Synchronous cylinders for special applications

Synchronous cylinders, also referred to as “synchronous-running cylinders” or “steering cylinders”, are hydraulic cylinders with a special technical specification: double-acting operation.

A characteristic feature of the synchronous cylinder is that the piston rod can extend out on both sides.

Design of the synchronous cylinder

The synchronous cylinder consists of a conventional cylinder tube fitted with two hydraulic ports. The piston rod protrudes from both sides of the cylinder and is sealed with shaft seals. The piston plate is located in the middle of the piston rod. It divides the interior of the cylinder into two halves. A seal reliably separates the two chambers from each other. Both chambers are always filled with hydraulic oil. Air inclusions are not permitted, as they would reduce the reliable operation of the synchronous-running cylinder.

The chambers can only be pressurized with hydraulic pressure one after the other. This makes the use of control and regulating valves necessary when using a synchronous cylinder. If the piston rod extends out of the cylinder on one side, it retracts at the same speed on the other side, and vice versa.

Applications of synchronous cylinders

Synchronous cylinders are primarily used for the precise control of a rudder, a flap, or a steering axle. Thanks to the absolutely synchronized speed and identical feed of the piston rod, control and rudder applications can be implemented with exceptional precision using this component. This eliminates the need for complex synchronization of individual cylinders. As a result, synchronous cylinders are less commonly used for work processes such as lifting different loads or pressing recyclate (recycled plastic). Their function is mainly to move permanently installed components with a predefined, constant counterforce.

Custom designs for synchronous cylinders

Synchronous cylinders are very popular in maritime applications. They provide a powerful, reliable, yet very simple solution for moving a rudder or a drive. However, these hydraulic cylinders are very close to, or directly exposed to, salt water. This makes adaptations to material selection and coating necessary. Today, synchronous cylinders are available that can withstand years of use in salt water without damage.

Faults in synchronous cylinders

A typical malfunction in a synchronous cylinder is jerky movement of the piston rod. This may be due to a failing seal at the center section. Another possible cause is an air inclusion in the hydraulic oil. Unlike liquids, gases are compressible, which can trigger this malfunction. Before dismantling the synchronous cylinder, it should first be checked whether the problem can be resolved by bleeding the hydraulic system. In terms of maintenance and repair, synchronous-running cylinders are just as forgiving as standard hydraulic cylinders. The seals can be replaced at any time. As long as the piston rod is not bent or the housing is not damaged, a synchronous cylinder can therefore be reconditioned repeatedly to an almost as-new condition.