How can the size of the carton be designed to meet the above five constraints?
1) Constraints on ergonomics. The strength of the person carrying the object and the person's posture (this mainly involves bending over, moving halfway, the distance between the two hands leaving the body, the distance between the two hands, the height of the two hands, etc.) and the operation method (this mainly involves Whether one-handed or two-handed, whether it is lifting or lifting, whether pushing or pulling, and whether the center of gravity of the object falls within the plane formed by both hands and the body, whether it is on the connecting line of the hands, etc. The relevant ergonomics information manual should be viewed. Here just want to simply start from one or two factors, discuss how to grasp the size of the carton from the ergonomic point of view.
Figure 1 shows the average weight and height of an object lifted by two hands when the forward distance of the hand leaving the knee is 25 cm (the best knee forward distance) and 50 cm. Figure 2 is a graph of the relationship between the average weight of an adult man using a dual-use liftable object and the forward distance of the hand away from the knee when the vertical distance above the knee is 102 cm.
It can be seen from Figure 1 that the weight that can be lifted by both hands is closely related to the height at which both hands are located, and is also seriously affected by the distance from the hands in front of the body. In the process of using the carton in this example, the process of affecting the height of the hand carrying box has half a process, a stacking process, and placing the clothing on a matching shelf. This factor directly affects the allowable maximum gross weight of the carton, and indirectly also influences. The volume of the carton is the three dimensions of the carton.
Figure 2 clearly shows that when the hands are within 50 cm of the chest, the lifting force remains almost constant, and when this distance is exceeded, the lifting force decreases sharply with the distance, which is actually a factor. Limits the width of the carton. According to this restriction, the carton can theoretically be 1 meter wide, but since both hands need to send the carton forward a certain distance during the carrying process, the width of the carton is actually much smaller than this. Between the opening distance of the hands and the lifting (lifting) force of the hands, there is also a curve similar to that shown in Fig. 2, which will restrict the length of the carton.
In addition, it is worth pointing out that one hand's weight-bearing ability is less than half of the negative gravity of both hands. In the handling process, except that the open distance of the hands remains basically unchanged, the height and the forward distance of the hands are constantly changing, so the problems should be analyzed dynamically.
For ease of operation, except for special circumstances, one person should consider handling.
From the point of view of man's operation, the cartons are certainly smaller, but this does not mean that the smaller the better. Too small cartons will undoubtedly increase the use of packaging materials, increase the operation and affect the area usage rate of other transportation tools (such as trays).
2) Tray constraints. A pallet is a medium that converts static cargo into dynamic cargo. It can pile together many items and form containers of the same size and shape, facilitating product circulation and mechanized loading and unloading. It is therefore a commonly used storage and transportation package. There are many different types of tool trays, but the factors that most affect the size of the cartons are the size of the trays and the way of stacking. International ISO organizations have established international standards for tray sizes, which are 800×1000mm, 800×1200mm, and 1000× respectively. Three kinds of 1200mm, and China's current promotion of the use of the tray size has some differences, such as the Department of Transportation to promote the use of the tray size is 850 × 1250mm. Obviously, exports should be subject to international standards. For the sake of simplicity, we only take the closest international standard tray (800×1200mm) as an example. Similarly, only 5 positive and negative interleaved pallets and 4 rotary interleaved pallets are analyzed in the palletizing mode. Examples are analyzed. As for the use of overlapping pallets or crisscross pallets, the analysis can be similarly performed.
The palletizing method shown in FIG. 3 can be rectangular in cross-section, and can effectively utilize the surface area of ​​the pallet. In the palletizing method shown in FIG. 4, the section must be square, and the center forms a cavity, which will reduce the pallet's capacity. Surface utilization, but the stability of this palletizing method is good.
If the palletizing method shown in Fig. 3 is used, the width a of the carton should be 120/3=4cm. However, due to the actual palletizing, the items are allowed to exceed the pallets, theoretically each side can exceed 5cm, so the carton's The width can be slightly larger than 40 cm. If no gap is left, the length b of the carton should be 120/2=60 cm. Since 60+40=100 centimeters have more than 80 centimeters in tray width (theoretically allowing more than 4 centimeters per side), the length should be 44 centimeters, but only from the stacking stability if it is not allowed to accommodate various vehicle volumes. It is possible to use a length of 60 cm or more. If you use the palletizing method shown in Figure 4, you can only use the method that only considers the stability of the pallet, otherwise the surface utilization of the pallet is too high. Low. In order to reduce the central hole, the aspect ratio of the carton should be reduced as much as possible. The minimum value is the above 60 (length)×40 (width) cm, and the maximum value can reach 70 (length)×50 (width) cm.
3) Constraints on the transport vehicle compartments and containers. Transport vehicles mainly refer to van-type trucks. Currently, there is no uniform standard for the size of vehicles. If the truck is used with the pallets, the length and width of the cartons have been analyzed and considered when considering the constraints of the pallets. The height of the cartons should be determined based on the height of the interior of the vehicle. That is, the height of the cartons = height of the interior of the vehicle - pallets Thickness - Job Clearance / Carton Stacking The job clearance is generally 10 cm.
If the goods are directly placed in the compartment, the length, width and height of the cartons must be compatible with the internal dimensions of the vehicle to fully utilize the volume of the compartments, ensure the stable placement of the goods, and facilitate the loading and unloading operations. There is a multiple relationship between the length and width dimensions of the carton and the length and width of the car. This is similar to the analysis of container constraints. Containers are currently a commonly used transport packaging tool. China has issued a series of national standards for the external dimensions and weight of cargo containers in 1978. It is basically compatible with the international ISO standards and should refer to the corresponding standards when designing. For the sake of simplicity, the following analysis and discussion will be made on the case of a one-ton container for rail freight. Its dimensions are as follows:
External dimensions: 900×1300×1300mm
Internal dimensions: 830×1260×1144mm
Weight: 186kg
Load: 814kg
Total weight: 1000kg
Obviously, the size of the carton is 620 (length) × 570 (width) × 400 (height) mm is the best, then just put eight cartons, taking into account only the second floor, and the tray size constraints, the carton Two dimensions, width and height, can be swapped. It is also worth pointing out that in the end it should be checked whether the load requirements are met. Moreover, international transportation containers are generally over 20 tons, which is mainly for the convenience of container ship transportation. (to be continued)

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