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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to suspended ceiling grid and more particularly, to improvements in splice connections for main runners for such systems.  
       PRIOR ART  
       [0002]     Suspended ceiling grid customarily comprises main runners and cross runners that intersect the main runners. The main runners are produced in fixed lengths, typically in 12 foot lengths, and are spliced end-to-end to extend across a room. For connecting their ends, current grid tee or runner products commonly utilize an integral splice or connector cut and formed from the grid runner web material. The splice uses a lanced pocket pushed out from the vertical web plane in one direction and a protruding stiffened tongue with a locking detent pushed out in the opposite direction. Upon installation, the tongue of each runner or tee inserts into an opposing pocket making a double lock. When all of the physical features of the splice are formed in the ideal or desired configuration and location, the tees interlock with a light predictable insertion pressure, aligned both vertically and horizontally with each other. The resultant connection adequately resists pull-apart forces. The geometry of various physical features, however, tends to vary positionally with variations or change in material thickness of the tee material requiring repeated tooling adjustments as necessary to achieve acceptable part function. Complaints of hard splice assembly and face misalignment are the result of compromise in ordinary variation in the supply of material, tool wear, and sometimes a lack of constant vigilance at the point of manufacture.  
       SUMMARY OF THE INVENTION  
       [0003]     The invention provides a splice connection for main runners or tees comprising an end assembly with a uniquely formed pocket made in a cavity between the central web of the runner and a separate spring steel clip attached to the web to align and interlock with an identical opposed end assembly. The result is an in-line connection for main runners or tees. Because the disclosed pocket is formed by the cavity created between an embossed recess on one side of the tee web and an inside clip surface, the pocket can be made with a fixed width, regardless of variations in material thickness of the tee itself. The disclosed concept enables a connection to exhibit consistent insertion pressure as a result of the fixed geometry of the tee cavity and the resilient nature of the clip and web assembly.  
         [0004]     The disclosed clip is configured to connect directly with an identical clip so that a reliable high strength joint is produced independent of any variation in the properties of the material of the tee. The clip and pocket are configured to initially self-align the ends of the runners being joined and, when finally connected, to accurately register the butted ends of the runners. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a fragmentary perspective view of the ends of two grid runners prior to being joined;  
         [0006]      FIG. 2  is a side elevational view of an end clip embodying the invention;  
         [0007]      FIG. 3  is a longitudinal cross-sectional view of the clip taken in the plane  3 - 3  indicated in  FIG. 2 ;  
         [0008]      FIG. 4  is a cross-sectional view of the clip taken in a vertical plane  4 - 4  indicated in  FIG. 2 ;  
         [0009]      FIG. 5  is a cross-sectional view of the clip taken in the staggered planes indicated by the lines  5 - 5  in  FIG. 2 ;  
         [0010]      FIG. 6  is a showing of the clip of the invention after being progressively stamped but prior to being separated from a continuous strip of successively stamped clips;  
         [0011]      FIG. 7  is a side elevational view of an end portion of a grid runner;  
         [0012]      FIG. 8  is a cross-sectional view of the web of the grid runner of  FIG. 7  taken in the staggered plane indicated by the lines  8 - 8 ;  
         [0013]      FIG. 9  is an end elevational view of the grid runner of  FIG. 7 ;  
         [0014]      FIG. 10  is a cross-sectional view taken in a horizontal plane of the end portions of a pair of butted grid runners and associated coupled connector clips;  
         [0015]      FIG. 11  is a fragmentary side elevational view of two grid runners being assembled with a lead-end portion of one connector clip being guided into vertical registration with an opposing grid runner by contact of the right hand clip with the flange of the left hand grid runner; and  
         [0016]      FIG. 12  is a view similar to  FIG. 11  with the ends of the runners further advanced towards abutting contact and the right-hand clip still bearing on the flange of the left-hand grid runner to vertically align the grid runners. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     A main runner or grid tee  10  is assembled at each of its longitudinal ends with a connector clip  11 . The illustrated grid tees  10  are generally conventional in construction having a lower flange  12 , a web  13  extending vertically upwardly from the center of the flange, and a hollow reinforcing bulb  14  at the upper edge of the web. In a conventional manner, the tee  10  can be made by roll forming continuous strips of mild steel sheet stock so that the bulb  14  has a single wall and the web  13  is formed by two layers of sheet stock and the flange  12  has two portions  16 . The flange portions  16  are retained together and concealed from a view below by a cap strip  17  of sheet metal, as is conventional. The roll formed stock is cut into tees of predetermined length, for example, nominally 12 feet. The opposite ends of the tees are cut so that its edges  18  at the flange  12  are perpendicular to the longitudinal direction of the tee and the edges of the web  13  and bulb  14  can be formed in a plane tilted slightly rearwardly (e.g. 1 to 3 degrees) away from a vertical plane through the flange edge  18 . This slight rearward tilt assures that upon assembly with a mating tee, the respective flange edges  18  will form a tight butt joint for a good appearance. When describing the tees  10  and clips  11  herein, the forward direction is a direction away from the center of a tee and, when reference is made to a standard tee, the flanges  12  are, as mentioned, at the lower edge of the vertical web consistent with the orientation of the tee in a normal installed condition.  
         [0018]     Each end of a tee  10  has-its web  13  pierced with a notch  21  open at an edge  22  of the web. Rearward of the web edge  22 , a portion of the web  13  is formed or stamped with a lateral offset or embossment  23  that includes a cantilever tab  24 . The tab  24  is free of connection with surrounding areas of the web in a zone forward of its connection with the remainder of the embossment  23 . Apart from the embossment  23 , including the tab  24 , the material of the web  13  surrounding the notch  21  remains in the original plane of the web  13 . Lower and upper edges  26 ,  27  of the notch  21  are spaced from the flange portion  16  and bulb  14  a substantial distance preferably, for example, a distance at least several times the thickness of the stock forming the tee thereby enabling the tooling that creates the notch to be robust in this area for long tool life. Two holes  28  are punched through the web  13  to receive parts of the clip  11  for their permanent assembly as described below.  
         [0019]     The clip  11  is stamped from sheet metal stock preferably in strip form processed in progressive dies or tooling in which various features or formations are made on the clip body. The clip  11 , preferably, is formed of a high strength spring steel such as Martinsite −130 having a thickness by way of example of 0.020 inch. The clip material is thus substantially harder than the mild steel material of the tee  10 .  
         [0020]     The clip  11  has an elongated form with an inner face  31  adapted to abut the web  13  and an opposite outer face  32 . The clip  11  includes stiffening or reinforcing flanges  33 ,  34  at its top and bottom edges projecting outwardly from the outer face  32 . The clip  11  is lanced and formed at two locations  36  to form integral projections  37  that after being inserted in corresponding holes  28  in the tee web  13  are staked or clinched in the manner of a rivet to permanently assemble the clip  11  to the grid tee  10 . The areas of the clip  11  surrounding the projections  37  is planar and, for reference purposes can be considered to be the plane of the clip body or clip proper. Apart from the projections  37 , the clip  11  is bilaterally symmetrical about a longitudinal medial plane.  
         [0021]     A central major polygonal or chevron-shaped hole  39  through the clip  11  has at its upper and lower regions, a pair of opposed flanges  41  bent out of the plane of the clip. The flanges or tabs  41  as seen in  FIG. 4  are bent out of the clip plane by more than 90 degrees so that they converge towards one another with increasing proximity to the plane of the clip. On its forward side, the hole  39  is bounded by a rearwardly facing edge surface  42 . Forward of the major hole  39 , in succession, are a minor round hole  44  and a square hole  46 . The round hole  44  is centered on an imaginary vertical line through the end edge  18  of a runner flange when the clip is assembled on the runner. A triangular depression  47  formed in the inner face or side  31  of the clip opposite the side seen in  FIG. 2  bridges the area between the minor holes  44 ,  46 . A lateral projection  48 , centered on the imaginary center line or medial plane of a clip  11  is formed on the clip inner face forward of the square hole  46 . The projection  48  has a cam surface  49  that tapers laterally away from surrounding areas of the clip from a forward portion  50  rearwardly to a rearwardly facing locking edge surface  51  that forms part of the hole  46 . A small spherical projection  52  is formed on the outer side of the clip  11  longitudinally between the projection  48  and a lead edge  53  of the clip  11 . The lead edge  53  has a vertical portion  54  and lower and upper inclined portions  56 ,  57 , respectively, trailing the vertical portion  54 .  
         [0022]      FIG. 6  shows that the forward tapered end of a clip bounded by the lead edge portions  54 ,  56 ,  57  nests within a V-shaped notch  58  pierced in a rearward part of a preceding clip made in progressive stamping equipment. This technique produces a clip  11  that is considerably longer than the effective length of stock used per clip. The extended length of the clip  11  enhances its stability when assembled on the tee  10 .  
         [0023]     The lead edge portions  56 ,  57  extend to horizontal edges  59  spaced a predetermined distance from one another. Rearward of the horizontal edges  59 , are inclined surfaces  61 ,  62  formed by extensions of the clip flanges  33 ,  34 .  
         [0024]     The body of the clip  11  forward of the major hole  39  between horizontal bend lines indicated at  63 ,  64 , extended from the edge portions  59  and surrounding the projections  52  and  48  and recess or depression  47 , is planar and bent slightly laterally, from the plane of the clip body rearward of the major hole  39 , to the side to which the projection  48  extends ( FIG. 3 ).  
         [0025]     The geometry of the clip  11  and formations on the end of the tee  10  are arranged to connect with an identical clip, or a similar clip, and a tee end with features described above in the manner of a handshake. Therefore, as is customary, the tee  10  has identical or essentially the same clips on each of its ends. Tees are connected end-to-end by roughly aligning them end-to-end and pushing their clips into the pockets  66  formed between the inside of the web embossment  23  and the related clip  11  of the opposed tee end. The initial alignment need not be perfect since the tapered nose of the connector formed by the surfaces  56 ,  57  and  61 ,  62  is adapted to guide or cam the clips into vertical alignment. Lateral alignment is initially accomplished by simply abutting the clips laterally or side-by-side. If the clip  11  of the tee being installed is simply laid onto the top of the flange portion  16  of the previously installed tee, with the clip abutting the correct side of the clip on the previously installed tee, the lower inclined edges or surfaces  56 ,  61  of the clip being installed will cam the clip vertically upward when it is pushed longitudinally against the opposing tee. This camming action is depicted in  FIGS. 11 and 12  where the surfaces  56  and  61  engage the forward edge of a flange portion  16  of an opposing previously installed tee  10 . The spherical projection  52  prevents the lead edge  53  of the clip being forced into a pocket  66  from cutting into the surface of the opposing tab  24  or rearward part of the embossment  23 , typically of a softer material than a clip. The angular or oblique orientation of the receiving tab  24  and associated embossment  23 , urges the installing clip laterally towards the plane of the web  13  of the receiving tee. Towards the end of the insertion motion, the flanges or tabs  41  of a receiving clip  11  register with the parallel edges  59  of the clip being inserted to closely vertically register the clips together. The converging distance between the flanges  41  avoids any unnecessarily tight fit between the edges  59  of an installing clip and the flanges of a receiving clip until the clips are very nearly fully connected. When the clip being installed is longitudinally fully advanced relative to the receiving clip, the rearwardly facing edge surface or locking edge  51  of the projection  48  snaps into the major hole of the mating clip and locks against this hole edge. This snap action produces audible and tactile signals to the installer that the connection is completed. Prior to the last increment of assembly motion, the recess or depression  47  can reduce interference between this area and the advancing projection  52  and can assist in vertically aligning the clips by vertically guiding the advancing projection. The tapered profile of the lead edge  53  of the clip, the geometry of the flanges  41  and pocket  66  prevent the mating clips from connecting if the clips, and their runners are vertically misaligned.  
         [0026]     The clips  11  can be precisely formed from a sheet metal strip since the stock can be held to exacting thickness tolerances while being reasonably economical due to its relatively small size compared to the volume of material comprising the grid tee proper. The pocket  66  formed between the embossment  23  including the tab  24  and the inside surface of the clip  10  does not vary in width despite regularly experienced variations in the thickness of the tee material stock. Variation in the width of the pocket  66  is avoided because the tab  24  and associated embossment  23  can be readily stamped by tooling with a lateral offset from the plane of the tee web by a fixed predetermined amount regardless of the thickness of the tee material stock. Consistent lateral sizing of the pocket  66  ensures that only a low consistent force is required to establish a full connection between a pair of tees. The connection between abutted tees is quite strong, because the locking surfaces are part of the clips and, therefore, have very high yield strength. With a pair of clips  11  coupled to one another their respective round holes  44  are in alignment and a screw or other fastener can be inserted through these holes where an exceptionally strong joint is required.  
         [0027]     A coupled pair of grid tees can be conveniently disconnected without tools by simply twisting one of the coupled tees about its longitudinal axis. This twisting action results in resilient deflection of the tabs  24 , embossments  23  and clips to a degree sufficient to enable the locking edges  51  to move laterally out of engagement with the receiving edge  42  of the main hole  39  of the opposing clip to thereby release their locking engagement. This resilient deflection is permitted by the geometry of the related embossment and tab on the web and the absence of direct affixing of the clip to the web forward of the locking edge of the major hole in the web.  
         [0028]     The flat angled portion of the clip between the lines  63 ,  64  at the forward end of the clip that is angled relative to the plane of the clip at the rear acts when connected to another clip to “sandwich” or force the tee web above and below the notched forward web area into planar alignment with another connected tee regardless of the tee material thickness.  
         [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:
A main tee with separate clips affixed on its ends for splicing the tee with identical tees in end-to-end butt joints. The tee and clip form a pocket for receiving the projecting end of an opposing clip with a uniform low insertion force. The clip is self-aligning with the pocket and when interconnected the clips precisely align the coupled tees both vertically and horizontally. The clips, formed of relatively strong material, have mutually engageable locking surfaces that ensure a strong joint.