In this article from our series on Lift tables types and their advantages and disadvantages, we take a detailed look at the push chain drive of lift tables.
How a lift table with push chain works
In a conventional scissor lift table, the lifting and lowering movement is achieved by the scissor mechanism extending and retracting. In contrast, in a lift table with push chain, the scissor mechanism only serves as a guide. The actual lifting and lowering movement is performed by the mounted chain, which is redirected towards the platform by the drive. The chain consists of special links designed to transmit both tensile and compressive forces. When extending, the chain links stabilize each other and raise the platform by transferring compressive forces. When retracting, the chain pulls the platform back down.
Relief of the scissor mechanism
As previously explained, the scissor mechanism is relieved by the push chain. The force required to lift the load is transmitted directly to the platform via the push chain, rather than through the scissor mechanism. As a result, the scissor mechanism only serves as a guide for the platform. This allows for a lighter and more compact design of the scissor mechanism, which reduces the overall weight of the lift table. The lower weight to be lifted has a positive effect on energy consumption and the required drive power.
No hydraulic oil required
While hydraulic lift tables often use mineral oils for power transmission, lift tables with a push chain drive operate purely mechanically. This eliminates the risk of leaks and makes the use of special oils unnecessary in sensitive areas such as the food industry. Mineral oils are only used here as lubricants in the drivetrain.
High positioning and holding accuracy
In belt-driven lift tables, position deviations can occur due to belt stretching. Hydraulic lift tables, on the other hand, tend to gradually sink during longer idle periods. Since power transmission in lift tables with push chain is purely mechanical, such deviations do not occur. This allows for precise positioning, which can be reliably maintained over long periods of time.
Point load transmission
In contrast to conventional lift table designs, where the load is distributed across the four contact points of the platform’s scissor mechanism, a push chain transmits force through a single point. This places special demands on the design, as the platform must be sufficiently rigid. However, a more rigid platform results in increased weight, which in turn raises the energy requirements for the drive and increases acquisition costs.
Alternatively, the use of multiple push chains can be considered to achieve a more even force distribution — this is especially beneficial for larger platforms. However, this also increases the investment costs and the complexity of ensuring the synchronization of all chains. A lack of synchronization could lead to platform misalignment.
High construction height
Although a push chain can be "rolled up" when not under tension, the redirection mechanism itself requires a certain construction height. As a result, lift tables with a push chain drive can only be used when the construction height of the lift table does not need to be minimized.
"Overriding" of the scissor construction
Unlike conventional lift tables, using a push chain drive eliminates the stabilizing effect of the scissor mechanism, which is achieved by the applied load. This means that the play between the individual components becomes more noticeable, making the scissor mechanism less stable.
To ensure sufficient stability, precise guidance is required, with particularly tight manufacturing tolerances needing to be maintained — a significant challenge, especially with the floating bearing of the guiding scissor mechanism. If these tolerances are not met, it can result in the loss of the guiding function and ultimately lead to instability of the entire lift table.
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