RU2418331C1 - Electromagnetic lifting device for transportation of hot-rolled steel rolls and control method for it - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: electromagnetic lifting device (1) includes at least two poles (2, 3) of certain shape for transportation of roll (4) of hot-rolled steel with horizontal location of axis; at that, the above poles (2, 3) are connected through ferromagnetic section (5), and appropriate cores (6, 7) enclosed with two magnetising solenoids (8, 9). In addition, device contains on each of the above cores the device intended to detect magnetic flow related to roll (4) of hot-rolled steel, as well as control device (16) functionally related to those detection devices and intended to compare the values measured by each of them, to allow or to forbid the transportation. Control method involves the first check whether difference between the values measured by means of two measuring coils (10, 11) is below the specified threshold value; and in case of confirmation the second check whether the complete decrease of magnetic flow is below the second specified threshold value. Supply of signal allowing the transportation is possible only in case of positive result of both checks.

EFFECT: simplifying the safety device design.

11 cl, 5 dwg

Description

The present invention relates to hoisting devices for transporting hot rolled steel coils, and more specifically, to an electromagnetic hoisting device comprising a locking device.

It is known that hot-rolled steel coils represent a spiral-wound electromagnetic strip with a length of up to 3000-3500 meters and a weight in the range of 15-45 tons, with a spiral wound coil being tied to maintain shape. In this connection, such a roll is similar to a large spring, which, when untwisted, exhibits strong dynamic properties inherent in spring systems, therefore, such a roll cannot be considered as a monolithic block.

These dynamic properties accumulate in the wound strip under the influence of high temperature (500-600 ° C or more) and subsequently when the roll is placed on the base for cooling. Being in this state, the strip becomes shorter, its thickness becomes smaller, and the last turns are wound with energy, which tends to untwist the strip back. This is due to natural shrinkage deformation, which does not complete completely, since the roll is tied up, tightening the coils, and placed on the base or in the locking device with the horizontal axis position when the roll is still hot.

The combination of these factors in the roll causes weakening of the turns and physical deformation concentrated in the upper layers, and this deformable region coincides with the grip area of the lifting device when moving the roll. For this reason, hoists for transporting rolls use grippers, mainly of a mechanical type, ensuring the safety of lifting the roll regardless of deformations in the gripping area and dynamic changes in the spiral structure. However, it would be desirable to use electromagnetic lifting devices, which are more efficient and faster than mechanical lifting devices, which are still used because of the specific properties of the hot rolled steel coils.

In fact, standard electromagnetic lifting devices are suitable for this purpose until mechanically dynamic changes occur in the rolls, which can cause sharp changes in the magnetodynamic properties, leading to a decrease in traction and a drop in load during transportation, but this phenomenon cannot be foreseen with conventional lifting devices.

Initially, under the action of magnetization, an electromagnet can compact the weakened turns of a roll in the pole region, even simply due to its own weight. Further, the magnetic flux passing through the electromagnet and the coil reaches a value such that the cohesive force holding the coil exceeds more than twice its weight, which is a prerequisite in accordance with EN 13155. Magnetic flux meter (fluxmeter) ) positioned as close as possible to the poles of the electromagnet for periodic measurement of magnetic flux and using the measured value of magnetic induction assess compliance with the requirements of the standard.

The problem of the electromagnetic lifting device is the measurement at the initial stage of lifting the spring coils, which affect the magnetic field. In fact, mechanical-dynamic changes can cause a more or less noticeable separation of the external turns, which really leads to a decrease in magnetic induction in the cross section, followed by a quadratic decrease in the adhesion force of the electromagnet, which is proportional to the square of the induction. This averaged mechanical-magnetic effect arising between the roll and the electromagnet is hereinafter referred to as "magnetic dynamism" for simplicity.

If this magnetic dynamism exceeds a critical threshold value, it is likely that the weakening of the steel coils of the coil will cause a further decrease in magnetic induction. This in turn can cause a chain reaction with a further separation of the turns and a decrease in magnetic induction until a situation arises in which the rise becomes dangerous and does not meet the requirements of EN 13155, with a real risk of cargo loss during transportation. A problem can arise even if magnetic dynamism occurs only at one of the poles, in this case the other pole, which generates a large traction force, also produces a lever effect relative to the region with lower induction. This can cause accelerated weakening of the turns on the side that is already weakened by magnetic dynamism, significantly increasing the likelihood of a roll falling.

Disclosure of invention

The present invention is the creation of an electromagnetic lifting device that does not contain the above-mentioned disadvantages. This goal is achieved by an electromagnetic lifting device comprising a safety device designed to check at the beginning of the lifting of the magnetic dynamism at each pole, as well as the full magnetic dynamism of the lifting device, before obtaining permission for transportation. Other advantages of the proposed lifting device are disclosed in the dependent claims.

The main advantage of the proposed lifting device is that it can transport hot rolled coils under the condition of absolute safety, thus combining the practicality of electromagnetic lifting devices and the safety of mechanical lifting devices.

The second significant advantage is that safety is achieved through the use of a simple, inexpensive and reliable device.

Other advantages and characteristics of the lifting device in accordance with the proposed invention will be clear to a specialist from the following detailed description of an embodiment of this device with reference to the drawings.

Brief Description of the Drawings

Figure 1 is a schematic cross-sectional front view of a lifting device according to the invention;

figure 2 is a view similar to the previous one, which schematically shows the action of the lifting device;

figure 3 is a view similar to the previous one, which shows a system of forces acting when lifting a load;

4 is a view similar to the previous one, which schematically shows the action of the system of forces in the condition of asymmetric magnetic dynamism, and

FIG. 5 is a view similar to that of FIG. 2, which schematically shows the action of a lifting device in the case of symmetrical magnetic dynamism.

The implementation of the invention

Referring first to FIGS. 1-3, it can be seen that the electromagnetic lifting device in accordance with the present invention typically includes two poles 2, 3 of a certain shape, adapted to transport rolls 4, with a horizontal axis and connected through a ferromagnetic section 5, and two the core 6, 7. Two solenoids 8, 9, respectively, mounted around these cores 6, 7, create a magnetomotive force that allows you to lift the roll 4. It should be noted that, although the electromagnet 1 described here is preferably etsya bipolar specified range is not limiting, since the magnets with different numbers of poles, designed for the required devices can be made on the principle. A new aspect of the present lifting device is the presence of two measuring coils 10, 11, preferably made of enameled copper, placed respectively around the cores 6, 7 near the poles 2, 3. It is desirable to protect said coils 10, 11 with the respective plates 12, 13 from the effects of heat transmitted from roll 4, which in some cases is still transported hot.

The coils 10, 11 can measure magnetic dynamism at the beginning of the lifting of the load, since they are crossed by the lines of force of the magnetic flux generated by the solenoids 8, 9 and connected to the roll 4, and the coils are able to measure the decrease in the magnetic induction of the associated magnetic flux (negative magnetic dynamism) caused by mechanical dynamism of the turns of roll 4 when lifting. This information is transmitted to two corresponding ADCs (analog-to-digital) converters 14, 15, which transmit data in digital format to the control unit 16, designed to issue a signal, allowing or not allowing the transportation of goods.

The control of this lifting device is quite simple, effective and understandable: the poles 2, 3 are brought into contact with the roll 4, which must be raised, after which the solenoids 8 and 9 are activated, the magnetic flux crosses the roll 4, as shown in figure 2. At the beginning of the rise, in the absence of magnetic dynamism, the balance condition is shown using the system of forces in figure 3.

In the said system, Fa denotes the traction force of the pole a (N pole shown in FIG. 2); Fb denotes the adhesion force of the pole b (S pole in figure 2); Fsa and Fsb denote the vertical components of the adhesion forces; L1 and L2 denote the lever shoulders, measured as the distance between the barycentric axis of the load (P) and the vertical components Fsa and Fsb, each of which holds half the load (P / 2).

Figure 4 shows a similar system of forces under the condition of asymmetric magnetic dynamism, for example, larger at the pole b. In this case, Fa> Fb, therefore, Fsa> Fsb and Fsa · L1> Fsb · L2, as a result of which the lever effect relative to the pole b can cause accelerated attenuation of the turns on the same side, significantly increasing the probability of a load fall.

At the start of the lift, the control unit 16 compares the magnetic dynamism that occurs at each individual pole, based on the data received from the measuring coils 10, 11 through the transducers 14, 15. If the difference between the two values measured using the coils 10, 11 exceeds Given a threshold value in the range from 3% to 10%, for example 5%, a signal is sent to stop the lift and return the load to the base.

Conversely, a decrease in the associated magnetic flux, which remains below the emergency threshold value, does not cause further separation of the coil turns and blocks magnetic dynamism, maintaining the adhesion force at such a level that transportation can be safely carried out in accordance with the standards of EN 13155.

If the two signals measured by the coils 10, 11 are almost equivalent, as shown in Fig. 5, the control unit 16 immediately proceeds to the next stage - to verify that the full magnetic dynamism of the system remains below the threshold value to allow transportation, and in this In case of indication are in the range from 3% to 10%. Indeed, if the initial attenuation of the turns remains within the specified parameters, this phenomenon ceases, due to which a complete decrease in the associated magnetic flux of less than, for example, 5% allows safe transportation. It should be noted that the considered safety and magnetic dynamism coefficients can be changed in accordance with the requirements for the case in question.

A method for controlling an electromagnetic lifting device in accordance with the present invention can be determined by the following steps:

a) the inclusion of magnetizing solenoids 8, 9;

b) checking that the magnetic flux associated with the transported roll 4 is sufficient to create a lifting force of more than two times the weight of the roll 4;

c) the initial rise of the roll 4 and the simultaneous comparison of the magnetic dynamism occurring in the individual bands to verify that the difference between the values measured with the coils 10, 11 is below a predetermined threshold value;

d) in case of a negative test result, signaling to stop the lift and return of the load to the base, and in the case of a positive test result, a second check that the total magnetic dynamism of the system is below the second predetermined threshold value;

e) in the case of a negative result of the second test, a signal to stop lifting and the return of the load to the base, and in the case of a positive test, a signal allowing the transport of roll 4.

It is understood that the above-described and illustrated embodiment of a lifting device in accordance with the invention is only an example capable of various modifications.

In particular, the converters 14, 15 can be combined in the control unit 16, and the coils 10, 11 can be replaced by similar devices designed to measure changes in the associated magnetic flux.

Claims (11)

1. An electromagnetic lifting device (1) containing at least two poles (2, 3) of a certain shape for transporting a coil (4) of hot-rolled steel with a horizontal axis, and these at least two poles (2, 3) are connected through a ferromagnetic section (5) and corresponding cores (6, 7) covered by two magnetizing solenoids (8, 9), characterized in that it further comprises a device on each of these cores for detecting changes in magnetic flux associated with the roll m (4) hot-rolled steel, and a control device (16) operatively associated with said detecting device and for comparing the values measured by each of them, to permit or not permit transportation. 2. An electromagnetic lifting device according to claim 1, characterized in that the device for detecting changes in the associated magnetic flux is a measuring coil (10, 11) located near the corresponding pole (2, 3). 3. An electromagnetic lifting device according to claim 2, characterized in that the measuring coil (10, 11) is made of enameled copper. 4. An electromagnetic lifting device according to claim 2 or 3, characterized in that it further comprises plates (12, 13) for protecting the measuring coils (10, 11) from the heat coming from the coil (4) of hot-rolled steel. 5. An electromagnetic lifting device according to any one of claims 1 to 3, characterized in that it contains analog-to-digital converters (14, 15) located between devices designed to detect changes in the associated magnetic flux and the control device (16). 6. An electromagnetic lifting device according to claim 4, characterized in that it contains analog-to-digital converters (14, 15) located between devices designed to detect changes in the associated magnetic flux and the control device (16). 7. A method for controlling an electromagnetic lifting device (1) according to any one of claims 1 to 6, comprising the following steps:
a) inclusion of magnetizing solenoids (8, 9);
b) checking that the magnetic flux associated with the transported roll (4) is sufficient to create a grip force that is more than twice the weight of the roll (4);
characterized in that it further includes the following steps:
c) the initial rise of the roll (4) and at the same time verify that the difference between the values measured using devices designed to measure changes in the associated magnetic flux is below a predetermined threshold value;
d) depending on the result of the first test, performing or not performing a second test to determine that the total decrease in the associated magnetic flux is below the second predetermined threshold value;
e) depending on the result of the second inspection, issuing or not issuing a signal authorizing transportation. 8. The control method according to claim 7, characterized in that if as a result of the first check in step c) a negative result is obtained, then in step d) a signal is issued to stop the lift and return the load to the base. 9. The control method according to claim 7, characterized in that if a negative result is obtained as a result of the second check in step d), then in step e) a signal is issued to stop the lift and return the load to the base. 10. The control method according to claim 7, characterized in that the threshold value for the first check in step c) is set in the range from 3 to 10%, preferably 5%. 11. The control method according to claim 7, characterized in that the threshold value for the second test in step d) is set in the range from 3 to 10%, preferably 5%.

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