Title of Invention

APPARATUS FOR SURFACE TREATMENT BY IMMERSION AND METHOD FOR THE SAME

Abstract

An apparatus for surface treatment by immersion and method for the same, in particular for electrochemical coating followed by electrophoretic coating, the material to be treated is moved through coating vessels in one or more planes. This is carried out using stepped cage conveyors(14) which are provided, at different heights, with bearing arms(19) for trays(20) on which the material to be treated is located. Horizontal electrodes(10), past which the trays are moved, project between the bearing arms of each plane or into the space between each tray.

Full Text

1A The invention relates to an apparatus and a method for surface treatment, wherein the items to be treated are passed through a bath where they are chemically, galvanically and/or electrophoretically treated. Methods and apparatus of this kind serve to provide objects which consist at least in part of a conductive material with a surface of which the technical or optical properties are adapted to the particular application. This can be done by chemical or electrochemical treatment of the surface, for example chromium plating of the surface of a metallic workpiece or by electrolytic or electrophoretic application of a coating. The known wet processes are very expensive and, since the items to be treated must be passed through a series of containers with a very wide variety of different treatment liquids, for example cleansing agents, electrolytes and electrophoretic enamels. This is done discontinuously by dipping individual objects or batches of small parts, or in continuous plant with the use of conveyors which move the items to be treated either individually or, in the case of small parts, one after another in rows, successively along a treatment line from one dipping bath to the next. A suitable means of doing this is, for example, a conveyor which holds the items to be treated. Such an apparatus is known,from German specification 41 42 997. Since the processes used both for chemical surface treatment and for electrolytic and electrophoretic coating are time-dependent, a predetermined dwell time of the items being treated in the individual dipping baths is required, this time depending on the particular treating agent and items being treated. This dwell time, which can differ widely in individual cases, determines at any given conveyor speed or rate of passage the length of the treatment path and accordingly the dimensions of the individual dipping baths in the direction of transport. 2 Since large items to be treated have to be passed through the individual baths individually, and small parts, with a view to surface uniformity, can only be passed though in layers of limited depth, conventional plants are extremely complicated and expensive and have a relatively low throughput. A particular problem is to obtain a uniform surface treatment in all parts, for example galvanising over the whole surface and/or defect-free enamelling. Such defects occur particularly at the points of contact between the items being treated and the conveying means used to transport the items being treated through the individual baths. Means of transportation which come into consideration, particularly for small parts or loose items, are drums or in some cases conveyor belts, and for larger parts special transportation racks which are shaped according to the configuration of the items to be treated and are therefore expensive. Medium-sized and large parts can also be moved through the individual dipping tanks by means of a conveyor belt, but in this case the parts must be arranged to lie one behind the other on the conveyor in order to make their surfaces as accessible as possible to the treating agent. Such an arrangement in one plane is however associated with the disadvantage that the throughput is considerably reduced compared with transportation on racks with parts arranged one above the other within particular boundaries. The object of the invention is to improve the economics of the known processes and apparatus without impairing the surface quality of the items being treated. The approach we adopt to achieving this object is to multiply the throughput at a given speed of transportation in the individual dipping baths by passing the items to be treated through the individual dipping baths in several planes one above another. This can be done by means of a movable multistage rack, between the stages of which, at the same spacing, treating elements such as stationary electrodes or nozzles for treatment liquids or drying air are arranged in several planes. 3 In this way the items to be treated are passed by the stationary treatment elements with optimum accessibility of their surfaces and the throughput is increased according to the number of the transportation planes or stages. In addition, with the process of the invention it becomes possible to act on the items to be treated both from above and from below, for example by spraying or by blowing drying air on to them. Furthermore, there is improved distribution of coating thickness, since the electrodes are arranged linearly to the items being treated. To obtain as uniform a surface as possible, without defects, the items to be treated can be rearranged in the bath or between two baths in order to expose points of contact,and make them accessible to the treating agent. The rearrangement can be performed by shaking, by means of magnets or by means of a rake of which the fingers intermesh like a comb between rods or blades of a carrier for the items to be treated, for example a tray. A particularly suitable apparatus for putting the process of the invention into practice is one in which the items to be treated are arranged lying or hanging in several floors or levels on the multistage rack of a conveyor which carries the items to be treated through at least one tank, for example a dipping tank. The items to be treated are preferably on a tray and can be placed in the multistage rack by a delivery conveyor, preferably a double-track conveyor. To enable the individual stages or levels of the rack to be filled, the multistage rack preferably comprises a vertically movable carriage having carrier arms arranged spaced apart from one another. This enables the carrier arms to be brought successively into the plane of the conveyor in order for example to lift and thus pick up a blade tray from the conveyor. The lifting carriage can for its part be carried in a horizontally movable rack carriage which moves the rack through the respective coating tanks. The fact that during the loading of the multistage rack the items to be treated enter the dipping bath successively, i.e. at intervals, into the immersion bath does not cause any disadvantage, and in particular does not result in any difference in residence time, if during this phase no current is being applied to the material to be treated. In this way, the material to be treated can be moved gently into the immersion bath, since it is moving vertically downward and, due to its weight, is held securely on its support. The invention is now described in details with referance to the accompanying drawings: The invention is explained in more detail below with reference to an exemplary embodiment which is illustrated in the drawing, in which: FIG.l shows a diagrammatically depicted plan view of a device according to the invention, FIG.2 shows a vertical longitudinal section through an immersion vessel from FIG.l, FIG.3 shows a cross-sectional view of FIG.2, FIG.4 shows a tray for transporting the material which is to be treated. FIG.5 shows a section on line IV-IV in FIG.3, FIG.6 shows a side view of a transfer station with a conveyor and a gripper, FIG.7 shows a plan view of the gripper from FIG.6, FIG.8 shows a side view of a transfer station, FIG.9 shows a tray which is connected as an electrode, FIG.10 shows an enlarged view of a tray contact point, 4 FIG.11 shows a boat with two trays, and FIG.12 shows a section on line XII-XII in FIG.11. The device essentially comprises an immersion vessel 1, an unloading station 2 with a removal conveyor 3 and a transverse conveyor 4, a return path 5, a further transverse conveyor 6 and a loading station 7 with a feed conveyor 8. The immersion vessel 1 is located in a trough 9 and is equipped with electrodes 10 which are arranged in stationary positions above one another in a plurality of planes. At each of its end sides, the immersion vessel leaves an area 11, 12 clear in order for the material which is to be treated to be introduced and removed. There may be a spray bath at each of these areas. Next to the immersion vessel 1 or trough 9 there is a rail 13 which extends in the longitudinal direction and on which a plurality of carriages 15, which are each provided with a drive 14 and are designed in the form of a claw in cross section, are guided. Vertically, displaceable lifting or stepped cages 16 are guided in the carriages 15. These cages essentially comprise a frame with two U-shaped rails 17 in which driven rollers 18 which are mounted on the carriage 15 engage. Horizontal bearing arms 19 for trays 20 are connected to the rails 17. The support for the trays 20 comprises individual bars or lamellae 21, for example with a sawtooth profile, as described in detail in German Laid-Open Specification 4428789. FIG.2 shows a simplified cross-sectional view, from the 5 left-hand side in FIG.l, through the first lifting or stepped cage 16, which has not yet been lowered, and the third lifting or stepped cage 16, which has been fully lowered, in the immersion vessel 1. In the immersion vessel 1 there is a rearrangement cage 22 with protruding fingers 23 which are arranged in the form of a comb and are arranged in the same distribution as the bars or lamellae 21 of the trays 20 in the stepped cage 16. These fingers enable the material which is to be treated and is resting on the bars or lamellae 21 of the trays 20 to be lifted and rearranged when the bars 21 of the trays 20, on the one hand, and the fingers 23 of the rearrangement cage 22, on the other hand, are arranged opposite to and offset from one another. When the lifting carriage 17 or the bearing arms 19 is/are lowered, the fingers, which are arranged in a stationary position, engage beneath the material which is to be treated and is located on the trays 20, so that the trays, with the aid of the stepped cage 16, can be displaced a small distance to the side without the material which is to be treated. When the lifting cage is then raised again, and in the process, the bearing arms 19 or the trays 20 move back into their previous positions, the material to be treated is again positioned on the trays, but with different points of contact with the sawtooth lamellae. During loading of the stepped cages 16, the trays 20 which have been supplied by the conveyor 8 are gradually placed onto 6 the bearing arms 19, while the stepped cage 16 moves upwards in a stepwise manner into the feed area. In the process, the bearing arms each move beneath a tray which is located on the conveyor and, during the next movement step, lift this tray off the conveyor, while the conveyor moves forward by the width of one pallet, moving the next tray into the transfer position. As soon as all the bearing arms 19 are covered by trays, the carriage 15 moves the stepped cage 16 to above the immersion vessel. After the stepped cage has been lowered, resulting in immersion, the carriage 15 moves the stepped cage 16 past the electrodes 10 into the transfer station, where the stepped cage resides for the time required to lift the material to be treated with the aid of the fingers 23 of the lifting cage 22. As soon as this has taken place, the carriage 15 moves the stepped cage 16 a small distance, which is shorter than the distance between two tray bars 21, after which the lifting cage 22 lowers the fingers 23 again and, in the process, the fingers deposit the material to be treated back onto the bars of the trays. The relative movement between the material to be treated which is resting on the fingers 23 and the pallet thus results in new points of contact, so that the previous points of contact become accessible to the immersion bath. After the transfer, the carriage 15 moves the stepped cage 16, in the lowered position, further past the electrodes 10 to the other end of the immersion vessel 1 or, after the cage has been moved upward, to above the removal area 12, where the stepped cage 16 moves downward, in a stepwise manner, over the 7 distance of the bearing arms 19, during which movement the trays 20 are deposited on the removal conveyor 3 while the bearing arms 19 are lowered into the conveyor 3. A removal gripper 24 moves the material which is to be treated onto trays for the next treatment stage, which may be a rinsing station, downstream of which there are, for example, a chromating stage and a station for electrophoretic coating with soluble or insoluble anodes. These stations differ from the stations illustrated in FIGS. 1 to 7 for electroplating essentially only in that a material for anodic or cathodic coating is located in the respective immersion vessel. However, the coating station may also comprise a device as described in German Laid-Open Specification 4428789, the disclosure of which is to be regarded as a part of this description. Since this device also operates with trays or pallets, the material to be treated only has to be transferred onto these trays or pallets, so that no labour is required at the transition from one method step to the next method step. A gripper 24 which is arranged between a horizontal tray conveyor 25 and the loading station of the next immersion vessel is used for transfer purpose. The gripper 24 has a drive (not shown) and can be moved on rails 26 between the conveyor 25 and the immersion vessel, in the longitudinal direction of the conveyor; it is provided with two driven spindles 27, on which bridges 28, which are positioned opposite one another, with bearing arms 29 are arranged. When the spindles 27 are rotated, 8 the bridges 28 move toward one another and engage beneath the material which is to be treated on the particular tray 20 which is located on a lifting table 30 which is arranged as an extension of the conveyor 25. When the lifting table is lowered, the bearing arms take the material to be treated off the tray 20. By means of lateral displacement of the longitudinal carriage 28, the material to be treated is moved over a tray 31 for the next treatment step, which tray is likewise located on a lifting table which is integrated into a conveyor. As the lifting table is raised, the tray 31 takes the material to be treated off the bearing arms 29 of the gripper 24. When the gripper is opened and the lifting table is then lowered, a tray moves onto the conveyor, from where it is transferred, in the manner described in connection with FIG.l, into a stepped cage of the next immersion vessel or into a suspension rail according to German Laid-Open Specification 44 28 789. The tray then takes over those bearing arms of the stepped cage (which is located on the feed side of the immersion vessel) which are positioned slightly below the plane of movement of the tray. When the stepped cage is moved a small distance upward, the bearing arms in question take the tray 20 off the conveyor which comes from the gripper. In order to be able to connect the trays 20 as electrodes, they are equipped with at least one contact chamber 32. The contact chambers 32 are open at the bottom and contain contact sleeves 33 which are also open at the bottom and in which contact pins 34 on the bearing arms 19 of the stepped cages 16 engage. The contact pins have a conical point 35 which creates a linear 9 contact with the inner edge of the contact sleeve. In this way, the tray 20 is connected as an electrode to the material which is to be treated and is resting on the tips of the lamellae 21. Since only small amounts of the solution of coating agent enter the contact chamber, there is no risk of the contact pins and the contact sleeves also being coated and of the electric contact being lost in this way. The material to be treated may also be guided through the immersion vessel with the aid of a suspension rail as described in German Laid-Open Specification 44 28 789. In this case, a boat 36 which is provided with centering pins 37 and holds two trays 38, 39 is used. These trays are one electroplating tray 38 and one enameling tray 39, which fit accurately inside one another. The electroplating tray 38 is insulated from the boat 36 and is therefore not at risk of being coated. Following enameling, the electroplating tray is pulled upward away from the centering pins 37 and the material 40 to be treated is transferred back onto the electroplating tray. The trays do not have to be equipped with sawtooth lamellae; other bearing elements which ensure that the contact area with the material to be treated is as small as possible are also suitable. Contact which is essentially punctiform is the most advantageous solution. The method according to the invention is extremely economical primarily because the outlay on labour is extremely low and the throughput is considerably higher than with a method 10 which operates with conventional conveyor devices for the material to be treated, with a single conveying plane. In addition, the surface quality is high due to the ease of access to the material to be treated for the treatment agent. The invention is suitable in particular for an electrochemical surface treatment, for example for the application of a layer of zinc, zinc/iron or zinc/nickel, which is subsequently chromated, if the chromating is followed by electrophoretic coating. In this way, it is possible to provide surfaces with a metal/enamel coating in an extremely economical manner. 11 We claim :- 1. An apparatus for surface treatment by immersion comprising: an immersion vessel(1); a horizontally displaceable carriage(15); a vertically displaceable cage(16) provided within the carriage, the cage comprising bearing arms(19) arranged at a vertical distance from one another; stationary treatment elements(10) that project between the bearing arms(19) of the vertically displaceable cage(16); and a conveyor(14); wherein the conveyor is arranged and configured to move the carriage and the vertically displaceable cage in a horizontal direction. 2. An apparatus for surface treatment by immersion as claimed in claim 1, such that the vertically displaceable cage(16) consists of a vertically displaceable lifting carriage(17) with the bearing arms(19) connected thereto. 3. An apparatus for surface treatment by immersion as claimed in claim 2, such that the horizontally displaceable carriage(15) guides the lifting carriage(17). 4. An apparatus for surface treatment by immersion as claimed in claim 1, such that the treatment elements(10) consists of electrodes, and wherein the bearing arms(19) are electrodes. 5. An apparatus for surface treatment by immersion as claimed in claim 1, such that the immersion vessel consists of protruding electrodes(10) that are arranged at a vertical distance from one 12 another. 6. An apparatus for surface treatment by immersion as claimed in claim 1, such that support for the material to be treated are in the form trays(20) with bars(21). 7. An apparatus for surface treatment by immersion as claimed in claim 6, such that the trays(20) are provided with contact chambers(32) that are open at the bottom. 3. An apparatus for surface treatment by immersion as claimed in claim 7, such that contact pins(34) engage in the contact chambers(32). 9. An apparatus for surface treatment by immersion as claimed in claim 8, such that the contact pins(34) are in contact with contact sleeves(33) that are in the contact chambers(32). 10. An apparatus for surface treatment by immersion as claimed in claim 6, such that a rearranging cage(22) with protruding fingers(23) is arranged in the immersion vessel, a distribution of and distance between which fingers corresponds to a distribution of and distance between the bars(21) of all the trays(20) which are arranged in the vertically displaceable cage(16). 11. A method for surface treatment by the apparatus as claimed in claim 1, characterized in that a material to be treated is arranged on a vertically displaceable cage(16), the cage being within a horizontally displaceable carraige(15), the cage comprising bearing arms(19) 13 arranged at a vertical distance from one another ; and moving the material horizontally and vertically through a treatment zone comprising fixed treatment elements(10) at a plurality of levels, the treatment elements projecting between the bearing arms of the vertically displaceable cage. 12. The method for surface treatment as claimed in claim 11, such that the material to be treated is moved through an electrolyte. 13. The method for surface treatment as claimed in claim 12, such that the material to be treated is coated electrophoretically after moving the said material through the electrolyte. 14. The method for surface treatment as claimed in claim 11, such that the material to be treated is rearranged during its passage through the treatment zone. 15. The method for surface treatment as claimed in claim 11, such that the material to be treated is rearranged between two passages through the treatment zone. ( B.G.RAY ) Of Datta & Associates Agent for the Applicant. Dated this 27th day of March 1998. 14

Documents:

00535-cal-1998 abstract.pdf

00535-cal-1998 claims.pdf

00535-cal-1998 correspondence.pdf

00535-cal-1998 description(complete).pdf

00535-cal-1998 drawings.pdf

00535-cal-1998 form-1.pdf

00535-cal-1998 form-2.pdf

00535-cal-1998 form-3.pdf

00535-cal-1998 form-5.pdf

00535-cal-1998 letters patent.pdf

535-cal-1998-granted-abstract.pdf

535-cal-1998-granted-acceptance publication.pdf

535-cal-1998-granted-claims.pdf

535-cal-1998-granted-correspondence.pdf

535-cal-1998-granted-description (complete).pdf

535-cal-1998-granted-drawings.pdf

535-cal-1998-granted-examination report.pdf

535-cal-1998-granted-form 1.pdf

535-cal-1998-granted-form 2.pdf

535-cal-1998-granted-form 3.pdf

535-cal-1998-granted-form 5.pdf

535-cal-1998-granted-form 62.pdf

535-cal-1998-granted-letter patent.pdf

535-cal-1998-granted-reply to examination report.pdf

535-cal-1998-granted-specification.pdf

535-cal-1998-granted-translated copy of priority document.pdf