Grommet for cables

A cable grommet system for installation in data centers, offices and the like, for sealing cable openings in raised flooring, wall or ceiling panels, server cabinets, etc. to facilitate the installation and revision of wiring and cabling to server installations while minimizing losses of any provided conditioned air. A wide variety of grommet configurations is possible with a limited number of component parts. An advantageous acute angle mounting of sealing brushes enhances the sealing effectiveness thereof, particularly for smaller sizes of cable openings. In some embodiments, a novel arrangement of electrical conductors is incorporated into the grommet structures for dissipation of electrostatic charges, enabling the basic frame components to be formed of a flame retardant material.

BACKGROUND OF THE INVENTION

This invention relates to a cable grommet system, particularly for use in connection with data centers, offices and the like to accommodate the passage of cables from one side to another of a floor, cabinet, rack, or other enclosure serving as a containment between two areas, particularly where the areas are under unequal air pressure, such as for conditioned air (heating or cooling) under positive pressure. The term “cable”, as used herein, refers not only to flexible electrical wires and cables but also to rigid elements, such as pipes, conduits and the like that may be extended through openings in floor or other panels, especially where it is desired to restrict the flow of air through such openings.

In data centers and the like, large numbers of computer servers typically are arranged in a compact configuration of cabinets or racks. Large numbers of the cabinets or racks may be housed in a common area, to facilitate access to the servers by technicians for wiring and rewiring, servicing, etc. Commonly in such installations, a raised floor structure is provided, creating a space under the floor for the passage of the necessary wiring and cabling to power the servers and to transmit the input and output signals therefrom. The wiring and cabling for a particular server rack is extended through the space below the floor, and is passed upward through the floor to enable connection with the servers, typically, but not necessarily, at the back of the rack.

Modern high speed servers generate significant heat during operation, and this heat must be dissipated effectively in order to avoid damage to and/or malfunction of the servers. Accordingly, it is customary to provide an air conditioned environment for the servers, typically by providing the conditioned air under pressure (e.g., 0.1 inch of water) in the space provided underneath the raised flooring. Outlets for the conditioned air are located at each of the server cabinets or racks, typically at the front thereof, such that the cooled air may flow upward along the front of the cabinet rack and be drawn into and passed through the individual servers from front to back.

Openings provided in the flooring for the passage of cable can result in the undesired flow of some of the cooling air through the cable openings. The leakage of cooling air through such openings can represent a significant economic loss, because cooling air that simply mingles with the general atmosphere of the data center, and does not flow properly to intake openings at the front of the servers, does not function effectively to cool the servers and its cooling effort is simply lost. In a typical large data center, there can be large numbers of such cable openings (for example, as many as sixty openings per thousand square feet of floor space). Collectively, this can represent a significant loss of cooling capacity, if conditioned air is allowed to escape through these openings.

Heretofore, various efforts have been made to seal off these openings. However, because the cabling of data centers is very dynamic, in the sense that the server setups, and the cabling for servicing them, are constantly changing, many sealing concepts that would otherwise be suitable for wiring and cabling are not suitable for use in dynamically changing data centers and the like.

A significant advance in the design of cable grommets for data centers and the like is reflected in the Sempliner et al. U.S. Pat. No. 6,632,999, which discloses and claims a particularly advantageous form of cable grommet comprising a frame, suitable for fitting into a cable opening in a floor, cabinet or other pressurized space, and provided with a unique arrangement of one or more brush-like sealing elements comprising a large plurality of filamentary elements forming a substantial seal of the opening in the grommet frame. The arrangement enables cables and the like to be easily passed through the filament-sealed opening, such that frequent wiring and rewiring is greatly facilitated. After the wires and cables are passed through the grommet opening, the opening is automatically effectively sealed by the multitude of filaments which deflect and close around the cable elements. The cable grommet of the Sempliner et al. '999 patent has been very successful commercially and has achieved very significant economies in the operation of data centers, and even in less densely wired areas, such as offices, for example.

SUMMARY OF INVENTION

The present invention is directed to a new and improved cable grommet which readily accommodates a wide variety of sizes and shapes of cable openings utilizing a standardized set of component elements. Pursuant to one aspect of the invention, a cable grommet of closed configuration can be formed utilizing a pair of grommet-forming end units of generally U-shaped configuration, or using a pair of such U-shaped units together with one or more pairs of extension units between the U-shaped units, or using a pair of opposed extension elements of suitable length to fill the entire opening. A pair of such U-shaped end units, joined with their open sides facing each other, define a grommet of closed configuration. Operative cable grommets may also be provided using a single U-shaped end unit arranged with its open end suitably closed or confined, as by an edge or surface of an adjacent panel, an element of a rack or cabinet, or by other means. In other configurations, extension units corresponding in cross section to side sections of the U-shaped grommet-forming end units, are mounted in substantial alignment and contact with the side sections of a primary U-shaped end unit, effectively extending its length. An elongated grommet of closed configuration may comprise a pair of opposed, U-shaped end units, optionally with one or more pairs of the extension units, depending on requirements.

According to one aspect of the invention, the side sections of the U-shaped grommet-forming end units are formed with channels for reception of brushes provided with cantilever mounted bristles. The brushes are mounted at an acute angle of about 30 degrees to a plane defined by peripheral mounting flanges of the end units. A pair of brushes extend from opposite sides of the end unit and meet mid-way to provide effective sealing against significant air leakage from one side of the brush pair to the other, while readily accommodating the easy passage and removal of cabling. By mounting the brushes at an angle of around 30 degrees, the effectiveness of the brushes is enhanced, and the effective length of the brushes may be increased within a grommet opening of a given width. In the illustrated and preferred embodiments of the invention, the brush filaments extend upwardly from their cantilever mountings. However, in appropriate cases the brush filaments could be extended downward at an acute angle.

In accordance with another feature of the invention, the grommet-forming end units and extension units advantageously are formed of a flame retardant plastic material. Heretofore, such flame retardant materials have not been widely used, because they tend to lack conductivity, which is important for dissipating static electric charges developed in and around the brush elements and around the cabling passing through the brush elements. In accordance with the invention, a conductive element is incorporated into each of the U-shaped end units, arranged so that a portion thereof underlies a mounting flange and other portions thereof have contact with a conductive backing structure of the brushes. The arrangement is such that static charges developed on the cables or brushes are effectively dissipated into the flooring or other panel in which the grommet is installed, which panels typically are formed of a conductive material, such as metal.

The invention provides for a versatile set of grommet-forming components that can be manufactured and installed on an economical and flexible basis to enable data centers and the like to operate with a desired high level of cooling efficiency. The grommet system of the invention, while particularly advantageous for use in high density data centers, can also be employed to great advantage in other venues, such as offices incorporating raised flooring structures for the passage of wires and cables and, in many cases also forming an enclosure for HVAC air.

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 embodiments, and to the accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawings, the reference numeral10designates generally a basic grommet-forming end unit according to the invention. The end unit comprises a frame11of generally U-shaped configuration, comprising an end section12and spaced-apart, opposed side sections13,14. The entire frame, consisting of the sections12-14, advantageously is a unitary molding of structural plastic material, and particularly a plastic material having fire retardant characteristics. A preferred form of such material, for example, is available from GE Plastics, under their trademark “CYCOLAC”, and particularly Cycolac Resin FR23. This product is a flame retardant ABS, which is desirable for the purposes of this invention.

The end and side sections12-14of the end unit10are formed with laterally extending flanges15-17, which define a flat plane and provide means for supporting and securing the end unit10on a panel (not shown) having an opening therein. The panel most typically is a floor panel, but may be any form of panel defining an enclosure, such as a wall panel, a panel of an enclosure cabinet, rack, or the like, where openings are provided for the passage of cables, and it is desired to prevent the uncontrolled flow of air through such opening.

As shown inFIG. 5, the respective side sections13,14include side walls18,19angling downward and inward from the side flanges16,17at an angle of about 60 degrees to the plane defined by the flanges15-17. At the base of each of the side walls18,19, there is a channel20, shown in detail inFIG. 10. The channel20extends along the full length of the walls18,19and preferably is formed with inwardly projecting flanges21,22at its open side, extending along the length of the channel, which serve to restrict the channel opening in the manner reflected inFIG. 10. The channels20are adapted to receive and mount first and second brush elements23. As shown inFIG. 6, the brush elements23comprise a rigid backing24mounting a plurality of flexible bristles25in cantilever fashion. To advantage, the backing24is formed by a conductive strip to provide electrical continuity from the bristles25. The bristles themselves advantageously are provided with an electro conductive coating material so as to be able to conduct away any static charges that might develop between the bristles and cable elements passing therethrough.

To advantage, the brush elements23are inserted longitudinally in the channels20such that the backing24and conductive strip of the brush elements are engaged by the channel side walls, and retained in the channel by the restricting flanges21,22. In the illustrated and preferred form of the invention, the brush elements23, which are in generally flat configuration as shown inFIGS. 5 and 6, are disposed generally at right angles to the side walls18,19, such that the brush elements are disposed at an acute angle of about 30 degrees with respect to the plane of the flanges. The length of the bristles is such that the free outer end portions23aof an opposed pair of brushes meet generally along the longitudinal center line of the end unit10. In the illustrated arrangement, the outer ends of the bristles are arranged at an angle such that the opposed bristle ends meet substantially along a vertical plane. Typically, the bristle ends will at least slightly overlap, such that there is positive contact between the bristle ends of an opposed pair of brush units, to assure that they will form a proper seal between them and also that there will be good conductivity between the brush units to facilitate dissipation of static charges. In some cases, it may be acceptable, or even desirable, to utilize brush elements with bristles that are all of substantially the same length such that the free end portions of the brushes are squared off, whereby the lower bristles or one brush overlap significantly and intermingle with lower bristles from the opposing brush element.

In the illustrated and preferred form of the invention, the end section12is provided with an end wall structure27consisting of upper end wall portions28and a lower end wall portion29, with the lower end wall portion29being offset longitudinally outward from the upper end wall portions28and joined thereto by inclined walls30(FIG. 4) extending outwardly from the upper end wall portions28. When the brush elements23are inserted longitudinally into their mounting channels20, the side edges of the brushes adjacent the end wall structures27are arranged to underlie the inclined walls30, to assure good sealing between the brushes and the ends of the U-shaped frame11. The end wall portion29may also advantageously be provided with inwardly projecting flanges31positioned to underlie side edge portions of the brushes23to provide additional support for the brush elements and to enhance the sealing action at the closed end of the frame11. The length of the brush elements23, measured along the backing24, is such that, when the brush elements are fully inserted into the channels20, and the side edges of the brushes at the closed end of the frame are seated underneath the inclined wall30, the side edges of the brushes at the open end of the frame11are aligned with the end edges32of the frame side sections13,14.

In the illustrated form of the invention, the side sections13,14may be provided with downwardly extending skirt walls33,34, which extend downward from lower corner areas of the channels20for a short distance. The lower end wall29likewise can extend downward a corresponding distance, so that the lower edges of the side and end walls define a common plane parallel to the flange plane. The walls33,34and29also define a lower bottom opening for the grommet end unit10. When desired, all or part of the skirt walls33,34may be eliminated.

Pursuant to one aspect of the invention, a single grommet-forming end unit10can be used by itself to form a functioning cable grommet in a floor or other panel, as where a cable opening is formed immediately adjacent a wall or panel which serves to close the open side of the U-shaped end unit. For example, cable openings frequently are formed in floor panels immediately adjacent another panel or to a vertical wall, or in a vertical (cabinet or wall) panel adjacent to a floor panel, and in such cases a single, U-shaped grommet-forming end unit10can form a suitable cable grommet by itself.

More typically, a pair of grommet-forming end units10are arranged open-end-to-open-end, as shown inFIGS. 1-3to form a two-unit cable grommet of closed configuration. Where the closed grommet configuration is employed, it is unnecessary to provide for the physical joining of one end unit10to the other. More preferably, and more economically, the two units are simply placed together end-to-end within an opening in a panel member, in the configuration shown inFIGS. 1-3. The individual grommet-forming end units10are then secured individually to the panel, by screws or other fasteners inserted through suitable openings35provided in the side flanges16,17. The units10are thus fixed in proper alignment as a result of being fastened to the surface of the panel.

Although the grommet-forming end units10can be of any size, the invention lends itself particularly well to utilization in connection with relatively small cable openings. For example, the two-unit configuration as shown inFIGS. 1-3is ideally suited for cable openings of approximately 4×6 inches in size. Advantages are derived from disposing opposed pairs of brush elements23at an upwardly (or downwardly) inclined acute angle, as shown, particularly in connection with grommets of smaller size. The angular relation of the opposing brushes allows for better closure of the bristles around the cable elements passing therethrough. Additionally, for a given opening, the angularly disposed bristles can be of somewhat greater length, which further enhances the sealing action thereof.

As heretofore mentioned, the desirable plastic material used in the formation of the frame11has a significant fire retardant characteristic. At the same time, the electric conductivity of such material is very low. Accordingly, the cable grommet of the invention incorporates a simplified yet highly effective arrangement for conducting away static electrical charges that may develop on the cables or on the bristles of the brush elements23. To this end, each of the frames11is provided in the upper extremity of its outer end wall structure27with a small opening36for the reception of a projecting portion37of a conductor38(FIGS. 6,12-13). The conductor38includes two angularly disposed elements39arranged at an angle of about 120 degrees, each carrying an angular tip portion40at its outer end. When the conductor38element is installed, its projecting portion37is passed through the wall opening36and extends longitudinally outward, partly received in a recess15ain the underside of the end flange15, as best shown inFIG. 2. The angularly disposed elements39extend laterally outward and downward, on the inside of the end wall structure29, substantially in alignment with the planes of the brush elements23. When the brush elements are inserted longitudinally in their channels20and pushed to the full depth thereof to engage the end wall portion29, the innermost ends of the conductive backings24, engage the ends40of the conductors38to establish electrical contact. When the grommet-forming end unit10is installed on a conductive panel, the projecting portion37is pressed into contact with the panel, to establish the desired electrical contact. The arrangement is such that any electrostatic charges developed on the cables and brushes are conducted away via the surrounding conductive backing24and the conductors38into the flooring or other paneling on which the unit is installed.

In some cases, and particularly where a cable grommet is to be formed using a single grommet-forming end unit10, it may be desirable to dress the open outer ends of the brush-receiving channels20. To this end, the open outer ends of the channels20are enlarged slightly, as indicated at41inFIG. 11. This enlargement may extend inward for a short distance, providing a small clearance space surrounding the outer end surfaces of the backing of a brush element23installed in the channel. A molded plastic end cap element42, shown inFIG. 14, has outer walls43shaped and sized to fit within the enlarged area41surrounding outer portions of the brush backing. This portion of the end cap is inserted into the enlarged open end of the channel20and is tightly held therein by friction and/or adhesive. An end wall44of the cap covers the exposed end of the brush element and provides a neater appearing unit.

In accordance with one of the features of the invention, the cable grommet may be configured to be installed in cable openings of greater length than could be dressed and covered by one or two of the grommet-forming end units10. To this end, special side extension units45(FIG. 16) are positioned between two end units10. These side extension units are substantially identical in cross sectional configuration to the respective side sections13,14of a grommet-forming end unit10, being provided with laterally extending flanges46, downwardly and inwardly angled side walls47, brush retaining channels48, depending bottom wall sections49and openings50in the flanges46for the reception of fasteners. The side extension units45normally are utilized in pairs and advantageously, although not necessarily, are of a length equal to the longitudinal (length) dimension of a standard brush element23, measured along its backing24. If desired, of course, the side extension units may be of greater or lesser length than that of a standard brush element, in which case longer or shorter brush elements could be utilized. In any case, the side extension units generally will be used in pairs of the same length.

As reflected inFIG. 15, a four-unit cable grommet may be assembled utilizing a pair of grommet-forming end units10in spaced-apart relation, bridged by a pair of side extension units45mounting brush elements123. In the illustration ofFIG. 15, the brush elements123are of the identical construction to the brush elements23in the adjacent end units10. However, in the side extension units45, the entire brush123is visible, whereas in the end units10, inner end portions of the brushes23are received under the inclined end walls30and are not visible from above the assembled grommet.

In the four-unit, extended grommet ofFIG. 15, none of the sections10,45are joined directly together. Instead, they are secured in assembled relation, as shown inFIG. 15, by being secured to a surrounding panel (not shown) by fasteners received in the openings35,50. As will be readily appreciated, the length of the assembly15may be extended to any desired dimension, by simply adding additional pairs of the side extension units45or, if appropriate, modifying one or both of the units10,45.

The invention provides a uniquely advantageous, highly flexible cable grommet arrangement which, with a simplified set of component parts can be assembled in a wide variety of lengths. The system requires only three standardized parts, the basic grommet-forming end unit10of U-shaped configuration, the side extension unit45, and the brushes23(123). With those three component parts, many different sizes of cable grommets may be installed, from a single grommet-forming end unit10positioned against a confronting panel, to a more conventional grommet comprising two of the U-shaped standard end units installed open-end-to-open-end, to an elongated unit as suggested inFIG. 15, incorporating a pair of the standard end units10and one or more pairs of the side extension units45. Additionally, in appropriate cases, a grommet assembly may be constructed using one or more pairs of individual extension units45arranged in opposing relation, with panel edges at opposite ends of the extension units serving to close the ends of the grommet structure. In such cases, the opening to be dressed and closed will be of the same length as one or more pairs of the side extension units45, so that the entire area of the opening is closed by brushes123of the extension units.

The angular disposition of the sealing brushes, in relation to the plane of the mounting flanges15-17or46, optimizes their sealing characteristics, particularly for smaller cable openings, where bristles of somewhat greater length in relation to the size of the cable opening may be accommodated.

By providing for the direct conductivity from the brush elements to a panel on which the grommet is mounted, it becomes feasible to form the molded plastic grommet frame elements of a flame retardant material, which is considered of great significance in modern data centers in which large numbers of servers may be concentrated.

While a significant use of the grommet of the invention is in connection with floor openings in data centers and the like, the grommet has widespread usage elsewhere in data centers and also in office buildings. In data centers, the grommets can be used to great advantage in connection with openings formed in the cabinets and racks housing servers, in order to maximize the cooling efficiency of conditioned air provided to those cabinets and racks. Additionally, it is becoming increasingly common in office buildings to provide raised floor arrangements, with wiring and cabling being routed in the space under the raised flooring. The grommet configurations of the invention are ideally suited for such applications, which may or may not involve conditioned air.

The grommet system of the invention is uniquely advantageous with respect to the ability to be configured to an unusually large variety of grommet arrangements using three basic elements, the U-shaped end elements, the side extensions and the brush elements. Accordingly, product costs and inventory costs are minimized while allowing a substantial variety of configurations to be assembled to suit the requirements of the end user.

It should be understood, of course, that the specific forms of the invention herein illustrated and described are intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclosure. In the claims, and throughout the specification, the term “cable” shall be interpreted to mean not only ordinary flexible electrical cable comprising one or more electrical conductors within an insulating cover, but shall include other elements, including rigid elements such as conduit or pipe and may be extended through an opening in a floor or other panel. Likewise, a grommet according to the invention may be installed in a floor panel, wall or ceiling panel, cabinet wall or the like, where its features and functions may be used to advantage. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention.