Dashpot Needle Valve for Temperature-Stable Closing Damping
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Solution Overview
Problem
Existing dashpots fail to provide effective temperature compensation over a wide range, leading to operational issues such as stalling or inconsistent performance due to material expansion differences and manufacturing tolerances, particularly in outdoor applications.
Innovation Solution
A compensation mechanism with a second restricted fluid passage and a needle valve design that includes an elongated body with a temperature-dependent tip, ensuring continuous fluid flow and stable viscosity compensation across varying temperatures without relying on multi-material pistons or clearances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyoxymethylene is used for the piston to achieve temperature compensation, then the thermal expansion coefficient is high enough to compensate for viscosity changes, but the clearance disappears at temperatures between 30-45°C causing the piston to get stuck
Solution Approach 1:
The piston is divided into two distinct parts: a base made of glass fibre reinforced polymeric material providing structural strength and dimensional stability, and an outer cover layer made of polymeric material with high thermal expansion coefficient that interfaces with the hydraulic fluid. This segmentation allows each part to fulfill its specific function without the drawbacks of using a single material throughout.
Solution Approach 2:
The piston uses composite construction combining glass fibre reinforced polymeric material for the base with a separate polymeric outer cover layer. This composite approach enables the piston to simultaneously achieve mechanical strength, dimensional stability, and appropriate thermal expansion characteristics for viscosity compensation without the piston getting stuck at elevated temperatures.
2Reliability
If glass fibre reinforced polymeric material is used for the entire piston to reduce thermal expansion, then the thermal expansion coefficient is reduced for better temperature compensation, but the piston becomes abrasive towards the metal cylinder barrel
Solution Approach 1:
Different parts of the piston have different material properties optimized for their specific functions: the base uses glass fibre reinforced polymeric material for dimensional stability and strength, while the outer cover layer uses a softer polymeric material that is less abrasive to the metal cylinder barrel. This local differentiation of material quality resolves the contradiction between thermal expansion control and abrasion prevention.
3Reliability
If multi-material piston is used to balance thermal expansion and abrasion, then both temperature compensation and reduced abrasion are achieved, but manufacturing complexity and costs increase
Solution Approach 1:
The piston is segmented into a base and an outer cover layer that can be manufactured separately using optimized processes for each material, then assembled together. This segmentation enables independent manufacturing and quality control of each component, reducing overall manufacturing complexity despite using multiple materials.
4Reliability
If clearance between piston and cylinder barrel is used for temperature compensation, then viscosity changes are compensated, but manufacturing tolerances cause inconsistent performance across units
Solution Approach 1:
The invention changes the material parameter (thermal expansion coefficient) of the piston components to achieve temperature compensation through material selection rather than relying on precise dimensional tolerances. By using materials with appropriate thermal expansion characteristics, the system compensates for viscosity changes without being sensitive to manufacturing tolerances in clearance dimensions.
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 ensures reliable and consistent damping performance across a wide temperature range, preventing stalling and maintaining fluid flow, while reducing manufacturing complexity and costs.
Implementation Method 1
an elongated body extending between a first end fixed to the housing and a second end opposite the first end, wherein a length of the elongated body is temperature dependent
Implementation Method 2
A dashpot for damping a closing movement of a closure system
Data Source
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AI summary
A dashpot (5) comprising a housing (17); a closed cylinder cavity filled with hydraulic fluid; a slideable piston (47) within the housing and dividing the closed cylinder cavity into a high pressure compartment (48) and a low pressure compartment (48); a one-way fluid passage (57) allowing fluid flow from the low pressure compartment to the high pressure compartment when the dashpot is being opened; a first restricted fluid passage (66) determining a closing speed of the dashpot; and a mechanism for compensating temperature-induced viscosity changes of the hydraulic fluid. The compensation mechanism comprises: a second restricted fluid passage (10) and a needle valve (12) comprising: an elongated body (14) whose a length is temperature dependent. The tip (15) of the needle valve has a shape so that fluid flow along the second restricted fluid passage is always possible.