Gas separation – Combined or convertible – In environmental air enclosure
Reexamination Certificate
1999-07-02
2001-01-16
Upton, Christopher (Department: 1724)
Gas separation
Combined or convertible
In environmental air enclosure
C055S426000, C055S438000, C055S444000, C055S463000, C055S473000, C096S385000
Reexamination Certificate
active
06174342
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to fan filter units useful in clean rooms and like applications. More particularly, the invention relates to a fan filter unit that simultaneously achieves all the major objectives for such a unit:
1. Filtration efficiency of 99.999% at 0.12 micron particles, at
2. Air flows of about 90 FPM,
3. Energy usage of about 100 watts, and
4. Lower BTU output for reduced air conditioning load.
Fan filter units typically are suspended individually or in banks above a workspace, each individual fan filter unit combines a motorized fan, a fan enclosure supporting the fan, and filter media in a filter unit downstream from the fan enclosure all arranged to introduce, e.g. HEPA or ULPA filter-processed air into the workspace environment. The invention advantageously uses a filter pack of relatively increased depth, e.g. 5 inches of depth and greater, no metal separators, and increased pleat count, e.g. 5 to 7 pleats per inch, for maximum energy efficiency. Prior art fan filter units use more energy, are less efficient, and comprise, typically, less deep packs, e.g. 2-4 inches in depth.
2. Related Art
Known filter fan units are desirably improved in terms of filtration efficiency, quietness of operation and energy efficiency including both energy consumed directly by the filter units to drive the fans and energy consumed indirectly by the units through heat output into the air-conditioned room. Achieving the one should not detract from achieving the other. Presently popular fan filter units use trough-like transverse baffles to redirect the air flow from a first direction, generally radially outward from the fan, to a second, opposite direction, generally toward the fan and within the height of the filter fan unit enclosure, see generally U.S. Pat. No. 5,470,363 to Leader et al. Reversing flow will usually entail excess energy consumption and prevent achieving of the desired low energy consumption of about 100 watts or less.
SUMMARY OF THE INVENTION
The present invention uses linear, unidirectional flow of pressurized air from a motorized fan through perimetrically distributed outlet ports. The occurrence of backflows and the backpressure development common in reverse flow devices like that shown in U.S. Pat. No. 5,470,363 and the concomitant unnecessarily high energy consumption is avoided in the invention. Linear, unidirectional flow of pressurized air in the present invention derives from use of baffle structures in advance of the outlet ports, not within the ports, and the use of baffle structures that direct all air flow linearly through the fan enclosure outlet ports. Linear air flow is obtained by extending the baffle structures vertically from about 25% of the enclosure height to the full enclosure height, i.e. from the bottom wall to top wall of the enclosure, giving them a wedge shape that is conducive to smooth air flow, and extending them laterally for at least substantially the width of the outlet ports along their respective side walls. Thus avoided is a reverse flow of air within the height of the filter fan unit enclosure and within the port. Baffle structures extending at least about 25% of the enclosure height limit air flow to lateral (from the side) flows and “waterfall” flows over the baffle structure into the port, all linear flows, while baffles the full height of the enclosure limit air flow to paths extending laterally about the baffle structures. Both types of flow ensure the absence of reverse air flow within the fan surrounding enclosure. The baffles are suitably covered with sound-absorbing material such as foam and, with the walls of the enclosure, define a non-straight air flow path to control and absorb any noise generated within the enclosure. Typical of the prior art is the fan filter unit shown in the above-mentioned U.S. Pat. No. 5,470,363. There the fan filter unit has an integrated fan filter unit and filter. The pressurized air from the centrally located fan is redirected from its normal centrifugal path upward by a deflector to provide a separate path below the deflector for the air to flow to the filter. The air flow path is thus reversed within the fan enclosure and above the filter, and within the port since the trough-shaped baffle is within the outlet port for air flow from the fan. While the noted patent provides a curvilinear guide defined by the trough to ease the flow transition from one direction to another, the flow direction is undoubtedly reversed and this requires more energy than a linear, or non-reversed path. The industry desires lower energy costs and units using 100 watts or less have been a major goal in the industry. The present invention through creation of a linear, non-reversing air flow path that has the pressurized air enter the fan enclosure outlet ports only from directly above and/or the sides and other means to be described hereinafter reaches this goal, while maintaining a high filtering efficiency of 99.999% at 0.12 micron particle size, air flows of 90 FPM, and a reduced BTU output of approximately only 200 BTU/hr to lessen the refrigeration load in the clean room.
It is an object, therefore, of the present invention to provide an improved fan filter unit for filtering air entering a clean room, a surgery, or other meticulously controlled environment. It is a further object to provide fan filter units that are more filtering-efficient, more energy efficient to lower electrical costs, less demanding of cooling capacity, and less noise generating for a quieter workplace; and withal simply installed. A still further object is to provide a fan filter unit that uses a system of baffles arranged to conduct linear air flow laterally or vertically into outlet ports from the fan enclosure and to block reverse flows in the enclosure or in the outlet port where the air is returned in the direction whence it came. Another object is to provide a fan filter unit achieving higher filtering efficiency and increased energy efficiency through the use of separator-less filter media packs of increased pleat depth and greater pleat density. A further object is to provide a mating fan filter unit enclosure and filter media containing frame that are conjoined above the filter media to define a plenum, one or the other of the enclosure and frame carrying air flow distributors opposite the outlet ports.
These and other objects of the invention to become apparent hereinafter are realized in a higher filtering efficient, lower energy consuming, less heat generating, and lower noise generating fan filter unit for flowing air filtered through a higher efficiency particulate air filter into a clean room, the fan filter unit being normally horizontally disposed and comprising a longitudinally and laterally extended enclosure having an air inlet and an air outlet, a high efficiency particulate air filter unit in air-flow communication with the enclosure outlet across a plenum defined by the enclosure and the air filter unit, a motorized fan in air flow communication with the enclosure inlet and the outlet, the fan being supported centrally within the enclosure, the enclosure outlet comprising a longitudinally spaced ports and laterally spaced ports, the ports lying in a normally horizontal common port plane below the fan and collectively being of sufficient cross-sectional area to pass without substantial back pressure the air flow generated by the motorized fan, individual baffle structures extending substantially normal to the common port plane adjacently before each port and between the fan and the port, the baffle structures being arranged to block all direct air flow from the motorized fan into the ports, whereby air flow from the ports is linear and free of reversal in flow direction within the enclosure and within the ports.
In this and like embodiments, typically, the enclosure comprises side walls, a top wall defining the inlet and a bottom wall defining the outlet ports, the air filter unit comprising a frame attached to the fan unit, and a filter, the filter being
Bachand Louis J.
HEPA Corporation
Upton Christopher
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