EP2741980A1

EP2741980A1 - Continuous conveyor for transporting heavy bulk material or articles

Info

Publication number: EP2741980A1
Application number: EP12719677.2A
Authority: EP
Inventors: Sepp Lachenmaier
Original assignee: Powertrans SA
Current assignee: Caterpillar Global Mining Europe GmbH
Priority date: 2011-08-10
Filing date: 2012-05-03
Publication date: 2014-06-18
Also published as: WO2013020725A1; UA109733C2; US10589936B2; AU2012292578B2; EA028453B1; EA201400209A1; US20170022013A1; US20140151197A1; CN103906691A; US9527670B2; AU2012292578A1

Abstract

A continuous conveyor, for example a conveying belt for transporting heavy bulk material or articles, comprises an endless transporting belt (1) which circulates between a drive roller (2) and a deflecting roller (3). The drive roller (2) is driven by a permanently excited high-pole synchronous motor (6) which, at a comparatively low nominal rotational speed, provides for a very high torque. The synchronous motor (6) can drive the drive roller (2) directly or, as an alternative, can also drive the same via a single-stage reduction-gear mechanism (15) with a low step-down factor. The drive according to the invention is distinguished by a mass moment of inertia which is up to 10 times lower than that of conventional drive systems. This vastly reduces the risk of damage to, or even cracking of, the transporting belt (1) in the event of problems, and therefore the operational reliability is significantly increased.

Description

Continuous conveyor for transporting heavy bulk or general cargo

The invention relates to continuous conveyors, which are used for the transport of large quantities of bulk material such as sand, stone or ore and for the transport of heavy cargo, for example in mining, over or underground mining or loading and unloading of ships, silos, etc. The bulk or general cargo is charged in a loading station on the transport traction means and transported to a dispensing or transfer station. A typical example of a continuous conveyor is a conveyor belt for the removal of crushed ore. The conveyor belt runs on support rollers which are mounted in an elongated support structure made of steel profiles. The drive station comprises, in addition to one or more drive shafts, at least one electric motor, which is usually designed as an asynchronous motor and runs at a relatively high rotational speed, for example 1500 rpm. By contrast, the drive roller driving the conveyor belt rotates relatively slowly, with a speed between 5 and 100 rpm. Therefore, a reduction gear must be provided between the asynchronous motor and the drive roller, which is typically designed as a multi-stage spur gear or planetary gear. leads and has a reduction ratio between 15: 1 and 150: 1. There are also gearboxes with variable translation used, with the help of the working speed of the drive roller can be adjusted. The drive motor and possibly also the reduction gear can be integrated in the drive roller as a so-called drum motor. The continuous conveyor may also comprise a plurality of drive stations, for example two head stations and one or more intermediate stations, each drive station having one or two electric motors and a corresponding number of drive rollers.

Faults during transport are passed as shock loads on the drive roller on the output shaft of the transmission and transmitted from there into the drive motor. For larger disturbances, for example due to jamming of the bulk material or jamming of objects, the transport traction means can suddenly come to a standstill for a short time. Rotor of the engine, shafts and gears of the transmission and the coupled drive roller but move because of the large inertia of the entire drive system on, at least until an automatic shutdown or decoupling of the engine takes place when certain forces are exceeded. This can lead to strong mechanical stresses in the gearbox, engine and transport traction means, as a result of which the traction means is damaged, e.g. tears. To avoid such inadmissibly high impact loads with possible damage to the transport traction means, an overload clutch is often installed in the prior art between the drive roller and the reduction gear which automatically opens when predetermined loads are exceeded above the normal operating loads, thus separating the electric drive from the drive roller.

Especially with large and very large ascending conveyors, such as those used in mining or opencast mining, a tearing of the transport traction device is associated with such a high expenditure of time and costs for the then necessary repair that such damage is avoided in all circumstances. that must be. Accordingly high is the design effort for the overload clutch and the monitoring and control systems that trigger a timely emergency shutdown. It thus sets itself the task of designing a continuous conveyor especially for heavy bulk or general cargo so that it is less susceptible to interference during transport and the risk is reduced that the transport traction means is overloaded by such disturbances and damaged. The invention is based on the finding that the large mass inertia of conventional drive systems is responsible for the fact that the transport traction means is rapidly mechanically overloaded in the event of a malfunction, and that therefore the reduction of the mass inertia of the drive system must be a developmental goal.

The object is achieved according to the characterizing part of the first claim, characterized in that instead of a high-speed electric motor with flanged multistage reduction gear, a permanently excited high-pole synchronous motor is used, whose speed is at most 15 times as high as the working speed of the drive shaft he delivers a torque of at least 30 kNm. Such a slow-running electric motor with high torque makes a complex multi-stage reduction gear superfluous. The acting on the drive roller mass moment of inertia of the drive is thereby reduced to less than 20% of the moment of inertia of a conventional drive. The kinetic energy of the drive system is considerably smaller due to the much lower engine speed. In the event of a malfunction during the transport of bulk or piece goods, the relatively light drive unit reacts faster. In an externally controlled deceleration or even a brief stoppage of the transport traction means, the driving force of the motor can be reduced or turned off before unacceptably high forces are introduced via the drive roller in the traction means. In case of error, eg short-circuit in the inverter or motor, the occurring impact torque is significantly lower, whereby the load on the mechanical components is significantly reduced. A deformation or even a crack of the transport traction means is thus practically impossible, an overload clutch unnecessary.

In a consistent and advantageous development of the inventive concept, as far as possible to reduce the moment of inertia of the drive, the electric motor can drive the drive roller of the transport traction device directly. In such a rotary torque drive with high torque, also called torque motor, the engine speed corresponds to the working speed of the drive shaft. A reduction gear is thus completely unnecessary, the mass moment of inertia of the drive is reduced to a minimum. In such a direct drive, the mass moment of inertia can be reduced by a factor of 10 compared to a conventional drive with a high-speed asynchronous motor and an intermediate reduction gearbox.

The efficiency of a drive system with torque motor is about 5% greater. This means lower energy consumption and lower cooling capacity. Rotor cooling is not required for torque motors.

The synchronous motors with a large number of pole pairs used here are, in principle, large hollow shaft servomotors optimized for high torques. Rotary direct drives or torque motors have hitherto been used primarily in production machines, such as Laser cutting machines, milling and grinding machines or extruders used, but not in heavy carriers.

The rated speed of the synchronous motor is preferably between 5 and 100 revolutions per minute, in particular between 20 U / min and 50 U / min, when the motor drives the drive shaft directly. The output torque is preferably between 50 and 800 kilonewtons, in particular 100 kNm to 500 kNm. Such slow-running synchronous motors with such high torque allow only the direct drive of the transport traction means. The power output of the drive is preferably between 50 and 2000 kilowatts, in particular 100 kW to 1000 kW.

5

If the synchronous motor drives the drive roller via a one-step reduction gear, the preferred rated speed is higher by a factor of 2 to 10, depending on the reduction ratio, and the torque output by the motor is preferably about half lower. Even in this case, a significant reduction of the moment of inertia results by at least a factor of 5 in comparison to conventional drives. The drive with synchronous motor and single-stage reduction gear has significantly fewer moving parts compared to conventional gearboxes. This means higher system reliability. A torque

15 Single stage gearbox engine results in a much more compact drive.

High-pole synchronous motors or rotary direct drives can be controlled quickly and precisely by means of a frequency converter. Thanks to the use of variable-speed drives, considerable system advantages can be achieved compared to conventional solutions without speed control. Due to the speed and torque control, the conveying process can be fundamentally optimized. This includes monitoring and limiting the speed and torque of the synchronous motor as well as the performance data of the synchronous motor

25 funding process, and further the associated documentation of the actual loads (condition monitoring). By controlling the speed of the transport traction means the load can be fixed and thus a smooth and gentle operation of the ascending conveyor can be achieved.

For the continuous conveyor according to the invention preferably find engines

Use, depending on the number of pole pairs, the required engine speed at an engine frequency between 20 and 150 hertz, preferably wise in the range 5 Hz to 100 Hz, deliver. The number of pole pairs is preferably between 6 and 50, in particular around 10.

An embodiment of the invention will be described in more detail below with reference to the accompanying figures.

Show it:

1 shows a conveyor belt for heavy bulk material, schematically, in an i o horizontal section;

Figure 2 shows the conveyor belt of Figure 1, schematically, in plan view.

FIG. 3 shows the electric motor of the conveyor belt according to FIG.

15 cut;

4 shows the electric motor of Figure 3, in cross section.

FIG. 5 shows a block diagram of a continuous conveyor with rotary direct-injection

20 drifted;

Figure 6 is a block diagram of a continuous conveyor with slow-running

Synchronous motor and reduction gear.

As an example of a continuous conveyor, a conveyor belt is shown schematically in Fig. 1. Whose endless conveyor belt 1 runs between a drive roller 2 and a guide roller 3 in a circle. On the part of the conveyor belt 1, which forms just the upper strand, a heavy bulk material 4, such as ore or broken rock, abandoned and transported substantially horizontally, in the figure from left to right. Under the conveyor belt 1 are Support rollers 5 are arranged, which support the weight of the conveyor belt 1 and the bulk material 4.

The conveyor belt is driven by a low-speed, high-poled synchronous motor 6 with high torque. As can be seen in Fig. 2, the synchronous motor 6 drives the drive roller 2 of the conveyor belt directly, i. without intermediate mechanical gearbox, on. The working speed of the drive roller 2 is about 40 revolutions per minute, so that the synchronous motor 6 has a rated speed of 40 U / min. The synchronous motor 6 outputs a torque in the region of 300 kilonewtons.

With increased power requirements, a second synchronous motor of the same type can be coupled to the drive roller 2. If for reasons of space, the length of the synchronous motor 6 is limited, and a single-stage 15 reduction gear between the drive roller 2 and synchronous motor 6 may be provided, which reduces the speed of the synchronous motor 6, for example by a factor of 5.

According to the sectional images of FIGS. 3 and 4, the synchronous motor 6 is about 20 times as long as it is wide. The segmented design modular synchronous motor 6 has a housing jacket 7, which extends between two end-side end plates 8a and 8b. In the bearing plates 8a, 8b are the bearings 9a, 9b for the rotor shaft 10, on which the rotor 1 1 sits. At its periphery, the rotor 1 1 carries a plurality of magnetic poles 12. Through

25 separated a small air gap from the rotor 1 1, the stator 13 sits in the housing shell 7. So this is an internal rotor. The rotor shaft 10 protruding from the end shield 8b on one (right) side is coupled to the drive roller 2 of the conveyor belt (compare FIG. 2).

The block diagram of Fig. 5 illustrates the advantages associated with the direct

Drive of the conveyor belt 1 are connected by a permanently excited high-pole synchronous motor with high torque. An electronic frequency converter 14 is connected to the 3-phase AC power supply and generates a changeable in amplitude and frequency AC voltage, which is given to the stator 6 of the Synchronmo- sector 6. The rotating alternating field drives the rotor. By driving the frequency converter 14, the speed of the synchronous motor 6 between zero and the rated speed can be varied, so that the conveyor belt can be approached from standstill with high torque without between drive roller 2 and synchronous motor 6, a clutch must be interposed io. Correspondingly small is the total mass moment of inertia of the drive, which essentially consists of the mass moment of inertia M _{m of} the synchronous motor 6, the mass moment of inertia M _{t of} the conveyor belt 1 together with the drive roller 2 and the mass moment of inertia M _{u of} the deflection roller 3. Since the synchronous mode

15 tor 6 drives the drive roller 2 directly and is therefore operated at a relatively low speed, the mass moment of inertia M _{m of} the entire drive system is much smaller than in conventional drives with fast-running asynchronous motor, multi-stage transmission and overload clutch. The transformed mass moment of inertia of the drive system according to the invention

20 tems is about 10 times smaller than with conventional drives.

The spring and damping characteristics of the powertrain are also significantly better. The drive system, which in principle comprises only the synchronous motor 6 and the drive roller 2, is capable of torsional vibration due to the mechanical elasticities 25 both in the axial and in the radial direction. The spring stiffness F _M of the elasticities on the motor side comprises the torsional stiffness of the motor shaft of the synchronous motor 6 and the axial spring rigidity. The friction damping in the bearings and the damping in the air gap by magnetic reversal are characterized by the damping D _m . at

30 of the direct coupling of the synchronous motor 6 to the drive roller 2, the spring stiffness F _m can be practically neglected. The drive system for the conveyor belt 1 shown in Fig. 6 differs from the drive of FIG. 5 only by the interposition of a single-stage reduction gear 15 between the synchronous motor 6 and drive roller 2 of the conveyor belt 1. In this variant, the synchronous 5 motor 6 no longer necessarily run at the same speed as the drive roller 2. This allows a smaller-sized synchronous motor 6, however, has a slightly higher rated speed. But it suffices a small single-stage reduction gear 15, since the speed must be reduced only by a maximum of 15 times. Correspondingly simple, small and light, the io reduction gear 15 can be executed.

The additional mass moment of inertia M _g for the reduction gear 15 increases the total inertia of the drive by two to three times, which is still five to ten times smaller than in conventional drives.

15

Also, the spring and damping characteristics of the powertrain worsened by the relatively small reduction gear only slightly. The motor-side spring stiffness F _m is increased by the additional spring stiffness F _{g of} the transmission-side elasticities. The torsion spring stiffness flows in

20 th gear shafts and the shaft-hub connections in the transmission, the

Tooth stiffness due to elastic tooth deformation as well as the radial spring rigidity and axial spring stiffness of the shaft-hub connections, shafts, bearings and gear meshes within the gearbox. At the damping constant D _{m of} the synchronous motor 6, the damping constant D _{g of} the transmission side 25 damping is taken into account, which results from the friction damping in the bearings in the transmission, the degree of damping of the gear pairings by torsion, the friction damping in the gear pairings and the friction damping in the oil bath. Overall, the spring and damping properties of the entire drive train are also

30 dersteifigkeit F _g and the transmission-side damping D _{g of} the reduction gear 15 is still much better than in conventional drive systems. LIST OF REFERENCE NUMBERS

conveyor belt

capstan

idler pulley

bulk

support rollers

synchronous motor

housing jacket

a, 8b bearing shields

a, 9b bearings

0 rotor shaft

1 rotor

2 magnetic poles

3 stators

4 frequency inverters

5 reduction gear

Claims

claims

Continuous conveyor for transporting heavy bulk or general cargo, with an endless transport traction means, which rotates between a drive roller and a guide roller, and an electric motor drive which is coupled to the drive roller, characterized in that the drive at least one permanently excited high-pole synchronous motor (6) whose speed is at most 15 times as high as the working speed of the drive roller (2) of the transport traction means (1).

Continuous conveyor according to claim 1, characterized in that the synchronous motor (6) drives the drive roller (2) directly, so that the engine speed corresponds to the working speed of the drive roller (2).

Continuous conveyor according to claim 2, characterized in that the rated speed of the synchronous motor (6) in the range 5 U / min to 100 U / min, preferably 20 U / min to 50 U / min.

Continuous conveyor according to claim 2 or 3, characterized in that the synchronous motor (6) outputs a torque between 50 kNm and 800 kNm, preferably 100 kNm to 500 kNm.

Continuous conveyor according to one of claims 2 to 4, characterized in that the synchronous motor (6) outputs a power in the range 50 kW and 2000 kW, preferably 100 kW to 1000 kW.

Continuous conveyor according to claim 1, characterized in that the synchronous motor (6) drives the drive roller (2) via a single-stage reduction gear (15) with a reduction in the range 2 to 15, preferably 5 to 10, drives.

7. Continuous conveyor according to claim 6, characterized in that the

5 nominal speed of the synchronous motor in the range of 10 U / min to 700 U / min, preferably 50 U / min to 300 U / min.

8. continuous conveyor according to claim 6 or 7, characterized in that the synchronous motor, a torque between 30 kNm and 400 kNm, i o preferably 50 kNm to 250 kNm, outputs.

9. Continuous conveyor according to one of claims 1 to 6, characterized in that the motor frequency of the synchronous motor (6) is between 20 and 150 Hz.

15

10. Continuous conveyor according to one of claims 1 to 7, characterized in that the number of pole pairs of the synchronous motor (6) between 6 and 50, preferably between 8 and 15, is located.

20 1 1. Continuous conveyor according to one of claims 1 to 8, characterized in that the synchronous motor (6) is controlled by an electronic frequency converter (14).

12. Continuous conveyor according to claim 1 1, characterized in that rotational torque and speed of the synchronous motor (6) in dependence on

Funding process to be monitored, regulated and limited.

13. Continuous conveyor according to claim 12, characterized in that by the speed control of the synchronous motor (6), the speed of the 30 transport traction means is controlled, and thus a stabilization of the loading of the transport traction means. Continuous conveyor according to claim 12, characterized in that the actually driven loads are detected and documented via the frequency converter (14).