345B Series II Excavator Hydraulic System SmartBoom Hydraulic System Caterpillar


SmartBoom Hydraulic System
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1.1. SmartBoom Control in the INACTIVE Position
2.2. BOOM RAISE Operation
3.3. High Speed Operation
4.3. Low Speed Operation
5.2. BOOM LOWER Operation
6.3. Low Speed Operation
7.1. SmartBoom Control in the DOWN Position
8.1. SmartBoom Control in the UP AND DOWN Position

SmartBoom Control in the INACTIVE Position

BOOM RAISE Operation

High Speed Operation




Illustration 1g00921842

(1) Boom cylinder

(2) Line

(3) Line

(4) Check valve

(5) Spool

(6) Boom lowering control valve

(7) Relief valve

(8) Manifold

(9) Line

(10) SmartBoom control valve

(11) Check valve

(12) Pressure switch

(13) Pilot line

(14) Parallel feeder passage

(15) Return passage

(16) Line

(17) Main control valve

(18) Pilot line

(19) Port

(20) Pilot line

(21) Pilot line

(22) Port

(23) Boom I control valve

(24) Check valve

(25) Boom II control valve

(26) Check valve

(27) Pilot line

(28) Parallel feeder passage

(29) Return passage

(30) Port

(31) Pilot line

(32) Upper pump

(33) Pilot pump

(34) Pilot control valve

(35) Lower pump

(36) Return line

A BOOM RAISE operation at high speed is accomplished when the oil delivery from both upper pump (32) and lower pump (35) is supplied to the head end of boom cylinders (1). Boom I control valve (23) and boom II control valve (25) operate during the high speed operation. A BOOM RAISE operation at low speed is accomplished when the oil delivery from only upper pump (32) is supplied to the head end of boom cylinders (1). Boom II control valve (25) does not operate during a low speed operation.

The oil delivery from upper pump (32) flows through parallel feeder passage (28) in main control valve (17) to boom I control valve (23). The oil delivery from lower pump (35) flows through parallel feeder passage (14) in main control valve (17) to boom II control valve (25).

When the joystick for the boom is moved to the full BOOM RAISE position, the pilot oil flows from pilot control valve (34) through pilot line (31). The pilot oil flow then divides into two flow paths. Part of the pilot oil flows to pressure switch (12). The remainder of the pilot oil flows through pilot line (21). The oil then divides into two additional paths. Part of the pilot oil flows through pilot line (20) to port (19) of main control valve (17). The remainder of the pilot oil flows through pilot line (13) and the pilot oil divides into two additional paths. Part of the pilot oil flows through pilot line (18) to manifold (8). The remainder of the pilot oil flows through pilot line (27) to port (30) of main control valve (17) .

The pilot oil flow from port (30) shifts boom I control valve (23) upward. The oil delivery from upper pump (32) in parallel feeder passage (28) flows through check valve (26) and boom I control valve (23) to line (9). The oil flows from line (9) through manifold (8) to boom lowering control valve (6). The oil flows through boom lowering control valve (6) through check valve (4) to line (2). Then, the oil flows through line (2) to the head end of boom cylinders (1) .

The pilot oil flow from port (19) shifts boom II control valve (25) upward. The oil delivery from upper pump (35) in parallel feeder passage (14) flows through boom II control valve (25) and check valve (24) to port (22). The oil flows from port (22) through line (16) to line (9). The oil flows from line (9) through manifold (8) to boom lowering control valve (6). The oil flows through boom lowering control valve (6) through check valve (4) to line (2). Then, the oil flows through line (2) to the head end of boom cylinders (1) .

Return oil from the rod end of boom cylinders (1) flows through line (3) to main control valve (17). The return oil flows through boom I control valve (23) to passage (29). The return oil flows from passage (29) through return passage (15) to return line (36). Then, the return oil flows through return line (36) back to the hydraulic tank.

Low Speed Operation

When the joystick for the boom is moved less than half of the travel distance for BOOM RAISE, low pilot oil pressure is supplied to boom I control valve (23) and to boom II control valve (25) .

When the boom is raised at a low speed, boom I control valve (23) opens and boom II control valve (25) remains closed. The force of the spring in boom I control valve (23) is less than the force of the spring in boom I control valve (25). Since low pilot pressure is delivered to both control valves, only boom I control valve (23) will open.

The oil delivery from upper pump (32) flows to the head end of boom cylinders (1). Without the oil delivery from lower pump (35), the cylinder rod movement slows down when the boom is raised.

BOOM LOWER Operation




Illustration 2g00929539

(1) Boom cylinder

(2) Line

(3) Line

(4) Check valve

(5) Spool

(6) Boom lowering control valve

(7) Relief valve

(8) Manifold

(9) Line

(10) SmartBoom control valve

(11) Check valve

(23) Boom I control valve

(26) Check valve

(29) Return passage

(32) Upper pump

(33) Pilot pump

(34) Pilot control valve

(36) Return line

(37) Line

(38) Passage

(39) Line

(40) Spool

(41) Spool

(42) Passage

(43) Pilot line

(44) Pilot line

(45) Pilot line

(46) Solenoid valve

(47) Pilot line

(48) Pilot line

When the joystick for the boom is moved to the full BOOM LOWER position, the pilot oil flows from pilot control valve (34) through pilot line (48). The flow of the pilot oil splits into two paths.

In the first path, the pilot oil flows through pilot line (44) to SmartBoom control valve (10). The pilot oil flows through solenoid valve (46) of SmartBoom control valve (10) to pilot line (45). The pilot oil is divided further into two additional paths. In one path, the pilot oil flows to the spring side of spool (41) in manifold (8). In the other path, the pilot oil flows through pilot line (47) to Boom I control valve (23) .

In the second path, the pilot oil flows through pilot line (43) to manifold (8). The pilot oil divides further and some of the pilot oil flows to spool (40). The pilot oil shifts spool (40) to the right. The rest of the pilot oil flows through passage (42) and the pilot oil divides again. Some of the pilot oil flows through passage (38) to spool (41). Since there is equal pressure on both sides of spool (41), spool (41) does not shift. The rest of the pilot oil flows through pilot lines (39) to spools (5). The pilot oil shifts spool (5) and oil from the head end of cylinders (1) is allowed to flow through spools (5) .

The pilot oil pressure in pilot line (47) shifts boom I control valve (23) downward. Supply oil from upper pump (32) flows through check valve (26) to boom I control valve (23). The supply oil flows from boom I control valve (23) through line (3) to the rod end of boom cylinders (1) and the supply oil forces the rods of boom cylinders (1) downward. As the rods move downward, oil from the head end of boom cylinders (1) flows through line (2) to spools (5) of boom lowering control valves (6). The oil flows from boom lowering control valves (6) through lines (37) to manifold (8). Some of the oil flows through spool (39) and return line (36) back to the hydraulic tank. The rest of the oil flows through line (9) to boom I control valve (23). Then, the oil flows from boom I control valve (23) through return passage (29) back to the hydraulic tank.




Illustration 3g00935534

Boom I control valve

(3) Line

(9) Line

(23) Boom I control valve

(26) Check valve

(29) Return passage

(32) Upper pump

(49) Check valve

(50) Orifice

If the boom lowers faster than the oil supply from upper pump (32) to the rod end of cylinders (1), a portion of the return oil in line (9) will flow through orifice (50) to check valve (49). If the pressure in line (3) is lower than the return oil pressure in line (9), check valve (49) opens and some of the return oil flows through check valve (49) to line (3). This prevents cavitation in the rod end of cylinders (1) .

Low Speed Operation

When the joystick for the boom is moved less than half of the travel distance for BOOM DOWN, low pilot pressure is supplied to spool (40) and to spool (41) .

When the boom is lowered at a low speed, the force of the spring for spool (40) is greater than the low pilot oil pressure and the force of the spring for spool (41) is greater than the low pilot oil pressure. As a result, the spools remain closed.

All of the return oil from boom cylinders (1) flows through line (9) to boom I control valve (23). The return oil flows from boom I control valve (23) through return passage (29) back to the hydraulic tank.

SmartBoom Control in the DOWN Position

The DOWN mode is used for hammering in extremely hard rock. This mode prevents the hammer from bouncing.




Illustration 4g00936259

(1) Boom cylinder

(2) Line

(3) Line

(4) Check valve

(5) Spool

(6) Boom lowering control valve

(7) Relief valve

(8) Manifold

(9) Line

(10) SmartBoom control valve

(11) Check valve

(23) Boom I control valve

(26) Check valve

(29) Return passage

(32) Upper pump

(33) Pilot pump

(34) Pilot control valve

(36) Return line

(37) Line

(38) Passage

(39) Line

(40) Spool

(41) Spool

(42) Passage

(43) Pilot line

(44) Pilot line

(45) Pilot line

(46) Solenoid valve

(47) Pilot line

(48) Pilot line

The SmartBoom modes are selected by pressing a switch to the rear of the left console. When the operator activates the DOWN mode with the SmartBoom switch, solenoid valve (46) is energized.

The stem of solenoid valve (46) is pushed down, and pilot oil in pilot line (44) cannot pass through the solenoid valve. Therefore, pilot oil cannot flow to boom I control valve (23), and pump oil cannot flow to the rod end of boom cylinders (1). Pilot oil flows only through manifold (8) to boom lowering control valves (6). This action allows oil in the head end of the boom cylinders to flow out of the head end through line (9) .

Check valve (11) prevents oil in the rod end of the boom cylinders from flowing out of the rod end. Therefore, the rod cannot extend, and the boom cannot be raised. The boom is capable only of BOOM DOWN movement.

SmartBoom Control in the UP AND DOWN Position

The UP AND DOWN mode is used for excavating, loading, and hammering operations that are not in extremely hard rock.




Illustration 5g00936275

(1) Boom cylinder

(2) Line

(3) Line

(4) Check valve

(5) Spool

(6) Boom lowering control valve

(7) Relief valve

(8) Manifold

(9) Line

(10) SmartBoom control valve

(11) Check valve

(23) Boom I control valve

(26) Check valve

(29) Return passage

(32) Upper pump

(33) Pilot pump

(34) Pilot control valve

(36) Return line

(37) Line

(38) Passage

(39) Line

(40) Spool

(41) Spool

(42) Passage

(43) Pilot line

(44) Pilot line

(45) Pilot line

(46) Solenoid valve

(47) Pilot line

(48) Pilot line

(51) Check valve

(52) Pilot line

(53) Spool

(54) Solenoid valve

When the operator activates the UP and DOWN mode, both solenoid valve (46) and solenoid valve (54) are energized. Pilot oil cannot pass through solenoid valve (46). Therefore, pilot oil cannot flow to boom I control valve (23), and pump oil cannot flow to the rod end of boom cylinders (1).

Pilot oil flows from pilot pump (33) through solenoid valve (54) to spool (53) and spool (53) shifts downward. This action allows pilot oil to unlock check valve (51). Oil in the rod end of boom cylinders (1) can now flow out of the rod end.

Pilot oil also flows through manifold (8) to boom lowering control valves (6). This action enables oil to flow out of the head end of the boom cylinders through line (9).

In the UP AND DOWN mode, no pressure oil flows to the rod end of the boom cylinders or to the head end of the boom cylinders. Therefore, the boom will follow the contours of the ground as machine operations are performed.

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