NFPA-Tie Rod Cylinders The National Fluid Power Association (NFPA) has standardized the dimensions of hydraulic tie rod cylinders. This enables cylinders from different manufacturers to interchange within the same mountings.
The cylinder skews the rollers to either bring the conveyor belt toward the sensor or push it away from the sensor. When the conveyor belt is not pushing the paddle, the valve is not activated. This causes rollers to be skewed to bring the conveyor belt towards the sensor paddle. When it hits the sensor paddle, the valve is activated causing the air cylinder to move to the opposite position. http://www.brand4india.com/pneumatic-textiles-spares-suppliers/pneumatic/