A POWDER SPRAY WITH THE ABILITY TO CHARGE ELECTROSTATICALLY

Abstract: A powder spray (1) with the ability to charge electrostatically, consisting of a plurality of elongated, curved charging ducts (2) made of an electrically non-conducting material such as a plastic material, for example, which are coated with an electrically-conducting layer over part of their length, wherein the coating layer can be connected to a lead extending therefrom and intended to be connected to earth or to a voltage source, so that when the spray (1) is being used the powder material is charged by close contact with the internal walls of the ducts (2) as it passes through the said charging ducts (2). The aim of the invention is to provide a powder spray (1) of the above type which, amongst other things, charges the powder effectively and is compact and simple to use. This is made possible due, amongst other things, to the fact that the ducts (2) are curved round to form at least one loop (18) and/or undulation (19) with their longitudinal centre plane extending substantially in the supply direction of the powder.

Description: A Powder Spray with the Ability to Charge Electrostatically The present invention relates to a powder spray with the ability to charge electrostatically, consisting of a plurality of elongated, curved charging ducts made of an electrically non-conducting material such as a plastic material, for example, which are coated with an electri¬ cally conducting layer over part of their length, wherein, the coating layer can be connected to a lead extending therefrom and intended to be connected to earth or to a voltage source, so that when the spray is being used the powder material is charged by close contact with the internal walls of. the ducts as it passes through the said charging ducts. The main aim of the present invention is to provide a powder spray of the above-mentioned type which, in addition to functioning faultlessly . and charging the powder effectively, is also compact, due to the fact that it enables charging ducts of considerable length to be disposed in a small space. The said aim is achieved with a powder spray accord- iag to the present invention which is primarily character¬ ised in that the ducts are curved to form at least one loop and/or a curve with its longitudinal central plane extending substantially in the supply direction of the powder. The invention is described in the following with reference to the accompanying drawings, on which Figure shows a partially sectioned perspective view of a powder spray constructed according to the invention, Figure 2 shows the rear end of the spray in a partially sectioned view, Figure 3 shows the front end of the spray in a partially _ sectioned view, Figures 4- - 8 show various embodiment examples of possible loop formations for the charging ducts, and Figure 9 shows a charging duct curved in an undulating formation. A powder spray constructed according to the invention which has the ability to charge electrostatically and which is designated with the numeral 1 on the drawings is formed by a plurality of elongated charging ducts 2 made of electrically non-conducting material. Suitable materials are plastics, for example, or other similar materials. The charging ducts 2, which are appropriately coated over part of their length with an electrically- conducting layer such as metal, are accommodated via one of their respective ends, preferably their rear end, in a core 3- The core 3 which is exemplified on the drawing in Figure 2 is formed of two circular plates and 5 which have a number of openings 6 and 7 respectively round their periphery, distributed in a circle and corres- ponding to the number of ducts 2, being adapted to the said charging ducts 2. The openings 6 in one core plate 4* form.passageways 6 for the respective ducts 2 and this plate 4- is made of a material which is electrically con¬ ducting, such as aluminium, for example. The openings 7 in the other core plate 5 which is expediently manu¬ factured from a plastic material have a shape such that the ends 2A of the tubular ducts 2, which are distorted after they have been inserted through the openings 6 in the other plate , can be accommodated therein in that, for example, the plate 5 is provided with larger bores 8 OMPI Λ. WIPO « on the side -A- of the plate which lies against the plate 4. On the other side 5B of the plate 5* i.e. the side 5B which is furthest away from the plate 4, the openings have, for example, funnel-shaped outlets 9 to allow the powder to pass in through the qpenings 7 into the tubes 2. The .plate 5 is expediently attached to the plate by means of a screw 10 as shown on the drawing in Figure 2. The plate 4 has a connection 11 with which the spray can be connected to earth or to a voltage source via a line which is not shown on the drawing, and connected to the coating on the charging ducts 2. A seal in the form of an 0-ring 3A- . for example, is arranged to rest between the core 3 and a sleeve-type connection 12 which is designed to be used for connecting the powder spray 1 to a powder-supplying hose or the like. As shown in Figure 3 5 the other ends.of the ducts 2, i.e. the ends which are furthest forwards, viewed in the transportation direction of the powder, . are accommodated in another core 13. This other core 13 . which is ex¬ pediently also made of a plastic material, similarly has passage holes 14 distributed in a circle around its peri¬ phery, corresponding in number to the number of charging ducts 2 and adapted to the respective charging ducts 2, • as can be seen in Figure 3. The said core 13 is supported by a front sleeve-type connecting part 15, which is equipped with a threaded part 15A designed to be used for connecting the spray to a dispersing nozzle, for example. -ks is clearly shown in Figure 1, the charging ducts 2, the connecting parts 12, 5 and the other associated parts can be enclosed in a preferably box-shaped casing 16 which is formed in the example shown here of two parts 15A and 16B with respective joining surfaces disposed extending in the longitudinal direction of the spray 1. • fδ lΛC / -- * OMPI IPO ^EΓATI^ The ends 16C and 16D of the casing 16 are drawn in some¬ what so that the connecting parts 12, 15, which can be provided,, for example, with their own respective stop-type parts 12A and 15B, can be accommodated in their respective ends 16C, 16D of the casing 16. A fixing 7 is expediently attached to the casing 16 and is designed to be used when the spray is to be supported on and manipulated via a manipulator, for example, or a similar device. The characteristic feature of the present invention is the way in which the charging ducts 2 are curved. In the embodiment examples which are shown in Figures 1 - 8 the respective ducts 2 are curved so that they form at least one loop 18, while a duct 2 which is shaped to form at least one undulation 19 is shown in the embodiment example in Figure 9- Figure 4 shows how a duct 2 is curved.so that it form a plurality of loops 18 arranged in sequence one after the other, having a regular formation. In Figure 5 an embodiment is shown where the loops 18 are curved so that the transportation direction for the powder in them is reversed in the adjoining successive loops 18. Figure 6 shows an arrangement of the loops 18 similar to that which is shown in Figure 5 except that certain loops 18 are given differently-sized curvature diameters. Figure 7 shows an embodiment where a plurality of loops 18 disposed transverse to the transportation 1 direction of the powder form groups 18 of loops 18 which are displaced sideways relative to each other, viewed in the transportation direction, but are still arranged to form a continuous powder duct 2. It is also possible to bend the charging duct 2 so that a plurality of loops 18 forms a .spiral, with the loops 18 disposed closely adjacent to each other. Also the curving of the duct 2 into an undulating formation 19 nay be varied in a large number of ways. The longitudina central plane of the respective loops 18 and undulations 19 extends substantially in the supply direction of the powder in all the embodiment examples. In order to increase further the charging capacity of the spray 1 an electrically-conducting layer of metal foil, for example, may be wrapped round the curved ducts 2. A protective layer of plastic film, such as heat- shrunk film 20, for example, may also be disposed around the charging ducts 2 when these are made into a single unit, as shown in Figure 1. The functioning of a powder spray as described above, which can be used, for example, for charging colouring powder, is as follows. The rear end 12 of the spray 1 is connected by means . of a hose to a powder container so that colouring powder, for example, can be transported with the air of a stream of air to the spray 1 and throug the ducts 2. During this process, due to the loopsand/or undulating curves of the ducts 2, the powder comes into close contact with the internal walls of the ducts 2, and due to the fact that the ducts 2 are connected to earth or a voltage source, is charged effectively over the whole of the surface of the powder. Due to the fact that the powder is flung towards the internal walls of the respective ducts 2, and especially if the loops 18 change direction, virtually all the powder comes into contact with the walls and is charged, which has not been the case with the sprays known until now. The charged powder is then supplied through the connecting part 15 and onwards out of the spray 1 through the dispersion nozzle and, due to the fact that it has been charged, it strives to seek out the object which it is desired to coat with the powder. In particular, sites on the object which are hard to reach can be coated effectively with the powder. The invention is not restricted to the embodiments which are described above and are shown on the drawings merely by way of example, but it may be modified with regard to its details within the scope of the following Patent Claims.

Claims: P a t e n t C l a i m s 1. A powder spray (1) with the ability to charge electro statically, consisting of a plurality of elongated, curved charging ducts (2) made of an electrically non¬ conducting material, such as a plastic material, for 5 example, which are coated with an electrically-conducting layer over part of their length, wherein the coating layer can be connected to a lead extending from them and intended to be connected to earth or to a voltage source, so that when the spray (1) is being used the powder 10 material is charged by close contact with the internal walls of the ducts . (2) as it passes through the said . charging ducts (2), characterised in that the ducts (2) are curved to form at least one loop (18) and/or undulation (19) with the longitudinal centre plane 15 extending substantially in the supply direction of the powder. 2. A powder spray according to Patent Claim 1, characterised in that a plurality of loop-shaped (18) -charging ducts (2) are assembled together to form a 20 bundle with the loops (18) disposed adjacent to each other. 3. A powder spray according to either of Patent Claims 1 - 2, characterised in that each separate charging duct (2) has a plurality of loops (18, 18 ) which are located 25 adjacent to each other in the transverse direction, viewed in the supply direction of the powder. O 4. A powder spray according to one of Patent Claims 1 - 3, characterised in that the respective loops (18) extend in the form of a spiral line (Figure 8) with a plurality of 30 revolutions substantially over a common plane. - REAIΓ OMPI 5. A powder spray according to any of the preceding Patent Claims, characterised in that the respective charging ducts (2) are enclosed in a stocking-like casing, preferably common to all the ducts (2), and preferably made of electrically-conducting material. 6. A powder spray according to any of the preceding Patent Claims, characterised in that the ducts (2) are accommodated in a common housing (16) which can be taken apart, preferably along its longitudinal extent. 7- -k powder spray according to Patent Claim 6, characterised in that each of the ends (16C, 16D) of the housing (16) is adapted to its respective holding devices (3, 13) for holding all the ducts separate from each other. 8. A powder spray according to Patent Claim 7 » characterised in that the said holding devices (3 5 13) are designed to hold and enclose the respective ends of the ducts (2) distributed in a circle around their periphery. 9- -^ powder spray according to Patent Claim 8, characterised in that one of the said . holding devices (3) is formed of a preferably two-part (4, 5) core (3) equipped with holes, at least one part (4) consisting of ' aluminium or a similar material and being connected to the said coating layer on the ducts (2), and able to be connected to earth or to a voltage source. 10. A powder spray according to Patent Claim 9 S characterised in that one (5) of the said two holding device parts has recesses for accommodating a seal (3-&*) which co-acts with a holding part (12) and with pre¬ ferably clamped duct ends (2A) equipped with flanges. O PI ft, WIPO

Inventors: RUUD JAN
Applicants: ICAB IND COATING AB, RUUD JAN
Application year: 1982
Main classification: B05B5
IPC codes: B05B5