[ToddF]

You are correct that the term "pneumatic rotary cylinder" isn't the most descriptive. But, having worked with pneumatics for years, this phrase brings to mind two types of pneumatic actuators. The first is a rotary actuator where a cylinder drives a rack gear, which is mated to a circular gear connected to an output shaft or stage. The output axis is perpendicular to the axis of the cylinder, and has only rotary motion. These are often used to actuate a rotary joint through 90 or 180 degrees.

The second type has a pneumatic cylinder that drives a rotary cam through a coarse pitch helical track. The output shaft is coaxial with the cylinder and moves both axially and rotationally, usually 90 degrees. These are usually used as hold down clamps in automation, and especially fixturing applications.

Both types are shown in a google image search for "pneumatic rotary cylinder". If I were an inspector, I would allow both types as allowed under the rules, even without the clarifying QA question. Similarly to how any transmission mechanism or gearbox is legal, as long as it is driven by a legal motor, as long as the device is powered by a pressure cylinder, I would consider the form of the resultant motion to be irrelevant.

It sounds like what you are asking about is commonly referred to as an "air motor". These commonly convert air flow into continuous rotary motion. The most familiar examples of air motors would be those in dentist's hand pieces or some air powered hand tools. There is no way I would include air motors within the definition of "pneumatic rotary cylinder".