Retractable aircraft step

A retractable aircraft step for attachment to an airframe, said step comprising:

• a support member;
• a step member connected to said support member and movable from a retracted position to an extended position wherein said step member is engaged with said support member and positions a tread surface on said step member generally under and adjacent to a doorway in said airframe;
• linkage means interconnecting said step member and said support member for moving said step member between said positions, said linkage means including first link means pivotally connected to said support member and said step member, second link means pivotally connected to said support member at a point spaced from said pivotal connection of said first link means to said support member, said second link means being pivotally connected to said step member at a point spaced from the pivotal connection of said first link means to said step member;
• said pivotal connection between said first link means and said step member is displaced in the direction of movement to extend said step member from its retracted position from the point at which said pivotal connection between said first link means and said step member is over center and on a line extending between the pivot axis of said first link means and said support member and the pivot axis of said second link means and said step member when said step member is in the extended position so that a load placed on said tread surface biases said step member into a stable load bearing position in engagement with said support member.

An aircraft step module for attachment to the exterior of an aircraft fuselage, said step module comprising:

• a body member including a recess formed therein and a mounting surface engageable with said fuselage;
• a step member connected to said body member and movable between a retracted position wherein said step member is substantially disposed in said recess and an extended position wherein said step member extends generally under and adjacent to a doorway in said fuselage;
• linkage means interconnecting said step member and said body member for moving said step member between said positions, said linkage means including a first pair of links pivotally connected at one end, respectively, to said body member and at their opposite ends, respectively, to opposite lateral sides of said step member at a point intermediate the ends of said step member, a second pair of links pivotally connected at one end, respectively, to said body member at a point spaced from said pivotal connection of said first pair of links to said body member, and at their opposite ends, respectively, to said step member at a point spaced from said pivotal connection of said first pair of links to said step member and adjacent one end of said step member opposite a nosing of said step member;
• and
• a beam mounted on said step member and including opposed end portions forming the pivotal connections between respective ones of said second pair of links and said step member, said end portions being elastically deflectable at an interference point on the path of rotation of the pivotal connections between said second pair of links and said step member whereby said interference point may be passed to permit said step member to be retracted and extended and wherein said step member is biased in the retracted position.

A step module for attachment to a transport vehicle, said step module comprising:

• a support member for supporting said step module on said vehicle;
• a step member connected to said support member and movable between a retracted position and an extended position wherein said step member extends generally under and adjacent to a doorway of said vehicle;
• linkage means interconnecting said step member and said support member for moving said step member between said positions;
• said linkage means including first link means pivotally connected to said support member and said step member and second link means pivotally connected to said support member and at said step member at respective points spaced from said pivotal connections of said first link means to said support member and said step member, respectively, said support member, said first and second link means and said step member forming a four bar linkage, one of said first and second link means and said step member being of incorrect length to permit unrestricted rotation of said one link means with respect to said support member between said retracted and extended positions of said step member;
• and
• a pivot member forming at least part of the pivotal connection between one of said link means and one of said step member and said support member, said pivot member being elastically deflectable to permit rotation of said one link means with respect to said support member between said retracted and extended positions of said step member and to bias said step member toward said retracted position.