Patent ID: 6692217
Filing Date: 2004-02-17
Classification: A61G,B60P,Y10S

Abstract:
A hydraulic circuit in a wheelchair lifting platform, comprising:a foldable platform structure for carrying a passenger; a moveable rollstop gate pivotally connected to the platform structure raisable for the safety of the passenger; a fluid reservoir; a primary hydraulic lifting cylinder having a primary hydraulic lifting cylinder main port and having a primary hydraulic lifting cylinder auxiliary drainage port in fluidic communication with said fluid reservoir for lifting the platform structure with the primary hydraulic cylinder; an unfold valve having a first unfold valve port in fluidic communication with said primary hydraulic lifting cylinder main port, said unfold valve further having a second unfold valve port and a third unfold valve port, and said unfold valve having a first unfold valve position and a second unfold valve position for unfolding the platform structure with the primary cylinder; a bridging valve having a first bridging valve port in fluidic communication with said second unfold valve port and said third unfold valve port, said bridging valve further having a second bridging valve port, and said bridging valve having a first bridging valve position and a second bridging valve position; a secondary hydraulic rollstop cylinder having a secondary hydraulic rollstop cylinder main port in fluidic communication with said second bridging valve port, and said secondary hydraulic rollstop cylinder further having a secondary hydraulic rollstop cylinder auxiliary drainage port in fluidic communication with said fluid reservoir for moving the rollstop gate with the secondary cylinder; a down valve having a first down valve port in fluidic communication with said second bridging valve port, said down valve further having a second down valve port in fluidic communication with said fluid reservoir, and said down valve having a first down valve position and a second down valve position; a pump having a pump inlet in fluidic communication with said fluid reservoir, and said pump further having a pump outlet in fluidic communication with said first down valve port, said second bridging valve port, and said secondary hydraulic rollstop cylinder main port; wherein placing said unfold valve in said first unfold valve position, said down valve in said first down valve position, and said bridging valve in said first bridging valve position and de-energizing said pump actuates fluid flow from said primary hydraulic lifting cylinder to said reservoir; wherein placing said down valve in said first down valve position and said bridging valve in said first bridging valve position, placing said unfold valve in said second unfold valve position and de-energizing said pump actuates fluid flow from said primary hydraulic lifting cylinder to said reservoir; wherein placing said bridging valve in said second bridging valve position and said unfold valve in said second unfold valve position, placing said down valve in said first down valve position and de-energizing said pump prevents fluid flow from said primary hydraulic lifting cylinder and actuates fluid flow from said secondary hydraulic rollstop cylinder; and wherein placing said bridging valve in said second bridging valve position, said down valve in said second down valve position and said unfold valve in said second unfold valve position and energizing said pump actuates fluid flow into said primary hydraulic lifting cylinder.