Sewing Machine Air Pump with Cam-Driven Piston for Stable Flow
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Solution Overview
Problem
Conventional compressed air supplying devices for sewing machines are prone to inconsistent airflow due to varying user operation forces, leading to incomplete thread delivery to loopers in overlock sewing machines.
Innovation Solution
A compressed air supplying device with an air pump, piston biasing mechanism, and an operating force transmitting mechanism that includes a ratchet mechanism to ensure consistent airflow by allowing the piston to move only in the intake air direction, using a lever-like operating member and a cam-driven piston returning arm to manage airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a lever is manually pushed down to push the piston of an air pump, then the air pump can supply compressed air, but the flow velocities of compressed air vary depending on operation forces, leading to inconsistent thread delivery
Solution Approach 1:
The patent introduces a cam mechanism that converts the manual lever operation into a standardized piston motion. The cam profile is designed to ensure the piston moves through a fixed stroke length at controlled speeds during both intake and exhaust phases, regardless of variations in user-applied force to the lever. This dynamic mechanism standardizes the air pump's output characteristics.
Solution Approach 2:
The cam mechanism acts as an intermediary between the manually operated lever and the piston. Instead of the lever directly controlling piston motion (which transmitted force variations), the cam mediates this relationship by imposing a fixed geometric constraint on piston movement, thereby decoupling the user's input force variations from the piston's actual motion characteristics.
2Device complexity
If the piston is directly linked with lever operations, then the structure is simple, but the velocities for pushing the piston differ with operation forces, causing unstable compressed air flow
Solution Approach 1:
The cam mechanism introduces a dynamic element that standardizes piston motion. The cam profile geometry dictates the piston's velocity and acceleration patterns during each cycle, ensuring stable and repeatable motion characteristics even though the lever operation may vary in force application. This adds controlled complexity to achieve flow stability.
Solution Approach 2:
The cam serves as a mechanical intermediary that decouples the direct linkage between lever and piston. It translates varied lever inputs into standardized piston motions, adding a layer of mechanical complexity that actually reduces overall system instability by filtering out operator variability.
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
The device stabilizes compressed air supply irrespective of user operation manner, ensuring reliable thread delivery to loopers without the need for external power sources like motors or compressors, thus enhancing operational consistency and reducing noise.
Implementation Method 1
a piston biasing portion for biasing force to the piston in the direction which the air pump exhausts air, and for driving the piston in the exhaust air direction, by applying biasing force
Implementation Method 2
the operating force transmitting mechanism constitutes a ratchet mechanism outputting only rotations in one direction from among rotations generated by reciprocating movements of the operating member
Implementation Method 3
a piston returning arm portion provided to be swingably and integrally with the driving arm portion and being rotationally moved by means of a cam portion provided at the operating force transmitting mechanism
Data Source
AI summary
A compressed air supplying device of a sewing machine includes an air pump unit including a piston; a piston driving spring applying biasing force to the piston in an exhaust air direction which is a direction in which the air pump unit exhausts air for driving the piston in the exhaust air direction by the biasing force; a lever making the air pump unit perform intake air movements; and an operating force transmitting mechanism transmitting operating force of the lever to the piston for actuating the piston only in an intake air direction which is a direction in which the air pump unit intakes air against the biasing force of the piston driving spring by the operating force.