RU2521138C2 - Device and method for specific loads balancing in friction pairs of drill winch belt-shoe brake - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to machine building and can be used in heavy-loaded drill winch belt-shoe brakes. Device for specific loads balancing in friction pairs of drill winch belt-shoe brake contains brake pulley on shaft, main and additional brake belts. The brake belt is made multicomponent and consists of main and additional belts. Running-on end of the main belt is attached to crankshaft butterfly necks, and its running-off end - to balancer, herewith, the belt along its length rests on cylindrical axles the ends of which rest on recesses of additional belt. At lateral sides of additional belt there are longitudinal grooves allowing friction pads attachment plates to move in them. They are limited by cylindrical axles. The main belt contacts by its inner surface with nonworking surfaces of friction pads between their attachment plates. Method of specific loads balancing in friction pairs of drill winch belt-shoe brake consists in redistribution of specific loads by changing areas of friction pads along perimeter of multicomponent belt.

EFFECT: higher efficiency of brake and static and dynamic redistribution of specific loads during braking.

2 cl, 8 dwg

Description

The invention relates to mechanical engineering and can be used in tape-shoe brakes of drill hoists.

A tape brake is known in which, to ensure uniform wear of the friction linings, the latter are located on the working surface of the brake pulley and are equipped with elastic elements that connect them to each other and spring to the working surface of the pulley, and the dynamic coefficient of sliding friction between the outer surface of the linings and the inner surface of the brake the tape is larger than between the working surface of the pads and the brake pulley [1, analogue]. The disadvantage is that it is necessary to have friction materials with different dynamic coefficients of sliding friction for the outer and inner surfaces of the linings. In addition, the brake band is subject not only to dynamic, but also to thermal loads.

A tape brake is known with movable friction linings, which contains separate stationary linings at the beginning of the oncoming branch of the brake belt, in the middle of the belt and at the end of the runaway branch of the belt, and between the fixed linings there are movable linings, which have cuts in their upper part along their width seated in the L-shaped grooves of the tape, while the movable pads have the ability to move relative to the inner surface of the tape and the working surface of the pulley, and on the incoming and outgoing branches x tape there is an unequal number of movable plates, interconnected by springs of different stiffness [2, prototype]. The disadvantage is that when the outer movable friction linings interact with the inner surface of the brake band, a large coefficient of their mutual overlap is not realized.

The proposed technical solution in comparison with the analogue and prototype has the following distinctive features:

- the main brake tape has greater flexibility due to a decrease in its thickness and the absence of stress concentrators in its body;

- the use of the inner surface of the main brake tape as a working one for realizing dynamic sliding friction coefficients between interacting external pairs;

- ensures the fit of the outer surfaces of the moving friction linings to the inner surface of the main brake band with a large coefficient of mutual overlap due to its greater flexibility;

- there is no need to select friction materials with different dynamic coefficients of sliding friction for the outer and inner working surfaces of the friction linings.

The objective of the invention is to increase the effectiveness of the brake due to the targeted use of the main brake band in tension, as well as a metal friction element of its inner surface in sliding friction pairs and to provide static and dynamic redistribution of specific loads between moving friction linings along the additional brake band relative to the main brake band and pulley.

This goal is achieved in that the brake band is made integral, i.e. consists of the main one, the running end of which is attached to the crank neck of the crankshaft, and the running end of which is attached to the balancer, while the tape is supported along its length by cylindrical axes, for the ends of which the supports are the hollows of the additional tape, and there are gaps greater than the thickness above the cylindrical axes the main tape, while along the sides of the additional tape, longitudinal grooves are made with the possibility of moving the fastening plates of the friction linings in them, the restrictions for which are cylindrical axis, and the main tape in its inner surface is in contact with the non-working surfaces of the friction linings between their mounting plates.

The method of balancing the specific loads in the friction pairs of the drawworks brake of the drawworks is carried out in a static way due to the fact that before the installation of the compound tape over the brake pulley in the middle part of the additional brake tapes, lining widths 2L are placed at the angle of π, and π / 2 at the angle of circumference from the side of the run-down end of the main brake tape - lining of width L, and in this case in the friction pairs "slip-pulley" and "slip-main tape" is achieved the dynamic alignment of specific loads due to the movement of Dock for additional and main brake bands under regulated compliance and safety factor main brake band, thus providing for the inhibition by the variable pitch between the moving plates.

Figure 1 shows the kinematic diagram of a drawworks with a tape-shoe brake; figure 2 is a kinematic diagram of a tape-shoe brake; figure 3 is a cross section of figure 2 along aa; figure 4 shows a view of B in figure 2 - the main and additional brake tapes; figure 5 illustrates a cylindrical axis with protrusions; in Fig.6 and 7 - longitudinal grooves in areas of additional brake tape; on Fig - the main and additional brake bands with sprung retractable devices with wide and narrow friction linings.

The following conventions are used: R _Ш , D _Ш - radius and diameter of the working surface of the brake pulley; r is the radius of the crank of the crankshaft; ω is the angular speed of rotation of the pulley; φ, α are the girth angles of one and all the overlays of the working surface of the brake pulley; S _H , S _C - tension of the running and running branches of the brake belt; F _P is the force exerted by the driller on the brake control lever.

According to the kinematic scheme (see Fig. 1), the friction linings 3 are mounted on brake bands 2, which are attached to the balancer 11 at one end (from the side of the runaway branch II of the belt 11) and to the crank necks 6 from the side of the branch of the branch I) and 9 crankshaft 10.

Serial tape-shoe brakes of a drawworks operate as follows. By moving the handle 1, the crankshaft 10 is rotated, as a result of which the driller tightens the brake belts 2 with friction linings 3, and they sit on the brake pulleys 4. The braking process with a tape-block brake (see figure 2) is characterized by the following stages: initial (first ), intermediate (second) and final (third). Let us dwell on each of the stages separately.

At the initial stage of braking, the friction linings 3 located in the middle part of the brake belt 2 interact with the working surface of the brake pulley 4. The front of interaction extends towards the friction linings 3 of the running branch (I) of the brake belt 2.

The intermediate stage of braking is characterized by the further spread of the interaction front towards the friction linings 3 of the runaway branch (II) of the brake belt 2.

The final stage of braking is characterized by the fact that almost all the fixed pads 3 of the brake belt 2 interact with the working surface of the rotating pulley 4. During braking, the sequence of friction surfaces coming into contact is repeated. The complete braking cycle is completed by stopping the brake pulleys 4 with the drum 5. The control of the winch brake is also carried out by supplying compressed air through the driller's valve 7 to the pneumatic cylinder 8, the rod of which is connected to one of the crank necks 6 of the crankshaft 10 of the brake. The pressure value of the compressed air in the pneumatic cylinder 8 is regulated by turning the crane 7 of the driller.

When uneven wear of the friction linings 3 mounted on the belts 2, the balancer 11 at the time of braking slightly deviates from the horizontal position and evens the load on the runaway branch (II) of the brake belts 2, while ensuring uniform and simultaneous girth of the brake pulleys 4. Thanks to ball joints the implementation of the loads from the brake bands 2 to the balancer 11 is not changed.

The weakest link in the brake assembly is the friction linings. They are made in the form of individual parts, which can be mounted in various ways (for example, using strips) with a relatively flexible steel tape. When installing overlays on a tape with a constant step, their number is always even (12; 16; 18; 20; 22; 26).

The total number of friction linings on the brake belt depends on their geometrical parameters, as well as on what angle of rotation of the brake pulley of the brake pulley working surface is realized in the given drawbar brake of the drawworks.

When assigning the number of friction linings falling on the running and running branches of the brake belt, which must be installed with a constant gap, it is necessary to determine the coefficient of mutual overlap of the contacting friction pairs separately for each of the belt branches. The mutual overlap coefficient is the ratio of the contact areas of the pads and the pulley (A ₁ , and A ₂ ) to the annular area A ₀ covered by them

,

- коэффициенты взаимного перекрытия контактирующих пар трения, которые реализуются набегающей и сбегающей ветвями тормозной ленты.Where

,

- the coefficients of mutual overlap of the contacting pairs of friction, which are implemented by the running and running branches of the brake belt.

к

равно соотношению удельных нагрузок, реализуемых на набегающей (р_н) и сбегающей (р_с) ветвях тормозной ленты. Полученное соотношение (р_н/р_с) и укажет, на сколько площади рабочих поверхностей накладок должно быть больше на набегающей ветви по сравнению с площадью рабочих поверхностей накладок сбегающей ветви тормозной ленты. Таким образом реализуется статический способ выравнивания удельных нагрузок в парах трения тормоза перед установкой тормозной ленты над тормозным шкивом.Attitude

to

equal to the ratio of the specific loads realized on the running (p _n ) and running (p _s ) branches of the brake belt. The resulting ratio (r _n / r _s ) will also indicate how much the area of the working surfaces of the linings should be larger on the oncoming branch compared with the area of the working surfaces of the linings of the runaway branch of the brake band. Thus, a static method of balancing specific loads in the friction pairs of the brake before installing the brake band over the brake pulley is implemented.

The drawbar brake with a device for balancing the specific loads in its friction pairs contains a composite brake band, which consists of the main 12 and an additional 14 brake bands. The main brake bands 12 are fastened with their running ends to the crank necks 6 and 9 of the crankshaft 10, and the end of the brake is attached to the balancer 11. An additional brake band 14 is put on the main brake band 12, and cylindrical axles 16 are mounted in the hollows 15 on its sides 15 with protrusions on which plastic sleeves are worn 17. On the sides of the additional brake tape 14, longitudinal grooves 18 are made of the same cross section, but of different lengths. The longitudinal grooves are made shorter in length in the additional brake band 14 above the ramming branch I of the main brake band 12 and large - above its ramping branch.

In the middle of each of the grooves 18 of the additional tape 14, the protrusions of the mounting plates 21 are introduced, which are reinforced with wire 22 in the body of the movable wide 19 and narrow 20 friction linings having an outer 23 and working 24 surface. The cylindrical axis 16 is a limiter when moving wide 19 and narrow 20 friction linings relative to the surfaces of the composite brake tape.

In this case, one narrow pad 20 is installed on the additional brake band 14 from the side of the oncoming branch (I) of the main brake band 12, since it almost does not bear a dynamic load. According to the static regulation of specific loads by changing the areas of the linings 19 and 20 around the perimeter of the main brake tape 12, i.e. above its middle part, on the additional brake band 14 at the angle of circumference π, the linings 19 are 2L wide, and on the angle of the π / 2 from the runaway end of the main brake tape 12, the linings 20 of the width L. are placed on the secondary tape 14. When the linings 19 and 20 with a constant step on an additional brake tape 14 were used in the calculations of dependencies (1) and (2).

To open the composite brake belt after braking is complete, sprung release devices 25 are used, which are attached to the additional brake belt 14.

Installation of a composite brake tape is as follows. A fastening eye (not shown in FIG. 8) is disconnected from the downstream end of the main brake band 12, which is bolted to it from the indicated end of the main brake band 12, and an additional brake band 14 is put on its surface, to which it is then attached narrow 20 and wide 19 lining. The ends of the latter abut against the ends of the mounting ears of the main brake band 12. Dismantling the additional brake band 14 from the main 12 is carried out in the reverse order.

Thus, the principle of unloading the main brake tape 12 is implemented in a composite brake belt by eliminating stress concentrators from its body (holes: for rivets for attaching spacer bars for linings; for attaching rings of sprung tensioning devices; longitudinal grooves for mounting antennae of linings). In this case, the total deformation of the on-going (I) and on-going (II) main brake bands 12 increases, and as a result there will be more S _Н -S _С , i.e. friction force on interacting surfaces and created braking torque. This ensures good flexibility of the main brake tape 12 with a regulated coefficient of strength factor.

An additional brake tape 14 provides fastening of the wide 19 and narrow 20 friction linings, as well as the gap between the internal friction pairs by attaching to it a sprung pull device 25.

The compound brake tape carries only a weight load from wide 19 and narrow 20 friction linings. In this case, it is necessary to take into account the fact that the thickness of the composite brake tape does not exceed the thickness of the serial brake tape.

During the operation of the tape-shoe brake, the inner surface 13 of the main belt 12 and the outer surfaces 23 of the wide 19 and narrow 20 friction linings form the external friction pairs, and the working surfaces 24 of the wide 19 and narrow 20 friction linings with the working surface of the pulley 4 are the internal friction pairs.

The condition for operability in the resulting friction pairs due to the immobility of the wide 19 and narrow 20 friction linings is as follows. Dynamic coefficients of sliding friction in friction units: "working surface of the brake pulley 1 - working surfaces 24 of the movable linings 19 and 20"; "The inner surface 13 of the main brake tape 12 - the outer surface 23 of the movable lining 19 and 20" should be the same. For this, the cleanliness of the inner surface 13 of the main brake band 12 should be the same as the cleanliness of the working surface of the brake pulley 4. In addition, the outer surfaces 23 of the movable linings 19 and 20 must be machined so that the microgeometry is the same with the microgeometry of their working surfaces 24.

Tape-shoe brake of a drawworks with a device for balancing specific loads in its friction pairs works as follows. By moving the handle 1, the crankshaft 10 is rotated, as a result of which the driller tightens the main brake bands 12, which sit almost without a gap between their outer surfaces and the inner surfaces of the additional brake bands 14. Are there wide 19 and narrow 20 friction linings on the latter? which, with their working surfaces 24, interact with the working surface of the brake pulley 1. This is how the internal friction pairs of the band brake shoe work.

As for the external friction pairs of the band brake? then their work is somewhat different, since the tightening of the main brake tape 12 is not instantaneous.

The implementation of the static regulation of specific loads along the length of the composite brake band due to the areas of the working surfaces of 24 wide 19 and narrow 20 friction linings using the dependencies (1) and (2) does not guarantee dynamic alignment of specific loads along the length of the main brake band 12. Depending on the distribution the front of interaction of external and internal friction pairs at various stages of braking and the movement of the outer surfaces of 23 wide 19 and narrow 20 pads relative to the inner surface of 13 os ovnoy brake tape 12 on the one hand and on the other hand - the working surfaces 24 wide 19 and narrow 20 linings relative to the working surface of the brake pulley 4, and thereby a fixed variable pitch is set between the movable linings 19 and 20 for braking. As a result, dynamic alignment occurs specific loads in the external and internal friction pairs of the tape-shoe brake at the same time ends with the stop of the brake pulleys 4 with the drum 5, which leads to the opening of the brake by removing the composite t rmoznoy tie-down strip by the cushioning device 25 on the working surfaces of the brake pulley 4.

Thus, through the use of a composite brake band, consisting of the main and secondary, in the tape-shoe brake of the winch, static and dynamic equalization of specific loads are achieved simultaneously in the external and internal friction pairs.

Information sources

1. Auto USSR 576455 A1, F15d 49/08 from 10/15/1977 (analog).

2. Russian patent 2263832 C2, IPC7 F16D 49/08 from 10.11.2005, (prototype).

Claims (2)

1. The device for balancing the specific loads in the friction pairs of the drawbar brake of the drawworks containing a brake pulley on the shaft and an additional brake belt with friction linings mounted on it, and the main belt is attached with its ends to a mechanical brake control drive, characterized in that that the brake tape is made integral and consists of the main one, the running end of which is attached to the crank crankshaft necks and its end to the balancer, while the tape relies on its length on cylindrical axes, for the ends of which the supports are the hollows of the additional tape, and over the cylindrical axes there are gaps greater than the thickness of the main tape, while longitudinal grooves are made on the sides of the additional tape with the possibility of moving the fastening plates of the friction pads in them, with restrictions which are cylindrical axes, and the main tape with its inner surface is in contact with the non-working surfaces of the friction linings between their mounting plates. 2. The method of balancing the specific loads in the friction pairs of the drawbar brake of the drawworks, which consists in the fact that the static method achieves the equalization of specific loads by redistributing the specific loads by changing the areas of the friction linings around the perimeter of the composite brake band, above its middle part at the angle of circumference - π linings with a width of 2L are installed, and π / 2 on the circumference angle from the side of the run-off end of the main brake tape - linings of a width L, and in this case in friction pairs “pad-pulley” and “pad ka-main tape ”, dynamic equalization of specific loads is achieved by moving the linings relative to the additional and main brake tapes with regulated compliance and safety factor of the main brake tape, thereby ensuring a variable pitch between the moving pads for braking.

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