner _* The spray head body 3 and the sideplates 10 are bearing up against one another on a large surface, consequently, -efficiency of dissipation heat transfer between them is good. The part of the sideplates 10 extending over

the frontal surface of the spray head body 3 incorporat¬ ing the rows 7 of bores is formed similarly, as the teeth of a comb _* This comb-teeth-like parts confine the flame space 8, accordingly the space, into which the combustible gas is discharged from the bores of the rows 7 of bores, as indicated by the arrows "c". Here the flame melts the pulverized material arriving together v/ith the pressurized air from the groove 6, therefrom the melt powder is trans¬ ported by the pressurized air and combustion products - as indicated by the arrows ^M d ^M - to the surface, which is intended to coat with the melt powder _*

In dependence of the quality of the applied pulverized material and operative circumstances of coating it may happen that oxygen content of pressurised air delivering the powder through the nozzle pipe 5 and the groove 6 to the combustion space 8 does not suffice for proper burn ing to the combustible gas. In this case, .through the slots of the comb-teeth-like shaped part of the side¬ plates 10 the required air excess can get unhindered into the combustion space 8, at the same time the teeth of the comb-teeth-like formed part of the sideplates hinders the laterally incoming air streams in disturbing stability of the flame. To increase stability, at both ends of the spray head body 3 _> between the sideplates 10 an endplate. is also inserted, in such a manner the combustion space 8 becomes essentially closed, it is open only in direction of the surface to be coated _*

As a consequence of the closed formation of the flame space 8 the parts of the sideplates 10 and endplates 11 enclosing the flame space 8 are considerably heated and

a significant part of the heat is transferred to the spray head body 3, accordingly, the spray head body 3 becomes also hot, and the combustible gas arriving through this pipe 4 will be also considerably heated in the bore- system 9, so the heated gas is streaming through the bores of the rows 7 of bores into the flame space 8, where it is mixed with air and burnt _*

It goes without saying that the flame of the combustible gas arriving at the flame space 8 in a heated state is far more stable and richer in calory, as if the combustibl gas arrived in a cold state into the flame space 8 _*

In course of our experimental tests is could be observed that v/ith the apparatus according to the invention for powder.spraying, operated with a flame jet, when a mixture of P3-gas and uir was used, when ignited, the flame burnt somewhat uncertainly. ..a soci as the temperatu of the whole apparatus and so the temperature of the mixture of combustible gas allowed to flow through the spray head body 3 reached the value of 80 G°, the flame became apparently more defined. If after some minutes - reckoned from the time of i nition - the mixture of combustible gas reached the temperature of 200 to 250 G°, the flame resisted excellently to ambient air streams and took up a compact stable spatial form, never seen before _* In course of our experiments we could also observe that on effect of the heated side-plates 10 and endplates 11 the effect of the lateral external air streams was reduced almost to zero, even, if the spray head 1 was moved sudden ly, with a quick motion laterally _* Summing up what has been said, the most advantageous

features of the apparatus for powder spraying, operating with a flame jet are, as follows:

Applying of the powder coating to the selected surface can be performed relatively quickly and always in an excellent quality, ϋnergy content of the combustible gas having been consumed for preparing the coating is prac¬ tically without any losses, or at least it can be utiliz¬ ed with a minimal loss. Process of coat formation can be performed easily, without any difficulty, as temperature and shape, geometric form of the flame melting the powder are always constant, temperature is considerably higher, than v/ith flames attainable under similar operative pre¬ requisites. In addition, the apparatus can be cheaply - manufactured, manipulation is simple, maintenance is hardly required _*