Three-Position Pneumatic Cylinder Without Position Sensors
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Solution Overview
Problem
Existing pneumatic cylinders with three positions face challenges in maintaining precise control over piston rod movements and adapting to varying stroke lengths without requiring complex position sensing mechanisms.
Innovation Solution
A pneumatic cylinder design with a first and second piston, each with a cushion assembly and flow rate control valves, allowing differential pressure control to achieve three distinct positions of the piston rod, including a fully retracted, fully extended, and discrete intermediate position, without needing position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If back-to-back cylinders are used to achieve three positions, then position control is achieved, but the cylinder casings move relative to a fixed reference point causing instability
Solution Approach 1:
The patent merges two cylinder assemblies into a single integrated structure where both pistons operate within a common casing system. The first piston operates in a first cylinder, and the second piston operates in a second cylinder that is integrated with the first, sharing common mounting points and reference structures. This integration ensures that both cylinder casings remain stable relative to a fixed reference point while achieving three-position control through coordinated piston movements.
2Measurement precision
If series cylinders are used to achieve three positions, then position control is achieved, but the structure becomes complex requiring multiple tubes and connectors
Solution Approach 1:
The patent implements a nested configuration where the second piston and its rod are positioned within the space occupied by the first cylinder assembly. The second piston rod extends through the first cylinder, and the second cylinder is arranged concentrically or adjacently within the same structural envelope. This nesting reduces the overall footprint and simplifies the external structure while maintaining the three-position control capability through the coordinated action of both pistons.
3Measurement precision
If position sensors are added to achieve precise three-position control, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs mechanical self-service positioning mechanisms where the pistons and rods inherently define their positions through physical constraints and mechanical stops. The first piston has a rod that can be fully retracted, fully extended, or partially extended to engage with the second piston assembly. The second piston similarly has defined travel limits. These mechanical arrangements automatically establish three distinct positions without requiring external sensors, feedback systems, or complex control electronics, thereby maintaining simplicity while achieving precise position control.
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
Enables precise and adaptable movement of the piston rod to three positions using differential gas pressures, simplifying control and allowing easy adjustment for different stroke lengths and diameters, enhancing operational flexibility.
Implementation Method 1
a first flow rate control valve communicating this first chamber with the first port to control the flow rate of the gas from this first chamber to the first port as the first piston moves toward its extended position
Data Source
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AI summary
A pneumatic cylinder with a piston rod movable to fully extended, intermediate and fully retracted positions. The cylinder may have a first head engaging one end of a first tube with a first piston slidably received therein, an intermediate connector engaging the other end of the first tube and one end of a second tube with a second piston slidably received therein, and a second head engaging the other end of the second tube. The piston rod may be attached to the second piston for movement therewith and extend through the intermediate connector, first piston, first tube, and the first head to the exterior thereof.