AU2019348266B2

AU2019348266B2 - Belt conveyor device and method for stopping a belt of a belt conveyor device

Info

Publication number: AU2019348266B2
Application number: AU2019348266A
Authority: AU
Inventors: Norbert Becker; Torsten Hellmuth
Original assignee: Innomotics GmbH
Current assignee: Innomotics GmbH
Priority date: 2018-09-28
Filing date: 2019-09-17
Publication date: 2022-03-31
Anticipated expiration: 2039-09-17
Also published as: EP3629469A1; WO2020064422A1; PE20210815A1; AU2019348266A1; EP3830945A1; EP3830945B1; RS63708B1; CL2021000742A1

Abstract

The invention relates to a belt conveyor device (1) and to a method for stopping a belt conveyor device (1) in a controlled manner. In particular for directly driven belt conveyor devices (1), an event (E) such as a power failure can lead to a fast stoppage of a belt driving roller (5). A fast stoppage of the belt driving roller (5) leads locally to a reduction in the belt tension of the belt (3). Due to the local reduction in the belt tension, a compression of the belt (3) or even creasing of the belt (3) can damage the belt (3). The aim of the invention is to prevent damage to the belt (3). This aim is achieved, according to the invention, in that when the event (e) occurs the motor (7) is slowly decelerated to a standstill. The electrical power for the slow deceleration is preferably drawn from an energy accumulator (13), the energy accumulator (13) being associated with a power supply (9) for the motor (7). The deceleration preferably takes place according to a characteristic curve (K), the characteristic curve (K) specifying the rotational speed (w) of the motor (7) as a function of the time (t).

Description

Belt conveyor device and method for stopping a belt of a belt

conveyor device

The invention relates to a belt conveyor device and a method

for stopping a belt of a belt conveyor device.

Belt conveyor devices serve to transport bulk material over

long distances, in particular several kilometers. Belt

conveyor devices typically comprise a belt, which is driven by

at least one belt driving roller. A motor serves to drive the

belt driving roller. A gear unit is typically positioned

between the motor and the belt driving roller in order to

change the rotational speed and the torque. Directly driven

belt conveyor devices having no gear unit between the motor

and the belt driving roller have also been known for some

time.

When the belt of the belt conveyor device is stopped on

account of an unforeseen event, a high inertia of the bulk

material leads to a disadvantageous mechanical straining of

the belt.

Particularly upon occurrence of a power failure or a similar

event resulting in a failure of the drive, the moving bulk

material continues to exert pressure on the belt on account of

its inertia, while the motor and the belt driving roller

associated therewith have already come to a standstill.

The inertia of the moving bulk material and the lack of

rotation of the belt driving roller result in a local reduction in the belt tension. This leads to a disadvantageous compression of the belt or even a creasing of the belt.

To reduce the strain on the belt and to prevent the belt from

creasing, an increased tension of the belt currently occurs.

Although an increased tension of the belt reduces the danger

of a creasing of the belt, it nevertheless leads to an

increased basic strain on the belt.

The document M. Z. BEBIC et al.: "Speed Controlled Belt

Conveyors: Drives and Mechanical Considerations", ADVANCES IN

ELECTRICAL AND COMPUTER ENGINEERING, Vol. 18, No. 1, January

1, 2018 (2018-01-01), pages 51-60, describes a belt conveyor

device with variable conveying speed, in which a reference

speed is varied in order to improve energy efficiency. Motors

for driving the belt conveyor device are supplied with power

via a frequency converter, which comprises a rectifier, an

intermediate circuit and a voltage transformer. Capacitors are

arranged in the intermediate circuit for reactive power

compensation.

The document DE 10 2011 085 387 Al describes a dynamoelectric

machine for driving a PET stretch blow molding machine, which

in order to increase efficiency and dynamics comprises a

stator, a rotor and blow molds for receiving PET preforms.

The document DE 199 43 663 Al describes a method for

decelerating a frequency converter-controlled asynchronous

motor, in which an alternating voltage with a frequency

smaller than approximately half of the current motor

rotational speed is applied to said motor.

The document WO 2013/020725 Al describes a continuous conveyor with a conveyor belt which circulates between a driving roller and a deflection roller. The driving roller is driven by a permanently excited multi-pole synchronous motor, which produces a very high torque at a comparatively low rated rotational speed.

The document CN 103 950 702 B describes a control method for an energy-generating apparatus for supplying a belt conveyor device for transporting mineral bulk materials.

It is an object of the present invention to substantially overcome, or at least ameliorate, one or more of the above disadvantages of existing arrangements, or provide a useful alternative. Some embodiments of the present invention are intended to reduce the strain on the belt in the event of a power failure.

One aspect provides a belt conveyor device comprising at least one belt driving roller and a drive, wherein the drive comprises a motor for driving the belt driving roller, the motor being coupled with an energy accumulator configured to supply electricity to the motor during a stopping time, wherein the belt conveyor device is configured to provide electrical energy from the energy accumulator to supply electricity to the motor in order to effect deceleration of the belt driving roller by reducing a rotational speed of the motor to a standstill within the stopping time following a power failure event.

Another aspect provides a method for stopping a belt driving roller of a belt conveyor device according to the above aspect, the method comprising:

3a

reducing the rotational speed of the motor connected to the belt driving roller to a standstill within the stopping time upon occurrence of the power failure event; providing electrical energy for supplying the motor during the stopping time from the energy accumulator such that the belt driving roller is stopped in a decelerated manner.

The disclosure is based on the knowledge that, particularly in the case of a directly driven belt conveyor device, the inertia of bulk material on the belt strains the belt in the event of a power failure by causing localized compression.

Particularly in the case of conventionally driven belt conveyor devices, a power failure results in a slow coasting down of the drive and the belt driving roller. The slow coasting down of the drive takes place on account of the high moment of inertia of the drive via the gear unit. The coasting down of the drive without a gear unit takes place significantly faster, since the moment of inertia of the drive is smaller.

In order to equalize the moment of inertia, the rotational

movement of the motor continues to be maintained for a

stopping time. During the stopping time, the electrical energy

for the motor is provided from an energy accumulator. The

energy accumulator is preferably embodied as an intermediate

circuit energy accumulator, in particular as an intermediate

circuit capacitor or as a rechargeable battery.

A stopping of the motor and thus of the belt driving roller

advantageously takes place according to a characteristic

curve, wherein the characteristic curve provides setpoint

values for the rotational speed of the motor as a function of

the time.

Kinetic energy which is released during the stopping of the

motor is advantageously provided by an energy accumulator. The

energy accumulator is preferably charged during the operation

of the belt conveyor device. Accordingly, the regulation of

the rotational speed in conjunction with the energy

accumulator advantageously serves to slowly reduce the

rotational speed of the motor.

The regulation accordingly serves to equalize the friction

losses so that the motor reduces its rotational speed within

the predefined stopping time until it comes to a standstill.

A flywheel coupled to an electric motor is advantageously used

as the energy accumulator. Advantageously, an electric motor

configured in accordance with the energy consumption without

an additional flywheel can also serve as the energy

accumulator. The electric motor is preferably connected via a

frequency converter to the intermediate circuit of the power supply of the motor, wherein the motor is embodied to drive the belt conveyor device.

The belt conveyor device is in particular a directly driven belt conveyor device. The belt conveyor device has at least one belt driving roller and one drive, wherein the drive comprises a motor, wherein an energy accumulator is associated with the motor, wherein the motor is provided for driving the belt driving roller, wherein the belt conveyor device is embodied to provide electrical energy from the energy accumulator following an event such as a power failure in order to retard the rotational speed of the motor to a standstill within a stopping time.

A directly driven belt conveyor device typically has no gear unit between the motor and the belt driving roller. The motor is preferably a synchronous motor. The motor preferably has permanent magnets. Alternatively, the motor can also be embodied to be externally excited, in other words with current-carrying coils.

The motor is advantageously supplied with electrical energy from a power supply during operation of the belt conveyor device. The power supply can be embodied as a frequency converter with an intermediate circuit.

The energy accumulator is preferably associated with the power supply. The energy accumulator is preferably integrated into the intermediate circuit of the frequency converter. The energy accumulator is preferably embodied as a capacitor unit, as a rechargeable battery or as a flywheel with a motor.

The stopping time depends

- on the alignment of the belt conveyor device; - on a pretensioning of the belt;

- on the loading of the belt conveyor device; - on the friction losses of the belt conveyor device and/or - on the torque of the belt driving roller.

A suitable stopping time is preferably determined by a simulation of the belt conveyor.

An event can be a power failure or a defect in the power supply of the motor.

When the event occurs, electrical energy is advantageously provided to the motor from the intermediate circuit of the frequency converter. With the help of the electrical energy, the motor can continue to be operated at least during the stopping time.

A regulating device for the rotational speed is preferably associated with the motor. If an event occurs, the regulating device serves to supply the electrical energy to the motor such that the motor is retarded according to a characteristic curve.

Such a regulating device is preferably embodied such that the stopping time can be varied according to the electrical energy stored in the energy accumulator.

By way of the disclosure, a straining of the belt by a fast stoppage of the belt driving roller following an unforeseen event can be reduced. In particular a very different belt tension in different regions of the belt and, under certain circumstances, a creasing of the belt resulting therefrom can be prevented effectively by some embodiments of the invention.

In an advantageous embodiment of the invention, the

retardation of the motor takes place according to a

characteristic curve, wherein the characteristic curve

specifies the course of a setpoint value of the rotational

speed of the motor as a function of the time.

Alternatively or in addition, further characteristic curves

for different loading states of the belt conveyor device can

be determined and stored.

The characteristic curve is preferably associated with the

motor, a power supply or a rotational speed regulating device

for the motor. The characteristic curve can preferably be

determined by means of a series of experiments.

An advantageous method for determining the characteristic

curve can look as follows:

- Determining the belt tension at a standstill and during

operation. It is preferably possible to determine the one

maximum belt speed during the acceleration of bulk material if

the belt of the belt conveyor device is loaded only in regions

with bulk material;

- Optionally, it is also possible to determine a maximum

deviation of the belt tension with respect to the position of

the belt conveyor device;

- Calculating the minimum stopping time in order to maintain

the difference in belt tensions at different positions below a

maximum permissible difference for a belt which is loaded in

regions.

The characteristic curve can be used to ensure that no

creasing of the belt takes place for a predefined loading of the belt. The strain on the belt can be reduced to a minimum by retarding the rotational speed of the motor according to the characteristic curve.

In a further advantageous embodiment of the invention, the characteristic curve specifies a linear reduction of the rotational speed.

The retardation of the rotational speed of the motor preferably takes place in a linear manner. The belt is particularly protected by a linear retardation of the rotational speed of the motor.

In a further advantageous embodiment of the invention, the stopping time has a duration of between 10 and 150 seconds, in particular between 30 and 90 seconds.

The stopping time is preferably the duration required by the motor or the belt driving roller to reach a standstill starting from the initial rotational speed.

A plurality of stopping times is preferably determined and/or stored for different loading states of the belt conveyor device. Depending on the loading state, the regulating device can select a suitable stopping time.

The stopping time is preferably defined as a function of the loading of the belt with bulk material and/or a pretensioning of the belt.

As a general rule, the longer the stopping time, the more protective a stopping is for the belt. On the other hand, a larger energy accumulator is advantageous for a long stopping time. Accordingly, an experimental determination of the stopping time is advantageous in order to give due consideration to different loading states of the belt or the belt conveyor device.

In a further advantageous embodiment of the invention, the belt conveyor device has a regulating device for the rotational speed of the motor, wherein the regulation regulates the rotational speed of the motor on the basis of setpoint values, in particular of the characteristic curve.

The regulating device is preferably embodied as a PID regulation. The regulating device preferably serves to regulate the rotational speed and/or torque of the motor. As the setpoint value for the regulation, rotational speed values from the characteristic curve are preferably provided to the regulator.

The regulating device is preferably embodied as a voltage regulation for an intermediate circuit voltage in a frequency converter. Use is preferably made here of an existing regulating device, which is modified accordingly.

A regulation of the rotational speed preferably results in a particularly precise retardation of the rotational speed of the belt driving roller. The belt is advantageously protected by the precise regulation of the rotational speed over the stopping time. The regulating device is preferably integrated in a frequency converter, which is embodied to supply power to the motor.

In a further advantageous embodiment of the invention, the

belt conveyor device has a power supply for the motor, wherein

the power supply is embodied as a frequency converter and the

energy accumulator is embodied as an intermediate circuit

energy accumulator.

The energy accumulator is preferably embodied as a

rechargeable battery, as a capacitor unit or as another

electrical energy accumulator. Alternatively or in addition,

the energy accumulator can also be embodied as a flywheel

energy accumulator. An electric motor coupled to the flywheel

acts as a drive for the flywheel and/or as a generator in

order to transmit the kinetic energy from the rotating

flywheel back to the intermediate circuit.

Advantageously, the integration of the energy accumulator in

the intermediate circuit means that an existing frequency

converter can simply be expanded.

The use of a flywheel-based energy accumulator is cost

effective in terms of acquisition and ongoing operation. In

particular, commercially available flywheel-based energy

accumulators can store a great deal of electrical energy and

are therefore particularly suitable for use in mining or in

heavy industrial applications.

In a further advantageous embodiment of the invention, the

belt conveyor device has a free-wheeling clutch, wherein the

free-wheeling clutch is positioned between the motor and the

belt driving roller, wherein the free-wheeling clutch is

embodied to decouple the connection to the motor if the

rotational speed of the belt driving roller is higher than the

rotational speed of the motor.

"Decouple" means to separate the connection of the motor shaft

to the belt driving roller.

A free-wheeling clutch is preferably arranged in the

connection, e.g. a shaft, between the motor and the belt

driving roller. If the rotational speed of the belt driving

roller is higher than the rotational speed of the motor, the

free-wheeling clutch uncouples/decouples the belt driving

roller from the motor. If, on the other hand, the motor has a

higher rotational speed than the belt driving roller, then the

free-wheeling clutch couples the belt driving roller and the

motor together, thus restoring a rotationally fixed

connection.

By way of the free-wheeling clutch, the moment of inertia of

the drive can be reduced to the moment of inertia of the belt

driving roller. On account of the very low moment of inertia,

a straining of the belt is advantageously reduced because the

motor with its moment of inertia no longer acts against the

movement of the belt. As a result, only a weak counter-force

is effective during a stopping of the motor. On account of the

weak counter-force, deviations in the belt tension are

significantly reduced, thus protecting the belt.

In the method for stopping a belt driving roller of a belt

conveyor device, upon occurrence of an unforeseen event, in

particular a power failure, the rotational speed of the motor

is retarded to a standstill.

The belt conveyor device for the method typically has a motor,

which is connected to the belt driving roller.

In the method, the motor is supplied with electrical energy

from an energy accumulator as it is retarded to a standstill.

The rotational speed of the motor is preferably regulated with

the aid of a regulating device.

The regulating device retards the motor on the basis of

predefined or predefinable setpoint values for the rotational

speed.

The regulating device serves to regulate the supply of

electrical energy from an energy accumulator to the motor.

Using the supplied electrical energy, the motor can continue

to drive the belt driving roller for the duration of the

stopping time.

The retarded stopping of the belt driving roller enables a

fast stopping of the drive on account of a low moment of

inertia and thus a straining of the belt to be effectively

avoided.

In a further advantageous embodiment of the invention, the

motor is associated with a power supply, in particular a

frequency converter with an intermediate circuit, wherein the

energy accumulator is associated with the intermediate

circuit, wherein the retardation of the rotational speed of

the motor takes place with the aid of a regulating device for

a voltage in the intermediate circuit.

The rotational speed of a drive can preferably be controlled

or regulated very easily via the voltage in the intermediate

circuit. The intermediate circuit is preferably the

intermediate circuit of the frequency converter which supplies

the motor of the belt conveyor device with electrical energy.

The energy accumulator is preferably associated with the intermediate circuit. A reduction of the rotational speed of the motor preferably takes place by way of a reduction of the voltage in the intermediate circuit. To maintain the voltage in the intermediate circuit, the energy accumulator is preferably associated with the intermediate circuit.

A particularly easy regulation of the rotational speed of the motor is possible as a result of the regulation of the rotational speed of the motor through the regulation of the voltage of the intermediate circuit. The easy regulation of the rotational speed enables the stopping time to be set particularly precisely.

In a further advantageous embodiment of the invention, the retardation of the motor takes place according to a characteristic curve.

The retardation of the motor is understood to mean a reduction of the rotational speed of the motor.

A characteristic curve preferably provides the course over time of the setpoint rotational speed of the motor until the stopping time. The characteristic curve preferably provides setpoint values for the regulating device. The characteristic curve is preferably provided to the regulating device. An encoder or a determination of the actual rotational speed by a measurement of the motor voltage and/or of the motor current with the aid of the frequency converter is preferably used to provide actual values of the rotational speed for the regulating device.

In the case of regulation of the rotational speed of the motor

by regulation of the energy provided or regulation of the

voltage in the intermediate circuit, the characteristic curve

can also correspond to the course over time of the electrical

energy supplied to the motor or the course over time of the

voltage in the intermediate circuit.

Embodiments of the invention will now be described and

explained in greater detail making reference to the figures.

The embodiments shown in the figures are merely exemplary and

in no way limit the invention.

In the drawings,

FIG 1 shows an exemplary belt conveyor device,

FIG 2 shows an exemplary characteristic curve, and

FIG 3 shows a further exemplary belt conveyor device with

a free-wheeling clutch.

FIG 1 shows an exemplary belt conveyor device 1. The belt

conveyor device comprises a belt 3 for transporting bulk

material 11. The belt 3 is retained by a belt driving roller 5

on each side. By way of the belt driving rollers 5, the belt 3

is tensioned to a definable belt tensile stress. The belt

driving rollers 5 are positioned on the respective side. The

belt 3 is further supported by belt driving rollers which are

embodied as support rollers 5a. The belt driving roller 5

arranged on the respective side is also referred to as the

belt drum 5a. The belt driving rollers 5 positioned between

what are referred to as the belt drums 5a are also referred to

as support rollers 5b.

At least one of the belt driving rollers 5 is coupled to a motor 7. The motor 7 serves to drive the respective belt driving roller 5 and thus to drive the belt 3 of the belt conveyor device 1. The motor 7 is connected to a power supply 9. The power supply 9 is preferably embodied as a frequency converter.

The power supply is connected to an energy accumulator 13. The energy accumulator 13 is charged with electrical energy during the operation of the belt conveyor 1. The capacity of the energy accumulator 13 is preferably selected to be sufficiently large that the motor 7 can bring the belt 3 to a standstill within a stopping time t S in a controlled manner, in particular according to a characteristic curve K. Advantageously, the capacity of the energy accumulator 13 is selected such that the motor 7 can continue to operate for a stopping time tS at a reduced rotational speed.

The energy accumulator 13 is preferably embodied as an intermediate circuit capacitor, as a (free-running) motor with a dedicated frequency converter, or as a rechargeable battery.

Upon occurrence of an event E, such as a power failure, the motor is supplied with electrical energy from the energy accumulator 13. When energy is drawn from the energy accumulator, the motor is decelerated slowly along a characteristic cure K, in other words brought to a standstill.

FIG 2 shows an exemplary characteristic curve K. The characteristic curve K specifies setpoint values of a rotational speed w of the motor 7 as a function of the time t. Setpoint values of the rotational speed w of the motor 7 are provided according to the characteristic curve K for a rotational speed regulating device. The regulating device provides setpoint rotational speeds as a function of the time t of the power supply 9 of the motor 7. The motor is preferably retarded to a standstill within the stopping time tS.

Following an event E, for example a voltage drop or a power failure, the motor 7 is decelerated slowly according to the characteristic curve K. The required electrical energy which is required for the slow deceleration of the motor 7 is drawn from the energy accumulator 13. The energy from the energy accumulator 13 enables the motor 7 to be decelerated to a standstill within a stopping time tS. The stopping time tS is preferably determined experimentally for the respective belt conveyor device 1. Alternatively or in addition, the stopping time is determined with the aid of a simulation of the belt conveyor device 1. For a commercially available belt conveyor device 1, an advantageous stopping time t S of 30 seconds has been determined.

FIG 3 shows a further exemplary belt conveyor device 1 with a free-wheeling clutch 15. The further exemplary belt conveyor device corresponds essentially to the exemplary belt conveyor device according to FIG 1. The free-wheeling clutch 15 separates the rotationally fixed connection of the motor 7 to the driving roller 5 if the motor 7 has a lower rotational speed w than the driving roller 5.

In summary, the disclosure relates to a belt conveyor device 1 and a method for stopping a belt conveyor device 1 in a controlled manner. In particular for directly driven belt conveyor devices 1, an event E, such as a power failure, can result in a fast stoppage of a belt conveyor device 5. A fast stoppage of the belt driving roller 5 leads locally to a reduction in the belt tension of the belt 3. On account of the local reduction in the belt tension, a compression of the belt

3 or even a creasing of the belt can damage the belt 3. In

order to prevent damage to the belt, the disclosure proposes

to decelerate the motor 7 slowly to a standstill when the

event E occurs. The energy for the slow deceleration is

preferably drawn from an energy accumulator 13, wherein the

energy accumulator 13 is assigned to a power supply 9 for the

motor 7. The deceleration preferably takes place according to

a characteristic curve K, wherein the characteristic curve

specifies the rotational speed w of the motor 7 as a function

of the time t.

Claims

Claims 1. A belt conveyor device comprising at least one belt driving roller and a drive, wherein the drive comprises a motor for driving the belt driving roller, the motor being coupled with an energy accumulator configured to supply electricity to the motor during a stopping time, wherein the belt conveyor device is configured to provide electrical energy from the energy accumulator to supply electricity to the motor in order to effect deceleration of the belt driving roller by reducing a rotational speed of the motor to a standstill within the stopping time following a power failure event.
2. The belt conveyor device as claimed in claim 1, wherein the belt conveyor device is a directly driven belt conveyor device.
3. The belt conveyor device as claimed in claim 1 or 2, wherein the energy accumulator comprises at least one of a capacitor, a rechargeable battery and an electric motor.
4. The belt conveyor device as claimed in claim 3, wherein the electric motor is coupled to a flywheel.
5. The belt conveyor device as claimed in any one of the preceding claims, wherein deceleration of the motor takes place according to a characteristic curve, wherein the characteristic curve specifies the course of a setpoint value of the rotational speed of the motor as a function of time.
6. The belt conveyor device as claimed in claim 5, wherein the characteristic curve specifies a linear reduction of the rotational speed.
7. The belt conveyor device as claimed in any one of the preceding claims, wherein the stopping time has a duration of between 5 and 150 seconds.
8. The belt conveyor device as claimed in any one of the preceding claims, wherein the stopping time has a duration of between 30 and 90 seconds.
9. The belt conveyor device as claimed in any one of the preceding claims, further comprising a regulating device for the rotational speed of the motor, wherein the regulating device uses setpoint values to regulate the rotational speed of the motor.
10. The belt conveyor device as claimed in any one of the preceding claims, further comprising a power supply for the motor.
11. The belt conveyor device as claimed in claim 10, wherein the power supply is a frequency converter.
12. The belt conveyor device according to any one of the preceding claims, wherein the energy accumulator is an intermediate circuit energy accumulator.
13. The belt conveyor device as claimed in any one of the preceding claims, further comprising a free-wheeling clutch, wherein the free-wheeling clutch is positioned between the motor and the belt driving roller, wherein the free-wheeling clutch is configured to decouple a connection between the belt driving roller and the motor if a rotational speed of the belt driving roller is higher than the rotational speed of the motor.
14. A method for stopping a belt driving roller of a belt

conveyor device as claimed in any one of the preceding claims,

the method comprising:

reducing the rotational speed of the motor connected to

the belt driving roller to a standstill within the stopping

time upon occurrence of the power failure event;

providing electrical energy for supplying the motor during

the stopping time from the energy accumulator such that the

belt driving roller is stopped in a decelerated manner.
15. The method as claimed in claim 14, wherein the motor is

coupled with a power supply.
16. The method as claimed in claim 15, wherein the power

supply is a frequency converter with an intermediate circuit.
17. The method as claimed in claim 16, wherein the energy

accumulator is associated with the intermediate circuit.
18. The method as claimed in claim 16 or 17, wherein reduction

of the rotational speed of the motor takes place with the aid

of a regulating device controlling voltage in the intermediate

circuit.
19. The method as claimed in any one of claims 14 to 18,

wherein deceleration of the motor takes place according to a

characteristic curve.

Siemens Aktiengesellschaft Patent Attorneys for the Applicant/Nominated Person SPRUSON&FERGUSON