Advanced guard rail

Abstract

An advanced guard rail connectable between two respective end frames to create an access tower, the advanced guard rail comprising: a frame; and a hook provided at each respective corner of the frame, each hook configured to receive a rung of a respective end frame therein, wherein the distances between the upper hook centres and the lower hook centres are dissimilar, to add additional stiffness to the access tower in use.

We claim: 
     
         1 . An advanced guard rail connectable between two respective end frames to create an access tower, the advanced guard rail comprising:
 a frame; and   a hook provided at each respective corner of the frame, each hook configured to receive a rung of a respective end frame therein, wherein the distances between the upper hook centres and the lower hook centres are dissimilar, to add additional stiffness to the access tower in use.   
     
     
         2 . An advanced guard rail connectable between two respective end frames to create an access tower, the advanced guard rail comprising:
 a frame; and   a hook provided at each respective corner of the frame, each hook configured to receive a rung of a respective end frame therein, wherein the two lower hooks further comprise a locking mechanism, the advanced guard rail being configured such that as the locking mechanism is closed, the advanced guard rail is secured to the end frames by the inner surface of the upper hooks applying a force on an upper surface of the frame and a part of the locking mechanism applying a force on a lower surface of the frame   
     
     
         3 . An advanced guard rail according to  claim 2 , wherein the locking mechanism is an over centre lock comprising a lever and a clamping arm, the clamping arm applying a force on a lower surface of the frame when the locking mechanism is closed. 
     
     
         4 . An advanced guard rail according to  claim 2 , wherein the lever comprises a cam surface in contact with a part of the hook, configured such that as the lever is rotated, the locking mechanism is caused to close. 
     
     
         5 . An advanced guard rail according to  claim 2 , further comprising a spring washer between a lower hook and lever to provide the mechanism with compliance to lock against an end frame over a variable position. 
     
     
         6 . An advanced guard rail according to  claim 2 , wherein the distances between the upper hook centres and the lower hook centres are dissimilar, to add additional stiffness to the access tower in use. 
     
     
         7 . An advanced guard rail connectable between two respective end frames to create an access tower, the advanced guard rail comprising:
 a frame; and   a hook provided at each respective corner of the frame, each hook configured to receive a rung of a respective end frame therein, wherein the distance between the centre of the upper hooks and the centre of the lower hooks is intentionally less than the distance between the centre of the rungs with which the hooks engage in use.   
     
     
         8 . An access tower comprising
 at least one advanced guard rail according to  claim 1 ; and   two end frames, each comprising a pair of stiles connected by a plurality of rungs spaced apart from one another,   wherein the advanced guard rail is connected between the two end frames.   
     
     
         9 . An access tower comprising
 at least one advanced guard rail according to  claim 2 ; and   two end frames, each comprising a pair of stiles connected by a plurality of rungs spaced apart from one another,   wherein the advanced guard rail is connected between the two end frames.   
     
     
         10 . An access tower comprising
 at least one advanced guard rail according to  claim 7 ; and   two end frames, each comprising a pair of stiles connected by a plurality of rungs spaced apart from one another,   wherein the advanced guard rail is connected between the two end frames.