Pneumatic Tools & Equipments

Cylinder Variants

Cylinders are of various types based on their applications. These are as follows:

1) Double Acting Cylinder:

These cylinders have power strokes in both directions (viz. Forward and return motion). Compressed air is let in through both the ports alternately to achieve the above result. Alternate air supply to the cylinder is achieved by a 5 port / 4 port valve as illustrated in the section for valves.

2) Single Acting Cylinder:

These cylinders have power strokes in one direction only.

Return Types available are:

a) Sping return: 1) Air to forward piston / spring to return piston.

2) Air to retract piston / spring to forward piston. b) Return by external load: Air to forward or return piston and original position achieved by external load.

Power Stroke in single acting cylinder is achieved only in one direction of piston movement. Return stroke is achieved by any of the methods mentioned above. Seed and pull force of return stroke is dependent on the stiffness of the spring used and the mode of flow control available. These cylinders are used in applications where the piston is to be in the original / neutral position in the case of power failures etc.

3) Double Ended Cylinder:

The piston rod in this case is extended from both the sides of the piston and the power stroke is available in both the directions. An example could be the clamping of the workpiece to be moved onto the cylinder body rather than the piston shaft.

4) Tandem Cylinder:

These are two double acting cylinders coupled together with a common piston rod and find applications where there is space constraint to use a larger bore for achieving the requisite force. The force achieved by a tandem cylinder is 1.8 times that of a double acting cylinder of the same bore eg. force obtained by 200 mm bore cylinder at 5 bar is around 1.6 tonnes. This same force can be obtained using a tandem cylinder of bore size 150 mm.

5) Continuous Reciprocating Type:

Also known depicted as linear air motor, these units are self reciprocating air cylinders which require no external valves or limit switches. Just one air input is required to operate the cylinders. Speed of forward and return stroke can be adjusted by the flow control valves mounted on the cylinders.

6) Valve Mounted Cylinder:

This incorporates a double acting cylinder with valve mounted directly on it. This avoids excessive piping as just an inlet pressure is required to be given to the inlet of the valve. Outlets ports of the valve are pre-connected to the ports of the cylinders. This cylinder is not continuously reciprocating type. On / Off switches are required to enable the forward and return stroke.

7) Feed Control Cylinder:

In general applications, the speed of a cylinder can be controlled using flow control valves. However, in applications which require very precise speed control without jerks, the feed control cylinder is recommended. Hydro-pneumatic system provided in the cylinder enables achievement of velocities as low as 50 mm per minute.

Working Characteristics of Pneumatic Cylinder

Material Specification:

Cylinder tube	Seamless hard drawn low carbon steel tube, honed and hard chrome plated internally to 60 RC increases seal life. Bores: 40 to 300 mm. Seamless Hard drawn brass tube internally polished : Bores : 19 to 65 mm
Piston rod	EN8 ground, micro finished and hard chrome plated for lasting seal life and corrosion resistance.
Seals	Piston and cushion seals made from a wear resistant nitrile rubber compound. The double lip seal design automatically self compensates against wear.
Piston	Cast iron
End covers	Cast iron oxidised to prevent corrosion

Media	Air, Oil and inert gas
Temperature range	-20 to 85 degrees cen.
Pressure	150 p.s.i. / 10 bar
Cushioning	available in bore sizes 32 and above only.

Note: The internal finish of brass tube has been known to improve in continuous operation with the passage of time thereby reducing friction.