Monolithic Flat Spring Seismic Sensor Design
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Solution Overview
Problem
Existing seismic sensors face issues with undesirable resonances, spurious signals, susceptibility to mechanical shock, and thermal modulation due to the use of flexible wires and kinematic adjustment mechanisms in main springs.
Innovation Solution
A seismic sensor design featuring a monolithic flat spring with distinct regions for restoring force and suspension, providing a negligible bending moment and adjustable tension to balance a pendulum at an equilibrium position, reducing unwanted signals and enhancing robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flexible wire is used to tension the spring end, then the adjustment mechanism can be positioned at a convenient distance and have more degrees of freedom, but the wire is susceptible to breaking due to mechanical shock and creates stress concentration at attachment points
Solution Approach 1:
The patent extracts the flexible wire from the system and replaces it with a rigid or semi-rigid structural element integrated into the frame. The adjustment mechanism is directly coupled to the spring end through rigid connections, eliminating the wire while maintaining positioning capability through direct mechanical coupling.
Solution Approach 2:
The patent employs composite structural elements combining rigid frame materials with flexible structural sections. The spring end connection uses composite construction that provides both rigidity for shock resistance and flexibility for adjustment, eliminating stress concentration points while maintaining operational ease.
2Ease of manufacture
If a lumped mass attachment (screw, washer, nut) is used at the spring end, then the wire can be attached, but this creates undesirable resonances
Solution Approach 1:
The patent merges the attachment function with the spring structure itself. The spring end is directly formed as an integral part of the frame structure, eliminating separate attachment components like screws, washers, and nuts. This integration removes the lumped mass that causes resonances while maintaining manufacturing simplicity through monolithic construction.
Solution Approach 2:
The patent removes the lumped mass attachment components entirely from the design. The spring end connection is achieved through direct structural integration rather than separate fastening elements, eliminating the source of undesirable resonances.
3Adaptability or versatility
If the wire is made thin to be sufficiently flexible, then flexibility is achieved, but it becomes susceptible to breaking due to mechanical shock
Solution Approach 1:
The patent employs dynamic structural design where the connection between the spring end and frame provides flexibility through controlled deformation zones rather than thin wires. The structure can flex during normal operation but maintains sufficient cross-section to resist mechanical shock, achieving both adaptability and strength.
Solution Approach 2:
The patent uses composite structural elements that combine rigid sections for strength with flexible sections for adaptability. The flexible portions have sufficient mass and cross-section to resist shock while providing the necessary flexibility for operation.
4Ease of operation
If the wire is used for tensioning, then adjustment is possible, but stress concentration occurs at the ends where it is attached making it particularly susceptible to breakage
Solution Approach 1:
The patent merges the tensioning function directly into the structural connection between the spring end and frame. The rigid or semi-rigid connection provides tension adjustment through structural design rather than wire tensioning, eliminating stress concentration at attachment points while maintaining adjustment capability.
5Ease of manufacture
If bends or kinks are present in the wire when installed, then assembly is easier, but they may creep or relax over time causing unwanted spurious signals
Solution Approach 1:
The patent removes the wire entirely from the design, replacing it with rigid or semi-rigid structural connections that cannot develop bends or kinks. This eliminates the source of creeping deformations that cause spurious signals while maintaining assembly simplicity through direct structural coupling.
Solution Approach 2:
The patent integrates the spring end connection directly into the frame structure, eliminating separate wire components that could develop bends. The monolithic construction ensures no relative movement or deformation over time, preventing spurious signals.
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 minimizes spurious signals, increases robustness against mechanical shock, and reduces thermal modulation effects, providing a more reliable seismic measurement.
Implementation Method 1
an operating region for providing a restoring force to the pendulum proportional to an angular displacement of the pendulum
Implementation Method 2
a suspension region for transmitting a force to a portion of the operating region and applying a negligible bending moment to said portion of the operating region
Data Source
AI summary
A seismic sensor includes a frame, a pendulum pivotably mounted to the frame, a mechanism for sensing angular position of the pendulum, and a monolithic flat spring oriented between the frame and the pendulum for balancing the pendulum at an equilibrium position. The monolithic flat spring includes: (i) an operating region for providing a restoring force to the pendulum proportional to an angular displacement of the pendulum; and (ii) a suspension region for transmitting a force to a portion of the operating region and applying a negligible bending moment to the portion of the operating region.