RU2162434C1 - Tension regulator for flexible member wound off drum - Google Patents

Abstract

FIELD: space engineering for control of tension of trailing-out rope; textile, paper-making and other industries. SUBSTANCE: proposed regulator has drum with flexible member, rocker on hinged support, two fixed rollers and one roller fitted on rocker arm and brake block mounted on other rocker arm. Flexible member embraces in succession first fixed roller, fitted on rocker arm and second fixed roller. Brake block is spring-loaded and is engaged with drum rim. Force of compression of spring is equal to:

where P is force of compression of spring; N_* is preset tension of flexible member; "a" is length of rocker arm with roller; "b" is length of rocker arm with brake block. Relationship of main sizes of regulator satisfies the following condition:

, where r_max is maximum radius of winding flexible member off drum; R_o is drum rim radius; k_{0 min} is minimum coefficient of sliding friction between brake block and drum rim; ε is permissible relative error of flexible member tension control. EFFECT: enhanced accuracy of tension force control. 1 dwg

Description

 The proposed device can be used in space technology to regulate the tension of the manufactured cable when deploying an orbital cable system - a bunch of two spacecraft. In addition, the device can find application in textile, paper and other industries. In particular, the device can be used to maintain, with the required accuracy, a given tension force of a flexible element (thread, wire, etc.), reeled from a drum, for example, when it is rewound to another drum.

 A device for regulating the tension of the paper web according to the application of Germany N2256882 (IPC B 65 H 23/18), containing a tension roller. The tension of the web is adjusted by setting the speed of the tension roller in accordance with the deviation of the adjustable value from its predetermined value, determined by measuring the tension and speed of the web before and after the tension roller and comparing the product of the speed difference behind and in front of the roller and the tension behind the roller and the difference product tension behind and in front of the roller at a speed behind the roller. In this device, the web passes through a complex system of rollers and, in one of the sections, first sequentially covers one fixed roller, then a roller mounted on an articulated lever, and finally a second fixed roller. The disadvantages of this device are excessive complexity and the need for power.

 Known regulator of constant tension of a flexible product according to the application N 2308717 France (IPC B 65 H 17/02), containing a tension probe in the form of a pivotally mounted rocker arm, provided at the end with a roller through which the reeled product passes. The tension probe is connected to a parallel-mounted integrating element and a proportional element, which are connected through a common summing output to the drive element of the product supply regulatory body. This regulator responds to deviations in the tension of a flexible product by changing the angular velocity of its unwinding mechanism. The disadvantage of this device is the need for energy for the forced unwinding of the coil with a flexible product.

 A device for controlling the tension of the thread according to US patent N 3991954 (IPC B 65 H 59/22), containing a brake with two clamping discs, between which the thread passes. A closing electromagnet acts on one of the disks, pressing the disks against each other with a force proportional to the applied voltage, by changing which the tension of the thread is regulated. The thread passes through one end of the pivotally attached lever and, turning it, closes the electrical contacts of the control circuit connected to the solenoid of the closing electromagnet. A return electromagnet is connected to the other end of the lever, which returns the lever to its original position, counteracting the force from the side of the thread. The disadvantage of this device, along with the consumption of electricity, is that the friction of the pressure disks acts directly on the thread itself, which can lead to its clamping and rupture.

 It is also known a device for controlling the tension of the canvas according to US patent N 3913855 (IPC B 65 H 25/22), containing a frame on which the lever is mounted - a rocker mounted on a hinge support with a bracket mounted on it. On the bracket there is a rotating pin with a brake device, the design of which allows it to enter the roll of the web so that when the roll rotates when it is unwound, the pin rotates with the roll. The unwinding web in its movement sequentially covers one fixed roller, a swinging roller and another fixed roller. A web tension control system is connected to the swinging roller, comprising a web tension sensor and a measuring instrument for measuring a web tension deviation from a predetermined value. These elements give signals to the control device, to which a large number of mounting elements are connected, with the help of which the magnitude of the braking moment created by the braking device on the axle and, therefore, the web tension, is regulated. The disadvantages of this device are the relative complexity of the device and the need for power consumption, which can cause insufficient reliability.

 The closest analogue of the claimed invention is a tension regulator of a flexible element, reeled from the drum, according to US patent N 3520485, IPC B 65 H 77/00, 07/14/1970, containing a drum with a flexible element, a rocker on a hinged support, rollers, two of which are stationary, and one is mounted on one arm of the rocker arm, and a brake shoe mounted on the other arm of the rocker arm, the flexible element sequentially covering the first stationary roller, the roller on the rocker arm and the second stationary roller. The disadvantages of this device are the design complexity, lack of reliability and accuracy of the regulation of the tension force.

 The claimed invention is directed to solving the problem of providing regulation of a relatively low tensile force of a flexible element reeled from a drum. The technical result that can be obtained by carrying out the invention is to simplify the design of the device for adjusting the tension of the flexible element, increase reliability and ensure accurate control of the tension force.

,
где P - усилие поджатия пружины;
N_* - заданное натяжение гибкого элемента;
a - длина плеча коромысла с роликом;
b - длина плеча коромысла с тормозной колодкой,
а соотношение основных размеров регулятора соответствует условию

где r_max - максимальная величина радиуса смотки гибкого элемента с барабана;
R_о - радиус обода барабана;
k_{o min} - минимальная величина коэффициента трения скольжения между тормозной колодкой и ободом барабана;
ε - допускаемая относительная погрешность регулирования натяжения гибкого элемента.This technical result is achieved by the fact that, in contrast to the known device, the brake shoe is spring-loaded and interacts with the rim of the drum, while the spring force is

,
where P is the spring preload force;
N _* is the given tension of the flexible element;
a is the shoulder length of the rocker arm with a roller;
b is the arm length of the rocker arm with the brake pad,
and the ratio of the main dimensions of the regulator meets the condition

where r _max - the maximum radius of the winding of the flexible element from the drum;
R _about - the radius of the rim of the drum;
k _{o min} - the minimum value of the coefficient of friction between the brake shoe and the rim of the drum;
ε is the permissible relative error in the regulation of the tension of the flexible element.

 The drawing shows a diagram of the proposed controller, which includes: a flexible element 1, drum 2, rocker 3, articulated support 4, rollers 5 and 6, brake pad 7, spring 8. Flexible element 1 is wound on drum 2, rocker 3 is mounted on articulated support 4, the roller 5 is mounted on one end of the rocker arm 3, the rollers 6 are fixedly mounted, the brake shoe 7 is mounted on the other end of the rocker arm 3, spring-loaded with a spring 8 and interacts with the rim of the drum 2. The flexible element 1, when it is wound from the drum 2, covers in seriesbeginning one fixed roller 6, then the roller 5 is mounted on one end of the rocker 3, and finally, the second fixed roller 6.

 When winding the flexible element 1 from the drum 2, the brake pad 7, pressed by the spring 8, rubs against the rim of the drum 2 and creates a braking moment on it, as a result of which the flexible element 1 is stretched. On the other hand, when tensioning the flexible element 1, it acts on the brake shoe 7 through the beam 3 on the hinge support 4, reducing the force of its pressing against the rim of the drum 2, as a result of which the braking moment and, accordingly, the tension of the flexible element 1 are reduced. Thus, feedback is implemented in the tension control circuit of the flexible element 1, reeled from the drum 2.

 The choice of design parameters of the controller can provide a given level and the required accuracy of the tension control of the flexible element 1. Below are the formula relations that allow you to set the basic parameters of the controller that determine the mode of winding of the flexible element 1 from the drum 2.

где N - сила натяжения гибкого элемента 1;
r - текущий радиус смотки гибкого элемента 1 с барабана 2;
k_о - коэффициент трения скольжения тормозной колодки 7 об обод барабана 2.In the steady state mode of operation of the regulator, the torque on the drum 2, created by the tension force of the flexible element 1 pulled from it, must be balanced by the braking friction moment created on the rim of the drum 2 by the brake shoe 7 pressed by the spring 8. This condition can be written in the form of an equation

where N is the tension force of the flexible element 1;
r is the current radius of the winding of the flexible element 1 from the drum 2;
k _about - the coefficient of friction of sliding brake pads 7 about the rim of the drum 2.

В процессе смотки гибкого элемента 1 с барабана 2 радиус смотки r постепенно уменьшается, при этом коэффициент трения скольжения k_о является нестабильной и случайной величиной. Вследствие этого натяжение гибкого элемента 1 при его смотке изменяется, отклоняясь от заданной величины. Однако параметры регулятора можно выбрать такими, чтобы влиянием переменной величины r в знаменателе (4) можно было пренебречь:

Чтобы обеспечить регулирование натяжения гибкого элемента 1 с относительной погрешностью, не превышающей допустимой достаточно малой (намного меньшей единицы) величины ε, должно выполняться условие

Условие (6) должно выполняться на протяжении всего процесса смотки гибкого элемента 1, то есть должно охватывать полные диапазоны возможного изменения величин r и k_о. В самом критическом случае условие (6) должно выполняться для максимальной величины радиуса смотки r=r_max и минимального ожидаемого значения коэффициента трения скольжения k_о=k_{о min}. Таким образом, условие (6) для такого критического случая следует записать в виде приведенного выше условия (2), левая часть которого представляет собой безразмерное соотношение основных геометрических размеров регулятора.From equation (3), you can determine the tension of the flexible element 1 in the steady state mode of operation of the controller:

During the winding of the flexible element 1 from the drum 2, the radius of the winding r gradually decreases, while the coefficient of sliding friction k _о is an unstable and random variable. As a result of this, the tension of the flexible element 1 during its winding changes, deviating from a predetermined value. However, the parameters of the controller can be chosen so that the influence of the variable r in the denominator (4) can be neglected:

To ensure the regulation of the tension of the flexible element 1 with a relative error not exceeding the permissible sufficiently small (much smaller unit) ε, the condition must be met

Condition (6) must be fulfilled throughout the winding process of the flexible element 1, that is, it should cover the full ranges of possible changes in the values of r and k _о . In the most critical case, condition (6) must be satisfied for the maximum value of the radius of the winding r = r _max and the minimum expected value of the coefficient of sliding friction k _о = k _{о min} . Thus, condition (6) for such a critical case should be written in the form of condition (2) above, the left side of which is a dimensionless ratio of the main geometric dimensions of the controller.

Согласно формуле (7) натяжение сматываемого гибкого элемента 1 пропорционально усилию поджатия пружины 8, причем коэффициент пропорциональности определяется соотношением длин плеч коромысла 3.To fulfill condition (2) it is possible, for example, to make the shoulder of the rocker arm 3 from the side of the roller 5 substantially longer than its shoulder from the side of the brake shoe 7 (a >> b). When condition (2) is fulfilled, formula (4) can be written in an approximate form

According to the formula (7), the tension of the reeled flexible element 1 is proportional to the force of compression of the spring 8, and the proportionality coefficient is determined by the ratio of the arm lengths of the rocker arm 3.

 Under the condition a >> b, which provides a small error of regulation, the tension force of the flexible element 1 will be much less than the force of compression of the spring 8. This circumstance allows a fairly accurate control of the tension of the flexible element 1 with its relatively small predetermined value. Such regulation may be required, for example, when releasing a cable of a bundle of two spacecraft during its deployment in orbit, especially in cases where the masses of vehicles and / or the length of the cable connecting them are small and, accordingly, gravitational-centrifugal forces act very weakly on the bundle . In addition, the need for such regulation may occur when rewinding thin fibers and threads having a very low tensile strength.

From formula (7), formula (1) is derived, which determines the spring pressing force P necessary to ensure the tension of the flexible element 1 is controlled at a given level N _* . By changing the arm lengths of the rocker arm 3 and / or the preload force of the spring 8, it is possible to set a predetermined level of tension control of the flexible flexible element 1. In this case, a predetermined control accuracy will be ensured by the fulfillment of condition (2). Thus, the proposed controller, with the appropriate choice of its parameters, allows for the adjustment of the tension of the reeled flexible element 1 at a predetermined level defined by formula (1), with an acceptable sufficiently small error determined by formula (2).

Claims (1)

The tension regulator of the flexible element, reeled from the drum, containing a drum with a flexible element, a rocker on a hinged support, two of which are fixed and one mounted on one arm of the rocker arm, and a brake pad mounted on the other arm of the rocker arm, and the flexible element covers in series the first stationary roller, the roller on the rocker arm and the second stationary roller, characterized in that the brake shoe is spring-loaded and interacts with the drum rim, while the spring force is

where P is the spring preload force;
N _* is the given tension of the flexible element;
a is the shoulder length of the rocker arm with a roller;
b is the arm length of the rocker arm with the brake pad,
and the ratio of the main dimensions of the regulator meets the condition

where r _max - the maximum radius of the winding of the flexible element from the drum;
R _about - the radius of the rim of the drum;
k _{o min} - the minimum value of the coefficient of friction between the brake shoe and the rim of the drum;
ε is the permissible relative error in the regulation of the tension of the flexible element.