Sewing Unit Bobbin Case Lifter for Thick-Thread Friction Reduction
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Solution Overview
Problem
Existing sewing units struggle to maintain high efficiency during mass production when using thick threads, particularly at high sewing speeds, due to increased thread friction and the need for manual thread exchange.
Innovation Solution
A modified bobbin case lifter and looper design that reduces thread friction by enlarging the free space between the looper bobbin case and the holding component, allowing for the use of thick threads up to 50 tex (20 NM) at speeds over 2000 stitches per minute, combined with a semi-automatic bobbin exchange system and a thread cutting device for precise seam formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thick threads are used for sewing, then seam strength and durability are improved, but thread friction increases causing reduced sewing speed and efficiency
Solution Approach 1:
a bobbin case lifter (37) is provided which can be actuated in a controlled manner for lifting the looper bobbin case (32) relative to the holding component (34, 35) in a direction away from the workpiece bed plate (6) along a z-coordinate of a sewing unit coordinate system
2Device complexity
If manual thread exchange is used, then device complexity is reduced, but productivity decreases due to time loss during thread changes
Solution Approach 1:
The lower sewing part (5) can be designed in such a way that a semi-automatic or fully automatic bobbin exchanging system can be used for the correspondingly automated exchange of the lower thread supply
3Productivity
If high sewing speed is used with thick threads, then productivity increases, but thread friction and heat generation increase causing reliability issues
Solution Approach 1:
The free space for the thread-which is enlarged by the bobbin case lifter-between the looper bobbin case and the bobbin case holding component reduces thread friction during sewing operation in the looper-side workpiece bed area
Data Source
AI summary
A sewing unit has a CNC controller and a sewing machine. The sewing machine has a workpiece bed plate, an upper sewing part and a lower sewing part. The lower sewing part has a looper with a lower thread supply in a looper bobbin case. The looper can rotate about an axis which extends parallel to the workpiece bed. A bobbin case holding component disposed in the region of the workpiece bed is in engagement with the looper bobbin case such that it does not co-rotate the looper bobbin case during a rotation of the looper. The lower sewing part has a bobbin case lifter to displace the looper bobbin case between a neutral position and an opened position in which a free space for a thread between the looper bobbin case and the bobbin case holding component is enlarged in comparison with the neutral position.