Railways: surface track – Fastenings – Rail anchors
Reexamination Certificate
2000-08-16
2001-10-23
Morano, S. Joseph (Department: 3617)
Railways: surface track
Fastenings
Rail anchors
C238S336000, C187S408000
Reexamination Certificate
active
06305615
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a rail clip, and specifically to a rail clip that is ideally suited for use in securing the guide rails of an elevator system to underlying support brackets.
BACKGROUND OF THE INVENTION
In traction elevator systems the elevator cab is connected to a counterweight unit by hoist ropes and a sheave or pulley system. The cab and the counterweight unit are each typically mounted between a pair of vertically extended guide rails and are arranged to ride along the rails upon rollers or guide shoes. The guide rails are generally T-shaped sections that are normally erected in sixteen foot lengths and are attached to the building housing the elevator system by support brackets.
In assembly, the base flange of the T-shaped vertical sections are attached to support brackets by clips so that the blade or web section of each rail points inwardly towards the cab or the counterweight unit as the case may be. The guide roller or shoes ride along the blades along with the safeties which are designed to apply a sufficient frictionally holding force against the rails to bring the cab to a rapid and safe stop in the event an overspeed condition is sensed. As can be seen, the rail sections must be precisely aligned in assembly because they determine the positioning of the elevator in the hoistway and the related positioning of much of the operating equipment.
The clips used to mount the rail sections to the support brackets must permit the rail sections to shift or move longitudinally in the event the building housing the elevator system settles or the support brackets and/or the building to which the brackets are attached deform non-uniformly due to thermal stresses. The requirements for rail clips are thus not necessarily mutually compatible. The clips must, on one hand, provide sufficient hold force to support the rail weight plus the dynamic load produced by a car moving over the rail and the car during safety engagements. On the other hand, the clips must allow the rail to slide vertically in the event the building housing the elevator system settles or there is a difference in thermal expansion between the building and the rails. This requires that the clamping force exerted by the clips must be within a certain predetermined range. A change in the lateral distance between the support bracket and the contact point, due to rail tolerances or a rust build-up under the rail, will effect preload force moving the force outside the predetermined range. This can, in turn, cause the rail to buckle, thus adversely effecting the smoothness of the ride as the cab moves over the rails. Accordingly, the clips must be soft enough under normal conditions to accommodate the change in the lateral distance between the support bracket and the contact point without significant change in a clamping force, yet stiff enough to resist lateral displacement of the rails under excessive lateral displacement.
The disadvantage of a soft clip is that although they accommodate a rust build up under the rail or variation in the rail tolerances without substantial change in clamping force, it generally cannot meet the code requirements for seismic applications. On the other hand, for rigid seismic clips, any such change in lateral displacement can dramatically increase the holding force that the clip exerts on the rail and thus adversely effect the rail's ability to slide longitudinally.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to improve clips for holding the elevator guide rail sections to support brackets.
It is a further object of the present invention to provide an elevator rail clip that increases its effective stiffness as the lateral displacement of the rail beneath the clip increases.
Another object of the present invention is to provide a rail clip that exhibits a soft response to small changes in the lateral displacement of the rail beneath this clip and increases its effective stiffness in response to increases in the lateral displacement of the rail beneath the clip.
A still further object of the present invention is to provide an elevator guide rail clip that will accommodate a normal rust build up beneath the rail sections without producing an appreciable change in the clip's effective clamping force.
These and other objects of the present invention are attained by a rail clip that is ideally suited for use in securing T-shaped elevator guide rail sections to underlying support brackets. The clip is generally symmetrical about a central axis and includes a base section that can be secured to a support bracket adjacent to the base flange of a rail. An arm extends outwardly over the base flange of the rail which has a flat lower surface that is in parallel alignment with the support surface of the bracket. A pair of wings extend outwardly from opposed side walls of the arm and slope downwardly toward the rail flange. Contact dimples or pads are contained on the underside of each wing at its distal end and are adapted to reside in holding contact against the flange when the base section of the clamp is secured to the bracket. Any lateral upward displacement of the rail toward the arm such as that produced by rust or the like, causes the wings to deflect upwardly until such time as the base flange of the guide rail contacts the distal end of the arm whereupon a line of contact is established across the width of the arm and the effective stiffness of the clip increases. Further upward displacement of the rail beneath the clip, as produced by random seismic induced loads or other similarly high induced loads, will cause the line of contact between the rail and the arm to move inwardly toward the base section whereupon the effective stiffness of the clip increases as the distance between the line of contact and the base section decreases.
REFERENCES:
patent: 2051982 (1936-08-01), Boyd et al.
patent: 4324360 (1982-04-01), Sun et al.
patent: 5135165 (1992-08-01), Greenhow
McCarry, Jr. Robert J.
Morano S. Joseph
Otis Elevator Company
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