Patent Publication Number: US-6701562-B2

Title: Span lock with centering guide

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §120 to U.S. Provisional Application Serial No. 60/341,509 filed on Dec. 12, 2001 and to U.S. Provisional Application Serial No. 60/367,997 filed on Mar. 26, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to span lock systems for single and double leaf drawbridges; and more particularly to a novel and improved span lock centering guide and mounting in a single or double leaf drawbridge. 
     Span lock systems, in addition to securing the leafs of a drawbridge in the closed position, also provide for vertical shear load transfer between their outer ends whereby the leaf tips deflect uniformly during passage of vehicular traffic. U.S. Pat. No. 5,327,605 to Robert L. Cragg discloses such a system in which a rectangular lock bar, retractable parallel to the drawbridge span length, fits through a guide mounted on a rectangular base on the outer end of one leaf of the bridge and into a receiver mounted on a rectangular base on the outer end of the other leaf. The bases are secure to the bridge structure by bolts which are spaced apart along the top and bottom edges of both bases, and along the edge of the receiver base away from the outer leaf end. Stiff annular springs are vertically supported by guide pins which are fixed to the wear shoes with sliding clearance in the guide and receiver, respectively. The springs urge the wear shoes in firm and continuous contact against the lock bar. The top and bottom surfaces of the lock bar and the shoes at their confronting outer ends are beveled to accommodate slight vertical misalignments between the guide and receiver during insertion of the lock bar. In a fully locked position, vertical shock loads to the bar from road traffic are cushioned by the springs, and uncontrolled bounce of the leaf ends is eliminated. The sides at the outer ends of the lock bar are also beveled to accommodate slight lateral misalignments, but there are no provisions for limiting shear stresses in the lock bar from more severe lateral misalignments as may occur due to wind, thermal expansion, uneven wear, uneven settlement of bridge structure, or marine vessel collision. 
     While the span lock system of U.S. Pat. No. 5,327,605 has distinct advantages over prior art designs for cushioning vertical shock loading, it does not limit horizontal bending and shear stresses in the lock bar due to substantial lateral misalignment of the span leaf locking elements as may occur due to side winds, thermal expansion or contraction, uneven settlement of bridge structure, or marine vessel collision. 
     U.S. Pat. No. 2,610,341 to Gilbert discloses a span lock system with means for horizontally aligning the leafs of a double leaf bascule bridge but does not limit horizontal bending or shear stress in the lock bar lock. A slotted alignment disc is loosely rotatable within a male member at the tip of one leaf. A lock bar reciprocates lengthwise on an axis normal to the bridge span in a receiving member at the tip of the adjoining leaf includes and engages the slotted disc. The receiving member includes a vertical slot slightly flared at the upper and lower ends for capturing the male member and laterally positioning the alignment disc along the length of the lock bar. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a centering guide for a span lock system in a single or double leaf drawbridge which will limit horizontal misalignment of the locking components. 
     Another object of the invention is to limit the horizontal stresses transferred to the lock bar in a span lock system as may occur due to strong side winds, thermal expansion or contraction, uneven wear of bridge components, or uneven settlement of bridge structure. 
     Another object of the present invention to provide a mounting for a span lock with a centering guide in a single or double leaf drawbridge which will maximize the ability of the wear shoes to accept misalignments of the wear shoes experienced during passage of heavy traffic on the bridge leafs. 
     Still another object of the invention is to provide a centering guide for aligning locking components in span lock system which is of relatively simple design for facilitating ease of manufacture, maintenance, repair and replacement of parts. 
     These and other objects and advantages of the invention are accomplished by a span lock centering guide and mounting in a drawbridge. A guide housing mounted on either side by two columns of bolts to the outer end of one leaf of the bridge includes an opening with vertically opposed cushioned wear shoes slidably supporting an elongate lock bar reciprocative lengthwise in a direction along the length of the drawbridge. A receiver housing mounted by two columns of bolts to the outer end of the other leaf is positioned to interlock with the guide housing and includes a like opening slidably receiving the lock bar between vertically opposed cushioned wear shoes. A pair of springs, spaced apart along the length of the lock bar, in each housing, urge the shoes in continuous contact with the upper and lower surfaces for reducing shock loads and eliminate bounce of the leaf ends. Each spring comprises a stack of coaxial Belleville discs retained by a cylindrical guide pin fixed to the wear shoes and is slidable in the housings. The center lines of the guide pins are parallel to and substantially between the center lines of the bolt columns. A pair of vertical guide columns project from either side of the guide housings opening with the upper and lower ends of the distal sides tapering inwardly, and another pair of vertical guide columns project from the on either side of the receiver housing opening with the upper and lower end of the proximal sides tapering outwardly. Within a specified maximum limit of misalignment, the guide and receiver columns interengage causing their openings to closely align and facilitate insertion of the lock bar into the opening of the receiver housing with limited horizontal bending and shear. The distance between the proximal sides of the receiver housing exceeds the distance between the distal sides of the guide housing for specified maximum misalignment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding and appreciation of the invention and its many attendant advantages, reference will be made to the following detailed description taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a plan view of a span lock system as applied to a double leaf bascule bridge locked in the closed position having a centering guide according to the invention; 
     FIG. 2 is an elevation view of the span lock system of FIG. 1 with supporting bridge structure shown in broken outline; 
     FIG. 3 is a larger elevation view of the outer end of the span lock system of FIG. 2, partially in broken outline, with supporting bridge structure; 
     FIG. 4 is an end view of a bar guide assembly according to the invention with a lock bar in cross section taken in a plane along the line  4 — 4  of FIG. 3; 
     FIG. 5 is an end view of a bar receiver assembly according to the invention with the lock bar in cross section, taken in a plane along the line  5 — 5  of FIG. 3; 
     FIG. 6 is a plan view of the bar guide assembly with supporting bridge structure; 
     FIG. 7 is an elevation view of the bar guide assembly with supporting structure taken in partial cross section in a plane along the line  7 — 7  of FIG. 6; 
     FIG. 8 is an elevation view of the bar guide assembly and supporting structure taken in cross section in a plane along the line  8 — 8  of FIG. 6; 
     FIG. 9 is plan view of the bar receiver assembly with supporting bridge structure; 
     FIG. 10 is an elevation view of the bar receiver assembly and supporting structure taken in partial cross section in a plane along the line  10 — 10  of FIG. 9; and 
     FIG. 11 is an elevation view of the bar receiver assembly and supporting structure taken in cross section in a plane along the line  11 — 11  of FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein like reference characters and numbers denote like or corresponding parts throughout the several views, a span lock system with a novel centering guide according to the invention, is represented generally by the numeral  10  in FIGS. 1 and 2, and comprises a guide housing  16  and a receiver housing  26  mounted, respectively, in box trusses  12  and  14  at the facing tips of a double-leaf drawbridge, shown in the closed and locked position. A lock bar assembly  18  mounted on truss  12  includes a motor  22  and gear train  24  for reciprocating a lock bar  20  through guide housing  16  lengthwise and parallel to the bridge span length. A travel limit member  28  is operatively connected to a slot  30  in lock bar  20  and functions to limit the travel of lock bar  20  in either direction. In the bridge closed position, guide housing  16  and receiver housing  26  are aligned to receive an extended portion of lock bar  20  and to lock the bridge leafs in place. It will be appreciated that the system is applicable to other forms of drawbridges such as a single-leaf span where the movable leaf end connects to stationary structure. 
     Elongate stiffeners  17  (FIGS. 6 and 8) extend from opposite sides of housing  16  in a plane normal to the length of lock bar  20  and terminate in opposed lateral flanges  17   a.  Stiffeners  17  could be formed integral with housing  16 , or as a separate element that is connected to housing  16 . A column of bolts  13  in each flange  17   a,  aligned in parallel to stiffeners  17 , function to secure guide housing  16  to box truss  12  and gusset plates  12   a.  Similarly, receiver housing  26  includes stiffeners  27  with opposed flanges  27   a  and  27   b  (FIGS. 9 and 11) secured to the sides of box truss  14  and gusset plates  14   a  by a columns of bolts  15  aligned in parallel with stiffeners  27 . 
     The portion of lock bar  20  extending through housings  16  and  26  is generally rectangular in cross section, and is slidable between movable upper and lower wear shoes  32  within housing  16  (FIG.  7 ), and between movable upper and lower wear shoes  34  within housing  26  (FIG.  10 ). Pairs of upper and lower springs  36 , spaced apart along the length of lock bar  20  in each housing, urge the shoes  32  and  34  into continuous contact with the upper and lower surfaces of lock bar  20  for reducing shock loads and eliminating bounce of the leaf ends. Each spring  36  comprises a stack of coaxial Belleville discs  46  retained by a cylindrical guide pin  37  fixed to wear shoes  32  and  34  and slidable in housings  16  and  26 , respectively. The center lines C of guide pins  37  are disposed parallel to and substantially between the center lines D of the columns of bolts  13  and  15 . The sliding clearance allowed between the guide pins and the housings, together with positioning the pins between the bolts, maximizes the ability for the wear shoes to accept misalignments of the wear shoes experienced during passage of heavy traffic on the bridge leafs, and minimizes the shear loads on the mounting bolts. 
     A guard  29  (FIGS. 6 and 7) projects from guide housing  16  above and adjacent to the inlet end of upper wear shoe  32  to deflect any fluids or debris from gathering within proximity of the lock bar-shoe interface. Guards  29  (FIGS. 5,  9 ,  10 ) similarly project from receiver housing  26  above and adjacent to both ends of upper wear shoe  34 . 
     The upper and lower surfaces at the ends of lock bar  20  (FIGS. 2 and 7) and the corresponding meeting ends of wear shoes  34  (FIG. 10) in receiver housing  26  are tapered to enable initial capture of lock bar  20  in receiver housing  26  when there is any small amount of vertical misalignment as the bridge leafs meet. As lock bar  20  is inserted between wear shoes  34 , housings  16  and  26  are aligned vertically between their respective wear shoes  32  and  34  when the forces of springs  36  are counterbalanced in a static position. Springs  36  are designed with sufficient stiffness to accommodate displacement from the static position under maximum anticipated vertical shock loadings. 
     The side surfaces at the ends of lock bar  20  (FIG. 1) are also tapered to enable lock bar  20  to be captured in receiver housing  26  with limited horizontal bending or shear when there is only a small amount of horizontal displacement between of housings  16  and  26 . More substantial horizontal displacements are adjusted by complementary pairs of guide and receiver columns  38  and  40  projecting respectively from the confronting ends of guide and receiving housings  16  and  26  in amounts sufficient to insure they fully overlap and intermesh as the bridge leafs close. Guide columns  38  have parallel distal sides  48  disposed on opposite sides of the guide housing opening and the upper and lower edges of the distal sides  48  are beveled. Receiver columns  40  have parallel proximal sides  42  disposed on opposite sides of the receiver housing opening with the upper and lower edges of the proximal sides  42  beveled. The distance A (see FIG. 5) between the proximal sides  42  of receiver housing  26  exceeds the distance B (see FIG. 4) between the distal sides  48  of guide housing  16  by an amount corresponding to the maximum allowed horizontal displacement for a specified application. Thus, as the bridge leafs near closure, any horizontal bending or stress resulting in the misalignment of housings  16  and  26  that is less than the difference A-B is corrected and the housings  16  and  26  are moved into closer alignment as a result of the sliding engagement of guide columns  38  and receiver columns  40 . As a result of this initial alignment of housings  16  and  26  by guide columns  38  and receiver columns  40  when the lock bar  20  is moved by the motor  22  and gear train  24  through the housings  16  and  26 , lock bar  20  need only complete or fine tune the alignment. In an actual construction of housings  16  and  26 , for example, the distance A between the proximal sides  42  of columns  40  is 14¾ inches, and distance B between the distal sides  48  of columns  38  is 14⅛ inches. This allows housings  16  and  26  to be aligned from a maximum horizontal misalignment of ⅝ of an inch. The lock bar  20  is capable of reducing the horizontal misalignment to less than ⅝ of an inch. 
     It will be understood, of course, that various changes in the details, materials, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principles and scope of the invention.