Bellows for sensorsThe type load cell, also known as the bending beam structure sensor, adopts the metal sensor with bellows welding and sealing form. If the sensor cannot be effectively and reliably sealed in a very harsh environment, the sensor will fail in a short time. In order to ensure that the sensor can work normally and stably for a long time in this environment, many companies generally adopt the full sealing method of bellows for metal sensors. This completely sealed method is a very effective solution to ensure sensor reliability and long-term stability.

The bellows for metal sensor is an important component of the sensor, which plays a role of sealing and protection, and is one of the commonly used elastic sensing elements. It is an axisymmetric cylindrical thin-walled tube shell with multiple transverse corrugations. Due to its geometric characteristics, it can be elongated or shortened along the axis under the action of pressure or axial force to produce large displacement or output concentrated force. If a transverse force generating a bending moment is applied to it, a corresponding displacement can be generated in the axial plane. The typical structure of the bellows for the sensor in the micro switch is composed of a metal shell, a bellows for the sensor, a base, a button, a push rod and a momentary mechanism of the micro switch. The two ends of the metal sensor bellows are respectively welded with the button and the base, the base and the sleeve are welded to achieve sealing, and the sleeve and the main body are welded to achieve sealing. The sensor with bellows instead of the traditional rubber sealing ring structure, can achieve axial dynamic sealing, to achieve the plunger drive micro switch sealing function.

Compared with the traditional micro switch, the structure has the following characteristics:

(1) The regular micro switch body and shell are usually made of plastic, and the packaging process is adhesive; the base and body of the high-temperature sealed switch are made of metal materials. According to the different materials and structures, the packaging of each component uses Different welding processes.

(2) The driving mechanism is a device that the micro switch transmits the external force or stroke to the internal mechanism of the switch to realize the dynamic sealing of the switch driving mechanism. This is the structure and process difficulty of high temperature micro switch, and it is also its core technology.

(3) The terminal of the switch is connected to an external port. Traditional non-sealed microswitches use resin or plastic sealed terminals; temperature-sealed microswitches should consider the sealing performance and insulation performance between the metal substrate and the glass or ceramic sealing process.

The failed portion of the hose is located at the metal hose weld ring near the end of the piping system interface. The failure phenomenon is that the stainless steel mesh sleeve and the bellows are completely broken. The faulty metal hose is installed between the fourth stage exhaust port of the air compressor and the piping system. The working environment is the engine room of the ship, the ambient air is the hot and humid marine atmosphere, and the surface of the pipeline is often condensed water. The hose is broken in the installed part, and the break occurred during the pressurization of the compressor. When the fracture occurs, the two-layer stainless steel mesh sleeve of the hose is first broken, and then the bellows is stretched and broken. Check whether there are visible rust spots at and around the fracture, and there are also rust spots at the fracture of the stainless steel mesh sleeve. The broken surface of the bellows is like a cut caused by tension fracture.