How does pressure switch work?
13 Apr '22, 06:36
Pressure switches are designed to automatically control pressure in systems by opening and closing the electrical control circuit. The principle the device operation is based on balancing the pressure force on the bellows by the force of elastic deformations of the adjusting spring. The movement of the movable end of the bellows under the action of pressure through the lever closes or opens the contact device of the relay.
The relay is a scaleless device with a constant non-adjustable differential. The entire mechanism is mounted on a base and covered with a lid with a sealing gasket. The relay consists of a bellows assembly, a transfer-tuning mechanism and a contact device.
The bellows assembly consists of a body with a connecting fitting, a bellows 2 with a bottom and a stem 9. The transmission and tuning mechanism includes a lever 4, a tuning spring 5, a screw 6 and an lever stop 3. The control device is a microswitch 8. The relay closes the contacts when the pressure drops to the set value and opens when the pressure rises by the differential value. When the pressure in the chamber 1 decreases, under the action of the spring 5, the lever 4 rotates around the axis counterclockwise. When the medium pressure drops to the value specified by the setting, the right end of the lever will release the stem of the microswitch 8, the contacts of which are automatically closed. With an increase in pressure in the chamber, the bellows 2 is compressed, and its rod 9 moves up and turns the lever around the axis clockwise, overcoming the resistance of the spring. When the pressure of the medium rises by the value of the differential, the lever will press the end of the micro switch rod, opening the contacts. The pressure force acting on the bellows 2 is balanced through the bellows rod and the lever 4 by the force of elastic deformation of the cylindrical spring 5. At one end, the spring rests against the lever 4, and at the other end against the nut of the adjustment screw 7. By turning the screw 6, the relay is adjusted to the required response pressure.
13 Apr '22, 08:34