Apparatus for decorating stiff objects by screen printing
View Patent ↗In an apparatus for decorating stiff articles using a screen printing process, an object carried by an object carrier and the stencil are advanced synchronously along a transport path during a printing operation. A doctor co-operable with the stencil is movable in an opposite relationship to the direction of movement of the stencil and the object. In the region of the at least one screen printing station is a transport screw with at least one screw flight as a drive for the object carrier, which is in engagement with the screw flight of the screw. During a printing operation the object carrier with object, on the one hand, and the stencil, on the other hand, pass synchronously through an acceleration phase and a deceleration phase. The printing stroke of the stencil is less than the total stroke thereof in the direction of movement of the object carrier.
1. An apparatus for decorating inherently stiff objects using at least a screen printing process, comprising
a transport path in the apparatus,
at least one screen printing station on the transport path,
object carriers for carrying respective objects along the transport path,
at least one screen printing stencil in the at least one screen printing station,
a drive operable during a printing operation to advance the object carriers with objects carried thereby and the at least one screen printing stencil synchronously along the transport path, the drive for the object carriers including, at least in a region of the at least one screen printing station, a transport screw with at least one screw flight engageable with the object carriers,
a doctor co-operable with the at least one screen printing stencil,
means for moving the doctor in the printing operation in an opposite relationship to a direction of movement of the at least one screen printing stencil and the object carriers, and
means for actuating the drive for the object carriers and the at least one screen printing stencil during the printing operation to cause the object carriers with respective objects and the at least one screen printing stencil to pass synchronously through at least an acceleration phase and a deceleration phase,
such that a printing stroke movement of the at least one screen printing stencil is less than a total stroke movement thereof in the direction of movement of the object carriers.
2. The apparatus as set forth in claim 1 , wherein the means for actuating the drive for the object carriers and the at least one screen printing stencil are operable during the printing operation to implement, between the acceleration phase and the deceleration phase, a phase in which the object carriers with respective objects and the at least one screen printing stencil are moved synchronously at a constant speed.
3. The apparatus as set forth in claim 1 , further comprising means for rotating the transport screw at a constant speed.
4. The apparatus as set forth in claim 1 , wherein the drive for the at least one screen printing stencil includes a cam, and a transmission drivingly connecting the cam to the at least one screen printing stencil.
5. The apparatus as set forth in claim 4 , wherein the stencil drive includes a swing lever, the cam being operable to transmit reciprocating movements to the swing lever, at least one carriage carrying the at least one screen printing stencil, and means drivingly connecting the swing lever to the carriage.
6. The apparatus as set forth in claim 5 , further comprising a thrust rod connecting the swing lever and the respective stencil carriage.
7. The apparatus as set forth in claim 6 , wherein the swing lever is connected to the thrust rod intermediate first and second ends of the thrust rod, and each end of the thrust rod is connected to a respective stencil carriage.
8. The apparatus as set forth in claim 1 , further comprising means for driving the means for moving the doctor from the drive for the at least one screen printing stencil.