How Does Scissor Lift Work

Any scissor lift relies on the elongation mechanism to provide vertical lifting
depending on a rotational or linear input. These machines are widely used and are capable of lifting significant loads safely and efficiently.

The name - scissor lift - is inspired by the shape of the steel supporting beams under the work platform, which are hinged with pivot points to make the assembly looks like several sets of connected scissor blades, as they move up and down, they perform an open-close motion similar to scissors, so we called it a Scissor Lift.

Thanks to its mechanism that uses the linked, folding supports in the criss-cross X pattern which known as a pantograph or scissor mechanism.

Pantograph Mechanism

Scissor lifts owe their mechanical capability to the pantograph mechanism. Presented in a mechanical device that is a series of connected parallelograms with hinged intersections that permit the operator to elongate the mechanism whereas maintaining the integrity of the geometric figure.

As L ,the length of the base, increases, the pantograph contracts, and X° decease while Y° increase.

When the base of the beams is pushed together, the structure extends, raising the work platform vertically which is too easy to control. As the length of the base increases, the scissors get folded. As the length of the base decreases, the scissors extend.

Scissor lifts need a linear motion to produce elevation and this force is provided by a pneumatic or hydraulic mechanism, or a mechanical input such as a leadscrew or rack and pinion drive.

Hydraulic system

The most common type of scissor lifts comes with a hydraulic system. This system uses hydraulic fluid to maintain pressure on the lift and keep it in place when extended. You can lower the scissor lift by releasing the pressure. A scissor lift under fluid power is preferred because its valve which allows the lift to be lowered during any malfunctions.

Most scissor lifts are often consist of main five elements

1. The Platform
The products being lifted will be put on the top of the table, commonly referred to as the platform.

2. The Base

The bottom of the scissor lift that consists of strong rigid brackets. Besides being the heart for the unit, the base is engineered to guide the rollers at the bottom of the scissor legs. 

Bases have a minimum size they have to adhere to, upon the size of the platform, the capacity, the amount of travel, and how the unit is being loaded and unloaded.

3. Scissor Legs 

Bridging the gap between the bottom and the platform are the vertical scissor legs. The legs carry the platform through the different elevation changes.

4. Hydraulic Cylinders

Raising and lowering the scissor lift is actuated by high pressure hydraulic cylinders. On the common hydraulic scissor lift tables, the number of cylinders will typically vary from 1 to as many as 4 cylinders.

5. Power supply

Hydraulic lift tables are usually power-driven by diesel, gas or electrical motor. They can even be power-driven pneumatically via a high industrial compressor. 

Hydraulic scissor Lift Operation

A hydraulic lift table raises and lowers once hydraulic fluid is forced into or out of the hydraulic cylinder. As hydraulic fluid is forced into a cylinder, the cylinder strokes outward forcing the scissor legs apart.

Raising the scissor Lift

Raising a scissor lift since one finish of each the inner and outer connected to the bottom and platform, the platform rises vertically because the scissors legs close. The free finish of the scissors legs fitted with rollers that run on the base.

Any time a scissor lift is raised, it's being supported by a column of fluid. The lift table or platform remains in a high position as a result of the fluid is control within the cylinder by an easy check valve.

The desired up speed and capability to be raised verify the number of the motor needed, therefore the power unit needed. If a scissor lift must move quicker, it'll take additional power unit. If a scissor lift needs to have bigger capability, it will need additional power unit.

You should know that the journey up is not very smooth especially if you are using a scissor lift for the first time, but it is very safe and controlled. Also, the platform travels at different speeds as it raises due to the construction of the beams of the scissors lifting it.

lowering the scissor Lift

Even high capacity scissor lift is lowered by opening a down valve that allows fluid out of the cylinder at a controlled rate. This down valve is magnet operated and a normally closed sort valve, which suggests it stays closed till the electrical magnet is motivated. This feature prevents the platform from lowering if there have been any failure. When the operator opens the down valve, the fluid returns to the reservoir.

As mentioned above, the pressure on the base of the criss-cross supports can be supplied with hydraulic pneumatic or mechanical systems, but it will usually not need any power to low the working platform, this makes the scissor lift is a uniquely safe type of work access platforms. Even if power of the system fails suddenly, the scissor lift has the fail-safe ability to low the platform to the ground safely.

Pneumatic system

A pneumatic lift is usually powered with an air compressor to lift and position product for easy loading and unloading. It typically uses some type of airbag, either single, double, or multiple, depending on the size of the lift and its application. 

The obvious advantage of using a pneumatic lift is the fact that it does not require any electricity. This also means there are no risks of hydraulic exposure or process failure.

This type of lifts requires minimal maintenance and could be used in clean rooms and food processing plants. However, pneumatic lift tables are typically not used in heavy-duty applications with lower maximum capacities, where a large vertical lift is needed, or where accurate placement is required.

Pneumatic scissor lifts are appropriate for applications and industries whereby precise positioning for assembly work isn't a demand. These lifts are also used for light loads and places where the use of hydraulics is not allowed.

Pneumatic scissor lifts could be used in clean rooms additionally as in food process plants. In addition to these applications, they could also be used in garages and workshops.

Mechanical system

The least common type of systems is the mechanical system. Mechanical scissor lift raises and lowers the platform by a powered leadscrew or rack and pinion system. The mechanical system is more common on older scissor lifts.

Control

Most scissor lifts have an easy interface that enables height adjustment by the operator, although a little variety of lift tables might have preconfigured elevate heights. 

Many lifts are equipped with a security mechanism to stop uncontrolled descent to keep the operator safe and away from ant potential danger. 

Elevation and steering command is usually controlled by one joystick with a toggle.

Mobility

Motor-driven propulsion may be a valuable attribute in several jobs that require scissor lifts. This allows workers to reposition the lift easily especially in maintenance and construction applications. 

Slab scissor lifts are restricted to paved and smooth surfaces. Rough terrain scissor lifts rely on robust tires and four-wheel drive to traverse off-road conditions.

Parking brakes guarantee elevate location, and tires and casters come in non-marking, off-road, anti-slip, press-on, and urethane varieties. 

Some economical and legal reasons prevents scissor lifts from road travel but they could be hauled or towed between job sites. However, some scissor lifts is also flatbed or railcar-mounted for some specific applications. Many mobilized scissor lifts utilize outriggers for more foundational stability.

Types of mobility of scissor lifts

Most scissor lifts are designed to be very mobile, but some models have a better moving than others.

Self-propelled scissor lift

Most scissor lifts are self-propelled which means that you can drive them anywhere you want to go as long as they are capable of moving on the ground.

Manual push scissor lift

Smaller scissor lifts may require being pushed where they will be used, they are lightweight and easy to maneuver, and they are best suited for light indoors work.

Trailer scissor lift

Some scissor lifts can be mounted to a truck via a trailer hitch. You can pull these lifts wherever you need to go by truck.

Power Supply

Stationary scissor lifts are nearly always fed by associate AC electrical provide. Mobilized scissor lifts are most ordinarily charged by variable speed DC motors. They generally utilize 6V batteries that are kept in the maintenance panel beside a charging outlet that connects to AC power provides.

It is worth mentioning that most scissor lift are usually equipped with an emergency shut-off prevents operators from accidentally removing the lift throughout the recharge.

Types of motors of scissor lifts

Basically, any scissor lifts is powered by either a hydrocarbon or electrical engine. Electricity or hydrocarbon from a right away outlet or battery is utilized to power the complete scissor lift. 

Areas that have too several fumes like combustion areas and construction are more likely to have a hydrocarbon or diesel powered scissor lift. 

Electrically supercharged scissor lifts are ideally used indoors or in places wherever burnable materials and objects are unallowed. Electric scissor lifts could be used outdoors and are more likely to be utilized in stocking materials and product jobs. This type of lifting machines is capable of reaching 9 to 40 feet.

Electric motor

Most slab scissor lifts are powered by an electric motor which eliminates fuel emissions, making them ideal for indoor use. However load capacities and work platforms are smaller than internal-combustion engine scissor lifts.

Diesel motor

Gas, diesel or propane engine scissor lifts have higher load capability with better traction management creating them ideal for outdoors worksites. Some might embody a hybrid drive for operating in closed job sites. This type of scissor lifts are the most popular in construction applications.

Finally 

There is some main characteristics that could describe the vertical capabilities of any scissor lift like stroke, size and capacity.

Stroke is the vertical distance that earned by using the scissor lift mechanism which is directly correlate with number of supported beams and the length of each element utilized in the scissor lift. Many scissor lifts are associated with an extendable platform to extend the size and the area of the work space elevated by the lift. And capacity which is the maximum load that the lift is designed to safely support, be it personnel, construction tools or any other load.