In the industrial and manufacturing places, lifting of equipment, work pieces and people is a necessary activity. This is done by a scissor lift table which is a raised podium with wheels that act as a forklift. It simply lifts things above the ground to a height up to 21-62 feet above the ground and carries up to a maximum load of 10,000 pounds. These lift tables can rotate, incline and freely move along straight lines. There are a variety of scissor lift tables in the market and although they involve an identical construction mode, hydraulic scissor lift tables are commonly used. Many people think that a hydraulic scissor lift table is complicated equipment that is best left to engineers but if you are curious just like me, there is a lot to learn about it.
Components of hydraulic scissor lift table
A hydraulic scissor lift table has many components as follows:
• The platform: This is the top part that is like the table top. It is where the pieces that need to be lifted are placed. The size of the platform varies depending on the purpose that is being used.
• Scissor legs: These are vertical structures that are connected to the base and allow for the change of elevation.
• The base: This is the bottom part that allows the structure to rest on the floor. It also has the tracks that scissor legs travel as it changes inclination.
• Hydraulic cylinders: These cylinders allow the lift table to move up and down.
• Power source: Can either be electric or air motor and provide power to the hydraulic pump.
Operations of hydraulic scissor lift table
The raising and lowering of the hydraulic lift table happens when the hydraulic fluid is forced in and out of the hydraulic cylinders. When hydraulic fluid is forced into the cylinders, the cylinders bulge outwards. This act forces the scissor legs to move apart. So the raising and lowering of the lift table depends on the movement of hydraulic fluid. To understand this better, it is necessary to take a look at what happens during individual movements.
The rising process
Remember that there are the inner and the outer scissor legs and one end of each is connected to the platform and the other end to the base. When the scissor legs move apart as a result of the movement of hydraulic fluid, the platform raises vertically. This means that, it is the fluid column that supports the platform every time that it is being raised. What holds the hydraulic fluid in these columns are the check valves.
Well, the speed at which the lift table moves is determined by the hydraulic pump and the motor that is being used. Usually, there is a desired speed that the lift table is required to operate and the capacity that is needed to carry. Such specifications are reached at depending on the amount of work done by the motor hence the horsepower. The power of any engine is measured in terms of its horsepower. It is a unit of power equal to 745.7 watts. A higher horsepower is needed for the lift table to move faster as well as to lift heavy loads.
The lowering process
You would say that the lowering process is brought by forcing the hydraulic lift out of the hydraulic cylinder. That is true, but it does not happen just like that. It happens in a process. First, a down valve has to be opened. This valve allows the hydraulic fluid to move out at a controlled rate. The valve is operated by a solenoid which in normal circumstances is closed and requires to be activated for it to start working. This feature prevents the lift table from lowering in case of a power failure. When the solenoid opens the valve, the fluid goes back to the reservoir and the lift table moves downwards.
The speed at which the lift table is lowered does not depend on the horse power this time, but the rate at which the hydraulic fluid leaves the hydraulic cylinder. This rate is controlled by a flow control (FC) valve. This valve is pressure independent and puts the flow rate constant irrespective of the load that is in the lift table. Usually, the FC valves rates are fixed and the speed of the lift table is the same when it is moving up and down.
The mystery surrounding the hydraulic scissor lift table is now solved. If you think that you need one, it is good to understand how it works to not only appreciate its necessity, but also know what to look out for when choosing the right hydraulic scissor lift table for your kind of work. As you have seen, it is not complicated as it seems and you do not need to enroll for a forklift course to know how a hydraulic scissor lift table works!