Patent Publication Number: US-RE43175-E

Title: Toolless, self closing floor grommet closure for cable openings and the like in raised floors of data centers office buildings and other air conditioned structures

Description:
Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 6,632,999. The reissue applications are applications Ser. No. 11/250,137, now U.S. Pat. No. Re. 41,863, and Ser. No. 12/616,627, (the present application) which are divisional reissues of U.S. Pat. No. 6,632,999. The present application claims the priority of the Oct. 13, 2005 filing date of reissue application Ser. No. 11/250,137. 
     RELATED APPLICATIONS 
     This application claims priority of Provisional Application Ser. No. 60/318,763, filed Sep. 13, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     In certain building and office structures, it is advantageous to supply air conditioning by way of a raised floor structure forming an under floor plenum. By way of openings provided selectively in the flooring elements, the air conditioning flows are controllably directed into the room space or spaces above the floor. Such arrangements are widely employed in data centers, for example, but are also usefully employed to provide air conditioning on a controllable and efficient basis to modern offices. 
     Computers and related equipment utilized in offices, business, industry, government telecommunications, the internet, data storage facilities, and the like quite commonly are located in great numbers in dedicated buildings or dedicated areas of buildings, in which the equipment is arranged in relatively high density configuration, in racks, for example, for convenient supervision and maintenance. A common practice in connection with such high density data centers is to provide a raised floor structure made up of individual floor tiles supported on a suitable skeletal framework, providing a convenient plenum space underneath for the passage of cooling air and the necessary data and power cables. Suitable cable cut-outs or openings are provided in the floor tiles to accommodate the passage of the power and data cables from the space underneath the floor upward for connection to the computer units within the room above. Typically, large numbers of such cable openings are provided. For example, there may well be as many as sixty cable openings (of a typical size of about 4″×8″) per thousand square feet of floor space. 
     Because the set up and operation of the computer equipment within a large data center can be very dynamic, in order to accommodate the rapid growth and change within the industries served, it is necessary not only to have relatively large numbers of grommet openings, but also that they be conveniently accessed and used in order to facilitate frequent re-routing of power and data cables. 
     In the operation of high density data centers, significant heat is generated by the operating units, and it is necessary to provide suitable air conditioning in order to maintain the equipment at a suitable operating temperature. Conventionally, the necessary air conditioning is provided by discharging cool air into the cable space provided below the elevated floor structure. Selected perforated floor tiles, provided with a desired pattern of openings, are appropriately positioned in relation to the operating units, sometimes directly beneath, and sometimes alongside, arranged to discharge cooled air upwardly, where the air may be drawn into the operating units by their internal fans. 
     The air conditioning of the operating units is complicated significantly by the presence of large numbers of cable openings throughout the floor space. Large quantities of the cool air escape through these large openings into the general ambient of the room, where the cool air cannot be efficiently utilized. The escape of conditioned air through the cable openings can be such as to reduce the static pressure in the cable space underneath the floor from a desired 0.10″ of water, for example, to as little as 0.01″. While this “lost” cooling air does enter the ambient space of the data center, it is not effectively and efficiently available to be drawn into the operating units, and often simply mixes with hot air being discharged from the operating units by their internal cooling fans. The loss of efficiency can be as great as the equivalent of a 20 ton cooling unit for each thousand square feet of computer room floor space. 
     Some attempts have been made to reduce the loss of conditioned air through floor openings, by stuffing the openings with foam pads, rags, small pillows, etc. These have been haphazard at best and generally of minimal usefulness. 
     In a similar manner, controlled air conditioning of modern office space is sometimes accomplished by providing the conditioned air via an under floor plenum associated with a swirled diffuser supply system, with selectively located under floor diffusers and floor grates to provide for controlled upward discharge of the conditioned air into the office space. Such arrangements often seek to increase efficiency by providing for a swirling action of the discharged air, a technique that tends to provide for equivalent comfort levels while maintaining the ambient temperature at least slightly higher than otherwise, to achieve greater air conditioning efficiencies. For such systems, uncontrolled leakage of conditioned air through cable openings and the like provided in the flooring can reduce the operating efficiencies of the system, and a need is indicated for efficient means for sealing such openings. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a novel and improved form of floor grommet for use in large, high density data centers, under floor office air conditioning and the like, which substantially seals off the cable openings around the power and data cables or other elements passing therethrough. There is thus a minimal loss of cooling air through the multiple cable openings and a maximized flow of such air is directed through the intended discharge openings, e.g., adjacent to and/or underneath the operating units, or through special outlets to provide a desired swirling action. In a particularly preferred embodiment of the invention, a standard cable opening of 4″×8″ or 5″×8″ dimensions is “sealed” by a plurality of thin filamentary elements extending from opposite sides of a grommet frame and meeting in the central area of the grommet opening. The density of these filamentary elements is such that power and data cables may be easily threaded through the grommet opening by displacement of the elements, which then largely close around the cables to minimize any opening for the escape of conditioned air. To a particular advantage, the filamentary elements may be provided by brush-like bristle assemblies, formed of relatively fine bristles of materials such as nylon, polypropylene or natural horsehair. 
     In a particularly advantageous form of the invention, a plurality of layers of the bristle assemblies of different lengths and configurations are provided within a grommet frame. A first layer of opposed bristles extends from one side of the grommet frame, meeting in the center of the grommet opening. A second layer of bristles is disposed directly below the first, and advantageously consists of bristles of a somewhat shorter length which do not extend completely to the center of the grommet opening. Advantageously, the two levels of bristles are disposed so that the shorter bristles and the longer bristles are in contact in their outer areas. 
     For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiment to the invention and to the accompanying drawings. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a top perspective view of a typical form of floor tile of a raised floor system, illustrated with a floor grommet according to the invention installed therein; 
         FIG. 2  is an enlarged top perspective view of a preferred embodiment of the new floor grommet; 
         FIG. 3  is a bottom perspective view of the floor grommet of  FIG. 2 ; 
         FIG. 4  is an exploded view of the floor grommet of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view as if taken generally on line  5 - 5  of  FIG. 2 , illustrating a slightly modified form of grommet intended for installation at an edge of a floor tile; 
         FIG. 6  is a top perspective view of a typical floor tile element shown with a central cable opening for receiving the floor grommet of the invention; 
         FIG. 7  is a top perspective view showing a modified form of the invention useful particularly in connection with retrofit installation of grommets in an elevated floor system; 
         FIG. 8  is an exploded view of the retrofit device of  FIG. 7 ; 
         FIG. 9  is a perspective view of a locking element advantageously utilized with the retrofit unit of  FIG. 7 ; 
         FIG. 10  is a fragmentary cross-sectional view illustrating a marginal edge portion of the retrofit unit of  FIG. 7  installed in a floor tile unit. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings, the reference numeral  20  ( FIG. 1 ), designates generally a typical floor tile utilized in raised floor installations. Known constructions of such raised floor structures are made available commercially by, for example, Tate Access Floors, Inc., Norwood, Mass. The individual floor tiles  20 , typically flat on their upper surfaces, are formed with supporting structure  21  on their undersurfaces. The individual floor tiles may be supported by a grid structure engaging undersurfaces of the tiles at their edges, typically with supporting posts (not shown) supporting the grid structure at an elevated level from the base floor (not shown) of the enclosing structure. The particular type and style of raised floor structure does not form a part of this invention, and the description of such raised floor structures is simply to illustrate the environment in which the floor grommet system of the invention is employed. 
     In a typical installation, the floor tiles  20  may be approximately 2 feet square, and the entire elevated floor is made up of these tiles arranged edge to edge. Floor tiles and supporting structure have adequate strength to support all the necessary computer or office equipment, personnel, etc., typically involved in high density data centers, office buildings, and the like. 
     In the illustration of  FIG. 6 , the floor tile  20  is shown with a center cable opening  22  to enable power and data cables to be passed from the space below the elevated flooring upward for connection to the various units of computer or other equipment installed in the office or data center. As previously mentioned, there may be a large number of such openings, as many as sixty openings per thousand square feet of floor space, in a typical data center, for example. In many cases, these openings are simply lined with a hole dressing material, to protect the cables from sharp metal edges, the holes otherwise being left open except perhaps for makeshift attempts to reduce airflow losses therethrough. 
     Pursuant to the present invention, the cable openings  22  are nominally closed by means of floor grommet assemblies  23 , which are designed to be received in the cable openings and hence serve both to dress the opening and protect the cables from sharp edges, and also to effectively seal the openings against significant airflow. At the same time, the floor grommet units of the invention allow power and data cables to be easily passed through the floor openings and through the grommets, accommodating easy routing and re-routing of such cables as is frequently necessary in an active office data center. 
     To advantage, the floor grommet  23  of the invention comprises a surrounding frame  24 , preferably formed of a structural plastic material, such as polypropylene, compounded to have anti-static characteristics as well as fire-retardant characteristics. The frame  24  has a cross-sectional configuration as reflected in  FIG. 5 , with a horizontal flange portion  25  defining a rectangular central opening  26 , typically of 8″×5″ dimensions. Peripheral flanges  27  project downward from the horizontal flange  25  and are of a suitable size and shape to cover the raw edges of the floor tiles  20 . 
     In the specific illustration of  FIG. 5 , a special depending flange  28  is provided along one side, for purposes that will be described hereafter. In all other respects the features shown in  FIG. 5  relate to the embodiment shown in  FIGS. 1-4 . 
     Immediately surrounding the opening  26 , the horizontal flange  25  is formed with an offset to define a rectangular recess  29  adapted to receive a cover plate  30 , partially shown in  FIG. 5 . The cover plate  30  may be employed to completely close the opening  26  when no cables are extending therethrough, so that no air at all escapes through the opening, and the opening may be walked upon as if it were a normal part of the floor tile surface. 
     Along each of the longer sides of the vertical flanges  27 , there are installed multiple channel extrusions  31 , advantageously formed of aluminum. The channel forming extrusions are mounted along the inside walls of the vertical flanges  27 . Upwardly extending locating ribs  33  are provided along upper edges of the channel forming extrusions and are received in recesses  34  formed in the frame  24 . The channel forming extrusions are locked in place by means of screws  35  ( FIG. 4 ) which extend through openings  36  in the side flanges  27  to secure the channel forming extrusions tightly against the insides of the flanges. 
     As shown in  FIGS. 4 and 5 , the multi-channel extrusions of the preferred embodiment consist of three inwardly facing channels  37 - 39  which extend lengthwise of the extrusions. The upper channels  3 - 38  are arranged to tightly receive upper and lower bristle assemblies  40 - 41 . 
     The bristle assemblies  40 - 41  are comprised of backbone structures  42 - 43  which mount, and from which extend, a mass of fine, flexible filaments or bristles  44 - 45 . To advantage, the bristles may be formed of nylon or polyethylene filaments, for example, having a thickness of 10-20 mils and compounded or treated to have anti-static and flame-retardant characteristics. The individual bristles are closely packed to a thickness of around one-fourth inch. 
     As evident in  FIG. 5 , the upper bristle assemblies  40  are disposed generally horizontally and incorporate bristles of a length to extend to, and preferably just slightly beyond the center line of the grommet opening  26 . The arrangement is such that the upper bristle assemblies, in an undisturbed state, substantially close the grommet opening  26 , forming a highly effective barrier against the flow of conditioned air under a pressure of, for example, 0.10″ of water. 
     As shown in  FIGS. 3 and 5  in particular, the lower bristle assemblies  41  preferably are comprised of bristles  45  of a length shorter than the bristles  44  of the upper assemblies  40 . The lower bristles thus terminate a short distance, for example, ⅝″ or so, from the center line of the grommet opening. Additionally, upper and lower bristle assemblies are convergently disposed, preferably by mounting the lower assemblies  41  with an upward incline, such that the ends of the lower bristles  45  make contact with outer portions of the upper bristles  44 . 
     When a cable is passed through the grommet opening  26 , bristles  44  of the upper bristle assemblies are displaced laterally to accommodate the presence of the cable in the opening. The individual bristles, being mounted in cantilever fashion by the backbone structures  42 - 43 , bend laterally at their outer ends and close together a short distance away from the cable. The displacement of the bristles necessarily leaves a small V-shaped opening between the body of the cable and the point where the bristles merge together. In the grommet structure of the present invention, these small V-shaped openings are greatly minimized by the presence of the lower bristle assemblies  41  will have been displaced to a lesser extent, and in many cases not at all. In the illustration of  FIG. 5 , for example, a cable  46  of modest diameter can be passed through the grommet by laterally displacing the ends of the upper bristles  44 , without displacing the bristles  45  of the lower assemblies. The lower bristles  45  thus tend to partially close off and thus minimize any small openings adjacent to cable  46  resulting from lateral displacement of the upper bristles  44 . Additionally, in the case of cables of larger diameter, sufficient to result in lateral displacement of the lower bristles  45 , it will be understood that the displacement of the lower bristles is significantly less than that of the upper bristles, so that the two sets of bristle assemblies, working in combination with each other, greatly minimize any openings for the passage of conditioned air. 
     It is contemplated that the bristle assemblies may be provided in more than two layers if desired. Likewise, it may be feasible to construct a single composite bristle structure employing tiers of bristles of different lengths. Likewise it may be possible to form at least some of the tiers with materials other than bristles or filaments, for example, panels of material slit to form narrow strips, panels of soft foam material, etc. 
     Where the grommet of the invention is installed in the center of a floor tile  20 , as reflected in  FIG. 1 , the downwardly projecting rib  28  will be omitted. In some cases, however, it is desired to position the grommet along an edge of the floor tile. In such a case, the floor tile may be formed with an open sided cut-out, as indicated by broken line  50  in  FIG. 1 . The grommet frame will then be installed in a manner to position the projecting rib  28  at the open side of the cut-out  50 , to rest upon a support element  51  under the edge of the floor tile. 
     A modified form of the new floor grommet structure, shown in  FIGS. 7-10 , is designed for easy retrofit installation in an existing floor. In the modified device, a frame  60 , comprised of two parts  61 - 62 , is arranged with flange portions  63 - 64  secured to mounting panels  65 - 66 . The frame parts  61 - 62  include upwardly extending flange portions  67 - 68  and inwardly projecting flange portions  69 - 70 . The inwardly extending flanges  69 - 70  define the grommet opening. 
     Each of the frame sections  61 - 62  mounts a pair of upper and lower bristle sets, of which only the upper sets  71 - 72  are visible in the drawings. It will be understood, however, that the arrangement of the bristle sets in the device of  FIGS. 7-10  is similar to that shown in  FIG. 5 . 
     A preferred method for installing the retrofit unit of  FIGS. 7-10  is by means of adhesive applied to the undersurfaces of the mounting panels  65 - 66 . Each of the adhesively coated panels is provided with a release paper  73 - 74 , which may be pulled away to expose the adhesive. Typically, the unit  62  will be positioned over a floor tile opening, and the release paper  74  then pulled out from under it, to allow the adhesive to contact the surface of the floor tile. The second section  61  is then positioned immediately adjacent to the section  62 , and the release paper  73  is pulled out from under it, to expose the adhesive of the second component to the floor tile. 
     Desirably, mechanical locking tabs  75 , shown in  FIG. 9 , are inserted in recesses  76 - 77  provided in each of the frames  61 - 62 , so that the two sections are mechanically locked together as well as being secured by adhesive means. 
     In a typical retrofit installation, a pre-cut cable opening in the floor tile will have been lined by a plastic floor dressing  80 , shown in  FIG. 10 . Typically, this will include a flange  81  supported on the top surface of the floor tile  82 . To accommodate the thickness of the flange  81 , the edge margins of the mounting plates  65 - 66  advantageously are provided with a layer  83  of foam material, with the adhesive being applied to the downwardly facing surface of such material. 
     The retrofit unit of  FIGS. 7-10  can be installed in an existing cable opening having previously installed cables passing through. It is not necessary to interrupt service by unplugging the cables because the retrofit grommet device can be installed around the existing cables. 
     The retrofit unit of  FIGS. 7-10  can also be employed to advantage for sealing of an opening which is located immediately adjacent a side wall of the room. In such a case, only one half of the two-part unit is employed, that is either one of the panels  65 ,  66 . The panel is installed tightly against the side wall, with the free ends of the bristles engaging the side wall, allowing the cable to pass through the opening closely adjacent to the side wall. 
     In certain instances, it may be desirable to provide the floor grommet with centering guide means, positioned in the lower portions of the grommet, to urge cables passing through the grommet toward the center of the grommet opening such that the cables pass more or less symmetrically between the opposed sets of flexible elements. An advantageous form of such guide means may be resilient plastic or rubber vanes  90 , shown in broken lines in  FIG. 5 . The vanes  90  can be anchored in the lowermost channels  39  of the multi-channel extrusion, extending therefrom to the center of the grommet opening and advantageously substantially meeting edge to edge along the longitudinal center line of the grommet opening. The vanes  90  have sufficient stiffness to urge cables toward a centered position between them. Because of that stiffness, however, the vanes  90  normally will not close effectively around the cables and thus by themselves do not form an effective cable seal. However, that function is taken care of by the bristle assemblies  40 - 41  as previously described. When no cable is present in the grommet opening, however, the resilient vanes  90  can close tightly at the center and form a complete seal of the grommet opening. 
     The new floor grommet arrangement provides very important economic and other advantages in the operation of high density data centers and of office buildings in which conditioned air is provided by an under floor plenum arrangement. One such advantage is the significant reduction of required air conditioning capacity to service an area of given heat load. With the new system, the uncontrolled loss of conditioned air through floor openings is reduced to a small fraction of normal experience, which translates directly into decreased capital requirements for air conditioning equipment, as well as to significant reductions in operating cost required to deliver the conditioned air. 
     Additionally, and importantly, the system of the invention also provides greater assurance that the cooling air provided will be directed to the areas where it is needed and discharged in the manner intended. For data centers, this assures that system outages from localized overheating problems are greatly minimized or eliminated. Among other things, this makes it possible to increase the density of computer equipment installed in a given space. For office buildings using under floor delivery of conditioned air, it becomes practical to operate at a higher overall ambient with equivalent comfort because a higher proportion of the conditioned air is delivered with a swirling effect in the manner intended by the HVAC engineers. 
     It will be understood, of course, that the invention is not limited to the specific structures illustrated and described and that the inventive concepts expressed herein can be incorporated into other embodiments.