Sewing Machine Presser-Foot Force Switching Through Feed Dog Position
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional sewing machines require a complex configuration for changing the pressing force applied by the presser foot to the workpiece.
Innovation Solution
A sewing machine with an adjusting mechanism that includes an adjustment part and a restricting part to control the transmission of urging force from the presser bar spring to the presser foot, allowing the pressing force to be switched based on the position of the feed dog, simplifying the configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional pressing device uses multiple connecting members and elastic members to change pressing force, then the pressing force can be adjusted, but the device configuration becomes complex
Solution Approach 1:
The patent extracts the essential function of pressing force adjustment by removing unnecessary connecting members and elastic members. The presser bar directly transmits urging force from the presser bar spring without intermediate components, achieving pressing force adjustment through the feed dog's position-based restriction mechanism rather than complex mechanical linkages.
Solution Approach 2:
The patent introduces the feed dog as an intermediary element that mediates between the presser bar spring and the presser foot. The feed dog's position (above or below the throat plate) acts as a mediator to control whether the presser bar spring's urging force is transmitted to the presser foot, enabling pressing force adjustment without complex direct mechanical connections.
2Reliability
If the presser bar spring continuously urges the presser bar downward, then stable pressing force is maintained, but the ability to switch pressing force for different sewing operations is reduced
Solution Approach 1:
The patent makes the pressing force transmission dynamic by allowing the feed dog's position to control the connection state between the presser bar spring and presser foot. During feed dog emergence, the urging force is restricted; during retraction, the urging force is transmitted. This dynamic switching enables different pressing forces for different sewing phases while maintaining reliability within each phase.
Solution Approach 2:
The patent implements periodic switching of pressing force transmission synchronized with the periodic motion of the feed dog. The presser bar spring's urging force is periodically restricted during feed dog emergence and periodically transmitted during feed dog retraction, creating a rhythmic pattern of high and low pressing forces that matches the sewing operation requirements.
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
Enables easier switching of pressing force applied by the presser foot, facilitating both normal and curved line sewing by mechanically adjusting the pressing force at prescribed timings.
Implementation Method 1
The presser bar spring has an upper end and a lower end in the up-down direction. The presser bar spring is configured to urge the presser bar downward with an urging force.
Implementation Method 2
The adjustment spring has an upper end and a lower end in the up-down direction. The adjustment spring is configured to urge the presser bar downward with an urging force smaller than the urging force of the presser bar spring.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
In a sewing machine, a feed dog feeds a workpiece placed on a throat plate. A presser bar has a lower end portion on which a presser foot is mountable. A presser bar spring urges the presser bar downward. During a first prescribed period of time in which a top of the feed dog is above a top surface of the throat plate, an adjustment part of an adjusting mechanism is spaced apart from a restricting part of the adjusting mechanism to cause an urging force of the presser bar spring to be transmitted to the presser foot. During a second prescribed period of time in which the top of the feed dog is beneath the top surface of the throat plate, the adjustment part is in contact with the restricting part to prevent the urging force of the presser bar spring from being transmitted to the presser foot.