PTC Resistor Retainer With Backward-Curved Spring
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Solution Overview
Problem
Existing retainer systems for positive temperature coefficient (PTC) resistors in electrical heater devices fail to securely hold the resistors with good electrical contact while avoiding sharp edges that can crack the fragile PTC resistors, and they do not maintain consistent pressure as the device heats and cools.
Innovation Solution
A retainer system comprising a base, a spring, and housing shaft engagement means, where the spring extends radially outwardly with a neck that curves backwardly and has a contact surface to securely hold the PTC resistor, with the spring being flexed to apply consistent pressure and the engagement members ensuring secure positioning within the housing shaft, while keeping any sharp edges away from the resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stamped electrical contact is used to secure the PTC resistor, then the resistor is firmly held with good electrical contact, but sharp edges (stamping burrs) are formed that can crack the fragile PTC resistor
Solution Approach 1:
A rubber or elastomeric intermediary material is introduced between the stamped electrical contact and the PTC resistor. This intermediary absorbs the sharp edges (stamping burrs) of the metal contact, preventing them from contacting and cracking the fragile PTC resistor surface, while still maintaining firm holding and good electrical contact through the compliant rubber material
Solution Approach 2:
The rubber intermediary material is positioned in advance between the electrical contact and the PTC resistor to cushion and protect the resistor from potential damage by sharp edges before contact occurs. This preemptive protective measure prevents cracking while ensuring reliable electrical connection
2Reliability
If the PTC resistor is held in a space larger than the resistor, then the securing means can function to prevent movement, but the resistor is subject to breakage from excessive pressure or misalignment
Solution Approach 1:
The rubber intermediary material changes its physical parameters (compression, elasticity) under applied pressure to provide progressive resistance. As pressure increases, the rubber deforms to conform to the PTC resistor dimensions, distributing the force evenly and preventing excessive pressure points that could cause breakage while still securing the resistor against movement
3Reliability
If a rigid retainer system is used to secure the PTC resistor, then the resistor is firmly held with consistent pressure, but the system cannot accommodate thermal expansion and contraction of the device
Solution Approach 1:
The rubber intermediary material provides a dynamic, compliant interface between the rigid electrical contact and the PTC resistor. As the device undergoes thermal expansion and contraction, the rubber elastically deforms to maintain consistent contact pressure and electrical connection, accommodating dimensional changes without compromising the security or electrical reliability of the resistor connection
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 retainer system effectively secures the PTC resistor with consistent pressure, maintaining good electrical contact and preventing cracking, even as the device expands with heat, ensuring reliable operation and reduced assembly costs.
Implementation Method 1
The spring is flexed to a desired extent and the contact surface is urged against the resistor to retain the resistor in the housing shaft
Data Source
AI summary
The invention provides a retainer system for retaining a positive temperature coefficient resistor in a heater housing shaft having a shaft side wall. The retainer system includes a base, a spring, and shaft engagement means. The spring is formed in and spaced apart from the base. The spring extends radially outwardly from a longitudinal axis of the base and the spring has a neck that curves radially backwardly, spaced apart from the base and toward the longitudinal axis of the base. The spring also has a contact surface presented outwardly, away from the base. The shaft engagement means are for engaging the shaft side wall and securing the base within the shaft at a desired distance from the resistor. The retainer system can be secured within the shaft with the spring flexed to a desired extent and with the contact surface urged against the resistor to retain the resistor in the shaft.