How to choose a cardboard belt

With the popularization and application of high-speed carton machinery, proper selection of matching conveyor belts has attracted widespread attention from cartons. In addition to the inherent performance of carton machinery, as a supporting accessory, the quality and function of the conveyor belt largely determine the economic and technical indicators such as speed, efficiency, quality, consumption, and energy saving in the processing of corrugated board. Therefore, how to choose the conveyor belt has become an important issue in production.

Conveyor belts, as the name suggests, are belts for conveying materials. The main function is to drag the cardboard through the drying chamber. To ensure that the board is dried, the quality of the box is guaranteed, energy is saved, consumption is reduced, and the service life of the conveyor belt is an essential supporting function. Therefore, when selecting the conveyor belt, we must first start with the function of the conveyor belt to see what kind of conveyor belt can meet the requirements of high speed, high efficiency, high quality, low consumption, and long service life.

From the material point of view

Most of the conveyor belts currently used by many cartons are woven from cotton or polyester spun yarns. The disadvantage of this conveyor is that it cannot meet the high speed, high-tension transfer requirements and can only be used in low-speed carton machinery. In recent years, a conveyor belt made of a combination of polyester spun yarn and polyester industrial filament has been newly introduced on the market. Unlike conventional belts, the upper and lower surface layers and the intermediate layer of the conveyor belt of this material play different roles in operation. The upper and lower surfaces of the conveyor belt are mainly subjected to friction, while the middle layer is mainly subjected to tension. It is the skeleton of the conveyor belt and is also called a strong layer. The new conveyor belt combines the polyester staple fiber yarns and the polyester industrial filaments in a scientific and rational combination. The polyester spun yarns with a good coefficient of friction are used on the double surfaces of the conveyor belts. The use of high-strength, high-initial-modulus and polyester filaments with good dimensional stability after heat setting for the intermediate layer meets the requirements of high-speed and high-tension, and at the same time ensures that the length of the conveyor belt body changes minimally. The service life of the conveyor belt can be extended.

Satisfy high-speed operation

Whether the conveyor belt can adapt to the high speed of the carton machinery, that is, whether the conveyor belt can synchronously drive the movement of the cardboard on the hot plate at a high speed, and the friction between the conveyor belt and the cardboard is a key technical indicator. In the drying process, the processed object is a corrugated board that needs to be dried after being coated with a paste. Therefore, increasing the positive pressure on the conveyor belt has a certain range of limits. If the pressure limit is exceeded and the friction is increased, not only the corrugation of the cardboard is broken down. The cocoon shape makes the paperboard thinner, and the friction between the paperboard and the heating iron plate increases accordingly, resulting in a decrease in the conveying speed. As a result, the result is counterproductive and worthless. From this point of view, if increasing the positive pressure on the belt does not increase friction, it is only by increasing the coefficient of friction on the surface of the belt to increase the friction.

How to increase the friction coefficient? In the case where the surface material of the conveyor belt has been fixed, the friction coefficient can only be increased by improving the flatness of the conveyor belt body surface and increasing the frictional contact area between the belt surface and the cardboard. Therefore, it is very important to design the surface structure of the conveyor belt. At present, some of the new conveyor belts (faces in direct contact with the cardboard) adopt a three-up and one-off twill structure, the middle layer (strong layer) is an under-net structure, and the lower layer is a two-under-two broken twill structure or It is a two-on-two chevron structure. This process design greatly improves the function of the conveyor belt.

Three on a broken twill structure

Breaking the diagonal twill structure (including the two upper and lower broken twill structures) on the three sides greatly improves the flatness of the belt surface, maximizing the contact area between the belt surface and the board area per unit area, increasing the friction coefficient value, and thus increasing the friction. force. At the same time, due to the large contact area.

The pressure of the strip body on the paperboard becomes smaller, which creates the conditions for increasing the positive pressure properly. Both of these factors can increase the friction force. Therefore, the conveyor belt can adapt to the friction required by the high speed of the carton machinery, and thus the conveyor belt can adapt to the carton machinery. The friction needed for speeding up.

In addition, the broken twill structure also has the effect of preventing the oblique pull.

Two middle and two lower plain layers

The middle layer of the belt body has two upper and lower plain weave structures. This structure is less than half of the cross point of the warp threads of the upper and lower tissues, so the structure length of the warp threads is much smaller, so that the conveyor belt is structurally stretched under great tension. A lot smaller, together with the material of the middle layer, the high strength, low elongation, and low shrinkage properties of the polyester industrial filament ensure that the length of the belt when the conveyor belt is running under severe tension, high temperature, and high-speed harsh environments is extremely small, and therefore also Reduced belt width changes. The stability of the vertical and horizontal structures of the belt body ensures that the belt structure is strong, durable and has a long service life. Some companies produce belts that can withstand 50 tons per meter of width with only one intermediate strength layer.

Two structures on the back surface

The two structures on the back surface have their own characteristics. The herringbone structure is mainly characterized by a good anti-stretching effect, but with many grooves and poor flatness. The two upper and lower broken twill structures not only have the effect of anti-stretching, but also can be turned over when the front of the belt body cannot be used due to damage or Other reasons. This is the biggest advantage of this structure, due to the use of an extended conveyor belt for overturning. ÷ The service life is very attractive for the user to purchase a conveyor belt.

From the perspective of tape body weaving

The tightness of the strip body weaving (warp tightness and zonal tightness) directly affects the length change and width change of the conveyor belt during use: Generally, the small warp tightness makes the width narrower and narrower. The small zonal tightness will make the length of the belt longer and longer, so the warp and weft tightness of the belt body is better, avoiding the unnecessary loss caused by the large dimensional change in warp and weft. In addition, the tightness of the belt has a great influence on the drying speed and thermal energy consumption of the board.

In order to have a more intuitive understanding, we must first understand the drying mechanism of the cardboard production line. When the corrugated paperboard with the paste is dragged into the drying box by the conveyor belt and directly contacts the heated iron plate, the heat plate rapidly transfers heat to the paperboard, and the paperboard gradually heats up from the bottom up to evaporate water in the paste. Take single-layer corrugated paperboard as an example: the high-temperature steam between the upper and lower paperboards forms a high-pressure zone in the corrugated cavity, and at the same time, both sides of the paperboard are conveyed. When the belt is fed at high speed, the high speed air flow creates a low pressure zone so that the high pressure water vapour will be quickly discharged from both sides of the carton board along the winch path, and most of the water will evaporate.

Since the paper moisture is invasive, a small amount of steam is generated on the upper surface of the paperboard. However, most of these steams pass through small gaps between the tape and the paper under the effect of high temperature and high pressure. Excretion, a small part of the steam through the belt body between the fibrous tissue through the body upward discharge.

High-temperature thermal energy is the main condition for rapid drying of the paperboard. The lower part of the paperboard moves against the hotplate, so the drying of the lower part is no problem. However, the upper layer of light paper can only evaporate water vapor by the heat energy transmitted from the lower part. Therefore, how to ensure that the upper high temperature environment is the key to drying the glossy paper. If too much heat is dissipated on the conveyor belt, it will affect the drying effect of the glossy paper, so the moisturizing function of the conveyor belt when purchasing is important. The tightness of the fabric of the conveyor belt is greater, and it has enough thickness to prevent the hot air from directly dissipating from the gaps of the fabric, ensuring the rapid formation of high temperature and high pressure between the belt body and the cardboard, facilitating the rapid drying of the cardboard, and reducing the energy consumption. The new conveyor belt is The tightness of fabrics meets the requirements of fast drying and energy conservation.

The new conveyor belt not only uses high strength, high friction coefficient and high drying performance, but also adapts to the application of high-speed cardboard production lines. It also brings about considerable economic benefits for carton enterprises by saving energy and prolonging the service life.