Forklifts are designed based on standard forks and rated lifting capacity. Since the attachment is configured after the forklift is manufactured and the weight is generally larger than the original fork, the load center is also different, which causes the center of gravity of the entire forklift system to change. In order to ensure the safe and reliable work of the forklift, the allowable lifting capacity of the forklift should be re-determined after the attachment is configured without changing the structure of the forklift body and various safety indicators. At present, the types of forklift attachments continue to increase, and the correct determination of the allowable lifting weight after the forklift is equipped with attachments is of great significance for ensuring the safe use of forklifts and making full use of the lifting capacity of electric forklifts. 1 Determine the allowable lifting weight according to the principle of stability. The load before and after the forklift is replaced with attachments shall not exceed the allowable value, that is, the maximum load moment of each component remains unchanged. At this time, the allowable lifting weight after using the attachment can be determined by the stability calculation. Based on the center of the front wheel of the forklift, make the rated lifting weight of the forklift and the torque of the removed standard fork weight to the center of the front axle equal to the new allowable lifting weight and the weight of the replaced attachment to the same center. (Refer to Figure 1) It can be deduced: where Q-rated lifting weight Sc-load center distance a-fork weight Gc-fork weight Gcx-weight of the new attachment Sbc-center of gravity of the new attachment Horizontal distance to the vertical front surface Sbx-the horizontal distance from the center of gravity of the new attachment to the front surface of the fork Z-the horizontal distance from the rear surface of the vertical section of the fork to the front axle Scx-the load center specified for the new attachment to the original fork The horizontal distance Qx of the front surface of the vertical section-the allowable lifting capacity when the attachment is configured is given by the formula (1-2) to obtain the allowable lifting capacity after the forklift is configured with the attachment. When the forklift works under this kind of allowable lifting capacity, it will not damage the performance of the whole machine, which is the same as when using standard forks. This method can be used as the basic principle for determining the allowable lifting capacity after the forklift is equipped with attachments. 2 Comprehensive analysis According to formula (1-2) and formula (2-2), the relationship graph of Q, Qx, Qy and Sc, Scx can be roughly drawn, as shown in Figure 2. In the figure, the Q curve is the load curve under the original use of the fork; Qx is the new allowable load curve calculated according to formula (1-2) after the forklift is equipped with attachments; Qy is according to formula (2-2) The calculated new allowable load curve. The shaded part where the curves intersect below is the safe area, that is, the allowable load range of the forklift after the attachment is configured. According to the graph, the following situations can be obtained: (1) When Scx>Sc, use formula (1-2) to calculate the new allowable lifting weight, which is the most restrictive, because the Qx value obtained is the smallest, and the safety factor the best. (2) When Scx>Sc, use formula (2-2) to calculate the new allowable lifting weight, which is the most restrictive, because the Qy value obtained has the best insurance value for forklift operation and will not The forklift caused damage. (3) When Scx is close to Sc, because the fork weight Gc and the attachment weight Gcx have a greater impact, they can be calculated using equations (1-2) and (2-2) respectively, and then take the smaller value as the allowable starting point. weight. 4 Overload protection of forklifts under different load center distances From the foregoing analysis, it can be seen that the same cargo has different effects on the forklift's carrying capacity when its center of gravity is at different positions along the length of the fork. When the weight of the cargo is unknown, there is a danger of overloading when lifting with a forklift. The following is divided into three situations to discuss. Assume that the weight of the cargo is greater than the rated lifting capacity of the forklift. (1) The horizontal distance between the center of gravity of the cargo and the vertical surface of the fork is less than the distance between the forklift's load center. At this time, from equation (2-2) and Figure 2 we can see that the lifting capacity of the forklift is: Q1u003dQu003dQy (2) The center of gravity of the cargo is close to or approximately the distance of the forklift's load center from the front surface of the vertical section of the fork. At this time, Scxu003dSc, from equation (1-2), equation (2-2) and Figure 2, we can see that the lifting capacity of the forklift is: Q2u003dQu003dQx (3) The center of gravity of the goods is from the front surface of the vertical section of the fork The horizontal distance is greater than the forklift load center distance. At this time, Scx>Sc, from equation (1-2) and Figure 2, we can see that the lifting capacity of the forklift is: Q3u003dQx
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