Where there are machines, there is danger; if there is danger, people need to be protected. This is not only the stipulations of laws and regulations, but also the responsibilities and obligations of the company. After nearly 120 years of development, plant and machine safety protection technologies have been developed to form many international/national standards, and many safety protection products that meet and meet these standards have emerged. Among these safety standards, there are representative standards such as EU EN series standards, US ANSI standards, and IEC international standards. For machines only, these standards are agreed: The machine's state of motion is more of a threat to people than it is at rest. Therefore, most of the machine safety protection technologies are to stop the machine as soon as necessary, reduce the risk, and minimize the loss of materials and human injuries. Common safety protection products include safety switches, safety door (lock) switches, safety hinge switches, safety magnetic switches, safety edges/carpets, safety cables, safety foot switches, and various other switches, as well as safety relays, safety PLCs, AS-I safety bus system and its components and other complex electronic products.

Safety carpet protection system

Among various kinds of switch protection components, the safety carpet is one of the special protection switches. It has the characteristics of large protection scope, low price, long life, safety, reliability, freedom of installation and convenience, etc., which makes the on-site channel unimpeded and convenient for transportation and feeding. Widely used. At present, safety carpet has been widely used around the robot unit (Figure 1), laser welding and cutting equipment, packaging machines, wood processing machinery, stacking and packaging machines, raw material processing, metal bending equipment and stamping equipment (Figure 2). And other places.

[center] Figure 1 Around the Robot [/center]

[center] Figure 2 Around the Press [/center]

SMS3 series safety carpets, as safety switching elements, must be connected with safety relays and laid on dangerous machinery, equipment and other surrounding grounds to achieve the warning of dangerous areas and the protection of people and machinery. The working principle is: When a person steps on a carpet, the carpet senses pressure changes and outputs a switch signal. The signal passes the detection of the safety relay, and then amplifies and outputs a switching signal, which directly cuts off the power supply of the machine and equipment, thereby realizing the protection of humans and machines. Due to the special role of the safety carpet, safety must be achieved throughout the entire control process. Therefore, continuous detection of safety relays is required to ensure that personnel can be safely protected when entering dangerous areas. The safety carpet is a sensitive type of pressure switch element. Its manufacturing standard complies with the European standard EN1760-1, and it is used in conjunction with the safety relays in the AZR series. It can greatly improve the reliability and safety level standards and meet the safety level 3 requirements in EN954-1.

Safety carpet structure features

The SMS3 type safety carpet (see Figure 3) is a contact type switch that is pressed and contacted. The working principle is simple, and the manufacturing process and structure are relatively complicated. It uses a mold to fill the hot melt plastic once it is formed, so it is maintenance-free. It is waterproof, oil-proof, anti-mineral and phyto acid, petrochemical, organic solvents, etc., with protection class IP67. Specially designed non-slip surface prevents the operator from slipping. The upper and lower two layers of elastic steel plate can withstand 2000N/cm2 pressure, but the operating force is very small, only 6 N/cm2. Only 12mm thickness, coupled with a special fixed edge, can achieve 100% response area, and can prevent people from tripping. The 6m long sol-sheathed lead allows the user to freely splicing a variety of shapes and sizes up to 20 m2. The many advantages make it able to meet almost any working environment, even wet, oily, corrosive and bad sites. The structural section of the safety carpet is shown in Figure 4, where:

1 - anti-slip surface
2 - upper electrode plate
3 - Edge Department
4 - conductive strip
5 - Compressible elastic insulating strip
6 - lower electrode plate
7 - carpet floor

[center] Figure 3 SMS3 Security Carpet [/center]

[center] Figure 4 Structure of safety carpet [/center]

Safety distance calculation

The use of security carpets requires consideration of how much area should be laid in a dangerous area that needs protection, so that it is safe and economical. Here, we need to introduce a commonly used standard-EN999. EN999 is a standard related to safety distance. It mainly introduces the method of defining the position of the safety protection device in combination with the human body movement speed in the machine safety.

For a security rug, the potential lag of the carpet and the delay caused by the control system's response speed must be taken into consideration for potential threats to people entering the hazardous area, especially if the person quickly enters. In other words, when designing the safety carpet, not only the installation position of the carpet but also the laying area of ​​the carpet should be determined to ensure that the person steps on the carpet and the machine is in a safe state before the person reaches the dangerous machine. The use of SMS3 series safety carpets for regional security protection must be designed and laid down in accordance with the requirements of safety standard EN999, so as to fundamentally prevent personnel from crossing the carpet into the danger zone, or to escape the carpet and approach the danger zone. In this standard, some safety distance calculation formulae when using different safety protection switches are given. For the safety carpet, after simplified:

S=K(T1 +T2)+ 1200
among them,
S - The minimum safety distance, ie the minimum distance from the machine to the carpet on the danger point of the machine. Unit: mm.
K - the empirical coefficient, usually derived from the speed of movement of people and their limbs, generally takes 1600. Unit: mm/s.
T1 - Total response time of carpet switch and safety relay system. Unit: s.
T2——The total response time of the machine system, unit: m.

With the use of a security rug, only in accordance with the EN 999 standard, a safety carpet protection system can be installed to completely eliminate potential safety hazards from the standpoint of the safety distance that can be measured in all directions that can enter the danger zone. That kind of safety carpet as long as there is no matter the size or area; or not equipped with safety relay practices and ideas are dangerous.

Safety carpet precautions

SMS 3 series safety carpets are pressure sensitive components. They must be careful during transportation and use. During handling and laying, they should be handled in a flat and flat manner to prevent them from dropping in high places and being thrown or thrown by humans. Before and after laying, inspect and clean the floor to be laid to ensure that the floor is clean, smooth, smooth and free of hard protrusions and foreign objects. During use, make sure that no sharp hard objects have landed on the carpet and clean it regularly. All of these contribute to the rational use of carpets and extend the lifespan and service life of safety blankets.

As long as the design is standardized and the safety carpets are properly laid and used, the road to safety is at its feet. With the advancement of technology and the improvement of the degree of automation and complexity of the machine, the safety protection technology will continue to develop and progress in accordance with the needs. At present, people have developed and designed safety carpets in the form of photoelectric, resistive and other safety carpets. There will be more and more applications. Because, taking the road to safety is our eternal pursuit.