Patent Publication Number: US-7717231-B2

Title: Ladder guard

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application claims priority from Australian Patent Application No. 2004905266, filed Sep. 13, 2004. 
   FIELD OF THE INVENTION 
   The present invention relates to ladder guards for preventing unauthorised use of a ladder. 
   BACKGROUND OF THE INVENTION 
   It is often desirable to be able to prevent use of a ladder, especially when ladders provide ready access to buildings, vehicles or towers. 
   On both domestic and commercial building sites, ladders are commonly left on site, overnight and on weekends, ready for use on the next working day. During this time they allow easy access to upper levels and roofs, which may be unsafe. As well as the dangers of locations able to be accessed by ladders left on site, the ladders themselves can present a hazard to unauthorised users. 
   Unauthorised users may be children, vandals, thieves or people wishing to survey the progress of the building works. 
   Ladder guards have been developed that block access to a ladder in a number of alternative ways. U.S. Pat. No. 4,126,206 discloses a ladder guard having two sheets of metal pivotally joined together. The upper sheet hooks over a rung of the ladder. The lower sheet includes a portion that engages a rung from behind. The lower sheet is locked into position to prevent removal of the guard and access to the ladder. This guard must be completely removed and installed at the beginning and end of every day. 
   There are a number of other ladder guards disclosed in patent specifications, that simply sit over the front of the ladder engaging one rung at one end and locking onto the ladder at the other end. As with the previously described ladder guard, each of these devices must be fully removed and installed at the beginning and end of every day. Whilst installation is relatively straightforward, the ladder guard must be retrieved from its storage location, installed onto the ladder and locked into position. This process means that many of the people working on a typical building site, such as builders and other trades people, are likely to leave at the end of the day without installing the ladder guards. That is, there is a significant disincentive to reliable daily use of the ladder guards. 
   U.S. Pat. No. 3,225,863 discloses a ladder guard having a panel which is hingedly mounted at one side to the ladder, such that the panel can swing around to allow or prevent access to the ladder. The ladder guard is permanently installed on the ladder and therefore a site worker would simply swing the panel across the ladder and lock it into a closed position. 
   While this construction overcomes the problems of a separate ladder guard, it presents new problems. The ladder guard takes up space next to the ladder when open, thus preventing the ladder from being positioned next to an access opening or doorway. The ladder guard could be easily broken as people move past it, catching things on it when in the open position. The ladder guard, when in a closed and locked position, does not prevent access to the rear of the ladder, and indeed the ladder can still be used unless it is permanently affixed to a wall. 
   It is therefore an object of the present invention to provide an improved ladder guard that overcomes at least some of the problems with the prior art described. 
   The applicant does not concede that the prior art discussed above forms part of the common general knowledge in the art in Australia at the priority date. 
   SUMMARY OF THE INVENTION 
   The invention provides a ladder guard for use with a ladder, the ladder having a plurality of rungs, the ladder guard having: 
   a first position, in which respective portions of the ladder guard are located in front of a number of said rungs to prevent access to the rungs; and 
   a second position, in which said portions of the ladder guard are located behind rungs of the ladder to allow access to the rungs of said number of rungs; 
   wherein the ladder guard includes means for supporting the ladder guard on a ladder for movement from said first to said second position by lifting said portions of the ladder guard up and over the rungs of said number of rungs; 
   and wherein the ladder guard further includes means to releasably lock the ladder guard in said first position. 
   Preferably, the rungs behind which said portions of the ladder guard are located in said second position are the same rungs to which access is prevented in said first position. 
   Preferably, said portions of the ladder guard comprise respective panel members for each rung to which access is prevented in said first position. The ladder guard is then moveable between said first and second positions by moving the ladder guard to lift said panel members up and over a respective rung of said number of rungs. 
   Advantageously, said number of rungs is at least three successive rungs, preferably four or five successive rungs. 
   Said means for supporting the ladder guard on a ladder comprises at least one segment, preferably at the top of the ladder guard, having hook means for hooking said segment on a rung. This segment advantageously includes a handle suitable to be grasped by hand for lifting the ladder guard. 
   Said means for locking the ladder guard in said second position includes means to lock at least one said portion onto a rung with a padlock or the like. 
   Advantageously, said ladder guard is wholly between the side rails of the ladder in both of said first and second positions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  is a perspective view of a ladder guard according to an embodiment of the invention, shown in its locked position preventing access to the three rungs above the bottom rung of a ladder; 
       FIG. 2  is a vertical cross-sectional of view of the ladder guard in the access preventing position; and 
       FIG. 3  is a view similar to  FIG. 2  of the ladder guard in its retracted access permitting position, and also shows an intermediate position in dashed lines. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   The illustrated ladder guard  10  is intended to be left permanently in position on a ladder  8  that is itself in position and upright, but is adapted to be readily moved by hand between an access preventing position ( FIGS. 1 and 2 ) and a retracted or access permitting position ( FIG. 3 ). It is dimensioned to block access to three successive rungs  8   b - 8   d  of a ladder. The three rungs above the bottom rung are thought to be an optimum location. 
   The ladder guard  10  has upper and lower support assemblies  12 , 14  for supporting the ladder guard from the second and fifth rungs from the bottom, and a blocking structure  20  having three discrete light metal (eg. aluminium) plates  21 - 23  pivotably attached to assemblies  12 , 14  for movement between a first, access preventing position in which plates  21 - 23  are located in front of and block access to the respective rungs  8   b - 8   d , and a second, retracted, access permitting position ( FIG. 3 ) in which the plates are located behind the respective rungs. 
   The upper support assembly  12  has respective side plates  30 , 31  linked at the rear by an upper crossbar  32  that also serves as a handle, and shaped at their front to form a hook  34  for hanging the plates off a ladder rung  8   e.  Lower support assembly  14  similarly has respective side plates  36 , 37  with separate hook seats  38 , 39  for hanging the plates off rung  8   b  at the respective positions of the ladder guard. The two support assemblies are linked together by respective tie rods  40 , at the sides, pivotably attached to the respective plates  30 , 31 ;  36 , 37 , and by blocking structure  20 , also pivotably attached to and between plates  30 , 31 ;  36 , 37 . 
   Blocking structure  20  is a rigid assembly of the three generally rectangular plates  21 - 23 . Each is dimensioned to be able to extend obliquely from in front of and just below its respective rung and up behind the next rung above. The plates are arranged in a staggered, slightly overlapping relationship, joined together at each overlap point on both sides by metal straps  55  welded to each plate. The top plate  23  is attached to side plates  30 , 31  via brackets  41 , 42 , which are fixed to top plate  23  and pivotably attached to side plates  30 , 31  by pin  56 . 
   In the access preventing position, shown in  FIGS. 1 and 2 , upper side plates  30 , 31  are hooked forwarding onto rung  8   e  by shaped seats  51  on the side plates. The respective plates  21 - 23  extend from behind each rung to in front of the next lowest rung, and the position is locked by applying a padlock  5  or similar to a chain  62  suspended through an eye  60  at the bottom edge of lowermost plate  21 , and about rung  8   b.  It will be seen that no-one can place their feet on the ladder rungs  8   b - 8   d  from the front, nor from behind. 
   To move the ladder guard to its retracted position, an operator removes padlock  5  and chain  62  and grasps crossbar  32  to lift the whole device up, back and down to relocate side plates  30 , 31 ;  36 , 37  from seats  51  to seats  38 ,  39  on the respective rungs  8   e,    8   b,  and to lift plates  21 - 24  up over and behind the respective rungs. 
   The retracted position is defined by engagement of hooks  34  with rung  8   e.  It will be seen that plates  21 - 23  lie a distance behind the rear edges of rungs  8   b - 8   d,  thereby giving good room for a firm foothold on each rung. The weight of ladder guard  10  holds it away from ladder  8 . 
   At the end of a work session, a site worker need simply grasp crossbar  32  to lift the guard up, forward and down to its access preventing position, and then apply chain  62  and padlock  5 . Access is blocked until the commencement of the next work session. 
   It will be seen from the drawings that no part of the device protrudes laterally of the ladder side rails in either position of the device, and there is therefore no lateral restriction on the location of the ladder, and no protruding components to cause difficulty to those passing or working near the ladder.