Rack-Pinion Alignment Mechanism for Control Rod Drive Assembly
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Solution Overview
Problem
Existing drive mechanisms with rack and pinion gears face challenges in aligning engagement during disassembly and assembly, particularly in control rod drive mechanisms for pressurized water reactors, which can lead to misalignment and require manual intervention in radiation regions.
Innovation Solution
A drive mechanism with a rack gear, pinion gear, positioning member, and abutting members that ensure proper rotational alignment through abutment, allowing secure and easy engagement by defining the rotational position of pinion teeth with rack teeth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rack gear and pinion gear are used in a drive mechanism, then the mechanism can effectively drive control rods in and out of the reactor core, but misalignment between the rack gear and pinion gear during assembly makes engagement difficult and requires manual intervention
Solution Approach 1:
The drive mechanism incorporates self-aligning features including a positioning protrusion on the pinion gear that fits into a positioning groove on the rack gear, and a positioning plate with positioning holes that guide the pinion gear during assembly. These features enable the mechanism to automatically align and engage the rack and pinion gears without requiring manual intervention or precise alignment skills, thus resolving the contradiction between reliable engagement and ease of assembly
Solution Approach 2:
A positioning plate is introduced as an intermediary component between the rack gear and pinion gear. This positioning plate includes multiple positioning holes that guide the pinion gear's rotational position during assembly, ensuring proper engagement. The intermediary positioning plate simplifies the assembly process while maintaining reliable engagement, directly addressing the technical contradiction
2Manufacturing precision
If manual intervention is required to align and engage the rack gear and pinion gear, then proper engagement can be achieved, but workers must enter radiation regions which reduces safety and increases complexity
Solution Approach 1:
The drive mechanism uses self-aligning features including a positioning protrusion on the pinion gear that automatically fits into a positioning groove on the rack gear, and a positioning plate with positioning holes that guide alignment. These features enable automatic engagement without requiring workers to manually align components in radiation regions, thus achieving precise engagement while reducing maintenance complexity and eliminating the need for human entry into radiation zones
Solution Approach 2:
The positioning plate and positioning groove are designed to pre-establish the correct rotational position of the pinion gear relative to the rack gear before engagement occurs. This preliminary positioning action ensures that when the pinion gear is brought into engagement with the rack gear, the teeth are already correctly aligned, eliminating the need for manual adjustment during assembly and reducing maintenance complexity
Data Source
AI summary
To securely and easily disassemble and assemble a rack gear and a pinion gear. A drive mechanism 5 includes a rack gear 5A, a pinion gear 5B engaging with the rack gear 5A, a positioning member 5D fixed to a portion in the rack gear 5A where rack teeth 5Ab are not included, and a plurality of abutting members 5E disposed along a rotation direction of the pinion gear 5B. In a case in which at least one of the rack gear 5A and the pinion gear 5B is moved in a relative movement direction at the time when the rack gear 5A engages with the pinion gear 5B, abutment between the positioning member 5D and the abutting member 5E defines a rotational position of pinion teeth 5Bb of the pinion gear 5B to be an engaging position with the rack teeth 5Ab of the rack gear 5A.