GB1202528A - Control system for civil engineering machines - Google Patents

Abstract

1,202,528. Jib cranes. PRIESTMAN BROS. Ltd. 9 Oct., 1967 [27 Oct., 1966] No. 48277/66. Heading B8B. [Also in Division E1] A control system for a crane or an excavator comprises a joystick which is universally displaceable from a central upright neutral position, displacement of the joystick in one direction or the other away from a central vertical plane controlling a rope drum to pay out or take in the rope, respectively, and displacement of the joystick in one direction or the other away from a second vertical plane, perpendicular to the first plane, causing luffing of a boom of the crane or excavator, displacement of the joystick away from the second plane being inoperative to cause luffing unless a spring-loaded finger piece mounted on the joystick is held depressed. The joystick 1 is similar to that described in Specification 1,135,458. When it is displaced it puts air lines 2 and 6 selectively in communication with lines 3, 5, 7, 9, the lines 2 and 6 being supplied from compressed air sources 4, 21. Line 3 leads to a clutch of a first rope drum, e.g. for a drag line of an excavator or a hoist rope of a grab, and line 5 leads to a brake for the first rope drum. Lines 7 and 9 lead to solenoid operated spool valves 8 and 10 controlled by a two way electrical selector switch 11 on the control panel and energized from a 24V D.C. source 12. In the open position of the switch 11 lines 7, 9 communicate with lines 14, 15 leading respectively to a clutch and a brake of the luffing rope drum, and in the closed position of the switch 11 lines 7, 9, communicate with lines 16, 17 leading respectively to a clutch and a brake for a second rope drum, e.g. for a bridle or a hold rope for a grab. A light 18 warns when the switch 11 is closed. The line 6 leads from the source 21 through a solenoid operated spool valve 19 which when unenergized vents the line 6 to atmosphere so that the joystick cannot operate either the luffing rope drum or the second rope drum. However, the spring-loaded finger piece formed by a push button can be depressed to close an electrical switch 22 to energize the valve 19. A light 25 on the push button also warns when the switch 11 is closed to indicate that the second rope drum may be operated after closing the switch 22. Cutout switches 27, 28 for minimum and maximum luffing radius and a cutout switch 29 opened by a gear change from a low speed position are provided. In operation two motions can be proportionately selected simultaneously by displacing the joystick at an angle intermediate the two planes, and by closing the switch 11 other two motions may be selected. With the switch 11 open the luffing rope drum can only be operated by closing the switch 22.