Overmolded Brush Caps for Fuel Pump End Cap Sealing
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Solution Overview
Problem
Existing end cap assemblies for electrically driven fuel pumps require heat staking of shunt wires, increasing processing time and cost, while also posing challenges in maintaining a fluid-tight seal around electrical terminals.
Innovation Solution
The end cap assembly features cone-shaped brush caps overmolded onto shunt wires, incorporating a snap-fit feature and annular lip for retention, which eliminates the need for heat staking and ensures a fluid-tight seal through compression by high-pressure fuel, using an overmolded resin such as nylon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat staking is used to seal shunt wires in the end cap assembly, then a fluid-tight seal is achieved, but processing time and manufacturing cost increase
Solution Approach 1:
The patent replaces the thermal field (heat staking) with a mechanical field solution. The brush cap's conical outer surface mechanically engages with the conical inner surface of the elongated opening, using compression forces instead of thermal energy to achieve sealing. This mechanical interference fit eliminates the need for heat staking equipment and processing time while maintaining the fluid-tight seal.
Solution Approach 2:
The patent changes the sealing mechanism from thermal parameters (heat staking temperature and time) to mechanical parameters (compression force and geometric fit). The conical geometry with specific angle ranges (30-60 degrees for outer surface, 20-50 degrees for inner surface) creates a mechanical lock that seals under compression, transforming the sealing approach from thermal to mechanical parameter control.
2Reliability
If heat staking equipment and processes are used to seal shunt wires, then sealing is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent eliminates complex thermal processing equipment by substituting it with simple mechanical components. The conical brush cap and its engagement with the conical opening provide sealing through geometric interference and compression, requiring no heat staking equipment, temperature control systems, or specialized sealing machinery.
Solution Approach 2:
The brush cap serves as a disposable sealing component that is molded with integrated sealing features. Rather than using expensive, reusable heat staking equipment and replaceable sealing elements, the patent employs a low-cost molded plastic cap that provides sealing functionality through its geometric design, eliminating the need for complex equipment investment.
3Reliability
If the end cap assembly uses traditional sealing methods, then sealing is achieved, but assembly time and production efficiency decrease
Solution Approach 1:
The sealing geometry is pre-formed during the molding of the brush cap. The conical outer surface is created in the molding process itself, so no additional sealing operations are needed during assembly. The cap is pre-configured with the exact geometric profile required for mechanical engagement and sealing, enabling direct installation without preliminary sealing preparation.
Solution Approach 2:
The patent merges the sealing function with the structural brush cap component. Rather than using separate sealing elements (gaskets, O-rings, or heat-staked portions), the sealing capability is integrated directly into the brush cap's conical geometry. This consolidation eliminates multiple steps and components, streamlining the assembly process while ensuring reliable sealing.
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 solution reduces assembly time and costs by eliminating the need for heat staking and provides a reliable, fluid-tight seal around electrical terminals without the use of heat staking, sonic welding, or melt flowing, ensuring efficient and cost-effective manufacturing.
Implementation Method 1
The spring is positioned axially between the brush and the brush cap, and the spring biases the brush into direct electrical contact with a commutator contained in the fuel pump.
Implementation Method 2
High pressure fuel urges the brush cap into engagement with the sloped sidewall of the elongated opening, such that the elongated opening is sealed by compression.
Data Source
AI summary
An improved an end cap assembly for a fuel pump is provided. The end cap assembly includes first and second brush caps herein that are overmolded onto first and second shunt wires to ensure a fluid-tight seal around the shunt wires without requiring heat staking, sonic welding, or melt flowing the end cap to the shunt wires. The brush caps are cone-shaped and include a snap-fit feature that retains the brush caps in place when the endcap assembly is transported prior to being assembled to a fuel pump body.