Bobbin (mining)

Double bobbin from above

In mining and conveyor technology, a reel is a cable carrier with a flat cable as a conveyor cable , which is wound on top of each other. Carriers can be equipped with one or two reels. Machines with two bobbins are known as double bobbin conveyors.

Today reels are mainly used for shaft sinking, since no structural devices need to be present in the shaft for their operation. They have design-related disadvantages which, compared to a cable conveyor system with a lower cable and counterweight and thus constant torque over the entire depth, mean that their use is mostly limited to this special application.

construction

Working principle

The bobbin is a rope carrier, which consists of a large, slender drum, which has the shape of a spool, on which a flat rope is wound. The bobbin consists of a core with a hub in the middle . The core has the width of the ribbon rope that can be wound on it. With smaller bobbins, the core consists of one piece, with larger bobbins it can be divided into up to four parts. So that the rope does not slide back and forth during winding and unwinding, it is forcibly guided between a lateral guide. This lateral rope boundary consists of two discs with spokes. Either wood or cast iron is used as the material for the spokes. The spokes must be lined with special materials to protect the rope. The upper ends of the spoke are designed so that the rope can run properly. To prevent the rope from slipping too much to the right or left, the inner dimension between the lined spokes of the rope carrier is only one dimension wider than the flat rope. The entries are made as slim as possible to ensure that the rope is guided safely onto the bobbin. So that the first layer of rope has a secure hold on the hub, the rope is attached to the reel by means of clamps.

Rope binding on a flat rope of a bobbin

Flat rope

Total torque of a double bobbin with one-sided load

function

In the case of reels, the individual turns of the hoisting rope, unlike in the case of reels (mining) , are not wound next to one another, but one on top of the other.

When the rope is wound onto the bobbin, the drum diameter increases; when it is unwound, it decreases accordingly. The torque changes accordingly.

A complete or constant torque compensation is not possible with a reel, unlike a cable conveyor system with a lower cable and counterweight, due to the design.

As the graphic shows, there is no constant torque with a bobbin, even with a counter-rotating double bobbin. The fluctuations are only minimized with a counter-rotating double bobbin. The changing torque, which reaches its maximum at the critical depth, must be compensated for by the controllable motor or the brake.

Calculation of the torque for the drive or the brake

Since the flat rope is wound on top of one another in the bobbin, the torque from the rope load is not constant. It can be calculated as follows.

The flat rope is wound up equidistantly: If d represents the thickness of the flat rope, the radius r increases by the thickness d with each revolution of the reel cage.

Equidistant spiral as a model for the geometry of the storage of the flat rope in a bobbin

If U is the symbol for the circumference of the winding, r is the current radius of the winding and l is the length of the wound flat rope and dU, dr and dr are the difference between the same parameters, then an equidistant spiral is described with the following equations:

${\ displaystyle dU ^ {2} + dr ^ {2} = dl ^ {2}}$

and

${\ displaystyle dU / dr = (2 \ pi r) / d}$

So the change in the circumference dU and the change in the radius dr form a right-angled triangle with the change in the rope length dl on the winding as a hypotenuse.

And the gradient of the increase in circumference dU after dr => dU / dr are a function of the quotient . ${\ displaystyle (2 \ pi r) / d}$

This system of equations can be solved for the ordinary differential equation by eliminating dU

${\ displaystyle dl / dr = {\ sqrt {(}} d ^ {2} + (2 \ pi r) ^ {2}) / d}$

This can be solved through integration:

${\ displaystyle \ int _ {0} ^ {l} dl = \ int _ {r_ {inside}} ^ {r_ {outside}} {\ frac {{\ sqrt {(}} d ^ {2} + (2 \ pi r) ^ {2})} {d}} dr}$

${\ displaystyle l = {\ frac {d ^ {2} \ left (\ log \ left ({\ sqrt {4 \ pi ^ {2} r _ {\ text {outside}} ^ {2} + d ^ {2 }}} + 2 \ pi r _ {\ text {outside}} \ right) - \ log \ left ({\ sqrt {d ^ {2} +4 \ pi ^ {2} r _ {\ text {inside}} ^ {2}}} + 2 \ pi r _ {\ text {inside}} \ right) \ right) +2 \ pi r _ {\ text {outside}} {\ sqrt {4 \ pi ^ {2} r _ {\ text {outside}} ^ {2} + d ^ {2}}} - 2 \ pi r _ {\ text {inside}} {\ sqrt {d ^ {2} +4 \ pi ^ {2} r _ {\ text { inside}} ^ {2}}}} {4 \ pi d}}}$

This equation cannot be solved analytically for the radius and , so it has to be done numerically in order to u. a. to calculate the lever arm for the torque. ${\ displaystyle r_ {inside}}$ ${\ displaystyle r_ {outside}}$

Finally, the flat rope load hanging in the shaft (product of the hanging rope length with the mass per meter and the acceleration due to gravity and the current winding radius) must be multiplied by the associated winding radius. The winding radius must also be added to the force from the payload. Then the total torque is known and the brake or the drive train can be dimensioned taking into account the necessary safety factors.

The graphic above clearly shows the critical depth at which the greatest torque is applied.

This must be mastered in terms of control technology.

use

Today reels are only used in certain exceptions. They are especially in Germany, the sinking of shafts used because the Abteufkübel not out to be. Single bobbin conveyors are used for single-section conveyance and double bobbins are used for double-section conveyance. If a drum hoisting machine is planned for the shaft to be sunk for later shaft hoisting, the later drum hoisting machine is often also used as a sinking machine. This approach is mainly used in foreign ore mining. The advantages here are that no additional foundations for the sinking machines, no further machine equipment or accessories are required. In the case of so-called secondary shafts or emergency drive systems, reels are also used as hoisting machines. In the Belgian and French mining industry, bobbin winding machines were also used for hoisting shafts. However, instead of steel flat ropes, flat ropes made of aloe fibers were used. In order to be able to convey reels from different depths , the machines must be equipped with a hiding device.

Security aspects

So that the hoisting ropes do not become detached from the fastening on the cable carrier, they must be attached to the cable carrier with at least two cable clamps. The hauling rope must be at least long enough that two rope windings remain on the rope carrier even when the conveyor is in its lowest position. For safety reasons, additional rope lengths are usually taken into account when dimensioning the rope length. In the case of double bobbins, it is possible to equip them with a so-called hiding device. With these machines it is imperative that a separate brake is available for the lottery wheel to hide it. If reels are used to sink the shaft , the critical depth, i.e. the depth at which the greatest load moment occurs on the cable carrier, must be observed.

Individual evidence

^ ^A ^b ^c Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7
^ ^A ^b Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1
↑ ^a ^b ^c Gustav Köhler: Textbook of mining science. 6th improved edition, published by Wilhelm Engelmann, Leipzig 1903
^ ^A ^b Julius Ritter von Hauer: The conveyors of the mines. 3rd increased edition, published by Arthur Felix, Leipzig 1885
^ ^A ^b Julius, Ritter von Hauer: The conveyors of the mines. 2nd edition, published by Arthur Felix, Leipzig 1874
↑ ^a ^b ^c H. Hoffmann, C. Hoffmann: Textbook of mining machines (power and work machines). 3rd edition, Springer Verlag OHG, Berlin 1941, pp. 218-221
↑ ^a ^b ^c ^d ^e Technical requirements for shaft and inclined conveyor systems (TAS). Verlag Hermann Bellmann, Dortmund 2005
^ ^A ^b ^c ^d Karl Teiwes, E. Förster, Hans Bansen: Die Bergwerksmaschinen, Third Volume, Die Schachtfördermaschinen, published by Julius Springer, Berlin 1913
↑ Walter Buschmann: Collieries and coking plants in the Rhenish coal mining industry, Aachen district and western Ruhr area. Gebr. Mann Verlag, Berlin 1998, ISBN 3-7861-1963-5 , pp. 80-82
↑ ^a ^b ^c Horst Roschlau, Wolfram Heintze: Bergmaschinentechnik. VEB German publishing house for basic industry, Leipzig 1977

[Quelle_1-1] A ^b ^c Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7

[Quelle_8-2] A ^b Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1

[Quelle_6-3] Gustav Köhler: Textbook of mining science. 6th improved edition, published by Wilhelm Engelmann, Leipzig 1903

[Quelle_4-4] A ^b Julius Ritter von Hauer: The conveyors of the mines. 3rd increased edition, published by Arthur Felix, Leipzig 1885

[Quelle_5-5] A ^b Julius, Ritter von Hauer: The conveyors of the mines. 2nd edition, published by Arthur Felix, Leipzig 1874

[Quelle_11-6] H. Hoffmann, C. Hoffmann: Textbook of mining machines (power and work machines). 3rd edition, Springer Verlag OHG, Berlin 1941, pp. 218-221

[Quelle_7-7] Technical requirements for shaft and inclined conveyor systems (TAS). Verlag Hermann Bellmann, Dortmund 2005

[Quelle_3-8] A ^b ^c ^d Karl Teiwes, E. Förster, Hans Bansen: Die Bergwerksmaschinen, Third Volume, Die Schachtfördermaschinen, published by Julius Springer, Berlin 1913

[Quelle_10-9] Walter Buschmann: Collieries and coking plants in the Rhenish coal mining industry, Aachen district and western Ruhr area. Gebr. Mann Verlag, Berlin 1998, ISBN 3-7861-1963-5 , pp. 80-82

[Quelle_2-10] Horst Roschlau, Wolfram Heintze: Bergmaschinentechnik. VEB German publishing house for basic industry, Leipzig 1977