Injection Molding Tool for Piston Seals Without Parting Lines
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Solution Overview
Problem
The sealing of cartridges for multi-part fluids, such as adhesives, is challenging due to the fine nature of resin and catalyst components, which can leak through small gaps, and previous piston manufacturing methods are costly and require post-forming machining to achieve accurate sealing edges.
Innovation Solution
A piston is injection molded with integrally formed circumferential seals and a tool comprising movable segments that form the piston without a longitudinal parting line, featuring a deflection member to facilitate removal and prevent damage during ejection, allowing for the formation of undercuts without additional machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional injection molding is used to form pistons with sealing edges, then the manufacturing process is simple, but the sealing edge accuracy is insufficient and requires post-forming machining
Solution Approach 1:
The molding tool is divided into multiple segments (first segment, second segment, third segment) that can move independently along the longitudinal axis. The first and second segments form the sealing edge of the rearward seal, while the third segment forms the sealing edge of the forward seal. This segmentation allows each segment to be precisely positioned and adjusted to achieve accurate sealing edges without requiring post-forming machining.
Solution Approach 2:
The segments are designed to be movable along the longitudinal axis during the molding process. The first, second, and third segments can be positioned at different axial locations to form sealing edges at specific positions on the piston. This dynamic positioning capability enables precise control over sealing edge location and geometry, eliminating the need for additional machining operations.
2Reliability
If a longitudinal parting line is used in the piston seal, then the tool structure is simplified, but sealing reliability is reduced due to potential leakage paths
Solution Approach 1:
The tool is segmented into multiple axially movable segments that can independently form different portions of the seal. By distributing the seal formation across multiple segments, the design eliminates the need for a longitudinal parting line while maintaining tool manageability. Each segment contributes to forming a continuous seal without gaps or parting lines that could allow leakage.
Solution Approach 2:
Instead of using a longitudinal parting line (one-dimensional solution), the invention uses axial movement of segments (adding a dimensional approach). The segments move along the longitudinal axis to form the seal, transforming the problem from a static parting line design to a dynamic multi-position formation process that eliminates leakage paths.
3Manufacturing precision
If undercuts are formed in the piston, then the sealing performance is improved, but the tool design becomes more complex and removal of the piston becomes difficult
Solution Approach 1:
The undercut formation is distributed across multiple segments rather than requiring a single complex tooling feature. The first, second, and third segments can be positioned to form undercuts at different axial locations, allowing the undercut geometry to be achieved through coordinated segment movement rather than a single complex tool design.
Solution Approach 2:
The segments are designed to be movable along the longitudinal axis, allowing the tool to dynamically adjust segment positions during the molding process to form undercuts. This dynamic capability enables undercut formation without requiring permanent, fixed tooling features, simplifying the overall tool design while maintaining the ability to create precise undercut geometries for improved sealing.
Data Source
AI summary
A piston for use in a cartridge for dispensing multi-part fluids, the piston being injection molded and having integrally formed circumferential seals, wherein the piston is molded in the absence of a longitudinal parting line across the seals. A tool for forming a piston having a plurality of circumferential seals for use in a cartridge for dispensing multi-part fluids, the tool comprising a plurality of segments together defining a piston cavity corresponding to an outer periphery of the piston.