SU934229A1 - Level limit indicator - Google Patents

Description

one

The invention relates to instrument engineering and can be used to control and regulate the level of a liquid.

A level indicator is known, comprising a housing with a diamagnetic cover, two magnetic-controlled contacts of the upper and lower limit levels fixed on its outer side, a lever with a float and magnets located on the arms of the lever 1 hinged to the cover on its inner side.

The disadvantage of such a signaling device is the low reliability of operation with level fluctuations caused by repeated closing and opening of the magnetic contacts.

The closest in technical essence to the present invention is a limit level signaling device comprising a float with a magnet, a magnetically controlled limit level switch enclosed in the excitation winding, and an additional switch 2 installed below the limit level.

However, this detector also does not have sufficient reliability in the case of a rapidly changing level or when the magnetic properties of a permanent magnet are weakened.

The purpose of the invention is to increase the reliability of the detector.

 This goal is achieved by the fact that the additional switch is made in the form.

0 winding, excitation, and a normally open contact is connected to a power source in series with the excitation winding, while the permanent magnet is provided with a stop interacting with a mechanical

, 5 actuated limit switch.

FIG. 1 shows the device, a general view; in fig. 2 - circuit diagram in principle.

The detector includes a housing I with a pipe 2 of non-magnetic material. These parts are mounted on the panel 3. Inside the pipe 2 there is a float 4 connected to the rod 5, at the other end of which a fixed magnet 7 is fixed with a stop 8. A guide 9 in which the rod 5 performs a return translational movement, fixed on panel 3 coaxially with pipe 2. Due to this, sticking of the float in the pipe is prevented, since there is always a gap between the float and the inner surface of the pipe. Pipe 2 acts as a quencher for the float 4 in the turbulent circulation of fluid in a controlled reservoir.

A scale (risks) is applied along the rod in the upper part to visually read the readings relative to panel 3 and place the magnet in a position corresponding to the liquid level, when reached, the magnetically controlled switch 10 should operate.

The housing 1 contains a magnetically controlled switch 10 with a winding AND excitation and a terminal two-position additional switch 12 with a mechanical drive 13. A normally closed contact of the limit switch 12 is connected parallel to the excitation winding, and the normally open contact is connected to the power supply in series with the excitation winding 11. A plug is used to connect the device to the actuators of the control or monitoring system.

The device works as follows.

When there is no pressing by the stop 8 of the magnet 7 on the actuator 13 of the limit switch 12, its normally closed contact bypasses the excitation winding 11 of the magnetically controlled switch 10, and the normally open contact disconnects this winding from the power supply circuit of the external source.

A change in the level of the monitored fluid causes the float 4 to move with the bis magnet 7 rod. When the magnet moves relative to the magnetically controlled switch 10 to the position, when the field lines of the magnet 7 pass through the magnetically controlled contacts, this switch operates and a signal is supplied to the control system control or protection. In this case, when the magnet moves relative to the excitation winding 11, an electromotive force is induced in it and the additional magnetic field created by this (when the winding is closed), combined with the magnetic field of the permanent magnet 7, contributes to the operation of the magnetically controlled switch 10.

If, for some reason, the magnetically controlled switch 10 did not operate under the action of the magnet field, then with further movement of the magnet 7 relative to the contacts, the limit switch 12 is activated by the mechanical pressing of the stop 8 of the magnet 7 to the actuator 13 of the limit switch 12. At the same time, the normally closed contact The limit switch 12 opens the closed circuit of the excitation winding 11, and a normally open contact connects this winding to the power supply circuit. At this moment, the magnetically controlled switch is activated by the current of the power supply.

Instead of an electromechanical limit switch, photoelectric switches can be used that are activated when the photosensitive element is darkened or illuminated. In this case, a magnet is used as a damper or reflector, which during movement displaces or reflects the light beam of the light source directed at the photocell. By introducing a mechanically driven end-of-position switch into the device, the control circuit is redundant, the level detector even increases in reliability

when a magnet loses its magnetic properties. In addition, the electrical supply circuits for the elements of the proposed detector and the executive (secondary) organs of the monitoring and control systems are different, as a result of which the possibilities of using various secondary elements are created and, thus, conditions are created to increase the reliability of the device due to the optimal choice of elements. the need to harmonize the parameters of the excitation winding of the magnetic switches and the characteristics of the actuators.

Claims (2)

1. Author's certificate of the USSR 5 No. 420882, cl. G 01 F 23/12, 1972. 2. USSR author's certificate for application No. 2862440 / 18-10, cl. G 01 F 23/12, .05.12.79 (prototype).