Flat cylinders – when pressure needs to go around the corner

Flat cylinders are hydraulic linear actuators with a special design. They are engineered so that movement is executed at a right angle to the pressure supply. They are only a few centimeters high, which leads to limitations in their range of application and specific design features.

Construction of a flat cylinder

Fundamentally, a flat cylinder does not differ from a conventional hydraulic cylinder. It consists of a housing, a piston, and a hydraulic connection. Most flat cylinders have only one connection, making them single-acting. An external force must be applied for the return stroke.

Use of flat cylinders

Flat cylinders are typically installed upright. The piston extends vertically upwards, lifting a load. To retract, the pressure is released. Gravity pushes the piston back to its starting position. Therefore, a check valve must be installed upstream of the flat cylinder.

In principle, it can also be used horizontally. However, the return stroke must then be implemented through other measures, such as mechanical levers. In this capacity, flat cylinders are frequently used for assembly, maintenance, and repair tasks. In these cases, they serve to separate heavy components. To release the cylinder, it is usually pushed back with a crowbar or a pry bar until it can be removed from the site of operation.

In addition to mobile applications, this component is primarily used wherever installation space is limited. However, its range of applications is restricted.

Limitations of flat cylinders

The low-profile housing only allows for a correspondingly short piston. Consequently, a simple flat cylinder has a very short stroke length. Its function is therefore limited to slightly lifting heavy components.

To circumvent this problem, many flat cylinders are designed as telescopic cylinders. These specialized hydraulic cylinders do not have just one piston, but several nested ones. They extend telescopically. Together, they can achieve a significant stroke length that approaches that of a standard cylinder. However, since they are considerably more expensive and more prone to failure than normal linear cylinders, they are only used for specific tasks.

Applications for flat cylinders

Flat cylinders are used where no other linear actuator can fit due to design constraints. The component can withstand and transmit very high pressures. Since these pressures are transferred to the surrounding environment, the environment must be designed to accommodate them. Otherwise, the flat cylinder may increasingly press itself into both surfaces. This not only disrupts the intended movement but also makes the cylinder increasingly difficult to remove. Therefore, during prolonged use, the impact of the flat cylinder on its surroundings should be checked regularly.