US3277638A - Ultraclean enclosure - Google Patents

Description

oct. 11, 1966 wlunlm'uhilhlmmmmzmmm l Y, |IIII IIHIII1H HHHH WMM :111| 1 ww /ff/ n@ 11111211 H n||||| 1 l l| II //w1n14|l|l l 1l( 5 HHHH E l, HHHHH-HHHHH|\I|I|1 1. 1 1 w Q ll|||| l l l|| |1 Egezzz United States Patent O 3,277,638 ULTRACLEAN ENCLOSURE Charles W. Soltis, Albuquerque, N. Mex., assgnor to Envirco, Inc., a corporation of New Mexico Filed Jan. 17, 1964, Ser. No. 338,521 1 Claim. (Cl. 55-473) My invention relates generally to contamination-free enclosures, and more particularly to such enclosures having uniform airtiow through submicron lter media.

In recent years there has been considerable progress in the science of providing contamination-free environments in which sensitive instruments may be fabricated, or for hospital operating rooms, etc. Enclosures providing such environments have .become known generally as cleanrooms, and now that submicron filters are available another new class of enclosures has come about. This new class is called ultraclean enclosures, the term ultraclean being applied generally to those enclosures meeting Federal Specification 209 for cleanrooms, Class 100, which calls for fewer than 100 particles one-half micron or greater in diameter per cubic foot of air.

Typical prior ultraclean enclosures employ rigid, conventional cleanroom design wherein the walls are inflexible and are connected more or less permanently to a floor and ceiling. One entire surface of the enclosure is made up of subm-icron filter media, otherwise known as absolute filters and air is forced through this media and exhausted through an opposite surface at a rate of at least 75 feet per minute. Ultraclean enclosures of this design are briey described in Sandia Corporation Report SC- 4673 (RR) available from the Oliice of Technical Services, Department of Commerce, Washington 25, D C.

Although such ultraclean enclosures fill a long-felt need, they are not readily portable even when constructed for easy disassembly. There still remains in industry a requirement for an ultraclean enclosure which may be moved about easily, and into which objects approaching lthe size of the enclosure can .be moved, without the timeconsuming disassembly of the enclosure. Another application for an ultraclean enclosure is where operations must be performed on the human body under field couditions, such as in the armed forces on the battleeld.

It is, therefore, a general object of my invention to provide an ultraclean enclosure which is lightweight, portable, and which is easily entered with equipment approaching its general size.

Briey, this and other objects which will become apparent are accomplished by means of an enclosure having as its ceiling submicron filter media through which air is forced downward. The ceiling is supported by a preferably skeletal means, and itself supports a curtain which is sealed to the periphery of the ceiling in an airtight or air-impervious manner and which preferably is made of airtight or air-impervious material. The curtain hangs fairly close to the iioor or other supporting surface, leaving a space for the exit of the introduced air.

A better understanding may be had of my invention by reading the more detailed description to follow in conjunction with the appended claim and the attached drawing, in which:

FIG. 1 shows a top plan view of a preferred embodiment of my invention with the upper surface thereof partially cut away; and

FIG. 2 is a sectional View of the same embodiment, taken along the line 2 2 of FIG. 1.

Referring now to the drawing, a plurality of absolute filters are seen to form the ceiling of an enclosure. The filters, which include submicron filter media, may be joined together in a sealed relationship 'by a supporting and sealing means 11 such as that described in my co- 3,277,638 Patented Oct. 11., 1966 "ice pending patent application Serial No. 293,597, filed July 9, 1963, although the present invention is not confined thereto. It is conceivable also that the ceiling could be made up of one continuous body of submicron filter med-ia. Enclosing means 12 is mounted above the ceiling, forming therewith a plenum. Blowers 13 are rotated by motor 14 so as to pull air through coarse filter 15 and move it into the plenum through filters 10.

Since the entire ceiling is made up of submicron filter media there will be no particles in the air leaving the ceiling larger than one-half micron in diameter. Airflow will be laminar, that is, it will be directly straight downward unless interrupted by equipment or persons located with-in the enclosure.

Supporting the ceiling at each corner is a skeletal pillar 20 which may be mounted on a roller 21 for easy moving. It is preferable that the pillars be attached to the ceiling at its periphery to make maximum use of the enclosed work space. Curtain 22, which is preferably made of airtight or air-impervious material such as exible plastic, lis sealed in an airtight or air-impervious manner to the periphery of the ceiling at 23. It hangs therefrom by its own weight towards supporting surface 24, with its lower edge spaced therefrom.

For ease of entrance and exit the curtain is mounted to hang within the bounds of pillars 20 rather than outside them. For further ease of entrance and exit the curtain optionally is not made continuous, but has ends overlapping extensively at 25, the outside edge of the curtain being shown as a broken line.

Earlier cleanroom design required that the ioor and all other inside surfaces be kept extremely clean so that there would be no danger of unwanted particles contaminating the material being worked with inside the room. Prior cleanrooms also required a perforated floor or some other way of preventing the accumulation of dirt within the enclosure. Prior to the development and testing of my invention it was felt that perhaps supporting surface 24 would have to be kept scrupulously clean, but tests have proven this not to be necessary. The enclosure I have invented may be rolled or otherwise moved any where in a manufacturing plant, or for that matter, outdoors, and used in that environment as an ultraclean enclosure without any special attention being paid to the cond-ition of supporting surface 24. All that is required is that blowers 13 have sufficient capacity, and that curtain 22 end sufiicient distance above the supporting surface as to allow air movement at a minimum rate of feet per minute. It is not advisable that curtain 22 have its lower edge more than one foot above the floor because of the possibility of air currents exterior to the enclosure causing air turbulence inside which will lift up unwanted particles regardless of the airflow.

In scientific tests conducted with the preferred embodiment of my invention it was found that floor dirt did not travel upstream to a work piece when the work piece was located at various heights between six and forty-eight inches above the floor. When the embodiment was filled with smoke with the blowers olf, total removal of the smoke was accomplished within 15 seconds after turning on the blowers. In general, my invention performs as well as ultraclean enclosures of more conventional construction, and it has the advantages of economy of manufacture, easy portability, and lightness of weight.

In describing a preferred embodiment of my invention I have not intended to limit my patent protection thereto. Numerous variations will be thought of by those skilled in the art without departing from the sphere and scope of my invention as defined in the claim below.

I claim as my invention:

A portable ultraclean enclosure for resting on a supporting surface defining a compartment having therein laminar flow of air comprising: a ceiling comprising a supporting frame having a plurality of openings of predetermined conguration, a corresponding number of lter cells disposed in said openings and having a corresponding configuration, each of said filter cells including lter media means for removing sub-micron particles and for passing therethrough less than one hundred particles one-half micron or greater in diameter per cubic foot of air passing therethrough; pillar means for supporting the ceiling at a predetermined elevation above said surface; a curtain extending around the periphery of the ceiling and made of substantially exible air-impervious material suspended downwardly from the ceiling and the juncture between the ceiling and curtain being sealed in an air-impervious manner, the curtain extending downwardly close 15 to the surface on which the enclosure rests and in substantial spaced relationship thereto; an enclosing means mounted above the ceiling and spaced therefrom and de ning a plenum having opposedV ends and extending for at least substantially the entire surface area of said ceiling and being supported above said ceiling, a blower mounted at one end of the plenum mounted with its intake open to a supply of air and its outlet coupled with the interior of the plenum in communication with each of the filter cells whereby air forced into the plenum by said :blower is adapted to pass through the filter cells and into the compartment with laminar ow characteristics, and a coarse lter mounted at the intake of the blower with the blower and coarse filter being mounted at approximately the predetermined elevation of the ceiling.

References Cited by the Examiner UNITED STATES PATENTS` 2,214,821 9/1940 Lucius.

2,291,220 7/ 1942 Germonprez.

2,486,251 10/ 1949 Braun.

2,550,810 5/1951 Heidbrink 98-89 3,151,929 10/ 1964 Potapenko.

3,170,384 2/ 1965 Krantz et al.

OTHER REFERENCES Levenson et al.-A Plastic Isolator for Operating in a Sterile Environment, In American Journal of Surgery 104 (6), pages 891-899 December 1962.

Crane-Design Techniques for Industrial Clean Rooms 20 In Airconditioning Heating and Ventilating, Volume 60 pages 58-63 December 1963.

Whiteld, W. I., A New Approach To Cleanroom Design In Sandia Corporation Report SC-4673 (RR), March 1962.

HARRY B. THORNTON, Primary Examiner. B. NOZICK, Assistant Examiner.

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