Patent ID: 6070699
Filing Date: 2000-06-06
Classification: B66F

Abstract:
A hydraulic platform lift, comprising:(a) a parallelogram chassis including a sub-frame, a top-frame and first and second lifting arms displaced from one another along and extending between said sub-frame and top-frame in a generally parallel relationship to one another, each of said first and second lifting arms having a pair of opposite ends pivotally coupled about respective pivot axes to said sub-frame and top-frame so as to support said top-frame above said sub-frame and in a generally parallel relationship therewith for undergoing movement toward and away from said sub-frame between retracted and extended positions relative to said sub-frame;(b) a first projection attached respectively on said first lifting arm adjacent to the one of said opposite ends thereof at which said first lifting arm is pivotally coupled to said sub-frame, said first projection projecting from said one opposite end of said first lifting arm and having a first articulation point spaced from and a second articulation point coaxial with said pivot axis about which said one opposite end of said first lifting arm is coupled to said sub-frame;(c) a hydraulic cylinder having a pair of opposite ends being movable relative to one another toward and away from one another, one of said opposite ends of said hydraulic cylinder being pivotally connected to said sub-frame at a stationary pivot axis thereon, the other of said opposite ends of said hydraulic cylinder being pivotally connected to said first projection on said first lifting arm at said first articulation point thereon such that relative movement of said opposite ends of said hydraulic cylinder toward and away from one another causes pivotal movement of said first and second lifting arms relative to said sub-frame and top-frame and movement of said top-frame between said extended and retracted positions relative to said sub-frame; and(d) a tie member having a pair of opposite ends and extending between and pivotally connected at one of said opposite ends of said tie member to said sub-frame at said stationary pivot axis of said hydraulic cylinder with said sub-frame and at the other of said opposite ends of said tie member with one of said first lifting arm at said pivot axis of said one end thereof and said first projection at said second articulation point thereon such that a lifting force produced by said hydraulic cylinder is not transferred to said sub-frame but instead is shunted via said tie member onto said first projection on said first lifting arm whereby loading of said sub-frame via said hydraulic cylinder is substantially neutralized.