Pneumatics Vacuum Generators


#1

What is the vacuum generator and why is it used?

The Pneumatics Vacuum Generators is the method of using compressed air to generate a vacuum. Normal vacuum pumps driven by electric motors are available, but they are in general quite substantial in size. If the vacuum pump is not closely located to the suction cup, there is also a time delay while the connecting hose draws down to the vacuum level.

If one needs a suction cup to grip something in a tight environment, or if the load restrictions eliminate the possibility of a vacuum pump, a Venturi vacuum generator can create an incredible amount of suction in a very short period of time.

A venturi vacuum generator is shown below:

image

Working:

The Venturi device has compressed at flowing through from the left-hand side. The restriction in flow near the middle of the device creates a pressure drop (this is perhaps the only useful item found in a fluids course textbook that automation engineers can use to their advantage).

There are only two real limitations to this device. The first is that they take a constant supply of air pressure flowing through them to hold an item. This is different to an air cylinder, which does require continued pressure to keep something in place, but not the continued flow rate of a Venturi device. Secondly, if the environment is dirty, the device will pick up particles. There is nothing as frustrating as cleaning out instant cocoa drink powder from a Venturi device when some of the transported pouches break apart.

If an automation application requires multiple suction cups, and there is even the slightest possibility that one of the cups does not have a good seal, so that a vacuum would not be achieved, it is common to see that all or a couple of suckers have their own Venturi generator. The incremental cost is not unreasonable, in particular compared to losing control over an expensive transferred product.