US 3895570 A
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.
Description (OCR text may contain errors)
United States Patent [1 1 Eagleson, Jr.
[ July 22, 1975 AIR-INSULATED WORK STATION  Inventor: John M. Eagleson, Jr., Kennebunk,
Maine [731' Assignee: The Baker Company, Inc., Stanford,
Maine 22 1 Filed: Sept. 27, 1973  Appl. No.: 401,196
[521' US. Cl. 98/115 LH; 55/D1G. 18  Int. Cl. F23J 11/00; F24F 9/00  Field of Search 98/115 Ll-l, 115 R, 36; SS/DIG. 18, 473
 References Cited UNITED STATES PATENTS 2,886,124 5/1957 Scharmer 98/115 K 3,301,167 1/1967 Howard et a1... 3,318,076 5/1967 Baker 98/115 LH 1/1968 Taylor ct al. 98/115 LH 3,470,679 10/1969 Ramsey 55/473 3,729,905 5/1973 Diccianni 98/115 LH 3,752,056 8/1973 Chamberlin et al 98/1 15 LH 3,811,250 Fowler. Jr. 98/115 LH Primary Examine'r-Charles J. Myhre Assistant Examiner-Paul Devinsky 1 71 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.
8 Claims, 4 Drawing Figures llllilllllll' ill, fl l g H1"H1@ l 'l ll' J Lll|lll lllllvvllvlrvqvlltllll lltllllllllllg PATENTEDJUL22|97s 3.895570 SHEET 1 FIG 60 AIR-INSULATED WORK STATION 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.
2. Description of the Prior Art I Various work stations have been developed with the object of permitting the operator to insert his hands or instruments through an access opening into theinterior 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, I
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 ofa 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 intoor out ofthe work space through the access opening. Exhaust means are included to vent some ofthe 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 frontwall. 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 outany 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 walledwork 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 statior is operated. Air passageways are provided to admit out side 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 th'epartition 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 leakingthrough the plenum walls 34 enters the duct system and is sucked back into the blowers 28 and 30 and returned to the plenum 32.
Frofn 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 intothe 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 workstation 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 contaihment 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. 24, 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.
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 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.