SU781417A1 - Pneumatic pulse generator - Google Patents

Description

one

The invention relates to pneumatic automation, relates to generators of pneumatic signals made, for example, on USEPA elements and used for solving control problems of 5 technological processes, and can be used in the chemical, pharmaceutical and vitamin, and other industries.

Pneumatic generators are known, used in control devices, where to form upward and downward sawtooth branches; the signal is used separate devices or nodes 13 15

The disadvantages of the generator are complexity and unreliability (the range of variation of the pneumatic signals in such devices is limited).

The closest technical solution to the present invention is a pneumatic pulse generator of a pulse-width modulator containing a front shaping unit implemented on two following chambers, two throttles and pneumatic capacitance, a signal comparison unit connected to the signal reference channel and consisting from relay and reference element, and AOR unit

switching performed on a three-membrane relay f2.

The generator lack is limited frequency range in the low frequency range.

The aim of the invention is to increase the frequency range of the generator.

The goal is achieved by connecting the channel setting the lower boundary of the zone of change of the sawtooth signal to the second input of the switching unit.

The drawing shows a diagram of the proposed device.

The generator contains a sawtooth signal forming unit 1 performed on a five-membrane comparison element 2, throttle 3 and pneumatic capacity 4, a signal comparison unit 5 consisting of a comparison element 6 and a relay 7, and a switching unit 8 containing a relay amplifier 9 and two relays 10 and 11.

The generator works as follows.

Channel 12 and 13 of the reference speed and the sign of the signal change are connected to the first 14 and BTOpo viy 15 outputs of the switching unit 8. The inputs of the comparison unit 16 are connected to the output of the unit 1, the third output 17 of the unit. 8 commutations and with channels for setting the upper 18 and lower 19 borders of the zone for changing the saw-tooth signal. The first input 20 of the switching unit 8 g is connected to the output of the comparison unit 5. The second input 21 of block 8 podklk) whose channel to set the 19 lower limit. The channel is supplied with the setpoint pressure (P) from the setpoint, channel 12 is connected to the atmosphere and into the chamber 22 of the element 6 cf; external pressure PQ is supplied to the upper setpoint pressure from the second setter.1, ...

Since it remains unchanged,. then a constant differential pressure is established on the throttle 3. Consequently, the weight flow rate of air through the choke 3 is also constant, and the pressure P-signal of the sweep in the core of the tank 4 linearly increases. Sig-20 P P is supplied to the chamber 23 of the comparison element 6, Until the signal P is less than the upper reference pressure, j, the output of the element b is connected to the atmosphere, the nozzle in the lower 25 chamber is open and the nozzle in the upper chamber is closed . At the time of comparison. pressure P with a reference pressure (RLB) at the output of element b, a pressure signal arises. This signal is amplified by -jn with a relay-amplifier 9 and fed to the output of the Pjijy generator and to the chambers corresponding to the relays 7, 10, 11. Under the action of this signalp, the relays are diverted, and then channel 13 is connected to the atmosphere, to the channel 12 pressure is applied fjad, to the cell of the element

.. § -....- :: signal RzaA. RO.N

In element 2, the top air from tank 4 is vented to atmosphere

through the choke 3 and the nozzle in the upper 40 chamber of the element 2, and since a constant overpressure is established on the choke, the air flow through the air; e.: it remains unchanged, and let

capacitance 4 is reduced linearly ..-. ,

) Meyt. coincidence of the sweep signal P with RODD element b is thrown and its output is connected to

the atmosphere. At the output of the generator 1B, there will be zero, the circuit comes to its original position and the formation of the next pulse begins. Thus, in the proposed pneumatic pulse generator, connecting the channel for setting the lower zone of the sawtooth signal to the second input of the switching unit allows increasing the range of variation of the oscillation frequency in the low frequency region due to the joint change in the lower limit of the oscillation zone of the sawtooth signal (lower reference pressure yal). and the inclination angle of the leading and trailing edges of the saw-tooth signal by varying the pressure differential across the throttle of the front-shaping unit equal to Pjjg. .

Claims (2)

1. Berends T.K. and other elements and schemes of pneumatic automation. 1U6b, s. 111 fig. 78a. 2. Proceedings of the TSNIIK, M., 1966j p. 197 fig. 3 (prototype).