SU148687A1 - Pulse Position Relay - Google Patents

Description

Positional relays are known, consisting of a positioner and a pneumatic oscillator, designed to oscillate the stem of the pneumatic valve relative to that set by the position controller. However, these relays do not provide stable output oscillations in a wide frequency range.

In the proposed relay, this disadvantage is eliminated due to the fact that the oscillator is made in the form of two chambers connected via an adjustable choke, separated by a sensitive element consisting of two membranes with different effective areas.

The proposed relay provides stable oscillations of the rod with the variable frequency and amplitude relative to the position set by the controller.

FIG. shows the scheme of the proposed pulse positional relay; in fig. 2-oscillator circuit.

I: M11ulz poztsI01; noy relay consists of a positioner and a pneumatic oscillator 2.

The commanded air pressure from the regulator is supplied to the control valve of the positioner through a constant choke 3. Pneumatic oscillations from generator 2 are applied to the same chamber through an adjustable choke 4, as a result of which the air signal with a given frequency and amplitude is applied to the command signal. This leads to the fact that the rod of the executive mechanism will oscillate with respect to a given command with the necessary frequency and amplitude.

The pneumatic oscillation generator consists of two chambers A and B, separated by a membrane assembly, freely moving in the vertical direction. Chambers A to B are sealed and communicated with each other through an adjustable choke 5.

Chamber A communicates with a compressed air supply source through a constant choke 6. At the bottom of chamber A, a ball valve 7 is installed, which, when the membrane assembly is moved down, opens and communicates chamber A with the atmosphere.

No. 148687-2. The membrane assembly consists of two rubber membranes 8 and 9 and a fungus 10. The effective area of the upper membrane 8 is larger than the effective area of the lower membrane 9.

Air to the positioner is taken from chamber A. An adjustable throttle is mounted on the line. The generator works as follows. At the initial moment, when the power is turned on, the air through the constant choke 6 enters chamber L, the membrane assembly is pressed upwards and the ball valve is held by Spring / 2 in the closed position.

Gradually, the air from chamber A flows through an adjustable choke into chamber B, and the time it takes to fill chamber B is determined by the resistance of the choke 5.

When the force on the membrane assembly, created by the pressure of air in the chamber, exceeds the force on the membrane assembly created by the pressure of air in chamber L (due to the difference in effective areas), the membrane assembly moves into and out of the ball valve, communicating chamber A with the atmosphere.

The air pressure in chamber A will drop sharply to atmospheric.

Subsequently, the air from chamber B through the adjustable choke 5 will flow in the opposite direction from chamber B to chamber A and through the ball valve 7 to the atmosphere.

When the pressure in chamber B drops to a value close to atmospheric, the spring closes the ball valve and the air from the supply line will again fill chamber A, and the cycle will again be repeated.

A distinctive feature of such a generator is that it fundamentally cannot be located in a stable state of equilibrium. Moreover, in practice, the oscillation frequency of the generator does not depend on the rigidity and mass of its moving parts.

Indeed, the oscillation period of the generator is equal to the time of filling and emptying of chamber B, which is determined only by the resistance of adjustable throttle 5 and the capacity of chamber B.

If one assumes the presence of an equilibrium state of the generator, then the equality of forces on the membrane assembly on the camera side A and on the chamber side B should be observed (the force from the valve spring is small compared with the forces under consideration).

At the same time, due to the difference in effective -flows of the membrane assembly, the pressure in chamber B will be significantly less than the pressure in chamber A.

Such a state cannot be equilibrium, since in this case air will flow from chamber A to chamber B and pressure in chamber B will increase.

The frequency of oscillation is controlled by the change in resistance of the throttle 5.

The amplitude of the oscillations is adjusted by changing the resistance of chokes 4.

The positional relay is not described, as it is meant for industrial relays.

Subject invention

A pulsed position relay having a positioner and a pneumatic oscillator designed to oscillate the stem of the Pneumatic valve relative to the position set by the controller, characterized in that, in order to provide stable output oscillations in a wide frequency range, the oscillator

made in the form of two chambers connected through an adjustable choke, separated by a sensitive element consisting of two membranes with different effective areas.