SU1650447A1 - Control of steam-curing of concrete products - Google Patents

Abstract

The invention relates to a technique for regulating the heat treatment regime according to a predetermined program, can be used to control the heat and moisture treatment of concrete and reinforced concrete products and improves the quality of control. The device includes a temperature sensor 1 installed in the heat treatment chamber 2, a measuring bridge 3, an error amplifier 4, an actuator 5, a valve 6, an integrator 8, a differential amplifier 9, a reset unit 10, a trigger 11. a signaling device 12. a generator 13, a pulse counter 14 , OR 15 items, analog switches 16, adjustable resistors 17, 18, and 19, voltage source 20, and a start button. 3 il. SL C a (L o XI

Description

Thebes /

The invention relates to a technique for controlling the heat treatment regime according to a given program and can be used to control the heat and humidity treatment of concrete and reinforced concrete products.

The purpose of the invention is to improve the quality of control.

FIG. 1 shows a block diagram of the device: FIG. 2 is a diagram of a differential amplifier and integrator; Fig. 3 shows time diagrams of the device operation: the state of the Start button (a), the voltage at the trigger output (b), the output signal of the pulse generator (c); output signals of the pulse counter (r-z); pulse counter overflow output (s); differential amplifier output (k); integrator output (l).

The device includes a temperature sensor 1 installed in the heat treatment chamber 2, a measuring bridge 3, an error amplifier 4, an actuator 5 of a valve 6 located in pipe 7, an integrator 8, a differential amplifier 9, a reset unit 10, a trigger 11, a signaling device 12, a generator 13 , counter 14 pulses, n-1 elements OR 15, n + 1 keys (analog) 16, where n is the number of heat treatment sites, the first 17 and second 18 adjustable resistors, the moving contacts of which are mechanically interconnected, n + 1 third adjustable resistors 19, voltage source 20 and Start button 21.

The integrator 8 and the differential amplifier 9 (FIG. 2) can be performed according to known schemes based on operational amplifiers. The integrator 8 includes an operational amplifier 8-1, a capacitor 8-2, and a constant resistor 8-3. In this case, a capacitor 8-2 is connected between the output of the amplifier 8-1 and its inverting input, to which the first and second outputs of the third potentiometer are also connected, the third output of which is connected to the integrator's input through a fixed resistor 8-3. The non-inverting input of amplifier 8-1 is connected to the common power supply bus, and the output is connected to the output of integrator 8. Differential amplifier 9 is formed by operational amplifier 9-1 and fixed resistors 9-2 -9-5.

 The device works as follows.

When the device is turned on, the reset unit 10 generates a pulse that sets the trigger 11 to the logical G state, which causes the detector 12 to indicate the end of the heat treatment process, the generator 13 does not work, and the counter 14 is reset. The outputs of all logical elements. OR 15 voltage corresponds to a low logic level.

Therefore, the analog switches 16 are locked and the voltages at both inputs of the differential amplifier 9 are zero. The voltages at the outputs of the differential amplifier 9 and integrator 8 are also equal

to zero.

As a rule, the temperature regime for processing concrete and reinforced concrete products can be represented by a set of n-final number (usually small)

linear plots. According to the number n of the outputs of the counter 14, the processing program is divided into n equal segments and the temperature value at their boundaries is determined. The first adjustable resistor 17 set the frequency of the generator 13 is equal to

P

f

Tpr

where TPR is the duration of the heat treatment process.

Mechanically connected to the mobile

the contact of the first adjustable resistor 17 movable contact of the second adjustable resistor 18 is set in this position, which corresponds to

the time constant of the integrator 8, is equal to the pulse period of the generator 13:

g TPE

P

The resistance of the adjustable resistor 18 is equal to

,

. Where C - capacitor capacity 8-2; RO is the resistance of the resistor 8-3.

The movable contacts of the adjustable resistors 18 at the inputs of the analog switches 16 set the voltages corresponding to the limiting temperatures 0 of the graph sections.

Let measuring bridge 3 together with sensor 1 convert temperature in chamber 2 to voltage

UM (t) Ki (), where t is the temperature in chamber 2;

tc is the ambient temperature; Ki is a constant coefficient. Then, taking into account the gain factor Ka of the differential amplifier 9, the voltage at the moving contact of the adjustable resistor 19 will be

UM (Q) -U (Q) Kifl

K2K2

moreover, the voltage on the engine of the potentiometer must match the ambient

and - | a.

For convenience, the moving contact scales of adjustable resistors 19 can be distributed in units of temperature, the moving contact scale of adjustable resistor 17 in units of process time, and the values of gi for various heat treatment programs are tabulated.

Adjustable resistors 17 and 19 are supplied with a stable voltage of source 20, equal to

Uct

Ki K2

She is

where $ cax is the maximum temperature that the program thermostat performs.

Then chamber 2 is loaded with semi-finished products and the Start button 21 is pressed briefly. Trigger 11 is reset to logical O, alarm 12 indicates an incomplete heat treatment process, generator 13 and counter 14 are enabled. Generator 13 output with frequency f causes the counter content to rise 14. At the same time, at the 1st moment, the pair of keys 16 and 16 (1 + 1) is turned on, and the inputs Ui and Ui-n are supplied to the inputs of the differential amplifier 9. The output voltage of amplifier 9 is equal to UA, K2 (Ui - Ui +1) UM fl) –C, (fl +1).

The output of integrator 8 is described by the equation

"-Ifcf

Un, (t)

+ Uni (0).

where t is the current time between two switches of the counter 14 t t-l g.

The initial value of the output voltage of the integrator 8 after the 1st switching of the counter 14

Un ((0) Um-i {r)

J-1

-K2 (and | -io-in (B1),

so

u, M-u ff + tj | Wy + tl, No.

The output signal of the integrator 8 is compared by the error amplifier 4 with the output signal of the measuring bridge 3. In the presence of a mismatch of these voltages, the corresponding output signal of the error amplifier 4 is affected

to an actuator 5 that moves the valve 6 of the steam line in such a way that the steam consumption changes in the direction of decreasing the error. Wherein

UM t + UM (60

0

five

e

five

0

five

0

five

or

0

0-g

Thus, the temperature regime in chamber 2 corresponds to a given processing program, represented by a set of linear sections. In the case of f + 1 $ they have

five

the temperature increase area, at $ +1 f, the isothermal holding section, and at and, the temperature decrease section.

At the end of the heat treatment process, a pulse appears at the exit of the overflow of the counter 14, resetting the trigger 11 to the initial state. The detector 12 thus indicates the completion of the heat treatment process. The operating personnel releases the chamber 2 for processing the next batch of products, after which the process can be loaded by pressing the Start button 21.

The use of analog switches, adjustable resistors, a differential amplifier and an integrator, as well as OR logic elements in the device ensures program development without the use of a memory block, which eliminates the need for a microprocessor programmable memory chip and qualified personnel for its maintenance.

The use of a trigger and a reset unit in the device eliminates the need for manually setting the initial state of the device and the possibility of destruction of products s as a result of thermal shock when the device is turned on.

The proposed device reduces the cost of working time for operational intervention in the course of the process and the requirements for the qualifications of service personnel.

Claims (1)

Invention Formula A process control unit for the heat treatment of concrete and reinforced concrete products, comprising a temperature sensor in the product heat treatment chamber, connected to the input of the measuring bridge, the output of which is connected to the first input of the error amplifier, the output of which is connected to the actuator of the steam line damper, a start button, a signaling device, a generator, one of the outputs of which is connected to a counting input of a pulse counter, characterized in that, in order to improve the quality of control, it is equipped with a reset unit, a trigger, a differential amplifier, an integrator, first and second adjustable resistors, moving contacts mechanically connected between me, n-1 elements OR, where n is the number of heat treatment areas, n + 1 analog keys and third adjustable resistors and voltage source, with the reset unit, the Start and exit button overflow pulse counter connected to the corresponding inputs of the trigger, the output of which is connected to the inputs of the detector, generator and to the reset input of the pulse counter, one of the inputs of the first and n-And analog keys and inputs of elements OR are connected to the corresponding inputs of the pulse counter, the outputs of the elements OR are connected to one of the inputs of the remaining analog switches, the moving contacts of the third adjustable resistors are connected to other inputs of the analog switches, the corresponding outputs of which are connected to the corresponding inputs of the differential amplifier, the output of which is connected to one integrator input, the other inputs of which are connected to the terminals and the moving contact of the second adjustable resistor, the integrator output is connected to the second input of the usi Itel misalignment, the moving contact of the first adjustable resistor is connected to another output of the generator, one of the terminals of the first and third adjustable resistances is connected to the source tension