Goat double-cantilever crane

Contents

Introduction

1. Description of the device and operation of the goat

two-cantilever crane

2. Calculation of lifting mechanism

3. Calculation of freight trolley movement mechanism

4. Calculation of steel structure of crane bracing

5. Labor protection during operation of single-beam bridge cranes

Conclusion

List of sources used

Appendix A: Specification

Introduction

Lifting and transportation machines are widely used in many industries, agriculture, all types of transport, which use both the general industrial types of these machines and their systems and designs that reflect the specifics of this field of national economy.

Mechanization and automation of production processes require a worldwide expansion of the areas of effective use of various lifting and transporting machines and mechanisms. Extensive use contributes to the mechanization of labor-intensive and heavy work, reducing the cost of production, improving the use of the volume of production buildings, and reducing the movement of goods in the production chain.

High technological efficiency of machines for logging and sawing is ensured by the fact that the production chain is connected with a modern system of lifting and transporting machines and mechanisms, lifting and transportation machines.

Main nodes

The load lifting mechanism consists of a cable winch, a polyspast and a load-gripping element (hook, gripping crossbar, grab, etc.). Winch comprises drive motor coupled via coupling with input shaft of cylindrical gear reduction gear. The latter rotates the drum, on which one or two branches of the lifting polyspast rope are wound. Brake pulley is installed on input shaft of reduction gear. Single or double rope polyspasts are used in load lifting mechanisms.

The length of the ropes and the dimensions of the rope drums are chosen so that at the lowest possible position of the load-gripping element (hook, grab, etc.) on the drum there is at least 1.5 turns of each of the ends of the ropes (excluding the portion of the rope used to attach to the drum). If the winch is mounted on the crane bridge, the lifting mechanism includes a system of diverting blocks of the cargo rope [3].

Movement mechanisms are made of two types: with a drive to the running wheels of the trolley and rope. The mechanism of the first type comprises a drive motor, which rotates a vertical cylindrical reduction gear through an intermediate Qualik with clutches. Output shaft of the latter is connected by means of toothed coupling clutch with shaft of driving running wheels of cargo bogie. Brake pulley is mounted on reduction gear shaft or on one of engine shaft ends.

Winch of rope mechanism of movement according to scheme is similar to lifting winch, on drum of which traction ropes are stored in opposite directions, which are attached by their other ends to load bed. To remove the weakness and create the necessary preliminary tension of the rope at one of its ends, a screw tensioner is provided, in the form of a manual worm winch, etc.

Typically, cranes travel mechanisms are in the form of a single or two-wheeled running trolley. Drive bogies are equipped with motors rotating running wheels through reduction gears.

The latter are mounted on rotating shafts or on fixed axes. In this case, they have toothed crowns.

On cranes for lifting the load or for auxiliary purposes, electric hoists are used, which are a compact lifting mechanism. The mechanism is suspended from two- or four-wheeled bogies moving along suspended monorail tracks.

On goat cranes, mainly double-deck brakes with spring closure are used, controlled using AC MO-B valve electromagnets or electric hydraulic pushers.

Basic parameters

The main parameters of the goat cranes, in addition to the lifting capacity, include: span, working flight of the console, lifting height of the gripping element above the level of the heads of the crane rails, as well as speeds of working movements. Significant, also important are the dimensions that determine the conditions for transporting the cargo from the cantilever to the span: for cranes with two-post supports, this is the distance in light between the supports, which largely depends on the support base, and for cranes with single-post supports, the distance from the cargo suspension to the front face of the support. For stable movement of cranes along crane tracks, a certain (usually 1:5... 1:7) span-to-wheelbase ratio. The width of the running trolleys and the lower parts of the crane determines the possible limits of approaching the crane tracks of stacks of cargo, vehicles, structures and ground equipment. Also important is the level of arrangement of the projecting elements of the chassis. Vertical loads on crane running wheels, which largely determine the costs for the construction and operation of crane tracks, should also be included in the number of main parameters of goat cranes.

Typical scheme for installing a goat crane on the object of the most common type - a warehouse served by rail and road transport. Span L is determined, as a rule, by the planning conditions of the object; the necessary storage capacity, the size of the steaming chambers for the manufacture of reinforced concrete products, etc.

It is advisable to accept the departure of Lc consoles based on the condition of equality of moments from the movable load in the span and at the supports. However, departure must ensure the storage of cargo and unhindered safe maintenance of vehicles.

In all cases, in accordance with the requirements of the Rules of Gosgortekhnadzor [4], the distance between the protruding parts of the crane and ground objects or vehicles at a height of 2.0 m from the ground level must be at least 700 mm, and at a height of more than 2 m - at least 400 mm. At the same time, these parts should not protrude beyond the limit size line established by GOST 9238-73. The departure of the cantilever shall be sufficient to cover the entire width of the carriage or platform of the rail-less vehicle (2, 5.., 3, 3 m). When transporting large-sized goods, for example railway containers weighing 5 and 20 tons, it is often sufficient if the departure will be 150... 250 mm exceed the distance from the supports of the crane rail to the center of the car.

Usually it is enough to have a departure of 4, 2... 4, 5 m; when working with large-capacity containers, the minimum permissible departure is 3, 4... 3, 6 m. The departure of the console should be. 0,20... 0.30 span. It is recommended to avoid increasing the departure of the console, as their deflections increase sharply, which may require additional reinforcement of the bridge. In addition, when the load is released to such a cantilever, it is difficult to provide the necessary grip margin for the running wheels of the opposite support [3].

Lifting height is determined on the condition that the clearance between transported, cargo and ground objects should be at least 0, 5 m. When working with railway transport, the lifting height should be at least 8 m; for cranes used for: container reloading, it should be increased to 9 m. In most cases, the lifting height is 9... 10 m is sufficient both for servicing vehicles and for stacking goods. Sometimes, for example, for cranes of forest warehouses, it is taken at the highest permissible storage height of 16 m.

The distance in the light between the struts of the supports should provide the possibility of movement without turning the most often transported goods and turning - loads of all types, for work with which the crane is intended.

It should be borne in mind that the turning of the load by weight, even with a water swivel, increases the duration of the reloading cycle. To manually turn long loads weighing more than 5 tons, at least two people are needed. In order to avoid turning the load over the railway platforms and especially gondola cars, the distance between the posts should be sufficient to move at the required height of the transversely located load. The load suspended on the free-rotating hook can turn spontaneously when passing through the support. Therefore, for heavily operated cranes, the distance between the struts should be assigned based on the largest size of the load (for example, the diagonal of the package or container). Clearance between load and supports struts shall be not less than 500 mm. The same applies to cases when you have to deploy the load in the span or under the consoles.

Practice shows that for cranes with a lifting capacity of 3.2... 5 tons of universal purpose at wheelbase B = 6.5... 7.5 m it is possible to ensure almost unhindered transportation of cargo through supports; for larger cranes, this size should be 9... 11 m.

At B > (1,2... 1.5) The design and operating conditions of the support posts and their abutment units to the bridge are complicated. At the same time, with an increase in the reference base, the crane paths are extended. Therefore, in some cases, to increase the distance between the posts at a given height, they are L-shaped or reinforced with additional transverse brackets.

Similarly, the smallest allowable distance between the load suspension and the front face of the support strut at the crane with single-strut supports is provided. Here, the dimensions of the support base are determined based on the condition of unhindered movement of the crane along the tracks, as well as the need to ensure approximate equality of vertical loads on the running wheels. The width of the running trolleys and the lower parts of the cranes shall be as limited as possible. Protruding parts of movement mechanisms, including gearbox housings and gear rims of running wheels, must not be located below the rail head. Experience has shown that a lower location of these elements rec increases the risk of contamination and breakdowns.

General instructions given in the technical literature can be used to select the speeds of movement [1] This should also take into account the safety of operation, the convenience of control, the required accuracy of installation of the load.

At production facilities (assembly sites, open landfills for the manufacture of reinforced concrete products, etc.), where people working at technological operations cannot monitor the movement of the crane, in the absence of crane railings, the speed of crane movement should not exceed 1 m/s. This applies to cranes with control from the cockpit. However, for warehouses and sites where a small number of workers directly related to transshipment operations are located, there is no such restriction. The speed limit of the cargo trolley Vmax shall be assigned in view of the length of its running travel limited by the length of the bridge normally associated with the crane span.

For heavy-duty cranes, Vmax values ​ ​ can be increased by 20... 25%. With a relatively limited lifting height, lifting speeds of more than/0.25... 0.50 m/s are impractical. This is also due to the fact that a further increase in the lifting speeds of the load leads to the need to install electric motors of increased power, as a result of which the mass and size of the freight trolley, as well as the cross sections of the current supply cables of the freight trolley and the crane increase. Lifting speeds and horizontal movement of the load are also limited by the requirements of accuracy of operation. Limit values of rated operating speeds, with currently widely used drive systems not equipped with additional control devices, are recommended to be taken as per Table 3 [1]. It also lists the acceleration values.

Conclusion

This course design contains the following:

1) general calculations of goat crane mechanisms with lifting capacity of 10 t, load lifting speed of 10 m/min, load lifting height of 8 m, span of 20 m;

2) procedure for selection and check of electric motors, reduction gears, couplings and brakes of load lifting mechanisms and trolley movement;

3) procedure for calculation of steel structure of crane bracing.