Extended Nip Press Mechanical Stop for Pressure Control
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Solution Overview
Problem
In extended nip press devices, it is challenging to accurately control and determine the pressure in the nip, leading to potential damage to rolls and personnel due to unknown or uncontrolled loading, and there is a risk of pressure deviation from optimal levels, especially when the press must be stopped, which can cause damage to felt materials due to heat from heated rolls.
Innovation Solution
A press device with a mechanical stop system that connects bearing housings of the extended nip roll and counter roll using actuators, allowing for precise control of the nip closure and pressure, and includes a load sensor to monitor and adjust pressure, preventing excessive load and ensuring safe operation, even when the exact loading of the support body is unknown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If hydraulic pressure is used to press the support body against the flexible jacket, then the press force can be applied, but the actual pressure in the nip cannot be accurately determined due to hysteresis effects
Solution Approach 1:
The patent introduces a mechanical stop as an intermediary element that physically limits the closing movement of the press device. This stop acts as a mediator between the hydraulic pressing mechanism and the rolls, ensuring that the press force does not exceed predetermined limits. The mechanical stop provides a tangible reference point that eliminates the measurement uncertainty caused by hysteresis in the hydraulic system.
2Ease of manufacture
If the press device is stopped during operation, then maintenance or changes can be performed, but heat from the heated counter roll can damage the felt material
Solution Approach 1:
The patent implements preliminary action by automatically opening the press nip (separating the rolls) before maintenance operations begin. The control system detects when maintenance is required and proactively opens the nip to prevent heat damage to the felt material. This preliminary separation ensures that the felt is not exposed to harmful heat during maintenance periods, while still allowing the counter roll to maintain its heating capability for subsequent operations.
3Ease of operation
If the closing movement is not limited, then the press can operate freely, but the linear load may exceed maximum permissible levels causing damage
Solution Approach 1:
The patent applies preliminary anti-action by pre-positioning mechanical stops that prevent excessive closing movement before it can cause damage. These stops are arranged to limit the closing movement to predetermined positions, creating a physical barrier against over-compression. The control system works in conjunction with these stops to ensure the press force is released before maximum permissible load levels are exceeded, thereby protecting the rolls and other components from damage while maintaining operational freedom within safe limits.
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
This solution ensures that the maximum pressure in the nip is controlled within predetermined limits, preventing roll damage and ensuring safe operation, while allowing for accurate pressure determination and control, and prevents heat damage to felt materials by allowing for controlled separation of rolls during stops.
Implementation Method 1
The pressure in the nip is typically caused by hydraulic pressure that acts to press the support body against the inner surface of the flexible jacket and thereby also against the counter roll
Implementation Method 2
a mechanical stop is arranged to halt the closing movement when the closing movement has brought the rolls so close to each other that the axial ends of the extended nip roll and the axial ends of the counter roll are at a predetermined distance from each other
Implementation Method 3
The mechanical stop may comprise at least one load sensor that is arranged between one of the first bearing housings and one of the second bearing housings
Implementation Method 4
The counter roll may be a heatable roll. A heating device may be arranged to heat the counter roll to a predetermined temperature
Implementation Method 5
The flexible hose is connected to a source of pressurized fluid such that the flexible hose can be pressurized. When this happens, the flexible hose expands in its channel such that a top surface of the flexible hose is pressed against the inner surface of the flexible jacket
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present invention relates to a press device (1) that comprises an extended nip roll (2) and a counter roll (3). The extended nip roll (2) has a flexible jacket (4) and a support body (5) inside the flexible jacket (4). The extended nip (2) roll also has internal means for causing the support body (5) to move or expand radially towards an inner surface (6) of the flexible jacket (4) to form a nip with the counter roll. The rolls (2, 3) have axial ends (7, 8, 10, 11) that are supported in bearing housings (9, 12). One or several actuators (13) such as hydraulic cylinders connects bearing housings (9, 12) to each other and the actuator or actuators (13) are arranged to act on the bearing housings (9, 12) to cause them to move to each other in a closing movement. A mechanical stop (14) which is separate from the rolls (2,3) is arranged to halt the closing movement. The invention also relates to a machine that uses the press device and to a method of operating the press device.