Radial Compensating Gas Spring for Stable Force Across Temperature

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Solution Overview

Problem

Gas pressure springs exhibit temperature-dependent spring force, leading to inefficiencies in applications like vehicle tailgates, requiring stronger springs at low temperatures and increased motor power, which results in higher energy consumption and reduced ease of use at higher temperatures.

Innovation Solution

A gas pressure spring design incorporating a compensating cylinder and medium that expands with temperature, along with a restoring medium, to maintain a consistent volume and reduce temperature dependence, allowing for a shorter and more versatile spring without extending its length.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the gas spring is designed to provide sufficient spring force at low temperatures, then the spring force is adequate for cold conditions, but the motor power requirement increases and energy consumption rises at moderate temperatures

Engineering Contradiction:
Improvespring force sufficiency at low temperatureVSAvoidmotor power consumption at moderate temperature
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the physical parameters of the working gas (pressure, volume, temperature) by introducing a temperature-dependent volume adjustment mechanism. The compensating piston responds to temperature changes by adjusting the volume of the working chamber, thereby modifying the pressure-volume-temperature relationship of the working gas to maintain consistent spring force across different temperatures.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The compensating piston acts as an intermediary element between the temperature environment and the working gas. It mediates the temperature effect by expanding or contracting in response to temperature changes, which in turn adjusts the volume available to the working gas, thereby compensating for temperature-induced spring force variations without requiring additional motor power.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Force

If the gas spring is designed with higher spring force for low temperature operation, then it can reliably hold the tailgate open at cold temperatures, but it requires higher motor power to compress at moderate temperatures

Engineering Contradiction:
Improvespring force at low temperatureVSAvoidmotor power requirement at moderate temperature
Core Design Contradiction:
ForceVSPower

Solution Approach 1:

The patent introduces dynamic adaptability to the gas spring system through the compensating piston, which automatically adjusts the working chamber volume based on temperature conditions. This dynamic adjustment allows the spring force to adapt to changing temperature requirements, providing high force when cold and reducing resistance when warm, thereby optimizing both holding force and motor power requirements across different operating conditions.

Inventive Principle:
Principle #15Dynamics

3Reliability

If a compensating piston arrangement is added to adjust volume with temperature, then temperature dependence is reduced, but the overall length of the gas spring increases significantly

Engineering Contradiction:
Improvetemperature compensationVSAvoidoverall length of gas spring
Core Design Contradiction:
ReliabilityVSLength of moving object

Solution Approach 1:

The compensating piston is nested within the existing gas spring structure, utilizing the annular space between the working cylinder and compensating cylinder. This nested arrangement allows the compensating mechanism to be integrated without significantly increasing the overall length of the gas spring, as the compensating piston operates within the radial dimensions of the existing cylindrical structure.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent transitions the temperature compensation mechanism from a linear extension (increasing length) to a radial arrangement (increasing diameter). By positioning the compensating piston and compensating medium in the radial dimension between the working cylinder and compensating cylinder, the system achieves temperature compensation without proportionally increasing the overall length, instead utilizing the radial space efficiently.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

4Reliability

If the working chamber volume is extended to achieve temperature compensation, then the spring force becomes less temperature-dependent, but the overall length increases and application possibilities are limited

Engineering Contradiction:
Improvespring force consistency across temperatureVSAvoidapplication suitability
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent implements a dynamic volume adjustment mechanism where the compensating piston automatically modifies the working chamber volume in response to temperature changes. This dynamic adaptation maintains consistent spring force characteristics across different temperatures without requiring a permanently extended chamber, thereby preserving the gas spring's compact dimensions and broad applicability to various installation scenarios.

Inventive Principle:
Principle #15Dynamics

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 compensates for temperature-induced pressure changes, reducing the spring force's temperature dependence, resulting in a cost-effective, long-lasting, and energy-efficient gas pressure spring suitable for various applications.

Implementation Method 1

a compensating medium arranged radially to the stroke axis in a compensating chamber between the working cylinder and the compensating cylinder, which expands when the temperature increases

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the gas pressure p increases or decreases (for an ideal gas, according to: p*V = n*R*T)

Methodology Applied
Scientific EffectIdeal gas law:

Data Source

PatentEP3967898B1Gas compression spring, method for manufacturing the gas compression spring, drive for a flap with the gas compression spring
Publication Date: 2023.03.22 STABILUS GMBH
  • EP3967898B1 patent drawingFigure 1
  • EP3967898B1 patent drawingFigure 2

AI summary

The invention relates to a gas spring (50) comprising an outer working chamber (12a) arranged radially to the stroke axis (H) between the working cylinder (1) and the compensating cylinder (12), wherein the outer working chamber (12a) is gas-conductingly connected to the inner working chamber (1a), a compensating piston (10) surrounding the working cylinder (1) radially to the stroke axis (H), wherein the compensating piston (10) is slidably mounted along the stroke axis (H), the outer working chamber (12a) is bounded on one side transversely to the stroke axis (H) and is subjected to a pressure of the working medium and a pressure of the compensating medium in a direction that increases the volume of the outer working chamber (12a), and a restoring medium arranged in a restoring chamber (15a) radially to the stroke axis (H) between the working cylinder (1) and the compensating cylinder (12).wherein the compensating piston (10) is subjected to pressure from the restoring medium in a direction that reduces the volume of the outer working chamber (12a). The invention further relates to a method for manufacturing the gas spring (50) and a drive for a flap with the gas spring (50).