The technological evolution of domestic refrigerators demands today higher thermal insulation performances and lower power consumption than in the past. For refrigerators producers, reaching these targets keeping an affordable industrial cost means use the new injection and polymerization tools for rigid PU foams processing.
The multi-head “Breakers Down” injection system patented by Cannon is the solution for these manufacturers.
As you may know, in recent years, the refrigerator market has been marked by an intense search for improvements in energy efficiency (we talked about it in this article). This challenge passes through the increase of the insulating power of polyurethane foams thanks to the use of HFO as blowing agents (replacing those harmful to the environment). If combined with faster reactivity formulations, HFO-based foams also help the reduction of typical cell size. But with this kind of foam, conventional breakers up injection from one point is not enough to correctly fill the whole cabinet.
Injecting large quantities of a fast-reacting formulation in the walls of a refrigerator body – a task often complicated by the presence of VIP panels, cables, pipes, and inserts in the cavity to be filled – thus requires new technical solutions.
“Breakers Down” Foaming
Leading fridge manufacturers commonly use four mixing heads, injecting simultaneously. Due to the peculiar design of a refrigerator cabinet – featuring a large solid back wall and the thinnest possible side walls – it is necessary to inject the formulation through four holes located in the four corners of the back wall.
While most domestic refrigerator models are injected in a “Breakers Up” cabinet positioning, the four-head rear wall injection in the “Breakers Down” position requires the fridge compartment to look downwards.
In this kind of foaming method, the male part of the mold (the plug) must be positioned on the lower side of the fixture. It is fixed on a shuttling pallet extracted from the jig to load and unload the fridge with a manipulator automatically. Once inserted on the plug, the empty cabinet must be shuttled back into the jig and lifted to lock it in the fixture, ready for the injection. This operation requires numerous seconds – depending on the size of the cabinet – and electric power.
Cannon developed a new polymerization fixture to improve the productivity of these “Breakers Down” foaming plants. In this new device, a lower shuttling pallet holds the male plug that also hosts the two tilting lids of the fixture that define the top and bottom walls of the fridge.
This design allows the plug to be shuttled freely outside the fixture (to unload a filled cabinet and load an empty one with an aerial double manipulator) and move back in its final foaming position without finding its path the obstacle above mentioned two hinged lids.
A simple vertical short stroke of a few centimeters makes the device immediately ready for injection.
This short-stroke closing system saves at least 6 seconds for each movement: 12 seconds per cabinet means at least a 7 to 10% higher productivity for each foaming line.
Four mixing heads –typically the new FPL SR type – are installed on the upper part of the structure. Handled by numerically controlled vertical manipulators, the heads perform the simultaneous injection of the liquid formulation, fed by a double high-pressure metering unit.
Advantages of this solution
- Cycle time reduced by at least 12 seconds
- Easy regulation, cleaning, and inspection of the plug
- Simple and ergonomic adjustment of the back wall of the mold
- Relevant reduction of the electricity consumed to operate the vertical stroke of the jig twice per cycle
- The reduced sheer size of the fixture, for a smooth operator’s access for service and cleaning
- Small footprint for easy placement within the facility
This new Cannon polymerization device is the perfect solution for the industrial production of large domestic or commercial refrigerators with a complex internal configuration, requiring a high volume of formulation dispensed in a short time.