EP0176501B1

EP0176501B1 - Apparatus for treatment of objects, preferably elongated objects of uniform cross-section, with a liquid

Info

Publication number: EP0176501B1
Application number: EP83902299A
Authority: EP
Inventors: Bo JÖNSSON
Original assignee: Casco Nobel AB
Current assignee: Casco Adhesives AB
Priority date: 1983-06-01
Filing date: 1983-06-01
Publication date: 1987-12-09
Also published as: WO1984004705A1; DE3374845D1; EP0176501A1; ATE31256T1

Abstract

An apparatus for treatment of elongated objects (51) comprises a vessel (7, 45, 46, 47, 48 and 55) in which it is arranged for a liquid bath to be maintained. Openings (36) in each of two opposite side walls (45, 46) are adjusted to the cross-section of the objects and the objects are intended to be conveyed through the bath via the openings. The liquid bath is maintained partly by pumping treating liquid from a storage sump (15) to the vessel and partly by subjecting the apparatus to a vacuum by means of a fan (4). The storage sump (15) is provided with means for level regulation (17, 19) so that an essentially constant liquid level can be maintained. The storage sump can be replaceably mounted to the vessel. According to one embodiment the vessel (7, 45, 46, 47, 48 and 55) can be provided with a housing (2, 7, 47, 48, 5) which has openings (37) in front of the respective openings (36) of the vessel. As the housing communicates with the vessel and the storage sump ambient air will be sucked in through the openings in the housing and thereby reducing foaming of the treating liquid in the apparatus will be obtained.

Description

The present invention relates to an apparatus for treating objects, preferably elongated objects of uniform cross-section, with a liquid, comprising a vessel in which it is arranged for a liquid bath to be maintained and a storage sump or reservoir, whereby an opening is arranged in each of two opposite side-wall areas of the vessel, which openings are adjusted with respect to the cross-section of the objects and whereby the objects are arranged to be conveyed through the bath via the openings, and whereby the liquid bath is maintained partly by liquid conveyed from the storage sump and partly by means of a vacuum source communicating with the storage sump and the vessel for producing a negative pressure above the liquid bath.
A suitable paint apparatus simplifies the surface treatment work at painting or impregnating boards, strips, metal or plastic profiles. A previously known type of suitable painting apparatus which is easy to use and gives good treatment results comprises a vessel in which it is arranged for a liquid bath to be maintained and which vessel has an opening in each of two opposite side-wall areas. The openings are adjusted relative to the cross-sections of the objects and the objects are conveyed through the bath via the openings. The paint bath in the vessel is maintained by means of a paint pump. The fan creates a partial vacuum in the vessel and this means that ambient air will be sucked in through the openings in the vessel and paint will be prevented from flowing out through any gaps between the object and the edge of the openings. The air sucked in through the mentioned gaps will at the same time remove excess of paint and bring this back into the vessel. The paint pump sucks the paint from a storage sump which is built-in with the apparatus. This sump has a fairly large volume since it is intended to work both as a storage for the paint and as a collecting means for the foam formed in the apparatus. An apparatus of this type is described in the British patent 2 064 996.
When devices of the type described above are used for painting a foam is formed from the paint, to a greater or smaller extent, since the air that is sucked in has to pass through the paint bath. This foam is unfavourable .and must be removed to a large space in the device in which the foam will be allowed to settle before the paint is brought back to the bath. If the paint level in this space, the storage sump, is too high the form will fill all of the space and this means that it can be sucked out from the device via a liquid trap. This results in deposits of substance both in liquid traps and conduits and in the exhaust fan.
Another, and more serious, disadvantage in known devices is that the viscosity of paint varies irregularly during the treatment and this impairs the reproducability. When agents containing solvents are applied in these apparatuses at a high air speed and a high air consumption there will be an uncontrollable and high loss of solvent. When the level in the storage pump is decreasing the loss of solvent will rapidly increase the dry content of an agent and thereby its properties will be changed relative to penetration capability; drying properties, colour and layer thickness. If the level in the storage sump is high the solvent loss, and thus the dry content, is not influenced to the same degree, but, on the other hand, the device is filled to the brim with foam, leading to the disadvantages mentioned above.
Known devices are also disadvantageous in that they are easily blocked, eg by wood chips and flakes at painting rough wood, and the cleaning is complicated and requires long shutdown times. At change of paint a thorough cleaning of the entire device is also required and this most often makes it necessary for the user to acquire different apparatuses for different paints.
It is an object of the present invention to offer a surface treatment device of the mentioned kind in which the disadvantages in the known type of device are avoided. Further objects and advantages of the device of the present invention will be evident from the following.
In an apparatus of the type indicated in the prior art portion of claim 1 (known from GB-A-2 064 996) this object in conformity with the present invention is reached in that means are provided to obtain an essentially constant liquid level in the storage sump. The liquid is suitably conveyed from the sump by means of a pump and it is advantageous to arrange an overflow in the vessel, making the pump give a liquid flow which is greater than the consumption of liquid at use, whereby excess of liquid flows back into the storage sump via the overflow. As a result of the negative pressure in the device liquid is prevented from emerging through the openings in the side-walls of the vessel. Consequently air will flow in through the openings, which are sealed mainly by the objects treated in the device, and the air will cause foaming of the treatment liquid. This foam will also flow down into the storage sump, together with excess paint, via the overflow. The sump has been given such a volume that it normally will accept all the foam until it has settled without giving an overflow through the suction means. According to the invention the device has further been provided with means for level regulation so that the storage sump will have an essentially constant liquid level, and thus also a constant volume, during the entire treatment procedure.
By this, the risk of over-foaming, resulting in blocking of the suction means, is essentially eliminated. Since the liquid level in the sump is kept almost constant the evaporation or solvent release from the liquid, if the liquid contains a solvent, will be kept constant, and this means for example that the penetration capability and the drying properties of the liquid will vary to a very low extent, and so will the colour and covering degree when the liquid is a paint. The storage sump preferably contains only a small amount of liquid, which is advantageous also with respect to pigment sedimentation for paint.
The sump can have a connection to a liquid vessel and the connection is then suitably provided with a valve, controlled by a level regulator which senses the liquid level in the sump to offer refilling of liquid from the reservoir, via the valve, to the sump when the liquid level in the sump falls below a certain value and to interrupt the refilling with liquid when the liquid level in the sump is above the set value.
The mentioned sump can be replaceably mounted to the vessel. Means in the form of a lift jack or similar means can be arranged to lift the sump so that its brim is brought into or from tight contact with the lower part of the vessel. Sealing strips, for example of rubber, can be mounted on the lower part of the vessel to obtain a tight connection to the upper brim of the sump.
It is hereby possible to have a separate sump of the mentioned kind containing a solvent, and when it is desired to clean the device, eg for changing paint, the paint sump can quite simply be lowered and rolled away and the solvent sump can be put in place, and the device can be operated with an object inserted through the openings of the vessel and the housing to cut off these. Should the treating liquid be contaminated a new sump can be put in place and the device can be used during the cleaning.
According to another embodiment the vessel is positioned in a housing which has an opening straight in front of the respective openings of the vessel, where the respective adjacent walls of the housing and the vessel, which are provided with openings, are positioned at a distance from each other, whereby ambient air is sucked into the housing via the gap between the objects and the openings of the housing, and the air pressure above the liquid bath in the vessel is arranged to be at least as high as the air pressure in the housing.
The openings in the vessel and the housing are preferably arranged in replaceable pairs of aperture plates, which pairs are positioned between the housing and the vessel, whereby the aperture plates are in tight contact with the adjacent wall surfaces of the vessel and the housing around notches in these, which notches are screened by the places, the apertures of the plates forming the mentioned openings.
With this embodiment the atmosphere in the housing and above the bath will have essentially the same negative pressure. Hereby the air which is sucked in will not pass through the openings into the liquid bath and bubble through this which means that the foaming of the liquid bath will be eliminated to a considerable extent. This embodiment is very suitable for use when the treating agent has a great tendency to foaming.
By providing, in a suitable manner, a table, on which the vessel can rest, with sealing means and fastening means for a housing of the described kind a device according to the invention can simply be provided with a housing which reduces the tendency to foaming.
The mentioned pair of aperture plates can be provided with means, eg rigging screw means or the like, which allow parallel displacement of the plates in the pair so that these can be fixed in, respectively removed from, contact with the vessel and the housing respectively. The mentioned pair of aperture plates can be removed upwards in the respective space between vessel and housing if this space opens upwards. The housing and the vessel preferably have a common upper wall which can rest loose on the walls of the vessel and the housing respectively and be secured in position during operation by influence of the negative pressure in the housing.
A guide bar having a uniform cross-section along its length can be arranged to extend through the vessel and its openings, which bar has an axial recess with edges intended to be turned towards the central parts of the openings and be in tight contact with the objects, whereby the common outline of the bar and the object will substantially be in contact with the edges of the openings in the vessel. The earlier mentioned fact that the openings of the vessel shall be adjusted to the cross-section of the objects is to be interpreted so, that if a guide bar of the mentioned kind is used, the common outline of the guide bar and the object shall correspond to the outline of the opening. If a housing is present, the openings in this should suitably be designed to essentially correspond to the cross-section of the objects, so that the airflow sucked in via the small gap between the edge of the opening in the housing and the outline of the objects will remove excess of paint from the objects so that the excess of paint can be released into the sump via the space between the walls of the vessel and the housing.
The object of the above mentioned guide bar is to avoid liquid treatment of the objects in the axial area thereof which is limited by the edges of the bar.
The invention is further defined in the appended claims.
The invention will in the following be described in the form of an illustrating example with references to the accompanying drawings.
Figure 1 is a schematic sectional view of a device according to the invention. Figure 2 shows a section taken along the line II-II in Figure 1. Figure 3 shows a section taken along the line II-II in Figure 1 of an embodiment with a housing overthe vessel.
In Figure 1 and 2 an apparatus for surface treatment of elongated objects, such as boards, with a liquid, eg paint, is shown. The apparatus comprises a storage sump 15 and the brim of the sump is kept in sealed contact with a sealing strip 16 on the underside of a table 5 supported from a floor by legs 6. The sump 15 is kept raised to the strip 16 by means of a lift jack 30, which is schematically shown. The sump 15 can preferably be rolled on wheels 31. On the table 5 a parallelepiped box is positioned and this box is formed from walls 45,46,47,48 which are tightly sealed to each other and to the table 5 and to a top-board 7, lying closely on the walls. At a distance from and inside the wall 48 there is an overflow 44. Together with the walls 45, 46, 47 and the bottom 55 the overflow forms a vessel intended to contain a liquid bath 20. Excess of liquid flows down between the walls 44 and 48 through an opening 33 in the table 5 and into the sump 15.
The walls 45 and 46 have fairly large notches 10, in which aperture plates 13 are positioned. The plates have openings 36 and are replaceably mounted in the notches. It is suitable to have aperture plates in a number of varying sizes intended to fit the cross-sections of the objects to be treated in the apparatus. The aperture plates are suitably provided with adjusting means, in a known manner, so that different cross-section configurations can be obtained with one plate. The edges of the openings 36 can be designed as elastic lips to allow passage of objects with deviations in the shape and optionally also in order to get a better conformity with the shape of the objects.
At a low level the sump 15 has an exit for liquid with a quick-coupling 18 to which a pipe 35 is connected and the pipe has an outlet in the vessel through the wall 47. The conduit 35 contains a liquid pump 3. A liquid inlet is connected to the sump 15 at a level above the liquid outlet and is provided with a quick-coupling 17 so that a liquid reservoir can be connected to the liquid inlet. The liquid inlet contains a valve 19 controlled by a conventional level regulator, eg of the floating body type, as shown schematically in Figure 2 or 3.
A suction conduit 40 extends through the table inside the strip 16 and contains a fan 4 which creates a vacuum in the sump 15. The sump 15 is in communication with the space above the liquid bath 20 via the gap 33 and the overflow 44.
The apparatus shown in Figure 3 has a housing placed over the vessel. This housing is formed from the top-board 7, the walls 47 and 48 of the vessel and the walls 2, at a distance from and outside the walls 45 and 46.
The walls 2, 45 and 46 have fairly large notches 9 and 10 respectively. In the respective space 50 between the walls 2, 45 and 46 pairs of aperture plates 8 are positioned. The pairs of aperture plates 8 each consists of two aperture plates 12 and 13 respectively, which by means of an expander device 60 can be moved away from each other to have their edge areas lying close to the edge areas of the notches 9 and 10. The aperture plates 12 and 13 have openings 37 and 36 which are coaxial. The pairs of aperture plates 8 are positioned to make their openings 36, 37; 36, 37 coaxial.
According to this embodiment the sump 15 is in communication with the gaps 50 via the openings 21, 22 and 33 in the table 5, and with the space above the liquid bath via the overflow 44.
The bottom 55 of the vessel is connected to the walls 45 and 46 just below the lower edge of the notches 10 and has a cup-shaped recess between the walls, and the pipe 35 is connected to the lowest point of the recess which allows a complete drainage of the liquid bath 20.
An elongated masking bar 14 having uniform cross-section along its length is positioned through the sump in the openings 36. The bar 14 has an axial cavity 41, facing upwards. The object 51 (see Figure 1) to be treated in the apparatus and the bar 14 have a combined outline which closely conforms to the edges of the openings 36 and optionally those of the openings 37. The edges of the bar 14 limiting the cavity 41 are in sealed contact with the object 51 so that the underside of this wall will not get in contact with the liquid bath 20 during the passage through the apparatus.
In Figure 3 the bar 14 has been positioned in such a manner that liquid leakage will be drained via the edges of the bar down through the gaps 50 and the openings 21, 22 to the sump.
Above, an embodiment of the apparatus has been described which comprises a masking bar 14 extending through the openings 36. The object of the bar 14 is to prevent treatment of an object along a pre-determined part of the circumference. It should, however, be evident that to obtain a liquid treatment of the entire circumference is possible to make the openings 36, 37 have an outline substantially conforming to the outline of the object 51.
The apparatus advantageously also comprises a device 1 for feeding the objects, which device comprises two parallel cylinders of which at least one is operated and the relative distance between the cylinders is adjustable.
At operation of the apparatus aperture plates with openings 36 (and optionally also 37) conforming to the outline of the object to be treated or to the common outline of masking bar and object respectively, are mounted. If the apparatus is provided with a housing the pairs 8 are adjusted so that the openings will be coaxial. Then one or several objects, eg boards, are inserted to extend through the apparatus and so that they together with the guide bar will essentially screen the openings 36 (and optionally 37). The fan 4 is then started and the pump 3 activated so that a liquid bath is established. The objects are then conveyed through the apparatus, end to end. At shutting off the apparatus the operation of the pump 3 can be cut off to let liquid flow out via the paint conduit 35 back to the sump 15. The sump 15 can then be disconnected at the couplings 17 and 18 and a corresponding vessel, eg filled with cleaning agent, can be put in place in the apparatus and this can then again be used with inserted objects and the apparatus operated with solvent as a liquid to clean its interior.
In the apparatus according to the invention objects can be treated with a great number of treating liquids, such as paints, stain, varnish, lacquer, binders, impregnating agents, surface protective agents, pickling agents degreasing agents, plastisols, organosols and similar agents. The apparatus is preferably used for surface treatment but can also be used for example for impregnation. The apparatus can be provided with heating or cooling means as desired with respect to the treating liquid.

Claims

1. Apparatus for treatment of preferably elongated objects (51) with a liquid, comprising a vessel (7, 45, 46, 47, 48, 55) in which it is arranged for a liquid bath to be maintained and a storage sump (15), whereby the vessel has openings (36), adjusted to the cross-section of the object, in each of two opposite side-wall areas (45, 46), through which openings it is intended to convey the objects through the liquid bath, and whereby the liquid bath is maintained partly by liquid conveyed from the storage sump and partly by means of a vacuum source (4) communicating with storage sump (15) and the vessel (7, 45, 46--48, 55) for producing a negative pressure above the liquid bath (20), characterized in that means (17, 19) are provided to obtain an essentially constant liquid level in the storage sump (15).

2. Apparatus according to claim 1, characterized in that the storage sump (15) has a connection (17) to an external liquid reservoir and that the connection (17) is provided with a valve (19) controlled by a regulator sensing the liquid level in the sump (15) to offer refilling of the sump when the level is below a certain value and to interrupt the liquid refilling when the liquid level is above this value.

3. Apparatus according to claim 1 or 2, characterized in that the sump (15) is replaceably mounted to the vessel (7, 45, 46, 47, 48, 55).

4. Apparatus according to claim 3, characterized in that the sump comprises means (30) for lifting and lowering the sump to, respectively, from sealed contact with the vessel.

5. Apparatus according to any of the preceding claims, characterized in that the vessel is supported by a table (5) in which there is a recess (33) arranged for flow of liquid from the vessel to the storage sump and that the latter is kept in sealed contact with the underside of the table.

6. Apparatus according to claim 5, characterized in that the table also has a socket for a vacuum source (4).

7 Apparatus according to any of the preceding claims, characterized in that the vessel (7, 45, 46, 47, 48, 55) is positioned in a housing (2, 7, 47, 48, 5) which has an opening (37) straight in front of the respective openings of the vessel, in that the adjacent walls (2, 45, 46) of the housing and the vessel respectively, which are provided with openings are arranged at a distance from each other whereby ambient air is sucked in by the vacuum source via the gap between the object and the edge of the openings (37) in the housing and whereby the air pressure above the liquid bath (20) will be essentially as high as the air pressure in the housing.

8. Apparatus according to claim 6, characterized in that the openings (36, 37) in the vessel and the housing are arranged in replaceable pairs (8) of parallel aperture plates (12, 13), which pairs (8) are positioned in the spaces (50) between the housing and the vessel, whereby the aperture plates (12, 13) are arranged in tight contact with the adjacent wall surfaces (2, 46) of the vessel and the housing, around notches (9, 10) in these, which notches are screened by the plates (12, 13), the apertures of these forming the mentioned openings (36, 37).

9. Apparatus according to any of claims 1, 7 or 8, characterized in that a masking bar (14) is arranged to extend through the openings (36) of the vessel, which bar (14) has an axial cavity (41) with edges intended to be turned towards the central parts of the openings (36) and be in sealed contact with the objects, and in that the bar (14) and the objects (51) together essentially screen the openings (36) of the vessel.

10. Apparatus according to claim 4, characterized in that the vessel has an overflow (44) over which excess liquid in the bath (20) can be removed and flow down into the sump (15), and in that a pump (3) is arranged to give a liquid flow greater than the liquid consumption.