Tie Rod End Dust Boot Bearing for High-Frequency Sickle Bars
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Solution Overview
Problem
Sickle bar assemblies in combine harvesters face durability issues due to tears in the dust boot caused by rotational stresses, leading to increased maintenance costs and downtime.
Innovation Solution
A tie rod end assembly featuring a plastic boot bearing with radially inwardly extending ribs and grooves for dynamic sealing engagement with the shank portion of the stud, reducing surface-to-surface contact and friction, and an elastic boot body with a polyoxymethylene material for improved durability and reduced stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional dust boot is used in the tie rod end, then the seal provides initial protection, but the boot tears due to rotational stresses from high-frequency operation
Solution Approach 1:
A boot bearing is introduced as an intermediary component between the dust boot and the rotating stud. The boot bearing has a bore that receives the stud and presents sealing surfaces that contact the stud during rotation, thereby mediating the interaction between the rotating stud and the dust boot. This intermediary absorbs the rotational stresses and friction, preventing the dust boot from tearing while maintaining sealing effectiveness.
Solution Approach 2:
The sealing interface is changed from direct contact between the dust boot and the rotating stud to contact between the boot bearing's sealing surfaces and the stud. The boot bearing is made of a material with appropriate friction characteristics that reduces stress on the dust boot. This parameter change in the sealing mechanism transforms the high-stress direct seal into a lower-stress mediated seal, improving durability.
2Productivity
If the ball stud rotates at high frequency relative to the housing, then the sickle bar oscillates to cut grain, but the dust boot tears from the rotational stresses
Solution Approach 1:
The boot bearing serves as a mediator that allows the high-frequency rotation necessary for productive cutting while protecting the dust boot from the associated stresses. The boot bearing's bore receives the rotating stud and its sealing surfaces contact the stud during high-speed rotation, absorbing the mechanical stresses and preventing them from being transmitted to the dust boot, thus maintaining both productivity and reliability.
3Reliability
If the boot bearing has a large surface-to-surface contact area with the stud, then sealing is effective, but friction and stress increase reducing operating life
Solution Approach 1:
The sealing surface of the boot bearing is segmented into multiple discrete contact zones rather than a continuous large-area contact. The boot bearing presents multiple radially inwardly extending sealing ribs or segments that contact the stud at separated points along the axial direction. This segmentation maintains sealing effectiveness through multiple contact points while significantly reducing the total surface-to-surface contact area, thereby lowering friction and stress to extend operating life.
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
The solution enhances the operating life and durability of the tie rod end by minimizing stress and friction, allowing the gearbox to operate at high frequencies with reduced maintenance needs.
Implementation Method 1
The plastic material of the boot bearing is polyoxymethylene. The dynamic sealing engagement between the plastic material of the boot bearing and the shank portion of the stud allows the gearbox to operate at a very high frequency while imparting minimal stresses into the elastic boot body
Data Source
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AI summary
The tie rod end includes a housing (30) with an inner bore that extends along a central axis. A stud is partially received in the inner bore and has a shank portion (42) which extends out of the inner bore for attachment with a gearbox. The tie rod end further includes an elastic boot body (50) which extends from a first boot end (52), which is sealed with the housing, to a second boot end (54). A boot bearing (56), which is made of a plastic material, is secured with the second boot end. The boot bearing is in a dynamic sealing engagement with the shank portion of the stud. The boot bearing presents a plurality of radially inwardly extending and annularly-shaped ribs (62) that contact the shank portion.