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Rotating floor improves oven throughput

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THREE new glass mould pre-heating ovens delivered to ACI Glass include a number innovative design improvements that will substantially improve throughput, according to Roger Brockway, manager of furnace manufacturer B & L Tetlow.

The ovens are used to pre-heat moulds to 450°C, prior to the moulds being inserted into a bottle making machine which applies red hot glass.

The oven utilises recirculating air which is drawn up into the main chamber over the load and then into a mesh-covered fan involute and false roof cavity.

The air is then recirculated back into the work chamber through a perforated 5mm false floor plate. The oven recirculates air about ten times a minute depending on load.

Mr Brockway claims a number of new design features will make the new ovens attractive to potential users. He notes the two small facing doors allow products to be loaded while previously heated product can be simultaneously unloaded.

The angled doors are designed for the use of lifting devices, a factor that substantially improves operator safety since moulds normally weigh from 30 to 50kg.

Operator safety has also been substantially improved by the door design which has a centre pivot. The pivot movement keeps the hot face of the door away from the operator and avoids exposure to excessive heat.

The oven also features a rotating false floor made from 5mm 5CR12 steel plate. The floor is perforated to allow a free airflow and can be rotated to suit loading or unloading requirements.

The floor is supported by a substantial two bearing shaft. The table takes approximately 2.5 minutes to complete one revolution. It is driven by a 4-pole SEW gearmotor.

Both doors are fitted with microswitches that automatically operate a flap located on the exhaust fan outlet. When the flap is in the open position hot air is drawn out of the chamber while cool air is drawn into the oven past the operator (keeping hot oven chamber air away for the operator).

Mushroom head emergency stops are fitted adjacent to both doors while heated air flowing down the annular side wall cavities is blocked by channels near each door opening.

These safety features are supported by an interlocked floor movement control station which allow the floor to only rotate when one door is open and the operator holds down the button. The floor can only be rotated in continuous mode when both doors are closed.

A completely separate oven temperature controlling circuit is designed to prevent overfiring. The controller must be operated before the main temperature controller or programmer can be started.

The oven temperature relay is first in line on the input power and has the capacity to override all other functions of the system.

Oven temperature is controlled by a Shimaden microprocessor-based temperature controller which provides digital displays of process and set values, along with auto tune function of PID parameters. B&L Tetlow 03 9 877 4188.

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