| 摘要 |
978,822. Safe load indicators for jib cranes. R. L. AITKEN. Feb. 6, 1963 [Feb. 9, 1962], No. 5096/62. Heading B8B. When the maximum safe load of a jib crane is approached switches 26, 27, Fig. 1, are closed by a lever 11, the position of which is controlled by the angle of the jib of the crane through a link 12 and by the weight of the load which acts through a link 1. The load on the link 1 tends to raise the lever 11 against the resistance of an adjustable spring 7. Angular changes of the jib turn a cam 13 through links 12, 12a and a shaft 14 so that a lever 15 with a camfollower 16 pivots about a pin 17 to move a crosshead 18, which forms a second pivot for the lever 11, in a slot 20. One of the switches is operated before the other to provide a warning of the approach of the maximum safe load. In a second embodiment, Fig. 2, a bell-crank 49 operates switches 60, 61 and is pivoted about a pin 50 by the load which acts through links 31, 32, 51 and a crosshead 54. Change of jib angle causes rotation of a cam 43 through links 42, 42a and a shaft 44. This rotation is transmitted to the bell-crank 49 by a cam-follower 46, a lever 48 and a control wire 56 which slides the crosshead 54 on the bell-crank 49 against the force of a spring 55. The switches may operate audible or visible warning systems and the coil springs 7, 37 may be replaced by compression springs, compressed gas, or rubber blocks. |
