Classifications

• • 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

• This invention relates in particular to the coating of tinplate lids for containers such as cans, and more generally to a machine for coating thin metal objects by an electrophoretic process.
• tinplate lids are obtained by usual punching/drawing operations starting with a flat thin metal sheet.
• the lids are sometimes subjected to a conversion operation after their formation.
• This conversion involves the formation of a preferential fracture line, plus possibly a small hole for fixing (by riveting) a tearing tab, such converted lids commonly being known as "easy opening type”.
• Said machine comprises a process tank containing an electrophoretic bath, and within which there is arranged at least one conveyor line on which the lids are placed flat with their turned edge facing upwards, and completely immersed in the bath.
• an anode positioned parallel to said at least one conveyor line to preferably traverse at the same speed as this latter while resting on each individual lid for the entire period during which they traverse the process tank.
• Said conveyor line comprises in particular an endlessly extending horizontal conveyor such as a toothed belt or chain, comprising a plurality of equidistant projecting elements which urge the lids along two opposing longitudinal guides at an adjustable distance apart.
• a part of the electrophoretic bath discharges continuously via these latter into an underlying collection tank, from which it is again returned to the process tank.
• the positive electrode or anode consists according to the invention of a rectilinear length of wire or metal tape able to follow an endless path, its outward portion resting on an edge portion of the conveyed lids in such a manner as to define two points (in the case of wire) or lines (in the case of tape) of electrical contact with the cut periphery of the turned edge of the lid.
• the wire forming the positive electrode or anode becomes covered with a large quantity of coating, which is practically impossible to remove and soils the entire wire guide means in a manner which cannot be remedied.
• the object of the present invention is to obviate the aforesaid drawback.
• anode consisting of an endless metal chain located entirely outside the bath and provided with vertical perpendicular appendices which along the lower part of the chain path touch the lids immersed in the bath.
• Figures 1A and IB are two sectional elevations showing the upstream and downstream parts of the machine respectively.
• Figure 2 shows part of the section on the line II-II of Figure 1A, to an enlarged scale.
• Figure 3 is a section on the line III-III of Figure IB, to an enlarged scale.
• Figure 4 is an enlarged view of the part shown within the circle indicated by IV in Figure 2.
• FIGS. 1A, IB and 3 show a casing 1 divided into various service compartments by suitable walls, and comprising a process chamber indicated by 2.
• a tank 3 for containing the electrophoretic bath 4 the tank being positioned between an overlying tank 5 for containing a cleaning liquid 6 ( Figure 3), and an underlying tank 7 for collecting and recirculating the electrophoreti liquid falling from above.
• said electrophoretic liquid 4 consists of a solution, suspension or dispersion usually comprising from 1 to 5% of varnish or other suitable material, and from 99 to 95% of deionized water.
• the tank 3 receives the outwardly travelling branches of two conveyors 44 provided for advancing the lids 8.
• a chain 50 is provided in the form of a vertical endless loop such that its rectilinear outwardly travelling branch lies above the liquid surface of the bath contained in the tank 3, and its return branch is immersed in the bath of the tank 5 ( Figures 1A, IB, 3).
• Perpendicular appendices 55 extend outwards from the chain 50 to form the electrodes to make contact with the lids to be coated.
• the conveyors 44 a d electrodes 55 can be provided in any number.
• the electrode 55 will also be known hereinafter as the anode (or positive pole of the bath 4), but this does not exclude the possibility of the electrode 55 acting as the cathode (or negative pole of the bath) if certain types of objects and/or varnishes or lacquers are present.
• the conveyor 44 consists of a toothed band (or toothed belt or chain) extending as a horizontal loop about two opposing pulleys 9 and 10.
• the pulleys 9, 10 and ring gears 91, 101 are suitably electrically insulated.
• said three conveyors 44, 66 and 77 are provided with respective projecting elements or pushers 40, 60 and 70 respectively, these being provided for advancing the lids 8 and being distributed at a constant pitch.
• This distribution pitch is particularly large, enabling said conveyors to handle lids 8 of considerably different diameters or side dimensions.
• the arriving conveyors 66 are connected to a convenient feed device, such as a conversion press followed by a pretreatment module, the departing conveyors 77 being connected to a convenient collecting and/or treatment device, such as a wash chamber followed by an oven for curing the coating.
• a convenient feed device such as a conversion press followed by a pretreatment module
• the departing conveyors 77 being connected to a convenient collecting and/or treatment device, such as a wash chamber followed by an oven for curing the coating.
• a convenient collecting and/or treatment device such as a wash chamber followed by an oven for curing the coating.
• Said conveyors 66, 44 and 77 are driven at the same speed by a geared motor unit 11 (see Figures IB, 3) with an incorporated variable speed gear, the drive being via a toothed belt 12 which rotates the shaft 100.
• the shaft 120 ( Figure 3) which drives said toothed belt 12 drives a further toothed belt 13 which moves the chain 50 at the same speed as the conveyors 66,
• the lids 8 traverse while resting in a flat position with their turned edge 88 having its concavity facing upwards (Figure 4), the liquid surface of the bath 4 in the tank 3 being maintained above the upper (inner) face of the lids 8.
• the outward and return branches of the conveyor 44 are rectilinear, the former entering and leaving the tank 3 through corresponding weired apertures 14 (see Figure 2) provided in the end walls 140 of said tank 3.
• the liquid 4 continuously discharges from said apertures and is collected in the underlying tank 7, from which it is again fed to the tank 3 by a pumping unit (not shown) which is arranged to maintain a level of liquid 4 within the tank 3 such as to ensure that the lids 8 and the ends of the appendices 55 forming the anode are completely immersed.
• Suitable guide walls 15 direct towards the tank 7 the liquid 4 leaving the apertures 14, the liquid falling from the return branch of the conveyor 44 and the liquid removed from the recoated lids 8 by air nozzles 19 shown in Figure IB. It should be noted that the continuous recirc ⁇ lation and remixing of the liquid 4 eliminate any inconvenient dilution of the coating particles in the lid transit region.
• said apertures 14 are conveniently shaped both to allow passage of the elements described hereinafter and to limit the discharge of liquid 4.
• Said elements comprise for each individual conveyor 44 a longitudinal metal plate 16 for the support and sliding of the conveyor outward branch and two opposing lateral longitudinal metal guides 17.
• Said plate 16 and guides 17 are suitably electrically insulated from the surrounding metal machine components and are preferably constructed of stainless steel or surface treated/hardened steel.
• the two guides 17 associated with each conveyor 44 comprise two longitudinal grooves 18 with their openings facing each other, to receive the corresponding opposing portions of the turned edge 88 of the lid 8.
• Said two grooves 18 provide two lower narrow horizontal support surfaces which maintain the lids 8 raised from the conveyor 44, two opposing vertical surfaces to prevent derailing of the lids 8 pushed by the pushers 40, and two upper horizontal surfaces to prevent untimely rocking of the lids 8 in those vertical planes transverse or parallel to their direction of advancement.
• said two groups of anodes 55 are in the form of perpendicular appendices of a chain 50 of stainless steel or another suitable hard good conducting material, however a narrow steel tape could also be used.
• Each chain 50 passes about sprockets 20, not electrically insulated, and slides in a suitable guide 80 of insulating material which in the lower branch ensures that the appendices or anodes 55 make electrical contact with the upper surface of the lids 8.
• Figure 4 shows the coating film 110 which forms on the anode 55 as it traverses the bath 4, and which is subsequently removed as stated hereinafter.
• Figure 3 in a position opposite said wheels 80 there is fixed to the corresponding guide 17 a flat band 116 extending for the total length and projecting towards the underlying lids 8 in transit, to form together with the plate 16 the negative electrode or cathode of the bath 4.
• Said cathode 16, 116 is suitably connected to an electrical power supply, indicated by 21 in Figure IB, which applies to the bath a d.c. voltage adjustable for example from 100 to 500 volts depending on the specific parameters governing the electrophoretic process underway.
• the same power supply 21 is also connected to one of the pairs of sprockets 20 by suitable contactors 22, indicated schematically in the upper part of Figure 3 and consisting for example of graphite brushes, slide shoes or the like.
• the chain 50 which is not immersed in the bath, is always clean, whereas the ends of the electrodes 55 are cleaned by immersion in the overlying bath 6 during the return travel of the chain.
• Two vessels 25 and 26 are provided for the cleaning liquid 6 and the concentrated coating material respectively, there being also provided, although not shown, suitable apparatus for measuring the bath temperature, conductivity and pH, for temperature control of this latter and of the cleaning liquid tank 5, for adjusting the power supply 21, etc.
• indicator lamps 28 are provided, plus a transparent panel 27 ( Figure 3) for visually monitoring the essential components contained in the chamber 2.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Coating Apparatus (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=11398391

Family Applications (1)

Country Status (4)

Families Citing this family (6)

Family Cites Families (3)

• 1993
  • 1993-04-30 IT ITRE930041A patent/IT1262316B/it active IP Right Grant
• 1994
  • 1994-03-28 EP EP94914548A patent/EP0700453A1/de not_active Withdrawn
  • 1994-03-28 AU AU66883/94A patent/AU6688394A/en not_active Abandoned
  • 1994-03-28 WO PCT/IT1994/000036 patent/WO1994025645A1/en not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events