Vacuum Generation

Vacuum only when needed, where it matters

Vacuum Generation: Continuous vs Intermittent Systems

Industrial vacuum generation can be achieved using rotary vacuum pumps for continuous high-flow applications or venturi vacuum generators for intermittent gripping.

Rotary pumps provide constant suction but consume energy continuously. Venturi systems operate only when needed, reducing compressed air consumption, minimizing response time, and allowing installation close to suction cups.

CONTINUOUS VACUUM, USING ROTARY VACUUM PUMPS

Rotary Vacuum Pump Principle

The most commonly used type of rotary pump is the vane pump (illustration). The blades are spun at high speed by the rotor, and the centrifugal force pushes them against the pump housing. The air is displaced and pushed out, creating a vacuum at the inlet.For low vacuum levels only, turbines (or regenerative blowers) are also used, which operate in a similar manner to vacuum cleaners: a rotor with blades that do not make contact with the housing, causing air to move at high speed.

Range of Rotary Vacuum Pumps

To maintain optimum output, rotary pumps must remain within average power levels: from 1 to 10 Kw. The suction capacity generated is much higher than the normal requirements of 
industrial suction cups.

Operation Applications and Practice

Rotary pumps are used where a constant, high level of suction fl ow rate is required. Vacuum packaging machines are a typical example of this. However, in the vast domain of vacuum gripping, rotary pumps are only used in rare instances, where an object requires a high level of suction fl ow rate that needs to be maintained for a long time during the cycle.

Rotary Vacuum Pumps

  • Constant consumption, continuous generation of vacuum, even for intermittent requirements: not suitable for intermittent vacuum generation requirements.
  • Located far from the suction cups.

Applications

  • Vacuum sources for various processes such as vacuum packing, etc.
  • Clamping maintained throughout the cycle, with high suction fl ow rate (porous objects etc.)

A Typical Application

The example shown below is a digital control manufacturing robot, which uses suction cups to clamp porous parts. Note that the pump, which is bulky, noisy and causes vibrations, must be installed well away from the operational section of the machine. It is connected via a tube, which must have a large diameter (40 to 80 mm) to reduce the loss of vacuum, which can sometimes be dangerous.

INTERMITTENT VACUUM, USING VENTURI VACUUM PUMPS 

Venturi Vacuum Pump Principle

Using the "venturi" effect : a nozzle of diameter Ø is supplied with compressed air. The air jet carries along ambient air in its turbulence and then passes through the mixer on its way out. This suction effect of ambient air creates the depression that generates the vacuum.

Unlike rotary vacuum pumps which must turn continuously, venturi vacuum pumps can operate intermittently, only when the suction cups require vacuum.

Nozzle diameter Ø
The diameter defines the force generated and therefore the suction capacity:

  • Ø 0.5mm for micro suction cups, 
  • Ø = 3mm with a suction capacity of 450 Nl/min for several large suction cups.

Mixer profile
This profile defines the maximum level of vacuum achieved by the venturi.

Two standard levels offered by COVAL:

  • 60% for porous material (30 to 55% vacuum)
  • 85% for airtight materials (55 to 80% vacuum)

Venturi Vacuum Pumps

  • Consumption only when needed, results in low air consumption.
  • Installation very close to the suction cups.
  • Suction flow rate and vacuum level optimized for each application.

Applications

  • All intermittent gripping operations, i.e. which only last for a part of the full cycle of the machine

Applications and Practice

Venturi vacuum pumps are used for all normal vacuum gripping applications.

Compact and light, venturis are installed as close as possible to the suction cups: little pressure loss and a minimum volume to purge, resulting in short response times and minimum energy consumption.

  • simple, pneumatically-controlled venturi pumps, which are miniaturized for installation on suction cups

  • complete, electrically-controlled venturi pumps, for installation as near as possible to thesuction cups.