Suspended ceiling grid structure
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to improvements in a suspended ceiling grid structure, and more particularly concerns improvements in a suspended ceiling grid structure adapted to support ceiling tiles or the like, and improvements in connecting means between the elements of the grid structure. 
     2. Description of the Prior Art 
     Suspended ceiling grid structures for supporting ceiling tiles are known in the art. Typically, such grid structures have a plurality of main beams ccnnected together by a plurality of cross tees. 
     When it is desired to gain access to the space above the suspended ceiling, a problem with known grid structures has been providing a connecting means that allows a cross tee to be removed without damage so that it subsequently may be reattached. 
     Another problem has been providing a grid structure with a means of assuring proper alignment of opposing cross tees. 
     Still another problem has been providing a grid structure having a reinforced connecting means that allows for a reduction in the amount of metal required in the connecting means, thereby decreasing costs. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of this invention to provide a suspended ceiling grid structure which overcomes the foregoing problems. 
     Another object of this invention is to provide a grid structure that has a connecting means with a slidelock feature. Another object is to provide a grid structure having a connecting means that allows for easy installation as well as easy disassembly. 
     These and other objects are accomplished by providing a suspended ceiling grid structure adapted to support ceiling tiles or the like that comprises a plurality of inverted T main beams arranged in spaced-apart, substantially parallel relationship, each main beam having a central fin or web and oppositely disposed flanges, cross tees connecting adjacent main beams, each cross tee having a central fin or web and oppositely disposed bottom flanges, vertically disposed belt loops formed in the central fin of the main beams, a locking tongue extending from each end of the cross tees in opposite directions at substantially right angles from the cross tee central fin, the locking tongue being releasably engaged by the belt loop, a stiffening bead formed in the central fin of the cross tees at each end of the cross tees and extending through the central portion of the locking tongues to an outer end portion of the locking tongues, a locking bump formed in the stiffening bead in the outer end portion of the locking tongues, positive stop shoulders at the top and bottom of the locking tongue contacting the belt loop on the main beam when the locking tongue is fully inserted into the belt loop, and sloping means on the bump which the loop presses against to urge the stop shoulders against the rear edge of the loop. 
    
    
     BRIEF DESCRIPTIN OF THE DRAWINGS 
     FIG. 1 is a fragmentary view in perspective of a suspended ceiling grid structure constructed in accordance with the invention; 
     FIG. 2 is a view in section taken as indicated by the lines and arrows 2--2 which appear in FIG. 1; 
     FIG. 3 is a view in section taken as indicated by the lines and arrows 3--3 which appear in FIG. 1; 
     FIG. 4 is a view in section taken as indicated by the lines 4--4 which appear in FIG. 3; and 
     FIG. 5 is a partial enlarged view of the area indicated by FIG. 4. 
    
    
     DETAILED DESCRIPTION 
     Turning now to the drawings, there is shown a suspended ceiling grid structure 11 adapted to support ceiling tiles or the like, which comprises a plurality of main beams 15 arranged in spaced-apart, substantially parallel relationship, and cross tees 17 which connect the adjacent main beams 15 together. 
     Each main beam 15 has an inverted T shape, and includes a central fin or web 21 having a reinforcing bead 23 at the top and a pair of oppositely disposed flanges 25 at the bottom. A capping 27 is mounted on flanges 25. Pairs of vertically disposed belt loops 29, 29a are formed in the central fin 21 of main beam 15 with one belt loop 29 of each pair being formed on one side of main beam fin 21 and the other loop 29a of each pair being formed on the opposite side. 
     Cross tees 17 are also of inverted T construction and each includes a central fin or web 31, a reinforcing bead 33 at the top of central fin 31, flanges 35 extending from the bottom of central fin 31, and a capping 37 mounted on flanges 35. 
     Locking tongues 39, 41 are formed integrally with each cross tee 17 and extend in opposite directions from each end of cross tee 17 at substantially right angles to cross tee central fin 31. A stiffening bead or rib 43 is formed in the central fin 31 at each end of cross tee 17 and extends through the central portion of locking tongues 39, 41 to an outer end portion of locking tongues 39, 41. Ribs 43 are provided to strengthen the ends of cross tees 17 and locking tongues 39, 41. 
     A locking bump 45 is formed in the outer end portion of each rib 43, and has an entrance ramp or forward surface 45a which slopes rearwardly and outwardly from the fin of the tongue, and a rear surface 45b that slopes rearwardly toward the fin. Belt loop 29, 29a presses against rear surface 45b to urge the locking tongues 39, 41 into tight engagement, since the belt loops 29, 29a tend to spring back and to ride down the sloped surface 45b of locking bump 45. Since the rear surface 45b of locking bump 45 is sloped, the tongues may be removed from belt loops 29, 29a without causing damage to the cross tee 17 by sliding the locking tongues 39, 41 rearwardly out of the belt loops 29, 29a. A hump or shoulder 45c is positioned between forward surface 46a and rear surface 45b. 
     Positive stop shoulders 47, 49 are provided at the top and bottom of each locking tongue 39, 41 for contacting the rear edge of belt loops 29, 29a on main beam 15 to assure proper alignment of the opposing cross tees 17. When both stop shoulders 47, 49 are abutting the rear edge of the belt loop, the center line of the cross tee lines up with the center line of another cross tee connected to the other side of main beam 15. 
     When locking tongues 39, 41 are fully inserted through belt loop 29, 29a, stop shoulders 47, 49 are pulled tightly against the rear edge of the belt loops due to the belt loop snapping back toward the fin and riding down the rear surface 45b of locking bump 45. 
     Belt loops 29, 29a are provided with entrance portions 51 that extend outwardly from main beam central fin 21 to form a loop opening for easy insertion therein of tongues 39, 41. The loop opening extends outwardly from main beam fin 21 a smaller distance than bump 45 so that the forward surface 45a of bump 45 moves the loop of steel away from the fin when the bump 45 is being inserted into the loop, and the loop snaps back toward the fin when the tongue is fully inserted. 
     Hanger holes 53 are formed in main beam central fin 21, and are adapted to receive wire hangers that support the grid structure. 
     Main beam 15 is provided with a vertical slot 59 in main beam central fin 21 for receiving the tongues of straight through cross tees, and is also provided with outwardly projecting lugs 61 which act as a stop for the tongues of other types of slide lock cross tees. 
     In operation, main beams 15 are suspended from the ceiling by wire hangers attached to hanger holes 53, and cross tees 17 are attached to main beams 15 by sliding locking tongues 39, 41 through belt loops 29, 29a so that stop shoulders 47, 49 contact the rear edge of the belt loops and locking bump 45 passes through the belt loop and its rear surface 45b is engaged by loop 29, 29a. Complete insertion of locking tongues 39, 41 is marked by an audible click which is heard when hump 45c of bump 45 passes the front edge of the belt loop, a sure, mistake proof signal to the installer that the tongue has been fully inserted into the loop. 
     ADVANTAGES 
     The suspended ceiling grid structure 11 of the present invention is provided with stiffening rib 43 that reinforces and greatly strengthens the ends of cross tees 17 and locking tongues 39, 41. By increasing the strength of the ends of cross tees 17 and locking tongues 39, 41, the invention provides for reducing the amount of steel required as compared to cross tees of the prior art. 
     Positive stop shoulders 47, 49 assure proper alignment of opposing cross tees 17, thereby assuring a continuous run of the cross tees 17. 
     Installation of cross tee 17 is easily accomplished by simply sliding a locking tongue 39, 41 through belt loop 29, 29a so that stop shoulders 47, 49 contact the rear edge of the belt loop and locking bump 45 passes through the belt loop and clicks into place. Further, the position of locking tongue 39, 41 in the belt loop 29, 29a positions cross tee bottom flanges 35 flush with bottom flanges 25 of main beam 15. 
     When it is desired to gain access to the space above the suspended ceiling, cross tees 17 may be removed easily by simply sliding locking tongues 39, 41 back through the belt loops. Further, the cross tees 17 are not damaged by removal because locking bump 45 does not have an upwardly extending cut surface, like a locking lug or lance, which would have to be pushed in to permit rearward passage of the locking tongues through the belt loops. The sloped surface 45b of locking bump 45 permits easy removal without damage to the cross tees. 
     The cross tee is provided with a universal type connector so that either end of the cross tee may be inserted into a belt loop. 
     The sloped surface 45b of locking bump 45 causes locking tongue 39, 41 to be pulled tightly into belt loop 29, 29a by urging stop shoulders 47, 49 tightly against the rear edge and entrance portion 51 of belt loop 29, 29a since the belt loop rides down the sloped rear surface 45b of locking bump 45 when locking tongue 39, 41 is fully inserted in belt loop 29 as the loop snaps back to its original position. 
     One of the advantages of sliding the tongues 39, 41 sideways through belt loops 29, 29a is that this grid system 11 can be flat to an existing ceiling, or even to an existing grid system, so as to provide more head room below the suspended ceiling. With prior art grid systems having straight through cross tee tongues that extend along the central axis of the cross tee web or fin, a grid system could not be flat to an existing ceiling or to an existing grid system because the cross tee tongues had to be inserted straight ahead into a vertical slot 59 in the cross beam and this required enough room above the cross beam so that the straight through tongue could be inserted at an angle to the horizontal. Also, with the straight through cross tee tongues, an operator could insert the tongues in the wrong side of beam vertical slot 59, so the cross tees did not align themselves properly in a straight line. 
     The drawings show 2-foot cross tees. In 4-foot cross tees, another set of loops 29, 29a would be formed at the two foot mark between the ends of the cross tees and would accept another cross tee.