Rack Exchange Jig for Multi-Pinion Gearbox Calibration
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Solution Overview
Problem
Rack and pinion drive arrangements with multiple pinions face challenges in load distribution and calibration due to the need for rotational compliance, and the handling and transportation of long, heavy racks are cumbersome and risky, risking damage to the rack and gearbox.
Innovation Solution
A method and jig assembly that allow for the exchange of a utility rack with an auxiliary rack, enabling calibration and maintenance while maintaining the rack's calibration during transportation, by aligning and connecting the auxiliary rack with the pinions, and then replacing it with the utility rack for normal operation, using a coupling arrangement with a rod and tensioning mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rack is made long and heavy to achieve the required strength and durability for transforming great forces and torques, then the load transmission capability is improved, but the handling and transportation becomes cumbersome and the risk of damage increases
Solution Approach 1:
The rack is divided into a first rack portion that remains installed in the gearbox and a second rack portion that can be detached and exchanged. This segmentation allows the heavy, long rack to be handled in smaller, more manageable sections while maintaining the overall functionality of the drive arrangement.
Solution Approach 2:
The second rack portion is extracted from the complete rack assembly, allowing it to be removed and exchanged independently. This extraction enables the rack to be handled in parts rather than as a single heavy unit, reducing transportation difficulties and damage risk.
2Length of moving object
If the rack is made long to achieve the required stroke length for the application, then the operational range is improved, but the straightness tolerance and geometry control become more difficult to maintain
Solution Approach 1:
Dividing the long rack into multiple portions allows each section to be manufactured and calibrated separately with controlled length, making it easier to maintain straightness and tooth geometry tolerances within acceptable ranges for each segment.
Solution Approach 2:
The second rack portion can be manufactured as a precise copy or replica of the first rack portion, ensuring that both segments have identical tooth geometry and straightness characteristics, thereby maintaining overall precision across the complete rack length.
3Measurement precision
If the rack remains installed in engagement with the pinions during transportation to maintain calibration, then the calibration accuracy is preserved, but the transportation difficulty and risk of damage increase
Solution Approach 1:
By segmenting the rack into detachable portions, the second rack portion can be removed and transported separately from the gearbox, reducing transportation difficulty while the first rack portion remains installed to maintain calibration during the process.
Solution Approach 2:
The second rack portion is extracted from the assembly for separate transportation, allowing the gearbox with the first rack portion to be transported or handled independently while maintaining calibration, and the extracted portion to be transported separately without adding to the overall transportation burden.
4Force
If multiple pinions are used to divide the torque load, then the load distribution is improved, but the calibration complexity and adjustment difficulty increase due to over-determination
Solution Approach 1:
The exchangeable second rack portion serves as an intermediary calibration tool that simplifies the calibration process for multiple pinions. By using this dedicated calibration rack with precisely controlled geometry, the complex task of calibrating multiple pinions simultaneously becomes more manageable and less prone to errors.
Data Source
Figure 1
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AI summary
Method of exchanging a rack of a rack and pinion drive arrangement, which arrangement comprises a first toothed rack (10) and a gearbox (20) comprising a plurality of pinions which are arranged to mesh with the first rack (10). The method comprises; providing a rack and pinion drive arrangement with a first rack (10) installed in meshing engagement with the pinions of the gearbox (21); providing a jig assembly comprising a second toothed rack (31) and a coupling arrangement (40, 50, 60); arranging the second rack (31) in longitudinal coaxial alignment with the first rack (10); connecting a first end (32a) of the second rack (31) to a proximal end (11b) of the first rack (10), by means of the coupling arrangement (40, 50, 60); bringing the second rack (31) into meshing engagement with the pinions of the gearbox (21) by linear displacement of the first (10) and second (31) rack, and disconnecting the first rack (10) from the second (31) rack. A jig assembly (30) for use when carrying out the method is also disclosed.