Definition Of Hydraulic Jack 5x4hj

Definition Of Hydraulic Jack:A hydraulic jack is a device used to lift heavy loads. The device itself is light, compact and portable, but is capable of exerting great force. The device pushes liquid against a piston; pressure is built in the jack's container. The jack is based on Pascal's law that the pressure of a liquid in a container is the same at all points. 1.2-Introduction:A hydraulic jack is a jack that uses a liquid to push against a piston. This is based on Pascal’s Principle. The principle states that pressure in a closed container is the same at all points. If there are two cylinders connected, applying force to the smaller cylinder will result in the same amount of pressure in the larger cylinder. However, since the larger cylinder has more area, the resulting force will be greater. In other words, an increase in area leads to an increase in force. The greater the difference in size between the two cylinders, the greater the increase in the force will be. A hydraulic jack operates based on this two cylinder system.

1.3-Pascal’s law :Pressure on a confined fluid is transmitted undiminished and acts with equal force on equal areas and at 90 degrees to the container wall.

A fluid, such as oil, is displaced when either piston is pushed inward. The small piston, for a given distance of movement, displaces a smaller amount of volume than the large piston, which is proportional to the ratio of areas of the heads of the pistons. Therefore, the small piston must be moved a large distance to get the large piston to move significantly. The distance the large piston will move is the distance that the small piston is moved divided by the ratio of the areas of the heads of the pistons. This is how energy, in the form of work in this case, is conserved and the Law of Conservation of Energy is satisfied. Work is force times distance, and since the force is increased on the larger piston, the distance the force is applied over must be decreased.

1.4-History:The Origin Of Hydraulic Jacks Can Be Dated Several Years Ago When Richard Dudgeon, The Owner And Inventor Of Hydraulic Jacks, Started A Machine Shop. In The Year 1851, He Was Granted A Patent For His Hydraulic Jack. In The Year 1855, He Literally Amazed Onlookers In New York When He Drove From His Abode To His Place Of Work In A Steam Carriage. It Produced A Very Weird Noise That Disturbed The Horses And So Its Usage Was Limited To A Single Street. Richard Made A Claim That His Invention Had The Power To Carry Near About 10 People On A Single Barrel Of Anthracite Coal At A Speed Of 14 M.P.H. Dudgeon Deserves A Special Credit For His Innumerable Inventions

Including The Roller Boiler Tube Expanders, Filter Press Jacks, Pulling Jacks, Heavy Plate Hydraulic Hole Punches And Various Kinds Of Lifting Jacks.

1.5-Features:The jack uses compressible fluid, which is forced into a cylinder by a plunger. Oil is usually used for the liquid because it is self-lubricating and has stability compared with other liquids. When the plunger comes up, it pulls the liquid through a check valve suction pump. When the plunger is lowered again, it sends liquid through another valve into a cylinder. A ball used for suction in the cylinder shuts the cylinder and pressure builds up in the cylinder. The suction valve present in the jack opens at each draw of the plunger. The discharge valve, which is outside the jack, opens when oil is pushed into the cylinder. The pressure of the liquid enables the device to lift heavy loads. 1.6-Classification Of Jack:-

1.6.1-Mechanical jack:-

Fig 1.1 Mechanical jack Jackscrews are integral to the Scissor Jack, one of the simplest kinds of car jacks still used. A mechanical jack is a device which lifts heavy equipment. The most common form is a car jack, floor jack or garage jack which lifts vehicles so that maintenance can be performed. Car jacks usually use Mechanical advantage to allow a human to lift a vehicle by manual force alone. More powerful jacks use hydraulic power to provide more lift over greater distances. Mechanical jacks are usually rated for a maximum lifting capacity (for example, 1.5 tons or 3 tons). The jack shown at the right is made for a modern vehicle and the notch fits into a hard point on a unibody. Earlier versions have a platform to lift on the vehicles' frame or axle. 1.6.2-Hydraulic jack:-

Hydraulic jacks are typically used for shop work, rather than as an emergency jack to be carried with the vehicle. Use of jacks not designed for a specific vehicle requires more than the usual care in selecting ground conditions, the jacking point on the vehicle, and to ensure stability when the jack is extended. Hydraulic jacks are often used to lift elevators in low and medium rise buildings. A hydraulic jack uses a fluid, which is incompressible, that is forced into a cylinder by a pump plunger. Oil is used since it is self lubricating and stable. When the plunger pulls back, it draws oil out of the reservoir through a suction check valve into the pump chamber. When the plunger moves forward, it pushes the oil through a discharge check valve into the cylinder. The suction valve ball is within the chamber and opens with each draw of the plunger. The discharge valve ball is outside the chamber and opens when the oil is pushed into the cylinder. At this point the suction ball within the chamber is forced shut and oil pressure builds in the cylinder. In a bottle jack the piston is vertical and directly s a bearing pad that s the object being lifted. With a single action piston the lift is somewhat less than twice the collapsed height of the jack, making it suitable only for vehicles with a relatively high clearance. For lifting structures such as houses the hydraulic interconnection of multiple vertical jacks through valves enables the even distribution of forces while enabling close control of the lift. In a floor jack (aka 'trolley jack') a horizontal piston pushes on the short end of a bellcrank with the long arm providing the vertical motion to a lifting pad, kept horizontal with a horizontal linkage. Floor jacks usually include castors and wheels, allowing compensation for the arc taken by the lifting pad. This mechanism provide a low profile when collapsed, for easy maneuvering underneath the vehicle, while allowing considerable extension.

1.6.3- Pneumatic jack:A pneumatic jack is a hydraulic jack that is actuated by compressed air - for example, air from a compressor instead of human work. This eliminates the need for the to actuate the hydraulic mechanism, saving effort and potentially increasing speed. Sometimes, such jacks are also able to be operated by the normal hydraulic actuation method, thereby retaining functionality, even if a source of compressed air is not available.

1.6.3- Pneumatic jack:-

Fig 1.2 Threaded rod 7" fully extended

Fig 1.3 2.5 ton house jack that stands 24 inches from top to bottom fully threaded out. A house jack, also called a screw jack is a mechanical device primarily used to lift houses from their foundation. A series of jacks are used and then wood cribbing temporarily s the structure. This process is repeated until the desired height is reached. The house jack can be used for jacking carrying beams that have settled or for installing new structural beams. On the top of the jack is a cast iron circular pad that the 4" × 4" post is resting on. This pad moves independently of the house jack so that it does not turn as the acme-threaded rod is turned up with a metal rod. This piece tilts very slightly but not enough to render the post dangerously out of plumb

1.6.4- Strand jack:A strand jack is a specialized hydraulic jack that grips steel cables often used in concert, strand jacks can lift hundreds of tons and are used in engineering and construction. 1.7-Working Principal:The hydraulic jack is a device used for lifting heavy loads by the application of much smaller force. It is based on Pascal’s law, which states that intensity of pressure is transmitted equally in all directions through a mass of fluid at rest. The working principle of a hydraulic jack may be explained with the help of Fig. Consider a ram and plunger, operating in two cylinders of different diameters, which are interconnected at the bottom, through a chamber, which is filled with some liquid.

Fig 1.4 Consider a ram and plunger, 1.8-Working Of Hydraulic Jack:Hydraulic jacks and many other technological advancements such as automobile brakes and dental chairs work on the basis of Pascal's Principle, named for Blaise Pascal, who lived in the seventeenth century. Basically, the principle states that the pressure in a closed container is the same at all points. Pressure is described mathematically by a Force divided by Area. Therefore if you have two cylinders connected together, a small one and a large one, and apply a small Force to the small cylinder, this would result in a given pressure. By Pascal's Principle, this pressure would be the same in the larger cylinder, but since the larger cylinder has more area, the force emitted by the second cylinder would be greater. This is represented by rearranging the pressure formula P = F/A, to F = PA. The pressure stayed the same in the second cylinder, but Area was increased, resulting in a larger Force. The greater the differences in the areas of the cylinders, the greater the potential force output of the big cylinder. A hydraulic jack is simply two cylinders connected as described above.

An enclosed fluid under pressure exerts that pressure throughout its volume and against any surface containing it. That's called 'Pascal's Principle', and allows a hydraulic lift to generate large amounts of force from the application of a small Assume a small piston (one square inch area) applies a weight of 1 lbs. to a confined hydraulic fluid. That provides a pressure of 1 lbs. per square inch throughout the fluid. If another larger piston with an area of 10 square inches is in with the fluid, that piston will feel a force of 1 lbs/square inch x 10 square inches = 10 lbs

Fig 1.5 Working Of Hydraulic Jack:-

So we can apply 1 lbs. to the small piston and get 10 lbs. of force to lift a heavy object with the large piston. Is this 'getting something for nothing'? Unfortunately, no. Just as a lever provides more force near the fulcrum in exchange for more distance further away, the hydraulic lift merely converts work (force x distance) at the smaller piston for the SAME work at the larger one. In the example, when the smaller piston moves a distance of 10 inches it displaces 10 cubic inch of fluid. That 10 cubic inch displaced at the 10 square inch piston moves it only 1 inch, so a small force and larger distance has been exchanged for a large force through a smaller distance. Hydraulic jacks have six main parts. These are the reservoir, pump, check valve, main cylinder, piston, and release valve. The reservoir holds hydraulic fluid. A pump will draw the fluid up and then create pressure on the down stroke as it pushes the fluid through the check valve. This valve allows the fluid to leave the reservoir and enter the main cylinder. In the main cylinder, the piston is forced up as the cylinder is filled with the fluid. When it is time to release the pressure and allow the piston to return to its starting position, the release valve is opened. This allows the fluid to return to the reservoir.

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Design of Hydraulic Jack 2.1 Hydraulic Basics:Hydraulics is the science of transmitting force and/or motion through the medium of a confined liquid. In a hydraulic device, power is transmitted by pushing on a confined liquid.Figure 1-1 shows a simple hydraulic device. The transfer of energy takes place because quantity of liquid is subject to pressure. To operate liquid-powered systems, the operator should have a knowledge of the basic nature of liquids. This chapter covers the properties of liquids and how they act under different conditions.

2.1.1:- Pressure and Force.:Pressure is force exerted against a specific area (force per unit area) expressed in pounds per square inch (psi). Pressure can cause an expansion, or resistance to compression, of a fluid that is being squeezed. A fluid is any liquid or gas (vapor). Force is anything that tends to produce or modify (push or pull) motion and is expressed in pounds a. Pressure. An example of pressure is the air (gas) that fills an automobile tire. As a tire is inflated, more air is squeezed into it than it can hold. The air inside a tire resists the squeezing by pushing outward on the casing of the tire. The outward push of the air is pressure. Equal pressure throughout a confined area is a characteristic of any pressurized fluid.

Confined liquid is subject to pressure

Figure 2.1 Basic hydraulic devices

For example, in an inflated tire, the outward push of the air is uniform throughout. If it were not, a tire would be pushed into odd shapes because of its elasticity. There is a major difference between a gas and a liquid. Liquids are slightly compressible (Figure 2.1). When a confined liquid is pushed on, pressure builds up. The pressure is still transmitted equally throughout the container. The fluid's behavior makes it possible to transmit a push through pipes, around corners, and up and down.

D2=F1*D1/F2 Where F1 = force of the small piston, in pounds D1 = distance the small piston moves, in inches

D2 = distance the larger piston moves, in inches F2 = force of the larger piston, in pounds

2.2-Basic Systems:The advantages of hydraulic systems over other methods of power transmission are • Simpler design. In most cases, a few pre-engineered components will replace complicated mechanical linkages. • Flexibility. Hydraulic components can be located with considerable flexibility. Pipes and hoses in place of mechanical elements virtually eliminate location problems. • Smoothness. Hydraulic systems are smooth and quiet in operation. Vibration is kept to a minimum. • Control. Control of a wide range of speed and forces is easily possible. • Cost. High efficiency with minimum friction loss keeps the cost of a power transmission at a minimum. • Overload protection. Automatic valves guard the system against a breakdown from overloading. The main disadvantage of a hydraulic system is maintaining the precision parts when they are exposed to bad climates and dirty atmospheres. Protection against rust, corrosion, dirt, oil deterioration, and other adverse environment is very important. The following paragraphs discuss several basic hydraulic systems.

A- Hydraulic Jack:In this system a reservoir and a system of valves has been added to Pascal's hydraulic lever to stroke a small cylinder or pump continuously and raise a large piston or an actuator a notch with each stroke. Diagram A shows an intake stroke. An outlet check valve closes by pressure under a load, and an inlet check valve opens so that liquid from the reservoir fills the pumping chamber. Diagram B shows the pump stroking downward. An inlet check valve closes by pressure and an outlet valve opens. More liquid is pumped under a large piston to raise it. To lower a load, a third valve (needle valve) opens, which opens an area under a large piston to the reservoir. The load then pushes the piston down and forces the liquid into the reservoir.

Figure 2-2. Hydraulic jack

B- Motor-Reversing System:Figure 2-2, shows a power-driven pump operating a reversible rotary motor. A reversing valve directs fluid to either side of the motor and back to the reservoir. A relief valve protects the system against excess pressure and can by pump output to the reservoir, if pressure rises too high.

C-Open-Center System:In this system, a control-valve spool must be open in the center to allow pump flow to through the valve and return to the reservoir. this system in the neutral position. To operate several functions simultaneously, an open-center system must have the correct connections, which are discussed below. An open-center system is efficient on single functions but is limited with multiple functions. The return from the first valve is routed to the inlet of the second, and so on. In neutral, the oil es through the valves in series and returns to the reservoir, as the arrows indicate. When a control valve is operated, the incoming oil is diverted to the cylinder that the valve serves. Return liquid from the cylinder is directed through the return line and on to the

next valve. This system is satisfactory as long as only one valve is operating at a time. When this happens, the full output of the pump at full system pressure is available to that function. However, if more than one valve is operating, the total of the pressures required for each function cannot exceed the system’s relief setting.

2.3-Parts Of Hydraulic Jack:    

Gland (End Cap) Piston Road Cylinder Base Plate Hose Pipe

2.3.1-Parts Of Cylinder:2.3.1.1-Cylinder Barrel:The cylinder barrel is mostly a seamless thick walled forged pipe that must be machined internally. The cylinder barrel is ground and/or honed internally. 2.3.1.2-Cylinder Base Or Cap:In most hydraulic cylinders, the barrel and the bottom portion are welded together. This can damage the inside of the barrel if done poorly. Therefore, some cylinder designs have a screwed or flanged connection from the cylinder end cap to the barrel. In this type the barrel can be disassembled and repaired. 2.3.1.3-Cylinder Head:The cylinder head is sometimes connected to the barrel with a sort of a simple lock. In general, however, the connection is screwed or flanged. Flange connections are the best, but also the most expensive. A flange has to be welded to the pipe before machining. The advantage is that the connection is bolted and always simple to remove. For larger cylinder sizes, the disconnection of a screw with a diameter of 300 to 600 mm is a huge problem as well as the alignment during mounting. 2.3.2-Piston Rod:The piston rod is typically a hard chrome-plated piece of cold-rolled steel which attaches to the piston and extends from the cylinder through the rod-end head. In double rod-end cylinders, the actuator has a rod extending from both sides of the piston and out both ends of the barrel. The piston rod connects the hydraulic actuator to the machine component doing the work. This connection can be in the form of a machine thread or a mounting attachment, such as a rod-clevis or rod-eye. These mounting attachments can be threaded or welded to the piston rod or, in some cases, they are a machined part of the rodend. 2.3.2.1:-Piston Rod Construction:-

The piston rod of an hydraulic cylinder operates both inside and outside the barrel, and consequently both in and out of the hydraulic fluid and surrounding atmosphere. 2.3.2.1.1:-Metallic Coatings:Smooth and hard surfaces are desirable on the outer diameter of the piston rod and slide rings for proper sealing. Corrosion resistance is also advantageous. A chromium layer may often be applied on the outer surfaces of these parts. However, chromium layers may be porous, thereby attracting moisture and eventually causing oxidation. In harsh marine environments, the steel is often treated with both a nickel layer and a chromium layer. Often 40 to 150 micrometer thick layers are applied. Sometimes solid stainless steel rods are used. High quality stainless steel such as AISI 316 may be used for low stress applications. Other stainless steels such as AISI 431 may also be used where there are higher stresses, but lower corrosion concerns. 2.3.2.1.2:-Ceramic Coatings:Due to shortcomings of metallic materials, ceramic coatings were developed. Initially ceramic protection schemes seemed ideal, but porosity was higher than projected. Recently the corrosion resistant semi ceramic Lunac2+ coatings were introduced. These hard coatings are non porous and do not suffer from high brittleness. 2.3.2.1.3:-Length:Piston rods are generally available in lengths which are cut to suit the application. As the common rods have a soft or mild steel core, their ends can be welded or machined for a screw thread. 2.3.2.3:-Gland (End Cap):The cylinder head is fitted with seals to prevent the pressurized oil from leaking past the interface between the rod and the head. This area is called the rod gland. It often has another seal called a rod wiper which prevents contaminants from entering the cylinder when the extended rod retracts back into the cylinder. The rod gland also has a rod wear ring. This wear ring acts as a liner bearing to the weight of the piston rod and guides it as it es back and forth through the rod gland. In some cases, especially in small hydraulic cylinders, the rod gland and the rod wear ring are made from a single integral machined part.

CALCULATIONS:Distance the larger piston moves

D2=F1*D1/F2 Where F1 = force of the small piston, in pounds D1 = distance the small piston moves, in inches D2 = distance the larger piston moves, in inches F2 = force of the larger piston, in pounds

 The definition of fluid pressure is a force per unit area, or in equation form, P=F/A where P = pressure (N/m2, psi), F = force (N, lbf), and A = area (m2, in2).

TO FIND INNER DIAMETER OF CYLINDER TUBE:-

p

where, P = total pressure

D = Inner diameter p = working pressure

3 *1000 = 0.785 × D2 × 300

D=3000/0.785*300

D2 = 12.76

D = 6CM = 60MM. (inner diameter of cylinder tube)

TO FIND OUTER DIAMETER OF CYLINDER TUBE:-

We have already a equation = Where,

= working stress P = working pressure = outer diameter of cylinder tube = inner diameter of cylinder tube = Working stress = 4200/4= 1050 KG/CM2

1050 = 300 ×

1050do -3780000=300do +1080000 750do =2700000 do =2700000*750 do =202500000 do=73mm

THICKNESS OF THE CYLINDER TUBE:-

Tube thickness = =73-60/2 =6.5mm

DESIGN OF PISTON

We know that cylinder’s inner diameter is equal to piston’s outer diameter so piston outer diameter is 60mm . Generally piston’s are maded from MILD STEEL & SUITABLE MATERIAL……

DESIGN OF PISTON ROD Material strength EN9 = 1750 kg/cm2

P=0.785*60*60*1750 P=4945500kg/mm