Abstract:
A ceiling support system for a suspended ceiling is provided that includes resilient clamps for attachment to the undersigned surface of a structural ceiling and interengaging ceiling runners that are shaped to be fitted into and be grasped by such clamps. The engagement edge of the runner is shaped to allow the runner to maintain a bistable positions: a normal, ceiling panel supporting orientation, and a canted orientation for installation of ceiling panels.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to suspended or drop ceilings. More particularly it relates to the structural grid of a suspended ceiling system that holds ceiling panels in place and to methods for installing and removing such ceiling panels.  
         BACKGROUND TO THE INVENTION  
         [0002]    Suspended ceilings are employed today in many structures because they provide an aesthetic presentation while enabling the routing of hardware such as conduits, electrical wiring, etc, in the gap between the suspended ceiling panels and the structural ceiling of the building itself. This gap also provides a convenient “headspace” whereby ceiling panels may be inserted through openings in a ceiling support grid system and manipulated into an orientation whereby the panels may be lowered onto supporting flanges within the grid system that provide shelves or ledges onto which the edges of the ceiling panels may rest.  
           [0003]    According to one mode of construction, the support grid for a suspended ceiling relies on the use of longitudinally extending strips or “runners” that are generally of an inverted “T”-shape in cross-section, having outwardly protruding lateral flanges which provide the ledges upon which the ceiling panels rest. In this type of existing system wires or other connectors descend from the ceiling proper, through the headspace, to connect with the ceiling runners.  
           [0004]    In conventional suspended ceiling systems having substantial headspace, the procedure for installing or removing a ceiling panel is to lift the ceiling panel clear of the grid support structure, turn it somewhat in the headspace, and then maneuver it down through the opening within the grid structure. The headspace required for lifting and maneuvering a ceiling panel in order to install or remove it is at least several inches and may, in some cases, take-up considerably more space.  
           [0005]    However, in many cases provision of adequate headroom is impractical due to the relatively low height of the structural ceiling. Examples include the basements of homes where even the loss of a few inches in vertical height can give the impression that the ceiling is oppressively low. A need exists for a low headroom suspension ceiling support system that will permit tiles to be installed in place without reliance on the presence of headroom.  
           [0006]    It is known to provide support for a drop ceiling through the use of resilient ceiling clips resilient clamps or clamps. Examples of this type of construction are described in the following U.S. patents: U.S. Pat. Nos. 2,059,483; 2,229,064; 3,228,163; 3,969,865; and 4,549,375. An advantage of using resilient mounting clamps is that ceiling panels can be placed in position without the necessity of manipulating them in a headspace provided above the gridwork system. This is advantageous when it is desired to keep the drop of the suspended ceiling at a minimum. Using resilient mounting clamps, ceiling tiles can be installed very nearly directly adjacent to the structural ceiling itself. nondestructive disassembly of components by the application of a sufficient disengagement force. They may also be nonreversible, or not readily reversible in that they employ engagement mechanisms that may permit “snap-in” assembly procedures, but disassembly cannot be readily affected without risking the deformation of the engagement elements of the grid support system. Examples in this latter category are U.S. Pat. Nos. 3,784,184; and 4,7200,946.  
           [0007]    A specific example of a prior art reference addressing these requirements through use of resilient means is found in U.S. Pat. Nos. 3,263,388 to Bogert. This document discloses a system of interfitting runners and resilient clamps, the clamps being fastened to the structural ceiling itself. The clamps are provided with a serrated grasping face which engages a corresponding serrated face on an upwardly directed flange that forms the stem portion of the inverted T-shaped cross-section for this member. Employing the Bogert system, ceiling panels are placed in position with their peripheral edges resting on the ledges provided by the lateral flanges of the runners. When the upwardly directed stem portion is pressed into the reception slot of the resilient clamps, the ceiling panels are carried along with the runners into their final position, A disadvantage of this system is that the ceiling tiles and runners must both be manipulated simultaneously. For a person standing on ladder or scaffolding, this requirement complicates the procedure of installing ceiling panel.  
           [0008]    A need exists for a convenient support: system for a suspended ceiling that can be readily installed and which permits the easy removal of the ceiling panels for replacement or access to the headspace behind such panels. It is an object of this invention to address such requirements.  
           [0009]    The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.  
         SUMMARY OF THE INVENTION  
         [0010]    According to the invention in one aspect, a supporting framework for a suspended ceiling is provided based on a plurality of resilient clamps which are fastened in place beneath a structural ceiling. This may include the installation of clamps to the lower edges of joists or to strapping or other components of the structural ceiling. These clamps have a baseplate and resiliently expandable sides terminating at a pair of lips that define a nip. Within the clamps is an internal receiving space that is preferably open at both ends. The clamps may be intermittently disposed with their receiving spaces aligned, or may be in the form of continuous clamping bars.  
           [0011]    A supporting grid for ceiling panels is provided through the use of longitudinal ceiling runners which are generally of an inverted “T” shaped in cross-section, having a pair of laterally extending support flanges that provide ledge surfaces for carrying ceiling panels. These ledges may underlie the ceiling panels or fit into slots on the edges of the ceiling panels in the known manner. Runners, according to the invention, also have an upwardly directed leg having a web portion and an enlarged, peripheral, clamp-engaging edge that is remote from the lateral flanges. In use, the clamp engaging edge of a runner is pressed through the lips of a clamp to penetrate into the internal receiving space of the clamp. A runner is held in place by the clamp through the action of the lips grasping the web portion of the runner and/or the sides of the clamp grasping the surfaces on the peripheral edge of the clamp-engaging leg.  
           [0012]    The runner is installed by passing the clamp-penetrating peripheral edge through the yielding nip of the clamp to permit the clamp to grasp the runner and hold it in place. The sidewalls of the clamp spread resiliently to permit such insertion by the application of modest manual force. Further, the lips on the clamp apply a sufficient retention force on the runner to resist the retraction of the clamp engaging end of the runner under forces of a magnitude that would normally arise from the supporting of ceiling panels. For this purpose, the peripheral edge of the clamp engaging leg may be enlarged and in contact with the sides of the clamp.  
           [0013]    To improve the retention capacity of the runners with respect to the clamps, the sides of the clamps may be angled as they approach the nip so as to tend to intersect at a greater angle than the sides remote from the nip.  
           [0014]    As a preferred feature of the invention the enlarged, peripheral edge of the clamp-engaging leg of the runner is preferably pointed and tapered with an entry taper that provides an easy entry and passage of such edge through the lips of the nip. On the flange side of the peripheral edge, the enlargement may or may not be provided with a peripheral taper. In a preferred variant, the flange side of the enlarged peripheral edge is formed with a niche that gives the edge an arrow-head shape in cross-section.  
           [0015]    Preferably, the height of the web from the lateral flanges to the enlarged edge allows the enlarged edge to pass into the internal receiving space of the clamp until the enlarged edge does not tend to spread the sides of the clamp. At this position the lips grasp the web. The runner may also be engaged by the clamp along its web with a range of penetrations of the engaging leg into the clamp by providing a web of extended depth. This “free play”, if present, conveniently permits runner alignment to be adjusted to accommodate an uneven structural ceiling surface and provide a drop ceiling surface which is more nearly planar. Alternately, the clamps may be fastened to the structural ceiling through washers by which they may be adjusted into alignment.  
           [0016]    It is a preferred feature of the invention that the engaging edge of the runner is of a shape which permits the runner to maintain a bistable orientation with respect to the clamp when the clamp is engaged with the runner. In one orientation the engagement leg of the runner is aligned for direct entry into the interior space of the clamp. In this configuration the leg or web is generally perpendicular to the surface of the structural ceiling with the lateral flanges in a horizontal plane. Generally, in this orientation, either the enlarged edge on the runner is grasped by the sides on the clamp, or the web is grasped by the lips.  
           [0017]    In another orientation, the engagement leg of the runner is canted laterally, with the leg or web obliquely oriented with respect to its normal entry into the interior receiving space of the clamp. In this configuration the lateral flanges of one or a pair of runners intended for the support of a specific ceiling panel may be forced to one side or spread apart to receive the ceiling panel. When two runners are spread apart the parallel, opposed, runners are canted in opposite directions. Alternately, only one runner need be canted with an edge of the panel first being inserted into the slot provided by the uncanted runner.  
           [0018]    The degree of cant, and the length of the engagement leg, e.g. the depth of its web, is sufficient to provide a gap through which the ceiling panel may be manipulated without the necessity for the ceiling panel to penetrate into the headspace that is normally required to exist between a suspended ceiling and a structural ceiling. With the ceiling panel in place, the orientation of the supporting runners may be adjusted to the vertical, aligned position. In this orientation, the ceiling panel will be contained laterally and supported by the ledge surfaces of the lateral flanges on the respective runners.  
           [0019]    According to one aspect of the invention, a bistable action may be achieved by providing the peripheral end of the engagement leg of the runner with a shape that creates resistance to the rotation of the runner from the clamp when the runner is in its canted orientation. This may be achieved in one variant by providing the peripheral end with a shape that is approximate to a rhombic in cross-section. The opposed sides of this rhombic cross-section may be a so nearly parallel to the sides of the clamp as to permit the clamp to engage and stably maintain the runner in the canted orientation.  
           [0020]    By a further preferred variant of the invention, the peripheral edge of the runner is substantially arrow-head in cross-section whereby one of the lips of the clamp may engage the runner in the niche beneath the arrow-head when the runner is at a canted orientation to provide a stable grasp on the runner. In all events, a bi-stable state will exist if rotation of the runner in either direction tends to spread the lips of the clamp apart.  
           [0021]    The clamps may be generally triangular in cross-section and may be formed of any suitable resilient material e.g. spring steel, resilient plastic. The baseplate of the clamp may be flat or it may be dished inwardly into the interior receiving space of the clamp. In either case a fastening hole is formed in this baseplate through which a fastener may pass to engage with the structural ceiling.  
           [0022]    By adoption of a baseplate which is dished inwardly, the retention force at the nip of the clamp can be increased in accordance with the tightness with which this fastener engages the structural ceiling. The farther the dished configuration is flattened, the greater the increase in the grasping force at the nip.  
           [0023]    To access a fastener seated in the fastening hole on the base plate a notch may be present in the lips, the notch having sufficient width to allow a screwdriver to penetrate into the internal receiving space of the clamp.  
           [0024]    In this manner a ceiling supporting framework is provided that extends longitudinally beneath a ceiling.  
           [0025]    In the foregoing description the runners are mounted longitudinally in a parallel orientation to each other. To accommodate ceiling panels of limited length, transverse cross bars or cross runners may be provided.  
           [0026]    Such cross runners may have an inverted “T” cross-section or the cross-section of an “I” beam. Lower flanges extending outwardly from one or both sides of the cross runners engage with the edges of ceiling panels to provide support and/or to conceal a seam.  
           [0027]    The outer ends of the lower flanges on the cross-runners may be stepped upwardly by the thickness of the flange to provide a protruding plate that will rest on the lateral flange of a longitudinal runner. The height of the step aligns the lower surfaces of both classes of runners.  
           [0028]    As an alternative to providing a bent step in the lower flange, a separate engagement piece may be fitted to the web at the end of a length of a cross runner to provide the protruding plate. In this arrangement, the engagement piece may be fitted to a standard longitudinal type runner, reducing the number of distinct components required.  
           [0029]    To stabilize the cross-runners, a central notch is formed in the protruding plates or engagement piece at each end. This notch engages an upright connector plate that extends transversely through a slot in the web of the longitudinal runner. The transverse connector plate is held in a vertical orientation at a fixed location along the web of the longitudinal runner by the sides of the slot into which it is fitted.  
           [0030]    As a preferred variant, to stabilize and centralize the penetration of the upright plate through the slot in the web, two locking tabs may be erupted out of the surface of the upright plate. The edges of these tabs are positioned to bear against opposite sides of the longitudinal runner&#39;s web, adjacent to the slot. At least one of such tabs is resiliently compressible into alignment with the surfaces of the upright plate to permit such tab to penetrate into the slot to its final position.  
           [0031]    A further feature of the invention is that a second drop ceiling may be installed beneath an existing drop ceiling. Existing runners of a conventional drop ceiling are used to support clamps of the invention through joining pieces which attach to the existing runners. Coupling means, such as threaded fasteners hold the clamps in place beneath the joining pieces.  
           [0032]    Due to the minimal and near-zero head space requirements of the invention, an existing drop ceiling that needs painting or cleaning may be left in place with a new second ceiling installed directly below and adjacent to the existing drop ceiling through use of such joining pieces.  
           [0033]    The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]    [0034]FIG. 1 is a pictorial view of a ceiling fitted with the suspended ceiling system of the invention.  
         [0035]    [0035]FIG. 2 is a cross-sectional end view of a runner positioned for entry into a clamp fastened to a joist.  
         [0036]    [0036]FIG. 3 is an end view of the runner of FIG. 2 engaged with the clamp.  
         [0037]    [0037]FIG. 4 is an end view of the runner of FIG. 3 partially lowered within the clamp to a canted orientation to receive a ceiling panel.  
         [0038]    [0038]FIG. 5 is an end view of a clamp.  
         [0039]    [0039]FIG. 6 is a pictorial view of the clamp of FIG. 5.  
         [0040]    [0040]FIG. 7 is a pictorial view of a runner with slots for transverse plates.  
         [0041]    [0041]FIG. 8 is a cross-sectional end view of a runner with a transverse plate in place.  
         [0042]    [0042]FIG. 9 are plan, side and bottom views of a transverse plate.  
         [0043]    [0043]FIG. 10 is a pictorial view of a cross-runner with a stepped and notched end.  
         [0044]    [0044]FIG. 11 depicts the cross-runner of FIG. 10 positioned to rest on the runner of FIG. 8.  
         [0045]    [0045]FIG. 12 is a pictorial view of an engagement piece fitted to the end of a cross-runner.  
         [0046]    [0046]FIG. 13 is a pictorial view of the engagement piece of FIG. 12.  
         [0047]    [0047]FIG. 14 is a side view of a cross-runner with an engagement piece as in FIG. 12 fitted to rest on a runner as in FIG. 8.  
         [0048]    [0048]FIG. 15 is a pictorial view of two runners joined end-to-end by a clamp and two dowels.  
         [0049]    [0049]FIG. 16 is a cross-sectional end view through the clamp, runner and dowels of FIG. 15.  
         [0050]    [0050]FIG. 17 is an end view showing details of a canted runner as in FIG. 4.  
         [0051]    [0051]FIG. 18 is a cross-sectional end view of a joining plate for allowing a drop ceiling of the invention to be fastened to a conventional runner.  
         [0052]    [0052]FIG. 19 is a cross-sectional end view of an alternate joining plate with a clamp and runner as in the invention coupled to a conventional runner.  
         [0053]    [0053]FIGS. 20, 21 and  22  are pictorial views on alternate variants on the joining plate of FIG. 19. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0054]    In FIG. 1 a structural ceiling  1  includes joists  2  to which are fastened clamps  3  according to the invention. Runners  4  snap into the clamps  3  to provide support for ceiling panels  5  (not shown in FIG. 1).  
         [0055]    In FIG. 2 a runner  4  is about to have its peripheral engagement edge  13 , arrow-head shaped in cross section, pressed through the nip  6  formed by lips  7  to penetrate the interior space  8  within the clamp  3 , c.f. FIG. 3. In this process, ceiling panels  5  may be carried-up with the runners  4 , resting on lateral flanges  9  that provide ledges  10  for the ceiling panels  5  to rest on.  
         [0056]    While the ceiling panels  5  are shown as resting on the ledges  10 , such ledges  10  may penetrate slots (not shown) in the edge faces of the panels  5  to support the panels S.  
         [0057]    The clamp  3  has sides  12  as shown in FIG. 3 that are  10  tapered proceeding towards the nip  6 . The angle between the side portions  12 A is preferably more obtuse in the side portions  12 A proximate to the nip  6 . This provides an increased resistance to removal of the engagement edge  13  on the runner  4  from the clamps  3 .  
         [0058]    In FIGS. 2 and 3 the runners  4  are aligned with the web portion  14  on the runner  4  being in a vertical orientation. In FIG. 4 the runner  4  is canted sideways to allow for removal or insertion of a ceiling panel  5 .  
         [0059]    As shown in FIGS. 5 and 6 the clamp  3  has a base is that may be inwardly bowed and pierced by a fastener opening  16 . An access notch  17  is formed in the lips  7  to provide access for a tool (not shown) to fastener  18  present in the fastener opening  16 . The lips  7  of the clamp  3  may have a slight outward curl  19  to permit ready spreading of the lips  7  by the engagement edge  13  of the runners  4 .  
         [0060]    As shown in FIGS. 3, 4 and  7 , a transverse connector plate  20  is fitted into a slot  21  in the web  14  of a longitudinal runner  4 , preferably stabilized by the lower side  35  of the enlarged, engagement edge  13 . This plate  20  generally rests on and largely spans both lateral flanges  9 . Tabs  29  erupted from the plate  20  serve as fingers with web-engaging edges  22  which bear against the runner web  14  to stabilize the plate  20  in place.  
         [0061]    As shown in FIG. 10, transverse cross runners  23  have at their outer ends a upwardly-stepped, protruding, ledge-engaging ends or plates  24  that are notched with a notch  25  to engage with a flange  9  with the notch  25  fitted into a transverse plate  20  - c.f. FIG. 11.  
         [0062]    As an alternative to integrally-formed engaging end plates  24 , separate engagement pieces  26  may be fitted to the end of a runner  4 A as shown in FIGS. 12, 13 and  14 . With engagement pieces  24 , longitudinal runners  4  may serve as cross runners. An upward flange  27  on the engagement piece  26  and central web-embracing notch  28  serve to stabilize such pieces  26  on the ends of the runner  4 A. When either form of cross runner  23 , 4 A is fitted to a longitudinal runner  4 , the lower faces  25  of both runners will be approximately coplanar.  
         [0063]    [0063]FIGS. 15 and 16 show the abutting connection of the ends of runners  4  using a pair of dowels  28 . The dowel diameter is preferably selected to fill, together with the peripheral edge  13  and web  14  of a runner  4 , the interior space  8  within a clamp  3 . This ensures the true alignment of adjacent runners  4 .  
         [0064]    In FIG. 17 an enlarged detail of an arrow-headed peripheral edge  13  grasped by lips  7  of a clamp  3  is depicted. The runner  4  is in a bi-stable orientation when canted sideways because the lips  7  must separate, at least slightly, if the runner  4  is rotated in either lateral direction. A variety of cross-sectional shapes can be provided for the peripheral edge  13  to meet this criterion. In FIG. 17, the side portions  12 A are conveniently angled to lie against the underside face of the arrowhead, in near parallel alignment for maximum stability.  
         [0065]    In FIG. 18 a joining plate  30  is shown held in place by a thumb screw  31  engaging the flange  10  on a conventional installed runner  42 . A threaded hole  32  is provided in the plate  30  for attachment of a clamp  3  by a screw (not shown) passing through clamp fastener hole  16 .  
         [0066]    In FIG. 19 an alternate joining plate  33 , corresponding to FIG. 21, is attached to the flanges  10  of a conventional runner  42 . In this case the holes  34  on the two-piece plate  33  are engaged by the threads  35  on screw  36  so as to force a clamping action to be applied by curled edges  37  on the flange  10 .  
         [0067]    [0067]FIGS. 20 and 22 show alternate forms of joining plates  38 ,  39  with thread couplings  40 ,  41  to receive screws  36  and fix the joining plates  38 ,  39  to a conventional runner flange  10 .  
         [0068]    By these features a second drop ceiling may be installed directly below a first drop ceiling  
         [0069]    On the basis of the foregoing, a cost-effective and labor-efficient system is provided for installing ceiling panels for a drop ceiling.  
         [0070]    Conclusion  
         [0071]    The foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use. These embodiments are only exemplary. The invention in its broadest, and more specific aspects, is further described and defined in the claims which now follow.  
         [0072]    These claims, and the language used therein, are to be understood in terms of the variants of the invention which have been described. They are not to be restricted to such variants, but are to be read as covering the full scope of the invention as is implicit within the invention and the disclosure that has been provided herein.