Linear Stepper Motor Actuating Rod with Replaceable Coupling Shank

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Solution Overview

Problem

Existing linear stepper motors face challenges in replacing the actuating rod and coupling shank, making it difficult to adapt to customer-specific applications and extending the motor's service life.

Innovation Solution

A linear stepper motor design featuring a two-part actuating rod with fork legs and a coupling shank that can be easily assembled and locked in a non-axial direction, using a bearing shield with guide cut-outs and a dovetail press fit for secure attachment, and made from thermoplastic material for durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the actuating rod and coupling shank are made as integrated components in conventional linear stepper motors, then the structural integrity and stability are improved, but the adaptability and ease of replacement are worsened

Engineering Contradiction:
Improvestructural integrityVSAvoidcustomization capability
Core Design Contradiction:
Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The actuating rod is divided into multiple separable components: a spindle nut portion, fork legs, and a coupling shank. These segments can be independently replaced or customized while maintaining structural integrity through precise mechanical connections. The bearing shield is also segmented into multiple parts that can be assembled together.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The fork legs are inserted through guide cut-outs in the bearing shield, creating a nested arrangement where components fit within each other. The coupling shank is radially plugged onto the fork legs, forming another nested connection. This nesting provides secure attachment while allowing easy disassembly and replacement.

Inventive Principle:
Principle #7Nested doll (Nesting)

2Reliability

If the actuating rod components are securely locked in conventional designs, then the reliability under load is improved, but the ease of assembly and replacement is worsened

Engineering Contradiction:
Improvestability under loadVSAvoidassembly ease
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

Instead of requiring complex tools or procedures to secure components, the design uses simple radial plug-on connections that can be assembled and disassembled without tools. The fork legs pass through guide cut-outs and are secured by elastic deformable zones that provide automatic locking through material elasticity, reversing the typical approach where more secure connections require more complex assembly.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The elastic deformable zones in the coupling shank automatically engage with the fork legs through permanent mechanical preloading, creating a self-securing connection that does not require external fastening elements or complex assembly procedures. The components self-lock through their own elastic properties.

Inventive Principle:
Principle #25Self-service

3Manufacturing precision

If the bearing shield is constructed as a single-piece component, then the manufacturing precision and structural stability are improved, but the adaptability for different applications is worsened

Engineering Contradiction:
Improvecomponent precisionVSAvoidapplication-specific customization
Core Design Contradiction:
Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The bearing shield is divided into multiple complementary segments that can be assembled together. Each segment can be manufactured with high precision independently, and the segments are joined to form the complete bearing shield with guide cut-outs. This segmentation allows the same basic segments to be configured for different applications by assembling them in various ways or modifying individual segments.

Inventive Principle:
Principle #1Segmentation

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 enhances the service life of the linear stepper motor by allowing for easy customization and secure attachment of components, ensuring stable operation under tensile and thrust forces, and facilitating tool-less assembly and replacement.

Implementation Method 1

the rotor comprises a threaded shaft, the actuating rod comprises a spindle nut portion engaged with the threaded shaft

Methodology Applied
Scientific EffectMechanical threading: Screw

Implementation Method 2

two opposing parallel fork legs which link the spindle nut portion and the coupling shank and which are guided in a rotation-locked manner through the two guide cut-outs

Methodology Applied
Scientific EffectGeometric constraint: Geometry

Implementation Method 3

a bearing bridge forming a bearing seat for the threaded shaft

Methodology Applied
Scientific EffectRolling bearing: Ball Bearing

Implementation Method 4

The coupling shank has elastically deformable zones in the area of the hook-shaped contours of the fork legs

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP3361605B1Linear stepper motor and valve utilizing the same
Publication Date: 2020.02.19 JOHNSON ELECTRIC INTERNATIONAL AG
  • EP3361605B1 patent drawingFigure 1
  • EP3361605B1 patent drawingFigure 2
  • EP3361605B1 patent drawingFigure 3a

AI summary

A linear stepper motor (100) with an actuating rod (5) in a housing with a stator (1), a rotor (102) and a replaceable bearing shield (2) fixed on the stator (1) is provided. The rotor (102) includes a threaded shaft (103). The bearing shield (2) defines two guide cut-outs (7). The actuating rod (5) includes a spindle nut portion (9) engaged with the threaded shaft (103), a replaceable coupling shank (8) for a customer-specific actuating element, and two opposing parallel fork legs (6) which link the spindle nut portion and the coupling shank (8) and which are guided in a rotation-locked manner through the two guide cut-outs (7). The bearing shield (2) and the coupling shank (8) are easy to be replaced, thereby prolonging the service life of the linear stepper motor (100).