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Horizontal tempered glass production line

The horizontal tempered glass production line is an equipment system that transports glass horizontally and tempers the glass through heating and rapid cooling processes.

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Horizontal tempered glass production line refers to a production line in which the glass is heated, formed, quenched and other processes are carried out on a horizontal roller to finally complete the tempering of the glass flat surface, single curved surface, double curved surface, folded surface, S-shaped surface, etc.The production process of horizontal tempered glass is shown in Figure 3-15

The horizontal tempered glass production line consists of a loading platform, a heating furnace, a bending device, a cooling device, an air supply system, an unloading platform, a control system, and other equipment. There are two types of horizontal reciprocating tempered glass production lines and horizontal continuous tempered glass production lines. The horizontal reciprocating tempered glass production line refers to the glass making horizontal reciprocating motions in the heating and cooling parts, which can save equipment investment and equipment space. The horizontal continuous tempered glass production line refers to the production line where the glass runs continuously in one direction from the loading platform to the unloading platform. Relatively speaking, the continuous production line has a large output, occupies a large area, and has a large investment.

(1) Loading/unloading platform The loading platform is at the beginning of the tempered glass production line. This part can be connected to the pre-treatment washing and drying machine. Its other end is connected to the furnace entrance of the heating furnace. The loading platform is mainly composed of a rubber roller surface, a transmission sprocket, a glass table, an automatic rotating wheel, a motor and a reducer, a frame, etc.

The unloading platform is at the end of the tempered glass production line. It is mainly composed of an asbestos rope winding roller, a transmission sprocket, a glass receiving platform, an automatic rotating wheel, a motor and a reducer, a frame, etc.
The loading platform and the unloading platform are respectively equipped with photoelectric switches and counters to measure and control the glass travel distance. The programmable controller used for the loading/unloading platform conveying control measures the length of the glass through the photoelectric switch and the counter, and makes this length prepare for the heating operation time, operation speed, and output time of the glass in the heating zone. When the glass initial point is measured, the heating furnace door can automatically calculate and open. When the glass end is measured, the furnace door automatically closes after a few seconds. After all the glass enters the furnace, the loading platform automatically stops moving. The unloading station is just the opposite. When the glass runs to the photoelectric switch on the roller, the equipment automatically stops moving. The loading/unloading station is equipped with a stop button for manual control to facilitate loading and unloading.

(2) Heating furnace The heating furnace is the key equipment of the tempered glass production line. It is mainly composed of heating wire, hanging/support device, heat insulation heating system, rapid cooling system, insulation layer, furnace shell, furnace roller, and furnace external transmission system.
① Arrangement of heating wire The arrangement of heating wire is divided into straight-through type and block-shaped distributed type. The installation inside the furnace body is flat installation and dome installation. The arrangement of furnace wire in front of the furnace door is different from that inside the furnace, mainly to isolate the entry of cold air when the furnace door is opened to prevent the furnace temperature from dropping. The furnace wire is mainly nickel-chromium wire, and the shape is divided into round and rectangular.

② Hanging/support device The hanging device is above the furnace and is mainly used to hang the upper furnace heating element. The support device is below the furnace and is mainly used to support the lower furnace heating element. At the same time, it protects the furnace wire from being damaged by broken glass after the glass explodes. The distance of hanging/support is related to the heating radiation rate of the glass. The hanging/support device can also isolate the furnace, keep the furnace clean, and prevent the heating material from being damaged.

③ Insulation heating system According to the principle of glass heating, glass absorbs less infrared radiation consumes more energy at low temperatures, and receives radiation heating faster at high temperatures. Therefore, choosing suitable radiation materials is an excellent way to heat glass evenly and save energy. In the 1980s, foreign companies began to use insulation heating materials, to improve the heat absorption rate and heating uniformity of glass. Foreign countries also use furnace wires to directly heat glass, causing the glass to heat too quickly locally, and the glass warping is higher than the insulation heating furnace. The stress uniformity of glass cooling is lower than that of uniform heating devices. To reduce this phenomenon, a dome furnace wire arrangement can be used so that the distance of furnace wire radiation to glass is equal, reducing the problem of tempering stress non-uniformity.

④ Rapid cooling system is used when special conditions occur in glass and the heating furnace needs to be cooled rapidly. Cold air is quickly introduced into the furnace for cooling through the air pipe and upper air inlet in the furnace. Another purpose of the air pipe in the furnace is to adjust the upper and lower heating balance of glass in the furnace.

⑤ The roller in the furnace is generally made of fused quartz or ceramic rollers. The glass is driven by the friction with the roller to reciprocate in the furnace. The processing quality of the roller directly affects the flatness of the glass and the cleanliness of the glass surface. The flatness of the control roller abroad is less than 0.1mm, while it reaches 0.15mm in China. The straightness is 0.1mm abroad and 0.15mm in China.

⑥ The transmission system of the heating furnace roller is mainly composed of chains, sprockets or friction wheels, steel belts or friction wheels, point motors, and reducers. The belt rotates under the drive of the DC or AC motor and the reducer and drives the glass to reciprocate. The transmission device is equipped with an emergency DC fast operation system, the purpose of which is to quickly send the glass in the furnace to the outside of the furnace in the event of a sudden power outage, to prevent the glass from falling into the furnace and keep the furnace clean.

The transmission system also has an emergency furnace body lifting device. This part can be manual, pushing up the upper furnace body through a balancing device and a chain device; it can also be automatic, automatically lifting the upper furnace body through an electric motor, a reducer, and lead screw nuts set up around the furnace body.

(3) Cooling equipment At present, the horizontal tempering process adopts a variety of jet forms, including nozzle type, spray hole type, and slit type. The cooling device of the horizontal tempering process should meet the following conditions: ensure the process requirements, blow air evenly on the glass, cool it evenly, effectively dissipate the hot air, and facilitate the removal of broken glass; reduce noise, improve the production environment; reduce energy consumption. The quality of the cooling device can be tested by the final product quality. For example: the flatness of the product, the drop ball test height of the glass with the same composition and the same thickness, the size and shape of the fragments, etc. The flatness, drop ball test height, and fragment size of the product can be adjusted by a microcomputer or manual input program, which plays an effective control role in glass tempering and can ensure the tempering quality of glass of various thicknesses.
The horizontal tempering wind grid is generally composed of several upper and lower wind boxes, a lifting device, a guide device, a balancing system, a broken glass conveying system, an air supply system, and a rack.
① The upper wind grille is composed of steel support, a wind grille lifting device, a wind grille, a compressed air pipe, etc. The wind grille is composed of multiple branch wind grilles, each of which is composed of two trapezoidal steel plates and a strip plate hole nozzle plate. The trapezoidal steel plate is molded with a thin steel plate and assembled with a strip plate hole nozzle to form a trapezoidal flat tube. Its large end is connected to the wind box air duct and is equipped with an air volume adjustment butterfly valve. The strip plate hole nozzle is made of heat-resistant steel and installed at the lower end of the flat tube. There are two rows of nozzle holes on it with a larger hole diameter. Compressed air nozzles are also sleeved in the holes. Each branch wind grille is installed horizontally and perpendicular to the direction of glass movement. A guide plate is installed between the two branch wind grilles. After the air and compressed air are ejected from the wind grille to cool the glass, the exhaust gas is discharged through the guide plate. This can eliminate the interference of the exhaust gas and make the blowing cooling more effective. The wind grid of a tempering furnace of a foreign company uses compressed air and cooling air to cool 4mm thin glass.
② The lower wind grid consists of a roller conveyor, a wind grid, a broken glass conveyor, etc. The use of a roller with fiber rope wrapped in the cooling device is an advanced technology that can ensure the tempering quality of the glass. After the heat-resistant steel pipe is wrapped with fiber rope, the contact state between the glass and the roller is changed. When the fiber rope is not wrapped, the contact between the glass and the roller surface is in a star-shaped contact. After the fiber rope is wrapped, the contact between the glass and the roller is point contact, and the contact area becomes smaller, which is conducive to reducing the probability of glass scratches. In addition, the gaps between the spiral intervals of the fiber rope increase the airflow space for the lower cooling of the glass, making the cooling airflow uniform and increasing the cooling effect of the glass. If the fiber rope is not wrapped, the cooling air will be restricted between adjacent conveying rollers, especially when cooling thin glass, there will be obvious local bulges, which will cause uneven cooling of the glass, resulting in uneven stress distribution on the glass surface and rainbow.
The structure and number of the wind grille of the lower wind grille are the same as those of the upper wind grille, but the nozzle of the wind grille is installed at the upper end of the wind distribution flat tube, and there is a certain gap between each wind grille. When the glass is occasionally broken during production, the broken glass falls into the broken glass conveyor below through this gap.
The cooling device design of a new tempering furnace of a foreign company has four characteristics: it is equipped with a nozzle with a special structure, the thin glass can be cooled simultaneously with cold air and compressed air, the speed of the fan is adjusted by the frequency converter to control the wind speed and wind pressure, and the equipment structure is simplified.

③ The broken glass conveyor is generally a plate or crawler conveyor. The conveyor is installed under the lower wind cabinet, from the cooling device near the heating furnace to the bottom of the unloading platform, and baffles are provided above the transport plate and near the steel frame structure on both sides. After the broken glass falls into the conveyor plate, the broken glass conveyor can be turned on to send the broken glass to the bottom of the unloading platform, directly falling into the broken glass trolley or manually cleaned.

 ④The outer shell of the anechoic chamber is made of small steel and steel plates with four walls and a top cover, forming a sealed chamber. Except for a slit at both ends, for glass to pass through, the components in the cooling device are covered in it; there are doors and observation windows on the side, and many noise reduction plates are installed on the top. These noise reduction plates are composed of many exhaust channels. Exhaust gas can be discharged from these channels to reduce noise. The anechoic chamber also limits the noise generated by the gas flowing out of the wind grid to spread outward, thereby reducing the intensity of noise in the workshop and environmental pollution.

⑤The air curtain is set between the heating furnace and the cooling device and consists of air ducts. A row of small nozzles are drilled on the corresponding surfaces of the two air ducts, and the air inlet is connected to the air distributor, and there is an adjusting valve to control its air supply. The air is ejected from the closely packed small nozzles to form an air curtain. When the wind grid blows cold air to cool the glass, the air curtain blows air at the same wind pressure, and the formed air curtain is sealed at the inlet end of the cooling device, thereby preventing the cold air in the wind grid from entering the heating furnace. One of the functions of the air curtain is to quickly pre-cool the glass through the air curtain, and the tempering degree is improved to a certain extent. The tempering degree of the glass produced by the tempering equipment without the air curtain is about 10MPa higher, and the heating time can be reduced by about 10s.

⑥ The lifting device is composed of a drive device, a pulley group, and a steel wire rope. It is automatically controlled by a microcomputer and can adjust the height of the nozzle to the glass surface according to the thickness of the tempered glass. This height refers to the distance from the tip of the upper wind grid to the highest point of the roller glass fiber rope or heat-resistant soft material belt. The lifting height can be adjusted between 300 and 600mm. The lower wind grid is opened or closed with the upper follower through a linkage mechanism such as a sprocket and a chain.

⑦ The balance system uses the upper and lower wind grids to have roughly equal mass and connects the upper and lower wind grids through a chain. When one end is pushed, the entire upper and lower mechanisms move relative to each other under very little power, which not only ensures the consistency of equipment adjustment but also uses the least energy.

⑧ The air supply device should match the structure of the wind grid and the size of the cooling capacity. It is mainly composed of a fan, a mixing air box, a wind grid, a butterfly valve, a pressure transmitter, an air outlet adjustment plate, and a pipeline. The mixing air box fully mixes the air sent by the fan in the air box and then sends it to each wind grid to ensure that the output air volume of the wind grid is as uniform as possible at each point and the cooling of the glass is uniform.

The air volume of the fan is generally adjusted in two ways. One is to adjust the inlet and outlet air volume by rotating or moving the butterfly valve or the air outlet adjustment plate, and the other is to adjust the air volume by controlling the speed of the fan operation through the frequency conversion device.

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