Shield type and selection method

Shield definition

The protective cover can prevent dust, chips and hard sand from entering the track, and reduce the damage of the hard-grained foreign matter on the sliding rail surface, which can reduce the influence of the guide rail on the machining accuracy due to the operation deformation, and maintain the machining accuracy of the machine tool!

Shield classification

Universal protective cover

The indoor enclosure must be able to protect the camera and lens from dust, foreign matter and corrosive gases, and at the same time be able to match the installation site to prevent vandalism. Interior guards are typically made of painted or anodized aluminum, painted steel, brass or plastic. If plastic is used, fire resistant or flame retardant type should be used. The shield must be strong enough that the mounting interface must be secure and the window should be clear and transparent safety glass, PMMA or polycarbonate. The electrical connections are designed to be easy to install and maintain.

The camera's operating temperature is -5 ° C ~ 45 ° C, and the most suitable temperature is 0 ° C ~ 30 ° C, otherwise it will affect the image quality, and even damage the camera. The main functions of the outdoor protective cover are sun protection, rainproof, dustproof, antifreeze and anti-condensation. Therefore, the outdoor type shield is generally equipped with a temperature relay, which automatically turns on the fan to cool when the temperature is high, and automatically heats when it is low. [2] The outdoor type cover will be equipped with different equipment such as sunshade, interior/external fan, heater/defroster, wiper, washer and other auxiliary equipment.

First, the outdoor enclosure is highly sealed to prevent rain from entering. At the same time, the inlet should be opened under the protective cover to prevent rainwater from flowing down the cable into the protective cover. A wiper should also be installed in front of the shield to clean up the accumulated rain and dirt in time so that the camera can pass through the glass and capture clear images. A defroster in front of the hood or on the glass melts the window when it is frosted or snowy.

Secondly, the protective cover should be equipped with a heater, which is heated in a low temperature environment to raise the internal temperature of the protective cover to ensure the normal operation of the camera/lens; the internal or external fan can circulate the air inside the cover and reduce the temperature inside the protective cover. In the place where there is less wind and less rain, consider installing a washer so that the window glass can be cleaned at any time with the wiper to ensure image monitoring.

The auxiliary equipment control function of the outdoor type shield has two kinds of automatic control and manual control. For example, the heater/defroster and the fan are automatically activated or turned off by the temperature sensor inside the shield, and like a wiper, a washer, etc. The action is achieved by the controller through the operation of the control device.

Outdoor shrouds are typically made of aluminum, coated steel, stainless steel or plastic that can be used in outdoor environments. The manufacturing material must be able to withstand the irradiation of ultraviolet rays, otherwise the aging phenomenon such as cracking, fading, and strength reduction will occur soon. Stainless steel shrouds should be used in environments where helmets are required to be durable, highly safe, and resistant to vandalism; properly treated aluminum shrouds are also a good performance shroud. There are three treatment methods: polyurethane baking varnish, anodizing , anodizing and painting. Aluminum or steel mutual aid should not be used in corrosive atmospheres; stainless steel or special plastic shields should be used in salt spray environments.

In addition, in order to increase the safety performance of the protective cover and prevent human damage, many protective covers are also equipped with a tamper switch, and an alarm signal will be issued once the protective cover is opened.

There are many types of protective covers in the monitoring system, and generally can be divided into rectangular shields, wall or ceiling shields, ball shields, corner shields, and slope shields according to their shapes.

Protective cover selection method

The protective cover is used to protect the camera and lens, and is divided into indoor and outdoor. When choosing a protective cover, you should pay attention to:

1) According to the installation position, use the indoor or outdoor protective cover correctly. The main function of the indoor protective cover is dustproof, and the outdoor protective cover is protected from dust, and the main function is to protect the camera from working in various harsh natural environments (such as rain, snow, low temperature, high temperature, etc.). Therefore, the outdoor all-weather protective cover not only has a stricter sealing structure, but also has various functions such as a wiper, a spray, a heating and a cooling. This determines that the price of the outdoor shield is much higher than the indoor shield. It should be noted that because the temperature of the four seasons in some areas does not change much, it is within the working temperature of the camera. This can be used to reduce the cost by using a common outdoor shield without a constant temperature function.

2) Use a protective cover of the corresponding size. The size of the shield should be larger than the sum of the camera and lens size, otherwise the camera and lens cannot be loaded.

3) If you choose a protective cover with constant temperature function, you should consider the power supply problem for the protective cover; use a protective cover with a wiper function, if any, you can pass the control, if not, you should consider adding a relay to control.

Rectangular shield

Rectangular shrouds are the most common shields for surveillance systems, and are low cost, rugged, versatile, and aesthetically pleasing. The indoor rectangular shield does not require special anti-rust treatment. Generally, it is painted or anodized aluminum, steel or high-impact plastic such as polyvinyl chloride (PVC), engineering plastic (ABS) or polycarbonate. Materials such as Lexan.

The opening structure of the rectangular protective cover has a top cover detachable type, a front and rear cover disassembling type, a slide pull-out type, a top cover strut type, a hinge suspension type, a top cover sliding type, etc., and various structural forms are installed and overhauled. Easy maintenance.

Ball shield

Ball-type shields are available in both hemispherical and global versions. Most of the outdoor applications use global domes. In indoor applications, hemispheres or global shields are selected depending on the site environment. Global shields are typically mounted with brackets or ceiling mounts, and hemispherical shields are most commonly ceiling mounted and ceiling mounted.

There are three types of plastic domes that provide scene light for the inside of the hood: transparent, coated (translucent aluminum or chrome) and brown. A transparent dome is often used when the dome is only used to protect the camera and lens without the need to conceal the camera's pointing. The transparent dome has minimal light loss (10% to 15%). If you want to hide the camera's pointing for additional security, you will need a coated or brown dome. After the light passes through the coated dome, it decays by about two f-stops (about 75% of the attenuation). The brown dome is relatively good, and the light attenuation is only about 1 f-stop, about 50%.

Unlike the flat plastic or glass used in rectangular shroud windows, the excellent optical quality and light transmission properties of all the domes give the image a degree of optical distortion, and the high quality spherical shield has little optical distortion. The axis of the camera must be perpendicular to the circumscribed plane of the point at which the dome is intersected. The distortion is at least uniform. The main effect is that the focal length of the lens changes slightly. This change is generally not noticeable or not annoying, otherwise the image There will be horizontal or vertical stretching, especially if the pan/tilt is installed in the dome. When the camera is rotated frequently, the distortion of the image is easily found. Therefore, optical distortion is an important indicator for testing the dome.

The outdoor dome is also similar to the rectangular shield. In addition to the sealing protection level to meet the outdoor environment, the interior is equipped with fans, heaters and other devices to compensate for changes in the outdoor ambient temperature. Since the dome can not be installed like a rectangular shield, it is generally equipped with a rain-proof device or the like to prevent excessive rain from dripping through the lower dome to form water stains, and also has a certain shading effect. .

Corner shield

The corner shield is a shield designed for interior corners (the junction of two walls and ceiling). Generally installed in a small room or hall, elevator car, stairwell or prison cell.

The camera is tilted into the corner guard and points to the surveillance area under the ceiling. The viewing window of the shield is perpendicular to the lens axis. There is also a special angle cover. The camera is pointed above the ceiling in the protective cover. The front of the camera is equipped with a front reflector, which can reflect the scene under the ceiling to the camera. The position of the mirror can be adjusted up and down, left and right. Change the field of view of the camera. Since the scene image of the mirror is an inverted image, the camera must be installed upside down.

Embedded shield

The built-in shield is usually on the ceiling and wall, partially exposed and partially enclosed. This type of shield is suitable for applications where a more concealed installation is required.

Special purpose shield

Sometimes, the camera must be installed in a highly harsh environment, not only like a general-purpose outdoor protective cover, but also has the characteristics of high sealing, high cold resistance, heat resistance, sand resistance, rain and snow resistance, as well as anti-smashing, anti-shock and anti-corrosion. It even needs to be used in an explosive environment, so special shields with high safety must be used.

High security shield

This type of protective cover is also commonly referred to as an armored protective cover. It is suitable for installation in prisons or other places where it is easily damaged by politics. It is made of 0.134 inch thick 10 gauge welded steel with 1/2 window material. Inch thick, abrasion resistant polycarbonate. The shroud can withstand the impact of hammers, stones or certain bullets without being pierced or cracked. The casing is closed with a large mechanical lock and should not be taken apart.

Special protective cover for elevators

This is a shroud designed for use in elevators and hardened. The shroud is made of stainless steel and has a tamper-proof function. The lead-in wire is on the back of the shroud and is generally inaccessible to the guard; the window is a wear-resistant polycarbonate. The best orientation of the camera is 45° angle to the wall perpendicular to each other, and at the same angle of 45° to the ceiling plane. When the horizontal angle of view exceeds 90° (wide angle), the entire car can be observed. Any dead ends.

High dust shield

The high dust shield is similar to the universal shield, except that it is completely isolated from the outside world and can be used in sandy and dusty environments. It can also be used in corrosive environments if stainless steel is used. The window material is tempered glass for maximum safety, corrosion and wear resistance. In order to avoid excessive temperature inside the hood, a sun visor and a fan are often provided, and the internal temperature can be maintained by a filtered external compressed air source.

Explosion-proof shield

The explosion-proof protective cover is the same as the explosion-proof pan/tilt, and must also comply with the safety regulations for explosion-proof and dust-proof explosion electrical equipment. The material used is the same as the gimbal, usually a thick-walled all-aluminum structure or a stainless steel structure. The diameter of the explosion-proof protective cover is generally 6", 8", 10", etc. The inlet line excuses are equipped with explosion-proof seals. If the space inside the explosion-proof protective cover is accommodated in the camera and lens assembly, it will be avoided to re-create the explosion-proof casing. The troubles.

High pressure shield

The high pressure shield can be used in hazardous atmospheres. The requirements of the National Fire Protection Association can be met by filling the casing with pressurized inert gas. The shroud is made of corrosion-resistant thick-walled aluminum with a 1/2-inch thick tempered polished glass. The shroud was filled with low pressure nitrogen at a pressure of 15 psi. Nitrogen is completely inert and avoids explosions caused by electrical sparks or electrical faults in the shroud. An O-ring seal for sealing is placed between the shield body and the outer cover. All electrical connections are routed through a hermetic seal.

High temperature shield

The high temperature shield refers to the shield that protects the camera and the lens from working normally when the camera is used in an environment where the temperature is greater than 40 ° C and the natural convection and radiation heat transfer cannot reach the normal working temperature. For high temperature environments, the shield should be specially cooled and cooled. Common cooling systems include air cooling systems, water cooling systems, semiconductor cooling systems, as well as vortex cooling, Freon, and ammonia refrigeration.

The air-cooling system still uses the principle of air flow cooling. The forced air is used to send the coolant (purified air) into the shield or the shield compartment to remove the heat from the shield for cooling purposes. The forced air cooling system has both direct cooling and indirect cooling.

When the ambient temperature is greater than 80 ° C (such as heating furnace, steelmaking furnace, etc.) * forced air cooling can not control the temperature rise, forced water cooling system can be used. The thermal conductivity and specific heat of water are both larger than that of air. Therefore, compared with air cooling, the thermal resistance of the heat exchanger is greatly reduced, and the heat exchange efficiency is improved. The shield contains a built-in water jacket that effectively isolates the camera and lens from the outside environment. Depending on the application, the material can be aluminum or stainless steel. A fan is arranged inside the shield to circulate air in the cover to improve heat transfer efficiency. There are two basic types of forced water cooling systems, one is water-cooled and dustproof. The structure is relatively simple, without alarm device and air filtration system. The lens can use fixed focus or zoom lens for 80 °C environment. The other is a high temperature type in the furnace, which can be used in environments with temperatures up to 1600 °C. The structure is complex. The whole system has alarm, air filtration system, maintenance shutter and high temperature automatic exit system.

High-temperature automatic exit system When the camera cooling function is detected to be faulty, the electro-pneumatic control exit device will automatically withdraw the camera from the combustion chamber to avoid camera and lens damage. The system is normally started when: (1) the temperature of the cooling water at the top of the probe exceeds a predetermined value (≤ 40 ° C); (2) the compressed air failure or pressure drops to a predetermined value (≤ 0.4 Mpa); (3) the air hole failure or pressure at the probe Drop to a predetermined value (≤ 0.02 MPa); (4) water flow is less than a predetermined value (≤ 6.8 liters / min); (5) air or water monitoring line interruption; (6) main power supply voltage failure; (7) control device or control center room to issue an exit command.

Semiconductor cooling systems, also known as thermoelectric cooling, are cooling methods based on several different semiconductor effects. When two different conductors form a galvanic couple and a direct current is applied, endothermic and exothermic phenomena occur at the corresponding joints of the galvanic couple. This effect is very similar in metals, but is more pronounced in semiconductors. The semiconductor refrigeration has no mechanical rotating parts, and has the characteristics of no noise, no vibration, long life, simple structure, easy installation, high reliability, no coolant, and the degree of cooling can be adjusted according to the current. The disadvantage is that the consumption law is higher. Large, must use direct current, the working current is large.

Mechanical protective cover

Mechanical protective cover: The protective cover is divided into a steel plate cover and an organ type protective cover (nylon cloth + PVC plate support). Steel plate and stainless steel protective cover, with good sealing, anti-iron filings, anti-cooling liquid, anti-tool accident, durable and beautiful appearance. The organ type protective cover adopts German advanced technology, external German nylon cloth, and PVC board support. It can resist oil, corrosion, hard impact and deformation, long life, good sealing, stable walking, strong and durable, etc. Protection of various mechanical confidential parts, extending the service life of important mechanical parts and machinery.

Machine tool cover features:

★ This kind of shield has the characteristics of not being afraid of foot, hard object collision, deformation, long life, good sealing and light operation.

★ The shield has a long stroke and small compression. The ratio of length is 1:10.

One of the most advanced forms of this folding shield, it can make up for the problems that can not be solved by various shields. This type of shield has a leading position in the world.

★ This product uses special materials, coolant resistance, oil proof, grinding wheel and iron xiao, etc.

★ The protective cover has the advantages of long stroke and small compression;

★ The bellows speed of the shield can reach 200m/min;

Roller shutter

☆ In the case of small space and no need for strict protection, the roller blind cover can replace other shields. Can be installed horizontally, vertically or in any mixing direction. It is an ideal protective component because it takes up less space, has a large stroke, is fast, has no noise, and has a long life.

☆The structure of this product is mainly composed of outer casing (stainless steel plate, cold plate), spring shaft, driven shaft, scraping tongue, nylon fiber cloth (three anti-cloth), etc., with adjustment device, elastic adjustable, single spring, double Two kinds of springs are available for users to choose. The protective belt can be divided into two types: box type and bracket type.

Steel shield

★ Suitable for high-speed motion machine tool guide rail protection is stable and no vibration noise. (The speed can be operated normally at 80m/min)

★ Each guard plate is pulled in parallel at the same time, and simultaneously retracted in parallel, running freely.

★It will not make the guard board disjointed, there will be impact sound, which is both beautiful and improves the service life of the guard board.

★ On the basis of the original sealing strip, a layer of stainless steel cover is added to prevent the high temperature burnt strip of iron filings from rubbing into the rail surface and pulling the guide rail.

★ This device not only protects the service life of the guard plate, but more importantly guarantees the precision of the machine tool. It is worthy of the “protection god” of the machine tool.