Patent ID: 6308916
Filing Date: 2001-10-30
Classification: B64C,F15B,F16F

Abstract:
A dual mode positioner filled with hydraulic fluid for positioning an aircraft landing gear axle beam, the axle beam being pivotally attached to a shock strut configured for attachment to an aircraft in a manner that permits retraction, the aircraft having a hydraulic system with a high pressure supply and a low pressure return, comprising:(a) a first hydraulic line;(b) a second hydraulic line;(c) a hydraulic actuating device comprising,a housing that defines a cavity with an aperture at one end and a first end configured for pivotal attachment to the shock strut,a basic piston received within said cavity protruding through said aperture and having a second end configured for pivotal attachment to the axle beam, said basic piston being sealed against said housing and defining a first hydraulic area, and,a floating piston disposed inside said cavity and having one end sealed against said housing thereby dividing said cavity into a first sub-cavity and a second sub-cavity and defining a second hydraulic area therebetween greater than said first hydraulic area, said first sub-cavity being in fluid communication with said first hydraulic line and said second sub-cavity being in fluid communication with said second hydraulic line, said floating piston and said basic piston being translatable in a common direction relative to said housing and relative to each other;(d) a control valve connected to said first and second hydraulic lines and having a taxi configuration wherein said second hydraulic line is in fluid communication with the high pressure supply and said first hydraulic line is in fluid communication with the low pressure return thereby applying a greater pressure to said second sub-cavity than said first sub-cavity which contracts said hydraulic actuating device by forcing said basic piston away from said floating piston into engagement with a forward portion of said floating piston, and by forcing said floating piston away from said aperture into engagement with a rearward portion of said housing, said basic piston being incrementally translatable into and out of said aperture relative to said housing while in said taxi configuration, anda retract configuration wherein said first hydraulic line is in fluid communication with said high pressure supply and said second hydraulic line is in fluid communication with said low pressure return thereby applying a greater pressure to said first sub-cavity than said second sub-cavity which extends said hydraulic actuating device by forcing said floating piston toward said basic piston into engagement with a rearward portion of said basic piston and by forcing said basic piston out said aperture into engagement with a forward portion of said housing;(e) a hydraulic shunt line in fluid communication with said first hydraulic line and said second hydraulic line wherein incremental translation of said basic piston both into and out of said aperture while in said taxi configuration causes flow of hydraulic fluid through said shunt line;(f) a hydraulic damper device disposed in said hydraulic shunt line configured to provide a predetermined amount of damping during said incremental translation while in said taxi configuration, wherein said hydraulic damping device is a pressure relief valve; and,(g) a one way valve between said high pressure supply and control valve that permits flow of hydraulic fluid only into said control valve.