The forklift truck is planned according to the standard fork and the extra weight. Since the equipment is made of forklift and the weight is generally larger than the original cargo fork, the load center is different, which leads to the change of the center of gravity of the whole forklift system. In order to ensure the safety and reliability of the forklift operation, on the premise of not changing the structure of the forklift itself and other safety objectives, the allowable starting component of the forklift should be determined from the beginning. Now, the variety of forklift equipment keeps increasing, and it has very important meaning for ensuring the safe use of forklift and fully using the lifting ability of electric forklift.
The allowable starting component is determined according to the stability criterion
The load accepted before and after the forklift replacement equipment shall not exceed the allowable value, that is, the maximum load moment of each component remains unchanged. At this point, you can determine through the stability of the accounting application of the promised component. Based on the front wheel center of forklift truck, the torque of the forklift extra lifting weight and the removed standard forklift deadweight on the front axle center is equal to that of the new allowable starting weight and the replaced one on the same center. (see figure 1) can be deduced:
In the formula, Q is the extra starting component
Sc -- load center distance
A -- the weight of the fork
Gc -- fork weight
Gcx - the component of a new genus
Sbc - new genus with center of gravity to exterior horizontal separation
Sbx - new has a center of gravity to the outer horizontal spacing of the fork
Z -- horizontal separation between the outer surface of the straight part of the fork and the front axle
Scx - the horizontal separation between the specified load center and the outer surface of the straight section of the original cargo fork for the new genus
Qx - when the equipment is equipped, the starting weight is allowed
The forklift equipment can be obtained from formula (1-2) after the equipment is provided.
The forklift working under such allowable starting component will not damage the function of the whole machine, the same as when the standard fork was used. This method can be used as the basic criterion for determining the allowable starting component of forklift equipment.
Determine the allowable starting component according to the load criterion
In the first equation (1-2), it can be concluded that when the new load center distance Scx is larger than the original load center distance Scx, the new starting component can be determined by this equation. If the load center distance is reduced and Scx is smaller than Sc, the new allowable starting component derived from equation (1-2) may be larger than the original additional starting component. This situation, in the practice of forklift operations is definitely not allowed. Because the door frame, lifting chain, lifting hydraulic cylinder, the bearing part of the drive axle and the multi-way valve and other hydraulic system allowable safety factor should not be changed. In the overall planning of forklift, each component only constitutes the security guarantee for the forklift under the extra load. Therefore, under this condition, the new allowable starting component can be determined according to the criterion that the load of forklift and components should be equal before and after the equipment. The following formula can be obtained:
In the above formula, Qy refers to the new allowable components of forklift equipment which is determined by this criterion.
The forklift can still maintain its original function under this allowable starting component, which is the necessary criterion to determine the allowable starting component after the forklift equipment is provided.
3. Inductive analysis
According to equations (1-2) and (2-2), the relation graphs of Q, Qx, Qy, Sc and Scx can be roughly drawn, as shown in figure 2. In the figure, the Q curve is the load curve under the condition of using the cargo fork. Qx is the new allowable load curve after the forklift equipment is calculated according to formula (1-2). Qy is a new allowable load curve calculated according to formula (2-2).
Each curve intersects the shadow part below for the safe area, that is, the allowable load scale of the rear forklift truck of the equipment.
According to the figure, the following situations can be obtained:
(1) when Scx>Sc, formula (1-2) is used to calculate the new allowable starting component, which is the most restrictive, because the Qx value obtained is the smallest and the safety coefficient is the best.
(2) when Scx>Sc is used, equation (2-2) is used to calculate the new allowable starting component, which is the most restrictive, because the Qy value obtained is the best stable value for the operation of forklift and will not cause damage to the forklift.
(3) when Scx is similar to Sc, since the weight Gc of cargo fork and the weight Gcx have a greater influence, equations (1-2) and (2-2) can be respectively used to calculate, and then the small value is taken as the allowable starting component.
Overload protection of forklift at different load center distances
From the foregoing analysis, it can be seen that the same goods, when their center of gravity is at different positions in the direction of the length of the fork, have different effects on the bearing capacity of the forklift. When the weight of goods is not known, the lifting operation with the forklift has the risk of overload. Here are three situations to review.
It is assumed that the component of the goods is greater than the additional starting component of the forklift.
(1) the vertical outward horizontal interval between the barycenter of the goods and the fork is smaller than that between the load center of the forklift.
At the moment, it can be seen from equation (2-2) and figure 2 that the lifting capacity of forklift is: Q1=Q=Qy
(2) the barycenter of the goods is close to or close to the load center of forklift before the straight part of the fork.
At the moment, Scx=Sc, it can be seen from equations (1-2), (2-2) and figure 2 that the lifting capacity of forklift is: Q2=Q=Qx
(3) the outer horizontal distance between the barycenter of the goods and the fork is larger than the distance between the load center of the forklift.
At the moment, Scx>Sc, according to equation (1-2) and figure 2, the lifting capacity of forklift is: Q3=Qx
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