The present invention relates to an apparatus for moving and rotating objects in a printing system. In particular, the apparatus comprises a moveable carrying device and a separate drive device. The drive device couples to a rotatable section of the carrying device and provides a torque to the rotatable section.

BACKGROUND

In industrial printing processes for printing in a series of steps onto discrete objects such as packaging containers, it is common for a series of objects to be carried between printing stations by a series of carrying devices. In order for printing devices at the printing stations to access a large portion of a three-dimensional object's surface, the carrying devices typically manipulate the object at the print station, for example, by rotating a cylindrical object around its longitudinal axis to expose an entire outer surface. Beverage cans and aerosol cans are examples of cylindrical objects that may be printed on such a system.

Existing types of apparatus for handling discrete objects through such a printing process include mandrel wheel systems, also known as spindle disc systems. Published U.S. Pat. No. 6,769,357 shows an example of a mandrel wheel system.

In mandrel wheel systems, a plurality of mandrels are fixed with equal spacing around a rotating or indexing wheel. In some examples, each mandrel has an associated in-built servo motor that provides rotation of the object. In these examples, the servo motors require power and control connections provided by a rotating coupling system on the central axis of the mandrel wheel. In other examples, each mandrel is mechanically driven by belt or gears from a single motor. Because all mandrels on the mandrel wheel are constrained to index at the same time, throughput is limited to the speed of the slowest process in the sequence. As a result, processing stations performing fast processes are required to have an inactive period while slower processes are completed at other stations. Indexing distance and dwell time at stations cannot be varied to suit the size or process time of that station.

Also known are linear track systems in which one or more mandrels or object holders are moved in a group between stations along a linear track. The mandrels return along the track to the start position after printing. This reciprocating motion allows power and control connections to be provided to the mandrel motors via flexible cabling without moving contacts. Such reciprocating systems, however, have low throughput because the cycle time has to accommodate the return of the mandrels in the reverse direction along the track to its start position.

To address the issues described above, more complex carrying systems are being developed that allow greater flexibility in how objects may be carried through a printing process. By removing constraints on object movement imposed by the known systems described above, more efficient processes may be developed where, for example, time during which processing stations are inactive is minimized.

A challenge to be overcome in the provision of more complex/flexible printing systems is how to provide services to each of the carrying devices in order to power, control and measure the rotation of objects while undergoing printing processes. Known arrangements of connections such as those used in mandrel wheel or linear track systems are suited to simple systems, and it would be difficult (requiring a complex arrangement of moving contacts, rotatable couplings, slip-rings, etc.) to adapt these arrangements to more complex systems where, for example, the relative positions of carrying devices vary throughout a printing cycle.

Consequentially, there is a need for an improved system for providing controlled rotation to moveable objects.

SUMMARY OF INVENTION

The present disclosure provides an apparatus for handling objects, the apparatus comprising: a carrying device that is configured to move along a track;

a handling device that is adapted to hold an object and is mounted to the carrying device such that it is rotatable with respect to the carrying device about a handling axis; a drive device disposed at a position along the track and configured to produce a torque around a drive axis; wherein the carrying device can be moved along the track in a direction perpendicular to the drive axis into and out of a drive position, wherein: in the drive position, the handling axis of the handling device is in substantial alignment with the drive axis of the drive device whereupon the drive device induces a torque in the handling device causing the handling device to rotate, thereby causing the object held by the handling device to rotate.

The provision of an apparatus in which the drive device that generates a torque in the rotatable handling device is not part of the carrying device is advantageous over known devices because it removes the need for electrical or other connections to the independently moveable carrying device to rotate the carried object.

The provision of a system in which the carrying device moves in a direction perpendicular to the drive axis into and out of a drive position is advantageous because it provides a system in which the drive device can couple to the handling device without requiring active control of the axial separation between the drive device and the handling device.

Preferably, the handling device comprises at least one magnetic element, and wherein the drive device generates a rotating magnetic field, which acts on the at least one magnetic element of the handing device to produce the torque.

Preferably, the rotating magnetic field is produced by at least one magnetic coil that is driven with an alternating electric current.

Preferably, the drive device comprises a rotating drive element comprising at least one permanent magnet.

Preferably, the drive device couples torque to the handling device by friction.

Preferably, the rotation of the handling device is synchronised with the rotation of the drive device when the carrying device is in the drive position.

Preferably, the path along which the carrying device is configured to move is defined by a track, and, preferably, wherein the track forms a closed path on which the carrying device can be moved.

Preferably, the drive device is positioned adjacent a processing station, wherein the processing station is configured to perform at least one of the following processes on the object carried by the handling device: loading, inspecting, cleaning, surface treatment, printing, drying, coating, curing, unloading.

Preferably, the apparatus comprises a rail or pad mounted adjacent to the track and wherein the handling device comprises a wheel configured to contact the rail or pad as it moves along the track, thereby causing the handling device to rotate as it is moved along the track.

Preferably, the handling device is adapted to hold a cylindrical object with its longitudinal axis parallel to the handling axis, and, preferably, wherein the cylindrical object is a can or tube.

Preferably, the drive device is positioned adjacent to a printing device comprising a printhead, and wherein, when the handling device is holding the cylindrical object, rotation of the handling device by the drive device causes the cylindrical object to be rotated such that the printhead is able to print a swathe around the entire circumference of the cylindrical object.

Preferably, wherein the drive device is one of a plurality of drive devices arranged along the path, and wherein the carrying device can be successively moved to each of the drive devices.

Preferably, the carrying device is one of a plurality of carrying devices, each of which is independently moveable with respect to the other carrying devices.

Preferably, the handling device comprises an encoder-ring having encoded thereon information identifying the angular position of the handling device, and wherein the apparatus further comprises a read-head proximate to each driving device configured to measure the angular position of the handling device by reading the encoder ring.

Preferably, the encoder ring has a diameter which is substantially the same as the diameter of the cylindrical object, such as to provide an equivalence, in an output from the read-head, between a linear displacement of the carrying device along the path and a circumferential displacement of the rotating cylindrical object on the handling device, thereby to compensate for an error in the position of the carrying device with respect to the printhead.

In another aspect of the disclosure, a method is provided for printing on objects using the printing apparatus, the method comprising: moving an object held by the handling device into the vicinity of a printhead by moving the carrying device into the drive position; rotating the handling device by operating the drive device when coupled to the handling device in the drive position; printing onto the object held by the handling device while the handling device is rotated.

Preferably, moving the carrying device into the drive position comprises moving the carrying device along the path in a direction perpendicular to the drive axis.

Preferably, while the object is being printed on, a further carrying device is moved along the track.

