| 摘要 |
In a device to make adjustable the relative length of the side-rails of a ladder, to facilitate use on non-level supporting surfaces, a lockable, releasable, longitudinally slidable leg is attached to a side-rail by one or more bracket arrangements which freely embrace the sliding leg and provide a mounting base for attaching a lever hawing an eccentric cam that can optionally bind the sliding leg between that cam and the side-rail of a ladder. When the lever is moved to force the eccentric cam against the slidable leg until the eccentric is very slightly past it's point of highest compression, it is located in this position in it's arc around the lever fulcrum because being past the point of highest compression it tends to move on, away from that point towards a point of lower compression but is prevented from doing so because the lever handle has contacted the slidable leg also. To release this compressed locking action the operator applies force on the lever in the opposite direction to force the eccentric back past the point of highest compression and on to release the compression as desired. In this invention the strength of the operator is greatly augmented by the mechanical advantage of the lever when the lever is manipulated by simple movements in a single plane. This device is adaptable for use on many ladder designs as the bracket arrangements may be attached to side-rails of a ladder without interfering with operation of normal extension ladders while the brackets array be sized to fit smaller side-rails and may be expanded to fit larger ladder side-rails on installation by inserting appropriate spacer shims and washers between bracket parts and lever assemblies. The sliding leg may be made from material of sufficient size and strength and may be shaped so one end view would reveal a simple capital letter "L" form to allow convenient slidability along side-rails of various widths. This invention may be manufactured, installed and used without complicated machinery and highly skilled labour.
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