Abstract:
A rail clip that is generally symmetrical about a central axis. The clip has an L-shaped base section having a horizontal leg that is securable to a support member upon which the rail rest and a vertical leg that extends upwardly from the base adjacent to the rail. An arm extends outwardly over the rail from the vertical leg of the base section and an elongated beam is mounted in the distal end of the arm that extends outwardly to either side of the arm so that beams run longitudinally along the rail. A contact pad is carried on both ends of the beam which normally rest in holding contact against the rail. As the rail is displaced upwardly in reference to the arm, second contact points are established to progressively stiffen the clip.

Description:
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&#39;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&#39;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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a further understanding of these and other objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, wherein: 
     FIG. 1 is a perspective view illustrating an elevator rail clip embodying the teachings of the present invention; 
     FIG. 2 is a top view showing the clip attached to a support bracket and being mounted in engagement with an elevator guide rail section; 
     FIGS. 3-6 are side elevations illustrating the rail clip engaging a rail section under varying load conditions; 
     FIG. 7 is a diagram showing the effective stiffness of the clip at varying contact points; and 
     FIG. 8 shows the overall response curve of the clip as the contact point changes due to the lateral displacement of a guide rail section secured by clip changes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to FIGS. 1 and 2, there is illustrated a rail clip, generally referenced  10 , that is ideally suited for securing an elevator guide rail section  12  to underlying support brackets  13 . As noted above, the typical guide rail presently employed in many elevator systems has a T-shaped cross sectional configuration and includes a base flange  15  and a centrally positioned web or blade  16  that runs longitudinally along the length of the flange. The elevator guide rail sections are aligned vertically end to end in assembly. As is well known, the elevator cab and the associated counterweight unit are each arranged to move freely along a pair of spaced apart rails upon rollers or guide shoes which ride along the blade portion of each rail. 
     Each rail section is attached to a plurality of support brackets using a number of rail clips. As will be explained in greater detail below, each clip exhibits an initial linear response that is soft enough to provide for longitudinal movement of the rail section and to accommodate for variances in tolerances and the build-up of rust between the bottom of the rail and the top of the supporting bracket. The effective stiffness of the clip, however, increases non-linearly as the lateral movement of the rail beneath the clip increases beyond a predetermined point. 
     The present clip  10 , as illustrated in FIGS. 1 and 2, includes a base plate  22  that is adapted to set upon a support bracket  13  adjacent to the base flange  15  of a guide rail section  12 . A second end plate  23  extends along one end of the base plate and rises perpendicularly to a desired height above the base plate. An arm  24  is mounted along the top edge of the end plate and extends outwardly over the base flange of the guide rail section. The arm is a flat member that is generally mounted parallel with the base plate. Preferably, the base plate, the side plate, and the extended arm are integrally formed to create a Z-shaped member, generally referenced  20 , that is symmetrical about a central axis  29 . A bolt receiving hole  35  is provided in the base plate which is centered upon the axis  29 . In assembly, a bolt  34  is passed through the hole and secured in the underlying support bracket. The hole  34  can be circular as shown, or slotted to allow for some adjustment of the clip in assembly. 
     A pair of wings  27 — 27  are mounted upon the opposed side walls  54  of the extended arm  24 . The wings are generally mounted in perpendicular alignment with the axis  29  of the clip. The root  25  of each wing extends back from the distal end  26  of the arm, some distance toward the proximal end of the arm so that the length of each root is about one-half the length of the arm. The root length may, however, be of greater or lesser length without departing from the teachings of the present invention. The width of each wing tapers downwardly from the root section toward the wing tip and also slopes downwardly from the root toward the tip so that each wing has a negative dihedral, much like the wings of many airplanes. 
     As best illustrated in FIG. 2, each wing, in assembly, extends longitudinally along the base flange  15  of the rail section in generally parallel alignment with the rail blade  16 . A contact pad  31  is located on the underside of each wing at the tip thereof and serves as the point that initially contacts the base flange of the rail section. The contact pad may be a simple dimple shaped protrusion that is integrally formed with the wing, or, as illustrated, may be a removable pad that is secured to the wing by means of a threaded fastener  39 . A series of receiving holes  38  for receiving the threaded fastener are located along the leading edge of each wing that allows the contact pads to selectively reposition along the length of each wing. The holes are located along a common axis  40  that is perpendicular to the central axis  29  of the clip. The wings  27  may be integrally joined to arm  24  of the clip and thus the entire clip fabricated from a single piece of material, such as steel, having a desired modulus of elasticity. Alternatively, each wing may be fabricated separately from a material that has a different modulus of elasticity and/or a difference in wing thickness then that of the Z-shaped supporting member and is attached to the arm using well known joining techniques. 
     FIG. 3 depicts the position of the clip  10  prior to tightening the base plate down against the underlying support bracket. At this time, the contact pads  31  of the wings  27  are resting upon the top of the guide rail flange  15  and the base plate  22  is held in a canted position upon the supported bracket  13 . 
     As illustrated in FIG. 4, tightening the base plate  22  of the Z-shaped support member  20  down into support bracket  13  causes the wings to flex upwardly to apply an initial holding force upon the rail flange. The initial holding force is dependent upon the effective stiffness of the wings and the downward slope of the wings and is predetermined to provide for the necessary longitudinal movement of the rail. 
     As in most elevator systems, a rust build up  42  can build up over time between the bottom of the rail sections and the support bracket. As the radial displacement between the wings and the support bracket increases, the wings will continue to flex upwardly, however, the effective stiffness of the clip remains within a range so that the rail flange can still move longitudinally beneath the clip. 
     The wings continue to respond linearly as the lateral displacement increases until such time as the flange comes in contact with the distal end of the arm  24  along a line of contact depicted at  43 . This condition is illustrated in FIG.  5 . Accordingly, the effective stiffness is moved form the wings to the extended arm, and as will be explained in greater detail below, the effective stiffness of the clip at this time increases. 
     The effective stiffness of the clip increases as the line of contact between the clip and the rail moves inwardly toward the anchor bolt. In the event the elevator system experiences a seismic event, the lateral displacement of the clip can be increased by high random vibrator forces, as illustrated in FIG.  6 . The line of contact at this time has moved inwardly toward the proximal end of the extended arm at point  48 . 
     FIG. 7 is a graphic representation showing the effective stiffness of the clip at the three noted contact sites  31 ,  43  and  48 . Curve  80  identifies the effective stiffness of the clip when the distal ends of the two wings are in contact with the base flange of the guide rail as shown in FIG.  4 . The clip, at this time, exhibits a soft response which allows for longitudinal movement of the rail sections. Curve  80  is shown as a solid unbroken line and, as can be seen, the effective stiffness of the wing is linear. 
     Curve  81 , which is a dot dash line, depicts the effective stiffness of the clip when the contact has moved to contact line  43  (FIG. 5) at the distal end of the arm. Here again, the response of the clip is relatively linear, however, the effective stiffness as evidenced by the slope of the curve has increased. Curve  82 , which is depicted as a dashed line, illustrates the effective stiffness of the clip when the contact has moved to contact line  48  close to the proximal end of the arm as shown in FIG.  6 . At this time, the contact has moved closer to the center of the tie down bolt and the effective stiffness of the clip as experienced by the slope of the curve has increased dramatically. As clearly illustrated, the effective stiffness of the clip increases as the wings deflect upwardly and as the contact point moves from the wings to various points along the arm. 
     FIG. 8 is a graphic illustration of the effective stiffness of the present clip as the contact point moves from the wings to the extended arm  27  and then back along the arm toward the tie down bolt  35 . Initially, the effective stiffness increases linear from point  1  to point  2 . As rust builds up under the base flange of the rail, the wings continue to deflect due to an increase in the lateral displacement of the wings. This occurs between points  2  and  3  after which the rail flange moves into contact along the line of contact  43  (FIG.  5 ). The effective stiffness of the clip now increases between points  3  and  4 . In the event the elevator system experiences high induced loads such as those produced by a seismic event, the lateral displacement between the arm and the support bracket will increase as illustrated in FIG.  6  and the line of contact is moved back from point  43  to point  48 . Accordingly, the effective stiffness of clip is now more pronounced as depicted by the overall response curve  85  and is high enough to meet the code requirement relating to seismic applications. 
     While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.