RU2424067C1 - Two-hammer impact screen - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to construction sand classifiers and may be used in mining, construction and agriculture. Proposed screen comprises frame mounted via dampers on foundation, screen and vibrator. Screen comprises screen box mounted via dampers on frame. Screen is arranged inside screen box. Rigid hammers spaced apart by clearance "e" are arranged on aforesaid frame and box to act in oscillating at phase angle ët varying in the range of: ^ where n - 0, 1, 2, 3 is number of oscillations, tIM.S. is impact start moment. Vibrator may be arranged on either screen frame or screen box. ^ EFFECT: higher efficiency. ^ 3 cl, 4 dwg

Description

The invention relates to devices for classifying building sands and can be used in mining, construction, agricultural industries.

It is known to clean sieves using the impact of various impact means on a sieve element. In the patent [1], a screening device is disclosed comprising a vibrating frame to which a vibrating body supporting a vibrating screen is connected. Below the sieve is attached a set of fixed rods, each of which is supported on two levers connected at the ends by flexible connections. The vibrating housing is equipped with the first electric motor as a drive, which is used during normal operation. The second motor, which rotates at a lower speed, serves to clean the sieve, while the movable rods are tuned in resonance so that they hit the bottom surface of the vibrating sieve.

Known cleaning sieve vibrating screens using many elastic loaded levers [2]. The levers are integrally formed, so that they are attached to one or both sides of the elastically mounted strip and are in direct contact with the bottom surface of the sieve. The vibrational action of the sieve causes the oscillating movement of the elastically suspended levers and thus creates a shock effect of the massive ends of the levers on the lower surface of the sieve, as a result releasing particles of material stuck in the holes and cleaning it.

In the device [3] the screening surface is a frame in which swinging inserts are installed, which are located directly in contact with the screen of the screen. During the movement of the material, the inserts oscillate, striking the grid - thereby cleaning it.

A common drawback of these analogues, with a mechanical effect on a woven wire sieve (which in most cases are used on vibrating screens), is the intensive wear of the sieve web in contact with the mechanical impact of impact devices on the sieve. In this case, a constant contact occurs at each impact, i.e. the contact of impact devices with a sieve and further mechanical deformation of the fabric, and hence the sieve wires, which leads to intensive abrasion of the sieve wires. As a result, intensive wear of the sieve cloth leads to a violation of the linear dimensions of the openings of the screening surface of the sieve, and this, in turn, leads to a decrease in the quality of the resulting product (classified material) and the need for frequent replacement.

Another solution to the problem of cleaning the screening surface of a device for classifying materials is known - the use of screens with a two-mass system in which such masses and spring stiffness are structurally selected, in which sieve sheets are subjected to resonant vibrations.

, где C - жесткость пружины в Н/м; Ca - жесткость амортизатора в Н/м; n - количество амортизаторов в шт; M - масса рамы в кг; ω - резонансная угловая частота колебаний рамы в рад/с. Обмотки вибратора подключены к питающей сети через преобразователь частоты, выполненный с возможностью изменения частоты электрического тока, а на раме установлен датчик колебаний, соединенный с устройством управления преобразователем частоты, выход которого соединен с каналом управления преобразователя частоты, при этом устройство управления преобразователем частоты выполнено с возможностью работы в двух режимах: режиме ручной настройки колебаний рамы и режиме автоматического поддержания заданных колебаний рамы.The closest technical solution to the present invention is a resonant sieve [4], including a bed, a frame mounted with shock absorbers, sieve sheets mounted on the frame, a device for changing the angle of the frame, a feed chute, a vibrator mounted on the beam attached to the side of the frame. A spring is installed between the vibrator and the beam, the rigidity of which, together with the stiffness of the shock absorbers in the direction of the oscillation vector of the frame and the mass of the frame, are related by

where C is the spring stiffness in N / m; Ca — shock absorber stiffness in N / m; n is the number of shock absorbers in units; M is the mass of the frame in kg; ω is the resonant angular frequency of the frame oscillations in rad / s. The vibrator windings are connected to the supply network through a frequency converter, configured to change the frequency of the electric current, and an oscillation sensor is mounted on the frame connected to a frequency converter control device, the output of which is connected to a frequency converter control channel, while the frequency converter control device is configured to work in two modes: the mode of manual setting of the frame oscillations and the mode of automatic maintenance of the set frame vibrations.

The main disadvantages of this prototype are the increased vibration load of the screen cloth from the resonant mode of oscillation, as well as the low ability to self-clean the screen surface during the operation of the screen.

The present invention can eliminate these drawbacks of the prototype, if you make the mass of the two-mass screen in contact during the operation of the screen, which will provide a mutual impact of the mass of the screen.

The objective of the invention is to increase the operational performance of a two-mass vibrating screen due to the continuous cleaning of the sieve cloth during operation of the screen.

To solve this problem, a two-mass vibration impact screen is proposed, which, like the prototype, includes a frame mounted with shock absorbers on a bed, a screen cloth and a vibrator.

, где n - 0, 1, 2, 3 - число периодов колебаний, момент начала удара.Unlike the prototype, the two-mass vibrating screen is equipped with a sieve box mounted on the frame using shock absorbers, and the sieve cloth is installed inside the sieve box, while on the screen frame and on the sieve box are hard impactors with adjusting shims, between which there is a gap “e” , providing a shock effect of the vibrating screen masses at the moment of finding the phase angle ωt of vibrations of the vibroorgan in the range

, where n - 0, 1, 2, 3 - the number of periods of oscillations, the moment of the beginning of the impact.

In addition, the vibrator can be located either on the screen frame or on the sieve box.

, где n - 0, 1, 2, 3 - число периодов колебаний, t^н.уд. - момент начала удара.The essence of the proposed technical solution lies in the fact that the vibration load of the sieve sheet from the resonant mode of vibration is reduced and the ability to self-clean the screening surface during the operation of the screen is increased, due to the fact that the masses of the two-mass screen are made in contact during operation, which ensures a mutual impact of the screen masses, the impulse which is transferred to the screen cloth, cleaning it. This is achieved by the fact that the screen frame interacts by means of shock absorbers with a sieve box on which the screen cloth is fixed. In the lower part of the screen frame, as well as in the upper part of the sieve box, rigid impactors are installed with adjusting spacers that are installed perpendicular to the line of action of the driving force. Between the drummers installed on the sieve box and on the screen frame there is a gap “e”, the size of which is regulated by adjusting shims of various thicknesses, which are mounted under the drums in the places of their fastening on the screen. From the size of the gap "e" depends on the moment of contact of the two masses and the magnitude of the shock load. Drummers impede the movement of the screen frame and the sieve box when moving towards each other during the operation of the screen. The shock must be carried out at the moment of finding the phase angle ωt of vibrations of the vibroorgan in the range:

where n - 0, 1, 2, 3 - the number of periods of oscillations, t ^n.a. - the moment of the start of the strike.

The application of the proposed set of essential features in a two-mass vibro-impact screen allows to obtain a new technical result, which consists in increasing the operational performance of a two-mass vibration screen due to the continuous cleaning of the sieve cloth.

The invention is explained by the drawings, which depict: in Fig. 1 is a schematic diagram of a two-mass vibration impact screen (the vibrator is mounted on the screen frame); figure 2 is a schematic diagram of a two-mass vibration impact screen (the vibrator is mounted on a sieve box); figure 3 - diagram of the movement of the material on the screening surface of the screen in shock-free mode; figure 4 is a diagram of the movement of material along the screening surface of the screen in the mode with a shock that occurs when the gap "e" is equal to zero, at the moment at which the phase angle ωt of vibrations of the vibroorgan is equal to ωt = 2πn, where n - 0, 1, 2 , 3 - the number of periods of oscillation.

The two-mass vibro-impact screen contains a bed 1, a screen frame 2, which is supported on the bed by means of shock absorbers 3 and is equipped with a vibrator 4. A screen box 6 is mounted on the screen frame by means of shock absorbers 5, on which a screen web 7. is installed. At the bottom of the screen frame, as well as the upper part of the sieve box has rigid rubber or polyurethane impactors 8 installed perpendicular to the line of action of the driving force. Under each drummer, in places of their fastening to the screen, shims 9 are installed to regulate the size of the gap “e”. From the size of the gap "e" depends on the impact time of two masses and the magnitude of the shock load.

- коэффициент режима работы виброустановки, характеризующий ускорение колебаний сита по отношению к ускорению свободного падения g с учетом угла вибрации β, где А и ω - соответственно амплитуда и круговая частота колебаний виброоргана). Режим с интенсивным периодическим подбрасыванием позволяет эффективно использовать процесс виброперемещения для осуществления классификации материалов. Перемещение материалов происходит за счет инерционных свойств материалов. Характерные этапы движения слоя материала по ситу представлены на фиг.3, где приведена схема движения сита и материала по вертикали (y - вертикальная координата перемещения) в зависимости от фазового угла колебаний виброоргана (ωt - ось абсцисс, где t - время), когда сито совершает гармонические колебания по закону y_сита=Asinωt (где А - амплитуда колебаний виброоргана, ω - частота колебаний виброоргана). Поскольку в горизонтальном направлении характер перемещения сита и слоя подобен движению их по вертикали, то схема перемещения слоя в горизонтальном направлении будет аналогичной и в описании не приводится.The operating mode of the two-mass vibro-impact screen under consideration is adopted in such a way that the material is moved with continuous tossing over the load-bearing surface of the sieve, this corresponds to the value of the vibration mode of the sieve box with a sieve cloth fixed to it - K _v > g

is the coefficient of the operating mode of the vibroinstallation, which characterizes the acceleration of vibrations of the sieve with respect to the acceleration of gravity g, taking into account the angle of vibration β, where A and ω are the amplitude and circular frequency of vibrations of the vibroorgan). The regime with intensive periodic tossing allows you to effectively use the process of vibration displacement to classify materials. The movement of materials occurs due to the inertial properties of the materials. The typical stages of the movement of the material layer along the sit are presented in Fig. 3, which shows a diagram of the movement of the sieve and the material vertically (y is the vertical coordinate of movement) depending on the phase angle of vibrations of the vibroorgan (ωt is the abscissa axis, where t is time), when the sieve performs harmonic oscillations according to the law of y _sieve = Asinωt (where A is the amplitude of vibrations of a vibroorgan, ω is the frequency of vibrations of vibroorgan). Since in the horizontal direction the nature of the movement of the sieve and the layer is similar to their vertical movement, the pattern of moving the layer in the horizontal direction will be similar and not described.

In Fig. 3, the dashed line shows the movement of the material layer, and the solid line shows the movement of the sieve:

- from the moment t _neg. to t _pad. - the stage of flight of the material (where t _neg. and t _pad. , respectively, the moments of separation and fall of the material on the sieve);

- from the moment t _pad. to t _neg. - stage of the joint movement of the layer of material and sieve.

The material classified on the screening cloth of the screen, during its transportation, clogs the sieve cells and reduces the operational performance of the screen. In the present invention, this problem of sifting of sieves is solved by the impact of the oscillating masses of the screen frame and the sieve box due to the received shock pulse, stuck particles of material are released from the sieve openings.

, где n - 0, 1, 2, 3 - число периодов колебаний, t^н.уд. - момент начала удара.Vibro-shock two-mass screen works as follows. The masses of the screening frame 2 and the screen box 6, as well as the shock absorbers 5 of these two masses are selected in such a way as to provide a screening mode in which the masses move synchronously and in antiphase in each period of the screening oscillations. The impact of the masses moving against each other must be performed in each period of the screen vibrations at the moment when the oscillation speed of the screen box 6, on which the screen web 7 is fixed and the screen frame 2, had a maximum value, i.e. at the moment of finding the phase angle ωt of vibrations of the vibroorgan in the range:

where n - 0, 1, 2, 3 - the number of periods of oscillations, t ^n.a. - the moment of the start of the strike.

The design of the screen provides that the impact occurs at the moment when the sieve box 6 moves up, and the screen frame 2 moves towards it - down, the impact occurs when the impactors 8 begin to touch (the moment the impact starts - t ^n.ud. ) and lasts until the moment of separation of the strikers (moment of the end of the impact t ^kud ), i.e. impact does not occur instantly, but has a duration equal to t ^beats. = t ^K.ud. -t ^n.a. (where t ^beats. - stroke time). Such a distribution of the directions of motion of the oscillating masses during the operation of the screen is determined by the fact that the material breaks away from the surface of the sieve and, due to inertia forces, flies above the plane in the direction of its transportation during the entire stage of free movement, i.e. from time t _neg. to t _pad .

From the moment of the start of the impact t ^n.a. the material breaks away from the screening retardant movement and then flies above the surface, i.e. the screen cloth becomes unloaded material, and the impact is not yet completed, i.e. the shock pulse still extends and acts on the sieve box up to the moment t ^k.ud. . In this period t ^beats. (t ^beats. - time of the impact) there are favorable conditions for the release of stuck particles of material from the holes of the sieve cloth due to inertia. Thus, during each period of screening oscillations, the screen cloth is cleaned and thereby maintains a constant living section of the screening surface of the screen during screening.

To regulate a given moment of the beginning and end of the impact, a change in the size of the gap “e” by the shims 9 is provided. In this case, the gap “e” can be “positive”, “zero” or “negative”. The “positive” value is the gap at which the impactors 8 are in contact at the moment when the phase angle ωt of vibrations of the vibroorgan corresponds to ωt> 2πn, where n - 0, 1, 2, 3 is the number of periods of vibrations. The “zero” gap corresponds to the phase angle ωt of vibrations of the vibroorgan equal to ωt = 2πn, where n - 0, 1, 2, 3 is the number of oscillation periods. The “negative” value is the gap at which the impactors are in contact at the moment when the phase angle ωt of the vibrations of the vibroorgan corresponds to ωt = 2πn, where n - 0, 1, 2, 3 is the number of periods of vibrations.

) продолжительность полета t_пол=t_пaд-t_отр (где t_пол - время полета слоя над плоскостью) материала над плоскостью не превышает этот период (t_пол≤T), т.е. колебания слоя материала и вибросита носят равный однопериодный режим колебаний. Этот режим колебаний наиболее эффективен при грохочении сыпучих сред. Таким образом, границы зазора «e», при котором ударное воздействие существенно, и при этом изменение K_v лежит в пределах от 1,5 до 3,5 g, время полета t_пол слоя материала над плоскостью не превышает времени периода колебаний T, т.е. t_пол≤T, что соответствует следующему диапазону значений фазового угла ωt колебаний виброоргана

, где n - 0, 1, 2, 3 - число периодов колебаний, t^н.уд. - момент начала удара.Note that in the zone when the phase angle of vibrations of the vibroorgan corresponds to ωt = 2πn (the gap “e” is equal to zero), the shock momentum of the two masses is the largest, because at this moment, the vibrational speed of the sieve box 6 and the screen frame 2 is the highest. Given that in practice, the coefficient of the operation mode of the screens is assigned in the range of 1.5≤K _v ≤3.5, which corresponds to the regime of vibration displacement of the material layer, in which T (where

) Flight duration t = t _{floor pad Neg} -t (where t _floor - time of flight of the plane layer) above the plane of the material does not exceed the period (t _floor ≤T), i.e. the vibrations of the material layer and the vibrating screen have an equal one-period oscillation mode. This mode of oscillation is most effective when screening bulk media. Thus, the boundary of the gap "e", at which the impact is significant, and the change in K _v lies in the range from 1.5 to 3.5 g, the flight time t _{floor of the} material layer above the plane does not exceed the time of the oscillation period T, t .e. t _floor ≤T, which corresponds to the following range of values of the phase angle ωt of vibrations of the vibroorgan

where n - 0, 1, 2, 3 - the number of periods of oscillations, t ^n.a. - the moment of the start of the strike.

Information sources

1. US patent No. 53001815, IPC B07B 1/40, 1/42,

2. US patent No. 4288320, IPC B07B 1/40, 1/42,

3. International patent WO No. 93/16815, IPC B07B 1/40, 1/42, IPC B07B 1/40, 1/42,

4. Patent of the Russian Federation No. 2268785, IPC B07B 1/40, 1/42, January 27, 2006 - prototype.

Claims (3)

1. A two-mass vibration impact screen, including a frame mounted with shock absorbers on the bed, a screen cloth and a vibrator, characterized in that the device is equipped with a screen box mounted on the frame with shock absorbers, and a screen cloth installed inside the screen box, while on the screen frame and rigid impactors with adjusting gaskets are installed on the sieve box, between which there is a gap “e”, which ensures the impact of the vibrating screen masses at the moment of finding the phase angle ωt of vibrations of the vibroorgan in range:

where n = 0, 1, 2, 3 - the number of periods of oscillation;
t ^n.ud - the moment of the start of the impact. 2. Two-mass vibration impact screen according to claim 1, characterized in that the vibrator is located on the screen frame. 3. Two-mass vibration impact screen according to claim 1, characterized in that the vibrator is mounted on a sieve box.

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