Low Speed Pinched Roller Drive for Lifts on Curves (Patent Pending)

The principle and construction of the “Univator” is simple and a small scale prototype was built for exhibition at the 2014 Venice Biennale and, as can be seen here, was successfully up and running at the opening of the exhibition on June 7, 2014.

This is the world’s first electric traction rope-less lift that can travel on a curve. A full scale version of this new drive would be required for safety certification which would take around six months to assemble. Once the drive is proven at full scale the design and specifications for the cabins and track can be completed and a prototype cab built.

For the first time in 125 years architects and building designers can now plan lifts in buildings that can travel on a curved trajectory and perform as reliably and as smoothly as regular vertical passenger lifts. The major advantages of such a traction drive are the lack of ropes and counterweight which mean that cabins can be driven along a curved track and multiple cabins can be driven along the same track independently of each other.

Key Components:
All the motors are fed from a common supply bus that extends along the entire length of the track. The motors are serially activated as a cabin passes along the track to impart the necessary force to maintain, increase or decrease speed. Safety is assured in a very similar manner to a standard traction driven elevator. When loss of power occurs all motors shut down and the cabins are brought to a stop. Each cabin can be fitted with a battery that will provide sufficient energy to complete the lift’s current journey and allow passengers to alight in the normal manner.

In addition there is a “failsafe” feature incorporated that allows a cabin to descend under gravity dissipating the necessary energy as it does so within the motor assemblies enabling constant slow speed descent until it reaches the nearest landing entrance whereupon it can open its doors, allow passengers to exit and park permanently pending resumption of power to the system.

The cabins will be lightweight construction built to the minimum size to comply with wheelchair access codes and fitted with standard automatic doors and door operators. The cabins naturally hang vertically but will also have a damper mechanism to smooth out any sway caused by accelerations the cabin experiences.

Pinched Roller Drive for Univator:
The pinched roller drive principle can be used to drive a passenger lift or cabin through various trajectories unlike rope driven lifts. This is now possible because the materials necessary e.g. American Maraging 300 steel, used for the moving bar and the pinch rollers are now available and can withstand the very high surface stress levels. The smoothness and quietness of a passenger lift can therefore be achieved from such a drive.

Each set of pinch rollers is driven with a compact motor assembly which also has an inverter drive mounted on the unit. The pinch rollers and their motors are installed at appropriate intervals along the track such that the rod element engages a number of pinched rollers simultaneously in order to transfer enough force to the rod. The rod may have multiple “wings” or connection points to the cabins that are connected to the rod. The rod is cast and the track formed to match the curvature of the cabin trajectory.

Trains move by traction drive – heavy engines exert high pressure on the rails on which they run due to the very small area of contact. Even with low coefficient of friction when the wheels turn the train moves. Accurate alignment of wheels and rails enables quiet smooth motion. In fact, traction drive is used in most lift applications where the suspension ropes make line contact with the traction sheave of the winding machine. Traction drive with pinched rollers has been used in many industrial applications for accurately moving large masses horizontally without slip. The “pinched roller” drive can be seen here in operation on the prototype model where the curved steel bar can also be seen being driven by three sets of pinched roller assemblies.

The “Univator” invention envisages two forms of “pinched roller” drive dependent upon the mass of the cabin and the angle of incline. For vertical or near vertical inclines the pinched roller drive assemblies are used along a track structure which drive a circular bar which is the moving element attached to the lift cabin. For lower angles of incline it will be possible to mount the pinched roller drive assemblies on the cabin itself. The latter is a much more economic solution. Either way this novel form of drive offers an ultra smooth, quiet and zero backlash linear motion.