Sewing Machine Pedal Actuation Device with Adjustable Preload
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Solution Overview
Problem
Existing sewing machine actuating devices require time-consuming adjustments to accommodate operator preferences for actuating force, often necessitating the replacement of preload springs.
Innovation Solution
An actuating device with a preload spring and associated setting device allows for simple adjustment of actuating force, using a preload guide rod for linear movement and a guide wall with latching sections to provide haptic feedback and reduce wear, enabling easy setting of prestressing force without the need for spring replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a preload spring is used to generate actuating force, then the actuating force can be maintained, but the adjustment of actuating force becomes time-consuming and complex requiring spring replacement
Solution Approach 1:
The invention replaces the static preload spring system with a dynamic adjustment mechanism. The adjustment sleeve can be rotated to different angular positions, each corresponding to a different effective preload force on the friction disk. This allows the actuating force to be dynamically adjusted without replacing the spring itself, resolving the contradiction between maintaining spring-based force and enabling easy adjustment.
Solution Approach 2:
The invention changes the parameter of effective preload force by altering the angular position of the adjustment sleeve rather than changing the physical spring. The sleeve has different angular positions that correspond to different effective forces on the friction disk, allowing parameter adjustment without time-consuming spring replacement, thus resolving the time loss contradiction.
2Ease of operation
If a nut is used to adjust the preload force of a disc spring, then the actuating force can be adjusted, but the adjustment mechanism becomes more complex
Solution Approach 1:
The invention segments the adjustment function from the spring itself. Instead of using a complex nut-and-thread mechanism that directly compresses the spring, the adjustment sleeve is segmented into discrete angular positions, each corresponding to a specific preload force. This segmentation simplifies the adjustment mechanism while maintaining the ability to vary the actuating force.
Solution Approach 2:
Instead of using a nut to compress the spring directly (conventional approach), the invention inverts the approach: the adjustment sleeve rotates to change the effective leverage or contact point, thereby adjusting the force transmission from the spring to the friction disk. This inversion simplifies the mechanism while achieving the same adjustment goal.
3Measurement precision
If the guide wall always interacts with the counter-body at the same place, then the positioning is consistent, but wear on the adjustment device increases
Solution Approach 1:
The guide wall is designed with a curved or parabolic profile rather than a straight line. This curvature allows the interaction point between the guide wall and counter-body to move along the curved surface during adjustment, distributing wear across multiple locations rather than concentrating it at a single point, thus resolving the contradiction between consistent positioning and wear reduction.
Solution Approach 2:
The curved guide wall creates a periodic interaction pattern where the contact point moves cyclically along the curve during adjustment operations. This periodic movement of the contact point distributes wear uniformly across the guide wall surface, preventing localized wear accumulation while maintaining positioning accuracy.
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 solution allows for efficient and cost-effective adjustment of actuating force, providing stable support and reducing wear, while enabling easy reading and setting of prestressing force through a simple and intuitive mechanism.
Implementation Method 1
a pretensioning spring (23) arranged in the housing body (21) which serves to generate a prestressing force on a friction disk (not visible)
Implementation Method 2
The guide rod of the preloading body ensures a defined, guided linear movement of the preloading body and thus reduces the risk of the preloading device tilting or becoming sluggish in some other way
Implementation Method 3
The operator has simple haptic feedback that a desired change in the actuating force has been set via the latching of the latching sections with the counter-body
Implementation Method 4
a prestressing force of a disc spring on a friction disk is adjusted via a nut
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The pedal device (8) has a pretensioning unit, an actuating unit e.g. foot pedal (13), with a pedal pretensioning body (20), and lower and upper pretensioning springs (23, 24) e.g. compression springs, for pretensioning a releative movement of the pretensioning body to a housing body (21) based on a movement of the actuating element. An adjusting sleeve (29) is provided for setting a pretensioning force of one of the pretensioning springs. The pretensioning body has a guiding rod (26), which is linearly guided into a retainer of the housing body.