Abstract: According to the stability of the forklift, the strength of the components, the safety and the actual application in the work, this paper discusses the allowable lifting weight of the forklift configuration and the overload protection of the forklift.
Key words: forklift attachment weight overload protection forklift is designed according to the standard fork and rated lifting weight. Since the attachment is configured after the forklift is made and the weight is generally larger than the original fork, the load center is also different, causing the center of gravity of the entire forklift system to change. In order to ensure the safety and reliability of the forklift truck, the allowable lifting weight of the rear forklift truck should be re-determined without changing the structure of the forklift truck and the safety indicators. At present, the types of forklift attachments are increasing, and the correct weight is determined after the forklift is configured. It is of great significance to ensure the safe use of the forklift and make full use of the lifting capacity of the forklift.
1 According to the stability principle, it is determined that the load before and after the transfer of the lifting forklift is allowed to exceed the allowable value, that is, the maximum load torque of each component is constant. At this time, the allowable lifting weight after the attachment is used can be determined by the stability calculation. Based on the front wheel center of the forklift, the rated weight of the forklift and the weight of the standard fork removed from the center of the front axle are equal to the new allowable lifting weight and the weight of the attached weight to the same center. (See Figure 1) Available:
In the formula, Q - rated lifting weight
Sc - load center distance
A——fork weight
Gc - fork weight
Gcx - the weight of the new attachment
Sbc - new attachment center of gravity to vertical front surface horizontal distance
Sbx - the new attachment has a center of gravity to the horizontal distance of 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 horizontal distance from the load center specified by the new attachment to the front surface of the vertical section of the original fork
Qx——The allowable lifting weight when configuring the attachments can be obtained by the formula (1-2).
The forklift works under this allowable lifting capacity and will not cause damage to the performance of the whole machine, just like when using the standard fork. This method can be used as a basic principle for determining the allowable lifting weight after the forklift is equipped with the attachment.
2 According to the component bearing principle, the allowable lifting weight is determined in the first article. From equation (1-2), it can be concluded that if the new load center distance Scx is greater than the original load center distance Sc, the new permission can be determined by the formula. weight. If the load center distance is reduced and Scx is less than Sc, the new allowable lifting weight obtained by the formula (1-2) may be greater than the original rated lifting capacity. This situation is absolutely not allowed in the actual operation of the forklift. Because the safety factors of the hydraulic system such as the door frame member, the lifting chain, the lifting hydraulic cylinder, the load-bearing portion of the transaxle, and the multi-way valve are not suitable for change. When the forklift is designed as a whole, each component only constitutes a safety guarantee for the forklift under rated load. Therefore, under such conditions, the new allowable lifting weight can be determined based on the principle that the load on the forklift and the component should be equal before and after the configuration of the attachment. You can get the following formula:
In the above formula, Qy is the new allowable lifting weight of the forklift configuration fixture determined by this principle.
Here, the forklift can still maintain the original performance when the weight is allowed to work. This method is the necessary principle for determining the allowable lifting weight after the forklift is equipped with the attachment.
3 Comprehensive analysis According to formula (1-2) and formula (2-2), the relationship diagrams of Q, Qx, Qy and Sc, Scx can be roughly obtained, as shown in Fig. 2. In the figure, the Q curve is the load curve in the case of the original fork; Qx is the new allowable load curve after the forklift configuration is calculated according to the formula (1-2); Qy is according to the formula (2-2) Calculated new allowable load curve.
The shaded part of each curve intersecting below is a safe area, that is, the allowable load range of the rear forklift is configured.
According to the graph, the following situations can be drawn:
(1) When Scx>Sc, the new allowable lifting weight is calculated by using the formula (1-2), which is the most restrictive, because the obtained Qx value is the smallest and the safety factor is 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 the working operation of the forklift, it will not The forklift caused damage.
(3) When Scx is close to Sc, since the weight of the fork Gc and the weight of the attachment Gcx are large, it can be calculated by using equations (1-2) and (2-2) respectively, and then taking small values ​​as permission. weight.
4 Overload protection of forklift trucks at different load center distances As can be seen from the above analysis, the same cargo has different effects on the load capacity of the forklift when its center of gravity is at different positions in the length direction of the fork. When the weight of the cargo is unknown, if it is lifted by a forklift, there is a danger of overload. The following three situations are discussed.
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 center distance of the forklift load.
At this time, from equation (2-2) and Figure 2, the lifting capacity of the forklift is: Q1=Q=Qy
(2) The horizontal distance of the cargo's center of gravity from the front surface of the vertical section of the fork is close to or approximately the center distance of the forklift load.
At this time, Scx=Sc, from Equation (1-2), Equation (2-2) and Figure 2, the lifting capacity of the forklift is: Q2=Q=Qx
(3) The horizontal distance of the cargo's center of gravity from the front surface of the vertical section of the fork is greater than the load center distance of the forklift.
At this time, Scx>Sc, from equation (1-2) and Figure 2, the lifting capacity of the forklift is: Q3=Qx
Key words: forklift attachment weight overload protection forklift is designed according to the standard fork and rated lifting weight. Since the attachment is configured after the forklift is made and the weight is generally larger than the original fork, the load center is also different, causing the center of gravity of the entire forklift system to change. In order to ensure the safety and reliability of the forklift truck, the allowable lifting weight of the rear forklift truck should be re-determined without changing the structure of the forklift truck and the safety indicators. At present, the types of forklift attachments are increasing, and the correct weight is determined after the forklift is configured. It is of great significance to ensure the safe use of the forklift and make full use of the lifting capacity of the forklift.
1 According to the stability principle, it is determined that the load before and after the transfer of the lifting forklift is allowed to exceed the allowable value, that is, the maximum load torque of each component is constant. At this time, the allowable lifting weight after the attachment is used can be determined by the stability calculation. Based on the front wheel center of the forklift, the rated weight of the forklift and the weight of the standard fork removed from the center of the front axle are equal to the new allowable lifting weight and the weight of the attached weight to the same center. (See Figure 1) Available:
In the formula, Q - rated lifting weight
Sc - load center distance
A——fork weight
Gc - fork weight
Gcx - the weight of the new attachment
Sbc - new attachment center of gravity to vertical front surface horizontal distance
Sbx - the new attachment has a center of gravity to the horizontal distance of 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 horizontal distance from the load center specified by the new attachment to the front surface of the vertical section of the original fork
Qx——The allowable lifting weight when configuring the attachments can be obtained by the formula (1-2).
The forklift works under this allowable lifting capacity and will not cause damage to the performance of the whole machine, just like when using the standard fork. This method can be used as a basic principle for determining the allowable lifting weight after the forklift is equipped with the attachment.
2 According to the component bearing principle, the allowable lifting weight is determined in the first article. From equation (1-2), it can be concluded that if the new load center distance Scx is greater than the original load center distance Sc, the new permission can be determined by the formula. weight. If the load center distance is reduced and Scx is less than Sc, the new allowable lifting weight obtained by the formula (1-2) may be greater than the original rated lifting capacity. This situation is absolutely not allowed in the actual operation of the forklift. Because the safety factors of the hydraulic system such as the door frame member, the lifting chain, the lifting hydraulic cylinder, the load-bearing portion of the transaxle, and the multi-way valve are not suitable for change. When the forklift is designed as a whole, each component only constitutes a safety guarantee for the forklift under rated load. Therefore, under such conditions, the new allowable lifting weight can be determined based on the principle that the load on the forklift and the component should be equal before and after the configuration of the attachment. You can get the following formula:
In the above formula, Qy is the new allowable lifting weight of the forklift configuration fixture determined by this principle.
Here, the forklift can still maintain the original performance when the weight is allowed to work. This method is the necessary principle for determining the allowable lifting weight after the forklift is equipped with the attachment.
3 Comprehensive analysis According to formula (1-2) and formula (2-2), the relationship diagrams of Q, Qx, Qy and Sc, Scx can be roughly obtained, as shown in Fig. 2. In the figure, the Q curve is the load curve in the case of the original fork; Qx is the new allowable load curve after the forklift configuration is calculated according to the formula (1-2); Qy is according to the formula (2-2) Calculated new allowable load curve.
The shaded part of each curve intersecting below is a safe area, that is, the allowable load range of the rear forklift is configured.
According to the graph, the following situations can be drawn:
(1) When Scx>Sc, the new allowable lifting weight is calculated by using the formula (1-2), which is the most restrictive, because the obtained Qx value is the smallest and the safety factor is 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 the working operation of the forklift, it will not The forklift caused damage.
(3) When Scx is close to Sc, since the weight of the fork Gc and the weight of the attachment Gcx are large, it can be calculated by using equations (1-2) and (2-2) respectively, and then taking small values ​​as permission. weight.
4 Overload protection of forklift trucks at different load center distances As can be seen from the above analysis, the same cargo has different effects on the load capacity of the forklift when its center of gravity is at different positions in the length direction of the fork. When the weight of the cargo is unknown, if it is lifted by a forklift, there is a danger of overload. The following three situations are discussed.
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 center distance of the forklift load.
At this time, from equation (2-2) and Figure 2, the lifting capacity of the forklift is: Q1=Q=Qy
(2) The horizontal distance of the cargo's center of gravity from the front surface of the vertical section of the fork is close to or approximately the center distance of the forklift load.
At this time, Scx=Sc, from Equation (1-2), Equation (2-2) and Figure 2, the lifting capacity of the forklift is: Q2=Q=Qx
(3) The horizontal distance of the cargo's center of gravity from the front surface of the vertical section of the fork is greater than the load center distance of the forklift.
At this time, Scx>Sc, from equation (1-2) and Figure 2, the lifting capacity of the forklift is: Q3=Qx
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