Shaking chute
The vibrating chute is funding , which in mining underground was used. In German hard coal mining , shaking chutes were used in the face for mechanical conveyance from 1920. From the mid-1950s onwards, the vibrating chute was replaced by fully mechanical extraction using a coal plow and chain scraper conveyor and no longer used.
construction
The shaking slide consists of a trapezoidal channel, the slide line, which is moved back and forth by a motor . The slide line is made up of individual slide sections, which are made of up to 5 mm thick sheet steel (St 37.11). The individual slide sections are usually 3 meters long, as this length is advantageous due to the spacing between the pistons in longwall faces (1 - 1.5 m). The flat and trapezoidal cross-section has less friction than trough-shaped or rectangular cross-sections. The dimensions of the individual slide profiles are standardized and divided into four sizes, with the filling cross-sections being 340, 420, 530, 720 cm 2 . Small or medium-sized profiles have the advantage of better utilization compared to large profiles, and slides with large profiles also have the disadvantage that a relatively large dead load has to be moved along with them.
In order to transfer the movement forces to the slide line, special attack slides are integrated into the slide line. These slide pieces, on which the force of the slide motor acts, are reinforced because they are particularly stressed. So that the attack rod of the drive can be attached variably, angle irons with multiple holes are attached to the underside of the slide channel. The horizontal or vertical guidance of the point of attack on the slide prevents harmful effects of forces from attack rods attacking at an angle. Several jogging slides are built one behind the other for longer distances. If there are several lines of slides connected in series, a larger slide profile is used for the lower slides than for the upper slides.
Slide connections
The connections of the individual slide sections are subject to alternating pressure and tensile loads as well as vibrations during operation. That is why they have to be as rigid as possible, but at the same time they have to be easily detachable to make it easier to move the slide. There are two types of slide connections, screw connections and quick connections. The screw connection is the simplest slide connection that has been used very often due to its relatively low price.
T-head bolts are used as screws , which are inserted through special ears. These ears are riveted or welded to the underside of the slide plate. The disadvantage of the screw connection is that the thread of the screw is very stressed by the sliding movements. In addition, opening and closing the screws is very time-consuming.
The defects of the screw connection are avoided by means of quick connections. So-called tension wedge connections have proven themselves as quick connections. With these quick connections, the slide ends are provided with tabs. At the ends of the chute, a swivel bracket is attached to the tabs on both sides. Two pressure wedges and a wedge screw are inserted into the bracket. The pressure wedge and the wedge screws together form an expansion body. If the expanding wedge is actuated, the brackets are braced with the swivel bracket.
Relocation
There are three methods of relocation from shaker slides, ball slides, impeller slides, and hanging slides.
The ball slide was the predominantly used type because it has decisive advantages over the impeller slide. Since the ball friction is lower than the roller friction, the friction is reduced to a minimum with the ball slide. In addition, the balls are slowed less by mountains or coal. In addition, the balls can work themselves free again. Another advantage of ball slides is their lower overall height. This is particularly advantageous with thin seams. The ball slide consists of the slide channel and the slide chair, also known as the ball chair. A guide carriage is attached to the top of the ball chair, which absorbs axial movements like a linear ball bearing . It consists of several angle steels through which the balls are guided. The slide channel is laterally movable or detachable within certain limits on the guide carriage in order to relieve the bearing of permanent transverse forces. The channel has a driver that engages in a transverse groove made of two angle irons.
In the case of the impeller slide, wheel axles are attached to the underside of the channels. There are wheels on these axles. The wheels run on special support plates to which flat iron is welded to guide the wheels. Impeller slides are only partially suitable for thin seams. When lying undulating , there are often difficulties in moving the slides. The slide chair can lift off especially in deeper places. To prevent this, special guide chairs are screwed to the side of the slide chair. To fasten the slide chair, the connecting screws of the slide sections are passed through holes in the guide chair and screwed to the guide chair. The management chair is fed with a stamp against the hanging wall. Due to the horizontal and vertical guidance, the management chair forces the shaking slide to move smoothly.
Hanging slides are slides that are hung from the extension with chains or ropes. However, this type of relocation was only able to establish itself in certain routes. The hanging slide was not used in the face because the strong lateral pendulum movements of the slide are difficult to control and represent a considerable potential risk in a confined space. Another disadvantage is the considerable amount of time required to return the slide, since all suspensions have to be unscrewed.
drive
The kinetic energy required for the exit can either be generated by machine power or gravity. The gravity method only works if there is a sufficient gradient of at least 15 gons for the entrance. Machine power by means of a slide motor is always required for the decline. The vibrating chute can be driven by a compressed air motor as well as by an electric motor. However, in the coal mining industry, the compressed air motor has prevailed over the electric motor due to its simplicity.
Drive with compressed air motor
A piston motor is required for the shaking chute drive, which sets the chute in back and forth movements. The drives are equipped with stroke adjustment devices so that they can work with a correspondingly smaller or larger stroke depending on the angle of fall, conveying capacity, slide length and friction between the conveyed goods and slide. The reciprocating engine consists of a cylinder body in which the piston moves. On the side of the piston rod , two guide rods are carried for stabilization. The piston rod and guide rods are connected to one another via a so-called attack bridge. The drive motors are usually placed under the slide. For thin seams, low multi-piston engines that can be adjusted for single or double-acting operation are used. The most common are twin motors, which are mounted to the left and right of the slide. Since only the kinetic energy is required for the decline in the case of a dip over 15 gons , a single-sided slide motor that only pulls the slide up is sufficient. With this type of drive, the weight of the slide is used for the downward movement. For higher top speeds, the stroke is increased or a double-acting motor is used. The power of the engine is essentially dependent on the cylinder diameter.
Counter motor
Counter-motors are used when the incline is not large enough to cause the slide to descend automatically. The counter motor works together with the single-acting slide motor. The counter motor is mounted in the lower part of the slide to effect the exit. The motor for the fall is mounted in the upper part of the slide. The slide line is pulled back and forth between the two motors and is constantly kept under tension. This avoids alternating stresses. In order to be able to adapt to the tension exerted by the main motor, the counter motor has its own pneumatic control. Instead of a single-acting motor with a counter motor, double-acting motors can also be used. These motors can be used in all storage conditions that are suitable for shaking chutes. However, double-acting motors put more stress on the chute line than single-acting motors.
Engine lubrication
Air motors need constant lubrication as they move in order to function properly. For this purpose, the slide motors have an oil container, from which the lubrication takes place automatically. The incoming compressed air pulls small amounts of oil with it. The oil container is dimensioned so that one filling is sufficient for one layer.
Electric motor drive
Electric chute drives were mainly used in pits without a compressed air network. Since the electric motor performs a pure rotary movement, this rotary movement must be converted into a back and forth movement. This is usually done with an elliptical drive. This drive consists of two elliptically shaped gears, each of which is seated on a shaft mounted at the focal point. On one of the gears there is a crank disk to which the pull rod is attached, also concentrically. The electric motor drives the gear 1 and sets it in elliptical motion. The gear 2 is driven via the teeth of the gear 1. The pull rod is set in back and forth movements via the crank disk, thereby moving the slide line. Other designs of electric slide drives work on the principle of non-round wheels. The back and forth movement is generated by a gear template that is equipped with elliptical gears. The output of the three-phase motors depends on the size of the vibrating chute and is between 15 and 22 kW.
Position of the drive
The installation of the slide motor depends on the slide length. For short slides, the slide motor can be set up at the top of the slide. In the case of longer slides, the position at the upper end has not proven effective due to the heavy load on the upper slide connections. Setting up the drive at the lower end of the slide is also very disadvantageous due to the shift in the center of gravity of the slide line and the resulting rolling movement of the slide. In practice, the end of the upper third has proven to be a point of attack. So that the slide connections are not overstrained by the motor movements, several motors are attached at a distance of 100 meters for longer slides. The motors can be placed below or to the side of the slide. Installation below the slide is preferred over installation on the side. Since when the motor is installed on the side, the motor power is divided into two components depending on the angle between the slide and the attack line at the point of attack of the slide, the full motor power cannot be used to drive the slide. This disadvantage is partially compensated for by special double bar attacks. With electric drives, the motor is always installed under the slide.
function
The movement of the conveyed material is comparable to throwing the shovel. The movement of the chute consists of going down and going down. During the movement process in the conveying direction, the conveyed material is given a certain movement force. Shortly before the end of the slope, the chute is slowed down and reversed in the direction of movement at the end of the slope. The chute is then accelerated against the conveying mechanism. With the sudden sudden decrease in the channel, the material to be conveyed slides a little further in the conveying direction due to the inertia. This movement process is repeated over and over again. The conveying path per stroke depends on two factors. These are, on the one hand, the acceleration achieved by the chute and, on the other hand, the friction between the chute and the material being conveyed. The lower the sliding friction between the chute and the material being conveyed and the stronger the impact of the drive, the greater the conveying path per stroke. From an angle of incidence of 27 gons, the conveyed material slides without the chute moving. This angle is called the critical angle of incidence.
Delivery rate
The conveying capacity of the shaking chute depends on the cross section of the chute, the number of strokes of the drive and the length of the path that the conveyed material travels on the chute with each stroke. Since the conveyed material is often taken back with it, the maximum conveying capacity of the chute cannot usually be achieved. The collapse of the seam has a positive effect on the conveying capacity . The conveying capacity per hour is the theoretical maximum capacity of the vibrating chute. However, this maximum output is only taken into account for the calculation of the drive, not as a continuous output, as standstills can definitely occur during operation.
Individual evidence
- ↑ Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH, Essen, 1982, ISBN 3-7739-0390-1 .
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac Carl Hellmut Fritzsche: Textbook of Mining Studies. First volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1961.
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x Fritz Heise, Fritz Herbst: Textbook of mining science with a special focus on hard coal mining. Second volume, fifth increased and improved edition, published by Julius Springer, Berlin 1932, pp. 334–362.
- ↑ a b c d e f g B. W. Boki, Gregor Panschin: Bergbaukunde. Kulturfond der DDR (Ed.), Verlag Technik Berlin, Berlin 1952, pp. 487–492.
- ^ Joachim Huske: The coal mining in the Ruhr area from its beginnings to the year 2000. 2nd edition, Regio-Verlag Peter Voß, Werne, 2001, ISBN 3-929158-12-4 .
- ↑ a b c d H. Hoffmann, C. Hoffmann: Textbook of mining machines (power and work machines). 3rd edition, Springer Verlag OHG, Berlin 1941, pp. 384-393.