GB1458506A - - Google Patents

Abstract

1458506 Luffing arm apparatus SIMON ENG DUDLEY Ltd 5 Feb 1974 [21 Feb 1973] 8526/73 Heading B8H In an apparatus wherein a cage is mounted on an articulated luffable boom, a mechanical interlock prevents the cage from reaching an unstable condition and also slows down the movement of the boom as it approaches said unstable condition or the actuators, for effecting the luffing, approach the limit of their travel. The boom comprises a first section 10 pivotally mounted on a turntable 9, itself mounted on a vehicle (not shown), a second section 11 pivotally mounted on the first section and an auxiliary boom 12 pivoted to the second section and pivotally mounting the cage 13. Levelling links 14, 17, 19 extending parallel with the respective boom sections 10, 11, 12, maintain the cage level for all inclinations of the boom sections and hydraulic actuators 20, 20a effect the movements of the boom sections. The actuator 20a operates a rod 21 connected to the second boom section. A rod 22 connected to the rod 21 is pivoted at 23 and through links 24, 25 transmits the movement of the second boom section to a common link 26 to which the levelling rod 14 is also connected to transmit the movement of the first boom. The link 26 is coupled by a further link 31 to an arm 32 pivoted on the first boom section and coupled by a rod 34 to a further arm 32a also pivoted on the first boom section. The rod 34 carries stops A, B, C, D which are displaced therewith on movement of the first or second boom section singularly or jointly so that when the cage approaches an unstable position they engage control levers 50, 51, controlling the movement of the first and second boom sections respectively, to move same to a non-operative position. A further link 27, coupled to the common link 26, is coupled to an arm 28 pivoted on the first boom section and having abutments 29, 29a for engagement with an arm 35 at the extremes of operation of the actuator 20a. The arm 35 is coupled by a rod 38 to an arm 36 spring biased into a neutral position. Stops E, F are mounted on the rod 38 and act on control lever 51 to move same to a non-operative position as the actuator 20a approaches its extreme positions. A further arm 39, also spring biased into a neutral position and pivoted about a common pivot with arm 36, is coupled by a rod 41 to an arm 40 pivoted about a common pivot with the arm 32a. The levelling link 14 carries stops X, Y which in the extreme positions of the actuator 20 engage the arm 39 to move stops G, H on the rod 41 into engagement with the control lever 50 to move same into a non-operative position