Hollow Electromagnetic Brake for Extended Linear Actuator Travel

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Solution Overview

Problem

Existing linear actuators have a restricted moving distance for the ball screw output shaft due to the closed end of the rotary shaft, and they are prone to impurity intrusion into the electromagnetic brake device, which can reduce braking force.

Innovation Solution

A linear actuator design with a hollow electromagnetic brake device and a brake cover that allows the rotary shaft to pass through, incorporating a labyrinth structure to prevent impurities from entering, and a ball screw mechanism that extends beyond the rotary shaft's length, enhancing the moving distance and preventing contamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the electromagnetic brake device is attached to the closed second end of the rotary shaft, then the braking function is achieved, but the moving distance of the ball screw is restricted

Engineering Contradiction:

Improvemoving distance of ball screwVSAvoidbraking function

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The patent inverts the conventional design by making the electromagnetic brake device hollow to allow the rotary shaft to pass through, rather than attaching the brake to the closed end. This inversion enables the ball screw to extend beyond the rotary shaft and achieve longer travel distance while the brake device maintains its braking function through the hollow structure.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies nesting by placing the rotary shaft inside the hollow electromagnetic brake device, creating a nested configuration where the shaft passes through the brake device. This allows both components to coexist without interfering with each other's function, enabling extended ball screw travel while maintaining braking capability.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Length of moving object

If the rotary shaft is made open to allow ball screw extension, then the moving distance is increased, but impurities can intrude into the electromagnetic brake device

Engineering Contradiction:

Improvemoving distance of ball screwVSAvoidimpurity intrusion

Core Design Contradiction:

Length of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a seal as an intermediary component between the open second end of the rotary shaft and the electromagnetic brake device. This seal prevents impurities from entering the brake device while allowing the rotary shaft to pass through freely, thus maintaining both the extended travel distance and protection against contamination.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the potential harm of an open shaft structure (impurity intrusion) into a benefit by using the seal to selectively block contaminants while permitting necessary motion. The open structure provides extended travel, and the seal converts the risk of contamination into a controlled interface that maintains both openness and protection.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design achieves a longer moving distance for the ball screw output shaft while effectively blocking impurities, thus maintaining braking force and preventing contamination within the electromagnetic brake device.

Implementation Method 1

The electromagnetic coil is configured to generate an electromagnetic force, when energized, which causes the rotary brake disc and the stationary brake disc to contact each other or separate from each other

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 2

The stationary brake disc is configured to stop rotation of the rotary shaft b means of a frictional force when brought into contact with the rotary brake disc

Methodology Applied

Scientific EffectFrictional force: Friction

Data Source

PatentUS8692428B2Linear actuator

Publication Date: 2014.04.08 SANYO DENKI CO LTD

AI summary

A linear actuator having an output shaft with a long moving distance is provided. A linear actuator includes a rotary shaft, a motor portion having a rotor and a stator, a ball screw mechanism including a ball screw nut fixed to a first end of the rotary shaft and a ball screw, a casing assembly including a first end bracket and a second end bracket, an electromagnetic brake device including a rotary brake disc, a stationary brake disc, and an electromagnetic coil, and a brake cover for covering the electromagnetic brake device. The electromagnetic brake device has a hollow structure allowing a second end of the rotary shaft to pass therethrough.