Safety workbench with regulated circulation flow and method of operating the same
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing safety workbenches face challenges in precisely measuring and controlling the volume flow of circulating air fans, leading to inadequate personal and product protection due to system-related coupling with exhaust air flow, which results in complex adjustments and increased energy consumption.
Innovation Solution
A safety workbench design with a differential pressure sensor arrangement that includes a first pressure sensor near the fan blades and a second in a flow-calmed area on the low-pressure side, allowing for direct proportional measurement of volume flow, enabling precise regulation of the circulating air fan and independent control from the exhaust air fan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single blower is used for both circulating air and exhaust air, then device complexity is reduced, but measurement precision and control accuracy of volume flow deteriorate due to system-related coupling
Solution Approach 1:
The patent divides the air flow system into two independent measurement paths: one for circulating air volume flow and one for exhaust air volume flow. By using separate measurement circuits with individual differential pressure sensors and flow meters for each air stream, the system enables independent and accurate measurement of each flow without mutual interference, thus resolving the measurement precision issue while maintaining the simplicity of using a single blower.
2Reliability
If iterative adjustment of recirculation and exhaust air fans is performed to achieve proper protection, then protection quality improves, but adjustment time and operational complexity increase
Solution Approach 1:
The patent enables the system to automatically determine and maintain optimal operating parameters without requiring iterative manual adjustment. The independent measurement circuits provide real-time feedback on actual circulating air and exhaust air volume flows, allowing the control system to automatically adjust the blower to achieve the desired protection quality in a single setup, eliminating time-consuming iterative adjustments.
3Ease of manufacture
If flow measurement is performed downstream of the circulating air fan, then measurement is simplified, but measurement precision deteriorates due to flow turbulence and pressure conditions
Solution Approach 1:
The patent introduces a differential pressure sensor as an intermediary measurement device that measures pressure differences at strategic locations in the air flow path. By measuring the pressure difference between upstream and downstream sides of the circulating air fan, the system accurately determines the volume flow without being directly exposed to the turbulent flow conditions, thus maintaining measurement precision while simplifying the measurement implementation.
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 provides more accurate and stable volume flow measurement and control of the circulating air fan, enhancing personal and product protection by reducing energy consumption and extending the safe operating time of the workbench.
Implementation Method 1
determines a pressure difference between a first position and a second position within the safety workbench using a differential pressure sensor with two pressure sensors connected to it
Implementation Method 2
a circulating air fan (9), which promotes a partial air flow of the total air flow sucked in from the work interior (3) as circulating air flow (14) through a circulating air filter (13) into the work area (3)
Implementation Method 3
an exhaust air fan (8), which promotes a partial air flow of the total air flow sucked in from the work interior (3) as exhaust air flow (12) through an exhaust air filter (11) out of the safety workbench (1)
Implementation Method 4
These filters are high-performance particulate filters, for example HOSCH, HEPA or ULPA filters, which are able to filter out the relevant particles or microorganisms from the air flow
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a safety workbench (1) with a work chamber (3) surrounded by a housing (2) and having a working opening (6) located in the front of the housing (4) and adjustable by means of an adjustable front window (5) for admitting an air inlet flow (7) into the work chamber (3), an exhaust fan (8) and a recirculation fan (9) for conveying an airflow (10) in the safety workbench (1), which are designed such that a partial airflow drawn in by the exhaust fan (8) is blown through an exhaust filter (11) as an exhaust airflow (12) out of the safety workbench (1) and a partial airflow drawn in by the recirculation fan (9) is blown through a recirculation filter (13) as a downwardly directed recirculation airflow (14) into the work chamber (3), as well as a control device (15), a differential pressure sensor (16) and two pressure transducers (17) connected thereto. 18)the pressure sensors (17) are designed to measure pressure at two different positions within the safety cabinet, wherein a first pressure sensor (17) is arranged in the immediate vicinity of the fan blades (90) on the low-pressure side (91) of the recirculating air blower (9) and a second pressure sensor (18) is arranged in a flow-stabilized area (20) on the low-pressure side (91) of the recirculating air blower (9). The invention further relates to a method for operating a safety cabinet according to one of the preceding claims, comprising the steps: a) determining a pressure difference between the first pressure sensor (17) and the second pressure sensor (18) using the differential pressure sensor (16), b) comparing the pressure difference determined in a) with a target pressure difference stored in the control device (15), which corresponds to a target volume flow rate,or b2) converting the pressure difference measured in a) into a corresponding volume flow rate and comparing the calculated volume flow rate with a volume flow rate setpoint stored in the control device (15), and c) controlling the recirculating air blower (9) such that the set volume flow rate is delivered.