You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to accessories for edge trimming pan-shaped downwardly accessible suspended ceiling panels. 
       PRIOR ART 
       [0002]    A category of ceiling panels are of a type hung below a suspended grid. Panels of this style are typically attached to the grid with torsion springs carried on the panels. The torsion springs draw the panels up against a lower face of the grid elements. This type of panel allows for downward accessibility into the plenum above the ceiling and can be arranged to conceal the grid and provide a monolithic appearance for the ceiling. 
         [0003]    There exists a need for componentry for trimming or finishing the edges of the described panels where the edges are exposed such as where the ceiling is interrupted for lighting or other utilities. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides a trim strip having a unique configuration enabling it to be attached to a grid member and to conceal both the grid member and an edge of an adjacent pan-shaped underhung ceiling panel. The trim strip is proportioned to match the depth of the ceiling panels so that it is visually integrated with the ceiling panels. The disclosed trim strip is arranged to receive a unique splice plate that can be conveniently used for both miter joints and butt joints. The splice plate is received in a track on the inside face of the trim strip. Locking tabs on the splice plate are deployed, typically without tools, to tightly lock the splice plate to joined ends of two lengths of the trim strip. The locking elements of the splice plate are arranged to bear against areas remote from the material directly behind the strip faces so that the risk of distorting a face with a locking force is eliminated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a fragmentary perspective view of a corner of a perimeter frame embodying the invention for a light fixture or other utility opening in a suspended ceiling constructed of a trim strip of the invention; 
           [0006]      FIG. 2  is a side perspective view of a butt joint between two spliced trim strip lengths embodying the invention; 
           [0007]      FIG. 3  is an end view of one form of the trim strip of the invention installed on a grid member and visually finishing the edge of a pan-shaped ceiling panel shown in phantom; 
           [0008]      FIG. 4  is an end view of another form of the trim strip of the invention installed on a grid member and visually finishing the edge of a pan-shaped ceiling panel shown in phantom; 
           [0009]      FIG. 5  is a perspective view of a trim strip splice plate of the invention; 
           [0010]      FIG. 6  is a plan view of the splice plate; 
           [0011]      FIG. 7  is a side view of the splice plate; 
           [0012]      FIG. 8  is an end view of the splice plate; and 
           [0013]      FIG. 9  is a sectional view of a lever tab of the splice plate taken in the plane  9 - 9  indicated in  FIG. 7 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]      FIG. 1  illustrates an outer view of an “inside” miter joint  10  of two lengths of the inventive trim strip  11 . The broken lines illustrated in  FIG. 1  show a rectangular form fabricated of four lengths of the trim strip  11  in a rectangular frame  12 . The illustrated frame  12  has the rectangular shape of a square that has nominal 2 foot by 2 foot dimensions of a conventional suspended ceiling grid module. The frame  12  can be assembled in other standard nominal rectangular sizes such as 2 foot by 4 foot. Dimensions used herein may be replaced by industry metric equivalents. 
         [0015]    Different versions of a trim strip  11  and  13  are disclosed. Herein, the term “trim strip” relates to both versions  11  and  13  unless the context indicates otherwise. 
         [0016]    The trim strip is preferably formed as an elongated unitary or one piece aluminum extrusion and may be painted or powder coated with a white or other desired color on its visible surfaces. The trim strip has the general shape of a channel with upper and lower horizontal flanges  16 ,  17 , respectively, jointed by a vertical web  18 . An extension  19  of the web  18  extends somewhat above the upper flange  16 . Each trim strip  11 ,  13  is nominally 1⅝ inch tall. A top surface  21  of the horizontal flange  16  is 1½ inch above a lower surface  22  of the lower horizontal flange  17 . The trim strip  13  of  FIG. 4  has a horizontal extension  26  of the lower horizontal flange  17  on the side of the web  18  opposite the side on which the main part of the flange exists. 
         [0017]    The lower flange  17  has a vertical lip  27  at its distal edge. The trim strip includes a pair of mutually facing angles  28 ,  29  integral with the web  18 . The angles  28 ,  29  include a horizontal leg  31 ,  32  and a distal vertical leg  33 ,  34 . The vertical spacing between the horizontal legs  31 ,  32  and the spacing of the vertical legs  33 ,  34  from the web  18  is maintained with sufficient accuracy such that collectively they form a track  36  in which is received a splice plate, discussed below, with a close sliding fit. Preferably, the elements of the trim strip have a uniform wall thickness except for the upper flange  16  which is made thinner to facilitate reception of a self-drilling screw as discussed below. 
         [0018]      FIGS. 3 and 4  illustrate a typical mounting of a trim strip  11 ,  12  on a grid member  38 . The image of the grid member  38  represents a standard grid tee or grid runner typically in the form of a main runner and special cross runners having slotted lower flanges for reception of torsion springs as is known in the industry and illustrated, for example, in U.S. Pat. No. 9,228,347. A trim strip is mounted on a grid member  38  by abutting the upper surface  21  of the upper flange  16  against the lower face of a flange  39  of the grid runner  38  and the upper extension  19  of the web  18  against a distal edge of the grid member flange  39 . A series of short self-drilling screws (only one is shown in  FIGS. 3 and 4 ) spaced along the length of the trim strip are driven downwardly through the grid member flange  39  and the trim strip upper flange  16  to fix the trim strip to the grid runner  38 . 
         [0019]    A principle use of the trim strip is to finish the edge of a pan-shaped metal ceiling panel  46 , shown in phantom in  FIGS. 3 and 4 , where the panel edge would be otherwise exposed. This situation will occur, for example, where an adjoining panel is omitted to leave an opening for a light fixture or other utility such as an air supply or return vent or an audio speaker. 
         [0020]    It will be understood, as suggested in  FIGS. 3 and 4 , the trim strip  11  or  13  will occupy one-half the width of the grid runner flange  39  while the periphery of a ceiling panel will occupy the other half. Note that the trim strips are proportioned so that when installed, their lower faces  22  are coplanar with a main face  47  of the adjacent ceiling panel  46 . 
         [0021]    Where a full module space in a suspension grid is devoted to a light fixture or other utility device, the trim strip  11  or  13  is fabricated into a rectangular frame dimensioned so that the upper part or extension  23  of the web of each trim strip side fits closely with the grid flanges  39  at the inner periphery of the module. To accomplish this, the lengths of the trim strip are cut at 45 degrees to produce miter joints such as shown in  FIG. 1 . Upper flanges  16  of the assembled lengths of the trim strip are raised up against the lower surface of the flanges  39  of the grid members  38  defining the module. The rectangular frame  12  is then fixed in place preferably with self-tapping screws  41  down through the grid flanges  39  into the upper flanges  16  or with equivalent fastening elements. 
         [0022]      FIGS. 5-9  illustrate a metal splice plate  50  preferably formed as a one-piece sheet steel stamping of, for example, 0.047 inch hot dipped galvanized stock. The illustrated splice plate  50  is an elongated element having a flat rectangular mid-section  51  and inclined lever tabs  52  at each end. The mid-section  51  is weakened across two transverse lines by edge notches  53  and a hole  54  to form potential hinge lines for bending the splice plate  50  into a 90 degree angle. The splice plate  50  is embossed across land areas  55  between the notches  53  and hole  54  in the direction the lever tabs  52  are displaced before being deployed. A weakened hinge line is similarly provided at the juncture between the mid-section  51  and each lever tab  52  by edge notches  56  and a central slot  57 . The lever tabs include laterally outlying grips  58  adjacent the mid-section  51 . Lower edges  59  of the grips at the edge notches  53  are maintained relatively sharp during the stamping process to facilitate their “bite” onto a trim strip as discussed below. To augment the biting or gripping action of the tab edges  59 , the grips  58  are stamped slightly downwardly out of the plane of the lever tab proper as shown in  FIG. 9 . 
         [0023]    The splice plate  50  is used to make miter and butt joints between lengths of the trim strips  11 ,  13 .  FIG. 1  illustrates the splice plate  50  holding joined lengths of trim strip abutted in an “inside” corner construction. Use of the term “inside” is in a traditional sense where the visible sides of the webs  18  are facing generally towards one another. The thickness and width of the plate mid-section  51  is proportioned to provide a close sliding fit within the track  36  established by the angles  28 ,  29 . With the splice plate  50  bent into a right angle at one of the lines of the edge notches  53  and hole  54 , each end of the mid-section  51  is inserted in a respective track  36  of one of the two lengths of trim strip to be joined at a corner. Initially, the lower edges  59  of the lever tab notches  56  are displaced from the plane of the top of the mid-section  51  a distance greater than the wall thickness of the vertical legs  33 ,  34  of the trim strip track  36 . This spacing of the edges  59  allows the lever tab grips  58  to pass freely along outer surfaces of the vertical legs  33 ,  34 . The initial orientation of the lever tabs  52  is shown in  FIGS. 5 and 7 . 
         [0024]    The lever tabs  52  are deployed to lock the splice plate  50  and an associated trim strip length. As a lever tab  52  is depressed towards the web  18  of the respective trim strip length, the sharp edges  59  of the grips  58  bite into and lock onto respective track legs  33 , the material of a trim strip preferably being softer than that of the splice plate  50 . The material of the splice plate  50  is sufficiently malleable that a lever tab  52  does not appreciably spring back towards its original incline position. 
         [0025]    The embossed area  55  where the splice plate  50  is hinged, avoids an interference of this hinge area with the ends of the trim strips at their webs  18  at a frame corner. With four splice plates  50  installed at the four corners, the frame  12  is a rigid assembly. 
         [0026]    The trim strips  11  or  13  can be used to form the edges of several adjacent ceiling panels such as in narrow utility channel systems. More than one full length of trim strip may be needed to span the collective length of the panel edges. In such a case, two trim strips can be spliced by the disclosed splice plate  50 . In this situation, shown in  FIG. 2 , the splice plate mid-section remains flat and is centered over the abutted ends of the lengths of trim strips. The splice plate  50  is locked in place on the two ends of the trim strips in the same manner as described in connection with the miter joint shown in  FIG. 1 . Specifically, the lever tabs  52  are pressed towards respective trim strip webs  18  to cause the edges  59  to lock on the track angle legs  33 . 
         [0027]    It will be appreciated that the locking forces developed by the lever tab grips  58  is supplied to parts of the trim strip that are remote from the exposed or finished face of the trim strip so that there is no risk that this locking force will cause a visible distortion in the visible face. 
         [0028]    The version of the trim strip  13  shown in  FIG. 4  is useful where it is desired that a ceiling opening such as for a light or air duct have a semi-flush membrane of, for example, transparent or translucent material, or a grill. In such a case, the membrane  61  can be installed on top of the horizontal extension  26 . In a square opening, the horizontal extension  26  will extend on four sides of the opening. In a narrow utility channel, the horizontal extension can be arranged on both sides of the channel to support opposite edges of the membrane  61 . 
         [0029]    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.

Summary:
In combination, extruded aluminum trim strips joined end-to-end and a splice plate, the trim strips together, the trim strip cross-sections including a web and a pair of opposed angles, the angles and web forming a track for receiving a mid-section of the splice plate with a close sliding fit, the splice plate having lever tabs at opposite ends, notches at sides of the plate, the plate being disposed in the tracks of both lengths of trim strips, the lever tabs and associated edges of the lever tabs formed by the notches being outside of the tracks, the associated edge being arranged in a locking manner with outer surfaces of the angles as a result of the lever tabs being bent in place towards the web.