Weighing Chamber Closure Control Using Differentiated Proximity Sensing
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Solution Overview
Problem
Weighing devices, particularly those used for pipette calibration, face challenges in efficiently controlling the closure element to minimize operator effort and reduce errors due to sensitivity issues with existing reflection sensors, which are affected by aging and contamination, leading to ergonomic stress and inaccurate actuation.
Innovation Solution
A differentiating element is used to generate a secondary sensor signal from the reflection sensor's primary signal, allowing the control unit to distinguish between approaching and receding objects, incorporating hysteresis to prevent unnecessary actuation, and using digital or analog sensors with noise suppression techniques to improve accuracy and adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a reflection sensor with a defined sensitivity range is used to control the closure element, then the closure element can be automatically actuated when objects enter the sensitivity range, but the sensor's sensitivity range is not clearly defined due to varying reflection properties of different objects, leading to erroneous actuation
Solution Approach 1:
The patent changes the evaluation parameter from static reflection intensity to dynamic reflection intensity change over time. By evaluating the rate of change of reflection intensity rather than absolute values, the system can distinguish between objects moving toward the sensor (increasing reflection intensity) and objects moving away (decreasing reflection intensity), thereby clearly defining the sensitivity range for opening and closing operations.
2Ease of operation
If the closure element is opened for each pipetting process to allow pipette access, then the operator can manipulate the sample container, but the weighing chamber atmosphere is disrupted too much by opening entire wall sections
Solution Approach 1:
The patent segments the closure element into a small localized opening mechanism rather than opening entire wall sections. The closure element (flap, slide, or iris) creates a minimal aperture just large enough for pipette access, thereby maintaining the protective housing's integrity and minimizing atmosphere disruption while still enabling necessary manipulation of the sample container.
3Extent of automation
If a non-contact switch in the form of a light barrier is used to detect object approach, then the closure element can be actuated automatically, but the operator must always carry out the same movement sequence of passing the light barrier, which becomes ergonomically stressful
Solution Approach 1:
The patent implements dynamic control where the closure element responds to the direction of movement of objects. The control unit evaluates whether reflection intensity is increasing (object approaching) or decreasing (object receding) and actuates the closure element accordingly. This allows natural, varied operator movements without requiring precise repetition of the same movement sequence, reducing ergonomic stress while maintaining automatic actuation.
4Loss of time
If the reflection sensor's sensitivity range is extended to detect objects from farther away, then the closure element can be actuated earlier, but the extent of the sensitivity range changes as a result of aging or contamination of sensor components, leading to actuation errors
Solution Approach 1:
The patent changes from evaluating absolute reflection intensity values to evaluating the rate of change of reflection intensity over time. This dynamic evaluation method is insensitive to aging or contamination of sensor components because it depends on the temporal derivative rather than absolute thresholds. The system can therefore extend the sensitivity range to detect objects from farther away while maintaining reliable and consistent actuation timing throughout the sensor's operational life.
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 enables more precise control of the closure element based on the user's movement, reducing ergonomic stress and minimizing errors caused by aging or contamination, while maintaining the weighing chamber's integrity during pipette calibration processes.
Implementation Method 1
a reflection sensor with a radiation transmitter for emitting sensor radiation that can be reflected by a reflection object and with a radiation receiver for receiving a sensor radiation from the reflection object reflected sensor radiation component
Data Source
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AI summary
The invention relates to a weighing device comprising – a receptacle (20) for the goods to be weighed, – a protective housing (14, 16, 18) which surrounds the receptacle (20) for the goods to be weighed and has an access opening (181) and a closure element (26) which closes the access opening (181) in the closed state thereof and releases the access opening in the open position thereof, – a reflection sensor (34a, b, c) with a radiation transmitter (37) for emitting a sensor radiation (38) that can be reflected by a reflecting object (39) and with a radiation receiver (42) for receiving a sensor radiation portion (40) reflected by the reflecting object (39), and – a control unit (32) which is connected to a motorized drive (30) of the closure element (26) and to the reflection sensor (34a, b, c), and which is designed to control the motorized drive (30) according to a signal of the reflection sensor (34a, b, c) for transferring the closure element (26) between the closed and open positions thereof. The invention is characterized in that a differentiation element is also comprised, which subjects a sensor primary signal (52) of the reflection sensor (34a, b, c) to differentiation, said sensor primary signal depending on a reflection intensity of the reflected sensor radiation portion (40), for generating a sensor secondary signal (60), and the control unit (32) is designed to control the motorized drive (30) according to the sign of the sensor secondary signal (60).