|Publication number||USRE40276 E1|
|Application number||US 10/800,357|
|Publication date||Apr 29, 2008|
|Filing date||Mar 15, 2004|
|Priority date||Apr 20, 2000|
|Also published as||US6368206|
|Publication number||10800357, 800357, US RE40276 E1, US RE40276E1, US-E1-RE40276, USRE40276 E1, USRE40276E1|
|Inventors||Jim Hunter, Kevin Gilkison, Larry Nelson, Burt Rhea, Jerry O'Dell, Greg Krueger, Gary Roepke, Gerhard W. Knutson, Mary Ellen Kennedy|
|Original Assignee||Labconco Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (12), Referenced by (6), Classifications (7), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates generally to biological safety cabinets.
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 air flow forms an air curtain at the front of the cabinet work area and passes beneath the floor of the work area and a portion is directed to the back of the cabinet where it is drawn upwardly through a plenum chamber. This air may be contaminated by materials being used within the working environment. Therefore, prior to being exhausted into the room or a fume system, the air is first passed through a HEPA exhaust filter.
The blower is operated so there is sufficient air flow through the work area to insure that any harmful materials are contained and eventually passed to a filter area rather than escaping into the room or exhausted into the atmosphere. To this end some air is drawn into the safety cabinet about the open perimeter formed when the sash is in an open or partially open position.
The prior art safety cabinets are typically provided with a sash grill located below the bottom of the sash. This sash grill forms the lower-most surface of the opening into the work area. Typically, the sash grill is provided with a number of perforations, through which air can flow. Air flows downwardly from the blower along the back of the sash and into these perforations. Air is also drawn inwardly from the exterior of the cabinet along the surface of the sash grill and into the perforations. The air flowing through the sash grill flows under the work surface and upwardly through the plenum at the back of the cabinet to be recirculated or exhausted.
Safety cabinets have heretofore utilized a sash grill having a generally flat surface which gives rise to a number of disadvantages. The flat surface may be used by those operating the safety cabinet as a surface on which to place a variety of labware. 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. The flat sash grills of the prior art also present a right angle with the work surface which projects far enough above the work surface that labware is sometimes broken when it bumps against the projecting vertical face. It is thus desirable to provide a sash grill which does not provide a flat surface and does not present a right angle corner at the entrance to the work area opening.
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 turbulence is increased by the right angle relationship, as the air encountering the front face of the grill will be partially directed upwardly over the front face before being drawn through the perforations in the flat top of the grill. Therefore, a biological safety cabinet is needed with a sash grill that improves the air flow and safety of the cabinet.
Similarly, air may be drawn into the opening of the safety cabinet along the sides of the cabinet adjacent the opening when the sash is in an open or partially open position. In prior art safety cabinets, the front sides of the cabinet are oriented at right angles relative to the interior side walls. When air is drawn into the cabinet along these sides, it will initially be directed away from the interior surface of the interior walls. However, it is much more desirable to cleanly “sweep” the interior walls of the cabinet, to ensure the best possible containment of any harmful materials. A biological safety cabinet having a construction that draws air inwardly to cleanly sweep the interior side walls is needed.
After the safety cabinets have been used for a certain period of time, they must be decontaminated. One method for performing this decontamination involves sealing the front of the safety cabinet with a plastic sheet. When the prior art safety cabinets are being decontaminated, it is often necessary to first remove the sash to insure proper decontamination. This is attributable to the location of the sash within a U-shaped channel where contaminants may accumulate. This procedure is time consuming and risks damage to the sash. If the sash is dropped it may shatter, and contaminate an entire room. Thus, a biological safety cabinet which can be decontaminated without removal of the sash is needed.
Another drawback of prior art safety cabinets involves the lower edge or handle of the moveable sash. When the sash is in an open or partially open position, two bodies of air are coming together adjacent the handle of the sash. One body of air is flowing from the exterior of the cabinet into the interior thereof. The second body of air is flowing downwardly from the blower unit of the safety cabinet along the back of the sash. In prior art cabinets, the sash handle has transitioned from the front face to the bottom face at a right angle. 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. A sash handle that reduces turbulence would represent an improvement over the prior art.
As stated above, the biological safety cabinet is operated with the benefit of a blower which provides an air flow so that harmful materials are contained within the cabinet. The cabinets are constructed with the blower above the working environment, and the working environment is subject to a continual flow of air to contain contaminants and then move them to a filter area. Above the working environment and beneath the blower, is a supply filter and a positive pressure plenum. The pressure plenum receives air from the blower and directs it through the supply filter.
To monitor the pressure within the cabinet, prior art safety units have used a pressure gauge mounted on the exterior of the cabinet, with the pressure being monitored in the positive pressure environment of the pressure plenum immediately below the blower. Monitoring the positive pressure allows a more meaningful pressure reading to be obtained and used by the laboratory personnel. 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. In some instances this concern has been addressed by placing a HEPA filter in the pressure line to the readout gauge. This of course results in additional expense both initially and for ongoing maintenance. Another method of addressing the potential problem of contamination through the pressure gauge has been to monitor the air pressure in a negative pressure environment (relative to the atmosphere surrounding the cabinet) thus eliminating the possibility of contamination as a result of leakage through the gauge into the room. Monitoring and displaying a negative pressure, however, is more difficult to translate into meaningful and usable numbers by laboratory personnel. A monitoring apparatus is therefore needed which does not require any additional filters and allows the monitoring and display of a positive pressure, while eliminating the risk of possible contamination of the room environment.
It has been found that it is desirable to equip the safety cabinet with a “towel catch” to catch or filter out large objects from the returning air flow prior to being recirculated through the blower. This towel catch removes such things as paper towels and small laboratory items from the returning air stream. Prior art safety cabinets have located this towel catch in the plenum formed by the rear wall of the work area and the rear wall of the safety cabinet. While this location is effective in removal of the desired items, it is impossible to visually inspect without taking the cabinet apart. One method typically utilized for inspecting these prior art towel catchers is to reach up within the plenum and feel the towel catch to determine if any paper towels or other objects are lodged within or against the towel catcher. 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. Therefore, a towel catch that is readily accessible and can be visually inspected is needed.
Another drawback of prior art safety cabinets involves the construction of the sash. The sash of the safety cabinet is moveable upwardly and downwardly, to allow better access to the working environment when needed and to more fully enclose the working environment when access is no longer needed. In prior art safety cabinets, the rear of the sash is provided with a seal to prevent any contaminated air from escaping the working environment. The seal wipes the back of the sash as the sash is raised. 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. Thus, an arrangement is needed for a biological safety cabinet that eliminates the need for a wiping seal at the rear of the sash and instead provides for a uniform negative pressure which will insure removal of any contaminated air from the back side of the sash.
Yet another drawback of existing prior art safety cabinets involves the design of the positive pressure plenum box. This box is located in the area below the blower and above the work area. More specifically, in prior art cabinets, air leaving the blower is directed to a perforated plate and then through a supply filter prior to be recirculated downwardly through the work area. The perforated plate is used to more evenly distribute the air flow over and through the supply filter. 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. Therefore, a structure is needed that both evenly distributes the flow over and across the supply filter while not overly increasing the load on the blower or interfering with the function of the supply filter.
Prior art safety cabinets are typically equipped with exhaust control systems. As contaminated air passes through the blower of the safety cabinet, some of the air is recirculated through the supply filter as described above and some of the air is routed through an exhaust filter. This exhaust air is either discharged into the room, or it passed to an exhaust system associated with the safety cabinet which moves the air out of the building. In cabinets routing the exhaust air directly back into the room, the prior art cabinets have merely routed the air directly upwardly. Prior art units routing the air into a building exhaust system direct typically employ duct work coupling the safety cabinet exhaust to the building exhaust system. Both prior art embodiments require a certain amount of additional space above the ceiling of the safety cabinet to allow for the exhaust control systems. This need for space can place limitations on the rooms in which the safety cabinets can be used.
In addition to routing the exhaust air, the exhaust control systems of the safety cabinets are used to balance the air flow through the safety cabinet. Prior art exhaust control systems use a guillotine damper to allow more or less air to be exhausted, as needed to balance the air flow through the safety cabinet and achieve the proper pressure within the cabinet. 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. Therefore, a more efficient exhaust control system is needed for a biological safety cabinet that reduces undesired blower loading, makes better utilization of available filter surface area and is readily accessible.
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.
It is another object of this invention to provide a sash grill for a biological safety cabinet that prevents objects from being placed thereon.
It is a further object of the invention to provide a biological safety cabinet having exterior front side panels that allow incoming air to more effectively sweep the sides of the cabinet and that allow the cabinet to more easily be decontaminated.
It is yet another object of the invention to provide a handle for the sash of a biological safety cabinet that allows air to more effectively flow thereover.
It is still another object of the present invention to provide a biological safety cabinet in which the pressure gauge measures a positive pressure environment while being contained within the safety cabinet so that any risk of contamination through the gauge is reduced while also eliminating the need for a separate HEPA filter for the gauge.
Another object of the present invention is to provide a towel catch for a biological safety cabinet that is visible to the user thereof and that can be easily removed without disassembling the safety cabinet.
Yet another object of the present invention is to provide a biological safety cabinet that eliminates the need to wipe the back of the sash with a seal so that still another risk of contamination is reduced.
It is another object of the present invention to provide a biological safety cabinet with a plenum box that evenly distributes the air flow across a supply filter without increasing the load on the blower of the cabinet.
A still further object of the present invention is to provide a biological safety cabinet with a low profile, externally adjustable exhaust control that does not require decontamination before adjusting and provides for more uniform distribution of air across the exhaust filter.
It is yet another object of the present invention to provide a plenum chamber seal and tensioning device for the exhaust filter of a biological safety cabinet that allows the supply filter and exhaust filter to be simultaneously sealed.
According to the present invention, the foregoing and other objects are attained by a biological safety cabinet that includes a frame that defines a protected working environment and encloses the working environment 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 working environment. The blower is adapted to circulate air through the working area so that harmful materials are confined. A sash grill is coupled to the frame generally below the sash and has a curved top surface. The curved sash grill provides a superior and less turbulent air-flow into the working environment, 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 the user's arms and other objects. The curvature of the sash grill also presents a surface on which objects cannot be easily placed, thereby avoiding a safety hazard. The curved grill also eliminates a protruding right angle corner at the cabinet opening which has been known to cause breakage of labware being placed inside the cabinet.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention.
In the accompanying drawings which form a part of this specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:
Referring initially to
As best seen in
As best seen in
In use, blower 28 of cabinet 10 is operated to provide an air-flow through the cabinet, and particularly through work area 44. Prior to the air entering the work area 44, it is first passed through supply filter 32 to remove any contaminants. Cabinet 10 may be operated with sash 42 located a specified distance away from sash grill 24, as is shown in FIG. 3. To ensure that contaminants do not escape through the opening between sash 42 and grill 24, blower 28 will direct air downwardly along the rear of sash 42 and into the perforations of grill 24 from above the work area to provide a protective curtain of air that facilitates containment within work area 44. A portion of the air from blower 28 also moves toward the rear of the surface 22 as will be explained hereinafter. The action of blower 28 provides a certain amount of suction, causing an air flow inwardly along the opening defined by the bottom of sash 42, side panels 16 and sash grill 24. Air which is drawn through this opening also passes through the perforations in sash grill 24. The air, once drawn through sash grill 24, will travel beneath work surface 22 and through the plenum defined by baffle 20 and real panel 18 as it is drawn upwardly by blower 28. The air moving from the blower to the rear of surface 22 will also be drawn into this same plenum.
Air that has passed through working environment 44 is likely to contain contaminants and thus, before being recirculated or exhausted to the room, is first passed through a HEPA filter. Prior to being recirculated into working environment 44 the air passes through supply filter 32. Similarly, prior to being exhausted to the room, the air is passed through exhaust filter 30. Filters 30 and 32 are both High Efficiency Particulate Air (HEPA) filters of a type well known to those skilled in the art. Thus, cabinet 10 is used to perform experiments within work area 44 and to contain any contaminated air within the cabinet. Particular and novel details of construction are more fully set out below.
As best seen in
Sash grill 24 extends between the front of work surface 22 and bottom panel 14 from one side panel 16 to the other. As best seen in
As best seen in
Turning to the rear of cabinet 10, baffle 20 is mounted between side panels 16 and can be secured in place such as by bolting or welding. The lower-most edge of baffle 20 may be provided with a support lip 58 as best seen in FIG. 3. Lip 58 is used to support work surface 22 and may be provided with a number of threaded holes to secure work surface 22 to baffle 20. Located above the lower most surface of baffle 20 and extending from one side of baffle 20 to the other, are a number of slots 60, as best seen in FIG. 8. Slots 60 are provided to allow air flowing downwardly from blower 28 to pass there through and into the plenum formed by baffle 20 and rear panel 18.
As best seen in
As best seen in
Turning to details of the plenum box 33 and associated filters, and as best seen in
As best seen in
To adjust the position of filter 30, the upper bracket 104 includes a pair of threaded holes 112, through which are placed a plurality of bolts 114. A retaining nut 116 is rigid with bracket 104 and in alignment with each bolt 114. Each bolt 114 has a head 114a, a threaded portion 114b and a length such that it extends to the upper surface of plenum box 64, and as shown in
Any air that is not recirculated through supply filter 32 and work area 44 must be filtered and exhausted from the cabinets. If air is to be exhausted into the room, exhaust control cap 36 is used. As best seen in
The above described embodiment of control cap 36 is utilized when the exhaust air from safety cabinet 10 is exhausted directly into the room. In an alternative embodiment, the air is not exhausted directly into the room, but rather is directed into an exhaust system that removes the air from the building. In this embodiment, a different exhaust control cap 131 used, and is shown in FIG. 9. As shown, control cap 131 has mounting flanges 132 that secured to top panel 34. In this embodiment, rather than the side surfaces 133 being provided with apertures 128, the side surfaces 133 are solid. In this embodiment however, a top surface 134 is provided with an exhaust duct 135. Preferably, duct 135 is cylindrical. Duct 135 may be provided with a damper 136 as is known to those of skill in the art. An apertured plate 138 mounted below duct 135 and above the exhaust filter 30 provides a mechanism for controlling the flow of air through the exhaust filter in much the same manner as control cap 36 described above. As shown in
The front of cabinet 10 also has a novel construction. As best seen in
As best seen in
As can be seen in
As can be seen from the above, the invention provides a biological safety cabinet with a number of improved features and achieves a better air-flow into and through the cabinet. From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects herein above set forth, together with other advantages which are inherent to the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.
Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
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|U.S. Classification||454/58, 312/209, 454/57|
|Cooperative Classification||B08B2215/003, B08B15/023|
|Nov 16, 2009||REMI||Maintenance fee reminder mailed|
|Jan 8, 2010||SULP||Surcharge for late payment|
Year of fee payment: 7
|Jan 8, 2010||FPAY||Fee payment|
Year of fee payment: 8
|Jun 13, 2013||FPAY||Fee payment|
Year of fee payment: 12