U.S. patent number 3,895,570 [Application Number 05/401,196] was granted by the patent office on 1975-07-22 for air-insulated work station.
This patent grant is currently assigned to The Baker Company, Inc.. Invention is credited to John M. Eagleson, Jr..
United States Patent |
3,895,570 |
Eagleson, Jr. |
July 22, 1975 |
Air-insulated work station
Abstract
A work station having a work space bounded by an air duct
system. Air is sucked out of the ducts for filtering, part of the
air being circulated downwardly through the work space and back to
the ducts, and the remainder vented from the system. Air
passageways adjacent to an access opening permit outside air to
replenish the air in the ducts, the air flows established within
the station serving to insulate the work space from gaseous
communication with the outside atmosphere.
Inventors: |
Eagleson, Jr.; John M.
(Kennebunk, ME) |
Assignee: |
The Baker Company, Inc.
(Stanford, ME)
|
Family
ID: |
23586750 |
Appl.
No.: |
05/401,196 |
Filed: |
September 27, 1973 |
Current U.S.
Class: |
454/57;
55/DIG.18 |
Current CPC
Class: |
B08B
15/02 (20130101); B08B 15/023 (20130101); B08B
2215/003 (20130101); Y10S 55/18 (20130101) |
Current International
Class: |
B08B
15/00 (20060101); B08B 15/02 (20060101); F23J
011/00 (); F24F 009/00 () |
Field of
Search: |
;98/115LH,115R,36
;55/DIG.18,473 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Devinsky; Paul
Claims
What is claimed is:
1. An air-insulated work station comprising the combination of:
bottom, side, and rear walls defining a work space, said bottom
wall including a work surface for said work space, baffles
cooperating with each of said walls to define air ducts exterior to
said work space,
a front wall having an opening providing access to said work
space,
blower means having an air intake from said ducts and adapted to
blow air down into said work space toward said work surface, said
ducts forming a return path to said blower means for air which has
passed through said work space,
said work surface being perforated and at least one of said air
ducts provided with air passageways to admit air respectively from
said work space and from outside of said work station into said
ducts,
exhaust means adapted to vent some of the air in said ducts from
said work station, and thereby establish a flow of air from outside
of said work station through said air passageways and into said air
ducts to replenish the vented air, and
filter means in the path of air impelled by said blower means for
removing contaminants therein, said filter means intermediate said
blower means and both said work space and said exhaust means,
the air flow produced within said ducts serving to insulate said
work space from gaseous communication with the outside atmosphere
resulting from leaks of unfiltered gas into said ducts, by passing
substantially all the gas in said ducts through said filter
means.
2. The work station of claim 1, wherein said air passageways are
distributed along the forward edge of each of the air ducts defined
by said side walls.
3. The work station of claim 2, wherein air passageways are
provided adjacent to said access opening to inhibit the flow of gas
into or out of said work space through said access opening.
4. The work station of claim 3, wherein said blower means, exhaust
means, and air passageways are adapted to produce an air flow
velocity into said air passageways of from about 50 to about 100
feet per minute.
5. The work station of claim 3, and further including a partition
slideable between first and second positions respectively covering
and revealing said access opening, an enclosure for said partition
mounted on said front wall, said partition slideably lodged in said
enclosure through a slit in the lower portion thereof, said front
wall defining an air duct exterior to said work space, said air
duct providing an air intake to said blower means, and air
passageways between said partition enclosure and said front wall
air duct, said blower means adapted to impel gas in said partition
enclosure through said air passageways and said front wall air duct
and thence to said filter means.
6. The work station of claim 1, wherein said filter means comprises
a first filter disposed in the path of air blown into said work
space and a second filter disposed in the path of air vented
through said exhaust means.
7. The work station of claim 6, wherein said front wall defines an
air duct exterior to said work space, said front wall duct
providing an air intake to said blower means, and including a
plenum supplied by said blower means and surrounded by said blower
means, filter means, and said front, side, and rear air ducts,
whereby any unfiltered gas escaping from said plenum is returned
thereto through said ducts by said blower means.
8. The work station of claim 1, wherein the perforations in said
work surface are distributed along the forward and rear portions of
said work surface, and including means to direct a greater air flow
rate from said blower to the forward and rear portions of said work
space than to the central portion thereof, thereby inhibiting the
flow of gas outwardly to the front or rear from said central work
space portion.
Description
BACKGROUND
1. Field of the Invention
This invention relates to work stations having an enclosed work
space and an access opening thereto, and more particularly to such
work stations that are constructed to segregate the work space from
the ambient atmosphere.
BACKGROUND
2. Description of the Prior Art
Various work stations have been developed with the object of
permitting the operator to insert his hands or instruments through
an access opening into the interior of a work space, and at the
same time to prevent contamination of the work space by outside
gases or airborne particulates. Two approaches frequently followed
have been blowing a continuous stream of air through the work space
and out the access opening, or circulating air down into the work
space, through openings in a lower work surface, and back up
through the station for re-entry into the work space.
The first approach cannot be used if it is desired to fully
segregate the work space from the outside environment by preventing
the passage of untreated gas in either direction between the two.
With the second approach it is possible to seal off the access
opening to the passage of gas either into or out of the work space,
but to accomplish total segregation, it has heretofore been
necessary to surround the remainder of the work space with a
completely gas impervious enclosure, with all joints sealed by
welding, gasketing, or the like. Even with such construction, it is
possible for cracks to develop, which if unnoticed, may endanger
personnel in the area by permitting a leakage of contaminated gases
from inside of the work station, or spoil the material within the
work station by permitting entry thereinto of ambient air. In
addition, a problem of gas leakage along the edges of the access
opening has been encountered with many heretofore known work
stations.
BRIEF SUMMARY OF THE INVENTION
In view of the above-stated problems encountered in the prior art,
it is an object of the present invention to provide a novel and
improved work station having a work space that is insulated from
gas flows both to and from the outside atmosphere. Another object
is the provision of a novel and improved work station having a work
space and an access opening permitting the introduction of solid
objects into the work space, in which gas leaks through the access
opening and through the work station walls are effectively
prevented. A further object is the provision of a novel and
improved work station having a work space in which only
non-contaminated air is permitted to enter the work space or to
leave the work station.
In the accomplishment of these and other objects, a work station is
provided, according to the present invention, with a work space
defined by bottom, side, and rear walls, each wall defining an air
duct exterior to the work space, and the bottom wall including a
perforated work surface. A front wall is also included, and has an
opening providing access to the work space. A blower means takes in
air from the air ducts and blows the air downwardly through the
work space, through the perforations (preferably distributed along
the forward and rear portions of the work surface), and back into
the ducts for recirculation back to the blower. Air passageways are
also provided in at least one of the ducts to admit outside air.
The passageways are preferably distributed along the forward edge
of each of the side wall ducts, adjacent to the access opening, to
inhibit gas leakage into or out of the work space through the
access opening. Exhaust means are included to vent some of the air
in the ducts to the outside atmosphere, thereby establishing a flow
of air into the ducts through the air passageways to replenish the
vented air. Filter means are emplaced in the path of substantially
all the air impelled through the air ducts to remove airborne
contaminants before the air is either vented or blown into the work
space. Any leaks of unfiltered gas are thereby captured within the
ducts and delivered to the filter means for decontamination.
The filter means preferably comprises a pair of filters, one
disposed in the path of air blown into the work space, and the
other set in the exhaust means. According to another feature of the
invention, the front wall also defines an air duct exterior to the
work space, with the two filters acting on air contained in a
plenum that is supplied by the blower means and surrounded by the
blower means, the front, side, and rear air ducts, and the filters.
By this means any gas leaving the plenum is either filtered or
captured in the air ducts and returned to the plenum. In a related
feature a partition for the access opening is slideably lodged
through a slit in an enclosure mounted on the front wall. Air
passageways in the front wall provide a path for air in the
enclosure to be sucked through the front wall air duct and into the
blower means, to filter out any impurities that may have entered
the enclosure through the slit.
In a particular embodiment, the work station comprises an inner
housing mounted within an outer housing and separated therefrom by
an air space. The blower means is adapted to suck in air from the
air space between the two housings and to blow air downwardly
through a work space defined by the inner housing, towards a
perforated work surface. Air is vented from the air space through
an exhaust means, the vented air being replenished by outside air
entering through air passageways in the outer housing, and the
remainder of the air in the air space being supplied from the work
space through the perforated work surface. Filter means remove
contaminants from the air prior to venting and entry into the work
space. In this embodiment a plenum may be established by the blower
means within the outer housing and above the inner housing, with a
first filter disposed between the plenum and the work space and a
second filter disposed between the plenum and the exhaust
means.
The invention also comprehends the method of insulating a work
space contained within a walled work station from gaseous
communication with the atmosphere which includes bounding the work
space with walls spaced inwardly from the work station walls,
sucking out the air from the air space between the work station and
the work space walls, and filtering the sucked air to remove
contaminates. A portion of the sucked air is vented from the work
station, and the remainder impelled downwardly through the work
space and returned to the air space, inducing the entry of
atmospheric air into the air space to replenish the vented air.
According to one feature of this method, air from the air space is
sucked into a blower means and then blown into a plenum above the
work space. A portion of the plenum air is vented from the work
station through a first filter, the remainder of the plenum air
being admitted into the work space through a second filter.
For the purpose of more fully explaining a preferred embodiment of
the invention, reference is now made to the following detailed
description thereof, together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a work station constructed
according to my invention, with a portion of the front wall cut
away;
FIG. 2 is a cross-sectional view of the work station in frontal
elevation;
FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG.
2; and
FIG. 4 is a fragmentary view of a corner of the work station
showing the flow of air from the outside atmosphere and from the
work space into air ducts surrounding the work space.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 1-3, a work station is shown having a generally
rectangular outer housing with side walls 2 and 4, rear wall 6, and
top and bottom walls 8 and 10, respectively. The housing is mounted
on legs 12, which provide suitable leg space for the work station
to be used while seated. A slideable glass partition 14,
counterbalanced by a spring loaded steel tape (not shown), permits
the interior of the station to be viewed, and can be raised to
provide an access thereto. A fluorescent light assembly 16
illuminates the interior of the station.
A work space generally indicated by numeral 18 is defined by an
inner housing having side walls 20 and 22, and rear and bottom
walls 24 and 26, respectively. A pair of one-third horsepower
blowers 28 and 30, mounted above the inner housing, have an intake
from the air space between the inner and outer housings and are
adapted to blow air downwardly into a plenum 32, bounded in part by
plenum walls 34. A first, elongate filter 36 of the high efficiency
particulate arrestant (H.E.P.A.) type, designed to remove 99.99% of
airborne particles .3 microns or greater in diameter, is disposed
between the plenum 32 and the open top of the work space 18. An air
diffuser 38 is mounted in the work space 18 below the filter 36 to
distribute air coming down through the filter 36 from the plenum
32, and preferably produces a greater air flow rate at the forward
and rear portions of the work space 18 than at the central portion
thereof.
The bottom wall 26 of the inner housing forms a work surface to
support material placed within the work space 18. It is provided
with a series of perforations 40, preferably distributed along the
forward and rear portions of the work surface 26, permitting air
blown into the work space 18 to pass downwardly through the work
surface 26 and circulate back through the air space between the
inner and outer housings to the blowers 28 and 30.
A second H.E.P.A. filter 42 is set in a plenum exhaust opening 44
to remove particulates from air vented from the work station
through the exhaust opening 44.
The inner and outer housing walls define a system of air ducts
surrounding the portion of the work space 18 that is interior to
the work station, the air within the ducts being sucked into the
blowers 28 and 30 and processed through the filters 36 and 42 when
the station is operated. Air passageways are provided to admit
outside air into the ducts and thereby replenish the air vented
from the station through the exhaust opening 44. Preferably the air
passageways are distributed along the forward edge of each of the
two volumetric side walls formed respectively from inner and outer
side walls 2 and 20, and from inner and outer side walls 4 and 22,
the passageways comprising a series of slots 46 adjacent to the
sides of the access opening.
The glass partition 14 is slideably lodged through a slit 48 in an
enclosure 50 that is mounted on the upper front wall 52 of the
outer housing, the partition 14 providing a unitary front wall for
the inner housing and the remainder of the outer housing. A
plurality of air passageways, preferably in the form of a series of
slots 54 distributed along the forward edge of each of the
aforesaid volumetric walls, provide an air flow path between the
partition enclosure 50 and an air duct defined by the upper front
wall 52 in conjunction with the forward plenum wall 34. Any air
entering the enclosure 50 through slit 48, as the partition is
raised or lowered to respectively reveal or cover the access
opening, is drawn through the slots 54 into the interior of the
work station by the action of blowers 28 and 30. The plenum 32
itself is bounded by the plenum walls 34, blowers 28 and 30, and
the filters 36 and 42, whereby any gas leaking through the plenum
walls 34 enters the duct system and is sucked back into the blowers
28 and 30 and returned to the plenum 32.
From the above description it can be seen that the work space 18 is
entirely enclosed by air ducts at its rear, bottom, and sides,
filter 32 at its top, and glass partition 14 at its front. The only
direct path for gaseous flow between the work space 18 and the
outside atmosphere is through the access opening when the partition
14 is raised. This flow is effectively prevented, however, by the
downward directed airstream established within the work space 18 by
blowers 28 and 30, which carries the gas just inside the access
opening down through the work surface perforations 40 and into the
air duct system, and by the intake of outside air into the duct
system through slots 46, which intake prevents gas leakage in
either direction along the sides of the work space 18. Any gas that
may leak into the air ducts either through the walls of work space
18 or from outside of the station, due to cracks or the like in the
work station walls, is sucked into the blowers 28 and 30 and
delivered to one of the filters 36 and 42 for decontamination. The
work space 18 is thereby completely insulated from gaseous
communication with the outside atmosphere by the various air flows
established within the work station. It has been found that the
best containment is achieved when the ratio of the air mass
traversing the work space filter 36 to that vented through the
exhaust filter 42 is about 3:1, and the air flow velocity into the
slots 46 is from about 50 to about 100 feet per minute.
Several control features are displayed on a control panel 56. A
magnehelic pressure guage 58 measures the pressure drop across the
work space filter 36. When the filter becomes dirty enough to
increase the pressure differential and reduce the air flow velocity
below the desired level, the operator is notified by the guage
needle crossing into a marked area on the guage to increase the
blower speeds by adjustment of control knobs 60 for solid state
speed controls. A constant rate of air flow may thus be obtained as
the filter becomes dirty, thereby increasing the filter life while
maintaining a constant working condition. In addition, a warning
light 62 is connected to light when the unit is in operation and
the glass partition 14 is raised by more than 8 inches, the access
opening dimension that produces the best gas containment
efficiency.
The operation of the work station is best described with reference
to FIGS. 2-4, in which arrows represent air flow. Air is sucked
into the blowers 28 and 30 from all of the air ducts surrounding
the work space 18 and from the partition enclosure 50, establishing
a less than atmospheric pressure in the ducts. The air is blown
into the plenum 32 at an elevated pressure, from whence about 25%
of the air is vented and decontaminated through the exhaust filter
42. The remainder of the air is impelled through the work space
filter 36 and formed by air diffuser 38 into a substantially
downward laminar flow with the majority of the air directed to the
front or rear portions of the work space. Gases contained within
the work space are drawn by the airstream downward through the work
surface perforations 40 to the lower air duct, and thence upward
principally through the rear duct and also through the side ducts
back to the blowers 28 and 30, where the cycle is repeated. The
vented air further reduces the pressure within the air ducts,
producing an inflow of air through the slots 46 adjacent to the
access opening, into the side ducts, and up to the blowers 28 and
36.
The air ducts thus serve as a barrier between the work space and
the outside environment, any gas leaking into the ducts being
sucked into the blowers 28 and 30 and delivered to one of the
filters 36 and 42 before being introduced into the work space or
vented from the unit. The air flowing downward through the work
space and into the intake slots 46 also serves to seal off the
access opening to gas flows in either direction, while an operator
is provided with convenient access to the work space when the glass
partition 14 is raised.
While a particular embodiment of the invention has been shown and
described, there are modifications thereof which will be apparent
to those skilled in the art, and therefore it is not intended that
the invention be limited to the disclosed embodiment or the details
thereof, and departures may be made therefrom within the spirit and
scope of the invention as defined in the claims.
* * * * *