First, the type of tensioning device
Common with screw tensioning device tensioning device, gravity tensioning device, fixed winch tensioning device, automatic tensioning devices.
1 screw tensioning device. Screw tension device structure is simple, taut trip is too small, only a short distance conveyor for general use when the captain is less than 80m and disadvantages of self-elongation when the tape, you can not automatically tighten.
2 gravity tensioning device. Gravity tensioning device structure is the simplest, most widely used as a tensioning device. It is the use of a heavy hammer to automatically tighten, tighten the hammer by weight, so it can ensure the tension of which remains constant in a variety of conditions, can automatically compensate for belt elongation. Gravity tensioning device is characterized by constant tension force, tension displacement variable, which applies to fixed long-distance transport, high security and reliability advantages, disadvantage is that you can not adjust the tension of the space requirements of large, in the space- place restrictions can not be used.
3 fixed winch tensioning device. Fixed tensioning device is the use of a small winch to tighten the winch, winch worm gear drive for general use to winding wire rope reel, so taut tape. The tensioning device has the advantage of small size, Rally, it is widely used in underground belt conveyor. The disadvantage is that it can only adjust the tension of the need to set resulting from constant tension, the tension force can not be adjusted automatically when the winch and control systems problems, on the tape machine can not produce a constant tension or pull force tight power failure, security and reliability is relatively lower.
4 automatic tensioning device. Not only under the automatic tensioning device active traction roller to automatically adjust the tension force, but also to compensate for elongation of the tape. Automatic tensioning device consists of motor, brake, reducer, steel wire rope drum and other components, using a large pull tensioning device tensioning conveyor belt equipped with tension sensors to measure belt tension, when the belt tension changes, more than the normal conveyor operating range, automatic tensioning device moves quickly, adjust the belt tension to ensure the normal operation of the conveyor. Automatic tensioning device and self-moving tail used in conjunction with the conveyor can be achieved under the conditions of non-stop to realize the tail conveyor belt stretching movement and greatly enhanced the efficiency of the delivery conveyor. Automatic winch tensioning device by the pressure sensor belt conveyor according to the needs of operating conditions the size of the tension of automatic control, hydraulic tensioning device produced by the hydraulic fluid pressure through the station on the tape machine Shijia La tight cylinder power, according to the tape machine operating conditions need to adjust the tension of the size.
Second, during normal operation conveyor tensioning force calculation
Conveyor at various points of tension is the use of calculated point by point calculation method. The tension on the conveyor belt is equal to a certain point along the direction of a movement that the tension between these two points running resistance, with the formula is:
Si = Si-1 + W (i-l) ~ i (1)
Where: Si-1, Si-, respectively before and after the two conveyor tension;
W (i-l) ~ i-before and after the running resistance between two points.
Points in the calculation of belt tension, usually starting from the point of minimum tension, while the minimum belt tension to satisfy two conditions:
(1) satisfies the tension between the friction traction, that does not meet the belt slipping on the drum conditions:
Sy = Sl 1 + eμa-1 n (2)
Where: Sy-driven roller conveyor and meeting point of tension, N;
Sl-belt drive pulley and the tension of the separation point, N;
μ-belt and the coefficient of friction between the drive pulley;
α-belt around corners, rad;
n-coefficient of friction spare, taking 1.15-1.20.
(2) meet the requirements of belt sag, namely:
Smin = (q + qd) l2ggcosβ8ymax (3)
Where: Smin-belt tension in the heavy segment of the smallest, N;
lg-heavy section of roller spacing, m;
ymax-belt maximum allowable deflection, the general ymax = 0.025lg;
q-unit length of the amount of material on the conveyor belt loading;
qd-long conveyor belt unit mass;
β-angle conveyor work.
Using the above two conditions to (1) and (3) obtain the minimum tension in the big to the smallest for the tension of the conveyor, and in accordance with the formula (3) Find all points of tension. Calculated according to the points of tension can be conveyor tension during normal operation. Belt tension is equal to the tension in the tension at both ends of the drum and, namely:
F = Si-1 + si (4)
Where: F-taut tension of the device, N;
Si-1-belt tension roller in the meeting point of tension, N;
si-belt tension roller separation point in the tension, N.
Tension of belt required, at the start, stable operation and the braking process is different. Therefore, the calculation of tension force, should be a variety of conditions on the conveyor belt does not slip in the drive pulley calculation conditions, the ideal tension device should be based on conditions in different conveyor automatically adjusts the tension of the requirements This can meet the conveyor belt and friction in the vertical traction requirements, but also to ensure that conveyor belt is not to put too much tension.
Third, the applicability of tensioning device
In the process of belt arrangement, the tensioning device to determine a reasonable, is to ensure the normal operation of conveyor, starting and braking safety and reliability, a necessary prerequisite for economic rationality. The tensioning device of the applicability of various engineering and technical personnel concerned with one of the important issues. According to the literature in the rigid body dynamics of belt conveyor, the characteristics of the three tensioning device is analyzed. As shown, the vertical axis for the introduction of three tensioning device tape maximum tension ratio, the F Ⅱ max / F Ⅰ max, F Ⅲ max / F Ⅰ max, which, F Ⅰ max, F Ⅱ max, F Ⅲ max, respectively, in the automatic, heavy hammer, and fixed tensioning device cases, the maximum tape tension, the abscissa for the transport distance. 从图中可得出如下结论： From the figure, the following conclusions can be drawn:
(1) horizontal transport β = 0 ° . In this case, the use of fixed-tensioning device, belt tension F Ⅲ max than the maximum automatic belt tension F Ⅰ max maximum 1.35 times that large, when L> l000m, its ratio will reach 1.45, and no downward trend; the use of Hammer-type tensioning device, belt tension F Ⅱ max than the maximum automatic belt tension F Ⅰ max maximum 1.12 times more than large, the ratio of F Ⅱ max / F Ⅰ max length with the tape machine increases with the increase in volume, the ratio will also slightly increased.
From an economic perspective, such as the level of transport and in the case of large distance, the fixed tensioning device tensioning device and compared with the other two, the former is likely to make tape strength and the whole equipment upgrades, such as by tape l High-level rise in the price of 80 yuan / m terms, the 1500m-long tape tensioning device due to the inappropriate choice of opportunities, resulting in only one tape to increase investment to more than 80 yuan / m × 1500 × 2 = 24 万元 on the rope in terms of core tape . It is suggested that, in the level of long distance transport and the case should be automatic tensioning device, instead of the fixed tensioning device, in the case of the shorter distance, for example, less than 1000m, can be heavy hammer tensioning device.
(2) upward transport (β> 0 °). In this case, as the angle increases, the largest fixed belt tensioning device and automatic tension F Ⅲ max maximum tension-type tape and the heavy hammer F Ⅰ max belt tension F Ⅱ max maximum difference between the less and less inclined to a certain extent when When using the fixed tensioning device tensioning device and weight are similar effects. Can also be seen from Figure 1, the largest fixed belt tension and maximum tension than hammer-type tape, the former is influenced by the angle, which greatly influenced by the distance. In short, the large dip in improving β> 10 ° , recommended hammer tensioning device.
(3) downward transport (β <0 °). Power generation and motor transport in the next run, F Ⅱ max and the ratio between F Ⅰ max between l-1.1, and with the increase of distance and angle showed a decreasing trend. For F Ⅲ max and F Ⅰ max ratio, its value is greater than 1.2, the smaller the angle, the greater its value, but not too large, and distance relationships. When the volume becomes large, regardless of F Ⅱ max / F Ⅰ max, F Ⅲ max / F Ⅰ max were tested slightly decreased. The electric current is transported but the motor is running, the situation is similar to the case of horizontal transport.
In this way, the next transportation and power generation, the recommended the next hammer tensioning device is in operation and electric operation, automatic tensioning device is recommended, and the best tensioning device without the other two.
IV, Conclusion
(1) pull the belt conveyor belt conveyor transport routes by the length, angle, cargo and other factors, the choice of tensioning device according to the tape machine when the working conditions of a reasonable calculation.
(2) reasonable choice of tape machine tape taut position help extend the life span and reduce the tape machine starting and braking the process of shock and vibration and improve stability.
(3) When the belt tension on the material than when the transfer material when the transfer without tension, dynamic load should be large, the dynamic load and cargo status.
(4) When using the head tensioning device, in the other conditions remain unchanged, the rear tensioning device than using a large dynamic loads.
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