Steady Rest Sensor Sealing and Drainage Against Coolant Ingress
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Solution Overview
Problem
Existing bezels for holding workpieces on machine tools face issues with liquid ingress, which damages the displacement sensor and impairs position detection during machining, especially due to cooling lubricants and splash water.
Innovation Solution
A bezel design with a sealing air supply to create overpressure in the housing, using a distance sensor with a drain hole and air-operated drain valve to prevent liquid ingress during operation and allow drainage after shutdown, along with a separate sealing air connection for the drain valve to ensure reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance sensor is located below the lowest position of the pressure element to detect the entire travel path, then position detection precision is improved, but liquid can accumulate in front of the sensor causing measurement errors and potential damage
Solution Approach 1:
A drain valve is introduced as an intermediary component between the distance sensor and the housing interior. This drain valve, actuated by sealing air pressure, selectively opens to drain accumulated liquid from the front cavity of the distance sensor while maintaining the sensor's low position for accurate measurement. The drain valve mediates between the conflicting requirements of sensor positioning and liquid protection.
Solution Approach 2:
The system performs preliminary drainage action by opening the drain valve before liquid can cause damage or significant measurement errors. The sealing air pressure continuously actuates the drain valve to maintain the front cavity in a drained state, preventing liquid accumulation before it becomes problematic. This proactive approach ensures the distance sensor remains protected while positioned optimally for measurement.
2Reliability
If sealing air is supplied to the housing to prevent liquid ingress during operation, then protection against liquid is improved, but liquid that penetrates after shutdown cannot be drained
Solution Approach 1:
The drain valve transitions from a static closed state during operation to a dynamically controlled state based on sealing air pressure. During operation, sealing air pressure actuates the drain valve to a closed position, preventing liquid ingress. After shutdown, when sealing air pressure is reduced or removed, the drain valve automatically opens to allow drainage. This dynamic behavior resolves the contradiction between protection during operation and drainage capability after shutdown.
Solution Approach 2:
The drain valve operates periodically based on the operational cycle of the steady rest. During the operational phase, sealing air pressure keeps the drain valve closed for protection. During the shutdown/drainage phase, the drain valve opens to drain accumulated liquid. This periodic switching between closed (protection) and open (drainage) states resolves the contradiction between these two opposing requirements.
3Loss of substance
If the drain hole remains open to allow liquid drainage, then liquid removal is improved, but sealing air cannot be maintained and liquid ingress prevention is compromised
Solution Approach 1:
The drain valve creates a localized controlled opening at a specific position in the housing, rather than having a continuously open drain hole. This localized quality allows the drain hole to be closed by default (maintaining sealing air) and opened only when drainage is required. The drain valve provides local control over the drainage function without compromising the overall sealing integrity of the housing during operation.
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
Prevents liquid from entering the housing during operation, ensuring accurate position detection and preventing damage to the sensor, while allowing liquid to drain after shutdown, maintaining the integrity of the measurement system.
Implementation Method 1
a sealing air supply is assigned to the housing to prevent the penetration of liquid... the housing is pressurised with a barrier pressure, preferably in the range of 0.5 to 1.0 bar overpressure
Implementation Method 2
the pressure element has a reflective surface opposite the distance sensor for reflecting a distance signal emitted by the distance sensor
Implementation Method 3
a front cavity of the distance sensor has a drain hole that can be closed via a sealing air-actuated drain valve
Data Source
Figure 1
Figure 2~3
AI summary
A steady rest for holding a workpiece (2) on a machine tool, with a substantially vertically disengaging actuating piston (7), which is flanked on both sides by two angle levers (6) and interacts with these within a housing (3) via a pressure element (8), wherein the housing (3) is provided with a sealing air supply to prevent the ingress of liquid, characterized in that a disengagement position of the pressure element (8) can be detected by means of a distance sensor, which is assigned to the housing (3) below a lowest position of the pressure element (8) and a preliminary cavity (13) of the distance sensor has a drain bore (14) that can be closed via a sealing air-operated drain valve (15) for draining the same.