GB1163073A - Improvements relating to a Backhoe. - Google Patents

Abstract

1,163,073. Scoop-arm machines. OKLAHOMA STATE UNIVERSITY OF AGRICULTURE & APPLIED SCIENCE. 5 Sept., 1967, No. 40599/67. Heading E1F. A backhoe mounted on a tractor 10 comprises a boom 12 including a lift arm 16 pivoted by a hydraulic jack 22 and a crowd arm 18 pivoted by a hydraulic jack 24 and provided with a bucket 20 pivoted by a hydraulic jack 26, the boom movements during a digging cycle being controlled automatically by a hydraulic circuit including means which are responsive to over pressure in the jack 24 to automatically operate the jack 26 to cause decrease in the bucket digging attitude and which are responsive to simultaneous overload-pressures in the jacks 24, 26 to automatically operate the jack 22 to cause decrease in the lift arm digging attitude. The hydraulic circuit is illustrated in Fig. 2 (not shown) and the operation is started when the lift arm 16 is low and the crowd arm 18 and the 'bucket 20 extends outwardly in the maximum digging attitude. To start digging the operator pulls the lever for the crowd valve 28A towards himself to move the crowd arm inwards. A valve (40) senses overload in the jack 24 and sends a signal (51) to a valve (30) controlling the jack 26, and a valve (46) senses overload in -the jack (26) and, if signal (51) is still present, sends a signal (54) to a valve (34) controlling the jack 22. Fig. 7 (not shown) illustrates a hydraulic circuit for automatic digging and retraction control, the retraction cycle being started by the operator moving the valve 28A in the opposite direction which also actuates a valve 68. The increase in pressure in the jack 24 as the crowd arm moves outwardly is monitored by a valve (78) which sends a signal (57) to the valve (30) controlling the jack 26 to maintain the bucket substantially level as the crowd arm is moved. A valve 64 is operated by a cam on the lift arm 16 and sends a signal (S6) or (S9), depending on whether the lift arm is too high or too low to the valve (34) controlling the jack 22. Hydraulic jacks (90, 92) are used to swing the boom to either hand of the tractor the direction being chosen by a manually operated valve (96). With the lift arm at its correct height when the crowd arm reaches its outermost position the terminal pressure in the jack 24 is sensed by a valve (80) which sends a signal (S8) to a valve (94) controlling the jacks (90, 92), the operator subsequently stopping the swinging of the boom by moving the valve 28A to its centre position. Fig. 8 (not shown) illustrates a hydraulic circuit for automatic control for a full cycle of operation. Two valves 108, 110 which designate a dump position and a dig position are operated by adjustable cams 112, 114 on the boom support base 116. When the boom reaches the dump position the appropriate valve, e.g. valve 108 is operated to send a signal (S10) to the valve (30) controlling the jack 26 to empty the bucket, and to the valve (94) to stop the boom swinging. Valve (132) sense when the bucket has finished its emptying movement and sends a signal (S11) to the valve (94) to swing the boom back to the dig position at which the other valve 110 is actuated to send a signal (S12) to stop the boom swinging and if required to lower the boom. A manually operated valve (140) permits the operator to decide whether the boom should be lowered or not at the end of the cycle.