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FLUID POWER TRANSMISSION
The inline piston type pump shown in (Fig. 3) has a series of pistons
arranged in a circular pattern within a cylinder block. The engines rotary
motion is transferred to the cylinder block by the shaft. The ends of the
pistons contact a circular plate held at an angle. As the cylinder block
rotates, the pistons are pushed into their bores, where they pressurize
oil in the cylinder. The pressurized oil flows through passages from the
ends of the cylinders to a hydraulic motor.
Click for a closer view
Inline piston motors (Fig. 4) are
constructed like the pump, and in many instances use identical parts. Oil
passages at the ends of the cylinders transport the pressurized oil to the
ends of the motor pistons.
The opposite ends of the pistons contact a
stationary plate fixed at an angle. The pressure in the cylinder causes
the piston to slide across the angled face resulting in movement of the
cylinder block. The rotational energy is transmitted through the
motor housing by a drive shaft to move the tractor.
During the second half of the pump rotation, the pistons
withdrawing into their cylinders create a negative pressure (or vacuum)
which allows the oil which is not under pressure during the second half of
the motor rotation, to return to the cylinder. In effect, oil is
constantly flowing from pump to motor under positive pressure, and
returning from motor to pump under negative pressure.
Click for a closer view
Click for a closer view
[Source: Simplicity publication, Hydraulic Systems Training
Information, #840172, Principles and Operation of Tractor Hydraulic Systems]
