Small Hydraulic Cylinders for Power in Confined Spaces

Large hydraulic cylinders with long strokes and high force application are always very impressive. However, a large proportion of hydraulic linear actuators are installed in locations where high forces must be applied in confined spaces. The industry therefore developed particularly compact and small hydraulic cylinders very early on. They can be divided into manual and high-performance miniature cylinders.

Manual Small Hydraulic Cylinders in Practice

Manual hydraulic cylinders are all linear actuators that do not have an electromechanical pump for drive but are operated manually. Especially when the hydraulic unit is to be mobile, this limits the size and weight of the hydraulic cylinder. Typical examples of these small hydraulic cylinders can be found in the following applications:

• hydraulic jack
• hydraulic engine hoist
• hydraulic transmission jack
• portable hydraulic cylinders
• straightening tools

With the help of these manual force multipliers, the operator can move heavy loads without a power connection. The main limitation when operating manual hydraulic cylinders is the slow movement. These tools are also very heavy. Therefore, engine hoists, jacks, or transmission jacks are mounted on trolleys. If the small hydraulic cylinder is to be portable, this further limits its size.

Small Hydraulic Cylinders in Technical Applications

Hydraulics offer a number of advantages. The simple provision of large forces is only part of the possibilities this technology offers. Another special feature is the flexible arrangement of pressure generator and actuator.

This means the position of the hydraulic pump is largely flexible. Every consumer can be reached via rigid or flexible lines and operated with consistent reliability. This makes hydraulics interesting for technologies where the external profile is subject to strict requirements and installation space is severely limited. Typical examples are vehicles and aircraft of all types. In cars, brake pressure is transmitted via the master cylinder and brake lines to the wheel brake cylinders. In addition, the clutch can also be operated by two small hydraulic cylinders. Master cylinders and wheel brake cylinders are among the smallest hydraulic cylinders of all. They have a diameter of only a few millimeters, which does not diminish their reliability and operational capability.

In larger aircraft, the entire control of external moving components such as rudders, flaps, or landing gear functions exclusively hydraulically. The small hydraulic cylinders used do not have to apply large forces. However, they must be reliable, precisely controllable, and function at any outside temperature or flight speed. Similar applications for small hydraulic cylinders can be found in ships.

Maintenance of Small Hydraulic Cylinders

Small hydraulic cylinders are subject to the same stresses as large linear actuators. Only the lower internal pressures reduce the risk of cavitation damage. Nevertheless, they can be damaged by contaminated oil and lose performance. With regular servicing and maintenance, however, small cylinders can also achieve an impressive service life.