Biological safety cabinet with improved air flow

Abstract

A biological safety cabinet is provided that includes a frame. The frame defines a protected work area and encloses the work area on all but one side. A sash is coupled to the frame that at least partially encloses the side that is not enclosed by the frame. A blower is coupled to the frame generally above the work area. The blower is adapted to circulate air through the work area to make the work area a negative pressure area so that harmful materials are confined. A sash grill is coupled to the frame generally below the sash that has a curved top surface. The curved sash grill provides a superior and less turbulent air-flow into the work area, thereby better containing any harmful materials. The curved sash grill is perforated, and the curvature and perforations of the sash grill compensate for partial blockage by such things as the user's arms and other objects. The curvature of the sash grill also avoids a sharp angle at the same height as the work surface which reduces the chance of contact and possible breakage of labware as it is moved into the cabinet.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates generally to biological safety cabinets.[0002]Biological safety cabinets are laboratory containment devices equipped with High Energy Particulate Air (HEPA) filters. These cabinets are used in microbiological laboratories and provide a work area with safe environment in which a variety of experiments and studies can be performed. Rather than providing only a hood above a working surface, these cabinets provide a more protective working environment. The safety cabinet has a frame that surrounds the work area on all but one side. The remaining open side is enclosed by a moveable sash. The sash may be moved upwardly to provide access to the work area, so that work can be performed. The sash may be moved downwardly to partially or completely close the work area. A blower unit is provided in the cabinet above the work area. The blower is used to circulate air downwardly through the safety cabinet. A portion of this downward a...

AI Technical Summary

Benefits of technology

[0017]It is an object of the present invention to provide a biological safety cabinet having a novel sash grill that more effectively prevents contaminated air from leaving the cabinet, and more effectively draws air into the cabinet.

Problems solved by technology

This air may be contaminated by materials being used within the working environment.

This is undesirable because objects located on the sash grill present a source of possible contamination of the room, and may be inadvertently broken if bumped or knocked onto the floor.

Moreover, by placing an object on the sash grill, a portion of the perforations therein may be blocked, which can adversely affect the air flow of the safety cabinet.

The flat surface of the sash grill also results in a large portion of the perforations therein becoming blocked by a user's arm as the user performs work within the safety cabinet.

As the user's arm blocks the perforations in this fashion, it is difficult to properly maintain the negative pressure environment about the user's arm, thereby risking possible contamination.

Another drawback of prior art sash grills is attributable to the fact that the grills are formed with a front face that is at a right angle to the flat top of the grill.

This orthogonal relationship results in an air flow that is less than desirable.

When air is drawn inwardly and through the perforations in the sash foil, it may cause a turbulence in the air flowing downwardly along the back of the sash and through the working environment.

This procedure is time consuming and risks damage to the sash.

If the sash is dropped it may shatter, and contaminate an entire room.

Another drawback of prior art safety cabinets involves the lower edge or handle of the moveable sash.

This results in the inwardly flowing air meeting the downwardly flowing air at a right angle, causing turbulence.

As noted above, turbulent air flow adjacent the opening of the cabinet is undesirable.

However, the air within the pressure plenum immediately below the blower has not yet been filtered.

As such, the air may contain harmful materials from the working environment below.

If the gauge on the exterior of the cabinet were to leak, contaminated air would be allowed into the room.

This of course results in additional expense both initially and for ongoing maintenance.

Monitoring and displaying a negative pressure, however, is more difficult to translate into meaningful and usable numbers by laboratory personnel.

While this location is effective in removal of the desired items, it is impossible to visually inspect without taking the cabinet apart.

This method can be uncomfortable and dangerous to the extent that pieces of broken laboratory glass and other sharp objects may be lodged within the towel catch.

The towel catch itself is normally formed from metal with sharp edges which presents a safety hazard in and of itself if it is placed in a traditional location where it is not visible to a worker cleaning it.

Another drawback of prior art safety cabinets involves the construction of the sash.

This arrangement is disadvantageous in that the wiping action may create an aerosol containing contaminants from the rear of the sash.

While in other prior art constructions holes communicating with the exhaust system have been utilized in place of seals, such constructions have not been particularly effective, largely because there has been no means for insuring a uniform negative pressure across the exhaust holes.

Yet another drawback of existing prior art safety cabinets involves the design of the positive pressure plenum box.

The perforated plate creates an undesirable increased load on the blower and can interfere with the function of the supply filter.

Moreover, this prior art construction does not distribute air across the supply filter as evenly as desired.

This need for space can place limitations on the rooms in which the safety cabinets can be used.

This damper places some additional load on the blower by restricting air flow to the filter.

Furthermore, a damper is not aerodynamically efficient and interferes with the uniform flow of air.

Such dampers are normally not readily accessible for making adjustments.

The use of such a damper also tends to cause air to flow unevenly through the filter thus not effectively using the entire filter surface area.

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