Fluid Cushion Piston Seal With Expanding Ring for Low Friction
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Solution Overview
Problem
Conventional sealing devices for pistons, especially in high-temperature applications, face challenges with lubrication issues due to oil coking and limited durability of materials like PTFE and metal cutting segments, and they generate significant friction losses and are not suitable for dry air compressors or high-temperature environments.
Innovation Solution
A fluid cushion sealing device using a continuous perforated ring with a pressure distribution chamber and calibrated orifice, which allows the ring to adjust diameter under fluid pressure, maintaining a seal without lubrication and minimizing friction, compatible with temperatures up to a thousand degrees Celsius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sealing devices (rings, segments) are used for piston sealing, then sealing effectiveness is improved, but friction losses increase and durability decreases at high temperatures
Solution Approach 1:
The patent applies hydraulic principles by introducing a fluid cushion (liquid or gas) between the piston and cylinder wall to create a hydrodynamic seal. This fluid film replaces direct solid-to-solid contact, eliminating friction losses while maintaining sealing effectiveness. The fluid pressure generates a lift force that separates the piston from the cylinder, allowing the piston to float on the fluid cushion without mechanical contact.
Solution Approach 2:
The invention replaces the conventional mechanical sealing system (rings, segments with physical contact) with a non-contact fluid cushion system. Instead of relying on mechanical friction and wear for sealing, the system uses fluid dynamics to create a separating film that provides both sealing and lubrication, substituting mechanical interaction with hydrodynamic interaction.
2Loss of energy
If lubrication is applied to reduce friction, then friction losses decrease, but oil coking occurs at high temperatures reducing reliability
Solution Approach 1:
The fluid cushion acts as an intermediary substance between the piston and cylinder wall, preventing direct contact and eliminating the need for conventional oil lubrication. The fluid film (which can be water, air, or other non-coking fluids) provides the necessary lubrication effect without undergoing thermal degradation, thus maintaining both low friction and high-temperature reliability.
Solution Approach 2:
The invention changes the physical state and properties of the lubricating medium from conventional oil to a fluid that remains stable at high temperatures. By using a fluid cushion with appropriate physical properties (viscosity, compressibility) that do not decompose at operating temperatures, the system maintains effective lubrication without oil coking, enabling reliable operation at temperatures where conventional lubrication fails.
3Reliability
If small clearance is left between piston and cylinder for sealing, then sealing effectiveness improves, but manufacturing precision requirements increase
Solution Approach 1:
The invention transforms the static clearance concept into a dynamic fluid cushion system. Instead of relying on a fixed, precision-machined clearance to maintain sealing, the system uses the dynamic properties of the fluid cushion (pressure, viscosity, flow) to adapt and maintain the sealing film. The fluid cushion automatically adjusts to variations in clearance, compensating for manufacturing tolerances and maintaining effective sealing without requiring extremely precise clearances.
Solution Approach 2:
The fluid cushion serves as an intermediary that fills and maintains the clearance space between piston and cylinder. Rather than requiring the clearance to be precisely controlled and maintained, the fluid cushion actively occupies this space, creating a consistent sealing film that compensates for clearance variations. This intermediary fluid layer ensures sealing effectiveness regardless of the exact clearance dimension, reducing manufacturing precision requirements.
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 device achieves a robust, durable seal with minimal friction losses, suitable for high-temperature applications, and can be used in both gas and liquid sealing applications, enhancing energy performance and extending the operational range of sealing devices.
Implementation Method 1
a source of pressurized fluid (112) which delivers a flow of ring fluid (113) whose pressure is always greater than that prevailing in the chamber to be sealed (104)
Implementation Method 2
said ring (105) being sufficiently flexible to allow its diameter to increase or decrease relative to that of said groove under the effect of pressure from a source of pressurized fluid
Implementation Method 3
A fluid cushion sealing device... allows the ring to adjust diameter under fluid pressure, maintaining a seal without lubrication and minimizing friction
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a sealing device with a fluid cushion (100) for a piston (101) moving in a cylinder (102) and defining with the latter a chamber to be sealed (104), which comprises a perforated continuous ring (105) with a calibrated opening (111) passing through the radial thickness thereof and sealingly inserted in a ring groove (109) arranged in the piston (101) so as to define with said groove (109) a pressure-distribution chamber (119) connected to a pressurised fluid source (112) while an axially blind counter-pressure recess (115) is formed in an outer cylindrical surface of the ring (107) which faces the cylinder (102) and which includes the perforated continuous ring (105), the calibrated opening (111) leading into said recess (115).