Oleopneumatic suspension with variable throttle orifices, especially for aircraft landing gear

An oleopneumatic suspension for use in an aircraft landing gear, comprising:

• two hollow movable members which are movable relatively to each each other, one of said movable members being movable within said other of said movable members, said one of said movable members being adapted for coupling to the frame of the aircraft and the other of said movable members being coupled to a landing wheel of the aircraft;
• piston means operatively intercoupled between said two movable members and including first and second valves, said piston means having an equilibrium position, said piston means together with said one movable member separating the other of the two hollow members into at least first, second and third variable volume chambers, said first chamber being enclosed by said piston means and said one hollow movable member, said second chamber being enclosed by said piston means and said other hollow movable member, and said third chamber being enclosed by said piston means and said one and said other hollow movable members, the volume of said second and said third chambers being variable in opposition to each other, said three chambers each containing hydraulic liquid and said piston means having its face in contact with said liquid;
• a guide rod fixed to a base of said other movable member;
• said first valve having an opening and including first throttle means between said first chamber and said second chamber, said first throttle means being oriented for providing for free flow in a first direction of the hydraulic liquid from said first chamber to said second chamber through said first valve and throttling the hydraulic liquid passing during its flow from said second chamber to said first chamber through said piston means;
• a second valve having an opening and including second throttle means between said second chamber and said third chamber, said second throttling means being oriented for providing for free flow in a second direction of the hydraulic liquid opposite to said first direction from said second chamber to said third chamber and throttling the flow of the hydraulic liquid passing during its flow from said third chamber to said second chamber through said piston means;
• said first throttling means cooperating with the opening of said first valve to provide throttling in a compression phase of said two hollow movable members and said second throttling means cooperating with the opening of said second valve to provide throttling in an extension phase of said two hollow movable members;
• said first throttling means including a first throttling orifice cooperating with said first valve opening, and said second throttling means including a second throttling orifice cooperating with said second valve opening, said first throttling orifice having a cross-sectional opening greater than the cross-sectional opening of said second throttling orifice;
• by-pass groove means, including one by-pass means in said second chamber and another by-pass means in said third chamber and each of said by-pass means having a portion beginning substantially proximate to said piston means when in its said equilibrium position;
• said by-pass groove means including a pair of grooves in the outer face of said guide rod, one of said pair of grooves being longer than the other, said longer groove extending past said piston means and connecting said first and said second chambers when said piston means is in said neutral position, and said one of said two by-pass grooves being shorter and being only in said second chamber in said equilibrium position;
• and
• each of said grooves having an effective section which varies in dependence on the position and the direction of displacement of said piston means in the outer of said two hollow movable members so that over at least one predetermined distance on both sides of said equilibrium postion of said piston means, under load or in the absence of an external load being applied, said first and said second grooves which provide throttling in the compression and extension phases have cross-sections which are respectively greater than those of said first throttling orifice ensuring throttling in the compression phase and said second throttling orifice ensuring throttling in the extension phase for the remainder of the distance which said piston means moves;
• whereby the suspension is operative in an extension phase or a compression phase so that in the extension phase any displacement out of the equilibrium position will be braked by throttling through said second valve and said other by-pass means in said third chamber, and in the compression phase any displacement out of the equilibrium position will be braked by throttling through said first valve and said one by-pass means in said second chamber.