EP2684986A1 - Method for anodising areas on metallic hollow bodies - Google Patents

Abstract

Anodizing surfaces of metallic hollow bodies, comprises clampingly fixing the hollow body (11) at projecting fingers of electrically conductive workpiece support and supplying the workpiece support in a predetermined operating cycle gradually over a series of treatment baths. The treatment baths comprise at least one anodic bath (4). A cathode, which is arranged between the workpiece support and the treatment bath (14), carries the anodic oxidation at the surfaces of the hollow bodies over a closed circuit. The workpiece support is lowered in a transfer station (8) of the treatment baths. Anodizing surfaces of metallic hollow bodies, comprises clampingly fixing the hollow body (11) at projecting fingers of electrically conductive workpiece support and supplying the workpiece support in a predetermined operating cycle gradually over a series of treatment baths. The treatment baths comprise at least one anodic bath (4). A cathode, which is arranged between the workpiece support and the treatment bath (14), carries the anodic oxidation at the surfaces of the hollow bodies over a closed circuit. The workpiece support is lowered in a transfer station (8) of the treatment baths with a horizontal orientation in the treatment bath. The workpiece support within the treatment bath in the horizontal orientation is supplied into at least one removal station of the treatment bath through the steps specified to the operating cycle. The workpiece support is raised in the removal station in a subsequent operating cycle and turned by 180[deg] so that the liquid from the hollow bodies drips off into the treatment bath. The workpiece support is moved in the anodic bath on a metallic rail (15), which is connected with the anode of the circuit.

Description

The invention relates to a method for anodizing surfaces on metallic hollow bodies, in which the hollow bodies are fixed in a clamping manner on projecting fingers of electrically conductive workpiece carriers and the workpiece carriers are guided stepwise through a series of treatment baths in a predetermined working cycle, wherein the treatment baths comprise at least one Eloxalbad, in which anodic oxidation takes place on the surfaces of the hollow body through a closed circuit between the workpiece carrier and a cathode arranged in the treatment bath. The hollow bodies are also referred to below as workpieces.

Anodizing is also called anodic oxidation and is an electrochemical process that converts the metal surface of a workpiece into metal oxide. The resulting oxide layer is firmly connected to the metallic base material. The layer thickness can be set defined by the choice of process parameters. Anodizing is primarily used for surface finishing of aluminum or aluminum alloy workpieces. The anodized coating permanently protects the aluminum from environmental influences, makes it easy to clean and, thanks to the structure of the oxide layer, allows decorative color entries. The method is used in practice to provide sleeves, caps and similar workpieces with a high quality decorative surface.

The treatment baths comprise, in addition to an eloxal bath, further baths in which the workpieces are degreased, chemically treated, rinsed and sealed. Between the treatment baths further rinsing baths are provided. The color effect and gloss effect can be influenced by different immersion times in the different process liquids. In a method known from practice, workpiece carriers, which have been previously loaded with the workpieces to be treated, suspended from a conveyor, transported with vertical alignment and immersed vertically in the process liquids of the treatment baths. The arranged at the lower end of the workpiece carrier workpieces are exposed in this process, the process liquid longer than the fixed at the upper end of the workpiece carrier workpieces. The different dwell time in the anodizing bath and in a downstream dye bath has an adverse effect on the quality of the workpiece surfaces. The anodized and colored surfaces of the workpieces differ, for example, in terms of color intensity, which is highly dependent on the residence time of the workpieces in the dye bath. In addition, resulting from the lateral orientation of the workpieces quality differences between the anodized surfaces on the top and the bottom of the hollow body. Another disadvantage of the known method is that the process liquid does not run completely from the workpieces after the removal of the vertically oriented workpiece carriers from the treatment baths within the limited time, which is determined by the power stroke. This results in large carry-over losses of the process fluid during a movement of the workpiece carriers from bath to bath. This has an adverse effect on, among other things, the sanitation and the consumption of chemicals.

At one off US 2008/0257717 A1 known processes are workpiece carrier, which have been previously equipped with the hollow bodies to be treated, transferred to a drum which executes stepwise clocked rotational movements within the treatment bath. The workpiece carriers move on a helical path through the treatment bath. Depending on the required dwell time, the drum will make one or more full turns out. Several treatment baths, which are equipped with a corresponding device, are arranged in series one behind the other, so that the workpiece carriers can be performed with the workpieces to be treated through several different treatment baths. The residence time in the treatment baths depends on the number of revolutions of the drum and can only be varied in change steps which amount to an integer multiple of a full revolution. It is difficult to set a short treatment time and to combine with baths that require a very long residence time of the workpieces. If the drum requires several revolutions to set a long residence time, it is also disadvantageous that the workpieces leave the process liquid repeatedly during the treatment in the process liquid and submerge again in the process liquid. The procedural limitations adversely affect the surface quality of the workpieces.

At one off DE 12 74 979 known processes for anodizing hollow bodies, the workpieces are fixed on an endless belt, which consists of a titanium sheet or a Zirkonblech, which is guided to form belt loops through a plurality of series-arranged treatment baths. By the number of belt loops in a treatment bath, the residence time of the workpieces can be varied. Also in this method, a large carryover of the process liquid from treatment bath to treatment bath is unavoidable.

Against this background, the invention has for its object to provide a method for anodizing surfaces on metallic hollow bodies, which is characterized by a low carryover of the process liquids from treatment to treatment bath and with which it is possible to workpieces finished with an anodized and in particular colored To produce a surface of high quality. In particular, all fixed on a workpiece carrier workpieces should be identical in terms of color intensity and gloss surface and should in particular quality differences between the top and bottom of the anodized hollow body can be avoided.

The object of the invention and solution of this problem is a method according to claim 1.

According to the invention, the workpiece carriers are lowered in a transfer station of the treatment baths with a horizontal orientation into the treatment bath and supplied within the treatment bath in this horizontal orientation in one or more predetermined by the power stroke steps of a removal station of the treatment bath. In a subsequent cycle, the workpiece carriers are raised in the removal station and turned by 180 ° so that liquid drips from the hollow bodies into the treatment bath. In the Eloxalbad the workpiece carriers are moved on a metallic rail, which is connected to the anode of the circuit.

In the method according to the invention, the workpiece carriers in the process fluid of the treatment baths are always aligned horizontally. The protruding fingers of the tool carriers, on which the workpieces are clamped, extend downwards in the treatment bath, so that the process liquid can flow into the interior of workpieces which have the shape of a cap without impairing gas cushions. Since the workpiece carriers are lowered into the treatment bath with a horizontal orientation and are accordingly lifted out of the treatment bath after the treatment, each workpiece has the same residence time in the process fluid. This results in a particularly uniform treatment result. Workpieces that are dyed after anodizing in the dipping process, obtain a uniform color intensity, with no differences between the inside and the outside of the hollow body. The workpiece carriers are moved horizontally on a rail system through the treatment baths, with the movement occurring in steps dictated by the working cycle of the process. The required dive time in the process fluids is determined by the number of steps and the stride length. In the removal station of the treatment baths, the workpiece carriers are raised and turned by 180 °. Due to the overhead position of the workpiece carriers, process liquid can drip almost completely from the interior of the hollow bodies as well as from the outer surfaces of the workpieces into the treatment bath. A vertical alignment of the workpieces on the workpiece carriers in conjunction with a 180 ° rotation of the workpiece carrier as it is removed from the treatment bath causes a low carryover of the process liquids from treatment bath to treatment bath. This reduces the consumption of chemicals and energy requirements z. B. for pumps and for heating the process fluids. Furthermore, the cost of a sanitation can be reduced.

In the method according to the invention a plurality of workpiece carriers moved in a row is simultaneously passed through a treatment bath, wherein a workpiece carrier is lowered in the transfer station of the treatment bath in the treatment bath, at the same time a workpiece carrier is removed in the removal station from the treatment and at least one further workpiece carrier the treatment bath is moved.

The workpiece carriers are turned in accordance with a preferred embodiment of the invention in the transfer station at least one treatment bath by a rotary motion and thereby lowered from a first position above the bath liquid of the treatment bath in a second position within the liquid. The turning device is designed and arranged so that only by the rotational movement of the workpiece carrier, both the required stroke movement and the essential for the inventive method turning movement is performed by 180 °. The removal station of the treatment bath can be equipped with a structurally identical turning device, which lifts the workpiece carrier out of the treatment bath by means of a rotary movement through 180 °.

A further embodiment of the method according to the invention provides that the workpiece carriers are turned in the transfer station at least one treatment bath by a rotary motion and lowered after turning from a position above the treatment bath by means of a vertical movement in the bath liquid. The workpiece carriers carry out both a translational movement and a rotational movement. The embodiment has the advantage that all of the workpiece fixed to the workpiece carrier reach the liquid level of the treatment bath at the same time and submerge in the process liquid of the treatment bath. The embodiment described is particularly suitable for treatment baths in which the residence time must be set very accurately and it is necessary that all fixed to the workpiece carrier hollow body have the same residence time in the bathroom. The described embodiment of the transfer station is preferably used for dye baths in which the workpieces with tight tolerances require a defined residence time, for example between 15 and 30 seconds and deviations from the award value affect the color intensity.

The workpiece carriers are located within the treatment baths on a rail and are preferably moved by translational movements of a slider. The anode of the electric circuit associated with the eloxal bath is connected to the rail, which bridges a distance between the transfer station and the removal station of the treatment bath. The rail is thus connected to the positive terminal of a DC voltage source, wherein the contact point between the anode and the rail is within the bath liquid. This ensures a good electrical transmission. The electrical contact within the process fluid is more effective and störunanfälliger than a contact outside the bath.

The cathode for the anodizing process is expediently arranged below the rail electrically connected to the anode. Preferably, the cathode is disposed on the bottom of the anodizing bath.

Since the workpiece carriers are lowered horizontally into the processing baths and guided horizontally through the processing baths, shallow processing baths having a low liquid level can be used. Compared to the prior art can be worked in the inventive method with smaller amounts of liquid. This has energy advantages in terms of heating and temperature control of the baths. Furthermore, the treatment baths can be exchanged more easily and the process of the invention can be operated economically even for small batches of workpieces to be anodized.

For the inventive method workpiece carriers are used, the base frame and attached to the base frame strips with a plurality of paired elastically deformable fingers for Have fixation of the hollow body. The base frame of the workpiece carriers can be guided on opposite sides in C-shaped rail elements. For overhead movements in the transfer station and removal station of the treatment baths no additional fixations between the rail elements and the workpiece carrier are necessary. The C-shaped rail elements can be made of wire elements, so that they can be well bathed by the process liquid and forms no accumulation of liquid in the rail system when replacing the bath liquid.

Fig. 1

ein Anlagenschema für ein Verfahren zum Eloxieren von Flächen an metallischen Hohlkörpern,

Fig. 2

ein Behandlungsbad für das in Fig.1 dargestellte Verfahren,

Fig. 3

eine Draufsicht auf eine Übergabestation für das in Fig. 2 dargestellte Behandlungsbad,

Fig. 4

eine alternative Ausgestaltung einer Übergabestation für das in Fig. 2 dargestellte Behandlungsbad.

In the following the invention will be explained with reference to a drawing showing only one embodiment. It show schematically

Fig. 1

a plant scheme for a method for anodizing surfaces on metallic hollow bodies,

Fig. 2

a treatment bath for the in Fig.1 illustrated method,

Fig. 3

a plan view of a transfer station for in Fig. 2 illustrated treatment bath,

Fig. 4

an alternative embodiment of a transfer station for in Fig. 2 illustrated treatment bath.

This in Fig. 1 The system diagram presented shows the process steps of a process for anodizing surfaces on metallic hollow bodies of aluminum or aluminum alloys. Hollow-body-shaped workpieces are fixed in a clamping manner on projecting fingers of electrically conductive workpiece carriers 1 and the workpiece carriers 1 are moved in a predetermined working cycle gradually passed through a series of treatment baths. The treatment baths comprise in particular an acid bath 2, a bath 3 for neutralizing the workpieces, an eloxal bath 4, a bath 5 for dyeing and a bath 6 for sealing the treated workpiece surface. Between the mentioned treatment baths 2 to 6, the workpieces are rinsed, whereby the rinses in the dipping process in treatment baths 7 can be carried out.

One of the treatment baths, for example the anodizing bath 4, is in Fig. 2 shown schematically. The workpiece carriers 1 are lowered in a transfer station 8 of the treatment bath with a horizontal orientation in the treatment bath and are supplied within the process liquid 9 of the treatment bath in this horizontal orientation in one or more predetermined by the power stroke steps of a removal station 10 of the treatment bath. In a subsequent working cycle, the workpiece carrier 1 'positioned in the removal station 10 is raised and turned by 180 ° so that the liquid drips out of the hollow body-shaped workpieces 11 into the treatment bath. The representation in Fig. 2 It can also be seen that a plurality of moving in a row workpiece carriers 1, 1 ', 1 "are simultaneously passed through the treatment bath, wherein a workpiece carrier 1 is lowered in the transfer station 8 of the treatment bath in the treatment bath, at the same time a workpiece carrier 1' in the removal station 10 is removed from the treatment bath and at least one further workpiece carrier 1 "is moved through the treatment bath.

The workpiece carriers 1 are turned in the transfer station 8 of the treatment bath by a rotational movement and thereby from a first position I above the bath liquid of the treatment bath in a second position II lowered within the bath fluid. In the second position II, the projecting fingers 12 of the workpiece carrier 1 are aligned vertically downwards, so that the fingers 11 clamped fixed to the hollow body 11 are open at its upper end and the process liquid can flow into the interior of the hollow body 11 without being affected by gas bubbles , Outside the treatment bath, the projecting fingers 12 of the workpiece carrier 1 are oriented upward, so that the hollow bodies 11 are fixed over the head to the fingers and any liquid from the interior of the hollow body 11 can drain freely.

The removal station 10 of the treatment bath has a structurally identical turning device 13. By a rotational movement of the turning device 13, the workpiece carrier 1 'is both raised to a level above the liquid level of the treatment bath and simultaneously turned by 180 °.

The inventive method is characterized by a low carryover of the process liquid from treatment bath to treatment bath. Furthermore, the dwell time of the workpiece 11 fixed to a workpiece carrier is uniform within the process fluid. This results in a very uniform treatment result.

The treatment baths for the in Fig. 1 System diagrams shown preferably have the structure described and differ only by their length. The required immersion times in the process liquids are achieved by the working cycle and the length of the treatment bath.

In the anodizing 4 takes place by a closed circuit between the workpiece carrier 1 "and arranged in the treatment bath cathode fourteenth Anodic oxidation on the surfaces of the hollow body 11. In this case, the metallic surfaces of the existing aluminum or an aluminum alloy workpieces 11 are converted into aluminum oxide. The workpiece carriers 1, 1 '. 1 "are preferably made of titanium and are not attacked by the anodic oxidation Within the anodizing bath 4, the workpiece carriers 1, 1 ', 1" rest on a rail 15 and are moved by translatory movements of a slide 16. The anode of the Eloxalbad 4 associated circuit is connected to the rail 15, which bridges the distance between the transfer station 8 and the removal station 10. The contact point between the anode and the rail 15 is within the bath liquid. The cathode 14 is disposed below the rail 15 electrically connected to the anode, preferably at the bottom of the treatment bath.

From a comparative analysis of the Fig. 2 and 3 shows that the workpiece carriers 1, 1 ', 1 "a flat base frame 17 and attached to the base frame 17 strips 18 having a plurality of paired elastically deformable fingers 12 for fixing the hollow body 11. The base frame 17 of the workpiece carrier 1 is at opposite sides in C-shaped rail members 20 and also held by C-shaped rail members 20 in overhead movements in the transfer station 8 and the removal station 10. The rail members 20 are made of metal wires and do not form cavities for the process liquid.

The Fig. 4 shows a variant of the transfer station. In the in Fig. 4 Transfer station shown 8 ', the workpiece carriers are turned with a rotational movement and after turning from a position above the treatment bath by means of a vertical movement in the bath liquid lowered. The movement is composed of a rotational movement through 180 ° and a translatory movement a. In the Fig. 4 illustrated transfer station 8 'has the advantage that all fixed to the workpiece carrier hollow body 11 at the same time reach the process liquid by a translational lowering movement. In the Fig. 4 illustrated transfer station 8 'is preferably used for treatment baths in which all fixed to a workpiece carrier 1 workpieces 11 while maintaining close tolerances require the same residence time. In the Fig. 4 Transfer station shown is therefore used in particular for dye baths in which the previously anodized workpieces 11 are dyed in the dipping process. The dwell time in the dye bath is short and must be set exactly to produce consistent color intensities.

Claims (8)

Method for anodizing surfaces on metallic hollow bodies, in which the hollow bodies (11) are clamped on projecting fingers (19, 19 ') of electrically conductive workpiece carriers (1, 1', 1 ") and the workpiece carriers (1, 1 ', 1 ") are guided in a predetermined power stroke stepwise through a series of treatment baths, wherein the treatment baths comprise at least one Eloxalbad (4), in which by a closed circuit between the workpiece carrier (1") and arranged in the treatment bath cathode (14) anodic oxidation takes place on the surfaces of the hollow body (11), characterized in that the workpiece carriers (1) are lowered in a transfer station (8, 8 ') of the treatment baths with a horizontal orientation into the treatment bath, that the workpiece carriers (1, 1', 1 ") within the treatment bath in this horizontal orientation in one or more predetermined by the power stroke steps of a removal station (10) of the treatment bath and raised in a subsequent cycle in the extraction station and turned by 180 °, so that liquid from the hollow bodies (11) drips into the treatment bath, and that the workpiece carrier (11) in the Eloxalbad (4) a metallic rail (15) are connected, which is connected to the anode of the circuit. A method according to claim 1, characterized in that a plurality of moving in a row workpiece carriers (1, 1 ', 1 ") are simultaneously passed through a treatment bath, wherein a workpiece carrier (1) in the transfer station (8) of the treatment bath in the treatment bath is lowered, at the same time a workpiece carrier (1 ') in the removal station (10) is removed from the treatment bath and at least one further workpiece carrier (1 ") is moved through the treatment bath. A method according to claim 1 or 2, characterized in that the workpiece carrier (1) in the transfer station (8) at least one treatment bath turned by a rotational movement and thereby lowered from a first position I above the bath liquid of the treatment bath in a second position II within the bath liquid become. Method according to one of claims 1 to 3, characterized in that the workpiece carrier (1) in the transfer station (8 ') at least one treatment bath by a rotational movement (a) and turned after turning from a position above the treatment bath by means of a vertical movement ( b) are lowered into the bath liquid. Method according to one of claims 1 to 4, characterized in that the workpiece carriers (11) rest within the treatment baths on a rail (15) and are moved by translational movements of a slide (16). A method according to claim 5, characterized in that the anode of the Eloxalbad (4) associated circuit to a metallic rail (15) is connected, which bridges a distance between the transfer station (8, 8 ') and the removal station (10) the contact point between the anode and the rail (15) is within the bath liquid. A method according to claim 6, characterized in that the cathode (14) in the anodizing bath (4) below the electrically connected to the anode rail (15), preferably on the bottom of the treatment bath, is arranged. Method according to one of claims 1 to 7, characterized in that workpiece carriers (1, 1 ', 1 ") are used, a base frame (17) and on the base frame (17) fixed strips (18) having a plurality of elastically deformable fingers (12) arranged in pairs for fixing the hollow body (11), wherein the base frame (17) of the workpiece carrier on opposite sides in C-shaped rail elements (20 ) guided.

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