Nested Cylinder Actuator for Constant-Volume Hydraulics
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Solution Overview
Problem
Hydraulic systems with single-rod cylinder actuators face challenges due to fluid force and volume asymmetry, which are difficult to address without increasing complexity or size, especially in closed systems, and existing solutions like double-rod cylinders or accumulators come with performance and packaging penalties.
Innovation Solution
A five-chamber cylinder actuator design where a first cylinder is nested within a second cylinder, with a piston assembly having two pistons and two piston rods, creating five separable fluid chambers that maintain constant fluid volume by balancing fluid pressures across the chambers, eliminating the need for a third chamber and simplifying porting geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-rod cylinder actuator is used, then the device complexity is reduced, but fluid force and volume asymmetry occurs
Solution Approach 1:
The single-rod cylinder is segmented into multiple fluid chambers (first fluid chamber, second fluid chamber, third fluid chamber) separated by the piston. This segmentation allows each chamber to be independently managed for fluid volume, enabling constant-volume operation while maintaining the simple single-rod structure. The piston divides the cylinder into distinct zones that can be controlled separately to achieve force and volume symmetry.
2Stability of the object's composition
If a double-rod cylinder actuator is used to eliminate volume asymmetry, then fluid volume symmetry is improved, but the cylinder size envelope increases
Solution Approach 1:
The invention uses a nested chamber configuration where the first fluid chamber, second fluid chamber, and third fluid chamber are arranged concentrically within the single-rod cylinder. The piston creates nested fluid zones that allow constant-volume operation without requiring the larger double-rod structure. This nesting approach achieves volume symmetry while maintaining a compact size envelope.
3Stability of the object's composition
If an accumulator is added to accommodate volume asymmetry, then fluid volume symmetry is improved, but additional fluid control componentry is required
Solution Approach 1:
The invention extracts the accumulator function from the system by integrating constant-volume capability directly into the cylinder structure through the nested fluid chambers. The third fluid chamber acts as an integrated volume compensation mechanism, eliminating the need for external accumulators and associated fluid control components. This extraction approach maintains volume symmetry while reducing overall system complexity.
4Ease of operation
If a single-rod cylinder is used, then mounting simplicity is improved, but bidirectional damping capability is limited
Solution Approach 1:
The invention applies different local qualities to different fluid chambers to enable bidirectional damping. The first fluid chamber and second fluid chamber are configured with specific compressibility characteristics, while the third fluid chamber provides volume compensation. This local differentiation of fluid chamber properties allows the simple single-rod structure to achieve reliable bidirectional damping 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 five-chamber design achieves constant fluid volume without the size and complexity penalties of double-rod actuators, providing bidirectional damping and hydraulic locking with simplified mounting and porting, while maintaining efficient fluid communication and pressure balance.
Implementation Method 1
maintain constant fluid volume by balancing fluid pressures across the chambers
Implementation Method 2
The first volume of working fluid being only in contact with the first side of one of the first or second pistons, and the second volume of working fluid being only in contact with the second side of at least one of the first and second pistons
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A cylinder actuator includes a body assembly and a piston assembly. The body assembly includes a first cylinder nested concentrically within a second cylinder. The piston assembly slides linearly within the first and second cylinders. The piston assembly includes a first piston assembly end and a second piston assembly end. The first piston assembly end includes first and second pistons. The first piston moves within the first cylinder. The second piston moves within the second cylinder. The piston assembly includes first and second piston rods. The first piston rod extends from the first piston through a first end of the first cylinder. The second piston rod extends from the second piston through a first end of the second cylinder. The piston rods are joined at the second end of the piston rod assembly located outside of the first and second cylinders.