EP0678719A2

EP0678719A2 - Installation and method for drying surfaces of water-borne paints

Info

Publication number: EP0678719A2
Application number: EP95201023A
Authority: EP
Inventors: Nicolaas Van Der Avoort
Original assignee: Rota Cab BV
Current assignee: Rota Cab BV
Priority date: 1994-04-21
Filing date: 1995-04-21
Publication date: 1995-10-25
Also published as: NL9400639A; EP0678719A3

Abstract

The invention relates to an installation for drying for instance a spray painted object (16), comprising a closable booth (1) having means for supplying air thereto and means for discharging air therefrom, as well as moveable means (9) for accelerating and directing towards the object (16) to be dried at least part of the air supplied to the booth (1). The installation further comprises programmable control means (19) which control the air accelarating and directing means (9), which are arranged for being moved along the object (16) to be dried during a drying operation.

The position of the air accelerating and directing means (9) is adjustable, and they are arranged for being adjusted in position during the movement along the object (16).

The invention further relates to a method for drying especially a spray painted object, by accelerating and directing at the object at least part of the air surrounding the object, wherein during the drying operation the accelerated air is subsequently directed at different parts of the object in accordance with a predetermined programme.

Description

The present invention relates to an installation for drying for instance a spray painted object, comprising a closable booth having means for supplying air thereto and means for discharging air therefrom, as well as moveable means for accelerating and directing towards the object to be dried at least part of the air supplied to the booth. The invention is particularly suitable for drying water-borne paints, viz. inter alia thixotropic and structureviscous products which are placed in a watery environment, from which the water must escape through evaporation, thus obtaining the coating thickness to be applied. Coating thickness, hardness and gloss are important criteria herein, while no tendency to running and sagging may occur.
Industrial water-borne paints have many practical advantages when compared to paints with organic solvents. Water as solvent and diluent is non-toxic, non-flammable, colourless and sufficiently volatile. The spraying further is environmentally friendly because no hydrocarbons or other organic solvents are used. Working with water-borne paints give good results and does not cause any nuisance or any threat to health. Besides, water-borne paints usually result in an improved positioning of the pigment, whereby the appearance becomes exceptionally attractive, particularly in the case metallic pigments are used, wherein the correct position of the flakes is especially critical.
A drawback to painting with water-borne products is however the longer drying time and the remaining in the space of watery vapour which can cause wear and rust. For both these reasons attempts have been made to accelerate drying. Heating, for instance by infrared radiation can be useful for this purpose but is quite expensive and not suitable for all substrates and water-soluble paints. Specifically when performing repair spray work on for instance motor vehicles, drying by heating is not practicable.
Drying with an air flow can then provide a solution. To this end the European patent publication 0 568 179 discloses a spraying booth for water-borne paints which comprises one or more air feed lines which supply drying air in a pre-adjusted position and direction and, from nozzles fixed thereto, blow it to edges of surfaces to be dried. From these edges, the jets of air then spread along the surfaces to be dried in a laminar flow. This method of drying is however less suitable for curving sufaces in particular, such as car bodywork, because it has the drawback that due to the fixed direction of the laminar air flow, particularly in the starting phase of the drying, a more or less fine wave movement of the paint coating for drying can occur, resulting in wrinkles, and adhesion, smoothness and gloss are hereby adversely affected.
The present invention seeks to provide a drying installation and method with which the drawbacks of too long a drying time, the persistent presence of a watery vapour and the occurrence of wrinkles or the "orange-peel" effect are obviated.
According to the invention this is accomplished in a drying installation of the type descibed above, in that the installation further comprises programmable control means and in that the air accelerating and directing means are controllably connected to the control means and are arranged for being moved along the object to be dried during a drying operation under control by the control means.
The method according to the invention for drying for instance a spray painted object comprises accelerating and directing at the object the air surrounding the object, and is characterized in that during the drying operation the accelerated air is subsequently directed at different parts of the object.
The invention is now elucidated on the basis of an example, wherein reference is made to the annexed drawing, in which:

Fig. 1 is a front elevational view, partially in section, of a drying installation in accordance with the invention;
Fig. 2 is a cross-sectional detail view of a nozzle used in the drying installation of fig. 1; and
Fig. 3 is a side elevational view of an alternative embodiment of the drying installation of fig. 1

The installation for drying a spray painted object, for instance a motor vehicle 16, comprises a closable booth 1, means for supplying air to the booth 1 and means for discharging air from the booth 1, as well as moveable means 9 for accelerating and directing at the vehicle 16 to be dried part of the air supplied to the drying booth 1. The drying installation 1 further comprises programmable control means 19, for instance a computer mounted in a console, which is controllably connected with the air accelerating and directing means 9. The drying booth 1 comprises front, side and rear walls 2, a ceiling 3 and a bottom 4. The bottom 4 is provided with suction opening 5 for discharging air from the booth 1. In the booth 1 a separation wall 6 is arranged at a given distance below the ceiling 3, which wall separates a plenum 7 for the supply air from the actual drying space 8.
The air accelerating and directing means 9 comprise a portal 10 moveable in lengthwise direction through the booth 1 along the arrows L, and suspended on guide rails 11 arranged along the walls 2 of the booth 1. A drive means, for instance a variable speed electric motor 12 is connected to the portal 10, and has a sprocket 17 mounted on its driveshaft, which cooperates with a cable or chain 18 running the length of the booth 1, whereby the portal 10 may be moved. The portal 10 further comprises suspended legs 13 along which arms 14 are arranged which are slidable in height direction along the arrow H. In the arms 14 nozzles 15 are arranges, which may be rotated in all directions.
The nozzles 15 each take the shape of a venturi tube, which is formed by a lower part 28 and a upper part 30 connected thereto, the parts 28 being provided with an inlet orifice 29 for pressurized air (arrow P) and an annular conduit 33 connected to the inlet orifice 29. The upper part 30 is provided with an inlet 31 and a progressively narrowing duct 36. This duct is continued in the lower part 28, where the duct 37 progressively widens from a narrowmost part or "throat" 35 towards an exhaust 32. At the "throat" 35 the pressurized air is blown along the wall of the duct through an annular slit 34, whereby surrouding air S is sucked in and after passing the throat 35 is accelerated out along the arrow A.
In an alternative embodiment the portal 20 comprises wheels 22 and may be rolled through the booth 1. The arms 14 are herein displaceble in heightwise direction along a guide rail 21.
The control means 19 are housed in a console, which comprises a keyboard 24 and a display 25. The control means 19 are connected to the air accelerating and directing means 9 by means of a control cable 23, which is suspended on carriages 26 which are moveable along a rail 27. Other cables and conduits, for instance for powering the drive means 12 and for supplying pressurized air may also be mounted in this manner. Through the keyboard 24 specific control commands or even a complete control programme may be entered. These control commands control the movement of the portal 10 or 20 through the booth 1, the movement of the arms 14 along the portal, and the position of each of the nozzles 15.
The installation 1 operates as follows. At the start of a drying operation an object, like for instance the vehicle 16 is placed in the booth 1 and subsequently the booth 1 is sealed air tight. The portal 10, 20 respectively and the arms 14 are then in a starting position. Subsequently the position of the nozzles 15 is adjusted, and the arms 14 are moved along the portal to a predetermined height. Then the portal is moved over the object 16 to be dried at a slow speed, for instance approximately 0,5 m/minute, with the nozzles 15 switched on. When the end of the object 16 to be dried is reached, the nozzles 15 are switched of, the arms 14 are moved back along the portal 10,20 to their initial positions, and then the portal 10,20 is moved back to its initial position at a relatively high speed. If so desired, it is also possible to repeat the drying operation in reverse direction after reaching the end of the object 16, until the portal 10, 20 reaches its initial position again. If only a part of the object 16, for instance a front wing 38 should be dried, only part of the nozzles 15 are activated, and the portal 10 is only moved to the end of the part 38 to be dried.
The drying programme described above may be performed step by step by subsequently entering control commands through the keyboard 24, but can also be performed under control of a programme stored in the control means 19 earlier. The programme may if neccesary be interrupted prematurely by means of an emergency stop provision. The speed at which the portal is moved along the object 16 to be dried and the force with which air is accelerated through the nozzles 15 may be adjusted separately, dependent on the shape, dimensions and nature of the object to be dried and the paint used.

Claims

Installation for drying for instance a spray painted object, comprising a closable booth having means for supplying air thereto and means for discharging air therefrom, as well as moveable means for accelerating and directing towards the object to be dried at least part of the air supplied to the booth, characterized in that the installation further comprises programmable control means and in that the air accelerating and directing means are controllably connected to the control means and are arranged for being moved along the object to be dried during a drying operation under control by the control means.
Drying installation as claimed in claim 1, characterized in that the position of the air accelerating and directing means is adjustable, and in that they are arranged for being adjusted in position during the movement along the object under control of the control means.
Drying installation as claimed in claims 1 and 2, characterized in that the air accelerating and directing means comprise a plurality of nozzles mounted adjustably in moveable carriers.
Drying installation as claimed in claim 3, characterized in that the carriers are moveable in at least two mutually perpendicular directions.
Drying installation as claimed in claim 4, characterized in that the carriers are arranged for following the contours of the object to be dried under control of the control means during the drying operation.
Drying installation as claimed in any of the claims 3-5, characterized in that the carriers comprise a portal that is moveable in lengthwise direction through the booth and a plurality of arms carrying the nozzles and moveable in heightwise direction along the portal.
Drying installation as claimed in any of the claims 3-6, characterized in that the nozzles are arranged in the arms such as to be rotatable in all directions.
Drying installation as claimed in any of the claims 3-7, characterized in that the nozzles are formed by venturi tubes connected to a source of pressurized air and open on both sides.
Method for drying especially a spray painted object, by accelerating and directing at the object at least part of the air surrounding the object, characterized in that during the drying operation the accelerated air is subsequently directed at different parts of the object.
Method according to claim 9, characterized in that directing of the accelerated air towards the different parts of the object is performed in accordance with a predetermined programme.