Ball Screw Nut Retaining Ring Assembly for Compact Axial Locking
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Solution Overview
Problem
Conventional ball screw devices face challenges in preventing relative displacement between the nut and piston in the axial direction without increasing manufacturing costs, while also aiming to reduce device size and enhance load capacity.
Innovation Solution
The ball screw device incorporates a fitting cylinder with a retaining ring system, where the nut and fitting cylinder have matching outer diameters, and the retaining ring spans between grooves on both components to prevent axial displacement, allowing for press or clearance fitting and ensuring effective axial force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piston is externally fitted over the nut to cover the entire nut, then relative displacement in the axial direction between the nut and piston is prevented, but the device size increases and load capacity is restricted
Solution Approach 1:
The invention divides the fitting cylinder into two separate components: the nut and a separate fitting cylinder portion. This segmentation allows the fitting cylinder to be composed of multiple parts rather than requiring a single large component, thereby reducing the overall device size while maintaining the function of preventing axial displacement between components.
Solution Approach 2:
The invention employs a nested configuration where the nut is positioned inside the fitting cylinder, and the retaining ring is nested within grooves on both components. This nesting arrangement allows compact integration of multiple functional elements, preventing axial displacement without requiring the fitting cylinder to externally cover the entire nut, thus reducing device size.
2Reliability
If the piston is externally fitted over the nut to cover the entire nut, then relative displacement in the axial direction between the nut and piston is prevented, but the load capacity is restricted
Solution Approach 1:
By segmenting the fitting cylinder into separate components (nut and fitting cylinder portion), the invention allows each component to be optimized independently for load-bearing capacity. The nut can be designed with appropriate wall thickness and material properties to handle axial loads, while the separate fitting cylinder portion provides the necessary constraint without unnecessarily restricting the nut's load capacity.
Solution Approach 2:
The nested arrangement of the retaining ring within grooves on both the nut and fitting cylinder creates an efficient load path. The retaining ring transfers axial forces between the nut and fitting cylinder through the groove interfaces, enabling effective load transmission without requiring the fitting cylinder to completely enclose the nut, thus preserving load capacity.
3Reliability
If a retaining ring is engaged with the inner peripheral surface of the piston to prevent axial displacement, then relative displacement is prevented, but manufacturing cost increases
Solution Approach 1:
The invention segments the retention mechanism by providing separate grooves on both the nut and fitting cylinder portions, with the retaining ring spanning between them. This segmentation allows each component to be manufactured independently using standard machining processes, avoiding the need for complex integrated retention features that would increase manufacturing cost.
Solution Approach 2:
The retaining ring is nested within grooves that are machined into the surfaces of the nut and fitting cylinder. This nested groove configuration uses simple, conventional machining operations to create the retention features, avoiding complex assembly steps or specialized manufacturing processes, thereby controlling manufacturing costs while effectively preventing axial displacement.
Data Source
AI summary
The nut has a first fitting surface provided with a first retaining ring groove on an end portion on the other side in the axial direction; the fitting cylinder, at an end portion on the one side in the axial direction, has a second fitting surface provided with a second retaining ring groove in a portion facing the first retaining ring groove with regard to a radial direction; and the retaining ring is engaged so as to span between the first retaining ring groove and the second retaining ring groove.