Cylinder Piston End Detection via Remote Pressure Sensing

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Solution Overview

Problem

Conventional cylinder operation state monitoring devices face issues with sensor corrosion in food-related applications and mechanical contact wear, and existing non-contact methods may not be suitable for environments where sensors and wiring are exposed to cleaning liquids.

Innovation Solution

A cylinder operation state monitoring device that uses pressure detecting units to determine the piston's position based on differential pressure changes within the cylinder chambers, eliminating the need for sensors near the cylinder and thus preventing corrosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If position detecting sensors are installed in the vicinity of the cylinder to detect piston arrival, then piston position detection is achieved, but the sensors and wiring may become corroded when exposed to cleaning liquids in food-related applications

Engineering Contradiction:
Improvepiston position detectionVSAvoidsensor corrosion resistance
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The invention extracts the position detection function from the mechanical contact domain (sensors near the cylinder) to the fluid pressure domain. By using pressure detecting units connected to the cylinder chambers via tubes, the system detects piston position indirectly through pressure changes, eliminating the need for sensors and wiring in the vicinity of the cylinder that would be exposed to cleaning liquids.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces fluid pressure as an intermediary medium to transfer information about piston position. Instead of directly detecting piston position with sensors near the cylinder, the system uses pressure changes in the cylinder chambers (transmitted through tubes to remote pressure detecting units) as a mediator to convey position information, thereby protecting against sensor corrosion.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If limit sensors are used to detect piston arrival through mechanical contact, then position detection is achieved, but the contact points experience wear and have limited service life

Engineering Contradiction:
Improvepiston arrival detectionVSAvoidcontact point service life
Core Design Contradiction:
Measurement precisionVSDuration of action of moving object

Solution Approach 1:

The invention replaces the mechanical contact-based detection system (limit sensors with contact points) with a fluid pressure-based detection system. By using pressure detecting units to monitor pressure changes in the cylinder chambers, the system eliminates mechanical contact between the piston rod and detection elements, thereby avoiding wear and extending service life.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention applies pneumatic/hydraulic principles by using fluid pressure changes in the cylinder chambers as the detection mechanism. Pressure detecting units monitor the pressure in each chamber, and the determination unit identifies piston arrival based on pressure differential changes, replacing mechanical contact with fluid-based sensing.

Inventive Principle:
Principle #29Pneumatics and hydraulics

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 reliable piston position detection without mechanical contact, preventing sensor corrosion and allowing safe use in food-related equipment by monitoring pressure changes within the cylinder chambers.

Implementation Method 1

a first pressure detecting unit configured to detect a pressure of the fluid inside the first tube, a second pressure detecting unit configured to detect a pressure of the fluid inside the second tube

Methodology Applied
Scientific EffectDifferential pressure sensing: Pressure Gradient

Data Source

PatentEP3450774B1Cylinder operation state monitoring device
Publication Date: 2021.07.07 SMC CORP
  • EP3450774B1 patent drawingFigure 1
  • EP3450774B1 patent drawingFigure 2
  • EP3450774B1 patent drawingFigure 3

AI summary

A monitoring device (10) has a first pressure sensor (50) that detects a first pressure value (P1) of a pressurized fluid in a first pipe (26), a second pressure sensor (52) that detects a second pressure value (P2) of a pressurized fluid in a second pipe (30), and a detector (54) that determines, on the basis of the first pressure value (P1) and the second pressure value (P2), whether or not a piston (16) has reached one end or the other inside a cylinder body (14).