GB1307081A - Safe load apparatus for a material handling device - Google Patents

Abstract

1307081 Safe-load indicators BALDWINLIMA-HAMILTON CORP 17 Feb 1970 [17 Feb 1969] 7483/70 Heading B8B [Also in Division E1] A safe-load indicator for a material handling device is shown applied to a mobile crane 10 with an extensible boom 14 mounted for luffing at pivot pin 20 on a support 18 arranged for slewing on a vehicle 12. The indicator includes a boom orientation responsive linkage 46 with a support arm 62 pivoted at 70 on boom base section 16 and having a horizontal leg 63 maintained always horizontal by a parallelogram effect due to link 67 pivoted thereto and to the support 18. The linkage 46 comprises first and second parallel arms 72, 74 respectively pivoted at 68, 70 to the leg 63 at their lower ends, and at 76, 78 at their upper ends to opposite ends of a horizontal leg 80 of a T cam follower bar assembly 82 including a ventical leg 84 with a slot 86 therein. The slot 86 receives a roller 87 which is part of a boom extension responsive assembly 50. comprising as spring, motor 104 tensioned to reel in a cable 108 attached at its free end to boom head block 28. Bevel gears 112, 114 drive a screw-shaft 116 on which is threaded a. travelling block 120 carrying the roller 87. The linkage 46 thus pivots one way. in response to raising of the boom 14 and in the opposite direction in response to extension of the boom. 14, the position of the linkage being indicative of the maximum permissible moment allowable. One or other of. two potentiometers 142, 144, adjusted from the linkage 46 by drive links 132, 158, is selected by a switch 154 to correspond to operation with or without outriggers and the selected output, representing the allowable load moment, is passed to an indicator assembly 44 where it is compared with the load moment; measured by a strain gauge 40 connected to pivot pin 23 of luffing cylinder 22. A meter 58 is calibrated to show percentage of the permissible moment and a light 60 warns of an overload condition. A linkage movement modifying mechanism 48 is connected by a push-pull cable 124 to a cam bar 122 pivoted to a block 118 and contacted on its, lower face by a roller 121 on the travelling block120. The lower face of the cam bar 122 is cut to correspond to the required permissible load moment curve, Fig. 2 (not shown), and may thus take into account the crushing strength of the boom 14 when operating at a small working radius, as well as the normal tipping effect.