Hydrostatic Shoe Face Seal for Low-Leakage Swashplate Contact
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Solution Overview
Problem
Hydraulic piston pumps and motors experience significant volumetric losses and increased wear due to fluid leakage through the shoes that interface with the swashplate, particularly in low-speed applications where leakage is more pronounced.
Innovation Solution
A shoe design incorporating a face seal and elastomeric seal within a hydrostatic bearing, utilizing low-friction materials and preloaded C-shaped seals to minimize fluid leakage and improve force balance, reducing friction and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional shoes without face seals are used, then the device complexity is lower, but fluid leakage increases and volumetric efficiency deteriorates
Solution Approach 1:
The shoe is divided into multiple functional segments: an upper portion receiving the piston, a lower portion contacting the swashplate, a counterbore formed in the lower portion, and a vertical channel extending through both portions into the counterbore. This segmentation allows each part to perform its specific function while collectively solving the leakage problem.
Solution Approach 2:
A seal is introduced as an intermediary component disposed within the counterbore and extending around its circumference. This seal acts as a mediator between the hydraulic piston and the swashplate interface, preventing fluid leakage through the shoe while maintaining the necessary mechanical interface.
2Loss of substance
If shoes without proper sealing are used, then manufacturing is simpler, but fluid leakage through shoes increases particularly in low-speed applications
Solution Approach 1:
The counterbore is pre-formed in the lower portion of the shoe, and the vertical channel is pre-formed extending into the counterbore. These preliminary structural preparations allow the seal to be properly positioned and preloaded, ensuring effective sealing before the shoe enters service.
Solution Approach 2:
The seal is preloaded within the counterbore, creating a predetermined contact pressure between the seal and the counterbore surface. This parameter change (applying preload force) ensures the seal maintains sufficient contact pressure to prevent fluid leakage without requiring complex adjustment mechanisms.
3Loss of substance
If face seals are added to the shoe, then fluid leakage is reduced, but friction and wear characteristics need optimization
Solution Approach 1:
The seal functions as a flexible thin film component disposed within the counterbore. This flexible membrane structure allows the seal to conform to the counterbore surface while maintaining continuous contact to prevent fluid leakage, and its flexibility accommodates minor misalignments or surface irregularities.
Solution Approach 2:
The shoe incorporates a combination of materials with different properties: the shoe body structure, the seal material with low friction characteristics, and the elastomeric material. This composite approach allows each material to be optimized for its specific function - structural integrity, sealing, and friction reduction.
4Reliability
If seals are not preloaded, then the device is simpler, but sealing effectiveness decreases and fluid leakage increases
Solution Approach 1:
The seal is designed to be self-loading through its placement within the counterbore and the application of preload force. The preload mechanism allows the seal to self-adjust and maintain optimal contact pressure without requiring external control systems or complex adjustment mechanisms, ensuring reliable sealing.
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 proposed shoe design significantly reduces fluid leakage and wear, enhancing volumetric efficiency and extending the usable life of hydraulic piston pumps and motors, especially in low-speed applications.
Implementation Method 1
a seal disposed within the counterbore and extending around a circumference of the counterbore
Implementation Method 2
the face seal is comprised of a low friction material
Implementation Method 3
the elastomeric seal is disposed between the face seal and the lower portion
Data Source
AI summary
A shoe for use with a hydraulic piston motor or pump is disclosed herein. The shoe includes an upper portion configured to receive the hydraulic piston, a lower portion configured to contact a swashplate, a counterbore formed in the lower portion, a vertical channel extending through the upper portion and the lower portion into the counterbore, and a seal disposed within the counterbore and extending around a circumference of the counterbore.