Injection molded housing
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Solution Overview
Problem
HVAC systems face challenges with injection molded plastic housings that warp during cooling, leading to mating issues and air leakage due to snap-fit designs that cannot fully engage without preventing separation, and lack a means to compress the joint effectively for a seal.
Innovation Solution
A fastening mechanism featuring a tongue and groove joint with a central catch, latch, and retention clips that allow for controlled engagement and disengagement, ensuring proper alignment and sealing without additional parts or costs, using a latch with living hinges and a hinge pin to secure the pieces together.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If snap-fit designs are used to join housing pieces, then assembly is simplified, but the joint cannot be fully engaged without preventing separation
Solution Approach 1:
The fastening mechanism is segmented into distinct functional components: a latch member with living hinges for engagement, a hinge pin for rotation, and a separate compression member for applying force to the joint. This segmentation allows each component to perform its specific function independently, enabling both easy assembly and controlled disengagement.
Solution Approach 2:
The latch member incorporates living hinges that provide flexibility and elasticity, allowing the latch to dynamically engage and disengage from the catch. The hinge pin enables rotational movement of the latch, transforming the static snap-fit into a dynamic system that can be controlled for both assembly and disassembly operations.
2Productivity
If housing pieces are cooled immediately after molding, then production time is reduced, but warping occurs leading to mating issues
Solution Approach 1:
The fastening mechanism is designed to be installed on the housing pieces while they are still warm and flexible, before warping occurs during cooling. The latch and catch are engaged in advance, and the compression member is positioned to apply force to the joint during the critical cooling period, preventing warping before it can compromise mating alignment.
Solution Approach 2:
The compression member changes the physical state of the joint by applying compressive force, which counteracts the thermal contraction and warping tendencies of the plastic housing pieces during cooling. This parameter change (applying force) compensates for the dimensional changes occurring due to temperature reduction.
3Reliability
If additional fastening parts are added to prevent warping, then sealing is improved, but manufacturing cost increases
Solution Approach 1:
The fastening mechanism merges multiple functions into an integrated system: the latch member with living hinges provides engagement, the hinge pin provides rotation, and the compression member provides joint compression - all working together as a unified mechanism. This merging reduces the need for separate fastening components while maintaining sealing effectiveness.
Solution Approach 2:
The living hinges in the latch member provide self-service by automatically returning to their original position after deformation, enabling the latch to engage and disengage without additional springs or complex return mechanisms. The compression member is positioned to automatically apply force to the joint during assembly, eliminating the need for separate adjustment mechanisms.
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 solution provides a reliable, cost-effective sealing mechanism that prevents warping and ensures proper assembly of HVAC components, enhancing air tightness and reducing air leakage by allowing controlled engagement and disengagement of the housing pieces.
Implementation Method 1
The latch is bendable at the living hinges to align the hinge pin with the half-knuckle. The latch is rotatable about the hinge pin to engage the central catch
Data Source
AI summary
An injection molded housing includes a first piece, a second piece, and a wall defined by the first piece removably joined to the second piece by a joint at abutting surfaces of the first piece and the second piece. A central catch is integrally molded with the first piece, protruding from the wall. A latch is integrally molded with the second piece, and connected to the second piece first and second living hinges. A half-knuckle is integrally molded with the second piece, protruding from the wall. A hinge pin is fixedly attached to the latch. The latch is bendable at the living hinges to align the hinge pin with the half-knuckle. The latch is rotatable about the hinge pin to engage the central catch and selectably prevent the first piece from being disengaged from the second piece.