SU910318A1 - Apparatus for controlling mixture mouldability - Google Patents

Description

(54) DEVICE FORMULATABLE REGULATION

MIXTURES

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The invention relates to foundry and can be used in the mixing and preparation departments of foundries. .

A device I is known for controlling the formability of the mixture, whose operation is based on the control of the formability — the property of the mixture to sift through the non-slit of a certain size. The device consists of a formatio network sensor containing a tray with two peaks of different widths, under each of which a photo sensor is installed, water containing two parallel channels with coarse and precise metering valves, and a control unit whose inputs are connected to the photo formers of the formability sensor and the outputs - respectively with coarse and precise dosing valves. The mixture coming from the mixer, sifting through the slots of the formability sensor tray, overlaps the photocells of the photosensors.

which through the control units include a water metering valve. As the moisture is moistened, the mixture becomes less free-flowing and stops spilling through a smaller gap. At the same time, the signal from the photo sensor mounted against this slit, the control unit turns off the coarse metering valve, and the area is adjusted to the required formability through the precision-adjusting channel.

However, this device often operates in the following modes: valve first holes for a long time are turned on, the mixture goes out under-humidified, its formability is high second — both valves do not turn on for a long time, the mixture goes out wet, its formability is low; In the first case, the expense

20 water is insufficient, in the second one it is excessive, in both cases the mixture at the mixer outlet is defective, and this can be caused by significant fluctuations in the moisture content of the used mixture, as well as the pressure of water supplied to the mixer Most closely to the proposed formability control device 2, containing a sampling unit mounted on the mixer, a formability sensor, the output of which is connected to the inlet of the control unit of the water metering unit with two stop valves installed in the coarse and precise metering channels, been consistent with that set the control valve with the reversing drive, whose input is connected to the output stepper regulator, signal generator of low and high formability. In normal mode, the device operates similar to the known. At that, the dosing channels are switched on and off by the dosing unit by the control unit using the photocell signals of the formability sensor. The device is considered to be optimally adjusted if the signal is kept at the output of the former for a long time. The moldability is normal. This state corresponds to the on or off of another dosing channel. However, this state cannot be stable due to frequent fluctuations in the humidity of the waste mixture or water pressure. If the humidity of the waste mixture supplied to the mixer decreases or the pressure of the water supplied to the dosing unit drops, the water flow in both channels of the dosing unit is insufficient and the mixture leaves the mixer under-absorbed, its formability is high, although both dosing channels are included. In this case the torus automatically turns on the drive of the control valve, which in steps increases the flow rate of the water supplied to the mixer until the exact metering channel is turned off. Odita waterlogged from the mixer, signals are not output to the sensor, both channels are disabled dosing, water does not flow into the mixer and through formers and stepper regulator 84 is automatically turned on the rotary control valve which closes ve steps; til. The main disadvantage of such a device is a reduction in the yield of high-quality molding sand due to poor quality control, because the mixer is an inertial element with delay, and the regulator is a relay element, which, in any settings, leads to a self-oscillating mode. For example, when there are no signals at the output of the formeability sensor, both channels are disconnected, no water is supplied to the mixer,. there is no control action, the control valve in steps can be almost completely closed. After a time equal to the lag time when the overmixed mixture in the mixer is displaced again by the mixture, both valves are turned on for a long time, as the water flow is insufficient and the control valve will be unwound (increase the flow) in the opposite direction. Due to the delay, the overwetting occurs, and both channels are again switched off for a long time, and the control valve closes in steps, etc. Thus, at the exit of the mixer, a defective mixture periodically appears (either dry or wetted). The purpose of the invention is to increase the yield of the quality mixture by improving the quality of regulation. This goal is achieved by the fact that the device for adjusting the formability of the mixture, which contains a sampler, a formability sensor, a two-channel water metering unit with two shut-off valves and a regulating valve, a control unit, a two-channel signal conditioner of low and high formability, a controller connected to the sensor outputs, formability, and the outputs through the controller are connected to the valve drive, additionally equipped with a mixture presence sensor at the mixer inlet, and the output of the sensor is The mixture is connected to the control input of one stop valve installed in the dispenser in series with the coarse channels

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and accurate dosing, and the second shut-off and control valves are installed respectively in the channels of exact and coarse dosing of the dispenser.

Installing the mixture presence sensor at the mixer inlet and connecting it to a shut-off valve installed in the dispenser in series with the dispensing channel, allows simultaneously with the supply of bulk components to turn on the water supply, eliminating the adverse effect of spraying (i.e. enters the mixer during the lag time), Eliminating the stop valve in the coarse metering channel and the connection between the control unit and the gate valve, replacing it with a connection to the mixture presence sensor at the mixer inlet, In addition, by installing a control valve in the coarse metering channel, they provide continuous water supply with continuous flow of bulk components, while ensuring automatic continuous control of water flow depending on the moisture content of the bulk components fed to the mixer.

The control valve reduces water consumption in steps: if the molding mixture at the mixer outlet is in the low moldability zone, increases with high formability and does not change the flow if the molding mixture at the mixer outlet is in the normal moldability zone. The settings for the period and the pitch of the control valve are selected when configuring the device at the facility (mixer) in the dependence. on the size of the zone of normal formability and time lag. Thus, the change in water flow caused by one step h of the control valve should change the formability at the mixer outlet by an amount smaller than the zone of normal formability, and the period of steps of the control valve should be no longer than the lag time. With such an adjustment of the regulator, auto-oscillations are eliminated in the steady state, and the adjustable parameter does not exceed the limits of normal moldability.

FIG. 1 shows a block diagram of the device, FIG. 2 and 3 - curves corresponding to the change in the forme86

at the output of the mixer F (t), the control Q (t) and the disturbing ACtJ effects, respectively, with the proposed device and without it.

The device consists of a sampling probe 1, a formability sensor 2 containing a vibrating channel with two peaks 3 of different widths (the first is already, and the second is Sh), each of which is equipped with photo sensors 4, two-fold. water metering device 5 supplying water to the mixer 6, with a control valve 7 in the coarse metering channel and a shut-off valve 8 in the exact metering channel and a shut-off valve 9 installed in series with the channels of the dispenser 5, sensor 10 for the mixture loaded into the mixer 6 installed on the conveyor 11 waste mixture, and. output of sensor 10 is connected to a shut-off valve actuator 9, a control unit 12, the input of which is connected to photosensors 4, and the output is connected to a shut-off valve 8 of a dispenser 5, a former 13 high, low and normal formability, whose inputs are connected to photosensors 4, a regulator 14 , the input of which is connected to the output of the actuator 13, and the output - with the drive of the control valve 7.

The device works as follows. The dry mix from the mixer 6 is supplied with a probe tube to the vibrating channel of the sensor 2 and, waking up through the slots 3, blocks the light fluxes of the photosensors 4.

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After switching on the conveyor 11

loading when a mixture appears at its outlet, the mixture presence sensor 10 turns on a shut-off valve 9, and simultaneously with the bulk components a water is supplied through the coarse metering channel through the control valve 7 to the mixer 6. As the mixer 6 is filled, in a time equal to the lag time, a mixture appears at the output of the sampler 1. If the mixture is dry, it passes through the vibratory flow of sensor 2, wakes up through the slots 3, blocks the light flow of the photosensors 4j and the last signals to the control unit 12, which turns on the exact dosing shut-off valve 8, and thus the water is fed into the mixer simultaneously through two channels ..

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Until then, both light streams of photosensors 4, i.e., are blocked. as long as the signal formability is present at the output of the imaging unit 13, the high regulator 14 provides pulse signals to the input of the actuator of the control valve 7, and the latter increases the water flow through the coarse metering channel in steps. The parameter; step steps (gain factor) are selected during the adjustment process and set in the setter. An increase in the flow rate through the coarse metering channel occurs until a signal is established at the output of the former 13, the formability is normal, i.e. the mixture will overlap only the last in the course of the movement of material through the tray of the sensor 2 light flux. Thus, water flow is automatically selected, which continuously stabilizes the normal level of formability at the outlet of sensor 2.

If the moisture content of the bulk components has sharply increased at the mixer inlet (the spent mixture of non-filled casings has entered the mixer), the mixture stops spilling through the slots 3, oh both photo sensors 4 are hidden, the signal that turns off the valve 8 in the exact metering channel leaves the control unit 12, and water is fed into the mixer only through the coarse dosing channel. At the same time, at the output of the imaging unit 13 a signal is formed, the formability is low. As long as the signal formability is not normal at the output of the imaging unit 13, the controller 14 provides the impulse signals to the input of the drive of the control valve 7, and the latter reduces the flow through the coarse metering channel in steps,

Thus, in this case, the regulator automatically sets the water flow rate so that the output of sensor 2 stabilizes the normal level of formability.

FIG. Figure 2 shows the transient curves that control and perturbing effects (curves 15, 16) obtained as a result of the simulation of the analog device on the analog computer of the proposed device with a mixer represented by a periodic link with a delay.

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As a result of the disturbing effect (curve 1b), the formability at the exit of the mixer is reduced (curve 17), and at point a moves from the zone of normal to the zone of high formability. At this point, the control valve (curve 16) begins to incrementally increase the flow in steps until the formability of the mixer and its output to the normal zone (point b). Due to the delay, overshoot may occur (point B), and the formability will go to the low zone. At the point in, the channel of exact dosing is turned off and in addition, the regulator will reduce the flow by one step. At point 4, the formability will go to the zone of the normal 5 and the exact metering channel will turn on. After that, the formability at the mixer outlet will be established in the zone of the normal one. At point 2, formability leaves the normal zone due to a new disturbance. In this case, the regulator, in the same way as steps, works out the mismatch in the direction opposite to the perturbation.

FIG. Figure 3 shows for comparison the curves obtained as a result of a similar simulation of the protomeability adjustment device of the prototype. As can be seen from curve 17 of FIG. 2, in a steady state, after the end of the transition process, the controlled parameter is always in the zone of normal formability, while the steady state in the prototype in FIG. 3 is self-oscillating around the zone of normal formability, which in most cases is unacceptable, since the release of the controlled parameter to the zone of normal formability is equivalent to the marriage of the molding mixture.

Thus, the positive effect created by the inventive device is to increase the yield of the quality mixture by formability by eliminating the self-oscillating steady state, since after the end of the transient process the controlled parameter does not go beyond the normal formability zone.

Claims (2)

1. US patent number 3222376, CL, 22-29 15 1975. 2. USSR author's certificate number 549239, cl. B 22. C 5/04, 1975. f-of §  0op / yeffocfff /, n & znul FSH  f / foffofji g, 0s ii "H F1 / yr as (t) I it) / ff Ii. I 4i t- ffff / if