GB274832A - Lifting jack - Google Patents

Abstract

274,832. Nilson, L. D. July 26, 1926, [Convention date]. Jacks. -A lever lifting-jack comprises a toothed sector fixed to the frame of the jack, a pivoted lifting arm to which a pawl supporting frame is pivoted, the pawl frame carrying a lifting pawl on a separate pivot and engageable with the sector, and means for actuating the lever arm. The frame is formed of triangular plates 16 spaced apart and mounted on the axles 12 of wheels 20 and also carrying a toothed sector 30. The operating handle 84, Fig. 3, is pivotally mounted on the rear axle 12. The crutch 40 has a pivoted extension head 54 and is connected to the frame by a parallel motion linkage 48, 36 of which the lower arm 36 forms the lifting lever. The lever 36 carries on a pivot 62 a pawl carrying frame 64 the upper end of which is connected by links 94 to the operating handle. The lifting pawl 72 is mounted on a pivot 66 on the frame 64 and the locking pawl 68 is mounted on the frame pivot 62. The pawls are connected by a spring 78 which tends to keep them in engagement with the toothed sector. To raise the load, the operating handle is moved downwards and through the links 94 pulls the pawl frame 64 causing it to fulcrum on the pivot of the lifting pawl 72 and raise the lifting arm 36 and crutch, the locking pawl 68 moving up and engaging the next tooth of the sector. Upward movement of the handle then causes the lifting pawl to engage the next higher tooth ready for the next lifting movement.. To lower the load, pawl disengaging mechanism is brought into action. A cam-engaging lever 106 mounted on the crutch pivot 38 is connected by cables 108 passing round pulleys 112 to a trigger 120 on the operating handle. By pulling the trigger over the dotted line position, Fig. 3, the lever 106 is brought into the operative position with respect to cams 70, 76, Fig. 5, on the pawls and by manipulating the operating handle the pawls are engaged alternately with the sector and the load lowered. When the load is released from the crutch, springs 116 forming part of the cable mechanism disengage, both pawls so that a quick return to the starting position can be effected.