Patent Application
20110131913
The invention relates to improvements in suspended ceiling grid construction and, in particular, to improvements in connector clips for ceiling grid members.
Suspended ceiling grid members or runners typically comprise relatively long main runners and shorter cross runners. Both types of grid runners have connectors to join their ends to the ends of like members to construct a ceiling expanse of greater size than the length of individual main or cross runners. These end connectors, as the industry has advanced, are typically separate clip elements permanently attached to the grid runners themselves. The end connectors or clips are metal stampings, ordinarily of steel, formed with features that enable them to couple with identical units when one connector is pushed endwise into a lap joint with an opposing end connector. Depending on the clip design, the clips may directly abut or may have runner web areas disposed between them. In general, the features stamped or otherwise formed into a connector that establish a connection are a lateral projection and the edge of a hole. The projection of one connector is received in the hole of the opposing connector and, vise versa, the projection of the opposing connector is received in the hole of the one connector. The result is a joint with two locks. In practice, a connection may fail under tension at a force level substantially below the design or normally expected capacity of the joint. This can occur when the joined connectors slip sideways and disconnect one lock engagement resulting in a severe reduction in the load capacity of the joint.
The invention provides an end connector clip for suspended ceiling grid runners with improved clip-to-clip locking action. The improved locking function, in accordance with the invention, is achieved by orienting the locking surfaces with an angle relative to the plane of the clip body proper greater than what results from conventional practice. A preferred manner of forming the inventive locking surfaces is by increasing the clearance between the punch and die elements that create the locking surfaces. This technique, it has been found, develops an orientation of a locking surface that, in use, counteracts forces that tend to laterally separate mating locking surfaces of a pair of coupled clips which otherwise could result in a major loss of retention force. Ideally, the inventive technique is applied to both a locking projection and a projection receiving area of the clip.
Referring now to the drawings and in particular to
The illustrated connectors 14 are of the general type disclosed in U.S. Pat. Nos. 5,517,796 and 5,761,868, the disclosures of which are incorporated herein by reference. Typically, the connectors 14 are stamped from steel sheet stock that is stronger and harder than that of the tees 10, 11. The numeral 16 indicates the forward end of a connector 14.
When two connectors 14 are positioned from opposite sides of the main tee 10 into a common slot 12, they form a joint of their respective cross tees 11 by establishing a double connector-to-connector lock. The relationship between a pair of joined connectors 14 is analogous to a handshake. More specifically, when clips 14 are joined they lap one another, preferably in direct abutment. The clips 14 are locked together when a lock area 17 of one clip 14 snaps or is otherwise received behind a forward one of two opposing projections 18, 19 stamped into the body of the other clip 14. This same action occurs where the corresponding lock area 17 of the other clip is received behind the forward projection 18 of the one clip 14. With both sets of lock areas 17 and projections 18 engaged, a double lock clip connection is established. The lock area 17 and projection 18 interengagement serves to resist tensile loads on the associated cross tees 11 tending to separate them and under proper conditions can sustain relatively high forces.
Experience reveals that a joint between a pair of clips 14 will separate under relatively low forces if one of a set of locking area 17 and projection 18 slips laterally, i.e. perpendicular to the planes of the clips 14. This can leave only one lock set between a lock area 17 and projection 18.
Such sidewise slipping may result, inter alia, from variations in the clip material, the clip manufacturing process, deviation from an ideal clip shape, installation technique, and eccentric forces imposed on the joined clips or combinations of these factors.
The failure of a lock set by lateral movement between lock area 17 and projection 18 is related to the orientation of their respective contacting edges, designated 21, 22. The closer these edge surfaces 21, 22 are to lying in planes that are perpendicular or are obtuse to the planes of the clip bodies, the greater the risk that they will separate laterally. Locking surfaces with such orientations have little or no resistance to forces tending to laterally separate the clips 14 and when the angle is measurably obtuse a reaction force is developed by the locking surfaces in response to a tensile force between the tees that may actually cause the clips to spring laterally apart and out of contact. A locking edge surface of a projection corresponding to the projection 18 when produced with conventional practice is prone to assume an obtuse angle relative to the plane of the clip. When this edge surface is originally formed by stamping a hole in the plane of the original sheet stock forming the clip it can be slightly acute, i.e. less than 90 degrees. However, when the projection is thereafter formed out of the plane of the main part of the clip body, the edge surface can be drawn into an obtuse orientation.
As shown in
In
It has been discovered that by significantly departing from traditional practice and increasing the clearance between the punch elements 26, 27, and die openings 33 and 34, the angularity of the lock edges 21, 22 can be advantageously increased. For example, the clearance between the punch elements 26 and 27 and their respective die openings 33, 34 corresponding to the lock edges 21, 22 can be about 25% of the thickness of the sheet metal used to form the connector or clip 14. The illustrated clip 14 can be formed of 0.015/0.017 inch high tensile steel (160 KSI), stress relieved or type 301/302 stainless steel, half hard.
Those skilled in the art will recognize the applicability of the invention to main tee clips such as shown, for example, in U.S. patent application Ser. No. 11/135,058 and U.S. Pat. No. 6,523,313. In the clips shown in U.S. Pat. No. 6,523,313, the material of the tee web is interposed in the area of the locks; nevertheless, the invention has application in such constructions where the connectors, while separated by grid runner stock, are lapped with one another and the locking edges serve the same function as described herein.
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.
