Controlled Environmental Apparatus For Industry

Abstract

Apparatus is provided for controlling the environment in localized areas or zones of manufacturing and/or assembly plants and the like. A gas or air treating apparatus is connected to an outlet plenum positioned above the space or zone to be controlled. The plenum is provided with a plurality of controlled outlets for directing the treated air, generally downward at a rate progressively increasing in volume from the center of the controlled zone outwardly. The system also includes a plurality of inlet plenums spaced at floor level or slightly thereabove at controlled points adjacent but outside of the area or zone to have the controlled environmental conditions.

Description

BACKGROUND OF THE INVENTION

This invention relates to an apparatus or system for controlling the environmental conditions in a localized area or zone and, more particularly, to such a system or apparatus for providing controlled environment within an area or zone of a large assembly or manufacturing plant or factory.

Many manufacturing and assembly procedures in the electronic, electrical, optical, and electro-optical fields require substantially "clean room" environmental conditions to insure the proper functioning of the apparatus or components being assembled.

The invention has further utility as means for providing a sterile and clean area in the manufacture of candies, foods, and the like during which manufacture contamination may not only produce a non-saleable product but may also create a health hazard to the purchasing public.

While difficulty is experienced in providing for "clean room" conditions in relatively isolated rooms of hospitals, the problems are even more complex in zones or areas in manufacturing facilities which must provide means for receiving components and subcomponents and for removal of the finished products.

Attempts to solve these problems have generally consisted of providing glass or plastic enclosures which are maintained at positive pressure conditions relative to the ambient atmosphere. However, it has been found that conventional air outlets in such enclosures create air movements which stir up dust and other particulate materials thereby preventing the maintenance of proper atmospheric conditions within the enclosures. Further, it has been found that even when operators are robed, gloved, and masked body convection currents, exhaled breath, and the like provide a major source of gaseous and particulate contaminants which often result in early failure of intricate electrical and optical components and food contamination.

THE INVENTION

It is a primary objective of the present invention to provide controlled environmental zones within manufacturing and assembly plants which reduce to a minimum the ingress of gaseous and particulate contaminates from uncontrolled zones and the controlled removal of body-produced gaseous and solid particles from the controlled zone.

A further objective is to provide such a system or apparatus that may be installed, with a minimum of expense, in existing plants or factories or installed at the time of factory construction to provide optimum environmental conditions of a desired type in confined zones or areas.

It is the further objective to provide a self-contained unit by means of which the environmental gases may be scrubbed, filtered, heated and/or cooled, and dehumidified or humidified as required.

The invention will be more particularly described in reference to the accompaying drawings wherein:

FIG. 1 is a transverse partial sectional view through a factory, having installed therein three controlled environmental zones constructed in accordance with the teachings of the present invention;

FIG. 2 is a fragmentary, partially diagrammatic view taken at right angles to the illustration of FIG. 1;

FIG. 3 is a top plan view of the outlet face of one of the outlet plenums shown in FIGS. 1 and 2;

FIG. 4 is an enlarged partial sectional view of another form of the present invention;

FIG. 5 is a section, substantially on line 5--5 of FIG. 4;

FIG. 6 is a plan view of the outlet surface of a modified form of outlet plenum; and

FIG. 7 is a vertical sectional view of gas treating apparatus for use with the environmental control system of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to the drawings, and in particular FIGS. 1, 2, 3 and 7, 10 generally designates a factory having a floor 12 and a ceiling 14. Within the factory 10 are positioned a plurality of elongated assembly tables, generally designated 16, supported above the floor 12. Associated with each of the assembly tables 16 is a controlled environmental zone, generally designated 18, extending from just below the exposed surface of the ceiling 10 to just above the exposed surface of the floor 12 and extending laterally in the plane of the top surface of the tables 16, a width and length slightly greater than the width and length of the tables.

In order to provide and maintain the controlled zones 18, the factory 10 is equipped with a plurality of outlet plenum chambers, generally designated 20, 22 and 24, positioned immediately adjacent to the ceiling 10 and having length and width dimensions generally coextensive with the plane area of the zone to be controlled. The lower surface 26 of each plenum chamber 20, 22 and 24, as more clearly shown in FIG. 2, is provided with a plurality of perforations varying in area with the smallest 28a appearing in the center portion of the zone to be controlled, and the largest 28z appearing adjacent to the peripheral margins of the plate 26 with openings intermediate in area 28b, c, d, e, etc. being provided therebetween.

In FIG. 3 certain of the openings 28a, b and c are illustrated as being circular in plan, whereas openings 28d, e and z appear as quadrangular slots. It will be apparent to those skilled in the art that the specific configuration of the openings is not critical; however, the area of the openings is critical as the size of these openings determines for a given pressure the volume of the gases which will issue therefrom as to be more fully described hereinafter.

The system also includes a plurality of return or inlet plenums, generally designated 30a, 30b, 30c and 30d. The inlet plenums 30a through 30d are positioned at floor level or slightly thereabove and just outwardly of the peripheral extent of the controlled environmental zone.

The outlet plenum 20, 22 and 24, etc. are connected to apparatus generally designated 32 for providing a source of properly conditioned air or gas. The apparatus 32 comprises an enclosure having top 34, bottom 36, and side walls 38. A refrigeration unit, generally designated 40, is mounted separate from the main housing 32 in order to permit its location externally of the building or factory containing the zones, the environment of which is to be controlled. Such units are well known in the art and may comprise conventional freon-type refrigeration units or one wherein the primary refrigerant liquid is in heat exchange relationship to a relatively inert fluid such as brine whereby the cooling medium brine may be safely transmitted into the control cabinet 32 without danger of contamination of the air to be cleaned in the case of rupture of one of the refrigerant lines.

In FIG. 7 a freon/brine system is illustrated with heat exchange between the brine and the freon taking place in heat exchanger 42 and the chilled brine being circulated to a cooling bath, tank or pond 44, maintained in a lower portion of the chamber 32.

A vertical interior wall 44 and a perforate horizontal wall 46 are arranged within the enclosure defined by the aforedescribed walls and panels to form therein a gas purifying chamber 48. A horizontal wall 50 is disposed surjacent the perforate wall 46 and in spaced relation thereto to define therewith a pre-treatment plenum chanber 52. The chamber 52 has disposed therein a heating coil 54 connected, through a a control 56, to a suitable source of electric power (not shown). A temperature sensing device 58, located in the chamber 48, is also connected to the control 56.

A transverse channel 60, formed in conjunction with the horizontal wall 44, interconnects the plenum chamber 62 with the return conduit 64. A fan or blower 66 is disposed between the channel 60 and the return conduit 64 to circulate the gas as is shown by the arrows in the figure.

The fluid holding tank 44, located subjacent the channel 60, is in communication therewith through openings 68 and 70. A valve means, illustrated as a movable flapper valve 72, is disposed in the channel 60 between the opening 68 and the opening 70 whereby a portion of gas stream passing along the channel 60 may be bypassed from the gas treating zone 62 in the tank 44 and recirculated directly to the plenum 48. This valve means provides additional control for the controlled environment device as will be described hereinafter.

Arranged in the tank 44 is a heater coil 72' connected to a suitable source of electric power (not shown) through a control device 74. A sensing element, which may comprise a thermister 76, is disposed in the tank 44 and is connected to the control 74. The coil 72 and sensing element 76 are submerged in the liquid sump formed in the tank 44.

Above the perforated air diffusing plate 46 in chamber 48 are one or more filters 80 which remove particles from the gas stream not removed by the spray device 82, connected via pump 84 to the cooling liquid in the tank 44. Further, where the air is to be sterile, the upper portion of the chamber 48 may be fitted with a plurality of banks of ultra-violet ray tubes, generally designated 86.

In operation of the apparatus 32, air from the plurality of inlets 30a, b, c and d is drawn via conduit 88 by fan 66 forced through the cooling chamber 62, the re-heating chamber between transverse plate 50 and perforated plate 46, thence through the filter 80 and, where desired, about the ultra-violet lights 86 to exit from the chanber 32 via outlet conduit 90 and into one or more of the outlet plenum chambers 20, 22 and 24. It will be appreciated that each of the outlet plenum chambers 20, 22 and 24 may be provided with its own air conditioning and purifying means 32, or one such unit may serve a plurality of outlet plenum chambers, depending upon the size or capacity of the conditioning unit and the area served by the outlet plenum chambers.

Referring to FIGS. 5 and 6, the outlet plenum chamber, generally designated 100, is circular in cross section and serves a generally cylindrical zone 102 extending from the floor 104 upwardly to the outer surface of the perforated wall 106 of the plenum chamber 100. In FIG. 5, the cylindrical zone encompasses a circular work table, generally designated 108.

Referring particularly to FIG. 6, it will be seen that the wall 106 of the plenum chamber 100 is provided with a plurality of concentric ring-type outlets 108a, b, c, d, e, and f which, like those illustrated in FIG. 3, increase in area from the center outwardly. Referring again to FIG. 5, the flow arrows 110 diagrammatically illustrate that the flow volume increases from the center of the controlled zone, indicated by broken line 112, outwardly and forms a downwardly moving blanket of air. The blanket of air has a greater velocity head at the periphery than at the center and the arrows in FIGS. 1, 2, 4 and 5 have lengths which generally and diagrammatically represent typical velocity heads at the stated points. Preferably, the air issuing from the outlet plenums is such that the entire air within the controlled zone is replaced on the order of 100 to 400 plus changes per hour. While the air enters the controlled zone at a rate of, for example, 50 to 100 linear feet per minute, air movement immediately adjacent to the surface of the work table 108 is practically undetectable by operators stationed about the table. Notwithstanding, the almost undetectable nature of the air movement, exhaled breath, and particles from the body of the operator are moved downwardly and outwardly to exhausts through outlet chambers 114 and 116, again positioned at or slightly above the level of the floor 104.

Referring to FIG. 4 of the drawing, the air flow pattern for the controlled zone 200 is illustrated by flow arrows 202 which again illustrate that the volume of air passing through the plural outlets 204 of the upper plenum chamber 206 is less in the center of the zone and increases near the peripheral margins thereof. While the air flow is greatest adjacent to the periphery of the controlled zone, the rate of flow is not such as to create what is conventionally known as an "air curtain." "Air curtains" operate at a very high velocity and are unsuited for maintaining a controlled environmental space as the turbulance created by the high velocity air has been found to re-suspend particulate materials and prevent outward movement of those initially in the zone to be controlled or brought into the zone by operators and the like.

For an area having transverse cross dimensions of, for example, 10 feet by 10 feet total air movement in the order of from about five to ten thousand cubic feet per minute has been found to be about optimum. Thus, an area eight feet by eight feet can be effectively controlled by a flow rate of from about 4,000 to 8,000 cubic feet per minute.

Claims

I claim:

1. A system for controlling the environment in a zone such that the gas flow in the zone moves generally downwardly at a rate progressively increasing in volume from the center of the zone outwardly comprising an enclosure having top, bottom and side walls, at least one outlet plenum chamber associated with the top wall, the outlet plenum chamber having a planar bottom panel, means defining a plurality of gas outlet openings in the bottom panel, said openings varying in area with the smallest in the center and progressively increasing in area toward the peripheral margins of the controlled zone to thereby provide gas flow within the controlled zone having a progressively increasing velocity head from the center outwardly and substantially coextensively with the cross dimensions of the controlled zone, a plurality of gas inlet plenums positioned surjacent the bottom wall of the enclosure and about the outer periphery of the controlled zone, a gas treating means having a gas inlet and a gas outlet, first conduit means connecting the gas inlet of the gas treating means and the gas inlet plenums, second conduit means connecting the outlet plenum chamber and the outlet from the gas treating means, said gas treating means containing in serial arrangement between the gas inlet and the gas outlet gas moving, heating, cooling, humidifying, dehumidifying and filtering means.

2. The system for controlling the environment in a zone as defined in claim 1 wherein the volume of air issuing from the openings in the bottom panel of the outlet plenum chamber is such as to replace the air in the control zone from about 100 to about 400 plus changes per hour.

3. A system for controlling the environment in a zone as defined in claim 1 wherein the air issuing from the openings in the bottom panel of the outlet plenum chamber is in the order of from about 5,000 to about 10,000 cubic feet per minute per 100 sq. ft. of area.

4. A system for controlling the environment in a zone as defined in claim 1 wherein the planar bottom panel of the outlet plenum chamber is rectangular.

5. A system for controlling the environment in a zone as defined in claim 1 wherein the planar bottom panel of the outlet plenum chamber is circular.