Sewing Machine Hook Bobbin Sliding Bearing Friction Control
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Solution Overview
Problem
Existing double-lockstitch sewing machines experience fluctuations in looper thread tension due to the design of the gripper, which affects the quality of the seam.
Innovation Solution
A sliding bearing is formed between the locking lever and the spool's flange, providing uniform friction conditions over the entire circumference, eliminating the driver groove's impact on friction and maintaining constant braking torque during bobbin rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking device with a locking lever is used to secure the bobbin in the bobbin case, then the bobbin can be firmly held during operation, but the driver groove necessary for winding machines creates non-uniform friction conditions during bobbin rotation
Solution Approach 1:
The driver groove, which causes non-uniform friction, is removed from the bobbin design. Instead, the bobbin is driven through direct contact with the locking lever's pressing surface, eliminating the groove and its associated friction variations while maintaining the winding function.
Solution Approach 2:
Instead of using a driver groove to transmit rotational motion, the invention inverts the approach by using the locking lever's pressing surface directly against the bobbin's outer surface. The friction between these surfaces provides the driving force, reversing the traditional mechanism and eliminating the harmful groove.
2Reliability
If a braking and ejection spring is compressed to secure the bobbin, then the bobbin can be held in position, but the presence of the driver groove causes fluctuations in friction conditions during rotation
Solution Approach 1:
The driver groove is extracted from the bobbin design, eliminating the source of friction fluctuations. The bobbin surface becomes uniform, allowing smooth rotation without the intermittent friction variations that previously affected seam quality.
Solution Approach 2:
The friction interface is localized to a specific annular pressing surface on the locking lever that contacts a corresponding surface on the bobbin. This localized, uniform contact area ensures consistent friction conditions throughout the rotation, improving operational smoothness and seam quality.
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
This design significantly reduces fluctuations in hook thread tension, enhancing the consistency and quality of the seam produced by the sewing machine.
Implementation Method 1
A sliding bearing is formed between the locking lever and the spool's flange, providing uniform friction conditions over the entire circumference
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The hook has bobbin case (21) attached to cup type hook portion (24), and receiving pin (25) arranged coaxial with axis (9) of bobbin case. A lock lever (36) extends at right angle to the axis, to contact top flange (28) of hook thread bobbin (26) in its locked position, and extended parallel to the axis in its release position respectively. An annular sliding bearing (43) arranged between locking lever and top flange, has continuous annular region (44) to contact top flange, and pressure surface (44a) to contact locking lever, in the locked position.