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Meter OUT Circuit A typical meter out circuit is shown in figure. Here the flow control valve is installed in the return line metering the fluid being discharged. In that way, this circuit also gives the control over the actuating speed. But this way of control offers altogether different characteristics to the circuit. Now, the circuit pressure has to overcome the load resistance and the pressure drop across the flow control valve. However, as the flow control valve is on the right side of the piston, the differential area will cause rise in the pressure.

When pilot signal of pressurized oil is used to control movement of poppet in the check valve, it is called as pilot operated check valve. It is used when no flow characteristics of the valve is desired only for a portion of the system cycle. Figure shows the pilot operated check valve. A pilot piston is introduced below moving poppet. This pilot piston can move up by introducing pilot signal. Working: In normal position there is no flow from (A) to (B) because the movable valve poppet has blocked the flow. Now pilot signal is given through port (C).

Counter Balance Valve It is basically a relief valve but it is used to set up a back pressure in a circuit to prevent load from falling. They are frequently employed in vertical presses, loaders, lift trucks and other machines that must maintain a particular position or hold a suspended load. In such applications, the counterbalance valve creates a back pressure to prevent the movement of piston rod of cylinder

1) Centreline mounting Centreline mounts are used to take care of thrust that can occur linearly or along a centreline with the cylinder. Proper alignment is essential to prevent compound stresses that may cause excessive friction and bending, as piston extends. Additional holding strength may be essential with long stroke cylinders. 2) Foot mounting It consists of mounting the cylinder with the help of side end lungs or side covers. These mountings are used where cylinders are to be mounted on to surface parallel to the axis of cylinder

4/2 puppet valve Figure shows a cross sectional schematic view of a poppet type 4/2 direction control valve. Inside the valve housing, a number of bores are engraved and interconnected through number of valve elements. The ports ‘P’, ‘R’, ‘A’, and ‘B’ shown in the diagram are designated as ‘Ppressure port, ‘A’ and ‘B’ – cylinder port and ‘R’ – exhaust port. In the position shown in the sketch, it is found that ‘P’ connects to ‘A’ and ‘B’ to ‘R’, When the elements are actuated by means of the push button, they are unseat and ‘P’ connects to ‘B’ and ‘A’ to ‘R’.

The keyway is a slot machined either on the shaft or in hub to accommodate the key. It is cut by vertical or horizontal milling cutter. A little consideration will show that the keyway cut into the shaft reduces the load carrying capacity of the shaft. This is due to the stress concentration near the corners of the keyway and reduction in the crosssectional area of the shaft. It other words, the torsional strength of the shaft is reduced. The following relation for the weakening effect of the keyway is based on the experimental results by H.F. Moore.