GB303993A - Improvements in or relating to lifting jacks - Google Patents

Abstract

303,993. Machray, G. Dec. 10, 1927. Jacks and the like. -A wheeled trestle jack for lifting aircraft &c. comprises a lifting frame slidably arranged in a base frame and provided with gearing which effects the sliding movement and also brings the wheels into and out of action as required. The base frame 1 normally rests on the ground and has vertical guides 2 at each end in which the lifting frame 9 slides. Vertical screws 3 are mounted at each end of the base frame and are fitted with nuts 12 pivoted in bridge-pieces 10 secured to the lifting frame by pegs and holes 14. The screws are rotatable by ratchet levers 6 operating ratchet wheels fixed on the screws, and the ratchet levers may be linked together for simultaneous operation. Handles 19 are provided at the lower ends of the screws for rapid adjustment when the bridge-pieces are disconnected. The lifting frame may be temporarily supported on counterweighted pivoted arms 15 or on bars, not shown, placed across the upper members of the base frame, to facilitate the setting of the nuts and bridge-pieces. In operation, the lifting frame is supported by turning inwards the arms 15 and the bridge-pieces are adjusted and pegged to the frame. The ratchet handles are then rocked to rotate the screws and raise the lifting frame, the arms 15 swinging to the free position and the lifting frame engaging and raising the load. When the load has to be traversed, the lifting frame is lowered until its lower ends rest on pivoted carriages 21 mounted on the base frame and carrying wheels 20, so that the wheels now carry the load and the jack can be moved bodily. The gearing and other parts of the mechanism may be modified. The lifting frame may carry a pivoted load-engaging frame having at its lower end an adjustable screw connection to the lifting frame.