Laser Gyroscope Activation Wheel Hub Design for Thermal Stress
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Solution Overview
Problem
The existing mechanical structures for assembling the optical block of a laser gyroscope are either expensive or fail to achieve the desired metrological precision over a wide operational and storage temperature range, due to the use of materials with high thermal expansion differentials, leading to stress and potential slippage issues.
Innovation Solution
A novel activation wheel design featuring a polygonal faceted hub with bulging and thinned portions allows for radial displacement, enabling the use of less expensive steel instead of Invar™, while maintaining mechanical rigidity and accommodating thermal expansion differentials without excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parts of the mechanical activation structure are made of Invar™ to minimize thermal expansion differentials, then thermal stress and slippage are reduced, but manufacturing cost increases
Solution Approach 1:
The hub is designed with non-uniform thickness, featuring thicker portions for rigid support and thinner portions for flexibility. This local variation in geometry allows the steel hub to accommodate thermal expansion differentials between the steel activation wheel and Invar™ tulip, reducing thermal stress without requiring the entire structure to be made of expensive Invar™ material
Solution Approach 2:
The invention changes the geometric parameters of the hub, specifically varying its thickness throughout the structure. This parameter modification enables the steel hub to flex and accommodate thermal expansion, allowing the use of cheaper steel instead of Invar™ while maintaining thermal stability
2Strength
If a thick activation wheel is used to provide translational rigidity, then mechanical rigidity improves, but thermal expansion accommodation decreases
Solution Approach 1:
The hub features localized thickness variations with thicker regions providing mechanical rigidity for load-bearing functions and thinner regions providing flexibility for thermal expansion accommodation. This spatial differentiation of structural properties resolves the contradiction between rigidity and thermal adaptability
Solution Approach 2:
The non-uniform hub design introduces controlled flexibility into the otherwise rigid activation wheel structure. The thinner portions allow the wheel to dynamically adapt to thermal expansion changes while maintaining overall structural integrity and mechanical rigidity
3Ease of manufacture
If fewer screws are used for assembly, then ease of manufacture improves, but mechanical rigidity may decrease
Solution Approach 1:
The thicker portions of the hub are strategically positioned to provide rigid mounting surfaces for the tulip, allowing secure attachment with fewer screws. The localized reinforcement at critical mounting points compensates for the reduced number of fasteners while maintaining overall mechanical rigidity
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 design reduces thermal loads by 40% and maintains high rotational stiffness, allowing for cost-effective production and assembly with fewer screws, while ensuring the necessary precision and stability of the optical block.
Implementation Method 1
a faceted hub (32) with at least one thinned portion (34b) allowing a radial displacement degree of freedom of the fixing part relative to the rim (31) when there is a differential thermal expansion between the tulip (20) and the activation wheel (30)
Implementation Method 2
each wall (34) comprising at least one bulging portion (37) and one thinned portion (34b), the bulging portion (37) serving for the plane-to-plane fixing of one face of the tulip (20)
Data Source
AI summary
In a laser gyroscope, an activation wheel has a polygonal cylindrical hub formed by continuous assembly of vertical walls, wherein two adjacent walls of the cylindrical hub between them form a dihedron. Each radial plate of the activation wheel is connected to the cylindrical hub along the edge of a dihedron. The walls are formed with bulging portions, serving for plane-to-plane fixing of one face of the tulip to an optical block, and thin parts allowing a radial displacement degree of freedom of the fixing parts relative to the rim when there is a differential thermal expansion between the tulip and activation wheel. The activation wheel may be produced in a material having a thermal expansion coefficient higher than the tulip, for example steel, with plane-to-plane fixing of the tulip to the activation wheel hub, advantageously by screws, the assembly effectively accommodating the thermal expansion differential between the two materials.