Compensating Drive Nut Assembly for Lead Screw Misalignment
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Solution Overview
Problem
Existing drive assemblies with lead screws often experience binding due to misalignment between the drive axis and the bearing axis, leading to increased friction and potential wear, which can result in reduced performance and increased maintenance costs.
Innovation Solution
A compensating drive nut assembly with a two-piece design featuring an inner and outer nut component, including anti-rotation features and a controlled clearance fit, decouples the lead screw drive from guiding bearings, allowing axial compliance while preventing rotation, thus reducing binding and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a lead screw is directly coupled to guiding linear bearings, then the structure is simple, but binding occurs due to misalignment between drive axis and bearing axis
Solution Approach 1:
The drive nut assembly is segmented into an inner nut component and an outer nut component. The inner nut threadably engages the lead screw while the outer nut provides bearing support. This segmentation allows the drive function and guiding function to be separated, enabling axial compliance in the inner nut while the outer nut maintains precise positioning, thereby eliminating binding caused by misalignment.
Solution Approach 2:
The compensating drive nut assembly acts as an intermediary between the lead screw and the guiding bearings. It decouples the drive axis from the bearing axis, allowing relative movement and compliance while maintaining the mechanical linkage. This intermediary structure absorbs misalignment and prevents direct transmission of binding forces to the lead screw.
2Manufacturing precision
If the lead screw drive is coupled to guiding bearings, then positioning is precise, but friction and wear increase due to binding
Solution Approach 1:
By separating the drive nut into inner and outer components, the patent allows the inner nut to accommodate axial compliance while the outer nut maintains precise positioning. This segmentation enables the system to achieve both precise positioning and reduced friction by preventing binding between the lead screw and bearings.
Solution Approach 2:
The patent introduces axial compliance as a new parameter in the drive nut assembly. This compliance allows the system to adapt to misalignment dynamically, maintaining optimal contact conditions and reducing friction and wear while preserving positioning precision through the controlled clearance fit between nut components.
3Device complexity
If a single-piece drive nut is used, then the assembly is simple, but it cannot accommodate axial compliance while preventing rotation
Solution Approach 1:
The drive nut is divided into two threadably coupled components: an inner nut that engages the lead screw and an outer nut that provides structural support. The anti-rotation feature is implemented on the inner nut, allowing it to prevent rotation while accommodating axial compliance. This segmentation provides both compliance and rotational control without significantly complicating the assembly process.
Solution Approach 2:
The inner nut is nested within the outer nut, with the inner nut's outer surface threadably engaging the outer nut's inner surface. This nested configuration allows the inner nut to move axially independently while the outer nut provides external support and positioning. The anti-rotation feature on the inner nut prevents it from rotating with the lead screw, achieving both compliance and rotational control.
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 effectively reduces binding and friction, enhances precision, and extends the lifespan of the lead screw by allowing it to operate with normal calculated friction, reducing wear and maintenance needs, and enabling the use of various materials and thread configurations.
Implementation Method 1
an inner nut component threadably coupled to the lead screw and an outer nut component threadably coupled to the inner nut component
Implementation Method 2
reduces binding and friction
Data Source
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AI summary
An objective mount assembly includes a housing having a body and a drive assembly supported by the body. The drive assembly includes a drive shaft, a lead screw rotatably coupled to the drive shaft, and a compensating drive nut assembly. The compensating drive nut assembly has an inner nut component threadably coupled to the lead screw and an outer nut component threadably coupled to the inner nut component. The objective mount assembly further includes an objective mount coupled to the drive assembly. Other aspects of the assembly are further disclosed.