System for spraying the inside of can bodies

Abstract

A system for spraying a coating such as lacquer on the internal surface of a can body (2) comprising vacuum chuck gears (42) for each vacuum chuck (16). The vacuum chucks hold the can body as it rotates about a main process turret (10) and to a spray station (32, 34). A ring gear rotates independently of main turret rotation and further gearing connects the ring gear to a vacuum chuck drive motor (11). The spray system provides tight process control and allows flexibility of process revolutions or use of higher machine production speed.

Claims

1. A system for spraying the inside of can bodies comprising: a spray station and a main rotary turret, the main rotary turret being connected to and driven by an indexing device, the indexing device being mounted to a main frame; one or more spray guns on a spray gun support frame; and vacuum chucks arranged circumferentially around the turret for holding can bodies; wherein each vacuum chuck has a vacuum chuck gear and each vacuum chuck gear is in constant mesh with a ring gear; the ring gear being rotatably mounted on a hub, the hub being a static machine element which is mounted to the main frame such that the hub is rotatably fixed relative to the main frame, the hub being positioned about a center of the main rotary turret, the main rotary turret being rotatable relative to the hub; and constant mesh gearing connects the ring gear to a vacuum chuck drive motor, such that each vacuum chuck is configured to be driven independently of the main rotary turret.

2. A system according to claim 1, in which the vacuum chuck drive motor is a variable speed control motor.

3. A system according to claim 1, in which the vacuum chuck drive motor is static mounted to the main frame.

4. A system according to claim 1, in which the vacuum chucks are arranged on a pitch circle diameter about the centre of the turret.

5. A system according to claim 1, further comprising one or more ring gear bearings arranged between the ring gear and the hub.

6. A system according to claim 1, in which the indexing device is a servo motor and gearbox.

7. A system according to claim 1, wherein the vacuum chuck drive motor is located on an opposite side of the main rotary turret with respect to the spray station.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic of a conventional prior art machine including a spray station;

(2) FIG. 2 is a section along X-X of FIG. 1;

(3) FIG. 3 is an enlarged view of the spray station of FIG. 2;

(4) FIG. 4 is a schematic of a spray machine of the present invention;

(5) FIG. 5 is a section along X-X of FIG. 4; and

(6) FIG. 6 is an enlarged view of the gear drive of FIG. 5.

DESCRIPTION OF EMBODIMENTS

(7) In FIGS. 4 to 6, parts which are like with those of FIGS. 1 to 3 have been given the same reference numerals. In this way it is immediately apparent that the spray machine of the present invention does not include such features as a chuck spinner drive motor and pulley, idler pulley or chuck spinner drive belt. Instead, in FIG. 4 only a motor gear 40 is shown. Further features of the present invention are described in the following paragraphs.

(8) The schematic of FIG. 4 shows that, like in the known machine, cans 2 are fed along infeed trackwork 4 to a main (process) turret 10. Cans are indexed to a spray station where a coating such as an internal lacquer is sprayed by a spray gun 32 mounted on a support frame 34. There is one spray gun per spray station with several spray stations mounted off the support frame. As in the known machine, cans are discharged via a discharge turret 36 and along trackwork 38.

(9) The novel use of motor gear 40 becomes more clear in the section along X-X and enlarged view of FIGS. 5 and 6 respectively. The main turret 10 is connected to and driven by main turret index box 12 and its index box drive motor 11 which are mounted on one side of the main frame 24 as in the prior art, with a hub 25 on the other side of the frame 24. Vacuum chucks 16 are mounted on the main turret and arranged about a pitch circle diameter PCD about the main turret centre.

(10) Of note in the present invention is not simply a chuck vacuum supply 41 which passes through the main frame 24, but more particularly a vacuum chuck gear (also referred to as a vacuum chuck drive gear) 42 one of which is supplied for each vacuum chuck 16. The vacuum chuck gears 42 are in constant mesh with a ring gear 44. To keep rolling friction low, rolling element bearings are used whatever material is used for the ring gear. A set of ring gear bearings 45 is arranged between the ring gear 44 and hub 25. The hub 25 is a static machine element which is mounted back to the main frame 24 and about the main turret centre 14. The hub provides additional static support on which to mount the ring gear bearing. The ring gear 44 is thus able to rotate independently of main turret rotation.

(11) Further constant mesh gearing 46 connects the ring gear 44 to a vacuum chuck drive motor 48. Both the main turret index box 12 and the vacuum chuck drive motor 48 are static mounted to the main frame 24. The vacuum chuck drive motor 48 is variable speed control because the system needs to respond to variations in line production speed and keep can wraps constant.

(12) Not only does the spray system of the present invention completely eliminate the prior art belt drive, but it also tightly controls vacuum chuck speed. In turn, the number of process revolutions during the spray process is tightly controlled, leading to flexibility to change the number of process revolutions for machine product range and exploitation of higher machine production speed. Further parameters relevant to internal can coating and therefore to the present invention include spray pressure, spray pattern, coating weight, spray media temperature, spray gun position and can size.

(13) The invention has been described above by way of example only and changes are possible within the scope of the attached claims. For example, it is possible to use a system with 12 motors, one for each chuck and mounted on the turret although this would add a substantial amount of mass, increase radius of gyration and inertia, and so limit the selection of the indexing device. This option would also require a slip ring for obtaining power and any control signals between static elements and the 12 motors.