CA1044740A - Cabinet for biohazardous materials - Google Patents

Abstract

A B S T R A C T

An imperforate tubular-like cabinet is disclosed having a hinged viewing panel in the front portion providing a gap at the lower portion of the hinged viewing panel with the balance of the cabinet for the two-fold purpose of admitting makeup recirculatory air and permitting the hands of an operator to work with biohazardous material atop a tray provided in the inner portion of the cabinet. A lower and plenum chamber as well as recirculatory and exhaust filters are provided to recirculate laminar flow air and filter the same before exhaust. The hinged viewing panel is provided with an airfoil section for the two-fold purpose of creating a negative pressure and accelerated airflow in front of the access opening at its lower portion, and to permit the operator to position the head for viewing the work table interiorly of the outer confines of the cabinet.

Description

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BACKGROUND OF THE INVENTION

Field of the Invention The invention relates to the handling of biohazardous and potentially hazardous material such as cancer tumors, T.B., -fungi, viruses, parasites, bacteria, tissue cultures, dust, radio-active material, allergens, toxic materials, and preparation of materials for tissue culture and microbiological investigation, and can also be used where ultra clean air is required as for plate pouring, packaging, and sterility testing. Federal Standard 209a, Class 100, is directed to the environmental air control within clean rooms and clean wor~
stations. Units commercially available in the prior art include the CCI Biohazardous I.aminar ~irflow SaEety Hoods manufactured by Contamination Control, Inc., oE Culpsville, Pennsylvania; a Bioguard Hood Vertical ~aminar Flow Cabinet manufactured by the Baker Company of Sanford, Maine; sio-hazardous Safety Cabinets of S. Blickman, Inc., of Weehawken, -~
New Jersey; and the Biological Cabinet of Bioquest Division of Becton, Dickinson and Company of Cockeysville, Maryland. The units are closed recirculatory systems using HEPA filters (high eficiency, particu:late air) which remove organism and particles 0.3 micron in size with 99.97~ efficiency.
Description of the Prior Act The prior act of the character set forth above to pinpoint the field of invention are generally rectangular tubular cabinets having a breakfront inspection panel at the front portion. The breakfront extends outwardly from the general outline of the cabinets, and in most instances is covered by glass or other transparent material to permit ~ interior inspection. The opening at the lower portion may be of a glovebox-type, or unobstructed for access by the hands ~,1~ '' '

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of the worker. In the prior art the interior airflow is :-diverted from the vertical by postitioning the HEPA filters at an angle, rather than perfectly horizontal. The airflow further is disrupted from laminar and full control by the breakfront cabinets which generally break at an angle of 14 to 15 outwardly thereby permitting the air in the laminar flow to expand at that point adjacent the opening where the same can escape and render the conditions hazardous for the operator. ~ .
Furthermore, the full standing units of the prior art are . .
10 fabricated from several panels bolted in place requirlng ~ ;
extensive gasketing and other sealing to insure a closed .
system without leaks. Cabinets of the character just described ~ :
having an outwardly extending front are exemplified in Un.ited States patent 3,470,679. E'urther indica-ting the failure of :, the prior art to develop a circulatory flow in biohazardous insulated relationship is patent 3,494,112 where, see FIG. 5(b), the air is directed out towards the worker.
Summary of Invention ::
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The present invention is directed to a cabinet for biohazardous materials being formed of an imperforate recirculatory rectangular tube and having a viewing panel providing access of the interior elements which has an .~
aerodynamic airfoil-type recess for directing the downwara :
flow of the air at an accelerated rate as compared to the :. --.
.: . :
balance of the air in the unit and also permitting the .~
.. .. .
operator to position the head at ~he recessed portion of the .
viewing panel thereby obtaining a closer view of the work table ;.

provided in the interior portion. The work table or tray is removably secured in a hori~ontal plane in the interior . : .
~: ' .
30 portion of the cabinet atop a perforated support which is also ~ :
. . .
removable. The viewing panel is hinged at its upper portion :

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and removable therefrom permitting the positioning interiorly of the cabinet of large work pieces which would not otherwise pass through the gap provided at the lower portion of the viewing screen for the twofold purpose of permitting access of the hands, and also admitting makeup air" The aerodynamic characteristics including the plenum chamber, blower and filters is such that the airflow rate immediately in front of the unit . .
at the gap for permitting the hands to enter is greater than that interiorly of the unit and also at a negative pressure ~ ;
thereby insuring that the makeup air moved inwardly as dist~
inquished from any interior recirculatory contaminated air moving outwardly, ~
In view of the foregoing, it is a principal objec-t oE :.
the present invention to provide a cabinet for b.ohazardous materials in which the airflow is so confined to inhibit the .::
exhausting of the potentially contaminated air within the unit, while at the same time facilitating a closer view to the operator of the materials being handled on the work tray.
Another object of the present invention is to prov:lde 2Q a cabinet construction which is generally imperforate thereby ; .
eliminating the leaks which may otherwise occur during the degradation of gasket materials where a plurality of panels are :
bolted in place. A related and more detailed object of the invention is -to provide such cabinet which nevertheless provides ready access to the removal of the HEPA filters, work tray, motor, and other WlitS which may require repair and replacement during the lifetime of the use of the cabinet.
A further object of the present invention is the added ; .
safety obtained by the double wall construction which surrounds the positive pressure element of the full standing unit,, Still another object of the present invention is to JED:do'c 8/4/75 321-2-CA~

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provide a viewing panel which is hinged in position with removable hinges so that the same can be easily opened for the insertion oE large objects, or completely removed for cleaning and servicing the unit including the removal of filters.
Yet another object of the present invention ls to ~.
provide a cabinet for biohazardous materials the main elements ~
of which can be readily modified for a desk too unit from a ~ :
full standing unit with knee access therebeneath. . :
DES~RIPTION OF DRAWINGS ...
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Further object and advantages of the present invention .
will become apparent as the following description of an illustrative embodiment takes place taken in conjunction with :
the accompanying drawings in which: ,.
FIG. 1 is a front partially perspective view illustrating the subject cabinet and its principal exterior .~ -elements. .`
FIG 2 is a front perspective view of an alternative desk model cabinet illustrating its principal elements viewed : ~
externally. ~ ;. .
FIG. 3 is a vertical sectional view taken along ~ection line 3-3 of FIG. 1 of the larger cabinet illustrative .. ;
of the present invention. . .
FIG. 4 is a transverse sectional view of the subject :-cabinet along section line 4-4- of FIG. 3.
FIG. 5 is an enlarged broken transverse sectional view ;~
illustrating the gasketed mating relationship between the ~:.
viewing panel and the body of the cabinet.
FIG. 6 is a further vertical sectional view of the sub~ect cabinet taken along section line 6-6 of FIG. 3 and illustrating the relationship between tha plenum chamber, :.
blower, work table, and filters. . . ~ .

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FIG. 7 is a vertical sectional view of the desk top alternative embodiment cabinet taken along section line 7-7 of FIG. 2. `
DETAILED DESCRIPTION ~-The subject cabinet for biohazardous materials 10 as shown in FIG. 1 is fully encased in an imperforate closed ~ :
tubular housing 11 with the exception of those openings. ~ ~
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provided for the viewing panel 20 in front, and the exhaust filter 14 at the rear top. The biohazardous materials which ;~ ;
are positioned atop the work tray 15 are the subject of a bath of recirculating filtered air which circulates in the -~
interior of the cabinet 10. Any openings in the closed :
tubular houæing.ll, therefore, are a possible source of a leak whereby such blohazardous materials may pass into the workroom and infect persons wor]sin~ there. Thus with only .
two openings to the closed tubular housing 11 as pointed out :
above, only two areas of potential difficulty need be dealt .
with in the sealing of the cabinet 10.
Referring now to FIG. 3, it will be seen there that the recirculating filter 12 is positioned interiorly of the closed ~ .-tubular housing 11 and in airflow communication with the plenum chamber 19. The exhaust filter 1~, however, can be positioned atop or within the uppermost aspect of the unit and diverts, recirculating air, preferably in the quantity of 20 to 25 percent, to the outside. Conventional ducting :~
may be used to convey the exhausted air out of the room into exhaust ducts or to a remote air incinerator~ .
Airflow is provided by means of a blower 18 driven by an electric motor which pumps air from the kneehole chamber 27 as the same passes throu~h the perforated support 30 for the worktray 15. The blower 18 has its speed controlled JED:do'c 8/4/75 321-2-CAN

through one of the control members on the control panel 29 (see FIG. 1) and i5 SO adjusted to maintain a laminar flow of air in the cabinet 10 above the worktray 15 at approximately 100 ft. a minute. The viewing panel 20, as will be particularly observed in FIG. 3, is provided with an airfoil :~
recess 22 terminating at a makeup air slot 25 at its lower portion, the makeup air slot being de~ined by the support legs .
24 of the viewing panel 20. The viewing panel 20 is formed into the shape required, and also transparent to the operator.
It will be noted that the makeup air slot 25 also provides the hand access for the worker to the materials po.sitioned atop the worktray 15. :
The nature of the air~oil recess 22 is to accelerate the Elow o~ air immediately adjacent its sur:Eace.and provide a negative pressure portion downstream of the maximum point of penetration of the airfoil recess 22. This accelerated flow .
creates a sligh~ negative pressure over the viewing panel 20 and particularly adjacent the makeup air slot 25 to the end ..
that the makeup air is constantly being drawn into the interior :
of the cabinet 10, and affirmatively inhibited from exiting through the makeup air slot 25 even though passing around the . .
hands and forearms of the technician utilizing the cabinet 10.
In addition the makeup air is directed beneath the work tray by the negative pressure from the motor blower and does not . ~ ~:
contaminate work being carried out on the work tray. A further .
advantage created by the utilization of the airfoil recess 22 .

is that it is close to the approximate position where the operator will position h.is head to look forwardly at his ..
specimens on the worktable 15~ Normal studies have indicated ~ :.
that the average person inclines his body at approximatel.y 14 to 16 degrees when worlcing over a flat surface in order to .. .

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obtain the best view of his work. To this end, the angle of the viewing panel with the vertical is approximately 15 .~
degrees thereby providing the best access for the operator, as :
well as sufficient hi~hlift characteristics to the airfoil recess 22 to achieve the accelerated airflc,w rate and negative pressure at the makeup air slot 25. For the further com~ort of the operator, a kneehole recess 26 is provided beneath the ;
forward position of the work tray 15 and its associated support 30. The kneehole recess 26, in turn, defines a knee~ :~ :
hole chamber 27 which serves as the collecting area for the ~
blower 18 which thereafter recirculates the-air upwardly :.. ;:
through the plenum chamber 19. .
Removability for servicing is also accomodatecl in the construction shown. For example, it will be seen that t:he work tray 15 is gravity supported in a perforated support 30.
As noted in FIG. 4, the perforated support 30 has a plurality ~ :
of perforations 33. The support is also removably fi~ted atop the support legs 32 which define the undertable opening 34 which is in airflow open communication with the kneehole chamber 27~ The worktray 15 may be removed ~or cleaning as well as its per~orated support 30. To further facilitate removal, the viewing panel 20 is secured by means of liftout . .
hinges 21 to the front o~ the closed tubular portion 11 of the cabinet 10. When a large specimen is to be positioned atop the worktray 15 r raising the viewing panel 20 readily -permits the same. In addition, the viewing panel 20 may be readily removed from its hinges 21, and the transparent .
portion cleaned, sterilized, or otherwise serviced.
In addition, while the viewing panel ~0 is removed, access may be had by the technician from underneath to the : .

recirculating HEPA filter 12 and ~rom above to the motor .:
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17 and blower 18. The light box 28 provided at the front :.-. ': ~ ,' .~ .. .
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upper portion of the viewing panel 20 may be easily removed ~ .
without removing the viewing panel 20 or entering the cabinet ~;,::i ;
10 .
The shape of the plenum chamber l9 is best shown in FIG. 6 where it will be seen that it flares outwardly and ~:
upwardly to the horizontal portion l9 of the plenum chamber ~
at the top of the cabinet 10. The air therefore circulates ~;
in the rear of the cabinet 10 in a chamber defined by sidewalls which are interior of the back 31 of the working area, and the back of the cabinet 10 defined by the closed tube housing 11.
Desirabl~ the housing is provided with a double wall construction ~5 to further inhibit leakage. Air within :its confines is under negative pressure and sucked back by the blower to be recirculated. : .
To further insure against air leaks of the recirculating :.
air within the interior of the cabinet lO, a gasket 35 is provided around the marginal closed edges of the viewing panel :
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20 and engages an offset sealing edge 38 provided around the `
marginal edges of the viewing panel 20, and at its upper edge portion where the same is hinged by means of hinges 21 to the cabinet 10. Specifically as ~own in FIG. 5, the serrated gasket 35 has a plurality of ridges 37, and is positioned within a channel 36 which is slightly undersized so that the resiliency of the gasket 35 secures the same in place, and is further reinforced by means of the pressure of the sealing edge 38 against the ridges 37, ALTERNATIVE E~BODI~ENT ~
The alternative embodiment or desk model 50 is illustrat- :

ed in FIGS. 2 and 7. As will be observed, all o.f the reference -.,.
materials in connection with the description of the desk model 50 are the same where they are common with the e:Lements of the freestanding cabinet 10. Turning now to FIG. 7~ it will be _9_ : : .
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seen that the principal difference in construction relates to the provision of a desk top chamber 54 beneath the worktray 15 and its perforated support 30 and receives recirculating air in open communication with the undertable opening 34. By ~ :
mounting the blower motor 41 above the closed tubular housing -11 of the desk model 50, and on support pla~e 55, a plenum .
chamber 19 is provided below the blower and above the filter 12. A diverting baffle 56 is positioned below the output of the blower to distribute the air flow across the filter 12.
A communicating duct 57 directs air to be exhausted from the :
plenum chamber 19 to the exhaust filter 14. The provisions for mounting the viewing panel 20 and its removabl~ features ,.. ~
remain the same in the desk model 50 as in the freestand.ing unit 10.
In a typical commercial embodiment of the freestanding cabinet 10, the same is 53 inches wide and 76 1/2 inches high with a depth of 30 inches. A 2-foot wider un.it is also commercia].ly available. Provision can be further made to direct the exhaust air to an aix incinerator, should additional .;
security be desired, The kneehole depth is 12 inches and the kneehole access provided is 26-1/2 inches high. Desk top models are commercially available in 3~ , and 6-Eoot widths.
The viewing panel 20 oE the commercial embodiment ;~.
cabinets 10 and 50 are as wide as the work area. The curved - -portion in the viewing panel 20 defining the airfoil recess ~ .
22 is recessed approximately Ç inches from the vertical plane :. -defined by the viewing panel 20. Also in the commercial ~
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embodiment of the freestanding unit the support ledge 32 which supports the removable perforated support 30 and worktray 15 : -~
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serves as a spill tray which ma,v be cleaned at the time the ~ .

worktray 15 and its associated support 30 are removed for ,-" ' .
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cleaning. ~ 4 ~7 Although particular embodiments of the invention have been shown and described in full here, there is no intention to thereby limit the invention to the detai.ls of such embodiments. On the contrary, the invention is to cover all modifications, alternatives, embodiments, usages and equiva-lents of a cabinet for biohazardous materials as fall within the spirit and scope of the invention, specification and the appended claims.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
-- 1. Cabinet for biohazardous materials having a rectangular housing comprising, in combination, - a vertical tube defining a portion of said cabinet, - a blower mounted interiorly of said housing, - a plenum chamber in open communication with said blower for directing contaminated air upwardly in the rear portion of said tube, - a recirculating filter and an exhaust filter in airflow communication with said plenum chamber, - a work tray positioned in a midportion of said tube, - an opening having upper, lower, and side edges in said vertical tube the major portion of which is above the work tray, - a curvilinear viewing panel secured to said upper edge of the opening and depending downwardly and inwardly there-from and thence forwardly thereby defining an airfoil recess with its deepest penetration in the upper half of said vewing panel, - said recirculating filter being positioned adjacent to and above said viewing panel, - a slot at the lower portion of said viewing panel permitting operator access to the work tray and for admitting makeup air laterally spaced from said work tray, whereby interiorly recirculating laminar flow air passes over the viewing panel thereby further directing the makeup air through contaminated air. ---- 2. In the cabinet of Claim 1, - a double wall construction in spaced relation to the vertical tube with the space thereby defined being in airflow communication with negative pressure inside the vertical tube to thereby assist in reducing potential leakage of biohazardous material. ---- 3. In the cabinet of Claim 1, - removable support means for said tray, - means defining uniform openings in said support means for uniformly transmitting the air around the periphery of said tray. ---- 4. In the cabinet of Claim 1, - said tube being formed of imperforate welded construction, - said tube having a front face and rear face which are substantially parallel with the front face being interupted by the viewing panel and a base and top sub-stantially perpendicular to said front and rear faces. ---- 5. In the cabinet of Claim 1, - said filters being parallel with the work table and substantially perpendicular to the air flow.

-- 6. In the cabinet of Claim 1, - said removable viewing screen being secured to the unit by means of hang-on-type hinges, - gasket means interposed in pressure relationship to the marginal edges and bottom of said viewing screen and along the top edge, and - pressure locking means at the lower portion of said viewing screen to secure the same in non-communicable airtight relationship to the cabinet when in the fixed working position.

-- 7. In the cabinet of Claim 1, - a support above the recirculating filter defining a second plenum chamber above the filter and serving to support the blower. ---- 8. In the cabinet of Claim 1, - blower means provided in the lower portion in open communication with the plenum chamber which is under positive pressure, and in open communication with the work tray and double wall which are under negative pressure. ---- 9. In the cabinet of Claim 1, - said blower being mounted at a lower and rearward portion of the cabinet, and - means defining a kneehole beneath a portion of the work tray and the viewing panel, whereby an operator may conveniently sit at the cabinet, place his hands through the makeup air slot, and view the work table at a natural inclined position.