Fume hood with air chamber and pressure pipe

Details Fume hood with air chamber and pressure pipe Fume hood with air chamber and pressure pipe

2001-12-11

2003-05-27

Boles, Derek S. (Department: 3749)

Ventilation

Workstation ventilator

Covered workbench chamber

C312S209000

Reexamination Certificate

active

06569007

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fume hood apparatus, and in particular to a fume hood apparatus with an air chamber that allows a lower sash face velocity while maintaining fume containment, thereby improving fume hood performance.
2. Description of the Related Art
Fume hoods are protective enclosures that provide ventilated and illuminated workspaces for laboratory or other applications. A fume hood in its most basic form is a box with an inlet and an outlet. The inlet generally has a movable sash (vertically, horizontally or a combination of both), which provides an opening that allows access to the workspace. The procedures performed inside the fume hood are exhausted at the back through the top of the fume hood to a heating, venting and air conditioning (HVAC) system.
An ideal fume hood system would use the least amount of conditioned room air possible while optimizing the containment levels necessary in order to perform the procedure. The need to exhaust less air is extremely important because it reduces the amount of conditioned air that is exhausted from the room through the hood, thereby lowering the operating cost of the fume hood.
The inventors of the present invention have recognized this problem and have developed a fume hood that provides containment levels dramatically better than the current industry standard recommendations. In addition, the inventors have developed a fume hood that can be adaptable to fume hoods with different types of airfoils, such as a raised airfoil, or an airfoil that is flush with the work surface, and the like.
SUMMARY OF THE INVENTION
The present invention comprises a fume hood apparatus including an enclosure, a movable sash and an air chamber. The air chamber includes an inlet for drawing air into the air chamber. Initially, the airflow travels upward into the air chamber. A backpressure redirects the airflow to travel downward through one or more baffles that evenly distribute the airflow within the air chamber as the airflow travels through the air chamber. A discharge positioned proximate to the face of the fume hood directs an unimpeded flow of air through the face of the fume hood. When the air moves into the fume hood around the technician's body a reverse vortex is created between the technician's body and face of the fume hood in the breathing zone. By directing an unimpeded flow of clean air downward across the breathing zone of the technician, the clean air from the air chamber reduces the forward momentum of air trying to escape the fume hood, thereby preventing airborne contaminants from escaping through the face of the fume hood. Airborne contaminants are prevented from escaping from the workspace even when the movable sash is fully opened resulting in improved containment performance.
In an alternative embodiment of the invention, the fume hood includes an air chamber located in front of the movable sash and above the technician. As in the earlier embodiment, the air chamber draws room air in and redirects the airflow in a controlled manner down in front between the technician and the movable sash. In addition, the alternative embodiment includes a pressure pipe that draws in a small quantity of air from the air chamber and distributes the airflow between the backside of the movable sash and the front of the header panel. When the airflow that is directed out the bottom of the air chamber clears the bottom of the movable sash, the airflow is then drawn into the workspace and exhausted. The small quantity of airflow from the pressure pipe introduced between the movable sash and the front header sweeps the area clean and the airflow is also drawn into the workspace and exhausted. The air chamber in combination with the pressure pipe maintains fume containment at lower face velocities as compared to conventional fume hood designs.


REFERENCES:
patent: 3604333 (1971-09-01), Nelson
patent: 3752056 (1973-08-01), Chamberlin et al.
patent: 3811250 (1974-05-01), Fowler, Jr.
patent: 4637301 (1987-01-01), Shields
patent: 4723480 (1988-02-01), Yagi et al.

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