US 3318076 A
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y 9, 7 A. K. BAKER 3,318,076
DUST-FREE BENCH Filed Aug. 14, 1964 3 Sheets-Sheet 1 H66 z L \U f 34 a? 39'" a 35 39- j: a? 37 40 T 15 40 R: 7 )NVEFJOR. V ARTHUR K. BAKER BY f SM ATTORNEY 1967 A. K. BAKER 3,318,076
DUST-FREE BENCH Filed Aug. 14, 1964 3 Sheets-$fieet 2 F 35 l 3 24 I I4 II II II' II TITI II II II II II II II II Ir" INVENTOR. ARTHUR K. BAKER f? /wfi ATTORNEY United States Patent 3,318,076 DUST-FREE BENCH Arthur K. Baker, Chandler, Ariz., assignor, by mesne assignments, to Arthur K. Baker and Esther M. Baker, Chandler, Ariz.
Filed Aug. 14, 1964, Ser. No. 389,581 4 Claims. (Cl. 55-350) This invention relates generally to dust-free benches and has reference more particularly to a bench of this character having novel means for maintaining a dust-free upper working surface and a dust-free working space thereabove.
Duse-free benches as heretofore constructed generally provide for the movement of air substantially over the upper surface of the bench flowing as from the back thereof or from above, but such prior type benches do not prevent the lodging of dust on the bench surface, nor do they prevent dust from entering the open front of the bench, due to back flow of air currents produced by various causes such as eddy currents and backwash produced as by work lying upon the bench obstructing the normal flow of air, or by the worker, himself.
The principal object of the present invention is to provide a novel dust-free bench that is so constructed and arranged as to direct highly filtered air over the bench surface in smooth laminar or uniform flow, thereby maintaining a zone of dust-free air over the surface of the bench and throughout the working space above the same, the free edge or edges of the bench and the edges of the hood or dividing partitions adjacent to the bench working area having apertures, means being provided for drawing air inwardly through said apertures, whereby turbulent air due, for example to irregular flow over objects on the bench or the workers movements and the eddy currents or backwash currents produced thereby are sucked in through the openings at the front of the bench and along the side edges of the hood or dividing partitions, thereby preventing external dust-laden air from entering the bench working area and depositing dirt thereon.
A feature of the present invention is to provide a novel, dust-free bench of the above character wherein an exceptionally clean environment over the bench and within the working space results in the recirculation of some of the same air over and over through the system, i.e., most of the air flowing only over the bench instead of flowing on into the room and becoming contaminated, being drawn back into the filter system of the bench through the openings in the hood or dividing partitions and in the bench top.
Another feature of the present invention is to provide a dust-free bench of the above character that eliminates operator discomfort, since most of the air flowing over the bench is sucked back into the bench interior and is not felt by the operator, the novel circulating method of the present invention enabling the use of a fully open front hood, for example, and hence easy access to the interior thereof without any danger of contamination, the hood top when used preferably overlying the forward edge of the bench to prevent dust or other particles from falling on the bench from above.
Still another feature of the present invention is to provide a novel bench of the above character wherein the velocity of the air passing outwardly of the hood toward the operator can be kept relatively low so as to eliminate operator discomfort while higher velocities exist over the bench working surface and still higher velocities are present in the air being drawn into the hood or dividing partition side edges and or into the bench free edge.
These and other features and advantages of the present invention will be more apparent after a perusal of the 3,318,076 Patented May 9, 1967 "ice following specification taken in connection with the accompanying drawings, wherein:
FIG. 1 is a perspective view of one form of the novel dust-free bench of the present invention with arrows indrcating the flow of the air over the bench within the hood and into the openings at the bench front and hood side edges;
FIG. 2 is a side View with parts broken away of the bench of FIG. 1 and also shows circulation of air throughout the bench and hood structure in use;
FIG. 3 is a front view taken of the bench of FIG. 2 with parts broken away;
FIG. 4A is a fragmentary schematic view illustrating the formation of eddy currents and the drawing of dust onto the bench top where the suction slots are not provided in the bench top and in the hood sides;
FIG. 4B is a view similar to FIG. 4A illustrating the air circulation when using the slots of this invention;
FIG. 5 shows a plurality of benches arranged in tandem for a plurality of workers; and
FIG. 6 is a plan view of the structures of FIG. 5.
Similar characters of reference are used in the above figures to designate corresponding parts.
Referring now to the drawings, the reference numeral 1 designates a bench housing or casing providing an interior lower chamber 2 having a motor 3 therewithin positioned for driving a blower 4 that sucks a controllable amount of external air in through an adjustable area grid or grille 5, as of the type used in wood-burning or coalburning stoves or in forced-air heating systems and well known to those skilled in the art, said grid being located at the front of the housing and also sucks air from a bench plenum chamber or duct 6 within a hollow horizontal bench 12 through openings 7 in the bench bottom wall communicating with the interior of housing lower chamber 2. The bench is shown as having a hood 14 provided with side partitions or walls 11 and 11 that are also hollow providing therewithin side wall plenum chambers or ducts 8 and 8 provided with lower apertures 9 provided in inverted channel stiffening members 10 provided at the interior lower edges of the hollow hood side walls 11 and 11'. The hollow bench 12 has spaced top and bottom walls providing the plenum chamber or duct 6 therebetween and is shown having its upper working surface 12 interiorly reinforced by reinforcing members 13.
The forward edge portion 42 of the hollow bench 12 and the forward edge portions 43, 43' of the hollow side Walls 11 and 11 are vented contiguous to the interior working area of the bench by being provided with a series of mutually spaced slots arranged in rows and designated 15 in the bench forward free edge and 16 in the partitions or hood sides 11 and 11 so that air drawn in by the blower 4 not only passes in through grid 5 in controlled amounts depending upon the adjustment of this grid, but also flows in through the slots 16 at the inner sides of the partitions 11 and 11' and through the hood plenum chambers 8 and 8', through apertures 9 and corresponding aperture 9' in the upper surface 12' of the bench, and into the bench plenum chamber or duct 6 and from thence to openings 7 into the lower chamber 2. Likewise, air will flow in through slots 15 of the bench top through the plenum chamber 6, through apertures 7, and to the blower 4. This air is then driven by the blower 4 through the bench circulatory system as will further appear.
The adjustable area grid 5 is shown provided with a primary or coarse filter 17, and a similar filter is shown provided at 18 at the intake of the blower 4. Actually, the coarse filter 17 may be eliminated, if desired. The blower 4 forces the air upward into the rear hood plenum chamber or duct 19 provided within casing 1, whence this air flows through a fine or positive filter 20 that may be a mechanical filter having a fine screen composed of cellulose glass material, for example. This filter is of rectangular shape and is made somewhat larger than the hood interior 21 so that there will be a uniform flow of air from the fine filter 20 and through a grille 22 into the interior of the hood chamber 21, whereby there is no opportunity for eddy currents to be formed around the edges of the filter within the hood which would otherwise take place should the filter have a solid frame portion projecting into the confines of the hood interior 21.
The multi-apertured grille 22. directs the air from the filter forward and parallel to the side and top interior walls of the hood 14 and also protects the filter 21) against physical damage, the air passing over the surface of the bench 12, providing a uniform laminar flow of air forwardly through the hood in use.
The filter is removably retained within its position in the plenum chamber 19 by means of wedge members 23 or screws or other means and angle type guides 24 attached to the side interior walls of the casing 1. When the filter is used up, it can be removed by opening the top hinged section 25, whereupon the wedges 23 can be removed, allowing the filter to be replaced, the replacement of the wedges serving to hold the new filter in place so as to completely cover the grille 22. The upper part of the hood 14 over the bench 12 is provided with a lighting chamber 26 containing fluorescent lights 27 which shine through a translucent plate 23 provided at the top of the hood chamber 21.
All surfaces in the hood chamber are smooth and are arranged for smooth flow of air throughout the interior 21. As the air moves forward within the chamber 21 it reaches the forward edges of the hood wall partition sides of the bench and a certain amount of this air is sucked into the slots 15 and 16 due to the suction of fan 4, so that only a portion of the air leaving filter 20 moves forward :and out of the hood 14. The slots 15 and 16, being subject to interior negative pressure, prevent the formation of any eddy currents at the front of the bench which might tend to draw dirt back onto the bench. For example, the work piece 29, resting on top of the bench 12, would ordinarily set up eddy currents due to the flow of air thereover, as illustrated in FIG. 4A, the eddy currents being in front of the work piece, and these currents whirling around would suck in contaminated air from the room surrounding the bench and from the operators clothing and hands so that dust would be deposited upon the bench and upon the work, which is highly objectionable.
On the other hand, by using the slots 15 and 16, the eddy currents are eliminated as shown by the circulation of air as indicated in FIG. 4B, for example. Actual tests have shown that where the slots 15 and 16 are not present, definite quantities of dirt will move onto the bench top and onto the work on the bench, but where these slots are used, no such dust can enter, because it will be sucked into the slots 15 and 16, and thence through the blower to be eliminated from the circulating system.
FIG. 4A shows in detail the formation of eddy currents by a piece of work on the bench where the slots 15 and 16 are not employed, these eddy currents serving to draw in dust and deposit it upon the bench and upon the work. Since a lot of the air blown through the hood is sucked back into the circulating system, a much cleaner environment is provided within the work space than would otherwise be the case, and as a consequence of such recirculation, the life of the filter is greatly prolonged, since dust from the surrounding room is not drawn into the system 7 except that passing through the adjustable grid 5, the
load on both coarse and fine filters is reduced greatly. The apertures 9 are so proportioned that ordinarily air is sucked into apertures 16 at the sides of the hood at a much higher velocity than the air moving forward from filler 20 through the work space. Also, the air moving backwardly through slots 15 at the front of the bench top flows at a higher velocity than the air moving from the filter 20 forwardly over the work space. In a typical instance, air may flow through filter 20 and through work space at a velocity of feet a minute, whereas the velocity intake at the slots 16 at the sides of the hood may be as high as 2000 feet a minute. Since a large portion of the air moving forwardly through the work space is drawn back into the circulating system, the operator feels no uncomfortable draft from the operation of the bench.
Through the use of the vented slots 16 and 15 in the side partition walls 11 and 11 of the hood and in the front of the bench, it is possible to have a fully open hood, or the hood may be eliminated entirely if desired, enabling easy access to the work on the bench top 12 without interference from any windows or panels. Also, higher velocities of air can be passed through the work space since much of it is withdrawn at the forward edges of the same.
In FIGS. 5 and 6 there is illustrated a continuous bench 40 adapted to provide a number of working spaces for a plurality of workers. In these figures filtered air from fine filter 20 passes through ducts 30, 31, 32, 33, etc., to hollow side partition walls 34, 35, 36, etc., and through grilles 37 transversely across the work spaces 38, 38, 38", etc. and into plenum chambers 39, 39', etc., from whence the air fiows back to blower 4 through coarse filter 18. A grid 5 can be set to allow a desired amount of exterior air to enter the circulating system. In these figures the slots 15 are provided in the front edges of the hollow bench and if it is desired to have two workers in each working space slots 15 are provided in the rear edge of the bench where the second row of workers sit, in which case the bench is made wider to accommodate the extra row of workers. Where only one row of workers is used the back wall of the bench can be closed, if desired, in which case the slots 15 would not be essential. Slots 15 and 15 are connected through the hollow bench plenum and apertures 7 to the interior of casing 1' leading to blower 4, whereby suction applied to slots 15 and 15' prevents dust and dirt from moving onto the bench working spaces between the side partition walls 34, 35, 36, etc.
Since many changes could be made in the above construction of the novel dust-free bench of this invention and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above descripion or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
What is claimed is: V
1. A dust-free bench structure comprising a bench housing, a hollow bench having a substantially impervious and horizontal upper working surface and a spaced lower surface, said surfaces terminating at the front of said bench in a forward edge portion, said bench being supported upon said housing and projecting forwardly thereof to provide knee-space therebelow, said hollow bench defining a duct therewithin and being provided with a series of mutually spaced apertures arranged in a tranverse row along the forward edge portion thereof communicating with said duct, the upper working surface of said bench being substantially horizontal for supporting work thereon and extending to said apertures at the forward edge portion thereof, said bench duct communicating with the interior of said bench housing, a blower within said housing having its input communicating through said housing and said bench duct with said apertures, a coarse filter at the intake of said blower for filtering air sucked in use through said bench forward apertures and through said duct and entering a d housing, a fine filter positioned adjacent said hollow bench, a mulit-apertured grille adjoining said bench working surface and extending substantially perpendicularly to and substantially vertically above the same, and an output duct connecting the output of said blower to said multi-aperturcd grille and including said fine filter for driving air through the latter and through said grille, said grille serving to direct the air over said bench working surface in substantially laminar flow, a portion of this air being sucked back in through said bench forward apertures and returned to said blower in use, thereby effecting recirculation of such air, thusly not only providing a cleaner environment above the work bench but also preventing the ingress of outside contaminated air resulting, in the the absence of said apertures, from the production of eddy currents over the forward upper surface of the bench due to the presence of work thereon or of the operators hands, as Well as reducing the velocity of air flow past the bench operator and improving his comfort.
2. A dust-free bench structure as defined in claim 1 wherein said housing has a front wall provided with an opening, a grid mounted in the opening of said housing front wall, said grid communicating through the interior of said housing with the intake of said blower and coarse filter, for permitting a controlled volume of outside air to enter said housing and mix with the returning air from said bench duct before entering said coarse filter at the intake of said blower, thus controlling the speed and volume of the air entering said bench forward apertures, to suit a desired environment, said bench forward row of apertures extending substantially completely across the front edge of said bench.
3. A dust-free bench structure as defined in claim 2 comprising a hood having a hollow top and side walls and open at its front overlying said bench and supported by said housing, said hood hollow side walls having ducts thereWithin and being provided with a series of mutually spaced apertures along the forward edges only thereof communicating with said side wall ducts, said side wall ducts communicating at the lower edges of said side walls with the interior of said bench housing and through said housing interior to the input of said blower, said fine filter being positioned at the rear of said hood for directing filtered air therethrough and over said bench, said blower in use serving to suck air in through said hood side wall forward apertures, through said side wall ducts, into the interior of said bench housing, wherein the same mixes with air entering said housing from said bench duct and from said grid, such mixed air then passing through said coarse filter, said blower and connected output duct to and through said fine filter.
4. A dust-free bench structure as defined in claim 3 wherein the forward mutually spaced apertures in each hood side Wall extend in a row for substantially the full height of the interior of said hood, stiffening members within the hollow interior of said hood side walls and fixed thereto adjacent said bench upper working surface, and stiffening members within said hollow bench and fixed therewithin, said hood stiffening members and said bench upper working surface being apertured to enable air from said side wall ducts to enter said housing, said stiffening member and bench apertures being of sufi'icient size as to cause return air to enter said hood side apertures at a higher speed than that of the air flowing forwardly over said bench working surface.
References Cited by the Examiner UNITED STATES PATENTS 1,194,527 8/ 1916 McNamara.
2,150,252 3/1939 Shure 98-36 X 2,172,944 9/ 1939 Norris 98-40 2,291,220 7/ 1942 Germonprez.
2,332,174 10/1943 Shreve 98-36 X 2,341,628 2/ 1944 Koweindl.
2,999,448 9/ 1961 Abler et al.
3,021,776 2/ 1962 Kennedy.
3,123,988 3/1964 Richman 98-36 X 3,158,457 11/ 1964 Whitfield -473 X 3,229,611 1/1966 Berger.
OTHER REFERENCES Crane, V. 6.: Design Techniques for Industrial Clean Rooms in Air Conditioning, Heating and Ventilating, pp. 58 to 63. December 1963.
HARRY B. THORNTON, Primary Examiner.
FRANK W. LUTTER, B. NOZICK,