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Abstract: - A jack is a device that uses force to lift heavy loads. The primary mechanism with which force is
applied varies, depending on the specific type of jack, but is typically a screw thread or a hydraulic cylinder.
Jacks can be categorized based on the type of force they employ: mechanical or hydraulic. Mechanical jacks,
such as car jacks and house jacks, lift heavy equipmentand are rated based on lifting capacity (for example, the
number of tons they can lift). Hydraulic jacktend to be stronger and can lift heavier loads higher, and include
bottle jacks and floor jacks. HYDRAULIC JACKSdepend on force generated by pressure. Essentially, if two
cylinders (a large and a small one) are connected and force is applied to one cylinder, equal pressure is
generated in both cylinders. However, because one cylinder has a larger area, the force the larger cylinder
produces will be higher, although the pressure in the two cylinders will remain the same. Hydraulic jacks
depend on this basic principle to lift heavy loads: they use pump plungers to move oil through two cylinders.
The plunger is first drawn back, which opens the suction valve ball within and draws oil into the pump chamber.
As the plunger is pushed forward, the oil moves through an external discharge check valve into the cylinder
chamber, and the suction valve closes, which results in pressure building within the cylinder.
THEORY
HYDRAULICS:The word hydraulics is based on the Greek word for water, and originally covered the study of
the physical behavior of water at rest and in motion. Use has broadened its meaning to include the behavior of
all liquids, although it is primarily concerned with the motion of liquids. Hydraulics includes the manner in
which liquids act in tanks and pipes, deals with their properties, and explores ways to take advantage of these
properties.
Although the modern development of hydraulics is comparatively recent, the ancients were familiar
with many hydraulic principles and their applications. The Egyptians and the ancient people of Persia, India, and
China conveyed water along channels for irrigation and domestic purposes, using dams and sluice gates to
control the flow. The ancient Cretans had an elaborate plumbing system. Archimedes studied the laws of
floating and submerged bodies. The Romans constructed aqueducts to carry water to their cities. Torricelli,
French physicist, EdmeMariotte, and later, Daniel Bernoulli conducted experiments to study the elements of
force in the discharge of water through small openings in the sides of tanks and through short pipes. During the
same period, Blasé Pascal, a French scientist, discovered the fundamental law for the science of hydraulics.
Hydraulic jack is based on the Pascal’s law whichstates that increase in pressure on the surface of a confined
fluid is transmitted undiminished throughout the confined vessel or system.
Two common types of hydraulic jacks includeBOTTLE JACKS & FLOOR JACKS..
II. BOTTLE JACKS
BOTTLE JACKS became popular in the early 1900s when the automobile industry began to take off. Also
called hand jacks, bottle jacks provided an easy way for an individual to lift up a vehicle for roadside inspection
or service. Their resemblance to milk bottles earned bottle jacks their name—today, they range in size and weight to offer a lifting capability ranging from one hundred to several tons. Bottle jacks feature a vertical shaft,
which supports a platform (called a bearing pad) that directly bears the weight of the object as it is lifted.
Although they are most commonly used in the automobile industry (1.5 to 5 ton jacksare frequently used to lift
cars), bottle jacks have other uses as well. In the medical industry they can be used in hydraulic stretchers and
patient lifts. In industrial applications, they can be found as pipe benders used in plumbing, as cable slicers for
electrical projects, and as material lifts within warehouses. Their ability to lift heavy loads plays a big role in
enabling the repair of large agricultural machinery and in many construction operations. Bottle jacks can be
secured within a frame, mounted on a beam, or simply used as they are for easier jack transportation.
III. FLOOR JACKS
Unlike bottle jack shafts, the shaft in a floor jacksis horizontal—the shaft pushes on a crank that connects to a
lifting pad, which is then lifted horizontally. Floor jacks typically provide a greater range of vertical lift than
bottle jacks, and are available in two sizes. The original jack is about four feet long, a foot wide, and weights
around 200 pounds—they can lift 4-10 tons. A more compact model was later made, which is about three feet in
length, and can lift 11/2 tons. Although mini jack are also produced, they are not a recognized standard type of
floor jack. Typically, one of the first two sizes should be used.
IV. HYDRAULIC JACK
It is a short stroke hydraulic lift which is fed from hand pump. The hydraulic jack may be portable.
This is extensively used for lifting automobiles usually to facilitate and repair. And for replacing the punctured
wheels. The hydraulic jack is perhapsone of the simplest forms of a fluid power system. By moving the handle
of a small device, an individual can lift a load weighing several tons. A small initial force exerted on the handle
is transmitted by a fluid to a much larger area.
The operation of hydraulic jack depends on ―Pascal‘s law‖. This states that when a fluid is at rest in a closed
vessel and if a certain pressure is applied at any point the pressure will be transmitted equally in all direction.
Mechanical advantage is obtained by a practical application of Pascal‘s law of transmission of fluid
pressure. Two pistons of different sizes operate inside two cylinders suitably connected with a pipe so that
pressure in each is the same. If ―p ―is pressure and ―a1,a2‖ are the cross sectional area of cylinders, then a force
―F‖ applied to the smaller plunger will make available a load ―W‖ is lifted.
Where ,p = pressure of the fluid,
a1 = small cylinder area,
a2 = larger cylinder area,
F = force acting on smaller plunger,
W = load lifted.
If the volume of liquid is constant. The displacement of large piston will be proportionately to smaller plunger.
V. WORKING OF HYDRAULIC JACK
Hydraulic jack works on the principle of ―Pascal‘s law‖.
When the handle is operated, the plunger reciprocates then the oil from the reservoir is sucked into the
plunger cylinder during upward stroke of the plunger through the suction valve. The oil in the plunger cylinder
is delivered into the ram cylinder during the downward stroke of the plunger through the delivery valve. This
pressurized oil lifts the load up, which is placed on top plate of the ram. After the work is completed the
pressure in the ram cylinder is released by unscrewing the lowering screw thus the pressure releases and the ram
is lowered, then the oil is rushed into the reservoir.It consists of plunger cylinder on one side and ram cylinder
on the other side. These two cylinders are mounted on base which is made of mild steel. Plunger cylinder
consists of plunger which is used to build up the pressure by operating the handle. Plunger cylinder consists of
two non-return valves i.e. one for suction and other for delivery. Ram cylinder consists of ram which lifts the
load. The ram cylinder connected to delivery valve of plunger cylinder. It is also consists of lowering screw this
is nothing but a hand operated valve used for releasing the pressure in the ram cylinder for get down the load.
VI. SPECIFICATIONS OF HYDRAULIC JACK
• Rated capacity in tone
• Jack dimensions
• Lifting range in - cm
• Oil capacity in - cc
• Net weight in - kg