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MODULE-I
CHAPTER 2
HYDRAULIC PUMPS
• Introduction to hydraulic pumps
• Classification of pumps
• Construction of pumps

Introduction to hydraulic pumps
• A pump is the heart of a hydraulic system
...

• The mechanical energy is delivered to the pump by a prime mover
such as an electric motor
...

• The pump is then pushes the fluid into the hydraulic system with high
pressure
...
Centrifugal pump
2
...
GEAR PUMPS :- External gear
pump, Internal gear
pump,Lobe pump, Gerotor
pump and screw pump
2
...
PISTON PUMPS:- Axial type
and Radial type

Classification of pumps
• Non Positive displacement pumps:- • Positive displacement pumps:- its
these pumps are used in
used in hydrostatic systems, in
hydrodynamic systems in which
which power transmission takes
power transmission take place due
place through fluid pressure
...
They pump fluid by
pumps input a fixed amount of
spinning the fluid with an impeller
fluid into the hydraulic system per
running with a casing
...

throwing outward radially in the
• These pumps do not pump fluids
impeller by centrifugal force
...

pressure, high volume applications
...


Gear pumps
1) External gear pump

Gear pumps
1) External gear pump
• External gear pump is a positive displacement pump, it consists of two mating
external gears, running within a suitable pump casing
...
The other gear is driven
by the drive gear
...

• In operation, the gears rotate such that they come out of mesh at the inlet port
causing volume expansion
...

• The fluid is then carried between the gear teeth along the casing
...

• The volume decrease between the mating teeths, and the fluid is forced out
from the outlet chamber
...
The pinion and ring gear are mounted eccentrically in a pump casing
...

• In operation, the meshing teeth coming out of mesh cause an increase in
volume, creating a partial vacuum in the cavity close to the inlet
...

• A stationary crescent between the two gears, acts as a seal between the
inlet and outlet ports
...
As
the teeth engage, they tend to reduce the volume in the outlet cavity and
pressurized the fluid through the discharge port
...
The two gears are
replaced by the lobes
...

• In operation, as the lobes rotate, they come out of meshing and lead
to an increase in volume at the inlet cavity
...

• The oil is carried in the chamber within the lobes along the pump
casing
...


Gear pumps
4) Gerotor pump

Gear pumps
4) Gerotor pump
• Gerotor pump is similar to an internal gear pump both in construction
and operation
...
Meshing with
the teeth surfaces of the outer ring gear
...

• In operation, the power driven gerotor meshes With the outer ring
gear
...

• As the gears enter into meshing action, cause an increase in pressure
and push out the oil through the outlet line
...
It has a
power driven screw mounted on the shaft
...
This idler rotor
acts as the rotating seal
...
With continuous rotation more
and more fluid is pushed to the outlet chamber, and delivered to the
fluid outlet

Vane pumps
• The gear pumps are simple in construction and operation, they have
high leakage rates through the gaps between the teeth and pump
casing
...

• This problem can be overcome with the use of vane pumps
...
The rotor has slots and
the vanes are slipped into slots
...
The rotor is mounted to
the drive shaft driven by a prime mover
...

• In operation, as the rotor rotates the vanes slid along the came ring surface, held
under the centrifugal force, assisted by the spring pressure
...

• This creates a partial vacuum,Due to this the oil is sucked in from the inlet line
...
In the next half revolution, the vane
start moving into the slots in the rotor resulting in a decrease in volume and the
fluid is ejected to the outlet port
...

• This Unbalanced pressure condition results in a net force on the
pump shaft, and in turn on the bearings
...
This problem of Unbalanced loading is
eliminated in a balanced vane pump
...
Vane are
provided in the slots of the rotor
...
The inlet and outlet
chambers are positioned diagonally opposite to each other
...

• In operation, due to the elliptical shape of the cam ring, the oil
suction at the inlets and pumping at the outlets occurs
simultaneously
...


Piston pumps
1) Swash plate type (In-line piston pump)

Piston pumps
1) Swash plate type (In-line piston pump)
• The pump Consists of multiple pistons whose axis are parallel to the pump shaft axis
...
The pistons mate
in the cylinders in a cylinder block mounted on the pump shaft
...
The swash plate is held stationary, at a fixed angle
...

• In operation, as the pump cylinder block rotates, the piston reciprocate since the piston
shoes follow angled surface of the swash plate
...

• The piston on the outlet groove, at the same time undergo gradual forward stroke, there
by pushing the oil from their cylinders through the outlet port
...


Piston pumps
2) Bent-axis type axial pump

Piston pumps
2) Bent-axis type axial pump
• The construction is similar to the swash plate type pump except that the
angle required to create the Piston stroke is provided by the bent axis drive
shaft,instead of the swash plate
...

• The piston are connected to the drive plate with ball and socket joints
...
The bent axis of the
drive shaft leads to the reciprocatory motion of the pistons in the cylinder
block
...


Piston pumps
3) Radial piston pump

Piston pumps
3) Radial piston pump
• In radial piston pumps, the pistons are located radially around the pump axis,
hence the name radial piston pumps
...
The pistons
mate in the cylinders and are kept in the housing such that they are in continuous
contact with the cam surface
...
The drive shaft rotates the cylinder block along with the pistons,
while the cam surface remain stationary
...
The inlet and outlet ports are separated by a pintle
...
The pistons above the pintle move away from the centre
thus drawing in the oil from the inlet port in the first half revolution
...




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