Conveyors called machines of continuous action, the working bodies of which allow you to move bulk and lumpy goods in a continuous stream or piece goods at certain intervals.

Conveyors are most often used as a means of transport moving cargo from one transshipment operation to another. In the designs of many continuous loading and unloading machines, conveyors are the most important component that transports cargo from the gripping body (receiving hopper) to the place of loading into wagons, cars, bunkers or warehouse areas.

According to the design features conveyors are divided into belt, rope-belt, chain, lamellar, trough, scraper, screw, inertial, vibratory and gravitational.

BELT CONVEYOR

In belt conveyors ribbon is both a traction and a load-bearing body. These conveyors are stationary and mobile . Belt conveyors are used to move bulk, lumpy and piece goods over long distances.

The performance of belt conveyors varies widely and reaches 1000 t/h or more, depending on the width and speed of the belt. Its width ranges from 300 to 2000 mm, and the recommended speed is 0.8-4 m/s.

Stationary belt conveyors designed for horizontal and inclined movement of bulk, lumpy, container and piece cargo. The length of one section of the conveyor reaches 4.5 km, and the length of conveyor lines - 12 km or more. The capacity of stationary belt conveyors is up to 20,000 t/h.

Stationary belt conveyors can be installed horizontally or inclined. The angle of elevation (maximum) depends on the properties of the transported load (angle of repose, coefficient of internal friction).

Mobile belt conveyors are used to move bulk, lumpy and small-piece cargo to other transporting devices and to the dump both in horizontal and in inclined planes. Loading takes place through a hopper installed above the tension drum, and unloading is provided directly from the belt that wraps around the drive drum. Move the conveyor manually.

Advantages of belt conveyors in comparison with other types of conveyors:

– great performance;

- simplicity of design;

– movement of cargo on the bearing surface;

- low power consumption;

- noiseless operation;

– Possibility of full automation.

Disadvantage: Sagging conveyor belt.

SCREW CONVEYOR

Screw conveyors used when transporting in horizontal and inclined directions (at an angle of up to 20 °) dry bulk materials (cement, lime, sand, mineral fertilizers, etc.). Their working body is a screw (auger), solid, tape or bladed, installed in a metal chute. The top of the trough is covered with a lid. When a rotational motion is imparted to the screw, its blades move the load poured in the chute.

Rice. Screw conveyor: 1 - electric motor; 2 - reducer; 3 - gutter; 4 - outboard bearing; 5 - auger; 6 - loading pipe; 7 - discharge pipe.

The advantages of screw conveyors include:

- simplicity of design;

– small overall dimensions;

– convenience of intermediate unloading;

- tightness, which is very important when transporting dusty, hot and smelly goods.

The disadvantages include:

- high specific energy consumption associated with the method of moving goods;

– significant crushing and abrasion of the cargo;

– increased wear of the screw and chute;

- sensitivity to overloads, leading to the formation of loads inside the groove (especially at intermediate bearings).

INERTIA CONVEYORS

Inertial conveyors are used to move bulk, a little less often small-piece cargo over relatively short distances in horizontal or inclined (up to 20 °) directions. In inertial conveyors, particles of the transported cargo slide along the load-carrying body or fly in space under the action of inertia. Inertial type conveyors are divided into two groups: vibrating - with a small amplitude and a high frequency of oscillations and swinging, characterized by significant amplitudes and a low frequency of oscillations.

In a swing conveyor the gutter is located on elastic racks, which are rigidly fixed to the supporting frame structure at a certain angle to the vertical. A crank mechanism driven by an electric motor transmits variables in the direction of movement to the chute. The chute rises during such a forward movement, and lowers (i.e. swings) when moving backward. In this case, the pressure of the load on the chute changes. When the chute moves in the opposite direction, the load slides forward along it, moving a certain distance.

On vibrating conveyors asymmetrical vibrations are transmitted to the load. As a result of the smooth movement of the conveyor pipe up and a sharp movement down, the particles of the cargo are separated from the surface of the pipe and transported along it. Depending on the diameter of the chute - 350, 500 and 750 millimeters - the productivity of vibrating type conveyors is 50, 75 and 150 tons per hour, respectively. Their highest possible productivity is 400 tons per hour, the largest length is 100 meters. Special types of vibratory conveyors are used, among other things, for transporting goods upwards (vibratory transport).

Oscillating conveyors cannot transport sticky and very wet goods (e.g. wet clay, etc.).

Advantages of oscillating conveyors:

Comparative simplicity of design;

Possibility of complete sealing of transport of dusty, poisonous and hot cargoes;

Ability to perform various technological operations (screening, drying, cooling) simultaneously with transportation.

For vibratory conveyors, it should also be noted that the chute is not worn even when transporting abrasive goods and the relatively low energy consumption.

Flaws:

Significant reduction in performance when transporting uphill;

Inability to transport sticky goods;

Transfer (in one size or another) of vibration loads to supporting structures, and for inertial conveyors,

Increased chute wear when transporting abrasive goods

Increased energy consumption.

PLATE CONVEYORS

To move large-sized, heavy, hot, sharp-edged, abrasive goods, as well as in situations where it is necessary to overcome steep slopes (more than 18 °) apron conveyors .

Rice. Plate Conveyor

The speed of movement of plate conveyors does not exceed 0.6–1.0 m/s. You can move loads weighing up to 150 kg.

The advantage of apron conveyors: the rigidity of the design of the traction body gives minimal sagging and allows you to move loads with a large mass.

Disadvantage: the movement of a large heavy canvas and cargo on it requires a lot of energy.

SCRAPER CONVEYOR

IN scraper conveyors the load is moved by dragging along a chute or a pipe of rectangular or circular cross section by moving scrapers.

Scraper conveyors are widely used in coal mines, processing plants, food and chemical industries.

Scraper conveyors are used to transport various dusty, granular and lumpy goods. Conveyors with solid scrapers are used for transporting and cooling hot cargoes of ash, slag - and various cargoes of the chemical and metallurgical industries. Scraper conveyors are not applicable for transporting fragile, wet and sticky goods: fragile goods are crushed by scrapers, wet and sticky goods stick to the scrapers and are poorly unloaded, the conveyor productivity decreases sharply and its return branch becomes clogged.

The main parameter of the scraper conveyor is the width of the scraper or scraper chain (in some cases the width of the chute).

The advantages of scraper conveyors are:

- simplicity of design;

– intermediate loading and unloading device;

– the possibility of hermetic transportation of dusty, gassing and burning cargoes.

The disadvantages include:

– intensive wear of the undercarriage and chute, especially when transporting abrasive goods, since the scrapers and the traction chain rub against the chute in the cargo environment;

- significant energy consumption due to friction of the load and the running gear on the chute;

- crushing of the cargo when moving by dragging, which is unacceptable for some cargoes, for example, for coke, and for many it is undesirable.

elevators

elevators called machines of continuous action, designed for vertical or close to it inclined movement of piece, lumpy or bulk cargo.

Depending on the type of gripping devices, elevators are bucket (norias) for bulk cargo, cradle or with hard grips for piece cargo.

In elevators, traction elements with buckets are enclosed in a metal casing, which isolates the working body from the external environment and prevents material from spilling and dusting. In the upper part of the elevator (head), equipped with an unloading inclined toe, there is a drive station, in the lower part (shoe) - a tension station and a loading toe. The guide shields (deflectors) installed inside the elevator casing prevent swinging of the traction body.

Rice. chain elevator ( A ) and tape ( b ) traction body: 1 – traction body ; 2 - ladle ; 3 – drive sprocket ( drum ); 4 - shoe .

The advantages of bucket elevators include:

– small overall dimensions in cross section;

– the possibility of delivering cargo to a considerable height (up to 60–75 m);

– large performance range (5–500 m³/h).

The disadvantages are:

- the possibility of separation of buckets during overload;

- the need for uniform supply.

The belt conveyor consists of the following elements (Fig. 4.1): a closed (endless) flexible belt 5 ; tail tensioner 1 and front drive 7 drums; working rollers 4 , which support the upper (working) branch of the tape and form its profile (straight or grooved); lower non-working rollers 10 , which support the lower (non-working) branch of the tape; roller battery 13 ; boot device 2 ; plow unloader 3 or unloading funnel 8 ; cleaning device 9 ; drive 11 , including an electric motor, gearbox and couplings; tensioner 12 ; metal structures (beds) 6 . The main components of mass-produced general purpose conveyors are standardized.

Rice. 4.1. Belt conveyor diagram

The main advantages of belt conveyors are: simplicity of design, reliability in operation, ease of maintenance and repair, relatively small weight, the ability to move goods at significant angles of inclination and unload them anywhere along the conveyor route, continuity of transportation with a high degree of automation.

The disadvantages of belt conveyors include the relatively high cost and low durability of the belt, the inability to operate at high temperatures, the difficulty of transporting goods with sharp edges, etc.

The performance of belt conveyors depends on the width, profile and speed of the belt and the bulk density of the transported cargo and can reach 30,000 tons / h.

At metallurgical enterprises, standard tapes with a width of 300 ... 3000 mm are usually used. The belt speed is usually 1...3 m / s and more (up to 8 m / With). The length of belt conveyors is determined by the strength of the belt and the features of the drive. With one drive drum and when using a belt with a textile base, the conveyor length is usually 25 ... 100 m, the use of multi-drum drives and modern high-strength belts makes it possible to increase the conveyor length up to 8 ... 10 km. The routes of belt conveyors are very diverse and can be horizontal (Fig. 4.2, A), oblique (Fig. 4.2, b), combined (Fig. 4.2, V, G, d, e), etc. In this case, to eliminate shedding of the load, the lifting angle β is taken equal to no more than 2 / 3 angles of repose of the transported cargo in motion φ D; usually the value of β is 20°.

Conveyors are divided into stationary, mobile and portable. At metallurgical enterprises, stationary conveyors are most common. Mobile conveyors are used to supply goods to several points, as a rule, located along a certain line (bunker compartments, loading funnels of process equipment, etc.). Portable conveyors are commonly used for various maintenance and repair work.

By design and purpose, general-purpose conveyors are distinguished (from GOST 22644-77 to GOST 22647-77) and special ones - for the food industry, instrument making, etc.

Rice. 4.2. Belt conveyor routes:
A – e, l– with single drum drive; and – To– with double drum drive; P - drive; NU - tension device;
r issue and r vog - conveyor rounding radii on the convex and concave sections, respectively

Introduction

Lifting and transport installations are widely used in all industries. It is difficult to imagine a plant where even the simplest means of transport would not be used.

In the food industry, literally all production facilities are presented in the form of a line, the main link of which are conveyors and lifting equipment.

Lifting and transport machines can be divided into the following groups:

1. Machines and installations used as a means of intershop and intrashop movement of goods.

2. Machines and tools for general purposes.

3. Special installations.

Depending on the type of transported cargo, conveyors are used to move piece cargo, loose small and large lumpy cargo. Therefore, the shape of the load-carrying element can be different. For belt conveyors, the shape of the belt can be straight or grooved.

With belt conveyors, you can move goods in horizontal or inclined directions. The length of the conveyor route is from several meters to kilometers (mining industry).

Description of the operation of a belt conveyor

Unlike lifting machines that move goods in certain portions and return without load for a new portion of cargo, conveyors transporting machines are designed to move goods in a continuous stream without stopping to load and unload them. Conveyors are designed to work with bulk cargo, i.e. goods consisting of a large number of homogeneous particles or pieces, or piece goods moving in large quantities.

All continuous transport machines can be divided into two groups - transport machines with a traction element (tape, chain, rope), in which the load moves along with a traction element, and transport machines without a traction element.

The main characteristic of conveyors is their productivity - volume V, m 3 / h, mass Q t / h or piece C pcs / h.

By abrasive properties, cargoes are divided into categories:

Non-abrasive - silage products, grain, sawdust, wood chips, piece packaged goods,

Low abrasive - brown coal, hard coal, molding earth, sex sulfur, clay, fireclay, sand, gravel, cement,

Abrasive - iron ore, anthracite, medium hard rocks, coke, ore concentrate, limestone, magnesite, crushed stone,

Highly abrasive - polymetallic ores, non-ferrous metal ore, hard rocks, iron ore.

Many parameters of the conveyor and unloading devices, including the shape of the chute, etc., depend on the degree of mobility.

The shape and cross-sectional area of ​​a load freely poured onto a fixed plane is determined by the angle of repose in the flow. The value of this angle depends on the adhesion forces between individual particles determined by the moisture content of the cargo, and on the friction forces arising from the relative movement of the particles.

Belt conveyors remain the most common type of continuous conveying machine in all industries. More than 90% of the conveyor installations are belt conveyors. They are used in the mining industry - for transporting mineral ores and coal during open-cast mining, in metallurgy - for supplying land and fuel, at enterprises with mass production - for transporting workpieces between workplaces, etc.

Typically, belt conveyors have a traction element in the form of an endless belt, which is also the bearing element of the conveyor, a drive that drives the drum, a tensioner, roller bearings on the working and cavity branches of the belt, as well as loading and unloading devices, devices for cleaning the belt. All elements of the conveyor are mounted on the frame.

With the help of installations equipped with belt conveyors, it is possible to transport bulk goods over very long distances.

Belt conveyors are characterized by high productivity up to 30-40 thousand tons / h, simple design, low material consumption, and as a result, relatively low cost, reliable operation and ease of use, relatively low energy consumption. They can have a curved track with turns in the horizontal plane and with ascents and descents in the vertical plane, depending on the terrain. However, the creation of a curved path is fraught with difficulties in ensuring a reliable and stable position of the tape on a curved section. The turning radius of the belt in the horizontal plane depends on the design of the conveyor, the type of belt and its width and has a wide range of values.

Schemes of belt conveyors are very diverse and are determined by the purpose of the conveyor. Feasibility studies and experience show that for the transportation of bulk cargo with a turnover of 5-25 million tons per year for a distance of up to 100 km, it is more economical to use belt conveyors than to use rail or road transport. The advantages of conveyor belts are their relatively low weight, the absence of high-wear hinges, the ability to move goods at high speeds. The service life of conveyor rubber-fabric belts, depending on the operating conditions, the characteristics of the transported cargo, the type of fabric frame and the time of one turn of the belt run, is 15-48 months.

The use of belt conveyors is limited by the temperature range from 60 to 200 0 С.

The disadvantages of belt conveyors include dusting when transporting small bulk cargo.

When moving piece goods, the width of the belt is chosen so that free margins of 50-100 mm wide remain on the belt on both sides.

In order for the load not to slide down, along the belt it is necessary to take the angle of inclination of the conveyor 10 0 less than the angle of friction of the load on the conveyor belt, because due to the sagging of the belt, its lifting angle is greater than the angle of inclination of the conveyor axis.

In addition, the canvas is shaken on the supports, which contributes to the sliding of the load. This shaking is the greater, the higher the speed of the web.

The belt conveyor for moving beets (Fig. 1) consists of a drive drum 1, belts 2, a tension drum 3.

The drive drum is a hollow metal drum that receives torque from the engine through a transmission. The main parameters characterizing the drive drums are the diameter, width, as well as the coefficient of friction. To reduce belt slippage on the drum, it must be lined with rubber or wood.

Tapes are the main load-carrying and traction element. Rubberized fabric tapes are the most widely used.

The tape consists of a technical fabric - belting, a rubber layer and a rubber lining. Usually, the number of fabric gaskets is at least 3. Special tapes are also used, made from special grades of rubber, heat-resistant - T, frost-resistant M, oil-resistant MC, food - P. Rubber-cord tapes are used to absorb heavy loads.

The ends of the tape are connected by various methods (vulcanization, stitching, fixed, etc.). The width of the tape is from 300 to 3000 mm.

Tensioners are used to create the necessary tension of the tape and ensure the transfer of traction from the drum to the tape. Basically, screw and load tension devices are used, less often - load-spring, hydraulic. This conveyor uses a screw tensioner.

The belt conveyor is driven by a motor through a drive. Unloading occurs by pouring through the drive drum. Conveyor length__meters. The speed of this type of conveyor is within __m/s.

Belt conveyors are designed for continuous movement of bulk and small-piece cargo in horizontal, inclined directions. They are widely used in all industries due to their advantages:

• · Continuity of transportation, which helps to increase the productivity of machines that work in conjunction with belt conveyors;
• · Simplicity of a design, reliability in work and convenience of service;
• · Possibility of full automation with the use of means of regulation and control;
• · Possibility of transporting goods at tilt angles up to 24 0 , and with special conveyors - up to 90 0 , which significantly reduces transport communications compared to other modes of transport;
• · Possibility of unloading the transported cargo anywhere along the conveyor route. Disadvantages of belt conveyors: high cost and insufficient durability of the belt, impossibility of transporting high-temperature, sticky, sharp-edged cargoes.

Rice. 1.

The belt conveyor (Fig. 1) consists of a flexible closed, pre-tensioned belt 1, which is both a load-carrying and traction body, a drive 2 and a tension 7 drums; idler 5 to support the working and non-working branches, a drive consisting of one or more drive drums, a gearbox 3, an engine 4 and couplings, a tensioner 8, a supporting metal structure 6, a loading 9 and unloading devices, cleaning devices 10.

Belt conveyors are stationary and mobile.

Conveyor plants have a wide range of productivity: from several tons to 20 thousand tons. t/h with belt width from 300 to 3000 and speed up to 8m/s. With the use of modern high-strength belts and multi-drum drives, it became possible to create conveyors 8–10 km long in one line, and conveyor lines are operated up to several kilometers long (and even up to more than 200 km in open-pit mining).

Conveyors installed horizontally, inclined upwards and inclined downwards up to 5…8 0 operate in motor mode, and conveyors with a downward inclination angle of more than 5…8 0 operate in generator mode.

The bearing and traction body of a general-purpose belt conveyor is an endless flexible belt, resting with its working and idle branches on roller bearings and enveloping the drive and tension drums at the ends of the conveyor.

For short conveyors designed for general cargo, the working branch of the belt can slide on a wooden or metal deck. The transfer of movement to the tape is carried out in a frictional way from the drive drum. The necessary initial tension on the running branch of the tape is created by a tension drum using a tension device, which is mainly performed by a load one. Belts are loaded with bulk material through a hopper, which is usually installed at the beginning of the conveyor near the end drum. The unloading of the tape can be end from the drive drum or intermediate, for which a mobile unloading trolley or stationary plow ejectors are used. The direction of the flow discharged from the material drum is provided by the discharge box.

To clean the tape from the working side of the remaining particles, rotating brushes (nylon, rubber) or a fixed scraper are installed. For many transported materials, the installation of a cleaning device is necessary, since adhering particles, forming a hard-to-remove uneven crust on the rollers of an idle branch, can lead to their uneven rotation and accelerated wear of the belt. The rotating drum with spiral scrapers cleans the belt well.

It is recommended to install an additional throwing scraper in front of the tension drum in order to throw off particles that accidentally fell on the inner surface of the idle branch of the belt. Cleaning the belt after the drive drum is also necessary because adhering particles, crumbling from shaking under each support of the idle branch, can form blockages that complicate the operation of the conveyor.

To center both branches of the tape and avoid its excessive transverse displacement, various centering roller bearings are used. The belt conveyor drum drive consists of an electric motor, a gearbox and couplings. On the turning sections of the branches of the route, roller batteries are installed to ensure a smooth bend of the tape, or rotary drums. All elements of the conveyor are mounted on a metal structure attached to the foundation or to the bearing parts of the building. Metal structures with a drive drum, a drive and an unloading box are called a drive station. Structural elements with a tensioner make up a tension station. Everything else refers to the middle part of the conveyor, which is made of the same linear sections. All linear sections, transition sections, drive and tension stations are connected by bolts. As a rule, for bulk cargo, multi-roller supports are used, forming a grooved belt. This shape of the tape at the same width and speed allows you to get more than a twofold increase in productivity.

Double-drum dumping carts are designed for intermediate unloading of bulk materials only away from the belt along one of the discharge pipes. Stationary plow ejectors can be used for both bulk and piece goods. Known constructions of mobile plow ejectors on trolleys. In addition to the above elements, conveyors are equipped with locking devices or two-block normally closed brakes, as well as tape catchers located on inclined sections of the route in case of a break, safety devices and automatic control devices.

The design features of the conveyor depend on the type of belts used. Belt conveyors with a steel belt, with the same scheme as general-purpose conveyors, differ from the latter in separate structural elements due to the increased rigidity of the belt. Drums for steel strip are large, and roller bearings are made in the form of discs on the same axis, spring rollers, flooring with or without sides. For wire belt conveyors it is possible to use supports with one horizontal roller. On these conveyors, due to the looseness of the belt, mainly piece goods are transported. Wire belt conveyors can operate at high temperatures up to 1100°C.

The desire to eliminate the tape as a traction element led to the development of rope-belt conveyors with two traction ropes based on blocks and a tape with a load lying on them. The combination of a belt with a traction chain made it possible to create belt and chain conveyors. The traction chain of this conveyor rolls along guide blocks, and the side parts of the belt rest on inclined support rollers.

When using belt conveyors to supply cargo to a greater height, the length of the conveyor depends on the angle of its inclination; the steeper the conveyor, the shorter its length. Reducing the length of the conveyor reduces its cost and reduces the area it occupies in the production room or on the territory of the serviced facility. Therefore, to reduce the length and cost of the conveyor and in case of production necessity, steeply inclined and vertical conveyors with large inclination angles up to 90 ° are used. Here we can note conveyors with upper clamping elements: with a chain mesh belt, rubberized fabric belt and rollers with an additional paddle belt. In many cases, an increase in the angle of inclination is achieved by using special corrugated belts with ledges or ridges on the working side. For highly dusty materials, conveyors with a tubular belt with a zipper and a device for opening and closing it are used. In rough terrain, it is convenient to use conveyors with a belt suspended on chains from brackets and steel wire ropes lying on support blocks. A variation of these conveyors are conveyors with a tubular belt, also suspended from steel wire ropes on chains.

From a large family of mobile and portable belt conveyors, a light type steeply inclined belt loader with a variable angle of inclination and cross bars on the belt is shown. Most mobile belt conveyors use a drum motor with a built-in drive and a screw tensioner located at the top of the machine.

Belt conveyors for underground transportation of goods are designed to be used in cramped overall conditions, as well as to move people and heavy piece goods.

Belt conveyors of high power and considerable length are similar in design to general purpose conveyors. However, individual elements of high-capacity conveyors are distinguished not only by a proportional increase in size, but also by specific qualitative features. The drive, for example, is made with two drive drums, the tensioner has a system for changing the tension in the tape during start-up and when changing its load with material.

To load the tape, feeders are used that provide a certain supply of cargo corresponding to the productivity of the conveyor. On conveyors, belt catchers, powerful brakes and devices for controlling work and maintenance safety are used.

The calculation of high power conveyors must be carried out according to refined methods. Of particular importance in the design of these conveyors is the use of well-founded exact values ​​of the resistance to the movement of the belt and the resistance at the loading point.

feed conveyor belt

The bearing and traction element of a general purpose belt conveyor (Fig. 2.2) is an endless flexible belt 9, supported by the upper (working) and lower (idle) branches on roller bearings 6, 17 and envelope at the ends of the conveyor drive 10 and tension 2 drums. On short conveyors, often used for moving piece goods, the working run of the belt can slide over a wooden or metal deck. The movement is transmitted to the belt in a frictional way from the drive drum. The necessary initial tension on the running branch of the tape is created by the tension drum using the tensioner 1 cargo or screw type. Bulk cargo is fed onto the belt through a loading funnel 3, usually installed at the beginning of the conveyor at the end drum 2. The unloading of the tape can be end or intermediate, for which a mobile unloading cart 7 or stationary plow ejectors are used. The direction of the flow of the cargo discharged from the drum is provided by the unloading box 8, having one or two funnels.

Rotating brushes 11 are installed to clean the working side of the belt from the remaining particles. (kapron, rubber) or fixed scraper. For many types of cargo, the installation of a cleaning device is absolutely necessary, since adhering particles form an uneven crust that is difficult to remove on the rollers and can lead to their uneven rotation, causing accelerated wear of the belt. The rotating drum with rubber spiral scrapers cleans the belt well.

It is recommended to install an additional throwing scraper in front of the tension drum in order to throw off particles accidentally falling on the inner surface of the lower branch of the belt. 16. Cleaning the belt after the drive drum is also necessary because adhering particles, crumbling from shaking on each support of the lower branch, can form blockages of small particles that complicate the operation of the conveyor.

To center the course of both branches of the tape and exclude its excessive transverse displacement, various centering roller bearings are used. 5.

The belt conveyor drive consists of a drum, an electric motor 14 , gearbox 13 and couplings 12. On the turning sections of the branches of the route, roller batteries are installed, creating a smooth bend of the tape, or deflecting drums 4.

All elements of the conveyor are mounted on metal structures 15, attached to the foundation or to the supporting parts of the building. A metal structure with a drive and an unloading box is called a drive station. Part of the structure with tensioning device and hopper is the tensioning station. Between both stations is the middle part of the conveyor, which is made of the same linear sections. Linear sections, transition sections, drive and tension stations are connected by bolts. As a rule, for bulk cargo, multi-roller supports are used that form a grooved belt. This shape of the belt at the same width and speed allows you to get more than a twofold increase in productivity while excluding spillage of the load.

Two-drum dropping trolleys are designed for intermediate unloading of only bulk cargoes away from the belt along one of the outlet pipes. Stationary plow ejectors can be used for both bulk and piece goods. Known designs of plow ejectors on mobile carts.

In addition to the above elements, conveyors are equipped with locking devices or two normally closed shoe brakes, as well as tape catchers located on inclined sections of the route in case of a break, safety devices and automatic control devices.

The design features of the conveyor depend on the type of belts used. Conveyors with a steel belt, with the same scheme as general-purpose conveyors, differ from the latter in separate elements due to the increased rigidity of the belt. Drums for steel tape have a larger diameter, and roller bearings (Fig. 2.3, A) performed in the form of disks 1 on one axis, spring rollers 4, flooring 2 with sides 3 or without boards. For conveyors with wire belts (Fig. 2.3, b) supports with one horizontal roller can be used. On these conveyors, due to the looseness of the belt, mainly piece goods are transported.

Conveyors with wire belts can operate at temperatures up to 1100 ºС, and with steel belts (heat-resistant) - up to 850 °С.

In rope-belt conveyors, the belt 5 (Fig. 2.3, V) performs the function of only a carrier element. It is located on two traction ropes 6, based on supporting blocks 7, placed along the entire route of the conveyor.

Ribbon Combination 8 with traction chain 9 made it possible to create belt-chain conveyors (Fig. 2.3, G). Traction chain supported by guide blocks 11, and the side parts of the belt rest on inclined support rollers 10.

To reduce the length of an inclined conveyor and, accordingly, reduce its cost and the production area it occupies, it is recommended to use steeply inclined and vertical conveyors. These conveyors can be with upper clamping elements (Fig. 2.4, a): with chain mesh belt /, rubber-fabric belt 2 and rollers 3, with additional paddle belt 4. For highly dusty materials, tubular belt conveyors are used. 6 (Fig. 2.4, b) having a zipper 5 and device 7 to open and close it. In rough terrain, it is convenient to use conveyors (Fig. 2.4, c) with a tape 11, suspended on chains from brackets 10 and steel wire rope 8, lying on supporting blocks 9. A variation of these conveyors are conveyors with a tubular belt and a zipper, also suspended from steel wire ropes on chains.

On fig. 2.5, A Shown is a light vari-angle, high-angle belt loader with crossbars. 2 on the tape, and in Fig. 2.5, b- mobile conveyor for loading works on construction. Most mobile belt conveyors use a drum motor 3 (Fig. 2.5, A) with a built-in drive and a screw tensioner / located at the top of the machine.

If the installation conditions of conveyors require a significant reduction in their weight, for example, on spreader bridges, then belts without supporting roller bearings are used, the mass

which can reach 35% of the mass of the conveyor. In this case, an air cushion (Fig. 2.6) or permanent magnets (Fig. 2.7) are used to suspend the tape. The upper and lower branches of the tape 1 in the first case are supported by thin (0.4 ... 1.0 mm) layers 2 and 3 air with a slight overpressure (2 10 3 Pa), the creation of which requires 0.3 ... 0.8 kW of energy for every 1 m of the conveyor length. The spread of conveyors with air suspension of the belt is constrained by the need to use energy-intensive blower equipment, the difficulty of maintaining a gap between the belt and the chute, and dusting of the transported goods.

Replacement of rollers with permanent ferrite-barium magnets 2 (see Fig. 2.7) in the form of plates (120 X 80 X 15 mm) is possible in combination with a special tape /, in the rubber lining of which barium ferrite powder is vulcanized, which gives the tape permanent magnetic properties.

When the tape is combined with supporting elements with the same poles, the tape is held in a suspended state by a lifting repulsive magnetic force reaching 3 kN per 1 m 2 of the tape. With complete noiselessness and low power consumption, magnetic suspension conveyors have significant drawbacks. For them it is necessary to use special tapes, it is difficult to ensure their transverse stability. Materials with magnetic properties cannot be transported on these conveyors.

A special place is occupied by underground conveyors. They are designed for use in height-constrained dimensions, as well as for moving people and heavy piece cargo, which requires, first of all, compliance with safe operation standards.

Belt conveyors of high power and considerable length are similar in design to general purpose conveyors. However, their individual elements differ not only in a proportional increase in size, but also in qualitative specific features. For example, the drive can be made with two drive drums, the tensioner has a belt tension control system during start-up and when its load changes. Conveyors of high power must be calculated according to refined methods. In this case, it is especially important to use reasonably accurate values ​​of the coefficients of resistance to the movement of the belt and concentrated resistances at the points of loading and intermediate unloading.

To load the conveyor, feeders with a forced and strictly defined supply of cargo are used, corresponding to the calculated productivity of the conveyor. For the purpose of service safety, conveyors use devices to control the operation of mechanisms and switches that allow the conveyor to be stopped at any point along its route.