Analysis of the Working Process of Piston Vacuum Pressure Switch

The piston-type vacuum pressure switch is an automated device that uses a piston as a pressure-sensitive element and controls the on-off of the circuit by sensing changes in vacuum pressure within the system. Its working process can be divided into four stages: pressure sensing, mechanical transmission, contact switching, and circuit control. The following is a detailed analysis:

Pressure perception stage

The core component of a piston-type vacuum pressure switch is the piston, which is directly connected to the system under test and senses the changes in vacuum pressure within the system. When the vacuum pressure within the system changes, the piston will be subjected to pressure. For instance, in a vacuum system, as the vacuuming process of the system proceeds, the internal pressure gradually decreases, and the piston will be affected by the difference between the external atmospheric pressure and the internal vacuum pressure of the system. If the pressure within the system increases (the vacuum degree decreases), the inward pressure exerted on the piston will increase. Conversely, if the pressure within the system decreases (the vacuum degree increases), the inward pressure exerted on the piston will decrease.

Mechanical transmission stage

The piston is connected to a set of mechanical transmission mechanisms. When the piston is subjected to pressure and moves, it will drive the mechanical transmission mechanism to move. Common mechanical transmission mechanisms include levers, springs, etc. The displacement of the piston is amplified or the direction of the force is changed by the lever, while the spring serves to balance and reset. For example, when the piston moves inward, it will push one end of the lever, and the other end of the lever will exert a force on the microswitch. The spring will deform according to the displacement of the piston. When the system pressure returns to normal, the elastic force of the spring will restore the piston and the mechanical transmission mechanism to their initial positions.

Contact switching stage

The movement of the mechanical transmission mechanism will eventually act on the microswitch, causing the contacts of the microswitch to switch. Microswitches usually have normally open contacts and normally closed contacts. When the system pressure reaches the set action pressure value, the mechanical transmission mechanism will overcome the elastic force of the spring inside the microswitch, causing the normally open contact to close and the normally closed contact to open. When the system pressure returns to the set reset pressure value, the mechanical transmission mechanism resets under the action of the spring, and the contacts of the microswitch will also return to their initial state, that is, the normally open contacts are open and the normally closed contacts are closed.

Circuit control stage

The switching of the microswitch contacts will directly control the on and off of the circuit. In industrial production, piston-type vacuum pressure switches are often used to control the operation of vacuum equipment. For instance, in a vacuum packaging machine, when the vacuum degree inside the packaging machine reaches the set value, the contact of the vacuum pressure switch closes, connecting the control circuit and causing the packaging machine to stop vacuuming and enter the next working stage. When the vacuum degree inside the packaging machine drops to a certain extent, the contacts of the vacuum pressure switch open, cutting off the control circuit, triggering an alarm or starting the backup vacuum extraction equipment to ensure the stability of the packaging process and product quality.