There are many kinds of compact cylinders available in the marketplace—these pneumatic actuators have been shortened relative to standard pneumatic cylinders. In fact, they can be as much as 50% shorter than the normal cylinder, but still maintain the capacity to exert the same force as their larger counterparts.
The “Pancake cylinder” was the original compact pneumatic cylinder. It was invented by Al Schmidt in 1958, to fill a need for force in a tight, enclosed space. The basic intent was to get the most stroke in a short overall length using common machined parts and seals. Through the years, this design has been further developed, with many features and options to satisfy an extreme variety of customer applications.
This round body cylinder has a smooth, clean outside diameter for ease of machinery cleaning. Even though it was initially used for strokes less than 1-inch, manufacturing methods have allowed increased strokes to as much as 4 inches. Non-metallic rod bushings and piston bearings can accommodate extreme or unforeseen loads to provide long-term durability.
When selecting a compact cylinder, the following application data is needed:
• Operating pressure in pounds per square inch
• Force required
• Stroke
• Preferred mounting and footprint, and
• Spring return or double acting
There are some other items that you may want to consider when selecting a pancake cylinder. These can include:
• Ambient temperature
• Media temperature
• Environment
• Excessive loads other than required axial force, and
• Load guiding requirement.
I think the concept has been adapted in hydraulic cylinders as well. People also refer to them as flat body or low profile cylinders.