Screw and nut driven lifts (electric lifts) are changing the way lifts and elevators can be used, maintained and installed. They are a less well known system than hydraulic lifts or traction lifts, but are coming to the forefront with smaller projects as budgets, time and space are reduced.
By understanding how platform lifts work you can keep an eye on yours and know when maintenance or attention is required, saving money and time. If you are looking at purchasing a lift for your commercial or public building, our guide can help you decide if this is the best type of lift for the job.
What is in a Screw and Nut Lift?
Screw and nut drive lifts are one of the most simple systems of elevation. Growing in popularity due to simplicity, cost, maintenance requirements and size, Gartec platform lifts are driven by a screw and nut system.
The main components of screw and nut drive lifts are:
- threaded steel bar (“screw”)
- large drive nut (“nut”)
- electrical supply
With so few components, screw and nut drive lifts are generally machine-room-less (MRL). A very small footprint is possible due to minimal machinery and equipment.
Also it is worth noting that there is no deep oil pit with screw and nut drive lifts. This saves you space and reduces building work requirements.
How Do Screw and Nut Lifts Work?
Screw and nut drive lifts are incredibly simple. The lift car (or platform) is attached to the drive nut. When a control button is pressed in the lift, the motor turns the drive nut in the corresponding direction.
When the motor turns the drive nut one way, the lift car goes up. When the motor turns the nut the other way, it goes down.
And that’s basically it!
There is oil required for the system to keep it running smoothly and quietly. In a Gartec platform lift, we include a small container of oil which is attached at the base of the screw. When the drive nut reaches the bottom, it dips into the oil. When the lift is taken up again, the oil is carried up the threaded bar and keeps it lubricated.
The screw and nut lift system is used for a range of lift types. Open platform lifts with enclosed shafts, like the Gartec 7000, use an “L” shaped carrier driven up and down within a shaft, so you can see the walls around you moving. In contrast, enclosed cabin platform lifts, like the Gartec 9000, are a classic box enclosure which is driven up and down in the same way, feeling much more like a conventional lift.
Pros & Cons of Screw and Nut Drive Lifts
Screw and nut drive lifts have many great features but may not be suitable in every environment. If you are choosing a lift for your business, make sure your requirements can be met and any downsides won’t be a deal breaker.
The simplicity of the mechanism means it is easy to maintain and service. Usually screw and nut drive lifts are relatively low cost initially and over the lifetime.
As the system has so few parts, screw and nut drive lifts have a small footprint. The shaft or enclosure is usually not much larger than the size of the platform you choose. Platform lifts are ideal for small spaces.
Screw and nut drive lifts are incredibly safe. If the motor stops, the lift basically sits on the thread so cannot fall or do the classic ‘dead drop’ situation associated with lifts in films.
With no huge oil pits, and generally no head fixing or similar, screw and nut drive lifts are usually very quick and easy to install. There are minimal building works required and, in the case of Gartec lifts, the lift structure is modular so takes around 2-3 days to install.
If the system is used in an open platform lift, such as our 7000 lift, then the buttons on the platform are hold-to-run. This is due to the machinery directive being the governing regulation, rather than the lift directive.
The speed of a screw and nut drive lift is not quite as fast as traction lifts or hydraulic lifts, making them not as suitable for tall buildings (over around 6 floors). Open platform lifts (such as the Gartec 7000) are restricted to 0.15m/s, instead of 0.2-0.3m/s for other drive types.
Weight restrictions on screw and nut drives are a little lower than hydraulic or traction lifts. Gartec platform lifts go up to 500kg, so the difference is only noticeable if you need a very large lift. A large goods lift will normally use a different system for example.