Screw-Nut Linear Drive Assembly With Torque-Decoupling Force Transfer
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Solution Overview
Problem
Existing screw and nut linear drive assemblies experience increased friction and wear due to torque transmission from the push rod to the nut, leading to mechanical stress and degradation.
Innovation Solution
The axial force transfer arrangement incorporates a sequential configuration of axial force transferring components that allow tilting movements about two perpendicular axes, decoupling torque transfer to the nut by orienting the first axis perpendicular to the screw axis and enabling tilting of components to absorb torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If force is transmitted from the push rod to the nut through the axial force transfer arrangement, then the member to be actuated is driven, but torque is transmitted to the nut causing increased friction and wear
Solution Approach 1:
The axial force transfer arrangement is segmented into multiple components (first axial force transferring component, second axial force transferring component, and optional third axial force transferring component) arranged in sequence between the nut and push rod. This segmentation allows each component to handle specific portions of the force transmission while enabling tilting movements that prevent torque transmission to the nut, thereby resolving the contradiction between actuation capability and reduced friction/wear.
Solution Approach 2:
The first and second axial force transferring components act as intermediaries between the nut and push rod. These intermediate components are configured to tilt about a first axis perpendicular to the screw axis, absorbing torque through their tilting capability while still transmitting axial force. This intermediary mechanism enables force transmission without transmitting harmful torque to the nut, resolving the friction and wear issue.
2Ease of operation
If the push rod is offset from the screw axis to act on the clutch lever, then the clutch lever can be pivoted effectively, but torque acts on the pressure piece and nut increasing mechanical stress
Solution Approach 1:
The axial force transferring components are designed with dynamic tilting capability about the first axis. This dynamic feature allows the components to adapt their orientation based on the applied load and offset position of the push rod, absorbing torque through controlled tilting movements while maintaining effective force transmission to pivot the clutch lever. This resolves the contradiction between ease of operation and reduced mechanical stress.
Solution Approach 2:
The solution introduces a new degree of freedom by allowing tilting movements about the first axis (which is perpendicular to the screw axis). This additional dimensional movement capability enables the axial force transferring components to absorb torque that would otherwise be transmitted to the pressure piece and nut, while still maintaining effective linear actuation of the clutch lever.
Data Source
AI summary
A screw and nut linear drive assembly includes a housing, a screw within the housing, an electric motor for rotating the screw, a nut which is driven, when the screw is rotated, to move linearly in a longitudinal direction coinciding with the screw axis, and an axial force transfer arrangement to transfer force from the nut to a push rod to be connected to a member to be actuated by the assembly. The transfer arrangement includes a sequential arrangement of a first and a second axial force transferring component in force transmitting contact that are configured such that first contact points between the first and second axial force transferring components define a first axis (in a plane perpendicular to the longitudinal direction, about which the second axial force transferring component is capable of tilting with respect to the first axial force transferring component to reduce torque transfer to the nut).