The present invention relates to hinged columns, in particular but not exclusively lampposts, and hinge assemblies for use in such columns.
Most lampposts or similar columns are in the form of a rigid column supporting a load, such as a lamp or camera. When the lamp fails it has to be replaced or repaired and access to the top of the column is required. Where there is access by road a sky-lift can be used but in confined spaces access may only be possible by climbing a ladder. Recently the UK Health and Safety Executive has recommended against the use of ladders to service lampposts because there have been numerous accidents when workmen lean a ladder against a lamppost which is corroded and subsequently collapses.
The raise and lower type of post has been developed to address such problems. This is a post with a hinge positioned above, but accessible from, the ground, and arranged so that the main body of the post can be tilted such that the end of the post and the lamp may be readily accessed by a worker standing on the ground.
Such posts generally comprise lower and upper portions mutually attached by a hinge. Several mechanisms have been used to lower and raise the upper portion. One mechanism is to attach a rope or cord to the upper portion, the operator holding the rope and lowering and raising the upper portion as desired. This relies on the strength and control of the operator to lower and raise the upper portion safely. This is an intrinsically unsafe method. A further known mechanism is to provide a piston which is attached externally to the post, with one end removably attached below the hinge and the other end being removably attached above the hinge such that the piston acts to control and slow the fall of the upper portion once the hinge is broken. This relies on a piston unit being transported to each post. Alternatively, a spring arrangement may be provided inside the post to control the movement of the upper portion of the post.
Some of these prior art devices (such as U.S. Pat. No. 2,645,511 and WO03029581) use chains to connect the upper portion of the post to a spring arrangement. The applicant has found that chains are complex and often comprise weak regions or links. Other coupling arrangements have been suggested, such as that described in GB2362396, wherein the upper portion of the post is directly connected to a yoke bearing a rod that exerts pressure onto a spring. A housing containing the rod and spring is permitted to pivot to facilitate the movement of the housing. Such an arrangement is complicated and unwieldy.
Many raise to lower posts are provided with safety devices that are used to prevent unauthorised or unwanted activation of the hinging mechanism. WO03029581 discloses a mechanism to lock the upper portion and lower portion together so as to prevent motion about the hinge when the post is upright or when the upper portion is fully lowered for maintenance or replacement of the lamp. U.S. Pat. No. 2,645,511 discloses a raise to lower post with a lockable door that prevents unauthorised or unwanted tilting; the door may be removed to allow tilting to occur. The door, however, is detached from the post to allow tilting, resulting in possible loss and/or accidental damage of the door. Furthermore, once the bolt has been removed from the door, then unwanted or accidental removal of the door may occur all too readily.
The column of the present invention mitigates against some or all of these problems.