1 Generally, the product has such a pattern in the development of technology: In the initial stage, various forms of structures were developed. In the actual use process, the survival of the fittest was progressively eliminated, the structural forms tended to be unified, and then the products were merged with new technologies. Develop in depth and create new competition at a higher stage. Such a reciprocal... If this rule is used to measure the current self-loading and loading vehicle of the shelter, it can be considered that it is still in the initial stage of product development. This is because, despite the fact that China has experienced nearly 20 years of research and development, shelter loading and unloading vehicles are still developing in parallel with various types of structures. Each structure has its own characteristics and applies within a certain range. Even some varieties have formed certain production batches, but because they have certain limitations, they cannot be widely promoted. This situation certainly benefits the full technical competition among manufacturers. However, if the situation lasts for a long time, it will seriously affect the technical progress of the product itself, creating obstacles to the standardization and generalization of the other party, and also creating participation in the development. The enormous waste of technical resources of various manufacturers.
At present, shelter loading and unloading vehicles are at a critical stage of development. At this time, if we can comprehensively examine the technical conditions of products and compare the advantages and disadvantages of various structures, we may be able to explore the reasons why products have stagnated in technology for many years. For products to get out of the current predicament and get help at a higher level of development.
2 structural type classification
The structure of self-loading and loading vehicles for shelters varies greatly from one another. This difference is mainly due to the different modes of operation of the opposite cabin during operation. This mode of operation is called loading and unloading mode. In order to facilitate the comparison of the structures, the structure types will be divided according to the loading and unloading modes. This can be divided into three categories: full lifting mode, semi-lifting, semi-dragging mode, full-dragging mode.
2.1 Introduction to the full lifting mode structure
The full lifting mode is to move the shelter in the way of lifting during the entire loading and unloading operation (see 1). The structural feature of the vehicle is to install a laterally extending truck-mounted crane at the front and rear ends of the loading platform, and lift the shelter as a whole by hoisting the lower wrap angles at the front and rear ends of the shelter through the steel ring chain. The loading and unloading of the shelter is carried out laterally (usually right). Since the vehicle needs to have a very high supporting stability in the lateral direction during operation, the main configuration of the loaded vehicle is a large-span lateral support device in addition to the crane.
2.2 Structure of semi-lifting and semi-dragging mode Introduction Semi-lifting and semi-dragging mode means that only the front of the shelter is lifted off the ground during loading and unloading, and the rear part is followed by dragging. This model can be divided into two types of structures, one called gantry type (see figure) and the other type called tray type (see 3). The name of the gantry type stems from the fact that the shelter to be loaded and unloaded needs to install a gantry type lifting frame at the front, and the structural feature is to equip the vehicle with an L-shaped pull arm that is both telescopic and tiltable.
At the beginning of the operation, the pull arm is in a contracted state, and the front of the shelter is lifted by tilting and catching the gantry, and is taken to the back of the loader; then, the hook is reversed and the shelter is dragged onto the carrier; The arm pulls the shelter into the loading position through a stretching action. In the tray type, the shelter is first fixed on the pallet, and then the crane is unloaded through the hanger at the front of the lifting pallet, and the lifting process is basically the same as the gantry type.
2.3 Introduction to Full Drag Mode Structure
The structural feature of the full-drag mode is that a carrying platform hinged with the frame girder, a folding movable bridge and a winch mechanism are mounted on the chassis of the carrier. Its hydraulic system is divided into two ways: all the way to drive the hydraulic cylinder, all the way to drive the hydraulic motor driven hoisting mechanism. During the loading operation, the carrying platform is tilted rearwards by the hydraulic cylinder, after which the movable bridge in the folded state is extended and the bridge crosses the ground when the platform tilts about 30°. At this moment, the towing device dragged by the hoisting mechanism is manually connected with the two wrap angles at the lower end of the front of the shelter, and then the shelter is dragged onto the platform by the hoisting mechanism through the bridge. The unloading process is performed in the opposite process. Throughout the loading and unloading process, the shelters are dragged up and down the platform, so it is called a fully-dragging loading and unloading mode (see 4).
3 structural source flow and technology inheritance analysis
The structure of any product is impossible to design out of thin air, in addition to the basic principles and basic structure of the design, but also learn from other known product structures. The products designed will not only use the functionally similar product structure, but also use some product structures with different functions to combine. This has a lot to do with the design style and technical expertise of the development unit, and it also has a lot to do with the designer's way of thinking, knowledge structure, and personal technical experience, which makes the same product with a different style. The analysis of the product's structural origin and technological heritage will provide a deeper understanding of the current development of the parallel development of various types of structures in the cockpit's self-loading and unloading vehicle, and will also be of great help in exploring the future development direction of the shelter's self-loading and unloading vehicles. .
3.1 Structure flow source of full lifting mode
The shelter originates from the container. Therefore, many application technologies of the shelter are also transplanted from the container, and the self-handling technology of the shelter is no exception. The full lifting mode is derived from the structure of container self-loading and loading. It is simply to transplant the structure originally installed on the semi-trailer to the off-road vehicle chassis.
3.2 Structure flow of semi-lifting and semi-dragging modes
The structure of semi-lifting and semi-dragging models is basically borrowed from the foreign cabin dump trucks, so the design level of domestic and foreign models on this model is roughly the same.
The tray structure in both structures is an improved design of the gantry structure.
3.3 Structure of full drag mode
The full drag mode structure is very innovative. The overall structure and other products have no direct structural inheritance relationship, but analysis of each assembly can still be seen in the structure of the integration of a variety of special vehicle technology: a. The platform's tiltable structure comes from ordinary dump trucks, but the platform's The tilt angle (30°) is much smaller than the tilt angle (50° to 55°) of the bulk tipper compartment. Therefore, the hydraulic cylinder push type lifting mechanism is adopted, and the connecting rod without ordinary dump truck is used to amplify the lift. Institutions, the structure is more simplified.
b. The activity bridge was inspired by the activity of the low slab semi-trailer crossing the bridge. The specific application was improved, and the structure was designed into a two-section structure that can be folded under the platform when folded.
c. The installation and drive of the hoisting mechanism is basically transplanted to the hoisting mechanism of the truck crane.
4 advantages and disadvantages of various loading and unloading modes and scope of application
4.1 Full lifting mode
4.1.1 Advantages and Scope of Application
The unique advantage of the full lifting mode is that the carrier can not only be self-loaded but also can be loaded and unloaded for other vehicles. Therefore, the vehicle is suitable for use in group cabin transportation. That is, when a group of cabins are being transported, a full-lifting model of the truck is provided, while other vehicles may be ordinary cabin vehicles that do not have loading and unloading capabilities. This vehicle can not only complete the loading and unloading operations for other vehicles, but also can carry a relatively light weight cabin.
4.1.2 Disadvantages and Deficiency
a. Due to the lifting operation, the truck platform that requires the full-lift mode can have excellent stiffness conditions, which makes the weight of the sub-frame much higher than that of the ordinary shelter carrier. In addition, the two truck-mounted cranes and lateral support devices have the same overall quality as the original vehicle chassis, which reduces the payload capacity of the vehicles.
b. Due to the installation of the lateral support device, the departure angle of the vehicle is greatly reduced. The inability to perform tasks on off-road conditions is a fatal drawback of this type of vehicle ().
The lateral support device affects the departure angle. c. The lifting points are at the front and rear ends of the cabin during loading and unloading operations. This loading and unloading mode requires that the cabin has no protruding appendages at the front and rear ends. At present, the shelters with better man-machine environment require the air conditioners to be installed outside the cabin (front or rear end), and many development units of the shelters need to install antenna poles and other accessories outside the cabin. Therefore, such shelters should not be used with full-lift loading and unloading mode carriers, thus limiting the application and promotion of such loading and unloading modes.
4.2 Semi-lifting, half-dragging mode
4.2.1 Advantages and Scope of Application
The difficulty in the operation of the semi-lifting and semi-dragging self loading and unloading vehicle is the docking of the pull arm hook and the hoisting point.
However, this process only occurs when the shelter is loaded, and the unloading process does not have this problem. Therefore, a prominent advantage of this loading and unloading mode is that the unloading speed is fast, and a single person can complete it, and the time will generally not exceed 1 minute.
Since only the front of the shelter is lifted during loading and unloading, the front bilge is already on the platform of the carrier when the tail of the cabin contacts the ground. At this time, it must be ensured that the loading and unloading inclination angle can not be too large (the loading and unloading inclination angle is generally not more than 30°, and it is too large to adversely affect the equipment installed in the opposite side), so this loading and unloading mode is applicable to the shelters with large length and size. So far, it is only used in the loading and unloading of 6 m shelters.
4.2.2 Drawbacks of gantry dump trucks
a. Poor generality. The gantry type dump truck relies on a locking mechanism to lock the specific opening of the cabin skid during transportation, so it is required that the shelter skid must be specially designed to adapt to this specific structure. In addition, in order to ensure the ready handling capacity, the gantry will always be attached to the shelter.
Therefore, the loading and unloading of the gantry-type self-loading and loading vehicles can only be handled by the shelter of a specific structure, and it is incapable of acting on the shelters of ordinary structures.
b. The service life is shortened. The locking mechanism locks the specific opening of the cabin skid and does not meet the pre-determined force conditions of the shelter structure of the shelter. The shelters are usually transported by means of wrap-around corners, and violation of the load-bearing principle will shorten the service life of the shelter.
4.2.3 Disadvantages of Tray Dumper a. Tray type structure is installed as a gantry-type improved structure, which overcomes the disadvantages of unreasonable locking of the shelter, but at the same time it also has another disadvantage: Tray The mass is very large (approximately 1 t), which limits its loading capacity accordingly, while also increasing manufacturing costs.
b. Versatility is still poor. In order to ensure ready loading and unloading capacity, the trays must be fixed under the shelter.
If there is no tray, the ordinary shelter still cannot be loaded or unloaded.
4.3 full drag mode structure
4.3.1 Advantages and Scope of Application
One of the characteristics of the shelter that distinguishes it from the container in its structure is that it is equipped with a skid underneath and has the ability to drag at short distances. The full drag mode utilizes this feature to completely turn the loading and unloading process into a drag mode. Full-drag self loading and unloading vehicles are currently only used in the loading and unloading of small squares (4 m), but from the structural analysis, there should be no technical problems in the loading and unloading of large squares.
Compared with the hoisting loading and unloading mode, the drag mode has many advantages: a. Since the opposite compartment is loaded with drag during the entire loading and unloading process, the energy consumed is the least, the power demand is the smallest, and the method of lateral power take-off of the transmission can be satisfied. Power requirements, the minimum cost of power conversion.
b. The power required for the loading and unloading process is small and stable. The medium and low pressure hydraulic systems can meet the requirements of their use. The reliability and service life of the hydraulic components can be greatly improved.
c. Versatility. There is no special requirement for the self-loading and loading vehicle counterparts of the fully-dragging structure. As long as the length and width dimensions meet the requirements, it can be handled and transported.
d. High security. The movement of the loading and unloading process is small and smooth and soft. Even if the system malfunctions, malfunctions, or operation errors during loading and unloading, the chance of major damage to personnel and equipment is also small.
4.3.2 Disadvantages and Deficiency
The biggest drawback of the full-drag mode is that the process of unfolding and retracting the active bridge requires human assistance to complete the process, affecting the loading and unloading speed, and has a certain safety hazard. This is also an important reason why the car has not been promoted so far.
5 Development Prospects of Various Loading and Unloading Modes
a. The full lifting mode is a very mature technology when it comes to loading and unloading containers. The problems that arise after loading and unloading into shelters are mainly due to the corresponding changes in the handling objects, the use environment, and the use requirements, which are structurally “unsatisfiedâ€. Therefore, if the model is improved in terms of structure, it will be very difficult. , The related research and development manufacturers need to make more efforts if they want to achieve further development.
b. There are also many problems in the semi-lifting, semi-dragging, self-loading and loading modes, and even a tray-type improved structure is not completely successful. Relevant manufacturers should not be satisfied with following foreign technology and go out of their own innovation.
c. The structure of the full-drag mode has been used for more than ten years in the self-handling area of ​​shelters, but for now, its structural disadvantages are technically insurmountable. At present, the scope of application and promotion is not large, and it is not entirely the cause of technology. Therefore, this type of loading and unloading model will have more room for development.
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