A sheet metal fastener and method of use with a low density porous ceiling panel, the fastener comprising a plurality of blades adapted to be manually driven into a backside of a low density fibrous ceiling panel core, each blade being arranged to be pivoted about a horizontal axis in a direction opposite another one of the blades while embedded in the core to fix the fastener to the panel and an upstanding structure attached to said blades adapted to project upwardly from a rear side of the panel and having an aperture for receiving a suspension wire.

BACKGROUND OF THE INVENTION 
     The invention relates to an anchor clip or fastener for attaching suspension wires or the like directly to an acoustical ceiling panel. 
     PRIOR ART 
     Suspended ceilings are used extensively in commercial buildings. Typically, the suspended ceilings comprise a rectangular grid and panels lying across the grid spaces. The grid elements are suspended from superstructure above the plane of the ceiling. Important attributes of suspended ceilings include the creation of a space or plenum above the plane of the ceiling. Utilities can exist in the plenum and ready accessibility is afforded to the plenum for service, repair, alteration and additions to the utilities, for example. Typically, the grid is suspended by wires that extend downwardly from the overlying superstructure such as bar joists, I-beams and/or a floor or roof deck. Usually, suspended ceilings are provided with acoustical panels which serve to diminish noise in an occupied space below the ceiling. 
     Architects and interior designers are regularly charged with the task or have a personal desire to develop ceiling arrangements that depart from the ubiquitous ceiling panel and grid look. For example, designers may want to avoid the look of the typical ceiling grid and traditional sizes and shapes of the ceiling panels, but still want to provide accessibility and noise reduction. 
     SUMMARY OF THE INVENTION 
     The invention provides a method and arrangement for suspending ceiling panels without the need of a supporting grid. The panels, according to the invention, are attached to suspension wires or other support elements with “blind” fasteners secured to the panels at their rear faces. The fasteners are blind in the sense that they do not penetrate the visible face of the panel. 
     The disclosed fastener is a stamped sheet metal anchor clip. The fastener is embedded in the body or core of the ceiling panel with an area, projected in horizontal plane, that is sufficiently large to assure that a retention force substantially greater than the portion of the weight of the panel associated with the fastener is developed. 
     The clip is configured to work as a type of plier where finger grips, analogous to plier handles, are drawn together and a pair of blades, analogous to plier jaws, open up and spread apart. The fastener is a unitary or monolithic body having “living hinge” elements that form pivot points for relative movement between the finger grips and between the blades. 
     The fastener is manually installed on the rear side of a ceiling panel by plunging a set of opposed blades vertically into the panel core. When the length of the blades is fully received in the core, the finger grips are pivoted from an original horizontal orientation to an upstanding generally vertical orientation. The blades are simultaneously spread into a generally horizontal orientation. The finger grips include a hole for receiving a suspension wire or the like. A plurality of fasteners is used to suspend a single panel. Preferably, the fasteners are spaced inwardly from the edges of a panel to minimize the visibility of the suspension elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary isometric view of a ceiling panel suspended with the fastener of the invention in an installed configuration; 
         FIG. 2  is an isometric view of the inventive fastener in an initial configuration; 
         FIG. 3  is a plan view of the inventive fastener; 
         FIG. 4  is a side view of the inventive fastener; 
         FIG. 5  is an edge view of the inventive fastener; 
         FIG. 6  is a diagrammatic representation of an initial stage of the assembly of the fastener and a ceiling panel; 
         FIG. 7  is a diagrammatic representation of an intermediate stage of the assembly of the fastener and ceiling panel; 
         FIG. 8 , taken along the staggered vertical plane  8 - 8  in  FIG. 1 , is a diagrammatic representation of a final stage of the assembly of the fastener and ceiling panel; and 
         FIG. 9  is an isometric view, from above, of a representative suspended ceiling construction in accordance with the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The various figures illustrate a clip anchor or fastener  10  for coupling a suspension element such as a wire  10  directly to a ceiling panel, preferably an acoustical ceiling panel  12 . The fastener  10 , with other identical fasteners, permits the construction of a suspended ceiling of multiple panels without a conventional rectangular metal grid supporting the edges of the panels. 
     The fastener  10  is preferably made of sheet metal, for example hot dipped, galvanized steel of 0.036 inch thickness. The fastener  10  is stamped into the configuration illustrated in  FIGS. 2-7 . With particular reference to  FIGS. 2-5 , the fastener  10  has a planar mid-part  13  comprising a major section  14  and a minor section  15 . The fastener includes a set of blades or jaws  17 ,  18  depending perpendicularly from the plane of the mid-part  13 . It will be seen that two of the blades  18  are formed of sheet stock material that originally lay alongside the minor section  15 . A central blade  17  is cut from an area of the sheet stock lying between outlying portions of the major section  14 . Distal edges  19  of each of the blades  17 ,  18  are shaped with laterally outwardly, upward inclined portions  21  and a short central horizontal portion  22 . 
     Outlying zones of the planar sections  14 ,  15  have associated tabs  26 ,  27  from bent up from the plane of these sections at lines  28 ,  29 . A hole,  32 , is punched in respective sections  14 ,  15 . The perimeters of the tabs  26 ,  27  and portions of the major section  14  are trimmed at their respective corners  33 ,  34  to avoid sharp points of 90 degree edge intersections. 
     The blades  17 ,  18  initially as manufactured lie in a common plane perpendicular to the planar mid-part  13 . As most clearly shown in  FIG. 3 , the major and minor sections  14 ,  15  are joined by relatively small webs  41  that bridge across the plane of the blades  17 ,  18 . 
     The fastener  10  is used, ideally, with commercially known ceiling panels  12  having a core made of porous fibrous material such as non-woven glass fiber bonded together with a suitable resin. The panel  12  can be, for example, 1 to 1⅛ inch thick or thicker and can have a weight of about ½ pound per square foot. It is expected that a fastener  10  will be installed on a panel at the site where the panel is to be used in a suspended ceiling installation.  FIGS. 6-8  illustrate the manner in which the fastener  10  is installed on a panel  12 . A location on the back or reverse side  42  of a ceiling panel  12  corresponding to the location of a suspension element is determined. Ordinarily, the fasteners  10  are located inwardly from the peripheral edges of the panel  12  so that the suspension elements, typically the wires, are not visible or are inconspicuous. The technician installing the suspended ceiling or a helper manually presses the fastener  10 , with the blades  17 ,  18  oriented downwardly, into the panel  12  from the backside at the pre-determined location. This step is depicted in  FIG. 6 . The fastener  10  is pressed into the panel core until, as shown in  FIG. 7 , the planar mid-part  13  abuts the rear side  42  of the panel  12 . At this position, the blades  17 ,  18  are fully extended into the panel core, designated  43 . The length of the blades  17 ,  18  is less than the thickness of the panel  12  so that there is no risk in normal circumstances that the blades  17 ,  18  will penetrate a front face  44  of the panel. 
     The core  43 , as mentioned, is preferably porous while having adequate structural integrity and stiffness to support itself across an expected span. The blades  17 ,  18  are capable of severing through the fibrous matte of the core  43 . Once the planar mid-portion  13  of the fastener  10  has been driven against the rear side  42  of the panel, the major and minor sections  14 ,  15  are manually bent upwardly as suggested in  FIGS. 7 and 8 . The sections  14 ,  15  are bent upwardly by getting a fingertip hold on the tabs  26 ,  27  and prying up the respective sections. The sections  14 ,  15  are manually squeezed towards one another until the tabs  26 ,  27  abut or nearly abut. The sections  14 ,  15 , during this pivotal movement serve in a manner analogous to the handles of a pair of pliers. During the upward pivoting movement of the section  14 ,  15 , the webs  41  act as hinge points or pivot centers for relative movement between the sections. The joint between each of the blades  17 ,  18  and the respective section  15 ,  14 , is far stronger than that of the webs  41  as well as the compressive strength of the core  43 . The right angle configuration of the blades  17 ,  18  to their respective sections  15 ,  14 , remains as the sections are pivoted from horizontal orientations to generally vertical orientations. Material of the core  43  in the path swept by the blades  17 ,  18  as the blades pivot with their respective sections  15 ,  14 , is compressed into a dense fibrous mass above the now deployed, pivoted blades  17 ,  18 . The webs  41  are twisted beyond their yield point or elastic limit and hold the sections  14 ,  15  in their upright, generally vertical orientations once they are squeezed into this position. The holes  31 ,  32  are aligned with one another when the sections  14 ,  15  are squeezed together enabling a wire to be assembled through both holes. The various figures show a suspension wire, of the type typically used in suspended ceilings, assembled through the holes  31 ,  32  and twisted to lock the fastener  10  and the panel at an appropriate height. Suspension elements other than wires, such as hooks, can be used with the fasteners  10  in areas where limited clearance is available above the plane of a ceiling panel. 
     Ordinarily three or more fasteners  10  are assembled on a single ceiling panel  12 .  FIG. 9  represents one of a myriad of potential gridless suspended ceiling systems employing fasteners of the present invention. The system  46  includes a plurality of rectangular panels  47  of the type described above. Each panel  47  has a plurality of fasteners  10  attached to its rear upper face and each fastener is supported by a suspension wire  48 . It will be understood that the panels  47  can be non-rectangular in shape and of a variety of shapes in a particular ceiling installation. 
     It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.