APPARATUS AND METHOD FOR MONITORING A TRACTION UNIT

OF A LIFTING PLANT

Technical field

This invention relates to a monitoring apparatus and method intended for predictive maintenance of the traction unit of a lifting plant, in particular as regards the emergency brake.

Background art

There are prior art apparatuses for monitoring lifting plant, such as those described in the following patent documents: CN109813422A, CN205397757U, CN104925613A, US2004/094366A1.

Despite the various regulations regarding the safety of lifting plant such as lifts, hoists or lifting platforms, first and foremost regulation EN.81 :2014 20 & 50, there is no apparatus capable of remotely monitoring the operating status of the traction unit of the plant. The few parameters relating to operation of the traction unit are only available to the inverter which controls the traction units with frequency control and they only relate to the number of motor revolutions in the various steps of acceleration, running at nominal speed and deceleration ramp, as well as current drawn during each of these operating steps. As regards the emergency brake, controlled by the control panel of the plant, the only information collected relates to the brake open or brake closed condition, whilst there are no devices which allow constant monitoring of it and are able to prevent faults.

In the lifts sector, the motor of the traction unit may be asynchronous frequency controlled or synchronous, of the brushless type, usually with permanent magnets.

In the case of the asynchronous motor, a reduction unit is used in order to obtain a suitable reduction ratio between the motor and the traction pulley. The reduction unit could comprise for example a worm screw fixed to the rotor shaft of the electric motor and acting on a ring gear fixed to the shaft on which the traction pulley of the lift is installed. The holding brake of this type of traction unit is constituted of an electromagnet equipped with two independent circuits, as required by regulation EN.81 :2014 20 & 50.

The brake control electromagnet is an electrotechnical device constituted of a core of ferromagnetic material around which a solenoid is wound. The core may, for example, be made of soft iron. The solenoid may be a winding or coil having many turns of copper wire which causes the magnetic field which will be proportionate to both the number of turns of the winding and the current circulating in the winding. The electromagnet is associated with a movable part, made of ferromagnetic material, usually called the armature, by means of a piston connected to the armature. The armature acts on the brake arms which in turn are usually pressed on the drum due to the force applied by springs and are equipped with friction linings. The electromagnet causes the brake arms to move away from the surface of the drum which is fixed to the rotor shaft of the electric motor. Consequently the holding brake must be open, with the brake arms at a distance from the surface of the drum, when the traction unit of the lift is moving, whilst it would normally be closed, with the brake arms pressed on the drum thanks to their springs, without the effect of the electromagnet. Therefore, the longer the brake remains open, the higher the temperature of the coils rises.

On the traction units equipped with synchronous motors, in which the rotor shaft of the electric motor is fixed to the traction pulley, an electromechanical disc brake is installed, constrained to the rotor shaft and controlled by an electromagnet which acts on the disc in such a way as to force it to remain open. That disc brake performs the dual function of holding brake and emergency brake.

At present, there is no plant available which allows constant monitoring of operation of the holding brake and which can prevent faults in it by verifying the temperatures of the coils. Currently, the only monitoring systems present on electromagnetic disc brakes are mechanical or optical micro-switches which allow verification of the “closed” or “open” status of the brakes, but there are no devices available for monitoring the operating status of the brake and capable of preventing any brake faults.

At present, all electric motors used for lift traction units, whether they are asynchronous or synchronous, lack systems for monitoring their operating status, instead they only have devices protecting them against thermal overload.

Moreover, in the prior art, there are no systems capable of detecting anomalies in the various components of the traction unit, such as electric motor, bearings, traction pulley, etc., whether a winch or a brushless motor, and there are absolutely no systems capable of indicating the anomalies and performing predictive maintenance functions.

Aim of the Invention

A monitoring method in accordance with this description and/or in accordance with any of the appended method claims allows a continuous real-time analysis to be performed of the operating status of an electric traction unit, including its holding brake and its emergency brake, which is installed on a lifting plant such as a lift plant, a lifting platform or a hoist intended for transporting people or objects. Such continuous analysis allows predictive maintenance to be carried out for the lifting plant, predicting and therefore avoiding any faults, in such a way as to reduce the maintenance time and therefore the costs of the maintenance.

The method allows the convenient provision of objective real-time information about critical conditions of components important to the operation of the lifting plant, whether electrical or mechanical, without the maintenance operator having to go to the plant in order to carry out an uncertain fault search activity, obtain the necessary spare parts and return to the plant so as to carry out a further intervention. The method allows the convenient provision of objective real-time information about the operating status of the brake and/or of the emergency brake of the traction unit of the lifting plant, with the possibility of preventing faults and guaranteeing the necessary and constant fully safe status of the lifting plant.

The method allows the convenient provision of objective real-time information about the causes which result in operating anomalies and faults. For example, if the temperature of the electromagnet of the holding brake or of the emergency brake were always high due to high traffic in the lift plant, the maintenance technician could install a coil overexcitation device with the higher starting voltage necessary to open the brake, for a limited time, subsequently maintaining only the minimum voltage necessary to keep the brake open by means of shunt resistance or the like, thereby avoiding faults which compromise the overall safety of the lift plant.

The method allows monitoring of the spectrum of vibrations produced by the components of the traction unit, so that sudden faults can be prevented and predictive and scheduled maintenance work can be carried out, therefore with minimum impact for the lifting plant traffic, even preventing very serious accidents caused by breakage due to fatigue of the shafts or other component parts of the traction unit subjected to heavy mechanical work. The method allows lifting plant maintenance to be made more economical, benefiting companies which provide the service, but also benefiting users, who also enjoy the significant benefit of not being affected by sudden faults, such as people or goods being trapped in the plant loading car and they can continuously make use of the lifting plant service.

An apparatus in accordance with this description and/or in accordance with any of the appended apparatus claims is configured and/or designed specifically to perform a method in accordance with this description and/or a method in accordance with any of the appended method claims.

A method in accordance with this description comprises collecting, transmitting and processing of the data relating to the lifting plant traction unit, including the braking system, and allows vibrational and thermal analysis of traction unit electrical and electromechanical components, as well as identification of mechanical and electrical anomalies, objectively and unequivocally demonstrating that a component is worn or, in the case of traction unit electrical and electromechanical components, problems linked to the power supply from the electricity network, for example harmonics beyond the limits allowed, or incorrect feeding of the inverter connected to the machine. Brief descrlDtlon of the drawinas

The features of a method and an apparatus according to this description will become clearer from the following detailed description of respective possible example embodiments of that method and apparatus.

The following detailed description refers to the accompanying drawings, in which:

- Figure 1 is a block diagram of a possible example embodiment of an apparatus in accordance with this description;

- Figure 2 is a flow chart of a possible example embodiment of a method in accordance with this description.

Detailed description of preferred embodiments of the Invention

The accompanying drawings refer to a possible example embodiment of an apparatus according to the present description. Hereinafter,“apparatus” shall mean that possible embodiment of the apparatus.

The accompanying drawings refer to a possible example embodiment of a method according to the present description. Hereinafter,“method” shall mean that possible embodiment of the method.

The apparatus 1 is configured to perform the method.

The apparatus 1 is for monitoring a lifting plant LP. The lifting plant LP could be a lift, or a lifting platform, or a hoist. The apparatus 1 comprises a local monitoring system 2. The local monitoring system 2 is configured to perform locally a step of automatically monitoring a time trend of one or more operating parameters of a traction unit U of the plant LP. The operating parameters are correlated with the operation or effectiveness of any part of the traction unit U.

The traction unit U comprises an electric motor or an electric machine.

The local system 2 is configured to perform a step of automatically obtaining monitoring data indicative of said time trend. The monitoring data is shown in Figure 1 by the arrow MD.

The method comprises that monitoring step. In Figure 2 the monitoring step is shown by the block mp.

The local system 2 comprises a sensor unit 21 and hardware 22, for performing that monitoring step.

The sensor unit 21 is configured for acquiring detection signals indicating said time trend. The local system 2 is configured so that the hardware 22 can receive from said sensor unit 21 intermediate signals indicating said detection signals. In Figure 1 the detection signals are shown with the arrow DS. In Figure 1 the intermediate signals are shown with the arrow IS.

The method comprises that obtaining step. In Figure 2, the obtaining step is shown with the block op.

The hardware 22 of the local system 2 is configured, by means of a software, to perform that obtaining step op.

The apparatus 1 comprises a remote processing system 3. The remote system 3 is configured to perform a step of automatically processing said monitoring data MD. For that purpose, the remote processing system 3 comprises a hardware loaded with a software.

The method comprises that processing step. That processing step is shown by the block ep in Figure 2.

The remote system 3 is configured to perform, as a function of the results of said processing step, a step of automatically generating maintenance data. That maintenance data is indicative of one or more maintenance actions for the maintenance of the traction unit U. The maintenance data is shown by the arrow SD in the figure. The maintenance data is a function of the monitoring data MD.

The method comprises that generating step. In Figure 2 the generating step is shown by the block gp.

The apparatus 1 comprises a communication system 4. The communication system 4 is configured to perform a step of automatically transferring monitoring data MD from said local system 2 to said remote system 3, in such a way that the remote system 3 can perform that processing step ep and therefore also that generating step gp.

The method comprises that transferring step. In Figure 2, the step of transferring is represented by the block cp.

The traction unit U comprises a brake B for braking a traction pulley TP. The brake B may be a holding brake or an emergency brake, or a brake both for holding and for emergencies.

The local system 2 is such that said monitoring step mp comprises monitoring of a time trend of at least a temperature of at least one component of said brake B. In that way the monitoring data MD comprises temperature data of said brake B.

For that purpose, the sensor unit 21 could comprise at least one temperature sensor (for example a thermistor) for detecting said temperature of the brake B. For that purpose, the sensor unit 21 could also comprise an ambient temperature sensor. The ambient temperature sensor is configured to detect an ambient temperature value. The remote processing system (or the local monitoring system) is configured to process the temperature value of the brake as a function of the ambient temperature value. In particular, the remote processing system recommends maintenance if the temperature of the brake is higher than a predetermined threshold value; the remote processing system can select the threshold value as a function of the ambient temperature (as the ambient temperature rises, so does the threshold value). The brake B could be an electromechanical brake comprising a coil wound around ferromagnetic material. In particular, the electromagnetic brake B comprises an electromagnet; the electromagnet includes a core made of ferromagnetic material (for example, soft iron) and a coil (or solenoid) wound around the ferromagnetic material core. In that case the temperature sensor (for example, the thermistor) would be configured to detect the temperature of at least one part of the electromagnet (in particular of the coil); that temperature of the brake B would be considered the temperature of that at least one part of the coil. In particular, there may be a thermistor for each of a plurality of windings of the coil. Therefore, said monitoring data MD may comprise temperature data representative of a temperature of the coil of the electromagnet (or of a winding of the coil).

In one embodiment, the electromechanical brake B comprises a movable part, or armature, preferably made of ferromagnetic material, movable as a result of an energising of the electromagnet. The brake B comprises brake arms configured to act on a drum fixed to a shaft of the motor M, so as to apply the braking action. The brake B comprises a spring which, when the electromagnet is not energised, holds the brake arms in contact with the drum so as to apply the braking action. When it is energised, the electromagnet is configured to move the armature and to oppose the action of the spring, so as to move the arms away from the drum and allow the traction unit U to move. Therefore, the longer the brake remains open, the higher the temperature of the coil rises.

In one embodiment, the electromechanical brake B comprises a disc associated with the shaft of the motor M. The brake B comprises a spring which applies a braking action so that, when the electromagnet 18 is not energised, the spring holds the disc in an active position, in which it brakes the driving shaft. When it is energised, the electromagnet is configured to compensate for the braking action of the spring and move the disc into a deactivated position, in which it allows the traction unit U to move. There may be a brake B comprising the arms, for performing the function of holding brake, and also a disc brake, for performing the function of emergency brake.

The local system 2 is configured so that the monitoring step mp comprises the monitoring of a time trend of at least a vibration of at least one component of said unit U. In that way the monitoring data MD comprises vibrational data of at least one component of said unit U. That at least one component may comprise for example a bearing and/or a shaft and/or a motor and/or the brake B and/or the pulley TP.

For that purpose, the sensor unit 21 could comprise an accelerometer or another sensor capable of detecting the vibration. In particular, the accelerometer is associated with the motor M; in particular, the motor M includes a shaft rotating about an axis of rotation and the accelerometer may be configured to detect vibrations of the rotary shaft. Preferably, the accelerometer is configured to detect the vibrations of the shaft in one or more of the following directions: axial direction, parallel to the axis of rotation, vertical direction, parallel to the weight force, and transversal direction, perpendicular to the vertical direction and to the axial direction. Measurement of the vibrations in the vertical direction allows the diagnosis of a possible axial play of bearings associated with the rotary shaft. Measurement of the vibrations in the transversal direction allows diagnosis of bearing faults. Measurement of the vibrations in the axial direction provides indications about the seriousness of shaft misalignment. Preferably, the accelerometer is a three-axis accelerometer, configured to detect the vibrations in all three of the above-mentioned directions.

The processing step ep could comprise the comparison of said vibrational data with at least one library containing typical vibrational spectra for said at least one component of the traction unit U.

If that component whose vibration is monitored were a bearing of the traction unit motor shaft, the monitoring of the vibration in the transversal direction or orthogonal to the axis of the shaft around which the bearing is mounted allows detection of any bearing play. In that case, the monitoring of the vibration of the direction of the axis of the shaft allows detection of any bearing malfunction or fault.

The vibrational monitoring ensures that the subsequent processing by the remote system is an analysis of a vibrational spectrum. In that way the remote system 3 can define, by means of the processing step, an accurate picture of operation of the traction unit U, highlighting all cases of wear in progress: from those justified due to the hours of operation completed to those which are already anomalies present (both mechanical and electrical), since the vibrations having different frequency objectively and unequivocally demonstrate that the component is worn.

The possible situations which could lead to faults, and which may be taken into account by means of processing of the vibrational data by the remote system 3, include loose supports, worn bearings, misalignments between components of the electric machine, or electrical problems linked to the power supply from the electricity network (harmonics beyond the limits allowed) or incorrect feeding of an inverter of the traction unit U.

The remote system 3, by means of the processing step ep which it is configured to perform, is configured to take into account those situations when generating maintenance data SD.

In contrast, the processing of the temperature data by the remote system 3 takes into account any excessive temperature of any element of the brake B, in such a way as to predict and avoid any brake B faults and/or malfunctions.

In that way the maintenance defined by the maintenance data SD predicts the possible malfunctions and/or faults so as to avoid those malfunctions and/or faults.

The monitoring of a time trend of at least a vibration of at least one component of said unit U could be periodic. In that way with the monitoring data MD the remote system 3 can calculate, during the processing step, practically a time forecast of the progress of that at least one component, being able to establish for it, for example, the stop times for maintenance before a breakage or fault occurs during normal operation of the lifting plant

LP.

The traction unit U comprises a motor which drives said traction pulley TP. That motor is electric, synchronous or asynchronous.

The local system 2 is configured so that said monitoring step mp comprises the monitoring of a time trend of at least a speed of rotation of said motor M. In that way the monitoring data MD comprises speed data indicative of said speed trend.

In order to generate said maintenance data SD, the remote system 3 is configured to correlate together said temperature data and said speed data. The correlation between the temperature data and the speed data allows an even more reliable reconstruction of the operating status of the traction unit, as different time trends of the brake temperature as a function of the motor speed may indicate different types of events.

For that purpose, the sensor unit 21 could comprise a proximity sensor positioned in such a way as to read the presence of a specific reference positioned on the traction pulley TP.

In general the local system 2 could be configured so that the monitoring step mp comprises the monitoring of a time trend of a current and/or of a voltage of the motor and/or of the brake B.

In particular, the local monitoring system could include one or more sensors associated with the electric motor M (in particular, with a stator of the electric motor) and configured to detect data relating to the current and/or voltage of the motor M during its operation.

In one embodiment, the monitoring step mp comprises the monitoring of a time trend of at least a temperature of the electric motor M; in particular, the apparatus includes a thermistor configured to detect a temperature of a winding of the stator of the electric motor M.

In one embodiment, the traction unit U comprises an inverter configured to feed the electric motor M. The remote processing system 3 (or the local monitoring system 2) may be connected to the inverter for receiving inverter data. Therefore, the monitoring step may include a monitoring of the inverter data. Moreover, the remote processing system 3 may be configured to generate the maintenance data as a function of the inverter data.

The inverter data may include one or more of the following data: currents drawn by the electric motor M, during a plurality of operating steps of the electric motor M; voltage of the electric motor M during said plurality of operating steps of the electric motor; speed of rotation of the electric motor M during said plurality of operating steps of the electric motor M. In particular, it is useful to monitor the current drawn trend, because if there are big variations in the current drawn, this may be due to unwanted friction. Said plurality of operating steps of the electric motor include an accelerating step, a nominal step and a decelerating step. Therefore, the inverter data allows said monitoring of a time trend of a current and/or of a voltage of the motor and/or of the brake B, and/or the monitoring of a time trend of at least a speed of rotation of said motor M.

The communication system could be wireless.

Preferably, the local monitoring system is connected to an electricity network, for receiving an electric power supply.

This description also provides a lifting plant. The lifting plant comprises a traction unit U including a traction pulley TP and an electric motor M configured to drive said traction pulley TP. Preferably, the lifting plant includes an inverter for feeding the motor M. Preferably, the lifting plant includes a brake B for braking the traction pulley TP. The lifting plant also includes a monitoring apparatus according to one or more of the aspects of this description.