6.3.3 Parking Tower Chain
Shortage of parking in large cities created a demand for carousel-type (vertical-rotation) multilevel parking, that first appeared in Japan in 1962 (Figure 6.17). Tower parking lots permit the storage of many vehicles (usually more than 30 cars) in a small space. Over the years, tower parking has become increasingly popular. Currently there are more than 10,000 of them in Japan.
Parking Tower Chain supports and rotates the cage containing the vehicle. As an interesting note: Elevator parking garages, which use transmission roller chains or wire ropes to raise and lower the vehicles, are increasing in number. But vertical-rotation garages are still the majority.
Construction and Features
There are only a few manufacturers producing parking tower systems. However, each manufacturer produces a specific design.
Figure 6.18 shows an example of Parking Tower Chain.
The entire assembly consists of chain, attachments, and side rollers. The chain receives tension, which can be summarized as follows:
Chain tension = weight of automobiles and cages + weight of the chain + friction on the side roller + tension from take-up.
Figure 6.17 Vertical Rotation Parking Elevator
Figure 6.18 Example of Parking Tower Chain
Each attachment must support the weight of an automobile and a cage. The side rollers prevent the attachments from tilting. Spacing of each cage is between 1,600 and 2,000 mm, and attachments are installed on every fourth chain link. Therefore, the chain pitch is 400 to 500 mm. Tensile strength varies between 1,333 and 1,500 kN, depending on the type of chain that is used (the largest one is 2,940 kN). Standard chain speed is 16 m/min., but in some applications speeds reach 25 m/min.
The special shape sprocket with 12 teeth is used with this chain. Usually the sprocket is made by the original equipment manufacturer.
Selection and Handling
- Safety is a major concern with this application. The technical standards developed by the Japan Parking Industry Association require a safety factor of more than seven.
- It is very important that the original equipment manufacturer (OEM) and the chain manufacturer work closely to select the design and size of the chain for the application. Only manufacturers with experience in this type of application should be considered.
- Make sure to include the weight of the chain itself in calculations. It is an important factor, since the number of cars that can be stored may be affected by the weight of the chain.
- Pins, bushings, and side rollers must be lubricated regularly, and all components must be inspected frequently. These should be included in the maintenance contract from the OEM.
Desirable characteristics for Parking Tower Chain include low noise, high-speed stability, light weight, and maintenance free.