Flap Stopper Torque Distribution via Segmented Design
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Solution Overview
Problem
Flap controllers in air-conditioning systems experience high torsional stresses due to direct drive mechanisms, leading to the use of more resistant materials like polyamide for flap stoppers, which increases costs.
Innovation Solution
A flap stopper design featuring two annular disks and stop elements, formed as an integral plastic injection-molded part, allowing the use of softer materials like polypropylene to distribute torque evenly and reduce stress, eliminating the need for harder plastics like polyamide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a direct drive mechanism with integrated flap stop is used, then the flap can be controlled effectively, but high torsional stresses occur at the flap-side actuator receptacle and flap stopper
Solution Approach 1:
The flap stopper is segmented into two separate disk-shaped support plates (bearing support plate and stopper support plate) spaced apart axially, with stop elements positioned between them. This segmentation distributes the torsional stress across multiple components rather than concentrating it at a single point, reducing peak stresses while maintaining effective flap control.
Solution Approach 2:
The design transitions from a single-plane stopper to a three-dimensional structure with two axially spaced support plates. By distributing stop elements across different axial positions and utilizing the space between the plates, the torsional load is distributed through multiple engagement points, reducing stress concentration.
2Strength
If intermediate members made of harder plastic like polyamide are used, then higher resistance and durability are achieved, but manufacturing costs increase
Solution Approach 1:
The flap stopper combines multiple materials strategically: softer polypropylene for the main body (bearing support plate and stopper support plate) to absorb and distribute stress, and harder polyamide only for the stop elements that require high resistance. This composite approach achieves the necessary strength where needed while keeping overall manufacturing costs lower than using hard plastic throughout.
Solution Approach 2:
Different material properties are applied to different parts of the flap stopper based on functional requirements. The stop elements use hard polyamide for wear resistance, while the larger bearing support plate and stopper support plate use softer polypropylene for stress distribution and cost efficiency. This local differentiation optimizes both performance and cost.
3Ease of manufacture
If polypropylene is used for the flap stopper, then cost efficiency is improved, but the material is too weak for traditional single-disk designs
Solution Approach 1:
The polypropylene flap stopper is segmented into two axially spaced disk-shaped support plates with multiple stop elements distributed between them. This segmentation allows the softer polypropylene material to distribute loads across multiple engagement points rather than relying on a single high-stress point, enabling cost-effective polypropylene usage while maintaining adequate strength.
Solution Approach 2:
By transitioning to a two-plate axial configuration, the design creates additional load paths through the axial spacing. The polypropylene material benefits from distributed stress across multiple plates and stop elements, compensating for its lower inherent strength compared to polyamide and enabling cost-effective manufacturing.
4Power
If stop elements are in direct contact with the bearing pin or axial extension, then torque transmission is efficient, but the flap leaf experiences high stress
Solution Approach 1:
The stop elements serve as intermediaries that engage with the bearing pin or axial extension indirectly through the two support plates. When the flap reaches its stop position, the stop elements contact the bearing pin, but the torque is distributed through the plate structure rather than being directly transmitted to the flap leaf, reducing stress on the flap while maintaining effective torque transmission for position control.
Data Source
AI summary
A flap stopper for a rotatable flap for controlling an air flow may include a round bearing support disc, a round stopper support disc, stop elements, and connecting ribs. The stopper support disc may be spaced apart from the bearing support disc in an axial direction. The stop elements may be arranged on the stopper support disc. The connecting ribs may be arranged between the bearing support disc and the stopper support disc. The bearing support disc, the stopper support disc, the stop elements, and the connecting ribs may be formed as an integral plastic injection-molded part.