The present invention relates to a heddle frame for a loom, and in particular to improved means in the heddle frame for preventing distortion with respect to the top and bottom rails of the heddle frame. 
A known heddle frame with an improved center brace assembly is disclosed in U.S. Pat.  No.  4,924,916.  In this patent, the heddle frame comprises top and bottom rails which are typically made of extruded aluminum.  The top and bottom rails are connected to each other at their ends by end struts or members to provide a rigid connection between the rails and to define a generally rectangular harness or heddle frame.  The frame includes top and bottom heddle supporting rods upon which heddles are slideably mounted, as is commonly understood in the art.  A center brace is mounted midway between the ends of the frame, and in some cases a plurality of braces may be employed.  These center braces serve to prevent distortion of the frame and to maintain the parallel relationship between the top and bottom rails. 
In the '916 patent, the center brace extends through an opening into the top rail and into an opening into the bottom rail.  A top sleeve is disposed in the opening in the top rail and extends about the center brace to separate the brace from the opening in the top rail.  Likewise, a bottom sleeve is disposed in the bottom rail and is threaded onto the center brace.  Means are provided on the upper surface of the top rail to secure and retain the center brace within the opening, thereby supporting and maintaining the parallelism of the top and bottom rails.  The lower end of the center brace is supported by a nut block which is attached to the upper surface or bottom surface of the bottom rail.  The center brace is threadedly engaged within the nut block. 
Although the device disclosed in the '916 patent provides a significant improvement in the art, a problem has existed in that a degree of play inherently exists between the threads on the center brace and the threads in the connecting nut block.  The heddle frames are in continuous motion and experience continuous vibration.  This vibration is transmitted to the center brace, and particularly to the threaded connection between the center brace and the bottom nut block.  Thus, due to the inherent play between the threads and the members, a degree of vibration exists between the center brace and the bottom nut block.  This continuous vibration results in wear of the threads and the nut block or the center brace requiring frequent replacement of the center brace or the attaching nut block. 
The present invention eliminates the vibration between the center brace and the top and bottom rails and provides a significantly improved center brace assembly.