Issue 4/2006


07/02/06

New Lift Machines for MRLs

Improved Accessibility for Maintenance and Emergency Operations
Ing. Luciano Faletto (S.A.L.A. Consulting S.a.s. Italy)
With the spreading of MRL lifts, there is growing evidence within the Coordination Committee of the Notified Bodies – Lift and the representatives of the Member States at the Standing Committee Meeting for the implementation of the Lift Directive that many of the new type of lifts need to be improved in some major issues, such as:
Category: Issue 4/2006
Posted by: Editor
  • Easier accessibility to the drive machine for the emergency operations.
  • Safe access to the working places for adjusting, repairing, replacing of machine parts, even when the machine is out of operation.
  • Need to have available hand winding wheel for rescue of trapped passengers in any load conditions.
  • Readily available means for the operations of easy disengagement of the safety gear, as traditionally possible when the machine is placed in a machine room.
The above needs are supported by the Essential Safety Requirements of the Lift Directive, including also the applicable ones of the Machinery Directive.
There are also other requirements coming from the market, such as:
  • Highly efficient machines and drives in order to reduce overall energy consumption
  • Highly performing machines and drives able to guarantee accurate leveling and good ride comfort
BRAVO SpA started a project of a set of new machines based specifically on all the above requirements and the outcome of the development work is the YoYo series of gearless machines that, together with the relevant drives and an example of their possible convenient applications, are the subject of this presentation.
Specifications of new lift machines
As the target of BRAVO was to develop a machine with high performance and high efficiency, the first decision was to select a gearless type of synchronous machine, with permanent magnets rotor, which would have also the advantage of assuring a self braking effect in case of emergency operation with free rotation under load and lack of energy supply. At present three machine sizes have been planned:
  • YoYo 1 for lifts up to 630 kg capacity at 1,6 m/s
  • YoYo 2 for lifts up to 1200 kg capacity at 1,6 m/s
  • YoYo 3 for lifts up to 2000 kg capacity at 1,6 m/s
For optimized MRL lift arrangements with guaranteed possibility to access the machine in the various working conditions, there was the need to keep the overall size of the machine as limited as possible and this brought to the selection of solutions less common, but quite convenient, such as the adoption of an external rotor to which the traction sheave can be directly flanged (Figure 1).
In this case the stator is fixed to the stationary shaft and the coil expansion windings can extend inside the traction sheave, with further saving of space, while the inside of the motor can accommodate also internal position sensors which help assuring a perfect feedback of the rotor movement and a consequent high quality control of the supply wave- form. For this specific purpose even a dedicated drive has been developed, with use of the latest technologies that allow extremely fast and accurate torque and speed control, such that there is no need for any external devices that detect unbalanced car load in the initial starting of the lifts.
The rotating parts are carried by two separate bearings in order to reduce stress, deflections and overall weight, while low stroke electromagnetic brakes operate directly on the outside of the rotor surface. There are a minimum of two independent modular brakes, whose total number can be adapted to suite the torque output range of the machine. All the brakes are easily accessible for maintenance checks, adjustment and repair (Figure 2).
The direct mechanical connection between the traction sheave and the brake acting elements is such that there is no need for additional devices to prevent uncontrolled upward movement of the lift car. The machine is of the foot mounted construction, suitable for both MRL applications and traditional ones with machine room, which makes it also suitable for replacement of traditional gears in case of upgrade of lift performance. On the outside of the traction sheave there is an easily operated emergency handwinding device, suitable for manually moving the lift car in case of power failure and almost balanced load conditions (Figure 3).
The handwinding wheel is directly connected with a rubber tired roller which, when necessary, can be firmly positioned against the external surface of the traction sheave and suspension ropes, so that the latter can be moved through friction in the direction most favourable according to the load conditions inside the lift car. The positioning of the rubber tired roller is done manually by means of an eccentric bearing which is properly controlled by electrical safety contacts in both the engaged and the released positions (Figure 4).
Manual operation of the lift is facilitated by the limited free rotating speed of the machine in case of loss of power, with manually released brakes, even in the worst loading conditions, thanks to the self braking effect of the permanent magnet rotor construction. To complete the features that facilitate emergency operation, the traction sheave is fitted with special attachments suitable for fixing rope clamping devices that guarantee the possibility to disengage the car safety gear in case of need.
The overall shape of the machine is such that one end has a thickness smaller than the other end so that it is easier to fit it at the side of the car and of the door in those MRL applications where the full accessibility of the machine is guaranteed in all working conditions. In these applications, which are described further on, the centre distance of rope grooves on the traction sheave is about twice the traditional one, in order to allow the crossing of the ropes, when necessary due to these specific lift layouts.
Example of MRL lift with fully accessible machine
The Se.Sa.Mo. Tre certified model lift, produced by Centoducati Spa in full conformity with the Lift Directive requirements, is one example of MRL lift that is already available in the market and makes use of the YoYo machine and drive to achieve the result of assuring full accessibility of the equipment in all operating conditions, including maintenance, repair and emergency operations. The basic layout for a 630 kg – 8 persons lift at 1,00 m/s is shown in Figure 5.
In this type of lift the gearless drive machine is placed adjacent to the landing door of the top floor, on one side of the upper part of the door. The car has a 2:1 underslung suspension and the car guide rails are placed across the width of the car. The car sling is made of a top beam in one single piece of bent sheet steel, with a vertical thickness limited to 50 mm. The car suspension pulleys are placed parallel to the bottom beam of the car sling.
The counterweight is placed at the same side of the car as the drive machine and its suspension pulley is conveniently tilted compared to the plane of cwt guide rails. The car door is three panel telescopic type and the side of opening is opposite to the side where the drive machine is positioned. The landing doors are two panel telescopic type, except the door at the top floor which is three panel type as the car door.
The lift is fitted with a main diverter pulley that is placed, with its rotating axis only slightly inclined compared to the plane of the car guide rails, behind the guide rail on the same side as the drive machine. The number of grooves of the main diverter pulley is two times the number of ropes so that the ropes can pass two times over the main diverter pulley. As a matter of fact this pulley has two functions: it supports both the ropes that come from the upper part of the traction sheave and go towards the counterweight and also supports the ropes that come from the lower part of the traction sheave and go towards the car suspension pulleys. The inclination of the axis of the pulley facilitates the crossing of the ropes and the double wrapping of the ropes on the pulley itself (Figure 6).
The ropes travel from the traction sheave to the main diverter pulley and widely wrap on the diverter pulley so that their bending is concurrent and avoids increasing the fatigue stress in the rope wires.
The ropes coming from the top of the traction sheave are accommodated in grooves that are alternated with those where the ropes coming from the bottom part of the traction sheave are accommodated and this explains why the number of grooves of the main diverter pulley shall be twice the number of ropes.
The ropes coming from the bottom part of the traction sheave can wrap for more than 180° on the main diverter pulley and go to an additional secondary pulley from where they can travel vertically towards the car suspension pulley. Along this path these legs of ropes cross each other where their path is controlled by the nearby pulley grooves.
The rope fixings are placed near the upper part of the car guide rails and are supported largely by the guide rail and partly by the building structure. The speed governor is suitable for remote test and reset operations and is placed in the upper part of the lift well, supported by one of the beams bearing the main diverter pulley and the rope end fixing on the counterweight side.
The drive machine is of the YoYo type and is placed at the side of the upper part of the top floor landing door. There are two fixing means for the machine: a bedplate anchored to the side wall of the lift shaft and also a short structural element connecting the machine to the supporting structure of the main diverter pulley, in order to compensate the forces between these two items.
The volume in which the machine is placed is in direct connection with the lift well and lays partly within the landing floor area, from which it is separated by the enclosure of a machinery cabinet (Figure 7).
The inside of the machinery cabinet can be easily accessed from the landing through suitable front access doors placed at the side of the lift landing door. The machine can be accessed both from the landing side, through the cabinet door, and from the lift well side, where the car can be stopped and retained with the ceiling at floor level so that the car top can act as a safe working area easily accessed through the lift landing door (Figure 8).
The doors of the machinery cabinet are fitted with all the necessary safety features to allow safe inspection to the electrical and mechanical equipment, including the manual operation of the lift in case of rescue of trapped passengers. The operation of the handwinding equipment, necessary only when the load in the car is almost balanced, so that the car does not move due to the unbalanced load, is performed as described for the YoYo machines.
The accessibility of the traction sheave from the landing allows the attachment of rope clamps that enable also the disengagement of the safety gear when it is tripped for test or emergency purposes.
Conclusions
The component manufacturers have always been very concerned about the correct compliance of their products with the requirements of existing standards, in the past, and with the requirements of the Lift Directive, since its implementation. They are fully understanding the mounting pressure from some Member States and some Notified Bodies to have fully guaranteed not only the safety of lift passengers, but also the safe working conditions of the lift maintenance, inspection and rescue operators. This has brought to the development of some new products that, although still somehow more expensive, efficiently help attaining the expected safety levels.
The products presented here are only examples of this new wave of projects that should be followed by others, similarly developed and placed in the market by all the manufacturers and installers. This in order to make sure that, in some years from now, there is not the need to urgently upgrade the safety level of the lifts made today, while there is mounting evidence that the one guaranteed now is not always adequate to fully comply with the Essential Safety Requirements of the Lift Directive.
If we do not comply with this imperative need for mere cost factors, although minimal, or for other even less accept able reasons, the spreading of the new types of lifts might easily bring to an unexpected increase in casualties among the operators in the lift service business. Many people doubt that this is what we should expect from the implementation of new technologies.
Lecture on the occasion of the European Lift Congress Heilbronn (ELCH), 28 and 29 June 2005
Ing. Luciano Faletto graduated in mechanical engineering at the Polytechnic University of Naples in 1965, while already working at FIAM, a lift company based in Milan. He spent one year at the Express Lift Co. Ltd. in Northampton then he continued his career at FIAM where he became Engineering Director. Since 1987 he was part of Kone organization in which he had various responsibilities such as General Manager of Bassetti Elevatori, Project Manager in the Far East, and General Manager of Sabiem production unit. He retired from employment work in 1998 and since then he is director of SALA Consulting, which provides technical and managerial advice to lift components manufacturers and to their Associations. Ing. Faletto is a member of several CEN, ISO and UNI code committees.
4/2006

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