GB837891A - Improvements in or relating to aircraft undercarriages - Google Patents

Abstract

837,891. Vehicle power steering. BRITISH MESSIER Ltd. July 11, 1956 [July 20, 1955], No. 21053/55. Class 79(5) In an aircraft steerable undercarriage having a rotatable member 112 carrying landing wheels and supported for a limited range of rotation by a fixed element 111 secured to the airframe (not shown), the member 112 is connected to a member capable of rotating it by a set of two driving abutments for each direction of rotation, the sets comprising steps 167, 168 on one member and roller-carrying arms 137, 138 pivoted to the other member, the arms being movable between positions in which the rollers 149, 150 engage the steps and are clear of the steps. As further shown a collar 163 keyed to the member 112 has the steps 167, 168 and the rollers 149, 150 are mounted by pins 147, 148 on the arms 137, 138, the pins also carrying further rollers 153, 154 engaging slots 173, 174 having end seats 175 formed in flanges 171, 172 secured to the element 111. The arms 137, 138 are interconnected by a spring 166 and are pivoted by pins 139, 140 to bosses 133, 134 on a flange 120 on an annular member 119 rotatably mounted on the member 112. Spigots 125 on the flange 120 and a further flange 121 on the member 119 support a power cylinder 128, the piston rod 130 of which is pivoted to a flange 132 on the element 111. Power steering is effected by axial movement between the rod 130 and cylinder 128 whereby the cylinder is rotated relatively to the element 111, the cylinder being connected to a control valve (not shown) of the follow-up type for centralizing purposes, the valve being connected to a pilot's control (not shown) having a cam adapted to cooperate in the extreme positions of the control with a micro-switch connected with a limiting valve in the pressure line leading to the control valve. Such rotation causes similar rotation of the member 119 resulting through a thrust on one of the arms 137, 138 and co-operation between one of the rollers 149, 150 and its associated step 167 or 168 in rotation of the member 112 and hence steering the aircraft landing wheels. When the aircraft is being towed through a bar (not shown) connected to the member 112, the member 112 can be rotated beyond the normal range of rotation (which may be 35 degrees from the straight ahead position) by one of the rollers 153, 154 being forced into one of end seats 175 thus permitting the associated step 167 or 168 to pass under the roller 149 or 150.