Splined and Threaded Marine Drive Shaft for Compact Gear Case
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Solution Overview
Problem
Existing marine drive units face challenges in compact design when multiple units are installed on a single boat's transom, leading to potential interference and damage, as they require additional space for clamping and preloading mechanisms that are not efficiently integrated with the existing shaft structures.
Innovation Solution
The implementation of propeller shafts with external splines and threads that allow for axial clamping and preloading of driven gears without requiring access to the end of the shaft, enabling a more compact gear case design by using nuts to secure the gears in place, thus reducing overall axial dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If traditional clamping and preloading mechanisms are used on marine drive shafts, then the gears can be securely held, but the axial dimensions of the gear case increase, preventing compact design
Solution Approach 1:
The patent combines the clamping function and preloading function into a single integrated nut structure that threads onto the propeller shaft. This merged mechanism eliminates the need for separate clamping and preloading components, thereby reducing axial dimensions while maintaining secure gear attachment. The nut simultaneously performs both functions by engaging with the threaded bore in the gear and the external threads on the shaft.
Solution Approach 2:
The nut structure serves multiple functions: it acts as both a clamping element to secure the gear to the shaft and a preloading element to apply axial force to the gear. This multi-functional design eliminates the need for dedicated separate components for each function, achieving compact axial dimensions without sacrificing structural integrity or gear security.
2Reliability
If additional space is allocated for clamping mechanisms, then gear security is improved, but the overall drive unit size increases, causing interference between multiple drive units
Solution Approach 1:
The patent merges the clamping and preloading functions into a single nut structure, eliminating the need for additional space-consuming separate mechanisms. This integrated approach maintains reliable gear attachment while minimizing the overall volume of the drive unit, allowing multiple units to be installed on a single transom without interference.
3Ease of manufacture
If conventional shaft designs are used, then manufacturing is simpler, but the axial space requirements prevent compact gear case design
Solution Approach 1:
Instead of providing internal threading within the shaft (which would consume axial space), the patent inverts the approach by providing external threads on the shaft surface. This allows the nut to engage from the end of the shaft, eliminating the need for deep internal threaded bores and reducing axial dimensions while maintaining ease of manufacture through standard external threading processes.
Data Source
AI summary
A propeller shaft includes a cylindrical outer surface having a series of external splines formed thereupon and having a series of external threads formed in the series of external splines. The series of external splines engages with a mating series of internal splines on a driven gear. The series of external threads engages with a mating series of internal threads on a nut that holds the driven gear axially in place on the propeller shaft. A shaft for a marine drive unit and a marine drive assembly are also described.