Abstract:
An emergency release mechanism for a railway drawbar, which reduces stress in two piece machine bolts inserts in emergency release mechanisms, includes a two sided threaded stud which screws into a release rail using one of the threaded stud ends, passes through a drawbar body, and is secured to the drawbar body by a nut screwed onto the other threaded stud end.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/493,754, filed Aug. 8, 2003, and which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to railway drawbars and, more specifically, to shear mechanisms for railway drawbars. 
   2. Description of Related Art 
   Prior art emergency release mechanisms, such as the shear bolts shown in U.S. Pat. No. 6,499,613 to Grau et al., are subject to premature failure. These premature failures can be expensive to repair and can cause inconvenience. 
   Therefore, it can be appreciated that an emergency release mechanism which lessens the number of premature failures of emergency release mechanisms is desirable. 
   BRIEF SUMMARY OF THE INVENTION 
   In one aspect the present invention generally provides an emergency release mechanism for a railway drawbar having a fastener stud, the fastener stud passing through an opening in a drawbar body, and a body of the fastener stud secured to a release rail. A fastener is secured to one end of the fastener stud to hold the release rail proximate to the drawbar body. 
   In a further aspect of this invention a method of attaching a shear mechanism to a railroad drawbar includes securing a body of a stud to a release rail, passing the stud through an opening in a drawbar body, and securing a fastener to one end of the stud to thereby draw together the release rail and the drawbar body such that they are proximate to each other. 
   OBJECTS OF THE INVENTION 
   It is, therefore, one of the primary objects of the present invention to provide an emergency release mechanism which reduces the number of premature failures of emergency release mechanisms. 
   Another object, of the present invention, is to provide an emergency release mechanism which lessens the amount of fatigue in the emergency release mechanism during normal operation of the drawbar. 

   
     DESCRIPTION OF THE DRAWING 
     The aforementioned and other features, characteristics, advantages, and the invention in general will be better understood from the following more detailed description taken in conjunction with the accompanying drawing. 
     The sole FIGURE is a cross sectional view of an emergency release mechanism according to the present invention. 
   

   It will be appreciated that for purposes of clarity and where deemed appropriate, that the various elements in the drawings have not necessarily been drawn to scale in order to better show the features of the invention. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Turning now to the drawing, the sole FIGURE shows an emergency release mechanism  10  together with a drawbar body  12  and a release rail  14  and are shown generally as  16 . The emergency release mechanism  10 , in the preferred embodiment, consists of a fastener stud such as a two sided threaded stud  16 , having a first threaded end  18 , a cylindrical body  20  and a second threaded end  22 , together with a fastener such as a lock nut  24 , a through hole  26  in the drawbar body  12 , a recess  28  having a machined surface  30  in the release rail  14 , an aperture such as a tapped opening such as a threaded hole  32  in the release rail  14 , the rim of which is located in the recess  28 , and a chamfered dowel extension  34  of the first threaded end  18  having a hole  36  there through. A retaining wire  38  passes through the hole  36 . 
   The dowel extension  34  is flattened such that a wrench interface is formed so that a wrench can be used on the dowel extension  34  to screw the second threaded end  22  securely into the release rail  14 . 
   Prior to the present invention the drawbar body and the release rail were held together by a two piece machine bolt insert through the drawbar body into threads in the release rail. Because of manufacturing tolerances, the drawbar body and the release rail were not pulled tightly together at the site of the two piece machine bolt insert, but rather a space was present between the two piece machine bolt insert and the release rail. This space caused a potential bending moment on the threaded portion of the two piece machine bolt insert of the mechanism during a buff (compressive loading) application to the drawbar. This bending moment could cause premature failures of the emergency release mechanism in the drawbar. 
   The emergency release mechanism  10  of the present invention eliminates this space in the sense that there is a solid contact between the release mechanism  10  and the release rail  14  via the stud  16  such that the drawbar body  12  and the release rail  14  are held proximate to each other. In the assembly of the drawbar, in the preferred embodiment, the stud  16  is placed through the through hole  26  of the drawbar body  12  and is tightened into the threaded hole  32  in the recess  28  in the release rail  14 . The lock nut  24  is then attached and tightened to draw together the drawbar body  12  and the release rail  14  such that they are proximate each other. Any lateral or vertical forces applied to the drawbar body  12  with respect to the release rail  14  are withstood mainly by the body  20  and the flat machined surface  30  of the recess  28  which is engageable with the surface  44  of the body  20 . In the prior art emergency release mechanisms these forces were withstood solely by the threaded portion of the two piece machine bolt insert which produced fatigue in the two piece machine bolt insert. 
   With the space eliminated, the bending moment on the threaded portion of the two piece machine bolt insert of the prior art mechanism during a buff application to the drawbar is no longer present. This improvement lowers the bending stress and adds increased fatigue life to the emergency release mechanism  10  and reduces the rate of premature failure. 
   The width of the recess  28  is made wide enough so that it doesn&#39;t interfere with the shearing of the stud  16 . That is, the maximum width of the body  12  of the two sided threaded stud  16  is less than the maximum width of the recess  28 . Also, in the preferred embodiment, the two sided threaded stud  16  is manufactured by forming a one sided or single threaded stud consisting of the body  16  and the first threaded end  18 , then forming threads  40  in the end of the stud  16  opposite the threaded end and screwing into the threads  40  a threaded bar  42  to form the two sided threaded stud  16 . 
   A cutout  46  in the center of a portion of the second threaded end  22  is formed for regulating the amount of shear force that the second threaded end  22  can withstand before it shears. 
   Testing of the emergency release mechanism  10  has shown considerable improvement in the fatigue life of the mechanism  10  without changing the required intent of the shear capabilities for an emergency release mechanism. 
   Although the invention has been described in part by making detailed reference to a certain specific embodiment, such detail is intended to be, and will be understood to be, instructional rather than restrictive. It will be appreciated by those skilled in the art that many variations may be made on the structure and mode of operation without departing from the spirit and scope of the invention as disclosed in the teachings contained herein.