Centre-Seeking Actuator Sealing Layout for Reduced Fluid Leakage
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Solution Overview
Problem
Known centre seeking actuators are prone to working fluid leakage due to seal abrasion, which is challenging to mitigate given the difficulty in achieving a uniform surface finish on the inner surface of the outer cylinder.
Innovation Solution
The centre seeking actuator incorporates second dynamic seals that act against the outside surface of the sidewall of the slave cylinder, rather than the inner surface of the outer cylinder, and may be coated with a high velocity oxygen fuel (HVOF) coating to reduce seal abrasion and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If second dynamic seals act against the outside surface of the slave cylinder sidewall, then seal abrasion and oil leakage are reduced, but the device complexity increases
Solution Approach 1:
The patent inverts the conventional seal arrangement by moving the dynamic seals from the inner surface of the outer cylinder to the outer surface of the slave cylinder sidewall. This inversion allows the seals to contact the externally finishable slave cylinder surface rather than the internally finishable outer cylinder surface, reducing seal abrasion and improving reliability.
2Reliability
If a coating is applied to the outside surface of the slave cylinder sidewall, then seal abrasion is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent applies a protective coating (such as HVOF coating) specifically to the outside surface of the slave cylinder sidewall where the dynamic seals make contact. This localized coating application provides enhanced durability and reduced abrasion at the critical sealing interface without requiring coating of the entire actuator assembly.
3Adaptability or versatility
If the outer cylinder has a through-hole for rod passage, then the actuator can extend and compress, but working fluid may leak through the hole
Solution Approach 1:
The patent segments the sealing function from the rod passage function by providing separate dynamic seals at the through-hole location. These seals are specifically positioned to prevent working fluid leakage through the rod passage opening while allowing the piston rod to move freely in and out of the outer cylinder.
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
This arrangement improves the surface finish on the outside surface of the slave cylinder, reducing seal abrasion and oil leakage compared to prior art configurations, while allowing for a more uniform and repeatable coating application.
Implementation Method 1
The coating can comprise a high velocity oxygen fuel (HVOF) coating comprising metal, metal alloy, ceramic, plastic or composite materials
Data Source
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AI summary
A centre seeking actuator (10) comprising: an outer cylinder (102); a slave cylinder (14) slidably disposed within the outer cylinder; a rod assembly (120, 122), the piston (122) of which is slidably disposed within the slave cylinder and the rod (120) of which extends from the outer cylinder; one or more first dynamic seals (121) arranged to act on a side wall of the rod to inhibit working fluid leaking from the outer cylinder; and one or more second dynamic seals (12) arranged to act on a sidewall of the slave cylinder to inhibit working fluid leaking from the outer cylinder.