Resin Pipe Joining Structure with Recess for Sink Mark Suppression
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Solution Overview
Problem
The joining of resin and metal pipes in endoscope treatment tools faces challenges due to sink marks during molding, leading to reduced airtightness and joining strength, as the resin molded product's hollow portion diameter changes, affecting the reliability of the connection.
Innovation Solution
A joining structure and method involving a cylindrical first member with a hollow portion and a cylindrical second member, where a concave portion is formed on the first member to accommodate the second member, ensuring proper fitting and reducing diameter changes by pouring resin into a metal mold from a position different from the insertion point, thereby minimizing sink marks and enhancing airtightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resin is molded to form a hollow portion for joining pipes, then the joining structure is formed, but sink marks occur during molding causing diameter changes that reduce airtightness
Solution Approach 1:
A recess portion is formed in advance on the outer circumference of the first member at the position where the second member will be pressed. This preliminary structural preparation allows the resin to be discharged during pressing, preventing sink marks and maintaining hollow portion diameter consistency, thereby ensuring airtightness without requiring additional corrective operations.
Solution Approach 2:
The outer circumference of the first member is segmented by forming a recess portion that divides the resin flow path. This segmentation allows controlled resin discharge during the pressing operation, preventing the accumulation of excess resin that causes sink marks and diameter variations, thus maintaining manufacturing precision and airtightness.
2Reliability
If the hollow portion diameter is maintained to improve airtightness, then joining reliability improves, but the molding process becomes more complex
Solution Approach 1:
The recess portion formation is integrated into the molding process itself, combining the structural preparation and the joining operation into a single integrated process. This eliminates the need for separate operations to prevent sink marks or correct diameter variations, maintaining airtightness while avoiding additional process complexity.
Solution Approach 2:
The recess portion is designed to automatically discharge excess resin during the pressing operation without requiring external control or intervention. The structure itself performs the function of preventing sink marks, maintaining hollow portion diameter consistency and airtightness through its own geometry, thereby simplifying the overall molding process.
3Strength
If traditional pressing method is used to join pipes, then joining is achieved, but sink marks reduce joining strength
Solution Approach 1:
The recess portion is formed in advance on the outer circumference of the first member at the pressing position. This preliminary preparation provides a designated path for resin discharge during pressing, preventing the formation of sink marks on the hollow portion surface. The result is maintained joining strength through proper fitting while achieving smooth surface quality without sink marks.
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 approach effectively suppresses sink marks, maintains consistent hollow portion diameter, and improves the airtightness and reliability of the pipe connection, reducing manufacturing time and costs by eliminating the need for adhesive hardening and simplifying the manufacturing process.
Implementation Method 1
molding the resin member by pouring a liquid resin constituting the resin member into a metal mold from a portion different from a portion into which the cylindrical member is to be pressed, and then solidifying the liquid resin
Data Source
AI summary
A joining structure includes a first member having a cylindrical hollow portion, and a second member that is cylindrical in shape, has an outer circumferential diameter equal to or larger than a diameter of the hollow portion, and is to be pressed into the hollow portion. A concave portion, which is cut out inward from an outer circumference of the first member, is formed on part of a portion of the first member into which the second member is pressed.