HEAD AS-COMPRESSOR 7N7447 - Caterpillar

Illustration 1 g00826581
Trailer mounted pumper
(1) Quick disconnects
(2) Solenoid operated valve
(3) Hydraulic motor
(4) Starter motor
Illustration 2 g00853405
Truck mounted pumper
(3) Hydraulic motor
(4) Starter motor
Illustration 3 g00822762
Hydraulic starting motor
(3) Hydraulic motor
(4) Starter motor
(5) Pinion
Illustration 4 g00824836The hydraulic starting system consists of a hydraulic starting motor that is driven by a hydraulic pump. The hydraulic pump is driven by the tractor transmissions power take-off. A solenoid valve (2) is used to direct oil to hydraulic starting motor (4) when the engine start switch is engaged.
Illustration 5 g02665740
Hydraulic starting system diagram (typical example)
(6) Reservoir.
(7) Low-pressure filter
(8) Hand pump
(9) Control valve
(10) Hydraulic starter
(11) Soft engage valve
(12) recharging pump
(13) High-pressure filter
(14) Accumulator Hydraulic starting motor (10) is used to turn the engine flywheel fast enough to get the engine started. When the engine is running, hydraulic pump (12) pushes oil through filter (13) into accumulator (14). Accumulator (14) is a thick wall cylinder. The accumulator has a piston which is free to move axially in the cylinder. A charge of nitrogen gas is sealed in one end of the cylinder by the piston. The other end of the cylinder is connected to hydraulic pump (12) and hydraulic starting motor (10). The oil from hydraulic pump (12) pushes the piston which puts more compression on the nitrogen gas in the cylinder. When the oil pressure gets to 20700 kPa (3000 psi), accumulator (14) has a full charge. This point the piston is approximately in the middle of the cylinder. When control valve (9) is activated, the oil is pushed from accumulator (14) by the nitrogen gas. The oil flow is through hydraulic starting motor (10), where the energy from the compression of the fluid is changed to mechanical energy for turning the engine flywheel.
Illustration 6 g02666296
Hydraulic Starting Motor
(15) Rotor
(16) Pistons
(17) Thrust bearing
(18) Starter pinion
(A) Oil inlet
(B) Oil outlet The hydraulic starting motor is an axial piston hydraulic motor. The lever for the starter control valve pushes starter pinion (18) into engagement with the engine flywheel. At the same time it opens the way for high-pressure oil to get into the hydraulic starting motor.When the high-pressure oil goes into the hydraulic starter motor, it goes behind a series of pistons (16) in a rotor (15). The rotor (15) is a cylinder which is connected by splines to the drive shaft for starter pinion (18). When pistons (16) are under the force of the oil, the piston moves until the piston is against the thrust bearing (17). The thrust bearing is at an angle to the axis of rotor (15). This action makes pistons (16) slide around thrust bearing (17). As the piston slides, the piston turns rotor (15) which connects through the drive shaft and starter pinion (18) to the engine flywheel. The pressure of the oil makes pinion (18) turn fast. In turns the engine flywheel fast enough for quick starting.