Patent Description:
In order to maximise installation efficiency while maintaining cost-effectiveness, elevators are conventionally designed and commissioned to operate within predetermined nominal operating conditions, such as rated load and speed, to satisfy the specified transport requirements for a specific installation.

There are, however, temporary and infrequent occasions when it would be useful for the building owner to be able to operate the elevator outside of the nominal operating conditions e.g. for transporting a heavy article, such as an electrical transformer, that would otherwise overload the elevator.

Conventionally, a solution has been used whereby the mass of the counterweight is increased in proportion to the intended overload of the car so as to maintain the balancing factor between the car and counterweight. After the overload has been transported to the desired location, the additional mass is removed from the counterweight and the elevator can be returned to normal operation.

An alternative solution has been described in <CIT> wherein an additional hoist is attached to the elevator car to supplement the existing elevator drive and thereby compensate for the overload. As with the previous example, after the overload has been transported to the desired location, the additional hoist can be detached from the car and the elevator can be returned to normal operation.

In both the methods described above the technician is required to attach additional equipment to an elevator component which is designed to move substantial distances within the hoistway, such as affixing a substantial additional mass to the counterweight or attaching an additional hoist to the elevator car. Not only are these procedures time-consuming and cumbersome but they can also be inherently dangerous. Futhermore, in the first procedure described above, the additional mass is generally added to the counterweight from the pit of the elevator installation. The resultant severely overbalanced elevator is then moved by the drive so that the overload, e.g. transformer, can be loaded into the empty car from the ground floor. This severely unbalanced trip requires the drive to produce and the motor to consume substantially larger electrical currents than during normal operation which can greatly reduce the lifespan of both electrical components.

The above issues are, in at least some cases, addressed through the technologies described in the claims.

<CIT> discloses traction enhancement for a traction elevator system that has an elevator car and counterweight connected by a plurality of wire ropes reeved about a drive sheave with a predetermined angle of wrap. ·An arcuate frame having a plurality of rollers has one end pivotally and adjustably fixed, while its other end biases the rollers against the ropes in the angle of wrap with a tension spring. Over travel of the elevator car releases the bias to allow the ropes to slip should the counterweight reach an end of its travel path.

<CIT> discloses that a motor of a rope type elevator is provided with a rotational quantity detecting device, and a car is provided with a car position detecting device and a live load detecting device. A sheave is provided with a balance sensor. Whether a slip occurs between a rope <NUM> and the sheave or not is estimated from the weight unbalance calculated based on the weight unbalance from the balance sensor or the signal from the live load detecting device before an elevator operation. Whether the detected weight unbalance is below a tolerance or not is judged by collating the obtained value with a friction coefficient database prepared in advance, and a slip distance reducing process is conducted when the weight unbalance exceeds the tolerance.

<CIT> discloses an elevator device that is constituted in such a way that a car and a counterweight are suspended on one end side and the other end side of the main rope stretched around a traction sheave to raise and lower the car and the counterweight in mutually opposing directions. A first idler sheave and a second idler sheave supported rotatably on a fixed side shaft and a displacement side shaft, respectively, are arranged in the vicinity of sheave circumference on the right and left sides by required distance from the uppermost part of the traction sheave. An endless belt is stretched around these idler sheaves. A rope bearing pressure increasing device provided with a tensile force adding mechanism for adding required tensile force to the endless belt by giving displacement force to the idler sheave on the displacement shaft side is provided to constitute the traction increasing device for the elevator rope for adding pressing force to the main rope stretched around the traction sheave in accordance with tensile force of the endless belt.

<CIT> discloses that a machine frame with two side members at its ends comprises support arms, which are pivotably mounted in semi-circular cut-out bearing supports. The bearing supports may be arranged on differently high pedestals, which may result in different inclined positions for the machine frame with respect to a machine room floor. The inclined position may provide for a variable looping angle beta at the drive pulley and variable cable spacing between the cage cables and the counterweight cables. Furthermore, the deflecting roller may be mounted in laterally displaceable bearing plates. The deflecting roller may be inserted above or below a pair of side members. The position of the deflecting roller with respect to the side members may also have an effect on the looping angle beta and the cable spacing. The combination of these adjustment possibilities enables the substantially universally adaptability of the machine frame to different elevator systems and applications.

<CIT> discloses a controller for an elevator that is equipped with a converter that converts alternating current power to direct current, an inverter that converts the output of the converter into variable voltage alternating current power, and an induction motor that is powered by the inverter and drives an elevator car. In an elevator control device, the windings of the induction motor are normally delta-connected, and when the elevator is operated for a short period of time at low speed and with a heavy load, the delta-connection is switched to a y-connection for operation.

An objective of the present invention is to enable the temporary transportation of an overload within an elevator installation having a car and a counterweight interconnected by one or more suspension ropes engaging a traction sheave which is driven by a motor. This objective is achieved by a method according to claim <NUM> and an elevator installation according to claim <NUM>.

Instead of adding an additional hoist to the car or additional mass to the counterweight, the traction between the suspension ropes and the traction sheave is enhanced independently of the counterweight. Instead of adding additional mass to the counterweight as in the prior art previously discussed, the enhanced traction between the suspension ropes and the traction sheave according to the present invention facilitates the temporary operation the elevator outside of normal, nominal operating conditions so as to enable the transportation of a heavy, overload from one floor to another.

Preferably, enhanced traction is achieved by increasing the tension on a compensation rope suspended between the car and counterweight. An actuator can be provided for selectively applying force to the compensation rope.

Alternatively, the traction can be enhanced by squeezing the ropes in grooves on the traction sheave. In such a case, the traction sheave may be provided with an undercut to improve traction between the suspension ropes and the traction sheave or V-grooves can be provided on the traction sheave. In another example a liner is introduced between the traction sheave and the suspension ropes to enhance traction.

In an alternative arrangement, a device may be installed to exert pressure on the suspension ropes as they engage with the traction sheave over a wrap angle. The pressure exertion device may comprise a tensioned, closed-loop belt entrained over one or more rollers.

Traction may be enhanced by increasing the wrap angle over which the suspension ropes engage the traction sheave. If the suspension ropes between the car and the counterweight follow a path over the traction sheave and a deflection pulley, the deflection pulley can be displaced to change the wrap angle. Alternatively, an additional pulley can be introduced between the sheave and the deflection pulley to change the wrap angle.

In accordance with the claims, the motor is switchable between parallel and series configuration.

During intended overload operation, the speed and acceleration of the elevator can be reduced, forced cooling can be introduced through the drive and the motor, the travel path to transport the overload can be broken up with intermediate stops and/or the number of starts the elevator can make in an hour can be restricted.

Other objectives, features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings, in which:.

<FIG> illustrates an exemplary embodiment of an arrangement of components within a typical high-rise elevator installation <NUM>. An elevator drive <NUM>, a deflection pulley <NUM> and an elevator controller <NUM> are arranged in a machine room above a hoistway <NUM>. Within the hoistway <NUM>, an elevator car <NUM> and a counterweight <NUM> are supported on suspension ropes <NUM>. In this example, the suspension ropes <NUM> have a <NUM>:<NUM> roping ratio whereby they extend from an end connection fixed to the car <NUM> up the hoistway <NUM> for engagement through a wrap angle α with a traction sheave <NUM> which is rotated by a motor <NUM> of the elevator drive <NUM>, subsequently over the deflection pulley <NUM> and back down the hoistway <NUM> to a further end connection fixed to the counterweight <NUM>. Naturally, the skilled person will easily appreciate other roping arrangements, such as <NUM>:<NUM>, <NUM>:<NUM> or x:<NUM> roping ratios, are equally possible and the invention can also be implemented with elevators using belts instead of conventional suspension ropes.

Preferably, the counterweight <NUM> is designed so that its total mass is equal to the sum of the mass of the empty elevator car <NUM> plus <NUM>% of the nominal rated load.

In high-rise applications particularly, not only must the imbalance between the car <NUM> and counterweight <NUM> be considered, but also the imbalance caused by the weight of the suspension ropes <NUM> is appreciable. For example, if the car <NUM> is at the lowest landing within the hoistway <NUM> and thereby the counterweight <NUM> is at high level within the hoistway <NUM>, the majority of the length of the suspension ropes <NUM> is located on the car side of the traction sheave <NUM> rather than on the counterweight side of the sheave <NUM>. To offset this imbalance due to the suspension ropes <NUM> it is conventional practise to install one or more compensation chains or ropes <NUM> suspended between the car <NUM> and the counterweight <NUM>. For convenience only one compensation rope <NUM> is illustrated in the drawing, but it will be appreciated that more than one compensation rope can be installed. The compensation rope <NUM> is guided under pulleys <NUM> in a weighted pulley box <NUM> located in a pit of the hoistway <NUM>.

Accordingly, the suspension ropes <NUM>, the car <NUM>, the counterweight <NUM> and the compensation rope <NUM> form a closed-loop system where the length of the suspension ropes <NUM> and compensation rope <NUM> on the car side of the traction sheave <NUM> is substantially equal to that on the counterweight side of the traction sheave <NUM>.

In normal operation, the elevator controller <NUM> receives signals from conventional landing operating panels and car operating panels (not shown) to determine the travel path that the elevator <NUM> must undertake in order to satisfy passengers' travel requests. Once the travel path has been determined, the controller <NUM> outputs signals to the drive <NUM> so that the traction sheave <NUM> can be rotated by the motor <NUM> in the appropriate direction. The traction sheave <NUM> engages with the suspension ropes <NUM> to vertically move the car <NUM> and counterweight <NUM> in opposing directions along guiderails (not shown) within the hoistway <NUM>. Additionally, from signals generated by a load measurement device <NUM> mounted to the elevator car <NUM>, the controller <NUM> can monitor load within the car <NUM>, and particularly, can determine whether the car <NUM> is overloaded while stationary at any landing. In this case an overload alarm can be issued within the car <NUM> to allow some passengers to disembark from the car <NUM>.

If the overload alarm is overridden in the elevator controller <NUM>, and a heavy overload, such as a transformer, is subsequently introduced into the elevator car <NUM> from a landing, the substantial imbalance between the overloaded car <NUM> and counterweight <NUM> will ultimately cause the suspension ropes <NUM> to slip in the traction sheave <NUM> resulting in unintended if not uncontrollable car movement. In such an overload condition, the elevator <NUM> can be severely underbalanced since the mass of the counterweight <NUM> with the <NUM>% balancing factor as discussed previously is no longer capable of balancing the overloaded elevator car <NUM>.

A solution to this problem is provided for with a compensation rope tensioning device according to the invention as illustrated in <FIG>. In this embodiment, the compensation rope pulley box <NUM> is attached through a damper or spring <NUM> to an actuator <NUM> mounted to the pit floor <NUM> of the hoistway <NUM>. In normal operation when the elevator <NUM> is operating under nominal, rated load conditions, as shown in <FIG>, the actuator <NUM> and spring <NUM> impose a downward force Fc1 on the pulley box <NUM>. This force Fc1 is ultimately transmitted through the compensation rope <NUM>, the car <NUM> and counterweight <NUM>, to act as tension within the suspension ropes <NUM>.

If however, the elevator installation <NUM> is to be used for the temporary transportation of an overload within the car <NUM>, the actuator <NUM> draws the spring <NUM> and the pulley box <NUM> downwards imparting a greater downward force Fc2 on the pulley box <NUM> resulting in greater tension the suspension ropes <NUM>. This greater tension in the suspension ropes <NUM> about the traction sheave <NUM> improves or enhances the traction therebetween reducing the likelihood of slippage when an overload is introduced into the car <NUM>.

The actuator <NUM> may be hydraulic, pneumatic, electromechanical or purely mechanical and can be automatically operated via command signals from the elevator controller <NUM> or it can be manually operated from the pit <NUM> of the hoistway.

Although, in the illustrated embodiment, the actuator <NUM> is used for both normal and overload conditions, it will be appreciated that the weight of the pulley box <NUM> may be used exclusively to impose the required tension to the compensation rope <NUM> during normal operation, as in <FIG>, and the actuator <NUM> may be temporarily installed to the pit floor <NUM> to increase the downward force Fc on the pulley box <NUM> for intended overload operation only.

Naturally, the person skilled in the art will also appreciate that instead of the actuator <NUM>, additional weights can be added to the pulley box <NUM> to increase the downward force Fc acting on the compensation rope pulley box <NUM> for intended overload operation. Alternatively, additional compensation chains or ropes <NUM> can be installed to increase the tension in the suspension ropes <NUM> about the traction sheave <NUM> resulting in enhanced traction therebetween.

<FIG> is a plan view of the drive <NUM> and deflection pulley <NUM> arrangement from <FIG>. As previously described, in normal operation, the suspension ropes <NUM> extend from the car <NUM> for engagement through a wrap angle α over the traction sheave <NUM> which is rotated by a motor <NUM>, subsequently over the deflection pulley <NUM> and back down the hoistway <NUM> to the counterweight <NUM>.

For overload operation, the arrangement can be modified as illustrated in <FIG> to enhance traction between the traction sheave <NUM> and the suspension ropes <NUM>. In the example of <FIG>, the deflection pulley <NUM> is vertically displaceable, so that for intended overload operation the pulley <NUM> is displaced downwards as shown which results in the suspension ropes <NUM> having a greater wrap angle α<NUM> about the traction sheave <NUM>. Naturally, the deflection pulley <NUM> could be horizontally displaceable to achieve the required change in the wrap angle α.

In the alternative shown in <FIG>, the deflection pulley <NUM> remains in the same position as in <FIG> but an additional pulley <NUM> is introduced between the sheave <NUM> and the deflection pulley <NUM> to engage with the suspension ropes <NUM> and thereby again increase the wrap angle α<NUM>.

It will be apparent to the skilled person that other arrangements are possible in order to increase the wrap angle to enhance the traction between the suspension ropes <NUM> and the traction sheave <NUM>. For example, instead of having a single wrap arrangement as shown in <FIG>, the suspension ropes <NUM> may be double wrapped, as shown in <FIG>, or even triple wrapped around the traction sheave <NUM> and the deflection pulley <NUM>.

<FIG> is an exploded view of the machine <NUM> and deflection pulley <NUM> of <FIG>. If an overload operation is intended, a pressure exertion device <NUM> is provided to exert a pressure (shown by the arrows) on the suspension ropes <NUM> as they engage the traction sheave over the wrap angle α. The device <NUM> comprises a tensioned, closed-loop belt <NUM> entrained over two rollers <NUM>. Accordingly, the traction between the ropes <NUM> and the sheave <NUM> is enhanced by the additional pressure exerted on the ropes <NUM> by the closed-loop belt <NUM> of the device <NUM>. In most conventional high-rise elevator installations <NUM>, as depicted in <FIG>, the suspension ropes <NUM> are manufactured from steel and engage with a steel surface on the traction sheave <NUM>. The coefficient of friction of steel-to-steel is relatively low. In such a situation, in order to accommodate overload operation, the arrangement illustrated in <FIG> can be implemented wherein a traction sheave liner <NUM> is introduced between the traction sheave <NUM> and the suspension ropes <NUM>. The liner <NUM> is preferably made of a plastics material which enhances the coefficient of friction and thereby the traction of the system.

<FIG> is an axial cross-section through the top of the traction sheave <NUM> shown in <FIG>. The suspension ropes <NUM> are accommodated in and engage with half-rounded grooves <NUM> provided around the circumference of the traction sheave <NUM>. In order to enhance the contact and thereby the traction between the suspension ropes <NUM> and the traction sheave <NUM> it is possible to provide undercuts <NUM> as shown in <FIG>. Alternatively, V-shaped grooves <NUM> as shown in <FIG> can be implemented to improve contact between the suspension ropes <NUM> and the traction sheave <NUM>. The person skilled in the art will readily recognise that other groove arrangements on the traction sheave <NUM> which squeeze the ropes <NUM> as they engage the traction sheave <NUM> can be employed to improve contact and thereby traction between the sheave <NUM> and the ropes <NUM>.

<FIG> illustrate a traction sheave <NUM> having an alternate sequence of half-rounded grooves <NUM> and V-shaped grooves <NUM> in the axial direction. In <FIG> the ropes <NUM> are accommodated in the half-rounded grooves <NUM> for normal operation. If overload operation is intended, the ropes <NUM> can be transferred into the neighbouring V-shaped grooves <NUM> as shown in <FIG> to enhance contact and traction between the suspension ropes <NUM> and the traction sheave <NUM>.

Although each of the previous embodiments of the invention have been described separately, it will be appreciated that features of the individual embodiments can be combined to enhance traction between the traction sheave <NUM> and the suspension ropes <NUM>.

In addition to any of the techniques described above to enhance traction between the traction sheave <NUM> and the suspension ropes <NUM>, it is also beneficial to increase the torque transmitted from the motor <NUM> to the traction sheave <NUM> when operating the elevator <NUM> in overload conditions. A typical drive <NUM> for the elevator installation <NUM> is depicted in <FIG>. Electrical power is drawn from a three phase AC mains power supply, passed through an AC-DC power converter <NUM> which supplies DC in a DC bus or link <NUM>, inverted by a DC-AC power inverter <NUM> and fed in three phases U, V and W onto the three phase AC motor <NUM>.

Within the three phase AC motor <NUM>, the armature windings are arranged in double star configuration with the winding pairs of each phase U, V, W arranged in parallel, as shown in <FIG>. In order to increase the motor torque for operation in overload conditions, the drive <NUM> should deliver more current, which could exceed the maximum allowable value or overheat the drive's semiconductors. A commutation from parallel to series connection of the motor windings as shown in <FIG> decreases the needed current for the required torque. This commutation from parallel to series connection can be conducted manually by a certified technician by appropriate re-wiring of the terminal box of the motor. More preferably, however, the commutation can be achieved by means of an electrical switch attached to the terminal box. The electrical switch can be actuated manually by a technician or can be activated automatically by the elevator controller <NUM>.

By reconfiguring the armature windings as discussed above for intended overload operation, the operating voltage will inherently rise. In order to mitigate against the deleterious effects of over-voltage on the drive <NUM>, the speed and/or the acceleration of the elevator <NUM> can be reduced, enhanced forced cooling can be implemented through the drive <NUM> and motor <NUM> and the travel path to transport the overload can be broken up with intermediate stops. Preferably, during intended overload operation, the number of starts that the elevator <NUM> can make in an hour is restricted.

An example of a procedure to temporarily operate the elevator <NUM> outside of normal, nominal operating conditions so as to enable the transportation of a heavy, overload from one floor to another is explained with reference to the flowchart illustrated in <FIG>. The process commences at step S1 when the elevator car <NUM> in response to a call arrives at a landing of the building and the doors are subsequently opened. At this point, the elevator controller <NUM> can monitor the load within the car from signals generated by the load measurement device <NUM>. If no overload is detected by the controller <NUM> at stage S2, the doors can close and the elevator <NUM> can commence a normal trip at stage S3 in response to conventional elevator calls.

On the contrary, if an overload is detected at S2, the procedure progresses to step S4 where a determination is made as to whether the controller <NUM> has been switched or enabled for an overload trip. If at stage S4 the controller <NUM> has not been enabled for an overload trip, then the car <NUM> remains stationary at the landing with its doors open and an overload alarm can be issued at step S5 within the car <NUM> to allow some passengers to disembark from the car <NUM>.

If an overload trip has been enabled within the controller <NUM> at stage S4, then traction between the ropes <NUM> and the traction sheave <NUM> is enhanced at stage S6 in accordance with the examples illustrated in and described previously with respect to <FIG>. Furthermore, at stage S7 internal parameters of the drive <NUM> can be switched by software or keyswitch so as to protect the drive <NUM> and motor <NUM> during the intended overload travel. For example the speed and/or the acceleration of the elevator <NUM> can be reduced, enhanced forced cooling can be implemented through the drive <NUM> and motor <NUM> and the travel path to transport the overload can be broken up with intermediate stops. Preferably, during intended overload operation, the number of starts that the elevator <NUM> can make in an hour is restricted.

In stage S8, the armature windings are commutated from parallel to series connection as shown in <FIG>.

For safety reasons, it is preferable that no person travels in the elevator car <NUM> with the overload during the overload trip. In step S9, the controller <NUM> can receive signals from a conventional person detector such as an infrared sensor to determine whether any personal are present in the car <NUM>. If anyone is detected in the car <NUM>, then the car <NUM> remains stationary at the landing with its doors open and an alarm can be issued at step S10 within the car <NUM> to allow the detected personnel to disembark from the car <NUM>.

When nobody has been detected in the car <NUM> at stage S9, the doors can close and the elevator <NUM> can commence an overload trip at stage S11.

The procedural steps outlined above can be carried out automatically by the elevator controller <NUM>, manually by a trained technician or there can be a combination with some of the steps manually implemented and others automatically implemented.

Claim 1:
A method for temporary transportation of an overload within an elevator installation (<NUM>) having a car (<NUM>) and a counterweight (<NUM>) interconnected by one or more suspension ropes (<NUM>) engaging a traction sheave (<NUM>) which is driven by a motor (<NUM>) the motor (<NUM>) having armature windings arranged in double star configuration with a winding pair for each phase, the method comprising the step of
enhancing traction between the suspension ropes (<NUM>) and the traction sheave (<NUM>) independently of the counterweight (<NUM>), further comprising the step of switching the motor armature windings from parallel to series configuration.