GB808438A - Mechanism for controlling the direction of rotation of a rotatable element - Google Patents

Abstract

808,438. Vehicle power steering. CLEVELAND PNEUMATIC TOOL CO. May 10, 1956, No. 14559/56. Class 79(5) [Also in Group XXXIII] Mechanism for controlling the direction of rotation of a rotatable element, e.g. a steerable aircraft undercarriage leg comprises a support element for the rotatable element, first and second cylinder members and associated fluid actuated piston members, a mounting portion on each member extending generally in the same direction, each cylinder mounting portion being connected to one of said elements and each piston mounting portion to the other element, at least one cylinder pivot and its associated piston pivot being equally spaced from the axis of rotation of the rotatable element, and stabilizing means between the cylinder members to prevent uncontrolled rotation thereof. In Figs. 2 and 3 twin-aircraft ground wheels are mounted at the foot of an inner cylinder 11 forming a shock absorber with an outer cylinder 10. A collar 14 is rotatably mounted on the cylinder 10, and is connected to the cylinder 11 by a scissors linkage 16, so that the wheel may be steered by rotating collar 14. Two mounting portions 19 on cylinders 17, 18 are pivoted at 22 to lugs 21 on cylinder 10, and two mounting portions on the piston rods 26 are pivoted at 31, 32 to lugs 29 on the collar 14. The cylinders have fluid pressure ports 33 and 34. The collar is rotated by admitting fluid under pressure to the port 33 of one cylinder and the port 34 of the other. At some point in the steering range, pivot 32 will be aligned with its associated piston rod pivot 22, whereupon the cylinder 18 will be free to swing about these pivots. To prevent this a bar 36 is pivoted to the cylinders at 37, 38. Similarly, when pivot 31 is aligned with its associated piston rod pivot 22, the cylinder 18 and bar 36 prevents cylinder 17 from swinging. The pivots 37, 38 are equidistant from the associated pivots 22. In Fig. 9, the arrangement is such that when the wheel is in the neutral position, the associated cylinder and piston rod pivots of cylinder 119 coincide at 136, and those of cylinder 121 at 138 and both cylinders are free to swing. To prevent this, a bar 143 is pivoted to the cylinders at 144, 146, and is formed with a tooth 147 engaging a notch 148 formed in the collar. Each cylinder rotates relatively to the fixed cylinder 10 with half the angular velocity of the collar, and the tooth 147 and notch 148 are located half way between the axis of bar 143 and the axis of the collar, whereby the tooth and notch have the same velocity when the wheel is turned from the neutral position, and their successive positions are shown in chain dot lines in Fig. 9. Fig. 10 (not shown) shows a modification in which the two pivots associated with cylinder 119 are further from the axis 137 than those of cylinder 121, though the pivots of each associated pair are equidistant from axis 137. Co-operating abutments on the collar and fixed cylinder limit the range of steering.