Spring-Biased Filter Element Bypassing High Pressure Drop

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Solution Overview

Problem

Existing hydraulic system filters with fixed filter elements can cause a high pressure drop under certain conditions, such as cold startup, which is detrimental to pump operation.

Innovation Solution

A fluid filter assembly with a spring-biased filter element that moves to a bypass position when the pressure drop exceeds the spring force, allowing fluid to bypass the filter element, thereby reducing pressure on the pump.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fixed filter element is used in hydraulic systems, then filtration is maintained under normal conditions, but high pressure drop occurs under certain conditions such as cold startup

Engineering Contradiction:
Improvefiltration reliabilityVSAvoidpressure drop
Core Design Contradiction:
ReliabilityVSStress or pressure

Solution Approach 1:

The filter element is made movable rather than fixed, allowing it to dynamically adjust its position based on pressure differential. The filter assembly includes a filter element that can move between a filtration position and a bypass position, transitioning from static to dynamic operation to resolve the contradiction between maintaining filtration and avoiding high pressure drop

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system changes the operational state of the filter element based on pressure differential parameters. When pressure drop exceeds a threshold, the filter element moves to bypass position; when pressure drop is within acceptable range, it returns to filtration position, dynamically adjusting system parameters to resolve the contradiction

Inventive Principle:
Principle #35Parameter changes

2Device complexity

If a fixed filter element is used, then simple structure is maintained, but pump damage can occur under high pressure drop conditions

Engineering Contradiction:
Improvefilter structure simplicityVSAvoidpump damage from pressure drop
Core Design Contradiction:
Device complexityVSObject-affected harmful factors

Solution Approach 1:

A spring mechanism serves as an intermediary element between the filter element and the housing, providing the force necessary to move the filter element to bypass position when pressure differential is high. This intermediary mechanism protects the pump from pressure-related damage while maintaining relative structural simplicity

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The filter assembly uses the pressure differential itself as the driving force to move the filter element to bypass position when needed, and the spring provides the return force. The system serves itself by using its own operational parameters (pressure drop) to trigger the protective action, reducing the need for external control systems

Inventive Principle:
Principle #25Self-service

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 solution effectively mitigates high pressure drops during cold startup conditions, preventing damage to the pump while ensuring continuous fluid flow and filtration, with the filter element returning to its standard position as conditions normalize.

Implementation Method 1

A spring biases the face against a housing structure at the inlet

Methodology Applied
Scientific EffectSpring force: Spring

Implementation Method 2

A pressure drop across the filter assembly biases the filter element against the spring force such that if the pressure drop exceeds the spring force, the filter element can move to a bypass position

Methodology Applied
Scientific EffectPressure drop: Pressure Drop

Data Source

PatentEP2992941B1Fluid inlet screen being moveable to bypass position
Publication Date: 2020.01.22 HAMILTON SUNDSTRAND CORP
  • EP2992941B1 patent drawingFigure 1~3

AI summary

A fluid filter assembly (22) comprises an outer housing (24), a filter element (26) including a face (30), and a filter portion (28) extending from the face (30). The housing (24) has an inlet and an outlet. A spring (36) biases the face (30) against a housing structure (24) at the inlet. A pressure drop across the filter assembly (22) biases the filter element (26) against the spring force such that if the pressure drop exceeds the spring force, the filter element (26) can move to a bypass position. A hydraulic system (20) is also disclosed.