Q.1. What is a hydropneumatic circuit? Where they are used?
In some applications, the hydraulic and pneumatic circuits are coupled to get best use of the advantages of both oil and air medium. This combination circuit is known as Hydropneumatic or Pneumohydraulic circuit.Uses : It is used in the situation where quick action of air is desirable but high pressure/force of hydraulic system is required.
Q.2. A hydraulic press is operated by 4/2 spring returned pilot(air) operated dc valve. Draw Hydropneumatic circuit to operated the press using one 3/2 press button pneumatic valve.
Ans: As shown in circuit the main cylinder of press machine is operated by 4/2 spring returned valve which is operated by pneumatic pulse.Pneumatic pulse is provided by pressing the press button which triggers the 3/2 dc valve. When the valve is pressed the compressed air moves to the 4/2 dc valve and shifts it towards the right side causing the oil flow to the top side of the hydraulic press piston.As soon as the press button is released it causes the release of pressure on the 4/2 dc valve and spring of the 4/2 dc valve returns it to normal position, in normal position the pressurized oil is supplied to bottom side of the cylinder, hence the piston moves in upward direction.
Q.3. A hydraulic press machine can be operated from both the sides. Draw a pneumatic circuit which ensures both hands safely of the worker while operating the machine from any side