Standard Grade Technological Studies Flow control valves Flow

Flow control valves • Normally pneumatic pistons move very quickly. • This can be

The Restrictor • Often referred to as a throttle valve. • Works by reducing

The Restrictor • The restrictor slows the flow of air in both directions. •

The Unidirectional Restrictor • This restrictor slows the flow of air in one direction

The Unidirectional Restrictor • Air flows into port 1. . . • Some of

The Unidirectional Restrictor • Air flows into port 2. . . • Again, some

Restrictor circuits • Unidirectional restrictors are more useful to us. • We must ensure

Assignment 8 1. Back to the car park barrier. Some one suggests further modifying

Assignment 8 2. For safety reasons, the entrance door to a store room must

Assignment 8 2. The circuit diagram for the door mechanism is shown, with some

Assignment 8 3. Part of a manufacturing process involves dipping components in a chemical

Assignment 8 • Design a circuit that will solve this problem. • Using computer

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Standard Grade Technological Studies Flow control valves

Flow control valves • Normally pneumatic pistons move very quickly. • This can be dangerous. • To slow the speed of a piston down we can use a flow control valve. • There are generally two types available to us.

The Restrictor • Often referred to as a throttle valve. • Works by reducing the amount of space the air can flow through. • Can be adjusted by turning the small screw on top of the valve. • The symbol for a restrictor is shown.

The Restrictor • The restrictor slows the flow of air in both directions. • In the circuit shown, a restrictor is used to slow the speed of the single acting cylinder. • The problem with this type of restrictor is that it slows the piston in both directions.

The Unidirectional Restrictor • This restrictor slows the flow of air in one direction only. • The symbol for a unidirectional restrictor is as follows. . .

The Unidirectional Restrictor • Air flows into port 1. . . • Some of the air takes the bypass route. . . • This blows a small ball against a valve and blocks this path. . . • The air is forced through the restriction, slowing down the airflow. By-pass Air flow Restriction

The Unidirectional Restrictor • Air flows into port 2. . . • Again, some of the air takes the bypass route. . . • The ball is blown away from the valve. . . • The air is flows through the bypass unrestricted. By-pass Air flow

Restrictor circuits • Unidirectional restrictors are more useful to us. • We must ensure that they are inserted into a circuit in the correct orientation. • We always restrict the exhaust air coming from the cylinder. • This makes the piston operate much more smoothly.

Assignment 8 1. Back to the car park barrier. Some one suggests further modifying the circuit. . . • Build and test the circuit shown to raise the barrier slowly • Describe how the system operates. • Why do we restrict the exhaust air when slowing down the speed of the piston?

Assignment 8 2. For safety reasons, the entrance door to a store room must open and close slowly. A double acting cylinder is used to slide the door.

Assignment 8 2. The circuit diagram for the door mechanism is shown, with some of the piping missing. • Copy and complete the circuit diagram. • Build and test the door opening circuit. • Describe how the circuit operates and why two restrictors are needed in this circuit.

Assignment 8 3. Part of a manufacturing process involves dipping components in a chemical solution to prepare them before they are painted. A double acting cylinder controls the process. For safety reasons the cylinder must outstroke and instroke slowly.

Assignment 8 • Design a circuit that will solve this problem. • Using computer simulation, build and test your solution. • Construct your circuit using the pneumatic components. • Describe how your circuit operates to solve the problem. • Why is it important that the cylinder operates slowly in both directions?