Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
METHOD AND MACHINE FOR PAINTING METAL LIDS
Document Type and Number:
WIPO Patent Application WO/2002/072284
Kind Code:
A2
Abstract:
A method and machine for painting metal lids (2), whereby each lid (2) is both spray painted and electropainted, and is stabilized after both the spray painting step and the electropainting step.

Inventors:
Baldassari, Gianfranco (Via Bellini, 4 Frazione Monticelli Terme, Montechiarugolo, I-43023, IT)
Application Number:
PCT/IT2002/000148
Publication Date:
September 19, 2002
Filing Date:
March 11, 2002
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
CORIMA INTERNATIONAL MACHINERY S.R.L. (Via Zucchini, 43/45, Ferrara, I-44100, IT)
Baldassari, Gianfranco (Via Bellini, 4 Frazione Monticelli Terme, Montechiarugolo, I-43023, IT)
International Classes:
B05B13/02; B05D7/00; C25D13/22; B05D1/00; B05D1/18; (IPC1-7): B05D7/00
Attorney, Agent or Firm:
Jorio, Paolo c/o Studio Torta S.r.l. (Via Viotti 9, Torino, I-10121, IT)
Download PDF:
Claims:
CLAIMS
1. 1) A method of painting metal lids (2), characterized by comprising a first painting step in which said lids (2) are spray painted; a first drying step to stabilize the spraypainted lids (2) ; and a second painting step in which said lids (2) are electropainted.
2. A method as claimed in Claim 1, and also comprising a second drying step to stabilize the electropainted lids (2).
3. A method as claimed in Claim 2, wherein said first painting step, said first drying step, said second painting step, and said second drying step are performed successively in that order.
4. A method as claimed in any one of the foregoing Claims, wherein each said lid (2) is a substantially flat lid (2) defined axially by two opposite faces (3a); at least said second painting step being performed in the course of a feed step in which each said lid (2) is fed in a feed direction (11) and along a path (P) which are substantially perpendicular to said faces (3a).
5. A method as claimed in Claim 4, wherein, in the course of said feed step, each said lid (2) is retained by two portions on opposite sides of said path (P).
6. A method as claimed in Claim 4 or 5, wherein, in the course of said second painting step, each said lid (2) comes into contact with a relative electrode (43a) shaped to engage the lid (2) at both said faces (3a).
7. A machine for painting metal lids (2), comprising conveying means (8,9,10) for feeding said lids (2) successively along a given path (P); and characterized by also comprising first painting means (25) for spray painting said lids (2); first drying means (35) for stabilizing the lids (2) painted by said first painting means (25); and second painting means (40) for electropainting said lids (2).
8. A machine as claimed in Claim 7, and also comprising second drying means (58) for stabilizing the lids (2) painted by said second painting means (40).
9. A machine as claimed in Claim 8, wherein said first painting means (25), said first drying means (35), said second painting means (40), and said second drying means (58) are arranged successively and in that order along said path (P).
10. A machine as claimed in any one of Claims 7 to 9, wherein each said lid (2) is a substantially flat lid (2) defined axially by two opposite faces (3a); said conveying means (8,9,10) comprising first conveying means (9) for feeding each said lid (2), in a feed direction (11) substantially perpendicular to said faces (3a), through at least one painting station (39) at which said second painting means (40) are located.
11. A machine as claimed in Claim 10, wherein said first conveying means (9) have supporting means (31) for retaining each said lid (2) by at least two portions on opposite sides of said path (P).
12. A machine as claimed in Claim 10 or 11, wherein said second painting means (40) comprise an electrophoretic bath (42); a first electrode immersed in said electrophoretic bath (42); and, for each said lid (2), a second electrode (43a) opposite in polarity to said first electrode, and which is brought into contact with the relative lid (2) at said painting station (39).
13. A machine as claimed in Claim 12, wherein said second electrode (43a) is formed so as to engage, in use, the relative said lid (2) at both the relative said faces (3a).
14. A machine as claimed in Claim 12 or 13, wherein said second electrode (43a) is defined by two adjacent turns of a coil spring (43).
15. A machine as claimed in Claim 14, wherein said first conveying means (9) comprise two parallel endless conveyors (27) facing each other and looped about pairs of pulleys (28), the pulleys (28) in each said pair of pulleys (28) being coaxial with each other; and said coil spring (43) being annular and being movable to and from a work position in which the coil spring (43) is coaxial with the pulleys (28a) in a first of said pairs of pulleys (28).
16. A machine as claimed in Claim 15, wherein each pulley (28a) in said first pair of pulleys (28) has a first diameter; and wherein each lid (2) has a second diameter; said coil spring (43) having a third diameter substantially equal to the difference between said first and said second diameter.
Description:
METHOD AND MACHINE FOR PAINTING METAL LIDS TECHNICAL FIELD The present invention relates to a method of painting metal lids, in particular pull-off can lids of the type normally used, for example, in the food industry.

BACKGROUND ART Lids of the above type are normally produced by combined blanking/drawing of flat painted metal sheets, so that each lid is substantially circular and comprises a central portion, and an outer annular edge which is normally folded substantially into a U to hook the lid on to the can.

The central portion and the outer annular edge are connected to each other by a grooved pull-off line, and the lid is provided with a pull-off tab fixed to the central portion by a riveted joint and which, when pulled, detaches the central portion relatively easily from the outer annular edge.

In connection with the above, it should be pointed out that, when forming the grooved pull-off line and the

riveted joint, the original paint on the metal sheets is normally fractured and/or cracked, so that the exposed parts of the lid with no paint must be repainted to prevent corrosion caused, for example, by atmospheric agents.

After blanking/drawing, lids are normally repainted using one of two methods: spray painting and electropainting.

Spray painting has several drawbacks, foremost of which is that it fails to provide for fully and effectively repainting the exposed parts of the lid that are hard to reach, i. e. the U-folded outer annular edge, the riveted joint, and certain portions of the pull-off tab.

While ensuring all the exposed parts of the lid are repainted, electropainting is relatively ineffective in the event the surfaces of the lid are not thoroughly clean.

Moreover, since, after blanking/drawing, the layer of paint on the more severely drawn areas of the lid may undergo cracking which does not reach the base metal of the lid, electropainting also has the further drawback of failing to repaint the areas corresponding to such cracks, so that, when drying and/or sterilizing to stabilize the lid, the cracks may widen to the extent of forming respective exposed areas.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide

a method of painting metal lids, designed to eliminate the aforementioned drawbacks.

According to the present invention, there is provided a method of painting metal lids, characterized by comprising a first painting step in which said lids are spray painted; a first drying step to stabilize the spray-painted lids; and a second painting step in which said lids are electropainted.

The present invention also relates to a machine for painting metal lids.

According to the present invention, there is provided a machine for painting metal lids, comprising conveying means for feeding said lids successively along a given path; and characterized by also comprising first painting means for spray painting said lids; first drying means for stabilizing the lids painted by said first painting means; and second painting means for electropainting said lids.

BRIEF DESCRIPTION OF THE DRAWINGS A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a schematic side view, with parts removed for clarity, of a preferred embodiment of the machine for painting metal lids according to the present invention; Figure 2 shows a schematic view in perspective, with parts removed for clarity, of a first detail of the

Figure 1 machine; Figure 3 shows a first schematic side view, with parts removed for clarity, of a second detail in Figure 1; Figure 4 shows a larger-scale second schematic side view, with parts removed for clarity, of the Figure 3 detail; Figure 5 shows a first plan view of a metal lid painted on the machine according to the present invention; Figure 6 shows a second plan view of the Figure 5 lid.

BEST MODE FOR CARRYING OUT THE INVENTION Number 1 in Figure 1 indicates as a whole a machine for painting metal lids 2 (Figures 5 and 6), each of which is substantially circular, and comprises a substantially flat central portion 3 defined axially by two parallel faces 3a, and an outer annular edge 4 which extends about portion 3, is connected to portion 3 by a grooved pull-off line 5, and has a substantially U-shaped fold 4a by which to hook lid 2 on to a respective can (not shown).

Each lid 2 also comprises a pull-off tab 6 by which to open the can (not shown) easily, and which is fixed to portion 3 by a riveted joint 7.

Machine 1 comprises three conveyor devices 8,9 and 10 arranged in series to feed lids 2 along a given path P and in a given direction 11 ; and two transfer stations

12, 13 connecting device 9 to device 8 and device 10 respectively.

Device 8 extends along an initial portion P1 of path P and between an input station 14, where device 8 receives lids 2 successively from a known hopper 15, and station 12. More specifically, device 8 comprises three chain conveyors 16,17 and 18 arranged in series along portion Pl, and of which conveyors 16 and 18 extend beneath portion P1, and conveyor 17 above portion P1.

Conveyors 16,17 and 18 move in the same substantially vertical plane, and are looped about respective pulleys 19 fitted to a fixed frame 20 (Figures 2 and 4) of machine 1 and rotated continuously, with respect to frame 20 and by a known actuating device (not shown), about respective horizontal axes 21 crosswise to path P. Each conveyor 16,17,18 comprises a number of push members 22 equally spaced along relative conveyor 16,17,18 and defining a succession of pockets 23, each of a length at least equal to the diameter of a lid 2.

Conveyors 16,17 and 18 are operated to feed each pocket 23 on conveyor 17 forward in time with a corresponding pocket 23 on each of conveyors 16 and 18, and so feed lids 2 successively along portion P1 and along two supporting rails 24 (Figure 2), which extend between stations 14 and 12, are parallel to each other and to portion P1, are mounted on opposite sides of conveyors 16,17 and 18, and are separated by a distance approximately equal to but no larger than the diameter of

a lid 2, so that rails 24 support each lid 2 by respective edge 4.

Machine 1 also comprises a painting device 25 located along portion PI and in turn comprising two known spray nozzles 26, one mounted beneath rails 24, at conveyor 17, to paint the downward-facing faces 3a, and the other mounted over rails 24, at conveyor 18, to paint the upward-facing faces 3a.

With reference to Figures 1 and 2, device 9 comprises two chain conveyors 27, which move in respective vertical, substantially parallel planes, are positioned facing each other, and feed lids 2 successively along an intermediate portion P2 of path P extending between stations 12 and 13. Each conveyor 27 is looped about a number of pulleys 28 fitted to frame 20, each coaxial with a corresponding pulley 28 of the other conveyor 27, and rotated continuously, with respect to frame 20 and by an actuating device 29 described in detail later on, about respective axes 30 substantially parallel to axes 21.

Each conveyor 27 also comprises a number of supporting members 31 attached in known manner to conveyor 27, and each having two longitudinal grooves 32 extending crosswise to direction 11. Each groove 32 faces a corresponding groove 32 on the other conveyor 27, and is separated from the corresponding groove 32 by a distance substantially equal to the diameter of a lid 2, so as to define a pocket 33 for receiving and retaining a

respective lid 2, and which is advanced in time with a relative pocket 23 on conveyor 18.

At transfer station 12, conveyor 18 extends between the two conveyors 27 to enable each push member 22 to feed respective lid 2 into a respective pocket 33.

In connection with the above, it should be pointed out that portion P2 comprises nonvertical portions where the two conveyors 27 cooperate with fixed guides 34 for supporting lids 2 underneath.

Machine 1 also comprises a drying device 35 located along portion P2, downstream from station 12 in direction 11, and in turn comprising a number of (in the example shown, four) known infrared-ray plates 36 located successively along portion P2 to stabilize the paint applied to lids 2 by device 25; and a cooling device 37 defined by a known cold-air diffuser 38 downstream from device 35 in direction 11.

At the output of device 37, lids 2 are fed successively through a painting station 39 where they are electropainted by a painting device 40. As shown in Figures 1 and 3, device 40 comprises a tank 41 located beneath two pulleys 28 (hereinafter indicated 28a) and containing an electrophoretic bath 42 defined by a water and paint solution in which a known electrode (not shown) - in the example shown, a cathode-is immersed.

At the input of tank 41, each lid 2 comes into contact with a relative electrode 43a-in the example shown, an anode-defined by two adjacent turns of a coil

spring 43 polarized electrically and looped about a pulley 44 (Figure 4), which has a diameter substantially equal to the difference between the diameter of a pulley 28a and the diameter of a lid 2, is fitted to a plate 45, and is rotated, with respect to plate 45 and by actuating device 29, about an axis substantially parallel to axes 30.

Plate 45 defines a slide fitted to run along two parallel guides 46 fitted to frame 20, and which is movable, manually or by means of a known actuating device (not shown), between a work position (Figures 1,3 and 4) in which pulley 44 extends between and coaxial with the two pulleys 28a, and a rest position (not shown) for servicing or changing spring 43.

In connection with the above, it should be pointed out that the level of bath 42 in tank 41 is controlled selectively so that, when in the work position, spring 43 is always located outside bath 42.

Device 29 comprises a known powered transmission 47 - in the example shown, a chain transmission-having a central motor 48, the output shaft 49 of which is connected to an intermediate pulley 50 by a chain 51.

Pulley 50 is in turn connected to pulleys 28a by two chains 52, and to pulley 44 by a chain 53 looped about a further pulley 54 fitted in rotary manner to plate 45.

At the output of painting station 39, lids 2 are released from respective electrodes 43a and fed to transfer station 13, where they are picked up

successively by conveying device 10.

Device 10 comprises a chain conveyor 55 looped about a number of pulleys (not shown)-one of which is powered continuously-with respective axes (not shown) substantially parallel to axes 30.

Conveyor 55 comprises a number of push members 56 equally spaced along conveyor 55 and defining a succession of pockets 57, each of which is of a length at least equal to the diameter of a lid 2, and is advanced in time with a pocket 33 of device 9 to receive the lid 2 housed inside pocket 33.

At station 13, conveyor 55 extends between the two conveyors 27 to enable each push member 56 to push the relative lid 2 out of relative pocket 33 and into relative pocket 57. Finally, lids 2 are fed through a known drying device 58 for stabilizing the paint applied to lids 2 at station 39.

Operation of machine 1 is easily deducible from the foregoing description with no further explanation required.

Machine 1 has several advantages, foremost of which is that, by combining the spray painting and electropainting processes, and by interposing drying device 35 between the two painting devices 25 and 40 to completely fracture any cracks in the paint coat on lids 2 before lids 2 are fed through device 40, machine 1 provides for completely and effectively repainting lids 2.

Moreover, since each electrode 43a engages respective lid 2 at at least two points on lid 2, and, given the flexible structure of spring 43, the points of contact may vary at each operating cycle of each electrode 43a, machine 1 has the further advantage of operation of electrodes 43a being relatively unaffected by electrical corrosion phenomena.