Linear Actuator With Integrated VFD for Precise Speed and Positioning

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Solution Overview

Problem

Existing linear actuators lack integrated solutions for efficient speed control and positioning accuracy, often requiring external variable frequency drives that increase complexity and reduce motor lifespan due to high inrush currents and shock loads.

Innovation Solution

A linear actuator with an integrated variable frequency drive (VFD) and a gearbox, coupled with an AC motor and screw assembly, which includes a position sensor and cooling fins for heat dissipation, allowing for reduced space requirements and improved control algorithms for precise positioning and extended motor life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If an external variable frequency drive is used for speed control, then speed control capability is achieved, but device complexity increases and installation space requirements increase

Engineering Contradiction:

Improvespeed control capabilityVSAvoiddevice complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The variable frequency drive is integrated directly into the actuator housing, merging the motor control function with the actuator structure. This eliminates the need for separate external VFD mounting and reduces overall system complexity while maintaining full speed control capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The actuator housing serves multiple functions: it encloses the motor, provides structural support, and acts as the mounting platform for the variable frequency drive. This multi-functionality reduces the number of separate components needed in the system.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Speed

If an external variable frequency drive is used for speed control, then speed control capability is achieved, but installation space requirements increase

Engineering Contradiction:

Improvespeed control capabilityVSAvoidinstallation space

Core Design Contradiction:

SpeedVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

3Power

If high inrush currents are allowed during motor startup, then motor power is sufficient, but motor lifespan decreases due to shock loads

Engineering Contradiction:

Improvemotor powerVSAvoidmotor lifespan

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The variable frequency drive performs preliminary action by controlling the motor startup process. It gradually increases the motor speed from zero to the desired operating speed, preventing high inrush currents and shock loads that would otherwise occur during direct-on-line startup, thereby extending motor lifespan while maintaining full power capability.

Inventive Principle:

Principle #10Preliminary action

4Device complexity

If the variable frequency drive is mounted inside the actuator housing, then installation complexity is reduced, but heat dissipation becomes more challenging

Engineering Contradiction:

Improveinstallation complexityVSAvoidheat dissipation

Core Design Contradiction:

Device complexityVSTemperature

Solution Approach 1:

The removable cover is specifically designed with heat dissipation features (such as vents or fins) to provide localized thermal management for the variable frequency drive. This allows the VFD to be mounted inside the housing while addressing the heat dissipation challenge through targeted design modifications to the cover structure.

Inventive Principle:

Principle #3Local quality

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 integrated VFD and gearbox configuration enhances positioning accuracy, reduces shock loads, increases motor lifespan, and allows for adjustable speed, increasing the duty cycle and reducing installation complexity while facilitating efficient heat transfer and easy maintenance.

Implementation Method 1

The VFD (61) is mounted on the bracket (73) adjacent to the inside surface (70) of the removable cover (28) to facilitate heat transfer out of the actuator housing (31) through the removable cover (28)

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

The removable cover (28) has a plurality of cooling fins (64) disposed on an outer surface (67) thereof

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS11808327B2Linear actuator with an integrated variable frequency drive

Publication Date: 2023.11.07 COLUMBUS MCKINNON CORP

AI summary

A linear actuator with an integrated variable frequency drive. The linear actuator includes an AC motor. A screw assembly with an output shaft is mechanically coupled to the AC motor. An extension tube is provided with a front mount. The extension tube is configured and arranged to be driven in translatory motion in either direction by the screw assembly. A cover tube encloses the extension tube and screw assembly. An actuator housing is operatively associated with the screw assembly and the AC motor. The actuator housing has a removable cover. A bracket is attached to the inside surface of the removable cover. The VFD is mounted within the actuator housing. The VFD may be mounted on the bracket adjacent to the inside surface of the removable cover. The removable cover may facilitate heat transfer out of the actuator housing.