Sheet Transport Pinch Roller Differential Speed Alignment
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Solution Overview
Problem
Existing sheet transport systems are complex and expensive due to the need for specific moving means to correct y-position errors, which complicates achieving high print quality by aligning sheet edges and correcting skew errors.
Innovation Solution
A sheet transport system with a detection system and control system that uses differential speeds of pinch rollers to rotate and align sheets, allowing z-position correction without additional moving means, and subsequently corrects skew angles by controlling the second pinch roller set's rotation timing to maintain the sheet's z-position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If specific moving means are used to correct z-position errors, then sheet alignment accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The pinch rollers are designed to perform multiple functions: their primary function is to transport sheets in the x-direction, but they are also configured to correct z-position errors by differential rotation. The control unit enables the pinch rollers to rotate at different speeds to induce sheet rotation, thereby aligning the sheet in the z-direction without requiring separate correction mechanisms.
Solution Approach 2:
The invention merges the sheet transport function and sheet alignment correction function into a single mechanism (the pinch rollers). By controlling the pinch rollers to rotate at differential speeds, the system simultaneously achieves sheet transport and z-position correction, eliminating the need for separate moving means dedicated solely to alignment correction.
2Device complexity
If pinch rollers are used for both transport and z-position correction, then device complexity is reduced, but control complexity increases
Solution Approach 1:
The control unit receives feedback from sensors that detect the sheet's position and orientation. Based on this feedback, the control unit calculates the required differential rotation speeds for the pinch rollers to correct both z-position errors and skew angles, enabling precise control despite the multi-functional requirement.
Solution Approach 2:
The system dynamically adjusts the rotation speeds of the pinch rollers based on real-time sheet position and orientation detection. The control unit continuously modifies the speed differential between left and right pinch rollers to achieve the desired sheet alignment while maintaining transport function.
3Device complexity
If sheet rotation is used to correct z-position, then additional moving means are eliminated, but skew angle correction becomes more complex
Solution Approach 1:
The correction process is segmented into two distinct phases: first, z-position correction is performed by rotating the sheet while it is still being transported by the first pinch roller set; second, skew angle correction is performed by the second pinch roller set after the sheet has left the first set. This segmentation allows each phase to be optimized independently.
Solution Approach 2:
The first pinch roller set performs preliminary z-position correction by inducing sheet rotation before the sheet reaches the second pinch roller set. This preliminary action positions the sheet's leading edge at the correct z-coordinate, preparing it for subsequent skew angle correction without interfering with the second correction phase.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system simplifies sheet transport by controlling z-positions and skew angles using pinch rollers, eliminating the need for specific moving means, ensuring accurate sheet alignment and correction of x-position errors, thereby enhancing print quality without increasing system complexity or cost.
Implementation Method 1
each pair forming a nip for pinching and driving the sheet with an individually controllable speed
Data Source
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AI summary
A sheet transport system for moving a sheet (24e, 24f) in a transport direction x while adjusting a position of the sheet in a lateral direction z normal to the transport direction x to a target position (zR), the system comprising first and second pinch roller sets (10, 12) spaced apart from one another in the transport direction x, each pinch roller set comprising two pairs (14, 16; 18, 20) of pinch rollers spaced apart from one another in the lateral direction z, each pair forming a nip for pinching and driving the sheet with an individually controllable speed, characterized by comprising a detection system for detecting a position of the sheet in the lateral direction z while the sheet is pinched by the first pinch roller set (10), and a control system configured for carrying out the following actions: - by controlling the speeds of the pinch rollers (14, 16) of the first pinch roller set (10) before the sheet has reached the second pinch roller set (12), rotating the sheet by a first rotation angle for adjusting a given reference point (32) on a leading part of the sheet to its target position (zR); and - when the sheet has left the first pinch roller set (10) and while the reference point travels along a path segment (36) that is symmetric with respect to the second pinch roller set (12), rotating, by controlling the speeds of the pinch rollers of the second pinch roller set, the sheet by a second rotation angle for aligning a leading edge of the sheet in the lateral direction z.