Fluid Pressure Switch Composite Actuator Thermal Drift
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Solution Overview
Problem
Existing fluid pressure responsive electric switches in high-pressure applications, such as HVAC and industrial settings, experience significant shifts in pressure switch points over a wide temperature range (-25°C to 125°C), leading to inaccurate cutout operations due to temperature variations.
Innovation Solution
A fluid pressure responsive electric switch with a composite actuator member composed of stacked disc members made from materials with varying coefficients of thermal expansion (CTE), including low and high CTE stainless steel discs, and an optional membrane layer, which maintains consistent pressure switch points by minimizing thermal drift through precise material selection and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If homogeneous layers of nested disc stacks are used for the actuator member, then the device structure is simple and robust, but the pressure switch points shift significantly over the temperature range
Solution Approach 1:
The actuator member is constructed from composite materials with different coefficients of thermal expansion (CTE). Specifically, it combines a first material with a first CTE and a second material with a second CTE that is different from the first CTE. This composite structure compensates for thermal drift by balancing the expansion and contraction effects of different materials, thereby maintaining stable pressure switch points across the temperature range from -25°C to 125°C while preserving structural robustness.
2Adaptability or versatility
If the switch operates over a wide temperature range, then the application versatility is improved, but the measurement precision of pressure switch points deteriorates
Solution Approach 1:
The invention changes the physical parameters of the actuator member by selecting materials with specific coefficients of thermal expansion. The first material has a first CTE and the second material has a second CTE, and these parameters are carefully chosen to compensate for thermal effects. This parameter optimization allows the switch to maintain pressure switch point accuracy within 1% of room temperature values across the wide temperature range of -25°C to 125°C, achieving both versatility and precision.
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 ensures pressure switch points remain within 1% of room temperature values across the temperature range, providing more accurate and stable operation compared to homogeneous switches, as demonstrated by reduced average deviation in actuation pressure.
Implementation Method 1
a composite actuator member composed of stacked disc members made from materials with varying coefficients of thermal expansion (CTE), including low and high CTE stainless steel discs
Data Source
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Figure 2
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AI summary
A pressure responsive electric switch is described having an elongated base containing an electrical switch and terminals. The base is attached to a sensor assembly (60) which actuates and de-actuates the electric switch in response to pressure to be measured. The sensor assembly has a composite actuator member (62) comprising a plurality of stacked snap-acting disc members which includes at least one snap-acting disc member (17) of a chosen low coefficient of thermal expansion and at least one snap-acting disc member (18) of chosen high coefficient of thermal expansion material so as to provide precise pressure activation/deactivation points over a wide temperature range. In a second embodiment, the composite actuator member includes a thermal adjustment member.