Screw-Nut Fluid Power Actuator for Precise Self-Locking Positioning
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Solution Overview
Problem
Conventional fluid power, electric, and electro-hydraulic linear actuators face issues such as imprecise position control, susceptibility to leaking, requirement for external locking devices, high costs for high-force applications, and difficulties in manual operation during power loss.
Innovation Solution
A fluid power actuator utilizing a screw and nut assembly with self-locking or recirculating ball screw geometry, combined with a motor or brake for precise control, provides high precision positioning, mechanical locking, and convenient manual backup operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional fluid power actuators are used, then high force capability is achieved, but position control precision deteriorates
Solution Approach 1:
The patent replaces the direct fluid power mechanical connection with a screw and nut assembly mechanism. The screw thread converts rotational motion from a motor into precise linear motion of the piston rod, providing mechanical advantage and precise position control while maintaining high force capability through the mechanical advantage of the thread geometry.
2Force
If conventional fluid power actuators are used, then high force capability is achieved, but reliability deteriorates due to leaking and drifting
Solution Approach 1:
The patent replaces the direct fluid power connection with a mechanical screw and nut assembly that provides inherent mechanical locking through friction in the thread interface. This mechanical linkage eliminates the leaking and drifting problems associated with fluid seals while maintaining high force transmission capability through the threaded connection.
3Measurement precision
If conventional electric linear actuators are used, then precise position control is achieved, but cost deteriorates for high-force applications
Solution Approach 1:
The patent merges the advantages of fluid power (high force capability at lower cost) with the precision control of electric actuators by combining a motor-driven screw mechanism with a fluid power piston. The motor provides precise rotational control for accurate positioning, while the fluid power piston delivers high force capability, creating a hybrid system that achieves both precision and affordability for high-force applications.
4Measurement precision
If conventional electric linear actuators are used, then precise position control is achieved, but ease of operation deteriorates during loss of electric power
Solution Approach 1:
The patent replaces the electric motor-driven mechanism with a manual screw and nut assembly that can be operated by hand or simple mechanical means. The threaded connection provides mechanical advantage that allows manual operation to move heavy loads, eliminating dependence on electric power while maintaining precise position control through the screw thread geometry.
5Force
If conventional electro-hydraulic linear actuators are used, then high force capability is achieved, but device complexity deteriorates
Solution Approach 1:
The patent extracts and separates the motor component from the hydraulic system, placing the motor at one end of the actuator and the hydraulic piston at the other, with the screw and nut assembly connecting them. This separation simplifies the overall packaging by eliminating the need to integrate motor, pump, and valve assemblies into a single complex unit, reducing device complexity while maintaining high force capability.
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 fluid power actuator achieves high precision positioning, mechanical locking, and convenient manual backup operation, overcoming the deficiencies of conventional actuators and ensuring reliable performance in precision material handling applications.
Implementation Method 1
a screw and nut assembly comprising a screw that couples the blind end of the cylinder to the nut, wherein the screw extends in part or in whole inside the piston rod
Implementation Method 2
the screw and nut assembly has a self-locking thread geometry (e.g., ACME threads)
Implementation Method 3
the screw and nut assembly has a recirculating ball screw or roller screw geometry for low friction operation
Data Source
AI summary
A fluid power actuator includes a housing, a piston rod assembly, and a screw and nut assembly. The housing includes a cylinder, a blind end cap, rod end cap, and mounting provisions. The piston rod assembly connects to an external load and is constructed and arranged to move relative to the fluid power actuator housing in response to changes in fluid pressure within the cylinder. The screw and nut assembly couples with the housing and the piston rod assembly. The screw and nut assembly is constructed and arranged to control movement of the piston rod assembly relative to the housing using a motor or a brake. Such a fluid power actuator provides precision positioning, is self-locking on loss of power, and allows back-up manual operation, making it well-suited for various material handling applications such as precision munitions loading, among others.