For refrigerators producers, reaching energy efficiency targets while keeping costs affordable means using newer injection and polymerization tools for rigid PUR foams processing. Learn more about our patented method.
August 4, 2021
In recent years, the refrigerator market has been marked by intense research into improving energy efficiency. This challenge passed through the increase of the insulating power of polyurethane foams thanks to the use of HFOs as blowing agents. If combined with faster reactivity formulations, HFO-based foams also help reduce the 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.
Advantages of this solution
- Cycle time reduced by at least 12 seconds
- Easy plug regulation, cleaning, and inspection
- Simple, ergonomic adjustment of the mold’s back wall
- Relevant electric consumption reduction for operating the jig’s vertical stroke twice per cycle
- Reduced sheer fixture size, for smoother access for service and cleaning
- Small footprint for easy floor placement
Our polymerization device is perfect for producing large domestic or commercial refrigerators with a complex internal configuration, requiring a high volume of formula dispensed quicky.
We 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 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.
