Blocks and pulleys- simple mechanisms used to lift loads either with little effort or with effort in a position convenient for the user.
Blocks and pulleys consist of two parts: a wheel with a circumferential groove (pulley) and a rope or cable. A block, as a rule, is a device consisting of one pulley in a frame with a suspension and one cable. A pulley block is a combination of pulleys and cables. The principle of its operation is similar to the operation of a lever - the gain in force affects the increase in distance with theoretical equality of the work performed.
These mechanisms can be used independently of other lifting units, such as winches, hoists, cranes, and also as their parts.
The pictures show the operating principle block and pulley:
In Fig. 1a, a load weighing W1 is lifted using a single block with a force P1 equal to the weight. In Fig. 1b, the load W2 is lifted with the simplest multiple pulley system, consisting of two blocks, with a force P2 equal to only half the weight of W2. The impact of this weight is divided equally between the branches of the cable on which pulley B2 is suspended from pulley A2 by hook C2. Consequently, in order to lift the load W2, it is sufficient to apply a force P2 equal to half the weight of W2 to the branch of the cable passing through the groove of the pulley A2; Thus, the simplest chain hoist gives a double gain in strength. Fig. 1,c explains the operation of a pulley with two pulleys, each of which has two grooves. Here the force P3 required to lift the load W3 is only a quarter of its weight. This is achieved by distributing the entire weight of W3 between the four suspension cables of block B3. Note that the multiple of the gain in strength when lifting weights is always equal to the number of cables on which the movable block B3 hangs.
Rice. 2
In the past as a cable for blocks and pulleys flexible and durable hemp rope was used. It was woven with a braid of three strands, each of which consisted of many small strands. Pull blocks with such ropes were used wherever it was necessary to lift loads: on sea vessels, in agriculture, on construction sites. The most complex of them (Fig. 2) were often used on sailing ships. There they were needed to work with sails, spar parts and other movable equipment.
Over time, hemp edgings were replaced by steel cables and ropes made of synthetic and mineral fibers. They are more durable and wear-resistant. Pulley hoists with steel cables and multi-groove pulleys are integral parts lifting mechanisms all modern lifting equipment. Pulleys blocks usually rotate on roller bearings and all their moving surfaces are forcibly lubricated.
The weight of objects can be such that one, or even five people, cannot move them manually, but it is necessary. In such cases it will be useful homemade device for lifting or moving heavy objects. A hand winch is the most popular device in this business. It’s not at all difficult to make a manual winch for a garage with your own hands, even at home. But first you need a calculation and a drawing of the mechanism.
What the block for lifting loads and construction crane is to use the idea of increasing force - the rule of leverage. In order to balance the load on the short side of the lever, you need to apply less force to its long side to the extent that the short arm is less than the long one. The ratio of forces at the ends of the lever is called the gear ratio.
You can balance and even lift a weight with an effort less than its weight, but the path made by the end of a long lever will be longer than that of a short one, just as less force was applied to lift it. There is no gain in work (F1*L1=F2*L2), but this is not required.
The use of Archimedes' principle is implemented in different lifting mechanisms, and how depends on the purpose of the lift. Designs differ in gear ratio, principle of force transfer, mobility, strength, and energy used. Most popular for self-made kinds:
- chain hoists;
- drum structures;
- lever mechanism.
To choose the type of device needed for specific work, it is worth familiarizing yourself with their capabilities and limitations.
The only simpler device for moving heavy objects is a metal scrap. The main element is a wheel with a chamfer in the middle of the outer surface, the axis of which is fixed to ceiling beam. You can throw a hoist over it, and the lift with a gear ratio of 1 to 1 is ready. To increase the leverage, let's pass the hoist through another loose wheel, the axis of which is connected to the load, and fix the hoist at the top of the structure.
The gear ratio will become equal to 2. Now let's attach another wheel to the ceiling, and pass the end of the hoist through it, securing it to the axis of the lower wheel. The gear ratio will become equal to 3. And so on, by adding one wheel at a time and changing the mounting location of the hoist, you can increase the gear ratio.
The location of the wheels relative to each other may be different.
The most compact designs are those with single-axle wheels. The design of such devices has two wheel holders. Having studied the drawings of the chain hoist, it will not be difficult to assemble it with your own hands. You will need two clips:
The end of the hoist is fixed to one of the clips.
Pulley hoists also have disadvantages. To increase the gear ratio by 1, you need to add one wheel each time, as a result the weight of the mechanism increases. In addition, force is wasted on each wheel to bend the cable, reducing Device efficiency. You can reduce these losses by increasing the diameter of the wheels, but at the same time there will be an increase in the weight and dimensions of the pulley. Other types of lifts do not have these disadvantages.
The principle of operation of winches resembles a simple lever fixed at a fulcrum. If the short arm of the lever is the surface of the cylinder, and the load is attached to it by a cable, you will get a winch with a gear ratio equal to the ratio of the length of the lever and the radius of the cylinder. To prevent reverse rotation, a ratcheting mechanism with a spring-loaded pawl is installed on the axis - a ratchet. You can assemble such a hand winch with your own hands according to the drawing:
However, the high gear ratio of the system will require a very long handle, which is inconvenient. The solution is found in two types of drum winches, which increase the gear ratio using gears or a worm gear.
How to make a winch with your own hands using a worm gear can be seen in the drawing:
A ratchet is not needed in this design; the gear ratio, when the worm flange passes over each gear tooth, is equal to the number of gear teeth multiplied by the ratio of the length of the handle to the radius of the worm. But a significant disadvantage will be the friction between the teeth and the comb. The mechanism requires constant lubrication.
A gearbox made of gears operates with much less friction. When using the principle of transmitting force through a pair of gears of different diameters, the easiest way to make a manual drum winch with your own hands is this:
Please note that a stopper is required in such devices. This design is used when low altitude or the length of the load movement. A cable guide will help increase the movement distance by evenly distributing the cable along the length of the cylinder. The easiest way to get the result is to use a spring-loaded plate or rod that presses the cable to the drum:
The most popular use for lever jacks is as a car jack. As universal device it is used less frequently, since the lifting height is small and limited.
The lifting of the load occurs as a result of repeated small movements of the platform between fixed positions on the rail. IN household rarely finds use. Positive quality lever systems are reliable and durable.
At home, you can use improvised materials and ready-made transfer units. For example, the ratchet used in a KAMAZ vehicle to equalize the braking force is a ready-made worm gear mechanism.
You can get rid of manual lifting for a long time if you assemble the motorized winch system with your own hands for work once. To do this, you need to put a gear on the winch drive axis, connecting it with a chain to the chainsaw drive sprocket on a rigid housing structure.
By combining block mechanisms with drum winches, you can work to compensate for the shortcomings of each type of lift. For example, pulley hoists do not provide a lock that prevents reverse movement thali, and drum swans eliminate this very simply. But the angle between the lifting force vector and the weight vector of the pulley can be almost anything, which winches cannot boast of.
You can use purchased lifts on the farm, but, as a rule, winches are needed where stores are far away - and always urgently. It's worth looking in the garage for some parts to get out of the situation.
A pulley block is a system of movable and fixed blocks connected by a flexible connection (ropes, chains) used to increase the force or speed of lifting loads. A chain hoist is used in cases where it is necessary to lift or move a heavy load with minimal effort, provide tension, etc. The simplest pulley system consists of just one block and a rope, and at the same time it allows you to halve the traction force required to lift a load.
Typically, lifting mechanisms use power pulleys to reduce the tension of the rope, the moment from the weight of the load on the drum and the gear ratio of the mechanism (hoist, winch). High-speed pulleys that allow you to gain a gain in the speed of movement of the load at low speeds of the drive element. They are used much less frequently and are used in hydraulic or pneumatic lifts, loaders, and mechanisms for extending telescopic booms of cranes.
The main characteristic of the pulley is the multiplicity. This is the ratio of the number of branches of the flexible body on which the load is suspended to the number of branches wound on the drum (for power pulleys), or the ratio of the speed of the leading end of the flexible body to the driven end (for high-speed pulleys). Relatively speaking, the multiplicity is a theoretically calculated coefficient of gain in strength or speed when using a chain hoist. Changing the multiplicity of the pulley system occurs by introducing or removing additional blocks from the system, while the end of the rope with an even multiplicity is attached to a fixed structural element, and with an odd multiplicity - on the hook clip.
Depending on the number of rope branches attached to the drum of the lifting mechanism, single (simple) and double pulley hoists can be distinguished. In single pulley hoists, when winding or winding up a flexible element due to its movement along the axis of the drum, an undesirable change in the load on the drum supports is created. Also, if there are no free blocks in the system (the rope from the hook suspension block directly passes to the drum), the load moves not only in the vertical, but also in the horizontal plane.
To ensure strictly vertical lifting of the load, double pulleys (consisting of two single ones) are used; in this case, both ends of the rope are fixed to the drum. To ensure the normal position of the hook suspension in case of uneven stretching of the flexible element of both pulleys, a balancer or equalizing blocks are used. Such pulleys are used mainly in overhead and gantry cranes, as well as in heavy tower cranes so that two standard cargo winches can be used instead of one large one high power, as well as to obtain two or three speeds of lifting the load.
In power pulleys, when the multiplicity increases, it is possible to use ropes of reduced diameter, and as a result, reduce the diameter of the drum and blocks, reduce the weight and dimensions of the system as a whole. Increasing the multiplicity allows you to reduce the gear ratio, but at the same time requires a larger rope length and rope capacity of the drum.
High-speed pulleys differ from power ones in that they work force, usually developed by a hydraulic or pneumatic cylinder, is applied to a movable cage and the load is suspended from the free end of the rope or chain. The gain in speed when using such a pulley is obtained as a result of increasing the height of the load.
When using pulleys, it should be taken into account that the elements used in the system are not absolutely flexible bodies, but have a certain rigidity, so the oncoming branch does not immediately fall into the stream of the block, and the running branch does not straighten out immediately. This is most noticeable when using steel ropes.
Simple devices at a construction site
Any construction site cannot do without effective and simple devices to facilitate labor and increase the speed and quality of the constructed object. Today in this article I will talk about some of them, the simplest and most effective.
The easiest way to climb along guides, two ropes and fixed guides are enough for it.
This method is simple, but there are some tricks and difficulties; you need to pull at the same time and the guides must be securely fastened.
This is a very simple device, but it also makes the work easier, since the force is applied downwards, and this is always easier than simply pulling on the rope.
A lift in the form of a well crane perfectly reduces the time for lifting loads. The only negative is that. that lifting heavy loads using such a device is very difficult.
But lifting the load is much easier than without a counterweight.
Types of chain hoist fastenings.
With the help of chain hoists, you can make your work several times easier. It all depends on the method of securing it.
If you apply fastening number 1, then the force will be equal to the weight of the load being lifted;
2- two times less than in the first case;
3 – three times less;
4 – four times less than in the first case.
With the help of a chain hoist you can lift a load without making much effort.
The figure shows the types and methods of fastening simple lifts with pulley blocks. Lifting mechanisms are made rotating and simple non-rotating.
To facilitate lifting, an electric drive is installed and beam cranes are installed. Such mechanisms completely replace a truck crane.
This is, of course, only a small part of all the devices and you can’t tell about them all in one article. So, wait for the continuation.
When building any object, be it a house or something else that requires lifting heavy objects to a height, you need to go in two ways.
The first and easiest way is to hire people to lift heavy materials such as mortar, concrete or something similar.
Second, do lifting mechanism, capable of lifting heavy loads.
This device can replace at least three people and it is made of an aluminum ladder and an electric hoist.
Such a lift is capable of lifting three buckets of concrete and can be used alone. It’s not difficult to make a welded frame on bearings, and anyone with a little knowledge of electric welding can easily attach an electric hoist to the top of a ladder.
If you attach the electric hoist as shown in the photo to a well-reinforced beam, then you will get very convenient device, which may well replace a faucet.
This simple device will speed up your work on grinding grooves during construction from round timber. Using the same principle, you can make other devices for carpentry work.
With the help of such a simple device, you can not only break walls with virtually no noise, but also press metal parts during installation and hold together floor boards during installation.
A very convenient device, especially in the manufacture of fencing and other work involving a large amount of work with bent wire and fittings.
I also have experience working with almost the same device when making fences, and I liked that the speed of work increases significantly.
Making such a device for cleaning walls from paint will not take much time; for this you need welding machine, an old drill and by welding a metal plate to the drill, you can increase the speed of cleaning walls using a hammer drill.
Using a nozzle, which today can be bought in a store and construction vacuum cleaner, you can remove paint from the wall with virtually no dust.
How to make useful mechanisms and tools for construction with your own hands
It doesn’t matter whether you are building your dream home or renovating an old one country house, you cannot do without reliable tools and construction equipment. Almost any device today can be bought in a store, but purchases are not always pleasing with quality and even less often with prices. Our forum members know how to reduce the burden on the family budget and offer recipes for proven mechanisms and tools for construction, made with their own hands.
Truck...from the old four
Bring sand, crushed stone, boards, transport a concrete mixer and an old refrigerator... The need to deliver materials and tools during construction arises constantly. Member FORUMHOUSE g8o8r8 found a way to save on freight transportation: he converted his old four into a truck!
Budget auto tuning cost the craftsman 3.5 thousand rubles - this was the cost of materials: an iron square, corners, galvanized steel for the loading body. Loading body g8o8r8 made it high to protect it from rainwater: to close the gaps between it and the car body, metal canopies were welded around the perimeter.
The rear side of the body is lifted with a 12-volt electric winch. This is convenient when unloading bulk materials and loading boards, stones, furniture, etc. into the body by dragging.
g8o8r8 (FORUMHOUSE Member ):
At our metal collection point, they give five thousand rubles for any car. This inspired the idea of using my decommissioned four-wheeler for household needs: bringing earth, peat, stones, sand to the dacha. And if you install a subframe, weld a blade, install chains, you’ll see that you’ll be able to throw snow in the winter.
Construction materials lift
Another one useful homemade product, which will make life at a construction site much easier - a building materials lift. For example, like the one from the FORUMHOUSE member Ali-bastre.Starting to pour monolithic walls, a forum member was tired of manually lifting heavy buckets of concrete and made a simple but ingenious design.
The basis of the lift was metal staircase. To securely fix the ladder on the wall, in a profiled steel pipe 15×15 Ali-bastre drilled the holes and reverse side put a washer on the pipe, securing it with a cotter pin. The trolley on which building materials are placed moves up and down on bearings No. 304 using an electric winch. It is located almost parallel, at a slight angle to the stairs, due to which the movement occurs smoothly.
Ali-bastr ( FORUMHOUSE member ):
It’s not for nothing that they say: laziness is the engine of progress. My lift lifts six buckets of concrete easily!
Planer for aerated concrete
Aerated concrete is one of the most popular modern materials for construction stone houses. The large format of the blocks and the installation technology, which can be easily mastered, allow even novice builders to erect buildings quickly.
But despite all the advantages, aerated concrete has a significant disadvantage - the blocks do not match in size and the need to adjust them to each other. You can use a shop tool for these purposes. But our forum members suggest making a plane for aerated concrete with your own hands. For this you will need: a board 5 cm thick, 3 wood files, universal glue, a door handle.
worodew (FORUMHOUSE Member):
Cut the files in half. We cut grooves in the board to half the thickness of the blade, lubricate the grooves with glue and insert the files. Screw the handle on and you're done.
Mobile foam cutting machine
And for those who insulate their house with polystyrene foam, another homemade product from the forum will come in handy - a machine for cutting polystyrene foam, which allows you to cut pieces of the required size simply and quickly, without bothering with a hacksaw and a ruler.
User of our forum Oleg Lvovich used to make a mobile machine wooden slats 25×25 mm long 1.3 meters, nichrome wire with a cross section of 1 mm, a spring, two steel strips 20x4 mm, a 220/36V transformer and a wire of 15-20 meters.
On FORUMHOUSE, a forum member shares a diagram of a homemade machine:
Unlike stationary cutting machines, this device can be freely moved around scaffolding and cut foam directly on site. At the same time, the sheet can be expanded not only in length, but also in thickness - for this, two profiles are additionally attached to the EPS with nails. According to a forum member, the cost of a mobile machine is 800-1000 rubles, and even with intensive use it will faithfully serve several construction seasons contract.
Other examples of machines for cutting foam plastic, including stationary ones, are in this topic.
Comfortable grinder
Have you noticed that holding a small grinder by the top handle is convenient, but a large one is not? The big one always tries to escape from your hands when biting into metal. Having such a sad experience, some are generally afraid to use a large grinder. So that the grinder always remains in your hands, forum member chichic designed for instrument homemade pen under natural grip.
chichic (FORUMHOUSE Member):
A powerful grinder can break out a cutting disc stuck in the metal, but it always remains in your hands. Proven by ten years of experience and cutting metal up to 14mm.
DIY cyclone vacuum cleaner
Dust and small debris during construction or major repairs are a real problem, which is difficult and ineffective to combat with a broom and rag. To make the cleaning process easier without spending money on expensive equipment, FORUMHOUSE member zalman3000 on a quick fix I assembled a cyclone for a vacuum cleaner from scrap materials.
Zalman3000 (FORUMHOUSE Member):
I needed: a 20 liter plastic barrel, a 45 degree 40 mm angle, a 90 degree 32 mm angle, an oil filter from Moskvich (it fits tightly at the 32nd angle).
The simple design is attached to the vacuum cleaner, and waste is collected directly into a capacious plastic container.
Ropes and lifting devices
Depending on the material, ropes are divided into steel (cables), hemp and cotton. Steel ropes are made of single lay, when the rope is twisted directly from wires, and double lay, when the wires are twisted into strands, and the strands into a rope. According to the type of laying of wires and strands, steel ropes are divided into cross laying, in which the directions of twisting of wires into strands and strands into a rope are opposite to each other, and one-way, in which these directions coincide. Cross lay cables are less susceptible to unwinding than single lay cables.
Compared to hemp and cotton ropes, steel ropes are more reliable and durable and therefore find primary use in lifting and load-handling devices. Hemp and cotton ropes are used only for guy ropes or for lifting small loads (feeding tools and devices, lifting garlands when installing outdoor switchgear busbars, etc.).
The disadvantages of steel cables include their relatively low elasticity (flexibility). The flexibility of ropes depends on the diameter of the wires: the smaller the diameter of the wires in the rope strands, the greater the flexibility of the rope. Rope made from thinner wires wears out faster and costs more. Therefore, the choice of ropes should be made depending on their purpose.
Steel ropes are stored in coils or on drums in closed, dry rooms on wooden supports. Each rope must be equipped with a tag indicating the type, diameter, length and weight of the rope. Ropes in operation must be lubricated with rope ointment at the following times: cargo (pulley) - 1 time in 2 months, mooring and slings - 1 time in 1.5 months, braces - 1 time in 3 months. Ropes stored in warehouses are lubricated once every 6 months.
The selection of ropes for lifting mechanisms and load-handling devices is made according to the value of the actual breaking force of the rope in N (the load at which the rope sample breaks when tested on a tensile testing machine). This force is usually given in the passport (certificate act) of the rope. If the passport does not indicate the actual breaking force, but the total breaking force of all individual wires (Rsum), then the actual breaking force should be taken equal to 0.83 Rsum.
When using ropes, it is necessary to monitor the degree of wear and discard ropes that have dangerous wear. Dangerous wear of the rope is determined by the number of broken wires at the laying step (the length of the rope during which the strand makes a full revolution around its axis). On the section of the rope where it was found greatest number broken wires, mark the laying step and count the number of breaks on it.
If the diameter of the rope wires decreases by more than 40% of the original value as a result of surface wear or corrosion, the rope is rejected.
Steel, hemp and cotton ropes, slings of all types and load-handling devices must be subject to periodic inspections during operation by the person responsible for their maintenance, and also undergo static load testing.
Slings are used to secure the load to the hook of the lifting mechanism. Slings are made from steel ropes. Depending on the purpose of the slings and the elements of electrical equipment to be lifted and installed, slings are used various designs. The free end of the cable is connected to the main branch to form a sling loop using a braid. Braiding cables is a complex operation requiring highly qualified performers, and must be performed by special braiders.
The choice of sling size is made depending on the weight, configuration and places of slinging of equipment and cargo. The load per one branch of the sling is determined by the formula S = Q/(n x cos α) ,
where S is the load per one branch of the sling, kg, Q is the mass of the load being lifted, kg, n is the number of branches of the sling, α is the angle between the vertically lowered axis and the branch of the sling (Fig. 1).
Rice. 1. Schemes for slinging loads: a - with a single-branch sling, b - with a two-branch sling.
Slings must be chosen such a length that the angle between the branches of the sling and the vertical does not exceed 45°. When lifting, elements of electrical equipment must be suspended from parts specially designed for this purpose (frames, brackets, mounting loops). In case technical specifications or factory instructions prohibit subjecting lifting devices (eyes) to tension with slings at an angle; lifting must be done using traverses (Fig. 2).
Rice. 2. Traverse for lifting electrical equipment with a lifting capacity of up to 10 tons. 1 - pipe, 2 - coupling, 3 - sling with two loops, 4 - detachable suspension (spider), 5 - pin, 6 - straight bracket.
Each sling must be equipped with a token on which the brand of the sling and the date of its test are applied. The tokens are braided into a strand of cable when making a sling.
Only riggers and electricians who have undergone special training and have a certificate for permission to carry out slinging work may be allowed to work on slinging and lifting equipment and other loads. Lifting critical heavy loads must be carried out under the direct supervision of a foreman or work performer.
Blocks and pulleys
Blocks are applied when executing rigging work to change the direction of traction ropes (diverter blocks) or as part of pulley blocks. Branch blocks are mainly manufactured with a folding jaw, since in this case there is no need to pull the rope through the block.
The choice of tap-off block is made according to the formula Q = PK,
where Q is the load-carrying capacity of the block, N, P is the force acting on the rope, N, K is a coefficient depending on the angle between the directions of the rope (Fig. 3).
Rice. 3. Forces acting on the tap block
The value of the coefficient K is taken depending on the angle α: 0 o - 2, 30 o - 1.94, 45 o - 1.84, 60 o - 1.73, 90 o - 1.41
Rice. 4. Blocks
The pulley is used for lifting or horizontal movement of loads when the traction force required for lifting or moving exceeds the carrying capacity of the traction mechanism. The pulley consists of two blocks, movable and fixed, connected to each other by a rope, which is attached to the eye of one of the blocks, sequentially goes around the rollers of both blocks and is attached to the traction mechanism with the other, running end.
The magnitude of the force at the running end of the pulley rope is determined by the formula S = 9.8Q/ (ηn)
where S is the magnitude of the force, N, Q is the mass of the load being lifted, kg, η is the efficiency of the pulley, n is the number of threads of the pulley. The magnitude of the traction force S must not exceed the load capacity of the traction mechanism. The selection of a chain hoist design depending on the mass of the load being lifted and the load capacity of the traction mechanism (tractor, winch) can be made according to Table 1.
Winches and hoists
When operating winches and hoists, constant supervision of their condition and the serviceability of all parts must be ensured, periodic preventive inspections with the elimination of noticed faults and the mark of the person responsible for the condition of the winches or hoists in a special journal, as well as their periodic testing at least once a year for a special test bench or on an installation site with a static load exceeding the nominal load by 25%. Test data must be recorded in a protocol stored in the mechanism passport.
A plate shall be attached to the winch or hoist indicating the date of the test performed and the date of subsequent testing. Winches and hoists that have not passed the next test in a timely manner must be removed from service until testing is carried out.
Winches are widely used for loading and unloading operations, rigging transformers, switches and other equipment of indoor switchgear, switchboard panels and outdoor switchgear busbars. Depending on the type of drive, winches used in electrical installations are divided into manual, electric and unified. Hand winches are used in production electrical installation work mainly of two types - drum and lever.
Lightweight drum winches and lever-driven winches are predominantly used due to their small dimensions and relatively low weight. Manual winches are recommended for use with a lifting capacity of no more than 3 tons due to their bulkiness, large mass and significant forces on the handle of hand winches with a lifting capacity of more than 3 tons.
Manual lever winches operate on the principle of pulling the working traction rope of which the rope has a clip. The forward drive handle is mounted on the end of the driver shaft, which is a double-armed lever with an axis of rotation in the middle. To thread the rope into the traction mechanism, move the guy towards the handle. In this case, both pairs of clamps will separate and make it possible to push the end of the traction rope through the hole in the fitting until it exits through the fastener hole.
Rice. 5. Lever hand winch
Manual winches are recommended for use when performing small volumes of work, in the absence of a source of electricity and in the absence of mechanized lifting devices on the site (forklifts, cranes, electric winches).
The electric winch consists of the following main components: frame, drum, gearbox, braking device and electric motor. Engine voltage is 380/220 V. The frame is used to accommodate all winch components. The braking device with an electromagnetic drive is interlocked with the winch electric motor and operates automatically when the latter is turned off. Torque is transmitted from the engine to the winch drum through a gearbox. The coupling of the drum with the gearbox shaft is carried out by a gear or claw coupling.
The kinematic diagram of the electric winch is shown in Fig. 6.
Rice. 6. Kinematic diagram of an electric winch: 1 - drum, 2 - 7 - gear wheels, 8 - 10 - gear shafts, 11 - braking device, 12 - electric motor.
Talya is called a lift hanging type with manual or electric drive. Manual hoists are manufactured with worm and gear drives and are used for the installation of reactors in closed switchgear cells, for inspection and disassembly of electric motors, etc. A manual worm hoist consists of an upper and lower unit connected to each other by a load chain. Top knot contains a housing, a worm pair, including a wheel with a weight sprocket and a worm with braking device, traction wheel with endless chain and top hanging hook. The lower assembly consists of a cage, a load roller and a lower hook.
The hoist is suspended from a fixed support by the upper hook. When the traction wheel rotates using a chain, a worm rotates, the shaft of which is rigidly connected to the traction wheel. The worm drives the worm wheel with the load sprocket, selecting the load chain and causing the lower hook and the load suspended from it to rise or fall. Manual hoists with gear transmission are manufactured with a load capacity of up to 5 tons.
The electric hoist is designed for vertical lifting and lowering, as well as for horizontal movement of loads along a single-rail track along which the hoist moves. Electric hoist type TE consists of two main components: a lifting mechanism and a running trolley, to which the lifting mechanism is suspended.
The lifting mechanism consists of a housing with a drum and an electric motor built into it, a gearbox, an electromagnetic brake and hanging device(block with hook). The brake is automatically applied when the electric motor is turned off and released when the engine is turned on.
Rice. 7. Electric hoist type TE
The undercarriage consists of two cheeks, to one of which are attached two axles with freely rotating wheels, and to the other - two drive wheels, on the flanges of which gears are cut. The hoist motors are started using reversible magnetic starters. Control of ascent, descent and horizontal movement to the right or left of the passages. Electric hoists are most widely used in rooms for the assembly of equipment parts into blocks and assemblies, as well as for inspection of parts of switches (separator chambers, extinguishing chambers) and other equipment in mobile inventory rooms and devices. Electric hoists type TE are manufactured for lifting heights of 6, 12 and 18 m.
Jacks
Jacks are used mainly for rigging and installation of power transformers, synchronous compensators and other heavy equipment, when these works cannot be performed by cranes.
According to their design, jacks are divided into rack and pinion, screw and hydraulic. The rack and pinion jack consists of a fixed base 1 with a welded vertical gear rack 4, a lifting body 3 with a gearbox and a handle 2. The load is lifted on the upper central head or on the lower leg.
Rice. 8. Rack jack
The presence of a lower leg distinguishes the rack and pinion jack from other designs, as it allows lifting loads with low support surfaces. To lift the load, rotate the jack handle clockwise. In this case, the rotation is transmitted to the gear, which, rolling along rack 4, lifts along with it the gearbox and the jack body with the load.
When the rotating force on the handle is weakened, a special pawl holds the handle through the ratchet disk from reverse rotation under the pressure of the load and, thus, prevents the load from falling. However, for safety reasons, do not remove your hand from the handle while lifting or lowering a load, or while the load remains in the raised position.
The screw jack (Fig. 9) consists of a body 1, a load screw 2 and a handle 3 with a ratchet, a pawl and a locking rod with a spring. The load is lifted by rotating the handle in a counterclockwise direction. In this case, the load screw 2 rotates in the fixed internal screw and the movable screw with the jack head and the load resting on the head is lifted. When lowering the load, switch the pawl lock and rotate the handle in the opposite direction.
Rice. 9. Screw jack
The hydraulic jack (Fig. 10) consists of a housing 1, a reservoir 2 and a pump 3. A pump 3 and a cam shaft 6 are mounted in a hermetically sealed reservoir 2. The cam 10 drives the plunger 9. In this case, liquid is sucked through valve 7 or pumped through valve 8 into the housing under piston 4. The piston, rising, lifts the load. To lower the load, the liquid is transferred back into the tank. The liquid is filled through plug 11, and drained through plug 5. To fill reservoir 2, industrial oil is used.
Rice. 10. Hydraulic jack
Telescopic towers and hydraulic lifts
Telescopic towers are used mainly when performing work on outdoor switchgear busbars. Telescopic towers provide safe conditions work when lifting workers with tools, devices and loads for work at heights, and also provide favorable conditions for high-performance work when installing garlands, wires and fittings.
Hydraulic lifts with an articulated boom have the great advantage over telescopic towers that their design allows, thanks to the presence of an articulated boom, to move the cradle with the load in a raised state in any direction without moving the lift.