WO2000050670A2 - Apparatus for electro-dipcoating - Google Patents
Apparatus for electro-dipcoating Download PDFInfo
- Publication number
- WO2000050670A2 WO2000050670A2 PCT/EP2000/001437 EP0001437W WO0050670A2 WO 2000050670 A2 WO2000050670 A2 WO 2000050670A2 EP 0001437 W EP0001437 W EP 0001437W WO 0050670 A2 WO0050670 A2 WO 0050670A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- delivery tube
- small
- tank
- electrode
- small parts
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
- C25D17/16—Apparatus for electrolytic coating of small objects in bulk
- C25D17/28—Apparatus for electrolytic coating of small objects in bulk with means for moving the objects individually through the apparatus during treatment
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D13/00—Electrophoretic coating characterised by the process
- C25D13/22—Servicing or operating apparatus or multistep processes
Definitions
- the present invention concerns an apparatus for electro-dipcoating small electrically conductive parts, having
- a delivery tube which is rotatable about its axis, for transporting the small parts in its longitudinal direction, having a small-part inlet opening, a small-part outlet opening and a ribbon screw attached to the inner side of the delivery tube,
- the delivery tube being arranged in relation to the tank in such a way that a coating section of the delivery tube extending in the longitudinal direction of the said delivery tube lies partly below the predetermined filling height of the tank, and - a first electrode, which is connected to one pole of a current source and is arranged on the inner side of the coating section of the delivery tube, and a second electrode, which is connected to the other pole of the current source.
- a first electrode which is connected to one pole of a current source and is arranged on the inner side of the coating section of the delivery tube
- a second electrode which is connected to the other pole of the current source.
- electrically conducting contacts Arranged on the inner side of the delivery tube are electrically conducting contacts, as a first electrode, which is connected to one pole of a current source.
- the electrically conducting contacts are distributed over the inner circumference of the coating section of the delivery tube and serve the purpose of applying an electric potential to small parts, which are electrically conductive, located at the bottom of the delivery tube.
- the second electrode is formed by a contact plate which is arranged underneath and outside the delivery tube in the dip tank.
- the delivery tube is provided with perforations which allow the liquid coating agent to pass through, also creating the possibility for electric field lines to pass from the first electrode to the second electrode through the perforations in the delivery tube.
- the delivery tube By rotating the delivery tube, small parts to be coated are taken by the ribbon screw along the bottom of the delivery tube, the said parts initially making contact with the electrical contacts, so that the electrolytic coating can take place.
- the small parts By rotating the delivery tube further, the small parts leave the coating section of the delivery tube, characterized by the electrical contacts, and can drip off by way of the perforations, after which they leave the delivery tube.
- the coating agent leaves the delivery tube via a separate discharge.
- Such an apparatus has the disadvantage that short-circuits occur during operation of the apparatus and lead to material burned off from the electrodes being present in the coating agent as coagulate. This leads to an inferior quality of the small parts coated.
- a further disadvantage of the known apparatus is due to the fact that the coated small parts are subjected to abrasion on their way through the delivery tube on account of the perforation of the delivery tube. This abrasion leads to the possibility of the electrolytically applied coating of the small parts being reduced locally in its thickness or even removed. Furthermore, it is necessary in the case of the known apparatus to work with a relatively high operating current .
- the invention is based on the object of further developing the known apparatus, described above, in such a way that the quality of the small parts coated with the apparatus is improved .
- the second electrode being arranged within the coating section of the delivery tube, in the tank, below the predetermined filling height of the tank.
- the two electrodes required for the electrolytic coating now lie directly opposite one another.
- the small parts to be coated are located at the bottom of the delivery tube in contact with the first electrode, while the second electrode lies inside the tank, on account of the intended arrangement at a distance from the small parts.
- the electric field which is present between the two electrodes is consequently undisturbed, so that in particular the operating current of the apparatus can be reduced to approximately half the value to be used in the case of the known apparatus .
- the arrangement of the second electrode allows the inside surface of the delivery tube to be formed without openings, so that this surface can be made planar. Abrasion of the coated small parts is consequently considerably less than in the case of the known apparatus.
- a further advantage of the apparatus is that, with the new electrode arrangement, far fewer short- circuits occur, as a result of which contamination of the coating agent with coagulate is effectively restricted and the quality of the coated small parts is improved .
- the second electrode may be advantageously arranged in such a way that it lies vertically above the small parts to be coated.
- the outer form of the second electrode is restricted only to the extent that an adequately favourable ratio between the surface area of the second electrode and the surface area of the small parts, to be regarded as the first electrode, is ensured.
- a typical value for the "surface area of the second electrode : surface area of the small parts to be coated" ratio lies in the range from 1:1 to 1:5.
- the second electrode which provide the specified surface area ratio may be used in the case of the apparatus.
- the second electrode may be designed as a plurality of rods which are interconnected in an electrically conducting manner .
- the second electrode is, however, preferably designed as a plate which in cross section is in the form of a segment of a circle, for example as a perforated plate, it being possible for the centre point of the circle assigned to the segment to lie on the longitudinal axis of the delivery tube. If the surface area of the plate is not adequate for the surface area ratio specified above, the plate preferably has bars extending radially outwards with respect to the delivery tube.
- the second electrode preferably has a plastic mesh on its radially outer side.
- This plastic grid may rest for example on the exposed ends of the bars of the plate and be fastened there.
- the plastic mesh has the advantage that the occurrence of short-circuits between the electrodes is reduced still further.
- the delivery tube preferably has an essentially (first electrode) planar inside surface between the small-part inlet opening and the small-part outlet opening. This feature is not absolutely necessary for the novel apparatus, but offers the advantages already specified above with respect to the abrasion of the coated small parts.
- the small-part outlet opening is preferably arranged on the circumference of the delivery tube downstream of the coating section of the delivery tube and of the tank, as considered from the direction of delivery. Owing to gravity, small parts fall downwards out of the small-part outlet opening when the delivery tube is at a corresponding angle of rotation.
- a transporting device with which the small parts are further transported, may be provided underneath the region of the delivery tube of the small-part outlet opening .
- the small-part outlet opening is advantageously assigned a transporting device which is arranged relative to the small-part outlet opening in such a way that downwardly falling small parts are taken up by the transporting device and transported essentially perpendicularly with respect to the delivery tube.
- a rinsing device for applying rinsing liquid to the small parts may preferably be arranged above the transporting device. In this way, an effective rinsing of the small parts is achieved, removing adhering coating agent.
- the transporting device may be designed as a conveyor-belt arrangement, the small parts being well exposed for rinsing liquid to be applied to them.
- the coating section of the delivery tube is preferably arranged at such a distance in the direction of delivery from the small-part inlet opening that air is removed from the small parts before the coating operation. It has been found that the quality of the coated small parts is improved if air present between the small parts, which are typically in the form of piece goods, can escape. On the way from the small- part inlet opening to the coating section of the delivery tube, air present between the bulk small parts can rise upwards within the dipping bath as bubbles.
- a circuit for the coating agent which has a cooling means, at least one filter and an ultrafiltration module, is preferably provided for operating the apparatus .
- These devices contribute to the stability of the dipping bath and ensure a well- applied coating of small parts and of threads, with forces acting from the inside.
- a circuit for the rinsing liquid in which the rinsing liquid contains filtrate formed by the ultrafiltration module (closed circuit) , may also be provided. In this way, economical rinsing of the small parts is achieved.
- Figure 1 shows an overall view of an apparatus for electrolytically coating small parts, partly in section
- Figure 2 shows a cross-sectional view of the coating section of the apparatus according to Figure 1;
- Figure 3 shows a schematic representation of the apparatus according to Figure 1 together with a plurality of liquid circuit systems for operating the apparatus .
- the apparatus for electro-dipcoating electrically conductive small parts has a delivery tube 1 made of plastic for transporting small parts in the longitudinal direction of the delivery tube 1.
- the feeding in of small parts takes place via a balance 2 , which, when a predetermined weight of small parts is reached, is tipped in the direction of a run-in chute 3, via which the small parts are introduced into the delivery tube 1 through a small-part inlet opening 4, which is formed by an open end of the delivery tube 1.
- the delivery tube 1 is provided over its entire length with a ribbon screw 5 fastened to its inner side, so that an appropriate rotation of the delivery tube 1 about its longitudinal axis brings about transportation of the small parts in a direction of delivery.
- the first half of the delivery tube 1 lies in a tank 6 which is filled up to a predetermined level with coating agent for the small parts.
- the tank 6 has over its entire length an essentially U-shaped cross section, that edge 7 of the tank 6 which is at the front in the direction of delivery running horizontally, while that edge 8 of the tank 6 which is at the rear in the direction of delivery is adapted in its shape to the radial dimensions of the delivery tube 1 and is sealed off from the delivery tube 1.
- the height of the ribbon screw 5 in the region 5a of the rear edge 8 of the tank 6 is chosen such that the coating agent in the tank 6 cannot flow over the ribbon screw 5 in the region 5a, but instead, like the small parts, is moved by the ribbon screw 5 in the direction of delivery.
- the delivery tube 1 has a coating section 9 which is provided on its inner side with electrical contacts 10 forming a first electrode 16.
- the electrical contacts 10 are distributed over the entire circumference of the coating section 9, so that in every rotational position o of the delivery tube 1 the potential of the electrical contacts 10 is applied to small parts located in the region of the electrical contacts 10.
- the electrical contacts 10 are in electrical connection with a contact bar 11 with sliding contact, which is arranged on the outer side of the delivery tube 1 and is connected to a first pole of a direct-current source (not represented) .
- the electrical contacts 10 are removably fastened, for example plugged or screwed on, so that they can easily be exchanged, to cross-connection links that pass through openings in the delivery tube 1 and are welded onto the contact bar 11.
- the rear end of the coating section 9 in the direction of delivery corresponds in its position to the rear edge 8 of the tank 6.
- a small-part outlet opening 12 which is formed as a cutout in the delivery tube 1.
- a conveyor belt 13 Arranged underneath the region of the delivery tube of the small-part outlet opening 12 is a conveyor belt 13, which serves for further transporting of the small parts.
- a second electrode 14 which is at least partly submerged in the coating agent.
- the outer form of the second electrode 14 will be described in more detail later with reference to Figure 2.
- the entire apparatus is secured in a framework and set up on the ground.
- the framework comprises bearing rollers 15 for the delivery tube 1 and a drive motor for the rotary drive of the delivery tube 1.
- the small parts are electrolytically coated by the electric field which is present between the small parts to which a potential is applied (cathode) and the second electrode 14 (anode) .
- the small parts are transported by the ribbon screw 5 to the small-part outlet opening 12, at which they fall downwards onto the conveyor belt 13 for further transporting.
- This takes place together with the coating agent, since, in contrast with the prior-art apparatus described above, the inside surface of the delivery tube 1 does not have a separate outlet opening for the coating agent. Consequently, the coated small parts wetted with coating agent fall onto the conveyor belt, as a result of which mechanical damage of the coating caused by impact on the conveyor belt or by small parts hitting one another is avoided to the greatest extent.
- the unit comprising delivery tube 1, tank 6 and conveyor belt 13 is arranged above a coating agent reservoir 17 , so that coating agent lapping over the edge of the tank 6 or running out of the small-part outlet opening 12 is caught.
- a pump 18 serves for delivering the coating agent from the reservoir 17 via a supply line to the tank 6 for the coating agent.
- Figure 2 reveals the outer form of the second electrode 14 and its relative arrangement with respect to the delivery tube 1.
- the electrical contacts 10 on the inner side of the delivery tube 1 can also be seen.
- the second electrode 14 has a perforated plate
- the second electrode 14 is in electrical connection with the second pole of the current source
- the second electrode 14 is attached via an arm 21 to a fastening rod 22 which is arranged on the longitudinal axis of the delivery tube 1.
- the second electrode 14 is arranged symmetrically with respect to the lowest point of the delivery tube 1, the centre points of the circular segment of the plate 19 and of the delivery tube 1 coinciding.
- the arm 21 is designed in such a way that it can be adjusted in length, so that the height of the second electrode 14 can be changed, for example in order to carry out an adaptation of the position of the second electrode 14 to the filling height of the delivery tube 1 with small parts .
- FIG. 3 shows the flow diagram for the operation of the apparatus for electro-dipcoating electrically conducting small parts.
- the pump 18 delivers coating agent from the reservoir 17, which agent, after passing through a cooling means 37, which maintains a coating agent temperature of approximately 28 to 30° C, and a following filter 23 (50 to 75 ⁇ ) , is introduced into the tank 6 and the delivery tube 1.
- a pump 24 delivers coating agent from the reservoir 17 and leads it via a filter 25 (50 ⁇ m) to an ultrafiltration module.
- the ultrafiltration module 26 has the effect that, for example, water, acids and amines, referred to hereafter as rinsing liquid, are removed from the coating agent as filtrate.
- the coating agent filtered in the ultrafiltration module 26 to stabilize the bath can be returned directly into the reservoir 17, so that a second coating agent circuit, parallel to the first, is closed.
- the rinsing liquid in the form of filtrate, passes from the ultrafiltration module 26 via a flowmeter 37 into a filtrate receiver 28.
- filtrate is fed via a second flowmeter 30, the measured value of which should lie below the measured value of the first flowmeter, to a rinsing device 31.
- the rinsing device 31 is formed by a total of three nozzles 32a, 32b, 32c, from which rinsing liquid emerges.
- the nozzle 32a is arranged above the conveyor belt 13, and rinses coated small parts from the delivery tube 1.
- the small parts transported by the conveyor belt 13 fall at the end of the conveyor belt 13 remote from the delivery tube 1 into a rinsing liquid tank 33, to be specific onto a further conveyor belt 34, which runs obliquely upwards in its conveying direction and partly extends out of the rinsing liquid.
- the nozzles 32b and 32c are arranged and apply to the small parts rinsing liquid which passes from the conveyor belt 34 into the rinsing liquid tank 32.
- a pump 35 delivers rinsing liquid, which is supplied to the nozzles 32a and 32b.
- a mixing tank 35 to which rinsing liquid and a starting coating agent are supplied by means of the filtrate pump 29.
- the starting coating agent is brought to a desired coating agent concentration, reduced in comparison with the starting product, by mixing in filtrate and is subsequently fed to the reservoir 17.
- a rinsing pump 36 used only ⁇ when rinsing the apparatus, delivers rinsing liquid which originates from the filtrate receiver 28 and serves for rinsing the membrane of the ultrafiltration module 26.
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Abstract
In the case of an apparatus for electro-dipcoating small electrically conductive parts, having a tank (6) with a predetermined filling height for receiving a dipping bath of electrically conductive, liquid coating agent, a delivery tube (1), which is rotatable about its axis, for transporting the small parts in its longitudinal direction, having a small-part inlet opening (4), a small-part outlet opening (12) and a ribbon screw (5) attached to the inner side of the delivery tube (1), the delivery tube (1) being arranged in relation to the tank (6) in such a way that a coating section (9) of the delivery tube (1) extending in the longitudinal direction of the said delivery tube (1) lies partly below the predetermined filling height of the tank (6), and a first electrode (16), which is connected to one pole of a current source and is arranged on the inner side of the coating section (9) of the delivery tube (1), and a second electrode (14), which is connected to the other pole of the current source. The object is to improve the quality of the coated small parts. This object is achieved by the second electrode (14) being arranged within the coating section (9) of the delivery tube (1), in the tank, below the predetermined filling height of the tank.
Description
Apparatus for electro-dipcoating
The present invention concerns an apparatus for electro-dipcoating small electrically conductive parts, having
- a tank with a predetermined filling height for receiving a dipping bath of electrically conductive, liquid coating agent (KTL; ATL) ,
- a delivery tube, which is rotatable about its axis, for transporting the small parts in its longitudinal direction, having a small-part inlet opening, a small-part outlet opening and a ribbon screw attached to the inner side of the delivery tube,
- the delivery tube being arranged in relation to the tank in such a way that a coating section of the delivery tube extending in the longitudinal direction of the said delivery tube lies partly below the predetermined filling height of the tank, and - a first electrode, which is connected to one pole of a current source and is arranged on the inner side of the coating section of the delivery tube, and a second electrode, which is connected to the other pole of the current source. Such an apparatus for electro-dipcoating small electrically conductive parts is known from DE 42 05 672 C2. In the case of the apparatus described there, the delivery tube is designed as a screw conveyor, the delivery tube having a ribbon screw fastened to its inner circumference as a pushing element for small parts received in the delivery tube. Arranged on the inner side of the delivery tube are electrically conducting contacts, as a first electrode, which is connected to one pole of a current source. The electrically conducting contacts are distributed over the inner circumference of the coating section of the delivery tube and serve the purpose of applying an electric potential to small parts, which are electrically conductive, located at the bottom of the
delivery tube.
The second electrode is formed by a contact plate which is arranged underneath and outside the delivery tube in the dip tank. For adequate flooding of the delivery tube with coating agent, the delivery tube is provided with perforations which allow the liquid coating agent to pass through, also creating the possibility for electric field lines to pass from the first electrode to the second electrode through the perforations in the delivery tube.
By rotating the delivery tube, small parts to be coated are taken by the ribbon screw along the bottom of the delivery tube, the said parts initially making contact with the electrical contacts, so that the electrolytic coating can take place. By rotating the delivery tube further, the small parts leave the coating section of the delivery tube, characterized by the electrical contacts, and can drip off by way of the perforations, after which they leave the delivery tube. The coating agent leaves the delivery tube via a separate discharge.
Such an apparatus has the disadvantage that short-circuits occur during operation of the apparatus and lead to material burned off from the electrodes being present in the coating agent as coagulate. This leads to an inferior quality of the small parts coated.
A further disadvantage of the known apparatus is due to the fact that the coated small parts are subjected to abrasion on their way through the delivery tube on account of the perforation of the delivery tube. This abrasion leads to the possibility of the electrolytically applied coating of the small parts being reduced locally in its thickness or even removed. Furthermore, it is necessary in the case of the known apparatus to work with a relatively high operating current .
Setting out from this situation, the invention is based on the object of further developing the known
apparatus, described above, in such a way that the quality of the small parts coated with the apparatus is improved .
This object is achieved in the case of the apparatus of the type stated at the beginning by
- the second electrode being arranged within the coating section of the delivery tube, in the tank, below the predetermined filling height of the tank.
On account of the arrangement of the second electrode within the coating section of the delivery tube below the predetermined filling height of the tank, the two electrodes required for the electrolytic coating now lie directly opposite one another. During the operation of electro-dipcoating, the small parts to be coated are located at the bottom of the delivery tube in contact with the first electrode, while the second electrode lies inside the tank, on account of the intended arrangement at a distance from the small parts. In contrast with the prior art, the electric field which is present between the two electrodes is consequently undisturbed, so that in particular the operating current of the apparatus can be reduced to approximately half the value to be used in the case of the known apparatus . Furthermore, the arrangement of the second electrode allows the inside surface of the delivery tube to be formed without openings, so that this surface can be made planar. Abrasion of the coated small parts is consequently considerably less than in the case of the known apparatus.
A further advantage of the apparatus is that, with the new electrode arrangement, far fewer short- circuits occur, as a result of which contamination of the coating agent with coagulate is effectively restricted and the quality of the coated small parts is improved .
It has also been observed that the coating of electrically conducting parts of the first electrode that occurs during the electro-dipcoating is much less
than in the case of the known apparatus . The second electrode may be advantageously arranged in such a way that it lies vertically above the small parts to be coated. The outer form of the second electrode is restricted only to the extent that an adequately favourable ratio between the surface area of the second electrode and the surface area of the small parts, to be regarded as the first electrode, is ensured. A typical value for the "surface area of the second electrode : surface area of the small parts to be coated" ratio lies in the range from 1:1 to 1:5.
All forms of the second electrode which provide the specified surface area ratio may be used in the case of the apparatus. For example, the second electrode may be designed as a plurality of rods which are interconnected in an electrically conducting manner .
The second electrode is, however, preferably designed as a plate which in cross section is in the form of a segment of a circle, for example as a perforated plate, it being possible for the centre point of the circle assigned to the segment to lie on the longitudinal axis of the delivery tube. If the surface area of the plate is not adequate for the surface area ratio specified above, the plate preferably has bars extending radially outwards with respect to the delivery tube.
The second electrode preferably has a plastic mesh on its radially outer side. This plastic grid may rest for example on the exposed ends of the bars of the plate and be fastened there. The plastic mesh has the advantage that the occurrence of short-circuits between the electrodes is reduced still further. In contrast with the apparatus according to the prior art, the delivery tube preferably has an essentially (first electrode) planar inside surface between the small-part inlet opening and the small-part outlet opening. This feature is not absolutely
necessary for the novel apparatus, but offers the advantages already specified above with respect to the abrasion of the coated small parts.
Added to this is the fact that the small parts leave from the small-part outlet opening together with the liquid coating agent. The small parts are consequently wetted with coating agent. In the case where the small parts fall downwards out of the small- part outlet opening, their impact is cushioned by wetting coating agent, even small parts hitting one another not being damaged for the most part.
The small-part outlet opening is preferably arranged on the circumference of the delivery tube downstream of the coating section of the delivery tube and of the tank, as considered from the direction of delivery. Owing to gravity, small parts fall downwards out of the small-part outlet opening when the delivery tube is at a corresponding angle of rotation. In this case, a transporting device, with which the small parts are further transported, may be provided underneath the region of the delivery tube of the small-part outlet opening .
The small-part outlet opening is advantageously assigned a transporting device which is arranged relative to the small-part outlet opening in such a way that downwardly falling small parts are taken up by the transporting device and transported essentially perpendicularly with respect to the delivery tube.
A rinsing device for applying rinsing liquid to the small parts may preferably be arranged above the transporting device. In this way, an effective rinsing of the small parts is achieved, removing adhering coating agent.
The transporting device may be designed as a conveyor-belt arrangement, the small parts being well exposed for rinsing liquid to be applied to them.
The coating section of the delivery tube is preferably arranged at such a distance in the direction of delivery from the small-part inlet opening that air
is removed from the small parts before the coating operation. It has been found that the quality of the coated small parts is improved if air present between the small parts, which are typically in the form of piece goods, can escape. On the way from the small- part inlet opening to the coating section of the delivery tube, air present between the bulk small parts can rise upwards within the dipping bath as bubbles.
A circuit for the coating agent, which has a cooling means, at least one filter and an ultrafiltration module, is preferably provided for operating the apparatus . These devices contribute to the stability of the dipping bath and ensure a well- applied coating of small parts and of threads, with forces acting from the inside.
A circuit for the rinsing liquid, in which the rinsing liquid contains filtrate formed by the ultrafiltration module (closed circuit) , may also be provided. In this way, economical rinsing of the small parts is achieved.
The features of the apparatus which relate to the described removal of air from the small parts or rinsing of the small parts are respectively regarded as separate inventions, independently of the arrangement of the electrodes.
The invention is explained in more detail below with reference to drawings, which represent preferred embodiments and in which:
Figure 1 shows an overall view of an apparatus for electrolytically coating small parts, partly in section;
Figure 2 shows a cross-sectional view of the coating section of the apparatus according to Figure 1;
Figure 3 shows a schematic representation of the apparatus according to Figure 1 together with a plurality of liquid circuit systems for operating the apparatus .
As can be seen in Figure 1, the apparatus for electro-dipcoating electrically conductive small parts,
in particular metal parts, has a delivery tube 1 made of plastic for transporting small parts in the longitudinal direction of the delivery tube 1. The feeding in of small parts takes place via a balance 2 , which, when a predetermined weight of small parts is reached, is tipped in the direction of a run-in chute 3, via which the small parts are introduced into the delivery tube 1 through a small-part inlet opening 4, which is formed by an open end of the delivery tube 1. The delivery tube 1 is provided over its entire length with a ribbon screw 5 fastened to its inner side, so that an appropriate rotation of the delivery tube 1 about its longitudinal axis brings about transportation of the small parts in a direction of delivery.
Seen in the direction of delivery of the small parts, approximately the first half of the delivery tube 1 lies in a tank 6 which is filled up to a predetermined level with coating agent for the small parts.
The tank 6 has over its entire length an essentially U-shaped cross section, that edge 7 of the tank 6 which is at the front in the direction of delivery running horizontally, while that edge 8 of the tank 6 which is at the rear in the direction of delivery is adapted in its shape to the radial dimensions of the delivery tube 1 and is sealed off from the delivery tube 1. The height of the ribbon screw 5 in the region 5a of the rear edge 8 of the tank 6 is chosen such that the coating agent in the tank 6 cannot flow over the ribbon screw 5 in the region 5a, but instead, like the small parts, is moved by the ribbon screw 5 in the direction of delivery.
At a distance from the small-part inlet opening 4, the delivery tube 1 has a coating section 9 which is provided on its inner side with electrical contacts 10 forming a first electrode 16. The electrical contacts 10 are distributed over the entire circumference of the coating section 9, so that in every rotational position
o of the delivery tube 1 the potential of the electrical contacts 10 is applied to small parts located in the region of the electrical contacts 10. The electrical contacts 10 are in electrical connection with a contact bar 11 with sliding contact, which is arranged on the outer side of the delivery tube 1 and is connected to a first pole of a direct-current source (not represented) . The electrical contacts 10 are removably fastened, for example plugged or screwed on, so that they can easily be exchanged, to cross-connection links that pass through openings in the delivery tube 1 and are welded onto the contact bar 11. Here, too, there is an advantage over the known apparatus in which contacts are welded into a delivery tube. The rear end of the coating section 9 in the direction of delivery corresponds in its position to the rear edge 8 of the tank 6.
Provided downstream of the coating section 9, in the direction of delivery, on the circumference of the delivery tube 1 is a small-part outlet opening 12, which is formed as a cutout in the delivery tube 1.
Arranged underneath the region of the delivery tube of the small-part outlet opening 12 is a conveyor belt 13, which serves for further transporting of the small parts.
Also provided in the coating section 9 is a second electrode 14, which is at least partly submerged in the coating agent. The outer form of the second electrode 14 will be described in more detail later with reference to Figure 2.
The entire apparatus is secured in a framework and set up on the ground. The framework comprises bearing rollers 15 for the delivery tube 1 and a drive motor for the rotary drive of the delivery tube 1. During the operation of the apparatus, small parts introduced into the delivery tube 1 via the run- in chute 3 firstly cover the distance corresponding to the distance from the small-part inlet opening to the coating section 9, no electrolytic coating taking place
as yet. Over this distance, air trapped between the small parts can escape in the form of bubbles and be removed from the coating agent. The small parts with air removed from them subsequently pass into the coating section 9, an electric potential being applied to them when they make contact with the electrical contacts 10.
The small parts are electrolytically coated by the electric field which is present between the small parts to which a potential is applied (cathode) and the second electrode 14 (anode) . After completion of the coating operation, the small parts are transported by the ribbon screw 5 to the small-part outlet opening 12, at which they fall downwards onto the conveyor belt 13 for further transporting. This takes place together with the coating agent, since, in contrast with the prior-art apparatus described above, the inside surface of the delivery tube 1 does not have a separate outlet opening for the coating agent. Consequently, the coated small parts wetted with coating agent fall onto the conveyor belt, as a result of which mechanical damage of the coating caused by impact on the conveyor belt or by small parts hitting one another is avoided to the greatest extent. The unit comprising delivery tube 1, tank 6 and conveyor belt 13 is arranged above a coating agent reservoir 17 , so that coating agent lapping over the edge of the tank 6 or running out of the small-part outlet opening 12 is caught. A pump 18 serves for delivering the coating agent from the reservoir 17 via a supply line to the tank 6 for the coating agent.
Figure 2 reveals the outer form of the second electrode 14 and its relative arrangement with respect to the delivery tube 1. Represented in Figure 2, from outside to inside, are the contact bar 11, the delivery tube 1, the ribbon screw 5, the ribbon screw section 5a of increased height and the second electrode 14. The electrical contacts 10 on the inner side of the delivery tube 1 can also be seen.
The second electrode 14 has a perforated plate
19 which in cross section is in the form of a segment of a circle and has bars 20 extending ■ radially outwards for increasing the surface area of the electrode. Arranged on the radially outer ends of the bars 20 is a polypropylene fabric 38, which serves for the avoidance of short-circuits between the second electrode and the small parts.
The second electrode 14 is in electrical connection with the second pole of the current source
(not represented) and is fixed in its position in the coating section 9, i.e. it does not follow the rotational movement of the delivery tube 1. For this purpose, the second electrode 14 is attached via an arm 21 to a fastening rod 22 which is arranged on the longitudinal axis of the delivery tube 1. The second electrode 14 is arranged symmetrically with respect to the lowest point of the delivery tube 1, the centre points of the circular segment of the plate 19 and of the delivery tube 1 coinciding. The arm 21 is designed in such a way that it can be adjusted in length, so that the height of the second electrode 14 can be changed, for example in order to carry out an adaptation of the position of the second electrode 14 to the filling height of the delivery tube 1 with small parts .
Figure 3 shows the flow diagram for the operation of the apparatus for electro-dipcoating electrically conducting small parts. The pump 18 delivers coating agent from the reservoir 17, which agent, after passing through a cooling means 37, which maintains a coating agent temperature of approximately 28 to 30° C, and a following filter 23 (50 to 75 μ ) , is introduced into the tank 6 and the delivery tube 1. Coating agent leaving the tank 6 via the delivery tube 1, in particular the small-part outlet opening 12, returns into the reservoir 17, so that a first coating agent circuit is closed.
A pump 24 delivers coating agent from the
reservoir 17 and leads it via a filter 25 (50 μm) to an ultrafiltration module. The ultrafiltration module 26 has the effect that, for example, water, acids and amines, referred to hereafter as rinsing liquid, are removed from the coating agent as filtrate.
The coating agent filtered in the ultrafiltration module 26 to stabilize the bath can be returned directly into the reservoir 17, so that a second coating agent circuit, parallel to the first, is closed.
The rinsing liquid, in the form of filtrate, passes from the ultrafiltration module 26 via a flowmeter 37 into a filtrate receiver 28. By means of a filtrate pump 29, filtrate is fed via a second flowmeter 30, the measured value of which should lie below the measured value of the first flowmeter, to a rinsing device 31. In the exemplary embodiment represented, the rinsing device 31 is formed by a total of three nozzles 32a, 32b, 32c, from which rinsing liquid emerges. The nozzle 32a is arranged above the conveyor belt 13, and rinses coated small parts from the delivery tube 1.
The small parts transported by the conveyor belt 13 fall at the end of the conveyor belt 13 remote from the delivery tube 1 into a rinsing liquid tank 33, to be specific onto a further conveyor belt 34, which runs obliquely upwards in its conveying direction and partly extends out of the rinsing liquid. In the region of the part of the conveyor belt 34 extending out of the rinsing liquid, the nozzles 32b and 32c are arranged and apply to the small parts rinsing liquid which passes from the conveyor belt 34 into the rinsing liquid tank 32. A pump 35 delivers rinsing liquid, which is supplied to the nozzles 32a and 32b. Also provided is a mixing tank 35, to which rinsing liquid and a starting coating agent are supplied by means of the filtrate pump 29. In the mixing tank 35, the starting coating agent is brought to a desired coating agent concentration, reduced in
comparison with the starting product, by mixing in filtrate and is subsequently fed to the reservoir 17.
A rinsing pump 36, used only ~ when rinsing the apparatus, delivers rinsing liquid which originates from the filtrate receiver 28 and serves for rinsing the membrane of the ultrafiltration module 26.
Claims
1. Apparatus for electro-dipcoating small electrically conductive parts, having - a tank (6) with a predetermined filling height for receiving a dipping bath of electrically conductive, liquid coating agent (KTL; ATL) ,
- a delivery tube (1) , which is rotatable about its axis, for transporting the small parts in its longitudinal direction, having a small-part inlet opening (4), a small-part outlet opening (12) and a ribbon screw (5) attached to the inner side of the delivery tube (1) ,
- the delivery tube (1) being arranged in relation to the tank (6) in such a way that a coating section
(9) of the delivery tube (1) extending in the longitudinal direction of the said delivery tube (1) lies partly below the predetermined filling height of the tank (6), and - a first electrode (16), which is connected to one pole of a current source and is arranged on the inner side of the coating section (9) of the delivery tube (1) , and a second electrode (14) , which is connected to the other pole of the current source, characterized in that
- the second electrode (14) is arranged within the coating section (9) of the delivery tube (1), in the tank, below the predetermined filling height of the tank.
2. Apparatus according to Claim 1, characterized in that the second electrode (14) is designed as a plate (19) which in cross section is in the form of a segment of a circle.
3. Apparatus according to Claim 2, characterized in that the plate (19) has bars (20) extending radially outwards with respect to the delivery tube.
4. Apparatus according to one of Claims 1 to 3 , characterized in that the second electrode (14) has a plastic mesh (38) on its radially outer side
5. Apparatus according to one of Claims 1 to 4, characterized in that the delivery tube (1) has essentially a planar inside surface between the small- part inlet opening (12) and the small-part outlet opening (4) .
6. Apparatus according to one of Claims 1 to 5 , characterized in that the small-part outlet opening (12) is arranged on the circumference of the delivery tube (1) downstream of the coating section (9) of the delivery tube and of the tank (6) , as considered from the direction of delivery.
7. Apparatus according to Claim 6, characterized in that the small-part outlet opening (12) is assigned a transporting device (13) for the small parts, which is arranged relative to the small-part outlet opening (12) in such a way that downwardly falling small parts are taken up by the transporting device (13) and transported essentially perpendicularly with respect to the delivery tube (1) .
8. Apparatus according to one of Claims 6 or 7 , characterized in that a rinsing device (31; 32a, 32b, 32c) for applying rinsing liquid to the small parts is arranged above the transporting device (13).
9. Apparatus according to one of Claims 6 to 8, characterized in that the transporting device (13) is designed as a conveyor belt.
10. Apparatus according to one of Claims 1 to 9 , characterized in that the coating section (9) of the delivery tube (1) is arranged at such a distance in the direction of delivery from the small-part inlet opening
(12) that air is removed from the small parts before they reach the coating section (9).
11. Apparatus according to one of Claims 1 to 10, characterized in that a circuit for the coating agent, which has a cooling means (37) , at least one filter
(23, 35) and an ultrafiltration module (26), is provided.
12. Apparatus according to Claim 11, characterized in that a circuit for the rinsing liquid, in which the rinsing liquid contains filtrate ■ formed by the ultrafiltration module (26) , is provided.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU28066/00A AU2806600A (en) | 1999-02-23 | 2000-02-22 | Apparatus for electro-dipcoating |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE1999107863 DE19907863C1 (en) | 1999-02-23 | 1999-02-23 | Apparatus for electro dip lacquering comprises a second electrode which is located in the basin below a predetermined level of the dipping liquid |
DE19907863.7 | 1999-02-23 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2000050670A2 true WO2000050670A2 (en) | 2000-08-31 |
WO2000050670A3 WO2000050670A3 (en) | 2000-12-07 |
Family
ID=7898631
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2000/001437 WO2000050670A2 (en) | 1999-02-23 | 2000-02-22 | Apparatus for electro-dipcoating |
Country Status (3)
Country | Link |
---|---|
AU (1) | AU2806600A (en) |
DE (1) | DE19907863C1 (en) |
WO (1) | WO2000050670A2 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102009025620A1 (en) | 2009-06-18 | 2010-01-14 | Daimler Ag | Method for lacquering a hollow chamber of a roof frame element of a vehicle chassis comprises arranging a foamed element in the region of the opening of the hollow chamber, lacquering, drying and further processing |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1557474A (en) * | 1923-06-27 | 1925-10-13 | Harry B Farrand | Continuous rotary electroplating machine |
FR702863A (en) * | 1929-12-28 | 1931-04-18 | Waldberg | Horizontal axis electroplating apparatus |
FR844447A (en) * | 1938-04-05 | 1939-07-25 | Improvement in automatic chemical, electro-chemical and electrolytic treatment devices, for small mass parts | |
US2624728A (en) * | 1949-07-14 | 1953-01-06 | United Chromium Inc | Electroplating barrel |
FR2446871A1 (en) * | 1979-01-17 | 1980-08-14 | Rymland Robert | Electrolytic treatment vat - has rotatable cylinder with concentric squirrel-cage cathode and bar anode rotating with cylinder |
US4427518A (en) * | 1981-07-10 | 1984-01-24 | Siemens Aktiengesellschaft | Electroplating device |
DE4205672A1 (en) * | 1992-02-25 | 1993-08-26 | Doerken Ewald Ag | DEVICE FOR THE ELECTROLYTIC COATING OF SMALL PARTS |
-
1999
- 1999-02-23 DE DE1999107863 patent/DE19907863C1/en not_active Expired - Lifetime
-
2000
- 2000-02-22 AU AU28066/00A patent/AU2806600A/en not_active Abandoned
- 2000-02-22 WO PCT/EP2000/001437 patent/WO2000050670A2/en active Application Filing
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1557474A (en) * | 1923-06-27 | 1925-10-13 | Harry B Farrand | Continuous rotary electroplating machine |
FR702863A (en) * | 1929-12-28 | 1931-04-18 | Waldberg | Horizontal axis electroplating apparatus |
FR844447A (en) * | 1938-04-05 | 1939-07-25 | Improvement in automatic chemical, electro-chemical and electrolytic treatment devices, for small mass parts | |
US2624728A (en) * | 1949-07-14 | 1953-01-06 | United Chromium Inc | Electroplating barrel |
FR2446871A1 (en) * | 1979-01-17 | 1980-08-14 | Rymland Robert | Electrolytic treatment vat - has rotatable cylinder with concentric squirrel-cage cathode and bar anode rotating with cylinder |
US4427518A (en) * | 1981-07-10 | 1984-01-24 | Siemens Aktiengesellschaft | Electroplating device |
DE4205672A1 (en) * | 1992-02-25 | 1993-08-26 | Doerken Ewald Ag | DEVICE FOR THE ELECTROLYTIC COATING OF SMALL PARTS |
Also Published As
Publication number | Publication date |
---|---|
DE19907863C1 (en) | 2000-03-16 |
WO2000050670A3 (en) | 2000-12-07 |
AU2806600A (en) | 2000-09-14 |
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