WO1996025238A1

WO1996025238A1 - Powder spraying booth

Info

Publication number: WO1996025238A1
Application number: PCT/EP1996/000364
Authority: WO
Inventors: Franciscus Petrus Wilhelmus Van Bakel
Original assignee: Balak Coatings N.V.
Priority date: 1995-02-14
Filing date: 1996-02-13
Publication date: 1996-08-22
Also published as: NL9500266A

Abstract

A powder spraying booth for applying a paint layer in powder form on products comprises: a base; side walls comprising transparent side panels provided with openings for admitting powder spraying equipment, air exhaust means, etc., which side walls comprise light transparent side panels; a ceiling having a channel extending over the entire axial length of the booth for admitting transport means of a transport system which conveys the products to be sprayed in a hanging situation along the axial length of the booth; as well as open front sides through which the said products are transported by the transport system into and out of the booth, respectively. The side walls are comprised substantially completely of a plurality of transparent side panels and the openings are present in the transparent side panels themselves.

Description

Powder spraying booth.

The invention relates to a powder spraying booth for applying a paint layer in powder form on products and comprising: a base; side walls comprising transparent side panels and provided with openings for admitting powder spraying equipment, air exhaust means, etc.; a ceiling having a channel extending over the entire axial length of the booth for admitting transport means of a transport system into the booth for transporting the said products which are to be sprayed in a hanging situation along the axial length of the booth; open front sides through which the said products are transported by the transport system into and out of the booth respectively.

Spraying booths of the above-indicated type are well known in several embodiments and are being used increasingly for the coating of products with a paint layer in powder form. The products are conveyed through the production facility using a hanging transport system. Prior to conveying the products on the transport system into the spraying booth the products are attached manually to hangers belonging to the transport system. In the spraying booth the slowly conveyed products are provided with a layer of paint in powder form by powder spraying devices which extend into the booth through the openings which are present in the side walls. In modern arrangements the powder spraying devices are automatically moved up and down by so-called industrial robots in order to achieve satisfactory spraying of the products. In order to achieve satisfactory adhesion of the powder on the product use is made of electrostatic techniques. Nevertheless a certain amount of powder does not arrive on the products and in the booth the powder moves downwardly to the bottom or adheres to the side walls and the ceiling of the booth.

After leaving the spraying booth the sprayed products are conveyed by the transport system to an appropriate baking oven where the paint in powder form is melted in order to achieve a well adhering layer of paint on the product. After leaving the baking oven and after cooling down the products are manually removed from the hangers of the transport system.

Using the above-described method products may be provided with paint layers of a colour according to order. As soon as production has to be switched over from spraying in one colour to spraying in a different colour the spraying booth first has to be subjected to high intensity cleaning prior to the start of production with the new colour. The intensive cleaning is absolutely necessary because otherwise paint powders of different colours would mix which would result in mixed colours. Powder which is not sprayed onto the product itself but into the surrounding space of the booth is usually, with a view to efficiency and economy, removed from the spraying booth using air exhaust means connected to the spraying booth, while separation means such as cyclones are used to separate the powder from the exhausted air, after which the recycled powder is returned to a supply container from which the powder is again fed to the powder spraying devices. Any mixing of powders of different colours, even to minute amounts, would inevitably lead to undesirable mixing of colour in the finished paint layer and therefore lead to rejection of products.

The necessity of intensive cleaning of the inside of the booth after each batch of production in a certain colour signifies an important loss of production as the booth cannot be used for other purposes during cleaning. It is therefore of eminent importance that intensive cleaning of the booth may be carried out in a minimum of time. Commercially available spraying booths are sometimes provided with special arrangements for automatically cleaning the side walls, the ceiling and the base floor of the booth automatically. These arrangements, however, are very costly and nevertheless are still not capable of cleaning a booth completely by itself without additional cleaning by human operators. A further disadvantage of such known arrangements is that much space is needed below the base of the booth. It is therefore necessary to position such spraying booths on a raised platform which entails a number of disadvantages. For instance the transport system needs to be positioned at a higher lever so that extra space is needed in the production facility. The manual provision of products on the hangers of the transport system and the manual removal of the products from the transport system is made more difficult. Operators that need to carry out the usually necessary additional spraying operations through an opening in a side wall of the booth will have to be positioned on a raised platform on the side of the spraying booth.

In the magazine "O&C, Tijdschrift voor Oppervlakte- technieken en Corrosiebestrijding", No. 1, January 1995, a new kind of spraying booth is discussed on page 29 which spraying booth is designated in the article as a glass booth. The application of light transparent panels in the side walls of the booth more particularly side panels made of security glass has a number of advantages. The powder adheres only little to security glass. The glass is extremely smooth and therefore is easily cleaned. As the glass has a very hard surface it will stay smooth even though the powder has a slightly abrasive character. Another advantage is that light may penetrate into the booth from the outside which is of advantage more particularly with a view to manual auxiliary spraying of the products. Nevertheless the problems which are caused by the necessity of intensive cleaning of the booth have not be satisfactory solved. The glass panels are placed in rebates of a metal frame. The parts of the frame as well as other obstacles and irregularities present on the inside of the booth still make cleaning of the booth a lengthy operation. Moreover, because of the use of an automatic base cleaning system the booth is very costly and the base is positioned on a relatively large distance from the floor of the production facility.

The invention aims to provide a powder spraying booth of the kind indicated above more particularly with a view to improving the cleaning of the booth so that the time needed for cleaning is decreased with smaller loss of production time and is characterized in that the side walls are comprised substantially completely of a plurality of transparent side panels and in that the said openings are present in the said transparent side panels.

By using completely transparent, for example glass, side walls having side openings which are directly present in the transparent side panels a maximum of light transparency is achieved while the walls are easily cleaned. The effect of the invention can be obtained by application of a preferred embodiment of the invention which is characterized in that the said transparent side panels in each of the said side walls are positioned in a coplanar arrangement with intermediate joints between the said side panels, which joints comprise an elastic intermediate substance. In this way spraying booths may be built having side walls entirely made out of glass and in which all the side panels are positioned in a coplanar arrangement which means that the entire wall of the booth consists of a single smooth surface. In this respect it is important that the joints comprising an elastic intermediate substance can easily be made to lie in the same plane as the surfaces of the side wall as a whole. In a spraying booth of this kind there are no frame parts projecting on the inside of the booth. The side panels have an entirely self-supporting function so that the side walls, with the exception of the narrow joints, can be considered to be comprised of a single wall of light transparent material. The joints between the separate panels in practice need to be only 7 mm wide and may be filled up with any suitable elastic kit, for example on a silicon basis.

A further improvement may be achieved with a further embodiment of the invention which is characterized in that the said ceiling is comprised substantially completely of transparent ceiling panels. By using this feature also the ceiling is very smooth and easily cleaned but moreover transparent. The general lighting fixtures which are normally present in the production facility over the spraying booth therefore contribute to the lighting in the spraying booth. The whole booth therefore is extremely transparent so that there is no need for providing any lighting fixtures inside the booth or penetrating into the booth. With conventional spraying booths lighting fixtures are present in the frame parts in the side walls of the booth. As a consequence the presence of these fixtures complicates the cleaning of the booth. With a booth according to the invention, however, all lighting fixtures which are needed are entirely outside of the booth. There is therefore no influence on the ease of cleaning of the spraying booth.

An interesting further embodiment of the invention is characterized in that the said side panels extend up to the ceiling and are connected to the ceiling by connecting brackets disposed on the outside of the booth. The importance of this embodiment is twofold. In the first place the fact that the ceiling of the spraying booth is arranged between the walls of the booth increases the strength and the stability of the booth. A further advantage is that the necessary connecting brackets are disposed on the outside of the booth. These are connected to the upper surface of the ceiling and the inner surface of the side panel portions which extend above the ceiling. In so far as connecting means may be needed which project through the side panels or the ceiling panels such as bolts, etc., these may be covered on the inside of the booth by means having an outer surface disposed in the same plane as the inner surface of the panels. The flat and smooth character of the side panels and the ceiling is therefore not disturbed.

As the ceiling of the spraying booth is positioned below the upper edge of the side panels the upper part of the booth will have a general shape resembling a shallow reservoir in which dirt could accumulate, impairing the transparency of the ceiling. A further embodiment of the invention is important in this respect and is characterized in that a space between the upper edge of the said side panels and the upper surface of the said ceiling is covered by a transparent ceiling. The roof preferably is made entirely smooth again so that also the cleaning of the roof can be effected quickly and easily.

Significant advantages may be achieved by using a further embodiment of the invention which is characterized in that the said base consists of a receptacle having vertically extending receptacle walls and in that the said side panels are supported at a lower edge portion in formed supporting sections which are connected to the said vertically extending receptacle walls. This embodiment has a number of advantages. In the first place, the positioning of the side panels in supporting sections connected to the vertically extended receptacle walls will have the effect of a simple design and easy assemblage of the spraying booth. The fact that the base is placed on the floor (if necessary with insertion of a supporting layer or supporting means of small vertical dimension) will result in a spraying booth which is generally of a small vertical dimension and products may be conveyed through the booth at a minimum distance with respect to the floor. Along the side of the booth powder spraying robots and air exhaust means may be placed directly on the floor. Manual spraying can be carried out by operators standing on the floor. The transport system for conveying the products does not need to be increased in height. Manually placing or manually removing products on and from the hangers respectively can be carried out at normal working distance from the floor. The base may be provided with a smoothly curved transition between the bottom and the vertical walls which will add to easy cleaning of the booth.

A further interesting embodiment is characterized in that the said channel in the said ceiling is delimited at its lateral sides by transparent slats which extend partly above and partly below said ceiling, the said slats being connected to the said ceiling by means of further connecting brackets disposed on the outside of the booth. The disposition of the slats prevents spraying powder from escaping from the booth through the channel in the ceiling. The slats are connected to the ceiling on the outside of the booth so that also in this case on the inside the flat and smooth character of the surface of the ceiling is not disturbed. As the slats are also made of a transparent material and may for example consist of glass there is no decrease of transparency of the ceiling and easy cleaning is ensured.

A further embodiment of the invention is characterized in that at least one of the said openings which are present in the said transparent side panels are defined by cut-outs at the edge of certain of the said side panels. The importance of this embodiment is that the integrity of the side panels is only slightly attenuated. The provision of a side edge cut-out at the edge of a panel is easily carried out, more easily than the provision of a hole at a certain distance from the edge.

The invention will now be explained merely by way of example by reference to the schematic drawing showing a non limiting embodiment of the invention and in which: Fig. 1 is a general schematic perspective view of a spraying booth according to the invention;

Fig. 2 is a front side view of the spraying booth; Fig. 3 is a lateral view of the spraying booth of Fig. l; Fig. 4 is a plan view of the spraying booth of Fig. i;

Fig. 5 is a fragmentally cross sectional front view of the method of connecting of the ceiling of the spraying booth to a side panel; Fig. 6 shows the detail of Fig. 5 in a lateral view;

Fig. 7 shows the detail of Fig. 5 in a plan view; and

Fig. 8 is a cross sectional view of another detail for the supporting of a side panel by a transverse wall of the base of the spraying booth according to the preceding figures.

The spraying booth 1 shown in the drawing comprises a base 2 and side walls 3 and 4 having a number of openings 5 and 6. The openings 5 are used to permit spraying guns (not shown) which are connected to spraying robots (not shown) to penetrate into the interior of the spraying booth, which robots are designed to move the spraying guns up and down through the opening, while the opening 6 is an entrance opening for an operator so that the operator may use a manually operated spraying gun inside the booth for additional spraying of products which are conveyed through the booth. In many instances additional spraying is necessary to reach places on the products where the automatic robot sprayers do not achieve a satisfactory spraying result. Further openings, for example for the purpose of air exhaust means are not shown in the drawing but may be present for example in the side wall 4. The side wall 3 comprises a plurality of light transparent side panels 3.1, 3.2, 3.3, etc. The side wall 4 is similarly comprised of side panels 4.1, 4.2, etc. In the ceiling 7 of the booth a channel 8 extending over the entire axial length of the booth is present for admitting transport means of a transport system (not shown) which transport system conveys the products to be sprayed in hanging condition through the spraying booth. Open front sides 9 and 10 are present through which the products may be made to enter and leave the spraying booth by the operation of the transport system.

The feature of the spraying booth according to the invention is that the side walls 3 and 4 are substantially completely comprised of light-transparent side panels and that the openings 5 and 6 and possible further openings not shown in the drawing are present in the light transparent side panels themselves. The side walls 3 and 4 are thus completely light transparent. The panels in principle could be made from any suitable light-transparent material. At present security glass panels are preferred as these possess the required hardness of surface and therefore resistance to scratches, the smoothness of the surface and the fact that the powders which are used have a small tendency of adhering to the surface. It is, however, not excluded that other materials, more particularly plastics, could be suitable in the future for the required purpose.

As can be seen in Figs. 1, 4, 6 and 7 the light transparent side panels are positioned in a coplanar arrangement with intermediate joints 9 which have been filled up with a suitable elastic filling material such as a silicon based kit. The joints are approximately 7 mm wide and have been finished in such a way that the surface of the material in the joints at least on the inside of the cabin is positioned in the same plane as the inner surface of the panels.

Also the ceiling 7 is completely comprised of light transparent ceiling panels 7.1, 7.2, etc. which are arranged in coplanar fashion with intermediate joints.

As can be clearly seen from Figs. 1, 2, 5 and 6 the side panels extend above the ceiling and have been connected to the ceiling by means of connecting brackets 13 which are disposed on the outside of the booth. In this way it is prevented that projecting parts may project into the inside of the booth which projecting parts could interfere with the cleaning of the inside of the booth. Therefore, bolts 14 are used having tapered heads which on the inside of the booth are covered by a suitable material in such a way that the smooth inside surface is not disturbed. Furthermore, the bolts have been provided in such a way, for instance by leaving some free space between the bolts and the edge of the hole through which the bolts are inserted or by using a elastic material in the said space, that also at the location of the connecting brackets a somewhat elastic connection is present between the respective panels. This is important with a view to inevitably occurring thermal expansion phenomena.

Only Fig. 2 indicates in dashed lines the presence of a roof 15 which covers the space between the upper edge of the side panels and the upper surface of the ceiling 7. By using a roof dust and other contaminants are prevented from settling on the ceiling 7. A suitable flat embodiment of the roof 15 provides the advantage that the top of the booth is much easier to keep clean than the space having the general shape of a shallow receptacle which is present between the ceiling and the side panels, in which space moreover the connecting brackets 13 are provided which would further interfere with cleaning operations. The roof 15 itself is also comprised of light transparent material so that, also because the roof is easily cleaned, light is enabled to penetrate easily into the interior of the booth from the upper side. The base of the spraying booth consists of a receptacle 2 placed on the floor. Depending on circumstances the receptacle may be placed directly on the floor or means may be inserted between the base and the floor, which means however should have a vertical dimension which should be as small as possible in order to keep the operational height in the spraying booth as low as possible. It has been confirmed that with a spraying booth according to the invention it may be ensured that products may be sprayed at a minimum distance from the floor. This minimum distance is determined by practical considerations such as the ease of applying and removing products on and from the hangers of the transport system respectively but also the fact that the lowest products hanging from the transport system should still be easily accessible for spraying purposes and of course should not rest on the floor or on the bottom of the spraying booth.

The base 2 may for example comprise suitably formed stainless steel welded plates. On the outside supporting sections 17 of U-shaped cross section have been welded to the vertically extending receptacle walls 16. A rubber supporting strip 18 has been inserted on the bottom of the U-shaped sections. The side panels, see more particularly Fig. 8, have been placed with their lower edge in the U- shaped sections on the rubber supporting strip and the space which is present between the side panels and the vertical portions of the U-shaped sections is filled with a suitable elastic material. The transition between the side panels of the booth and the vertically extending walls of the base should be finished as smoothly as possible with a view to easy cleaning of the booth.

The channel 8 in the ceiling 7 is delimited at its lateral side by transparent slats 20 which extend partly above and partly below the ceiling. Since a part of the slats also extend below the ceiling, powder which has not adhered to a product is prevented from escaping easily through the channel which is present in the ceiling of the booth. The slats are made of the same or similar light transparent material as the ceiling panels or the side panels so that the slats do not interfere with the transmission of light from the outside to the interior of the booth. At the same time the same flatness and smoothness of surface is ensured and therefore the same ease of cleaning. For the attachment of the slats to the ceiling preferably the same means are used as for the attachment of the ceiling to the side panels, i.e. the same or similar connecting brackets 13 are used which are disposed on the outside of the booth so that no unnecessary obstacles are created on the inside of the booth where spraying powder could accumulate.

As can be seen easily in Figs. 1 and 3 the openings 5 and 6 in the side panels are formed by edge cut-outs in the respective panels. As already indicated side cut-outs at the side edge of a panel are easier to realize than openings at a place removed from an edge of the panel. For example for the realization of the openings 5, side edge cut-outs need to be made having only three sides, the fourth side edge of the opening being comprised by a straight edge of the next side panel, which fourth edge of the opening therefore can be used as is. Also, realizing a cut-out at an edge of a panel is always more simple than the provision of a hole in a panel while moreover the panel is attenuated to only a minimum extend. At the entrance opening 6 care has been taken that panels 3.5 and 3.6 are provided with identical side edge cut-outs which together form the entrance opening. The upper edge of the entrance opening is curved. This is suitable for the prevention of cracks in the material of the panels and also minimizes the amount of material to be removed.

As is usual with spraying booths, the front sides are provided with openings having an area which is as small as feasible. The area of the openings determines primarily the air flow which can be sucked in per unit of time by the air exhaust system and therefore also determines the capacity and the dimensions of the air exhaust system. The booth therefore has been provided at both ends with a section of smaller lateral dimensions. The auxiliary panels used, such as the panels 2.1 - 2.3, are similar to the side panels, the ceiling panels, as well as the slats 20 in the ceiling and are made of light-transparent panels which are connected in the same way by connecting brackets to other parts of the booth, which brackets are disposed on the outside of the booth, and with supporting sections at the lower edge portion so that all the advantages which are present with the remaining parts of the spraying booth are also present here.

Since the channel 8 extends over the entire axial length of the booth, the ceiling 7 is comprised of two separate parts which are not connected to each other. Consequently, the booth is assembled at the production site using external supporting structures to prevent lateral movement of the parts of the booth. This structure, which is not a part of the invention and which may be of conventional nature, should not interfere with the transport system.

A spraying booth is thus provided which is practically completely light-transparent and is preferably made of security glass, is practically completely smooth on the inside, allows a maximum amount of light to penetrate into the interior and is placed at a very low position on the floor. The spraying booth excels in simplicity of structure and surprisingly is not more costly and possibly even less costly than a conventional spraying booth. Also the use of the spraying booth entails further economic advantages. As the spraying booth is easily and quickly cleaned only little production time is lost. The low profile facilitates the application and removal of products on/from the hangers of the transport system. Additional manual spraying can be carried out through the entrance opening 6 at floor level. A complicated mechanical automatic cleaning device is superfluous. The invention thus provides a booth which has been reduced to the bear minimum and exactly for the reason provides important advantages.

Claims

________

1. Powder spraying booth (1) for applying a paint layer in powder form on products and comprising:

- a base (2) ;

- side walls (3; 4) comprising transparent side panels (3.1-3.6; 4.1-4.6) and provided with openings (5, 6) for admitting powder spraying equipment, air exhaust means, etc. ;

- a ceiling (7) having a channel (8) extending over the entire axial length of the booth for admitting transport means of a transport system into the booth for transporting the said products which are to be sprayed in a hanging situation along the axial length of the booth;

- open front sides (11; 12) through which the said products are transported by the transport system into and out of the booth respectively, characterised in that the side walls (3; 4) are comprised substantially completely of a plurality of transparent side panels (3.1-3.6; 4.1-4.6) and in that the said openings (5, 6) are present in the said transparent side panels.

2. Powder spraying booth according to claim 1, characterised in that the said transparent side panels (3.1- 3.6; 4.1-4.6) in each of the said side walls (3; 4) are positioned in a coplanar arrangement with intermediate joints between the said side panels, which joints comprise an elastic intermediate substance.

3. Powder spraying booth according to claim 1, characterised in that the said ceiling (7) is comprised substantially completely of transparent ceiling panels (7.1- 7.6).

4. Powder spraying booth according to claim 3, characterised in that the said side panels (3.1-3.6; 4.1- 4.6) extend up to the ceiling and are connected to the ceiling by connecting brackets (13) disposed on the outside of the booth.

5. Powder spraying booth according to claim 3, characterised in that a space between the upper edge of the said side panels (3.1-3.6; 4.1-4.6) and the upper surface of the said ceiling (7) is covered by a transparent roof (15) . 6. Powder spraying booth according to claim 1, characterised in that the said base consists of a receptacle (2) having vertically extending receptacle walls (16) and in that the said side panels (3.1-3.6; 4.1-4.

6) are supported at a lower edge portion in formed supporting sections (17) which are connected to the said vertically extending receptacle walls.

7. Powder spraying booth according to claim 1, characterised in that the said channel (8) in the said ceiling (7) is delimited at its lateral sides by transparent slats (20) which extend partly above and partly below said ceiling (7) , the said slats (20) being connected to the said ceiling (7) by means of further connecting brackets (13) disposed on the outside of the booth.

8. Powder spraying booth according to claim 1, characterised in that at least one of the said openings (5, 6) which are present in the said transparent side panels (3; 4) are defined by cut-outs at the edge of certain of the said side panels (3.1-3.6; 4.1-4.6).