Rotating Hook Needle for Eyelet Damage Prevention
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Solution Overview
Problem
Existing methods for thread-stitching folded printed sheets, particularly when using thin sheets to produce thick book blocks, risk damaging the eyelets formed from the thread loop due to misalignment of the hook needle, leading to poor quality book blocks.
Innovation Solution
The hook needle is rotated to position its hook at an angle of +/- 85°, preferably +/- 50°, or +/- 15° from a vertical plane before penetrating the eyelet, ensuring the thread loop is securely gripped and reducing the risk of damage, with adjustable rotary positions and a servo motor for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the hook needle is used in fixed rotational positions to sew printed sheets, then the stitching process is simple and fast, but the eyelet formed from the thread loop of the previously sewn printed sheet may be damaged, especially when using thin sheets to produce thick book blocks
Solution Approach 1:
The hook needle is made rotatable about its longitudinal axis, transforming from a fixed-position component to a dynamically adjustable one. The rotation angle can be varied depending on the thickness of the printed sheets being sewn, allowing the system to adapt to different working conditions and prevent eyelet damage while maintaining stitching efficiency.
Solution Approach 2:
The rotational angle of the hook needle is changed as a controllable parameter. By adjusting this angle, the positioning of the hook relative to the eyelet is optimized for different sheet thicknesses, preventing the hook from catching and damaging the eyelet while still allowing efficient stitching operation.
2Manufacturing precision
If the hook needle is rotated to precise angular positions to prevent eyelet damage, then the quality of book blocks improves, but the device complexity increases due to additional rotation control mechanisms
Solution Approach 1:
The rotation control mechanism serves multiple functions: it positions the hook needle at precise angles to prevent eyelet damage, and it can be integrated with the existing stitching mechanism's control system. The same rotational mechanism that positions the hook needle also controls the stitching operation, reducing the need for separate control systems.
Solution Approach 2:
The system can incorporate sensors to detect the thickness of printed sheets and automatically adjust the rotation angle of the hook needle accordingly. This feedback mechanism allows precise positioning without requiring complex manual adjustment systems, as the controller automatically optimizes the hook angle based on real-time sheet thickness measurements.
Data Source
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Figure 5~11
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AI summary
The invention relates to a method and a device for thread-stitching folded printed sheets (5), in which individual folded printed sheets (5) are successively placed flat next to one another and sewn together to form a book block (6) using at least one sewing needle (13) and at least one hook needle (14). Before the hook needle (14) penetrates the fold (10) of the printed sheet (5) to be sewn and the eyelet (22) of the previously sewn printed sheet (5) from the inside out, it is rotated about its longitudinal axis (27) such that its hook (15) is positioned in a vertical plane of symmetry (33) of this eyelet (22) and on a side of the hook needle (14) facing the previously sewn printed sheet (5). For this purpose, the hook needle (14) is rotatable about its longitudinal axis (27) at any angle (α), and the hook (15) is designed to be positionable in any rotational position.