GB1202530A - Control systems for civil engineering machines - Google Patents

Abstract

1,202,530. Steering and controlling vehicles. PRIESTMAN BROS. Ltd. 12 Oct., 1967 [27 Oct., 1966], No. 48279/66. Heading B7H. [Also in Divisions B8 and E1] A control system for a crane or an excavator comprises a joystick which is universally displaceable from a central upright neutral axis, displacement of the joystick in one direction or the other away from a first central vertical plane controlling a hoist rope drum to pay out or take in the hoist rope, respectively, and displacement of the joystick in one direction or the other away from a second central vertical plane, perpendicular to the first plane, causing either slewing in one sense or the other, respectively, or travelling forwards or backwards, respectively, depending upon the position of a slew/ travel selector. The system includes means for automatically rendering displacement of the joystick from the first plane to cause the hoist rope to be taken in inoperative when the selector switch is set to travel. The joystick 10 is similar to that described in Specification 1,135,458 and when it is displaced it puts air lines 11, 16 selectively in communication with lines 12, 14, 17, 19, air being supplied by a source 28. Lines 12, 14 lead respectively to a clutch 13 and a brake 15 of the hoist rope drum, and lines 17, 19 lead to clutches 18, 20 for selectively driving the main drive shaft in opposite directions. A button 21 on the joystick 10 when depressed closes an electric switch 22 to energize a solenoid operated spool valve 23 controlling the air supply to a gear change selector 29 so that when the switch 22 is closed a higher gear is engaged for driving the main drive shaft. The latter may be selectively connected by an air cylinder 32 via dog clutches to a slewing pinion or to crawler tracks, under the control of a fourway selector having a rotatable cam 38 adapted to operate spring-biased valves 40 . . . 43. Air is supplied to the valves 40, 41, 42 through lines 44, 45 via a spool valve 46 and to the valve 43 through lines 47, 48. When the valve 41 is operated both tracks may be driven, while operation of either of the valves 40, 42 respectively permits the right- or left-hand track to be driven. Since when the machine is travelling, the valve 43 is not operated, the slew brake 83 is then always applied. A valve 64 is open for air to pass to the cylinder 32 to engage the travelling clutch, and to a manually controlled normally closed spool valve 70 controlling air flow to an automatic change-over valve 71 leading to the line 11. Consequently, when the machine is travelling unless a button 72 is depressed to open the valve 70 no air will pass to the line 11 and therefore the hoist rope drum clutch 13 and brake 15 cannot then be operated, but air will reach the line 16 via a line 73 so that the clutches 18, 20 can be operated. The track brakes can be engaged at any time during travelling by movement of a lever which closes the valve 46 so that no air can pass to release the brakes. When the valve 43 is operated the cylinder 32 is moved to engage the slewing clutch, and air will only pass to the line 16 through the line 75 when a low gear is being selected by the selector 29. The slewing brake 83 will be released but it can be applied by movement of a lever which closes a valve 82. In operation two motions can be proportionately selected simultaneously by displacing the joystick at an angle intermediate the two planes, and the hoist rope drum can only be operated when travelling, e.g. in case of emergency to drop the load, by depression of the button 72.