U.S. patent number 3,811,250 [Application Number 05/354,217] was granted by the patent office on 1974-05-21 for contamination control apparatus.
This patent grant is currently assigned to Becton, Dickinson and Company. Invention is credited to James McFarland Fowler, Jr..
United States Patent |
3,811,250 |
Fowler, Jr. |
May 21, 1974 |
CONTAMINATION CONTROL APPARATUS
Abstract
The contamination control apparatus of this invention includes a
hollow cabinet having a work area in one portion thereof and an
opening therein permitting access to the work area from the
exterior of the cabinet. Decontamination and air supply means are
in the cabinet and positioned so that air discharge therefrom will
be decontaminated and then passed into the work area. Diffusion
means are mounted in the cabinet and positioned between the
decontamination and supply means and the work area to facilitate
the diffusion of the air as it enters the work area. Consequently,
the air flows uniformly through the work area and assist in
providing a clean air curtain over the access opening to the work
area to facilitate the prevention of contaminated air from leaving
or entering the work area through the access opening. A series of
interconnected air plenum chambers are in the cabinet in
communication with the work area, decontamination and air supply
means, and the opening to the exterior of the cabinet to permit the
air passing through the work area and a portion of air from outside
of the cabinet to be directed to the decontamination and air supply
means. Negative pressure reducing means are in the cabinet to
direct a predetermined amount of decontaminated air out of the
cabinet sufficient to maintain a lesser pressure within the cabinet
and exteriorly thereof and, finally, air velocity indicator and
control means are mounted on the cabinet to facilitate the control
of air flow within the cabinet.
Inventors: |
Fowler, Jr.; James McFarland
(Albuquerque, NM) |
Assignee: |
Becton, Dickinson and Company
(East Rutherford, NJ)
|
Family
ID: |
26903210 |
Appl.
No.: |
05/354,217 |
Filed: |
April 25, 1973 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
208454 |
Dec 15, 1971 |
|
|
|
|
839967 |
Jul 8, 1969 |
|
|
|
|
Current U.S.
Class: |
96/422;
55/DIG.29; 454/56; 55/473 |
Current CPC
Class: |
B08B
15/026 (20130101); B01D 46/00 (20130101); B08B
15/023 (20130101); B08B 2215/003 (20130101); Y10S
55/29 (20130101) |
Current International
Class: |
B01D
46/00 (20060101); B08B 15/00 (20060101); B08B
15/02 (20060101); B01d 031/00 () |
Field of
Search: |
;55/467,470-472,473,274,DIG.29 ;98/115LH ;62/256 ;73/212
;417/43 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nozick; Bernard
Attorney, Agent or Firm: Kane, Dalsimer, Kane, Sullivan and
Kurucz
Parent Case Text
This is a division of application Ser. No. 208,454, filed Dec. 15,
1971, which is a continuation of Ser. No. 839,967 now abandoned.
Claims
I claim:
1. A contamination control apparatus comprising:
a hollow cabinet having a work surface mounted in one portion
thereof and an opening in the front wall of the cabinet permitting
access and being adjacent to a portion of the work surface;
air supply means mounted in said cabinet;
high efficiency filter means mounted in said cabinet and connected
to the air supply means by a plenum and positioned so that air
discharge from said air supply means passes therethrough for
decontamination and diffusion of the air;
diffusion means mounted in the cabinet between the high efficiency
filter means and the work surface for diffusion as air enters the
work area so that laminar flow is provided on the work surface and
providing a controlled flow passage for a substantial portion of
the air from the air supply means to the work surface;
means defining a channel mounted in said cabinet adjacent the
access opening and adjacent the diffusion means for communication
with flow from the filter for directing a predetermined portion of
the filter air discharge from the air supply means across the
access opening at a higher velocity than the air passing through
the diffusion means and to thereby form an air curtain across the
access opening within the cabinet and prevent interchangeability of
air between the work area and the exterior of the cabinet;
exhaust means from said cabinet communicating with said work
surface to direct a predetermined amount of air from said
cabinet;
said exhaust means including negative pressure producing means
sufficient to maintain a lesser pressure within a portion of said
cabinet than exteriorly thereof;
said exhaust means including air direction means within said
cabinet to direct the flow of air therethrough with only a negative
pressure condition present in that portion of the cabinet adjacent
to the exterior walls thereof to minimize the danger of leakage of
air from the interior of the cabinet; and
means for directing a portion of the air from the work surface to
the air supply blower.
2. The invention in accordance with claim 1 wherein a series of
interconnected air plenum chambers are in said cabinet in
communication with said work surface, said filter and diffusion
means, said air supply means, said access opening, and said exhaust
means, to facilitate the direction of air flow with respect to the
interior of said cabinet.
3. The invention in accordance with claim 1 wherein said air supply
means includes an air supply blower mounted in said cabinet and
positioned so that air discharge therefrom will be directed into
said work area, and said exhaust means including an exhaust blower
mounted in said cabinet and in communication with the exterior of
said cabinet to direct a predetermined amount of air out of said
cabinet, and an exhaust filter mounted in said cabinet between the
exhaust blower and the exterior of said cabinet to assure that only
clean air is removed from the exterior of said cabinet.
4. The invention in accordance with claim 1 wherein said work
surface includes the zone defined by a horizontal table and at
least two substantially vertical plates spaced from one another and
spaced above said table to permit removal of air from said work
surface.
5. The invention in accordance with claim 1 wherein said diffusion
means is a screen forming a substantial portion of the upper
boundary of the work area and is positioned with respect to said
filter means and air supply means so that a substantial portion of
the air supply therefrom passes through said screen.
6. The invention in accordance with claim 1 wherein said channel
means includes two substantially vertical plates in said cabinet
adjacent to said work area and terminating above said access
opening with the channel formed between said plates communicating
at one end with the exhaust side of said filter and at the other
end with the access opening so that a portion of the air exhausted
from said filter passes at a relatively high velocity through said
channel and across said access opening to provide an air
curtain.
7. The invention in accordance with claim 1 wherein air velocity
indicator means are mounted on said cabinet to monitor the air
velocity in said cabinet.
8. The invention in accordance with claim 7 wherein control means
are on said cabinet in connection with said air supply means to
facilitate the adjustment of air flow within said cabinet in
response to an indication of said air velocity indicator.
Description
BACKGROUND OF THE INVENTION
When working in a biological environment it is extremely
advantageous to provide means for controlling airborne
contamination. In addition to being able to control airborne
contamination within the work area it is also particularly useful
to provide easy access to the work area so that normal and
efficient operation within the area can be carried out. So, it is
valuable to the art to be able to contain the work area within a
protected atmosphere while simultaneously permitting easy access to
the work area to carry out whatever functions are necessary within
the area. Naturally, it is desirable to provide both protection
against contamination from the exterior of the work area as well as
protection against contaminating media from escaping from the
confined work area into the surrounding atmosphere. In short, it is
desirable to control the airborne contamination in a biological
work environment by both preventing the ambient aerosols from
contaminating a work sample and also preventing contaminating
aerosols from escaping from the work sample into the surrounding
environment.
A suggested method for accomplishing these objectives is to provide
a cabinet to generally contain a work area and the work sample
therein while providing an access means for a workman to handle the
work sample. Simultaneously, a laminar flow environment is provided
in the cabinet to provide an air curtain over the access means to
prevent cross flow of aerosols between the work area and the
exterior of the cabinet.
It is naturally advantageous to provide the most efficient means of
insuring that no cross contamination occurs and by providing close
control over the laminar flow air barrier provided by the cabinet
arrangement. Therefore, control means which facilitates the control
of the flow and the particular atmosphere and pressure within a
contamination control cabinet would also be extremely advantageous
to the art.
Naturally, the best possible protection and the most efficient and
accurate working conditions should be provided when working in the
presence of possible contamination produced by air flow. An
apparatus which provides close control over the laminar flow of air
in a biological contamination control cabinet so that the most
uniform and positive protection is achieved during the greatest
percentage of the work time is desirable. At the same time the ease
of access and handling of the work sample should not be lessened
thereby providing the greatest protection and most efficient
working conditions while handling a sample subject to emanation or
reception of ambient aerosols during handling thereof.
SUMMARY OF THE INVENTION
With the above comments in mind, among the primary objectives of
this invention is to provide a biological contamination control
cabinet for controlling airborne contamination in a biological work
environment. The cabinet and the apparatus associated therewith
provide a filtered air barrier to prevent ambient aerosols from
contaminating the work sample contained within the cabinet and also
provides a filtered air curtain over the access opening of the
cabinet to prevent ambient aerosols from leaving or entering the
cabinet itself.
Furthermore, a negative pressure is provided in the cabinet to
prevent contamination from the work sample from escaping into the
surrounding environment through the access opening in the cabinet
or through any other portion of the cabinet where leakage might
occur. All air recirculated through the cabinet and exhausted from
the cabinet by the apparatus in general is filtered by absolute
filters or, as commonly designated in the trade by HEPA filters, to
remove contaminating aerosols.
The apparatus provide a high velocity clean air curtain across the
front opening which provides a kinetic air barrier between the
inside and outside of the access opening in the cabinet front of
the apparatus. Furthermore, all air plenums containing
contaminating aerosols are at a negative pressure with respect to
the surrounding environment or completely contained within a
surrounding negative pressure region. Thus preventing leakage of
contaminated air out into the laboratory.
Cooperating with the contamination control cabinet as part of the
apparatus is a device which indicates the air velocity within the
laminar flow cabinet by means of a pitot tube, or similar device,
located the blower discharge within the cabinet and connected
differentially across a sensitive flow meter. The air velocity
through the cabinet is indicated by calibrating the flow meter to
read the velocity pressure in the blower discharge against the air
volume delivered by the blower. The air velocity is controlled by
means of a solid state electronic speed controller of a common
commercial type, on the blower motor with the entire velocity
indicator, speed control and switches being incorporated into an
injection molded control panel which may be mounted on the laminar
flow cabinet. The air velocity indicator and control indicates air
velocity and is independent of static pressure while providing a
combination velocity indicator and control which is incorporated as
a one-piece unit adapted to be mounted on the contamination control
cabinet with easy access and operability available to a person
working with the contamination control apparatus in general.
In this manner, close control may be maintained at all times over
the environment contained within the work area in which the work
sample is located thereby providing an effective and efficient
contamination control apparatus which is a significant improvement
over the known art.
Briefly, the contamination control apparatus of this invention
includes a hollow cabinet having a work area in one portion thereof
and an opening therein permitting access to the work area from the
exterior of the cabinet. Decontamination and air supply means are
in the cabinet and positioned so that air discharge therefrom will
be decontaminated and then passed into the work area. Diffusion
means are mounted in the cabinet and positioned between the
decontamination and supply means and the work area to facilitate
the diffusion of the air as it enters the work area. Consequently,
the air flows uniformly through the work area and assists in
providing a clean air curtain over the access opening to the work
area to facilitate the prevention of contaminated air from leaving
or entering the work area through the access opening. A series of
interconnected air plenum chambers are in the cabinet in
communication with the work area, decontamination and air supply
means, and the opening to the exterior of the cabinet to permit the
air passing through the work area and a portion of air from outside
of the cabinet to be directed to the decontamination and air supply
means. Negative pressure reducing means are in the cabinet to
direct a predetermined amount of decontaminated air out of the
cabinet sufficient to maintain a lesser pressure within the cabinet
and exteriorly thereof and, finally, air velocity indicator and
control means are mounted on the cabinet to facilitate the control
of air flow within the cabinet.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of a contamination control apparatus
of this invention;
FIG. 2 is a side elevation view thereof with the front panels and
base portions having been removed;
FIG. 3 is a sectional end elevation view thereof taken along the
plane of line 3--3 of FIG. 2 with arrows showing the direction of
air flow within the apparatus;
FIG. 4 is a schematic wiring diagram of the electrical system
incorporated in the apparatus of this invention;
FIG. 5 is an exploded perspective view of the air velocity
indicator and control portion of the apparatus of the invention;
and
FIG. 6 is a schematic view of a portion of the apparatus of the
invention showing the connection of the air velocity indicator and
control portion with the cabinet portion thereof with the remainder
of the apparatus broken away and removed and showing an end
elevation view of the air velocity indicator and control panel with
arrows indicating the flow of air through the interconnected
portions of the apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Initially, reference should be made to FIGS. 1-3 which depict the
entire contamination control apparatus 20 in assembled and
operational condition. As shown in FIG. 1, the apparatus consists
of a cabinet 21 and a removable floor stand 22. The removable floor
stand is usable to facilitate bringing cabinet 21 to a more
comfortable working level for the operator. A glove port panel 23
is provided on the exterior of cabinet 21 with two glove ports 24
and 25 provided therein to facilitate reception of the hands of the
operator when he is working on a work sample within cabinet 21. The
glove port panel may be fastened by any common fastening means such
as the thumb screws 26 shown in FIG. 1. A portion of the front side
of cabinet 21 is constructed of a transparent material such as
glass. This portion 27 facilitates viewing of the interior of the
cabinet 21 during operation. It might also be noted that the front
portion of the cabinet which includes transparent portion 27 and
glove port panel 23 is tapered outwardly from top to bottom with
respect to the cabinet thereby providing a greater work area within
the cabinet on which to rest the work element such as horizontal
surface or work deck 28.
The velocity indicator and control panel 29 is located on the front
side of cabinet 21 above transparent portion 27. The upper outer
front portion of cabinet 21 contains a removable panel 30 which
when removed permits access to the interior of the cabinet in the
area where the blowers are located. This facilitates maintenance of
the working components of the apparatus. Once again, removable
panel 30 is fastened in position by any common means such as thumb
screws 31.
Cabinet 21 itself takes a substantially rectangular configuration
with the exception of the outwardly extending portion of the front
side which was discussed above. The remainder of the cabinet is
completely enclosed and includes a top panel 32, a rear panel 33,
opposing side panels 34 and 35 and base panel 36. If the removable
floor stand is employed, it is designed to mate with the bottom
surface of bottom panel 36 so as to maintain cabinet 21 in an
upright supported position.
Also to be noted in FIG. 1 in viewing the top panel 32, a
protective screen 37 is present through which the exhaust air is
expelled from the cabinet in a manner which will be explained in
greater detail below. Also present on the top panel 32 is a make-up
prefilter 38 and a slidable make-up prefilter damper 39 to close
make-up prefilter 38 when it is not desirable to utilize this
element. The make-up prefilter is utilized primarily only in
facilitating initiation of operation of apparatus 20 and thereafter
damper 39 is in the closed position. The exhaust protective screen
is necessary to provide the exhaust outlet for the exhaust blower
as will be described in detail below.
Turning to FIG. 2 in particular, it will be noted that in this
Figure the front panels of cabinet 21 have been removed and the
interior of cabinet 21 as seen from the front view without the
presence of removable panels is shown. On the lower portion of
cabinet 21, a rear exhaust screen 40 is shown mounted to back panel
33 of the cabinet. The entire access opening 41 is exposed one
glove port panel 23 has been removed. Gas air or water cocks 42 may
be provided for the introduction of whatever fluid is desirable for
a particular use to which the cabinet is to be put. Furthermore,
adjacent thereto at the lower portion of the cabinet is a standard
outlet 43 to which proper electrical connections for the system may
be attached.
Velocity indicator and control panel 29 is mounted on the permanent
portion of the front side of cabinet 21 and noted thereon is the
variable air velocity control knob 44 as well as an off-on switch
45 to turn the blowers off and on and a light switch 46 to turn the
lights within the unit off and on as will be described in detail
below. Also on control panel 29 is the velocity indicator 47 shown
in connection with the air supply blower 58 exposed with the
removal of upper front panel 30 from cabinet 21. The particular
elements of control panel 29 will be described in detail at a later
point in this disclosure. It may be noted that an input hose 49 for
air is connected between the blower 48 and the lower end of
velocity indicator or flow meter 47 and a corresponding output line
50 is also connected between air supply blower 48 and the upper end
of flow meter 47 to return the air to the blower exhaust when it
has passed through flow meter 47.
A supply filter 51 is mounted on the interior of cabinet 21 below
air supply blower 48 and above the work area 52 within cabinet 21.
Air supply blower 48 and air supply filters 51 may be mounted in
any convenient manner to maintain them in their relative positions
within the cabinet. Suitable mounting shelves are shown in the
drawings in particular in FIG. 2.
All of the filters employed with the apparatus of this invention
are filters which are generally known in the art as absolute
filters which prevents the transferring of contamination along with
air flow into and out of the cabinet. A designation well known in
the art for a filter which will work satisfactorily with a cabinet
of this type is a filter known as an HEPA filter which will achieve
the desired results during the operation of the apparatus 20.
Mounted adjacent to air supply blower 48 within the upper portion
of cabinet 21 is exhaust blower 53 which is also suitably mounted
within the cabinet by means of any convenient means such as the
shelving and bracketing shown in FIG. 2. The exhaust end of exhaust
blower 53 is connected to exhaust filter 54 which is also an
absolute filter of the HEPA type as mentioned above. The upper end
of exhaust filter 54 communicates with screen 37 and therethrough
to the atmosphere out of cabinet 21. Exhaust filter 54 is mounted
within cabinet 21, as shown, in an enclosed arrangement so that the
only communication with screen 37 and the exterior of the cabinet
is by passage through filter 54. Consequently, all air exhausted
through exhaust blower 53 passes through filter 54 and in this
manner contaminating aerosols are filtered out and prevented from
leaving the cabinet through the opening in which screen 37 is
mounted.
The remaining elements of the interior apparatus of the cabinet
which are subject to air flow within the cabinet are depicted most
clearly in FIG. 3 of the drawings. A description of the flow
patterns of the air within the cabinet would be an effective way to
describe the cooperation between the various portions of the
cabinet structure. To initiate operation of the laminar flow
cabinet, switches 45 and 46 are initiated to turn on the lights
within cabinet 21 and air supply blower 48 respectively. The lights
are located in the upper forward portion of the work area and
mounted to the cabinet walls. Two conventional white lights 55 and
56 are located adjacent an ultraviolet light 57. As will be
described in connection with the wiring diagram of the electrical
system of the apparatus 20, either the conventional lighting or the
ultraviolet lighting may be utilized as desired.
Air supply blower 48 then discharges a volume of air into discharge
chamber 58 where it passes through air supply filter 51. Air
chamber 58 and air supply filter 51 are confined in bracketing
within the cabinet 21. The clean filtered air from filter 51 then
passes through openings in the bracketing at the lower side of the
filter 51 into a plenum chamber 59 from where it continues its
downward flow through diffusion screen 60. Diffusion screen 60 is
mounted to two opposing substantially vertical bracket plates
mounted within the cabinet and horizontally bridges the two
vertical plates at a point adjacent the upper ends thereof. Screen
60 forms a diffusion means for forming uniform laminar flow of the
air as it passes therethrough and continues on down through work
area 52. Screen 60 is constructed so that a laminar flow transfer
of air is accomplished between plenum 59 and work area 52.
The uniform flow of air downward through work area 52 and over the
work surface protects the work sample located within work area 52
from external airborne contamination. A horizontal deck 28 is
located at the base of work area 52 and forms a working surface.
Deck 28 may be formed of a formica material or any other common
working surface for an apparatus of this type. The two previously
mentioned vertical plates 61 and 62 along with deck 28 and screen
60 form substantially the entire confining dimensions of the work
area 52 particularly when taken in combination with side panels 34
and 35 of cabinet 21 itself.
There are three potential exits points from work area 52 for the
downwardly flowing air through the work area. These are through the
front access opening 41 previously discussed and through bottom
return screen 63 or rear return screen 40. In actual operation as
will be discussed in greater detail at a later point in the
disclosure, the air passing through work area 52 is prevented from
exiting through access opening 41 by means of an air curtain formed
across this opening. Therefore all of the air passing through
screen 60 and downward through work area 52 must exit the work area
through bottom return screen 63 and rear return screen 40.
Therefore, contamination generated by the work sample itself is
picked up by the clean air flow passing downwardly through work
area 52 and swept out of the work area through return screens 63
and 40.
The nature of the confining internal support structure within the
cabinet to form work area 52, plenum 59, filter 51 and air chamber
58 is all support structure which is mounted in a conventional
manner to the interior framework of the cabinet and also serves to
form a series of interconnected plenum chambers between this
confining structure and the interior surface of the outer confining
walls of cabinet 21. This interconnected plenum system consists of
plenum 65 adjacent the bottom of cabinet 21 which communicates with
vertical rear plenum 66 which in turn communicates with upper
plenum 67. Therefore, contaminated air passing through screen 63
and 40 is picked up in plenums 65 and 66 and returned to air supply
blower 48 where it recirculates back through the work area after
being filtered by HEPA filter 51.
Additionally, a portion of the contaminated air passing through
plenum 65 and 66 enters upper plenum 67 at a position where it is
picked up by exhaust blower 53 and this portion of contaminated air
is exhausted from the cabinet through filter 54 and screen 37 at
the top of cabinet 21. This portion of air is clean since the
contaminated aerosols contained therein are removed by filter 54.
In turn, this clean exhausted air which passes through screen 37
causes a negative pressure within cabinet 21, particularly in the
areas defined by plenums 65, 66 and 67. This prevents contaminated
air contained within these plenums from escaping through any
construction joint leaks which might exist in the outer cabinet
wall construction into the laboratory. The slight negative pressure
is sufficient to assure that the outside atmospheric pressure
presents any air from the inside of the cabinet 21 which is
contained in areas such as plenum 65, 66 and 67 from escaping the
interior of the cabinet. This is a particular advantageous feature
because these plenums generally contain contaminating aerosols
which should not be allowed to escape from the interior of the
cabinet. All air which is permitted to escape from the cabinet
passes through an HEPA filter before it is allowed to pass
therefrom.
As shown by the arrows, in order to maintain equilibrium within the
cabinet 21 during operation of the apparatus, an equal quantity of
air to that exhausted through screen 37 is made up or drawn into
the cabinet through access opening 41 and mixes with internally
contaminated air passing out of work area 52 through screen 63 and
into plenum chamber 65. Additionally, screen 60 creates a slight
pressure in plenum area 59 and causes a higher air flow velocity
through slot 68 provided between plate 62 and transparent outer
surface 27 on the front of the cabinet. This slightly increased
higher air flow velocity passing slot 68 provides a curtain across
access opening 41 as it extends out of the bottom of slot 68 and
continues downwardly through screen 63 into return plenum chamber
65 at the bottom of cabinet 21.
The isolation between the air inside and outside of cabinet 21
across front access opening 41 is accomplished by three adjacent
sheets of downwardly flowing air. These sheets of air are
substantially parallel and provide a triple thickness curtain to
assure that no contamination can pass between work area 52 and the
exterior of cabinet 21. This triple curtain is formed by the air
being drawn into the cabinet by reason of the negative pressure
condition within the cabinet, the high velocity air passing
downward through slot 68 which is sandwiched between the outside
air being drawn in and the laminar flow clean air passing
downwardly through work area 52 from air supply blower 48.
Contaminated air from inside of the cabinet 21 is drawn into the
inner edge of bottom screen 63 and therefore all of the
contaminated air from inside the cabinet passes into plenum 65 and
contaminated air from outside the cabinet is drawn into the outer
edge of bottom return screen 63 as shown by the arrows in FIG. 3.
Thus, all of the contaminated air from outside of the cabinet
passes into plenum chamber 65 and does not reach work area 52 in
contaminated condition. The high velocity air curtain extending
downwardly from slot 68 positively separates these two contaminated
flows and creates an additional positive kinetic barrier. Thus, for
air to move from inside of the cabinet out or from outside in, it
must in effect cross three air streams. The resultant cabinet 21 in
operation provides a filtered air barrier across access opening 41
which prevents ambient aerosols from contaminating the work sample
in work area 52 and also provides a filtered air curtain and a
negative pressure within the cabinet to prevent contamination from
the work sample from escaping into the surrounding environment. All
air recirculated through the cabinet and exhausted from the cabinet
is filtered by HEPA filters to remove contaminating aerosols.
Naturally, the air curtain across access opening 41 in no way
interferes with an operator working on a work sample contained
within working area 52. Only a kinetic air barrier seals access 41
and prevents cross flow of air between the inside and outside of
the cabinet.
Turning to consideration of the controls employed in operating the
apparatus 20 of this invention, FIGS. 5 and 6 best depict these
features. The support panel 29 itself which is mounted on the front
wall of cabinet 21 is of one-piece integral construction and
contains a flow meter 47 therein and openings therethrough in which
to mount the variable velocity control 44, the off-on switch for
the air blowers, and the off-on switch for the lights contained
within the cabinet. These openings are designated by the numeral
69, 70 and 71 respectively in FIG. 5. Variable control 44 is
mounted in opening 69, air blower off-on switch 45 is mounted in
opening 70, and light off-on switch 46 is mounted in opening 71. An
external knob 72 is provided to rotate variable speed control 44 to
vary the blower speed and knob 72 and control 44 are mounted by any
convenient means such as lock nut 73 as shown in FIG. 5. Suitable
electrical terminals are shown on variable controller 44 as well as
on switches 45 and 46. A mounting bracket 74 is also provided to
assure that blower variable control 44 is mounted in the most
desirable fashion.
Turning to consideration of the flow meter 47, FIGS. 5 and 6 should
be considered together. The internal chamber of flow meter 47 is
formed in panel 29 and has a tapered frusto conical configuration
which is of a wider diameter at the upper end thereof than at the
lower end thereof. This chamber 55 is initially open at the upper
and lower ends thereof, however plug 76 and 77 are fitted to
suitable recesses in the upper and lower end of chamber 75 so that
the ends thereof are sealed prior to operation of the
apparatus.
Extending from the rear of panel 29 are tubular extensions 78 and
79 in vertical arrangement so that tubular extension 78 extends
horizontally from a position adjacent the upper portion of panel 29
and tubular extension 79 extends horizontally in substantially the
same vertical plane from a position adjacent the lower portion of
panel 29. A bore 80 extends through tubular extension 78 and
through panel 29 into communication with chamber 75 in a
substantially perpendicular relationship therewith. Similarly, a
bore 81 extends through tubular section 79 and through panel 29
into communication with the lower portion of chamber 75 also at
substantially a perpendicular relationship with respect thereto.
Tube 49 has one end mounted in any convenient manner within tubular
extension 79 so that the passage therethrough communicates with
bore 81 and the lower end of chamber 75. Similarly, one end of tube
50 is conveniently mounted within tubular extension 78 and the
passage therethrough communicates with bore 80 and the upper
portion of chamber 75. As previously discussed, the opposite ends
of tubes 49 and 50 are mounted to the blower discharge portion of
air supply blower 48 so that a portion of tubes 49 and 50 extend
within blower 48 in the air discharge portion thereof. Convenient
sealing gaskets 82 and 83 may be employed to insure that no air
escapes at the point where tubes 49 and 50 enter the air exhaust
portion of air supply blower 48. Gasket 82 assists in sealing the
entrance of tube 49 and gasket 83 assist in sealing the entrance of
tube 50 into air supply blower 48.
Positioned within chamber 75 of flow meter 47 is a movable
indicator 84 which is free to move vertically within chamber 75.
Movable member 84 may take any convenient form such as a ball
shaped as shown in FIG. 6 and may be formed of any convenient
material such as nylon. If it is desirable for any reason to remove
or replace indicator 84 for calibration purposes or other reasons,
a transverse passage 85 is located adjacent the lower end of
chamber 75 and communicates with the front of panel 29. Passage 85
is normally closed by set screw 86 so that no air can escape
therethrough. Set screw 86 may easily be removed to replace
indicator 84 when it is desirable. As shown in FIG. 5, the front
face of flow meter 47 is constructed of a transparent material with
a series of vertical graduated calibration markings thereon so that
as indicator 84 is moved vertically within chamber 75, it will
correspond with a reading on the outer calibrated transparent face
of flow meter 47.
The ends of tubes 49 and 50 contained within blower 48 are sealed
by plugs 86 and 87 respectively. A plurality of spaced openings 88
are located in tube 49 along the portion thereof contained within
blower 48 and face the direction from which air is being discharged
from the blower. Therefore, air will enter openings 88 and pass
through tube 49. Correspondingly, tube 50 has a plurality of spaced
openings 89 located on its surface on the portion thereof which is
inside of blower 48 and these openings face the direction in which
air is being discharged from air supply blower 48. This is depicted
by the arrows in FIG. 6. Therefore, air passing through tube 50
will exit through openings 89 into the discharge portion of air
supply blower 48.
The above arrangement of openings facilitates operation of flow
meter 47. As air is discharged from air supply blower 48, it will
enter openings 88 in tube 49 and pass therethrough into the lower
end of chamber 75. The air will pass upward through chamber 75 and
exit through passage 80 into tube 50. It will pass through tube 50
and exit through openings 89 back into the discharge portion of air
supply blower 58 and subsequently exit therefrom. The arrangement
of openings within the discharge portion of air supply blower 48
may take the arrangement as is used in a common air velocity
indicating device known in the art as a pitot tube. The force with
which the air passes through chamber 75 will determine the height
to which indicator 84 is driven upward within chamber 75. The
height at which indicator 84 is located is read in accordance with
a calibration marking on the transparent outer surface of flow
meter 47. Therefore, if a marked change in the height of indicator
84 is noted, a subsequent change in the speed at which the blower
discharges air may be made by adjusting variable speed controller
44. This is accomplished as discussed above by merely turning knob
72 on control panel 29.
Thus, a device is provided which indicates the velocity within the
cabinet 21 by means of a pitot tube or similar device located in
the blower discharge and connected differentially across a
sensitive flow meter. Air velocity through the cabinet is indicated
by calibrating the flow meter to read the velocity pressure in the
blower discharge versus the air volume delivered by the blower. Air
velocity is controlled by means of a speed controller, which may be
of the solid state electronic type commonly known in the art,
located on the blower motor. The entire velocity indicator, speed
control variation mechanism and switches for operation of apparatus
20 are incorporated into a single control panel. Control panel 29
may be conveniently injection molded of a common plastic material
if desired. The control panel indicates air velocity and is
independent of static pressure and the entire velocity indicator
and control system is incorporated into a one-piece construction.
Naturally if it is desirable to change the calibration, it may be
accomplished in many ways one of which would be to change the
diameter, weight or configuration of indicator 84.
Finally, consideration should be given to a suggested wiring
arrangement which may be utilized with the apparatus of this
invention such as the schematic arrangement shown in FIG. 4 of the
drawings. A normal 120 volt system may be employed as indicated by
leads 90 and 91 with a separate ground utilized as indicated by
ground 92. The blower switch 45 is connected to the blower portion
of the circuit and the light switch 46 is of the type which may be
in an off position or which may be connected in one of two "on"
positions. In one on position it would provide a close circuit to
light two common types of white light devices such as common
commercial neon lights as indicated by the reference numerals 55
and 56. Alternatively in the other on position it may be connected
to form a close circuit with a common type of ultraviolet light as
indicated by the reference numberal 57 in the drawings. A circuit
containing switch 46 and lights 55 and 56 will generally also
contain a ballast means 93 for use with the conventional neon or
fluorescent lights 55 and 56. Similarly, when switch 46 is
connected so as to close the circuit with ultraviolet light 57 to
permit current to flow along that particular path, a transformer
means 94 is included in the circuit as is conventionally done in
accordance with the use of a commonly used ultraviolet light such
as designated by the reference numeral 57. As shown in the
drawings, the light circuit is such that the fluorescent lights are
lit as current flows through the circuit formed by lead 90, switch
46, lights 55 and 56, ballast 93 and lead 91 and the ultraviolet
light is lit when current flows through the circuit formed by lead
90, switch 46, light 57, transformer 94 and lead 91.
As shown in FIG. 4, switch 45 for initiating operation of air
supply blower motor 48 and exhaust motor 53 is in the open position
so that the apparatus of the invention is not in operable position.
Upon the closing of switch 45, current will flow through lead 90,
switch 45 and the respective motors of air supply blower 48 and
exhaust blower 53, and lead 91. It should be noted that each of the
blower motors are individually grounded and a capacitor is
connected to the motor of the air supply blower 48 to prevent any
premature surge of power to that motor which could cause an
undesirable static discharge in the electrical system. Variable
speed controller 44 is shown connected to both the motor of the air
supply blower and the exhaust blower. This is to assure that a
uniform amount of air is constantly being circulated through
cabinet 21. A variation in speed of the motor of air supply blower
48 should be accompanied by a proportional variation and speed in
the motor of exhaust blower 53. This assures that a constant volume
of air is being circulated through cabinet 21 and that the slight
negative pressure is maintained at all times within the cabinet to
prevent the cross contamination as discussed in detail above.
Thus, the above objectives of the invention, among others, are
effectively attained.
* * * * *