RU2489619C2 - Stabilisation method of operating parameters of band-shoe brakes of drilling winches with fixed straps on brake band - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: depending on geometrical parameters of straps and angle of contact of a brake band of a pulley working surface in friction assemblies there determined are ratios of coefficients of mutual overlapping, which is equal to ratio of specific loads occurring on straps of branches. Then, as per values of ratio of specific loads there determined is how many straps there shall be on an incident branch of the band in comparison to a diminishing branch.

EFFECT: stabilisation of operating parameters of friction assemblies of band-shoe brakes of drilling winches by redistributing specific loads on branches of a brake band due to different layout schemes of straps on it, variation of their angle of contact of a brake pulley and selection for each strap of friction material with various friction properties.

4 cl, 10 dwg

Description

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

(где S_H, S_C - натяжение набегающей и сбегающей ветви тормозной ленты). Кроме того, S_H-S_C=F_T (где F_T - сила трения при взаимодействии пар трения тормоза). Неравномерное распределение нормальных нагрузок на рабочие поверхности пар трения, и как следствие, удельных нагрузок. Это приводит к неравномерному износу рабочих поверхностей фрикционных накладок. На набегающей ветви они изнашиваются намного быстрее, чем на сбегающей [1, аналог].Known brake tape with a uniform installation pitch along its arc of grasping the friction linings. With this layout arrangement of the pads along the arc of grasping the tape, there is an uneven distribution of the tension forces, since the ratio $$\raisebox{1ex}{$S_H$}\!\left/ \!\raisebox{-1ex}{$S_C$}\right.\ge \mathrm{one}$$

(where S _H , S _C - tension of the running and running branches of the brake band). In addition, S _H -S _C = F _T (where F _T is the friction force in the interaction of brake friction pairs). Uneven distribution of normal loads on the working surfaces of friction pairs, and as a result, specific loads. This leads to uneven wear of the working surfaces of the friction linings. On the oncoming branch, they wear out much faster than on the oncoming branch [1, analog].

(где e - основание натурального логарифма; f - коэффициент трения скольжения; α - угол обхвата накладками тормозного шкива), было предложено устанавливать накладки на ленте с неравномерным шагом на дуге обхвата, увеличивая шаг размещения накладок в направлении от набегающей ветви ленты к сбегающей. Основным принципом, заложенным в определение величины шага между накладками, является выравнивание удельных нагрузок между двумя ветвями. В этом случае материал накладок будет использоваться более рационально вследствие уменьшения того его количества, который идет в выбраковку из-за неравномерности износа рабочих поверхностей накладок, расположенных на разных ветвях ленты [2, прототип].For some leveling off of specific loads changing on the arc of the brake belt circumference according to the Euler dependence $$\raisebox{1ex}{$S_H$}\!\left/ \!\raisebox{-1ex}{$S_C$}\right.=e^{f\alpha }$$

(where e is the base of the natural logarithm; f is the coefficient of sliding friction; α is the angle of circumference of the brake pulley lining), it was proposed to install the lining on the tape with an uneven pitch on the arc of the girth, increasing the step of placing the lining in the direction from the oncoming branch of the tape to the runaway. The basic principle laid down in determining the step size between the pads is the equalization of specific loads between the two branches. In this case, the material of the linings will be used more efficiently due to a decrease in the amount that goes into culling due to uneven wear of the working surfaces of the linings located on different branches of the tape [2, prototype].

The main disadvantage of this method is that it does not give an answer to the question, in what interval of change in specific loads can be redistributed between the branches of the brake band.

The objective of the invention is the development of a method for stabilizing operational parameters (specific loads, wear of the working surfaces of friction linings) of friction units of tape and shoe brakes of drill hoists by redistributing specific loads on the branches of the brake belt due to various layout schemes for the location of linings on it, varying the angle of their circumference of the brake pulley and selection for each lining of friction material with various wear-friction properties.

The problem is achieved in that, depending on the geometric parameters of the linings made of the same friction material and the angle of the brake belt around the working surface of the pulley in specific friction nodes, the ratios of the mutual overlap coefficients are determined, which is equal to the ratio of the specific loads occurring on the branch linings, according to the values which determines how much there should be more overlays on the running in comparison with the running branch of the tape. In the future, to determine the number of overlays with a variable pitch, one overlap is installed on the tape branches at its ends, and at least two overlays are installed in its middle part with a minimum pitch between them, which are the boundaries of the incident and descending branches of the ribbon; in this case, the step between the overlays on the running branch of the tape is determined by the dependence of arithmetic progression, and on the running - by the dependence of geometric progression, asking the first member of the arithmetic progression and considering that the last gap between the overlays of the running branch of the tape is the first member of the geometric progression, and the difference and denominator progression is determined from the value of the total gap between the overlays of each branch of the tape.

In the second method, friction pads with a constant pitch and with a girth angle n times larger in area of interaction with the working surface of the brake pulley are installed along the arc of girth of the running branch of the tape than on the runaway branch, and the first is the specific weight of the lining material is n times less, than the second, which allows the adjusting devices of the gaps to maintain a constant gap between the working surfaces of the friction brake assemblies.

The third method consists in the fact that friction linings made of various materials are installed with a constant pitch and with the same geometric parameters on the arc of the brake belt circumference, made of various materials, i.e. have different frictional properties, but the same linear wear of their working surfaces from the first lining of the running branch to the last lining of the running branch of the brake belt.

Compared with the analogue and prototype, the proposed methods for the redistribution of specific loads between the branches of the brake belt when the friction lining is located along the arc of its girth with a constant and variable pitch have the following distinctive features:

- it is possible to purposefully control the redistribution of specific loads on the incoming and outgoing branches of the tape due to the rearrangement of overlays from the outgoing branches to the incoming, based on the values of the coefficients of mutual overlap (ratios) of the areas of overlays of the incoming and outgoing branches of the tape, which are proportional to the loads on the indicated branches of the tape ;

- the stress-strain state of the brake belt decreases and, as a result, the contact interaction of the friction pairs, the friction forces increase and, as a result, the braking moment increases;

- provides an analytical determination of the number of friction linings with a constant step along the arc of the brake band, having an area of their interaction on the incoming branch is n times greater than on the runaway branch, as well as the use of linings with the same geometric parameters, but having different wear-friction properties, redistribute specific loads between the branches of the brake belt, and thereby stabilize them;

- increase the life of the friction linings of the running branch of the brake belt by reducing the specific loads that act on their working surfaces and thereby stabilize them along the circumference of the brake band.

Figure 1 shows the kinematic diagram of the tape-shoe brake; figure 2 is a cross section along aa of figure 1 of the friction brake assembly; figure 3, 4, 5 - the first, second and third stages of installation of the friction linings with variable pitch along the arc of grasping the brake band; 6, 7 and 8 - brake tape (scan) with the location on it of the friction linings with a variable and constant pitch of their location; Figures 9 and 10 - friction units with the angles of coverage of sections of the brake belt with overlays equal to α and 2α, and diagrams of specific loads. The following conventions are used: S _H , S _C - tension of the running and running branches of the brake band; F _p - the force exerted by the driller to the brake control lever; ω is the angular speed of rotation of the brake pulley; α, 2α, α ₁ and α ₂ are the girth angles; R _W - the radius of the working surface of the brake pulley; p _min , p _max - minimum and maximum specific loads; I-VIII serial number of the friction lining.

Serial tape brake shoe winch operates as follows. By moving the handle 1, the crankshaft is rotated (not shown in Fig. 1), as a result of which the driller tightens the brake bands 2 with friction linings 3 and they sit on the brake pulleys 4. The braking process with a tape-block brake 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 expands towards the linings 3 of the running branch (I) of the belt 2.

The intermediate stage of inhibition is characterized by the further spread of the interaction front towards the lining 3 of the runaway branch (II) of the tape 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 the braking, the sequence of friction surfaces coming into contact is repeated. A complete braking cycle is completed by stopping the brake pulleys 4 with a drum (not shown in Fig. 1).

One of the means to improve the performance and operational parameters of the friction units of serial band hoist brakes of drill hoists is to increase the number of friction linings on the running branch of the belt and reducing them on the runaway branch. For overlays of the same geometrical parameters, placed on the arc of grasping the brake belt, this can be achieved only due to the variable step of their installation.

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.

равно отношению удельных нагрузок, возникающих на набегающей (р_н) и сбегающей (р_с) ветвях тормозной ленты. Таким образом, по величине отношения р_н/р_с можно определить, на сколько больше фрикционных накладок необходимо установить на набегающей ветви ленты, чем на сбегающей. Способ определения рационального количества фрикционных накладок, устанавливаемых с переменным шагом на ветвях тормозной ленты, приведен на фиг.3 и 5. Данный способ реализуется в три этапа.When determining the rational number of friction linings installed with a variable gap on the incoming and outgoing branches of the brake belt, determine the coefficient of mutual overlap of the contacting surfaces separately for each of its branches. Since the coefficient of mutual overlap is proportional to the ratio of the areas of the contacting friction surfaces, then, in turn, the ratio $${\mathrm{to}}_{\mathrm{at}{s}_n}/{\mathrm{to}}_{\mathrm{at}{s}_{\mathrm{from}}}$$

equal to the ratio of specific loads arising on the running (p _n ) and running (p _s ) branches of the brake belt. Thus, by the magnitude of the ratio p _n / p _c, it is possible to determine how much more friction linings must be installed on the oncoming branch of the tape than on the off-branch. The method for determining the rational number of friction linings, installed with a variable pitch on the branches of the brake tape, is shown in figure 3 and 5. This method is implemented in three stages.

The first stage consists in the placement of the friction linings along the working length of the brake band, which allows you to uniquely outline the border of its oncoming and descending branches. According to figure 3 at the ends of the brake tape 2 set the friction linings V and VI, as well as two friction linings VII and I in its middle part with a minimum clearance between them. The installation of the friction linings VII and I in the middle part of the belt 2 is connected with the fact that when the brake closes, the working surfaces of precisely these linings will be the first to interact with the working surface of the brake pulley (not shown in the drawing).

The second stage consists in determining the values of the variable pitch between the friction linings on the incident branch of the tape according to the dependences of the arithmetic progression.

между накладками V и VII. Для этого используют зависимость вида $${\alpha }_1^0=\frac{360l}{\pi D}$$

, где l - расстояние по дуге ленты между накладками V и VI; D - диаметр тормозной ленты (D=d_ш+2h_н); d_ш - диаметр тормозного шкива; h_н - толщина фрикционной накладки. В дальнейшем воспользуемся значением произведения ширины серийной накладки на количество накладок, которые будут размещены на угле α₁. После этого от общей длины l набегающей ветви

ленты 2 отнимаем длину, которую занимает намеченное количество накладок (n). Для распределения длины, которая осталась для зазоров между накладками, используем основные зависимости арифметической прогрессии, задавшись при этом первым ее членом (a₁). В дальнейшем, используя особенность арифметической прогрессии, из зависимости $$S_m=\frac{2a_1+d\left(m-1\right)}{2}m$$

(где S_m - суммарная длина зазоров (m) между накладками набегающей ветви ленты; d - разность прогрессии) определяют разность прогрессии d. Величины переменных зазоров между накладками на набегающей ветви тормозной ленты определяют по зависимости $$a_{m_1}=a_m+d$$

. На этом второй этап заканчивается.First, according to figure 3, determine the Central angle $${\alpha }_{\mathrm{one}}^0$$

between linings V and VII. For this, a dependence of the form $${\alpha }_{\mathrm{one}}^0=\frac{360l}{\pi D}$$

where l is the distance along the arc of the tape between the plates V and VI; D is the diameter of the brake tape (D = d _w + 2h _n ); d _W - the diameter of the brake pulley; h _n - the thickness of the friction lining. In the future, we use the value of the product of the width of the serial lining by the number of overlays that will be placed at an angle α ₁ . After that, from the total length l of the incident branch

tape 2 subtract the length that the intended number of pads (n) takes. To distribute the length that remains for the gaps between the overlays, we use the main dependences of the arithmetic progression, having asked the first term (a ₁ ). In the future, using the feature of arithmetic progression, from the dependence $$S_m=\frac{2a_{\mathrm{one}}+d\left(m-\mathrm{one}\right)}{2}m$$

(where S _m is the total length of the gaps (m) between the overlays of the incident branch of the tape; d is the difference in progression) determine the difference in progression d. The magnitude of the variable gaps between the linings on the incident branch of the brake belt is determined by the dependence $$a_{m_{\mathrm{one}}}=a_m+d$$

. At this second stage ends.

The third stage is to determine the magnitude of the variable gap between the friction linings on the runaway branch of the tape according to the geometric progression.

дугой, которая осталась на сбегающей ветви

тормозной ленты 2 между накладками VII и VI.First, according to figure 4 determine the angle $$\left({\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="00000016.png,00000017.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_2^0\right)$$

an arc that remained on the runaway branch

brake tape 2 between the lining VII and VI.

ленты 2, и последней VII, находящейся в средней ее части, является первым членом (b₁) геометрической прогрессии. Используя особенность геометрической прогрессии, по формуле $$S_m=\frac{b_1\left(q^{m_1}-1\right)}{q-1}$$

, (где S_m - сумма членов геометрической прогрессии, которая отвечает суммарному зазору между фрикционными накладками сбегающей ветви тормозной ленты; q - знаменатель геометрической прогрессии; m₁ - количество зазоров между фрикционными накладками сбегающей ветви тормозной ленты) находят численное значение знаменателя геометрической прогрессии. После этого используют зависимость вида $$b_{m_1}=b_1\cdot q^{m_1-1}$$

, где $$b_{m_1}$$

, b₁ - величины последнего зазора между VII-й и I-й накладками сбегающей ветви

ленты 2 и первой и VI-ой накладками. Величину первого зазора между VII-ой и I-ой накладками сбегающей ветви

ленты 2 определяют по зависимости вида b₁=a_m·q, где a_m - последний член арифметической прогрессии, т.е. величина последнего зазора между последней накладкой набегающей ветви

и I-ой накладкой, установленной в средней части ленты.All actions are similar to calculating the basic parameters of a geometric progression. In this case, we take into account the fact that the last member of the arithmetic progression, i.e. the size of the gap between the penultimate pad, which is located on the oncoming branch

ribbon 2, and the last VII, located in its middle part, is the first member (b ₁ ) of geometric progression. Using the feature of geometric progression, according to the formula $$S_m=\frac{b_{\mathrm{one}}\left(q^{m_{\mathrm{one}}}-\mathrm{one}\right)}{q-\mathrm{one}}$$

, (where S _m is the sum of the terms of the geometric progression, which corresponds to the total gap between the friction linings of the runaway branch of the brake belt; q is the denominator of the geometric progression; m ₁ is the number of gaps between the friction linings of the runaway branch of the brake belt) find the numerical value of the denominator of the geometric progression. After that, use the dependence of the form $$b_{m_{\mathrm{one}}}=b_{\mathrm{one}}\cdot q^{m_{\mathrm{one}}-\mathrm{one}}$$

where $$b_{m_{\mathrm{one}}}$$

, b ₁ - the size of the last gap between the VIIth and Ith overlays of the runaway branch

tape 2 and the first and VIth overlays. The size of the first gap between the VIIth and Ith overlays of the runaway branch

tapes 2 are determined by the dependence of the form b ₁ = a _m · q, where a _m is the last member of the arithmetic progression, i.e. the size of the last gap between the last overlay branch

and I-th pad installed in the middle of the tape.

Thus, for the purposeful redistribution of specific loads between the running and running branches of the brake belt, taking into account its operational capabilities, it is necessary to correctly set only the first gap between the friction linings of the running branch of the tape. All other gap values between the plates are determined analytically.

For comparison, we analyze the operation of serial tape-shoe brakes of drill hoists with a constant and variable step of installing friction linings on the brake belt (see figure 5).

As mentioned above, the deformation of the steel strip occurs only due to the areas located between the plates. The larger the step between the overlays, the greater the deformation of the tape sections, the greater the difference in the tension of the branches of the tape S _H -S _C. In this case, the actual contact surface area of the friction and the friction forces in the friction units increase, which leads to an increase in the braking torque. A significant role in the effectiveness of the brake is played by the general deformation of the runaway branch of the brake band.

For example, consider a brake band with a 270 ° grip angle, on which it is necessary to install with variable pitch 12, 20 and 26 serial friction linings (a × b × h = 120 × 230 × 30 mm) of the U2-5- drawworks brake brake 5. Table 1 shows the initial data for determining the magnitude of the variable pitch of the placement of the friction linings on the brake belt. Using the proposed methodology, regularities were established for changing the gap between the overlays (Table 2). The analysis of the results

Table 1 Initial data for determining the variable pitch between brake linings The total number of pads, pcs. Brake tape branches Oncoming Runaway The number of lining branches, pcs. Arithmetic progression The number of lining branches, pcs. Geometric progression First term a ₁ , mm Difference The first member b ₁ mm Denominator n = 12 8 40 25 four 190 1,1659 n = 20 12 10 5 8 60 1,0902 n = 26 fifteen 2 one eleven fifteen 1,1037

calculations allowed to establish the following. When mounting 12 friction linings on the brake belt, 8 linings were installed on the oncoming branch, and 4 on the runaway branch. At the same time, the liner installation step varied from 40.0 to 351.07 mm. This led to a significant decrease in specific loads on the oncoming branch. When installing 20 pads, the above ratio was 1.5, and with 26 pads - 1.333.

From the above examples it follows that with an increase in the number

brake linings, i.e. with a decrease in the step of their installation, there is a sharp drop in the ratio of specific loads on the overlays of the oncoming and running branches, which indicates a more uniform distribution along the length of the tape.

According to the second method, friction linings with a constant pitch and with a circumference of the girth are n times larger in area of interaction with the working surface of the brake pulley than on the running branch (see Fig. 7) along the arc of girth of the running branch of the belt. In this case, the pads are made of various friction materials. So, the specific gravity of the friction material of the linings installed on the incident branch of the tape is n times less than the overlays of the runaway branch. It is necessary to strive to ensure that the total weight of the friction linings located on the running branch of the tape is equal to the total weight of the plates of the runaway branch of the tape. Observance of this condition will allow the adjusting devices of the gaps to maintain a constant gap between the working surfaces of the friction brake assemblies. With regard to the stabilization of the specific loads in the friction pairs of the brake, an increase in the angle of grasp of one lining by a factor of n, located on the oncoming branch of the belt compared to the running branch will help to reduce the difference p _max -p _min . The latter circumstance is quite convincingly illustrated in figures 9 and 10.

The most promising is the third way to achieve the same linear wear of the linings by selecting friction material for each of them with different friction properties from the first lining of the running branch to the last lining of the running branch of the brake band. In this case, the condition of a constant step between them is observed (see Fig. 8).

In addition, from the proposed methods for stabilizing the operational parameters of tape winch brakes of drill hoists with fixed brake linings on the brake belt, it follows that stabilization of specific loads can be achieved by manufacturing linings from one friction material having a variable angle of coverage — maximum on the running branch of the belt, and minimum on the last lining of the runaway branch, while maintaining a constant gap between the lining along the arc of grasping the brake band.

Thus, the implementation of the method of stabilizing the operational parameters of the brake by redistributing the specific loads on the branches of the tape due to: the introduction of variables analytically reasonable values of the gaps between the plates; the variation of the girth angles of the linings and their friction materials with different wear and friction properties, while maintaining a constant step between them, will increase the braking torque and significantly increase the life of the linings.

Information sources

1. Alexandrov M.P., Lysyakov A.G., Fedoseev V.N. etc. Braking devices (reference book). - M.: Mechanical Engineering, 1985. - 308 p. (Fig. 3.18, p. 121) [analog].

2. Alexandrov M.P. Braking devices in mechanical engineering. - M: Mechanical Engineering, 1965 .-- 675 p. (Fig. 127, p.206-207) [prototype].

Claims (4)

1. A method of stabilizing the operational parameters of the drawbar brakes of drawworks with fixed brake linings, comprising brake pulleys attached with protrusions to a flange of a brake drum located on a lifting shaft, a brake band with an on-board and run-off branch to which friction linings are attached made of one material and a drive, characterized in that, depending on the geometric parameters of the pads and the angle of the brake band around the working surface of the pulley in friction nodes define the relation of mutual overlapping factors, which is the ratio of the specific loads encountered in the linings of branches, according to the values of which determine how much should be more overlap upwind compared to the trailing branch tape. 2. A method of stabilizing the operational parameters of tape and shoe brakes of drawworks with fixed brake linings according to claim 1, characterized in that to determine the number of friction linings with a variable pitch on the branches of the tape, one liner is installed at their ends, and in its middle parts - at least two overlays with a minimum step between them, which are the boundaries of the oncoming and escaping branches of the tape, while the step between the overlays on the incoming branches of the tape is determined by the arithmetic progression, and on the runaway - according to the geometric progression dependencies, and taking into account that the last gap between the overlays of the incoming branch of the ribbon is the first member of the geometric progression, and the difference and denominator of the progressions is determined from the total gap between the overlays of each ribbon branch. 3. A method of stabilizing the operational parameters of tape and shoe brakes of drawworks with fixed brake linings mounted on a brake belt, with a constant pitch on its branches, according to claim 2, characterized in that friction linings with an angle are installed at a constant arc around the incoming branch of the tape the girth is n times larger in the area of interaction with the working surface of the brake pulley than on the runaway branch, and in the first case, the specific gravity of the material is n times less than in the second, which allows adjusting devices Am maintain constant clearance gaps between the bearing surfaces of the friction brake assemblies. 4. The method of stabilizing the operational parameters of the tape-shoe brakes of drawworks with fixed brake linings installed at a constant pitch on its branches, according to claim 3, characterized in that the friction frictions are installed along the arc of the brake band around the same geometrical parameters and a constant pitch pads, but made of various materials, i.e. have different frictional properties and the same linear wear of their working surfaces from the first lining of the running branch to the last lining of the running branch of the brake belt.

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