Multi-lead Thread Axle Assembly Cross-threading
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Solution Overview
Problem
Conventional single-lead thread engagements in vehicle wheel axle assemblies are time-consuming and prone to cross-threading, requiring full revolutions for initial engagement and multiple turns for axial advancement, while also being costly and structurally weak due to high thread depth, and quarter-turn fasteners have limited axial engagement and high contact stresses.
Innovation Solution
Implementing a multiple-lead thread profile with multiple thread starts, such as a double-lead or triple-lead thread, which reduces the angle of rotation required for initial engagement and the number of turns needed for axial advancement, providing faster and more secure thread engagement with reduced cross-threading propensity and increased axial load-bearing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a single-lead thread engagement is used, then the thread structure is simple and easy to manufacture, but the installation and removal time is excessive requiring full revolutions for engagement
Solution Approach 1:
The thread is segmented into multiple leads (e.g., double-lead, triple-lead) where each lead is a separate helical path. This segmentation allows the bolt to engage the nut along multiple simultaneous paths, reducing the number of revolutions needed for full engagement while maintaining manufacturing feasibility through standardized thread cutting methods.
Solution Approach 2:
The invention transitions from a single helical path (one-dimensional engagement) to multiple helical paths winding around the same cylinder (multi-dimensional engagement). This adds the dimension of parallel thread paths, enabling faster axial advancement per rotation without increasing radial complexity.
2Reliability
If a single-lead thread engagement is used, then the thread structure is simple, but the propensity for cross-threading is high
Solution Approach 1:
By dividing the single thread path into multiple segmented leads spaced circumferentially, the invention creates multiple independent engagement points. This segmentation distributes the loading and alignment requirements, reducing the likelihood that misalignment will cause cross-threading while maintaining the same basic thread form.
Solution Approach 2:
The invention changes the lead parameter from a single value to multiple values (e.g., lead1, lead2, lead3) while keeping the pitch constant. This parameter modification increases the angular spacing between engagement points, providing a larger tolerance window for proper alignment and reducing cross-threading risk.
3Strength
If a multiple-lead thread profile is used, then the axial load-bearing capacity is increased, but the thread depth and material removal increase
Solution Approach 1:
Instead of increasing thread depth radially to achieve higher load capacity, the invention utilizes the circumferential dimension by adding multiple thread leads. This allows the same or greater axial load-bearing capacity to be achieved through parallel engagement paths without increasing the radial material removal, thus preserving more of the original material.
Solution Approach 2:
The invention changes the load-bearing mechanism from depending on single-thread depth to depending on multi-thread contact area. By increasing the number of leads while maintaining or reducing pitch, the total engaged surface area increases, providing higher load capacity with less material removal compared to a single deep-thread design.
4Productivity
If a multiple-lead thread profile is used, then the number of turns for axial advancement is reduced, but the thread manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into creating multiple identical thread leads offset from each other. This can be achieved through indexed cutting operations or specialized single-point threading tools that can cut multiple leads in sequence, making the manufacturing complexity manageable while achieving high engagement speed.
Solution Approach 2:
The invention modifies the threading parameters by introducing multiple leads with specific angular spacing (e.g., 180 degrees for double-lead, 120 degrees for triple-lead). These standardized parameter changes allow for the development of dedicated manufacturing tools and processes that efficiently produce multi-lead threads without excessive complexity.
Data Source
AI summary
A vehicle wheel hub assembly including: an axle assembly that is rotationally stationary about an axial axis; a hub shell rotatable about the axle assembly and about the axial axis; and a frame member to interface with the hub assembly. The axle assembly is secured to the frame member by means of a multi-lead threadable engagement. This threadable engagement may be manipulated between a threadably engaged arrangement to provide a retaining means to retain the hub shell to the frame member and a threadably released arrangement serving to remove the retaining means.