increase the strength and bending resistance.
Top
Platform-The material used for the construction of this component is mild steel angle bar for the frame and timber for the base of the platform. The angle bar is cut into the required sizes and welded to form a rigid platform. The timber was equally into the required dimensions, drilled at the edges and fastened using bolt and nut to secure it in position at the base of the platform.
Assembling of various components of the hydraulic scissors
lift-The scissors assemblage was mounted on the base frame with one end hinged and the other fitted with roller (bearing) to produce the needed motion of rolling along the rail to cause lifting and lowering of the scissors lift. The scissors arm connected to the platform is also connected with one end hinged and the other fitted with roller to effect extension and contraction of the lit. The hydraulic cylinder is connected to the first arm of the scissors lift with both ends hinged.
This cylinder provides the force needed to lift the load on the platform.
The force is as a result of the pressure of the hydraulic supplied to the cylinder by the pump from the reservoir.
The lift is fitted with wheels to aid mobility from one location to another.
Painting of the entire unit is done to improve it aesthetics and increase the corrosion and resistance to rust.
CHAPTER- 4
WORKING
4.1 WORKING
PRINCIPLE-Hydraulic lift is a system where a liquid, usually crude oil, is pumped down hole under high pressure to operate a reciprocating pump or a jet pump. This is a very flexible pumping system
and can be used to produce low- to high-volume wells. This system is capable of producing a higher volume of fluid than the mechanical lift pump. Hydraulic lift uses a pump and pumps oil very high pressure. The pump pressure is usually between 300-400 pounds per square inch (PSI) and pushes the liquid to the bottom of the piston to lift it from its seat which relatively lifts the load connected to the head of the piston-cylinder assembl y. The required power oil or produced water is reclaimed and reused to continue operating the wells. The pump produces oil on both the upstroke and the down stroke. The pump stroke speed is not easily adjustable due to varying load.
Fig 4.1.- Pascal Law
Hydraulic Lift basically works on the principle of Pascal Law. Pascal Law Pascal's law or the principle of transmission of fluid-pressure is a principle in fluid mechanics that states that pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure variations (initial differences) remain the same. The basic idea behind any hydraulic system is very simple: Force that is applied at one point is transmitted to another point using an incompressible fl uid. The fluid is almost always
an oil of some sort. The force is almost always multiplied in the process. The picture below
shows the simplest possible hydraulic system: A Simple hydraulic system consisting of two pistons and an oil-filled pipe connecting them.
Fig 4.2.- Hydraulic Multiplication
Because of the shape of the original device, a pantograph also refers to a kind of structure that can compress or extend like an accordion, forming a characteristic rhomboidal pattern. This can be found in extension arms for wall-mounted mirrors, temporary fences, scissor lifts, and other scissor mechanisms such as the pantograph used in electric locomotives and trams. A Scissors lifts provide the most economical, dependable, and versatile method of lifting heavy loads. Scissors lifts have few moving parts, are well lubricated, and provide many years of trouble free operation. These lift tables raise the loads smoothly to any desired height, and can be easily configured to meet the specific speed, capacity, and foot print requirement of any hydraulic lifting application. And is by far the most popular and efficient of all styles of scissors tables used in material handling applications.
In this drawing, two pistons (red) fit into two glass cylinders filled with oil (light blue) and connected to one another with an oil-filled pipe. If you apply a downward force to one piston (the left one in this drawing), then the force is transmitted to the second piston through the oil in the pipe. Since oil is incompressible, the efficiency is very good -- almost all of the applied force appears at the second piston. The great thing about hydraulic systems is that the pipe connecting the two cylinders can be any length and shape, allowing it to snake through all sorts of things separating the two pistons. The pipe can also fork, so that one master cylinder can drive more than one slave cylinder if desired. The neat thing about hydraulic systems is that it is very easy to add force multiplication (or division) to the system. In a hydraulic system, all you do is change the size of one piston and cylinder relative to the other, as shown here:
The piston on the right has a surface area nine times greater than the piston on the left. When force is applied to the left piston, it will move nine units for every one unit that the right piston
moves, and the force is multiplied by nine on the right-hand piston. Click the red arrow to see the animation. To determine the multiplication factor, start by looking at the siz e of the pistons.
Assume that the piston on the left is 2 inches in diameter (1-inch radius), while the piston on the right is 6 inches in diameter (3-inch radius). The area of the two pistons is Pi * r 2. The area of the left piston is therefore 3.14, while the area of the piston on the right is 28.26. The piston on the right is 9 times larger than the piston on the left. What that means is that any force applied to the left-hand piston will appear 9 times greater on the right-hand piston. So if you apply a 100-pound downward force to the left piston, a 900-pound upward force will appear on the right. The only catch is that you will have to depress the left piston 9 inches to raise the right piston 1 inch. The brakes of a car are a good example of a basic piston-driven hydraulic system. When you depress the brake pedal in your car, it is pushing on the piston in the brake's master cylinder. Four slave pistons, one at each wheel, actuate to press the brake pads against the brake rotor to stop the car. (Actually, in almost all cars on the road today two master cylinders are driving two slave cylinders each. That way if one of the master cylinders has a problem or springs a leak, you can still stop the car.) In most other hydraulic systems, hydraulic
cylinders and pistons are connected through valves to a pump supplying high-pressure oil.
Scissors lifts has developed overtime, and at each stage of its development, critical problems are solved.
The hydraulic type, but this time, the load screw is replaced by a hydraulic ram powered by a pump and on electric motor and generator. One outstanding feature about this design however.
Is its independent operation and increased efficiency. Fluid power is one of the greater form of power where small input results in a very large output. This scissors lift can be handled by one person to a place of use, and power the generator. The lift does not lifting immediately, the operators climbs on the platform and switches open the hydraulic circuit thereby leading to an upward extension. When the required height is reached the circuit is closed, and lifting stops the control panel or station is located on the top frame. When work is done, the scissors lift is folded by hydraulic means and handled back to the point of collection.
4.2 PRINCIPLE OF OPERATION OF A HYDRAULIC LIFT (EXTENSION AND CONTRACTION)
A scissors lift is a type of platform that can usually only move vertically. The mechanism to achieve this is the use of linked, folding supports in a criss-
cross “X” pattern, known as a
scissors mechanism. The upward motion is achieved by the applicati on of pressure to the outer side of the lowest set of supports, elongating the crossing pattern and propelling the work platform vertically. The platform may
also have extending “bridge” to allow closer access to
the work area, because of the inherent limits of vertical