Fluid-Loaded Pressure Cushion for Extended Nip Wear Reduction
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Solution Overview
Problem
Existing apparatus for forming an extended nip in press sections and calendars, such as those used in dewatering fibrous webs, face issues with pressure cushion wear due to friction and stick-slip effects, leading to short maintenance intervals and loss of cost advantages compared to more complex systems.
Innovation Solution
A fluid-loadable pressure cushion with a rollable wall that unfolds from a flat to a higher profile, reducing friction and enabling a lifting movement of the press shoe, allowing for adjustable pressure and lower wear, and is made from flexible materials like fibre-reinforced plastic or rubber, with U-shaped tubes or clamped parts for easy fitting and variable pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pressure cushion from elastic material is used to apply contact pressure, then cost advantages are achieved compared to complex cylinder-type loading systems, but the pressure cushion is liable to wear and requires short maintenance intervals
Solution Approach 1:
The patent replaces the traditional elastic material pressure cushion with a fluid-loaded pressure cushion system. Instead of relying on elastic deformation of solid material, the invention uses hydraulic or pneumatic pressure transmitted through a fluid to a flexible diaphragm or membrane, which then applies the contact pressure to the press shoe. This substitution eliminates the wear and degradation issues associated with elastic materials while maintaining the cost-effectiveness and simplicity of the pressure application mechanism.
Solution Approach 2:
The patent directly applies pneumatic or hydraulic principles by introducing a fluid-loaded pressure cushion system. A fluid (hydraulic oil or gas) is contained in a chamber and pressurized to generate the required contact force. The fluid pressure acts on a flexible element that transfers the force to the press shoe, enabling wear-free pressure application while allowing for easy adjustment of pressure levels through fluid pressure control.
2Ease of operation
If a pressure cushion is used to adjust line load, then ease of operation is improved, but frictional effects and stick-and-slip effects cause wear and reduce reliability
Solution Approach 1:
The patent eliminates the mechanical friction interface by replacing the elastic material pressure cushion with a fluid-loaded system. The fluid transmits pressure without friction, and the flexible diaphragm or membrane transfers the pressure to the press shoe without the stick-and-slip effects that plague elastic materials. This substitution maintains ease of operation through fluid pressure adjustment while eliminating wear and reliability issues.
Solution Approach 2:
The patent introduces a fluid as an intermediary medium between the pressure source and the press shoe. Instead of direct mechanical contact between elastic materials that causes friction and wear, the fluid acts as a mediator that transmits pressure forces without friction. The flexible diaphragm or membrane serves as another intermediary that transfers the fluid pressure to the press shoe while maintaining a friction-free interface.
3Adaptability or versatility
If the pressure cushion is made from flexible material, then adaptability is improved for conforming to the press shoe, but friction increases leading to higher wear
Solution Approach 1:
The patent uses a flexible diaphragm or membrane in the fluid-loaded pressure cushion system to achieve conformability. The flexible element can deform to match the contour of the press shoe and mating roll surface, ensuring uniform pressure distribution. However, instead of using elastic material that experiences friction and wear, the flexibility is achieved through the diaphragm's ability to deform under fluid pressure, eliminating the friction-related wear problems while maintaining adaptability.
Solution Approach 2:
The patent employs a flexible diaphragm or membrane as a thin film element that can conform to the press shoe surface. This flexible shell or film provides the necessary adaptability and conformability to ensure even pressure distribution across the contact area, while being part of the fluid-loaded system that eliminates friction and wear associated with traditional elastic material pressure cushions.
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 significantly reduces wear on the pressure cushion, avoids stick-and-slip effects, and allows for adjustable pressure profiles across the nip, enhancing the durability and operational efficiency of the apparatus while maintaining cost advantages.
Implementation Method 1
the press shoe (6) generates pressure by way of at least one fluid-loadable pressure cushion (10)
Implementation Method 2
the rollable wall (13) forms a rolling fold (14) between the male form portion (12) of the press shoe (6) and an inner side wall (15) of the groove-type chamber (11)
Data Source
AI summary
Disclosed is a device for forming an extended nip between a counter roll and a shoe roll for machining a material web, wherein the shoe roll has a support and a flexible roll shell, which can rotate around the support (4) and which rests in the region of the extended nip upon a head surface of a press shoe guided on the support, and the press shoe displaceably rests on the support in order to generate a press pressure via a pressure chamber to which fluid can be applied, the pressure chamber is disposed as a pressure pad, on which the press shoe rests surficially on the rear side, wherein the pressure pad is inserted into a groove-like chamber, wherein the press shoe has a stamp-like section on the rear side, which stamp-like section descends into an invaginable pressure pad in order to perform reciprocating movements, and the pressure pad is guidedly supported on the groove-like chamber along a pressure pad lateral wall that forms a roll wall.