Linear Actuator Hydraulic Locking Without Mechanical Brakes
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Solution Overview
Problem
Existing linear actuators face challenges in maintaining a constant length despite external forces due to the need for complex valve configurations and mechanical brakes, which complicate design and operation.
Innovation Solution
A linear actuator design featuring a fluid-tight annular piston with a switching valve that connects the annular fluid space and the first region, allowing for hydraulic braking without mechanical brakes, using pressure relief valves to manage pressure and prevent damage to seals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical brake is used to lock the threaded spindle and maintain constant length, then the linear actuator can hold position against external forces, but the device complexity increases due to additional installation space and control requirements
Solution Approach 1:
The patent replaces the mechanical brake system with a hydraulic locking mechanism. The threaded nut itself is configured as a piston that can be held in position by hydraulic pressure in a fluid space, eliminating the need for separate mechanical brake components and their associated controls.
Solution Approach 2:
The threaded nut serves dual functions: it converts rotational motion to linear motion through threading, and simultaneously acts as a piston for hydraulic pressure transmission to maintain position. This multi-functionality eliminates the need for separate braking components.
2Reliability
If a valve configuration is used to connect the second region with the surroundings for pressure control, then the pressure in the second region can be limited, but the device complexity increases due to the need for flow connections from the movable extension arm tube
Solution Approach 1:
The patent extracts the pressure control function from a separate valve system and integrates it into the piston/ fluid space configuration. The threaded nut as a piston with fluid-tight sealing provides inherent pressure control without requiring additional valve components or flow connections.
Solution Approach 2:
The pressure control function is merged with the piston mechanism. The fluid-tight sealing between the piston and extension arm tube creates a self-contained pressure control system that eliminates the need for separate valve assemblies and their associated flow connections.
3Force
If the threaded nut is made large to provide sufficient hydraulically effective surface area, then the braking force is sufficient, but the linear actuator length increases
Solution Approach 1:
The patent transitions from a single-region hydraulic system to a two-region system with a fluid-tight piston. This creates an annular fluid space around the threaded spindle, providing large hydraulically effective surface area without increasing the overall length of the actuator, as the surface area is generated in the radial dimension rather than the axial dimension.
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 effectively holds the threaded nut in position using hydraulic pressure, preventing length changes under external forces and protecting components from damage, while simplifying the installation space and control mechanisms.
Implementation Method 1
the first region and the annular fluid space can be fluidically connected to one another by means of a switching valve having an open and a closed position
Implementation Method 2
using pressure relief valves to manage pressure and prevent damage to seals
Data Source
AI summary
A linear actuator has a screw drive having a threaded nut connected to an extension arm tube and a threaded spindle couplable to a motor. A first end of the spindle always projects into the tube and is connected to a piston which partitions an interior space formed by the tube into a first region on the side of the piston opposite to the nut and a second region on the side of the piston facing the nut. The regions are separated in a fluid-tight manner. The spindle is held in position since the nut comprises an annular piston that delimits an annular fluid space between a housing of the linear actuator and the tube in a fluid-tight manner, the hydraulically effective surface of which is the same size as that of the first region. The first region and the annular fluid space are fluidically connected by a switching valve.