Ball Screw Nut Sleeve Structure for Weldable Hard Ball Grooves
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Solution Overview
Problem
The production of threaded nuts for ball screw drives is economically challenging due to the need for materials that balance weldability and hardness, leading to complex material selection and production efforts.
Innovation Solution
A threaded nut design featuring an inner and outer sleeve made of sheet metal, where the inner sleeve is molded into the outer sleeve to form a non-rotatable connection, allowing for the selection of steels based on weldability and hardness, and utilizing forming technology to create ball grooves efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single material is used for the threaded nut to ensure both weldability and hardness, then material selection is restricted and production effort increases, but if different materials are used for different parts, then production complexity increases
Solution Approach 1:
The threaded nut is divided into two separate sleeves (inner sleeve and outer sleeve) that can be manufactured independently. The outer sleeve is made from material optimized for weldability, while the inner sleeve is made from material optimized for hardness and ball groove formation. This segmentation allows each component to be produced with the most suitable material for its specific function, reducing overall production complexity while maintaining both weldability and hardness requirements.
Solution Approach 2:
The threaded nut employs a composite structure consisting of two different sheet metal materials. The outer sleeve uses a material with good weldability for easy attachment to machine parts, while the inner sleeve uses a material that is easily hardenable for durable ball grooves. This composite approach combines the advantages of different materials in a single functional component, resolving the contradiction between weldability and hardness requirements.
2Strength
If carburization is applied to achieve sufficient hardness for ball grooves, then hardness is improved, but production time and cost increase
Solution Approach 1:
The inner sleeve is separated from the outer sleeve, allowing the inner sleeve to be made from a material that is naturally easily hardenable. This eliminates the need for time-consuming carburization processes while still achieving the required hardness for durable ball grooves. The segmentation enables direct use of inherently hard materials without additional heat treatment time.
Solution Approach 2:
Instead of applying a time-consuming surface hardening process like carburization to a weldable material, the invention changes the material parameter by selecting an easily hardenable sheet steel for the inner sleeve. This material selection approach achieves the desired hardness directly through material properties rather than through extended chemical heat treatment processes, significantly reducing production time.
3Stability of the object's composition
If the inner sleeve material is molded into the outer hole, then a non-rotatable connection is achieved, but forming complexity increases
Solution Approach 1:
The formation of the ball groove on the inner sleeve and the molding of inner sleeve material into the outer hole are combined into a single integrated forming operation. The forming tool that creates the helical ball groove simultaneously displaces material into the outer hole, achieving both the functional ball groove and the rotational locking connection in one step. This merging of operations reduces overall forming complexity despite the sophisticated material displacement required.
Solution Approach 2:
The inner sleeve material itself serves dual purposes: it forms the ball groove geometry and simultaneously fills the outer hole to create the non-rotatable connection. The material displacement required for ball groove formation automatically provides the locking mechanism, eliminating the need for separate operations to achieve rotational stability. The structure is self-servicing, where the primary forming action creates both functional and structural benefits.
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
This design facilitates a cost-effective production process by enabling the selection of suitable steels for each sleeve, ensuring a strong and weldable threaded nut while reducing production complexity and costs.
Implementation Method 1
Material of the inner sleeve is molded into the outer hole of the outer sleeve with a forming tool that acts on the inner circumference of the inner sleeve from radially inside and deforms the material thereof
Data Source
AI summary
The disclosure relates to a threaded nut of a ball screw drive. The threaded nut includes an inner sleeve made of sheet metal and an outer sleeve made of sheet metal. The inner and outer sleeves are nested axially in one another to form a nut sleeve. A thread of the nut sleeve is helically wound about a longitudinal axis of the threaded nut and forms a ball groove on the inner circumference of the inner sleeve. The outer sleeve is provided along the thread with at least one outer hole into which material of the inner sleeve is molded.