Screen Printing Unit Cylinder Radius Asymmetry
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Solution Overview
Problem
Existing sheet-fed printing units designed as screen printing units face challenges in maintaining the stability of round screens due to differences in circumferential speeds and radii between the screen printing forme cylinder and the counter-pressure cylinder, leading to potential instability and damage during the printing process.
Innovation Solution
The design incorporates a counter-pressure cylinder with a support surface having a constant barrel radius extending over 170°, allowing for a smaller effective screen radius, and a fixing element with inner and outer contact surfaces that maintain the screen's stability by ensuring all grippers rotate at the same peripheral speed, along with a method where the screen printing forme cylinder and counter-pressure cylinder have different drives to maintain synchronized rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the screen printing forme cylinder has the same effective circumference as the counter-pressure cylinder, then the printing process can be simplified, but the round screen becomes unstable and may be damaged
Solution Approach 1:
The invention applies asymmetry by deliberately designing the counter-pressure cylinder with a larger radius than the screen printing forme cylinder. This asymmetric configuration creates different circumferences but ensures that both cylinders rotate at the same peripheral speed through synchronized drives, resolving the contradiction between simplified printing process and round screen stability
Solution Approach 2:
The invention changes the radius parameter of the counter-pressure cylinder to be larger than that of the screen printing forme cylinder. This parameter change allows the system to maintain constant peripheral speed across both cylinders while providing adequate space for the cylinder channel, thus ensuring round screen stability without oversimplifying the printing process
2Ease of operation
If the counter-pressure cylinder has a large channel to accommodate sheets, then sheet transport is improved, but the cylinder circumference becomes larger requiring larger radius
Solution Approach 1:
The invention resolves this contradiction by transitioning from considering only the radial dimension to incorporating the angular dimension. By ensuring that both cylinders rotate through the same angle at the same peripheral speed, the system can accommodate the large channel needed for sheet transport while maintaining synchronized operation with the smaller screen printing forme cylinder
3Manufacturing precision
If all grippers rotate at the same peripheral speed, then sheet transfer precision is improved, but the drive system becomes more complex
Solution Approach 1:
The invention employs feedback control through synchronized drives that monitor and adjust the rotation of both cylinders to maintain equal peripheral speeds. This feedback mechanism ensures precise sheet transfer while managing the complexity of the drive system through coordinated control
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
The invention relates to a screen printing unit (700), which comprises a screen printing plate cylinder (752), an impression cylinder (708) and at least one additional rotational transport body (709; 711; 712; 713), wherein: a fixing element (743) of the impression cylinder (708) has inner and outer contact surfaces (748; 749) for clamping sheets (02), the inner contact surface (748) having a base radius (R0) as the distance from an axis of rotation (716A) of the impression cylinder (708); a cylinder body (741) of the impression cylinder (708) has a support surface (744) for sheets (02), which has an impression portion (746) with a constant body radius (R1) extending over at least 170° about the axis of rotation (716) of the impression cylinder, the body radius (R1) being greater than the base radius (R0); a fixing element of the additional rotational transport body (709; 711; 712; 713) has an inner and an outer contact surface for clamping sheets, the inner contact surface having the base radius (R0) as the distance from an axis of rotation (717; 718; 719; 721) of said rotational transport body (709; 711; 712; 713).