Pressure Intensifier Circuits

 As we know, usually a heavy punching press requires two pumps (a low-pressure pump and a high-pressure pump) to obtain the high-pressure outlet flow required for the operation.

PRESSURE INTENSIFIER CIRCUITS

1. Intensifier Circuit in Punching Press Application

As we know, usually a heavy punching press requires two pumps (a low-pressure pump and a high-pressure pump) to obtain the high-pressure outlet flow required for the operation. But with the use of a pressure intensifier, one can eliminate the expensive high-pressure pump in the punching press application.

1. Circuit

Fig.9.21 shows a basic hydraulic circuit employing an intensifier for use in a punching operation. This circuit consists of a low-pressure pump, 4/3 DC valve, pilot check valve, sequence valve, pressure intensifier, and cylinder. As shown in Fig.9.21, the intensifier should be installed closer to the cylinder to shorten the high-pressure lines.

2. Operation

First operator places workpiece in fixture and shifts handle of 4/2 DC valve. When the 4/2 DC valve is shifted to the right side position, the oil flows to the blind end of the cylinder through the check valve. When the pressure in the cylinder reaches the sequence valve pressure setting, the sequence valve opens and supplies the flow to the intensifier. Now the intensifier starts to operate and gives high-pressure output. This high-pressure output of the intensifier closes the pilot check valve and pressurizes the blind end of the cylinder to perform the punching operation.

When the 4/2 DC valve is shifted to the left side position, the oil flows to the rod end of the cylinder. When it builds-up the pressure, the pilot signal opens the check valve. Thus-the ' cylinder is retracted to the starting position.

2. Air-Over-Oil Intensifier Circuit

• In some applications, the hydraulic and pneumatic circuits are coupled to best use of the advantages of both oil and air mediums.

• This combination circuit is also known as hydro-pneumatic or pneumo-hydraulic circuits or dual pressure systems.

1. Circuit

Fig.9.22 shows a typical air-over-oil intensifier. This circuit can be used for drawing a cylinder over a large distance at a low pressure and then over a small distance at high pressure (such as in punch press applications). This circuit consists two lines-air lines and oil lines. In the circuit, the air lines are shown by single lines and oil lines by double lines.

2. Operation

Extension: When the first 4/2 DC valve (valve 1) is shifted to left mode, the air from the reservoir flows to the approach tank. In the approach tank, the air forces the oil to the blind end of the cylinder through the bottom of the intensifier, as shown by double lines in Fig.9.22. Now the cylinder extends.

Useful Work: When the cylinder experiences its load, the second 4/2 DC valve (valve 2) is actuated to the left mode. This valve position sends air to the top end of the intensifier. Now the intensifier moves down, and the piston of the intensifier blocks the path of oil from the approach tank. Now the cylinder receives high pressure oil at the blind end to perform the useful work such as punching operation.

Retraction: When the valve 2 is released (shifted to right mode), the air flow from the reservoir, is blocked. The air from the top end of the intensifier is vented to the atmosphere. This completes the high pressure portion of the cycle.

When valve 1 is released (i.e., shifted to right mode), the air flow is diverted to return tank and also the air in the approach tank is vented. The diverted air flow pushes the oil to the rod end of the cylinder. This causes the cylinder to retract. The oil from the piston end of the cylinder is diverted back to the approach tank through the bottom end of the intensifier. This completes the entire cycle of operation.