Rotary Piston Actuator Central Actuation Assembly
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Solution Overview
Problem
Rotary hydraulic actuators face challenges in maintaining positional accuracy due to internal leakage, which is difficult to minimize in typical rotary designs, especially in applications requiring long-term load holding without external fluid power, such as aircraft flight controls.
Innovation Solution
A rotary piston-type actuator design featuring a central actuation assembly with a radial recess and commercially available seal assemblies, similar to those used in linear actuators, to create a compact and lightweight system that maintains rotational position with minimal leakage, using pressurized fluid to rotate the rotor shaft and maintain position by blocking fluid ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If typical rotary vane or rotary piston configurations are used, then rotational actuation is achieved, but internal leakage prevents leak-free performance and positional accuracy
Solution Approach 1:
The actuator is divided into a stationary housing containing the piston and arcuate chamber, and a rotatable rotor assembly containing the vane. This segmentation allows the piston to remain stationary while the rotor rotates, enabling the use of linear piston sealing techniques in a rotary application. The stationary piston with radial seals can maintain leak-free performance while the rotor assembly handles the rotational motion.
2Duration of action of stationary object
If rotary actuator designs are used for long-term load holding, then continuous inertial loading is achieved, but internal leakage causes positional drift over time
Solution Approach 1:
The actuator is pre-filled with hydraulic fluid that is trapped between the piston and the rotor vane. This preliminary action of filling and sealing the chamber before operation allows the system to hold position for extended periods. The trapped fluid column acts as a mechanical memory, maintaining positional information without requiring continuous external fluid supply or active control.
3Measurement precision
If external fluid power supply is used for position holding, then positional accuracy is maintained, but system complexity and external dependencies increase
Solution Approach 1:
The actuator uses its own internal hydraulic fluid and trapped pressure to maintain position, without requiring external fluid power supply during the holding phase. The stationary piston and sealed chamber create a self-contained system that maintains position through the trapped fluid column, making the system independent of external fluid sources once actuated.
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 provides positional holding characteristics similar to linear piston-type actuators in a compact rotary format, maintaining rotational position with less than 5 degrees of movement under load, using standard seal technology and achieving constant torque over stroke.
Implementation Method 1
applying pressurized fluid to the first pressure chamber, urging the first piston partially outward from the first pressure chamber to urge rotation of the rotary output shaft
Implementation Method 2
a first seal, the first cavity, and the first piston define a first pressure chamber
Data Source
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AI summary
A rotary actuator (2900) includes a housing defining an arcuate chamber including a cavity, a fluid port in fluid communication with the cavity, and an open end. A rotor assembly includes an output shaft (2912) and a rotor arm (2914) extending outward. An arcuate- shaped piston is disposed in said housing for reciprocal movement in the arcuate chamber through the open end, wherein a seal, the cavity, and the piston define a pressure chamber, and a portion of the piston contacts the first rotor arm. A central actuation assembly (2960) includes a central mounting point (2964) formed in an external surface of the output shaft, said central mounting point proximal to the longitudinal midpoint of the shaft, and an actuation arm (2962) removably attached at a proximal end to the central mounting point, said actuation arm adapted at a distal end for attachment to an external mounting feature of a member to be actuated.